Botulinum Toxin A Combined with Penile Traction Therapy: A Minimally invasive Method for Penile Retraction.

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Xiaowei Zhang, ZIhaio Li, Hailong He, Tao Xu This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8852031/v1 This work is licensed under a CC BY 4.0 License Status: Under Revision Version 1 posted 10 You are reading this latest preprint version Abstract This study evaluated a novel minimally invasive approach combining Botulinum Toxin A injection with penile traction therapy (PTT) for the treatment of penile retraction. A retrospective single-arm exploratory analysis was conducted on 168 males with retractile penis treated between October 2023 and June 2025. Flaccid penile length was assessed under basal conditions and after thermal stimulation, while erectile length, penile retraction ratio, psychological outcomes, and erectile function were evaluated using validated questionnaires. Mean baseline flaccid penile length was 4.4 ± 0.66 cm, increasing significantly to 6.9 ± 0.81 cm at 6 months ( P < 0.001). Improvements were also observed under thermal stimulation and in the penile retraction reduction ratio, which decreased from 27.3% to 11.6% at 6 months ( P < 0.001). Erectile penile length and International Index of Erectile Function scores remained unchanged. Psychological outcomes improved significantly, with Self-Esteem and Relationship and Index of Male Genital Image scores increasing from 28.8 ± 4.3 and 39.3 ± 5.7 to 54.4 ± 5.6 and 59.0 ± 7.3, respectively ( P < 0.01). Mild transient injection-site pain occurred in 11.3% of patients without other complications. This combined therapy appears safe and effective for reducing penile retraction and improving visible flaccid penile exposure and psychosocial outcomes, although it does not achieve true anatomical penile elongation. Prospective controlled studies with longer follow-up are warranted. Health sciences/Health care/Quality of life Health sciences/Health care/Therapeutics Botulinum Toxin A Penile Traction Therapy Penile Retraction Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 INTRODUCTION The penis has long carried substantial social and psychological significance across cultures, often symbolizing masculinity, fertility, and sexual competence [ 1 ] . In contemporary society, concerns regarding penile size and appearance remain common, and many men seek penile enhancement not due to true anatomical insufficiency but rather dissatisfaction with perceived size or visibility [ 2 – 4 ] . This phenomenon has been described as “locker room syndrome” or small penis syndrome (SPS), wherein men with objectively normal penile dimensions experience disproportionate psychological distress related to genital appearance [ 5 ] Retractile penis is a distinct clinical condition characterized by excessive retraction of the flaccid penis, leading to reduced external visibility despite normal or satisfactory erect penile length [ 6 ] . This phenomenon is commonly exacerbated by cold exposure, psychological stress, or physical activity and may cause embarrassment, anxiety, and diminished genital self-image [ 7 ] . Anatomically, the Scarpa fascia of the lower abdominal wall continues into the perineum and penile root, forming the dartos fascia, which contains smooth muscle fibers [ 8 ] . Hyperactivity or heightened reflex contraction of the dartos muscle plays a central role in flaccid penile retraction, particularly in individuals with an exaggerated retraction reflex [ 9 ] . Consequently, a primary concern among affected patients is not true penile shortening, but rather insufficient visible length of the flaccid penis [ 10 ] . Over recent decades, penile lengthening has become an increasingly popular yet controversial topic in urology and genital plastic surgery [ 11 ] . Surgical lengthening procedures, such as division of the suspensory ligament with skin plasty, lack standardized indications and are associated with high complication rates, reported to range from 33% to 75% [ 12 – 16 ] . These limitations underscore the need for less invasive approaches that improve penile appearance while minimizing morbidity. Penile traction therapy (PTT) is a non-invasive conservative modality originally developed for Peyronie’s disease (PD) and later applied in penile rehabilitation following procedures such as penile prosthesis implantation and radical prostatectomy [ 17 ][ 18 ] . Several studies have demonstrated modest but statistically significant increases in flaccid, stretched, and erect penile length following prolonged traction therapy [ 19 – 22 ] . For example, Nowroozi et al. reported mean gains of 1.7 cm (flaccid), 1.3 cm (stretched), and 1.2 cm (erect) after 6 months of daily traction (P < 0.001) [ 23 ] . However, traction therapy alone may be insufficient in patients with pronounced penile retraction due to dartos muscle hyperactivity. Botulinum Toxin A, an exotoxin produced by Clostridium botulinum, inhibits the presynaptic release of acetylcholine and other neurotransmitters, resulting in temporary chemical denervation and muscle relaxation [ 24 ] . Its clinical applications span neurology, rehabilitation medicine, urology, and aesthetic procedures [ 11 ][ 34 ][ 35 ] . Previous studies have suggested that Botulinum Toxin A injection into the penile dartos muscle may temporarily reduce the frequency and amplitude of penile retraction [ 9 ] . Based on these observations, we hypothesized that combining Botulinum Toxin A injection with penile traction therapy could synergistically reduce dartos-mediated retraction and enhance the externally visible length of the flaccid penis. Importantly, this approach is intended to reduce excessive retraction rather than induce true anatomical penile elongation. The present study introduces this combined minimally invasive therapy and evaluates its safety and preliminary efficacy in a cohort of men with retractile penis. PATIENTS AND METHODS Patients This retrospective, single-arm exploratory study was conducted between October 2023 and June 2025. Adult male patients receiving Botulinum Toxin A injection combined with penile traction therapy for penile retraction at Peking University People’s Hospital (Beijing, China) and Eden Hospital (Beijing, China) were enrolled. Exclusion criteria included major psychiatric disorders, penile deformity, concealed penis, prior penile surgery, or impaired manual dexterity preventing proper use of the traction device. Written informed consent was obtained from all participants. Ethical approval was granted by the Ethics Committee of Eden Hospital (No. S2017011). Botulinum Toxin A Injection The procedure was performed in an outpatient setting. Botulinum Toxin A powder was reconstituted in 0.9% sterile, non-preserved saline (100U in 2.5ml). After antiseptic preparation of the penile shaft and application of topical local anesthetic cream, Botulinum Toxin A was injected into the dartos muscle at the penile root. Aspiration was performed prior to each injection to avoid intravascular administration. A total dose of 100 U was distributed as follows: approximately 60 U at the 5 and 7 o’clock positions, 1 cm above the penoscrotal junction, and 40 U at the 2 and 10 o’clock positions, 1 cm above the penopubic junction. No dressing was applied after injection. Penile Traction Therapy Penile traction therapy was initiated on the day of Botulinum Toxin A injection and recommended for at least 3 hours daily. A minimum treatment duration of 3 months was advised, with longer use encouraged when tolerated. The traction device (ProExtender, China) consists of a plastic base ring, two adjustable metallic rods providing traction force, and a glans-holding mechanism with silicone bands (Fig. 1 –2). Physical assessment The flaccid unstretched penile length was measured under standard ambient conditions. With the patient in a supine and relaxed state. Measurements were taken sequentially under three defined conditions: (1) at the basal resting state; (2) immediately following a 10-minute topical application of a medical-grade instant cold pack (surface temperature < 6°C); and (3) after a subsequent 10-minute application of a moist hot compress (45°C). Measurements were taken from the penile base to the tip of the glans using a standardized, non-elastic tape. The penile retraction reflex was methodically elicited by the same attending urologist through gentle cutaneous stimulation of the medial thigh, scrotum, and/or perineum using a standard sterile needle. Penile length was recorded before and after eliciting the reflex. The penile retraction reduction ratio was calculated as: (length before reflex − length after reflex) / length before reflex *100%. Baseline measurements of flaccid penile length, erect penile length, and retraction reflex were obtained prior to treatment and repeated at 3 and 6 months after treatment initiation. Each measurement of penile length described above was performed in triplicate by the same investigator, and the mean value was calculated for analysis to ensure reliability and consistency. Psychological assessment Psychological outcomes were evaluated using validated questionnaires. The Self-Esteem and Relationship (SEAR) questionnaire assessed sexual relationship satisfaction, overall relationship satisfaction, confidence, and self-esteem, with total scores ranging from 14 to 70, higher scores indicating less impairment [ 25 ] . The Index of Male Genital Image (IMGI), a 14-item scale, evaluated satisfaction with genital appearance and was selected as the primary psychological outcome measure [ 26 ] . Erectile function was assessed using the International Index of Erectile Function (IIEF) questionnaire [ 27 ] . All questionnaires were completed at baseline and at 3 and 6 months after treatment initiation. Safety assessment Medical records were reviewed for adverse events. General physical and andrological examinations were performed at each follow-up visit. Any adverse effects reported by patients would be verified and documented by the same senior urologist. Statistical analyses Descriptive statistics were applied to demographic data. Continuous variables are presented as mean ± standard deviation. Within-group comparisons between baseline and follow-up measurements were performed using paired t-tests. Statistical analyses were conducted using SPSS version 25.0 (SPSS Inc., Chicago, IL, USA). A two-sided P < 0.05 was considered statistically significant. RESULTS A total of 168 patients were included in this study, all of whom completed followed up (Figure 3.). Baseline characteristics of patients are presented in Table 1. Table 1. Baseline characteristics of patients. Variables Age (years) 26 ± 4.6 BMI (kg/m 2 ) Waist circumference (cm) 25.3 ± 2.2 91.5 ± 6.8 Prior to treatment, baseline externally visible flaccid penile length measured 4.4 ± 0.66 cm (basal state), 5.2 ± 0.68 cm (after hot foments), and 3.1 ± 0.54 cm (after ice packs). Following treatment initiation, significant increases from baseline were observed at both follow-ups. At 3 months, lengths were 5.4 ± 0.72 cm (basal state; P <0.001), 6.8 ± 0.91 cm (hot foments; P <0.001), and 5.1 ± 0.68 cm (ice packs; P<0.001). By 6 months, lengths were 6.9 ± 0.81 cm (basal state; P <0.001), 7.2 ± 0.74 cm (hot foments; P <0.001), and 5.6 ± 0.88 cm (ice packs; P <0.001). The increase in basal state length at 6 months was 2.5 ± 0.08 cm (95% CI: 2.341-2.659) compared to pre-treatment. No significant changes were observed in erect penile length at 3 or 6 months compared with baseline ( P >0.1). The penile retraction reduction ratio decreased significantly from 27.3% at baseline to 14.8% at 3 months ( P <0.001) and 11.6% at 6 months ( P <0.001). Psychological assessments demonstrated significant improvements in SEAR and IMGI scores at both follow-up time points ( P <0.001), whereas IIEF scores showed no significant change. (Table2. and Figure6.) Mild pain at the injection site within 48 hours after Botulinum toxin A injection was observed in 19 (11.3%) patients, and no other complications were observed in any of the patients. Table 2. Patient's physiological and psychological assessment data Baseline (M±S.D.) 3 Months (M±S.D.) 6 Months (M±S.D.) P ( vs. Baseline) Flaccid penile length(cm) Basal state Hot foments Ice packs Erect penile length(cm) Retraction reflex(cm) Before eliciting After eliciting Penile length decrease (%) Score of SEAR Score of IMGI Score of IIEF 4.4±0.66 5.2±0.68 3.1±0.54 11.3±1.21 4.4±0.58 3.2±0.44 27.3% 28.8±4.34 39.3±5.71 23.4±2.82 5.4±0.72 6.8±0.91 5.1±0.68 11.2±1.14 5.4±0.64 4.6±0.73 14.8% 49.3±7.12 54.7±6.65 24.1±3.51 6.9±0.81 7.2±0.74 5.6±0.88 11.3±0.92 6.9±0.55 6.1±0.57 11.6% 54.4±5.62 59.0±7.33 24.3±4.33 ＜0.001 ＜0.001 ＜0.001 ＞0.5 ＜0.001 ＜0.001 ＜0.001 ＞0.5 DISCUSSION This preliminary exploratory study introduces a novel minimally invasive approach for the management of retractile penis using combined Botulinum Toxin A injection and penile traction therapy. Importantly, the observed improvement reflects an increase in externally visible flaccid penile length rather than true anatomical elongation. This distinction is critical for appropriate interpretation of the clinical outcomes. Many patients experiencing penile retraction tend to seek penile lengthening surgery. At present, the method of division of the penile suspensory ligament (ligamentolysis), in combination with V-Y-shaped skin plasty, is most widely used to elongate the penis [ 14 ][ 16 ] . James J. Elist et al. used subcutaneous soft silicone implantation (Penuma penile implant, PPI) in the pubic region to increase the visible length of the penis [ 7 ] . However, such surgical procedures remain associated with substantial morbidity, aesthetic dissatisfaction, and inconsistent functional benefit [ 28 ][ 29 ] . Several non-invasive methods of penile lengthening have been described, such as vacuum devices and penoscrotal rings [ 11 ] . Most of these techniques, however, are not supported by any scientific evidence. A study assessed the long-term effect of repeated vacuum treatment for penile lengthening and concluded that there was no significant physical change after 6 months of therapy [ 22 ] . Vacuum treatment of the penis was not found to be effective for penile elongation, although it provided some sort of psychological satisfaction for some men [ 30 ] . Other devices include penoscrotal rings that, in association with phosphodiesterase-5 inhibitors, might help to augment penile size and maintain erections in men suffering from anxiety [ 31 ] . Penile traction therapy (PTT) has gained recognition within urology as a non-surgical therapeutic modality for two primary indications: penile size dissatisfaction and acquired penile shortening (e.g., secondary to Peyronie's disease, post-surgical fibrosis, or post-prostatectomy) [ 17 ] . Current evidence positions PTT as a first-line, non-invasive alternative for patients considering invasive lengthening procedures, with some analyses identifying it as the only non-invasive technique substantiated by clinical data for mild length augmentation [ 38 ][ 39 ] .The traction device was first developed in 2008 [ 22 ] . It uses a plastic support ring at the base of the penis and another plastic ring at the coronal groove to screw the parallel stabilizer bar to the appropriate position to provide traction. However, long-term traction can also lead to penile pain. The second-generation traction device (Restorex; pathright medical, Plymouth, MN) has improved the relevant defects and is currently widely used [ 21 ] . Some studies have found that the physiological changes brought about by traction therapy mainly come from mechanical conduction, that is, through traction to expand tissue, and then form new collagen tissue [ 22 ] . Some molecular studies have also shown that the continuous expansion of fibrous plaques through traction therapy leads to a significant increase in collagenase and metalloproteinase, which contributes to the softening and expansion of fibrous plaques [ 22 ] . In an animal model study, penile traction therapy can preserve smooth muscle and tissue and reduce fibrosis by reducing the expression of TGF-β1 [ 18 ] The chemical nature of botulinum toxin is a protein composed of two polypeptide chains, of which the heavy chain can recognize and bind to specific receptors on the presynaptic membrane of nerve terminals; The light chain, as a zinc titanium endonuclease, hydrolyzes the N-ethylmaleamide-sensitive factor attachment protein receptor complex, thus affecting the fusion of synaptic vesicles and presynaptic membrane, blocking the release of acetylcholine and other neurotransmitters, and causing muscle relaxation, gland secretion and other chemical neurotransmitters [ 24 ] . In December, 1989, the food and Drug Administration (FDA) approved the listing of the world's first botulinum toxin A for clinical treatment. In recent years, the application of botulinum toxin A in urology has been supported by accumulating evidence, with its therapeutic use expanding to include conditions such as overactive bladder, chronic non-bacterial prostatitis, and premature ejaculation [ 34 – 37 ] . A study by Osama shaeer et al. showed Botox may have a potential effect in temporarily decreasing penile retractions in terms of frequency and amplitude [ 9 ] . Based on the temporary nature of Botulinum Toxin A's smooth muscle relaxant effects and the potential inadequacy of penile traction therapy as a standalone treatment for pronounced penile retraction, we propose a combined therapeutic strategy targeting the underlying pathophysiology of retractile penis by relaxing the dartos muscle while simultaneously applying mechanical traction to maintain penile extension. Preliminary results from this study elucidate the initial feasibility of the combined therapeutic regimen. At 6 months post-treatment initiation, the externally visible length of the flaccid penis at basal state increased by 2.5 ± 0.08 cm compared to pre-treatment measurements. However, given the temporary mechanism of action of Botulinum Toxin A, clinical application typically necessitates repeat injections at 3- to 6-month intervals [ 40 ] . Concurrently, adherence to the requisite minimum 3-month course of self-administered penile traction therapy may wane over time. Therefore, all patients were explicitly informed prior to treatment that the physical changes are not permanent, with therapeutic effects anticipated to gradually regress after 6–9 months, mandating repeat treatment cycles. Owing to the minimally invasive and convenient nature of this regimen, all patients expressed acceptance of this approach. Given that only a subset of patients has undergone repeat treatment to date, data on long-term follow-up will be updated in our future studies. A notable limitation of this study is the inability to delineate the independent contributions of Botulinum Toxin A and traction therapy due to the absence of monotherapy control groups. While a randomized controlled design would be methodologically ideal, our previous clinical experience suggested limited efficacy of either intervention alone in patients with marked retraction, raising ethical considerations for withholding combined therapy. Further research is warranted to clarify this issue. Additional limitations include the retrospective design, potential measurement variability, self-reported traction adherence, and limited follow-up duration. CONCLUSION The combined use of Botulinum Toxin A injection and penile traction therapy appears to be a safe and promising minimally invasive approach for reducing excessive penile retraction and enhancing visible flaccid penile exposure. Although this intervention does not produce true anatomical penile elongation, it is associated with significant improvements in genital self-image and sexual self-esteem. Prospective controlled studies with longer follow-up are required to confirm efficacy, durability, and mechanistic contributions of each treatment component. Declarations COMPETING INTERESTS All authors declare no competing interests. AUTHOR CONTRIBUTIONS Zihao Li and Hailong He contributed to surgical procedures, study design, patient follow-up, data acquisition and analysis, and manuscript drafting. Zihao Li and Hailong He contributed equally to this work. Tao Xu contributed to study design. Xiaowei Zhang performed all surgical procedures and was responsible for study conception, design, and overall supervision. All authors critically revised the manuscript and approved the final version. ACKNOWLEDGMENTS This study was supported by grants from the Beijing Municipal Natural Science Foundation (No. 7194327). 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Cite Share Download PDF Status: Under Revision Version 1 posted Editorial decision: revise 23 Mar, 2026 Review # 2 received at journal 17 Mar, 2026 Review # 1 received at journal 09 Mar, 2026 Reviewer # 2 agreed at journal 02 Mar, 2026 Reviewer # 1 agreed at journal 24 Feb, 2026 Reviewers invited by journal 20 Feb, 2026 Submission checks completed at journal 19 Feb, 2026 First submitted to journal 19 Feb, 2026 Unknown event 12 Feb, 2026 Editor assigned by journal 11 Feb, 2026 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8852031","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":594413548,"identity":"c0ff44db-4410-4a02-874b-60f8db88b280","order_by":0,"name":"Xiaowei Zhang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAyUlEQVRIiWNgGAWjYDCCA0DM2AAk2BsbH3wgTQvP4WbDGaRpkUhvk+YgRgff8eaHH37usMuTj3zYIM3AYCen20BAi+SZY8aSvWeSiw1vJzYYFzAkG5sdIKDF4EYOgzRjG3PixtmJDckzGA4kbiNCC/Nvxrb6xI0zDzYc5iFSCxvQlsOJ8yUYG5uJ0gL0i5llb9vxxA08ic2MMwyI8AswxB7f+NlWnTi//fjzHx8q7OQIakG4EKzSgFjlICDfQIrqUTAKRsEoGFEAADFpSkRB8U2UAAAAAElFTkSuQmCC","orcid":"","institution":"Peking University People's Hospital","correspondingAuthor":true,"prefix":"","firstName":"Xiaowei","middleName":"","lastName":"Zhang","suffix":""},{"id":594413549,"identity":"076c0622-d0c7-45ea-8826-d6359d99c54f","order_by":1,"name":"ZIhaio Li","email":"","orcid":"https://orcid.org/0009-0005-1148-9117","institution":"","correspondingAuthor":false,"prefix":"","firstName":"ZIhaio","middleName":"","lastName":"Li","suffix":""},{"id":594413550,"identity":"5f12b697-5096-490c-8ba6-e97d22f04563","order_by":2,"name":"Hailong He","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Hailong","middleName":"","lastName":"He","suffix":""},{"id":594413551,"identity":"b631b555-407f-42a1-9a62-820f1f19065c","order_by":3,"name":"Tao Xu","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Tao","middleName":"","lastName":"Xu","suffix":""}],"badges":[],"createdAt":"2026-02-11 13:06:26","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8852031/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8852031/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":103437820,"identity":"5debf69d-5ad8-4545-b316-b75644aa015e","added_by":"auto","created_at":"2026-02-25 16:52:06","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":205724,"visible":true,"origin":"","legend":"\u003cp\u003eProExtender, China\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-8852031/v1/4e1c83ba5c85546c8159dccb.png"},{"id":103437821,"identity":"1b6d998a-8f6a-47cc-89a6-a542759113c2","added_by":"auto","created_at":"2026-02-25 16:52:07","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":139013,"visible":true,"origin":"","legend":"\u003cp\u003eExtender wearing\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-8852031/v1/377f91f2b28d2af81f327c99.png"},{"id":103437824,"identity":"46d3201c-81fa-4884-95d4-067000295eb7","added_by":"auto","created_at":"2026-02-25 16:52:07","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":147450,"visible":true,"origin":"","legend":"\u003cp\u003eFlowchart of the study.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-8852031/v1/9c27b05d794a84741ff3f0fe.png"},{"id":103437823,"identity":"1aa92329-8824-47dd-85ec-3f6a7386fb65","added_by":"auto","created_at":"2026-02-25 16:52:07","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":285856,"visible":true,"origin":"","legend":"\u003cp\u003eFlaccid penile changes in a 28-year-old male patient.A) One day before treatment; B)6 months after treatment initiation.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-8852031/v1/339d8341d2a8fc40521cddf4.png"},{"id":103437825,"identity":"6e58d664-9f4b-49ef-bfad-b9b0ac7da83d","added_by":"auto","created_at":"2026-02-25 16:52:07","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":232966,"visible":true,"origin":"","legend":"\u003cp\u003eErectile penile changes in a 28-year-old male patient. A) One day before treatment; B)6 months after treatment initiation.\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-8852031/v1/6b46cc31d7b8708d92f1ec90.png"},{"id":103507888,"identity":"9fe03ec3-4b1e-4d7e-9ac5-550dc7978023","added_by":"auto","created_at":"2026-02-26 13:46:14","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":227531,"visible":true,"origin":"","legend":"\u003cp\u003ePatient's physiological and psychological assessment data. A) Flaccid penile length; B)Score of SEAR, IMGI and IIEF; C) Flaccid penile length before and after eliciting penile retraction reflex.\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-8852031/v1/17a1366403ef95d24baab061.png"},{"id":103510076,"identity":"6b788d50-86cd-402d-bfa5-1defea4d00fa","added_by":"auto","created_at":"2026-02-26 14:03:40","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1818391,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8852031/v1/4353af6d-e820-4f84-869b-f24f80b3249f.pdf"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e conflict of interest to disclose.","formattedTitle":"Botulinum Toxin A Combined with Penile Traction Therapy: A Minimally invasive Method for Penile Retraction.","fulltext":[{"header":"INTRODUCTION","content":"\u003cp\u003eThe penis has long carried substantial social and psychological significance across cultures, often symbolizing masculinity, fertility, and sexual competence\u003csup\u003e[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]\u003c/sup\u003e. In contemporary society, concerns regarding penile size and appearance remain common, and many men seek penile enhancement not due to true anatomical insufficiency but rather dissatisfaction with perceived size or visibility\u003csup\u003e[\u003cspan additionalcitationids=\"CR3\" citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]\u003c/sup\u003e. This phenomenon has been described as \u0026ldquo;locker room syndrome\u0026rdquo; or small penis syndrome (SPS), wherein men with objectively normal penile dimensions experience disproportionate psychological distress related to genital appearance\u003csup\u003e[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eRetractile penis is a distinct clinical condition characterized by excessive retraction of the flaccid penis, leading to reduced external visibility despite normal or satisfactory erect penile length\u003csup\u003e[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]\u003c/sup\u003e. This phenomenon is commonly exacerbated by cold exposure, psychological stress, or physical activity and may cause embarrassment, anxiety, and diminished genital self-image\u003csup\u003e[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]\u003c/sup\u003e. Anatomically, the Scarpa fascia of the lower abdominal wall continues into the perineum and penile root, forming the dartos fascia, which contains smooth muscle fibers\u003csup\u003e[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]\u003c/sup\u003e. Hyperactivity or heightened reflex contraction of the dartos muscle plays a central role in flaccid penile retraction, particularly in individuals with an exaggerated retraction reflex\u003csup\u003e[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]\u003c/sup\u003e. Consequently, a primary concern among affected patients is not true penile shortening, but rather insufficient visible length of the flaccid penis\u003csup\u003e[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eOver recent decades, penile lengthening has become an increasingly popular yet controversial topic in urology and genital plastic surgery\u003csup\u003e[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]\u003c/sup\u003e. Surgical lengthening procedures, such as division of the suspensory ligament with skin plasty, lack standardized indications and are associated with high complication rates, reported to range from 33% to 75%\u003csup\u003e[\u003cspan additionalcitationids=\"CR13 CR14 CR15\" citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]\u003c/sup\u003e. These limitations underscore the need for less invasive approaches that improve penile appearance while minimizing morbidity.\u003c/p\u003e \u003cp\u003ePenile traction therapy (PTT) is a non-invasive conservative modality originally developed for Peyronie\u0026rsquo;s disease (PD) and later applied in penile rehabilitation following procedures such as penile prosthesis implantation and radical prostatectomy\u003csup\u003e[\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e][\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]\u003c/sup\u003e. Several studies have demonstrated modest but statistically significant increases in flaccid, stretched, and erect penile length following prolonged traction therapy\u003csup\u003e[\u003cspan additionalcitationids=\"CR20 CR21\" citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]\u003c/sup\u003e. For example, Nowroozi et al. reported mean gains of 1.7 cm (flaccid), 1.3 cm (stretched), and 1.2 cm (erect) after 6 months of daily traction (P\u0026thinsp;\u0026lt;\u0026thinsp;0.001)\u003csup\u003e[\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]\u003c/sup\u003e. However, traction therapy alone may be insufficient in patients with pronounced penile retraction due to dartos muscle hyperactivity.\u003c/p\u003e \u003cp\u003eBotulinum Toxin A, an exotoxin produced by Clostridium botulinum, inhibits the presynaptic release of acetylcholine and other neurotransmitters, resulting in temporary chemical denervation and muscle relaxation\u003csup\u003e[\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]\u003c/sup\u003e. Its clinical applications span neurology, rehabilitation medicine, urology, and aesthetic procedures\u003csup\u003e[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e][\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e][\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]\u003c/sup\u003e. Previous studies have suggested that Botulinum Toxin A injection into the penile dartos muscle may temporarily reduce the frequency and amplitude of penile retraction\u003csup\u003e[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eBased on these observations, we hypothesized that combining Botulinum Toxin A injection with penile traction therapy could synergistically reduce dartos-mediated retraction and enhance the externally visible length of the flaccid penis. Importantly, this approach is intended to reduce excessive retraction rather than induce true anatomical penile elongation. The present study introduces this combined minimally invasive therapy and evaluates its safety and preliminary efficacy in a cohort of men with retractile penis.\u003c/p\u003e"},{"header":"PATIENTS AND METHODS","content":"\u003cp\u003ePatients\u003c/p\u003e \u003cp\u003eThis retrospective, single-arm exploratory study was conducted between October 2023 and June 2025. Adult male patients receiving Botulinum Toxin A injection combined with penile traction therapy for penile retraction at Peking University People\u0026rsquo;s Hospital (Beijing, China) and Eden Hospital (Beijing, China) were enrolled. Exclusion criteria included major psychiatric disorders, penile deformity, concealed penis, prior penile surgery, or impaired manual dexterity preventing proper use of the traction device. Written informed consent was obtained from all participants. Ethical approval was granted by the Ethics Committee of Eden Hospital (No. S2017011).\u003c/p\u003e \u003cp\u003eBotulinum Toxin A Injection\u003c/p\u003e \u003cp\u003eThe procedure was performed in an outpatient setting. Botulinum Toxin A powder was reconstituted in 0.9% sterile, non-preserved saline (100U in 2.5ml). After antiseptic preparation of the penile shaft and application of topical local anesthetic cream, Botulinum Toxin A was injected into the dartos muscle at the penile root. Aspiration was performed prior to each injection to avoid intravascular administration. A total dose of 100 U was distributed as follows: approximately 60 U at the 5 and 7 o\u0026rsquo;clock positions, 1 cm above the penoscrotal junction, and 40 U at the 2 and 10 o\u0026rsquo;clock positions, 1 cm above the penopubic junction. No dressing was applied after injection.\u003c/p\u003e \u003cp\u003ePenile Traction Therapy\u003c/p\u003e \u003cp\u003ePenile traction therapy was initiated on the day of Botulinum Toxin A injection and recommended for at least 3 hours daily. A minimum treatment duration of 3 months was advised, with longer use encouraged when tolerated. The traction device (ProExtender, China) consists of a plastic base ring, two adjustable metallic rods providing traction force, and a glans-holding mechanism with silicone bands (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e\u0026ndash;2).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003ePhysical assessment\u003c/p\u003e \u003cp\u003eThe flaccid unstretched penile length was measured under standard ambient conditions. With the patient in a supine and relaxed state. Measurements were taken sequentially under three defined conditions: (1) at the basal resting state; (2) immediately following a 10-minute topical application of a medical-grade instant cold pack (surface temperature\u0026thinsp;\u0026lt;\u0026thinsp;6\u0026deg;C); and (3) after a subsequent 10-minute application of a moist hot compress (45\u0026deg;C). Measurements were taken from the penile base to the tip of the glans using a standardized, non-elastic tape.\u003c/p\u003e \u003cp\u003eThe penile retraction reflex was methodically elicited by the same attending urologist through gentle cutaneous stimulation of the medial thigh, scrotum, and/or perineum using a standard sterile needle. Penile length was recorded before and after eliciting the reflex. The penile retraction reduction ratio was calculated as: (length before reflex\u0026thinsp;\u0026minus;\u0026thinsp;length after reflex) / length before reflex *100%.\u003c/p\u003e \u003cp\u003eBaseline measurements of flaccid penile length, erect penile length, and retraction reflex were obtained prior to treatment and repeated at 3 and 6 months after treatment initiation. Each measurement of penile length described above was performed in triplicate by the same investigator, and the mean value was calculated for analysis to ensure reliability and consistency.\u003c/p\u003e \u003cp\u003ePsychological assessment\u003c/p\u003e \u003cp\u003ePsychological outcomes were evaluated using validated questionnaires. The Self-Esteem and Relationship (SEAR) questionnaire assessed sexual relationship satisfaction, overall relationship satisfaction, confidence, and self-esteem, with total scores ranging from 14 to 70, higher scores indicating less impairment\u003csup\u003e[\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]\u003c/sup\u003e. The Index of Male Genital Image (IMGI), a 14-item scale, evaluated satisfaction with genital appearance and was selected as the primary psychological outcome measure\u003csup\u003e[\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]\u003c/sup\u003e. Erectile function was assessed using the International Index of Erectile Function (IIEF) questionnaire\u003csup\u003e[\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]\u003c/sup\u003e. All questionnaires were completed at baseline and at 3 and 6 months after treatment initiation.\u003c/p\u003e \u003cp\u003eSafety assessment\u003c/p\u003e \u003cp\u003eMedical records were reviewed for adverse events. General physical and andrological examinations were performed at each follow-up visit. Any adverse effects reported by patients would be verified and documented by the same senior urologist.\u003c/p\u003e \u003cp\u003eStatistical analyses\u003c/p\u003e \u003cp\u003eDescriptive statistics were applied to demographic data. Continuous variables are presented as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation. Within-group comparisons between baseline and follow-up measurements were performed using paired t-tests. Statistical analyses were conducted using SPSS version 25.0 (SPSS Inc., Chicago, IL, USA). A two-sided \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05 was considered statistically significant.\u003c/p\u003e"},{"header":"RESULTS","content":"\u003cp\u003eA total of 168 patients were included in this study, all of whom completed followed up (Figure 3.). Baseline characteristics of patients are presented in Table 1.\u003c/p\u003e\n\u003cp\u003eTable 1. Baseline characteristics of patients.\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"59%\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 75px;\"\u003e\n \u003cp\u003eVariables\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 24px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 75px;\"\u003e\n \u003cp\u003eAge (years)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 24px;\"\u003e\n \u003cp\u003e26 \u0026plusmn; 4.6\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 75px;\"\u003e\n \u003cp\u003eBMI (kg/m\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e\n \u003cp\u003eWaist circumference (cm)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 24px;\"\u003e\n \u003cp\u003e25.3 \u0026plusmn; 2.2\u003c/p\u003e\n \u003cp\u003e91.5 \u0026plusmn; 6.8\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003ePrior to treatment, baseline externally visible flaccid penile length measured 4.4 \u0026plusmn; 0.66 cm (basal state), 5.2 \u0026plusmn; 0.68 cm (after hot foments), and 3.1 \u0026plusmn; 0.54 cm (after ice packs). Following treatment initiation, significant increases from baseline were observed at both follow-ups. \u0026nbsp;At 3 months, lengths were 5.4 \u0026plusmn; 0.72 cm (basal state; \u003cem\u003eP\u003c/em\u003e\u0026lt;0.001), 6.8 \u0026plusmn; 0.91 cm (hot foments; \u003cem\u003eP\u003c/em\u003e\u0026lt;0.001), and 5.1 \u0026plusmn; 0.68 cm (ice packs; P\u0026lt;0.001). By 6 months, lengths were 6.9 \u0026plusmn; 0.81 cm (basal state; \u003cem\u003eP\u003c/em\u003e\u0026lt;0.001), 7.2 \u0026plusmn; 0.74 cm (hot foments; \u003cem\u003eP\u003c/em\u003e\u0026lt;0.001), and 5.6 \u0026plusmn; 0.88 cm (ice packs; \u003cem\u003eP\u003c/em\u003e\u0026lt;0.001).\u0026nbsp;The increase in basal state length at 6 months was 2.5 \u0026plusmn; 0.08 cm (95% CI: 2.341-2.659) compared to pre-treatment. No significant changes were observed in erect penile length at 3 or 6 months compared with baseline (\u003cem\u003eP\u003c/em\u003e\u0026gt;0.1). The penile retraction reduction ratio decreased significantly from 27.3% at baseline to 14.8% at 3 months (\u003cem\u003eP\u003c/em\u003e\u0026lt;0.001) and 11.6% at 6 months (\u003cem\u003eP\u003c/em\u003e\u0026lt;0.001). Psychological assessments demonstrated significant improvements in SEAR and IMGI scores at both follow-up time points (\u003cem\u003eP\u003c/em\u003e\u0026lt;0.001), whereas IIEF scores showed no significant change. (Table2. and Figure6.)\u003c/p\u003e\n\u003cp\u003eMild pain at the injection site within 48 hours after Botulinum toxin A injection was observed in 19 (11.3%) patients, and no other complications were observed in any of the patients.\u003c/p\u003e\n\u003cp\u003eTable 2. Patient\u0026apos;s physiological and psychological assessment data\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eBaseline (M\u0026plusmn;S.D.)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e3 Months\u003c/p\u003e\n \u003cp\u003e(M\u0026plusmn;S.D.)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e6 Months\u003c/p\u003e\n \u003cp\u003e(M\u0026plusmn;S.D.)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u003cem\u003eP\u003c/em\u003e\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;(\u003cem\u003evs.\u0026nbsp;\u003c/em\u003eBaseline)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eFlaccid penile length(cm)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; Basal state\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; Hot foments\u003c/p\u003e\n \u003cp\u003eIce packs\u003c/p\u003e\n \u003cp\u003eErect penile length(cm)\u003c/p\u003e\n \u003cp\u003eRetraction reflex(cm)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp; Before eliciting\u003c/p\u003e\n \u003cp\u003eAfter eliciting\u003c/p\u003e\n \u003cp\u003ePenile length decrease (%)\u003c/p\u003e\n \u003cp\u003eScore of SEAR\u003c/p\u003e\n \u003cp\u003eScore of IMGI\u003c/p\u003e\n \u003cp\u003eScore of IIEF\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e4.4\u0026plusmn;0.66\u003c/p\u003e\n \u003cp\u003e5.2\u0026plusmn;0.68\u003c/p\u003e\n \u003cp\u003e3.1\u0026plusmn;0.54\u003c/p\u003e\n \u003cp\u003e11.3\u0026plusmn;1.21\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e4.4\u0026plusmn;0.58\u003c/p\u003e\n \u003cp\u003e3.2\u0026plusmn;0.44\u003c/p\u003e\n \u003cp\u003e27.3%\u003c/p\u003e\n \u003cp\u003e28.8\u0026plusmn;4.34\u003c/p\u003e\n \u003cp\u003e39.3\u0026plusmn;5.71\u003c/p\u003e\n \u003cp\u003e23.4\u0026plusmn;2.82\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e5.4\u0026plusmn;0.72\u003c/p\u003e\n \u003cp\u003e6.8\u0026plusmn;0.91\u003c/p\u003e\n \u003cp\u003e5.1\u0026plusmn;0.68\u003c/p\u003e\n \u003cp\u003e11.2\u0026plusmn;1.14\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e5.4\u0026plusmn;0.64\u003c/p\u003e\n \u003cp\u003e4.6\u0026plusmn;0.73\u003c/p\u003e\n \u003cp\u003e14.8%\u003c/p\u003e\n \u003cp\u003e49.3\u0026plusmn;7.12\u003c/p\u003e\n \u003cp\u003e54.7\u0026plusmn;6.65\u003c/p\u003e\n \u003cp\u003e24.1\u0026plusmn;3.51\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e6.9\u0026plusmn;0.81\u003c/p\u003e\n \u003cp\u003e7.2\u0026plusmn;0.74\u003c/p\u003e\n \u003cp\u003e5.6\u0026plusmn;0.88\u003c/p\u003e\n \u003cp\u003e11.3\u0026plusmn;0.92\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e6.9\u0026plusmn;0.55\u003c/p\u003e\n \u003cp\u003e6.1\u0026plusmn;0.57\u003c/p\u003e\n \u003cp\u003e11.6%\u003c/p\u003e\n \u003cp\u003e54.4\u0026plusmn;5.62\u003c/p\u003e\n \u003cp\u003e59.0\u0026plusmn;7.33\u003c/p\u003e\n \u003cp\u003e24.3\u0026plusmn;4.33\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e＜0.001\u003c/p\u003e\n \u003cp\u003e＜0.001\u003c/p\u003e\n \u003cp\u003e＜0.001\u003c/p\u003e\n \u003cp\u003e＞0.5\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e＜0.001\u003c/p\u003e\n \u003cp\u003e＜0.001\u003c/p\u003e\n \u003cp\u003e＜0.001\u003c/p\u003e\n \u003cp\u003e＞0.5\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e"},{"header":"DISCUSSION","content":"\u003cp\u003eThis preliminary exploratory study introduces a novel minimally invasive approach for the management of retractile penis using combined Botulinum Toxin A injection and penile traction therapy. Importantly, the observed improvement reflects an increase in externally visible flaccid penile length rather than true anatomical elongation. This distinction is critical for appropriate interpretation of the clinical outcomes.\u003c/p\u003e \u003cp\u003eMany patients experiencing penile retraction tend to seek penile lengthening surgery. At present, the method of division of the penile suspensory ligament (ligamentolysis), in combination with V-Y-shaped skin plasty, is most widely used to elongate the penis\u003csup\u003e[\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e][\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]\u003c/sup\u003e. James J. Elist et al. used subcutaneous soft silicone implantation (Penuma penile implant, PPI) in the pubic region to increase the visible length of the penis\u003csup\u003e[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]\u003c/sup\u003e. However, such surgical procedures remain associated with substantial morbidity, aesthetic dissatisfaction, and inconsistent functional benefit\u003csup\u003e[\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e][\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eSeveral non-invasive methods of penile lengthening have been described, such as vacuum devices and penoscrotal rings\u003csup\u003e[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]\u003c/sup\u003e. Most of these techniques, however, are not supported by any scientific evidence. A study assessed the long-term effect of repeated vacuum treatment for penile lengthening and concluded that there was no significant physical change after 6 months of therapy\u003csup\u003e[\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]\u003c/sup\u003e. Vacuum treatment of the penis was not found to be effective for penile elongation, although it provided some sort of psychological satisfaction for some men\u003csup\u003e[\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]\u003c/sup\u003e. Other devices include penoscrotal rings that, in association with phosphodiesterase-5 inhibitors, might help to augment penile size and maintain erections in men suffering from anxiety\u003csup\u003e[\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003ePenile traction therapy (PTT) has gained recognition within urology as a non-surgical therapeutic modality for two primary indications: penile size dissatisfaction and acquired penile shortening (e.g., secondary to Peyronie's disease, post-surgical fibrosis, or post-prostatectomy)\u003csup\u003e[\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]\u003c/sup\u003e. Current evidence positions PTT as a first-line, non-invasive alternative for patients considering invasive lengthening procedures, with some analyses identifying it as the only non-invasive technique substantiated by clinical data for mild length augmentation\u003csup\u003e[\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e][\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e]\u003c/sup\u003e.The traction device was first developed in 2008\u003csup\u003e[\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]\u003c/sup\u003e. It uses a plastic support ring at the base of the penis and another plastic ring at the coronal groove to screw the parallel stabilizer bar to the appropriate position to provide traction. However, long-term traction can also lead to penile pain. The second-generation traction device (Restorex; pathright medical, Plymouth, MN) has improved the relevant defects and is currently widely used\u003csup\u003e[\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]\u003c/sup\u003e. Some studies have found that the physiological changes brought about by traction therapy mainly come from mechanical conduction, that is, through traction to expand tissue, and then form new collagen tissue\u003csup\u003e[\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]\u003c/sup\u003e. Some molecular studies have also shown that the continuous expansion of fibrous plaques through traction therapy leads to a significant increase in collagenase and metalloproteinase, which contributes to the softening and expansion of fibrous plaques\u003csup\u003e[\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]\u003c/sup\u003e. In an animal model study, penile traction therapy can preserve smooth muscle and tissue and reduce fibrosis by reducing the expression of TGF-β1\u003csup\u003e[\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eThe chemical nature of botulinum toxin is a protein composed of two polypeptide chains, of which the heavy chain can recognize and bind to specific receptors on the presynaptic membrane of nerve terminals; The light chain, as a zinc titanium endonuclease, hydrolyzes the N-ethylmaleamide-sensitive factor attachment protein receptor complex, thus affecting the fusion of synaptic vesicles and presynaptic membrane, blocking the release of acetylcholine and other neurotransmitters, and causing muscle relaxation, gland secretion and other chemical neurotransmitters\u003csup\u003e[\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]\u003c/sup\u003e. In December, 1989, the food and Drug Administration (FDA) approved the listing of the world's first botulinum toxin A for clinical treatment. In recent years, the application of botulinum toxin A in urology has been supported by accumulating evidence, with its therapeutic use expanding to include conditions such as overactive bladder, chronic non-bacterial prostatitis, and premature ejaculation\u003csup\u003e[\u003cspan additionalcitationids=\"CR35 CR36\" citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e]\u003c/sup\u003e. A study by Osama shaeer et al. showed Botox may have a potential effect in temporarily decreasing penile retractions in terms of frequency and amplitude\u003csup\u003e[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eBased on the temporary nature of Botulinum Toxin A's smooth muscle relaxant effects and the potential inadequacy of penile traction therapy as a standalone treatment for pronounced penile retraction, we propose a combined therapeutic strategy targeting the underlying pathophysiology of retractile penis by relaxing the dartos muscle while simultaneously applying mechanical traction to maintain penile extension.\u003c/p\u003e \u003cp\u003ePreliminary results from this study elucidate the initial feasibility of the combined therapeutic regimen. At 6 months post-treatment initiation, the externally visible length of the flaccid penis at basal state increased by 2.5\u0026thinsp;\u0026plusmn;\u0026thinsp;0.08 cm compared to pre-treatment measurements. However, given the temporary mechanism of action of Botulinum Toxin A, clinical application typically necessitates repeat injections at 3- to 6-month intervals\u003csup\u003e[\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e]\u003c/sup\u003e. Concurrently, adherence to the requisite minimum 3-month course of self-administered penile traction therapy may wane over time. Therefore, all patients were explicitly informed prior to treatment that the physical changes are not permanent, with therapeutic effects anticipated to gradually regress after 6\u0026ndash;9 months, mandating repeat treatment cycles. Owing to the minimally invasive and convenient nature of this regimen, all patients expressed acceptance of this approach. Given that only a subset of patients has undergone repeat treatment to date, data on long-term follow-up will be updated in our future studies.\u003c/p\u003e \u003cp\u003eA notable limitation of this study is the inability to delineate the independent contributions of Botulinum Toxin A and traction therapy due to the absence of monotherapy control groups. While a randomized controlled design would be methodologically ideal, our previous clinical experience suggested limited efficacy of either intervention alone in patients with marked retraction, raising ethical considerations for withholding combined therapy. Further research is warranted to clarify this issue. Additional limitations include the retrospective design, potential measurement variability, self-reported traction adherence, and limited follow-up duration.\u003c/p\u003e"},{"header":"CONCLUSION","content":"\u003cp\u003eThe combined use of Botulinum Toxin A injection and penile traction therapy appears to be a safe and promising minimally invasive approach for reducing excessive penile retraction and enhancing visible flaccid penile exposure. Although this intervention does not produce true anatomical penile elongation, it is associated with significant improvements in genital self-image and sexual self-esteem. Prospective controlled studies with longer follow-up are required to confirm efficacy, durability, and mechanistic contributions of each treatment component.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eCOMPETING INTERESTS\u003c/h2\u003e \u003cp\u003eAll authors declare no competing interests.\u003c/p\u003e \u003ch2\u003eAUTHOR CONTRIBUTIONS\u003c/h2\u003e \u003cp\u003eZihao Li and Hailong He contributed to surgical procedures, study design, patient follow-up, data acquisition and analysis, and manuscript drafting. Zihao Li and Hailong He contributed equally to this work. Tao Xu contributed to study design. Xiaowei Zhang performed all surgical procedures and was responsible for study conception, design, and overall supervision. All authors critically revised the manuscript and approved the final version.\u003c/p\u003e\u003ch2\u003eACKNOWLEDGMENTS\u003c/h2\u003e \u003cp\u003eThis study was supported by grants from the Beijing Municipal Natural Science Foundation (No. 7194327).\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eTwisselmann B. \u003cem\u003eA Mind of Its Own: A Cultural History of the Penis\u003c/em\u003e. BMJ. 2002;325:1427.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eVeale D, Miles S, Read J, Troglia A, Wylie K, Muir G. Sexual functioning and behavior of men with body dysmorphic disorder concerning penis size compared with men anxious about penis size and with controls: a cohort study. 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Urology. 2006;68(Suppl):45\u0026ndash;46.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"international-journal-of-impotence-research","isNatureJournal":false,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"ijir","sideBox":"Learn more about [International Journal of Impotence Research](http://www.nature.com/ijir/)","snPcode":"41443","submissionUrl":"https://mts-ijir.nature.com/cgi-bin/main.plex","title":"International Journal of Impotence Research","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"ejp","reportingPortfolio":"Nature AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Botulinum Toxin A, Penile Traction Therapy, Penile Retraction","lastPublishedDoi":"10.21203/rs.3.rs-8852031/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8852031/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis study evaluated a novel minimally invasive approach combining Botulinum Toxin A injection with penile traction therapy (PTT) for the treatment of penile retraction. A retrospective single-arm exploratory analysis was conducted on 168 males with retractile penis treated between October 2023 and June 2025. Flaccid penile length was assessed under basal conditions and after thermal stimulation, while erectile length, penile retraction ratio, psychological outcomes, and erectile function were evaluated using validated questionnaires. Mean baseline flaccid penile length was 4.4\u0026thinsp;\u0026plusmn;\u0026thinsp;0.66 cm, increasing significantly to 6.9\u0026thinsp;\u0026plusmn;\u0026thinsp;0.81 cm at 6 months (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001). Improvements were also observed under thermal stimulation and in the penile retraction reduction ratio, which decreased from 27.3% to 11.6% at 6 months (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001). Erectile penile length and International Index of Erectile Function scores remained unchanged. Psychological outcomes improved significantly, with Self-Esteem and Relationship and Index of Male Genital Image scores increasing from 28.8\u0026thinsp;\u0026plusmn;\u0026thinsp;4.3 and 39.3\u0026thinsp;\u0026plusmn;\u0026thinsp;5.7 to 54.4\u0026thinsp;\u0026plusmn;\u0026thinsp;5.6 and 59.0\u0026thinsp;\u0026plusmn;\u0026thinsp;7.3, respectively (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.01). Mild transient injection-site pain occurred in 11.3% of patients without other complications. This combined therapy appears safe and effective for reducing penile retraction and improving visible flaccid penile exposure and psychosocial outcomes, although it does not achieve true anatomical penile elongation. Prospective controlled studies with longer follow-up are warranted.\u003c/p\u003e","manuscriptTitle":"Botulinum Toxin A Combined with Penile Traction Therapy: A Minimally invasive Method for Penile Retraction.","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-02-25 16:51:57","doi":"10.21203/rs.3.rs-8852031/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"revise","date":"2026-03-23T10:10:44+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"This content is not available.","date":"2026-03-17T10:36:19+00:00","index":2,"fulltext":"This content is not available."},{"type":"editorInvitedReview","content":"This content is not available.","date":"2026-03-09T08:22:45+00:00","index":1,"fulltext":"This content is not available."},{"type":"reviewerAgreed","content":"This content is not available.","date":"2026-03-02T18:07:00+00:00","index":2,"fulltext":"This content is not available."},{"type":"reviewerAgreed","content":"This content is not available.","date":"2026-02-24T08:44:25+00:00","index":1,"fulltext":"This content is not available."},{"type":"reviewersInvited","content":"","date":"2026-02-20T11:24:14+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-02-19T15:17:48+00:00","index":"","fulltext":""},{"type":"submitted","content":"International Journal of Impotence Research","date":"2026-02-19T09:32:52+00:00","index":"","fulltext":""},{"type":"checksFailed","content":"","date":"2026-02-12T11:41:54+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-02-11T13:03:13+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"international-journal-of-impotence-research","isNatureJournal":false,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"ijir","sideBox":"Learn more about [International Journal of Impotence Research](http://www.nature.com/ijir/)","snPcode":"41443","submissionUrl":"https://mts-ijir.nature.com/cgi-bin/main.plex","title":"International Journal of Impotence Research","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"ejp","reportingPortfolio":"Nature AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"c1ff7e43-4a65-44f7-83b7-689e65815aad","owner":[],"postedDate":"February 25th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"in-revision","subjectAreas":[{"id":63257181,"name":"Health sciences/Health care/Quality of life"},{"id":63257182,"name":"Health sciences/Health care/Therapeutics"}],"tags":[],"updatedAt":"2026-05-11T14:20:59+00:00","versionOfRecord":[],"versionCreatedAt":"2026-02-25 16:51:57","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8852031","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8852031","identity":"rs-8852031","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}