CT IDENTIFIES THE PROXIMO-DORSO-MEDIAL SUBCHONDRAL BONE OF EQUINE CENTRAL TARSAL BONES AS A PREDILECTION SITE FOR SCLEROSIS, DEMINERALIZATION AND ASSOCIATED FRACTURES

CT IDENTIFIES THE PROXIMO-DORSO-MEDIAL SUBCHONDRAL BONE OF EQUINE CENTRAL TARSAL BONES AS A PREDILECTION SITE FOR SCLEROSIS, DEMINERALIZATION AND ASSOCIATED FRACTURES | Authorea try { document.documentElement.classList.add('js'); } catch (e) { } var _gaq = _gaq || []; _gaq.push(['_setAccount', 'G-8VDV14Y67G']); _gaq.push(['_trackPageview']); (function() { var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true; ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s); })(); Skip to main content Preprints Collections Wiley Open Research IET Open Research Ecological Society of Japan All Collections About About Authorea FAQs Contact Us Quick Search anywhere Search for preprint articles, keywords, etc. Search Search ADVANCED SEARCH SCROLL Equine Veterinary Journal This is a preprint and has not been peer reviewed. Data may be preliminary. 27 January 2025 V1 Latest version Share on CT IDENTIFIES THE PROXIMO-DORSO-MEDIAL SUBCHONDRAL BONE OF EQUINE CENTRAL TARSAL BONES AS A PREDILECTION SITE FOR SCLEROSIS, DEMINERALIZATION AND ASSOCIATED FRACTURES Authors : Sandra Campana , Marie Dittmann , Patrick Kircher , and Brice Donati 0000-0002-7811-2526 [email protected] Authors Info & Affiliations https://doi.org/10.22541/au.173797939.90306848/v1 354 views 214 downloads Contents Abstract Supplementary Material Information & Authors Metrics & Citations View Options References Figures Tables Media Share Abstract Summary Background: The distribution pattern of central tarsal bone (CTB) changes has not been described, except for slab- and dorsomedial-plantarolateral fractures. Objectives: The goal was to describe CTB changes in CT, their distribution and associations, hypothesizing that changes occur mainly dorsomedially and that most fissure/fractures are linked to demineralization. Study design: Retrospective Methods: Standing and recumbent tarsal CTs from 94 clinical cases were retrospectively evaluated. Besides general case information, degree of sclerosis (none-severe), lesions (demineralization, cystoid, fissure/fracture) and their location were recorded dividing CTBs in 8 regions. Results: 85/94 tarsi showed at least one region of moderate to severe sclerosis, with 90% affecting the dorsomedial region. The prevalence of lesions was significantly associated with higher degrees of sclerosis (p=0.037) at this site. Of 32 demineralizing lesions, 21 were in the proximal subchondral bone dorsomedially. 24 CTBs showed fissures/fractures and 19/24 were in a dorsomedial-plantarolateral direction, mostly associated with demineralization (17/19). Of 5 fissures/fractures with different configurations, none had associated demineralization. There were 27 cyst-like lesions, 21/27 in the distal subchondral bone and almost half (13/27) were located medially. Main limitations: Retrospective nature; heterogeneous, warmblood oriented, population; no clinical correlation of findings nor histologic confirmation of described changes . Conclusions: Given the links between sclerosis, demineralization and fissures/fractures, the dorsomedial proximal subchondral bone plate of the CTB must be scrutinized both in CT and radiography. CT IDENTIFIES THE PROXIMO-DORSO-MEDIAL SUBCHONDRAL BONE OF EQUINE CENTRAL TARSAL BONES AS A PREDILECTION SITE FOR SCLEROSIS, DEMINERALIZATION AND ASSOCIATED FRACTURES Summary Background: The distribution pattern of central tarsal bone (CTB) changes has not been described, except for slab- and dorsomedial-plantarolateral fractures. Objectives: The goal was to describe CTB changes in CT, their distribution and associations, hypothesizing that changes occur mainly dorsomedially and that most fissure/fractures are linked to demineralization. Study design: Retrospective Methods: Standing and recumbent tarsal CTs from 94 clinical cases were retrospectively evaluated. Besides general case information, degree of sclerosis (none-severe), lesions (demineralization, cystoid, fissure/fracture) and their location were recorded dividing CTBs in 8 regions. Results: 85/94 tarsi showed at least one region of moderate to severe sclerosis, with 90% affecting the dorsomedial region. The prevalence of lesions was significantly associated with higher degrees of sclerosis (p=0.037) at this site. Of 32 demineralizing lesions, 21 were in the proximal subchondral bone dorsomedially. 24 CTBs showed fissures/fractures and 19/24 were in a dorsomedial-plantarolateral direction, mostly associated with demineralization (17/19). Of 5 fissures/fractures with different configurations, none had associated demineralization. There were 27 cyst-like lesions, 21/27 in the distal subchondral bone and almost half (13/27) were located medially. Main limitations: Retrospective nature; heterogeneous, warmblood oriented, population; no clinical correlation of findings nor histologic confirmation of described changes . Conclusions: Given the links between sclerosis, demineralization and fissures/fractures, the dorsomedial proximal subchondral bone plate of the CTB must be scrutinized both in CT and radiography. INTRODUCTION Distal tarsal pathology is common in horses, with arthrosis of the distal joints, colloquial bone spavin, historically being the more commonly recognized entity 1-3 . The central tarsal bone is commonly involved in arthritic changes, as it contributes with subchondral bone to both the proximal and distal intertarsal joints. These secondary arthritic changes include osteophytosis, subchondral sclerosis and subchondral osteolysis. Changes primarily affecting the central tarsal bone, and thus not secondary to joint disease, have sparely been reported. Rather frequently reported primary lesions of the central tarsal bone (CTB) are fractures, with other changes such as sclerosis and demineralization or osteolysis being occasionally described 4-9 . History and clinical signs in horses with CTB fractures can be unspecific and include regional swelling, mild effusion of the tarsocrural joint and positive distal tarsal blocks 2,10 . Peroneal and tibial nerve blocks, as well as tarsometatarsal or tarsocrural joint anesthesia may show significant improvement helping in the diagnosis 7 . In racehorses, CTB fractures most commonly show slab configuration in a dorsal or slightly oblique plane 11 . They often arise during strenuous exercise, and a conformational predisposition has been proven, where incompletely ossified small tarsal bone in foals develop into abnormally wedge-shaped third and central tarsal bones which are associated with slab fractures 12 . In radiography, dorsal slab fractures are best appreciated in lateromedial projections according to their conformation 8,11,13 . More recently, after isolated reports 9,14 , a different, consistently dorsomedial-plantarolateral configuration for CTB fractures has been described in non-racehorses, almost simultaneously by two different groups 7,8 . These fractures were more readily detected in CT or slightly dorsomedial-plantarolateral radiographic projections and often showed concurrent surrounding sclerosis and occasionally ill-defined fracture margins, both attributed to chronicity. This dorsomedial-plantarolateral configuration was confirmed in two other studies. The first reported a common coincidence of these fractures with sclerosis, but postulated some degree of increased bone density to represent normal adaptation of the CTB to stress in particular in sport horses. 6 The second study reported incomplete fractures of the CTB in the same direction but only affecting the proximal dorsomedial aspect of the CTB, again together with marked sclerosis surrounding the fractures lines and additionally variable degree of bone marrow lesions, as well as mild degree of osteoarthropathy of the adjacent joints 5 . The authors postulated a stress related etiology for these fractures, as well as similarities with other more commonly reported areas affected by incomplete stress fractures such as the sagittal groove of the proximal phalanx 5 . Independently of their orientation, radiographic detection of CTB fractures can be difficult depending on degree of displacement and chronicity, and multiple projections can be advantageous in identifying them 10,15 . Scintigraphy can be helpful in diagnosing CTB fractures, especially in the early stage before they become radiographically evident by onset of remodeling and widening secondary to margin resorption. 16 Both conservative and surgical therapies have been described for central tarsal bone fractures, with lag screw fixation seemingly representing the therapy of choice resulting in best prognosis by reducing degree of late secondary osteoarthritic changes. 2,10,13,16-19 The increasing availability of CT and MRI systems for imaging of the equine tarsus, in particular in standing horses, is boosting earlier detection and more accurate diagnosis of subtle or more complex tarsal and subtarsal pathology, which has shown to be easily missed in radiography 20 . Cross-sectional techniques such as CT and MRI are important for a definitive diagnosis of CTB lesions, detailed assessment of fracture configuration as well as for preoperative surgical planning purposes 2,10,15,21 . Besides identification of fractures, increased use of cross-sectional imaging also allows more detailed detection of other CTB changes such as sclerosis, osseous cyst-like lesions, demineralization and osteolysis 4-9 . Variable subchondral bone thickness and sclerosis have been described to be common at the distal tarsus in horses and being dependent on activity 22 , often with greater thickness medially at the most proximal locations and greater thickness laterally further distal, which reflects a shift of compressive loading of the hindlimbs from medial to lateral at the level of the distal tarsus 23,24 . Subchondral bone thickness at the distal tarsus is altered in horses with tarsal pain, with additional increase in thickness medially which was postulated to reflect adaptative processes, but whether the abnormal loading pattern is the origin of disease or result of tarsal pain of other origin is unclear. 25 The distribution of changes of the CTB, in particular sclerosis, and fractures in non-racehorses match our clinical observation, with focal demineralization and osteolysis also being subjectively more commonly located at these areas. Thus, this article aims to clarify the spectrum and spatial distribution of CTB changes in horses, often difficult to detect on radiographs, but effectively evaluated with CT scans, and to investigate for their associations. We hypothesize that: 1) CTB changes are commonly located in the same areas as dorsomedial-plantarolateral fractures, mainly affecting the dorsomedial region and proximal subchondral bone; 2) both complete and incomplete fractures with typical orientation are commonly associated with demineralization and marked to severe sclerosis. MATERIAL AND METHODS Computer tomographic examinations of equine tarsi performed at the XX were searched in the PACS system and retrospectively evaluated. Inclusion in the study required presence of diagnostic quality scans of the pelvic limb from the distal aspect of the tibia to the proximal aspect of the metatarsus, including all the tarsal structures, independently of indication for performing the study. Information regarding age, weight, breed and use/activity of the horse was gathered from clinical histories. Image evaluation Each scan was evaluated by a Diplomate of the European College of Veterinary Diagnostic Imaging (Dipl. ECVDI) together with a doctoral student and equine veterinarian with 5 years of equine practice experience. For evaluation of CTB changes, the transverse section of the bone was divided into 4 regions and an additional subdivision was made along the transverse plane dividing the bone into a proximal and a distal half, in total resulting in 8 regions. Lines were drawn as shown in figure 1, based on the centroquartal tarsal joint, one perpendicular to it at the most lateral aspect of the centroquartal intertarsal ligament fossa, one perpendicular to it at the most dorsolateral aspect of the intertarsal ligament fossa between the CTB and the fused first and second tarsal bone and one parallel to it through the resulting middle third of the CTB midway through its dorsoplantar length. Subdivision into a proximal and distal half of the CTB was made halfway through its proximodistal thickness. For each of these regions, the presence of abnormalities or lesions was recorded, including sclerosis, areas of demineralization, osseous cyst-like lesions, fissures and fractures. If an abnormality or lesion affected more than one region, its presence was noted in each region. Sclerosis was graded into four groups based on recognition of normal osseous structure, trabecular pattern and compact-trabecular distinction as shown in figure 2. Normal/no sclerosis was assigned when normal osseous structure, homogeneous trabecular pattern and clear distinction between compact and trabecular bone were present. Mild increased attenuation of trabecular bone resulting from thickened trabecles and reduction of intertrabecular space, as well as reduced but clear definition between compact and trabecular bone was graded as mild sclerosis. Moderate sclerosis was assigned when trabecular pattern was no longer clearly visible, compact to trabecular definition was moderately reduced by compact bone thickening and longer transition zone to spongious bone and only punctate hypoattenuating inclusions were still visible representing the residual markedly reduced intertrabecular space. A severe grade was assigned when the region was homogemeously mineralattenuating and the trabecular pattern was completely lost. Demineralization was defined as a focal, ill-defined area of abnormally reduced attenuation, both in normal or sclerotic bone. An osseous cyst-like/cystoid lesion was defined as a focal, rounded, well defined, hypoattenuating region with a thin, sharply defined rim. A fissure was defined as an incomplete linear hypoattenuating discontinuity within the CTB, not extending all the way through compact bone but fading in the trabecular bone. A fracture instead was defined as a complete linear hypoattenuating discontinuity of the CTB extending through compact bone in all directions. Examples of types of lesions are shown in figure 3. Statistical anaylsis Data of all cases were collected in an Excel file. Due to the low number of cases without visible signs of sclerosis, this variable was reduced to two levels: no or mild sclerosis and moderate or severe sclerosis. In addition to the variables for each region of the CTB, binary variables were created based on the overall presence or absence of each of the lesions regardless of their localization (demineralization, cystoid lesion, fissure, fracture, fissure and/or fracture). All analyses were carried out in R Studio (R version 4.3.1). To test for differences between proportions, two-proportion Z-tests were applied. To test for differences between case numbers, Chi-square tests were applied. Significance levels were set to P=0.05. RESULTS The PACS search yielded 93 tarsal scans in 82 horses, whereby bilateral tarsal scans were present in 11 horses. Patients included 44 geldings (53.7%), 33 mares (40.2%) and 5 stallions (6.1%) and the mean age was 10.8 years (SD±4.8 years, range: 1-26y). Breeds included 56 warmbloods (68.3%), 7 large/middle sized ponies/icelandic horses (8.5%), 5 horses each of iberian (6.1%) and western breeds (6.1%), 3 Freiberger/Haflinger horses (3.7%), 2 thoroughbreds (2.4%), one horse each of arab (1.2%), draught (1.2%) and miniature breed (1.2%) as well as one donkey (1.2%). Weight was recorded for 54 patients, of which the mean was 521kg (SD±117 kg, range: 140-700kg). Information about main activity of the patient was available for 33 cases and included showjumping (n=13, 15.9%), leisure (n=8, 9.8%), dressage (n=5, 6.1%), driving (n=2, 2.4%), western disciplines (n=2, 2.4%), endurance (n=1, 1.2%), eventing (n=1, 1.2%) and racing (n=1, 1.2%). In 19 horses there was a concurrent previous diagnosis of proximal suspensory desmopathy on the scanned limb. Of 93 scanned legs, only in 39 the patient file included information about diagnostic analgesia. Seventy tarsal CT scans (75.3%) were performed on recumbent horses in general anesthesia, and 23 (24.7%) were performed on standing horses. When the horse underwent a diagnostic CT scan standing and later surgery planning/guiding CT scan, only the latter was included, as this is often of inherently higher quality given less motion. CT examinations included 49 (52.7%) scans of the right pelvic limb and 44 (47.3%) scans of the left pelvic limb. In 25 tarsi, the CTB was identified as the primary site of pathology responsible for the clinical signs. For 14 of these 25 tarsi, information about diagnostic analgesia was available. This included 4 legs with a positive tarsometatarsal joint block, 3 legs with a positive tarsocrural joint, 3 legs with positive blocks proximal to the tarsus, 2 legs with positive high 4-point block, and two legs with positive plantar lateral nerve block. Sclerosis 98.4% of examined regions (366/372) showed at least a mild degree of sclerosis. The medial aspect of the central tarsal bone was free of sclerosis in 4 (4.3%), affected by mild sclerosis in 69 (74.2%) cases, by moderate sclerosis in 13 (14.0%) and severe sclerosis in 7 (7.5%). The dorsomedial aspect of the central tarsal bone was free of sclerosis in 1 case (1.1%), affected by mild sclerosis in 8 (8.6%) cases, by moderate sclerosis in 54 (58.1%) and severe sclerosis in 30 (32.3%). The plantarolateral aspect of the central tarsal bone was free of sclerosis in 1 case (1.1%), affected by mild sclerosis in 75 (80.6%) cases, by moderate sclerosis in 12 (12.9%) and severe sclerosis in 5 (5.4%). The lateral aspect of the central tarsal bone showed some degree of sclerosis in all tarsi, affected by mild sclerosis in 24 (25.8%) cases, by moderate sclerosis in 61 (65.6%) and severe sclerosis in 8 (8.6%). Demineralization An area of demineralization was present in 28/372 (7.5%) examined regions. In the medial aspect of the central tarsal bone there was one case with demineralization at the distal subchondral bone. In the dorsomedial aspect there were 24 cases with demineralization, 21 located at the proximal subchondral bone, 2 located at the distal subchondral bone and one with demineralization at both the proximal and distal subchondral bone. In the plantarolateral aspect there were 5 cases with demineralization, one located at the proximal subchondral bone and 4 located at the distal subchondral bone. In the lateral aspect there were 2 cases with demineralization, one located at the proximal subchondral bone and one located at the distal subchondral bone. Cystoid lesions A cystoid lesion was present in 23/372 (6.2%) examined regions. In the medial aspect of the central tarsal bone there were 13 cystoid lesions, all of which were located at the distal subchondral bone. In the dorsomedial aspect there were 8 cystoid lesions, 5 located at the proximal subchondral bone and 3 located at the distal subchondral bone. In the plantarolateral aspect there were 5 cystoid lesions, 1 was located at the proximal subchondral bone and 4 located at the distal subchondral bone. In the lateral aspect there was one cystoid lesion, located at the distal subchondral bone. Fissures/fractures Fissures or fractures of the CTB were present in 24/93 (25.8%) examined tarsi and 43/372 (11.6%) regions. In the medial aspect of the central tarsal bone there were 2 fractures. In the dorsomedial aspect there were 7 fissures and 15 fractures. In the plantarolateral aspect there were 4 fissures and 12 fractures. In the lateral aspect there were 3 fractures. 7/7 fissures and 12/17 fractures were in a dorsomedial-plantarolateral direction. Associations The proportion of tarsi with moderate or severe sclerosis in the dorsomedial region (90%) was significantly higher than the proportion of cases with moderate or severe sclerosis in the other regions (lateral 74%, Z-statistic: 2.9, P=0.004; medial 22%, Z-statistic: 9.5, P<0.001; plantarolateral 18%, Z-statistic: 11.4, P<0.001). The proportion of tarsi showing lesions dorsomedially was significantly higher in tarsi with moderate or severe sclerosis dorsomedially (35 out of 84), compared to tarsi showing no or mild sclerosis dorsomedially (0 out of 9) (Chi-square: 4.4, P=0.036). The proportion of tarsi showing lesions in the plantarolateral region was higher in tarsi with moderate or severe sclerosis plantarolaterally (10 out of 17), than in tarsi with no or mild sclerosis in this region (13 out of 76) (Chi-square: 10.8, P=0.001). The proportion of tarsi showing demineralization in the plantarolateral region was higher in the presence of severe or moderate sclerosis (4 out of 17) than in cases with mild or no sclerosis in this region (1 out of 76) (Chi-square: 9.5, P=0.002). The proportion of tarsi showing fissures in the plantarolateral region was higher in cases with severe/moderate sclerosis (3 out of 17) than in cases with no/mild sclerosis in this region (1 out of 76) (Chi-square: 5.5, P=0.02). Of 24 tarsi with fissures or fractures, 17 showed concurrent demineralization. This is significantly higher than in tarsi without fissures or fractures (69), of which only 11 showed demineralization (Chi-square 23.0, P<0.001). The proportion of tarsi that showed lesions (demineralization, cystoid, fissure, fracture) in any region of the tarsus, was higher in tarsi with moderate or severe sclerosis centrodorsally (57%, 48 out of 84), than in tarsi without or with mild sclerosis centrodorsally (0 out of 9) (Chi-square: 8.5, P=0.004). The proportion of tarsi that showed lesions in any region of the tarsus, was higher in tarsi with moderate or severe centroplantar sclerosis (82%, 14 out of 17), than in tarsi without or with mild centroplantar sclerosis (45%, 34 out of 76) (Chi-square: 6.4, P=0.01). The prevalence of lesions in tarsi with moderate or severe centroplantar sclerosis was thus 1.84 times higher than in tarsi with no or mild centroplantar sclerosis. DISCUSSION By retrospective analysis of all tarsal CTs scans preformed at our institution, we were able to identify a multitude of central tarsal bone (CTB) changes along with consistent patterns and predilections sites for changes. CTB sclerosis in particular, as already reported in multiple studies, was very common. By applying our grading system, the vast majority of CTBs evaluated showed some degree of sclerosis in at least one of the assessed regions. The slightest increase in density or attenuation of the spongious bone was classified as mild sclerosis. This might be inadequate to evaluate clinical cases and should not be directly interpreted as pathologic or clinically significant, as some degree of CTB sclerosis, just as at other predilection sites, reflects normal osseous adaptation to stress and loading, which in turn is dependent on conformation, age, discipline and intensity of training amongst other factors. Still, even when grouping cases with no and mild sclerosis to disregard the sensitivity in the grading, 85 out of 93 tarsi examined displayed at least one area with moderate or severe sclerosis. Additionally, we found sclerosis to be significantly more common and of significantly higher degree in the dorsomedial region of the CTB, which raises the suspicion for this region to be the area of main subchondral bone stress/loading. Previous studies have identified areas of increased stress of the central tarsal bone, which were explained to reflect a shift of compressive load from medial to lateral at the level of the distal tarsal joints. 24 The question whether, if low degree of sclerosis can be normal, high degree of sclerosis necessarily means pathology and clinical relevance, cannot be answered. Modalities identifying bone fluid or increased osseous metabolism such as MRI and scintigraphy/PET respectively, might be helpful to answer this question in the future. The distribution of fissures and fractures was highly consistent, often affecting the dorsomedial and plantarolateral areas in our study, which is in agreement with the previously identified dorsomedial-plantarolateral direction of fractures described on other studies. 7,8 We additionally showed a significant association between the presence of fissure/fractures with higher degrees of sclerosis, supporting the hypothesis of a stress related etiology. A previously underestimated observation was the presence of demineralization at the proximal aspect of the dorsomedial region of the CTB, in the center of the often-encountered sclerotic area. Also, the vast majority of fissures and fractures were associated with or coursed through this areas of demineralization at the proximal aspect of the dorsomedial region of the CTB (fig. 4). The association of fissures and fractures with a diffuse area of sclerosis and a focal area of demineralization additionally corroborates the hypothesis of stress related aetiology, as this has shown to be present at other more often described sites 26,27 . It can only be speculated whether this type of CTB demineralization represents a focus of subchondral bone failure in the center of sclerosis leading to a weak spot and resulting fissure or rather margin resorption of an already existing fissure, primarily developing in less elastic sclerotic bone. Observations from our study, with horses displaying demineralizing foci in sclerotic bone without evidence of fissure and in turn no typical DMPtL fissure/fractures without a surrounding demineralizing area are in favour of the former hypothesis. Nevertheless, a combination or continuum of overlapping osseous remodeling processes is likely present. In contrast to this observation, fractures with other configurations, not in a DMPtL direction, were independent of sclerosis and not associated with demineralization. Subchondral bone damage can be clinically relevant and cause relevant lameness in absence or before the development of fissures and fractures, as shown at other locations of subchondral bone stress such as in POD or sagittal proximal P1 fractures respectively. We must therefore assume a clinical relevance of CTB lesions also when macrofissures and fractures are not present. Bone metabolism imaging modalities such as scintigraphy or PET could help determine activity of a CTB abnormality such as severe sclerosis, demineralization or cyst-like lesions, if clinical relevance is questioned. An additional important observation with practical clinical relevance, is that dorsomedial sclerosis which extends to affect the plantarolateral area of the CTB, was significantly associated with the presence of lesions such as demineralization, fissures and fractures. As CT might not be readily available to diagnose CTB lesions in detail, and some lesions might only be visible when projected exactly tangential to the x-ray beam, this is of particular interest in practice as the presence of sclerosis visible in the plantarolateral half of the CTB on a DLPtMO projection should alert for the presence of additional lesions (figure 5). In contrast with sclerosis, demineralization, fissure and fractures, osseous cyst like lesions showed a more random distribution and were more often identified at the distal aspect of the medial region of the CTB. A different etiology has therefore to be postulated, either not related to subchondral bone stress or related to different types of stress. Subchondral osseous-cyst-like lesions have been described to happen at site of increased subchondral bone stress, 28 but the reason for subchondral bone to develop a cyst rather than a fissure is unclear. An association with a different type of loading pattern, possibly more focal than linear, or association with individual CTB shape and conformation can only be hypothesized without further research. This study has multiple limitations. First, it’s affected by limitations inherent to its retrospective design where standardized clinical history documentation and imaging protocols were not available, leading to missing information and variability in image quality. As the findings are purely correlative, causative explanations for the associations between the observed changes are speculative and warrant experimental confirmation. Also, the described findings and discussed hypotheses and postulations, might only apply to a heavily warmblood-oriented population engaging in English disciplines in particular showjumping, dressage and eventing. We sporadically encountered difficulties in assessing degree of sclerosis in CTs performed on standing horses, as motion artifacts limit interpretation of fine trabecular bone structure, possibly leading to erroneously higher degree of sclerosis assigned. Agreement was found between observers by reviewing these cases based on previously stated definitions of sclerosis degrees. Another limitation was the chosen subdivision of the CTB in not evenly sized regions, which might be responsible for a bias, resulting in more changes and lesions present in the larger regions, in particular the dorsomedially and plantarolaterally. A more evenly sized subdivision might have mitigated this, but the definition of regions based on anatomic landmarks allowed for a more standardized subdivision across all tarsi. In isolated cases, we had difficulties in the differentiation between osseous cyst-like lesions and a focal area of demineralization in our study, in particular if the quality of the image was affected by motion. The distinction of the two is further complicated by variation in the description or definition of rounded areas of reduced subchondral attenuation in the literature. The descriptors/terms round demineralization, cystoid and osseous cyst-like lesions, are sometimes used interchangeably, although a marked difference is present in the eye of the authors of the present study. Round hypo- but still mineral attenuation in sclerotic subchondral bone, with poorly defined margins should be regarded separately from rounded, well defined, soft tissue attenuating lesions surrounded by a thin sclerotic rim surrounded by normal, non-sclerotic trabecular subchondral bone. An association between the two, the former representing a more immature lesion, possibly developing into the latter but possibly also developing into a fracture, is plausible, but studies definitively proving these assumptions in horses are lacking. Little information was available in the patients records that could help derive causality and clinical relevance of the described CT changes in our population. While most of the severe lesions such as fissure and fractures where easily identified to be the only plausible explanation for the presenting complaint. In cases of mild changes or sclerosis only, the question arises if these findings were the cause of the lameness. Also, marked heterogeneity was present in the pattern of positive diagnostic anesthesia when information was available, and most of positive blocks overlap with other common sites of pathology such as the tarsometatarsal joint and proximal suspensory ligament origin. Additional studies, including precise blocking history and advanced imaging displaying osseous composition and metabolism are required to address these issues, investigate the association between CTB changes and clinicals signs, in particular define clinical relevance of sclerosis alone and smaller lesions. In conclusion, sclerosis of the CTB is a common finding of questionable clinical relevance if found alone, but shows consistency in its distribution, particularly prevalent at the dorsomedial aspect. Lesions of the CTB often occurred in combination with higher degree of sclerosis and fissures/fractures were associated with demineralization. The combination of these findings suggests similarities with other more recognized areas of subchondral bone injury resulting in fractures. CT is helpful in recognizing full extent and detailed configuration of lesions, but results of this study are encouraging for the use of radiography as proximodorsomedial demineralization and sclerosis extending into the plantarolateral aspect of the CTB should alert the clinician for the presence of subchondral bone injury and possibly prodromal stage of fissure or fracture. Bibliography https://doi.org/10.1111/eve.13659 1. Murray RC, Dyson SJ, Weekes JS, Short C, Branch MV. Scintigraphic evaluation of the distal tarsal region in horses with distal tarsal pain. Vet Radiol Ultrasound . 2005;46(2):171-8. doi:10.1111/j.1740-8261.2005.00032.x2. Lischer CJ, Auer JA. Tarsus. In: Auer JA, Stick JA, Kümmerle JM, Prange T, eds. Equine Surgery . Fifth Edition ed. Elsevier; 2019:1710-1725:chap 99.3. Gabel AA. Lameness caused by inflammation in the distal hock. Vet Clin North Am Large Anim Pract . May 1980;2(1):101-24. doi:10.1016/s0196-9846(17)30177-54. Dyson S. Lameness Associated with Mineralization of the Central Tarsal Bone and a Small Osseous Cyst-Like Lesion in Two Sport Horses. Journal of Equine Veterinary Science . 2013;33(1):51-56. 5. Zimmerman M, Schramme M, Eberlé O, et al. Low-field MRI findings and follow-up of central tarsal bone fractures in four non-racehorses. Equine Veterinary Education . 2023;35(2):e112-e120. doi:6. Barrett MF, Selberg KT, Johnson SA, Hersman J, Frisbie DD. High field magnetic resonance imaging contributes to diagnosis of equine distal tarsus and proximal metatarsus lesions: 103 horses. Vet Radiol Ultrasound . Sep 2018;59(5):587-596. doi:10.1111/vru.126597. Gunst S, Del Chicca F, Fürst AE, Kuemmerle JM. Central tarsal bone fractures in horses not used for racing: Computed tomographic configuration and long-term outcome of lag screw fixation. Equine Vet J . Sep 2016;48(5):585-9. doi:10.1111/evj.124988. Knuchell JA, Spriet M, Galuppo LD, Katzman SA. Fracture of the central tarsal bone in Nonracehorses: four cases. Vet Radiol Ultrasound . Jul 2016;57(4):403-9. doi:10.1111/vru.123529. Raes E, Bergman HJ, Van Ryssen B, Vanderperren K, Stock E, Saunders JH. Computed tomographic features of lesions detected in horses with tarsal lameness. Equine Vet J . Mar 2014;46(2):189-93. doi:10.1111/evj.1209710. Redding WR. The Tarsus. In: Baxter GM, ed. Adams & Stashak’s Lameness in Horses . 7th Edition ed. Wiley-Blackwell; 2020:chap 5.11. Vanderperren K, Raes E, Bree HV, Saunders JH. Diagnostic imaging of the equine tarsal region using radiography and ultrasonography. Part 2: bony disorders. Vet J . Feb 2009;179(2):188-96. doi:10.1016/j.tvjl.2007.08.02512. Baird DH, Pilsworth RC. Wedge-shaped conformation of the dorsolateral aspect of the third tarsal bone in the Thoroughbred racehorse is associated with development of slab fractures in this site. Equine Vet J . Nov 2001;33(6):617-20. doi:10.2746/04251640177656339113. Murphey ED, Schneider RK, Adams SB, Santschi EM, Stick JA, Ruggles AJ. Long-term outcome of horses with a slab fracture of the central or third tarsal bone treated conservatively: 25 cases (1976-1993). J Am Vet Med Assoc . Jun 15 2000;216(12):1949-54. doi:10.2460/javma.2000.216.194914. Kelleher ME, Charles EM, Werpy NM. What is your diagnosis? Acute lameness. J Am Vet Med Assoc . Apr 15 2011;238(8):977-8. doi:10.2460/javma.238.8.97715. Bolt DM, Williams J, Burba DJ. Fracture of the small tarsal bones and luxation of the tarsal joints in horses. Compendium on Continuing Education for the Practicing Veterinarian . 2003;25(4):310 - 315. 16. Dabareiner RM, Carter GK, Dyson SJ. The Tarsus. In: Ross MW, Dyson SJ, eds. Diagnosis and Management of Lameness in the Horse . 2nd Edition ed. Elsevier Saunders; 2011:508-526:chap 45.17. Tulamo RM, Bramlage LR, Gabel AA. Fractures of the central and third tarsal bones in horses. J Am Vet Med Assoc . Jun 01 1983;182(11):1234-8. 18. Lindsay WA, McMartin RB, McClure JR. Management of slab fractures of the third tarsal bone in 5 horses. Equine Vet J . Jan 1982;14(1):55-8. doi:10.1111/j.2042-3306.1982.tb02335.x19. Winberg FG, Pettersson H. Outcome and racing performance after internal fixation of third and central tarsal bone slab fractures in horses. A review of 20 cases. Acta Vet Scand . 1999;40(2):173-80. doi:10.1186/BF0354703420. Laverty S, Stover SM, Bélanger D, et al. Radiographic, high detail radiographic, microangiographic and histological findings of the distal portion of the tarsus in weanling, young and adult horses. Equine Vet J . Nov 1991;23(6):413-21. doi:10.1111/j.2042-3306.1991.tb03753.x21. Kelmer G. Computed tomography assisted repair of a central tarsal bone slab fracture in a horse EQUINE VETERINARY EDUCATION . 2008; Equine vet. Educ. (2008) 20 (6) 284-287 : 284-287 . doi: 10.2746/095777308X301929 22. Barneveld A, van Weeren PR. Early changes in the distal intertarsal joint of Dutch Warmblood foals and the influence of exercise on bone density in the third tarsal bone. Equine Vet J Suppl . Nov 1999;(31):67-73. doi:10.1111/j.2042-3306.1999.tb05316.x23. Murray RC, Branch MV, Dyson SJ, Parkin TD, Goodship AE. How does exercise intensity and type affect equine distal tarsal subchondral bone thickness? J Appl Physiol (1985) . Jun 2007;102(6):2194-200. doi:10.1152/japplphysiol.00709.200624. Branch MV, Murray RC, Dyson SJ, Goodship AE. Is there a characteristic distal tarsal subchondral bone plate thickness pattern in horses with no history of hindlimb lameness? Equine Vet J . Sep 2005;37(5):450-5. doi:10.2746/04251640577447995125. Branch MV, Murray RC, Dyson SJ, Goodship AE. Alteration of distal tarsal subchondral bone thickness pattern in horses with tarsal pain. Equine Vet J . Mar 2007;39(2):101-5. doi:10.2746/042516407x16675626. Faulkner JE, Joostens Z, Broeckx BJG, Hauspie S, Mariën T, Vanderperren K. Follow-Up Magnetic Resonance Imaging of Sagittal Groove Disease of the Equine Proximal Phalanx Using a Classification System in 29 Non-Racing Sports Horses. Animals (Basel) . Dec 21 2023;14(1)doi:10.3390/ani1401003427. Peloso JG, Cohen ND, Vogler JB, Marquis PA, Hilt L. Association of catastrophic condylar fracture with bony changes of the third metacarpal bone identified by use of standing magnetic resonance imaging in forelimbs from cadavers of Thoroughbred racehorses in the United States. Am J Vet Res . Feb 2019;80(2):178-188. doi:10.2460/ajvr.80.2.17828. Jeffcott LB, Kold SE, Melsen F. Aspects of the pathology of stifle bone cysts in the horse. Equine Vet J . Oct 1983;15(4):304-11. doi:10.1111/j.2042-3306.1983.tb01806.x Table 1. Supplementary Material File (figureslegends.docx) Download 13.30 KB File (image1.emf) Download 1.46 MB Information & Authors Information Version history V1 Version 1 27 January 2025 Copyright This work is licensed under a Non Exclusive No Reuse License. Collection Equine Veterinary Journal Authors Affiliations Sandra Campana Universitat Zurich Vetsuisse-Fakultat View all articles by this author Marie Dittmann Forschungsinstitut fur biologischen Landbau Departement fur Nutztierwissenschaften View all articles by this author Patrick Kircher Universitat Zurich Vetsuisse-Fakultat View all articles by this author Brice Donati 0000-0002-7811-2526 [email protected] Universitat Zurich Vetsuisse-Fakultat View all articles by this author Metrics & Citations Metrics Article Usage 354 views 214 downloads .FvxKWukQNSOunydq8rnd { width: 100px; } Citations Download citation Sandra Campana, Marie Dittmann, Patrick Kircher, et al. CT IDENTIFIES THE PROXIMO-DORSO-MEDIAL SUBCHONDRAL BONE OF EQUINE CENTRAL TARSAL BONES AS A PREDILECTION SITE FOR SCLEROSIS, DEMINERALIZATION AND ASSOCIATED FRACTURES. Authorea . 27 January 2025. DOI: https://doi.org/10.22541/au.173797939.90306848/v1 If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download. For more information or tips please see 'Downloading to a citation manager' in the Help menu . Format Please select one from the list RIS (ProCite, Reference Manager) EndNote BibTex Medlars RefWorks Direct import Tips for downloading citations document.getElementById('citMgrHelpLink').addEventListener('click', function() { popupHelp(this.href); return false; }); $(".js__slcInclude").on("change", function(e){ if ($(this).val() == 'refworks') $('#direct').prop("checked", false); $('#direct').prop("disabled", ($(this).val() == 'refworks')); }); View Options View options PDF View PDF Figures Tables Media Share Share Share article link Copy Link Copied! Copying failed. Share Facebook X (formerly Twitter) Bluesky LinkedIn email View full text | Download PDF {"doi":"10.22541/au.173797939.90306848/v1","type":"Article"} Now Reading: Share Figures Tables Close figure viewer Back to article Figure title goes here Change zoom level Go to figure location within the article Download figure Toggle share panel Toggle share panel Share Toggle information panel Toggle information panel Go to previous graphic Go to next graphic Go to previous table Go to next table All figures All tables View all material View all material xrefBack.goTo xrefBack.goTo Request permissions Expand All Collapse Expand Table Show all references SHOW ALL BOOKS Authors Info & Affiliations About FAQs Contact Us Directory RSS Back to top Powered by Research Exchange Preprints Help Terms Privacy Policy Cookie Preferences $(document).ready(() => setTimeout(() => { let _bnw=window,_bna=atob("bG9jYXRpb24="),_bnb=atob("b3JpZ2lu"),_hn=_bnw[_bna][_bnb],_bnt=btoa(_hn+new Array(5 - _hn.length % 4).join(" ")); $.get("/resource/lodash?t="+_bnt); },4000)); (function(){function c(){var b=a.contentDocument||a.contentWindow.document;if(b){var d=b.createElement('script');d.innerHTML="window.__CF$cv$params={r:'a02452391e001b23',t:'MTc3OTg3NzU4NA=='};var a=document.createElement('script');a.src='/cdn-cgi/challenge-platform/scripts/jsd/main.js';document.getElementsByTagName('head')[0].appendChild(a);";b.getElementsByTagName('head')[0].appendChild(d)}}if(document.body){var a=document.createElement('iframe');a.height=1;a.width=1;a.style.position='absolute';a.style.top=0;a.style.left=0;a.style.border='none';a.style.visibility='hidden';document.body.appendChild(a);if('loading'!==document.readyState)c();else if(window.addEventListener)document.addEventListener('DOMContentLoaded',c);else{var e=document.onreadystatechange||function(){};document.onreadystatechange=function(b){e(b);'loading'!==document.readyState&&(document.onreadystatechange=e,c())}}}})();