The Results of Patient-Specific Instrument Guided Chevron-cut Distal Femur Osteotomy: A Retrospective Analysis

Abstract BackgroundDistal femur osteotomy (DFO) has been gaining popularity in treating subjects with genu valgum and the associated lateral compartment osteoarthritis. However, the risk of non-union and a period of protective weight bearing still remain unsolved even with the advent of locking plates. To improve the inherent stability of medial close-wedge DFO, we create bone cut in chevron shape with the guidance of a patient-specific instrument (PSI). The patients were allowed immediate weight-bearing as tolerated. The objective of the study was to assess the results of this technique.MethodsTwenty-five knees in twenty-three consecutive patients with genu valgum and lateral compartment osteoarthritis received chevron-cut medial close-wedge DFO. The alignment parameters of the knee, including the weight-bearing line (WBL) ratio, hip-knee-ankle angle (HKA), and mechanical lateral distal femoral angle (mLDFA) were assessed. We defined outliers as those with a difference of more than 10% from the targeted 50% WBL ratio. Patient-reported evaluation included the Oxford Knee Score (OKS), Knee Society Score (KSS), and a visual analog scale (VAS) pain scale.ResultsThe WBL ratio, HKA, and mLDFA were corrected from a mean of 78.7% ± 12.0%, 9.3° ± 2.8° valgus, and 83.6° ± 1.9° to 48.7% ± 2.9%, 0.5° ± 1.1° varus, and 91.4° ± 3.5° (respectively) postoperatively. A mean operative time of 58.8 ± 18.3 minutes, and 6.2 ± 1.3 intraoperative radiographs were taken. A mean Hb drop of 1.4 g/dl was found, while no patient required transfusion. Only one knee (4%) postoperatively fell in the defined range of correction outliers. Consolidation of the osteotomy was achieved at 11.3 ± 2.8 weeks. The OKS, KSS, and VAS pain scale were significantly improved compared with the pre-operative data. Complications developed in three patients, including one periprosthetic fracture, one loss of fixation, and a case of non-union.ConclusionThe PSI-guided chevron-cut close-wedge DFO, followed by immediate weight-bearing as tolerated is accurate, safe, and effective in the correction of genu valgum deformity and the associated lateral compartment osteoarthritis.Level of evidence IV