Abstract: Purpose To evaluate the incidence, morphology, and associated complications of medial cortical hinge fractures after lateral closing wedge distal femoral osteotomy (LCW-DFO) for varus malalignment and to identify constitutional and technical factors predisposing for hinge fracture and consecutive complications. Methods Seventy-nine consecutive patients with a mean age of 47 ± 12 years who underwent LCW-DFO for symptomatic varus malalignment at the authors' institution between 01/2007 and 03/2018 with a minimum of 2-year postoperative time interval were enrolled in this retrospective observational study. Demographic and surgical data were collected. Measurements evaluating the osteotomy cut (length, wedge height, hinge angle) and the location of the hinge (craniocaudal and mediolateral orientation, relation to the adductor tubercle) were conducted on postoperative anterior-posterior knee radiographs and the incidence and morphology of medial cortical hinge fractures was assessed. A risk factor analysis of constitutional and technical factors predisposing for the incidence of a medial cortical hinge fracture and consecutive complications was conducted. Results The incidence of medial cortical hinge fractures was 48%. The most frequent morphological type was an extension fracture type (68%), followed by a proximal (21%) and distal fracture type (11%). An increased length of the osteotomy in mm (53.1 ± 10.9 vs. 57.7 ± 9.6; p = 0.049), an increased height of the excised wedge in mm (6.5 ± 1.9 vs. 7.9 ± 3; p = 0.040) as well as a hinge location in the medial sector of an established sector grid (p = 0.049) were shown to significantly predispose for the incidence of a medial cortical hinge fracture. The incidence of malunion after hinge fracture (14%) was significantly increased after mediolateral dislocation of the medial cortical bone > 2 mm (p 0.05).brbrConclusionbrMedial cortical hinge fractures after LCW-DFO are a common finding. An increased risk of sustaining a hinge fracture has to be expected with increasing osteotomy wedge height and a hinge position close to the medial cortex. Furthermore, dislocation of a medial hinge fracture 2 mm was associated with malunion and should, therefore, be avoided. Level of evidence Prognostic study; Level IV

Abstract: Purpose To investigate functional and clinical outcomes, and physical activity after arthroscopic suture fixation of tibial eminence fractures with regard to postoperative stability, range of motion (ROM), complications, and return to sports. Methods Patients undergoing arthroscopic reduction and internal fixation (ARIF) of tibial eminence fractures using a suture fixation technique were included. Outcome was evaluated retrospectively after a minimum follow-up of 24 months using KT-1000 arthrometer measurements, clinical examination, outcome scores (Lysholm score, Tegner Activity Scale), and a questionnaire about sport activities. Results A total of 23 patients (44% male, 57% female) with a mean age of 25 ± 15 years were included. Mean follow-up was 57 ± 25 months. KT-1000 arthrometer measurements of anterior tibial translation revealed a mean side-to-side difference of 0.9 ± 1.0 mm. Clinical examination showed 100% normal or nearly normal anterior translation of the tibia. Two patients (9%) received an ACL reconstruction due to traumatic ACL re-instability and were, therefore, considered as failures. An extension deficit concerning hyperextension occurred in 29% of patients postoperatively. Further postoperative complications occurred in 14% of patients and included postoperative stiffness with ROM limitations and secondary dislocation of a fragment. Mean postoperative Lysholm score was 89 ± 14. Comparing pre- and postoperative values, no significant change of the Tegner Activity Scale was observed. All patients (failures excluded) returned to high impact sports activities after ARIF. Conclusion Excellent reliable ligamentous stability and high rates of return to high impact sports can be expected after ARIF using a suture fixation technique for type II-IV tibial eminence fractures. Complications, such as limitations in ROM, commonly occur in up to 30% after ARIF. Therefore, regular follow-up examinations remain important in this usually young patient cohort. Level of Evidence Level IV

Abstract: Purpose To perform a detailed deformity analysis of patients with varus alignment and to define the ideal osteotomy level (tibial vs. femoral vs. double level) to avoid an oblique joint line. Methods A total of 303 digital full-leg standing radiographs of patients aged 18-60 years and varus alignment [mechanical tibiofemoral varus angle (mFTA) ≥ 3°] were included. All legs were analyzed regarding mFTA, mechanical medial proximal tibia angle (mMPTA), mechanical lateral distal femur angle (mLDFA), and joint line convergence angle. Based on mFTA, varus alignment was categorized as "mild" (3°-5°), "moderate" (6°-8°), or "severe" (≥ 9°). Deformity location was determined according to the malalignment test described by Paley. Two osteotomy simulations were performed with different upper limits for mMPTA: anatomic correction (mMPTA ≤ 90°, mLDFA ≥ 85°) and overcorrection (mMPTA ≤ 95°, mLDFA ≥ 85°). If a single osteotomy exceeded these limits at the intended mFTA of 2° valgus, a double-level osteotomy was simulated. If even a double-level osteotomy resulted in deviations from the defined limits, the leg was categorized as "uncorrectable". Results Mean mFTA was 6° ± 11° of varus (range 3°-15°). A tibial deformity was observed in 28%, a femoral deformity in 23%, a combined tibial and femoral deformity in 4%, and no bony deformity in 45%. The prevalence of a tibial deformity did not differ between varus severity groups, whereas a femoral and bifocal deformity was significantly more prevalent in knees with more distinct varus (p 0.001). Osteotomy simulation revealed that isolated high tibial osteotomy (HTO) was appropriate in only 12% for anatomic correction, whereas a double-level osteotomy was necessary in 63%. If overcorrection of mMPTA was tolerated, the number of HTOs significantly increased to 57% (p 0.001), whereas the number of double-level osteotomies significantly decreased to 33% (p 0.001). Isolated DFO was considered ideal in 8% for both simulations. Significantly more knees were considered "uncorrectable" by simulating anatomic correction (18 vs. 2%; p