Objective To explore the effect of the posterior condylar offset (PCO) on clinical results after total knee arthroplasty (TKA) using a high-flex posterior-stabilized (PS) fixed-bearing prosthesis.Methods Clinical and radiographic materials of 107 consecutive female patients (107 knees),who had undergone primary TKAs for end-stage osteoarthritis was prospectively analyzed.All operations were performed by using the same operative technique.Based on the corrected PCO change,all cases were divided into two groups:66 knees in which the corrected PCO change ≥0 mm (aged 48-73 years,with an average of 61.4 years) and 41 knees in which the corrected PCO change ＜ 0 mm (aged 52-75 years,with an average of 62.2 years).One-year postoperatively,clinical and radiographic variables from the two groups were compared by independent t-test.The associations between the corrected PCO changes and the improvements of clinical variables in all patients were analyzed by Pearson linear correlation.Results The corrected PCO change was 2.49±1.71 mm in the PCO change ≥0 mm group and-1.28±1.41 mm in the PCO change ＜ 0 mm group.One-year postoperatively,the Knee Society scores,the Western Ontario and McMaster Universities Osteoarthritis Index,non-weight-bearing active and passive range of knee flexion,flexion contracture,and their improvements had no statistical differences between the two groups.The corrected PCO change was not significantly correlated with the improvement of any clinical variable.While the PCO change ≥0 mm group (130.40°± 11.63°) demonstrated greater flexion than the PCO change ＜ 0 mm group (123.80°±13.12°) during active weight-bearing one year after TKA,which was significantly different between the two groups (t=2.11,P=0.0401).Conclusion Restoration of PCO plays an important role in the optimization of active knee flexion during weight-bearing conditions after posterior-stabilized TKA,while it had no benefit to non-weight-bearing knee flexion and any other clinical result.

Objective To determine the accuracy of femoral components sizing predicted by standardized digital templating in total knee arthroplasty (TKA).Methods Fifty consecutive patients (50 knees),who underwent primary TKAs for endstage osteoarthritis,were prospectively studied.The intra-operative and radiographic data were collected.All operations were performed by the same surgical techniques with PS type,open box Vanguard Complete Knee System.All patients underwent lateral and AP radiography of the involved knee under fluoroscopy before and after surgery.The distal femoral anteroposterior dimension (DFAP) were measured and the femoral components size were predicted on preoperative radiographs by two different methods:measurement of DFAP did not include (group A) the cartilage thickness of the medial posterior condyle or included that (group B).Cutting errors were corrected gradually,and DFAP was measured consequently.The most appropriate size was chose after each step respectively based on postoperative radiographs.The accuracy of femoral size predicted under different conditions was compared within two groups.Results During correction of cutting errors,the correct rate ranged from 18％ to 44％ in group A and from 26％ to 34％ in group B,the accuracy within one size ranged from 54％ to 84％ in group A and from 58％ to 84％ in group B.The cartilage thickness of medial posterior condylar,external rotation of femoral component,under-resected of anterior condylar,flexion of femoral component,and over-resected of posterior condylar can change the DFAP by 1.97±0.85 mm,1.56±2.06 mm,1.15±1.31 mm,-2.86±1.52 mm,and-0.87±0.77 mm,respectively.Conclusion Variation of intraoperative cutting errors and the cartilage thickness of medial posterior condyles can influence the accuracy of templating to some extent.Standardized digital radiography templating cannot predict femoral sizes accurately.