Mid-term Outcomes of Primary Constrained Condylar Knee Arthroplasty for Severe Knee Deformity

This study aimed to examine the clinical and radiographic outcomes of primary total knee arthroplasy（TKA） with use of Nex Gen#174; Legacy#174; Constrained Condylar Knee（CCK） prosthesis for severe knee deformity. Clinical data of 46 patients（48 knees in total, aged 61 years on average） with severe knee deformity who underwent TKA with Nex Gen#174; Legacy#174; CCK prosthesis between December 2007 and February 2012 were retrospectively analyzed. There were 34 knees with severe valgus with incompetent medial collateral ligament, 11 knees with severe flexion contracture with inability to achieve knee balancing in flexion and extension by posterior soft tissue release, 2 knees with Charcot arthritis with severe varus and bone loss, and 1 with traumatic osteoarthritis with severe varus and ligamentous instability. The mean duration of follow-up was 71 months（range 40–90 months）. The New Knee Society scoring（NKSS） system and the Hospital for Special Surgery（HSS） score were used to evaluate the functional and clinical outcomes. Visual Analogue Scale（VAS） was used for pain measurement and Knee Society criteria for evaluation of radiological images. The results showed that, in the total 48 knees, 1 case of loosening due to short-stem tibial component at 3 months post-operatively underwent revision. The 6-year prosthesis survival rate in this cohort was 97.9%. There was no component infection occurring within 6 years. Significant post-operative improvements were found in NKSS and HSS scores. Patient satisfaction was significantly increased. Pain score was decreased significantly. Total functional score was improved from 31.46±11.43 to 86.42±8.87, range of motion（ROM） from 42.42°±23.57° to 95.31°±23.45° and the flexion contracture from 5.31°±7.87° to 0.92°±1.80°. Preoperative radiographic study showed excessive valgus（≥7°） in 37 knees, and varus deformity in 3 knees. Post-operative femorotibial alignment was valgus 3.88°±1.76° in 48 knees. Antero/posterior（A/P） view of X-ray films showed 4 radiolucent lines（RLL） in 48 tibial components. It was concluded that TKA with CCK is effective for the treatment of the severe unstable knee that cannot be balanced by soft tissue.

Effect of posterior condylar offset on clinical results after posterior-stabilized total knee arthroplasty

Purpose： To determine 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： We prospectively studied the clinical and radiographic materials of 89 consecutive female patients （89 knees）, who had undergone primary TKAs for end-stage osteoarthritis. All operations were performed by a single senior surgeon or under his supervision using the same operative technique. Based on the corrected PCO change, we divided all cases into two groups： group A （corrected PCO change _〉0 mm, 58 knees） and group B （corrected PCO change 〈0 ram, 31 knees）. One-year postoperatively, clinical and radiographic variables from the two groups were compared by independent t-test. The as- sociations between the corrected PCO changes and the improvements of clinical variables in all patients were analyzed by Pearson linear correlation. Results： One-year postoperatively, the Knee Society Scores, the Western Ontario and McMaster Uni- versities Osteoarthritis Index, non-weight-bearing active and passive range of knee flexion, flexion contracture, extensor lag, and their improvements had no statistical differences between the two groups （all p 〉 0.05）. The corrected PCO change was not significantly correlated with the improvement of any clinical variable （all p 〉 0.05）. Group A demonstrated greater flexion than group B during active weight bearing （p 〈 0.05）. Conclusions： Restoration of PCO plays an important role in the optimization of active knee flexion during weight-bearing conditions after posterior-stabilized TKA, while it has no benefit to non-weight-bearing knee flexion or any other clinical result.