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.

Results of a Second-generation Constrained Condylar Prosthesis in Complex Primary and Revision Total Knee Arthroplasty： A Mean 5.5-Year Follow-up

Background： The application of second-generation constrained condylar knee （CCK） prostheses has not been widely studied. This retrospective study was carried out to evaluate the clinical and radiographic outcomes of a second-generation CCK prosthesis for complex primary or revision total knee arthroplasty （TKA）. Methods： In total, 51 consecutive TKAs （47 patients） were performed between June 2003 and June 2013 using second-generation modular CCK prostheses. The follow-up was conducted at 3~a day, 1% 6＇h, and 12~h months postoperatively and later annually. Anteroposterior （AP）, lateral, skyline, and long-standing AP radiographs of the affected knees were taken. The Hospital for Special Surgery （HSS） Knee Score, the Knee Society Knee Score （KSKS）, the Knee Society Function Score （KSFS）, and range of motion （ROM） were also recorded. Heteroscedastic two-tailed Student＇s t-tests were used to compare the HSS score and the Knee Society score between primary and revision TKAs. A value ofP 〈 0.05 was considered statistically significant. Results： Four knees （two patients） were lost to follow-up, and 47 knees （31 primary TKAs and 16 revision TKAs） had a mean follow-up time of 5,5 years. The mean HSS score improved from 51.1 ±15.0 preoperatively to 85.3 ± 8.4 points at the final follow-up （P 〈 0.05）. Similar results were observed in terms of the KSKS and KSFS, which improved from 26.0 ± 13.0 to 80.0 ± 12.2 and from 40.0 ± 15.0 to 85.0± 9.3 points, respectively （P 〈 0.05）. No significant difference in the HSS, KSKS, KSFS, or ROM was found between primary and revision TKAs （P 〉 0.05）. Two complications were observed in the revision TKA group （one intraoperative distal lemur fracture and one recurrence of infection） while one complication （infection） was observed in the primary TKA group. No prosthesis loosening, joint dislocation, patella problems, tibial fracture, or nerve injury were observed. Radiolucent lines were observed in 4% of the knees without progressive osteolysis. Conclusions： Second-generation modular CCK prostheses are a safe and practical treatment for both primary and revision knees that cannot be balanced. However, further studies focusing on different types of constrained prostheses are required to validate these results.