FACTORS PREDICTIVE OF MOBILITY AFTER TOTAL KNEE ARTHROPLASTY: A PROSPECTIVE STUDY IN 256 GLIDING PROSTHESES WITH PRESERVATION OF THE POSTERIOR CRUCIATE LIGAMENT

Abstract

Purpose: The purpose of this work was to evaluate function of 256 total knee arthroplasties (TKA) (Wallaby) with preservation of the posterior cruciate ligament and to compare the femorotibial angle obtained postoperatively.

Material and methods: This prospective study included 256 consecutive TKA (cemented Wallaby 1) in 249 patients (mean age 68 years) with osteoarthritis (n=249) or rheumatoid polyarthritis (n=7). Pre- and postoperative clinical findings (HKS score, flexion, extension, laxity, walking distance, use of crutches) and AP full leg views with 20° loaded lateral views pre- and postoperatively (mechanical femoral, mechanical tibial, and femorotibial angles, tibial slope, patellar height, anterior tibial translation) were recorded.

Results: The 256 TKA were reviewed at a mean 3-year follow-up. Flexion amplitude was the evaluation criterion. Mean preoperative flexion was 109° (40–130°) with mean persistent flexion of 5° (0°–40°). Mean postoperative flexion was 98° (30–130°) with no persistent flexion. The mean preoperative femorotibial angle was 181.8° (160–201°) and was 180.4° (172–195°) postoperatively. The mean preperative mechanical femoral angle was 88° (82–96°) and 89.8° (80–96°) postoperatively. Mean mechanical tibial angle was 93° (85–104°) and 90.4° (84–86°) postoperatively.

Discussion: For certain authors, the only parameter predictive of postoperative flexion after gliding TKA with preservation of the posterior cruciate ligament is preoperative flexion. The statistical analysis of our series showed that correction of the femorotibial malalignement in the frontal plane was not correlated with postoperative knee function and precisely with postoperative flexion. Postoperative flexion was correlated with preoperative flexion. Our results on postoperative flexion of TKA related to preoperative flexion are in agreement with earlier analyses reported in the literature that do not find any absolute correlation with a neutral femorotibial angle in the frontal plane.

Conclusion: The quality of the functional outcome after total knee arthroplasty cannot be predicted solely on the correction of the initial deformity.