INFLUENCE OF APPROACH ON PATELLAR POSITION IN TOTAL KNEE ARTHROPLASTY FOR DEGENERATIVE JOINT DISEASE WITH MAJOR LATERAL DISPLACEMENT OF THE PATELLA

Abstract

Purpose: Re-establishment of correct patellofemoral kinetics is a major challenge in patients with major dislocation of the patella. Several factors affect the position of the patella, rotation of the prosthetic components, lateral section of the patella, and …perhaps…surgical access.

Material and methods: Between 1994 and 1999, 26 knees with major dislocation of the patella were treated by the same operator with total knee arthroplasty (TKA) using a Cedior (Sulzer) implant. The operative technique was the same for all patients with the exception of the surgical access. For group 1 knees (n=13) a medial access was used (medial parapellar approach, 2 lateral patellar sections). For group 2 knees (n=13) a lateral access was used (lateral parapatellar approach lifting the anterior tibial tendon and refixing it after the procedure with systematic lateral fixation of the patella). Patellar tilt and lateral displacement and the patellar index (PI) (distance using head of the fibula as the fixed point) were the main judgement criteria. Student’s t test was used for statistical analysis. The two groups were comparable for: preoperative axial deviation (176.8±6.45°), lateral displacement (8.65±3.74 mm), and PI (0.789±0.166), and postoperative position of the femorotibial implants.

Results: Patellar displacement persisted in one knee in group 1 requiring a new prosthesis. Anterior impaction of the tibial piece in one knee in group 2 did not require reoperation. Radiographically, lateral displacement was minimal in both groups (0.692 and 0 mm in groups 1 and 2) (p=0.17). Residual postoperative tilt was +3.8° in group 1 and −3.3° in group 2 (p=0.06). PI was 0.859 in group 1 and 0.956 in group 2 (p=0.24). In group 2, the postoperative PI (0.956±0.231) was not changed from the preoperative PI (0.831±0.152) an expression of the absence of ascension of the anterior tibial tendon (p =0.1).

Dicussion: Lateral displacement of the patella was entirely corrected in both groups. Unlike the lateral access, medial access, even with lateral section of the patella, did not correct for the tilt. Raising the anterior tibial tendon did not in our experience have any iatrogenic effect in itself. Irrespective of the femorotibial axis, lateral access for degenerative knees with major dislocation of the patella appears to be the best approach for implantation of total knee arthroplasty.