LONG-TERM COMPLICATIONS AFTER TOTAL KNEE ARTHROPLASTY WITH OR WITHOUT RESURFACING OF THE PATELLA

The long-term complications related to the patella were retrospectively evaluated for 891 knees (684 patients) that had had a total arthroplasty, with or without resurfacing of the patella, with use of an unconstrained, condylar, posterior-cruciate-preserving prosthesis. The study population comprised two groups of patients who were similar in size, age, sex distribution, and diagnosis. One group (396 knees [303 patients]) had had a total knee arthroplasty with patellar resurfacing and the other group (495 knees [381 patients]) had had the same procedure without resurfacing. The average duration of follow-up was six and one-half years (range, two to fifteen years). The decision to resurface the patella was based on subjective inspection of the articular surface and on assessment of patellar tracking at the time of the operation. Resurfacing was performed if there was loss of cartilage, exposed bone, gross surface irregularities, or tracking abnormalities. Complications occurred an average of three years (range, immediately postoperatively to nine years) after the operation in the group that had had resurfacing and an average of four years (range, immediately post-operatively to ten years) postoperatively in the group that had not had resurfacing. In the group that had had resurfacing, there was loosening of the patellar component in five knees, patellar subluxation in four knees, fracture of the patella in three knees, rupture of the patellar tendon in three knees, and chronic peripatellar pain in one knee. In the group that had not had resurfacing, the complications included patellar subluxation in five knees, rupture of the patellar tendon in two knees, and chronic peripatellar pain in fifty-one knees. The over-all rate of complications was 4 per cent (sixteen of 396 knees) in the group that had had resurfacing and 12 per cent (fifty-eight of 495 knees) in the group that had not had resurfacing; this difference was significant (p < 0.0001). The over-all rate of loosening of the patellar component, which was determined on the basis of both clinical and radiographic criteria, was 1 per cent. Chronic pain in the group that had not had resurfacing was noted in forty (13 per cent) of the 300 knees that were affected by inflammatory arthritis and in eleven (6 per cent) of the 195 knees that were affected by degenerative osteoarthrosis; this difference was significant (p < 0.0093). A revision to resurface the patella was performed in all fifty-one knees that caused chronic pain and had not had resurfacing of the patella, an average of sixty-three months (range, fifteen to 119 months) after the index total knee arthroplasty. On the basis of our findings, we recommend that the patella be resurfaced when an unconstrained prosthesis of this type is used in patients who have inflammatory arthritis or osteoarthrosis. Failure to resurface the patella in patients who have these diagnoses may result in an increased rate of revision, including early revision, for the treatment of chronic patellar pain.