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Wednesday, March 15, 2000

Less Pain after TKR when patella not resurfaced

A femoral component that conforms closely to an unresurfaced patella has lower incidence of anterior knee pain after total knee arthroplasty than when the patella is resurfaced, according to a study in scientific exhibit 38.

The researchers compared clinical and radiographic results of nonresurfaced patellae in two groups of patients after using two different total knee arthroplasty systems.

Between Jan. 1, 1990 and Dec. 31, 1996, 578 primary cementless total knee replacements were performed without resurfacing the patella. Severity of arthritic patellar disease at the time of surgery was noted. Two matched groups--a group of 63 patients (87 knees) with femoral components having a flat lateral flange and a group of 54 patients (79 knees) with components having a curved lateral femoral flange surface that provides full patellar support--were reviewed retrospectively at an average follow-up of four years. The average patient age was 67 years in both groups and all patients had a diagnosis of osteoarthritis. Clinical results were evaluated with the Knee Society Clinical Rating System at each follow-up interval. Lateral and skyline radiographs taken at three months, 12 months, 24 months, 36 months and 48 months were reviewed to identify changes in patellar cartilage thickness, patellar tendon length, patellar bone quality and incidence of patellar osteophytes.

The researchers said no patellar revisions were required in either group. By the 48-month postoperative visit, 15 patients (17.2 percent) whose femoral component had a flat lateral femoral flange had anterior knee pain and eight patients (10. 1 percent) whose femoral component had a curved lateral femoral flange had anterior knee pain. The group with the flat lateral femoral flange had 49 knees with moderate or severe patellar disease intraoperatively, and 11 (22.4 percent) of these had anterior knee pain postoperatively. The group with the curved lateral femoral flange had 41 knees with moderate or severe patellar disease intraoperatively, and five (12 percent) of these had anterior knee pain postoperatively.

Patellar tendon length was shorter in both groups for those patients who had anterior knee pain than for those who did not. No statistically significant correlation was found between postoperative anterior knee pain and clinical score, decrease of patellar cartilage thickness, patellar osteophytes or patellar bone quality in either group.

The researchers said these results suggest that patellofemoral design influences postoperative anterior knee pain, and the severity of patellar osteoarthritic changes does not affect the results of unresurfaced patellae that articulate against a well-designed femoral component.

The study was conducted by Gen Emoto, MD; Takeshi Arizono, MD; F. Thane DeWeese, MD; and Leo A. Whiteside, MD, director, Missouri Bone and Joint Center, St. Louis.

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2000 Academy News March 15 Index B

Last modified 06/March/2000 by IS