A randomized, controlled, prospective study evaluating the effect of patellar eversion on functional outcomes in primary total knee arthroplasty.

ABSTRACT

BACKGROUND: Patellar mobilization technique during total knee arthroplasty has been debated, with some suggesting that lateral retraction, rather than eversion, of the patella may be beneficial. We hypothesized that patients with knees surgically exposed using patellar lateral retraction would have comparable outcomes with patients with knees surgically exposed using patellar eversion. METHODS: After an a priori power analysis, 120 patients with degenerative arthrosis were prospectively enrolled and were randomized to one of two patellar exposure techniques during the primary total knee arthroplasty lateral retraction or eversion. The primary outcome measure was one-year, dynamometer-measured quadriceps strength. The secondary outcome measures evaluated during hospital stay included the ability to straight-leg raise, visual analog scale in pain, walking distance, and length of stay. The secondary outcome measures that were evaluated preoperatively and through a one-year follow-up included the Short Form-36 Physical Component Summary and Mental Component Summary scores, range of motion, quadriceps strength, and radiographic rate of patella baja and tilt. RESULTS: A mixed-model analysis of variance showed no significant differences between the two groups in the one-year outcome measures. At one year postoperatively, quadriceps strength was not different between groups (p = 0.77), and the range of motion significantly improved (p < 0.01) from preoperative values by a mean value (and standard deviation) of 6° ± 17°, with no significant difference (p = 0.60) between groups. The Short Form-36 Physical Component Summary score and Mental Component Summary score significantly improved (p < 0.01) for both study groups from preoperatively to one year postoperatively with no significantly different effects between groups (time × group, p = 0.85 for the Physical Component Summary score and p = 0.71 for the Mental Component Summary score), and the scores were not different at one year after surgery. There were no significant differences between groups in the change in frequency of the radiographic patella baja (p = 0.99) or the radiographic patellar tilt (p = 0.77) from before surgery to one year after surgery. CONCLUSIONS: Lateral retraction of the patella did not lead to superior postoperative results compared with eversion of the patella during total knee arthroplasty as evaluated using our primary outcome measure of one-year, dynamometer-measured quadriceps strength or our secondary outcome measures. LEVEL OF-EVIDENCE Therapeutic Level II. See Instructions for Authors for a complete description of levels of evidence.