STRENGTH AND FUNCTIONAL OUTCOMES IN UNILATERAL VERSUS SIMULTANEOUS BILATERAL TOTAL KNEE ARTHROPLASTY. (2006)

Purpose/Hypothesis: Osteoarthritis (OA) is a leading cause of disability in the United States. 50% of individuals with radiographic evidence of knee OA have bilateral involvement and require total knee arthroplasty (TKA). Whether to recommend a staged procedure or a simultaneous, bilateral procedure remains a point of contention. A major concern surrounding the simultaneous procedure is higher risk of perioperative complications. To date, no studies have assessed differences in long-term strength and functional outcomes. Purpose: The purpose of the present study was to compare outcomes in individuals with primary knee OA undergoing simultaneous, bilateral TKA to those undergoing unilateral TKA. Subjects: 12 patients having unilateral TKA and 12 gender, age, and BMI-matched patients having simultaneous, bilateral TKA were tested preoperatively and 4, 7, 12, 24, and 52 weeks following TKA. Mean age was 62.0±6.7 years and mean BMI was 30.5±4.3 for both groups. Materials/Methods: All TKAs were performed using a medial parapatellar surgical approach and received 6 weeks of outpatient physical therapy 3 days per week. Self-reported function was measured using the mental and physical component summary scores of the SF-36(MCS and PCS, respectively) and the Activity of Daily Living Scale of the Knee Outcome Survey (KOS). Functional assessment included Timed Up and Go (TUG), Stair-Climbing Test (SCT), and Six-Minute Walk (6MW). A burst superimposition test was used to assess quadriceps strength (MVIC) and activation (CAR). A repeated measures ANOVA was used to assess differences in outcomes between groups over time. Preoperative measures were used as a covariate to account for inherent group differences. The level of significance was set at 0.05. Results: There were no significant differences in mean preoperative SF-36 or KOS scores, functional performance, quadriceps strength, or activation between the Unilateral and Bilateral Group. All assessment scores at 4, 7, 12, 24, and 52 weeks were similar between groups. At last follow-up (52 weeks), the Unilateral Group had a mean PCS score of 50.36±8.09, MCS score of 56.60±6.61, KOS score of 0.88±0.10, TUG of 7.72±2.71 seconds, SCT of 12.16±4.80 seconds, 6MW of 2000±420 feet, MVIC of 18.28±8.27 N/BMI, and CAR of 0.89±0.09. The Bilateral Group had a mean PCS score of 50.89±2.19, MCS score of 59.98±2.77, KOS score of 0.87±0.09, TUG of 6.44±0.87 seconds, SCT of 9.88±1.52 seconds, 6MW of 2003±278 feet, MVIC of 20.69±7.23 N/BMI, and CAR of 0.89±0.11. Conclusions: Short and long term outcomes were not affected by the simultaneous, bilateral TKA. All patients regardless of group equaled all preoperative scores by 12 weeks with the exception of MVIC which was achieved by 52 weeks. Clinical Relevance: While it appears that simultaneous, bilateral TKA does not hinder strength and functional outcomes, future research should determine differences between the simultaneous and staged, bilateral procedure to add to the literature that the simultaneous procedure has a 50% shorter hospital stay and 18% lower hospital costs.