Both medial and lateral UKA yield excellent functional outcomes including significantly increased abilities to climb stairs, kneel, and squat. We recommend medial and lateral UKA for patients with isolated unicompartmental knee OA as intervening earlier in the disease process may optimize outcomes in this patient population.
Studies have reported that 80% of knee arthroplasty patients described kneeling as impossible/extremely difficult before surgery, with 38.5% of patients who underwent TKA and 32.3% of patients who underwent UKA (compartment unspecified) still reporting kneeling as impossible 1 year following surgery. Additionally, medial UKA patients reported rising from kneeling as significantly harder than all other activities on the Oxford knee questionnaire. However, as medial UKAs are performed more frequently, there are few lateral UKA studies and little data on functional outcomes following the procedure exists. The purpose of this study was to assess and compare specific functional outcomes, including stair climbing, kneeling, and squatting, in both medial and lateral UKA patients. We hypothesized that both groups would show preoperative to postoperative improvements in their ability to perform each activity with no significant difference in these abilities between medial and lateral UKA patients.
Prospectively collected data was retrospectively reviewed from 170 consecutive patients (198 knees; 150 medial, 48 lateral) treated with UKA between 1999-2015. Patients lacking preoperative data or =1-year follow-up data were excluded. Eighty-four patients (93 knees; 68 medial, 25 lateral) were included. Surgical indications included pain on only one side of the knee, conservative treatment failure, and x-ray evidence of severe unicompartmental OA. Patients completed pre- and postoperative physical, radiographic, and functional evaluations including report of sporting participation. Sports were categorized based on American College of Sport Medicine guidelines. Self-reported abilities to climb stairs, kneel, and squat were determined from the International Knee Documentation Committee (IKDC) questionnaire.
Follow-up was 3.18±1.9 years and 5.36±2.6 years for the medial and lateral cohorts, respectively. There were two revisions in the medial group at 1.5 and 9 years post-surgery. Both groups demonstrated significant pre- to postoperative improvements in abilities to descend and ascend stairs, kneel, and squat (p<0.0001 for each) and no significant differences in postoperative abilities to descend stairs (p=0.1665), ascend stairs (p=0.4248), or squat (P=0.3845); however, a significant difference in postoperative kneeling ability was demonstrated (p= 0.001), with lateral UKA patients demonstrating greater ease in postoperative kneeling. Total postoperative IKDC scores were 95.02±7.04 and 94.25±2.30 for the medial and lateral cohorts, respectively (p=0.6117). 100% of patients returned to sports with 37% and 46% of medial and lateral patients, respectively, returning to vigorous sports and 63% and 54% of medial and lateral patients, respectively, returning to moderate sports (p=0.635).
Both medial and lateral UKA yield excellent functional outcomes including significantly increased abilities to climb stairs, kneel, and squat. Lateral UKA patients demonstrated significantly less difficulty kneeling compared to medial UKA patients. This difference may be due to the tibiofemoral biomechanics in each compartment, as the increase in joint contact area in the lateral compartment is larger and more widespread than that experienced by the medial compartment during kneeling despite both experiencing similar total contact pressures, allowing for better load distribution. We recommend medial and lateral UKA for patients with isolated unicompartmental knee OA as intervening earlier in the disease process may optimize outcomes in this patient population.