Anterior-stabilized TKA is inferior to posterior-stabilized TKA in terms of postoperative posterior stability and knee flexion in osteoarthritic knees: a prospective randomized controlled trial with bilateral TKA.

purposeTo determine whether knee stability, range of motion (ROM) and clinical scores differ between anterior-stabilized (AS) and posterior-stabilized (PS) total knee arthroplasty (TKA).

methodsThis prospective randomized controlled trial included 34 patients with severe bilateral knee osteoarthritis who underwent bilateral TKA between June 2010 and July 2011 using AS and PS designs of a single-implant system. AS TKA with ultracongruent inserts was performed in one knee and PS TKA with a cam-post mechanism was performed in the other knee in each patient. Clinical and radiological data from a mean follow-up period of 5 years, including ROM, clinical scores, peak knee torque determined by isokinetic test, knee joint laxity determined by Telos stress views, tourniquet time and subjects' preference were analyzed.

resultsThe mean postoperative knee flexion angle did not differ between groups until 1 year. Beginning 2 years postoperatively, the knee flexion angle decreased slightly in the AS group and was smaller than that in the PS group (p = 0.004). The mean Knee Society knee score was higher in the PS group than in the AS group after 2 years. The quadriceps strength did not differ between groups. The mean posterior laxity after TKA was 6-8 mm greater in the AS group than in the PS group. No radiological loosening was observed in either group. More subjects preferred PS knees to AS knees. However, this difference was not significant.

conclusionAS primary TKA was inferior to PS TKA in terms of posterior knee stability, postoperative knee flexion and clinical scores after 2 years. LEVEL OF EVIDENCE: Therapeutic study, Level 1.