The conventional approach for total knee arthroplasty (TKA) is a medial parapatellar approach (MPA). We aimed to study patient outcomes and kinematics with a quadriceps sparing lateral subvastus lateralis approach (SLA). Patients with neutral/varus alignment undergoing primary TKA were consented to undergo the SLA. At 1-year postoperative, patients underwent radiostereometric analysis. Patients were administered the Short Form 12 (SF-12), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and Knee Society Score (KSS). Kinematics and outcome data were compared to a group undergoing TKA via conventional MPA. Fourteen patients underwent TKA via SLA with a mean age 71.5 ± 8.0 and mean body mass index (BMI) 31.0 ± 4.5. The MPA group had 13 patients with mean age 63.4 ± 5.5 (p = 0.006) and mean BMI 31.2 ± 4.6 (p = 0.95). The SLA resulted in a significantly more posterior medial contact point at 0 (p = 0.011), 20 (p = 0.020), and 40 (p = 0.039) degrees of flexion. There was no significant difference in medial contact point from 60 to 120 degrees, lateral contact point at any degree of flexion, or axial rotation. There was no difference in improvement in postoperative WOMAC, SF-12, KSS function, and total KSS knee scores between groups. The MPA group had a significantly greater improvement in KSS knee scores at 3 months (p < 0.001), 1 year (p = 0.003), and 2 years (p = 0.017). The SLA resulted in increased medial femoral rollback early in flexion. Although both approaches resulted in improved postoperative outcomes, the MPA group showed significantly greater improvements in KSS knee scores at 3 months, 1 year, and 2 years. Further studies are required to identify any benefits that the SLA may offer. LEVEL OF EVIDENCE: Therapeutic Level II.
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