Clinical implications of an additional mediolateral implant option for a primary total knee system in an ethnically diverse population: 5-year interim results from a prospective, multicenter cohort study.

BACKGROUND: Femoral component overhang can cause complications following primary total knee arthroplasty (TKA) and occurs more frequently in non-Caucasian populations due to anatomical differences insufficiently addressed by contemporary implants. The ANTHEM™ posterior-stabilized (PS) TKA system was designed to improve anatomical compatibility and reduce overhang. This prospective cohort study investigated implant survivorship, overhang frequency, and its clinical impact in Asian/Caucasian patients. Five-year interim results are reported.

METHODS: 148 knees (120 patients; mean age 67.1 years; 77.5% female; 50% Asian, 50% Caucasian) underwent primary TKA for osteoarthritis at 6 international centers. Follow-up occurred at 6 weeks, 1, 2, and 5 years. Primary outcome was implant survivorship. Secondary outcomes included KOOS, 2011 KSS, EQ-VAS, EQ-5D3L, and radiographic assessments. Femoral component fit and safety events were collected.

RESULTS: At 5 years, Kaplan-Meier survivorship estimates were 98.88% (95% CI: 92.29-99.84) for standard femorals and 96.88% (95% CI: 79.81-99.55) for narrow femorals. Six serious adverse device effects were reported - two possibly/directly related to the device/procedure. Radiographs showed 1 periprosthetic fracture and 5 non-progressive radiolucencies. No migration, loosening, osteolysis, or heterotopic ossification was observed. Overhang occurred in 12.8% of knees. All patient-reported outcomes improved significantly (p < 0.0001).

CONCLUSION: This knee system demonstrated excellent survivorship, strong clinical performance, minimal complications, and low overhang rates across diverse populations, supporting the value of enhanced anatomical fit in achieving optimal TKA outcomes.