Multiple-Offset Titanium Slot-Stems Versus Limited-Offset Cobalt-Chromium Stems in Hybrid-Fixation Revision Total Knee Arthroplasty: A Comparative Study With 5- to 14-Year Follow-up.

BACKGROUND: Multiple-offset titanium slot-stem (MOT) systems in revision total knee arthroplasty (rTKA) are designed to enhance component positioning, optimize gap balancing, and improve load transfer; however, clinical evidence remains limited. This study compared the clinical and radiographic outcomes of MOT and limited-offset cobalt-chromium stem (LOC) systems in hybrid-fixation rTKA and evaluated implant survivorship.

METHODS: A retrospective cohort study included patients undergoing rTKA (2012 to 2020) with a minimum five-year follow-up. Patients received either MOT or LOC systems. Clinical outcomes included the modified Western Ontario and McMaster Universities Osteoarthritis Index (mWOMAC), the Knee Society Score (KSS), knee flexion, and stem-tip pain. Implant survivorship was analyzed using Kaplan-Meier methods with aseptic revision as the endpoint. Radiographic evaluation included component overhang, hip-knee-ankle (HKA) alignment, posterior condylar offset (PCO), joint-line level (JLL), and constrained liner use. There were 63 rTKAs (39 MOT and 24 LOC) evaluated at a mean follow-up of 8.6 years (range, five to 14).

RESULTS: There were no significant differences observed in mWOMAC, KSS, or knee flexion (P > 0.05). Aseptic survivorship was also similar (100 MOT versus 96% LOC; P = 0.200). The MOT group showed lower stem-tip pain (0 versus 17%; P = 0.043), less medial tibial overhang (0.2 ± 1.4 versus 2.2 ± 2.5 mm; P = 0.002), greater PCO (33.0 ± 4.7 versus 30.2 ± 4.6 mm; P = 0.020), lower joint line elevation (4.6 ± 6.9 versus 9.4 ± 8.4 mm; P = 0.022), and less constrained liner use (13 versus 38%; P = 0.025). The HKA alignment was similar between groups.

CONCLUSION: The MOT system was associated with reduced stem-tip pain, improved tibial fit, greater PCO, improved JLL restoration, and reduced constrained liner use compared with the LOC system. However, these advantages might not translate into measurable improvements in patient-reported outcomes or implant survivorship.