The effect of interposition arthroplasty on the contact mechanics of the elbow joint

Dysfunctional elbow osteoarthritis poses a therapeutic dilemma in young patients with high activity levels and corresponding demands on elbow mobility. In selected cases, interposition arthroplasty of the elbow remains a viable salvage option and alternative to primary prosthetic replacement. The primary objective of this study was to evaluate the effects of interposition arthroplasty on elbow joint contact mechanics, comparing Achilles tendon (AT) and fascia lata (FL) grafts. Ten fresh-frozen human elbow specimens underwent static axial loading (50-400 N) at 20° flexion in native state and following AT and FL graft interposition. Contact pressure distributions were analyzed using intraarticular digital pressure mapping sensors. The interposition of AT and FL grafts resulted in a significant reduction of the peak joint pressure (p = 0.003) and the high-pressure area with a contact pressure > 1 MPa (p = 0.002). Following interposition of the AT graft, a significantly increased contact area compared to the native joint was observed at high axial loads (p = 0.045). The relative radiocapitellar force transmission (p = 0.089) did not differ significantly between the conditions. A direct comparison of the grafts revealed no significant differences in any of the parameters examined. This study provides the first direct biomechanical comparison of AT and FL grafts for interposition arthroplasty under physiological joint loading, revealing comparable, significant reductions in peak contact pressure and novel evidence for increased load distribution independent of graft type.