Relative Motion of Cementless Tibial Trays: Time-Elapsed Micro-CT and DVC Analysis During Stair Descent and Deep-Knee-Bend

An interference fit is employed for cementless tibial total knee arthroplasty components to ensure stability post-operatively. Relative motion between implant and underlying bone should be minimised, facilitating osseointegration. Previous experimental limitations have prevented quantification of this motion across the entire bone-implant interface. Furthermore, the intended (nominal) interference fit differs to that actually achieved. This study aimed to 1) experimentally quantify the relative motion across the entire interface of a commercially available cementless tibial component and underlying bone, for cadaveric tibiae through micro-computed tomography (micro-CT) imaging and digital volume correlation (DVC); and 2) assess the relationship between relative motion, actual interference fit, post-impaction strain and bone volume fraction (BV/TV).Seven cadaveric tibiae were micro-CT scanned when intact, following resection and, once implanted with a cementless titanium tibial component (Attune, DePuy Synthes), during two time-elapsed mechanical loading sequences that replicated stair descent (SD, 0.0 - 2.5 bodyweight) and deep knee bend (DKB, 0.0-3.5 bodyweight). Actual interference fit was quantified from micro-CT datasets. DVC was employed to extract the post-impaction strain field and, for each load case, the relative motion at the bone-implant interface.A sagittal rocking motion of the tray was detected in both SD and DKB, that increased with increased load applied. Tray lift-off was enhanced in the central- and lateral-anterior regions during DKB. Reduced relative motion was significantly related to higher interference in most cases, whilst it was not related to post-impaction strain or BV/TV. This study provides a comprehensive insight into the mechanical environment surrounding a cementless tibial tray in the immediate post-implantation period.