Abstract:
Osteoarthritis is a common debilitating condition, resulting in pain and loss
of normal joint function in 10% of New Zealanders [1]. Unicompartmental
Knee Replacement (UKR) and Total Knee Replacement (TKR) are both
effective end stage solutions for this condition. UKR offers significant
benefits over TKR in patient recovery, trauma and bone ligament retention,
due to the retention of the ACL and unaffected knee compartments.
Kinematic comparisons between UKR and TKR designs also show
increases in force production, walking speed and range of motion in UKR
designs. However, failure rates of UKR are greater than those in TKR,
preventing this surgery to be widely implemented [2] [3] [4]. The surgical
variance in vertical wall placement and bearing size were identified as
potential areas of failure and a finite element model, validated with x-ray
fluoroscopy, was used to explore this variance. Gait data was inputted and a
range of bearing thicknesses from 3mm to 7mm and vertical wall shifts from
-4mm to +4mm were explored. Medial forces increased by ~100N with
every mm change in bearing thickness and lateral bearing placement of
more than 2 mm was found to be unstable and cause bearing lift-off. This
study introduces a proof-of-concept workflow to use computational models
to improve preoperative planning for unicompartmental knee joint
replacement.
