Balance lower limb loads and 3D spine modifications after total hip joint replacement: effects of leg length discrepancy correction.

Following total hip joint replacement (THJR), the durability of a prosthesis is limited by: wearing of frictional surfaces and loosening and migration of the prosthesis-cement-bone system. Literature review witnesses biomechanical studies focused mainly/only on hip functional state while none of them approached leg length discrepancy (LLD), posture unbalancing or spine related problems after THJR. Conversely, these latter could be critical elements for surgery and rehabilitation success, given the possible induction of asymmetric loading patterns. This study presents the results obtained by using a recently proposed methodology, to measure 3D subject posture balance and spine morphology and to evaluate its usefulness in individual therapy tuning/follow up. 3D subject's posture has been measured by means of 3D opto-electronic device, force platform and baropodography. 90 subjects after THJR have been included in this study. The subjects have been evaluated in two different epochs: 3 weeks after surgical intervention and after 3 months. 77/90 patients presented a LLD, pelvic obliquity and posture unbalancing. More than 90% of this group showed an overall postural re-balancing induced by the use of simple underfoot wedge. 70/77 patients needed wedge under the healthy side showing the surgical intervention produced a leg lengthening. 60/90 (52 LLD) patients underwent up to now to control and patients who wore the suggested wedge (63.4%) presented an improvement over all the considered quantitative parameters. Patients who wore a shorter than suggested wedge (23.1%), or that did not wear the suggested wedge (13.5%) presented a moderate or significant worsening of their postural balancing respectively.