Lumbar Spinal Stiffness Overshadows Polyethylene Wear A Modern Explanation for Late Dislocation in Total Hip Arthroplasty

Instability or dislocation after total hip arthroplasty (THA) is a dreaded complication, occurring with rates ranging from 0.3% to 10% [1-4], and is the most common reason for revision surgery [5]. Risk factors for instability following THA include patient-specific factors such as non-compliance, neuromuscular or cognitive disorders, as well as surgical considerations including approach [6], soft tissue tension, component size; positioning, implant choice and polyethylene wear [7]. Traditionally, it is thought that the THA dislocation occurs in a bimodal distribution, based on timing after surgery (early and late). Early dislocations, which occur within the first two years following THA, are more common than late dislocations, and are more commonly attributed to component malposition [8], patient non-compliance (drug abuse or dementia) or neurocognitive disability (Parkinson Disease), or conditions affecting soft tissue quality and tension including soft tissue repair, rheumatoid arthritis and a vascular necrosis [9-11]. Late THA dislocations, which usually occur many years after THA, have been largely attributed to (based on our classic adult reconstruction teaching dogma) eccentric polyethylene wear [12].