Lower functioning patients demonstrate atypical hip joint loading before and following total hip arthroplasty for osteoarthritis

Previous studies have established that up to one year post a total hip arthroplasty (THA), patients do not recover normal function and the magnitude of hip joint loading remains reduced compared to healthy individuals. However, the temporal nature of the loading profile has not been considered to identify individuals who are at a greater risk of poor functional outcomes following THA. This study aimed to determine the changes to the profile and magnitude of the resultant hip joint reaction force before and up to six months post primary THA, and factors associated with atypical loading profiles. Hip joint loading was computed using a personalised lower-limb musculoskeletal model in 43 participants awaiting primary THA for osteoarthritis (mean age: 65 SD 14 years; BMI: 30 SD 5 kg/m2 ) before and up to 6 months after THA. Atypical, single peak loading profiles were observed for 11 patients before surgery, where four showed a single peak at 6 months. Patients displaying a single peak profile walked slower (mean difference: -0.4 m·s-1 ) compared to individuals displaying double peak profile (p = <.001) and had significantly reduced sagittal plane hip range of motion during gait (mean difference -9.6 degrees, p = <.001). Self-reported pain, function and stiffness did not differentiate between patients with a single or double peak loading profile. Individuals with a single peak force profile did not meet the minimal clinically important hip range of motion during gait and would be classified as low functioning THA patients. CLINICAL RELEVANCE: The temporal nature of the force profile may help to identify individuals who are at the greatest risk of poor functional outcomes after a THA. This article is protected by copyright. All rights reserved.Jasvir S. Bahl, John B. Arnold, Mark Taylor, Lucian B. Solomon, Dominic Thewli