Pre-Operative Musculoskeletal Comorbidities Limit Improvement In Functional Outcomes And Hip Pain In Total Hip Arthroplasty Patients

Background/Purpose:   Identifying clinical factors predictive of total hip arthroplasty (THA) outcomes is valuable for clinicians and patients to make a data-driven surgical decision. While factors such as age, weight, and medical comorbidities have been shown to affect post-operative pain and/or functional gains following THA, musculoskeletal comorbidities have not been investigated. We evaluated whether lumbar pain and pain in the knees and non-operative hip joints predict poorer 6 month pain relief and functional gain.

Methods:   Data were collected from 2,848 patients enrolled in FORCE-TJR, a national prospective cohort of patients who underwent a primary unilateral total hip replacement due to osteoarthritis. Data including patient demographics, medical comorbidities, emotional health (SF/MCS), low back pain (Oswestry), pain in both hips and knees (HOOS/KOOS pain score), and pre-operative and post-operative function (SF/PCS) were collected pre-operatively and six months post-operatively. Post-THA pain relief and functional gain were analyzed using descriptive statistics as well as linear mixed  regression models, in relation to musculoskeletal comorbid conditions and traditional patient and clinical factors.       

Results:   This cohort was 59% female, with a mean age of 65.4 years and mean BMI of 28.9 (kg/m^2). Out of the 2,848 patients, 992 (34.8%) reported moderate to severe low back pain pre-operatively. In addition, 264 (9.3%) reported moderate to severe pain in at least two non-operative hip or knee joints. After adjusting for gender, age, BMI, emotional health and medical co-morbidities, moderate to severe pre-THA back pain and pain in one or more non-operative hip or knees was significantly correlated (p<0.001) with a smaller improvement in hip pain and function after THA. Additionally, the greater the number of nonsurgical hip and knee joints with pain pre-operatively, the stronger the negative effect on pre-to-6 month post-THA gain in pain and function outcomes.

Conclusion:   The presence of low back pain and pain in non-operative hip and knee joints has a significant negative impact on post-THA pain relief and functional outcome. In addition to traditionally reported clinical factors (i.e. age, weight and medical co-morbidities) the burden of musculoskeletal co-morbidity is an important consideration in predicting post-THA gains.