Background: The purpose of this study was to explore whether subgroups of patients with different functional recovery trajectories after total hip arthroplasty can be discerned, as well as their predictors, using data from the Dutch Arthroplasty Register (Landelijke Registratie Orthopedische Implantaten [LROI]).
Methods: We retrospectively reviewed prospectively collected Oxford Hip Scores (OHS) up to 1 year postoperatively for patients who had undergone a primary total hip arthroplasty. Latent class growth modeling was used to classify subgroups of patients according to the trajectory of functional recovery represented by the patients' OHS. We used multivariable multinomial logistic regression analysis to explore factors associated with class membership.
Results: A total of 6,030 patients were analyzed. Latent class growth modeling identified fast starters (fast initial improvement, high 12-month scores; 87.7%), slow starters (no initial change and subsequent improvement; 4.6%), and late dippers (initial improvement and subsequent deterioration; 7.7%). Factors associated with slow starters were female sex (odds ratio [OR], 1.63 [95% confidence interval (CI), 1.14 to 2.33]) and smoking (OR, 1.95 [95% CI, 1.26 to 3.03]); an anterior approach (OR, 0.47 [95% CI, 0.29 to 0.78]) had a protective effect against a less favorable response. Factors associated with late dippers were age of >75 years (OR, 1.62 [95% CI, 1.22 to 2.15]), smoking (OR, 1.68 [95% CI, 1.17 to 2.42]), American Society of Anesthesiologists (ASA) grade of III or IV (OR, 1.41 [95% CI, 1.05 to 1.91]), obesity (OR, 1.96 [95% CI, 1.43 to 2.69]), poorer EuroQol-5 Dimensions (EQ-5D) Self-Care (OR, 1.41 [95% CI, 1.09 to 1.82] for "some problems" and OR, 2.90 [95% CI, 1.39 to 6.03] for "unable"), poorer EQ-5D Anxiety/Depression (OR, 1.31 [95% CI, 1.00 to 1.71] for "moderately" and OR, 1.86 [95% CI, 1.06 to 3.24] for "extremely"), poorer EQ-5D visual analog scale (OR, 0.91 [95% CI, 0.86 to 0.97] per 10 points), direct lateral approach (OR, 2.18 [95% CI, 1.58 to 3.02]), and hybrid fixation with a cemented acetabular implant (OR, 1.79 [95% CI, 1.00 to 3.21]).
Conclusions: We discerned fast starters, slow starters, and late dippers after total hip arthroplasty. Female sex, older age, obesity, higher ASA grades, and worse EQ-5D scores were associated with a less favorable response to total hip arthroplasty, as well as hybrid fixation (cemented acetabular implant) and direct lateral approach. Anterior approach had a protective effect against a less favorable response. However, all subgroups experienced functional improvement following total hip arthroplasty.
Level of evidence: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.