Abstract
Background
Total Hip Arthroplasty (THA) has long been the standard treatment for cases in which non-surgical alternatives have failed to improve pain and function in hip osteoarthritis (OA) patients. Outcomes from THA have improved over time with better surgical techniques and improved implant designs. While conventional neck-sacrificing implants have been associated with favorable outcomes, there is evidence to suggest biomechanical advantages of newer, femoral neck-preserving short-stem implants, including the Corin MiniHip. However, there is a still a gap of knowledge regarding the potential benefits of the MiniHip stem over conventional neck-sacrificing stems in regards to patient-reported outcomes (PROs). In this study, we investigated the differences between a neck-sacrificing stem design and neck-preserving short-stem design (MiniHip, Corin Inc.) arthroplasty concerning PROs, and considering the known features of the short stem design, we hypothesized that MiniHip THA would be associated with improved PROs in comparison to a neck-sacrificing implant system. We further sought to investigate gender effects related to MiniHip or conventional stem surgery.
Methods
Neck-sacrificing implant patients (n=90, age 57±7.9 years, female=58, male=32) and a matched (matching criteria: follow-up period, BMI, age) cohort group of MiniHip patients (n=105, age 55.16±9.88 years, female: 25, male: 80) reported both pre-operative and post-operative Hip disability and Osteoarthritis Outcome Scores (HOOS) at a minimum interval of 6 months post-operatively and up to three years postoperatively. We applied MANCOVA analysis to compare patient-reported outcome subscores from each group using follow-up period as a covariate and employing gender as an additional grouping factor to evaluate gender effects. Statistical significance was set at α=0.05 and Bonferroni corrections were applied to account for multiple comparisons.
Results
There was a main effect of time, showing that all HOOS subscores of both groups increased significantly after surgery (p<0.001). There was a main effect of surgery for subscores Symptoms (p=0.038), ADL (p=0.046), and Sports and Recreation (p=0.039). There was a gender effect only for the subscore Symptoms (p=0.007). There were significant time by surgery interactions for HOOS subscores Symptoms (p=0.002), Pain (p=.009), Sports and Recreation (p=0.004), and QOL (p<0.001) subscores. We also observed a significant time by gender interaction effect for all HOOS subscores (p<0.001).
Discussion
The interaction effects regarding most HOOS subscores and surgery/implant type indicate an advantage of MiniHip surgery regarding post-operative reported outcomes. The observed results may be due to previously described improved physiological loading and native hip structure preservation with neck-preserving short-stem designs. While longer-term studies are required for further investigation, evidence suggests the MiniHip may provide a significant benefit to primary THA patients. The additional gender/time interaction effect observed in our study highlights the necessity to consider potential sex differences regarding both the potential/expected improvement in PROs from THA and the requirement to account for such differences when designing osteoarthritis outcome studies based on PROs.
