Summary

Previous literature has presented conflicting data as to whether weightbearing and supine radiographs present different measurements for joint space width at the hip; we demonstrate no significant difference between measurements obtained during weightbearing and supine radiographs, and thus, orthopaedic surgeons may be able to avoid obtaining multiple radiographs.

Abstract

Introduction

Osteoarthritis and joint space narrowing of the hip have been correlated with poor outcomes and conversion to arthroplasty after hip arthroscopy. However, a standardized protocol for radiographic measurement of minimal joint space width of the hip has not been developed and there is conflicting data as to whether weightbearing and supine radiographs present different measurements for joint space width at the hip. We hypothesized that minimal joint space width would be significantly lower on the affected side in weightbearing anteroposterior pelvis radiographs versus supine radiographs. We also hypothesized that radiographs with single-leg stance would show the lowest minimal joint space width. Lastly, we hypothesized that patients older than 50 years would have significantly lower joint space width compared to younger patients.

Methods

Adult patients with hip pain were prospectively enrolled and each had single-leg and double-leg weightbearing and supine anteroposterior pelvis radiographs in a standardized position. Two independent investigators determined minimal joint space width by measuring joint space width at the lateral sourcil, middle sourcil and fovea of the hip. Differences between minimal JSW as well as interobserver reliability (interclass correlation coefficient, ICC) were calculated. One and 2-way analyses of variance (ANOVA) were used to compare the measurements. Power analysis determined that recruitment of 30 patients was necessary to achieve 90% power. P<0.05 was considered significant.

Results

Thirty-one consecutive adult patients were prospectively enrolled after informed consent and institutional review board approval. The mean ± SD age of participants was 53.8 ± 14.1. Female and male participants comprised 61.3% and 38.7% of the sample, respectively. Interobserver reliability was good (0.75 = ICC = 0.9) at the lateral sourcil and excellent (ICC > 0.9) at the middle sourcil and fovea. No significant differences in joint space width were found between supine or weightbearing radiographs for any pelvis site (P>0.770). Joint space width was significantly lower in those over 50 years of age as compared to younger patients for all stances (P=0.002).

Conclusion

These findings suggest that either weightbearing or supine anteroposterior pelvis radiographs can be used to evaluate hip joint space width. Thus, orthopaedic surgeons may be able to avoid obtaining multiple radiographs for patients who are being evaluated for hip preservation surgery presenting with hip pain.