Groin pain after metal on metal hip resurfacing: mid-term follow-up of a prospective cohort of patients

Abstract

Background and purpose: Groin pain after metal on metal hip resurfacing has been previously reported. The purpose of this study was to determine the natural history of a cohort of patients with groin pain after hip resurfacing previously reported on and incidence of revision surgery.

Methods: Our group previously reported an 18% incidence of groin pain at a mean of 18 months post hip resurfacing. This cohort of groin pain patients was prospectively followed. Patients were evaluated using a visual analog pain rating score, the University of California at Los Angeles (UCLA) Physical Activity Index, and the Western Ontario and McMaster Universities Osteoarthritis (WOMAC) Index. Functional outcome scores were compared from initial to latest follow up using the paired Student's t test. Further diagnostic evaluation and/or intervention or other complication was also recorded.

Results: The latest mean follow up from surgery was 63 ± 15 months. The mean pain rating, UCLA, and WOMAC scores all improved at latest follow up, although WOMAC score improvement was not statistically significant. Mean pain rating score improved from 5.2 ± 2.0 to 2.5 ± 1.4 (p = 0.0001). UCLA activity score improved from 6.4 ± 2.0 to 6.9 ± 1.6 (p = 0.03). Total WOMAC score improved from 75.6 ± 20.5 to 84.5 ± 14.8 (p = 0.15). Only one patient was revised for an adverse local tissue reaction.

Conclusion: Groin pain post hip resurfacing has a multifactorial etiology, and in the vast majority of cases improves over time with no significant functional limitations. However, the surgeon should be aware of the many potential causes, and help minimize the possibility with proper patient selection and surgical technique.

Keywords: groin pain; hip resurfacing; metal-on-metal.

Fig. 1

Graphic comparison of the visual analog pain rating scale and UCLA scores at short- and mid-term follow-up. F/U1 was at a mean of 18 months post-surgery. F/U2 was at a mean of 63 months post-surgery. There is a statistical difference between the visual analog pain rating scores at the two follow-up points (F/U1=5.2±2.0, F/U2=2.5±1.4; p=0.00001). There is a statistical difference between the UCLA scores at the two follow-up points (F/U1=6.4±2.0, F/U2=6.9±1.6; p=0.03)

Fig. 2

Graphic comparison of the WOMAC scores and short- and mid-term follow-up. F/U1 was at a mean of 18 months post-surgery. F/U2 was at a mean of 63 months post-surgery. There is no statistical difference between any of the WOMAC individual or total domain scores at the two follow-up points. Pain: f/u1=77.6±20.2, f/u2=88.1±13.2; p=0.09; stiffness: f/u1=71.1±24.7, f/u2=75.7±21.2, p=0.31; function: f/u1=75.5±20.7, f/u2=85.5±15.1, p=0.15; total: f/u1=75.6±20.5, f/u2=84.5±14.8, p=0.15

Fig. 3

Cross-table lateral hip radiograph demonstrating retro-acetabular component. a Cross-table lateral radiograph of the left hip 12 months post-surgery. b Cross-table lateral radiograph of the left hip 35 months post-surgery. The yellow arrows outline the new areas of radiolucency at least 1 mm around the acetabular component in De Lee and Charnley zones 1 and 3. These radiolucencies measure 1–3 mm

Fig. 4

Graphic comparison of the WOMAC scores and short- and mid-term follow-up in patients who had psoas block. F/U1 was at a mean of 18 months post-surgery. F/U2 was at a mean of 63 months post-surgery. There is no statistical difference between any of the WOMAC individual or total domain scores at the two follow up points. Pain: f/u1=50.0±15.0, f/u2=93.8±6.3, p=0.08; stiffness: f/u1=45.8±14.4, f/u2=75.0±17.7, p=0.32; function: f/u1=50.0±16.3, f/u2=91.2±12.9, p=0.16; total: f/u1=49.7±14.0, f/u2=88.9±10.9, p=0.15