Abstract
Introduction
Female gender, old age (men >60y and women > 55y), severe acetabular dysplasia, poor proximal femoral bone geometry, large (>1cm) femoral head cysts, limb-length discrepancy (> 2cm) and small prosthetic head size (less than 50mm for men and less than 46mm for women) are risk factors for hip resurfacing arthroplasty (HRA).
Purpose
To present clinical and radiographic results of HRA in patients having risk factors.
Patients and methods: A total of 39 HRA was inserted in 33 patients (11 men and 22 women). Birmingham hip resurfacing (Smith & Nephew, UK) was used in 9 hips and Adept (Finsbury, UK) was used in 30 hips. Among the 30 hips inserted Adept, 11 cups were fixed with rim screws. The mean age of the patients at the time of operation was 52 years. The mean weight and height of the male and female patients were 70.4kg and 167cm, 58.5kg and 154.4cm, respectively. The median head size of the male and female patients was 50mm and 42mm, respectively. Preoperative diagnosis was primary osteoarthritis in 6 hips and secondary osteoarthritis due to aceatbular dysplasia (DDH) in 33 hips. Risk factors of HRA were listed for each patient. The Harris hip score and visual analogue pain scale (VAS) were measures of clinical outcome. Radiographic review was performed retrospectively. MRI and CT images were acquired in 29 hips and 2 hips, respectively, at a mean of 4.8 years after HRA to find periprosthetic soft tissue abnormality such as a psedotumor. Kaplan-Meier method was used to calculate implant survivorship.
Results
Two hips had no risk factor, whereas 37 hips had at least one risk factor. Risk factors were listed as follows: female gender in 27, old age in nine, severe acetabular dysplasia in 25, poor proximal femoral bone geometry in 11, head cysts in 13, limb-length discrepancy in three and small head size in 21. There were two revisions in two men. One hip was revised because of acute infection. The patient had a risk factor (old age). Another hip was revised because of cup loosening. The patient had two risk factors (severe acetabular dysplasia and small head size). The mean follow-up period for unrevised hips was 5 years (range, 2 to 8 years). The Harris hip score improved from 47.3 points preoperatively to 96.5 points at the latest follow-up (p<0.001). VAS improved from 65 preoperatively to 5 at the latest follow-up (p<0.001). Using revision for any reason as the endpoint, the Kaplan-Meier survivorship was 94.9% at 5years. No implant was loose at the latest radiographic examination. MRI and CT of the hip revealed no pseudotumor.
Discussion
In this series, only two patients had no risk factor for HRA. Although majority of our patients were women with acetabular dysplasia and small head size, clinical and radiographic results of HRA were good up to five years (Figs 1 and 2: pre- and post-operative X-ray of 49y women having five risk factors).
Conclusion
Clinical and radiographic results of HRA were good in patients who have risk factors.
