Author(s): Carlos A. Higuera, MD, Bay Village, Ohio; Kurt P. Spindler, MD, Garfield Hts, Ohio; Gregory J. Strnad, MS, Lyndhurst, Ohio; Peter J. Brooks, MD, FRCS(C) Cleveland, Ohio
Hip resurfacing has been proposed as a suitable procedure for young, active patients. Given the concerns with metal-on-metal bearings, and the recall or withdrawal of certain devices, it is appropriate to review our results using a resurfacing device with a relatively good clinical record. As our experience and understanding of these bearings grew, we now describe changes to our preferred component position, and have used additional imaging to narrow our indications for this procedure, which we continue to perform in significant numbers.
We performed 1,333 hip resurfacing procedures, with minimum two-year follow up, at a single US institution following FDA approval in 2006. All patients were followed using a validated prospective observational registry, and an IRB approved database. All surgery was performed by a single surgeon, using an antero-lateral approach. The average patient age was 53.1 (12-84), and 70% (938) were male. Patients were seen at six weeks, then one, two, and five years after surgery. Our weight-bearing protocol was 75% partial weight-bearing for six weeks, then avoidance of strenuous exertion for one year, then unrestricted activity. Over time, and in response to reports of poor outcomes from other centers, we modified our target socket inclination from the traditional 45 degrees to 35-40 degrees, and introduced previously undescribed imaging strategies for patient selection. Metal ion levels and cross-sectional imaging using MRI were utilized only in symptomatic patients.
The average femoral component size in males was 51 mm, in females 45 mm. Less than 1% of cases were < 42mm. Preoperative Harris Hip Score was 59.6 + 10.6, and postoperative score was 98.7 + 3.3. Hip-related Physical Limitation score improved from a baseline of 2.6 to 6.6. There were no dislocations, no femoral component loosening, and one socket loosening (0.08%). We had two femoral neck fractures (0.15%), three deep infections requiring component removal (0.23%), and one late traumatic acetabular fracture requiring revision. One patient was revised for unexplained pain, and continues to be symptomatic.
There were three cases of excessive metal debris (0.23%), but no destructive pseudotumors. Two of these were attributed to socket malposition. The third was a small female (40 mm head) with dysplasia, accurately resurfaced, but with excessive femoral neck anteversion, and a pelvis which tipped backwards 14 degrees in the standing position. Retrieval analysis showed anterior edge loading. This case led us to modify our patient selection criteria and recommend new imaging protocols. In total, five males and six females required revision. Overall survivorship was 99.2%, at 2 to 5.7 years follow up. Aseptic survivorship in males under the age of 50 was 100%.
To our knowledge, this is the largest US series of hip resurfacing involving a single device, by a single surgeon. Hip resurfacing can be highly successful in the mid-term with careful patient selection and attention to technical detail. Metal-related complications in our series were rare, and could be explained by either inaccurate surgical technique, or by patient characteristics which we would now deem unacceptable for resurfacing. We have had very few complications, but based upon this experience we have the following recommendations:
- Aim for socket inclination of 35-40 degrees.
- Avoid resurfacing patients with head diameters less than 44 mm.
- Obtain CT scans of all females, and males with apparent hip dysplasia, in order to avoid resurfacing patients who have excessive femoral anteversion.
- Obtain preoperative standing lateral pelvis x-rays, and avoid resurfacing smaller patients whose pelvis tips backwards, risking anterior edge loading.
Disclosure: C. Higuera: 5 – KCI, Stryker K. Spindler: 5 – KCI, Stryker G. Strnad: 5 – KCI, Stryker P. Brooks: 5 – KCI, Stryker