Alternative Bearing Surfaces (Hip)
Presented at AAOS by Dr. Peter J. Brooks on Tuesday, March 24, 2015 7:00 AM

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

INTRODUCTION:

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.

METHODS:

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.

RESULTS:

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%.

CONCLUSIONS:

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