Comparative Arthroplasty Alternatives for the Young Arthritic
By Thomas P. Schmalzried, MD
ORTHOPEDICS 2007; 30:756
September 2007
Thomas P. Schmalzried
Hip resurfacing is embraced by patients. In principle, the attraction is similar
to smaller incisions: patient satisfaction is related to the degree of invasion
of their body.
Hip resurfacing is driven by the Internet, with an Internet pro-resurfacing
culture perceiving total hip replacement (THR) as an older technology and an
older person’s operation. This perspective is fueled by the historical risk of
dislocation, traditional activity restrictions, and concerns of component
loosening with bone loss leading to morbid revision THR. There is a paucity of
patient awareness regarding the outcomes of current-generation THR. In fact,
there is a paucity of studies comparing current-generation THR and total
resurfacing.
Indications for Total Hip Resurfacing
Total resurfacing and THR are not directly competing technologies. The
indications for hip resurfacing are more limited. Not all patients who are
candidates for THR are good candidates for resurfacing .
Categorically, total hip resurfacing should be considered for those patients at
increased risk for failure of THR. Historically, such patients are young and
healthy, with men being at greater risk than women. Patients who have been told
they are too young for THR have embraced resurfacing. The operative parameters
for conversion of a failed resurfacing to THR are similar to those for a primary
THR.(1)
With current technology, the acetabular component size and position are
essentially the same for total resurfacing and THR.2 The issues are on the
femoral side and include:
Bone Density. The risk of femoral neck fracture following resurfacing is related
to bone density, with an increased risk in women and men >65 years.3,4
Head-to-Neck Ratio. Because resurfacing occurs around the femoral neck, it is
technically helpful to have a head-to-neck ratio >1.2.
Femoral Offset and Limb Length. With resurfacing, femoral offset and limb length
cannot be changed to a practically significant degree; therefore, these
parameters should be close to normal (>120° neck-shaft angle and limb-length
difference within 1 cm).2
Focal Defects. Because focal defects undermine support for the component, large
necrotic segments or cystic defects are undesirable.5
Hips that have all 4 of these criteria are arthritic hip grade (AHG) A, which is
basically a normal hip with no cartilage. Grade B hips lack 1 factor, grade C
hips lack 2 factors, and grade D hips lack 3 factors.6
Clinical Results
In our series of more than 350 consecutive total hip resurfacings(7),
there have been no femoral neck fractures. After a 2-year minimum follow-up, AHG
was significantly associated with preoperative Harris Hip score (A>B>C),
occurrence of mild to moderate postoperative pain (A<B & C), and hip range of
motion. In other words, hips with a lesser degree of secondary arthritic changes
had a higher AHG and a better outcome. The mean UCLA activity score was 8.2, but
activity scores were higher for higher hip grades. These data support the
selection criteria and also support relatively early intervention.
During the same period, we compared our first 50 consecutive hip resurfacings in
50 patients to 44 THRs performed in 35 patients.7 Surgeries were performed by
the same surgeon using a posterior approach. The same postoperative protocol was
followed in both groups with no activity restrictions; minimum follow-up was 2
years.
As one might expect, there were differences between the two groups. Average age
was 46 years for resurfacing patients versus 55 years for THR patients.
Resurfacing patients were predominantly men and taller, and had a lower body
mass index.
Resurfacing patients had a lower preoperative Harris Hip score (ie, reported
more pain), but they had a higher preoperative UCLA activity score and greater
preoperative range of motion. The resurfacing patients had a lower mean ASA
score (ie, better general health).
On average, it took 18% longer to perform the surface replacements than the THRs.
However, total blood loss was 250 cc lower with the resurfacings (despite a
larger exposure), probably because there was no femoral canal violation or
bleeding. Less transfusions were given in the resurfacing group because of the
lower blood loss and the better general health status of the patients. There was
no significant difference in the length of hospital stay between the two
groups.(7)
With regard to outcomes, hip resurfacing patients had the same 2-year Harris Hip
score (97 versus 96). Hip resurfacing patients had greater functional
improvement, resulting in a greater increase in the Harris Hip score. The
resurfacing patients also had a greater increase in UCLA activity score and a
higher postoperative SF-12 physical score. There was no difference between the
groups in postoperative range of motion. In fact, the THR group had greater
improvement. There was one dislocation in each group.
The bottom line is both technologies performed very well in our series. Because
patient characteristics are the main determinant of outcome, we must be careful
with simple technology-based comparisons.(7)
References
1. Ball ST, Le Duff MJ, Amstutz HC. Early results of conversion of a failed femoral component in hip resurfacing arthroplasty. J Bone Joint Surg Am. 2007; 89:735-741.
2. Silva M, Lee KH, Heisel C, Dela Rosa MA, Schmalzried TP. The biomechanical results of total hip resurfacing arthroplasty. J Bone Joint Surg Am. 2004; 86:40-46.
3. Shimmin AJ, Back D. Femoral neck fractures following Birmingham hip resurfacing: a national review of 50 cases. J Bone Joint Surg Br. 2005; 87:463-464.
4. Australian Orthopaedic Association National Joint Replacement Registry 2006. Available at: www.dmac.adelaide.edu.au/aoanjrr/ .
5. Amstutz HC, Beaule PE, Dorey FJ, Le Duff MJ, Campbell PA, Gruen TA. Metal-on-metal hybrid surface arthroplasty: two to six-year follow-up study. J Bone Joint Surg Am. 2004; 86:28-39.
7. Fowble VA, dela Rosa MA, Schmalzried TP. A comparison of total hip resurfacing and total hip replacement patients and outcomes. Clin Orthop Relat Res. In press.
Correspondence should be addressed to: Thomas P. Schmalzried, MD, Joint
Replacement Institute at St Vincent Medical Center, S. Mark Taper Bldg, 2200 W
Third St, Ste 120, Los Angeles, CA 90057.
Comparative Arthroplasty Alternatives for the Young Arthritic
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