Doctors

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.

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Metal-metal Hip Resurfacing Offers Advantages Over Traditional Arthroplasty in Selected Patients

By Robert L. Barrack, MD
ORTHOPEDICS 2007; 30:725
September 2007

Total hip arthroplasty (THA) is among the most successful interventions in medicine. It is the best option for most patients with end-stage arthritis of the hip. However, THA has some limitations, and problems with THA are far from nonexistent. Revisions account for almost 20% of hip cases in the United States, and this number is growing.1 These revision cases pose a greater risk for patients.

Avoiding the need for revision would be a substantial benefit, and diminishing the morbidity should revision become necessary would be equally important. Potential problems also exist in performing a THA in many young, active patients, and hip resurfacing offers advantages in many of these areas.

Indications and Advantages of Hip Resurfacing
Managing Femoral Deformity and Suboptimal Anatomy

An uncommon, but useful indication for hip resurfacing is for patients with proximal femoral deformity, in whom a total hip can be difficult if not impossible (Figure 1). More commonly, suboptimal anatomy is an issue, as with patients in whom even the smallest stem requires reaming, which puts patients at long-term risk for stem fracture (Figure 2). Conversely, a large canal presents problems for implanting a cementless stem (Figure 3).


Avoiding Stress Shielding

The presence of a femoral stem inevitably causes some degree of thigh pain, which is more common with larger stems.2 Stress shielding occurs over time from nonphysiologic hoop stresses. The long-term sequelae include bone loss, thigh pain, and stem fracture. The only hip arthroplasty associated with maintaining or increasing bone density is metal-metal hip resurfacing.3

Preventing Limb-length Difference and Dislocation

The major long-term complications of THA leading to more morbidity, dissatisfaction, and lawsuits are limb lengthening and dislocation. With hip resurfacing, the incidence of dislocations is markedly less than with THA. In the Medicare database, 4% of THA patients experience a dislocation in the first 6 months following surgery.4

Retaining Bone Stock for Future Revisions

Another major advantage of hip resurfacing is retaining bone stock for future revisions. Conversion to a THA is more similar to a primary than a revision procedure in terms of operative time, blood loss, and clinical success.5

Enabling Patients’ Return to a High Activity Level

The most compelling argument in favor of hip resurfacing is activity level. The fastest growing segment of the THA marketplace is patients <55 years. These patients want to maintain an active lifestyle, and they shun limitations.

In a study completed this year, a survey of the leading hip surgeons in the United States was performed regarding what activities they recommend to their patients. Activities prohibited by approximately 80%, even with the new bearing surfaces or large metal heads, included virtually every activity that required any impact.6

In contrast, surgeons generally do not limit activities after hip resurfacing. In a recently published study, following hip resurfacing, 92% of patients participated in sports, and none gave up their preferred sport.7 This high level of activity apparently does not compromise the clinical result. In a study of 446 hips in patients <55 years who were given no activity restrictions, 90% of patients returned to sports, and there was only 1 revision in 2 to 8 years of follow-up.8

We are now dealing with a new generation of hip patients. They are more informed and involved, educated, and active. The concepts of maintaining bone and less activity restriction resonate with them. They know others who have had hip replacement, and they have researched all of the available data on hip replacement, including the data on new bearing options. A high percentage of these patients have rejected THA and prefer the resurfacing concept.

Conclusion
Resurfacing is not for every patient or for every surgeon. However, it offers substantial advantages in properly selected patients. Because of this, metal-metal hip resurfacing has become the fastest growing arthroplasty procedure in the world in recent years outside the United States. With the US Food and Drug Administration granting approval in 2006 for one component, and approval for a second component pending, this trend will continue for the foreseeable future.

References

Zhan C, Kaczmarek R, Loyo-Berrios N, Sangl J, Bright RA. Incidence and short-term outcomes of primary and revision hip replacement in the United States. J Bone Joint Surg Am. 2007; 89:526-533.
Vresilovic EJ, Hozack WJ, Rothman RH. Incidence of thigh pain after uncemented total hip arthroplasty as a function of femoral stem size. J Arthroplasty. 1996; 11:304-311.
Kishida Y, Sugano N, Nishii T, Miki H, Yamaguchi K, Yoshikawa H. Preservation of the bone mineral density of the femur after surface replacement of the hip. J Bone Joint Surg Br. 2004; 86:185-189.
Phillips CB, Barrett JA, Losina E, et al. Incidence rates of dislocation, pulmonary embolism, and deep infection during the first six months after elective total hip replacement. J Bone Joint Surg Am. 2003; 85:20-26.
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.
Klein GR, Levine BR, Hozack WJ, et al. Return to athletic activity after total hip arthroplasty. Consensus guidelines based on a survey of the Hip Society and American Association of Hip and Knee Surgeons. J Arthroplasty. 2007; 22:171-175.
Narvani AA, Tsiridis E, Nwaboku HC, Bajekal RA. Sporting activity following Birmingham hip resurfacing. Int J Sports Med. 2006; 27:505-507.
Daniel J, Pynsent PB, McMinn DJ. Metal-on-metal resurfacing of the hip in patients under the age of 55 years with osteoarthritis. J Bone Joint Surg Br. 2004; 86:177-184.
Author
Dr Barrack is from the Department of Orthopedic Surgery, Washington University School of Medicine, Barnes-Jewish Hospital, St Louis, Mo.

“Orthopaedic Crossfire” is a registered trademark of A. Seth Greenwald, DPhil(Oxon).

Correspondence should be addressed to: Robert L Barrack, MD, Dept of Orthopedic Surgery, Washington University School of Medicine, One Barnes-Jewish Hospital Plaza, 11300 W Pavilion, St Louis, MO 63110.

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