BRINGING SCIENCE TO TREATMENT

Scratching beneath the surface: hip resurfacing arthroplasty in athletes

Hip osteoarthritis is an uncommon finding in the active young population, and its incidence increases with age. For the relatively young athlete who desires to continue training and competing, the diagnosis of hip OA may pose a dilemma. Chris Mallac shines a light on hip resurfacing in athletic populations and provides rehabilitation guidelines for practitioners.

Rugby League – England v New Zealand – KCOM Stadium, Hull, Britain – England’s George Burgess and New Zealand’s Kodi Nikorima in action Action Images/Ed Sykes

English Rugby League player George Burgess recently underwent a hip resurfacing arthroplasty (HRA) to return to the elite level sport. This follows the successful return of Sean O’Brien to the international Rugby Union scene after undergoing a similar procedure. These are the first publicly documented cases of young elite-level contact sport athletes undergoing HRA to return to competition.

The primary form of treatment of advanced hip osteoarthritis is total hip replacement (THR). Practitioners are hesitant to advise THRs in younger athletic populations due to the anticipated breakdown of the mechanical components of the prosthetic over a 10–15-year period. For this reason, surgeons are most often reluctant to perform THR on those younger than 60 years old.

Hip resurfacing arthroplasty is an alternative to THR, and younger patients with decent femoral head bone stock may have successful outcomes. In addition, this allows future revisions to THR in the event of HRA failure.

The surgical procedure

In HRA, surgeons place an acetabular cup into the socket, and a thin layer of the femoral head is removed and capped with a prosthesis. The ‘cap’ is similar to the native femoral head and articulates directly with the acetabular component. The components are typically metal on metal (MoM). The size approximates the native hip joint architecture and allows a greater range of motion compared with the smaller components used in a THR (see figure 1)(1,2).

Figure 1: The difference between THR and HRA

Surgeons replace the femoral head and the damaged acetabulum with metal, plastic, or ceramic component in a traditional THR. In comparison, the femoral head is not removed in an HRA but is trimmed and capped with a smooth metal covering. The damaged bone and cartilage within the socket are removed and replaced with a metal shell.

Surgical outcomes

Hip resurfacing arthroplasty offers greater retention of the biomechanical characteristics of a typical hip joint, lower dislocation rates, high femoral bone preservation, and potentially easier revision surgeries in active young patients(3,4,5). The type of sporting activity, level of impact, and repetition of hip loading cycles influence the level of wear and breakdown on hips treated with MoM. The surgical technique and type of device are also essential to allow clearance between the resurfaced head of the femur and the acetabular component(6).

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The benefits of MoM HRA(4,5,6).

  1. Mimics the anatomy of the natural hip joint.
  2. Avoids overlengthening of the limb
  3. Preservation of the femoral head and neck
  4. Inherent stability and reduced risk of dislocation
  5. High resistance to wear

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The athlete’s age and size of the femoral prosthesis impact the surgery’s success rate, with athletes younger than 55 years of age and femoral heads >50mm showing a success rate of 96.3%(7). In addition, researchers at the Hospital for Special Surgery in New York concluded that in professional athletes, HRA surgery for hip OA and femoroacetabular impingement (FAI) allowed for 100% return to elite level sports activities, with 75% being able to compete for at least one year(1).

The mean time to return to running following HRA is 16.4 weeks, with >90% of athletes returning to preoperative activity levels(8). One critical outcome for HRA is the restoration of typical gait characteristics, whereas THR may negatively alter gait mechanics(9). However, no surgery is without its risks, and the most common post-surgical complication is the aseptic loosening of HRA components(10).

The factors that lead to poor prognosis in HRA(3):

  1. Gender

The rate of failure in females is approximately three times greater than males at the 10-year follow-up. This may be due to inherent smaller femoral head size, a greater chance of fracture of the femoral neck due to poorer bone mineral density, or malformed acetabular sockets from congenital abnormalities.

  1. The femoral head size

A femoral head size <50mm may lead to greater wear on a smaller surface area and less lubrication around the femoral head.

  1. Congenital hip disorders

Childhood hip disorders influence the architecture of the acetabular component.

  1. Poor inherent bone stock

Co-morbidities such as rheumatoid arthritis and avascular necrosis could impact the bone stock.

A further consideration is that an HRA requires a much larger incision to access the acetabulum. This requires surgical detachment of the gluteus maximus from the femur and leads to post-operative scar tissue, pain, and potential loss of gluteal function(11).

Furthermore, significant wear of the MoM prosthesis may lead to elevated metallic ion levels and an adverse reaction. The high levels of these ions may persist long term and lead to prosthetic loosening, autoimmune responses, and cardiotoxic or genotoxic side effects(4,12).

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Surgical challenges of HRA(13).

  1. The surgical incision is extensive to expose the femoral head.
  2. The acetabular component may be difficult to implant in hip dysplasia.
  3. Structural deformities around the head and the neck of the femur may make the fixation of the femoral cap challenging.

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Rehabilitation

Post-operative rehabilitation requires early controlled motion to prevent disuse atrophy and associated hip stiffness. As tolerated, early mobilization is encouraged with crutches for balance and not to offset weight-bearing (see table 1). In high-impact and contact sports, the rehabilitation period is protracted (six to nine months) due to the risk of femoral neck fracture(1).

Table 1: Rehabilitation guidelines following HRA(1,14).

 GoalDuration (weeks)Guidelines
Phase 1Protection 1 - 4 FWB on crutches as tolerated.
Progress pain-free ROM of the hip.
Gait retraining
Proximal hip muscle control.
Balance and proprioception
Phase 2Restore Range of Motion (ROM)5 - 12Continue to improve hip ROM – stretching anterior hip capsule, iliotibial band, and hip flexors.
Restore functional hip strength.
Aid-free mobility.
Graded return to 80% preoperative function.
Phase 3Regain strength and function12+Full ROM
Progress strengthening
Introduction of sports-specific skills and activities.
Return to low-impact activities at three months.
Return to high impact activities at six months (allows time for bone density of the femoral neck to increase).

Conclusion

Hip resurfacing arthroplasty is a viable alternative for active young individuals with hip OA. Males with sufficient bone stock and a femoral head diameter >50mm may achieve the most favorable outcomes. In addition, a successful HRA surgery and robust rehabilitation may allow a return to high-impact sports such as running, and cutting sports. Practitioners should clinically reason and select athletes based on the criteria that support a favorable prognosis and understand the sports-specific rehabilitation requirements for returning to high-level competition.

References

  1. The Ortho J of Sports Med, 2021. 9(5), 1-8.
  2. D. (2009). Modern Hip Resurfacing. Springer-Verlag London Limited
  3. J of Ortho, 2021.23, 123–127
  4. Am J Sports Med, 2007. 35(5):705–711.
  5. J Bone Joint Surg, 2006, 88-B:721-6.
  6. Bone Joint J 2019;101-B:1186–1191.
  7. Nat Joint Replace Reg AOANJR. Hip, Knee & Shoul Arthro Ann Rep
  8. Amer J of Sports Med, 2012. 40(4). 889-894.
  9. J Arthroplasty 2007; 22:100.
  10. Bone Joint J, 2020;102-B(10):1289–1296.
  11. Acta Ortho 2013; 84 (3): 246–253
  12. Bone Joint Surg, 2011;93-B:572-9
  13. The J of Arthroplasty, 2007; 22(7), Suppl. 3. 61-65.
  14. Clin Orthop Relat Res. 2012;470(1):299-306
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