Resurfacing Hip Replacement (RHR)

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Introduction
Surgical Approaches
Advantages
Disadvantages
Indications
Contraindications
Possible Complications
Recovery

Introduction

Resurfacing Hip Replacement (RHR) or Resurfacing Arthroplasty (RA) replaces the surface of the femoral head. This is the top part or “head” of the bone in the upper leg (the femur) and is subject to wear caused by arthritis. Only the surface of the femoral head will be reshaped and resurfaced during RHR. This leaves more of the bone in place and does not remove the femur neck shaft as occurs with total hip replacements.

Surgical Approaches

Access to the hip joint takes advantage of the muscular planes surrounding the joint. There are four approaches.

Anterior (front) Approach: The anterior approach has been revitalised for minimally invasive surgery (MIS).
Lateral (side) Approaches: The anterolateral approach is the most commonly used approach for total hip replacements.; The direct lateral approach exposes the hip joint by detaching the upper end of the thigh bone (the greater trochanter).
Posterior (rear) Approach: The posterior approach is the second most common approach when performing a total hip replacement and commonly used for minimally invasive surgery (MIS).

Advantages

Preservation of the femoral head/neck
Low-wear rate
Maintenance of biomechanics of the hip joint
Reduction in periprosthetic osteolysis

Resurfacing hip replacements are used for patients who have a higher activity profile as compared with others of similar age, as it allows for preservation of femoral bone stock. Patients with neuromuscular disorders, those on immunosuppressant therapy, or those who have a previous history of sepsis in the hip region, may benefit from such resurfacing devices. The shape of the hip joint allows for inherent constraints and stability, as the radius of curvature of the acetabulum matches the articular surface of the femoral head. Therefore, resurfacing the articular surfaces makes fundamental sense.

The concept of RHR remains attractive to the high activity profile patient as it allows for preservation of femoral bone stock. The Federal Drug Administration (FDA) has approved the use of metal on metal devices in the USA.

To accommodate the metal shell, a minimum amount of bone is shaved from the femoral head. The femoral canal is not violated, and the anatomy and biomechanics, as well as stability of the hip joint, are preserved (see conventional hip replacement). This inherent stability reduces the dislocation rate as compared with a conventional hip replacement. The operative technique is more difficult than a total hip replacement and requires an orthopaedic surgeon with a specialist interest in hip problems to do the surgery.

A metal on polyethylene bearing articulation can generate 500,000 polyethylene wear particles for every step the patient makes. Wear debris is dramatically reduced with metal on metal articulations; the volumetric wear is decreased by some sixty fold. Evert Smith coined the phrase “a lysis crisis” identifying the significant resorption of bone surrounding the implant, due to debris mainly from acrylic cement but also from polyethylene and metal particles.

The design and machining of the implant is critical, as is the optimum acetabular cup metal shell clearance, which allows for lubrication of the articulation.

There are now around fifteen types of modern RHRs on the market. The number of components used in the UK (as documented in the National Joint Registry for England and Wales) initially increased from 2638 in 2003 to 6638 in 2007, with a fall in use to 4099 in 2009.

In the Australian National Joint Replacement Registry, females are reported to have more than twice the cumulative percent revision than males, 8.7% compared with 3.8%. There is no significant difference between genders in the risk of revision after adjusting for femoral component head size. At 7 years, patients with a femoral head size component 44mm or less, have more than quadruple the risk of revision compared with patients in whom a femoral head component 55mm or more has been used.

On 22 April 2010 Medical Device Alert [MDA/2010/33] was generated, due to reports received by the Medicines and Healthcare Products Regulatory Agency (MHRA) UK. In the revision of these implants, soft tissue reactions were noted, which may be associated with unexplained hip pain.

On 7 September 2010 a further Medical Device Alert [MDA/2010/069] was issued for the DePuy ASR system, which includes the ASR surface replacement heads for hip resurfacing arthroplasty, the ASR XL femoral heads for total hip replacement and ASR acetabular cups for hip resurfacing arthroplasty or total hip replacement.

DePuy Orthopaedics, Inc. removed the ASR system from the market and established a website for patients to gain information concerning their implants and further treatment.

Disadvantages

Technically demanding operation
Fracture of neck of femur
Avascular necrosis of the femoral head
Leg length discrepancy
Pain
Loosening and lysis
Dissemination and elevation of metal ions
Fluid collections
Cystic and/or solid masses - 'pseudotumours'
Inflammatory reaction and tissue necrosis
Potential carcinogenesis

The relative contra–indications for RHR are related to abnormalities of the bony architecture of the pelvis and femur, as these cannot be corrected, or the device cannot be correctly and accurately seated. It is more appropriate to treat an elderly patient with osteoporosis with a conventional total hip replacement.

Femoral neck fractures occur in about 1.5% of patients and tend to happen in the early period following the procedure. Like avascular necrosis (bone cell death), femoral neck fractures are a unique complication of RHR. With avascular necrosis, there is subsequent progressive collapse of the femoral head. Both conditions require conversion to a THR to remove the metal on metal bearing surface.

When there is loss of bone in the proximal femur and problems of leg length discrepancy then an alternative device should be selected for example a ceramic on ceramic THR.

The Nuffield Orthopaedic Centre, Oxford have identified that patients at high risk of problems with resurfacing arthroplasty are those with small femoral heads, and young female patients. (Pandit H, Glyn-Jones S, McLardy-Smith P, et al. Pseudotumours associated with metal-on-metal hip resurfacings. J Bone Joint Surg 2008; 90B: 847-51 and Australian National Joint Replacement Registry, 2009).

Debris is generated from any bearing surface. Cobalt and Chromium ions can cause pain, lysis and loosening, dissemination and elevation of metal ions, fluid collections and cystic and/or solid masses - ‘pseudotumours’. This term was originally used to describe swellings around the hip joint which were associated with resurfacing hip replacements. An inflammatory reactions and tissue necrosis in the periprosthetic region with or without periprosthetic fractures of the acetabulum and/or femur have also been documented. Hip implant failure secondary to an adverse reaction to metal debris (ARMD) is the ‘hot’ issue in orthopaedics today. The response can occur with any metal on metal bearing, whether it is a resurfacing hip replacement or total hip replacement.

Metal wear products are known to be transported from the implant site and may be stored in numerous tissues in the body and eliminated in urine. There remains a possibility that metal bi-products, particularly Cobalt and Chromium ions, can induce carcinomatous changes. Due to the long latent period (around fifteen to thirty five years) between exposure and the time of tissue transformation, the correlation between the presence of an implant and the development of cancer, is difficult. Careful long term surveillance of resurfacing hip replacements is therefore essential.

Indications

Patients who have a high activity profile and who have minimal loss of bone architecture.

Contraindications

Patients who have loss of bone architecture, poor bone quality, focal bone defects, and an abnormal anatomy of the hip region.
Small sized femoral heads – these patients are, more often than not, female.
Pregnancy
Renal Insufficiency

Possible Complications

Dislocation: When the ball of the femoral component is dislocated from the acetabular cup. This is less common with RHR due to innovations in big head technology.
Infection: A bacterial invasion of the hip joint.
A lengthened or shortened limb.
Fracture of femur: A crack or break of thigh bone.
Femoral neck fracture: A crack or break in the femoral neck.
Avascular necrosis of the femoral head: Death of the bone in the head.
Vascular injuries: Penetration or incision of an artery or vein.
Non union of the greater trochanter: Following an osteotomy, the bone fails to unite.
Heterotopic ossification: New bone formation where bone is not normally present.
Stem breakage: A crack or fracture of the femoral stem.
Loosening: Loosening of the hip joint prostheses.
Wear: Erosion of the surface where two materials are in contact with one another.
Pseudomembranous colitis: A bowel problem related to antibiotic treatment.
Anaesthetic complication: (Rare) Complications may result from a general and/or spinal or epidural anaesthetic.
Death: (Rare).

Recovery

The first day most patients will have had their intravenous drip removed. The physiotherapist will see you after surgery and from then on begin with muscle strengthening and stretching exercises. You will be taught the safe way of getting in and out of bed.

You will learn how to use a support by the physiotherapist and you will be encouraged to take exercise on a regular basis. By the time of discharge from around 3 to 7 days you will be able to perform all activities unassisted. You will be able to go home in a car and it is best to have some help at home.

Walking is good for your resurfacing hip replacement and excellent exercise. Non-impact sports are advisable and these include swimming, cycling and golf. Your functional ability will improve rapidly week by week until you are able to drive a car at 6 weeks.