Resurfacing Hip Replacement (RHR)

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Introduction
Surgical Approaches
Advantages
Disadvantages
Indications
Contraindications
Possible Complications
Recovery

Introduction

Resurfacing Hip Replacement replaces the surface of the femoral head (the top of the femur). This is the top part or “head” of the bone in the upper leg that is subject to wear caused by arthritis. Ordinarily, 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 like total hip replacement.

Surgical Approaches

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

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. Patients with neuromuscular disorders and 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.

There are now fifteen types of modern RHRs on the market responding to the increased use of these devices by orthopaedic surgeons. The Federal Drug Administration (FDA) has now approved a metal on metal device and one would expect a rapid increase in the use of RHRs in the USA.

The concept of RHR remains attractive to the high activity profile patient as it allows for preservation of femoral bone stock. Minimal bone is shaved from the femoral head to accommodate the metal shell. The anatomy and biomechanics as well as stability of the hip joint are preserved and the femoral canal is not violated (see conventional hip replacement). Thus the inherent stability reduces the dislocation rate as compared with a conventional hip replacement.

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.

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.

The operative technique is somewhat more difficult than a total hip replacement and does require an orthopaedic surgeon who has a specialist interest in hip problems.

Evert Smith coined the phrase “a lysis crisis” identifying the significant resorption of bone surrounding the implant from debris mainly from acrylic cement but also polyethylene and metal particles.

The tissue reaction tends to be less around metal on metal resurfacing hip replacements. The minimal response relates to the fact that there is little wear of the bearing surface and near retention of the original shiny surface finish.

Disadvantages

Fracture of neck of femur
Avascular necrosis of the femoral head
Leg length discrepancy
Dissemination of metal ions
Inflammatory reaction
Potential carcinogenesis
Technically demanding operation

The relative contra–indications for RHR are based on abnormalities of the bony architecture which cannot be corrected or the device cannot be seated due to abnormal bony contours. It is more appropriate to treat an elderly patient with osteoporosis with a conventional total hip replacement.

Femoral neck fractures tend to occur in the early period following the procedure in about 1.5% of patients, and like avascular necrosis (bone cell death), are unique complications of RHR. Avascular necrosis of the femoral head occurs with subsequent progressive collapse of the head. Both conditions require conversion to a large head metal on metal THR.

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 large head metal on metal THR.

Debris is generated from any bearing surface. Cobalt chrome ions can cause a tissue reaction in the periprosthetic region and are known to be transported from the implant site and eliminated in urine. Wear products can be distributed systemically and stored in numerous tissues in the body.

There remains a possibility that metal bi-products can induce carcinomatous changes. Because of long latent periods of around fifteen to thirty five years between exposure and the time of tissue transformation, the correlation between the presence of an orthopaedic implant and the development of cancer is difficult. Careful surveillance of resurfacing metal on metal hip replacements is essential.

Indications

Patients who have a high activity profile and minimal loss of bone architecture. In general bone quality is maintained in males to around 65 years and females to around 55 years old such that the risk of femoral neck fracture increases above these ages when utilising a resurfacing hip replacement.

Contraindications

Patients who have loss of bone architecture and poor bone quality, focal bone defects and an abnormal anatomy of the hip region.

Possible Complications

Dislocation: This occurs 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.
Leg length discrepancy.
Fracture of femur: A crack or split/break of thigh bone.
Femoral neck fracture.
Avascular necrosis of the femoral head.
Vascular injuries: Penetration or incision of an artery or vein.
Non union of the greater trochanter: The upper end of the thigh fails to unite following an osteomy.
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: The erosion of the surface of two materials 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 may be best to have some help when you return 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.