FDA Devices

FDA Approved Hip Resurfacing Devices in the US

FDA New Device Approval - Birmingham Hip Resurfacing (BHR) System - P040033

The BHR, Birmingham Hip Resurfacing, offers younger, active patients more ROM, no restrictions of activities and almost no possiblity of dislocations as many of the older THR hip devices.

Derek McMinn and Ronan Treacy at the Royal Orthopaedic & Nuffield Hospitals, Birmingham, UK, have more than 9 years experience with metal on metal hip resurfacing devices. Hip Resurfacing offers a patient a bone conserving operation since the femur head does not have to be removed, just reshaped to accept the cap of the BHR.  Should  a revision be required at some time in the future, there is still an intact healthy femur allowing for a 'primary' hip without the normal complications associated with revision.

Hip resurfacing has been shown to eliminate the problems of proximal femoral stress shielding and osteolysis caused by plastic wear debris associated with traditional plastic/metal THR hips. Hip resurfacing eliminates the problems of hip dislocation and significantly reduces the problem of leg lengthening.

For patients with defects of the acetabulum, the BHR offers the Dysplasia Cup.  These are available in 6 sizes from 46mm to 66mm in 4mm increments. The Dysplasia Cups are available in 6 sizes from 46mm to 66mm in 4mm increments. The cup has 2 superolateral threaded lugs which allow for a unique screw fixation to ensure solid cup fixation in the deficient acetabulum. Structural bone grafting is not required.

Metallurgy

The BHR* is produced using the investment casting process from high carbon cobalt chrome in the As Cast micro-structural condition.

Wear studies have shown that Cobalt Chrome in its As Cast form has superior wear resistance to other forms of the alloy.

Heat treating, which includes hot isostatic pressing (HIP), solution heat treatment (HT), wrought forging or sintering modifies the microstructure, reducing the block carbides in both quantity and quality. This directly affects the wear resistance of the metal.

The importance of carbide structure has been demonstrated in independent testing with other devices. A recent publication highlighted the difference in the wear rates of heat treated and As Cast products. The cumulative linear wear rate data showed substantially more wear with the heat treated metallurgy when compared to the As Cast devices.

Cormet Hip Resurfacing

The Cormet System of metal on metal hip resurfacing was begun by Corin. The Corin system has been in use since 1991. It claims to be the older of the current hip resurfacing systems.

The Cormet Design has:

• head sizes from 40 mm to 56 mm
• 10 cup sizes from 46mm to 64 mm
• A unique Displasis cup in 5 sizes
• Small Incision instrumentation allowing it's use in Minimal Incision Surgery
• Equatorial expansion of cup to optimise the initial press fit
• Plasma sprayed Ti and HAP coating to ensure long life
• 98% survivorship in patients at seven years and average age of 50
• Modular head allow revision to a large diameter THR if needed

In the late 1980’s Corin collaborated with a group of UK orthopaedic surgeons to develop a metal-on-metal resurfacing hip designed to provide a solution for treatment of this high demand patient group. This new generation of metal-on-metal hip resurfacing implants offered a number of key advantages to these patients compared to conventional total hip replacement:

• Hip Resurfacing is a conservative operation, since the femoral head and neck are not removed - the femoral head is simply reshaped and resurfaced with a metal cap.
• Elimination of polyethylene in the bearing removes the possibility of polyethylene-induced osteolysis and accompanying failure of the implant.
• The metal-on-metal bearing is expected to last much longer than a conventional metal-on-polyethylene bearing, delaying the need for revision surgery in high demand patients.
• The large diameter bearing is much more stable than the small diameter bearing of a conventional total hip replacement, all but eliminating the risk of dislocation and allowing patients to return to a more active lifestyle.

Unlike a total hip replacement, a surface replacement is designed to conserve more of your natural thigh bone. By saving all of this bone stock, your physician is able to more accurately reproduce your natural anatomy.

Wright's new CONSERVE® PLUS Total Resurfacing Hip System has many design advantages:

• Designed to preserve bone
• Designed to more accurately reproduce a patient's anatomy
• Designed to contain no plastic parts
• Designed to allow patients to maintain an active lifestyle
• Designed to more easily allow revision (if necessary) since it does not violate the femoral canal

The CONSERVE® PLUS Total Resurfacing Hip System is composed of the following parts: the CONSERVE® PLUS Acetabular Shell and the CONSERVE® PLUS Femoral Component. Both parts are available in many different sizes.