The Furlong® Hydroxy-apatite Ceramic (Supravit®) Coated Femoral Stem

The Furlong H-A.C. Supravit® Coated Femoral Stem is based on the biomechanical teaching of Pauwels and has three distinct sections providing separate functions to satisfy the stressing requirements at different locations in the femur. The distal portion prevents toggle and because it is cylindrical will not allow axial distal loading.

The distal femur is reamed 2mm larger than the size of the stem so that trabeculae bridge the gap and provide an elastic cradle. The central section is in the form of a cone to provide good transfer of body weight under hoop stressing. A cone is the most effective method of conveying compressive stress from one component to another. The proximal section is rectangular and tapered to resist torsion and to allow proximal body weight transfer, thus avoiding stress bypass. The femoral stem is fully coated with a vacuum plasma sprayed hydroxy-apatite coating of high density, purity and crystallinity, named Supravit®. This ensures no metal to bone contact and allows the transfer of all forces over the maximum surface area possible.

Furlong® Revision Plus System

JRI has introduced the Furlong® Revision Plus range of implants to add greater versatility to the current revision range. They specifically address the problems of the 'arum lily' type of femoral canal, which has a disproportionately larger metaphysis compared to the diaphysis.

The Furlong® Revision Plus range has an increased body section for the corresponding stem size in order to occupy the space of this larger metaphysis.

Supravit® Zoned Coating

Push out tests have shown an increased shear strength at the hydroxy-apatite to bone interface as a function of surface roughness. The greater surface area and interdigitation of the increased surface roughness provides an improved proximal bonding - a great advantage in revision surgery. With the Furlong® Revision Plus System the cone area of the implant needs to be in close contact with the mouth of the diaphysis, and the distal stem should not take axial bodyweight forces, the smoother Supravit® coating is required. The overall surface finish is therefore a Supravit® Zoned coating.

99% Success

The results at nine to twelve years of the use of a hydroxyapatite-coated femoral stem.

Scarlett A. McNally, John A. N. Shepperd, Charles V. Mann, Jonathan P. Walczak From Conquest Hospital, Hastings, England

Abstract

We describe the clinical and radiological outcome of 100 consecutive total hip replacements in 86 patients using the JRI Furlong hydroxyapatite-coated femoral component. The follow-up was 100% at a mean of ten years (9.0 to 12.0). All 54 living patients (62 hips) were examined annually. Their mean Merle d' Aubigné score was 5.8 / 5.6 / 4.6. A total of 32 patients had died. Their notes at the last annual assessment recorded a similar outcome to that of the living patients. Radiographs showed no radiolucent lines around any femoral component and there were no signs of impending failure. One patient required exision arthroplasty, but the femoral component had been bonded satisfactorily. There have been no other revisions of femoral components. Our findings suggest that the hydroxyapatite coating gives a satisfactory prosthesis-bone interface which is preferable to any other system.

Journal of Bone and Joint Surgery, April 2000
(J Bone Joint Surg (Br) 2000:82-B:378-82.)

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