Birmingham Hip Resurfacing - Literature Review

Device Description
   
The BIRMINGHAM HIP Resurfacing (BHR) prosthesis is a metal-on-metal hip resurfacing prosthesis. The device consists of a stemmed femoral head resurfacing component designed for cemented fixation, and a hemispherical acetabular cup designed for cementless, press-fit, fixation. Both components are manufactured from high carbon, as-cast, cobalt chrome (CoCr) alloy (ASTM F75 and ISO 5832-4). The acetabular cups are configured in standard, dysplasia, and bridging designs. All acetabular cups have a single layer of integrally-cast CoCr-alloy (ASTM F75 and ISO 5832-4) beads on the outer surface that are coated with hydroxyapatite (HA) (ASTM F1185). Instrumentation sets are provided as standard; several additional instruments are available as options.

Resurfacing Femoral Head
The resurfacing femoral head is supplied in a range of eleven sizes. The femoral head central stem is parametric and varies proportionally with the external diameter. There are 6 equally spaced internal recesses intended to provide anti-rotational locking for the cement mantle.

Acetabular Cups
The standard acetabular component is supplied in a range of twenty two sizes (two for each femoral head size to address the condition of occasional head cup mismatch). For those patients with a deficiency in the superolateral aspect of the acetabulum, the dysplasia cup is available. The dysplasia cup is designed with two superolateral screw holes that accommodate CoCr-alloy dysplasia cup screws. There is a range of eleven sizes for the dysplasia cup. A bridging cup is designed with a thicker wall section than the dysplasia cup to allow for mismatch between femoral head size and surgically prepared acetabulum. The bridging cup is also designed with two superolateral screw holes that accommodate the CoCr-alloy dysplasia cup screws. The bridging cup is available in ten sizes.

Dysplasia Cup Screws
The dysplasia cup screws are threaded through a threaded lug on the superolateral aspect of either the dysplasia or bridging cup and lock in situ. The screws also lock into the posterior cortical bone of the ilium. Screws are available in sizes ranging from 24mm to 88mm, in 2mm increments.

Sizing and System Compatibility
Each femoral head resurfacing component is compatible with two standard acetabular cup sizes and one dysplasia or bridging cup size (Table 1).

Table 1: BHR Head and Cup Sizing and System Compatibility
BHR Femoral Head
Resurfacing Component
(identified by head outer
diameter)		 Mating BHR
Standard Cup Sizes
(2 cups available per
head component size)		 Mating BHR
Dysplasia Cup
Sizes		 Mating BHR
Bridging Cup
Sizes
38mm 44mm or 46mm 46mm 50mm
40mm 46mm or 48mm 48mm 52mm
42mm 48mm or 50mm 50mm 54mm
44mm 50mm or 52 mm 52mm 56mm
46mm 52mm or 54mm 54mm 58mm
48mm 54mm or 56mm 56mm 60mm
50mm 56mm or 58mm 58mm 62mm
52mm 58mm or 60mm 60mm 64mm
54mm 60mm or 62mm 62mm 66mm
56mm 62mm or 64mm 64mm 68mm
58mm 64mm or 66mm 66mm -


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2/4/2007

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