Improved implantation technique for resurfacing arthroplasty of the hip.

OBJECTIVE

Prevention of incorrect positioning of the surface replacement, whereby the center of the femoral head for the implantation of the replacement surface is ascertained by central drilling of the femoral neck under image intensifier control.

INDICATIONS

An arthritically damaged, but not too severely deformed femoral head that can be reamed without injuring the femoral neck.

CONTRAINDICATIONS

Hip ankylosis. Femoral head necrosis. Severe deformity of the femoral head. State after varus osteotomy.

SURGICAL TECHNIQUE

Using a 6-mm drill bit, the femoral neck of the affected hip is drilled from lateral to medial under anteroposterior and lateral imaging deliberately perforating the femoral head. The hip joint is exposed through a minimized invasive anterolateral, lateral, or posterior approach and dislocated. A guide rod corresponding in size to the 6-mm drill channel is inserted into the drill hole; it serves as a guide for all subsequent preparations of the femoral head, depending on the type of prosthesis. After implantation of the corresponding acetabular component, resurfacing of the femoral head is done. Reduction of the joint completes surgery.

RESULTS

In the first 14 hips the midpoint of the femoral head was ascertained by using the manufacturer's centering device. In 31 subsequent hips the midpoint of the femoral head was found by central drilling of the femoral neck. Using the centering device, the average deviation of the angle of the prosthesis from the preoperative CCD angle was 7 degrees (+/- 5.7 degrees ); for central drilling of the femoral neck it was only 3 degrees (+/- 3.4 degrees ). The exact alignment of the resurfacing component is crucial for the success of surgery. It is achieved with greater precision with central drilling of the neck than with the manufacturer's centering device.