The combined effect of parathyroid hormone and bone graft on implant fixation.

Impaction allograft is an established method of securing initial stability of an implant in arthroplasty. Subsequent bone integration can be prolonged, and the volume of allograft may not be maintained. Intermittent administration of parathyroid hormone has an anabolic effect on bone and may therefore improve integration of an implant. Using a canine implant model we tested the hypothesis that administration of parathyroid hormone may improve osseointegration of implants surrounded by bone graft. In 20 dogs a cylindrical porous-coated titanium alloy implant was inserted into normal cancellous bone in the proximal humerus and surrounded by a circumferential gap of 2.5 mm. Morsellised allograft was impacted around the implant. Half of the animals were given daily injections of human parathyroid hormone (1-34) 5 µg/kg for four weeks and half received control injections. The two groups were compared by mechanical testing and histomorphometry. We observed a significant increase in new bone formation within the bone graft in the parathyroid hormone group. There were no significant differences in the volume of allograft, bone-implant contact or in the mechanical parameters. These findings suggest that parathyroid hormone improves new bone formation in impacted morsellised allograft around an implant and retains the graft volume without significant resorption. Fixation of the implant was neither improved nor compromised at the final follow-up of four weeks.

A new minimally invasive transsartorial approach for periacetabular osteotomy.

BACKGROUND: A new minimally invasive transsartorial approach for the Bernese periacetabular osteotomy was developed. We investigated whether this technique was safe and successful with regard to minimizing tissue trauma and, more importantly, whether it was possible to obtain optimal reorientation of the acetabulum. METHODS: Our experience with this approach was retrospectively assessed by means of database inquiry and the evaluation of radiographs. We assessed ninety-four procedures performed between April 2003 and August 2005 to determine perioperative and early postoperative outcome measures, the achieved acetabular reorientation, and hip joint survival. RESULTS: The mean duration of surgery was 73.1 minutes, the median perioperative blood loss was 250 mL, and the mean reduction in the hemoglobin level was 33 g/L. Blood transfusion was required following 3% of the procedures. No injuries to the great vessels or nerves, arterial thromboses, unintended extension of the osteotomy, or deep infections occurred. The postoperative acetabular reorientation was assessed by measuring the center-edge and acetabular index angles, the medians of which were 34 degrees and 3 degrees , respectively. With total hip arthroplasty as the end point, the hip joint survival rate was estimated to be 98% at 4.3 years. CONCLUSIONS: Osteotomy with use of this minimally invasive transsartorial approach appears to be a safe, relatively short surgical procedure associated with a relatively small amount of blood loss and minimal transfusion requirements. Optimal acetabular reorientation can be achieved with this technique.