EXPERIENCES AFTER 600 MINIMAL INVASIVE THR VIA THE ANTEROLATERAL APPROACH – THE SUCCESS IS IN THE DETAIL

Abstract

In fall 2004 we started with minimal invasive hip surgery at our clinic. Our requirements: Use of our standard implant system (Bicon threaded cup and Zweymüller stem), fast realization of the minimal invasive procedure through the continuation of the used, anterolateral Watson-Jones approach, modified for this technique, retaining the supine position with unchanged orientation concerning the positioning of the implant parts. Our expectations: Reduction in operative trauma through lower blood loss with less post-operative pain, less limping especially during the first weeks, less trochanter pain through the preservation of the gluteal muscle tendons, fewer posterior dislocations by preservation of the dorsal capsule, and a better cosmetic result.

The patient is placed in supine position on the standard OR table with the option of tilting the legs down. The contralateral leg lies on a leg holder in extended position, flexed by approx. 20 degrees. This allows to bring the leg in hyperextension (without hyperlordosis of the lumbar spine), adduction and external rotation during broaching the femur. The main criterion of the minimal invasivness is the preservation of the gluteal tendons and not primarily the reduction of the length of the skin incision. An extensive capsular release with partial dissection of the rectus tendon for exposure of the acetabulum is necessary. For the stem implantation a notching of the piriformis can be necessary in addition to this. During the stem preparation the soft tissues should not influence the axial entrance of the rasps into the femoral canal otherwise there is a danger of a dorsolateral perforation. Right-left-lateral-double-offset rasps and the use of manipulation rasps as trial prostheses have worked satisfactorily. Retrospective analyses of numerous peri- and post-operative data were accomplished, as well as radiological evaluations regarding the optimal position of the implanted joints, and compared with a conventional control group.

After a learning curve the OP duration was the same in both groups. The development of the haemoglobin and hematocrit levels were identical, 1/3 of the patients needed blood subsitution (autologous or stored blood). 90% of the analysed postoperative x-rays in standing position showed equal bilateral leg length corresponding to the preoperative planning, the planned offset was achieved in 93%. Deviations of the remaining were without clinical relevance. The complication rate was 2,5%.

Conclusions: The anterolaterale approach in supine position is standardised for the minimal invasive THR. The compliance with the developed implantation technique is a requirement for the optimal positioning of the prosthesis and to avoid complications. The subjective patient assessments, especially of those who experienced both methods, are impressive.