[Reproduction of the anatomy (offset, CCD, leg length) with a modern short stem hip design--a radiological study]

The purpose of the study was to analyse different parameters before and after implantation of a modern short-stem hip design.

In this prospective radiological study 250 consecutive hips with degenerative hip osteoarthritis were included (246 patients). The patients were operated by five different surgeons at 4 different hospitals and a metadiaphysial fixed short-stem prothesis (Mini Hip, Corin) was used. Standardised X-rays were performed with the same technique pre- and postoperatively in all patients. Different anatomic parameters of the hip were documented by using the pre- and postoperative Xrays (ofset, CCD angle, length of leg). All measurements were performed by an independent examiner. The 246 patients included 129 females and 117 males. The average age of the patients was 59.7 years (range: 27-82 years).

The offset only changed by + 0.28 cm (SD: 0.45 cm) after surgery. We could document only a small decrease of -0.51° (SD: 4.10°) of the CCD angle. The length of the leg increased on average by + 0.09 cm (SD: 0.34 cm). We found no difference between the measurements of female and male patients. Conspicuous was also the increasing use of small protheses (size 2) for hips with a small CCD angle and the increasing implantation of large protheses (size 9) in hips with a high CCD angle.

Our results showed that we could reconstruct the individual geometry of the hip quite well by using the metadiaphysial short-stem prothesis. The tendency of an increasing CCD angle and a decrease of the offset seems not to be existent with the design of this kind of short-stem prothesis.