Introduction: Progressive retroversion of the stem within the femur has been suggested to be an important initial mode of hip prosthesis failure. We have assessed the relationship between postoperative stem anteversion angle, measured with CT, and the rotational stability as measured with repeated radiostereometric analysis (RSA) with 5 years follow up.

Patients and methods: 57 patients were operated on with THA using a cemented, matt and collared stem. The achieved stem anteversion angles were measured postoperatively with 3-D CT-examinations. The patients were divided into three groups depending on their ante-version angle: ≤10°, 11°–25° and ≥25°. They were followed with repeated RSA examinations for 5 years to determine the stem migration pattern.

Results: The mean postoperative anteversion angle was 20.5° (range 1°–43°). At 5 years, all except one stem had rotated into retroversion. There was a strong correlation between the postoperative anteversion angle and later rotation into retroversion (p=0.007). The group with ≤10° of stem anteversion rotated significantly more into retroversion, seen as early as 3 months (p=0.02), but more obvious at 5 years (p=0.002) with a mean of 9.9° of retroversion compared to 3.8° in the 11°–25° group and 2.4 ° in the ≥25° group. The distal stem migration results were accordant with more migration at 5 years (p=0.008) for the ≤10° anteversion group (1.6 mm subsidence compared to 0.5 and 0.3 mm respectively). Two stems have been revised because of aseptic loosening, both with a low initial anteversion angle (7° and 1°) and large retroversion at 5 years (7 ° and 31° respectively).

Conclusion: Measured by RSA, rotation into retroversion of the femoral stem was a regular finding in this study using a conventional prosthesis design. We propose that such rotation is a common finding in hip arthroplasty, but the degree may be design sensitive. Our results strongly suggest that the initial rotational position of the femoral component during surgery is decisive for the degree of later retroversion and probably prosthetic longevity; the less anteverted position the more the stem will migrate into a more retroverted position after the operation. This rotational migratory pattern is correlated to subsidence and eventual loosening. Hence, meticulous attention should be paid to the rotational position of the femoral stem during surgery, with less than 10° of anteversion appearing deleterious. However, too much anteversion will risk impingement and possibly other unwanted biomechanical effects, and an upper limit still remains to be established.

In treatment of scaphoid nonunions age of nonunions, stability of reconstructions and particularly vitality of proximal fragments are regarded as important prognostic factors for healing. The value of preoperative MRIscans in predicting intraoperative vitality and final osseous union prospectively was investigated.

Scaphoid nonunions in 60 patients (7 female, 53 male, mean age 30 years) primarily were reconstructed between 1/2000 and 7/2003. Preop they underwent a standardized MRIscan using i.v. Gadolinium to assess vitality of proximal fragments. The scaphoids were reconstructed per palmar or dorsal approach implanting nonvascularized iliac-crest or distal radius bone grafts stabilized with cannulated or mini Herbert screws. Intraop vascularity (vital/nonvital) was documented estimating blood spots occurring on the debrided fragments cancellous surface (none/medium/many). After immobilization for 6–8 weeks osseous union was ruled out performing repeated radiographic and CT studies up to 6 months. Apart from demographic data, age and type of nonunion, intraop fragment vitality and postop osseous union were correlated to vitality stated in preop MRIs. A p-value of 0.5 was regarded as significant.

50 proximal fragments preoperatively were stated vital. Overall fragment vitality was predicted correctly in 52 patients. 5 were false negative, 3 false positive. No significant correlation between age or type of nonunion and the predicted vitality could be obtained. Osseous union was gained in 55 scaphoids. Patients with predicted avital fragments had no significantly higher incidence of osseous union than those with avital fragments.

Preop MRIscans are of value in detecting avascular proximal fragments in scaphoid nonunions. In these cases reconstruction with vascularized bone grafts is proposed. Our data however indicate that vascularity of proximal fragments is not predictive of bony healing. High rates of osseous union can be achieved even with nonvascularized grafts in pateients having avascular proximal fragments.