Adequate resection of malignant osseous tumors of the pelvis within wide margins is demanding surgery. To avoid disabling hemipelvectomies, during the seventies of the last century internal hemipelvectomy combined with a partial pelvic replacement had become a new surgical and meanwhile standard procedure. To achieve adequate reconstructions of the osseous pelvis custom-made replacements were recommended. In the very early stages of this type of surgical procedure using megapros-theses, individual pelvic models were manufactured but, until recently, little is known about the accuracy of such models. Thus, it was the aim of this retrospective study to evaluate this.

We analysed the charts of 24 patients (25 pelvic models) for whom an individual model of the osseous pelvis had been constructed to manufacture such a tool and to enable the surgeon a better intraoperative orientation. Two patients refused surgery. Thus, in 23 patients surgical resection of parts of the bony pelvis was performed followed by either a partial pelvic replacement (13 x), hip transposition procedure (5 x), ilio-sacral resection (4 x) or revision surgery (exchange of a partial pelvic replacement).

In all patient who received a partial pelvic replacement, the fit of the replacement was optimal, in none of them a major unplanned resection was necessary. The same was observed in patients who received a hip transposition procedure or an ilio-sacral resection.

Oncologically, in most of the patients we achieved wide resection margins (14 x). In only 5 patients the margins were marginal (4x) or intralesionsal (1 x). In two cases the aim was a palliative resection because of a metastatic disease (1x) or benign entity (1 x).

Thus, pelvic models are helpful tools to planning the manufacture of partial pelvic replacements and ensuring optimal osseous resection of the involved bone. Further attempts have to be made to evaluate the aim of navigational techniques regarding improvement of the accuracy of the osseous and the soft tissue resection.

The idea of resurfacing the femoral head instead of removing it has been attractive for a long time.

Unfortunately the results have been invariably poor if compared with contemporary available conventional hip prosthesis. In the last decade metal on metal technology with very accurate manufacturing made hip resurfacing a viable option. The main complication of this operation is early failure due to femoral neck fracture. This event is still incompletely understood and probably multi-factorial. Accurate placement of the femoral component to avoid notching the femoral neck, cementing technique to avoid over-penetration of the cement, small implantation forces and careful soft tissue handling to minimize the damage to the bone vascularity are thought to be the main issues. The ideal candidates for this operation are young and active patients because they have good bone quality and will take advantage of the improved performances that hip resurfacing can offer.

Unfortunately young men are also the group of patients at higher risk for the formation of heterotopic ossifications.). To prevent this complication radiotherapy was administered in a single dose of 6 Gy with two opposite fields of 18 MV generally the first post operative day. When we started to perform hip resurfacing we did not consider changing our protocol. Between March 2004 and May 2005, 55 hip resurfacings were performed using the ASR implant (DePuy) by a single surgeon (LM). Most males under the age of 60 received radiotherapy. There were 4 femoral neck fractures in the 23 male patients who received radiotherapy (17.3 %) and 1 fracture in the 32 patients who did not receive radiotherapy (3.1 %, Chi-square test: p= 0.07). All the fractures occurred between the 90th and the 120th postoperative day. No fractures were reported in the 12 women included in this study. What arouse our attention was the unacceptably high number of femoral neck fractures. The learning curve alone could not explain what was happening. At first the radiotherapy was not considered at all as factor but errors in the surgical technique were looked for. The clue came from the observation that there were no women in the fracture group in spite of the fact that the surgical technique was the same and also in spite of the fact that women should be at higher risk due to poorer bone quality as shown in the literature. This led us to check the incidence of fractures in the radiotherapy and in the non radiotherapy group. At this stage things became quite clear. Subsequently the histology of the specimen was re-examined with regard to this factor. Bone necrosis of the femoral head in the patients who underwent radiotherapy was much more pronounced then in other failures which show different degrees of necrosis. In conclusion there are strong indications that radiotherapy of the femoral head should not be performed in combination with hip resurfacing.