Page 215 - Reconstructive Techniques in Musculoskeletal Tumor Surgery

A number of factors should be considered. During pelvic resection, patients are positioned in the lateral decubitus position, allowing them to be rotated to nearly prone or supine positions. As a result, during reconstruction, it can be hard for the surgeon to adequately assess how the implant should be inserted. It was hypothesized that modularity of the implant would resolve part of these di culties, because it would allow for adjustment of acetabular cup orientation – even after the stem has been implanted. With the LUMiC prosthesis, modularity was introduced in the eld of pelvic reconstruction. In our study on the short- term clinical results of LUMiC endoprosthetic reconstructions, we found that recurrent dislocations occurred in four out of 47 patients (9%), one of whom had a rst dislocation after resection of an extensive recurrence40. Although results are di cult to compare because of inherent heterogeneity in terms of the extent of resection and surgical approach, modularity in our experience made it easier to adequately position the cup. Cup position has been reported as an important factor for prosthetic dislocation risk, functional outcome and polyethylene wear in studies on total hip arthroplasty52, 53.
Additional factors may help to further improve cup positioning in pelvic tumor reconstructions. First, computer-assisted surgical techniques can be used for adequate intraoperative visualization of prosthetic orientation. Second, modi cation of prosthetic design may allow for further intraoperative adjustment: although the acetabular cup can be rotated with reference to the stem, the acetabular cup-stem angle is xed in the LUMiC. The exact in uence of acetabular cup positioning on outcome of pelvic reconstructions should be determined in future studies.
In an attempt to further reduce the risk of dislocation, the possibility of dual- mobility articulation was introduced for the LUMiC prosthesis. Previously, it was reported that dual-mobility cups can be e ective in treatment of recurrent instability in total hip replacements or instability encountered during hip revision arthroplasty54. Interposition of a mobile polyethylene component increases the e ective head diameter and allows greater movement of the femoral head before subluxating or dislocating55, 56. Indeed, we found that the risk of dislocation was signi cantly lower in reconstructions with a dual-mobility cup, as compared with conventional acetabular cups. We are of the opinion that any internal hemipelvectomy for a primary tumor should be reconstructed with a dual-mobility cup to reduce the risk of dislocation.
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General discussion
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