Page 87 - Reconstructive Techniques in Musculoskeletal Tumor Surgery

dual-mobility cups for any LUMiC reconstruction after en bloc tumor resection.
Owing to the frequently massive extent of soft tissue resection, muscular function
can be heavily impaired and distorted after pelvic resection. Therefore, obtaining
a stable reconstruction can be di cult. In a study on 27 reconstructions with the
“ice-cream cone prosthesis” (Stanmore Implants Worldwide, Elstree, UK), Fisher et
al6 noted that dislocations occurred mainly after type 2-3 resection and attributed
this to the fact that virtually all muscles that attached the leg to the pelvis had
been resected. The authors stated that patients should be instructed to contract
their gluteal muscles before attempting to move their leg. Although we found
no di erence in the risk of dislocation between resection types, their ‘‘buttock-up’’ 4 instruction may aid to reduce dislocation rates. We aimed to prevent dislocations
by introducing an implant that would o er optimal possibilities for cup orientation and positioning and by using large-diameter femoral heads. Orientation can be di cult with the patient loosely in lateral decubitus; in experience of the leading center, computer assistance is of added value in these situations. An in uence of femoral head size was not demonstrated in our study, whereas it has been reported that large-diameter heads o er advantages in terms of stability both in hip arthroplasty and pelvic reconstruction6, 17, 28.
Loosening occurred in three reconstructions (6%): one in a patient who received uncemented xation in a previous allograft reconstruction, one as a result of an intraoperative fracture, and one cemented stem. Our results compare favorably with the loosening rate we found in our study on the pedestal cup prosthesis (16%)9. On the other hand, Fisher et al6 reported comparable results; they described loosening in one patient with insu cient bone stock (3%). Others reported loosening of the pelvic component in 12% to 15%14, 25. Because the long axis of the conical stem is in line with the load-bearing axis, loading of the LUMiC causes it to anchor itself into the iliac wing. This is fundamentally di erent from the biomechanics of custom three-dimensional-printed or modular hemipelvic implants. Furthermore, the stem is coated with HA, which reportedly reduces the risk of loosening of uncemented implants by enhancing bony ingrowth29. For the aforementioned reasons, we consider this design suitable for long-term stable xation, and we prefer uncemented press- t xation. Possible indications for cemented xation include radiation, metastatic disease, and the inability to obtain rigid primary xation.
Infection was the most common complication (28%). Although most infections (nine of 13) were successfully eradicated with debridement and antibiotics, many
LUMiC
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