Page 196 - Reconstructive Techniques in Musculoskeletal Tumor Surgery

Chapter 9
of bushing wear and of loosening, the latter by reducing torsional stresses at the implant-bone interface5, 7, 8. Myers et al6 reported a reduction in loosening rates after the introduction of rotating hinges, although it is unclear whether this reduction should be ascribed to the rotating hinge, the HA-coated collar, or a combination of both6. We are of the opinion that uncemented HA-coated implants with a rotating hinge o er the best possibility to achieve stable xation and therefore durable results, although we cannot de nitively support this contention from our results. Loosening appeared to be a particular problem in those implants that were used as a revision of a previously failed reconstruction. Foo et al31 discussed the di culties encountered with the use of uncemented MUTARS prostheses after failed allograft reconstructions. We concur with their conclusion that cemented xation is preferred in case of poor remnant bone quality as may be the case after allograft reconstruction or loosened endoprostheses.
Structural complications (Henderson type 3) occurred in 15%. Introduction of the PEEK-OPTIMA lock has not resulted in a reduction of long-term structural complication rates. Since 2010, we routinely use the MUTARS metal-on-metal locking mechanism because we believe this mechanism should be able to better withstand the high mechanical stresses. Our prosthetic fracture rate (3%) is comparable with the rate reported by Myers et al (2%)6 and compares favorably with other studies (5% – 7%)11, 12, 32, whereas our follow-up is among the longest reported in the literature (table 3). All three fractured implants had a total resection length of ≥ 15.5 cm and two had 12-mm stems. Previously, Gosheger et al7 reported stem fractures in four MUTARS reconstructions, all with a stem diameter of 12 mm or less. We believe that careful reaming and implantation of the largest possible stem diameter are advisable to reduce the risk of stem fractures and recommend using stems of at least 12 mm.
Infection (Henderson type 4) occurred in 13% and resulted in removal of the implant in 9%, which is comparable with most previous studies (6% – 20%)5, 6, 8, 11, 12, 14. We could not demonstrate a di erence among early and late infections with regard to the possibility of implant retention. However, three late infections occurred after operative intervention for another complication; such infections may be treated as an acute infection as opposed to late-occurring low-grade infections. Currently, we routinely use silver-coated implants, which may reduce the risk of infection and increase the likelihood of being able to retain the implant in case it gets infected7, 27. Others previously reported a reduction in the frequency of infection since the routine use of muscle aps5.
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