Page 224 - Reconstructive Techniques in Musculoskeletal Tumor Surgery

Chapter 11
be reduced to one-third of the stem length. MUTARS stems are coated for more than one third. Although resorption of the outer cortex is often evident following uncemented xation, particularly in the zone nearest to the reconstructed joint, we did not observe this as a reason for implant failure in our long-term follow-up study58. This supports our idea that this process stabilizes over time, and therefore, the clinical relevance of the phenomenon remains unclear.
For biological reconstructions, structural complications can be divided into (1) osteosynthesis material breakage leading to construct instability, and (2) fractures through the graft. The most common cause of osteosynthesis material breakage is metal fatigue. The occurrence of fatigue fractures is likely associated with diastasis at the osteotomy junction and delayed or nonunion; repetitive mechanical stresses on the osteosynthesis materials will eventually lead to failure. Fractures are a serious complication of segmental allograft reconstructions, occurring in 16-29% of patients33, 101, 113, 123. Its treatment is problematic because the fracture site is generally composed of non-vascular bone tissue. Several techniques have been described for treatment of allograft fractures, including the addition of a vascularized bular graft or new allograft at the fracture site, or the application of recombinant bone morphogenetic protein-2124-126. The chance of successful healing is limited and most surgeons therefore prefer to revise the entire allograft. Vascularized grafts o er an obvious advantage over allografts in this regard.
2.4 Infection
Strategies to reduce the risk of infection after endoprosthetic reconstruction are discussed in paragraph 1.4; most of these also apply to reconstructions in the appendicular skeleton. The overall rate of deep infection after endoprosthetic or allograft reconstruction for extremity bone tumors is approximately 10%82, 127. Reconstructions of the proximal tibia are associated with a higher rate of infection (up to 36% in early series on endoprostheses)109. Some surgeons started to routinely perform a gastrocnemius muscle ap rotation, and reported that the risk of infection had reduced to 12% by doing so109. Later studies demonstrated that the e ect was less profound than was initially believed65. Moreover, dissection of the medial gastrocnemius muscle may impair functional outcome. We therefore prefer to perform a gastrocnemius muscle ap only in high-risk cases, when soft- tissue coverage is poor. Further follow-up will have to prove if this approach is equally e ective.
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