Dolph Houben

13 Introduction and Outline of the Thesis 1 from mechanical loads during the hypertrophic process because they are often poor structural replacements for metaphyseal defects and grossly mismatch the shape and size for humerus, femur and tibia diaphysis [22-24] . Limited donor site availability, donor site morbidity, and size/ shape mismatch at the recipient site are therefore frequent problems with VBGs [16, 22] . Due to the enhanced healing potential, a primary union rate of 61% has been reported [16] . Further evaluation of the free fibular flap as a reconstructive method will be discussed in chapter two. Currently, the use of vascularized bone autografts remain the gold standard in the reconstruction of large segmental defects since the use of vascularized composite allotransplantation requires the use of life-long immunosuppression for non-life-critical tissue allotransplantation. Other reconstructive methods Diaphyseal or periarticular defects can also be reconstructed with custom endoprosthetic replacements that allow immediate restoration of function [25-28] , but have limited longevity. Complication rates for prosthetic reconstruction range from 33% to 100% and are most serious requiring revision or amputation due to mechanical failure or infection [29, 30] . Allograft/prosthetic hybrids have generally failed due to implant loosening, fracture or separation [25, 31, 32] . The re- implantation of resected tumor bone has been described as a reconstructive method after devitalizing the tumor bone by autoclaving [33, 34] , pasteurization [35, 36] , irradiation [37] or cryotherapy [38] . Re-use of devitalized tumor bone carries the risk of incomplete tumor death and an incidence of a stress fracture and infection similar to or even greater than CBAs [30, 34] . Bone transport is best suited for modest segmental bone defects, with healing times of 1-3 years, [39] and is associated with pin-tract infections, soft tissue problems, and non-union at the docking site [40, 41] . The induced membrane technique, also known as the Masquelet technique [42] , is a two-stage procedure utilizing a cement spacer in the first stage and a mixture of autologous cancellous bone in the second stage. The downsides of this two-stage reconstruction are the requirement of a substantial time delay allowance of full weight-bearing, along with associated complications as infection, resorption, and non-union [43] . A combination of a vascularized fibula flap with CBA does provide the benefit of enhanced healing and hypertrophy capacity of VBG with the strength and bulk of a CBA in a one-stage reconstruction. This technique has been known as the Capanna technique [44] and is widely used in the reconstruction of segmental bone defects after primary tumor resection. The Capanna technique is especially suitable for the younger patient after primary tumor resection in the lower extremity [23] . It results in good long-term outcomes with relative high complication rates, reintervention rates and requires a donor site [23, 43-47] . This technique will be further discussed in Chapter 3.