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The healing of critical sized segmental defects is an ongoing clinical problem. No method has achieved pre-eminence. The Masquelet technique is a relatively new innovation involving the induction of a fibrous tissue membrane around the bone defect site taking advantage of the body’s foreign body reaction to the presence of a polymethylmethacrylate (PMMA) spacer. The aim of this study was to investigate the properties and characteristics of this induced membrane and its effectiveness when used in conjunction with allograft or an allograft/autograft mix as filler materials in an ovine critical sized defect model. The resultant induced membrane was found to be effective in containing the graft materials in situ. It was demonstrated to be an organised pseudosynovial membrane which expressed bone morphogenic protein 2 (BMP2), transforming growth factor- beta (TGFβ), vascular endothelial growth factor (VEGF), von Willerbrand factor (vWF), interleukin 6 (IL-6) and interleukin 8 (IL-8). While more new bone growth was evident in the test groups compared to the controls animals at 12 weeks, the volumes were not statistically different and no defects were fully bridged. Of the two graft material groups, the allograft/autograft mix was shown to have a more rapid graft resorption rate than the allograft only group. While the Masquelet technique proved effective in producing a membrane to enclose graft materials, its ability to assist in the healing of critical sized segmental defects when compared to empty controls remained inconclusive.

ABSTRACT:The ovariectomized (OVX) rat is widely used in osteoporosis research, but no standard model exists. The individual effects of rat age, skeletal site, and time post-ovariectomy (post-OVX) on bone have been examined. However, the relationship between them is not yet fully explored. This study examined how various combinations of rat age, skeletal site, and time post-OVX affect bone mineral and microarchitecture. The rats used were 12 (n = 28), 24 (n = 28), and 44 (n = 31) weeks old. In each age group, approximately half underwent OVX and other half underwent Sham surgeries. Bone mineral (content and density) and trabecular morphology was assessed at 2, 5, 10, 15, 20, 25, and 30 weeks post-surgery. Sites examined included the proximal tibia, spine, distal femur, and proximal femur. Overall, the proximal tibia showed the earliest and greatest differences between OVX and Sham groups. The 24-week-old group showed the best osteoporotic response. The 12-week-old group showed growth effects, whilst the 44-week-old group showed aging effects. The response of certain sites to OVX was also found to depend on the rat age used. These findings may aid in explaining discrepancies reported in the literature as well as synergistic combinations that may signify advanced conditions. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J. Orthop. Res. 29: 189-196, 2011 Keywords: osteoporosis; OVX rat; skeletal site; bone density; micro-computed tomography Osteoporosis is characterized by low bone mass leading to an increased susceptibility to fractures. 1 The ovariectomized (OVX) rat is the most widely used animal model for osteoporosis research, as it has been validated to express similar pathophysiological features of estrogen deficiency induced or post-menopausal bone loss to an adult human, 2 particularly during the early stages of osteoporosis. 3,4 However, a standard OVX model does not exist. Throughout the literature the majority of osteoporosis studies have used OVX rats ranging in age from 8-5,6 to 12-month old, 7,8 with the main focus on the proximal tibia. Previous investigators have also used various time points post-OVX in which to perform procedures such as induction of fractures, placement of implants, administration of treatments, and general data collection. Whilst many studies have been conducted to examine the individual effects of age, skeletal site, and length of time post-ovariectomy (post-OVX) on bone, the relationship between these factors and how they in turn affect bone is yet to be fully explored. The influence of age (or time) and skeletal site on non-OVX rats have been demonstrated to influence bone development. 3,9-12 Thus, it is possible that certain combinations of age, skeletal site, and time post-OVX could lead to varying levels of bone deterioration in response to estrogen deficiency. Such data may be useful for understanding discrepancies between different works as well as improving study design and interpretation.For the purpose of this study, we hypothesized that...