Fixation principles in metaphyseal bone—a patent based review

Abstract

Osteoporotic changes start in cancellous bone due to the underlying pathophysiology. Consequently, the metaphyses are at a higher risk of "osteoporotic" fracture than the diaphysis. Furthermore, implant purchase to fix these fractures is also affected by the poor bone quality. In general, researchers and developers have worked on three different approaches to address the problem of fractures to osteoporotic bone: adapted anchoring techniques, improved load distribution as well as transfer with angular stable screws, and augmentation techniques using bone substitutes. A patent-based review was performed to evaluate which ideas were utilized to improve fixation in osteoporotic, metaphyseal bone, especially in the proximal femur, and to analyze whether the concept had entered clinical use. Anchoring devices that are either extramedullary or intramedullary have a long clinical history. However, demanding surgical techniques and complications, especially in poor quality bone, are justification that such implants and their corresponding surgical techniques need to be improved upon. Expanding elements have been evaluated in the laboratory. The results are promising and the potential of this approach has yet to be fully exploited in the clinics. Internal fixators with angular stable screws open the door for many new anchorage ideas and have great potential for further optimization of load distribution and transfer. Augmentation techniques may improve anchorage in osteoporotic bone. However, the properties of bone substitute materials will need to be modified and improved upon in order to meet the demanding requirements. If we summarise the development process and the clinical use of implants to date, we have to clearly state that more factors than simply biomechanical advantage will determine the clinical success of a new fixation principle or a new implant. Instead, fracture treatment of patients with osteoporosis really needs an interdisciplinary approach!

Internal fixation of fragility fracturesof the femoral neck

“…In fact, a recent cohort study including 140 patients with femoral neck fractures did not find an association between BMD and failure rate following internal fixation (Viberg et al 2014). Numerous attempts have been made to improve the stability of an implant operated into porous bone (Curtis et al 2005). Several options exist to anchor the implant within the femoral head: screws with varying tread designs, screws with additional talons, pins with hooks and helical blades (Olsson et al 2002, Bramlet and Wheeler 2003, Roerdink et al 2009, O'Neill et al 2011.…”

Fractures of the hip and osteoporosis

“…In addition to the development of newerimplants, 15,16 bone substitutes may be beneficial for the augmentation of implant stability in these fractures. Studies on the However, before any conclusions can be made there are several issues to be considered when cements are implanted in general and in patients with hip fractures in particular.…”

“…[8][9][10][11][12][13][14] In order to address this problem, new implants more applicable for fixation in osteoporotic bone have been developed. 15,16 Another option, however, to avoid failure of fixation is to augment the bone stock or to enhance the implant-bone interface and thus the primary stability. [17][18][19][20][21][22][23] In this context, the use of autograft is still the method of choice for bone grafting because of its biological characteristics, [24][25][26] but in the osteoporotic environment it is not suitable due to its poor mechanical properties.…”

Absence of positive effect of black cohosh (Cimicifuga racemosa) on fracture healing in osteopenic rodent model

“…Bone mineral density (BMD) is decreased, bone micro-architecture is disrupted, and the amount and variety of non-collagenous proteins in bone are altered (Boonen et al, 2008). These changes occur primarily in the trabecular bone of the metaphyses, resulting in increased fragility (Curtis et al, 2005). The fracture healing process in osteoporotic bone is delayed and qualitatively reduced (McCann et al, 2008;Hao et al, 2007).…”