Defining the impaction frequency and threshold force required for femoral impaction grafting in revision hip arthroplasty. A human cadaveric mechanical study.

BACKGROUND AND PURPOSE: The two most common complications of femoral impaction bone grafting are femoral fracture and massive implant subsidence. We investigated fracture forces and implant subsidence rates in embalmed human femurs undergoing impaction grafting. The study consisted of two arms, the first examining the force at which femoral fracture occurs in the embalmed human femur, and the second examining whether significant graft implant/subsidence occurs following impaction at a set force at two different impaction frequencies. METHODS: Using a standardized impaction grafting technique with modifications, an initial group of 17 femurs underwent complete destructive impaction testing, allowing sequentially increased, controlled impaction forces to be applied until femoral fracture occurred. A second group of 8 femurs underwent impaction bone grafting at constant force, at an impaction frequency of 1 Hz or 10 Hz. An Exeter stem was cemented into the neomedullary canals. These constructs underwent subsidence testing simulating the first 2 months of postoperative weight bearing. RESULTS: No femurs fractured below an impaction force of 0.5 kN. 15/17 of the femurs fractured at or above 1.6 kN of applied force. In the second group of 8 femurs, all of which underwent femoral impaction grafting at 1.6 kN, there was no correlation between implant subsidence and frequency of impaction. Average subsidence was 3.2 (1-9) mm. INTERPRETATION: It is possible to calculate a force below which no fracture occurs in the embalmed human femur undergoing impaction grafting. Higher impaction frequency at constant force did not reduce rates of implant subsidence in this experiment.

Assessment of a new undergraduate module in musculoskeletal medicine.

BACKGROUND: Despite the high prevalence of musculoskeletal disorders seen by primary care physicians, numerous studies have demonstrated deficiencies in the adequacy of musculoskeletal education at multiple stages of medical education. The aim of this study was to assess a newly developed module in musculoskeletal medicine for use at European undergraduate level (i.e., the medical-school level). METHODS: A two-week module in musculoskeletal medicine was designed to cover common musculoskeletal disorders that are typically seen in primary care. The module incorporated an integrated approach, including core lectures, bedside clinical examination, and demonstration of basic practical procedures. A previously validated examination in musculoskeletal medicine was used to assess the cognitive knowledge of ninety-two students on completion of the module. A historical control group (seventy-two students) from a prior course was used for comparison. RESULTS: The new module group (2009) performed significantly better than the historical (2006) control group in terms of score (62.3% versus 54.3%, respectively; p < 0.001) and pass rate (38.4% versus 12.5%, respectively; p = 0.0002). In a subgroup analysis of the new module group, students who enrolled in the graduate entry program (an accelerated four-year curriculum consisting of students who have already completed an undergraduate university degree) were more likely to perform better in terms of average score (72.2% versus 57%, respectively; p < 0.001) and pass rates (70.9% versus 21.4%, respectively; p < 0.001) compared with students who had enrolled via the traditional undergraduate route. In terms of satisfaction rates, the new module group reported a significantly higher satisfaction rate than that reported by the historical control group (63% versus 15%, respectively; p < 0.001). CONCLUSIONS: In conclusion, the musculoskeletal module described in this paper represents an educational advance at undergraduate (i.e., medical-school) level as demonstrated by the improvement in scores in a validated examination. As pressure on medical curricula grows to accommodate advancing medical knowledge, it is important to continue to improve, assess, and consolidate the position of musculoskeletal medicine in contemporary medical education.