Femoroplasty-augmentation of mechanical properties in the osteoporotic proximal femur: a biomechanical investigation of PMMA reinforcement in cadaver bones.

OBJECTIVE: To determine the feasibility of polymethyl-methacrylate injection into the osteoporotic proximal femur and its effect on the mechanical properties.

DESIGN: In vitro pairwise comparison of non reinforced and reinforced bones in a load to failure loading mode.

BACKGROUND: Hip fractures represent an important public healthcare problem. Continued growth in the elderly population will raise the incidence of hip fractures and their associated costs dramatically in the near future.

METHODS: Twenty pairs of osteoporotic femurs were mechanically tested either in a single-limb stance configuration or simulating a fall on the greater trochanter. From each pair, one femur was augmented with bone cement, with the contralateral femur serving as a control. The surface temperature at the femoral neck was recorded until twenty minutes after injection. The fracture load and the energy absorption were calculated. The Wilcoxon signed rank test was used to test for differences in fracture load and energy absorption between the reinforced femurs and the native controls.

RESULTS: Volumes of 28-41 ml of cement (mean, 36 ml) could be injected. The increase of surface temperature at the femoral neck ranged from delta18.4 to delta29.8 degrees C. For the single limb stance configurations, the peak fracture load was increased by 21%, (P < 0.002) and for the simulated fall on the hip by 82%, (P < 0.002). The corresponding values for energy absorption were +48%; and +188% (P < 0.002) respectively.

CONCLUSIONS: The feasibility and mechanical effectiveness of the in vitro procedure could be demonstrated. The heat generation due to polymethyl-methacrylate polymerisation is high.

RELEVANCE: Prophylactic reinforcement of the femur could become a treatment option to solve the problems with osteoporotic hip fractures in patients at risk. Reinforcement materials with less exothermic reaction need to be evaluated further and also the feasibility of fracture repair after reinforcement.