Abstract
Pertrochanteric fractures (TF) due to osteoporosis constitute nearly half of all proximal femur fractures. TFs are treated with a surgical approach and fracture fixation is achieved using metallic fixation devices. Poor quality cancellous bone in osteoporotic patients makes anchorage of a fixation device challenging, which can lead to failure of the fracture fixation. Methods to reinforce the bone-implant interface using bone cement (PMMA) and other calcium phosphate cements in TFs have been described earlier but a clear evidence on the advantage of using such biomaterials for augmentation is weak. Furthermore, there is no standardized technique for delivering these biomaterials at the bone-implant interface. In this study, we firstly describe a method to deliver a calcium sulphate/hydroxyapatite (CaS/HA) based biomaterial for the augmentation of a lag-screw commonly used for TF fixation. We then used an osteoporotic Sawbones model to study the consequence of CaS/HA augmentation on the immediate mechanical anchorage of the lag-screw to osteoporotic bone. Finally, as a proof-of-concept, the method of delivering the CaS/HA biomaterial at the bone-implant interface as well as spreading of the CaS/HA material at this interface was tested in patients undergoing treatment for TF as well as in donated femoral heads. The mechanical testing results indicated that the CaS/HA based biomaterial increased the peak extraction force of the lag-screw by 4 times compared with un-augmented lag-screws and the results were at par with PMMA. The X-ray images from the patient series showed that it was possible to inject the CaS/HA material at the bone-implant interface without applying additional pressure and the CaS/HA material spreading was observed at the interface of the lag-screw threads and the bone. Finally, the spreading of the CaS/HA material was also verified on donated femoral heads and micro-CT imaging indicated that the entire length of the lag-screw threads was covered with the CaS/HA biomaterial. In conclusion, we present a novel method for augmenting a lag-screw in TFs, which could potentially reduce the risk of fracture fixation failure and reoperation in fragile osteoporotic patients.
Highlights
More than 200 million individuals are suffering from osteoporosis and the number is expected to double in 2050 (Odén et al, 2015)
By modifying the biomaterial delivery technique using a specialized delivery device, which increased the calcium sulphate/ hydroxyapatite (CaS/HA) biomaterial spreading at the screw-bone interface, we report that the extraction force of the lag-screw augmented with the CaS/HA biomaterial increased by >350% in the same experimental setup, which is a substantial increase compared with the previous report
We describe a novel method of augmenting a lagscrew by delivering a CaS/HA biomaterial at the interface of lowdensity osteoporotic bone and the screw threads
Summary
More than 200 million individuals are suffering from osteoporosis and the number is expected to double in 2050 (Odén et al, 2015). A common manifestation of the disease is a pronounced reduction in the bone mineral density (BMD) and an increase in porosity of trabecular bone (NIH Concensus development panel, 2001). This makes anchorage of fracture fixation devices such as screws challenging in fragile cancellous bone. It is estimated that nearly 2.5 million individuals sustain a proximal femur fracture yearly and the number is expected to reach 5 million in the year 2050 (Gullberg et al, 1997; Odén et al, 2015). Failures due to loss of fixation in the femoral head is a prominent risk attributed to these internal fixation methods, mostly caused by inferior quality of the cancellous bone around the screw or insufficient reposition. An additional re-operation in an already fragile patient, reduces quality of life and most importantly, increases the risk of premature death
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