Abstract
Objectives:Surgical treatment of proximal humerus fractures can be challenging due to osteoporosis. The weak bone stock makes stable implant anchorage difficult, which can result in low primary stability. Accordingly, significant failure rates, even with modern locking plates, are reported in the literature. Intraoperative knowledge of local bone quality could be helpful in improving results. This study evaluates the feasibility of local bone quality quantification using breakaway torque measurements.Materials and Methods:A torque measurement tool (DensiProbe™) was developed to determine local resistance to breakaway offered by the cancellous bone in the humeral head to quantify local bone quality. The tool was adapted to a standard locking plate (PHILOS, Synthes), allowing measurement in the positions of the six humeral head screws, as provided by the aiming device of the plate. Two hundred and seventy measurements were performed in 44 fresh cadaveric human humeri.Results:Handling of the tool was straight forward and provided reproducible results for the six different positions. The method allows discrimination between the respective positions with statistical significance, and thus provides reliable information on the local distribution of bone quality within the humeral head.Discussion:This study introduces a new method using breakaway torque to determine local bone quality within the humeral head in real time. Because DensiProbe is adapted to a standard locking plate, there is the potential for intraoperative application. The information provided could enable the surgeon to improve fixation of osteoporotic proximal humerus fractures.
Highlights
Treatment of proximal humerus fractures, the third most common fracture in those aged over 65 years, remains a challenge [1]
The DensiProbe tool presented in this study is based on an already existing application for the femur and spine, and allows for direct measurement of local bone quality of the humeral head in real time [15,9]
The good correlation between the DensiProbe measurements and local bone mineral density (BMD) was confirmed in the study of Brianza et al comparing the results of DensiProbe to high-resolution peripheral quantitative computed tomography (HR-pQCT) in the identical volume of interest [8]
Summary
Treatment of proximal humerus fractures, the third most common fracture in those aged over 65 years, remains a challenge [1]. The failure rate, despite the development of better implants, remains very high, being 13.7% in a study of 153 patients performed by Krappinger et al [2]. One important reason for failure is the osteoporotic bone stock in elderly patients. To assess the cancellous bone quality in the humeral head, various techniques have been used. Tingart et al showed that the proximal half of the humeral head has a significantly higher trabecular BMD than the distal half. In a second investigation focusing on mechanical testing, they found that the superior anterior region has a significantly lower BMD and pull-out strength than all the other regions, and that the central region has a higher BMD compared to the inferior
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