Influence of Bone Strength Measured by DensiProbe on Bone Related Fixation Failure

Overview

Hip fractures mostly occur in elderly people with low bone strength. Bone strength is determined by bone mineral density (BMD), bone turnover, microarchitectural and geometrical properties of the bone. Dual energy x-ray absorptiometry (DXA) is the standard technique to measure BMD. However, BMD just provides information regarding the quantity of mineral in bone, which is only one component of bone strength. To date there is no reliable method to assess bone strength in vivo. Therefore, a method to assess bone strength beyond BMD would provide additional information regarding the patients' risk of bone related fixation failure after fracture fixation. DensiProbe is a new diagnostic device that was developed for intra-operative assessment of mechanical stability of the bone in the proximal femur. It consists of a drill bit like tool and an electronic system to measure the peak torque to break-away of trabecular bone in the femoral head of patients undergoing DHS surgical treatment. In a cadaver study comparing bone mineral density measured by quantitative computed tomography with bone strength measured by DensiProbe a high correlation between these two parameters could be shown. In a clinical pilot study a significant correlation between DensiProbe measurements and BMD measured by DXA at the femoral neck in patients with hip fractures could be shown. However, no perfect correlation was expected because DensiProbe measures bone strength, which is only partly caused by BMD. Bone related fixation failure, such as secondary loss of reduction, is influenced by bone strength, bone mineral density, fracture type, fracture reduction and primary positioning of the implant. The predictive value of DensiProbe measurements for secondary loss of reduction needs to be investigated. If DensiProbe turned out to be an effective screening tool for patients with low bone strength that are on higher risk of the aforementioned complications these patients may in future benefit from alternative treatment methods (e.g. augmentation techniques) in order to reduce bone related fixation failure. The primary aim of the present study is to investigate if bone strength measured by DensiProbeTM Hip (DensiProbe) is an independent factor to predict secondary loss of reduction (screw migration of 5 mm or more and / or telescoping of 10 mm or more) in patients with hip fractures after fracture fixation with DHS.