Measuring stiffness can define healing of tibial fractures

Abstract

We measured fracture stiffness in 212 patients with tibial fractures treated by external fixation. In the first 1 17 patients (group 1) the decision to remove the fixator and allow independent weight-bearing was made on clinical grounds. In the other 95 patients (group 2) the frames were removed when the fracture stiffness had reached 15 Nm/degree. In group 1 there were eight refractures and in group 2 there was none (p = 0.02, Fisher's exact test). The time to independent weight-bearing was longer in group 1 (median 24 weeks) than in group 2 (21.7 weeks, p = 0.02). The greater precision ofour objective measurement was associated with a reduction in refracture rate and in the time taken to achieve independent weight-bearing. We consider that a stiffness of 15 Nm/degree in the sagittal plane provides a useful definition of union of tibial fractures.

Quantification of Fracture Healing from Radiographs Using the Maximum Callus Index

“…By pressing on the fracture and causing a small (typically \ 1-2°) angular deflection in the sagittal plane, the stiffness of the fracture can be calculated in Newton meters per degree (Nm/deg) [11]. This device has previously been well-validated as a measure of fracture stiffness [9] and the refracture rate has been shown to be reduced when a value of bending stiffness of 15 Nm/deg is used as a guide to removal of the external fixator [20]. Data recording, display, and analysis were performed using Microsoft1 Office Excel 2003 (Microsoft Corp., Redmond, WA) and all statistical analyses were performed using Minitab 15 for Windows (Minitab Inc., State College, PA).…”

“…Most require specialized equipment that is not available in fracture clinics and are not applicable to many common fractures or fracture treatment methods. For example, fracture stiffness [4,5,20,26] and acoustic emission [12] measurements can only be performed in those cases treated with external fixators and the fractured bone must be subcutaneous to enable testing using vibration or ultrasonic measurements [1,7,15,18,23].…”

Monitoring the Mechanical Properties of Healing Bone

“…For a direct measurement of callus stiffness, the most accurate method to determine the stiffness of the fracture callus is the measurement of the deflection of the healing bone under loading with all the fixation devices removed [21,23,24,32]. In principle, this is only really possible for patients who are treated by external fixators or by cast.…”

“…Unfortunately, there are only a few studies [4,8,21,23,25,32,41] which monitored the stiffness of healing fractures in a sufficiently large number of patients to be able to draw conclusions from the results. The largest study of direct measurement of bone stiffness was presented by Richardson et al [32] on 212 patients with tibial fractures treated by external fixation.…”

“…The largest study of direct measurement of bone stiffness was presented by Richardson et al [32] on 212 patients with tibial fractures treated by external fixation. The measurements were performed after removal of the fixator as described before.…”