Interfragmentary movements in the early phase of healing in distraction and correction osteotomies stabilized with ring fixators

Abstract

Background: Experimental analyses have demonstrated the impact of mechanical conditions on bone healing. In critical clinical cases the mechanical conditions may be even more demanding than those in experimental studies. This study set out to examine the gap movements in distraction and correction osteotomies and to determine the suitability of initial fixation. Patients and methods: Interfragmentary movements, ground reaction forces, and stability (ground reaction force divided by interfragmentary movement) were measured in 18 patients with tibial osteotomies stabilized by Ilizarov hybrid constructs until either bone union or conversion to internal fixation occurred (9 distraction treatments, 9 correction osteotomies). Consolidation was determined by clinical evaluation and standard radiographic techniques. Results: In both groups cocontraction led to gap movements comparable to level walking. Although the in vitro stiffness was slightly increased in the correction constructs, the interfragmentary movement in vivo was initially comparable between the groups. Patients undergoing distraction returned later to full weight bearing than patients undergoing correction treatment. In the correction group the stability increased with treatment time, while in the distraction group the stability remained relatively small. Conclusions: The in vivo mechanical conditions in challenging clinical cases appear far more demanding than those in experimental studies. In distraction, mechanical conditions at the defect appear to be more critical than during correction osteosynthesis. According to the persistence of shear motion, even after 80 days of treatment, it may from the clinical point of view be important to maintain interfragmentary compression during the whole healing process and thereby reduce shear.

The influence of a weight-bearing platform on the mechanical behavior of two Ilizarov ring fixators: tensioned wires vs. half-pins

“…At an axial load of only 20 kg, which corresponds clinically to partial weight bearing, we identified movements of approximately 2 mm in the half-pin frame and 2.7 mm in the all-wire frame. From in vivo measurements of patients treated with an Ilizarov frame, Duda et al [40] demonstrated interfragmentary movements as large as 4 mm in the early treatment phase under a partial weight load of 20 kg. Conversely, the results for indirect loading demonstrated that the amount of movement is decreased by 50% in with respect to the applied load.…”

Direct and indirect loading of the Ilizarov external fixator: the effect on the interfragmentary movements and compressive loads

“…A slight axial weight load resulted in a relatively large extent of axial movements. Duda et al [6] detected in vivo interfragmentary movements up to 4 mm in patients treated with an Ilizarov frame and mobilised with direct weight loading and a maximum load of 20 kg. At the same applied load in our experimental set-up, there were axial gap movements of 3 mm.…”

“…The extent of micromotion and the load transferred to the fracture depend on the stability of the Ilizarov frame and on the amount and manner of weight bearing [6, 7]. To gain control of the interfragmentary motions requires an understanding of the various factors affecting the overall characteristics of the fixation device.…”

New method for detection of complex 3D fracture motion - Verification of an optical motion analysis system for biomechanical studies

“…The optimal range for this micromotion seems to be 400 μm [8]. Therefore, current biomechanical analyses have focused on the development of osteosynthetic implants for optimal interfragmentary motion [1,2,9,12]. In the context of the development of new implants biomechanical tests are highly important.…”