Abstract
Introduction
Patients undergoing limb reconstruction with the Taylor Spatial Frame (TSF) often perceive that their frame is loose due to the rattle they hear when mobilising. Our aim was to determine how much and where this movement is in the various frame/bone constructs currently on the market.
Method
Using standard tibial saw bones three frames (TSF, Ilizarov and Hexapod) were made in an identical fashion. Constructs were cyclically loaded 4 times to 200 N in tension and compression using the Instron MTS. This was repeated three times. A seventh strut was also placed in the TSF construct and the tests repeated. Bones were then removed and the tests repeated for the frames alone.
Results
Movement was noted between the frame and bone in all the frames in compression (average 1.5mm) and tension (average 4.5mm). Frames alone in compression moved between 0.5mm (Ilizarov) and 1.2mm (hexapod). The rattle was audible and was apparent on the TSF more than the other devices. On measuring separate components of the TSF, the ring height measured 7.9mm compared to a screw gap of 8.05mm. The locking clasp mechanism of the strut moved 0.1mm, thus allowing 0.45mm movement between compression/extension.
Conclusion
This rattle is due to the combination of movement seen between the ring and screw fixation, the clasp mechanism and the universal joint. A seventh strut reduces this rattle by splinting the frame in compression or tension. All frames show movement between the frame and the bone. The stiffest bone/frame construct in tension/compression is the TSF followed by the Ilizarov and Hexapod frames. Further work is needed to determine what effect this movement has on fracture healing.
