Introduction: The Staffordshire Orthopaedic Reduction Machine (STORM) was developed to assist in the reduction of tibial shaft fractures prior to the application of an external fixator. Its use has now been extended to fractures of the tibial plateau and plafond, where it has been utilised to gain and hold a good reduction prior to the application of various internal and external fixation techniques.

Methods: The STORM was used sterile within the operative field on a standard radiolucent operating table. It was applied with two tensioned 2 mm wires: the distal through the calcaneum; the proximal through the proximal tibia for shaft and pilon fractures, and through the distal femur for plateau fractures.

Controlled traction was applied through these two wires. Torsion was independently corrected and locked. Translation and angulation was corrected using two translation arms each applied to the tibia with a single unicortical screw. The STORM was removed at the end of each operation.

Results: The STORM was used in 241 cases.

Pilon (n=42): bridging hinge 23 (t [mean operation time in minutes]=102.9), percutaneous plate 10 (t=131.4), ring fixator 5 (t=140), screws and fibula plate 3 (t=77), other 2.

Discussion: The STORM is a safe device for reliable reduction of tibial plateau, shaft and pilon fractures which allows good access for internal or external fixation. No significant complications attributable to the use of the current design of the STORM were encountered.

Introduction: In a new external fixation system for tibial fractures, accurate reduction was achieved with a complex temporary device, the Staffordshire Orthopaedic Reduction Machine (STORM) following which the fracture was fixed using a simple titanium bar fixator (IOS). The fixator was designed to allow controlled bending to optimise movement at the fracture site for callus growth. Ideal mechanical properties are approached: elastic return is to the reduced position; epicentric placement minimises shear and distraction on weightbearing. Integral healing assessment measures bending stiffness. The device is single-use.

Methods: Closed or grade I compound unstable tibial shaft fractures in 38 patients were externally fixed using the STORM in the operating theatre to reduce the fracture prior to application of an IOS fixator. Immediate full weight-bearing was encouraged. Bending characteristics of the fixator allowed 1 mm of axial movement for 20 kg loading. Fixator removal time was determined by fracture stiffness measurements against which the integral IOS stiffness measurement was compared.

Results: Mean healing time was 18.1 weeks, shortest time 9.5 weeks. The healing endpoint was fixator removal at a bending stiffness of 15 Nm/deg in two orthogonal axes. There was no subsequent creep or re-fracture. Good reduction, defined as less than 3 deg of maximum angulation and less than 3 mm of maximum translation, was achieved and maintained.

Discussion: The IOS/STORM system allows safe and effective treatment of tibial shaft fractures. With the fracture reduced, the external fixator screws can be placed in optimum positions. Good reductions were achieved and maintained. The IOS bending characteristics appear to approach the optimum for callus growth. The simple integral fracture stiffness measurement method has been validated against more complex devices.

This is a clinically based study to assess the reliability of fracture stiffness as a measurement of clinical union and investigate other indicators which may aid the clinician to accurately determine when fracture fixation may be removed.

A fracture bending stiffness in the sagittal plane of 15Nm/deg. has been stated as a satisfactory endpoint at which an external fixator may be removed from diaphyseal fractures of the tibia. However using this as a measure to determine when to remove support in a study of 76 patients 4 continued to a malunion. Fracture callus properties were measured in clinic. The fixator was removed for the tests and a specially designed system was used to measure displacement and load. Fracture stiffness was measured in different planes and at various loading rates. Passive stressing of the leg was performed whilst fracture displacement was recorded. A constant load was applied for a longer period to assess creep properties.

Fracture stiffness was found to vary between different planes of measurement and on load rate. The visco-elastic characteristics of the callus changed with time. In early measurements, the callus absorbed a large proportion of energy when a load was applied. Later tests showed a progressive change with the callus absorbing less energy. This demonstrates that the properties of the callus changed with time, with the viscous element diminishing and the elastic element increasing. This sometimes occurred with no change in the measured fracture stiffness.

Further investigation is needed, focusing on the visco-elastic properties of callus, to develop a more reliable method of determining clinical union.