Tibial Fractures: Reduction and Mechanics

It is self-evident that all tibial fractures should be reduced as perfectly as possible. The reduction of tibial fractures tends to be best in those plated or nailed and worst in those treated by external fixation or plaster cast. This is because the plate or nail can assist in the reduction of the fracture: a conventional plate will pull the bone surfaces onto itself as the screws are tightened; the open technique can allow for the use of interfragmentary lag screws; the nail will tend to line up the medullary cavity as it passes across the fracture.

Fig 1. Fractures reduced using STORM

While the plating of tibial shaft fractures is commonplace in some countries, it carries a high risk of infection, and nailing can still allow angulatory malunions in metaphyseal fractures and tortional malunions at any level. In addition, the new generation of locking plates no longer assist the surgeon with reduction: for these the fracture must be perfectly reduced before the first screw is inserted. Therefore it is not possible to rely on the method of fixation in order to consistently achieve perfect anatomical reductions. Over the years several devices have been developed specifically to assist in the reduction of tibial fractures: notable are the Bohler frame (1928), Anderson's “veritable fracture robot” (1934) and the device of Reynders-Frederix (1992).

At the University Hospital of North Staffordshire we set out to develop a system in which the two mutually exclusive functions of reduction and fixation of the tibia are separated. By separating the two functions of reduction and fixation we have managed to improve the quality and reliability of reduction of fractures. (Fig 1)

Fig 2. STORM

Reduction of the fracture is achieved using the Staffordshire Orthopaedic Reduction Machine (STORM) (Fig 2). STORM is used in the operating theatre as a form of traction table within the sterile field. It is applied with tensioned wires in the proximal tibia and calcaneum, through which strong controllable axial traction can be applied, and torsion can be corrected. Two translation arms are used to pull the fracture fragments horizontally and vertically to fine-tune any remaining angulation or translation (Fig 3). Once a perfect reduction has been achieved, the fracture is fixed by whichever means are considered the most appropriate. The fracture may be nailed, fixed with a percutaneous locking plate or externally fixed.

Fig 3. Translation arms

STORM is used to reduce fractures throughout the tibia including pilon and plateau fractures, where its ability to help achieve and hold a good reduction is also useful for percutaneous screw, plate or fine-wire fixation. For plateau fractures the proximal tensioned STORM wire can be placed through the femoral condyles.

Most presently available monolateral external fixators have lockable joints which allow a fracture to be manipulated after the bone-screws are in place, but none of these fixators has any capacity for assisting the surgeon to gain a good reduction. The lockable joints in most external fixators make it complex, costly and bulky and with the added complication that the lockable joints can come loose causing loss of fracture reduction and malunion.

We studied 100 consecutive tibial fractures treated with external fixation at the University Hospital of North Staffordshire, measuring the fracture length and the distance required between the fixator bone-screws to span each fracture safely. We have found that 10mm is a safe distance from the nearest fixator bone-screw to the fracture. Adhering to this safe distance we have not seen infection pass from a fixator bone-screw to the fracture in over 300 externally fixed tibial fractures. In the 100 fractures studied for length we found that 97% fitted between bone-screws separated by 110mm while 50% fitted between bone-screws separated by 70mm. With just two lengths of fixator we are therefore able to accommodate most tibial shaft fractures. We found that very long oblique fractures are not suitable for monolateral external fixation, so the 3% which cannot be fitted between the bone-screws of the long IOS fixator are best treated with a circular frame arrangement.

We have established a set of principles for external fixation which, when adhered to, will maximise the healing potential of the fracture while minimising the risk of malunion and non-union. These principles are as follows:

  • Elastic return should be to the reduced position.
  • There should be no play.
  • The forces of weight-bearing should all act to reduce the fracture and not to distract it.
  • A symmetrical frame will tend to produce angulation & compression on weight-bearing.
  • An asymmetrical frame will tend to produce distraction & shear on weight-bearing.
Fig 4. Symmetrically placed distal tibial fracture held with the short IOS fixator

For monolateral fixators a symmetrical arrangement is one in which the centre of movement of the fracture is equidistant from the two sets of bone-screws. To achieve this in a fracture near to a joint the fixator must be short. The commonest fracture of the tibial shaft is at the junction of the middle and distal thirds, where a long fixator can only be placed asymmetrically. However, using a short fixator will allow the fracture to be placed symmetrically between the two sets of bone-screws thus optimising the movement of the fracture ends on weight-bearing (Fig 4).

For the external fixation of shaft fractures we have developed a device utilising a titanium bar with optimised mechanical properties (the IOS fixator). It had

Fig 5. The IOS fixator

been developed specifically for use with the STORM and must be applied to a perfectly reduced fracture. IOS has no facility for adjustment of the fracture position, but none is required if the fracture is already anatomically reduced. Because there are no adjustable elements, there is nothing that can come loose or cause a loss of reduction (Fig 5).

In our experience the use of STORM will provide a quick, easy and reliable method of achieving a perfect reduction for fractures throughout the tibia. More information is available at www.intelligent-orthopaedics.co.uk.

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