Introduction and Aims: Cyclic pneumatic pressure applied to the musculature proximal to a fracture of the distal radius has been shown to produce compressive loading of the fracture. The aim of this randomised controlled in vivo study in an ovine model was to investigate the effect of the pneumatic pressure on fracture healing.

Method: Thirty-seven sheep underwent a transverse osteotomy of the right radius. All sheep were managed in a plaster cast and splint to ensure non-weight bearing during rehabilitation. Nineteen of the sheep were randomised to receive cyclic loading by the application of a pressure cuff around the muscles of the proximal forearm deep to the cast. The other 18 sheep acted as controls. The sheep in the experimental group received 120 cyclic loads over two 10-minute sessions each day starting one week post-osteotomy. Sheep from both groups were sacrificed at either four or six weeks. X-rays, ultrasonography, biomechanical testing and histomorphometry were used to assess differences between the groups.

Results: The area of periosteal callus on lateral and antero-posterior x-ray, the peak torsional strength, the fracture stiffness, the energy absorbed over the first 10 degrees of torsion and histomorphometric analysis all showed that the fractures in the group treated with the cyclic pneumatic pressure achieved the same level of union at four weeks as the control group fractures at six weeks (not significantly different p> 0.05). The density of the woven bone in the periosteal callus of the treated sheep was significantly greater than the controls (p< 0.01). Ultrasonography showed no significant difference (p> 0.05) in the amount of muscle wasting between the treated group and the control group.

Conclusion: This study has shown that the rate of healing is enhanced when cyclic pneumatic pressure is applied to the musculature proximal to a transverse fracture of the distal radius in an adult sheep model. There is potential for this treatment to be used in a human population.

Introduction and Aims: The radiographic appearance of fractures is often used as an evaluative tool when assessing the status of healing fractures. The aim of this study was in the first instance to assess the reliability of orthopaedic surgeons to measure the area of periosteal callus and secondly to compare the area with the biomechanical strength of the fractures.

Method: Thirty-seven sheep underwent a transverse osteotomy of the right radius. All sheep were managed in a plaster cast and splint to ensure non weight-bearing during rehabilitation. Nineteen of the sheep were ran-domised to receive cyclic loading by the application of a pressure cuff around the muscles of the proximal forearm deep to the cast. The other 18 sheep acted as controls. Sheep from both groups were sacrificed at either four or six weeks. Fractures were x-rayed and subjected to biomechanical testing following sacrifice. X-rays were transferred to a Labview program from which the area of callus was measured. Biomechanical testing of the fractures was a torsional test to failure. The peak torque, stiffness and energy absorbed over the first 10 degrees of torsion were measured for each fracture.

Results: The two orthopaedic surgeons who measured the area of callus showed a positive correlation (r = 0.85). When the four-week fractures that were treated with cyclic loading were compared with the four-week control fractures, the periosteal callus measurement along with the peak torque, fracture stiffness and energy absorbed over the first 10 degrees of torsion all showed a significant difference (p < 0.05). In addition, when the six-week fractures that were treated with cyclic loading were compared with the six-week control fractures, the periosteal callus measurement along with the peak torque, fracture stiffness and energy absorbed over the first 10 degrees of torsion were not significantly different (p > 0.05).

Conclusion: The results show that the area of periosteal callus on radiographs can be related to the biomechanical status of a healing fracture. Further research is required to determine if other characteristics of the periosteal callus plus quantification of the callus area is able to accurately predict fracture strength.