Abstract
Introduction: Proper correction of proximal tibial deformities includes correction of the mechanical axis and parallelism of the knee to the ankle and ground. Optimally placed osteotomies are away from the very proximal deformity requiring controlled diaphyseal translation. The Metaphyseal Arc Correction System, a major simplification over the Ilizarov or Spatial Frame systems, is assessed in this study, as are methods to identify the plane of deformity.
Method: Thirty-one consecutive cases of proximal tibial deformity in 18 patients were treated using the Metaphyseal Arc Correction Sysytem. There were six valgus deformities (three pts), one Morquio, two metaphyseal dwarfs ages six and eight years. The rest were varus deformities, 12 achondroplasia (six pts), eight infantile Blount’s (four pts) and five adolescent Blount’s (five pts). Comparison of two methods of identifying the plane of deformity was done in six cases: Herzenberg’s graphic method and the image method (rotating the limb until the maximum deformity is in the plane of the intensifier).
Results: All but eight tibiae (five pts) were properly corrected. Four tibiae (two pts) were over corrected, two tibiae (one pt) were corrected but the knee and ankle were not parallel. Analysis of these six limbs revealed unrecognised deformity of the distal femur. Thus to get the joints parallel in four limbs the axis was overcorrected and in two limbs the axis was proper but the joints were not parallel. One failure occurred because the device was not placed in the plane of deformity, another because of premature fibula consolidation (or incomplete osteotomy). All other cases achieved deformity and axis correction with joint parallelism. Both methods of identifying the plane of deformity yielded similar results as long as the proximal tibia was centered to avoid image parallax. The graphic method gives accurate angles but could only be approximated clinically. There was one failure from inaccurate device placement using the image method. Ideally both methods should be used.
Conclusion: The Metaphyseal Arc Correction System is convenient method of correcting proximal tibial deformities. It is easily applied and when properly positioned automatically corrects deformity, axis and joint parallelism, allowing optimum osteotomy placement. Positioning should use both the graphic and image methods. Failures were iatrogenic due to poor analysis, not the device.
These abstracts were prepared by Editorial Secretary, George Sikorski. Correspondence should be addressed to Australian Orthopaedic Association, Ground Floor, The William Bland Centre, 229 Macquarie Street, Sydney, NSW 2000, Australia.
At least one of the authors is receiving or has received material benefits or support from a commercial source.
