Abstract
Introduction and Aims: The chronic ACL deficient knee has a natural history of degeneration and deterioration in function. It is unclear whether reconstruction will prevent this sequela. Reconstruction using hamstrings graft techniques have not been yet been evaluated over the long term. This prospective study used MRI to measure tibio-femoral contact patterns pre-and post-reconstruction.
Method: There were 20 subjects with an ACL injury of three years standing. The diagnosis was clinical and confirmed at surgery. They performed a closed chain leg-press, relaxed and against a 150N load. MRI recorded the tibio-femoral contact position at 15-degree intervals from zero to 90 degrees of knee flexion. Passive laxity was measured with a KT1000, and knee outcomes recorded using a Cincinnati score. Testing was performed pre-operatively, at 12 weeks and two years post-operatively.
Results: KT1000 showed a side-to-side difference of 5.1 ± 2.6mm pre-operatively, 2.5 ± 2.2mm at 12 weeks and 2.1 ± 2.3 at two years. Using Cincinnati ratings five rated ‘fair’, five rated ‘good’, and eight rated ‘excellent’. Tibio-femoral contact patterns loaded were not different loaded or unloaded, but medial and lateral compartments of the knee were significantly different (p< 0.001), demonstrating the longitudinal rotation of the knee during flexion, for healthy and injured knees. Pre-operatively the tibio-femoral contact patterns for the ACL injured knee were different to the healthy knee (p=0.014). At 12 weeks post-operatively the tibio-femoral contact patterns were not significantly different (p=0.117), and at two years the contact patterns were restored to those of the healthy knee (p=0.909). However, there were changes to the lateral compartment contact pattern that affected both the ACL injured, reconstructed and healthy knees over the two-year time period. In the healthy knees and also the reconstructed knees the lateral compartment showed less tibio-femoral rollback at two years.
Conclusion: The knee reconstruction restored the tibio-femoral contact pattern to that of the healthy contralateral knee, but both the healthy and reconstructed knees showed changes over time independent of surgery. One or more of the listed authors are receiving or have received benefits or support from a recognised academic body for the pursuance of the study.
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.
