Abstract
Purpose: The radiological appearances of tibial tunnel enlargement following anterior cruciate ligament reconstruction in the short and medium term have been described. This study compares the tibial tunnel appearances at 1 year and again at 8 years post-operatively in 44 patients, and correlates the findings with the longer term clinical outcome.
Patients and Methods: The study was conducted on 44 consecutive patients who had undergone isolated central anterior cruciate reconstruction using a four thickness hamstring technique. All patients were reviewed at one year postoperatively, the assessment including full clinical examination, arthrometer testing and weight bearing AP and lateral radiographs. They were reviewed again at a mean of 8 years (range 5–10 years) post reconstruction. At the 8 year review, full clinical examination, Arthrometer testing, Lysholm and IKDC scoring, Tegner activity level recording were done and standardised weight bearing AP and lateral radiographs were taken.
The Tibial tunnel diameters were measured by two independent observers on both one year and 8 year radiographs. The proximal tunnel measurement was made 5 mm from the tibial articular surface and the distal, 5mm from the lower end of the tunnel. Tunnel enlargement was calculated from the known drill size after correction for magnification. The tunnel enlargements were correlated with clinical outcome and the results were analysed statistically.
Results: There were 6 failures of stability for which an additional operative procedure had been undertaken. The remaining 38 knees were functionally stable. 28 (75%) had negative Lachman and jerk tests and 34 (90%) had a side to side arthrometer difference of less than or equal to 3mm.
The mean tibial tunnel enlargement at one year was 31% at the proximal and 23% at the distal end of the tunnel. At 8 years the enlargements were 20% at the proximal and 13 % at the distal end of the tunnel (p< .001).
There were 10 patients (26%) whose distal tunnel diameter at 8 years was less than the initial drill size. Only one of these had a positive Lachman test. This negative association was significant (p< .05). There was no significant correlation between enlargement at the proximal end of the tunnel, the Lysholm score or clinical stability at 8 years.
Conclusion: Cruciate ligament reconstruction persists at 8 years. However there was a previously unreported reduction in radiographic tunnel size at the 8 year review and this reduction was significant at the distal end of the tibial tunnel. There was no correlation between tunnel enlargement and functional outcome even at 8 year review.
The abstracts were prepared by Mr R. B. Smith. Correspondence should be addressed to him at the British Orthopaedic Association, Royal College of Surgeons, 35-43 Lincoln’s Inn Fields, London WC2A 3PN.
