Validation of the 65° Howell Guide for Anterior Cruciate Ligament Reconstruction

Purpose: to study in cadaver knees the position of the tibial tunnel in anterior cruciate ligament (ACL) reconstruction using the 65° Howell guide. Type of study: controlled laboratory study in vitro Methods: 21 fresh-frozen cadaver knees were employed. The ACL was resected and its tibial attachment was demarcated. To drill the guide wire we employed the Howell 65 degrees tibial guide which references off of the intercondylar roof in extension to avoid impingement. The intraarticular position of the wire was digitised with a digital camera and referred to a transverse axis passing through the ‘over the back’ position and a sagittal axis passing through the lateral aspect of the medial spine. The percentage position of the wire within the ACL attachment was also calculated, taking the posterior and medial limits as the 0% positions. Results: all the wires were within the ACL attachment: 17 were in the ACL posterolateral bundle attachment and the other 4 in the anteromedial. The average distance of the wire from the transverse and sagittal axes was 12 mm (SD 3 mm) anterior and 1 mm (SD 1 mm) lateral, respectively. The wire was positioned at 38% (SD 16%) of the length of the ACL attachment and at 40% (SD 17%) of the width. Eighty percent of the wires were positioned at between 35% and 48% of the attachment length. Conclusions: the 65° Howell guide, which positions the tibial tunnel in extension to avoid roof impingement, ensures anatomical positioning of the graft on the tibial side and reproducibility can be expected. Clinical relevance: this study proves that a commonly used drill guide succeeds in placing the ACL graft in the tibial anatomical attachment.