Summary
Two thirds of all cases feature a combination of tunnel malpositioning and critical tunnel widening, potentially requiring a two-stage revision ACLR. On the other hand, most patients with anatomic tunnel positioning do not show critical tunnel widening and can therefore safely be treated in a single-stage approach. In addition, a slope reduction may be considered in every eighth revision ACLR.
Abstract
The treatment of ACL graft failure bears numerous challenges and requires a profound understanding of the preexisting tunnels, the bone stock, and anatomic risk factor that potentially had been underrated beforehand. Therefore, aim of the present study was to systematically analyse CT scans, categorise and evaluate the findings and carefully draw conclusions to improve surgical approaches.
152 consecutive patients with ACL graft failure of a three-year period were identified from the groups database. CT scans were available in all cases. CT scan analyses encompassed determination of tunnel positioning applying the grid method to the tunnel apertures in a 3D rendered volume model, measuring of tunnel widening perpendicular to the tunnel axis in axial, coronal and sagital planes and quantification of the medial, lateral and global posterior tibial slopes according to Hudek et al.
47 patients (30.9%) featured anatomic positioning of both, the femoral and the tibial tunnel (group A). 105 patients (69.1%) showed malpositioning of the femoral and/or the tibial tunnel (group B). Regarding the malpositioning, predominately a too shallow placement of the femoral tunnel was evident. In patients with anatomic tunnel positioning mean widths of 11.0 (SD 2.9) and 12.3 mm (SD 2.5) were determined for the femoral and the tibial tunnels, respectively. With 12.7 (SD 2.0) and 14.2 mm (SD 2.0), the femoral and tibial tunnels were significantly wider in patients with tunnel malpositioning. A critical widening of the femoral and/or the tibial tunnel of more than 12 mm was evident in 37.5% in group A and in 88.2% in group B. Across the two groups there were no significant differences regarding the medial, lateral or global posterior tibial slopes. Overall, the mean posterior tibial slopes were 4.2° (SD 3.0) medially, 7.0° (SD 2.8) laterally and 5.6° (SD 2.6) globally. In 13.8% of all cases a critical lateral tibial posterior slope of more than 10° was detected.
High prevalences of tunnel malpositioning, critical tunnel widening and critical lateral tibial posterior slope are evident in ACL graft failures. Two thirds of all cases feature a combination of tunnel malpositioning and critical tunnel widening, potentially requiring a two-stage revision ACL reconstruction. On the other hand, most patients with anatomic tunnel positioning do not show critical tunnel widening and can therefore safely be treated in a single-stage approach. Besides a simultaneous anterolateral tenodesis a slope reduction may be considered in every eighth revision ACL reconstruction.