A complete radiographic series including Merchant view for patellar evaluation, weight-bearing antero-posterior (AP) view in 45° of flexion, lateral radiographs in 45° of knee flexion, and full extension AP radiographs are appropriate in the initial imaging analysis of a reinjured knee. These films allow evaluation of hardware position, degenerative changes, previous deformities, and associated fractures or avulsions. In addition, femoral and tibial tunnel widening, angle, and position can be assessed. Illingworth et al. showed that in AP radiographs a femoral tunnel angle less than 30° is non-anatomic and more than 30° is most probably located in the anatomic position [14] (Fig. 14.2).

In cases of valgus or varus extremity malalignment, a weight-bearing long-cassette radiograph is obtained for objective quantification of the lower limb axes.

MRI has been used as the gold standard exam to confirm ACL graft tear and identify concomitant intraarticular pathology. In addition to the regular MRI views (sagittal, coronal, and axial), special sequences such as oblique coronal and oblique sagittal, with sections at the same anatomic alignment of the ACL, should be obtained to allow a complete visualization of the ligament [15]. In addition to the diagnosis of graft rupture, MRI also allows for additional data on the previous surgery such as associated injuries, tunnel positioning, and graft orientation. Tibial insertion site size, ACL length, ACL inclination angle, and quadriceps and patellar tendon thickness on sagittal views are routinely obtained to assist in ACL revision technique and graft source decision. These measurements are even more meaningful if the primary injury MRI is available, allowing a direct comparison of the native insertion sizes, estimation of ACL length, and inclination angle (Fig. 14.3). This evaluation provides information on the initial restoration of native ACL anatomy, which is of fundamental importance for the preoperative planning of revision ACL reconstruction.

We routinely utilize a CT scan with three-dimensional reconstruction for evaluation of failed ACL reconstruction to identify previous tunnel placement and bony deficiencies irrespective of prior technique (Fig. 14.4). After a primary DB reconstruction, this exam is even more important as numerous tunnels are present and single-stage or two-stage revision procedures must be meticulously planned.

Overall, the indications and contraindications for a revision after double bundle ACL reconstruction follow the same principles as the primary surgery. Patients with recurrent instability after double bundle ACL reconstruction are better treated with revision reconstruction. Patients who participate in cutting, jumping, and pivoting sports are also appropriate candidates for surgical treatment.

On the other hand, asymptomatic, low demand, or elderly patients should have nonoperative treatment. Similarly, patients that have had multiple ACL reconstruction failures must be analyzed carefully before indicating another surgery. Individual anatomic, biomechanical, and behavioral factors that may have contributed to the previous failures must be addressed to increase the likelihood of a successful outcome.