Radiological evaluation for conflict of the femoral tunnel entrance area prior to anterior cruciate ligament revision surgery

Abstract

Purpose Anterior cruciate ligament (ACL) revision surgery is a demanding procedure and requires meticulous pre-operative clinical and radiological assessment. In clinical practice the position of the femoral tunnel is identified mainly using plain radiographs (XR). Two-dimensional computed tomography (2D-CT) and magnetic resonance imaging (MRI) are not yet routine imaging methods and are only performed in specific clinical indications or in the scientific setting. Several measurement methods describe the femoral tunnel after ACL reconstruction and indicate 'ideal or wrong' placement to the surgeon. The aim of this study is to provide a reliable measurement method to predict potential conflict between the preexisting and the planned femoral tunnel entrance area (FTEA). Methods Ten patients with primary ACL reconstruction served as a reference group to describe our desired FTEA. Their femoral tunnel positioning was measured on XR and 2D-CT according to published measurement methods. These results were compared to the FTEA measured with a new technique on 3-dimensionally reconstructed CT-images (3D-CT) based on intra-operative landmarks. Twenty patients requiring ACL revision surgery underwent identical radiological examination. The mean values of the reference group were compared to each measurement of the patients requiring revision surgery. Results 3D-CT measurements found potential conflicts in nine out of 20 patients, which all proved to be true during arthroscopic revision surgery. Only one of these patients was identified in all XR and 2D-CT measurements. In 12 out of all 30 patients some measurements on XR or 2D-CT could not be recorded.Conclusion 3D-CT reconstruction shows the most accuracy in depicting conflict of the pre-existing and desired femoral tunnel prior to ACL revision surgery. The desired FTEA must be defined for each surgeon and his individual technique. In contrast, precision of conventional measurement techniques on XR and 2D-CT is low and does not qualify for this purpose.

3-Dimensional Printed Models May Be a Useful Tool When Planning Revision Anterior Cruciate Ligament Reconstruction

“…7,[13][14][15][16] With revision ACL surgery, proper tunnel placement becomes more complex, as index tunnels may preclude drilling of subsequent tunnels in an anatomic position. 17,18 Moreover, tunnel widening may preclude single-stage surgery, requiring a 2-stage procedure with bone grafting. The higher complexity of revision ACL surgery results in reoperation rates as high as 35% in patients <20 years of age.…”

One-Stage ACL Revision Using a Bone Allograft Plug for a Semianatomic Tibial Tunnel That Is Too Anterior

“…A widened tunnel or overlapping between the existing and new tunnel can compromise the tendon graft fixation and, thereby, require two-stage revision with a bone graft. 26 Use of outside-in instrumentation for the femoral tunnel reduces the risk of overlap, helping to control the intra- and extra-articular positioning and reduces the risk of breaking the posterior cortex. 27 , 28 …”

Outside-In Anterior Cruciate Ligament Revision With Lateral Tenodesis and High-Strength Suture Augmentation Is Easy to Perform With the Iliotibial Band

“…Attaching the graft is more difficult when the tunnel drilled for the previous reconstruction is large or has widened, which may require a 2-stage revision and bone grafting. 13 Using an outside-in femoral tunnel makes it easier to drill the new tunnel by limiting the risk of overlap, controlling the intra- and extra-articular exit points, and reducing the risk of posterior cortical collapse. 14 In addition, according to Hiramatsu et al., 15 the outside-in technique yields a more acute femoral graft bending angle, longer mean femoral tunnel length, and larger contact ratio than the inside-out technique.…”