Revision anterior cruciate ligament reconstruction

Classification of anterior cruciate ligament failures

There are a multitude of contributing factors to the rupture of a reconstructed ACL graft. The Multicenter Center Orthopaedic Outcomes Network (MOON), through the establishment of a long-term prospective cohort, has identified younger age, higher activity level as well as allograft use especially in younger populations as significant risk factors for ACL reconstruction failure. Undiagnosed concomitant injuries such as the posterolateral corner insufficiency or lateral meniscal root tears as well as preexisting coronal or sagittal malalignment also contribute to ACL graft failure. Technical error in tunnel placement, typically involving anterior or vertical placement of the femoral tunnel ( Fig. 84.1 ) is the most common issue identified in primary failure. Anterior tunnel placement causes the graft to stretch when the knee flexes, thereby resulting in deformation and eventual graft incompetence. Vertical femoral tunnel placement corrects posteroanterior plane stability but does not control rotation resulting in subjective instability with cutting and pivoting. Abnormal biomechanics are observed, and patients may report subjective instability even though they have a normal Lachman test result and minimal KT1000 side-to-side difference. ^,

Technical errors in the tibial tunnel also place the graft at risk for early failure. Historically, concern for ACL-roof impingement in extension led some surgeons to place their tibial tunnels too posteriorly. If the femoral tunnel is then drilled transtibial through the posterior tibial tunnel, a subsequent high graft position will result from the orientation of the drill guide. The ACL graft is then malpositioned between a posterior tibial tunnel and a high or vertical femoral position. It should also be noted that even with an independent femoral tunnel in an “anatomic” position on the femoral wall, a posterior tibial tunnel will creates a vertical graft in the sagittal plane, may not adequately address rotational stability. It is important to keep in mind that range of motion may provide important clues regarding the presence of notch impingement and, most important, accurate tunnel placement.

History

Patients who experience recurrent instability may benefit from a revision reconstruction to stabilize the knee and restore function. Key historical factors to consider are the time since the index reconstruction, the rehabilitation protocol, and the occurrence of a discrete new traumatic injury and if the patient ever experienced a stable knee since return to activity. Preoperative data collection and planning are important to ensure success of the reconstruction. If available, previous operative notes, arthroscopic images, and imaging are reviewed to determine previous surgical tunnels, graft location, meniscal status, and cartilage defects. While rare, any symptoms of indolent infection should also be determined.

Physical examination

A thorough physical examination is performed to assess knee stability not only anteriorly but also posteriorly, medially, and laterally. It is critical to exclude a subtle posterolateral or posteromedial laxity that may be contributing to graft attenuation. Dynamic varus and valgus thrust during gait should be assessed. All test results should be compared with those of the opposite knee. The affected knee’s range of motion should be recorded, with particular attention to subtle knee flexion contractures. Patellofemoral crepitation and mobility should be assessed. If it is available, a KT1000 measurement should be performed on both knees to provide objective anterior-posterior translation parameters. Coronal and sagittal alignment should be assessed and finally, all skin incisions should be recorded for preoperative planning.

Imaging

We recommend obtaining at least four views to determine tunnel orientation and to help decide whether hardware will need to be removed during revision surgery (AP in extension, posteroanterior [PA] Rosenberg, lateral, and skyline). Full-length standing radiographs are also recommended to assess sagittal and coronal alignment in both knees. Magnetic resonance imaging can help evaluate concomitant pathologic changes, such as meniscal tears and posterior cruciate ligament (PCL) or posterolateral corner injuries. If there is any suggestion of tunnel widening on conventional radiographs, we routinely obtain a computed tomographic scan to better delineate tunnel expansion.