CORR Insights^®: What Is the Mid-term Failure Rate of Revision ACL Reconstruction? A Systematic Review

Where Are We Now?

Revision ACL reconstruction procedures can be challenging for orthopaedic surgeons. If a revision ACL graft is placed in an anatomically correct position with good quality bone and intact cartilage and menisci, stability and knee function are likely to be restored similar to a primary ACL reconstruction. More limited, but still encouraging, results can be expected in patients with complex multiligament instabilities, major associated cartilage lesions, limited quality bone stock, or in patients with long-standing symptoms of instability and pain. In these complex situations, ACL revision reconstruction should be considered a salvage procedure with distinctly different goals (eg, return to function and sports) from those of primary ACL reconstruction. Associated procedures like osteotomies or meniscal transplantations may be part of the picture, each of which raise the stakes considerably.

Given this wide clinical spectrum, evaluating the outcome of revision reconstruction—particularly the likelihood of recurrent instability or the unsuccessful restoration of full knee function—can be burdensome. Still, the authors of the current study managed to report on the outcomes and the most-common complications associated with postrevision ACL reconstruction. The authors found that the risk of retear after revision ranged from 2% to 25% in the studies they identified. On average, the rate of repeat revision reconstruction was under 5%. At first sight, this may be considered as an excellent outcome in a challenging group of patients. But when they added objective criteria of clinical failure like pathologic laxity measurements, pivot shift phenomenon, Lachman test, or Grade C or D objective IKDC values, they identified a much higher failure rate, in the range of 20% to 30%.

It is important to note that the authors did not include criteria like return to activity, nor functional evaluations like hop tests or strength measurements. These measures represent the ultimate assessment of outcome after ACL surgery, especially in the context of athletic patients. If the authors had included those measurements, the clinical failure rate may have been even worse.

In my view, we are only beginning to fully understand the spectrum of injuries associated with the ACL. We have seen an increased focus on the morphological aspects of ACL injury like the lateral tibial slope [8], as well as pathological aspects like extraarticular lesions of the anterolateral capsuloligamentous complex [2], impression fractures of the lateral femoral condyle [5], root tears [1], and ramp lesions of the menisci [6].

Where Do We Need To Go?

The full extent of the roles those structures play is not completely understood, and so their treatments remain controversial. Recognizing and treating injuries to these associated structures may be important both in primary and revision ACL reconstructions.

The reported discrepancy between graft and clinical failure rates reflects the multiple clinical presentations that can occur in patients who undergo ACL revision. A retear of an ACL revision reconstruction could be the result of a missed initial diagnosis (ie, an unrecognized associated collateral ligament injury), the early loss of a meniscus, a technical mistake during previous surgery, or an unfavorable morphological feature like an excessive tibial slope [10]. In these more-challenging circumstances, restoring full knee function is a major obstacle because it is difficult to individualize patients with this wide spectrum of associated injuries. As a result, patients with possibly predictable inferior knee function can potentially be diluted into a larger number of patients with more-favorable outcomes.

Furthermore, patients with injured or reconstructed ACLs are highly diverse in terms of morphology, physiology, anatomic pathology, and psychology. In my view, this variability is somewhat underrepresented, even in studies of primary ACL reconstructions. Based on recent findings showing that one out of three patients with injured ACLs under the age of 20 will experience a repeat ACL injury [3, 11], subdividing the categories according to age and gender will be of paramount importance in future outcome studies [9]. From a morphological context, a patient presenting with recurvatum and/or a Grade 3 pivot shift sign cannot be compared to a patient with a Grade 0 or 1 pivot and no hyperextension. In other words, patients with physiological and pathological high-grade laxity should be differentiated from low-grade laxity [7].

Looking deeper, the current study’s clinical failure rate discrepancy could also be related to inconsistencies in the reporting of existing studies. Another weakness relates to our lack of consensus regarding a definition of failure after ACL revision reconstruction. We can close the knowledge gap by developing international consensus on the required standard criteria for future ACL revision outcome studies.

How Do We Get There?

Developing consensus could be a task for expert groups like the ACL study group or scientific subspecialized societies. Additionally, further collaborative work will be required to collect a critical amount of data through representative numbers of patients [4]. This can be done either through initiatives like the Multicenter ACL Revision Study, patient registries, or standardized data collection in high-volume centers. However, multicenter studies that meet the necessary ethical and data protection requirements have been difficult to perform thus far, particularly on an international scale. In order to develop a consensus, multicenter collaboration needs to be improved and facilitated.