In this paper three authors review the literature up to 2018 relating to several important factors that they feel commonly contribute to failure revision anterior cruciate ligament (ACL) reconstruction if they are not addressed at the time of the surgery, in the hope that today's surgeons will pay especial attention to them and avoid failure of the revision surgery. The four issues they discuss include (and we will define these as we go along):
- posterior tibial slope
- varus malalignment
- incompetent anterolateral ligament (ALL)
- meniscal deficiency
What constitutes failure of Anterior Cruciate Ligament Reconstruction?
The authors point out that there is no clear definition of what constitutes failure of anterior cruciate ligament reconstruction (ACLR) but concepts include:
- recurrent pain or arthritis
- arthrofibrosis or loss of motion
- extensor mechanism dysfunction
- recurrent instability
Failure is often multi-factorial and due to a combination of technical error, trauma &/or a biological factor. Objective assessment of failure includes measurements that compare the operated knee to the normal one, or that compare previous activity level to the current level that is achievable.
Important factors to consider when revising an ACLR
Posterior tibial slope
As the posterior tibial slope (PTS) increases, a greater force is applied to the ACL graft. They discuss the literature relating to this.
Although there are only a relatively small number of publications relating to this issue, the authors consider that an osteotomy should be considered (slope-changing tibial deflexion osteotomy) when a failed revision ACLR is accompanied by a PTS of 13 degrees or more, and they point out that studies suggest this can safely be performed at the same time as the revision.
This is calculated from standing weightbearing Xrays, and the authors give a definition of >3% of bowing from the mechanical axis of femur and tibia, or a weightbearing line that passes medial to the centre of the knee.
Bowing like this puts increased strain on the ACL, and the authors point to studies that suggest a reconstruction is more likely to fail if varus alignment is not addressed at the time of the reconstruction via a high tibial valgus osteotomy.
The addition of such an osteotomy is particularly relevant in patients who want to return to a high level of activity. The authors also point out that the rate of progression of arthritis is lower if an osteotomy has been added.
The authors refer to recent literature that suggests there is no particular issue with the combined procedure. They also go into details about related issues of varus thrust, and double or triple varus and hyperextension, which I have not covered here.
Anterolateral ligament incompetence
The authors discuss the publications that suggest that varying degrees of instability on pivot shift and Lachman examination manoeuvres correlate closely to damage to the anterolateral ligament (ALL), which is often torn in association with damage to the ACL.
Again they point to publications that suggest that the ALL should be repaired at the same time as a revision reconstruction, although they caution that it may lead to over-restraint if done initially with the primary procedure.
In the paper, studies are pointed to that show that the intact menisci play a role as a secondary restraint in the ACL-deficient knee, and the lateral meniscus specifically helps to prevent abnormal joint rotation. Patients who had a meniscectomy before, during or after primary or revision ACLR had significantly compromised stability.
There is recent interest in ramp lesions which disrupt the stabilisation offered by the meniscus and the authors feel that repair of ramp lesion should be undertaken at the time the ACLR is done.
They point also to recent papers advocating meniscal allograft transplantation at the same time as the ACLR where the meniscus has already been removed - in order to restore stability and protect the ACL graft. This is especially indicated in the younger meniscectomised patient where pain persists but the alignment is still normal and there is minimal joint damage. The authors themselves would consider it even if a bit of the meniscus (up to 40%) remains.
The authors conclude that revision aCLR is technically challenging and requires careful attention to details and consideration of all those factors that may have contributed to previous failures.