Unfortunately, not all patients are suitable candidates for revision, and some have arthritis which is too far advanced for the operation to be considered to have a benefit. But in many cases, knee stability can be restored to at least allow the return of light recreational activities and a healthy lifestyle.
We begin all patients on immediate knee motion and muscle strengthening exercises on the first day after surgery. We prescribe a brace for the first six weeks.
Partial weight bearing is usually encouraged during the second week, progressing to full weight-bearing by the sixth week. An exception occurs in patients who also had a posterolateral ligament procedure, as weight bearing is progressed more slowly, with full weight bearing after twelve weeks. In these patients, an unloading brace, which decreases the loads on the posterolateral structures, is prescribed for six to nine months.
Patellar mobilisations are done from the first postop day. All patients are encouraged from the first day after surgery to regain range of motion (ROM), and we hope for a range of at least 0-90 degrees by the second week after surgery, except in those patients who have posterolateral surgery where 0-90 degrees are expected by the fourth week and 135 degrees by the eighth week. Patients who are slow to achieve these ranges are enrolled in a specific treatment programme.
Muscle strengthening is begun on the first post-op day, with isometric exercises (eg quad sets), straight leg raising and electrical muscle stimulation (EMS). As soon as patients are partial-weight-bearing, they begin simple closed-chain exercises. At 5-6 weeks, open chain exercises are introduced under carefully controlled and supervised conditions, as well as proprioception exercises and general fitness exercises. Provided all is proceeding normally, running is allowed by 6 months, and return to full activities by 9-12 months. Patients who have pre-existing joint arthritis are advised not to return to high impact activities, but to focus on low-impact activities such as swimming and bicycling.
- revision of the ACL alone
- revision of the ACL after high tibial osteotomy (HTO)
- revision of the ACL together with concurrent ligament procedures
We asked the patients to rate themselves (on the Cincinnati Knee Rating System) before and after the revision in terms of pain, swelling, giving way, functions of activities of daily living (ADL), and their ability to perform their normal occupation. We also measured the results of the operation with the KT-2000, Lachman, and pivot shift tests. Although the majority of patients felt subjectively improved, the best results were in the uncomplicated group, with poorer results from the HTO group and even poorer results from the patients who had both revision and another ligament procedure. In this latter group, 35% were deemed a surgical failure, compared to 16% in the uncomplicated group and 22% in the HTO group.
Four factors showed themselves to be significant predictors of outcome -
- KT 2000 values
- the score for twisting
- the score for walking
- the pivot shift values
The compounding problems inherent in knees requiring revision ACL surgery - joint cartilage damage, previous meniscectomy, loss of other ligament restraints, bow legs - together with the added challenge of concomitant ligament procedures and meniscal repair during the revision, lead inevitably to the poorer results of revision surgery over primary ACL surgery. Nonetheless, a high percentage of patients report a symptomatic improvement, which makes the revision procedure worthwhile in the majority of patients.
The best outcomes of ACL revision are in the subset that does not have joint cartilage damage, a previous meniscectomy, bow legs or other major ligament instabilities. In this group, I expect an outcome equivalent to a correctly performed primary reconstruction procedure. In order to give the patient this chance, if a graft fails the revision operation needs to be done early to avoid adding new joint surface and meniscal damage to the ligament problems.
In patients with a failed ACL graft in whom there is already joint cartilage damage and meniscal damage, and who perhaps continued to challenge their knee after graft failure with inappropriate activity, we generally find a poorer outcome of a subsequent ACL revision. This group of patients typically may not return to strenuous athletic activities after revision surgery. The condition of the joint cartilage before revision has a significant effect on outcome, and we counsel patients with joint cartilage damage to be realistic in their expectations - pain and instability with ordinary daily activities is likely to be improved, and about half the patients in this group are able to return to light recreational activities, but return to full sporting activities is likely to be out of the question.
The third subset of patients, whose failed ACL graft is further complicated by other ligament inadequacy - due often to pre-existing lateral collateral ligament and posterolateral damage - need immediate motion exercises and a very comprehensive rehabilitation programme after surgery. This group of patients has a less predictable outcome, although some patients may have reasonable results.
Finally, the fourth subset includes those patients who require a high tibial osteotomy. Varus alignment (bow legging) and varus thrust (the knee thrusting out with each step) increase the forces on the lateral (outer) and posterolateral tissues which may become strained and damaged, allowing increased lateral joint opening and subluxation (slipping) backwards of the tibia under the femur. This group is the most challenging to manage. Really, the osteotomy to correct the alignment needs to be performed some months before continuing with the ACL graft revision. Again, the outcome is less predictable and patients may need to prepare for disappointment.