The bone may be weakened both by misuse and by pre-existing drilled tunnels, which may be in the wrong position. The options for taking new graft material may be limited by what procedures were done in the primary procedure.
What one has to keep in mind with respect to ACL revision is that in all likelihood graft material has already been harvested from the patient, most likely from the knee with the cruciate damage, and now for the revision procedure the surgeon and patient have to decide where to take the tissue for the second graft.
The new graft can be taken from someone else (allograft) via a tissue bank - or can be taken from the patient (autograft) either from the same side as the injured knee (ipsilateral) or the opposite side (contralateral).
Allografts (donor grafts) have been used in revision ACL cases, but because they have a higher failure rate compared to autografts, they are considered our last graft option in the majority of ACL revision cases.
In 1994 (ref 1), our Center reported the results of a study of revision replacement of the ACL with use of a bone-patellar tendon-bone allograft. Although of the successes a significant number of patients reported that they had fewer symptoms and were able to do more, there was a high rate rate of failure - 33%. Allografts are expensive, and also there continue to be concerns about the risk of transmission of disease. I recommend that this graft should not be the first choice for revision ACL replacements, and prefer to use an autogenous graft, reserving allografts for knees when options for a good size autogenous graft are exhausted.
The allografts we use are processed with chemicals and stored fresh-frozen. All are obtained from tissue banks which are certified by the American Association of Tissue Banks and have passed inspections from the Center for Disease Control. Donors must be under the age of 45.
Our studies have demonstrated also that a 'ligament augmentation device' used to supplement an allograft offers no beneficial effect, and may even cause failure of the graft by inducing 'stress-shielding', that is protecting the graft from stresses that would encourage ligamentisation. We discontinued use of the LAD many years ago.
Synthetic grafts have an unacceptably high rate of failure, and I mention them only to dismiss them.
'Ipsilateral' (same side) reharvest of the patient's patellar tendon
As the patellar tendon regrows, surgeons faced with the problem of revision in patients who originally had a bone-patellar tendon-bone autograft have tried taking a second graft from the same harvest site for the revision surgery. This may be taken from the same site or a few millimetres to either side of the previous graft. However, there are some problems with this -
- The harvested tendon is weaker than the original harvested tendon and there is a high chance of graft failure
- Complications may occur at the donor site, eg. patellar fracture and patellar tendon rupture.
For these reasons I do not recommend using a re-harvest of patellar tendon, even when the original tendon harvest occurred many years ago.
'Contralateral' (opposite side) bone-patellar tendon-bone graft autograft
My first graft choice for ACL revision reconstruction is the patellar tendon autograft. Studies show that this graft appears to have acceptable results in terms of restored knee stability. If the patellar tendon was previously used, then the opposite knee provides an excellent source to obtain the portion of the tendon required for the operation. There does not appear to be a negative effect on patient recovery when the patellar tendon is harvested from the opposite knee.
In our Center, this graft is harvested with a very small (1 inch) incision, the patellar tendon is carefully sutured back together, and the defect created in the patella is filled with bone obtained during other portions of the operation. These technical aspects of the procedure, along with a carefully designed rehabilitation programme, reduce graft site pain and enable patients to kneel after a few months.
'Ipsilateral' quadriceps tendon autograft
In patients who will not consider harvest of the patellar tendon from the opposite knee, the quadriceps tendon is a reasonable graft source according to its size and structural properties. Our study (ref 3) found acceptable success rates with the quadriceps tendon, comparable to those of the patellar tendon. This graft is especially appealing in patients in whom the original ACL tunnels were placed correctly, but became quite large after surgery. In these knees, a graft with a large diameter is required to completely fill the tunnels and provide a "snug" fit. The quadriceps tendon is large enough to address this problem.
A semitendinosus-gracilis four-strand hamstring autograft may be considered if the tibial and femoral tunnels are not enlarged and if there is no loss of bone stock at the prior tibial or femoral graft sites.
2 Noyes FR, Barber-Westin SD. Revision anterior cruciate surgery with use of bone-patellar tendon-bone autogenous grafts. J Bone Joint Surg Am. 2001;83:1131-43.
3 Noyes FR, Barber-Westin SD: Anterior cruciate ligament revision reconstruction: Results using a quadriceps tendon-patellar bone autograft. Am J Sports Med 34: 553-564, 2006.