Revision knee reconstruction requires careful consideration as to why the original surgery failed, as well as graft selection, whether the surgery needs to be performed in a single or staged procedure and the development of a careful rehabilitation program specific to the individual patient’s circumstances.
In general terms, the risk of failure of reconstructed knee ligaments is low. The most common knee ligament reconstruction is the ACL reconstruction, with the incidence of ACL rupture in the community being approximately 1 in 20 persons (5%). For those individuals that sustain an ACL rupture, they are from that time onwards considered an at risk individual, and the likelihood of them rupturing the ACL in their other knee, is higher than the general population, with approximately a 1 in 10 (10%) risk of rupture.
After undergoing a properly performed ACL reconstruction, the risk of graft rupture is usually only 1 in 20 or 5% which is equal to the general community incidence, and theoretically a lower likelihood (5%) of re-injuring their reconstructed knee when compared to the risk (10%) of rupturing the ACL in their other knee. There are many reasons why a ligament reconstruction can fail including factors involving; the patient, original surgery, post operative rehabilitation, and both the original and repeat injuries.
Some patients have familial ligamentous hyperlaxity, with excessively loose ligaments with easily stretched collagen and/or osteoporosis with poor bone stock allowing slippage of graft fixation leading to recurrent laxity and instability.
Common Reasons for Revision Knee Reconstruction
The most common surgical error is poorly positioned ligament reconstruction graft tunnels which can lead either to stiffness or laxity of the knee and eventual graft failure. In addition to graft tunnels, poor graft preparation and failure to address other ligament and meniscal injuries can lead to recurrent instability and graft failure.
Post Operative Complications
After surgery, post operative complications such as excessive bleeding or swelling can sometimes lead to a delay in regaining range of motion and stiffness, and infection can lead to graft and fixation failure.
Finally, the post-operative rehabilitation can also contribute to the suboptimal results, especially if uncontrolled activities are performed during the first four months whilst the grafts are remodeling from the harvested tendon to a neo-ligament, as this can lead to attrition and elongation of the graft with residual laxity, instability and high risk for failure.
Additionally, each pattern of ligament injuries requires a specific phased course of rehabilitation, to regain range of motion, strength, confidence and control both with straight line (uni-directional) and change in direction (multi-directional) activities.
If the rehabilitation is not completed fully, patients may lack the motor control and position sense (proprioception) needed to co-ordinate the muscle groups around the reconstructed knee, leaving them unco-ordinated and at risk for a recurrent episode of giving way and ligament injury.
A dedicated knee physiotherapist is usually able to provide patients with a specific physiotherapy programme that will take all of these patient, surgery and rehabilitation factors into consideration to develop the optimal rehabilitation program.
When Revision Knee Reconstruction Surgery is Required
If revision surgery is required, it is important to establish a cause as to why the original surgery failed, in order to address not only the necessary surgery to overcome the graft failure but to minimise the risk of it doing so again.
When considering revision reconstruction, graft selection is a major area to be decided upon, in order to have sufficiently large and adequately strong graft for reconstruction.
This usually includes a review of what tissue has already been used from the; same leg, other leg, synthetic grafts (LARS) and other persons donated tissues (allografts) stored in a tissue bank.
The preference is almost always to use an individual’s own tissue, from the same leg, then if necessary go to the other leg then to consider synthetic and allograft tissue sources.
Rehabilitation Program after Revision Surgery
Depending on the combination of pre-existing surgery, ligaments originally reconstructed, ligaments requiring reconstruction for the first time and ligaments requiring revision reconstruction, a specific rehabilitation program is imperative when revision surgery has been undertaken to optimise the functional outcomes and minimise the risk of recurrent injury.
Occasionally the bone tunnels used for ligament passage through the knee are excessively widened and prevent a straight forward revision and needs bone grafting to fill in these tunnels and may require consideration of the revision being done in two stages, with initial bone grafting of tunnels and then when adequate bone graft incorporation has occurred, usually at least 3 to 4 months later, revision ligament reconstruction.