If patients have symptomatic arthritis in either the medial or lateral part of the knee as well as instability from ACL deficiency, then depending upon the patient’s age and intended future activities, they may be suitable for a combined ACL reconstruction and high tibial osteotomy. This surgery is a “joint salvage” procedure with a view to achieving a more stable and pain improved knee and quite often, with a view to delaying or avoiding knee replacement.
Patients who have both medial compartment arthritis of the knee and anterior cruciate ligament deficiency can experience symptoms of both arthritis (pain, swelling, stiffness) and instability (giving way with change in direction) which together result in a significant loss of confidence with the affected lower limb. This combination of pathology usually arises from a longstanding ACL deficiency, where patients have either not undergone an ACL reconstruction, or have done so, but experienced ACL insufficiency from graft attenuation over time or repeat injury and re-rupture. The ACL helps keep the knee stable both in the frontal (sagittal) and side to side (coronal) planes, and when it is ruptured, the weight-bearing axis begins to migrate from towards the middle of the knee instead towards the medial or innermost part of the knee and also as the tibia begins to sublux forward, more through the posterior zones of the knee. Thus the natural history with ACL insufficiency is that over time, the posterior and medial most part of the tibia wears down to bone and the knee develops progressive bowing and can also develop a flexion contracture, with difficulty getting the leg out straight. Usually once patients begin experiencing pain with prolonged standing or walking or pain at rest, more so than the knee continuing to give way, they seek out medical attention. It is important to establish what the goals are for the patient, whether they are interested in attempting to perform high impact (jogging, running, jumping) or change in direction (tennis, squash, touch football) type activities in the future. A consideration of their goals plus the patient’s age will usually help decide whether knee reconstruction with either high tibial osteotomy (HTO) or HTO and ACL reconstruction together are the best options; or whether knee replacement with either total knee replacement (TKR) or unicompartmental (partial) knee replacement (UKR) and ACL reconstruction is the better way forward. The longest rehabilitation schedule for almost all knee procedures is that required for a high tibial osteotomy performed using opening wedge technique with bone grafting, needing crutches for at least three and often four months, with a much shorter rehabilitation schedule for a total knee replacement, which in the majority of cases only requires crutches for one to two weeks.
If reconstructive efforts are considered appropriate, then the next big decision is whether the patient intends on doing change in direction activities, working on uneven ground or performing jumping activities etc that may put the knee at risk for giving way, and if not, then usually an isolated HTO with an alteration (decrease) of the tibial downslope by positioning the HTO plate more posteriorly than the usual position, and using a locking plate with an anteriorly sloped “tooth” inserted into the osteotomy void to allow for this, will provide some increased sagittal plane stability helping to compensate for the ACL insufficiency whilst also correcting the bowing deformity of the lower limb, and alleviating the symptoms (pain, swelling, stiffness) of their medial compartment arthritis. Once the tibial plate and screws have been inserted it is not readily possible to do an ACL reconstruction due to the location of the plate and screws. Hence, if patient circumstances dictate they require both ACL reconstruction and HTO, it is preferable to perform the ACL reconstruction either in advance of the HTO in a staged manner (minimum of 6 weeks, preferably 3 months in advance) or if on the same day, immediately prior to undergoing the HTO surgery. The HTO utilises a similarly located incision as that used for hamstring graft harvest for the ACL reconstruction, albeit slightly longer and the harvesting of the hamstring tendons from the pes bursa, clears a space for the tibial osteotomy plate and screws. The tibial tunnel position for the ACL reconstruction is usually modified by making it slightly more proximal or closer to the joint line than otherwise to try to get above the HTO bony cut, and likewise the tibial osteotomy cut is made slightly lower than normal to allow ample room to contain and conceal the tibial tunnel (RCI screw) fixation device without protruding into the knee or overhanging outside the medial cortex. Once the tibial osteotomy has been performed and the ACL graft has been passed (ie. graft not passed until after the tibial osteotomy performed to avoid amputating the graft) the tibial plate and screws can be positioned. The osteotomy void is then packed with bone graft, the anteromedial wound closed in layers and the knee rehabilitation schedule is dictated by the HTO rehabilitation pathway, with graduated weight bearing and range of motion with serial X-rays taken immediately post operatively and again at weeks six, twelve and usually again at four months. In order to avoid arthrofibrosis, slightly faster graduated range of motion is performed within the first six weeks than would otherwise take place with a HTO alone. Once patients have early consolidation of their HTO void and the ACL graft is at or past three months, then the rehabilitation begins to resume a focus on the ACL reconstruction, usually one or two months slower than a normal ACL reconstruction schedule, with open chain leg weights at the four month rather than three month mark, and unidirectional jogging at the six month rather than four month mark. Multidirectional pivot drills take place at the eight month mark rather than the six month mark and sports specific drills at the nine to ten month rather than seven to eight month mark.
Thus, the primary goal of the combined ACL and HTO, is to achieve a pain free or pain improved and more stable confident knee, that allows patients to do more vigorous activities than they would otherwise be encouraged or allowed to do with a knee replacement. This procedure is ideally suited to younger (less than 55 years of age) manual labourers or tradesman or persons who wish to engage in high impact running type activities or a contact or combative sport, who accept the longer rehabilitation time necessary to achieve their end result. It is relatively contra indicated in patients who are smokers, due to the significantly increased risk of delayed bone healing (delayed-union) or failure to heal (non-union) and increased risk of infection, and patients with an inflammatory pattern of arthritis (ie. Rheumatoid) as its likely that the other compartments of the knee will have areas of arthritis and that the ligament reconstruction is at increased risk for graft failure due to synovitis. Finally, in order for the HTO to work, usually the knee will have to be swung into accentuated valgus alignment, or made to be quite knock kneed, which in my experience to date many female patients may feel is an unacceptable cosmetic result, and as such older, more sedentary or female patients may consider knee replacement (if appropriate) as a favourable alternative to combined ACL and HTO reconstruction, with younger, more active male patients or female patients who accept the cosmetic limitations and longer recovery, usually consider it as a good option to allow them to continue their current job or physical pursuits for the foreseeable future and at the same time avoiding a knee replacement.