OSTEOTOMY – HIGH TIBIAL (HTO), DISTAL FEMORAL (DFO), TIBIAL TUBERCLE (TTO)

There are several types of osteotomy that can be performed around the knee by cutting through part of either the tibia or the femur with the three most common being high tibial osteotomy (HTO), distal femoral osteotomy (DFO) and the tibial turbercle osteotomy (TTO).

The knee is a large joint divided into three compartments, which are termed as the inner or medial compartment, the outer or lateral compartment and the frontal or patellofemoral compartment. Whilst the knee can develop wear and tear arthritis in all three compartments in a generalised manner, quite often it will develop arthritis predominantly in one compartment, leading to pain, swelling and deformity. If the remainder of the knee is in reasonably good condition, pain relief and correction of the deformity can be achieved by making a bony cut (osteotomy) in either the femur – Distal Femoral Osteotomy (DFO) or tibia – High Tibial Osteotomy (HTO) or Tibial Tuberosity Osteotomy (TTO) and adjusting the alignment of the femur, tibia and patella. These techniques have existed for many decades, but recent developments in HTO and DFO have included a change from; cutting out a wedge of bone and forcing the remaining surfaces of cut bone together (“cut and shut”) to an “opening wedge” technique. The traditional closing wedge technique, always tended to shorten the already shortened leg further, lacked the fine tuning necessary to achieve an accurate correction as once the triangular piece of bone was removed there was no turning back and if too much was cut it just needed to be accepted, altered the “tibial downslope” or angle that the tibial joint surface sloped backwards, which quite often undermined the correction achieved in the side to side or coronal plane by having unfavourable forces applied in the front to back direction or sagittal plane forcing more weight through the area of maximal arthritis at the front of the medial tibia, leading to ongoing pain, and finally created a bayonet type contour on the bones outer surface, making future surgeries such as knee replacement more difficult to perform.

The more contemporary opening wedge technique where a cut is made in the bone, but no bone is removed, and instead the two cut surfaces of the bones are levered apart and are held in their carefully calculated new position with a small lightweight but strong titanium plate and locking screws. This technique creates a small triangular void which if is small enough is allowed to heal by itself or is filled in with some bone graft to facilitate healing. This opening wedge technique creates an angular change in the alignment of the lower limb, and is versatile enough to allow for corrections in deformity both in the side to side or coronal plane and the front to back or sagittal plane by modifications in where the plate is positioned and using an angular “titanium tooth” to alter the bones orientation after the osteotomy is performed. The overall correction is able to be finely tuned during surgery by using X-ray screening (fluoroscopy) techniques, from the smallest plate with a 5mm (0.5cm) titanium tooth, with fine incremental changes of between 1 to 2.5mm up to the largest plate available with a 17.5mm (1.75cm) tooth. Usually, if patients are being considered for this procedure one leg will be “bowed or knock kneed” and shorter than the other leg, and following the procedure the operated leg will have been lengthened, and the discrepancy between the legs reduced. The maximal correction in leg length discrepancy is approximately 2cms with the combination of the angular correction and lengthening acting in concert to help overcome the pre-existing shortening of the affected leg.

The commonest pattern of unicompartmental arthritis is wear in the inner or medial aspect of the knee, and if the degree of wear is advanced, the leg may actually be bowed at the knee, with associated medial joint line pain and swelling. If the patient still wishes to perform moderate physical activities for work (tradesman, manual labour) or recreational activities (running, jumping) and has symptomatic unicompartmental arthritis in the medial compartment, they may be suitable for a high tibial osteotomy (HTO). This involves a 5-6cm vertical skin incision just below the knee at the junction of the anterior (front) and medial calf. The upper tibia is then prepared by making an oblique osteotomy (bony cut) under fluoroscopy (X-ray imaging) control, and the gap created between the two cut surfaces gradually increased in increments until the weight bearing axis (a line measured from the centre of the hip to the centre of the ankle) has shifted from the diseased medial compartment to either the middle of the knee or the inner (medial) third of the lateral (disease free) compartment, with the degree of correction depending upon the patients pathology. The size of the osteotomy plate is then chosen based upon whichever gives the optimally corrected weight bearing axis, and it is carefully secured both above (proximally) and below (distally) with titanium locking screws, the gap filled in with bone graft, and the wound closed in layers over a small drain. The drain is removed the following day, and patients usually spend 2 nights in hospital to assist with pain relief, learning how to mobilise with the use of crutches and fitting and removing their knee brace, including an extension splint (which is used for 1-2 weeks) and a hinged range of motion brace (used for 8 -14 weeks), and how to self administer their anticoagulation injections (low molecular weight heparin – Clexane) which they use for the first 10 – 20 days. Patients will usually require a minimum of 2 weeks off work if performing office duties and longer if manual duties are necessary, and will usually not be able to resume driving a car for a minimum period of 2-4 weeks, depending on which leg has been operated on, whether the car is an automatic or manual, and the patient’s ability to concentrate and be alert which is influenced by the type and volume of medications the patient is requiring to manage their pain. Whilst the titanium plate and screws are very strong, repetitive load bearing (walking, knee bending) before the bone has healed may result in fatigue and failure of the implants, loss of the correction achieved and or delayed healing of the osteotomy (delayed union, non-union), hence a hinged knee brace and crutches are used with graduated increase in knee bending and weight bearing each week for approximately 3 months following surgery. X-rays are taken immediately post operatively after removal of the drain, and again at 6 weeks and 12 weeks, before progressing the range of motion and weight bearing. Further rehabilitation guidelines are outlined below.

The outer or lateral compartment of the knee can also develop unicompartmental arthritis and if the degree of wear is advanced, the leg may develop marked valgus, which is an angular deformity or “knock knee” appearance, with associated lateral joint line pain and swelling. If the patient still wishes to perform moderate physical activities for work (tradesman, manual labour) or recreational activities (running, jumping) and has symptomatic unicompartmental arthritis in the lateral compartment, they may be suitable for a distal femoral osteotomy (DFO). This involves an 8-9cm vertical skin incision on the outer or lateral aspect of the lower thigh, about 1 hands breadth above the knee joint. The distal femur is then prepared by making an oblique osteotomy (bony cut) under fluoroscopy (X-ray imaging) control, and the gap created between the two cut surfaces gradually increased in increments until the leg is no longer knock kneed but straight or slightly bowed, with the degree of correction depending on the patient’s pathology. The amount of correction necessary is measured intra-operatively using the hip to ankle axis (a line measured from the centre of the hip to the centre of the ankle).  Generally the axis is shifted from the diseased lateral compartment to either the middle of the knee or the outer (lateral) third of the medial (disease free) compartment. The size of the osteotomy plate is then chosen based upon whichever gives the optimally corrected weight bearing axis, and it is carefully secured both above (proximally) and below (distally) with titanium locking screws, the gap filled in with bone graft, and the wound closed in layers over a small drain. Whilst the titanium plate and screws are very strong, repetitive load bearing (walking, knee bending) before the bone has healed may result in fatigue and failure of the implants, loss of the correction achieved and or delayed healing of the osteotomy (delayed union, non-union), hence a hinged knee brace and crutches are used with graduated increase in knee bending and weight bearing each week for approximately 3 to 4 months following surgery. Patients usually spend 2-3 nights in hospital to assist with pain relief, learning how to mobilise with the use of crutches and fitting and removing their knee brace, including an extension splint (which is used for 1-2 weeks) and a hinged range of motion brace (used for 8 -14 weeks), and how to self administer their anticoagulation injections (low molecular weight heparin – Clexane) which they use for the first 10 – 20 days. Patients will usually require a minimum of 2 weeks off work if performing office duties and longer if manual duties are necessary, and will usually not be able to resume driving a car for a minimum period of 2-4 weeks, depending on which leg has been operated on, whether the car is an automatic or manual, and the patient’s ability to concentrate and be alert which is influenced by the type and volume of medications the patient is requiring to manage their pain. Whilst the titanium plate and screws are very strong, repetitive load bearing (walking, knee bending) before the bone has healed may result in fatigue and failure of the implants and loss of the correction achieved, hence a hinged knee brace and crutches are used with graduated increase in knee bending and weight bearing each week for approximately 3-4 months following surgery. X-rays are taken immediately post operatively after removal of the drain, and again at 6 weeks and 12 weeks, before progressing the range of motion and weight bearing. Further rehabilitation guidelines are outlined below.

If the patella (knee cap) does not travel up and down the front of the femoral trochlea groove as it should (maltracking), comes out of the patellofemoral joint (instability) and/or has arthritis on one side of the patellofemoral joint – it may benefit from repositioning by performing a tibial tuberosity osteotomy (TTO). The tibial tuberosity is a bony prominence on the front of the upper tibia, which receives the attachment of the patella tendon as it runs from the lower pole of the patella. Once the tibial tuberosity osteotomy has been performed, it can be moved medially, laterally and if necessary also anteriorly and/or proximally, to improve its tracking, stability and if necessary try to decrease the contact pressures across the patellofemoral joint. One of the more common reasons for doing this procedure is for patients with recurrent lateral patellofemoral instability with an increased Q-angle, and the tibial tuberosity is moved medially towards the inside of the knee, before securing with two screws (see Reconstruction, Patellofemoral Realignment and Stabilisation). Additional procedures are sometimes combined with the tibial tuberosity osteotomy, including a lateral retinacular release, medial quadriceps (VMO) advancement, and medial patellofemoral ligament (MPFL) reconstruction. Patients usually require 2 nights stay in hospital to assist with pain relief, learning how to mobilise with the use of crutches and fitting and removing their knee brace, including an extension splint (which is used for 1-2 weeks) and a hinged range of motion brace (used for 4-6 weeks), and how to self administer their anticoagulation injections (low molecular weight heparin – Clexane) which they use for the first 10 – 20 days. Patients will usually require a minimum of 2 weeks off work if performing office duties and longer if manual duties are necessary, and will usually not be able to resume driving a car for a minimum period of 2-4 weeks, depending on which leg has been operated on, whether the car is an automatic or manual, and the patient’s ability to concentrate and be alert which is influenced by the type and volume of medications the patient is requiring to manage their pain. The two screw fixation holding the TTO is reasonably strong, but repetitive load bearing (walking, knee bending) before the TTO has healed may result in loosening and failure of the screw fixation and loss of the TTO correction achieved and or delayed healing of the osteotomy (delayed union, non-union), hence a hinged knee brace and crutches are used with graduated increase in knee bending and weight bearing each week for approximately 6-8 weeks following surgery. X-rays are taken immediately post operatively after removal of the drain, and again at approximately 6 weeks and 12 weeks, before progressing the range of motion and weight bearing. Further rehabilitation guidelines are outlined below.

Once patients are given the all clear to commence mobilising without crutches, it is best advised to concentrate on regaining confidence with normal walking or “gait pattern” for approximately a month and developing some basic muscle conditioning before commencing a dedicated gym strengthening program including leg weights, exercise bike, and accelerated walking on a treadmill for a two month period before more vigorous activities are considered and/or commenced pending clinical and radiological confirmation that the osteotomy has healed fully. Usually a minimum of 4 months following a tibial tuberosity (TTO) osteotomy and 6 to 9 months following a high tibial or distal femoral (HTO, DFO) osteotomy is required before patients are able to recommence higher demand outdoor and sporting activities which involve running and jumping activities.