Dr. Peter McEwen - M.B.B.S. F.R.A.C.S(Ortho).F.A.Ortho.A.DipModLang - Surgery Knee Dr. Peter McEwen - Surgery Knee: (123) 456789
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Joint Preserving Surgery

High Tibial Osteotomy


High Tibial Osteotomy (HTO) is a realigning, joint sparing operation for osteoarthritis and malalignment of the knee. Unlike a knee replacement (unicompartmental or total) that requires resection and replacement of the worn ends of the bone and in the case of a total knee replacement, resection of the anterior cruciate ligament as well, a HTO preserves the joint and works by shifting load from the worn, arthritic side of the joint to the unworn side. This is achieved by changing the shape of the tibia (shin bone) and therefore where weight is transferred across the knee. HTO is not applicable to all arthritic knees, is not as predictable as TKR (Total Knee Replacement) and is therefore reserved for those who are likely to wear out a TKR. Consequently the person undergoing HTO tends to be, but is not restricted to, a young male with a physical occupation and/or lifestyle. The indications for HTO are quite specific and outside these indications the technique does not produce worthwhile results. These indications pertain to numerous factors including:

  1. Arthritis: HTO is a treatment for osteoarthritis affecting only one side of the knee (unicompartmental arthritis). If both sides are affected then there is no undamaged side to take the load after the realignment in which case the procedure will not relieve pain but merely move it from one side of the knee to the other. By the same reasoning HTO is not used to treat other types of arthritis that affect the whole joint (Rheumatoid Arthritis, Crystal Arthropathy (gout)). Medial arthritis (inside of the knee) is much more common than lateral arthritis (outside of the knee) and the overwhelming majority of HTOs will be done to take weight off a worn medial side and place it on an undamaged lateral side.

  2. Alignment: HTO is a realigning procedure. This implies that there must be a deformity or malalignment present with the arthritis. A HTO is therefore not applicable if the there is unicompartmental arthritis without deformity as the HTO would create the exact situation it is meant to relieve.

  3. Range of Movement (ROM): Typically an arthritic joint loses ROM as the arthritis progresses. Beyond a certain point a TKR becomes a much better treatment option as this ROM can be improved. HTO does not improve ROM and therefore is done only when there is still good movement in the joint despite the arthritis.

  4. Weight: HTO realigns the limb so nearly all the weight is taken across the undamaged side of the knee. This necessarily involves loading the good side well beyond what it would normally take and excess weight will cause the good side to wear quickly. Lean patients get the best results in terms of both the quality and duration of pain relief.

  5. Smoking: Smoking and HTO do not mix. Non-union (the bone not joining back together) and infection are dreadful complications and are much more likely in smokers. Dr McEwen does not do HTO in smokers.

HTO is a reliable and durable treatment option if done in the right patient and if limb malalignment is corrected to the ideal angle. However, many patients undergoing HTO will need a TKR eventually. Converting an HTO to a TKR in a 65 year old who had an HTO in their 40’s or 50’s is however a vastly better situation than converting a failed TKR to revision TKR.

Types of HTO

Many different techniques of HTO exist. Each technique has it’s pros and cons and no technique is applicable to all situations. In most cases Dr McEwen uses a medial opening wedge technique with a Tomofix plate. This technique involves cutting (the osteotomy) the top of the shin bone (the high tibia) in a self stabilizing geometric configuration. The two edges of the osteotomy are pushed apart creating a triangular space. The space is widened until the correct angle is achieved. Everything is then held in place in the corrected position with a rigid titanium plate and screws (the Tomofix). The triangular defect is grafted with bone if large and left alone to heal on its own if small. The medial opening wedge technique combined with the strength and rigidity of the Tomofix plate has three particular advantages:

  1. Accuracy of correction. The correction is infinitely adjustable so achieving the ideal angle is more predicatable.

  2. Rotational stability. The self stabilizing geometry of the osteotomy prevents the foot rotating outwards as the correction is done.

  3. Early weight bearing. The self stabilizing geometry and the rigidity of the Tomofix allows early weight bearing in most cases. Off crutches sooner!

Computer Navigation

Setting the osteotomy to the correct angle is critical to the success of HTO. Undercorrection does not relieve pain and overcorrection is worse than doing nothing. Computer navigation allows very accurate positioning and combined with the infinite adjustability of the medial opening wedge technique is a very powerful tool. Dr McEwen performs all HTO with computer navigation.


HTO is a major procedure that should be undertaken under optimal conditions. This means that your general health needs to be assessed and any correctable problems dealt with prior to surgery. This is especially important if you have a known heart condition and have not been seen by your cardiologist in the recent past. This is very important to minimize surgical risk to yourself. Take note of the following:

  1. High Blood Pressure (Hypertension) should be controlled and stable.

  2. Diabetes should be controlled and stable with blood sugar levels checked regularly.

  3. Any cardiac symptoms (chest pains, shortness of breath, palpitations) should be investigated and treated.

  4. Sleep apnoea should be investigated and treated.

  5.  BMI should be less than 35. BMI is a measure of obesity and is calculated by dividing weight in kg by the square of height in meters. For example someone who weighs 100kg and is 1.89m tall will have a BMI 100/1.89x1.89 = 100/3.57 = 28. The normal range for a BMI is 20-25. If your BMI is over 35 you should lose weight before seeking a HTO. This should be done with the aid of a dietitian and exercise physiologist.

  6.  Smoking is very dangerous when combined with major surgery. Smoking must be ceased. Dr McEwen will not undertake a HTO if you're smoking.

  7. Many medications have an effect on bleeding, blood clotting and wound healing. Blood thinning medications (Aspirin, Clopidogrel, Warfarin, Pradaxa) will need to be ceased at least 5 days prior to surgery. Dr McEwen will give specific instructions regarding this. Seek clarification well before surgery if unsure.

  8. Cease any naturopathic or herbal medications 10 days before surgery.

  9. Look after your skin. The skin on the leg being operated on must be free of cuts, scratches, grazes and bites.

Day of Your Surgery

You will be admitted to the hospital on the day of your surgery. Blood tests may be required on admission. You will meet the nurses and answer some questions for the hospital records.You will meet your Anaesthetist, who will ask you a few questions. You will be given hospital clothes to change into and have a shower prior to surgery. The operation site will be shaved and cleaned. Approximately 30 minutes prior to surgery you will be transferred to the operating theatre complex.

Surgical Procedure

Surgery is performed under sterile conditions in the operating room under spinal or general anaesthesia. You will be positioned on your back and a tourniquet applied to your upper thigh. The surgery takes approximately 80 minutes. There are a number of components to the procedure:

  1. An arthroscopy of the knee is done to remove any loose pieces of cartilage.

  2. Trackers for the computer navigation system are attached via keyholes to the skeleton above and below the knee.

  3. The arthroscope is reintroduced and the knee is registered, a process by which the navigation system is taught the specifics of the limb and knee.

  4. The osteotomy is done through a 6-7cm long incision on the shin.

  5. The correction is done, checked with the computer navigation system and fixed in place with the Tomofix device.

Accurate positioning and rigid fixation constitute only one part of the formula for success. The remainder of the formula is ensuring that pain and swelling are controlled. Numerous methods are employed in this regard:

  1. Spinal anaesthesia , peripheral nerve blockade and local anaesthetic infiltration are techniques that are used alone or in combination to reduce pain after HTO. The specific protocol is individualized to each patient.

  2. Cryocuff. A cryocuff is a mobile, patient operated ice delivery system that reduces pain and swelling. The cryocuff is applied to the knee after wound closure.

  3. Multimodal Analgesia. A combination of drugs are used to manage pain and ensure reasonable sleep after the TKR.

Dr McEwen employs all these strategies routinely. All HTO patients will discharge with a cryocuff which is returned after 2 weeks. The vast majority of TKR patients will discharge after 24-48 hours. This does not mean that there will be no pain or swelling but that pain will be manageable and much less likely to interfere with movement.


Getting over major surgery without any problems requires an active approach to prevent problems rather than reacting to problems once they occur. The rule with prevention is “the sooner the better”. Therefore there are a few things the patient should actively take responsibility for:

  1. Ice therapy. Turn over the water in the cryocuff at least hourly unless sleeping.

  2. Blood Clot Prevention. Drink plenty of fluids. Do calf pump exercises when lying or sitting. Be prepared to be out of bed a few hours after surgery. Being up quickly is the most important.

  3. Pain Control. Don’t let pain ramp up. As soon as you are aware that pain is increasing let the nursing staff know. Much less painkiller is required to keep pain away compared to beating severe pain into submission.

The nursing staff will assist you with these issues but remember to actively take control of your own well-being.

Physiotherapy begins the day of surgery and will be a daily event until discharge. The aim is to have you independently mobile and self caring as quickly as possible. Crutches will be required. Axillary crutches are best until some weight is being taken at which point Canadian crutches are less cumbersome.

The criteria for discharge are a dry wound, good pain control with oral medications, no high temperatures and a pass mark from the physiotherapist including on stairs. Most will achieve this within 24 hours. Make sure you have your discharge envelope with scripts, information sheets and appointment card when you leave. These information sheets are important and should be read. They are available on this website as well. Hit the Patient Info tab on the home screen and click on Patient Information Pamphlets.

Remember that swelling is the enemy of movement and causes infection. Use the cryocuff and keep the leg up. Lots of small walks around the house followed by periods of elevation and ice is the correct approach.

Sleep in whatever position is most comfortable. There is no need to sleep only on your back with the knee straight.

The wound should be clean and dry. Notify Dr McEwen immediately if this is not the case.

You will have a postoperative appointment scheduled for 2 weeks after the surgery. Sutures will be removed at this time. Paul Parker, a very senior and experienced musculoskeletal physiotherapist will see you at the same time so leave plenty of time for this. There is no need for supervised physiotherapy between discharge from hospital and your appointment with Paul.

Sleep disturbance is very common after HTO and tends to persist long after walking is easy. Sleep in whatever position is most comfortable, use ice, and use the provided sleeping tablets and painkillers if needed (as long as they are causing no side effects).

Risks and Complications

As with any major surgery, there are potential risks involved. The decision to proceed with the surgery is made because the advantages of surgery outweigh the potential disadvantages

It is important that you are informed of these risks before the surgery takes place.

  • Infection. Infection can occur with any operation. Around an HTO this can be superficial or deep. Superficial infections are treated with antibiotics. Deep infections always require surgical treatment as well as antibiotics. Deep infection is an uncommon but very serious complication and many measures are employed during the course of having a HTO to prevent it. The Tomofix device and osteotomy are just under the skin. Swelling and haematoma formation put pressure on the skin which can cause the wound to break down. Keeping the limb up to preventing this is critical to minimizing the risk of a deep infection.

  • Blood Clots (Deep Venous Thrombosis).These can form in the calf muscles and can travel to the lung (Pulmonary embolism). These can occasionally be serious and even life threatening. If you get calf pain or shortness of breath at any stage, you should notify your doctor. As with infection, many measures are employed to prevent this complication. These include compression stockings, calf compressors, IV fluids, blood thinning medications but by far the most important is early mobility.

  • Neurovascular injury (Damage to nerves and blood vessels). The major nerves and vessels that pass the knee are within a centimetre of the surgical envelope of a HTO. Great care is taken to avoid damage to these important structures.

  • Non-union. Biologically an HTO healing is exactly the same as a fracture healing. The happens reliably if the HTO is sterile, mechanically rigid and attached to a non-smoker. Non-union is very uncommon but requires bone grafting and revised fixation if it occurs.

  • Numbness. The skin on the outside edge of the incision will be numb after the surgery. Most people are very aware of this in the first 6 months after surgery. The sensation of numbness fades with time but probably never returns absolutely to normal.


HTO changes the shape and therefore the appearance of the limb. A medial opening wedge HTO will in every case:

  1. Lengthen the limb. By making a bowed leg straighter and by opening a wedge to do the limb is invariably lengthened. Frequently this will in the range of 1 cm in magnitude. You will be very aware of the differences in length and angles for at least 6 months. This is especially so if the other leg is also bowed.

  2. Shape of the limb. A medial opening wedge HTO will make a bowed leg straighter. If the other leg is bowed the difference of appearance will be noticeable. If the other leg is straight the HTO will make the limbs more symmetrical.


Surgery is not a pleasant prospect for anyone, but for some people with arthritis, it could mean the difference between leading a normal life or putting up with a debilitating condition. Surgery can be regarded as part of your treatment plan—it may help to restore function to your damaged joints as well as relieve pain.

Surgery is only offered once non-operative treatment has failed. It is an important decision to make and ultimately it is an informed decision between you, your surgeon, family and medical practitioner.

Although most people are much improved after HTO, complications can occur and you must be aware of these prior to making a decision. If you are undecided, it is best to wait until you are sure this is the procedure for you. Full recovery from an HTO takes around months. This is the time required for the brain and muscles to adjust to changes in limb length and angle and for inflammation in the arthritic half of the knee to resolve.

Dr. Peter McEwen - Surgery of Knee
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