The midfoot is a term that refers to the middle third of the foot. This includes several rows of joints. One row is the talo-navicular joint and the calcaneo-cuboid joint. The next row is the naviculo-cuneiform joint. The next row consists of five joints which are side by side across the whole foot, between the tarsal and metatarsal bones. These are called the tarso-metatarsal joints, or Lisfranc Joints.
The talonavicular joint is a ball and socket joint on the inner two thirds of the foot. It allows side to side movement of the foot. If this joint becomes arthritic, then this movement is lost and the foot cannot adjust well to uneven ground, and attempting this is painful. If the joint alone is stiffened then almost all side to side movement of the foot is lost.
The calcaneo-cuboid joint is on the outer third of the foot. It also allows side to side movement. If this joint alone is stiffened then 25% of the side to side movement of the foot is lost.
The naviculo-cuneiform joint is on the inner side of the foot. It is normally quite stiff, but can become painful if a flat foot develops. If this joint is stiffened then there is no appreciable loss of movement.
The tarsometatarsal joints are a set of five joints. The inner joint and the outer joint are normally quite mobile. The middle joints are normally quite stiff. If the middle joints are stiffened then there is no appreciable loss of movement. If the inner joint is fused, then there is some loss of flexibility in the foot. The outer joint is never fused.
What is Arthritis?
Arthritis means inflammation of a joint. There are two common types of arthritis. One is inflammatory arthritis, when the body attacks a component of the joints, leading to pain and swelling. Another type is osteoarthritis, which is caused by wear and tear changes, which again cause pain, swelling and stiffness. Walking will lead to worsening pain, and this may continue even at night as a ‘hangover’ pain. Joints can become increasingly swollen and stiff, leading to a limp.
Arthitis leads to the destruction of cartilage within a joint. Cartilage allows your joint to move with virtually no friction, as it has a very smooth slippy surface. If cartilage is damaged, then it loses these properties and acts more like sandpaper, grinding away remaining cartilage over time.
The joint space gradually disappears, until there is bone rubbing on bone within the joint. This loss of space can be seen on an xray. The body reacts to the joint damage by forming spurs of bone that stick out from the edges of the joint.
If you have pain in the midfoot, it is best to see an orthopaedic surgeon who specialises in foot and ankle surgery. You should have x-rays taken in a standing position – this will show the degree of damage within a joint, and also what deformity may have resulted. Sometimes scans are also required.
talonavicular joint fusion
tarsometatarsal joint fusion
How is the Surgery Performed?
The operation you have depends on which joints are causing you pain. If a joint is worn out through wear and tear or inflammatory arthritis, we normally give you an injection of local anaesthetic into the joint as an initial procedure. If this relieves pain, then we can be sure that the joint we are addressing is the cause of your pain. If the joint is severely damaged, then this may not work, and if it is clear that the joint is responsible for the pain, then this step may be omitted.
As rubbing of bone on bone causes the pain, the aim of surgery is to prevent any further movement. This is achieved by joining two adjacent bones together to form one solid bone.
Through an incision, the joint is cleared of any remaining cartilage and then prepared to give it a chance of healing to the adjacent bone. Sometimes, we add honeycomb bone taken from inside the shin bone to stimulate the healing process.
The bones are fixed together with screws or special staples, both of which compress the raw surfaces together to give the maximum chance of success.
Surgery is carried out under general anaesthetic, but can be augmented with local anaesthetic injections behind the knee or around the ankle. The injections are normally given while you are asleep for your comfort. They can give good pain relief for the first day after the operation. You can go home 48 hours later, as long as the pain is controlled and you are mobile with crutches.
first six weeks
second six weeks
Risks of Surgery
Bleeding, infection, poor bone healing, poor skin healing, injury to tendons, injury to nerves, recurrence, and a need for further surgery.
There is a small risk of blood clots in the legs or lungs (DVT and PE), and there are also risks from anaesthesia – the process of being put to sleep for your operation.
Risks of Anaesthesia
The injection behind your knee is given using an ultrasound machine to guide the needle. There is a less than 1% chance of injury to the nerve. General anaesthetic also carries risks. These risks are proportional to your general health. You will need to be assessed for your fitness for surgery and an Anaesthetist will be able to advise you on your individual risk.
What Happens After Surgery?
You will have had injections to numb your foot so that you are not in pain after the operation. This injection will wear off after 18-24 hours, so you must take regular painkillers so that you are not in severe pain when the injection wears off. Ibuprofen and Diclofenac should not be used for more than a few days after the operation as they can interfere with bone healing.
The pain will settle over a few weeks. You may see blood stains on the dressings. This is normal and not a cause for alarm. If blood is dripping from the dressings however, return to hospital.
The foot will be swollen as well as sore. You should keep the foot elevated as much as possible for the first two weeks. Keep walking down to a minimum – going to the toilet or for meals. Letting the leg hang down will cause the foot to become more swollen. Most of the swelling will settle within the first few months, but swelling can continue for up to one year.
If you are resting on your sofa, keep your foot elevated on the back rest or arm rest. If you are resting in bed, then place a few pillows under the foot to keep it elevated.
You will normally be in plaster for a total of six weeks after surgery for ankle or midfoot arthritis. During this time, you should not weight bear on this foot. You will need crutches or a walking frame to get about.
Two weeks after the operation, you will have your plaster removed, and the stitches removed. You will then have a further plaster applied for four more weeks.
After this, you will have an xray and if this is satisfactory, you will be given a removable plastic boot, in which you can put your weight through the operated foot. You will use this for a further six weeks. This can be removed for washing, performing exercises and at night.
If you are in plaster for a prolonged period, you will be at risk of developing a blood clot in your leg. You will be given injections to thin the blood to cut this risk down. These can be self-administered, even in the elderly. You can stop taking these as soon as you progress to a plastic boot.
While you are in plaster, you can perform exercises to keep the leg muscles above the knee strong, as these will become weaker as you are not weight bearing.
You can removed the plastic boot to wash, and perform exercises depending on your operation. If you have had a triple fusion, you will still be able to perform up and down movement of the ankle. If you have had a hindfoot nail, this should not be attempted.
After twelve weeks, you will be seen in the clinic and a further xray will be taken. From this time, you will start to wean yourself off the plastic boot, and have physiotherapy.
After an ankle fusion, some patients find it beneficial to have an adaptation to their shoes to make their walking more normal. This rocker bottom can protect the other joints that may be put under more stress by an ankle fusion.
RETURNING TO WORK
You will be unable to weight bear while in plaster. I advise that you do not return to work before the plaster is removed, especially if you are on your feet all day at work. Most people will be off work for four months as a minimum, but if you have a workplace with disabled access that allows you to use crutches and you are sitting down most of the day, you may be able to return to work while wearing the plastic boot. Remember that not everyone is the same, and some people take a longer time to recover from their surgery. Please request a sick note before you leave hospital, if you need one.