Midfoot osteoarthritis: A guide for patients

The midfoot is made up of five bones, which form the arch of your foot. The bones and the joints of the midfoot can be compared to the keystone in a bridge; they assist in stabilising the foot and they also adapt to the ground’s surface. Each day these joints are put under a great amount of stress, generally they are able to withstand these forces. However, in certain cases the joints can become damaged and osteoarthritis can develop (wear and tear).

When arthritis develops the joints become less stable and unable to withstand the weight of the body and the force of walking. Depending on how many joints are affected determines the extent to which the arch profile collapses and becomes unstable. This joint instability can produce flattening of the arch and over time the forefoot begins to roll out and move away from the rear/hind foot. Other signs of midfoot arthritis include thickening of the instep area. This is caused by the formation of new bone around the joints. This new bone tries to restrict the amount of motion at the joints; its aim is to reduce the pain and discomfort. Unfortunately, the new bone is rather ineffective at achieving this and often causes problems with footwear fitting.

Midfoot arthritis can become debilitating and have a negative effect on both your daily activities and quality of life.

Treatment of the condition can range from simple conservative (non- surgical) to surgical management. Before any surgery, all conservative and medical treatments should have been exhausted.

Midfoot arthritis can affect multiple joints or can be in isolation. Treatment of this condition is the same whether one or more joints are affected.

Initially, alteration of footwear and an insole can help by stabilising the foot and reducing the amount of motion at the joints. The best type of shoe is a walking trainer. This shoe has a thick rigid sole so it prevents excess movement of the foot. When coupled with an insole (orthosis) it can produce excellent stability to the foot and reduce the level of pain. However, some patients find that the bony thickening can become sore as the foot is constricted, putting more pressure on to the painful areas. This type of shoe does not need to be worn all the time. The key thing to remember is: the right shoe for the right occasion. If you know you are going for a long walk or will be on your feet for an extended period of time it is advisable to wear it.

Other treatments can include steroid injections and may be carried out under ultrasound guidance.

A certain percentage of patients respond well to this treatment; however, if this is not the case surgical management may be required.

Surgical management

The aims of surgery are to reduce the pain and discomfort from the joint or joints and to make it easier and more comfortable for you to do your daily activities and enjoy quality of life.

The principle of the surgery is to fuse the opposing bony surfaces by removing the remaining articular cartilage and bringing the two bony surfaces together, while at the same time correcting any deformity/malposition.

Once the bony surfaces have been approximated they are held in place by metal work - screws, plates or staples. The metal work prevents movement between the bones and allows for healing. When the bone has healed, the joint is stable enough for weight-bearing. Generally, the metal work stays in the foot unless it begins to cause discomfort.

Following the operation, the foot and leg (below the knee) is placed in a non-weight bearing below knee cast for about eight to ten weeks. It is important to remain non-weight bearing, if you walk on the foot there is a high chance that the metal work will fail and the bony surfaces will separate and produce a bony non-union. This can be a serious complication and, if painful, may require further surgery and cast immobilisation. Once out of the cast, there will be a period of partial weight-bearing before returning to full weight-bearing. You will be shown how to use crutches and they will be given to you before the operation so that you can practise using them. If you feel you are going to have difficulties using crutches, please speak to your podiatric surgeon as there are other mobility aids available.

Sometimes, a bone graft may be required to fill any voids between the bones or help in repositioning the foot. It is always best to obtain the graft from the patient and, if this is the case, it is harvested from the heel bone. There are many advantages to this type of graft. A graft taken from your own body has a much greater chance of integration as it has all the properties required for bone healing. However, sometimes obtaining a bone graft from you may not be practical or not provide a sufficient amount of bone. If this is the case, freeze dried bone is used. This is bone that has been donated and sterilised. Donated bone can take a little longer to integrate.

About day case surgery under local anaesthetic

Surgery is carried out under local anaesthetic as a day case procedure. This means that you are awake during the operation but a screen will prevent you from seeing the operation.

To numb your foot, you will be given an injection behind the back of the knee. You can eat and drink on the day of surgery; there is no need for fasting.

The length of the operation can vary and is dependent on the number of joints that need to be fused.

If you decide on surgical management you will be invited back to attend a pre- surgical clinic. A member of the nursing team will take your medical history. If you are on any medication, please bring a list with you. This is a good opportunity to ask questions and discuss any concerns you may have about the procedure.

You must have a competent adult at home for the first day and night after surgery.

Recovery after your operation

Following this procedure, you will be in a non-weight bearing cast for up to eight weeks.

The first two days

• You will be in a plaster of Paris below knee cast. This cast is rather heavy but allows for foot swelling. This cast will be on for about two weeks.
• You should not walk on the foot that had surgery.
• You must rest, with your feet up, as much as possible. You should restrict your walking to bathroom visits only. When getting about, you must use your crutches. The nursing team will show you how to use your crutches and provide you with a leaflet.
• If you experience pain, you should take the prescribed painkillers. Any pain is usually worse for the first two days.
• If you are still experiencing pain after three to four days that is not relieved by the painkillers, you should contact the department directly.
• If you have any concerns over your foot you should contact the department directly.
• The department is closed at the weekend. Out-of-hours, you should contact your GP or go to your local accident and emergency (A&E) department.

Two weeks after surgery

• The plaster of Paris cast will be removed and replaced with a lightweight fibreglass cast, which stays on for a further four to six weeks. You must continue to bear no weight on the foot and use the crutches.

Eight to ten weeks after surgery

• An X-ray will be taken to assess bony healing.
• Providing there is sufficient bony healing the cast is removed.
• You will then be able to lightly bear weight through your foot (partial weight-bearing) using your crutches and a rigid-soled trainer.
• Partial weight-bearing is carried out for a further two weeks. No high impact activities are allowed.

Ten to twelve weeks after surgery

• You can begin to fully weight-bear on the foot and can gently start to return to normal activities. You should still avoid high-impact activities and remain in your running trainer.
• You can now return to driving. However, you must feel able to perform an emergency stop without hesitation or pain. (It is advisable to check with your insurance company about your cover).
• You may return to work, but this is dependent on the type of work and footwear required for your job. For certain jobs, return to work in less than 12 weeks can be an unrealistic expectation.

Twelve weeks after surgery

• Although the foot should now be comfortable and returning to normal, there will still be noticeable swelling, particularly towards the end of the day; this is normal.

Nine months after surgery

• The residual swelling should now be slight, although the healing process continues for 18 months
• You should be getting the full benefit of the surgery.

Eighteen months after surgery

• All healing is now complete, swelling should be completely resolved.

Frequent or serious risks

All operations carry a small risk of complications. In foot surgery complications are uncommon and most resolve without permanent disability or pain. General and specific complications of this procedure include:

• infection (two in 100)
• delayed healing of the skin (eight in 100)
• non-compliance of patients (four in 100)
• bone fracture associated with non-compliance (two in 100)
• prolonged swelling post operatively (four in 100)
• thick or sensitive scar formation (four in 100)
• loosening or movement of the screws or wires used to fix the bones (two in 100)
• delayed/non-union of the fusion site
• blood clot deep vein thrombosis (DVT).

Specific complications include:

Bony non-union: this is where the bony surfaces fail to knit together. There can be a number of different reasons behind the development of a non-union, of which one non-compliance is, for example walking around on the foot when you should be non-weight bearing. Osteoporotic bones also have an increased chance of developing a non-union and often require an extended period of cast immobilisation. Smoking can also delay bone healing.

Complications following foot surgery are rare but can happen. It is important to remember that if a complication arises, you will be need to visit the hospital more frequently and there could be a significant impact on your recovery and return to work time. Foot surgery should be avoided if only for cosmetic gains.