Humped tarsus
The humped tarsus is a deformity of the instep that can cause pain similar to other conditions such as metatarsalgia or exostoses.
What is a Humped Tarsus?
The humped tarsus corresponds to a deformation of the instep with the presence of prominent dorsal bony protrusions. These bony bumps are found between the cuneiform bones and the metatarsals. Physiologically, there is a prominent bony ridge dorsally at the level of the cuneo-metatarsal joint of the first ray. A humped tarsus is not necessarily symptomatic and can be confused with other foot osteoarthritis conditions.
What are the symptoms of a humped tarsus?
The main symptoms of the bossed tarsus are pain and a bursitis.
- In the absence of osteoarthritis, the pain mainly occurs when wearing shoes, either in closed, rigid shoes or in open shoes with straps passing over the bony protrusions.
- The pressure from the shoe or strap at the level of the bony prominence leads to a thickening of the glide bursa, causing a painful red spot on the top of the foot. This is an inflammatory bursitis.
- There is often a sensory branch of the superficial fibular nerve that runs over the bony prominences. This sensory branch is compressed between the shoe and the bony relief, causing neuropathic-like pain such as burning, electric shocks, and tingling.
What are the causes of a humped tarsus
A humped tarsus may be due to foot morphology, the presence of osteoarthritis in the cuneometatarsal joints, and footwear habits.
- The high-arched foot morphologically shows a dorsal protrusion of the cuneometatarsal joints, making footwear conflict more frequent.
- In cases of osteoarthritis of the cuneometatarsal joints or osteoarthritis of Lisfranc, there is a dorsal bony growth called osteophytosis, which can be painful.
- Wearing rigid shoes or shoes with straps passing over this area is a contributing factor to pain in the tarsus.
What are the possible treatments?
Initially, changing footwear habits is considered. Wearing canvas shoes or shoes made from soft fabric helps to limit conflict with the instep. The use of appropriate orthopedic insoles can also relieve symptoms.
In cases of osteoarthritis, wearing soft leather shoes with rigid soles can help to reduce joint pain. Corticosteroid injections may also be offered to reduce inflammation.
If these measures fail, surgical treatment may be considered.
What operations are possible?
Preoperative assessment is crucial because although a humped tarsus can be painful due to the foot's morphology, isolated resection of the bony blocks in cases of osteoarthritis may worsen the symptoms.
In the absence of osteoarthritis, surgical treatment consists of making an incision over the prominent bony protrusion, freeing the sensory nerve branch, opening the affected joint, and resecting the conflicting bony blocks. This procedure is similar to the foot exostosis operation and can be performed using percutaneous surgery.
In cases of osteoarthritis, bone production is due to a loss of cartilaginous substance in the joint. The pressure within the bones is therefore increased, leading to bone growth to enlarge the bone surface, allowing better distribution of pressure when there is a cartilage deficit. These are osteophytes. This bone production is thus a means of joint stabilization. In this case, isolated resection of the bony blocks will result in osteoarthritic decompensation with increased joint pain. In cases of humped osteoarthritic tarsus, resection of the bony blocks is accompanied by arthrodesis of the affected joint or joints, mainly a foot arthrodesis.
Diagnosis of bumpy tarsus
The diagnosis of dorsal hump on the tarsus is based on a thorough clinical examination and imaging tests. The clinical examination makes it possible to identify the dorsal bony prominence, assess joint mobility, and look for signs of local inflammation. Palpation generally reveals a hard, fixed swelling that is sometimes painful on the top of the foot.
Standard weight-bearing X-rays of the foot allow visualization of abnormal bony contours and the search for signs of associated osteoarthritis. A CT scan or MRI may be necessary to accurately assess the extent of the deformity and the condition of the surrounding soft tissues, especially in cases of suspected nerve compression.
Postoperative care and rehabilitation
After the surgical procedure, post-operative care is essential for a good recovery. Weight-bearing is generally allowed gradually with a offloading shoe. The duration of immobilization varies depending on the type of procedure performed.
Rehabilitation begins early with gentle mobilization and drainage exercises. Returning to normal activities is done gradually, with resumption of sports after 3 to 6 months depending on the extent of the surgical intervention. Regular follow-up allows for monitoring of healing and functional progress.
FAQ
Modifying footwear habits can help relieve conflicting pain on the instep from shoes. Shoes made of soft leather or canvas should be preferred.
The duration of work leave after surgical intervention for a humped tarsus depends on the professional activity and the presence or absence of osteoarthritis.
If there is no osteoarthritis, tissue healing is achieved after 45 days. In case of osteoarthritis, joint fusion occurs after 3 months.
For a humped tarsus, it is preferable to consult an orthopedic surgeon specialized in foot surgery.