Interdigital Neuroma Morton’s Neuroma

Morton’s neuroma is a compressive neuropathy of the interdigital nerve. It occurs most commonly in the third interdigital space. Perineural fibrosis and entrapment of the interdigital nerve may be the cause of this problem. The patient usually describes a forefoot pain on the plantar aspect of the foot, especially during standing and walking. This is usually associated with radiation of tingling and burning into the toes that are affected. The pain is usually localized to a specific area, and it does not involve the entire forefoot. It occurs predominantly between the 3rd and 4th web space in 80% of the time and between the 2nd and 3rd web space 20% of the time. The pain is radiating distally in about 60% of the time and numbness occurs about 40% of the time. When you examine the patient, the area of focal and localized tenderness is in the plantar webspace and not over the joints. The interdigital neuroma (Morton’s neuroma) occurs in middle aged females with forefoot pain that is worse with shoe wear. The pain is worse with weight bearing or wearing tight shoes with high heels. The weight transfer to the metatarsal heads will aggravate the condition. Dorsiflexion of the toes will also aggravate the condition. The symptoms are relieved by removing the shoes and massaging the foot. The paresthesia is most commonly on the plantar aspect of the web space. The patient will have chronic pain in the interdigital space between the 3rd and 4th toes that occasionally radiates down distally into the toes, and the foot exam is normal. Compression test of the web space may be positive. Compression of the metatarsals medially and laterally (squeezing the metatarsals) while pushing on the plantar tissue dorsally. The bursal tissue may crease a “click”, and if this happens it is the classic test. Ultrasound and MRI are helpful, but it is usually not as good as the history and physical examination. MRI has a very limited role in the diagnosis of Morton’s Neuroma. EMG and nerve studies are of little benefit. The history and physical exam is the gold standard for the diagnosis of interdigital neuroma. You can add diagnostic injection to see the result. Injection of local anesthesia into the are of the interdigital nerve can be diagnostic for Morton’s neuroma. Differential diagnoses include metatarsalgia, stress fractures, MTP synovitis, complex regional pain syndrome, arthritis, osteonecrosis of the metatarsal head, neoplasm, and lumbar radiculopathy. X-rays are helpful in excluding metatarsal stress fractures. Consider MTP synovitis especially after digital nerve block. Treatment can be conservative or surgical. To treat conservatively, start with shoe wear modification (no high heals or tight shoes). Conservative treatment also includes injection of steroids. This will give relief of symptoms in 1/3 of the patients with multiple injections. Injection is usually done dorsally, and it may be more diagnostic than therapeutic. Surgery an be neurectomy, done after failure of nonoperative treatment (approach the neuroma through dorsal or plantar approach). Dorsal approach is most commonly used. Incise the transverse metatarsal ligament. Resect the nerve 3 cm proximal to the metatarsal heads. Bury the proximal stump within the intrinsic muscles. If the neuroma is recurrent, then there may be a retained neuroma distal to the metatarsal heads. In this case, you may want to do surgery through the plantar approach, and you may want to do the research of the nerve and transpose it to muscle on the plantar foot (there might be about 70% success rate). The most likely cause of recurrent symptoms following excision of a 3rd web space neuroma is a traumatic neuroma tethered by plantar neural branches. When a recurrent neuroma occurs at the end of the resected nerve, it does not retract far enough because the transection may not be far proximal enough or it may be tethered by the plantar neural branches. Stump neuroma can also occur due to inadequate resection. Causes of surgical failure include resection of the common plantar nerve is too distal, there may be a coexisting tarsal tunnel syndrome, wrong diagnosis, or wrong interdigital space.

Osteoarthritis of the Fingers

Osteoarthritis is a degenerative condition of the cartilage. There is no clear etiology identified for osteoarthritis. Osteoarthritis is not related to tumor, inflammation, infection, gout, or trauma. Osteoarthritis is different from rheumatoid arthritis which is an inflammatory condition. The distal interphalangeal joint (DIP) is the joint that is most often involved with osteoarthritis. The trapeziometacarpal joint (TM) is the second most involved joint with osteoarthritis. When the trapeziometacarpal joint is involved, it causes pain with weak pinch and grip. DIP (Heberden’s Nodes) are bony swellings (osteophytes) that can develop in the distal interphalangeal joints (DIP) due to the affects of osteoarthritis on these joints. Heberden’s nodes are a sign of osteoarthritis caused by osteophytes formation (bony outgrowth) of the articular cartilage in response to repeated microtrauma at the joint. Heberden’s nodes are more common in women than in men. PIP (Bouchard’s Nodes) are also associated with osteoarthritis, and they are similar bony growths which develop in the proximal interphalangeal (PIP) joints. Bouchard’s nodes, like Heberden’s nodes, may or may not be painful. Swollen, hard and painful finger joints (Heberden’s and Bouchard’s nodes) are the classical signs of DIP and PIP joint osteoarthritis. Mucous cysts are small, fluid-filled sacs that form between the DIP joint of the finger and the bottom of the fingernail are another sign of osteoarthritis. The best treatment for the mucous cyst is surgical excision of the cyst and removal of the underlying osteophyte to decrease the risk of recurrence.

Mallet Finger Treatment

Treatment for mallet finger is extension splinting of the DIP only for about 6 weeks or more is the usually treatment. Acute injuries with minimal displacement and no joint subluxation are treated with extension splinting of the DIP joint for 6-8 weeks. You will need to keep the splint on for 24 hours daily. The splinting can be volar splinting or dorsal splinting. Allow the PIP joint to move freely in flexion and extension. After 6 weeks of splinting, night splinting may be needed for longer periods. It appears that supplemental night splinting after full time splinting treatment is controversial and may not really improve the outcome. Wearing the splint may not be liked by professionals such as doctors, hair dressers, or dentists, and they may desire the surgery of percutaneous pin fixation. Conservative treatment can be tried even if the treatment is delayed up to four weeks with low, long term complication rates. There is an increased complication rate with surgical treatment. The goal of surgery is to keep the DIP extended until the bone or the tendon heals. K-wire utilization is a very common technique. Indications for surgery include volar subluxation of the distal phalanx, avulsion fracture with a large joint fragment more than 50%, and some physicians think that 30% of articular involvement is an indication for surgery. Some orthopaedic surgeons will continue to treat this injury by closed means (splint), even if there is a volar subluxation of the joint. The rationale is that a stiff finger that is treated by closed means is better than a stiff finger that is treated by surgery. A closed injury with or without a small avulsion fracture is different than a closed injury that involves a large fragment (more than 50% of the joint) or an injury that causes subluxation of the DIP joint. Mallet finger with subluxation of the DIP joint is clearly an indication for surgery. It may require open or closed reduction and pinning of the fracture or the joint. A single pin is usually sufficient for the treatment of a purely tendon injury. When pinning a purely tendon injury, make sure you mark the affected finger on the dorsal aspect as well as the volar aspect of the finger preoperatively. Make the finger, because the x-ray will not show any evidence of injury, and this will help you to avoid pinning the wrong finger. The finger position will change if the finger is pinned with palm down or with the palm up. For extension block pinning technique, flex the DIP and insert the k-wire from distal to proximal direction. The k-wire is passed dorsal to the bony fragment and through the extensor tendon into the middle phalanx. Then extend the DIP and the k-wire will help in buttressing and reducing the fracture with extension of the DIP. After the surgery, the patient may experience an extensor lag, but without functional deficit. Complications of mallet finger include residual deformity that usually does not affect the function and swan neck deformity. Care must be taken during treatment to avoid this deformity. The PIP should be moving freely in extension and flexion to avoid this deformity.