In this chapter, we examine the common causes of foot pain, evaluate the appropriate laboratory and imaging modalities used in diagnosis, review the relevant clinical examination, and detail the effectiveness of current treatments.
Foot pain, not unlike pain experienced in other areas of the body, can be debilitating. One aspect separating it from other areas is that the entire weight of the body rests on the feet. It is difficult to ambulate while maintaining a non-weight-bearing position and almost impossible without assistive devices. Although the geographic region of foot pain may be visible, palpable, or reproducible, its etiology is more difficult to determine, and a definitive treatment may not exist.
This chapter examines the common causes of foot pain, evaluating the appropriate laboratory and imaging modalities used to diagnose foot pain. Coupled with a review of the relevant clinical examination, the effectiveness of current treatments is detailed for regularly encountered foot pathologies.
The following six sections guide the clinician in diagnosis and treatment of foot pain, beginning with the most commonly seen painful pathologies. The remaining sections review pain caused by overuse injuries, trauma, and neurologic, metabolic, and iatrogenic causes.
The diagnosis of distal extremity pain is usually not difficult in that there is often either a visible malformation or the pain has a trigger point and is reproducible. In this section, the most common pathologies seen in the foot are discussed in detail. The cause of deformity is addressed along with clinical, laboratory, and imaging tools that aid in the diagnosis. Treatment modalities are discussed for the following pathologies: onychocryptosis, hyperkeratosis, soft-tissue tumors, tinea pedis, hammertoes, hallux valgus, pes plano valgus, neuroma, gout, and plantar fasciitis.
The normal appearance of the nail is a translucent nail plate with an underlying nail bed; the matrix is deep and proximal with surrounding periungual tissue medially and laterally. Discomfort presents when external pressures such as tight shoe gear, a misshapen nail, or a thickened nail from a fungal infection of the nail (onychomycosis) impinge on the nail plate that has been driven into the periungual tissue. Internal pressure from abnormal bone growth (subungual exostosis) may also cause an ingrown toenail. Pain is a result of inflammation or resulting soft-tissue infection caused by a break in the skin, allowing the entry of bacteria (see Table 43-1).
Common Causes of Onychocryptosis
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Common Causes of Onychocryptosis
Etiology of Nail Pathology
Tight shoe gear
Trauma to matrix
The diagnosis is based on clinical examination, noting the ingrown nail with erythema, or edema to the surrounding soft tissue. If the nail plate is misshapen, an x-ray is beneficial to help rule out an underlying deformity such as a subungual exostosis. Treatment involves removal of the ingrown border followed by twice daily diluted salt or warm water foot soaks for up to 7 days to help drain and dry the wound. If there is a local infection, a short course of antibiotics is recommended.1 Prevention of recurrence requires addressing the underlying cause such as removal of the subungual exostosis when present, surgical matrixectomy, or treatment of onychomycosis with antifungal medications (see Fig. 43-1).
Picture of an ingrown nail with worsening paronychia: The rolled borders can be appreciated as well as the erythema and drainage. A partial nail avulsion is recommended for relief of the patients’ symptoms.
HYPERKERATOSIS/CORNS AND CALLUSES
Corns and calluses are a result of pressure over a bony deformity. A “corn” is seen on the dorsal surface of the digits and is usually a result of a joint buckling. The head of the proximal or middle phalanx becomes more prominent and, combined with superficial pressure of shoes, irritates the epidermis, resulting in increased keratinization and a resultant corn.2 A callous is the result of abnormal plantar pressures from either a biomechanical disturbance or bony malalignment. Shear forces between the plantar foot and ground reactive forces create a thickening of the skin, resulting in point tenderness. Corns and calluses are sometimes confused with other skin lesions such as verruca, porokeratoma, or intractable plantar keratomas. Diagnosis is clinical evaluation of the hyperkeratotic lesion and radiographs to detect any osseous abnormalities. Treatment consists of debridement of the lesion followed by padding and a topical emollient to soften the corn or callus. In intractable lesions, surgical correction of the underlying bone deformity (exostosis, hammertoe, etc.) may be necessary (see Fig. 43-2).
Image of a common off-loading technique. These can be incorporated into orthotics or dispensed over-the-counter and in-office in various shapes and sizes. A: Indicates the painful area, typically a callous. B: Indicates the pad or off-loading material that is built up to take on more pressure, with a central cut-out over the painful region to reduce contact.
Verruca, or a plantar wart, can be mistaken for a corn or callus. On clinical examination, verruca appears different from a callus in that it has dark spots, which represent capillary ingrowths and result in pinpoint bleeding on debridement. Additionally, plantar warts demonstrate obliteration of skin lines and are painful with side-to-side compression or a pinching of the lesion compared to direct compression. Warts can appear on non-weight-bearing areas as opposed to a callus, which results from plantar pressures. There are countless treatments for verruca, primarily involving paring of the lesion to pinpoint bleeding followed by desiccation of the lesion with topical preparations.3 Topical preparations commonly used include salicylic acids, cantharidin, cryotherapy, and electrodesiccation, though numerous other topical treatments are often employed (see Table 43-2 and Fig. 43-3).
Picture of a wart on the dorsal surface of the toe; this is different from a corn, which would be atop the joint, and different from a callus, which would be on the bottom or side of the foot atop a weight-bearing area or bony prominence. Though difficult to visualize, the lesion has dark spots on close inspection, showing the capillary ingrowths. It is also soft and spongy on palpation, as opposed to a callus, which has a hard center.
Characteristic Differences of a Wart and Callus Differentiate the Lesions and Help the Clinician with Diagnosis and Treatment
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Characteristic Differences of a Wart and Callus Differentiate the Lesions and Help the Clinician with Diagnosis and Treatment
Pain with lateral compression
Pain with direct pressure
Breaks through skin lines
Contains skin lines
No location predilection
Soft center, pinpoint bleeding
Common in children
Common in adults
Common soft-tissue tumors of the foot include cysts and fibromas. Various forms of cysts exist, but ganglionic, synovial, and mucinous are seen most commonly in the foot.4 Trauma or excessive stretching creates an out-pouching similar to an aneurismal sac or cyst, which is found along the course of a tendon near the joint. Clinical exam reveals a firm mass that can be tender to palpation. Transillumination of the mass with a pen light will demonstrate an orange glow consistent with a fluid-filled mass. Initial treatment consists of aspiration with or without the administration of a steroid. In the event of recurrence, surgical intervention can be performed to excise the cystic sac and its stalk (see Fig. 43-4).
Picture of a cyst being excised intraoperatively; its fluid-filled appearance can be appreciated as it is being removed in toto.
Plantar fibromas are benign, solid, soft-tissue tumors deep to the subcutaneous tissue and present as a painful bump or raised area. Commonly originating from the plantar fascial ligament, imaging studies such as MRI help determine the location of the mass and its characteristics. Soft-tissue biopsy is necessary for definitive diagnosis along with evaluation of malignant potential. These masses can be treated with pressure off-loading and custom orthotics, and topical preparations have shown relief, though some require surgical excision.
TINEA PEDIS/ATHLETE'S FOOT
Tinea pedis, more commonly referred to as “athlete's foot,” is a condition that begins with an itchy rash and scaling of the skin. On clinical examination, the rash can involve the webspaces or the entire foot in a slipper-like distribution. The itching can result in excoriation of the skin, which can then become very painful. Breaks in the skin from the rash and scratching may lead to a soft-tissue infection or cellulitis. The fungus is typically caused by the dermatophyte trichophyton rubrum, though others can be isolated and identified with potassium hydroxide testing and periodic acid-Schiff staining. Treatment typically consists of topical as well as systemic antifungal therapies.5
Hammertoes involve a flexion deformity of the proximal and/or distal toe joint. There are different terms to describe this deformity, depending on the plane of the deformity and the combination of deformities: mallet toe, hammer toe, curly or claw toe, and overlapping toe.6 Painful hyperkeratotic lesions may develop as a result of the pressure from shoes and activity on the underlying digital deformity.
Hammertoes and callus/corns can be appreciated during the clinical exam with occasional soft-tissue inflammation. Radiographic evaluation will demonstrate the flexion deformity at the involved joint and are helpful in preoperative planning when surgery is required. Conservative care consists of off-loading of the digital deformities with wider shoes and larger toe boxes. Padding and off-loading devices can also reduce pressure on the prominent areas or space out the digits. These are temporary treatments, which do not correct the underlying osseous deformities (see Fig. 43-5).
Hammertoe deformities cause pain due to a dorsal callous and retrograde pressure on the metatarsal. A: Indicates the painful area, typically a corn or callous. B: Indicates the pad or off-loading material that is built up. This helps to relieve pressure on the lesion directly and disperse weight over a greater area. B’: Metatarsal pad modification with loop around the phalanx helps to decrease MPJ extension and retrograde buckling as well as padding plantar to the metatarsal.
Surgical correction of hammertoe deformities includes realigning the joint with arthroplasty or arthrodesis procedures. Skin plasties are also helpful for angular deformities and straightening the toe in long-standing deformities. Digital vessels and nerves are small in caliber and thus can be severed during surgery. Swelling and edema are usually expected postoperatively and can take more than 6 months to fully resolve.
Classically, bunions (hallux valgus) present with pain on the medial, or inside, aspect of the first metatarsal-phalangeal joint (MTPJ). There may be surrounding redness and swelling with a possible underlying bursitis. Clinically, there is a “bump” on the medial aspect of the first metatarsal with lateral deviation and valgus rotation of the big toe (see Fig. 43-6).
Radiograph depicting a bunion deformity. There is a prominent medial eminence off of the first metatarsal. Also, the sesamoid apparatus is lateral to the metatarsophalangeal joint. The proximal phalanx is deviated in an abducuted and valgus position compared to the metatarsal.
There have been a number of postulated etiologies for the development of bunions, with the prevailing theory indicating that they are caused by a biomechanical abnormality; there is, however, a genetic component. These deformities are progressive and pain is exacerbated with tight shoes such as high heels or athletic cleats. Clinically, the medial column of the foot should be evaluated for hypermobility or decreased range of motion (hallux limitus). If the bunion is severely worse on one side, there may be a limb length discrepancy, which can be measured during the biomechanical exam. Orthotics, padding, and splints may help to relieve the pain from pressure on the boney prominence, but surgery correction is often indicated.
PES PLANO VALGUS/FLAT FOOT
Flat feet can result from a number of different etiologies. If seen in children, it is usually genetic or resulting from a coalition, or inappropriate differentiation, of a joint. In adults, it is generally biomechanical in origin, where there is overpronation of the talus. Usually, flat-footed patients complain of “tired feet” with aching joints and arch pain. Arthritis can develop, and the foot accommodates, resulting in joint contractures and soft-tissue attenuation.
If a unilateral flat foot occurs suddenly, it may be the result of a tendon rupture or insufficiency of the tibialis posterior. Clinically, the deformity involves collapse of the midfoot along with heel valgus. Tenderness may be elicited with palpation along the course of the posterior tibial tendon in addition to associated weakness during muscle testing. The single heel raise, in which patients are asked to raise their heel off the ground and “stand on their toes,” is highly suggestive of posterior tibial tendon dysfunction when the patient is unable to perform this maneuver.7 Plain radiographs will reveal the collapse of the midfoot joints, while MR imaging will assist in evaluation of tendon integrity. Depending on the severity of the deformity, treatment consists of conservative care with orthoses and bracing with surgical intervention warranted in more advanced deformities (see Fig. 43-7).
A: Within the shoe, a functional orthotic can be molded to help build up the arch and control pronation. B: A medial heel skive can also transfer pressure and invert the rearfoot.
Originally described in 1876, the third webspace is the most common location for a neuroma to occur because the medial and lateral plantar nerve branches join together via a communicating branch to form the third common plantar digital nerve, making this nerve enlarged compared with its medial and lateral counterparts.8 The patient will commonly describe the pain as a “burning” sensation to the forefoot, though it may also be described as “knifelike” and “electric.” The pain can radiate distally, with numbness experienced to the toes. Another common description is a feeling of walking on a pebble or a wrinkled sock. The pain is relieved when the shoe gear is removed and activity is stopped, but it can be reproduced by squeezing the forefoot together, essentially compressing the metatarsal heads together against the neuroma. On physical exam, a silent “click” may be felt when the neuroma is manually compressed, shifting between the metatarsal heads9 (see Fig. 43-8).
Image of the plantar nerve distribution to the foot. A represents the tibial nerve. B represents the lateral plantar nerve. C represents the medial plantar nerve. D represents a Morton's neuroma – commonly found between the third webspace, between the third and forth metatarsal heads.
Radiographs may be used to rule out other pathologies such as stress fractures or other bony abnormalities. However, the most sensitive imaging study is an MRI, which typically shows nerve thickening and edema surrounding the nerve. Treatment consists of injections with corticosteroids, diluted alcohol, or other analgesics. These can help confirm the diagnosis as well as be therapeutic. Sclerosing injections of ~4% diluted alcohol solution have been described to cause chemical neurolysis and nerve dehydration (Wallerian degeneration).10 Off-loading the neuroma with orthotics or a metatarsal pad may help reduce pressure on the metatarsal and the neuroma. If conservative care is unsuccessful, surgical decompression of the nerve or neurolysis may be necessary (see Figs. 43-9 and 43-10).
Metatarsal pads help alter the biomechanics when the patient is weight-bearing and cushion the painful area. Rocker bottom shoes help with metatarsalgia. A: Represents the painful area. B: Represents the metatarsal pad and rocker bottom area of the shoe. Both ultimately disperse the pressure more evenly off of the metatarsal head.
Gross image of a neuroma surgically removed. The medial and lateral distal branches and the bulbous neuroma proximally that was irritated by the metatarsal heads can be seen.
Gout involves the deposition of uric acid in a joint and most commonly manifests in the first MTPJ of the foot due to a cooler temperature gradient, which results in crystal formation. Gout is the result of overproduction or underexcretion of uric acid. Gout was originally titled the “disease of kings” because it was seen most frequently in wealthy citizens who could afford more expensive foods such as wines, red meats, and cheeses, which are rich in purines.11 Uric acid is the end product of purine metabolism, and when present in excess, crystal formation results (see Table 43-3).
Two Etiologies of Gout: Overproduction Versus Underexcretion
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Two Etiologies of Gout: Overproduction Versus Underexcretion
Etiology of Gout
10% of cases
90% of cases
Genetic deficit, metabolic, diet
Increased uric acid, renal
Treated with allopurinol
Treated with probenecid
On clinic examination, the first MTPJ is red, hot, swollen, and exquisitely painful to the touch. There is also pain on range of motion, and allodynia is present where even light percussion is barely tolerable. Other pathologies that present similarly are a septic joint or inflammatory arthritis. To adequately diagnose gout, blood work is used to assess for an elevated uric acid concentration (above 6 mg/dl in women and 7 mg/dl in men).11 Joint aspiration with crystal analysis remains the gold standard for diagnosis, with negatively birefringent, needle-shaped gold crystals noted.
Treatment of acute gout consists of addressing the inflammation with a strong anti-inflammatory agent. Additionally, monotherapy with colchicine—a natural plant product derived from the autumn crocus—is often employed. For chronic gout, medicinal therapy should be directed on the overproduction or underexcretion of uric acid. The majority of chronic gout (90%) is the result of underexcretion of uric acid. In this instance, inhibition of uric acid reabsorption in the proximal renal tubules with probenecid is recommended along with avoidance of foods high in purines. If overproduction is the cause, allopurinol, a xanthine oxidase inhibitor, blocks uric acid synthesis. Gout can destroy the joint, and radiographs may reveal joint destructions and a “rat-bitten” appearance termed “Martel's sign.”12
PLANTAR FASCIITIS/HEEL PAIN
Plantar fasciitis, a common cause of heel pain, is a condition in which the plantar fascia becomes irritated due to microtearing of the ligament. The patient will classically describe pain with the first step in the morning when getting out of bed or with the first step after sitting due to a sudden pulling of the tight ligament, or poststatic dyskinesia. Pain improves with use but feels sharp and “knife-like” on initial presentation. On clinical exam, direct palpation to the origin or insertion of the fascia at the heel reproduces the symptoms.
While diagnosis is primarily based on the history and physical exam, imaging modalities may help exclude differential etiologies of heel pain not limited to stress fractures. Plain radiographs often reveal a plantar spurring of the calcaneus as a result of the inflammation to the ligament; however, this is rarely the cause of the pain. Other diagnostic modalities include ultrasound and MRI, which may reveal thickening of the plantar fascia ligament consistent with chronic inflammation or microtears.
Treatments should begin conservatively with a course of stretching to include the Achilles tendon and plantar fascial ligaments. Reduction of increased strain to the plantar fascia ligament with orthoses, strappings, and supportive shoes helps by maintaining the longitudinal arch of the foot and thus relaxing the pull on the plantar fascia. Addressing the inflammation of the ligament with oral non-steroidal inflammatory medications (NSAIDs), ice, and corticosteroid injections is also beneficial. A night-splint can be worn to keep the tendon and fascia stretched throughout the night when not ambulating. Plantar fasciitis is a self-limiting condition, but it is very disabilitating, and surgical intervention (fasciotomy) may be warranted if daily functions are lost.
Overuse injuries are most commonly seen in athletes but are also present in previously sedentary individuals beginning a new activity. Excessive repetitive trauma causes inflammation, adaptation, and tissue disorganization that can lead to rupture or fracture. Soft-tissue structures involved in the foot and ankle are tendons, ligaments, and fascia. Overuse injuries to the bone can result in bone contusions and stress fractures.
Tendonitis involves inflammation of a tendon that has been stretched or pulled with individual collagen fibers subsequently disrupted. The Achilles tendon is often involved and can be painful at its insertion into the calcaneus or midsubstance behind the ankle. Pain can be reproduced with direct palpation of the tendon or when the joint is brought through range of motion, but there is also, occasionally, a palpable thickening of the tendon and swelling. An MRI is useful in evaluation of partial tears and surrounding edema or bursal formations.
The usual treatment regimen is highlighted by the acronym PRICE, which stands for: protection (with bracing), rest from activity or activity modification, ice, compression of swelling if present, and elevation to help minimize the edema. NSAIDs can also be used to help decrease the swelling and pain. Steroid injection around this major tendon is typically avoided given the increased incidence of tendon rupture.
It is important to distinguish tendonitis from tendinosis, which involves degeneration of the tendon without inflammation.13 Tendinosis is likely the more common condition and is seen in athletes due to repetitive microtrauma and disorganization of the collagen tissues. Where tendonitis should resolve in a short amount of time by decreasing inflammation, tendinosis is more refractory to PRICE, and the opposite treatment algorithm should be applied—with eccentric stretching and emphasis on strengthening the tissues. It typically takes longer for the pain associated with tendinosis to resolve compared to tendonitis (see Table 43-4).
Tendonitis Versus Tendinosis
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Tendonitis Versus Tendinosis
Inflammatory cells within/around tendon
Weeks to recovery (2–6)
Months to recovery (2–6)
Treated with stretching and strengthening, emphasizing reorganization
Treatment by controlling inflammation
Bursitis can occur in any area of the foot where a bursa is found anatomically that helps cushion the tendon's insertion from the bone. Adventitious bursa can occur as a result of shearing or direct force atop a bony deformity. This can present as a raised area over the protuberance. The adventitious bursa initially acts as an area of extra padding, but it becomes painful when it results in swelling and when combined with tight shoe gear. A common location of an adventitious bursitis is on the lateral aspect of the fifth metatarsal head caused from tight shoe gear. The correction is off-loading with accommodative shoes, padding, or surgical excision (see Fig. 43-11).
Clinical presentation of adventitious bursitis on the lateral aspect of the fifth metatarsophalangeal joint; erythema as a result of direct pressure from too tight of shoes is appreciated.
Stress fractures are a result of increased pressure on an area of bone. This is more commonly seen after repetitive stress on one area as opposed to an isolated incident. Common areas for stress fractures in the foot include the lesser metatarsals and the calcaneus as a result of increased biomechanical load during a normal walking heel-toe gait cycle. This can be aggravated by poorly supportive shoe wear or in a foot with biomechanical abnormalities such as overpronation or oversupination.
On clinical examination of stress fracture, pain is reproducible with direct palpation of the involved area. Calcaneal stress fractures often demonstrate pain with direct percussion to the bottom of the heel with the clinician's palm as well as lateral compression of the calcaneus. Radiographs may be helpful, revealing periosteal reaction or a healing bone callous to the affected bone. However, these radiographic signs may lag 3 to 4 weeks following the injury. MRI is more sensitive, often revealing increased fluid to the area of injury (see Fig. 43-12).
T2-saggital MRI of the foot. The calcaneal stress fracture almost jumps out where the increased fluid accumulation is appreciated from the resultant inflammation within the calcaneus.
Treatment consists of rest and immobilization to facilitate bone healing. Immobilization can be performed with casting, walking boots, stiff-soled shoes, and assistive devices such as crutches or a walker. The type of immobilization employed and length of time will vary with the individual fracture location and pattern, but it is usually patient-driven and based on comfort.
Sesamoiditis is another common overuse injury seen in runners and dancers where there is irritation to the sesamoid apparatus of the foot. The sesamoids articulate with the plantar aspect of the first metatarsal and, with repetitive trauma, become inflamed. The diagnosis is made by reproduction of the pain symptoms with direct palpation of the sesamoids. Imaging studies such as radiographs, MRI, and bone scans may help with the diagnosis in addition to ruling out the possibility of a fractured sesamoid. Treatment consists of off-loading with padding and orthotics, rest, NSAIDs, and ice. Injections can also be of benefit to locally reduce inflammation with an analgesic or corticosteroid (see Fig. 43-13).
Sesamoids (A) may become irritated and cause a trigger point. These can be off-loaded with moleskin (B) to take pressure off of the “hot spot”.
Blunt, sharp, and penetrating trauma can affect any area of the body. The foot is a common place for sprains and fractures, although high-velocity injuries can also be seen. Common soft-tissue traumas of the foot and ankle include subungual hematomas, strains, sprains, tendon and ligament ruptures, and compartment syndrome. Traumatic injuries to the bone are contusions, fractures, and dislocations.
Diagnosis of foot trauma is achieved with a thorough history and physical examination of the affected extremity. The mechanism of injury, as well as direct visualization and palpation of the injury, may help guide imaging of the involved foot. Imaging should begin with radiographs followed by more advanced studies to further evaluate soft-tissue or joint structures. Most traumatic conditions of the foot are initially treated with PRICE (protection/protected weight bearing, rest/activity modification, ice, compression and elevation).
A subungual hematoma is usually caused by a direct blow to the nail plate from dropping a heavy object. If more than 25% of the nail bed shows hematoma, the nail should be removed to assess for a nail bed laceration. The pain is often described as throbbing and worsens in a dependent position. Radiographs can be taken to assess for fracture of the distal phalanx, which is treated similarly to an open fracture if the nail bed is violated. Pain is relieved by draining the hematoma—either by complete removal of the nail plate or by drilling a hole with a needle or heat cautery.
Sprains are a result of excess force on a joint with subsequent stretching of the ligaments, muscle, or tendons. Sprain is typically reserved to describe the stretching and partial tearing of ligamentous fibers, while strain is used to describe the stretching and possible partial tearing of muscle fibers and/or tendinous fibers. Clinically, bruising and ecchymosis are visualized to the injured area and are indicative of the severity. If the injury is chronic and instability is present, stress radiographic views may reveal opening of the joint and increased motion compared with the contralateral or unaffected side. The medial ankle ligaments are dense and stable, collectively grouped together, and called the deltoid ligaments. They are substantially stronger than the lateral ankle ligaments and, thus, are less commonly affected than the lateral ligaments, which are affected 85% of the time.14 The anterior talofibular ligament is the most commonly affected ankle ligament involved, and injury to this ligament is tested with the anterior drawer test, whereby the foot is pulled in an anterior direction away from the leg a greater distance compared to the unaffected side.15
In more severe strain or sprain injuries, the ligaments may be ruptured. This is seen in conjunction with excessive ecchymosis and loss of function and joint stability. The patient may also report a snapping sound—for instance, with an Achilles tendon rupture, which is often described as the feeling of someone striking the back of the heel with a racket. Clinical evaluation for Achilles tendon ruptures may employ the Thompson test, in which the patient lies prone on a table and the calf is squeezed.16 If the foot does not plantarflex, the Achilles tendon is thought to be disrupted. Radiographs may also reveal disruption of Kager's fat triangle, a normally dark-appearing area between the calcaneus and Achilles tendon.17 MRI is sensitive in identifying the level and severity of the injury.
Compartment syndrome is a severe sequela of trauma resulting from increased foot compartment pressures and the potential for injury to muscle and nerve structures. Typically, the patient presents with pain out of proportion with the symptoms clinically described as the five P's: pain out of proportion, pallor, paresthesia, paralysis, and pulselessness. If pulselessness is found, there is likely already irreversible damage to muscle and other tissues. Some surgeons elect to forgo compartment pressure, instead measuring with a Wick catheter (normal range is <10 mm Hg, affected range is >30 mm Hg at rest) and bringing the patient to the operating room for immediate fasciotomies, opening up all potentially involved compartments.18
Bone injuries may range from direct trauma resulting in contusions of bone to more severe fracture patterns. A history of the mechanism of injury—in addition to baseline radiographs to evaluate acute osseous injury—usually suffices in establishing the diagnosis. Fractures of the foot commonly involve the digits, metatarsals, and calcaneus. The “bedpost fracture” is a classic example in which the patient reports accidently catching or kicking the bedpost in the middle of the night, resulting in a digital fracture. When the fracture demonstrates minimal displacement, treatment with buddy taping (to the next digit) along with a stiff-soled shoe is the appropriate treatment for central digits two, three, and four.
Metatarsal fractures may result from dropping a heavy object on top of the foot where the neck may be fractured or from excessive twisting where the base can be disrupted. The MTPJ may be affected as well with forced hyperextension of the joint, commonly termed “turf toe.” Calcaneal fractures typically result from falling from a height with an associated injury to the lumbar spine. A clinical sign of severe heel pain, swelling, and a specific distribution of ecchymosis extending from the ankle to the sole of the foot is termed “Mondor's sign.”
Baseline radiographs of the foot and ankle are essential in the initial diagnosis as well as suggestive for more advanced imaging studies such as CT (computed tomography) and MRI to evaluate for soft-tissue and intraarticular fracture patterns. Depending on the extent of displacement and intraarticular involvement, conservative management with immobilization or surgical reduction followed by a period of immobilization is often the recommended treatment course.
Complex regional pain syndrome (CRPS), previously referred to as RSD (reflex sympathetic dystrophy), can be seen following surgery or with both mild and severe trauma. The pain experienced is typically out of proportion to the injury described, and the patient is often unable to bear weight on the affected extremity. Furthermore, the affected area may exhibit changes in color, temperature, and hydration regulation (see Figure 43-15). Treatment of this complex process is multifactorial, including injections, antidepressants, antiseizure medications, ketamine hydrochloride, physical therapy, nerve transmission interference, and psychotherapy. The key to effective treatment is early diagnosis and aggressive and early intervention. Should this condition fail to be treated in a timely manner, muscle atrophy and loss of limb function result.19
There are several systemic neuropathies that can present primarily as foot pain. One prime example is pain associated with peripheral neuropathy commonly seen in patients with poorly controlled diabetes, but it is also seen in alcoholics. Other neuropathies that may present with painful feet include inflammatory, vasculitic, sarcoid, renal disease associated, viral, parasitic, tumor associated, radiation, cold-induced, drug/nutrition related (alcohol, B12), and entrapment. The diagnosis of these neuropathies may be performed with laboratory testing and nerve conduction velocities. Treatment is focused on identifying the cause and removing the negative stimulus or supplementing the deficiency. Other treatments may include non-narcotic analgesics, antidepressants, anticonvulsants, local blocks, topical agents, vitamins, and antipsychotics.
Nerve entrapments can occur in a number of different locations in the foot as a result of anatomical variation. The reported complaint may include symptoms of pain associated with numbness, burning, and tingling. Advanced imaging studies with ultrasound and MRI may reveal fluid surrounding the affected nerve suggestive of inflammation. The gold standard remains nerve conduction and EMG (electromyography) testing. Treatment often involves conservative removal of the pressure on the nerve with padding and orthotic management, NSAIDs to reduce local inflammation, and surgical decompression of the nerve when conservative management fails (see Table 43-5).
Neuroma Nicknames Based on Forefoot Location
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Neuroma Nicknames Based on Forefoot Location
Medial 1st MPJ
1st interspace (1st common digital nerve)
2nd interspace (2nd common digital nerve)
3rd interspace (3rd common digital nerve)
4th interspace (4th common digital nerve)
Tarsal tunnel syndrome involves entrapment of the posterior tibial nerve in the sulcus just inferior to the medial malleolus of the ankle. Compression of the nerve leads to pain, numbness, and burning symptoms. This pain can also feel like pins and needles and can radiate both proximally and distally along the foot or leg.20 Causes of tarsal tunnel syndrome include space-occupying lesions, biomechanical faults such as overpronation, trauma, and inflammatory conditions. Examples of space-occupying lesions that cause tarsal tunnel syndrome include varicosities, ganglions, lipomas, and edema. Biomechanical faults usually involve excess stretch on the tibial nerve from overpronation. No matter the lesion, pain is caused from an entrapment or compression of the tibial nerve or its branches: medial and lateral plantar nerves and the medial calcaneal nerve. Upon clinical examination, symptoms can be reproduced by maximally everting the foot, thus stretching the tibial nerve and compressing the tarsal tunnel. Tapping on the medial aspect of the tarsal tunnel may also reveal a shooting electrical pain sensation toward the toes (Tinel's sign) or proximally up the foot (Valleix's sign). Treatment includes NSAIDs, local nerve blocks, physical therapy, and orthotic management to address biomechanical etiologies. Surgical treatment consists of decompressing the nerve by releasing the flexor retinaculum or removing the space-occupying lesion and freeing up the tibial nerve and its branches (see Figure 43-16).
Metabolic conditions can manifest in the feet, with gout as one of the most common conditions. Other metabolic conditions include pseudogout, chondrocalcinosis, and calcium pyrophosphate dehydrate (CPPD), which is an acute or chronic inflammatory arthritis. It typically runs a longer course than gout and affects larger joints like the ankle as opposed to the big toe joint seen in classic gout. Laboratory tests can be of benefit to rule out increased uric acid levels. An arthrocentesis and microscopic examination show rhomboid-shaped crystals. Treatment of pseudogout typically involves immobilization and oral pain control during acute flares (see Table 43-6).
Gout Versus Pseudogout
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Gout Versus Pseudogout
Calcium pyrophosphate dihydrate
Larger joints—ankle, knee
Negative birefringent crystals
Positive birefringent crystals
Gold, needle-shaped crystals
Blue, rhomboid-shaped crystals
Rheumatoid arthritis (RA) is an inflammatory arthritis that affects the entire body. In the foot, pain is described as an insidious aching with reports of morning stiffness. Multiple joints are involved, and the pain and swelling often improve with motion. Painful rheumatoid nodules may also arise, affecting the small joints of the digits. Located in the subcutaneous tissue, these nodules are comprised of fibrous tissue and commonly located over bony prominences.
In contrast, osteoarthritis (OA) is a degeneration of the articular joint surfaces secondary to excessive “wear and tear.” The cartilage is damaged, and, once the subchondral bone is exposed, it becomes sclerotic. Pain is asymmetric and worsens during activity, with changes in weather aggravating symptoms. There is usually subsequent decreased range of motion, classically seen in the first MTPJ, coined hallux limitus or rigidus if severe. It can also be seen in the midfoot following a trauma or in the anterior ankle joint with decreased ankle range of motion. Diagnosis is made clinically, though severity can be depicted radiographically with loose bodies and uneven joint disruption. Treatments include NSAIDs, joint injections, orthotic therapy, and physical therapy to ease the pain symptoms. If surgery is indicated, the joint is usually remodeled, replaced, or fused (see Table 43-7).
Osteoarthritis Versus Rheumatoid Arthritis
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Osteoarthritis Versus Rheumatoid Arthritis
Pain worse at end of day, worse with motion
Pain worse in morning, improves with motion
Larger joints (MPJ, knees, hips)
Small joints (IPJs, MPJs)
No swelling, noninflammatory
Soft-tissue swelling, inflammation
Treated with joint replacement or fusion
Treated with corticosteroids, NSAIDs
Iatrogenic causes of foot pain can be as simple as a surgical scar. Both hypertrophic and keloid formation, when the scar extends beyond the incision line, can be uncomfortable physically and emotionally to the patient. Hypertrophic scars can be excised, and the underlying tissue can be freed up and better approximated. Keloid treatment is more controversial, but steroid injections can be utilized to help with the pain.21 Physical therapy, massage, therapeutic heat, stretching, paraffin wax, and ultrasound treatments have also been recommended to assist in releasing the adhered tissues.
During surgery, or trauma, there may be injury to the nerve, leading to compression, entrapment, or complete severance. Compression can result from a tight dressing and cast or even if the nerve is retracted too aggressively during the procedure. The nerve may be bruised with pain, and numbness may result following the removal of the inciting trauma and the decrease in inflammation. If the nerve axon is injured and subsequent Wallerian degeneration occurs, it may take months to repair. If the nerve is completely severed, it is usually irreversible22,23 (see Table 43-8).
Nerve Trauma Describing Severity, If Axonal Involvement or Complete Transection of the Nerve
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Nerve Trauma Describing Severity, If Axonal Involvement or Complete Transection of the Nerve
Nerve Trauma Classification
Bruised nerve, axon unaffected, reversible
Injured axon, Wallerian degeneration, regeneration possible
Axon injured, with irregular regeneration
Axon destroyed but nerve trunk remains intact
Nerve completely severed; irreversible numbness
Nerve conduction tests can be used to determine the distribution of deficit, and, if possible, an end-to-end repair is recommended. The consulted chronic pain medicine physician can expect the lesion to be located near the incisional scar. Gabapentin, pregabalin, and other anticonvulsant medications may help diminish the symptoms. It is important to appreciate the sensory distribution and spinal nerve root in cases where a local nerve block or proximal nerve stimulator is indicated (see Figs. 43-14 and 43-15).
A: Saphenous nerve distribution (L3,4). B: Sural nerve distribution (S1,2). C: Medial calcaneal nerve distribution (S1,2). D: Lateral plantar nerve distribution (S1,2). E: Medial plantar nerve distribution (L4,5). F: Superficial peroneal nerve distribution (L5, S1);. G: Deep peroneal nerve distribution (L4,5).
Clinical presentation of a patient with chronic CRPS already treated with Transcutaneous Electrical Nerve Stimulator and several oral medications. This limb has lost its function due to pain, swelling, and resultant disuse atrophy.
Bone healing complications, as a result of trauma or operative in origin, can also cause foot pain. Bone healing complications include delayed union, nonunion, and pseudoarthrosis. Differentiation of each bone healing complication primarily involves the length of time from the attempted arthrodesis procedure. In delayed union (3–6 months to heal), there may be swelling and pain secondary to continued motion and further non-weight-bearing may be required to allow the bone to heal. If there is a nonunion—defined as up to 9 months without fusion or absence of healing—the addition of a bone stimulator in addition to immobilization is necessary.24 In the case of pseudoarthrosis, reoperation with removal of the nonunion and bone graft is often indicated to stimulate osteogenesis and eventual healing (see Fig. 43-16).
Intraoperative picture of a tarsal tunnel release; the space-occupying lesion was discovered and evacuated with further release of the nerve branches.
As depicted in this chapter, the origins of foot pain are varied, originating from several anatomic, physiologic, and mechanical etiologies. The medical history and physical examination are essential to finding the etiology of foot pain. Coupled with appropriate diagnostic laboratory and radiographic tests, the diagnosis is made, and treatment typically addresses the underlying cause. For complicated and chronic pain situations, a multidisciplinary team approach is necessary to adequately treat the pain symptoms fully.
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