Drop Claw Foot

DROP FOOTBackgroundFoot drop is a deceptively simple name for a potentially complex problem. It can be defined as a significant weakness of ankle and toe dorsiflexion. The foot and ankle dorsiflexors include the tibialis anterior, the extensor hallucis longus, and the extensor digitorum longus. These muscles help the body clear the foot during swing phase and control plantar flexion of the foot on heel strike.Weakness in this group of muscles results in an equinovarus deformity. This is sometimes referred to as steppage gait, because the patient tends to walk with an exaggerated flexion of the hip and knee to prevent the toes from catching on the ground during swing phase. During gait, the force of heel strike exceeds body weight, and the direction of the ground reaction vector passes behind the ankle and knee center (see the image below).

Foot drop is caused by weakness or paralysis of the muscles that lift the front part of the footDiagram of ground reaction vector during heel strike.This causes the foot to plantar-flex and, if uncontrolled, to slap the ground. Ordinarily, eccentric lengthening of the tibialis anterior, which controls plantar flexion, absorbs the shock of heel strike. Foot drop can result if there is injury to the dorsiflexors or to any point along the neural pathways that supply them.Foot drop can be associated with a variety of conditions, including dorsiflexor injuries, peripheral nerve injuries, stroke, neuropathies, drug toxicities, or diabetes. The causes of foot drop may be divided into 3 general categories: neurologic, muscular, and anatomic. These causes may overlap. Treatment is variable and is directed at the specific cause (see Treatment).EpidemiologyPeroneal neuropathycaused by compression at the fibular head is the most common compressive neuropathy in the lower extremity. Foot drop is its most notable symptom. All age groups are affected equally, but the condition is more common in males (male-to-female ratio, 2.8:1). About 90% of peroneal lesions are unilateral, and they can affect the right or the left side with equal frequency.A foot drop of particular concern to orthopedic surgeons is the peroneal nerve palsy seen aftertotal knee arthroplasty(TKA; 0.3-4% of cases) or proximal tibial osteotomy (3-13% of cases). Ischemia, mechanical irritation, traction, crush injury, and laceration can cause intraoperative injury to the peroneal nerve. It has also been suggested that correction of a severe valgus or flexion deformity can stretch the peroneal nerve and lead to palsy. Postoperative causes of peroneal nerve palsy include hematomas and constrictive dressings.In a study by Cohen et al, the relative risk of palsy was 2.8 times higher with epidural anesthesia for TKA than with general or spinal anesthesia.[2]Epidural anesthesia probably decreased proprioception and sensation (intraoperatively and to some extent postoperatively), allowing the limb to rest in an unprotected state susceptible to local compression. In addition, intraoperative neurologic damage may not have been readily apparent in the immediate postoperative period because of ongoing effects of epidural anesthesia.In the same study, the relative risk of palsy was 6.5 times greater in patients who had a prior lumbar laminectomy.[2]A series of patients who developed foot drop after primary hip arthroplasty were carefully examined and found to havespinal stenosis.[3]As many as 70% of patients undergoing hip arthroplasty have electromyographic (EMG) evidence of nerve injury, but they rarely have clinical symptoms.[4]Patients with preexisting spinal stenosis are believed to be at increased risk for foot drop after hip arthroplasty because of this proximal compromise; this is the double-crush phenomenon.

PrognosisPrognosis and outcome vary according to the cause of the foot drop. In a peripheral compressive neuropathy, recovery can be expected in up to 3 months, provided that further compression is avoided. A partial peroneal nerve palsy after total knee replacement has a uniformly good prognosis.[5]A variable amount of recovery is seen with a complete postoperative palsy. Follow-up EMG and nerve conduction studies may be useful for assessing recovery.A partial palsy recovers faster because of local sprouting. With complete axonal loss, reinnervation is achieved solely through proximal-to-distal axonal growth, which usually proceeds at a rate of 1 mm/day. Thus, injuries of a nerve close to its target muscle also have a more favorable outcome. In a nerve root compressive neuropathy, one study concluded that severe motor weakness lasting longer than 6 months, a negative straight leg-raising test, and old age were poor prognostic factors for recovery of dorsiflexion.[6]When there is direct injury to the peroneal nerve, the outcome is more favorable for penetrating trauma than for blunt trauma; a traction or stretch injury to the nerve has an intermediate outcome. When nerve grafting is performed, functional recovery depends on the severity of injury and thus on the length of the graft used. With grafts longer than 12 cm, good functional recovery is rare.Wound infection may occur after surgical treatment, as may nerve graft failure. In tendon transfer procedures, recurrent deformity has been reported. In arthrodeses or fusion procedures, pseudoarthrosis, delayed union, or nonunion may be noted.

Claw footClaw foot is a deformity of the foot. The toejoint nearest the ankle is bent upward and the other toe joints are bent downward. The toe looks like a claw.ConsiderationsClaw toes present at birth (congenital). Thecondition can also can develop later in life because of other disorders (acquired). Claw toes may be caused by a nerve problem in the legs ora spinal cord problem. The cause is unknown in many cases.Claw toes are not usually harmful in themselves.They may be the first sign of a more serious disease of the nervous system.Claw toes may cause pain and lead tocalluseson the top of the toe over the first joint, but may also be painless. The condition may createproblems wearing shoes.Causes Ankle fractures or surgery Cerebral palsy Charcot-Marie-Tooth disease Other brain and nervous system disorders Rheumatoid arthritis