Foot Drop
Foot drop is also known and "drop foot." This is where the patient cannot lift their forefoot secondary to weakness of the dorsiflexor muscles. Foot drop can be caused by muscular, skeletal, or nervous system disorders.
Anatomy
Compartments
| Compartment | Muscles | Action | Nerve Supply | Blood Supply |
|---|---|---|---|---|
| Anterior | Sartorius and quadriceps muscles (rectus femoris, vastus lateralis, vastus intermedius, vastus medialis) | Hip flexion | Femoral nerve | Superficial femoral artery |
| Medial | Pectineus, obturator externus, gracilis, and adductor muscles (longus, brevis, magnus, minimus) | Hip adduction | Obturator nerve | |
| Posterior | Biceps femoris, semimembranous, and semitendinous muscles | Hip extension | Sciatic nerve | Deep femoral artery |
| Compartment | Muscles | Action | Nerve Supply | Blood Supply |
|---|---|---|---|---|
| Anterior | Tibialis anterior, extensor hallucis longus, extensor digitorum longus, and peroneus tertius | Dorsiflexion and inversion/eversion of the ankle and extension of the toes | Anterior tibial artery | Deep peroneal nerve |
| Lateral | Peroneus longus and peroneus brevis | Eversion of the foot and ankle, and weak plantarflexion of the foot | Peroneal artery | Superficial peroneal nerve |
| Superficial posterior | gastrocnemius, the soleus, +/- plantaris | Plantarflexion and inversion of the foot at the ankle, and toe flexion | Posterior tibial and peroneal arteries | Tibial nerve |
| Deep posterior | Tibialis posterior, flexor hallucis longus, flexor digitorum longus, and popliteus muscles. | Plantarflexion and inversion of the foot at the ankle, and toe flexion | Posterior tibial and peroneal arteries | Tibial nerve |
Innervation
| Nerve | Segment | Motor Supply | Action | Sensory Supply |
|---|---|---|---|---|
| Iliohypogastric nerve | T12/L1 | Transversus abdominis and internal oblique muscles | N/A | Lower abdomen |
| Ilioinguinal nerve | L1 | Inferior abdominal muscles | N/A | Inguinal region, small area of media thigh, and upper scrotum/labia |
| Genitofemoral nerve | L1, L2 | Cremasteric muscle in men | N/A | Skin of femoral triangle. Lower scrotum/labia |
| Lateral femoral cutaneous nerve | L2,L3 | N/A | N/A | Lateral thigh |
| Obturator nerve | L2, L3, L4 anterior rami | Adductor magnus (anterior half), adductor longus, adductor brevis, gracilis, obturator externus | Hip adduction | Medial thigh |
| Femoral nerve | L2, L3, L4 anterior rami, posterior divisions | Quadriceps femoris, sartorius, pectineus, iliacus | Knee extension | Medial lower leg (through saphenous nerve |
| Lumbosacral trunk / furcal nerve | L4-5, mainly L5 | Ankle dorsiflexion, eversion, inversion | L5 sensory loss |
| Nerve | Segment | Motor Supply | Action | Sensory Supply |
|---|---|---|---|---|
| Superior gluteal | L4-S1 | Gluteus medius, gluteus minimus, tensor fasciae latae | hip abduction | buttock pain |
| Inferior gluteal | L5-S2 | Gluteus maximus | hip external rotation and power extension | N/A |
| Sciatic trunk/nerve | L5–S3 | Tibial portion: Posterior compartment of the thigh and leg Common peroneal division: short head of biceps femoris, and anterior, and lateral compartments of the leg, and extensor digitorum brevis. and leg through common peroneal and tibial nerves |
Tibial portion: Sole of the foot (medial and lateral plantar nerves) Common peroneal division: Anterolateral surface of the leg (sural nerve), first webspace of foot (deep peroneal nerve), and dorsal aspect of the foot (superficial peroneal nerve) | |
| Posterior femoral cutaneous nerve | - | - | Posterior surface of the thigh, leg, and perineum (perineal branches and inferior cluneal nerves) | |
| Pudendal nerve | S2-4 | Muscles of the perineum | Penis, clitoris, most of the perineum | |
| Nerve to piriformis | ||||
| Nerve to obturator internus and superior gemellus |
Aetiology
Compressive Disorders
Compression of the peroneal nerve can anywhere along its course. It is more common in patients with a history of significant weight loss, in those who frequently cross their legs, or who do squatting exercises.
- The most common site is at the fibular head. This area is vulnerable due to the bony prominence of the fibular head, the superficial position of the nerve, and tethering of the nerve by the peroneus longus tendon in the peroneal tunnel.
- Less common areas of compression are at the hip and ankle.
- There can be an anatomical variation of the biceps femoris muscle resulting in the formation of the muscular tunnel between the gastrocnemius muscle and distal biceps femoris, resulting in peroneal nerve entrapment.
- It can also be trapped when there is a high division of the sciatic nerve. In this situation the peroneal component pierces the piriformis muscle and especially in cases of piriformis scarring or hypertrophy it may become entrapped.
- The presence of a fabella, an accessory sesamoid bone, can cause compression at the lateral gastrocnemius attachment.
- Intraneural or extraneural lesions can cause compression.
Lumbar spine disease can also cause foot drop such as with lumbar disc herniation and lumbar spinal stenosis. The L5 nerve root at the L4-5 segment is the most commonly affected nerve root, often in association with S1 or L4 (double nerve root compression), or all of L4-S1 (triple nerve root compression).[1]
Trauma
Prognosis
In a study of the post operative course of 135 patients with foot drop due to lumbar degenerative disease, the muscle strength of tibialis anterior (TA) improved in 83.7%. The strength recovered to grade 4 or 5 in 15.6%, with only one third of those recovered achieving grade 5 power. The most important influences on prognosis were duration of palsy, preoperative muscle strength of TA, and age. The recovered group had a median symptom duration of 86.3 days, while the unrecovered group had a median symptom duration of 204.9 days. The preoperative muscle strength was 2.55 and 1.83 in the recovered and unrecovered groups respectively. All patients with grade 0 power recovered to grade 1 but no higher. Overall, postoperative strength seems to have been at its maximum at three months.[1]
