CHAPTER 67 • NERVE ENTRAPMENTS OF THE LOWER EXTREMITY 397DIFFERENTIALDIAGNOSIS ANDEVALUATION
- Differential diagnosis includes proximal and systemic
neurological conditions; stress fractures; MTP syn-
ovitis, instability or arthritis; and flexor-extensor
tenosynovitis (Smith and Dahm, 2001).
TREATMENT
- Activity modification, nonsteroidal anti-inflammatory
drugs (NSAIDs), physical therapy, biomechanical
intervention to reduce toe dorsiflexion, control hyper-
pronation, and maintain greater metatarsal separation
(i.e., a well-padded supportive sole, wide shoe,
metatarsal bar or pad, Achilles tendon flexibility, and
corticosteroid injections) (McCluskey and Webb,
1999). Surgery is indicated upon failure of conserva-
tive care.
TIBIAL NERVE: TARSAL TUNNEL SYNDROME
DEFINITION
- A constellation of processes affecting the TN or it
branches at the level of the ankle, producing neuro-
pathic pain along the posteromedial ankle, medial
foot, or plantar foot (Smith and Dahm, 2001; Lau and
Daniels, 1999).
ANATOMY, PATHOPHYSIOLOGY, ANDRISKFACTORS
- The TN originates from the L4-S3 spinal segments
and is the larger terminal branch of the sciatic nerve
(McCluskey and Webb, 1999). The TN supplies mus-
cular innervation in the posterior thigh and leg, and a
cutaneous contribution to the SN, prior to becoming
superficial medial to the Achilles tendon and entering
the tarsal tunnel posterior to the medial malleolus. - The tarsal tunnel is a fibro-osseous space formed by
the flexor retinaculum, medial calcaneus, posterior
talus, distal tibia, and medial malleolus; and extends
from the distal tibia to the navicular bone.
•Over 90% of the time, the TN will divide into the
MPN and LPN within the tarsal tunnel, typically at
the medial malleolar-calcaneal line (Lau and Daniels,
1999). Within 1 to 2 cm below/distal to the medial
malleolar-calcaneal line, the MPN and LPN enter sep-
arate fibro-osseous canals at the origin of the abduc-
tor hallucis muscle (AHM) (Schon and Baxter, 1990;
Park and Del, 1998). - Ta r sal tunnel syndrome TTS can involve the TN,
MPN, LPN, and at times the medial calcaneal nerve
(MCN). - Risk factors include repetitive trauma and hyperprona-
tion. Compression from stiff orthoses or space-occu-
pying lesions such as an os trigonum, tenosynovitis,
tumor, or ganglion is less common.
SYMPTOMS ANDSIGNS- Cramping, burning, and tingling at the medial ankle,
medial and/or plantar foot. Diffuse foot pain has been
reported. The medial heel is usually spared due to the
proximal origin of the MCN. Symptoms increase with
activity. - Examination includes inspection for malalignment,
deformity, and muscular atrophy causing or resulting
from TTS, such as forefoot pronation, claw toe, tal-
ipes calcaneus, or calcaneovalgus. Nerve palpation
and percussion testing is completed over the TN and
all its terminal branches (Dumitru, 1995). Provocation
maneuvers include sustained passive eversion or great
toe dorsiflexion to stretch affected nerves, and postex-
ercise examination. - In severe cases, weakness of toe plantarflexion mani-
fests by reduced push-off on the affected side
(McCluskey and Webb, 1999).
DIFFERENTIALDIAGNOSIS ANDEVALUATION- Differential diagnosis includes polyneuropathy;
proximal neuropathy (including double crush
injuries from radiculopathy or sciatic neuropathy);
deep posterior compartment syndrome; popliteal
artery entrapment; vascular claudication; venous dis-
ease; tenosynovitis or ganglia; plantar fasciitis; tibio-
talar or subtalar synovitis, instability or arthritis
(Sammarco, Chalk, and Feibel, 1993; Turnipseed
and Pozniak, 1992). Examination will help differen-
tiate proximal TN injuries. Tibial nerve injury just
distal to the SN contribution will spare lateral cal-
caneal and foot sensation and gastrocnemius-soleus
function. Injury distal to the midportion of the leg
will affect plantar sensation and result in claw toe
deformity due to imbalance between the affected
foot intrinsic and unaffected flexor digitorum longus
(FDL) and extensor digitorum brevis (EDB) muscles
(McCluskey and Webb, 1999). - TTS is primarily a clinical diagnosis. In acute TTS or
in failed nonoperative management, MRI is recom-
mended to determine the presence of synovitis or a
space-occupying lesion (Frey and Kerr, 1993). EDX
studies assist in excluding alternative neurological
disorders. They may be positive in up to 90% of
patients with well-established TTS, but do not corre-
late with surgical findings or clinical outcome
(Galardi et al, 1994).
TREATMENT- Activity modification, NSAIDs, neuromodulatory
medications (tricyclic and antiseizure medications),
physical therapy, and biomechanical interventions.
Physical therapy includes ( 1 ) strengthening the
foot intrinsic and medial arch supporting muscles,