Tarsal Tunnel Syndrome: Causes and treatment

Courtesy: Prof Nabil Ebraheim, University of Toledo, Ohio, USA

TARSAL TUNNEL SYNDROME

• Compressive neuropathy of the posterior tibial nerve or its branches within the tarsal tunnel
• Tarsal Tunnel- a fibro-osseous space located on the medial side of the ankle
• Equivalent to carpal tunnel syndrome

ANATOMY OF TARSAL TUNNEL

• Narrow fibro-osseous passage located on the medial side of the ankle, just posterior and inferior to the medial malleolus.
• Serves as a conduit for several important neurovascular and tendinous structures that pass from the leg into the foot.

BOUNDARIES

• Roof: Flexor retinaculum (laciniate ligament), a strong fibrous band that stretches from the medial malleolus to the calcaneus.
• Floor: Medial surfaces of the talus, calcaneus, and the distal tibia.

CONTENTS

• Tibialis posterior tendon
• Flexor digitorum longus tendon
• Posterior tibial artery
• Posterior tibial vein(s)
• Tibial nerve
• Flexor hallucis longus

TIBIAL NERVE

• Origin :- One of the two terminal branches of the sciatic nerve(tibial nerve and common peroneal nerve)
• Motor and sensory innervation to the posterior leg and plantar surface of the foot.
• Root value:- L4–S3.

COURSE

• Arises from the apex of popliteal fossa
• Descends vertically through the popliteal fossa lying superficial to the popliteal artery and vein.
• Passes deep to the tendinous arch of soleus and runs between the superficial and deep flexor muscles
• Travels down the posterior compartment of the leg, accompanying the posterior tibial vessels
• In the ankle it passes behind the medial malleolus that is through the tarsal tunnel and terminate as medial and lateral plantar nerves.

BRANCHES

IN THE POPILITEAL FOSSA

Muscular branches:-

• Gastrocnemius (Medial and lateral head)
• Soleus
• Plantaris
• Popliteus
• Cutaneous branches
• Sural nerve:-Provides sensation to the posterior leg and lateral foot
• Articular branches to the knee joint

IN THE LEG:-

• Muscular branches to
• Tibialis posterior
• Flexor Digitorum longus
• Flexor Hallucis longus

AT THE ANKLE/FOOT:-

Medial plantar nerve:-

• Innervates abductor hallucis, flexor digitorum brevis ,flexor hallucis brevis, and first lumbrical
• Supplies medial 3.5 digits

Lateral plantar nerve:-

• Innervates the remaining intrinsic foot muscles
• Supplies the lateral 1.5 digits
• Medial calcaneal branches :-sensory innervation to the heel

ETIOLOGY

• Anatomical/structural causes:-
• Ganglion cysts, Lipoma, Varicose veins
• Medial malleolus or Talus fracture
• Tenosynovitis of the posterior tibial tendon

BIOMECHANICAL ABNORMALITIES

• Pars planus

SYSTEMIC CONDITIONS

• Diabetes Mellitus
• Inflammatory arthritis

CLINICAL FEATURES

• Burning or sharp pain along the medial ankle ,heel and sole of the foot
• Tingling, numbness or pins and needles sensation
• Intrinsic foot muscle weakness(Rare)
• Swelling near the medial malleolus(if inflammatory cause)

CLINICAL SIGNS

• Tinel’s sign-Tapping over the tarsal tunnel reproduces pain or tingling in the distribution of the tibial nerve
• Sensory loss:-Reduced sensation over the plantar surface of the foot
• Positive dorsiflexion-eversion test:-Stretching of the nerve[by dorsiflexing and everting the foot] can provoke symptoms
• Muscle wasting:-Late stage or chronic cases may show wasting of small foot muscles.

INVESTIGATIONS

IMAGING STUDIES

MRI–

• Gold standard to see soft tissue causes including ganglion cysts, tenosynovitis ,or muscle hypertrophy

ULTRASOUND

• Cost effective
• Can detect cysts, varicosities or tendon pathology compressing the nerve

X-RAY

• Helps to identify bone abnormalities, spurs or fractures that might contribute to compression

DIAGNOSTIC INJECTIONS

• Local anesthetic injection into the tarsal tunnel can cause temporary relief of symptoms supporting the diagnosis of tarsal tunnel syndrome

ELECTROPHYSIOLOGICAL STUDIES

• Nerve conduction studies:-
• Delayed conduction across the tarsal tunnel suggests compression

ELECTROMYOGRAPHY-

• Assesses muscle response and helps detect denervation in intrinsic foot muscles
• distal motor latencies of 7.0 msec or more
• prolonged sensory latencies of more than 2.3 msec
• decreased amplitude of motor action potentials of
  -abductor hallucis
  -or abductor digiti minimi

MANAGEMENT

NON OPEARATIVE MANAGEMENT-

Activity Modification-

• Avoid prolonged standing, walking or high impacted activities
• Adequate rest to reduce inflammation and nerve irritation
• Footwear Modifications-
• Use well-cushioned ,supportive shoes

Physical Therapy-

• Stretching and strengthening exercises for the posterior tibial tendon and intrinsic foot muscles
• Ultrasound therapy may also help to reduce soft tissue tension

Anti- inflammatory Measures-

• NSAIDS to reduce pain and inflammation
• Ice pack application
• Corticosteroid injections
• Weight Management

SURGICAL MANAGEMENT

INDICATIONS-

• after 3-6 months of failed conservative management
• Compressive mass identified
• Positive EMG
• Reproducible physical findings

TARSAL TUNNEL RELEASE

• Extend the incisions from 1 cm plantar to the navicular tuberosity in a proximal direction, bisecting the area between the medial malleolus and the medial aspect of the tuberosity of the calcaneus, ending 1cm anterior to the achilles tendon
• Dissect through the subcutaneous tissue carefully ,preserving the saphenous vein and nerve
• Retract the soft tissues to expose the flexor retinaculum
• Release of the flexor retinaculum by incising along its length to decompress the tarsal tunnel
• The tibial nerve and its branches are gently dissected free from surrounding structures
• Any fibrous band, ganglia, varicosities pr space occupying lesions are released or excised
• Hemostasis achieved and wound closed in layers

POST OPERATIVE CARE

• Immobilisation in a splint for 1-2 weeks
• Gradual weight bearing and physical therapy
• Monitor for complications like infection or nerve injury