Sports Medicine: Just the Facts

CHAPTER 67 • NERVE ENTRAPMENTS OF THE LOWER EXTREMITY 401

TREATMENT

• Footwear changes to avoid direct pressure, neuromod-
  ulatory and anti-inflammatory medication, TENS,
  ankle stability rehabilitation, and steroid injections.
  •Surgery is performed via a dorsomedial approach, and
  involves partial sectioning of the extensor retinaculum
  and osteophyte removal.

MISCELLANEOUS NERVE
ENTRAPMENT SYNDROMES

MEDIAL CALCANEAL NERVE

• The MCN usually arises from the TN, but may arise
  from the LPN or at the MPN–LPN bifurcation (Smith
  and Dahm, 2001).


• The MCN pierces the flexor retinaculum to provide
  cutaneous innervation to the posterior, medial, and
  plantar surfaces of the heel, providing no motor inner-
  vation.


• Entrapment usually occurs as the MCN pierces the
  flexor retinaculum. Excessive pronation may be con-
  tributory. Direct compression from external sources
  such as footwear.


• Neuropathic pain is limited to the medial heel and
  there is no motor or reflex deficit. Symptoms increase
  with activity. The most useful clinical sign is percus-
  sion tenderness and paresthesias when palpating the
  MCN as it pierces the retinaculum posterior to the
  TN. Examination will less commonly reveal proximal
  readiation, or a lamp cord sign (a hypersensitive,
  tender thickening of the MCN along its oblique-
  posterior course) (Cohen, 1974).


• Differential diagnosis resembles that for TTS, but
  medial heel involvement suggests MCN entrapment.


• EDX studies assist in the differential diagnosis, but
  are rarely useful in making the diagnosis.
  •Treatment includes pronation control, corticosteroid
  injections, and cut-out pads and footwear alterations
  to reduce direct pressure on the MCN as necessary.
  The lamp cord sign is often a poor prognostic factor,
  and surgery is often recommended to remove the
  pseudoneuroma, often with excellent outcome.

SURALNEUROPATHY

• The SN is formed by branches of the TN and CPN in
  the posterior calf, proximal to the lateral malleolus.
  Two centimeters proximal to the malleolus, the SN
  provides a sensory branch to the lateral heel, then
  courses subcutaneously inferior to the peroneal ten-
  dons to the base of the fifth metatarsal, where it ram-
  ifies into distal sensory branches.
  
  
  • Etiologies include recurrent ankle sprains, calcaneal
    or fifth metatarsal fractures, Achilles tendinopathy,
    space-occupying lesions such as ganglia, direct contu-
    sion, footwear-induced pressure, or iatrogenic (post-
    biopsy neuroma). Symptoms consist of achy,
    posterolateral calf pain, with neuropathic pain in the
    SN distribution.
  
  
  • Examination should include percussion testing along
    the nerve and provocative testing by passive dorsi-
    flexion and inversion.
    •Treatment emphasizes reduction of pressure from
    footwear, Achilles stretching, neuropathic pain treat-
    ment, and ankle stability rehabilitation. Surgery con-
    sists of exploration and decompression.
  
  
  
  

SAPHENOUS NERVE

• The saphenous nerve is the largest cutaneous branch of
  the femoral nerve. This purely sensory nerve arises
  from the femoral nerve in the femoral triangle and
  courses with the femoral artery to the medial knee,
  where its infrapatellar branch supplies cutaneous sen-
  sation to the medial knee. It then courses inferiorly
  with the saphenous vein to supply cutaneous sensation
  to the medial calf to the level of the ankle. At the ankle,
  a branch passes anterior to the medial malleolus to
  innervate the medial foot. The saphenous nerve is most
  vulnerable at the medial knee, where it pierces the
  fascia and emerges from the distal subsartorial canal
  (Hunter’s adductor canal) (Smith and Dahm, 2001).


• Etiologies include entrapment at the adductor canal,
  pes anserine bursitis, contusion, and postsurgical
  (knee) iatrogenic injury. The athlete will typically
  report neuropathic pain and numbness in the area of
  the medial knee and/or calf, depending on whether
  there is isolated infrapatellar branch or complete
  saphenous nerve involvement. There should be no
  motor deficits.


• Examination includes percussion testing along the
  nerve starting at the adductor canal, and a search for
  underlying etiologies. Differential diagnosis includes
  all proximal femoral nerve, plexus, and root lesions,
  as well as musculoskeletal disorders about the knee.


• Diagnosis and treatment principles resemble those for
  SN entrapment, but focus upon different anatomical
  areas. Surgical release may be necessary.

OBTURATOR NERVE

• Obturator nerve (ON) entrapment has received
  increased attention as a potential source of groin pain
  in athletes (McCroy and Bell, 1999).