Sports Medicine: Just the Facts

( 2 ) Achilles stretching in subtalar neutral, ( 3 ) lower

limb kinetic chain rehabilitation, and ( 4 ) propriocep-

tive enriched rehabilitation in cases of ankle or subta-

lar instability (Lau and Daniels, 1999).

• Biomechanical management includes pronation con-
  trol. If symptoms are reproduced by dorsiflexion, tem-
  poral use of a heel lift (in combination with appropriate
  stretching) may be useful.
  •Treatment should address contributing underlying
  systemic conditions. A steroid injection at the entrap-
  ment site may help, provided that the PT tendon is
  avoided (Lau and Daniels, 1999).
  •Surgery may be indicated when nonoperative treat-
  ment fails (Lau and Daniels, 1999).

FIRST BRANCH OF THE LATERAL PLANTAR NERVE

DEFINITION

• Isolated LPN entrapments are relatively rare. More
  commonly, entrapment specifically affects the FB-
  LPN, sometimes called Baxter’s nerve, the nerve to
  the abductor digiti quinti muscle (NADQ), or the infe-
  rior calcaneal nerve (ICN). FB-LPN entrapment is
  reported to be the most common neurologicalcause
  of heel pain (Smith and Dahm, 2001; Baxter and
  Pfeffer, 1992).

ANATOMY, PATHOPHYSIOLOGY, ANDRISKFACTORS

• After penetrating the abductor hallucis muscle
  (AHM) and its fascia, the FB-LPN courses inferiorly,
  passing between the deep, taut fascia of the AHM
  medially and the medial, caudal margin of the medial
  head of the quadratus plantae muscle laterally (Baxter
  and Pfeffer, 1992). The nerve then abruptly turns lat-
  erally, coursing toward the lateral foot between the
  flexor digitorum brevis and quadratus plantae mus-
  cles. The FB-LPN ramifies into three terminal
  branches supplying the flexor digitorum brevis, the
  medial calcaneal periosteum, and abductor digiti
  quinti. The branch to the calcaneal periosteum often
  supplies branches to the long plantar ligament as well
  as an inconsistent branch to the quadratus plantae
  muscle (Schon and Baxter, 1990). There is no cuta-
  neous innervation.


• The actual site of FB-LPN entrapment most com-
  monly occurs at the site of direction change from an
  inferior to lateral course deep to the AHM (Baxter and
  Pfeffer, 1992).


• Risk factors include chronic plantar fasciitis and a cal-
  caneal spur.

SYMPTOMS ANDSIGNS

• Medial heel pain; no sensory or reflex deficits.

DIFFERENTIALDIAGNOSIS

• Differential diagnosis includes the following:
  
  
  • Plantar fasciitis and fat pad disorder. Sensory losses
    on the medial heel suggest a disorder affecting the
    MCN, L4 radiculopathy, plexopathy, or diffuse neu-
    rological disease.
  
  
  • MRI and EDX testing are not accurate enough to
    confirm or refute the clinical diagnosis of FB-LPN
    entrapment, but may assist in differential diagnosis.
  
  
  
  

TREATMENT

• Nonoperative measures follow treatment principles
  used for plantar fasciitis. Physical therapy should
  focus on muscle rebalancing about the ankle-foot and
  the entire lower limb kinetic chain. Neuromodulatory
  medication and local corticosteroid injections may be
  useful.


• Most authors advocate at least 6 to 12 months of non-
  operative care prior to considering surgery.


• Decompression includes the deep fascia of the AHM
  and a portion of the contiguous medal plantar fascia.

MEDIAL PLANTAR NERVE: JOGGER’S FOOT

DEFINITION

• Local entrapment of the MPN results in a syndrome of
  neuropathic pain radiating along the medial heel and
  longitudinal arch (Smith and Dahm, 2001).

ANATOMY, PATHOPHYSIOLOGY, ANDRISKFACTORS

• After the MPN and LPN exit the tarsal tunnel, each
  nerve enters a fibro-osseous canal bounded superi-
  orly by the calcaneonovicular or spring ligament and
  inferiorly by the attachment of the AHM to the nav-
  icular bone. The MPN then enters the sole of the foot,
  passes superficial to the traversing FDL tendon at the
  master knot of Henry, and continues distally along
  the flexor hallucis longus(FHL) tendon to divide into
  terminal medial and lateral branches at the level of
  the base of the first metatarsal. These branches
  ramify and terminate as three common plantar digital
  nerves within the medial three web spaces. The MPN
  is a mixed sensorimotor nerve providing sensation to
  the medial sole and plantar aspect of the first, second,
  third, and medial fourth toes, as well as motor inner-
  vation to the abductor hallucis, flexor hallucis
  brevis, flexor digitorum brevis, and first lumbrical
  muscles.


• MPN entrapment typically occurs at the AHM fibro-
  osseous canal or master knot of Henry (Baxter, 1993).


• Risk factors include AHM hypertrophy, a valgus run-
  ning style, functional hyperpronation (e.g., calcaneo-
  valgus, hallux rigids), and high-arched orthoses

398 SECTION 4 • MUSCULOSKELETAL PROBLEMS IN THE ATHLETE