- ON arises from the L2–L4 spinal segments, and exits
the pelvis via a fibro-osseous tunnel (obturator canal),
in which it divides into terminal anterior and posterior
branches. These branches provide the predominant
motor innervation to the thigh adductor group and
sensory innervation to the distal half to two thirds of
the medial thigh. ON entrapments most commonly
occur at the exit of the obturator canal (McCroy and
Bell, 1999; Bradshaw et al, 1997). The athlete will
typically complain of activity-related groin pain of a
deep, burning, achy quality. - EDX studies may reveal fibrillation potentials in the
adductor muscles in some cases, but is not uniformly
helpful (Bradshaw et al, 1997; Williams and Trzil,
1991). Local anesthetic and corticosteroid injections
may assist in making the diagnosis. Surgical treatment
may become necessary.
LATERAL FEMORAL CUTANEOUS NERVE:
MERALGIA PARESTHETICA
- Lateral femoral cutaneous nerve(LFCN) injury has
been reported in runners. The LFCN arises from the L2-
L3 spinal segments, and typically exits the pelvis via a
small tunnel formed by a split in the lateral ilioinguinal
ligament at its insertion into the anterior superior iliac
spine(ASIS) (McCroy and Bell, 1999). Just distal to the
tunnel, the LFCN will split into two terminal branches
supplying cutaneous innervation to the anterolateral
thigh. There is no motor innervation. LFCN injury usu-
ally occurs at the level of the ilioninguinal ligament. - Specific etiologies include rapid weight change, com-
pression from tight clothing or belts, and systematic
disease affecting nerves such as thyroid disease and
diabetes. - Burning, aching discomfort over the anterolateral thigh.
- Sensory deficit occurs in the cutaneous distribution.
Differential diagnosis includes focal musculoskeletal
pathologies, lesions affecting the lumbosacral plexus
L2-L3 nerve roots, and systemic disease such as
hypothyroidism and diabetes. Local anesthetic and
corticosteroid injections may not only be diagnostic,
but therapeutic. Treatment involves removal of incit-
ing factors, treatment of neuropathic pain, observa-
tion, and injections. Up to 90% of cases resolve with
nonoperative management (Williams and Trzil, 1991).
Surgical release is sometimes necessary.
MEDIAL HALLUCAL NERVE ENTRAPMENT
- The medial hallucal nerve is a distal terminal branch
of the MPN providing sensation to the medial aspect
of the great toe. This nerve may rarely be entrapped as
it exits the distal end of the AHM, producing medial
first MTJ pain.- Etiologies include pressure from hallux valgus,
prominent tibial sesamoid disorders, MTJ disorders,
and polyneuropathy. - Diagnosis is clinical based on symptoms, percussion
tenderness or a percussion sign over the nerve.
•Treatment includes removal of inciting factors,
and treatment of neuropathic pain as previously
described.
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1999.402 SECTION 4 • MUSCULOSKELETAL PROBLEMS IN THE ATHLETE