Ganglion cyst arising from the transverse acetabular ligament (TAL):
a rare cause of entrapment of the anterior branch of the obturator nerve.
Case report and review of the literature
Satyanarayana T. V. Sankara
Received: 19 April 2018 /Revised: 13 May 2018 /Accepted: 25 May 2018
The transverse acetabular ligament is an unusual location for ganglion cysts. Only a few cases have been reported in the literature.
They can be asymptomatic and represent an incidental finding or can cause an atypical pattern of hip joint/groin pain. We report a
case of ganglion cyst arising from the TAL causing entrapment of the anterior branch of the obturator nerve with associated acute
denervation of the abductor longus (AL), adductor brevis (AB), and gracilis muscles.
Keywords Obturator nerve entrapment
Transverse acetabular ligament
Ganglion cysts (GC) are fluid-filled synovial lined lesions
usually described in close association to the joint capsules,
tendon sheaths, and ligaments. GC around the hip represent
a relatively common finding [1, 2]. Those arising from the
joint capsule have usually been reported as extending from
the anterior aspect and causing compression on the femoral
triangle. Both vascular compression syndromes on the femo-
ral vein  and entrapment syndromes on the common femo-
ral nerve  have been reported in the literature.
Two cases of symptomatic cysts arising from the transverse
acetabular ligament (TAL) causing atypical groin pain not
responding to conventional therapy have been described .
One case report of obturator nerve compression secondary to a
large GC arising from the anterior joint capsule and with pos-
terior extension has been reported in the literature [6, 7].
We report the first case of a GC arising from the TAL
causing isolated entrapment of the anterior branch of the ob-
turator nerve and consequent acute muscular denervation.
The obturator nerve arises from the L2, L3, and L4 rami of
the lumbar plexus. It follows the iliopectineal line, then runs
within the obturator canal and exits the pelvis through the
obturator foramen . Many different causes of obturator neu-
ropathy have been described in the literature. These include
iatrogenic (in particular related to hip replacement), traumatic,
hematomas involving the psoas muscle, inguinal hernias, ar-
terial aneurysms, neoplastic pathologies .
A 35-year-old man, farmer by occupation, presented with
chief complaints of dull aching pain in the right buttock and
groin for 5 months, which was aggravated by weight bearing,
walking, and flexing the right hip. The symptoms had a right
L4 distribution. There was no history of trauma, fever, or
weight loss. He was neither diabetic nor hypertensive. On
clinical examination, a mild to moderate degree of adduction
weakness was demonstrated. X-ray of the lumbar spine and
pelvis were negative. No significant abnormalities were de-
tected on the MRI of the whole spine. MRI of the pelvis
demonstrated a 3.5 × 1.8 × 1.8-cm multiloculated ganglion
cyst arising from the TAL, extending anteromedially and
causing marked compression on the obturator nerve. The
* Alessandro Vidoni
MSK Radiology Department, Cardiff & Vale University Health
Board, Cardiff, UK
Orange Imaging, Vijayawada, India
Trust Hospital, Vijayawada, India
Msk Radiology Department, Royal Orthopaedic Hospital NHS
Foundation Trust, Birmingham, UK