Traumatic Myositis Ossificans of The Iliacus Muscle
H Argekar, PD Samant, CJ Thakkar, AB Goregaonkar
A case of traumatic myositis
ossificans of the iliopsoas muscle in 30 year old farmer is presented. A history
of fall from a tree one year ago with blunt trauma to the region of the left
hip in addition to the radiographic appearance of calcification were indicative
of ectopic bone formation. The lesion was explored surgically to excise the
tumour. Histological examination demonstrated the zoning effect of myositis
ossificans with patterns varying from a cellular central zone to a peripheral
one of fairly well oriented bone. The patient remained symptom-free and no radiographic
evidence of recurrence was observed one year postoperatively.
A thirty year old male farmer presented with restricted left hip movements since
one year. Patient had a history of fall from tree following which he was treated
by a local bonesetter with massage. He started walking within a week and complained
of restricted range of movements within a month. He was unable to squat to sit
cross-legged. His stiffness gradually increased over six-month period and at
the time of presentation he had an immobile hip.
Left lower limb was in an attitude of external rotation. Wasting of the left
quadriceps and calf muscles. No obvious swelling seen in iliac fossa or the
femoral triangle. Palpation revealed a well localized bony swelling in the left
femoral triangle extending below the inguinal ligament into the iliac fossa.
There was no rise in temperature over the swelling, no tenderness. The mass
was fixed to underlying bone and was about 15 cms X 6 cms X bone deep below
the femoral vessels and nerve. Left hip had a ten degree flexion rotation deformity
and a fifteen degree external rotation deformity. No further movement at the
hip. Ipsilateral knee contralateral hip and knee were normal in all respects.
X-ray pelvis with both hips (Figs. 1 and 2) showed calcification of the iliacus
muscle. This was confirmed on CT scan (Figs. 3,4). Alkaline phosphatase was
normal. All other haematological investigations were within normal range. Needle
biopsy was unsuccessful.
Surgical excision of the mass was done through a Smith Peterson’s approach.
Adequate mass of bone was resected so as to get a full range of movement intraoperatively
(Figs. 5 and 6). Histopathology of the excised tissue confirmed myositis ossificans.
Indwelling epidural catheter was kept for 1 week post op. Patient was put on
continuous passive movements under epidural analgesia immediately post op. Patient
was given indomethacin 100 mg per day for six weeks. Patient regained ninety
degree of left hip flexion and thirty degree of rotations at the end of two
months and was able to squat and sit cross-legged at the end of one year.
Heterotopic bone formation was first described in 1692 when Guy Patin described
myositis ossificans progressiva in children.1 Descriptions of HO in children
have been described following ilio-psoas release11-13, and femoral osteotomy,10
spinal cord injury,4 and spinal fusion4,12 in recent literature. Heterotopic
ossification (HO) is the formation of lamellar bone (which may mature with time)
where bone does not usually form in soft tissues. Myositis ossificans is a condition
in which HO occurs in muscles and other soft tissue.14 There are three types
of myositis ossificans circumscripta, myositis ossificans progressiva, and localized
traumatic myositis ossificans.17 Ectopic calcification is mineralization of
soft tissue structures usually due to physical or chemical trauma such as calcific
tendonitis-histologically the deposits are not bone forming.4 Aetiologies of
HO include trauma, neurogenic, and myositis ossificans progressiva. Traumatic
aetiologies include after spinal fusions, total hip arthroplasty, ORIF of acetabular
fractures, soft tissue releases about the hips and burns. Myositis ossificans
progressiva is a rare autosomal dominant disease, which begins in early infancy
which initially, involves the muscles of the back, neck, and shoulders and then
progresses to immobilize the patient in early life.4 Pathophysiology of HO is
unclear. Histologic studies of heterotopic bone reveal the percentage of osteoblasts
is typically double that of normal bone indicating that the bone being formed
is metabolically active.14 One distinguishing feature is that the new bone and
mature bone lacks periosteum.15 Heterotopic bone is often diffuse and does not
always follow anatomic planes of tissue. Bone morphogenic protein is a potential
inducer of undifferentiated mesenchymal cells, which are precursors of cartilage
and bone forming elements. It has been theorized that BMP may induce inappropriate
differentiation of pluripotential cells, mesenchymal cells or fibroblasts into
Evaluation of a patient includes an adequate physical exam. The initial clinical
finding is decreased range of motion. There may be localized tissue hyperaemia,
swelling and tenderness to palpation. Initial onset is usually 4-16 weeks but
ranges from two to fifty-two weeks.14 Differential diagnosis is infection,14,9
tumour, thrombophlebitis14,9 reflex sympathetic dystrophy, and many patients
will have multiple and complex problems.14 Traumatic type of HO is found near
focus of trauma. Radiographic findings of HO on plain films is evident at 4-6
weeks, usually trabeculation is absent. Payne and DeLuca10 define HO in soft
tissues as radiodensity 5 mm from the femoral shaft and not initially adjacent
to the femur which is periosteal callus and HO is usually a flocculent pattern.
Computed tomography can differentiate native vs. ectopic bone by revealing the
osseous architecture.14 Computed tomography may also be useful in planning surgical
approach. Magnetic resonance imaging can demonstrate soft tissue swelling but
receives only limited signal from calcified tissue.14 Ultrasound has been shown
to detect HO earlier than plain radiographs in eight consecutive patients by
Thomas and Amstutz.17
Surgical treatment should not be considered until the HO has matured. Many researchers
feel that six months after initial trauma (without neural injuries) that HO
can be resected. It should not be resected until it is considered mature bone.13
Surgery is usually delayed at least one year, but should be performed at 1.5
to 2 years in young males with anklyosis or near ankylosis of the hip, radiographic
evidence of progression of HO longer than six months, greater than moderate
amounts of HO.
Myositis of the iliacus muscle is relatively rare and presenting symptom is
ankylosis of hip. On excision of the myositis mass the patient can get a functional
range of hip movement. Before excision, the possibility of a tumour should be
kept in mind and a CT scan, biopsy and haematological investigations should
We thank the Dean, LTMGH and the Head of Department of Orthopaedics, LTMGH,
Sion Hospital for giving us permission to publish the above data.
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