Bilateral Iliopsoas Muscle Contracture and Spinous Process

Veterinary Surgery
38:946–953, 2009
Bilateral Iliopsoas Muscle Contracture and Spinous Process
Impingement in a German Shepherd Dog
GUILLAUME R. RAGETLY, DVM, DOMINIQUE J. GRIFFON, DVM, MS, PhD, Diplomate ACVS & ECVS,
ANN L. JOHNSON, DVM, MS, Diplomate ACVS, WILLIAM E. BLEVINS, DVM, MS, Diplomate ACVR, and
VICTOR E. VALLI, DVM, MS, PhD, Diplomate ACVP.
Objective—To report diagnosis and treatment of bilateral iliopsoas muscle contracture in a dog
with spinous process impingement.
Study design—Case report.
Animals—German Shepherd dog.
Methods—A dog with chronic progressive lameness, flexion contracture of the coxofemoral joints,
severe pain, and decreased femoral reflexes had severe spondylosis bridging the vertebral bodies
from L1 to L4 and enlarged dorsal spinous processes from T8 to L6 with impingement and bony
proliferation. Ultrasonographic and magnetic resonance imaging (MRI) findings were consistent
with fibrosis, mineralization, and atrophy of the iliopsoas muscles bilaterally which was treated by
staged tenectomy of the insertions of the iliopsoas muscles.
Results—Because of severe perivascular fibrosis, the femoral vessels required ligation. Bilateral
iliopsoas muscle tenectomy improved gait and provided pain relief. Histologic findings were consistent with fibrotic myopathy.
Conclusions—Slow progression of severe clinical signs observed bilaterally in this dog differs from
previous reports of iliopsoas myopathy. Findings were similar to the fibrotic myopathy of the
gracilis or semitendinosus muscles described in dogs.
Clinical Relevance—Iliopsoas muscle abnormalities should be considered in dogs with limited hip
extension and pain. MRI is useful for diagnosing muscle fibrosis. Iliopsoas tenectomy may improve
clinical function in dogs with fibrotic myopathy.
r Copyright 2009 by The American College of Veterinary Surgeons
Skeletal muscle pathology can cause debilitating lameness in dogs and is typically more severe when affected
muscles span appendicular joints. Degenerative and inflammatory changes may lead to irreversible fibrosis, resulting in decreased range of motion and function.7,8
Common abnormalities observed in dogs include infraspinatus7–15 and quadriceps muscle contracture.8,14,16,17 Fibrotic myopathy of the supraspinatus,8,14
teres minor,18 sartorius,19,20 gracilis, and semitendinosus
muscles8,14,21,22 has been reported but the cause(s) remain(s) elusive. Traumatically induced iliopsoas strain in
dogs5,23–25 can be unilateral or bilateral, causing lameness
INTRODUCTION
N AN epidemiologic survey of 110,000 dogs, o5%
of appendicular musculoskeletal disorders were attributed to muscular diseases.1 This is much lower than the
prevalence of muscular disorders in people (30% of appendicular musculoskeletal disorders)2,3; however, the
true incidence of small animal soft-tissue musculoskeletal disease may be underestimated because of failure
to report self-limiting injuries, inadequate classification
of traumatic lesions, and poor recognition of muscular
diseases.1,4–6
I
From the Department of Veterinary Clinical Medicine, University of Illinois, Urbana, IL; and the Department of Veterinary Clinical
Science, Purdue University, West Lafayette, IN.
Corresponding author: Guillaume R. Ragetly DVM, Veterinary Teaching Hospital, 1008 Hazelwood Drive, Urbana, IL 61802. Email: ragetly2@uiuc.edu.
Submitted May 2008; Accepted June 2009
r Copyright 2009 by The American College of Veterinary Surgeons
0161-3499/09
doi:10.1111/j.1532-950X.2009.00581.x
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RAGETLY ET AL
947
Fig 1. Lateral radiographic projections of the lumbosacral region. (A) Two years before admission. Mild changes consistent with
spondylarthritis are visible at L4–L5 (arrowhead). (B) Two months after the second surgery. The dorsal spinous processes are
enlarged with well-defined bony proliferation.
and pain during internal rotation and extension of the hip
that usually responds to rest and nonsteroidal anti-inflammatory drug therapy. Iliopsoas tenectomy has been
successfully used to treat traumatic iliopsoas strains unresponsive to conservative management.23,24
We are unaware of reports of progressive fibrotic myopathy of the iliopsoas muscle in dogs. Thus, our purpose
is to describe the clinical findings, diagnosis, and treatment of fibrotic myopathy of the iliopsoas muscles in a
dog with concurrent spondylosis and dorsal spinal process impingement of the thoracolumbar vertebrae.
CLINICAL REPORT
History and Clinical Findings
A 4-year-old, castrated male, German Shepherd dog
was admitted with a history of progressive bilateral pelvic limb lameness, worse on the left, and noticed on
adoption at 9 months of age. At 18 months of age, radiographs of the lumbosacral spine had evidence of mild
spondylarthritis of the 4th and 5th lumbar vertebrae
(L4–L5; Fig 1A). Left deep gluteal tenotomy was performed and resulted in temporary improvement. The dog
was treated intermittently with glucosamine and carprofen (100 mg orally twice daily) or deracoxib (50 mg orally
once daily). Rehabilitation exercises included passive
range of motion of both hips and walking. The dog deteriorated to the point he was unable to walk more than
a few meters at a time.
On admission, the dog (weight, 37 kg; body condition
score 4/9), was panting, had a heart rate of 70 beats/min
and rectal temperature of 391C, severe muscle atrophy of
both pelvic limbs, and was unable to stand without support. Gait was characterized by a few bunny hopping
steps, with the hips maintained in a flexed position, the
pelvic limbs positioned beneath the thorax, and the pelvic
paws generally dragged rather than lifted into position
(Fig 2). When walked 35% of the total peak vertical force
s
(Tekscan , Tekscan Inc., South Boston, MA)26 was
placed on each thoracic limb compared with 15% on
each pelvic limb. Palpation of the lumbar spine, pelvis,
Fig 2. Gait examination before (left) and after iliopsoas tenectomies (right). On admission, both pelvic limbs remained positioned
under the thorax preventing ambulation (left). Extension of the hips and gait were improved after surgery (right).
948
ILIOPSOAS MUSCLE CONTRACTURE AND SPINOUS PROCESS IMPINGEMENT
and hips elicited a marked pain response. Maximum angles of flexion and extension were 40–851 for the left hip
and 40–1001 for the right hip.27 Conscious proprioceptive
response appeared slightly decreased and both patellar
reflexes were decreased to absent. Results of complete
blood count, serum biochemical profile, and urinalysis
were unremarkable; however, creatine kinase (CK) activity was not evaluated.
Radiographic Examination
After sedation (medetomidine [6.6 mg/kg, intravenously (IV)], atropine [0.022 mg/kg, IV], hydromorphone
[0.1 mg/kg, IV]), range of hip motion did not improve and
the dog reacted to palpation of the iliopsoas muscles,
which were thickened and hard. There was no evidence of
coxofemoral degenerative joint disease or previous pelvic
fracture on radiographs (Fig 3); however, a cranioventral
tilt to the pelvis was noted. The angle between the long
axis of the pelvis (defined from the iliac crest to the most
distal point of ischium) relative to the axis of the cranial
lumbar spine was 541. The same angle measured on
lateral radiographs of German Shepherd dogs’ pelves
(n ¼ 15) with good to excellent hip conformation and
with the hip joint extended to 901 was 30 41. Mineralization was observed within the soft tissue medial to the
left proximal femur (Fig 3B).
Severe degenerative changes of the articular facets extended from the 10th thoracic vertebra (T10) to the
lumbosacral space, and severe ventral spondylosis, bridging the vertebral bodies of L1–L2 and L3–L4, was visible
(Fig 3C and D). The spinous processes of T8 to L6 were
enlarged with well-defined bony proliferation. Tentative
diagnoses of bilateral iliopsoas muscle contracture and
concurrent kissing-spine syndrome with severe spondylosis was made.28 Recommendations for intensive rehabilitation exercises and administration of carprofen (2.5 mg/
kg orally twice daily), gabapentin (3 mg/kg orally once
daily), and tramadol (2 mg/kg orally twice daily) were
made and the owners were advised to return the dog for
additional diagnostic imaging.
Ultrasonography
One week later, gait was unchanged when the dog returned for ultrasonographic examination of the iliopsoas
muscles and magnetic resonance imaging (MRI) of the
pelvic region. On ultrasonography, the iliopsoas muscles
were heterogeneous throughout their length (Fig 4) with
linear areas identified within both muscle bellies. Diffuse
hyperechogenic areas consistent with mineralization
were observed bilaterally within the psoas and iliopsoas
muscles.
Fig 3. Lateral and ventrodorsal radiographic projections of the pelvis (A and B) and thoracolumbar spine (C and D). The dorsal
spinous processes from T8 to L6 are enlarged with well-defined areas of bony proliferation. Severe ventral spondylosis affects the
caudal thoracic and cranial lumbar vertebrae, bridging the vertebral bodies from L1 to L4. Mineralization is present within the soft
tissue medial to the left proximal femur (arrowhead).
RAGETLY ET AL
949
Fig 4. Transverse (A) and longitudinal (B) sonograms at L7 and longitudinal sonogram obtained at the lesser trochanter (C) of the
left iliopsoas muscle. Note the heterogenic appearance of the muscle belly (areas between arrowheads) and the foci of mineralization
(arrows).
MRI
Surgical Procedure
MR images of the caudal lumbar spine and pelvis,
including dorsal, sagittal and transverse T1-weighted
and T2-weighted images were obtained (Fig 5). Because
of limited hip extension, it was not possible to position
the dog completely inside the coil, so the muscle insertions on the lesser trochanter were not fully visible.
There was no evidence of intervertebral disc herniation
or other compressive lesions within the vertebral canal;
however, MRI findings were consistent with atrophy,
fibrosis, and mineralization of both iliopsoas muscles.
Based on these collective findings, bilateral iliopsoas
fibrosis and contracture was suspected and staged tenectomy of the insertions of the affected muscles, starting with the left side, was recommended to improve hip
extension.
With the dog anesthetized and positioned in dorsal
recumbency, the insertion of the left iliopsoas muscle on
the lesser trochanter was exposed by a ventral approach
because of the inability to rotate or extend the limb.23,29
The skin was incised over the cranial border of the pectineus muscle, starting at the ventral rim of the acetabulum and extending distally along the pectineus
muscle for 10 cm. The fascia was incised similarly, exposing the pectineus muscle, which was mobilized by
blunt dissection while protecting the femoral artery and
vein, and saphenous nerve (Fig 6). The pectineus muscle
was transected at its origin on the iliopubic eminence of
the pelvis and reflected distally to reveal the iliopsoas
muscle and the medial circumflex femoral artery and
vein. The femoral artery and vein, the medial circumflex
femoral artery and vein, and their branches were adhered
to the iliopsoas muscle (Fig 6). The insertion of the iliopsoas muscle on the lesser trochanter was isolated, and
sharply incised and elevated. When 90% of the insertion tendon of the iliopsoas muscle had been cut, the limb
was fully extended to release any remnant of the tendon
and surrounding adhesions; however, this maneuver resulted in rupture of the femoral artery and vein and severe hemorrhage. The vessels were ligated and the
incision was closed. Because of blood loss, a packed red
blood cell transfusion was administered and the dog was
transferred to the intensive care unit.
After surgery, the dog had immediate improvement in
hip extension and ability to walk using the left pelvic
limb. Intensive rehabilitation was initiated with cold
packing, massage of the pelvic limbs, passive range of
motion and balancing exercises, and controlled leash
walks. Carprofen (2.5 mg/kg orally twice daily for 2
weeks), gabapentin (3.0 mg/kg orally once daily for 4
weeks), and hydromorphone (0.05–0.1 mg/kg subcutaneously 4–6 times/day as needed) were administered.
Tenectomy of the right iliopsoas muscle was performed similarly 6 days later; however, the skin incision
was extended cranially to obtain muscle biopsies. The
Fig 5. T2-weighted magnetic resonance image at the caudal
lumbar spine. Atrophy and mineralization of the iliopsoas
muscles are noted (arrows).
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ILIOPSOAS MUSCLE CONTRACTURE AND SPINOUS PROCESS IMPINGEMENT
medial circumflex femoral artery & vein
obturator branch m. pectineus obturator nerve
m. psoas minor
m. psoas major
femoral artery & vein
femoral nerve
saphenous nerve
m. Iliacus
superficial circumflex
femoral artery & vein
lateral circumflex
femoral artery & vein
Fig 6. Anatomy of the right coxofemoral region viewed from a ventral orientation. Note the proximity of neurovascular structures
that may be affected by fibrosis encircling the iliopsoas muscles.
cranial approach to the iliopsoas muscle belly consisted
of a 5-cm-long incision into the fascia cranial and parallel
to the inguinal ligament. Blunt dissection through the
fibers of the internal oblique muscle allowed identification of the iliopsoas muscle. Biopsies were taken from the
iliopsoas muscle belly and from its insertion. The insertion of the iliopsoas on the lesser trochanter was transected. Despite careful dissection, the hip could not be
extended without creating tension on the adjacent vessels,
which appeared shorter than normal. The femoral, medial circumflex femoral, lateral circumflex femoral arteries and veins, and several of their branches were ligated
and divided after which the hip could be fully extended
and flexed. The incision was closed and the postoperative
care outlined earlier continued.
Histopathology
Muscle tissue specimens were fixed in formalin, sectioned (longitudinal, transverse), and stained. Sections
stained with hematoxylin and eosin had areas of dense
connective tissue adjacent normal muscle fibers. There
was no evidence of inflammatory response or muscle degeneration. Associated vessels and nerves were sur-
rounded by marked fibrosis. Sections stained with
phosphotungstic acid–hematoxylin to assess muscle
cross-striations and presence of collagenous fibers had
normal appearing muscle except for infiltration with collagenous fibers (Fig 7), which were linearly arranged
parallel to the muscle fibers.
Outcome
Edema developed in the right pelvic limb after surgery
and was present when the dog was discharged at 3 days.
The rehabilitation protocol and the oral medications were
continued at home. Ten days later, the dog was returned
for evaluation of progressive lameness and right pelvic
limb swelling. An abscess in the right inguinal area was
drained and the dog was hospitalized for 2 weeks for
treatment and intensive rehabilitation.
At 8 weeks, the dog was ambulating well, and could
climb stairs without difficulty (Fig 2). Hip range of motion was improved, with maximum angles of flexion and
extension equal to 40–951 on the left and 40–1101 on the
right hip. Patellar reflexes were still decreased but no
conscious proprioceptive deficits were observed. The
cranioventral tilt of the pelvis was estimated at 421 on
RAGETLY ET AL
951
Fig 7. (A) Histologic appearance of the contracted iliopsoas muscles: collagenous tissue (arrow) invading skeletal muscle (arrowhead; H&E 50). (B) Detail of (A), stained with phosphotungstic-acid–hematoxylin (PTAH): collagen is stained in red and
skeletal muscle fibers in blue. Linearly arranged collagenous tissue is replacing the residual skeletal muscle of normal appearance
(PTAH 130).
recheck radiographs (Fig 1B). Peak vertical forces of each
pelvic limb had increased to 20% of the total peak vertical
force whereas 30% was placed on each thoracic limb.
At 9 months, the dog was still ambulating well with
no difficulties managing stairs or running. Hip range of
motion and neurologic examination findings remained
unchanged.
DISCUSSION
We report an unusual case of bilateral iliopsoas muscle
contracture that caused severe pain and loss of function
that was refractory to conservative therapy. Iliopsoas
muscle strain in small animals has generally been reported
in association with a recent history of trauma5,6,23–25 and
typically resolves with conservative management, although
some cases require surgical treatment.6,23,24 To our
knowledge fibrotic myopathy and contracture of the iliopsoas muscles has not been reported in a dog with
concurrent spondylosis and dorsal spinal process impingement of the thoracolumbar vertebrae.
A tentative diagnosis of iliopsoas pathology was made
based on gait observation and muscle palpation. The
tendon of insertion of the iliopsoas muscle can be palpated just cranial to the lesser trochanter of the femur on
the proximomedial aspect of the femur.4 The body of the
iliopsoas muscle can be palpated along the ventromedial
aspect of the body of the ilium. In smaller dogs, the origin
of the iliacus muscle may also be palpated per rectum.4
Pain was so severe in this dog that palpation was only
possible when the dog was sedated. Measuring CK activity may have contributed to a diagnosis of muscle pathology30 but, would not have allowed localization of the
specific muscular lesion.
Diagnosis of iliopsoas involvement was supported by
ultrasonography and MRI. Ultrasonographic examination helped localize the disease to both iliopsoas muscles
and define its fibrotic nature; however, decreased patellar
reflexes along with the radiographic abnormalities of the
spine and pelvis, warranted MRI to rule out compressive
lesions of the lumbosacral spine.
Slow progression and symmetrical severe involvement of both iliopsoas muscles in this dog do not support trauma as a primary cause; however, nontraumatic
muscular abnormalities are rare in dogs, and the lack of
information regarding the onset of signs precludes exclusion of a traumatic origin. Orthopedic disease can
promote secondary chronic muscle strain injury resulting in contracture.6 The smooth interface between the
skeletal muscle and the tendinous connective tissue,
along with the linear arrangement of the collagen fibers,
are more consistent with a congenital disease than previous muscular injury.31 Histopathologic findings did
not support presence of a neuropathic or classical myopathic process because there was no sign of inflammatory infiltration, degeneration, regeneration and
necrosis of the iliopsoas muscle fibers.32 Instead, the
presence of normal muscle fibers surrounded by dense
connective tissue and the progression of clinical signs
are similar to those reported for fibrotic myopathy of
the gracilis or semitendinosus muscles in dogs.14,21,22
Fibrotic myopathy has been reported in dogs, especially
in male German Shepherds, with bilateral involvement
in 61% of cases.22 Vaughan noted that affected dogs
were extremely active and proposed that repetitive
stress could give rise to muscle strain.14 No evidence of
immune-mediated disease has been identified in affected
dogs.21 The potential for a genetic component has not
been fully investigated, but study of pedigrees of 6 dogs
with fibrotic myopathy yielded no evidence of a common ancestor.22 The exact cause of this condition remains unclear.
Tenectomy is the treatment of choice for muscle contractures provided it can be performed without major
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ILIOPSOAS MUSCLE CONTRACTURE AND SPINOUS PROCESS IMPINGEMENT
impact on the gait.7,8 We recommended surgical treatment because of the severity of clinical signs and lack of
response to conservative management. The ventral surgical approach provided good observation of the muscle
and the vasculature (medially) and could easily be extended to expose the muscle belly. A lateral approach for
tenectomy of the iliopsoas muscle requires more dissection.24 A more cranial approach with myectomy instead
of tenectomy of the iliopsoas muscle would release the
psoas major muscle but not the iliacus muscle, and would
not have alleviated the flexure of the hip. A pectineal
tenotomy was performed to approach the iliopsoas tendon. The postoperative improvement observed is unlikely
to result from pectineal tenotomies because abduction of
the limbs was not restricted before surgery and the pectineus muscles appeared normal.33
Surgical management of this dog was complicated by
the marked fibrosis encircling vessels and nerves closely
associated with the muscle. The chronicity and potential
congenital nature of the muscle pathology may also have
contributed to the apparent shortening of the local vessels. Perivascular adhesions and apparent shortening of
the vessels resulted in severe hemorrhage during the initial surgery, when the limb was extended before complete
ligation of the vessels and dissection of all adhesions.
Particular care was taken to avoid vessel tearing while
preserving the main blood supply during surgery on the
contralateral limb. The femoral artery and vein can be
ligated in dogs without clinically significant side effects
because of good collateral circulation.34
The concurrent presence of bilateral iliopsoas contracture and spinous process impingement to our knowledge has not been reported in dogs, and these 2
conditions may be unrelated. Kissing-spine syndrome,
also known as spinous process impingement syndrome or
Baastrup syndrome, is characterized by a close approximation of adjacent spinous processes and dorsal laminae
in the lumbar spine and reactive bone sclerosis28 and is an
acquired disease in people.35 Although some authors
considered this disease congenital, findings at necropsy
were more consistent with developmental disease at later
stages in life.36 Incipient degenerative changes gradually
intensified with age and were established histologically
and histochemically in the interspinous ligaments of the
lumbar spine.36 This condition is believed to develop
when the tips of the vertebral spinous processes are
pressed against one another in patients with excessive
lordosis. The resulting trauma predisposes to hemorrhage
and gradual destruction of surrounding soft tissues.36
The radiographic appearance of this dog’s thoracolumbar spine was characteristic of kissing-spine syndrome with sclerosis and flattening in the cranial and
caudal portions of adjacent lumbar spinous processes,
which were in contact to each other.37,38 Spondylarthritis
of the articular facets is almost always associated with
kissing-spine syndrome. Spondylosis is a common condition in dogs, with a predisposition in German Shepherds.39 Spondylosis is believed to develop secondary to
stresses on the ligaments and periosteum associated with
activity, disk degeneration, trauma, or muscle weakness.
We cannot conclude whether the severe spondylosis
observed was primary, secondary, or unrelated to the iliopsoas pathology and the spinous processes abnormalities. Spondylosis has been noted in association with
kissing-spine syndrome in people.38 This dogs history
suggests that all spinal abnormalities were acquired. Indeed, no radiographic evidence of spondylosis or dorsal
spinous process abnormality was noted when the dog was
evaluated for gait abnormality 2 years before admission.
The spinal lesions may have developed as a result of the
abnormal posture of the dog or may be unrelated to the
muscle pathology. Their clinical significance also remains
unclear because function improved after tenectomy of the
iliopsoas muscles.
Iliopsoas muscles abnormalities should be considered
in dogs with pain and decreased hip extension. MRI is
especially relevant to localize the disease and confirm the
absence of a compressive lesion in the spinal canal of
dogs with bilateral disease and neurologic deficits. In
dogs with fibrosis and contracture, iliopsoas tenectomies
improve clinical function. Improvement of clinical signs
may be expected in spite of spondylosis and spinous process impingement of the spine in dogs with concurrent
iliopsoas contracture.
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