|
Dead bone in a young patient
When to investigate atraumatic
groin pain for osteonecrosis of the hip
by David Lee, MD and Edward J. Harvey,
MD
|
|
CASE
PRESENTATION
Vanessa is a 31-year-old college student
with a medical history of ulcerative colitis and past steroid
use. She comes to the office complaining of hip pain that
has been worsening progressively for the last 3 months. She
denies any recent trauma to the hips and describes the pain
as a deep groin pain, exacerbated by activity.
Physical exam
- healthy appearing
- vitals are stable and within normal
limits
- right hip neurovascular examination
is normal; no erythema, edema or skin changes
- right hip has near full range of
motion, but some limitation and pain with internal rotation
Investigations
- blood work all within normal limits
- x-ray reveals mild sclerosis of the
femoral head, normal articular surface with no evidence
of collapse
- MRI shows high signal intensity
of edema on right femoral head, no evidence of collapse
Diagnosis
and treatment
Vanessa was diagnosed with stage 3 osteonecrosis of the right
hip secondary to steroid use for her ulcerative colitis. She
was referred to an orthopedic surgeon and treated with a free
vascularized fibular graft. She continues to do well 2 years
after the operation, with only occasional hip pain.
|
MAKING THE CASE
Osteonecrosis of the femoral head is a progressive disease
that affects patients between their 30s and 50s. The average age
of presentation is 33, and the estimated incidence is 20,000 cases/year
in the U.S. In fact, the condition accounts for as many as 5-18%
of total hip replacements.
Osteonecrosis, formally known as avascular necrosis, is now the
preferred terminology to describe an "avascular" process
that leads to necrotic or "dead" bone. The process actually
isn't avascular except for the very early stage - it becomes hyperemic
as bone turnover progresses. While a list of potential risk factors
and conditions has been identified (Table 1),
to date, neither the etiology nor the natural history of the disease
has been definitively determined.
Symptoms
Patients are often asymptomatic during the early course of the disease.
The first sign of trouble is usually groin pain on ambulation or
a deep pain in the groin. You may also find limited range of motion
and pain with internal rotation of the hip. When young patients
present with atraumatic groin pain and a history of one or more
of the mentioned risk factors, you should investigate the person
without delay for the onset of osteonecrosis of the hip. Progression
can occur from a viable round head to advanced collapse within 4
months -- so urgent referral is needed.
Initial workup
Start with plain x-rays including anteroposterior
and frog-leg lateral views. Radiograph changes in the femoral head
are associated with the various stages of the disease (Table
2) and they include cysts (Figure 1), sclerosis
or a crescent sign (best visualized on a frog-leg lateral view [Figure
2]). A crescent sign represents a subcondral fracture line and
will progress to cystic changes and collapse. For earlier stages
of the disease, MRI has become the imaging modality of choice due
to its high sensitivity and specificity of 99% (Figure
3). Pertinent changes on the MRI include a serpiginious black
line on T1 that represents a bone reformation layer at the necrotic
margin.
|
