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necrosis, fractures of the femoral neck, synovial chon-
dromatosis, inflammatory joint disease and reflex sym-
pathetic dystrophy (RSD). Most of these disorders can
be distinguished from TMO by history, imaging and
lab studies. TMO is also often confused with RSD in
that localized bone edema may occur in each disorder.
As discussed above, sufficient differences exist between
TMO and RSD to permit their differentiation.
The diagnosis of transient osteoporosis may be diffi-
cult in the individual with OI because of the presence
of pre-existing bone deformity, particularly in individ-
uals with the more severe types who may have pelvic
deformity or previous fractures surrounding different
joints. In OI patients with bone edema, diagnostic clini-
cal laboratory studies are usually normal whereas there
may be serologic abnormalities in patients with inflam-
matory or infectious disorders of the proximal femur
or other involved joints. In this situation, contrast MRI
studies may be required to establish a proper diagnosis.
in OI because of multiple risk factors that may be
involved. These may involve pre-existing joint defor-
mity or deformity of the femur head, the basic lack of
mineralization and the susceptibility to minor degrees
of injury that may trigger a more generalized response
in the femur head. Experience suggests that when
pain and disability bring the patient to the physician
assumptions are that a fracture may have occurred
and conservative treatment may be recommended.
Considering the treatment recommendations discussed
below, a recommendation for conservative treatment
may impose an additional burden on the OI patient
because of the long time involved before symptoms
resolve. More aggressive treatment may be considered
once the diagnosis is confirmed.
Pregnancy
Transient osteoporosis characteristically occurs in
women during, or shortly following, pregnancy. As
noted previously, the first reports of transient osteopo-
rosis of the hip occurred during pregnancy.
1
Avascular Necrosis (AVN)
Transient osteoporosis may be misdiagnosed as
AVN.
24
In a series of 12 patients referred for surgical
treatment of suspected AVN Balakrishnan et al. found
that ten patients had radiologic and clinical features of
transient osteoporosis of the hip rather than AVN.
23
AVN is a more frequent cause of acute hip pain than is
transient osteoporosis and does not have the migratory
component. However, the individual with OI is at risk
for developing AVN because of susceptibility to injury.
With TMO, symptoms tend to come on more suddenly.
Patients with TMO typically do not have pain at night,
or with rest. TMO is self-limiting usually with complete
recovery. Symptoms are aggravated with weight bear-
ing and resolve with rest. Patients usually do not have
pain with joint range of motion except at the extremes of
joint motion. AVN pain comes on more gradually. Pain
continues at night and with rest. There is severe limita-
tion in range of motion. TMO responds to resting the
involved joint. Radiographs show diffuse osteopenia of
the femoral neck and head with TMO, whereas there is
a localized area of sclerosis present in AVN, but no femo-
ral head collapse or arthritis progression as seen in AVN.
TREATMENT OF TRANSIENT
OSTEOPOROSIS
The time course for resolution of TMO varies
depending on the extent of bone involvement, number
of joints involved and the sequential involvement of
multiple joints. Untreated, both pain and disability may
last for 6-12 months. The goals of treatment with TMO
include prompt relief of pain, return to previous func-
tional level and normal imaging studies.
Conservative Non-Pharmacological Therapy
Patients are advised to avoid weight bearing to
reduce pain and risk of fracture. Bed rest and immo-
bilization of an affected joint will relieve pain but lim-
its function. Sympathetic blockade was reported in
three cases by Boos et al., perhaps in the context of
reflex sympathetic dystrophy as an underlying mecha-
nism.
27
Hydrotherapy may be helpful in maintaining
muscle tone. However, ancillary methods have not all
been successful in reducing and shortening the time to
recovery.
3
As an illustrative example of conservative treatment
in OI, Noorda et al. report on a case of a 48-year-old
woman with OI and a history of hip pain. The diagno-
sis of TMO was made via MRI.
19
Bone biopsy revealed
small break lines in a bone trabecula. The patient expe-
rienced a decrease of pain and improvement in radio-
graphs and MRI after being non-weight bearing for 6
months. However, she then complained of pain in her
ankle and resumed non-weight bearing. One year after
DISORDERS RELATED TO TRANSIENT
OSTEOPOROSIS
OI
TMO is not a frequent occurrence in OI. However,
the true incidence is difficult to estimate inasmuch as
many cases may go unrecognized or are not reported.
It is particularly difficult to assign an etiology to TMO
