1118
U N I T 1 2
Musculoskeletal Function
nerve compression. Weight bearing may cause anterior
bowings of the femur and tibia. Softening of the femo-
ral neck can cause coxa vara (i.e., reduced angle of the
femoral neck), which in combination with involvement
of the pelvis can cause a waddling gait and secondary
osteoarthritis. Mild to moderate deep, aching pain char-
acteristically begins late in the course of the disease, per-
sists throughout the day and at rest, and becomes worse
at night. In some persons, the early hypervascularity of
the pagetic bone produces warmth of the overlying skin
and subcutaneous tissue. In persons with extensive dis-
ease, blood flow to the bones and subcutaneous tissue
can increase remarkably, leading to high-output heart
failure or exacerbation of underlying cardiac disease.
3
A variety of tumor and tumorlike conditions develop
in pagetic bone, the most dreaded of which is sarcoma.
Osteogenic sarcomas occur in 5% to 10% of persons
with extensive disease.
3
The bones most often affected, in
order of frequency, are the femur, pelvis, and humerus.
4
Diagnosis and Treatment.
Diagnosis of Paget disease
is based on characteristic bone deformities and x-ray
changes. Elevated levels of serum alkaline phosphatase
and urinary hydroxyproline support the diagnosis, and
continued surveillance of these levels may be used to
monitor the effectiveness of treatment. Bone scans are
used to detect the rapid bone turnover indicative of
active disease and to monitor the response to treatment.
The scan cannot identify bone activity resulting from
malignant lesions. Bone biopsy may be done to differen-
tiate the lesion from osteomyelitis or a primary or meta-
static bone tumor.
The treatment of Paget disease is based on the degree
of pain and the extent of the disease. Pain can be
reduced with nonsteroidal or other anti-inflammatory
agents. Suppressive agents such as the bisphosphonates
and calcitonin are used to prevent further progress of
the disease. Persons with Paget disease should receive
adequate doses of calcium and vitamin D. Orthopedic
surgery may be required for the management of pseu-
dofractures, pathologic fractures, and spinal stenosis.
32
Headache,
tinnitus,
vertigo
Deafness
Thick skull
Osteoblasts
Prominent
cement lines
Mosaic pattern of
osteosclerotic bone
Pain
Kyphosis
Warm skin due to
hypervascularity
of pagetic bone
Coxa vera
Bowed
femur,
tibia,
fibula
Waddling
gait
FIGURE 44-4.
Clinical manifestations of Paget disease.
SUMMARY CONCEPTS
■■
Metabolic bone disorders have their origin in the
bone remodeling process that involves an orderly
sequence of osteoclastic bone reabsorption, the
formation of new bone by the osteoblasts, and
mineralization of the newly formed osteoid tissue.
■■
Osteopenia is a condition that is common to
all metabolic bone diseases. It is characterized
by a reduction in bone mineral density greater
than expected for age, race, or gender, and it
occurs because of a decrease in bone formation,
inadequate bone mineralization, or excessive
bone deossification.
■■
Osteoporosis represents an increased loss of total
bone mass due to an imbalance between bone
absorption and bone formation that results in a
decrease in bone density and diminished bone
strength and is associated with an increase in bone
fragility and susceptibility to fractures. Although
the disease can occur as the result of a number
of disorders, the most common causes are age-
related changes in bone metabolism and a relative
absence of estrogen in postmenopausal women.
■■
Osteomalacia and rickets represent a softening
of bone due to inadequate mineralization of the
bone matrix caused by a deficiency of calcium or
phosphate. Osteomalacia is a disorder of adults
and is caused by insufficient calcium absorption
from the intestine because of lack of dietary
vitamin D, resistance to the action of the vitamin,
or a phosphate deficiency.
■■
Rickets, which affects children, is characterized by
failure or delay in calcification of the cartilaginous
growth plate, widening and deformation of the
metaphyseal regions in long bones, and a delay
in mineralization of trabecular, endosteal, and
periosteal bone surfaces.
