Heterotopic ossification is an odd phenomenon. It is as
if the natural healing process around a traumatized joint gets a glitch in the
program. The hip and elbow seem most vulnerable, and some movement is lost. The
remedy for the second hip replacement when ossification of the
first is staggered, bilateral hip replacements can inform the preparations for
the second. One thousand rads of radiotherapy and several weeks of indomethacin
or diclofenac can help. The bone deposition around the hip in some traumatic
paraplegias brings another factor into the curious mechanism of unwelcome bone
How can a synthetic version of thyroid hormone have a
H. Namazi and K. Mozaffarian (J Trauma.
2008; 65:849-851) used a rabbit model to study the effects of levothyroxin
on ossification in thigh muscles produced by the injection of autologous bone
marrow containing a high concentration of stem cells. Their group of 12 New
Zealand white rabbits acting as a control produced marked heterotopic bone
formation by 5 weeks after the 2-mL intramuscular injection. A second group of
12, using the same bone-producing model, were given levothyroxin orally 1 week
before the bone marrow injection at the rate of 20 µg/kg daily for 4
weeks. In a third group, the levothyroxin was started on the day of the bone
induction. In the pre-loaded group, 10 of 12 showed no ossification at 5 weeks.
Eight of 12 given levothyroxin on the day of induced ossification showed no
ossification. A small amount formed in the other 4. All results were
Interleukin I (IL-I), interleukin 6 (IL-6), and tumor
necrosis factor-α (TNF-α) stimulate bone resorption and inhibit
bone formation by interfering with osteoblast differentiation and
mineralization. Thyroid hormone also stimulates bone resorption and potentiates
the effects of IL-I, IL-6, and TNF-α on bone resorption and formation.
The synthetic form of thyroid hormone seems to be
effective in preventing heterotopic ossification, and apparently it did the
rabbits no harm during the 4-week period of prophylactic treatment.
| ||Blue Notes Editor: |
Charles Sorbie, MB, ChB, FRCS(E), FRCS(C)
Dr. Charles Sorbie is Professor of Surgery at Queens University and a member of the Attending Staff at the General and Hotel Dieu Hospitals in Kingston, Ontario.
A former chairman of the Department of Surgery at Queens University, Dr. Sorbie has been President of the Canadian Orthopaedic Research Society, the Canadian Orthopaedic Association, and the Societé Internationale de Chirurgie Orthopédique et de Traumatologie (SICOT).