Orthopedics

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Blue Notes 

Keeping Bugs Bunny on the Move

Charles Sorbie, MB, ChB, FRCS(E), FRCS(C)

Abstract

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 formation.

How can a synthetic version of thyroid hormone have a preventative effect?

H. Namazi and K. Mozaffarian (J Trauma. 2008; 65[4]: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 statistically significant.

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.

Dr. Charles Sorbie is Professor of Surgery at Queen’s 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 Queen’s 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).…

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 formation.

How can a synthetic version of thyroid hormone have a preventative effect?

H. Namazi and K. Mozaffarian (J Trauma. 2008; 65[4]: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 statistically significant.

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.

Dr. Charles Sorbie Blue Notes Editor:
Charles Sorbie, MB, ChB, FRCS(E), FRCS(C)

Dr. Charles Sorbie is Professor of Surgery at Queen’s 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 Queen’s 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).

10.3928/01477447-20081201-25

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