Marvin is a healthy, active 36-year-old who belongs to a martial ...

[jparksx]

Marvin is a healthy, active 36-year-old who belongs to a martial arts club. Once a week he takes lessons in Judo, and on the weekends, he participates in local competitions.
 
  At his last competition, Marvin was paired with a skilled participant from another club. His rival threw him to the mats, and as Marvin struggled, came down hard to pin him down. Marvin heard a snap, followed by instant pain in his left forearm. Radiographs at the local hospital confirmed he suffered a transverse fracture of the distal aspect of his left ulna.
 
  What are the typical signs and symptoms of a fracture? Why shortly after the injury does the pain temporarily subside?
 
  How does a hematoma form, and what function does it serve in the process of healing a fracture?
 
  Marvin was told he would be seeing a physiotherapist as his healing progressed. What are the muscular and joint changes that occur during immobilization and the ways Marvin and his physiotherapist can work to address these changes?

Question 2

Mandy is a 16-year-old competitive figure skater who practices several hours a day with her coach at the skating arena. Because of her extremely active lifestyle and restricted diet to maintain her athletic physique, she experiences ongoing amenorrhea.
 
  One day during practice, she landed a jump and fell to the ice in pain. Her left foot swelled up almost immediately, making it difficult for her coach to remove the skate. At the hospital, radiographs revealed a fracture of the fifth metatarsal bone and general radiolucency of all the bones in her foot. A follow-up DXA revealed a bone mass of 2.7 standard deviations below mean.
 
  What is the etiology of Mandy's premature osteoporosis, and how her condition is thought to contribute to a decrease in bone density?
 
  Knowing what you do about bone mineralization, why does a deficiency of estrogen in women lead to osteoporotic change?
 
  Osteoporosis and osteomalacia both involve abnormal bone mineralization. What are the general macroscopic differences of these two conditions?

[gstein359]

Answer to Question 1

The typical signs and symptoms of a fracture include pain, swelling, and loss of function. If long bones are involved, the deformity results from the angulation, rotation, or shortening of the involved bone. Typically, abnormal mobility is also evident at the site of injury.
A decrease in the feeling of pain shortly after the injury is termed local shock. It involves a temporary interruption of neural function at the fracture site so that both sensory and motor activity is lost.

A hematoma forms from the blood that escapes from the torn vessels of the injured periosteum and surrounding soft tissues. It encircles and invades the fracture site to deliver clotting factors so that a fibrin network can be laid down. This network forms a foundation for fibroblast activity and the migration of new capillary buds. The hematoma also contains activated inflammatory cells and platelets. The growth factors released from these cells stimulate the proliferation of osteoclasts and osteoblasts for the deposition and remodeling of new bone.

The immobilization necessary for fracture healing also promotes joint stiffness through tendon shortening and disuse atrophy of the muscles. The cast is therefore removed as soon as possible to minimize the negative effects of immobilization. Exercises introduced early in the healing process help to maintain tissue integrity and are done bilaterally. A thorough rehabilitation program would include a full range of motion exercises for his unaffected arm and isometric (or muscle-tensing) exercises for his affected arm.

Answer to Question 2

Mandy is likely demonstrating the effects of the female athletic triad. Disordered eating and intensive exercise in some athletes reduce fat stores and the fat-to-muscle ratio. The result is a decrease in estrogen production by the ovaries with amenorrhea. The reduction in circulating estrogen, coupled with an insufficient intake of vitamin D and calcium, accelerates bone resorption and the formation of osteoporosis.

Estrogen deficiency contributes to the development of osteoporosis in a number of ways. Lowered levels of estrogen encourage an increase in cytokine production that stimulates the proliferation of osteoclast precursors. Furthermore, when estrogen is low, the differentiation of osteoclasts becomes unregulated; osteoclast precursors are more responsive to the RANK ligand, and osteoclastic proliferation occurs. The result is a condition of bone resorption that occurs at a rate that cannot be matched by a compensatory increase in osteoblastic activity.

Osteoporosis is a disease characterized by a decline in bone mass. Osteoporotic bone is porous and brittle with a decreased amount of trabeculae and cortical volume. Osteomalacia, in contrast, is a disease characterized by the undermineralization of bone. Bone tissue exhibiting osteomalacia is soft and weak due to the lack of mineralization. Total bone mass, however, is unchanged.