MUSCULOSKELETAL TISSUES RESPONSE TO DISEASES AND INJURY

- BONE  
- EPIPHYSEAL PLATE
- SYNOVIAL JOINTS
- SKELETAL MUSCLE

BONE

There are just 4 basic ways in which bone can react to abnormal conditions:

1.       Local death

·         When an area of bone is completely deprived of its blood suply, its reaction is local death (avascular necrosis of bone).

2.       Bone deposition greater than bone resorption

·         Generalized Reactions

1. Osteopetrosis (Marble bones)

Bone deposition is normal but bone resorption is defective.

2. Acromegaly

Bone deposition is increase by excessive intramembranous ossification from the periosteum.

·         Localized Reactions:

1. Work Hypertrophy

The bone react to the extra stresses and strain of increased function by increased bone deposition. Varus deformity of the foot à the fifth metatarsal hypertrophies.

2. Degenerative Osteoarthritis

Subchondral sclerosis

3. Fractures

The periosteum and endosteum react to bony injury            with       localized increased in bone deposition to form callus.

4. Infection

The periosteum reacts to infection by          deposition of new           bone.

5. Osteosclerotic Neoplasm

·   Osteoid osteoma (benign neoplasm)

·   Osteosarcoma (malignant neoplasm)

3.  Bone deposition less than bone resorption

·         Generalized Reactions

1.       Osteoporosis

Bone deposition is decreased because of decreased formation of matrix and resorption is increased. Examples: osteogenesis imperfecta, disuse osteoporosis, steroid induced osteoporosis, postmenopausal osteoporosis.

2.       Rickets in Children and Osteomalacia in  Adults

Although the osteoblastic formation of  matrix is normal, there is decreased calcification (hypocalcification) of the matrix with a resultant decreased in the amount of calcified bone.

·         Localized Reactions

1.       Disuse Atrophy (disuse osteoporosis)

Decreased bone deposition whereas the bone resorption continues unchanged.

2.       Rheumatoid Arthritis

The bone reacts to the periarticular soft tissue inflammation of RA by decreased bone deposition and possibly increased bone resorption.

Decreased in functionàdisuse atrophy

4.    Mechanical Failure of Bone (Fractures)

        The periosteum and endosteum react to bony injury with localized increased in bone deposition to form callus.

EPIPHYSEAL PLATES

—  Normal growth requires:

                1. intact structure and a normal blood supply

                2. intermittent pressures à normal physical  activity.

—  There are just 3 ways in which an epiphyseal plate can react:

                1. increased growth

                2. decreased growth

                3. torsional growth

1. Increased in Growth

1. Generalized

                1.  Arachnodactyly (Hyperchondroplasia) (Marfan`s Syndrome)

There is excessive cartilaginous growth (hyperchondroplasia) in all epiphyseal plates.

                2.  Pituitary Gigantism

Excessive growth hormone from an eosinophilic adenoma of the anterior pituitary gland.

2. Localized

1.   Chronic Inflammat
             The prolonged hyperemia à stimulates local growth, such as chronic osteomyelitis and rheumatoid arthritis.
2.   Displaced Fracture of the shaft of a Long Bone

             The nutrient artery to the shaft of a long bone is disrupted à a temporary compensatory hyperemia at the epiphyseal ends.

3.   Congenital Arteriovenous Malformations

            The continuing hyperemia à stimulation the epipheseal plates.

2. Decreased in Growth

1. Generalized

        1.    Achondroplasia

                There is deficient cartilaginous growth

        2.    Pituitary Dwarfism (Lorain type)

                Deficient growth hormone

        3.    Rickets

                Hypocalcification of the preosseus cartilage of the epiphyseal plate in the zone of calcifying cartilage.

B.    Localized

        1.    Disuse Retardation

        2.    Physical Injury

                Fracture à local cessation of growth

        3.    Thermal Injury

                Epiphyseal plate is sometimes destroyed either by local cold (frostbite) or by local heat (burns).

        4.    Ischemia

        5.    Infection

                Chondrolytic action of pus à destroy epiphyseal plate.

3. Torsional Growth

—  When a growing long bone and its epiphyseal plate are subjected to either continual or intermittent twisting forces, the bone gradually becomes twisted.

—  The torsional deformity in the long bones occurs through torsional growth in the involved epiphyseal plate and can ussualy be reversed by applying corrective torsional force in the opposite direction.

SYNOVIAL JOINTS

—  Synovial joint the smooth and reciprocally shaped cartilagious

Sensitive --> Stretching --> Increased fluid pressure

SKELETAL MUSCLE

The skeletal muscle reacts to many disorders and injuries in a limited number of ways including:

1.            atrophy

2.            hypertrophy

3.            necrosis

4.            contracture

5.            regeneration

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