Pathological Fractures

Pathological fractures: refers to the break (in bone) that occurs in previously diseased or abnormal bone.

Two major conditions that may present with a pathological bone fracture involving the femur are as follows:

Osteoporosis: refers to a reduction in bone mass owing to small but incremental losses incurred in the constant turnover of bone. This common condition is seen most often in the elderly of both sexes but is more pronounced in postmenopausal women.

Osteoporosis may occur as a primary disorder of obscure origin or as a secondary complication of a large variety of diseases.

Osteoporosis may present with:

• Bone pain: owing to microfractures (especially in the back because of compression of vertebral bodies); this may result in loss of height and instability of the vertebral column ( kyphosis)

• Fractures: reduced bone mass leads to predisposes to fractures (even following minimal trauma) especially of femoral necks, wrists and vertebrae
  

Morphology of osteoporosis: laboratory or biopsy findings…

Macroscopically:

• Bones are lighter in weight, less dense on radiography and show thinning of the cortex.

• Lumbar vertebral bodies are more biconcave than normal, such that the intervertebral disc space appears more spherical (so-called ‘fish vertebrae’ because similar of that in fish)

Microscopically:

• Bone trabeculae are thinner and reduced in number (haversian systems are widened)

• Decrease in the number of osteoblasts

Note: such bone as remains is of normal composition (mineralization is not affected)

Paget’s disease of the bone: (osteitis deformans) is a chronic disease of excessive uncontrolled resorption and deposition of bone particularly affects the skull, backbone, pelvis and long bones.

Paget disease can be divided into the following stages:

1. An initial osteolytic stage, followed by

2. A mixed osteolytic-osteoblastic stage, evolving ultimately into

3. A burnt-out, quiescent osteosclerotic stage

[Is thought to be caused by a slow viral infection of osteoblasts and then osteoclasts by paramyxovirus]

Because the new bone formation in active disease is disordered and poorly mineralized, it is soft and porous, lacks structural stability and is vulnerable to fracture or deformation under stress.

Patients may demonstrate pathological fractures, nerve compression symptoms, osteoarthritis and skeletal deformities (tibial bowing, skull enlargement).

Pathological changes of Paget’s disease: laboratory or biopsy findings…

The osteolytic phase is marked by resorption by numerous overly large osteoclasts (some with >100 nuclei)

The mixed phase shows, in addition, disordered neo-osteogenesis of predominantly woven bone (but some lamellar) with areas of new bone formation producing tilelike or mosaic pattern pathognomonic of Paget disease.

Eventually, after many years, there is a burnt-out phase, marked predominantly by bone formation and osteosclerosis.

Other investigative findings are:

• Serology: normal calcium and phosphate, alkaline phosphatase

• Urine: increased urinary excretion of hydroxyproline

• Abnormal isotope bone sans

• X-ray: localized bone enlargement, altered trabecular pattern and alternating areas of rarefaction and increased density

Category: Orthopedics Notes , Pathology Notes