1
Chapter 12
Bone and joint diseases
Soft tissue tumours
Muscle diseases
1
Topics to be discussed in this chapter are
Fractures
Infection
Arthritis
Osteo arthritis
Rheumatoid arthritis
Gout
Paget’s disease
Metabolic bone disease
Tumours
benign
malignant
primary
secondary
Soft tissue tumours
Muscle diseases
Fractures
Perhaps the most frequent pathological condition of bones is fracture.
Bones are broken by many different types of physical trauma.
Most fractures are simple and can be ‘mended’ by keeping the two ends of the broken bone together and keeping them still until the natural healing process results in their repair.
This can be done by the application of a plaster of Paris bandage.
1 This X-ray shows a fracture of the forearm, one of the commonest fractures encountered.
The radius (yellow arrow) is broken. The ends of the broken bone are jagged and the two broken bones are not properly aligned.
To get a good healing result, the forearm is ‘manipulated’ to bring the fragments into alignment before applying a plaster of Paris bandage.
The red arrow indicates the unbroken ulna, and the yellow arrow the bones of the wrist.
This type of fracture is called a ‘closed’ fracture as distinct from a ‘compound’ one in which the skin is broken and the bone ends protrude through the skin.
The latter is a more serious fracture because it is exposed to the environment and infection is a likely complication.
Infection greatly slows the healing of the fracture and may result in further complications.
Fractures of some other bones do not heal easily with simple plaster fixation. They require ‘internal fixation’ using nails, plates and screws.
Orthopaedic surgeons use scrupulously aseptic techniques in treating such fractures because there is an ever present risk of infection.
Two fractures that need internal fixation for treatment are illustrated
Ankle
2(a) and (b) This combined image shows
(a) an X-ray of a fractured right ankle and
(b) an X-ray of a similar fracture that has been treated by internal fixation with a screw and a plate.
Red arrow tibia
Green arrow fibula
Yellow arrow talus bone of the ankle
A fracture of the ankle usually results in fracture of the lower end of the tibia and fracture of fibula as shown.
The X-ray of the fixation shows the fracture of the tibia fixed with a screw and that of the fibula by a plate.
After surgery, the ankle is immobilized in a plaster cast.
Hip
Fractures of the neck of the femur are common in elderly people.
They result from a fall.
The patient is unable to walk unless the two ends of the fractured bone become ‘impacted.’
If the patient is frail this is often the final episode that results in death.
In the middle of the 20th century,treatment of fractured neck of femur was revolutionized by the introduction of a ‘nail’ that is inserted as shown in the specimen. A number of different designs of this nail are in use.
3 Fractured neck of femur with a surgical nail that became infected.
Unfortunately the patient died of other causes about two weeksafter the operation.
Complications of fractures
Fractures may not unite properly and this results in a number of different problems which include
non union
malalignment and shortening of bone which is a problem in healing of fractures of weight bearing bones – vertebrae and leg bones.
Infection of compound fractures.
This leads to the complications listed under the heading of osteomyelitis.
Fat embolus
4 This brain specimen came from an autopsy on a young man who had a motor bike accident.
He suffered compound fractures of both femora and soon after the accident he became unconscious and died as a result of fat emboli.
In the slice of brain, the sites of the fat emboli can be seen as multiple petechial haemorrhages throughout the white matter.
As a result of the fracture, fat from the marrow cavity entered the lacerated vessels and caused fat emboli which blocked the small arteries to his lungs and the white matter of his brain.
This resulted in death.
Infection
Infection of bone is called osteomyelitis.
A wide range of organisms may cause osteomyelitis but the commonest one is Staphylococcus aureus.
Any bone in the body may become infected.
Treatment of osteomyelitis has always been difficult because of the relatively poor blood circulation to the bone.
Before the mid 20th century when antibiotics became readily available, chronic osteomyelitis was a medical ‘headache.’
In osteomyelitis, pus is enclosed within the bone marrow cavity by the thick cortical bone.
Over time, the pus breaks through this barrier and sinuses develop on the skin surface. The sinuses continue to discharge pus and fragments of necrotic bone for months or years.
Infection may spread by the blood stream to other organs resulting in metastatic abscesses.
Very rarely, squamous cell carcinoma developed on the skin adjacent to the discharging sinuses.
In the early part of the 21st century antibiotics are becoming less effective and some of the complications that used to be seen are being seen again.
5(a) and (b)
(a) PA and (b) lateral X-ray views of the tibia in a child.
They show the features of an acute osteomyelitis.
Brown arrow elevation of the periosteum by pus escaping from the medullary cavity.
Green arrow lytic destruction of a segment of the cortical bone by pus extending from the marrow cavity.
Clinically the patient will have a temperature and there will be pain over the site of the infection.
6(a) and (b) This image shows both front (a) and back (b) sides of a specimen of sterno clavicular joint that was affected by acute osteomyelitis.
This is a very unusual site for osteomyelitis, but it illustrates the features of this condition.
Green arrow sternoclavicular joint
Red arrow sternum.
The green arrow in (b) shows purulent exudate within the joint.
The joint has been destroyed by fibrosis that was part of the chronic inflammation that resulted as the acute process did not heal quickly.
7 This specimen of spine shows vertebral collapse (red arrow) from the effects of chronic osteomyelitis.
Figs. 6 and 7 show show old specimens from the days before the introduction of antibiotics.
Tuberculosis
Tuberculosis is still a very common infection in many countries in the world.
Bone tuberculosis tends to affect the big joints and the spinal column.
When it involves the vertebral bodies, it frequently destroys the vertebrae and produces a paravertebral abscess.
8 X-ray of a patient from Papua New Guinea. He has a tuberculous infection that is involving his thoracic vertebrae 8 to 10. T 9 has collapsed and pus has escaped and stripped along the periosteum of the vertebrae causing a paravertebral abscess.
The collapsed vertebra caused paraplegia as a result of pressure on the spinal cord.
Arthritis
Osteoarthritis
This is a degenerative condition which affects particularly the knees, hips and vertebral column.
Fingers are frequently involved and other joints are less frequently involved.
It is an ageing process and occurs in people past middle age.
Excessive trauma and injury to the large joints appear to predispose to an earlier onset of osteoarthritis.
Pathologically the articular cartilage of the joint particularly the hip and knee joints, becomes damaged, fragmented and eroded.
Fibrosis of the joint capsule occurs and overgrowths of bone (osteophytes) occur at the edges of the bone.
This results in progressive stiffness in the joint and pain which, at least in the earlier stages of the disease, is intermittent.
9 This knee joint shows the features of osteoarthritis. The condyles of the femur are above and the left one is seen best.
The articular cartilage is greatly eroded and the bare bone has been exposed.
The articular cartilage of both condyles of the tibia are also severely eroded.
The cruciate ligament that holds the femur and tibia together has been ruptured as well. (red arrow)
Since the late 20th century, joints affected like this one have been treated by knee replacement with various types of prosthetic joints.
Replacement of hip joints has also been done.
The results are on the whole satisfactory, but significant complications do occur.
Replacement of finger joints has not been as successful as replacement of hips and knees.
Rheumatoid arthritis
This is an autoimmune disease.
It is much more common in females than in males.
It usually occurs in middle age, but it can occur at any age.
It affects the joints of the hands and feet at first, but other joints become involved as the disease progresses.
It runs a prolonged and intermittent courseand the arthritic pathology is accompanied by systemic symptoms.
The joints are stiff, painful and become deformed.
The early pathology is a chronic inflammatory cell infiltration of the synovium and swelling of the joint.
The inflammatory process grows over the articular cartilage destroying it and causing adhesion between the articular surfaces of the joint with resultant stiffness, deformity and finally fusion.
10(a) and (b)
(a) a knee joint and
(b) a head of femur from the hip joint of a patient who during life suffered from advanced rheumatoid arthritis.
(a) The knee joint had to be dissected so that it could be opened and the pathology viewed.
Red arrow the articular surface of the patella in the patella tendon.
Yellow arrow the articular surface of the patella on the anterior surface of the femur.
Green arrow shows the adhesion between the articular surfaces of the femur and tibia.
Purple arrow eroded articular surface of the left tibial condyle.
(b) Articular surface of the head of the femur.
There is extensive destruction of the articular surface (blue arrow).
11 This is an unusual complication of rheumatoid arthritis.
The first and second cervical vertebrae become fused together, and the odontoid process of the second cervical vertebra protrudes through the first cervical vertebra and impinges on the brain stem. (red arrow).
Pressure at this point may cause sudden death.
Anecdote
The first cervical vertebra is called the atlas.
It has no body and is virtually a rim of bone that swivels around the odontoid process of the second cervical vertebra (the axis).
This allows the head to turn from side to side.
On its upper surface the atlas has two lateral articular surfaces that engage the two corresponding articular surfaces on the base of the skull.
This allows the head to ‘nod’ up and down.
The odontoid process is really the missing body of the atlas and it is fused to the upper surface of the body of the axis.
This ingenious arrangement allows the head to swivel around and to move forwards and backwards.
In a judicial hanging in which the prisoner is suddenly ‘dropped’ through a trapdoor at his feet, the sudden tightening of the hangman’s noose breaks the upper cervical vertebrae and the odontoid process presses on the midbrain as shown in this specimen. This results in sudden death.
Arthritis due to gout
Gout is a metabolic disease in which there is an impairment in the ability to metabolise uric acid, and the patient has a high serum uric acid.
This results in high levels of uric acid being passed in the urine, and resultant renal disease.
It is more common in men than in women.
It has a familial incidence.
Uric acid crystals are deposited in joints and in subcutaneous tissues.
In the latter this results in the formation of nodules called ‘tophi.’
In joints the uric acid crystals cause painful arthritis that is intermittent and progressive.
The first joint to be affected is very frequently the metatarsophalangeal joint of the big toe.
This presents as a very painful, red joint and is usually associated with systemic malaise and fever.
Other joints become progressively involved.
12 Knee joint, (red arrow)
MPJ of a big toe (purple arrow) and
patella (green arrow) from a patient who died from the complications of gout.
These specimens demonstrate the deposition of urate crystals in gout affected joints.
The toe and the patella are more affected than the knee.
13 Specimen of an ankle joint with a gouty tophus in the subcutaneous tissue adjacent to the fibula. (red arrow)
Paget’s disease
Paget’s disease of bone is a moderately common, non metabolic disease of bone whose cause is not known.
It occurs in both males and females, usually after middle age.
One or more bones may be affected and this is not symmetrical.
The cortices of the bones become thickened and they are soft and vascular.
When the tibia is involved it tends to bend with an anterior bowing.
The skull enlarges and causes pressure on the brain, and headache.
The vascularity of the bones may precipitate heart failure.
A rare complication is an osteogenic sarcoma arising in any of the diseased bones.
14(a) and (b) The skull (a) shows the gross thickening characteristic of Paget’s disease.
Even though the bone was thick, it cut easily with a scalpel blade.
(b) is a tibia which shows marked thickening of the cortical bone (red arrow).
In this case, the whole length of the tibia shows thickening of the cortical bone.
Quite often only portion of the bone is thickened and the rest is of normal thickness.
Metabolic bone disease
Osteoporosis
This is defined as a loss of bone mass.
The bones become thin and fragile.
Fractures of long bones occur, crush fractures of vertebrae occur with loss of height and pressure on spinal nerves.
There are a number of different causes:
Idiopathic which occurs particularly in postmenopausal women.
As a complication of long term steroid therapy.
Disuse atrophy in patients confined to bed or in limbs that are immobilized as a result of treatment of fractures.
15 X-ray lateral view of the thoracic vertebrae of a post menopausal woman.
It shows marked loss of bone density (osteoporosis), and wedging of vertebrae from collapse of vertebral bodies.
The red arrow indicates the most obvious one.
This deformity results in anterior bending of the thorax (kyphosis) and loss of height.
It may also result in pressure on nerve roots as they pass through vertebral foramena.
This causes local pain and sensory and motor loss in the distribution of the nerve root
16 This specimen of thoracic vertebrae shows collapse of osteoporotic vertebrae with extrusion of the nucleus pulposis posteriorly causing compression of the spinal cord. (red arrows)
The patient had paraplegia as a result of the compression.
17 X-ray showing osteoporosis of the lumbar vertebrae.
Some of the vertebrae are crushed or wedged anteriorly.
The red arrow indicates a point at which the nucleus pulposis of the intervertebral disc has herniated into the body of the vertebra below it.
Such herniations of the degenerate disc may occur posteriorly or laterally in which case they can compress either the spinal cord itself or the nerve root at the site of herniation.
18 Specimen of lumbar spine showing degeneration of a number of intervertebral discs.
The green arrow indicates a herniation of disc material into an adjacent vertebral body.
a x4
b x10
19(a) and (b)Normal cancellous bone.
The green arrow indicates the ostroblasts that form the bone.
The blue arrow shows mature osteocytes.
(a) x4
(b) x10
20(a) and (b)Osteoporotic cancellous bone.
21 Normal cortical bone. Green arrow an osteocyte. (x10)
Osteomalacia
This is a condition in which there is abnormal formation of bone that results from abnormality of calcium and phosphate metabolism. This in turn is caused by deficiency of vitamin D.
Causes of vitamin D deficiency
Dietary deficiency of vitamin D – rickets.
Decreased absorption of vit D in malabsorption syndrome.
Excessive amounts of circulating parathormone in hyperparathyroidism.
Disordered metabolism of calcium and phosphate occurs in chronic renal disease which causes secondary hyperparathyroidism.
Renal osteodystrophy occurs in chronic renal disease and this consists in a mixed pathology of hyperparathyroid bone disease and osteomalacia. (see Fig.)
X-ray features of osteomalacia
Pseudo fractures (cortical defects) are seen in a number of different bones.
The symphysis pubis develops a ‘moth eaten’ appearance.
22 X-ray of left humerus which shows a pseudo fracture of osteomalacia. (red arrow)
23Xray of pelvis of a normal reproductive aged woman. Note the normal symphysis pubis.
24X-ray of pelvis of a patient with osteomalacia. It shows a ‘moth eaten’ appearance of the symphysis pubis (red arrow).
(a) x10
(b) x10
25(a) and (b) Von Kossa stain showing the bone trabeculae stained black and the osteoid seams stained red.(green arrows)
In normal cancellous bone osteoid seams are not prominent and when seen they are thin.
In osteomalacia, as shown here, the seams are very obvious and very thick.
Bone biopsy to measure the thickness of osteoid seams is one of the definitive tests for the presence of osteomalacia.
Tumours
Benign
Malignant
Multiple myeloma (a tumour of haematopoietic cells)
Jaw tmours
Metastatic
Benign tumours
Many varieties of benign bone tumours are encountered, for example tumours of
Cartilage
Cancellous and cortical bone
Connective tissue, fibrous and vascular
Only a few will be demonstrated
Osteochondroma
These tumours appear as hard projections from the surface of long bones near one end. (the diaphysis.)
They are easily diagnosed by X-ray and they are treated by being shaved off the surface of the bone.
They consist of a growth of cancellous bone covered by a cap of cartilage.
(a) and (b)
(c) and (d)
26(a), (b), (c), (d)
(a) X-ray of an osteochondroma protruding from the posterior aspect of the upper end of the tibia.(red arrow)
(b) Osteochondroma (red arrow) gross specimen of the upper end of a humerus removed for other pathology.
(c) An osteochondroma that was shaved off the surface of a long bone.