GENERAL SURVEY OFORTHOPAEDIC

DISORDERS

CLASSIFICATION OF ORTHOPAEDIC DISORDERSMost orthopedic disorders fall within the following groups:

DeformitiesCongenital deformitiesAcquired deformities

General affections of the skeletonBone dysplasias Inborn errors of metabolismMetabolic bone diseaseEndocrine disorders

Local affections of boneInfections of bone

Tumors of boneOsteochondritis Cystic change Osteoid osteoma

Affections of soft tissueInflammatory lesions of soft

tissue Tumors of soft tissue

Affections of jointsArthritisDislocation and subluxationInternal derangements

Neurological disordersPoliomyelitis Cerebral palsy Spina bifida Peripheral nerve lesions

DeformitiesDeformities may be congenital or acquired, and they may

reflect an underlying abnormality of bone, joint or soft tissue.

CONGENITAL DEFORMITIES:Congenital deformities or malformations, by

definition, are attributable to faulty development and are present at birth, though they may not be recognized until later. They vary from severe malformations that are incompatible with life and may be found in still born infants, to minor abnormalities of structure that have no practical significance. Incidence varies in different countries and among different races: in Britain probably 2 or 3 per cent of infants are born with some significant developmental abnormality, but only about half of these affect the musculoskeletal system.

CausesAn abnormality of development may be caused by:1) Genetic abnormality; 2) Environmental abnormality; or 3)Combined genetic and environmental

abnormalities. Studies of families and twins have helped

geneticists to determine the influence of genetic and environmental factors, alone or combined, in the causation of many of the recognized malformations.

Genetic causes include mutation of a whole chromosome, as in Down‘s syndrome (mongolism), and mutation of a small part of a chromosome or of a single gene, as inachondroplasia. The defect is not necessarily always inherited from an affected parent, Itmay arise from a fresh mutation in the germ cell.

Environmental causes are not well understood. Experiments in animals have shown that many different types of environmental influence (dietetic, hormonal, chemical, physical or infective) may cause abnormalities of development, and the system of the body that is mainly affected depends upon the timing of the environmental 'insult'. But except for a few specific agents acting early in pregnancy there is no conclusive evidence that similar influences are important causes of malformations in man. The specific agents whose influence in man is well attested include radiation, the virus of rubella, and certain drugs (notably aminopterin and thalidomide).

Combined genetic and environmental factors seem to be the usual cause of the more common congenital malformations in man, on the evidence of twin and family studies. It is thought probable that developing embryos react differently to environmental influences: some have a natural resistance whereas others are susceptible. A malformation is therefore likely to arise when an environmental 'insult' is inflicted upon cells that have a genetically determined lack of resistance to it.

Practical significanceMany of the recognized congenital

abnormalities of the musculoskeletal system have little practical importance, either because they are very rare or because there is little that can be done for them. There are others, however, that present major problems to the orthopedic surgeon and may demand energetic treatment. These include congenital dislocation of the hip, congenital club foot , spina bifida , congenital scoliosis , osteogenesis imperfecta and cervical rib .

Inborn predisposition to disease in adultsIt is well recognized that, quite apart from

the overt congenital anomalies discussed above, there exists in some patients a genetically determined predisposition to abnormalities developing in later life. Examples of orthopedic conditions to which a susceptibility may exist include certain types of osteoarthritis (especially of the hips), ankylosing spondylitis, gouty arthritis, rheumatic fever, idiopathic scoliosis, osteochondritis dissecans, and Dupuytren's contracture.

ACQUIREDDEFORMITIES

Acquired deformities may be classified in two groups: those in which deformity arises at a joint, and those in which it arises in a bone.

Deformity may be said to exist at a joint when the joint cannot be placed voluntarily in the neutral anatomical position.

CausesThe causes of deformity arising at a joint may be summarized

under the following headings (Fig. 23): 1) Dislocation or subluxation . 2) Muscle imbalance.3) Tethering or contracture of muscles or tendons.4) Contracture of soft tissues .5) Arthritis . 6) Posture. 7) Unknown causes.

Fig. 23 Seven causes of deformity arising at a joint.- 1. Dislocation. 2. Muscle imbalance. 3. Tethering of muscle or tendon. 4. Soft-tissue contracture. 5. Arthritis. 6. Posture. 7. Idiopathic (cause unknown).

1-Dislocation or subluxation. This is usually caused by injury, but it may occur as a congenital deformity, or it may follow disease of the joint (pathological dislocation).

2-Muscle imbalance. Unbalanced action of muscles upon a joint may hold it continuously in a particular arc of its range. In time, secondary contractures occur in the dominant muscles or in the soft tissues, preventing the joint from returning to the neutral position (Fig. 23 (2)).

The two fundamental causes of muscle imbalance are:

1) weakness or paralysis of muscles; and 2) spasticity of muscles. Thus equinus deformity at the ankle

may follow paralysis of the dorsiflexor muscles (for instance, in poliomyelitis) because the action of the plantar flexors and of gravity is unopposed. Or a similar deformity may be caused by spasticity of the calf muscles, which overpower their antagonists. This occurs commonly in cerebral palsy.

3-Tethering or contracture of muscles or tendons. If something happens to muscles or tendons that prevents their normal to-and-fro gliding, or their elongation and retraction, the joint may be held in a position of deformity. Thus a muscle or tendon may be tethered to the surrounding tissues in consequence of local infection or injury (Fig. 2-3 (3)). An example is the anchoring of a flexor tendon of a finger within its fibrous sheath as a result of suppurative tenosynovitis, with consequent flexion deformity at the interphalangeal joints. Or a muscle may lose its elasticity and contractile power from impairment of its blood supply. An important example is Volkmann's ischemic contracture of the forearm flexor muscles from occlusion of the brachial artery or from increased intra-compartmental pressure, with consequent flexion deformity of the wrist and fingers.

4-Contracture of soft tissues. Apart from any disturbance of the muscles, contracture of soft tissues alone can account for joint deformity. An example is the common condition of Dupuytren's contracture, in which the thickened and contracted palmar aponeurosis pulls the metacarpo phalangeal and proximal interphalangeal joints of one or more fingers into flexion. Similarly, a flexion deformity of the knee or elbow, or indeed of any joint, may occur from contracture of the scarred skin after burns of the flexor surface of the limb (Fig. 23 (4)).

5-Arthritis. Any type of arthritis may lead to joint

deformity. In some cases the joint is firmly fixed in a deformed position by bony or fibrous ankylosis. In other instances the joint retains some movement but is prevented from reaching the neutral position. Thus flexion and adduction deformity is common in osteoarthritis of the hip, flexion deformity is common in arthritis of the knee, and the deformity of ulnar deviation of the fingers is a well known feature of rheumatoid arthritis of the metacarpo-phalangeal joints.

6-Posture. The habitual adoption of a deformed position

of a joint often leads in time to permanent deformity. A common example is the lateral deviation of the great toe at the metatarso-phalangeal joint—hallux valgus— so common in women who cramp their feet into narrow pointed shoes (Fig. 23 (6)). Another postural deformity that is still seen occasionally though it should never be allowed to occur—is fixed flexion of the knees in a patient confined to bed for a long time with the knees bent over a pillow.

7-Unknown causes. In some cases deformity occurs at a joint for no apparent reason. Thus many children develop knock-knee deformity between the ages of 3 and 5 years without demonstrable cause. It is usually unimportant because it tends to correct itself spontaneously. Another" common and more serious example is the inversion deformity of the foot known as talipes equino-varus or congenital club foot. A more sinister deformity that is equally ill explained is the idiopathic scoliosis of adolescents.

DEFORMITY ARISING IN A BONEDeformity exists in a bone when it is out of its normal

anatomical alignment.

Causes.There are three causes of deformity arising in bone: 1) Fracture;2) Bending; and 3) Uneven epiphysial growth (Figs 24-26).1-Fracture. This is by far the most common cause. Unless a

fracture is reduced so that the fragments are perfectly aligned deformity will result. Examples are the genu valgum (knock knee) that is often the consequence of compression fractures of the lateral condyle of the tibia, the cubitus valgus that may follow displaced fractures of the lateral condyle of the humerus, and the common 'dinner-fork' deformity of an unreduced fracture of the lower end of the radius

2-Bending of softened bone. Many unrelated conditions can cause softening of bone, with liability to bending and consequent deformity. They are mostly generalized disorders in which several or all of the bones are affected. The following are examples. Metabolic disorders: rickets, osteomalacia. Endocrine disturbances: parathyroid osteodystrophy, Cushing's syndrome. Affections of unknown cause: Paget's disease (osteitis deformans), fibrous dysplasia of bone, senile osteoporosis.

Three causes of deformity arising in a bone. Figure 24—Fracture. Figure 25—Bending of softened bone. Figure 26—Uneven

epiphysial growth.

3-Uneven growth of bone. In children any disturbance of the growing epiphysial cartilage (growth plate) may lead to uneven growth and consequent deformity. The usual effect of interference with a growing epiphysial cartilage is that its growth is retarded; occasionally it is accelerated. Deformity will follow only if the growing cartilage is affected more in one part than another, or if the interference with growth affects only one bone of a pair, as in the forearm or leg (Fig. 26). The most frequent causes of retarded epiphysial growth are:

• Crushing fracture involving the epiphysial growth plate; • Infection of the cartilage, usually from adjacent

osteomyelitis or joint infection;• Enchondroma (a benign tumour) adjacent to the cartilage,

as in Ollier's disease (multiple enchondromatosis. In the relatively uncommon cases in which epiphysial growth is accelerated the usual cause is local hyperemia induced by an adjacent focus of infection or by a vascular tumors such as a, haemangioma.

Treatment of deformitiesEach deformity must be considered as an

individual problem. Many do not require treatment, or are not amenable to it. In other cases an attempt may be made to correct or improve the deformity. One or more of the following methods may be used in appropriate cases;

1)Manipulative correction and retention in a plaster or splint (example—for displaced fracture);

2)Gradual correction by prolonged traction (example—for deformity in certain types of arthritis);

3) Division or excision of contracted or tethered soft tissue examples for Dupuytren's contracture or souring from burns);

4) Osteotomy or osteoclasts (examples-for deformity from rickets or mai led fracture);

5) Arthrodesis (example-for scoliosis); 6) Selective retardation of epiphysial growth (in

children) (example for deformity from uneven epiphysial growth).

General affections of the skeleton

A large number of general affections of the skeleton have been described. Fortunately many of these affections are so rare. Most of the others require only brief consider ation. Clearly, many of the affections to be described have a congenital basis and many of them cause deformity.

CLASSIFICATIONThe following classification is based on that of Wynne-Davies and Fairbank (1976).Bone dysplasias and malformationsAchondroplasia Osteogenesis imperfectaDiaphysial aclasisDyschondroplasia (Ollier's disease.) Paget's disease Polyostotic fibrous dysplasiaNeurofibromatosisFibrodysplasia ossificans progressiva Cranio-cleido dysostosisInborn errors of metabolismGaucher's disease Histiocytosis X

Metabolic bone diseaseHyperparathyroidism Nutritional" rickets Other forms of rickets Nutritional osteomalacia Other forms of osteomalacia Vitamin C deficiencyEndocrine disordersSenile osteoporosisHypopituitarismGigantismAcromegalyHypothyroidismGlucocorticoid excess

PAGET'S DISEASE(Osteitis deformans)

Paget's disease of bone is a slowly progressive disorder of one or several bones. Affected bones are thickened and spongy, and show a tendency to bend. The disease is one of the commonest general affections of the skeleton. The cause is unknown. It has been suggested that infection with a slow virus of the paramyxovirus family may be responsible, on the evidence

Paget's disease. Half pelvis, side by side with a normal one shown for com parison. Note the coarse trabeculae and slight distortion of the softened pelvic ring, with deepening of the acetabulum.