Chapter 10

INJURIES IN THE REGION OF THE ELBOW AND FOREARM

Surgical Anatomy--Examination of injured elbow--FRACTURE OF LOWER END OF HUMERUS: _Supra-condylar_; _Inter-condylar_; _Separation of epiphysis_; _Fracture of either condyle alone_; _Fracture of either epicondyle alone_--FRACTURE OF UPPER END OF ULNA: _Olecranon_; _Coronoid_--FRACTURE OF UPPER END OF RADIUS: _Head_; _Neck_; _Separation of epiphysis_--DISLOCATION OF ELBOW: _Both bones_; _Ulna alone_; _Radius alone_--FRACTURE OF FOREARM: _Both bones_; _Radius alone_; _Ulna alone_.

The injuries met with in the region of the elbow-joint include the various fractures of the lower end of the humerus, and upper ends of the bones of the forearm, including the olecranon; and dislocations and sprains of the elbow-joint. The differential diagnosis is often exceedingly difficult on account of the swelling and tension which rapidly supervene on most of these injuries, the pain caused by manipulating the parts, and the difficulty of determining whether movement is taking place _at_ the joint or _near_ it.

#Surgical Anatomy.#--The medial epicondyle of the humerus is more readily felt through the skin than the lateral. The two epicondyles are practically on the same level, and a line joining them behind passes just above the tip of the olecranon when the arm is fully extended. On flexing the joint, the tip of the olecranon gradually passes to the distal side of this line, and when the joint is fully flexed the tip of the olecranon is found to have passed through half a circle. The head of the radius can be felt to rotate in the dimple on the back of the elbow just below the lateral epicondyle. The coronoid process may be detected on making deep pressure in the hollow in front of the joint. As the line of the radio-humeral joint is horizontal, while that of the ulno-humeral joint slopes obliquely downwards, the arm forms with the fully extended and supinated forearm an obtuse angle, opening laterally--the "carrying angle." This angle is usually more marked in women, in harmony with the greater width of the female pelvis. The ulnar nerve lies in the hollow between the olecranon and the medial condyle, and the median nerve passes over the front of the joint, with the brachial artery and biceps tendon to its lateral side. The radial nerve divides into its superficial and deep (posterior interosseous) branches at the level of the lateral condyle.

In _examining an injured elbow_, the thumb and middle finger are placed respectively on the two epicondyles, while the index locates the olecranon and traces its movements on flexion and extension of the joint. The movements of the head of the radius are best detected by pressing the thumb of one hand into the depression below the lateral epicondyle, while movements of pronation and supination are carried out by the other hand. The uninjured limb should always be examined for purposes of comparison.

In injuries about the elbow much aid in diagnosis is usually obtained by the use of the X-rays; but in young children it is sometimes impossible, even with excellent pictures, to make an accurate diagnosis by means of radiograms alone. In cases of suspected fracture, a radiogram should be taken with the back of the limb resting on the plate, the forearm being extended and supinated. If a dislocation is suspected and a lateral view is desired, the arm should be placed on its medial side. In obscure cases it is useful to take radiograms of the healthy limb in the same position.

FRACTURES OF THE LOWER END OF THE HUMERUS

The following fractures occur at the lower end of the humerus: (1) supra-condylar fracture; (2) inter-condylar fracture; (3) separation of epiphyses; (4) fracture of either condyle alone; and (5) fracture of either epicondyle alone.

All these injuries are common in children, and result from a direct fall or blow upon the elbow, or from a fall on the outstretched hand, especially when at the same time the joints are forcibly moved beyond their physiological limits, more particularly in the direction of pronation or abduction. While it is generally easy to diagnose the existence of a fracture, it is often exceedingly difficult to determine its exact nature. Although the ulnar and median nerves are liable to be injured in almost any of these fractures, they suffer much less frequently than might be expected.

Ankylosis, or, more frequently, locking of the joint, is a common sequel to many of these injuries. This is explained by the difficulty of effecting complete reduction, and by the wide separation of periosteum which often occurs, favouring the production of an excessive amount of new bone, particularly in young subjects.

The #supra-condylar# fracture usually results from a fall on the outstretched hand with the forearm partly flexed, from a direct blow, or from a twisting form of violence. The line of fracture is generally transverse, or but slightly oblique from behind downwards and forwards, so that the lower fragment is forced backward together with the bones of the forearm, simulating backward dislocation of the elbow; the lower end of the upper fragment lies in front (Fig. 33).

_Clinical Features._--The elbow is flexed at an angle of 120 deg. or 130 deg., and the forearm, held semi-pronated, is supported by the other hand. Around the seat of fracture great swelling rapidly ensues. The olecranon projects behind, but the mutual relations of the bony points of the elbow are unaltered. The lower end of the upper fragment may be felt in front above the level of the joint, as a rough and sharp projection, and this sometimes pierces the soft parts and renders the fracture compound. Movement at the joint is possible, but unnatural mobility may be detected above the level of the joint. Crepitus and localised tenderness may be elicited. The displacement is readily reduced by manipulation, but usually returns when the support is withdrawn. The arm is shortened to the extent of about half an inch.

In rare cases the obliquity of the fracture is downward and backward, and the lower fragment is displaced forward.

The #inter-condylar# fracture is a combination of the supra-condylar with a vertical split running through the articular surface, and so implicating the joint. The condyles are thus separated from one another, as well as from the shaft, by a T- or Y-shaped cleft. As such fractures usually result from severe forms of direct violence, they are often comminuted and compound. In addition to the signs of supra-condylar fracture, the joint is filled with blood. The condyles may be felt to move upon one another, and coarse crepitus, which has been likened to the feeling of a bag of beans, may be elicited if the fragments are comminuted.

#Separation of the lower epiphysis# of the humerus is met with in children of three or four years of age, but it may occur up to the thirteenth or fourteenth year. The more common lesion, however, is a combination of separated epiphysis with fracture, and this lesion is produced by the same forms of violence as cause supra-condylar fracture. If the periosteum is not torn, there is little or no displacement, but as a rule the clinical features closely resemble those of transverse fracture above the condyles, or of dislocation of the elbow. In separation of the epiphysis there is a peculiar deformity of the posterior aspect of the joint, consisting of two projections--one the olecranon, and the other the prominent capitellum with a scale of cartilage which it carries with it from the lateral condyle (R. W. Smith and E. H. Bennett). The end of the diaphysis may be palpated through the skin in front. Muffled crepitus can usually be elicited, and there is pain on pressing the segments against one another. Sometimes the separation is _compound_, the diaphysis protruding through the skin.

Union takes place more rapidly than in fracture, but, owing to the excessive formation of callus from the torn periosteum in front of the joint, full flexion is often interfered with. If the displaced epiphysis is imperfectly reduced, serious interference with the movements of the elbow is liable to ensue, and may call for operative treatment.

#Fracture of either Condyle alone.#--The lateral condyle or trochlea is more frequently separated from the rest of the bone than is the medial or capitellum. In either, the size of the fragment varies, but the line of fracture is partly extra-capsular and partly intra-capsular, so that the joint is always involved. Pain, crepitus, and the other signs of fracture are present. As the ligaments of the joint are not as a rule torn, there is little or no immediate displacement of the fragment. Secondary displacement is liable to occur, however, during the process of union, producing alterations in the "carrying angle" of the limb--_cubitus varus_ or _cubitus valgus_.

#Fracture of Epicondyles.#--Fracture of the _lateral epicondyle_ alone is so rare that it need only be mentioned.

The _medial epicondyle_ may be chipped off by a fall on the edge of a table or kerbstone, or it may be forcibly avulsed by traction through the ulnar collateral (internal lateral) ligament, as an accompaniment of dislocation. It is usually displaced downwards and forwards by the flexor muscles attached to it, and may thus come to exert pressure on the ulnar nerve. The fragment may be grasped and made to move on the shaft, producing crepitus. Fibrous union is the usual result.

Up to the age of seventeen or eighteen the epiphysis of the epicondyle may be separated.

#Treatment of Fractures in Region of Elbow.#--The administration of a general anaesthetic is a valuable aid to accurate reduction and fixation of fractures in this region. Much discussion has taken place as to the best position in which to treat these fractures. In our experience the best approximation of the fragments, as shown by the X-rays, is obtained when the limb is fixed in the position of full flexion with supination. American surgeons favour the position of flexion at a right angle. In the region of the elbow there is a risk of promoting too much callus formation by early and vigorous massage, with the result that the movements of the joint are restricted by locking of the bony projections. This is probably due to bone cells being forced into the surrounding tissues, where they multiply and form new bone on an exaggerated scale.

The _supra-condylar fracture_ is reduced by first extending the elbow to free the lower fragment from the triceps, and then, while making traction through the forearm, manipulating the fragments into position, and finally flexing the elbow to an acute angle and supinating the forearm. In this way the triceps is put upon the stretch and forms a natural posterior splint. A layer of wadding is placed in the bend of the elbow to separate the apposed skin surfaces, the arm placed in a sling so arranged as to support the elbow, and fixed to the side by a body bandage. This position is maintained for three weeks, with daily massage and movement. The last movement to be attempted is that of complete extension. Operative treatment is rarely called for.

_Separation of the epiphysis_ and _fracture of the medial epicondyle_ are treated on the same lines as supra-condylar fracture.

_T- or Y-shaped fractures_ and _fractures of the condyles_, inasmuch as they implicate the articular surfaces, present greater difficulties in treatment, but they are treated on the same lines as the supra-condylar. In young subjects whose occupation entails free movement of the elbow-joint, it is sometimes advisable to expose the fracture by operation and secure the fragments in position. The details of the operation vary in different cases, and depend upon the line of obliquity of the fracture, and the disposition of the individual fragments, points which may usually be determined by the use of the X-rays. In performing the operation, care must be taken to disturb the periosteum as little as possible, otherwise there may follow excessive formation of new bone.

Operative interference is sometimes necessary for ankylosis or locking of the joint after the fracture is united, or to relieve the ulnar nerve when it is involved in callus. _Volkmann's ischaemic contracture_ is liable to occur after fractures in the region of the elbow from impairment of the blood supply as a result of tight bandaging.

FRACTURE OF THE UPPER END OF THE ULNA

#Fracture of the olecranon# is a comparatively common injury in adults. It usually follows a fall on the flexed elbow, and results from the direct impact, supplemented by the traction of the triceps muscle. In a few cases it has been produced by muscular action alone. The line of fracture may pass through the tip of the process, or through its middle, less frequently through the base. It may be transverse, oblique, T- or V-shaped, but is rarely comminuted or compound.

_Clinical Features._--As the fracture almost invariably implicates the articular surface, there is considerable swelling from effusion of blood into the joint. The power of extending the forearm is impaired, and other symptoms of fracture are present. The amount of displacement depends upon the level of the fracture, and the extent to which the aponeurotic expansion of the triceps is torn. As the fracture is usually near the tip, the displacement is comparatively slight, the prolongation of the fibres of insertion of the triceps on to the sides and posterior part of the process holding the small fragment in position; and the fracture may easily escape recognition. When the line of fracture is nearer the base, however, the contraction of the triceps tends to separate the fragments widely (Fig. 35), and a distinct gap, which is increased on flexing the elbow, may often be felt between them, and if the elbow is passively extended, the fragments may be brought into apposition, and crepitus elicited.

When there is little displacement, bony union may result, but in many cases the fragments are united only by fibrous tissue. The upper fragment sometimes forms attachments to the shaft of the humerus, and this leads to stretching of the fibrous band between the fragments and to marked wasting of the triceps.

Separation of the olecranon _epiphysis_ is one of the rarest forms of epiphysial detachment (Poland). When the epiphysis is displaced upwards and unites in this position, it may interfere with complete extension of the elbow.

_Treatment._--It would appear that too much stress has hitherto been laid on the necessity of bringing the fragments into perfect apposition, and too little attention paid to the importance of maintaining the functions of the triceps and the movements of the elbow-joint.

Massage and movements are carried out from the first, and the forearm is supported in a sling. Full flexion is the last movement to be attempted. In carrying out the movements, the tip of the olecranon is pressed down with the thumb, so that it is obliged to follow the movements of the ulna, and is prevented from adhering to the humerus.

It was formerly the practice to have the arm almost, but not quite, fully extended, and a Gooch splint, extending from the lower border of the axilla to the finger-tips, and cut to the shape of the extended limb, applied anteriorly and fixed in position by a bandage, the region of the elbow being covered by a convergent spica.

_Operative Treatment._--Operative treatment may be had recourse to, particularly in cases in which there is wide separation of the fragments. The fracture is exposed, the joint cavity opened up and cleared of clots, and silver-wire sutures passed through the fragments without encroaching upon the articular cartilage. The limb is fixed with the elbow-joint in the position of almost complete extension. Movement may be commenced at the end of a week, the angle at which the joint is fixed being changed morning and evening. During the day the flexed position should be maintained and the arm carried in a sling; during the night the limb is fixed to a pillow in the extended position. The patient is allowed to use the joint cautiously within a fortnight.

_Old-standing Fracture._--When union fails to take place, the interval between the fragments tends to increase by the contraction of the triceps gradually stretching the intermediate fibrous tissue, so that a wide gap comes to separate the fragments. It is quite common that the function of the arm is all that can be desired in spite of a gap between the fragments, but, if this is not the case, the fragments may be united by operation.

#Fracture of the coronoid process# is rare except as a complication of backward dislocation of the elbow. It may be produced by direct violence, as well as by muscular action. As the fracture is usually within a quarter of an inch of the tip, the fibres of insertion of the brachialis prevent displacement. The ordinary evidence of fracture is often absent, and the diagnosis is seldom completed without the aid of the X-rays. The treatment consists in flexing the elbow and supporting the forearm in a sling. In some cases associated with dislocation, however, the small fragment has been so far displaced as to become attached to the back of the humerus (Annandale).

FRACTURE OF THE UPPER END OF THE RADIUS

Intra-capsular fracture of the #head of the radius# may result from direct violence, from a fall on the pronated hand, or from forcible pronation or abduction--that is, deviation of the forearm to the radial side. It may accompany dislocation of the elbow or fracture of adjacent bones. The head may be completely separated, or may be split into two or more fragments. Up to the seventeenth year, the _epiphysis_, which is entirely intra-articular, may be separated.

The _clinical features_ are localised pain, crepitus, interference with pronation and supination, while the elbow can be almost fully extended and flexed, and in some cases the fragment may be felt through the skin, although it usually continues to move with the shaft in pronation and supination.

Union generally takes place satisfactorily, but in some cases the fragments form new attachments resulting in impaired movement at the elbow, and necessitating operative interference.

Fracture of the #neck of the radius# between the capsule and the tubercle is rare.

#Avulsion of the tubercle# may occur from forcible contraction of the biceps, or, in children, from traction made on the forearm (A. L. Hall).

These injuries are treated with the elbow in the flexed position, and massage and movement are carried out as already described.

DISLOCATION OF THE ELBOW

Dislocations of the elbow-joint may involve one or both bones of the forearm, and may be complete or incomplete.

#Dislocation of both bones backward# is the most common of all dislocations of the elbow, and is the only dislocation that is frequently met with in children. It usually results from a fall on the outstretched hand, causing hyper-extension of the joint with abduction--that is, deviation towards the radial side; but it may follow a direct blow on the back of the humerus, a fall on the elbow, or a twist of the forearm.

_Morbid Anatomy._--All the ligaments of the elbow, except the annular (orbicular), are torn or stretched. The radius and ulna pass backward, the coronoid process coming to rest opposite the olecranon fossa behind the humerus, and the head of the radius behind the lateral condyle. The condyles of the humerus bear their normal relations to one another. The olecranon and the triceps tendon form a marked prominence on the back of the elbow, the tip of the olecranon lying above and behind the condyles. The lower end of the humerus lies in the flexure of the joint with the biceps tendon tightly stretched over it. The coronoid process is often broken, or the tendon of the brachialis torn. The median and ulnar nerves may be stretched or torn. Not infrequently the bones of the forearm are displaced towards the medial side as well as backward.

Occasionally, as a sequel to the dislocation, processes of bone develop in relation to the insertion of the brachialis and interfere with the movements of the joint. These outgrowths are due to displacement of bone-forming elements, either at the time of the original injury or as a result of forcible efforts at reduction. According to D. M. Greig, they do not develop in the tendon of the brachialis, but under it, and are not of the nature of myositis ossificans. In from four to six weeks after reduction of the dislocation, the movements begin to be restricted, and a hard mass can be felt in the cubital fossa, which with the X-rays is seen to be a bony outgrowth springing from the quadrilateral space on the front of the elbow below the coronoid process (Fig. 37). This gradually increases in size and leads to fixation of the joint. In most cases the effects reach their maximum in about six months, and then reabsorption of the mass begins.

If the disability shows no sign of abatement within a year, or if the bony outgrowth is producing pressure effects on the median nerve, it should be removed by operation.

It is important not to mistake this condition for the effects of a fracture which has complicated the dislocation and been overlooked at the time of the accident.

_Clinical features._--The elbow is held fixed at an angle of about 120 deg., pronated or midway between pronation and supination. Any attempt at movement causes great pain, and is followed by an elastic rebound to the abnormal position. The antero-posterior diameter of the joint is increased, and the forearm, as measured from the lateral epicondyle to the tip of the styloid process of the radius, is shortened to the extent of about an inch. If examined before swelling ensues, the outlines of the articular surfaces may be recognised in their abnormal positions, but swelling usually comes on rapidly, and, by obscuring the bony landmarks, renders the diagnosis difficult.

This injury has to be diagnosed from supra-condylar fracture with backward displacement of the lower fragment and from separation of the lower humeral epiphysis. A general anaesthetic is often necessary to enable an accurate diagnosis to be made. When the deformity is once reduced, there is no tendency to its reproduction unless the coronoid process is also fractured. In a considerable number of cases--according to E. H. Bennett, in the majority--this dislocation is _incomplete_, the coronoid process resting at the level of the trochlea, and the backward projection of the olecranon being scarcely appreciable. The head of the radius, however, is unduly prominent. In such cases the lesion is liable to be overlooked, and therefore to go untreated, leading to permanent stiffness at the elbow.

#Dislocation forward# is much less common than the backward variety. It is produced by severe force acting from behind on the flexed elbow, the ulna being driven forward, tearing the ligaments of the joint and the muscles attached to the condyles. The olecranon is frequently fractured at the same time (Fig. 39). When it remains intact, it may rest below the condyles (incomplete or first stage of dislocation), or may pass in front of them, especially if the triceps is ruptured (complete or second stage). The forearm is lengthened, the elbow slightly flexed, the posterior aspect of the joint flattened, and the condyles, in their abnormal relationship, can be palpated from behind.

#Medial and Lateral Dislocations.#--Dislocation towards the ulnar side is always incomplete, some portion of the articular surface of the bones of the forearm remaining in contact with the condyles.

The dislocation to the radial side is also incomplete as a rule, although cases have been recorded in which complete separation had taken place.

These forms of dislocation are rare, that towards the ulnar side being more frequently observed. Each form is often combined with other injuries in the vicinity.

The most common cause of these dislocations is a fall on the outstretched hand, the forearm at the moment being strongly pronated. Forced abduction favours the displacement to the ulnar side; adduction to the radial side. The limb is held flexed and pronated, and the facility with which the bony points can be palpated renders the diagnosis easy.

In a few cases _diverging dislocations_ have been met with, the radius and ulna being separated from one another, the annular (orbicular) ligament being torn and no longer holding them together.

#Treatment of Dislocations of Elbow.#--The chief obstacle to reduction is the spasmodic contraction of the muscles passing over the joint, and, in the backward variety, the hitching of the coronoid process against the edge of the olecranon fossa. In recent cases, to effect reduction the patient is seated on a chair, while the surgeon grasps the humerus and wrist, and places his knee in the bend of the elbow. The limb is first fully extended, or even hyper-extended, to relax the triceps and free the coronoid process. Traction is then made in opposite directions upon the forearm and arm, the surgeon's knee meanwhile making pressure, in a backward direction, upon the lower end of the humerus. The joint is next slowly flexed, and the bones slip into position, often with a distinct snap. If the patient be anaesthetised, these manipulations must be adapted to the recumbent position.

When some days have elapsed before reduction is attempted, forcible manipulations are to be deprecated as they greatly increase the risk of ossification occurring in relation to the brachialis (D. M. Greig); and recourse should be had to open operation, and the tearing or bruising of the soft parts should be reduced to a minimum.

After reduction, the limb is flexed to rather less than a right angle and supported by a sling. Massage and movement are commenced at once.

Fracture of the coronoid process predisposes to recurrence of the dislocation; when this complication exists, therefore, the limb should be fixed at an acute angle, and movements of full extension postponed for a fortnight. Massage and limited movements, however, may be carried out from the first.

If there is a fracture of the olecranon, the treatment must be modified accordingly (p. 87).

Comminuted and compound injuries usually call for operative treatment, the fractured bones being wired after reduction of the dislocation, or the loose fragments removed.

The _forward dislocation_ is reduced by fully flexing the elbow, and then pushing the bones of the forearm backward, while the humerus is pulled forward.

_Old-standing Dislocations._--No attempt should be made to reduce by manipulation a dislocation of the elbow which has remained displaced for five or six weeks, especially when it has been complicated by a fracture. The joint surfaces become welded together by adhesions, and separated fragments often form attachments which lock the joint. Attempts to break these down are attended with considerable risk of re-fracturing the bone or of tearing the soft parts. In such cases it is best to expose the joint, and if reduction is not easily effected a sufficient amount of the lower end of the humerus should be removed to provide a movable joint.

#Dislocation of the ulna alone# is a rare injury, and is usually associated with fracture of one or other of its processes or of the inner condyle.

#Dislocation of the radius alone#, on the other hand, is comparatively common, especially as a concomitant of fracture of the upper third of the shaft of the ulna (Fig. 40).

The injury may result from a blow on the back of the upper end of the radius, a fall on the outstretched hand, or, in children, from forcible traction on the forearm while in the pronated position. The displaced head usually passes _forward_, and rests on the anterior edge of the capitellum, thus preventing complete flexion and supination of the limb.

The limb is held partly flexed and pronated. The displaced head of the radius can be felt to rotate with the shaft in its abnormal position, and the articular facet on the head of the radius may also be felt; there is a depression posteriorly below the lateral epicondyle where the head should be. The radial side of the forearm is slightly shortened. The superficial and deep (posterior interosseous) branches of the radial nerve are liable to be pressed upon or torn by the displaced head of the radius, especially if the ulna is fractured, leading to disturbances in the area of their distribution.

In a few cases the displacement of the head has been _backwards_ or _laterally_.

_Treatment._--To effect reduction, the forearm should be alternately flexed and extended, while traction is made upon it from the wrist, and the head of the radius is pressed backward with the thumb in the fold of the elbow. When reduction is prevented by the interposition of a portion of the torn ligaments between the bones, it is sometimes necessary to open the joint to ensure accurate adjustment. The joint is fixed in acute flexion to relax the biceps, to allow of union of the torn ligaments, and to prevent recurrence.

In old-standing cases, to obtain a useful joint, or to remove pressure from the branches of the radial nerve, resection of the head of the radius may be necessary.

#Sub-luxation of the head of the radius#, or "dislocation by elongation," is a comparatively common injury in children between the ages of two and six. It almost invariably results from the child being lifted or dragged by the hand or forearm. The traction and torsion thus put upon the radius causes the front part of its head to pass out of the annular ligament, the edge of which slips between the bones.

The person holding the child may feel a click at the moment of displacement. The child complains of pain in the region of the elbow: the arm at once becomes useless, and is held flexed, midway between pronation and supination. All movements are painful, but especially movements in the direction of supination. The deformity is slight, but the head of the radius may be unduly prominent in front. From the way in which the injury is produced the wrist also is often swollen, and in some cases the patient is brought to the surgeon on account of the condition of the wrist, and attention is not directed to the elbow.

_Treatment._--Reduction frequently takes place spontaneously or during examination, the function of the arm being at once completely restored. In other cases it is necessary, under anaesthesia, to manipulate the head of the bone into position. This is usually easily done by flexing the elbow, making slight traction on the forearm, and alternately pronating and supinating it. After reduction, a few days' massage is all that is necessary, the joint in the intervals being kept at rest in a sling.

#Sprain# of the elbow is comparatively common as a result of a fall on the hand or a twist of the forearm. The point of maximum tenderness is usually over the radio-humeral joint, the radial collateral and annular ligaments being those most frequently damaged. Effusion takes place into the synovial cavity, and a soft, puffy swelling fills up the natural hollows about the joint. The bony points about the elbow retain their normal relationship to one another--a feature which aids in determining the diagnosis between a sprain and a dislocation or fracture. In children it is often difficult to distinguish between a sprain and the partial separation of an epiphysis. Sprains of the elbow are treated on the same lines as similar lesions elsewhere--by massage and movement.

The condition known as _tennis elbow_ is characterised by severe pain over the attachment of one or other of the muscles about the elbow, particularly the insertion of the pronator teres during the act of pronation, and is due to stretching or tearing of the fibres of that muscle, and of the adjacent intermuscular septa. A similar injury--_sculler's sprain_--occurs in rowing-men from feathering the oar. The treatment consists in massage and movement, care being taken to avoid the movement which produced the sprain.

FRACTURE OF THE FOREARM

The _shafts_ of the bones of the forearm may be broken separately, but it is much more common to find both broken together.

#Fracture of both bones# may result from a direct blow, from a fall on the hand, or from their being bent over a fixed object. The line of fracture is usually transverse, both bones giving way about the same level. The common situation is near the middle of the shafts. In children, greenstick fracture of both bones is a frequent result of a fall on the hand--this indeed being one of the commonest examples of greenstick fracture met with (Fig. 41).

The _displacement_ varies widely, depending partly upon the force causing the fracture, partly on the level at which the bones break, and on the muscles which act on the respective fragments. It is common to find an angular displacement of both bones to the radial or to the ulnar side. In other cases the four broken ends impinge upon the interosseous space, and may become united to one another, preventing the movements of pronation and supination. There may be shortening from overriding of fragments.

When the radius is broken above the insertion of the pronator teres, its upper fragment may be supinated by the biceps and supinator muscles, while the lower fragment remains in the usual semi-prone position. If union takes place in this position, the power of complete supination is permanently lost.

The usual _symptoms_ of fracture are present, and there is seldom any difficulty in diagnosis.

The _prognosis_ must be guarded, especially with regard to the preservation of pronation and supination. These movements are interfered with if union takes place in a bad position with angular or rotatory deformity of one or both bones, or if callus is formed in excess and causes locking of the bones. In some cases the callus fuses the two bones across the interosseous space, and pronation and supination are rendered impossible.

Persistent angular deformity of the forearm is also liable to ensue, either from failure to correct the displacement primarily, or from subsequent bending due to ill-applied splints or slings. Want of union, or the formation of a false joint in one or both bones, is sometimes met with, particularly in children, and, like the corresponding fracture of the leg, is liable to prove intractable.

A considerable number of cases of gangrene of the hand after simple fracture of the forearm are on record. This is sometimes attributable to damage inflicted upon the blood vessels by the fractured bones, or to the force that caused the fracture, but is oftener due to a roller bandage applied underneath the splints strangulating the limb, to injudiciously applied pads, or to too tight bandaging over the splints. Volkmann's ischaemic contracture occasionally develops after fractures of the forearm.

In uncomplicated cases, union takes place in from three to four weeks.

_Treatment._--To ensure accurate reduction and coaptation, a general anaesthetic is usually necessary. In the greenstick variety the bones must be straightened, the fracture being rendered complete, if necessary, for this purpose.

To retain the bones in position, anterior and posterior splints are then applied. These are made to overlap the forearm by about half an inch on each side, to avoid compressing the forearm from side to side, and so making the fractured ends encroach upon the interosseous space. The dorsal splint is usually made to extend from the olecranon to the knuckles, and the palmar one from the bend of the elbow to the flexure in the middle of the palm, a piece being cut out to avoid pressure on the ball of the thumb (Fig. 42). The splints are applied with the elbow flexed to a right angle, and, except when the radius is broken above the level of the insertion of the pronator teres, with the forearm midway between pronation and supination. The limb is placed in a sling, so adjusted that it supports equally the hand and elbow in order to avoid angular deformity. The use of special interosseous pads is to be avoided.

When the fracture of the radius is above the insertion of the pronator teres, the forearm should be placed in the position of complete supination, with the elbow flexed to an acute angle, and retained in this position by a moulded posterior splint, and the arm fixed to the side by a body bandage. Great care is necessary in the adjustment of the apparatus to prevent pronation.

Massage and movement should be carried out from the first. It is usually necessary to continue wearing the splints for about three weeks.

In cases of _mal-union_, especially when the bones are ankylosed to one another across the interosseous space, operation may be necessary, but it is neither easy in its performance nor always satisfactory in its results. The seat of fracture should be exposed by one or more incisions so placed as to enable the muscles to be separated and to give access to the callus. When the limb is straight, it is only necessary to gouge away the exuberant callus that interferes with rotatory movements; but when there is an angular deformity the bones must, in addition, be divided and re-set, and, if necessary, mechanically fixed in good position. In comparatively recent cases it is sometimes possible, without operation, to re-fracture the bones and to set them anew.

_Un-united fracture_ of both bones of the forearm is not uncommon and is treated on the usual lines; the gap between the fragments of the radius is bridged by a portion of the fibula, that should be long enough to overlap by at least an inch at either end; it is rarely necessary to bridge the gap in the ulna, unless it alone is the seat of non-union.

#Fracture of the shaft of the radius alone# may be due to a direct blow; to indirect violence, such as a fall on the hand; or to forcible pronation against resistance, as in wringing clothes. It is rare in comparison with fracture of both bones. When broken above the insertion of the pronator teres, the upper fragment is flexed and supinated by the biceps and supinator, while the lower fragment remains semi-prone, and is drawn towards the ulna by the pronator quadratus.

When the fracture is below the pronator teres, the displacement depends upon the direction of the force and the obliquity of the fracture. In fractures of the lower third of the shaft, the hand may be flexed toward the radial side, and the styloid lies at a higher level, as in a Colles' fracture. From the frequency with which this fracture occurs while cranking a motor-car, it is conveniently described as _Chauffeur's fracture_; we have observed in doctors, who have sustained this fracture in their own persons, that they were under the impression that they had sustained a trivial sprain of the wrist.

In addition to the ordinary signs of fracture, there is partial or complete loss of pronation and supination. The head of the radius as a rule does not move with the lower part of the shaft, but may do so if the fracture is incomplete or impacted.

#Fracture of the shaft of the ulna alone# is also comparatively rare. It is almost always due to a direct blow sustained while protecting the head from a stroke, or to a fall on the ulnar edge of the forearm, as in going up a stair.

The upper third is most frequently broken, and this injury is often associated with dislocation of the head of the radius (Fig. 40), or some other injury implicating the elbow-joint. On account of the superficial position of the bone, this fracture is frequently compound.

The displacement depends on the direction of the force, the fragments being usually driven towards the interosseous space. There is seldom marked deformity unless the head of the radius is dislocated at the same time. The diagnosis is, as a rule, easy.

The _treatment_ is the same as for fracture of both bones, but the splints may be discarded at the end of a fortnight.

For some unexplained reason, a fracture of the upper third of the shaft of the ulna frequently fails to unite.