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Congenital Elbow Dislocations
Orthopedic Salvage Procedures
019~5616/87
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Congenital Elbow Dislocations
]. L. Milton, D.V.M., M.S.,* and R. D. Montgomery, D.V.M., M.S.t
The veterinary medical literature contains little information on congenital dislocations of the elbow, and the classification of certain elbow dislocations as congenital is not clearly defined. Three types of congenital elbow dislocations appear to occur: (1) humeroulnar, (2) humeroradial, and (3) dislocations or joint laxity (arthrodysplasia) associated with multiple congenital skeletal anomalies. Lateral rotation of the proximal ulna and subluxation or luxation of the humeroulnar joint, with or without concurrent dislocation of the radial head, is a clearly defined congenital problem that causes severe limb deformity and dysfunction. 1· 12· 15• 21 Because the major joint of the elbow is involved, humeroulnar dislocations can justifiably be referred to as congenital elbow dislocations. Lateral or caudolateral dislocation of the radial head causes comparatively mild deformity and dysfunction, and its classification as a congenital problem is difficult to establish because of the late presentation of many cases and the high incidence of occurrence as a secondary problem related to growth disturbance of the radius and ulna. 9 • 10· 12· 20 Dislocations of the elbow secondary to asynchronous growth of the radius and ulna (premature closure of the distal ulnar physis, synostosis, retained cartilage core, and chondrodysplasia or achondroplasia) should be considered separate entities from congenital problems and will not be included in this article. Dislocations of the elbow and joint laxity (arthrodysplasia) have been reported with other congenital skeletal abnormalities, especially ectrodactyly. 1. 4. 7. 8, 16
ANATOMIC CONSIDERATIONS The elbow is composed of three distinct articulations: humeroulnar, humeroradial, and proximal radioulnar. Joint movement is flexion and extension with limited rotation. *Diplomate, American College of Veterinary Surgeons; Professor, Department of Small Animal Surgery and Medicine, Auburn University College of Veterinary Medicine, Auburn, Alabama tResearch Associate, Department of Small Animal Surgery and Medicine, Auburn University College of Veterinary Medicine, Auburn, Alabama Veterinary Clinics of North America: Small Animal Practice-Val. 17, No.4, July 1987
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The humeroulnar joint is formed by the trochlear (semilunar) notch of the ulna and the trochlea of the humerus; this joint is the primary stabilizer of the elbow and restricts movement to a sagittal plane. The humeroradial joint is formed by the lateral condyle of the humerus (capitulum humeri) and the articular fovea of the radial head, and it transmits most of the weight-bearing forces through the elbow. The proximal radioulnar joint allows limited rotation between the radius and ulna. 11 • 14 The collateral ligaments stabilize the joint against lateral (valgus) and medial (varus) movement. The lateral collateral ligament (Fig. lD) attaches to the lateral epicondyle of the humerus, and, distally, it divides into two crura. The cranial crus attaches to the proximal radius, and the caudal crus attaches to the ulna. Fibers of the ligament blend with the annular ligament and may contain a sesamoid bone. The smaller and weaker medial collateral ligament (Fig. lA) attaches to the medial epicondyle of the humerus and divides into two crura. The weaker cranial crus attaches to the radial tuberosity, and the stronger caudal crus passes through the interosseous space and attaches to the radius and ulna. The thin, band-like annular ligament (Fig. lB) supports the radioulnar joint by forming a ring over the radial head. This ligament attaches to the medial and lateral extremities of the radial incisure of the ulna and accomodates rotation of the radial head. 11 • 14
INCIDENCE Congenital elbow dislocations occur infrequently but have been reported to comprise 17 to 20 per cent of nonfracture elbow lameness. 2• 17 This figure is possibly inflated, because authors may have included problems that were secondary to growth disturbances of the radius and ulna.
ETIOLOGY The specific cause of congenital elbow dislocations is speculative. Bingel and Riser proposed that dislocations of the ulna and radius result from a failure in the stage of formation of the intra-articular ligaments, principally the medial collateral (ulnar dislocation) and annular ligaments (radial dislocation). 1 After correlating the findings of their work with other studies, 9 • 17• 20 they suggested a hereditary basis for these dislocations. This genetic etiology was based on a high frequency of bilateral involvement, occurrence in more than one member of the litter, frequency of multiple anomalies, and the embryonic stage at which the joint failed to develop properly. Our clinical experience with congenital dislocations of the ulna, surgical dissections of affected joints, and anatomic dissections of normal joints raises some questions concerning their hypothesis with respect to the role of the medial collateral ligament and a genetic etiology. 15 The medial collateral ligament provided little if any support to the olecranon and
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Figure l. Arthrology of the elbow. Top , A = medial collateral ligament. Middle, B = annular ligament; C = oblique ligament; D = lateral collateral ligament. Bottom, D = lateral collateral ligament.
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proximal ulna, especially in respect to rotation, and it appeared normal in surgical reconstructions in which the ligament was exposed. There was no familial history of the problem, and other members of the litter were not affected. Too little information is available to postulate accurately on the etiology of congenital dislocations of the elbow.
CONGENITAL DISLOCATION OF THE HUMEROULNAR JOINT Most congenital dislocations of the elbow that have been reported involve the humeroulnar joint. 1• 6 · 13 • 15 • 21 In these studies, there has been uniformity in the signalment, clinical signs, radiographic and pathologic findings, and results of treatment. Signalment Small breeds of dogs are most often affected by congenital elbow dislocation. We have observed the condition in the Yorkshire Terrier, Boston Terrier, Pekingese, Miniature Poodle, Miniature Pinscher, Pomeranian, Pug, Chihauhau, Cocker Spaniel, English Bulldog, and ManchesterChihauhau cross. Male dogs appear to be affected more than female dogs. Because limb deformity and dysfunction are obvious, the problem is generally recognized when the animal is between 3 and 6 weeks of age. Clinical Signs Dislocations of the ulna cause gross deformity and obvious limb dysfunction. With lateral rotation and dislocation of the proximal ulna, the action of the triceps muscle is displaced laterally and dogs are unable to extend the elbow and support weight on the leg. The elbow is positioned in flexion, and the forearm and paw are internally rotated or pronated. With a unilateral problem, the limb is carried in flexion (Fig. 2A). With bilateral occurrence, weight is supported on the caudomedial aspect of the elbows and forearms, and, when walking, the dog attempts to shift body weight to the rear limbs but is forced to use the flexed forelimbs in a shuffiing manner similar to soldiers crawling on their elbows (Fig. 2B) The lateral displacement of the olecranon process, proximal ulna, and triceps muscle is obvious with observation or palpation. In long-haired dogs, clipping in the region of the elbow facilitates recognition of the deformity (Fig. 2C). Manipulation of the elbow usually does not elicit a pain response. Pathologic and Radiographic Findings Pathologic changes in the articular cartilage, osseous structures, ligaments, joint capsule, and associated muscles vary with the severity of the displacement (luxation, subluxation) and the age of the animal or chronicity of the problem. In dogs under 3 months of age, osseous structures have not undergone substantial remodeling and, other than being malpositioned, are near normal. Secondary remodeling and degenerative changes occur rapidly and include hypoplasia and remodeling of the trochlea and trochlear notch, lateral rotation of the olecranon process and caudal aspect of the
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Figure 2. Clinical signs of humeroulnar dislocation. A, Unilateral dislocation in a 6-week-old Miniature Poodle. The forearm and paw are internally rotated (90°) and the elbow is Hexed. B, Bilateral dislocations in a 5-month-old Pug that shows shifting of body weight to rear legs, internal rotation of the forearms and paws, flexion of the elbows, and lateral deviation of the olecranon. C, Caudal view of the elbow shows lateral displacement of the olecranon process and triceps muscle and medial displacement of the humeral condyles.
proximal ulna, hypertrophy of the lateral condyle and hypoplasia of the medial condyle, stretching of the medial joint capsule and medial collateral ligament, contracture of the lateral joint capsule and lateral collateral ligament, contracture and displacement of the triceps muscle, articular cartilage degeneration, and deformity of the anconeal and coronoid processes (Fig. 3A to D). In most cases, the radial head remains in articulation with the lateral condyle of the humerus but may exhibit deformity. Radiographs confirm lateral displacement and rotation of the proximal ulna, malarticulation, and various osseous deformities. The craniocaudal view of the elbow presents a lateral view of the proximal ulna (Fig. 4A), and .the mediolateral view presents a craniocaudal view of the proximal ulna (Fig. 4B). Secondary pathologic changes, which were described previously, are most evident in chronic cases. Treatment Reduction and stabilization of the joint should be performed as early as possible, before secondary degenerative and remodeling changes per-
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Figure 3. Pathologic changes with humeroulnar dislocation. Elbow (A), ulna (cranial view of radius) (B), and humerus (C) show characteristic lateral rotation of the proximal ulna, hypoplasia and remodeling of the trochlear notch, and deformity of the radial head and humerus. D, Surgical dissection of the caudal aspect of the elbow reveals lateral dislocation of the ulnar trochlear notch (1), articulation of the radial head with the lateral condyle (2), and the medial collateral ligament (3).
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Figure 4. Radiographic findings with humeroulnar dislocation. A , Craniocaudal view of the elbow shows luxation of the humeroulnar joint, with lateral displacement and rotation of the ulna. B, Mediolateral view shows superimposition of the laterally displaced and rotated proximal ulna on the humeral condyles.
manently and severely alter the normal anatomy. Closed and open reduction techniques have been described. 15· 21 The choice of technique is dictated by the chronicity of the problem and the pathologic changes. For both methods, general anesthesia is required, and the leg is prepared as for surgery. Closed Reduction. Closed reduction is indicated in dogs under 3 to 4 months of age with minimal osseous and soft tissue changes .. In these cases, reduction can be achieved manually by exte rnal means. Manual reduction is accomplished by rotating and forcing the ulna medially and the humeral condyle laterally. Two techniques have been used to maintain reduction: transarticular pinning, 21 and a modified external pin splint with elastic bands. 15 With transarticular pinning, one or two small, nonthreaded , trocar-pointed pins (0. 062 inch or 0. 045 inch) are driven from the caudal aspect of the proximal ulna or olecranon through the humeroulnar joint and into the condyle and distal metaphysis of the hume rus. The pin(s) is (are) transected adjacent to the skin, leaving sufficient length to accomodate removal (Fig. SA). With the external pin splint and elastic band, small, nonthreaded, trocar-pointed pins (0. 062 inch to 0. 045 inch) are driven transversely through the humeral condyles and the proximal ulna. A padded metal splint is placed over the caudal aspect of the ulna and elbow, and the elastic band is wrapped from the lateral aspect of the pin(s) in the ulna to the medial
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Figure 5. Stabilization of reduced humeroulnar luxation with transarticular pins (A), modified external pin split with rubber band (B and C), and reconstruction and transposition of the olecranon process (D).
aspect of the pin(s) in the humerus . Sufficient tension should be placed on the elastic band to maintain reduction, but not so much as to cause tissue necrosis (Fig. 5B and C). With both procedures, a protective bandage can be placed around the elbow. Exercise is restricted by cage confinement for 3 weeks. Prophylactic and postoperative antibiotic therapy is optional. The transarticular pin(s) or external pin splint is removed in approximately 10 days. Our results with both techniques have been good . Open Reduction and Reconstruction. Surgery is directed at establishing a satisfactory anatomic relationship between the humerus, ulna, radius , and triceps muscle so that the elbow can be extended and the limb can support weight. The major objective is restoration of function and not necessarily radical reconstruction to achieve completely normal joint anatomy. Procedures that have been used include : (1) lateral release- capsulotomy, desmotomy, and anconeus myotomy; (2) medial support-capsular imbrication and support sutures; (3) transposition of the olecranon process medially and distally on the ulna; (4) reduction of the humeroulnar joint by rotation of
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the ulna with or without ulnar osteotomy; and (5) reconstruction of the trochlea and trochlear notch. 15 When osseous anatomy has not been severely altered and there is congruency between the trochlea and trochlear notch, the ulna can be reduced and stabilized with minimal reconstruction. In these cases, lateral release, medial imbrication, and transposition of the olecranon process are usually sufficient (Fig. 5D). With severe remodeling of the articular and osseous anatomy (hypoplasia of the trochlea and trochlear notch, malformation of the anconeal and coronoid processes, deformity of the olecranon process), radical reconstruction is required to reduce the ulna and produce some degree of congruency in the humeroulnar and radioulnar joints. Simply transposing the olecranon process so that the action of the triceps muscle is directed over the caudal aspect of the joint and settling for some degree of malarticulation may be sufficient to restore satisfactory function in some cases. Exposure of the medial and lateral aspects of the joint is done through a caudal skin incision. Olecranon osteotomy provides the best exposure and is required for transposition of the olecranon process and triceps muscle. Arthrodesis. Arthrodesis is indicated in those chronic cases in which surgical reduction has failed or when deformity and degeneration of the joint are severe. Arthrodesis involves removal of the articular cartilage and rigid fixation of the joint in a normal anatomic position. A cancellous bone graft promotes osseous union. Stabilization of the joint is achieved by multiple pins, compression screws, or, preferably, with a compression plate placed along the caudal aspect of the ulna and humerus. 13 Prognosis. The prognosis is good for return of satisfactory function but guarded for the development of a normal joint. All cases that we have treated have obtained near-normal use of the affected limb (Fig. 6A and B). Some degree of malarticulation and osseous deformity is expected to persist, especially in chronic cases.
POSSIBLE CONGENITAL RADIAL HEAD DISLOCATION Although the literature contains references to the existence of congenital dislocation of the radial head, and a few authors describe congenital or isolated radial head dislocation in immature dogs, there is a lack of conclusive information on the subject. 9• 12• 20 Pass and Ferguson 17 listed one of five radial head dislocations as being congenital, and CampbelF briefly described their condition and surgical correction. Grondalen9 reported malformation of the elbow joint in three of nine 4-month-old Afghan Hound littermates. The primary abnormality appeared to be lateral dislocation of the radial head. He believed the problem was congenital and not related to disturbances of growth between the radius and ulna. Stevens and Sande 20 described caudolateral dislocations of the radial head in a 3-month-old male Labrador Retriever-Setter cross, a 3-month-old male Golden Retriever, and a 2-year-old female Doberman Pinscher. They could not determine the specific cause of the problem but discussed a number of possible etiologies, including an innate developmental failure of the medial aspect of the
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Figure 6. Results of surgical treatment with unilate ral humeroulnar dislocation 6 weeks postoperatively (A) and bilateral humeroulnar dislocations 3 years postoperatively (B).
proximal radial growth plate. Kene, Lee, and Bennettl 2 described the radiographic features of congenital elbow luxations and subluxations and included seven cases of caudolateral displace ment of the radial head. Age of presentation ranged from 2 months to 5.5 months, with a mean of 3.6 months. Breeds affected were the Bull Mastiff (two), Bearded Collie, Rough Collie, Bulldog (two), and Shetland Sheepdog. Four of the dogs were male and three were female. One case was bilateral. The basis for classification as congenital was not stated.
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Gurevitch and Hohn 10 presented 20 dogs with elbow problems associated with radius curvus due to abnormalities in the distal ulnar physis or portions of the distal radial physis. Seven of the 20 had lateral luxation or subluxation of the radial head as the primary elbow deformity. None were classified as congenital. Most had a history of a traumatic event. The ages at diagnosis ranged from 3 to 10 months, with an average of 5.45 months, but the age of onset, when known, ranged from 1.5 to 7 months, with an average of 3.2 months. In our experience, dislocation of the radial head is almost always associated with growth disturbances of the radius and ulna-that is, premature closure of the distal ulnar physis, synostosis, retained cartilage core, and chondrodysplasia or achondroplasia. Signalment Congenital or isolated radial head dislocation, as described in the literature, 9 • 12• 20 occurs most frequently in large breeds of dogs. The problem has been reported in the Afghan Hound, Golden Retriever, Bull Mastiff, Collie, Bulldog, Doberman Pinscher, and Shetland Sheepdog. The age at diagnosis is usually between 3 and 4 months. There does not appear to be a sex predisposition. Clini.cal Findings Lateral dislocation of the radial head causes mild deformity and lameness but progressive degenerative joint changes. The elbow appears to bow laterally, and the displaced radial head can be palpated as it protrudes from the lateral humeral condyle. Manipulation of the elbow may elicit a mild reaction of pain or discomfort. With chronic cases, signs of degenerative joint disease such as swollen joint, muscle atrophy, limited range of motion, and crepitation are evident. Radiographic and Pathologic Findings Craniocaudal and mediolateral views demonstrate caudolateralluxation or subluxation of the radial head (Fig. 7). Other findings include deformity of the proximal radial metaphysis and epiphysis, angular deformity of the distal end of the humerus, medial deviation of the olecranon process, hypoplasia of the medial coronoid process, and absence of the anconeal process. The humeroulnar joint is normal in most dogs but may show caudal displacement or subluxation of the humerus against the anconeal process and a widened joint space. Chronic cases evidence signs of osteoarthritis. In addition to those osseous changes that are observed with radiographic examination, the joint capsule around the radial head is stretched, and the annular ligament is stretched, torn, hypoplastic, or aplastic. Treatment Reports on the treatment of congenital radial head dislocations could not be found. Treatment should be similar to that reported for dislocations secondary to growth disturbances. Options in the treatment include: (1) conservative management; (2) surgical reduction and stabilization; (3) radial head ostectomy; and (4) arthrodesis. 5• 10• 13• 19
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Figure 7. Craniocaudal view of the elbow shows typical lateral luxation of the radial head secondary to asynchronous growth of radius and ulna, which is commonly observed in achondroplastic breeds.
Conservative Management. Conservative management or no treatment is indicated in those cases with minimal displacement of the radial head, no substantial physical impairment, and minimal potential for debilitating arthritic changes. In older animals or those with chronic cases of degenerative joint disease, medical management may provide satisfactory results. Surgical Correction. Surgical correction is indicated in immature dogs with substantial displacement of the radial head and deformity, lameness, or the potential for disabling arthritic changes. Procedures that have been used to reduce and stabilize the radial head involve osteotomy of the ulna or osteotomy of the radius. Osteotomy and lengthening of the ulna to facilitate reduction of the radial head and fixation of the proximal radius to the ulna with a compression screw have been advocated for congenital radial head dislocations and have been used to treat secondary radial head dislocations (Fig. 8). 3 • 10 The proximal radius and shaft of the ulna are exposed through separate incisions, and the interosseous membrane is disrupted. The procedure should be
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Figure 8. Postoperative radiographs (lateral view) of radial head luxation in a 6-month-old Pekingese treated by ulnar osteotomy and reduction and fixation of the proximal radius to the ulna with pins.
restricted to dogs approaching skeletal maturity because the proximal radial physis contributes more to growth in length than the proximal ulnar physis, and fixation of the two bones (in the actively growing dog, synostosis) can cause elbow malarticulation (Fig. 9A). Corrective osteotomy of the proximal radius has been used to treat dislocations in immature dogs. The procedure should be performed before extensive remodeling of the radial head prevents the establishment of some degree of congruency in the humeroradial joint. Following osteotomy, the radial head is reduced and fixed to the radial shaft with a small (0. 045 inch to 0.062 inch) pin(s). Excision of a small section of the radius at the osteotomy site may be required to achieve reduction. Unlike the ulnar osteotomy technique, this procedure does not allow correction of any deformity of the ulna (Fig. 9A and B). Radial Head Ostectomy. Radial head ostectomy has been used to treat chronic radial head dislocation. The procedure is simple to perform and has successfully provided relief of pain and near-normal use of the leg. The radial head is exposed through a lateral approach made between the common and lateral digital extensor muscles. 18 Following incision through the joint capsule and annular ligament, ostectomy is performed with an osteotome, Gigli saw, or ossilating saw (Fig. 10). 5 • 19 Arthrodesis. Arthrodesis is indicated in those cases in which previous treatment has failed or in which degeneration of the joint is advanced. 13 Prognosis. Results of treatment are not available in a sufficient number of cases to determine a prognosis. The prognosis with surgical treatment appears to be good for satisfactory use of the leg but guarded for the
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Figure 9. A, Craniocaudal view of radial head luxation in a 5-month-old Sibe rian Husky previously treated by reduction and screw fixation. Continued growth and synostosis of radius and ulna by screw fixation caused recurrence of the luxation. B , Postoperative radiographs show osteotomy and reduction of the radial head and fixation with a single pin. Note remodeling and degeneration of the elbow.
prevention of degenerative changes and long-te rm use of the leg without dysfunction. CONGENITAL ELBOW DISLOCATION AND OTHER SKELETAL ANOMALIES Luxation, subluxation, and joint laxity (arthrodysplasia) of the elbow have been reported comcomitantly with other congenital abnormalities. 1• 4 • 7 • 8 · 16 Congenital elbow dislocation commonly occurs with ectrodactyly or cleft hand deformity in dogs. t , 4 · 16 Nine of 15 cases of ectrodactyly reported in the literature had dislocation of the elbow in the same limb. In most of these cases, the primary elbow deformity seemed to be related to dislocation of the radius. Polyarthrodysplasia (congenital joint luxations) has been described in the dog and involved marked instability of multiple joints, including the elbows. Other skeletal anomalies that accompanied this condition included hypoplasia of the sesamoid bones, patellar ectopia, and absence of the distal ulnar epiphysis. 7 · 8 The complexity of the problems that exist with these multiple skeletal anomalies has prohibited treatment.
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Figure 10. Radial head ostectomy for treatment of chronic luxation.
SUMMARY Three categories of congenital elbow dislocations are described in the literature: (1) humeroulnar, (2) humeroradial, and (3) dislocation or joint laxity with other congenital anomalies. Congenital humeroulnar dislocation is a well-defined problem that occurs predominantly in small breeds of dogs and causes severe limb deformity and dysfunction. Early reduction and stabilization are simple to achieve and have provided good results. Radial head dislocations occur most often as a result of growth disturbance of the radius and ulna. There is a lack of conclusive information on congenital radial head dislocations. Regardless of the etiology, radial head dislocation causes rather mild deformity and lameness and can be treated by conservative management, surgical correction, or radial head ostectomy. Dislocation of the elbow may occur concurrently with other rare congenital anomalies and has been described with ectrodactyly and polyarthrodysplasia.
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REFERENCES l. Bingel SA, Riser WH: Congenital elbow luxation in the dog. J Small Anim Pract
18:445-446, 1977 2. Campbell JR: Nonfracture injuries to the canine elbow. JAm Vet Med Assoc 155:735-744, 1969 3. Campbell JR: Luxation and ligamentous injuries of the elbow of the dog. Vet Clin North Am 1:429-440, 1971 4. Carrig CB, Wortman JA, Morris EL, eta!: Ectrodactyly (split-hand deformity) in the dog. Vet Radio! 22:123-144, 1981 5. Dieterich HF: Repair of a lateral radial head luxation by radial head ostectomy. Vet Med Small Anim Clin 68:671-675, 1973 6. Flipo J: Treatment of dislocation of the canine elbow. Mod Vet Pract 45:46-51, 1964 7. Fox MW: Sesamoidean hypoplasia with distal ulnar hemimelia and arthrodysplasia. A multiple congenital skeletal anomaly in the dog. Vet Rec 75:938-939, 1963 8. Fox MW: Polyarthrodysplasia (congenital joint luxation) in the dog. JAm Vet Med Assoc 145:1204-1205, 1964 9. Grondalen J: Malformation of the elbow joint in an Afghan hound litter. J Small Anim Pract 14:83-89, 1973 10. Gurevitch R, Hohn RB: Surgical management of lateral luxation and subluxation of the canine radial head. Vet Surg 9:49-57, 1980 11. Johnson RG, Hampel NL: Elbow luxation. In Slatter DH (ed): Textbook of Small Animal Surgery. Edition l. Philadelphia, WB Saunders Co, 1985 12. Kene ROC, Lee R, Bennett D: The radiological features of congenital elbow luxation/subluxation in the dog. J Small Anim Pract 2(23):621-630, 1982 13. Lasser AS: Arthrodesis. In Slatter DH (ed): Textbook of Small Animal Surgery. Edition l. Philadelphia, WB Saunders Co, 1985 14. Miller ME, Christensen GC, Evans HE: Miller's Anatomy of the Dog. Edition 2. Philadelphia, WB Saunders Co, 1979 15. Milton JL, Horne RD, Bartels JE, eta!: Congenital elbow luxation in the dog. JAm Vet Med Assoc 175:572-582, 1979 16. Montgomery M, Tomlinson J: Two cases of ectrodactyly and congenital elbow luxation in the dog. JAm Anim Hosp Assoc 21:781-785, 1985 17. Pass MA, Ferguson JG: Elbow dislocation in the dog. J Small Anim Pract 12:327-332, 1971 18. Piermattei DL, Greeley RC: An Atlas of Surgical Approaches to the Bones of the Dog and Cat. Philadelphia, WB Saunders Co, 1979 19. Putnam RW, Archibald J: Excision of the canine radial head. Mod Vet Pract 49:32, 1968 20. Stevens DR, Sande RD: An elbow dysplasia syndrome in the dog. J Am Vet Med Assoc 165:1065-1069, 1974 21. Withrow SJ: Management of a congenital elbow luxation by temporary transarticular pinning. Vet Med Small Anim Clin 72:1597-1602, 1977 Department of Small Animal Surgery and Medicine College of Veterinary Medicine Auburn University Auburn, Alabama 36849
019~5616/87
$0.00
+ .20
Congenital Elbow Dislocations
]. L. Milton, D.V.M., M.S.,* and R. D. Montgomery, D.V.M., M.S.t
The veterinary medical literature contains little information on congenital dislocations of the elbow, and the classification of certain elbow dislocations as congenital is not clearly defined. Three types of congenital elbow dislocations appear to occur: (1) humeroulnar, (2) humeroradial, and (3) dislocations or joint laxity (arthrodysplasia) associated with multiple congenital skeletal anomalies. Lateral rotation of the proximal ulna and subluxation or luxation of the humeroulnar joint, with or without concurrent dislocation of the radial head, is a clearly defined congenital problem that causes severe limb deformity and dysfunction. 1· 12· 15• 21 Because the major joint of the elbow is involved, humeroulnar dislocations can justifiably be referred to as congenital elbow dislocations. Lateral or caudolateral dislocation of the radial head causes comparatively mild deformity and dysfunction, and its classification as a congenital problem is difficult to establish because of the late presentation of many cases and the high incidence of occurrence as a secondary problem related to growth disturbance of the radius and ulna. 9 • 10· 12· 20 Dislocations of the elbow secondary to asynchronous growth of the radius and ulna (premature closure of the distal ulnar physis, synostosis, retained cartilage core, and chondrodysplasia or achondroplasia) should be considered separate entities from congenital problems and will not be included in this article. Dislocations of the elbow and joint laxity (arthrodysplasia) have been reported with other congenital skeletal abnormalities, especially ectrodactyly. 1. 4. 7. 8, 16
ANATOMIC CONSIDERATIONS The elbow is composed of three distinct articulations: humeroulnar, humeroradial, and proximal radioulnar. Joint movement is flexion and extension with limited rotation. *Diplomate, American College of Veterinary Surgeons; Professor, Department of Small Animal Surgery and Medicine, Auburn University College of Veterinary Medicine, Auburn, Alabama tResearch Associate, Department of Small Animal Surgery and Medicine, Auburn University College of Veterinary Medicine, Auburn, Alabama Veterinary Clinics of North America: Small Animal Practice-Val. 17, No.4, July 1987
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The humeroulnar joint is formed by the trochlear (semilunar) notch of the ulna and the trochlea of the humerus; this joint is the primary stabilizer of the elbow and restricts movement to a sagittal plane. The humeroradial joint is formed by the lateral condyle of the humerus (capitulum humeri) and the articular fovea of the radial head, and it transmits most of the weight-bearing forces through the elbow. The proximal radioulnar joint allows limited rotation between the radius and ulna. 11 • 14 The collateral ligaments stabilize the joint against lateral (valgus) and medial (varus) movement. The lateral collateral ligament (Fig. lD) attaches to the lateral epicondyle of the humerus, and, distally, it divides into two crura. The cranial crus attaches to the proximal radius, and the caudal crus attaches to the ulna. Fibers of the ligament blend with the annular ligament and may contain a sesamoid bone. The smaller and weaker medial collateral ligament (Fig. lA) attaches to the medial epicondyle of the humerus and divides into two crura. The weaker cranial crus attaches to the radial tuberosity, and the stronger caudal crus passes through the interosseous space and attaches to the radius and ulna. The thin, band-like annular ligament (Fig. lB) supports the radioulnar joint by forming a ring over the radial head. This ligament attaches to the medial and lateral extremities of the radial incisure of the ulna and accomodates rotation of the radial head. 11 • 14
INCIDENCE Congenital elbow dislocations occur infrequently but have been reported to comprise 17 to 20 per cent of nonfracture elbow lameness. 2• 17 This figure is possibly inflated, because authors may have included problems that were secondary to growth disturbances of the radius and ulna.
ETIOLOGY The specific cause of congenital elbow dislocations is speculative. Bingel and Riser proposed that dislocations of the ulna and radius result from a failure in the stage of formation of the intra-articular ligaments, principally the medial collateral (ulnar dislocation) and annular ligaments (radial dislocation). 1 After correlating the findings of their work with other studies, 9 • 17• 20 they suggested a hereditary basis for these dislocations. This genetic etiology was based on a high frequency of bilateral involvement, occurrence in more than one member of the litter, frequency of multiple anomalies, and the embryonic stage at which the joint failed to develop properly. Our clinical experience with congenital dislocations of the ulna, surgical dissections of affected joints, and anatomic dissections of normal joints raises some questions concerning their hypothesis with respect to the role of the medial collateral ligament and a genetic etiology. 15 The medial collateral ligament provided little if any support to the olecranon and
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Figure l. Arthrology of the elbow. Top , A = medial collateral ligament. Middle, B = annular ligament; C = oblique ligament; D = lateral collateral ligament. Bottom, D = lateral collateral ligament.
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proximal ulna, especially in respect to rotation, and it appeared normal in surgical reconstructions in which the ligament was exposed. There was no familial history of the problem, and other members of the litter were not affected. Too little information is available to postulate accurately on the etiology of congenital dislocations of the elbow.
CONGENITAL DISLOCATION OF THE HUMEROULNAR JOINT Most congenital dislocations of the elbow that have been reported involve the humeroulnar joint. 1• 6 · 13 • 15 • 21 In these studies, there has been uniformity in the signalment, clinical signs, radiographic and pathologic findings, and results of treatment. Signalment Small breeds of dogs are most often affected by congenital elbow dislocation. We have observed the condition in the Yorkshire Terrier, Boston Terrier, Pekingese, Miniature Poodle, Miniature Pinscher, Pomeranian, Pug, Chihauhau, Cocker Spaniel, English Bulldog, and ManchesterChihauhau cross. Male dogs appear to be affected more than female dogs. Because limb deformity and dysfunction are obvious, the problem is generally recognized when the animal is between 3 and 6 weeks of age. Clinical Signs Dislocations of the ulna cause gross deformity and obvious limb dysfunction. With lateral rotation and dislocation of the proximal ulna, the action of the triceps muscle is displaced laterally and dogs are unable to extend the elbow and support weight on the leg. The elbow is positioned in flexion, and the forearm and paw are internally rotated or pronated. With a unilateral problem, the limb is carried in flexion (Fig. 2A). With bilateral occurrence, weight is supported on the caudomedial aspect of the elbows and forearms, and, when walking, the dog attempts to shift body weight to the rear limbs but is forced to use the flexed forelimbs in a shuffiing manner similar to soldiers crawling on their elbows (Fig. 2B) The lateral displacement of the olecranon process, proximal ulna, and triceps muscle is obvious with observation or palpation. In long-haired dogs, clipping in the region of the elbow facilitates recognition of the deformity (Fig. 2C). Manipulation of the elbow usually does not elicit a pain response. Pathologic and Radiographic Findings Pathologic changes in the articular cartilage, osseous structures, ligaments, joint capsule, and associated muscles vary with the severity of the displacement (luxation, subluxation) and the age of the animal or chronicity of the problem. In dogs under 3 months of age, osseous structures have not undergone substantial remodeling and, other than being malpositioned, are near normal. Secondary remodeling and degenerative changes occur rapidly and include hypoplasia and remodeling of the trochlea and trochlear notch, lateral rotation of the olecranon process and caudal aspect of the
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Figure 2. Clinical signs of humeroulnar dislocation. A, Unilateral dislocation in a 6-week-old Miniature Poodle. The forearm and paw are internally rotated (90°) and the elbow is Hexed. B, Bilateral dislocations in a 5-month-old Pug that shows shifting of body weight to rear legs, internal rotation of the forearms and paws, flexion of the elbows, and lateral deviation of the olecranon. C, Caudal view of the elbow shows lateral displacement of the olecranon process and triceps muscle and medial displacement of the humeral condyles.
proximal ulna, hypertrophy of the lateral condyle and hypoplasia of the medial condyle, stretching of the medial joint capsule and medial collateral ligament, contracture of the lateral joint capsule and lateral collateral ligament, contracture and displacement of the triceps muscle, articular cartilage degeneration, and deformity of the anconeal and coronoid processes (Fig. 3A to D). In most cases, the radial head remains in articulation with the lateral condyle of the humerus but may exhibit deformity. Radiographs confirm lateral displacement and rotation of the proximal ulna, malarticulation, and various osseous deformities. The craniocaudal view of the elbow presents a lateral view of the proximal ulna (Fig. 4A), and .the mediolateral view presents a craniocaudal view of the proximal ulna (Fig. 4B). Secondary pathologic changes, which were described previously, are most evident in chronic cases. Treatment Reduction and stabilization of the joint should be performed as early as possible, before secondary degenerative and remodeling changes per-
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Figure 3. Pathologic changes with humeroulnar dislocation. Elbow (A), ulna (cranial view of radius) (B), and humerus (C) show characteristic lateral rotation of the proximal ulna, hypoplasia and remodeling of the trochlear notch, and deformity of the radial head and humerus. D, Surgical dissection of the caudal aspect of the elbow reveals lateral dislocation of the ulnar trochlear notch (1), articulation of the radial head with the lateral condyle (2), and the medial collateral ligament (3).
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Figure 4. Radiographic findings with humeroulnar dislocation. A , Craniocaudal view of the elbow shows luxation of the humeroulnar joint, with lateral displacement and rotation of the ulna. B, Mediolateral view shows superimposition of the laterally displaced and rotated proximal ulna on the humeral condyles.
manently and severely alter the normal anatomy. Closed and open reduction techniques have been described. 15· 21 The choice of technique is dictated by the chronicity of the problem and the pathologic changes. For both methods, general anesthesia is required, and the leg is prepared as for surgery. Closed Reduction. Closed reduction is indicated in dogs under 3 to 4 months of age with minimal osseous and soft tissue changes .. In these cases, reduction can be achieved manually by exte rnal means. Manual reduction is accomplished by rotating and forcing the ulna medially and the humeral condyle laterally. Two techniques have been used to maintain reduction: transarticular pinning, 21 and a modified external pin splint with elastic bands. 15 With transarticular pinning, one or two small, nonthreaded , trocar-pointed pins (0. 062 inch or 0. 045 inch) are driven from the caudal aspect of the proximal ulna or olecranon through the humeroulnar joint and into the condyle and distal metaphysis of the hume rus. The pin(s) is (are) transected adjacent to the skin, leaving sufficient length to accomodate removal (Fig. SA). With the external pin splint and elastic band, small, nonthreaded, trocar-pointed pins (0. 062 inch to 0. 045 inch) are driven transversely through the humeral condyles and the proximal ulna. A padded metal splint is placed over the caudal aspect of the ulna and elbow, and the elastic band is wrapped from the lateral aspect of the pin(s) in the ulna to the medial
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Figure 5. Stabilization of reduced humeroulnar luxation with transarticular pins (A), modified external pin split with rubber band (B and C), and reconstruction and transposition of the olecranon process (D).
aspect of the pin(s) in the humerus . Sufficient tension should be placed on the elastic band to maintain reduction, but not so much as to cause tissue necrosis (Fig. 5B and C). With both procedures, a protective bandage can be placed around the elbow. Exercise is restricted by cage confinement for 3 weeks. Prophylactic and postoperative antibiotic therapy is optional. The transarticular pin(s) or external pin splint is removed in approximately 10 days. Our results with both techniques have been good . Open Reduction and Reconstruction. Surgery is directed at establishing a satisfactory anatomic relationship between the humerus, ulna, radius , and triceps muscle so that the elbow can be extended and the limb can support weight. The major objective is restoration of function and not necessarily radical reconstruction to achieve completely normal joint anatomy. Procedures that have been used include : (1) lateral release- capsulotomy, desmotomy, and anconeus myotomy; (2) medial support-capsular imbrication and support sutures; (3) transposition of the olecranon process medially and distally on the ulna; (4) reduction of the humeroulnar joint by rotation of
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the ulna with or without ulnar osteotomy; and (5) reconstruction of the trochlea and trochlear notch. 15 When osseous anatomy has not been severely altered and there is congruency between the trochlea and trochlear notch, the ulna can be reduced and stabilized with minimal reconstruction. In these cases, lateral release, medial imbrication, and transposition of the olecranon process are usually sufficient (Fig. 5D). With severe remodeling of the articular and osseous anatomy (hypoplasia of the trochlea and trochlear notch, malformation of the anconeal and coronoid processes, deformity of the olecranon process), radical reconstruction is required to reduce the ulna and produce some degree of congruency in the humeroulnar and radioulnar joints. Simply transposing the olecranon process so that the action of the triceps muscle is directed over the caudal aspect of the joint and settling for some degree of malarticulation may be sufficient to restore satisfactory function in some cases. Exposure of the medial and lateral aspects of the joint is done through a caudal skin incision. Olecranon osteotomy provides the best exposure and is required for transposition of the olecranon process and triceps muscle. Arthrodesis. Arthrodesis is indicated in those chronic cases in which surgical reduction has failed or when deformity and degeneration of the joint are severe. Arthrodesis involves removal of the articular cartilage and rigid fixation of the joint in a normal anatomic position. A cancellous bone graft promotes osseous union. Stabilization of the joint is achieved by multiple pins, compression screws, or, preferably, with a compression plate placed along the caudal aspect of the ulna and humerus. 13 Prognosis. The prognosis is good for return of satisfactory function but guarded for the development of a normal joint. All cases that we have treated have obtained near-normal use of the affected limb (Fig. 6A and B). Some degree of malarticulation and osseous deformity is expected to persist, especially in chronic cases.
POSSIBLE CONGENITAL RADIAL HEAD DISLOCATION Although the literature contains references to the existence of congenital dislocation of the radial head, and a few authors describe congenital or isolated radial head dislocation in immature dogs, there is a lack of conclusive information on the subject. 9• 12• 20 Pass and Ferguson 17 listed one of five radial head dislocations as being congenital, and CampbelF briefly described their condition and surgical correction. Grondalen9 reported malformation of the elbow joint in three of nine 4-month-old Afghan Hound littermates. The primary abnormality appeared to be lateral dislocation of the radial head. He believed the problem was congenital and not related to disturbances of growth between the radius and ulna. Stevens and Sande 20 described caudolateral dislocations of the radial head in a 3-month-old male Labrador Retriever-Setter cross, a 3-month-old male Golden Retriever, and a 2-year-old female Doberman Pinscher. They could not determine the specific cause of the problem but discussed a number of possible etiologies, including an innate developmental failure of the medial aspect of the
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Figure 6. Results of surgical treatment with unilate ral humeroulnar dislocation 6 weeks postoperatively (A) and bilateral humeroulnar dislocations 3 years postoperatively (B).
proximal radial growth plate. Kene, Lee, and Bennettl 2 described the radiographic features of congenital elbow luxations and subluxations and included seven cases of caudolateral displace ment of the radial head. Age of presentation ranged from 2 months to 5.5 months, with a mean of 3.6 months. Breeds affected were the Bull Mastiff (two), Bearded Collie, Rough Collie, Bulldog (two), and Shetland Sheepdog. Four of the dogs were male and three were female. One case was bilateral. The basis for classification as congenital was not stated.
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Gurevitch and Hohn 10 presented 20 dogs with elbow problems associated with radius curvus due to abnormalities in the distal ulnar physis or portions of the distal radial physis. Seven of the 20 had lateral luxation or subluxation of the radial head as the primary elbow deformity. None were classified as congenital. Most had a history of a traumatic event. The ages at diagnosis ranged from 3 to 10 months, with an average of 5.45 months, but the age of onset, when known, ranged from 1.5 to 7 months, with an average of 3.2 months. In our experience, dislocation of the radial head is almost always associated with growth disturbances of the radius and ulna-that is, premature closure of the distal ulnar physis, synostosis, retained cartilage core, and chondrodysplasia or achondroplasia. Signalment Congenital or isolated radial head dislocation, as described in the literature, 9 • 12• 20 occurs most frequently in large breeds of dogs. The problem has been reported in the Afghan Hound, Golden Retriever, Bull Mastiff, Collie, Bulldog, Doberman Pinscher, and Shetland Sheepdog. The age at diagnosis is usually between 3 and 4 months. There does not appear to be a sex predisposition. Clini.cal Findings Lateral dislocation of the radial head causes mild deformity and lameness but progressive degenerative joint changes. The elbow appears to bow laterally, and the displaced radial head can be palpated as it protrudes from the lateral humeral condyle. Manipulation of the elbow may elicit a mild reaction of pain or discomfort. With chronic cases, signs of degenerative joint disease such as swollen joint, muscle atrophy, limited range of motion, and crepitation are evident. Radiographic and Pathologic Findings Craniocaudal and mediolateral views demonstrate caudolateralluxation or subluxation of the radial head (Fig. 7). Other findings include deformity of the proximal radial metaphysis and epiphysis, angular deformity of the distal end of the humerus, medial deviation of the olecranon process, hypoplasia of the medial coronoid process, and absence of the anconeal process. The humeroulnar joint is normal in most dogs but may show caudal displacement or subluxation of the humerus against the anconeal process and a widened joint space. Chronic cases evidence signs of osteoarthritis. In addition to those osseous changes that are observed with radiographic examination, the joint capsule around the radial head is stretched, and the annular ligament is stretched, torn, hypoplastic, or aplastic. Treatment Reports on the treatment of congenital radial head dislocations could not be found. Treatment should be similar to that reported for dislocations secondary to growth disturbances. Options in the treatment include: (1) conservative management; (2) surgical reduction and stabilization; (3) radial head ostectomy; and (4) arthrodesis. 5• 10• 13• 19
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Figure 7. Craniocaudal view of the elbow shows typical lateral luxation of the radial head secondary to asynchronous growth of radius and ulna, which is commonly observed in achondroplastic breeds.
Conservative Management. Conservative management or no treatment is indicated in those cases with minimal displacement of the radial head, no substantial physical impairment, and minimal potential for debilitating arthritic changes. In older animals or those with chronic cases of degenerative joint disease, medical management may provide satisfactory results. Surgical Correction. Surgical correction is indicated in immature dogs with substantial displacement of the radial head and deformity, lameness, or the potential for disabling arthritic changes. Procedures that have been used to reduce and stabilize the radial head involve osteotomy of the ulna or osteotomy of the radius. Osteotomy and lengthening of the ulna to facilitate reduction of the radial head and fixation of the proximal radius to the ulna with a compression screw have been advocated for congenital radial head dislocations and have been used to treat secondary radial head dislocations (Fig. 8). 3 • 10 The proximal radius and shaft of the ulna are exposed through separate incisions, and the interosseous membrane is disrupted. The procedure should be
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Figure 8. Postoperative radiographs (lateral view) of radial head luxation in a 6-month-old Pekingese treated by ulnar osteotomy and reduction and fixation of the proximal radius to the ulna with pins.
restricted to dogs approaching skeletal maturity because the proximal radial physis contributes more to growth in length than the proximal ulnar physis, and fixation of the two bones (in the actively growing dog, synostosis) can cause elbow malarticulation (Fig. 9A). Corrective osteotomy of the proximal radius has been used to treat dislocations in immature dogs. The procedure should be performed before extensive remodeling of the radial head prevents the establishment of some degree of congruency in the humeroradial joint. Following osteotomy, the radial head is reduced and fixed to the radial shaft with a small (0. 045 inch to 0.062 inch) pin(s). Excision of a small section of the radius at the osteotomy site may be required to achieve reduction. Unlike the ulnar osteotomy technique, this procedure does not allow correction of any deformity of the ulna (Fig. 9A and B). Radial Head Ostectomy. Radial head ostectomy has been used to treat chronic radial head dislocation. The procedure is simple to perform and has successfully provided relief of pain and near-normal use of the leg. The radial head is exposed through a lateral approach made between the common and lateral digital extensor muscles. 18 Following incision through the joint capsule and annular ligament, ostectomy is performed with an osteotome, Gigli saw, or ossilating saw (Fig. 10). 5 • 19 Arthrodesis. Arthrodesis is indicated in those cases in which previous treatment has failed or in which degeneration of the joint is advanced. 13 Prognosis. Results of treatment are not available in a sufficient number of cases to determine a prognosis. The prognosis with surgical treatment appears to be good for satisfactory use of the leg but guarded for the
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Figure 9. A, Craniocaudal view of radial head luxation in a 5-month-old Sibe rian Husky previously treated by reduction and screw fixation. Continued growth and synostosis of radius and ulna by screw fixation caused recurrence of the luxation. B , Postoperative radiographs show osteotomy and reduction of the radial head and fixation with a single pin. Note remodeling and degeneration of the elbow.
prevention of degenerative changes and long-te rm use of the leg without dysfunction. CONGENITAL ELBOW DISLOCATION AND OTHER SKELETAL ANOMALIES Luxation, subluxation, and joint laxity (arthrodysplasia) of the elbow have been reported comcomitantly with other congenital abnormalities. 1• 4 • 7 • 8 · 16 Congenital elbow dislocation commonly occurs with ectrodactyly or cleft hand deformity in dogs. t , 4 · 16 Nine of 15 cases of ectrodactyly reported in the literature had dislocation of the elbow in the same limb. In most of these cases, the primary elbow deformity seemed to be related to dislocation of the radius. Polyarthrodysplasia (congenital joint luxations) has been described in the dog and involved marked instability of multiple joints, including the elbows. Other skeletal anomalies that accompanied this condition included hypoplasia of the sesamoid bones, patellar ectopia, and absence of the distal ulnar epiphysis. 7 · 8 The complexity of the problems that exist with these multiple skeletal anomalies has prohibited treatment.
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Figure 10. Radial head ostectomy for treatment of chronic luxation.
SUMMARY Three categories of congenital elbow dislocations are described in the literature: (1) humeroulnar, (2) humeroradial, and (3) dislocation or joint laxity with other congenital anomalies. Congenital humeroulnar dislocation is a well-defined problem that occurs predominantly in small breeds of dogs and causes severe limb deformity and dysfunction. Early reduction and stabilization are simple to achieve and have provided good results. Radial head dislocations occur most often as a result of growth disturbance of the radius and ulna. There is a lack of conclusive information on congenital radial head dislocations. Regardless of the etiology, radial head dislocation causes rather mild deformity and lameness and can be treated by conservative management, surgical correction, or radial head ostectomy. Dislocation of the elbow may occur concurrently with other rare congenital anomalies and has been described with ectrodactyly and polyarthrodysplasia.
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REFERENCES l. Bingel SA, Riser WH: Congenital elbow luxation in the dog. J Small Anim Pract
18:445-446, 1977 2. Campbell JR: Nonfracture injuries to the canine elbow. JAm Vet Med Assoc 155:735-744, 1969 3. Campbell JR: Luxation and ligamentous injuries of the elbow of the dog. Vet Clin North Am 1:429-440, 1971 4. Carrig CB, Wortman JA, Morris EL, eta!: Ectrodactyly (split-hand deformity) in the dog. Vet Radio! 22:123-144, 1981 5. Dieterich HF: Repair of a lateral radial head luxation by radial head ostectomy. Vet Med Small Anim Clin 68:671-675, 1973 6. Flipo J: Treatment of dislocation of the canine elbow. Mod Vet Pract 45:46-51, 1964 7. Fox MW: Sesamoidean hypoplasia with distal ulnar hemimelia and arthrodysplasia. A multiple congenital skeletal anomaly in the dog. Vet Rec 75:938-939, 1963 8. Fox MW: Polyarthrodysplasia (congenital joint luxation) in the dog. JAm Vet Med Assoc 145:1204-1205, 1964 9. Grondalen J: Malformation of the elbow joint in an Afghan hound litter. J Small Anim Pract 14:83-89, 1973 10. Gurevitch R, Hohn RB: Surgical management of lateral luxation and subluxation of the canine radial head. Vet Surg 9:49-57, 1980 11. Johnson RG, Hampel NL: Elbow luxation. In Slatter DH (ed): Textbook of Small Animal Surgery. Edition l. Philadelphia, WB Saunders Co, 1985 12. Kene ROC, Lee R, Bennett D: The radiological features of congenital elbow luxation/subluxation in the dog. J Small Anim Pract 2(23):621-630, 1982 13. Lasser AS: Arthrodesis. In Slatter DH (ed): Textbook of Small Animal Surgery. Edition l. Philadelphia, WB Saunders Co, 1985 14. Miller ME, Christensen GC, Evans HE: Miller's Anatomy of the Dog. Edition 2. Philadelphia, WB Saunders Co, 1979 15. Milton JL, Horne RD, Bartels JE, eta!: Congenital elbow luxation in the dog. JAm Vet Med Assoc 175:572-582, 1979 16. Montgomery M, Tomlinson J: Two cases of ectrodactyly and congenital elbow luxation in the dog. JAm Anim Hosp Assoc 21:781-785, 1985 17. Pass MA, Ferguson JG: Elbow dislocation in the dog. J Small Anim Pract 12:327-332, 1971 18. Piermattei DL, Greeley RC: An Atlas of Surgical Approaches to the Bones of the Dog and Cat. Philadelphia, WB Saunders Co, 1979 19. Putnam RW, Archibald J: Excision of the canine radial head. Mod Vet Pract 49:32, 1968 20. Stevens DR, Sande RD: An elbow dysplasia syndrome in the dog. J Am Vet Med Assoc 165:1065-1069, 1974 21. Withrow SJ: Management of a congenital elbow luxation by temporary transarticular pinning. Vet Med Small Anim Clin 72:1597-1602, 1977 Department of Small Animal Surgery and Medicine College of Veterinary Medicine Auburn University Auburn, Alabama 36849