History
A 4-month-old 13.45-kg (29.6-lb) sexually intact female Shar-Pei was examined for progressive left forelimb lameness of > 1 month's duration. Pertinent history included treatment for a dog bite to the left forelimb 4 weeks prior to examination. At that time, radiography revealed mild soft tissue swelling of the distal aspect of the limb with no bone or carpal and elbow joint abnormalities detected. The dog was administered carprofen (2.6 mg/kg [1.2 mg/lb], PO, q 12 h), tramadol (1.8 mg/kg, [0.8 mg/lb], PO, q 6 h), amoxicillin trihydrate and clavulanate potassium (17.9 mg/kg [8.14 mg/lb], PO, q 12 h), and enrofloxacin (2.4 mg/kg [1.1 mg/lb], PO, q 24 h) for 3 weeks. The distal aspect of the forelimb remained swollen after completion of the course of antimicrobials.
Physical examination revealed moderate left forelimb lameness. A firm swelling was palpated at the distolateral aspect of the left forelimb, and the left elbow joint had mild effusion. The remaining findings on physical examination were unremarkable. A CBC revealed leukocytosis (21,600 leukocytes/μL; reference range, 4,000 to 15,500 leukocytes/μL) characterized by neutrophilia (16,632 neutrophils/μL; reference range, 2,060 to 10,600 neutrophils/μL) with mild toxic change and monocytosis (2,160 monocytes/μL; reference range, 0 to 840 monocytes/μL). The dog also had thrombocytosis (460,000 platelets/μL; reference range, 170,000 to 400,000 platelets/μL). The patient was sedated with dexmedetomidine (5 μg/kg [2.3 μg/lb], IV) and butorphanol (0.2 mg/kg [0.09 mg/lb], IV), and radiographs of the left forelimb were obtained (Figure 1).
Lateral (A) and craniocaudal (B) radiographic views of the left forelimb of a 16-week-old sexually intact female Shar-Pei evaluated because of progressive left forelimb lameness.
Citation: Journal of the American Veterinary Medical Association 241, 11; 10.2460/javma.241.11.1429
Lateral (A) and craniocaudal (B) radiographic views of the left forelimb of a 16-week-old sexually intact female Shar-Pei evaluated because of progressive left forelimb lameness.
Citation: Journal of the American Veterinary Medical Association 241, 11; 10.2460/javma.241.11.1429
Lateral (A) and craniocaudal (B) radiographic views of the left forelimb of a 16-week-old sexually intact female Shar-Pei evaluated because of progressive left forelimb lameness.
Citation: Journal of the American Veterinary Medical Association 241, 11; 10.2460/javma.241.11.1429
Determine whether additional imaging studies are required, or make your diagnosis from Figure 1—then turn the page →
Radiographic Findings and Interpretation
The diaphysis of the ulna is severely thickened with poor corticomedullary definition (Figure 2). The margins of the bone are smooth. The distal ulnar physis is wide and irregular with a triangular lucency extending proximally into the distal metaphysis. The humeroulnar joint is severely incongruent (subluxated), with the ulnar trochlear notch having an elliptical shape resulting in widening of the humeroulnar joint space and a large step between the radial head and medial coronoid process of the ulna. Best seen on the lateral view, the radius is slightly bowed with mild cranial convexity. Additionally, the distal aspect of the forelimb is mildly laterally deviated with external rotation and supination. The soft tissues of the forelimb are mildly diffusely swollen. These findings are most consistent with chronic osteomyelitis and suspect physitis resulting in asynchronous growth of the radius and ulna and subsequent elbow incongruity (subluxation) and angular limb deformity (carpal valgus).
Same radiographic images as in Figure 1. A—Notice the severe diaphyseal thickening of the ulna (closed white arrow), wide and irregular distal ulnar physis, and lucency extending from the physis into the distal metaphysis (open white arrow). Also notice the subluxation of the humeroulnar joint with an elliptical shape of the trochlear notch of the ulna (black arrowheads) and step between the radial head (closed black arrow) and medial coronoid process of the ulna (open black arrow). The radius is slightly curved with cranial convexity (white arrowheads). B—The distal aspect of the forelimb is mildly laterally deviated (carpal valgus; indicated by bent line), and the humeroulnar joint is wide (white arrow).
Citation: Journal of the American Veterinary Medical Association 241, 11; 10.2460/javma.241.11.1429
Same radiographic images as in Figure 1. A—Notice the severe diaphyseal thickening of the ulna (closed white arrow), wide and irregular distal ulnar physis, and lucency extending from the physis into the distal metaphysis (open white arrow). Also notice the subluxation of the humeroulnar joint with an elliptical shape of the trochlear notch of the ulna (black arrowheads) and step between the radial head (closed black arrow) and medial coronoid process of the ulna (open black arrow). The radius is slightly curved with cranial convexity (white arrowheads). B—The distal aspect of the forelimb is mildly laterally deviated (carpal valgus; indicated by bent line), and the humeroulnar joint is wide (white arrow).
Citation: Journal of the American Veterinary Medical Association 241, 11; 10.2460/javma.241.11.1429
Same radiographic images as in Figure 1. A—Notice the severe diaphyseal thickening of the ulna (closed white arrow), wide and irregular distal ulnar physis, and lucency extending from the physis into the distal metaphysis (open white arrow). Also notice the subluxation of the humeroulnar joint with an elliptical shape of the trochlear notch of the ulna (black arrowheads) and step between the radial head (closed black arrow) and medial coronoid process of the ulna (open black arrow). The radius is slightly curved with cranial convexity (white arrowheads). B—The distal aspect of the forelimb is mildly laterally deviated (carpal valgus; indicated by bent line), and the humeroulnar joint is wide (white arrow).
Citation: Journal of the American Veterinary Medical Association 241, 11; 10.2460/javma.241.11.1429
Treatment and Outcome
The owner declined an initial recommendation for surgical intervention, and treatment with carprofen and tramadol was continued. The patient was reevaluated 2 weeks later because of continued lameness of the left forelimb, and radiography was repeated; radiographic findings were unchanged. Because of the concern about the mild carpal valgus as well as persistent lameness, the patient was admitted for surgical treatment. An approximately 2.5-cm long segment of ulna, including the distal physis, metaphysis, and diaphysis was excised. A fat graft harvested from the falciform ligament was placed in the resulting defect. The excised segment of bone was submitted for histologic examination. Tissue samples obtained at surgery were also submitted for bacterial culture, the results of which were negative for both aerobic and anaerobic growth. Histologic examination revealed disordered formation of trabecular bone, adjacent nodular irregularity of the physeal cartilage, and a linear zone of fibrosis in the physeal stroma. The zone adjacent to the physis of periosteal bone formation was of irregular thickness with random foci of ossification. The linear zone of fibrosis indicated premature closure of the ulnar physis, and the irregular periosteal bone formation correlated with the radiographic finding of severe diaphyseal thickening with loss of corticomedullary definition. These histopathologic findings were consistent with disruption of the ulnar physis.
Eight weeks following surgery, the lameness was resolved. On follow-up radiography, the ostectomy gap was not bridged by new bone formation. The previous ulnar sclerosis and diaphyseal thickening were markedly decreased. The radius remained mildly curved and the humeroulnar joint remained subluxated, although the degree of radial curvature may be a normal variant for this patient. In addition, there was mild formation of new bone (osteoarthritis) on the nonarticular surface of the anconeal process. On follow-up at 8 months after surgery, the dog had no complications associated with surgery and no lameness was reported.
Comments
Premature closure of the distal ulnar physis is the most common development following physeal injury.1 The distal ulnar growth plate in dogs is conically shaped, making it particularly prone to compression injury1; however, disruption of normal endochondral ossification because of any cause (eg, traumatic, infectious, metabolic, nutritional, or developmental) may result in stunted longitudinal growth of the ulna. A shortened, slowly growing ulna places constraints on the radius, resulting in curvature of the radius along with valgus deformity at the level of the carpus. Additionally, as the radius continues to grow, the proximal portion of the ulna is constrained at the elbow joint, resulting in joint incongruity (subluxation). This is seen radiographically as elongation of the ulnar trochlear notch, with the notch having an elliptical rather than semicircular shape; distal displacement of the ulna with a step visible between the radial head and medial coronoid process of the ulna and a wide humeroulnar joint space is also observed. On radiographic evaluation, widening of the humeroulnar joint space must be interpreted with caution because artifactual widening may be seen owing to positioning.
Recognition of a valgus deformity and elbow subluxation radiographically and on physical examination is necessary for proper patient management. Surgical management of ulnar physeal injuries aims to minimize the consequences of growth discrepancy of the radius and ulna. If detected prior to maturity, excision of the ulnar physis releases constraint on the radius, preserving length and elbow joint congruency.2,3 In immature animals, placement of an autogenous fat graft in the ostectomy site prevents bridging of new bone, which would effectively restore the presurgical state.4
In this patient, premature closure of the distal ulnar physis likely resulted from osteomyelitis and suspected physitis, which may represent extension of cellulitis of the forelimb into the underlying bone or hematogenous spread of infection. Lack of concurrent radiographic changes along the radius supports a hematogenous route of infection. The negative bacterial culture results are assumed to be either a false-negative result due to concurrent antimicrobial treatment or a true result supporting resolution of the underlying infection.
1. Boudrieau RJ. Fractures of the radius and ulna. In: Slatter D, ed. Textbook of small animal surgery. 3rd ed. Philadelphia: Saunders, 2003;1953–1972.
2. Samoy Y, Van Ryssen B, Gielen I, et al. Elbow incongruity in the dog; review of the literature. Vet Comp Orthop Traumatol 2006;19:1–8.
3. Loewen KG, Holmberg DL. Surgical management of premature closure of the distal ulnar growth plate in a growing dog. Can Vet J 1982;23:113–116.
4. Craig E. Autogenous fat grafts to prevent recurrence following the surgical correction of growth deformities of the radius and ulna in the dog. Vet Surg 1981;10:69–76.
