Image Gallery: Angular Deformities

Figure 1. Radial valgus and external torsion.

Physeal trauma is a common cause of ALD, particularly when paired bones are involved. Distal forelimb trauma in immature patients can cause a compression injury (Salter V fracture)² to the conical-shaped distal ulnar physis, leading to premature closure of the distal ulnar physis. This results in cessation of ulnar growth. Although the radius will continue to grow in affected patients, valgus deviation, cranial bowing of the radius, and torsional deformity can typically develop as a result of the constraining effect of the ulna.³

Image courtesy of Derek B. Fox, DVM, PhD, DACVS, University of Missouri

Figure 2 (A and B). Grade 4 medial patellar luxation.

Craniocaudal radiograph of the hindlimbs of a Chihuahua with grade 4 medial patellar luxation of the right hindlimb (A). Note the femoral varus and compensatory tibial valgus, as well as the medial location of the patella in the soft tissues. There was also a grade 3 medial patellar luxation of the left hind limb. Despite limb extension, femoral varus and severe (90 degrees) internal rotation of the tibia of the right hind limb made positioning for pre-operative radiographs difficult.  This dog had a closing wedge ostectomy of the distal femur as well as trochlear block recession, tibial tuberosity transposition, and an anti-rotational suture in the tibia. Note that the postoperative radiograph demonstrates improved positioning and joint alignment (B).

Medial patellar luxation can cause medial displacement of the stifle extensor mechanism and lead to ALD. In immature dogs, tension of the extensor mechanism on the medial aspect of the limb causes compression of the medial aspect of the distal femoral physis, slowing growth and leading to varus deformity of the distal femur, as there is no restriction in bone growth on the lateral aspect of the physis.⁴ This is often accompanied by compensatory valgus deformity of the proximal tibia. Patients with grades 3 and 4 medial patellar luxation frequently have significant bony deformities that require surgical correction of the patellar luxation.

Figure 3 (A and B). Varus deformities of the radius and ulna.

Craniocaudal (A) and lateral (B) radiographs of the right antebrachium in a mature dog with varus deformities of the radius and ulna. Note that the joints proximal (elbow) and distal (carpus) to the deformity are malaligned (black lines on craniocaudal view).

Diagnosis of ALD is based on physical examination findings and radiographic evaluation. Well-positioned radiography is essential for accurate assessment of limb deformities and must include at least 2 orthogonal views of the affected limb, along with the joints proximal and distal to the affected area. Radiography can also include views of the contralateral limb for comparison and surgical planning. Computed tomography with 3D reconstruction and printing of 3D models⁵ can greatly help in presurgical planning for correction of severe ALDs.

Figure 4 (A and B). Corrective osteotomy.

Craniocaudal (A) and lateral (B) radiographs obtained 12 weeks after corrective radial/cylindrical osteotomy of the radius of the same dog shown in previous image. An osteotomy of the ulna was also performed to facilitate rotation of the distal segment of the radius.

Because surgical planning and correction can often be complex, referral to a specialist surgeon for evaluation and treatment is advised. Surgical goals include reestablishment of limb length, alignment, and correction of joint incongruency. The type of surgical procedure may vary, depending on patient age, severity, and location of the deformity. In immature dogs with significant growth potential remaining, releasing the site of growth constraint may limit the development of further deformities (eg, partial distal ulnar ostectomy to treat premature closure of the distal ulnar physis). In other patients, angular deformities and limb length discrepancies may be corrected over time, using circular ring fixators and motors. It is, therefore, important to recognize an ALD or the potential for ALD to develop (eg, after physeal trauma) as early as possible. In mature patients, single-stage angular and/or torsional corrections can include wedge resections or opening osteotomies and stabilization with internal or external fixation.

Figure 5. Young adult dog with bilateral antebrachial varus deformities secondary to fracture malunions.

Because ALDs usually result from physeal trauma/compression or primary abnormalities in endochondral ossification, they develop in immature patients. However the abnormalities may not present for veterinary evaluation until after the patient has matured. Clinical signs can result from loss of limb alignment and/or incongruency of the joints proximal and/or distal to the deformity. Evaluation may reveal pain, lameness, joint effusion, crepitus, decreased range of motion, shortening of the limb, and a variety of deformities, including valgus/varus, torsional, or cranial/caudal bowing of the bone or limb.

Figure 6 (A and B). Preoperative antebrachial varus.

Craniocaudal (A) and lateral (B) radiographs of the left antebrachium of previous dog prior to surgical correction.

Figure 7 (A and B). Preoperative antebrachial varus.

Craniocaudal (A) and lateral (B) radiographs of the right antebrachium of previous dog prior to surgical correction.

Figure 8. Correction of antebrachial deformities of previous image.

Bilateral hybrid fixators to correct bilateral antebrachial deformities after ulnar and radial ostectomies.

Prognosis depends on patient age at presentation, severity of the deformity, and presence or absence of secondary osteoarthritis and soft tissue abnormalities.^6,7 Early identification and appropriate treatment offer the best chance for successful return to function.