Introduction

Congenital elbow luxation is an uncommon orthopedic disease in dogs and has been classified into three subtypes according to variations in luxation anatomy.¹ Type I (humeroradial) is characterized by a lateral or caudolateral luxation of the radial head with the ulna in a normal location. Type II (humeroulnar) involves disruption of the humeroulnar articulation with lateral rotation and luxation of the ulna, with or without radial head luxation. Type III (combined humeroradial and humeroulnar) consists of luxation of the radius and ulna. Type II luxation occurs most commonly in small-breed dogs such as the Yorkshire terrier, Boston terrier, Shetland sheepdog, miniature poodle, Pekingese, miniature pinscher, Pomeranian, pug, cocker spaniel, English bulldog, and Chihuahua.^2–4 There is little information in the literature regarding the treatment of this condition.⁴

Treatment options consist of both conservative and surgical management. Although conservative treatment with closed reduction and immobilization may be anecdotally selected for dogs with mild clinical signs, there are no previous reports of its efficacy. In patients with congenital elbow luxation, early reduction is necessary, as the development of a healthy joint will be disrupted if functional joint motion is not achieved.⁵ Several surgical treatments that combined closed or open reduction with joint stabilization have been reported.^3,4,6 Open reduction and joint stabilization involve ulnar osteotomy and radioulnar synostosis, transposition of the olecranon, and trochlea and trochlear notch reconstruction.^3,4,6,7 However, these are highly invasive methods that compromise the skeletal morphology and/or cause articular cartilage injury. In addition, a temporary transarticular pin or external fixator for maintenance of reduction are undesirable in very young dogs because the methods immobilize the elbow joint during the treatment period.

In this case report, a 10 wk old dog with severe congenital type II luxation was treated using antiluxation “stopper” pins,⁸ which were placed into the lateral humeral condyle. This technique maintains reduction without compromising the range of motion. This simple and less invasive technique provides an alternative option for congenital type II luxation in very young dogs. We describe the surgical technique and long-term outcome of a dog treated with antiluxation pins for congenital type II luxation.

Case Report

A 10 wk old 1.9 kg male shih tzu was presented with a 5-day history of non–weight-bearing lameness of the right thoracic limb (Supplementary Video I). There was no history of trauma. On physical examination, the proximal ulna of the right thoracic limb was located laterally with limited range of motion of the right elbow in both flexion and extension, and manipulation of the elbow was painful. Radiographs of the right elbow joint revealed lateral luxation of the humeroulnar joint, with lateral rotation of the proximal ulna and without concurrent luxation of the radial head (Figures 1A, B). There was no radiographic evidence of an antebrachial deformity or degenerative joint disease. Orthopedic and radiographic findings of the left thoracic limb and pelvic limbs were unremarkable.

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With the dog positioned in left lateral recumbency, the surgical approach to the lateral humeroulnar part of the right elbow joint was performed. The small skin incision was centered around the lateral humeral epicondyle and extended to the lateral epicondylar crest and the proximal radius. After gentle elevation of the triceps brachii fascia, the anconeus muscle was exposed and incised at its periosteal origin on the lateral epicondylar crest. The incision of the origin of the anconeus muscle exposed the caudolateral compartment of the elbow joint. After the joint capsule and fibrous tissue were incised, manual reduction of the ulna was achieved; however, the reduction was not maintained. With the ulna reduced, a 1.6 mm positive-profile threaded pin^a was placed into the lateral humeral condyle in a caudal to cranial direction, attempting to avoid the distal humeral growth plate. The joint was placed in range of motion to determine whether the reduction was maintained throughout the range of motion with this pin in the humeral condyle. The joint showed no obvious abnormal motion, and pin impingement to the soft tissues was not noted. When the joint was fully flexed, the joint stability was questionable; therefore, a second pin was placed distal to the first pin (Figures 1C–E). The shaft to these two pins had contact with the lateral bony surface of the ulna. Both pins were cut approximately 1.5 cm from the insertion points, and the surgical site was routinely closed. Postoperative radiographs demonstrated reduction of the joint and satisfactory positioning of the implants (Figures 1C, D). Postoperative analgesia was continued with morphine^b (0.5 mg/kg, intramuscularly) for 48 hr. A modified Robert-Jones bandage was applied for 12 days. Five days after surgery, the dog was bearing weight on the right thoracic limb. On 30-day postoperative examination, radiographs indicated loosening of the proximal pin, and both pins were removed (Figures 2A, B). The dog showed neither lameness nor pain on palpation of the right elbow at 44 days postoperatively. At the final follow-up at 6.8 yr (82 mo) postoperatively, the dog showed an excellent function without noticeable lameness (Supplementary Video II), with only a mild restriction of range of motion of the right elbow (50° in flexion and 160° in extension; normal range, 34 to 38° in flexion and 164 to 167° in extension⁹). Radiographic assessment confirmed mild humeroulnar incongruity and degenerative joint disease on the right elbow (Figures 2C, D).

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Informed consent was obtained from the dog owner to do the novel procedure and to seek publication of the report. The dog was clinically treated according to contemporary standards of care.

Discussion

In this report, a 10 wk old skeletally immature dog with congenital type II elbow luxation was treated with antiluxation stopper pins, which maintained reduction and joint movement without compromising range of motion. This pin method appeared to promote the relatively normal joint development and maintain long-term normal limb function without major complications.

Previously reported methods using transarticular pinning and external fixators inevitably immobilize the elbow joint for maintenance of reduction.⁴ Joint motion is allowed only after the implant removal, and these methods are likely to disrupt the proper development of the joint structure and function, especially in very young dogs. Prolonged immobilization decreases synovial fluid production as well as cartilage stiffness and thickness and leads to degenerative joint disease.^10–13 Maintaining the range of motion and the normal walking activities would help to minimize the formation of periarticular fibrosis and adhesions.

If diagnosis and treatment are delayed in dogs with congenital elbow luxation, highly invasive methods may be required. Therefore, early reduction and maintenance of reduction without compromising range of motion would allow early postoperative weight bearing and return to good limb function, leading to the development of a healthier joint. Weight bearing and joint motion minimize the risk of degeneration of articular cartilage, bone deformity, and muscle atrophy. This novel technique reported here is aimed to prevent reluxation and maintains reduction without compromising range of motion while minimizing the impact of immobilization on joint homeostasis. Therefore, we propose that this method is particularly useful in skeletally immature dogs with congenital type II elbow luxation.

The stopper effect of the pin depends on its insertion angle and plane. Because the normal elbow joint has the wide range of motion of ∼130°,⁹ the two pins were inserted at different angles to maintain reduction and prevent reluxation in both full extension and flexion. In a normal humeroulnar joint, the joint congruity, the anconeal process, and the olecranon fossa restrict the movement of the joint to a sagittal plane as a hinged joint. When these structures are abnormal, the single pin would not restrict the joint motion in the sagittal plane. The second pin was inserted so that the plane of the two pins aligned parallel to the sagittal plane.

A major limitation is the lack of quantitative assessment of functional recovery by kinematic or kinetic analysis, as subtle lameness or subtle limb dysfunction could be missed with subjective gait evaluation only. The surgical outcomes in cases with severe morphological abnormalities or degenerative joint disease remain unknown, and the appropriate age for surgical intervention also remains unclear. Further work is necessary to determine how morphological abnormalities, degree of degenerative joint disease, or age affect the feasibility of treatment.

Conclusion

A novel method of antiluxation pins provides an alternative for less invasive treatment for congenital humeroulnar luxation (type II) in skeletally immature dogs. This technique allows maintenance of reduction without compromising range of motion and early and satisfactory return to limb function.