All anatomical locations can be subject to ALD, or trauma that result in an angular deformity but the majority of cases we see fall into four categories (See below).
The human surgeon ‘Paley’ created certain principles relating to angular corrective surgery which work to establish the location or CORA (centre of rotation and angulation) from which calculations can be made about the magnitude of an ALD and how to correct it. Planning and execution of these procedures requires surgeons to have significant advanced training (such as that provided on the AO courses) to ensure outcomes are successful. We will often use a custom 3D printed saw and reduction guides for these cases to help maximise execution.
Short Ulnar Syndrome
Perhaps the simplest ALD condition to manage and most commonly encountered. Short Ulnar Syndrome occurs when the distal ulnar physis stops growing prematurely whilst the radius continues at a normal rate. The consequences of this are that it often causes an articular interference (incongruence) at the elbow joint as well as a ‘bow string’ effect of the ulnar (pulling the radius laterally and caudally) creating an arced shape to the bone which is relatively straight in normal circumstances. This is a condition seen more commonly in chondrodsytrophic breeds such as Miniature Dachshunds and Basset Hounds but can occur in Cocker Spaniels and other breeds.
Treatment is typically via a proximal ulnar osteotomy (PUO). This is usually executed in a way to maximise bone contact following the osteotomy and so the cut is bi-oblique. The osteotomy is not stabilised and so forces from the triceps muscle encourage the ulnar to sit in a more natural position at the level of the elbow joint. This ‘dynamic’ reduction results in healing by secondary bone healing. Read more on the aftercare here.
Pes Varus.
This ALD is largely limited to Miniature Dachshunds where there is early cessation of growth in the medial aspect of the distal tibial physis. The resultant continued growth of the rest of the physis means that there is typically a uniplanar varus deformity to the hindlimb. The pes (foot) is angled internally relative to the tibia. This is most commonly seen unilaterally but it can present bilaterally. Dogs will often compensate well, though we tend to see a significant improvement in function following surgical correction. It is believed that corrective surgery is likely to reduce stress and osteoarthritis in the tarso-crural joint which is loaded eccentrically. You can read about a case we have treated bilaterally for this on our Instagram account.
Antebrachial radial procurvatum and carpal valgus.
This ALD is characterised by a cranial curvature of the radius and lateral bowing of the carpus. Corrective surgery for this ALD is managed via an opening wedge osteotomy on the medial aspect of the distal radius which is filled with bone graft and stabilised with two locking plates. External skeletal fixators are sometimes also used (Chau and Wilson, 2022).
Femoral varus and torsion.
We commonly see femoral deformity as a medial or lateral patella luxation. Most frequently this is a higher grade (III and IV) medial luxation in dogs with distal femoral varus deformities. Without effective management of these deformities it is often not possible for the traditional technique of sulcoplasty, tibial tuberosity transposition and soft tissue imbrication to effectively stabilise the patella.
Corrective surgery involves planning using well positioned radiographs or a CT scan. Typically, a lateral closing wedge osteotomy is performed at the level of the CORA and this is stabilised with a laterally applied locking plate.
There are published base values for aLDFA recognised in certain breeds (eg. Labrador 97 degree), but we do not know the ‘true normal’ given the breed variation. Surgeon experience and surgical planning are key here to achieving a successful goal in realigning the patella mechanism with the distal femoral sulcus to achieve normal limb function.
References
Aghapour M, Bockstahler B, Vidoni B. Evaluation of the Femoral and Tibial Alignments in Dogs: A Systematic Review. Animals. 2021; 11(6):1804. https://doi.org/10.3390/ani11061804
Chau L, Wilson L. Pes varus correction in dachshunds with mini hybrid external skeletal fixators. Aust Vet J. 2022 Apr;100(4):135-145. doi: 10.1111/avj.13139. Epub 2021 Dec 14. PMID: 34907526.
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