34th Annual Scientific Meeting proceedings

The breed of a patient with humeral intracondylar fissure (HIF) or HIF-associated condylar fracture will affect treatment decision making in a number of ways.

Size
The mainstay of treatment for HIF (and a critical component to get right for HIF-associated fractures as well) is appropriate transcondylar screw placement. Surgeons will have their own preferences for the type of screw used and the literature does not support one screw over another. The size of the screw is important however and larger breed patients will require a larger screw. The implant’s outer diameter is not a helpful measure when considering the size of a screw, since this does not relate to its strength and resistance to fatigue failure. Rather, the area moment of inertia  (AMI) should be assessed. AMI is related to the core diameter of the screw and for a cylindrical implant such as a screw AMI = pr⁴/4;  i.e. small increases in core diameter can result in large increases in strength. An AMI/body weight ratio > 3 has been advised to avoid implant failure¹. Based on this 4.5 cortical screws (AMI 4.0) should be reserved for dogs less than 12kg with screws with greater AMI used for heavier dogs.

Presentation of HIF
HIF has historically been associated with spaniel breeds and much of our understanding of HIF is based on how the condition affects these breeds. Over the past 5 years or so there has been a greater awareness of the impact of HIF on French Bulldogs. Spaniels and French Bulldogs with HIF tend to present differently and HIF may be managed differently in these breeds.  It is now accepted that in most spaniels HIF develops as a stress fracture in adult dogs, often resulting in lameness without complete condylar fracture². In French Bulldogs however HIF is more often identified in skeletally immature dogs presenting with condylar fracture. These dogs generally present at a median age of around 4 months and HIF has been identified in the contralateral (intact) condyle in 44-68% of dogs^3,4.  In these young French Bulldogs with HIF it is not clear if the HIF represents a delayed closure of the cartilaginous plate separating the two secondary ossification centres of the humeral condyle (i.e. akin to the original ‘incomplete ossification’ theory of HIF) or if in this breed the cartilaginous plate naturally closes later than we expect it to in other breeds. It may be the latter since these HIFs go on to heal in the majority of dogs without specific treatment⁵ which is not expected for the adult spaniels that present with HIF. Based on this evidence surgeons should not rush to place prophylactic transcondylar screws in immature French Bulldogs with HIF.

Surgical implications
Condylar morphology varies between breeds, especially between breeds as anatomically disparate as spaniels and French Bulldogs. This will have implications for transcondylar screw placement whether that be as part of a fracture repair or management of HIF in the absence of condylar fracture.  Landmarks for transcondylar screw placement have been published but are largely based on spaniels and larger breeds⁶. These landmarks have not been validated in French Bulldogs and so screw placement should be carefully planned in these dogs, ideally with the assistance of preoperative CT.

Several companies have either developed or are in the process of developing breed-specific anatomic plates for the humeral condyle, focusing on plates specific to spaniels and to French Bulldogs. These are not certain to be a good fit for every dog of these breeds with a humeral condyle fracture but in many dogs they areand in these dogs they can simplify and  shorten fracture surgery.

References

1. Carwardine D, Mather A, Schofield I, et al. Medial versus lateral transcondylar screw placement for canine humeral intracondylar fissures: A randomized clinical trial. Vet Surg. 2024;53(2):264-276. doi:10.1111/vsu.13993
2. Moores AP. Humeral Intracondylar Fissure in Dogs. Vet Clin North Am - Small Anim Pract. 2021;51(2):421-437. doi:10.1016/j.cvsm.2020.12.006
3. Anderson OJ, Langley-Hobbs SJ, Parsons KJ. Humeral condylar fractures and fissures in the French bulldog. Vet Surg. 2023;52(1):134-145. doi:10.1111/vsu.13907
4. Lopez De La Oliva P, Arnott L, Roses L, Marshall W, Arnott D. Humeral Condylar Fractures in French Bulldogs: Prevalence of Contralateral Intracondylar Fissure, Treatment, and Outcome. Vet Comp Orthop Traumatol. 2023:236-242. doi:10.1055/s-0044-1785446
5. Hutchings VC, Rutherford S. Computed tomographic re-evaluation of skeletally immature French bulldogs previously diagnosed with humeral intracondylar fissure: 12 cases (2018-2022). J Small Anim Pract. 2024;65(November):817-821. doi:10.1111/jsap.13768
6. Barnes DM, Morris AP, Anderson AA. Defining a safe corridor for transcondylar screw insertion across the canine humeral condyle: a comparison of medial and lateral surgical approaches. Vet Surg. 2014;43:1020-1031.