34th Annual Scientific Meeting proceedings

Define failure!
Our efforts to repair these fractures may fail in many ways.  Complications are forms of failure - re-fracture, implant failure and infection for example.  Their significance depends on how they compromise bone healing and functional outcomes.  They may, but do not always, lead to delayed, non- or mal-union, and associated poor function.  Failure can be temporary – complications may be managed, ultimately leading to union and acceptable functional outcome.  True failure probably means complications that cannot be, or are not managed, and a catastrophic outcome such as persistent significant lameness, amputation or euthanasia.

Re-fracture, implant failure and infection
A recent study of radius/ulna fractures in small breed dogs found re-fracture occurred in 3.5% of dogs at the distal screw hole of bone plates left in situ, after fracture union.  Where the bone plate was removed, 12.5% re-fractured at the original fracture site¹.  The best strategy for managing re-fracture will depend in part on the location within the bone.  Those at the level of a distal screw hole can be challenging because of limited distal bone stock.  Trans-articular external skeletal fixation may be useful where it is not possible to revise with plate fixation.  Reducing the screw size distally may help prevent this complication¹.  The significance of implant failure, and the requirement for revision, depends on concomitant complications such as infection, as well as bone healing outcome and function.  Infection may be a rare cause of non-union:  Two data sets did not contain any infections from a combined total of 122 toy breed radius and ulna fractures^2,3.  One case report does describe management of infection with oral antimicrobials prior to debridement, stabilisation and grafting in a single procedure⁴.  Staged debridement and definitive stabilisation can also be considered.

Delayed, mal- and non-union
Delayed union is not failure, as union is achieved, albeit slower than expected.  Mal-union is failure where it causes significant lameness, but revision to correct the deformity is possible.  Non-union is probably to many surgeons almost synonymous with failure, but again all is not lost!  If the principles of managing infection, stabilizing and grafting are followed, non-unions may of course be successfully treated, with dogs returning to full or acceptable function in the long term⁵.  The type of stabilization and graft have been the subject of recent publications.  Bone morphogenetic protein-2 is a popular osteoinductive agent for managing non-union in toy breeds, typically combined with internal fixation^4,5.  Good outcomes have also been shown recently with traditional corticocancellous grafting and circular external skeletal fixation, and with a novel caudal vertebral autograft^6,7.  Finally, for severe radial atrophy in a toy poodle, a novel centralisation technique has been described, transposing distal radius to osteotomised ulna, with a good outcome⁸. 

References

1. Muroi N, Kanno N, Harada Y et al. (2024) A retrospective study of risk factors associated with refracture after repair of radial–ulnar fractures in small-breed dogs.  Vet Comp Orthop Traumatol; DOI https://doi.org/10.1055/s-0044-1790218
2. Marshall WG, Filliquist B, Tzimtzimis E et al. (2022) Delayed union, non-union and mal-union in 442 dogs.  Vet Surg; 1-9, DOI: 10.1111/vsu.13880
3. Aikawa T, Miyazaki Y, Shimatsu T et al. (2018) Clinical outcomes and complications after open reduction and internal fixation utilizing conventional plates in 65 distal radial and ulnar fractures of miniature- and toy-breed dogs.  Vet Comp Orthop Traumatol; 31:214–217.
4. Vezzoni L, Abrescia P, Vezzoni A (2021) Internal radioulnar fixation for treatment of nonunion of proximal radius and ulna fractures in a toy breed dog. VCOT Open; 4:e24–e31.
5. Castilla A, Filliquist B, Spriet M et al. (2023) Long-term assessment of bone regeneration in nonunion fractures treated with compression-resistant matrix and recombinant human bone morphogenetic protein-2 in dogs. Vet Comp Orthop Traumatol; 36:29–38.
6. Camilletti P, D’Amato M (2023) Long-term outcomes of atrophic/oligotrophic non-unions in dogs and cats treated with autologous iliac corticocancellous bone graft and circular external skeletal fixation: 19 cases (2014-2021). J Sm Anim Pract; 65, 123-131
7. Goto M, Ikeda H (2022) Use of an autologous bone graft derived from three caudal vertebrae for reconstruction in a dog with radioulnar atrophic nonunion and osteomyelitis. VCOT Open;5:e93–e97.
8. Camilletti P, D’Amato M (2024) Successful centralisation technique for treatment of post-traumatic absence of the radial shaft in a dog. J Sm Anim Pract; 65, 409-412.