34th Annual Scientific Meeting proceedings

Fractures of the distal radius and ulna occur frequently in toy breed dogs, and have a historical high complication rate when inappropriate methods of fixation are used.^1-3 Fractures of the distal radius and ulna are a unique challenge to the small animal surgeon, however, with progress in management and the use of appropriate implants, rapid healing and minimal complications have be achieved,⁴ but major complications are still reported.⁵ Higher complication rates are often confounded by the inappropriate initial treatment of these fractures,^3,6 which is largely overlooked when citing or comparing outcomes between studies. Today, there are several techniques which provide the stable fracture fixation required for the duration of healing, and which are likely to result in success.

The high incidence of non-union in distal radius/ulna fractures treated with closed reduction and external coaptation was first reported in 1964.¹ In a series of 20 cases with non-union, 60% involved fractures of the radius and ulna with all but one occurring in a toy breed dog. Importantly, initial treatment at the time of injury consisted of closed reduction and external coaptation. All cases were revised with a plate and screws, but unfortunately, outcome of these cases is not provided.

The use of inappropriate implants and the revision of complications of previous attempts at repair are illustrated in 2 studies commonly cited to reflect the historical high complication rate encountered when managing fractures of the distal radius and ulna in toy breed dogs. One study (1980) reviews complications of diaphyseal fracture repair in general, with no particular focus on radius fracture toy breed dogs.² However, the results are still relevant as complications occurred most commonly in the radius and ulna, and toy-breed dogs were included in the study. The authors identify infection, inappropriately sized implants and the inappropriate application of implants as the major factors in the failure of the repairs.

The second (1999) is a series of 29 cases of distal radius/ulna fractures in toy- breed dogs, however, an important factor which is generally overlooked when citing this study is that 16/29 had been repaired previously with other fixation methods.³ Complications occurred in 12/22 of the fractures with follow-up radiographs with catastrophic complications occurring in 4/22 cases. It is important to note that all four fractures with catastrophic complications had previous attempts at fracture repair. Three of the fractures were initially treated with an IM pin and in one case external coaptation was used.

More recently (2022), it was shown that, in contrast to previous studies, fractures of the radius and ulna of toy breed dogs were not at increased risk of delayed and non- union.7 This study describes the prevalence of delayed and non-union in fractures of the distal radius and ulna in toy breed dogs, in contrast to older studies8,9 in which the frequency of delayed and non-union is reported. It is unclear from the inclusion criteria if revisions of previous failed fracture repairs were included in this study. The authors of this study acknowledge the limited number of studies available for comparison and suggest that recent advances in fracture fixation techniques are the likely reason for the improved outcome in these cases. Perhaps, after ~60 years it is possible to say that the historically high incidence of delayed and non-union has been drastically reduced by changes in the management and the use of appropriately sized implants in these cases. However, outcomes are variable and inconsistencies in reporting make it difficult to compare between techniques.

Below are brief summaries of selected reports describing different strategies for the management of fractures of the distal radius and ulna in toy-breed dogs. All are retrospective case series and are included to highlight differences in reporting.

Circular external skeletal fixation (CESF) was used in 20 fractures in 16 dogs (<5.0kg).¹⁰ Mean (Range) time to radiographic union was 71 days (30 days–120 days). Resorption of the ulna (n=7) and synostosis (n=10) between the radius and ulna were also noted. All fractures achieved union and no infection or fixation failure were reported. Proximal radial fracture occurred through a wire hole and a further 3 dogs fractured the ipsilateral antebrachium between 30 and 50 days after frame removal. Recurrent fracture was not considered to be directly associated with the fixation.

Eight straight and twelve notched head T-Locking Compression Plates with sizes of 2.0 mm (n = 13) and 2.4 mm (n = 7) were used in a series of 20 toy and miniature breed dogs.⁴ At least one screw was locked in each fragment. Mean±SD (Range) time to radiographic union in18/20 cases was 6.9 ± 2.5 weeks (4–12 weeks). A single complication postoperative infection requiring plate removal was recorded. Excellent outcome in all cases but unclear if all cases were primary fracture repairs.

AO 1.5/2.0 mm veterinary mini ‘T’-plate were used in 14/63 cases with 10/14 primary repairs and 4/10 revision surgeries (all atrophic non-unions).⁶ All fractures were repaired in compression and all holes were filled in all plates except in one case. All primary repairs showed radiographic evidence of radial fracture healing at 4-6 weeks and an excellent outcome was reported in 6/8 cases available for follow up. Revision surgeries showed radial healing between 4-10 weeks with none reported to have an excellent outcome.

Orthogonal plating with non-locking cuttable plates (1.3mm and 1.5mmm with various screw diameters (between 1mm-2mm)) were used in 15 primary, and 5 revision repairs of distal radius/ulna fractures in toy-breed dogs.¹¹ Repair was successful in 19/20 cases and all dogs returned to full function. Mean±SD (Range) time at final radiographic follow up was 104.7 ± 67.1 days (35 to 248 days). Synostosis was seen in one case and refracture occurred in one dog after cranial plate removal.

Six 1.5-mm Locking Adaption plates and seven 2.0-mm LC-DCPs were used in a series of 13 distal radial and ulnar fractures in 12 dogs.⁵ Three major complications occurred in the 1.5mm locking adaption plate group (one plate fracture, one screw pull-out, and one fracture through a distal screw hole in which no locking screws were used). One major complication occurred in the 2.0-mm LC-DCP group due to fracture through a screw hole.

Above is a small sample of many similar reports using a wide variety of strategies and outcomes. It is unclear if any single technique is superior to all others or if compression of the fracture provides any advantage.

References cited

1. Vaughan LC. A clinical study of non-union fractures in the dog. Journal of Small Animal Practice. 1964;5(2):173-177. doi:doi.org/10.1111/j.1748-5827.1964.tb04233.x
2. Hunt JM, Aitken ML, Denny HR, Gibbs C. The complications of diaphyseal fractures in dogs: a review of 100 cases. J Small Anim Pract. Feb 1980;21(2):103-19. doi:10.1111/j.1748-5827.1980.tb01221.x
3. Larsen LJ, Roush JK, McLaughlin RM. Bone plate fixation of distal radius and ulna fractures in small- and miniature-breed dogs. J Am Anim Hosp Assoc. May-Jun 1999;35(3):243-50. doi:10.5326/15473317-35-3-243
4. Gibert S, Ragetly GR, Boudrieau RJ. Locking compression plate stabilization of 20 distal radial and ulnar fractures in toy and miniature breed dogs. Veterinary and Comparative Orthopaedics and Traumatology. 2015-01-01 2015;28(6):441-447. doi:10.3415/VCOT-15-02-0042
5. Nelson T, Strom A. Outcome of Repair of Distal Radial and Ulnar Fractures in Dogs Weighing 4 kg or Less Using a 1.5-mm Locking Adaption Plate or 2.0-mm Limited Contact Dynamic Compression Plate. Veterinary and Comparative orthopaedics and Traumatology. 2017-01-01 2017;30(6):444-452. doi:10.3415/VCOT-17-01-0005
6. Hamilton M, Hobbs S. Use of the AO veterinary mini "t"-plate for stabilisation of distal radius and ulna fractures in toy breed dogs (vol 18, pg 18, 2005). Veterinary and Comparative orthopaedics and Traumatology. 2005-01-01 2005;18(2):114-114.
7. Marshall W, Filliquist B, Tzimtzimis E, et al. Delayed union, non-union and mal- union in 442 dogs. Veterinary Surgery. 2022-08-27 2022;51(7):1087-1095. doi:10.1111/vsu.13880
8. Phillips IR. Survey of bone fractures in the dog and cat. Journal of Small Animal Practice. 1979-01-01 1979;20(11):661-674. doi:10.1111/j.1748-5827.1979.tb06679.x
9. Atilola M, Sumner-Smith G. Nonunion fractures in dogs. 1984;
10. Piras L, Cappellari F, Peirone B, Ferretti A. Treatment of fractures of the distal radius and ulna in toy breed dogs with circular external skeletal fixation: a retrospective study. Veterinary and Comparative Orthopaedics and Traumatology. 2011-01-01 2011;24(3):228-235. doi:10.3415/VCOT-10-06-0089
11. Higuchi M, Katayama M. Clinical outcomes of orthogonal plating to treat radial and ulnar fractures in toy-breed dogs. Journal of Small Animal Practice. 2021-07-14 2021;62(11):1001-1006. doi:10.1111/jsap.13397