Cuttable plate fixation for small breed dogs with radius and ulna fractures: Retrospective study of 31 dogs

Abstract

This retrospective study evaluated complication rates for radius and ulna fractures in small breed dogs in which 1.5 mm to 2.7 mm cuttable bone plates were used for internal fixation. The medical records of all cases from 2004 to 2011 that were presented to our clinic were reviewed. Inclusion criteria were: dogs with body weight < 9 kg, fracture of the radius and ulna with open reduction, and internal fixation utilizing a cuttable bone plate. Thirty-four fractures in 31 dogs met the inclusion criteria. Of 25 dogs that were available for follow-up, all achieved union, minor complications occurred in 9, and major complications occurred in 8. External coaptation was responsible for complications in 8 cases and the need for coaptation needs to be investigated. Excluding minor complications, 32% of patients required at least 1 additional surgery or additional hospitalization. All but 2 of the dogs returned to full function. The 1.5 mm straight plate was successfully used in all dogs with a body weight of 0.9 to 2.6 kg.

Introduction

Radius and ulna fractures represent the third most common fractures in dogs and account for approximately 17% of all fractures in dogs, with many of these occurring in small breeds (1). Although various techniques can be used for the treatment of radius and ulna fractures in small breed dogs, bone plating remains one of the most frequent methods of stabilization for these fractures. In a retrospective study of 22 small and miniature dogs with radial and ulna fractures treated with bone plates, 89% successfully returned to function. However, complication rates were high and reported to affect 54% of the cases with 18% considered major complications and 36% minor complications (2).

Bone size and small bone fragments are always significant challenges in miniature breeds and the surgeon must choose the most appropriate plate for each dog. Several types of plate are available for the repair of radial fractures in small and miniature dogs and the results for several of these types of plate have been described in the literature (2–4). Cut-to-length plates provide unique characteristics that make them appealing for the treatment of radial fractures in miniature breeds. They are versatile and economical; they come in multiple small sizes and generally offer a short hole-to-hole distance, allowing the placement of several screws in relatively short bone segments (5,6). On the other hand, their small size and high hole-to-plate ratio make them subjectively flexible and weak. Results associated with the use of these cut-to-length plates have not been reported.

It has been over 15 y since any literature has been published reviewing the complication rate and long-term outcome of radius and ulna fractures repaired by internal fixation in small breed dogs. The purpose of this retrospective study was to determine the current complication rate over an 8-year period treating small breed dogs with internal fixation for radial and ulna fractures using cut-to-length plates.

Materials and methods

Inclusion criteria

The medical records of all cases from 2004 to 2011 in which a 1.5 mm, 2.0 mm, or 2.7 mm cuttable bone plate was used were reviewed and totaled 97 cases. The criteria for inclusion of cases in the study were: fracture of the radius and ulna with open reduction and internal fixation utilizing a cuttable bone plate [1.5 mm straight plate; 2.0 mm straight plate; 2.0 mm/1.5 mm Cut-To-Length Plate; formerly known as Veterinary Cuttable Plates (VCP) or 2.7 mm/2.0 mm Cut-To-Length Plate] (DePuy-Synthes, Paoli, Pennsylvania, USA) in dogs with body weight less than 9 kg.

Data pertaining to breed, gender, age, body weight, clinical history, time from injury to surgery, fracture description, previous repair attempts, duration of surgical repair, plate size and configuration, utilization of cancellous bone graft, postoperative fracture alignment, postoperative management, postoperative complications, lameness outcome, and time from fracture fixation until last follow-up radiographs were recorded. Owner compliance was not recorded.

Complications were classified into major and minor based on criteria proposed by Cook et al (7). Major complications were defined as complications that required further treatment based on current standards of care (implant failure, surgical intervention, or hospitalization for bandage complications). Minor complications were defined as complications not requiring additional surgical or medical treatment to resolve (long-term lameness, bandage complications not requiring specific treatment or hospitalization) (7).

All referring veterinarians were contacted to determine if the patient was still living at the time of the survey. A questionnaire was created and mailed to all owners for long-term follow-up, excluding those clients whose dogs were known to have died. A $10 gift card incentive was offered and mailed to every client who completed and returned the questionnaire.

Results

Thirty-one dogs were included in the study. Pomeranians constituted 10 of the 31 dogs; other breeds were poodle (n = 7), Yorkshire terrier (n = 4), mixed breed (n = 3), Chihuahua (n = 3), Chinese crested hairless (n = 2), Jack Russell terrier (n = 1), and Italian greyhound (n =1). The mean (median) age at fracture repair was 14.9 mo (7.0 mo). Bilateral fractures occurred in 2 of 31 dogs and 1 dog was presented for fracture of the contralateral radius 7 mo following the first repair for a total of 34 fractures in 31 dogs. There were 14 females and 17 males. Clinical history for all cases included minimal trauma: falling (n = 12), jumping a short distance (n = 11), unknown trauma (n = 5), playing with other dogs (n = 2), or being stepped on (n = 1).

All fractures consisted of complete fracture of the radius and ulna. Of the 34 fractures that were treated initially, 20 were located in the distal diaphysis of the radius, 10 in the mid-diaphysis, 1 in the proximal diaphysis and the location was not recorded in 3 cases. All recorded fractures were either a short oblique or transverse fracture except for 3 cases: 1 case of bilateral fractures (both comminuted) which went on to experience implant failure and 1 mid-diaphyseal fracture (mild comminution) which was lost to follow-up (Table 1).

Table 1.

Summary of treatments, configuration of fractures, and complications in the 31 cases in this study

Case number	Bandage placed	Postoperative complications	Fracture configuration	Nature of complication
1	Soft padded	Major	Transverse	Implant failure, repaired with 2-0DCP, censored.
2	Splint	Major	Transverse	Implant failure, repaired with 2-0DCP, bandage, censored.
3	2 Splints Revision splint	Major	Comminuted (2)	Implant failure. Bandage — pressure sores — requiring hospitalization, intermittent lameness.
4	Splint Revision splint	Major	Oblique	Implant failure following screw removal, osteopenia, revised with smaller plate, healed without complications.
5	Splint Revision splint	Major	Transverse	Splinted for 9 wk before referral. Osteopenia, bone grafting, screw failure, and disuse osteopenia of carpus and manus.
6	No	Major	Transverse	Implant removal due to synostosis and cold sensitivity.
7	Splint	Major	Oblique	Implant removal for osteopenia, bandaged — olecranon wound. Hospitalized for 4 d for wound management. Valgus deformity.
8	Soft padded < 5 d	Major	Oblique	Mild decrease in range of motion of carpus/elbow. Osteopenia, staged plate removal.
9	Splint	Minor	Transverse	Bandage — pressure sores. Ulnar osteopenia.
10	Splint	Minor	Oblique	Bandage — olecranon wound.
11	Splint	Minor	Oblique	Bandage, osteopenia.
12	Soft padded < 5 d	Minor	Oblique	Bandage, chewing sutures.
13	Splint	Minor	Transverse	Bandage, osteopenia, lameness.
14	Splint	Minor	Oblique	Carpal swelling; non-weight-bearing lameness 8 wk after surgery, ulnar osteopenia.
15	Splint	Minor	Oblique	Valgus deformity
16	Splint	Minor	Oblique	Lameness
17	No	Minor	Transverse	Lameness
18	Splint	None	Transverse	None
19	2 Splints	None	Transverse/oblique (2)	None
20	2 Splints	None	Transverse (2)	None, contralateral radial fracture 7 mo following first fracture.
21	Splint	None	Oblique	None
22	Splint	None	Oblique	None
23	Splint	None	Oblique	None
24	Soft padded	None	Oblique	None
25	Soft padded < 5 d	Lost	Transverse	NA
26	Soft padded < 5 d	Lost	Transverse	NA
27	Soft padded < 5 d	Lost	Comminuted	NA
28	Splint	Lost	Transverse	NA
29	Soft padded	Lost	Transverse	NA
30	No	Lost	Oblique	NA
31	Splint	None	Oblique	None

NA = not applicable.

Most dogs had their fracture(s) treated within 3 d after the injury; 8 fractures were repaired between 4 to 10 d after injury. One dog had been treated unsuccessfully with a splint for 9 wk before presentation.

All fractures were repaired at our clinic. A total of 45 surgeries were performed on 31 dogs. Bilateral fractures were present in 3 dogs, 1 of which had bilateral radial fractures 7 mo apart. Implant failure requiring plate replacement occurred in 4 dogs (Table 1). Seven additional surgeries were performed to provide additional bone graft and/or to remove or replace screws during the healing process (n = 4) or to remove the plate following complete healing because of perceived ongoing complication associated with the implant (n = 3). Excluding the surgeries for bilateral fractures, 5 dogs required 2 surgeries and 3 dogs required 3 surgeries. Among the 4 dogs that suffered catastrophic implant failure, 2 were repaired using a plate other than a cuttable plate (2.0 mm DCP; DePuy-Synthes). For these 2 cases, the revision surgeries were counted as a complication but excluded from our analysis of plates.

Of the initial fracture fixation (34 fractures in 31 dogs), 21 fractures were stabilized with a 1.5 mm straight plate, 4 fractures with a 2.0 mm straight plate, 5 with a 2.0/1.5 mm VCP, and 4 with the 2.7/2.0 mm VCP. The average (median) weight of the dogs treated with each type of plate were 2.2 (2.2) kg for the 1.5 mm straight plate, 2.4 (2.8) kg for the 2.0 mm straight plate, 2.9 (2.0) kg for the 2.0/1.5 VCP, and 5.4 (4.9) kg for the 2.7/2.0 VCP. All fractures were initially repaired using a single plate. The 2 plate revision surgeries included were revised with a 1.5 mm straight plate (from a 2.0 mm straight plate) on a 0.94-kg dog and a stacked 2.0 mm straight plate (from a single 2.0 mm straight plate) on a 2.8-kg dog.

Either a cancellous or cortico-cancellous bone graft (autograft or allograft) was used in 8 of the initial 34 fractures. Three additional bone grafts were performed on 3 dogs during revision surgery (Table 1). Two of the bilateral fractures and the fracture that had been splinted for 9 wk before presentation were grafted at the time of initial surgery.

Immediately after surgery for the initial 34 fractures, 23 caudal splints were placed, including both of the bilateral fracture repairs. Caudal splints generally consisted of spoon splint, caudal splint made of fiberglass casting material, or a portion of a tongue depressor, at the discretion of the clinician. Splints or bandages were rechecked weekly. Three limbs had a soft padded bandage placed after surgery for an undetermined period of time (Table 1). Eight cases had either no bandage after surgery or only a soft padded bandage placed for a short time thereafter (1 to 5 d) (Table 1). Of these 8 cases, 4 were lost to follow-up immediately after surgery. One dog required bandage removal because of skin irritation and was lost to follow-up after 27 d. The other 3 were followed a minimum of 101 d after surgery and all 3 had healed fractures.

Of the 31 dogs, 6 were lost to follow-up after the initial surgery (Table 1). The remaining 25 dogs had at least 1 set of recheck radiographs with a follow-up range of 27 to 169 d. The mean (median) follow-up time was 64 (57) d. Complete fracture healing was recorded for 17 cases with the remaining 8 cases having evidence of progression of bony healing. The number of follow-up visits ranged from 2 to 15 and included 2 patients that were hospitalized for 4 d and 10 d each, to address severe bandage complications and associated wounds. Of the 25 cases with at least 27 d of follow-up, major postoperative complications were recorded in 8 patients and minor complications occurred in 9 patients (Table 1).

Major complications

Four dogs suffered a catastrophic plate failure (9 to 58 d following initial surgical repair) (Table 1, dogs 1 to 4). Two (dogs 1 and 2) were in the group repaired with the 1.5 mm mini straight plate and had a splint or padded bandage following surgery. The dogs weighed 3.5 and 5 kg and were the largest dogs in the 1.5 mm plate group. Both were successfully repaired with a 2.0 mm DCP and were censored from the study. The 2 other failures happened with the 2.0 mm straight plate. Dog 3 had a bilateral comminuted fracture with postoperative splints. One of the plates broke and the dog developed pressure sores requiring additional hospitalization. The surgery was revised with a stacked 2.0 mm straight plate and no coaptation. Bone graft was used for both the initial and revision surgeries. The fourth dog (#4) failed after a bone screw was removed because of delayed healing and progressive osteopenia. The dog was a 0.94-kg Chihuahua and the smallest dog in the series. The plate and screws were considered oversized and the surgery was revised successfully with a 1.5 mm straight plate. Bone graft and coaptation were used for both initial and revision surgeries.

Dog 5, which had been treated initially with a splint before a 2.0 mm straight plate was applied, developed a delayed union and required 2 additional surgeries, 1 for bone grafting, the other to replace failing screws. Healing was confirmed 151 d following surgery and required 15 hospital visits in total.

Three dogs (dogs 6,7,8) healed uneventfully but required the implant to be removed because of progressive osteopenia or cold sensitivity. One of these dogs was a 1-kg dog treated with a 1.5 mm straight plate and no coaptation, one was a 3-kg dog treated with a 2.0/1.5 mm VCP and no coaptation, and the third (dog 8) was a 4.6-kg dog treated with a 2.7/2.0 VCP and coaptation. This dog was also hospitalized for 4 d because of a deep olecranon ulcer. Two of these plates were removed in a single staged procedure and the third plate was removed in 2 stages.

Minor complications

Nine dogs suffered only minor complications; some dogs suffered more than 1 complication. Minor complications included: bandage complications that did not require specific treatment other than bandage change or removal (5 cases), premature suture removal by the animal (1 case), carpal swelling (l case), valgus deformity (1 case), intermittent lameness (3 cases), and 1 non-weight bearing lameness at 8 wk.

Long-term lameness outcome among the 25 cases with follow-up was as follows: full return to function in 15, acceptable function in 5, unacceptable function with continued lameness in 2 dogs, and undocumented lameness status in 3 dogs. One of the dogs with unacceptable function was the dog which had the fracture splinted before treatment and required multiple surgeries due to delayed union (Table 1, dog 5). This dog was also diagnosed with elbow incongruity. The other dog with unacceptable function was non-weight-bearing 8 wk following fracture fixation despite bone healing on radiographs (Table 1, dog 14). This dog had mild swelling of the carpal joint; however, no further follow-up was available. Of the 3 dogs that had undocumented lameness status; 2 had mild decrease in carpal and elbow range of motion.

Twenty-nine questionnaires were mailed to owners, excluding 5 whose dogs had died. Six questionnaires were returned. All owners were satisfied with the surgery and only 1 dog had residual lameness after strenuous activity. The overall use of the limb was satisfactory for all owners. Two of the 6 patients had implants removed. The long-term complications noted from surgery included a scar from a bandage sore and a little tenderness after running too hard, resulting in favoring of the leg for a brief period with a mild lameness. A third owner reported the leg to be sensitive and become cold easily. The questionnaire answers were factored into the overall complication rate.

Discussion

Small breed dogs appear to be predisposed to radial fractures with approximately 85% of radius and ulna fractures occurring in the distal third (1,8). Morphological differences in the antebrachium of small breed dogs compared to larger breeds are believed to be responsible for this predisposition (9). Radius and ulna fractures in small breed dogs have been associated with a high complication rate and a high incidence of delayed and non-unions (2,10). One study reported up to 54% of small breed dogs treated with plate osteosynthesis developed postoperative complications (2). The complication rate is approximately 83% if the radial fractures are treated with cast fixation (2). The reasons for this high rate of complication likely include the size and shape of the bones, technical difficulties associated with the size of the bone fragments, and the paucity of soft tissues surrounding the distal antebrachium.

Our retrospective study on radius and ulna fractures in small breed dogs treated with cuttable plates showed similar trends to previous studies but a higher complication rate with 8 major and 9 minor complications in 25 cases. The overall complication rate of 68% is higher than the previously reported overall complication rate of 54% (2). However, unlike previous publications, we adopted a stringent definition of complications as suggested by Cook et al (7). Furthermore, complications associated with coaptation were also counted as if they resulted in alteration of the original postoperative plan (such as premature bandage removal), even though they may not have influenced the final outcome.

In our study, coaptation was used in 23 of the 31 cases following the initial repair of the radius and ulna. External coaptation accounted for complications in 8 cases and resulted in prolonged hospitalization in some cases. A high complication rate associated with coaptation (up to 63%) has also been observed by others following the application of bandages, splints, or casts in small animals (11–14). External coaptation has the potential for causing pressure sores, swelling, and dermatitis (13,14) and in this study, all of these were observed within the minor complication category. Extensive lesions and a deep olecranon ulcer were observed in the major complication category.

The need for external coaptation following internal stabilization is controversial. The decision to apply postoperative coaptation was made by the surgeon, based on their evaluation of the surgical repair and the implant strength. In this study, out of the 21 fractures in which the smallest 1.5 mm straight plate was used, 16 had external coaptation placed after surgery. Four minor and 2 major complications were at least partially attributed to the bandage in that group. Bandages were also used with all other types of plate and complications occurred in all groups. There are, however, too few cases of other types of plate and our ability to make comparisons between groups was limited. One would expect that postoperative coaptation would be used in cases deemed at risk for implant failure and that coaptation would protect against plate breakage. Surprisingly, all 4 implant failure cases had postoperative coaptation. Two of those dogs were in the 1.5 mm straight plate group. Two of those dogs had body weights of 3.5 and 5 kg, well above the average weight of the dogs in that group (2.2 kg). Although there are no published guidelines for the use of these plates, it is likely that those dogs were too heavy for the plate. All dogs which had successful fracture repair with the 1.5 mm straight plate had an average body weight of 1.9 kg (range: 0.9 to 2.6 kg) and we therefore suggest that this plate be used for dogs within that body weight range. The other 2 cases that underwent catastrophic failure were in the 2.0 mm straight plate group and both had bone graft and postoperative coaptation. The failure of 1 of the cases remains unexplained as the dog weight (2.8 kg) was in the range of the other dogs in that group and no predisposing factor could be identified other than the fact that this dog had bilateral comminuted fractures. The last case that suffered implant failure was the smallest dog of the cohort and weighed only 0.94 kg. The fracture was initially stabilized with a 2.0 mm straight plate and 2.0 mm screws. In the face of progressing osteopenia and delayed healing, concerns of overly rigid fixation prompted the removal of 2 of the central screws and precipitated the implant failure and fracture of the bone. Fixation with a smaller plate and smaller screws, a bone graft and coaptation resulted in healing of the fracture.

Eight dogs did not have external coaptation following surgery or had coaptation for 5 d or less. Four of those dogs were immediately lost to follow-up. Interestingly, none of the remaining 4 dogs for which follow-up was available experienced implant failure, suggesting that postoperative coaptation may not always be required.

Osteopenia was diagnosed in several dogs. The degree of osteopenia was subjectively considered significant in 3 cases, prompting surgical removal of all or some of the implants. Self-limiting osteopenia not requiring treatment was not counted as a complication. Concerns about osteopenia, delayed healing, or non-union in small and miniature dogs are often raised following radius and ulna fractures (2,4,10). Although the causes of osteopenia following plate fixation have been extensively debated, it is generally accepted that vascular impairment to the bone cortex plays a larger role than stress protection in the development and progression of osteopenia (8,15).

Determination of the degree of osteopenia is often subjective and the need for the removal of the implant could be questioned. In 1 dog, the plate was believed to be oversized and although stress protection cannot be totally ruled out in this dog, vascular impairment caused by the oversized plate and screws was likely to also be a contributing factor.

In addition to the effect of the implant, vascular insufficiency of the distal radius has also been suggested as a cause of healing impairment in small and miniature breeds. Decreased vascular density of the intraosseous blood supply to the distal diaphyseal-metaphyseal junction of the radius has been demonstrated compared to large breeds (16). Although vascular density is not necessarily synonymous with blood flow, decreased vascular density may contribute to the decreased prognosis for fracture healing in small breed dogs and an increased frequency of delayed union and non-union compared to similar fractures in large breed dogs or compared to fractures in other bones (16). To the best of our knowledge, true vascular insufficiency has not been demonstrated. All fractures for which follow-up was available healed and non-union was not observed in this series. Because of the retrospective nature of the study, accurate time to healing was not available.

The lack of long-term follow-up, inability to compare risk factors due to small group sizes, inability to compare time to healing with or without external coaptation, and the retrospective nature of the study present significant limitations of this study. Because of institutional policy regarding client communication, we were not allowed to contact owners of pets that had died. Furthermore, the response rate to the long-term survey was low. These factors reduced our ability to collect long-term data on several of the dogs. It is possible that these limitations have biased our results. The direction of the bias is, however, unknown.

Our study on radial and ulna fracture fixation using 1.5 mm to 2.7 mm “cut-to-length” plates demonstrated a higher overall rate of complication than previously reported in the literature for other types of plate. The high complication rate may have been, at least in part associated with the strict definition of complications used in this publication. Despite the high complication rate, the results were similar to those reported for different plates in a similar population of dogs. All fractures that we could follow achieved clinical union and we believe “cut-to-length” plates remain a good choice for fracture repair. Bandages and splints were used in most cases and were responsible for a large number of complications. The fact that all catastrophic failures occurred despite the splint raises questions about the efficacy of coaptation or the need for coaptation. Perhaps more emphasis should be placed on strict exercise restriction and external coaptation reserved only for tenuous repairs; however, owner compliance could not be assessed and may have played a role. The retrospective nature of the study and the small number of cases that were treated without coaptation limit the strength of this conclusion and additional studies should be conducted. The 1.5 mm straight plate was successfully used in all dogs with a body weight between 0.9 and 2.6 kg. We suggest that this range is appropriate for use of this plate although plate selection and the decision to apply coaptation will remain subjective until stronger guidelines can be developed.