Introduction

External coaptation via splint placement is a valuable and commonly used tool for the treatment of long bone fractures in our companion animal species. While primary repair with implants is often preferred due to the superior capabilities for fracture reduction and stabilization, it is at times not feasible due to patient characteristics or comorbidities, owner constraints, or lack of access to veterinarians trained in fracture repair.^1,2 When splinting, achieving rigid stabilization is paramount, as excessive motion at the fracture site can result in delayed union or nonunion.^1,3–5 Careful application is important, as the use of poorly fitted splints, superfluous cast padding, excessive tightness, or improper splint placement can allow for too much motion at the fracture site or cause pressure sores.^1,4–7 Many published sources detail indications for external coaptation and provide guidance in their proper application.

Regardless of bandage or splint type, an often-repeated rule of thumb is the importance of leaving the third phalange of the 2 center digits (D3 and D4) “accessible,” “visible,” “palpable,” or otherwise exposed to monitor for swelling.^1–6,8–14 However, controversy exists regarding the distal extent of the splint. Some sources instruct clinicians to leave the distal, or middle and distal, phalange of D3 and D4 uncovered, or allowed to protrude from the bandage,^{4,6,8,9,13,14} while others recommend extension of the splint past the pads leaving only nails exposed.^1–3,5

In the exposed-digits group, there are diagrams that seem to suggest the animal should be weight bearing on these exposed digits rather than on the splint.^12,15 These are generally not explicit and are more implied. Nonetheless, it is not uncommon for practitioners to leave all or most of the third phalange of D3 and D4 uncovered by not only the soft padded bandage but also the splint, which could result in the animal bearing weight on these digits rather than the splint.² This allows easy assessment of toe swelling as an indication that the bandage is too tight.

Others emphasize the importance of extending the bandage to the base of the nails to fully encompass the digits. This leaves only the pads and toenails of D3 and D4 visible when looking into the end of the bandage.^1–3,5 In this case, one uses increased distance between the toenails as an indicator of digital swelling, rather than observing the exposed digits themselves.^3,4 The reason for extending the splint this distally is to force the animal to bear weight on the splint itself, rather than on its toes, as repeated extension of the toes from weight bearing could contribute to motion at a fracture site, especially in a fracture of the distal limb.² In addition, a splint that ends proximally to the ends of the toes has the potential to contribute to bandage sores due to the rigid splint material rubbing on the digits.^1,5

Unfortunately, these sources for bandage placement are based on anecdotal evidence and textbook information. There have been no studies to assess the consequences of exposed toes. The goal of this study was 2-fold: (1) to determine whether there is a measurable difference in weight bearing in a toes-in splint versus a toes-out splint and (2) to determine the difference in sub-bandage pressures exerted in the 2 splints. We hypothesized that (1) weight bearing would not be different between the 2 splints and (2) sub-bandage pressures would be distributed higher on the distal digits in the toes-out splint and pressures would be more evenly distributed across the paw in the toes-in splint.

Methods

The study protocol was approved by the IACUC (Approval No. 2404-42011A). Eleven dogs owned by employees were enrolled and data collected over a 2-week period of time in a private room dedicated to gait analysis. A sample size of 10 was calculated with an SD of 14 mm Hg, an effect of 20 mm Hg for a clinically important difference in sub-bandage pressure with α set at 0.05 and power set at 0.8. For dogs to be included in the study, they were required to be skeletally mature, in good health with 4 normally functioning limbs, and amenable to being restrained in lateral recumbency without the need for sedation or excessive restraint. An effort was made to enroll a variety of breeds, ages, and sizes. Signalment, weight, and body condition score were recorded for each patient. A coin flip determined whether the left or right forelimb was used and whether the toes-in or toes-out splint was placed first. Both types of splint were placed on the same forelimb for each dog. To maintain consistency, the same researcher was responsible for enrollment, performing the coin flip, and applying the splints. A caudal 180° splint was made with fiberglass casting tape (Vetcast Plus; 3M). Dogs were splinted with the carpus in a neutral position, with each splint extending from distal to the elbow joint, as would be recommended for a metacarpal fracture, to the toes-in or toes-out position distally. Toes-in splints encompassed the toes, ending just beyond the base of the toenails of D3 and D4 (Figure 1), which ensured that in weight bearing, the splint would touch the ground rather than the toes. Toes-out splints ended at the base of the third phalange of D3 and D4 (Figure 2). While some clinicians may end splints even more proximally, we chose to be conservative and leave only a small portion of the digits exposed, so our findings were not exaggerated.

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Toes-in bandage, with sensors visible at the end of the bandage. The red line marks the distal end of the splint.

Citation: Journal of the American Veterinary Medical Association 2025; 10.2460/javma.24.10.0684

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Toes-out bandage, with sensors visible at the end of the bandage. The red line marks the distal end of the splint.

Citation: Journal of the American Veterinary Medical Association 2025; 10.2460/javma.24.10.0684

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Pressures within the bandage were measured with a pressure measurement and positioning tool (BPMS; Tekscan Inc). The device handle (Evolution Handle; Tekscan Inc) was attached by a cable to a computer running proprietary software to aid with research and analysis (Research Software; Tekscan Inc). A sensor strip embedded with electrodes was inserted into the handle. The sensor strip was rectangular and contained individual sensels arranged in a 6 X 16 grid. When pressure was applied, the sensors in this grid reported pressures in real time and could be continuously recorded as a movie. Each sensor strip was calibrated per manufacturer instructions. The sensors were made of a semiflexible plastic material and could be curved around the caudal aspect of the forelimb, but care had to be taken not to tear or crease them, or they may have malfunctioned. After a sensor was used on 3 or 4 dogs, it subjectively became less sensitive, and some grid squares would no longer read. When these issues were observed, a new sensor was calibrated and used instead. To make the sensor more amenable to curving around the dogs’ toes, 5 longitudinal cuts were made with scissors, extending approximately 3 inches up from the bottom of the strip. These cuts were made between electrodes, so the integrity of the strip was unaffected. This resulted in 6 smaller strips, which could overlap one another without creasing or folding. The bottom 2 rows of the sensor strip were labeled rows 1 and 2, and the next 2 were labeled rows 3 and 4. Rows 1 and 2 were the part of the sensor that covered the distal aspect of the toes and were therefore fully encompassed by the toes-in splint, but were left exposed or at the splint interface along with the distal aspect of D3 and D4 for the toes-out bandage (Figure 2).

Each dog was restrained in the appropriate lateral recumbency, with the randomly predetermined limb upward. The sensor strip was laid lengthwise along the caudal aspect of the forelimb, distal enough to cover the entire foot and toe pads. A soft padded bandage was then applied over the sensor, extending from the middle of the third phalange on D3 and D4 to just distal to the elbow joint, which consisted of 4 layers of cotton padding (Medical Specialist; BSN) followed by 2 layers of roll gauze (McKesson Medical-Surgical Inc). A thin stockinette was then put over the roll gauze, and fiberglass casting tape (Vetcast Plus; 3M) was applied to the caudal limb, over the stockinette. A stockinette is not generally incorporated into soft padded bandages and was used for study purposes only. The stockinette prevented the fiberglass splint from adhering to the underlying soft padded bandage. Additional roll gauze was applied over the casting tape while it hardened, helping to conform it to the limb. Care was taken to avoid creating any wrinkles or pressure points in the splint. A self-adhesive tape (OVIK Health) was used as the tertiary layer. A single strip of white tape was gently placed over the bottom of the bandage, which encouraged the sensor strip to hug the ends of the toes rather than bend backward during walking. It was ensured that this did not elevate pressure readings. After each splint application, a baseline reading was taken while the dog remained in lateral recumbency. This reading was used to eliminate variation in sub-bandage pressure created by the bandager rather than bandage type.

Each dog was acclimated to the splint and force platform (Strideway Gait Analysis System; Tekscan Inc), which was appropriately calibrated according to manufacturer’s instructions. The version used was a single nonmodular 5-foot-long platform with no additional covers. Acclimation time was not consistent, as each dog was behaviorally different. When they were comfortable and consistently weight bearing on the splinted limb, the dogs were walked across the platform a minimum of 5 valid trials. A valid trial was defined as the dog walking in a consistent direction with no visible variation in velocity and acceleration or sudden changes in gait or head carriage. The dog was allowed to walk at a comfortable velocity. The same researcher walked all dogs for all trials. Each dog was walked on the researcher’s left side, traveling in the same direction. Treats were used for coercion as needed. The second bandage was placed and measurements were taken immediately after the first bandage. Dogs were allowed a short break if needed.

The peak vertical force (PVF), vertical impulse, velocity, and acceleration were measured for 5 valid footfalls of the bandaged limb for each group. Each of these were averaged for the toes-in and toes-out bandages. For sub-bandage pressures, the maximum pressure readings of sensor rows 1 and 2 (digital pads) and rows 3 and 4 (metacarpal pad area) were averaged and recorded for baseline (lateral recumbency), stance phase, and swing phase. Sub-bandage pressures (maximum) were measured in lateral recumbency (baseline) and in stance and swing phase while walking on the pressure walkway for rows 1 and 2 and rows 3 and 4.

Results

One dog was excluded due to an error with the pressure sensor, leaving 10 dogs of various breeds in the study. Eight of the 10 dogs were female, and no dogs were intact. The left forelimb was splinted in 4 of 10 dogs, the right in the remaining 6. The median (range) of age, body weight, and body condition score out of 9 was 6.5 years (1 to 11 years), 19.8 kg (6.3 to 27.5 kg), and 6 (4 to 7), respectively. There was no significant difference in baseline pressures, depicting relative consistency across participants and splint types.

Data for sub-bandage pressure measurements and gait values are summarized in Table 1. There was no difference in velocity and acceleration between the 2 bandage types. Dogs bore more weight on the toes-out bandage as measured by PVF and vertical impulse. There was a significant difference in sub-bandage pressure pattern even after the difference in weight bearing was taken into account (P < .001), with higher pressure at the distal toes in the toes-out group and more even distribution across toes and higher metacarpal pad pressure in the toes-in group.

Discussion

This study showed that if the distal aspects of D3 and D4 of the forelimb are left exposed, dogs will not only bear significantly more weight on the splinted limb overall, but also increase the sub-bandage pressure on the distal toes relative to the rest of the paw. Furthermore, the pattern of loading would imply that force is being transferred through bones rather than through the splint. This may be detrimental or beneficial to fracture healing, as loading the splint rather than bones is likely providing better stabilization depending on the fracture configuration.

Previous studies^17,18 in splint length and configuration have shown differences in sub-bandage pressures. Iodence et al¹⁸ found that hind limb splints that extended higher relative to the tibia decrease calcaneus pressure during walking. Similarly, the present study showed a decrease in focal pressure with increased length. Swaim et al¹⁷ investigated foot bandage configurations in an effort to reduce overall paw pad pressures for wound treatment. Similar to our study, there were decreased pressures over all of the paw pads when a clamshell that extended beyond the foot was added compared to a metal cup or no splint. This is likely because all the toes were within the bandage, forcing weight bearing on the splint rather than on the paw pads. However, 1 limitation to the Swaim et al study¹⁷ is that they could not evaluate the effect of overall weight bearing. It is possible that the dogs did not bear weight on the clamshell bandage, decreasing paw pad pressure rather than the force being distributed around the paw pads. In the current study, weight bearing was taken into consideration when the sub-bandage pressures were compared.

Contrary to our hypothesis, PVF was measured for both bandage types, showing overall more weight bearing when in the toes-out bandage. This was a clinically significant difference and may be considered if weight bearing through the limb is desired. We hypothesize that this is due to tactile input from the exposed digits, which has been shown to encourage weight bearing in humans.¹⁹ This phenomenon may become less pronounced with long-term use. Dogs in this study were acclimated for a short time prior to data collection. One study⁷ showed that bandages loosen over the first hour. It is possible that waiting an hour or longer would have changed the weight-bearing results. Unfortunately, it wasn’t practical in this study to leave the bandages on for a significant amount of time. The sensors are not conducive to longer-term studies (days or weeks). A different system would be required.

An additional factor that may affect weight bearing with different splint configurations is toenail length. In this study, nails were not measured or clipped for splint placement, but splints extending to the end of the pads may result in abnormal directionality or force on the toenails, encouraging minimal weight bearing. We could not evaluate this, as the toenails are too small to detect and measure force with confidence on the platform used and only the splint and/or toe pads were visible on the measurement software.

Long-term clinical studies would be helpful in determining the real effects of the splint types, including fracture healing and callous size, iatrogenic bandage wounds, and patient comfort. Careful consideration would be needed to balance covariates across groups, including type of fracture, owner compliance, activity level, weight bearing, body condition, weight, and comorbidities. Because of the complexity, a large sample size would be required.

Additional limitations to the generalizability of this study were bandager variability, low sample size, and specificity to bandage materials used (fiberglass splint). In this study, one bandager was used to limit the effect of bandager on results. Sub-bandage pressures have been shown to vary considerably between bandagers,⁷ which would reflect absolute pressure. However, we compared statistically the relative pressure in a model where effects of weight bearing and baseline pressure were removed. Therefore, the pattern of higher distal toe pressure in relation to the rest of the paw will likely be repeatable with other bandagers. Larger sample sizes are better for generalization and would be needed if the study were to be repeated with multiple bandagers or additional types of splints.

Our findings suggested that it may be important to consider fracture location when choosing a splint length. It is possible that high pressure on the exposed digits rather than on the splint could result in motion at any fracture site distal to the elbow, especially when stabilizing digital or metacarpal fractures. Because of this, it is appropriate to construct toes-in splints for all patients with new fractures. There may be some exceptions where more force through the bone is necessary in an attempt to stimulate bone healing, in accordance with Wolff’s Law.²⁰ However, further research would be needed to confirm this biomechanically or clinically. In the present study, bone strain and splint rigidity were not evaluated, and there is no minimal construct stiffness known for splints.

As previously mentioned, the reason often cited for leaving the digits exposed is to monitor for limb swelling. There are grave implications to undetected limb swelling, including severe tissue necrosis. The toes-out splint gives an easy method of observation, but the toes-in splint does not preclude swelling evaluation. Observing the distance between the nails of D3 and D4 is a practical way of monitoring for swelling without the digits themselves being exposed.^3,4 Anecdotally, 1 method for monitoring swelling is to use a permanent marker to record the location of the nails of D3 and D4 on the bandage at the time of placement. Lateral deviation from these marks indicates digital swelling. The digits can also be evaluated by looking up the end of the bandage or inserting a finger to palpate the digits.

In conclusion, leaving the distal aspect of D3 and D4 exposed by a splint results in better overall weight bearing, but also creates a sub-bandage pressure increase on the toes relative to the rest of the paw, implying force transfer through the bones of the limb rather than the splint in healthy dogs. These results suggested that splint length should be a conscious consideration when constructing a splint based on the individual needs of each patient.

Supplementary Materials

Supplementary materials are posted online at the journal website: avmajournals.avma.org.

Disclosures

The authors have nothing to disclose. No AI-assisted technologies were used in the generation of this manuscript.

Funding

Funding provided by the Tata Orthopedic Research Endowment.