Orthopedic injuries are a common occurrence in the racing greyhound and typically occur by a failure of the musculoskeletal structures to withstand the forces developed during a race (1). In the United States, greyhounds race exclusively in an anticlockwise direction on an oval track, resulting in asymmetric adaptive remodeling of both the skeleton and soft tissues, particularly the left front and right hindlimb (2–4), as the left forelimb acts as a pivot and the right hind limb provides propulsive effort when rounding bends (5). In other countries, they may race clockwise, or both directions. An injury rate of 3.4% was previously reported in racing greyhounds in the United States (6). Tarsal injuries accounted for 6% of total racing injuries with approximately 60% of all tarsal injuries being fractures. Central tarsal bone (CTB) fractures are the most commonly reported tarsal fracture, and numerous other tarsal bone fractures have been reported (7). Complications reported with surgical repair of tarsal fractures include infection, dehiscence, implant failure, implant loosening, delayed union, reduced range of motion, non-union, infective arthritis, and residual lameness secondary to implant irritation of soft tissue (1, 8–13). Many of these complications result in the necessity for additional surgical intervention with added patient morbidity and financial burden. Surgical site infections (SSIs) remain a frustrating and expensive complication in veterinary surgery (14). To the authors’ knowledge, there is no literature investigating the SSI and explantation rate in greyhounds undergoing tarsal surgery. As these injuries often occur in racing greyhounds, financial burden plays a role in their clinical management. Establishing what variables, if any, are associated with an increase in SSI and explantation rate is a first step in minimizing the cost of care and patient morbidity.

There has been no recent literature reviewing common tarsal fracture presentations and postoperative complications in greyhounds. The first objective of this retrospective study was to describe the type of tarsal injuries sustained, surgical intervention performed, and postoperative complications in the unique population of greyhounds presenting to a single referral veterinary medical center. An additional objective of the study, was to determine if any epidemiologic or intraoperative factors were associated with an increased risk of SSI and/or explantation. Based on our experience, we hypothesized that the SSI rate for greyhounds undergoing tarsal surgery would be higher than both the previously reported SSI rate for orthopedic surgery.

Tarsal injuries in greyhounds present significant management challenges due to their thin skin (19) and the minimal soft tissue coverage associated with the distal limb (20). Previous reports have examined the frequency of tarsal injuries in the racing greyhound with the majority involving fractures of the CTB (7). Of the 116 greyhounds evaluated in this study, CTB fractures were the most frequent injury component with calcaneal fractures and proximal intertarsal subluxation also reported with high frequency (57.8%, 56.9%, and 34.5% respectively). The most common surgical repair in this group of patients was a partial tarsal arthrodesis, most frequently performed at the level of the calcaneoquartal joint. A variety of postoperative complications were recorded in this cohort of patients. Of significant clinical importance, the overall SSI rate was noted to be higher than previously reported for orthopedic procedures allowing us to accept our hypothesis.

Of the 115 greyhounds that survived to discharge, 40.0% were diagnosed with an SSI via positive bacterial culture. Of these, 6 cases presented with an open fracture and were therefore not considered a clean procedure. Excluding these 6 cases, the overall SSI rate for clean procedures in this study was 36.7% (40/109). The SSI rate for clean orthopedic surgeries has been previously reported to range from 3.3% to 7.1% (21–25). Greyhounds in this study undergoing a clean orthopedic procedure were almost 5 times more likely to develop a surgical site infection compared to previously reported literature. Even when compared to the tibial plateau leveling osteotomy, an orthopedic procedure that has a surgical site infection rate as high as 15.8% (14), the reported infection rate in this study is more than double what has been historically reported. Armstrong et al. (26) reported a postoperative SSI rate of 10.7% in nonracing dogs with CTB injuries. We postulate that the reason for the higher SSI rate in our study is primarily secondary to patient population. Greyhounds have thinner skin which is more prone to damage compared to other breeds (19) increasing the risk of incision dehiscence, bandage associated morbidity, implant exposure, and SSI. Additionally, greyhounds have a paucity of subcutaneous tissue compared to other dog breeds. Previous literature has shown that subcutaneous tissue plays an important role in cutaneous wound healing (27). In a study by Bohling et al. (27) the removal of the subcutaneous tissue caused a significant reduction in perfusion of open wounds. This demonstrated the importance of the subcutis in 2nd intention healing which is elected on occasion in greyhounds when excessive tension would be noted with incisional closure (27). Interestingly, this is in direct opposition to several studies in human literature that have found that increased soft tissue thickness/coverage (>5 cm) in patients undergoing total hip arthroplasty (28), or repair of patellar fractures (29) is associated with an increase in infection rate.

In this study, we report the SSI rate for surgical repair of tarsal injuries in greyhounds. In people, the reported SSI rate for clean orthopedic procedures is 0.5% to 6.5% (30). While the specific SSI rate reported for foot and ankle surgery is similar at 1.0% to 5.3% (31–36), it is suspected that it might actually be higher due to reduced ability to mitigate bacterial load with surgical preparation compared to more superior (proximal) surgical sites (36, 37). This challenge in surgical preparation holds true for dogs, and may help explain why our SSI rate was higher than previously reported rates in clean veterinary orthopedic procedures. Additionally, higher bacterial loads on dogs’ skin (compared to humans) has been demonstrated in studies evaluating skin asepsis protocols (35). This is believed to be at least in part due to the presence of fur, low hygiene (bathing) frequency, and contact with a more contaminated environment (35).

Dogs undergoing both a medial and lateral surgical approach were significantly more likely to develop an SSI and require an explantation. In this study, 38.8% of dogs (45/116) underwent bilateral approaches for surgical repair of their orthopedic disease. Of these 45 dogs, 53.3% (24/45) were diagnosed with an SSI and 68.9% (31/45) required explantation. Cases receiving bilateral approaches were reported to have longer anesthesia and surgery times on average compared to dogs undergoing a single surgical approach. Despite the longer anesthesia and surgical times, multivariate statistical analysis revealed that undergoing both a medial and lateral surgical approach retained significant impact on SSI rate and need for explantation when controlling for the extended anesthesia/surgery time. We hypothesize that this increased likelihood of developing an SSI and need for explantation is likely secondary to additional tissue trauma and increased wound tension. When both medial and lateral approaches are performed, the thin skin and sparsity of subcutaneous tissue of greyhounds often poses a challenge with performing incisional closure over implants with some patients having incisions that are left partially open to avoid a tourniquet effect from excessive tension. We suspect that these challenges could contribute to an increase in wound dehiscence and implant exposure. In fact, of the 15 dogs that were reported to have implant exposure, 66.7% (10/15) had both a medial and lateral surgical approach performed. While this finding is of note, the need for both medial and lateral approaches is often unavoidable with specific injury conformations (CTB fractures with concurrent calcaneal fractures, CTB fractures with proximal intertarsal instability, etc.). When bilateral approaches are required, the surgeon should pay utmost attention to minimizing soft tissue trauma and diligent monitoring for SSIs postoperatively.

Dogs that received an elective spay or neuter at the time of surgery were more likely to develop an SSI and require an explantation using univariate analysis. Of the 21 dogs receiving an elective castration at the time of their orthopedic surgery, 61.9% (13/21) were diagnosed with an SSI and 81.0% (17/21) required an explantation. Dogs receiving elective castration were reported to have longer anesthesia and surgery times than those not receiving castration. A previous study in human literature found that undergoing multiple surgical procedures was associated with a significant increase in risk of developing a surgical site infection although this was mainly caused by prolonged duration of surgery (38, 39). However, in our univariate analysis, the effect of dogs undergoing elective castration had a higher impact on developing an SSI and need for explantation than anesthetic or surgery time. We hypothesize that the additional surgical procedure increased the surgical field and may have increased the risk of breaches in sterility. Additional studies are needed to elucidate these findings. Regardless, the potential for increased risk of surgical site infection and explantation should be considered when performing additional surgical procedures concurrently with orthopedic surgical intervention in greyhounds with tarsal injuries.

Longer anesthetic and surgical times were also found to have an increased risk of explantation in our univariate analysis. For each additional 20 min of surgery time, the odds ratio of explantation was 1.17. There was a spike in probability of explantation with anesthetic times less than 180 min and a dip in probability of explantation with surgical times greater than 240 min. This may be explained by the low number of cases with an anesthetic time less than 180 min (16/116) or a surgery time greater than 240 min (2/116). With the exception of these two deviations, there was a relatively regular progression of increasing risk of explantation with increasing anesthetic and surgical time. Increased duration of surgery has been previously reported as a risk factor for the development of SSI (which was associated with explantation in our study using univariate analysis) (40–44). It has been proposed that increased surgical time increases the amount of environmental contamination in surgical wounds (45). In addition to increased exposure to environmental contamination, increased surgical time may be associated with more complicated procedures and progressive wound desiccation allowing for increased ability of bacteria to enter the surgical field (46). In agreement with previous studies, our findings support that time under anesthesia and duration of surgery should be limited to minimize the risk of SSI and subsequent explantation.

Patients diagnosed with calcaneal fractures had 2.4 times the odds of requiring an explantation compared to patients without calcaneal fractures using univariate analysis. Additionally, of the 66 calcaneal fractures reported, 57 sustained additional tarsal injury, therefore increasing dissection and surgical time if the other injuries required specific surgical treatment. This may have increased the risk for wound dehiscence or SSI. Patients with calcaneal fractures commonly receive a bone plate as a component of the surgical intervention. The use of a locking plate was found to be associated with an increased risk of developing a surgical site infection and requiring explantation using univariate analysis. When directly comparing the use of locking and nonlocking plates, nonlocking plates show a decreased odds of developing an SSI. This relationship proved similar when evaluating the risk of requiring an explantation. The increased risk of developing an SSI when a locking plate was used (compared to a non-locking plate) is surprising. Locking bone plates and screws have been shown to reduce infection rates compared to conventional dynamic compression plates (DCPs) in previous literature (47–49). This protective effect was suggested to be secondary to a lack of perfusion disruption to the cortical bone underlying the plate (compared to DCPs), decreased incidence of inflammation from loosening hardware, and faster bone healing due to a more stable fixation (47). One explanation for our findings may be the lack of requirement for bone contact throughout the length of a locking plate, resulting in a prouder implant that may wear through the thin tissues of greyhounds, resulting in reduced soft tissue coverage and in some cases, implant exposure. An alternative explanation is that in our study, 72.3% of dogs undergoing plating received a locking plate (73/101). This resulted in unequal representation in the data between locking and nonlocking plates.

Patients undergoing arthrodesis of the proximal intertarsal joint had a decreased odds of requiring an explantation on univariate analysis. This finding is interesting as other publications have found explantation rates of up to 21% following partial tarsal arthrodesis (50) and 12.5% following tarsal arthrodesis (51). In this patient population, factors that increased risk of explantation were all surgical interventions requiring significant soft tissue disruption and manipulation. Partial tarsal arthrodesis requires less soft tissue manipulation compared to repair of complex calcaneal fractures. Additionally, proximal tarsal arthrodesis is performed through a single surgical approach compared to a bilateral approach, which is used to address CTB fractures with concurrent calcaneal fractures, the most common injury presentation in our study. Given that this association was found with the univariate analysis, it may be confounded by the effect of surgical approach, so further exploration is warranted.

Limitations to this study are primarily related to the retrospective nature which required a reliance on medical records. This design leads to the presence of confounding factors such as incomplete information regarding clinical signs and complications. Multiple doctors were scrubbed into surgery, and it was not always clear which doctor (and which experience level of doctor, i.e., resident vs. boarded surgeon) performed the procedure or if primary responsibility shifted throughout. Additionally, at the time of last follow up, several patients had a lack of complete healing on radiographs. This limitation in follow-up could have led to complications being missed in some patients. In some cases, these animals may have presented to other veterinarians for care related to the operated limb in the years following which may have led us to underestimate the infection rate and subsequent explant rate for this population of dogs. Lastly, we did not incorporate a control group into this study so we cannot report whether other dog breeds with tarsal injuries would have same complications and complication rates as greyhounds in our care.

It should be noted that our patient population is biased towards more severe, career ending racing injuries. Our institution receives referral for severe racing injuries from a regional racetrack such as comminuted fractures, long-bone fractures, severe intertarsal joint luxation, and calcaneal fractures, whereas greyhounds with CTB fractures that do not include subluxation typically undergo cast immobilization under local veterinary clinic care. This decision is made at the discretion of the overseeing Racing Commission State Veterinarian (52). In 2021 (the most recent report available at the time of this publication), a total of 220 track injuries (not limited to orthopedic injuries) were reported at a single race track. Of these 220 cases, only 21 were referred to our clinic (9.6%). Therefore, our findings cannot and should not be expected to apply to all greyhound tarsal injuries.

The greyhound racing industry has significantly evolved over the course of the last decade. At the time of this publication, only two greyhound racing tracks remain active in the United States and only 7 countries have active greyhound racing programs. As racing greyhounds become less prevalent in the veterinary field, it would be interesting to document the occurrence of tarsal injuries in non-racing or retired greyhounds. This point of investigation could be considered for future research.

We concluded that the SSI rate in this population of greyhounds undergoing surgical repair of closed tarsal injuries is higher than previously reported for clean orthopedic procedures. All greyhounds that presented with open fractures went on to develop a SSI. Additionally, over half of greyhounds undergoing ORIF of tarsal injuries will require explantation of the surgical implant. Although they can do well clinically following explantation, this increases the cost to the owner and the recovery period for the dog. Factors needing further exploration for their association with an increased rate of SSI and explantation included concurrent elective sterilization, calcaneal fractures, use of locking plates, and increased duration of anesthesia and surgery. The information in this study can help guide practitioners’ clinical expectations and client communications when undertaking these challenging cases. Practitioners performing surgical intervention for tarsal injuries in greyhounds should be prepared for the high likelihood that explantation will be required following healing, particularly those requiring both a medial and lateral surgical approach. Additionally, anesthesia and surgery time should be minimized in these cases due to the possible correlation with increased risk of SSI and explantation. Future consideration should be given to explore alternative surgical techniques for managing these cases such as minimally invasive approaches or the use of external skeletal fixation with the goal of lowering the SSI and explantation rate in this patient population.

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.

Ethical review and approval was not required for the animal study because this was a retrospective study.

NK and JD contributed to the conception and design of the study. NK, JD, AW, SJ, ST, MB, BC, KS, and CF contributed to the data collection and organization for the study. MB wrote the first draft of the manuscript. All authors contributed to the article and approved the submitted version.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could construed as a potential conflict of interest.

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