Heel Bulb Lacerations in Horses: 101 Cases

Horses sustaining a heel bulb laceration can successfully return to their intended use. The distal interphalangeal (DIP) joint was the most common synovial structure affected by the heel bulb laceration, and DIP joint problems resulted in a poorer prognosis for successful outcome.

1. Introduction

Lacerations of the palmar/plantar aspect of the pastern and the heel bulbs of horses occur commonly and usually result from traumatic injuries associated with wire or other metallic objects. A thorough examination of pastern/heel bulb lacerations is warranted because of the proximity of various synovial structures. Concurrent involvement of the digital synovial tendon sheath, deep digital flexor tendon (DDFT), proximal interphalangeal (PIP) joint, distal interphalangeal (DIP) joint, and navicular bursa can result in a poor prognosis for return to soundness [1-3]. Subsequent foot lesions resulting from heel bulb lacerations such as hoof cracks, coronary band avulsions, and collateral cartilage lesions may also limit return to soundness [1,2].

The management of lacerations involving the pastern and heel bulbs of horses has been described in conjunction with lacerations of the distal limbs and other hoof injuries [1,2,4,5]. The purpose of this study was to describe the clinical signs, structures involved, treatments used, and outcome in a series of horses with lacerations involving the pastern and heel bulb region of the distal limb.

2. Materials and Methods

Medical records of horses that had sustained distal pastern or heel bulb lacerations were retrieved from hospital records at the Texas Veterinary Medical Center from January 1988 to July 1994. Follow-up information was obtained by phone conversations with owners or trainers for 65 horses.

Information obtained from medical records included signalment, limb affected, time to initial treatment, antimicrobial administration before referral, radiographic findings, soft tissue structures involved (PIP joint, DIP joint, navicular bursa, digital tendon sheath, DDFT), and treatment modality (wound debridement and lavage, wound coaptation [cast versus soft bandage], type of suture material, lavage of open synovial structure(s), and use of antimicrobials). Follow-up information included time to follow-up (months), whether the horse survived or was euthanized, whether the laceration healed, cast complications, presence of lameness, if the horse was able to return to intended use, duration of soundness (months), whether a hoof wall defect resulted, presence of a chronic wound, and owner satisfaction.

On presentation, initial treatment in all cases included cleansing and lavage of the laceration with an antiseptic solution, followed by careful evaluation of the wound to identify potential involvement of the digital tendon sheath, DDFT, PIP joint, DIP joint, navicular bursa, and collateral cartilage(s). Perineural anesthesia was performed as needed to facilitate examination. Integrity of synovial structures was determined by infusing a sterile polyionic solution into the synovial cavity or digital tendon sheath in question aseptically at a site remote from the presenting wound. Synovial structures that communicated or were suspected to communicate with the wound were lavaged with 1 - 2 l of sterile polyionic solution and then treated by local infusion of amikacin [a] antimicrobial (500 mg). The synovial structure was lavaged under standing sedation initially at presentation and every other day until synovial fluid analysis or clinical signs indicated that the structure was no longer infected. If a synovial structure was involved, broad spectrum antibiotics were administered for a minimum of 2 wk.

Dorsopalmar (plantar) and lateromedial radiographic projections were obtained in some cases to evaluate the middle phalanx, distal phalanx, and navicular bone for osseous involvement and to determine if radiopaque foreign bodies were present.

The extent of the wound and the integrity of the synovial structure were accessed. Then, either primary closure and cast immobilization was used as treatment or the wound was immobilized and allowed to heal by second intention. Horses with chronic wounds that had granulation tissue present were treated with either delayed secondary closure and immobilization or were allowed to heal by second intention under a bandage or cast. If the wound was severely contaminated or traumatized, a foot bandage was used to allow debridement of the wound for 7 - 10 days before cast immobilization. When feasible, a foot cast was applied with the horse standing and sedated to allow the cast to conform to the normal axis of the hoof and pastern.

Follow-up information was obtained by telephone interviews with each horse’s owner, trainer, or both. Outcome was considered successful if the horse was sound and able to be used at a level of performance that equaled or exceeded the level achieved before injury. For horses that did not have successful outcomes, the reason for failure, degree of improvement of clinical signs, and alternate use were determined if possible.

3. Results

One hundred one horses met the study criteria (Table 1). Seventy-five of 101 horses (74%) were Quarter horses, 6 were Thoroughbreds (6%), 5 were Tennessee Walking horses (5%), 5 were Appendix-bred horses (5%), 3 were Paint horses (3%), 3 were Appaloosa horses (3%), 2 were Arabians (2%), and 2 horses were of unknown breeds (2%). Eleven of the 101 horses were stallions (11%), 32 were mares (32%), and 58 were geldings (57%).

Thirty-one of 101 horses (31%) had lacerated the left front limb, 30 horses (30%) lacerated the right front limb, 22 horses (22%) lacerated the left rear limb, and 18 horses (18%) lacerated the right rear limb. Seventy-five of the 101 horses (74%) did not receive any antimicrobials before referral, whereas 20 horses (20%) did receive antimicrobials before referral. Duration of injury before admission to our hospital was known in 60 horses (59%) and ranged from 1 to 168 h (mean, 72 h). The cause of injury was known in 87 horses (86%): wire cut in 41 horses (41%), metallic object in 46 horses (46%), and unknown in 14 horses (14%). The degree of lameness at admission was not recorded in the medical records.

Radiographs were available for retrospective study for 38 of 101 horses (38%). Of the 38 horses with radiographs of the foot, there were no bony lesions in 23 horses (61%). Nine horses (24%) had radiographic changes indicating damage to the distal phalanx, five horses (13%) had radiographic changes indicating damage to the middle phalanx, and one horse (3%) had radiographic evidence of damage to the navicular bone.

The majority of horses in this study (96%) were initially treated with wound debridement. A total of 19 horses (19%) had involvement of synovial structures. Thirteen horses (13%) had lacerations that involved the DIP joint. The digital tendon sheath was involved in three horses (3%), and in two of these horses, the DDFT was damaged. The PIP joint was affected in three horses (3%).

The wounds of 30 horses (30%) were sutured. All of these 30 horses presented with acute injuries of <8 h duration, and the laceration was noted to have minimal contamination in the medical record. Twenty-one horses (21%) had their wounds sutured using either #1 or #2 polypropylene. The wounds of 71 horses (71%) were not sutured and allowed to heal by second intention. The majority of these horses had contaminated wounds or sustained the injury several days before presentation to our hospital.

Fifty-two of 101 horses (52%) had a cast applied that incased the foot and extended to the proximal pastern region. Duration of cast immobilization ranged from 1 to 3 wk (mean, 3 wk; median, 3 wk). Forty-eight of 101 horses (48%) were managed by bandaging alone. The range of time for bandaging was 1 - 12 wk (mean, 4.1 wk; median, 3 wk).

Sixteen of 101 horses (16%) had synovial structures lavaged with 1 - 2 l of sterile polyionic fluid followed by a local injection of 500 mg of amikacin [a]. Three horses (3%) had their PIP joint lavaged, and 13 horses (12%) had their DIP joint lavaged.

Systemic antimicrobials were administered to 56 of 101 (55%) horses immediately after diagnosis and initial wound treatment had taken place. The antimicrobial treatment consisted of either trimethoprim-sulfadiazine [b] (15 mg/kg, q 12 h, PO) or enrofloxacin [c] (5 mg/kg, SID, PO or IV). The remaining 45 horses did not receive any type of antimicrobial therapy after diagnosis and wound treatment.

Follow-up information was obtained for 65 of 101 horses (64%) 1 - 116 mo after injury (mean, 42 mo; median, 31 mo). Fifty-eight of 65 horses (89%) survived with no complications during wound treatment. Six horses (9%) were euthanized because of complications with the heel bulb laceration; five of these horses had lacerations that involved the DIP joint, and one horse with tendon sheath involvement was euthanized because of deep digital tendon disruption. One horse died because of unrelated causes.

Sixty-two of 65 horses (95%) had complete healing of the laceration at the time of follow-up. The wounds in 2 of 65 horses had not completely healed at the time of follow-up, and the remaining horses had been euthanized. Fifty-two of 65 horses (80%) with follow-up information had been treated with a foot cast, and 2 (3%) of these horses had cast complications resulting from rub sores. The casts were changed in these two horses, and the clinical signs of lameness abated.

Fifty of 65 horses (77%) were judged by the owner or trainer to have a successful outcome and were able to return to their intended use without signs of lameness. Eight horses (12%) had unsuccessful outcomes; according to the owners, persistent lameness after complete heeling of the laceration did not allow these horses to return to their intended uses. Seven horses were euthanized.

Follow-up information was available for 8 of 13 horses with DIP joint involvement. Five of eight (62.5%) horses with DIP involvement and follow-up information were euthanized because of refractory sepsis. Two horses with a laceration involving the DIP joint survived treatment and the lacerations healed; however, they are persistently lame. One horse (13%) healed with no further complications.

A resultant hoof wall defect was present in 12 of 65 horses (19%), and 3 of 65 horses (5%) had chronic wounds necessitating further therapy. Owners were satisfied with the outcome of wound treatment in 58 of 65 cases (89%; owner satisfaction was unavailable for seven horses).

4. Discussion

Lacerations of the pastern/heel bulb region are injuries in horses that usually respond well to appropriate treatment. This treatment consists of wound debridement and lavage followed by wound immobilization alone or primary- or delayed-primary closure of the wound and wound immobilization, and it allows the progression of second intention healing. In this study, 50 of 65 horses (77%) with known follow-up were able to return to their intended use after complete healing of the heel bulb laceration.

Laceration of adjacent synovial structures, however, may result in permanent lameness and possibly loss of the horse. Nineteen of 101 (19%) horses in this study had synovial structure involvement. The DIP joint was most commonly affected in this study. Although follow-up information was only known for 8 of these 13 horses, 5 horses (63%) were euthanized because of unresolved joint sepsis, and 2 were persistently lame presumably because of osteoarthritis of the joint. Only two of six horses having either digital tendon sheath or PIP joint involvement had follow-up. One horse was euthanized, and one horse had persistent lameness. It would seem that a horse sustaining a heel bulb laceration should be closely evaluated for DIP joint involvement. Results from this study suggest that horses with heel bulb lacerations affecting the DIP joint have a poorer prognosis for complete recovery (13%) than horses without DIP joint involvement (77%). Although it seems logical to think that similarly poor results would occur for any synovial structure involvement, there were too few horses with PIP joint or digital tendon sheath involvement and follow-up to draw similar conclusions.

Initial treatment should consist of a combination of wound debridement, scrubbing, and lavaging with an antiseptic solution to remove gross contamination. However, extensive debridement of the laceration should be avoided to avoid potential damage to the neurovascular bundle. Dilute (0.1%) povidone iodine is considered the antiseptic of choice [6]. Chlorhexidine should be used cautiously in the region of joints and tendon sheaths [7]. Ninety-seven horses (96%) in the study were found to have followed this type of therapy on initial examination.

Exploration of the laceration to determine the severity of damage to the underlying soft tissue and synovial structures should be completed after thoroughly cleansing the wound. The PIP joint, DIP joint, and digital flexor tendon sheath should be examined thoroughly to ensure their integrity. Early recognition of joint involvement is important for initiating immediate treatment and preventing joint destruction.

There was no difference in the outcome of horses with follow-up that had their lacerations sutured versus those that had their lacerations healed by second intention. One horse (5%) that had its laceration surgically closed had an unsuccessful outcome, and two horses (3%) that had their lacerations managed with second intention healing had unsuccessful outcomes.

In this study, horses treated by cast immobilization wore the cast for a mean of 3 wk. Cast complications were uncommon in this group of horses; only 2 of the 52 casted horses with follow-up information reported cast complications consisting of rub sores. The foot cast provides protection of the wound by limiting movement of the wound edges, providing tension relief on the sutured wounds, decreasing exuberant granulation tissue, and providing a moist environment for faster epithelialization [8]. Casts often provide more complete immobilization than do bandages and are especially useful in wounds involving the foot and pastern regions that are in constant motion [8]. In this study, foot casts were shown to be an effective method for providing long-term immobilization of heel bulb lacerations. The authors’ clinical impression is that there are fewer cast complications seen with a foot cast than a lower-limb or full-limb cast application in horses. The reasons for this are unknown but may be location, the use of less cast material required for the foot cast, or its application. The foot casts were applied with the horse standing and the limb elevated off the ground. As soon as the cast was applied, the horse was allowed to bear weight on the affected limb; the cast then conformed to the dorsum of the hoof and pastern. One potential complication of long-term cast application is the development of dermal pressure necrosis at the top of the cast. It is for this reason that we apply these casts with the limb elevated off the ground and then make the horse stand on the cast limb before the fiberglass cures. This makes the inner surface of the cast conform to the dorsum of the pastern and may prevent the development of cast sores, even after long-term immobilization.

A properly maintained foot cast in which the top of the cast is secured to the skin with elastic tape to prevent organic matter (wood shavings, sand, manure, etc.) from the environment from gaining access to the inside of the cast can also decrease the incidence of potential wound contamination. All owners are instructed to monitor horses with foot casts for complications such as increased lameness, hair loss or sores located above the cast that may indicate developing pressure sores, and cast breakage before dismissal from the hospital.

The development of exuberant granulation tissue was more common after bandaging alone versus cast application; this is probably attributable to the unyielding nature of the fiberglass material. Bandages were managed for 1 - 12 wk (mean, 3.5 wk), which was a longer time period than casting alone (mean, 3 wk). It is apparent from this study that both foot casts and soft tissue bandaging can lead to a successful outcome for horses sustaining heel bulb lacerations; however, it is the authors’ impression that casting may have a better cosmetic outcome if the client is capable of proper cast management.

The DIP joint was the most frequently affected synovial structure associated with heel bulb lacerations in this study, and it resulted in a poorer outcome. Overall, horses sustaining a heel bulb laceration without involvement of a synovial structure have a good prognosis for returning to their intended use.

Footnotes

1. Amiglyde-V, Fort Dodge Animal Health, Fort Dodge, IA 5050.
2. Sulfamethoxazole and trimethoprim tablets, Mutual Pharmaceutical Co, Inc., Philadelphia, PA 19124.
3. Baytril 100, Bayer Health Care LLC, Shawnee Mission, KS 66201.