How to Make, Place, and Remove Transphyseal Staples

1. Introduction

Foals can have limb deformities that are classified as angular or flexural [1,2]. There can also be a rotational aspect with both types of deformities [1,2]. Most foals are born with at least some degree of limb deformity of either type [1,2]. Many of these correct without surgical intervention, but of those that are treated surgically, the carpal area is diagnosed and treated most often. Up to 85% of the deformities referred for surgery are carpal deformities [3]. Methods to correct angular limb deformities include hemicircumferential transection of periosteum and periosteal elevation (or periosteal stripping) and transphyseal bridging (or growth retardation). Transphyseal bridging is accomplished with screws and wires, staples, or more recently, with a lag screw across the physis [4,5]. Combinations of stripping and growth retardation have also been used [1]. Various splints, casts, and leg braces have also been used to treat foals with deformities caused by incomplete ossification of the carpal or tarsal bones [2]. Corrective trimming of the hoof, in addition to the above treatments, is almost always recommended. Some foals have shoes with extensions (medial extensions for valgus deformities and lateral extensions for varus deformities) placed to assist in correcting the deformity. Most of these treatments also are accompanied with instructions for the owner to stall rest or otherwise confine the foal.

Periosteal stripping is a technique that became very popular and was widely accepted after the mid 1980s [3,6,7]. However, the true efficacy of this technique is controversial, and in a recent study, periosteal stripping was no more effective in correcting experimentally induced angular limb deformities than stall rest and hoof trimming alone [8]. Transphyseal bridging is also often used to correct angular deformities. A popular technique for doing so is placement of two cortical screws and one or two figure-eight cerclage wires. This technique was compared with staple placement in a retrospective study published in 1978 [4]. From this study, it was concluded that the overall success rate did not differ, but surgical complications were greater with staple application. The authors reported marked blemishes, wound dehiscence, staple spreading, and staple extrusion needing reinsertion. The staples used in that study were vitallium staples originally manufactured for use in humans. The complications described in that study have led to a negative view of using staples for transphyseal bridging. The staple technique has been seldom recommended and is widely considered not to be as secure as screws and wire.

Figure 1. Heavy pliers used to bend Steinmann pin.

Figure 2. Cutting the pin.

Our experience with staples has been to the contrary. In our hands, transphyseal bridging is accomplished using custom-made staples. Staples can be readily made by any practitioner with materials that are easy to obtain. Surgery time is short using this method, and the cosmetic result is excellent in almost all cases. We experience very few incisional complications, and the staples are secure and are easy to remove.

2. Materials and Methods

We reviewed records from all foals that had transphyseal staples placed between January 1, 2000 and September 12, 2006. Surgery was performed on 63 foals. A staple was placed for unilateral deformity across the medial distal radial physis in 32 foals and placed bilaterally in 20 foals. Three foals had a staple inserted across the lateral distal radial physis. The lateral distal metacarpal physis was bridged with a staple in five foals with unilateral deformity and five foals with bilateral deformity.

Transphyseal Staples

Steinmann pins [a] of 2.7 mm diameter are used to make staples. A 90° angle is bent in the end of the Steinmann pin with heavy pliers at ≈3 cm from the end (Fig. 1). An identical bend is placed ≈3cm from the first, and the pin is cut at ≈3 cm from the second bend (Fig. 2). The cut end is sharpened on a bench grinder (Fig. 3). This yields a U-shaped staple ≈3 cm on all three sides (Fig. 4). The same procedure is repeated on the other end of the pin, and thus two staples are made from one pin. The staples are sterilized individually or in pairs in an autoclave and stored until use. Smaller staples can be made in the same manner with smaller Steinmann pins for fetlocks and miniature horses (Fig. 4).

Case Management

Radiographs are performed before surgery to rule out severe crushing of the cuboidal bones as a cause of the angular limb deformities before recommending tranphyseal bridging to the owners. If the foal has carpal valgus and is young (<2 mo old), and the deformity is mild to moderate (less than ≈15°), the owners are encouraged to restrict exercise for 30 - 60 days. We recommend this because many foals correct with no surgical intervention. If the foal does not correct, has a fetlock deformity, or if the abnormality is severe, transphyseal bridging by placement of the custom-made staples is recommended.

Surgery

Depending on the surgeon’s preference, foals may be administered non-steroidal anti-inflammatories and antibiotics. Foals are sedated with butorphanol (0.05 mg/kg, IV) and/or xylazine (0.1 mg/kg, IV), nasotracheally intubated, and induced with isoflurane to effect. Foals are placed in lateral recumbency to allow access to the appropriate physis. For example, foals with valgus are placed in recumbency so that medial physis is accessible. Foals with bilateral deformities are turned to the opposite recumbency during surgery for completion of the other leg.

Figure 3. Sharpening the cut end of the staple.

Figure 4. Examples of commonly used staple sizes.

After draping, towel clamps are used to retract skin dorsally. This prevents the skin incision, when released, from being located directly over the staple. The skin incision is made centered over the widest part of the physeal area with a no. 10 scalpel through the skin and subcutaneous tissues. The incision is ≈4 cm in length. The physis is identified using a needle, the antebrachial carpal or fetlock joint is identified through palpation, and the staple is centered over the physis. The staple is inserted into the bone using a hammer. The proximal end is not driven down flush with bone, leaving it slightly "proud." This makes palpation and elevation of the proximal edge of the staple easier during removal. It is possible to take intraoperative radiographs or use fluoroscopy to verify placement of the staple at this point in the surgery, but with experience, this is not necessary. The skin is released and it is closed with 2 - 0 poliglecaprone 25 in a continuous horizontal mattress or subcuticular pattern. The leg is bandaged, and the feet are trimmed if necessary before moving to recovery.

Aftercare

Owners are instructed to keep the leg or legs bandaged for at least 2 wk with a padded pressure bandage. They are instructed to change the bandage every 3 - 4 days or sooner if the bandage becomes torn or slips down. The bandage is made up of a cotton roll [b], brown gauze [c], and elastic cohesive bandaging tape [d]. Both ends of the bandage have elastic tape [e] applied to seal the top and bottom of the bandage. Stall confinement is recommended to owners until the legs are 50% corrected. After that, they are told they can give the foal small paddock turnout. Owners are cautioned to bring the foals back as soon as the legs appear straight to prevent overcorrection. If bilateral, they are instructed to return if one of the legs is straight, even if the other is not.

Figure 5. Blocking the site before standing staple removal.

Staple Removal

Staple removal is accomplished under anesthesia or standing with sedation and local anesthesia. If anesthetized, foals are induced as described above and placed in the same recumbency. The leg is draped and towel clamps are used as described above to move the skin dorsally over the staple. The staple is usually easily palpable under the skin. The skin incision is made on the scar from the previous surgery site through the skin, subcutaneous tissues, and down to the staple. A Langenbeck periosteal elevator is inserted under the proximal end of the staple, which should be slightly proud, and is used as a lever to loosen the staple. Sterile pliers are used to grasp and remove the staple. The skin is released and closed as described above.

For standing removal, foals are sedated with detomidine, and the staple is palpated under the skin. The area is anesthetized with mepivicaine using a subcutaneous block after palpation and location of the staple (Fig. 5). The leg is prepared routinely. Towel clamps are used to retract the skin as described above until the scar from the previous surgery is over the staple. An incision is made and the staple is elevated and removed as described above. 2 - 0 poliglecaprone 25 is used to close the skin in a cruciate pattern, and the leg is bandaged.

3. Results

A total of 63 foals had staples placed during the time period we reviewed. Twenty foals had bilateral carpal valgus, 32 foals had unilateral carpal valgus, 3 foals had unilateral carpal varus, 5 foals had bilateral fetlock varus, and 5 foals had unilateral fetlock varus.

Figure 6. Foal with unilateral carpal valgus.

The average length of surgeries (recorded from skin incision to end of skin closure; end of second skin closure for bilateral procedures) are as follows: bilateral insertion of staples, 32 min; unilateral insertion of a staple, 19 min; bilateral removal of staples, 31 min; unilateral removal of a staple, 16 min.

The average time for removal of staples in standing foals was ≈10 min. Nineteen foals had their staples removed by their referring veterinarian.

The average age of all foals at presentation was 59 days. Foals with carpal valgus or varus were an average of 60 days old on presentation. Foals with fetlock varus were an average of 43 days old at presentation, except for one foal that was 181 days old and had a staple placed at the owner’s request. The average number of days from placement of the staples until correction and removal was 47 days and ranged from 13 to 193 days. In addition, one owner waited 262 days before bringing the foal back, and the foal had overcorrected. A staple was placed across the opposite physis to correct the deformity. Four foals that had bilateral staple placement had the staples removed separately.

One Clydesdale foal had severe unilateral carpal valgus and returned to our clinic 7 wk after placement of the staple with little correction. Radiographs revealed that the staple was spreading. That staple was removed, and two additional staples were placed. The foal eventually corrected, and the staples were removed by the referring veterinarian. Another foal had crushing of the cuboidal bones caused by incomplete ossification as a neonate, and the initial staple was removed 121 days post-operatively and replaced with two more staples. The deformity eventually resolved, and both staples were removed at 193 days from the initial surgery.

Results of one foal with severe unilateral deformity are shown in Fig. 6 and Fig. 7.

Figure 7. Same foal in Figure 6 after limb had straightened.

Incisional complications were encountered in six foals (9.5%). All were minor complications that resolved with continued bandaging and conservative management. Two foals had seromas; these resolved after treatment with drainage and bandaging. One foal’s bandages were not maintained by the owner after surgery, and the surgical incisions dehisced. The foal was returned to our clinic, and with bandaging, the wounds healed. The staples remained in place during this time. One foal had severe carpal valgus, and when bandaging was discontinued by the owner, the distal radii rubbed together and caused dehiscence of the surgical site (Fig. 8). Bandages were replaced, the wounds healed, and staples remained in place. The end cosmetic result of the incision sites were excellent (Fig. 9) One foal that had bilateral staples was noted to have drainage at one of the surgery sites at the time of staple removal. Both staples were removed, and the infected site was left partially open after staple removal. This site was kept in a bandage by the owner until drainage had ceased and the area was healed. One foal had scar tissue at the surgery site that was noted during a recheck 1.5 mo after staple removal. None of the staples were extruded, and only one staple was found to be spreading (the Clydesdale foal discussed above).

4. Discussion

Transphyseal stapling is an effective method for growth retardation in foals with valgus or varus deformities. Staples can easily be made with equipment and supplies available to most practitioners. Insertion and removal of the staples is accomplished with little time and effort, and removal can be performed standing. Incisions to insert and remove the staples are small, and the appearance is cosmetic after healing. The staples are easy to remove standing compared with screws and wires. Using the heavier custom-made staples from Steinmann pins seems to reduce the spreading and extrusion encountered with vitallium staples. Incisional complications were minor, and all healed with continued bandaging. Incisions healed normally in the rest of the foals, and cosmetic results were excellent in those foals (see Fig. 9).

Figure 8. Dehiscence of surgical sites in a foal with severe bilateral deformity.

Figure 9. Cosmetic appearance of foal in Figure 8 after incision sites healed.

Footnotes

[a] Miltex Instrument Company, Bethpage, NY 11714.
[b] CombiRoll, Franklin-Williams, Lexington, KY 40581.
[c] Brown "Cling" Gauze, Jorgensen Laboratories, Loveland, CO 80358.
[d] Vetrap, 3M, St. Paul, MN 55144.
[e] Elastikon, Johnson and Johnson, New Brunswick, NJ 08933.