Use of a New Investigational Interlocking Nail Supplement in the Repair of Comminuted Diaphyseal Tibia Fractures in Two Dogs

Case No. 1

A 5-month-old, 10-kg, castrated male, cocker spaniel cross was referred for treatment of a closed, comminuted, mid-diaphyseal fracture of the left tibia. The fracture had occurred 3 days previously as a result of a motor vehicle accident. On physical examination, the dog was nonweight bearing in the left hind limb. Substantial soft-tissue swelling was noted in the tibial area. Mediolateral and craniocaudal radiographic views of the left tibia were obtained [Figures 1A, 1B]. A comminuted, closed, diaphyseal fracture was identified, with a caudomedially displaced comminuted fragment.

The dog was premedicated with atropine^a (0.04 mg/kg intramuscularly [IM]), acepromazine^b (0.03 mg/kg IM), and butorphanol^c (0.3 mg/kg IM). General anesthesia was induced with a combination of ketamine^d (5.5 mg/kg intravenously [IV]) and diazepam^e (0.5 mg/kg IV) and was maintained with isoflurane in oxygen. Cefazolin sodium phosphate^f (22 mg/kg IV q 2 hours) was given at the time of induction.

The left rear limb was prepared for aseptic surgery, and a medial parapatellar incision was made. The tibial plateau was drilled with a 3.5-mm drill bit, allowing for the introduction of a 4-mm diameter, 101-mm long, 02–02 model 11 ILN.^g

The proper length of the ILN was chosen by measuring it against the radiographs of the intact, left tibia. A tibial extension^h was attached to the selected ILN to assist nor-mograde insertion of the nail distally.

A limited surgical approach was then made over the fracture site, and the ILN was directed into the distal fracture fragment, incorporating the comminuted piece under direct visualization. Once the ILN was seated, the ILN jigⁱ was attached to the tibial extension, and stab incisions were made on the skin over the ILN holes at the medial aspect of the limb, under the guidance of the jig. Through these stab incisions, 1.5-mm holes were made with a 1.5-mm drill bit in the proximal and the distal fracture fragments using the appropriate holes in the jig. The jig was removed, and the holes were over-drilled with a 2.0-mm drill bit to accept the hybrid ILN bolt/ESF pins. Next, the holes were measured. Four, 2.5-mm external diameter, 2-mm “bolt diameter,” hybrid ILN bolt/ESF pins^j were cut to the desired length to engage both cortices with the threaded part of the pin. The pins were placed using a Jacob’s chuck. Finally, the tibial extension was detached. The surgical site was lavaged, and the repair was examined for stability. All surgical incisions were closed in a routine manner.

The hybrid ILN bolt/ESF pins were connected using medium SK clamps^k and a connecting bar, creating a type I ESF construct. A sterile bandage was applied over the ESF, and the entire leg was placed in a soft-padded bandage because of distal limb swelling. Postoperative radiographs documented acceptable alignment and proper implant location [Figures 2A, 2B]. The owner was advised to limit exercise to leash walking for the first 4 weeks and then to increase exercise gradually. The ESF bandage was kept clean and changed every second day for 2 weeks on an out-patient basis. The skin-pin interfaces were cleaned and covered with sterile antibiotic ointment at each bandage change. After the suture removal at 14 days, the bandage over the ESF was changed every second week or as necessary.

Six-week follow-up radiographs taken under general anesthesia documented bony callus that bridged the fracture gap on both radiographic views. The ESF hybrid pins were removed, leaving the ILN in the medullary canal [Figures 3A, 3B]. No further bandaging was necessary. Ten weeks postoperatively, the dog had a normal gait.

Case No. 2

A 9-year-old, 23-kg, intact male Australian cattle dog was presented for evaluation of a highly comminuted left tibial fracture and a right inguinal laceration, sustained after motor vehicular trauma. On physical examination, the dog was non-ambulatory in the left rear limb. Radiographs documented a closed, highly comminuted fracture of the proximal one-third of the left tibia [Figures 4A, 4B].

The animal’s anesthesia and perioperative protocol was identical to case no. 1. A limited medial parapatellar was performed to approach the proximal left tibia. The tibial plateau was predrilled with a 3.5-mm drill bit in order to facilitate the ILN insertion into the bone. Next, the medullary cavity was opened and prepared for ILN placement with a 6-mm reamer.^l A tibial extension was attached to a 6-mm diameter, 140-mm long, 02–02 model 11 ILN. The ILN was inserted and directed in a normograde fashion into the distal fragment. The tibia was predrilled through stab incisions over the ILN holes in a medial to lateral direction with a 2.0-mm drill bit, using the ILN jig as a guide. The ILN jig was removed, and the holes were over-drilled with a 2.7-mm drill bit and measured for the hybrid ILN bolt/ESF pin placement. Four, 3.2-mm external diameter, 2.7-mm “bolt diameter,” hybrid ILN bolt/ESF pins were cut to the desired length and inserted with a Jacob’s chuck. The tibial extension was removed. Through a stab incision, an 18-gauge, full-cerclage wire was placed in order to secure the butterfly fragment. The surgical site was lavaged and closed in a routine fashion.

The hybrid ILN bolt/ESF pins were secured to a connecting bar medially using medium SK clamps, creating a type I ESF supplement. The limb was placed in a soft-padded bandage. The inguinal laceration was debrided and primarily sutured. Postoperative radiographs documented satisfactory alignment and proper implant placement [Figures 5A, 5B]. The owner was advised to limit exercise for 4 weeks and then increase exercise gradually. Bandage care was identical to that described for case no. 1.

Radiographs taken at 7 weeks postoperatively showed maturing callus. At a 12-week follow-up, radiographs suggested establishment of a bony bridge. The ESF connecting bar with the SK clamps were removed, and all four hybrid ILN bolt/ESF pins were cut below the skin under general anesthesia, leaving the ILN locked [Figures 6A, 6B]. The tool was now functioning as a regular ILN (without any supplementation) in order to decrease the stability of the repair and increase the loading forces on the weight-bearing limb. No further bandages were applied.

Recheck radiographs at 17 weeks were consistent with a healed fracture, and the dog was using the limb normally. The hybrid ILN bolts were removed under general anesthesia for further destabilization of the repair. The ILN was left in the medullary canal [Figures 7A, 7B]. At last contact with the owner (i.e., 9 months postoperatively), no repair complications were reported.