A 7-month-old female neutered Bengal cat was referred to the Queen Mother Hospital for Animals following unknown trauma that had occurred the same day. Clinical examination revealed non-weightbearing left pelvic limb lameness secondary to two grade IIIB open fractures. A left, comminuted, mid-diaphyseal tibial fracture was present, with a 35 x 23 mm soft tissue defect on the medial aspect of the crus, resulting in exposure and contamination of the fracture site. Ipsilateral mid-diaphyseal fractures of metatarsals II-V were also present, with a 60 x 30 mm wound on the dorsolateral pes. Nociception and vascularity were intact. The remainder of the examination was unremarkable.
The cat was initially treated with methadone (0.2 mg/kg IV q4h [Synthadon; Animalcare]), amoxicillin-clavulanate (20 mg/kg IV q8h [Augmentin; GlaxoSmithKline]) and intravenous fluid therapy (2 ml/kg/h [Hartmanns; Dechra]). The wounds were lavaged using 6 l sterile saline (Hartmanns; Dechra). Bacteriology samples were then taken to identify residual contamination, and sterile dressings (Primapore; Smith & Nephew) were applied. Venous blood gas analysis was unremarkable aside from mild respiratory acidosis, hyperkalaemia (potassium 5.0 mmol/l, reference interval [RI] 3.6-4.6), hypercalcaemia (calcium 1.41 mmol/l; RI 1.13-1.33) and hyperglycaemia (glucose 11.9 mmol/l; RI 4.7-7.3). Thoracic radiographs revealed a small-volume pneumothorax, which was treated conservatively. Pelvic limb radiographs confirmed left tibial and metatarsal fractures as previously described and a mid-diaphyseal fibular fracture (Figure 1a,b; Figure 2a,b). Abdominal and thoracic-focused assessment with ultrasonography for trauma was performed and was unremarkable.
Fracture repair was pursued under general anaesthesia (GA) 36 h after presentation. Anaesthetic protocol included methadone (0.2 mg/kg IV [Synthadon; Animalcare]) and medetomidine (0.005 mg/kg IV [Sedator; Dechra]), ketamine (0.5 mg/kg IV [Anesketin; Dechra]) and alfaxalone (1.8 mg/kg IV [Alfaxan; Jurox]) coinduction. A bupivacaine (2 mg/kg, up to a total volume of 0.8 ml per site [Marcain 0.5%; Aspen]) femoral and sciatic nerve block was performed to achieve circumferential locoregional anaesthesia of the crus and pes. The tibial fracture was stabilised with a modified bilateral uniplanar (modified type 2) ESF (Figure 1c,d; Figure 3a,c,e,g,i). The metatarsal fractures were stabilised with a modified type 2 freeform ESF (Figure 2c,d; Figure 3b,d,f,h,j). The wounds were surgically debrided and lavaged, bacteriology samples were taken and wet-to-dry dressings were placed. Microbial culture following surgical debridement and lavage isolated Bacillus species, Acinetobacter species and a third, unidentified isolate; a course of amoxicillin-clavulanate (20 mg/kg q12h [Kesium; Ceva]) and pradofloxacin (5.5 mg/kg q24h [Veraflox; Bayer]) was required to ensure susceptibility of all isolates. Antibiotics were discontinued when all wounds were covered with granulation tissue.
Ongoing open wound management consisted of daily surgical layered debridement and replacement of wet-to-dry dressings, which were changed to a foam dressing (Allevyn; Smith&Nephew) with hydrocolloid gel (Intrasite; Smith&Nephew) when no devitalised tissue remained. After 10 days of wound management, both wounds had a small amount of healthy granulation tissue circumferentially in the periphery of the wound, but there was minimal evidence of wound contracture or epithelialisation and large areas of tibial and metatarsal bone remained exposed (Figure 3e,f).
Ten days postoperatively, forage of the exposed tibial diaphysis, partial apposition of the cranial and caudal musculature within the tibial wound, and placement of NPWT was performed under GA using the same aforementioned protocol. Under aseptic conditions the ESF bars and pins were padded with cohesive bandage (VetWrap; 3M). Black polyurethane foam (400-600 mum pore size) was applied to the cranial and caudal aspect of the limb, including the wounds and incorporating both ESFs, from the pes to the level of the proximal tibia. The construct was sealed with adhesive polyurethane film (Opsite; Smith&Nephew). Continuous negative pressure (-125 mmHg) was applied. The dressing was replaced at 48-84 h intervals (Figure 4), totalling 8 days of NPWT.
At cessation of NPWT, the tibial wound was completely covered by healthy granulation tissue (35 x 15 mm; Figure 3i). This wound was left open to heal by second intention. Healthy granulation tissue was present throughout the pes wound (55 x 30 mm), although a small portion of metatarsals III and V remained exposed (2 x 8 mm and 3 x 16 mm, respectively; Figure 3j). Hydrogel (Intrasite gel; Smith&Nephew) and foam (Allevyn; Smith&Nephew) dressing was applied over this wound, and was replaced twice within 11 days. At that stage, granulation tissue covered the entirety of the wound, while the size of the wound remained unchanged. A free meshed skin graft from the left flank was used for closure. The graft was covered with paraffin gauze (Jelonet; Smith&Nephew) and polyurethane foam (Allevyn; Smith&Nephew). The dressing was changed three times in 14 days.
Six weeks after admission, a weightbearing left pelvic limb lameness was present (4/10), with reduced tarsal range of motion, attributed to prolonged immobilisation. The graft donor site wound and the tibial wound were fully healed and there was 100% graft take (Figure 5). The cat was discharged with instructions to continue crate rest, with short periods of controlled exercise (5 mins, 3-5 times daily, increasing by 5 mins each fortnight), as well as continued monitoring of the skin graft site and ESFs.
The cat was re-examined 16 weeks after the initial surgery. A 4/10 left pelvic limb lameness remained. Radiographs revealed delayed union of the tibial fracture (Figure 1e,f), functional malunions of metatarsals II-IV and an atrophic non-union of metatarsal V. After the cat was anaesthetised with the same protocol as previously described, the metatarsal ESF was removed (Figure 2g,h) and two loose pins from the tibial ESF were removed. A Jamshidi needle biopsy sample from the distal tibial fragment and a pin tip from the metatarsal ESF were submitted for microbial culture, which were both negative.
Twenty weeks postoperatively, repeat radiographs of the tibia confirmed non-union of the tibia; thus, revision surgery was performed (Figure 1g,h). The tibial ESF was removed. Autologous bone graft was harvested from the left ilial wing. Following transverse ostectomies of the tibial and fibular fracture margins to reopen the medullary canals and allow a transverse surface for compression, the graft was applied to the fracture site and the tibia was stabilised with a medially positioned 2.7 mm locking compression plate (LCP; Synthes) placed in load (Figure 6a,b). Histopathology (for completeness) of the ostectomised fracture margins revealed immature callus and bone remodelling, and culture was negative.
The cat was discharged 5 days postoperatively with meloxicam (0.05 mg/kg q24h PO [Metacam; Boehringer Ingelheim]), restricted exercise and a physiotherapy plan.
Re-examination of the cat 10 weeks after internal fixation (30 weeks after trauma) showed a 3/10 left pelvic limb lameness. Both tarsus and stifle had full range of motion. Radiographs revealed radiographic union of the tibial fracture; the radiographic appearance of the pes was unchanged from the previous description (Figure 6c,d; Figure 2i,j). Gradual return to normal exercise was recommended.