Acute limb shortening and modified pantarsal arthrodesis for the treatment of a highly comminuted distal tibial articular fracture in a dog

Abstract

A three-year-old female spayed Lurcher was referred for the treatment of a highly comminuted distal tibial articular fracture. Resection of the area of comminution with a transverse osteotomy of the tibial diaphysis and talar ridges was performed, followed by modified pantarsal arthrodesis and a calcaneotibial screw. The treatment resulted in 7 cm of tibial shortening, equating to a 28% reduction in the total tibial length. Radiographic union of the arthrodesis was successful. Fair use of the pelvic limb was documented long-term. Combined acute limb shortening and modified pantarsal arthrodesis resulted in an acceptable outcome and could be considered in cases of highly comminuted distal tibial fractures.

INTRODUCTION

Fractures of the tibia and fibula are common in dogs, and fractures involving the distal tibia represent 21% of canine tibial fractures [1]. Comminuted and articular fractures of the distal tibia are relatively rare [1,2]. Treatment of articular fractures involves anatomic reconstruction, rigid fixation to achieve perfect congruity of the articular surface and early return to function [2,3]. Arthrodesis is indicated if preserving a functional joint is impossible [2,4,5].

Pancarpal (PCA) or pantarsal arthrodesis (PTA) are described [6] as treatment options for comminuted distal radial and tibial articular fractures when preserving a joint is impossible [2,3,6], but clinical reports are sparse [6]. To the best of the authors’ knowledge, no reports have described the outcome of acute pelvic limb shortening and modified PTA for treating a highly comminuted distal tibial fracture in dogs. This paper reports the surgical technique and long-term outcome of a dog that underwent this procedure.

CASE PRESENTATION

A three-year-old, 22 kg female spayed Lurcher was referred for the management of a comminuted right distal tibial fracture following a fall in the garden less than 12 hours prior to presentation. Radiographs obtained at the primary veterinary hospital had identified a distal tibial fracture with the suspicion of articular involvement. A bandage with a lateral splint was placed. Meloxicam was administered, and the dog was referred.

The dog was anesthetized at the authors’ institution, and radiographs confirmed a closed, highly comminuted right distal tibial articular fracture (Fig. 1A). Computed tomography (CT) identified a highly comminuted non-reconstructable right distal tibia fracture, with severe fragmentation of the articular surface but no evidence of a pathologic fracture (Fig. 2). A modified Robert Jones bandage with a lateral splint was reapplied.

Fig. 1. Preoperative (A), immediate (B), seven weeks (C), 16 weeks (D), and 15 months (E) postoperative mediolateral and caudocranial radiographs after modified pantarsal arthrodesis demonstrating complete healing of the ostectomy site and tarsal arthrodesis. Note the mild bending of the calcaneotibial screw.

Fig. 2. Preoperative computed tomographic sagittal (A), dorsal (B), and axial (C) images of the right distal tibial articular fracture.

The surgery was performed 24 h after CT to allow the surgical planning. The surgical plan consisted of an ostectomy of the comminution, acute limb shortening, and modified pantarsal arthrodesis. Preoperative medication included intravenous (IV) constant rate infusion (CRI) of ketamine (Ketamidor; Chanelle Pharma, Ireland) and morphine (Morphine sulfate; Mercury Pharma, Ireland). Tranexamic acid was also prescribed (Cyklokapron solution; Pfizer, UK) to prevent breed-associated hyperfibrinolysis [7]. The dog was premedicated with medetomidine (Sedator; Dechra, UK) combined with preoperative CRIs. Anaesthesia was induced with propofol (Propofol-Lipuro; B. Braun Melsungen AG, Germany) and maintained with isoflurane (Isothesia; Henry Schein Animal Health, Ireland) in oxygen. Cefuroxime (Zinacef; GlaxoSmithKline, UK) was started at induction and given every 90 min intraoperatively. A preoperative epidural with bupivacaine (Marcain Polyamp, Aspen, Ireland) and preservative-free morphine (Morphine sulfate, Mercury Pharma, Ireland) was performed.

Following the medial approach from the right mid-tibia to the distal metatarsal II (Fig. 3A), the comminuted bone fragments and fracture hematoma were debrided (Fig. 3B), and a transverse osteotomy perpendicular to the tibial long axis was performed immediately proximal to comminution (Fig. 3C). The distal third of the fibula and tibiofibular ligament were excised. A talar ridge ostectomy was performed at an approximately 50° angle to the long axis of pes, effectively excising medial and lateral talar ridges, producing a flat talar surface (Fig. 3D). The articular cartilage of the tarsal joints was debrided with a pneumatic burr. An autogenous cancellous bone graft was harvested from the humerus, and joint spaces were packed before a 3.5/2.7-mm hybrid PTA plate (Veterinary Instrumentation, UK) was applied to achieve interfragmentary compression and load sharing. Perfect limb alignment in all planes was confirmed subjectively (Fig. 3F). A 3.5-mm calcaneotibial cortical screw was placed (Fig. 3G and H). Radiographs confirmed correct implant positioning, excellent apposition, and alignment (Fig. 1B). There was a 7 cm (28% total tibial length) reduction in tibial length compared with the left. A full limb-modified Robert Jones bandage was applied.

Fig. 3. Intraoperative pictures taken at different stages of the procedure: (A) Intra-articular view after the medial approach to the distal tibia and tarsus; (B) Surface of the distal tibia after ostectomy of the malleoli and dissection of the fracture hematoma. Note the complete loss of articular surface; (C) Transverse osteotomy of the tibia at the proximal aspect of comminution; (D) Defect created after ostectomy of the tibia and talus ridges; (E) Predrilled plate holes for the medially applied pantarsal arthrodesis plate and following burring of articular cartilage; (F, G, H) Final plate and calcaneotibial screw position.

The dog remained hospitalized for bandage changes and analgesia for seven days. Cefuroxime was continued for 24 h and transitioned to oral cephalexin (Cephacare; Ecuphar, Belgium) for 14 days. The IV CRIs were discontinued 24 h postoperatively, and morphine boluses (Morphine sulfate, Mercury Pharma, Ireland) were administered for a further 36 h. The dog was transitioned to oral meloxicam for 14 days (Loxicom; Norbrook Laboratories, UK), gabapentin for 10 days (Neurontin; Upjohn, UK), and paracetamol for seven days (Paracetamol; GlaxoSmithKline, UK). Tranexamic acid (Cyklokapron solution, Pfizer, UK) was continued orally for seven days.

Mild lameness but consistent weight bearing was observed 24 h postoperatively at slow walk. Bandage changes were performed at 3, 6, 11, 14, and 18 days postoperatively and were removed 21 days postoperatively. Moderate lameness was noted immediately after bandage removal. Good limb use was described at seven weeks, with consistent weight bearing at a slow walk. The dog was allowed 10–15-min lead walks three times daily and was receiving no medication. On examination, there was intermittent non-weight-bearing lameness at the walk. Increased thickness of the right common calcaneal tendon (CCT) with pain was identified. The arthrodesis was stable on palpation. The radiographs identified the static implants and the progression of the joint fusion but there was persistence of joint spaces, with a moderately increased CCT thickness (Fig. 1C). Ultrasound identified an increased thickness of CCT with a moderately irregular shape, heterogenicity, and reduced fiber pattern. Meloxicam (Loxicom, Norbrook Laboratories) was prescribed for four weeks, and marked improvement in limb use was noted after two days. The dog returned to being mildly lame but with consistent weight bearing at the walk.

At 16 weeks, gradual improvement in gait was reported, with persistent mild lameness at a slow walk. The dog was receiving 20-min lead walks three times daily with meloxicam for analgesia. On examination, there was mild lameness at a slow walk, intermittent skipping at a faster pace, and non-weight-bearing lameness at the trot. The CCT was not painful and mildly thickened, with definitive improvement. The radiographs identified complete healing of arthrodesis but also mild bending of the calcaneotibial screw (Fig. 1D). Ultrasound identified a mild reduction in the thickness of CCT, with preserved fibrillar pattern. Short periods of off-lead activity and discontinuation of meloxicam was recommended.

At 15 months, no lameness at a slow walk was reported, but mild lameness could be seen after prolonged exercise. The dog was not receiving medication, and exercise was not restricted. On the examination, no lameness was observed at a slow walk, intermittent skipping was noted at a fast walk, and non-weight bearing was noted at the trot. There was a mild reduction in stifle extension and persistent mild non-painful CCT thickening. Radiographs documented static implant positioning and persistent mild CCT thickening (Fig. 1E). Ultrasound identified a mildly increased CCT thickness.

DISCUSSION

To the best of the authors’ knowledge, this is the first report describing long-term outcomes after acute limb shortening and modified PTA for the treatment of a highly comminuted distal tibial fracture in a dog. The dog achieved acceptable long-term outcome, with mild weight-bearing lameness at a slow walk but intermittent skipping at a faster pace and non-weight bearing at a trot at the final follow-up. The modified PTA described herein healed without complications. CCT thickening was observed postoperatively, as reported after traditional PTA [5], and was believed to be secondary to the acute tibial shortening.

CT confirmed a highly comminuted and non-reconstructable fracture. The authors considered using a longer limb salvage PTA plate extending from the proximal tibia to the metatarsus, effectively bridging the comminution, but there were concerns regarding the inability to achieve compression and load sharing. Orthogonal plating with extended limb salvage plate and additional cranial/dorsal plate was also considered [8], but there were concerns with a closure with poor soft tissue coverage [8]. Transarticular external skeletal fixation was considered but avoided due to the reported high rate of implant-related complications [9]. Removal of the comminution in the present case facilitated load sharing and interfragmentary compression. One report [6] described a distal radial ostectomy and ostectomy of proximal radiocarpal bone followed by PCA for managing highly comminuted distal radial articular fractures in two greyhounds. One dog achieved a full functional long-term outcome (normal gait or mechanical gait alteration), and the other had an acceptable outcome with persistent mild lameness [6].

Options considered to fill critical bone created in the present case included bone allograft [10], endoprosthesis [11,12], 3D-printed polycaprolactone/β-tricalcium phosphate scaffold [13], distraction osteogenesis [14], and partial amputation with endo/exo-prosthesis [15,16]. A limitation of the use of allograft was the high infection rate reported [10]. Catastrophic failure of a patient-specific porous titanium endoprosthesis in the distal tibia at 280 days postoperatively was reported [11]. Additionally, this technique may be associated with a delay in treatment associated with implant production [11,12]. Distraction osteogenesis has been described for restoring a distal tibial defect after tumor excision but was associated with numerous complications [14].

Acute pelvic limb shortening has been described experimentally [17]. They suggested that dogs can adapt to having up to 20% of their femoral diaphysis removed by increasing the standing angle of the stifle of the shortened limb and decreasing the standing angle of the stifle in the contralateral pelvic limb [17]. Acute thoracic limb shortening has been described for treating distal radial osteosarcoma with a 6 cm radius excision and PCA [18]. The procedure was well tolerated, and the postoperative function was described as good, with mild mechanical lameness [18]. A compensatory carpal hyperextension was reported in the contralateral limb. A custom external prosthesis was also required and fitted 15 weeks postoperatively to aid the limb length differential and subsequent excellent limb use [18]. In the present case, the effective reduction in the tibial length was 7 cm, translating to approximately 28% of the total tibial length. The dog achieved an acceptable long-term functional outcome, with no lameness at a slow walk but persistent lameness at the trot. In addition to the limb shortening, the compensatory extension of the tarsus at faster-paced walks was not possible due to the fusion of the tarsal joint, contributing extensively to the lameness detected. Owing to the lack of pain on CCT palpation and complete radiographic healing of the PTA, the lameness was attributed to acute limb shortening and the lack of compensatory tarsal hyperextension as a result of joint fusion. Considering the postural compensation noted in the mentioned literature to limb shortening [17], adjustment of the PTA plate angle, increasing the 140° established by the commercially available pre-contoured PTA plate used, might have been beneficial to compensate partially for the limb shortening, effectively mimicking the extension of the tarsus. However, for this to happen a custom plate would be necessary.

The complications encountered herein included CCT thickening and persistent postoperative lameness, some of which may have been mechanical. The reason for the CCT tendinopathy is not entirely understood [4,5], with some investigators advocating a CCT tenotomy/tenectomy when performing PTA to prevent this complication [5]. In one study [5], one case was resolved with medical treatment, while two cases were treated with surgical transection [5]. In the present case, a conservative approach was elected, with improvement after four weeks of anti-inflammatory use. In the same study, a surgical site infection rate of 30.5% was documented for pantarsal arthrodesis [5]. Therefore, the authors prescribed postoperative cephalexin for 14 days after surgery.

The limitations are inherent to a single case, and the follow-up gait assessment was subjective as force plate analysis was unavailable. The follow-up clinical and radiographic assessments were non-standardized. The technique described may be suitable for dogs with complex, highly comminuted distal tibial fractures or primary bone tumors of the distal tibia. Further studies, including larger cohorts, will be needed to specify the long-term outcome.