Orthopedics in Reptiles and Amphibians

Orthopedics in Reptiles and Amphibians

SYNOPSIS

Musculoskeletal disorders are a common cause for presentation of reptiles and amphibians to the veterinarian. Clinical approach to orthopedic cases starts with a thorough history and review of husbandry, and identification of any underlying or concomitant disease. Medical management is indicated for pathologic fractures. Traumatic fractures may require surgical intervention. Stabilization options include external coadaptation and external and internal fixation. Special considerations must be given to shell fractures in chelonians. Many techniques used in mammalian practice can be applied to reptiles and amphibians, although these species may require prolonged healing times by comparison.

KEYWORDS

•Secondary hyperparathyroidism •Osteomyelitis •Snake •Lizard •Chelonian •Anuran •Urodele •External coadaptation •Shell repair

KEY POINTS

• The clinical approach to orthopedic cases in reptiles and amphibians starts with a thorough history and review of husbandry and any underlying disease processes should be diagnosed and addressed.
• Local and systemic analgesia and general anesthesia should be provided as indicated and diagnostic imaging and ancillary tests (e.g. hematology and blood biochemistry panels) should be considered to further characterize the patient’s condition.
• Medical management is indicated for pathological fractures and for the treatment of underlying disease and may include antimicrobials as indicated, appropriate nutritional support, bandaging and external coadaptation.
• In cases of traumatic fractures, surgical stabilization may include external and/or internal fixation and, in the case of chelonians, shell repair.
• Many techniques used in mammalian practice can be applied to reptiles and amphibians, although these species may require prolonged healing times by comparison.

INTRODUCTION

The clinical approach to any orthopedic presentation in a reptile patient begins with a thorough history and review of husbandry. Signalment and inappropriate husbandry may predispose some patients to orthopedic disease, including pathologic fractures, or make them particularly susceptible to traumatic injury. In cases for which surgery is considered, underlying medical problems should be identified and may need to be addressed prior to surgical intervention.

Reviews of the effect of husbandry on the health of captive reptiles and amphibians are available (Chinnadurai & Kane 2014; Watson & Mitchell 2014; Antwis & Browne 2009). However, significant knowledge gaps in species-specific natural history still inhibit evidence-based husbandry recommendations, especially for amphibian species (Michaels et al. 2014; Pessier et al. 2014). Husbandry recommendations should attempt to mimic the natural history and environment, with attention to microclimates and gradients, for each species as much as possible.

UNDERLYING AND CONCOMITANT CONDITIONS

Hyperparathyroidism is a common condition of captive reptiles and amphibians and is often secondary to dietary, nutritional deficiency, lack of exposure to ultraviolet B (UVB) radiation, or primary renal disease. Secondary nutritional hyperparathyroidism (SNHP) should be suspected in reptiles and amphibians fed diets deficient in calcium, vitamin A, and cholecalciferol and those without UVB exposure (Michaels et al. 2015; Tapley et al. 2015; Pessier et al. 2014; Watson & Mitchell 2014; Hoby et al. 2010). Physical exam findings in reptiles and amphibians consistent with SNHP may include skeletal deformities (scoliosis or kyphosis of the spine, rounded skull or shortened mandible), inappropriate posture or non-specific signs of weakness, and swollen long bones or mandible or signs of “rubber jaw” due to fibrous osteodystrophy (Liu et al. 2016; Wright 2008). Reptile owners may report muscle fasciculation or tremors which are presumed to be secondary to hypocalcemia (Wright 2008). The episodic nature of these events may correlated with periods of growth in juveniles or with periods of reproductive activity in adult females. Reproductive physiology of egg-laying reptiles requires females to mobilize calcium stores in response to ovulation in order to form shells around their eggs. Therefore, gravid females may be more susceptible to osteomalacia, osteoporosis and pathologic fractures than males kept under similar husbandry conditions (Raiti & Haramati 1997). Pathologic fractures and orthopedic disease should be considered in female reptiles presented for signs of dystocia.

Due to the chronic nature of SNHP, orthopedic disease may be occult and many patients may present for concomitant problems. Therefore diseases of captivity, including SNHP and associated orthopedic disease should be considered for all patients. In a retrospective study of captive bearded dragons (inland bearded dragon [Pogona vitticeps] and black-soil bearded dragon [P. henrylawsoni]), a majority of patients for which a blood biochemistry profile was performed had a reverse calcium:phosphorus (Ca:P) ratio regardless of presenting complaint (Schmidt-Ukaj et al. 2017). Over a third of animals presented or constipation also had evidence of metabolic bone disease (Schmidt-Ukaj et al. 2017). Chronic stress may predispose young, growing reptiles to skeletal disease. Elevated plasma corticosterone concentrations have been associated with osteoporosis in juvenile, growing American alligators (Alligator mississippiensis) (Elsey et al. 1990).

Other than SNHP, reptiles may present for an orthopedic manifestation of other systemic diseases, particularly infection and neoplasia. Hematogenous spread is often suspected in cases of osteomyelitis and infectious osteoarthritis in reptiles. Bony lesions were the most common clinical sign associated with detection of Salmonella sp. by fecal cultures in reptiles in a zoological collection (Clancy et al. 2016). Although most of these animals were sub-clinical, snakes were the most common taxa to exhibit signs of illness when testing positive for Salmonella (Clancy et al. 2016). Necrotizing osteomyelitis, granulomatous inflammation, osteomalacia and fractures of vertebral bodies and intervertebral spaces due to systemic infection (most commonly Salmonella, but also Pseudomonas and Streptococcus) has been well-documented in a variety of captive snakes (Hardt et al. 2017; de Souza et al. 2014; Di Girolamo et al. 2014; Ramsay et al. 2002; Isaza et al. 2000). Blood samples may be used as a proxy for direct sampling of spinal lesions for culture and sensitivity testing in order to support the diagnosis and to direct antimicrobial therapy (Isaza et al. 2000). Epipterygoid bone Salmonella enterica Kintambo abscess was described in a savannah monitor (Varanus exanthematicus), which was treated using local antibiotic instillation without aggressive debridement.¹ Disseminated infection with Mycobacterium chelonae was diagnosed in a free-ranging Kemp’s ridley sea turtle (Lepidochelys kempii) with a swollen elbow joint and osteolytic lesions on the proximal radius and ulna (Greer et al. 2003). Progressive destruction of both humero-scapular joints, associated with Nocardia sp., Corynebacterium sp., alpha hemolytic Streptococcus sp., and Gram-negative nonfermenters was described in a stranded green sea turtle (Chelonia mydas).² Due to the lack of external wounds, septic arthritis secondary to hematogenous spread was suspected.² Systemic mycoplasmosis has been associated with polyarthritis characterized by erosion of articular cartilage and bone and osteophyte formation in Nile crocodiles (Crocodylus niloticus) (Huchzermeyer et al. 2013). Paravertebral boney masses believed to be secondary to soft-tissue infection were identified in a blue-tailed monitor (Varanus dorianus) with no lesions of the associated vertebral bodies themselves (Rothschild 2014).

For amphibians, water quality is also paramount to musculoskeletal and systemic health. Metabolic bone disease was documented in captive colonies of New Zealand frogs (Archey’s frog [Leiopelma archeyi]and Hochstetter’s New Zealand frog [L. hochstetteri]) due to excessive fluoride in water from municipal water sources (Shaw et al. 2012). Dietary calcium supplementation, UVB exposure, and use of defluorinated water reduced the morbidity, incidence of bone fractures, and mortality rates in these colonies. Other musculoskeletal abnormalities of amphibians, such as limb deformities, are caused by trematode cysts (Ribeiroia sp.) that disrupt the cellular organization of limb buds and have been well-documented in free-ranging anurans (Stopper et al. 2002).

Neoplasia has been well-documented in snakes (Page-Karjian et al. 2017) and other squamates. Neoplasia may directly affected the skull and jaw or the axial skeleton. In a retrospective study of 358 tumor samples, 13 were bone neoplasia. In lizards, benign proliferations of the bone (ossifying fibroma [n=2], fibrous dysplasia [n=1]) as well as malignant cartilage (chondrosarcoma [n=2]) and bone tumors (fibroblastic osteosarcoma [n=2], small cell osteosarcoma [n=1]) were found on the head (n=5) and limbs (n=3) were reported.³ In snakes only malignant cartilage neoplasms (chondrosarcoma [n=2], dedifferentiated chondrosarcoma [n=3]) of the spine were diagnosed.³ An ameloblastoma was documented to cause mandibular osteolysis in a free-ranging black rat snake (Pantherophis alleghaniensis) (Comolli et al. 2015). An osteosarcoma originating from the ribs of an 18-month old captive-bred woma python (Aspidites ramsayi) (Cowan et al. 2011). Chondroblastic osteosarcoma associated with the pelvic girdle was diagnosed in two related spiny-tailed monitor lizard (Varanus acanthurus) (Needle et al. 2013). An oral fibrosarcoma was diagnosed in a geriatric black iguana (Ctenosaura pectinate) (Salinas et al. 2013). These cases suggest that advanced age and genetic predisposition may play roles in neoplasia of reptiles as they do for mammals.

When approaching reptile orthopedic cases, other diseases processes to consider included osteitis deformans (Paget’s disease) and congenital and developmental abnormalities. Osteitis deformans is a chronic focal disorder of bone remodeling that results in a disorganized mosaic of woven and lamellar bone (Preziosi et al. 2007). The condition was documented in a Burmese python (Python molurus bivittatus) with impaired mobility and boney masses of the vertebral column similar to those documented in snakes with infectious vertebral osteomyelitis (Preziosi et al. 2007). Exposure to inappropriate temperatures and humidity gradients has been documented to cause skeletal deformities developmentally in various reptile species. Besides development abnormalities from improper incubation, hereditary skeletal abnormalities have also been documented in reptiles. Congenital kyphosis that was present from hatching and progressively worsened with age has been reported in a Brazilian rainbow boa (Epicrates cenchria crassus) (Sesoko et al. 2011). The deformity was characterized by multiple dorsal deviations of the spinal column without the presence of osteoarthrosis and was believed to be congenital since no other individuals in the clutch were affected despite the eggs having been incubated in an identical manner. Other congenital abnormalities of the axial skeleton including kyphosis and scoliosis have been documented in free-ranging viperids, jararaca (Bothrops jararaca) and Cascabel rattlesnake (Crotalus durissus terrificus) (Nogueira de Carvalho et al. 2017).

TRIAGE AND DIAGNOSTICS

The clinician’s intent should be to provide the same standard of care for reptile patients as for mammals. As such, analgesia is imperative for all patients with orthopedic problems. Discussion of analgesia in reptile and amphibian medicine is beyond the scope of this article, but thorough, evidence-based reviews may be found elsewhere (Perry & Nevarez 2018; Stevens 2011). Signs of pain in reptiles may be more subtle than those in mammalian patients. Changes in feeding behavior may be the only indication of pain in some patients. In a study of ball pythons (Python regius), animals subjected to noxious chemical or surgical stimuli exhibited delays in striking prey items or would skip meals altogether relative to control animals (James et al. 2017). Therefore, a thorough history should include detailed information on the patient’s food consumption and feeding behavior. Fractures and open-wounds should be assumed to be painful and treated accordingly with systemic analgesics, general and/or local anesthesia. As in other species, manipulation and treatment of fractures should be performed under general anesthesia.

Consider administration of analgesics or induction of anesthesia prior to physical examination. Findings of orthopedic examination may include lameness, swelling, necrosis of extremities, joint luxation, impaired or inappropriate range of motion (Schmidt-Ukaj et al. 2017). Obvious wounds should be further characterized by severity (open vs. closed; clean vs. contaminated vs. infected), chronicity, and anatomic location. Open wounds should be thoroughly lavaged and debrided and systemic and/or local antimicrobial therapy instituted prior to surgical closure.

Diagnostic imaging is often necessary to characterize orthopedic disease and institute appropriate treatment. Grossly apparently skeletal lesions and a history of trauma were cited as the most common indications for radiographic evaluation of lizards in one referral hospital (Lojszczyk-Szczepaniak et al. 2018). Radiography is indicated in all cases where orthopedic disease is suspected. In addition to identifying traumatic and pathologic fractures, clinical radiography and CT have been used to subjectively evaluate (Tapley et al. 2015) and to quantify (van Zijll Langhout et al. 2017) bone density in amphibians, respectively. Radiographic techniques for reptiles and amphibians follow similar principles to those applied for mammals and have been reviewed elsewhere (Schumacher & Toal 2001). Orthogonal views are indicated as in other species. Additionally, in chelonians an anterior-posterior projection is recommended in order to evaluate the lung fields as well as the carapace.

Computed tomography (CT) may not be readily available in most practices, but can be used to identify skeletal lesions not apparent radiographically. For chelonians, it is particularly useful for evaluation of proximal joints of the thoracic and pelvic limbs (shoulder and coxofemoral joints, respectively) and shell lesions. CT has been used to diagnose shoulder luxation in a radiated tortoise (Geochelone radiata), and scapular fracture and coxofemoral luxation in a common snapping turtle (Chelydra serpentina) (Abou-Madi et al. 2004). Because the bones of the shell do not align with the external scutes, CT is particularly useful in evaluating the axial skeleton of chelonians in order to make aid clinical decision-making, especially when evidence of trauma is not externally apparent (Spadola et al. 2016; Abou-Madi et al. 2004). In boa constrictors (Boa constrictor imperator), CT has been used to guide biopsies of proliferative bone lesions observed radiographically on vertebral bodies (Di Girolamo et al. 2014). Reviews on the application of CT in reptile practice are available (Gumpenberger & Henninger 2001).

Ancillary diagnostics, including blood biochemistry profiles, low total serum calcium concentrations, low ionized calcium, inverse Ca:P ratios, high parathyroid hormone, and low serum calcidiol concentrations, may be used to support this diagnosis. Elevated alkaline phosphatase may reflect bone remodeling (Preziosi et al. 2007) and elevated creatinine kinase may reflect recent tissue damage. Renal disease may lead to azotemia and, when severe, is one of the causes of secondary hyperparathyroidism. In a study of juvenile veiled chameleons (Chamaeleo calyptratus), total serum calcium concentrations below 2.3 mmol/L (9.2 mg/dL) were consistent with nutritional metabolic bone disease and serum calcidiol (25-hydroxycholecalciferol) concentrations >100 µg/L (>250 nmol/L) were considered ideal (Hoby et al. 2010). Underlying and concomitant problems should be addressed.

Joint disease of the shoulder joint, e.g. septic arthritis or degenerative osteoarthritis, is occasionally described in reptiles, and it is usually diagnosed on diagnostic imaging. Arthroscopy is a surgical procedure use to visualize, diagnose, and potentially treat problems inside a joint. This diagnostic tool has not been well investigated in reptiles, however, it may be of use for cases of osteoarthritis and potential joint infections. Fluoroscopic-guided arthroscopy was used in the case of a yellow-headed snapping turtle (Elseya irwini) with focal degenerative joint disease of the left glenohumeral joint.⁴ Arthroscopy allowed the assessment of the joint and collection of samples for aerobic bacterial, fungal, and mycobacterial cultures.⁴ The authors suggest that arthroscopy can provide a minimally invasive surgical technique to evaluate joint pathology in turtles.⁴

FRACTURE STABILIZATION

Once a fracture has been identified, the site should be immobilized promptly in order to promote healing and avoid complications associated with osseous non-union. Urodelid amphibians and axolotls (Ambystoma mexicanum) in particular have been used in experimental models of bone healing and tissue regeneration (Cosden et al. 2011; Hutchison et al. 2007). They are capable of successfully healing non-stabilized fractures if the fragments are within close proximity (Hutchison et al. 2007). Therefore, in these species, stabilization may be recommended for displaced fractures.

External coadaptation___________________________________________________________

External coaptation is indicated for immediate stabilization of fracture sites upon triage, for patients that are poor surgical or anesthetic candidates due to concomitant disease, and for patients too small for internal or external surgical fixation. External coadaptation may be the only treatment option for some patients, as surgical fixation of fractures should not be pursued in cases in which the strength of the bone is compromised due to SNHP or other metabolic bone diseases. In order to stabilize the fracture site, the joints immediately proximal and distal to the fracture bone must be immobilized.

Ball bandages may be used to stabilize digit luxations and fractures by taping the digits to a ball of cotton or rolled gauze placed in the center of the palmar or plantar aspect of the manus or pes, respectively (Alworth et al. 2011; Raftery 2011). Non-adhesive dressing is used to incorporate the digits and the entire foot proximal to the carpal or tarsal joint into the bandage. In smaller lizards and crocodilians, fractures of the radius and/or ulna of the thoracic limb and of the tibia and/or fibula of the pelvic limb may be stabilized by extending the limb and binding it to the body wall or tail base, respectively, with adhesive medical tape or non-adhesive bandaging (Alworth et al. 2011; Raftery 2011; Mitchell 2002). The use of custom made foam material between the limb and the body may improve the fracture alignment (Figure XXX), and stabilization may be improved by including a splint in the bandage. Risk of malunion is greater for humeral and femoral fractures using this technique and so casting the thoracic or pelvic girdles, respectively, is recommended (Alworth et al. 2011; Raftery 2011). Care must be taken not to occlude the vent when including the pelvic girdle in bandaging or casting. In chelonians, the limb maybe taped or bandaged into place within the shell in order to restrict movement (Alworth et al. 2011). Scapulohumeral luxation and scapular fracture have been successfully treated in chelonians using this technique (Abou-Madi et al. 2004). Only one thoracic or one pelvic limb should be restricted at a time chelonians may experience difficulty respiring if all limbs restricted simultaneously.

In reptiles, some skull and jaw fractures may be successfully treated by restrictive bandage around the head and mouth. Prior placement of an esophagostamy tube allows for nutritional support and enteral medication administration during the convalescent period (Raftery 2011). Experimentally induced unilateral mandibular fractures in adult spotted salamanders (Ambystoma maculatum) healed without treatment with osseous union noted by 21 weeks post-fracture (Hall & Hanken 1985).

Amputation____________________________________________________________________

In one retrospective of captive bearded dragons, limb or tail amputation was the most common orthopedic surgery reported (Schmidt-Ukaj et al. 2017). Digits should be amputated at the level of the metacarpus or metatarsus (Alworth et al. 2011). In smaller lizards, partial limb amputation may leave a stump to be used to aid in locomotion, although there is risk of dehiscence, infection, and recurrent trauma at the site (Alworth et al. 2011; Raftery 2011). When possible, surgical incision closure should be performed in manner that the incision is not in direct contact with the ground. In larger reptiles, complete amputation through the scapulohumeral or coxofemoral joints may be indicated (Alworth et al. 2011). A rolling prosthetic or wheel can be affixed to the plastron of chelonians in order to allow for walking (Alworth et al. 2011; Raftery 2011). Surgical excision of the femoral head and neck has been described to successfully treat an adult leopard tortoise (Stigmochelys pardalis) with chronic, non-weight bearing lameness due to a coxofemoral luxation (Naylor 2013). A cranial approach through the prefemoral fossa was used to access the joint.

Tail amputation follows the same surgical principles as in mammals. In male squamates, care must be taken not to damage the hemipenes should amputation at the proximal end of the tail be indicated. Some lizard species of the iguana (Iguanidae), skink (Scincidae), and gecko (Gekkonidae and Phyllodacylidae) families are capable of caudal autotomy. In these species, the skin may be incised caudal to the site of amputation and the tail snapped and slightly twisted at the intended site of amputation in order to break the tail through the natural fracture plane of a coccygeal vertebra (Alworth et al. 2011). This does not obviate the need for general anesthesia, analgesia, and aseptic technique. If amputated as such, iguanids may regenerate their tail, although primary closure is indicated for all other taxa.

Limb amputation is often indicated for comminuted fractures of the long bones of amphibians (Gentz 2007). Urodelid amphibians are capable of regenerating cartilage at articular surfaces, digits and entire limbs and may do so following surgical amputation (Cosden et al. 2011). In anurans, amputation of the hind limb at the coxofemoral joint is recommended (Gentz 2007). Since male anurans require use of their forelimbs to achieve amplexus during mating, partial forelimb amputation is recommended especially for animals intended for breeding or release into the wild (Gentz 2007). In Eastern newts (Notophthalmus viridescens), the missing limb skeletal elements are restored in a proximal-to-distal direction, which reiterates the developmental pattern, however, the portion of the humerus distal to the amputation site failed to ossify in synchrony with the regenerating radius and ulna.⁵ By 270 days, most regenerated skeletal parts were undergoing ossification, but those of the wrist remained entirely cartilaginous.⁶

External fixation_______________________________________________________________

External fixation cannot be applied to the limbs of chelonians because the devices are prone to damage and failure when the patient attempts to withdraw the limb into the shell (Alworth et al. 2011). External skeletal fixation (ESF) devices can be fashioned using materials readily available in most practices. Bone pins or hypodermic needles are inserted through each fragment of the affected bone at various angles. A connecting bar is fashioned across the needles parallel to the bone by using an intravenous fluid line tubing or a Penrose drain filled with dental acrylic or polymethylmethacrylate (PMMA). ESF devices may be used for fractures of long bones and the mandible (Nau & Eshar 2018). In some cases, stabilization may be improved with the use of cerclage or Kirschner wires. Hypodermic needles may be inserted through the bone on each side of the fracture site and used to guide the passage of the wire through the bone. The needles are removed before twisting the ends of the wire to create an interfragmentary loop. Internal fixation________________________________________________________________

Generally, internal fixation techniques include intramedullary pins and bone plates and follow the same principles in reptiles and amphibians as in other species (Raftery 2011; Gentz 2007).

The successful treatment of a complete fracture of the ramus of the mandible of a boa constrictor with a plate and compression screws has been described (Castro et al. 2014). A closed comminuted fracture of the femur of an American bullfrog (Rana catesbeiana) was successfully treated with internal fixation by use of interfragmentary Kirschner wires and securing a positive profile pin along the femur with encircling sutures and modeling PMMA around the apparatus (Royal et al. 2007). A common chameleon (Chamaeleo chamaeleon) with an oblique fracture of the metaphisis of the left humerus was treated by internal fixation using a 22-gauge needle placed in a retrograde approach (Di Giuseppe et al. 2013). After 3-months a cartilaginous callus was formed and the implant was removed (Di Giuseppe et al. 2013).

Other procedures_______________________________________________________________

Joint injury and intervertebral disease may be diagnosed and treated similarly as in mammals. The successful stabilization of a stifle joint using an extra-articular surgical approach has been described in an American bullfrog with presumptive cruciate rupture (Van Bonn 2009). A dorsal laminectomy successfully resolved clinical signs associated with proliferative boney lesions and kyphosis of the spine in a two-toed amphiuma (Amphiuma means) although the animal required subsequent euthanasia due to recurrence of an unidentified, underlying problem causing ongoing vertebral pathology (Waffa et al. 2012).

Shell fracture repair_____________________________________________________________

Chelonians have their internal organs protected by an exoskeleton (the shell), which is composed of the carapace (dorsal) and plastron (ventral). The two structures are connected by the lateral bridges. The shell is constructed of modified bony elements such as the ribs, parts of the pelvis and other bones. Altogether, the shell contains over 50 dermal bones.⁷ The shell is comprised of the endochondral axial elements of the trunk overlain by a mosaic of dermal bones and an outer epidermal layer made of keratinous scales (also called scutes or shields). Scute margins do not correspond with dermal bone margins, and this overlap contributes to the strength of the shell.⁸ This unique structure was developed by nature to protect the reptile from predator attacks by sustaining impact loads and dissipating energy.⁹ A central longitudinal row of neural plates cap the neural spines of the dorsal vertebrae; a lateral row of costal plates is closely associated with the dorsal ribs; a marginal row of marginal plates, an anterior nuchal plate, and one or two posterior pygal plate(s) complete the carapace.¹⁰

Traumatic shell fracture is a common presenting complaint of chelonians, especially free-ranging individuals. Sea turtles are often presented with traumatic shell fracture or erosion due to boat or propeller strike (Orós et al. 2005). Terrestrial turtles are prone to lawn mowers (Mitchell 2002) and terrestrial and aquatic turtles prone to vehicular trauma, especially during nesting seasons when the search for appropriate nesting sites leads gravid females across roadways (Sack et al. 2017).

Wounds should be thoroughly cleaned by lavage and surgical debridement under general anesthesia prior to primary closure. In all cases, the wound should be lavaged with warm antiseptic solution (e.g. dilute iodine) followed by sterile saline (Alworth et al. 2011). Standard wet-to-dry bandaging may be indicated to decontaminate infected wounds. Wounds that communicate with the coelom carry a poorer prognosis. Vacuum assisted closure (VAC) has been described as an alternative method for wound management in chelonians. VAC may lead to improvement of wound perfusion, reduction of interstitial edema and inflammatory or inhibitory cytokines, stimulation of the production of biochemical mediators or changes in cellular function that may result in the enhancement of granulation tissue formation, reduction in bacterial contamination, and enhanced removal of exudative material from a wound.¹¹ Comparison of VAC and traditional bandages has not been investigated in chelonians.

For partial thickness, ulcerative shell lesions, photopolymerizable nano-hybrid dental composite can be used to close the wounds in addition to local and systemic antibiotics and analgesics as needed (Spadola & Morici 2016). Healing may be expected within 3 months (Spadola & Morici 2016). For shell wounds in aquatic turtles that require recurrent dressing or topical treatment, the bottom can be removed from a resealable plastic container and affixed directly to the shell with epoxy or dental acrylic in order to provide a waterproof, but accessible environment (Sypniewski et al. 2016).

Reduction and stabilization of shell fractures may be achieved using screws and wire or plates mounted through the shell itself. (Figure XXX) Alternative, a top-closure system may be used by affixing mounts for cable ties or wires to the outer surface of the shell using epoxy or dental acrylic (Horowitz et al. 2015). This allows for reduction of central and marginal shell fractures without having to drill holes through the tissue to secure interfragmentary wires. Larger defects can be bridged with sterilized fiberglass patches or aluminum mesh (Alworth et al. 2011). Chelonians require appropriate care post-operatively including analgesics, antibiotics, and nutritional support. Repeat diagnostic imaging may be used to confirm osseous union of the bony plates below the visible scutes. Closely apposed fractures may heal within 12-18 weeks, while larger defects may require significantly longer healing times (Alworth et al. 2011). For free-ranging animals, all medical devices should be removed following rehabilitation prior to release to the wild.

Covering infected wounds/fractures may provide an environment that allows bacteria to proliferate. The use of bacterial cultures and cytology may provide the clinicians with information regarding the presence of contamination. Ideally, the wound bed or fracture site should not be infected, however this may be difficult to determine. Alternatively, the use of stabilization devices that do not directly cover the wounds allow for fracture healing and application of treatments. (Figure XXX) Anecdotally, plastic food containers have been attached to the shell of chelonians, providing protection to the wound while allowing for the application of treatments. (Figure XXX)

CONVALESCENCE

Appropriate nutritional support, maintenance within species-specific preferred optimal temperature zones, and local and systemic analgesia and antimicrobial therapy as indicated, are essential during the convalescent period in order for healing to occur (Pritchard & Ruzicka 1950). Gavage feeding and esophagostamy tubes should be considered in anorectic patients.

Generally, wounds and bone fractures in reptiles take longer to heal than in mammals of similar sizes (Pritchard & Ruzicka 1950). In some cases of complete bone fractures, it can take up to 3 months until radiographic evidence of bony callus and over 5 months until radiographic confirmation of osseous union (Nau & Eshar 2018). Following stabilization, reptiles generally form a larger cartilaginous callus than may be expected in mammals (Pritchard & Ruzicka 1950). Radiographically, this may cause the ends of the fractures to appear further apart in the weeks following stabilization than at time of initial presentation. In an experimental model, endochondral ossification was first apparent radiographically at 3 weeks in a common lizard (Zootoca vivipara)model (Pritchard & Ruzicka 1950). Additionally, unlike in mammals, experimental models of Italian wall lizards (Podarcis muralis) have shown that the articular cartilage of reptiles has high regenerative potential (Alibardi 2015).

Unlike in other taxa, amphibians achieve fracture healing by subsequent ossification of a callus formed by periosteal hyperplasia rather than by secondary cartilage (Hall & Hanken 1985). In untreated spotted salamanders with mandibular fractures, the callus was apparent by 5 weeks post-fracture and calcified bony tissue was observed between 7 and 11 weeks post-fractures with complete osseous union by 21 weeks (Hall & Hanken 1985).

ESF devices, interfragmentary wires, and intramedullary pins can be removed after radiographic confirmation of bony callus and osseous union.

SUMMARY

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