Trionychidae is a taxonomic family of numerous turtle genera, commonly known as softshell turtles. Softshells include some of the world’s largest freshwater turtles, but many can acclimate to living in highly brackish areas. Members of this family occur in Africa, Asia, and North America (18). They are called “softshell” because their carapaces lack horny scales, and they are leathery and flexible, particularly at the sides. Just like other species of turtles, a layer of hard bone is underneath the central part of the carapace, but this does not extend to the outer edges (6). Pelodiscus maackii, commonly known as the Amur softshell turtle (3), or the northern Chinese softshell turtle, is a species of turtle in the family Trionychidae. The species is found in the Russian Far East, northeastern China, Korea, and Japan (26).

Shell injuries are frequently observed lesions in chelonians (2,7,10,13). Traumatic shell fractures in Chelonians are usually the result of bite wounds caused by dogs or wild animals, car accidents, lawnmower accidents, or electric shutters, which can cause catastrophic injuries to the shells and internal organs of wild chelonians (2,14,23). Medical treatment is generally required because the condition rarely resolves independently and may lead to severe sepsis (15,29).

Several materials and techniques have been used to treat hard-shelled turtles (5,15,28,29), but there are few reports of treatment trials for softshell turtles. This paper reports the use of polymethyl methacrylate (PMMA) and fiberglass to treat an Amur softshell turtle, which led to the successful repair of a shell puncture wound on the carapace along with routine supportive therapy, such as intracelomic and subcutaneous fluids, antibiotics, analgesia, and thermal support.

On 19th May 2021, an Amur softshell turtle with multiple injuries on the shell was presented to the Seoul Wildlife Center. A physical examination showed a puncture wound on the carapace located on the cranial left pleural and vertebral carapace, 9.8 cm caudal to the cranial apex of the carapace, and 1.9 cm left lateral to the dorsal midline (Fig. 1). The wound size was approximately 1.5 cm in length, 1 cm in width, and 0.7 cm in depth, and the shape was oval with a relatively slick rim and ulceration (Fig. 2). Approximately 70% of the wound was covered with non-adherent slough, while 30% was covered with granulation tissue. The wound was suspected to be caused by trauma, as its shape was artificial. All vital signs were within the normal range, and the animal weighed 2.37 kg. The mental status was comparatively alert and responsive. Mild dehydration was suspected from reduced activity and movement of the limbs, though oral mucous membrane was pink. Slight bleeding present on the surface of the carapace, even though no signs of significant blood loss or rupture of internal organs were observed.

Figure 1. Severe puncture wound on the carapace of the Amur softshell turtle upon arrival. The wound was located on the cranial left pleural and vertebral carapace, 9.8 cm caudal to the cranial apex of the carapace, and 1.9 cm left lateral to the dorsal midline. The lesion was marked with an arrow.

Figure 2. After hemostasis and dressing, the prominent puncture wound on the carapace of the Amur softshell turtle (A). Wound approximately 1.5 cm in length, 1 cm in width, and 0.7 cm in depth, with an oval shape and a relatively slick rim with ulceration (B). Approximately 70% of the wound was covered with non-adherent slough, while 30% was covered with granulation tissue. The wound was suspected to be caused by trauma, as its shape was artificial. The lesion was marked with arrows.

A routine radiographic examination was proceeded after the physical examinations, and no other internal damage was sustained. Relatively mild inflammatory signs around the wound site were observed on the dorsoventral radiographic image (Fig. 3).

Figure 3. Right lateral view (A), caudocranial view (B), and dorsoventral view (C) of radiographic images of the Amur softshell turtle. Signs of wound penetration through the lung or inflammation were not presented on the right lateral view. Radiopacity in both the left and right lungs did not show a significant difference on craniocaudal view as well. The arrow indicate the puncture wound site.

As an initial treatment, direct pressure with sterile gauze was exerted on the wound to stop further bleeding. The wound was dressed after hemostasis and cleansing with normal saline (0.9% sodium chloride) and 2% povidone iodine. A polyurethane dressing (Tegaderm; 3M; MN, USA) was applied to the wound as a temporal sterile covering. Irrigating and flushing were done repeatedly daily for three days. A nonsteroidal anti-inflammatory drug (meloxicam [Metacam; Boehringer Ingelheim] 0.2 mg/kg, intramuscularly, once in a day for three days) and antibiotics (enrofloxacin [Baytril; Elanco] 5 mg/kg, intramuscularly, once in a day for three days) was prescribed to relieve pain and inflammation and prevent secondary infections (9). Intracelomic fluid was also administrated to correct the mild dehydration. Ringer’s solution for reptiles (Hartmann’s solution and 0.45% sodium chloride with 2.5% glucose in a ratio of 1:2) was administered (9,11,23) by 25 mL/kg/day for the initial two days, then 15 mL/kg/day for next six days.

After three days, the turtle was stabilized and adapted to the environment. Surgical repair was chosen for the carapace lesion. The carapace was initially washed with warm water, followed by a 10% povidone iodine solution. The turtle was then dried and positioned in ventral recumbency on a heating pad. Premedication with tramadol (10 mg/kg; Tridol; Yuhan), meloxicam (0.2 mg/kg; Metacam; Boehringer Ingelheim), and cefotaxime (20 mg/kg; Cefotaxime Sodium Injection; DaeWoong) were administered intramuscularly, and anesthesia was induced using isoflurane with an induction chamber. The breathing circuit was equipped with a T-piece system. In 4% isoflurane with 2 L/minute oxygen, the time to the initial relaxation was 11 minutes, and complete relaxation occurred after additional seven minutes. After induction, a surgical plane of anesthesia was maintained with 2% isoflurane in 1 L/minute oxygen using manual ventilation with a mask. The turtle was monitored closely during anesthesia and recovery with Doppler to assess its cardiac function.

After disinfection, the necrotic tissue around the wound lesion was debrided using surgical blades (numbers 10 and 11) and iris scissors. Surgical curettage was then performed with periosteal elevators, bone curettes, surgical blades, and iris scissors to produce a base and expose the underlying subcarapacial tissue, forming a proper surface for the bone cement and dental acrylic applications. The debrided cavity was irrigated, flushed with normal saline, and dried cautiously using sterile gauzes (Fig. 4).

Figure 4. Debridement and surgical curettage conducted prior to the procedure. Periosteal elevators, bone curettes, surgical blades, and iris scissors were used to produce a base and expose underlying subcarapacial tissue, forming a proper surface for the bone cement and dental acrylic application.

As shown in Table 1, bone cement (DePuy CMW 1; DePuy International Ltd; Leeds, UK) was mixed gently according to the manufacturer’s guidelines, retaining the documented time for the working steps, room temperature, and humidity. At three minutes, the cement reached the dough state and was considered to be appropriate for application. It was applied using a standard regime; bone cement was kneaded thoroughly and spread onto the tissue of the subcarapacial surface with hand. The cement was applied to be spread widely to prevent reaching the soft tissue beneath the carapacial surface. This process could be regarded as the classic surface-cementation technique (31).

Table 1 . Major components of PMMA used in the report.

Material	Application	Manufacturer	Powder ingredients	Liquid ingredients
Vertex Self-Curing	Denture	Vertex-Dental B.V. (Zeist, Netherlands)	Polymethyl methacrylate, dibenzoyl peroxide, barbituric acid, various pigments	Methyl methacrylate, N-dimethyl-p-toluidine, ethylene glycol, dimethacrylate
DePuy CMW 1	Bone cement	Depuy International Ltd (Leeds, UK)	Polymethyl methacrylate, benzoyl peroxide, barium sulfate	Methyl methacrylate, N-dimethyl-p-toluidine, hydroquinone

PMMA, polymethyl methacrylate..

Cold-cured acrylic resin (Vertex self-curing; Vertex-Dental B.V.; Zeist, Netherlands) was then mixed according to the manufacturer’s instructions. Approximately 3.4 g of polymer was added to 2 mL of monomer, and the components were mixed gently for 20 seconds. After two minutes of rest, a fiberglass cast was trimmed to 2.5 cm × 2.5 cm in size and immersed in the mixture in a colloidal state. When the mixture reached the dough stage, the fiberglass cast and the acrylic resin mixture were considered applicable. The fiberglass cast with acrylic resin was then applied to the bone cement layer (Fig. 5). This step strengthened the fixation area and provided additional waterproof capability on the punctured site.

Figure 5. After the procedure with biocompatible PMMA materials. Impermeable closure and stable cover were confirmed, ensuring rapid healing beneath the seal. There were no signs of edema, inflammation, bleeding, skin discoloration, or any complication.

As postoperative care, meloxicam (0.2 mg/kg; Metacam; Boehringer Ingelheim) and enrofloxacin (5 mg/kg; Baytril; Elanco) were administered orally once a day for three days. The turtle was kept warm and dry-docked on a moist towel for a day. Shallow water was provided to maintain hydration, food intake, urination, and defecation. Four days after the procedure, vital signs of the turtle were within normal range, mental status was completely alert and responsive, and feeding response was normal. Overall condition of the turtle was active and vigorous. There were no signs of edema, inflammation, bleeding, skin discoloration, or complications on the wound site. The structure was waterproof, and the wound healing process was accessed to be in progress beneath the provided cover with bone cement and fiberglass with acrylic resin.

In many chelonian species, the bony structures, such as ribs, vertebrae, and dermal bones, are covered with keratinous tissue. These species generate a two-component shell that almost surrounds the body in a bony exoskeleton (19,21). The ectoderm covering the shell generates epidermal scutes shaped in a stable pattern. In some species, however, the bones of the shell and their ectodermal covering are reduced or lost, which is commonly related to their different ecological habits and genetic trees (19,21). The tough corneous layer in the carapace and plastron of hard-shelled turtles derives from the accumulation of beta-keratins, while these proteins are believed to be absent in soft-shelled turtles (8). In all reptiles, beta-keratins are associated with the harder corneous parts of scales and epidermal derivatives, such as claws, rhamphotheca, or frills, while alpha-keratins are present in the basal, spinosus, and pre-corneous keratinocytes and in the softer regions of the corneous layer (8). The soft-shelled turtles lack beta-keratins in their epidermises (1) and are instead composed of alpha-keratin (33), resulting in a relatively soft carapace. Therefore, in soft-shelled turtles, the epidermis of the shell is not keratinized, and the peripheral, suprapygal, and pygal plates are often lost (21,24).

Although several methods have been applied clinically for chelonian shell repair, such as various bridging methods (14,27,28), adhesives (9,28), orthopedic fixations (6,16,28), or vacuum-assisted wound closure, (28) the distinguishing characteristics of soft-shelled turtles narrow the choice of treatment options. They lack keratinous tissue covering the carapace. The shells are relatively smooth and leather-like, and the edges of the shell are flexible (21). Given such characteristics, the carapace puncture in soft-shelled turtles should be treated as open and contaminated wounds rather than as fracture repair. Numerous variations of fracture repair techniques, such as external fixation or plate fixation, have been applied to shell injuries of hard-shelled turtles (9,23,28). Despite this, the treatment approach to shell injuries of soft-shelled turtles is unique and challenging in clinical aspects.

Polymethyl methacrylate (PMMA) is used as bone cement or dental acrylic resin. It is used widely for implant fixation in various traumas, orthopedic surgery, and diverse dentistry techniques (30,35). PMMA is an acrylic polymer that can be shaped by mixing two components: a liquid methyl methacrylate (MMA) monomer and a powered MMA-styrene co-polymer. When the two components are blended, the liquid monomer polymerizes around the pre-polymerized powder particles to form solidified PMMA (4,35). PMMA serves as a space-filler that forms a tight structure that holds the implant against the bone (35). Bone cements have no elemental adhesive traits, but they work on a close mechanical interlock between the irregular surface and prosthesis (35). Most importantly, it is biocompatible according to the FDA standards (34). Fiberglass, however, is one of the most preferred fibers in various medical fields because of its strength and suitable bonding. Several studies also have reported that the addition of fiberglass improved the flexural strength of PMMA (12,17,20,25).

Rather than using modified orthopedic approaches for the keratinized carapace in hard-shelled turtles, which may cause further damage to the soft carapace during the invasive procedure, covering the wound site with a biocompatible adhesive would prevent further infections and induce the healing process inside the seal. Although there is the potential for the development of cellulitis, soft tissue infection, or shell osteomyelitis caused by the artificial materials, it is an effective method for repairing shell fractures on chelonians with appropriate wound management, suitable course of antibiotics, and a procedure with non-toxic adhesive materials (22,28). In addition, the habitat and traits of the species, the character and disposition of the wound, and the possibility of future complications should be considered when assessing for the appropriate method of repair (22). Hence, PMMA was assessed to be the choice of treatment in this case, considering the animal anatomical structure and state of the lesions.

Extra care is needed when applying PMMA because of possible iatrogenic infections or exothermic reactions during polymerization, leading to tissue injury and pain. In addition, direct contact between the adhesive material and mucous membranes can lead to complications. The permanence of the dressing may cause problems, such as growth distortion or enclosed infection (32) if not performed correctly. An additional layer of fiberglass can be applied with minimal risk of exothermic reactions because the procedure is performed on the existing PMMA layer, providing extra strength and waterproof capability on the site of repair safely. The treatment of a puncture wound on carapace in a soft-shelled turtle using PMMA affords an impermeable closure, stable cover that ensures rapid healing, and safe biocompatibility with minimal side effects along with antibiotic therapy and wound management. Accordingly, it is an inevitable method of choice in cases with softshell turtles using biocompatible materials to cover the lesion in the carapace providing appropriate wound management, supportive therapy, and a suitable course of antibiotics considering all other circumstances, such as the traits of the species, habitat, or condition of the patient. The treatment was successful without significant side effects. This paper reports the management of a puncture wound on the carapace of a softshell turtle.

The authors thank Seoul Wildlife Center, Seoul National University Veterinary Teaching Hospital, and the National Institute of Wildlife Disease Control and Prevention as “Specialized Graduate School Support Project for Wildlife Disease Specialists” for providing necessary support.

The authors have no conflicting interests.