Management of intertarsal septic arthritis in an ostrich (Struthio camelus)

Abstract A 7‐year‐old female ostrich (Struthio camelus) presented with lameness, left intertarsal joint swelling and a healing wound on the caudomedial aspect of the joint. Synovial culture revealed Corynebacterium species and radiographs were consistent with progressive septic arthritis. Multiple treatments were attempted including through‐and‐through joint lavage, intra‐articular antibiotics, caudomedial arthrotomy, and regional limb perfusion in conjunction with systemic antibiotics and analgesia. Euthanasia was ultimately performed due to prolonged recumbency and poor prognosis. This report describes novel therapies and a surgical approach utilized for treatment of intertarsal septic arthritis in an ostrich and exemplifies the poor prognosis described in other species presenting with non‐responsive septic arthritis of critical joints.

F I G U R E 1 Radiographic progression of osteomyelitis following diagnosis of intertarsal septic arthritis in an ostrich (Struthio camelus). (a) Craniomedial-caudolateral oblique projection of the left intertarsal joint, one day post-clinical presentation. The "L" marker indicates the craniolateral surface. There is proximal and caudal soft tissue thickening, severe lysis of the caudal aspect of the proximal tarsometatarsus, and irregular bone fragments caudal to the joint. (b) Craniocaudal view of the left intertarsal joint 15 days post-initial presentation. The "L" marker is on the lateral aspect of the limb. There is progressive severe soft tissue thickening and ongoing lysis of the proximal tarsometatarsus. Gas lucencies adjacent to the medial epicondyle of the tibiotarsus were attributed to iatrogenic introduction of air during arthrocentesis. (c) Craniocaudal view of the left intertarsal joint 48 days post-initial presentation. The "L marker denotes the lateral surface. There is ongoing lysis, progressive soft tissue thickening, irregular periosteal proliferation along the proximal tarsometatarsus and development of joint space collapse. of effusion, three 16-gauge catheters were placed into areas of effusion on the craniomedial, craniolateral and caudomedial aspects of the intertarsal joint. The joint was kept in slight flexion throughout the procedure to allow for maximum joint space separation. Lavage was performed with saline (1000 ml Intra-articular, 0.9% Sodium Chloride injection, Hospira, Lake Forest, IL, USA) followed by intra-articular gentamicin (500 mg IA, VetOne, Boise, ID, USA). Catheter sites were allowed to heal by second intention. Bloodwork revealed no abnormalities, most notably, no elevations in white blood cell count. The patient was reversed with atipamezole (1 mg/kg IM, Zoetis Inc., Kalamazoo, MI, USA) and prescribed clindamycin (5 mg/kg PO q8h for 7 days, Aurobindo Pharma Inc., East Windsor, NJ, USA), enrofloxacin (2 mg/kg PO q12h for 10 days, Dechra Veterinary Products, Overland Park, KS, USA), phenylbutazone (10 mg/kg PO q12h for 3 days, VetOne, Boise, ID, USA) and tramadol (5 mg/kg PO q12h for 4 days, Sun Pharmaceutical Industries Inc., Cranbury, NJ, USA).
Lameness and effusion remained static over the course of two weeks following the initial presentation. On day 15 post-presentation, radiographs and transarticular lavage were repeated under the same anaesthetic protocol mentioned previously, following collection of synovial fluid into a sterile, transfer media culturette for aerobic culture at a local laboratory (IDEXX, Memphis, TN, USA). Aerobic cultures were performed using both Macconkey and blood agars at 35 • C (95 • F).
Radiographs revealed progressive severe soft tissue thickening, ongo-ing lysis of the proximal tarsometatarsus, and irregular periosteal proliferation ( Figure 1b). Medications were continued as previously prescribed. Within 5 days, culture results were negative, however septic arthritis was still suspected.
On day 25 post-presentation, the patient became acutely nonambulatory. More aggressive therapy was deemed necessary and an arthrotomy was performed using a novel surgical approach to the caudomedial aspect of the intertarsal joint. Standard arthrotomy principles were utilized for surgical planning from similar descriptions in cattle and an ostrich (Mulon et al., 2016;Tully et al., 1995). Anaesthesia  have been reported in an ostrich (Amer et al., 2019;Marcon et al., 2019;Nairn, 1973). Although surgical management of phalangeal septic arthritis in an ostrich has been described, the critical nature of the intertarsal joint (particularly in this large, flightless species) made this case a unique challenge (Burba et al., 1996). Minimal literature for this disease process in ratites makes both treatment and determination of prognosis difficult.
To the author's knowledge, this is the first published report of Corynebacterium septic arthritis in a ratite. Corynebacterium is a notoriously difficult to eliminate, gram-positive, non-spore-forming bacillus (Boltin et al., 2009;Funke et al., 1997). This bacterium is typically an opportunistic, environmental pathogen that was likely introduced or migrated into the joint from the proximate wound (Funke et al., 1997).
Despite broad spectrum antibiotics and copious flushing, it is unlikely full clearance of this organism would have been achieved.
In mammalian species, necessary therapies for septic arthritis due to environmental pathogens, such as Corynebacterium and Arcanobacterium, often require a combination of transarticular lavage, systemic and intra-articular antibiotics, arthrotomies, and intra-articular drains (Desrochers, 2004). Due to avian physiology and the nature of the species, a drain was not a viable option (Smith et al., 1998). Avian abscessation is not conducive to active drainage, and formation of caseous exudate likely resulted in an environment which harboured the bacterium (Smith et al., 1998).
This report also presents novel therapies not previously described in ratites. A regional limb perfusion (RLP) was performed to aid in the treatment of septic arthritis by increasing drug concentrations in tissues not well vascularized (Knafo et al., 2019). In recent years, this technique has been briefly described and utilized in the avian model, allowing for extrapolations to be made for ratite medicine (Knafo et al., 2019;Ratliff & Zaffarano, 2016). The technique for RLP is relatively simple and should be considered for aggressive treatment of septic arthritis and other inflammatory conditions of the distal extremity in ratites.
An arthrotomy was also performed utilizing a novel caudomedial approach based on lesion location. A similar technique has also been described for treatment of a distal tibiotarsal bone cyst in an ostrich utilizing a dorsomedial approach (Tully et al., 1995). In ostriches, nearly all vasculature, ligaments, tendons and nerves are located on the posterior, anterior, medial or lateral surfaces of the distal extremity, allowing for oblique approaches to the joint (Hutchinson et al., 2015;Smith et al., 1998). The distal articular surface of the tibiotarsal bone is convex, with medial and lateral condyles of the tibiotarsus articulating with the concave cotyles of the proximal tarsometatarsus. This anatomy can lead to decreased visualization of all articular surfaces (Hutchinson et al., 2015;Schaller et al., 2009). Caution should be taken if attempting to locate a lesion in the central portion of the articular surface (i.e., the intercondyloid fossa).
Most importantly, determining integrity of the intertarsal joint is critical for treatment success. There are complex ligamentous and osseous anatomical structures needed for proper biomechanics of ostrich ambulation, including the engage-disengage system (Schaller et al., 2009). For appropriate range of motion, the ostrich intertarsal joint require at least 168 • of extension and 80 • of flexion, achieved during daily physical therapy for this patient (Schaller et al., 2009). The menisci, tendons and ligamentous apparatus are necessary for swing phase mechanics and passive locomotion that allow for decreased energy expenditure and appropriate movement (Schaller et al., 2009).
Pathology involving this apparatus can lead to inefficient or complete loss of ambulation, as seen in this case. More specifically, osteomyelitis affecting the articular surfaces in conjunction with severe fibrinous adhesions disrupting ligamentous and joint capsule integrity contributed to causes of prolonged recumbency and decubital sequelae.
The complex nature of the intertarsal joint of ostriches and other ratites may be a limiting factor when managing non-responsive septic arthritis. Improved clearance of pathogens within the joint may be possible with more aggressive therapies, such as an arthrotomy and RLP, at time of presentation. Caution is advised if significant osteomyelitis involving the articular surfaces has already occurred, as return to full function may not be possible.

CONCLUSION
The novel therapies utilized in this report are areas of interest for further research to determine efficacy of regional limb perfusions and success of arthrotomies in ratites. Additional work is also needed in determining prognosis of infections involving Corynebacterium and cases of non-responsive septic arthritis of the intertarsal joint.