Abstract
Scoliosis, or "bent-back," in koi is being seen with increased frequency in the clinical setting. Vitamin C deficiency5,7 and electrocution2,8,13 are commonly reported causes. Tryptophan deficiency,6,9,11,12,15 trauma, organophosphates,1,3,14 and bacterial cold water disease10 have also been implicated. Although some fish continue to do well with a noticeable curvature of the spine, other fish become debilitated over time and intervention becomes necessary.
Two koi from the same pond presented with similar lesions of scoliosis. Radiology revealed malalignment of the spine due to vertebral compression fractures involving T14-16. Vertebral stabilization was performed using screws, k-wire, and polymethylmethacrylate. Post-operative care included physical therapy and enrofloxacin (Baytril 2.27 percent, Bayer Corporation, Shawnee Mission, KS), impregnated paste food, fed for two weeks. Although the fish appeared to improve after surgery, both fish began an eventual decline consisting of severe weight loss, parasitism, and bacterial infection. They were treated with additional supportive care and medications as their conditions indicated. Despite extensive efforts, both fish died within three months post-surgery. Necropsy revealed multi-organ inflammation including meningitis, pneumocystitis, branchitis, enteritis, dermatitis, myositis, myelitis, myocarditis and steatitis, which could not be definitively linked to the surgical implants.
Prior intervention and increased management and supportive care may have provided the first koi with a better outcome. Anti-inflammatory and muscle relaxant medication given immediately after the initial trauma may have precluded the subsequent necessity for surgical intervention. By the time the surgery was performed, the koi had had noticeable scoliosis for nine months, appreciable muscle atrophy, severe skeletal changes, and difficulty swimming. More continuous follow-up consultations with the owner may have been beneficial. In the second koi, the scoliosis was less severe, and the surgery was performed much sooner, at two months after the suspected time of injury. Muscle atrophy however, had already developed, and increased management and supportive care did not prevent this animal from deteriorating.
Future surgeries may benefit from using antibiotic impregnated polymethylmethacrylate or hydroxyapatite cement,4 in place of the plain polymethylmethacrylate placed over the screws to provide local, sustained concentrations of antimicrobial agents to the compromised area. Keeping animals on oral or injectable antibiotics for a prolonged duration may also improve the outcome. It was our observation that horizontal mattress sutures tended to close and hold this surgical approach better than simple interrupted sutures.
Spinal vertebral stabilization offers a possible therapeutic treatment for scoliosis due to vertebral fracture in fish. Although the technique and post-operative management is not yet perfected, these cases provide information that will guide and benefit future piscine implant surgeries.
Acknowledgements
The authors wish to thank Nancy Love, Lenore Mohammadian, and Sandy Wang, for their radiological assistance and interpretations, Taylor Reynolds for her pathological interpretations, Craig Harms for his manuscript comments, and Shane Christian for his dedication to the cases.
References
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