Septic Arthritis/Osteomyelitis May Lead to Osteochondrosis-Like Lesions in Foals

Abstract

Failure of the cartilage canal blood supply leads to ischemic chondronecrosis which causes osteochondrosis, and osteochondral lesions. Osteochondrosis is a disease with a heritable component and usually occurs under aseptic conditions. Because bacteria can bind to growth cartilage and disrupt the blood supply in pigs and chickens, we considered whether this might play a role in development of equine osteochondrosis. The aim of this study was to examine whether bacteria are present in canals in the growth cartilage of foals with septic arthritis/osteomyelitis, and whether this is associated with osteochondrosis. The material consisted of 7 foals aged 9-117 days euthanized because of septic arthritis/osteomyelitis. The 7 cases had 16 lesions in growth cartilage that were evaluated histologically. Bacteria were present in cartilage canals in foals with septic arthritis/osteomyelitis. Portions of necrotic canals adjacent to bacteria frequently contained neutrophils, termed acute septic canals; or granulation tissue with neutrophils, termed chronic septic canals. Acute and chronic septic canals were associated with ischemic chondronecrosis in the articular-epiphyseal cartilage complex (AECC) of 5 cases and in the physis of 2 cases, and ossification was focally delayed in 5 of those 7 cases. Lesions occurred with and without adjacent osteomyelitis. Bacteria were present in cartilage canals and were associated with focal chondronecrosis in both the AECC and the physis. This establishes sepsis as a plausible cause of some osteochondral lesions in horses. It is recommended that horses with sepsis-related osteochondral lesions may be used for breeding without increasing the prevalence of OCD-predisposing genes in the population.

Clinical and Radiographic Findings of Septic Physitis in Foals

“…[5][6][7]11,12 It has also been reported that necrotic growth cartilage, secondary to infection, may not ossify correctly and could form areas of retained cartilage that can protrude to the epiphysis and/ or metaphysis which can appear as radiolucent areas on radiographs when compared with adjacent areas with normal ossification. 18 Aseptic physitis is a non-infectious, inflammatory condition of the physes. 11,12 Most often observed in foals, weanlings and yearlings, the condition is associated with high- energy nutrition and rapid phase of bone growth.…”

Prevalence of osteochondral lesions in the fetlock and hock joints of Standardbred horses that survived bacterial infection before 6 months of age

“…Bacteria injected into the circulation or joints of skeletally immature individuals colonise the cartilage canal blood supply, where they cause obstruction and vascular failure [ 20 – 23 ]. Bacterial vascular failure was also recently documented in foals suffering spontaneous infections [ 25 ]. Septic failed cartilage canals were differentiated from aseptic failed canals based on presence of bacteria and perivascular neutrophils [ 25 ].…”

“…Bacterial vascular failure was also recently documented in foals suffering spontaneous infections [ 25 ]. Septic failed cartilage canals were differentiated from aseptic failed canals based on presence of bacteria and perivascular neutrophils [ 25 ]. In the studied foals, septic vascular failure was associated with cartilage infarction, delayed ossification and pathologic fracture [ 25 ], i.e.…”

“…Septic failed cartilage canals were differentiated from aseptic failed canals based on presence of bacteria and perivascular neutrophils [ 25 ]. In the studied foals, septic vascular failure was associated with cartilage infarction, delayed ossification and pathologic fracture [ 25 ], i.e. the same pathogenesis as described for aseptic, heritably predisposed OCD.…”

“…The study of spontaneous infections documents that bacteria can cause osteochondral lesions in foals before 150 days/4.9 months of age [ 25 ]. This immediately raises the question: do horses that survived bacterial infections as foals have increased prevalence of osteochondral lesions at screening age for heritably predisposed disease?…”