Multimodal 2D and 3D microscopic mapping of growth cartilage by computational imaging techniques - a short review including new research.

Being able to image the microstructure of growth cartilage is important for understanding the onset and progression of diseases such as osteochondrosis and osteoarthritis, as well as for developing new treatments and implants. Studies of cartilage using conventional optical brightfield microscopy rely heavily on histological staining, where the added chemicals provide tissue-specific colours. Other microscopy contrast mechanisms include polarization, phase- and scattering contrast, enabling non-stained or 'label-free' imaging that significantly simplifies the sample preparation, thereby also reducing the risk of artefacts.

Closure of the neuro-central synchondrosis and other physes in foal cervical spines.

Background: The neuro-central synchondrosis (NCS) is a physis responsible for the growth of the dorsal third of the vertebral body and neural arches. When the NCS of pigs is tethered to model scoliosis, stenosis also ensues. It is necessary to describe the NCS for future evaluation of its potential role in equine spinal cord compression and ataxia (wobbler syndrome).

Osteochondrosis in the central and third tarsal bones of young horses.

Recently, the central and third tarsal bones of 23 equine fetuses and foals were examined using micro-computed tomography. Radiological changes, including incomplete ossification and focal ossification defects interpreted as osteochondrosis, were detected in 16 of 23 cases. The geometry of the osteochondrosis defects suggested they were the result of vascular failure, but this requires histological confirmation.

A method for labelling lesions for machine learning and some new observations on osteochondrosis in computed tomographic scans of four pig joints.

Background: Osteochondrosis is a major cause of leg weakness in pigs. Selection against osteochondrosis is currently based on manual scoring of computed tomographic (CT) scans for the presence of osteochondrosis manifesta lesions. It would be advantageous if osteochondrosis could be diagnosed automatically, through artificial intelligence methods using machine learning.

Osteochondrosis and other lesions in all intervertebral, articular process and rib joints from occiput to sacrum in pigs with poor back conformation, and relationship to juvenile kyphosis.

Background: Computed tomography (CT) is used to evaluate body composition and limb osteochondrosis in selection of breeding boars. Pigs also develop heritably predisposed abnormal curvature of the spine including juvenile kyphosis. It has been suggested that osteochondrosis-like changes cause vertebral wedging and kyphosis, both of which are identifiable by CT.

Radiological, vascular osteochondrosis occurs in the distal tarsus, and may cause osteoarthritis.

Background: Osteochondrosis occurs due to failure of the blood supply to growth cartilage. Osteochondrosis lesions have been identified in small tarsal bones and suggested to cause distal tarsal osteoarthritis; however, it has not been determined whether distal tarsal osteochondrosis lesions were the result of vascular failure.

Objectives: To perform post-mortem arterial perfusion and micro-computed tomography (CT) of the central (CTB) and third tarsal bones (TIII) of fetuses and foals up to 5 months old, to describe tarsal development and any lesions detected.

Quantifying the hydroxyapatite orientation near the ossification front in a piglet femoral condyle using X-ray diffraction tensor tomography.

While a detailed knowledge of the hierarchical structure and morphology of the extracellular matrix is considered crucial for understanding the physiological and mechanical properties of bone and cartilage, the orientation of collagen fibres and carbonated hydroxyapatite (HA) crystallites remains a debated topic. Conventional microscopy techniques for orientational imaging require destructive sample sectioning, which both precludes further studies of the intact sample and potentially changes the microstructure. In this work, we use X-ray diffraction tensor tomography to image non-destructively in 3D the HA orientation in a medial femoral condyle of a piglet.

Development of the blood supply to the growth cartilage of the medial femoral condyle of foals.

Background: Growth cartilage is found in the articular-epiphyseal cartilage complex (AECC) and the physis. It has a temporary blood supply organised as end arteries. Vascular failure is associated with osteochondrosis, but infection can also obstruct vessels.

Computed tomographic development of physeal osteochondrosis in pigs.

Background: Articular osteochondrosis follows a dynamic development pattern. Lesions arise, in incidence peaks compatible with failure of cartilage canal vessels during incorporation into bone, and can also resolve. Lesions that resolve before examination at a single time point will constitute false-negative diagnoses.

Osteochondrosis in the Distal Femoral Physis of Pigs Starts With Vascular Failure.

Articular osteochondrosis (OC) arises due to vascular failure and ischemic chondronecrosis. The aim of the study was to describe the histological and computed tomographic (CT) characteristics of changes in the distal femoral physis of pigs, to determine if they represented OC lesions and if the pathogenesis was the same as for articular OC. The material included 19 male Landrace pigs bred for predisposition to OC.

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

Background: Young Standardbred horses frequently develop fragments in joints. Some fragments represent osteochondrosis; others are considered developmental, but it is uncertain whether they result from preceding osteochondrosis. Osteochondrosis occurs as a consequence of failure of the cartilage canal blood supply and ischaemic chondronecrosis.

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

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.

Characterization of cellular and matrix alterations in the early pathogenesis of osteochondritis dissecans in pigs using second harmonic generation and two-photon excitation fluorescence microscopy.

Osteochondritis dissecans is a joint disease that is observed in several species. The disease can develop as a cause of ischemic chondronecrosis in the epiphyseal growth cartilage. Some lesions of chondronecrosis undergo spontaneous resolution, but it is not possible to predict whether a lesion will resolve or progress and require intervention.

Non-linear optical microscopy of cartilage canals in the distal femur of young pigs may reveal the cause of articular osteochondrosis.

Background: Articular osteochondrosis is a common cause of leg weakness in pigs and is defined as a focal delay in the endochondral ossification of the epiphysis. The first demonstrated steps in the pathogenesis consist of loss of blood supply and subsequent chondronecrosis in the epiphyseal growth cartilage. Blood vessels in cartilage are located in cartilage canals and become incorporated into the secondary ossification centre during growth.

Cartilage canals in the distal intermediate ridge of the tibia of fetuses and foals are surrounded by different types of collagen.

Some epiphyseal growth cartilage canals are surrounded by a ring of hypereosinophilic matrix consisting of collagen type I. Absence of the collagen type I ring may predispose canal vessels to failure and osteochondrosis, which can lead to fragments in joints (osteochondrosis dissecans). It is not known whether the ring develops in response to programming or biomechanical force.

Second harmonic generation imaging reveals a distinct organization of collagen fibrils in locations associated with cartilage growth.

Purpose: The articular-epiphyseal cartilage complex (AECC) is responsible for the expansion of the bone ends and serves the function of the articular cartilage in juvenile mammals. Bundles of collagen fibrils surrounding cells were in the literature observed more frequently near the articular surface of the AECC. The articular surface, the perichondrium, and cartilage canals are interfaces where appositional growth of the AECC has been demonstrated.

Discontinuities in the endothelium of epiphyseal cartilage canals and relevance to joint disease in foals.

Cartilage canals have been shown to contain discontinuous blood vessels that enable circulating bacteria to bind to cartilage matrix, leading to vascular occlusion and associated pathological changes in pigs and chickens. It is also inconsistently reported that cartilage canals are surrounded by a cellular or acellular wall that may influence whether bacterial binding can occur. It is not known whether equine cartilage canals contain discontinuous endothelium or are surrounded by a wall.

Consequences of the natural course of articular osteochondrosis in pigs for the suitability of computed tomography as a screening tool.

Background: A significant heritability has been documented for articular osteochondrosis. Selection against osteochondrosis has historically been based on macroscopic evaluation, but as computed tomography (CT) now is used to select boars with optimal body composition it can potentially also be used to screen for osteochondrosis. False negative diagnosis will occur if defects have not developed or have resolved prior to screening at a single time point.

Ossification defects detected in CT scans represent early osteochondrosis in the distal femur of piglets.

The purpose of the current study was to validate the use of CT for selection against osteochondrosis in pigs by calculating positive predictive value and comparing it to the positive predictive value of macroscopic evaluation, using histological examination as the reference standard. Eighteen male, hereditarily osteochondrosis-predisposed piglets underwent terminal examination at biweekly intervals from the ages of 82-180 days old, including CT scanning, macroscopic, and histological evaluation of the left distal femur. Areas of ischemic chondronecrosis (osteochondrosis) were confirmed in histological sections from 44/56 macroscopically suspected lesions, resulting in a positive predictive value of 79% (95% CI: 67-84%).

Local Morphological Response of the Distal Femoral Articular-Epiphyseal Cartilage Complex of Young Foals to Surgical Stab Incision and Potential Relevance to Cartilage Injury and Repair in Children.

Objective: Describe the local morphological response of the articular-epiphyseal cartilage complex to surgical stab incision in the distal femur of foals, with emphasis on the relationship between growth cartilage injury, enchondral ossification, and repair.

Design: Nine foals were induced into general anesthesia at the age of 13 to 15 days. Four full-thickness stab incision defects were created in the cartilage on the lateral aspect of the lateral trochlear ridge of the left distal femur.

Micro-computed tomography of early lesions of osteochondrosis in the tarsus of foals.

Introduction: Osteochondrosis (OC) is an important developmental orthopedic disease of human and equine patients. The disease is defined as a focal disturbance in enchondral ossification. In horses, the disturbance can occur secondary to failure of the blood supply to growth cartilage.

Early lesions of osteochondrosis in the distal tibia of foals.

Material available for research into osteochondrosis (OC) in humans tends to represent chronic lesions. Comparative studies of early lesions in young animals are, therefore, important in clarifying the pathogenesis of OC in humans. Recent studies in pigs provide strong evidence that lesions of articular OC are associated with a focal failure in the cartilage canal vascular supply to epiphyseal growth cartilage (articular-epiphyseal cartilage complex excluding the articular cartilage).