Navicular disease: podotrochlitis chronica aseptica podotrochlosis

Genome-wide search for microsatellite markers associated with radiologic alterations in the navicular bone of Hanoverian warmblood horses

The aim of this study was to identify quantitative trait loci (QTLs) for pathologic changes in the navicular bone in Hanoverian warmblood horses. Seventeen paternal half-sib groups comprising 192 individuals were analyzed in a whole-genome scan. These families included 144 progeny and grandchildren, which were randomly chosen from the Hanoverian warmblood. Three different traits were considered: deformed canales sesamoidales and radiographic changes in the contour and in the structure of the navicular bone. The genome scan included in total 214 highly polymorphic microsatellite markers. The putatively linked genomic regions on equine chromosomes (ECA) 2, 3, 10, and 15 were refined using 53 additional microsatellites. Chromosome-wide significant QTLs were located on five different equine chromosomes (ECA2, 3, 4, 10, and 26). Genome-wide significant QTLs were on ECA2 at 48 cM and on ECA10 from 45.5 to 49.8 cM. This study was a first step to get more insight into the molecular genetic determination of radiologic changes in the equine navicular bone.

A comparison of the palmaroproximal-palmarodistal view of the isolated navicular bone to other views

A collection of 69 isolated navicular bones, normal or affected with navicular disease, was examined radiographically using dorsopalmar, lateromedial and palmaroproximal-palmarodistal views. Radiographic findings on each view were recorded. A radiographic diagnosis of normality or navicular disease was made, first on each view separately and afterwards based on the combination of the 3 views. Forty-four navicular bones were considered radiographically normal and 25 navicular bones had distinct signs of radiographic navicular disease. The dorsopalmar and the lateromedial views of each navicular bone were assessed together and compared with the palmaroproximal-palmarodistal view. In not a single bone was the palmaroproximal-palmarodistal view considered indispensable to make the final diagnosis.

A study of 118 cases of navicular disease: radiological features

Dorsoproximal-palmarodistal oblique, lateromedial and palmaroproximal-palmarodistal oblique radiographic projections were used with standard techniques to examine 118 horses with clinical signs of navicular disease. All radiological features which have previously been reported as significant changes in the navicular bones of horses with navicular disease were recorded. Comparisons were made between these features in lame limbs and sound limbs in unilaterally lame horses and most lame limbs and least lame limbs in bilateral but asymmetrically lame animals. Their relationship to the degree of lameness was also analysed. No relationships were identified between the characteristics of distal border synovial invaginations, flattening and/or thinning of the flexor cortex and limb distribution or severity of lameness. Defects in the flexor cortex, proximal border remodelling, medullary trabecular disruption and medullary sclerosis appeared to be related to limb affliction and severity of lameness while proximal border enthesophytes, and poor flexor corticomedullary demarcation presented evidence of a relationship to the grade of lameness. Poor flexor corticomedullary demarcation and fragmentation of the distal border were related to the severity of lameness in bilateral but asymmetrically affected horses. The presence of peri-articular osteophytes and mineralisation of the flexor digitorum profundus were too infrequently recognised to permit meaningful data evaluation.

A study of 118 cases of navicular disease: treatment by navicular suspensory desmotomy

The 118 horses diagnosed as suffering from navicular disease by prospective criteria were treated by desmotomy of the ligamenta sesamoidea collateralia (navicular suspensory desmotomy). Three techniques were used and a standard post-operative programme was followed with clinical and radiological evaluations at 6-monthly intervals for periods of 6-36 months after surgery. At 6 and 36 months after treatment, 76% and 42.9% of horses were sound respectively. The clinical features of age, period of lameness, severity of lameness and angular limb deformities adversely affected response to surgery. The presence of flexor cortex defects, proximal border enthesophytes, mineralisation of the flexor digitorum profundus tendon and medullary sclerosis were also associated with a diminished response. There were few (1.7%) changes in the radiological appearance of distal border synovial invaginations during the follow-up period. By contrast, the majority (67.3%) of flexor cortex defects changed. Other radiological features changed at a low frequency but there was no association between radiological change and clinical outcome.

Radiographic assessment of navicular bones, based on changes in the distal nutrient foramina

Radiographic examination of the navicular bones of 258 horses was carried out. Of these 258 horses, 83 were sound (Group A), 151 had been diagnosed clinically as having navicular disease (Group B), and 24 had a forefoot lameness of unknown aetiology (Group C). Seven basic shapes of distal nutrient foramina were identified from these radiographs. A scoring system was then developed based on these different types of distal nutrient foramina. When this scoring system was applied to the radiographs of the 258 horses examined significant differences were found between the mean navicular scores of the horses in Groups A, B and C. It is considered that this navicular scoring system could be very useful for comparing radiographs of the navicular bones of different horses and recording serial radiographs of navicular bones of the same horse.