2 3 6 8 n = 43; 86 joints.months. Subsequent progression was usually followed by regression and resolution, the appearance returned in most cases to normal at age 8 months. At 5 months, 20% of the stifles were abnormal, but at 11 months this percentage had decreased to 3%. Normal and abnormal appearances were permanent from age 8 months.Osteochondrosis of the main predilection sites in the hock and stifle develops very early in life. The majority of the lesions were temporary, the 'age of no return' was 5 months for the hock and 8 months for the stifle.

Summary: A retrospective study of 220 horses was performed to investigate the association between the clinical signs and the radiological findings of impinging dorsal spinous processes (DSPs) in warmblood sporthorses. For this purpose radiographic records were assessed to identify all horses that had undergone radiographic examination of the back as part of a pre-purchase examination between January 2009 and December 2012. The dorsal spinous processes of 239 horses were assessed and each dorsal spinous process was individually graded (0 -3) using a modified 4-group grading system appropriate for routine grading of dorsal spinous processes as part of a pre-purchase examination. Fifty-five percent (n =121) had no radiological abnormalities of the DSPs (grade 0). However, 26,4 % had at least one DSP with grade 1 impingement, 11,8 % had at least one DSP with grade 2 and 6,8 % had at least one DSP with grade 3. Follow-up information was obtained by telephone responses from owners or trainers. The horses were assessed at a mean follow up time after pre-purchase examination of 25,19 ±12,52 months. Based on the clinical signs included in the questionnaire answers horses were divided into two groups; i) thoracolumbar back pain and ii) no thoracolumbar back pain. Only 11,5 % (N = 23) of the 220 horses had shown thoracolumbar back pain. There was no significant association between gender, age or discipline and clinical signs of thoracolumbar back pain. High maximum DSP grade is associated with an increased risk of clinical signs. The specificity of a grade 3 DSP on radiographic screening at pre purchase examinations is high, however the sensitivity is low. This suggests that there is a high risk of clinical signs in horses with grade 3 DSPs and no warranty can be offered for absence of clinical signs for grade 0,1,2.Keywords: back pain / horse / kissing spines / pre purchase / radiology Citation: de Graaf K., Enzerink E., van Oijen P., Smeenk A., Dik K. J. (2015) The radiographic frequency of impingement of the dorsal spinous processes at purchase examination and its clinical significance in 220 warmblood sporthorses. Pferdeheilkunde 31, 461-468

The closure of the body wall defect at the umbilicus was studied in relation to the development of umbilical hernias in a group of 44 normal foals, 25 of which were followed from birth until five months of age, and 19 from birth until 11 months of age. At birth, 19 of the foals had a defect in the body wall at the umbilicus that was termed a 'palpable umbilical ring'. In 18 of them this defect disappeared within four days, but in the other the ring did not close and a hernial sac with abdominal contents was palpable. This foal was considered to be the only foal to have a truly congenital umbilical hernia. Twelve foals developed an umbilical hernia between five and eight weeks of age. The prevalence of umbilical hernias was much higher than in other studies, possibly owing to the prospective nature of the study.

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Summary The aim of this study was to monitor the postnatal radiographic development of the proximal and distal double contours and the modelling of the shape of the proximal articular border. In mature horses, the proximal and distal contours of the navicular bone on dorsopalmar dorsoproximal‐palmarodistal oblique (upright pedal) radiographs are commonly visualised as 2 lines, one being the articular border and the second representing the border of the cortex facing the deep digital flexor tendon (flexor border). The shape of the proximal articular border may be concave, undulating, straight or convex in the mature animal. These shapes have been found to be hereditary and to constitute a predisposing factor in the pathogenesis of navicular disease. This predisposing role may result from a shape dependent distribution of the biomechanical forces exerted on this region. There is no agreement in the literature with respect to the moment when the navicular bone takes its mature radiographic appearance. Upright pedal radiographs of the left front foot of 19 Dutch Warmblood foals were made at age 1 month and subsequently at intervals of 4 weeks, until the age of 11 months. The distal double contour developed soon after birth and the radiographic visibility of the articular border improved from ill‐defined at 1 or 2 months to clear manifestation at 3 or 4 months. The proximal double contour developed later. The articular border became usually visible at age 3 or 4 months and was clearly visible from age 9 months. The mature shape of the proximal articular border usually became recognisable from age 7 months and was always obvious between 9 and 11 months. This development was associated with a gradual modelling of the lateral and medial extremities of the navicular bone. It was concluded that the navicular bone adopts its mature radiological appearance during the first year postpartum. Considering this early manifestation of the mature shape of the proximal articular border and its previously demonstrated inheritance, a force‐dependent development of this shape, as predicted by the trajectional theory/Wolffs law, is improbable. The predisposing role of this shape in the pathogenesis of navicular disease may therefore be explained by a shape‐dependent distribution of the biomechanical forces exerted on the navicular bone. Considering the potential application of these findings, from age 1 year shape determination enables identification of the individual and breed susceptibility for the development of navicular disease.