Aims: To determine improvements in third metacarpal (Mc3) condylar microanatomy attributable to preconditioning exercise. To investigate developmental causes of Mc3 condylar fracture. Methods: Twelve Thoroughbred horses were raised at pasture; six received preconditioning exercise from 10 days. Calcein labels were administered 19 and 11 days prior to euthanasia at 18 months. Six horses also received 2 seasons of race-training and were euthanised at 3 years. Slices were taken from the distal Mc3 condyle in the frontal and dorsal- and palmar-oblique frontal planes, scanned with DXA and macerated (frontal slices) or embedded in PMMA (oblique slices). Articular calcified cartilage (ACC) and subchondral bone (SCB) in oblique slices were imaged using confocal scanning light microscopy and quantitative backscattered electron scanning electron microscopy. ACC and SCB in the palmar slice lateral parasagittal grooves were imaged using μCT and nanoindentation tested. Results: Characteristic spatial variations in ACC and SCB histomorphometric parameters were present, none of which was significantly related to preconditioning exercise. Thickened, aberrantly mineralised ACC was found in 13/24 parasagittal grooves in the palmar slices and on the sagittal ridge of 4/12 dorsal slices of 18-month-old horses. Deep to thickened ACC, SCB had an open marrow structure, having not adopted the buttress morphology of the normal SCB plate. SCB in 3-year-old horses had incorporated early ACC defects as notches in parasagittal grooves and a hyaline cartilage island in a sagittal ridge. ACC was less stiff and SCB more stiff in affected than unaffected parasagittal grooves. Chondroclastic resorption in the parasagittal groove may be retarded as early as 3-6 months, possibly due to localised inhibition of ACC mineralisation. Linear defects in the Mc3 parasagittal groove may develop prior to entry to race training and are not significantly affected by preconditioning exercise. Early identification of affected individuals should aid in reducing condylar fracture risk.

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Die Arbeit beschäftigt sich mit der suprakondylären und y-kondylären Humerusfraktur im Kindesalter. Die suprakondyläre Humerusfraktur ist die häufigste Ellenbogenfraktur beim Kind, die y-kondyläre Fraktur ist der suprakondylären ähnlich, tritt aber nur selten auf. Es wurden 172 suprakondyläre und 6 y-kondyläre Humerusfrakturen retrospektiv untersucht. Dazu wurden die Daten von 55 ambulant und 123 stationär behandelten Kindern bezüglich Unfallursache, Therapie und Komplikationen ausgewertet. Die Röntgenbilder der stationären Patienten wurden nachbefundet. 32,5% der stationär behandelten Kinder konnten nachuntersucht werden. Die häufigste Unfallursache war ein Sturz aus der Höhe. Im Patientengut waren Frakturen nach Baumann Klassifikation I, II und III zu ähnlichen Teilen vorhanden. Häufigste Behandlungsverfahren waren, ggf. nach geschlossener Reposition, Ruhigstellung in Gipslonguetten oder Blountscher Schlinge, und geschlossene oder offene Reposition und anschließende Fixation mittels Kirschner Drähten. Die häufigsten Komplikationen waren primäre und sekundäre Nervenstörungen, Abweichung der Ellenbogenachse oder Bewegungseinschränkung nach Therapie. 68,5% der nachuntersuchten Patienten hatten ein exzellentes oder gutes Behandlungsergebnis. Die Analyse der Ergebnisse und deren Vergleich mit den Ergebnissen anderer Autoren zeigen Folgendes: Nicht dislozierte Extensionsfrakturen sollten in der Blountschen Schlinge ruhiggestellt werden. Dislozierte Frakturen müssen exakt und schonend, möglichst geschlossen, reponiert werden. Gekreuzte Kirschner Drähte bieten gute Stabilität. Primäre und sekundäre Nervenstörungen haben eine gute Prognose. Radiologische Hilfsmittel wie Baumannwinkel, Rotationsfehlerquotient und Epiphysenachsenwinkel geben nur eine Orientierung bei der Vermeidung von Abweichungen der Ellenbogenachse oder Bewegungseinschränkungen. Y-kondyläre Frakturen mit nur geringer Dislokation der Kondylenfragmente können primär wie suprakondyläre Frakturen behandelt werden. / This paper deals with supracondylar and y-condylar humerus fractures in childhood. The supracondylar humerus fracture is the most frequent elbow fracture in children, the y-condylar fracture is similar to the supracondylar one, but occurs only rarely. 172 supracondylar and 6 y-condylar humerus fractures have been analysed retrospectively. For that purpose data of 55 outpatients and 123 in-house treated children have been analysed with regard to the cause of accident, therapy and complications. The radiographs of the in-patients have been revaluated. 32.5% of the in-patients have been seen for follow-up. Most frequent cause of accident was a fall from a height. Within the group of patients, fractures that were classified to Baumann I, II and III occurred to equal rates. The treatments which were used mostly are immobilization in plaster casts or Blount´s loop, after closed reduction if necessary, and closed or open reduction followed by fixation by Kirschner wires. The most frequent complications were primary and secondary nerval disorders, deviation of the axis of the elbow or limitation of elbow function after therapy. 68.5% of the follow-up patients had an excellent or good outcome. The analysis of the results including their comparison to the results of other authors have led to the following conclusion: Nondisplaced extension fractures should be immobilized by Blount`s method. Displaced fractures have to be reduced accurately and sparing, if possible by closed reduction. Crossed Kirschner wires provide a good stability. Primary and secondary nerval disorders have got a good prognosis. Radiological tools like angle of Baumann, rotation error quotient and angle of epiphyseal axis only provide an orientation in avoiding deviation of elbow axis or limitation of elbow function. Y-condylar fractures with only slight dislocation of the condylar fragments can primary be treated like supracondylar fractures.