Adaptation of trabecular bone to very high mechanical loads

Summary

It is well known that bone adapts to increased mechanical loading by the apposition of newly formed bone. The correlation between load-induced bone stress and strain with bone formation has often been investigated in cortical bone, however, little is known about this relationship in trabecular bone. In particular, nothing is known about trabecular bone adaptation in response to very high mechanical loading close to its fatigue load. Here, we investigated trabecular bone formation in a sheep osteotomy model of the femoral condyle in a region of interest close to the osteotomy, where local stresses in the range of the fatigue strength of trabecular bone occurred. After eight weeks, the trabecular bone volume and the mineral apposition rate increased two-fold and threefold, respectively, at this highly loaded location, compared to the corresponding region of interest in intact femoral condyles under physiological loading. This study demonstrated, for the first time, the remarkable capability of trabecular bone to adapt to stress and strain close to its failure load.

Zusammenfassung

Es ist seit Langem bekannt, dass sich Knochen an erhöhte mechanische Belastung durch Knochenapposition anpassen kann. Die Korrelation zwischen erhöhten Spannungen und Dehnungen im Knochen und der Knochenformation wurde häufig in kortikalen Knochen, aber sehr selten in trabekulären Knochen untersucht. Speziell für sehr hohe mechanische Belastungen nahe der Bruchbelastung des Knochens gibt es keine Studien. In dieser Studie untersuchten wir die Knochenneubildung im spongiösen Knochen in der Nachbarschaft zu einer partiellen Osteotomie im Schafskondylus, wo es lokal zu sehr großen Spannungen kam, die nahe der Bruchspannung des Knochens lagen. Nach acht Wochen war das Knochenvolumen an dieser hochbelasteten Stelle um das ca. Zweifache und die Knochenneubildungsrate um das ca. Dreifache im Vergleich zum normalen spongiösen Knochen der nicht operierten, physiologisch belasteten kontralateralen Kondyle erhöht. Diese Studie zeigt zum ersten Mal die erstaunlich hohe Anpassungsfähigkeit des spongiösen Knochens unter extrem hohen Spannungen und Dehnungen nahe der Bruchbeanspruchung des Knochens.

Keywords

Bone adaptation - mechano-biology - bone formation - strain

Schlüsselwörter

Knochenadaptation - Mechanobiologie - Knochenformation - Dehnung

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