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Strain-mode-specific mechanical testing and the interpretation of bone adaptation in the deer calcaneus
Journal of Anatomy ( IF 1.8 ) Pub Date : 2023-11-12 , DOI: 10.1111/joa.13971 John G Skedros 1 , Michael R Dayton 2 , Roy D Bloebaum 1 , Kent N Bachus 1, 3 , John T Cronin 1
Journal of Anatomy ( IF 1.8 ) Pub Date : 2023-11-12 , DOI: 10.1111/joa.13971 John G Skedros 1 , Michael R Dayton 2 , Roy D Bloebaum 1 , Kent N Bachus 1, 3 , John T Cronin 1
Affiliation
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The artiodactyl (deer and sheep) calcaneus is a model that helps in understanding how many bones achieve anatomical optimization and functional adaptation. We consider how the dorsal and plantar cortices of these bones are optimized in quasi-isolation (the conventional view) versus in the context of load sharing along the calcaneal shaft by “tension members” (the plantar ligament and superficial digital flexor tendon). This load-sharing concept replaces the conventional view, as we have argued in a recent publication that employs an advanced analytical model of habitual loading and fracture risk factors of the deer calcaneus. Like deer and sheep calcanei, many mammalian limb bones also experience prevalent bending, which seems problematic because the bone is weaker and less fatigue-resistant in tension than compression. To understand how bones adapt to bending loads and counteract deleterious consequences of tension, it is important to examine both strain-mode-specific (S-M-S) testing (compression testing of bone habitually loaded in compression; tension testing of bone habitually loaded in tension) and non-S-M-S testing. Mechanical testing was performed on individually machined specimens from the dorsal “compression cortex” and plantar “tension cortex” of adult deer calcanei and were independently tested to failure in one of these two strain modes. We hypothesized that the mechanical properties of each cortex region would be optimized for its habitual strain mode when these regions are considered independently. Consistent with this hypothesis, energy absorption parameters were approximately three times greater in S-M-S compression testing in the dorsal/compression cortex when compared to non-S-M-S tension testing of the dorsal cortex. However, inconsistent with this hypothesis, S-M-S tension testing of the plantar/tension cortex did not show greater energy absorption compared to non-S-M-S compression testing of the plantar cortex. When compared to the dorsal cortex, the plantar cortex only had a higher elastic modulus (in S-M-S testing of both regions). Therefore, the greater strength and capacity for energy absorption of the dorsal cortex might “protect” the weaker plantar cortex during functional loading. However, this conventional interpretation (i.e., considering adaptation of each cortex in isolation) is rejected when critically considering the load-sharing influences of the ligament and tendon that course along the plantar cortex. This important finding/interpretation has general implications for a better understanding of how other similarly loaded bones achieve anatomical optimization and functional adaptation.
中文翻译：
应变模式特异性机械测试和鹿跟骨骨适应的解释
偶蹄动物（鹿和羊）跟骨是一个模型，有助于了解有多少骨骼实现了解剖优化和功能适应。我们考虑这些骨骼的背侧和足底皮质如何在准隔离（传统观点）中进行优化，而不是在“张力构件”（足底韧带和浅表屈肌腱）沿跟骨轴分担负载的情况下进行优化。这种负载共享概念取代了传统观点，正如我们在最近的一篇出版物中所论证的那样，该出版物采用了鹿跟骨的习惯性负载和骨折风险因素的先进分析模型。与鹿和羊的跟骨一样，许多哺乳动物的四肢骨也普遍存在弯曲，这似乎是有问题的，因为与压缩相比，骨骼在张力下更脆弱且更不易疲劳。为了了解骨骼如何适应弯曲载荷并抵消张力的有害后果，重要的是检查特定应变模式 (SMS) 测试（对习惯性承受压力的骨骼进行压缩测试；对习惯性承受张力的骨骼进行拉伸测试）和非短信测试。对成年鹿跟骨背侧“压缩皮层”和足底“张力皮层”的单独加工样本进行机械测试，并独立测试这两种应变模式之一的失效情况。我们假设，当独立考虑这些区域时，每个皮层区域的机械特性将针对其习惯应变模式进行优化。与这一假设一致，与背侧皮层的非 SMS 张力测试相比，背侧/压缩皮层 SMS 压缩测试中的能量吸收参数大约高出三倍。 然而，与这一假设不一致的是，与足底皮层的非 SMS 压缩测试相比，足底/张力皮层的 SMS 张力测试并未显示出更大的能量吸收。与背侧皮质相比，足底皮质仅具有更高的弹性模量（在这两个区域的 SMS 测试中）。因此，背侧皮层更大的强度和能量吸收能力可能会在功能负荷期间“保护”较弱的足底皮层。然而，当严格考虑沿着足底皮质延伸的韧带和肌腱的负载分配影响时，这种传统的解释（即单独考虑每个皮质的适应）被拒绝。这一重要的发现/解释对于更好地理解其他类似负载的骨骼如何实现解剖优化和功能适应具有普遍意义。
更新日期：2023-11-13
中文翻译：
应变模式特异性机械测试和鹿跟骨骨适应的解释
偶蹄动物（鹿和羊）跟骨是一个模型，有助于了解有多少骨骼实现了解剖优化和功能适应。我们考虑这些骨骼的背侧和足底皮质如何在准隔离（传统观点）中进行优化，而不是在“张力构件”（足底韧带和浅表屈肌腱）沿跟骨轴分担负载的情况下进行优化。这种负载共享概念取代了传统观点，正如我们在最近的一篇出版物中所论证的那样，该出版物采用了鹿跟骨的习惯性负载和骨折风险因素的先进分析模型。与鹿和羊的跟骨一样，许多哺乳动物的四肢骨也普遍存在弯曲，这似乎是有问题的，因为与压缩相比，骨骼在张力下更脆弱且更不易疲劳。为了了解骨骼如何适应弯曲载荷并抵消张力的有害后果，重要的是检查特定应变模式 (SMS) 测试（对习惯性承受压力的骨骼进行压缩测试；对习惯性承受张力的骨骼进行拉伸测试）和非短信测试。对成年鹿跟骨背侧“压缩皮层”和足底“张力皮层”的单独加工样本进行机械测试，并独立测试这两种应变模式之一的失效情况。我们假设，当独立考虑这些区域时，每个皮层区域的机械特性将针对其习惯应变模式进行优化。与这一假设一致，与背侧皮层的非 SMS 张力测试相比，背侧/压缩皮层 SMS 压缩测试中的能量吸收参数大约高出三倍。 然而，与这一假设不一致的是，与足底皮层的非 SMS 压缩测试相比，足底/张力皮层的 SMS 张力测试并未显示出更大的能量吸收。与背侧皮质相比，足底皮质仅具有更高的弹性模量（在这两个区域的 SMS 测试中）。因此，背侧皮层更大的强度和能量吸收能力可能会在功能负荷期间“保护”较弱的足底皮层。然而，当严格考虑沿着足底皮质延伸的韧带和肌腱的负载分配影响时，这种传统的解释（即单独考虑每个皮质的适应）被拒绝。这一重要的发现/解释对于更好地理解其他类似负载的骨骼如何实现解剖优化和功能适应具有普遍意义。
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