Maeda Eijiro, Asanuma Hiroyuki, Noguchi Hitoshi, Tohyama Harukazu, Yasuda Kazunori, Hayashi Kozaburo
Biomechanics Laboratory, Department of Mechanical Science and Bioengineering, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka, Japan.
J Biomech. 2009 Aug 7;42(11):1592-7. doi: 10.1016/j.jbiomech.2009.04.039. Epub 2009 May 31.
Central third of patellar tendon (PT) is used as an autograft for anterior cruciate ligament (ACL) reconstruction. Previous studies investigated temporal changes in material properties of healing tissues in PT after resection of the central third. However, no study has been performed on effects of stress shielding (SS) and restressing (RS) on the properties of healing tissues. The present study hypothesised that SS adversely affects the mechanical integrity of healing tissues, which is recovered by subsequent RS. An entire rectangular defect was created in the central third of rabbit PT. Operated PTs were subjected to either SS or no stress shielding (NSS). A subgroup of stress-shielded PTs was followed by the resumption of normal loading, namely RS. Tensile properties of tissues regenerated in the defect and residual tendons were evaluated. Regenerated tissues of SS for 3 weeks resulted in significantly lower strength than NSS, which was recovered to NSS level by 3 weeks of RS. Strength of residual tissues in RS reversed SS effects, leading to the strength at NSS level after 12 weeks. However, tangent modulus of residual tissues in RS was still significantly lower than that of NSS at 12 weeks. Therefore, SS induces detrimental effects on the mechanical integrity of healing PTs, and the response to RS was different between regenerate and residual tissues, the latter of which took longer period to reach NSS level.
髌腱（PT）中央三分之一被用作前交叉韧带（ACL）重建的自体移植物。先前的研究调查了切除中央三分之一后PT中愈合组织材料特性的时间变化。然而，尚未有关于应力屏蔽（SS）和再应力加载（RS）对愈合组织特性影响的研究。本研究假设SS会对愈合组织的机械完整性产生不利影响，而随后的RS可使其恢复。在兔PT的中央三分之一处制造一个完整的矩形缺损。对手术处理后的PT施加SS或无应力屏蔽（NSS）。对一组应力屏蔽的PT随后恢复正常负荷，即RS。评估缺损处再生组织和残余肌腱的拉伸特性。SS处理3周的再生组织强度显著低于NSS，经过3周的RS后恢复到NSS水平。RS处理下残余组织的强度逆转了SS的影响，在12周后达到NSS水平。然而，RS处理下残余组织的切线模量在12周时仍显著低于NSS。因此，SS对愈合PT的机械完整性产生有害影响，并且再生组织和残余组织对RS的反应不同，后者达到NSS水平所需时间更长。
