Borazjani Boris H, Chen Albert C, Bae Won C, Patil Shantanu, Sah Robert L, Firestein Gary S, Bugbee William D
Department of Orthopaedic Surgery, University of California-San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA.
J Bone Joint Surg Am. 2006 Sep;88(9):1934-43. doi: 10.2106/JBJS.E.00992.
Osteochondral grafts, used to treat chondral and osteochondral defects, require high insertional forces that may affect the viability of chondrocytes in the graft. The objectives of this study were to (1) measure the loading impact during insertion of osteochondral grafts, (2) evaluate the effect of insertional loading on chondrocyte viability, and (3) assess this effect on chondrocyte apoptosis and activation of caspase-3.
The distal parts of twelve fresh femora from six adult human cadavers were harvested within seventy-two hours after the death of the donor. From each femur, four 15-mm-diameter cylindrical osteochondral grafts were isolated; two of these grafts (a total of twenty-four grafts in the study) were transplanted with standard impact insertion into recipient sockets in the other condyle of the ipsilateral femur. The other two grafts served as unloaded controls. Loads were measured during the insertion of ten of the twenty-four transplanted grafts. Full-thickness cartilage disks were then removed from the grafts, incubated for up to forty-eight hours, and analyzed for cell viability, TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling)-positive reactivity, and caspase-3 activation, each as a function of the depth from the articular surface.
The insertion of an osteochondral graft was characterized, on the average (and standard deviation), by 10 +/- 4 impacts, each generating 2.4 +/- 0.9 kN of load and 13.3 +/- 4.9 MPa of stress for a duration of 0.57 +/- 0.13 ms with a 0.62 +/- 0.25 N.s impulse. Impact insertion increased cell death in the superficial 500 mum to 21% at one hour (p < 0.001) and 47% at forty-eight hours (p < 0.001) and also increased cell death in deeper layers at forty-eight hours. Some cell death was due to apoptosis, as indicated by an increase in caspase-3 activation at eight hours (p < 0.01) and TUNEL-positive cells at forty-eight hours (p < 0.05) in the superficial 500 mum of impacted cartilage.
Impact insertion of osteochondral grafts generates damaging loads that cause chondrocyte death, particularly in the superficial zone, mainly as a result of apoptosis mediated by the activation of caspases.
Chondrocyte death that occurs during impact insertion of osteochondral grafts may lead to compromised function. Understanding the mechanisms and consequences of such impact loading may provide insights into potential therapeutic interventions, or lead to changes in the insertion technique, to decrease the cell injury associated with impact loading.
用于治疗软骨和骨软骨缺损的骨软骨移植需要较大的插入力，这可能会影响移植组织中软骨细胞的活力。本研究的目的是：（1）测量骨软骨移植插入过程中的负荷影响；（2）评估插入负荷对软骨细胞活力的影响；（3）评估这种影响对软骨细胞凋亡和半胱天冬酶 -3 激活的作用。
从六具成年人类尸体的十二个新鲜股骨远端在供体死亡后七十二小时内获取样本。从每个股骨中分离出四个直径 15 毫米的圆柱形骨软骨移植组织；其中两个移植组织（本研究共二十四个移植组织）采用标准冲击插入法移植到同侧股骨另一髁的受体窝中。另外两个移植组织作为未加载对照。在二十四个移植组织中的十个插入过程中测量负荷。然后从移植组织中取出全层软骨盘，孵育长达四十八小时，并分析细胞活力、TUNEL（末端脱氧核苷酸转移酶介导的 dUTP 缺口末端标记）阳性反应以及半胱天冬酶 -3 激活情况，每一项均作为距关节表面深度的函数。
骨软骨移植的插入过程平均（及标准差）具有 10±4 次冲击，每次冲击产生 2.4±0.9 千牛的负荷和 13.3±4.9 兆帕的应力，持续时间为 0.57±0.13 毫秒，冲量为 0.62±0.25 牛·秒。冲击插入使表层 500 微米处的细胞死亡在 1 小时时增加到 21%（p<0.001），在 48 小时时增加到 47%（p<0.001），并且在 48 小时时深层的细胞死亡也增加。一些细胞死亡是由于凋亡，如在冲击软骨表层 500 微米处，8 小时时半胱天冬酶 -3 激活增加（p<0.01），48 小时时 TUNEL 阳性细胞增加（p<0.05）所示。
骨软骨移植的冲击插入产生破坏性负荷，导致软骨细胞死亡，特别是在表层区域，主要是由于半胱天冬酶激活介导的凋亡。
骨软骨移植冲击插入过程中发生的软骨细胞死亡可能导致功能受损。了解这种冲击负荷的机制和后果可能为潜在的治疗干预提供见解，或导致插入技术的改变，以减少与冲击负荷相关的细胞损伤。
