Guettler Joseph H, Demetropoulos Constantine K, Yang King H, Jurist Kenneth A
Department of Orthopaedic Surgery, William Beaumont Hospital, Royal Oak, Michigan, USA.
Am J Sports Med. 2004 Sep;32(6):1451-8. doi: 10.1177/0363546504263234. Epub 2004 Jul 20.
To determine the influence of osteochondral defect size on defect rim stress concentration, peak rim stress, and load redistribution to adjacent cartilage over the weightbearing area of the medial and lateral femoral condyles in the human knee.
Eight fresh-frozen cadaveric knees were mounted at 30 degrees of flexion in a materials testing machine. Digital electronic pressure sensors were placed in the medial and lateral compartments of the knee. Each intact knee was first loaded to 700 N and held for 5 seconds. Dynamic pressure readings were recorded throughout the loading and holding phases. Loading was repeated over circular osteochondral defects (5, 8, 10, 12, 14, 16, 18, and 20 mm) in the 30 degrees weightbearing area of the medial and lateral femoral condyles.
Stress concentration around the rims of defects 8 mm and smaller was not demonstrated, and pressure distribution in this size range was dominated by the menisci. For defects 10 mm and greater, distribution of peak pressures followed the rim of the defect with a mean distance from the rim of 2.2 mm on the medial condyle and 3.2 mm on the lateral condyle. An analysis of variance with Bonferroni correction revealed a statistically significant trend of increasing radius of peak pressure as defect size increased for defects from 10 to 20 mm (P = .0011). Peak rim pressure values did not increase significantly as defects were enlarged from 10 to 20 mm. Load redistribution during the holding phase was also observed.
Rim stress concentration was demonstrated for osteochondral defects 10 mm and greater in size. This altered load distribution has important implications relating to the long-term integrity of cartilage adjacent to osteochondral defects in the human knee. Although the decision to treat osteochondral lesions is certainly multifactorial, a size threshold of 10 mm, based on biomechanical data, may be a useful adjunct to guide clinical decision making.
确定骨软骨缺损大小对人膝关节内侧和外侧股骨髁负重区域缺损边缘应力集中、边缘峰值应力以及相邻软骨负荷再分配的影响。
将八个新鲜冷冻的尸体膝关节在材料试验机中屈曲30度固定。数字电子压力传感器放置在膝关节的内侧和外侧间室。每个完整的膝关节首先加载至700 N并保持5秒。在整个加载和保持阶段记录动态压力读数。在内侧和外侧股骨髁30度负重区域的圆形骨软骨缺损（5、8、10、12、14、16、18和20 mm）上重复加载。
未显示8 mm及更小的缺损边缘存在应力集中，该尺寸范围内的压力分布主要由半月板主导。对于10 mm及更大的缺损，峰值压力分布沿缺损边缘，在内侧髁距边缘的平均距离为2.2 mm，在外侧髁为3.2 mm。经Bonferroni校正的方差分析显示，对于10至20 mm的缺损，随着缺损大小增加，峰值压力半径呈统计学显著增加趋势（P = .0011）。当缺损从10 mm扩大到20 mm时，边缘峰值压力值未显著增加。在保持阶段也观察到了负荷再分配。
对于尺寸为10 mm及更大的骨软骨缺损，显示出边缘应力集中。这种改变的负荷分布对人膝关节骨软骨缺损相邻软骨的长期完整性具有重要意义。尽管治疗骨软骨损伤的决定肯定是多因素的，但基于生物力学数据的10 mm尺寸阈值可能是指导临床决策的有用辅助依据。
