Senthi Suren, Blyth Phil, Metcalfe Russell, Stott Ngaire Susan
Department of Orthopaedics, Auckland City Hospital, Auckland, New Zealand.
J Pediatr Orthop. 2011 Jun;31(4):388-92. doi: 10.1097/BPO.0b013e318217270d.
Unrecognized pin penetration in the treatment of slipped capital femoral epiphysis has serious long-term sequelae. The purpose of this study was to use postoperative computerized tomographic (CT) scans to determine the true position of the screw tip when compared with standard radiograph views.
Twenty-four patients with 33 slipped capital femoral epiphyses were included in the study. Intraoperative or postoperative radiographs [anteroposterior (AP) and frog lateral] were compared with postoperative CT scans (coronal and axial) to determine (1) distance of the screw tip from the subchondral bone of the femoral head, (2) the number of screw threads across the physis, and (3) the 3-dimensional placement of the screw tip in the femoral head.
The positions of 38 screws in 33 hips were assessed. Screw position within specific quadrants of the femoral head was more anterior and superior than appreciated on radiographs. AP radiographs overestimated the distance between the screw tip and the subchondral bone, the average distance being 5.5 mm on AP radiographs and 3.4 mm on coronal CT (P<0.0001). Bland-Altman analysis confirmed 95% limits of agreement of -5.6 to 1.5 mm, indicating that screws could be up to 5.6 mm closer to the subchondral bone than estimated by the AP radiograph. Closer agreement was found between the frog lateral radiograph and the axial CT views, with the distance from the subchondral bone averaging 4.7 mm on frog lateral radiographs and 4.1 mm on axial CT (P<0.01). Bland-Altman analysis showed 95% limits of agreement between the 2 measures of -3.5 to 2.3 mm, suggesting that some screws were up to 3.5 mm closer to the subchondral bone. Three more anteriorly placed screws seemed to penetrate subchondral bone on CT, findings not shown on standard radiographs.
Frog lateral radiographs of the hip provide a more accurate estimation of screw placement than AP radiographs. Screws closer than 4 mm to the subchondral bone on frog lateral radiographs or 6 mm on AP radiographs may penetrate subchondral bone.
在治疗股骨头骨骺滑脱时，未被识别的钢针穿透会导致严重的长期后遗症。本研究的目的是通过术后计算机断层扫描（CT）来确定与标准X线片相比时螺钉尖端的真实位置。
本研究纳入了24例共33个股骨头骨骺滑脱患者。将术中或术后的X线片[前后位（AP）和蛙式侧位]与术后CT扫描（冠状位和轴位）进行比较，以确定：（1）螺钉尖端与股骨头软骨下骨的距离；（2）穿过骨骺的螺纹数量；（3）螺钉尖端在股骨头内的三维位置。
对33个髋关节中的38枚螺钉位置进行了评估。螺钉在股骨头特定象限内的位置比X线片显示的更靠前和靠上。AP位X线片高估了螺钉尖端与软骨下骨之间的距离，AP位X线片上的平均距离为5.5 mm，冠状位CT上为3.4 mm（P<0.0001）。Bland-Altman分析确定一致性界限为-5.6至1.5 mm，表明螺钉可能比AP位X线片估计的更接近软骨下骨达5.6 mm。蛙式侧位X线片与轴位CT视图之间的一致性更高，蛙式侧位X线片上与软骨下骨的距离平均为4.7 mm，轴位CT上为4.1 mm（P<0.01）。Bland-Altman分析显示两种测量方法之间的一致性界限为-3.5至2.3 mm，表明一些螺钉比软骨下骨更近达3.5 mm。在CT上，另外3枚靠前放置的螺钉似乎穿透了软骨下骨，而标准X线片未显示此结果。
髋关节蛙式侧位X线片比AP位X线片能更准确地评估螺钉位置。蛙式侧位X线片上距离软骨下骨小于4 mm或AP位X线片上小于6 mm的螺钉可能会穿透软骨下骨。
