Reif Ullrich, Dejardin Loic M, Probst Curtis W, DeCamp Charlie E, Flo Gretchen L, Johnson Allen L
Department for Small Animal Clinical Sciences, College of Veterinary Medicine-Michigan State University, East Lansing, MI, USA.
Vet Surg. 2004 Jul-Aug;33(4):368-75. doi: 10.1111/j.1532-950X.2004.04053.x.
To evaluate the effect of limb positioning and measurement technique on the magnitude of the radiographically determined tibial plateau angle (R-TPA).
In vitro study, R-TPA was determined by 6 blinded observers and image measurement software.
Five canine cadaver hind limbs.
The legs were positioned on a custom-made positioning device simulating a radiographic tabletop technique in lateral recumbency. True lateral positioning was defined by superimposition of femoral and tibial condyles on the radiographic projection. Radiographs were taken while the specimens were relocated in a proximal, distal, caudal, and cranial direction with respect to the radiographic beam. For each specimen, 25 different radiographic views were obtained and 6 blinded observers determined the radiographic TPA using 2 different methods. The conventional method used precise anatomic landmarks to determine the tibial plateau. To simulate osteoarthritic changes complicating identification of these landmarks, the tangential method estimated the tibial plateau as the tangent to the central portion of the tibial plateau. After periarticular soft tissue dissection the anatomic tibial plateau angle (A-TPA) was determined. The A-TPA and the R-TPA were compared.
The R-TPA significantly decreased as limb position with respect to the X-ray beam changed from cranial proximal to caudal distal. The maximal mean radiographic R-TPA difference was 3.6 degrees with the first and 5.7 degrees with the second method. Regardless of the method used there was no significant difference between A-TPA and R-TPA in the true lateral position. In the peripheral positions, however, significant differences between anatomic and radiographic TPA were seen.
Limb positioning influenced the radiographic appearance of the tibial plateau and the magnitude of the measured TPA. Cranial and proximal positioning of the limb relative to the X-ray beam leads to overestimation whereas caudal and distal positioning leads to underestimation of the TPA.
True lateral positioning of the tibia defined by superimposition of the femoral and tibial condyles should be used for accurate TPA determination before tibial plateau leveling osteotomy.
评估肢体位置和测量技术对X线片测定的胫骨平台角（R-TPA）大小的影响。
体外研究，R-TPA由6名不知情的观察者和图像测量软件测定。
5只犬类尸体后肢。
将腿部放置在定制的定位装置上，模拟侧卧位的X线片台面技术。真正的侧位定位通过股骨和胫骨髁在X线投影上的重叠来定义。在标本相对于X线束向近端、远端、尾端和头端重新定位时拍摄X线片。对于每个标本，获得25个不同的X线片视图，6名不知情的观察者使用2种不同方法测定X线片TPA。传统方法使用精确的解剖标志来确定胫骨平台。为模拟使这些标志难以识别的骨关节炎变化，切线法将胫骨平台估计为胫骨平台中央部分的切线。在关节周围软组织解剖后，测定解剖学胫骨平台角（A-TPA）。比较A-TPA和R-TPA。
随着肢体相对于X线束的位置从近端头端向远端尾端改变，R-TPA显著降低。第一种方法最大平均X线片R-TPA差异为3.6度，第二种方法为5.7度。无论使用何种方法，在真正侧位时A-TPA和R-TPA之间均无显著差异。然而，在周边位置，解剖学和X线片TPA之间存在显著差异。
肢体位置影响胫骨平台的X线片表现和所测TPA的大小。肢体相对于X线束的头端和近端定位会导致TPA高估，而尾端和远端定位会导致TPA低估。
在胫骨平台平整截骨术前，应使用通过股骨和胫骨髁重叠定义的胫骨真正侧位定位来准确测定TPA。
