Loder Randall T, Browne Richard, Bellflower Joseph, Kayes Kosmas, Wurtz Daniel, Loder Andrew J
James Whitcomb Riley Hospital for Children, Indianapolis, IN 46202, USA.
J Pediatr Orthop. 2007 Apr-May;27(3):338-46. doi: 10.1097/BPO.0b013e3180340db2.
Angular measurements are commonly used in orthopaedic surgery. No study has addressed measurement variability due to the measurement device itself. It was the purpose of this study to assess measurement variability of articulated versus fixed devices.
Three articulated and 4 fixed goniometers were randomly selected. Thirty-two different angles, ranging from a few degrees to nearly 180 degrees, were drawn with a standard soft-lead marking pencil. The angles were measured by 5 different observers with 7 different goniometers on 2 separate occasions separated by a minimum of 3 weeks. We wished to determine whether the variability of any goniometer was within a +/-1-degree range.
There were 1023 (91.3%) absolute differences of 1 degree or less and 97 (8.7%) of more than 1 degree. Intraobserver agreement was 92.0%; 96.9% for fixed and 84.0% for hinged goniometers. Interobserver agreement was of 90.7%; 96.2% for the fixed and 83.4% for the hinged goniometers. Intragoniometer agreement was 91.3%; 96.9% for fixed and 84.0% for hinged goniometers. Intergoniometer agreement was 87.0% with fixed goniometers demonstrating better agreement than hinged goniometers. The overall intraobserver and interobserver measurement variability was +/-2.33 and +/-2.26 degrees, respectively; the overall intragoniometer and intergoniometer measurement variability was +/-2.26 and +/-2.30 degrees, respectively. For fixed goniometers, the intergoniometer measurement variability is +/-2.0 degrees, for hinged goniometers, +/-2.9 degrees, and when using both fixed and hinged goniometers, +/-2.4 degrees. Thus, the fixed goniometers are the ideal type with overall better agreement and measurement variability.
Any one orthopaedic surgeon should use the same goniometer at all times, preferably a fixed type, so that measurement variability can be reduced by +/-2.0 degrees. If a physician uses a particular published measurement variability from the literature in which different goniometers were used, then the intraobserver measurement variability will be less than the published value by approximately +/-2 degrees. This is important when faced with the question of a change in an angular measurement being a true change or simply a reflection of measurement error.
角度测量在骨科手术中常用。尚无研究探讨测量设备本身导致的测量变异性。本研究旨在评估关节式与固定式设备的测量变异性。
随机选取3个关节式和4个固定式测角仪。用标准软铅笔绘制32个不同角度，范围从几度到近180度。5名不同观察者使用7个不同测角仪在2个不同时间测量这些角度，两次测量间隔至少3周。我们希望确定任何测角仪的变异性是否在±1度范围内。
绝对差值在1度及以内的有1023个（91.3%），超过1度的有97个（8.7%）。观察者内一致性为92.0%；固定式测角仪为96.9%，关节式测角仪为84.0%。观察者间一致性为90.7%；固定式测角仪为96.2%，关节式测角仪为83.4%。测角仪内一致性为91.3%；固定式测角仪为96.9%，关节式测角仪为84.0%。测角仪间一致性为87.0%，固定式测角仪的一致性优于关节式测角仪。观察者内和观察者间的总体测量变异性分别为±2.33度和±2.26度；测角仪内和测角仪间的总体测量变异性分别为±2.26度和±2.30度。对于固定式测角仪，测角仪间测量变异性为±2.0度，对于关节式测角仪为±2.9度，同时使用固定式和关节式测角仪时为±2.4度。因此，固定式测角仪是总体一致性和测量变异性更好的理想类型。
任何一名骨科医生应始终使用同一测角仪，最好是固定式，这样测量变异性可降低±2.0度。如果医生使用文献中特定的已发表测量变异性数据，而其中使用了不同测角仪，那么观察者内测量变异性将比已发表值约低±2度。当面临角度测量变化是真正变化还是仅仅是测量误差反映的问题时，这一点很重要。
