Laino Daniel K, Petchprapa Catherine N, Lee Steve K
Department of Orthopedic Surgery, NYU Hospital for Joint Diseases, New York, NY, USA.
J Hand Surg Am. 2012 Jan;37(1):90-7. doi: 10.1016/j.jhsa.2011.09.040. Epub 2011 Nov 25.
Several techniques used to measure ulnar variance on a posteroanterior wrist radiograph have been described. It remains unclear whether they accurately represent the true ulnar variance of the patient. The purpose of this study was to correlate ulnar variance measurements on plain radiographs, computed tomography (CT), magnetic resonance imaging (MRI), and anatomic dissection.
Posteroanterior (PA) radiographs, coronal and sagittal CT scans, and coronal MRI scans were obtained on 8 fresh-frozen cadaver wrists. The ulnar variance was measured by 5 reviewers. The specimens were then dissected, exposing the wrist joint. The ulnar variance was measured directly on each specimen using digital calipers. The inter-rater reliability was calculated for each imaging modality. The bias for each imaging modality was calculated using the digital caliper measurements as the true ulnar variance.
Intraclass correlation coefficients demonstrated excellent inter-rater reliability for each imaging modality. The average bias from the true variance was the following: PA radiograph, 0.77 mm; coronal CT, 0.96 mm; sagittal CT, 0.96 mm; MRI with articular cartilage, 0.73 mm; MRI excluding cartilage, 0.49 mm. The variance measured on all imaging modalities tended to underestimate the magnitude of the true variance.
Ulnar variance measured on coronal MRI best reflected the true ulnar variance as measured directly using calipers. The CT scans demonstrated the greatest deviation from the true variance. However, differences were small and might not be clinically meaningful. All imaging modalities demonstrated excellent inter-rater reliability, with MRI being highest. All imaging modalities tended to underestimate the magnitude of the true variance.
The imaged underestimation of true ulnar variance should be taken into account when performing surgical procedures that alter the relative lengths of the radius and ulna.
已经描述了几种用于在腕关节后前位X线片上测量尺骨变异的技术。目前尚不清楚它们是否准确反映了患者的真实尺骨变异。本研究的目的是将X线平片、计算机断层扫描（CT）、磁共振成像（MRI）和解剖学解剖测量的尺骨变异进行相关性分析。
对8个新鲜冷冻尸体手腕进行腕关节后前位（PA）X线片、冠状面和矢状面CT扫描以及冠状面MRI扫描。由5名评估者测量尺骨变异。然后对标本进行解剖，暴露腕关节。使用数字卡尺直接在每个标本上测量尺骨变异。计算每种成像方式的评估者间可靠性。以数字卡尺测量值作为真实尺骨变异，计算每种成像方式的偏差。
组内相关系数表明每种成像方式均具有出色的评估者间可靠性。与真实变异的平均偏差如下：PA X线片为0.77 mm；冠状面CT为0.96 mm；矢状面CT为0.96 mm；有关节软骨的MRI为0.73 mm；排除软骨的MRI为0.49 mm。所有成像方式测量的变异均倾向于低估真实变异的大小。
冠状面MRI测量的尺骨变异最能反映直接使用卡尺测量的真实尺骨变异。CT扫描显示与真实变异的偏差最大。然而，差异很小，可能在临床上无意义。所有成像方式均显示出出色的评估者间可靠性，其中MRI最高。所有成像方式均倾向于低估真实变异的大小。
在进行改变桡骨和尺骨相对长度的手术时，应考虑到影像上对真实尺骨变异的低估。
