Gourineni P V, Knuth A E, Nuber G F
Department of Orthopaedic Surgery, Northwestern University Medical School, Chicago, Illinois, USA.
J Bone Joint Surg Am. 1999 Mar;81(3):364-9. doi: 10.2106/00004623-199903000-00008.
Displaced transverse fractures of the medial malleolus are commonly treated with open reduction and internal fixation with two screws or wires. A mortise radiograph is often used to verify the position of the implants relative to the joint space. However, because the medial and lateral talomalleolar spaces are normally not parallel, the mortise projection (which is colinear with the lateral space) does not provide an accurate radiograph of the medial joint space.
In ten cadaveric ankles, two wires were inserted into the medial malleolus, as is done for fixation of a fracture, and the distance of the wires from the joint space was measured on an anteroposterior radiograph, on mortise radiographs made with the foot in 15 and 30 degrees of internal rotation, and on anatomical cross section.
The measurement on the anteroposterior radiograph exceeded the anatomical measurement in only two specimens, and the discrepancy was 0.5 millimeter in both instances. Measurement of the osseous thickness between the joint surface and the posterior wire on the mortise radiographs always revealed a lower value than the measurements on the anteroposterior radiograph and the anatomical cross section of the same specimen. There was a false appearance of intra-articular placement of the posterior wire on the 15-degree mortise radiographs of four specimens and on the 30-degree mortise radiographs of eight specimens.
These findings demonstrate that the mortise projection provides an oblique radiograph of the medial joint space that can inaccurately reflect the true position of fixation implants in the medial malleolus. Because an anteroposterior radiograph is made with the articular surface of the medial malleolus tangential to the beam, it provides a more accurate representation of implants in the medial malleolus.
内踝移位横行骨折通常采用双螺钉或钢丝切开复位内固定治疗。常使用踝关节正位X线片来验证植入物相对于关节间隙的位置。然而，由于内侧和外侧距踝关节间隙通常不平行，踝关节正位投照（与外侧间隙共线）不能提供内侧关节间隙的准确X线片。
在10具尸体踝关节中，如同骨折固定那样将两根钢丝插入内踝，并在前后位X线片、足部内旋15度和30度时拍摄的踝关节正位X线片以及解剖横断面测量钢丝与关节间隙的距离。
前后位X线片测量值仅在两个标本中超过解剖测量值，且两次差异均为0.5毫米。踝关节正位X线片上关节面与后侧钢丝之间的骨厚度测量值始终低于同一标本的前后位X线片和解剖横断面测量值。在4个标本的15度踝关节正位X线片和8个标本的30度踝关节正位X线片上，后侧钢丝出现关节内放置的假象。
这些结果表明，踝关节正位投照提供的内侧关节间隙斜位X线片可能无法准确反映内踝固定植入物的真实位置。由于前后位X线片是在内踝关节面与X线束相切时拍摄的，它能更准确地显示内踝植入物的情况。
