Department of Orthopaedic Surgery, Naval Medical Center San Diego, 34800 Bob Wilson Drive, Suite 112, San Diego, CA 92134, USA.
J Bone Joint Surg Am. 2010 Apr;92(4):911-5. doi: 10.2106/JBJS.I.00084.
The treatment of ankle fractures often depends on the integrity of the deltoid ligament. Diagnosis of a deltoid ligament tear depends on the measurement of the medial clear space. We sought to evaluate the impact of ankle plantar flexion on the medial clear space.
Mortise radiographs were made for twenty-five healthy volunteers, with the ankle in four positions of plantar flexion (0 degrees, 15 degrees, 30 degrees, and 45 degrees). Four observers measured the medial clear space and the superior clear space on each radiograph. The mean medial clear space at 0 degrees was defined as the control, and the deviation of the medial clear space from the control value was calculated at 15 degrees, 30 degrees, and 45 degrees of plantar flexion. The ratio of the medial clear space to the superior clear space was determined on all radiographs, and ratios that were false-positive for a deltoid ligament injury were identified.
Fourteen male and eleven female volunteers were evaluated. The average increase in the medial clear space when ankle plantar flexion was increased from 0 degrees to 45 degrees was 0.38 mm (95% confidence interval, 0.18 to 0.58 mm). This increase was significant (p = 0.005). The average increase in the medial clear space was 0.04 mm when ankle plantar flexion was increased from 0 degrees to 15 degrees and 0.22 mm when it was increased from 0 degrees to 30 degrees. Neither of these changes was significant (p = 0.99 and 0.20). The prevalence of false-positive findings of deltoid injury based on the ratio of the medial clear space to the superior clear space increased as ankle plantar flexion increased, but this increase did not reach significance in our study group (p = 0.18).
Plantar flexion of the ankle produces changes in radiographic measurements of the medial clear space. The potential for false-positive findings of deltoid disruption increases with increasing ankle plantar flexion.
踝关节骨折的治疗通常取决于三角韧带的完整性。三角韧带撕裂的诊断取决于内侧间隙的测量。我们试图评估踝关节跖屈对内侧间隙的影响。
对 25 名健康志愿者进行了踝部矢状位 X 线检查，踝关节分别处于跖屈 0 度、15 度、30 度和 45 度 4 个位置。4 名观察者分别测量了每条 X 线片上的内侧间隙和上侧间隙。0 度时的内侧间隙平均值定义为对照值，计算 15 度、30 度和 45 度时内侧间隙与对照值的偏差。确定所有 X 线片上的内侧间隙与上侧间隙的比值，并确定假阳性的三角韧带损伤比值。
共评估了 14 名男性和 11 名女性志愿者。当踝关节从 0 度跖屈增加到 45 度时，内侧间隙的平均增加量为 0.38 毫米（95%置信区间，0.18 至 0.58 毫米）。这种增加具有统计学意义（p = 0.005）。当踝关节从 0 度跖屈增加到 15 度时，内侧间隙的平均增加量为 0.04 毫米，从 0 度增加到 30 度时，内侧间隙的平均增加量为 0.22 毫米。这两种变化均无统计学意义（p = 0.99 和 0.20）。随着踝关节跖屈的增加，基于内侧间隙与上侧间隙比值的三角韧带损伤假阳性发现的患病率增加，但在我们的研究组中，这种增加没有达到统计学意义（p = 0.18）。
踝关节跖屈会改变内侧间隙的 X 线测量值。随着踝关节跖屈的增加，三角韧带断裂的假阳性发现的可能性增加。
