一种新型动态牵引外固定架治疗近指间关节骨折脱位的实验研究

A new dynamic external fixator for fracture-dislocations of the proximal interphalangeal joint： a cadaver study

目的报告一种新型动态牵引外固定架治疗手指近指间关节（PIPJ）骨折脱位的研究结果。方法于新鲜标本手指中节指骨基底掌侧做斜形截骨，游离掌侧半关节面，制备PIPI骨折脱位模型。行X线侧位片透视，测量以下指标：截骨块累及关节面的比例；截骨前、后和外固定架牵引下，PIPJ处于伸直、屈曲45°及屈曲90°位时，近节指骨头中心（Cpl）到中节指骨头与指骨基底关节面背侧缘连线（L）的距离（h）；截骨后和外固定架牵引下，PIPI处于上述角度时Cp1到中节指骨基底残余关节面掌侧缘的距离（a）和背侧缘的距离（b）；记录外固定架所能维持关节复位的最大活动范围。通过比较h、a、b值来判断关节复位程度。结果截骨块平均累及关节面的（49．5±4．9）％。截骨后，Cp1到L的距离h1均大于截骨前距离h0，b值均大于a值（P〈0．01），差异有统计学意义，提示唧处于动态半脱位状态。外固定架牵引下，Cpl与L的距离112和h0比较及a值和b值比较（P〉0．05），差异均无统计学意义，提示关节复位良好。X线透视显示PIPJ关节面清晰可见，外固定架牵引能在0°-（102．2±5．1）。的范围内维持关节复位状态。旋转弹簧，可轻松调节牵引力。结论该新型动态牵引外固定架轻巧易用、不遮挡关节面、可调节牵引力，能获得并维持关节复位状态。

Objective To evaluate the effectiveness of the new adjustable dynamic external fixator （Adynex） for treatment of unstable fracture-dislocations of the proximal interphalangeal joint （PIPJ）. Methods An unstable PIPJ fracture-dislocation model was created in 8 fresh cadaveric fngers by oblique osteotomy along the volar base of the middle phalanx and detachment of volar half of the joint. Adynex was fixed onto two parallel K-wires which were drilled through the rotational center of the head of the proximal phalanx （P1） and middle phalanx （P2）. The PIPJ was passively moved throughout its full range of motion （ROM） under dynamic lateral fluoroscopy before osteotomy, after osteotomy and under distraction. The following measurements were taken： the percentage of the articular surface involved by osteotomy; the distances between the center of the P1 （Cpl） and the line （L） connecting the dorsal rims of P2 head and base joint surface before osteotomy, after osteotomy and under distraction; the distances between Cpl and the palmar tip （a） and dorsal tip （b） of the remaining joint surface of P2 after osteotomy and under distraction; the range of motion of the PIPJ which could be maintained in reduction by Adynex. Results The mean percentage of the articular surface involved by osteotomy was （49.5 ± 4.9） %. Adynex established satisfactory reduction of PIPJ and congruency of the PIP joint surfaces. The fracture site was not obscured on a lateral view. The distraction force could be easily modified by turning the springs on either side of the device during the distraction period. The stable ROM of PIPJ under distraction was 0° to （ 102.2° ±5.1°）. Conclusion Adynex has fulfilled its objectives in a cadaver model. It is light weight, easy to use, adjustable for distraction forces and can maintain joint reduction during range of motion. It will next be applied in the clinical setting.