Department of Hand Surgery, Beijing Jishuitan Hospital, Beijing 100035, China.
Department of Human Anatomy, Histology and Embryology, Peking University School of Basic Medical Sciences,Beijing 100191, China.
Chin Med J (Engl). 2020 Mar 20;133(6):657-663. doi: 10.1097/CM9.0000000000000676.
Mallet fracture is avulsion of the terminal extensor tendon from the base of the distal phalangeal bone with a bony fragment. This study was performed to evaluate the anatomical characteristics of mallet fractures, investigate a new mallet fracture classification system using anatomical and imaging methods, and discuss the treatment schemes for different types of mallet fracture.
Sixty-four fresh cadaveric fingers were divided into four groups, and models of different types of mallet fracture with distal interphalangeal joint instability were established by dissecting 25%, 50%, 75%, and 100% of the bilateral collateral ligaments. The effect of mallet fractures on the stability of the distal interphalangeal joint was then observed. The lateral radiographs of mallet fractures in 168 patients were analyzed and classified according to the involvement of the joint surface in the fracture, the thickness of fracture, the untreated time after injury, and the complication of distal interphalangeal joint palmar subluxation. Forty-seven patients were surgically treated by reconstruction of extensor tendon insertion, the Ishiguro method, or single Kirschner wire fixation.
The established mallet fracture model showed that the distal interphalangeal joint was stable when the bilateral collateral ligaments were cut off by 25% (t = -0.415, P = 0.684) and significantly unstable when this range was ≥50% (50% transection: t = -6.363, P < 0.001; 75% transection: t = -17.036, P < 0.001; 100% transection: t = -30.977, P < 0.001, respectively). The mallet fractures were divided into Types I, II, and III (fracture involving <20%, 20%-50%, and >50% of the joint surface, respectively). Type II was further divided into Types IIa and IIb according to whether the course of injury was < or ≥2 weeks, respectively. The mean post-operative flexion of the distal interphalangeal joint was 63.4° ± 7.9°, and the mean extension lag was 6.7° ± 4.6°.
The lateral collateral ligament is the main factor that maintains the stability of the distal interphalangeal joint. Classification that combines the involvement of the joint surface in the fracture, the thickness of the fracture, and the untreated time after injury is reasonable and will help to choose an appropriate operational method.
锤状指是末节指骨基底部撕脱的伸肌腱止点伴有骨片。本研究旨在评估锤状指的解剖学特征，采用解剖学和影像学方法建立新的锤状指骨折分类系统，并探讨不同类型锤状指骨折的治疗方案。
将 64 个新鲜的手指尸体标本分为 4 组，通过解剖切断 25%、50%、75%和 100%的双侧侧副韧带，建立不同类型伴有远侧指间关节不稳定的锤状指骨折模型，观察锤状指骨折对远侧指间关节稳定性的影响。对 168 例锤状指骨折患者的侧位 X 线片进行分析，根据骨折累及关节面、骨折厚度、受伤后未治疗时间以及远侧指间关节掌侧半脱位的并发症进行分类。47 例患者采用伸肌腱止点重建、Ishiguro 法或单根克氏针固定进行手术治疗。
建立的锤状指骨折模型显示，当双侧侧副韧带切断 25%时，远侧指间关节稳定（t=-0.415，P=0.684），当该范围≥50%时关节明显不稳定（50%切断：t=-6.363，P<0.001；75%切断：t=-17.036，P<0.001；100%切断：t=-30.977，P<0.001）。将锤状指骨折分为 I 型、II 型和 III 型（分别累及关节面<20%、20%-50%和>50%）。根据受伤时间<或≥2 周，II 型进一步分为 IIa 和 IIb 型。术后远侧指间关节平均屈曲 63.4°±7.9°，平均伸肌迟滞 6.7°±4.6°。
侧副韧带是维持远侧指间关节稳定性的主要因素。结合骨折累及关节面、骨折厚度和受伤后未治疗时间的分类是合理的，有助于选择合适的手术方法。
