Mayo Clinic, 200 First St. SW, Rochester, MN, 55905, USA.
Skeletal Radiol. 2021 Aug;50(8):1687-1695. doi: 10.1007/s00256-021-03728-5. Epub 2021 Feb 3.
To update the prevalence and morphology of the accessory abductor digiti minimi muscle using 3T MRI.
A retrospective study of 3T wrist MRI was performed. Presence and morphology of the accessory abductor digiti minimi were evaluated in addition to its relationship to the ulnar nerve. Charts were reviewed for demographics, EMG, neuropathic symptoms, and initial MRI interpretation.
Analysis of 396 wrist MRI studies yielded 25% prevalence of the accessory abductor digiti minimi, of which the majority (69%) demonstrated fascial-type morphology proximal to Guyon's canal. A minority (31%) demonstrated a contiguous muscle belly throughout its course. Overall, prevalence of a muscular type was only 8%. All patients were asymptomatic with normal EMG, unremarkable ulnar nerve, and no significant nerve compression. Anterior-posterior muscle dimension was larger in males. Only 1 of 98 accessory abductor digiti minimi muscles was prospectively identified.
The accessory abductor digiti minimi is not uncommon; however, patients are usually asymptomatic without neuropathic symptoms. The most common anatomic variant is a small muscle belly at the level of the pisiform with fascial morphology proximal to Guyon's canal and origin from the distal antebrachial fascia. A contiguous muscle belly extending from the distal forearm through the wrist occurs much less frequently. Clinicians should be familiar with these anatomic variants to enhance its recognition, understanding that a muscular variant is rarer than previously reported, but historically can serve as a potential source of clinical symptomatology and could be encountered during physical examination or wrist surgery.
使用 3T MRI 更新小指外展肌的患病率和形态。
对 3T 腕部 MRI 进行回顾性研究。评估小指外展肌的存在和形态及其与尺神经的关系。对病历、肌电图、神经病变症状和初始 MRI 解释进行了回顾分析。
分析了 396 项腕部 MRI 研究，发现小指外展肌的患病率为 25%，其中大部分（69%）在 Guyon 管近端表现为筋膜样形态。少数（31%）在整个行程中表现为连续的肌腹。总体而言，肌肉型的患病率仅为 8%。所有患者均无症状，肌电图正常，尺神经无明显异常，无明显神经压迫。男性的前后肌维度较大。仅在 98 个小指外展肌中发现了 1 个。
小指外展肌并不少见，但患者通常无症状，无神经病变症状。最常见的解剖变异是在豌豆骨水平有一个小的肌腹，近端 Guyon 管的筋膜样形态，起源于前臂远端筋膜。从远端前臂延伸通过手腕的连续肌腹则少见得多。临床医生应熟悉这些解剖变异，以增强其识别能力，了解肌肉型变异比以前报道的更为罕见，但历史上可能是引起临床症状的潜在原因，在体格检查或腕部手术中可能会遇到。
