Ryu J Y, Watson H K
Clin Orthop Relat Res. 1987 Mar(216):195-202.
Supernumerary muscle bellies (SMBs) of the forearm, common anatomic variant, are usually asymptomatic but can produce a debilitating pain syndrome that is secondary to a tendon-muscle shear phenomenon. This shear phenomenon seems to occur when a SMB is attached to another muscle and the excursion of the two units are different, thus parts of a muscle unit are prevented from migrating proximally on contraction of the entire muscle. The anomalous muscle may have either greater excursion, as in an anomalous palmaris longus attached to the flexor digitorum superficialis, or less excursion, as in an anomalous superficialis muscle attached to the carpus. The shear at the interface between different muscle-tendon units produces a burning pain that usually is localized to the distal one-third of the forearm. Surgical excision of the abnormal restricting muscle or tendon component relieves the symptom complex and restores the ability to apply full power. Observation on typical cases, diagnostic methods, operative technique, and results of the syndrome suggest that SSMB may be responsible for undiagnosed and untreated instances of distal forearm complaints.
前臂额外肌腹（SMB）是一种常见的解剖变异，通常无症状，但可因肌腱-肌肉剪切现象继发导致使人衰弱的疼痛综合征。当一条SMB附着于另一块肌肉且两个单元的活动范围不同时，似乎就会发生这种剪切现象，这样一来，在整块肌肉收缩时，肌肉单元的某些部分就无法向近端迁移。异常肌肉的活动范围可能更大，比如附着于指浅屈肌的异常掌长肌；也可能更小，比如附着于腕部的异常浅表肌肉。不同肌腱单元之间的界面处发生的剪切会产生灼痛，通常局限于前臂远侧三分之一处。手术切除异常的限制肌肉或肌腱成分可缓解症状并恢复充分用力的能力。对典型病例的观察、诊断方法、手术技术及该综合征的结果表明，SSMB可能是前臂远端未被诊断和治疗的不适病例的病因。
