Flexor Digitorum Accessorius Longus: Importance of Posterior Ankle Endoscopy

Abstract

Endoscopy for the posterior region of the ankle through two portals is becoming more widespread for the treatment of a large number of conditions which used to be treated with open surgery years ago. The tendon of the flexor hallucis longus (FHL) travels along an osteofibrous tunnel between the posterolateral and posteromedial tubercles of the talus. Chronic inflammation of this tendon may lead to painful stenosing tenosynovitis. The aim of this report is to describe two cases depicting an accessory tendon which is an anatomical variation of the flexor hallucis longus in patients with posterior friction syndrome due to posterior ankle impingement and associated with a posteromedial osteochondral lesion of the talus. The anatomical variation (FDAL) described was a finding during an endoscopy of the posterior region of the ankle, and we have spared it by sectioning the superior flexor retinaculum only. The accessory flexor digitorum longus is an anatomical variation and should be taken into account when performing an arthroscopy of the posterior region of the ankle. We recommend this treatment on this type of injury although we admit this does not make a definite conclusion.

Bilateral Tensor Fasciae Suralis Muscles in a Cadaver with Unilateral Accessory Flexor Digitorum Longus Muscle

“…From clinical and cadaveric studies, the prevalence of AFDL has been estimated to be ~6% [ 14 , 15 ] to 13-14% [ 16 , 17 ]. This accessory muscle may exist bilaterally; however a unilateral presentation of AFDL is more common [ 18 ].…”

Anatomical variations of flexor hallucis longus tendon increase safety in hindfoot endoscopy

“…In the present study, the mean distance between the neurovascular bundle and FHL tendon without anatomical variants at the level of the ankle—where the working area is created during hindfoot endoscopy—was of 0.9 mm, and the median of 0.7 mm (range 3.7–0 mm). In contrast to the general opinion [2, 23], the presence of an anatomical variation related to the FHL is, from an anatomical point of view, safer than in its absence. In the former scenario, the mean distance measured in the current study was 1.3 mm, and the median of 1.0 mm (range 3.8–0 mm).…”

“…They are typically asymptomatic and encountered as incidental findings. However, some anatomical muscle variations have been considered to be a potential source of clinical symptoms [1, 5, 8, 13, 16, 19, 28, 29, 32, 38] or to facilitate iatrogenic injury due to the presence of a non‐recognized anatomical structure during surgical procedures [2, 26]. A thorough knowledge of foot and ankle anatomy and anatomical variants is therefore absolutely paramount to reduce the risk of iatrogenic injury during endoscopic procedures.…”

“…Anatomical variations related to the FHL or a false FHL tendon have been reported [2, 26, 34], and they can jeopardize the tibial nerve and posterior tibial vessels during hindfoot endoscopy if unrecognized by the surgeon during the procedure or on preoperative magnetic resonance imaging (MRI) [2, 26]. Previous reports have evaluated the anatomical risk of hindfoot endoscopic portals [15, 33] or the normal relationship between the tibial neurovascular bundle and the FHL tendon in the posterior area of the ankle [11].…”

An Erratic Origin of Quadratus Plantae: An Embryological Error

“…The flexor digitorum accessorius longus is a variant muscle with a reported prevalence of 2 to 12% in cadaveric studies, and 6% of asymptomatic individuals on MRI. Detecting the accessory muscle would prevent the muscle structure lesions and they have to be taken into consideration during posterior ankle arthroscopy [6].…”