Changes in carpal tunnel compliance with incremental flexor retinaculum release

Abstract

BackgroundFlexor retinaculum transection is a routine surgical treatment for carpal tunnel syndrome, yet the biomechanical and clinical sequelae of the procedure remain unclear. We investigated the effects of flexor retinaculum release on carpal tunnel structural compliance using cadaveric hands.MethodsThe flexor retinaculum was incrementally and sequentially released with transections of 25, 50, 75, and 100 % of the transverse carpal ligament, followed by the distal aponeurosis and then the antebrachial fascia. Paired outward 10 N forces were applied to the insertion sites of the transverse carpal ligament at the distal (hamate-trapezium) and proximal (pisiform-scaphoid) levels of the carpal tunnel. Carpal tunnel compliance was defined as the change in carpal arch width normalized to the constant 10 N force.ResultsWith the flexor retinaculum intact, carpal tunnel compliance at the proximal level, 0.696 ± 0.128 mm/N, was 13.6 times greater than that at the distal level, 0.056 ± 0.020 mm/N. Complete release of the transverse carpal ligament was required to achieve a significant gain in compliance at the distal level (p < 0.05). Subsequent release of the distal aponeurosis resulted in an appreciable additional increase in compliance (43.0 %, p = 0.052) at the distal level, but a minimal increase (1.7 %, p = 0.987) at the proximal level. Complete flexor retinaculum release provided a significant gain in compliance relative to transverse carpal ligament release alone at both proximal and distal levels (p < 0.05).ConclusionsOverall, complete flexor retinaculum release increased proximal compliance by 52 % and distal compliance by 332 %. The increase in carpal tunnel compliance with complete flexor retinaculum release helps explain the benefit of carpal tunnel release surgery for patients with carpal tunnel syndrome.

Thickness and Stiffness Adaptations of the Transverse Carpal Ligament Associated With Carpal Tunnel Syndrome

“…The mechanical properties of the TCL have been shown to vary with location. For example, cadaveric studies have found differences in the compliance of the proximal and distal TCL regions [36, 48], as well as differences in the elastic modulus [10] and amount of strain [3] between radial and ulnar ligament portions. Shear wave elastography methods, such as ARFI, provide a means to non-invasively quantify the elasticity of tissues in vivo , including those of the TCL.…”

“…The TCL has many biomechanical functions, including serving as an origin site for the thenar and hypothenar muscles [6, 8, 17, 39], stabilizing the carpal tunnel structure [4, 44, 48], acting as a pulley for the flexor tendons [14, 16], and contributing to carpal tunnel compliance [13, 19, 36]. Clinically, the TCL is closely associated with carpal tunnel syndrome (CTS) which is demonstrated by the ligament’s surgical transection as a common treatment to relieve median nerve compression within the carpal tunnel.…”

The prognostic value of median nerve thickness in diagnosing carpal tunnel syndrome using magnetic resonance imaging: a pilot study

“…If data that includes different levels can be obtained from CTS patients and compared with a control group, much better information can be obtained. Fourth, the cause of CTS has multiple sources, including the transcarpal ligament, soft tissues, and flexor retinaculum [30,31]; however, we only focused on the median nerve. Fifth, because this study is not randomized and is a casecontrol group, an adjustment of baseline characteristics should be considered to compare the two groups.…”

Comparison of Metzenbaum scissors and Y‐shaped fasciotome for deep metatarsal fasciotomy for the treatment of proximal suspensory ligament desmopathy in horses

“…Surgical management of CTS involves transection of the flexor retinaculum to reduce compartmental pressure . It has been shown that complete transection of the flexor retinaculum is required to achieve maximum compliance of the carpal canal (ie, the greatest reduction in compartmental pressure) . Given the similarities between both syndromes in man and in horses, it could be concluded that release of a greater length of the deep metatarsal fascia should result in a greater reduction in compartmental pressure in horses with PSLD.…”