Gliding resistance of flexor tendon associated with carpal tunnel pressure: A biomechanical cadaver study

Abstract

ABSTRACT:The purpose of this study was to investigate the effect of carpal tunnel pressure on the gliding characteristics of flexor tendons within the carpal tunnel. Eight fresh human cadaver wrists and hands were used. A balloon was inserted into the carpal tunnel to elevate the pressure. The mean gliding resistance of the middle finger flexor digitorum superficialis tendon was measured with the following six conditions: (1) as a baseline, before balloon insertion; (2) balloon with 0 mmHg pressure; (3) 30 mmHg; (4) 60 mmHg; (5) 90 mmHg; (6) 120 mmHg. The gliding resistance of flexor tendon gradually increased as the carpal tunnel pressure was elevated. At pressures above 60 mmHg, the increase in gliding resistance became significant compared to the baseline condition. This study helps us to understand the relationship between carpal tunnel pressure, which is elevated in the patient with carpal tunnel syndrome (CTS) and tendon gliding resistance, which is a component of the work of flexion. These findings suggest that patients with CTS may have to expend more energy to accomplish specific motions, which may in turn affect symptoms of hand pain, weakness and fatigue, seen commonly in such patients. © Carpal tunnel syndrome (CTS) in one of the most common compression neuropathies, with an estimated lifetime risk of 10% and a prevalence of about 3%.1-3 It is generally accepted that repetitive hand motion is a risk factor for CTS. [4][5][6][7] While the etiology of CTS is in most cases idiopathic, it is known that CTS is a result of increased pressure within the carpal tunnel, which is a confined anatomic space bounded by the carpal bones on the dorsal side, the trapezium on the radial side, the hook of the hamate on the ulnar side and the flexor retinaculum on the volar side. [8][9][10] However, while the effect of increase pressure on the median nerve has been well studied, the effect of pressure on tendon function has received little attention, even though tendons make up the majority of the cross section of the carpal tunnel contents. The purpose of this study was to investigate the effect of pressure changes on the gliding resistance of a representative tendon, the middle finger flexor digitorum superficialis (FDS), within the carpal tunnel in a human cadaver model. We hypothesized that the gliding resistance would increase with carpal tunnel pressure elevation. MATERIALS AND METHODSAfter IRB review and approval, eight human fresh frozen cadavers, amputated approximately 15 cm proximal to the wrist joint, were harvested and thawed at room temperature immediately prior to testing. The cadaver donors included five males and three females, with an average age of 76 years (range 40-91). There were five right and three left upper extremities. A medical record review was performed on each cadaver donor, to obtain demographic data and to be sure the individual did not have a recorded antemortem diagnosis of CTS. The FDS tendons of the second, third, and fourth digits were exposed proximal and distal to the flexor re...

Collagen gel contraction as a measure of fibroblast function in an animal model of subsynovial connective tissue fibrosis

“…1,2 It is typified by median nerve compression and results in various levels of disability. 3,4 Non-inflammatory subsynovial connective tissue (SSCT) fibrosis is present in patients with CTS, 5,6 even though the cause is still unclear. The SSCT fibrosis is also associated with elevated activity of transforming growth factor β1 (TGF-β1), which regulates fibroblast proliferation and reorganization of structural proteins linking the tissues in the extracellular matrix (ECM).…”

Collagen gel contraction as a measure of fibroblast function in carpal tunnel syndrome

“…CTS can be associated with repetitive manual activities, anatomic anomalies, autoimmune or hematologic disorders, arthritis, trauma, or neoplasms . Although etiology is unknown in most cases, studies have shown that symptoms and subsequent work‐related disabilities are created by increased pressure within the carpal tunnel, which causes compression and ischemia of the median nerve …”

“…Noninflammatory subsynovial connective tissue (SSCT) fibrosis is the most common histopathologic finding reported in patients with CTS . Moreover, studies of median nerve motion in idiopathic CTS patients and control subjects have clearly shown that nerve mobility is hampered in patients . SSCT fibrosis is also known to be associated with elevated activity of transforming growth factor (TGF)‐β1, which can upregulate fibroblast proliferation and activation.…”

Delineation of the mechanisms of tendon gliding resistance within the carpal tunnel

“…Both increased pressure and high-velocity tendon motion result in increased GR, which suggests that high GR is related to CTS (Filius et al, 2014; Kociolek et al, 2015; Tat et al, 2013; Zhao et al, 2011). A good understanding of GR in the carpal tunnel is, therefore, important to better understand the pathology of CTS.…”

“…Wrist flexion and finger flexion, especially isolated flexion of a single finger (as may occur in typing or other repetitive work), are associated with high tendon gliding resistance (GR) and increased carpal tunnel pressure, which also increases GR (Ettema et al, 2004; Filius et al, 2014; Kociolek et al, 2015; Seradge et al, 1995; Zhao et al, 2011), but little work has been done to elucidate the mechanisms that contribute to tendon GR in the carpal tunnel.…”