Elsevier

Clinical Biomechanics

Volume 18, Issue 8, October 2003, Pages 685-693
Clinical Biomechanics

Review
Biomechanical and anatomical consequences of carpal tunnel release

https://doi.org/10.1016/S0268-0033(03)00052-4Get rights and content

Abstract

Carpal tunnel syndrome is an exceedingly common orthopaedic problem in the United States. When conservative management is unsuccessful, most surgeons proceed to surgical treatment. Though the carpal tunnel release procedure is usually curative, many patients experience postoperative complications, such as scar sensitivity, pillar pain, recurrent symptoms, and grip weakness, regardless of whether the release was done through an open, mini-open, or endoscopic approach. The exact causes of these and other complications of carpal tunnel release remain unclear. Release of the carpal tunnel has an effect on carpal anatomy and biomechanics, including an increase in carpal arch width, carpal tunnel volume, and changes in muscle and tendon mechanics. We set out to review the morphological and biomechanical changes caused by carpal tunnel release with the goal of better understanding the root causes of postoperative complications. This article first reviews normal carpal tunnel anatomy and anatomic variations, then available surgical techniques for carpal tunnel release, and finally the literature on morphologic, physiologic and biomechanical alterations in the wrist after carpal tunnel release.

Section snippets

Introduction and clinical significance

Carpal tunnel syndrome is one of the most common orthopedic conditions, with an estimated incidence of nearly 1% annually in the United States (Einhorn and Leddy, 1996), which translates into almost 2.8 million new cases per year. If conservative therapy fails, surgical release of the carpal tunnel is the preferred method of treatment. Though the majority of patients have relief of symptoms postoperatively, there are still a significant number of patients who experience disabling postoperative

Anatomy

The carpal bones and intercarpal ligaments at its medial, lateral, and posterior borders form the carpal tunnel. The anterior border is formed by the transverse carpal ligament and flexor retinaculum (Hoppenfeld Sd, 1984; Tanabe and Okutsu, 1997). The terms “flexor retinaculum” and “transverse carpal ligament” have been considered synonyms, however, Cobb et al. demonstrated that they are distinct structures (Cobb et al., 1993). The flexor retinaculum as a whole can be divided into three parts

Carpal tunnel anatomic variations

Phalen originally reported on his 17-year experience in 1966, suggesting that thickening of the flexor synovium was the most common direct cause of median nerve compression and carpal tunnel syndrome in his patients (Phalen, 1996). Tanzer, however, noted three of 21 patients with cystic masses in the carpal tunnel and seven of these 21 hands had various congenital anomalies (Tanzer, 1959). Singer retrospectively looked for anatomic variations in 147 hands undergoing carpal tunnel release via an

Pressure changes and mechanism of relief after carpal tunnel release

When considering complete release of the carpal tunnel, one must consider the relevant anatomy (Tanabe and Okutsu, 1997; Cobb et al., 1993); neglecting to release the distal part of the flexor retinaculum or the proximal part described above may fail to completely relieve pressure on the median nerve or may result in failure of surgery to relieve symptoms of carpal tunnel syndrome (Tanabe and Okutsu, 1997; Phalen, 1996; Cobb and Cooney, 1994). Tanabe noted that release of only the transverse

Surgical techniques

To serve as background for understanding the biomechanical and anatomic changes after different types of carpal tunnel release, a brief review is presented here. A thorough review of the methods for carpal tunnel release and their pros and cons is beyond the scope of this paper.

Potential biomechanical complications of carpal tunnel release

Generally reported complications of carpal tunnel release include incomplete release, neuropraxia or injury to the median or ulnar nerve, and inadvertent entrance into Guyon’s canal, injury to digital nerves, the ulnar artery and the superficial palmar arch (Lee et al., 1992; Seiler et al., 1992). However, there exist several biomechanical changes after carpal tunnel release, which may be considered “complications”, not merely “expected” postoperative, changes.

The phenomenon of pillar pain is a

Biomechanical change after carpal tunnel release

A number of studies have examined the effect of dividing the transverse carpal ligament on the carpal arch. The transverse carpal ligament has been shown to serve three functions: anchor thenar and hypothenar musculature, provide transverse stability to the carpus, and act as a pulley for the flexor tendons (Seradge and Seradge, 1989; Garcia-Elias et al., 1989b). Thus, division of this ligament could alter the normal function of the wrist and contribute to such postoperative complications as

Carpal arch and carpal tunnel volume

Cobb et al. (1993) determined normal carpal tunnel dimensions by injecting contrast material into the carpal tunnel and examining antero-posterior (AP) radiographs. On the AP view, the carpal tunnel is shaped like an hourglass (Fig. 4), with the narrowest part at the level of the hook of the hamate. The mean width of the carpal tunnel was 25 ± 1.2 mm proximally, 20 ± 1.2 mm at the hook of the hamate, and 25 ± 1.5 mm at its distal extent, a significant difference (P<0.0001). This is an important

Conclusion

Carpal tunnel surgery has been performed for nearly 80 years, yet despite the majority of patients who recover without complication, there are still a significant number that suffer postoperative pain and weakness. A successful decompression of the median nerve provides symptomatic relief of carpal tunnel symptoms, and generally allows patients to return to activities of daily living and employment. However, complete release of the carpal tunnel probably has a small but significant effect on

Acknowledgements

We would like to thank Ted Trafton for his tireless illustrative effort.

References (49)

  • N Einhorn et al.

    Pitfalls of endoscopic carpal tunnel release

    Orthop. Clin. North Am.

    (1996)
  • G.R Fisk

    The influence of the transverse carpal ligament (flexor retinaculum) on carpal stability

    Ann. Chir. Main.

    (1984)
  • M Garcia-Elias et al.

    Stability of the transverse carpal arch: an experimental study

    J. Hand Surg. [Am.]

    (1989)
  • M Garcia-Elias et al.

    Dynamic changes of the transverse carpal arch during flexion-extension of the wrist: effects of sectioning the transverse carpal ligament

    J. Hand Surg. [Am.]

    (1992)
  • G.M Gartsman et al.

    Carpal arch alteration after carpal tunnel release

    J. Hand Surg. [Am.]

    (1986)
  • J Greening et al.

    Reduced movement of median nerve in carpal tunnel during wrist flexion in patients with non-specific arm pain

    Lancet

    (1999)
  • J.M Hunter

    Recurrent carpal tunnel syndrome, epineural fibrous fixation, and traction neuropathy

    Hand Clin.

    (1991)
  • T Kato et al.

    Effects of endoscopic release of the transverse carpal ligament on carpal canal volume

    J. Hand Surg. [Am.]

    (1994)
  • J.N Katz et al.

    Symptoms, functional status, and neuromuscular impairment following carpal tunnel release

    J. Hand Surg. [Am.]

    (1995)
  • P.G Kiritsis et al.

    Biomechanical changes after carpal tunnel release: a cadaveric model for comparing open, endoscopic, and step-cut lengthening techniques

    J. Hand Surg. [Am.]

    (1995)
  • U Lanz

    Anatomical variations of the median nerve in the carpal tunnel

    J. Hand Surg. [Am.]

    (1977)
  • D.H Lee et al.

    Endoscopic carpal tunnel release: a cadaveric study

    J. Hand Surg. [Am.]

    (1992)
  • K.S Ludlow et al.

    Pillar pain as a postoperative complication of carpal tunnel release: a review of the literature

    J. Hand Ther.

    (1997)
  • M.A Mirza et al.

    Palmar uniportal extrabursal endoscopic carpal tunnel release

    Arthroscopy

    (1995)
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