Endoscopic carpal ligament release lets surgeon see nerve variance before cutting

Rates of complications and failures <1% occurred in 4,000 cases performed by one surgeon.

Issue: October 2007

ISAKOS

FLORENCE — Surgeons can optimize results with endoscopic carpal tunnel release by familiarizing themselves with the carpal canal anatomy, according to James C.Y. Chow, MD.

A carpal ligament release done endoscopically provides full visualization of the carpal ligament before making the cut and preserves the wrist’s anatomical structures, he said.

James C.Y. Chow, MD
James C.Y. Chow

“I don’t believe any kind of blind procedures for carpal tunnel ligament release are necessary with the advancement of arthroscopy today,” Chow said in a lecture at the 2007 International Society of Arthroscopy, Knee Surgery and Orthopaedic Sports Medicine Congress, here.

“Young surgeons need to learn both procedures – open and also the endoscopic for treating carpal tunnel syndrome patients,” Chow said. “Most people are unaware that I have performed over 4,000 open carpal ligament releases and therefore understand the importance of both procedures.”

Long experience

Over the last 20 years, Chow said he has performed more than 3,900 endoscopic carpal tunnel ligament releases with a 0.74% failure rate. “These ECTR cases failed for different reasons, ie, the open exploration of one failed patient revealed gout crystal deposits and severe synovitis with required tenosynovectomy,” he told Orthopedics Today.

Among the endoscopic cases he has completed since September 1987, complication and recurrence rates were even lower; just five complications (0.13%) and 16 recurrences of carpal tunnel syndrome (0.41%). Chow has converted to an open procedure from endoscopy only twice due to anatomical nerve variances.

“The five complications happened in the first 300 cases I did,” he explained. They included two ulnar nerve neuropraxia related to the placement of the retractor, which he has since changed. Other complications were minor. “There have been no arterial injuries, no tendon lacerations, no permanent nerve injuries and no RSD,” he said.

The anatomy of the interthenar soft tissue band (ISTB) is visible in this open procedure. The ISTB lies palmar to the transverse carpal ligament.

View of ligament's undersurface
Prior to completing endoscopic release of the carpal ligament, the surgeon can easily view the ligament’s undersurface and see whether the median nerve is abnormal. That was helpful in this case where the transligamental motor branch of the median nerve was extremely ulnar.

Local anesthesia

During the lecture, Chow shared some practices he has incorporated into his surgical technique over the years, which may help others learn the endoscopic method and attain similar outcomes, such as using a hand table with two monitors.

He recommended local anesthesia without a tourniquet, which makes it easy for patients to indicate intraoperatively if he has gotten too close to the nerve or encountered an abnormality of the median nerve.

Local anesthesia also facilitates checking his patients’ hand sensation and movement in the operating room immediately postop. “Therefore, if you have an intraoperative complication you are still in a sterile environment and can correct it,” Chow said.

Given the anatomy of the carpal ligament — thin distal and proximal portions and a thick center — Chow uses a specially shaped knife to make small cuts in the middle of the ligament.

Studying cadaver resections helped him better delineate between the carpal ligament and such soft tissue structures as the rectangular-shaped interthenar soft tissue band (ISTB), which lies palmar to the transverse carpal ligament. The carpal ligament is made of compact collagen fibers while the ISTB is full of small vessels and nerves and they look different through the scope, he said.

“The fundamental difference between the open surgery and the endoscopic release: Open surgery is cutting from outside in. Endoscopic [release] is cutting from inside out,” Chow noted. “The surgeon can see the undersurface of the carpal ligament, and any nerve variance before releasing it.”

Compact collagen fibers of the transcarpal ligament
This cross-sectional microscopic view of the transcarpal ligament shows it consists of compact collagen fibers.

Researchers studied the structure of the ISTB as seen in this microscopic cross-sectional view. They found it full of small vessels and nerves.

Images: Chow JCY

For more information:
James C.Y. Chow, MD, can be reached at the Orthopedic Center of Southern Illinois, 4121 Veteran’s Memorial Drive, Mt. Vernon, IL 62864; 618-242-3778; e-mail: ocsijc@charter.net. He receives royalties from Smith & Nephew Endoscopy.
Reference:
Chow JY. AANA Lecture: Endoscopic carpal ligament release. Presented at the 2007 International Society of Arthroscopy, Knee Surgery and Orthopaedic Sports Medicine Congress. May 27-31, 2007. Florence.