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Endoscopic carpal tunnel release with the Chow technique shows high success rate
An anatomic study finds a soft tissue band lying just palmar to the TCL that should be retained.
HOLLYWOOD, Fla. – After 17 years of experience, Southern Illinois researchers found that endoscopic carpal tunnel release with the Chow technique is reliable and safe, with 93% of patients indicating that their hands were completely normal.
The researchers performed a retrospective clinical follow-up study on more than 3,500 hands, and an anatomic study on six fresh, undissected cadaver hands to investigate the anatomy and histology of the soft tissue structures.
They found that the Chow technique’s retention of the soft tissue structures just palmar to the transverse carpal ligament — named the interthenar soft tissue band (ISTB) – optimizes clinical outcome.
Images: Papachristos A |
“Preservation of the wrist and hand anatomic structures leads the patient to return to work and resume daily activities quicker, less postoperative pillar pain, an earlier restoration of grip strength, and the patients felt that their hands were completely normal,” said Athanasios Papachristos, MD, a fellow at the Orthopedic Research Foundation of Southern Illinois in Mount Vernon, Ill.
The researchers cautioned, however, that proper training is necessary before performing this procedure. “It is a safe and effective procedure, but the surgeon must be able to recognize different anatomical structures through the scope to avoid complications,” Papachristos said at the Arthroscopy Association of North America 25th Annual Meeting.
Clinical study method
James C.Y. Chow, MD, treated 3,536 hands of 2,479 patients from September 1987 through April 2005 with the use of the endoscopic surgical technique that he developed. The diagnosis of carpal tunnel syndrome is based on patient history, clinical examination and nerve conduction velocity (NCV) tests.
Researchers measured preoperative and postoperative grip strength in 635 patients, and assessed the return-to-work status of 1,463 working patients, Papachristos said.
Over the 17-year study, researchers found 2,990 completely asymptomatic wrists (93.3%), which the patients’ described as “normal hands.” Also, 174 cases had minor complaints (5.4%), 24 cases were classified as failure (0.7% failure rate), 18 cases were classified as recurrent (0.6%) and five cases reported complications (0.14%).
“Of the five cases with complications, there wasn’t any permanent nerve injury, tendon laceration, superficial palmar arch laceration or complex regional pain syndrome (CRPS), formerly known as reflex sympathetic dystrophy (RSD),” Papachristos said.
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| Macroscopically, the ISTB appears as a rectangular band, measuring about 16 mm wide, 12.3 mm long and 2.1 mm thick. | |
Of the 635 patients measured for grip strength, 61.6% could achieve 80% of the mean preoperative grip strength by week four. Also, within four weeks, 70.3% of the 1,463 working patients returned to work.
Papachristos said the researchers observed an average operating time of 8 minutes. They also found an extremely ulnar transligamental motor branch of the median nerve in one of every 200 cases.
Chow had to convert two cases to open procedures. “In the first case, a variant of the median nerve was located at the entry portal. In the second case, there was a large communicative branch from the median nerve to the ulnar nerve located at the exit portal,” Papachristos said.
Researchers performed endoscopic carpal tunnel release with the Chow technique on the six cadaver hands from two males and two females. They then performed an open layer-by-layer surgical dissection to the six cadaver hands on the volar aspect of the wrist and proximal palm, Papachristos said.
After dissection, researchers obtained specimens from the transverse carpal ligament and surrounding soft tissues, which were processed and examined under light microscopy for the histological examination.
Anatomic and histological study
“Our anatomical inspection indicates there was a soft tissue layer that was bridging the thenar and the hypothenar muscles’ epimysium just palmar to the transverse carpal ligament,” Papachristos said. “We named this structure the interthenar soft tissue band, or ISTB.”
The ISTB dimensions measured 16±3.6 mm wide, 12.3±1.4 mm long and 2.1±0.1 mm thick, Papachristos said.
Histology findings showed that the ISTB composed of areolar fibrous connective tissue being admixed with abundant adipose tissue, thereby having the architectural structure of the fibroadipose loose connective tissue with small vessels and neural branches running within its substance. The transverse carpal ligament consisted of dense fibrous connective tissue without vessels or nerves.
For more information:
- James C. Chow, MD, Orthopedic Center of Southern Illinois, 4121 Veterans Memorial Drive, Mt. Vernon, IL 62864.
- Papachristos AA, Chow JCY. Endoscopic carpal tunnel release: Seventeen years’ experience with the Chow technique and specific anatomic considerations regarding the volar aspect of the wrist. #SS-61. Presented at the Arthroscopy Association of North America 25th Annual Meeting. May 18-21, 2006. Hollywood, Fla.