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Published 5/1/2016

Face Off: Open Versus Endoscopic Carpal Tunnel Release

Carpal tunnel syndrome (CTS)—a compressive neuropathy resulting in numbness and paresthesia—is recognized as one of the most common hand disorders. CTS manifests most commonly in middle-aged and elderly women, with a general population prevalence of 50 cases per 1,000 subjects. Carpal tunnel release (CTR) has become the most common hand and wrist procedure performed in the United States, with an estimated 400,000 patients undergoing open or endoscopic surgery every year.

Recently, the AAOS released an updated Clinical Practice Guideline (CPG) on the Management of Carpal Tunnel Syndrome (see "Academy Updates Clinical Practice Guideline on Carpal Tunnel Syndrome," AAOS Now, April 2016). According to the CPG, "limited evidence supports that if surgery is chosen, a practitioner might consider using endoscopic carpal tunnel release based on possible short-term benefits." The CPG cites 11 high-quality and six moderate-quality studies that "evaluated whether endoscopic carpal tunnel release provided any benefit over open or 'mini-open' release at early follow-up (3 months to 1 year)." In addition, it notes that "three high-quality studies favored endoscopic release for symptom relief in the first 3 to 6 months after surgery, and one study demonstrated an earlier return to work."

Furthermore, the CPG notes that "one high-quality and one moderate-quality study examined long-term outcomes for endoscopic release versus open release and did not find any advantage of one method over the other," while "studies comparing 'mini-open' to standard release were inconclusive."

The purpose of this "Face Off" is to present compelling arguments in support of open and endoscopic techniques, as appropriate, in the surgical management of CTS.

Open technique: The gold standard since 1946
Robert L. Parisien, MD, and N. George Kasparyan, MD, PhD

The remarkable history of the surgical approach to carpal tunnel syndrome started when Arthur Dickson Wright, MD, performed an "incision of the carpal ligament" through an open procedural technique. Dr. Wright's approach has since been modified and is now known as the mini-open release (MOR), with a small incision similar to that used in the endoscopic carpal tunnel release (ECTR).

The open procedure has long been the standard surgical treatment for CTS. Results are exceptional based on patient-reported satisfaction outcomes and low complication rates. The introduction of the MOR technique provided the added benefit of reducing tissue trauma and morbidity while maintaining the safety of the traditional open procedure. This resulted in subjective cosmetic outcomes similar to those of ECTR.

Scar tenderness, along with grip and pinch weakness, have been historic concerns regarding the open carpal tunnel release (OCTR). However, given the increased use of the MOR technique, these concerns are antiquated. A Cochrane Database Systematic Review performed in 2014 reporting on 28 studies (2,586 hands) found ECTR resulted in a slight increase in grip strength compared to OCTR but concluded that this finding was likely not clinically significant.

In addition, the review found no differences between OCTR and ECTR with respect to functional outcomes recorded via the Symptom Severity Scale and the Functional Status Scale. Nor were any differences in short- and long-term postoperative pain found between ECTR and OCTR. Patients undergoing ECTR were able to return to work 8 days faster than those who underwent OCTR but utilization of the MOR approach in the OCTR cases was unclear. MOR has an incision equivalent to that of ECTR and both return-to-work and scar tenderness appear to correlate directly with length of incision.

Increased complication rates have also been reported when the ECTR technique is used, as compared to OCTR. One randomized multicenter evaluation found a greater incidence of complications in the endoscopic group including a partial transection of the superficial palmar arch, a digital-nerve contusion, an ulnar-nerve neurapraxia, and a wound hematoma.

Given the inherent differences in technique, distal release remains a concern for ECTR just as proximal tethering is a concern for OCTR. However, OCTR has consistently demonstrated high success rates suggesting full and complete release of the transverse carpal ligament (TCL). A prospective randomized controlled trial comparing OCTR and ECTR found no statistical differences in longitudinal excursion (gliding) and volar displacement (bowstringing) of the median nerve in patients with idiopathic primary CTS. This suggests that the two procedures have comparable rates of complete release of the TCL.

The open technique has consistently proven to be exceptionally effective in relieving the primary symptoms of CTS, namely numbness and paresthesia. A prospective randomized trial of 159 hands (OCTR = 82, ECTR = 77) found that 98 percent of those who underwent OCTR demonstrated effective symptomatic relief. Additionally, the authors found "no differences between the two groups with regard to the secondary quantitative-outcome measurements including two-point discrimination, postoperative interstitial-pressure data, Semmes-Weinstein monofilament testing, and motor strength." Furthermore, a 2007 Cochrane Database Systematic Review evaluating the efficacy and outcomes of "various surgical techniques for the treatment of carpal tunnel syndrome" in large randomized controlled trials found "no strong evidence supporting the need for replacement of standard open carpal tunnel release by existing alternative surgical procedures for the treatment of carpal tunnel syndrome."

Robert L. Parisien, MD, is an orthopaedic surgical resident at Boston University Medical Center in Boston, and can be reached at Robert.L.Parisien@gmail.com

N. George Kasparyan, MD, PhD, is chairman of the department of orthopaedic surgery and chief of hand & upper extremity surgery at Lahey Hospital and Medical Center in Burlington, Mass.


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Endoscopic approach gets patients back to work
Kenneth J. McAlpine Jr, MD, and Scott F.M. Duncan, MD, MBA, MPH

Proximal fascia release performed during the open technique. Reproduced from Diao E: Carpal tunnel release, in Flatow E, Colvin AC, eds: Atlas of Essential Orthopaedic Procedures. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2013, p 237.
Intraoperative photograph shows the surgeon's nondominant index and long digits palpating the tip of the endoscopic tunnel release device as it emerges into the subcutaneous space just distal to the transverse carpal ligament. Reproduced from Diao E: Carpal tunnel release, in Flatow E, Colvin AC, eds: Atlas of Essential Orthopaedic Procedures. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2013, p 238.

Endoscopic carpal tunnel release (ECTR) was first described by Ichiro Okutsu, MD, in 1989. His technique was further refined to a two-incision approach by James C.Y. Chow, MD, and to a single-portal approach by John M. Agee, MD.  Dr. Okutsu believed the development of an endoscopic approach would accomplish the following three goals:

  • decrease injury to healthy tissue
  • make use of a minimally invasive approach
  • improve activities of daily living following surgery as compared to an open approach

Some contend ECTR successfully accomplishes all of these goals more efficiently than OCTR. ECTR has been shown to enable patients to return to work one week sooner, on average, compared to OCTR. Additional subgroup analysis, with regard to patients being treated under worker's compensation, has further demonstrated shorter return-to-work rates for ECTR versus OCTR. However, this finding is multifactorial with decreased scar tenderness and earlier return of grip strength favoring ECTR over OCTR. 

The exact mechanism as to why ECTR results in less pain and scar tenderness compared to OCTR is unknown. One explanation is that the palmaris brevis muscle and palmar fascia are not incised with ECTR. Scar tenderness affects the patient's ability to return to work, specifically in cases of laborers, because of the anatomic position of the incision. This may be due to the fact that the incision for an OCTR is made over the portion of the hand that is subject to considerable pressure during work activities, while the incision for ECTR is not.

Cosmesis of the scar may also be a factor in a patient's decision to undergo ECTR because the incision for ECTR can always be hidden within one of the wrist flexion creases, allowing for a virtually undetectable scar. For OCTR, the incision can possibly be hidden within the thenar crease, but this depends on the patient's specific anatomy.

Multiple studies comparing ECTR to OCTR have used grip strength as an objective outcome. In a recent Cochrane review, a significant difference was demonstrated with regard to grip strength at short-term follow-up, favoring ECTR. The authors further reported a direct correlation of time between return of grip strength and patients' rate of return to work.

Another common concern with regard to ECTR is an increased rate of nerve injury stemming from early investigations when the endoscopic technique was in its infancy. With the advent of new technology and increased physician experience, we believe this is no longer a factor as nerve injury rates appear to be similar for both ECTR and OCTR.

Finally, those opposed to ECTR often cite its increased cost compared to OCTR. Although the immediate cost of ECTR is more than OCTR due to the price of the endoscope and cutting instruments, the overall societal cost of the two procedures is much harder to determine. ECTR enables patients to return to work earlier, therefore leading to a minimized loss of productivity due to missed workdays.

Part of the increased cost associated with early studies on ECTR was the need for the procedure to be performed in a main operating room versus an outpatient setting. Increased surgical time also leads to increased anesthesia time with its additional associated cost. However, a recent meta-analysis found that surgical time for ECTR was shorter, on average, than that for OCTR.

Surgical time is also dependent on the skill of the surgeon performing the operation and his or her familiarity with the procedure. To the best of our knowledge, no current studies provide a definitive answer to the steepness of the learning curve for ECTR and how this learning curve differs from that of OCTR.

Overall, both open and endoscopic CTR have demonstrated comparable long-term results. However, ECTR has more of an immediate effect in that it enables patients to return to work sooner with less scar pain and quicker return of grip strength. Therefore, we contend that ECTR should be considered the preferred technique for treating CTS, especially in those patients who value an expeditious return to work.

Kenneth J. McAlpine Jr, MD, is an orthopaedic surgical resident at Boston University Medical Center. Scott F.M. Duncan, MD, MBA, MPH, is chairman of the department of orthopaedic surgery, chief of hand & upper extremity and microsurgery at Boston University Medical Center, and a member of the AAOS Now editorial board.


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More about the updated CTS CPG
The AAOS Management of Carpal Tunnel Syndrome Evidence-Based Clinical Practice Guideline (CTS CPG) represents a substantive update to the CTS guidelines originally issued in 2008 and revised in 2011. The 2016 CPG carries the endorsement of the American Society for Surgery of the Hand, the American College of Radiology, and the American College of Surgeons.

Among other things, the guideline:

  • supports the use of diagnostic scales (eg, CTS-6 and Katz Hand Diagram) to aid in the diagnosis of CTS
  • supports a greater treatment benefit for patients who are treated surgically, compared with patients who are treated with splinting, NSAIDs, or steroid injections

Nine recommendations are characterized as "strong," including one stating that thenar atrophy is strongly associated with ruling in CTS, but poorly associated with ruling it out. For treatment, the guideline recommends surgery, when necessary, to release the transverse carpal ligament to relieve symptoms and improve hand function. There was not strong evidence to recommend supervised over unsupervised postsurgical therapy.

An AAOS CTS Appropriate Use Criteria (AUC) is in development.

To access the CPG in its entirety, visit www.orthoguidelines.org