A prospective, randomized, controlled trial was performed comparing the double incision technique to the conventional open method used in carpal tunnel decompression surgery, with pillar pain, scar sensitivity, and recovery of grip strength each assessed independently. Forty patients (40 hands) were operated on, 21 hands with the standard single-incision technique and 19 hands with the double-incision technique. Patients were assessed throughout 6 months of follow-up.
The results showed that the double-incision technique caused less pillar pain and scar sensitivity compared to the single-incision technique. No difference in recovery of grip strength was noted between the 2 techniques. The limited open technique using the double incision in carpal tunnel decompression surgery is advantageous over the standard technique in tackling scar-related morbidities.
Carpal tunnel syndrome is one of the most frequently encountered conditions in the orthopedic practice, affecting 1% to 2% of the general population in the United States1 and 7% to 16% in the United Kingdom.2 Surgical decompression results in satisfactory outcomes regardless of the technique used. Open median nerve release via a straight or curved longitudinal incision has been a reliable method for most surgeons.3 Pillar pain (thenar and hypothenar pain)4 and scar sensitivity,5 however, are recognized complications of open surgery.
In an attempt to reduce scar-related complications, minimally invasive approaches have been advocated,6,7 including endoscopic release,8 double-incision technique,9 limited-open incision,10 and approach through the flexor carpi radialis.11 Endoscopy involves less tissue violation, minimizes scar-related morbidities, and allows earlier return to activities in patients.12,13 However, it has a steep learning curve and requires costly equipment and specific setup. In addition, complications such as neurovascular and tendon injuries or incomplete decompression have been reported.14-16 A modification to the classical open technique described by Biyani and Downes9 uses a double-incision technique whereby an intact bridge of the skin is left at the base of palm. This approach causes less scar tenderness compared with the single palmar incision.9,17
This study prospectively compared the double-incision technique described by Biyani and Downes9 to the conventional open method with respect to pillar pain, scar sensitivity, and recovery of grip strength, each of which was assessed independently.
Materials and Methods
We prospectively enrolled 40 patients (40 wrists) in whom carpal tunnel syndrome was diagnosed both on clinical and neurophysiological background. Patients were randomized into either a single-incision group (group S=21 patients) or double-incision group (group D=19 patients). Ethical approval was obtained prior to initiating the study, and patients gave informed consent for participating in the trial. The characteristics of the 2 groups are demonstrated in Table 1.
Randomization was performed using an envelope technique. Sequentially numbered opaque sealed envelopes were randomized by the orthopedic secretary just prior to surgery. Preoperative grip strength was measured by an adjustable handgrip JAMAR dynamometer (Asimow Engineering Co, Santa Monica, California) using an average of 3 readings. All procedures were performed by a single orthopedic surgeon (R.C.), and none of the operative procedures was changed from either of the techniques to the other in the course of the operation.
Postoperatively, patients were assessed for any residual signs or symptoms of carpal tunnel syndrome, but the main outcome measures evaluated scar-related morbidities as well as hand grip strength between the 2 groups at 6 weeks, 3 months, and 6 months postoperatively.
For noncategorical data, the unpaired t test was used to compare the means of the grip strength between the 2 groups postoperatively. The difference was considered statistically significant when P<.05. for="" outcomes="" measured="" using="" ordered="" categories="" (pillar="" pain,="" scar="" sensitivity),="" chi-square="" test="" for="" a="" linear="" trend="" was="" used="" and,="" similarly,="" the="" difference="" between="" the="" 2="" groups="" was="" considered="" significant="" when="">P<.05. we="" also="" added="" yates’s="" correction="" for="" continuity="" when="" calculating="" data="" with="" the="" chi-square="" test="" to="" adjust="" more="" accurately="" the="" type-1="" error="" rate="" to="" be="" more="" compatible="" with="" the="" prespecified="" alpha="" level=""><.05).>
Standard single-incision technique: group S. A longitudinal straight incision (Figure 1) was made along the axis of the ring finger just ulnar to the thenar crease, extending from the level of the outstretched thumb distally to the distal transverse crease of the wrist. The transverse carpal ligament was then identified and divided proximally and distally. The carpal tunnel was inspected for any pathology and the skin sutured with 4/0 nylon sutures.
Figure 1: The standard single and longitudinal incision for open carpal tunnel decompression along the axis of the ring finger just ulnar to the thenar crease. Figure 2: The double-incision technique as described by Biyani and Downes.9 Incision A divides the flexor retinaculum distally and inspects the median nerve. Incision B completes the division of the flexor retinaculum proximally. Note the intact bridge of skin at the heel of the hand.
Double-incision technique: group D. A 2- to 3-cm longitudinal incision was made along the proximal palmar crease, leaving intact a bridge of skin at the heel of the hand between the thenar and hypothenar eminences (Figure 2). The distal part of the transverse carpal ligament was then exposed and divided under direct vision. The carpal tunnel was inspected for any pathology that may warrant conversion to a single-incision technique. If no pathology was found, a second transverse incision was made at the distal wrist crease between the palmaris longus and flexor carpi ulnaris tendons. Using blunt dissection, a plane was developed between the proximal end of the transverse carpal ligament and the skin. The transverse carpal ligament was then divided proximally from the proximal transverse incision while the median nerve was protected with a McDonalds dissector. On occasion the decompression was completed using scissors.
Postoperatively, both groups were treated identically with an adhesive dressing, wool, and crepe. The padded bandage was reduced at 48 hours and the sutures removed at 10 to 12 days. Follow-up occurred in the dressing clinic at 10 to 12 days and in the outpatient clinic at 6 weeks and 3 and 6 months.
Pre- and postoperatively, pillar pain was assessed subjectively by questioning patients regarding pain at the palm of the hand while rising up from a chair and objectively by the application of pressure over the thenar and hypothenar regions. Scar sensitivity was evaluated by applying a continuous stimulus using a pen over the scar. The motor and sensory functions of the median and ulnar nerves were tested clinically. Grip strength was remeasured postoperatively using same JAMAR dynamometer with 3 readings.
The majority of neurological symptoms had resolved in both groups by final follow-up (6 months). There were no neurovascular injuries or incompletely divided carpal ligaments in either group. By final follow-up, residual numbness persisted in 3 patients (15%) in group D vs 4 (19%) in group S. Two patients (10%) in group D and 2 (9.5%) in group S had mild parasthesia. Recurrence of symptoms was seen in 2 patients (1 in each group); for the patient in group D, serological tests demonstrated rheumatoid arthritis, and the synovitis associated with this was believed to be responsible for the recurrence. One patient in group D developed a partial sensory abnormality of the ulnar nerve.
Table 2 demonstrates the number of patients experiencing pillar pain and scar sensitivity in both groups.
The double-incision group reported less pillar pain compared to the single-incision group. This difference was statistically significant throughout the follow-up period (chi-square test for linear trend). Although scar sensitivity was also reported less by the double-incision group at each follow-up, this was only statistically significant at 6 weeks and 3 months postoperatively (P=.03 and P=.02, respectively).
When grip strength was compared, it was noted to be similar in both groups preoperatively and gradually improved in both groups postoperatively. Although the hands that had undergone a double incision had slightly better grip strength than those that had undergone a single incision, the difference was not statistically significant (Table 3).
Pillar pain and scar sensitivity are known complications of the classical open longitudinal incision for carpal tunnel release.4 This incision, whether placed along the axis of the ring finger or ulnar to it,18 leaves a scar at the base of the palm, an area subject to pressure bearing. Extending the incision further proximal to the wrist crease to visualize the palmar cutaneous nerves has been adopted by Eversmann19 but still resulted in pillar pain and other scar problems. Advocates of endoscopic carpal tunnel release cite the advantages of this technique in reducing pillar pain and scarring and thus promoting recovery.20,21 However, specialized equipment and setup are required, and complications such as digital and palmar cutaneous nerve injuries and incomplete division of transverse carpal ligament have been reported.4,16 Also, compared to endoscopy, the double-incision technique was found to yield similar results in terms of grip strength and scar morbidities, as reported by Wilson.22
Only a few studies in the literature compare the double-incision technique to the standard longitudinal incision. Biyani and Downes9 conducted a retrospective review comparing the single-incision to the double-incision technique and found less scar-related morbidities from the double incision. Their study, however, evaluated pillar pain between 2 to 4 months postoperatively but did not address grip strength.
In a prospective, randomized trial, Zyluk and Strychar23 reported a better recovery of grip and pinch strength in patients who had undergone the single-incision technique compared to patients who had undergone the double-incision technique. Although they found no difference in pillar pain or scar sensitivity between the 2 groups, they did not state how these scar-related morbidities was assessed. Their outcome measures were focused on grip, sensory, and motor tests.
In our prospective, controlled, randomized study, the double-incision technique was compared with the single-incision technique mainly with respect to scar-related morbidities along with the recovery of grip strength. It showed less occurrence of pillar pain and scar sensitivity in patients who had undergone the double-incision technique. Leaving an intact bridge of skin at the base of the palm avoids the damage of the twigs of the medial palmar cutaneous nerve, which are often entangled in the scar in patients with a full-length incision.19,24
As pillar pain is due to the division of the carpal ligament itself, it would therefore occur regardless of the technique used. However, in the standard open technique, the carpal ligament is often divided under the tension of the commonly used self-retaining retractor. Such a distraction on the carpal bony pillars does not occur with the double-incision technique; this could explain why the double incision method in our study caused less pillar pain.
Although it was not possible to blind the assessors due to the obvious difference in skin incisions, we believe that this did not create bias, as the clinical assessment was mostly guided by patient satisfaction in the evaluation of pillar pain and scar sensitivity. Although we did not categorize patients into groups based on their preoperative activity level, when assessing their return to preoperative normal activities, we believe that randomization into the 2 groups excluded any bias.
However, and despite all the statistical measures taken, it is arguable that the small sample size in our study could impose a statistical bias. There are also some limitations concerning the double-incision technique, as it does not allow internal neurolysis of the median nerve. There is evidence, however, that this does not improve the results of carpal tunnel decompression.25 If an abnormal pathology of the carpal tunnel is demonstrated during this limited open approach—such as ganglia and for flexor tendon synovitis—the first palmar incision must be extended to appropriately deal with the pathology.
Although both procedures proved to be safe and most neurological symptoms resolved in the majority of patients in both groups, the double-incision technique offered advantages over the single-incision technique, including a reduction in both pillar pain and scar sensitivity, which often impede patients’ daily activities. This technique did not imply a higher risk of postoperative complications, expense, or increase in surgical time; therefore, we recommend it as a superior technique in carpal tunnel surgery.
- Tanaka S, Wild DK, Seligman PJ, Behrens V, Cameron L, Putz-Anderson V. The US prevalence of self-reported carpal tunnel syndrome: 1988 National Health Interview Survey data. Am J Public Health. 1994; 84(11):1846-1848.
- Ferry S, Pritchard T, Keenan J, Croft P, Silman AJ. Estimating the prevalence of delayed median nerve conduction in the general population. Br J Rheumatol. 1998; 37(6):630-635.
- Phalen GS. The carpal-tunnel syndrome. Seventeen years’ experience in diagnosis and treatment of six hundred fifty-four hands. J Bone Joint Surg Am. 1966; 48(2):211-228.
- Ludlow KS, Merla JL, Cox JA, Hurst LN. Pillar pain as a postoperative complication of carpal tunnel release: a review of the literature. J Hand Ther. 1997; 10(4):277-282.
- Citron ND, Bendall SP. Local symptoms after open carpal tunnel release. A randomized prospective trial of two incisions. J Hand Surg Br. 1997; 22(3):317-321.
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- Bromley GS. Minimal-incision open carpal tunnel decompression. J Hand Surg Am. 1994; 19(1):119-120.
- Agee JM, McCarroll HR, North ER. Endoscopic carpal tunnel release using the single proximal incision technique. Hand Clin. 1994; 10(4):647-659.
- Biyani A, Downes EM. An open twin incision technique of carpal tunnel decompression with reduced incidence of scar tenderness. J Hand Surg Br. 1993; 18(3):331-334.
- Lee WP, Strickland JW. Safe carpal tunnel release via a limited palmar incision. Plast Reconstr Surg. 1998; 101(2):418-424.
- Weber RA, Sanders WE. Flexor carpi radialis approach for carpal tunnel release. J Hand Surg Am. 1997; 22(1):120-126.
- Brown RA, Gelberman RH, Seiler JG III, et al. Carpal tunnel release. A prospective, randomized assessment of open and endoscopic methods. J Bone Joint Surg Am. 1993; 75(9):1265-1275.
- Erdmann MW. Endoscopic carpal tunnel decompression. J Hand Surg Br. 1994; 19(1):5-13.
- Kelly CP, Pulisetti D, Jamieson AM. Early experience with endoscopic carpal tunnel release. J Hand Surg Br. 1994; 19(1):18-21.
- Murphy RX Jr, Jennings JF, Wukich DK. Major neurovascular complications of endoscopic carpal tunnel release. J Hand Surg Am. 1994; 19(1):114-118.
- Seiler JG III, Barnes K, Gelberman RH, Chalidapong P. Endoscopic carpal tunnel release: an anatomic study of the two-incision method in human cadavers. J Hand Surg Am. 1992; 17(6):996-1002.
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- Taleisnik J. The palmar cutaneous branch of the median nerve and the approach to the carpal tunnel. An anatomical study. J Bone Joint Surg Am. 1973; 55(6):1212-1217.
- Eversmann WW. Entrapment and compression neuropathies. In: Green DP, ed. Operative Hand Surgery. Vol 2. 2nd ed. New York, NY: Churchill Livingstone; 1988:1423-1478.
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- Trumble TE, Diao E, Abrams RA, Gilbert-Anderson MM. Single-portal endoscopic carpal tunnel release compared with open release: a prospective, randomized trial. J Bone Joint Surg Am. 2002; 84(7):1107-1115.
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- Ahcan U, Arnez ZM, Bajrovic F, Zorman P. Surgical technique to reduce scar discomfort after carpal tunnel surgery. J Hand Surg Am. 2002; 27(5):821-827.
- Gelberman RH, Pfeffer GB, Galbraith RT, Szabo RM, Rydevik B, Dimick M. Results of treatment of severe carpal-tunnel syndrome without internal neurolysis of the median nerve. J Bone Joint Surg Am. 1987; 69(6):896-903.
Drs Hamed and Makki and Messrs Chari and Packer are from the Department of Orthopedics, Southend University Hospital, Westcliff-on-sea, Essex, United Kingdom.
Drs Hamed and Makki and Messrs Chari and Packer have no relevant financial relationships to disclose.
Correspondence should be addressed to: Daoud Makki, MD, MRCS, DipSEM(UK&NI), Princess Alexandra Hospital, Harlow, Essex, England, United Kingdom, CM20 1QX.