Distribution of nerve fibers in the standard incision for carpal tunnel decompression

Density mapping of nerve endings in the skin of the palm and flexor retinaculum of the hand. Application to open carpal tunnel release

In order to re-evaluate the safest area to incise skin and the flexor retinaculum (FR) when performing a carpal tunnel release (CTR), we carried out a mapping study of the nerve endings in the skin and FR on cadaver specimens, which, unlike previous studies for the first time, includes histomorphometry and image digital analysis. After dividing the skin and FR into 20 and 12 sections, respectively, we carried out a histomorphological analysis of nerve endings. The analysis was performed by two neutral observers on 4-μm histological sections stained with hematoxylin-eosin (H-E), and Klüver-Barrera with picrosirius red (KB + PR) methods. A semi-automatic image digital analysis was also used to estimate the percentage of area occupied per nerve. We observed a lower quantity of nerve endings in the skin of the palm of the hand in line with the ulnar aspect of the 4th finger. The ulnar aspect of the FR was the most densely innervated. However, there are no statistically significant differences between sections in the percentage of area occupied per nerve both in the skin and in the FR. We concluded that there is not a safe area to incise when performing carpal tunnel surgery, but taking into account the quantity of nerve endings present in skin and FR, we recommend an incision on the axis of the ulnar aspect of 4th finger when incising skin and on the middle third of the FR for CTR.

Palmar Creases and Their Implication on Carpal Tunnel Surgery

BACKGROUND

A thorough knowledge of normal and variant anatomy of the wrist and hand is fundamental to avoiding complications during carpal tunnel release. The purpose of this study was to document variations of the surface anatomy of the hand to identify a safe zone in which the initial carpal tunnel incision could be placed. The safe zone was identified as the distance between the radial side of hook of hamate and the ulnar edge of the origin of the motor branch of the median nerve (MBMN).

METHODS

Kaplan's cardinal line and other superficial markers were used to estimate the size of the safe zone, in accordance to prior published anatomical studies. The presence of a longitudinal palmar crease (thenar, median, or ulnar creases) within the safe zone was recorded.

RESULTS

Of the 150 participants (75 male, 75 female) examined, the average safe zone widths were 10.85 (right) and 10.28 (left) mm. In all the hands examined, 86.33% of the safe zones (259 of 300) contained a longitudinal palmar crease. In the White population (n = 50), the average safe zone widths were 11.49 (right) and 10.01 (left) mm; in the African American population (n = 50), the average safe zone widths were 12.27 (right) and 12.01 (left) mm; and in the Asian population (n = 50), the average safe zone widths were 8.79 (right) and 8.82 (left) mm. On overage, males had a larger safe zone width than females by 4.55 mm.

CONCLUSIONS

Although there seems to be variability between race and sex with regard to safe zone width, finding 86.33% of longitudinal palmar creases within the safe zone suggests that, for most patients, the initial carpal tunnel surgery incision may be hidden within the palmar crease while minimizing the risk of motor branch of the median nerve injury. Overall, the safe zone width is on average up to 10.5 mm measured from the hook of the hamate along Kaplan's cardinal line.

The experience of the free superficial palmar branch of the radial artery perforator flap application

PURPOSE

The purpose of this study is to retrospect and summarize clinical efficacy and experience of the free perforator flap base on the superficial palmar branch of the radial artery for tissue defect reconstruction in hand.

METHOD

17 patients who underwent tissue defect in hands reconstruction by the free superficial palmar branch of the radial artery (SPBRA) perforator flaps in our department from July 2014 to October 2018 were reviewed.

RESULTS

All the flaps in our series application were survival uneventful except one, which was necrosis because of venous thrombosis postoperative 5 days, and then the abdominal pedicle flap was executed to recover the defect in second stage. The first dorsal metacarpal artery flap and the arterial venous flap were utilized to cover the defect in one right index finger and one right ring finger due to the absence variation of the SPBRA. 2 cases presented tension vesicle of superficial skin and 1 case occurred venous congestion. All donor sites were closed primarily. The follow-up period means 13.5 months (range, 4-50 months). The static 2 point discrimination test mean 7.53 mm (range, 4-11 mm). All flaps acquire protective feeling at the latest follow-up. The self-assessment of patients: 13 cases in good, 4 cases in fair.

CONCLUSION

The goal of physiological reconstruction and esthetic effect can be achieved for hand tissue defect by the free SPBRA perforator flap, multiple tissues of the flap can be contained according to the defect. Even though the SPBRA is variation, arterial venous flap could be applied thanks to abundant superficial cutaneous veins.

Preoperative Pain Sensitization Is Associated With Postoperative Pillar Pain After Open Carpal Tunnel Release

BACKGROUND

Postoperative pillar pain (deep-seated wrist pain worsened by leaning on the heel of the hand) sometimes occurs after carpal tunnel release (CTR), leading to weakness in the hand and delayed return to work. Increased pain sensitivity has been found to be associated with worse symptoms and poorer treatment response in a number of chronic musculoskeletal conditions, but few studies have investigated the association of pain sensitization with pillar pain after CTR.

QUESTIONS/PURPOSES

(1) Is preoperative pain sensitization in patients with carpal tunnel syndrome (CTS) associated with increased severity of pillar pain after open CTR? (2) What other demographic, electrophysiological, or preoperative clinical characteristics are associated with pillar pain after CTR?

METHODS

Over a 35-month period, one surgeon performed 162 open carpal tunnel releases. Patients were eligible if they had sufficient cognitive and language function to provide informed consent and completed a self-reported questionnaire; they were not eligible if they had nerve entrapment other than CTR or if the surgery was covered by workers compensation insurance. Based on these criteria, 148 (91%) were approached for this study. Of those, 17 (9%) were lost to followup before 12 months, leaving 131 for analysis. Their mean age was 54 years (range, 32-78 years), and 81% (106 of 131) were women; 34% (45 of 131) had less than a high school education. We preoperatively measured pain sensitization by assessing the patients' pressure pain thresholds by stimulating pressure-induced pain in the pain-free volar forearm and administering a self-reported Pain Sensitivity Questionnaire minor subscale, an instrument that assesses pain intensity in daily life situations. We evaluated postoperative pillar pain using the "table test" (having the patient lean on a table with their weight on their hands placed on the table's edge with elbows straight) with an 11-point ordinal scale at 3, 6, and 12 months after their surgical procedures. We conducted bivariate and multivariable analyses to determine whether the patients' clinical, demographic, and pain sensitization factors were associated with their postoperative pillar pain severity after CTR.

RESULTS

After controlling for relevant confounding variables such as age, education level, and functional states, we found that increased pillar pain severity was associated with the pressure pain threshold (β = -1.02 [-1.43 to -0.61], partial R = 11%, p = 0.021) and Pain Sensitivity Questionnaire minor (β = 1.22 [0.73-1.71], partial R = 17%, p = 0.013) at 3 months, but by 6 months, only Pain Sensitivity Questionnaire minor (β = 0.92 [0.63-1.21], partial R = 13%, p = 0.018) remained an associated variable for pillar pain. Additionally, gender (women) was associated with increased pain severity at 3 (β = 0.78 [0.52-1.04], partial R = 9%, p = 0.023) and 6 months (β = 0.72 [0.41-1.01], partial R = 8%, p = 0.027). At 3 months, pressure pain threshold, Pain Sensitivity Questionnaire minor, and gender (women) collectively accounted for 37% of the variance in pillar pain severity; at 6 months, Pain Sensitivity Questionnaire minor and gender (women) accounted for 21% of the variance, but no relationship between those factors and pillar pain was observed at 12 months.

CONCLUSIONS

Gender (women) and preoperative pain sensitization measured by pressure pain threshold and self-reported Pain Sensitivity Questionnaire were associated with pillar pain severity up to 3 and 6 months after CTR, respectively. However, the influence of pain sensitization on pillar pain was diminished at 6 months and it did not show persistent effects beyond 12 months. Pain sensitization seems to be more important in the context of recovery from surgical intervention (in the presence of a pain condition) than in healthy states, and clinicians should understand the role of pain sensitization in the postoperative management of CTS. Future research may be needed to determine if therapeutic interventions to reduce sensitization will decrease the risk of pillar pain.

LEVEL OF EVIDENCE

Level III, prognostic study.

Comparison of short wrist transverse open and limited open techniques for carpal tunnel release: a randomized controlled trial of two incisions

The purpose of this randomized controlled trial was to compare outcomes of limited open and short wrist transverse techniques in patients with carpal tunnel syndrome. In a single centre randomized controlled trial, 84 patients with idiopathic carpal tunnel syndrome were randomized before surgery to limited open or short wrist transverse open carpal tunnel release. The patients were evaluated at 6 weeks, 3 months, 6 months, and 1 and 2 years after surgery. At every follow-up, the Brigham and Women's Carpal Tunnel Questionnaire scores, scar discomfort, and subjective patient satisfaction were evaluated. Two years after surgery, five patients were lost to follow-up. The groups had similar Brigham and Women's Carpal Tunnel Questionnaire Symptom Severity and Functional Status scores and subjective satisfaction scores. The incidence of scar discomfort was not significantly different between the two groups on serial postoperative follow-up. Short wrist transverse open release surgery showed similar early postoperative symptoms and subjective and functional outcomes to limited open release.

LEVEL OF EVIDENCE

II.

Extracorporeal shock wave therapy in pillar pain after carpal tunnel release: a preliminary study

"Pillar pain" is a relatively frequent complication after surgical release of the median nerve at the wrist. Its etiology still remains unknown although several studies highlight a neurogenic inflammation as a possible cause. Pillar pain treatment usually includes rest, bracing and physiotherapy, although a significant number of patients still complain of painful symptoms two or even three years after surgery. The aim of this study was to investigate the efficacy of low-energy, flux density-focused extracorporeal shock wave therapy (ESWT) in the treatment of pillar pain. We treated 40 consecutive patients with ESWT who had pillar pain for at least six months after carpal tunnel release surgery, and to our knowledge, this is the first study that describes the use of ESWT for treating this condition. Our results show that in all of the treated patients, there was a marked improvement: the mean visual analogue scale (VAS) score decreased from 6.18 (±1.02) to 0.44 (±0.63) 120 d after treatment, and redness and swelling of the surgical scar had also decreased significantly.

Predictors of scar pain after open carpal tunnel release

PURPOSE

To identify the predictors of scar pain after open carpal tunnel release (CTR).

METHODS

We enrolled 83 patients with idiopathic carpal tunnel syndrome treated by open CTR. All patients completed the Brigham and Women's (Boston) carpal tunnel questionnaire (BCTQ) preoperatively. We assessed levels of depression preoperatively using the Center for the Epidemiological Study of Depression (CES-D) scale, and pain anxiety using the Pain Anxiety Symptoms Scale. At 3 months after surgery, patients were asked to self-assess treatment satisfaction and scar pain using a 10-point ordinal scale and to complete the BCTQ.

RESULTS

The mean BCTQ-symptom (BCTQ-S) score decreased significantly from 2.7 ± 1.1 preoperatively to 1.6 ± 1.0 at 3 months postoperatively, and mean BCTQ-function score decreased significantly from 2.4 ± 1.1 to 1.4 ± 1.0. Overall, scar pain intensity at 3 months postoperatively ranged from 0 to 8 (mean, 2.4 ± 2.2), and overall satisfaction ranged from 2 to 10 (mean, 7.6 ± 2.6). The intensity of the scar pain was significantly correlated with the CES-D scale and BCTQ-S. Multivariable regression analysis showed that depression, assessed using the CES-D scale, and postoperative symptoms, assessed using the BCTQ-S, predicted scar pain intensity, which accounted for 38% of scar pain intensity variance.

CONCLUSIONS

Depression score and postoperative symptoms predicted scar pain intensity after open CTR. However, the most important contributor to scar pain intensity variance remains unidentified.

TYPE OF STUDY/LEVEL OF EVIDENCE

Prognostic I.

Comparison of transverse carpal ligament and flexor retinaculum terminology for the wrist

PURPOSE

To investigate the macroscopic anatomy and histological characteristics of the transverse carpal ligament and the flexor retinaculum of the wrist and to investigate their anatomical relationships and define appropriate terminology.

METHODS

The volar regions of the wrists of 30 unembalmed subjects were examined by dissection and by histological and immunohistochemical staining. In vivo magnetic resonance imaging studies were also carried out on 10 subjects.

RESULTS

The dissection study showed that the antebrachial fascia at the volar aspect of the wrist presents a reinforcement. From a histological point of view, it is composed of 3 layers of undulated collagen fiber bundles. Adjacent layers show different orientations of the collagen fibers. Many nerve fibers and Pacini and Ruffini corpuscles were found in all specimens. Under this fibrous plane is another fibrous structure, placed transversely between the ulnar-sided hamate and pisiform bones, and the radial-sided scaphoid and trapezium bones. The deeper fibrous structure shows completely different histological characteristics, having parallel, thicker collagen fiber bundles and few nerve fibers. Magnetic resonance images confirm the presence of 2 clearly distinguished fibrous structures in the wrist, the first in continuity with the antebrachial fascia and the second located in a deeper plane between the hamate and scaphoid.

CONCLUSIONS

Two different fibrous structures with different histological characteristics are present in the volar wrist: the more superficial one is in continuity with the antebrachial fascia and could be considered its reinforcement; the deeper one is composed of strong lamina, with histological features similar to those of a ligament. For these reasons, we suggest that the term transverse carpal ligament should be used to indicate the fibrous lamina connecting the hamate and pisiform to the scaphoid and trapezium and that the term flexor retinaculum of the wrist should be abandoned because it does not correspond to any specific, autonomous structure.

Endoscopic versus open carpal tunnel release

PURPOSE

This study compared endoscopic carpal tunnel release with the conventional open technique with respect to short- and long-term improvements in functional and clinical outcomes.

METHODS

We assessed 72 outpatients diagnosed with carpal tunnel syndrome. Of these patients, 37 underwent the endoscopic method according to Chow and 35 were assigned to the open method. Improvement in symptoms, severity, and functionality were evaluated at 2 days, 1 week, 2 weeks, and 1 year postoperatively. Changes in clinical outcomes were evaluated at 1 year postoperatively. Complications were also assessed.

RESULTS

Both groups showed similar improvement in all but 1 outcome 1 year after the release; increase in grip strength was significantly higher in the endoscopic group. However, the endoscopic method showed a greater improvement in symptoms and functional status compared with the open method at 2 days, 1 week, and 2 weeks postoperatively. Separate analysis of the questions referring to pain showed that the delay in improvement in the open group was because of the persistence of pain for a longer period. Paresthesias and numbness decrease immediately after the operation with comparable rates for both groups.

CONCLUSIONS

Endoscopic carpal tunnel release provides a faster recovery to operated patients for the first 2 weeks, with faster relief of pain and faster improvement in functional abilities. Paresthesia and numbness subside in an identical manner with the 2 techniques. At 1 year postoperatively, both open and endoscopic techniques seem to be equivalently efficient.

Standard open decompression in carpal tunnel syndrome compared with a modified open technique preserving the superficial skin nerves: a prospective randomized study

PURPOSE

A common surgical treatment for carpal tunnel syndrome is open carpal tunnel decompression. This involves skin incision followed by sharp dissection straight down through fat and palmar fascia to the transverse carpal ligament, which is then divided. The incidence of scar discomfort ranges from 19% to 61%, and its cause is not fully understood. We conducted a prospective randomized controlled trial to investigate whether preservation of superficial nerve branches crossing the incision site reduces the incidence and severity of postoperative scar pain after open carpal tunnel release.

METHODS

Forty-two patients with bilateral idiopathic carpal tunnel syndrome (84 hands) were included in the study. The patients were randomized to determine which hand was to have carpal tunnel decompression using a technique that would try to preserve the superficial nerve branches. The other hand had open carpal tunnel decompression without any attempt to preserve the superficial nerve branches. An assessment of each hand in each patient was performed immediately before surgery and at 6 weeks, 3 months, and 6 months after surgery. This assessment was performed with a questionnaire based on the Patient Evaluation Measure.

RESULTS

We found no evidence of a difference in scar pain between the 2 methods at 6 weeks, 3 months, and 6 months. There was a significant difference in the length of surgery between the 2 groups.

CONCLUSIONS

Scar pain scores in this series of open carpal tunnel decompressions were similar, whether or not an attempt was made to identify and preserve superficial nerve branches crossing the wound.

Nerve fibre composition of the palmar cutaneous branch of the median nerve and clinical implications

Fifteen fresh human cadaver hands were dissected, using x2.8 loupe magnification, to study the subcutaneous innervation at the site of the incision (in the line with the radial border of the ring finger) for standard open carpal tunnel decompression. Subcutaneous nerve branches were detected and traced proximally to determine their origin. Morphometric analysis of nerve cross sections from the site of the incision and from the main nerve trunk proximal to cutaneous arborisation was performed using light and transmission electron microscopy and a computer-based image analysis system. At the site of the incision, the ulnar sub-branch (US) of the palmar cutaneous branch of the median nerve (PCBMN), which innervates the skin over the hypothenar eminence, was found in 10 of 15 cases. Branches from the ulnar side were not detected. The main trunk of PCBMN consisted on average of 1000 (SD 229) myelinated axons arranged in 1-4 fascicles. In the US of the PCBMN there were on average 620 (SD 220) myelinated axons, 80% of them smaller than 40 microm(2) i.e. thin myelinated axons, and on average 2037 (SD 1106) unmyelinated axons, arranged in 1-3 fascicles. The ratio of the number of myelinated axons in the US and the main trunk of the PCBMN was on average 63% (SD 19%). Frequency distribution of cross-sectional areas of myelinated axons shows no significant difference between the US and the main nerve trunk of the PCBMN. The importance of incision trauma to subcutaneous innervation of palmar triangle is emphasised and possible mechanisms of scar discomfort are discussed.

Surgical technique to reduce scar discomfort after carpal tunnel surgery

A total of 379 patients (416 hands) with clinically diagnosed and electromyographically confirmed carpal tunnel syndrome were enrolled in a prospective study to determine the influence of a modified open decompression technique on postoperative scar discomfort. The new technique used in 184 patients (200 hands) is presented. Special attention was focused on identification and preservation of macroscopically detectable subcutaneous nerves. After using this method, which permits complete visualization of the entire transverse carpal ligament, the incidence of postoperative scar discomfort was 2.5%. This was significantly lower compared with the group of 195 patients (216 hands) treated by standard open decompression technique, without preservation of subcutaneous nerves. Primary results regarding relieving symptoms were comparable in both groups. Five anatomic variations of subcutaneous innervation, at the site of the incision in the line with the radial border of the ring finger, are described. The etiology of scar discomfort is discussed.

The detailed anatomy of the palmar cutaneous nerves and its clinical implications

The forearms and hands of 40 fresh-frozen cadavers were dissected under the microscope to study the palmar cutaneous branch of the median nerve (PCBm) and the palmar cutaneous branch of the ulnar nerve (PCBu). Branches of the PCBm innervating the scaphoid were typically found, but in no specimen did we find a 'typical' cutaneous branch of the ulnar nerve. According to our findings, standard incisions for open carpal tunnel release carry a significant risk of damaging branches of the PCBm or PCBu. The chance of injury to these sensory nerves can be minimized by using a short incision in the proximal palm or a twin incision approach, which we describe. Because the PCBm is closely associated with the ulnar side of the flexor carpi radialis (FCR) sheath, this sheath should be opened on the radial side during harvest of the FCR tendon for transfer. When transferring the palmaris longus tendon, it should be cut proximal to the distal wrist crease to avoid possible damage to the PCBm.