Comparison of Ligament Z-Plasty and Conventional Surgery for the Treatment of Carpal Tunnel Syndrome: A Randomized Clinical Trial

Abstract

Background:

Conventional surgery performed to treat carpal tunnel syndrome (CTS) is associated with complications such as pillar pain or loss of strength. This study aimed to compare the incidence of pillar pain between 2 techniques at the 3-week and 6-month follow-up and to determine differences in the recovery of grip strength (GS), pinch strength (PS), and Boston Carpal Tunnel Questionnaire scores.

Methods:

This randomized clinical trial included 109 patients, 55 of whom underwent ligament Z-plasty and 54, conventional surgery (longitudinal section of the transverse carpal ligament without posterior closure). GS, PS, pillar pain, and Boston Carpal Tunnel Questionnaire scores were assessed preoperatively and 3 weeks and 6 months after surgery.

Results:

The incidence of pillar pain 3 weeks after surgery was lower in patients undergoing Z-plasty than in those undergoing conventional surgery (25.5% versus 44.4%; P = 0.04). Moreover, the absolute change in PS 3 weeks after surgery (P = 0.01) and GS 6 months after surgery (P = 0.05) and the absolute and relative changes in PS after 6 months (P = 0.008 and P = 0.01, respectively) were significantly higher in the Z-plasty group than in the conventional surgery group.

Conclusions:

Z-plasty is a valid surgical procedure for treating CTS. It is associated with a lower incidence of pillar pain and better recovery of postoperative strength compared with the conventional surgical technique, with both techniques showing similar results in CTS recovery.

CLINICAL QUESTION/LEVEL OF EVIDENCE:

Therapeutic, II.

Carpal tunnel syndrome (CTS) is a common pathology that causes pain and paresthesia in the area innervated by the median nerve, caused by compression of the median nerve as it passes under the transverse carpal ligament (TCL).¹ The surgical technique used to release the median nerve traditionally involves complete opening of the TCL. Despite its extensive use, this approach is associated with complications, including pillar pain and loss of strength.^2,3

Pillar pain is defined as a sensation of deep pain and allodynia that appears in the thenar and/or hypothenar eminence zone and is sometimes associated with pain and peri-incisional hyperalgesia.² The etiology of this complication remains unknown. The possible causes described include injury of the superficial branches of the median or ulnar nerves, alteration of the structure of the carpal arch, and intrinsic muscle pain due to the traction of the released TCL.^2,4,5 The etiology of postsurgical strength loss seems to be associated with loss of the pulley effect performed by the TCL on the flexor tendons of the wrist.^6,7

The incidence of pillar pain was studied by Povlsen and Tegnell⁸ over a follow-up period of 3 years. They found an estimated incidence of 41% in the first month after surgery, followed by a subsequent decrease to 25% after 3 months, 6% after 12 months, and 6% after 36 months. We conducted a study of 78 patients, and the incidence of pillar pain 1 month after surgery was 35.9%.

This study aimed to analyze whether patients undergoing Z-plasty presented a lower incidence of postsurgical pillar pain and loss of strength than those undergoing conventional surgery for CTS at the 3-week and 6-month postoperative follow-up.

PATIENTS AND METHODS

Study Design

This randomized parallel-group clinical trial comprised 109 patients and was performed in accordance with the Consolidated Standards of Reporting Trials guidelines and the ethical standards of the 1964 Declaration of Helsinki. The study was approved by the Research Ethics Committee (act no. 331) and registered in the international clinical trials registry (https://www.clinicaltrials.gov; identification no. NCT05468814).

Three surgeons performed both surgical techniques. The medical examinations and the measurements were recorded by an external collaborator, and the data were analyzed by the investigator. This was a double-blind study, where both the patients and investigators were unaware of the surgical technique used. With an estimated 10% loss to follow-up, the sample size was calculated using public sample size calculator software, which determined a sample size of 120 patients.

Variables

Pillar pain was defined as pain or sensation of allodynia in the thenar or hypothenar eminence zone, hyperalgesia of the scar, pain when supporting the heel of the hand, or dysesthesia at rest.

The Boston Carpal Tunnel Questionnaire (BCTQ), a self-administered questionnaire, was used. The BCTQ is divided into 2 parts: a clinical scale (11 items), assessing the severity of CTS symptoms from 1 to 5, and a functional scale (8 items), assessing the patient’s ability to perform daily activities by grading from 1 to 5.^9,10 Grip strength and pinch strength were measured in kilograms using specific dynamometers.

Inclusion and Exclusion Criteria

Inclusion criteria were age older than 18 years, moderate to severe CTS, symptoms interfering with daily activities, and unsuccessful conservative treatment. Exclusion criteria were previous CTS surgery, traumatic or congenital hand conditions, or inability to comprehend the study procedures or tests.

Preoperative Visit and Follow-Up

Patients were evaluated at 3 visits: before surgery and 3 weeks and 6 months after surgery. The preoperative visit involved patient screening and recruitment, recording patient information and obtaining informed consent, applying the inclusion and exclusion criteria, and performing clinical and exploratory diagnosis of CTS (ie, pain and paresthesia in the first 3 fingers and radial edge of the fourth finger, nocturnal paresthesia, atrophy of the thenar musculature, loss of opposition of the first finger, presence of positive Durkan, Phalen, and Tinel signs). Measurement of baseline BCTQ, grip strength, and pinch strength values was performed. Patients were randomly assigned to 1 of 2 treatment groups in a 1:1 ratio using a computer-generated list. We used digitally created cards: 60 labeled “conventional surgery” and 60 labeled “Z-plasty.” Before the surgery, the system randomly assigned each patient a card for group allotment.

The postsurgical follow-up (3 weeks and 6 months) involved clinical examination and evaluation of median nerve compression. Pillar pain was assessed based on clinical symptoms and physical examination (ie, direct pressure to the thenar and hypothenar regions and “table test”). In the table test, the patient is asked to rest the palms on a table with the elbows stretched. If pain is triggered, results are considered positive. Measurement of postoperative BCTQ, grip strength, and pinch strength values was performed.

Surgical Techniques

Both surgery types were performed under local anesthesia (mepivacaine 2%) with an ischemic cuff pressure of 250 mm Hg. The Taleisnik approach was used, where an incision of approximately 2 to 3 cm was made starting at the wrist crease and ulnar to the axis of the fourth finger in flexion.

The conventional technique consists of a complete longitudinal division of the TCL. The Z-plasty technique is based on a Z-shaped opening of the TCL: 2 partial longitudinal incisions (the radial one at the proximal level and the ulnar one at the distal level) joined by a transverse section. This generates 2 flaps, which are subsequently sutured using a double-resorbable 3/0 suture (Figs. 1 and 2). (See Video [online], which demonstrates the Z-plasty technique.)

Fig. 1.

The surgical technique of ligament Z-plasty.

Fig. 2.

(Left) After the Z-cut, the ulnar and radial flaps are exposed. (Right) Result after double stitch using resorbable sutures.

Video. This video demonstrates the Z-plasty technique.

Download video file ^{(90.2MB, mp4)}

In both techniques, the skin is sutured directly using silk 3/0 sutures.

From the immediate postoperative period, the patients were urged to perform flexion/extension exercises of the wrist and fingers. Contact sports and lifting any weight greater than 3 kg by hand was avoided in the first month after surgery.

Statistical Analysis

Statistical analyses were performed using the free R software program, version 4.0.4. P values less than 0.05 were considered statistically significant.

A t test was performed for quantitative variables and the chi-square test for qualitative variables. A Fisher test was performed for the variable “atrophy.” Mixed analysis of variance was conducted using the patient as a random effect and the visit and surgical technique as the fixed effects to analyze the absolute change in grip and pinch strengths and the BCTQ scores 3 weeks and 6 months postoperatively.

For data analysis, 2 new variables were created for the quantitative variables. The absolute change and relative change in the grip strength, pinch strength, and BCTQ scores were calculated as the absolute and percentage calculations, respectively, of the difference between the baseline values and those at 3 weeks and 6 months postoperatively (ie, comparing each patient with themselves by calculating the variation in these variables throughout the follow-up period). A t test was used to evaluate the absolute and relative changes in grip and pinch strengths and BCTQ scores.

RESULTS

Eleven cases were lost to follow-up, including 6 from the Z-plasty group and 5 from the conventional group (Fig. 3). Therefore, the study sample included 109 patients, of whom 55 underwent Z-plasty and 54 underwent conventional CTS surgery. There were 80 women and 29 men, with a mean age of 56.1 ± 11.8 years. All the variables were balanced between the 2 groups, with significant differences in sex (Z-plasty group, 45 women versus conventional surgery group, 35 women; P = 0.05) and the baseline level of pinch strength (Z-plasty group, 2.9 kg versus conventional surgery group, 3.9 kg; P = 0.02) (Table 1).

Fig. 3.

Consolidated Standards of Reporting Trials diagram of the study sample and the cases lost to follow-up.

Table 1.

Baseline Clinical Characteristics^a

Characteristics	Total (n = 109)	Z-Plasty (n = 55)	Conventional (n = 54)	P
Age, yrs	56.1 ± 11.8	55.5 ± 10.8	56.7 ± 12.7	0.6
Female sex	80 (73.4)	45 (81.8)	35 (64.8)	0.05
Laterality (right)	61 (56.0)	29 (52.7)	32 (59.3)	0.5
Atrophy	3 (2.8)	1 (1.8)	2 (3.7)	0.6
Baseline grip strength, kg	17.9 ± 9.5	16.3 ± 8.2	19.6 ± 10.4	0.06
Baseline pinch strength, kg	3.4 ± 2.4	2.9 ± 2.2	3.9 ± 2.4	0.02
Baseline clinical BCTQ	3.4 ± 0.8	3.5 ± 0.8	3.3 ± 0.7	0.2
Baseline functional BCTQ	3.0 ± 0.9	3.1 ± 0.9	2.8 ± 0.8	0.1

^aData are presented as mean ± SD or no. (%).

Pillar Pain

Pillar pain was reported by 38 patients 3 weeks postoperatively, of whom 14 had undergone Z-plasty (25.5%) and 24 conventional surgery (44.4%). The incidence of pillar pain after 3 weeks was significantly lower in the Z-plasty group than in the conventional surgery group (P = 0.04). No significant differences were observed between the groups after 6 months (Table 2).

Table 2.

Incidence of Pillar Pain 3 Weeks and 6 Months after Surgery^a

Pillar Pain	Z-Plasty	Conventional	P
3 wk	14 (25.5)	24 (44.4)	0.04b
6 mo	5 (9.1)	9 (16.7)	0.3

^aData are presented as no. (%).

^bSignificant.

Strength Values and BCTQ Scores

At the 6-month postoperative follow-up, the pinch strength improved significantly in the Z-plasty group compared with the conventional surgery group, but no significant differences were observed in the other variables (Tables 3 and 4).

Table 3.

Clinical and Functional Boston Carpal Tunnel Questionnaire Scores and Grip and Pinch Strength Values^a

Values	Baseline	3 Weeks	6 Months	P
Grip strength, kg
Z-plasty	16.3 ± 8.1	13.8 ± 7.0	18.6 ± 8.9	0.1
Conventional	19.6 ± 10.4	15.6 ± 9.5	19.1 ± 9.0
Pinch strength, kg
Z-plasty	2.9 ± 2.2	3.8 ± 2.8	5.4 ± 3.0	0.008b
Conventional	3.9 ± 2.4	3.5 ± 2.5	5.1 ± 2.4
Clinical BCTQ
Z-plasty	3.5 ± 0.8	1.9 ± 0.8	1.5 ± 0.8	0.6
Conventional	3.3 ± 0.7	1.8 ± 0.7	1.5 ± 0.7
Functional BCTQ
Z-plasty	3.1 ± 0.9	2.2 ± 0.9	1.7 ± 0.8	0.6
Conventional	2.8 ± 0.8	2.1 ± 0.8	1.6 ± 0.7

^aData are presented as mean ± SD.

^bSignificant.

Table 4.

Two-Way Analysis of Variance Results

Two-Way ANOVA	Grip Strength, kg	Pinch Strength, kg	Clinical BCTQ	Functional BCTQ
Differences between visitsa	<0.001	<0.001	<0.001	<0.001
Differences between groupsb	0.4	0.5	0.3	0.1
Interaction between technique and visitc	0.1	0.008	0.6	0.6

ANOVA, analysis of variance.

^aDifferences in the variable over time.

^bDifferences between the 2 techniques.

^cThe synergy between the follow-up time and the surgical technique does or does not have an impact on the variable.

However, when we studied the changes in the absolute and relative values of grip strength, pinch strength, and clinical and functional BCTQ scores using the t test, we observed significant differences between the 2 groups (Table 5). After 3 weeks, the absolute change in the pinch strength was significantly greater in the Z-plasty group than in the conventional surgery group (P = 0.01). However, no differences were observed in the other variables between the 2 groups. After 6 months, the absolute change in grip strength (P = 0.05) and the absolute and relative (percentage) changes in pinch strength (P = 0.008 and P = 0.01, respectively) were significantly greater in the Z-plasty group than in the conventional surgery group. No differences were observed in the other variables between the 2 groups.

Table 5.

Summary of the Results of the Absolute and Relative Changes in Grip Strength, Pinch Strength, and Clinical and Functional BCTQ Scores after 3 Weeks and 6 Months

Change	Conventional versus Z-Plasty, P Values
	Grip Strength	Pinch Strength	Clinical BCTQ	Functional BCTQ
Absolute
3 Weeks	0.2	0.01a	0.6	0.5
6 Months	0.05a	0.008a	0.4	0.3
Relative, %
3 Weeks	0.8	0.06	0.8	0.8
6 Months	0.2	0.01a	0.5	0.3

^aSignificant.

DISCUSSION

After reviewing the anatomy and anatomic variations of the carpal tunnel and the different surgical techniques used to open it, Brooks et al.¹¹ determined that complete release of the TCL might involve a small but significant change in the carpal biomechanics and morphology. Thus, complications such as pillar pain or postsurgical loss of strength may be due to a change in the carpal anatomy or alteration of the pulley system exerted by the TCL on the flexor tendons of the hand. Therefore, other surgical techniques have been developed to minimize or avoid these adverse effects.¹² Numerous TCL elongation techniques have been described, such as the Simonetta technique,¹³ the modified Simonetta technique,¹⁴ zigzag opening techniques with subsequent closure,¹⁵ an elongation technique similar to Z-plasty,¹⁶ or subneural reconstruction.¹⁷ TCL elongation techniques are based on an approach similar to conventional surgery; however, they avoid complete exposure of the median nerve and instead focus on partial sections of the ligament to achieve elongation or reconstruction after opening.

Cadaver studies revealed that reduction of pressure inside the carpal tunnel in Z-elongation is similar to that with complete opening of the TCL.¹⁸ Therefore, we decided to assess the ligament Z-plasty technique.

Although 11 patients were lost to follow-up from the initial 120 and results were finally obtained for 109 patients, the calculation of the sample size was conducted assuming a 10% loss; hence, the results obtained present statistical validity.

During the 3-week follow-up in our study, the incidence of pillar pain was lower in the Z-plasty group than in the conventional surgery group, with similar long-term results. We probably did not obtain significant differences in the incidence of pillar pain in the last postsurgical follow-up at 6 months because the natural course of this complication is to resolve with time. Although the incidence of pillar pain after 6 months differed between the groups, it was not statistically significant.

Previous studies have analyzed pillar pain as a variable; however, they did so using the Simonetta technique or the modified Simonetta technique.^14,19,20 No concrete analysis of pillar pain after Z-plasty has been conducted before this study. Dias et al.¹⁹ did not observe statistically significant differences, but they did observe a trend similar to ours. Faour-Martín et al.²⁰ concluded that the incidence of pillar pain was lower with the Simonetta technique than with complete opening of the TCL, and Castro-Menéndez et al.¹⁴ did not observe any advantages with the modified Simonetta technique to avoid the occurrence of pillar pain.

None of the previous studies that used Z-plasty as a comparative technique^21,22 analyzed pillar pain. Xu et al.²¹ describe “less pillar pain morbidity in the reconstruction group due to less nerve involvement at skin level”; however, it is not a variable that they studied in their patients. Saravi et al.²² relied on the visual analog pain scale for postsurgical pain assessment and concluded that the postsurgical pain was significantly lower in the Z-plasty group than in the conventional surgery group.

As for the recovery of grip strength, we have already shown that because one of the etiologies for decreased postsurgical strength could be the loss of the pulley effect of the TCL on the flexor tendons of the hand, reconstruction of the tunnel roof by lengthening the ligament can maintain this effect and improve postsurgical strength recovery.³ The pinch strength is less likely to be associated with the continuity of the TCL and is more closely related to median nerve recovery.

Better results were obtained in the Z-plasty group than in the conventional surgery group for the absolute change in the pinch strength at 3 weeks and in pinch and grip strength at 6 months and for the relative change in pinch strength at 6 months. One of the limitations of our study is the use of an absolute analysis of quantitative variables, given that the true mathematical relevance lies in the relative change. Although we cannot definitively conclude that absolute change translates to relevant statistical significance, we consider the statistical significance of the relative change to be conclusive; therefore, we assert that there was an improvement in pinch strength at the 6-month follow-up.

Dias et al.¹⁹ conducted a study that assessed pinch strength as a variable; however, they did not observe differences in terms of grip and pinch strengths between the 2 groups. Castro-Menéndez et al.¹⁴ only assessed grip strength and performed the same data analysis as we did by calculating the absolute change for each patient; however, they did not observe significant differences between the groups. Xu et al.²¹ only studied grip strength and observed differences between the groups after 6 and 12 months but not in the immediate postoperative period. Saravi et al.²² observed statistically significant differences in grip strength after 3 weeks with better strength recovery in the Z-plasty group than in the open surgery group but no differences after 6 and 12 months.

Analyses of the BCTQ scores had disparate results. Because it involves a questionnaire with 2 scales with 11 items and 8 items, respectively, the analysis can differ depending on how the data are grouped. Similar to Dias et al.,¹⁹ we wanted to perform a differentiated analysis of the clinical and functional BCTQ scores to assess the symptoms and activity separately, given that the effect of each of these variables on the patient is different. Neither Xu et al.²¹ nor Saravi et al.²² used the BCTQ to study median nerve compression treatment.

Regarding the minimal clinically important difference (MCID) for BCTQ, De Kleermaeker et al.²³ determined it as 0.46 for clinical BCTQ and 0.28 for functional BCTQ, and Ozer et al.²⁴ found an MCID of 1.6 points for clinical BCTQ and 1.45 points for functional BCTQ at 6 months. When we applied the MCID values from De Kleermaeker et al.²³ to our results, we observed that we achieved them with Z-plasty and only at 6 months of follow-up with conventional surgery. When we applied the values from Ozer et al.²⁴ to our results, we achieved the MCID at the clinical BCTQ with both techniques.

Saravi et al.²² studied the difference in the duration of surgery, which was significantly higher in the Z-plasty group than in the conventional surgery group (27.4 ± 3.6 versus 13.8 ± 2.2 minutes).

Fucs et al.²⁵ conducted a study comparing the Z-plasty technique and complete opening of the TCL. They performed a zigzag opening with subsequent closure, as published by Karlsson et al.¹⁵ They did not specifically analyze pillar pain as a postsurgical complication but instead focused on differences in QuickDASH scores, and did not observe any differences. Furthermore, their results contradicted ours because they obtained better strength results in the complete opening of the TCL group than in the Z-plasty group; hence, they concluded that there is no advantage in using the Z-plasty technique. Although both are randomized clinical trials methodologically, our study had a considerably larger sample size, and the other did not study pillar pain.

Limitation

We did not include an analysis of surgical time, but it would be important to determine whether these differences in surgical time had any clinical or functional effect on the patients.

CONCLUSIONS

Our study determined that Z-plasty had a lower incidence of pillar pain at 3 weeks and better recovery of pinch strength at 6 months postoperatively, without significant differences in the BCTQ scores. Therefore, it is a valid technique for median nerve treatment resolution, and offers advantages in the prevention and improvement of complications associated with conventional surgery.

DISCLOSURE

None of the authors received financial or material support for the research, authorship, or publication of this article.

ACKNOWLEDGMENTS

This study received a Research Initiation Project grant from the Spanish Society of Orthopaedic Surgery and Traumatology (SECOT). The authors thank the nursing staff for their collaboration in the surgical and follow-up processes.