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1
Modified mini-incision surgery for
carpal tunnel syndrome:
Technique and clinical outcome
Saran Malisorn
Department of Orthopedics, Faculty of Medicine, Naresuan University, Phitsanulok 65000, Thailand
*Corresponding author:
Saran Malisorn
saranm@nu.ac.th
Received: 27 August 2023
Revised: 17 January 2024
Accepted: 14 February 2024
Published: 5 August 2024
Citation:
Malisorn, S. (2024). Modified
mini-incision surgery for carpal
tunnel syndrome: Technique
and clinical outcome. Science,
Engineering and Health
Studies, 18, 24050005.
ABSTRACT
Carpal tunnel syndrome (CTS) is caused by the shortening of the median nerves
in the wrist, resulting in hand pain and paralysis necessitating surgical operation
for relief. Conventional open carpal tunnel release (CTR) procedures, involving
long incisions, often lead to complications, delaying patients’ recovery for weeks
or months. Therefore, mini-incision surgery has emerged as a preferred option,
offering reduced pain, smaller wounds, and improved appearance. This study
aimed to compare the outcomes of modified mini-incision surgery for CTS before
and after the operation. It was a retrospective study involving 80 patients, with
data collected from medical records pre- and post-operation, specifically at the 2nd
week, 3rd month, 6th month, 12th month, and 24th month intervals. Variables
included operation time, incision length, pinch strength, gripping strength, two-
point discrimination (2-
PD), visual analogue scale (VAS), Levine score, quick
disabilities of the arm, shoulder and hand (Quick-DASH), wound pain, and pillar
pain. Data were analyzed using descriptive statistics and logistic regression, with
a significant level of 0.05. The mean incision length was 11.54 mm. At the 2-week
post-operative mark, the pinch strength was 5.43, gripping strength was 14.96, 2-
PD was 5.84, the VAS score was 2.86, the Levine symptom was 3.84, and the
DASH score was 69.43. There was a relationship (p-
value<0.05) between
preoperative and postoperative measures for pinch strength, gripping strength, 2-
PD, and Levine symptom condition. The study on 80 patients who underwent
modified mini-incision surgery for CTS at Naresuan University
Hospital in
Phitsanulok, Thailand, found that
these parameters showed significant
improvement postoperatively. Patients demonstrated good recovery and condition
2 weeks after the mini-incision surgery for CTS.
Keywords: mini-incision surgery; carpal tunnel syndrome; satisfactory surgical outcomes
1. INTRODUCTION
Carpal tunnel syndrome (CTS) is caused by the shortening
of the median nerves in the wrist. Patients experience pain
and paralysis in their hands, which often requires surgical
intervention to alleviate symptoms (Saw et al., 2003). The
long incision or classic open carpal tunnel release (CTR)
can lead to complications. The most common issues are
large scars and pillar pain (Townshend et al., 2005), which
can prevent patients from returning to their routine
activities for weeks or months. Studies have shown that
approximately 30,000 workers with CTS had to take an
average of 25 working days off from their jobs (Patterson
and Simmons, 2002). In general, patients can tolerate the
scar since it is primarily an aesthetic concern. However,
pillar pain is often unbearable. Pillar pain is a common and
expected symptom following CTR. Patients experience
pain at the base of their hands, particularly in the heel of
their palms. The common areas of tenderness are thenar
eminence (the thumb base muscles) and hypothenar
Science, Engineering and Health Studies
https://li01.tci-thaijo.org/index.php/sehs
ISSN (Online): 2630-0087
Research Article
Modified mini-incision surgery for carpal tunnel syndrome: Technique and clinical outcome
2
eminence (small finger base muscles). Sometimes, patients
experience a sensation known as allodynia, which is a
symptom of nerve pain that makes the skin extremely
sensitive to touch and cause intense pain during normal
activities such as brushing hair or wearing cotton clothing.
When patients suffer from allodynia, the pain can be worse
than the compression syndrome (Matloub et al., 1998). It
has been proposed that these complications occurr due to
technical defects such as injuries to the small sensorial
branches of the ulnar and median nerves or the presence
of neuromas in the subcutaneous tissue in Figure 3.
However, no definitive incidence has been found. Povlsen
and Tegnell (1996) followed-up the symptom of pillar pain
after the operation for three years and found that 41% of
symptoms occurred after one month, 25% after 3 months,
6% after one year, and 6% after 3 years. To reduce
complications, various mini-incision approaches have
been tested to develop a new approach that minimizes
complications, yields satisfactory surgical outcomes, and
results in aesthetically pleasing wounds and appearances.
CTS is the most common neurodegenerative ailment.
The primary causes of CTS are genetic and structural
factors. Occupational and environmental are secondary
contributors. The main symptom of CTS is intermittent
paralysis of the thumb, index finger, middle fingers, and
half the ring finger. Since CTS often leads to losing ability
to work, patients with severe symptoms who cannot be
treated with traditional approaches often need to undergo
open surgery using different techniques.
In the study by Bai et al. (2018), which collected data
from CTS patients over a year involving 85 patients. It is
found that 50% underwent treatment using the mini-
incision approach, while the remaining 50% were treated
with classical long incision approach. Objective tests and
subjective assessments were performed to compare the
outcomes of the classical long incision approach, followed
by a comparison of postoperative complications between
both approaches. The study concluded that the mini-
incision approach yielded satisfactory surgical results
with lower postoperative complications and better
aesthetic wound appearance. In addition, the duration of
mini-incision operation was 15.15 ± 2.20 min, which is
65.08% shorter than classic CTS operation duration of
25.01 ± 2.15 min (Malisorn, 2023). Consequently, the
hospital can efficiently utilize its limited resources,
including surgeons and operation rooms, to treat more
patients.
After assessing the advantages and disadvantages of all
approaches used to treat CTS, is has been determined that
patient goals are symptom relief, faster recovery and
aesthetic satisfaction (Wongsiri et al., 2022). Many of the
approaches employed in CTR surgery achieve these goals.
Moreover, the overall infection rate following CTR surgery
is notably low. To address these considerations, a study
focusing on decompression reduction of the carpal tunnel
was conducted utilizing a 1.5 cm microsurgical procedure.
The findings of this study elucidate the advantages and
disadvantages of this technique, highlighting the benefits
of limited incision, and various endoscopic techniques
known for minimal tissue damage and effective scar
prevention. In addition, to enhance aesthetic outcomes,
post-surgical physical therapy is essential. This therapy
plays a crucial role in aiding recovery and strengthening
wrist functionality. The objective of this study was,
therefore, to evaluate the outcomes of modified mini-
incision surgery for CTS.
2. MATERIALS AND METHODS
This study received approval from the Ethics Committee of
Naresuan University Hospital. It was a retrospective analysis
of patient records from individuals diagnosed with CTS at
Naresuan University Hospital between 2018 and 2022,
involving a total of 80 patients. Inclusion criteria include
CTS patients who underwent mini-incision surgery and
aged over 30 years old. Exclusion criteria were established
for patients allergic to amoxicillin or xylocaine anesthesia.
In this study, a single surgeon performed all surgery.
Xylocaine viscous (1%), administered in amounts ranging
from 1–2 mL, served as the anesthetic agent. The
researcher conducted a comparative analysis of patient
conditions before and after the operation, focusing on the
following parameters: (1) operation time, (2) incision
length, (3) pinch Strength, (4) gripping strength, (5) two-
point discrimination (2-PD), (6) visual analogue scale
(VAS), (7) Levine score, (8) quick disabilities of the arm
shoulder and hand (Quick-DASH), (9) wound pain, and
(10) pillar pain.
Data were collected from patient records spanning the
years 2018 to 2022, adhering to the following criteria.
1) Operation wound size of 1.5 cm.
2) All records underwent electromyography (EMG)
assessment.
3) Evaluation via the Boston CTS questionnaire (BCTSQ)
4) Daily wound dressing was performed.
5) Administration of antibiotics amoxicillin-clavulanate,
along with an NSAID
6) Arm sling were used for two days after three day s in the
postoperative period.
7) Stitches were removed on the 12th – 14th day post-
surgery.
8) BCTSQ assessments were conducted on 12th – 14th day
as well as the 1st, 3rd, 6th, 12th , 24th month post-
operation, and the results were compared before and
after the surgery.
The surgery technique
This surgery aims to minimize the wound size to
approximately 1.5 cm. The surgeon identified the incision
site at the crossing point between Kaplan’s cardinal line
and a line traced along the third web space (Figure 1). In
contrast, the traditional open surgery has larger incisions,
ranging from approximately 2.5 to 5 cm.
A retractor was inserted to separate the transverse
carpal ligament from fat tissue layer. The side of the
retractor was elevated to expose the transverse carpal
ligament, then it was cut with Metzenbaum scissors
(Figure 2 and 3). The tip of the TCL is visually cut under
direct visualization to avoid injury to the median branch
nerve. In addition, the proximal margin was also cut inside
the palmaris longus tendon to prevent injury to the median
nerve of the palmar skin, as this nerve consistently lies on
the radial side of the palmaris longus tendon.
Malisorn, S.
3
Figure 1. locating the incision site and specifying the wound size
Figure 2. A small incision of approximately 1.5 cm.
Figure 3. The subcutaneous tissue is cleared
Modified mini-incision surgery for carpal tunnel syndrome: Technique and clinical outcome
4
Figure 4. The wound after stitching, with a size of 1.5 cm.
The operation started from the administration of
anesthesia to numb the hand and wrist of the patient.
Then, the surgeon proceeded with the incision surgery,
making a 1.5-cm cut on the palm and utilizing surgical
instrument to dissect the carpal ligament and widen the
carpal tunnel. After that, the wound was closed by
stitching (Figure 4), with the wound size approximately
1.5 cm. This is smaller compared to the wound size in the
classic CTS operations, which typically measure 5 cm
(Liawrungrueang and Wongsiri, 2020). The operation
duration was brief, taking only 10 – 15 min, which is
shorter than the classic CTS operation lasting more than
20 min (Liawrungrueang and Wongsiri, 2020). Following
surgery, the patient’s hand was bandaged or splinted for
1 or 2 weeks, in contrast to the 3 weeks of bandaging
required after a classic CTS operation (Hu et al., 2022).
The surgeon monitored the wound’s recovery and the
patient’s palm movement. After the splint was removed,
the patient underwent physical therapy program to
improve hand movement. The follow-up program is
scheduled at the 1st, 3rd, 6th, 12th and 24th month intervals.
3. RESULTS
From Table 1, it is evident that the size of the incision is
only 11.54 mm, significantly smaller compared to the
approximately 5-cm wound in classic long incision. As a
result, patients experienced faster recovery times.
Moreover, they were able to perform wound dressing at
home on a daily basis, as they had been provided with a
fact sheet detailing the procedure. This saves both time
and expenses for the patients, making it more convenient
and worthwhile option.
Table 1. The records of the patients (n = 80)
Factor Before surgery 2 weeks 1 month 3 months 6 months 1 year 2 years
Incision length 0 11.54 11.54 11.54 11.54 11.54 11.54
Pinch strength (kg) 5.26 5.43 6.23 6.99 7.73 8.39 9.04
Gripping strength (kg) 14.77 14.96 16.34 17.69 19.06 20.4 21.87
2-PD 5.94 5.84 4.74 3.98 3.43 2.99 2.74
VAS score 8.73 2.86 1.63 0.65 0.06 0 0
Levine symptom 4.23 3.80 2.86 1.94 1.12 1 1
Levine function 4.32 3.84 2.88 2.88 1.10 1 1
DASH score 81.42 69.43 45 22 3 0 0
Wound pain 0 0.98 0.01 - - 0.01 0
Pillar pain 0 0.94 0.30 0.04 - 0 0
Examining the muscle strength, it was observed that
pinch strength and gripping strength increased after
only 2 weeks post-incision. This improvement allows
the patients to resume normal hand and finger usage.
Over time, both pinch and gripping strength gradually
increased, with nearly 30% improvement observed at 6
months and nearly 50% improvement at 1 year.
The 2-PD test involves placing caliper points at
varying distances on the skin to determines the minimal
distance at which the patient can distinguish whether one
or two points are in contact with the skin. A smaller value
indicates better discrimination ability. It’s noteworthy
that 2-PD showed significant improvement, reaching 3.98
at 3 months post-operation.
The VAS measures the severity of paralysis and pain,
with lower scores indicating less discomfort. It was found
that after 6 months post-operation, the VAS score was
nearly 0, indicating that the patients almost recovered
from baseline numbness and pain.
Malisorn, S.
5
Levine symptom and Levine function scores assess the
hand's ability to perform routine activities, such as pick up
objects or rolling the hand. It was found that, after 6
months post-operation, both Levine symptom and Levine
function scores improved to 1, indicating recovery from
the inability to move the hand and fingers, which is
commonly experienced in CTS.
The DASH score is used to measure the disability in hand
usage, with lower scores indicating better functionality. As
shown in Table 1, after 1 year post-operation, the DASH score
was 0, indicating complete recovery from hand disability.
Regarding wound pain and pillar pain, the goal of the
incision surgery is to alleviate the pain as quick as possible.
As indicated in Table 1, would pain disappeared after one
month post-operation, while pillar pain subsides after 3
months post-operation.
In summary, the outcomes of modified mini-incision
surgery for CTS demonstrate significant improvements
when comparing pre-operation to post-operation
conditions. The operation time was only 15.49 min,
significantly shorter than classical open CTS, and it can be
performed on outpatient (OPD) basis. The incision length
was only 11.54 mm compared to 5 cm of classic open
operation. Moreover, pinch strength, gripping strength,
2-PD, VAS, Levine score, Quick-DASH, wound pain, and
pillar pain showed better and faster rate of recovery post-
operation.
Patient records data were analyzed using SPSS with
ANOVA for variance analysis, with a significant level set
at p < 0.05. After analyzing the data, the data analysis is
shown in Table 2.
Table 2. ANOVA analysis
Variables
R
2
DF
MS
F
Significance
Pinch strength
.908
6
15.238
13.09
.000
*
Grip strength .972 6 84.255 459.453 .000*
2-PD
.787
6
6.423
49.588
.000
*
VAS
.003
4
.781
.933
.450
Levine symptom .159 4 .615 4.737 .002*
Levine function
.145
4
.902
4.337
.002
*
DASH
.082
4
154.848
2.766
.033
*
*p < 0.05
The findings of the analysis revealed significant
improvements after mini-incision surgery for CTS,
compared to pre-operation conditions. Specifically, there
were improvement in pinch strength grip strength, 2-PD,
Levine symptom, Levine function, and DASH. However, the
improvement in VAS was not statistically significant.
4. DISCUSSION
The findings of this study provide valuable insights into the
treatment of the patients suffering from CTS through
newly modified mini-incision surgery. The pinch strength
and grip strength were observed to recover after just 2
weeks post-operation, aligning with the study of studied
the outcomes of the surgery of small incision wrist surgery
by a single senior surgeon on a group of 72 patients (53
female and 19 male patients, 24 – 94 years old; mean age
57.8 ± 15.3 years) during June 2015 and June 2016.
Patients were assessed using Boston CTS questionnaire
pre- and post-mini incision operations. The follow-up
sessions were monitored at 3 months and 1- year post-
operation. The patients were tested on strength
assessment by picking up objects with their thumb tip and
other fingers to show the efficacy of the surgery of 1.5 cm
mini incision wrist operation in both short and long term
recovery (van den Broeke et al., 2019). The findings are in
concordance with the study by Wongsiri et al. (2022),
showing that single incision surgery is popular and
provided better recovery, reduced pillar pain, minimal
scaring, and faster return to routine activities. Moreover,
endoscopic CTR procedures offer advantages such as
smaller incisions (Orak et al., 2016) (typically
1.5 – 2 cm), less scar tenderness and quicker recoveries,
compared to conventional open techniques. However, Klein
et al. (2023) found in his study that complications included
three wound infections and one CTS recurrence, 18 months
after the first operation. Despite this, Michigan hand
outcomes questionnaire scores improved significantly
postoperatively. Similarly, Hu et al. (2022) concluded that
mini-open incision surgery for CTS is a reliable procedure,
offering precise therapeutic effect, minimal surgical trauma,
and high postoperative comfort for patients, leading to
enhanced recovery.
The findings of this study generated new knowledge
and perceptions for treatment of CTS. The main objective
of this mini-incision surgery is to alleviate the pain and
paralysis in patients’ hands, addressing concerns
associated with classic open CTR, such as complications
and significant scaring. The results successfully achieved
these goals by providing symptom relief, facilitating rapid
recovery and minimizing the scar size to be less than 1.5
cm. The procedure could be an alternative method in
treatment of CTS for both academic and clinical purposes.
The use of a 1.5-cm mini-incision is valuable and
acceptable due to it minimal tissue disruption and quick
surgical time. Although early and late complications, such
as bleeding, pain, palmer tenderness, sensitivity to scars,
stiffness, and limited strength may occur, these issues are
generally less severe compared to traditional approaches.
In addition, the procedure had less aesthetic issues and a
shorter recovery period, allowing patients to return to
their daily activities sooner. However, this procedure
requires more experience to ensure optimal outcomes for
patients.
5. CONCLUSION
The study on modified mini-incision surgery for CTS
involving 80 patients found significant improvement in
pinch strength, gripping strength, 2-PD, Levine symptom
Modified mini-incision surgery for carpal tunnel syndrome: Technique and clinical outcome
6
and Levine function conditions post-operation. Patients
showed recovery and good condition just 2 weeks after
undergoing mini-incision surgery.
This research holds educational value as it highlights
that specialized medical instruments are not necessary
for the operation, emphasizing the importance of skilled
and attentive surgeon. Such findings are beneficial for
both study and practice, aiding in the development of
better surgical technique and enhancing patient’s
satisfaction. Moreover, CTS physical therapy can benefit
from this study as by tailoring their rehabilitation plans
from the 2nd week to 6 months post-operation according
to the patients' needs.
The study's conclusions provide patients with more
treatment alternatives for CTS that can relieve the pain,
facilitate fast recovery and result in smaller scar. In
addition it offers valuable insights into improving
medical treatment options for patients with CTS.
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