Relationship between clinical outcomes and nerve conduction studies before and after surgery in patients with carpal tunnel syndrome

doi:10.21203/rs.3.rs-445381/v1

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Relationship between clinical outcomes and nerve conduction studies before and after surgery in patients with carpal tunnel syndrome

https://doi.org/10.21203/rs.3.rs-445381/v1

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Background:

Nerve conduction study (NCS) is the only useful test for objective assessment of carpal tunnel syndrome (CTS). However, the relationship between pre- and postoperative NCS and clinical outcomes was unclear. This study aimed to determine whether pre- and postoperative (6 months) NCS could predict patient-oriented and motor outcomes (6 and 12 months postoperatively) in patients with CTS.

Methods:

Of the 85 patients with CTS, 107 hands were analyzed from March 2011 to March 2020. All patients underwent open carpal tunnel release and were examined using the disabilities of the arm, shoulder and hand (DASH) questionnaire and grip strength (GS) preoperatively and 6 and 12 months. Moreover, NCS was examined preoperatively and 6 months postoperatively. Distal motor latency (DML) and sensory conduction velocity (SCV) were the parameters used for NCS. The correlation coefficient between NCS and DASH or GS was calculated. A receiver operating characteristic curve was utilized to determine the NCS threshold value to predict DASH and GS improvement.

Results:

The average scores of GS preoperatively and 6 and 12 months postoperatively were 21.3, 22.3, and 22.8, respectively. On the other hand, the average scores of DASH preoperatively and 6 and 12 months postoperatively were 28.8, 18.3, and 12.2, respectively. The average NCS scores (DML and SCV) preoperatively/6 months postoperatively were 7.3/5.4 and 27.8/36.7, respectively. Preoperative NCS did not correlate with DASH and GS. Postoperative SCV correlated with the change in grip strength (6–12 months, r = 0.67; 0–12 months, r = 0.60) and DASH (0–12 months, r = 0.77). Moreover, postoperative DML correlated with the change in DASH (6–12 months, r = -0.33; 0–12 months, r = -0.59). The prediction for the improvement of GS/DASH achieved a sensitivity of 50.0%/66.7% and a specificity of 100%/100%, at an SCV cutoff score of 38.5/45.0 or above. The prediction for improvement of GS/DASH achieved a sensitivity of 83.3%/66.7% and a specificity of 100%/66.7% at a DML cutoff score of 4.4/4.4 or below.

Conclusions:

NCS at 6 months postoperatively can be used to predict the improvement of clinical outcome after 6 months postoperatively in patients with CTS.

Orthopedics

Carpal tunnel syndrome

Nerve conduction study

The Disability of the Arm

Shoulder and Hand questionnaire

Clinical outcomes

Carpal tunnel syndrome (CTS) is the most frequent entrapment neuropathy. In the general population, the prevalence of CTS is reported to be 3.8–10% [1, 2], and among people > 50 years old in Japan, it is reported to be 5.1% [3].

Clinical manifestation and physical findings are used to diagnose CTS. Nerve conduction study (NCS) help to diagnose and decide on the treatment plan (conservative treatment or surgery) as well as predict the surgery prognosis for patients with CTS [4]. Furthermore, NCS is the only useful test for objective CTS assessment. NCS and the clinical symptom severity scale were found to be correlated [5]. Moreover, NCS was reported as a predictor of poor outcomes for surgical release [6]. The clinical success of surgical release for CTS occurs at a rate of 75–90%, whereas the recurrence is reported in 4–57% of cases [7]. Thus, predicting clinical outcomes following surgical release is very useful for patients and surgeons.

However, the relationship between clinical outcomes following surgical release and pre-/postoperative NCS is unclear. In addition, few studies have reported a correlation between NCS and motor outcome (e.g., power or pinch grip). This study aimed to examine the prediction improvement in patient-oriented and motor outcomes after operation using preoperative NCS. Furthermore, whether NCS at 6 months postoperatively can predict clinical outcomes at 12 months postoperatively was investigated.

This study analyzed 107 hands of 85 patients with CTS from March 2011 to March 2020. All patients underwent open carpal tunnel release (OCTR), which was performed by two orthopedic hand surgeons. CTS was diagnosed based on the patient’s medical history, thenar muscle atrophy, NCS, and physical examination (e.g., ring-finger splitting, Tinel-like sign, and Phalen’s test). The patients underwent NCS preoperatively and 6 months postoperatively. Grip strength was also measured, and disabilities of the arm, shoulder and hand (DASH) questionnaire was administered before surgery and at the time of outpatient visits at 6 and 12 months postoperatively. Patients with rheumatoid arthritis, artificial dialysis, polyneuropathy, and unavailable NCS waveform at the median nerve were excluded. Finally, 85 hands of 67 patients were included in this study.

This study was approved by the institutional ethics committee at Okayama University Hospital, and informed consent was obtained in the opt-out form on the website.

NCS was conducted using a Neuropack MEB-2300 (Nihon Kohden, Tokyo, Japan). The filter settings were between 20 and 2,000 Hz. Stimulation was performed with a square wave pulse of 0.2-ms duration. The compound muscle action potential, distal motor latency, and motor nerve velocity of the median nerve were recorded via orthodromic stimulation at the wrist, 70-mm proximal to recording electrodes placed over the abductor pollicis brevis muscle. Sensory nerve conduction velocity (SCV) was recorded via antidromic stimulation at the wrist, 140-mm proximal to recording electrodes placed over the proximal phalanx of the middle finger using ring electrodes around the proximal and middle phalanxes of the middle finger. The skin temperature of the hand was maintained between 32°C and 34°C. Grip strength was measured using Smedley hand dynamometer (Igarashi Ikakougyou, Tokyo, Japan).

Grip strength and DASH were used as parameters for objective and patient-oriented assessments, respectively. DASH is a self-administered questionnaire consisting of a disability/symptom (DASH-DS) scale and two optional modules, namely, work and sport/music modules. Moreover, it was widely used for shoulder, hand, elbow, and wrist problem evaluations. The patients were asked to achieve a score of 1–5 on all 30 items, and the scores increased with the increase in disability. The obtained raw score was then converted to a 0–100 scale. The reliability, validity, and responsiveness of the Japanese version of DASH had equivalent evaluation capacity to those of the DASH original versions [8]. Moreover, this study focused on the score of the DASH-DS scale.

The prediction of functional prognosis following surgical release using NCS was explored using the receiver operating characteristic (ROC) curve. A previous study reported the minimal clinically important differences (MCID) for DASH in patients with isolated tendinitis, arthritis, or nerve compression syndromes [9–11]. Therefore, a cutoff score of > 10 for postoperative clinical improvement in DASH was set. Although no study on the MCID of grip strength in patients with CTS was conducted, the MCID of grip strength was estimated to be 2.69–2.44 kg in the healthy group without conditions [12]. Thus, we set a cutoff value of > 2 kg for postoperative clinical grip strength improvement. Moreover, the ROC curve is a commonly used statistical graphical plot to help evaluate the performance of a diagnostic test by plotting the true-positive (sensitivity) rate against the false-positive (1-specificity) rate at various threshold settings. Youden’s criterion was used to select the ideal cutoff point in order to determine the result of the NCS on the ROC curve. The efficacy of the NCS to predict functional prognosis was described using an area under the curve (AUC), sensitivity, specificity, and positive and negative likelihood ratios.

Statistical analyses were conducted using the Bell Curve (Social Survey Research Information Co., Ltd., Shinjuku-ku, Japan) with the significance level set at < 0.05 for all statistical tests. The correlations between the results of preoperative NCS and clinical outcomes that include grip strength and DASH score were assessed via a nonparametric test (Spearman’s correlation).

Participant Characteristics

Table 1 presents the patients’ characteristics. This study included 67 (18 men and 49 women) patients, and 85 hands with CTS were analyzed. The average age was 64.5 years ([SD] = 13.3; range = 34–87), and the average symptom duration was 19.5 months (range = 2–72). No reoperation cases were included in this study.

NCS and Clinical Outcomes (Grip Strength and DASH Score)

The mean pre-/postoperative values at 6 and 12 months for grip strength, DASH, and NCS results are presented in Table 2. Grip strength at 6 and 12 months postoperatively improved by an average of 1.9 kg (0–6 months, 95% confidence interval [CI] = 0.5–3.4) and 3.7 kg (6–12 months, 95% CI = 2.6–4.9), respectively, compared with preoperative measurements. Improvement in grip strength between 6 and 12 months postoperatively was higher compared with that between preoperative and 6 months postoperatively. Grip strength in all patients at 12 months postoperatively improved compared with preoperative measurements. The average DASH scores increased to 11.9 (0–6 months, 95% CI = 3.2–20.6) and 14.1 (6–12 months, 95% CI = 2.1–26.1), respectively. The improvement in DASH score between 6 and 12 months postoperatively was also higher compared with that between preoperatively and 6 months postoperative.

Relationships Between Nerve Conduction Measures and Clinical Outcome

Tables 3 and 4 present the correlation coefficients between pre-/postoperative NCS and change in the grip strength and DASH scores at 6 and 12 months. A no significant correlation was observed between preoperative NCS (SCV) and change in the grip strength scores (0–6 months, r = 0.23; 6–12 months, r = 0.21; 0–12 months, r = 0.27). Moreover, a significant correlation was not observed between preoperative NCS (SCV) and change in DASH scores (0–6 months, r = 0.16; 6–12 months, r = -0.03; 0–12 months, r = 0.26). SCV at 6 months postoperatively had modest and significant correlation with the change in grip strength scores (6–12 months, r = 0.67; 0–12 months, r = 0.60) and DASH score (0–12 months, r = -0.59). NCS (DML) at 6 months postoperatively had no correlation with the change in grip strength scores but modest and significant correlation with the change in DASH scores (6–12 months, r = 0.12; 0–12 months, r = 0.77).

Area Under the Curve in the Receiver Operating Characteristic Curve Analysis

An NCS ROC analysis at 6 months postoperatively (SCV, DML) was conducted to set a cutoff point for predicting grip strength and DASH improvements at 12 months. The SCV results on grip strength demonstrated that the AUC was 0.67 (Fig. 1; 95% CI for AUC, 0.20–1,13). A cutoff value of 38.5 m/s higher for SCV predicts improvement with sensitivity and specificity of 50.0% and 100%, respectively. The DML results indicated that the AUC was 0.91 (Fig. 2; 95% CI for AUC, 0.69–1.15). A cutoff value of 4.4 ms lower for DML predicts improvement with sensitivity and specificity of 83.3% and 100%, respectively. The SCV results on DASH improvement indicated that the AUC was 0.83 (Fig. 3; 95% CI for AUC, 0.48–1,19). A cutoff value of 45.0 m/s lower for SCV predicts improvement with sensitivity and specificity of 66.7% and 100%, respectively. The DML results demonstrated that the AUC was 0.72 (Fig. 4; 95% CI for AUC, 0.33–1,11). A cutoff value of 4.4 ms higher for DML predicts improvement with sensitivity and positive predictive value of 66.7% and 66.7%, respectively.

This retrospective study found a moderate and significant correlation between NCS (SCV) and the change in the grip strength and DASH scores at 6 and 12 months postoperatively. However, a no significant correlation exists between preoperative NCS and clinical outcomes (DASH and grip strength).

The clinical success rate of OCTR was reported to be about 75–90% [13]. Thus, the prediction of postoperative clinical outcomes for patients and surgeon is beneficial. For surgeons, the prediction of the postoperative clinical course is helpful for the selection of patients with poor prognoses as well as explanations for patients and considerations for operation. Several studies were conducted using NCS and patient-reported outcomes (PRO) to predict prognosis following operation [6, 14, 15]. However, there are conflicting reports on the severity of conduction disturbances and surgery outcomes. Heybeli et al. reported that NCS improvements did not correlate with improvement in the self-administered Boston Questionnaire preoperatively and 6 months preoperatively [16]. Itubo et al. also reported that no significant correlation was observed between the preoperative and 3 months postoperative patient-oriented questionnaires and preoperative and 3 months postoperative NCS [15].On the other hand, Bland et al. reported that preoperative NCS correlated with postoperative clinical outcomes and that patients with middle-grade abnormalities achieved better results compared with those with severe abnormalities [6]. This study demonstrated a no significant correlation between preoperative NCS and improvement in clinical outcomes (grip strength and DASH). In addition, the follow-up period was short (within 6 months) in most studies that investigated the correlation between postoperative clinical outcomes and NCS [10, 15, 17]. Furthermore, this study revealed that a significant and modest correlation was observed between NCS (SCV) at 6 months postoperatively and the change in grip strength and DASH at 12 months postoperatively.

Setting a threshold value is useful for determining CTS severity and predicting clinical outcome prognosis following operation. Concerning the threshold value of NCS, Bland et al. reported that distal motor latency to abductor pollicis brevis < 6.5 ms was utilized to evaluate the severity of CTS [18]. In addition, Lo et al. reported that a cutoff value of 6.0 ms or lower for preoperative sensory latency predicts a good outcome (in terms of paresthesia score) with sensitivity/certainty and positive predictive values of 84.6% and 86.8%, respectively, in patients with CTS following endoscopic carpal tunnel syndrome surgery [10]. This study revealed the improvement in grip strength/DASH at 12 months postoperatively in patients with > 38.5 m/s (SCV) and < 4.4 ms (DML)/ > 45.0 m/s (SCV) and < 4.4 ms (DML) at 6 months postoperatively, respectively. To the best of our knowledge, this study is the first to reveal the NCS threshold value to predict PRO and grip strength improvement following surgery. Nolan et al. reported that even at 66 months postoperatively, only 50% of hands demonstrated normal DML [19]. This study demonstrated that 2.4%/13.1% of hands exhibited normal DML/SCV preoperatively, and 57/71% of hands exhibited normal DML/SCV at 6 months postoperatively. Even if the results of NCS at 6 months postoperatively are not normal, the results of this study can help predict improvements in grip strength and DASH. Thus, these results suggested that NCS at 6 months postoperatively can be used not only to evaluate the degree of postoperative NCS improvement but also to predict the improvement in grip strength/DASH at 12 months postoperatively.

This study used grip strength for postoperative clinical motor evaluation. However, there is no consensus as to what method for motor function assessment of patients with CTS following surgical treatment is the most useful [20]. However, grip strength was one of the major objective motor outcomes. Yoshida et al. reported the grip strength-related disability of the upper extremity in patients with CTS [21]. Some other studies also used grip strength as motor outcomes in patients with CTS following surgery [22–26].

Grip strength at 6 months postoperatively decreased in 40% of the patients compared with the preoperative measurement. However, grip strength improved from preoperative levels in all patients who were followed up at 12 months postoperatively. Scar pain or tenderness may influence grip strength weakness at 6 months postoperatively.

The follow-up period in this study is limited to 1 year. Thus, whether NCS at 6 months postoperatively will be related to long-term (more than 1 year) follow-up was not determined. According to the preceding study, the clinical outcomes following surgical release improved up to 6 months postoperatively. The same outcome was obtained after 6 years [27]. De Kleermaeker et al. investigated the long-term outcome after operation in patients with CTS at 8 months postoperatively and the median follow-up at 9 years. They reported that the most important factor associated with the long-term outcome is treatment outcome after about 8 months, and its effect persists after 9 years [13]. Atroshi et al. also reported the clinical outcome at 1 year postoperatively, which was maintained at the final follow-up (11–16 years) [28]. Although the evaluation of outcomes and NCS in this study was conducted within a year, clinical outcome prognosis at 1 year postoperatively may represent a long period of functional prognosis of more than 1 year. Patients with unavailable NCS (MCV and SCV) waveform at the median nerve were excluded. Therefore, the very severe cases with no available waveform were not included in this study. Thus, the result of this study may not be applied to patients with very severe CTS.

This study found that preoperative NCS is not used to predict postoperative clinical outcomes. However, the results of the 6 months postoperative NCS can predict the improvement in the DASH score at 12 months postoperatively.

Ethics approval and consent to participate

This study was approved by the Ethics Committee of Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences in accordance with the Declaration of Helsinki (K2009–006). We have obtained informed consent form with opt-out method from patients. All methods were conducted in accordance with relevant guidelines and regulations.

Consent for publication

Not applicable

Availability of data and materials

The datasets used and analyzed during the current study are available from the corresponding author on reasonable request.

Competing interests

The authors declare no competing interests

Funding

Not applicable

Authors' contributions

Conception and research design: TS, RN, MS, and TO

Data acquisition: MI, TS, YK, YS, MH, and MS

Data analysis and interpretation: RN, TS, MI, MH, MS, and TO

Statistical analyses: RN and MI

Drafting of the article: MI and TS

All other authors contributed to writing and revising the manuscript for scientific content and approved the final version before submission.

Acknowledgments

The authors would like to thank Enago (www.enago.jp) for the English language review.

Atroshi I, Gummesson C, Johnsson R, Ornstein E, Ranstam J, Rosen I: Prevalence of carpal tunnel syndrome in a general population. JAMA 1999, 282(2):153-158.
de Krom MC, Knipschild PG, Kester AD, Thijs CT, Boekkooi PF, Spaans F: Carpal tunnel syndrome: prevalence in the general population. J Clin Epidemiol 1992, 45(4):373-376.
Hashimoto S, Ikegami S, Nishimura H, Uchiyama S, Takahashi J, Kato H: Prevalence and Risk Factors of Carpal Tunnel Syndrome in Japanese Aged 50 to 89 Years. J Hand Surg Asian Pac Vol 2020, 25(3):320-327.
Jordan R, Carter T, Cummins C: A systematic review of the utility of electrodiagnostic testing in carpal tunnel syndrome. Br J Gen Pract 2002, 52(481):670-673.
You H, Simmons Z, Freivalds A, Kothari MJ, Naidu SH: Relationships between clinical symptom severity scales and nerve conduction measures in carpal tunnel syndrome. Muscle Nerve 1999, 22(4):497-501.
Bland JD: Do nerve conduction studies predict the outcome of carpal tunnel decompression? Muscle Nerve 2001, 24(7):935-940.
Louie D, Earp B, Blazar P: Long-term outcomes of carpal tunnel release: a critical review of the literature. Hand (N Y) 2012, 7(3):242-246.
Imaeda T, Toh S, Nakao Y, Nishida J, Hirata H, Ijichi M, Kohri C, Nagano A: Validation of the Japanese Society for Surgery of the Hand version of the Disability of the Arm, Shoulder, and Hand questionnaire. J Orthop Sci 2005, 10(4):353-359.
Franchignoni F, Vercelli S, Giordano A, Sartorio F, Bravini E, Ferriero G: Minimal clinically important difference of the disabilities of the arm, shoulder and hand outcome measure (DASH) and its shortened version (QuickDASH). J Orthop Sports Phys Ther 2014, 44(1):30-39.
Lo YL, Lim SH, Fook-Chong S, Lum SY, Teoh LC, Yong FC: Outcome prediction value of nerve conduction studies for endoscopic carpal tunnel surgery. J Clin Neuromuscul Dis 2012, 13(3):153-158.
Roy JS, MacDermid JC, Woodhouse LJ: Measuring shoulder function: a systematic review of four questionnaires. Arthritis Rheum 2009, 61(5):623-632.
Villafañe JH, Valdes K, Bertozzi L, Negrini S: Minimal Clinically Important Difference of Grip and Pinch Strength in Women With Thumb Carpometacarpal Osteoarthritis When Compared to Healthy Subjects. Rehabil Nurs 2017, 42(3):139-145.
De Kleermaeker F, Meulstee J, Bartels R, Verhagen WIM: Long-term outcome after carpal tunnel release and identification of prognostic factors. Acta Neurochir (Wien) 2019, 161(4):663-671.
Giannini F, Cioni R, Mondelli M, Padua R, Gregori B, D'Amico P, Padua L: A new clinical scale of carpal tunnel syndrome: validation of the measurement and clinical-neurophysiological assessment. Clin Neurophysiol 2002, 113(1):71-77.
Itsubo T, Uchiyama S, Momose T, Yasutomi T, Imaeda T, Kato H: Electrophysiological responsiveness and quality of life (QuickDASH, CTSI) evaluation of surgically treated carpal tunnel syndrome. J Orthop Sci 2009, 14(1):17-23.
Heybeli N, Kutluhan S, Demirci S, Kerman M, Mumcu EF: Assessment of outcome of carpal tunnel syndrome: a comparison of electrophysiological findings and a self-administered Boston questionnaire. J Hand Surg Br 2002, 27(3):259-264.
Conzen C, Conzen M, Rübsamen N, Mikolajczyk R: Predictors of the patient-centered outcomes of surgical carpal tunnel release - a prospective cohort study. BMC Musculoskelet Disord 2016, 17:190.
Bland JD: A neurophysiological grading scale for carpal tunnel syndrome. Muscle Nerve 2000, 23(8):1280-1283.
Nolan WB, 3rd, Alkaitis D, Glickel SZ, Snow S: Results of treatment of severe carpal tunnel syndrome. J Hand Surg Am 1992, 17(6):1020-1023.
Greenslade JR, Mehta RL, Belward P, Warwick DJ: Dash and Boston questionnaire assessment of carpal tunnel syndrome outcome: what is the responsiveness of an outcome questionnaire? J Hand Surg Br 2004, 29(2):159-164.
Yoshida A, Kurimoto S, Iwatsuki K, Saeki M, Nishizuka T, Nakano T, Yoneda H, Onishi T, Yamamoto M, Tatebe M et al: Upper extremity disability is associated with pain intensity and grip strength in women with bilateral idiopathic carpal tunnel syndrome. NeuroRehabilitation 2019, 44(2):199-205.
Gellman H, Kan D, Gee V, Kuschner SH, Botte MJ: Analysis of pinch and grip strength after carpal tunnel release. J Hand Surg Am 1989, 14(5):863-864.
Bednarski M, Zyluk A, Zyluk B: [Changes of grip and pinch strength after carpal tunnel release]. Chir Narzadow Ruchu Ortop Pol 2005, 70(1):21-26.
Young VL, Logan SE, Fernando B, Grasse P, Seaton M, Young AE: Grip strength before and after carpal tunnel decompression. South Med J 1992, 85(9):897-900.
Sayegh ET, Strauch RJ: Open versus endoscopic carpal tunnel release: a meta-analysis of randomized controlled trials. Clin Orthop Relat Res 2015, 473(3):1120-1132.
Singh GK, Srivastava S: Grip strength of occupational workers in relation to carpal tunnel syndrome and individual factors. Int J Occup Saf Ergon 2020, 26(2):296-302.
Pensy RA, Burke FD, Bradley MJ, Dubin NH, Wilgis EF: A 6-year outcome of patients who cancelled carpal tunnel surgery. J Hand Surg Eur Vol 2011, 36(8):642-647.
Atroshi I, Gummesson C, Johnsson R, Ornstein E: Diagnostic properties of nerve conduction tests in population-based carpal tunnel syndrome. BMC Musculoskelet Disord 2003, 4:9.

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Relationship between clinical outcomes and nerve conduction studies before and after surgery in patients with carpal tunnel syndrome

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