Predicting Clinical Outcome After Surgical Treatment in Patients With Carpal Tunnel Syndrome

  • M.C. Jansen
    Correspondence
    Corresponding author: M.C. Jansen, MSc, Department of Plastic, Reconstructive and Hand Surgery, Erasmus Medical Center, s-Gravendijkwal 230, Room EE 15.89, 3015 CE Rotterdam, the Netherlands.
    Affiliations
    Department of Plastic, Reconstructive and Hand Surgery, Rotterdam, the Netherlands

    Department of Rehabilitation Medicine, Erasmus Medical Center, Rotterdam, the Netherlands
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  • S. Evers
    Affiliations
    Department of Plastic, Reconstructive and Hand Surgery, Rotterdam, the Netherlands

    Department of Rehabilitation Medicine, Erasmus Medical Center, Rotterdam, the Netherlands
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  • H.P. Slijper
    Affiliations
    Department of Plastic, Reconstructive and Hand Surgery, Rotterdam, the Netherlands

    Department of Plastic, Reconstructive and Hand Surgery, Xpert Clinic, Rotterdam, the Netherlands
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  • K.P. de Haas
    Affiliations
    Department of Plastic, Reconstructive and Hand Surgery, Xpert Clinic, Rotterdam, the Netherlands
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  • X. Smit
    Affiliations
    Department of Plastic, Reconstructive and Hand Surgery, Rotterdam, the Netherlands

    Department of Plastic, Reconstructive and Hand Surgery, Xpert Clinic, Rotterdam, the Netherlands
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  • S.E. Hovius
    Affiliations
    Department of Plastic, Reconstructive and Hand Surgery, Rotterdam, the Netherlands

    Department of Plastic, Reconstructive and Hand Surgery, Xpert Clinic, Rotterdam, the Netherlands
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  • R.W. Selles
    Affiliations
    Department of Plastic, Reconstructive and Hand Surgery, Rotterdam, the Netherlands

    Department of Rehabilitation Medicine, Erasmus Medical Center, Rotterdam, the Netherlands
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      Purpose

      Carpal tunnel release (CTR) is typically offered to symptomatic patients with electrophysiological abnormalities when night orthoses no longer prevent waking with numbness and preferably before there is any static numbness, weakness, or atrophy. The ability to predict the amount of symptom relief after CTR could be beneficial for managing patient expectations and, therefore, improve treatment satisfaction. Therefore, the aim of this study was to identify predictors for symptom relief after CTR and to determine their contribution to symptom relief at 6 months after surgery.

      Methods

      A total of 1,049 patients who underwent CTR between 2011 and 2015 at 1 of 11 Xpert Clinics in the Netherlands were asked to complete online questionnaires at intake and 3 and 6 months after surgery. Patient demographics, comorbidities, and baseline scores were considered potential predictors for the amount of symptom relief on the Boston Carpal Tunnel Questionnaire (BCTQ) score, which was the primary outcome measure.

      Results

      A low score on the BCTQ at intake, a codiagnosis of a trigger finger, ulnar nerve neuropathy, trapeziometacarpal joint arthrosis, and instability or arthrosis of the wrist were associated with a smaller improvement in the BCTQ domains after a CTR at 6 months after surgery and accounted for 35% to 42% of the variance on the BCTQ domains in our multivariable regression models.

      Conclusions

      In this study, we showed that clinical severity of carpal tunnel syndrome at intake is the most important factor in estimating symptom relief after surgical treatment. Furthermore, this study contributes to a more precise understanding of the capabilities of CTR in relieving symptoms for different subgroups of patients. Results of our study can be used to manage patient expectation on symptom relief from CTR.

      Type of study/level of evidence

      Prognostic II.

      Key words

      The Journal of Hand Surgery will contain at least 2 clinically relevant articles selected by the editor to be offered for CME in each issue. For CME credit, the participant must read the articles in print or online and correctly answer all related questions through an online examination. The questions on the test are designed to make the reader think and will occasionally require the reader to go back and scrutinize the article for details.
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      Disclosures for this Article

      Editors

      Jennifer Moriatis Wolf, MD, has no relevant conflicts of interest to disclose.

      Authors

      All authors of this journal-based CME activity have no relevant conflicts of interest to disclose. In the printed or PDF version of this article, author affiliations can be found at the bottom of the first page.

      Planners

      Jennifer Moriatis Wolf, MD, has no relevant conflicts of interest to disclose. The editorial and education staff involved with this journal-based CME activity has no relevant conflicts of interest to disclose.

      Learning Objectives

      Upon completion of this CME activity, the learner should achieve an understanding of:
      • Those factors predictive of outcome after carpal tunnel release
      • Which factors have the greatest impact on how patients function postsurgical carpal tunnel release
      Deadline: Each examination purchased in 2018 must be completed by January 31, 2019, to be eligible for CME. A certificate will be issued upon completion of the activity. Estimated time to complete each JHS CME activity is up to one hour.
      Copyright © 2018 by the American Society for Surgery of the Hand. All rights reserved.
      It has already been shown that surgical treatment for carpal tunnel syndrome (CTS) is generally more effective than nonsurgical treatment (such as orthosis fabrication or corticosteroid injections) in terms of recurrence rate, improvement of symptoms, and hand function.
      • Gerritsen A.A.
      • de Vet H.C.
      • Scholten R.J.
      • Bertelsmann F.W.
      • de Krom M.C.
      • Bouter L.M.
      Splinting vs surgery in the treatment of carpal tunnel syndrome: a randomized controlled trial.
      • Jarvik J.G.
      • Comstock B.A.
      • Kliot M.
      • et al.
      Surgery versus non-surgical therapy for carpal tunnel syndrome: a randomised parallel-group trial.
      Although the main goals of carpal tunnel release (CTR) are to resolve symptoms of a sensory disturbance and prevent further progression of disease, some patients continue to have symptoms after surgery.
      • Katz J.N.
      • Keller R.B.
      • Simmons B.P.
      • et al.
      Maine Carpal Tunnel Study: outcomes of operative and nonoperative therapy for carpal tunnel syndrome in a community-based cohort.
      • Nancollas M.
      • Peimer C.
      • Wheeler D.
      • Sherwin F.
      Long-termresults of carpal tunnel release.
      Although clinical trials can establish whether a treatment is effective on average, further research is needed to improve the predictability of outcomes after surgical treatment for CTS in individual patients.
      The ability to predict symptom relief after CTR is desirable because it could help manage patient expectation of the treatment and, therefore, improve self-reported postoperative well-being.
      • Henn III, R.F.
      • Kang L.
      • Tashjian R.Z.
      • Green A.
      Patients’ preoperative expectations predict the outcome of rotator cuff repair.
      • Iversen M.D.
      • Daltroy L.H.
      • Fossel A.H.
      • Katz J.N.
      The prognostic importance of patient pre-operative expectations of surgery for lumbar spinal stenosis.
      Because patients present with different symptoms and levels of median nerve conduction abnormalities as measured by electrodiagnostic testing,
      • Stevens J.C.
      • Smith B.E.
      • Weaver A.L.
      • Bosch E.P.
      • Deen H.G.
      • Wilkens J.A.
      Symptoms of 100 patients with electromyographically verified carpal tunnel syndrome.
      it is at present difficult to predict the outcome after CTR for individual patients with CTS.
      Therefore, the aim of this study was to identify those factors that can predict the amount of symptom relief after surgical treatment and to determine the contribution of these factors in predicting the amount of symptom relief for individual patients. By identifying these predictive factors, our goal is to create a risk model to quantify the amount of symptom relief when patients are treated surgically for CTS.

      Materials and Methods

      Study sample

      All patients with CTS who were offered surgical treatment between November 2011 and November 2015 in a hand clinic (Xpert Clinic, The Netherlands) were asked to complete online questionnaires in our Web-based outcome registration system at intake and at 3 and 6 months after surgery. Xpert Clinic is a group of specialized clinics in 11 locations throughout the Netherlands with, at the time of the study, 12 European board-certified hand surgeons performing procedures.
      We included patients who received a CTR and had filled-in the Boston Carpal Tunnel Questionnaire
      • Levine D.W.
      • Simmons B.P.
      • Koris M.J.
      • et al.
      A self-administered questionnaire for the assessment of severity of symptoms and functional status in carpal tunnel syndrome.
      (BCTQ) as part of routine clinical care at intake and at 6 months after surgery. We excluded patients with previous surgical treatment for CTS on the ipsilateral hand. In patients who underwent bilateral CTR, only the first treated hand was included. For this study, we decided not to exclude patients with specific comorbidities or concomitant surgeries because these factors could be potential predictors of symptom relief after CTR. We adhered to the STrengthening the Reporting of OBservational studies in Epidemiology (STROBE) guidelines. Furthermore, the study was approved by the local institutional review board and written informed consent was obtained from all patients.

      Treatment

      All patients underwent an open CTR. Subsequently, all patients received standard postoperative care, which consisted of 3 to 5 days of bandages and a sling around the operated hand. After this, standardized hand therapy, consisting of nerve and tendon gliding exercises, was started by a hand therapist. Patients were seen at our outpatient clinic within 14 days after surgery to monitor progress and to remove sutures.

      Measurements

      Baseline characteristics

      We collected sociodemographic data before surgery from all patients including age, sex, hand dominance, duration of symptoms, body mass index, occupation, and smoking and alcohol usage. Patients were diagnosed with CTS by a physician based on a combination of symptoms, physical examination findings, and electrodiagnostic testing. In addition, information on the presence of comorbidities was retrieved from the medical record. Comorbidities were diagnosed by a physician based on the medical history, physical examination, radiographic imaging, or electrodiagnostic testing. We defined that comorbidities and concomitant procedures needed a minimum of 10 cases, within the sample, to be included in the analyses. Moreover, the comorbidities ulnocarpal impingement, scaphoid nonunion collapse wrist, pisotriquetral arthrosis, distal radioulnar arthrosis, and scapholunate dissociation were grouped under the variable “instability and/or arthrosis of the wrist.” Cubital tunnel syndrome, Guyon canal syndrome, and unspecified ulnar nerve neuropathy were also grouped under a separate “ulnar nerve neuropathy” variable.

      Primary outcome measurement: BCTQ

      To assess the symptom intensity of CTS, patients filled out the BCTQ (Dutch Language Version
      • Smits F.V.M.
      • Ottenhof M.
      • Feitz R.
      • Kreulen M.
      Dutch translation of the ‘Boston Carpal Tunnel Questionnaire’ for the evaluation of carpal tunnel syndrome (BCTQ-DLV) [in Dutch].
      : 1, no complaints; 5, maximum complaints possible) at baseline and 3 and 6 months after surgery. The BCTQ covers 2 domains; the symptom severity scale (SSS) and the functional status scale (FSS), including 11 and 8 items, respectively.

      Complications

      Complications were registered during a 6-month period after surgery. These included infections treated with antibiotics, wound dehiscence, iatrogenic median nerve injury, and postoperative bleeding.

      Statistical analysis

      A proportion of the data from the included patients had missing values owing to nonresponse. At baseline, there was a proportion of nonresponse for the following variables: body mass index (33% missing), duration of symptoms (18% missing), smoking status (33% missing), and alcohol intake (33% missing). Nonresponse for all other baseline characteristics was 0% to 3%. Regarding the outcome measurements, there was a nonresponse of 0%, 8%, and 0% for the BCTQ at baseline, 3 months, and 6 months, respectively. Because information on the presence of comorbidities and concomitant surgery was retrieved from the medical record for every patient, we had no missing data for these variables. However, it should be noted that some information might not have been well documented within the medical records.
      Because of the proportion of missing values and to check for selection bias in our inclusion criteria, a nonresponder analysis for baseline variables was performed (Table E1, available on the Journal’s Web site at www.jhandsurg.org). This analysis was done by conducting analyses of variance, chi-square statistics, and unpaired t tests. After Bonferroni correction for multiple testing, we concluded that the missing data were independent of both observable and unobservable variables and could, therefore, be classified as missing completely at random.
      • Schafer J.L.
      • Graham J.W.
      Missing data: our view of the state of the art.
      Therefore, Multiple Imputation
      • Royston P.
      Multiple imputation of missing values.
      was used to impute the missing values at baseline and follow-up 10 times. The collected data were used as auxiliary variables in our imputation model. Auxiliary variables are variables that are not imputed during the imputation process but are used to impute the missing values.
      Bivariable analyses were done to identify potential predictive baseline factors for clinical outcome, defined as the difference between scores at baseline and at 6 months after surgery on the SSS score, the FSS score, and the total BCTQ score. From these bivariable analyses, all associated variables with a significance of P less than .20 were considered for a backward multivariable regression analysis. Subsequently, variables with a pooled significance level of less than .05 were used in the final multivariable models.
      Because the convergent pattern of the postoperative courses of the different subgroups of patients presented in Figure 1 might be partly explained by regression to the mean, a correction for regression to the mean was done to adjust the postoperative scores of the SSS, FSS, and BCTQ-total by using the method suggested by Kelly and Price.
      • Kelly C.
      • Price T.D.
      Correcting for regression to the mean in behavior and ecology.
      Figure thumbnail gr1
      Figure 1A Postoperative course of the BCTQ-SSS, B BCTQ-FSS, and C the BCTQ-Total score of subgroups of patients grouped on their score at intake, corrected for regression to the mean. The error bars represent the standard error of the mean.

      Results

      Study sample and baseline characteristics

      Between November 2011 and November 2015, 2,748 patients underwent a primary CTR. After exclusions, the cohort consisted of 1,049 patients (Fig. 2). Baseline characteristics of the included patients can be found in Table 1.
      Table 1Baseline Characteristics of the Study Population
      Baseline CharacteristicsStudy Population (n = 1,049)
      Categorical Variables(%)
      Sex
       Female72
      Operated hand
       Right61
      Smoking48
      Alcohol usage58
      Comorbidities
       Trigger finger15
       Trapeziometacarpal joint arthrosis7
       Diabetes6
       History of wrist trauma3
       De Quervain tenosynovitis3
       Dupuytren disease2
       Rheumatic diseases2
       Guyon canal syndrome1
       CTR2
       Unspecified ulnar nerve neuropathy1
       Radial tunnel syndrome1
       Instability and/or arthrosis of the wrist1
      Concomitant procedures
       Trigger finger release10
       CTR2
       De Quervain release1
       Guyon tunnel release1
      Workload
       No work37
       Light physical work24
       Moderate physical work24
       Heavy physical work15
      Dominance
       Left8
       Right89
       Codominant3
      Continuous variablesMean ± SD
      Age (y)53.9 ± 12.1
      BMI (kg/m2)27.6 + 5.0
      BCTQ (1–5)
       SSS2.87 ± 0.6
       FSS2.48 ± 0.8
       Total2.68 ± 0.6
      Duration of complaints (mo)34.9 ± 61.3
      BMI, body mass index.

      Surgical outcome

      Figure 3 shows a significant mean improvement on all primary and secondary outcomes at 6 months after surgery and shows the distributions of these outcomes at intake and 6 months after surgery. After 6 months, 985 patients (93.8%) showed improvement on the BCTQ-total score with a mean improvement of 1.15 points (± 0.63). However, 64 patients showed a deterioration on the BCTQ-total score at 6 months with a mean increase of 0.31 (± 0.26). Furthermore, there were 21 complications in 20 patients, consisting of 14 infections and 6 wound dehiscences. One patient had an infection and a wound dehiscence. All 20 patients with a complication did not show deterioration on the BCTQ-total score at 6 months after surgery.
      Figure thumbnail gr3
      Figure 3Pre- and postoperative distributions of the A BCTQ-FSS, B the BCTQ-SSS, and C the BCTQ-total score within the study population at intake and 6 months after surgery, with the y axis representing the frequency of the different scores situating on the x axis. Values in the right upper corner represent t test P values and the deltas for the mean differences between the intake and 6 month postoperative score with the corresponding SD.

      Predictive factors

      Several potential predictive factors were identified from our bivariable analyses (Table 2). Subsequently, these potential predictive factors were used in creating our multivariable models (Table 3). The multivariable models could explain 42%, 38%, and 35% of the variance in the model for the change score of the BCTQ-SSS, BCTQ-FSS, and BCTQ-total score, respectively, at 6 months. Generally, a more severe score at intake was predictive for a greater improvement on the score at 6 months for the BCTQ-SSS score, whereas the presence of trapeziometacarpal joint arthrosis, a trigger finger, ulnar nerve neuropathy on the ipsilateral hand and a high BCTQ-FSS score at intake were predictive for a smaller improvement on the BCTQ-SSS score at 6 months after surgery. Likewise, a more severe score at intake and a more physically demanding job were predictive for greater improvement at 6 months on the BCTQ-FSS score, whereas the presence of trapeziometacarpal joint arthrosis, a trigger finger, and instability or arthrosis of the ipsilateral hand were predictive for a smaller improvement on the BCTQ-FSS score at 6 months after surgery. For the BCTQ-total score at 6 months, a more severe score at intake for the BCTQ-SSS and the BCTQ-FSS were predictive for a greater improvement, whereas the presence of a trigger finger or trapeziometacarpal joint arthrosis was predictive for a smaller improvement compared with the score at intake.
      Table 2Bivariable Analyses With Correlation Coefficients Representing the Relation Between Baseline Variables and Surgical Effect on the BCTQ Domains
      Empty cells indicate a nonsignificant correlation at P level > .20.
      Baseline Variables6 Mo After Surgery
      Δ SSS ScoreΔ FSS ScoreΔ Total BCTQ Score
      Sex
       Female0.065
      Association found to be significant at P level < .05.
      0.106
      Association found to be significant at P level < .01.
      0.094
      Association found to be significant at P level < .01.
      Age0.117
      Association found to be significant at P level < .01.
      0.085
      Association found to be significant at P level < .01.
      Dominance operated hand
       Yes/no–0.058
      Association eligible for multivariable analysis at P level < .20.
      Duration of complaints in months0.075
      Association found to be significant at P level < .05.
      0.046
      Association eligible for multivariable analysis at P level < .20.
      0.066
      Association found to be significant at P level < .05.
      Workload
       Unemployed (reference)–0.043
      Association eligible for multivariable analysis at P level < .20.
      –0.062
      Association eligible for multivariable analysis at P level < .20.
       Light physical labor
       Moderate physical labor
       Severe physical labor
      BMI
      Smoking
       Yes/no–0.082
      Association found to be significant at P level < .05.
      –0.093
      Association found to be significant at P level < .05.
      Alcohol usage
       Yes/no0.062
      Association eligible for multivariable analysis at P level < .20.
      0.060
      Association eligible for multivariable analysis at P level < .20.
      0.067
      Association eligible for multivariable analysis at P level < .20.
      Comorbidities
       Trigger finger
      Yes/no0.098
      Association found to be significant at P level < .01.
      0.044
      Association eligible for multivariable analysis at P level < .20.
      0.078
      Association found to be significant at P level < .05.
       Trapeziometacarpal joint arthrosis
      Yes/no0.069
      Association found to be significant at P level < .05.
      0.070
      Association found to be significant at P level < .05.
      0.076
      Association found to be significant at P level < .05.
       Diabetes
      Yes/no
       History of wrist trauma
      Yes/no0.075
      Association found to be significant at P level < .05.
      0.048
      Association eligible for multivariable analysis at P level < .20.
       De Quervain tenosynovitis
      Yes/no
       Dupuytren contracture
      Yes/no
       Rheumatoid arthritis
      Yes/no0.045
      Association eligible for multivariable analysis at P level < .20.
       Radial tunnel syndrome
      Yes/no
       Instability and/or arthrosis of the wrist
      Yes/no0.042
      Association eligible for multivariable analysis at P level < .20.
      Ulnar nerve neuropathy
       Yes/no–0.041
      Association eligible for multivariable analysis at P level < .20.
       CTS
      Yes/no
       Guyon canal syndrome
      Yes/no
      Concomitant procedures
       Trigger finger release
      Yes/no0.062
      Association found to be significant at P level < .05.
      0.042
      Association eligible for multivariable analysis at P level < .20.
      0.057
      Association eligible for multivariable analysis at P level < .20.
       CTR
      Yes/no
       De Quervain release
      Yes/no
       Guyon tunnel release
      Yes/no
      BCTQ
       Total–0.519
      Association found to be significant at P level < .01.
      –0.554
      Association found to be significant at P level < .01.
      –0.583
      Association found to be significant at P level < .01.
       SSS–0.634
      Association found to be significant at P level < .01.
      –0.374
      Association found to be significant at P level < .01.
      –0.553
      Association found to be significant at P level < .01.
       FSS–0.302
      Association found to be significant at P level < .01.
      –0.605
      Association found to be significant at P level < .01.
      –0.500
      Association found to be significant at P level < .01.
      Empty cells indicate a nonsignificant correlation at P level > .20.
      Association found to be significant at P level < .05.
      Association found to be significant at P level < .01.
      § Association eligible for multivariable analysis at P level < .20.
      Table 3Multivariable Regression Analysis With Beta Coefficients Representing the Relation Between Baseline Variables and the Surgical Effect on the BCTQ Domains
      Empty cells indicate a nonsignificant correlation at P level > .05.
      Baseline Variables6 Mo After Surgery
      Δ SSS Score

      β (SE)
      Δ FSS Score

      β (SE)
      Δ Total BCTQ Score

      β (SE)
      R2 (% explained variance) for the complete model423835
      Constant0.834
      Association found to be significant at P level < .01.
      (0.084)
      0.750
      Association found to be significant at P level < .01.
      (0.070)
      0.756
      Association found to be significant at P level < .01.
      (0.084)
      Sex
       Female
      Age (y)
      Dominance operated hand
       Yes/no
      Duration of complaints (mo)
      Workload
       Unemployed (reference)–0.057
      Association found to be significant at P level < .01.
      (0.018)
       Light physical labor
       Moderate physical labor
       Severe physical labor
      BMI
      Smoking
       Yes/no
      Alcohol usage
       Yes/no
      Comorbidities
       Trigger finger
      Yes/no0.155
      Association found to be significant at P level < .01.
      (0.050)
      0.111
      Association found to be significant at P level < .05.
      (0.053)
      0.133
      Association found to be significant at P level < .01.
      (0.049)
       Trapeziometacarpal joint arthrosis
      Yes/no0.151
      Association found to be significant at P level < .05.
      (0.071)
      0.174
      Association found to be significant at P level < .05.
      (0.075)
      0.163
      Association found to be significant at P level < .05.
      (0.069)
       Diabetes
      Yes/no
       History of wrist trauma
      Yes/no
       De Quervain tenosynovitis
      Yes/no
       Dupuytren disease
      Yes/no
       Rheumatoid arthritis
      Yes/no
       Radial tunnel syndrome
      Yes/no
       Instability and/or arthrosis of the wrist
      Yes/no0.552
      Association found to be significant at P level < .05.
      (0.235)
      Ulnar nerve neuropathy
       Yes/no0.182
      Association found to be significant at P level < .05.
      (0.085)
       Guyon canal syndrome
      Yes/no
       Cubital tunnel syndrome
      Yes/no
      Concomitant procedures
       Trigger finger release
      Yes/no
       Cubital tunnel release
      Yes/no
       De Quervain release
      Yes/no
       Guyon tunnel release
      Yes/no
      BCTQ
       Total
       SSS–0.864
      Association found to be significant at P level < .01.
      (0.036)
      –0.432
      Association found to be significant at P level < .01.
      (0.035)
       FSS0.137
      Association found to be significant at P level < .01.
      (0.031)
      –0.636
      Association found to be significant at P level < .01.
      (0.025)
      –0.247
      Association found to be significant at P level < .01.
      (0.030)
      BMI, body mass index; SE, standard error.
      Empty cells indicate a nonsignificant correlation at P level > .05.
      Association found to be significant at P level < .01.
      Association found to be significant at P level < .05.
      Figure 1 further illustrates that the clinical severity of CTS at intake is the most important factor in estimating the effect of surgical treatment. This figure shows the effect of surgery on the BCTQ scores after 3 and 6 months for subgroups of patients defined by their score at intake, corrected for regression to the mean. This figure also indicates that patients with severe CTS symptoms at baseline have approximately the same level of residual symptoms at 6 months after surgery as those with less severe CTS symptoms at baseline.

      Discussion

      In this study, we showed that clinical severity of CTS at intake is the most important factor in estimating the symptom relief after surgical treatment because patients with more severe CTS at intake experienced greater effect of CTR on the BCTQ. Although the amount of symptom relief after CTR is higher for patients with more severe CTS, these patients might also have more residual symptoms. However, Figure 1 shows that the amount of residual symptoms at 6 months after surgery in patients with severe CTS symptoms at baseline is close to the amount of residual symptoms at 6 months after surgery of patients with less severe CTS symptoms at baseline. By using multivariable models, we could explain 37% to 41% of the variation in treatment effect on the BCTQ. This means that the majority of the variation between the outcomes of different patients cannot be explained by the variables included in the present study.
      This study confirms that surgical treatment of CTS is, on average, effective for improving function and symptom intensity.
      • Gerritsen A.A.
      • de Vet H.C.
      • Scholten R.J.
      • Bertelsmann F.W.
      • de Krom M.C.
      • Bouter L.M.
      Splinting vs surgery in the treatment of carpal tunnel syndrome: a randomized controlled trial.
      • Brown R.A.
      • Gelberman R.H.
      • Seiler III, J.
      • et al.
      Carpal tunnel release. A prospective, randomized assessment of open and endoscopic methods.
      • Hui A.
      • Wong S.
      • Leung C.
      • et al.
      A randomized controlled trial of surgery vs steroid injection for carpal tunnel syndrome.
      However, our study also shows that mean improvement might not be a relevant measure for individual patients because of the wide variation in symptom relief between individual patients. Our study also shows that the BCTQ score might be influenced by the presence of other, unrelated conditions. The presence of comorbidities might, therefore, not be predictive for the response to CTR because patients with these comorbidities might also have been responding to the BCTQ for their persistent symptoms related to these comorbidities. This could mean that the BCTQ is an insensitive outcome measure because it does not only reflect median nerve dysfunction. Therefore, patients with multiple comorbidities of the hand should also be clearly counseled that they have symptoms related to more than 1 etiology and that CTR is meant to address only the symptoms related to the median nerve compression. This information could be of importance in adjusting the individual patient’s expectations of surgical treatment for CTS.
      • Kadzielski J.
      • Malhotra L.R.
      • Zurakowski D.
      • Lee S.G.
      • Jupiter J.B.
      • Ring D.
      Evaluation of preoperative expectations and patient satisfaction after carpal tunnel release.
      Although we tested 28 variables, only a few variables were found to have predictive value for the effect of surgery on the BCTQ-score. At present, few and relatively small studies have performed similar analyses. Conzen et al
      • Conzen C.
      • Conzen M.
      • Rübsamen N.
      • Mikolajczyk R.
      Predictors of the patient-centered outcomes of surgical carpal tunnel release—a prospective cohort study.
      found similar results in the way that the amount of improvement after CTR is largely independent of sociodemographic characteristics. Moreover, our study is in line with that of Burke et al
      • Burke F.D.
      • Wilgis E.F.
      • Dubin N.H.
      • Bradley M.J.
      • Sinha S.
      Relationship between the duration and severity of symptoms and the outcome of carpal tunnel surgery.
      who found that patients with more severe symptoms, as determined by patient self-assessment at intake, have a greater improvement in the symptom severity and hand function after surgery. However, this finding might also be explained as a characteristic of the imperfect measurement scales of the BCTQ.
      The lack of predictive value of most of our evaluated baseline characteristics, as well as the approximately 60% unexplained variance, may indicate that other variables that were not examined play a role. For example, multiple studies have shown that mental health plays an important role when evaluating treatment effect on self-reported upper extremity health.
      • Ring D.
      • Kadzielski J.
      • Fabian L.
      • Zurakowski D.
      • Malhotra L.R.
      • Jupiter J.B.
      Self-reported upper extremity health status correlates with depression.
      • Katz J.N.
      • Losina E.
      • Amick III, B.C.
      • Fossel A.H.
      • Bessette L.
      • Keller R.B.
      Predictors of outcomes of carpal tunnel release.
      In addition, preoperative expectations influence postoperative patient-reported outcomes and could be of importance when predicting success of CTR in an individual.
      • Flood A.B.
      • Lorence D.P.
      • Ding J.
      • McPherson K.
      • Black N.A.
      The role of expectations in patients’ reports of post-operative outcomes and improvement following therapy.
      Furthermore, it could be that the BCTQ shows a relatively small change because of other comorbidities that are not treated by the CTR influencing its score. Therefore, patient expectations of the effect of CTR on other comorbidities of the hand should be addressed before surgery. Future research should focus on the role of nonphysical factors in predicting treatment outcome after CTR as well as on developing more valid and sensitive outcome measures of CTS.
      Several limitations of our study should be considered. First, some comorbidities present within our study sample could have been missed by the physician and, therefore, remained undiagnosed. Second, because the completion of our questionnaires in daily clinical practice was voluntary, we have a high amount of missing data. Because of the amount of missing data, we could not conduct a complete case analysis and only identified 40% of our CTS patients as eligible for inclusion. Because of this missing data, our study sample might not be a valid representation of our CTS patient population and imputing the data could then give misleading results.
      • Sterne J.A.
      • White I.R.
      • Carlin J.B.
      • et al.
      Multiple imputation for missing data in epidemiological and clinical research: potential and pitfalls.
      However, a nonresponder analysis indicated that the missing data pattern was at random and that there were no differences between included and excluded patients at baseline. We therefore assumed that our study sample is a valid representation of our CTS patient population. Third, our study lacked information on nerve conduction study results. At Xpert Clinic, all patients receive electrodiagnostic testing as a part of routine practice for CTS. However, the outcomes of electrodiagnostic testing were not reported in a consistent and standardized format. Therefore, this information was of insufficient quality to be included in our analyses. Although the predictive value of electrodiagnostic measurements in predicting surgical outcome after CTR is heavily debated in the literature and does not seem to be of additional value in predicting surgical outcome,
      • Concannon M.J.
      • Gainor B.
      • Petroski G.F.
      • Puckett C.L.
      The predictive value of electrodiagnostic studies in carpal tunnel syndrome.
      • Glowacki K.A.
      • Breen C.J.
      • Sachar K.
      • Weiss A.P.
      Electrodiagnostic testing and carpal tunnel release outcome.
      • Braun R.M.
      • Jackson W.J.
      Electrical studies as a prognostic factor in the surgical treatment of carpal tunnel syndrome.
      information on median nerve conduction might have improved the explained variance of our model. Fourth, information on chronic pain and centralized pain conditions such as fibromyalgia and complex regional pain syndrome was also not accessible in a consistent and accessible format. Fifth, CTR procedures in our cohort were performed by specialists highly trained in hand surgery and that may lead to a larger effect on the BCTQ than procedures performed by other medical specialists. However, because CTR is considered a relative simple procedure, this is not likely to influence the generalizability of the results of our study. Sixth, the BCTQ might not be able to distinguish between symptoms that are permanent, such as static numbness, from those that are correctable, such as intermittent numbness. Also, caution should be advised for patients who have asymptomatic median nerve entrapment. In addition, although Figure 1 is corrected for regression to the mean, the postoperative course of the BCTQ scores of subgroups of patients might be influenced by ceiling and floor effects of the BCTQ.
      In conclusion, this study contributes to a more precise understanding of the capabilities of surgical treatment in relieving symptoms and improving function for different subgroups of patients as well as the management of expectations. However, a significant proportion of the variability in symptom relief remains unexplained. Furthermore, our study shows that the BCTQ might be an insensitive outcome measure because it may not only reflect median nerve dysfunction. We suggest that future research on predictive factors focus more on nonphysical factors such as mental health, preoperative expectations, and disease awareness. This way, patients at risk for a low postoperative satisfaction can be identified and targeted for expectation management. In addition, future research should focus on developing more valid measures so that the evaluation of outcomes in CTS patients is less influenced by unrelated comorbidities of the hand.

      Acknowledgments

      We want to thank the patients and physicians that participated in this study.

      Appendix

      Table E1Nonresponder Analysis for Completing the BCTQ With the Variables Representing Patient Characteristics at Intake
      Baseline CharacteristicsNonresponder Analyses (n = 2,748)
      Responders at Intake and 6 Mo (n = 1,049)Responders at Intake and Nonresponders at 6 Mo (n = 942)Nonresponders at Intake and Responders at 6 Mo (n = 93)Nonresponders at Intake and 6 Mo (n = 664)P Value
      Categorical variables%%%%
      Sex
       Female727468740.53
      Operated hand
       Right615968550.02
      Indicates statistical significance (P < .05).
      Smoking182613260.02
      Indicates statistical significance (P < .05).
      Alcohol usage565652590.44
      Workload
       No work363436330.29
       Light physical work24242025
       Moderate physical work24262527
       Heavy physical work16161915
      Dominance
       Left88127.09
       Right89898289
       Codominant2264
      Continuous VariablesResponders at Intake and 6 Mo (n = 1,049)Responders at Intake and Nonresponders at 6 Mo (n = 942)Nonresponders at Intake and Responders at 6 Mo (n = 93)Nonresponders at Intake and 6 Mo (n = 664)P Value
      Mean ± SDMean ± SDMean ± SDMean ± SD
      Age (y)53.9 ± 12.155.3 ± 14.255.6 ± 12.453.9 ± 16.0.14
      BMI (kg/m2)27.5 ± 4.827.0 ± 5.026.6 ± 4.327.3 ± 5.6.25
      BCTQ (1–5)
       SSS2.87 ± 0.62.87 ± 0.7.91
       FSS2.49 ± 0.82.48 ± 0.8.69
       Total2.68 ± 0.62.68 ± 0.7.80
      Duration of complaints (mo)30.6 ± 78.135.1 ± 58.927.6 ± 37.031.9 ± 50.6.49
      Indicates statistical significance (P < .05).

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