Efficacy of high frequency ultrasound in postoperative evaluation of carpal tunnel syndrome treatment

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Polish Ultrasound Society (Polskie Towarzystwo Ultrasonograficzne)

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VOLUME 16 , ISSUE 64 (March 2016) > List of articles

Efficacy of high frequency ultrasound in postoperative evaluation of carpal tunnel syndrome treatment

Katarzyna Kapuścińska * / Andrzej Urbanik

Keywords : median nerve, carpal tunnel syndrome, entrapment neuropathy, ultrasound

Citation Information : Journal of Ultrasonography. Volume 16, Issue 64, Pages 16-24, DOI: https://doi.org/10.15557/JoU.2016.0002

License : (CC BY-NC-ND 3.0)

Received Date : 23-June-2015 / Accepted: 27-August-2015 / Published Online: 29-March-2016

ARTICLE

ABSTRACT

Aim

The aim of the study is to assess the usefulness of high frequency ultrasound in the postoperative evaluation of CTS treatment efficacy.

Material and methods

Sixty-two patients (50 women and 12 men aged 28–70, mean age 55.2) underwent surgical treatment of CTS. Ultrasound examinations of the wrist in all carpal tunnel sufferers were performed 3 months after the procedure with the use of a high frequency broadband linear array transducer (6–18 MHz, using 18 MHz band) of MyLab 70/Esaote. On the basis of the collected data, the author has performed multiple analyses to confirm the usefulness of ultrasound imaging for postoperative evaluation of CTS treatment efficacy.

Results

Among all 62 patients, 3 months after surgical median nerve decompression: in 40 patients, CTS symptoms subsided completely, and sonographic evaluation did not show median nerve entrapment signs; in 9 patients, CTS symptoms persisted or exacerbated, and ultrasound proved nerve compression revealing preserved flexor retinaculum fibers; in 13 patients, scar tissue symptoms occurred, and in 5 of them CTS did not subside completely (although ultrasound showed no signs of compression).

Conclusions

Ultrasound imaging with the use of a high frequency transducer is a valuable diagnostic tool for postoperative assessment of CTS treatment efficacy.

Cel pracy

Celem pracy jest określenie przydatności badania USG z wykorzystaniem głowicy wysokiej częstotliwości w pooperacyjnej ocenie skuteczności zastosowanego leczenia.

Materiał i metoda

Materiał pracy stanowi grupa 62 pacjentów (50 kobiet i 12 mężczyzn w wieku od 28 do 70 lat; średnia wieku 55,2 roku) operowanych z powodu ZKN. U wszystkich wykonano badania USG 3 miesiące po zabiegu głowicą liniową szerokopasmową wysokiej częstotliwości (6–18 MHz, z zastosowaniem pasma 18 MHz), aparatem MyLab 70 firmy Esaote. Na podstawie uzyskanych danych przeprowadzono analizę mającą na celu potwierdzenie przydatności badania USG w pooperacyjnej ocenie skuteczności zastosowanego leczenia.

Wyniki

Wśród 62 osób, u których wykonano badanie kontrolne USG po zabiegu odbarczenia nerwu pośrodkowego na poziomie nadgarstka: u 40 osób objawy ZKN ustąpiły całkowicie, a w badaniu USG nie wykazano cech ucisku nerwu pośrodkowego; u 9 osób objawy ZKN przetrwały bądź nasiliły się, a w badaniu USG wykazano ucisk nerwu przez zachowane włókna troczka; u 13 osób pojawiły się objawy ze strony blizny, w tym u 5 dodatkowo nie ustąpiły całkowicie objawy ZKN (przy braku ucisku w badaniu USG).

Wnioski

Badanie USG z wykorzystaniem głowicy wysokiej częstotliwości jest wartościową metodą diagnostyki obrazowej w pooperacyjnej ocenie skuteczności zastosowanego leczenia.

Graphical ABSTRACT

Introduction

The basic treatment of carpal tunnel syndrome (CTS) is an operation which consists in the division of the flexor retinaculum and release of pressure on the entrapped median nerve(1). Sometimes, however, patients do not experience any improvement after the procedure and even report exacerbation of symptoms.

Compared with numerous publications on the usefulness of ultrasound imaging in diagnosing CTS and selecting patients eligible for a surgery, there are relatively few papers on its value in the evaluation of postoperative CTS treatment efficacy(26). That is why the authors attempted to evaluate certain parameters that are essential in postoperative median nerve assessment.

The publication was prepared on the basis of a doctoral dissertation entitled: High-frequency ultrasound in carpal tunnel syndrome: assessment of patient eligibility for surgical treatment and postoperative treatment efficacy by Katarzyna Kapuścińska, MD, PhD (defended on October, 8 2014 in Kraków, Poland).

Aim

The aim of the paper was to determine the usefulness of high frequency ultrasound in postoperative evaluation of CTS treatment efficacy.

Material and methods

The study involved 62 patients (50 women and 12 men aged 28–70, mean age 55.2) referred to the Ultrasound Laboratory of the Department of Medical Imaging of the University Hospital in Krakow from the Neurosurgery Outpatient Clinic of the University Hospital in Krakow, Poland. Three months post-treatment, all patients under-went a follow-up ultrasound examination.

US scans were performed with the use of a broadband linear array transducer (6–18 MHz, using 18 MHz band) of MyLab 70/Esaote.

The following parameters were assessed 3 months after surgery:

  • cross-sectional area of the median nerve in the widest place at the level of the wrist (in mm2);

  • nerve echogenicity and echotexture;

  • evidence of hypervascularization of the median nerve at the wrist level using the Power Doppler (PD) technique;

  • evidence of compression, deformation or absence of compression of the median nerve at the wrist level;

  • movability of the median nerve at the wrist level.

Based on information delivered by US examinations, a correlation analysis was conducted involving signs of median nerve hypervascularization in a PD scan and nerve compression in a US scan.

US presentation of the median nerve and the carpal tunnel with incompletely divided flexor retinaculum

In a situation when no improvement is reported due to incomplete division of the flexor retinaculum, a US examination presents preserved flexor retinaculum fibers as well as persisting “notch sign” or “inverted notch sign.”

Early examinations enable incompletely divided fibers to be easily differentiated from scars since they present different echogenicity. Scars are initially hypoechoic and amorphous whilst flexor retinaculum fibers are hyperechoic and present a typical course in the ligament line (Fig. 1 and 2). The differentiation becomes more difficult, and sometimes even impossible, as fibrous remodeling of scar tissue progresses. No improvement (symptoms do not subside) after surgery can therefore be an indication for conducting a US examination in the first 1–3 months post-treatment.

Fig. 1

Transverse view of the carpal tunnel 3 months after surgical median nerve decompression: asterisks mark visible preserved fibers of the flexor retinaculum and an ellipse encircles the entrapped median nerve

JoU-2016-0002-g001.jpg
Fig. 2

Longitudinal view of the median nerve 3 months after surgical median nerve decompression: red asterisks mark preserved fibers of the flexor retinaculum, yellow asterisks indicate scar tissue between divided parts of the flexor retinaculum and blue arrows point to the “notch” and “inverted notch” sign

JoU-2016-0002-g002.jpg

US imaging enables the visualization of fixation or damage to the nerve or its branches.

Based on information delivered by a follow-up US examination and based on symptoms reported by patients, a correlation analysis was conducted involving the presence of CTS symptoms typically reported after median nerve decompression and:

  • the difference in cross-sectional median nerve areas in the widest place pre- and post-treatment;

  • evidence of hypervascularization of the median nerve in a PD examination;

  • presence of median nerve compression in a follow-up US examination post-treatment;

  • movability of the median nerve at the wrist level after surgery.

The following tests were applied in the statistical analysis: Student's t test for independent samples, single-factor analysis of variance (ANOVA), a post-hoc multiple comparison Tukey test and the χ2 test of independence.

Results with the significance level lower than or equal to 0.05 were deemed statistically significant (p ≤ 0.05). The statistical calculations were conducted with the use of a Statistica 10 PL and StatsDirect 2.7.9.

Results

Of 62 patients examined after surgery, symptoms subsided completely in 48 cases (77.4%), incomplete symptom resolution was reported by 5 patients (8.1%) and no improvement or exacerbation of complaints – by 9 patients (14.5%).

The average cross-sectional area of the median nerve in the widest place was 16.6 mm2 (9–29 mm2).

All 62 patients (100%) presented lower echogenicity of the median nerve at the wrist level.

In 14 patients (22.58%), the echotexture of the median nerve was preserved whereas in 48 patients (77.42%), it was blurred.

Of 62 patients, 10 (16.1%) presented evidence of hypervascularization of the median nerve at the carpal level. No increased vascularity was observed in the remaining 52 patients (83.9%).

Ultrasound showed median nerve entrapment in 9 of 62 patents (14.52%).

In 53 of 62 patients (85.48%), no signs of median nerve entrapment at the carpal tunnel were observed.

In 44 of 62 patients (71%), the movability of the median nerve at the wrist level was normal.

In 9 of 62 patients (14.5%), the movability of the median nerve at the wrist level was reduced.

In 9 of 62 patients (14.5%), there was no movability, or there was minimum movability of the median nerve against scars or flexor digitorum tendons.

Figure 3 presents a division of the main group into subgroups based on the manner of patient conduction after surgical median nerve release.

Fig. 3

Division of the main group into subgroups based on the manner of patient conduction after surgical median nerve release

JoU-2016-0002-g003.jpg

It was found that there is a statistically significant correlation (p < 0.001) between median nerve compression visible in a follow-up US examination and median nerve hypervascularization. All patients with evidence of nerve entrapment after surgery also presented enhanced vascularity, whereas 100% of patients without evidence of entrapment did not demonstrate median nerve hypervascularization.

All patients with persisting or exacerbated symptoms presented with enhanced nerve vascularization, whilst none of the patients in whom symptoms subsided completely showed any signs of vessels in a PD scan (p < 0.001).

The patients who presented nerve entrapment in a US examination reported persisting or exacerbated symptoms. However, nearly all patients in whom no compression was observed upon a US examination, reported complete resolution of symptoms (92.16%; p < 0.001).

Moreover, another analysis tested the existence of correlations between the movability of the median nerve at the level of the wrist, seen in a US examination, and the presence of symptoms typical of CTS (p < 0.001). The symptoms subsided in 97.73% of patients with restored movability and persisted in 77.78% of patients who presented no nerve movability.

Discussion

Compared with numerous publications on the usefulness of ultrasound imaging in diagnosing CTS and selecting patients eligible for a surgery, there are relatively few papers on its value in the evaluation of postoperative CTS treatment efficacy(714).

According to various reports published so far(714), follow-up US examinations are performed at various times after surgical CTS treatment (from 3 week to 8 months). They are conducted with transducers of the frequently not greater than 12 MHz. Currently, ultrasound probes of even higher frequencies are available (up to 22 MHz). They enable more accurate assessment of slight nerve branches, such as the palmar branch of the median nerve(15).

Parameters that are most commonly evaluated in postoperative ultrasound examinations of the carpal tunnel are the cross-sectional area of the median nerve at its widest site and the comparison between these values obtained pre- and post-operatively. Most authors(79, 1114) have confirmed that the separation of the flexor retinaculum and median nerve release results in a reduction of median nerve edema. In most cases, a US examination does not show a return of a completely normal image of the median nerve. The cross-sectional values are usually greater than 10 mm2 (which is the most commonly applied cut-off point for median nerve edema and the diagnosis of median nerve pathology at the carpal tunnel).

Only Lee et al.(10), in a postoperative follow-up US examination of the carpal tunnel, observed an increase in the median nerve cross-sectional area at the level of the hook of the hamate bone and pisiform bone by approximately 2 mm2 (0.9–3 mm2; p = 0.01).

In the author's own material, the values of the cross-sectional area decreased and correlated with the resolution of symptoms (p = 0.026). In the group with complete resolution of symptoms, the author found that the cross-sectional area of the median nerve decreased by approximately 1.48 mm2 (p = 0.002). These results are similar to those presented in most previous studies.

In the group of patients who reported no improvement (or even exacerbation of symptoms) and the preserved flexor retinaculum fibers were observed, the cross-sectional area of the median nerve increased by approximately 2.22 mm2 (p = 0.002). This study has also demonstrated that the greatest reduction in the cross-sectional area occurred in patients with complete resolution of symptoms.

Most quoted papers emphasize the value and usefulness of US imaging in the postoperative evaluation of the median nerve in CTS(711, 14). Only Naranjo has found that ultrasound imaging is of limited value(12), but in the opinion of the author of the present study, the final conclusions raise doubts. Naranjo et al. analyzed the median nerve cross-sectional area at the widest site (i.e. at tunnel inlet) and at tunnel outlet as well as the nerve flattening ratio. In patients with noted improvement, the cross-sectional area of the nerve at the widest site decreased from 14.2 to 13.3 mm2. In those with no or little improvement, however, a decrease of this value was also noted (from 12.5 to 11.6 mm2). There were no significant changes in the cross-sectional value at the tunnel outlet or flattening ratio.

The limitations of the study carried out by Naranjo et al. include the lack of assessment of: nerve movability prior to and after surgery, nerve vascularity and possible postoperative scar, fiber continuity, restoration of bundle echotexture and no correlation analysis between individual parameters. In the author's own opinion, the assessment of retinaculum division and nerve movability against the scar are very significant data. If the symptoms of median nerve damage persist, US findings direct the further diagnostic process and indicate the necessity of median nerve assessment along its entire course as well as brachial plexus evaluation (including spinal nerve roots at the level of the spine).

Smidt et al., based on a study in which decreased cross-sectional area was observed in six of ten patients with no improvement after surgery, concluded that median nerve US may serve as a tool for selecting patients eligible for re-operation(13). The author's own research has shown that the lack of median nerve compression signs and its normal movability indicate that re-operation is not necessary. No clinical improvement or exacerbation of changes in a nerve image as well as the identification of persistent compression at the level of preserved fibers is an indication for re-operation.

High usefulness of ultrasound imaging (both in selecting patients for surgery and in postoperative evaluation) is emphasized by Toros(16). Postoperative US can be helpful in detecting the cause of the lack of improvement and facilitate the decision-making regarding re-operation. One of the most common causes of surgical treatment inefficacy in CTS is incomplete separation of the retinaculum(17). It is well-visible in a US image and, therefore, some surgeons use intraoperative ultrasonography to ensure that the flexor retinaculum has been divided completely(18).

Another parameter assessed in certain studies is the cross-sectional area of the median nerve at the tunnel outlet (10, 11). The results of these studies have confirmed the limited value of this criterion.

In some studies, groups of patients with no reported improvement in spite of surgical treatment were distinguished(9, 1214). It is surprising that the presence of preserved flexor retinaculum fibers, which could be a potential cause of ineffective treatment, was not assessed in any of these studies. Their authors were mostly focused on the image of the median nerve at the wrist level. Only one study(14) presents a detained analysis of the causes of this inefficacy.

The author, in her own study, noted the lack of improvement or exacerbation of CTS symptoms in nine patients. In a postoperative follow-up US examination, all of them presented preserved retinaculum fibers which compressed the median nerve. A surgical procedure confirmed the diagnosis.

The ability of US to assess median nerve movability against adjacent structures in dynamic examination is an advantage of this modality in postoperative assessment. In a study of Yoshii et al., conducted with the use of cadaver dmaterial, it was found that nerve and tendon movability increases after flexor retinaculum separation(19).

None of the quoted studies presents a degree of improvement of median nerve movability at the carpal tunnel after CTS surgical treatment. In the author's own material, median nerve movability was decreased or absent prior to the procedure in all patients. After surgery, it improved in all patients in whom clinical signs subsided.

The assessment of median nerve vascularity with the Power Doppler before surgery is the most sensitive parameter that indicates entrapment neuropathy. None of the quoted studies presents the assessment of median nerve vascularity after surgery.

In the author's own study, nerve hypervascularization was observed in a PD scan in all patients presenting with persisting or exacerbated symptoms after CTS surgery (9 of 62 patients). All patients with complete resolution of symptoms presented normal nerve vascularity (i.e. no hypervascularity was detected in a PD scan). These results suggest that the presence of hypervascularity may indicate that treatment has been ineffective. This, however, requires further investigation since, at least in theory, hypervascularity can result from an ongoing repair process.

Conclusions

Ultrasound imaging with the use of a high frequency transducer is a valuable imaging modality for postoperative assessment of CTS treatment efficacy.

Conflict of interest

Authors do not report any financial or personal connections with other persons or organizations, which might negatively affect the contents of this publication and/or claim authorship rights to this publication.

References


  1. Żyluk A,Puchalski P,Historia naturalna zespołu kanału nadgarstka – przegląd piśmiennictwa Pol Orthop Traumatol 2010 75 261 266
  2. Campagna R,Pessis E,Feydy A,Guerini H,Le Viet D,Corlobé P,MRI assessment of recurrent carpal tunnel syndrome after open surgical release of the median nerve AJR Am J Roentgenol 2009 193 644 650
    [PUBMED] [CROSSREF]
  3. Mosier BA,Hughes TB,Recurrent carpal tunnel syndrome Hand Clin 2013 29 427 434
    [PUBMED] [CROSSREF]
  4. Kerasnoudis A,Which ultrasound method has the upper hand in the follow-up of the patients with recurrent carpal tunnel syndrome? Ann Rheum Dis 2013 72 e11
    [PUBMED] [CROSSREF]
  5. Klauser AS,Faschingbauer R,Bauer T,Wick MC,Gabl M,Arora R,Entrapment neuropathies II: carpal tunnel syndrome Semin Musculoskelet Radiol 2010 14 487 500
    [PUBMED] [CROSSREF]
  6. Wilson D,Allen GM,Imaging of the carpal tunnel Semin Musculoskelet Radiol 2012 16 137 145
    [PUBMED] [CROSSREF]
  7. Abicalaf CA,de Barros N,Sernik RA,Pimentel BF,Braga-Baiak A,Braga L,Ultrasound evaluation of patients with carpal tunnel syndrome before and after endoscopic release of the transverse carpal ligament Clin Radiol 2007 62 891 896
    [PUBMED] [CROSSREF]
  8. Colak A,Kutlay M,Pekkafali Z,Saraçoglu M,Demircan N,Simşek H,Use of sonography in carpal tunnel syndrome surgery. A prospective study Neurol Med Chir (Tokyo) 2007 47 109 115
    [PUBMED] [CROSSREF]
  9. Kim JY,Yoon JS,Kim SJ,Won SJ,Jeong JS,Carpal tunnel syndrome: clinical, electrophysiological, and ultrasonographic ratio after surgery Muscle Nerve 2012 45 183 188
    [PUBMED] [CROSSREF]
  10. Lee CH,Kim TK,Yoon ES,Dhong ES,Postoperative morpho-logic analysis of carpal tunnel syndrome using high-resolution ultrasonography Ann Plast Surg 2005 54 143 146
    [PUBMED] [CROSSREF]
  11. Mondelli M,Filippou G,Gallo A,Frediani B,Diagnostic utility of ultrasonography versus nerve conduction studies in mild carpal tunnel syndrome Arthritis Rheum 2008 59 357 366
    [PUBMED] [CROSSREF]
  12. Naranjo A,Ojeda S,Rúa-Figueroa I,Garcia-Duque O,Fernández-Palacios J,Carmona L,Limited value of ultra-sound assessment in patients with poor outcome after carpal tunnel release surgery Scand J Rheumatol 2010 39 409 412
    [PUBMED] [CROSSREF]
  13. Smidt M.H,Visser L.H,Carpal tunnel syndrome: clinical and sonographic follow-up after surgery Muscle Nerve 2008 38 987 991
    [PUBMED] [CROSSREF]
  14. Vögelin E,Nüesch E,Jüni P,Reichenbach S,Eser P,Ziswiler HR,Sonographic follow-up of patients with carpal tunnel syndrome undergoing surgical or nonsurgical treatment: prospective cohort study J Hand Surg Am 2010 35 1401 1409
    [PUBMED] [CROSSREF]
  15. Tagliafico A,Pugliese F,Bianchi S,Bodner G,Padua L,Rubino M,High-resolution sonography of the palmar cutaneous branch of the median nerve AJR Am J Roentgenol 2008 191 107 114
    [PUBMED] [CROSSREF]
  16. Toros T,Commentary on Zyluk et al. No correlation between sonographic and electrophysiological parameters in carpal tunnel syndrome; and Yalçın et al. Ultrasound diagnosis of ulnar neuropathy: comparison of symptomatic and asymptomatic nerve thickness J Hand Surg Eur Vol 2014 39 172 174
    [PUBMED] [CROSSREF]
  17. Tan TC,Yeo CJ,Smith EW,High definition ultrasound as diagnostic adjunct for incomplete carpal tunnel release Hand Surg 2011 16 289 294
    [PUBMED] [CROSSREF]
  18. Nakamichi K,Tachibana S,Yamamoto S,Ida M,Percutaneous carpal tunnel release compared with mini-open release using ultrasonographic guidance for both techniques J Hand Surg Am 2010 35 437 445
    [PUBMED] [CROSSREF]
  19. Yoshii Y,Zhao C,Henderson J,Zhao KD,Zobitz ME,An KN,Effects of carpal tunnel release on the relative motion of tendon, nerve, and subsynovial connective tissue in a human cadaver model Clin Biomech (Bristol Avon) 2008 23 1121 1127
    [CROSSREF]
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FIGURES & TABLES

Fig. 1

Transverse view of the carpal tunnel 3 months after surgical median nerve decompression: asterisks mark visible preserved fibers of the flexor retinaculum and an ellipse encircles the entrapped median nerve

Full Size   |   Slide (.pptx)

Fig. 2

Longitudinal view of the median nerve 3 months after surgical median nerve decompression: red asterisks mark preserved fibers of the flexor retinaculum, yellow asterisks indicate scar tissue between divided parts of the flexor retinaculum and blue arrows point to the “notch” and “inverted notch” sign

Full Size   |   Slide (.pptx)

Fig. 3

Division of the main group into subgroups based on the manner of patient conduction after surgical median nerve release

Full Size   |   Slide (.pptx)

REFERENCES

  1. Żyluk A,Puchalski P,Historia naturalna zespołu kanału nadgarstka – przegląd piśmiennictwa Pol Orthop Traumatol 2010 75 261 266
  2. Campagna R,Pessis E,Feydy A,Guerini H,Le Viet D,Corlobé P,MRI assessment of recurrent carpal tunnel syndrome after open surgical release of the median nerve AJR Am J Roentgenol 2009 193 644 650
    [PUBMED] [CROSSREF]
  3. Mosier BA,Hughes TB,Recurrent carpal tunnel syndrome Hand Clin 2013 29 427 434
    [PUBMED] [CROSSREF]
  4. Kerasnoudis A,Which ultrasound method has the upper hand in the follow-up of the patients with recurrent carpal tunnel syndrome? Ann Rheum Dis 2013 72 e11
    [PUBMED] [CROSSREF]
  5. Klauser AS,Faschingbauer R,Bauer T,Wick MC,Gabl M,Arora R,Entrapment neuropathies II: carpal tunnel syndrome Semin Musculoskelet Radiol 2010 14 487 500
    [PUBMED] [CROSSREF]
  6. Wilson D,Allen GM,Imaging of the carpal tunnel Semin Musculoskelet Radiol 2012 16 137 145
    [PUBMED] [CROSSREF]
  7. Abicalaf CA,de Barros N,Sernik RA,Pimentel BF,Braga-Baiak A,Braga L,Ultrasound evaluation of patients with carpal tunnel syndrome before and after endoscopic release of the transverse carpal ligament Clin Radiol 2007 62 891 896
    [PUBMED] [CROSSREF]
  8. Colak A,Kutlay M,Pekkafali Z,Saraçoglu M,Demircan N,Simşek H,Use of sonography in carpal tunnel syndrome surgery. A prospective study Neurol Med Chir (Tokyo) 2007 47 109 115
    [PUBMED] [CROSSREF]
  9. Kim JY,Yoon JS,Kim SJ,Won SJ,Jeong JS,Carpal tunnel syndrome: clinical, electrophysiological, and ultrasonographic ratio after surgery Muscle Nerve 2012 45 183 188
    [PUBMED] [CROSSREF]
  10. Lee CH,Kim TK,Yoon ES,Dhong ES,Postoperative morpho-logic analysis of carpal tunnel syndrome using high-resolution ultrasonography Ann Plast Surg 2005 54 143 146
    [PUBMED] [CROSSREF]
  11. Mondelli M,Filippou G,Gallo A,Frediani B,Diagnostic utility of ultrasonography versus nerve conduction studies in mild carpal tunnel syndrome Arthritis Rheum 2008 59 357 366
    [PUBMED] [CROSSREF]
  12. Naranjo A,Ojeda S,Rúa-Figueroa I,Garcia-Duque O,Fernández-Palacios J,Carmona L,Limited value of ultra-sound assessment in patients with poor outcome after carpal tunnel release surgery Scand J Rheumatol 2010 39 409 412
    [PUBMED] [CROSSREF]
  13. Smidt M.H,Visser L.H,Carpal tunnel syndrome: clinical and sonographic follow-up after surgery Muscle Nerve 2008 38 987 991
    [PUBMED] [CROSSREF]
  14. Vögelin E,Nüesch E,Jüni P,Reichenbach S,Eser P,Ziswiler HR,Sonographic follow-up of patients with carpal tunnel syndrome undergoing surgical or nonsurgical treatment: prospective cohort study J Hand Surg Am 2010 35 1401 1409
    [PUBMED] [CROSSREF]
  15. Tagliafico A,Pugliese F,Bianchi S,Bodner G,Padua L,Rubino M,High-resolution sonography of the palmar cutaneous branch of the median nerve AJR Am J Roentgenol 2008 191 107 114
    [PUBMED] [CROSSREF]
  16. Toros T,Commentary on Zyluk et al. No correlation between sonographic and electrophysiological parameters in carpal tunnel syndrome; and Yalçın et al. Ultrasound diagnosis of ulnar neuropathy: comparison of symptomatic and asymptomatic nerve thickness J Hand Surg Eur Vol 2014 39 172 174
    [PUBMED] [CROSSREF]
  17. Tan TC,Yeo CJ,Smith EW,High definition ultrasound as diagnostic adjunct for incomplete carpal tunnel release Hand Surg 2011 16 289 294
    [PUBMED] [CROSSREF]
  18. Nakamichi K,Tachibana S,Yamamoto S,Ida M,Percutaneous carpal tunnel release compared with mini-open release using ultrasonographic guidance for both techniques J Hand Surg Am 2010 35 437 445
    [PUBMED] [CROSSREF]
  19. Yoshii Y,Zhao C,Henderson J,Zhao KD,Zobitz ME,An KN,Effects of carpal tunnel release on the relative motion of tendon, nerve, and subsynovial connective tissue in a human cadaver model Clin Biomech (Bristol Avon) 2008 23 1121 1127
    [CROSSREF]

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