Magnetic Resonance Imaging Acutely After Endosopic Carpal Tunnel Release
Anil Akoon, MD, Joel C. Klena, MD; Benjamin R Wagner, MD
Geisinger Medical Center, Danville, PA
Introduction: Persistent or recurrent symptoms after carpal tunnel release (CTR) represent a diagnostic challenge in deciding whether to pursue possible revision surgery. In the peri-operative period following open carpal tunnel release (OCTR), magnetic resonance imaging (MRI) has been proposed as a viable diagnostic test to evaluate complete release of the flexor retinaculum. Previous studies have demonstrated an ability to detect complete release of the flexor retinaculum at 3 months following OCTR. In contrast, MRI 3 months following endoscopic carpal tunnel release (ECTR) failed to demonstrate a discrete defect in the flexor retinaculum. MRI has been shown to have some utility in evaluating median nerve morphology following ECTR. The primary objective of this study was to determine if MRI can conclusively demonstrate a complete release of the flexor retinaculum immediately after ECTR and 6 weeks following ECTR. The secondary objective was to evaluate, in comparison to pre-operative baseline MRI studies, the morphologic changes to the median nerve within one hour of ECTR and at 6 weeks following ECTR.
Methods: We enrolled 10 consecutive patients with carpal tunnel syndrome confirmed by both clinical exam and EMG study. Patients received a preoperative MRI followed by repeat MRI scans within one hour post-operatively and at 6 weeks post-operatively. Images were analyzed to determine median nerve morphologic changes and to determine if a discrete gap or separation of the flexor retinaculum could be appreciated.
Results: 10 patients were enrolled. 9 patients completed all imaging studies and were included in the study. All patients achieved complete relief of their preoperative symptoms by their 6 weeks post-operative visit. At one hour post-operatively all patients demonstrated a distinct gap and separation of the flexor retinaculum consistent with a complete release. By 6 weeks, a clear gap or separation in the flexor retinaculum was not clearly visible on MRI. Median nerve width-to-height ratios did not change by a statistically significant amount. Median nerve cross-sectional area at the level of the pisiform increased from baseline by 37.5% immediately postoperatively, declining to 28.0% at 6 weeks postoperatively.
Conclusions: MRI of patients immediately after ECTR demonstrates a discrete gap in the flexor retinaculum overlying the median nerve, consistent with a complete release. In contrast, complete release cannot be verified by MRI at 6 weeks postoperatively. While morphologic changes can be noted in median nerve immediately and 6 weeks after ECTR, MRI after ECTR may be of limited clinical value.
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