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Sueleyman Tas, Frank Staub, Thomas Dombert, Gerhard Marquardt, Christian Senft, Volker Seifert and Stephan Duetzmann

OBJECT

Carpal tunnel syndrome causes increased cross-sectional area (CSA) of the median nerve, which can be assessed by high-definition ultrasonography. It is unclear today, however, whether high-definition ultrasonography may play a role in the postoperative period. This prospective study aimed to determine the natural history of the morphology of the median nerve at the carpal tunnel after surgical decompression assessed by high-definition ultrasonography.

METHODS

Between October and December 2014, patients with suspected carpal tunnel syndrome who were referred to the authors’ center for peripheral neurosurgery were prospectively enrolled and underwent pre- and postoperative (3 months) high-definition ultrasonography, electrophysiology, and clinical testing.

RESULTS

Eighty-one patients were enrolled in the study, and 100% were clinically better at the 3-month follow-up. The mean CSA decreased from 14.7 ± 4.9 mm2 to 12.4 ± 3.4 mm2 (mean ± SD, p < 0.0001). The mean distal motor latency decreased from 6.6 ± 2.4 msec to 4.8 ± 1.0 msec (mean ± SD, p < 0.0001). Ninety-eight percent of patients who were available for electrodiagnostic follow-up showed an improvement of the distal motor latency; only 80% had a reduction in the CSA.

CONCLUSIONS

The authors present the second-largest series of patients with sonographic follow-up after surgical decompression of the carpal tunnel reported in the literature so far. This study, which showed a decrease in size of the median nerve after surgical decompression, suggests that the preoperative increase in median nerve CSA at the carpal tunnel may be due to compression and that enlargement of the median nerve is (partially) reversible.

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Blake N. Staub, Renaud Lafage, Han Jo Kim, Christopher I. Shaffrey, Gregory M. Mundis Jr., Richard Hostin, Douglas Burton, Lawrence Lenke, Munish C. Gupta, Christopher Ames, Eric Klineberg, Shay Bess, Frank Schwab, Virginie Lafage and the International Spine Study Group

OBJECTIVE

Numerous studies have attempted to delineate the normative value for T1S−CL (T1 slope minus cervical lordosis) as a marker for both cervical deformity and a goal for correction similar to how PI-LL (pelvic incidence–lumbar lordosis) mismatch informs decision making in thoracolumbar adult spinal deformity (ASD). The goal of this study was to define the relationship between T1 slope (T1S) and cervical lordosis (CL).

METHODS

This is a retrospective review of a prospective database. Surgical ASD cases were initially analyzed. Analysis across the sagittal parameters was performed. Linear regression analysis based on T1S was used to provide a clinically applicable equation to predict CL. Findings were validated using the postoperative alignment of the ASD patients. Further validation was then performed using a second, normative database. The range of normal alignment associated with horizontal gaze was derived from a multilinear regression on data from asymptomatic patients.

RESULTS

A total of 103 patients (mean age 54.7 years) were included. Analysis revealed a strong correlation between T1S and C0–7 lordosis (r = 0.886), C2–7 lordosis (r = 0.815), and C0–2 lordosis (r = 0.732). There was no significant correlation between T1S and T1S−CL. Linear regression analysis revealed that T1S−CL assumed a constant value of 16.5° (R2 = 0.664, standard error 2°). These findings were validated on the postoperative imaging (mean absolute error [MAE] 5.9°). The equation was then applied to the normative database (MAE 6.7° controlling for McGregor slope [MGS] between −5° and 15°). A multilinear regression between C2–7, T1S, and MGS demonstrated a range of T1S−CL between 14.5° and 26.5° was necessary to maintain horizontal gaze.

CONCLUSIONS

Normative CL can be predicted via the formula CL = T1S − 16.5° ± 2°. This implies a threshold of deformity and aids in providing a goal for surgical correction. Just as pelvic incidence (PI) can be used to determine the ideal LL, T1S can be used to predict ideal CL. This formula also implies that a kyphotic cervical alignment is to be expected for individuals with a T1S < 16.5°.