The scratch collapse test in the diagnosis of compression of the median nerve in the proximal forearm

Percutaneous Ultrasound-Guided Release of the Lacertus Fibrosus for Median Nerve Entrapment at the Elbow

PURPOSE

The aim of this technical note is to present a microinvasive percutaneous ultrasound-guided release of the lacertus fibrosus of the biceps brachii for pronator syndrome, i.e., entrapment of the median nerve at the elbow.

METHODS

Fifteen consecutive patients were included. Patients showed isolated pronator syndrome including pain plus reduced strength of specific median nerve innervated muscles. The release was performed in a non-operating interventional room under wide-awake local anesthesia no tourniquet (WALANT). It was conducted superficial to the pronator teres with in-plane ultrasound guidance. The recovery of strength was first assessed peroperatively, and then systematic visits at postoperative weeks 1 and 4 included assessments of both strength and pain.

RESULTS

Procedures were comfortably completed with no immediate surgical or anesthetic complication. Muscle strength returned immediately and persisted at postoperative visits. Visual analog scores for pain reduced from 6.2 to 2.5 and 0.6 at weeks 1 and 4, respectively. All working patients were able to perform in their professional activities at week 1. The millimetric skin incision healed with no hypertrophic scar tissue. A small hematoma occurred at week 1 and resorbed spontaneously. No other delayed complication was observed. The procedure appeared effective with improved invasiveness compared to existing techniques. Real-time monitoring with ultrasound may improve the safety. The technique could be regarded as a new ultrasound-guided alternative to surgery.

CONCLUSION

Performed superficial to the pronator teres muscle under WALANT anesthesia, the microinvasive percutaneous ultrasound-guided release of the lacertus fibrosus may be an effective treatment of pronator syndrome.

Median Nerve Compression in the Forearm: A Clinical Diagnosis

Background: Median nerve entrapment in the forearm (MNEF) without motor paralysis is a challenging diagnosis. This retrospective study evaluated the clinical presentation, diagnostic studies, and outcomes following surgical decompression of MNEF. Methods: The study reviewed 147 patient medical charts following MNEF surgical decompression. With exclusion of patients with combined nerve entrapments (radial and ulnar), polyneuropathy, neurotmetic nerve injury, or median nerve motor palsy, the study sample included 27 patients. Data collected include: clinical presentation and pain, strength, provocative testing, functional outcomes, and Disabilities of the Arm, Shoulder and Hand (DASH) scores. Results: The study included 27 patients (mean follow-up = 7 months), and 13 patients had previous carpal tunnel release (CTR). Clinical presentation included pain (n = 27) (forearm, n = 22; median nerve innervated digits, n = 21; and palm, n = 21) and positive clinical tests (forearm scratch collapse test, n = 27; pain with compression over the flexor digitorum superficialis arch/pronator, n = 24; Tinel sign, n = 11). Positive electrodiagnostic studies were found for MNEF (n = 2) and carpal tunnel syndrome (n = 11). Primary CTR was performed in 10 patients and revision CTR in 7 patients. Postoperatively, there were significant (P < .05) improvements in strength, pain, quality of life, and DASH scores. Conclusions: The MNEF without motor paralysis is a clinical diagnosis supported by pain drawings, pain quality, and provocative tests. Patients with persistent forearm pain and median nerve symptoms (especially after CTR) should be evaluated for MNEF. Surgical decompression provides satisfactory outcomes.

Objective evaluation of the ``scratch collapse test'' for the diagnosis of carpal tunnel syndrome

PURPOSE

Evaluate the Scratch Collapse Test in an objective way, by replacing the subjective evaluation made by the physician with an objective evaluation measure, made with a digital dynamometer.

METHODS

Observational study carried out, in 90 patients divided into three groups of 30 patients, taking into account the electromyographic study of the median nerve in the carpal tunnel (no alteration, moderate, severe).The external rotation of the shoulder was measured in four different situations (no scratch, scratch over the carpal tunnel, scratch in the dorsum of the wrist and scratch in the shoulder).

RESULTS

There were no statistical differences in the result of the strength in any of the four different situations in patients without carpal tunnel of with moderate carpal tunnel syndrome. However, there were statistical differences between the basal measurement (without scratching) and the measurement after tunnel scratching in patients with severe carpal tunnel syndrome. But this statistical difference was only 0.08 kg in the average measure, and this difference is clinically undetectable and far for producing a real collapse of the external rotation of the shoulder.

CONCLUSION

The Scratch Collapse Test is not a valid diagnostic exam for carpal tunnel syndrome if the strength is measured in an objective manner.

The scratch collapse test: A systematic review

The diagnosis of nerve compression relies on collecting diagnostic clues from the history, physical examination, imaging and diagnostic testing. There are several provocative tests to aid in the diagnosis of nerve compression. The 'Scratch Collapse Test' (SCT) has emerged as a new provocative test to assist in the localisation of peripheral nerve compression. This study aims to perform a systematic review of literature to assess the data on the reliability of the SCT as a diagnostic test for entrapment neuropathy. Ten articles were reviewed. Five articles had sufficient numerical data for analysis, and in these five articles, the positive predictive values and specificity were high, i.e. between 0.71 and 0.99 and 0.6 and 0.99, respectively, whereas other values were very variable, i.e. individual negative predictive values ranged from 0.15 to 0.92 and the sensitivity values ranged from 0.24 to 0.77. Another main finding was the versatility of the test in that it can be used for various nerve entrapments and to localise the exact level of compression. Literature suggests that SCT has potential to be used as a clinical diagnostic tool for entrapment neuropathy. However, wide variations in early literature suggest that SCT should not be used as a sole diagnostic tool but as an adjunct to a surgeon's diagnostic repertoire.

Scratch Collapse Test for Carpal Tunnel Syndrome: A Systematic Review and Meta-analysis

Background:

Despite the fact that carpal tunnel syndrome (CTS) is the most common entrapment neuropathy, the diagnostic accuracy of clinical screening examinations for CTS is controversial. The scratch collapse test (SCT) is a novel test that may be of diagnostic advantage. The purpose of our study was to determine the diagnostic accuracy of the SCT for CTS.

Methods:

A literature search was performed using PubMed (1966 to April 2018); Ovid MEDLINE (1966 to April 2018); EMBASE (1988 to April 2018); and Cochrane Central Register of Controlled Trials (The Cochrane Library, to April 2018). We examined the studies for the pooled sensitivity, specificity, and likelihood ratios of the SCT. This review has been registered with PROSPERO (CRD42018077115).

Results:

The literature search generated 13 unique articles. Seven articles were included for full text screening and 3 articles met our inclusion criteria, all of which were level II evidence with low risk of bias (165 patients). Pooled sensitivities, specificities, positive likelihood ratio, and negative likelihood ratios were 0.32 [95% CI (0.24–0.41)], 0.62 [95% CI (0.45–0.78)], 0.75 [95% CI (0.33–1.67)], and 1.03 [95% CI (0.61–1.74)], respectively. The calculated area under the summary receiver operating characteristic (AUSROC) curve was 0.25, indicating a low diagnostic accuracy.

Conclusion:

The SCT has poor sensitivity; however, it is moderately specific. Based on the current literature and their variable quality of the evidence, we conclude that the SCT is not an adequate screening test for detecting CTS.