The empty can scratch test (ECST) for suspected anterior cutaneous nerve entrapment syndrome (ACNES) - a pilot study.

OBJECTIVES: Chronic abdominal wall pain may be caused by Anterior Cutaneous Nerve Entrapment Syndrome (ACNES). The diagnostic cornerstone is a characteristic physical examination including a localized area of altered skin sensation covering a point of maximum pain. Recently, the Scratch Collapse Test (SCT) emerged as a sensitive noninvasive test for ACNES. However, this test relies on manual force application, which introduces potential examiner bias and raises concerns regarding its objectivity. Therefore, we modified the Empty Can Test, used to detect rotator cuff injuries, into the Empty Can Scratch Test (ECST). During this test, patients hold weights, thereby eliminating any manual force application. We hypothesized that this more objective ECST would elicit similar results to the SCT through a comparable spinal inhibitory reflex mediated by the common efferent suprascapular nerve. If so, the ECST would have diagnostic potential in suspected ACNES.

METHODS: This single-center, prospective, cross-sectional cohort study, conducted between April and August 2022 at the outpatient department of SolviMáx, Centre of Expertise for Complex Abdominal Wall Pathology, included adult participants with suspected unilateral ACNES who underwent both the SCT and ECST.

RESULTS: Twenty participants were analyzed (median age 50 years [IQR 38.5-57.5], 75 % women). The SCT was positive in 19 patients (95 %), but the ECST was positive in only 10 patients (50 %). There was no level of agreement between both tests (Cohen's Kappa=0.100, p=0.305).

CONCLUSIONS: The ECST does not have a diagnostic role in ACNES. The high diagnostic yield of a SCT in ACNES is confirmed.

ETHICAL COMMITTEE NUMBER: METC N22.023.