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Published on: November 17, 2023
Estimating the Minimal Detectable Change (MDC) of the Disability of the Arm, Shoulder and Hand (DASH) scale in
Michele Mercurio1, Umile Giuseppe Longo2, Simone Cerciello3
1Department of Orthopaedic and Trauma Surgery, "Magna Græcia" University, "Renato Dulbecco" University Hospital, Catanzaro, Italy; Research Center on Musculoskeletal Health, MusculoSkeletalHealth@UMG, Magna Graecia University, Catanzaro, Italy.
Background:
Idiopathic frozen shoulder is a disabling condition characterized by pain and restricted range of motion, often evaluated using patient-reported outcome measures such as the Disabilities of the Arm, Shoulder and Hand (DASH) score. However, the clinical interpretation of DASH changes remains unclear without defined thresholds for meaningful improvement. While the minimal detectable change (MDC) has been established for various musculoskeletal conditions, poor data exist for patients with frozen shoulder treated with focal extracorporeal shock wave therapy (f-ESWT). This study aims to address this gap. Our primary aim was to establish the MDC of the DASH score in this population. Secondary goals included: (1) identifying the MDC values for Constant-Murley Score (CMS) (2) evaluating the patients' improvement over time; and (3) studying treatment influence outcomes over time.
Hypothesis:
The primary hypothesis was that a clinically meaningful MDC for the DASH score can be identified in patients with idiopathic frozen shoulder treated with f-ESWT, and that this threshold would be consistent with or slightly higher than values reported in other upper limb disorders.
Patients And Methods:
A prospective cohort of 94 patients with idiopathic frozen shoulder treated with f-ESWT was analyzed, with 77 patients completing 12-month follow-up. Inclusion criteria required clinical diagnosis and intact rotator cuff. Outcomes included DASH, CMS, and VAS scores assessed at baseline, end of treatment, and at 2-, 6-, and 12-month follow-ups. Subgroup analysis evaluated early (<3 months) versus delayed treatment.
Results:
Significant improvements were observed in all outcome measures over time (p < 0.001). DASH scores decreased significantly from baseline to all follow-ups, with continued improvement up to 12 months. The MDC for DASH scored 18.3. The MDC of CMS was 18.9. Patients treated within 3 months showed significantly better DASH scores at 2 months (p = 0.034). No complications were reported.
Discussion:
This study establishes clinically relevant MDC thresholds for DASH in idiopathic frozen shoulder treated with f-ESWT, supporting its use as a meaningful outcome measure. The findings align with previous literature in upper limb disorders but suggest slightly higher thresholds, likely due to greater baseline disability in this population. Early treatment may enhance recovery, emphasizing the importance of timely intervention. These results provide valuable benchmarks for clinical interpretation and trial design, although limitations include reliance on distribution-based methods and absence of a control group.
Level Of Evidence:
II; prospective cohort study.
