title: Acromiohumeral distance measurement in rotator cuff tendinopathy: is there a reliable, clinically applicable method? A systematic review.
abstract: BACKGROUND
  Narrowing of the subacromial space has been noted as a common feature of rotator cuff (RC) tendinopathy. It has been implicated in the development of symptoms and forms the basis for some surgical and rehabilitation approaches. Various radiological methods have been used to measure the subacromial space, which is represented by a two-dimensional measurement of acromiohumeral distance (AHD). A reliable method of measurement could be used to assess the impact of rehabilitation or surgical interventions for RC tendinopathy; however, there are no published reviews assessing the reliability of AHD measurement.
  
  
  OBJECTIVE
  The aim of this review was to systematically assess the evidence for the intrarater and inter-rater reliability of radiological methods of measuring AHD, in order to identify the most reliable method for use in RC tendinopathy.
  
  
  METHODS
  An electronic literature search was carried out and studies describing the reliability of any radiological method of measuring AHD in either healthy or RC tendinopathy groups were included. Eighteen studies met the inclusion criteria and were appraised by two reviewers using the Quality Appraisal for reliability Studies checklist.
  
  
  RESULTS
  Eight studies were deemed to be of high methodological quality. Study weaknesses included lack of tester blinding, inadequate description of tester experience, lack of inclusion of symptomatic populations, poor reporting of statistical methods and unclear diagnosis. There was strong evidence for the reliability of ultrasound for measuring AHD, with moderate evidence for MRI and CT measures and conflicting evidence for radiographic methods. Overall, there was lack of research in RC tendinopathy populations, with only six studies including participants with shoulder pain.
  
  
  CONCLUSIONS
  The results support the reliability of ultrasound and CT or MRI for the measurement of AHD; however, more studies in symptomatic populations are required. The reliability of AHD measurement using radiographs has not been supported by the studies reviewed.
authors.affiliation: Department of Clinical Therapies, University of Limerick, Limerick, Ireland.
authors.forename: Karen M
authors.initials: KM
authors.lastname: McCreesh
authors.affiliation: Department of Radiology, University Hospital Limerick, Limerick, Ireland.
authors.forename: James M
authors.initials: JM
authors.lastname: Crotty
authors.affiliation: Department of Allied Health Professions and Midwifery, School of Health and Social Work, University of Hertfordshire, Hatfield, UK Musculoskeletal Services, Health at the Stowe, Central London Community Healthcare NHS Trust London, London, UK.
authors.forename: Jeremy S
authors.initials: JS
authors.lastname: Lewis
mesh_terms: D000174:Acromion / Q000473:pathology*; D003952:Diagnostic Imaging / Q000379:methods; D006801:Humans; D006811:Humerus / Q000473:pathology*; D015588:Observer Variation; D017006:Rotator Cuff / Q000473:pathology*; D019534:Shoulder Impingement Syndrome / Q000209:etiology / Q000473:pathology; D020069:Shoulder Pain / Q000209:etiology / Q000473:pathology; D052256:Tendinopathy / Q000150:complications / Q000473:pathology*
keywords: Evidence based reviews; Orthopaedics; Shoulder injuries