title: The Effects of Arthroscopic Lateral Acromioplasty on the Critical Shoulder Angle and the Anterolateral Deltoid Origin: An Anatomic Cadaveric Study.
abstract: OBJECTIVE
  To investigate if (1) an anterolateral acromioplasty and (2) a lateral acromion resection alter the critical shoulder angle (CSA) without affecting the deltoid origin.
  
  
  METHODS
  First, the native CSAs of 10 human cadaveric shoulders (6 male and 4 female specimens; mean age, 54.2 years) were determined with the use of fluoroscopy. Setup allowed for consistent repetitive measurements. Next, a standard arthroscopic anterolateral acromioplasty was performed to create a type 1 acromion, and the CSA was reassessed fluoroscopically. Afterward, a lateral acromioplasty was performed with a 5-mm lateral acromion resection using a 5-mm burr, and the CSA was measured again. The native CSA was compared with (1) the CSA after acromioplasty and (2) the CSA after acromioplasty and lateral acromion resection using a paired t test. Finally, the acromial deltoid attachment was evaluated anatomically for damage to the anterolateral origin.
  
  
  RESULTS
  The mean native CSA (34.3° ± 2.1°) was reduced significantly by acromioplasty (33.1° ± 2.0°, P < .001) and further reduced by lateral acromion resection (31.5° ± 1.7°, P < .001). Anterolateral acromioplasty reduced the CSA by a mean of 1.4° (95% confidence interval boundaries, 0.8° and 1.9°), and in combination with lateral acromion resection, the CSA was reduced by a mean of 2.8° (95% confidence interval boundaries, 2.1° and 3.5°). In all specimens (5 of 5) with a presurgery CSA of 35° or greater, the CSA was reduced to the range of 30° to 35° by the combination of both techniques. However, in 2 specimens with a CSA of approximately 32°, the CSA was reduced to less than 30°. The acromial deltoid attachment was found to be well preserved in all specimens.
  
  
  CONCLUSIONS
  Arthroscopic anterolateral acromioplasty and a 5-mm lateral acromion resection each reduced the CSA significantly and did not damage the deltoid origin.
  
  
  CONCLUSIONS
  The combination of both techniques could potentially be used in clinical practice to reduce a CSA greater than 35° to the desired range of 30° to 35°.
authors.affiliation: Department of BioMedical Engineering, Steadman Philippon Research Institute, Vail, Colorado, U.S.A.
authors.forename: J Christoph
authors.initials: JC
authors.lastname: Katthagen
authors.affiliation: Department of BioMedical Engineering, Steadman Philippon Research Institute, Vail, Colorado, U.S.A.
authors.forename: Daniel Cole
authors.initials: DC
authors.lastname: Marchetti
authors.affiliation: Department of BioMedical Engineering, Steadman Philippon Research Institute, Vail, Colorado, U.S.A.
authors.forename: Dimitri S
authors.initials: DS
authors.lastname: Tahal
authors.affiliation: Department of BioMedical Engineering, Steadman Philippon Research Institute, Vail, Colorado, U.S.A.
authors.forename: Travis Lee
authors.initials: TL
authors.lastname: Turnbull
authors.affiliation: Department of BioMedical Engineering, Steadman Philippon Research Institute, Vail, Colorado, U.S.A.; The Steadman Clinic, Vail, Colorado, U.S.A.. Electronic address: drmillett@thesteadmanclinic.com.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Millett
mesh_terms: D000174:Acromion / Q000601:surgery*; D000328:Adult; D001178:Arthroplasty / Q000379:methods*; D001182:Arthroscopy / Q000379:methods*; D002102:Cadaver; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012785:Shoulder Joint / Q000601:surgery*