title: Defining a safety margin for labral suture anchor insertion using the acetabular rim angle.
abstract: BACKGROUND
  Suture anchors are commonly used to reattach a torn labrum to the acetabular rim. The acetabular rim anatomy is not uniform, and the safety margin for inserting suture anchors is unknown. The acetabular rim angle is an anatomic measurement that is indicative of the safety margin for inserting suture anchors.
  
  
  OBJECTIVE
  To investigate the acetabular rim angle as a function of clock position, to evaluate the effect of drill depth on the acetabular rim angle, and to evaluate the effect of rim trimming on the acetabular rim angle.
  
  
  METHODS
  Descriptive laboratory study.
  
  
  METHODS
  Three-dimensional acetabular models were reconstructed from computed tomography scans of 20 nonpaired cadaveric hip specimens, and the acetabular rim angle, which quantifies the angle between the subchondral margin and the outer cortex of the acetabulum, was measured from the 8- to 4-o'clock positions. At each position, the acetabular rim angle was measured for 5 drill depths (10, 12.5, 15, 20, and 25 mm) to simulate different lengths of suture anchors or drill bit depths on the acetabular rim angle. To simulate rim trimming, the acetabular rim angle was measured at the points that would become the suture anchor insertion points after 2.5- and 5-mm rim trimming.
  
  
  RESULTS
  Clock position, drill depth, and rim trimming all had significant effects on the acetabular rim angle (P < .0001). The acetabular rim angle was largest at the 2-o'clock and smallest at the 3-o'clock position. Greater drill depths provided smaller acetabular rim angles, whereas rim trimming provided larger acetabular rim angles.
  
  
  CONCLUSIONS
  The acetabular rim angle varied significantly as a function of the location on the acetabular rim. A shorter drill depth and a greater amount of rim trimming provided a larger acetabular rim angle.
  
  
  CONCLUSIONS
  Surgeons should be aware of the acetabular rim variations, especially in the anterosuperior quadrant, as well as the effects of drill depth and rim trimming, when selecting the optimal insertion angle for suture anchor placement to avoid articular cartilage penetration. The acetabular safety angle was smallest at the 3-o'clock position. Therefore, extra care must be taken when drilling or inserting anchors around the 3-o'clock position.
authors.affiliation: Steadman Philippon Research Institute, 181 W. Meadow Dr, Suite 1000, Vail, CO 81657, USA.
authors.forename: Pisit
authors.initials: P
authors.lastname: Lertwanich
authors.forename: Leandro
authors.initials: L
authors.lastname: Ejnisman
authors.forename: Michael R
authors.initials: MR
authors.lastname: Torry
authors.forename: J Erik
authors.initials: JE
authors.lastname: Giphart
authors.forename: Marc J
authors.initials: MJ
authors.lastname: Philippon
mesh_terms: D000077:Acetabulum / Q000502:physiology*; D002358:Cartilage, Articular / Q000601:surgery*; D006801:Humans; D012449:Safety; D013514:Surgical Procedures, Operative / Q000379:methods*; D053441:Suture Anchors; D013536:Suture Techniques / Q000592:standards*