title: Does acetabular retroversion affect range of motion after total hip arthroplasty?
abstract: BACKGROUND
  Increasingly, acetabular retroversion is recognized in patients undergoing hip arthroplasty. Although prosthetic component positioning is not determined solely by native acetabular anatomy, acetabular retroversion presents a dilemma for component positioning if the surgeon implants the device in the anatomic position.
  
  
  OBJECTIVE
  We asked (1) whether there is a difference in ROM between surface replacement arthroplasty (SRA) and THA in the retroverted acetabulum, and (2) does increased femoral anteversion improve ROM in the retroverted acetabulum?
  
  
  METHODS
  Using a motion analysis tracking system, we determined the ROM of eight cadaveric hips and then created virtual CT-reconstructed bone models of each specimen. ROM was determined with THA and SRA systems virtually implanted with (1) the acetabular component placed in 45° abduction and matching the acetabular anteversion (average 23° ± 4°); (2) virtually retroverting the bony acetabulum 10°; and (3) after anteverting the THA femoral stem 10°.
  
  
  RESULTS
  SRA resulted in ROM deficiencies in four of six maneuvers, averaging 25% to 29% in the normal and retroverted acetabular positions. THA restored ROM in all six positions in the normal acetabulum and in four of the six retroverted acetabula. The two deficient positions averaged 5% deficiency. THA with increased femoral stem anteversion restored ROM in five positions and showed only a 2% deficiency in the sixth position. Compared with the intact hip, ROM deficits were seen after SRA in the normal and retroverted acetabular positions and to a lesser extent for THA which can be improved with increased femoral stem anteversion.
  
  
  CONCLUSIONS
  Poor ROM may result after SRA if acetabular retroversion is present.
authors.affiliation: Department of Orthopaedic Surgery, Adult Reconstructive Surgery, The Methodist Hospital for Orthopaedics, 6550 Fannin, Suite 2500, Houston, TX 77030, USA. SJIncavo@tmhs.org
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Incavo
authors.forename: Jonathan E
authors.initials: JE
authors.lastname: Gold
authors.forename: Jesse James F
authors.initials: JJ
authors.lastname: Exaltacion
authors.forename: Matthew T
authors.initials: MT
authors.lastname: Thompson
authors.forename: Philip C
authors.initials: PC
authors.lastname: Noble
mesh_terms: D000077:Acetabulum / Q000000981:diagnostic imaging / Q000601:surgery*; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects / Q000295:instrumentation; D001696:Biomechanical Phenomena; D002102:Cadaver; D003198:Computer Simulation; D005269:Femur / Q000601:surgery; D006621:Hip Joint / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D006622:Hip Prosthesis; D006801:Humans; D008875:Middle Aged; D008953:Models, Anatomic; D011474:Prosthesis Design; D016059:Range of Motion, Articular; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome