title: Posterior Soft Tissue Repair After Primary THA is Durable at Mid-term Followup: A Prospective MRI Study.
abstract: BACKGROUND
  The enhanced posterior soft tissue repair has reduced the frequency of dislocation after primary THA performed through the posterolateral approach. However, the long-term integrity of the repair is unknown and could influence surgeon choice regarding surgical technique and THA approach.
  
  
  OBJECTIVE
  We asked: (1) What is the durability of the enhanced posterior soft tissue repair at a minimum of 49 months using MRI to evaluate soft tissue to bone integrity? (2) How does the appearance of the posterior soft tissues change during this time? (3) Are there patient characteristics associated with the long-term imaging appearance of the posterior repair?
  
  
  METHODS
  All patients without a contraindication for MRI who were undergoing unilateral primary uncemented THA through a posterior approach between February and May 2005 were eligible for inclusion. Ninety percent consented to participate (36 of 40 patients), and 30 patients were followed prospectively with MRI postoperatively and again at 3 months; of those, 22 (73%; 12 men, 10 women) completed the study by having another MRI study at a minimum of 49 months (mean, 51 months; range, 49-59 months). Each patient underwent metal-artifact-reduction sequence MRI to evaluate the integrity of the posterior soft tissues, which had been repaired anatomically during primary THA at a minimum of 4 years earlier. The results were compared with those of prior MR images obtained immediately after surgery and at 3 months postoperatively. All patients were given a self-reported modified Harris hip score at the time of the most recent MRI study (maximum score = 81).
  
  
  RESULTS
  At latest followup, 21 of 22 (96%) patients had a posterior capsule in contact with bone, and 21 of 22 (96%) had an intact quadratus femoris. Twenty-one patients (96%) had soft tissue or a scar from the piriformis and conjoined tendons in continuity with bone. In these cases, the interface between the piriformis and conjoined tendons and the greater trochanter observed immediately postoperatively and at 3 months postoperatively became filled with hypointense tissue, with signal characteristics similar to tendon. Time from surgery was most associated with changes in native tendon-to-bone distances (p < 0.001) and MRI signal intensity of the repair (p < 0.001).
  
  
  CONCLUSIONS
  At followup of just more than 4 years, the posterior capsule and quadratus femoris most often were healed to bone. In the majority of patients, scar tissue between the piriformis and conjoined tendons and bone matured to achieve orientation and signal intensity resembling native tendon. We believe the enhanced posterior soft tissue repair facilitates this process. Our results provide a plausible explanation for improved postoperative stability observed in patients receiving an enhanced soft tissue repair compared with those in whom a repair is not performed.
  
  
  METHODS
  Level IV, therapeutic study.
authors.affiliation: Orthopedic Surgery, Hospital for Special Surgery, 535 East 70th Street, New York, NY, 10021, USA, mclawhorna@hss.edu.
authors.forename: Alexander S
authors.initials: AS
authors.lastname: McLawhorn
authors.forename: Hollis G
authors.initials: HG
authors.lastname: Potter
authors.forename: Michael B
authors.initials: MB
authors.lastname: Cross
authors.forename: Friedrich
authors.initials: F
authors.lastname: Boettner
authors.forename: Weiyang
authors.initials: W
authors.lastname: Lim
authors.forename: Yuo-yu
authors.initials: YY
authors.lastname: Lee
authors.forename: Paul M
authors.initials: PM
authors.lastname: Pellicci
mesh_terms: D019644:Arthroplasty, Replacement, Hip; D005260:Female; D005500:Follow-Up Studies; D006615:Hip; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000473:pathology* / Q000601:surgery*; D011182:Postoperative Care; D011446:Prospective Studies; D013710:Tendons / Q000473:pathology* / Q000601:surgery*; D013997:Time Factors