title: [Larger heads compensate for an increased risk of THA dislocation in high-risk patients].
abstract: BACKGROUND
  Dislocation is a devastating complication after total hip arthroplasty (THA) and occurs in 2-5% of primary THA cases and 5-10% of revision THA cases. Assuming correct implantation, dislocation risk can be reduced primarily by capsular repair and the use of larger prosthetic heads. However, larger heads are also associated with risks like accelerated wear or implant loosening, which is why heads with a maximum diameter of 36 mm are currently standard in primary THA. In cases with high dislocation risk, the use of 40 mm and 44 mm heads should be considered.
  
  
  OBJECTIVE
  This study aimed to quantify THA dislocation risk and retrospectively analyze the course of disease in high-risk patients treated with 40 mm or 44 mm femoral heads after primary or revision THA, concerning dislocation and other complications suffered.
  
  
  METHODS
  All patients with increased THA dislocation risk, treated from 2009-2014, were evaluated regarding dislocations. The cases with installation of 40 mm or 44 mm prosthetic heads were classified using a self-developed 5-level risk score and retrospectively analyzed.
  
  
  RESULTS
  During the observation period, 288 THA interventions with increased dislocation risk were performed. In 278 cases with ball diameters ≤ 36 mm the dislocation rate was 15.1% (n=42). In 10 high dislocation-risk cases (3A to 4B according to recommended scoring system), 40 mm and 44 mm heads were used. After a 22.8 month mean follow-up, no THA dislocations were reported.
  
  
  CONCLUSIONS
  Our results with 40 and 44 mm heads and the existing literature confirm much higher joint stability and, thus, significantly reduced dislocation risk with larger prosthetic heads in THA. Their use is, therefore, justified in high-risk patients and should be considered in future THA.
authors: Klinik und Poliklinik für Orthopädie, Unfallchirurgie und Plastische Chirurgie, Universitätsklinikum Leipzig, Liebigstr. 20, 04103, Leipzig, Deutschland.
authors: D
authors: D
authors: Zajonz
authors: H
authors: H
authors: Philipp
authors: S
authors: S
authors: Schleifenbaum
authors: R
authors: R
authors: Möbius
authors: N
authors: N
authors: Hammer
authors: R
authors: R
authors: Grunert
authors: T
authors: T
authors: Prietzel
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000295:instrumentation* / Q000706:statistics & numerical data*; D019544:Equipment Failure Analysis; D005260:Female; D005858:Germany / Q000453:epidemiology; D006617:Hip Dislocation / Q000453:epidemiology* / Q000517:prevention & control; D006622:Hip Prosthesis / Q000706:statistics & numerical data*; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications / Q000453:epidemiology* / Q000517:prevention & control; D011474:Prosthesis Design; D018570:Risk Assessment