title: A pilot trial comparing the tear-out behavior in screw-sockets and cemented polyethylene acetabular components - a cadaveric study.
abstract: The removal of well-fixed acetabular components following THA (total hip arthroplasty) is a difficult operation and could be accompanied by the loss of acetabular bone stock. The optimal method for fixation is still under debate. The aim of this pilot study was to compare the tear-out resistance and failure behavior between osseo-integrated and non-integrated screw cups. Furthermore, we examined whether there are differences in the properties mentioned between screw sockets and cemented polyethylene cups.
  
  
  
  Tear-out resistance and related mechanical work required for the tear-out of osseo-integrated screw sockets are higher than in non-integrated screw sockets.
  
  
  
  Ten human coxal bones from six cadavers with osseo-integrated screw sockets (n=4), non-integrated (implanted post-mortem, n=3) screw sockets and cemented polyethylene cups (n=3) were used for tear-out testing. The parameters axial failure load and mechanical work for tear-out were introduced as measures for determining the stability of acetabular components following THA.
  
  
  
  The osseo-integrated screw sockets yielded slightly higher tear-out resistance (1.61±0.26kN) and related mechanical work compared to the non-integrated screw sockets (1.23±0.39kN, P=0.4). The cemented polyethylene cups yielded the lowest tear-out resistance with a failure load of 1.18±0.24kN. Compared to the screw cups implanted while alive, they also differ on a non-significant level (P=0.1). Osseous failure patterns differed especially for the screw sockets compared to the cemented polyethylene cups.
  
  
  
  Osseo-integration did not greatly influence the tear-out stability in cementless screw sockets following axial loading. Furthermore, the strength of the bone-implant-interface of cementless screw sockets appears to be similar to cemented polyethylene cups. However, given the high failure load, high mechanical load and because of the related bone failure patterns, removal should not be performed by means of tear-out but rather by osteotomes or other curved cutting devices to preserve the acetabular bone stock.
  
  
  
  Level III, case-control-study.
authors.affiliation: Institute of anatomy, faculty of medicine, university of Leipzig, 13, Liebigstraße, 04103 Leipzig, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Möbius
authors.affiliation: Department of orthopedics, trauma surgery and plastic surgery, university hospital of Leipzig, 20, Liebigstraße, 04103 Leipzig, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Schleifenbaum
authors.affiliation: Department of orthopedics, trauma surgery and plastic surgery, university hospital of Leipzig, 20, Liebigstraße, 04103 Leipzig, Germany; Fraunhofer institute for machine tools and forming technology, 44, Nöthnitzer Straße, 01187 Dresden, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Grunert
authors.affiliation: Institute of anatomy, faculty of medicine, university of Leipzig, 13, Liebigstraße, 04103 Leipzig, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Löffler
authors.affiliation: Fraunhofer institute for machine tools and forming technology, 44, Nöthnitzer Straße, 01187 Dresden, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Werner
authors.affiliation: Department of orthopedics, trauma surgery and plastic surgery, university hospital of Leipzig, 20, Liebigstraße, 04103 Leipzig, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Prietzel
authors.affiliation: Department of anatomy, university of Otago, Lindo Ferguson Building, 270, Great King St, 9016 Dunedin, New Zealand. Electronic address: nlshammer@googlemail.com.
authors.forename: N
authors.initials: N
authors.lastname: Hammer
mesh_terms: D000077:Acetabulum; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip; D001843:Bone Cements; D001863:Bone Screws; D002102:Cadaver; D005260:Female; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D010865:Pilot Projects; D020959:Polyethylene; D011475:Prosthesis Failure; D013314:Stress, Mechanical
chemical_list: D001843:Bone Cements; D020959:Polyethylene
keywords: Acetabular component; Acetabular revision; Cementless fixation; Osseo-integration; Screw socket; THA