R Möbius1, S Schleifenbaum2, R Grunert3, S Löffler1, M Werner4, T Prietzel2, N Hammer5. 1. Institute of anatomy, faculty of medicine, university of Leipzig, 13, Liebigstraße, 04103 Leipzig, Germany. 2. Department of orthopedics, trauma surgery and plastic surgery, university hospital of Leipzig, 20, Liebigstraße, 04103 Leipzig, Germany. 3. 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. 4. Fraunhofer institute for machine tools and forming technology, 44, Nöthnitzer Straße, 01187 Dresden, Germany. 5. Department of anatomy, university of Otago, Lindo Ferguson Building, 270, Great King St, 9016 Dunedin, New Zealand. Electronic address: nlshammer@googlemail.com.
Abstract
BACKGROUND: 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. HYPOTHESIS: 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. PATIENTS AND METHODS: 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. RESULTS: 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. DISCUSSION: 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 OF EVIDENCE: Level III, case-control-study.
BACKGROUND: 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. HYPOTHESIS: 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. PATIENTS AND METHODS: 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. RESULTS: 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. DISCUSSION: 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 OF EVIDENCE: Level III, case-control-study.
Authors: Luigi Pelliccia; Mario Lorenz; Christoph-E Heyde; Maximilian Kaluschke; Philipp Klimant; Sebastian Knopp; Stefan Schleifenbaum; Christian Rotsch; René Weller; Michael Werner; Gabriel Zachmann; Dirk Zajonz; Niels Hammer Journal: Sci Rep Date: 2020-09-03 Impact factor: 4.379