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MINERVA ORTOPEDICA E TRAUMATOLOGICA
A Journal on Orthopedics and Traumatology
Minerva Ortopedica e Traumatologica 2004 April;55(2):45-50
Long term analysis of stress shielding and load transfer in hydroxyapatite-coated ABG I total hip prosthesis: an 8-13 years follow-up study
La Russa M., Blonna D., Rossi R., Bruzzone M., Sibelli P.
Dipartimento di Ortopedia e Traumatologia Ospedale Umberto I Università degli Studi di Torino, Torino
Aim. The ABG total hip prosthesis had been studied to prevent any kind of stress shielding and to allow the localization of the loads in the metaphyseal region of the femur. The aim of this study was to analize the effective behaviour of the loads in long-term implants and the possible correlations of those findings with the clinical situation of the patients.
Methods. We considered 87 total hip arthroplasty implants executed from 1989 to 1995 and performed by using Anatomique Benoist Girard I uncemented prosthesis. The radiographical findings have been classified observing Engh’s stability criteria according to Gruen’s subdivision of the periprosthetic femoral zones.
Results. The radiographical analysis shows a higher presence of cancellous densification in Gruen’s zones 3 and 5 than the one found in zones 2 and 6. Furthermore, the presence of a cortical reaction is more relevant in the distal zones. Radiolucent lines are present in 16% of the cases in zone 4; their percentage in zones 3 and 5 decreases to 7.14% and 10.71%.
Conclusion. Our study shows the certain presence of the stress shielding mechanism in long-term analysis and underlines that the main region of late anchorage is the distal, not hydroxyapatite-coated, one. The comparison with other similar studies shows the decrease of the presence of radiolucent lines in proximal femoral zones with the rise of the follow-up: it can be interpreted as the lesser presence of micromovements of the tip of the prosthesis due to the distalization of the anchorage.