[Periprosthetic osseous changes 2, 4, and 6 years after implantation of cementless Zweymüller-stems-- A cross-sectional study].
OBJECTIVE
According to the results of longitudinal studies, the use of distally anchored femoral prostheses leads to marked proximal stress shielding. Zweymüller stems should be controlled some years after implantation.


METHODS
In a cross-sectional study, we examined 92 patients clinically, radiologically, and osteodensitometrically 2, 4, and 6 years after implantation in order to assess the osseointegration of Zweymüller shafts as independently as possible of age. The non-operated contralateral limb or Gruen's zone 4 below the prosthesis was used as a control group.


RESULTS
At no time did the parameters assessed indicate any reduction in proximal bone density as compared with the control group. Zone 7 (medial-proximal) even showed an increase in bone density after 2 and 4 years. Nevertheless, absolute bone density was lowest proximally both pre- and postoperatively. Six years after implantation women even showed a 15 % increase in summated periprosthetic bone density as compared with the control group. No influence of femoral shape on bony remodeling was demonstrated.


CONCLUSIONS
Periprosthetic bony remodeling cannot be attributed exclusively to the shape of the shaft. Longitudinal studies do not adequately reflect the reduction in periprosthetic bone mass that occurs as a function of age and altered activity level. The osseointegration of hip prostheses is influenced by other factors such as musculoskeletal lines of force, sex, and age.
Hasart
O
O
Klinik für Orthopädie der Charité Berlin, Germany. olaf.hasart@charite.de
Hanebeck
J
J
Labs
K
K
Perka
C
C
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015519:Bone Density / Q000502:physiology; D003430:Cross-Sectional Studies; D005260:Female; D005500:Follow-Up Studies; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D016348:Osseointegration / Q000502:physiology*; D011183:Postoperative Complications / Q000209:etiology* / Q000503:physiopathology; D011474:Prosthesis Design