High long-term loosening rate of conical screw cups.
BACKGROUND
Acetabular screw cups seem to give high primary stability. We analyzed the migration and loosening behavior of a first-generation screw cup in a longterm follow-up.


METHODS
We examined 92 uncemented titanium alloy conical screw cups prospectively. Implant migration was assessed with a digital high-precision method (EBRA) with an accuracy of 1.0 mm.


RESULTS
After mean 11 (0.5-18) years, 87 patients were available for examination and 5 patients had died. 32 implants had been revised and 7 cases showed radiographic evidence of loosening. The 10-year survival rate was 71%. Migration of more than 1 mm occurred in 53 hips. Implant survival was strongly associated with an annual migration of greater than 0.2 mm.


CONCLUSIONS
The long-term behavior of this cup is not satisfactory. In spite of extraordinarily high primary implant stability, secondary osseointegration of this cup often fails. The annual migration rate represents a valid parameter for prediction of implant survival.
Hendrich
Christian
C
Department of Orthopaedics, Werneck, Germany. christian.hendrich@kh-schloss-werneck.de
Sauer
Ulf
U
Kirschner
Stephan
S
Schmitz
Helge
H
Martell
John M
JM
D000077:Acetabulum / Q000601:surgery; D000328:Adult; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects* / Q000295:instrumentation; D001863:Bone Screws / Q000009:adverse effects; D005260:Female; D005500:Follow-Up Studies; D006622:Hip Prosthesis / Q000009:adverse effects*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011474:Prosthesis Design; D011475:Prosthesis Failure; D014025:Titanium
D014025:Titanium