Abstract
Survivorship analysis was performed on 479 Link V-Type cementless threaded acetabular cups on 310 cases with inflammatory arthritis, 138 cases with osteoarthritis and 31 cases with dysplastic hip. The average follow-up was 8. 6 ± 3. 2 years. The same analysis was performed on a modified cup with a smaller primary coil (type ”Bad Bramstedt”). This analysis had a mean follow-up period of 4. 5 ± 0. 7 years in 110 cases, including 49 with inflammatory arthritis, 49 with osteoarthritis and 12 with dysplastic hip. In a second approach 264 Link V-cups with a mean follow-up period of 8. 2 ± 2. 7 years and 59 modified cups with a mean follow-up period of 4. 6 ± 0. 7 years were radiologically examined for radiolucent lines according to Delee and Charnley and cup migration with regard to the method of Nunn et al.
The cumulative survival rate for the former Link V-Type acetabular cup was 94. 5% after 5 years, 88. 1% after 10 years and 71. 2% after 15 years. The ”Bad Bramstedt” cup showed a 5 year survivorship rate of 97. 9%. Migration greater than 3 mm or tilting of the cup greater than 5 degrees was seen in 73% of the former type and in 39% of the modified cup. Radiolucent lines greater than 2 mm and detectable in two zones appeared in 6. 4% of the former Link V-Type and in 1. 7% of the ”Bad Bramstedt” cup design. Significant influence on cup migration was found in primary implant positioning and time elapsed. Due to the high rates of migration of the two implant designs and the frequent late aseptic loosening of the former Link V-Type acetabular component these two types of threaded cups were abandoned in favor of cementless press-fit cups.
