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.

The aim of this study was to analyse the long-term results of a cementless conical threaded cup with elevated inlay-rim, without bone grafting in joint replacement of dysplastic compared to non-dysplastic hips, and concerning the survival rate and the rate of cup migration.

Most techniques of joint replacement of dysplastic hips contain bone grafting with more or less large-scale procedures. Without bone grafting, medialisation of the cup is often necessary. The conical threaded Link-V cup has the opportunity of stabilising the joint by using a polyethylene inlay with an elevated rim so that implantation in high angles of flexion and anteversion is possible. This is a technically easy procedure in dysplastic hips, but higher rates of loosening and cup migration are possible.

A cementless conical threaded cup (Link V) with elevated inlay-rim was followed in 36 dysplastic hips (DH) and 167 non-dysplastic osteoarthritic hips (OA) over a minimum follow-up of five years. Mean follow-up in DH-hips was 8.4 2.3 years and in OA-patients 8.6 3.2 years. Survival analysis was performed and cup migration was radiographically analysed using the method of Nunn et al.

The 10-year survival rate of the cup was 87% in DHhips compared to 92% in OA-hips. Luxation occurred in three OA-joints and none in DH-hips. Radiological cup migration was seen in 75% of DH-hips and in 70% of OA-joints. A change of the angle of flexion (mostly decrease) of more than two degrees was found in 50% of DH-hips and in 72% of OA-joints. There was vertical migration of more than 2 mm in 75% of DH-hips and in 70% of OA-hips, and a horizontal migration of more than 2 mm in 45% of DH-joints and in 40% of OA-hips. A radiolucent line of minimum 2 mm was seen in one case of each group.

Using a cementless threaded cup with elevated inlayrim is a practicable and technically easy procedure for treatment of destroyed dysplastic hips. Although cup migration is frequent in dysplastic and non-dysplastic hips, failure-rate is still acceptable but tends to be higher in dysplastic than in non-dysplastic hips.