[The uncemented self-threading Ultima cup: first 5 years' experience].

PURPOSE OF THE STUDY: To present the first 3-5 year experience in primary implantation of the Ultima cementless hemispherical threaded cup.

MATERIAL: In the period between October 1995 and June 1997 we implanted in total 30 Ultima cementless cups in 28 patients (10 men, 18 women). The average age of the operated on was 60 years (41-74 years). Twenty-four patients, i.e. 26 hips were available for the follow up. From the viewpoint of diagnosis the group of patients included 15 cases of primary osteoarthritis, 9 cases of acute intracapsular femoral neck fracture, 3 cases of postdysplastic osteoarthritis, 2 cases (1 female patient with bilateral affection) of rheumatoid osteoarthritis (RA) accompanied with the protrusion of acetabulum and 1 case of idiopathic necrosis of the head.

METHODS: The average follow up was 39 months (31-51 months). Subjectively, we followed the patients' satisfaction with the result of the surgery, i.e. subsidence of pain, range of motions and the willingness to undergo the surgery once more on the basis of its result. Radiologically, we assessed the shape of acetabulum prior to operation, the position of the implanted cup in ap projection on the postoperative radiograph, on the last control radiograph we evaluated osteointegration of the cup and also potential particular ossification.

RESULTS: Nineteen patients out of 24 were subjectively satisfied with the result of the operation. The primary shape of acetabulum was in 24 cases spherical, 4 times dysplastic slightly lower CE (Wiberg) angle and twice there occurred protrusion of the head (the female patient with RA). The position of the cup in ap projection was evaluated in 25 cases as correct (45 degrees declination), in 2 cases as valgus (more than 55 degrees declination), in 3 cases as varus (less than 35 degrees declination) and in 1 case the cup was inserted too deep. Osteointegration was evaluated in 25 cases. In 22 cases we considered the osteointegration as good, i.e. without signs of a radioluscent line around the circumference of the cup. This line we encountered in 2 patients around the whole circumference of the cup but without any signs of a change in the position of the cup and without subjective complaints (pain in the hip). Both patients operated on for the primary osteoarthritis had a spherical shape of acetabulum and the declination of the cup was assessed as satisfactory. In 1 case we had to re-operate on due to the migration of the cup in the pelvis, namely in the female patient with RA and bilateral affection. The migration occurred on the left side 2.5 year after the primary surgery. Particular ossification was encountered 3 times, one case required extirpation. Complications were recorded in 8 patients. In one case the lateral cortex was peroperatively perforated by the stem of the femoral component. In another patient with a dysplastic acetabulum the cup was inserted to deep in the medial wall of the acetabulum. In the third patient the greater trochanter got broken, remained displaced and only the ligaments healed. Early postoperative complications were recorded twice. In one case it was a serous secretion from the wound which subsided after a few days without the necessity of revision. Revision was required in the second case when the R-drainage broke in the course of its removal. Late complications occurred in 3 patients. In one case there developed a mitigated infection requiring revision surgery, in case of the female patient with RA the cup protruded in the pelvis which necessitated a revision surgery.

DISCUSSION: So far there are no literary data on this type of cup. The only existing information relates to the preceding type of a similar design, i.e. Mecring cup, which failed.

CONCLUSION: Despite relatively good but short-term results of this small series the unusual design of the Ultima hemispherical threaded cup requires a great prudence in its application and additional long-term follow-up. Therefore the cup cannot be recommended for a regular use for the time being.