[Long-term results of the Schenker cementless femoral component].

PURPOSE OF THE STUDY: The aim of the work is to evaluate the results achieved in the group of patients with implanted Schenker cementless femoral component (Schenker, Switzerland) and discuss the method of solution of loosening of these components in the group of patients who underwent revision surgery.

MATERIAL: The first part of the followed-up group comprised 16 patients (11 women, 5 men) with the total of 18 operated on hips who underwent primary hip arthroplasty between 1989 and 1992 (Poidi cemented cup, Schenker cementless femoral component). The average follow-up period was 140 months (range 120 to 156 months). The second part of the group included patients who underwent revision for loosening of the Schenker cementless femoral component. This part consisted of 18 patients (11 women, 7 men) with 20 operated on hips. The average interval after primary hip arthroplasty was 65 months (range 36 to 118 months).

METHODS: In the period between May and December 2002, 34 patients were examined in the out-patient department. The evaluation involved only patients who did not undergo revision surgery. The clinical condition was evaluated on the basis of the Harris Hip Score and a radiograph was made to monitor any signs of linear wear of the cup, the extent of the radiolucent zone in both components and a potential migration of components.

RESULTS: Results were evaluated in 16 patients (11 women, 5 men) with 18 operated on hips. The average follow-up period was 140 months. Harris Hip Score averaged 76 points (range, 56 to 97 points). The linear wear up to 1 mm was recorded in 4 cups and that of up to 2 mm in 2 cups. The radiolucent line surrounding the cup in zone III after DeLee and Charnley was present in 5 cups, in zones II and III in another 1 patient. No cup showed any signs of migration. The radiolucent line surrounding the femoral component was present in 9 hips. The progress of subsiding as compared to the preceding radiograph check (interval of 1 to 2 years) was evident in 3 femoral components. At the time of the check 20 femoral components had been already revised, of this 7 hips were after repeated revision.

DISCUSSION: Between 1986 and 1992, 74 primary hip arthroplasties in 61 patients were performed at the authors' department using Schenker cementless femoral component always in combination with Poldi cemented cup. Of 61 patients, the follow-up was not completed in 27 (10 patients died, 6 of them underwent a revision surgery at other hospitals, 11 patients were lost for the follow-up). In the evaluated 18 hips only 7 were without pain, another 3 patients from suffered occasional pain which responded to common analgesics. The results of clinical evaluation after Harris are unconvincing. During the follow-up 29 joints (39% of the original cohort) had been revised or indicated for revision surgery. Repeated revision surgery was performed in 7 hip joints where the Schenker cementless femoral component was originally replaced by cemented stem and this cemented component loosened within 3 to 7 years after the first revision. With regard to the success rate of other double tapered femoral components, the authors consider the material of the component (vitalium) as the main cause of failure. The surface of this stem did not provide for a long-term osteointegration and is at present successfully used only for production of femoral heads rather than for cementless femoral components.

CONCLUSION: A favourable clinical finding and a good integration of the cementless femoral component Schenker were recorded within the average follow-up of 12 years only in 5 patients. All of them were young at the time of surgery and had a very good quality of bone. As a conclusion authors state that in general, Schenker cementless femoral component has not proved to be successful in clinical practice. For revision surgery of the loosened Schenker cementless femoral component it is necessary to use a titanium cementless component with a surface allowing long-term osteointegration.