[Survivorship of the cemented hip prosthesis].

OBJECTIVES: To asses a survival-time of the cemented hip prostheses and to find factors causing its loosening.

MATERIALS AND METHODS: 211 patients (282 hip prostheses) were analyzed, of the 1693 patients (2096 hip prostheses) treated between 1970-2000. The follow-up ranged from 7 to 34 years (mean: 12.2 ++/- 5.4 years). The age of the patients at the operation procedure ranged from 25 to 74 years (mean 52 +/- 12 years). Only aseptic prosthesis loosening were considered and Kaplan-Meyer method was used for the prosthesis survivorship assessment.

RESULTS: Of the 282 prostheses, implant exchange was performed in 39 cases, where in 15 cases only cup was revised, in 5 cases the stem exclusively, and in 19 patients the whole implant was exchanged. Only 1.1% of implants were exchanged during first 5 years after surgery but from the 6th year the percentage of loosening increased several percents each year. Respectively 88.6, 70 and 65% survivorship of prosthesis was found after 10, 15, 20 years of follow-up. In the group of bilateral prosthesis implantation, the first implanted prosthesis was more susceptible for loosening. Seven cases of aseptic loosening (5.4%) of the 129 prostheses implanted between 1974 and 1995, occurred within 7 years after initial surgery where only one prosthesis (0.7%) was revised of the 152 implanted between 1996-2000 in the same time of follow-up. The age, growth, weight, BMI and sex did not influence the risk of implant loosening.

CONCLUSION: The mean survivorship of the hip prosthesis is 65% in 20- years follow up. When a proper initial fixation of the cemented hip prosthesis is performed, the risk of implant loosening increases gradually especially from the 6th year after surgery. The modern implants are less susceptible for loosening.