Ceramic-on-ceramic THA Implants in Patients Younger Than 20 Years.

BACKGROUND

Poor survival of THA implants in very young patients has been attributed to use of cemented implants, wear of conventional polyethylene, and the presence of morphologic deformities in the proximal femur or in the acetabulum. Few studies have reported the long-term results of ceramic-on-ceramic implants in THAs in patients younger than 20 years.

QUESTION/PURPOSES: We determined: (1) the proportion of patients who experienced complications related to the ceramic bearing (squeaking, fracture); (2) the survivorship free from loosening and free from revision for any reason; (3) whether patients with osteonecrosis had inferior survivorship compared with patients whose surgical indication was all other diagnoses including sequelae of pediatric hip disorders (developmental dysplasia of the hip, Legg-Calvé-Perthes disease, slipped capital femoral epiphysis); and (4) clinical function.

METHODS

Between 1979 and 2013, we performed 113 primary THAs in 91 patients younger than 20 years at the time of surgery. Of those, 105 THAs (83 patients) were done with ceramic-on-ceramic bearings (91% of the 91 patients); during that period, a ceramic-on-ceramic bearing couple was indicated in all patients younger than 20 years. In eight patients (eight hips), a cemented polyethylene cup was implanted because the diameter of the acetabulum was smaller than the smallest available ceramic cup (46 mm), or because adequate fixation of a ceramic press-fit cup could not be achieved despite careful reaming of the acetabulum. The most common diagnosis indicating THA was avascular necrosis of the femoral head (56.2%; 59 hips). Thirty-five patients (40 hips) had undergone previous operations before the replacement. Three patients (4%; four hips) died from unrelated causes, nine patients (11%; 13 hips) were lost to followup, and four patients (five hips) had a followup greater than 8.5 years but have not been seen in the last 5 years. Patients were assessed clinically (using the Merle d'Aubigne-Postel score, Hip disability and Osteoarthritis Outcome score (HOOS), and the SF-12(®) Health Survey, and radiographically for signs of radiolucencies, subsidence, or osteolysis on plain films. The mean followup was 8.8 ± 6.1 years (range, 2-34.4 years).

RESULTS

Five patients experienced transient noise generation, defined as a snap in four patients and squeaking in one. Seventeen hips underwent revision surgery-16 for aseptic loosening and one for septic loosening. The implant survival rate at 10 years with aseptic loosening as the endpoint was 90.3% (95% CI, 82.4%-98.9%). No hip had acetabular or femoral osteolysis. Survivorship in patients with osteonecrosis did not differ from survivorship in patients with other diagnoses. The Merle d'Aubigne-Postel score increased from 10.1 ± 4.0 to 17.6 ± 1.1 (p < 0.01); the mean HOOS score was 79.3 ± 13.8 (range, 50.6-100); the mean SF-12(®) physical and mental component scores were 48.1 ± 7.9 (range, 21.4-57.6), and 47.4 ± 12.2 (range, 24.5-99.4), respectively.

CONCLUSIONS

We found that patient-reported outcomes scores improved in most patients undergoing THA in this very young study group. Underlying diagnosis did not affect long-term survivorship. However, the revision-free survival rate at 10 years is lower than published estimates in older patients, and with 11% of patients lost to followup, our estimates may represent a best-case scenario. Therefore, we believe THA should be performed as a last resort in this population.

LEVEL OF EVIDENCE

Level IV, therapeutic study.