OSTEOLYSIS AFTER PRIMARY TOTAL HIP ARTHROPLASTY USING FIRST-GENERATION CROSS-LINKED POLYETHYLENE: ANALYSIS USING 3D CT SCAN AT FOLLOW-UP OF 15 YEARS

Abstract

We evaluated (1) wear rate, (2) prevalence and volume of osteolysis using 3D-CT scan, (3) other bearing-related complications, (4) HHS and survivorship free from revision at 15 years after THA using first-generation XLPE (1G XLPE).

One-hundred sixty THAs were evaluated regarding bearing-related complication, HHS and survivorship. Among them, 112 hips underwent 3D-CT to analyze wear rate and osteolysis. All THAs were performed by single surgeon using cup of identical design, a 28-mm metal head and 1G XLPE (10 Mrad). Average age were 57 years and mean follow-up was 15.2 years. 3D-CT scan was performed at average of 13.0 years. Clinical evaluation included HHS and radiographic analysis was performed regarding stem alignment, cup anteversion and inclination angle, component stability, wear rate and osteolysis. Wear was measured using digital software. The prevalence and volume of osteolysis were also evaluated. Complications included XLPE dissociation/rim fracture, dislocation, periprosthetic fracture, infection, HO and any revision. Survivorship free from revision at 15 years was estimated.

Average inclination and anteversion angle of cups were 40.7° and 20.6°. Mean stem alignment was 0.1° valgus. Average bedding-in and annual wear rate wear rate was 0.085 mm and 0.025 mm/yr. Eleven hips (10%) demonstrated osteolysis; pelvic osteolysis with average volume of 1.4 cm³ in six and femoral osteolysis with mean size of 0.4 cm² in seven hips. Of 160 THAs, 5 hips (3%) dislocated. Overall, bearing-related complications occurred in 16 hips (10%). Other complications included postoperative periprosthetic fracture in 4 (3%), infection and HO in 3 hips, respectively. No hip demonstrated loosening, XLPE rim fracture/dissociation. Seven THAs (4%) were revised; recurrent dislocation in 5 and periprosthetic joint infection in 2 hips. Average HHS at last follow-up improved from 47.7 preoperatively to 91.2 points (p<0.001). Estimated survivorship free from revision at 15 years was 95.6 %.

THA using 1G XLPE demonstrated low wear rate as well as low incidence of osteolysis at average follow-up of fifteen years. Longer-term studies will be necessary to determine if XLPE will continue to demonstrate this improved osteolysis characteristics.