Omnifit-HA stem in total hip arthroplasty. A 2- to 5-year followup

Outcomes of the first 60 noncemented Omnifit-HA total hip arthroplasties in 56 patients were studied prospectively for 2 to 5 years. The femoral prosthesis had a proximal third circumferential hydroxyapatite coated surface treatment. The acetabular component was a hemispheric modular, porous, nonhydroxyapatite press fit cup, supplemented with screw fixation. One cup was revised for recurrent dislocation, with no femoral revisions. The mean Harris hip score was 54 (range, 20-76) before surgery and 96 (range, 83-100) at final followup, with all patients having an excellent or good outcome. Mild thigh pain occurred in 6% of hips. Subsidence occurred in 9% of hips (range, 1-2.8 mm); in all cases, subsidence was nonprogressive after 1 year. Stable bone ingrowth fixation was evident at the hydroxyapatite coated portion in 100%. A sclerotic reactive line adjacent to the nonhydroxyapatite portion of the stem occurred in 81% but was not adjacent to the hydroxyapatite coated portion of any stem. Endosteal condensation occurred in 90% and correlated with a higher Harris hip score (mean score, 96 with, 91 without). Endosteal lysis adjacent to or distal to the hydroxyapatite coating did not occur. Lytic lesions at the calcar occurred in 19% and correlated with a greater linear acetabular polyethylene wear rate (mean, 0.30 mm/year with lytic lesions, 0.17 mm/year without). This noncemented stem with proximal third hydroxyapatite coating showed excellent short term clinical and radiographic outcome. Absence of distal endosteal lysis, along with correlation of calcar erosion to polyethylene wear, suggests that early circumferential bony ingrowth afforded by hydroxyapatite coating prevents distal endosteal access to polyethylene debris at short term followup.