Similarly low blood metal ion levels at 10-years follow-up of total hip arthroplasties with Oxinium, CoCrMo, and stainless steel femoral heads. Data from a randomized clinical trial

Abstract

The use of inert head materials such as ceramic heads has been proposed as a method of reducing wear and corrosion products from the articulating surfaces in total hip arthroplasty, as well as from the stem-head taper connection. The aim of the present study was to compare the blood metal ion levels in patients with Oxinium and CoCrMo modular femoral heads, as well as monoblock stainless steel Charnley prostheses at 10 years postoperatively. The 150 patients with osteoarthritis of the hip joint included in a randomized clinical trial were grouped according to femoral head material. One group (n = 30) had received the Charnley monoblock stainless steel stem (DePuy, UK). The other patients (n = 120) received a Spectron EF CoCrMo stem with either a 28 mm CoCrMo or Oxinium modular head (Smith & Nephew, USA). After 10 years, 38 patients had withdrawn, 19 deceased, 7 revised due to aseptic loosening and 5 revised due to infection. The 81 patients with median age of 79 years (70-91) were available for whole blood metal ion analysis. The levels of Co, Cr, Ni and Zr in the blood were generally low with all the head materials (medians <0.3 micrograms/L) and no statistical difference between the groups were found (p = .2-.8). Based on the low blood metal ion values in our study groups, no indication of severe trunnion corrosion in patients with CoCrMo heads was observed, neither was there any beneficial reduction in metal ion exposure with the Oxinium femoral heads.

Keywords: RCT; arthroplasty; blood metal ion; chromium; cobalt; modular stem; oxidized zirconium; oxinium; trunnionosis.

FIGURE 1

Participant flow diagram describing the original five study groups based on the different head‐cup articulations and the final three groups based on head material (stainless steel, CoCrMo, and Oxinium). Exclusions after 10 years follow‐up are sorted after revision causes (infection or aseptic loosening) and reasons for drop out (deceased or lost to follow‐up). The gender distribution, age and Harris Hip Score (median and range) in the three study groups are specified

FIGURE 2

(A) Charnley flanged 40 monoblock, oval, 316 L stainless steel, matte surface (Ra 0.8 μm) femoral stem with a 22.2 mm head, which articulated with a Charnley Ogee UHMWPE acetabular cup. (B) Spectron EF CoCrMo femoral stem with a 28 mm CoCrMo modular femoral head, retrieved from study case n° 819, with abrasive marks on the stem‐cement interface, mainly on the posterior‐distal‐medial side. The collared Spectron EF stem was fabricated with a matte distal surface (Ra 0.7 μm) and a grit blasted roughened surface (Ra 7.3 μm) on the proximal third of the stem. The neck and collar are highly polished. The stem used in this RCT was supplied with three tantalum markers, one of which was attached to a cone in the neck, the second in the medial side of the collar and the third on the distal tip of the stem. (C) CoCrMo 28 mm femoral head (left) and Oxinium 28 mm femoral head (right). Spectron EF stem taper size 12/14, standard offset (in the middle). (D) Reflection All‐Poly UHMWPE cup.

FIGURE 3

Boxplot of blood metal ion levels (μg/L) for Cr, Co, Zr, and Ni, grouped on head material. Horizontal lines inside the boxes indicates median level. Whiskers represents min‐max values (range). SS, stainless steel