Is a hollow centralizer necessary when using a polished, tapered, cemented femoral stem?

Abstract

Background and purposeA tapered, polished and collarless stem is normally equipped with a hollow centralizer to prevent the stem from becoming end-bearing in the cement as the stem subsides. In a randomized clinical trial, we evaluated such a stem (MS-30), which was initially introduced with a solid centralizer but was later recommended to be fitted with a hollow centralizer. We hypothesized that while the stem would sink more, it would become rotationally stable and have less retroversion with a hollow centralizer than with a solid centralizer.Patients and methodsWe randomized 60 patients with primary hip arthritis to receive either a hollow centralizer or a solid centralizer with the stem. The effect was evaluated over a 10-year follow-up period with repeated RSA examinations, conventional radiographs, and clinical follow-ups using the WOMAC and SF-12 questionnaires.ResultsAt 10-year follow-up, the group with hollow centralizers had subsided more than the group with solid centralizers (1.99 mm (hollow) as opposed to 0.57 mm (solid); p < 0.001). However, rotation was similar at 10-year follow-up (mean retroversion 1.34° (hollow) and 1.30° (solid)). Both groups showed excellent 10-year results, with similar clinical outcome, and none of the stems were radiographically loose or had been revised.InterpretationAs expected, there was more subsidence in the group with hollow centralizers, and with similar magnitude to that reported in earlier RSA studies on conceptually similar prostheses. Interestingly, there was no difference in the rotational behavior of the prostheses. This stem type appears to have a design that, regardless of the type of centralizer and the possibility of subsidence, withstands the rotational forces it is subjected to very well. This study does not support the need for a hollow centralizer for these types of stems.

Temporal subsidence patterns of cemented polished taper-slip stems: a systematic review

“…Sixteen studies measured subsidence using Radiostereometric Analysis (RSA), 8 , 16 , 19 – 22 , 29 – 32 , 34 , 35 , 37 – 40 10 used measurements on plain X-rays 15 , 17 , 18 , 24 – 28 , 33 , 36 and two used Ein Bild Roentgen Analyse (EBRA, Table 3 ). 23 , 41 Twelve papers used the HHS 15 , 17 , 21 , 24 , 26 , 28 , 33 , 36 , 37 , 39 – 41 and six the OHS.…”

“…Amongst the included studies were six randomized controlled trials. 8 , 16 , 19 , 32 , 37 , 40 All papers included in this study were assessed to be of good or fair quality.…”

“…A single surgical approach was used in 16 studies, 8 , 16 , 30 , 33 , 37 – 40 , 18 – 23 , 25 , 29 with multiple approaches in nine 15 , 17 , 24 , 26 , 27 , 31 , 32 , 35 , 41 and three failing to detail the approach used ( Table 4 ). 28 , 34 , 36 …”

“…Third generation femoral cementing was used in 14 studies 16 , 19 – 21 , 24 , 26 , 29 – 33 , 36 , 40 , 41 and second generation in four. 15 , 17 , 18 , 25 Ten studies failed to specify the cementing technique used 8 , 22 , 23 , 27 , 28 , 34 , 35 , 37 – 39 and five of these also failed to specify the type of cement.…”

“… 15 , 17 , 18 , 25 Ten studies failed to specify the cementing technique used 8 , 22 , 23 , 27 , 28 , 34 , 35 , 37 – 39 and five of these also failed to specify the type of cement. 23 , 27 , 28 , 34 , 38 Nine studies documented the use of a centralizer 16 , 20 , 21 , 24 , 26 , 29 , 33 , 39 , 40 and 15 the use of a restrictor ( Table 4 ). 15 , 17 , 18 , 21 , 25 – 27 , 29 , 31 – 33 , 35 , 36 , 38 , 41 …”