Migration pattern of a short uncemented stem with or without collar: a randomised RSA-study with 2 years follow-up

Abstract

Background: There is an increasing interest in shorter, proximally loading, uncemented femoral stems. The aim of this study was to evaluate a new short stem type, its design based on a well-proven precursor, but with several new design features to facilitate easier insertion and possible preservation of proximal bone stock. It is available with or without a collar. Methods: The study includes 50 patients with primary osteoarthritis, mean age 59 (range 36–75) years, randomised to receive either the collar-fitted or the collarless stem. The patients underwent repeated radiostereometry (RSA) examinations (0, 0.5, 3, 12, 24 months), conventional radiography and filled out both hip-specific (HOOS) and general health (EQ-5D) questionnaires. Results: There was no statistically significant difference between the collared and collarless stems regarding migration and clinical outcome. Both stem types exhibit a similar pattern of initial subsidence (collared 0.63 mm vs. collarless 0.75 mm [ p = 0.50]) and retroversion (collared 0.71° vs. collarless 0.97° [ p = 0.36]) up to 3 months followed by stabilisation, in similarity with its precursors, suggesting good osseointegration. No stem has been revised or considered loose. Conclusions: The new design features, including shortening the stem, do not compromise migration pattern or osseointegration, regardless collar or not.

Preserved periprosthetic bone stock at 5 years post-operatively with uncemented short hip stem in both collared and collarless version

“…The primary effect variable was RSA migration and 50 patients; 25 patients in each group were included in the study based on a power calculation derived from expected RSA data. These results have been published previously [12]. The secondary DXA outcome measure was difference in bone density changes as measured in the seven Gruen zones at one year.…”

“…According to earlier published RSA data there were no significant difference between the two stem types regarding migration. Both had stabilised at three months and thereafter showed consistent almost steady state position, interpreted as good osseointegration [12]. This indicates that the lip does not have a major impact on either stem migration or bone density.…”

Outcomes of total hip arthroplasty using collared versus collarless uncemented HA-coated stems: a meta-analysis

“…A total of 446 records were excluded by examining their titles and/or abstracts, leaving 40 records for full-text review. Twenty-nine studies were excluded after full-text review: ten because they reported on non-conventional-length (short, long) or non-HA-coated stems ( 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 ), eight because they compared collared versus collarless stems with different designs or coatings ( 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 ), five because they were letters to the editor, technical notes, or correspondence ( 38 , 39 , 40 , 41 , 42 ), three because they did not report on any outcomes ( 14 , 43 , 44 ), one because it compared hemiarthroplasty versus THA ( 45 ), one because it was a cadaveric study ( 46 ), and one because it was a non-comparative study ( 47 ). A further three articles were excluded because the outcomes of interest were not presented separately for collared versus collarless stems (the authors were contacted at least three times but none responded) ( 4 , 6 , 48 ).…”

Surgical approach had minor association with femoral stem migration in total hip arthroplasty: radiostereometric analysis of 61 patients after 5-year follow-up

“…A review stated that the stabilization of migration can be more relevant than the absolute value of migration, when defining acceptable migration thresholds for uncemented stems [20]. Others have suggested that a continuous migration after 3 to 6 months could be a risk factor for later loosening, describing a "gold standard" type of migration, where postoperative migration is followed by almost complete stabilization within 3-6 months after surgery [21].…”