Effect of symmetrical restoration for the migration of uncemented total hip arthroplasty: a randomized RSA study with 75 patients and 5-year follow-up

Abstract

Background: Inferior placement of a femoral stem is predictive for early loosening and failure, but does restoration of the original hip anatomy benefit the function and survival of a total hip replacement? Methods: Seventy-five patients with primary unilateral hip osteoarthritis operated with an uncemented anatomical stem were randomized for either standard or modular stems. We used 50 ABG II stems with modular necks and 25 standard stems (control group). We measured the symmetry in hip anatomy between healthy and operated side. The anatomical restoration variables were anteversion, global offset, and femoral offset/acetabular offset (FO/AO) quota. We performed measurements using a CT-based 3D templating and measuring software. Migratory behavior of the stems was then measured postoperatively with repeated radiostereometry (RSA) examinations over 5 years. Results: Both stem types showed an early (within 3 months) good stabilization after an initial slight rotation into retroversion and subsidence. There were no significant differences in RSA migration between modular and standard stems. Postoperative anteversion and FO/AO quota had no impact on stem migration. The standard stem tended to result in insufficient global offset (GO), whereas the modular stem did not. Conclusions: The modular stem gave good symmetrical anatomical restoration and, like the standard version, a benign migratory behavior. Anteversion, GO, and FO/AO quota had no significant impact on stem migration. It therefore seems to be of no importance whether we choose a modular or a standard stem with regard to postoperative stem migration for this stem type. We overestimated the effect anatomical parameters have on stem movement; hence, we believe the study to be underpowered.

Unexpected varus deformity and concomitant metal ion release and MRI findings of modular-neck hip stems: descriptive RSA study in 75 hips with 8 years’ follow-up

“…The increased modification possibilities of modular stems with different neck options have previously been claimed as valuable for ROM, soft tissue balance, and to minimize leg length discrepancies (Barrack 1994, Jones 2004, Archibeck et al 2011, Srinivasan et al 2012. The RSA stem migration data showed that the ABG II proximal fit stem, in both the modular and non-modular version, is stable in its resting position after an initial slight subsidence and retroversion within the 3 first postoperative months (Kiernan et al 2020). There have, however, also been reports on disadvantages related to the additional neck-stem interface when using modular stems.…”

“…Of the 75 stems that we had in our cohort for the former ABG II study (Kiernan et al. 2020 ), we were able to include 47 modular stems with sufficient RSA data during the follow-up period and 25 non-modular standard stems (up to 5 years’ follow-up). We lost 1 patient to follow-up due to an early periprosthetic femoral fracture (PPFF); we excluded 2 because of problems in performing the postoperative RSA examination ( Table 1 ).…”

“…In 2010, we started a randomized controlled trial (Kiernan et al 2020) to evaluate the potential superiority of modular Background and purpose -Modular-neck hip stems have been identified with corrosion-related problems from the neck-stem junction. We report an ongoing varus deformity of modular-neck hip stems with simultaneous metal ion release observed during a study comparing the migration of modular vs. standard hip stems.…”

“…In 2010, we started a randomized controlled trial (Kiernan et al. 2020 ) to evaluate the potential superiority of modular stems in restoring hip symmetry and examine postoperative migration rates of ABG II modular vs. standard stems (ABG II system, Stryker, Exeter, UK) with RSA ( Figure 1 ). During the follow-up and data-processing, we achieved some unexpected results regarding the modular design.…”

Pre- and postoperative offset and femoral neck version measurements and validation using 3D computed tomography in total hip arthroplasty

“…The current cohort was based on a clinical study, reported elsewhere. 29 In that study, 75 patients were recruited for THA after informed consent and operated with the uncemented ABG II prosthesis (Stryker Orthopedics, Mahwah, NJ, USA). Due to incomplete imaging for various reasons, there were missing data for two patients preoperatively and two other patients postoperatively.…”