The Migration Pattern of a Cementless Hydroxyapatite-Coated Titanium Stem under Immediate Full Weight-Bearing—A Randomized Controlled Trial Using Model-Based RSA

• Published in: Journal of clinical medicine Vol. 9; no. 7; p. 2077
• Main Authors: Reiner, Tobias, Sonntag, Robert, Kretzer, Jan Philippe, Clarius, Michael, Jakubowitz, Eike, Weiss, Stefan, Ewerbeck, Volker, Merle, Christian, Moradi, Babak, Kinkel, Stefan, Gotterbarm, Tobias, Hagmann, Sébastien
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 02.07.2020; MDPI
• Subjects: Arthritis; cementless total hip arthroplasty; Clinical medicine; Clinical trials; Geometry; Hydroxyapatite; hydroxyapatite-coated femoral stem; implant stability; Migration; Orthopedics; Patients; radiostereometric analysis; RSA; Software; Standard deviation; Statistical analysis; Surgery; Surgical techniques; Titanium alloys; Transplants & implants; Variance analysis; United States > US; Switzerland; Netherlands
• ISSN: 2077-0383; 2077-0383
• DOI: 10.3390/jcm9072077

(1) Background: High primary stability is important for the long-term survival of cementless femoral stems in total hip arthroplasty (THA). The objective of this study was to investigate the migration pattern of a hydroxyapatite-coated cementless hip stem developed for minimally invasive surgery using model-based radiostereometric analysis (RSA). (2) Methods: In this randomized controlled trial, 44 patients with an indication for cementless primary THA were randomly allocated to receive either the SL-PLUS MIA stem, developed for minimally invasive surgery, or the SL-PLUS stem (Smith & Nephew Orthopaedics, Baar, Switzerland) which served as a control group. Unlimited weight-bearing was permitted postoperatively in both groups. Model-based RSA was performed after six weeks and after 3, 6, 12 and 24 months postoperatively. (3) Results: Mean total stem subsidence at two-year follow-up was 0.40 mm (SD 0.66 mm) in the SL-PLUS group and 1.08 mm (SD 0.93 mm) in the SL-PLUS MIA group (p = 0.030). Stem subsidence occurred during the first six weeks after surgery, indicating initial settling of the stem under full weight-bearing. Both stem designs showed good osseointegration and high secondary stability with no further migration after initial settling. (4) Conclusions: Settling of a cementless straight femoral stem occurs during the first six weeks after surgery under full weight-bearing. Although initial stem migration was higher in the SL-PLUS MIA group, it had no influence on secondary stability. All implants showed good osseointegration and high secondary stability with no signs of implant loosening during this two-year follow-up period.