Effect of femoral stem surface coating on clinical and radiographic outcomes of cementless primary total hip arthroplasty: a patient-matched retrospective study

Abstract

Purpose This study aims to determine whether changing the stem coating grants superior outcomes at a minimum followup of five years. Methods Retrospective review of a consecutive series of primary total hip arthroplasties (THAs) operated by direct anterior approach between 01/01/2013 and 31/12/2014. Two stems were compared, which were identical except for their surface coating; "the Original stem" was fully coated with hydroxyapatite (HA), while "the ProxCoat stem" was proximally coated with plasma-sprayed titanium and HA. Matching was performed. Clinical assessment included modified Harris hip score (mHHS), Oxford hip score (OHS), and forgotten joint score (FJS). Radiographic assessment evaluated alignment, subsidence, pedestal formation, heterotopic ossification, radiolucent lines ≥ 2 mm, spot welds, cortical hypertrophy, and osteolysis. Results 232 hips received the Original stem and 167 the ProxCoat stem, from which respectively five hips (2.2%) and no hips (0%) underwent revision. Matching identified two groups of 91 patients, with comparable patient demographics. At > five years follow-up, there were no differences in OHS (16 ± 6 vs 15 ± 5; p = 0.075) nor FJS (81 ± 26 vs 84 ± 22; p = 0.521), but there were differences in mHHS (89 ± 15 vs 92 ± 12; p = 0.042). There were no differences in alignment, subsidence, pedestal formation, heterotopic ossification, cortical hypertrophy, and osteolysis. There were differences in prevalence of proximal radiolucent lines (12% vs 0%; p < 0.001) and distal spot welds (24% vs 54%; p < 0.001). Conclusion At a minimum follow-up of five years, this study on matched patients undergoing primary THA found that ProxCoat stems results in significantly fewer radiolucent lines, more spot welds, and less revisions than Original stems, thus suggesting better bone ingrowth.

Contact states with femoral cortical bone and periprosthetic bone mineral density changes differ between traditional and newly introduced fully hydroxyapatite-coated stems

“…10,11 It has a triple-tapered design with a reduced lateral flare, a short length, and both the proximal and distal cross-sections are rectangular (Figure 2). 10,11 Three arthroplasty surgeons with 23, 26, and 26 years of experience, respectively, performed all the operations as part of the same surgical team. The modified Watson-Jones approach was used in the T-HA group, 12 and the direct anterior or modified Watson-Jones approach was used in the N-HA group.…”

“…7,8 The AMIStem (N-HA) is made of 5 µm sand-blasted TiAl 6 Nb 7 and plasma sprayed with an 80 µm layer of HA over its entire surface. 10,11 It has a triple-tapered design with a reduced lateral flare, a short length, and both the proximal and distal cross-sections are rectangular (Figure 2). 10,11 Three arthroplasty surgeons with 23, 26, and 26 years of experience, respectively, performed all the operations as part of the same surgical team.…”

“…In this study, we compared a newly introduced fully HA-coated (N-HA) stem whose design is based on the characteristics of a rectangular, tapered, straight uncemented stem (Khanuja's classification type 3 C), 9 with the T-HA stem. 10,11 While good clinical outcomes have been reported when using this N-HA stem, 10,11 to our knowledge, few authors have described its initial fixation pattern or periprosthetic changes in BMD. The hypothesis of this study was that different fully HA-coated stems would have different initial patterns of fixation and different local changes of BMD.…”

Over ten-year follow-up results of a prospective and consecutive series of primary total hip arthroplasty with an original cementless total hip prosthesis

“… One Endo medullary cortical thickening in zone 3, and 1 in zone 9. This should probably be avoided if the HA coating is limited to the proximal two-thirds of the stem [ 25 ]. …”

The influence of prosthetic positioning and proximal femoral morphology on leg length discrepancy and early clinical outcomes of cementless total hip arthroplasty

“…Literature has shown better radiographic outcomes and osseointegration in proximally coated compared to fully coated stems [ 24 ]. Yet it is unclear whether there are differences in clinical outcomes and LLD between different coated stems, and understanding the effect of stem design on LLD and clinical outcomes can help surgeons choose the proper prosthesis before surgery.…”