Abstract
Background Femoral bone remodeling around hip prosthesis after total hip arthroplasty (THA) is definite but unpredictable in time and place. This study aimed to investigate the implant-specific remodeling and periprosthetic bone mineral density (BMD) changes after implantation of the Ribbed anatomic cementless femoral stem. Methods After power analysis, 41 patients who had undergone primary unilateral THA with the Ribbed anatomic cementless stem were included. BMD of the seven Gruen zones was measured by dual-energy X-ray absorptiometry, and the contact, fitness, and fixation of the femoral stem and proximal femur were analyzed by X-ray. Additional clinical outcome parameters were also recorded. Results Compared with the contralateral unoperated side, significant reductions of BMD were detected in the distal zone (Gruen zone 4: 1.665±0.198 versus 1.568±0.242 g/cm2, P=0.001) and middle distal zone (Gruen zone 5: 1.660±0.209 versus 1.608±0.215 g/cm2, P=0.026) on the prosthetic side, but no significant differences in BMD were detected in other zones (Gruen zones 1, 2, 3, 6, and 7). Subgroups analyses indicated no significant correlation between periprosthetic BMD changes and clinical factors including primary disease and body mass index. Visible areas of bone ingrowth indicated solid fixation of the femoral stem and there was no case of loosening. Clinical and functional outcome scores were excellent with mean HHS of 93.13 points and mean WOMAC score of 5.20 points, and three patients described intermittent mild thigh pain at the final follow-up. Conclusions For the Ribbed femoral stem, the periprosthetic BMD was well maintained in the proximal femur, while periprosthetic BMD was significantly reduced in the distal and middle distal zones of the femur. Further clinical investigations are required to examine the efficacy of the Ribbed stem, particularly with regard to long-term survival. This trial is registered with ChiCTR1800017750.
Highlights
Total hip arthroplasty (THA) is one of the most successful surgical procedures in the world, with universally high patient satisfaction above 90% [1,2,3]
The inclusion criteria were as follows: (1) adult patients who undergo primary unilateral total hip arthroplasty (THA) with the Ribbed (Ribbed5 Hip system, Waldemar Link5, Hamburg, Germany) anatomic cementless hydroxyapatite (HA) coated femoral stem in our department; (2) surgeries were performed by two senior surgeons using posterior-lateral approach under general anesthesia in laminar air flow operation room; (3) patients understood the scope of the study and agreed to participate at followup
Previous studies stated that the periprosthetic remodeling stabilizes in the second year, and only marginal changes of bone mineral density (BMD) occurred after the 12th postoperative month [19, 20]; patient who had undergone primary unilateral THA within one year would be excluded
Summary
Total hip arthroplasty (THA) is one of the most successful surgical procedures in the world, with universally high patient satisfaction above 90% [1,2,3]. The implant survival following THA is the most commonly investigated outcome, and recent studies suggested increased survivorship of implant in long-term follow-up [4,5,6]. Engendering clinical longevity of implants, achieving higher long-term survivorship of primary THA, and reducing revision rate should be given top priority. This study aimed to investigate the implant-specific remodeling and periprosthetic bone mineral density (BMD) changes after implantation of the Ribbed anatomic cementless femoral stem. Further clinical investigations are required to examine the efficacy of the Ribbed stem, with regard to long-term survival.
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