Periprosthetic femoral bone reaction after total hip arthroplasty with preservation of the collum femoris: CT-assisted osteodensitometry 1 and 3 years postoperatively

Orthopädische Universitätsklinik im Waldkrankenhaus St. Marien gGmbH, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Deutschland.
Der Orthopäde (Impact Factor: 0.36). 03/2011; 40(7):591-8.
Source: PubMed


Short-stemmed cementless femoral components in total hip arthroplasty have been designed to preserve the proximal femoral bone stock by load transfer to the femoral metaphysis. An in vivo method of computed tomography-assisted (CT) osteodensitometry after total hip arthroplasty is presented which differentiates between cortical and cancellous bone density (BD) changes around uncemented femoral components.
Cortical and cancellous periprosthetic femoral BD (mg Ca HA/ml) was determined prospectively in 31 patients at day 10, 1 year and 3 years after total hip arthroplasty with preservation of the collum femoris (C.F.P.-stem, Link, Hamburg, Germany) using computed tomography-assisted osteodensitometry. Clinical results (Harris hip score) and plain x-rays were assessed in all cases.
Progressive proximal cortical BD loss was observed between the 1 year (Ø -8%) and 3 year (Ø -22%) postoperative measurements. Distal to the trochanter minor no significant cortical BD changes were observed. Proximal cancellous BD decreased progressively between the 1 year (Ø -33%) and 3 year (Ø -45%) analyses. The Harris hip score improved from 45 points pre-operatively to 93 points at the 3 year follow-up. All x-rays showed signs of stable ingrowth.
Periprosthetic CT osteodensitometry has the technical ability to discriminate between cortical and cancellous bone structures with respect to strain-adapted remodeling. Progressive proximal cortical and cancellous BD loss indicates that metaphyseal fixation cannot be achieved with the analyzed C.F.P. stem design. The lack of cortical BD loss below the trochanter minor suggests diaphyseal fixation of the implanted stem.

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    • "However, several studies using periprosthetic CT osteodensitometry and DXA have shown progressive loss of metaphyseal cortical and cancellous bone density loss with use of a short stem. Furthermore, bone density loss in Gruen zones 3, 4, and 5, below the trochanter minor, was significantly lower or absent, thereby suggesting diaphyseal fixation (Roth et al. 2005, Logroscino et al. 2011, Schmidt et al. 2011, Kress et al. 2012, Lazarinis et al. 2013). "
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    ABSTRACT: Background and purpose The aim of short-stem total hip arthroplasty is to preserve proximal bone stock for future revisions, to improve biomechanical reconstruction, and to make minimally invasive approaches easier. It is therefore being increasingly considered to be a sound alternative to conventional total hip arthroplasty, especially for young and active patients. However, it is still unknown whether survival rates of short-stem hips match current standards. We made a systematic summary of reported overall survival after short-stem total hip arthroplasty. Materials and methods We conducted a systematic review of English, French, German, and Dutch literature. 2 assessors independently identified clinical studies on short-stem hip arthroplasty. After recalculating reported revision rates, we determined whether each implant had a projected revision rate of 10% or less at 10 years of follow-up or a revision rate per 100 observed component years of 1 or less. Stems were classified as “collum”, “partial collum”, or “trochanter-sparing”. Results and Interpretation We found 49 studies, or 51 cohorts, involving 19 different stems. There was a large increase in recent publications. The majority of studies included had a follow-up of less than 5 years. We found a large number of observational studies on “partial collum” and “trochanter-sparing” stems, demonstrating adequate survival rates at medium-term follow-up. Clinical evidence from “collum stem” studies was limited to a small number of studies with a medium-term follow-up period. These studies did not show a satisfactory overall survival rate.
    Full-text · Article · Apr 2014 · Acta Orthopaedica
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    • "Our findings of substantial bone loss around the CFP stem in the calcar region are strengthened by other studies on this type of stem using plain radiography or computer tomography-assisted bone densitometry. It has been described that the " […] proximal part of the femur became relatively osteopenic " after insertion of the CFP stem , and that " […] proximal cancellous [bone density] decreased progressively " from the first to the third year after surgery using this stem (Schmidt et al. 2011). However, to our knowledge, no other studies have investigated periprosthetic BMD around the CFP stem using the highly accurate DXA method. "
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    ABSTRACT: Background and purpose Short femoral stems have been introduced in total hip arthroplasty in order to save proximal bone stock. We hypothesized that a short stem preserves periprosthetic bone mineral density (BMD) and provides good primary stability. Methods We carried out a prospective cohort study of 30 patients receiving the collum femoris-preserving (CFP) stem. Preoperative total hip BMD and postoperative periprosthetic BMD in Gruen zones 1–7 were investigated by dual-energy x-ray absorptiometry (DXA), stem migration was analyzed by radiostereometric analysis (RSA), and the Harris hip score (HHS) was determined. Results 2 patients were excluded intraoperatively and 1 patient was revised due to a deep infection, leaving 27 patients for analysis. The mean HHS increased from 49 (24–79) preoperatively to 99 (92–100) after 2 years. DXA after 1 year showed substantial loss of BMD in Gruen zone 7 (–31%), zone 6 (–19%), and zone 2 (–13%, p < 0.001) compared to baseline BMD determined immediately postoperatively. The bone loss in these regions did not recover after 2 years, whereas the more moderate bone loss in Gruen zones 1, 3, and 5 partially recovered. There was a correlation between low preoperative total hip BMD and a higher amount of bone loss in Gruen zones 2, 6 and 7. RSA showed minor micromotion of the stem: mean subsidence was 0.13 (95% CI: –0.28 to 0.01) mm and mean rotation around the longitudinal axis was 0.01º (95% CI: –0.1 to 0.39) after 2 years. Interpretation We conclude that substantial loss in proximal periprosthetic BMD cannot be prevented by the use of a novel type of short, curved stem, and forces appear to be transmitted distally. However, the stems showed very small migration—a characteristic of stable uncemented implants.
    Full-text · Article · Jan 2013 · Acta Orthopaedica
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    ABSTRACT: Uncemented hip replacement matches the best results of classic cemented replacements. With the aim of preserving bone and soft tissue, implants with shorter stems and proximal metaphyseal support have been developed. Likewise, the lack of distal load should avoid cortical diaphyseal remodelling phenomena and the thigh pain of some cylindrical and wedge implants. The resurfacing implant, very popular as a conservative hip replacement in the young adult, has disadvantages associated with the fragility of the neck and with large head metal friction torque. Short stem hip replacement may be a reasonable alternative to classic implants and surface hip replacements. The different designs of conservative short stem implants are analysed, and are classified according to their morphology and biomechanical characteristics. Some medium term series show promising results.
    No preview · Article · Feb 2012 · Revista Española de Cirugía Ortopédica y Traumatología
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