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Form and Finish of Implants in Uncemented Hip Arthroplasty: Effects of Different Shapes and Surface Treatments on Implant Stability
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Orthopaedics.
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The design of an uncemented hip arthroplasty implant affects its long-term survival. Characteristics such as the form and the finish of the implant are crucial in order to achieve the best possible conditions for long-term implant survival. In this thesis we hypothesized that different shapes of stems and cups used in primary and revision total hip arthroplasty (THA), and their finish with hydroxyapatite (HA) coating affect implant stability and thus long-term survival.

In 2 prospective cohort studies the clinical outcome, the stability measured with radiostereometric analysis (RSA), and the periprosthetic changes in bone mineral density (BMD) measured with dual-energy x-ray absorptiometry (DXA) were investigated in 2 uncemented THA implants – the CFP stem and the TOP cup. In 3 register studies the effect of HA coating on uncemented THA implants used in primary and revision arthroplasty was investigated.

Both implants investigated in the prospective cohort studies showed an excellent short-term clinical outcome with good primary stability, but neither their novel form nor the finish with HA protected the implants from the proximal periprosthetic demineralization that usually occurs around other uncemented THA implants.

The register studies revealed that HA coating on cups used in primary and revision THA is a risk factor for subsequent revision of the implant. The use of HA coating on the stem in primary THA did not affect long-term survival. Additionally, the shape of an implant plays a crucial role for implant stability and survival.

In conclusion, this thesis highlights that the finish of implants with HA coating does not prevent periprosthetic proximal femoral bone loss and can even enhance the risk of revision of both primary and secondary cups. Importantly, the shape of uncemented THA implants affect their stability, showing that the implant form is a crucial factor for the long-term survival.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2013. , 74 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 845
Keyword [en]
Form, Finish, Total hip arthroplasty, Swedish Hip Arthroplasty Register, Hydroxyapatite, RSA, DXA, BMD, Stability.
National Category
Orthopedics
Research subject
Orthopaedics
Identifiers
URN: urn:nbn:se:uu:diva-185299ISBN: 978-91-554-8549-8 (print)OAI: oai:DiVA.org:uu-185299DiVA: diva2:572171
Public defence
2013-01-11, Grönwallsalen, Akademiska sjukhuset, Akademiska sjukhus, Uppsala, 09:00 (Swedish)
Opponent
Supervisors
Available from: 2012-12-21 Created: 2012-11-21 Last updated: 2013-08-06Bibliographically approved
List of papers
1. A prospective cohort study on the short collum femoris preserving (CFP) stem using RSA and DXA: Primary stability but no prevention of proximal bone loss in 27 patients followed for 2 years
Open this publication in new window or tab >>A prospective cohort study on the short collum femoris preserving (CFP) stem using RSA and DXA: Primary stability but no prevention of proximal bone loss in 27 patients followed for 2 years
Show others...
2013 (English)In: Acta Orthopaedica, ISSN 1745-3674, E-ISSN 1745-3682, Vol. 84, no 1, 32-39 p.Article in journal (Refereed) Published
Abstract [en]

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 radio-stereometric 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 0.01 (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.

National Category
Orthopedics
Identifiers
urn:nbn:se:uu:diva-185296 (URN)10.3109/17453674.2013.765623 (DOI)000314897500007 ()
Available from: 2012-11-21 Created: 2012-11-21 Last updated: 2017-12-07Bibliographically approved
2. Demineralization around a stable uncemented modular cup: A prospective cohort study on a hemispherical, partly threaded and hydroxyapatite-coated cup using RSA and DXA
Open this publication in new window or tab >>Demineralization around a stable uncemented modular cup: A prospective cohort study on a hemispherical, partly threaded and hydroxyapatite-coated cup using RSA and DXA
Show others...
(English)Manuscript (preprint) (Other academic)
National Category
Orthopedics
Identifiers
urn:nbn:se:uu:diva-185297 (URN)
Available from: 2012-11-21 Created: 2012-11-21 Last updated: 2013-02-11
3. Increased risk of revision of acetabular cups coated with hydroxyapatite: A Swedish Hip Arthroplasty Register study involving 8,043 total hip replacements
Open this publication in new window or tab >>Increased risk of revision of acetabular cups coated with hydroxyapatite: A Swedish Hip Arthroplasty Register study involving 8,043 total hip replacements
2010 (English)In: Acta Orthopaedica, ISSN 1745-3674, E-ISSN 1745-3682, Vol. 81, no 1, 53-59 p.Article in journal (Refereed) Published
Abstract [en]

Background Hydroxyapatite (HA) is the main inorganic component of bone, and HA coating is widely used on acetabular cups in hip arthroplasty. It has been suggested that this surface finish improves cup survival. Methods All patients registered in the Swedish Hip Arthroplasty Register between 1992 and 2007 with an uncemented acetabular implant that was available either with or without HA coating were identified. 8,043 total hip arthroplasties (THAs) with the most common cup types (Harris-Galante, Romanus, and Trilogy) were investigated. A Cox regression model including type of coating, age, sex, primary diagnosis, cup type, and type of stem fixation was used to calculate adjusted risk ratios (RRs) for the risk of revision. Results HA coating was a risk factor for cup revision due to aseptic loosening (adjusted RR 1.7; 95% CI: 1.3-2). Age at primary arthroplasty of < 50 years, a diagnosis of pediatric hip disease, the use of a cemented stem, and the Romanus and Harris-Galante cup types were also associated with statistically significantly increased risk of cup revision due to aseptic loosening. Interpretation Our findings question the routine use of HA-coated cups in primary total hip arthroplasty. With some designs, this practice may even increase the risk of loosening-resulting in revision surgery.

National Category
Surgery
Research subject
Orthopaedics
Identifiers
urn:nbn:se:uu:diva-112790 (URN)10.3109/17453670903413178 (DOI)000276167300011 ()19968603 (PubMedID)
Available from: 2010-01-20 Created: 2010-01-20 Last updated: 2017-12-12Bibliographically approved
4. Effects of hydroxyapatite coating on survival of an uncemented femoral stem: A Swedish Hip Arthroplasty Register study on 4,772 hips
Open this publication in new window or tab >>Effects of hydroxyapatite coating on survival of an uncemented femoral stem: A Swedish Hip Arthroplasty Register study on 4,772 hips
2011 (English)In: Acta Orthopaedica, ISSN 1745-3674, E-ISSN 1745-3682, Vol. 82, no 4, 399-404 p.Article in journal (Refereed) Published
Abstract [en]

Background and purpose: Hydroxyapatite (HA) is widely used as a coating for uncemented total hip arthroplasty components. This has been suggested to improve implant ingrowth and long-term stability. However, the evidence behind the use of HA coating on femoral stems is ambiguous. We investigated survival of an uncemented, tapered titanium femoral stem that was available either with or without HA coating (Bi-Metric).

Patients and methods: The stem had been used in 4,772 total hip arthroplasties (THAs) in 4,169 patients registered in the Swedish Hip Arthroplasty Register between 1992 and 2009. 59% of the stems investigated were coated with HA and 41% were uncoated. Kaplan-Meier survival analysis and a Cox regression model with adjustment for age, sex, primary diagnosis, and the type of cup fixation were used to calculate survival rates and adjusted risk ratios (RRs) of the risk of revision for various reasons.

Results: The 10-year survival rates of the HA-coated version and the uncoated version were about equal when we used revision for any reason as the endpoint: 98% (95% CI: 98-99) and 98% (CI: 97-99), respectively. A Cox regression model adjusting for the covariates mentioned above showed that the presence of HA coating did not have any influence on the risk of stem revision for any reason (RR = 1.0, 95% CI: 0.6-1.6) or due to aseptic loosening (RR = 0.5, CI: 0.2-1.5). There was no effect of HA coating on the risk of stem revision due to infection, dislocation, or fracture.

Interpretation: The uncemented Bi-Metric stem showed excellent 10-year survival. Our findings do not support the use of HA coating on this stem to enhance implant survival.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:uu:diva-159485 (URN)10.3109/17453674.2011.597699 (DOI)000294851100002 ()
Available from: 2011-10-03 Created: 2011-10-03 Last updated: 2017-12-08Bibliographically approved
5. Effects of hydroxyapatite coating of cups used in hip revisionarthroplasty: A Swedish Hip Arthroplasty Register study of 1,780 revisions
Open this publication in new window or tab >>Effects of hydroxyapatite coating of cups used in hip revisionarthroplasty: A Swedish Hip Arthroplasty Register study of 1,780 revisions
2012 (English)In: Acta Orthopaedica, ISSN 1745-3674, E-ISSN 1745-3682, Vol. 83, no 5, 427-435 p.Article in journal (Refereed) Published
Abstract [en]

Background and purpose

Coating of acetabular revision implants with hydroxyapatite (HA) has been proposed to improve ingrowth and stability. We investigated whether HA coating of revision cups can reduce the risk of any subsequent re-revision.

Methods

We studied uncemented cups either with or without HA coating that were used at a primary acetabular revision and registered in the Swedish Hip Arthroplasty Register (SHAR). 2 such cup designs were identified: Harris-Galante and Trilogy, both available either with or without HA coating. These cups had been used as revision components in 1,780 revisions of total hip arthroplasties (THA) between 1986 and 2009. A Cox proportional hazards model including the type of coating, age at index revision, sex, cause of cup revision, cup design, the use of bone graft at the revision procedure, and the type of cup fixation at primary THA were used to calculate adjusted risk ratios (RRs with 95% CI) for re-revision for any reason or due to aseptic loosening.

Results

71% of the cups were coated with HA and 29% were uncoated. At a mean follow-up time of 6.9 (0–24) years, 159 (9%) of all 1,780 cups had been re-revised, mostly due to aseptic loosening (5%), dislocation (2%), or deep infection (1%). HA coating had no significant influence on the risk of re-revision of the cup for any reason (RR = 1.4, CI: 0.9–2.0) or due to aseptic loosening (RR = 1.1, 0.6–1.9). In contrast, HA coating was found to be a risk factor for isolated liner re-revision for any reason (RR = 1.8, CI: 1.01–3.3). Age below 60 years at the index cup revision, dislocation as the cause of the index cup revision, uncemented cup fixation at primary THA, and use of the Harris-Galante cup also increased the risk of re-revision of the cup. In separate analyses in which isolated liner revisions were excluded, bone grafting was found to be a risk factor for re-revision of the metal shell due to aseptic loosening (RR = 2.1, CI: 1.05–4.2).

Interpretation

We found no evidence to support the notion that HA coating improves the performance of the 2 studied cup designs in revision arthroplasty. In contrast, patient-related factors such as younger age and dislocation as the reason for cup revision, and technical factors such as the choice of revision cup were found to influence the risk of subsequent re-revision of the cup. The reason for inferior results after revision of uncemented cups is not known, but it is possible that these hips more often had pronounced bone loss at the index cup revision.

National Category
Orthopedics
Identifiers
urn:nbn:se:uu:diva-185295 (URN)10.3109/17453674.2012.720117 (DOI)000310015700001 ()22937978 (PubMedID)
Available from: 2012-11-21 Created: 2012-11-21 Last updated: 2017-12-07Bibliographically approved

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