Abstracts Posters SICOT-SOF meeting Gothenburg 2010 _2_
Abstracts Posters SICOT-SOF meeting Gothenburg 2010 _2_ Abstracts Posters SICOT-SOF meeting Gothenburg 2010 _2_
Poster Topic: Arthroplasty - Hip Abstract number: 23740 THE EFFECT OF FEMORAL COMPONENT ALIGNMENT WITH THE BIRMINGHAM MID-HEAD RESECTION James P. WADDELL, Michael OLSEN, Peter M. LEWIS, Emil H. SCHEMITSCH St. Michael's Hospital, Toronto (CANADA) The Birmingham Mid-Head Resection (BMHR) is a short-stem alternative to hip resurfacing for patients with compromised femoral head anatomy. It is not known if femoral neck fracture risks associated with hip resurfacing pose the same risk to midhead resection arthroplasty. The current study investigated the effect of coronal alignment on proximal femoral strength with the BMHR.Sixteen pairs of fresh-frozen cadaveric femurs were divided into two equal groups. Individual pairs were divided into control and experimental specimens. The first alignment group prepared experimental specimens in 10 degrees of relative valgus alignment while the second group prepared experimental femurs in 10 degrees of relative varus. Control specimens were prepared with the implant aligned with the native femoral neck-shaft angle. Femurs were tested in axial compression in single-leg stance. Failure testing revealed no significant differences in peak failure loads between matched paired femurs prepared in relative varus (mean 4324 N, SD 2207) and controls (Mean 4114, SD 2153, p=0.996) or femurs aligned in valgus (mean 4623, SD 1608) compared to controls (Mean 4761, SD 1290, p=0.999). Femurs were well matched for BMD and anatomical parameters.The findings of the current study are in contrast to previous studies investigating implant alignment in hip resurfacing. A valgus aligned implant did not appear to strengthen, nor a varus implant weaken, proximal femoral strength compared to a neutrally aligned implant. Failure of the proximal femur implanted with a BMHR appears less sensitive to variations in implant alignment than a typical hip resurfacing. 22
Poster Topic: Arthroplasty - Hip Abstract number: 23745 METAL SENSITIVITY AFTER ARTHROPLASTY - A CONCERN REVISITED S. THOMAS, R. DHARMARAJAN Cumberland Infirmary, Carlsile, Newcastle Upon Tyne (UNITED KINGDOM) Introduction: Although metal sensitivity to orthopaedic implants has been reported several times, it still remains poorly understood. Metal implants frequently used in Orthopaedic surgery are alloys of cobalt, chromium and molybdenum. Metal implants have caused concerns as they are known to be potential allergens for the general population. IncidenceIt is estimated that metal sensitivity affects about 10- 15% of the population. The reported immune reactions are usually eczema, redness and itching. It is thought that following corrosion of the implants the electrochemical changes trigger the immune system causing these reactions. The incidence of contact allergy to nickel was 12% in females and 4% in males. Current literature Many still consider metal sensitivity to be a contributing factor for implant failure and recommend the removal of implants that have served its purpose. Other studies have suggested that a history of metal allergy or sensitivity is not reliable and recommendsthose patients about to undergo an arthroplasty have a patch testing pre operatively. After assessing currently available literature we agree with that until well designed studies are done to specifically look into the role of metal sensitivity in implant failure the risk is considered to be minimal.Summary: Even though metal sensitivity to Orthopaedic implants have been reported in arthroplasty, current available literature suggests that with use of metal on plastic prosthesis, the occurrence of allergy is minimal. Pre operative testing may be beneficial in those with positive history. 23
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Poster<br />
Topic: Arthroplasty - Hip<br />
Abstract number: 23740<br />
THE EFFECT OF FEMORAL COMPONENT ALIGNMENT WITH THE<br />
BIRMINGHAM MID-HEAD RESECTION<br />
James P. WADDELL, Michael OLSEN, Peter M. LEWIS, Emil H. SCHEMITSCH<br />
St. Michael's Hospital, Toronto (CANADA)<br />
The Birmingham Mid-Head Resection (BMHR) is a short-stem alternative to hip<br />
resurfacing for patients with compromised femoral head anatomy. It is not known if<br />
femoral neck fracture risks associated with hip resurfacing pose the same risk to midhead<br />
resection arthroplasty. The current study investigated the effect of coronal<br />
alignment on proximal femoral strength with the BMHR.Sixteen pairs of fresh-frozen<br />
cadaveric femurs were divided into two equal groups. Individual pairs were divided<br />
into control and experimental specimens. The first alignment group prepared<br />
experimental specimens in 10 degrees of relative valgus alignment while the second<br />
group prepared experimental femurs in 10 degrees of relative varus. Control<br />
specimens were prepared with the implant aligned with the native femoral neck-shaft<br />
angle. Femurs were tested in axial compression in single-leg stance. Failure testing<br />
revealed no significant differences in peak failure loads between matched paired<br />
femurs prepared in relative varus (mean 4324 N, SD 2207) and controls (Mean 4114,<br />
SD 2153, p=0.996) or femurs aligned in valgus (mean 4623, SD 1608) compared to<br />
controls (Mean 4761, SD 1290, p=0.999). Femurs were well matched for BMD and<br />
anatomical parameters.The findings of the current study are in contrast to previous<br />
studies investigating implant alignment in hip resurfacing. A valgus aligned implant<br />
did not appear to strengthen, nor a varus implant weaken, proximal femoral strength<br />
compared to a neutrally aligned implant. Failure of the proximal femur implanted with<br />
a BMHR appears less sensitive to variations in implant alignment than a typical hip<br />
resurfacing.<br />
22
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