- See:
Total Hip Replacement Menu:
- Discussion:
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design considerations:
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femoral stem collar
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cemented femoral stems (
radiology of cemented femoral stems):
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press fit femoral stems:
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femoral component offset:
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rotational position of femoral component:
- see:
adult femoral and acetabular anteversion:
- if component is placed in anteversion with respect to axis of knee, femur is placed posteriorly with respect to pelvis;
- this is a stable situation, because excessive internal rotation is needed before the hip dislocates posteriorly
and the abductors do not allow enough external rotation for hip to dislocate anteriorly;
- excessive anteversion of femoral component of THR does not lead to dislocation problem, but it does limit external rotation;
- excessive retroversion tends to produce posterior dislocation;
- femoral components with inherent anteversion should be placed in neutral with respect to the plane of flexion of the knee;
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stiffness of femoral stem:
- high modulus (stiffer material such as cobalt chrome) will increase stresses in the stem and decrease stresses in the cement;
- transfer of the stress into the distal stem might stress shield the proximal femur and lead to disuse bone resorption;
- lower modulus (more flexible material such as titanium) can increase stress on the proximal bone but might
also increase stress on, and thus fatigue, the proximal cement increasing incidence of loosening;
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femoral head size:
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metal on metal designs begin at 36 mm and go upto greater than 50 mm;
- the larger femoral head size allows for increased stability and less impingement;
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polyethylene liner: (traditional design)
- choice of femoral head size seems to have settled on 26 or 28 mm;
- less acetabular strain and lower revision rates are associated w/ use of a twenty-six or 28 mm head;
- 32 mm head: 32 mm allow increased ROM before it impinges against the acetabulum, and therefore theoretically has less dislocation;
- main disadvantage is that it has less net wall thickness, and produces too large a volume of wear debris;
- 22 mm head
- produces too much linear wear or creep;
- smaller diameter head (22 mm) allow less stress/torque but may result in increased central acetabular wear and dislocation;
- references:
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Effect of femoral head size on wear of the polyethylene acetabular component.
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Size of the femoral head and acetabular revision in total hip-replacement arthroplasty.
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Range of Motion and Stability in Total Hip Arthroplasty With 28-, 32-, 38-, and 44-mm Femoral Head Sizes.
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Effect of Femoral Head Diameter and Operative Approach on Risk of Dislocation After Primary Total Hip Arthroplasty.
- Femoral Revision:
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removal of press fit stems:
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removal of cemented femoral stems:
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femoral press fit revision
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cemented femoral revision:
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bone grafting for femoral defects:
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total femoral replacement:
- Complications:
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femur fractures following THR:
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femoral stem failure:
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types of loosening:
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bending cantilever
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cemented femoral component loosening:
Histologic analysis of a retrieved microporous-coated femoral prosthesis. A seven-year case report.
Hydroxyapatite-Coated Femoral Stems.
Histological Analysis Of Components Retrieved at Autopsy.
Loosening of the femoral component after use of the medullary-plug cementing technique. Follow-up note with a minimum five-year follow-up.
Histomorphological studies of the long-term skeletal responses to well fixed cemented femoral components.
The survival of the cemented femoral component of a total hip replacement.
Incidence of heterotopic ossification after total hip replacement: effect of the type of fixation of the femoral component.
Bone lysis in well-fixed cemented femoral components
Improved cementing techniques and femoral component loosening in young patients with hip arthroplasty. A 12-year radiographic review.
The femoral component in low-friction arthroplasty after ten years.
The removal of porous-coated femoral hip stems.
Operative correction of an unstable total hip arthroplasty.
Primary total hip reconstruction with a titanium fiber-coated prosthesis inserted without cement.
Complications of trochanteric osteotomy. Long-term implications.
Intergranular corrosion-fatigue failure of cobalt-alloy femoral stems. A failure analysis of two implants.
Aseptic loosening of straight- and curved-stem Muller femoral prostheses.
