- See:
- Post Op X-rays for THR:
- Press Femoral Stems:
- Normal Adaptive Changes:
- proximally coated femoral stems should show fusiform cortical hypertrophy along the coated portions of the stem and absence of radiolucent lines;
- distally radiolucent lines will surround the uncoated portion of the stem;
- densification & bidging of bone:
- densification & bidging of bone between cortex & porous ingrowth surfaces suggests bone ingrowth fixation (esp at border between
the coated and the uncoated portions);
- bone proximal to these areas may atrophy, presumably because it is stress shielded;
- spot welds:
- cancellous hypertrophy which arises from trabeculae from the cortex to the porous coated surface or to the distal aspect of the
porous coating;
- Stress Shielding:
- Radiolucent Interval:
- development of radiolucent interval around prosthesis suggests a fibrous interface between metal and bone;
- if this lucent interval is seen of ingrowth portion of prosthesis it suggests lack of ingrowth;
- divergent radiolucent lines in area of ingrowth indicate loosening;
- a press fit stem surrounded by fibrous ingrowth may be considered stable, if there is no evidence of subsidence;
- Reactive Sclerotic Line:
- if reactive sclerotic line is seen parallel to metal surface, fixation is probably fibrous rather than bony ingrowth;
- sclerotic pedicle of bone distal to stem tip is = lack of ingrowth;
- radiographic confirmation of lack of bone ingrowth exists when prosthesis either has subsided measurably or is noted to have divergent
sclerotic lines surrounding the stem;
- Pedistal Formation (Hypertrophy of Distal Tip):
- hypertrophy of bone near distal tip of component, although not directly indicative of loose component, certainly suggests an abnormal stress
concentration and may represent a stress shielding of proximal portion of femur;
- postoperative x-rays that demonstrates subsidence, endosteal pedestal formation (bridging bone) at tip of prosthesis, & lucent interval along medial
border of stem, are all signs of non cemented component that has not achieved bony ingrowth stabilization;
- Settling of Stem:
- settling of stem in canal & cortical hypertrophy occur distally on the medial aspect of the tip of the stem.
- technetium 99m bone scan shows increased uptake around stem on right side consistent with loosening of femoral component;
- radionuclide scanning is quite helpful in evaluation of painful THR because it is sensitive but nonspecific;
- although bone scans may help, many noncemented THR, esp long stems, may show some increase in activity;
- w/ lack of ingrowth, bone scan would show modest uptake around loose femoral component, however, mild uptake can be expected
at the tip of stable components;
- Bone Scan for THR:
- although bone scans may help, many noncemented THR, esp long stems, may show some increase in activity
Roentgenographic assessment of the biologic fixation of porous-surfaced femoral components.