DeLee and Charnley and Gruen classified the radiolucent lines between the total hip arthroplasty and the bone seen on the AP and lateral views of the operated hip in three acetabular zones and seven femoral zones, respectively.
Loosening induces the formation of a fibrous or 'synovial-like' membrane that can appear as linear radiolucent lines on radiographs and CT.
Classification
DeLee and Charnley zones (acetabulum)
zone 1: superior third (AP radiograph)
zone 2: middle third (AP radiograph)
zone 3: inferior third (AP radiograph)
zone 4: posterior third (lateral radiograph)
zone 5: middle third (lateral radiograph)
zone 6: anterior third (lateral radiograph)
Gruen zones (femur)
Zones 1-7 (anteroposterior radiograph)
zone 1: greater trochanter
zone 2: lateral mid stem
zone 3: lateral distal stem
zone 4: tip of the stem
zone 5: medial distal stem
zone 6: medial mid stem
zone 7: medial calcar
Zones 8-14 (lateral radiograph)
zone 8: anterior upper stem
zone 9: anterior mid stem
zone 10: anterior distal stem
zone 11: tip of the stem
zone 12: posterior distal stem
zone 13: posterior mid stem
zone 14: posterior upper stem
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