This 1988 retrospective study compared preoperative AP radiographs to intraoperative loosening findings in 200 consecutive Charnley low friction arthroplasty revisions. It asks whether the extent of radiolucent demarcation at the acetabular bone-cement interface predicts socket loosening at surgery. The result is a five-type classification that remains the standard for reporting cemented acetabular fixation.
When you review a post-THA radiograph and see circumferential radiolucency around the cemented acetabular component, this paper is your decision framework.
Prior to this classification, demarcation was poorly understood — a 12-15 year follow-up had reported patients with severe demarcation and even migration maintaining excellent clinical function, and prior intraoperative testing with hammer and chisel had systematically underestimated loosening rates.
Hodgkinson gave us a testable rule: Type 2 demarcation means the socket is loose 71% of the time, and Type 3 means it is loose 94% of the time. Regardless of whether the patient is symptomatic.
The clinical mandate from this paper: a loose socket rarely causes immediate symptoms, but ongoing micromotion causes progressive bone resorption. Intervene for radiographic changes before bone stock is lost.
JBJS America subsequently codified these findings. Migration or >1 mm of radiolucency in all DeLee and Charnley zones is now the standard definition of definite radiographic loosening when reporting THA outcomes.
This 1988 retrospective study compared preoperative AP radiographs to intraoperative loosening findings in 200 consecutive Charnley low friction arthroplasty revisions. It asks whether the extent of radiolucent demarcation at the acetabular bone-cement interface predicts socket loosening at surgery. The result is a five-type classification that remains the standard for reporting cemented acetabular fixation.
When you review a post-THA radiograph and see circumferential radiolucency around the cemented acetabular component, this paper is your decision framework.
Prior to this classification, demarcation was poorly understood — a 12-15 year follow-up had reported patients with severe demarcation and even migration maintaining excellent clinical function, and prior intraoperative testing with hammer and chisel had systematically underestimated loosening rates.
Hodgkinson gave us a testable rule: Type 2 demarcation means the socket is loose 71% of the time, and Type 3 means it is loose 94% of the time. Regardless of whether the patient is symptomatic.
The clinical mandate from this paper: a loose socket rarely causes immediate symptoms, but ongoing micromotion causes progressive bone resorption. Intervene for radiographic changes before bone stock is lost.
JBJS America subsequently codified these findings. Migration or >1 mm of radiolucency in all DeLee and Charnley zones is now the standard definition of definite radiographic loosening when reporting THA outcomes.