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The angle of penetration of the acetabular opening (PEC) influences rheumatoid arthritis hip joint destruction. A lower PEC angle correlates with faster disease progression, aiding in predicting coxitis development.
Area of Science:
- Rheumatology
- Orthopedic Surgery
- Radiology
Background:
- Rheumatoid arthritis (RA) commonly affects the hip joint, leading to inflammatory and destructive lesions.
- Understanding the factors influencing the rate of RA progression in the hip is crucial for patient management.
Purpose of the Study:
- To investigate the relationship between local anatomical factors in the coxofemoral joint and the rate of RA progression.
- To identify quantifiable parameters that can predict the speed of hip joint destruction in RA patients.
Main Methods:
- Geometrical analysis of anteroposterior X-rays from 81 hips with RA (1-17 years duration).
- Quantitative measurement of disease progression in millimeters per year.
- Calculation of the angle of penetration of the plane of the acetabular opening (PEC).
Main Results:
- The rate of RA hip joint destruction is dependent on local anatomy, specifically the PEC angle.
- A PEC angle ≤ 104 degrees was associated with a significantly higher rate of coxitis progression (twice as high) compared to PEC angles ≥ 105 degrees.
- Disease progression was most rapid in the initial years after hip affection, following a parabolic curve thereafter.
Conclusions:
- The PEC angle is a significant predictor of RA progression rate in the hip joint.
- This study provides a better clinical and radiological understanding of RA affecting the hip.
- The findings enable prediction of coxitis progression, aiding in patient care and treatment strategies.
Abstract:
Geometrical analyses of the anteroposterior X-rays of 81 hips affected by rheumatoid arthritis for 1 to 17 years, have shown that the rate of progression of the inflammatory destructive lesions in the hip, expressed quantitatively in millimeters per year, depends on the local anatomical relations in the coxofemoral joint itself. This relationship is expressed by the angle of penetration of the plane of the acetabular opening (PEC) (angle PEC = angle CCD + angle n - angle PE). The PEC angle was found to be within the range of 85 to 128 degrees, and its mean value for the whole group was 104.6 degrees. In hips affected by rheumatoid arthritis for the same period of time, the average rate of progression of coxitis was twice as high when the PEC angle was up to 104 degrees than when it was 105 or more degrees. This difference is statistically significant. Irrespective of the magnitude of the angle of penetration through the plane of the acetabular opening (PEC), coxitis was found to progress the most rapidly during the first years of hip affection, and to diminish thereafter along a parabolic curve. The knowledge gained in this study makes it possible to predict the rate of progression of coxitis and is a contribution to a better clinical and radiological understanding of rheumatoid arthritis of the hip joint.