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Migration of the femur head in rheumatoid coxitis
I Pucar1, T Dürrigl, P Dürrigl
1Institute of Rheumatic Disease and Rehabilitation, Medical School, Zagreb, Yugoslavia.
Insights
In rheumatoid coxitis, a new geometrical analysis determined the direction of femoral head displacement into the acetabulum. The study found this displacement direction remains constant throughout disease progression.
Area of Science:
- Orthopedics
- Rheumatology
- Biomechanical Engineering
Background:
- Rheumatoid coxitis leads to femoral head destruction and acetabular penetration.
- Understanding the direction of this displacement is crucial for treatment planning.
Purpose of the Study:
- To quantitatively determine the direction of femoral head penetration into the acetabulum in rheumatoid coxitis.
- To introduce and utilize a new geometrical parameter, the angle of transposition (delta), for this measurement.
Main Methods:
- Geometrical analysis of 81 hip joints affected by rheumatoid coxitis.
- Calculation of the 'transposition of the center of the femur head' and the 'angle of transposition' (angle delta).
Main Results:
- The mean delta angle was 27.6 degrees, ranging from -5 to +54 degrees.
- A delta angle of 0 degrees indicates cranial transposition; positive values indicate craniomedial transposition.
- The direction of femoral head transposition was constant within each hip joint throughout disease progression.
- No correlation was found between coxitis progression rate and displacement direction.
Conclusions:
- The direction of femoral head transposition in rheumatoid coxitis is a stable characteristic.
- The angle delta provides a reliable quantitative measure for assessing this displacement direction.
Abstract:
The direction of penetration of the destroyed femoral head into the acetabulum in rheumatoid coxitis has been determined by means of the method of geometrical analysis in 81 affected hip joints. Of 48 patients, the duration of coxitis was 1-17 years (mean 4 years). Displacement of the femur head, destroyed by rheumatoid inflammation, was expressed in millimeters by means of a geometrical parameter called "transposition of the center of the femur head". The direction of transposition of the femur head into the deepened acetabulum has been expressed quantitatively by authors making use of the new geometrical parameter "the angle of transposition of the center of the femur head" which is referred to as angle delta. The angle delta is an angle between the line of transposition of the femur head center (tC) and its vertical component. The mean value of the delta angle for the entire group investigated measured 27.6 degrees and ranged from -5 degrees to +54 degrees, whereby an angle of 0 degrees marked the cranial direction of transposition, positive values marked the craniomedial transposition direction of the femur head. The angle delta varied from 21 degrees to 40 degrees in the majority of affected hip joints. The values of the delta angle were constant in every hip joint, thus indicating that the direction of transposition of the femur head did not change in the course of the progression of rheumatoid coxitis. It was found and statistically confirmed that no reciprocal dependence existed between the rate of progression of coxitis and the direction of displacement of the femur head into the acetabulum.(ABSTRACT TRUNCATED AT 250 WORDS)