Scripties UMCG - Rijksuniversiteit Groningen
 
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The influence of posterior tilt of the femoral head on the failure rate of femoral neck fractures. Ananalysis of 164 undisplaced femoral neck fractures treated by Gannet osteosynthesis

(2016) Kalsbeek, J.H.

Introduction: Failure rates of the so called undisplaced femoral neck fractures (FNF) vary from 4-23%. Literature states that undisplaced FNF always should be treated by internal fixation. The classification in undisplaced and displaced FNF is most commonly performed by the Garden classification. This classification is solely based upon the AP radiographs. Consequently the tilting of the femoral head in the anterior and posterior direction is not included in this classification. Over the years there have been many studies to identify pre- and post-operative predicators for failure. Yet posterior tilt, also known as retroversion or anterior angulation, of the femoral head as a predictor is only described by several authors. This study investigates two different methods to measure posterior tilt of the femoral head and its influence on the failure rate of undisplaced FNF.
Patients and methods: The posterior tilt of 164 undisplaced FNF treated by Gannet osteosynthesis were measured on the lateral X-ray of the hip using the Lateral Garden Angle (LGA) and the Posterior Tilt Measurement (PTM). Correlation between posterior tilt of the femoral head and the failure rate after Gannet osteosynthesis was assessed. Furthermore an intra- and inter observer reliability study was done with the two different methods to assess the validity of these measure methods.
Results: The overall failure rate was 5.5%. No correlation could be found between the posterior tilt of the femoral head and the failure rate if it was measured according to the LGA (P=0.366). If the posterior tilt was measured using the PTM a larger angle was associated with a higher failure rate (P=0.030). Retroversion of ≥20° measured using PTM is associated with a 4 times higher failure rate (OR = 4.286 (CI 95% 1.092 – 16.826) (P-value = 0.037)). The intra and inter observer reliability of the LGA was 0.765 and 0.601(P <0.001). For the PTM the intra and inter observer reliability was 0.790 and 0.773 (P <0.001).
Conclusion: The Lateral Garden Angle should not be used to measure posterior tilt because its validity is inferior to the Posterior Tilt Measurement. If the posterior tilt of the femoral head is measured using the PTM it is associated with a higher failure rate. Posterior tilt of ≥20° can be used as a significant predictor for failure in undisplaced FNF treated by Gannet osteosynthesis. The introduction of the PTM may lead to a paradigm shift in the operative treatment of the undisplaced FNF because it identifies that ‘stable’ FNF with a posterior tilt greater than 20° in fact behave like unstable fractures. Therefore the indication for internal fixation in the elderly patients will shift to a hip replacement if the posterior tilt of the femoral head rises above 20°.






 
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