Abstract
Introduction
Femoroacetabular impingement (FAI) is a common cause of hip symptoms in younger patients. Failure to completely address the deformity yields a poor surgical result. Therefore accurate assessment is imperative to good outcome.
Dynamic motion analysis offers improved assessment of the morphological pathology causing FAI. This study aims to compare the differences in measurement reports produced by 3-Dimensional analysis of CT scans for FAI between two systems, Clinical Graphics (Delft, Holland) and Dyonics Hip Plan by Smith & Nephew (London, UK).
Patients/Materials & Methods
The senior author uses computerized tomography (CT) with three-dimensional reconstructions and dynamic motion analysis. A series of scans were analysed with both systems, and equivalent data was recorded from each.
This included femoral neck version, femoral neck inclination, acetabular anterior coverage (%), acetabular posterior coverage (%), alpha angle at 9, 10, 11, 12, 1, 2 and 3 o'clock positions, centre-edge angle at 12 o'clock, acetabular version and suggested resection.
Results
A total of 20 consecutive cases were analysed. Statistical analysis revealed significant differences in measurements of femoral neck version (p<0.001), acetabular anteversion (p=0.032), acetabular posterior coverage (p<0.001), cam deformity alpha angles at 0900, 1000 (p=<0.001), 1100 and 1200(p=0.014) between the two reports produced for each patient. Similar differences were found between the reports for areas of advised resection, particularly at 1200 (p=0.01).
Discussion
Dynamic motion analysis offers improved characterisation of FAI pathology. However, femoral head asphericity, off femoral head centre and pelvic tilt can influence FAI measurements. Also, patients may have measurements outside normal ranges, but this may not necessarily equal impingement.
Conclusion
Motion analysis software packages currently available work in different ways and produce different reports. It is imperative that the surgeon be aware of how their preferred system works to be able to accurately plan surgery.
