2017 ISAKOS Biennial Congress ePoster #1713

 

Medial Patellofemoral Ligament Femoral Tunnel Position in a Cohort of Patients with Recurrent Patellar Instability: A Radiographic Study

Túlio V.O. Campos, MD, MsC, PhD, Prof., Belo Horizonte, Minas Gerais BRAZIL
Akash Soogumbur , MD, BS, Norwich UNITED KINGDOM
Iain Robert McNamara, MA cantab, BM BCh, MRCS, Cambridge UNITED KINGDOM
Simon Donell, MD, FRCS(Tr&Orth), Norwich UNITED KINGDOM

Norwich & Norfolk University Hospital, Norwich, Norfolk, UNITED KINGDOM

FDA Status Not Applicable

Summary

Unlike the normal knee the dysplastic knee does not have a groove that is part of an arc of a circle. It is therefore not possible to define an isometric point. This study did not show a difference between those with significant trochlea dysplasia and those without, but this reflected that there was no agreement about the size and position of a circle used to match up with the dysplastic groove.

ePosters will be available shortly before Congress

Abstract

Background

In medial patellofemoral ligament (MPFL) reconstruction the position of the femoral tunnel is said to be critical to the results. The current favoured position is based on normal cadaveric knees.

Hypothesis

The MPFL tunnel position in patients with recurrent patellar instability is different to normal due to varying degrees of trochlear dysplasia.
Study design: Cross-sectional study

Methods

From a Patellar Instability database 40 consecutive patients with a perfect pre-operative lateral radiograph were analysed from the Patient Archive Computer System using proprietary software to define Schöttle’s point, and the arc of the circle of the trochlear groove to define the center of rotation, the latter being the “isometric” point for the MPFL. The distance from the Schöttle’s point was measured and compared to the boss height. A boss height = 5mm was defined as significant trochlear dysplasia. Inter- and intra-observer comparisons were measured in 20 radiographs.

Results

The inter- and intra-observer comparisons were not significantly different except for the radius of the circle defining trochlear dysplasia. The mean distance from Schöttle’s point to the center of the trochlea circle was 9.0mm (sd 1.0mm). There was no difference between those with significant dysplasia and those without. All patients had some degree of trochlea dysplasia.

Conclusions

Unlike the normal knee the dysplastic knee does not have a groove that is part of an arc of a circle. It is therefore not possible to define an isometric point. This study did not show a difference between those with significant trochlea dysplasia and those without, but this reflected that there was no agreement about the size and position of a circle used to match up with the dysplastic groove.