Management of an inveterate dislocation of the patella

• A 31-year-old male patient
• Knee trauma when he was 10 years old
• Failed soft tissue surgery 20 years ago
• On physical examination, he presented with a non-reducible patellar dislocation which causes pain and functional loss

Pre-operative X-rays

Pre-operative CT-scan

Pre-operative measurements

• HKA = 180°
• TT-TG = 24 mm
• Femoral neck anteversion (FNA) = 27.5°
• Dejour type C trochlear dysplasia

What are the normal values of the femoral neck anteversion and the TT-TG?

• ✔️ FNA = 15, TT-TG = 9

^{Scorcelletti M, Reeves ND, Rittweger J, Ireland A. Femoral anteversion: significance and measurement. J Anat. 2020 Nov}

^{Rhee, SJ., Pavlou, G., Oakley, J. et al. Modern management of patellar instability. International Orthopaedics (SICOT) 36, 2447–2456 (2012)}

How would you manage this condition?

• ✔️Tibial tubercle medialisation
• ✔️Femoral derotation osteotomy
• ✔️Lateral patellar release
• ✔️MPFL reconstruction

Final strategy decision

The patient presented with an increased femoral anteversion of 14° in comparison to his contralateral lower limb, and an increased TT-TG of over 20°.

We usually leave the trochleoplasty as the last surgical option. Our choice was then to perform...

1 - a femoral derotation osteotomy of 14° thanks to a personalized cutting guide (PSI-NEWCLIP).

2 - a tibial tubercle medialisation according to the Elmslie – Trillat technique, a TT-TG over 20 should be medialised

^{Cox JS. An evaluation of the Elmslie-Trillat procedure for management of patellar dislocations and subluxations: a preliminary report. Am J Sports Med. 1976}

3 - a lateral release

4 - an MPFL reconstruction using a gracilis tendon.

^{Ahmad R, Jayasekera N, Schranz P, Mandalia V. Medial patellofemoral ligament reconstruction: a technique with a "v"-shaped patellar tunnel. Arthrosc Tech. 2014 Sep 22}

Post-operative X-rays

Post-operative physical examination