Femoral and Tibial Derotational Osteotomies With MPFL Reconstruction and Lateral Retinacular Lengthening

Many anatomic factors contribute to patellar instability, including excessive femoral anteversion and external tibial torsion. Derotational osteotomies may be performed concomitantly with medial patellofemoral ligament (MPFL) reconstruction to address multiple factors and improve patellofemoral engagement.

Proper identification of axial plane abnormalities is important as recurrence of instability may be higher in patients when these factors are not addressed. Femoral anteversion or tibial torsion of >20° can generate abnormal lateral forces in the patellofemoral joint, although an angle of up to 30° may be considered normal. Patients with bony rotational malalignment between 30° and 40° may be suitable for surgery, but this should be considered in the context of all patellofemoral pathology that is present. In patients with >40° of bony rotational malalignment, surgical intervention is nearly always warranted.

The femur is derotated over a trochanteric entry nail. The distal portion of the isthmus is identified and vented with a drill bit. Overreaming of the intramedullary canal by 1.5 to 2 mm is performed. Two Schanz pins are placed proximal and distal to the osteotomy site, and they are oriented to produce external rotation of the distal femur to the degree desired. The osteotomy is then completed and the femur derotated to the desired correction with the Schanz pins aligned. The nail is placed and the proximal guide is used to place 1 proximal screw in dynamic position. With the Schanz pins still aligned, a perfect circle technique is used to place a distal screw in a static hole to maintain the correction. For the tibial osteotomy, the same process is repeated, only the venting of the tibia at the isthmus and the completion of the osteotomy are performed using an oscillating saw. In addition, Steinmann pins are used instead of Schanz pins.

Expected outcomes for this bilevel derotational osteotomy and MPFL reconstruction are very good. Patients have significant improvement in pain and patellofemoral stability.

Derotational osteotomies should be performed when long bone rotational deformity is identified as a primary risk factor contributing to instability during dynamic motion.

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