Table 1.

Pearls and Pitfalls of Trochleoplasty, MPFL Reconstruction, and Open Lateral Lengthening for Patellar Instability in Setting of High-Grade Trochlear Dysplasia

Pearls

The surgeon should ensure adequate exposure to ensure lateral and medial exposure of the patella prior to lateral arthrotomy; the soft-tissue planes should be undermined to create an adequate mobile window. This allows medial patellar access for graft placement for MPFL reconstruction.

The surgeon should plan to undermine the cartilage flap 1.0-1.5 cm distal to the new planned trochlear groove. This optimizes the contour of the trochlea from distal to proximal to prevent any acute angles.

Fluoroscopy should be used to ensure proper placement of the MPFL reconstruction tunnels in the femur and patella.

The MPFL reconstruction femoral tunnel should be drilled to an adequate length (40-50 mm) to avoid graft-tunnel mismatch.

The surgeon should fix the MPFL reconstruction at 45° of flexion and check range of motion and patellar stability after fixation.

Pitfalls

Excision of too much lateral-column bone during flap creation can compromise trochlear stability—removed bone should be saved because it can be used to build up the lateral column if needed.

Molding the cartilage flap can be difficult if it is too thick—additional subchondral bone should be carefully removed with a burr.

Suture cut-through on the cartilage can occur if the flap is too thin or long—holding manual reduction of the flap during anchor insertion can help minimize this and occasionally an additional anchor at the midpoint of the flap can help mitigate the stress on the suture.

Over- and under-tensioning of the lateral retinaculum should be avoided by closing it where the superficial layer lies comfortably with the knee at 70° of flexion—typically, 1-2 cm of length is achieved.

MPFL, medial patellofemoral ligament.