Deepening trochleoplasty combined with balanced medial patellofemoral ligament reconstruction for an adequate graft tensioning

Figure 1 Drawings of the preoperative situation and the biomechanical changes during surgery. A: Drawing of a type C dysplasia showing a too high lateral facet with a bump in the superolateral aspect and a trochlear facet asymmetry with hypoplastic medial facet. This trochlea is not effective in constraining a patellar displacement; B: After mobilization of a thin osteochondral flap off the medial and lateral trochlea, the trochlear bone is deepened. The lateral edge of the trochlea is not lowered to obtain a raised lateral inclination. This way, a recentralized groove is created. The flexible osteochondral flap is fixed into the new formed groove with a transosseous resorbable 3 mm Vicryl band. As depicted, a trochleoplasty leads to a more medial and dorsal biomechanical position of the patella with a reduced distance between the femoral and patellar insertions of the medial soft tissue restraints. As a consequence, a preexisting insufficiency of the medial patellofemoral ligament (MPFL) might be aggravated by these biomechanical changes; C: Hardware-free MPFL reconstruction technique for the alignment of the medial soft tissue restraints during a trochleoplasty.

Figure 2 Step-by-step description of the combined surgical procedure. A: Short skin incision running from the medial part of the patella to the distal part of the quadriceps tendon; B: Using a curved osteotome, a thin osteochondral flap is chiselled off the trochlea; C: Trochlear bone is deepened using chisels and a high-speed burr; D: Vicryl band is passed from the distal beginning of the formed groove through the condyle using a curved needle; E: Starting at the junction between the trochlear cartilage and the anterior femoral bone, the other end of the band is passed through the femur. After pressing the flap onto the bone, the band is fastened; F: Drilling of a V-shaped tunnel coming from the superomedial pole and from the middle of the medial facet of the patella; G: Gracilis tendon is passed through the drill holes; H: Femoral medial patellofemoral ligament (MPFL) insertion side is marked with a K wire under fluoroscopic guidance; I: Prepared soft tissue tunnel between both layers of the medial retinaculum is running down to the femoral MPFL insertion; J: Two divergent beath pins are passed from the blind ending tunnel through the lateral femoral cortex; K: After passing the strands to the lateral femur, a temporary knot is tied down in approximately 30° knee flexion; L: Arthroscopy of the trochlear groove after trochleoplasty.