Sulcus deepening trochleoplasty: Open and arthroscopic techniques

Chapter synopsis

Trochlear dysplasia has been recognized as the most common anatomical anomaly associated with recurrent lateral patellar dislocation. A thorough physical exam and imaging evaluation is important to identify the small percentage of patients with high-grade trochlear dysplasia amenable to surgical intervention. Trochleoplasty is a technically challenging procedure and a number of open and arthroscopic techniques have been described. The Dejour sulcus-deepening trochleoplasty is ideally suited for patients with trochlear dysplasia and an associated supratrochlear spur. Trochleoplasty may need to be combined with other procedures such as tibial tubercle osteotomy (TTO) or medial patellofemoral ligament (MPFL) reconstruction to provide the best chance of a positive postsurgical outcome.

Important points

• Trochlear dysplasia is present in 96% of the patellar instability population

• Abnormal patellar tracking is the most important physical exam indicator of high-grade trochlear dysplasia and occurs during knee flexion as the patella attempts to engage the trochlea.

• Lateral radiography is crucial in identifying patella alta and trochlear dysplasia when determining the most suitable operative treatment

• Identifying the “crossing sign”, “supratrochlear spur” and “double contour” on lateral radiography allows classification of trochlear dysplasia based on the Dejour classification

• Dejour B trochlear dysplasia (crossing sign, supratrochlear spur) and Dejour D dysplasia (crossing sign, double contour, and supratrochlear spur) are considered high-grade trochlear dysplasia well suited to a sulcus-deepening trochleoplasty

• The trochlea is typically medialized in patients with trochlear dysplasia

• The primary goal of Dejour’s sulcus deepening trochleoplasty is to (1) remove the trochlear and sub-trochlear prominence, (2) create a new trochlear groove with normal depth (flush with the anterior femoral cortex), and (3) to re-position the groove laterally to improve tracking

• The Dejour sulcus deepening trochleoplasty maintains a set depth of at least 5 mm osteochondral flap to protect the cartilage surface and subchondral bone

• The Blond and Bereiter’s techniques involve raising a thin osteochondral flake that remains pliable enough to be molded into the new shape of the trochlear groove, which may include a high risk of damaging the cartilage or exceeding the resection of subchondral bone.

• Trochleoplasty should always be combined with MPFL reconstruction or TTO based on an “a la carte” approach to improve outcomes

• Recurrent instability is very rare after trochleoplasty; however arthrofibrosis and pain in poorly indicated patients is a concern

• Physical therapy is crucial postoperatively to regain motion, prevent arthrofibrosis, and strengthen atrophied muscles

Clinical/surgical pearls

• Goals of surgery include decreasing the supratrochlear spur and deepening the sulcus angle

• Excellent exposure, including reflection of the synovium to visualize the anterior femoral cortex, is crucial in evaluating the height of the supratrochlear spur and determining the amount of required deepening

• The condylotrochlear grooves as well as the native trochlear groove are marked first, followed by the new, lateralized trochlear groove based on the preoperative tibial-tuberosity to trochlear groove (TT-TG) distance and using the femoral anatomic axis as a landmark.

• The undersurface of the trochlea is accessed through a cortical window created using an oscillating saw and osteotome under the supratrochlear spur

• Removal of cancellous bone from under the trochlear cartilage is facilitated by a drill with a depth guide set at 5 mm to ensure uniform thickness of the osteochondral flap. The bone removal must extend all the way to the notch. Sufficient bone removal is marked by the elastic nature of the trochlea when applying manual pressure.

• A scalpel is used to cut the new trochlear groove, lateral facet and medial facet

• An osteotome can be used to press down the osteochondral flap with gentle tapping along the trochlear groove from distal to proximal until the medial facet is flush with the anterior femoral cortex

• Excess bone can be used as a graft under the lateral facet in order to elevate the lateral condylotrochlear groove, further resisting lateral movement of the patella

• The trochlea is fixed with three absorbable suture anchors from the intercondylar notch

• Patellar tracking should be satisfactory after trochleoplasty and before additional procedures are performed

Clinical/surgical pitfalls

• Poor patient selection, especially those with patellofemoral pain and cartilage injury but not instability, can lead to poor postoperative outcomes and increased surgical difficulty

• Improper burr usage can lead to thermal necrosis or cartilage perforation especially distally as the trochlea curves posteriorly

• If the trochlea cannot be repositioned flush to the anterior femoral cortex then additional cancellous bone must be removed with a burr

• Arthrofibrosis is a common complication, and while postoperative rehabilitation is typically dictated by adjunct procedure, starting range of motion soon after surgery is critical to prevent arthrofibrosis