Sulcus-Deepening Trochleoplasty for Trochlear Dysplasia

Abstract

Background:

Patients who are refractory to initial management of trochlear dysplasia, which consists of bracing and physical therapy, may be candidates for trochleoplasty.

Indications:

Indications for trochleoplasty include Dejour classification type B or D trochlear dysplasia, supratrochlear spur height ≥7 mm, and a positive J sign on examination.

Technique Description:

The thick shell sulcus-deepening trochleoplasty technique involves removing the supratrochlear spur by creating a 5-mm–thick osteochondral shell with underlying cavity, dividing the thick shell into medial and lateral leaflets, and securing the leaflets with absorbable sutures. This establishes a new trochlear groove that is flush with the anterior cortex of the femur.

Results:

A review of 21 studies with length of follow-up from 8.8 months to 15 years found postoperative dislocation was present in 0% to 15% of patients and the patient satisfaction ranged from 81.0% to 94.4%. A prospective study with a minimum 2-year follow-up found no cases of recurrent dislocation, no progression of radiographic arthritis, 84.8% of patients returned to sport, and the patient satisfaction was a 9.1/10.

Discussion/Conclusion:

Sulcus-deepening trochleoplasty for trochlear dysplasia provides patellar stability and excellent patient satisfaction.

Graphical Abstract

This is a visual representation of the abstract.

Video Transcript

In this video, we will discuss the indications and surgical technique for sulcus-deepening trochleoplasty for trochlear dysplasia.

Here are our disclosures. We will review the following items in this video.

This case example is a 15-year-old girl who presents with recurrent episodes of left patella dislocation that is refractory to bracing and physical therapy. She has a history of similar presentation on the right side and underwent right tibial tubercule osteotomy, medial patellofemoral ligament (MPFL) reconstruction, and sulcus-deepening trochleoplasty with great results. Physical examination of the left knee demonstrated normal range of motion (ROM) with a markedly positive jumping J sign, mild effusion, patella instability with 4 quadrant translation, negative anterior cruciate ligament (ACL) testing, and negative collateral ligament testing.

Imaging helps identify and determine the degree of trochlear dysplasia if present. The sunrise view radiograph, seen here, tends to be of little utility to identify dysplasia, largely due to the variable degree of flexion with which these radiographs are taken. Trochlear dysplasia in the proximal part of the groove may not be visible and can cause clinicians to miss a supratrochlear spur. A true lateral radiograph is the first imaging modality to use to assess for trochlear dysplasia. In our patient’s lateral view radiograph, the crossing sign is present and extends up into a spur anterior to the anterior cortex of the femur. This supratrochlear spur is the pathologic entity with trochlear dysplasia.

An axial T2 magnetic resonance imaging (MRI) revealed a convex trochlea, a tibial tuberosity to trochlear groove (TT-TG) distance of 27 mm, and a patellar tendon to lateral trochlear ridge (PT-LTR) distance of 23 mm. In the patient’s sagittal MRI, the supratrochlear spur can be considered everything anterior to the blue line that was drawn in line with the anterior cortex. In this case, the spur height was 7 mm.

The diagnosis of trochlear dysplasia in this case is supported by recurrent patella dislocations, a positive jumping J sign, a convex trochlea on axial MRI, and a supratrochlear spur ≥7 mm on lateral x-ray and sagittal MRI. The patient was refractory to initial management involving bracing and physical therapy. Given the large, convex supratrochlear spur that directly affected patella tracking, a sulcus-deepening trochleoplasty was planned. In our practice, an MPFL reconstruction is always performed as well.

A sulcus-deepening trochleoplasty is performed if the patient has a Dejour classification type B or D trochlear dysplasia with a convex supratrochlear spur of a height ≥7 mm. The patient should also have a J sign on examination as evidence that the spur affects patellar tracking. If a patient has concomitant patella alta or a short trochlea, this should especially be considered as the spur exerts even greater influence on patellar tracking as the patella must navigate over this convexity through a longer arc of motion. In borderline cases with recurrent instability after failed previous procedures, consideration should be given to deepening the groove and spur removal as well. Patients with mild dysplasia do not always require correction of the spur itself. In some patients with a combination of increased patellar height and dysplasia, it is possible to work around the spur by distalizing the patella so that it does not engage with the spur. This can be done by performing a tibial tubercle osteotomy. A trochleoplasty is only indicated for a subset of patients with severe dysplasia. Patients with a flat trochlea do not require a change of the trochlear morphology, as a flat patella on a flat trochlea can be balanced with an MPFL reconstruction alone. Patients with good patella/trochlear overlap, evidenced by a Patella-Trochlear index >50% or Caton-Deschamps (CD) ratio less than 1.2, or those with no J sign on examination also do not typically require a trochleoplasty.

Recommended patient positioning for trochleoplasty is supine on a radiolucent, platform-type table with a radiolucent triangle for knee positioning.

This specific arthroscopy is from a 19-year-old female lacrosse player and viewed from the superior lateral portal. There is a very pronounced J sign on examination due to the large spur influencing patella tracking. Next, we move to the procedure that was performed in our 15-year-old female patient. The medial parapatellar arthrotomy is our preferred approach for optimal simultaneous exposure for the trochleoplasty, the MPFL reconstruction, and any lateral retinacular lengthening, plus would be the incision used for any potential future arthroplasty procedures. We start by measuring the height of the supratrochlear spur. The existing groove is marked with dots and a solid line is drawn for the planned “new” groove. If the TT-TG distance is elevated, it is possible to lateralize the new groove up to roughly 6 or 7 mm. Dysplastic trochlear grooves typically extend medially as the groove extends proximally, adding to the convex shape that tips the patella laterally. The new groove should extend along the direction of the shaft of the femur to better mirror the pull of the quadriceps. The distal extent of this line is at the point where a line down the anterior femoral cortex would intersect the trochlear surface distally. This allows the new groove to be flush with the anterior femoral cortex at the proximal extent. The medial and lateral margins of the trochlea and the resected bony cavity are next identified and marked at the transition or apex of the curve of the condyles when viewed from the side of the knee. A line is then drawn from these marks to the distal extent of the new groove. A wedge of bone is then removed all the way around the articular margin with an osteotome. It is important to start the osteotome proximal on the femoral shaft to ensure removal of the entire spur as well as slightly on the articular surface to fully remove the convex spur. This bone is to be saved for later bone-packing to aid in the transition at the margins. Next, a 3-mm egg-shaped burr on a high-speed handpiece is used free hand to initiate the bone resection and create a cavity. Again, this bone slurry is to be saved for later bone-packing. Then, switch to a commercially available offset guide attached to a drill bit. The drill bit only removes bone from its side, not the tip, so it must be used like a windshield wiper rotating around the distal point. Because this drill type device is not very aggressive, we find it more efficient to start the process with the high-speed burr. The offset guide allows a 5-mm roof of cartilage and subchondral bone. The less aggressive drill bit and the offset guide add a measure of safety to avoid a cartilage breach. This offset guide can be used to thin the entire shell to 5 mm with extra bone removal in the center to allow deepening of the new groove. A Freer elevator is useful to palpate for irregularities. A 20 blade and a bone tamp are used to crack or osteotomize the bone shell in the center of the desired new groove. Place the osteotome behind the shell to minimize bending that could crack the shell. The medial side is almost always malleable enough, but the lateral side often needs a small crack at the periphery to aid in manually reshaping the shell into a groove. Preserve a hinge and do not let this lateral cut intersect the central cut to avoid having a free shingle of bone. The pieces of bone that were saved from earlier are now packed into the distal cavity margins on both sides for a smooth transition and to help prevent settling. Additional bone pieces and slurry are placed deep in the cavity to fill any voids, and along the medial and lateral edges to provide extra lift and central depth for the new groove. A knotless anchor loaded with 2 number 2 absorbable sutures (just in case one breaks) is then inserted centrally in the groove and distal to where the flaps were cut. It is important to tap this deep beneath the cartilage so that it does not protrude from the surface. The pair of absorbable sutures are now draped over each triangular leaflet to hold them in place under compression, bringing each pair to another knotless suture anchor. Positioning of the sutures can be adjusted with emphasis on deepening the central groove and optimizing the contour. In large corrections, the leaflets can splay at the top upon compression; this will be filled with fibrocartilage and does not present with problems. The new groove is now flush with the anterior cortex of the femur, which is the primary goal of the trochleoplasty. The excess sutures from the proximal flap-compressing anchors are used to tie the supratrochlear fat down at the top of the trochlea. The surgery is completed with an MPFL reconstruction. Here is a before and after photo that demonstrates the removal of the entire supratrochlear spur. Additionally, a tibial tubercle osteotomy was performed to correct a TT-TG distance of 27 mm. The tubercle was moved 15 mm anteromedially, and the new trochlear groove was moved 2 mm laterally, creating a normal TT-TG of 10 mm. The CD ratio was normal, so the tubercle was not moved distally.

Presented here are radiographs from before and radiographs that were taken 2 weeks postoperatively. The lateral view radiograph clearly shows removal of the supratrochlear spur.

Potential complications that may be encountered are arthrofibrosis, recurrent instability, cartilage perforation, and settling of the shingles. Listed are a few pearls to help avoid these potential complications.

It is important to have the patients moving immediately, as postoperative stiffness is the most common issue. Physical therapy is started within 1 to 3 days. For these first 6 weeks, they will be 50% weight bearing and in a brace with settings up to 90°. The brace can be removed during supervised physical therapy for full ROM exercises. They will typically be back to sport after 5 to 6 months.

The outcome data for trochleoplasty demonstrate significant improvement in patients. A review of 21 studies with length of follow-up from 8.8 months to 15 years found postoperative dislocation ranged from 0% to 10.5% of patients. In total, 55% to 92% of patients returned to sport, and the patient satisfaction was between 81% to 94.4%. A prospective study with a minimum 2-year follow-up found no cases of recurrent dislocation and no further surgery was required. The most common complication was arthrofibrosis in 18.2% of patients. There was no progression of radiographic arthritis, 84.8% of patients returned to sport, and the patient satisfaction was a 9.1/10. Overall, trochleoplasty provides patellar stability and excellent patient satisfaction.

From the Department of Orthopaedics at the University of Virginia, we thank you.