Modified Recession Wedge Trochleoplasty

Abstract

Background:

Trochlear dysplasia represents one of the main anatomic risk factors for patellar instability, with risk of failure and unfavorable clinical outcomes in patients with unaddressed dysplasia undergoing patellar stabilization.

Indications:

Patients with trochlear dysplasia characterized by supratrochlear prominence (DeJour B or D) and recurrent patellar instability, especially following failed soft tissue or bony stabilization. This technique addresses an anterior trochlea without pathologic convexity, as convexity may require conversion to other techniques for groove deepening (eg, DeJour “thick flap” or Schottle “thin flap”).

Technique Description:

A 6-cm lateral parapatellar arthrotomy is created. A marking pen is used to identify the native center of the trochlea, as well as the location of the planned resection and bony hinge point laterally. An osteotome is used to remove a wedge of bone proximally, such that the posterior aspect of the osteotomy is in line with the anterior femoral cortex. A resection guide is then used to perforate the lateral cortex, with care to avoid damaging the cartilage, and carried laterally and distally to ensure the bony cuts are connected, creating the bony flap. To ensure that all bony bridges are eliminated, the arthroscope is placed into the osteotomy to visualize reduction of the trochlea with manual pressure. A knotless PEEK anchor loaded with 8 loaded sutures is then placed on the roof of the trochlear notch. Sutures are then secured using anchors placed at the center of the trochlea, at the superolateral corner and far lateral edge of the trochlea to reduce the osteotomy, with 2 to 3 sutures placed in each anchor depending on surgeon preference.

Results:

Trochleoplasty has been reported to decrease the rate of recurrent patellar dislocation while improving mean Kujala score and knee function. Benefits of trochleoplasty must be balanced against the high rate of potential complications, primarily pain and decreased knee range of motion, secondary to the technical challenges and steep learning curve inherent to effectively performing the procedure.

Discussion/Conclusion:

Patients with recurrent patellar instability with trochlear dysplasia and failed prior stabilization may experience improved stability and outcomes following trochleoplasty.

Graphical Abstract

This is a visual representation of the abstract.

Video Transcript

This video technique demonstrates the modified recession wedge trochleoplasty technique.

Disclosures can be found here as well as online.

Trochlear dysplasia is associated with recurrent instability after first-time dislocations, as well as an increased failure rate following isolated medial patellofemoral ligament (MPFL) reconstructions. There is lack of agreement on the indications for surgical alterations of trochlear morphology, including dysplasia; however, it certainly should be considered in a revision situation.

This patient is a 20-year-old woman with bilateral patellar instability starting in fifth grade. She had a prior lateral release, a well-done MPFL reconstruction, as well as a tibial tubercle osteotomy. She continues to have traumatic instability events, as well as on physical examination having lateral apprehension that is significant, not allowing her to fully straighten her leg due to the severity of the J sign that is present on examination.

Imaging demonstrates that she has a Wiberg type 2 patella, significant effusion from her recent event, as well as a prior lateral release. You can also see her lateral chondral defect on the proximal lateral trochlea, as well as a bone bruise pattern consistent with the lateral patellar dislocation. Her tibial tubercle-to-trochlear groove (TT-TG) distance and tibial tubercle-to-posterior cruciate ligament (TT-PCL) distance are within normal limits, as well as her Caton-Deschamps Index (CDI). She does have a DeJour type D trochlea, as well as 4° of valgus deformity. When looking at all of these factors taken together, the ones that are the most important for her situation is her type D trochlea, recurrent patellar instability, and prior well-done tibial tubercle osteotomy and MPFL reconstruction. Therefore, the recommended treatment was a trochleoplasty with revision MPFL reconstruction.

Examination under anesthesia demonstrates a jumping J sign where the patella engages in the trochlea by about 30° of flexion. Here, as we slowly straighten the knee, we can see that the kneecap starts to dislocate by 70° of flexion due to the high-grade dysplasia.

We start by making a lateral arthrotomy so that we can easily visualize the dysplastic part of the trochlea, placing guide pins to retract the soft tissue. We then mark out the native center of the trochlea which we can see here, which exits proximally medially. We then draw another line where the trochlea should be located with regard to the groove, and this typically will overlie the most prominent aspect of trochlear bump.

We then make a second dotted line that exits laterally, that will be where the trochleoplasty itself will end and be part of our hinge point. Here, we can see our planned area of resection, and we now use a scalpel to score the periosteum at our planned level of resection. We need to make sure that we take this far enough distally so that it finishes just above the notch. We then use an osteotome to start to remove a wedge of resection that the posterior aspect is in line with the anterior femoral cortex, and we bring this around to the lateral trochlea.

We then will take the resection guide to perforate the lateral cortex in a postage-stamp type configuration using the thicker depth of resection to make sure that we stay away from the cartilage and use a thick flap technique. We will then use this to guide how we connect these, and this will be our flap that we will use for our trochleoplasty. We then use the resection guide to make sure that these are connected and remove bone distal to this for the amount of resection that is calculated based on the preoperative imaging, as well as what we see intraoperatively, so we remove an appropriate amount of bone for the planned correction.

We move on to using an osteotome to finish this bone removal, so that we can allow for appropriate amount of movement of the trochlear flap so that it becomes flush with the anterior cortex of the femur after the resection is complete. We carry this down distal, laterally to make sure that our hinge is not too proximal. We save some of this bone for later grafting at the end of the procedure in any areas that were over-recessed. We then use the cutting guide to remove the bone underneath the flap, making sure that we go far enough distally and move side to side for an even resection. The arthroscope can then be used to verify the adequacy of the resection and to make sure that it is done in an even fashion with copious irrigation.

Once it has been completed, you should see an easy springboard effect of the trochlea that should take minimal force to bring this down. Once this is completed, we are using a knotless PEEK anchor with 8 0-vicryl sutures so that these can be placed proximally in multiple knotless anchors as well. In this setting, we used the resection guide set at the thick flap technique and utilized the thin flap setting distally to make sure we had an easy hinge without cracking distally.

After we made sure that there was good reduction, we then placed our proximal knotless suture anchors making sure that we had good placement proximally laterally, and centrally, and a proximal medial anchor is useful depending on how the flap is lying down at that stage.

It is important to keep these anchors outside of the cancellous bone so that they have good purchase as they are the primary form of fixation of the trochleoplasty. Headless compression screws can also be utilized directly through the cartilage and osseous flap; however, it is the author’s preference to utilize the knotless suture anchors with vicryl.

Patients will typically have a significant amount of crepitus in the joint with flexion extension that will improve by 6 weeks.

Here, we see arthroscopic footage of the finished trochleoplasty with the bump being completely eliminated and taking this from being anterior to flush to the anterior femoral cortex. The goal is not to create a groove but more so to improve the transition of the patella into the groove that already exists more distally.

Postoperatively, patients start full motion as tolerated with no restrictions and physical therapy 3 days a week. They can weight-bear as tolerated in a brace locked in full extension, and they wear it at all times during sleep and walking during the first 6 weeks. The next 6 weeks works on transitioning out of the brace and allowing weight bearing as tolerated during that time as well-limiting squatting and lunging with increased weight beyond body weight until 3 months. Once they have reached the 3-months timepoint, strength and activity can be increased as tolerated, likely taking 6 months for full recovery.

Here, we can see postoperative magnetic resonance imaging (MRI) of a patient undergoing trochleoplasty, and you can see the anterior prominence of the trochlea has been significantly improved, and there is excellent healing at the 6-month timepoint with no signs of nonunion or chondral damage.

Finite element analysis modeling has demonstrated that patients with significant trochlear dysplasia have less dislocation force necessary throughout flexion, and when you perform a trochleoplasty, this is normalized to similar forces required in normal healthy knees.

Looking at a summary paper of clinical outcomes after trochleoplasty, this demonstrates that there is increased pain postoperatively in about 10% to 11% of knees depending on the technique that is performed. There is also a concern for stiffness with a rate of about 6.7% on average. When looking at clinical outcomes, however, redislocation rates are very low and the patient-reported outcomes improvement of the Kujala scores are very significant. When we compare this with other work that has ignored dysplasia, we still see a very low dislocation rate when there is a significant number of patients that have DeJour type B or higher dysplasia when the dysplasia is ignored.

Therefore, trochleoplasties are still likely best served in the revision setting, unless there are other specific clinical circumstances making it relevant in a primary surgery.