Abstract
Background:
Several modifiable pathologic variables can contribute to lateral patellar instability, including trochlear dysplasia, increased tibial tubercle to trochlear groove (TT-TG) distance, femoral valgus alignment, and the integrity of the medial patellofemoral ligament (MPFL).
Indications:
For patients with a failed primary MPFL reconstruction or those with extreme pathoanatomy, adjunctive surgeries may be chosen in an a la carte approach to correct the pathoanatomy contributing to patellar instability. This case describes the treatment of a patient with severe trochlear dysplasia, femoral valgus alignment, increased TT-TG, and a torn MPFL treated with a 4-;pronged approach, including a trochleoplasty, distal femoral osteotomy (DFO), tibial tubercle osteotomy (TTO), and MPFL reconstruction.
Technique Description:
The patient is prepped and draped in a standard fashion. A medial incision is made over the distal femur. We begin with the DFO, utilizing a custom guide to remove a 6-;mm bone wedge before reduction and plating. Attention is then turned to the TTO. A freehand, 30° cut is made with an oscillating saw distally while an osteotome completes the osteotomy proximally. The tibial tubercle wedge is left without fixation while attention is turned to the trochleoplasty. A modified recession wedge technique is used to optimize the morphology of the trochlear groove. The trochleoplasty is secured with a central knotless polyether ether ketone (PEEK) anchor with sutures to 3 other anchors surrounding the lateral trochlea. The tubercle wedge is translated 10 mm anteromedially and 6 mm distally before fixation. Finally, the MPFL reconstruction is performed with 2 knotless PEEK patella anchors and a semitendinosus allograft. Care is taken to ensure the graft supplies appropriate patellar stabilization through flexion before final fixation.
Results:
Patients undergoing this 4-;pronged approach for severe lateral patellar instability are expected to return to activities of daily life. Rigorous physical therapy is needed immediately after surgery until at least 6 months postoperatively, with attention to restoring range of motion to prevent arthrofibrosis of the knee.
Discussion/Conclusion:
Patellar stabilization with concurrent trochleoplasty, DFO, TTO, and MPFL reconstruction can be used to treat patients with multiple pathoanatomic risk factors contributing to patellar instability. This level of surgery should only be implemented after careful selection of patients.
This is a visual representation of the abstract.
Video Transcript
Hi. My name is Adam Yanke from RUSH University Medical Center, and thank you for allowing me and my coauthors to present the surgical technique and indications for trochleoplasty, distal femoral osteotomy (DFO), tibial tubercle osteotomy (TTO), and concurrent medial patellofemoral ligament (MPFL) reconstruction. Here are our disclosures. In this talk, we are going to review the reasons for adding osseous realignment procedures to a patellar instability case. We will discuss the clinical workup of a patient undergoing a multiple osteotomy and ligament reconstruction procedure, and then we will review the postoperative course of this patient as well as the clinical outcomes for similar procedures.
Background
The question we should also ask ourselves regarding patellar instability is, When will an MPFL alone be good enough? For most patients, it usually is, and Bill Cregar helped us with a study that was published in the American Journal of Sports Medicine looking at the different studies that have defined redislocation as failure of isolated MPFL reconstruction. These studies generally show that risk factors included alta, dysplasia, the J sign, and the instability resolution angle (IRA), including a study in press that we are currently releasing. 1 We will discuss the IRA later in the talk. When we view patient-;reported outcomes as the failure mechanism, a lack of subjective clinical improvement is noted. In addition, the tibial tubercle and trochlear groove have been identified as risk factors, along with the IRA.
Specifically, we investigated our institution, looking at how it was associated with improvements in Kujala score at a 2-;year follow-;up after isolated MPFL reconstruction. The IRA is the angle at which patellar instability or significant lateral translation no longer occurs. In this patient, you can see that at about 90°, their kneecap becomes unstable. It is only at 100° that it becomes stable. When patients had significant instability past 70° of flexion, their chance of having improved clinical outcomes was only 60%. This was the most significant risk factor we found that was tied essentially to a tibial tubercle to trochlear groove (TT-TG) above 20 mm.
Indications
Alta was also a significant risk factor for failure of an MPFL alone with regard to reaching Kujala scores of subjective improvement. This IRA is usually made up by an abnormality of the mechanical axis, the TT-TG distance, and trochlear dysplasia. The current evidence that we have for failure of an isolated MPFL reconstruction involves several factors, including alta dysplasia, a J sign, an IRA over 70°, and an increased TT-TG over 20 mm, which seem to significantly increase the risk of failure with a ligament alone. We will now look at this patient’s case and see how this factors into the patient’s workup. This is a 14-year-old girl who had recurrent patellar instability for 3 years.
Technique Description
Treatment had included physical therapy and bracing. She could not participate in sports but wanted to and had no prior surgeries. Looking at standing radiographs, there was about 4.7° of valgus, 15° of rotation within the knee, 37° of femoral anteversion, and 17° of tibial torsion. On physical examination, the patient had a jumping J sign and flexion instability or an IRA in the setting of 115°. So, the patella did not become stable until the knee was flexed to 15°. We then looked at advanced imaging, and the TT-TG was 22 mm on MRI and 28.7 mm on the CT scan.
Bump height measured 10.31 mm, and the Caton-Deschamps Index (CDI) ratio was 1.48. Here, you can see all the factors taken into account in this patient, as well as those within normal levels, including tibial torsion and valgus TT–posterior cruciate ligament (PCL). Knee rotation angle was slightly abnormal, and the most abnormal findings were the IRA, TT-TG, CDI, DeJour D (presence of a supratrochlear spur/bump, crossing sign, and double contour sign), femoral anteversion, jumping J sign, and increased bump height. We grouped these factors as the jumping J sign. Inflection instability meant that we likely needed to do more than an isolated MPFL reconstruction, and the DFO would help improve tracking by removing the valgus. Trochleoplasty would help the bump height and DeJour, and the TTO would help all the other measurements for patellar height and lateralization of the tubercle. In this case, you can see the 3-;dimensional reconstructions of the femur, which demonstrate a significant medial cliff and some relative interrotation of the femur on the tibia.
If we look at what we’re trying to accomplish with the osteotomy, the TT-TG of 29 mm, we’ll see that as we look at where the groove should be located, it is the trochlea, which is very medial, and the tibial tubercle, which is very lateral. Utilizing a trochleoplasty, DFO, and TTO, we can essentially normalize these factors, as well as lower the trochlea to line up the putts, so to speak, and have a smoother transition. The order of events in this case is important. With regard to the osseous components, we do the DFO from start to finish. We then do the tibial tubercle cut while doing the trochleoplasty from start to finish, finish the TTO, and then finish the MPFL reconstruction.
We start with a lateral approach, sizing through the iliotibial band. Here, using a patient-;specific guide, cutting guide, and plate, we plan for a biplanar medial closing wedge DFO. Once this is in place, it will help us create an anterior flange, increasing the real estate available for the trochleoplasty. We perform the osteotomy first, from the cut to bone resection, and finally plate placement. The medial cortex is cut with a saw, and an osteotome is used to finish the remainder of the cuts.
We put the plate in place with temporary fixation, making sure the reduction is appropriate. We then use the rest of the drill holes, filling these with bicortical screws proximally and unicortical cancellous screws distally. After we have confirmed the appropriate positioning of the screws, we then move to the TTO. In this setting, we do a freehand cut in the setting of patellar instability. These are usually low cuts that are approximately 10°, ensuring that we do not posteriorize the tibial tubercle.
This also allows for correction of a very large TT-TG because it will still be a large shingle for the position of the bone after translation is complete. Before we fix the TTO, we then move to the trochleoplasty, where we can use an offset guide here, usually set at 5 mm. This is a modified resection wedge trochleoplasty, as we have previously described, where we do not make a formal groove, using a thinner or thicker cut. The essential plan here is to lower the prominence of the groove so that it is flush with the anterior cortex and the femur. In the case of a very convex trochlea, this will allow the trochlea to be flattened out in a modified thin-;flap technique.
Here we can see this being pushed down, and it is fixated in place using a peak anchor just superior to the notch and 3 peak anchors around the periphery, using Vicryl to bring these down to the anterior cortex. After this is complete, we can now see that the anterior cortex of the femur is flush with the trochlear cartilage. We then fixate the TTO using two 4.5-mm screws lagging in place and trying to place these perpendicular to the cut. After this is complete, we then perform a lateral lengthening approach and then the medial approach for the MPFL reconstruction. This is done with 2 polyether ether ketone (PEEK) screws in the patella, and we use fluoroscopy to find Schottle’s point.
We can easily avoid the DFO plate and screws and still have anatomic insertion, where we plan to place the 2 limbs of the graft into the femur and the loop on the patella. We close the lateral lengthening in 30° of flexion to make sure that it has its new length set after the TTO and trochleoplasty and DFO have been performed. We then ream a 7-;mm tunnel in the femur and place the loop end of our graft between the 2 PEEK suture anchors at the superior medial half of the patella. We trim the excess sutures here and take the remaining 2 limbs and tunnel these just superficial to the capsule so we can bring these directly into the 7-;mm tunnel. The graft is typically sized to 6 mm at the largest, so there is no interference fit of the graft with the tunnel until we place a 7 × 20-;mm interference screw.
Results
We now would like to review the outcomes of this procedure and other similar procedures. For this patient, they did extremely well. Their preoperative and postoperative radiographs are demonstrated here, and they had excellent healing of the osteotomies, as well as the trochleoplasty, and they had an elimination of the jumping J sign that they had prior to surgery. When we look at outcomes in general, isolated trochleoplasty, isolated TTO, and isolated MPFL reconstructions have variable risk factors, with trochleoplasty having slightly higher failures done in isolation, but all of these actually had a similar rate of improvement of the Kujala score. When we look at patients who were treated with DFO in isolation with soft tissue reefing or lateral release, this demonstrated that in 23 knees, every patient had a significant improvement in their visual analog scale, Lysholm, and Kujala scores. 3 If we look at a systematic review of patellar instability treated with distal femoral varus osteotomy, we can see here that there was a low rate of patellar instability, but it was persistent at 3%, and most patients had a significant improvement in their Kujala scores. 4 When we look at trochleoplasty outcomes, this systematic review demonstrated that most patients did extremely well. 2 Looking at this type of trochleoplasty, which we call a modified recession wedge osteotomy, most patients do extremely well with this and have a very low failure rate, and this likely has a lower risk than a thin-;flap trochleoplasty. 5 The take-;home points for this patient are that when they have a jumping J sign, they are unlikely to improve clinically with an MPFL alone.
Discussion/Conclusion
Trochleoplasty can be beneficial by lowering the bump prominence without formal groove creation to try to minimize the risk associated with a portion of the procedure. References are listed here. Thank you for your time and attention.
Footnotes
Submitted February 10, 2025; accepted August 17, 2025.
One or more of the authors has declared the following potential conflict of interest or source of funding: A.B.Y. is a paid consultant for AlloSource, JRF Ortho, and Stryker; is an unpaid consultant for Patient IQ and Sparta Biomedical; and holds stock or stock options in Patient IQ, Sparta Biomedical, and Icarus. AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto.
