Patellofemoral Instability: Video Presentation of MPFL Reconstruction and TTO Distalization Part 1—Background and TTO

Abstract

Background:

Patellofemoral instability is a common problem that requires personalized treatment for each patient based on the relevant pathoanatomy. There are many ways to perform soft tissue and osteotomy procedures, and here we present our lead author’s treatment algorithm, operative technique, and postoperative protocol.

Indications:

Medial patellofemoral ligament (MPFL) reconstruction, vastus medialis obliquus advancement, and MPFL repair are indicated in patients with unsuccessful nonsurgical treatment after primary dislocation, those with significant osteochondral fracture, and patients with excessively high-risk factors after primary dislocation. Osteotomy is a consideration in those with elevated tibial tuberosity–trochlear groove or patellar alta, while lateral retinacular lengthening is indicated for those with lateral patellar tilt.

Technique Description:

In part 1 of this 2-part series, diagnostic arthroscopy and tibial tubercle osteotomy (TTO) are demonstrated. In this patient case, both distalization and medialization are required. Diagnostic arthroscopy is performed, and in particular, the important role of the superomedial viewing portal is shown to assess patellar tracking and trochlear dysplasia better. Exposure and osteotomy of the tibial tubercle are shown, including predrilling unicortical holes in the planned osteotomy before completion with osteotomes. The distalization is measured and performed, and the tubercle is translated both medially by 1 cm and distally by 2 cm.

Results:

Patients can expect improved clinical and functional outcomes with patellar stability and low rates of complications.

Discussion/Conclusion:

PFI requires a patient-specific approach that takes into account the patient’s relative pathoanatomy and a surgical plan aimed at addressing each component. Multiple known risk factors can help predict the risk of recurrent instability and guide patient-informed decision-making. Consistent indications and technique can lead to very high patient satisfaction and improved clinical outcomes.

Patient Consent Disclosure Statement:

The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication.

Graphical Abstract

This is a visual representation of the abstract.

Video Transcript

This is a case presentation on a patient with patellofemoral instability with a video technique guide on medial patellofemoral ligament (MPFL) reconstruction and tibial tubercle osteotomy (TTO) with medialization and distalization. This video comprises part 1 of a 2-part series.

The authors include Jacob M. Modest, Maxwell C. Alley, Sercan Yalcin, and Lutul D. Farrow.

In this part 1 video, we will show the case presentation, background of patellofemoral instability, our surgical plan, and video demonstration of incision marking and the TTO.

Part 2 will show the soft tissue component of this surgery with video technique of lateral retinacular lengthening, MPFL reconstruction, and vastus medialis obliquus (VMO) advancement with MPFL repair. We will discuss our postoperative protocol and final outcome for this patient.

There are no relevant disclosures in this technique presentation, and those listed here are related to the primary author.

This patient case involves a 15-year-old girl with bilateral patellofemoral instability and pain that is worse in the left knee than the right. She has been symptomatic for 2 years on the right and for 1 year on the left. She has required multiple manual reductions bilaterally but most recently had 2 left patellar dislocations. She is a sophomore in high school with cheer being her main sport. She has had extensive prior treatment with physical therapy and patellar stabilization bracing, which have not been effective.

On examination of the left knee, the patient has a Beighton score of 4 of 9. She has normal alignment but lateral patellar tracking without a J-sign. Given her recent dislocation, she lacks 20° of full flexion, which is painful. She has no pain with patellofemoral compression or pain along the facets. She has a tight lateral retinaculum with a lateral tubercle position. She has apprehension with lateral patellar translation.

Plain-film 3V knee radiographs show patellar alta. In this next series, her alta is quantified with a Caton-Deschamps Index of 1.5 and a patellar trochlear index of 0%, indicating no overlap of the patellar cartilage with the trochlea when the knee is in extension. Magnetic resonance imaging evaluation shows no cartilaginous injury but is significant for MPFL rupture. The tibial tuberosity–trochlear groove (TT-TG) was measured at 21.2 mm with approximately 50% patellar tendon displacement, as shown in the right image.

Background

For a brief background on patellofemoral instability, this meta-analysis by Huntington et al ¹ was Level II evidence published in the American Journal of Sports Medicine in 2019. The study involved 17 studies and found that the overall redislocation rate after conservative treatment was 33.6%, or approximately 1 in 3.

This study further looked at risk factors. They found that 5 major risk factors included young age, open physis, presence of trochlear dysplasia, elevated TT-TG, and patellar alta. Trochlear dysplasia was the most significant risk factor. ¹

A simplified approach to patellofemoral instability includes identifying these risk factors and the overall risk of dislocation with nonoperative treatment. Patients with no risk factors can have rates of dislocation around 10%, whereas those with 3 risk factors can be as high as 70% to 80%. The take-home point here is that not all patients are created equal, and treatment must be patient specific and patient guided.

A simplified decision chart shows that, in general, after primary first-time dislocation, nonoperative treatment is oftentimes the leading approach, with physical therapy aimed at quad strengthening and utilization of patellar stabilization braces with gradual return to play. Surgery is considered in the setting of recurrent instability, significant osteochondral lesions, or primary instability with multiple significant risk factors after patient-guided discussion.

For operative management, patients with normal osseous anatomy are treated with a soft tissue procedure with MPFL reconstruction, VMO advancement, and MPFL repair. In patients with a lateral patellar tilt, which is most patients, lateral retinacular lengthening is performed. In patients with an elevated TT-TG, a TTO with medialization is performed, and in patients with patellar alta, a TTO with distalization is performed. It is this primary author’s (L.D.F.) preference to use hamstring autograft for MPFL reconstruction, although data have shown equivalent outcomes with allograft.

As discussed prior, the addition of TTO is considered for patients with an elevated TT-TG above 20 mm, lateral facet chondrosis, distal chondrosis, or revision instability.

Indications

Now back to our patient, who is a 15-year-old girl with recurrent patellofemoral instability that is worse in the left knee than the right. She also has severe patellar alta, an TT-TG, and unsuccessful nonoperative treatment.

The plan is for left knee diagnostic arthroscopy with lateral retinacular lengthening, MPFL reconstruction using an autograft hamstring, VMO muscle advancement with MPFL repair, and TTO with distalization of 2 cm and medialization of 1 cm.

Technique Description

The patient is positioned supine on the operating room table with an upper thigh tourniquet applied. Stacked blankets are placed below the operative leg to create a stable plateau to aid in obtaining a lateral radiograph. In patients with excessive external rotation, a trochanteric bump can be used for improved surgical access and lateral radiographs. A lateral stress post at the level of the tourniquet in the upper thigh is applied to the bed to allow for valgus stress during arthroscopy. The down leg is appropriately padded and taped down.

After appropriate draping, skin marks are placed in a standard arthroscopy position with the knee at 30°. The inferior pole of the patella and a standard lateral paratendinous portal are marked. The medial portal is made in the soft spot of the knee, a “low and inside” portal just above the joint line and approximately 1 cm lateral to the medial femoral condyle. Next, a superior outflow portal is marked in full extension at the medial aspect of the suprapatellar space.

Next, we are going to mark out the incision for the TTO and hamstring harvest.

In extension, the tibial tubercle is marked along the superior and lateral aspect of the tubercle. The pes tendons are palpated with a flexed thumb interphalangeal joint and marked with a transverse line.

An anterior longitudinal incision is marked along the medial aspect of the tibial tubercle, allowing access to both the tubercle laterally and the pes tendons medially. This is at least 4 cm in length, but for distalization procedures, it will be 4 cm plus the length of the planned distalization, in this patient’s case, with 2 extra centimeters. The adductor tubercle and medial femoral epicondyle are palpated and marked for planned access to Schottle’s point for later MPFL reconstruction.

Finally, the incision for the lateral retinacular lengthening and MPFL reconstruction is marked along the full length of the lateral patella, in line with the lateral paratendinous portal, approximately 4 cm in length.

First, a standard diagnostic arthroscopy is performed, paying particular attention to tracking the patella, potential cartilaginous injury, and loose bodies within the joint. For this patient, diagnostic arthroscopy, shown here from the lateral viewing portal, demonstrates the lateral tracking of the patella.

Additionally, in patellofemoral instability cases, the scope is introduced through the superomedial outflow portal to evaluate tracking from above, showing a bird’s-eye view. This can allow for best visualization of potential trochlear dysplasia. Here again in this patient, we see lateral patellar dislocation in full extension on the left, with some chondral fraying of the medial facet, and on the right lateral tracking of the patella as the knee is flexed slightly.

After the tourniquet is inflated, attention is turned toward the TTO and hamstring harvest. An incision is caried sharply with a No. 10 blade through skin and subcutaneous tissue to the level of the fascia. Electrocautery is used for hemostasis of crossing vessels. Flaps are developed both medially and lateral.

Medially, we dissect and look for paratenon once distal to the level of the tubercle. Flaps are elevated over the paratenon, both medial and lateral, to aid in exposure. Laterally, the anterior compartment is visualized. The Metzenbaum scissor is placed across the undersurface of the patellar tendon just superior to the tubercle to aid in complete exposure of the tubercle.

The anterior compartment fascia is released from the bone. The patellar tendon is retracted. A Cobb is used to elevate the anterior compartment off the bone. The top of the tubercle is marked with electrocautery. The distal extent of the osteotomy is marked based on preoperative templating. The medial fascia and periosteum are released from the bone.

A 3.2-mm drill bit is used first at the proximal tibia and then working out laterally first, spaced approximately 5 mm apart. The drill bit is aimed straight across the tubercle to ensure that not too thin of a block is elevated. The drill is passed unicortically only. This is completely circumferentially, including at the distal extent. An osteotome then completes the osteotomy on the tibial tubercle. The drill holes are connected along the lateral and medial tubercle and then distally. The osteotomy is completed.

A green towel is placed below the block to protect the underlying skin. The distalization is now performed. The distal periosteum is elevated sharply. The planned distalization is marked again. A towel clamp is used to hold the bone block, and the distalization is completed with a sagittal saw. This bone is saved and then press-fit into the proximal defect and impacted in with the use of a tamp and a small mallet.

The medialization is palpable at the lateral aspect of the defect. This is planned to correct the TT-TG to approximately 10 mm. Two 4.5-mm bicortical screws are placed using the standard lag screw technique, with sequential drilling using a 4.5- and 3.2-mm drill bit. These are measured, countersunk, and placed.

After both screws are placed, the knee is flexed to ensure stable fixation and full range of motion. Anteroposterior and lateral fluoroscopic images show planned distalization and appropriate hardware length and position.

This concludes part 1 of our video demonstration. Part 2 will include the rest of the operative procedure, the postoperative protocol, and the final patient outcome. Thank you.