Trochleoplasty With Combined Soft Tissue Reconstruction for Patellar Instability

Abstract

Background:

Patellofemoral instability is a relatively common condition and is multifactorial in its cause, with both soft tissue and bony components. Trochleoplasty is a newly described surgical procedure to help improve outcomes following patellar restabilization.

Indications:

Trochleoplasty is an emerging surgical technique during patellar stabilization surgery in those patients with underlying trochlear dysplasia.

Technique Description:

Trochleoplasty was performed via an open medial parapatellar arthrotomy. Using a combination of osteotome and guided bur, the subchondral surface was undermined to produce a deeper sulcus. The cartilage surface was then plastically deformed into the newly developed trochlea. Trochleoplasty was then secured with a central triple-loaded interference screw and 3 peripheral interference screws. Medial patellofemoral ligament reconstruction was then performed in standard fashion.

Results:

Postoperative course was complicated by arthrofibrosis, which required manipulation at 4 weeks. Following manipulation, the patient recovered uneventfully and had returned to full activities at 6 months with full strength, range of motion, and minimal pain.

Discussion/Conclusion:

Trochleoplasty with combined soft tissue reconstruction is a viable treatment option in those patients with recurrent patellar instability and underlying trochlear dysplasia. While not without complications, this surgical technique remains a powerful tool in the correctly indicated patient. Appropriate patient selection and adherence to postoperative rehabilitation are crucial for optimal 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

Hi, my name is Dr. Magister. I'm with NYU Langone Orthopedics and I will be presenting on trochleoplasty with combined soft tissue reconstruction for patellar instability. The authors’ disclosures are presented at the beginning of the article.

Background

So patellofemoral instability truly has a multifactorial cause, with both soft tissue and bony components. From a soft tissue standpoint, we often describe the medial patellofemoral ligament (MPFL), which is a defined structure that runs from the superior one-third of the patella and inserts on the medial aspect of the femur between the adductor tubercle, and the medial epicondyle. From a bony standpoint, we often discuss the relationship from the tibial tubercle (TT) and the trochlear groove (TG) such that lateral deviation or excessive lateral deviation of the tibial tubercle subsequently places a lateral force on the patella during active range of motion. Additionally, in recent years, the geometry of the trochlea has been further investigated such that we now appreciate that a shallow trochlea often described through the DEJOUR classification as listed below plays a significant role in patellofemoral instability.

Indications

Starting with the case, we have a 26-year-old woman who originally presented with left knee pain and instability. She reported 2 prior dislocations, the first of which occurred 2 years ago, followed by multiple subsequent dislocations. At the time of presentation, she was unable to return to gymnastics and exercise because of pain and apprehension with certain exercises. Her medical and surgical history was unremarkable. On examination, she had a mild effusion with neutral mechanical alignment bilaterally. She had a lateral resting position of her patella, and she had tender palpation at the medial patellar facet. Her range of motion was full, with extension to 110° of flexion. Clinically, she had +3 lateral translation with a glide without a firm endpoint and had a positive patellar apprehension test. She had a positive J sign and additionally had a positive lateral patellar tilt. On preoperative imaging, her mechanical alignment was confirmed to be neutral on full-length standing films on anteroposterior and lateral radiographs. She was measured to have a Caton-Deschamps ratio of 1.18, as well as a positive spur sign, a positive crossing sign, and a positive shallow trochlea. Advanced imaging was also obtained, which showed preoperative lateral patellar tilt and subluxation, an extremely dysplastic trochlea, and a TT to TG distance of 14.1. Both nonoperative and operative management strategies were discussed with the patient at great lengths. However, given her age and inability to perform activities of daily living and exercise, surgical options were discussed. These included medial quad-tendon femoral ligament (MQTFL) reconstruction as well as a trochleoplasty and possible lateral patellar lengthening. For this patient, we specifically discussed the trochleoplasty as a viable option, given her positive preoperative imaging and extremely dysplastic trochlea.

Technique Description

After induction under anesthesia, a physical examination is performed. This demonstrates the dislocating patella laterally as well as a positive J sign. Surgical arthroscopy is then performed before the open procedure. This demonstrates a dysplastic trochlea as well as some undersurface fraying of the patellar surface. Additionally, a stress examination is performed, confirming the lateral subluxation of the patella outside of the dysplastic trochlea. A lateral approach is then performed in a standard fashion, being careful to isolate the superficial and deep layers to allow for lateral lengthening at the end of our procedure. An arthrotomy is then performed along the lateral aspect of the trochlea and patella. Dissection is then further carried deep again, being sure to isolate our superficial and deep fibers to allow for future lateral lengthening. K-wires are then placed in the superior, medial, and lateral portions of the distal femur to assist with retraction. Excess fat surrounding the trochlea is then removed to assist with visualization. Here we see the identification of both the native and future desired center of the trochlea. Additionally, a horizontal line is created to denote the normal inferior portion of the trochlea as well as the superior dysplastic portion of the trochlea. This helps ensure that the osteochondral flap is maintained in good contour when we go to resecure it. At this point, soft tissue is then further released from the undersurface of the cartilage surface. A small osteotome is then used to elevate a thin osteochondral flap in a circumferential fashion. This is done in a methodical and slow way to not violate the cartilage surface itself. Once the subchondral surface is freed and loosened, we then further deepen the undersurface by using an aiming guide with a subsequent drill to further burr out the undersurface of the trochlea and subchondral bone. The goal is to allow for plastic deformation within the native cartilage surface to further deepen our future trochleoplasty. Here we see the drill being used to excavate the undersurface of the subchondral surface. Additionally, any superior lateral trochlear spurs are sharply debrided with an osteotome and rongeur. A burr is used to further deepen and remove the superior lateral spur. At this point, we then perform an osteoplasty to deepen the future center of the trochlea. Here, with the assistance of the burr, the undersurface of the subchondral flap is further debrided to remove as much bone as necessary from the undersurface until it is flexible enough to be reshaped. At this point, direct pressure is used to deepen the groove into the recessed area of bone. Fixation is then performed with a preloaded knotless anchor with a heavy absorbable suture. Our preloaded sutures are then placed into 3 knotless anchors along the superior pole of the trochlea. The sutures are subsequently tensioned to secure the new trochlea, being careful not to overtension the sutures. These sutures are expected to resorb in roughly 6 to 8 weeks. The free ends are then cut and the new, now deeper trochlea is appreciated and the patella is stressed, already demonstrating improved stability without the ability for lateral subluxation. We then go on to perform our medial soft tissue reconstruction. In this case, we use an MQTFL technique. A small rent is made in the superior medial aspect of the vastus medialis oblique (VMO), and a passing suture is used to identify layer 2 of the medial knee. Schottle's point is identified fluoroscopically, and a wire is passed in a standard fashion. This is then subsequently overreamed to the lateral aspect of the cortex of the femur. Soft tissue allograft is prepped and prepared on the back table in standard fashion and subsequently passed under direct visualization into the femur. This is then subsequently secured with a single interference screw. The graft is then passed through the rent and the VMO, and then we turn our attention to subsequently close our lateral arthrotomy with a lateral lengthening. This is done specifically before securing the MQTFL graft to not overtension and overmedialize the patella. The graft is then marked at the interface between the VMO. The knee is ranged, ensuring that the graft is properly tensioned. The rent within the VMO is then subsequently secured with multiple fiber wires within the quadriceps tendon. The excess graft is then further secured overlying the quadriceps tendon. The excess tendon is then trimmed. The knee is finally ranged, and manual stress is used to secure the patella without the ability for lateral subluxation. Additionally, the patella is noted to glide centrally within the new trochlea. The skin is closed in a layered fashion.

Immediately postoperative, we allow partial weightbearing with the knee locked in full extension at 2 to 6 weeks. We then transition to weightbearing as tolerated, locked in full extension at all times. We progress her range of motion with physical therapy to roughly 90° and then initiate a home exercise program as well at 6 to 12 weeks. We then discontinue the brace, assuming quadricep function has returned, to allow full range of motion and weightbearing as tolerated. We continue physical therapy until 3 to 6 months, when we begin a progressive jogging program in a sports-specific return to play.

Results

So for our patient, initial follow-up was complicated primarily due to reduced range of motion and arthrofibrosis. This subsequently went on to needing a manipulation under anesthesia at 4 weeks. Fortunately for this patient, she did regain her full range of motion, and at 6 months, she had full range of motion at 0° to 130° without pain and had resumed full activities. Additionally, 4-week postoperative radiographs and magnetic resonance imaging at 6 months were obtained, which showed good alignment without residual patella baja or patellofemoral osteoarthritis, as well as maintenance of our deepening TG osteotomy.

Additionally, clinical follow-up at 1 year continued to show full painless range of motion without any evidence of maltracking. The patient described no feelings of patellofemoral instability, and gait examination demonstrated a pain-free nonantalgic gait.

Discussion/Conclusion

In recent years, several studies have emerged with regard to looking at outcomes following trochleoplasty. One such study involved 27 patients who underwent trochleoplasty with various combined procedures with an average follow-up of 7 years, and in this study, no recurrences were noted, and no stiffness was noted in their patient population. Additionally, they had no evidence of patellofemoral osteoarthritis and maintained International Knee Documentation Committee (IKDC) scores and patient-reported outcomes. ³ Further, in 2021, a meta-analysis was performed that looked at 28 reports. ² This was a fairly large study that examined over 1000 trochleas and 890 patients. Their follow-up was varied, but overall, their outcomes were positive. However, they did note that there was a moderate degree of patellofemoral osteoarthritis at their varied follow-up as well as 17% of patients needing recurrent surgery. However, a note for this study was that the authors did discuss a large disparity between studies for most complications, and subsequently, they believed that further large-scale randomized and comparative studies are needed. Additionally, the discussion about whether a trochleoplasty is sufficient in isolation or whether an MPFL reconstruction is needed has also been investigated in 2 studies recently, the first of which had 18 knees with a 30-month follow-up. ¹ In their study, the patients who underwent combined MPFL reconstruction had maintained IKDC scores and patient-reported outcomes, as well as a decrease in their pain scores. They did note, though, that they had 1 recurrence in their study. Additionally, a recent systematic review that looked at 6 studies in patients who underwent isolated trochleoplasty versus trochleoplasty plus MPFL reconstruction found a slight decrease from 2% to 0% in those patients who underwent combined trochleoplasty and MPFL reconstruction. ⁴ However, the authors did note that Kujala scores were similar among their 2 groups. Taken together, these reports, as well as others, show support for using trochleoplasty when addressing patellofemoral instability. However, it should be noted that there are complications associated with this procedure, which are important to consider when counseling patients before undergoing this procedure.

With regard to some pearls and pitfalls important to address when discussing trochleoplasty and performing this procedure, we believe that first one should mark the native and desired center of the trochlea as this center is the desired deepening of the TG. Additionally, preservation of the height of the lateral femoral condyle is critical as this ensures that the osteoplasty is performed just under the trochlea. Special attention should be paid to the cartilage surface when thinning the undersurface of the trochlea to not violate this surface. In addition, when fixating the trochleoplasty, sutures should not be overtensioned, as this can lead to cartilage necrosis. Finally, additional procedures such as MPFL reconstruction and TT osteotomy should also be considered and primarily based on anatomic parameters and patient history.

These are our references.

Thank you very much.