Physeal-Sparing Medial Patellofemoral Ligament Reconstruction With Medial Patellotibial Ligament Augmentation for Recurrent Patellar Instability

Abstract

Patellofemoral instability is a common issue that may result in recurrent dislocation of the patella. Surgical reconstruction of medial patella–stabilizing structures is often necessary to relieve symptoms in patients with recurrence. Most commonly, the medial patellofemoral ligament (MPFL) is reconstructed using graft tissue. Some surgeons prefer to further stabilize the repair with bony augmentation procedures for the distal femur or proximal tibia. These augmentation procedures—and often the MPFL reconstruction itself—do not respect the physis, making them an unfavorable choice in skeletally immature patients. The purpose of this article is to describe a physeal-sparing technique for MPFL reconstruction plus augmentation with physeal-sparing medial patellotibial ligament reconstruction.

Patellofemoral instability (PFI) is subluxation or dislocation of the patella from its anatomic location within the trochlear groove. The reported rate of primary dislocation in the general population is 5.8 in 100,000, with the pediatric rate at 29 in 100,000.^1,2 Recurrent instability rates after primary dislocation range from 15%³ to 70%.^1,4,5 A careful balance between the bony articulations of the patellofemoral joint and the surrounding soft tissues is essential for patellar stability.⁶ The medial patellofemoral ligament (MPFL) has been described as the primary stabilizer of the patella, preventing lateral dislocation.⁷ When lateral patellar dislocations occur, the MPFL is often disrupted. Subsequent incompetence of the MPFL is regarded as the primary cause of recurrent PFI.⁸ Given the high rates of recurrent instability with non-operative treatment in pediatric populations, surgical reconstruction of the MPFL is a viable option.^9,10

Common MPFL reconstruction and bony augmentation techniques used in skeletally mature patients can violate the physeal-sparing concepts of pediatric orthopaedic surgery.^11,12 Violation of the growth plates about the knee has significant long-term consequences in the pediatric patient.^13,14 As such, soft-tissue reconstructive techniques are the mainstay of surgical management of PFI in this population. Reconstruction of the MPFL with physeal-sparing considerations is the technique of choice of most surgeons.15, 16, 17, 18 Augmentation with bony reconstruction is common in the adult population, and consideration of possible augmentation is of special interest in pediatric patients as well. A recent study examined MPFL reconstruction augmented by quadriceps tendon femoral ligament reconstruction and found improved results compared with nonoperative management in pediatric first-time dislocators.¹⁹ Although there are numerous described primary surgical techniques for the treatment of PFI in skeletally immature patients, few publications exist describing augmentation of MPFL reconstruction with open physes. The primary purpose of this article is to describe a physeal-sparing technique for MPFL reconstruction plus augmentation with physeal-sparing medial patellotibial ligament reconstruction (Video 1).

Surgical Technique

Diagnostic Arthroscopy

The patient is placed supine on the operating table. After general anesthesia is induced, the operative limb is examined for PFI and compared with the contralateral limb. The leg is prepared and draped using sterile technique. The tourniquet is inflated, and 0.5% bupivacaine solution is injected at the planned portal sites. Following the usual technique, an arthroscope is placed in the anterolateral portal to perform diagnostic arthroscopy. It is important to note patellar or trochlear chondral defects or chondromalacia signifying injury patterns, loose bodies, and patellar instability in the trochlear groove. The lateral femoral condyle and medial patellar edge should be carefully examined because injuries commonly occur at these locations during PFI events. Evaluation of patellofemoral laxity may be repeated under arthroscopic visualization.

Femoral, Patellar, and Tibial Preparation

The knee is flexed to approximately 60°, and dissection to the medial patella is performed. The paratenon is incised at the medial border, exposing the medial patella. A small rongeur is used to debride the medial border of the patella down to bleeding bone, ensuring an adequate site for anchor placement. Dissection to the medial distal femur is performed. The medial fascia and capsule are opened to expose the bone of the medial condyle.

Tunnel preparation in the distal femur is performed using a lateral radiograph of the knee to ensure sparing of the physis. A Beath needle is placed at the Schöttle point, approximating the insertion of the MPFL. The needle is advanced to the lateral cortex aiming slightly anterior and distal, ensuring no damage occurs to the physis (Fig 1). Next, an 8-mm cannulated drill is used over the Beath needle to a depth of 30 mm. After fluoroscopic images confirm no violation of the physis, drill debris and soft tissue are cleared from the tunnel. A passing suture is passed to the lateral side of the leg using the Beath needle (Fig 2). Another option is an adjustable tensioning looped all-suture anchor. The use of such an anchor allows for smaller-diameter tunnel drilling, decreasing the risk of physeal injury, and can be applied in smaller patients. This technique has been described in a previous article.²⁰

Fig 1.

Anteroposterior and lateral fluoroscopic images of a right knee with placement of a Beath pin (black arrows) at the Schöttle point. The pin is directed anteriorly and away from the physis. This pin will be over-drilled with a cannulated drill bit to create the femoral tunnel for a physeal-sparing medial patellofemoral ligament reconstruction.

Fig 2.

Transfemoral passing suture passing through a patient’s right distal femur. (A) Arthroscopic view inside the 8-mm tunnel in the medial distal femur with the passing suture in place. (B) Intraoperative photograph depicting the passing suture (black arrows) placed through the distal femur. Once the passing suture is set in place and pulled to the lateral side, the femur is ready for docking of the graft.

Three nonabsorbable all-suture anchors (JuggerLoc; Biomet, Warsaw, IN) are placed into the medial border of the patella in an evenly spaced fashion, approximating the insertion of the MPFL. Standard suture anchors or looped tension anchors can be used. The most inferior anchor is aimed superiorly during insertion to approximate the trajectory of the MPTL.

Proximal tibial preparation involves an incision over the anteromedial tibia, approximately 1 cm distal to the medial tibial eminence. Dissection is carried down to bone. Fluoroscopy confirms avoidance of the proximal tibial physis when planning MPTL anchor placement. The insertion of the MPTL is approximated in line with the medial tibial eminence, roughly 1 cm distal. A large all-suture anchor is placed at this point (Fig 3).

Fig 3.

Anteroposterior and lateral fluoroscopic images of a right proximal tibia during a physeal-sparing medial patellotibial ligament reconstruction. (A) A pin (green arrow) is placed approximately 1 cm distal to the medial tibial eminence in the epiphysis as the site of the medial patellotibial ligament insertion. (B) A cannulated drill bit (black arrow) is used to drill over the pin to create an anchor site. It is critical that the drill path does not damage the physis.

Graft Preparation and Placement

A tibialis anterior or tibialis posterior allograft is prepared for the previously drilled femoral tunnel. Sutures are placed in both ends of the graft using a whipstitch technique, consisting of No. 2 braided sutures (FiberWire; Arthrex, Naples, FL). This first graft, used for MPFL reconstruction, is folded in half at its midpoint. If using the tensioning looped anchor, the surgeon should deploy the soft suture-tensioning anchor and reduce the graft into the tunnel by tightening the loop. The looped ends are secured by hand tying of the graft over a knot pusher. Once the graft is properly positioned, a 7 × 20-mm biocomposite interference screw is placed into the femoral tunnel to secure the graft.

The free ends of the graft are tunneled to the patellar incision under the soft tissue but superficial to the joint capsule. Caution must be taken to avoid intra-articular passage of the graft. Forceps are passed between the joint capsule and soft tissues toward the medial femoral incision site. The graft suture ends are grasped and shuttled to the medial patellar incision. The free ends of the graft are secured to the 2 proximal patellar suture anchors using the Krackow suturing technique, with the knee held in extension and the patella reduced (Fig 4). The grafts are then trimmed, completing reconstruction of the MPFL.

Fig 4.

Photograph showing graft placement in the right knee of a patient receiving a physeal-sparing medial patellofemoral ligament reconstruction. The medial side of the knee is shown. Via the Krackow technique, suturing of both ends of the first graft (black arrows) to the 2 most superior anchors is performed in the superomedial patella (not shown), completing reconstruction of the medial patellofemoral ligament.

A second graft is used for MPTL reconstruction and is first sutured to the anchor in the proximal medial tibia using the Krackow technique. Once secured to the proximal tibia, the graft is tunneled subcutaneously to the patellar incision (Fig 5) and is secured to the inferior-most anchor in the medial patella using the Krackow technique. A repeated physical examination should be performed prior to closing to ensure adequate reduction of the patella with no maltracking. The patella should be stable with lateral translation and have a solid endpoint at completion. An example of the finished procedure with reconstruction of the MPFL and MPTL is shown in Figure 6.

Fig 5.

Photographs of the right knee of a patient receiving a physeal-sparing medial patellofemoral ligament reconstruction. The medial side of the knee is shown. The photographs show tunneling of the graft from the proximal tibial incision to the medial patellar incision. (A) A hemostat is passed between the soft tissue (black arrow) and the joint capsule. (B) The graft is pulled through the soft-tissue tunnel and out of the patellar incision (blue arrow). Once tunneled, the graft is sutured to the most inferior anchor in the patella, completing reconstruction of the medial patellotibial ligament.

Fig 6.

Three-dimensional model of completed physeal-sparing medial patellofemoral ligament (solid black arrows) and physeal-sparing medial patellotibial ligament (dashed blue arrows) reconstructions. (A) Anterior view. (B) Oblique view.

Discussion

Although the MPFL is known as the primary soft-tissue stabilizer of the patella, the MPTL also provides patellar stability. The MPTL’s contribution to stability is most pronounced at 90° of flexion, where it confers 45% of the total resistance to lateral patellar displacement, along with the medial patellomeniscal ligament.²¹ Sparse literature exists investigating the combination of MPFL and MPTL reconstruction. Abbaszadeh et al.²² published a meta-analysis regarding the topic, including 148 patients from 5 different studies, concluding that combination reconstruction leads to favorable outcomes with potentially less recurrence of instability. However, they mentioned that long-term data are lacking in the current literature.²²

Yang and Zhang²³ conducted the largest study on this topic, including 58 patients with a mean follow-up period of nearly 3 years (35.6 ± 10 months). The results showed that combination reconstruction of the MPFL and MPTL is a safe and effective surgical treatment for PFI. However, this study did not include pediatric patients. Sadigursky et al.²⁴ published a case series of 7 pediatric patients who underwent combination MPFL and MPTL reconstruction. Their results described resolution of instability symptoms, with no repeated dislocations, although their technique differed from our technique, using a single autograft and metallic anchors.

One benefit of our technique is a more anatomic reconstruction of the MPFL and MPTL, with the grafts being independent from one another rather than using one graft for both reconstructions. Additionally, all-suture anchors have a lower risk of disrupting the nearby physes because of a smaller attachment footprint. The tensioning looped suture provides tactile feedback while tightening and reducing the graft into the tunnel. One benefit of the all-suture anchor is the avoidance of rotating or twisting of the graft while placing an interference screw. Since the adoption of this tensioning looped all-suture anchor, we have noticed a reduction in graft rotation. Finally, using allograft tendon decreases autograft tendon harvest-site morbidity. Pearls and pitfalls of our technique are presented in Table 1.

Table 1.

Pearls and Pitfalls for Technically Important Aspects While Performing Pediatric MPFL and MPTL Reconstructions

Pearls

Femoral socket

In terms of the femoral pin placement, Schöttle's point is distal to the physis in a majority of cases.

When distal to the physis, the femoral drill pin should be aimed slightly distal and slightly anterior to avoid the physis and intercondylar notch.

The medial condyle width should be pre-measured to determine how deep to ream.

For a doubled-over graft that is 7 mm in diameter, the surgeon should ream with a 7.5 mm reamer and use an interference screw that is 7 mm in diameter.

Femoral suture anchor

When drilling the suture anchor, the surgeon should use a drill guide inserted in the more cephalad or superior aspect of the tunnel. This will keep the graft eccentric in the tunnel and avoid insertion of the suture anchor in the notch or joint.

The suture anchor drill should be aimed slightly proximal to avoid the intercondylar notch. If the drill path crosses the physis, it will be central in the physis. Suture anchors cause minimal issues to growth plates.25

After cinching down the adjustable tensioning loop, the surgeon should tie the suture with half-hitches for backup and cut the suture tails after tying.

A ≤20-mm-long interference screw should be used; a biocomposite screw is preferred.

The surgeon must remember to insert the interference screw distal and anterior—not the direction drilled for the suture anchor.

Patella

The grafts should be passed through the loops and then back down onto themselves.

The graft tails should be sutured back on the femoral side of the graft for extra security.

Tibia

The surgeon should use a guide pin and anteroposterior fluoroscopy to ensure a location 1 cm distal to the medial tibial eminence.

A hemostat slid to the bone can show the surgeon the aperture of the guide pin.

When using an adjustable-loop suture anchor, the surgeon should suture the graft end back onto itself for extra stability.

Pitfalls

Femoral socket

When dissecting in an epiphyseal location, the surgeon should avoid proximal dissection because this may damage the growth plate.

When using electrocautery to remove the periosteum at the tunnel, the surgeon should only perform removal at the distal aperture because proximal dissection may cause a physeal bridge.

The guide pin should not be aimed proximal or posterior to avoid damage to the growth plate or neurovascular bundle.

The surgeon should stop reaming once hard bone of the intercondylar notch is felt; the PCL may be just on the other side.

Large tunnels (i.e., >9 mm) should be avoided because these may be close to the physis.

Femoral suture anchor

When drilling the all-suture anchor, the surgeon must not aim distally or they will potentially place the anchor into the PCL or intra-articularly.

If the suture tails are left after tying, they will wind up during screw insertion.

Patella

When placing the patellar suture anchors, start by drilling for small anchors (i.e., <4.75 mm) and increase in size only if needed. The pediatric patella can be small, and large anchors can encroach on the subchondral cartilage.

Tibia

Distal dissection should avoided because this may damage the growth plate.

MPFL, medial patellofemoral ligament; MPTL, medial patellotibial ligament; PCL, posterior cruciate ligament.

As participation in youth sports increases, the population of pediatric patients experiencing PFI is also likely to increase, necessitating a safe and effective treatment for this issue in the skeletally immature population.²⁰ In this article, we have presented an easily reproducible technique that is theoretically safer for nearby growth plates and offers less morbidity to the patient.

Disclosures

All authors (D.D., A.P., C.V., R.R., P.M.) declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Supplementary Data

Video 1

Steps to complete physeal-sparing reconstruction of medial patellofemoral ligament and medial patellotibial ligament.