In this video, we present a surgical technique for MPFL reconstruction in pediatric patients. There are no conflicts of interest. Patellar instability is a fairly common problem in the active pediatric population. Surgical treatment may be recommended for recurrent instability after failing nonoperative treatment or if a chondral defect or loose body is noted on imaging after initial dislocation. Cadaver studies have demonstrated that the MPFL origin in pediatric patients is a few millimeters distal to the distal femoral physis. There is a risk to the physis with MPFL reconstruction as the typical tunnel trajectory would violate the physis. An MRI-based study showed that all epiphyseal techniques still have risk of injury to the physis with a large tenodesis screw. Therefore, a physeal-sparing MPFL reconstruction with all suture anchors and onlay technique addresses these issues. Here is a case presentation to demonstrate our technique. We have a 13-year-old female gymnast with bilateral recurrent patellar instability with daily activity for over one year. She's completed a course of physical therapy after each dislocation event, and while the right knee has remained stable, the left patella continues to dislocate. On clinical exams, she has full range of motion with an abnormal patellar tracking and a J-sign bilaterally. She has increased lateral patellar glide and a positive patellar tilt on the left, as well as patellar apprehension. Radiographic imaging shows a lateral patellar tilt and a shallow trochlear groove. She has a normal insole-silvati ratio and no apparent varus or valgus deformity. An MRI of the left knee demonstrates a large effusion. Lateral patellar tilt is again seen with subluxation of the patella laterally. The MPFL appears attenuated, and she has a normal TTTG and no apparent chondral injury. There are multiple treatment options for patellar instability in the skeletally immature patient. Treatment will typically begin with conservative options if there is no evidence of loose body or chondral injury on imaging. Surgical options may include MPFL repair or reconstruction. If there is evidence of valgus deformity, guided growth may be recommended. Other bony deformities may require various osteotomies, some of which are recommended to delay until skeletal maturity to protect the physis. Indications for MPFL reconstruction include recurrent patellar instability with MPFL tear or attenuation, failure of conservative treatment, or evidence of chondral injury on imaging. MPFL reconstruction may be contraindicated if the bony deformity appears significant and would be better addressed with other techniques. We will now show our surgical technique for MPFL reconstruction in pediatric patients. The patient is positioned supine on a radiolucent table with all bony prominences well padded. We begin with an examination under anesthesia to reassess the patellar lateral tilt, the patellar glide, and patellar tracking, or J sign, which are demonstrated in this video. We then proceed to a diagnostic arthroscopy using a standard anterolateral portal to assess for chondral injury. If no interarticular abnormalities are visualized, no further portals are needed. The arthroscopic picture on the bottom right demonstrates a typical injury to the lateral femoral condyle that occurs often during patellar relocation. The chondral injury in this patient did not require further fixation or treatment. For the open portion of the procedure, we begin with a 2 to 3 centimeter incision over the proximal half of the medial patella. Layer 1 of the medial knee is identified and full thickness flaps are created. Blunt dissection between layers 2 and 3 is used down to the medial epicondyle of the femur. Passing a Kelly clamp between these layers should be fairly easy. We use a bovie to remove the soft tissue off the medial patella followed by a runger to create a bleeding trough for anchor placement. Fluoroscopy is used to confirm placement of two anchors, one at the equator of the patella and the second in the proximal third. However, if the patella is still too small to accommodate two anchors, just one anchor can be placed proximally and the second limb of the graft can be sutured to the quadriceps in an MQTFL fashion. We next turn our attention to the medial femoral condyle. A 2 centimeter incision is localized with fluoroscopy over Schottel's point on a perfect lateral of the knee. Sharp dissection is carried down to the fascia which is then incised and the medial epicondyle is cleared off to access Schottel's point. The drill guide is placed firmly over Schottel's point on a perfect lateral radiograph. In pediatric patients, we then confirm the placement of the drill is distal to the physis on the AP view. The drill is aimed distal and anterior to avoid the notch, trochlea, and the physis. The authors prefer to place a Q-Fix 2.8 millimeter all suture anchor. Typically, a semi-tendinosis allograft is used as shown in the picture on the right. A Kelly clamp is then used to shuttle the limbs of the graft into the patellar incision while maintaining the loop of the graft in the femoral incision. We marked the mid-portion of the graft with a marker and hold a tot over the femoral anchor. We then use cerclage fixation with each set of sutures from the femoral anchor on either side of the marking to secure the graft to the femoral epicondyle with two points of fixation. Fixation on the patella is performed with the knee in 30 to 45 degrees of flexion, allowing the patella to engage in the trochlea. The two graft limbs are held top but without significant tension so that the graft acts as a check rein while still allowing for one to two quadrants of translation. We then mark the location of the patellar anchors on the graft. For each anchor, one suture is passed from deep to superficial in a locking Krakow stitch starting at the marking and working distal and then back up to the mark. The second suture from the same anchor is also passed from deep to superficial at the level of the mark and will act as a post, pulling the graft to the anchor. This is repeated for the second anchor, securing the other limb of the graft to the patella. The excess graft is then excised. The same sutures from the patellar anchors can then be used to close the layers back over the graft. The incisions are then irrigated and closed with absorbable suture. Finally, we repeat an exam under anesthesia. There are several potential complications of this technique. First of all, fixation of the graft is dependent on all suture anchors and suture fixation. Potential injury to the physis is still present though lowered through the onlay technique. There is risk of entering the notch due to the trajectory of the drill and there is risk of recurrent patellar instability if bony pathology is not adequately addressed. There are four phases involved in recovery postoperatively. The patient is weight bearing as tolerated immediately after surgery but in a brace for the first six weeks. The first two phases focus on maintaining and regaining range of motion. Phase three then progresses strengthening of the operative extremity and phase four involves progressing to sport specific activities. In order to return to sport without restriction, patients should demonstrate strength of the operative leg at 80% to 90% of the contralateral side. For high level athletes, functional testing can provide additional information for the surgeon and physical therapist before returning to play. Humerus studies have validated suture anchor fixation as equivalent to tenodesis screw fixation in both the humerus and the femur. Additionally, animal studies of onlay technique for biceps tenodesis shows equivalent healing as with fixation in bony tunnels. Healing occurs at the cortex and periosteum. In the author's experience using this onlay technique, there have been no recurrent patellar dislocations and no evidence of growth disturbance or angulation. One patient did find that the graft was prominent over the femoral epicondyle and returned to the operating room for debulking at nine months postoperatively. These are our references and thank you for listening.

surgical technique

MPFL reconstruction

pediatric patients

patellar instability

growth plate preservation