Special Considerations for Pediatric Patellar Instability

A potential reason some of these studies did not show any significant difference between the operative and nonoperative cohort could be that the surgical cohorts included a wide range of procedures including lateral releases and MPFL repairs. Recent publications have indicated that these techniques do not produce overall positive outcomes. While each surgical treatment plan is unique depending on the patient; recently, MPFL reconstruction has been shown to have better outcomes than both nonoperative management and simple medial repair and/or lateral
release.^67,88-90

MPFL RECONSTRUCTION

INDICATIONS/OVERVIEW

The MPFL is an important stabilizer for the knee that primarily resists lateral translation of the patella. Damage to the MPFL is very common in acute patellar dislocations with up to 90% of first-time dislocations resulting in injury to the MPFL.^91,92 Historically, simple medial and/or lateral MPFL repairs have not been shown to improve patellofemoral kinematics significantly and often result in recurrence.^90,93 To address this issue, during the past few decades, numerous MPFL reconstruction techniques have been developed to reconstruct a stronger ligament with the same kinematics as the anatomic MPFL.^{2,19,69,81,94-106} The ultimate goal of MPFL reconstruction is to reestablish the anatomic “checkrein” to guide the patella into the trochlea between 0° and 30° of knee flexion.^107,108 An essential secondary surgical goal in skeletally immature patients is to avoid damaging the distal femoral physis.

There are many variations in both the grafts used to replace the MPFL and the means by which to secure them. The ones discussed below include free semitendinosus or gracilis autografts or grafts constructed from a pedicled adductor, patellar, or quadriceps tendon.^69,105,109 While not used as frequently, allografts have also been used.¹¹⁰ Methods to secure these grafts in osseous tunnels include suture anchors or tenodesis screws. Incomplete osseous sockets or medial-sided bone tunnels have also been used as a method to decrease patellar fractures as they preserve the lateral patellar cortex.^111-114

DOUBLE-BUNDLE HAMSTRING AUTOGRAFT

The technique most often used by the author is a double-bundle hamstring autograft harvested from either the semitendinosus or the gracilis secured by short patellar and femoral sockets (Figure 3). After harvesting the hamstring graft from a posteromedial incision, an approximately 90-mm graft is prepared with Krackow stitches to secure 15 mm of the tendon in each socket.¹¹⁵ Lateral radiographs are used intraoperatively to ensure the guidewire for the femoral drill hole falls along the posterior cortex of the diaphysis of the femur while AP radiographs confirm placement distal to the physis. It is important to take both AP and lateral radiographs intraoperatively due to the concave curvature of the distal femoral physis. This unique anatomy can make a point that is located distally to the physis on the AP view appear on or proximal to it on the lateral cross reference view.^24,116 For the patellar socket, 2 short sockets are made in the superior half of the patella. Once the sockets have been drilled, the graft is adjusted so that the patella stays seated in the center of the trochlea between 20° and 30° of flexion. This anchoring is accomplished by securing the graft while the knee is kept at 30° of flexion. Proper tension is confirmed by ensuring that the graft does not allow lateral patella movement over one-fourth the width of the patella in extension while crepitation must not appear throughout the ROM.⁹²

QUADRICPETS TENDON TRANSFER

A combination of techniques by Steensen and colleagues,¹⁰⁵ Goyal,¹⁰⁹ Noyes and Albright,¹¹⁷ and Pinkowsky and Hennrikus¹¹⁸ describe an MPFL reconstruction in which the proximal end of a small medial portion of the quadriceps tendon is released and then attached to the medial epicondyle through a subcutaneous tunnel (Figure 4). This technique is particularly useful for cases in which the extra strength provided by the bone-quadriceps tendon is necessary to correct more severe dysplasia. Leaving the distal end of the quadriceps tendon intact at its patellar insertion, a graft of about 8 mm x 70 mm thickness is harvested from the tendon. The free distal end of the tendon is then run anatomically through the synovium and retinaculum to be either sutured to the medial intermuscular septum at the medial femoral epicondyle or fixed in femoral tunnel using interference screw.^105,109,118 The placement of the femoral fixation point is essential to ensure positive surgical outcomes. If the graft is secured too anteriorly, it may be too loose in extension and too tight in flexion, both of which can lead to postoperative pain, loss of normal kinematics, and overload of the medial patellofemoral cartilage.^119-121 Once the ideal placement of the femoral fixation point has been confirmed by intraoperative radiographs, the graft is secured with a small absorbable suture.^122,123 While this technique has good clinical results, the longitudinal scar that results from graft harvesting is cosmetically unappealing, and it is technically challenging to harvest a consistent strip of the quadriceps tendon. To address some of these concerns, Fink and colleagues¹²⁴ described a new harvesting technique that produces more consistent grafts and requires a smaller incision.

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