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Patellar Instability
Updated: Oct 4 2016

MPFL Reconstruction - Pediatric and Adolescent

Preoperative Patient Care
Operative Techniques

Preoperative Plan


Preoperative clinical assessment

  • Evaluate gait, lower extremity angular and rotational profile, Q angle, tibial torsion, patella tilt, femoral version, ligamentous laxity (Beighton score), and range of motion
  • Clinical questioning to assess Tanner stage


Preoperative radiographic assessment

  • Radiographs - AP, lateral, and sunrise of the injured knee
  • Assess physeal development, osteochondral injury, trochlear dysplasia, patella alta
  • MRI as indicated
  • More fully characterize osteochondral injuries, trochlear dysplasia, bone edema, location of MPFL injury, associated intraarticular pathologies, and tibial tubercle to trochlear groove distance
  • Angular profile as indicated
  • Full length standing hips to ankles AP radiograph if concern for angular (varus/valgus) malalignment on clinical exam
  • Bone age Xray as indicated
  • PA hand and wrist radiograph if skeletal age unclear on lower extremity radiographs


Examine the knee under anesthesia

  • Range of motion, Ligamentous stability, medial and lateral patellar translation in 25-30 degrees of knee flexion. Compare all exam findings to contralateral side

Room Preparation


Surgical instrumentation

  • Basic arthroscopy set
  • Basic orthopaedic set
  • K-wires
  • Bioabsorbable suture anchor with braided non-absorbable sutures


Room setup and equipment

  • Radiolucent OR table
  • Arthroscopy equipment - smaller patients will benefit from a small arthroscope to minimize iatrogenic cartilage damage
  • C-arm positioned on the opposite side of the injured extremity


Patient positioning

  • Supine
  • Lateral post for valgus stress for arthroscopic procedure
  • Radiolucent triangle under knee

Graft Exposure


Expose the graft

  • Graft exposure and preparation is performed after knee arthroscopy
  • A lateral release in carefully selected patients can be performed if tightness of the lateral retinaculum prevents normal medial patella translation or in cases of abnormal patella tilting
  • Longitudinal incision from superior pole of the medial aspect of patella, extending 5 to 6-cm proximally
  • Full-thickness flaps developed and dissected down to the quadriceps tendon and its insertion on patella


Femoral sided exposure

  • 2-cm longitudinal incision centered over medial epicondyle based on fluoroscopy and palpation
  • Dissection performed distal to physis to level of bone

Graft Preparation


Harvest graft

  • Identify VMO insertion on quadriceps tendon, harvest just lateral to VMO leaving 1-2-mm sleeve of remaining quadriceps tendon medially
  • Harvest an 8-mm by 70-mm full-thickness graft leaving the patella insertion intact
  • If tendon very thick can harvest partial-thickness graft


Place suture in graft

  • Suture the proximal free end of the graft with a whip stitch using a non-absorbable suture to prepare for passage of the graft

Graft Passage


Graft passage

  • Create tunnel for passing graft with large hemostat between the medial retinaculum and the synovium

Graft Tensioning


Identification of femoral insertion of MPFL

  • Use radiolucent triangle to flex knee to around 40 degrees to facilitate lateral radiograph
  • Find the "Schottle point": Identify MPFL insertion on lateral fluoroscopic radiograph 2-mm anterior to posterior cortex of the femur, and 2-mm distal to the posterior origin of the medial femoral condyle, and just proximal to Blumensaat line
  • Anatomic site for the femoral attachment of the MPFL lies a few millimeters distal to the medial aspect of the distal femoral physis
  • Place bioabsorbable suture anchor at this femoral insertion point


Tension the graft

  • Place knee in 30 to 45 degrees of flexion
  • Patella should translate about 10-mm laterally before end point to prevent overtensioning
  • Goal is to maintain the patella tracking centrally in the trochlea without any sign of medial subluxation
  • Provisional placement of pilot stitch
  • Place pilot suture through graft and periosteum of epiphyseal region of distal femur after setting tension of graft
  • Gently range knee through flexion and extension to assess graft tension and patellar position with motion
  • Make adjustments to this pilot stitch as indicated based on improper tensioning
  • Use sutures from previously placed suture anchor to secure graft on the femoral side in the position determined by pilot suture
  • Reinforcement of fixation on femoral side with additional non-absorbable sutures to medial intermuscular septum
  • Place non-absorbable sutures from periosteum of patella into graft
  • Assess patellar tracking through range of knee motion

Wound Closure


Deep closure

  • Quadriceps tendon graft site closed with absorbable vicryl suture


Superficial wound closure

  • Subcutaneous tissues closed with absorbable interrupted suture
  • Skin closed with running subcuticular suture


Dressings and immobilization

  • Place in a locked hinged knee brace in full extension
Postoperative Patient Care
Private Note

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