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A
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1343/2004
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428/2004
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84/2004
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Location A is known as “Schottle’s Point” and is the recommended location for the femoral tunnel for MPFL reconstruction. Lateral patellar dislocations most commonly occur after noncontact twisting injuries in which the knee is extended and the foot is externally rotated. The MPFL is the primary restraint to lateral forces on the patellar in the first 20 degrees of knee flexion, whereas bony structures account for the stability in deeper flexion. Anatomically, the MPFL originates on the femur between the medial epicondyle and the adductor tubercle, and is the most common site for avulsion with lateral patellar dislocations. Physical therapy and activity modifications are the mainstay of treatment for first time dislocators, however, MPFL reconstruction is the treatment of choice in patients with recurrent instability. LaPrade et al reviewed the anatomy of the medial side of the knee. They reported that the medial patellofemoral ligament attaches on the femur 1.9mm anterior and 3.8mm distal to the adductor tubercle. They concluded that structures on the medial aspect of the knee have a consistent attachment pattern in relation to bony landmarks. Dean et al reviewed patellofemoral joint reconstruction for patellar instability. They reported that patellofemoral reconstruction may necessitate MPFL reconstruction, tibial tubercle osteotomy, or trochleoplasty in any combination or individually. They conclude that treatment of this patellar dislocations should be individualized based on workup including evaluation of patellar height, trochlear dysplasia, retinacular structures and tibial tubercle anatomy. Schottle et al. in a cadaveric study looked at radiographic landmarks for femoral tunnel placement in MPFL reconstruction. A reproducible anatomical and radiographic point, 1 mm anterior to the posterior cortex extension line, 2.5 mm distal to the posterior origin of the medial femoral condyle, and proximal to the level of the posterior point of the Blumensaat line on a lateral radiograph with both posterior condyles projected in the same plane, represented the mean femoral MPFL isometric center. Figure A is the lateral radiograph of a knee in which “A” represents the location of the origin of the MPFL. Incorrect Answers: Answers 2-5: Figure A represents the anteroproximal quadrant, defined as Schottle’s Point, and is representative of the MPFL origin. Due to the cam shape of the distal femur with long AP axis placement of the femoral insertion proximal to point A will result in a graft that is tight in flexion ("high and tight"). Placement of a graft in a point distal to A will result in a graft that is loose in flexion (low and loose).
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