summary Patellar Sleeve Fractures are rare injuries seen in children between 8 and 12 years of age characterized by separation of the cartilage "sleeve" from the ossified patella. Diagnosis is made with radiographs of the knee. Treatment is cylindrical casting for nondisplaced fractures with intact extensor mechanism. Operative management is indicated for displaced fractures associated with disrupted extensor mechanism. Epidemiology Incidence <1% of pediatric fractures accounts for >50% of patella fractures in children Demographics more common in males (5:1) occurs in children 8-12 years old when patellar ossification is nearly complete Etiology Pathophysiology mechanism of injury indirect injury caused by powerful contraction of the quadriceps muscle applied to a flexed knee pathoanatomy separation between the cartilage "sleeve" and main part of the patella and ossific nucleus Anatomy Osteology patella is largest sesamoid bone in body ossification begins at 3-5 years old superior 3/4 of posterior surface covered by articular cartilage articular cartilage thickest in body (up to 1cm) posterior articular surface comprised of medial and lateral facets lateral facet is larger facets separated by vertical ridge Soft tissue attachments quadriceps tendon and fascia lata attach to anterosuperior margin quadriceps tendon comprised of 3 layers superficial layer formed from rectus femoris tendon middle layer formed by vastus medialis and vastus lateralis tendons deep layer formed by vastus intermedius tendon patellar tendon attaches to inferior margin Blood Supply derived from anastomotic ring originating from geniculate arteries most important blood supply to the patella is located at the inferior pole Classification Anatomic superior pole least common inferior pole most common Presentation History indirect injury not associated with a direct blow to the knee Symptoms severe knee pain inability to bear weight Physical exam inspection soft tissue swelling diffuse tenderness hemarthrosis of the knee joint is often present high-riding patella or palpable gap at the distal end of the patella indicates disruption of the extensor mechanism motion difficulty with active extension of the knee, especially against resistance Imaging Radiographs recommended views AP lateral tangential findings small flecks of bone adjacent to superior or inferior pole diagnosis may be missed because the distal bony fragment is not readily discernible on radiographs slight anterior tilt of superior pole seen with proximal fractures patella alta seen with distal fractures patella baja seen with proximal fractures MRI or ultrasound indications may be useful for identifying a sleeve fracture when the diagnosis is not clear from the clinical and radiographic findings Treatment Nonoperative cylinder cast for 6 weeks indications nondisplaced fractures with intact extensor mechanism rare (most require ORIF) Operative open reduction and internal fixation indications > 2-3mm displacement > 2-3mm articular step-off disrupted extensor mechanism Technique Open reduction and internal fixation approach medial parapatellar approach to knee soft tissue repair torn medial/lateral retinaculum and/or quadricept/patellar tendon instrumentation stabilize fracture using transosseous sutures modified tension band wiring intraosseous suture anchors interfragmentary screws post-operative care cylinder cast in extension for 2-3 weeks Complications Patella alta Extensor lag Quadriceps atrophy Malunion Nonunion Painful hardware Prognosis Higher risk of complications associated with greater degree of comminution displacement