management

Last reviewed 11/2021

Conservative therapy

  • majority of primary traumatic patellar dislocations are treated non operatively (except in cases with a loose fracture fragment in the joint)
  • the patella should be pushed back into position (if not reduced spontaneously)
    • should not be carried out in cases with suspected factures or fractures confirmed by radiograph
    • analgesics and procedural sedation may be necessary for patients with significant muscle spasm and pain before attempting manual reduction
    • post reduction radiograph done to identify associated fractures (1)
  • any significant haemarthrosis should be aspirated and the joint thoroughly irrigated (1).
  • the knee should be immobilised in a firm supporting bandage or a plaster cast for 3 weeks with the leg extended.
    • the time for immobilisation may vary from 0-6 weeks
    • preliminary results of a prospective randomized study has shown no difference at 2 years between  immediate mobilization and flexion restriction with a patellar brace
  • once this is removed, physiotherapy should be started immediately to strengthen the quadriceps muscles which are essential for patellar stability.

Surgery

  • may be advocated if the medial structures are torn or if there is an osteochondral fracture. Small osteochondral fragments should be removed but large ones, should be fixed back into position

  • arthroscopic examination is indicated if the extent of injury is in doubt.

  • surgery for chronic patellar dislocation
    • many surgical procedures have been described for the treatment of patellofemoral instability. Surgery should not be considered until non-operative treatment has failed and the recurrent nature of the disease has resulted in functional impairment
    • surgery may address either bone or soft-tissue components. Options include proximal, intra-articular or distal procedures
      • proximal to the joint
        • bony procedure - alignment or rotational osteotomy to the femur
        • soft tissue procedure - medial patellofemoral ligament reconstruction; medial imbrication; extra-articular lateral release
      • intra-articular
        • bony procedure - trochleoplasty
          • trochlear dysplasia is treated with a trochleoplasty, provided there is no degenerative change within the joint. The creation of a deepened groove also alters the tibial tubercle to trochlear groove distance as the depth of the trochlea is lateralised and may reduce the need for medialisation of the tibial tubercle. Occasionally, trochleoplasty alone will not provide sufficient stability and additional surgical procedures will be required
          • arthroscopic trochleoplasty
            • arthroscopic trochleoplasty is done with the patient under general or regional anaesthesia
            • using an arthroscopic approach, the articular cartilage of the trochlea is raised as a flap. A round burr shaver is then used to deepen the trochlear groove. The articular cartilage is then returned to the deepened groove and fixed in place
            • procedure is often done in combination with medial patellofemoral ligament reconstruction (3)
        • soft tissue procedure - arthroscopic lateral release
      • distal to the joint
        • bony procedure - tibial tubercle osteotomy (includes elevation, medialisation and distalisation)
        • soft tissue procedure - patellar ligament realignment

Note:

  • redislocation rates of patients treated with surgery has been shown to be o-17% while 50-100% had good-to-excellent results. The numbers in nonsurgical protocols were 13-52% for redislocation and 47-85% for good-to-excellent results (1) 
  • regardless of the treatment method, patients returning  to preinjury levels of physical activity after primary patellar dislocation may differ between 44% to 60%  (1)
  • patellar instability occurs when the patella fails to engage securely in the trochlea at the start of flexion; it slips laterally and either dislocates completely or slips back medially to its correct position as flexion continues. In some patients this happens because the trochlear groove is too shallow or uneven (trochlear dysplasia) (3)

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