Arthroscopically reduced, irreducible patella dislocation

Background

Acute patella dislocations account for approximately 2%–3% of knee injuries and are therefore a relatively common presentation in the accident and emergency department.1 Acute dislocations tend to occur relatively equally in men and women and usually present in the second and third decades. However, due to the nature of injury, active young women are at highest risk.1

In the short-term management of primary patellar dislocation, the current literature supports surgical over non‐surgical treatment due to recurrence of dislocation being as high as 60%.1 2 However, due to high risk of bias in the available literature, the quality of this evidence is low. Therefore, the modality of treatment is decided by the knee surgeon according to the associated injury and complexity of trauma.2 3 Nevertheless, the majority of patella dislocations can be reduced with simple manoeuvres or spontaneously and can be managed conservatively by bracing and rehabilitation.

In rare occasions, patella dislocations can be irreducible. Haemarthrosis and medial patellofemoral ligament rupture have long been recognised as the signs of primary traumatic dislocation of the patella.4 More recently, it has been reported that a characteristic sign of skin ‘puckering’ overlying the medial femoral condyle can be pathognomonic for irreducible posterior and posterolateral patella dislocation.5–7 Woon and Hutchinson debate that attempts of closed reduction and preoperative investigations such as MRI are unnecessary delays to open reduction.8

The aim of this report is to identify and review the main causes of the unique and unexpected event of irreducible patella dislocation and their characteristic presentations. This case study can shed light on the possible pathogenesis and pathognomonic features of this rare event and provide guidance on the available therapeutic approaches.

Case presentation

A middle-aged woman presented overnight to the accident and emergency, after misjudging the distance between herself and a metal bar, and thereby receiving a direct blow to her left knee. A backward fall followed and she was soon unable to bear weight or flex her knee.

On examination, the patient had no open wounds and she had a full range of motion to the left ankle and left hip. There were no associated neurovascular problems. Her medical and surgical history was unremarkable except for her body mass index which was 37.7. She had no history of patella dislocation or injuries to the left knee.

Investigations

An X-ray demonstrated a lateral patella dislocation (figure 1). Several attempts were made in the emergency department to reduce the patella under sedation but they proved to be unsuccessful. The following day, she was taken to theatre for a reduction under anaesthetic. Manipulation with digital pressure and following that percutaneous technique using a pointed reduction clamp to lever the patella were attempted. However, both manoeuvres were unsuccessful. Therefore, the decision to perform arthroscopy was made intraoperatively (figure 2).

Figure 1

X-rays.

Figure 2

Findings of arthroscopy and treatment: (A) osteochondral defect, (B) after debridement, (C) trochlear damage and (D) trochlear damage.

Treatment

Intra-articular haematoma was drained from the anterolateral portal. The patella was impacted against the lateral femoral condyle. After reducing the intra-articular pressure from the haematoma and using the arthroscopic probe for applying lateral leverage, the patella was easily reduced and the patellofemoral joint was checked again to ensure its stability.

A grade 3 deep chondral abrasion of the lateral facet and trochlea was recorded. Medial and lateral articulating surface and meniscus were intact. Anterior cruciate ligament and posterior cruciate ligament were intact. There was minor scuffing over the anterior fibres of the anterior cruciate ligament and an osteochondral fracture at the lateral femoral condyle edge. This was debrided with arthroscopic shaver. A chondroplasty of the chondral defect was performed with radiofrequency (figure 2).

The range of movement of the knee was also checked and proven to be stable. Collateral ligaments were intact. Levobupivacaine (30 mL of 0.5%) was infiltrated into the joint and portals for pain relief.

Outcome and follow-up

Final intraoperative X-rays of the knee were taken including skyline views, which confirmed a congruent patellofemoral joint.

Immobilisation of the knee in full knee extension with cricket pad splint for 2 weeks was recommended. The patient was advised full weight bearing and was reviewed in clinic at 2 weeks post-surgery. Then, a hinged knee brace was applied allowing gradual progressive flexion over the next 4 weeks and she was also referred to physiotherapists. The patient went back to normal activities following the rehabilitation programme without any further symptoms.