Patellar Instability after Total Knee Arthroplasty: A Surgical Case Report

Abstract

Introduction: Patella instability and maltracking is a serious complication following total knee replacement that can lead to poor outcomes for the patient and contribute to early failure. The incidence of patella maltracking ranges from 1% to 20% after total knee arthroplasty (TKA), with post-operative anterior knee pain being an important indicator. There are many different surgical approaches for the management of post-operative patella maltracking with very good outcomes. However, the most crucial step is to identify the underlying etiology.

Case report: A 71-year-old Caucasian woman presented to our orthopedic department due to chronic right knee pain, which had worsened over the past year. She was diagnosed with osteoarthritis and was scheduled for a TKA. Three years postoperatively, she returned for examination due to anterior knee pain. Patellar instability was observed and intensive extensor mechanism strengthening and physiotherapy were recommended. Three months later, she presented with severe pain and inability to move her knee. Imaging revealed a fracture and dislocation of the patella. She was surgically treated with lateral release and proximal realignment of the extensor mechanism, according to Insall procedure, with great post-operative outcome.

Conclusion: The etiology of post-operative patella instability and dislocation in most cases is due to component malposition or extensor mechanism imbalance. The surgeon should be careful and should take measures preoperatively and intraoperatively to prevent this scenario.

Keywords: Total knee arthroplasty; insall procedure; lateral release; patella instability.

Figure 1

Both knees anteroposterior radiograph, valgus knee alignment. This radiograph was taken when the patient first arrived at the orthopedic department, for the pre-operative evaluation.

Figure 2

Post-operative radiographs. Posterior stabilized arthroplasty. Good positioning of the components.

Figure 3

Merchant view. Patellar instability and subluxation.

Figure 4

Computed tomography scan. Dislocation and fracture at the lateral facet of the patella.

Figure 5

Insall technique. Midline incision supra and infrapatellar. A medial parapatellar approach from the quadriceps tendon, leaving about 2 mm of the vastus medialis for suturing. Lateral release and advancement of the vastus medialis distally and laterally overlapping about half of the upper pole of the patella.

Figure 6

Patella alignment. Centering of the patella in the trochlea groove throughout the full range of knee motion.

Figure 7

Post-operative radiograph. Good positioning of the patella in the trochlear groove.