Abstract
Surgical management of patellar instability is a matter of wide debate. While some
authors believe that isolated medial patellofemoral ligament (MPFL) reconstruction
is sufficient, others advocate procedures to treat the underlying pathology, namely,
patella alta and trochlear dysplasia. Radiological studies have been traditionally
used as a determinant of these pathologies and to determine the need for an additional
procedure. The value of examination under anesthesia (EUA) in formulating a treatment
plan remains unknown. Our aim is to assess the prognostic value of EUA in assessing
patients presenting for surgical treatment of recurrent patellar dislocations. We
retrospectively reviewed the outcome after surgical treatment of 23 patients who had
undergone isolated MPFL reconstruction for recurrent patella dislocation by a single
surgeon in our tertiary center. All data were completed at the time of index surgery.
Primary outcome was recurrent instability requiring revision surgery. The mean age
of the 23 patients undergoing MPFL reconstruction was 17.4 years of age. The median
trochlea tuberosity–trochlear groove (TT-TG) distance was 15 mm with a median Caton–Deschamps
ratio of 1.3. Of the 23 patients who underwent MPFL reconstruction, 9 failed (39%).
Median time to failure was 10.5 months. All patients who failed MPFL reconstruction
had a dislocating patella on EUA at >30 degrees of flexion. Radiological assessment
of the knee to assess its morphology is essential for preoperative surgical planning
for patients with recurrent patellar instability. Cutoff values to determine the need
for surgical procedures require a consistent method of imaging and are prone to flaws
in measurement. However, we demonstrated that EUA provides valuable additional information
toward an appropriate surgical approach.
Based on our small cohort, we suggest that patients in whom patella remains dislocated
past 30 degrees of knee flexion on EUA are unlikely to benefit from isolated MPFL
reconstruction.
Keywords
MPFL - patellofemoral instability - trochleoplasty
