Identifying Patients With Patella Alta and/or Severe Trochlear Dysplasia Through the Presence of Patellar Apprehension in Higher Degrees of Flexion

Abstract

Background: Recurrent patellar instability is frequently treated surgically with reconstruction of the medial patellofemoral ligament (MPFL). Patients with significant patella alta, trochlear dysplasia, and/or an elevated tibial tubercle–trochlear groove (TT-TG) distance may benefit from a concurrent bony procedure such as tibial tubercle osteotomy or trochleoplasty. The indications to perform such procedures are traditionally based on imaging criteria but remain controversial. Patellar apprehension is common in patients with patellar instability but typically resolves in higher degrees of knee flexion. Hypothesis: The persistence of patellar apprehension at greater than 60° of knee flexion is associated with patella alta, an increased TT-TG distance, and trochlear dysplasia. Study Design: Cross-sectional study; Level of evidence, 3. Methods: A total of 76 patients with recurrent patellar instability were prospectively identified in a sports medicine clinic. Patellar apprehension was evaluated in each patient. Apprehension was defined as the patient reporting that the patella felt unstable to lateral patellar translation. Apprehension was first assessed at full knee extension and repeatedly assessed as the knee was flexed in 10° intervals, as measured using a goniometer. The degree of flexion at which patellar apprehension disappeared was recorded. Plain radiographs and magnetic resonance imaging (MRI) scans were obtained for all patients. Patellar height was assessed with the Caton-Deschamps (CD) index, and trochlear morphology was assessed through measurements of the sulcus angle and depth on MRI and classified using the Dejour classification system. Imaging measurements of patients in whom apprehension resolved by 60° of knee flexion were compared with measurements for those with apprehension that persisted deeper into flexion. Results: Apprehension resolved by 60° of flexion in 56 patients and persisted into deeper flexion in 20 patients. The patients with a delayed resolution of apprehension demonstrated a higher CD index; elevated TT-TG distance; increased sulcus angle; decreased sulcus depth; and higher incidence of Dejour type B, C, or D dysplasia (all P < .05). Of the 20 patients with a delayed resolution of apprehension, 18 had either Dejour type B, C, or D dysplasia or a CD index of at least 1.30. A delayed resolution of apprehension was present in 11 of the 16 patients with Dejour type B, C, or D dysplasia. Conclusion: Overall, 90% of patients with significant patella alta and the majority of patients with high-grade trochlear dysplasia demonstrated patellar apprehension that persisted beyond 60° of knee flexion. Additionally, 90% of patients with persistent apprehension had significant patella alta and/or trochlear dysplasia. Further work is needed to evaluate the utility of these findings to inform surgical decision-making in this population.

When Should Bony Correction Be Considered in Addition to Medial Patellofemoral Ligament Reconstruction? Results of a Clinically Derived 2-Group Classification of Lateral Patellar Instability Based on 122 Patients at 2- to 5-Year Follow-up

“…Most notably, the results became positive at a mean knee flexion angle of 58 (20 -90 ). In addition, Colatruglio et al 8 reported that in 90% of patients with significant patella alta and in the majority of patients with high-grade trochlear dysplasia, patellar apprehension persisted beyond 60 of knee flexion; these findings are in line with the results obtained in this study and with biomechanical principles of the patellofemoral joint and might explain why isolated MPFL-R may not be sufficient in certain patients.…”

“…First, the dynamic evaluation of the patellar apprehension test represents the patient-specific end of stable patellar tracking and the beginning of patellar stabilizer insufficiency. 8,48 Second, the J-sign evaluates patellar tracking during active knee joint motion, thereby reflecting overall patellar tracking or maltracking of an individual's anatomy, and it affects clinical outcome scores and graft laxity after MPFL-R. 20,29,44,45 Accordingly, 2 major forms of recurrent LPI might be proposed 2 : a mild form characterized by a positive patellar apprehension test result ranging from 0 to 40 (50 ) of knee joint flexion and an absent or low-grade J-sign (grade 1) and a complex form characterized by a positive patellar apprehension test result >40 of knee joint flexion and/or severe patellar maltracking (grade 2 or 3 J-sign).…”

“…First, the dynamic evaluation of the patellar apprehension test represents the patient-specific end of stable patellar tracking and the beginning of patellar stabilizer insufficiency. 8 , 48 Second, the J-sign evaluates patellar tracking during active knee joint motion, thereby reflecting overall patellar tracking or maltracking of an individual’s anatomy, and it affects clinical outcome scores and graft laxity after MPFL-R. 20 , 29 , 44 , 45 …”

Accuracy of tibial tuberosity-trochlear groove distance and tibial tuberosity-posterior cruciate ligament distance in terms of the severity of trochlear dysplasia

“…In clinical practice, TT-TG measurements are often used to make surgical decisions about soft tissue stabilization and distal rearrangement [ 20 ]. This finding suggests that in patients with severe trochlear dysplasia, it seems the results obtained by TT-TG and TT-PCL are inconsistent, which will affect clinical judgment.…”

The Ali Krogius procedure for treatment of patellofemoral instability should be regarded as obsolete even in skeletally immature patients

“…The Caton-Deschamps index was used to evaluate patella alta (Caton-Deschamps Index > 1,2) [ 20 ]. High-grade trochlear dysplasia was defined as Dejour types B, C, and D [ 21 ].…”