The inferomedial patellar protuberance and medial patellar ossicle in patellar instability

Thin Flap Trochleoplasty With Medial Patellofemoral Ligament Reconstruction for Recurrent Patellofemoral Instability With High-Grade Trochlear Dysplasia: A Series of 63 Consecutive Cases

BACKGROUND

Trochlear dysplasia is present in 68% to 85% of patients with recurrent lateral patellofemoral instability (LPI) compared with 3% to 6% of healthy controls. Trochlear dysplasia has been associated with medial patellofemoral ligament (MPFL) graft failure and lower quality-of-life (QOL) outcome scores. The correction of trochlear dysplasia with trochleoplasty is indicated in patients with recurrent LPI and high-grade trochlear dysplasia with a trochlear bump and a significant J-sign.

PURPOSE

To assess the clinical and patient-reported outcomes after patella-stabilizing surgery, including thin flap sulcus deepening trochleoplasty, and to explore the influence of pathoanatomic variables on postoperative QOL scores in patients who have undergone patellar stabilization, including trochleoplasty.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

A total of 63 consecutive knees in 46 patients with recurrent LPI and high-grade trochlear dysplasia who underwent MPFL reconstruction with thin flap trochleoplasty were followed for 2 years postoperatively. Clinical outcomes and Banff Patellofemoral Instability Instrument (BPII) 2.0 scores were collected prospectively. The t test was used to determine changes in QOL. Multiple linear regression was conducted to determine significant pathoanatomic variables that affected outcomes after MPFL reconstruction.

RESULTS

Overall, 63 knees with a mean follow-up of 32.9 ± 17.0 months (range, 12-84 months) were included. All patients had preoperative high-grade trochlear dysplasia (Dejour type B: 46%; Dejour type D: 54%), with a mean trochlear bump height of 6.1 ± 1.8 mm (range, 3.2-10.5 mm). The BPII 2.0 score increased significantly from preoperatively (29.3 ± 12.4) to postoperatively (71.8 ± 17.4) (P < .001), with a large effect size (Cohen d = -2.41). There was 1 redislocation (1.6%) and 3 reoperations (4.8%). Persistent apprehension and the J-sign were present in 8.5% and 13.6% of the knees, respectively. Multiple linear regression analysis demonstrated no statistically significant predictive relationship between the 24-month postoperative BPII 2.0 score and the preoperative BPII 2.0 score, tibiofemoral rotation, the Beighton score, or trochlear bump height (R = 0.47; R2 = 0.22; F = 5.23; P = .13).

CONCLUSION

Thin flap trochleoplasty combined with MPFL reconstruction in patients with recurrent LPI and high-grade trochlear dysplasia resulted in low redislocation and reoperation rates at a mean of 33 months. Disease-specific QOL scores were statistically significantly improved from preoperatively to postoperatively.

Qualitative visual assessment of the J-sign demonstrates high inter-rater reliability

OBJECTIVES

To assess the inter- and intra-rater reliability of the classification of the J-sign as "large" versus "small or none" as compared to another two-level system ("present" versus "absent") and a three-level system ("large," "small," or "none") and to identify anatomical and patient factors associated with the presence of a large J-sign.

METHODS

Forty patients (40 knees) with recurrent patellar instability were prospectively enrolled and recorded on video actively extending their knee while seating. Four raters classified patellar tracking on two separate occasions using three systems: 1) two groups: J-sign versus no J-sign; 2) three groups: large J-sign, small J-sign, or no J-sign; and 3) two groups: large J-sign versus small or no J-sign. The intra- and inter-rater reliability of each system was assessed using kappa statistics. Anatomical (trochlear dysplasia, tibial tubercle-trochlear groove (TT-TG) distance, patellar height) and patient (Beighton score) factors as well as Knee Injury and Osteoarthritis Outcome Score (KOOS) subscales were compared between patients with a large J-sign and patients with a small or no J-sign.

RESULTS

Inter- and intra-rater reliability were found to be highest with the two-level classification system of a large J-sign versus a small or no J-sign (inter-rater kappa ​= ​0.76, intra-rater kappa ​= ​0.75). Patients with a large J-sign had more severe trochlear dysplasia as assessed with the sulcus angle (p ​= ​0.042) and were more likely to have a tight lateral retinaculum (p ​= ​0.032) and an elevated Beighton score (p ​= ​0.009). No significant differences in KOOS subscales were noted based on the presence of a large J-sign versus a small J-sign or no J-sign.

CONCLUSION

Qualitative visual assessment of patellar tracking with the J-sign demonstrates substantial inter- and intra-rater reliability, particularly when utilizing a two-group classification system to identify knees with a large J-sign. Patients with a large J-sign demonstrate an increased incidence of a tight lateral retinaculum, generalized ligamentous laxity, and trochlear dysplasia.

LEVEL OF EVIDENCE

Level III - cross-sectional study.

What is the J-sign and why is it important?

PURPOSE OF REVIEW

Recurrent lateral patellofemoral instability is a complex condition that requires a thorough evaluation to optimize treatment. The J-sign test is classically part of the physical examination, but its significance and importance remain unclear. This review aims to describe how to perform the test and classify the observation as well as to analyze the most recent literature on its clinical applications.

RECENT FINDINGS

The J-sign test has been described as positive (present) or negative (absent), and classified using the quadrant method and the Donnell classification. Suboptimal inter-rater reliability has been shown for both classifications, making comparison between clinicians and studies challenging. The J-sign is most predominantly associated with patella alta, trochlear dysplasia, lateral force vector, and rotational abnormalities. A growing number of studies have shown a correlation between a positive J-sign and lower clinical outcome scores and higher rate of surgical failure.

SUMMARY

The J-sign is an important aspect of the physical examination in patients with recurrent lateral patellofemoral instability. Although there is no consensus on how to perform or classify the test, it can be used as a marker of severity of patellofemoral instability and is one of the tools available to guide the treatment plan.

Inter-rater Reliability of the Classification of the J-Sign Is Inadequate Among Experts

OBJECTIVE

The purpose of this study was to determine the inter-rater and intra-rater reliability of the symmetry, classification, and underlying pathoanatomy associated with the J-sign in patients with recurrent lateral patellofemoral instability.

STUDY DESIGN

Blinded, inter-rater reliability study.

SETTING

N/A.

PARTICIPANTS

Thirty patellofemoral joint experts.

INTERVENTIONS

Thirty clinicians independently assessed 30 video recordings of patients with recurrent lateral patellofemoral instability performing the J-sign test.

MAIN OUTCOME MEASURES

Raters documented J-sign symmetry and graded it according to the quadrant and Donell classifications. Raters indicated the most significant underlying pathoanatomy and presence of sagittal plane maltracking. Intra-rater reliability was assessed by 4 raters repeating the assessments. Mean pairwise simple and/or weighted Cohen's kappa were performed to measure inter-rater and intra-rater reliability, as well as calculation of percent agreement.

RESULTS

J-sign symmetry demonstrated fair inter-rater reliability (k = 0.26), whereas intra-rater reliability was moderate (k = 0.48). Inter-rater reliability for the quadrant and Donell classifications indicated moderate agreement, k = 0.51 and k = 0.49, respectively, whereas intra-rater reliability was k = 0.79 and k = 0.72, indicating substantial agreement. Inter-rater reliability of the foremost underlying pathoanatomy produced only slight agreement (k = 0.20); however, intra-rater reliability was substantial (k = 0.68). Sagittal plane maltracking demonstrated slight inter-rater agreement (k = 0.23) but substantial intra-rater agreement (k = 0.64).

CONCLUSIONS

The symmetry, classification, and underlying pathoanatomy of the J-sign demonstrated fair to moderate inter-rater reliability and moderate to substantial intra-rater reliability among expert reviewers using video recordings of patients with recurrent lateral patellofemoral instability. These findings suggest individual raters have a consistent standard for assessing the J-sign, but that these standards are not reliable between assessors.

LEVEL OF EVIDENCE

III.

Common Physical Examination Tests for Patellofemoral Instability Demonstrate Weak Inter-Rater Reliability

Purpose

The purpose of this study was to assess the inter-rater reliability of 3 common physical examination assessments, the Q-angle, J-sign, and apprehension test, used to evaluate patients presenting with recurrent lateral patellofemoral instability.

Methods

A consecutive sample of 38 subjects with recurrent lateral patellofemoral instability in 2013 were included in this reliability study. Two orthopaedic surgeons performed the physical examination maneuvers blinded to each other. The physical examination tests were performed bilaterally and included the Q angle, the J-sign, and the apprehension test. To measure the inter-rater reliability, an intraclass correlation coefficient (ICC 2,κ) was used for both legs independently for Q-angle measurements. A Cohen’s kappa was used to measure the inter-rater reliability for the J-sign and the apprehension test.

Results

The measurement of the Q-angle demonstrated poor reliability (ICC 2,κ 0.18-0.44). The assessment of the J-sign demonstrated fair to moderate reliability (κ = 0.31 – 0.41), and the evaluation of apprehension demonstrated fair to substantial reliability (κ = 0.30 – 0.65). All 3 clinical tests demonstrated substantial variability comparing the reliability on the right and left limbs. Assessment of the quality of apprehension demonstrated good agreement between the examiners.

Conclusions

In this study of patients with recurrent lateral patellofemoral instability the common physical examination tests, Q-angle, J-sign, and apprehension demonstrated weak inter-rater reliability. These results indicate that these tests are not reliable for communication between health care practitioners or as evaluations for clinical research.

Level of Evidence

Level IV, therapeutic case series.