Patellar Morphology in Recurrent Lateral Patellofemoral Instability: Associations With Risk Factors and Postoperative...

Patellar morphology, most commonly described by the Wiberg classification, is a potential risk factor for recurrent lateral patellofemoral instability. However, the Wiberg classification has not been widely used in this population, and therefore its clinical utility remains unclear.

(1) To determine the incidence of Wiberg types and to explore relationships between the Wiberg classification and risk factors in a population of patients with recurrent lateral patellofemoral instability. (2) To evaluate the relationship between the Wiberg classification and disease-specific quality of life outcomes after primary medial patellofemoral ligament (MPFL) reconstruction.

Cohort study; Level of evidence, 3.

A population of 447 patients who underwent MPFL reconstruction for recurrent instability was enrolled. Preoperative demographic and pathoanatomic data were collected prospectively. Intrarater reliability of the Wiberg classification was assessed using a weighted kappa (κw). Pearson and Spearman correlation coefficients, as well as ordinal logistic regression, were used to explore relationships between the Wiberg classification and risk factors for patellofemoral instability. A 1-way analysis of variance assessed preoperative and 24-month postoperative Banff Patellofemoral Instability Instrument (BPII) scores in relation to the Wiberg classification.

The study enrolled 447 patients, including 539 knees (21.5% male knees; 78.5% female knees), with a mean age at first dislocation of 14.9 years (SD, 6.1). The distribution of patellae by the Wiberg classification was 30.6% type 1 (n = 165), 47.1% type 2 (n = 254), and 22.3% type 3 (n = 120). κw intrarater agreement for the Wiberg classification was substantial (κw = 0.75). An ordinal logistic regression demonstrated a statistically significant -2 log likelihood model (P < .001) that included high-grade trochlear dysplasia, age at first dislocation, and WARPS/STAID (WARPS [weak, atraumatic, risky anatomy, pain, subluxation] / STAID [strong, traumatic, anatomy normal, instability, dislocation]) score as predictive of Wiberg type. No significant differences existed between Wiberg types for pre- (F = 4.167; P = .02) or postoperative BPII scores (F = 0.121; P = .89).

In this large cohort of patients with recurrent patellofemoral instability, a statistically significant ordinal logistic regression model, including the combination of trochlear dysplasia, WARPS/STAID score, and age at time of first dislocation, predicted Wiberg classification. No relationship was determined between the Wiberg classification and pre- or postoperative BPII 2.0 quality of life scores.