Summary

Large supratrochlear spurs demonstrate a substantially increased risk of developing patellofemoral cartilage damage in patients with trochlear dysplasia, accentuated on the trochlea.

Abstract

Purpose

The presence of a supratrochlear spur has shown to influence outcome in patients with trochlear dysplasia and is thought to accelerate cartilage wear, hence its presence is often utilized for the indication of trochleoplasty to increase stability and preserve patellofemoral cartilage. However, the current literature does not provide an evidence-based threshold for a relevant supratrochlear spur height. Thus, the purpose of this study was to establish a clinically significant supratrochlear spur height, which is associated with patellofemoral chondral damage to guide surgeons in surgical decision-making.

Methods

This study evaluated 363 knees with trochlear dysplasia, who were scheduled to undergo surgery for the treatment of patellar instability at a single institution. All patients presented with a true lateral radiograph and preoperative MRI. Two independent reviewers analyzed the supratrochlear spur height by measuring the distance between a tangent at the anterior femoral cortex and the most prominent point of the trochlea on sagittal MRI slices. All MRIs were assessed for full-thickness cartilage lesions. Pearson correlation, Mann Whitney U test, Fisher’s exact and chi-square test were used to distinguish associations between age, sex, body mass index (BMI), trochlear dysplasia type, supratrochlear spur height, and patellofemoral cartilage defects.

Results

Of the included 363 knees, 91 (25.1%) showed full-thickness cartilage defects on the patella, while 21 (5.8%) had trochlea cartilage damage. Though sex was not associated with patellofemoral cartilage damage, BMI correlated significantly with patellar defects (r=0.148, p=0.005), and age was correlated with both patellar (r=0.237, p<0.001) and trochlear defects (r=0.160, p=0.002). Trochlear dysplasia type B and D showed a trend toward a higher prevalence of patellar defects (p=0.082) and displayed significantly more often trochlear damage compared to type A and C (p=0.003). Knees with patellar and trochlear cartilage defects had a significantly larger supratrochlear spur than their controls (5.1 +/- 2.0 vs. 4.3 +/- 1.7, p=0.001; 5.3 +/- 2.1 vs. 4.4 +/- 1.8, p=0.015, respectively). The odds ratio for a supratrochlear spur height with ≥6 mm demonstrating patellar and/or trochlear cartilage damage was 2.7 (95% Confidence Interval (CI) = 1.6 – 4.5; p < 0.001) and 4.6 (95% CI = 1.8 – 11.7; p = 0.001), respectively.

Conclusion

The supratrochlear spur is significantly associated with patellofemoral cartilage damage. Large supratrochlear spurs demonstrate a substantially increased risk of developing patellofemoral cartilage damage, accentuated on the trochlea. Hence, surgeons should be aware of the potential cartilage protective effect of reducing large supratrochlear spurs.