The Effect of a Supratrochlear Spur on Patellofemoral Cartilage in Patients With Trochlear Dysplasia

Background: The presence of a supratrochlear spur has been shown to influence outcomes in patients with trochlear dysplasia and is thought to accelerate cartilage wear. However, the current literature does not provide an evidence-based threshold for a relevant supratrochlear spur height. Purpose/Hypothesis: The purpose of this study was to establish a clinically significant supratrochlear spur height associated with patellofemoral chondral damage to guide surgeons in surgical decision-making. It was hypothesized that a supratrochlear spur negatively affects patellofemoral articular cartilage, with large spurs having the greatest effect. Study Design: Case series; Level of evidence, 4. Methods: This study evaluated 363 knees with trochlear dysplasia that were scheduled to undergo surgery for the treatment of patellar instability at a single institution. All patients underwent preoperative true lateral radiography and magnetic resonance imaging (MRI). There were 2 independent reviewers who 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 as well as other common patellofemoral parameters. All MRI scans were assessed for full-thickness cartilage lesions. Results: Of the included 363 knees, 91 (25.1%) showed full-thickness cartilage defects on the patella, while 21 (5.8%) had full-thickness trochlear cartilage damage. Patellar defects were significantly correlated with patient's age ( r = 0.237; P < .001), body mass index ( r = 0.148; P = .005), and supratrochlear spur height ( r = 0.196; P < .001). Trochlear defects were significantly associated with patient's age ( r = 0.160; P = .002), patellar tilt ( r = 0.202; P < .001), tibial tubercle–trochlear groove distance ( r = 0.128; P = .014), and supratrochlear spur height ( r = 0.151; P < .004). Trochlear dysplasia types B and D showed a trend toward a higher prevalence in patellar defects ( P = .082), while they were significantly associated with a higher prevalance of trochlear defects ( P = .003) compared with types A and C. Knees with patellar (5.1 ± 2.0 vs 4.3 ± 1.7 mm, respectively; P = .001) and trochlear (5.3 ± 2.1 vs 4.4 ± 1.8 mm, respectively; P = .015) cartilage defects had a significantly larger supratrochlear spur height than knees without patellar and trochlear defects. A supratrochlear spur height ≥6 mm had adjusted odds ratios of 2.7 (95% CI, 1.6-4.5; P < .001) and 3.4 (95% CI, 1.3-8.8; P = .014) for developing patellar and trochlear cartilage damage, respectively. Conclusion: A supratrochlear spur was significantly associated with patellofemoral cartilage damage. Large supratrochlear spurs demonstrated a substantially increased risk of developing patellofemoral cartilage damage.