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Preoperative Sagittal Tibial Tubercle-Trochlear Groove Distance Predicts Postoperative Outcome in Patients Undergoing
Sebastian Schmidt1,2, Luis Navas3, Felix Zimmermann3
1Department of Orthopaedic and Trauma Surgery, University Medical Centre Mannheim, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany.
Purpose:
To evaluate the association between the preoperative sagittal tibial tubercle-trochlear groove (sTTTG) distance and postoperative patient-reported outcomes after combined patellofemoral ligament reconstruction and deepening trochleoplasty in patients with recurrent lateral patellar instability and high-grade trochlear dysplasia.
Methods:
This retrospective study included patients who underwent combined medial patellofemoral ligament reconstruction and deepening trochleoplasty for recurrent lateral patellar instability with high-grade trochlear dysplasia (Dejour grade B-D) between 2016 and 2018. Eligibility required ≥2 documented patellar dislocations or persistent symptoms after ≥6 months of nonoperative treatment, high-grade trochlear dysplasia on magnetic resonance imaging, and a minimum follow-up of 18 months. The sTTTG distance was measured on preoperative axial T2-weighted magnetic resonance imaging sequences as the perpendicular offset between the trochlear cartilage and the tibial tubercle, referenced to the posterior condylar axis. Postoperative outcomes were assessed using the Banff Patellofemoral Instability Instrument 2.0 (BPII 2.0) score, alongside numeric rating scales for pain levels and subjective knee function. Univariable and multivariable linear regression analyses were performed, adjusting for age, body mass index, Caton-Deschamps index, Dejour classification of trochlear dysplasia, and tibial tubercle-trochlear groove distance.
Results:
A total of 101 patients (29 men, 72 women; mean age 22.7 ± 6.6 years; body mass index 24.3 ± 4.9) were included with a mean follow-up of 32.3 ± 8.7 months (range 19-60). Univariable analysis showed that a higher preoperative sTTTG was significantly associated with improved postoperative subjective function (β = 0.088, P = .014), lower pain levels (β = -0.10, P = .048), and higher BPII 2.0 scores (β = 0.98, P = .019). These associations remained statistically significant after adjusting for confounding variables (function: β = 0.096, P = .011; pain: β = -0.11, P = .044; BPII 2.0: β = 0.91, P = .037). Based on a cohort-specific minimal clinically important difference analysis, 89% of patients achieved clinically meaningful improvement in BPII 2.0, 77% in pain, and 88% in function. The multivariable models exhibited moderate explanatory power, with adjusted R2 values ranging from 0.03 to 0.06.
Conclusions:
The preoperative sTTTG distance is significantly associated with postoperative patient-reported outcomes in individuals undergoing deepening trochleoplasty. Higher sTTTG values were associated with better functional recovery, reduced pain, and enhanced patellofemoral quality of life.
Level Of Evidence:
Level IV, retrospective cohort study.
