Summary

Patients with excessive valgus alignment report worse outcomes on knee SANE, PROMIS physical function, and PROMIS Global 10 questionnaires 1-7 years after tibial tubercle anteromedialization when compared with less valgus knees.

Abstract

Introduction

Tibial tuberosity anteromedialization (AMZ), decreases tibial tubercle- trochlear groove (TT-TG) distance and has been shown to improve patellar tracking in patients with patellar instability. Although the procedure is utilized by many knee specialists in clinical practice, the specific indications, and contraindications, for AMZ require further investigation. The purpose of this study is to elucidate how the degree of valgus of a knee, one of the variables a surgeon considers when deciding to use AMZ, affects patient reported outcomes of the procedure.

Methods

Patients who underwent AMZ for patellar instability or chondral defects between 2014 and 2019 were identified by CPT code. These 29 patients (31 knees) were emailed a survey in March of 2021 through PatientIQ software with knee SANE, PROMIS physical function, and PROMIS pain interference questions. After receiving patient responses, the TT-TG distance measured by the senior author and pre surgical x rays were measured by the junior author for anatomic knee alignment via the Zampogna et al. TfA2 method.

Results

19 patient responses were received with data on 20 knees yielding a 64.5% response rate.

Knee SANE (P=0.03), PROMIS PF (P=0.04), and the Global 10 questions on carrying out usual activities and pain level (P=0.03 and P=0.05, respectively) were significantly better in the less valgus group.

The average SANE of a patient who underwent AMZ with a valgus knee less than 6.8 degrees was 90.7 +/- 6.7, significantly better than the average SANE for valgus knees over 6.8 degrees of 67.5 +/- 18 (P=0.0169). Additionally, the average physical function for a patient who underwent AMZ with a valgus knee greater than 6.8 as measured by Tfa2 was significantly worse than the less valgus group at 46.4 +/- 7.3 (P=0.0438). Sex, age, race, and ethnicity were not significantly different between the two groups.

Conclusion

Although anteromedialization of the tibial tubercle may lead to better outcomes for patients with lateral compartment defects or patellar instability than other osteotomy options, this research shows that anteromedialization appears to be more successful at fewer degrees of valgus. Therefore, further research should be performed to elucidate the best treatment option for patients with knees in more extreme valgus alignment, with this study suggesting better results for AMZ under 6.8 degrees valgus as measured by TFa2.

Reference

1. Zampogna B, Vasta S, Amendola A, et al. Assessing Lower Limb Alignment: Comparison of Standard Knee Xray vs Long Leg View. Iowa Orthop J. 2015;35.