Summary

Surgical indications of tibial derotational osteotomy for idiopathic tibial torsion are not well known, therefore we've identified the most common indications (anterior knee pain and patellar instability) and diagnostic thresholds for abnormal torsion on commonly used physical exam measurements (thigh foot angle and transmalleolar axis) and imaging (computed tomography) to assess tibial torsion.

Abstract

Introduction

Tibial torsion (TT) is a common rotational abnormality in children that spontaneously corrects by age 4 in most cases, however, a small percentage of cases persist into adulthood. TT can affect quality of life as it’s associated with anterior knee pain, patellofemoral instability, and osteoarthritis. It is known that idiopathic TT can be corrected by tibial derotational osteotomy (TDO), but indications for this surgery remain unclear. We conducted a systematic review to identify recommendations for surgical indications of TDO in patients with idiopathic tibial torsion.

Methods

We searched across nine databases with no limitations on publication date. All studies were independently screened by two authors to identify potentially relevant items according to predefined inclusion and exclusion criteria. The primary inclusion criteria were therapeutic clinical studies reporting clinical indications for surgery and measurement methods in patients who underwent TDO for idiopathic tibial torsion. Quality of evidence was assessed using an adapted version of the modified Coleman methodology score (MCMS). Level of evidence (LOE) was also determined. Descriptive statistics were employed to analyze data.

Results

A total of 1630 titles/abstracts were initially screened: 53 were included for full-text screening and 20 were selected for final inclusion. The 20 studies included 593 tibias in 434 patients for analysis. Most subjects were female (65%). Weighted mean follow-up was 43.2 months (range 1 – 240 months). The median level of evidence was LOE IV. The quality of evidence was classified as good in 1 study, fair in 7 studies, and poor in 12 studies. The most common surgical indication for TDO was anterior knee pain in 85% of included studies, followed by patellar instability (55%), gait dysfunction (45%), and cosmetic deformity (15%). Fourteen studies cited more than one symptom as reasons for surgery. The greatest overlap occurred between anterior knee pain and patellar instability; both were reported concurrently in 25% of studies. No investigators recommended surgery solely for cosmetic deformity or gait problems. For those studies measuring TT by physical exam to determine indications for surgery, 9 studies (45%) used thigh foot angle (TFA) and 4 (20%) used transmalleolar angle (TMA). For TFA, the most frequently reported cut-off for external tibial torsion (ETT) was > 30° (25%). For TMA, study measurement methods varied with the knee flexed and extended with additional variation in thresholds for ETT (20°, 30°, 45°). Computerized tomography (CT) was used by 10 studies (50%) to assess tibial torsion. The most common measurement method consisted of TMA with respect to the proximal posterior tibia condylar axis (line tangential to the posterior tibia condyles) or the bicondylar tibia axis (line bisecting the tibia condyles). Definitions of “normal” tibial torsion varied widely due to inconsistencies in axes used.

Conclusion

Anterior knee pain and patellar instability were the most common surgical indicators of TDO for idiopathic TT. Inconsistent thresholds on physical exam and CT scans for determining abnormal TT indicate the need for standard measurement guidelines. Further research is needed on surgical indications for tibial derotational osteotomy, including the best ways to measure abnormal TT.