Paediatric reference anatomy for ACL reconstruction and secondary anterolateral ligament or lateral extra-articular tenodesis procedures

Objectives: For iliotibial band (ITB) lateral extra-articular tenodesis or anterolateral ligamentous/capsular reconstruction with anterior cruciate ligament reconstruction, a clear understanding of the referenced anterolateral knee anatomy is critical—especially given the risk of injury to the physis or key anterolateral structures in the paediatric population, which is at high-risk for primary and secondary anterior cruciate ligament injury. The purpose of this study was to quantitatively assess the anatomy of the knee physes, paediatric lateral collateral ligament (LCL) origin, popliteus origin and ITB tibial insertion. Methods: Nine paediatric cadaveric knee specimens with average age 4.2 years (range 2 months–10 years) underwent dissection to identify the LCL's and popliteus’ femoral origins and the ITB's tibial insertion. Metallic marking pins demarcated precise anatomic attachment sites, and subsequent computerised tomography scans enabled quantified measurements among them. Results: LCL & Popliteus: On the femur, the popliteus origin lay consistently deep to the LCL and inserted both distally and anteriorly to the LCL, a mean distance of 4.6 mm (range 1.9–7.6; standard deviation 2.0). From the joint line, the LCL lay a mean distance of 12.5 mm proximally while the popliteus measured a mean of 8.2 mm. Both were consistently distal to the physis. The LCL was a mean distance of 4.4 mm (range 1.0–9.5) and the popliteus was a mean distance of 8.2 (range 1.7–12.5) from the physis. ITB insertion: The ITB insertion at Gerdy's tubercle had an average footprint measuring 28.2 mm² (range 10.3–58.4) and the ITB centre lay proximal to the physis in 6 specimens (mean age 4.2 years, median 2.5 years) and distal in 3 specimens (mean age 1.5 years, median 4 months). Mean distance from the footprint centre to the physis was 1.6 mm proximal (range 7.1 proximal – 2.2 distal). Conclusion: This study describes relative and quantitative positions of the femoral LCL and popliteus origins and tibial ITB attachment and their respective physeal relationships. Knowledge of paediatric anterolateral knee anatomy will help guide essential future research and procedures providing extra-articular anterolateral rotatory stabilisation and may help reduce iatrogenic physeal injury risk. Level of evidence: N/A (descriptive anatomic study).