Changes in Coronal and Sagittal Plane Alignment After Transphyseal ACL Reconstruction Performed Within Two Years of Skeletal Maturity: Results From the PLUTO Study Group

Background: For patients with open physes approaching skeletal maturity, transphyseal anterior cruciate ligament reconstruction (ACLR) with soft tissue autograft and metaphyseal fixation is often preferred. Although iatrogenic physeal injury is rare, growth disturbances have been reported. This study sought to evaluate postoperative changes in lower extremity alignment 1 year after transphyseal ACLR in skeletally immature patients within 2 years of skeletal maturity. Hypothesis: Transphyseal ACLR would not result in clinically significant changes in alignment. Study Design: Cohort study; Level of evidence, 2. Methods: This was a prospective multicenter study of skeletally immature patients with ≤2 years of remaining growth who underwent primary transphyseal soft tissue autograft ACLR. The change in the difference in alignment parameters between involved and uninvolved extremities from preoperative assessment to 1 year postoperative was calculated (difference of differences = Δ 2 ) to account for naturally occurring alignment changes during growth. Radiographic measurements included mechanical axis deviation (MAD), anatomic lateral distal femoral angle (aLDFA), mechanical medial proximal tibial angle (mMPTA), posterior tibial slope (PTS), and leg length discrepancy (LLD). Results: A total of 91 patients (48 males) merited inclusion with a median skeletal age of 14.0 years. Reconstructions were performed with hamstring (46%) or quadriceps (54%) autograft. The cohort-wide median Δ 2 values for MAD (2.9 mm), aLDFA (–1°), mMPTA (0°), and LLD (0.1 cm) were small. However, 28% of patients demonstrated a ≥10-mm Δ 2 in MAD (73% into valgus), and Δ 2 for aLDFA and mMPTA was ≥5° in 17% (73% into valgus) and 16% (43% into varus) of patients, respectively. One patient (1%) subsequently was recommended for intervention for growth disturbance at latest follow-up. Conclusion: This study of skeletally immature individuals with ≤22 years of growth remaining who underwent transphyseal ACLR with soft tissue autograft and metaphyseal fixation demonstrated minimal cohort-wide changes in alignment at 1 year postoperatively. However, a meaningful subset of patients (16%-28%) demonstrated clinically relevant changes in alignment, most commonly into valgus and decreased tibial slope. These findings warrant routine preoperative radiographic assessment and surveillance until skeletal maturity. Further study is needed to define thresholds for implant-mediated guided growth in patients with borderline valgus preoperatively who may be at risk of progressive deformity.