PREVENTION, TREATMENT, AND RISK FACTORS IDENTIFICATION IN DISTAL ADDING-ON PHENOMENON IN POSTOPERATIVE LENKE TYPE 1A IDIOPATHIC SCOLIOSIS OPERATED AT GHURKI TRUST TEACHING HOSPITAL, LAHORE

Abstract

Background: Distal adding-on is a frequent postoperative complication following selective thoracic fusion for Lenke type 1A adolescent idiopathic scoliosis (AIS). It can compromise correction, lead to imbalance, and necessitate revision surgery.

Objective: To determine the incidence, risk factors, prevention, and treatment strategies of distal adding-on among Lenke 1A AIS patients at Ghurki Trust Teaching Hospital, Lahore.

Methods: This prospective observational study included 20 patients (16 females, 4 males; mean age 14.3 ± 2.1 years) with Lenke 1A AIS who underwent selective thoracic fusion between November 2024 and April 2025. Demographic, surgical, and radiographic parameters were recorded. Distal adding-on was defined as an increase of ≥5 mm in LIV+1 deviation from the CSVL or ≥5° in LIV+1 disc angulation at 12 months. Univariate and multivariate analyses were performed to identify independent predictors.

Results:  At follow-up, distal adding-on occurred in 6/20 patients (30%). Significant risk factors included younger age, lower Risser grade, greater preoperative LIV+1 deviation, and larger LIV–stable vertebra difference. Preoperative LIV+1 deviation >10 mm was the independent predictor (OR 3.9; 95% CI 1.2–12.8; p = 0.02). Two patients required revision of the extension of fusion.

Conclusion: The incidence of distal adding-on (30%) in our series is comparable with international reports (19–33%). Preoperative LIV+1 deviation and skeletal immaturity were key predictors. Prevention requires optimal LIV selection (SV, LTV, Qin criterion), maintaining fusion mass balance, and minimizing LIV rotation. Attention to proximal alignment may further reduce risk.