f Principles of Management of Long-Term Complications in EOS
Meric Enercan, and Azmi Hamzaoglu
Early-onset scoliosis (EOS) in very young children is an extremely difficult problem that requires thorough knowledge of normal spine development as well as the aetiology, natural history, clinical evaluation, and available treatment options. Unlike adolescent spinal deformity, untreated progressive deformity can cause significant health problems for young children and later in their adult life [1, 2].
EOS is often associated with other comorbid conditions, and this increases the complexity in managing the spinal deformity. The management of EOS requires consideration of interrelated growth of spine and thorax and their impact on the lung development. The spine grows most rapidly in the first 5 years, with an average Tl-Sl segment length increase of 10 cm during this time (>2 cm/year) followed by a deceleration to 0.5 cm/year between 6 to 10 years of age and increases again during adolescent growth spurt (2 cm/year). The number of alveoli and lung volume also increase most rapidly in the first several years, and the total alveoli number completes development by 8 years of age [3, 4]. The progressive early-onset spinal deformity occurs during this critical time of lung development and may result in pulmonary dysfunction and cardiopulmonary compromise. Early recognition and proper treatment is essential for the management of EOS deformity [5,6].
The main goals of the treatment of EOS are to obtain and maintain curve correction while simultaneously preserving the spinal, trunk, and lung growth. Treatment options include conservative treatment and surgical interventions. Surgical treatment should be considered for patients with progressive deformity when cast or brace treatment have failed or is contraindicated [1, 2, 7].
Surgical treatment options include early definitive surgery or temporary surgery. Early definitive fusion before the age of 10 endangers thoracic growth and pulmonary functions and may not prevent the progression of deformity, development of crankshaft phenomenon, and/or thoracic insufficiency syndrome [5, 6, 8].
Many nonfusion options have been proposed, and various types of spinal implants have been used to control deformity while allowing spinal and thoracic growth in immature spines. Although growth potential is preserved in growth-friendly surgeries, complications are a common and inevitable part of the surgical treatment [9, 10, 11]. Complications increase the financial burden of the healthcare system and this can be even more challenging in resource-limited settings. Dealing with the challenges of EOS treatment requires a longterm commitment by the surgeon, the family, and the healthcare system.
Skaggs et al.  had classified these systems into three categories based on the forces of correction: distraction-based systems, compressionbased systems, and guided-growth systems.
Distraction-based implants are the most common devices used in EOS. Moe et al.  first described the distraction-based growing rod system in 1984. Four types of implants have been used: the traditional growing rod (TGR), vertical expandable prosthetic titanium rib (VEPTR) device, hybrid systems, and magnetically controlled growing rod (MCGR). With the development of dual rods, strong upper and lower anchors, and expandable connectors, TGR became a powerful tool and gold standard in the treatment of EOS. Several studies have shown growing rods to be effective for achieving spinal length increase on the immature spine [14, 15]. Regardless of the implant used for distraction-based treatment of the growing spine, all strategies have their own disadvantages and are associated with high complication rate .
The main disadvantage of distraction-based implants is the lack of apical and intermediate anchors along the main curve. These systems try to correct the spinal deformity by applying distractive forces across the apical segments of the deformity between proximal and distal anchors. As anterior spinal growth continues in the immature spine, rotational deformity at the apical and intermediate segments will continue to progress. Because there are no apical and intermediate anchors along the main curve, correction and control of the main deformity will be limited during treatment . Xu et al.  evaluated the effects of TGR on apical vertebra rotation (AVR) using computerised tomography (CT) scans. They reported significant AVR can be achieved after inital surgery; however, TGR could not prevent progression of AVR during long-term follow-up .
Another limitation of the distraction-based systems is the need for multiple surgeries for repeated lengthening procedures. The rods are periodically lengthened as the child grows to maintain spine curve correction every 6 to 8 months [14, 15]. The length gained from serial lengthening has also been shown to follow a law of diminishing returns, with decreased spinal length gained after each lengthening . The prolonged immobilisation between lengthening intervals creates a static fixation and may result in autofusion after repeated lengthenings . The utility of lengthening may decrease significantly after the sixth or seventh lengthening procedure, limiting the potential spinal growth to 4-5 years after initial surgery. Multiple surgeries for repeated lengthening procedures require repeated exposure to general anaesthesia. In addition to the physical effects on the spine, repetitive surgeries leads to increased anxiety and significant psychological effects on the patient. Patients with repeated surgery demonstrate abnormal psychosocial scores with a positive correlation between behavioural problems and the number of repetitive surgeries .
TGRs are associated with a high complication rate. Implant failure, rod breakage, junctional kyphosis, spontaneous fusion, wound problems, and infection are the most common complications of TGRs . The overall complication rate of TGRs can occur in 58%-86% with a 20% procedural complication rate. Forty percent of these complications required treatment with an unplanned procedure . Another study demonstrated that each lengthening surgery increases the risk of deep infection 3.3 times in EOS . Upasani et al.  tried to identify the preoperative factors that contribute to complications in 110 EOS patients treated with TGR. They reported that 79% of the patients had complications resulting in 84 unplanned surgeries. The most common complications were implant-related (49%), surgical site infection (23%), medical (19%), alignment (6%), and neurologic (3%). Earlier age at implantation, greater thoracic kyphosis (>40°), and larger major curves (>85°) increased the probability of complications following TGR .
Management of the long term complications is challenging. Optimal treatment strategy should minimise the complications that lead to unplanned surgical interventions and minimise the psychological effects on the patient and decrease the total cost of treatment and financial burden on the healthcare system.