Material and Methods
We retrospectively analyzed 2664 patients who underwent fusion surgery for scoliosis from 2002 to 2018 at a single institution. There were 61 patients who underwent preoperative HT for severe scoliosis. We excluded two patients with rigid scoliosis who underwent surgical procedure before HT: one had a triple curve with L2 hemivertebrae and therefore underwent HT after L2 hemivertebrectomy with release before finally undergoing T11–L4 posterior fusion, and the other patient had early-onset rigid scoliosis, and growing rods were initially applied. Moreover, patients whose kyphosis was more severe than their scoliosis were excluded for study homogeneity. Given the long duration of the study, the criteria for HT application were inconsistent and varied according to the surgeons' discretion. During the early study period, HT was implemented if the curve was very rigid, although the Cobb angle was relatively small.
Clinical data, such as patient age, height, weight, body mass index (BMI), type of scoliosis, apex of curvature, traction period, traction type, and traction/body weight ratio (TBWR), were investigated and recorded. The types of scoliosis were classified as idiopathic, neuromuscular, congenital, and syndromic scoliosis. The apex of the curvature was defined as thoracic, thoracolumbar, or lumbar spine, according to the Scoliosis Research Society definition. The types of traction were gravity, pelvic, or femoral. The TBWR was calculated by dividing the final traction weight by the patient weight.
All patients underwent radiographic evaluation, including standing whole-spine anteroposterior and supine side-bending views (bending radiographs). After applying HT, a supine anteroposterior radiograph was conducted twice per week to confirm the degree of curvature correction. The Cobb angle of the coronal plane was measured on these radiographs. The correction rate in the bending radiographs was calculated as the difference between the Cobb angle on the bending radiographs and that on the initial standing anteroposterior radiographs ([Initial Cobb angle–Cobb angle at bending radiograph]/Initial Cobb angle × 100 [%]). The correction rate per week was calculated according to the difference between the Cobb angle of each week after applying traction and that at the initial standing anteroposterior radiographs ([Initial Cobb angle–Cobb angle after traction for each week]/Initial Cobb angle × 100 [%]). The correction rate after traction was calculated according to the difference between the Cobb angle after final traction and the Cobb angle on the initial standing anteroposterior radiographs ([Initial Cobb angle − Cobb angle after traction]/Initial Cobb angle × 100 [%]). The postoperative correction percentage was calculated as the difference between the Cobb angle after the final deformity correction surgery and the Cobb angle on the initial standing anteroposterior radiographs ([Initial Cobb angle − Cobb angle after surgery]/Initial Cobb angle × 100 [%]).
To identify the clinical and radiological factors associated with HT, we divided the patients into two groups based on the relationship between two parameters: the post-bending correction angle (PBC), which denotes the flexibility of the original spinal curvature, and the post-traction correction angle (PTC), which describes the degree of correction beyond the original flexibility of the curvature. If the PTC was not significantly different from the PBC (PBC ≒ PTC), the deformity had not been corrected after traction, and the patient was assigned to group A. However, if the PTC was larger than the PBC (PBC < PTC), the deformity had been corrected to some degree after traction, and the patient was assigned to group B. The significant difference between the parameters was set at >8°, which is the maximum measurement error when measuring the Cobb angle. The radiographic parameters were measured by two orthopedic surgeons twice each, and intraobserver and interobserver errors were measured using the kappa value. Statistical analysis was performed using t test, χ 2 test, Pearson correlation, and Fisher exact test.
All patients underwent halo pin insertion surgery under local anesthesia and sedation. The type of traction (gravity, pelvic, or femur) was determined by the surgeon after considering factors such as magnitude of the Cobb angle and patient age (Figure 1A–C). On the first day of HT, weights were not applied to avoid nausea and vomiting. The first traction weight was 1 to 2 kg, applied at the head. If weight was applied at the pelvis and femur, the total weight was 2 to 4 kg. The weight was increased by 2 kg in the morning/afternoon, depending on the patient's adaptability (2–4 kg/day). The total traction weight was set to not exceed 50% of the body weight. In some patients in whom correction was not satisfactory and who could withstand heavy traction, however, the traction weight was increased incrementally. When patients felt pain in the neck or back, no further increase in weight was made. However, if the symptoms improved, the weight was continuously increased. A supine spine anteroposterior radiograph was taken twice a week. Neurological examination, including cranial nerve examination, was performed three times a day, and pin site sterilization was performed daily. Finally, operations were performed with the application of half the weight of the final HT weights.
The types of halo traction: (A) halo pelvic traction, (B) halo femoral traction, and (C) halo gravity traction.
Spine. 2020;45(18):E1158-E1165. © 2020 Lippincott Williams & Wilkins