Preventing Fusion Mass Shift Avoids Postoperative Distal Curve Adding-on in Adolescent Idiopathic Scoliosis.

BACKGROUND: Surgery for adolescent idiopathic scoliosis (AIS) is only complete after achieving fusion to maintain the correction obtained intraoperatively. The instrumented or fused segments can be referred to as the "fusion mass". In patients with AIS, the ideal fusion mass strategy has been established based on fulcrum-bending radiographs for main thoracic curves. Ideally, the fusion mass should achieve parallel endplates of the upper and lower instrumented vertebra and correct any "shift" for truncal balance. Distal adding-on is an important element to consider in AIS surgery. This phenomenon represents a progressive increase in the number of vertebrae included distally in the primary curvature and it should be avoided as it is associated with unsatisfactory cosmesis and an increased risk of revision surgery. However, it remains unknown whether any fusion mass shift, or shift in the fusion mass or instrumented segments, affects global spinal balance and distal adding-on after curve correction surgery in patients with AIS. QUESTIONS/PURPOSES: (1) To investigate the relationship among postoperative fusion mass shift, global balance, and distal adding-on phenomenon in patients with AIS; and (2) to identify a cutoff value of fusion mass shift that will lead to distal adding-on. METHODS: This was a retrospective study of patients with AIS from a single institution. Between 2006 and 2011 we performed 69 selective thoracic fusions for patients with main thoracic AIS. All patients were evaluated preoperatively and at 2 years postoperatively. The Cobb angle between the cranial and caudal endplates of the fusion mass and the coronal shift between them, which was defined as "fusion mass shift", were measured. Patients with a fusion mass Cobb angle greater than 20° were excluded to specifically determine the effect of fusion mass shift on distal adding-on phenomenon. Fusion mass shift was empirically set as 20 mm for analysis. Therefore, of the 69 patients who underwent selective thoracic fusion, only 52 with a fusion mass Cobb angle of 20° or less were recruited for study. We defined patients with a fusion mass shift of 20 mm or less as the balanced group and those with a fusion mass shift greater than 20 mm as the unbalanced group. A receiver operating characteristic (ROC) curve was used to determine the cutoff point of fusion mass shift for adding-on. RESULTS: Of the 52 patients studied, fusion mass shift (> 20 mm) was noted in 11 (21%), and six of those patients had distal adding-on at final followup. Although global spinal balance did not differ significantly between patients with or without fusion mass shift, the occurrence of adding-on phenomenon was significantly higher in the unbalanced group (55% (six of 11 patients), odds ratio [OR], 8.6; 95% CI, 2-39; p < 0.002) than the balanced group (12% [five of 41 patients]). Based on the ROC curve analysis, a fusion mass shift more than 18 mm was observed as the cutoff point for distal adding-on phenomenon (area under the curve, 0.70; 95% CI, 0.5-0.9; likelihood ratio, 5.0; sensitivity, 0.64; specificity, 0.73; positive predictive value, 39% [seven of 18 patients]; negative predictive value, 88% [30 of 34 patients]; OR, 4.8; 95% CI, 1-20; p = 0.02). CONCLUSIONS: Our study illustrates the substantial utility of the fulcrum-bending radiograph in determining fusion levels that can avoid fusion mass shift; thereby, underlining its importance in designing personalized surgical strategies for patients with scoliosis. Preoperatively, determining fusion levels by fulcrum-bending radiographs to avoid residual fusion mass shift is imperative. Intraoperatively, any fusion mass shift should be corrected to avoid distal adding-on, reoperation, and elevated healthcare costs. LEVEL OF EVIDENCE: Level II, prognostic study.

Cervical spinal canal stenosis first presenting after spinal cord injury due to minor trauma: An insight into the value of preventive decompression.

PURPOSE: Patients with pre-existing cervical spinal canal stenosis (CSCS) may have minimal or no symptoms. However, performing preventive decompression is controversial as the incidence of CSCS leading to severe cord injury is unknown. Hence, this study aims to revisit the threshold for surgery in "silent" CSCS by reviewing the neurologic outcomes of patients with undiagnosed CSCS who sustained a cervical spinal cord injury (CSCI). METHODS: Two groups of subjects were recruited for analysis. Firstly, patients with trauma-induced CSCI without fracture or dislocation were included. Pre-existing CSCS was diagnosed by MRI measurements. The second group consisted of asymptomatic subjects recruited from the general population who also had MRIs performed. Canal sizes were compared between this control group and the patient group. Within the patient group, neurological assessments and outcomes by Frankel classification were performed in patients treated surgically or conservatively. RESULTS: 32 patients with CSCS were recruited. The mean spinal canal sagittal diameter (disc-level) of all CSCS cases was 5.3 ± 1.4 mm (1.3-8.2). In comparison, the diameter was 10.5 ± 1.7 mm (6.6-14.6) in the 47 asymptomatic individuals recruited from the general population. Decompression was performed in 17 patients and conservative treatment in 15. Mean follow-up was 19.3 ± 17.0 months (6-84). At the final follow-up, 3 patients (9.3%) returned to their pre-injury Frankel grade, whereas 26 patients (83.3%) lost one or more neurological grade. Three patients (9.3%) died. CONCLUSIONS: Majority of patients with "silent" CSCS who sustained cervical cord injuries did not return to their pre-injury neurological status. All of these subjects have pre-existing canal stenosis hence the risk of cord injury. Given the poor neurological outcome of CSCS, a lower threshold for surgery could be indicated to avoid these disastrous injuries. However, before making any conclusive recommendation we must first identify the prevalence of "silent" CSCS in the general population and the risk of developing spinal cord injury with more prospective population-based studies.

Fijación lumbopelviana con tornillos en pacientes adultos / Lumbopelvic fixation with screws in adult patients

Introducción: Lograr una artrodesis sólida a nivel de L5-S1 constituye siempre una dificultad mayor que en otros niveles de la columna lumbar o torácica. La fijación con tornillos a las alas ilíacas representa una alternativa dentro de los diversos métodos de fijación. Objetivo: Evaluar los resultados de la fijación pelviana con tornillos en pacientes adultos sin problemas de la marcha, considerando especialmente la fijación en 4 puntos por debajo de L5. Materiales y métodos: Veinticinco pacientes, con un seguimiento mínimo de 12 meses. Diagnósticos predominantes: escoliosis, seudoartrosis. Resultados: Veintinueve pacientes con distintas patologías fueron tratados por medio de fijación con tornillos pelvianos y los resultados se evaluaron mediante control clínico (escala analógica visual [EAV] y escala de Oswestry) y control radiográfico. Los resultados obtenidos fueron: EAV preoperatoria 7,8 por ciento y EAV posoperatoria 3,1 por ciento. El puntaje para dolor ilíaco posoperatorio en la EAV fue del 3,3 por ciento y el puntaje Oswestry preoperatorio, del 74,4 por ciento, mientras que el del período posoperatorio fue, en promedio, del 31,5 por ciento. En cuatro pacientes fue necesario retirar el implante, en todos los casos por radiolucidez de los tornillos ilíacos. Se produjo la rotura de ambos tornillos ilíacos en 2 casos y se logró la fusión en los 24 casos restantes. Conclusión: La fijación con tornillos pelvianos en fusiones largas, si bien no está exenta de complicaciones, es un método eficaz para lograr un alto índice de fusión lumbosacra en casos especialmente complejos por el largo de la fusión o por el fracaso de cirugías previas; es una técnica sencilla y con un moderado índice de dolor pelviano no solo en el número de pacientes, sino también en la intensidad del dolor, lo que quedó evidenciado por el bajo número de pacientes que fueron reintervenidos para el retiro de los tornillos.