Michelle C. Marks

Evaluation of Proximal Junctional Kyphosis in Adolescent Idiopathic Scoliosis Following Pedicle Screw, Hook, or Hybrid Instrumentation

Study Design. Retrospective review. Objective. To compare the incidence of and risk factors for proximal junctional kyphosis (PJK) in adolescent idiopathic scoliosis (AIS) following posterior spinal fusion using hook, pedicle screw, or hybrid constructs. Summary of Background Data. Proximal junctional kyphosis is a recently recognized phenomenon in adults and adolescents after AIS surgery. The postoperative effect on PJK with the use of hooks, hybrid constructs, or screws has not been compared in a multicenter study to date. Methods. From a multicenter database, the preoperative and 2-year follow-up radiographic measurements from 283 patients with AIS treated with posterior spinal fusion using hooks (group 1, n = 51), hybrid constructs (group 2, n = 177), pedicle screws (group 3, n = 37), and pedicle screws with hooks only at the top level (group 4, n = 18) were compared. Results. The average proximal level kyphosis at 2 years after surgery was 8.2° (range −1 to 18) in the all screw constructs, representing a significant increase when compared with hybrid and all hook constructs, 5.7° (P = 0.02) and 5.0° (P = 0.014), respectively. Conversely, average postoperative T5–T12 kyphosis was significantly less (P = 0.016) in the screw group compared with the all hook group. Of potential interest, but currently not statistically significant, was the trend towards a decrease in proximal kyphosis in constructs with all pedicle screws except hooks at the most cephalad segment, 6.4°. The incidence of PJK (assuming PJK is a kyphotic deformity greater than 15°) was 0% in group 1, 2.3% in group 2, 8.1% in group 3, and 5.6% in group 4 (P = 0.18). Patients with PJK had an increased body mass index compared with those who did not meet criteria for PJK (P = 0.013). Conclusion. Adjacent level proximal kyphosis was significantly increased with pedicle screws, but the clinical significance of this is unclear. A potential solution is the substitution of hooks at the upper-instrumented vertebrae, but further investigation is required.

Evaluation of a functional position for lateral radiograph acquisition in adolescent idiopathic scoliosis.

Study Design. A retrospective examination of lateral spine radiographs of 50 patients with adolescent idiopathic scoliosis (AIS) was performed to evaluate the sagittal profile of patients in two different standing positions. Objectives. To evaluate segmental and global changes in the sagittal profile of the spine associated with two standing radiographic positions and determine if one position represents a more functional stance for accurate sagittal balance evaluation. Summary of Background Data. Studies of spinal sagittal balance during relaxed standing have indicated that the sagittal vertical axis (SVA), as determine by the horizontal displacement of a C7 plumb line from the posterior superior corner of the sacrum, is neutral or slightly positive. However, standing with the arms forward flexed to allow radiographic visualization of the spine results in a negative shift in SVA. Methods. Measurements were obtained from standing lateral radiographs in patients with AIS in two different standing positions: arms forward flexed to 45° with elbows fully extended versus elbows fully flexed with fists resting on clavicles. Sagittal plane parameters were analyzed using correlation analyses and repeated-measures analyses of variance with significance set at 0.005. Results. The study cohort included 25 patients who had undergone solely nonoperative treatment (without progression) and 25 patients who had undergone operative intervention for their scoliosis. In all patients, SVA was more negative (C7 shifted more posterior with respect to the sacrum) when the arms were in the forward flexed position compared to the fists on clavicles position (−4.2 ± 2.5 cm vs. −1.3 ± 2.4 cm, P < 0.001). In operative patients, the shoulder forward flexed position was associated with relative posterior rotation of the pelvis represented by an average increase of 2.7 ± 3.8° in pelvic tilt (P = 0.002) and an average decrease of 3.2 ± 4.5° in sacral slope (P = 0.002). There was no correlation between the degree of arm forward flexion and changes in sagittal measures between the two positions. Conclusions. The fists on clavicles position for lateral radiograph acquisition has less negative shift in SVA, and in patients with spinal instrumentation, less compensatory posterior rotation of the pelvis. This position is more representative of a patient’s functional balance while still allowing adequate lateral radiographic visualization of the spine.

Use of Video-Assisted Thoracoscopic Surgery to Reduce Perioperative Morbidity in Scoliosis Surgery

Study Design. A case series of idiopathic scoliosis patients treated with thoracoscopic anterior instrumentation was compared to a similar group of patients treated by open anterior instrumentation. Objectives. To evaluate the morbidity associated with thoracoscopic instrumentation compared to the open approach for thoracic scoliosis. Methods. A consecutive group of thoracoscopically treated patients with Lenke 1 adolescent idiopathic scoliosis was compared to similar patients gathered from the DePuy-AcroMed Harms Study Group database. Perioperative outcome measures as well as early postoperative functional outcomes (pulmonary function, shoulder strength) were compared. Results. There were 38 thoracoscopic instrumentation cases with greater than 6 months’ follow-up that were compared to 68 anterior open instrumentation cases. The radiographic outcomes were similar (60% ± 11%vs. 59% ± 17% thoracic curve correction for the thoracoscopic and open groups, respectively). The reduction in forced vital capacity was significantly (P = 0.01) greater in the open group (0.6 ± 0.3 L) compared to the endoscopic group (0.4 ± 0.3 L). There was a trend towards greater return of shoulder girdle strength and range of motion 6 weeks after surgery in the thoracoscopic patients. Conclusion. The thoracoscopic approach for instrumentation of scoliosis has advantages of reduced chest wall morbidity compared with the open thoracotomy method but allows comparable curve correction.

Correlation of Scoliosis Curve Correction With the Number and Type of Fixation Anchors

Study Design. Clinical and radiologic assessment derived from a prospective multicenter data base of adolescent idiopathic scoliosis (AIS) patients. Objective. We investigated if “implant density” or the number of screws correlated with the major curve (thoracic or lumbar) correction at 2 years in patients with AIS. We also investigated the effect of implant density on the change in sagittal contour before surgery to after surgery. Summary of Background Data. Controversy exists regarding number and type of spinal anchors and the number of implant sites used that result in improved correction in AIS. Methods. A prospective database of patients with AIS treated by posterior instrumentation between 1995 and 2004 was analyzed. The major curve correction expressed as % correction (from preoperative to 2 years postoperative) was correlated with the percentage of implants relative to the number of available implant sites within the measured Cobb angle. Correlation of % correction to the number of hooks, wires, and screws was also performed. We also analyzed the change in sagittal contour T2–T12, T5–T12, and T10–L2 before surgery and after surgery. This absolute change was then correlated with implant density, as was the number of hooks, wires, and screws. Results. There were 292 patients included with all 6 Lenke curve types represented (250 with major thoracic curves and 42 with major lumbar curves). The overall % coronal Cobb correction was 64% (range: 11%–98%). The implant density within the major curve averaged 61% (range: 6%–100%). There was a significant correlation between implant density and % curve correction (r = 0.31, P < 0.001). The number of each implant type (hooks, wires, and screws) in the construct did not correlate with the % correction; however, the average % correction of the major curve was greater when the Cobb levels were instrumented only with screws (64%) compared to hooks alone (55%), P < 0.01. The greatest % correction 78% was achieved when bilateral segmental screws were used (100% screw density). The higher the implant density within the major thoracic curve, the greater the postoperative loss of kyphosis at T2–T12 (r = −0.13, P < 0.01) and T5–T12 (r = −0.16, P < 0.001). At T10–L2, increasing screw implant density correlated with decreasingkyphosis (r = −0.40, P < 0.001), whereas increasing hook implant density correlated with increasing kyphosis (r = 0.33, P < 0.001). Conclusion. Major curve correction at 2 years correlates most with the implant density that is correction increases with the number of implants used within the measured Cobb levels. Although the absolute number of screws used did not correlate with correction, there was an advantage in lumbar and thoracic curves to using screws compared to hooks. Sagittal contour in the thoracic spine became less kyphotic than the higher the implant density.

Perioperative complications after surgical correction in neuromuscular scoliosis.

Purpose To evaluate the perioperative complications associated with surgical correction in neuromuscular scoliosis and to identify the risk factors associated with these complications. Methods A retrospective review of the hospital charts of patients with neuromuscular scoliosis who underwent surgical correction at a medical center was performed. Results Data was available on a total of 175 patients. The overall perioperative complication rate was 33.1% (96 complications in 58 patients). Complications were subdivided into pulmonary issues (19.4%), wound and implant infections (9.7%), cardiovascular complications (4.0%), intraoperative neurological changes (4.6%), miscellaneous complications (5.7%), and problematic instrumentation (3.4%). No patient had an identifiable permanent postoperative change in neurological status. The complication rate in patients who underwent single-stage procedures (37.4%) was found lower than that in patients who underwent staged procedures (57.1%). There were no deaths during the perioperative period. Conclusions Patients with neuromuscular scoliosis are at high risk of developing perioperative complications after surgical correction of their deformity (overall rate, 33.1%).

Factors involved in the decision to perform a selective versus nonselective fusion of Lenke 1B and 1C (King-Moe II) curves in adolescent idiopathic scoliosis.

Study Design. A retrospective evaluation of 203 adolescent idiopathic scoliosis patients with Lenke 1B or 1C (King-Moe II) type curves. Objectives. To evaluate the incidence of inclusion of the lumbar curve in the treatment of this type of deformity as well as radiographic factors associated with lumbar curve fusion. Summary of Background Data. In patients with structural thoracic curves and compensatory lumbar curves, many authors have recommended fusing only the thoracic curve (selective thoracic fusion). Studies have shown that correction of the thoracic curve results in spontaneous correction of the unfused lumbar curve; however, in some cases, truncal decompensation develops. Though there have been various attempts to define more accurately what type of curve pattern should undergo selective fusion, controversy continues in this area. Methods. Measurements were obtained from the preoperative standing posteroanterior and side-bending radiographs of 203 patients with Lenke Type 1B or 1C curves from five sites of the DePuy AcroMed Harms Study Group. Patients were divided into two groups depending on their most distal vertebra instrumented: the “selective thoracic fusion” group included patients who were fused to L1 or above and the “nonselective fusion” group included patients fused to L2 or below. A statistical comparison was conducted to identify variables associated with the choice for a nonselective fusion. Results. The incidence of fusion of the lumbar curve ranged from 6% to 33% at the different patient care sites. Factors associated with nonselective fusion included larger preoperative lumbar curve magnitude (42 ± 10°vs. 37 ± 7°, P < 0.01), greater displacement of the lumbar apical vertebra from the central sacral vertical line, (3.1 ± 1.4 cm vs. 2.2 ± 0.8 cm, P < 0.01), and a smaller thoracic to lumbar curve magnitude ratio (1.31 ± 0.29 vs. 1.44 ± 0.30, P = 0.01). Conclusions. The characteristics of the compensatory “nonstructural” lumbar curve played a significant role in the surgical decision-making process and varied substantially among members of the study group. Side-bending correction of the lumbar curve to <25° (defining these as Lenke 1, nonstructural lumbar curves) was not sufficientcriteria to perform a selective fusion in some of these cases. The substantial variation in the frequency of fusing the lumbar curve (6% to 33%) confirms that controversy remains about when surgeons feel the lumbar curve can be spared in Lenke 1B and 1C curves. Site-specific analysis revealed that the radiographic features significantly associated with a selective fusion varied according to the site at which the patient was treated. The rate of selective fusion was 92% for the 1B type curves compared to 68% for the 1C curves.

Prospective evaluation of 50 consecutive scoliosis patients surgically treated with thoracoscopic anterior instrumentation.

Study Design. Prospective, consecutive, single-surgeon case series of patients treated for scoliosis with thoracoscopic anterior spinal instrumentation. Background. A thoracoscopic approach for insertion of anterior instrumentation has been developed in the past 10 years, which obviates many of the disadvantages of the open anterior thoracic approach. The morbidity associated with a thoracoscopy is limited because of the minimal skin and chest wall dissection required with this method. Purpose. The purpose of this evaluation is to report a single surgeon’s experience with an initial series of 50 patients. The goal is to report the outcomes with regards to the radiographic findings, pulmonary function, and the SRS Outcomes Instrument, as well as a review of the perioperative data and complications. Methods. The primary author’s initial 50 thoracoscopic anterior spinal instrumentation patients were consecutively collected. Data collection included demographics, such as age, gender, and diagnosis. Data regarding the surgical procedure included the operative time, intraoperative estimated blood loss, as well as the number of levels instrumented anteriorly. In the perioperative hospital period, data were collected with regard to the length of the hospital stay, the number of days in the ICU, the number of days of ventilator support, and the number of days after surgery when conversion from IV to PO pain medication occurred. Radiographic data were obtained systematically on each patient and measured by authors other than the surgeon. The SRS 22 and/or 24 Outcomes Questionnaire and pulmonary function tests were administered to patients at similar intervals. Results. The series consisted of 44 females and 6 males with a mean age of 14 years (range, 9–48 years). Forty-five of the 50 patients were available for clinical and radiographic evaluation at greater than or equal to 2 years after surgery. The average length of follow-up for these 45 patients was 33 months (range, 2–5 years). The mean operative time for the procedure was 350 ± 50 minutes and ranged from 265 to 528 minutes. The estimated intraoperative blood loss averaged 431 ± 273 mL (range, 75–1,400 mL). Normalizing the operative time and estimated blood loss based on the number of levels treated resulted in an average operative time per level of 48 ± 6 minutes per level and an estimated intraoperative blood loss per level of 60 ± 37 mL per level. The preoperative thoracic Cobb averaged 53° ± 9° (range, 40°–80°). At most recent follow-up (≥2 years), the thoracic Cobb averaged 24° ± 7°. Implant failure occurred in 3 cases. Conclusion. Thoracoscopic anterior instrumentation for adolescent idiopathic scoliosis is a viable surgical option. The outcomes of this consecutive series of patients is comparable to prior open and endoscopic series presented in the literature. The technical challenges of this operation are evident in the learning curve effect, which has been demonstrated.

Complications of spinal fusion for scheuermann kyphosis: a report of the scoliosis research society morbidity and mortality committee.

Study Design. Retrospective review of a prospectively collected, multicentered database from the Scoliosis Research Society. Objectives. To evaluate incidences of complications in a series of spinal fusions for Scheuermann kyphosis (SK) and to assess whether the incidence of complications is associated with patient age and surgical approach. Summary of Background Data. Although there is some evidence that adolescents have lower complication rates for spinal deformity surgery, this has not been well-documented for SK. Moreover, there is a lack of consensus on surgical approach for the management of SK. Methods. The Scoliosis Research Society morbidity and mortality database was queried to identify cases of SK from 2001 to 2004. Complications rates were analyzed based on patient age and surgical approach. Pediatric and adult patients were defined as ≤19 and >19 year old, respectively. Results. A total of 683 procedures involving spinal fusion for SK were identified. Mean patient age was 21 years (range: 5–75 years), with the majority (73%) of patients ≤19 years old. Procedures included 338 (49%) posterior spinal fusions (PSF), 73 (11%) anterior spinal fusions (ASF), and 272 (40%) same-day ASF and PSF. Ninety-nine complications were reported (14%). The most common complication was wound infection (3.8%). The acute neurologic complication rate was 1.9%, including 4 spinal cord injuries (0.6%). The mortality rate was 0.6%. Complications were more common among adult (22%) compared with pediatric patients (12%) (P = 0.002). The overall incidence of complications did not differ significantly between the PSF (14.8%) and same-day ASF/PSF (16.9%) procedures (P = 0.5). Conclusion. The incidence of complications associated with spinal fusion for SK in adults is significantly greater than in pediatric patients. There were no significant differences in complication rates between PSF and same-day ASF/PSF procedures. These data may be used to counsel patients regarding complications associated with spinal fusion for SK in the hands of experienced spinal deformity surgeons.

Analysis of sagittal alignment in thoracic and thoracolumbar curves in adolescent idiopathic scoliosis: how do these two curve types differ?

Study Design. Retrospective chart review and radiographic analysis. Objective. To determine if differences exist in the sagittal alignment of adolescent idiopathic scoliosis (AIS) patients with thoracic versus thoracolumbar curve patterns. Summary of Background Data. Relative anterior overgrowth has been suggested as the possible pathomechanism behind thoracic scoliosis. Given the proposed importance of the sagittal alignment on the development of AIS and the known association between pelvic parameters and sagittal alignment, the authors postulate that pelvic incidence may influence the location of vertebral column collapse associated with different AIS curve types. Methods. A multicenter surgical database was used to compare preoperative radiographic measurements between patients with primary thoracic curves (Lenke 1A, B), primary thoracolumbar curves (Lenke 5), and normal adolescents. Results. Pelvic incidence was significantly greater in both groups of AIS patients compared with normal adolescents. Patients in the primary thoracic curve group were found to have a significantly increased sacral slope and a decreased thoracic kyphosis relative to the control group. Patients in the primary thoracolumbar curve group had a significantly increased pelvic tilt; however, a relatively normal thoracic kyphosis, lumbar lordosis, and sacral slope compared with the respective control values. Conclusion. An increased pelvic incidence, associated with both thoracic and thoracolumbar curves when compared with the normal adolescent population, does not appear to be the potential determinant of the development of thoracic versus thoracolumbar scoliosis, but may be a risk factor for the development of adolescent idiopathic scoliosis. The theory of anterior overgrowth may be supported by the identification of thoracic hypokyphosis, despite an increased pelvic incidence and lumbar lordosis, in patients with thoracic scoliosis. The association between sagittal measurements and the etiology of thoracolumbar curve formation is less clear; however, regional anterior overgrowth in the lumbar spine may also be responsible for the deformity.

Prospective Pulmonary Function Comparison of Open Versus Endoscopic Anterior Fusion Combined With Posterior Fusion in Adolescent Idiopathic Scoliosis

Study Design. Prospective clinical study. Objective. To evaluate pulmonary function tests at a minimum 2-year follow-up in patients with adolescent idiopathic scoliosis (AIS) undergoing either an endoscopic versus open anterior fusion along with posterior segmental fixation and fusion. Methods. A total of 21 patients with AIS underwent a video-assisted thoracoscopic (VAT group) release/fusion followed by a posterior spinal fusion (PSF) and segmental spinal fixation were compared to 16 patients who underwent an open thoracotomy (Open group) followed by a PSF. The mean preoperative thoracic Cobb was 70° in the VAT group versus 75° in the Open group. All patients had preoperative and a minimum 2-year postoperative pulmonary function tests consisting of forced vital capacity (FVC) forced expiratory volume in one second (FEV-1). Results. The average thoracic Cobb correction was to 27° (61%) in the VAT group versus 36° (52%) in the Open group. Preoperative and 2-year postoperative FVC in the VAT group averaged 2.48 L and 2.85 L, respectively (P = 0.006). The Open group corresponding results were 1.97 L and 2.43 L, respectively (P = 0.001). Preoperative and minimum 2-year postoperative FEV-1 in the VAT group averaged 2.06 L and 2.37 L, respectively (P = 0.005). Values for the Open group were 1.65 L and 2.08 L, respectively (P = 0.001). Although both groups had pulmonary function test parameters that were statistically improved postoperative versus preoperative, there were no significant differences comparing the VAT group to the Open group (P > 0.05) Conclusions. VAT versus Open release/anterior fusion in association with a PSF for select AIS curves requiring circumferential treatment both demonstrated similar radiographic and pulmonary function test improvement at 2 years postoperative, with no significant differences seen between the groups.