Tracey P. Bastrom

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.

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.

Preservation of thoracic kyphosis is critical to maintain lumbar lordosis in the surgical treatment of adolescent idiopathic scoliosis.

Study Design. Retrospective analysis of prospectively collected multicenter series. Objective. To evaluate the sagittal profile of surgically treated adolescent idiopathic scoliosis (AIS) patients. Summary of Background Data. With the increasing popularity of segmental pedicle screw spinal instrumentation, thoracic kyphosis (TK) is often sacrificed to achieve coronal and axial plane correction. Methods. Radiographs of AIS patients with a Lenke type 1 deformity and minimum 2-year follow-up after selective thoracic fusion (lowest instrumented vertebra of T11, T12, or L1) were evaluated. Changes in TK were correlated with changes in lumbar lordosis (LL). Patients were divided according to approach (open/thoracoscopic anterior vs. posterior). Analysis of variance was used to compare pre and postoperative radiographic measures. Results. Two hundred fifty-one patients (age: 14 ± 2 years) were included. Sixty seven percentages of the patients had anterior surgery (97 open anterior, 71 thoracoscopic) and 33% (83 patients) had posterior spinal fusion. A decrease in postoperative TK was significantly correlated (P ≤ 0.001) with a decrease in LL at first erect (r = 0.3), 1 year (r = 0.4) and 2 years (r = 0.4), independent of surgical approach. LL decreased significantly at the first erect regardless of approach (P = 0.003); however, at 2-year postoperative TK and LL were significantly decreased after a posterior approach (P ≤ 0.001) when compared with an anterior approach that added kyphosis. The decrease in LL (5.6° ± 9.7°) was nearly twice the decrease in TK (2.8° ± 11.4°) in the posterior group at 2-years. Conclusion. Given that thoracic AIS is often associated with a preexisting reduction in TK, ideal surgical correction should address this deformity. Procedures which further reduce TK also reduce LL. It is unclear if the loss of LL from thoracic scoliosis correction will compound the loss of LL that occurs with age and lead to further decline in sagittal balance. With this concern, we recommend a posterior column lengthening and/or an anterior column shortening to achieve restoration of normal TK and maximal LL.

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%).

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.

Predictors of Change in Postoperative Pulmonary Function in Adolescent Idiopathic Scoliosis: A Prospective Study of 254 Patients

Study Design. A multicenter study of prospectively collected pulmonary function testing and radiographic measures in patients surgically treated for adolescent idiopathic scoliosis (AIS). Objective. The objectives of this study were 1) to identify the factors that determine pulmonary function more than 2 years after surgery for AIS; and 2) to determine what factors, if any, can predict an increase or decrease in the percent predicted 2-year pulmonary function. Summary of Background Data. Thoracic spinal deformity can lead to significant pulmonary impairment. Studies have shown that patients with AIS experienced a significantly greater improvement in pulmonary function at 2 years after surgery when treated with a posterior approach compared to an anterior approach. Methods. Pulmonary function testing (PFT) and radiographic examination of 254 patients with AIS were completed prospectively. Demographic data, associations between radiographic measurements of spinal deformity, and the results of spirometry underwent correlation analysis and subsequent step-wise multiple regression analysis. Results. The variables found to be significant predictors of 2-year pulmonary function (FVC, FEV1, TLC) include: preop PFT (R2 = 0.20–0.39), having an open thoracotomy (as opposed to thoracoscopic or posterior) (R2 = 0.07–0.09), surgical time (R2 = 0.03–0.07), and thoracoplasty (R2 = 0.02–0.04). These models explain 40 to 51% of the variance in 2-year PFT. For patients undergoing open thoracotomy with a thoracoplasty, approximately 54% had a 15% decrease, or more, in percent predicted PFT. This compared with 11% and 15%, respectively of patients who either had posterior or thoracoscopic procedures with no thoracoplasty that had a 15% decrease or more in percent predicted PFT. Conclusion. Aside from preoperative PFT values, open anterior approaches predict the largest percent of variance in 2-year PFT. Additionally, a clinically significant reduction in the predicted 2-year pulmonary function is more likely when performing a thoracoplasty. The magnitude of the effects for both these variables, however, is modest. This may facilitate the decision-making process as regards to operative intervention.

Thoracoscopic scoliosis surgery affects pulmonary function less than thoracotomy at 2 years postsurgery.

Study Design. Prospective evaluation of pulmonary function before and 2 years after surgery following anterior scoliosis instrumentation. Objectives. To determine if thoracoscopic anterior scoliosis correction with instrumentation affected pulmonary function less than open thoracotomy approaches at 2 years follow-up. Summary of Background Data. The thoracoscopic approach has been shown to have a smaller reduction in pulmonary function tests (PFTs) compared with an open thoracotomy approach following anterior thoracic instrumentation for adolescent idiopathic scoliosis in the immediate postoperative period; however, it is unclear if a difference remains 2 years following the procedure. Methods. A total of 107 patients in a multicenter adolescent idiopathic scoliosis database underwent an anterior instrumented fusion for thoracic scoliosis. PFTs assessing forced vital capacity (FVC), forced expiratory volume (FEV1), and total lung capacity (TLC) were obtained prospectively before and 2 years after surgery. The patients were grouped as follows: Group I, thoracoscopic instrumented fusion (n = 36); Group II, open (thoracotomy) instrumented fusion without thoracoplasty (n = 28); and Group III, open instrumented fusion with thoracoplasty (n = 43). Results. Thoracoscopic instrumentation affected pulmonary function 2 years after surgery minimally, and on an average showed improvements in all parameters except the percent-predicted FVC, which decreased by 1% ± 11%, and percent predicted FEV, which decreased by 2% ± 9%. Improvements were noted in absolute FVC, FEV1, TLC, and percent-predicted TLC. This is in contrast to the patients treated with a thoracotomy, who had a greater persistent reduction in PFTs at follow-up. An added thoracoplasty to the thoracotomy approach, however, resulted in even greater residual reduction in PFTs at follow-up, with declines in percent-predicted FVC of 15%, percent-predicted FEV1 of 14%, and percent-predicted TLC of 8%. Conclusions. This study shows a clear advantage to the minimally invasive thoracoscopic approach with regards to pulmonary function when compared with the open thoracotomy approaches.

Variation in Tibial Tubercle–Trochlear Groove Measurement as a Function of Age, Sex, Size, and Patellar Instability

Background: The tibial tubercle–trochlear groove (TT-TG) measurement was developed to quantify morphologic abnormalities about the knee associated with patellar instability and to help guide surgical decision making. Purpose: To assess variations in TT-TG as a function of patient age and size in a population of patients with patellar instability compared with those with no instability. Study Design: Cross-sectional study; Level of evidence, 3. Methods: All patients younger than 20 years who underwent surgery for patellar instability from 2010 to 2012 were included in this retrospective study. A total of 180 patients with no history of patellar instability or patellofemoral complaints were used as a control group. The TT-TG was measured on magnetic resonance axial images using the centers of the tibial tubercle and the trochlear groove. Data were normalized based on patient height, weight, body mass index (BMI), and femur width. Alpha was set at P < .05 to declare significance. Results: The average age of the 45 patellar instability patients was 15.4 years (range, 10-18 years), their mean TT-TG was 16.3 mm (range, 6.5-26 mm), and 51% were male. By comparison, the mean age of the control group was 16 years (range, 10-19 years), the mean TT-TG was 11.7 mm (range, 3-22 mm), and 58% were male. The TT-TG and the normalized TT-TG for height, weight, BMI, and femur width were all greater in the patellar instability group compared with the control group (P ≤ .001). Thirty-one percent of patients had a TT-TG greater than 20 mm in the instability group compared with 3% in the control group (P < .05, specificity 97%, sensitivity 31%). The TT-TG was found to increase as a function of height in both groups (r = 0.14, P = .04) and decreased with age only in the instability group (r = −0.3, P = .04). Conclusion: An elevated TT-TG is associated with patellar instability both in pediatric and adolescent patients. However, this measurement varies as a function of patient age and height, with each centimeter in height increasing the TT-TG by 0.12. Normalization of TT-TG to patient height may control for size variations and should be undertaken in the work-up and management of patients with patellar instability.

Spontaneous lumbar curve correction in selective thoracic fusions of idiopathic scoliosis: a comparison of anterior and posterior approaches.

Study Design. A retrospective evaluation of adolescent idiopathic scoliosis (AIS) patients treated with selective thoracic instrumentation and fusion. Objective. To evaluate the predictors and the effect of surgical approach (anterior versus posterior) on spontaneous lumbar curve correction (SLCC) after selective thoracic fusion in patients with structural thoracic and compensatory lumbar curves. Summary of Background Data. Spontaneous coronal correction of the unfused lumbar curve has been described previously; however controversy continues regarding the effect of surgical approach on SLCC. Methods. One hundred thirty-two anterior and 44 posterior selective thoracic fusions instrumented distally to T11, T12, or L1 were identified from a multicenter AIS database. A 2-way ANOVA was used to compare SLCC with regards to surgical approach and the lowest instrumented vertebra (LIV). A Pearsons correlation analysis was utilized to identify radiographic variables associated with SLCC. A secondary analysis of surgical approach was then performed on 28 pairs of patients matching the factors that correlated positively with SLCC. Results. The average SLCC for the anterior approach (44% ± 19%) was less than that for the posterior approach (49% ± 19%; P = 0.07), and was found to increase significantly with a more distal LIV (P = 0.03). Pearsons correlation analysis revealed the strongest correlations between SLCC and preoperative lumbar curve flexibility (r = 0.20) and 2-year postoperative thoracic curve percent correction (r = 0.47). A secondary analysis of SLCC in paired curves matched by LIV, lumbar curve flexibility and thoracic percent correction revealed no difference between anterior (48%) and posterior (49%) approaches (P = 0.75). Conclusion. Anterior and posterior instrumented fusions performed selectively on the appropriate curves result in equal SLCC when matched by LIV, flexibility of the lumbar curve, and percent thoracic curve correction achieved. This suggests that the observed phenomenon of SLCC after selective thoracic fusion in AIS is independent of surgical approach and can be reliably achieved with either technique.

Outcomes of Extra-articular, Intra-epiphyseal Drilling for Osteochondritis Dissecans of the Knee

Background When conservative management fails to heal femoral condyle osteochondritis dissecans (OCD) lesions in a child, then drilling of the subchondral plate below the lesion to stimulate healing may be beneficial. This study reviews the outcomes of extra-articular, intraepiphyseal drilling of OCD lesions of the knee with intact articular cartilage. Methods Over an 8-year period, all children, who failed at least 6 months of nonoperative management, underwent arthroscopic knee surgery and extra-articular, intra-epiphyseal drilling for their symptomatic, nondisplaced femoral condyle OCD lesions. The clinical and radiographic outcomes were evaluated by using demographics, preoperative size of the lesion, intraoperative concomitant pathology, complications, postoperative range of motion, return to activities, radiographic progression of healing, and subsequent operative procedures. Results In all 59 children, the mean time to return to activities was 2.8 months (1.3 to 13.1 mo) and the mean percentage of radiographic healing was 98.2% (79% to 100%) at final follow-up. Forty-four (75%) of the OCD lesions were successfully treated to 100% radiographic healing with an average time for healing of 11.9 months (1.3 to 47.3 mo). The large lesions took significantly longer to heal than the small lesions, 15.3 months versus 8.8 months (P=0.032), and the percentage of radiographic healing at final follow-up approached significance with large (>3.2 cm2) lesions attaining a mean of 96.9% (standard deviation 6.4%) versus small lesions (<3.2 cm2) with a mean of 99.4% (standard deviation 2.1%, P=0.083). No operative complications were observed. Conclusions Extra-articular, intraepiphyseal drilling of OCD lesions produced excellent results over the historical controls using intra-articular drilling for those patients who failed initial conservative management. This technique allows for more drill holes to be placed perpendicular to the OCD lesions, especially the posterior lesions that may have limited intra-articular access. Furthermore, this technique avoids intraoperative damage to the overlying intact articular cartilage and promotes osseous healing by fenestration of the sclerotic rim surrounding the OCD lesion. Level of Incidence Prognostic study, Level IV (retrospective study).