The use of anterior approaches for spinal fusion for the treatment of adolescent idiopathic scoliosis (AIS) has been debated because of the concern that pulmonary function is compromised with procedures that violate the chest wall. Although both anterior and posterior spinal approaches have been indicated for the surgical correction of AIS and have comparable clinical and radiographic outcomes, each approach has advantages. 1 – 8 Anterior approaches may lead to shorter segment fusions, reduced operative blood loss, and reduced cost, and improved kyphosis restoration. 3 , 4 , 9 , 10 However, surgical approaches that signifi cantly disrupt the chest wall, including posterior-based thoracoplasty, have the potential to impair pulmonary function. 11 – 15 Potential explanations for the initial decline in pulmonary function include increases in chest cage stiffness, reduced diaphragmatic movement on the affected side, nonunion, and uneven air distribution. 16 These initial defi cits, however, do improve with time but the pattern of recovery and the long-term impact is not fully known. 3 , 9 , 10 ,15 – 19
In adolescents, pulmonary function may improve after surgical correction of the spinal deformity and indirect improvement of chest wall dimensions and mechanics. Pulmonary function is also impacted by growth. 16 , 17 The use of absolute versus percent predicted pulmonary function measurements have also been debated as percent predicted values are often calculated from the patient’s height, which typically increases after surgery. As a consequence, the predicted value would be underestimated in severe curvatures. Absolute measures of pulmonary function, however, do not account for vertical From the * Department of Orthopaedic Surgery, NYU Hospital for Joint Diseases, NY ; and † Stevens Institute of Technology, Hoboken, NJ . Acknowledgment date: October 7, 2009. Revision date: May 18, 2010. Acceptance date: May 24, 2010. The manuscript submitted does not contain information about medical device(s)/drug(s). No funds were received in support of this work. No benefi ts in any form have been or will be received from a commercial party related directly or indirectly to the subject of this manuscript. Address correspondence and reprint requests to Baron S. Lonner, MD, 820 2nd Ave, Sute 7A, New York, NY 10017; E-mail: BLonner@nyc.rr.com at 6 to 12 months until 2-years follow-up. The rate of recovery (K) was equivalent for all surgical approaches and curve types. Conclusion.
Compared to ASF or PSF, VATS procedures showed an initial decline in pulmonary function, which resolved fully by 6- to 12-months follow-up. Modest declines in maximal pulmonary function with VATS-I were seen when comparing all curve types together but not when comparing Lenke 1 curves alone. VATS procedures for thoracic scoliosis and open approaches for thoracolumbar curve types were associated with minimal to no permanent defi cits. Key words: posterior, anterior, VATS, adolescent idiopathic scoliosis, maximal pulmonary recovery . Spine 2011 ; 36 : 1086 – 1095 DOI: 10.1097/BRS.0b013e3182129d62 BRS204435.indd 1086 RS204435.indd 1086 22/05/11 3:09 PM 2/05/11 3:09 PM Spine www.spinejournal.com 1087 DEFORMITY Maximal Pulmonary Recovery • Verma et al Copyright © 2011 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. growth and may also underestimate defi cits at 2-years followup. 16 , 19 Since many retrospective studies also have multicenter or multisurgeon variability with respect to surgical technique and instrumentation, a single-surgeon study is advantageous for investigating subtle declines in pulmonary function.
Although posterior approaches have the advantage of being familiar and minimally disrupt the chest cage, anterior and video assisted thoracoscopic surgical release (VATS) procedures offer clinical benefi ts for patients with AIS. The purpose of our study was to characterize pulmonary function recovery in AIS for various surgical approaches to 2-years postoperatively. The model may also be used to predict maximal pulmonary function recovery. MATERIALS AND METHODS Patients After institutional review board approval, we studied one hundred eighty-four consecutive patients with AIS (mean age 15.6 ± 2.2; 113 women; 46 men) treated with spinal fusion by a single surgeon from 2003 to 2007. Data were retrospectively reviewed from a prospectively collected single-surgeon database. Pulmonary function was evaluated at baseline and at each offi ce visit up to 2-years follow-up.
Patients with prior spinal surgery or asthma were excluded from the study. Patients were classifi ed and treated based upon surgical classifi cation of AIS by the Lenke et al system. 20 Patients in each surgical subgroup was as follows: posterior spinal fusion (PSF) [Lenke 1: n = 50, Lenke 2,3: n = 20], anterior spinal fusion (ASF) [Lenke 5, n = 35], video-assisted thoracoscopic surgical release with instrumentation (VATS-I) [Lenke1: n = 31, Lenke 3: n = 1], and VATS + PSF (Lenke1: n = 9, Lenke 2–6: n = 13) ( Table 1 ). Radiographic Full-length posteroanterior and lateral radiographs of the spine were obtained on 36-long cassettes with the patient standing. All radiographic measurements were made by the senior author. 21 Surgical Technique All patients had their surgery performed by the senior author. The surgical approach was chosen on the basis of the curve magnitude, fl exibility, apex location, degree of deformity, and the preference indicated by the patient and their family. The patient and family were made aware that procedures performed thoracoscopically lacked long-term data. Informed consent was obtained from all patients.
PSF was performed in the standard fashion using pedicle screw instrumentation with a thoracoplasty performed only in rare cases where the appearance of the rib hump was a concern for the patient. Selection of fusion levels was based on established principles. 22 , 23 Patients with thoracolumbar (Lenke 5) curves underwent open anterior spinal instrumentation (single or dual rod, stainless steel, or titanium) and fusion via partial rib resection thoracotomy (9th or 10th rib, without thoracoplasty) with a thoracoabdominal approach. A structural graft or cage was used on the caudal one to two segments to increase distal construct stiffness. A VATS procedure with instrumentation was performed as previously described. 9 , 24 , 25 VATS release with PSF was performed through three posterior axillary line portals with the patient in the prone position.
As with any emerging instrumentation technology, there was an initial concern that the vertebral body screws placed with VATS would be less rigid and stable than posterior pedicle fi xation. For this reason, all patients treated with VATS procedures were braced postoperatively for 4 weeks after surgery, followed by another 8 to 12 weeks of use when the patient was out of bed and active. Bracing was not used on patients treated with an open anterior or posterior only approach. Pulmonary Function Test All patients in this study had pulmonary function tests (PFT) evaluating pulmonary volume and fl ow before surgery and at 1, 3, 6, 12, and 24-months follow-up. Each measurement for all patients was taken using a digital spirometer (Renaissance II, Puritan Bennett, Boulder, CO) with the patient in the standing position by an experienced physician assistant. The measurements were performed in triplicate with the highest reading saved in the patient record.
PFTs were recorded both as absolute and percent predictive values using height to approximate predictive pulmonary function. Pre and postoperative lung function was compared using forced vital capacity (FVC) and forced expiratory volume in one second (FEV 1 ). These two parameters have been well established as adequate TABLE 1. Patient Demographics and Preoperative Cobb Differences PSF ASF VATS-I VATS + PSF P Total N = 159; (113 Females, 46 Males) 70 (47 Females, 23 Males) 35 (28 Females, 7 Males) 32 (25 Females, 7 Males) 22 (13 Females, 9 Males) Average age (years) 15.6 ± 2.3 15.7 ± 1.7 15.1 ± 1.8 16.1 ± 3.2 Reop major Cobb (deg) 50.0 ± 7.5 45.5 ± 9.2 48.0 ± 6.1 69.0 ± 15.7 0.01* Percent Correction (%) 78.1 ± 9.1 87.5 ± 12.1 70.6 ± 9.3 65.5 ± 12.8 0.01* Lenke types 1,2,3 5 1 1, 2,3,4 Lumbar/sagittal modifi ers A,B,C N, +, − C N, + A,B,C N, − A,B,C N, +, − BRS204435.indd 1087 RS204435.indd 1087 22/05/11 3:09 PM 2/05/11 3:09 PM 1088 www.spinejournal.com June 2011 DEFORMITY Maximal Pulmonary Recovery • Verma et al Copyright © 2011 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. assessors of fl ow and volume status with respect to pulmonary function. Statistics The distribution of variables at baseline and at 1, 3, 6, 12 or 15, and 24-months follow-up was given as means and standard deviations (SD).
Absolute and percent predicted FEV 1 and FVC were plotted as function of time for each surgical approach. This analysis was performed once for Lenke 1 curve types (PSF, VATS-I, and VATS + PSF) and performed again for all curve types. The comparison of only Lenke 1 curve types was the most accurate as the potential impact of the spinal deformity on the chest wall is greatest with thoracic deformities. However, this study also aimed to report on the overall experience in AIS and impact of surgery on pulmonary function regardless of surgical approach or curve type. The absolute and percent predicted FEV 1 and FVC were plotted versus time. Nonlinear regression (Prism, GraphPad Inc, San Diego, CA) was utilized to fi t the most appropriate model using an F test to determine the simplest function that suffi ciently fi t the temporal data. It was determined that an exponential fi t was most appropriate. The resulting curve parameters included the immediate postoperative (at 1 month) pulmonary function (Yo), maximal recovery (Plateau) and rate of recovery (K) of pulmonary function ( Figure 1 ).
These parameters were compared using an unpaired t test to infer statistical differences between absolute and percent predicted FEV 1 and FVC. RESULTS Age, curve magnitude, curve correction, and curve type are provided in Table 1 . With regard to major Cobb angle, the VATS + PSF group had a signifi cantly larger preoperative Cobb angle than the other groups. Pulmonary Function: All Curves Baseline pulmonary function was lower in the VATS + PSF patients likely related to larger curve magnitudes in this group. Immediate postoperative %FEV 1 , %FVC, and FVC were signifi cantly lower in both VATS groups as compared to PSF ( P < 0.05). Immediate postoperative FVC was signifi cantly different in all groups with VATS + PSF having the lowest value, followed by VATS-I, ASF, and PSF. Percentage of FEV 1 , %FVC, and FVC were equivalent for ASF versus PSF ( Table 2 ). Maximal FEV 1 (plateau) was lower with a VATS-I procedure compared to PSF. Maximal recovery of FVC, %FEV 1 , and %FVC for VATS-I was equivalent to PSF but lower than VATS + PSF ( Figure 2 ). Of note, maximal FVC recovery was higher with VATS + PSF as compared to PSF ( P < 0.05). All measures of maximal pulmonary function were equivalent for ASF versus PSF. No differences were observed with respect to the relative rates of pulmonary function recovery (K) for all surgical approaches.
The statistical model matched pulmonary function recovery very well for each surgical approach ( R2 = 0.83–0.99). Pulmonary Function: Lenke 1 Curves For thoracic (Lenke1) curve types, %FEV 1, and %FVC were lower in the VATS + PSF group compared to PSF. However, absolute FEV 1 and FVC were similar for VATS + PSF and PSF. Immediate postoperative FEV 1 was signifi cantly lower for VATS-I, followed by VATS + PSF, and highest for PSF ( P < 0.05). Immediate postoperative FVC, %FEV 1 , and %FVC both VATS groups were signifi cantly decreased compared to the PSF group ( P < 0.05). Figure 1. Derivation of exponential decay model. Time is plotted on the X-axis from 1-month postoperatively to 2-years follow-up. Pulmonary function assessed by absolute and percent predicted FEV 1 or FVC is plotted on the Y-axis. Immediate postoperative pulmonary function (Yo) and maximal pulmonary function recovery (Plateau) at 2-years follow-up are estimated from the model.
The rate of recovery (K) relates to the speed at which FEV 1 or FVC approach maximal pulmonary function after surgery. BRS204435.indd 1088 RS204435.indd 1088 22/05/11 3:09 PM 2/05/11 3:09 PM Spine www.spinejournal.com 1089 DEFORMITY Maximal Pulmonary Recovery • Verma et al Copyright © 2011 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. TABLE 2. Model Coeffi cients* All Lenke Curve Types: Preop Baseline First Postop (Yo) Maximal (Plateau) R 2 P < 0.05 Abs FEV, PS (Lenke 1,2,3) 2.6 ± 0.7 2.36 ± 0.02 2.73 ± 0.00 0.989 Baseline: VATS + PSF < PSF ASF (Lenke 5) 2.7 ± 0.5 2.15 ± 0.08 2.58 ± 0.06 0.900 Yo: VATS + PSF < VATS-I < ASF < PSF VATS-I (Lenke 1,3) 2.5 ± 0.4 1.56 ± 0.02 2.51 ± 0.02 0.998 Plateau: VATS-I < PSF VATS + PSF (Lenke1–6) 2.0 ± 0.6 1.76 ± 0.03 2.91 ± 0.07 0.997 AbsFVC PSF (Lenke 1,2,3) 3.0 ± 0.8 2.67 ± 0.02 3.18 ± 0.02 0.993 Baseline: VATS + PSF < PSF ASF (Lenke 5) 3.2 ± 0.7 2.53 ± 0.08 3.20 ± 0.07 0.961 Yo: Both VATS groups < PSF VATS-I (Lenke 1,3) 3.0 ± 0.6 1.83 ± 0.09 2.99 ± 0.09 0.982 Plateau: PSF < VATS + PSF VATS + PSF (Lenke1–6) 2.5 ± 0.9 1.98 ± 0.03 3.50 ± 0.06 0.999 % FEV, PSF (Lenke 1,2,3) 80.3 ± 13.6 71.67 ± 0.90 78.76 ± 0.60 0.958 Baseline: VATS + PSF < PSF ASF (Lenke 5) 89.1 ± 11.7 68.68 ± 3.70 82.43 ± 2.62 0.830 Yo: Both VATS groups < PSF VATS-I (Lenke 1,3) 82.3 ± 11.2 52.62 ± 0.58 76.34 ± 0.60 0.998 Plateau: VATS-I < VATS + PSF VATS + PSF (Lenke1–6) 62.1 ± 22.0 57.10 ± 1.63 89.04 ± 4.28 0.987 % FVC PSF (Lenke 1,2,3) 81.4 ± 12.4 72.08 ± 0.93 82.66 ± 0.72 0.978 Baseline: VATS + PSF < PSF ASF (Lenke 5) 78.7 ± 16.5 70.38 ± 2.02 89.27 ± 1.53 0.968 Yo: Both VATS groups < PSF VATS-I (Lenke 1,3) 86.7 ± 12.4 53.80 ± 2.19 79.50 ± 2.04 0.977 Plateau: VATS-I < VATS + PSF VATS + PSF (Lenke1–6) 68.1 ± 21.7 57.08 ± 1.79 90.08 ± 3.65 0.987 Lenke 1 Curve Type: Preop Baseline First Postop (Yo) Maximal (Plateau) R 2 P < 0.05 Abs FEV, PSF 2.6 ± 0.7 2.39 ± 0.04 2.67 ± 0.03 0.945 Baseline: No Differences VATS-I 2.5 ± 0.4 1.56 ± 0.02 2.51 ± 0.03 0.998 Yo: VATS-I < VATS + PSF < PSF VATS + PSF 2.2 ± 0.6 1.90 ± 0.10 3.31 ± 0.50 0.965 Plateau: No Differences AbsFVC PSF 3.0 ± 0.8 2.69 ± 0.06 3.16 ± 0.06 0.943 Baseline: No Differences VATS-I 2.9 ± 0.6 1.83 ± 0.09 2.97 ± 0.09 0.980 Yo: Both VATS groups < PSF VATS + PSF 2.9 ± 0.8 2.03 ± 0.10 3.81 ± 0.45 0.979 Plateau: No Differences % FEV, PSF 80.4 ± 14.1 72.06 ± 1.24 77.50 ± 0.73 0.860 Baseline: VATS + PSF < PSF VATS-I 89.8 ± 2.2 52.63 ± 0.57 76.36 ± 0.59 0.998 Yo: Both VATS groups < PSF VATS + PSF 55.8 ± 25.5 56.22 ± 2.43 113.70 ± 24.57 0.982 Plateau: No Differences % FVC PSF 81.3 ± 12.3 71.83 ± 1.88 81.74 ± 1.41 0.906 Baseline: VATS + PSF < PSF VATS-I 90.0 ± 8.3 53.77 ± 2.28 79.19 ± 2.08 0.975 Yo: Both VATS groups < PSF VATS + PSF 64.1 ± 28.9 56.68 ± 3.13 92.24 ± 6.35 0.966 Plateau: No Differences * Comparison of baseline, immediate postoperative (Yo), and maximal pulmonary function recovery (Plateau) for various surgical approaches. All curve types are compared across four surgical groups, whereas main thoracic curves (Lenke 1) are compared across three groups.
Not included in the table was the rate of recovery (K), which was comparable for all surgical approaches and curve types. Bolded numbers indicate a statistically signifi cant difference between surgical groups (P < 0.05). BRS204435.indd 1089 RS204435.indd 1089 22/05/11 3:09 PM 2/05/11 3:09 PM 1090 www.spinejournal.com June 2011 DEFORMITY Maximal Pulmonary Recovery • Verma et al Copyright © 2011 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. Differences in early postoperative pulmonary function resolved by 6-months follow-up for FEV 1 , FVC, and %FVC and resolved by 12 months for %FEV 1 . As opposed to analysis (described earlier) for all curve types grouped together, the analysis of only thoracic curves showed no differences in maximal pulmonary function recovery with surgical approach ( Figure 3 ). The rate of recovery (K) was similar for PSF, VATS-I, and VATS + PSF. The statistical model matched pulmonary function recovery very well for each surgical approach ( R2 = 0.86–0.99). Pulmonary function improvement as a percentage of baseline pulmonary function was equivalent for all surgical approaches with the exception of %FEV1 in Lenke 1 curves in the VATS-I treated group (Table 3). Pulmonary Complications For the PSF group, there were a total of two pulmonary-related complications for a rate of 2.9% ( Table 4 ) .
There was one pleural effusion in which thoracoplasty was done. PFT values stabilized by the 3-month postoperative timepoint. The other was atelectasis and was treated with standard pulmonary toilet. In the ASF group, there was one pulmonary complication for a complication rate of 2.9%. The patient had a persistent pneumothorax treated by observation. There were a total of four complications in the VATS-I group for a complication rate of 12.5%. Complications included two mucus plugs requiring bronchoscopy, one unplanned conversion from a pure VATS to miniopen Figure 2. All curves FEV 1 , %FEV 1 , FVC, and %FVC were each plotted independently with respect to time for all curve types treated with four possible surgical approaches: PSF, ASF, VATS-I, and VATS + PSF. Maximal FEV 1 was signifi cantly lower with VATS-I-treated patients compared to PSF. No differences in maximal pulmonary function were observed, however, with regards to %FEV 1 , FVC, and % FVC. BRS204435.indd 1090 RS204435.indd 1090 22/05/11 3:09 PM 2/05/11 3:09 PM Spine www.spinejournal.com 1091 DEFORMITY Maximal Pulmonary Recovery • Verma et al Copyright © 2011 Lippincott Williams & Wilkins.
Unauthorized reproduction of this article is prohibited. pulmonary function is compromised. Pulmonary function in scoliosis is also impacted by the deformity itself depending on the curve magnitude and location. 12 ,26 – 28 Surgical and patient factors such as age, sex, preoperative lung function, thoracotomy versus thoracoabdominal (TA) approach, use of thoracoplasty, and time since surgery also contribute. 13 ,15 – 17 ,26 Anterior spinal fusion (ASF) continues to be a viable option as a stand alone approach for main thoracic (Lenke type 1) and thoracolumbar (Lenke type V) AIS deformities. 1 – 3 ,18 It is also of benefi t for the release of large rigid thoracic curvatures and for scoliosis associated with lordosis including Lenke 2, 3, 4, and 6 curve types. 9 , 24 Reported benefi ts of anterior over posterior fusion include shorter fusions, reduced blood loss, and transfusion requirements, 4 , 9 , 26 ability to maintain thoracic kyphosis, 2 , 5 , 6 , 29 improved spontaneous lumbar curve correction, 30 , 31 and the ability to save on average one to three distal motion segments. 4 , 9 , 10 More recently, the trend has been to avoid anterior approaches and utilize posterior-only segmental pedicle screw techniques with reports thoracotomy because of diffi culty maintaining single lung ventilation, and one pleural effusion. Finally, for VATS + PSF group, there were six pulmonary complications for a complication rate of 27.3%. Three patients had a persistent pneumothorax: two cases were observed and the other required chest tube application.
Two patients were converted to a mini-open thoracotomy, both could not tolerate single-lung ventilation. The last case suffered an injury of the lung parenchyma from placement of endoscopic instruments, which resulted in an air leak. This was resolved with chest tube placement for 4 days. DISCUSSION The principal goal of spinal surgery for idiopathic scoliosis is correction of the deformity and prevention of pulmonary and pain sequelae. Both anterior and posterior approaches have been used successfully for this purpose for a variety of curve types. Recently, however, the use of anterior spinal fusions (ASF) has declined due to a concern that long-term Figure 3. Lenke 1 FEV 1 , %FEV 1 , FVC, and %FVC were plotted independently with respect to time controlling for curve type (only Lenke 1) for three surgical approaches: PSF, VATS-I, and VATS + PSF. After 6 to 12 months, no differences in pulmonary function tests were noted between surgical groups until 2-years follow-up. BRS204435.indd 1091 RS204435.indd 1091 22/05/11 3:09 PM 2/05/11 3:09 PM 1092 www.spinejournal.com June 2011 DEFORMITY Maximal Pulmonary Recovery • Verma et al Copyright © 2011 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. TABLE 3. Pulmonary Improvement* All Curve Types Lenke 1 Only Abs FEV, PSF 104% 101% ASF 96% – VATS-I 101% 99% VATS + PSF 145% 149% Abs FVC PSF 105% 104% ASF 101% – VATS-I 100% 104% VATS + PSF 137% 131% % FEV 1 PSF 98% 96% ASF 93% – VATS-I 93% 86%* VATS + PSF 143% 204% % FVC PSF 102% 101% ASF 113% – VATS-I 92% 88% VATS + PSF 132% 144% * Pulmonary function improvement from baseline to 2-years follow-up. All curve types are compared across four surgical groups, whereas thoracic curves (Lenke 1) are compared across three groups. TABLE 4. (Continued) Abs FEV 1 Abs FEV %FEV 1 %FEV 1 VATS-I 1 Mucus plug Preop baseline 3.06 3.51 95 97 1 yr postop 2.65 2.95 78 75 2 Mucus plug Preop baseline 3.13 4.04 97 111 2 yr postop 2.48 2.75 71 69 3 Unplanned mini-open Preop baseline – – 87 87 2 yr postop 2.27 2.6 80 81 4 Pleural effusion Preop baseline 3.22 3.63 96 96 2 yr postop 2.61 2.78 78 73 VATS + PSF 1 Pneumothorax (observed) Preop baseline 1.57 1.7 66 63 2 yr postop 2.24 2.85 69 77 2 Pneumothorax (observed) Preop baseline 2.15 2.44 74 73 6 mos postop 2.75 2.38 65 86 3 Pneumothorax (chest tube) Preop baseline 2.55 3.91 53 69 1 yr postop 2.28 3.32 48 56 4 Unplanned mini-open Preop baseline 2.23 2.42 100 98 1 yr postop 2.49 2.55 105 97 5 Unplanned mini-open Preop baseline 2.2 3.01 57 67 1yr postop 2.58 3.44 64 74 6 Lung injury Preop baseline 1.61 2.07 52 59 1yr postop 1.54 1.96 56 61 * Pulmonary function data for complication cases from baseline to most recent follow-up with pulmonary function data available. TABLE 4. Pulmonary Function Data for Complication Cases* Abs FEV 1 Abs FEV %FEV 1 %FEV 1 PSF 1 Pleural effusion Preop baseline 1.57 1.9 61 66 1 yr postop 2.32 2.33 87 87 2 Atelectasis Preop baseline 2.11 2.36 85 85 1 yr postop 2.36 2.76 86 90 ASF 1 Pneumothorax Preop baseline 2.98 3.91 97 110 2 yr postop 2.97 3.77 88 96 BRS204435.indd 1092 RS204435.indd 1092 22/05/11 3:09 PM 2/05/11 3:09 PM Spine www.spinejournal.com 1093 DEFORMITY Maximal Pulmonary Recovery • Verma et al Copyright © 2011 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. of radiographic equivalence without the potential pulmonary impact of anterior procedures on thoracic and thoracolumbar curves. 15 , 18 ,32 – 34 However, authors utilizing posterior-only approaches have reported a 27% prevalence of proximal junctional kyphosis and conclude anterior approaches restore or maintain thoracic kyphosis better than posterior surgery perhaps in part due to the preservation of the posterior musculoligamentous tension band. 6 , 35
For thoracolumbar curves treated anteriorly, we have previously found no detectable change in pulmonary function and signifi cant improvement in SRS-22 outcomes at 2-years followup. 3 , 10 In agreement with our experience, Kim et al15 reported a decline in PFT scores at 2 years in patients treated with open thoracotomy, but not with the thoracoabdominal approach. Wang et al8 reported equivalent coronal curve correction with either ASF or PSF for the correction of thoracolumbar/lumbar deformities with notable reductions in operative blood loss and hospital cost with an anterior approach. However, this study did not report pulmonary function outcomes. For thoracic curves, we have previously reported that the anterior approach conferred minimal impact on pulmonary function at 2-years follow-up. 3 , 4 , 9 Patients that underwent VATS-I had similar curve correction and improved SRS-22 scores compared to PSF, but also experienced a slightly reduced peak fl ow at 2-years follow-up (411.7 versus 390 mL/s). 4 , 9 , 36
Other groups have also shown a reduction in pulmonary function immediately postoperatively and at 2-years follow-up when an open thoracotomy or thoracoplasty was performed. 13 , 15 Similarly, Graham et al17 reported a return to baseline pulmonary function at 2-years follow-up after surgical correction of AIS with ASF. The investigators reported a signifi cant decline in absolute and percent predicted FEV 1 , total lung capacity (TLC), and FVC at 3-months follow-up, but all measures of pulmonary function returned to 95% of baseline at 2-years. Zhang et al14 and Newton et al26 reported modest pulmonary declines immediately after ASF but noted these were most strongly related to preoperative pulmonary status rather than surgical approach. Similarly, Yaszay et al19 reported no decline in vital capacity and peak fl ow with PSF with or without thoracoplasty or VATS at 2-years follow-up. Kishan et al37 and Faro et al38 also reported VATS procedures confer little or no long-term impact on pulmonary function compared to open thoracotomy. Lastly, Wong et al11 and Kumano et al12 have argued that minor changes in percent predicted pulmonary function have little or no deleterious effects on an otherwise healthy patient. Despite these reports and other prior studies, the discussion over the use of anterior procedures for scoliosis remains active.
To our knowledge, we are the fi rst group to characterize the rate of pulmonary function recovery in AIS. Baseline pulmonary function was found to be lower in the VATS + PSF group as compared to the other groups. This is explained by a larger preoperative curve magnitude and lower baseline pulmonary status in VATS + PSF treated patients as reported by other authors. 12 ,26 – 28 Immediately after surgery, there was an initial postoperative decline in pulmonary function observed with both VATS-I and VATS + PSF procedures compared to PSF. Although not statistically signifi cant, PSF and ASF groups also experienced an initial defi cit in pulmonary function after surgery. There was, however, no difference in immediate postoperative pulmonary function between ASF and PSF. The rate of pulmonary recovery was equivalent for all surgical approaches and curve types.
When comparing all curve types together, VATS-I treated patients showed an equivalent maximal pulmonary function recovery compared to PSF with one exception, FEV 1 recovered to 101% of baseline as compared to 104% for the PSF group. Despite lower baseline pulmonary status, VATS + PSF patients showed dramatic improvements in pulmonary function from baseline and comparable maximal pulmonary function to PSF. Of note, maximal FVC was higher for VATS + PSF compared to PSF. Although the comparison of all curve types showed a small decline in maximal FEV 1 with VATS-I, this was not observed when comparing only Lenke 1 curves. Initial postoperative defi cits were undetectable at 6 to 12 months and remained equivalent to PSF up to 2-years followup. There was, however, a small but statistically signifi cant change only in %FEV 1 from baseline to 2-years follow-up in VATS-I treated patients with thoracic scoliosis. Absolute FEV 1 , however, remained unchanged. Maximal pulmonary function was equivalent between ASF and PSF. The overall message of both analyses was similar, that VATS procedures were associated with a mild depression of pulmonary function at 6- to 12-months follow-up but no clinically signifi cant impairment in maximal pulmonary function at 2 years compared to PSF. These fi ndings are in agreement with prior studies that reported minimal long-term pulmonary defi cits after ASF or VATS procedures in AIS. 13 – 15 ,17 , 19 , 26 ,37 – 39 A relative disadvantage of our study is that follow-up was limited to two years.
Although rapid growth of pulmonary alveoli peaks near 2 years of age, it continues until age 16 years in girls and 18 years in boys. 32 We cannot, therefore, comment on the potential impact of anterior approaches on pulmonary function after 2-years postoperatively. Newton et al39 recently reported that patients treated with VATS-I evaluated 5-years postoperatively had pulmonary, radiographic, and clinical fi ndings comparable to 2-year evaluations. Pulmonary function was found to be stable between 2- and 5-year follow-up. Another point of potential criticism is that a thoracoplasty was performed on one patient in the PSF group. Although comparative evidence has shown this procedure to have a deleterious effect on pulmonary function, it is unlikely that one patient could signifi cantly impact the pulmonary function of the entire PSF group. The sample size for both the “All curves” (n = 70) and “Lenke 1” (n = 50) analyses was relatively large.
Our analysis provides an understanding of the rate of pulmonary recovery after anterior procedures, which may be helpful for counseling patients regarding surgical expectations and guiding surgical decisions. No differences in pulmonary function recovery were observed between ASF and PSF. For all curve types, VATS-I seemed to minimally decrease FEV 1 at 2 years compared to PSF, but this was not seen with comparisons for thoracic scoliosis alone. For Lenke 1 curves, there also may have been a small decline in %FEV 1 in VATS-I patients from baseline BRS204435.indd 1093 RS204435.indd 1093 22/05/11 3:09 PM 2/05/11 3:09 PM 1094 www.spinejournal.com June 2011 DEFORMITY Maximal Pulmonary Recovery • Verma et al Copyright © 2011 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. to 2-years follow-up. We feel that anterior approaches remain feasible treatments options for adolescent idiopathic scoliosis with minimal or no long-term pulmonary impact and return of pulmonary function by 6 months for thoracic scoliosis. ➢ Key Points VATS procedures had an initial decline in measurements of pulmonary function as compared to ASF or PSF, but this diff erence resolved fully by 6- to 12-months follow-up. Modest declines in maximal pulmonary function with VATS-I were seen when comparing all curve types together, but not when comparing Lenke 1 curves alone. VATS procedures for thoracic scoliosis and open approaches for thoracolumbar curve types were associated with minimal to no permanent defi cits.
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