Treatment of idiopathic scoliosis with CD-instrumentation: lumbar pedicle screws versus laminar hooks in 66 patients

Does the size of the rod affect the surgical results in adolescent idiopathic scoliosis? 5.5-mm versus 6.35-mm rod

BACKGROUND CONTEXT

Favorable clinical outcomes of surgical treatment with Cotrel-Dubousset instrumentation (CDI) or instrumentations that follow the principles of CDI, for adolescent idiopathic scoliosis (AIS) have been reported. However, there are few studies concerning the results with rods of different sizes.

PURPOSE

To find out whether the rod size affects the surgical results for AIS.

STUDY DESIGN

A retrospective cohort study based on the same spinal system with different sizes of rod.

PATIENT SAMPLE

A consecutive series of 93 patients, who underwent posterior correction with posterior instrumentation and fusion for AIS, were included and retrospectively analyzed.

OUTCOME MEASURES

Postoperative radiologic outcomes were evaluated using coronal curves, percentage of curve correction, and coronal global balance.

METHODS

Ninety-three patients treated during the period January 2000 to December 2008 were included in this study; 48 patients were treated with the Cotrel-Dubousset Horizon (CDH) M10 system with a 6.35-mm rod from January 2000 through December 2004, and a CDH M8 was used with a 5.5-mm rod in another 45 patients from January 2005 through December 2008. The Cobb angle, Risser grade, coronal curves, flexibility of curve, percentage of curve correction, coronal global balance, operative time, and estimated blood loss were measured and analyzed. The same parameters were used when the patient was followed at the OPD. All of the patients underwent regular follow-up for at least 2 years.

RESULTS

No statistical significance was observed in the demographic data, including age, sex, BMI, and Risser grade, between these 2 groups. The overall average percentage of correction was 60.0%±12.7%: 60.7%±12.5% for the CDH M10 group, and 59%±13.1% for the CDH M8 group. At the final follow-up, the overall average loss of correction was 4.8±3.9° for the CDH M10 group, and 4.3±4.0° for the CDH M8 group. The average percentage of correction at the final follow-up was 50.9%±15.1% for the CDH M10 group, and 51.1%±16.1% for the M8 group. No statistical significance could be observed in the radiologic parameters between these 2 groups.

CONCLUSION

The radiologic results for the 5.5-mm rod and the 6.35-mm rod were comparable in terms of correction, loss of correction, and coronal global balance.

Are Breech Rates for Pedicle Screws Higher in the Upper Thoracic Spine?

STUDY DESIGN

A case-control study.

OBJECTIVES

To evaluate pedicle screw placement in pediatric patients with various etiologies of scoliosis, and to identify predictors of misplacement.

SUMMARY OF BACKGROUND DATA

Accuracy of placement of pedicle screws has not been well documented for posterior spinal instrumentation and fusion performed in the non-idiopathic population.

METHODS

A total of 54 patients (29 idiopathic, 16 neuromuscular, and 9 congenital/syndromic scoliosis), ages 5-19 years, were included. Computed tomography scans were obtained on patients postoperatively to assess screw position. Three pediatric orthopedic surgeons evaluated screw placement, and risk factors for misplacement were examined.

RESULTS

Of 1,042 pedicle screws, 8.3% were misplaced. Among all etiologies, screws placed at T1 (28.6%) and T2 (18.2%) had higher misplacement rates. T2 screws and curve correction greater than 75% had higher misplacement rates in congenital/syndromic patients; screws at T3, screws at upper end of construct, and proximal screws had significantly higher misplacement rates in neuromuscular patients; and no variables predicted misplacement in idiopathics. Screws placed at the most proximal end of the screw/rod construct also had a higher misplacement rate (14.1%) compared with all remaining levels (7.8%). Nonidiopathic patients had higher anterior misplacement compared with idiopathic. No screws were removed or revised, and no screw-related complications were observed.

CONCLUSIONS

Pedicle screw instrumentation in the thoracolumbar spine was safe for pediatric patients. We found that pedicle screws placed at top levels are at higher risk for misplacement among all pediatric scoliosis patients. Nonidiopathic patients are at higher risk for anterior screw misplacement, and the predictive effect of vertebral level is more profound in nonidiopathic patients. Because of these findings, we routinely use fluoroscopic guidance for the placement of T1 and T2 screws, and screws at the proximal end of construct.

Application of intraoperative computed tomography with or without navigation system in surgical correction of spinal deformity: a preliminary result of 59 consecutive human cases

STUDY DESIGN

A retrospective analysis of patients undergoing spinal deformity correction surgery by the assistance of intraoperative computed tomography (iCT) with or without navigation system.

OBJECTIVE

To share our preliminary experience and analysis of the iCT navigation system applied to spinal deformity surgery.

SUMMARY OF BACKGROUND DATA

The iCT navigation system has been shown to improve accuracy and safety in posterior instrumentation. It not only decreased the operation time but also prevented excessive radiation exposure to the medical staff. To date, there are only few reports about the application of the iCT navigation system in spinal deformity surgery.

METHODS

From April 2009 to September 2010, 59 patients who had a diagnosis of scoliosis, kyphosis, or scoliokyphosis and underwent iCT-assisted surgical correction were included. Without randomization, 28 patients were operated with the iCT-navigation system, and the other 31 patients were operated with standard procedure under iCT assistance. The detailed procedures, preoperative and intraoperative images were illustrated. The accuracy of screw placement, time for screw insertion, postoperative correction rate, and iCT scanning data were analyzed.

RESULTS

There were significant differences between 2 groups in (1) the preoperative Cobb angle (76.2° and 62.6° in the navigation and non-navigation groups), (2) the accuracy and the revision rate of thoracic pedicle screws and total pedicle screws, and (3) the average screw insertion time. The breach rate and the revision rate of thoracic pedicle screws and total pedicle screws were significantly lower and the average screw insertion time was significantly lesser in the navigation group than in the non-navigation group. There were no statistically significant difference in (1) the breach rate and the revision rate of lumbar pedicle screws, (2) the mean iCT scanning time and time-out, (3) the mean number of fusion segments, (4) the mean number of iCT scans, and (5) the postoperative correction rate. Complications were encountered in 2 patients in the non-navigation group but none in the navigation group. There was no reoperation due to implant malposition in both groups.

CONCLUSION

The iCT navigation system provides desirable accuracy of posterior spinal instrumentation for patients during surgical correction of spinal deformity without radiation exposure to the medical staff, especially in thoracic spine instrumentation. Meanwhile, the iCT in itself is an effective means of assessing complex instrumentation of the spinal deformity.

Fixation points within the main thoracic curve: does more instrumentation produce greater curve correction and improved results?

STUDY DESIGN

Prospective consecutive multicenter case series.

OBJECTIVE

To compare fixation type and amount to curve correction controlled for curve flexibility.

SUMMARY OF BACKGROUND DATA

The enhanced spinal purchase from segmental fixation should increase the force implants can exert without failure. This study evaluates whether this translates into correction beyond that expected from preoperative bending radiographs in thoracic curves where maximum correction was feasible (1A, 1B, and nonselective 1C fusions).

METHODS

One hundred seventy-one Lenke type 1 curves (118 1A, 36 1B, 23 1C) with 2-year follow-up were evaluated for the number and type of fixation points within the main curves compared to the correction obtained on preoperative bend films. SRS scores were compared to the amount of correction.

RESULTS

The number of fixation points both within the curve (P = 0.01) and for each vertebral body (P = 0.002) was larger for curves with greater correction compared to the bend films than those with less correction. Overall absolute correction was best for all screw and screw and wire constructs, followed by hook and screw, and least with hooks. However, compared to the bend films, these differences were not significant (P = 0.132). For all groups, the SRS scores significantly improved (P < 0.001), and was slightly more notable for the all screw constructs than other instrumentation patterns (P = 0.023). However, there were no significant difference in this improvement between those correcting more and those correcting less than the bend films (P = 0.578).

CONCLUSION

Absolute curve correction improved most with all pedicle screw and screw and wire constructs, but, when compared to bending films, the number of fixation points is more important than fixation type for curve correction. Although SRS scores improved the most in those with all screw constructs, the significance of this improvement is uncertain, and the SRS scores did not relate to whether curve correction was more or less than the bend films.

Pediatric pedicle screws: comparative effectiveness and safety: a systematic literature review from the Scoliosis Research Society and the Pediatric Orthopaedic Society of North America task force

BACKGROUND

Pedicle screws are widely used in spinal surgery. There is extensive published literature concerning the use of pedicle screw instrumentation for spinal surgery in adults. Now there is a trend to use pedicle screws in pediatric patients, including the very young. A systematic review of the current English-language literature on the use of pedicle screw instrumentation in the pediatric age group was performed to specifically determine (1) the pedicle screw placement accuracy in patients with spine deformity and (2) the effect size of all-pedicle screw constructs compared with other methods of spinal instrumentation in terms of the percentage of scoliosis correction.

METHODS

English-language studies of pedicle screw use in pediatric patients (defined as those younger than eighteen years of age) were included. Descriptive statistics synthesized the accuracy of pedicle screw placement. Accuracy rates were compared between pediatric and adult patients. The effect of pedicle screw instrumentation on scoliosis correction was calculated with use of Cobb angle measurements.

RESULTS

On the basis of the literature search, 1181 articles were screened, 320 abstracts were examined, and ninety full-text articles representing 5761 patients were reviewed in detail. Seventeen studies met the inclusion criteria for the analysis of pedicle screw placement accuracy. A total of 13,536 pedicle screws were placed in 1353 pediatric patients. The overall placement accuracy rate in pediatric patients was 94.9%, which was higher than the rate of 91.5% reported for adults. The weighted, geometric, and 5% trimmed mean accuracy rates of pedicle screw placement were 91.9%, 88.5%, and 89.1%, respectively (standard deviation = 10%; interquartile range = 10%). Sixteen comparative studies met the inclusion criteria for the analysis of the effect of pedicle screw instrumentation on scoliosis correction. Pedicle screw constructs had a significantly larger percentage of Cobb angle correction compared with hooks (Cohen's d = 1.14) and hybrid constructs (Cohen's d = 0.49).

CONCLUSIONS

The accuracy of pedicle screw placement in the pediatric spine exceeds the accuracy rate reported in adults. Pedicle screw instrumentation constructs are significantly more effective for scoliosis correction, as determined on the basis of Cobb angle measurements, than are hook constructs and hybrid constructs.

[Indications for deformity correction with minimally invasive spondylodesis]

The indications for surgical treatment of thoracic, lumbar, combined and thoracolumbar scoliosis are given for a curvature of the thoracic spine with a Cobb angle more than 50° and more than 45° in the lumbar spine. The maximum Cobb angle is 90°. The aim is the correction of more than 50% in the frontal plane and correction of scoliosis is possible in flexible curvatures up to 90%. By the minimally invasive surgical technique the muscular damage is completely avoided on the convex side but on the concave side this is only partly possible. This is the first report of a muscle preserving minimally invasive surgical technique for the convex side of scoliosis.

[Posterior operative correction of idiopathic scoliosis. Value of pedicle screws versus hooks]

Posterior correction and fusion of scoliosis with multisegmental instrumentation systems was developed by Cotrel-Dubousset in the 1980s. Initially correction and instrumentation was performed using hooks only. Later pedicle screws were implemented first for the lumbar and then for the thoracic spine. Nowadays instrumentation based on pedicle screws only is well established for posterior scoliosis surgery. Biomechanical studies demonstrated higher pull-out forces for pedicle than for hook constructs.In clinical studies several authors reported better Cobb angle correction of the primary and the secondary curves and less loss of correction in pedicle screw versus hook instrumentations. Furthermore, pedicle screw instrumentation allows fewer segments to be fused, especially caudally, and thus saving mobile segments. In most of these publications there were no differences in operation time, blood loss and complication rates. In summary, there is better curve correction without an increased risk using multisegmental pedicle screw instrumentation in modern posterior scoliosis surgery.

A century of spine surgery: what can patients expect?

PURPOSE

To evaluate the hypothesis that spinal fusion surgery is an effective method to address spinal deformity-associated clinical problems, including magnitude of curvature (Cobb angle), pulmonary dysfunction, and pain.

METHOD

A systematic review was carried out using Science Citation Index (SCI) Expanded (1900 - present), Social Sciences Citation Index (1956 - present), Arts and Humanities Citation Index (1965 - present), Medline (1950 - present) and PubMed Central databases (1887 - present) to access information regarding efficacy of spine surgery in preventing or improving the health and function of patients diagnosed with scoliosis in adolescence.

RESULTS

Since 1950, more than 12,600 articles on scoliosis have been published, and nearly 50% (5721) focus on methods, rationale, outcome, and complications of surgical intervention. Among these, 82 articles have documented outcome for groups of > or =10 patients, treated for adolescent idiopathic scoliosis, and followed for at least 2 years after treatment. These data provide an overview of the impact of spine surgery on scoliosis for 5780 patients as surgery methods and approaches have evolved.

CONCLUSIONS

For most patients, a reduced magnitude of spinal curvature can be achieved through one or more spinal fusion surgeries. There is no evidence to support the premise that this result is correlated with improved pulmonary function or reduced pain.

Financial analysis of circumferential fusion versus posterior-only with thoracic pedicle screw constructs for main thoracic idiopathic curves between 70 degrees and 100 degrees

PURPOSE

Reports on thoracic pedicle screw (TPS) constructs have demonstrated their safety and efficacy; however, concerns exist regarding their increased cost. This is a review of adolescents with main thoracic scoliosis surgically treated with anterior release and posterior fusion or posterior fusion only. The objectives were to compare the radiographic outcomes and financial data of two surgical treatments: anterior/posterior spinal fusion (APSF) versus posterior spinal fusion (PSF-TPS) alone with TPSs, in patients with large 70-100 degrees main thoracic adolescent idiopathic scoliosis (AIS) curves.

METHODS

We identified 43 patients with main thoracic Lenke type 1-4 AIS curves between 70 and 100 degrees who had been treated with either APSF or PSF-TPS.

RESULTS

Both groups had equivalent radiographic corrections postoperatively. The PSF-TPS group patients had higher implant charges, but the APSF group had higher surgeon procedural charges, operating room charges, anesthesia charges, and inpatient room charges. Total charges were $75,295 for the APSF group and $71,236 for the PSF-TPS group (P > 0.05). Analyses of two subgroups of the APSF group, anterior release via thoracotomy versus VATS and same-day versus staged surgeries, failed to change any of the above findings.

CONCLUSION

Based on this financial analysis, there was no statistically significant differences between the APSF and PSF-TPS groups, with equivalent radiographic corrections.

Impact of spine surgery on signs and symptoms of spinal deformity

Paediatric scoliosis is associated with signs and symptoms including reduced pulmonary function, increased pain and impaired quality of life, all of which worsen during adulthood, even when the curvature remains stable. Spinal fusion has been used as a treatment for nearly 100 years. In 1941, the American Orthopedic Association reported that for 70% of patients treated surgically, outcome was fair or poor: an average 65% curvature correction was reduced to 27% at >2 year follow-up and the torso deformity was unchanged or worse. Outcome was worse in children treated surgically before age 10, despite earlier intervention. Today, a reduced magnitude of curvature obtained by spinal fusion in adolescence can be maintained for decades. However, successful surgery still does not eliminate spinal curvature and it introduces irreversible complications whose long-term impact is poorly understood. For most patients there is little or no improvement in pulmonary function. Some report improved pain after surgery, some report no improvement and some report increased pain. The rib deformity is eliminated only by rib resection which can dramatically reduce respiratory function even in healthy adolescents. Outcome for pulmonary function and deformity is worse in patients treated surgically before the age of 10 years, despite earlier intervention. Research to develop effective non-surgical methods to prevent progression of mild, reversible spinal curvatures into complex, irreversible structural deformities, is long overdue.

Variability of spinal instrumentation configurations in adolescent idiopathic scoliosis

Surgical instrumentation for the correction of adolescent idiopathic scoliosis (AIS) is a complex procedure involving many difficult decisions (i.e. spinal segment to instrument, type/location/number of hooks or screws, rod diameter/length/shape, implant attachment order, amount of rod rotation, etc.). Recent advances in instrumentation technology have brought a large increase in the number of options. Despite numerous clinical publications, there is still no consensus on the optimal surgical plan for each curve type. The objective of this study was to document and analyse instrumentation configuration and strategy variability. Five females (12-19 years) with AIS and an indication for posterior surgical instrumentation and fusion were selected. Curve patterns were as follows: two right thoracic (Cobb: 34 degrees, 52 degrees), two right thoracic and left lumbar (Cobb T/L: 57 degrees/45 degrees, 72 degrees/70 degrees) and 1 left thoraco-lumbar (Cobb: 64 degrees). The pre-operative standing postero-anterior and lateral radiographs, supine side bending radiographs, a three-dimensional (3D) reconstruction of the spine, pertinent 3D measurements as well as clinical information such as age and gender of each patient were submitted to six experienced independent spinal deformity surgeons, who were asked to provide their preferred surgical planning using a posterior spinal approach. The following data were recorded using the graphical user interface of a spine surgery simulator (6x5 cases): implant types, vertebral level, position and 3D orientation of implants, anterior release levels, rod diameter and shape, attachment sequence, rod rotation (angle, direction), adjustments (screw rotation, contraction/distraction), etc. Overall, the number of implants used ranged from 11 to 26 per patient (average 16; SD +/-4). Of these, 45% were mono-axial screws, 31% multi-axial screws and 24% hooks. At one extremity of the spectrum, one surgeon used only mono-axial screws, while at the other, another surgeon used 81% hooks. The selected superior- and inferior-instrumented vertebrae varied up to six and five levels, respectively (STD 1.2 and 1.5). A top-to-bottom attachment sequence was selected in 61% of the cases, a bottom-up in 29% and an alternate order in 11%. The rod rotation maneuver of the first rod varied from 0 degrees (no rotation) to 140 degrees, with a median at 90 degrees. In conclusion, a large variability of instrumentation strategy in AIS was documented within a small experienced group of spinal deformity surgeons. The exact cause of this large variability is unclear but warrants further investigation with multicenter outcome studies as well as experimental and computer simulation studies. We hypothesize that this variability may be attributed to different objectives for correction, to surgeon's personal preferences based on their previous experience, to the known inter-observer variability of current classification systems and to the current lack of clearly defined strategies or rational rules based on the validated biomechanical studies with modern multi-segmental instrumentation systems.

A Large Adolescent Idiopathic Scoliosis Curve in a Skeletally Immature Patient: Is Early Surgery the Correct Approach?

The goal of this study was to determine whether the available studies provide enough evidence that, in a borderline case of adolescent idiopathic scoliosis with a large (35 to 50 degrees) curve in a skeletally immature patient (Risser 0 to 2) with significant growth potential left, a conservative line of management in the form of bracing can be considered, rather than to rush into a potentially unnecessary major spinal surgery. We reviewed the literature spanning the last 20 years for the results of bracing in this specific group of patients. From the 9 studies selected, a group-specific data extraction was carried out. Three hundred and five patients with a 36 to 50 degrees scoliosis curve and Risser stages 0 to 2 were treated by bracing and the treatment was termed successful in 160 patients. Thus, more than half (52.5%) of the patients were successfully managed with a brace and were spared surgery. The current trend for management of these curves is early surgical intervention, the rationale being the ineffectiveness of bracing in preventing the progression of such a large curve and the difficulty in obtaining satisfactory correction by postponing surgery to a later date. On the basis of our results, we propose a conservative line of management for these curves, in contrast with current views, rather than to rush into a major spine surgery, expecting a favorable outcome with a well-supervised bracing program. If the curve progresses, surgery can always be considered later, keeping in mind the excellent correction obtained with the pedicle screw systems even for large curves of 70 to 100 degrees.

Biomechanical evaluation of pedicle screws versus pedicle and laminar hooks in the thoracic spine

BACKGROUND CONTEXT

Pedicle screws have been shown to be superior to hooks in the lumbar spine, but few studies have addressed their use in the thoracic spine.

PURPOSE

The objective of this study was to biomechanically evaluate the pullout strength of pedicle screws in the thoracic spine and compare them to laminar hooks. STUDY DESING/SETTING: Twelve vertebrae (T1-T12) were harvested from each of five embalmed human cadavers (n=60). The age of the donors averaged 83+8.5 years. After bone mineral density had been measured in the vertebrae (mean=0.47 g/cm(3)), spines were disarticulated. Some pedicles were damaged during disarticulation or preparation for testing, so that 100 out of a possible 120 pullout tests were performed.

METHODS

Each vertebra was secured using a custom-made jig, and a posteriorly directed force was applied to either the screw or the claw. Constructs were ramped to failure at 3 mm/min using a Mini Bionix II materials testing machine (MTS, Eden Prairie, MN).

RESULTS

Pedicle claws had an average pullout strength of 577 N, whereas the pullout strength of pedicle screws averaged 309 N. Hooks installed using the claw method in the thoracic spine had an overwhelming advantage in pullout strength versus pedicle screws. Even in extremely osteoporotic bone, the claw withstood 88% greater pullout load.

CONCLUSION

The results of this study indicate that hooks should be considered when supplemental instrumentation is required in thoracic vertebrae, especially in osteoporotic bone.

Correction of adolescent idiopathic scoliosis using thoracic pedicle screw fixation versus hook constructs

This retrospective study was undertaken to determine the effectiveness and cost of thoracic pedicle screws versus laminar and pedicle hooks in patients undergoing surgical correction of adolescent idiopathic scoliosis (AIS). Immediate preoperative and 6-week postoperative radiographs were examined in 25 consecutive cases of children with AIS who were divided into two groups, those with thoracic pedicle screw constructs and those with thoracic hook constructs. Endpoints collected included radiographic measures, complications, surgical time, implant cost, and quality-of-life measures. Ten children underwent spinal fusion using thoracic pedicle screw fixation and 15 underwent thoracic constructs composed of hooks. Similar sex and age distribution were noted in both groups, and among the 20 girls and 5 boys the average age was 14.5. The mean preoperative Cobb angle was 53.5 degrees for the screw group and 52.5 degrees for the hook group. Correction averaged 70.2% for the screw group and 68.1% for the hook group. There were no significant differences between the two patient groups in terms of percentage of or absolute curve change after surgery. The apical vertebral translation, end vertebral tilt angle, and coronal balance did not differ significantly between the two patient groups. Comparison of operative time and quality of life revealed no significant differences. Screw constructs were significantly more expensive than hook constructs. The correction obtained from thoracic pedicle screw fixation is comparable to traditional hook constructs in AIS. Surgery using either construct effectively corrects AIS.

Thoracic adolescent idiopathic scoliosis curves between 70 degrees and 100 degrees: is anterior release necessary?

STUDY DESIGN

A retrospective review of adolescents with main thoracic scoliotic curves surgically treated with either anterior release and posterior fusion or posterior fusion only.

OBJECTIVES

To compare the radiographic and clinical outcomes of two surgical treatments: anterior-posterior spinal fusion (APSF) versus posterior spinal fusion (PSF) alone in patients with large 70 degrees to 100 degrees thoracic adolescent idiopathic scoliosis (AIS) curves.

SUMMARY OF BACKGROUND DATA

Surgical treatment of thoracic AIS curves between 70 degrees and 100 degrees often consists of anterior and posterior fusion to improve the coronal correction and fusion rate, with the anterior release and fusion performed through either an open thoracotomy or by video-assisted thoracoscopy.

METHODS

All patients (n = 84) with main thoracic major AIS curves between 70 degrees and 100 degrees who underwent spinal fusion (APSF or PSF) at one center between 1987 and 2001 were included for analysis. The minimum follow-up was 2 years after surgery (mean, 4.5 years; range, 2.0-10.2 years). The mean age of patients was 13.8 years (range, 10.7-18.2 years), with 66 females and 18 males. Multiple radiographic measures were assessed. The primary and secondary statistical analyses performed were nonparametric analyses, using the Wilcoxon-Mann-Whitney tests for the primary analysis of APSF and PSF groups. The PSF subgroup analysis was performed with the Kruskal-Wallis test.

RESULTS

There were 22 patients in the APSF (open ASF in 18, and video-assisted thoracoscopy in 4) group and 62 patients in the PSF group. There were no statistically significant differences between the groups for gender, age, number of levels fused, Cobb measurement of preoperative coronal or sagittal thoracic curve magnitude, or coronal curve flexibility. The APSF group, when compared with the PSF group, had greater intraoperative correction of the coronal curve (48.3 degrees vs. 38.7 degrees, P = 0.0087) as well as final overall correction (47.2 degrees vs. 34.2 degrees, P = 0.0008). There were no significant differences seen in the sagittal alignment from T5-T12 (P = 0.3150) or the SRS outcomes data between the APSF and PSF only groups. Subanalysis of the PSF only group identified three distinct groups based on implants: hook-only constructs (n = 36), hybrid constructs of proximal hooks and distal pedicle screws (n = 15), and pedicle screw-only constructs (n = 11). Pedicle screw-only constructs corrected the coronal Cobb measurements more than the other two groups (47.5 degrees vs. hooks 37.7 degrees vs. hybrid 34.4 degrees , P = 0.0110), and to a similar extent as to the APSF group with no statistically significant difference in coronal correction (PSF, 47.5 degrees; APSF 48.3 degrees; P = 0.9014), nor any other parameter except for sagittal T5-T12 changes. There were no reoperations for implant failure/pseudarthroses in any of the patients.

CONCLUSION

APSF of large thoracic curves allows greater coronal correction of thoracic curves between 70 degrees and 100 degrees, when compared with PSF alone using thoracic hook constructs, but not with the use of thoracic pedicle screw constructs. Scoliosis surgeons not using pedicle screw constructs need to decide if the modest improvement in coronal correction with a combined approach justifies its routine use in this patient population.

Cotrel-Dubousset (CD) or Universal Spine System (USS) instrumentation in adolescent idiopathic scoliosis (AIS): comparison of midterm clinical, functional, and radiologic outcomes

STUDY DESIGN

A retrospective comparison of the clinical, radiologic, and functional results of Cotrell-Dubousset (CD) and Universal Spine System (USS) instrumentation for adolescent idiopathic scoliosis (AIS).

OBJECTIVES

To establish whether there are any differences in outcome between the 2 instrumentation systems.

SUMMARY OF BACKGROUND DATA

CD is the first complex posterior double rod instrumentation system to provide multiple hook fixation. USS instrumentation permits the use of rod translation instead of rod rotation, the option to secure pedicle hooks with fixation screws, and the option to use transpedicular screws in the lower thoracic and lumbar spine. Midterm and long-term results of USS instrumentation are lacking.

METHODS

Fifty-seven (mean age, 28 years at follow up) patients treated with CD instrumentation and 55 (mean age, 23 years at follow up) patients treated with USS instrumentation for AIS participated in the study. The average follow-up rate was 80% and time 13.0 years for the CD group, and 95% and 7.8 years for the USS group. Radiographs were obtained before surgery, at 2-year follow up, and at final follow up. Additionally, a physical examination was performed by 2 independent observers, and the Scoliosis Research Society (SRS) questionnaire was completed; spinal mobility and nondynamometric trunk strength were measured at the final follow-up visit. RESULTS.: The mean Cobb angle of the instrumented thoracic curve was before surgery 55 degrees (range, 36-83 degrees for the CD and 52 degrees (range, 35-85 degrees) for the USS group. The mean number of instrumented vertebrae was 9.9 (range, 7-12) in the CD and 9.8 (range, 6-12) in the USS group. At final follow up, the mean angles were 32 degrees (range, 13-63 degrees) for the CD group and 29 degrees (range, 9-63 degrees) for the USS group (not significant). No significant difference was observed in thoracic kyphosis or lumbar lordosis between the study groups at final follow up. In the SRS questionnaire, the total score averaged 97 for the CD and 101 for the USS groups, respectively. In the questionnaire, 6 (11%) patients in the CD group, but none in the USS group, reported having low back pain often or very often at rest. No correlation was found between the Cobb angle of the thoracic or lumbar curves at follow up and the total score or back pain indexes of this questionnaire. Nondynamometric trunk strength measurements corresponded with age- and sex-adjusted reference values, on average, but patients in the CD group performed significantly better in the squatting test (P = 0.021) and patients in the USS group performed better in trunk side bending (P = 0.004). Complications were recorded in 15 (26%) patients in the CD and in 13 (24%) patients in the USS group (not significant).

CONCLUSIONS

The midterm radiologic and functional outcomes were quite similar in both groups as were the SRS scores. The patients performed, on average, as well as did the reference population in nondynamometric trunk strength measurements. Intraoperative and late complications were similar in both groups.