Preoperative Flexibility Research Articles

More preoperative flexibility implies adequate neural pliability for curve correction without prophylactic untethering in scoliosis patients with asymptomatic tethered spinal cord, a retrospective study

BackgroundTethered spinal cord is frequently associated with scoliosis. It is still controversial whether a prophylactic untethering is necessary before correction procedure in scoliosis patients with tethered spinal cord. In this study we determined the clinical outcome of a one-stage posterior scoliosis correction without a prophylactic untethering for treating scoliosis with an asymptomatic tethered spinal cord.MethodsSeventeen (5 males and 12 females) scoliosis patients with tethered spinal cords were retrospectively reviewed. All patients underwent a one-stage posterior scoliosis correction without preventive untethering. Parameters of radiograph were used to assess correction result. The Scoliosis Research Society (SRS)-22 questionnaire was analyzed pre- and post-operatively to evaluate the clinical outcomes. The modified Japanese Orthopaedic Association (mJOA) score was used to assess the pre- and post-operative spinal cord function.ResultsThe post-operative coronal Cobb angle was significantly decreased compared with preoperative. (23.8 ± 6.4° vs. 58.4 ± 12.6°, P < 0.01). The coronal Cobb angle was 22.4 ± 6.8° at the final follow-up evaluation. The apical vertebral translation (AVT) was also decreased significantly. (27.5 mm vs. 60.9 mm, P < 0.01). The SRS-22 total score was improved at the 1-year follow-up evaluation compared with the pre-operative SRS-22 total score (87 ± 4 vs. 70 ± 5, p < 0.05). The functional activities, pain, self-image, mental health, and surgery satisfactory scores at the final follow-up evaluation were all improved compared with the corresponding pre-operative scores, especially the self-image and mental health scores (p < 0.05). The spinal cord function was stable and there was no new neurological symptoms after scoliosis correction. No difference existed between the pre- and post-operative total mJOA score (26 ± 2 vs. 27 ± 2, p = 0.39), which including subjective symptom (p = 0.07), clinical symptom (p = 0.33), daily activities (p = 0.44) and bladder function (p = 0.67).ConclusionOne-stage posterior scoliosis correction is a safe and effective surgical procedure for scoliosis patients combined with asymptomatic tethered spinal cord who have adequate spinal cord function reserve.

Segmental vs non-segmental thoracic pedicle screws constructs in adolescent idiopathic scoliosis: is there any implant alloy effect?

The aim of this study is to understand how many anchor sites are necessary to obtain maximum posterior correction of idiopathic scoliotic curve and if the alloy of instrumentation, stainless steel or titanium, may have a role in the percent of scoliosis correction. We reviewed 143 consecutive patients, affected by AIS (Lenke 1-2), who underwent a posterior spinal fusion with pedicle screw-only instrumentation between 2002 and 2005. According to the implant density and alloy used we divided the cohort in four groups. All 143 patients were reviewed at an average follow-up of 7, 2years, the overall final main thoracic curve correction averaged 61.4%, whereas the implant density within the major curve averaged 71%. A significant correlation was observed between final% MT correction and preoperative MT flexibility and implant density. When stainless steel instrumentation is used non-segmental pedicle screw constructs seem to be equally effective as segmental instrumentations in obtaining satisfactory results in patients with main thoracic AIS. When the implant alloy used is titanium one, an implant density of ≥60% should be guaranteed to achieve similar results.

Multiple concave rib head resection improved correction rate of posterior spine fusion in treatment of adolescent idiopathic scoliosis.

Hybrid constructs have been widely used to surgically correct thoracic adolescent idiopathic scoliosis (AIS). To enhance the correction obtained with hybrid constructs, we perform concave rib head resection and convex costovertebral release as posterior release procedures. The objective of the study was to evaluate coronal and sagittal curve correction in patients with adolescent idiopathic scoliosis (AIS) treated with hybrid constructs combined with concave rib head resection and convex transverse process resection as posterior release procedures. The records of 24 patients with Lenke type 1 or 2 AIS treated with hybrid constructs combined with posterior release procedures were retrospectively reviewed. The mean age at surgery was 14.3 years. The mean follow-up period was 33.0 months (range, 24-60 months). Radiographs were evaluated before surgery, immediately postoperatively, and at latest follow-up. The average preoperative Cobb angle of the main thoracic (MT) curve was 58.1±12.6° (range, 45-88°). The MT curve was corrected to 12.8±9.0° (range, 0-38°) immediately after surgery. At the latest follow-up, the average Cobb angle was 13.6±9.9° (range, 0-44°; correction, 77.5±14.0%). The average loss of coronal correction was 0.8°. The average preoperative flexibility of the MT curve was 54.6±17.4%. The average Cincinnati correction index was 1.53±0.48at the latest follow-up. The average preoperative thoracic kyphosis (TK) was 13.7±12.0° (range,-12-34°). Immediately after surgery, TK was corrected to 18.6±5.9° (range, 10-29°). At the latest follow-up, TK measured 18.1±6.5° (range, 6-32°). Hybrid instrumentation combined with concave rib head resection and convex transverse process resection as posterior release procedures achieved satisfactory coronal and sagittal curve correction with little loss of correction at 2-year follow-up.

Choice of Lowest Instrumented Vertebras for Lenke I Adolescent Idiopathic Scoliosis Orthopedics

To discuss the impact of different lowest instrumented vertebras on the effect of posterior spinal pedicle screw-rod orthopedics for treatment of Lenke I adolescent idiopathic scoliosis. 45 patients with adolescent idiopathic scoliosis (AIS) who received posterior pedicle screw-rod orthopedics from July 2011 to September 2015 were analyzed retrospectively. All patients were divided into touched vertebra group (n=21 cases; 6 M and 15 F) and stable vertebra group (n=24 cases; 7 M and 17 F) according to the choice of different lowest instrumented vertebras. The indexes of the coronal and sagittal spinal imaging before and after operation as well as in the last follow-up were analyzed and SRS-22 questionnaire was performed to evaluate the curative effect. Through a 6-36-month follow-up visit, no significant difference was found in the pre-operative indexes (Cobb angle and pre-operative TS, SVA, TK and LL) of the coronal and sagittal spinal imaging between the two groups (P>0.05). Meanwhile, there was no statistical difference in the spinal coronal parameters (i.e., Cobb angle, TS, pre-operative thoracic-waist/waist scoliosis, pre-operative flexibility of thoracic scoliosis, correction rate and loss rate) after operation and in the last follow-up visit between the two groups (P>0.05). In touched vertebra group, the coronal spinal parameters (e.g., thoracic-waist/waist scoliosis) after operation and in the last follow-up visit were significantly higher than those of stable vertebra group (P 0.05). In the aspect of fusion segments, the touched vertebra group saved one centrum relative to stable vertebra group (P 0.05). In order to treat Lenke I AIS patients with posterior pedicle screw-rod orthopedics, touched vertebra should be used as lowest instrumented vertebra as it can not only obtain the similar therapeutic effect to stable vertebra, but also shorten the fixed segments.

Halo-gravity traction in the treatment of severe spinal deformity: a systematic review and meta-analysis.

Halo-gravity traction has been reported to successfully assist in managing severe spinal deformity. This is a systematic review of all studies on halo-gravity traction in the treatment of spinal deformity to provide information for clinical practice. A comprehensive search was conducted for articles on halo-gravity traction in the treatment of spinal deformity according to the PRISMA guidelines. Appropriate studies would be included and analyzed. Preoperative correction rate of spinal deformity, change of pulmonary function and prevalence of complications were the main measurements. Sixteen studies, a total of 351 patients, were included in this review. Generally, the initial Cobb angle was 101.1° in the coronal plane and 80.5° in the sagittal plane, and it was corrected to 49.4° and 56.0° after final spinal fusion. The preoperative correction due to traction alone was 24.1 and 19.3%, respectively. With traction, the flexibility improved 6.1% but postoperatively the patients did not have better correction. Less aggressive procedures and improved pulmonary function were observed in patients with traction. The prevalence of traction-related complications was 22% and three cases of neurologic complication related to traction were noted. The prevalence of total complications related to surgery was 32% and that of neurologic complications was 1%. Partial correction could be achieved preoperatively with halo-gravity traction, and it may help decrease aggressive procedures, improve preoperative pulmonary function, and reduce neurologic complications. However, traction could not increase preoperative flexibility or final correction. Traction-related complications, although usually not severe, were not rare.

Posterior Surgery for Adolescent Idiopathic Scoliosis With Pedicle Screws and Ultrahigh–Molecular Weight Polyethylene Tape

Study Design: Prospective clinical case series. Objectives: To describe our surgical procedure and results for posterior correction and fusion with a hybrid approach using pedicle screws, hooks, and ultrahigh–molecular weight polyethylene tape with direct vertebral rotation (DVR) (the PSTH-DVR procedure) for treatment of adolescent idiopathic scoliosis (AIS) with satisfactory correction in the coronal and sagittal planes. Summary of Background Data: Introduction of segmental pedicle screws in posterior surgery for AIS has facilitated good correction and fusion. However, procedures using only pedicle screws have risks during screw insertion, higher costs, and decreased postoperative thoracic kyphosis. We have obtained good outcomes compared with segmental pedicle screw fixation in surgery for AIS using a relatively simple operative procedure (PSTH-DVR) that uses fewer pedicle screws. Methods: The subjects were 30 consecutive patients with AIS who underwent the PSTH-DVR procedure and were followed for a minimum of 2 years. Preoperative flexibility, preoperative and postoperative Cobb angles, correction rates, loss of correction, thoracic kyphotic angles (T5–T12), coronal balance, sagittal balance, and shoulder balance were measured on plain radiographs. Rib hump, operation time, estimated blood loss, spinal cord monitoring findings, complications, and scoliosis research society (SRS)-22 scores were also examined. Results: The mean preoperative curve of 58.0 degrees (range, 40–96 degrees) was corrected to a mean of 9.9 degrees postoperatively, and the correction rate was 83.6%. Fusion was obtained in all patients without loss of correction. In 10 cases with preoperative kyphosis angles (T5–T12) &lt;10 degrees, the preoperative mean of 5.8 degrees improved to 20.2 degrees at the final follow-up. Rib hump and coronal, sagittal and shoulder balances were also improved, and good SRS-22 scores were achieved at final follow-up. Conclusions: The correction of deformity with PSTH-DVR is equivalent to that of all-pedicle screw constructs. The procedure gives favorable correction, is advantageous for kyphosis compared with segmental screw fixation, and uses the minimum number of pedicle screws. Therefore, the PSTH-DVR procedure may be useful for treatment of idiopathic scoliosis.

The Thoracic Lordosis Correction Improves Sacral Slope and Walking Ability in Neuromuscular Scoliosis.

Retrospective study. To report on neuromuscular patients with preserved walking ability, but forward bending of the body due to thoracic lordosis, and to suggest thoracic lordosis correction as the surgical treatment. It is an established fact that lumbar lordosis or pelvic parameter is directly related to thoracic sagittal balance. However, the reverse relationship has not been fully defined yet. Loss of thoracic kyphosis results in positive sagittal balance, which causes walking difficulty. Neuromuscular patients with thoracic lordosis have not been reported yet, and there have been no reports on their surgical treatments. This study analyzed 8 patients treated with thoracic lordosis correction surgery. Every patient was diagnosed with muscular dystrophy. In thoracic lordosis correction surgery, anterior release was performed in the first stage and posterior segmental instrumentation was performed in the second stage. Radiographic parameters were compared and walking ability was evaluated with gait analysis. All patients were classified according to the modified Rancho Los Amigos Hospital system preoperatively and 2 years postoperatively to evaluate functional ability. The average follow-up period was 2.9 years. Before surgery, the mean thoracic sagittal alignment was -2.1-degree lordosis, the mean Cobb angle and sacral slope increased to 36.3 and 56.6 degrees, respectively. The anterior pelvic tilt in gait analysis was 29.3 degrees. At last follow-up after surgery, the mean thoracic sagittal alignment changed to 12.6-degree kyphosis, and the Cobb angle and sacral slope decreased to 18.9 and 39.5 degrees, respectively. Lumbar lordosis and the sacral slope showed significant positive correlation (P<0.001). The improvement in thoracic lordosis showed a significant correlation to the preoperative flexibility of the major curve (P=0.028). The anterior pelvic tilt in gait analysis improved to 15.4 degrees. The functional ability improved in 2 (50%) of 4 patients in class 2 and maintained in remaining 6 patients 2 years after surgery. Thoracic lordosis correction surgery in neuromuscular scoliosis patients with thoracic lordosis improved the sacral slope in the standing position and the anterior pelvic tilt in gait. Sagittal imbalance was compensated by the spinopelvic mechanism, and back and hip extensor muscles seem to play a major role in this compensation.

A Uniquely Shaped Rod Improves Curve Correction in Surgical Treatment of Adolescent Idiopathic Scoliosis.

A retrospective cohort study. The aim of this study is to determine the initial curve correction in patients surgically treated for adolescent idiopathic scoliosis (AIS) using either beam-like rods (BRs) or traditional circular rods (CRs). Posterior fusion using all pedicle screw instrumentation has become the standard for the surgical treatment of AIS. Traditionally, the rod is circular in the cross-sectional plane. Recent biomechanical studies suggest that a beam-like structure of the rod may enhance the stiffness of the construct and thereby possibly improve curve correction. Two consecutive series of patients surgically treated for AIS between May 2011 and May 2015 were included in the study. Patients were all treated with an ultralow profile all-pedicle screw implant system. In the first series, conventional 5.5 mm CoCr CR were used, and in the second series, 5.5 mm CoCr BR were used. Antero-posterior and lateral radiographs preoperatively and within seven days after surgery were used to measure the correction obtained. The first 60 patients were operated with CR and the subsequent 69 with BR. There was no statistical difference in age, gender, preoperative curve magnitude, Lenke type, or number of levels instrumented (P = 0.451). Major curve correction was significantly better in the BR group than in the CR group (66 vs. 57%) (P < 0.001). We found no difference in preoperative flexibility, secondary curve correction, sagittal balance, or coronal balance (P > 0.058). A postoperative decrease in thoracic kyphosis was seen with no significant difference between groups. Median T5-T12 change was -7° versus -3° for BR and CR, respectively (P = 0.051). A BR design results in a significantly better curve correction than conventional rods, but the difference is moderate and the clinical value is uncertain. 3.

Flexibility analysis in adolescent idiopathic scoliosis on side-bending images using the EOS imaging system

IntroductionAnalysis of preoperative flexibility in adolescent idiopathic scoliosis (AIS) is essential to classify the curves, determine their structurality, and select the fusion levels during preoperative planning. Side-bending x-rays are the gold standard for the analysis of preoperative flexibility. The objective of this study was to examine the feasibility and performance of side-bending images taken in the standing position using the EOS imaging system. Material and methodsAll patients who underwent preoperative assessment between April 2012 and January 2013 for AIS were prospectively included in the study. The work-up included standing AP and lateral EOS x-rays of the spine, standard side-bending x-rays in the supine position, and standing bending x-rays in the EOS booth. The irradiation dose was measured for each of the tests. Two-dimensional reducibility of the Cobb angle was measured on both types of bending x-rays. ResultsThe results were based on the 50 patients in the study. No significant difference was demonstrated for reducibility of the Cobb angle between the standing side-bending images with the EOS imaging system and those in the supine position for all types of Lenke deformation. The irradiation dose was five times lower during the EOS bending imaging. ConclusionThe standing side-bending images in the EOS device contributed the same results as the supine images, with five times less irradiation. They should therefore be used in clinical routine. Level of evidence2.

The Usefulness of Employing an Electronic Traction Table to Determine Flexibility in Adolescent Idiopathic Scoliosis.

The aim of the study was to develop new equipment for the assessment of the flexibility of the spine with different forces. This new system should provide a different perspective to adolescent idiopathic scoliosis (AIS) for the selection of fusion levels and surgical success. Eighteen patients suffering from AIS who were scheduled to undergo posterior instrumented spinal fusion in our clinic were recruited in this study. The Electronic Traction Table (ETT) that was designed in our clinic was used to evaluate the radiogical and clinical parameters of the spine. The significant prescriptive angle of major Cobb angles between postoperative angles were longitudinal traction and lateral pushing Cobb angles. Longitudinal traction and lateral pushing angles were more correlated with correction ratios. There was a significant difference between longitudinal traction minor Cobb angle, longitudinal traction lateral pushing minor Cobb angle and postoperative minor Cobb angles. The deformity is needed to balance both tractional and rotational forces and useful technique to evaluate curve flexibility before the operation. Electronic traction table is a new device for determining preoperative flexibility with longitudinal traction and lateral pushing radiographs. It can be useful for choosing selective fusion levels at the proximal and distal end of the vertebral column.

All-Pedicle Screw Versus Hybrid Instrumentation in Adolescent Idiopathic Scoliosis Surgery

Comparative analysis of 2 groups of patients who underwent surgical treatment of adolescent idiopathic scoliosis (AIS). To compare a segmental pedicle screw only system with a hybrid system for the treatment of Lenke type 1 AIS curves. Although previous AIS studies have tried to compare various constructs with the all-pedicle screw fixation, all have failed to address important confounding variables, such as skeletal maturity, preoperative flexibility of the curve, and factors associated with a multicenter or multisurgeon analysis. The medical records and spinal radiographs of patients with AIS treated surgically by a single surgeon between 2000 and 2009 were retrospectively reviewed. Patients with Lenke type 1 curves and minimum follow-up of 2 years were divided into 2 groups that were meticulously matched: group 1 consisted of patients in whom the all-pedicle screw construct was used, whereas group 2 included patients who were treated with the hybrid hook-screw system. Group 1 included 34 patients and group 2 included 29 patients. At the last follow-up, thoracic curve correction averaged 70.4% for the all-pedicle screw group and 60% for the hybrid group (P = 0.19). The all-pedicle screw group showed a significantly greater increase in thoracic kyphosis than the hybrid group system (P = 0.04). Global sagittal balance showed greater improvement in the all-pedicle screw group during the immediate postoperative that was lost by the last follow-up. The all-pedicle screw system revealed less intraoperative blood loss but greater operating time than the hybrid construct. After controlling for length of follow-up, no statistical difference in any of the radiographical parameters measured was recorded. With the exception of global sagittal balance, the pedicle screw system provided better maintenance of its corrective parameters when followed for greater than two years. 3.

All-pedicle-screw versus hybrid hook-screw instrumentation for posterior spinal correction surgery in adolescent idiopathic scoliosis: a curve flexibility matched-pair study

Comparisons of all-pedicle-screw (PS) and hybrid hook-screw (HS) instrumentation for the treatment of adolescent idiopathic scoliosis (AIS) have produced conflicting results. The aim of this study was to compare all-pedicle-screw and hybrid hook-screw instrumentation for the treatment of AIS using a matched-pair study design in which preoperative flexibility was matched. In this retrospective study conducted at one medical center, 21 all-pedicle-screw/hybrid hook-screw pairs of Lenke type I AIS patients matched for age, height, weight, body mass index, sex, and preoperative curve flexibility who had been treated at our institution from January 2000 to October 2006 were selected. Postoperative and 2-year postoperative coronal curve correction, postoperative kyphosis, blood transfusion needs, operation time, and hospital cost were measured and analyzed statistically. The PS group compared with the HS group had better postoperative correction (P = 0.0231) and 2-year coronal curve correction (P = 0.016). While statistically significant (P = 0.0073), the postoperative Cobb angle was only 3° less in the PS group, Maintenance of correction after 2 years was better in the PS group (P = 0.0016). The PS group had less blood loss (P < 0.0001) and shorter operation time (P < 0.0001), but the hospital cost for the PS group was higher (P < 0.0001). All-pedicle-screw and hybrid hook-screw instrumentations are comparable with regard to curve correction, but all-pedicle screw instrumentation reduces blood loss during surgery and shortens the operation time, which may help shorten healing time.

Comparison of Selective Anterior Versus Posterior Screw Instrumentation in Lenke5C Adolescent Idiopathic Scoliosis

Retrospective review of anterior and posterior fusions for treatment of Lenke5C adolescent idiopathic scoliosis (AIS). To compare the clinical and radiographic results of anterior versus posterior pedicle screw instrumentation in Lenke5C AIS. Anterior and posterior pedicle screw instrumentations are 2 established methods of correcting Lenke5C AIS. However, there are few reports that compare the 2 methods. Forty-six consecutive patients with Lenke5C AIS curves underwent selective lumbar or thoracolumbar fusion (1999-2005). Twenty-two patients had anterior surgery, and 24 patients had posterior surgery. Patients were evaluated at a minimum 2-year follow-up. No complications occurred in either group. The number of levels involved in the major curve was similar for the anterior and posterior groups (5.5 vs. 5.7). Preoperative thoracic (24.13 degrees +/- 4.9 degrees vs. 22.88 degrees +/- 5.14 degrees) and lumbar/thoracolumbar (50.2 degrees +/- 7.52 degrees vs. 52.2 degrees +/- 6.40 degrees). Cobb values for the 2 groups were also similar. The percent correction of the lumbar curve was similar between the 2 groups at all stages of follow-up (56% vs. 57.7%), as was the percent of spontaneous correction of the unfused thoracic curve (25% vs. 27.2%). However, fusion levels were significantly shorter in the anterior group (mean, 5.09 vs. 6.13), and there were 8 patients (4 in the anterior group and 4 in the posterior group) whose thoracic curve became greater at the latest follow-up. The thoracolumbar/lumbar-thoracic Cobb ratio for these 8 patients was less than that for the other patients (1.34 vs. 2.43), and their curve flexibility was worse. Selective anterior and posterior screw instrumentation both achieved good surgical lumbar and subsequent spontaneous thoracic correction. There was no statistically significant difference between the 2 groups in lumbar correction or thoracic correction, but fusion levels were shorter in the anterior group. Patients with late thoracic curve decompensation had smaller thoracolumbar/lumbar-thoracic Cobb ratios and less preoperative flexibility than those who did not decompensate.

Posterior Multilevel Vertebral Osteotomy for Correction of Severe and Rigid Neuromuscular Scoliosis

Prospective study. To determine the effectiveness and correction with posterior multilevel vertebral osteotomy in severe and rigid curves without anterior release. For the correction of severe and rigid scoliotic curve, anterior-posterior combined or posterior vertebral column resection (PVCR) procedures are used. Anterior procedure might compromise pulmonary functions, and PVCR might carry risk of neurologic injuries. Therefore, authors developed a new technique, which reduces both. Thirteen neuromuscular patients (7 cerebral palsy, 2 Duchenne muscular dystrophy, and 4 spinal muscular atrophy) who had rigid curve >100 degrees were prospectively selected. All were operated with posterior-only approach using pedicle screw construct. To achieve desired correction, posterior multilevel vertebral osteotomies were performed at 3 to 5 levels (apex, and 1-2 levels above and below apex) through partial laminotomy sites connecting from concave to convex side, just above the pedicle; and repeated cantilever manipulation was applied over temporary short-segment fixation, above and below the apex, on convex side. On concave side, rod was assembled with screws and rod-derotation maneuver was performed. Finally, short-segment fixation on convex side was replaced with full-length construct. Intraoperative MEP monitoring was applied in all. Mean age was 21 years and average follow-up was 25 months. Average preoperative flexibility was 20.3% (24.1 degrees). Average Cobb's angle, pelvic obliquity, and apical rotation were 118.2 degrees, 16.7 degrees, and 57 degrees preoperatively, respectively, and 48.8 degrees, 8 degrees, and 43 degrees after surgery showing significant correction of 59.4%, 46.1%, and 24.5%. Average number of osteotomy level was 4.2 and average blood loss was 3356 +/- 884 mL. Mean operation time was 330 +/- 46 minutes. None of the patient required postoperative ventilator support or displayed any signs of neurologic or vascular injuries during or after the operation. This technique should be recommended because (1) it provides release of anterior column without anterior approach and (2) our results supports its superiority as a technique.

The Effect of Soft Tissue Properties on Spinal Flexibility in Scoliosis

Biomechanical analysis of the scoliotic thoracolumbar spine and ribcage using a three-dimensional finite element model. To explore how the mechanical properties of spinal ligaments and intervertebral discs affect coronal curve flexibility in the fulcrum bending test. Preoperative coronal curve flexibility assessment is of key importance in the surgical planning process for scoliosis correction. The fulcrum bending radiograph is one flexibility assessment technique which has been shown to be highly predictive of potential curve correction using posterior surgery; however, little is known about the extent to which soft tissue structures govern spinal flexibility. CT-derived spinal anatomy for a 14-year-old female adolescent idiopathic scoliosis patient was used to develop the three-dimensional finite element model. Physiologic loading conditions representing the gravitational body weight forces acting on the spine when the patient lies on their side over the fulcrum bolster were simulated. Initial mechanical properties for the spinal soft tissues were derived from existing literature. In 6 separate analyses, the disc collagen fiber and ligament stiffness values were reduced by 10%, 25%, and 40% respectively, and the effects of reduced tissue stiffness on fulcrum flexibility were assessed by comparison with the initial model. Finally, the effect of discectomy on fulcrum flexibility was simulated for thoracic levels T5-T12. Reducing disc collagen fiber stiffness resulted in a greater change in segmental rotations in the fulcrum bending test than reducing ligament stiffness. However, reductions of up to 40% in disc collagen fiber stiffness and ligament stiffness produced no clinically measurable increase in fulcrum flexibility. By contrast, after removal of the discs, the simulated fulcrum flexibility increased by more than 80% compared with the initial case. Homogeneous reduction in either the disc collagen fiber or ligament stiffness had minimal influence on scoliotic curve reducibility. However, discectomy simulation shows that the intervertebral discs are of critical importance in determining spinal flexibility.

A Pedicle Screw Construct Gives an Enhanced Posterior Correction of Adolescent Idiopathic Scoliosis When Compared With Other Constructs

Tricenter retrospective cohort study of 72 patients who underwent posterior correction of Lenke 1 adolescent idiopathic scoliosis (AIS). Each center represented a single surgeon using only one type of construct. Compare the initial postoperative and 2-year follow-up correction of Lenke 1 AIS curves, after accounting for the preoperative flexibility of the curves. There are multiple reports in literature of the enhanced posterior corrective ability of the pedicle screw in the treatment of AIS. Unfortunately, none of these reports took into account the preoperative flexibility of the curve. It stands to reason that rigid curves will not correct as much as flexible curves irrespective of the nature of the construct. Groups were as follows: Group 1 (proximal and distal hooks and segmental intraspinous collar button wires), 24 patients; Group 2 (proximal hooks, distal screws, and apical sublaminar wires), 23 patients; and Group 3 (pedicle screws only), 25 patients. The postoperative correction percentage was expressed as a ratio of the preoperative flexibility and was termed Cincinnati correction index (CCI). Mathematically speaking the CCI equals (postoperative correction/preoperative erect Cobb angle) divided by (supine bending preoperative correction/preoperative erect Cobb angle). The postoperative sagittal correction was also measured. CCI 2 (at 2-year follow-up) for Group 1 was 1.71, for Group 2 was 1.34, and for Group 3 was 1.41. The differences were not statistically significant. Within Group 1, however, there was a statistically significant difference between CCI (1.95) and CCI 2 (1.71), indicating a statistically significant loss of correction over 2 years. However, in terms of absolute values, there was only a 4 degree (average) difference between the initial and the 2-year postoperative Cobb measurement, rendering the loss off correction clinically insignificant. No such statistically or clinically significant differences were noted within Groups 2 and 3. Group 1 and Group 3 constructs further lordosed the curve by 8 degrees and 11 degrees, respectively, whereas the Group 2 construct retained or marginally increased the preoperative kyphosis. The Group 3 (pedicle screw only) construct did not give an enhanced correction of Lenke 1 AIS, when the preoperative flexibility of the curve was considered. Also, contrary to popular belief, the pedicle screw construct has a lordosing effect on the thoracic spine. Therefore, we think that there is no significant advantage in using a relatively expensive pedicle screw construct in the correction of Lenke 1 AIS.

Outcomes of Surgical Treatment in Male Versus Female Adolescent Idiopathic Scoliosis Patients

This research was part of a multicenter study of the surgical treatment of adolescent idiopathic scoliosis (AIS). To compare the radiographic and perioperative surgical treatment outcomes of male AIS patients with female AIS patients. The results of treatment in male patients with idiopathic scoliosis have not been widely reported. Only 1 study has evaluated the differences in operative treatment outcomes between male and female patients with AIS. Data were collected for patients who met the indications for surgical intervention at 8 separate institutions. Radiographic, perioperative, and pulmonary function variables for male and female AIS patients treated surgically were analyzed. A univariate analysis of variance with the alpha level adjusted to P < or = 0.01 was used. The data for 547 (449 females and 98 males) patients were included in this analysis. Posterior instrumentation (vs. anterior instrumentation) was performed slightly more often in males than females (51% vs. 44%, respectively). The preoperative primary curve magnitude was similar for both genders, but flexibility was less in males (44% vs. 49%; P = 0.01). Postoperative percent correction and the ratio of percent correction to preoperative flexibility were both similar in males versus females. Analysis of the perioperative variables yielded that estimated blood loss was higher in males than females (1342 vs. 898 cc, respectively; P = 0.001). Males reported greater pain on postoperative day 1 (6.1 vs. 5.4; P = 0.01), however, conversion to oral pain medication was similar for both. Preoperative and postoperative pulmonary function was similar for both genders. Male AIS patients had slightly more rigid primary curves compared to females but a similar degree of postoperative scoliosis correction. Differences in the preoperative status and perioperative course did not compromise the outcomes of surgical treatment as in all other measures; the results were comparable between the genders.

Can we predict the ultimate lumbar curve in adolescent idiopathic scoliosis patients undergoing a selective fusion with undercorrection of the thoracic curve?

Retrospective review of anterior and posterior fusions for treatment of adolescent idiopathic thoracic scoliosis. To delineate the best factors determining final lumbar curve magnitude in patients with adolescent idiopathic scoliosis undergoing a selective thoracic anterior or posterior spinal fusion at or proximal to the first lumbar vertebra. Although spontaneous lumbar curve correction occurs consistently following a selective thoracic anterior or posterior spinal fusion, the degree of correction is somewhat unpredictable. One hundred consecutive patients with major thoracic-compensatory lumbar adolescent idiopathic scoliosis treated by a single surgeon with either selective posterior spinal fusion (n = 44) or anterior spinal fusion (n = 56) of the main thoracic region with an unfused lumbar spine with a lumbar B modifier (lumbar apex touching the center sacral vertical line) or lumbar C modifier (lumbar apex completely lateral to the center sacral vertical line) were retrospectively reviewed. Those patients who maintained excellent postoperative coronal balance, with spontaneous lumbar curve correction, had their thoracic Cobb corrected intraoperatively to a measurement very close to but not more than that of the preoperative thoracic push-prone Cobb. Stepwise multiple linear regression analysis was used to develop a formula to help predict lumbar response in those patients undergoing selective thoracic fusion. This is represented in the following formula: Final lumbar Cobb = 14.4 + 3.06 (lumbar modifier; 0 = B, 1 = C) + 0.30 (preoperative standing lumbar Cobb) - 0.18 (preoperative supine lower Cobb) + 0.81(preoperative push/prone lumbar Cobb) - 0.15(preoperative standing thoracic Cobb) - 0.16(% thoracic Cobb change from preoperative to immediate postoperative). Final model R2 = 0.72. Of the preoperative measurements examined, the preoperative push-prone is the best preoperative flexibility radiograph to predict the final lumbar curve measurement and, along with other factors, can be used to formulate a model that will help the treating surgeon more confidently predict the final lumbar curve response in patients undergoing a selective thoracic fusion.

Lumbar Pedicle Screws Versus Hooks

A retrospective assessment of the effectiveness of lumbar pedicle screws versus laminar hooks in lumbar curve correction with double major curves in adolescent idiopathic scoliosis. To determine if pedicle screw fixation of the lumbar spine has any advantage compared with multiple laminar hook instrumentation in the treatment of double major curves in adolescent idiopathic scoliosis. Although hooks have been used most commonly, pedicle screws may offer advantages in correction and maintenance of reduction of the lumbar curve in adolescent idiopathic scoliosis. A consecutive series of 39 patients with double major curves underwent thoracic and lumbar instrumentation by a single surgeon. Lumbar pedicle screws and hooks were used in 20 patients (Group S) and in 19 patients only lumbar hooks were used (Group H). Thoracic Cotrel-Dubousset instrumentation with hooks was the same in both groups. Preoperative age, gender, bracing, and Cobb angles were similar in both groups. Preoperative, 1-month postoperative, and latest follow-up standing posteroanterior and lateral spine radiographs were blinded to the surgeon and lumbar instrumentation covered to hide its identity. Measurements included Cobb angles, preoperative flexibility, lumbar and thoracic apical vertebral deviation, and reduction of lateral tilt and lateral displacement of the first free lumbar vertebra below the instrumentation. Percent correction, maintenance of correction at follow-up, and total levels fused were calculated. The mean follow-up was 3.5 years (range, 2-8 years), which was similar for Groups H and S. Pedicle screws appear to offer some advantage in lumbar curve correction, maintenance of correction, and correction of the uninstrumented spine below the fusion when compared with the use of hooks alone. Horizontalization of the first free lumbar vertebra below the instrumentation percent correction of tilt: 62% screws vs. 11% hooks; P = 0.0003), residual tilt (8 degrees screws vs. 17 degrees hooks; P = 0.004), and loss of horizontalization at follow-up (5% screws vs. 26% hooks) were dramatically better for the group using screws. Lumbar curve correction (72% screws vs. 60% hooks; P = 0.026), loss of lumbar curve correction (5% screws vs. 13% hooks), and correction of lateral apical vertebral deviation (2.2-cm screws vs. 1.5-cm hooks or 63% vs. 31%; P = 0.013) were better when screws were used. There was no significant difference in loss of correction of the thoracic curves (35% vs. 37%) or any difference in loss of correction of lateral displacement of the thoracic apical vertebra (12% vs. 14%). There was no difference in total levels fused, operative blood loss, operative time, or ultimate patient outcome. No patients in either group had spinal imbalance at latest follow-up. There were no complications related to pedicle screw placement. Two cases of transient postoperative superior mesenteric artery syndrome (duodenal obstruction by the superior mesenteric artery) in the pedicle screw group are attributed to acute correction of the lumbar scoliosis and thoracolumbar kyphosis with resultant lordosis at the thoracolumbar junction. Lumbar pedicle screws may offer greater lumbar curve correction, better maintenance of correction, and greater correction of the uninstrumented spine below double major curves. No complications were associated with the placement of pedicle screws.

The segmental effect of Cotrel-Dubousset instrumentation on vertebral rotation, rib hump and the thoracic cage in idiopathic scoliosis.

The segmental effect of Cotrel-Dubousset instrumentation (CDI) on the spine and thoracic cage was investigated in 38 patients with adolescent idiopathic scoliosis by preoperative and postoperative postero-anterior and lateral radiographs and computed tomography from T1 to S1. Mean Cobb angle decreased by 67%. The T5-T12 kyphosis in the hypokyphotic patients increased on average by 8.4 degrees (P < 0.001). Average preoperative as well as postoperative maximal vertebral rotation was located at the apex level, and was reduced from 19.0 degrees to 14.3 degrees (P < 0.001). All vertebrae between the upper and lower instrumented vertebrae were significantly derotated. Average derotation for the apical zone was 4.8 degrees (P < 0.001), for the upper instrumented zone it was 2.5 degrees (P < 0.01), and for the lower instrumented zone it was 2.6 degrees (P < 0.01). Vertebral derotation was significantly higher in the apical zone than in the upper and lower instrumented zones. The apical rib hump index (RHi) decreased by 38% (P < 0.001) and the cumulative RHi for the five apical levels decreased by 34% (P < 0.001). The RHi for the two levels above and below the instrumentation each decreased by 20% (n.s.). No significant increase in sagittal or transverse rib cage diameter at any level was observed. The translation in the coronal plane of the apical vertebra of major right thoracic curves improved significantly (P < 0.001). The preoperative flexibility index of the major curve correlated positively (r = 0.47) with derotation at the apex level (P < 0.01). However, no correlation was found between flexibility index and reduction of RHi at the apex level. Vertebral derotation did not correlate with reduction in RHi at any level. The study shows that CDI results in a postoperative three-dimensional improvement of the spine and a limited improvement of the thoracic cage, with no tendency towards a worsened deformity at any level within or outside the instrumentation.