Contrasting catalytic profiles of multiheme nitrite reductases containing CxxCK heme-binding motifs.

The multiheme cytochromes from Thioalkalivibrio nitratireducens (TvNiR) and Escherichia coli (EcNrfA) reduce nitrite to ammonium. Both enzymes contain His/His-ligated hemes to deliver electrons to their active sites, where a Lys-ligated heme has a distal pocket containing a catalytic triad of His, Tyr, and Arg residues. Protein-film electrochemistry reveals significant differences in the catalytic properties of these enzymes. TvNiR, but not EcNrfA, requires reductive activation. Spectroelectrochemistry implicates reduction of His/His-ligated heme(s) as being key to this process, which restricts the rate of hydroxide binding to the ferric form of the active-site heme. The K M describing nitrite reduction by EcNrfA varies with pH in a sigmoidal manner that is consistent with its modulation by (de)protonation of a residue with pK a ≈ 7.6. This residue is proposed to be the catalytic His in the distal pocket. By contrast, the K M for nitrite reduction by TvNiR decreases approximately linearly with increase of pH such that different features of the mechanism define this parameter for TvNiR. In other regards the catalytic properties of TvNiR and EcNrfA are similar, namely, the pH dependence of V max and the nitrite dependence of the catalytic current-potential profiles resolved by cyclic voltammetry, such that the determinants of these properties appear to be conserved.

A functional description of CymA, an electron-transfer hub supporting anaerobic respiratory flexibility in Shewanella.

CymA (tetrahaem cytochrome c) is a member of the NapC/NirT family of quinol dehydrogenases. Essential for the anaerobic respiratory flexibility of shewanellae, CymA transfers electrons from menaquinol to various dedicated systems for the reduction of terminal electron acceptors including fumarate and insoluble minerals of Fe(III). Spectroscopic characterization of CymA from Shewanella oneidensis strain MR-1 identifies three low-spin His/His co-ordinated c-haems and a single high-spin c-haem with His/H(2)O co-ordination lying adjacent to the quinol-binding site. At pH 7, binding of the menaquinol analogue, 2-heptyl-4-hydroxyquinoline-N-oxide, does not alter the mid-point potentials of the high-spin (approximately -240 mV) and low-spin (approximately -110, -190 and -265 mV) haems that appear biased to transfer electrons from the high- to low-spin centres following quinol oxidation. CymA is reduced with menadiol (E(m) = -80 mV) in the presence of NADH (E(m) = -320 mV) and an NADH-menadione (2-methyl-1,4-naphthoquinone) oxidoreductase, but not by menadiol alone. In cytoplasmic membranes reduction of CymA may then require the thermodynamic driving force from NADH, formate or H2 oxidation as the redox poise of the menaquinol pool in isolation is insufficient. Spectroscopic studies suggest that CymA requires a non-haem co-factor for quinol oxidation and that the reduced enzyme forms a 1:1 complex with its redox partner Fcc3 (flavocytochrome c3 fumarate reductase). The implications for CymA supporting the respiratory flexibility of shewanellae are discussed.

Restoration of thoracic kyphosis after operative treatment of adolescent idiopathic scoliosis: a multicenter comparison of three surgical approaches.

STUDY DESIGN: Multicenter analysis of 3 groups of patients who underwent surgical treatment for adolescent idiopathic scoliosis (AIS). OBJECTIVE.: To evaluate 3 surgical approaches to determine the modality that has the greatest influence on improving thoracic kyphosis. SUMMARY OF BACKGROUND DATA: AIS is characterized by thoracic hypokyphosis which may be restored to normal to varying degrees with surgery. METHODS: A multicenter retrospective AIS surgical database was reviewed. Patients with only a structural main thoracic curve (Lenke 1, 2, or 3), and instrumentation of only the main thoracic curve were included. Lateral radiographs were analyzed to determine sagittal plane measurements before surgery, after surgery at 6 to 8 weeks, 1 year, and 2 years. The 3 groups were compared and statistical significance was defined as P < 0.05. RESULTS: Three groups were analyzed: (1) ASF group (n = 135), Anterior spinal fusion and instrumentation, (2) PSF-Hybrid group (n = 86), PSF with proximal hooks, +/- apical wires and distal pedicle screws, and 3) PSF-Hooks group (n = 132), PSF with only hooks. All groups had similar preoperative coronal main thoracic curve magnitudes (ASF: 50.6 degrees , PSF-Hybrid: 49.1 degrees , PSF-Hooks: 52.0 degrees ) and thoracic kyphosis (ASF: 23.7 degrees , PSF-Hybrid: 19.3 degrees , PSF-Hooks: 21.9 degrees ). After surgery, the T5-T12 kyphosis was greater in the ASF group (25.1 degrees ) compared with PSF-Hooks (19.0 degrees ) and PSF-Hybrid (18.5 degrees (P < 0.05). At 1 year, thoracic kyphosis (T5-T12) remained greater in the ASF group (28.8 degrees ) compared with PSF-Hooks (22.6 degrees ) and PSF-Hybrid (20.2 degrees ) (P < 0.05), and was also greater at 2 years (29.9 degrees vs. 23.8.8 degrees and 19.7 degrees ) (P < 0.05). Kyphosis at the thoracolumbar junction was not seen in the PSF-Hybrid group. Lumbar lordosis increased only in the ASF group in response to the increase in thoracic kyphosis. CONCLUSION: ASFI is the best method to restore thoracic kyphosis when compared with posterior approaches using only hooks or a hybrid construct in the treatment of thoracic adolescent idiopathic scoliosis.

Adolescent idiopathic scoliosis patients report increased pain at five years compared with two years after surgical treatment.

STUDY DESIGN: A multicenter study of changes in Scoliosis Research Society (SRS) outcome measures after surgical treatment of adolescent idiopathic scoliosis (AIS). OBJECTIVE: To evaluate changes in patient determined outcome measures between 2 and 5 years after AIS surgery. SUMMARY OF BACKGROUND DATA: Current surgical procedures have been shown to improve subjective measures in patients with AIS. At 2-year follow-up, AIS patients reported significant improvement in all 4 preoperative domains of the SRS questionnaire. In addition, the major Cobb angle was shown to be negatively correlated with preoperative scores in the pain, general self-image, and general function domains. Five-year SRS scores have not been evaluated previously. METHODS: A multicenter, prospectively generated database was used to obtain perioperative, radiographic, and SRS-24 outcomes data. The inclusion criteria were: a diagnosis of AIS, surgical treatment (anterior, posterior, or combined), a comprehensive set of radiographic measures, and completed preoperative, 2-year, and 5-year SRS questionnaires. Repeated measures analysis of variance was used to compare changes in patient responses for each of the 7 outcome domains. Univariate analysis of variance was used to compare the change in pain score at 5 years to the level of the lowest instrumented vertebrae and surgical approach. A correlation analysis was used to determine the association between changes in any of the radiographic variables and changes in SRS scores. The data were checked for normality and equal variances, and the level of significance was set at P < 0.01. RESULTS: Forty-nine patients (42 women, 7 men; 14.2 +/- 2.1 year old; 5.4 +/- 0.6 years follow-up) met the inclusion criteria for this study. Thirty-seven of 49 (76%) of these patients underwent an open or thoracoscopic anterior procedure. SRS-24 scores improved significantly in 3 of the 4 preoperative domains at the 2-year visit. At 5 years postop, a statistically significant decrease in the pain score (4.2 +/- 0.6 to 3.9 +/- 0.9, P = 0.003) and a trend toward worsening scores in 4 other domains was observed; however, Patient Satisfaction scores remained unchanged. Lowest instrumented vertebrae and surgical approach could not be correlated to changes in the pain score. In addition, no correlation was found between changes in any of the 21 radiographic measures evaluated and changes in SRS scores. CONCLUSION: There was a statistically significant increase in reported pain from 2 to 5 years after surgical treatment; however, the etiology of worsening pain scores could not be elucidated. Given continued patient satisfaction, the clinical relevance of this small reduction remains unknown. Nevertheless, this observation deserves further evaluation and must be considered in relation to the natural history of this disease.

The impact of perioperative complications on clinical outcome in adult deformity surgery.

STUDY DESIGN: Retrospective case-control series. OBJECTIVE: The purpose of this study is to determine whether perioperative complications alter subsequent clinical outcome measures in adult spinal deformity surgery. SUMMARY OF BACKGROUND DATA: Increasingly, the benefit of surgical intervention is being evaluated based on patient reported outcomes and standardized health related quality of life (HRQOL) measures. As improvement or deterioration in HRQOL scores becomes a standard for clinical evaluation in adult spinal deformity, the correlation between HRQOL outcome scores and historic benchmarks, such as curve correction, sagittal balance, fusion healing, or the occurrence of a complication, must be clarified. METHODS: This study analyzes a prospective multicenter data base for adult spinal deformity. Patients with major, minor, and no complications were matched using a logistic regression technique producing 46 patients in each group. Standardized outcome measures at baseline and at 1 year postop were compared. RESULTS: Forty-seven major complications were reported in 46 patients. Sixty-two minor complications were noted in 46 patients. Comparison between the 3 complication groups revealed that 1-year postoperative outcome measures were not statistically different for the Scoliosis Research Society Outcomes Instrument, Medical Outcomes Short Form-36 (SF-12), Oswestry Disability Index, or Numerical Pain Scales. The only significant interaction was in the rate of change from preop to 1-year postop for the SF-12 general health subscale. For the group with major complications, SF-12 general health deteriorated by 2.1 points from preop to 1-year postop. During the same period, the group with minor complications experienced an improvement of 4.2 points and the group with no complications experienced an improvement of 1.5 points. CONCLUSION: This study suggests that risk for minor complications may be a less substantial obstacle than previously assumed for surgical treatment in adult spinal deformity. In contrast, major complications were reported in approximately 10% of cases and adversely affected outcome as evidenced by the deterioration in SF-12 general health scores at 1 year after surgery.

Evidence based medicine: analysis of Scheuermann kyphosis.

STUDY DESIGN: : A review of the current literature using evidence-based medicine (EBM) regarding etiology, natural history, and treatment of Scheuermann kyphosis. OBJECTIVE: : To provide current concepts for the rational evaluation and treatment of Scheuermann kyphosis supported by EBM. SUMMARY OF BACKGROUND DATA: : The literature concerning etiology, natural history, and treatment of Scheuermann disease has mixed views and recommendations, most of which are not strongly supported with levels of evidence. METHODS: : A thorough database search was performed in order to obtain the best current information and levels of evidence on etiology, natural history, and treatment options for Scheuermann kyphosis based on EBM criteria. RESULTS AND CONCLUSION: : Scheuermann kyphosis is the most common cause of hyperkyphosis in adolescence. Its true etiology remains unknown, but there appears to be a strong genetic as well as an environmental contribution. The kyphotic deformity is frequently attributed to "poor posture" resulting in delayed diagnosis, and treatment indications remain debated because the natural history has not been clearly defined. When recognized early in adolescence with progressive kyphosis, bracing treatment will usually result in modest correction of the deformity. Symptomatic adolescents with severe deformity have demonstrated significant deformity correction following surgical intervention; however, clinical outcomes data are not yet available, and the studies available do not have strong levels of evidence.

Scheuermann's kyphosis.

Scheuermann's disease is the most common cause of structural kyphosis in adolescents. The kyphotic deformity is frequently attributed to "poor posture," resulting in delayed diagnosis and treatment. Indications for treatment remain somewhat debated, because the true natural history of the disease has not been clearly defined. Brace treatment is almost always successful in patients with kyphosis between 55 degrees and 80 degrees if the diagnosis is made before skeletal maturity. Kyphosis greater than 80 degrees in the thoracic spine or 65 degrees in the thoracolumbar spine is almost never treated successfully without surgery in symptomatic patients. Surgical treatment in adolescents and young adults should be considered if there is documented progression, refractory pain, loss of sagittal balance, or neurologic deficit. The major postoperative complication after surgical treatment is junctional kyphosis proximally or distally, which is usually related to not including all levels of the kyphosis or overcorrection of the deformity (>50%). With proper patient selection, excellent outcomes can be expected with nonoperative or operative treatment in patients with Scheuermann's disease.

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

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

Distal junctional kyphosis of adolescent idiopathic thoracic curves following anterior or posterior instrumented fusion: incidence, risk factors, and prevention.

STUDY DESIGN: This is a retrospective multicenter analysis of a subset of 375 patients with thoracic adolescent idiopathic scoliosis (AIS) treated with either anterior (238) or posterior (137) fusion with preoperative or postoperative distal junctional kyphosis (DJK) >or=10 degrees . OBJECTIVES: To determine the incidence of DJK before and after surgery in patients with AIS undergoing either anterior or posterior thoracic fusion, and provide recommendations for prevention. SUMMARY OF BACKGROUND DATA: DJK following surgical treatment for AIS may result in pain, imbalance, and unacceptable deformity. The true incidence of DJK following selective anterior or posterior instrumentation and fusion is unknown, as are "risk factors" for its development. METHODS: Mean age at surgery was 14.4 years (range 9.1-20.9) in the anterior group and 14.7 years (range 10.2-20.7) in the posterior. Analysis included the Cobb and instrumented levels of the thoracic curves, and sagittal measurements, all on preoperative and 2-year follow-up standing 36-in radiographs. RESULTS: In the anterior group, the incidence of preoperative DJK was 4.2%, and postoperative DJK was 7.1%. In the posterior group, the incidence of preoperative DJK was 5.0% and 14.6% after surgery. When postoperative DJK developed in the posterior group, mean postoperative T10-L2 was +17 degrees kyphosis compared to +2 degrees in the posterior group without DJK (P < 0.001). When postoperative DJK developed in the anterior group, mean postoperative T10-L2 was +12 degrees kyphosis compared to +2 degrees for the anterior group without DJK (P = 0.006). DJK was significantly more likely to occur in the posterior group if the Cobb was instrumented to less than Cobb +1 (P < 0.001). CONCLUSIONS: It appears that both posterior and anterior instrumentation for thoracic curves must include the junctional level to prevent postoperative DJK when postoperative DJK is present. The presence of increased kyphosis after surgery in the T10-L2 region seen in both anterior and posterior groups that had postoperative DJK develop constitutes a "risk factor" for the development of DJK.

Results of preoperative pulmonary function testing of adolescents with idiopathic scoliosis. A study of six hundred and thirty-one patients.

BACKGROUND: Previous research has suggested a correlation between pulmonary impairment and thoracic spinal deformity. The curve magnitude, number of involved vertebrae, curve location, and decrease in thoracic kyphosis independently contribute to pulmonary impairment, but the strength of these associations has been variable. The objectives of this study were to test the hypothesis that increased thoracic deformity is associated with decreased pulmonary function and to determine which, if any, radiographic measurements of deformity predict pulmonary impairment. METHODS: Preoperative pulmonary function testing and radiographic examination were performed on 631 patients with adolescent idiopathic scoliosis. Correlation analysis and subsequent stepwise multiple regression analysis were carried out to assess the associations between radiographic measurements of deformity and the results of pulmonary function testing. RESULTS: The magnitude of the thoracic curve, the number of vertebrae involved in the thoracic curve, the thoracic hypokyphosis, and coronal imbalance had a minimal but significant effect on pulmonary function. While these four factors were associated with an increased risk of moderate or severe pulmonary impairment, they explained only 19.7%, 18.0%, and 8.8% of the observed variability in forced vital capacity, forced expiratory volume in one second, and total lung capacity, respectively. The degrees of scoliosis that were associated with clinically relevant decreases in pulmonary function were much smaller than previously described, but the majority of the observed variability in pulmonary function was not explained by the radiographic characteristics of the deformity. CONCLUSIONS: Some patients with adolescent idiopathic scoliosis may have clinically relevant pulmonary impairment that is out of proportion with the severity of the scoliosis, and this may alter the decision-making process regarding which fusion technique will produce an acceptable clinical result with the least additional effect on pulmonary function.

A posterior tether for fusionless modulation of sagittal plane growth in a sheep model.

STUDY DESIGN: This was an in vivo and in vitro investigation of a minimally invasive posterior tether system for fusionless modulation of sagittal plane growth in an immature sheep model. OBJECTIVE: To determine whether fusionless modulation of spinal growth in the sagittal plane of an immature sheep model can be successfully performed. SUMMARY OF BACKGROUND DATA: Scheuermann's disease has been reported to affect 1% to 8% of the pediatric population. Varying degrees of spinal bone growth modulation has been successfully performed in the coronal plane of animal models. This represents the first attempt to modulate spinal growth in the sagittal plane in an animal model. Modulation of spinal growth in the sagittal plane may play a role in the treatment of pediatric kyphosis when brace treatment is unsuccessful. METHODS: There were nine immature sheep posteriorly tethered and five control animals, all with identical follow-ups. Pedicle screws were placed in adjacent vertebrae, bilaterally, at the thoracolumbar junction and the lower lumbar spine. Polyethylene cords were passed subcutaneously, and tensioned to 20 lbs. Tethers were released in four sheep at 6 months and four at 12 months. At 12 months and 2 weeks, all animals were sacrificed. RESULTS: At 13 months after surgery, the tethered groups had significantly less kyphosis and vertebral body wedging than the control group. In both the tethered groups, at 13 months after surgery, there was significantly less vertebral body wedging compared with the preoperative values. There was no evidence of facet arthropathy, but heterotopic ossification was seen in several specimens. Tethered spines had significantly less motion than control spines. Histologic evaluation demonstrated no detrimental results. CONCLUSIONS: Fusionless modulation of sagittal plane growth in an immature sheep model was successfully performed with changes in the overall sagittal profile of the instrumented segments and vertebral body wedging. Increased stiffness of the instrumented segments posttether release was thought to be related to heterotopic ossification. Results suggest that this may be a potential treatment for adolescents with Scheuermann's disease.

Single-rod versus dual-rod anterior instrumentation for idiopathic scoliosis: a biomechanical study.

STUDY DESIGN: Anterior single- and dual-rod instrumented human and ovine thoracolumbar spines, with and without structural interbody support (SIS), were biomechanically tested and compared in flexion, lateral bending, and torsion. OBJECTIVE: To determine significant differences in global stiffness of the constructs in an attempt to clarify specific indications for each in the treatment of spinal deformities. SUMMARY OF BACKGROUND DATA: Single- and dual-rod anterior systems have been used without any consensus as to indications for one versus the other. The potential added benefit of incorporating SIS and transverse connectors (dual-rod) with these constructs has also not been fully explored. METHODS: Four human cadaveric and six ovine spines were instrumented in single- and dual-rod constructs and biomechanically tested intact, postdiscectomy with and without SIS, with single- and dual-rod constructs, and with and without transverse connectors (ovine only). Biomechanical testing modes were flexion, lateral bending, and torsion. RESULTS: In the human cadaveric specimens, testing in flexion revealed that SIS was the major contributing factor for construct stiffness. In lateral bending, stiffness of single- and dual-rod constructs with and without SIS was equivalent. In torsion, both single- and dual-rod instrumentation and SIS appeared to contribute to global stiffness. In ovine specimens, dual rods were stiffer than single-rod constructs and SIS played only a minor role. Transverse connectors appeared to significantly stiffen dual-rod constructs in torsion only. CONCLUSIONS: Dual-rod constructs with SIS appear to be the best combination for providing stiffness in anterior instrumentation. The addition of cross-links to anterior constructs does not appear to increase stiffness except in torsion.

A biomechanical study of regional endplate strength and cage morphology as it relates to structural interbody support.

STUDY DESIGN: An in vitro biomechanical investigation to quantify the endplates resistance to compressive loads, in the thoracic and lumbar spine. Comparisons were made to determine the regional strength of the endplate, the optimal size and geometry of interbody support, and the effects of endplate removal on structural strength. OBJECTIVES: To biomechanically assess the regional variation of endplate strength in the thoracic and lumbar spine, the optimal geometry and cross-sectional area for structural interbody support, and endplate preparation techniques with respect to endplate failure or subsidence. SUMMARY OF BACKGROUND DATA: Anterior column interbody support plays an important role in spinal reconstruction. Subsidence of interbody structural support is a common problem and may be related to regional weakness of the endplate, the size and/or geometry of structural support, and the preparation of the endplate. Biomechanical data related to these issues should be of importance to spine surgeons and reduce the risk of subsidence and its inherent complications. METHODS: The indentation tests were performed in three subgroups, each with a different set of test variables. The first test consisted of 65 vertebrae at six different endplate test positions using a 9.53-mm diameter indenter. The second test was performed on 48 vertebrae at a central endplate test site using three hollow and two solid cylindrical indenters of varying diameter. The third test was done using 24 vertebrae with the endplate intact, partially removed, or fully removed. All tests were run using human cadaveric specimen using both the superior and inferior endplates. The maximum load to failure (MLF) was determined for each test performed. RESULTS: For all levels tested, the highest MLF occurred in the posterolateral region of the endplate. The lowest value occurred in the central and anterocentral regions for levels T7-L5 and T1-T6, respectively. Hollow indenters with a small diameter had the lowest MLF, whereas solid large-diameter indenters had the highest MLF. The ultimate compressive strength for all hollow indenters was significantly higher than all solid indenters. There was a significant reduction in the endplate strength with the complete removal of the endplate. CONCLUSIONS: The posterolateral region of the endplate provides the greatest resistance to subsidence while the central region provides the least resistance. A larger-diameter solid support has the greater MLF and the lower the risk of subsidence, suggesting a more efficient transfer of force to the endplate with the hollow indenters. Parameters such as the geometry of structural support and the position and preparation of the endplate can influence the resistance of an interbody support to subside. Partial removal of the endplate may provide both, for adequate mechanical advantage and a highly vascular site for fusion.

Kyphosis of the thoracic and thoracolumbar spine in the pediatric patient: surgical treatment.

Kyphosis of the thoracic or thoracolumbar spine is a common deformity in pediatric and adolescent populations. When it progresses to the point at which nonsurgical treatment is no longer an option, surgery is indicated. Surgical options available for the treatment of different types of pediatric kyphosis of the thoracic and thoracolumbar spine include posterior instrumentation and fusion, posterior instrumentation and fusion combined with anterior fusion, and anterior instrumentation and fusion.

Platelet calmodulin levels in adolescent idiopathic scoliosis (AIS): can they predict curve progression and severity? Summary of an electronic focus group debate of the IBSE.

There is no generally accepted scientific theory for the etiology of idiopathic scoliosis. As part of its mission to widen understanding of scoliosis etiology, the International Federated Body on Scoliosis Etiology (IBSE) introduced the electronic focus group (EFG) as a means of increasing debate of extant knowledge on important topics. This has been designated as an on-line Delphi discussion. The text for this EFG was written by Professor Thomas G Lowe MD and drawn from research carried out by himself and his co-workers on platelet calmodulin levels in patients with adolescent idiopathic scoliosis. To explain the relationship of platelet calmodulin levels to scoliosis curve changes in AIS brought about spontaneously, by brace treatment, or surgery Dr Lowe attributes the platelet calmodulin changes to paraspinous muscle activity and suggests that the calmodulin acts as a systemic mediator of tissues having a contractile system (actin and myosin). Controversy includes: 1) the lack of normal data and the large variability in baseline levels of platelet calmodulin, necessitating the use of the AIS subjects as their own controls; 2) calmodulin is not usually used as a marker of platelet activation; 3) whether the platelet calmodulin changes which appear to reflect an abnormality of a portion of the spine are related to local and/or regional changes in muscles, nervous system, or immature vertebrae. What is not controversial is the need for more research on platelets and the immature deforming skeleton in relation to etiology and prognosis.

Anterior single-rod instrumentation of the thoracic and lumbar spine: saving levels.

STUDY DESIGN: To evaluate the ability of single-rod anterior instrumentation to save or preserve fusion levels and improve thoracic hypokyphosis in patients with adolescent idiopathic thoracic, thoracolumbar, or lumbar scoliosis. OBJECTIVE: To provide indications for single anterior rod instrumentation for the treatment of adolescent idiopathic scoliosis and demonstrate effectiveness in properly selected cases. SUMMARY OF BACKGROUND DATA: Posterior multisegmented dual rod instrumentation is the most commonly used instrumentation for the surgical treatment of adolescent idiopathic scoliosis. The issue of longer fusion levels and inability to correct hypokyphosis with posterior instrumentation continues to be debated in the literature. Anterior instrumentation has the ability in certain curve patterns to preserve distal and proximal levels as well as correct thoracic hypokyphosis. METHODS: A brief discussion of the Lenke adolescent idiopathic scoliosis classification system is presented. Surgical treatment options for each of the curve types are discussed in detail. RESULTS: Single-rod anterior instrumentation for adolescent idiopathic scoliosis will predictably save levels in Type I curves without hyperkyphosis as well as Type 5 curves; however, it is usually contraindicated in Type 2, Type 4, and Type 6 curves. Single-rod anterior instrumentation can occasionally be utilized in Type 3 curves if the magnitude of the lumbar curve is significantly less than the thoracic curve and the flexibility of the lumbar curve approaches 25 degrees on the side-bending radiograph. CONCLUSIONS: Single-rod anterior instrumentation will often saved one to three distal fusion levels when treating isolated major thoracic, thoracolumbar, or lumbar curves. Fusion levels should include upper to lower Cobb levels. Additionally, anterior single-rod instrumentation because its kyphogenic nature will predictably correct hypokyphosis of the thoracic spine.

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

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

Anterior single rod instrumentation for thoracolumbar adolescent idiopathic scoliosis with and without the use of structural interbody support.

STUDY DESIGN: A radiographic and clinical outcomes analysis of 41 patients treated for thoracolumbar adolescent idiopathic scoliosis utilizing a single anterior rigid rod construct. OBJECTIVES: To evaluate the necessity of structural interbody support to improve primary curve correction and preserve or augment lordosis when used in conjunction with a single anterior rigid rod construct, to identify parameters that predict horizontalization of the lowest instrumented vertebra, adjacent disc angulation, and distal uninstrumented vertebrae, and to assess patient satisfaction following surgery. BACKGROUND DATA: Instrumentation-induced kyphosis has been a concern with nonrigid anterior systems used in the past for the treatment of scoliosis. Interbody structural support has been recommended to maintain appropriate sagittal profile when anterior systems are utilized. It has also been suggested that the use of structural interbody support creates a fulcrum to increase curve correction when compression is applied to the convexity of the deformity. However, the necessity of interbody structural support when used in conjunction with a rigid anterior system has not been previously evaluated in patients with adolescent idiopathic scoliosis. MATERIALS AND METHODS: Forty-one patients mean age 15.9 years (range 12.1-18.6 years) with thoracolumbar adolescent idiopathic scoliosis underwent anterior spinal fusion using a single 6.0 to 6.5 mm solid rod construct between June 1995 and August 1999 performed by the senior author (T.G.L.). Four additional patients with thoracolumbar curves with similar anterior instrumentation over the same time period were lost to follow-up or had incomplete records and were not included in the study. Structural interbody support was used in 21 patients and packed morselized autograft alone was used in 20 patients. The patients in the group with packed morselized bone alone generally underwent surgery earlier in the series before the author began using structural interbody support on a regular basis. Each patient had a minimum follow-up of 3 years. Preoperative, initial, and most recent (>3 years) follow-up radiographs were reviewed to determine in each group Cobb angle measurements, flexibility of primary, secondary, and fractional curves, apical and end vertebral translation, lowest instrumented vertebral and caudal disc angulation, global coronal and sagittal balance, and sagittal Cobb measurements in both instrumented levels as well as lumbar lordosis (T12-S1). In addition, the SRS outcomes instrument was completed by 38 of 41 patients. RESULTS: The mean preoperative primary curve in patients with structural support was 47 degrees (Group II) and 45 degrees in patients without structural support (Group I). Mean curve correction was to 13 degrees in Groups I and II. One patient in Group II became slightly more unbalanced at final follow-up; otherwise all were improved after surgery. Sagittal measurements over instrumented segments as well as total lumbar lordosis (T12-S1) was maintained between preoperative and final postoperative values in both groups. Similarly, in both groups, when horizontalization of the distal end instrumented vertebra was achieved on the preoperative reverse side-bending radiograph, more normal relationships were achieved between instrumented and distal noninstrumented segments (adjacent disc angulation and fractional lumbar curve) at final follow-up (P

Resorbable polymer implants in unilateral transforaminal lumbar interbody fusion.

OBJECT: Sixty patients underwent instrumentation-assisted posterior transforaminal lumbar interbody fusion (TLIF) with resorbable polymer cages and autograft bone for degenerative disease. This article discusses the technique of TLIF and its early outcomes. METHODS: Although the follow-up period is short and results are preliminary, no adverse events or complications were attributed to the resorbable polymer. CONCLUSIONS: Further multicenter clinical studies are underway with a minimum 2-year follow-up period chosen as an endpoint to provide insight as to the future of biodegradable polymers as spinal interbody devices.

Bioresorbable polymer implants in the unilateral transforaminal lumbar interbody fusion procedure.

Sixty patients from two centers have undergone instrumented transforaminal posterior lumbar interbody fusion (TLIF) with bioresorbable polymer cages and autograft bone for degenerative indications. This article discusses the technique of TLIF and its early outcomes. Although follow-up is short and results are preliminary, no adverse events or complications may be attributed to the bioresorbable polymer. Further multicenter clinical studies are underway with a minimum of 2 years of follow-up chosen as an endpoint to provide insight as to the future of biodegradable polymers as spinal interbody devices.