Spontaneous Facet Joint Osteoarthritis in NFAT1-Mutant Mice: Age-Dependent Histopathologic Characteristics and Molecular Mechanisms.

BACKGROUND: Facet joint (FJ) osteoarthritis (FJOA) is a widely prevalent spinal disorder but its pathogenesis remains unclear, largely due to the difficulties in conducting longitudinal human studies and lack of spontaneous-FJOA animal models for mechanistic investigations. This study aimed to investigate whether spontaneous FJOA occurs in mice bearing mutant NFAT1 (nuclear factor of activated T cells 1) transcription factor. METHODS: The lumbar FJs of 50 NFAT1-mutant mice and of 50 wild-type control mice, of both sexes, were examined by histopathology, quantitative gene expression analysis, semiquantitative immunohistochemistry, and a novel FJOA scoring system for semiquantitative assessment of the histopathologic changes at 2, 6, 12, and 18 months of age. Age-dependent and tissue-specific histopathologic and gene or protein expression changes were analyzed statistically. RESULTS: FJs in NFAT1-mutant mice displayed significantly increased expression of specific catabolic genes (p < 0.05) and proteins (p < 0.001) in cartilage and synovium as early as 2 months of age, followed by early osteoarthritic structural changes such as articular surface fissuring and chondro-osteophyte formation at 6 months. More severe cartilage lesions, osteophytes, subchondral bone changes, synovitis, and tissue-specific molecular alterations in FJs of NFAT1-mutant mice were observed at 12 and 18 months. Osteoarthritic structural changes were not detected in FJs of wild-type mice at any ages, although age-related cartilage degeneration was observed at 18 months. The novel FJOA scoring system had high intraobserver and interobserver reproducibility (correlation coefficients: r > 0.97). Whole-joint FJOA scoring showed significantly higher OA scores in FJs of NFAT1-mutant mice compared with wild-type mice at all time points (p = 0.0033 at 2 months, p = 0.0001 at 6 months, p < 0.0001 at 12 and 18 months). CONCLUSIONS: This study has identified the NFAT1-mutant mouse as a novel animal model of spontaneous FJOA with age-dependent and slowly progressing osteoarthritic features, developed the first FJOA scoring system, and elucidated the molecular mechanisms of NFAT1 mutation-induced FJOA. CLINICAL RELEVANCE: This murine FJOA model resembles the features of human FJOA and may provide new insights into the pathogenesis of and therapeutic strategies for FJOA in humans.

Establishment of a university academic spine center: from concept to reality.

In fewer than five years, the University of Kansas Hospital Spine Center became the largest and most comprehensive spine care facility in the greater metropolitan Kansas City area. The 22,000-square-foot facility has 27 exam rooms, four specialized diagnostic rooms, 11 pre-/post-interventional procedure rooms, and a 4000-square-foot outpatient rehabilitation gym. Patients can meet with their physicians, undergo diagnostic tests and treatment, and attend therapy sessions in one location. The multidisciplinary Spine Center brings together orthopedic surgeons, neurosurgeons, neurologists, physical medicine and rehabilitation physicians, psychiatrists, psychologists, pain-management anesthesiologists, radiologists, and physical and occupational therapists. The Spine Center became successful because a group of physicians bought into the philosophy of a comprehensive interdisciplinary program, were willing to sacrifice some territorial claims, and were willing to put patient care and the good of the institution above individual egos.

Radiographic and patient-based outcome analysis of different bone-grafting techniques in the surgical treatment of idiopathic scoliosis with a minimum 4-year follow-up: allograft versus autograft/allograft combination.

BACKGROUND CONTEXT: Autograft and allograft have been equally successful in achieving arthrodesis, but whether there is any difference in their effect on patient outcome, especially early, has not been determined. PURPOSE: To determine if autograft in addition to allograft is associated with decreased healing period pain, increased early function, or both. STUDY DESIGN: This is a retrospective comparative case series. PATIENT SAMPLE: A sample of 47 patients, 20 years or younger with adolescent idiopathic scoliosis treated by the same surgeon at the same institution using third-generation segmental spinal instrumentation and arthrodesis. OUTCOME MEASURE: Function and pain were quantified at periodic intervals using the Scoliosis Research Society (SRS) health-related quality of life (HRQoL) questionnaire. Clinical and radiographic follow-ups were completed. METHODS: Freeze-dried corticocancellous allograft (AL) was used in 26 patients and allograft plus iliac crest autograft (AL-AU) in 21 patients. Radiographs and outcome measures, including SRS-24 or SRS-22 HRQoL questionnaires, were obtained preoperatively and at intervals with a 4-year follow-up available for 92% (25/26) of AL patients and 90% (19/21) of AL-AU patients. RESULTS: There were no differences between the AL and AL-AU groups' ages, curve patterns, and complications. Neither group had a major complication or pseudoarthrosis. There were no main curve size differences at any interval. Pain scores were similar at all intervals: AL/AL-AU preoperative, 4.1/4.0; early follow-up (<1 year), 3.7/4.1; midterm follow-up (1-2 years), 4.4/4.6; and late follow-up (>3 years), 4.1/4.0. Function scores were also similar at all intervals: AL/AL-AU preoperative, 4.7/4.6; early follow-up, 4.2/4.3; midterm follow-up, 4.9/4.9; and late follow-up, 4.5/4.4. CONCLUSIONS: The addition of autograft to allograft did not result in decreased pain or increased function at any time interval up to 4 years. We conclude that the addition of iliac crest autograft does not result in any advantage over freeze-dried allograft alone in the treatment of adolescent idiopathic scoliosis.

Comparison of trunk and spine deformity in adolescent idiopathic scoliosis.

BACKGROUND: Cobb measurement of standing radiographs is the standard for clinical assessment of coronal spinal deformity. Angle of trunk inclination (ATI) is an accepted clinical measurement of trunk asymmetry, and has variable reported correlations with Cobb angles. Transverse plane spine deformity is most accurately measured using axial computed tomography. Aaro and Dahlbourn's technique for quantifying apical vertebral rotation with respect to the sagittal plane (RAsag) is commonly reported in the literature. To our knowledge no study has correlated ATI with RAsag. The purpose of this study was to determine the relationship between commonly used measures of trunk and spine deformity. METHODS: Sixteen females that underwent preoperative apical vertebra(e) CT scans were retrospectively studied. Thoracic and thoracolumbar RAsag measurements were date-matched to clinically obtained ATI and Cobb measurements. Two-tailed Pearson correlations were calculated; α = 0.01. RESULTS: Median patient age was 14.6 years (11-19); BMI 19.4 (16.0-25.5). Curve patterns: Lenke 1 (5); 2 (5); 3 (1); 4 (1); 5 (2): 6 (2). Twenty-six curves (15T; 11TL) with complete, date-matched data points were analyzed. In thoracic curves, ATI correlated with Cobb (r = 0.711, P < 0.004) and RAsag (r = 0.730, P <0.003). ATI was inversely correlated with Cobb flexibility (r = -0.647, P < 0.01). In thoracolumbar curves, ATI correlated with Cobb (r = 0.789, P < 0.005), and RAsag (r = 0.771, P < 0.006) but not Cobb flexibility (r = -0.452, P = 0.190). CONCLUSIONS: Trunk and spine thoracic and thoracolumbar transverse plane deformity are correlated, as are trunk transverse plane and spine coronal plane deformity. Increasing trunk deformity limits thoracic, but not thoracolumbar spine flexibility.

Subsequent, unplanned spine surgery and life survival of patients operated for neuropathic spine deformity.

STUDY DESIGN: Retrospective study of a prospectively assembled cohort. OBJECTIVE: To characterize the survival from subsequent spine surgery and the life survival of patients treated surgically for severe spinal deformity due to neuropathic diseases. SUMMARY OF BACKGROUND DATA: Survivorship analysis is widely used to study the natural history of disease processes and of treatments provided, but has very seldom been used to study patients' course after surgery for spinal deformity associated with neuropathic diseases. METHODS: Patients with neuropathic spinal deformity treated with primary posterior instrumentation and arthrodesis from 1989 through 2002 were identified and studied by review of charts and radiographs, and by mail survey. Subsequent spine surgery and death events, and the time interval from surgery were identified. Fifteen variables possibly influencing survivorship were studied. RESULTS: There were no perioperative deaths, spinal cord injuries, or acute wound infections in the 117 eligible patients. Reoperation and life survival statuses were available for 110 patients (94%) at an average follow-up of 11.89 years (±5.3; range: 2-20.9 yr). Twelve patients (11%) had subsequent spine surgery. Survival from subsequent spine surgery was 91% at 5 years, 90% at 10 and 15 years, and 72% at 20 years. Proximal fixation problems occurred in 4 patients. Twenty-two patients (20%) had died from 4 to 20 years postoperative. Life survival was 98% at 5 years, 89% at 10 years, 81% at 15 years, and 56% at 20 years. The only variable associated with life survival was the occurrence of one or more perioperative complications, P = 0.0032. The younger half of the series at operation (<13.75 yr) was significantly more likely to have one or more perioperative complications, P = 0.0068. Spinal deformity type and magnitude were similar for the younger and older halves of the patients. Life survival of the patients with cerebral-palsy and not-cerebral-palsy upper motor neuron disease was not different. One-hundred-two of 105 were at least satisfied or would have the surgery again for the same condition. CONCLUSION: Survival from subsequent spine operation was similar to adolescent idiopathic scoliosis series studied in the same manner. Life survival decline began at 4 years postoperative and was significantly associated with the occurrence of one or more perioperative complications. Even after successful spine deformity surgery, this population's health status is often precarious.

Converting SRS-24, SRS-23, and SRS-22 to SRS-22r: establishing conversion equations using regression modeling.

STUDY DESIGN: Cross-sectional mail questionnaire. OBJECTIVE: Assess the feasibility of translating total and domain scores from Scoliosis Research Society (SRS)-24, SRS-23, and SRS-22 to SRS-22r. SUMMARY OF BACKGROUND DATA: Three successive editions of the original SRS-24 health-related quality-of-life questionnaire have resulted from efforts to improve its psychometric properties and validate its use in patients down to 10 years of age. This resulted in the need to establish, if possible, conversion equations to the last and most thoroughly validated version, SRS-22r. METHODS: A consolidated questionnaire of 49 questions that incorporated the various questions in the four questionnaires was mailed to a consecutive series of 235 patients who had received primary posterior or anterior instrumentation and arthrodesis to treat adolescent idiopathic scoliosis. Regression modeling was used to establish conversion equations from the SRS-24, SRS-23, and SRS-22 to the SRS-22r. RESULTS: One hundred twenty-one of the 235 patients (51%), aged 23.3 ± 4.52 years (range 14.2-34.6 years), returned the questionnaire at 8.6 ± 4.00 years (range 2.3-15.9 years) following surgery. Estimation of SRS-22r questionnaire and nonmanagement domains total scores and mean scores from SRS-22 and SRS-23 scores is excellent (R2 scores of 0.97-0.99) and good for SRS-24 scores (R2 scores of 0.80-0.82, improving to 0.86 and 0.87 after minimal domain reconfiguration). Estimation of SRS-22r individual domain total scores and mean scores from SRS-22 and SRS-23 is good to excellent (R2 scores of 0.81-0.99). Minimal domain reconfiguration improves conversion from SRS-24 pain from R2 = 0.71 to 0.76, which are both fair; SRS-24 function from R2 = 0.69 and 0.74 to 0.83, from poor and fair to good; and SRS-24 satisfaction/dissatisfaction with management from R2 = 0.64 to 0.80, from poor to good. Conversion of SRS-24 self-image is poor (R2 = 0.60) despite the correlation being statistically significant. CONCLUSION: With one exception, SRS-24, SRS-23, and SRS-22 questionnaire, nonmanagement domains, and individual domain total scores and mean scores can be translated to SRS-22r scores with fair to excellent accuracy, which is further improved in some instances by minimal domain reconfigurations. The sole exception is SRS-24 self-image, which translates poorly.

Transverse plane pelvic rotation increase (TPPRI) following rotationally corrective instrumentation of adolescent idiopathic scoliosis double curves.

BACKGROUND: We have occasionally observed clinically noticeable postoperative transverse plane pelvic rotation increase (TPPRI) in the direction of direct thoracolumbar/lumbar rotational corrective load applied during posterior instrumentation and arthrodesis for double (Lenke 3 and 6) adolescent idiopathic scoliosis (AIS) curves. Our purposes were to document this occurrence; identify its frequency, associated variables, and natural history; and determine its effect upon patient outcome. METHODS: Transverse plane pelvic rotation (TPPR) can be quantified using the left/right hemipelvis width ratio as measured on standing posterior-anterior scoliosis radiographs. Descriptive statistics were done to determine means and standard deviations. Non-parametric statistical tests were used due to the small sample size and non-normally distributed data. Significance was set at P < 0.05. RESULTS: Seventeen of 21 (81%) consecutive patients with double curves (7 with Lenke 3 curves and 10 with Lenke 6) instrumented with lumbar pedicle screw anchors to achieve direct rotation had a complete sequence of measurable radiographs. While 10 of these 17 had no postoperative TPPRI, 7 did all in the direction of the rotationally corrective thoracolumbar instrumentation load. Two preoperative variables were associated with postoperative TPPRI: more tilt of the vertebra below the lower instrumented vertebra (-23° ± 3.1° vs. -29° ± 4.6°, P = 0.014) and concurrent anterior thoracolumbar discectomy and arthrodesis (5 of 10 vs. 7 of 7, P = 0.044). Patients with a larger thoracolumbar/lumbar angle of trunk inclination or larger lower instrumented vertebra plus one to sacrum fractional/hemicurve were more likely to have received additional anterior thoracolumbar discectomy and arthrodesis (c = 0.90 and c = 0.833, respectively).Postoperative TPPRI resolved in 5 of the 7 by intermediate follow-up at 12 months. Patient outcome was not adversely affected by postoperative TPPRI, whether or not it persisted. CONCLUSIONS: Our findings suggest that TPPRI is a decompensation caused by extension of the corrective thoracolumbar rotational load into the lumbosacral hemicurve below. As posterior instrumentation of adolescent idiopathic scoliosis becomes increasingly more effective in the transverse plane, postoperative TPPRI may become more widely noticed. This study provides some assurance that recompensation usually occurs, but that in either event TPPRI does not seem to affect clinical outcome.

The effect of starting point placement technique on thoracic transverse process strength: an ex vivo biomechanical study.

BACKGROUND: The use of thoracic pedicle screws in spinal deformity, trauma, and tumor reconstruction is becoming more common. Unsuccessful screw placement may require salvage techniques utilizing transverse process hooks. The effect of different starting point placement techniques on the strength of the transverse process has not previously been reported. The purpose of this paper is to determine the biomechanical properties of the thoracic transverse process following various pedicle screw starting point placement techniques. METHODS: Forty-seven fresh-frozen human cadaveric thoracic vertebrae from T2 to T9 were disarticulated and matched by bone mineral density (BMD) and transverse process (TP) cross-sectional area. Specimens were randomized to one of four groups: A, control, and three others based on thoracic pedicle screw placement technique; B, straightforward; C, funnel; and D, in-out-in. Initial cortical bone removal for pedicle screw placement was made using a burr at the location on the transverse process or transverse process-laminar junction as published in the original description of each technique. The transverse process was tested measuring load-to-failure simulating a hook in compression mode. Analysis of covariance and Pearson correlation coefficients were used to examine the data. RESULTS: Technique was a significant predictor of load-to-failure (P = 0.0007). The least squares mean (LS mean) load-to-failure of group A (control) was 377 N, group B (straightforward) 355 N, group C (funnel) 229 N, and group D (in-out-in) 301 N. Significant differences were noted between groups A and C, A and D, B and C, and C and D. BMD (0.925 g/cm2 [range, 0.624-1.301 g/cm2]) was also a significant predictor of load-to-failure, for all specimens grouped together (P < 0.0001) and for each technique (P <0.05). Level and side tested were not found to significantly correlate with load-to-failure. CONCLUSIONS: The residual coronal plane compressive strength of the thoracic transverse process is dependent upon the screw starting point placement technique. The funnel technique significantly weakens transverse processes as compared to the straightforward technique, which does not significantly weaken the transverse process. It is also dependent upon bone mineral density, and low failure loads even in some control specimens suggest limited usefulness of the transverse process for axial compression loading in the osteoporotic thoracic spine.

Identification of Scoliosis Research Society-22r Health-Related Quality of Life questionnaire domains using factor analysis methodology.

STUDY DESIGN: Cross-sectional mail questionnaire. OBJECTIVE: Examination of the underlying construct validity of the Scoliosis Research Society-22r (SRS-22r) Health-Related Quality of Life (HRQoL) Questionnaire using factor analysis. SUMMARY OF BACKGROUND DATA: The original SRS-24 HRQoL questionnaire has undergone a series of modifications in an effort to further improve its psychometric properties and validate its use in patients from 10 years of age until well into adulthood. The SRS-22r questionnaire is the result of this effort. To date, the underlying construct validity of the original English version has not been analyzed by factor analysis. METHODS: A questionnaire including all questions on the SRS-24, -23, -22, and -22r questionnaires (49 total questions) was mailed to a consecutive series of 235 patients who had received primary posterior or anterior instrumentation and arthrodesis. Domain structure of the SRS-22r questions was analyzed using iterated principal factor analysis with orthogonal rotation. RESULTS: One hundred twenty-one (51%) of the patients, age 23.34 +/- 4.52 years (range, 14.16-34.57 years), returned the questionnaire at 8.63 +/- 4.00 years (range, 2.32-15.94 years) following surgery. Factor analysis using all 22 questions resulted in 3 factors with many shared items because of significant collinearity of the satisfaction/dissatisfaction with management questions with the others. After 18 iterations, factor analysis using the 20 nonmanagement questions revealed 4 factors that explained 98% of the variance. These factors parallel the assigned domains of the SRS-22r questionnaire. Three questions (2 self-image and 1 function) were identified that had high loading in 2 factors. However, internal consistency was best when 2 of the questions (1 self-image and 1 function) were retained in their assigned SRS-22r domains and the third decreased self-image internal consistency by only 0.01%. The internal consistencies (Cronbach alpha) of the assigned SRS-22r nonmanagement domains were excellent or very good: function 0.83, pain 0.87, self-image 0.80, and mental health 0.90. For the management domain it was good: 0.73. CONCLUSION: Factor analysis of the SRS-22r HRQoL confirms placement of the 20 nonmanagement domain questions in the assigned 4 domains, all with excellent or very good internal consistency.

Analysis of instrumentation/fusion survivorship without reoperation after primary posterior multiple anchor instrumentation and arthrodesis for idiopathic scoliosis.

BACKGROUND: During the past 25 years, spinal instrumentation systems and surgical techniques used to treat idiopathic scoliosis have evolved, achieving fewer patient restrictions during arthrodesis healing, shorter constructs, and better correction. The purposes of this retrospective comparative study were to determine the survivorship of the implant/fusion without reoperation and the risk factors influencing such survival. METHODS: From 1989 through 2002, 208 consecutive patients (index patient included, age 10-20 years) underwent primary posterior instrumentation and arthrodesis with the same multiple anchor implant system by one surgeon, a co-designer of the system. Two hundred seven were followed for more than 2 years; reoperation status was available for them at an average follow-up of 8.3 years. Twenty-one independent demographic, deformity, instrumentation, and process variables possibly influencing the need for reoperation were studied by comparing the reoperated group with the unreoperated group. RESULTS: Nineteen patients (9.2%) had reoperation; 16 (7.7%) were for indications related to posterior spine instrumentation. Survival of the implant/fusion without reoperation for spine instrumentation-related indications was 96% (95% confidence interval [CI], 93.2-98.7%) at 5 years, 91.6% (95% CI, 86.9-96.3%) at 10 years, 87.1% (95% CI, 79.5-94.6%) at 15 years, and 73.7% (95% CI, 48.6-98.6%) at 16 years, when the number at risk was nine. Reoperation need was significantly influenced by two implant variables: transverse connector design (p=.0012) and the lower instrumented vertebra anchors used (p=.0004). At 9 years, the longest interval allowing comparison, survival of the implant/fusion without reoperation for these two variables was 100% (six subjects at risk) compared to 82% (95% CI, 74.2-90.3%) with 59 patients still at risk for reoperation for those who did not have them, p=.0014. CONCLUSIONS: The most stable lower instrumented vertebra anchor configuration, bilateral pedicle screws, and the stronger transverse connector design, closed drop entry, provided the best survival of the implant/fusion without reoperation with this system and the techniques used at 9-year follow-up. We hope that this post-market study using survivorship techniques will be a guide for studies of other spinal implants.

Pelvic fixation of growing rods: comparison of constructs.

STUDY DESIGN: Retrospective review. OBJECTIVE: To analyze outcomes and complications of growing rods fixed to the pelvis. SUMMARY OF BACKGROUND DATA: Growing systems with pelvic foundations are used for neuromuscular/syndromic scoliosis. There is little data comparing different constructs. This project analyzed the outcomes and complications of this population. METHODS: Records/radiographs of 36 patients from the Growing Spine database with growing rods anchored in the pelvis were studied. Diagnoses included spinal muscular atrophy-6, cerebral palsy-5, myelomeningocele-5, congenital-4, arthrogryposis-1, and miscellaneous/syndromic-15. Age at surgery was 6.8 +/- 3 years. Preoperative curve was 86 degrees +/- 22 degrees and pelvic obliquity was 27 degrees +/- 11 degrees . Follow-up was 40 +/- 23 months. Rod breakage rate was compared to that of 299 patients not fixed to the pelvis. RESULTS: Iliac screws were used in 20 patients, iliac rods in 10, S-rods in 3, and sacral fixation in 6. Dual rods were used in 30 patients; single in 6. At follow-up, mean Cobb improved to 48 degrees +/- 20 degrees and pelvic obliquity improved to 11 degrees +/- 7 degrees . Iliac screws achieved significantly better Cobb and pelvic obliquity correction than sacral fixation (47% vs. 29%, P = 0.04, 66% vs. 40%, P = 0.001). Pelvic obliquity correction exceeded major curve correction (P < 0.001). Total gain in T1-S1 length was 8.6 +/- 4.3 cm; gain during lengthenings was 4.0 +/- 4.7 cm. Bilateral rods provided better correction of both pelvic obliquity (67% vs. 44%, P = 0.006) and major curve (47% vs. 25%, P = 0.02) than unilateral rods. Six patients have undergone final fusion at mean 3.3 +/- 1.8 years after initial surgery. Five patients developed deep infections. There were 6 rod breakages; this rate did not differ from constructs not anchored in the pelvis (P = 0.36). There were 5 breakages of iliac screws and none of other anchors (P = 0.035). CONCLUSION: Growing rods can include pelvic fixation to correct pelvic obliquity or obtain adequate fixation. Dual iliac fixation provides the best correction. Both iliac screws and rods provide satisfactory distal fixation; iliac screws had a higher rate of breakage. Growing rods with pelvic fixation are effective in deformity correction and achieving growth.

Growing rods for infantile scoliosis in Marfan syndrome.

STUDY DESIGN: Retrospective review. OBJECTIVE: To evaluate the effectiveness of a new growing rod technique in controlling infantile scoliosis in patients with Marfan syndrome. SUMMARY OF BACKGROUND DATA: Infantile scoliosis in patients with Marfan syndrome is nearly always progressive and poorly controlled by bracing, yet previous studies have shown poor results with first-generation extensible spinal rod techniques. METHODS: Ten patients with Marfan syndrome and scoliosis developing before 3 years of age were treated with growing rods (3 single, 7 dual). Mean age at initial surgery was 5.3 years (SD, 2.7 years). Before surgery, the mean curve was 77.2 degrees (SD, 15.6 degrees ) and the mean thoracolumbar kyphosis was 56 degrees (SD, 21 degrees ). Patients on warfarin sodium were lengthened at yearly intervals; others, more frequently. Mean follow-up was 87 months (SD, 30.5 months). RESULTS: Mean curve correction was 51% (SD, 23%) overall, 31% (SD, 23%) for single rods, and 60% (SD, 19%) for dual rods. Mean coronal and sagittal imbalance improved from 56 to 18 mm and from 31 to 21 mm, respectively. The mean length obtained was 11.5 cm (SD, 3.6 cm) overall and 11.2 cm (SD, 3.60 cm) for the 5 patients with final fusion. Complications included 2 rod breakages and 3 intraoperative dural leaks. There was 1 anchor dislodgement and no postoperative dural leak. No patient developed clinically noteworthy junctional kyphosis. One patient died of unrelated causes 3 months after surgery. CONCLUSION: As life expectancy improves for patients with neonatal Marfan syndrome, spinal deformity becomes an important issue. Extensible spinal growing rods are an effective solution to the problem. Dual rods appear to be more corrective than single rods. Substantial spinal length can be obtained to minimize trunk disproportion. Growing rods may help prevent large infantile curves from becoming severe in Marfan syndrome, allowing definitive spinal fusion closer to skeletal maturity.

The effect of posterior thoracic spine anatomical structures on motion segment flexion stiffness.

STUDY DESIGN: This in vitro human cadaveric study tested the loss of thoracic motion segment flexion stiffness after sequential posterior upper instrumented vertebra anchor placement techniques and posterior column destabilization. OBJECTIVE: This study was designed to determine the possible destabilizing effects of upper thoracic instrumentation anchor site preparation. SUMMARY OF BACKGROUND DATA: Proximal junctional kyphosis after instrumentation and arthrodesis for scoliosis and related spine deformities has recently been reported to range from 10% to 46%. The effect of posterior skeletal dissection associated with upper instrumented vertebra anchor placement on adjacent motion segment flexion stiffness has not been previously studied. METHODS.: Twenty-three intact thoracic motion segments were obtained from 6 human cadavers. Biomechanical testing was performed with each motion segment flexed to approximately 3.2 degrees at a rate of 0.1 Hz, with corresponding torques recorded. Data were collected after a series of 6 posterior procedures. Differences with P value <0.01 were considered significant and those with P value <0.05 marginally significant. RESULTS: Supratransverse process hook, supralaminar hook, pedicle screw placement, or pedicle screw removal done, bilaterally, produced similar, small (range, 2.09%-6.03%), nonsignificant reductions in motion segment flexion stiffness. But when totaled, these 4 procedures resulted in a significant 16.31% loss of flexion stiffness. The fifth procedure of supraspinous and interspinous process ligament transection added a marginally significant 6.59% incremental loss of flexion stiffness. Supralaminar hook site preparation combined with supraspinous and interspinous process ligament transection resulted in a marginally significant 12.62% incremental loss of flexion stiffness. Transection of the remaining posterior structures (facet joints and all other posterior soft tissue structures) produced a significant additional flexion stiffness loss of 44.72%. The anterior column alone provided only 32.39% of the total motion segment flexion stiffness. Transection of all posterior stabilizing structures, similar to a Smith-Peterson/chevron/Ponte resection, decreased motion segment flexion stiffness significantly, 67.61%. CONCLUSION: Posterior thoracic skeletal structures involved in upper instrumented vertebra exposure andanchor placement were found to contribute to adjacent segment flexion stiffness. Although stiffness loss was small after individual procedures, the effects were additive for routinely used combinations.

Treatment of adolescent idiopathic scoliosis with quantified trunk rotational strength training: a pilot study.

STUDY DESIGN: Prospective clinical trial. OBJECTIVES: To test the hypothesis that quantified trunk rotational strength training will equalize any strength asymmetry, increase strength overall, and stabilize adolescent idiopathic scoliosis. SUMMARY OF BACKGROUND DATA: Bracing, the only generally accepted form of adolescent idiopathic scoliosis nonoperative therapy, has many shortcomings. Paraspinal muscle abnormalities, which have been extensively documented in these patients, are generally considered to be secondary. A normal female's trunk strength in flexion and extension decreases from her juvenile to adolescent years, whereas a male's increases. METHODS: Patients received a 4-month supervised followed by a 4-month home trunk rotational strength training program. Trunk rotational strength was measured in both directions at 5 positions at baseline, 4 months, and 8 months. The patients were followed clinically. RESULTS: Fifteen patients (12 females and 3 males), with an average age of 13.9 years and an average main Cobb of 33 degrees were enrolled. At baseline there was no significant asymmetry. After 4 months of supervised strength training, involving an average of 32 training sessions, each lasting about 25 minutes, their strength had significantly increased by 28% to 50% (P<0.005 to P<0.001). After 4 months of unsupervised home strength training their strengths were unchanged. The 3 patients with baseline curves of 50 to 60 degrees all had main or compensatory curve progression and 2 had surgery. For patients with 20 to 40-degree curves, survivorship from main curve progression of >or=6 degrees was 100% at 8 months, but decreased to 64% at 24 months. CONCLUSIONS: Quantified trunk rotational strength training significantly increased strength. It was not effective for curves measuring 50 to 60 degrees. It appeared to help stabilize curves in the 20 to 40-degree ranges for 8 months, but not for 24 months. Periodic additional supervised strength training may help the technique to remain effective, although additional experimentation will be necessary to determine this.

The prevalence of increased proximal junctional flexion following posterior instrumentation and arthrodesis for adolescent idiopathic scoliosis.

STUDY DESIGN: Retrospective case series. OBJECTIVE: To determine the prevalence of proximal junctional sagittal plane flexion increase after posterior instrumentation and arthrodesis. SUMMARY OF BACKGROUND DATA: Increased flexion proximal to the junction of the instrumented and fused spinal region with the adjacent mobile spine seems to be a relatively recent observation, may be increasing, and is occasionally problematic. METHODS: The proximal junctional sagittal angulation 2 motion segments above the upper end instrumentation levels was measured on lateral standing preoperative and follow-up radiographs. RESULTS: One hundred seventy-four of 208 consecutive patients (84%) at an average radiograph follow-up of 4.9 +/- 2.73 years had increased proximal junctional flexion in 9.2%. The preoperative junctional measurements were normal for both normal and increased flexion groups. At follow-up, proximal junctional flexion had increased significantly more in the increased flexion group (2.1 degrees vs. 14.1 degrees , P < 0.0001). None of the possible risk factors studied, including demographic comparisons, Lenke classification (including lumbar and sagittal modifiers), end-instrumented vertebrae, end vertebra anchor configurations, surgical sequence, additional anterior surgery, rib osteotomies, and instrumentation length, were significantly associated with increased proximal junctional flexion at follow-up. Lenke 6 curves were at marginal risk of increased proximal junctional flexion (P = 0.0108). There were no differences between the groups in total Scoliosis Research Society-22r scores at an average follow-up of 8.0 +/- 3.74 years. No patient had additional surgery related to increased proximal junctional flexion. CONCLUSION: The prevalence of increased proximal junctional flexion was 9.2%. No significant risk factors were identified. Total Scoliosis Research Society-22r scores were similar for groups with normal and increased proximal junctional flexion at follow-up.

Dual growing rod technique followed for three to eleven years until final fusion: the effect of frequency of lengthening.

STUDY DESIGN: Retrospective case review of children completing dual growing rod treatment at our institutions. Patients had a minimum of 2 years follow-up. OBJECTIVE: To identify the factors influencing dual growing rod treatment outcome followed to final fusion. SUMMARY OF BACKGROUND DATA: Published reports on dual growing rod technique results for early onset scoliosis demonstrate it to be safe and effective in curve correction and maintenance as well as in allowing spinal growth. METHODS: Between 1990 and 2003, 13 patients with no previous surgery and noncongenital curves underwent final fusion. All had preoperative curve progression over 10 degrees after unsuccessful nonoperative treatment. There were 10 females and 3 males. Average age was 6.6 +/- 2.9 years at initial surgery. There were 3 idiopathic, 1 nonspine congenital anomaly, and 9 syndromic patients. Analysis included age at initial surgery and final fusion, number and frequency of lengthenings, and complications. Radiographic evaluation included changes in Cobb angle, T1-S1 length, and instrumentation length over the treatment period. RESULTS: Cobb angle improved from 81.0 +/- 23 degrees to 35.8 +/- 15 degrees postinitial and 27.7 +/- 17 degrees after final fusion. Average number of lengthenings was 5.2 +/- 3 at an interval of 9.4 +/- 5 months. T1-S1 length increased from 24.4 +/- 3.4 to 29.3 +/- 3.6 cm postinitial and 35.0 +/- 3.7 cm postfinal fusion. Average growth was 1.46 +/- 0.66 cm/year. Those lengthened at

The effect of arthrodesis, implant stiffness, and time on the canine lumbar spine.

STUDY DESIGN: Canine posterior lumbar instrumentation and fusion. OBJECTIVES: To study effects of implant rod size and time on the stiffness of related spine construct elements. SUMMARY OF BACKGROUND DATA: The ideal stiffness of posterior spinal implants to successfully treat clinical instability or deformity with minimal side effects is unknown. METHODS: Twenty-six canines were divided into 7 groups: control, and 6 or 12-month survival after sham or lumbar L3-5 arthrodesis (facet, posterior, and posterolateral) with either 4.76 or 6.35 mm diameter rod-pedicle screw instrumentation. Axial flexion-compression stiffness of the L3-5 segment components and axial compression stiffness of the bypassed and adjacent anterior column elements were measured. RESULTS: Posterior instrumentation initially increased flexion-compression stiffness of the L3-5 segment more than the intrinsic stiffness of the implant due to control of spinal column flexion buckling. Sham operation did likewise, apparently by posterior scar tissue tethering. The percent contribution of the implant construct to instrumented segment stiffness was significantly less at 6 months without further change from 6 to 12 months; 14% and 22% for 4.76 and 6.35 mm rod constructs, respectively. Spinal column as well as posterior column stiffness after fusion was independent of rod size at 6 months and increased at 12 months in only the 4.76 mm rod group. Bypassed L4 vertebral body stiffness decreased significantly at 6 months, was not rod size dependent and changed little between 6 and 12 months. Bypassed disk stiffness responded in a biphasic manner, apparently increasing at 6 months with significant decrease from 6 to 12 months. Adjacent disk compression stiffness progressively decreased over time independent of rod size, also decreasing after sham operation. CONCLUSIONS: Both rod sizes were associated with 100% fusion and produced similar changes in bypassed bone and disks, and adjacent disks. There was delayed fusion stress shielding by 6.35 mm rod constructs.

Transverse plane pelvic rotation in adolescent idiopathic scoliosis: primary or compensatory?

Several studies have suggested that the pelvis is involved in the etiology or pathogenesis of adolescent idiopathic scoliosis (AIS). The purpose of this retrospective, cross-sectional radiographic study is to identify any correlation between the transverse plane rotational position of the pelvis in stance and operative-size idiopathic or congenital scoliosis deformities, using Scheuermann's kyphosis and isthmic spondylolisthesis patients for comparison. The hypothesis tested was that the direction of transverse pelvic rotation is the same as that for a thoracic scoliosis. As a group, AIS patients had a significant transverse plane pelvic rotation in the same direction as the thoracic curve. When subdivided into the six Lenke curve patterns, this was true for the groups with a major thoracic curve: thoracic (1), double thoracic (2) and double curve patterns (3). It was not true for patterns with a major thoracolumbar/lumbar curve: single thoracolumbar/lumbar (5) and double thoracic-thoracolumbar/lumbar (6). Nor was it true for triple (4) curves. The Lenke 1 and 2 major thoracic curves without compensatory thoracolumbar/lumbar curves did not have the predicted pelvic rotation. All congenital scoliosis patients studied had main thoracic curves and significant transverse plane pelvic rotation in the same direction as the thoracic curve. There was no transverse plane pelvic rotation in the Scheuermann's kyphosis or isthmic spondylolisthesis patients. We interpret these findings as consistent with a compensatory rotation of the pelvis in the same direction as the main thoracic curve in most patients with a compensatory thoracolumbar/lumbar curve as well as in patients with main thoracic congenital scoliosis.