Vidyadhar V. Upasani

Preservation of thoracic kyphosis is critical to maintain lumbar lordosis in the surgical treatment of adolescent idiopathic scoliosis.

Study Design. Retrospective analysis of prospectively collected multicenter series. Objective. To evaluate the sagittal profile of surgically treated adolescent idiopathic scoliosis (AIS) patients. Summary of Background Data. With the increasing popularity of segmental pedicle screw spinal instrumentation, thoracic kyphosis (TK) is often sacrificed to achieve coronal and axial plane correction. Methods. Radiographs of AIS patients with a Lenke type 1 deformity and minimum 2-year follow-up after selective thoracic fusion (lowest instrumented vertebra of T11, T12, or L1) were evaluated. Changes in TK were correlated with changes in lumbar lordosis (LL). Patients were divided according to approach (open/thoracoscopic anterior vs. posterior). Analysis of variance was used to compare pre and postoperative radiographic measures. Results. Two hundred fifty-one patients (age: 14 ± 2 years) were included. Sixty seven percentages of the patients had anterior surgery (97 open anterior, 71 thoracoscopic) and 33% (83 patients) had posterior spinal fusion. A decrease in postoperative TK was significantly correlated (P ≤ 0.001) with a decrease in LL at first erect (r = 0.3), 1 year (r = 0.4) and 2 years (r = 0.4), independent of surgical approach. LL decreased significantly at the first erect regardless of approach (P = 0.003); however, at 2-year postoperative TK and LL were significantly decreased after a posterior approach (P ≤ 0.001) when compared with an anterior approach that added kyphosis. The decrease in LL (5.6° ± 9.7°) was nearly twice the decrease in TK (2.8° ± 11.4°) in the posterior group at 2-years. Conclusion. Given that thoracic AIS is often associated with a preexisting reduction in TK, ideal surgical correction should address this deformity. Procedures which further reduce TK also reduce LL. It is unclear if the loss of LL from thoracic scoliosis correction will compound the loss of LL that occurs with age and lead to further decline in sagittal balance. With this concern, we recommend a posterior column lengthening and/or an anterior column shortening to achieve restoration of normal TK and maximal LL.

Analysis of sagittal alignment in thoracic and thoracolumbar curves in adolescent idiopathic scoliosis: how do these two curve types differ?

Study Design. Retrospective chart review and radiographic analysis. Objective. To determine if differences exist in the sagittal alignment of adolescent idiopathic scoliosis (AIS) patients with thoracic versus thoracolumbar curve patterns. Summary of Background Data. Relative anterior overgrowth has been suggested as the possible pathomechanism behind thoracic scoliosis. Given the proposed importance of the sagittal alignment on the development of AIS and the known association between pelvic parameters and sagittal alignment, the authors postulate that pelvic incidence may influence the location of vertebral column collapse associated with different AIS curve types. Methods. A multicenter surgical database was used to compare preoperative radiographic measurements between patients with primary thoracic curves (Lenke 1A, B), primary thoracolumbar curves (Lenke 5), and normal adolescents. Results. Pelvic incidence was significantly greater in both groups of AIS patients compared with normal adolescents. Patients in the primary thoracic curve group were found to have a significantly increased sacral slope and a decreased thoracic kyphosis relative to the control group. Patients in the primary thoracolumbar curve group had a significantly increased pelvic tilt; however, a relatively normal thoracic kyphosis, lumbar lordosis, and sacral slope compared with the respective control values. Conclusion. An increased pelvic incidence, associated with both thoracic and thoracolumbar curves when compared with the normal adolescent population, does not appear to be the potential determinant of the development of thoracic versus thoracolumbar scoliosis, but may be a risk factor for the development of adolescent idiopathic scoliosis. The theory of anterior overgrowth may be supported by the identification of thoracic hypokyphosis, despite an increased pelvic incidence and lumbar lordosis, in patients with thoracic scoliosis. The association between sagittal measurements and the etiology of thoracolumbar curve formation is less clear; however, regional anterior overgrowth in the lumbar spine may also be responsible for the deformity.

Spinal growth modulation with an anterolateral flexible tether in an immature bovine model: disc health and motion preservation.

Study Design. An immature bovine model was used to evaluate multilevel anterolateral flexible tethering in a growing spine. Objective. To evaluate radiographic, biochemical, histologic, and biomechanical results of tethered spinal growth. Summary of Background Data. An anterolateral flexible tether has been shown to create a kyphotic and scoliotic spinal deformity in calves. Subsequent disc health and spinal motion has not been analyzed. Methods. Four consecutive thoracic vertebral bodies (T6–T9) were instrumented anteriorly in 36 1-month-old calves. Seventeen animals (Tether Group) were instrumented with a vertebral staple-two screw construct connected by 2 flexible stainless steel cables. Nineteen animals (Control Group) were instrumented with 1 vertebral body screw with no connecting cable. After a 6-month survival period, the spines were harvest en-bloc and underwent radiographic, computed tomography, biochemical, histologic, and biomechanical analysis. Results. On average, 37.6° ± 10.6° of coronal and 18.0° ± 9.9° of sagittal deformity was created in the Tether Group, with significant vertebral wedging toward the tether (P < 0.001). Disc thickness decreased significantly in the Tether Group (P < 0.001), however, disc wedging was not observed. There was no change in gross morphologic disc health or disc water content (P = 0.73). However, proteoglycan synthesis was significantly greater in the tethered discs compared with controls (P < 0.001), and collagen type distribution was different with a trend toward increased type II collagen present on the tethered side of the disc (P = 0.09). Tethers significantly increased spinal stiffness in lateral bending and in flexion/extension (P < 0.05) without affecting torsional stiffness, however, after tether removal range of motion returned to control values. Conclusion. Tethering resulted in vertebral wedging while maintaining spinal flexibility. Although changes in proteoglycan synthesis, collagen type distribution, and disc thickness were observed, the tethered discs had similar water content to control discs and did not demonstrate gross morphologic signs of degeneration. Growth modulation is an attractive treatment option for growing patients with scoliosis, avoiding multilevel fusions or brace wear. Strategies for fusionless scoliosis correction should preserve disc health, as adolescent patients will rely on these discs for decades after treatment.

Spinal growth modulation with use of a tether in an immature porcine model.

BACKGROUND Spinal growth modulation by tethering the anterolateral aspect of the spine, as previously demonstrated in a nonscoliotic calf model, may be a viable fusionless treatment method for idiopathic scoliosis. The purpose of the present study was to evaluate the radiographic, histologic, and biomechanical results after six and twelve months of spinal growth modulation in a porcine model with a growth rate similar to that of adolescent patients. METHODS Twelve seven-month-old mini-pigs underwent instrumentation with a vertebral staple-screw construct connected by a polyethylene tether over four consecutive thoracic vertebrae. The spines were harvested after six (n = 6) or twelve months (n = 6) of growth. Monthly radiographs, computed tomography and magnetic resonance imaging scans (made after the spines were harvested), histologic findings, and biomechanical findings were evaluated. Analysis of variance was used to compare preoperative, six-month postoperative, and twelve-month postoperative data. RESULTS Radiographs demonstrated 14 degrees +/- 4 degrees of coronal deformity after six months and 30 degrees +/- 13 degrees after twelve months of growth. Coronal vertebral wedging was observed in all four tethered vertebrae and progressed throughout each animals survival period. Disc wedging was also created; however, in contrast to the findings associated with vertebral wedging, the tethered side was taller than the untethered side. Magnetic resonance images revealed no evidence of disc degeneration; however, the nucleus pulposus had shifted toward the side of the tethering. Midcoronal undecalcified histologic sections showed intact bone-screw interfaces with no evidence of implant failure or loosening. With the tether cut, stiffness decreased and range of motion increased in lateral bending away from the tether at both time-points (p < 0.05). CONCLUSIONS In this porcine model, mechanical tethering during growth altered spinal morphology in the coronal and sagittal planes, leading to vertebral and disc wedging proportional to the duration of tethering. The resulting concave thickening of the disc in response to the tether was not anticipated and may suggest a capacity for the nucleus pulposus to respond to the compressive loads created by growth against the tether.

Calcaneonavicular coalition: treatment by excision and fat graft.

Background Symptomatic calcaneonavicular coalitions treated with resection and interposition of the extensor digitorum brevis (EDB) muscle often have unpredictable improvement of symptoms. Concerns with regard to skin cosmesis from a bony prominence on the lateral aspect of the foot and inadequate filling of the resection gap potentially causing reossification have motivated us to use fat graft interposition instead. The purpose of this study was to describe our surgical technique and report our clinical and radiographic outcomes for fat graft interposition after resection of a calcaneonavicular coalition. Methods A retrospective review of all pediatric patients surgically treated with a calcaneonavicular coalition resection from January 1999 to December 2006, was performed. Presenting symptoms and examination findings were recorded. Postoperative examinations and imaging studies were evaluated to grade reossification, and functional outcomes were assessed for all patients with minimum 1-year postoperative follow-up. In addition, a cadaveric study was performed to compare the efficacy of EDB and fat graft interposition in terms of filling the postresection gap. Results Foot pain was the most common presenting complaint, though limitation of activities, stiffness, preoperative hindfoot malalignment, and associated injuries were also frequently observed. One year after resection, 87% of the patients returned to sport or their past activities, whereas 5% had symptomatic regrowth requiring repeat resection. Seventy-four percent had improvement of subtalar motion and 82% had improvement of plantarflexion; which was identified as an additional clinical sign of a calcaneonavicular bar. Preoperative pain averaged 7 of 10, whereas postoperative pain averaged less than 1 of 10 at rest, while walking, and with activities. The cadaveric study showed that the EDB was able to fill on average only 64% of the resected gap, leaving approximately 10 mm of the plantar gap unfilled. Conclusions Reossification and reoperation rates with fat graft interposition in our series were lower than in most published reports of EDB interposition. Ankle and subtalar motion improved in a vast majority of the patients, and most patients returned to sport without requiring further surgery. Resection of a calcaneonavicular coalition with interposition of fat graft, when meticulously performed, is an effective way to relieve symptoms, restore subtalar motion, and return patients to activities, while preventing reossification. Level of Evidence Level 4—Therapeutic study (retrospective case series).

Spontaneous lumbar curve correction in selective thoracic fusions of idiopathic scoliosis: a comparison of anterior and posterior approaches.

Study Design. A retrospective evaluation of adolescent idiopathic scoliosis (AIS) patients treated with selective thoracic instrumentation and fusion. Objective. To evaluate the predictors and the effect of surgical approach (anterior versus posterior) on spontaneous lumbar curve correction (SLCC) after selective thoracic fusion in patients with structural thoracic and compensatory lumbar curves. Summary of Background Data. Spontaneous coronal correction of the unfused lumbar curve has been described previously; however controversy continues regarding the effect of surgical approach on SLCC. Methods. One hundred thirty-two anterior and 44 posterior selective thoracic fusions instrumented distally to T11, T12, or L1 were identified from a multicenter AIS database. A 2-way ANOVA was used to compare SLCC with regards to surgical approach and the lowest instrumented vertebra (LIV). A Pearsons correlation analysis was utilized to identify radiographic variables associated with SLCC. A secondary analysis of surgical approach was then performed on 28 pairs of patients matching the factors that correlated positively with SLCC. Results. The average SLCC for the anterior approach (44% ± 19%) was less than that for the posterior approach (49% ± 19%; P = 0.07), and was found to increase significantly with a more distal LIV (P = 0.03). Pearsons correlation analysis revealed the strongest correlations between SLCC and preoperative lumbar curve flexibility (r = 0.20) and 2-year postoperative thoracic curve percent correction (r = 0.47). A secondary analysis of SLCC in paired curves matched by LIV, lumbar curve flexibility and thoracic percent correction revealed no difference between anterior (48%) and posterior (49%) approaches (P = 0.75). Conclusion. Anterior and posterior instrumented fusions performed selectively on the appropriate curves result in equal SLCC when matched by LIV, flexibility of the lumbar curve, and percent thoracic curve correction achieved. This suggests that the observed phenomenon of SLCC after selective thoracic fusion in AIS is independent of surgical approach and can be reliably achieved with either technique.

Three-dimensional analysis of thoracic apical sagittal alignment in adolescent idiopathic scoliosis.

Study Design. Retrospective review of a series of adolescent idiopathic scoliosis patients. Objective. To perform a 3-dimensional (3D) analysis of patients with thoracic scoliosis to identify differences in the thoracic sagittal alignment measured from the standard lateral projection as compared to the “true lateral” view. Summary of Background Data. It has been difficult to clinically obtain radiographs in the planes of maximum spinal deformity. Recently, 3D models of the spine have been developed using biplanar radiographic reconstructions that allow a more accurate assessment of spinal alignment. Methods. Three-dimensional spinal reconstructions using biplanar radiographs were used to evaluate the apical thoracic sagittal profile. A measurement of sagittal curvature from 2 vertebral levels above and below the thoracic apex (5 vertebrae) was recorded from the standard lateral view. The 3D reconstructions were then rotated to achieve a “true lateral” view of the apical thoracic vertebra and the sagittal apical curvature was remeasured. The difference in the 2 measures of sagittal thoracic apical alignment was compared using repeated measures ANOVA, and then correlated to the coronal thoracic Cobb magnitude using a Pearson correlation analysis (P < 0.05). Results. Sixty-six adolescent idiopathic scoliosis patients with right thoracic scoliosis (Cobb averaged 47° ± 10°) were evaluated. The apical thoracic sagittal curvature in the standard lateral view averaged 11° ± 10° of kyphosis (range: −8° to 38°). This was statistically greater (P < 0.001) than the apical sagittal curvature in the “true lateral” view that averaged 1° ± 9° (range:−23° to 22°). The standard lateral view was rotated an average of 13° ± 4° to achieve the ideal lateral view of the thoracic apex. Conclusion. This 3D analysis of thoracic scoliosis demonstrated a consistent loss of kyphosis within the 5 thoracic apical vertebrae. The true apical sagittal profile was found to be overestimated by an average of 10° as compared to the perceived alignment from standard lateral radiographs.

Complications after modified Dunn osteotomy for the treatment of adolescent slipped capital femoral epiphysis.

Background: Modified Dunn osteotomy has gained popularity over the past decade in the treatment of moderate to severe adolescent slipped capital femoral epiphysis. The purpose of this study was to retrospectively evaluate a consecutive series of adolescent slipped capital femoral epiphysis patients treated with the modified Dunn procedure at a single institution. We analyze the indications for the procedure as well as the complications after surgical treatment. Methods: Forty-three adolescent patients (18 boys and 25 girls) were treated with the modified Dunn procedure at our institution between September 2001 and August 2012. The average follow-up for this cohort was 2.6 years (range, 1 to 8 y). Complications were graded according to the modified Dindo-Clavien classification. Results: Twenty-six patients (60%) had an unstable injury with an inability to ambulate with our without crutches. Seventeen patients (40%) had an acute injury with duration of symptoms <3 weeks. Thirty-seven patients (86%) had a severe slip based on a Southwick slip angle of >50 degrees. Twenty-two complications occurred in 16 patients (37%) in this cohort. Fifteen revision procedures were performed for femoral head avascular necrosis, fixation failure with deformity progression, or postoperative hip dislocation. Two patients developed end-stage degenerative joint disease and severe femoral head avascular necrosis and were referred for a total hip arthroplasty. Conclusions: The complication rate in this series is higher than most previous reports. This may be in part because of the fact that as a tertiary referral center our patient population was more complex. However, we identified a clear inverse relationship between surgeon-volume and patient-outcomes. On the basis of our results we have modified our practice. A high-volume surgeon must be present during each modified Dunn procedure, and only patients that have sustained an acute severe (>50 degrees) epiphyseal displacement with mild chronic remodeling of the metaphysis that can be addressed within 24 hours of the slip may be treated with the modified Dunn technique. Level of Evidence: Level IV—therapeutic study.

Surgical treatment of main thoracic scoliosis with thoracoscopic anterior instrumentation. a five-year follow-up study.

BACKGROUND The surgical outcomes in patients with scoliosis at two years following anterior thoracoscopic spinal instrumentation and fusion have been reported. The purpose of this study was to evaluate the results at five years. METHODS A consecutive series of forty-one patients with major thoracic scoliosis treated with anterior thoracoscopic spinal instrumentation was evaluated at regular intervals. Prospectively collected data included patient demographics, radiographic measurements, clinical deformity measures, pulmonary function, an assessment of intervertebral fusion, and the scores on the Scoliosis Research Society (SRS-24) outcomes instrument. Perioperative and postoperative complications were recorded. Patient data for the preoperative, two-year, and five-year postoperative time points were compared. In addition, a univariate analysis compared selected two-year radiographic, pulmonary function, and SRS-24 data of the study cohort and those of the patients lost to follow-up. RESULTS Twenty-five (61%) of the original forty-one patients had five-year follow-up data and were included in the analysis. Between the two-year and five-year follow-up visits, no significant changes were observed with regard to the average percent correction of the major Cobb angle (56% +/- 11% and 52% +/- 14%, respectively), average total lung capacity as a percent of the predicted value (95% +/- 14% and 91% +/- 10%), and the average total SRS-24 score (4.2 +/- 0.4 and 4.1 +/- 0.7). Radiographic evaluation of intervertebral fusion at five years revealed convincing evidence of a fusion with remodeling and trabeculae present at 151 (97%) of the 155 instrumented motion segments. No postoperative infections or clinically relevant neurovascular complications were observed. Rod failure occurred in three patients, and three patients required a surgical revision with posterior spinal instrumentation and fusion. CONCLUSIONS Thoracoscopic anterior instrumentation for main thoracic idiopathic scoliosis results in five-year outcomes comparable with those reported previously for open anterior and posterior techniques. The radiographic findings, pulmonary function, and clinical measures remain stable between the two and five-year follow-up time points. Thoracoscopic instrumentation provides a viable alternative to treat spinal deformity; however, the risks of pseudarthrosis, hardware failure, and surgical revision should be considered along with the advantages of limited muscular dissection and improved scar appearance. LEVEL OF EVIDENCE Therapeutic Level IV. See Instructions to Authors for a complete description of levels of evidence.

Effects of Intraoperative Tensioning of an Anterolateral Spinal Tether on Spinal Growth Modulation in a Porcine Model

STUDY DESIGN in vivo analysis in an immature porcine model. OBJECTIVE to evaluate the effect of intraoperative tensioning of an anterolateral flexible spinal tether on growth modulation manifested as deformity creation, disc response, spinal motion, and screw fixation using radiographs, computed tomography, magnetic resonance imaging, biomechanical testing, and histology. SUMMARY OF BACKGROUND DATA spinal growth modulation using an anterolateral flexible tether has been proposed as a nonfusion surgical deformity correction strategy for idiopathic scoliosis and has been successfully demonstrated in a porcine model to create spinal deformity while maintaining disc viability. METHODS twelve 7-month-old mini-pigs were instrumented with a screw-staple and polyethylene tether construct over 4 consecutive thoracic vertebrae (T8-T11). Intraoperative tensioning of the tether (250 N) was performed in alternate pigs (Pretensioned and Untensioned groups, n = 6 per group). Screws were coated with hydroxyapatite in half of the animals in each surgical group. Preoperative, postoperative, and monthly radiographs were evaluated, comparing deformity creation, vertebral body wedging, and disc wedging between the groups. Vertebral body shape was evaluated by computed tomography. Magnetic resonance and histology evaluated disc health. Biomechanical testing was performed to determine the effect of tensioning the tether on spinal motion and screw fixation. RESULTS intraoperative tensioning produced immediate coronal deformity (8° ± 4° vs. 2° ± 1° in untensioned spines; P = 0.01) and apical disc (T9-T10) wedging, vertex on tethered side, (5° ± 2° vs. 2° ± 1°; P = 0.01). After 12 months, the groups were similar in coronal deformity (28° ± 18° pretensioned, 27° ± 11° untensioned, P = 0.88), sagittal deformity (25° ± 3° vs. 22° ± 3°; P = 0.14), vertebral body wedging (10° ± 5° vs. 8° ± 3°; P = 0.45), and disc wedging (-4° ± 1° vs. -4° ± 3°; P = 0.88). There was no radiographic evidence of screw loosening. One of the discs from each group had diminished T2 signal after 12 months of tethering. Tether pretensioning did not affect spinal stiffness or motion. Interestingly, screw fixation increased with pretensioning; however, there was no significant advantage with hydroxyapatite coating. Histology demonstrated normal-appearing discs. CONCLUSION pretensioning of the tether created immediate deformity without effecting ultimate vertebral or disc deformity creation. Spinal motion and stiffness were not altered by pretensioning; however, pretensioning increased the torque required for screw extraction.