Comparison of Scheuermann kyphosis correction by posterior-only thoracic pedicle screw fixation versus combined anterior/posterior fusion.

STUDY DESIGN: Retrospective comparison review. OBJECTIVE: Compare posterior-only treatment results with segmental thoracic pedicle screw constructs versus combined anterior/posterior fusion in patients with Scheuermann kyphosis. SUMMARY OF BACKGROUND DATA: Traditionally, operative Scheuermann kyphosis has been treated with combined anterior/posterior spinal fusion, with the anterior portion being performed via an open thoracotomy or a video-assisted thoracoscopic approach. METHODS: There were 18 patients with Scheuermann kyphosis who underwent a posterior-only thoracic pedicle screw (P/TPS) fusion and 21 who underwent an anterior/posterior fusion who were followed for a 2-year minimum. The 2 groups were well matched according to average age (anterior/posterior fusion 18.0 degrees and P/TPS 17.3 degrees; P = 0.60), maximum preoperative kyphosis (anterior/posterior fusion 89.1 degrees and P/TPS 84.4 degrees; P = 0.21), flexibility index (anterior/posterior fusion 0.408 degrees and P/TPS 0.407 degrees; P > 0.99), and posterior fusion levels (anterior/posterior fusion 12.1 degrees and P/TPS 12.2 degrees; P = 0.95). Of 21 patients with anterior/posterior fusions, zero versus 12 of 18 (67%) patients in the P/TPS group underwent apical Smith-Petersen osteotomies. Fixation in the anterior/posterior fusion group was achieved with hybrid hook/screw constructs. Posterior fixation in the P/TPS group was performed using segmental thoracic pedicle screw constructs. Both groups had posterior iliac bone autografting. Operating time and blood loss were noted, and radiographs were evaluated before surgery, after surgery, and at final follow-up. At final follow up, Scoliosis Research Society-30 questionnaire data and complications were recorded. RESULTS: At surgery, operating time and blood loss were significantly less in the P/TPS group (P = 0.009 and P = 0.05, respectively). The mean residual kyphosis of the P/TPS group averaged 38.2 degrees after surgery and 40.4 degrees at final follow-up versus anterior/posterior fusion group (51.9 degrees and 58.0 degrees, P < 0.001 and P = 0.001, respectively). Even without an anterior release, kyphosis correction in the P/TPS group averaged 54.2% after surgery and 51.8% at final follow-up versus the anterior/posterior fusion group (41.2% and 38.5%, P = 0.001 and P < 0.001, respectively). Scoliosis Research Society-30 outcome scores at final follow-up were comparable between the 2 groups (P/TPS = 120 and anterior/posterior fusion = 128; P = 0.14). The anterior/posterior fusion group had 8/21 (38%) patients with complications, including paraplegia in 1, proximal junctional kyphosis in 1, proximal hook pullout in 1, and infection in 2. The P/TPS group had no complications (P = 0.003). CONCLUSIONS: With less operating time and intraoperative blood loss, posterior-only Scheuermann kyphosis treatment with thoracic pedicle screws achieved and maintained better correction, and had significantly less complications than with circumferential fusion.

Prospective radiographic and clinical outcomes of dual-rod instrumented anterior spinal fusion in adolescent idiopathic scoliosis: comparison with single-rod constructs.

STUDY DESIGN: Anterior single or dual-rod instrumentation may be performed for the treatment of main thoracic, thoracolumbar, or lumbar adolescent idiopathic scoliosis (AIS) curves. OBJECTIVE: To compare the results of anterior dual-rod instrumentation in single-major AIS curves with our previous experience using single-rod constructs. SUMMARY OF BACKGROUND DATA: Several reports have described the use of anterior single-rod instrumentation for the treatment of AIS curves with acceptable correction rates but with pseudarthroses/implant failures of up to 31%. METHODS: A total of 60 consecutive patients with AIS (12 males and 48 females; average age 15.3 years) with major thoracic (n = 18) or thoracolumbar/lumbar (n = 42) curves were treated with dual-rod instrumented anterior spinal fusion. Follow-up was 2-5 years. Patients were evaluated prospectively with Scoliosis Research Society (SRS) questionnaires. RESULTS: Major thoracic curves were corrected from a mean of 55 degrees to 27 degrees (51% correction), while major thoracolumbar/lumbar curves were corrected from an average of 51 degrees to 17 degrees at latest follow-up (67% correction). No pseudarthroses were identified. With the use of single-rod constructs, a similar amount of coronal correction was obtained for both thoracic (47%) and thoracolumbar/lumbar curves (70%). However, the pseudarthrosis rate for single-rod constructs was 5.5%. The obvious trend toward a lower pseudarthrosis rate in dual-rod (0/60) versus single-rod (5/90) constructs was not statistically significant (P = 0.07). Follow-up SRS questionnaire data for patients with dual-rod instrumentation showed 95% satisfaction, and 93% would choose the same treatment with similar results in the single-rod instrumentation study, 88% patient satisfaction, and 89% choosing the same treatment. Overall SRS scores improved after treatment (P < 0.01). SRS domain scores improved at a significant level for pain (P = 0.05), self-image (P < 0.01), and function (P = 0.01). CONCLUSION: In this largest, to our knowledge, single-center report of dual-rod constructs for patients with AIS, a similar amount of radiographic deformity correction was obtained when compared to single-rod implants. However, the absence of any pseudarthroses in the 60 patients with dual-rod is a distinct advantage.

Apical sublaminar wires versus pedicle screws--which provides better results for surgical correction of adolescent idiopathic scoliosis?

STUDY DESIGN: The results of correction for adolescent idiopathic scoliosis (AIS) were compared using apical sublaminar wires versus pedicle screws. OBJECTIVE: To compare comprehensively the 2-year minimum postoperative results of posterior correction and spinal fusion using translational correction through either hybrid hook/sublaminar wire/pedicle screw constructs versus in situ rod-contouring correction with pedicle screw constructs in the treatment of AIS at 2 institutions. SUMMARY OF BACKGROUND DATA: Despite the reports of satisfactory correction of scoliotic curves by both apical (sublaminar wire) instrumentation and apical pedicle screw instrumentation, to our knowledge, no reports on the comprehensive comparison of hybrid (hook/sublaminar wire/pedicle screw) instrumentation versus segmental pedicle screw instrumentation exist. METHODS: A total of 50 patients with AIS at 2 institutions who underwent posterior spinal fusion with sublaminar wire (25 patients) or pedicle screw (25) constructs were sorted and matched according to 4 criteria: (1) similar age at surgery (14.2 years in the sublaminar wire and 14.4 in the pedicle screw group, P = 0.72); (2) similar number of fused vertebrae (11.4 in the sublaminar wire and 11.8 in the pedicle screw group, P = 0.36); (3) similar operative methods; and (4) identical Lenke curve types and similar preoperative major curve measurements (63.5 degrees in the sublaminar wire and 59.5 degrees in the pedicle screw group, P = 0.42). Patients were evaluated preoperatively, immediately postoperatively, and at 2-year follow-up according to radiographic changes in curve correction, operating time, intraoperative blood loss, implant costs, and the Scoliosis Research Society patient questionnaire (SRS-24) scores. RESULTS: After surgery, average major curve correction was 67.4% in the sublaminar wire and 68.1% in the pedicle screw group (P = 0.56). At 2-year follow-up, loss of the major curve correction was 4.6% in the sublaminar wire compared to 5.1% in the pedicle screw group (P = 0.79). Postoperative global coronal and sagittal balance were similar in both groups. No significant difference was found in the average number of levels fused from the distal end vertebra (1.48 in the sublaminar wire and 0.64 in the pedicle screw group, P = 0.21). Operating time averaged 350 minutes in the sublaminar wire and 357 in the pedicle screw group (P = 0.86). Intraoperative blood loss was significantly different in both groups (1791 +/- 816 mL in the sublaminar wire and 824 +/- 440 mL in the pedicle screw group) (P = 0.0003). Average implant cost in the sublaminar wire group (16.0 fixation points; 8,341 US dollars) was significantly lower than that of the pedicle screw group (17.1 fixation points; 13,462 US dollars) (P < 0.0001). Postoperative 2-year SRS-24 scores were similar in both groups (sublaminar wire = 107.3, pedicle screw = 103.5, P = 0.19). There were no neurologic or visceral complications related to sublaminar wire or pedicle screw instrumentation and no reoperations at a minimum 2-year follow-up. CONCLUSIONS: Apical sublaminar wire and pedicle screw instrumentation both offer similar major curve correction with similar fusion lengths without neurologic problems in the operative treatment of AIS. Although more expensive, pedicle screw constructs had significantly less blood loss and slightly shorter fusion lengths than the sublaminar wire constructs.

DEMONSTRATION OF CRYPTIC INCOMPATIBILITY IN DISTYLOUS AMSINCKIA DOUGLASIANA.

Hand pollinations experiments with distylous Amsinckia douglasiana A. DC. (Boraginaceae) revealed that legitimate (intermorph) crosses produce more seed than self-pollinations and that self-pollinations yield more seed than illegitimate (intramorph) crosses. We tested the occurrence of cryptic incompatibility in both style-length morphs by pollinating them with a mixture of legitimate and illegitimate pollen, each homozygous for a different electrophoretically distinguishable allele of phosphoglucose isomerase. The success of intramorph pollen was greatly reduced in mixture; only about 4% of the offspring of both pins and thrums were sired by illegitimate pollen. One pin and one thrum had sufficiently high seed set that the results cannot be attributed to selective abortion of embryos. In those individuals, discrimination against illegitimate pollen must have occurred on the stigma or in the style. Based on our findings, it appears that illegitimate matings are rare in natural populations. The progeny of legitimate crosses was biased toward pins, which suggests some regulation of morph ratios independent of the style-length locus. Prezygotic discrimination against the thrum genotype or selective abortion of embryos with the thrum genotype are both possible, but selective mortality of seedlings with the thrum genotype cannot be ruled out for some families.