Hong Zhang

This study aimed to introduce a novel angular kyphosis reduction device (AKRD) designed for vertebral column resection (VCR) in severe angular kyphosis and to evaluate its effectiveness and feasibility using a sawbones model and a porcine cadaver model. A thoracolumbar angular kyphosis deformity (apex at T11) was created in a sawbones spine model and corrected using the AKRD to assess mechanical performance. Subsequently, a five-month-old porcine cadaver model was used to simulate thoracolumbar angular kyphosis, followed by deformity correction with the AKRD to evaluate its feasibility during VCR. In the sawbones model, kyphosis was corrected from 51.9° ± 0.7° to 17.6° ± 0.8° (66.1% correction), with a 53.3% reduction in posterior elements (34.7 to 16.2 mm), 76.9% elongation of the anterior column (21.6 to 38.2 mm), and a mean apical vertebral translation of 65.9 ± 7.1 mm. In the porcine cadaver model, the AKRD maintained segmental stability during resection and achieved a 91% correction, with minimal spinal cord length change (10.8%). The AKRD provides controlled and effective deformity correction through a cage-hinge mechanism while maintaining construct stability. These findings demonstrate its mechanical feasibility and support its potential application in VCR for severe angular kyphosis, warranting further preclinical and clinical evaluation.

Triradiate cartilage (TRC) status is commonly used to assess skeletal maturity and progression risk in scoliosis; however, its traditional binary classification as open or closed may inadequately capture critical transitional growth periods. This study aimed to re-evaluate TRC maturation by subdividing it into four stages and to investigate scoliosis progression and growth patterns during the transitional phases. A retrospective longitudinal study was conducted of 179 patients with idiopathic scoliosis (126 girls, 53 boys) who were followed from childhood through early adolescence. Inclusion criteria were age > 6 years with an open TRC at baseline, initial major Cobb angle < 45° (mean 27.8° ± 10° in girls and 30.3° ± 9.5° in boys), and documented curve progression to ≥ 50° requiring surgical treatment during adolescence. TRC status was classified as open, closing, initial closed, or fully closed based on radiographic appearance and the Risser sign. Cobb progression rate, spine height increase rate, and standing height increase rate were measured and calculated for the open-, closing-, and initial-closed-TRC stages. In both sexes, Cobb progression peaked during the closing-TRC stage, increasing approximately fivefold in girls and more than 30-fold in boys compared with the open-TRC stage (p < 0.0001). Elevated Cobb progression rate persisted into the initial closed-TRC stage. Spine height increase rate did not peak during the closing-TRC and showed a significant inverse correlation with Cobb progression in girls, whereas standing height remained relatively stable and did not correlate with Cobb progression in either sex. The closing-TRC stage represents a critical transitional period associated with accelerated scoliosis progression, independent of overall somatic growth. A four-stage TRC framework may improve early risk stratification and clinical decision-making in skeletally immature patients with idiopathic scoliosis.

To introduce a novel uniplanar correction concept-termed the kyphoscoliosis plane (KSP); and evaluate the feasibility of a purpose-designed external hinge (EH) correction system for vertebral column resection (VCR) in severe thoracic kyphoscoliosis using 3D-printed life-size models. Seven life-size 3D-printed thoracic spine models were generated from CT scans of severe thoracic kyphoscoliosis patients (2 girls, 5 boys; mean age: 10.6 ± 3.7 years). The mean preoperative scoliosis and kyphosis angles were 88.1° ± 27 and 117.1° ± 22.4, respectively. Curve apices were located in the upper thoracic (T4-T7, n = 4), middle thoracic (T9-T10, n = 2), and lower thoracic (T11, n = 1) regions. The EH system, comprising a dual-axis hinge, L-shaped clamps, and a threaded reduction rod, was applied to simulate VCR correction. Pre- and post-correction measurements included Cobb angles, resection gap dimensions, apical spinal cord translation, and apical spinal cord length. Scoliosis improved to 19.1° ± 9.7° (78.3% correction) and kyphosis to 22.7° ± 13° (80.6% correction). At the resection gap, the concave side elongated by 52%, the convex side was reduced by 66.4%, and the anterior aspect elongated by 18.2%. The KSP remained stable, with only a 1 ± 2.9° (1.8%) change. Apical spinal cord length decreased by just 1.4 ± 1.5 mm (6.7%), indicating minimal spinal cord strain. Apical spinal cord translation averaged 55.7 ± 3.3 mm along the KSP, corresponding to a 57% reduction in both coronal and sagittal displacement. The KSP concept and EH system provide a controlled and effective uniplanar strategy for achieving 3D correction in severe thoracic kyphoscoliosis, particularly during VCR, while minimizing spinal cord tension.

Purpose To evaluate the growth modulation and corrective effects of a novel polyetheretherketone spring rib plate (PEEK-SRP) implant in a porcine model of early-onset thoracic scoliosis (EOS). Methods 15 one-month-old pigs underwent thoracic nerve transection to induce right thoracic scoliosis. After 1.5 months of curve progression, animals were assigned to 3 groups: Untreated Group (UG, n = 6): Observed without intervention; Treated Group (TG, n = 6): PEEK-SRP implanted at three ribs on the convex apical levels; and Sham Group (SG, n = 3): Underwent the same surgical procedures as TG without the PEEK plate implantation. Radiographic and CT-based assessments were performed to evaluate Cobb angle, apical vertebral rotation (AVR), rib hump index (RHI), vertebra–rib angle difference (RVAD), thoracic volume, and spinal growth over 2.5 months. Results Baseline curves averaged 43.7 ± 9.4° with no group differences. At 2.5 months, the Cobb angle decreased by 17.5% (41.8° ± 11° to 34.5° ± 14.6°) in TG, compared with progression of 27.6% (54° ± 15.9° to 68.9° ± 16.8°) in UG (p = 0.0036) and 72% (35.4° ± 11.7° to 60.9° ± 5.9°) in SG (p = 0.0223). The PEEK-SRP reduced AVR by 87.3% (p < 0.0104), RHI by 79.4% (p < 0.0340), and improved RVAD by 15.2% (p < 0.0489) compared with controls. TG also demonstrated a 44% increase in convex thoracic area and an 86.8% increase in convex thoracic width compared to UG (p < 0.0005). Spine growth rate (9.6 ± 2.4 mm/week in UG, 12.7 ± 4.6 mm/week in TG, and 9.4 ± 0.4 mm/week in SG) was not different among the three groups (p = 0.1844). Conclusion The PEEK-SRP system provided effective apical control, rib cage remodeling, and spinal correction while preserving thoracic growth in a porcine EOS model. This transverse load-sharing, non-fusion strategy directly targets rib–spine deformity and shows promise as a growth-friendly treatment for EOS. Key Points 1. The PEEK-SRP system offers a novel, non-fusion strategy for treating early-onset thoracic scoliosis by targeting rib cage deformities at the curve apex. 2. Unlike traditional growing rods, which are longitudinal load-bearing devices with high complication rates and no apical control, the PEEK-SRP system functions as a transverse load-sharing implant that directly modulates rib–spine growth. 3. In a porcine EOS model, PEEK-SRP implantation significantly reduced spinal curvature, apical vertebral rotation, and rib hump deformity, while increasing thoracic volume. 4. The implant preserved spinal growth and flexibility, confirming its role as a growth-friendly corrective system. 5. This study supports the clinical potential of PEEK-SRP for children with moderate progressive scoliosis, offering segmental correction without compromising thoracic development.

Purpose To introduce a novel uniplanar clamp-hinge (Uni-CH) correction system designed for vertebral column resection (VCR) of severe angular kyphosis and test its efficacy using a sawbone simulating model. Methods The Uni-CH was introduced and its functionality was demonstrated on a sawbone model simulating severe angular kyphosis. An 83° thoracolumbar angular kyphosis with the apex at T11 was simulated in the sawbone spine model. The deformity was then corrected using the Uni-CH to identify the optimal hinge position for VCR reduction of severe angular kyphosis. Results The thoracolumbar angular kyphosis, initially measuring a mean of 82.7 ± 0.5°, was corrected to 0°, achieving a 100% correction rate. The optimal hinge position was identified to be at the level of the posterior vertebral body wall (PVBW), which allowed for the maintenance of the spinal cord with a slight shortening of 3%. In contrast, hinge positions located more posteriorly to the PVBW resulted in a greater 42% lengthening of the spinal cord, while positions located more anteriorly led to a greater 27% shortening of the spinal cord. Conclusions The Uni-CH proves its efficacy in providing consistent stability to the spinal segments and acts as an adjustable and controllable hinge for VCR correction of severe angular kyphosis in the sawbone model. Placing the hinge pivot at the level of the PVBW preserves the spinal cord, preventing excessive shortening or lengthening during VCR reduction of severe angular kyphosis.

Purpose To test whether multiple-level unilateral thoracic spinal nerves (TSN) resection can induce the initial thoracic cage deformity to cause early onset thoracic scoliosis in an immature porcine model; and 2) to create an early onset thoracic scoliosis in a large animal model that can be used to evaluate growth-friendly surgical techniques and instruments in growing spine researches. Methods Seventeen one-month-old pigs were assigned to 3 groups. In group 1 (n = 6), right TSN were resected from T7 to T14 with the contralateral (left) paraspinal muscle exposing and stripping. In group 2 (n = 5), the animals were treated in the same way except the contralateral (left) side was intact. In group 3 (n = 6), bilateral TSN were resected from T7 to T14. All animals were followed up for 17-weeks. Radiographs were measured and analyzed the correlation between the Cobb angle and thoracic cage deformity. A histological examination of the intercostal muscle (ICM) was performed. Results In the groups 1 and 2, an average 62 ± 12° and 42 ± 15° right thoracic scoliosis with apical hypokyphosis of a mean − 5.2 ± 16° and − 1.8 ± 9° were created, respectively, during 17-weeks follow up. All curves were located at the operated levels with the convexity toward the TSN resection side. Statistical analysis demonstrated that the thoracic deformities were strongly correlated with the Cobb angle. In group 3, no scoliosis was created in any animal, but an average thoracic lordosis of − 32.3 ± 20.3° was seen. The histological examination showed the ICM denervation on the TSN resection side. Conclusion Unilateral TSN resection induced the initial thoracic deformity toward the TSN resection side resulting in thoracic hypokyphotic scoliosis in an immature pig model. This early onset thoracic scoliosis model could be used to evaluate the growth-friendly surgical techniques and instruments in future growing spine researches.

Purpose To introduce a novel Hinge-Link (HL) correction system for vertebral column resection (VCR) in the most severe scoliosis and surgically assess the device in a porcine scoliosis model. Methods The HL was introduced and described how it works on a reproduced three-dimensional spine model of severe scoliosis. A right thoracic scoliosis was surgically created in five 4-month-old pigs. Two weeks later, the VCR was performed to correct the deformity using the HL to test its feasibility and neurological safety in the pig scoliosis model. Results The surgically created right thoracic scoliosis averaged 32° ± 9.3 prior to the VCR. All animals tolerated the VCR procedure awakening neurologically intact and ambulated for 24 h. The HL takes advantage of the ability to provide three-dimensional correction of the deformity and excellent control of the spine segments to prevent damage to the spinal cord in the VCR procedure. The mean correction of the scoliosis was 94% correcting to 1.8° ± 0.8. At sacrifice, the pathological anatomy of the neural axis demonstrated no vertebral subluxation and no dural impingement in any animal. Conclusion The HL was feasible and neurologically safe for the VCR procedure in the pig scoliosis model. It can provide significant correction of the spinal deformity with appropriate mild shortening at the resected levels and overall lengthening without neurologic deficits. The rigid control of the spine segments provided by this device should allow for improved correction with decreased neurologic deficits and potentially shorter surgical time.

Study Design: Retrospective review. Objectives: To compare the Cobb >75° scoliosis correction obtained using a novel Rod-Link-Reducer (RLR) system versus traditional corrective techniques (TCT) in patients with severe adolescent idiopathic scoliosis (AIS). Summary of Background Data Current implant strategies provide for good correction, especially for moderate curves; however, severe scoliosis continues to be challenging to obtain correction in a safe and effective manner. Methods: A novel correction device was developed so that two provisional rods are placed on the convex side of the scoliosis proximally and distally, which are then linked to an external reduction device termed the RLR. A retrospective analysis was performed to compare the RLR versus the TCT in patients with curve >75° with the diagnosis of AIS with respect to the radiographic outcomes, operative time, intraoperative blood loss, complications, and SRS-30 scores of a minimum 2-year follow-up. Results: A total of 36 patients were evaluated (RLR-18, TCT-18). The data sets were similar for age, gender, coronal Cobb, curve flexibility, and follow-up period. The mean preoperative Cobb for the RLR group was 91.7° (76°–113°) and 91.8° (78°–108°) for the TCT group. The mean coronal Cobb correction rate was significantly greater for the RLR group (73.1% vs. 56.6%, p < .0001). The mean operative time was 74.8 minutes shorter in the RLR group (316.6 minutes vs. 391.4 minutes, p = .03). There were 2 late-developing infections and 3 intraoperative neuro-monitoring changes during the correction maneuvers in the TCT group compared with none in the RLR group (p = .02). Conclusion: In a matched cohort, the use of the RLR exhibited greater coronal Cobb correction, shorter operative time, and was less likely to have critical neuro-monitoring changes compared with the TCT group. The RLR provides safer and improved correction for severe curves without adding surgical risk. Level of Evidence: Level III.

Retrospective review. To assess whether the lumbar gap (LG) measurement, which is the distance between the center sacral vertical line and the concave edge of the apical vertebra of the lumbar curve, would be a useful tool to predict the need for lumbar curve fusion in the Lenke 1-4C curves. The current treatment guidelines of selective thoracic fusion in the Lenke 1-4C curves are not routinely accepted. One hundred three adolescent idiopathic scoliosis (AIS) patients had undergone either selective thoracic fusion (STF) or both thoracic and lumbar curves fusion (TLF) for Lenke 1-4C curves. The correlations between the fusion decision making and preoperative LG, coronal balance, thoracic and lumbar Cobb, apical vertebra translation, and rotation were analyzed. The radiographic outcomes and SRS-30 of a minimum 2-year follow-up were reviewed in each group. A total of 51 patients (49.5%) underwent an STF, and 52 patients (50.5%) underwent a TLF. The mean LG was 22.0 ± 8.8 mm in the TLF, which was 2.3 times greater than the STF (9.6 ± 3.9 mm) (p < .0001). Only 5% of the lumbar curves were fused when the LG was 10 mm or less. Ninety percent of the lumbar curves were fused when the LG was 16 mm or greater, and 100% lumbar curves were fused with an LG of 21 mm or greater. The preoperative coronal imbalance to the left in the TLF was significantly greater than the STF. A mean 47% thoracic correction corresponded to a mean 39% spontaneous correction of the lumbar curve obtained in the SFT, which was significantly different from the TLF (56% and 65%). There were no differences in the SRS-30 scores at 2 years postoperatively between the STF and the TLF. The lumbar curve should not be fused when the LG was 10 mm or less, and very likely should be fused when the LG exceeds 20 mm in the Lenke 1-4C AIS patients. Level III.