Improvement of pulmonary function and reconstructed 3D lung volume after deformity correction for thoracic spinal posttubercular kyphosis: a multicenter study.

OBJECTIVE: The aim of this study was to investigate the influence of corrective surgery on thoracic spinal posttubercular kyphosis (PTK) with respect to lung volume and pulmonary function. METHODS: This was a retrospective study of 126 patients (72 males and 54 females) who underwent posterior vertebral column resection (PVCR) for severe thoracic spinal PTK between September 2013 and June 2020. The patients' spinal parameters, results of their pulmonary function test (PFT), and CT-based 3D lung volume were recorded and analyzed preoperatively and at final follow-up. The correlation of kyphosis correction with the PFT and lung volume was evaluated. RESULTS: The mean local kyphosis decreased from 112.5° to 37.2°, and the mean local scoliosis decreased from 20.9° to 5.2°; C2-7 lordosis, thoracic kyphosis, and lumbar lordosis also significantly improved after surgery. The mean CT-based lung volume significantly increased from 2.9 L preoperatively to 3.6 L at the final follow-up. The indices of PFT, including forced vital capacity (FVC), percent predicted FVC, total lung capacity, and forced expiratory volume in 1 second, were also significantly improved, and 60 patients with pulmonary dysfunction recovered to normal at the final follow-up. The correlation analysis revealed that the correction of local kyphosis was closely correlated with the improvement in PFT and the increase in lung volume. CONCLUSIONS: PVCR cannot only effectively realign the spine in patients with severe thoracic spinal PTK deformity but also significantly improve pulmonary function. Adequate local kyphosis correction should be highly valued, as it is a key factor in increasing lung volume.

Independent Correlation of the C1-2 Cobb Angle With Patient-Reported Outcomes After Correcting Chronic Atlantoaxial Instability.

OBJECTIVE: To investigate three-planar radiographic results and patient-reported outcomes (PROs) after correcting chronic atlantoaxial instability (AAI) by translaminar screw (TLS) and pedicle screw (PS) fixation, and to explore the potential association of atlantoaxial realignment with PRO improvements. METHODS: Twenty-three patients who underwent C1 lateral mass screw (LMS)-C2 TLS and 29 who underwent C1 LMS-C2 PS with ≥ 2 years of follow-up were retrospectively analyzed. Three-planar (sagittal, coronal, and axial) radiographic parameters were measured. PROs including the Neck Disability Index (NDI), Japanese Orthopaedic Association (JOA) score and the Short Form 36 Physical Component Summary (SF-36 PCS) were documented. Factors potentially associated with PROs were identified. RESULTS: The radiographic parameters significantly changed postoperatively except the C1-2 midlines' intersection angle in the TLS group (p = 0.073) and posterior atlanto-dens interval in both groups (p = 0.283, p = 0.271, respectively). The difference in bilateral odontoid lateral mass interspaces at last follow-up was better corrected in the TLS group than in the PS group (p = 0.010). Postoperative PROs had significantly improved in both groups (all p < 0.05). Thereinto, NDI at last follow-up was significantly lower in the TLS group compared with PS group (p = 0.013). In addition, blood loss and operative time were obviously lesser in TLS group compared with PS group (p = 0.010, p = 0.004, respectively). Multivariable regression analysis revealed that a change in C1-2 Cobb angle was independently correlated to PROs improvement (NDI: ß = -0.435, p = 0.003; JOA score: ß = 0.111, p = 0.033; SF-36 PCS: ß = 1.013, p = 0.024, respectively), also age ≤ 40 years was independently associated with NDI (ß = 5.40, p = 0.002). CONCLUSION: Three-planar AAI should be reconstructed by C1 LMS-C2 PS fixation, while sagittal or coronal AAI could be corrected by C1 LMS-C2 TLS fixation. PROs may improve after atlantoaxial reconstruction in patients with chronic AAI. The C1-2 Cobb angle is an independent predictor of PROs after correcting chronic AAI, as is age ≤ 40 years for postoperative NDI.

Coronal Multiplane Reconstructed Computed Tomography Image Determining Lateral Vertebral Notch-Referred Pedicle Screw Entry Point in Subaxial Cervical Spine: A Preclinical Study.

OBJECTIVE: To evaluate feasibility of computed tomography (CT) coronal multiplane reconstruction image (CMRI) to determine subaxial cervical pedicle screw (PS) entry point and guide lateral vertebral notch (LVN)-referred technique for subaxial cervical PS insertion. METHODS: Cervical CT scans were performed in 40 volunteers. PS entry point was determined by quantitating PS entry point related to LVN on CMRI. Pedicle mediolateral angle (α) and cephalocaudad angle (ß) were also measured to guide the trajectory of PS insertion. Based on these quantitations, 12 human cadaveric subaxial cervical pedicles were inserted with PS referring to LVN. Cortical integrity of each pedicle was evaluated after dissecting the cadaveric vertebrae one by one and confirmed by radiography and CT. The cortical penetration and PS position were classified into 4 grades: 0 (excellent position), I (good position), II (fair position), and III (poor position). RESULTS: On CT CMRI, PS entry point was consistently located approximately 2.2 mm medial to LVN from C3 to C7 and approximately 1.4 mm lower to LVN from C3 to C6, but 1.2 mm higher at C7. Bilateral α angle and ß angle showed substantial decrease from cranial to caudal. Cortical integrity of PS positions was excellent and good in 88.33%, fair in 8.33%, and poor in 3.33%. CONCLUSIONS: CMRI is reliable for determining subaxial cervical PS entry point. LVN is a consistent landmark for the notch-referred technique, which is a practical and easy to master technique for subaxial cervical spine PS insertion.

The accuracy of the lateral vertebral notch-referred pedicle screw insertion technique in subaxial cervical spine: a human cadaver study.

STUDY DESIGN: This is a cadaver specimen study to confirm new pedicle screw (PS) entry point and trajectory for subaxial cervical PS insertion. OBJECTIVE: To assess the accuracy of the lateral vertebral notch-referred PS insertion technique in subaxial cervical spine in cadaver cervical spine. BACKGROUNDS: Reported morphometric landmarks used to guide the surgeon in PS insertion show significant variability. In the previous study, we proposed a new technique (as called "notch-referred" technique) primarily based on coronal multiplane reconstruction images (CMRI) and cortical integrity after PS insertion in cadavers. However, the PS position in cadaveric cervical segment was not confirmed radiologically. Therefore, the difference between the pedicle trajectory and the PS trajectory using the notch-referred technique needs to be illuminated. METHODS: Twelve cadaveric cervical spines were conducted with PS insertion using the lateral vertebral notch-referred technique. The guideline for entry point and trajectory for each vertebra was established based on the morphometric data from our previous study. After 3.5-mm diameter screw insertion, each vertebra was dissected and inspected for pedicle trajectory by CT scan. The pedicle trajectory and PS trajectory were measured and compared in axial plane. The perforation rate was assessed radiologically and was graded from ideal to unacceptable: Grade 0 = screw in pedicle; Grade I = perforation of pedicle wall less than one-fourth of the screw diameter; Grade II = perforation more than one-fourth of the screw diameter but less than one-second; Grade III = perforation more than one-second outside of the screw diameter. In addition, pedicle width between the acceptable and unacceptable screws was compared. RESULTS: A total of 120 pedicle screws were inserted. The perforation rate of pedicle screws was 78.3% in grade 0 (excellent PS position), 10.0% in grade I (good PS position), 8.3% in grade II (fair PS position), and 3.3% in grade III (poor PS position). The overall accepted accuracy of pedicle screws was 96.7% (Grade 0 + Grade I + Grade II), and only 3.3% had critical breach. There was no statistical difference between the pedicle trajectory and PS trajectory (p > 0.05). Compared to the pedicle width (4.4 ± 0.7 mm) in acceptably inserted screw, the unacceptably screw is 3.2 ± 0.3 mm which was statistically different (p < 0.05). CONCLUSION: The accuracy of the notch-referred PS insertion in cadaveric subaxial cervical spine is satisfactory.