Jae Hwan Cho

Does preoperative T1 slope affect radiological and functional outcomes after cervical laminoplasty

Study Design. Retrospective comparative study. Objective. To analyze changes in the clinical and radiological factors related to cervical sagittal balance, relative to preoperative T1 slope, in patients with cervical myelopathy after laminoplasty (LP). Summary of Background Data. T1 slope is an important factor that should be considered before LP. However, until now, there have been no studies on how preoperative T1 slope affects the sagittal balance of cervical spine and various functional outcomes after LP. Methods. Seventy-six patients with cervical myelopathy (M:F ratio = 50:26; mean age = 64.7 ± 9.1 yr) underwent a cervical LP and were followed for more than 2 years. Radiological measurements were performed to analyze the following parameters: (1) C2–C7 sagittal vertical axis; (2) T1 slope; (3) C2–C7 lordosis; and (4) thoracic kyphosis. The visual analogue scale, Japanese Orthopedic Association, neck disability index, and 36-Item Short-Form Health Survey were also investigated. Patients were divided into 2 groups according to preoperative T1 slope, with the cutoff value being the median preoperative T1 slope. Changes in clinical and radiological parameters were compared between the preoperative evaluation and final visit. Results. Overall, C2–C7 sagittal vertical axis increased from 21.2 to 24.5 mm (P = 0.004) and C2–C7 lordosis decreased from 13.9° to 10.3° (P = 0.007) postoperatively. The T1 slope did not show any postoperative differences. Preoperative C2–C7 lordosis was larger in the high-T1 group (19.1°) than in the low-T1 group (9.0°). However, postoperative changes in C2–C7 sagittal vertical axis and C2–C7 lordosis did not show any between-group differences. Clinical outcomes (except neck pain) demonstrated overall improvement in both groups. Comparing changes in both groups showed no differences in neck pain, arm pain, neck disability index, or 36-Item Short-Form Health Survey physical component score between groups. Conclusion. Cervical sagittal balance is compromised after cervical LP. However, the degree of aggravation does not correlate with the preoperative T1 slope. Most clinical parameters demonstrate overall improvement regardless of preoperative T1 slope. Level of Evidence: 3

The clinical importance of lumbosacral transitional vertebra in patients with adolescent idiopathic scoliosis.

Study Design. Retrospective review of radiographs. Objective. The objective of this study was to (1) determine the prevalence of lumbosacral transitional vertebra (LSTV) with computed tomography (CT) and (2) correlate LSTV presence with lumbar disc degeneration at each level by magnetic resonance imaging. Summary of Background Data. LSTV is a frequently observed abnormality. Although its prevalence in patients with adolescent idiopathic scoliosis (AIS) has been shown, no studies have yet examined the clinical importance of LSTV in patients with AIS. Methods. This study included 385 consecutive patients who underwent surgery for AIS at a single center. Plain radiographs and CT scans were used to detect LSTV. Disc degeneration was analyzed at the L3–4, L4–5, and L5–S1 disc levels with magnetic resonance imaging. The difference in disc degeneration at each level by the presence of LSTV was also analyzed. The effect of lumbar curve type on the disc degeneration of each level was then determined. To minimize confounding factors, logistic regression analysis was performed. Results. The overall prevalence of LSTV in patients with AIS confirmed by CT scans was 12.2% (47/385). The proportion of grade II or more disc degeneration at the L4–5 level was higher in the LSTV(+) group than in the LSTV(−) group (29.8% vs.19.2%) although it was not statistically significant (P = 0.093). Large lumbar curves showed a positive correlation with disc degeneration at the L5–S1 level (P = 0.022). Conclusion. The prevalence of LSTV in patients with AIS was 12.2%. A trend of early degeneration in L4–5 level discs was found in patients with AIS with LSTV although it was not statistically confirmed. Disc degeneration at the L5–S1 level is related to a large lumbar curve. If patients with AIS with large lumbar curves have LSTV, consideration should be given to stopping the distal fusion at L3 instead of L4. Level of Evidence: 4

A novel technique to correct kyphosis in cervical myelopathy due to continuous-type ossification of the posterior longitudinal ligament.

OBJECTIVE Although posterior decompressive surgery is widely used to treat patients with cervical myelopathy and multilevel ossification of the posterior longitudinal ligament (OPLL), a poor outcome is anticipated if the sagittal alignment is kyphotic (or K-line negative). Accordingly, it is mandatory to perform anterior decompression and fusion in patients with cervical kyphosis. However, it can be difficult to perform anterior surgery because of the high risk of complications. This present report proposes a novel greenstick fracture technique to change the K-line from negative to positive in patients with cervical myelopathy, OPLL, and kyphotic deformity. METHODS Four patients with cervical myelopathy, continuous-type OPLL, and kyphotic sagittal alignment (who were K-line negative) were indicated for surgery. Posterior laminectomy and lateral mass screw insertions using a posterior approach were performed, followed by anterior surgery. Multilevel discectomy and thinning of the OPLL mass by bur drilling was performed, then an intentional greenstick fracture at each disc level was made to convert the cervical K-line from negative to positive. Finally, posterior instrumentation using a rod was carried out to maintain cervical lordosis. RESULTS MRI showed complete decompression of the cord by posterior migration in all cases, which had been caused by cervical lordosis. Restoration of neurological defects was confirmed at the 1-year follow-up assessment. No specific complications were identified that were associated with this technique. CONCLUSIONS A greenstick fracture technique may be effective and safe when applied to patients with cervical myelopathy, continuous-type OPLL, and kyphotic deformity (K-line negative). However, further studies with more cases will be required to reveal its generalizability and safety.

A retrospective study to reveal factors associated with postoperative shoulder imbalance in patients with adolescent idiopathic scoliosis with double thoracic curve.

OBJECTIVE Postoperative shoulder imbalance (PSI) is a critical consideration after corrective surgery for a double thoracic curve (Lenke Type 2); however, the radiographic factors related to PSI remain unclear. The purpose of this study was to identify the radiographic factors related to PSI after corrective surgery for adolescent idiopathic scoliosis (AIS) in patients with a double thoracic curve. METHODS This study included 80 patients with Lenke Type 2 AIS who underwent corrective surgery. Patients were grouped according to the presence [PSI(+)] or absence [PSI(-)] of shoulder imbalance at the final follow-up examination (differences of 20, 15, and 10 mm were used). Various radiographic parameters, including the Cobb angle of the proximal and middle thoracic curves (PTC and MTC), radiographic shoulder height (RSH), clavicle angle, T-1 tilt, trunk shift, and proximal and distal wedge angles (PWA and DWA), were assessed before and after surgery and compared between groups. RESULTS Overall, postoperative RSH decreased with time in the PSI(-) group but not in the PSI(+) group. Statistical analyses revealed that the preoperative Risser grade (p = 0.048), postoperative PWA (p = 0.028), and postoperative PTC/MTC ratio (p = 0.011) correlated with PSI. Presence of the adding-on phenomenon was also correlated with PSI, although this result was not statistically significant (p = 0.089). CONCLUSIONS Postoperative shoulder imbalance is common after corrective surgery for Lenke Type 2 AIS and correlates with a higher Risser grade, a larger postoperative PWA, and a higher postoperative PTC/MTC ratio. Presence of the distal adding-on phenomenon is associated with an increased PSI trend, although this result was not statistically significant. However, preoperative factors other than the Risser grade that affect the development of PSI were not identified by the study. Additional studies are required to reveal the risk factors for the development of PSI.

What is the Fate of Pseudarthrosis Detected 1 Year After Anterior Cervical Discectomy and Fusion

Study Design. Retrospective comparative study. Objective. To investigate the consequences and appropriate management of pseudarthrosis after anterior cervical discectomy and fusion (ACDF). Summary of Background Data. Pseudarthrosis is a frequent complication of ACDF and causes unsatisfactory results. Little is known about long-term prognosis of detecting pseudarthrosis 1 year after ACDF. Methods. Eighty-nine patients with a minimum 2-year follow-up were included. ACDF surgery using allograft and plating was performed: single-level in 51 patients, two-level in 26 patients, and three-level in 12 patients. Presence of pseudarthrosis was evaluated 1 year postoperatively and then the nonunion segments were re-evaluated 2 years postoperatively. Demographic data were assessed to identify the risk factors associated with pseudarthrosis. A visual analogue scale for neck/arm pain and the Neck Disability Index were analyzed preoperatively and at 1 and 2 years postoperatively. Results. Pseudarthrosis was detected in 29 patients (32.6%) 1 year postoperatively: 15of 51 patients after single-level surgery, 9 of 26 patients after two-level surgery, and 5 of 12 patients after three-level surgery. Only eight patients showed persistent nonunion at 2 years: 3 of 15 patients after single-level surgery, 3 of 9 after two-level surgery, and 2 of 5 after three-level surgery. The remaining 21 patients (72.4%) achieved bony fusion 2 years postoperatively without any intervention. Patients who underwent two-level or three-level ACDF had a significantly higher pseudarthrosis rate than those who underwent single-level ACDF, with odds ratios of 1.844 and 3.147, respectively. The improvements in visual analogue scale for neck pain and Neck Disability Index scores in the persistent nonunion group were significantly lower than those in the final union group at 2 years. Conclusion. Patients with pseudarthrosis detected 1 year postoperatively may be observed without any intervention because approximately 70% of them will eventually fuse by the 2-year point. Early revision could, however, be considered if the pseudarthrosis is associated with considerable neck pain after multilevel ACDF. Level of Evidence: 3

Progression of trunk imbalance in adolescent idiopathic scoliosis with a thoracolumbar/lumbar curve: is it predictable at the initial visit?

OBJECTIVE Progression of trunk imbalance is an important finding during follow-up of patients with adolescent idiopathic scoliosis (AIS). Nevertheless, no factors that predict progression of trunk imbalance have been identified. The purpose of this study was to identify parameters that predict progression of trunk imbalance in cases of AIS with a structural thoracolumbar/lumbar (TL/L) curve. METHODS This study included 105 patients with AIS and a structural TL/L curve who were followed up at an outpatient clinic. Patients with trunk imbalance (trunk shift ≥ 20 mm) at the initial visit were excluded. All patients were followed up for more than 2 years. Patients were divided into the following groups according to progression of trunk imbalance: 1) Group P, trunk shift ≥ 20 mm at the final visit and degree of progression ≥ 10 mm; and 2) Group NP, trunk shift < 20 mm at the final visit or degree of progression < 10 mm. Radiological parameters included Cobb angle, upper end vertebrae and lower end vertebrae (LEV), LEV tilt, disc wedge angle between LEV and LEV+1, trunk shift, apical vertebral translation, and apical vertebral rotation (AVR). Each parameter was compared between groups. Radiological parameters were assessed at every visit using whole-spine standing anteroposterior radiographs. RESULTS Among the 105 patients examined, 13 showed trunk imbalance with progression ≥ 10 mm at the final visit (Group P). Multivariate logistic regression analysis identified a lower Risser grade (p = 0.002) and a greater initial AVR (p = 0.020) as predictors of progressive trunk imbalance. A change in LEV tilt during follow-up was associated with trunk imbalance (p = 0.001). CONCLUSIONS Risser grade and AVR measured at the initial visit may predict progression of trunk imbalance. Surgeons should consider the risk of progressive trunk imbalance if patients show skeletal immaturity and a greater AVR at the initial visit.

Clinical and radiographic outcomes following hinge fracture during open-door cervical laminoplasty

To investigate the clinical and radiographic fate of fractured hinges in open-door cervical laminoplasty, 135 segments of 36 patients who had undergone follow-up for more than two years after open-door cervical laminoplasty due to compressive cervical myelopathy were reviewed clinically and radiographically. Hinge fractures were identified by the intraoperative finding of obvious instability or click sounds (an obvious fracture), or by immediate postoperative computed tomography (CT) images showing a discontinuity of both the inner and outer cortex or a displacement of more than 1mm at the lamina hinge site (an occult fracture). At two years post-surgery, union and displacement of the fractured hinges were evaluated with CT and the clinical outcome was assessed by the Japanese Orthopedic Association (JOA) and Neck Disability Index (NDI) scores. Immediate postoperative CT scans revealed 28 hinge fractures in 16 patients. Only three fractures were identified during surgery, with most being identified on postoperative CT. Nineteen laminae showed non-displaced cortical discontinuity, five were anteriorly displaced by more than 1mm, and four were displaced posteriorly. Twenty-five laminae (89.3%) had achieved union according to the two-year postoperative CT scan. No de novo neurologic symptoms were found to be associated with hinge fracture. The two-year postoperative JOA and NDI scores did not differ significantly between patients with or without a hinge fracture. Most fractures at the hinge site occurred without intraoperative recognition, and usually re-unified without significant displacement or adverse clinical effects. When hinge fractures occur, careful observation without additional intervention is recommended.

Does Additional Uncinate Resection Increase Pseudarthrosis Following Anterior Cervical Discectomy and Fusion

Study Design. Retrospective comparative study. Objective. To investigate whether unilateral or bilateral uncinate resection (UR) combined with anterior cervical discectomy and fusion (ACDF) increases the risk of pseudarthrosis at long-term follow-up. Summary of Background Data. Uncoforaminotomy (or UR), performed along with ACDF, facilitates better and faster improvement of arm pain. As uncovertebral joints are important for maintaining stability, they may affect the fusion process by causing segmental instability if resected during ACDF. Methods. We retrospectively examined 167 patients (89 men, 78 women; mean age, 58.4u200a±u200a10.5 yr) who consecutively underwent single- or double-level ACDF and were followed for >2 years. UR was not performed in 46 patients (N-UR group). UR of at least one foramen was performed in 121 patients (UR group), including unilateral UR in 89 patients (U-UR group) and bilateral UR in 32 patients (B-UR group). Demographic data, fusion rate, visual analog scale (VAS) scores for neck/arm pain, and neck disability index (NDI) scores were compared between the N-UR and UR groups. Moreover, the fusion rates after the single- and double-level procedures were compared among the groups. Results. There was no difference in sex, age, weight, height, body mass index (BMI), and smoking history between the N-UR and UR groups. The fusion rates after single-level ACDF were not significantly different among the N-UR, U-UR, and B-UR groups (91.4%, 97.8%, and 88.2%; Pu200a=u200a0.290). Solid fusion was achieved in all groups after double-level ACDF (72.7%, 95.5%, and 86.7%), although the rates did not significantly differ among the groups (Pu200a=u200a0.071). The improvement in the VAS score for arm pain was significantly better in the UR group than in the N-UR group at short-term follow-up (Pu200a<u200a0.001). Conclusion. Unilateral or bilateral UR does not affect the fusion rate after single- or double-level ACDF. Hence, if necessary, additional UR can be performed during ACDF without concern regarding nonunion. Level of Evidence: 4

A Ct-based Simulation Study to Compare the Risk of Facet Joint Violation by the Cervical Pedicle Screw Between Degenerative and Nondegenerative Cervical Spines

Study Design. A retrospective case-control study. Objective. This study aimed (A) to compare entry points and trajectories of the cervical pedicle screw (CPS) between degenerative and nondegenerative spines, and (B) to evaluate the risk of facet joint violation by the CPS according to the degree of facet degeneration. Summary of Background Data. Entry point, trajectories, and risk of misplacement of the CPS have been widely researched; however, its application to degenerative cervical spine has to be elucidated. Methods. Sixty patients who underwent cervical surgeries at our institution were classified into two groups according to cervical facet joint degeneration. A simulation program with 0.7-mm thickness axial computed tomographic images was used to evaluate facet joint violation by the CPS from C3 to C6. Horizontal and vertical offsets of entry points were measured from two different anatomical landmarks on lateral mass, namely the lateral notch and the center of the superior ridge. The transverse and sagittal angles of the screws were also measured. Facet joint violation was evaluated and classified into either “minor” (<50% of screw diameter) or “major” (≥50% of screw diameter). Results. The mean transverse and sagittal angles showed no difference between the two groups. However, a more superior vertical offset from the superior ridge in terms of entry point was observed in the degenerative cervical spine group at all levels (Pu200a=u200a0.001–0.026). In addition, facet joint violation was more frequently found in severely degenerated facet joints than in mild to moderately degenerated facet joints (Pu200a=u200a0.011). Conclusion. The entry point of CPS was moved more superiorly in the degenerative cervical spine in this study, which increased the risk of facet joint violation in our patients. Thus, surgeons need to modify the insertion technique of the CPS or to insert lateral mass screw instead of the CPS when it is considered to insert screws at the uppermost vertebra in the degenerative cervical spine. Level of Evidence: 4

Can C3 Laminectomy Reduce Interlaminar Bony Fusion and Preserve the Range of Motion After Cervical Laminoplasty

Study Design. Retrospective comparative study. Objective. To investigate whether the resection of C3 lamina during cervical laminoplasty can prevent C2-C4 interlaminar bony fusion and preserve the range of motion (ROM) postoperatively. Summary of Background Data. Interlaminar bony fusion is a common complication after cervical laminoplasty, especially in the C2-C4. Laminectomy, rather than laminoplasty, of C3 has been recently introduced. Its advantages include minimizing muscle detachment at C2 and reducing postoperative neck pain. Methods. A total of 59 patients with cervical spondylotic myelopathy that involved three or more levels, including C3, were consecutively treated with laminoplasty and followed up for more than 3 years after surgery. The first 45 patients underwent open-door laminoplasty at C3 (Lp group) and the subsequent 14 patients underwent laminectomy at C3 rather than laminoplasty (Ln group). The Lp group was further divided into two subgroups based on the development of interlaminar bony fusion at C2-C3u200aand/or C3-C4: Lp-NF (nonfusion) and Lp-F (fusion) groups. Clinical outcomes and radiographic parameters were assessed pre- and postoperatively. Results. Nineteen out of 45 patients who underwent laminoplasty demonstrated fusion at 3-year follow up. Fusion developed more commonly in those patients who had a smaller preoperative ROM at C2-C4 segments (Lp-F 14.3°u200a±u200a6.9° vs. Lp-NF 21.4°u200a±u200a5.3°, Pu200a=u200a0.013). The neck disability index (range, 13.4u200a±u200a7.3 to 6.3u200a±u200a5.2, Pu200a<u200a0.001), visual analog scale for neck pain (range, 2.5u200a±u200a1.7 to 0.9u200a±u200a1.3, Pu200a=u200a0.027), Japanese Orthopedic Association (JOA) score (range, 14.3u200a±u200a1.9 to 16.0u200a±u200a2.4, Pu200a<u200a0.001), and JOA recovery rate (63.4u200a±u200a19.8%) in the Ln group improved postoperatively; however, there was no significant difference in the improvement of these clinical outcomes among all three groups. Postoperative cervical ROM was significantly reduced in all groups; however, the extent of reduction was significantly smaller in the Ln group (10.5°; range, 44.2°u200a±u200a9.1° to 33.7u200a±u200a6.0°) than in the Lp-NF (15.1°; range, 45.4°u200a±u200a8.5° to 30.3°u200a±u200a7.4°) or Lp-F (18.2°; range, 39.6°u200a±u200a9.3° to 21.4°u200a±u200a10.3°) groups (Pu200a<u200a0.05). Conclusion. C3 laminectomy with laminoplasty can prevent interlaminar bony fusion at C2-C4 and, ultimately, result in better preservation of cervical ROM than C3 laminoplasty. Furthermore, it yields similar clinical outcomes when compared with C3 laminoplasty. Level of Evidence: 3