Abstract
Objective
Surgical decision‐making for congenital kyphosis (CK) with failure of anterior segmentation (type II) has been contradictory regarding the trade‐off between the pursuit of correction rate and the inherent risk of the osteotomy procedure. This study was designed to compare the clinical and radiographic measurement in type II CK underwent SRS‐Schwab Grade 4 osteotomy and vertebral column resection (VCR), the most‐adapted osteotomy techniques for CK, and to propose the strategy to select between the two procedures.
Methods
This retrospective observational comparative study evaluated surgical outcomes in type II CK patients underwent VCR or SRS‐Schwab Grade 4 osteotomy at our institution between January 2015 and January 2020. Patients operated with VCR and SRS‐Schwab Grade 4 osteotomy were allocated to Group 1 and Group 2 respectively. Radiographic parameters and SRS‐22 quality of life metrics were assessed at pre‐operation, post‐operation, and during follow‐up visits for both groups, allowing for a comprehensive comparison of surgical outcomes.
Results
Thirty‐one patients (19 patients in Group 1 and 12 patients in Group 2) aged 16.3 ± 10.4 years were recruited. Correction of segmental kyphosis was similar between groups (51.1 ± 17.6° in Group 1 and 48.4 ± 19.8° in Group 2, p = 0.694). Group 1 had significantly longer operation time (365.9 ± 81.2 vs 221.4 ± 78.9, p < 0.001) and more estimated blood loss (975.2 ± 275.8 ml vs 725.9 ± 204.3 mL, p = 0.011). Alert event of intraoperative sensory and motor evoked potential (SEP and MEP) monitoring was observed in 1 patient of Group 2. Both groups had 1 transient post operative neurological deficit respectively.
Conclusion
SRS‐Schwab Grade 4 osteotomy was suitable for kyphotic mass when its apex is the upper unsegmented vertebrae or the neighboring disc, or when the apical vertebrae with an anterior/posterior (A/P) height ratio of vertebral body higher than 1/3. VCR is suitable when the apex is located within the unsegmented mass with its A/P height ratio lower than 1/3. Proper selection of VCR and SRS‐Schwab Grade 4 osteotomy according to our strategy, could provide satisfying radiographic and clinical outcomes in type II CK patients during a minimum of 2 years follow‐up. Patients undergoing VCR procedure might have longer operation time, more blood loss and higher incidence of peri‐ and post‐operative complications.
Keywords: Congenital kyphosis, Failure of segmentation, SRS‐Schwab Grade 4 osteotomy, Vertebral column resection
Illustration of our selection strategy for SRS‐Schwab Grade 4 osteotomy (A, B) and vertebral column resection (C) for patients with type II congenital kyphosis. Both techniques, if selected properly, could provide sufficient correction of kyphosis and satisfying clinical outcome.
Introduction
Congenital kyphosis (CK), a sagittal deformity derived from aberrant embryologic development in formation of vertebral column, 1 is traditionally classified into three types including failure of formation (type I), failure of segmentation (type II) and mixed anomalies (type III). 2 According to previous studies, the type II CK represents approximately 20%–36% of CK patients with the mean annual progression ranging from 1° to 2.5° depending on morphology and location of the curve, as well as patients' age. 3 , 4 In a classic study by Mayfield et al. 4 , the natural history of CK due to deficits of anterior segmentation was reported in eight pediatric patients aged 9.13 ± 3.83 (range 1 ~ 12) years old, reporting total progression of segmental kyphosis by 30.25 ± 27.96° (range, 7° ~ 94°) during a follow‐up period of 5.75 ± 2.49 (range, 3 ~ 11) years. Aside from the cosmetic problem, severe kyphosis due to type II CK could cause pain and neurological problems that requiring surgical correction. 2 , 3 , 4 , 5 The rigid nature of anterior or circumferential failure of segmentation in type II CK rendered indispensably radical and risky corrective surgery, raising the question on how to trade‐off between safety and effectivity regarding the selection of surgical techniques.
It has been widely accepted that 3‐column osteotomy techniques are the mainstay treatments for patients with moderate to severe CK, during which the vertebral column resection (VCR) of unsegmented vertebra is traditionally performed. 6 , 7 Though satisfactory clinical and radiographic outcomes could be expected in most patients undergoing VCR(s), 8 , 9 , 10 , 11 , 12 several inherent defects such as over‐shorting of spinal cord, the necessary of anterior support and massive blood loss were obstacles for this challenging procedure. 5 , 13 , 14 Recently, Shi et al. 8 proposed that the SRS‐Schwab Grade 4 osteotomy could be effectively applied in CK patients. However, the radiographic and clinical outcomes of these two specific techniques were not comprehensively compared, especially in type II CK patients. Therefore, this study was designed to: (i) compare the clinical and radiographic outcomes, as well as operation‐related data of SRS‐Schwab Grade 4 osteotomy and VCR(s) in type II CK patients; and (ii) propose individualized decision‐making strategy to select between SRS‐Schwab Grade 4 osteotomy and VCR in type II CK patients to balance the correction focal deformity and risk of osteotomy procedure.
Subjects and Methods
Patients
This is a retrospective comparative observational study. Patients undergoing corrective surgery for spinal deformity at our center between February 2015 and January 2020 were retrospectively reviewed. The inclusion criteria were: (i) patients with type II CK; (ii) with coronal Cobb angle less than 20°; (iii) undergoing SRS‐Schwab Grade 4 osteotomy or VCR procedure; and (iv) with at least 2 years post‐operative follow‐up to evaluate all peri‐operative and short‐term complications, and attempt to include long‐term complications for analysis. Patients with prior history of spinal surgery were excluded. Eventually, 19 patients (6 males and 13 females) with an average age of 16.3 ± 8.4 years undergoing VCR were enrolled as Group 1, while patients undergoing SRS‐Schwab Grade 4 osteotomy were enrolled as Group 2. This retrospective study was approved by the Clinical Research Ethics Committee of our hospital (Grant No. 2021‐LCYJ‐DBZ‐05). All participants were fully informed about the methods, purposes, and potential risks involved in the study protocol and signed the informed concent.
Surgical Procedure
The general goal of surgery was to restore ideal sagittal alignment, and short fusion level was preferably adapted for younger patients to preserve the growth potential unless otherwise indicated. The length of fused segments was mainly decided by the property of cephalad and caudal vertebrae of kyphosis.
The selection of SRS‐Schwab Grade 4 osteotomy and VCR(s) was determined based on an individualized and comprehensive evaluation of patients' pre‐operative x‐rays, CT, and MRI. Osteotomies were performed in the apical region for adequate correction of kyphotic deformity. As is described previously, 7 the SRS‐Grade 4 osteotomy were performed when: (i) the apex of kyphosis is the upper vertebra of the failed segmentation bar or the disc above; and (ii) the apex of kyphosis was located in the middle region of kyphotic mass with the ratio of anterior/posterior height of apical vertebra >1/3. Normally, for our patients undergoing SRS‐Grade 4 osteotomy, the kyphotic mass included no more than three consecutive unsegmented vertebrae. VCR(s) was preferably conducted when the apex of kyphosis was located in the middle region of unsegmented mass with the ratio of anterior/posterior height of apical vertebra < 1/3. 7 The resected structure during SRS‐Schwab Grade 4 osteotomy and VCR(s) in our cohort are illustrated in the graphical abstract.
For both groups, a cage or titanium mesh filled with bones, and satellite rods would be individually placed when necessary. The wake‐up tests were performed after completing instrumentation in patients aged more than 10 years. The sensory evoked potentials (SEP) and motor evoked potentials (MEP) were routinely monitored during surgery for all patients. Patients were routinely instructed to wear a brace for at least 3 months after surgery.
Clinical Outcomes and Radiographic Evaluations
Clinical data including the operation time, estimated blood loss (EBL), number of instrumented levels, application of anterior strut grafts and complications were recorded. Radiographic measurements were performed on whole standing X‐rays at pre‐, post‐operation and each follow‐up. The following radiographic parameters were measured in accordance to previous studies: 8 , 15 (i) segmental kyphosis (SK); (ii) thoracic kyphosis (TK); (iii) thoracolumbar kyphosis (TLK); (iv) lumbar lordosis (LL); (v) sagittal vertical axis (SVA); (vi) pelvic incidence (PI); (vii) pelvic tilt (PT); and (viii) sacral slope (SS). All radiographic parameters were independently measured by two spine surgeons and the mean values were calculated for analysis. The quality‐of‐life metrics were collected via Scoliosis Research Society (SRS)‐22 questionnaire at pre‐operation, 3‐month follow‐up and the latest follow‐up.
Statistical Analysis
All data were tabulated in the form of mean ± standard deviation and were analyzed via SPSS version 20.0 (SPSS, Chicago, IL, USA). The t test, Chi‐square test and Fisher's exact test were used to compare the differences of numeric variables and countable variables. Statistically significant difference was set at p < 0.05.
Results
Demographic Data
The detailed demographic data of the two groups are illustrated in Table 1. There was no statistical difference between Group 1 and Group 2 in terms of age, gender, location of the failed segmentation bar (ps > 0.05), but the number of unsegmented levels, surgically fused segments, operation time and EBL were significantly higher in Group 1. Six anterior strut grafts (five cage, one titanium mesh, 31.6%) were used in Group 1 and two cages (18.8%) were used in Group 2.
TABLE 1.
Comparison of demographic data between Group 1 and Group 2
| Group 1 (n = 19) | Group 2 (n = 12) | p value | |
|---|---|---|---|
| Mean age (year) | 16.5 ± 8.1 | 15.9 ± 9.0 | 0.775 |
| Gender (female/male) | 13/6 | 8/4 | 0.919 |
| Thoracic | 0 | 0 | ‐ |
| Thoracolumbar | 17 | 9 | ‐ |
| Lumbar | 2 | 3 | ‐ |
| Unsegmented levels (No.) | 3.9 ± 0.8 | 2.5 ± 0.5 | <0.001* |
| Fusion level (No.) | 8.4 ± 2.2 | 5.8 ± 2.1 | 0.003* |
| Anterior strut grafts | 6 | 2 | 0.684 |
| Follow‐up (month) | 58.5 ± 25.9 | 46.4 ± 19.2 | 0.174 |
| Operation time (min) | 365.9 ± 81.2 | 221.4 ± 78.9 | <0.001* |
| Estimated Blood loss (ml) | 975.2 ± 275.8 | 725.9 ± 204.3 | 0.011* |
| Complications | 8 | 5 | 0.981 |
| Intra‐operative dual tear | 2 | 1 | ‐ |
| Neurological deficit | 1 | 1 | ‐ |
| Neuromonitoring changes | 0 | 1 | ‐ |
| PJK/PJF | 3 | 2 | ‐ |
| PJL | 1 | 0 | ‐ |
| ST | 2 | 2 | ‐ |
| Rod/screw fracture | 2 | 1 | ‐ |
Abbreviations: PJK/PJF, proximal junctional kyphosis/Failure; PJL, proximal junctional lordosis; ST, sagittal translation; type II CK, type II congenital kyphosis.
Statistically significant.
Radiographic and Clinical Outcomes
Radiographic parameters at pre‐ and post‐operation and the latest follow‐up in both groups are summarized in Table 2. The pre‐operative radiologic parameters including SK, TK, LL, SVA, PI, PT, and SS were not statistically significant between groups (all ps > 0.05). At pre‐operation, SK was 78.3 ± 27.9° in Group 1 and 57.1 ± 21.2° in Group 2 (p = 0.063). Statistically higher SK was observed in at post‐operation (27.2 ± 23.0° in Group 1 vs 11.7 ± 11.2° in Group 2, p = 0.038) and the latest follow‐up (30.3 ± 21.0° in Group 1 vs 12.8 ± 15.4° in Group 2, p = 0.015).
TABLE 2.
Comparison of radiographic measurements between Group 1 and Group 2
| Group 1 (n = 19) | Group 2 (n = 12) | p value | |
|---|---|---|---|
| Pre‐operative | |||
| Coronal Cobb angle (°) | 11.1 ± 5.5 | 10.4 ± 8.4 | 0.780 |
| SK (°) | 78.3 ± 27.9 | 60.1 ± 21.2 | 0.063 |
| PI (°) | 27.8 ± 12.3 | 29.1 ± 14.3 | 0.790 |
| PT (°) | 6.7 ± 10.4 | 7.9 ± 13.3 | 0.781 |
| SS (°) | 20.7 ± 13.8 | 20.4 ± 11.6 | 0.951 |
| TLK (°) | 56.3 ± 42.4 | 37.1 ± 31 | 0.186 |
| TK (°) | 21.3 ± 38.5 | 20.1 ± 26.5 | 0.925 |
| LL (°) | 23.3 ± 53.4 | 16.1 ± 30.8 | 0.675 |
| PI(°) | 41.7 ± 9.3 | 40.9 ± 10.7 | 0.827 |
| PT(°) | 12.4 ± 6.8 | 11.9 ± 7.0 | 0.845 |
| SS(°) | 29.3 ± 7.0 | 29.0 ± 7.2 | 0.909 |
| SVA (mm) | −24.7 ± 31.5 | −6.1 ± 28.7 | 0.109 |
| Post‐operative | |||
| Coronal Cobb angle (°) | 3.3 ± 1.9 | 4.5 ± 4.0 | 0.268 |
| SK (°) | 27.2 ± 23.0* | 11.7 ± 11.2* | 0.038 # |
| PI (°) | 28.3 ± 11.3 | 30.3 ± 12.6 | 0.649 |
| PT (°) | 2.3 ± 10.2 | 8.4 ± 13.3 | 0.160 |
| SS (°) | 26.1 ± 14.3 | 24.3 ± 11.6 | 0.717 |
| TLK (°) | 16.8 ± 15.4 | 9.9 ± 9.0 | 0.171 |
| TK (°) | 19.4 ± 16.4 | 19.4 ± 10.6 | 1.000 |
| LL (°) | 38.0 ± 23.9 | 28.8 ± 13.1 | 0.233 |
| PI(°) | 41.1 ± 9.8 | 40.2 ± 10.8 | 0.926 |
| PT(°) | 10.2 ± 7.0 | 9.4 ± 7.4 | 0.788 |
| SS(°) | 31.9 ± 7.3 | 30.8 ± 7.6 | 0.881 |
| SVA (mm) | −6.2 ± 23.9 | 6.6 ± 13.8 | 0.082 |
| The latest follow‐up | |||
| Coronal Cobb angle (°) | 4.7 ± 1.7 | 4.9 ± 5.6 | 0.884 |
| SK (°) | 30.3 ± 20.0* | 12.8 ± 15.4* | 0.015 # |
| PI (°) | 31.7 ± 11.4 | 30.9 ± 17.3 | 0.877 |
| PT (°) | 6.8 ± 12.9 | 9.6 ± 11.2 | 0.541 |
| SS (°) | 24.5 ± 10.2 | 22.3 ± 14.6 | 0.625 |
| TLK (°) | 12.5 ± 20.7 | 11.7 ± 14.0 | 0.907 |
| TK (°) | 22.8 ± 20.8 | 32.4 ± 11.2 | 0.154 |
| LL (°) | 34.0 ± 21.4 | 28.8 ± 15.4 | 0.472 |
| PI(°) | 42.4 ± 10.6 | 41.2 ± 11.2 | 0.766 |
| PT(°) | 11.0 ± 7.1 | 10.2 ± 7.6 | 0.768 |
| SS(°) | 31.4 ± 7.3 | 31.0 ± 7.6 | 0.885 |
| SVA (mm) | −19.3 ± 21.6 | −7.3 ± 28.7 | 0.195 |
| Correction of SK | |||
| Pre‐operation minus post‐operation | 51.1 ± 21.6 | 45.4 ± 19.8 | 0.466 |
| The latest follow‐up minus pre‐operation | 48.0 ± 21.1 | 44.3 ± 20.1 | 0.588 |
Statistically different from pre‐operation (p < 0.05)
statistically different between groups (p < 0.05).
At pre‐operation, the SRS‐22 measures were similar between groups. Significant improvements were observed in terms of SRS‐22 Self Image, Function and Satisfaction domain in both groups at 3‐month and the latest follow‐up as compared to pre‐operative measures. At 3‐month follow‐up, patients in Group 2 had significantly worse SRS‐22 Function domain (p = 0.029). No significant difference of SRS‐22 measure was observed between groups at the latest follow‐up (Table 3). Representative cases undergoing SRS‐Schwab Grade 4 (Figures 1 and 2) osteotomy and VCR (Figure 3) were presented.
TABLE 3.
Comparison of health‐related quality‐of‐life parameters among pre‐operation, 3‐month follow‐up and the latest follow‐up
| SRS‐22 | |||||
|---|---|---|---|---|---|
| Pain | Self‐image | Function | Satisfaction | Mental Health | |
| Group 1 | |||||
| Pre‐operation | 3.4 ± 1.3 | 3.0 ± 0.8 | 3.4 ± 0.5 | 2.8 ± 1.3 | 3.9 ± 0.5 |
| 3‐month follow‐up | 3.9 ± 0.7 | 3.9 ± 1.0 | 3.6 ± 0.8 # | 3.8 ± 1.0 | 4.0 ± 0.6 |
| P (pre‐operation vs 3‐month follow‐up) | 0.047* | 0.004* | 0.898 | 0.012* | 0.580 |
| The latest follow‐up | 4.0 ± 0.8 | 3.9 ± 1.0 | 4.0 ± 0.5 | 3.7 ± 1.0 | 3.9 ± 0.7 |
| P (pre‐operation vs the latest follow‐up) | 0.028* | 0.004* | <0.001* | 0.022* | 1.000 |
| Group 2 | |||||
| Pre‐operation | 3.9 ± 0.7 | 3.2 ± 0.8 | 3.6 ± 0.4 | 3.0 ± 1.2 | 4.1 ± 0.4 |
| 3‐month follow‐up | 4.0 ± 0.8 | 4.1 ± 0.7 | 4.1 ± 0.4 # | 4.0 ± 0.9 | 4.2 ± 0.4 |
| P (pre‐operation vs 3‐month follow‐up) | 0.746 | 0.007* | 0.022* | 0.030* | 0.547 |
| The latest follow‐up | 4.1 ± 0.6 | 4.0 ± 0.7 | 4.1 ± 0.4 | 4.0 ± 1.1 | 4.1 ± 0.5 |
| P (pre‐operation vs the latest follow‐up) | 0.460 | 0.016* | 0.006* | 0.045* | 1.000 |
Statistically different from pre‐operation
significantly different between groups.
FIGURE 1.
A 12 years old female patient with T10‐T11 failure of anterior segmentation, though with minor coronal deformity, the Cobb angle was smaller than 20° (A–D). SRS‐Grade 4 osteotomy was performed at T9/10 level. During osteotomy, the patient experienced SEP and MEP alert event, the surgical operation ceased approximately 30 min until neuromonitoring signal went back. After surgery, the patient demonstrated sensory deficit of the left lower extremity. Considering the moderate ST found in the post‐operative CT, the patient was instructed to avoid sitting and standing until the neurological symptom improved, for which reason standing X‐rays were not conducted at discharge (E, F). At 3 months follow‐up, the nerve symptom recovered, and no mechanical complications was observed (G, H). At 4 years follow‐up, the patient achieved solid bone fusion and the correction was well maintained (I, J).
FIGURE 2.
A 12 years old male patient with L1‐L3 failures of anterior segmentation (A–D). The patient underwent SRS‐Schwab Grade 4 osteotomy at T11/12 level followed with posterior instrumented fusion (E, F). At 2 years follow‐up, the patient achieved solid bone fusion and the correction was well maintained (G, H).
FIGURE 3.
A 10 years old female patient with T12‐L2 failures of anterior segmentation (A–D). The patient underwent VCR at L1 level (E, F). At 6 years follow‐up, the patient achieved solid bone fusion and the correction was well maintained (G, H).
Complications
In Group 1, attenuated sensory of left lower extremity was observed in one case, who recovered at 6 months follow‐up. Incidental dual tear was observed in two cases, who both underwent dual repairment during operation. ST was observed in two patients in Group 1 and two patients in Group 2. Three patients demonstrated proximal junctional kyphosis/failure (PJK/PJF) during follow‐up, among whom two patients had loosening of screws of upper instrumented vertebra. In addition, proximal junctional lordosis (PJL) was observed in one case of this group. In Group 2, transient intraoperative sensory evoked potential (SEP) and motor evoked potential (MEP) alert event was reported in one case during osteotomy, with transient neurological deficit observed after operation. The nerve symptom was significantly improved at 3 months follow‐up. Dual tear was observed in one case and was successfully repaired intraoperatively. PJK/PJF was observed in two patients including one patient demonstrating loosening of proximal instrumentation.
No revision surgery was required till the latest visit since the proximal junctional kyphotic angle remained stable for all subjects enrolled in our study during follow‐up. No major complication (death, permanent nerve deficit, severe infection, etc.) was observed in the current study.
Discussion
Radiographical and Clinical Outcome of Type II CK Patients Underwent SRS‐Schwab Grade 4 Osteotomy and VCR
Correction of Focal Kyphosis
The correction rate of deformity seemed to be the first and visual parameter assessing the utilization of osteotomies. Though the instinctive experience implied that high grade of osteotomy could provide high correction rates, some evidence, however, showed limited increases in correction rate from SRS‐Schwab Grade 4 osteotomy to VCR(s). Liu et al. 10 reported similar correction of Cobb angle in congenital scoliosis patients undergoing radical hemivertebrae resection as compared to those undergoing VCR. On the contrary, Hengwei et al. 16 reported higher correction rate of SRS‐Schwab Grade 4 osteotomy than VCR in patients with severe thoracic kyphoscoliosis. They assumed that less degree of spinal cord buckling after limited spinal column shortening and bone‐on‐bone closure following SRS‐Schwab Grade 4 osteotomy allowed more posterior compression force, which might contribute to the higher correction rate of kyphosis. In the current study, comparable improvement of SK was observed at post‐operation (51.1 ± 21.6° in Group 1 vs 48.4 ± 19.8° in Group 2, p= 0.694) and the latest follow‐up (48.0 ± 21.1° in Group 1 vs 47.3 ± 20.1° in Group 2, p = 0.929), which was in accordance with previous studies. Therefore, the correction rate should not be the decisive factor for the decision‐making between SRS‐Schwab Grade 4 osteotomy and VCR in type II CK.
Clinical Outcome
Patients in Group 1 demonstrated more EBL (975.2 mL in Group 1 vs 725.9 mL in Group 2, p = 0.003) and longer operation time (275.9 min in Group 1 and 213.4 min in Group 2, p = 0.044) as compared to Group 2, which was partially associated with the increased amount of bony resection and technically challenging nature of VCR(s). In addition, VCR(s) are frequently associated with spinal bulking and incomplete closure of gap in the osteotomy site, rendering anterior support indispensable. In the present study, anterior strut grafts were applied in six cases in Group 1 and two cases in Group 2, which might further contribute to the higher EBL and prolonged operation time. 10 , 14 , 17 Moreover, the resection of partial vertebral body and upper or inferior adjacent disc could be performed via the intervertebral space to minimize blood loss during osteotomy procedure than traditional transpedicular apporach. 8 Therefore, the SRS‐Schwab Grade 4 osteotomy seemed to be relatively more “friendly” to the patients.
Improvement of Life Quality Measurements
As has been repeatedly reported and demonstrated, sagittal alignment is a critical spine factor affecting the health‐related quality of life. The rounded back due to type II CK caused significant cosmetic problems, with limitations of daily activity and accompanying pain, stiffness or even nerve symptoms. The osteotomy technique, including SRS‐Schwab Grade 4 osteotomy and VCR(s), if proceeded with properly without complications, could significantly improve the sagittal alignment, and thus provide satisfactory improvements of quality‐of‐life measures. 11 , 18 , 19 The present study demonstrated significant improvement in both groups in terms of SRS‐22 Self Image, Function and Satisfaction domains. To the best of our knowledge, few studies have compared the impact of osteotomy types on patients' quality of life. At pre‐operation, SRS‐22 measures were similar between groups. Meanwhile, at 3‐month follow‐up, patients in Group 1 demonstrated significantly worse outcomes of SRS‐22 Function domain. Zeng et al. 20 reported better improvement of ODI scores in patients without post‐operative neurological compromise. In the present study, two patients in Group 1 had transient sensory deficit, which might partially explain the worse scores of SRS‐22 Function domains (p = 0.031) at 3‐months follow‐up. The two groups did not demonstrate statistical difference in terms of SRS‐22 measures at the latest follow‐up, which might indicate similar effectiveness of both SRS‐Grade 4 osteotomy and VCR(s) in improving the living quality of type II CK patients during follow‐up.
Our Individualized Decision‐making Strategy to Pursue Adequate Correction Rate with Minimal Invasiveness of Osteotomy Procedure in Type II CK Patients
The type II CK is characterized by anterior failure of vertebral segmentation spanning two to multiple segments, which usually causes cosmetic problems and negative effects of life quality to the patients. 3 , 21 Due to the rigid nature of the anterior osseous bars, three‐column osteotomy techniques were usually inevitable in corrective surgeries for type II CK. Based on previous studies, the SRS‐Schwab Grade 4 osteotomy and VCR could be individually performed in patients with type II CK. 22 , 23 The treatment principle for type II CK is to pursue adequate correction and maintain neurologic integrity with minimum surgical invasiveness. The decision making between SRS‐Schwab Grade 4 osteotomy and VCR should be based on a comprehensive evaluation of several key factors including regional morphology of the deformed vertebrae and residual discs, length of unsegmented region, magnitude of regional kyphosis, and the desired correction angle to restore global sagittal alignment. 14 , 22 , 24 , 25 Generally, for type II CK patients with the apex of kyphosis being the upper vertebra of the failed segmentation bar or the disc above, SRS‐Schwab Grade 4 osteotomy is usually sufficient for satisfactory radiographic and clinical outcomes. 8 When the kyphotic apex was located within the unsegmented kyphotic bar, the decision‐making between SRS‐Schwab Grade 4 osteotomy and VCR(s) were based on the AP ratio of the apical vertebra. In our experience, an AP ratio > 1/3 indicates a well‐developed anterior column of the kyphotic apex, partial resection of the apical vertebra with a neighboring residual disc could provide adequate correction of kyphosis, and usually maintained sufficient anterior column height to prevent bulking of the spinal cord. An apical vertebra with AP ratio < 1/3 usually presented with insufficient bony structure in the anterior column, resection of the whole vertebra with both cephalad and caudal neighboring residual disc seemed necessary for the correction and stable reconstruction of sagittal morphology.
Strengths and Limitations of the Study
The present study had several limitations including the relatively small sample size and the retrospective nature, which might lead to bias. Patients in the two groups were not one‐to‐one matched, and the indications for SRS‐Schwab Grade 4 osteotomy and VCR were not totally consistent. In addition, the SRS‐Schwab Grade 4 osteotomy had been widely applied since 2015 in our center, which was significantly later than VCR, causing the significantly longer follow‐up period in Group 1. The recent applications of several advanced techniques such as ultrasonic osteotome and intra‐operative navigation contributed to the relatively less EBL and operation time in later patients undergoing correction surgeries. Although the radiographical and clinical outcomes were satisfactory during a minimum of 2 years follow‐up, longer observation was still necessary. Therefore, multicenter prospective trials, especially on‐to‐one matched studies are warranted to reach a firmer conclusion.
Nevertheless, these limitations may not affect the reliability and scientific correctness of our study due to the following strengths: (i) compared to previous observational studies, the indication of SRS‐Schwab Grade 4 osteotomy and VCRs was standardized in both groups, which indicated better quality of our data and made or comparative study more convincing; and (ii) the unique deformity feature of fixed focal deformity was not frequently observed in spine deformity patients with the exception of the rarely observed in type II CK, our study with relatively bigger sample size have provided adequate evidence to support our proposed strategy.
Conclusions
Both SRS‐Schwab Grade 4 osteotomy and VCR could be well applied in type II CK patients. SRS‐Schwab Grade 4 osteotomy is ideally indicated for type II CK patients with the apex of kyphosis being the upper vertebra of the failed segmentation bar or the disc above, or with apical vertebrae located within the unsegmented bar with anterior/posterior height ratio higher than 1/3, while VCR(s) is more indicated for those patients with broad‐sweeping kyphotic curve with the anterior/posterior height ratio of the apex lower than 1/3. Patients undergoing VCR suffered from longer operation time, more blood loss and higher inherent risks of peri‐ and post‐operative complications.
Funding Information
This work is financially supported by Jiangsu Provincial Medical Innovation Center of Orthopedic Surgery (CXZX202214).
Conflict of Interest Statement
The authors declare no conflict of interest.
Author Contributions
Hongru Ma: conception and design of the study; analysis and interpretation of data; revising it critically for important intellectual content; drafting the article; final approval of the version to be submitted. Benlong Shi: acquisition of data; analysis and interpretation of data; revising the article critically for important intellectual content. Dun Liu: acquisition of data; revising the article critically for important intellectual content. Wanyou Liu: acquisition of data; analysis and interpretation of data. Saihu Mao: acquisition of data; revising it critically for important intellectual content. Zhen Liu: acquisition of data; revising it critically for important intellectual content. Xu Sun: acquisition of data; revising it critically for important intellectual content. Zezhang Zhu: conception and design of the study; acquisition of data; revising the article critically for important intellectual content; final approval of the version to be submitted. Yong Qiu: conception and design of the study; administrative support; surpervising the study process, final approval of the version to be submitted.
Acknowledgments
The authors declare no acknowledgements.
References
- 1. Giampietro PF, Dunwoodie SL, Kusumi K, Pourquié O, Tassy O, Offiah AC, et al. Progress in the understanding of the genetic etiology of vertebral segmentation disorders in humans. Ann N Y Acad Sci. 2009;1151:38–67. 10.1111/j.1749-6632.2008.03452.x [DOI] [PubMed] [Google Scholar]
- 2. Winter RB, Moe JH, Wang JF. Congenital kyphosis. Its natural history and treatment as observed in a study of one hundred and thirty patients. J Bone Joint Surg Am. 1973;55(2):223–256. [PubMed] [Google Scholar]
- 3. McMaster MJ, Singh H. Natural history of congenital kyphosis and kyphoscoliosis. A study of one hundred and twelve patients. J Bone Joint Surg Am. 1999;81(10):1367–1383. 10.2106/00004623-199910000-00002 [DOI] [PubMed] [Google Scholar]
- 4. Mayfield JK, Winter RB, Bradford DS, Moe JH. Congenital kyphosis due to defects of anterior segmentation. J Bone Joint Surg Am. 1980;62(8):1291–1301. [PubMed] [Google Scholar]
- 5. Chehrassan M, Nikouei F, Shakeri M, Jafari B, Ameri Mahabadi E, Ghandhari H. Perioperative complications of symptomatic congenital kyphosis: a retrospective cohort study. Spine Deform. 2024;12(1):181–187. 10.1007/s43390-023-00751-5 [DOI] [PubMed] [Google Scholar]
- 6. Lenke LG, Newton PO, Sucato DJ, Shufflebarger HL, Emans JB, Sponseller PD, et al. Complications after 147 consecutive vertebral column resections for severe pediatric spinal deformity: a multicenter analysis. Spine (Phila Pa 1976). 2013;38(2):119–132. 10.1097/BRS.0b013e318269fab1 [DOI] [PubMed] [Google Scholar]
- 7. Li S, Mao S, Ma Y, Zhu Z, Liu Z, Shi B, et al. Posterior 3‐column osteotomy for treatment of congenital kyphosis with multiple thoracolumbar/lumbar anterior unsegmented vertebrae: a comparison between patients with increasing number of anterior unsegmented vertebrae. World Neurosurg. 2022;159:e172–e183. 10.1016/j.wneu.2021.12.021 [DOI] [PubMed] [Google Scholar]
- 8. Shi B, Zhao Q, Xu L, Liu Z, Sun X, Zhu Z, et al. SRS‐Schwab grade 4 osteotomy for congenital thoracolumbar kyphosis: a minimum of 2 years follow‐up study. Spine J. 2018;18(11):2059–2064. [DOI] [PubMed] [Google Scholar]
- 9. Qiao J, Xiao L, Sun X, Shi B, Liu Z, Xu L, et al. Vertebral subluxation during three‐column osteotomy in surgical correction of adult spine deformity: incidence, risk factors, and complications. Eur Spine J. 2018;27(3):630–635. 10.1007/s00586-017-5285-2 [DOI] [PubMed] [Google Scholar]
- 10. Liu D, Shi B, Shi B, Li Y, Xia S, Liu Z, et al. Partial Hemivertebra resection (grade 4 osteotomy) for congenital scoliosis: a comparison with radical Hemivertebra resection. World Neurosurg. 2019;130:e1028–e1033. 10.1016/j.wneu.2019.07.070 [DOI] [PubMed] [Google Scholar]
- 11. Passias PG, Naessig S, Para A, Pierce K, Ahmad W, Diebo BG, et al. External validation of the European spine study group‐international spine study group calculator utilizing a single institutional experience for adult spinal deformity corrective surgery. Int J Spine Surg. 2022;16(4):760–766. 10.14444/8245 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 12. Marques MF, Fiere V, Obeid I, Charles YP, el‐Youssef K, Lahoud A, et al. Pseudarthrosis in adult spine deformity surgery: risk factors and treatment options. Eur Spine J. 2021;30:3225–3232. 10.1007/s00586-021-06861-w [DOI] [PubMed] [Google Scholar]
- 13. Sun X, Zhu ZZ, Chen X, Liu Z, Wang B, Qiu Y. Posterior double vertebral column resections combined with satellite rod technique to correct severe congenital angular kyphosis. Orthop Surg. 2016;8(3):411–414. 10.1111/os.12265 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 14. Garg B, Bansal T, Mehta N. Clinical, radiological, and functional outcomes of posterior‐only three‐column osteotomy in congenital kyphosis: a minimum of two years' follow‐up. Bone Joint J. 2021;103:1309–1316. 10.1302/0301-620X.103B7.BJJ-2020-2162.R1 [DOI] [PubMed] [Google Scholar]
- 15. Vialle Rapha L. Radiographic analysis of the sagittal alignment and balance of the spine in asymptomatic subjects. Journal of Bone & Joint Surgery American. 2005;87(2):260. [DOI] [PubMed] [Google Scholar]
- 16. Hengwei F, Xueshi L, Zifang H, Wenyuan S, Chuandong L, Jingfan Y, et al. Is vertebral column resection (VCR) necessary in correcting severe and rigid thoracic kyphoscoliosis—a single‐institution surgical experience. World Neurosurg. 2018;116:e1‐e8. [DOI] [PubMed] [Google Scholar]
- 17. Singleton M, Ghisi D, Memtsoudis S. Perioperative management in complex spine surgery. Minerva Anestesiol. 2022;88(5):396–406. 10.23736/S0375-9393.22.15933-X [DOI] [PubMed] [Google Scholar]
- 18. Tarawneh AM, Venkatesan M, Pasku D, Singh J, Quraishi NA. Impact of pedicle subtraction osteotomy on health‐related quality of life (HRQOL) measures in patients undergoing surgery for adult spinal deformity: a systematic review and meta‐analysis. Eur Spine J. 2020;1‐7:2953–2959. [DOI] [PubMed] [Google Scholar]
- 19. Chau LTC, Hu Z, Ko KSY, Man GCW, Yeung KH, Law YY, et al. Global sagittal alignment of the spine, pelvis, lower limb after vertebral compression fracture and its effect on quality of life. BMC Musculoskelet Disord. 2021;22(1):476. 10.1186/s12891-021-04311-8 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 20. Zeng Y, Chen Z, Qi Q, Guo Z, Li W, Sun C, et al. The posterior surgical correction of congenital kyphosis and kyphoscoliosis: 23 cases with minimum 2 years follow‐up. Eur Spine J. 2013;22(2):372–378. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 21. Soliman HAG. Health‐related quality of life of adolescents with severe untreated congenital kyphosis and Kyphoscoliosis in a developing country. Spine (Phila Pa 1976). 2018;43(16):E942–e948. 10.1097/brs.0000000000002598 [DOI] [PubMed] [Google Scholar]
- 22. Hwang CJ, Lenke LG, Sides BA, Blanke KM, Kelly MP. Comparison of single‐level versus multilevel vertebral column resection surgery for pediatric patients with severe spinal deformities. Spine. 2019;44:E664–E670. [DOI] [PubMed] [Google Scholar]
- 23. Smith JS, Wang VY, Ames CP. Vertebral column resection for rigid spinal deformity. Neurosurgery. 2008;63(3 suppl):177–182. 10.1227/01.Neu.0000320429.32113.85 [DOI] [PubMed] [Google Scholar]
- 24. Cao Z, Cong Y, Yin C, Wang Y, Wang Z, Liu XW, et al. A review and summary of patients with symptomatic postoperative Discal Pseudocysts of the lumbar spine. Orthop Surg. 2023;15(5):1256–1263. 10.1111/os.13689 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 25. Xu S, Guo C, Liang Y, Zhu Z, Liu H. Sagittal parameters of spine‐pelvis‐hip joints in patients with lumbar spinal stenosis. Orthop Surg. 2022;14(11):2854–2862. 10.1111/os.13467 [DOI] [PMC free article] [PubMed] [Google Scholar]