Objective·To investigate the genetic etiology of a rare and complex case clinically suspected to be methylmalonic acidemia(MMA),but with negative whole exome sequencing(WES)results,using a multi-omics sequencing approach.Methods·DNA and RNA samples were extracted from the peripheral blood of the proband and both parents.Targeted MMA-related gene Panel sequencing and WES were first performed.Subsequently,RNA sequencing(RNA-seq)and whole genome sequencing(WGS)were conducted to comprehensively analyze the child's genetic variants,their origins and potential inheritance patterns.Results·No pathogenic variants associated with the patient's phenotype were identified through the MMA Panel or standard WES analysis.Extended analysis of WES suggested the possibility of uniparental disomy(UPD)of chromosome 4.WGS revealed a homozygous splice-site variant(c.-66+2T>C)in the non-coding region of the metabolism of cobalamin associated A(MMAA)gene.The variant was located in the 5'untranslated region(5'UTR),specifically at the second base downstream of the splice donor site of exon 1(reference sequence:NM_172250).In genomic coordinates(hg19),the variant was located at base 146540561 on chromosome 4(chr4:146540561).Sanger sequencing confirmed that the mother was heterozygous for this variant,while the father did not carry it.RNA-seq showed no detectable expression of the MMAA gene on chromosome 4 in the patient.This was further confirmed by reverse transcription real time quantitative PCR,indicating nearly absent mRNA expression,suggesting that the non-coding splice-site variant affected transcriptional expression.Conclusion·A homozygous splice-site variant(c.-66+2T>C)in the non-coding region of the MMAA gene—outside the coverage of WES—is likely the pathogenic cause in this case,presumably resulting from maternal UPD of chromosome 4.

Next generation sequencing (NGS) technology is playing an increasingly important role in the diagnosis of genetic diseases. Whole exome sequencing (WES), which targets the coding regions of the genome, has been widely used in the diagnosis of genetic diseases for its low cost and high efficiency. However, compared to conventional methods, the Next Generation Sequencing (NGS) process is intricate, and there is variability in the expertise of data analysts and variant interpreters, which may lead to inconsistencies in the outcomes. To ensure the quality of testing and enhance the diagnostic rate of diseases, this consensus has provided recommendations regarding the laboratory setup, operational procedures, data analysis, result interpretation, and quality control for WES, with an aim to standardize its application in the detection of genetic disorders.

Objective:To compare the incidence of instrumentation-related complications and health-related quality of life following pelvic fixation using iliac screws (IS) or second sacral alar-iliac (S 2AI) screws in adult spinal deformity (ASD). Methods:A retrospective cohort study was conducted on 108 ASD patients who underwent posterior corrective fusion and fixation extending to the pelvis at Nanjing Drum Tower Hospital between September 2010 and April 2021. According to the type of pelvic fixation, patients were divided into an IS group ( n=34; 12 males, 22 females; mean age 53.7±11.1 years, range 28-73 years) and an S 2AI group ( n=74; 23 males, 51 females; mean age 52.8±8.6 years, range 27-72 years). Pre- and post- operative standing anteroposterior and lateral radiographs were evaluated for Cobb angle, coronal balance distance (CBD), thoracic kyphosis (TK), lumbar lordosis (LL), sagittal vertical axis (SVA), pelvic incidence (PI), pelvic tilt (PT), and sacral slope (SS). At 2 years postoperatively, health-related quality of life were assessed using the Scoliosis Research Society-22 questionnaire (SRS-22), Oswestry disability index (ODI), and visual analogue scale (VAS) for pain. Instrumentation failure related to pelvic fixation during follow-up was recorded. Results:All patients completed follow-up. Mean follow-up duration was 28.5±3.6 months (range 24-37 months) in the IS group and 28.1±4.3 months (range 24-43 months) in the S 2AI group. Postoperatively, both groups showed significant improvement in Cobb angle, CBD, TK, LL, SVA, PT, and SS compared to baseline ( P<0.05), whereas PI remained unchanged ( t=0.664, P=0.509; t=1.227, P=0.222). Preoperative PT was greater in the IS group than in the S 2AI group (33.6°±8.7° vs. 29.3°±9.6°, t=2.228, P=0.028). No significant intergroup differences were observed in any other pre- or post- operative radiographic parameters ( P>0.05). Pelvic fixation failure occurred in 31 patients (28.7%, 31/108). Patients with fixation failure had a longer fusion segment extension than those without failure (12.0±2.8 vs. 10.8±2.4 segments; t=2.256, P=0.026). In the IS group, complications comprised 3 cases of screw loosening (8.8%), 2 of screw breakage (5.9%), and 4 of rod fracture within the pelvic region (11.8%), including 1 case with concurrent screw and rod failure. In the S 2AI group, there were 21 cases of screw loosening (28.4%) and 2 of screw breakage (2.7%). Screw loosening was less frequent in the IS group than in the S 2AI group (χ 2=5.154, P=0.023), whereas pelvic rod fracture was more common in the IS group (χ 2=9.041, P=0.003). Screw breakage rates did not differ significantly ( P>0.05). Mean VAS, ODI, and SRS-22 scores in the IS group were 3.2±2.4, 24.9%±18.8%, and 3.2±0.8, respectively; corresponding to 2.5±1.8, 18.9%±10.9%, and 3.3±0.6 in the S 2AI group. ODI was significantly higher in the IS group ( t=2.062, P=0.042), whereas VAS and SRS-22 were comparable ( P>0.05). Among S 2AI patients, VAS and ODI scores did not differ significantly between those with and without screw loosening ( P>0.05). Conclusions:The post-operative incidence of pelvic fixation failure following ASD surgery reached 28.7%. The predominant failure mode with S 2AI was screw loosening, whereas IS was more frequently complicated by rod fracture. Early postoperative health-related quality of life was superior with S 2AI screws compared with iliac screws.

Objective:To investigate the risk factors for postoperative coronal imbalance in patients with type A degenerative scoliosis and to refine the Qiu classification by reclassifying type A patients.Methods:A retrospective analysis was conducted on the clinical data of patients with type A degenerative scoliosis classified by the Qiu classification who underwent corrective surgery at our hospital from January 2017 to April 2022. A total of 69 patients were enrolled in the study, including 3 males and 66 females, with an age of 60.6±6.8 years (range: 47-71 years). Based on the preoperative CBD, type A patients were further divided into three subtypes: Aa with CBD≤1 cm, Ab with CBD>1 cm with C 7 plumb line deviation toward the concave side, and Ac with CBD>1 cm with C 7 plumb line deviation toward the convex side. The incidence of coronal imbalance was compared among subtypes. During follow-up, patients with CBD ≤3 cm were classified as balanced, and those with CBD>3 cm as imbalanced. Radiographic parameters including coronal Cobb's angle (CA), CBD, L 4 tilt angle, L 5 tilt angle, thoracic kyphosis (TK), lumbar lordosis (LL), pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), and sagittal vertical axis (SVA) were measured in the standing radiographs preoperatively, 2-weeks postoperatively and 2-years follow-up. Differences in radiographic parameters between balanced and imbalanced groups were compared, and binary logistic regression was used to identify risk factors for postoperative coronal imbalance. Results:In the imbalanced Group (22 patients), there were 6 patients of type Aa (27%), 5 patients of type Ab (23%), and 11 patients of type Ac (50%), and in the balanced Group (47 patients), there were 20 patients of type Aa (43%), 18 patients of type Ab (38%), and 9 patients of type Ae (19%). The difference in subtype distribution between the two groups was significant (χ 2=6.939, P=0.029). The CBD in the imbalanced group was significantly larger than in the balanced group at the 2-years follow-up (4.18±0.86 cm vs. 1.31±0.78 cm, t=-13.813, P<0.001). The preoperative L 4 tilt angle was significantly larger in the imbalanced group compared to the balanced group (23.59°±6.86° vs. 17.64°±8.34°, t=-2.914, P=0.005). And the postoperative and 2-years follow-up L 4 tilt angles were also significantly larger than the balanced group (18.6°±5.5° vs. 11.5°±5.7°, t=-4.904, P<0.001; 18.0°±5.6° vs. 11.1°±5.7°, t=-4.691, P<0.001). Regression analysis identified the Ac type [ OR=3.937, 95% CI(1.07, 14.55), P=0.040] and excessive postoperative L 4 tilt angle [ OR=1.288, 95% CI(1.09, 1.52), P=0.003] as risk factors for postoperative coronal imbalance in type A patients. Conclusions:In the A-type of Qiu classification, patients with preoperative CBD>1 cm and trunk tilting towards the convex side (Ac type), as well as those with a large L 4 tilt angle after surgery, are more likely to experience coronal plane imbalance after surgery.

Objective:To investigate the difference of Roussouly ideal classification in predicting postoperative proximal junctional kyphosis (PJK) between adult degenerative spinal deformity patients with and without pelvic fixation and the potential reasons.Methods:From January 2017 to January 2020, a total of 95 patients (4 males, 91 females; with an average age of 62.03±6.30 years) with degenerative spinal deformities were retrospectively analyzed. There were 35 patients in the non-pelvic group (1 male, 34 females) and 60 patients in the pelvic group (3 males, 57 females). The radiographic parameters included coronal Cobb's angle (CA), pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), thoracic kyphosis (TK), lumbar lordosis (LL), sagittal vertical axis (SVA), T1 pelvic angle (TPA), and proximal junctional angle (PJA) were measured in the standing radiographs preoperatively, postoperatively at 2 weeks, and 2-year follow-up. Changes in PT and SS were calculated for patients at 2 weeks and the 2-year follow-up. Based on the revised Roussouly classification, 95 patients were classified into different types preoperatively, postoperatively at 2 weeks, and during the 2-year follow-up. Changes in the classification of patients were documented postoperatively at 2 weeks. Roussouly types were determined using preoperative pelvic parameters, and a match was defined when the 2-week postoperative classification aligned with the ideal type. The occurrence of PJK and the relationship with classification matching were recorded in the group. Independent t-tests were used for intergroup comparisons of radiographic parameters, and chi-square tests were employed to assess classification changes and predictive accuracy of the Roussouly classification. Results:Preoperative PT, TPA and SVA in non-pelvic group were significantly smaller than those in pelvic group, and preoperative SS and LL larger than those in pelvic group ( P<0.05). The changes of PT and SS in non-pelvic group were significantly lower than those in pelvic group 2 weeks after surgery ( P<0.05). The proportion of classification changes in the pelvic group was significantly higher than that in the non-pelvic group (60% vs. 34%, χ 2=5.847, P=0.016). Among the 95 patients, a total of 29 experienced PJK during the follow-up, with 3 cases progressing to PJF. The incidence of PJK in mismatched patients was 37% with no significant difference compared with matched patients (19%) (χ 2=3.357, P=0.067). In the sacral spine group of 60 patients, 22 experienced PJK, with 3 cases progressing to PJF. Among them, 19 patients with PJK had a classification mismatch with the ideal classification at 2 weeks postoperatively. The PJK incidence was significantly higher in mismatched patients (45%) compared to matched patients (17%) (χ 2=4.429, P=0.035). In the non-pelvic group, 7 patients developed PJK, with 3 mismatched cases. The PJK incidence in mismatched vs. matched patients was 18% vs. 22%, showing no significant difference (χ 2=0.114, P=0.735). Conclusions:For the patients with degenerative spinal deformity, pelvic fixation leads to a more complete restoration of the ideal Roussouly classification. Restoration of the Roussouly type in patients with pelvic fixation is a reliable predictor of postoperative PJK. However, in patients without pelvic fixation, the alignment with the ideal Roussouly classification does not significantly correlate with PJK development.

Objective:To compare the incidence of instrumentation-related complications and health-related quality of life following pelvic fixation using iliac screws (IS) or second sacral alar-iliac (S 2AI) screws in adult spinal deformity (ASD). Methods:A retrospective cohort study was conducted on 108 ASD patients who underwent posterior corrective fusion and fixation extending to the pelvis at Nanjing Drum Tower Hospital between September 2010 and April 2021. According to the type of pelvic fixation, patients were divided into an IS group ( n=34; 12 males, 22 females; mean age 53.7±11.1 years, range 28-73 years) and an S 2AI group ( n=74; 23 males, 51 females; mean age 52.8±8.6 years, range 27-72 years). Pre- and post- operative standing anteroposterior and lateral radiographs were evaluated for Cobb angle, coronal balance distance (CBD), thoracic kyphosis (TK), lumbar lordosis (LL), sagittal vertical axis (SVA), pelvic incidence (PI), pelvic tilt (PT), and sacral slope (SS). At 2 years postoperatively, health-related quality of life were assessed using the Scoliosis Research Society-22 questionnaire (SRS-22), Oswestry disability index (ODI), and visual analogue scale (VAS) for pain. Instrumentation failure related to pelvic fixation during follow-up was recorded. Results:All patients completed follow-up. Mean follow-up duration was 28.5±3.6 months (range 24-37 months) in the IS group and 28.1±4.3 months (range 24-43 months) in the S 2AI group. Postoperatively, both groups showed significant improvement in Cobb angle, CBD, TK, LL, SVA, PT, and SS compared to baseline ( P<0.05), whereas PI remained unchanged ( t=0.664, P=0.509; t=1.227, P=0.222). Preoperative PT was greater in the IS group than in the S 2AI group (33.6°±8.7° vs. 29.3°±9.6°, t=2.228, P=0.028). No significant intergroup differences were observed in any other pre- or post- operative radiographic parameters ( P>0.05). Pelvic fixation failure occurred in 31 patients (28.7%, 31/108). Patients with fixation failure had a longer fusion segment extension than those without failure (12.0±2.8 vs. 10.8±2.4 segments; t=2.256, P=0.026). In the IS group, complications comprised 3 cases of screw loosening (8.8%), 2 of screw breakage (5.9%), and 4 of rod fracture within the pelvic region (11.8%), including 1 case with concurrent screw and rod failure. In the S 2AI group, there were 21 cases of screw loosening (28.4%) and 2 of screw breakage (2.7%). Screw loosening was less frequent in the IS group than in the S 2AI group (χ 2=5.154, P=0.023), whereas pelvic rod fracture was more common in the IS group (χ 2=9.041, P=0.003). Screw breakage rates did not differ significantly ( P>0.05). Mean VAS, ODI, and SRS-22 scores in the IS group were 3.2±2.4, 24.9%±18.8%, and 3.2±0.8, respectively; corresponding to 2.5±1.8, 18.9%±10.9%, and 3.3±0.6 in the S 2AI group. ODI was significantly higher in the IS group ( t=2.062, P=0.042), whereas VAS and SRS-22 were comparable ( P>0.05). Among S 2AI patients, VAS and ODI scores did not differ significantly between those with and without screw loosening ( P>0.05). Conclusions:The post-operative incidence of pelvic fixation failure following ASD surgery reached 28.7%. The predominant failure mode with S 2AI was screw loosening, whereas IS was more frequently complicated by rod fracture. Early postoperative health-related quality of life was superior with S 2AI screws compared with iliac screws.

Objective:To investigate the risk factors for postoperative coronal imbalance in patients with type A degenerative scoliosis and to refine the Qiu classification by reclassifying type A patients.Methods:A retrospective analysis was conducted on the clinical data of patients with type A degenerative scoliosis classified by the Qiu classification who underwent corrective surgery at our hospital from January 2017 to April 2022. A total of 69 patients were enrolled in the study, including 3 males and 66 females, with an age of 60.6±6.8 years (range: 47-71 years). Based on the preoperative CBD, type A patients were further divided into three subtypes: Aa with CBD≤1 cm, Ab with CBD>1 cm with C 7 plumb line deviation toward the concave side, and Ac with CBD>1 cm with C 7 plumb line deviation toward the convex side. The incidence of coronal imbalance was compared among subtypes. During follow-up, patients with CBD ≤3 cm were classified as balanced, and those with CBD>3 cm as imbalanced. Radiographic parameters including coronal Cobb's angle (CA), CBD, L 4 tilt angle, L 5 tilt angle, thoracic kyphosis (TK), lumbar lordosis (LL), pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), and sagittal vertical axis (SVA) were measured in the standing radiographs preoperatively, 2-weeks postoperatively and 2-years follow-up. Differences in radiographic parameters between balanced and imbalanced groups were compared, and binary logistic regression was used to identify risk factors for postoperative coronal imbalance. Results:In the imbalanced Group (22 patients), there were 6 patients of type Aa (27%), 5 patients of type Ab (23%), and 11 patients of type Ac (50%), and in the balanced Group (47 patients), there were 20 patients of type Aa (43%), 18 patients of type Ab (38%), and 9 patients of type Ae (19%). The difference in subtype distribution between the two groups was significant (χ 2=6.939, P=0.029). The CBD in the imbalanced group was significantly larger than in the balanced group at the 2-years follow-up (4.18±0.86 cm vs. 1.31±0.78 cm, t=-13.813, P<0.001). The preoperative L 4 tilt angle was significantly larger in the imbalanced group compared to the balanced group (23.59°±6.86° vs. 17.64°±8.34°, t=-2.914, P=0.005). And the postoperative and 2-years follow-up L 4 tilt angles were also significantly larger than the balanced group (18.6°±5.5° vs. 11.5°±5.7°, t=-4.904, P<0.001; 18.0°±5.6° vs. 11.1°±5.7°, t=-4.691, P<0.001). Regression analysis identified the Ac type [ OR=3.937, 95% CI(1.07, 14.55), P=0.040] and excessive postoperative L 4 tilt angle [ OR=1.288, 95% CI(1.09, 1.52), P=0.003] as risk factors for postoperative coronal imbalance in type A patients. Conclusions:In the A-type of Qiu classification, patients with preoperative CBD>1 cm and trunk tilting towards the convex side (Ac type), as well as those with a large L 4 tilt angle after surgery, are more likely to experience coronal plane imbalance after surgery.

Objective:To investigate the difference of Roussouly ideal classification in predicting postoperative proximal junctional kyphosis (PJK) between adult degenerative spinal deformity patients with and without pelvic fixation and the potential reasons.Methods:From January 2017 to January 2020, a total of 95 patients (4 males, 91 females; with an average age of 62.03±6.30 years) with degenerative spinal deformities were retrospectively analyzed. There were 35 patients in the non-pelvic group (1 male, 34 females) and 60 patients in the pelvic group (3 males, 57 females). The radiographic parameters included coronal Cobb's angle (CA), pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), thoracic kyphosis (TK), lumbar lordosis (LL), sagittal vertical axis (SVA), T1 pelvic angle (TPA), and proximal junctional angle (PJA) were measured in the standing radiographs preoperatively, postoperatively at 2 weeks, and 2-year follow-up. Changes in PT and SS were calculated for patients at 2 weeks and the 2-year follow-up. Based on the revised Roussouly classification, 95 patients were classified into different types preoperatively, postoperatively at 2 weeks, and during the 2-year follow-up. Changes in the classification of patients were documented postoperatively at 2 weeks. Roussouly types were determined using preoperative pelvic parameters, and a match was defined when the 2-week postoperative classification aligned with the ideal type. The occurrence of PJK and the relationship with classification matching were recorded in the group. Independent t-tests were used for intergroup comparisons of radiographic parameters, and chi-square tests were employed to assess classification changes and predictive accuracy of the Roussouly classification. Results:Preoperative PT, TPA and SVA in non-pelvic group were significantly smaller than those in pelvic group, and preoperative SS and LL larger than those in pelvic group ( P<0.05). The changes of PT and SS in non-pelvic group were significantly lower than those in pelvic group 2 weeks after surgery ( P<0.05). The proportion of classification changes in the pelvic group was significantly higher than that in the non-pelvic group (60% vs. 34%, χ 2=5.847, P=0.016). Among the 95 patients, a total of 29 experienced PJK during the follow-up, with 3 cases progressing to PJF. The incidence of PJK in mismatched patients was 37% with no significant difference compared with matched patients (19%) (χ 2=3.357, P=0.067). In the sacral spine group of 60 patients, 22 experienced PJK, with 3 cases progressing to PJF. Among them, 19 patients with PJK had a classification mismatch with the ideal classification at 2 weeks postoperatively. The PJK incidence was significantly higher in mismatched patients (45%) compared to matched patients (17%) (χ 2=4.429, P=0.035). In the non-pelvic group, 7 patients developed PJK, with 3 mismatched cases. The PJK incidence in mismatched vs. matched patients was 18% vs. 22%, showing no significant difference (χ 2=0.114, P=0.735). Conclusions:For the patients with degenerative spinal deformity, pelvic fixation leads to a more complete restoration of the ideal Roussouly classification. Restoration of the Roussouly type in patients with pelvic fixation is a reliable predictor of postoperative PJK. However, in patients without pelvic fixation, the alignment with the ideal Roussouly classification does not significantly correlate with PJK development.

Objective·To investigate the genetic etiology of a rare and complex case clinically suspected to be methylmalonic acidemia(MMA),but with negative whole exome sequencing(WES)results,using a multi-omics sequencing approach.Methods·DNA and RNA samples were extracted from the peripheral blood of the proband and both parents.Targeted MMA-related gene Panel sequencing and WES were first performed.Subsequently,RNA sequencing(RNA-seq)and whole genome sequencing(WGS)were conducted to comprehensively analyze the child's genetic variants,their origins and potential inheritance patterns.Results·No pathogenic variants associated with the patient's phenotype were identified through the MMA Panel or standard WES analysis.Extended analysis of WES suggested the possibility of uniparental disomy(UPD)of chromosome 4.WGS revealed a homozygous splice-site variant(c.-66+2T>C)in the non-coding region of the metabolism of cobalamin associated A(MMAA)gene.The variant was located in the 5'untranslated region(5'UTR),specifically at the second base downstream of the splice donor site of exon 1(reference sequence:NM_172250).In genomic coordinates(hg19),the variant was located at base 146540561 on chromosome 4(chr4:146540561).Sanger sequencing confirmed that the mother was heterozygous for this variant,while the father did not carry it.RNA-seq showed no detectable expression of the MMAA gene on chromosome 4 in the patient.This was further confirmed by reverse transcription real time quantitative PCR,indicating nearly absent mRNA expression,suggesting that the non-coding splice-site variant affected transcriptional expression.Conclusion·A homozygous splice-site variant(c.-66+2T>C)in the non-coding region of the MMAA gene—outside the coverage of WES—is likely the pathogenic cause in this case,presumably resulting from maternal UPD of chromosome 4.

Next generation sequencing (NGS) technology is playing an increasingly important role in the diagnosis of genetic diseases. Whole exome sequencing (WES), which targets the coding regions of the genome, has been widely used in the diagnosis of genetic diseases for its low cost and high efficiency. However, compared to conventional methods, the Next Generation Sequencing (NGS) process is intricate, and there is variability in the expertise of data analysts and variant interpreters, which may lead to inconsistencies in the outcomes. To ensure the quality of testing and enhance the diagnostic rate of diseases, this consensus has provided recommendations regarding the laboratory setup, operational procedures, data analysis, result interpretation, and quality control for WES, with an aim to standardize its application in the detection of genetic disorders.