Utility of Natural Sitting Lateral Radiograph in the Diagnosis of Segmental Instability for Patients with Degenerative Lumbar Spondylolisthesis.

BACKGROUND: Segmental instability in patients with degenerative lumbar spondylolisthesis is an indication for surgical intervention. The most common method to evaluate segmental mobility is lumbar standing flexion-extension radiographs. Meanwhile, other simple radiographs, such as standing upright radiograph, a supine sagittal magnetic resonance imaging (MRI) or supine lateral radiograph, or a slump or natural sitting lateral radiograph, have been reported to diagnose segmental instability. However, those common posture radiographs have not been well characterized in one group of patients. Therefore, we measured slip percentage in a group of patients with degenerative lumbar spondylolisthesis using radiographs of patients in standing upright, natural sitting, standing flexion, and standing extension positions as well as supine MRI. QUESTIONS/PURPOSES: We asked: (1) Does the natural sitting radiograph have a larger slip percentage than the standing upright or standing flexion radiograph? (2) Does the supine sagittal MRI reveal a lower slip percentage than the standing extension radiograph? (3) Does the combination of the natural sitting radiograph and the supine sagittal MRI have a higher translational range of motion (ROM) and positive detection rate of translational instability than traditional flexion-extension mobility using translational instability criteria of greater than or equal to 8%? METHODS: We retrospectively performed a study of 62 patients (18 men and 44 women) with symptomatic degenerative lumbar spondylolisthesis at L4 who planned to undergo a surgical intervention at our institution between September 2018 and June 2019. Each patient underwent radiography in the standing upright, standing flexion, standing extension, and natural sitting positions, as well as MRI in the supine position. The slip percentage was measured three times by single observer on these five radiographs using Meyerding's technique (intraclass correlation coefficient 0.88 [95% CI 0.86 to 0.90]). Translational ROM was calculated by absolute values of difference between two radiograph positions. Based on the results of comparison of slip percentage and translational ROM, we developed the diagnostic algorithm to evaluate segmental instability. Also, the positive rate of translational instability using our diagnostic algorithms was compared with traditional flexion-extension radiographs. RESULTS: The natural sitting radiograph revealed a larger mean slip percentage than the standing upright radiograph (21% ± 7.4% versus 17.7% ± 8.2%; p < 0.001) and the standing flexion radiograph (21% ±7.4% versus 18% ± 8.4%; p = 0.002). The supine sagittal MRI revealed a lower slip percentage than the standing extension radiograph (95% CI 0.49% to 2.8%; p = 0.006). The combination of natural sitting radiograph and the supine sagittal MRI had higher translational ROM than the standing flexion and extension radiographs (10% ± 4.8% versus 5.4% ± 3.7%; p < 0.001). More patients were diagnosed with translational instability using the combination of natural sitting radiograph and supine sagittal MRI than the standing flexion and extension radiographs (61% [38 of 62] versus 19% [12 of 62]; odds ratio 3.9; p < 0.001). CONCLUSION: Our results indicate that a sitting radiograph reveals high slip percentage, and supine sagittal MRI demonstrated a reduction in anterolisthesis. The combination of natural sitting and supine sagittal MRI was suitable to the traditional flexion-extension modality for assessing translational instability in patients with degenerative lumbar spondylolisthesis. LEVEL OF EVIDENCE: Level III, diagnostic study.

How does sagittal spinopelvic alignment of lumbar multisegmental spondylolysis differ from monosegmental spondylolysis?

OBJECTIVE: The aim of this study was to investigate sagittal alignment and compensatory mechanisms in patients with monosegmental spondylolysis (mono_lysis) and multisegmental spondylolysis (multi_lysis). METHODS: A total of 453 adult patients treated for symptomatic low-grade spondylolytic spondylolisthesis were retrospectively studied at a single center. Patients were divided into 2 subgroups, the mono_lysis group and the multi_lysis group, based on the number of spondylolysis segments. A total of 158 asymptomatic healthy volunteers were enrolled in this study as the control group. Radiographic parameters measured on standing sagittal radiographs and the ratios of L4-S1 segmental lordosis (SL) to lumbar lordosis (L4-S1 SL/LL) and pelvic tilt to pelvic incidence (PT/PI) were compared between all experimental groups. RESULTS: There were 51 patients (11.3%) with a diagnosis of multi_lysis in the spondylolysis group. When compared with the control group, the spondylolysis group exhibited larger PI (p < 0.001), PT (p < 0.001), LL (p < 0.001), and L4-S1 SL (p = 0.025) and a smaller L4-S1 SL/LL ratio (p < 0.001). When analyzing the specific spondylolysis subgroups, there were no significant differences in PI, but the multi_lysis group had a higher L5 incidence (p = 0.004), PT (p = 0.018), and PT/PI ratio (p = 0.039). The multi_lysis group also had a smaller L4-S1 SL/LL ratio (p = 0.012) and greater sagittal vertical axis (p < 0.001). CONCLUSIONS: A high-PI spinopelvic pattern was involved in the development of spondylolytic spondylolisthesis, and a larger L5 incidence might be associated with the occurrence of consecutive multi_lysis. Unlike patients with mono_lysis, individuals with multi_lysis were characterized by an anterior trunk, insufficiency of L4-S1 SL, and pelvic retroversion.

Does Vertebral End Plate Morphology Affect Cage Subsidence After Transforaminal Lumbar Interbody Fusion?

OBJECTIVE: To investigate the effect of end plate morphology on cage subsidence and to compare the surgical outcomes among patients with different vertebral end plate morphologies. METHODS: We reviewed a series of consecutive patients from January 2009 to January 2016 who had undergone monosegment L4/5 transforaminal lumbar interbody fusion (TLIF) with a follow-up >2 years. The enrolled patients were divided into 3 groups based on the preoperative vertebral end plate morphology on T1-weighed sagittal magnetic resonance scans: concave group (C group), flat group (F group), and irregular group (Ir group). Lumbar lordosis (LL), segmental lordosis (SL), and disc height (DH) were measured on the plain image at each follow-up, and three-dimensional computed tomography (3D-CT) was obtained at 1 year follow-up to evaluate the cage subsidence and solid fusion. RESULTS: A total of 145 consecutive patients (41 males and 104 females) were included in this study, with a mean follow-up of 33.8 ± 12.3 months. The age was significantly older in the Ir group than in the C group or F group (P < 0.05). Cage subsidence was detected in 23 patients (15.9%) at 1 year follow-up through 3D-CT. The incidence of cage subsidence was significantly higher in the Ir group than in the F group or C group (P < 0.05). Patients in the Ir group had significant loss of DH, SL, and LL at the latest follow-up, compared with those in the C group and F group (P < 0.05). Patients with cage subsidence had a significantly older age (P < 0.05). The presence of cage subsidence was associated with end plate morphology as shown by logistic regression analysis (P < 0.05). Before surgery, Oswestry Disability Index and visual analog scale back pain scores were significantly higher in the Ir group than in the C and F groups (P < 0.05). After surgery and until the latest follow-up, each group experienced significant improvement in contrast to preoperative scores regardless of end plate morphology (P < 0.05). CONCLUSIONS: Morphology of the end plate plays an important role in the development of cage subsidence after TLIF surgery. Fused segments with irregular end plates are prone to cage subsidence. Although cage subsidence does not affect short-term clinical outcomes, measures should be taken to prevent cage subsidence-related loss of SL and total LL.

Sagittal reconstruction of lumbosacral contiguous double-level spondylolytic spondylolisthesis: a comparison of double-level and single-level transforaminal lumbar interbody fusion.

BACKGROUND: Contiguous double-level lumbar spondylolytic spondylolisthesis is an extremely rare condition. There is a paucity of data of lumbosacral deformity and sagittal spino-pelvic malalignment among these patients. Moreover, the effect of transforaminal lumbar interbody fusion (TLIF) on sagittal realignment still remains largely unknown. The aim of the study is to investigate the reconstruction of sagittal alignment and the improvement of clinical outcomes after posterior instrumented double-level or single-level TLIF. METHODS: From January 2010 to September 2018, the records of patients with contiguous L4/5 and L5/S1 double-level spondylolytic spondylolisthesis were retrospectively reviewed. Patients who had undergone double-level or single-level TLIF and a minimum of 2 years' follow-up were included. The slippage parameters and spino-pelvic parameters were measured preoperatively, postoperatively, and at the latest follow-up. RESULTS: A total of 58 patients (21 males and 37 females, mean age of 57.1 ± 6.9 years) were enrolled. Thirty-eight patients were treated with double-level TLIF and the remaining 20 with single-level TLIF (L4/5 in 14; L5/S1 in 6). After surgery, the spondylolisthesis was significantly reduced at both L4/5 and L5/S1 level (all P < 0.001). There was a significant reduction in pelvic tilt (P < 0.001) and a significant increase in sacral slope (P < 0.001). Significant increase in L4-S1 height (P < 0.001) and L4-S1 lordosis (P = 0.012) and decrease in L5 slope (P = 0.004) and L5 incidence (P = 0.001) were also observed. Compared to single-level TLIF, double-level TLIF increased L4-S1 height (P < 0.001) and L4-S1 lordosis (P < 0.001) and reduced L4-SVA (P = 0.007) and L5 incidence (P = 0.013) more obviously, and the sagittal balance was better corrected in double-level TLIF group (P = 0.006). Double-level TLIF group showed larger increase in VAS scores for low back pain. The incidence of implant-related complications was lower in the double-level group. CONCLUSION: Posterior short-segment instrumented TLIF can bring favorable radiographic and clinical outcomes in patients with lumbosacral contiguous double-level spondylolytic spondylolisthesis. Double-level TLIF is more efficient to improve L4-S1 height, regional lumbar lordosis, and global sagittal balance.

Spinal Gorham-Stout syndrome: radiological changes and spinal deformities.

BACKGROUND: Gorham-Stout syndrome (GSS) involving the spine is a rare clinical entity, and there is a paucity of comprehensive study on its radiological features. We aimed to present the radiological changes and spinal deformities in patients with spinal GSS. METHODS: From January 2005 to December 2017, 11 consecutive GSS patients with spinal deformity were identified. Their medical records and imaging features were retrospectively reviewed. Computed tomography (CT) and magnetic resonance imaging (MRI) were used for a precise evaluation of spinal involvement. Posteroanterior and lateral standing radiographs were used to evaluate the spinal deformity. RESULTS: CT showed multi-level generalized osteolytic lesions, with ill-defined fluid attenuation adjacent to the osseous changes. MRI demonstrated hyperintense signals on both T1- and T2-weighted images, while the unaffected segments showed normal signal intensity. Seven patients (63.6%) had a dominant feature of kyphosis, and 4 (36.4%) had scoliosis when spinal GSS was diagnosed. Kyphosis variably spanned from C7 to L1, averaged 94° (range, 53° to 158°), and was associated with sagittal imbalance in 4 cases. In our series, the apex of kyphosis and scoliosis coincided within the most seriously osteolytic segment. All patients received medication for GSS. Two adolescents taking Boston braces showed a relatively stable deformity. Four patients received long posterior spinal fusion, but two had fusion failure. CONCLUSIONS: CT and MRI investigations are important in the initial diagnosis and continued management for spinal GSS. A typical spinal deformity secondary to GSS presents as kyphosis or kyphoscoliosis, which is usually highly variable but highly concordant with osteolysis in terms of span and apex.

Vertebra-disc ratio as a new predictor for curve progression in early thoracic AIS with bracing treatment.

OBJECTIVES: Previous studies have reported various predictors for curve progression in braced adolescent idiopathic scoliosis (AIS) patients. However, the reported predictors might be insufficient for patients with early AIS. The aim was to investigate whether the initial vertebra-disc ratio (VDR) could serve as an effective predictor for curve progression in early thoracic AIS (premenarchal and Risser 0) undergoing brace treatment. PATIENTS AND METHODS: This study reviewed a consecutive series of early thoracic AIS girls with thoracic curve. All patients had accepted brace treatment and had regular follow-up. According to the bracing outcomes, patients were divided into two groups: Group P (progressed, curve progressed over six degrees or indicated for surgery) and Group NP (non-progressed). RESULTS: Totally 203 girls were included. There were 73 and 130 patients in Groups P and NP, respectively. The patients in Group P had greater initial VDR (1.9 ± 0.5 vs. 0.8 ± 0.4, P < 0.01) than Group NP. During the follow-up, it showed continuous higher values in Group P than Group NP. The logistic regression analysis revealed that initial VDR had an effective value for predicting curve progression in the braced early AIS girls. The ideal cut-off point of initial VDR was 1.5 for the prediction of curve progression. CONCLUSION: The initial VDR could serve as an effective predictor for curve progression in braced early AIS girls. Evaluation of this new parameter should be carefully performed at the bracing initiation.

Does kyphotic configuration on upright lateral radiograph correlate with instability in patients with degenerative lumbar spondylolisthesis?

OBJECTIVE: To investigate the segmental instability of degenerative lumbar spondylolisthesis (DLS) with a kyphotic configuration at the involved segment, and to determine the most useful diagnostic modalities in the evaluation of instability. PATIENTS AND METHODS: This study reviewed a consecutive series of patients with L4/5 DLS between July 2010 and May 2016. The enrolled patients were divided into two groups based on preoperative neutral radiographs: the kyphotic group (Group K) and non-kyphotic group (Group NK). Translational and angular motion was determined by comparing upright lateral radiograph (U) with a supine sagittal MR image(S) (Combined, US) or flexion/extension radiographs (FE). RESULTS: There were 26 and 201 patients in Groups K and NK, respectively. In comparison to Group NK, Group K demonstrated significantly higher translational motion (12.4% vs. 7.0%, P < 0.001) on US analysis, but significantly lower translational motion (4.2% vs. 6.4%, P < 0.001) on FE analysis. Angular motion was detected to be significantly lower in US versus FE in Group NK (1.2° vs. 7.8°, P < 0.001), while of no difference in Group K (P > 0.05). In Group K, "instability" was recognized in 84.6% of patients using US versus 11.5% patients using FE (P < 0.001); While in Group NK, no significant difference was observed in the incidence of "instability" between FE and US (31.3% vs. 27.8%, P = 0.444). Overall, Group K had a significantly higher incidence of instability than Group NK (84.6% vs. 31.3%, P < 0.001). CONCLUSION: DLS with a kyphotic configuration is a distinct subgroup associated with segmental instability. The modality of US is shown to be superior to traditional FE in measuring translational motion and identifying instability for DLS patients with a kyphotic configuration.

Higher Improvement in Patient-Reported Outcomes Can Be Achieved After Transforaminal Lumbar Interbody Fusion for Clinical and Radiographic Degenerative Spondylolisthesis Classification Type D Degenerative Lumbar Spondylolisthesis.

BACKGROUND: Clinical and radiographic degenerative spondylolisthesis (CARDS) classification defines a distinct subset of patients with kyphotic angulation at the involved segment (type D). Research using CARDS classification to investigate motion characteristics at involved segments or patient-related outcomes (PROs) following surgical intervention is sparse. We investigated the relationship between CARDS type D spondylolisthesis and dynamic instability and PROs in type D versus non-type D spondylolisthesis. METHODS: We reviewed consecutive patients who received transforaminal lumbar interbody fusion for L4-5 spondylolisthesis between 2009 and 2015. Patients were assigned into type D and non-type D groups. Translational motion was determined by upright lumbar lateral radiography with supine sagittal magnetic resonance imaging or flexion and extension radiography. Demographics, radiographic parameters, and PROs were evaluated. RESULTS: Type D and non-type D groups comprised 34 and 163 patients, respectively. Compared with non-type D, type D group was characterized by lordotic angulation loss and higher degree of olisthesis on upright radiographs and demonstrated higher translational motion on upright lumbar lateral radiography with supine sagittal magnetic resonance imaging analysis. After surgery, mean reduction rate was significantly higher in type D group; type D had less slippage, but differences in slip angle and disc height were not significant. Preoperative Oswestry Disability Index and visual analog scale for back pain scores were higher in type D group. Type D spondylolisthesis and dynamic instability were associated with achieving minimal clinically important differences in PROs. CONCLUSIONS: CARDS type D spondylolisthesis is a distinct subset associated with dynamic instability and worse PROs. Higher improvement in PROs can be achieved in CARDS type D spondylolisthesis after surgery.