Chronic lower back pain is a potentially incapacitating condition associated with disc degeneration. Although therapy is primarily pharmaceutical, surgery comprising arthrodesis constitutes an alternative. Anterior intersomatic lumbar arthrodesis (ALIF, anterior interbody lumbar fusion) is the reference approach, although total disc arthroplasty may also be undertaken. Analysis of pelvic and spinal parameters provides the best indication of sagittal balance.
Materials and methods
This was a prospective study in a continuous series of 99 patients presenting chronic lower back pain due to disc disease. Pelvic incidence, sacral slope, pelvic tilt, spino-sacral angle (SSA) and the four back types in the Roussouly classification were studied in radiographs of the whole spine under load using an EOS imaging system.
The pre-operative SSA value for the study population was 126.09° ± 8.45° and the mean spine tilt angle was 90° compared with 95° in healthy subjects. Following surgery, the SSA was considerably increased in the discal arthroplasty, resulting in a significantly more balanced spinal position. In the group of patients undergoing arthrodesis using the ALIF technique, no such significant improvement was found despite the use of a lordosis cage. We showed that in cases of low pelvic incidence, it was necessary to maintain a Roussouly type 1 or 2 back without increasing lordosis. The results demonstrated the value of L4–L5 disc prostheses in these subjects. L5–S1 arthrodesis seemed a more suitable approach for treating patients with elevated sacral slope (back type 3 or 4). This new type of analysis of sagittal parameters should be performed prior to all surgical procedures involving lumbar prostheses.
Lumbar disc degeneration; ALIF; Total disc prosthesis; Sagittal balance; Spino-pelvic organisation; Spino-sacral angle
To evaluate the radiographic results of minimally invasive (MIS) anterior lumbar interbody fusion (ALIF) and transforaminal lumbar interbody fusion (TLIF).
Twelve and nineteen patients who underwent MIS-ALIF, MIS-TLIF, respectively, from 2006 to 2008 were analyzed with a minimum 24-months' follow-up. Additionally, 18 patients treated with single level open TLIF surgery in 2007 were evaluated as a comparative group. X-rays and CT images were evaluated preoperatively, postoperatively, and at the final follow-up. Fusion and subsidence rates were determined, and radiographic parameters, including lumbar lordosis angle (LLA), fused segment angle (FSA), sacral slope angle (SSA), disc height (DH), and foraminal height (FH), were analyzed. These parameters were also compared between the open and MIS-TLIF groups.
In the MIS interbody fusion group, statistically significant increases were observed in LLA, FSA, and DH and FH between preoperative and final values. The changes in LLA, FSA, and DH were significantly increased in the MIS-ALIF group compared with the MIS-TLIF group, but SSA and FH were not significantly different. No significant differences were seen between open and MIS-TLIF except for DH. The interbody subsidence and fusion rates of the MIS groups were 12.0±4% and 96%, respectively.
Radiographic results of MIS interbody fusion surgery are as favorable as those with conventional surgery regarding fusion, restoration of disc height, foraminal height, and lumbar lordosis. MIS-ALIF is more effective than MIS-TLIF for intervertebral disc height restoration and lumbar lordosis.
Minimally Invasive Interbody Fusion; Transforaminal Lumbar Interbody Fusion; Anterior Lumbar Interbody Fusion; Radiographic Results
Retrospective study of a prospective clinical and radiological database of subjects with adolescent (AIS) and adult (AS) idiopathic scoliosis undergoing surgical correction by posterior approach.
To evaluate the differences in sagittal alignment of the spine and pelvis in AIS and AS before surgery and changes after surgery in both populations.
Summary of background data
The relationship between the spine and pelvis highly influences the sagittal balance in adults and adolescents. However, the sagittal alignment of the spine and pelvis before and after surgery in idiopathic scoliosis, whatever the age, is poorly defined in the literature.
Clinical and radiological data were extracted from a prospective database of 132 AIS patients and 52 AS before and at last follow-up after surgical correction. Sagittal parameters were evaluated on AP and lateral radiographs using a custom software: pelvic incidence (PI), sacral slope (SS), pelvic tilt (PT), lumbar lordosis (LL), thoracic kyphosis (TK), C7 Barrey’s ratio, spino-sacral angle (SSA). A new algorithm of combination of balance parameters was proposed to characterize and compare the various pathological spino-pelvic settings. Based on PI subdivision in high (<55°) and low values (>55°), then on a range of PT indexed on PI giving the pelvis positioning (anteverted, normal or retroverted), the population was finally characterized by the C7 plumbline position with regard to the posterior edge of the sacrum and the center of the femoral heads, in balanced, slightly unbalanced and unbalanced. More specifically, the AIS study included the cervical shape alignment with cervical lordosis (CL) and sagittal thoracic profile assessment (hypo vs. normokyphotic). In AS, the study focused on thoraco-lumbar kyphosis (TLK) occurrence (LL length). Paired Student t tests were used for comparison (α = 0.02).
Pre-operatively, in AIS there was a prevalence of lower PI (57 %). Whatever the PI, PT remained anteverted or normal. Positioning of C7 was much more unbalanced, forward of the femoral heads (50 %), than in asymptomatic population (17 %). There was a notable loss and reversal of cervical lordosis in the majority of subjects, with an average cervical kyphosis measurement of 10 ± 18°. Thoracic kyphosis values were lower than average, while lumbar lordosis values were within normal limits. After surgery, in the entire group, a slight but significant increase of PT coupled to a decrease of SS and LL was noted, while no changes could be documented in thoracic kyphosis and cervical lordosis. However, when sub-classified according to thoracic hypo versus normokyphosis pre-op, there was a significant decrease of TK coupled to a decrease of LL and CL in the normokyphotic group, while TK and CL were improved in the hypokyphotic group. A significant number of patients improved their global balance. Changes in sagittal profile between Lenke curve types were minimal. In AS there were significant differences between low and high PI populations. Severity of unbalance increased in high PI population with association of retroverted pelvis and forward unbalance. In lower PI, increasing PT was generally sufficient to balance the patients. The occurrence of TLK was strongly increased in the entire population and became the rule in those with lower PI (76 %). Post-operatively, in those with high PI, PT did not change while global balance improved slightly. The strategy of correction in higher PI was to maintain TLK. In those with low PI, PT improved while C7 did not change. Correction of TLK was obtained in eight cases.
A decrease of cervical lordosis and thoracic kyphosis is commonly associated with AIS. The anterior unbalance frequently found in AIS does not seem to have the same significance of severity as in AS. In AIS PI does not change the balance criterions, while in AS the severity of unbalance is increased with higher PI. TLK seems to be a way of worsening the balance in elderly, mainly in lumbar and thoraco-lumbar scoliosis with low PI. Surgical correction of the thoracic and lumbar spine in AIS induces significant changes in the sagittal spino-pelvic profile. Changes in the cervical sagittal profile vary according to the pre-op sagittal profile of the thoracic kyphosis. Cervical lordosis and thoracic kyphosis are improved by surgical correction in subjects with pre-operative hypokyphosis, but a reverse effect is noted in those with normal pre-operative kyphosis. The clinical significance of these changes in sagittal shape remains to be determined. In AS, it appears easier to restore a good balance in the lower PI population than in those with less pre-operative unbalance.
Adolescent idiopathic scoliosis; Adult scoliosis; Kyphosis; Lordosis; Pelvis; Sagittal balance; Spine; Cervical spine
Comparatively little is known about the relation between the sagittal vertical axis and clinical outcome in cases of degenerative lumbar spondylolisthesis. The objective of this study was to determine whether lumbar sagittal balance affects clinical outcomes after posterior interbody fusion. This series suggests that consideration of sagittal balance during posterior interbody fusion for degenerative spondylolisthesis can yield high levels of patient satisfaction and restore spinal balance
A retrospective study of clinical outcomes and a radiological review was performed on 18 patients with one or two level degenerative spondylolisthesis. Patients were divided into two groups: the patients without improvement in pelvic tilt, postoperatively (Group A; n = 10) and the patients with improvement in pelvic tilt postoperatively (Group B; n = 8). Pre- and postoperative clinical outcome surveys were administered to determine Visual Analogue Pain Scores (VAS) and Oswestry disability index (ODI). In addition, we evaluated full spine radiographic films for pelvic tilt (PT), sacral slope (SS), pelvic incidence (PI), thoracic kyphosis (TK), lumbar lordosis (LL), sacrofemoral distance (SFD), and sacro C7 plumb line distance (SC7D)
All 18 patients underwent surgery principally for the relief of radicular leg pain and back pain. In groups A and B, mean preoperative VAS were 6.85 and 6.81, respectively, and these improved to 3.20 and 1.63 at last follow-up. Mean preoperative ODI were 43.2 and 50.4, respectively, and these improved to 23.6 and 18.9 at last follow-up. In spinopelvic parameters, no significant difference was found between preoperative and follow up variables except PT in Group A. However, significant difference was found between the preoperative and follows up values of PT, SS, TK, LL, and SFD/SC7D in Group B. Between parameters of group A and B, there is borderline significance on preoperative PT, preoperative LL and last follow up SS.
Correlation analysis revealed the VAS improvements in Group A were significantly related to postoperative lumbar lordosis (Pearson's coefficient = -0.829; p = 0.003). Similarly, ODI improvements were also associated with postoperative lumbar lordosis (Pearson's coefficient = -0.700; p = 0.024). However, in Group B, VAS and ODI improvements were not found to be related to postoperative lumbar lordosis and to spinopelvic parameters.
In the current series, patients improving PT after fusion were found to achieve good clinical outcomes in degenerative spondylolisthesis. Overall, our findings show that it is important to quantify sagittal spinopelvic parameters and promote sagittal balance when performing lumbar fusion for degenerative spondylolisthesis.
A retrospective cross-sectional study was designed to evaluate total sagittal spinal alignment in patients with lumbar disc herniation (LDH) and healthy subjects. Abnormal sagittal spinal alignment could cause persistent low back pain in lumbar disease. Previous studies analyzed sciatic scoliotic list in patients with lumbar disc herniation; but there is little or no information on the relationship between sagittal alignment and subjective findings. The study subjects were 61 LDH patients and 60 age-matched healthy subjects. Preoperative and 6-month postoperatively lateral whole-spine standing radiographs were assessed for the distance between C7 plumb line and posterior superior corner on the top margin of S1 sagittal vertical axis (SVA), lumbar lordotic angle between the top margin of the first lumbar vertebra and first sacral vertebra (L1S1), pelvic tilting angle (PA), and pelvic morphologic angle (PRS1). Subjective symptoms were evaluated by the Japanese Orthopedic Association (JOA) score for lower back pain (nine points). The mean SVA value of the LDH group (32.7 ± 46.5 mm, ± SD) was significantly larger than that of the control (2.5 ± 17.1 mm), while L1S1 was smaller (36.7 ± 14.5°) and PA was larger (25.1 ± 9.0°) in LDH than control group (49.0 ± 10.0° and 18.2 ± 6.0°, respectively). At 6 months after surgery, the malalignment recovered to almost the same level as the control group. SVA correlated with the subjective symptoms measured by the JOA score. Sagittal spinal alignment in LDH exhibits more anterior translation of the C7 plumb line, less lumbar lordosis, and a more vertical sacrum. Measurements of these spinal parameters allowed assessment of the pathophysiology of LDH.
Sagittal spinal alignment; Lumbar disc herniation; Radicular pain
Radiographic sagittal plane analysis of VATS (video-assisted thoracoscopic surgery) anterior instrumentation for adolescent idiopathic scoliosis. This is retrospective study. To report, in details about effects of VATS anterior instrumentation on the sagittal plane. Evaluations of the surgical outcome of scoliosis have primarily studied in coronal plane correction, functional, and cosmetic aspects. Sagittal balance, as well as coronal balance, is important in functional spine. Recently, scoliosis surgery applying VATS has been increasingly performed. Its outcome has been reported several times; however, according to our search of the literature, the only one study partially mentioned. The study population was a total of 42 cases of idiopathic scoliosis patients (8 male, 34 female). Their mean age was 15.6 years (13 to 18 years). The 18 cases were Lenke IA type, 16 cases were Lenke IB type, and 8 cases were Lenke IC type. The preoperative Cobb's angle was 54.5 ± 13.9°. All patients were followed up for a minimum of 2 years and implanted, on average, at the 5.9 level (5 to 8 levels). The most proximal implant was the 4th thoracic spine, and the most distal implant was the 1st lumbar spine. Whole spine standing PA and lateral radiographs were taken before surgery, 2 months after surgery, and at the last follow up (range 24-48 months, mean 35 months). The C7 plumbline proximal junctional measurement (PJM), distal junctional measurement (DJM), thoracic kyphosis, and lumbar lordosis angles were measured and compared. In all cases, follow-ups were possible and survived till the last follow up. The Cobb's angle in coronal plane at the last follow up was 19.7 ± 9.3° and was corrected to 63.8% on average. The preoperative C7 sagittal plumbline before surgery was -13.9 ± 29.1 mm, the final follow up was -9.9 ± 23.8 mm, and the average positive displacement was 4 mm. Thoracic kyphosis was increased from preoperative 18.2 ± 7.7° to 22.4 ± 7.2° on average at the last follow up, and the increase was, on average, 4.2°. The PJM angel was increased from 6.2 ± 4.3° preoperative to 8.8 ± 3.7° at the last follow up, and the increment was, on the average, 2.6°. The DJM angle before surgery was 6.8 ± 5.1° and 6.7 ± 4° at the last follow up, and did not change noticeably. Preoperative lumbar lordosis was 42 ± 10.7° and 43.5 ± 11.1° after surgery. Similarly, it did not change greatly. The scoliosis surgery applying VATS displaced the C7 sagittal plumb line by 4 mm to the anteriorly, increased thoracic kyphosis by 4.2°, and increased PJM by 2.6°. DJM and lumbar lordosis, before and after operation, were not significantly different. Although the surgical technique of VATS thoracic instrumentation is difficult to make the normal thoracic kyphosis, an acceptable sagittal balance can be obtained in Lenke type I adolescent idiopathic scoliosis using VATS.
Scoliosis; VATS; sagittal balance
The authors conducted a study to determine at what stage after surgery the subsidence occurred, and to assess the relationships of radiographic fusion and the recurrence of symptoms with the development of subsidence. Ninety patients underwent a single-level anterior lumbar interbody fusion (ALIF) using paired stand-alone rectangular cages between November 2000 and June 2002. All patients had regular clinical or imaging follow-up for a minimum of 19 months (range 19–38 months, mean = 27 months). The ratio of male to female patients was 1:3.1. The patients’ ages at the time of ALIF ranged from 25 to 72 years, with a mean of 53 years. The preoperative and postoperative intervertebral disc heights were serially measured by plain radiographs. The location of cage subsidence into the vertebral body and times until the presence of subsidence were also assessed. The mean preoperative intervertebral disc height was 11.6±3.1 mm, which spread immediately after surgery to 16.9±2.0 mm. This increase was statistically significant (P=0.001). At the last follow-up visit, the mean intervertebral disc height had been reduced to 13.2±2.4 mm. Sixty-nine of 90 patients (76.7%) developed cage subsidence into the surrounding vertebral body. Subsidence was more often noted in the superior endplate above the cage with regard to the location of cage subsidence [superior endplate: 27 patients (39.1%), inferior endplate: 12 patients (17.3%), both: 30 patients (43.6%)]. The onset of subsidence varied from 0.25 to 8 months after surgery (median, 2.75 months). The 8-, 12-, and 16-week actuarial rates for developing cage subsidence were 38.9, 63.4, and 70.7%, respectively, when using the Kaplan–Meier method. There was no statistical correlation between the recurrence of symptoms (P=0.3952) and radiographic fusion (P=0.9518) with the log-rank test in development of subsidence. This study demonstrates that cage subsidence is an expected occurrence after ALIF using stand-alone rectangular cages. The 3- and 4-month actuarial rates for developing cage subsidence were 63.4 and 70.7%, respectively, and cage subsidence had no correlation with recurrence of symptoms and radiographic fusion in our study.
Anterior lumbar interbody fusion (ALIF); Cage; Subsidence
Posterior lumbar interbody fusion (PLIF) restores disc height, the load bearing ability of anterior ligaments and muscles, root canal dimensions, and spinal balance. It immobilizes the painful degenerate spinal segment and decompresses the nerve roots. Anterior lumbar interbody fusion (ALIF) does the same, but could have complications of graft extrusion, compression and instability contributing to pseudarthrosis in the absence of instrumentation. The purpose of this study was to assess and compare the outcome of instrumented circumferential fusion through a posterior approach [PLIF and posterolateral fusion (PLF)] with instrumented ALIF using the Hartshill horseshoe cage, for comparable degrees of internal disc disruption and clinical disability. It was designed as a prospective study, comparing the outcome of two methods of instrumented interbody fusion for internal disc disruption. Between April 1994 and June 1998, the senior author (N.R.B.) performed 39 instrumented ALIF procedures and 35 instrumented circumferential fusion with PLIF procedures. The second author, an independent assessor (S.M.), performed the entire review. Preoperative radiographic assessment included plain radiographs, magnetic resonance imaging (MRI) and provocative discography in all the patients. The outcome in the two groups was compared in terms of radiological improvement and clinical improvement, measured on the basis of improvement of back pain and work capacity. Preoperatively, patients were asked to fill out a questionnaire giving their demographic details, maximum walking distance and current employment status in order to establish the comparability of the two groups. Patient assessment was with the Oswestry Disability Index, quality of life questionnaire (subjective), pain drawing, visual analogue scale, disability benefit, compensation status, and psychological profile. The results of the study showed a satisfactory outcome (score≤30) on the subjective (quality of life questionnaire) score of 71.8% (28 patients) in the ALIF group and 74.3% (26 patients) in the PLIF group (P>0.05). On categorising Oswestry Index scores into "excellent", "better", "same", and "worse", we found no difference in outcome between the two groups: 79.5% (n=31) had satisfactory outcome with ALIF and 80% (n=28) had satisfactory outcome with PLIF. The rate of return to work was no different in the two groups. On radiological assessment, we found two nonunions in the circumferential fusion (PLIF) group (94.3% fusion rate) and indirect evidence of no nonunions in the ALIF group. There was no significant difference between the compensation rate and disability benefit rate between the two groups. There were three complications in ALIF group and four in the PLIF (circumferential) group. On the basis of these results, we conclude that it is possible to treat discogenic back pain by anterior interbody fusion with Hartshill horseshoe cage or with circumferential fusion using instrumented PLIF.
Disc degeneration; Interbody fusion; Cages
Restitution of sagittal balance is important after lumbar fusion, because it improves fusion rate and may reduce the rate of adjacent segment disease. The purpose of the present study was to describe the impact of transforaminal lumbar interbody fusion (TLIF) procedures on pelvic and spinal parameters and sagittal balance.
Materials and methods
Forty-five patients who had single-level TLIF were included in this study. Pelvic and spinal radiological parameters of sagittal balance were measured preoperatively, postoperatively and at latest follow-up.
Age at surgery averaged 58.4 (±9.6) years. Mean follow-up was 35.1 months (±4.1). Twenty-nine percent of the patients exhibited anterior imbalance preoperatively, with high pelvic tilt (17.6° ± 7.9°). Of the 32 (71%) patients well balanced before the procedure, 22 (70%) had a large pelvic tilt (>20°), due to retroversion of the pelvis as an adaptive response to the loss of lordosis. Three dural tears (7%) were reported intraoperatively. Interbody cages were more posterior than intended in 27% of the cases. Disc height and lumbar lordosis at fusion level significantly increased postoperatively (p < 0.05 and p < 0.001). Pelvic tilt was significantly reduced (p < 0.01) postoperatively, whereas the global sagittal balance was not significantly modified (p = 0.07).
Single-level circumferential fusion helps patients reducing their pelvic compensation, but the amount of correction does not allow for complete correction of sagittal imbalance.
Lumbar fusion; TLIF; Sagittal balance; Degenerative spine
The restoration of disc space height (DSH) is essential in anterior lumbar interbody fusion (ALIF), while it is unclear whether the reduction of DSH may alter the mechanical status and adversely affect adjacent segment, and few literatures focused on the subject.
Ninety five patients who had undergone ALIF for degenerative disc disease at our institution between March 2004 and March 2007 were retrospectively reviewed and 76 patients were enrolled in this study. Preoperative, postoperative and the final follow-up segmental lordosis (SL), whole lumbar lordosis (WLL) and DSH were measured and compared in adjacent segmental degeneration (ASD) group and non-ASD group, and the relationship between DSH, SL, WLL and ASD were investigated retrospectively.
In 76 patients, the radiographic ASD was proven in 25 (32.9%) and symptomatic ASD in 2 patients. There was a significant correlation between DSH and SL, but was insignificant between DSH and WLL, and a significant correlation was noticed between ASD and SL, WLL and DSH at final follow-up.
The normal DSH and SL is important for preventing ASD and an anterior cage with appropriate height and lordotic angle to be used in ALIF to maintain the proper DSH and SL.
Adjacent segment degeneration; Anterior lumbar interbody fusion; Disc space height; Segmental lordosis; Whole lumbar lordosis
Risk factors for falling in elderly people remain uncertain, and the effects of spinal factors and physical ability on body balance and falling have not been examined. The objective of this study was to investigate how factors such as spinal sagittal alignment, spinal range of motion, body balance, muscle strength, and gait speed influence falling in the prospective cohort study.
The subjects were 100 males who underwent a basic health checkup. Balance, SpinalMouse® data, grip strength, back muscle strength, 10-m gait time, lumbar lateral standing radiographs, body mass index, and fall history over the previous year were examined. Platform measurements of balance included the distance of movement of the center of pressure (COP) per second (LNG/TIME), the envelopment area traced by movement of the COP (E AREA), and the LNG/E AREA ratio. The thoracic/lumbar angle ratio (T/L ratio) and sagittal vertical axis (SVA) were used as an index of sagittal balance.
LNG/TIME and E AREA showed significant positive correlations with age, T/L ratio, SVA, and 10-m gait time; and significant negative correlations with lumbar lordosis angle, sacral inclination angle, grip strength and back muscle strength. Multiple regression analysis showed significant differences for LNG/TIME and E AREA with T/L ratio, SVA, lumbar lordosis angle and sacral inclination angle (R2 = 0.399). Twelve subjects (12 %) had experienced a fall over the past year. Age, T/L ratio, SVA, lumbar lordosis angle, sacral inclination angle, grip strength, back muscle strength, 10-m gait time, height of the intervertebral disc, osteophyte formation in radiographs and LNG/E AREA differed significantly between fallers and non-fallers. The group with SVA > 40 mm (n = 18) had a significant higher number of subjects with a single fall (6 single fallers/18: p = 0.0075) and with multiple falls (4 multiple fallers/18: p = 0.0095).
Good spinal sagittal alignment, muscle strength and 10-m gait speed improve body balance and reduce the risk of fall. Muscle strength and physical ability are also important for spinal sagittal alignment. Body balance training, improvement of physical abilities including muscle training, and maintenance of spinal sagittal alignment can lead to prevention of fall.
Fall; Spinal sagittal alignment; Body balance; Muscle strength; Physical ability
Anterior instrumentation for the correction of scoliotic curves has recently been gaining in popularity. The problems of high mortality and morbidity that were associated with the employment of anterior instrumentation in the first years it was used have now been overcome. Efforts are now being concentrated on increasing the correction rates in the frontal plane and decreasing the kyphotic effect in the sagittal plane. The anterior Cotrel-Dubousset-Hopf (CDH) system is a recently developed instrumentation that has been claimed to decrease the kyphotic effect through the use of double rods. This study aimed to investigate the impact of the anterior CDH system on idiopathic scoliotic curves in frontal and sagittal planes. To this end, 26 idiopathic scoliosis patients treated with the CDH system were followed for a mean period of 32.8 ± 5.3 months. In the frontal plane, Cobb angles of major and secondary curves were measured, and postoperative and final correction rates determined. In the sagittal plane, sagittal contours of both the instrumented region and the thoracic and lumbar regions were measured, and their preoperative, postoperative and final control values were determined. In addition to clinical examination, lateral trunk shift (LT), shift of head (SH) and shift of stable vertebra (SS) were measured in vertebral units (VU), on the preoperative and postoperative radiographs in order to evaluate the effect of the system on trunk balance. It was established that in patients with single flexible thoracolumbar and lumbar curves and those with rigid thoracic curves, the correction rates obtained in the frontal plane were respectively 79.4 ± 14.8%, 68.0 ± 9.4% and 61.5 ± 8.0%, with statistical significance. Their final corrections at the last control were 76.3 ± 17.4%, 56.9 ± 9.1% and 52.3 ± 8.3%, respectively. Although the corrections in the lumbar rigid curves were relatively low, they were still statistically significant. Taking all the patients together, the mean preoperative Cobb angle of the major curves of 67.2°± 20.2° improved to a mean of 28.6°± 21.0°, which was a statistically significant difference (P < 0.05), giving a mean correction rate of 61.2 ± 20.3%. The mean correction loss of major curves in the frontal plane in all patients was 6.0°± 3.8° and the mean final correction rate was 52.6 ± 23.2%. In the sagittal plane, there was a favorable kyphotic effect on the thoracic region of patients with hypokyphosis and lordosis pattern, whilst in patients with kyphotic pattern, this effect was minimal. In patients with a single flexible lumbar curve, kyphotic effect was not observed except in two patients. In these two patients, it was thought that excessive compression force may have been used. As to the patients with a rigid lumbar curve, there was a slight decrease in lumbar lordosis. No postoperative complaints were made about imbalance, and the mean overall correction in LT values was 60.1 ± 21.7%. While preoperatively, the SH and SS values of all patients were over 0.5 VU, postoperatively, 12 patients (46.2%) were completely balanced (SH = 0 VU, SS = 0 VU) and 8 patients (30.8%) were balanced (0 VU < SH and SS < 0.5 VU). The remaining six patients, whose balance values were corrected with statistical significance but were still over 0.5 VU, were found to be the ones with rigid lumbar curves. Implant failure and systemic complications were not noted in the follow-up period. In view of these findings, it was determined that CDH instrumentation achieves significant correction rates in the frontal and sagittal planes, particularly in single flexible lumbar, thoracolumbar and thoracic rigid curves. It was found that the kyphotic effect was minimized with a double rod system. Significant clinical and radiological corrections were achieved in balance values, without any imbalance and decompensation problems.
Key words Idiopathic scoliosis; Anterior instrumentation; Surgical treatment; Complications
Background. The minimally invasive lateral interbody fusion (MIS LIF) in the lumbar spine can correct coronal Cobb angles, but the effect on sagittal plane correction is unclear. Methods. A retrospective review of thirty-five patients with lumbar degenerative disease who underwent MIS LIF without supplemental posterior instrumentation was undertaken to study the radiographic effect on the restoration of segmental and regional lumbar lordosis using the Cobb angles on pre- and postoperative radiographs. Mean disc height changes were also measured. Results. The mean follow-up period was 13.3 months. Fifty total levels were fused with a mean of 1.42 levels fused per patient. Mean segmental Cobb angle increased from 11.10° to 13.61° (P < 0.001) or 22.6%. L2-3 had the greatest proportional increase in segmental lordosis. Mean regional Cobb angle increased from 52.47° to 53.45° (P = 0.392). Mean disc height increased from 6.50 mm to 10.04 mm (P < 0.001) or 54.5%. Conclusions. The MIS LIF improves segmental lordosis and disc height in the lumbar spine but not regional lumbar lordosis. Anterior longitudinal ligament sectioning and/or the addition of a more lordotic implant may be necessary in cases where significant increases in regional lumbar lordosis are desired.
Anterior lumbar interbody fusion (ALIF) followed by pedicle screw fixation (PSF) is used to restore the height of the intervertebral disc and provide stability. Recently, stand-alone interbody cage with anterior fixation has been introduced, which eliminates the need for posterior surgery. We compared the biomechanics of the stand-alone interbody cage to that of the interbody cage with additional PSF in ALIF.
A three-dimensional, non-linear finite element model (FEM) of the L2-5 segment was modified to simulate ALIF in L3-4. The models were tested under the following conditions: (1) intact spine, (2) destabilized spine, (3) with the interbody cage alone (type 1), (4) with the stand-alone cage with anterior fixation (SynFix-LR®; type 2), and (5) with type 1 in addition to PSF (type 3). Range of motion (ROM) and the stiffness of the operated level, ROM of the adjacent segments, load sharing distribution, facet load, and vertebral body stress were quantified with external loading.
The implanted models had decreased ROM and increased stiffness compared to those of the destabilized spine. The type 2 had differences in ROM limitation of 8%, 10%, 4%, and 6% in flexion, extension, axial rotation, and lateral bending, respectively, compared to those of type 3. Type 2 had decreased ROM of the upper and lower adjacent segments by 3-11% and 3-6%, respectively, compared to those of type 3. The greatest reduction in facet load at the operated level was observed in type 3 (71%), followed by type 2 (31%) and type 1 (23%). An increase in facet load at the adjacent level was highest in type 3, followed by type 2 and type 1. The distribution of load sharing in type 2 (anterior:posterior, 95:5) was similar to that of the intact spine (89:11), while type 3 migrated posterior (75:25) to the normal. Type 2 reduced about 15% of the stress on the lower vertebral endplate compared to that in type 1. The stress of type 2 increased two-fold compared to the stress of type 3, especially in extension.
The stand-alone interbody cage can provide sufficient stability, reduce stress in adjacent levels, and share the loading distribution in a manner similar to an intact spine.
ALIF; Stand-alone cage; Pedicle screw fixation; Finite element analysis
This multi-center clinical study was designed to determine the long-term results of patients who received a one-level posterior lumbar interbody fusion with expandable cage (Tyche® cage) for degenerative spinal diseases during the same period in each hospital.
Fifty-seven patients with low back pain who had a one-level posterior lumbar interbody fusion using a newly designed expandable cage were enrolled in this study at five centers from June 2003 to December 2004 and followed up for 24 months. Pain improvement was checked with a Visual Analogue Scale (VAS) and their disability was evaluated with the Oswestry Disability Index. Radiographs were obtained before and after surgery. At the final follow-up, dynamic stability, quality of bone fusion, interveretebral disc height, and lumbar lordosis were assessed. In some cases, a lumbar computed tomography scan was also obtained.
The mean VAS score of back pain was improved from 6.44 points preoperatively to 0.44 at the final visit and the score of sciatica was reduced from 4.84 to 0.26. Also, the Oswestry Disability Index was improved from 32.62 points preoperatively to 18.25 at the final visit. The fusion rate was 92.5%. Intervertebral disc height, recorded as 9.94±2.69 mm before surgery was increased to 12.23±3.31 mm at postoperative 1 month and was stabilized at 11.43±2.23 mm on final visit. The segmental angle of lordosis was changed significantly from 3.54±3.70° before surgery to 6.37±3.97° by 24 months postoperative, and total lumbar lordosis was 20.37±11.30° preoperatively and 24.71±11.70° at 24 months postoperative.
There have been no special complications regarding the expandable cage during the follow-up period and the results of this study demonstrates a high fusion rate and clinical success.
Expandable cage; Degeneration; Interbody fusion; Lumbar spine
Clinical outcomes of the stand-alone cage have been encouraging when used in anterior cervical discectomy and fusion (ACDF), but concerns remain regarding its complications, especially cage subsidence. This retrospective study was undertaken to investigate the long-term radiological and clinical outcomes of the stand-alone titanium cage and to evaluate the incidence of cage subsidence in relation to the clinical outcome in the surgical treatment of degenerative cervical disc disease.
A total of 57 consecutive patients (68 levels) who underwent ACDF using a titanium box cage for the treatment of cervical radiculopathy and/or myelopathy were reviewed for the radiological and clinical outcomes. They were followed for at least 5 years. Radiographs were obtained before and after surgery, 3 months postoperatively, and at the final follow-up to determine the presence of fusion and cage subsidence. The Cobb angle of C2–C7 and the vertebral bodies adjacent to the treated disc were measured to evaluate the cervical sagittal alignment and local lordosis. The disc height was measured as well. The clinical outcomes were evaluated using the Japanese Orthopaedic Association (JOA) score for cervical myelopathy, before and after surgery, and at the final follow-up. The recovery rate of JOA score was also calculated. The Visual Analogue Scale (VAS) score of neck and radicular pain were evaluated as well. The fusion rate was 95.6% (65/68) 3 months after surgery.
Successful bone fusion was achieved in all patients at the final follow-up. Cage subsidence occurred in 13 cages (19.1%) at 3-month follow-up; however, there was no relation between fusion and cage subsidence. Cervical and local lordosis improved after surgery, with the improvement preserved at the final follow-up. The preoperative disc height of both subsidence and non-subsidence patients was similar; however, postoperative posterior disc height (PDH) of subsidence group was significantly greater than of non-subsidence group. Significant improvement of the JOA score was noted immediately after surgery and at the final follow-up. There was no significant difference of the recovery rate of JOA score between subsidence and non-subsidence groups. The recovery rate of JOA score was significantly related to the improvement of the C2–C7 Cobb angle. The VAS score regarding neck and radicular pain was significantly improved after surgery and at the final follow-up. There was no significant difference of the neck and radicular pain between both subsidence and non-subsidence groups.
The results suggest that the clinical and radiological outcomes of the stand-alone titanium box cage for the surgical treatment of one- or two-level degenerative cervical disc disease are satisfactory. Cage subsidence does not exert significant impact upon the long-term clinical outcome although it is common for the stand-alone cages. The cervical lordosis may be more important for the long-term clinical outcome than cage subsidence
Anterior cervical discectomy and fusion; Stand-alone cage; Cervical spine; Complication; Subsidence; Cervical alignment
A prospective analysis of the sagittal profile of 100 healthy young adult volunteers was carried out in order to evaluate the relationship between the shape of the pelvis and lumbar lordosis and to create a databank of the morphologic and positional parameters of the pelvis and spine in a normal healthy population. Inclusion criteria were as follows: no previous spinal surgery, no low back pain, no lower limb length inequality, no scoliotic deviation. For each subject, a 30×90-cm sagittal radiograph including spine, pelvis and proximal femurs in standing position on a force plate was performed. The global axis of gravity was determined with the force plate. Each radiograph was digitized using dedicated software. The spinal parameters registered were values for thoracic kyphosis and lumbar lordosis. The pelvic angles measured were: pelvic incidence, sacral slope and pelvic tilt. The global axis of gravity was on average 9 mm anterior of the center of the femoral heads. The anatomic parameter of pelvic incidence angle varied from 33° to 85° (mean: 51.7°, SD: 11°). The average lumbar lordosis was 46.5°. The average thoracic kyphosis was 47°. We found a statistical correlation between incidence angle and lumbar lordosis (r=0.69, P<0.001) and between sacral slope angle and lumbar lordosis (r=0.75, P<0.001). Spine and pelvis balance around the hip axis in order to position the gravity line over the femoral heads. We propose a scheme of sagittal balance of the standing human body.
Sagittal balance Gravity axis Pelvic incidence angle Lordosis Kyphosis
Prospective study. To study the validity of Hybrid construction (Anterior Lumbar Interbody Fusion) ALIF at one level and total disc arthroplasty (TDA) at adjacent, for two levels disc disease in lumbar spine as surgical strategy. With growing evidence that fusion constructs in the treatment of degenerative disc disease (DDD) may alter sagittal balance and contribute to undesirable complications in the long-term, total disc arthroplasty (TDA) slowly becomes an accepted treatment option for a selected group of patients. Despite encouraging early and intermediate term results of single-level total disc arthroplasty reported in the literature, there is growing evidence that two-level arthroplasty does not fare as well. Hybrid fusion is an attempt to address two-level DDD by combining the advantages of a single-level ALIF with those of a single-level arthroplasty. 42 patients (25 females and 17 males) underwent Hybrid fusion and had a median follow-up of 26.3 months. The primary functional outcomes were assessed before and after surgery with Oswestry Disability Index and the visual analogue score of the back and legs. Patients were divided into four groups according to the percentage improvement between preop and postop ODI scores. A total of 42 patients underwent a hybrid fusion as follows: 35 L5-S1 ALIF/L4-5 prosthesis, 3 L4-5 ALIF/L3-4 prosthesis, 2 L5-S1 ALIF/L4-5 prosthesis/L3-4 prosthesis, 1 L5-S1 prosthesis/L4-5 ALIF, and 1 L5-S1 ALIF/L4-5 ALIF/L3-4 prosthesis. At 2-years clinical outcomes, mean reduction in ODI is 24.9 points (53.0% improvement compared to preop ODI). The visual analogue score for the back is 64.6% improvement. At 2-year clinical outcomes, Hybrid fusion is a viable surgical alternative for the treatment of two-level DDD in comparison with two-level TDA and with two-level fusion.
Total disc arthroplasty; Anterior lumbar interbody fusion; Lumbar spine; Degenerative disc disease; Hybrid construct; Lumbar fusion
Sagittal balance of the spine is becoming an important issue in the assessment of the degree of spinal deformity. On a standing lateral full-length radiograph of the spine, the plumb line, or sagittal vertical axis (SVA), can be used to determine the spinal sagittal balance. In this procedure patients have to adopt a habitual standing position with the knees extended during radiographic examination, though it is not known whether small changes in the position of the lower extremities affects the location of the SVA. The purpose of the present study was to investigate the effect of postural change on shifts of the SVA, and to evaluate whether the SVA as measured on a standing full-length lateral radiograph can be used as an accurate measurement of spinal balance in clinical practice. Sagittal balance was analyzed using a patient with ankylosis of the entire spine due to ankylosing spondylitis, to eliminate segmental movement of the spine. A virtual SVA was constructed for seven different standing postures by cross-referring the coordinate systems from a standing full-length lateral radiograph of the spine with video analysis. The horizontal distance between the SVA and the anterior superior corner of the sacrum was measured for each posture. Small changes in the joint angles of the lower extremities affected the SVA significantly, and resulted in the horizontal distance between the SVA and the anterior superior corner of the sacrum varying from –4.5 to +14.9 cm. High correlations were found between this distance and the joint angle of the hip (r = –0.959), knee (r = –0.936), and ankle (r = 0.755) (P < 0.01). The results of the study showed that SVA translations during standing radiographic analysis in a patient with a fixed spine depend on small changes in the hip, knee, and ankle joints. Thus, sagittal spinal (im)balance in ankylosing spondylitis can not be measured from the SVA on a standing lateral full-length radiograph of the spine unless strict procedures are developed to control for the angle of the hip, knee, and ankle joints. The accuracy of the SVA as a measurement of sagittal spinal balance in other spinal deformities, with possible additional segmental movements, therefore remains questionable.
Key words Sagittal balance; Sagittal vertical axis; Spinal; deformities; Model; Human posture
Previous studies report an increase in thoracic kyphosis after anterior approaches and a flattening of sagittal contours following posterior approaches. Difficulties with measuring sagittal parameters on radiographs are avoided with reformatted sagittal CT reconstructions due to the superior endplate clarity afforded by this imaging modality.
A prospective study of 30 Lenke 1 adolescent idiopathic scoliosis (AIS) patients receiving selective thoracoscopic anterior spinal fusion (TASF) was performed. Participants had ethically approved low dose CT scans at minimum 24 months after surgery in addition to their standard care following surgery. The change in sagittal contours on supine CT was compared to standing radiographic measurements of the same patients and with previous studies. Inter-observer variability was assessed as well as whether hypokyphotic and normokyphotic patient groups responded differently to the thoracoscopic anterior approach.
Mean T5-12 kyphosis Cobb angle increased by 11.8 degrees and lumbar lordosis increased by 5.9 degrees on standing radiographs two years after surgery. By comparison, CT measurements of kyphosis and lordosis increased by 12.3 degrees and 7.0 degrees respectively. 95% confidence intervals for inter-observer variability of sagittal contour measurements on supine CT ranged between 5-8 degrees. TASF had a slightly greater corrective effect on patients who were hypokyphotic before surgery compared with those who were normokyphotic.
Restoration of sagittal profile is an important goal of scoliosis surgery, but reliable measurement with radiographs suffers from poor endplate clarity. TASF significantly improves thoracic kyphosis and lumbar lordosis while preserving proximal and distal junctional alignment in thoracic AIS patients. Supine CT allows greater endplate clarity for sagittal Cobb measurements and linear relationships were found between supine CT and standing radiographic measurements. In this study, improvements in sagittal kyphosis and lordosis following surgery were in agreement with prior anterior surgery studies, and add to the current evidence suggesting that anterior correction is more capable than posterior approaches of addressing the sagittal component of both the instrumented and adjacent non instrumented segments following surgical correction of progressive Lenke 1 idiopathic scoliosis.
Thoracoscopic anterior spinal fusion; Anterior spinal fusion; Adolescent idiopathic scoliosis; Sagittal profile; Computed tomography (CT); Thoracic kyphosis; Lumbar lordosis
Fusion of cervical spine in kyphotic alignment has been proven to produce an acceleration of degenerative changes at adjacent levels. Stand-alone cages are reported to have a relatively high incidence of implant subsidence with secondary kyphotic deformity. This malalignment may theoretically lead to adjacent segment disease in the long term. The prospective study analysed possible risk factors leading to cage subsidence with resulting sagittal malalignment of cervical spine. Radiographic data of 100 consecutive patients with compressive radiculo-/myelopathy due to degenerative disc prolapse or osteophyte formation were prospectively collected in those who were treated by anterior cervical discectomy and implantation of single type interbody fusion cage. One hundred and forty four implants were inserted altogether at one or two levels as stand-alone cervical spacers without any bone graft or graft substitute. All patients underwent standard anterior cervical discectomy and the interbody implants were placed under fluoroscopy guidance. Plain radiographs were obtained on postoperative days one and three to verify position of the implant. Clinical and radiographic follow-up data were obtained at 6 weeks, 3 and 6 months and than annually in outpatient clinic. Radiographs were evaluated with respect to existing subsidence of implants. Subsidence was defined as more than 2 mm reduction in segmental height due to implant migration into the adjacent end-plates. Groups of subsided and non-subsided implants were statistically compared with respect to spacer distance to the anterior rim of vertebral body, spacer versus end-plate surface ratio, amount of bone removed from adjacent vertebral bodies during decompression and pre- versus immediate postoperative intervertebral space height ratio. There were 18 (18%) patients with 19 (13.2%) subsided cages in total. No patients experienced any symptoms. At 2 years, there was no radiographic evidence of accelerated adjacent segment degeneration. All cases of subsidence occurred at the anterior portion of the implant: 17 cases into the inferior vertebra, 1 into the superior and 1 into both vertebral bodies. In most cases, the process of implant settling started during the perioperative period and its progression did not exceed three postoperative months. There was an 8.7° average loss of segmental lordosis (measured by Cobb angle). Average distance of subsided intervertebral implants from anterior vertebral rim was found to be 2.59 mm, while that of non-subsided was only 0.82 mm (P < 0.001). Spacer versus end-plate surface ratio was significantly smaller in subsided implants (P < 0.001). Ratio of pre- and immediate postoperative height of the intervertebral space did not show significant difference between the two groups (i.e. subsided cages were not in overdistracted segments). Similarly, comparison of pre- and postoperative amount of bone mass in both adjacent vertebral bodies did not show a significant difference. Appropriate implant selection and placement appear to be the key factors influencing cage subsidence and secondary kyphotisation of box-shaped, stand-alone cages in anterior cervical discectomy and fusion. Mechanical support of the implant by cortical bone of the anterior osteophyte and maximal cage to end-plate surface ratio seem to be crucial in the prevention of postoperative loss of lordosis. Our results were not able to reflect the importance of end-plate integrity maintenance; the authors would, however, caution against mechanical end-plate damage. Intraoperative overdistraction was not shown to be a significant risk factor in this study. The significance of implant subsidence in acceleration of degenerative changes in adjacent segments remains to be evaluated during a longer follow-up.
Cervical vertebrae surgery; Spinal fusion; Equipment failure analysis; Postoperative complications; Subsidence
From July 2004 to June 2005, 19 patients with 25 discs underwent anterior cervical discectomy and interbody fusion (ACDF) in which polyetheretherketone (PEEK) cages were filled with freeze-dried cancellous allograft bone. This kind of bone graft was made from femoral condyle that was harvested during total knee arthroplasty. Patient age at surgery was 52.9 (28–68) years. All patients were followed up at least 1 year. We measured the height of the disc and segmental sagittal angulation by pre-operative and post-operative radiographs. CT scan of the cervical spine at 1 year was used to evaluate fusion rates. Odom's criteria were used to assess the clinical outcome. All interbody disc spaces achieved successful union at 1-year follow-up. The use of a PEEK cage was found to increase the height of the disc immediately after surgery (5.0 mm pre-operatively, 7.3 mm immediately post-operatively). The final disc height was 6.2 mm, and the collapse of the disc height was 1.1 mm. The segmental lordosis also increased after surgery (2.0° pre-operatively, 6.6° immediately post-operatively), but the mean loss of lordosis correction was 3.3° at final follow-up. Seventy-four percent of patients (14/19) exhibited excellent/good clinical outcomes. Analysis of the results indicated the cancellous allograft bone-filled PEEK cage used in ACDF is a good choice for patients with cervical disc disease, and avoids the complications of harvesting iliac autograft.
This retrospective study was performed to evaluate the clinical and radiological results of anterior lumbar interbody fusion (ALIF) using two different stand-alone cages in the treatment of lumbar intervertebral foraminal stenosis (IFS).
A total of 28 patients who underwent ALIF at L5-S1 using stand-alone cage were studied [Stabilis® (Stryker, Kalamazoo, MI, USA); 13, SynFix-LR® (Synthes Bettlach, Switzerland); 15]. Mean follow-up period was 27.3 ± 4.9 months. Visual analogue pain scale (VAS) and Oswestry disability index (ODI) were assessed. Radiologically, the change of disc height, intervertebral foraminal (IVF) height and width at the operated segment were measured, and fusion status was defined.
Final mean VAS (back and leg) and ODI scores were significantly decreased from preoperative values (5.6 ± 2.3 → 2.3 ± 2.2, 6.3 ± 3.2 → 1.6 ± 1.6, and 53.7 ± 18.6 → 28.3 ± 13.1, respectively), which were not different between the two devices groups. In Stabilis® group, postoperative immediately increased disc and IVF heights (10.09 ± 4.15 mm → 14.99 ± 1.73 mm, 13.00 ± 2.44 mm → 16.28 ± 2.23 mm, respectively) were gradually decreased, and finally returned to preoperative value (11.29 ± 1.67 mm, 13.59 ± 2.01 mm, respectively). In SynFix-LR® group, immediately increased disc and IVF heights (9.60 ± 2.82 mm → 15.61 ± 0.62 mm, 14.01 ± 2.53 mm → 21.27 ± 1.93 mm, respectively) were maintained until the last follow up (13.72 ± 1.21 mm, 17.87 ± 2.02 mm, respectively). The changes of IVF width of each group was minimal pre- and postoperatively. Solid arthrodesis was observed in 11 patients in Stabilis group (11/13, 84.6%) and 13 in SynFix-LR® group (13/15, 86.7%).
ALIF using stand-alone cage could assure good clinical results in the treatment of symptomatic lumbar IFS in the mid-term follow up. A degree of subsidence at the operated segment was different depending on the device type, which was higher in Stabilis® group.
Anterior approach; Lumbar interbody fusion; Lumbar foraminal stenosis; Stand-alone cage
We sought to determine minimum 4 years of clinical outcomes including fusion rate, revision rate and complications of patients who underwent placement of rectangular stand-alone cages.
Thirty-three cases of degenerative spine that had been followed for at least 4-years were reviewed retrospectively. Cages were inserted at L4-L5 level or L5-S1 in 27 or in 6 cases respectively. Visual analogue scale (VAS), Odom's criteria, fusion rate, intervertebral disc height and lumbar lordosis were determined pre- and post-operatively on standing x-rays. Amount of intra- and postoperative blood loss, total volume transfused, duration of surgery and perioperative complications were also evaluated.
The mean VAS score of back pain and sciatica were improved from 8.0 and 7.0 points to 3.4 and 2.4 during 1 years follow-up visit and the scores was raised gradually. Also, during the follow-up, 94% of patients showed excellent or good outcomes by the Odom's criteria. Intervertebral disc height was increased from 8.2±1.4mm to 9.2±1.9mm at the first year of follow-up, however, found to be decreased and stabilized to 8.3±1.8mm after 2 years. The fusion rate was approximately 91% after 4 year postoperative. The segmental angle of lordosis was increased significantly by two years but it was not maintained after four years. A statistically insignificant change in total lumbar lordosis was also observed. Three patients (9%) had experienced perioperative complications.
The use of rectangular stand-alone cages for posterior lumbar interbody fusion (PLIF) resulted in a various degree of subsidence and demonstrate very low complication rate, high functional stability and improved clinical outcomes in patients with degenerative lumbar disc disease.
Posterior lumbar interbody fusion; Stand-alone cage; Rectangular cage
Aim To compare anterior fusion in standalone anterior lumbar interbody fusion (ALIF) using cage and screw constructs and anterior cage–alone constructs with posterior pedicle screw supplementation but without posterior fusion.
Methods Eighty-five patients underwent single- or two-level ALIF procedure for degenerative disk disease or lytic spondylolisthesis (SPL). Posterior instrumentation was performed without posterior fusion in all cases of lytic SPL and when the anterior cage used did not have anterior screw through cage fixation.
Results Seventy (82%) patients had adequate radiological follow-up at a mean of 19 months. Forty patients had anterior surgery alone (24 single level and 16 two levels) and 30 had front-back surgery (15 single level and 15 two levels). Anterior locked pseudarthrosis was only seen in the anterior surgery–alone group when using the STALIF cage (Surgicraft, Worcestershire, UK) (37 patients). This occurred in five of the single-level surgeries (5/22) and nine of the two-level surgeries (9/15). Fusion was achieved in 100% of the front-back group and only 65% (26/40) of the anterior surgery–alone group.
Conclusion Posterior pedicle screw supplementation without posterolateral fusion improves the fusion rate of ALIF when using anterior cage and screw constructs. We would recommend supplementary posterior fixation especially in cases where more than one level is being operated.
anterior lumbar interbody fusion; ALIF; locked pseudarthrosis; spondylolisthesis