Mechanical failure of spine posterior fixation in the lumbar region Is suspected to occur more frequently when the sagittal balance is not properly restored. While failures at the proximal extremity have been studied in the literature, the lumbar distal junctional pathology has received less attention. The aim of this work was to investigate if the spinopelvic parameters, which characterize the sagittal balance, could predict the mechanical failure of the posterior fixation in the distal lumbar region. All the spine surgeries performed in 2017-2019 at Rizzoli Institute were retrospectively analysed to extract all cases of lumbar distal junctional pathology. All the revision surgeries performed due to the pedicle screws pull-out, or the breakage of rods or screws, or the vertebral fracture, or the degenerative disc disease, in the distal extremity, were included in the junctional (JUNCT) group. A total of 83 cases were identified as JUNCT group. All the 241 fixation surgeries which to date have not failed were included in the control (CONTROL) group. Clinical data were extracted from both groups, and the main spinopelvic parameters were assessed from sagittal standing preoperative (pre-op) and postoperative (post-op) radiographs with the software Surgimap (Nemaris). In particular, pelvic incidence (PI), sagittal vertical axis (SVA), pelvic tilt (PT), T1 pelvic angle (TPA), sacral slope (SS) and lumbar lordosis (LL) have been measured. In JUNCT, the main failure cause was the screws pull-out (45%). Spine fixation with 7 or more levels were the most common in JUNCT (52%) in contrast to CONTROL (14%). In CONTROL, PT, TPA, SS and PI-LL were inside the recommended ranges of good sagittal balance. For these parameters, statistically significant differences were observed between pre-op and post-op (p<0.0001, p=0.01, p<0.0001, p=0.004, respectively, Wilcoxon test). In JUNCT, the spinopelvic parameters were out of the ranges of the good sagittal balance and the worsening of the balance was confirmed by the increase in PT, TPA, SVA, PI-LL and by the decrease of LL (p=0.002, p=0.003, p<0.0001, p=0.001, p=0.001, respectively, paired t-test) before the revision surgery. TPA (p=0.003, Kolmogorov-Smirnov test) and SS (p=0.03, unpaired t-test) differed significantly in pre-op between JUNCT and CONTROL. In post-op, PI-LL was significantly different between JUNCT and CONTROL (p=0.04, unpaired t-test). The regression model of PT vs PI was significantly different between JUNCT and CONTROL in pre-op (p=0.01, Z-test). These results showed that failure is most common in long fused segments, likely due to long lever arms leading to implant failure. If the sagittal balance is not properly restored, after the surgery the balance is expected to worsen, eventually leading to failure: this effect was confirmed by the worsening of all the spinopelvic parameters before the revision surgery in JUNCT. Conversely, a good sagittal balance seems to avoid a revision surgery, as it is visible is CONTROL. The mismatch PI-LL after the fixation seems to confirm a good sagittal balance and predict a good correction. The linear regression of PT vs PI suggests that the spine deformity and pelvic conformation could be a predictor for the failure after a fixation

Study Design: Retrospective chart review. Summary of Background Data: Spinal osteotomy in ankylosing spondylitis is performed to restore forward gaze and sagittal balance. Closing wedge lumbar osteotomy and polysegmental thoracic osteotomy in the same patient has not been reported. Objective: To study the factors affecting correction of sagittal balance. Subjects: 27 patients (23 male, 4 female) operated between 1989–2002: average age 46 years: minimum follow-up: 18 months. 19 patients had lumbar osteotomy alone, 6 had both lumbar and thoracic osteotomies and 2 had thoracic osteotomy alone. Three groups were identified: A) patients with decreased lumbar-lordosis and normal thoracic-kyphosis B) Normal / increased lumbar-lordosis and increased thoracic-kyphosis C) Decreased lumbar-lordosis and increased thoracic-kyphosis. Results: Preoperatively, mean sagittal balance was +103 mm, thoracic-kyphosis 61 degrees, and lumbar-lordosis 25 degrees. Three months postoperatively, sagittal balance was +36 mm, thoracic-kyphosis 55 degrees, and lumbar-lordosis 49 degrees. At final follow-up sagittal balance was +44 mm, thoracic-kyphosis 57 degrees and lumbar-lordosis 46 degrees. In patients who had thoracic osteotomies, thoracic-kyphosis of 78 degrees was corrected to 48 degrees. There were no spinal cord injuries or permanent nerve root palsies. Six patients had deterioration of sagittal balance (SB) (> 45 mm), 5 of them required cervical osteotomy. There was significant association between post-operative thoracic-kyphosis of > 60 degrees and SB deterioration (p-value < .001, sensitivity 100%, specificity 75%). Statistically there was no significant association between SB deterioration and post-operative sagittal balance, lumbar-lordosis, osteotomy-angle and extent of fixation. Conclusions: Correction of thoracic-kyphosis affected final sagittal balance significantly. Consideration should be given to the simultaneous performance of lumbar osteotomy and polysegmental thoracic osteotomies in selected patients to obtain greater correction and restoration of near normal sagittal balance

Objectives. The objective of this study was to assess the association between whole body sagittal balance and risk of falls in elderly patients who have sought treatment for back pain. Balanced spinal sagittal alignment is known to be important for the prevention of falls. However, spinal sagittal imbalance can be markedly compensated by the lower extremities, and whole body sagittal balance including the lower extremities should be assessed to evaluate actual imbalances related to falls. Methods. Patients over 70 years old who visited an outpatient clinic for back pain treatment and underwent a standing whole-body radiograph were enrolled. Falls were prospectively assessed for 12 months using a monthly fall diary, and patients were divided into fallers and non-fallers according to the history of falls. Radiological parameters from whole-body radiographs and clinical data were compared between the two groups. Results. A total of 144 patients (120 female patients and 24 male patients) completed a 12-month follow-up for assessing falls. A total of 31 patients (21.5%) reported at least one fall within the 12-month follow-up. In univariate logistic regression analysis, the risk of falls was significantly increased in older patients and those with more medical comorbidities, decreased lumbar lordosis, increased sagittal vertical axis, and increased horizontal distance between the C7 plumb line and the centre of the ankle (C7A). Increased C7A was significantly associated with increased risk of falls even after multivariate adjustment. Conclusion. Whole body sagittal balance, measured by the horizontal distance between the C7 plumb line and the centre of the ankle, was significantly associated with risk of falls among elderly patients with back pain. Cite this article: J. Kim, J. Y. Hwang, J. K. Oh, M. S. Park, S. W. Kim, H. Chang, T-H. Kim. The association between whole body sagittal balance and risk of falls among elderly patients seeking treatment for back pain. Bone Joint Res 2017;6:–344. DOI: 10.1302/2046-3758.65.BJR-2016-0271.R2

Introduction: Total lumbar disc replacement (TLDR) is a motion-preserving alternative to lumbar spinal fusion for degenerative disc disease. Although in vitro cadaveric studies have provided invaluable information in preserving motion and possibly prevent abnormal loading at the adjacent level for TLDR, there is still lack evidence of in vivo consequences for sagittal balance and movement. Purpose: Aim of our prospective non-randomized clinical study was to analyze the consequences for segmental and sagittal balance and movement of TLDR. Materials and Methods: From October 2001 trough December 2006, 1-year minimum follow-up, 78 TLDR were implanted in 57 patients. 31 (54.4%) were female, 26 (45.6%) male. Mean age at surgery was 41.77±7.46 ys (30–57). 36 (63.2%) had single level TLDR, 15 (26.4%) 2-level, 3 (5.2%) 3-level, and 3 (5.2%) hybrid constructs. Replaced discs were L3–L4 in 5 (6.4%) cases, L4–L5 in 32 (41%), and L5-S1 in 41 (52.6%). AP, lateral, and flexion-extension periodical lumbar X-rays allowed to measure segmental lordosis, lumbar lordosis, segmental motion, and lumbar motion pre-, post-op, and at follow-ups. Analyses were performed using 9.2 STATA statistical software, and 12.0 SPSS version. Differences were assessed using t or Mann-Whitney tests. Samples of 3-level and hybrid constructs were too small for comparative analysis. Results: Mean follow-up was 35.02±17.58 ms. Lumbar lordosis passed from 43.87°±11.82° pre-op to 46.42°±10.83° post-op (P=0.062379), and 47.98°±11.97° at last follow-up (P=0.008544). L3–L4 segmental lordosis passed from 6.90°±3.51° pre-op to 10.85°±5.22° post-op (P=0.026971), and 11.80°±2.59° at last f-u (P=0.064873). L4–L5 segmental lordosis passed from 9.86°±5.06° pre-op to 13.83°±6.21° post-op (P=0.000611), and 13.21°±6.11° at last f-u (P=0.000631). L5-S1 segmental lordosis passed from 17.02°±5.32° pre-op to 22.46°±6.27° post-op (P=0.000001), and 23.03±6.81° at last follow-up (P= P=0.000000). Concerning movement, there was no differences between pre- and post-op L3–L4 (P=0.656045), L4–L5 (P=0.458793), or L5-S1 (P=0.157879) ROM. Even lumbar motion had no difference between pre- and post-op. There was no differences between single and double level replacement about lumbar and segmental lordosis, and about lumbar and segmental ROM. Conclusion: In vivo implanted TLDR affected sagittal balance, increasing segmental and lumbar lordosis. TLDR avoid spinal fusion maintaining normal motion, both segmental and lumbar. Single and double level disc arthroplasty have similar effects

Objective. To determine if there is a differing effect between two spinal implant systems on sagittal balance and thoracic kyphosis in adolescent idiopathic scoliosis. Methods. Retrospective analysis of pre and post-operative radiographs to assess sagittal balance, C7-L1 kyphosis angles and metal implant density. Group 1 (Top loading system): 11 patients (9 females, 2 males) Single surgeon NB. Group 2 (Side loading system): 17 patients (16 females, 1 male) Single surgeon ED. Total 28 patients. All single right sided thoracic curves. Comparison of pre and postoperative sagittal balance and C7-L1 kyphosis angle for each spinal system. Assessment of implant density (i.e. proportion of pedicle screw relative to number of spinal levels involved in correction). Results. 16 patients demonstrated improved sagittal balance following surgery. There was no significant difference between the pre and post op C7-L1 kyphosis angle in either group (p value 0.06 and 0.83 respectively) although a greater discrepancy was noted in Group 1. In group 1, the mean angle pre op was 33.1 (95% CI 27.3 to 38.9) and post op was 26.2 (95% CI 22.5 to 29.9). In Group 2, the mean angle pre op was 28.9 (95% CI 20.3 to 37.5) and post op was 29.6 (95% CI 22.2 to 37.0). No correlation identified between sagittal balance correction and kyphosis angle. Metal density ranged from 60-100%. Conclusions. Although the numbers in this series are modest they do suggest that high density metal implants do not lead to a flatback deformity in the sagittal plane. There is no significant difference in the pre and post op kyphosis angles for either implant system used in this study although the results for Group 1 do approach statistical significance. Larger prospective multicentre studies are required to quantify the true significance of these results. Ethics Approval: Audit/Service Standard in Trust

This study is a retrospective monocentric analysis of changes in spinopelvic sagittal alignment after in situ fusion of L5-S1 spondylolisthesis. In situ fusion is a safety procedure with good functionnal outcome, but the consequences on the spinopelvic sagittal balance remains unclear. The aim is to evaluate the adaptative changes in the sagittal balance after such treatment. This is an analysis of 22 patients (mean age 13,5 years) with an average follow-up of 5,2 years (range 1–11 years). This study includes 6 grade II spondylolisthesis, 7 grade III and 9 grade IV. 13 patients were operated with a non instrumented posterolateral arthrodesis and 9 with a circumferential in situ fusion. Among the 13 grade II and III spondylolisthesis, 12 had a posterolateral arthrodesis and only 1 had a circumferential fusion. As for the grade IV spondylolisthesis 8 out of 9 had a circumferential arthrodesis and only 1 had a posterolateral fusion. Before and after surgery, all patients had lateral standing radiographs of the spine and pelvis. Different parameters were evaluated before surgery: pelvic incidence, sacral slope, pelvic tilt, lumbar lordosis, thoracic kyphosis, T9 sagittal tilt, L5 incidence, L5 slope and L5 tilt. After surgery, the pelvic parameters were not evaluated because of the difficulty to visualise the upper part of S1 after arthrodesis. The discs were evaluated by MRI. The functionnal outcome was evaluated with the Oswestry score. A global evaluation including all the patients doesn’t show any influence of the surgery on the sagittal alignment. But when evaluating the datas after classifying the patients in function of the severity of the spondylolisthesis, some differences raise. On one side, the patients with grade II and III spondylolisthesis keep a normal T9 sagittal tilt while slightly increasing lumbar lordosis and thoracic kyphosis. On the other side, the patients with grade IV spondylolisthesis operated with a circumferential in situ fusion worsen the T9 sagittal tilt, increase the L5 incidence, decrease their lombar lordosis (L4/L5 discal kyphosis) and thoracic kyphosis. To conclude, we can say that patients with grade II and III spondylolisthesis have good functionnal outcome and keep a balanced spine. Patients with grade IV have a good clinical outcome as well but keep worsening their sagittal balance despite the circumferential in situ fusion. An unbalanced sagittal alignment might theorically compromise the long term clinical results, but the radiological outcome doesn’t seem to be linked to the functionnal outcome. A long term follow-up has to be done in order to evaluate the outcome of these unbalanced spines and compare it to the functionnal and radiological results obtained with reduced high grade spondylolisthesis

Introduction Sagittal balance is a combination of a balance function (T1 maintained vertically over S1) that partially constrains the spine, the passive constraints provided by soft tissues and the active constraints – muscle force and gravity. Normal standing posture is likely to be the posture of minimum muscle activity and soft tissue energy. Observed deviation from this position would require muscle action. A mathematical model describing spinal balance without muscle activity is described. Methods The spine was modeled as a series of articulations between the hip and T1 that were controlled by a third degree polynomial ‘spring’ function that approximates the force displacement curves as measured by Panjabi et al. T1 was constrained to remain over S1. Geometric data imported from the erect radiograph of a 34 female without back pain was used to set the zero point for the stiffness functions. All spring functions except the hip function were identical. The system was then perturbed by changing the rest disc space (or hip) angles. An initial smoothing function was used to ‘distribute’ this perturbation amongst several adjacent vertebrae as a guess. The model then minimized the total soft tissue energy to find the new position by treating the system as a series of damped rotational spring – mass constructs. Minimization was achieved using Euler’s method to solve a system of second order nonlinear ordinary differential equations. The iterations were run until oscillations ceased. The model was then perturbed by creating a series of kyphotic deformities at multiple levels and the results were observed. Results Most perturbations converged to a minimum solution almost instantly. With the hip fixed, it was found that kyphotic deformities in the lower and mid lumbar spine led to compensatory lordosis at most other levels – particularly at the apex of the thoracic kyphosis. The spine tended to straighten and lengthen (possibly causing a rise in the centre of mass of the body). This tendency was substantially mitigated by allowing the hip joint to move. By trial and error, a spring function with of one tenth of the stiffness allowed the centre of gravity to move minimally and the compensatory lordosis occurred at segments closer to the induced kyphosis. When an apical thoracic kyphosis was applied with a fixed hip, the spine shortened with compensation being mostly by lordosis in the upper lumbar spine. When the hip was allowed to flex the tendency was for some of the compensation to occur at hip and for the spine to shorten further. The compensatory lordosis that developed at the level above an induced lumbar kyphosis could be partially corrected by applying a flexion moment. However as there is no muscle that is capable of applying such a moment over a single segment an alternative approach suggested that the hyperlordosis could be reduced by applying an extension moment to multiple segments above the hyperlordotic level. Discussion Sagittal Spinal balance is complex. A minimum energy stiffness model may lead to further understanding of spinal balance. The prototype model suggests that the hip joint may have a role in preventing excessive lengthening (with a rise in the centre of gravity) of the spine. The model predicts extensor muscle contraction more than one level above a lumbar kyphosis

Purpose: Single-segment wedge osteotomy is classically proposed to correct for kyphosis subsequent to ankylosing spondylitits. We analysed the usefulness of this technique for other indications (revision procedures for flat back and deformed calluses of the lumbar spine) by studying the overall sagittal balance of the spine and tilt of the sacrum. Material and methods: Between 1980 and 1999, we retained 68 patients with complet clinical and radiological data (37 patients with ankylosing spondylitis and 31 patients with “post-operative” flat back, including nine trauma cases and 22 degenerative spines). Opening osteotomy was performed in the first 19 patients and closure osteotomy in the next 49. The correction level was L2L3 in 26 patients and lower in 42. Digitalised lateral views of the entire spine were obtained at minimum follow-up of three years to measure:. - posterior displacement of T9 (between the vertical line and a line joining the geometric centre of T9 and the femoral heads (normal 11±5°),. - tilt of the sacrum (angle between the horizontal line and a line tangent to the superior surface of the sacrum (normal 41±5°). Results and discussion: The overall angle of local correction was 44° and the correction of T9 displacement was 30.6°. For the low osteotomies, the local correction was 49° and the T9 displacement was +28° (−2° to +26°). Tilt of the sacrum varied from 4° to 7°. Tilt of the sacrum was influenced more and more for lower and lower osteotomies. T9 displacement stabilised between 12° and 26° (mean 19°) irrespective of the osteotomy level, although the angle of local correction was greater (up to 60°). This discordance was explained by adaptation of the pelvis. Seven patients developed secondary functional kyphosis (limited hip movement preventing the necessary adaptation to the overall correction of the sagittal balance). Conclusion: Single-segment spinal osteotomy remains difficult but offers very important correction possibilities affecting the position of the trunk and adaptation of the pelvis. The level for the correction must be chosen with care because it conditions final adjustment and function consequences affecting the pelvis

Introduction: Surgical treatment is indicated in Scheuermann’s disease with severe kyphotic deformity, and/or unremitting pain. Proximal or distal junctional kyphosis and loss of correction have been reported in the literature, due to short fusion level, overcorrection, or posterior only surgery with failure to release anterior tethering. We reviewed surgically treated Scheuermann’s kyphosis cases, to evaluate the factors affecting the sagittal balance. Methods and results: 35 cases (22 male, 13 female) of Scheuermann’s kyphosis were treated surgically in this centre during 1993–1999. Mean age at operation was 21.5 years (14–53 years). The kyphosis was high thoracic (Gennari Type I) in two cases, mid thoracic (Type II) in 11 cases, low thoracic or thoraco-lumbar (Type III) in eight cases, and whole thoracic (Type IV) in 14 cases. Mean pre-operative kyphosis (Cobb angle) was 81° (range 70° to 110°). Ten cases (mean kyphosis 77°) had one stage posterior operation only with segmental instrumentation. Twenty-five cases had combined anterior and posterior (A-P) surgery. Fifteen cases (mean kyphosis 81°) had one stage thoracoscopic release and posterior instrumentation, and 10 cases (mean kyphosis 89°) had open anterior release, followed by second stage posterior instrumentation. Minimum follow-up was 14 months (mean 45 months, range 14–140 months). The mean post-operative kyphosis was 47.2°. Kyphosis correction achieved ranged from 39% after posterior surgery only, to 42% after thoracoscopic A-P surgery, and 48% after open A-P surgery. Mean loss of correction was 12° after posterior only surgery, 9.5° after thoracoscopic A-P surgery, and 6° after open A-P surgery. Four cases of open A-P surgery had additional anterior cages to stabilise the kyphosis before posterior instrumentation; a mean 55% kyphosis correction was achieved in this group, and there was no loss of correction. Younger cases, under 25 years (n=16) had significantly better kyphosis correction (p< 0.05). Two cases (6%) developed distal junctional kyphosis due to fusion short of the first lordotic segment, requiring extension of fusion. Four cases (12%) developed proximal junctional kyphosis requiring extension of fusion; all of them had primary posterior surgery only. Location of the curve (Gennari Type) had no significant influence on the initial curve, degree of immediate correction, or loss of correction. Complications included infection (4 cases), pneumothorax (1 case), haemothorax (1 case), instrumentation failure (3 cases); 3 cases had persistent back pain. Conclusion: Combined anterior release and posterior surgery achieves and maintains better correction of Scheuermann’s kyphosis. Loss of correction, and proximal junctional kyphosis are more frequent after posterior surgery only, and short fusion. Use of cages anteriorly prevents loss of correction. Correction is better achieved in younger patients, but is not influenced by the location of the curve

Purpose. compare the radiological results in sagittal balance correction obtained with pedicle subtraction osteotomy (PSO) versus anterior-posterior osteotomy (APO) by double approach in adults. Material and Methods. between January of 2001 and July of 2009, fifty-eight vertebral osteotomies were carried out in fifty-six patients: 9 Smith-Petersen osteotomy (SPO), one vertebral resection osteotomy (VRO), 30 anterior-posterior osteotomies (APO) and 18 pedicle subtraction osteotomies (PSO), being the lasts two groups the sample studied (48 osteotomies). The mean age of the patients was 56.3 years (17–72). Initial diagnose was: 28 posttraumathic kyphosis, 7 postsurgical kyphosis, 7 adult degenerative disease, 4 ankylosing spondylitis and 2 congenital kyphoscoliosis. We evaluated the preoperative standing radiographs, the postoperative and at final follow-up by digital measurements with iPACS system viewer (© Real Time Image, USA, 2001). The mean follow-up was 54 months (6–98), and complications were analized. Results. The group APO had a mean preoperative thoracic kyphosis of 67 °, a mean lumbar lordosis of −42° and a mean sagital balance of 8.6°. The group PSO had a mean preoperative thoracic kyphosis of 41°, a mean lumbar lordosis of −22° and a mean sagital balance of 12.3°. The mean correction in the APO group was 29° in its thoracic kyphosis, 8° of lumbar lordosis and 6.5° in its sagital balance. The mean correction in the PSO group was 12° of the thoracic kyphosis, 25 in the lumbar lordosis and 8.4 cm in the sagital balance. The local correction obtained at the osteotomy level was 28° in the APO group and 25.3° in the PSO group. There were no statistically significant differences in the percentage of correction between both groups (p>0.05). In terms of complications, PSO group had lower complication rate (26.6%) comparing to ODV group (44.5%). Conclusions. APO and PSO are useful techniques to correct the global sagital balance in patients with a disturbance of the sagittal profile. The correction obtained with the PSO is similar to obtained with the APO. Patients undergoing an OSP had a lower complication rate than patients undergoing APO

Background Context: Total disc replacement (TDR) gained enormous popularity as a treatment option for symptomatic degenerative disc disease in the last few years. But the impact of the prosthesis design on the segmental biomechanics in most instances still remains unclear. As TDR results in a distraction of the capsuloligamentous structures, the disc height seems to be of crucial importance for the further biomechanical function of the operated level. Yet the biomechanical role of disc height after TDR still remains unclear. Purpose: The purpose of study was to evaluate the influence of prosthesis height after total disc replacement on: 1) the sagittal balance and 2) the range of motion. Study design: A radiological and an in-vitro biomechanical study. Method: 6 human, lumbar spines L4–L5 were tested in vitro.The segmental lordosis of the specimen were measured on plain radiographs and the range of motion was measured for all six degrees of freedom with a previously described spine tester. The segmental lordosis and the range of motion at level L4–L5 was evaluated for following settings: 1) intact state 2) after implantation of a prosthesis with 5mm endplate 3) after implantation of a prosthesis with 7mm endplate. The prosthesis used was a prototyp and had a constrained design with a ball and socket principle. Results: Even the implantation of the lowest possible prosthesis height (5mm endplate) resulted in an increase of segmental lordosis (intact: 6.9; 5mm endplate: 8.8; p=0,027). Using a higher prosthesis (7mm endplate) further increased the segmental lordosis (10.5, p=0.041). The implantation of the lowest prosthesis resulted in significant increase of movement capability compared to the intact status for flexion-extension (8.6 vs 11.4; p=0.046) and axial rotation (2.9 vs 5.1; p=0.028). Lateral bending did not changed significantly (9.4 vs 8.6; p=0.345). The implantation of the higher prosthesis (7mm endplate) resulted in similar movement capability compared to intact status for flexion-extension (8.4 vs 8.6; p=0.116) and axial rotation (3.3 vs 2.9; p=0.600). Lateral bending decreased significantly compared to the intact status (5.1 vs 8.6; p=0.028). Conclusion: Total disc replacement with the lowest prosthesis height inherently increases segmental lordosis. Further increase of disc height results in a significant enhancement of segmental lordosis by decreasing the range of motion for all three degrees of freedom. Yet, methods for scheduling the ideal disc height preoperatively, to provide a physiological lordosis thereby maintaining physiological range of motion postoperatively, seems not to be established already

Aims

High-grade dysplastic spondylolisthesis is a disabling disorder for which many different operative techniques have been described. The aim of this study is to evaluate Scoliosis Research Society 22-item (SRS-22r) scores, global balance, and regional spino-pelvic alignment from two to 25 years after surgery for high-grade dysplastic spondylolisthesis using an all-posterior partial reduction, transfixation technique.

Introduction The main objective of this study is to describe the morphology and the mechanism of organization of the lumbar lordosis regarding the both position and shape of the pelvis. According to the orientation of the sacral plate, a classification of the lumbar lordosis is proposed. A symptomatic cohort of patient suffering of low back pain is analysed according to this new classification.

Methods 160 asymptomatic, young adult volunteers and 51 symptomatic low back patients were x-rayed in a standardized standing position. Analysis of the spine and pelvis was performed with the SagittalSpine® software. The pelvic parameters were: pelvic incidence, sacral slope, pelvic tilt. Thoracic kyphosis and lumbar lordosis were divided by the inflexion point. The lumbar lordosis was bounded by the sacral plate and the inflexion point. At the apex, the lumbar curve was divided in two tangent arcs of circle, quantified by an angle and a number of vertebrae. The upper one was geometrically equal to the sacral slope. Regarding the vertical line, a lordosis tilt angle was designed between the inflexion point and the anterior limit of the sacral end. The second group was operated with a disc prosthesis at the degenerated level.

Results The value of the lumbar lordosis was very variable. The best correlation was between lumbar lordosis and sacral slope, then between sacral slope and pelvic incidence in both groups. The upper arc of a circle remained constant, when the lower one changed with the sacral slope. There were good correlations of the sacral slope with the position of the apex, and with the lordosis tilt angle. When restoring the disc height at level L4L5 or L5S1 by a prosthesis insertion the local balance is modified but the global balance is unchanged. The prosthesis insertion at level L5S1 modifies significantly the balance at L4L5 which seems to be the most important level to restore a good lumbar lordosis.

Discussion Regarding the sacral slope, the lumbar lordosis can be classified in four types. When the sacral slope is low, the lumbar lordosis can be short and curved with a low apex and a backward tilt (type 1), either both long and flat with a higher position of apex (type 2). When the sacral slope increases, lumbar lordosis increases in angle and number of vertebrae with an upper apex, and it tilts progressively forward (type 3and 4). Depending of the both shape and position of the pelvis, the morphology of the lumbar lordosis could be the main mechanical cause of lumbar degenerative diseases. Total disc arthroplasty at one level L4L5 or L5S1 can significantly restore a good balance in the lumbar without modification on the global balance of the spine. When two levels are involved in the DDD process, the fusion at L5S1 and a prosthesis at L4L5 do not modify the global balance and the clinical results are similar to one level disc arthroplasty. This has to be underlined because all studies with two levels arthroplasties showed worst clinical outcomes than one level.

Ongoing debate exists as to the integrity of the abdominal musculature unit in maintaining spinal support and stability. It is thought that the intra-abdominal pressure generated is important in spine stabilisation. Congenital aplasia of the abdominal musculature, i.e. prune belly syndrome (PBS), might therefore result in loss of spinal function and stability. We discuss the possible role of an intact abdominal musculature mechanism in maintaining spinal saggital balance and its relevance to low back pain with this case illustration of PBS. We also review the literature for the incidence of spinal deformities related to PBS.

We present a unique case of a 33-year-old male with PBS that resulted in loss of spinal saggital balance and development of a thoracic hypokyphotic deformity and thoracolumbar scoliosis. The patient also suffered from mild low back pain. Literature review suggests that secondary scoliosis appears to be the most commonly reported spinal deformity with up to 36% of cases being affected in one study.

Unequal compressive forces on the vertebral end-plates as a result of changes in static rib support, dynamic paraspinal muscle support, and changes in intrathoracic and intra-abdominal pressures may be the proposed mechanisms for the spinal deformities. Compensatory lumbar paraspinal over-activity due to the inability to generate normal intra-abdominal pressures because of a deficient abdominal wall musculature mechanism seems to be the plausible explanation for the thoracic hypokyphotic deformity observed. As a corollary, a failing abdominal wall musculature mechanism has been implicated in the risk for low back pain and its sequelae. Our case implicates that an intact abdominal musculature unit might be important in the maintenance of overall spinal function and stability. Maintaining normal intra-abdominal pressures, and the effects of abdominal exercises on this mechanism, i.e. training specificity, remain an important adjunct to our routine treatment of patients with low back pain.

Purpose: Analysis of the sagittal balance of the spine is a fundamental step in understanding spinal disease and proposing appropriate treatment. The objectives of this prospective study were to establish the physiological values of pelvic and spinal parameters of sagittal spinal balance and to study their interrelations. Material and methods: Two hundred fifty lateral views of the spine taken in the standing position and including the head, the spine and the pelvis were studied. The following variables were noted: lumbar lordosis, thoracic kyphosis, sagittal tilt at 9, sacral slope, pelvic incidence, pelvic version, intervertebral angle, and the vertebral wedge angle from T9 to S1. These measures were taken after digitalising the x-rays. Two types of analysis were performed. A descriptive univariate analysis was used to characterise angular parameters and a multivariate analysis (correlation, principal component analysis) was used to compare interrelations between the variables and determine how economic balance is achieved. Results and discussion: Mean angular values were: maximal lumbar lordosis 61±12.7°, maximal thoracic kyphosis 41.4±9.2°, sacral slope 42±8.5°, pelvic version 13±6°, pelvic incidence 55±11.2°, sagittal tilt at T9 10.5±3.1°. There was a strong correlation between sacral slope and pelvic incidence (r=0.8), lumbar lordosis and sacral slope (r=0.86), pelvic version and pelvic incidence (r=0.66), lumbar lordosis pelvic incidence pelvic version and thoracic kyphosis (r=0.9), and finally between pelvic incidence and sagittal tilt at T9, sacral slope, pelvic version, lumbar lordosis, and thoracic kyphosis (r=0.98). Multivariate analysis demonstrated three independent parameters influencing sagittal tilt at T9, reflecting the lateral balance of the spine. The first was a linear combination of the pelvic incidence, lumbar lordosis and sacral slope. The second was pelvic version and the third thoracic kyphosis. Conclusion: This work provides an aid for analysis and comprehension of anteroposterior imbalance observed in spinal disease and also to calculate with the linear regression equations describing the corrections to be obtained with treatment

Introduction. Flexion instability of the knee accounts for, up to, 22% of reported revisions following TKA. It can present in the early post-operative phase or present— secondary to a rupture of the PCL— in the late post-operative phase. While most reports of instability occur in conjunction with cruciate retaining implants, instability in a posterior-stabilized knee is not uncommon. Due to the prevalence of revision due to instability, the purpose of constructing the following techniques is to utilize intraoperative sensors to quantify flexion gap stability. Methods. 500 posterior cruciate-retaining TKAs were performed between September 2012 and April 2013, by four collaborating surgeons. All surgeons used the same implant system, compatible with a microelectronic tibial insert with which to receive real-time feedback of femoral contact points and joint kinetics. Intraoperative kinematic data, as reported on-screen by the VERASENSE™ knee application, displayed similar loading patterns consistent with identifiable sagittal plane abnormalities. These abnormalities were classified as: “Balanced Flexion Gap,” “Flexion Instability” and “Tight Flexion Gap.” All abnormalities were addressed with the techniques described herein. Results. Balanced Flexion Gap. Flexion balance was achieved when femoral contact points were within the mid-posterior third (Figure 1) of the tibial insert, symmetrical rollback was seen through ROM, intercompartmental loads were balanced, and central contact points displayed less than 10 mm of excursion across the bearing surface during a posterior drawer test. Flexion Instability. The femoral contact point tracking option dynamically displayed the relative motion of distal femur to the proximal tibia during the posterior drawer test, and through range of motion. Excessive excursion of the femoral contact points across the bearing surface, and femoral contact points translating through the anterior third of the tibial trial, was an indication of laxity in the PCL. Surgical correction requires use of a thicker tibial insert, anterior-constrained insert, or a posterior-stabilized knee design (Figure 2). Tight Flexion Gap. Excessive tension in the PCL was displayed during surgery via femoral contact points and excessive high pressures in the posterior compartment during flexion. When a posterior drawer test was applied no excursion of the femoral tibia contact point was seen. Excessively high loading in the posteromedial compartment was corrected through recession of the PCL using an 19 gauge needle or 11 blade. Additional tibial slope was added when excessive loads were seen in both compartments (Figure 3). Discussion. Flexion gap instability, or excessive PCL tension, is a common error resulting in poor patient outcomes and early revision surgery. The techniques described, utilized intraoperative sensor data to address sagittal plane abnormalities in a quantified manner. By using technology to guide the surgeon through appropriate sagittal plane correction, the subtleties in soft-tissue imbalance or suboptimal bone cuts can be accounted for, which otherwise may be overlooked by traditional methods of subjective surgeon “feel.” Longer clinical follow-up of these patients will be necessary to track the outcomes associated with quantifiable sagittal plane balance

Introduction: The goal of the study was to analyse the modification of the sagittal lombo-pelvic equilibrium after total hip replacement for osteoarthritis.

Materials and Methods: The sagittal lombo-pelvic equilibrium was analysed among 89 patients who underwent total hip replacement for osteoarthritis, using lateral X-rays of the whole spine including the hips performed pre-operatively and at one year post-operatively. Reference values were calculated by carrying out the same analysis among 100 asymptomatic healthy volunteers. The studied parameters were: the sacral tilt (ST), the pelvic version (PV) and the sacral incidence (SI).

Results: The mean pre-operative value of STangle was significantly lower in the osteoarthritis group (20.6° +/−6) compared to the reference group (39.4 +/6, p< 0,00001). The mean pre-operative value of VP angle was significanlty higher in the osteoarthritis group (31°+/−8) compared to the reference group (13.5 +/−6 p < 0,00001). There was no significant difference between the two groups for the sacral incidence (p=0,3). At one year post-operatively, the sacral tilt has significantly increased by 5.5° (p< 0.00001).

Discussion: Compared to asymptomatic healthy volunteers, patients affected by osteoarthritis had a pelvic retroversion that has decreased post-operatively but still remained lower than the norm.

Conclusion: The lombo-pelvic equilibrium is different in case of osteoarthritis. After total hip replacement the pelvis remained retroverted. This phenomenon should be taken into account for the planning of total hip arthroplasty.

Aims. The effect of pelvic tilt (PT) and sagittal balance in hips with pincer-type femoroacetabular impingement (FAI) with acetabular retroversion (AR) is controversial. It is unclear if patients with AR have a rotational abnormality of the iliac wing. Therefore, we asked: are parameters for sagittal balance, and is rotation of the iliac wing, different in patients with AR compared to a control group?; and is there a correlation between iliac rotation and acetabular version?. Methods. A retrospective, review board-approved, controlled study was performed including 120 hips in 86 consecutive patients with symptomatic FAI or hip dysplasia. Pelvic CT scans were reviewed to calculate parameters for sagittal balance (pelvic incidence (PI), PT, and sacral slope), anterior pelvic plane angle, pelvic inclination, and external rotation of the iliac wing and were compared to a control group (48 hips). The 120 hips were allocated to the following groups: AR (41 hips), hip dysplasia (47 hips) and cam FAI with normal acetabular morphology (32 hips). Subgroups of total AR (15 hips) and high acetabular anteversion (20 hips) were analyzed. Statistical analysis was performed using analysis of variance with Bonferroni correction. Results. PI and PT were significantly decreased comparing AR (PI 42° (SD 10°), PT 4° (SD 5°)) with dysplastic hips (PI 55° (SD 12°), PT 10° (SD 6°)) and with the control group (PI 51° (SD 9°) and PT 13° (SD 7°)) (p < 0.001). External rotation of the iliac wing was significantly increased comparing AR (29° (SD 4°)) with dysplastic hips (20°(SD 5°)) and with the control group (25° (SD 5°)) (p < 0.001). Correlation between external rotation of the iliac wing and acetabular version was significant and strong (r = 0.81; p < 0.001). Correlation between PT and acetabular version was significant and moderate (r = 0.58; p < 0.001). Conclusion. These findings could contribute to a better understanding of hip pain in a sitting position and extra-articular subspine FAI of patients with AR. These patients have increased iliac external rotation, a rotational abnormality of the iliac wing. This has implications for surgical therapy with hip arthroscopy and acetabular rim trimming or anteverting periacetabular osteotomy (PAO). Cite this article: Bone Jt Open 2021;2(10):813–824

To determine if the use of high density implants (i.e. high proportion of pedicle screws relative to number of spinal levels involved) causes significant loss of thoracic kyphosis and its effect on sagittal balance in adolescent idiopathic scoliosis. Retrospective analysis of pre and post-operative radiographs to assess sagittal balance and C7-L1 kyphosis angle. 17 patients (16 females, 1 male). All right sided single thoracic curves. All surgery performed by single surgeon (Senior author, ED). Comparison of pre and post operative sagittal balance and C7-L1 kyphosis angle. Assessment of implant density (i.e. proportion of pedicle screw relative to number of spinal levels involved in correction). 9 patients demonstrated improved sagittal balance following surgery. There was no significant difference (p value 0.83) between the pre and post op C7-L1 kyphosis angle. Mean angle pre op 28.9 (95% CI 20.3 to 37.5). Mean angle post op 29.6 (95% CI 22.2 to 37.0). No correlation identified between sagittal balance correction and kyphosis angle. Metal density ranged from 79-100%. Although the sample size in this series is modest, high density implants do not significantly affect the kyphosis angle in the operative management of adolescent idiopathic scoliosis in the thoracic spine

Introduction Lumbar fusion may alter the sagittal balance of the spine, including a decrease in the sacral tilt ST and lumbar lordosis. Postoperative pain following a spinal fusion has been shown to be related to changes in sagittal balance, independent of other factors including pseudarthrosis. The goal of this radiological study was to prospectively determine the effect of a single-level, total disc replacement on the sagittal balance of the spine, especially on sacral tilt (ST), pelvic tilt (PT), and lumbar lordosis (Le Huec J, et al; Spine J. 2004). Method 35 patients received a single level disc replacement using the Maverick Total Disc Arthroplasty system (Medtronic Sofamor Danek). The preoperative and postoperative radiographic evaluation included standing anteroposterior and lateral full spine films that included the femoral heads. The parameters studied were ST, PT, global and segmental lordosis, and global kyphosis. The average age of the 35 patients studied was 44.3 years (range 35–57). There were 18 females and 17 males. The disc arthroplasty was performed at the L4–L5 level in 19 patients and at the L5-S1 level in 16 patients. The average follow-up was 14 months (range 6–22 months). Results The preoperative values of global lordosis, ST, PT and global lordosis were not significantly different at last follow-up. When the groups were compared according to the level operated, there was no statistical difference with regard to the overall lordosis, ST, PT or kyphosis from pre- to postoperative period or when the two groups were compared with each other. The level above the prosthesis has significantly less lordosis. Discussion In the present study with use of a motion-preserving intervertebral disc prosthesis, it appears that the patient is able to maintain the preoperative sagittal balance. The prosthesis has enough freedom of motion to allow the patient to maintain the natural sagittal and spinopelvic balance needed to prevent potentially undue stress on the muscles and the sacroiliac joint. Although the number of patients is small, this is the first study that evaluates the sagittal balance after motion-preserving total disc arthroplasty