Sagittal spinal balance after lumbar spinal fusion: the impact of anterior column support results from a randomized clinical trial with an eight- to thirteen-year radiographic follow-up

Three-dimensional vertebral shape changes confirm growth modulation after anterior vertebral body tethering for idiopathic scoliosis

PURPOSE

To evaluate three-dimensional (3D) vertebra and disk shape changes over 2 years following anterior vertebral body tether (AVBT) placement in patients with idiopathic scoliosis (IS).

METHODS

Patients with right thoracic IS treated with AVBT were retrospectively evaluated. 3D reconstructions were created from biplanar radiographs. Vertebral body and disk height (anterior, posterior, left and right) and shape (wedging angle) were recorded over the three apical segments in the local vertebral reference planes. Changes in height and wedging were measured through 2 years postoperatively. Change in patient height was correlated with changes in the spine dimensions.

RESULTS

Forty-nine patients (Risser 0-3, Sanders 2-4) were included. The mean age was 12.2 ± 1.4 years (range 8-14). The mean coronal curve was 51 ± 10° preoperatively, 31 ± 9° at first postoperative time point and 27 ± 11° at 2-year follow-up (p < 0.001). The mean patient height increased 8 cm by 2 years (p < 0.001). The left side of the spine (vertebra + disc) grew in height by 2.2 mm/level versus 0.7 mm/level on the right side (p < 0.001). This differential growth was composed of 0.5 mm/vertebral level and 1.0 mm/disk level. Evaluation of the change in disk heights showed significantly decreased height anteriorly (- 0.4 mm), posteriorly (- 0.3 mm) and on the right (- 0.5 mm) from FE to 2 years. Coronal wedging reduced 2.3°/level with 1.1°/vertebral level change and 1.2°/disk level. There was no differential growth in the sagittal plane (anterior/posterior height). Patient height change moderately correlated with 3D measures of vertebra + disk shape changes.

CONCLUSIONS

Three-dimensional analysis confirms AVBT in skeletally immature patients results in asymmetric growth of the apical spine segments. The left (untethered) side length increased more than 3 × than the right (tethered) side length with differential effects observed within the vertebral bodies and disks, each correlating with overall patient height change.

Biomechanical in vitro evaluation of the kangaroo spine in comparison with human spinal data

On the basis of the kangaroo's pseudo-biped locomotion and its upright position, it could be assumed that the kangaroo might be an interesting model for spine research and that it may serve as a reasonable surrogate model for biomechanical in vitro tests. The purpose of this in vitro study was to provide biomechanical properties of the kangaroo spine and compare them with human spinal data from the literature. In addition, references to already published kangaroo anatomical spinal parameters will be discussed. Thirteen kangaroo spines from C4 to S4 were sectioned into single-motion segments. The specimens were tested by a spine tester under pure moments. The range of motion and neutral zone of each segment were determined in flexion and extension, right and left lateral bending and left and right axial rotation. Overall, we found greater flexibility in the kangaroo spine compared to the human spine. Similarities were only found in the cervical, lower thoracic and lumbar spinal regions. The range of motion of the kangaroo and human spines displayed comparable trends in the cervical (C4-C7), lower thoracic and lumbar regions independent of the motion plane. In the upper and middle thoracic regions, the flexibility of the kangaroo spine was considerably larger. These results suggested that the kangaroo specimens could be considered to be a surrogate, but only in particular cases, for biomechanical in vitro tests.

Operative differences for posterior spinal fusion after vertebral body tethering: Are we fusing more levels in the end?

PURPOSE

Little is known about the perioperative characteristics associated with a posterior spinal fusion (PSF) in adolescent idiopathic scoliosis patients previously treated with vertebral body tethering (VBT). We aimed to determine if operative time, estimated blood loss, postoperative length of stay, instrumentation type, and implant density differed in patients that received a PSF (i.e., PSF-Only) or a PSF following a failed VBT (i.e., PSF-VBT).

METHODS

We retrospectively assessed matched cohort data (PSF-VBT = 22; PSF-Only = 22) from two multi-center registries. We obtained: (1) operative time, (2) estimated blood loss, (3) postoperative length of stay, (4) instrumentation type, and (5) implant density. Theoretical fusion levels prior to the index procedure were obtained for PSF-VBT and compared to the actual levels fused.

RESULTS

We observed no difference in operative time, estimated blood loss, or postoperative length of stay. Instrumentation type was all-screw in PSF-Only and varied in PSF-VBT with nearly 25% of patients exhibiting a hybrid construct. There was no added benefit to removing anterior instrumentation prior to fusion; however, implant density was higher in PSF-Only (1.9 ± 0.2) than when compared to PSF-VBT (1.7 ± 0.3). An additional two levels were fused in 50% of PSF-VBT patients, most of which were added to the distal end of the construct.

CONCLUSIONS

We found that operative time, estimated blood loss, and postoperative length of stay were similar in both cohorts; however, the length of the fusion construct in PSF-VBT is likely to be two levels longer when a failed VBT is converted to a PSF.

The preliminary outcomes of vertebral body tethering in treating adolescent idiopathic scoliosis: a systematic review

PURPOSE

VBT is a novel alternative to spinal fusion surgery to treat skeletally immature AIS and was approved to correct idiopathic scoliosis in August 2019 by US Federal Drug Administration (FDA). To systemically review the preliminary outcomes of vertebral body tethering (VBT) in treating adolescent idiopathic scoliosis.

METHODS

The electronic databases PubMed, EMBASE, and Web of Science were queried up to January 2022 for articles regarding VBT. Basic characteristics of patients, changes of radiographic parameters in coronal and sagittal planes, and clinical outcomes of surgical treatment of VBT including complication and revision rates were summarized.

RESULTS

Twenty five studies met the inclusion criteria. Most studies (23/25) included patients with only skeletal immaturity. The average % correction of the main/tethered curve at final follow-up, and % correction of thoracic kyphosis at final follow-up were reported to be 15.6-106.5% and - 31.8 to 20.0%, respectively. The most common complications for VBT were tether breakage (n = 145;21.3%), pulmonary complications (n = 49; 6.9%), and overcorrection (n = 30; 4.2%). The revision rate was 13.1%.

CONCLUSION

VBT could effectively and safely correct spinal deformity in skeletally immature patients with AIS and preserve the motion and growth of the spine. However, VBT has a relatively high complication and revision rates. Therefore, surgeons should cautiously consider VBT for treating AIS. Future research efforts are needed to lower the complication and revision rates. Whatever, VBT is still in its infancy and may have a promising future as a non-fusion solution for AIS.

Trunk Range of Motion and Patient Outcomes After Anterior Vertebral Body Tethering Versus Posterior Spinal Fusion: Comparison Using Computerized 3D Motion Capture Technology

BACKGROUND

Anterior vertebral body tethering (AVBT) for adolescent idiopathic scoliosis (AIS) is postulated to preserve motion compared with traditional posterior spinal fusion (PSF), but few studies exist to date. We used a validated computerized 3D model to compare trunk motion between patients treated with PSF and AVBT, and analyzed trunk motion in relation to the lowest instrumented vertebra (LIV).

METHODS

This was a single-center retrospective review of a consecutive series of skeletally immature patients with AIS who underwent motion analysis prior to PSF (n = 47) or AVBT (n = 65) and 2 years postoperatively. Patients were divided into 4 groups on the basis of the LIV (≤L1, L2, L3, L4). Computerized 3D kinematic evaluations included thoracic and lumbar flexion, extension, side-bending, and rotation. Patient outcomes were assessed using the Scoliosis Research Society (SRS)-22 questionnaire.

RESULTS

The LIV was ≤L1 in 48 patients treated with AVBT and 23 treated with PSF, L2 in 4 AVBT and 8 PSF patients, L3 in 10 AVBT and 8 PSF patients, and L4 in 3 AVBT and 8 PSF patients. PSF patients had a significant loss of motion in all 4 directions at 2 years postoperatively (e.g., flexion loss was 11° for ≤L1 to 30° for L4; p < 0.001). This equated to a 7° loss of trunk flexion per additional LIV level included in the fusion. AVBT patients only demonstrated loss of flexion and side-bending at 2 years postoperatively (e.g., flexion loss of 11° for L1 to 17° for L4; p < 0.001). Preoperative curve size and flexibility did not have any significant impact on differences in trunk motion between AVBT and PSF. SRS-22 scores were predominantly similar for AVBT versus PSF preoperatively and at 2 years postoperatively.

CONCLUSIONS

Patients treated with AVBT experienced predominantly less motion loss compared with PSF patients at 2 years postoperatively. Patients treated with PSF demonstrated loss of motion in all planes that increased with each additional LIV from ≤L1 to L4, with 7° loss of flexion per additional LIV. However, the differences in total trunk motions were relatively modest for PSF and AVBT with an LIV of ≤L1. Preoperative curve magnitude and flexibility had no significant impact on trunk motion in either group. SRS-22 scores were similar for both groups at 2 years postoperatively.

LEVEL OF EVIDENCE

Therapeutic Level III . See Instructions for Authors for a complete description of levels of evidence.

Intervertebral Disk Health Following Vertebral Body Tethering for Adolescent Idiopathic Scoliosis: A Preliminary Study

BACKGROUND

Interest in vertebral body tethering (VBT) as an alternative to posterior spinal fusion for adolescent idiopathic scoliosis (AIS) continues to grow. The purpose of this study was to prospectively assess intervertebral disk health on magnetic resonance imaging (MRI) at 1 year following VBT in AIS patients.

METHODS

AIS patients were enrolled in a prospective surgeon-sponsored Food and Drug Administration (FDA) Investigational Device Exemption (IDE) Study and underwent MRI at 1-year following VBT. All spanned disks and the untethered disks immediately adjacent to the upper instrumented vertebra and lowest instrumented vertebra levels were evaluated according to Pfirrmann grading criteria. Associations between patient factors and preoperative and postoperative disk health and patient-reported outcomes were evaluated.

RESULTS

Twenty-two patients were enrolled with a postoperative MRI (25 curves, 188 disks), and 7 patients (7 curves) had both preoperative and postoperative MRIs (67 disks). The mean age was 12.7 years. Most were Risser 0 (65%) and either Sanders Skeletal Maturity Score 3 (35%) or 4 (53%). In the 7 patients with preoperative and postoperative MRI, the mean Pfirrmann grade of the disks spanned by the tether was 1.88 preoperatively and 2.31 postoperatively ( P =0.0075). No statistically significant differences in preoperative versus postoperative Pfirrmann grade were identified in the disks adjacent to the upper or lower instrumented vertebrae. No association was found between patient-reported outcomes and Pfirrmann grade.

CONCLUSION

At 1 year postoperatively, increased degenerative changes in disks spanned by the tether was identifiable on MRI without evidence of adjacent segment disk disease. These changes were not associated with patient-reported outcomes.

LEVEL OF EVIDENCE

Level III.

Anterior vertebral body tethering for thoracic idiopathic scoliosis leads to asymmetric growth of the periapical vertebrae

PURPOSE

To evaluate 3D growth of the periapical vertebrae and discs in the 2 years after anterior vertebral body tether (AVBT) placement in patients with idiopathic scoliosis (IS).

METHODS

Patients with IS treated with AVBT, ≥ 2 years of follow-up, and 3D spine reconstructions created from simultaneous, biplanar radiographs were studied. Patients were divided into two groups: progressive scoliosis correction (PC) or no/limited correction (NPC). The average of the 3 apical vertebral and disc heights and angular measures were made. The rate of change for each measure (mm/mo, °/mo) from first erect to 2-year follow-up was compared between groups.

RESULTS

Fourteen (Risser 0, Sanders 2-3) patients aged 11.4 ± 1.4 years with right thoracic scoliosis of 52 ± 9° were included. There were 7 patients per group (6F, 1M). Mean follow-up was 3.6 ± 1.1 (range 2-5) years. PC left-sided vertebral height increased 0.13 mm/months compared to 0.05 mm/mo in the NPC group (p = 0.001). Right (tethered side) vertebral growth was not different (PC: 0.07 mm/mo, NPC: 0.05 mm/mo, p = 0.2). Coronal vertebral wedging occurred at - 0.11°/mo compared to - 0.02°/mo for the PC and NPC groups, respectively (p = 0.004). Coronal disc angulation change was - 0.12°/mo in the PC group and - 0.04°/mo in the NPC group (p = 0.03), and was associated with loss of right disc height (PC: - 0.06 mm/mo) with little effect on the left disc height (PC: -0.01 mm/mo).

CONCLUSIONS

AVBT in immature patients with thoracic scoliosis can asymmetrically modulate growth of the periapical vertebrae and discs. Progressive reduction in scoliosis after AVBT was associated with greater concave growth rates in the vertebrae and loss of disc height on the convex side.

Difference between radiographically suspected and intraoperatively confirmed tether breakages after vertebral body tethering for idiopathic scoliosis

PURPOSE

Vertebral body tethering (VBT) has shown promising results but also a high tether breakage rate, which has been reported in up to 48% of patients. Tether breakages can lead to loss of correction, and the most used definition for tether breakage is a loss of segmental correction of > 5°. However, there may also be some breakages that do not have a negative influence on curve correction. Analyzing the real breakage rate was the aim of this study.

METHODS

All patients who underwent anterior revision surgery after VBT were included in this retrospective study. Real (intraoperatively confirmed) tether breakages were compared to preoperatively suspected tether breakages. The definition for a suspected tether breakage was an angular change of more than 5° between an early and the latest radiograph.

RESULTS

Ten patients who received 11 revision surgeries with a total of 15 revised curves were analyzed. Of the 80 analyzed segments, 36 were found to have a breakage. Of these 36 segments, 20 were suspected to be broken preoperatively. Sixteen breakages were not identified on preoperative radiographs (44%). One suspected broken tether was intraoperatively found to be intact.

CONCLUSION

By using the > 5° rule, only 56% of the tether breakages could be diagnosed. On the other hand, many tether breakages will not result in a loss of correction.

Surgical risk factors associated with the development of adjacent segment pathology in the lumbar spine

Adjacent segment pathology (ASP) is a major cause of disability, and the recognition of the surgical risk factors associated with the development of this condition is essential for its prevention.

Different surgical approaches, from decompression without fusion to non-instrumented and instrumented fusion, have distinct contributions to the development of ASP.

Although motion-preservation procedures could reduce the prevalence of ASP, these are also associated with a higher percentage of complications.

Several risk factors associated with previous surgery, namely the chosen surgical approach and anatomical dissection, the choice of interbody fusion, the increment and length of the fusion, and the restoration of sagittal alignment, may influence the development of ASP.

Cite this article: EFORT Open Rev 2021;6:966-972. DOI: 10.1302/2058-5241.6.210050

Does vertebral body tethering cause disc and facet joint degeneration? A preliminary MRI study with minimum two years follow-up

BACKGROUND CONTEXT

Vertebral body tethering (VBT), a flexible compression-based growth modulation technique, was claimed to prevent disc degeneration due to its less rigid nature compared to other growth-friendly techniques. Yet, the consequences of VBT surgery on discs and facet joints have not been precisely acknowledged.

PURPOSE

The purpose of this study was to determine the changes in the intermediate and adjacent levels at least 2 years after surgery.

STUDY DESIGN/SETTING

Prospectively-followed consecutive patient cohort PATIENT SAMPLE: Adolescent idiopathic scoliosis patients who underwent thoracoscopic VBT between 2014 and 2017 were included.

OUTCOME MEASURES

Degeneration of the intervertebral discs using the Pfirrmann classification; Degeneration of facet joints using a scale of 0 to 3.

METHODS

Demographic, perioperative, clinical, radiographic data were collected. Skeletal maturity and height gain were assessed in every follow-up. Overcorrection, tether breakage, mechanical and pulmonary complications as well as readmission and reoperations were recorded. MRIs taken before surgery and at a minimum of 2 years follow-up were evaluated for degeneration at the intermediate and adjacent segment intervertebral discs and facet joints by a blinded senior radiologist and compared.

RESULTS

Twenty-five patients with a mean of 38.6±10.6 months (24-62) of follow-up were included. The mean age at surgery was 12.2 (10-14), and the median Sanders stage was 3 (1-7). A mean of 7.7±1.1 (6-11) levels were tethered. The mean preoperative main thoracic curve magnitude of 46°±7.7° was corrected to 23.3°±5.9° postoperatively, which was subsequently modulated to 12° ±11.5° during the follow-up. At the time of the MRI (mean 29±9.5 (24-62) months), the median Sanders stages was 7 (5-8). A total of 217 levels of discs and bilateral facet joints were evaluated in the preoperative and follow-up MRI images. Analyses of disc and facet scores revealed no significant differences between patients. Deterioration of previously degenerated discs was noted in one patient (from grade 2 to 3), while previously healthy lower adjacent facet joints were degenerated (grade 2) in another patient.

CONCLUSIONS

Intermediate discs and facet joints were preserved after growth modulation with VBT surgery at a mean of 29 months of follow-up. Studies in larger cohorts with longer follow-up are warranted to have more in-depth analyses of the effects of relative stabilization and altered biomechanical loads.

Anterior Vertebral Body Tethering for Treatment of Idiopathic Scoliosis in the Skeletally Immature: Results of 112 Cases

STUDY DESIGN

Prospective case series.

OBJECTIVE

Determine the efficacy of anterior vertebral body tethering (AVBT) in skeletally immature patients.

SUMMARY OF BACKGROUND DATA

The value of AVBT is currently unclear given the paucity of available data.

METHODS

Consecutive skeletally immature patients with idiopathic scoliosis were treated with AVBT between 2012 and 2018 by one of two surgeons working at two independent centers and followed up for >2 years. Data were collected prospectively and supplemented retrospectively where necessary. Outcomes were measured preoperatively, at first erect radiograph (FE), 1-year postoperatively and at most recent follow up (FU).

RESULTS

One hundred twelve patients underwent 116 primary tethering procedures (108 thoracic and eight lumbar tethers). Four patients had primary tethering of both lumbar and thoracic curves. At surgery mean age was 12.7 ± 1.4 years (8.2-16.7) and Risser 0.5 ± 0.9 (0-3). Follow up was mean 37 ± 9 months (15-64). Preoperative mean coronal Cobb angle of the 130 tethered curves was 50.8° ± 10.2 (31-81) and corrected significantly to 26.6° ± 10.1 (-3-61) at FE radiograph (P < 0.001). Further significant improvement was seen from FE to 1-year, to mean 23.1° ± 12.4 (-37-57) (P < 0.001). There was a small but significant increase between 1-year and FU to 25.7° ± 16.3 (-32-58) (P < 0.001), which appeared to reflect tether breakage. Untethered minor curves were corrected from 31.0° ± 9.5 (3-57) to 20.3° ± 10.3 (0-52) at FU (P < 0.001). Rib hump was corrected from 14.1 ± 4.8 (0-26) to 8.8° ± 5.4 (0-22) at FU (P < 0.01). Twenty-five patients (22%) had 28 complications. Fifteen patients (13%) requiring 18 revision operations including six completed and one awaited fusions.

CONCLUSION

AVBT of immature cases is associated with satisfactory deformity correction in the majority of cases. However, complication and revision rates suggest the need for improved implants and patient selection. Long-term follow-up remains crucial to establish the true efficacy of this procedure.Level of Evidence: 3.

Rate of Scoliosis Correction After Anterior Spinal Growth Tethering for Idiopathic Scoliosis

BACKGROUND

The purpose of the present study was to evaluate associations between changes in segmental vertebral coronal angulation (screw angulation) and overall height after anterior spinal growth tethering for the treatment of idiopathic scoliosis and to compare the rates of coronal angulation change using the preoperative Sanders stage.

METHODS

Patients with idiopathic scoliosis who underwent anterior spinal growth tethering between 2012 and 2016 and had ≥2 years of follow-up were retrospectively studied. We calculated each segment's screw angulation rate of change (degrees/month) and each patient's height velocity (cm/month) between each of the visits (3 to 12 visits/patient) and divided the visits into 4 groups by postoperative duration (<1 year, 1 to 2 years, >2 to 3 years, >3 years). Patients were divided into 2 groups according to the preoperative Sanders stage. Generalized estimating equations and repeated-measures correlation were utilized for analyses with non-independent samples.

RESULTS

We analyzed 23 patients (16 female, 7 male) with a mean age (and standard deviation) of 12.2 ± 1.6 years who had right thoracic idiopathic scoliosis (mean, 53° ± 8°). All patients were immature at the time of surgery (Risser stage 0 or 1, Sanders stage 2 or 3). The mean duration of follow-up was 3.4 ± 1.1 years (range, 2 to 5 years). The rate of change for each segment's screw angulation after anterior spinal growth tethering was -0.16°, -0.14°, -0.05°, and 0.03° per month (with negative values indicating a reduction in scoliosis) for <1 year, 1 to 2 years, >2 to 3 years, and >3 years, respectively (p ≤ 0.001), and the mean height velocity was 0.65, 0.57, 0.30, and 0.19 cm per month for <1 year, 1 to 2 years, >2 to 3 years, and >3 years, respectively (p < 0.001). Changes in screw angulation correlated with height increases after anterior spinal growth tethering (r = -0.46, p < 0.001). Scoliosis correction for patients in the Sanders stage-2 group continued for 3 years (0.23°, 0.23°, and 0.09° per level per month for the first 3 years, respectively) and occurred at more than twice the rate for patients in the Sanders stage-3 group, for whom scoliosis correction ceased 2 years postoperatively (0.11° and 0.09° per level per month for the first 2 years, respectively).

CONCLUSIONS

Scoliosis correction was associated with overall height changes and occurred primarily within 2 to 3 years after surgery in this cohort of largely Risser stage-0 patients. The correction rate was 2.8° per segment per year for the first 2 years in the Sanders stage-2 group, compared with 1.2° per segment per year for the Sanders stage-3 group. Surgical timing that considers the patient's skeletal maturity is an important factor in generating proper postoperative correction after anterior spinal growth tethering.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

A preliminary assessment of intervertebral disc health and pathoanatomy changes observed two years following anterior vertebral body tethering

PURPOSE

Vertebral body tethering (VBT) has been reported as a safe and effective non-fusion surgical technique for the treatment of adolescent idiopathic scoliosis, but the postoperative health of the bone and soft tissues of the spine following instrumentation remains unknown. We aimed to evaluate pathoanatomy and degenerative changes of the spine in adolescent idiopathic scoliosis patients both prior to and two years following VBT.

METHODS

We prospectively enrolled nine patients who underwent VBT for the treatment of progressive adolescent idiopathic scoliosis. All patients received preoperative and two-year postoperative magnetic resonance imaging of their spine; images were assessed for pathoanatomy (e.g. nucleus pulposus positioning and muscle atrophy) and degenerative changes (e.g. Schmorl nodes, endplate oedema, disc degeneration, and osteoarthritis) at each vertebral level between T1 and S1.

RESULTS

Four patients (44%) exhibited a shift of the nucleus pulposus from an eccentric position at baseline towards midline at three or more levels, most of which were in the tethered region. Tethering did not affect preexisting fatty atrophy of multifidus. No patients exhibited postoperative Schmorl nodes, endplate oedema, or disc degeneration in either the tethered or untethered regions. Four patients (44%) presented with mild facet osteoarthritis in the lower lumbar spine, which did not change postoperatively. One patient developed moderate facet osteoarthritis at L5-S1.

CONCLUSIONS

These preliminary data indicate that VBT may not result in significant degenerative changes in either the intervertebral discs or the posterior facets two years following instrumentation.

L5 Radiculopathy After Formal Reduction of High-Grade SDSG Type 5 and 6 L5-S1 Isthmic Spondylolisthesis with 2-Year Follow-Up

BACKGROUND

Surgery is the main treatment for patients with high-grade L5-S1 isthmic spondylolisthesis, which can result in neurologic complications, but little is known about its clinical course. The present study evaluated the presence of L5 radiculopathy in high-grade L5-S1 spondylolisthesis in adults in pre- and postoperative periods and after a 2-year follow-up.

METHODS

A series of 16 patients who underwent reduction and instrumented fusion for high-grade 5 and 6 spondylolisthesis between 2018 and 2019 were retrospectively evaluated in the pre- and postoperative periods as well as after 6 weeks, 3 months, 6 months, and 1 and 2 years of follow-up. Clinical and surgical data on possible neurological complications of L5 radiculopathy were prospectively collected.

RESULTS

The age was 20.1 ± 12.0 years, and preoperative L5-S1 slip was 89.0%. Five patients presented motor deficit in the preoperative period. In the immediate postoperative period, 9 patients (56%) experienced motor deficits or worsening of the preoperative condition. At the 6-week follow-up, only 1 patient showed resolution of the motor deficit. Three patients presented healed motor deficits after 3 months, and 1 patient demonstrated a healed L5 motor radiculopathy after 6 months. At the 1-year follow-up, only 1 patient exhibited an L5 radiculopathy motor deficit, and at the 2-year follow-up, none of the patients exhibited an L5 radiculopathy motor deficit.

CONCLUSION

L5 radiculopathy was frequent in the preoperative period and increased after reduction and instrumented fusion of high-grade L5-S1 spondylolisthesis in the postoperative period and in the 6-week follow-up. Three and 6 months after the surgery, there were consecutive motor improvements. After 2 years of follow-up, no patients showed neurological deficit of L5 radiculopathy.

LEVEL OF EVIDENCE

2.

CLINICAL RELEVANCE

This is the first study reporting a reduction in complications of L5 neurological motor deficit over a 2-year follow-up in high-grade L5-S1 spondylolisthesis in young adults.

Complications, Reoperations, and Mid-Term Outcomes Following Anterior Vertebral Body Tethering Versus Posterior Spinal Fusion: A Meta-Analysis

Background

Anterior vertebral body tethering (AVBT) is a growth-modulation technique theorized to correct adolescent idiopathic scoliosis (AIS) without the postoperative stiffness imposed by posterior spinal fusion. However, data are limited to small series examining short-term outcomes. To assess AVBT's potential as a viable alternative to posterior spinal fusion (PSF), a comprehensive comparison is warranted. The purpose of this meta-analysis was to compare postoperative outcomes between patients with AIS undergoing PSF and AVBT. Our primary objective was to compare complication and reoperation rates at available follow-up times. Secondary objectives included comparing mid-term Scoliosis Research Society (SRS)-22 scores, and coronal and sagittal-plane Cobb angle corrections.

Methods

We performed a systematic review of outcome studies following AVBT and/or PSF procedures. The inclusion criteria included the following: AVBT and/or PSF procedures; Lenke 1 or 2 curves; an age of 10 to 18 years for >90% of the patient population; <10% non-AIS scoliosis etiology; and follow-up of ≥1 year. A single-arm, random-effects meta-analysis was performed. Deformity corrections, complication and reoperation rates, and postoperative SRS-22 scores were recorded.

Results

Ten AVBT studies (211 patients) and 14 PSF studies (1,069 patients) were included. The mean follow-up durations were similar for both groups. Pooled complication rates were 26% for AVBT versus 2% for PSF, and reoperation rates were 14.1% for AVBT versus 0.6% for PSF with nonoverlapping confidence intervals (CIs). The pooled reoperation rate among studies with follow-up times of ≥36 months was 24.7% in AVBT versus 1.8% in PSF. Deformity correction, clinical outcomes, and mid-term SRS-22 scores were similar.

Conclusions

Our study showed greater rates of complications and reoperations with AVBT compared with PSF. Reoperation rates were significantly greater in AVBT studies with longer follow-up (≥36 months). Deformity correction, clinical outcomes, and mid-term SRS-22 scores were similar. While a potential fusionless treatment for AIS merits excitement, clinicians should consider AVBT with caution. Future long-term randomized prospective studies are needed.

Level of Evidence

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Comparison of outcomes between indirect decompression of oblique lumbar interbody fusion and MIS-TLIF in one single-level lumbar spondylosis

Minimal invasive spinal fusion has become popular in the last decade. Oblique lumbar interbody fusion (OLIF) is a relatively new surgical technique and could avoid back muscle stripping and posterior complex destruction as in minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF). Between December 2016 and September 2018, patients with single level degenerative spondylosis were selected to enroll in this retrospective study. A total of 21 patients that underwent OLIF and 41 patients that received MIS-TLIF were enrolled. OLIF showed significantly less blood loss and shorter surgery time compared to MIS-TLIF (p < 0.05). The improvement in segmental lordosis and coronal balance was significantly more in OLIF group than MIS-TLIF group (p < 0.05). When comparing with MIS-TLIF, OLIF was significantly better in Oswestry Disability Index (ODI) and visual analogue scale for back pain improvement at post-operative 6 months (p < 0.05). Both OLIF and MIS-TLIF are becoming mainstream procedures for lumbar degenerative-related disease, especially for spondylolisthesis. However, the indirect decompression of OLIF has shown to have less perioperative blood loss and shorter surgery time than that of MIS-TLIF. In addition, OLIF gives superior outcome in restoring segmental lordosis and coronal imbalance. While both OLIF and MIS-TLIF provide optimal clinical outcomes, upon comparison between the two techniques, the indirect decompression of OLIF seems to be a superior option in modern days.

Anterior vertebral body tethering shows mixed results at 2-year follow-up

STUDY DESIGN

Retrospective chart review.

OBJECTIVE

To report 2-4-year outcomes of anterior vertebral body tethering (AVBT) for adolescent idiopathic scoliosis (AIS). AVBT is a relatively new procedure to correct AIS spine curvature and few outcomes studies have been published.

METHODS

Patients from 2015 to 2017 with 2-year follow-up were included. Successful outcomes were defined as curves 35° or less without revision surgery. We also compared outcomes between thoracic and lumbar ABVT.

RESULTS

There were 19 AVBTs in 17 patients, 13 thoracic and 6 lumbar. Nine curves (47%) in nine patients (53%) were successful. Preoperative kyphosis averaged 26° in the successful group and 14° in the unsuccessful group (P = 0.0337). Immediate correction for lumbar ABVTs (76%) was greater than thoracic ABVTs (43%) (P = 0.0140). Correction per level per month was greater in lumbar ABVTs (2.9° vs. 0.1°) (0.0440). Preoperative Sanders Maturity Scale (SMS) was 3.7 for successful cases and 2.5 for unsuccessful cases (P = 0.0232). Final SMS was 7.7 for successful cases and 5.7 for unsuccessful cases (P = 0.0518). All successful cases and 50% of unsuccessful cases were mature at final follow-up (P = 0.0294). There were four (24%) revision procedures, and three involving lumbar AVBTs. There were nine (47%) broken tethers.

CONCLUSIONS

Despite several final curves > 35°, four revisions, and nine broken tethers, the majority of patients (53%) were considered successful. Lumbar ABVTs correct more intraoperatively and faster postoperatively. Patients who are tethered during or slightly after the curve acceleration phase of growth may have more successful outcomes than patients tethered prior to the curve acceleration phase. AVBT requires further study with longer outcomes to define best practices for indications, level selections, and surgical techniques.

LEVEL OF EVIDENCE

IV.

Safety and efficacy of anterior vertebral body tethering in the treatment of idiopathic scoliosis

AIMS

Spinal fusion remains the gold standard in the treatment of idiopathic scoliosis. However, anterior vertebral body tethering (AVBT) is gaining widespread interest, despite the limited data on its efficacy. The aim of our study was to determine the clinical efficacy of AVBT in skeletally immature patients with idiopathic scoliosis.

METHODS

All consecutive skeletally immature patients with idiopathic scoliosis treated with AVBT enrolled in a longitudinal, multicentre, prospective database between 2013 and 2016 were analyzed. All patients were treated by one of two surgeons working at two independent centres. Data were collected prospectively in a multicentre database and supplemented retrospectively where necessary. Patients with a minimum follow-up of two years were included in the analysis. Clinical success was set a priori as a major coronal Cobb angle of < 35° at the most recent follow-up.

RESULTS

A total of 57 patients were included in the study. Their mean age was 12.7 years (SD 1.5; 8.2 to 16.7), with 95% being female. The mean preoperative Sanders score and Risser grade was 3.3 (SD 1.2), and 0.05 (0 to 3), respectively. The majority were thoracic tethers (96.5%) and the mean follow-up was 40.4 months (SD 9.3). The mean preoperative major curve of 51° (SD 10.9°; 31° to 81°) was significantly improved to a mean of 24.6° (SD 11.8°; 0° to 57°) at the first postoperative visit (45.6% (SD 17.6%; 7% to 107%); p < 0.001)) with further significant correction to a mean of 16.3° (SD 12.8°; -12 to 55; p < 0.001) at one year and a significant correction to a mean of 23° (SD 15.4°; -18° to 57°) at the final follow-up (42.9% (-16% to 147%); p < 0.001). Clinical success was achieved in 44 patients (77%). Most patients reached skeletal maturity, with a mean Risser score of 4.3 (SD 1.02), at final follow-up. The complication rate was 28.1% with a 15.8% rate of unplanned revision procedures.

CONCLUSION

AVBT is associated with satisfactory correction of deformity and an acceptable complication rate when used in skeletally immature patients with idiopathic scoliosis. Improved patient selection and better implant technology may improve the 15.8% rate of revision surgery in these patients. Further scrutiny of the true effectiveness and long-term risks of this technique remains critical. Cite this article: Bone Joint J 2020;102-B(12):1703-1708.

Thoracoscopic Vertebral Body Tethering for Adolescent Idiopathic Scoliosis: Follow-up Curve Behavior According to Sanders Skeletal Maturity Staging

STUDY DESIGN

Retrospective analysis of prospectively collected data.

OBJECTIVE

To report the follow-up curve behaviors in different Sanders staging groups.

SUMMARY OF BACKGROUND DATA

Vertebral body tethering (VBT) is a growth modulation technique that allows gradual spontaneous follow-up curve correction as the patient grows. There is a lack of scientific evidence regarding appropriate patient selection and timing of implantation.

METHODS

Patients were grouped into five as: Sanders 1, 2, 3, 4-5, and 6-7. Data were collected preoperatively, at the day before discharge, and at each follow-up. Outcome measures were pulmonary and mechanical complications, readmission, and reoperation rates. Demographic, perioperative, clinical, radiographic, and complication data were compared using Fisher-Freeman-Halton exact tests for categorical variables and Kruskal-Wallis tests for the continuous variables.

RESULTS

Thirty-one (29 F, 2 M) consecutive patients with a minimum of 12 months of follow-up were included. The mean age at surgery was 12.1 (10-14). The mean follow-up was 27.1 (12-62) months. The mean preoperative main thoracic curve magnitude was 47° ± 7.6°. For all curves, preoperative and first erect curve magnitudes, bending flexibility, and operative correction percentages were similar between groups (for all comparisons, P > 0.05). The median height gained during follow-up was different between groups (P < 0.001), which was reflected into median curve correction during follow-up. Total curve correction percentage was different between groups (P = 0.009). Four (12.9%) patients had pulmonary and six (19.4%) had mechanical complications. One (3.2%) patient required readmission and two (6.5%) required reoperation. Occurrence of pulmonary complications was similar in Sanders groups (P = 0.804), while mechanical complications and overcorrection was significantly higher in Sanders 2 patients (P = 0.002 and P = 0.018).

CONCLUSION

Follow-up curve behavior after VBT is different in patients having different Sanders stages. Sanders 2 patients experienced more overcorrection, thus timing and/or correction should be adjusted, since Sanders 3, 4, and 5 patients displayed a lesser risk of mechanical complications.

LEVEL OF EVIDENCE

3.

Long-term impact of sagittal malalignment on hardware after posterior fixation of the thoracolumbar spine: a retrospective study

BACKGROUND

The importance of sagittal alignment in healthy individuals and in reconstructive spinal surgery has been studied over the last 15 years. The aim of the present study was to assess the long-term effects of abnormal sagittal alignment on hardware after posterior thoracolumbar spinal fusion.

METHODS

Patients who had undergone revision surgery (revision cohort, n = 34) due to breakage of their implants were compared retrospectively with patients who had intact implants at the final follow-up investigation after a long posterior thoracolumbar and/or lumbar spinal fusion (control cohort, n = 22). Clinical data and radiological parameters including the sagittal vertical axis (SVA), pelvic incidence (PI), lordosis gap (LG), pelvic tilt (PT), sacral slope (SS), lumbar lordosis (LL), thoracic kyphosis (TK), and the femoral obliquity angle (FOA) were assessed on full-spine lateral radiographs obtained in regular standing position. Data were analysed using descriptive statistics, parametric and non-parametric inferential statistics.

RESULTS

Patients in the breakage group (female n = 21, male n = 9, mean age 60.9 ± 15.6 years) had a higher anterior shift of the C7 plumb line (SVA) (p = 0.02), retroversion of the pelvis (PT) (p < 0.001), PI-LL mismatch (LG) (p = 0.001), and PI (p = 0.002) than the intact group (female n = 10, male n = 12, mean age 65.7 ± 12.4 years). No significant difference was registered between groups in regard of SS, LL, TK, FOA, and the mean number of comorbidities.

CONCLUSION

Failure of restoration of the SVA and the LG to the acceptable ranges, especially in patients with a high PI, may be regarded as a risk factor for the long-term failure of implants after posterior thoracolumbar spinal fusion.

Modic changes of the lumbar spine-their association with the lumbar sagittal parameters: A retrospective imaging study

Background

The Lumbar sagittal parameters might be related to modic changes (MCs). However, studies on this topic have rarely been reported. The aim of this study was to identify the relationships between the lumbar sagittal parameters and the development of MCs.

Methods

The lumbar sagittal parameters of 321 patients with chronic low back pain from May 2016 to August 2018 were measured on X-ray by using Surgimap surgical planning software. Univariable analyses were used to test the potential variables of interest. Logistic regression models were then performed for the significant parameters to identify the independent factors associated with the development of MCs.

Results

More patients in the MCs group were older with more number of female than in the disc degeneration group (p < 0.05). In the univariate analysis, significant differences were detected for the parameters of lumbar lordosis, sacral slope, intervertebral height index, endplate concave angle, and intervertebral angle only at the L5/S1 level between the two groups. The results of logistic regression analysis showed that a smaller intervertebral height index was positively associated with the development of MCs at the level of L3/4 (p < 0.05). However, the positive role of gender was only for MCs at the L5/S1 level (p < 0.05).

Conclusions

The results of this study revealed that there were negative relationships between the lumbar sagittal parameters and MCs. Furthermore, being female and having a narrow intervertebral space were the independent risk factors for the development of MCs at the corresponding lumbar levels. Interestingly, body mass index might be not associated with MCs for the Chinese population.

Anterior Spinal Growth Modulation in Skeletally Immature Patients with Idiopathic Scoliosis: A Comparison with Posterior Spinal Fusion at 2 to 5 Years Postoperatively

BACKGROUND

Anterior vertebral body tethering (AVBT) has been introduced as a means of correcting scoliosis without fusion. The purpose of this study was to compare outcomes for patients with thoracic idiopathic scoliosis between a group of patients who underwent AVBT and a matched cohort of patients treated with posterior spinal fusion and instrumentation (PSF).

METHODS

A retrospective study of patients who underwent AVBT and PSF for idiopathic scoliosis was conducted. The inclusion criteria were determined on the basis of the AVBT cohort: primary thoracic idiopathic scoliosis with a curve magnitude between 40° and 67°, Risser stage of ≤1, age of 9 to 15 years, no prior spine surgery, index surgery between 2011 and 2016, and minimum follow-up of 2 years. Demographic, radiographic, clinical, and patient-reported outcomes and revisions were compared between groups.

RESULTS

There were 23 patients in the AVBT cohort and 26 patients in the PSF cohort. The mean follow-up (and standard deviation) was similar between groups: 3.4 ± 1.1 years for the AVBT group and 3.6 ± 1.6 years for the PSF group (p = 0.6). Preoperatively, the groups were similar in all measurements of radiographic and clinical deformity, with mean main thoracic curves of 53° ± 8° for the AVBT group and 54° ± 7° for the PSF group (p = 0.4). At the time of final follow-up, the AVBT cohort had significantly more residual deformity, with a mean thoracic curve of 33° ± 18° compared with 16° ± 6° for the PSF group (p < 0.001). There were 9 revision procedures in the AVBT cohort (with 3 conversions to PSF and 3 more pending) and none in the PSF cohort. Revisions occurred at a mean postoperative time of 2.3 years (range, 1.2 to 3.7 years). Twelve patients (52%) had evidence of broken tethers; of these patients, 4 underwent revision. The post-intervention patient-reported outcomes were similar.

CONCLUSIONS

Both AVBT and PSF resulted in postoperative correction; however, 2-year correction was better maintained in the PSF group. There were no differences in post-intervention patient-reported outcomes. AVBT resulted in less deformity correction and more revision procedures than PSF, but resulted in the delay or prevention of PSF in the majority of patients.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Non-Fusion Surgical Correction of Thoracic Idiopathic Scoliosis Using a Novel, Braided Vertebral Body Tethering Device: Minimum Follow-up of 4 Years

Anterior vertebral body tethering to effect scoliosis correction in a growing spine has been shown to work with varying degrees of success. This report describes the mid-term results of this technique using a new device composed of a braided ultra-high molecular weight polyethylene (UHMWPE) cord anchored to bone screws applied without segmental compression.

Methods

This was a single-center prospective observational study of an investigational device. Five female patients aged 9 to 12 years with thoracic scoliosis underwent thoracoscopic insertion of the UHMWPE tether. Radiographs and magnetic resonance imaging (MRI) were performed, and the Scoliosis Research Society (SRS)-22 was administered, preoperatively and at regular intervals after surgery, with a minimum of 4 years of follow-up.

Results

All tethering devices spanning the end vertebrae (range, 7 to 8 vertebrae) were implanted successfully. Mean blood loss was 136 mL, and the mean operative time was 205 minutes. The mean preoperative main thoracic Cobb angle was 40.1°. Curve correction of the tethered segment ranged from 0% to 133.3% at 4 years. We observed greater correction in 2 patients with open triradiate cartilage (TRC), achieving full scoliosis correction at 2 years and 121.5% at 4 years. MRI showed improvement in periapical disc wedging morphology and 55% improvement of rotation at 3 years. There were 20 adverse events, of which 16 were mild and 4 were moderate in severity. The 4 moderate events of pneumonia, distal decompensation, curve progression, and overcorrection occurred in 3 patients, 2 of whom required fusion.

Conclusions

Anterior vertebral body tethering resulted in scoliosis deformity correction in the coronal and axial planes, with preservation of curve flexibility. Actual correction by growth modulation was noted only in patients with open TRC, whereas curve stabilization was noted in patients with closed TRC. Overcorrection, curve progression, and distal decompensation are problems with this technique.

Level of Evidence

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Early-term postoperative thoracic outcomes of videothoracoscopic vertebral body tethering surgery

Background

This study aims to discuss the early-term postoperative thoracic complications in videothoracoscopic anterior vertebral body tethering surgery.

Methods

The study included 56 patients (3 males, 53 females; mean age 12.6 years; range, 10 to 16 years) operated with a total of 65 videothoracoscopic anterior vertebral body tethering surgeries between April 2014 and November 2018. Surgical indications were adolescents with different growth potentials, who had thoracic, thoracolumbar or double curves less than 70°. Surgical details and postoperative thoracic complications were recorded.

Results

Forty-two patients were administered thoracic tether, whereas five and nine patients were administered thoracolumbar tether and both approaches concomitantly, respectively. Two patients developed ipsilateral total atelectasis, one patient contralateral lobar atelectasis, one patient chylothorax, one patient pleural effusion, and one patient pneumothorax after chest drain removal. Overall thoracic complication rate was 9.2% and 30-day readmission rate was 1.8%. All patients achieved their rehabilitation goals.

Conclusion

Videothoracoscopy-assisted anterior vertebral body tethering is a safe and efficient technique that yields low complication rates. Early postoperative functional results are promising with high patient satisfaction. Pre- and postoperative respiratory rehabilitation may decrease thoracic complication rates.

Dynamic Scoliosis Correction as Alternative Treatment for Patients with Adolescent Idiopathic Scoliosis: a Non-Fusion Surgical Technique

Anterior dynamic scoliosis correction is an innovative non-fusion option in the treatment of patients with severe adolescent scoliosis. Growth modulation and sometimes intraoperative curve correction is achieved by convex insertion of segmental screws and a flexible polyethylene cord. The present review analyses and discusses the current literature and proposes a new treatment algorithm that is based on our own experience. Short term results are published for approximately 100 patients from different institutions. Fusion could be prevented in the vast majority of patients. Perioperative complication rate is very low but a few cases of cord rupture and overcorrection are reported. Anterior dynamic scoliosis correction has promising short term results but there is a paucity of literature and optimal criteria for the best candidate has yet to be defined.

Sagittal Balance Correction Following Lumbar Interbody Fusion: A Comparison of the Three Approaches

STUDY DESIGN

Retrospective cohort study.

PURPOSE

The objective of this study was to compare three widely used interbody fusion approaches in regard to their ability to correct sagittal balance, including pelvic parameters.

OVERVIEW OF LITERATURE

Restoration of sagittal balance in lumbar spine surgery is associated with better postoperative outcomes. Various interbody fusion techniques can help to correct sagittal balance, with no clear consensus on which technique offers the best correction.

METHODS

The charts and imaging of patients who have undergone surgery through either open transforaminal lumbar interbody fusion (TLIF), minimally invasive TLIF (MIS TLIF), or oblique lumbar interbody fusion (OLIF) were retrospectively reviewed. The following sagittal balance parameters were measured pre- and postoperatively: segmental lordosis, lumbar lordosis, disk height, pelvic tilt, and pelvic incidence. Data on postoperative complications were gathered.

RESULTS

Only OLIF managed to significantly improve segmental lordosis (4.4°, p <0.001) and lumbar lordosis (4.8°, p =0.049). All approaches significantly augmented disk height, with OLIF having the greatest effect (3.7°, p <0.001). No approaches were shown to significantly correct pelvic tilt. Pelvic incidence remained unchanged in all approaches. Open TLIF was the only approach with a higher rate of postoperative complications (33%, p =0.009).

CONCLUSIONS

The OLIF approach might offer greater correction of sagittal balance over open and MIS TLIF, mainly in regard to segmental lordosis, lumbar lordosis, and disk height. MIS TLIF, although offering more limited access than open TLIF, was not inferior to open TLIF in regard to sagittal balance correction. A higher rate of complications was shown for open TLIF than the other approaches, possibly due to its more invasive nature.

Correlation of Functional Outcomes and Sagittal Alignment After Long Instrumented Fusion for Degenerative Thoracolumbar Spinal Disease

STUDY DESIGN

A retrospective function and radiography study of the patients who have received long instrumented thoracolumbar fusion.

OBJECTIVE

To investigate the correlation between the sagittal spinopelvic alignment and the functional outcomes after long instrumented fusion for degenerative thoracolumbar spinal disease.

SUMMARY OF BACKGROUND DATA

Restoring better sagittal alignment is known as a key factor to spine fusion surgeries. The relationship between function and radiographic results in the elderly group is barely known.

METHODS

Between 2009 and 2013, data of 120 patients with multilevel degenerative thoracolumbar spinal disease who underwent long instrumented fusion were collected retrospectively. Perioperative radiographic and functional parameters were measured and analyzed for their correlations. Receiver operating characteristic (ROC) method was used to define ideal cutoff points of postoperative spinopelvic alignment to avoid poor outcome.

RESULTS

Oswestry disability index (ODI) more than or equal to 20 or Visual analogue scale (VAS) more than or equal to 4 were defined as poor functional outcomes. The optimal cutoff points of the radiographic parameters were found as below: the mismatch between pelvic incidence and lumbar lordosis was 16.2°, sagittal vertical axis was 38.5 mm, and pelvic tilt was 23.4°. Poor functional outcomes were significantly correlated with bad sagittal alignment, older age, and poor preoperative function.

CONCLUSION

Postoperative functional outcomes were highly impacted by the spinopelvic sagittal alignment.

LEVEL OF EVIDENCE

4.

Relationship Between Modic Changes and Sagittal Balance Parameters in the Cervical Spine

Background

We explored the possible relationship between Modic changes (MCs) and sagittal parameters of the cervical spine.

Material/Methods

We enrolled 150 patients with cervical MC on the magnetic resonance imaging (MRI) scans in the MC (+) group and divided them into 3 sub-groups with 50 patients each: the MC1 sub-group, the MC2 sub-group, and the MC3 sub-group. Another 150 healthy subjects receiving routine health examinations were also enrolled in the study as the MC (−) group. The sagittal parameters in the cervical spine were measured and compared and multiple logistic regression analysis was performed to analyze the risk factor for the occurrence of MC.

Results

Four cervical sagittal parameters were measured and compared between all the enrolled groups, including neck tilt (NT), T1 slope (T1s), thoracic inlet angle (TIA), and Cobb C2–C7. The results confirmed that the parameter of Cobb C2–C7 was much smaller in the MC(+) group when compared with that in the MC(−) group (P<0.05), while no significant differences were detected between the MC(+) and MC(−) groups for the parameters of NT, T1 T1s, and TIA (P>0.05). Multiple logistic regression analysis showed that Cobb C2–C7 (less than 8.5°) could be regarded as the risk factor for the occurrence of MC, and the receiver operating characteristic (ROC) curve showed that moderate diagnostic significance was obtained with an area under curve (AUC) of 0.82.

Conclusions

The present study demonstrated that Cobb C2–C7 (less than 8.5°) is a potential risk factor for the development of MC.

Early-onset Scoliosis: Contemporary Decision-making and Treatment Options

Early-onset scoliosis (EOS) describes a wide array of diagnoses and deformities exposed to growth. This potentially life-threatening condition is still 1 of the biggest challenges in pediatric orthopaedics. The enlightenment of Bob Campbell's thoracic insufficiency syndrome concept and the negative impact of the earlier short and straight spine fusion approach on respiratory function and survival have fueled the evolution of EOS care. Despite all the progress made, growth-friendly spine surgery remains to be a burden to patients and caregivers. Even down-sized implants and remote-controlled noninvasive rod expansions do not omit unexpected returns to the operating room: failures of foundations, rod breakage, difficulties to keep the sagittal balance, progressive transverse plane deformities, stiffening, and the need for final instrumented fusion are still common. However, past experience and the current multitude of surgical strategies and implants have sharpened the decision-making process, patients with thoracic insufficiency syndrome require earliest possible vertical expandable prosthetic titanium ribs application. Flexible deformities below 60 degrees, with normal spinal anatomy and without thoracic involvement, benefit from serial Mehta casting which revived as a long available but not-used strategy. In case of progression, standard double growing rods or-if available, affordable, and applicable-magnetically controlled motorized rods provide deformity control and growth promotion. Shilla growth-guiding technique is a less costly alternative. Its lack of stiff lengthening boxes or actuators may be beneficial in difficult deformities. Anterior convex flexible tethering promises benefits of sparing the trunk muscles and keeping mobility. However, this step towards a true nonfusion concept has yet to stand the test of broad clinical application.

Maternal Diets Deficient in Vitamin D Increase the Risk of Kyphosis in Offspring: A Novel Kyphotic Porcine Model

BACKGROUND

The purpose of this study was to explore the role of perinatal vitamin-D intake on the development and characterization of hyperkyphosis in a porcine model.

METHODS

The spines of 16 pigs were assessed at 9, 13, and 17 weeks of age with radiography and at 17 weeks with computed tomography (CT), magnetic resonance imaging (MRI), histology, and bone-density testing. An additional 169 pigs exposed to 1 of 3 maternal dietary vitamin-D levels from conception through the entire lactation period were fed 1 of 4 nursery diets supplying different levels of vitamin D, calcium, and phosphorus. When the animals were 13 weeks of age, upright lateral spinal radiography was performed with use of a custom porcine lift and sagittal Cobb angles were measured in triplicate to determine the degree of kyphosis in each pig.

RESULTS

The experimental animals had significantly greater kyphotic sagittal Cobb angles at all time points when compared with the control animals. These hyperkyphotic deformities demonstrated no significant differences in Hounsfield units, contained a slightly lower ash content (46.7% ± 1.1% compared with 50.9% ± 1.6%; p < 0.001), and demonstrated more physeal irregularities. Linear mixed model analysis of the measured kyphosis demonstrated that maternal diet had a greater effect on sagittal Cobb angle than did nursery diet and that postnatal supplementation did not completely eliminate the risk of hyperkyphosis.

CONCLUSIONS

Maternal diets deficient in vitamin D increased the development of hyperkyphosis in offspring in this model.

CLINICAL RELEVANCE

This study demonstrates that decreased maternal dietary vitamin-D intake during pregnancy increases the risk of spinal deformity in offspring. In addition, these data show the feasibility of generating a large-animal spinal-deformity model through dietary manipulation alone.

Novel porcine experimental model of severe progressive thoracic scoliosis with compensatory curves induced by interpedicular bent rigid temporary tethering

Using flexible tethering techniques, porcine models of experimental scoliosis have shown scoliotic curves with vertebral wedging but very limited axial rotation. The aim of this experimental work was to induce a severe progressive scoliosis in a growing porcine model for research purposes. A unilateral spinal bent rigid tether was anchored to two ipsilateral pedicle screws in eight pigs. The spinal tether was removed after 8 weeks. Ten weeks later, the animals were sacrificed. Conventional radiographs and 3D CT-scans were taken to evaluate changes in the alignment of the thoracic spine. After the first 8 weeks of rigid tethering, all animals developed scoliotic curves (mean Cobb angle: 24.3°). Once the interpedicular tether was removed, the scoliotic curves progressed in all animals during 10 weeks reaching a mean Cobb angle of 49.9°. The sagittal alignment of the thoracic spine showed loss of physiologic kyphosis (Mean: -18.3°). Axial rotation ranged from 10° to 49° (Mean 25.7°). Release of the spinal tether results in progression of the deformity with the development of proximal and distal compensatory curves. In conclusion, temporary interpedicular tethering at the thoracic spine induces severe scoliotic curves in pigs, with significant wedging and rotation of the vertebral bodies, and true compensatory curves.

CLINICAL RELEVANCE

The tether release model will be used to evaluate corrective non-fusion technologies in future investigations. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:174-182, 2018.

Risk of Implant Loosening After Cyclic Loading of Fusionless Growth Modulation Techniques: Nitinol Staples Versus Flexible Tether

STUDY DESIGN

Biomechanical evaluation using porcine spines.

OBJECTIVE

Compare the fixation strength of two currently used fusionless adolescent idiopathic scoliosis correction techniques following cyclic loading using porcine spines.

SUMMARY OF BACKGROUND DATA

The ability of fusionless implants to control or correct scoliosis in a growing patient requires such implants to maintain spinal fixation. Because they cross the disc, motion may weaken fixation over time.

METHODS

Eight pig spines were divided into cycled segments (T10-T13) and uncycled segments (T7-T8, L2-L3). Initial range of motion (ROM) was determined in torsion, flexion-extension, and lateral bending (0.5°/s to 1.75 N·m).Staple group (n = 4): 6 mm parallel staples were inserted on the right anterolateral spine across each intervertebral disc. Cycled segments received six staples (three adjacent discs) and uncycled segments received four staples (two separate discs).Tether group (n = 4): 5.35 × 35 mm right anterolateral vertebral body screws were placed into each vertebra. Cycled segments received four screws and uncycled segments received four screws. Screws in cycled segments were connected with a flexible tether tensioned to straight alignment.ROM of instrumented cycled segments was measured, and then segments were loaded to the measured ROM in flexion-extension (2000 cycles), lateral bending (1000 cycles), and axial rotation (2000 cycles). Implants were axially loaded to failure. Parametric tests compared pre- to postimplant ROM; nonparametric tests compared staple to screw pullout strength; P < 0.05 was significant.

RESULTS

There were no differences in ROM before instrumentation between groups. ROM was not changed except tethers decreased left lateral bending (-6.2°). Although staple pullout was less than screw pullout for cycled and uncycled segments (P < 0.05 and P = 0.057, respectively), there was no difference in pullout strength with and without cyclic loading for either group (P = 0.4).

CONCLUSION

Tethers decreased lateral bending away from the tether. Screws had almost five times greater load to failure than staples. Five thousand cycles did not result in loosening of either staple or tether screws.

LEVEL OF EVIDENCE

N/A.

Utility of an allograft tendon for scoliosis correction via the costo-transverse foreman

Current convex tethering techniques for treatment of scoliosis have centered on anterior convex staples or polypropylene tethers. We hypothesized that an allograft tendon tether inserted via the costo-transverse foramen would correct an established spinal deformity. In the pilot study, six 8-week-old pigs underwent allograft tendon tethering via the costo-transverse foreman or sham to test the strength of the transplanted tendon to retard spine growth. After 4 months, spinal deformity in three planes was induced in all animals with allograft tendons. In the treatment study, the allograft tendon tether was used to treat established scoliosis in 11 8-week-old pigs (spinal deformity > 50°). Once the deformity was observed (4 months) animals were assigned to either no treatment group or allograft tendon tether group and progression assessed by monthly radiographs. At final follow-up, coronal Cobb angle and maximum vertebral axial rotation of the treatment group was significantly smaller than the non-treatment group, whereas sagittal kyphosis of the treatment group was significantly larger than the non-treatment group. In sum, a significant correction was achieved using a unilateral allograft tendon spinal tether, suggesting that an allograft tendon tethering approach may represent a novel fusion-less procedure to correct idiopathic scoliosis. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:183-192, 2017.

Thoracic spine morphology of a pseudo-biped animal model (kangaroo) and comparisons with human and quadruped animals

PURPOSE

Based on the structural anatomy, loading condition and range of motion (ROM), no quadruped animal has been shown to accurately mimic the structure and biomechanical function of the human spine. The objective of this study is to quantify the thoracic vertebrae geometry of the kangaroo, and compare with adult human, pig, sheep, and deer.

METHODS

The thoracic vertebrae (T1-T12) from whole body CT scans of ten juvenile kangaroos (ages 11-14 months) were digitally reconstructed and geometric dimensions of the vertebral bodies, endplates, pedicles, spinal canal, processes, facets and intervertebral discs were recorded. Similar data available in the literature on the adult human, pig, sheep, and deer were compared to the kangaroo. A non-parametric trend analysis was performed.

RESULTS

Thoracic vertebral dimensions of the juvenile kangaroo were found to be generally smaller than those of the adult human and quadruped animals. The most significant (p < 0.001) correlations (Rho) found between the human and kangaroo were in vertebrae and endplate dimensions (0.951 ≤ Rho ≤ 0.963), pedicles (0.851 ≤ Rho ≤ 0.951), and inter-facet heights (0.891 ≤ Rho ≤ 0.967). The deer displayed the least similar trends across vertebral levels.

CONCLUSIONS

Similarities in thoracic spine vertebral geometry, particularly of the vertebrae, pedicles and facets may render the kangaroo a more clinically relevant human surrogate for testing spinal implants. The pseudo-biped kangaroo may also be a more suitable model for the human thoracic spine for simulating spine deformities, based on previously published similarities in biomechanical loading, posture and ROM.

Local Epiphyseal Growth Modulation for the Early Treatment of Progressive Scoliosis: Experimental Validation Using a Porcine Model

STUDY DESIGN

Experimental study of a localized device for the control of the vertebral growth using an immature porcine model.

OBJECTIVE

The aim of the study was to experimentally evaluate a localized device acting on the epiphyseal growth plates without bridging the intervertebral disc of immature hybrid pigs over 3 months of growth.

SUMMARY OF BACKGROUND DATA

Based on current published literature, fusionless devices offer promising scoliosis treatment alternatives to conventional spinal instrumentation and fusion in the growing spine. Current compression-based devices achieve growth modulation while also compressing the intervertebral discs, increasing the risk of long-term disc degeneration.

METHODS

An intravertebral staple acting on both the superior and inferior growth plates was inserted locally over T7-T9 of seven healthy immature pigs. Four age-matched animals served as controls. Radiographs were acquired monthly to assess induced spinal curvature and vertebral wedging (inverse model). Global (spinal) and local (vertebral, discal) geometric changes were evaluated over 3-months follow-up. Final left/right vertebral height differences were also quantified.

RESULTS

The only postoperative complication observed was one pig that had a persistent deep infection and was excluded from the study. No significant changes in spinal alignment were reported in control animals. Final induced Cobb angle was 25.0° ± 4.2° measured over T7-T9, with no observable sagittal profile modification. Highest vertebral wedging occurred at T9 with 18.2° ± 2.7°. Cumulative vertebral wedging over T7-T9 accounted for 45.4°, demonstrating evidence of reversed disc wedge phenomenon. Vertebral height was 3.9 ± 1.0 mm shorter on the instrumented side suggesting full growth restraint. Local and regional induced deformities significantly differed from their control counterparts (P < 0.001).

CONCLUSION

In this animal model, the local epiphyseal device achieved significant localized growth modulation over as little as three instrumented levels, with explicit vertebral wedging exclusive of the intervertebral disc. By increasing the number of instrumented levels, one may achieve higher curvature control potentially providing a unique local correction method to correct spinal deformity without affecting the intervertebral disc.

LEVEL OF EVIDENCE

5.

Delayed lymphocele formation following lateral lumbar interbody fusion of the spine

PURPOSE

This paper aims to describe the rare post-operative complication of a lymphocele formation after lateral lumbar interbody fusion.

METHODS

The patient in this case was a 76-year-old lady with a 10 year history of low back pain and neurogenic claudication. She had previously underwent multiple spine surgeries for her condition. She presented to our institution for a recurrence of her low back pain and right anterior thigh pain. She then underwent surgery in two stages; first, a mini-open lateral interbody fusion at L3/4 and L4/5; second, posterior instrumentation of T3 to S1 with sagittal spinal deformity correction.

RESULTS

The patient recovered uneventfully in the initial post op period and was discharged within 8 days. However, she developed abdominal distension and discomfort 6 months after surgery. MRI and CT scan of her abdomen showed a retroperitoneal fluid collection compressing her left ureter, resulting in hydroureter and hydronephrosis. She was managed with a CT-guided drainage of the fluid collection. Fluid analysis was consistent with a lymphocele. Since the procedure, the patient has been asymptomatic for 2 years.

CONCLUSIONS

Delayed lymphocele formation is a potential complication of lateral lumbar interbody fusion. When present, it can be managed conservatively with good results. This case suggests that surgeons should have a low threshold to investigate for a lymphocele development post-anterior or lateral lumbar spine surgery. The authors recommend the placement of a post surgical retroperitoneal drain, as it might assist in the early detection of a lymphocele formation.

Addition of TLIF does not improve outcome over standard posterior instrumented fusion. 5-10 years long-term Follow-up: results from a RCT

PURPOSE

The use of inter-body device in lumbar fusions has been difficult to validate, only few long-term RCT are available.

METHODS

Between 2003 and 2005, 100 patients entered a RCT between transforaminal lumbar inter-body fusion (TLIF) or posterolateral instrumented lumbar fusion (PLF). The patients suffered from LBP due to segmental instability, disc degeneration, former disc herniation, spondylolisthesis Meyerding grade <2. Functional outcome parameters as Dallas pain questionnaire (DPQ), SF-36, low back pain questionnaire (LBRS), Oswestry disability index (ODI) were registered prospectively, and after 5-10 years.

RESULTS

Follow-up reached 93 % of available, (94 %, 44 in the PLF's and 92 %, 44 in the TLIF group p = 0.76). Mean follow-up was 8.6 years (5-10 years). Mean age at follow-up was 59 years (34-76 years p = 0.19). Reoperation rate in a long-term perspective was equal among groups 14 %, each p = 0.24. Back pain was 3.8 (mean) (Scale 0-10), TLIF (3.65) PLF (3.97) p = 0.62, leg pain 2.68 (mean) (Scale 0-10) 2.90 (TLIF) and 2.48 (PLF) p = 0.34. No difference in functional outcome between groups p = 0.93. Overall, global satisfaction with the primary intervention at 8.6 year was 76 % (75 % TLIF and 77 % PLF) p = 0.85.

CONCLUSION

In a long-term perspective, patients with TLIF's did not experience better outcome scores.

An initial biomechanical investigation of fusionless anterior tether constructs for controlled scoliosis correction

BACKGROUND CONTEXT

Conservative treatment for adolescent idiopathic scoliosis is often unsuccessful and requires surgical intervention. Theoretically, anterior fusionless surgery can achieve correction as the patient grows to skeletal maturity.

PURPOSE

The objective of the present study was to determine differences in range of motion (ROM) between multiple anterior tether constructs and tensioning techniques. Coronal plane Cobb angles were evaluated.

STUDY DESIGN/SETTING

This is a cadaveric biomechanical study.

METHODS

Cadaveric spines underwent biomechanical testing to investigate two factors relevant to anterior tether reconstruction: (1) effect of fixation at the T4, superior, and T12, inferior, levels (S-I), as opposed to fixation at all T4-T12 continuous levels (Cont.); and (2) tensioning of the tether sequentially (SEQ T) or only at terminal points (T). Reconstructions were conducted at Cont., and ROM and coronal plane Cobb angles were measured. Rigid rods (R) were used as control for the tether. Funding for the present study was provided by Globus Medical, Inc., and three of five authors are employees of Globus Medical, Inc.

RESULTS

Normalized lateral bending ROM for intact was 100(±33)%. The S-I R construct reduced motion to 39(±8)%. Tethering at terminal points resulted in ROM for S-I T and S-I No T of 61(±21)% and 70(±17)%, respectively. Screws placed at every level resulted in motion of 28(±9)% for the Cont. R construct, and a stepwise increase in motion to 44(±15)%, 47(±18)%, and 71(±19)%, respectively, for Cont. SEQ T, Cont. T, and Cont. No T. These relative trends were the same in all loading modes. Average change in overall coronal plane Cobb angle from intact was 4.6(±3.2)° and 9.9(±5.5)° for Cont. T and Cont. SEQ T constructs, respectively.

CONCLUSIONS

Tensioned tether constructs allowed greater ROM than rigid constructs, and no significant difference in ROM was noted between tensioning techniques. Sequential tensioning can produce greater correction with no biomechanical advantage.

Postoperative cervical sagittal imbalance negatively affects outcomes after surgery for cervical spondylotic myelopathy

STUDY DESIGN

Prospective observational cohort study.

OBJECTIVE

To determine if postoperative cervical sagittal balance is an independent predictor of health-related quality of life outcome after surgery for cervical spondylotic myelopathy.

SUMMARY OF BACKGROUND DATA

Both ventral and dorsal fusion procedures for CSM are effective at reducing the symptoms of myelopathy. The importance of cervical sagittal balance in predicting overall health-related quality of life outcome after ventral versus dorsal surgery for CSM has not been previously explored.

METHODS

A prospective, nonrandomized cohort of 49 patients undergoing dorsal and ventral fusion surgery for CSM was examined. Preoperative and postoperative C2-C7 sagittal vertical axis was measured on standing lateral cervical spine radiographs. Outcome was assessed with 2 disease-specific measures-the modified Japanese Orthopedic Association scale and the Oswestry Neck Disability Index and 2 generalized outcome measures-the Short-Form 36 physical component summary (SF-36 PCS) and Euro-QOL-5D. Assessments were performed preoperatively, and at 3 months, 6 months, and 1 year postoperatively. Statistical analyses were performed using SAS version 9.3 (SAS Institute).

RESULTS

Most patients experienced improvement in all outcome measures regardless of approach. Both preoperative and postoperative C2-C7 sagittal vertical axis measurements were independent predictors of clinically significant improvement in SF-36 PCS scores (P = 0.03 and P = 0.02). The majority of patients with C2-C7 sagittal vertical axis values greater than 40 mm did not improve from an overall health-related quality of life perspective (SF-36 PCS) despite improvement in myelopathy. The postoperative sagittal balance value was inversely correlated with a clinically significant improvement of SF-36 PCS scores in patients undergoing dorsal surgery but not ventral surgery (P = 0.03 vs. P = 0.93).

CONCLUSION

Preoperative and postoperative sagittal balance measurements independently predict clinical outcomes after surgery for CSM.

LEVEL OF EVIDENCE

2.

The role of minimally invasive lateral lumbar interbody fusion in sagittal balance correction and spinal deformity

PURPOSE

The recent proliferation of minimally invasive lateral lumbar interbody fusion (LLIF) techniques has drawn attention to potential for these techniques to control or correct sagittal misalignment in adult spinal deformity. We systemically reviewed published studies related to LLIF use in adult spinal deformity treatment with emphasis on radiographic assessment of sagittal balance.

METHODS

A literature review was conducted to examine studies focusing on sagittal balance restoration in adult degenerative scoliosis with the LLIF approach.

RESULTS

Fourteen publications, 12 retrospective and 2 prospective, reported data regarding lumbar lordosis correction (1,266 levels in 476 patients) but only two measured global sagittal alignment.

CONCLUSION

LLIF appears to be especially effective when the lumbar lordosis and sagittal balance correction goals are less than 10° and 5 cm, respectively. However, the review demonstrated a lack of consistent reporting on sagittal balance restoration with the MIS LLIF techniques.

Trunk Control Ability after Minimally Invasive Lumbar Fusion Surgery during the Early Postoperative Phase

[Purpose] Lumbar fusion has been used for spinal disorders when conservative treatment fails. The minimally invasive approach causes minimal damage to the back muscles and shortens the postoperative recovery time. However, evidence regarding functional recovery in patients after minimally invasive lumbar spinal fusion is limited. The purpose of this study was to investigate how trunk control ability is affected after minimally invasive lumbar fusion surgery during the early postoperative phase. [Subjects and Methods] Sixteen patients and 16 age- and sex-matched healthy participants were recruited. Participants were asked to perform a maximum forward reaching task and were evaluated 1 day before and again 1 month after the lumbar fusion surgery. Center of pressure (COP) displacement, back muscle strength, and scores for the Visual Analog Scale, and Chinese version of the modified Oswestry Disability Index (ODI) were recorded. [Results] The healthy control group exhibited more favorable outcomes than the patient group both before and after surgery in back strength, reaching distance, reaching velocity, and COP displacement. The patient group improved significantly after surgery in all clinical outcome measurements. However, reaching distance decreased, and the reaching velocity as well as COP displacement did not differ before and after surgery. [Conclusion] The LBP patients with lumbar fusion surgery showed improvement in pain intensity 1 month after surgery but no improvement in trunk control during forward reaching. The results provide evidence that the back muscle strength was not fully recovered in patients 1 month after surgery and limited their ability to move their trunk forward.

Guideline update for the performance of fusion procedures for degenerative disease of the lumbar spine. Part 11: Interbody techniques for lumbar fusion

Interbody fusion techniques have been promoted as an adjunct to lumbar fusion procedures in an effort to enhance fusion rates and potentially improve clinical outcome. The medical evidence continues to suggest that interbody techniques are associated with higher fusion rates compared with posterolateral lumbar fusion (PLF) in patients with degenerative spondylolisthesis who demonstrate preoperative instability. There is no conclusive evidence demonstrating improved clinical or radiographic outcomes based on the different interbody fusion techniques. The addition of a PLF when posterior or anterior interbody lumbar fusion is performed remains an option, although due to increased cost and complications, it is not recommended. No substantial clinical benefit has been demonstrated when a PLF is included with an interbody fusion. For lumbar degenerative disc disease without instability, there is moderate evidence that the standalone anterior lumbar interbody fusion (ALIF) has better clinical outcomes than the ALIF plus instrumented, open PLF. With regard to type of interbody spacer used, frozen allograft is associated with lower pseudarthrosis rates compared with freeze-dried allograft; however, this was not associated with a difference in clinical outcome.

Extraspinal ossifications after implantation of vertical expandable prosthetic titanium ribs (VEPTRs)

INTRODUCTION

Though developed for thoracic insufficiency syndrome, the spinal growth-stimulating potential and the ease of placement of vertical expandable titanium ribs (VEPTRs) has resulted in their widespread use for early-onset spine deformity. Observation of implant-related ossifications warrants further assessment, since they may be detrimental to the function-preserving non-fusion strategy.

PATIENTS AND METHODS

Radiographs (obtained pre and post index procedure, and at 4-year follow-up) and the records of 65 VEPTR patients from four paediatric spine centres were analysed. Ossifications were classified as type I (at anchor points), type II (along the central part) or type III (re-ossification after thoracostomy).

RESULTS

The average age at the index procedure was 6.5 years (min 1, max 13.7). The most prevalent spine problem was congenital scoliosis (37) with rib fusions (34), followed by neuromuscular and syndromic deformities (13 and 8, respectively). Idiopathic and secondary scoliosis (e.g. after thoracotomy) were less frequent (3 and 4, respectively). Forty-two of the 65 (65 %) patients showed ossifications, half of which were around the anchors. Forty-five percent (15/33) without pre-existing rib fusions developed a type II ossification along the implant. Re-ossifications of thoracostomies were less frequent (5/34, 15 %). The occurrence of ossifications was not associated with patient-specific factors.

CONCLUSIONS

Implant-related ossifications around VEPTR are common. In contrast to harmless bone formation around anchors, ossifications around the telescopic part and the rod section are troublesome in view of their possible negative impact on chest cage compliance and spinal mobility. This potential side effect needs to be considered during implant selection, particularly in patients with originally normal thoracic and spinal anatomy.

Evaluation of pelvic morphology in the sagittal plane

BACKGROUND CONTEXT

It is generally accepted that for normal subjects the angle of pelvic incidence (PI) increases during childhood and then remains unchanged throughout adolescence and adulthood. However, recent findings show that PI increases linearly throughout the lifespan due to morphological changes of the pelvis.

PURPOSE

A retrospective study aiming to determine the extent of morphological changes of the pelvis related to the age of the subjects.

STUDY DESIGN

Pelvic morphology was evaluated in a normal adult population by measuring the anatomical parameters of sagittal pelvic alignment.

PATIENT SAMPLE

The final study cohort consisted of 330 subjects (mean age, 45.3 years; standard deviation, 18.1 years; range, 18-87 years; 164 male and 166 female subjects).

OUTCOME MEASURES

Physiologic measures, obtained as measurements of PI, sacral end plate width (S1W), and pelvic thickness (PTH).

METHODS

Parameters of PI, S1W, and PTH were evaluated from computed tomography images of the subjects. The measured PTH was normalized according to S1W and age of the subjects, allowing the comparison among anatomies of different sizes. The normalized components of PTH in anteroposterior and cephalocaudal directions were computed to determine the configuration and extent of changes in pelvic morphology related to subject age.

RESULTS

Statistically significant correlation with both age and PI was obtained for all normalized parameters (except for the anteroposterior component of PTH for male subjects), and no statistically significant differences were observed between the sexes. With increasing PI that occurs due to the aging process, a decrease of PTH can be observed that is manifested not only as an increase of the distance between the sacrum and the hip axis in the anterior direction but considerably more as a decrease of the distance between the sacrum and the hip axis in the cephalic direction. By considering these morphological changes in the pelvis simultaneously, the hip axis can move only within a narrow area.

CONCLUSIONS

The changes in pelvic morphology due to the aging process occur in the anterior direction, which may be due to the remodeling process affecting the coxal bone that results in an anterior drift of the acetabulum relative to the sacrum. More importantly, the changes are considerably more evident in the cephalic direction, which may be the result of the weight-bearing loads and consequent wear of acetabular cartilage.