Motion preservation surgery for scoliosis with a vertebral body tethering system: a biomechanical study

Purpose

There is a paucity of studies on new vertebral body tethering (VBT) surgical constructs especially regarding their potentially motion-preserving ability. This study analyses their effects on the ROM of the spine.

Methods

Human spines (T10-L3) were tested under pure moment in four different conditions: (1) native, (2) instrumented with one tether continuously connected in all vertebrae from T10 to L3, (3) additional instrumented with a second tether continuously connected in all vertebrae from T11 to L3, and (4) instrumented with one tether and one titanium rod (hybrid) attached to T12, L1 and L2. The instrumentation was inserted in the left lateral side. The intersegmental ROM was evaluated using a magnetic tracking system, and the medians were analysed. Please check and confirm the author names and initials are correct. Also, kindly confirm the details in the metadata are correct. The mentioned information is correct

Results

Compared to the native spine, the instrumented spine presented a reduction of less than 13% in global ROM considering flexion–extension and axial rotation. For left lateral bending, the median global ROM of the native spine (100%) significantly reduced to 74.6%, 66.4%, and 68.1% after testing one tether, two tethers and the hybrid construction, respectively. In these cases, the L1-L2 ROM was reduced to 68.3%, 58.5%, and 38.3%, respectively. In right lateral bending, the normalized global ROM of the spine with one tether, two tethers and the hybrid construction was 58.9%, 54.0%, and 56.6%, respectively. Considering the same order, the normalized L1-L2 ROM was 64.3%, 49.9%, and 35.3%, respectively.

Conclusion

The investigated VBT techniques preserved global ROM of the spine in flexion–extension and axial rotation while reduced the ROM in lateral bending.

     

Minimally invasive cortical bone trajectory screws placement via pedicle or pedicle rib unit in the lower thoracic spine: a cadaveric and radiographic study

Purpose

To evaluate the feasibility of cortical bone trajectory (CBT) screws fixation via pedicle or pedicle rib unit in the cadaveric thoracic spine (T9–T12).

Methods

Computed tomography (CT) images of 100 patients are analyzed by multiplanar reconstruction. Ten cadaveric thoracic spines are used to insert 4.5 × 35.0 mm CBT screws at all levels from T9 to T12.

Results

Maximal screw length obtained by CT has a tendency to gradually increase from T9 (29.64 mm) to T12 (32.84 mm), and the difference reaches significant level at all levels except T9 versus T10 (P < 0.01). Maximal screw diameter increases from T9 (4.92 mm) to T12 (7.47 mm) and the difference reaches significant level among all levels (P < 0.01). Lateral angle increases from T9 (7.37°) to T12 (10.47°), and the difference reaches significant level among all levels except T11 versus T12. Cephalad angle from T9 to T12 are 19.03°, 22.10°, 25.62° and 27.50° (P < 0.01), respectively. The percentage of the inner and outer pedicle breakage are 2.5 and 22.5 %, respectively. The violation of lateral pedicle wall occurs at T9 and T10, especially for women at T9.

Conclusions

Both radiographic and cadaveric studies establish the feasibility of CBT screws placement via pedicle or pedicle rib unit in the lower thoracic spine (T9–T12). Furthermore, our measurements are also useful for application of this technique.

     

Residual motion of different posterior instrumentation and interbody fusion constructs

Purpose

To elucidate residual motion of cortical screw (CS) and pedicle screw (PS) constructs with unilateral posterior lumbar interbody fusion (ul-PLIF), bilateral PLIF (bl-PLIF), facet-sparing transforaminal lumbar interbody fusion (fs-TLIF), and facet-resecting TLIF (fr-TLIF).

Methods

A total of 35 human cadaver lumbar segments were instrumented with PS (n = 18) and CS (n = 17). Range of motion (ROM) and relative ROM changes were recorded in flexion/extension (FE), lateral bending (LB), axial rotation (AR), lateral shear (LS), anterior shear (AS), and axial compression (AC) in five instrumentational states: without interbody fusion (wo-IF), ul-PLIF, bl-PLIF, fs-TLIF, and fr-TLIF.

Results

Whereas FE, LB, AR, and AC noticeably differed between the instrumentational states, AS and LS were less prominently affected. Compared to wo-IF, ul-PLIF caused a significant increase in ROM with PS (FE + 42%, LB + 24%, AR + 34%, and AC + 77%), however, such changes were non-significant with CS. ROM was similar between wo-IF and all other interbody fusion techniques. Insertion of a second PLIF (bl-PLIF) significantly decreased ROM with CS (FE -17%, LB -26%, AR -20%, AC -51%) and PS (FE − 23%, LB − 14%, AR − 20%, AC − 45%,). Facet removal in TLIF significantly increased ROM with CS (FE + 6%, LB + 9%, AR + 17%, AC of + 23%) and PS (FE + 7%, AR + 12%, AC + 13%).

Conclusion

bl-PLIF and TLIF show similarly low residual motion in both PS and CS constructs, but ul-PLIF results in increased motion. The fs-TLIF technique is able to further decrease motion compared to fr-TLIF in both the CS and PS constructs.

     

‘Higher the grade-smaller the pedicle’: a study of pedicle dimensional variations in 100 cases of high grade lytic spondylolisthesis

Purpose

To measure the pedicle dimensions in high grade lytic spondylolisthesis (HGL) and to classify them, which helps the spine surgeon in proper selection of pedicle screws.

Methods

A study of CT scans in 100 consecutive patients between Jan 2017 and April 2021 diagnosed as single-level HGL on standing radiographs. Pedicle height (PH), Pedicle width (PW), Differential pedicle height (DPH), Screw length (SL) and Transverse pedicle angle (TPA) were measured and analyzed. PH and PW were classified into four grades as—grade A less than 5.0 mm, grade B between 5.0 and 6.0 mm, grade C between 6.0 and 7.0 mm, and grade D above 7.0 mm.

Results

5 males and 95 females with mean age of 49.1 years. PH in 44% lytic vertebra were grade A, B (less than 6 mm) and the rest 56% had grade C, D (greater than 6 mm). PH averaged 6.6 mm in grade 3 HGL, 5.61 mm in grade 4 HGL. Change in PW, SL and TPA was not statistically significant with regards to grade or level of listhesis. A total of 37 cases were noted to have DPH (25 cases had a difference < 2 mm and 12 had a difference > 2 mm).

Conclusion

44% of the PH in lytic vertebra was grade A and B (less than 6 mm) that stresses the importance of pre-op CT assessment and planning the appropriate screw dimensions. Change in PH was statistically significant with regards to the grade of listhesis (P-value < 0.01). Differential pedicle height also need to be looked for.

     

Computed tomographic-based morphometric study of thoracic spine and its relevance to anaesthetic and spinal surgical procedures

BackgroundTo collect a baseline computer software aided normative morphometric data of thoracic spine in the Indian population and analyze it to give pre-procedural guidelines to clinicians for safe surgical and anaesthetic procedures in the thoracic spine.MethodsCT scans of thoracic spine of patients free from spinal disorders were reviewed in a total of 600 vertebrae in 50 patients. Parameters recorded with the help of computer software were pedicle width, length and height, transverse pedicle angles, chord length, canal dimensions, body width and height, spinous process angle and transverse process length.ResultsPedicle width decreased from T1 (9.27 ± 1.01) to T4 (4.5 ± 0.93) and increased to T12 (8.31 ± 1.83). At T4 76% and at T5 62% of the pedicles were smaller than 5 mm and would not accept 4 mm screw with 1.0-mm clearance. However, at T1 2%, at T11 7% and at T12 8% would not accept a 4 mm screw. Chord length gradually increased in upper thoracic vertebrae and was relatively constant in middle and decreased in lower thoracic vertebrae. Shortest estimated chord length was at T1 (30.30 ± 2.11). On an average, from T1 to T6 and at T11 and T12, a screw length of 25–30 mm could be accommodated and from T7 to T10, 30–35 mm screw length could be accommodated. Transverse pedicle angle decreased from T1 (35.4 ± 2.21) to T12 (−9.8 ± 2.39). Canal dimensions were narrowest at T4/T5 (20.02 ± 1.23) in anteroposterior and 21.12 ± 1.23 in interpedicular diameters. Spinous process angle increased from T1 (30.11 ± 6.74) to T6 (57.89 ± 9.31) and decreased to 16.21 ± 7.38 at T12. Transverse process length increased from T1 to T7 (23.54 + 2.12 to 31.21 + 1.91) and then decreased to 12.11 + 2.3 at T12. Vertebral body dimensions showed increasing trends from T1 to T12.ConclusionsA thorough knowledge of anatomical and radiological characteristics of the spine and their variations is essential for the clinicians. Data collected in the present study provides baseline normative values in Indian population and will help in guiding safe and effective completion of both surgical and anaesthetic procedures in the thoracic spine. Computer software aided morphometric data can help in selecting appropriate size and optimal placement of the implant with minimal procedural difficulties and complications during spine surgery.     

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.

     

Determination of torque-limits for human and cat lumbar spine specimens during displacement-controlled physiological motions

Background contextQuadruped animal models have been validated and used as biomechanical models for the lumbar spine. The biomechanics of the cat lumbar spine has not been well characterized, even though it is a common model used in neuromechanical studies.PurposeCompare the physiological ranges of motion and determine torque-limits for cat and human lumbar spine specimens during physiological motions.Study design/settingBiomechanics study.Patient sampleCat and human lumbar spine specimens.Outcome measuresIntervertebral angle (IVA), joint moment, yield point, torque-limit, and correlation coefficients.MethodsCat (L2–sacrum) and human (T12–sacrum) lumbar spine specimens were mechanically tested to failure during displacement-controlled extension (E), lateral bending (LB), and axial rotation (AR). Single trials consisted of 10 cycles (10 mm/s or 5°/s) to a target displacement where the magnitude of the target displacement was increased for subsequent trials until failure occurred. Whole-lumbar stiffness, torque at yield point, and joint stiffness were determined. Scaling relationships were established using equations analogous to those that describe the load response of elliptically shaped beams.ResultsIVA magnitudes for cat and human lumbar spines were similar during physiological motions. Human whole-lumbar and joint stiffness magnitudes were significantly greater than those for cat spine specimens (p<.05). Torque-limits were also greater for humans compared with cats. Scaling relationships with high correlation (R² greater than 0.77) were established during later LB and AR.ConclusionsThe current study defined “physiological ranges of movement” for human and cat lumbar spine specimens during displacement-controlled testing, and should be observed in future biomechanical studies conducted under displacement control.     

Properties of an interspinous fixation device (ISD) in lumbar fusion constructs: a biomechanical study

BackgroundSegmental fixation improves fusion rates and promotes patient mobility by controlling instability after lumbar surgery. Efforts to obtain stability using less invasive techniques have lead to the advent of new implants and constructs. A new interspinous fixation device (ISD) has been introduced as a minimally invasive method of stabilizing two adjacent interspinous processes by augmenting an interbody cage in transforaminal interbody fusion. The ISD is intended to replace the standard pedicle screw instrumentation used for posterior fixation.PurposeThe purpose of this study is to compare the rigidity of these implant systems when supplementing an interbody cage as used in transforaminal lumbar interbody fusion.Study designAn in vitro human cadaveric biomechanical study.MethodsSeven human cadaver spines (T12 to the sacrum) were mounted in a custom-designed testing apparatus, for biomechanical testing using a multiaxial robotic system. A comparison of segmental stiffness was carried out among five conditions: intact spine control; interbody spacer (IBS), alone; interbody cage with ISD; IBS, ISD, and unilateral pedicle screws (unilat); and IBS, with bilateral pedicle screws (bilat). An industrial robot (KUKA, GmbH, Augsburg, Germany) applied a pure moment (±5 Nm) in flexion-extension (FE), lateral bending (LB), and axial rotation (AR) through an anchor to the T12 vertebral body. The relative vertebral motion was captured using an optoelectronic camera system (Optotrak; Northern Digital, Inc., Waterloo, Ontario, Canada). The load sensor and the camera were synchronized. Maximum rotation was measured at each level and compared with the intact control. Implant constructs were compared with the control and with each other. A statistical analysis was performed using analysis of variance.ResultsA comparison between the intact spine and the IBS group showed no significant difference in the range of motion (ROM) in FE, LB, or AR for the operated level, L3–L4. After implantation of the ISD to augment the IBS, there was a significant decrease in the ROM of 74% in FE (p<.001) but no significant change in the ROM in LB and AR. The unilat construct significantly reduced the ROM by 77% compared with FE control (p<.001) and by 55% (p=.002) and 42% (p=.04) in LB and AR, respectively, compared with control. The bilat construct reduced the ROM in FE by 77% (p<.001), LB by 77% (p=.001), and AR by 65% (p=.001) when compared with the control spine. There was no statistically significant difference in the ROM in FE among the stand-alone ISD, unilat, and bilat constructs. However, in both LB and AR, the unilat and the bilat constructs were significantly stiffer (reduction in the ROM) than the ISD and the IBS combination. The ISD stability in LB and AR was not different from the intact control with no instrumentation at all. There was no statistical difference between the stability of the unilat and the bilat constructs in any direction. However, LB and AR in the unilat group produced a mean rotation of 3.83°±3.30° and 2.33°±1.33°, respectively, compared with the bilat construct that limited motion to 1.96°±1.46° and 1.39°±0.73°. There was a trend suggesting that the bilat construct was the most rigid construct.ConclusionsIn FE, the ISD can provide lumbar stability comparable with Bilat instrumentation. It provides minimal rigidity in LB and AR when used alone to stabilize the segment after an IBS placement. The unilat and the more typical bilat screw constructs were shown to provide similar levels of stability in all directions after an IBS placement, though the bilat construct showed a trend toward improved stiffness overall.     

Incidence of complications associated with cervical spine surgery and post-operative physical therapy and implications for timing of initiation of post-operative physical therapy: a retrospective database study

Purpose

To describe the incidence of complications associated with cervical spine surgery and post-operative physical therapy (PT), and to identify if the timing of initiation of post-operative PT impacts the incidence rates.

Methods

MOrtho PearlDiver database was queried using billing codes to identify patients who had undergone Anterior Cervical Discectomy and Fusion (ACDF), Posterior Cervical Fusion (PCF), or Cervical Foraminotomy and post-operative PT from 2010–2019. For each surgical procedure, patients were divided into three 12-week increments for post-operative PT (starting at post-operative weeks 2, 8, 12) and then matched based upon age, gender, and Charlson Comorbidity Index score. Each group was queried to determine complication rates and chi-square analysis with adjusted odds ratios, 95% confidence intervals, and p-values were used.

Results

Following matching, 3,609 patients who underwent cervical spine surgery at one or more levels and had post-operative PT (ACDF:1784, PCF:1593, and cervical foraminotomy:232). The most frequent complications were new onset cervicalgia (2–14 weeks, 8–20 weeks, 12–24 weeks): ACDF (15.0%, 14.0%, 13.0%), PCF (18.8%, 18.0%, 19.9%), cervical foraminotomy (16.8%, 16.4%, 19.4%); revision: ADCF (7.9%, 8.2%, 7.4%), PCF (9.3%, 10.6%, 10.2%), cervical foraminotomy (11.6%, 10.8% and 13.4%); wound infection: ACDF (3.3%, 3.4%, 3.1%), PCF (8.3%, 8.0%,7.7%), cervical foraminotomy (5.2%, 6.5%, < 4.7%). None of the comparisons were statistically significant.

Conclusion

The most common post-operative complications included new onset cervicalgia, revision and wound infection. Complications rates were not impacted by the timing of initiation of PT whether at 2, 8, or 12 weeks post-operatively.

     

Biomechanics of the lower thoracic spine after decompression and fusion: a cadaveric analysis

Background contextFew studies have evaluated the extent of biomechanical destabilization of thoracic decompression on the upper and lower thoracic spine. The present study evaluates lower thoracic spinal stability after laminectomy, unilateral facetectomy, and unilateral costotransversectomy in thoracic spines with intact sternocostovertebral articulations.PurposeTo assess the biomechanical impact of decompression and fixation procedures on lower thoracic spine stability.Study designBiomechanical cadaveric study.MethodsSequential surgical decompression (laminectomy, unilateral facetectomy, unilateral costotransversectomy) and dorsal fixation were performed on the lower thoracic spine (T8–T9) of human cadaveric spine specimens with intact rib cages (n=10). An industrial robot was used to apply pure moments to simulate flexion-extension (FE), lateral bending (LB), and axial rotation (AR) in the intact specimens and after decompression and fixation. Global range of motion (ROM) between T1–T12 and intrinsic ROM between T7–T11 were measured for each specimen.ResultsThe decompression procedures caused no statistically significant change in either global or intrinsic ROM compared with the intact state. Instrumentation, however, reduced global motion for AR (45° vs. 30°, p=.0001), FE (24° vs. 19°, p=.02), and LB (47° vs. 36°, p=.0001) and for intrinsic motion for AR (17° vs. 4°, p=.0001), FE (8° vs. 1°, p=.0001), and LB (12° vs. 1°, p=.0001). No significant differences were identified between decompression of the upper versus lower thoracic spine, with trends toward significantly greater ROM for AR and lower ROM for LB in the lower thoracic spine.ConclusionsThe lower thoracic spine was not destabilized by sequential unilateral decompression procedures. Addition of dorsal fixation increased segment rigidity at intrinsic levels and also reduced overall ROM of the lower thoracic spine to a greater extent than did fusing the upper thoracic spine (level of the true ribs). Despite the lack of true ribs, the lower thoracic spine was not significantly different compared with the upper thoracic spine in FE and LB after decompression, although there were trends toward significance for greater AR after decompression. In certain patients, instrumentation may not be needed after unilateral decompression of the lower thoracic spine; further validation and additional clinical studies are warranted.     

Thoracic bone mineral density measured by quantitative computed tomography in patients undergoing spine surgery

BACKGROUND CONTEXTThe thoracic spine is a common location for vertebral fractures as well as instrumentation failure after long spinal fusion procedures. The association between those complications and bone mineral density (BMD) are well recognized. Due to the overlying sternum and ribs in the thoracic spine, projectional BMD assessment tools such as dual energy x-ray absorptiometry (DXA) are limited to the lumbar spine. Quantitative computed tomography circumvents several shortcomings of DXA and allows for level-specific BMD measurements. Studies comprehensively quantifying BMD of the entire thoracic spine in patients undergoing spine surgery are limited.PURPOSEThe objective of this study was: (1) to assess the reliability of thoracic QCT measurements, (2) to determine possible level-specific BMD variation throughout the thoracic spine and (3) to assess the correlation between BMDs of the T1-T12 spinal levels.STUDY DESIGN/SETTINGCross-sectional observation study.PATIENT SAMPLEPatients undergoing spine surgery from 2016–2020 at a single, academic institution with available preoperative CT imaging of the thoracic spine were included in this study.OUTCOME MEASURESThe outcome measure was BMD measured by QCT.METHODSPatients undergoing spine surgery from 2016–2020 at a single, academic institution with available preoperative CT imaging of the thoracic spine were included in this study. Subjects with previous instrumentation at any thoracic level, concurrent vertebral fractures, a Cobb angle of more than 20 degrees, or incomplete thoracic spine CT imaging were excluded. Asynchronous quantitative computed tomography (QCT) measurements of T1-T12 were performed. To assess inter- and intra-observer reliability, a validation study was performed on 120 vertebrae in 10 randomly selected patients. The interclass correlation coefficient (ICC) was calculated. A pairwise comparison of BMD was conducted and correlations between each thoracic level were evaluated. The statistical significance level was set at p<.05.RESULTS60 patients (men, 51.7%) met inclusion criteria. The study population was 90% Caucasian with a mean age of 62.2 years and a mean BMI of 30.2 kg/m². The inter- and intra-observer reliability of the thoracic QCT measurements was excellent (ICC of 0.97 and 0.97, respectively). The trabecular BMD was highest in the upper thoracic spine and decreased in the caudal direction (T1 = 182.3 mg/cm³, T2 = 168.1 mg/cm³, T3 = 163.5 mg/cm³, T4 = 164.7 mg/cm³, T5 = 161.4 mg/cm³, T6 = 152.5 mg/cm³, T7 = 143.5 mg/cm³, T8 = 141.3 mg/cm³, T9 = 143.5 mg/cm³, T10 = 145.1 mg/cm³, T11 = 145.3 mg/cm³, T12 = 133.6 mg/cm³). The BMD of all thoracic levels cranial to T6 was statistically higher than the BMD of all levels caudal to T6 (p < .001). Nonetheless, significant correlations in BMD among all measured thoracic levels were observed, with a Pearson's correlation coefficient ranging from 0.74 to 0.97.CONCLUSIONSThere is significant regional BMD variation in the thoracic spine depending on spinal level. This BMD variation might contribute to several clinically relevant phenomena. First, vertebral fractures occur most commonly at the thoracolumbar junction including T12. In addition to mechanical reasons, these fractures might be partially attributed to thoracic BMD that is lowest at T12. Second, the optimal upper instrumented vertebra (UIV) for stopping long fusions to the sacrum and pelvis is controversial. The BMD of surgically relevant upper thoracic stopping points (T2-T4) was significantly higher than the BMD of lower thoracic stopping points (T10-T12). Besides stress concentration at the relatively mobile lower thoracic segments, the low BMD at these levels might contribute to previously suggested higher rates of junctional failures with short fusions.     

Biomechanical analysis of the upper thoracic spine after decompressive procedures

Background contextDecompressive procedures such as laminectomy, facetectomy, and costotransversectomy are routinely performed for various pathologies in the thoracic spine. The thoracic spine is unique, in part, because of the sternocostovertebral articulations that provide additional strength to the region relative to the cervical and lumbar spines. During decompressive surgeries, stability is compromised at a presently unknown point.PurposeTo evaluate thoracic spinal stability after common surgical decompressive procedures in thoracic spines with intact sternocostovertebral articulations.Study designBiomechanical cadaveric study.MethodsFresh-frozen human cadaveric spine specimens with intact rib cages, C7–L1 (n=9), were used. An industrial robot tested all spines in axial rotation (AR), lateral bending (LB), and flexion-extension (FE) by applying pure moments (±5 Nm). The specimens were first tested in their intact state and then tested after each of the following sequential surgical decompressive procedures at T4–T5 consisting of laminectomy; unilateral facetectomy; unilateral costotransversectomy, and subsequently instrumented fusion from T3–T7.ResultsWe found that in all three planes of motion, the sequential decompressive procedures caused no statistically significant change in motion between T3–T7 or T1–T12 when compared with intact. In comparing between intact and instrumented specimens, our study found that instrumentation reduced global range of motion (ROM) between T1–T12 by 16.3% (p=.001), 12% (p=.002), and 18.4% (p=.0004) for AR, FE, and LB, respectively. Age showed a negative correlation with motion in FE (r=?0.78, p=.01) and AR (r=?0.7, p=.04).ConclusionsThoracic spine stability was not significantly affected by sequential decompressive procedures in thoracic segments at the level of the true ribs in all three planes of motion in intact thoracic specimens. Age appeared to negatively correlate with ROM of the specimen. Our study suggests that thoracic spinal stability is maintained immediately after unilateral decompression at the level of the true ribs. These preliminary observations, however, do not depict the long-term sequelae of such procedures and warrant further investigation.     

Anatomical variations of the foramen transversarium in cervical vertebrae: findings,review of the literature,and clinical significance during cervical spine surgery

Purpose

To describe certain anatomical variations of the foramen transversarium, in spine cervical vertebrae in a contemporary specimen of an Indo-European population and approach their clinical importance during cervical spine surgery.

Methods

102 cervical vertebrae (C₂–C₇) from 17 different skeletons, intact without any degenerative or traumatic disorders, which belonged to the collection of the Department of Anatomy, were examined. The age of specimens at the time of their death was between 25 and 65 years. All foramina were measured with a digital caliper.

Results

The average size of the normal foramina was: 6.49 mm × 5.74 mm on the right side and 6.65 mm × 5.76 mm on the left side. Regarding the variations, we found two cervical vertebrae (1.96 %), one C₃ and one C₆, in which the right foramen transversarium is clearly smaller than the left. The exact dimensions of these foramina are: 2.3 mm × 2.5 mm on the right side and 6.54 mm × 8 mm on the left side in the first vertebra and 2.8 mm × 3.74 mm on the right side and 6 mm × 7.5 mm on the left side, in the second one. We also observed double foramina in 14 vertebrae (13.72 %). In seven vertebrae, the duplication was bilateral (6.86 %). We finally found one vertebra (0.98 %) with triplication of the foramen transversarium on the left side.

Conclusions

Summarizing, 10 out of our 17 skeletons were presented with variations (extremely narrow or multiple foramina). This finding of hypoplastic, duplicated and triplicated foramina transversaria in unexpectedly high rates raises questions about the integrity of the contained structures, the possibility of a different path for them. These variations may induce an extra-osseous position of the vertebra artery, and the ignorance of such an event may have catastrophic consequences during a surgery in the cervical spine.

     

Effects of a microgravity SkinSuit on lumbar geometry and kinematics

Purpose

Astronauts returning from long ISS missions have demonstrated an increased incidence of lumbar disc herniation accompanied by biomechanical and morphological changes associated with spine elongation. This research describes a ground-based study of the effects of an axial compression countermeasure Mk VI SkinSuit designed to reload the spine and reduce these changes before return to terrestrial gravity.

Methods

Twenty healthy male volunteers aged 21–36 without back pain participated. Each lay overnight on a Hyper Buoyancy Flotation (HBF) bed for 12 h on two occasions 6 weeks apart. On the second occasion participants donned a Mk VI SkinSuit designed to axially load the spine at 0.2 Gz during the last 4 h of flotation. Immediately after each exposure, participants received recumbent MRI and flexion–extension quantitative fluoroscopy scans of their lumbar spines, measuring differences between spine geometry and intervertebral kinematics with and without the SkinSuit. This was followed by the same procedure whilst weight bearing. Paired comparisons were performed for all measurements.

Results

Following Mk VI SkinSuit use, participants evidenced more flexion RoM at L3–4 (p = 0.01) and L4–5 (p = 0.003), more translation at L3–4 (p = 0.02), lower dynamic disc height at L5–S1 (p = 0.002), lower lumbar spine length (p = 0.01) and greater lordosis (p = 0.0001) than without the Mk VI SkinSuit. Disc cross-sectional area and volume were not significantly affected.

Conclusion

The MkVI SkinSuit restores lumbar mobility and lordosis following 4 h of wearing during hyper buoyancy flotation in a healthy control population and may be an effective countermeasure for post space flight lumbar disc herniation.

     

Long-term Remission of Type 2 Diabetes and Patient Survival After Biliopancreatic Diversion with Duodenal Switch

Purpose

This study investigates the long-term effects of biliopancreatic diversion with duodenal switch (BPD-DS) on patients with advanced type 2 diabetes mellitus (T2DM) while paying special attention to preoperative diabetes severity.

Materials and Methods

A retrospective analysis was conducted using prospective and current data on patients who underwent an open BPD-DS 6–12 years ago. Patients were stratified according to preoperative diabetes severity into 4 groups (group 1: oral antidiabetic drugs only; group 2: insulin?<?5 years; group 3: insulin 5–10 years; group 4: insulin?>?10 years). The primary endpoint was T2DM remission rate 6–12 years after BPD-DS as a function of preoperative diabetes severity.

Results

Ninety-one patients with advanced T2DM were included. Sixty-two patients were available for follow-up (rate of 77%). Follow-up was performed (mean?±?SD) 8.9?±?1.3 years after surgery. Glycated hemoglobin (HbA_1c) levels were 9.4?±?2.0% before surgery and decreased to 5.1?±?0.8% after 1 year and 5.4?±?1.0% after 6–12 years. Insulin discontinuation rate after surgery as well as the rate of long-term remission decreased steadily from groups 1 to 4, while long-term mortality increased. T2DM remission rates were 93%, 88%, 45%, and 40% in groups 1, 2, 3, and 4, respectively. Late relapse of T2DM occurred in 3 patients (5%).

Conclusions

BPD-DS causes a rapid and long-lasting normalization of glycemic metabolism in patients with advanced T2DM. T2DM remission rate after 6–12 years varies significantly (from 40% to more than 90%) and is highly dependent on preoperative diabetes severity.

Graphical abstract

     

Modified percutaneous biopsy of the spine: improvement of the technique

Purpose

Biopsy of the spine can be performed by open surgery or percutaneous needle sampling. The first has the highest diagnostic yield while the second is a less invasive procedure with lower rate of complications and shorter hospitalization time. We described a modified technique of percutaneous biopsy using semi-rigid grasping forceps that may offer the advantages of both, open and minimally invasive surgery.

Methods

Thirty consecutive patients with spinal lesions requiring biopsy were admitted to Neurosurgical Unit of Belcolle Hospital (Viterbo, Italy) from January 2017 to September 2021. There was a suspicion of spondylodiscitis in 25 cases and of tumor in 5 cases. Percutanous trans-pedicular spine biopsy has been performed using this new semi-rigid grasping forceps. Combining the opening width, jaw length and full 360° rotation, the device allows a wide and precise sampling.

Results

Sampling was sufficient in all cases (100%); tumors was observed in 5 cases (16.7%%) with a percentage of definitive histopathologic diagnosis of 100% (n = 5); among the remaining patients histological examination yielded a diagnosis of spinal infection in 25 cases (100%), and microbiologic culture provided an aetiologic diagnosis in 23 cases (92%). All procedures were well tolerated, and no postoperative complications were observed. Levels involved included: thoracic (T5-T9) in 8 cases, thoracolumbar junction (T10-L2) in 12 cases and lumbar (L3-L5) in 10 cases.

Conclusions:

Percutaneous biopsy with the semi-rigid grasping forceps is a safe and effective procedure that can be used for diagnosis of both infectious and tumor lesions of the spine. It allows to obtain a larger specimen volume and to use a multidirectional trajectory for sampling, resulting in a minimally invasive technique with strong ability to yield etiologic diagnosis.

     

Characteristics affecting cervical sagittal alignment in patients with chronic low back pain

BackgroundSagittal spino-pelvic malalignment in patients with chronic low back pain (CLBP) have been reported in the past, which may also affect cervical spine lesions. The purpose of this study is to investigate the cervical alignment in patients with CLBP.MethodOf the patients who visited an orthopedic specialist due to low back pain lasting more than three months, 121 cases (average 71.5-years-old, 46 male and 75 female) with whole standing spinal screening radiographs were reviewed (CLBP group). Cervical parameters included cervical lordosis (CL), C2–C7 sagittal vertical axis (C2-7 SVA), and the T1 slope minus CL (T1S-CL). Cervical spine deformity was defined as C2-7 SVA >4 cm, CL <0°, or T1S-CL ≧20°. We compared the cervical alignment of these patients with 121 age and gender matched volunteers (control group).ResultsThe prevalence of cervical spine deformity was significantly higher in the CLBP group than in the control group (20.7% vs. 10.7%, P = 0.034). The mean CL was smaller in the CLBP group than in the control group (16.1° vs. 21.4°, P = 0.002). The mean C2-7 SVA was 17.6 mm vs. 18.7 mm in the CLBP group and in the control group, respectively (P = 0.817). The mean T1S-CL was larger in the CLBP group than in the control group (9.1° vs. 3.5°, P < 0.001). Multivariate analysis showed that people with CLBP were more likely to have cervical deformities than people without CLBP (odds ratio 2.16, 95% confidence interval 1.006 to 4.637).ConclusionsThis study results suggest that people with CLBP present with worse cervical sagittal alignment and higher prevalence of cervical spine deformities than age and gender matched volunteers with no CLBP. This means CLBP impacts cervical spine lesions negatively.Level of evidenceⅣ     

What Are the Biomechanical Properties of the Taylor Spatial Frame™?

Background

The Taylor Spatial Frame™ (TSF) is a versatile variant of the traditional Ilizarov circular fixator. Although in widespread use, little comparative data exist to quantify the biomechanical effect of substituting the tried-and-tested Ilizarov construct for the TSF hexapod system.

Questions/purposes

This study was designed to investigate the mechanical properties of the TSF system under physiologic loads, with and without the addition of a simulated bone model, with comparison to the standard Ilizarov frame.

Methods

The mechanical behaviors of three identical four-ring TSF and Ilizarov constructs were tested under levels of axial compression, bending, and rotational torque to simulate loading during normal gait. An acrylic-pipe fracture model subsequently was mounted, using fine wires and 5 mm half pins, and the testing was repeated. Load-deformation curves, and so rigidity, for each construct were calculated, with statistical comparisons performed using paired t-tests.

Results

Under axial loading, the TSF was found to be less rigid than the Ilizarov frame (645 ± 57 N/mm versus 1269 ± 256 N/mm; mean difference, 623 N/mm; 95% CI, 438.3–808.5 N/mm; p < 0.001), but more rigid under bending and torsional loads (bending: 42 ± 9 Nm/degree versus 78 ± 13 Nm/degree; mean difference, 37 Nm/degree; 95% CI, 25.0–47.9 Nm/degree; p < 0.001; torsion: 16 ± 2 Nm/degree versus 5 ± 0.35 Nm/degree; mean difference, 11 Nm/degree; 95% CI, 9.5–12.2 Nm/degree; p < 0.001). On mounting the bone models, these relationships broadly remained in the half-pin and fine-wire groups, however the half-pin constructs were universally more rigid than those using fine wires. This effect resulted in the TSF, using half pins, showing no difference in axial rigidity to the fine-wire Ilizarov (107 ± 3 N/mm versus 107 ± 4 N/mm; mean difference, 0.05 N/mm; 95% CI, −6.99 to 7.1 N/mm; p > 0.999), while retaining greater bending and torsional rigidity. Throughout testing, a small amount of laxity was observed in the TSF construct on either side of neutral loading, amounting to 0.72 mm (±0.37 mm) for a change in loading between −10 N and 10 N axial load, and which persisted with the addition of the synthetic fracture model.

Conclusions

This study broadly shows the TSF construct to generate lower axial rigidity, but greater bending and torsional rigidity, when compared with the Ilizarov frame, under physiologic loads. The anecdotally described laxity in the TSF hexapod strut system was shown in vitro, but only at low levels of loading around neutral. It also was shown that the increased stiffness generated by use of half pins produced a TSF construct replicating the axial rigidity of a fine-wire Ilizarov frame, for which much evidence of good clinical and radiologic outcomes exist, while providing greater rigidity and so improved resistance to potentially detrimental bending and rotational shear loads.

Clinical Relevance

If replicated in the clinical setting, these findings suggest that when using the TSF, care should be taken to minimize the observed laxity around neutral with appropriate preloading of the construct, but that its use may produce constructs better able to resist bending and torsional loading, although with lower axial rigidity. Use of half pins in a TSF construct however may replicate the axial mechanical behavior of an Ilizarov construct, which is thought to be conducive to bone healing.

     

Tibial alignment following intramedullary nailing via three approaches

Purpose

The purpose of this study is to evaluate the incidence of malalignment in patients undergoing IMN for tibial shaft fractures treated with the extra-articular lateral parapatellar, suprapatellar, and infrapatellar approaches.

Methods

A retrospective review of an institutional trauma database was completed at a single level 1 trauma academic medical centre. Quality of reduction was assessed using the following three parameters: (1) < 10°of angulation in orthogonal radiographic views (2) < 5 mm of displacement between the major fracture fragments (3) < 5 mm of gap between the major fracture fragments. A good reduction was one that met all 3 criteria, an acceptable reduction met 2 criteria, and a bad reduction met one or none of the criteria. All patients treated consecutively for tibial shaft fractures between June 1, 2019 and June 1, 2020 were identified. The final cohort included 57 tibia fractures in 56 patients. Of the 57 tibia fractures, 8 (14%) were proximal third, 32 (56%) were middle third, and 17 (30%) were distal third fractures.

Results

We found no significant difference in angulation, displacement, or gapping with respect to surgical approach utilized or location of fracture (proximal or distal tibia fractures) on one-way ANOVA. Quality of reduction was rated as “good” in 48 (84%) of the cases (19 supra, 13 infra, and 16 lateral). Nine reductions (16%) met only two of the three reduction quality criteria and were considered acceptable reductions. These included 2 suprapatellar (1 > 5 mm displacement, 1 > 5 mm gapping), 4 infrapatellar (4 > 5 mm displacement), and 3 lateral extra-articular parapatellar (2 > 5 mm displacement and 1 > 5 mm gapping). No reductions were determined to be bad according the Baumgaertner et al. criteria. There was no significant difference in the rate of combined fibula fractures or the rate of fibular fixation between the three cohorts.

Conclusions

In conclusion, no significant difference was found in fracture reduction angulation, displacement, and gapping in patients treated with an IMN with respect to approach for diaphyseal or metadiaphyseal tibial shaft fractures.

     

The effect of various options for decompression of degenerated lumbar spine motion segments on the range of motion: a biomechanical in vitro study

Background

Lumbar spinal stenosis is a common disease in the aging population. Decompression surgery represents the treatment standard, however, a risk of segmental destabilization depending on the approach and extent of decompression is discussed. So far, biomechanical studies on techniques were mainly conducted on non-degenerated specimens. This biomechanical in vitro study aimed to investigate the increase in segmental range of motion (ROM) depending on the extent of decompression in degenerated segments.

Methods

Ten fresh frozen lumbar specimens were embedded in polymethyl methacrylate (PMMA) and loaded in a spine tester with pure moments of ± 7.5 Nm. The specimens were tested in their intact state for lateral bending (LB), flexion/extension (FE) and axial rotation (AR). Subsequently, four different decompression techniques were performed: unilateral interlaminar decompression (DC1), unilateral with "over the top" decompression (DC2), bilateral interlaminar decompression (DC3) and laminectomy (DC4). The ROM of the index segment was reported as percent (%) of the native state.

Results

Specimens were measured in their intact state prior to decompression. The mean ROM was defined as 100% (FE:6.3 ± 2.3°; LB:5.4 ± 2.8°; AR:3.0 ± 1.6°). Interventions showed a continuous ROM increase: FE (DC1: + 4% ± 4.3; DC2: + 4% ± 4.5; DC3: + 8% ± 8.3;DC4: + 20% ± 15.9), LB(DC1: + 4% ± 6.0; DC2: + 5% ± 7.3; DC3: + 8% ± 8.3; DC4: + 11% ± 9.9), AR (DC1: + 7% ± 6.0; DC2: + 9% ± 7.9; DC3: + 15% ± 11.5; DC4: + 19% ± 10.5). Significant increases in ROM for all motion directions (p < 0.05) were only obtained after complete laminectomy (DC4).

Conclusion

Unilateral and/or bilateral decompressive surgery resulted in a statistically insignificant ROM increase, whereas complete laminectomy showed statistically significant ROM increase. If this ROM increase also has an impact on the clinical outcome and how to identify segments at risk for secondary lumbar instability should be evaluated in further studies.