Axial Rotation Range Of Motion Research Articles

Neck stiffness and range of motion for young males and females

Well characterised mechanical response of the normal head-neck complex during passive motion is important to inform and verify physical surrogate and computational models of the human neck, and to inform normal baseline for clinical assessments. For 10 male and 10 female participants aged 20 to 29, the range of motion (ROM) of the neck about three anatomical axes was evaluated in active-seated, passive-lying and active-lying configurations, and the neck stiffness was evaluated in passive-lying. Electromyographic signals from the agonist muscles, normalised to maximum voluntary contractions, were used to provide feedback during passive motions. The effect of sex and configuration on ROM, and the effect of sex on linear estimates of stiffness in three regions of the moment–angle curve, were assessed with linear mixed models and generalised linear models. There were no differences in male and female ROM across all motion directions and configurations. Flexion and axial rotation ROM were configuration dependent. The passive-lying moment–angle relationship was typically non-linear, with higher stiffness (slope) closer to end of ROM. When normalising the passive moment–angle curve to active lying ROM, passive stiffness was sex dependent only for lateral bending region 1 and 2. Aggregate moment–angle corridors were similar for males and females in flexion and extension, but exhibited a higher degree of variation in applied moment for males in lateral bending and axial rotation. These data provide the passive response of the neck to low rate bending and axial rotation angular displacement, which may be useful for computational and surrogate modelling of the human neck.

Coupled rotation patterns in cervical spine axial rotation can change when the head is kept level

The biomechanical literature describes axial rotation occurring coupled with lateral bending and flexion in the cervical spine. Since the head is kept level during some activities of daily living, we set out to investigate the changes in total and segmental motion that occur when a level gaze constraint is applied to cadaveric cervical spine specimens during axial rotation. 1.5Nm of left and right axial rotation moment was applied to sixteen C2-T1 cadaveric specimens with C2 unconstrained and C2 constrained to simulate level gaze. Overall and segmental motions were determined using optoelectronic motion measurement and specimen-specific kinematic modeling. Without a kinematic constraint on C2, motions were as described in the literature; namely, flexion and lateral bending to the same side as axial rotation. Keeping C2 level reduced that total axial rotation range of motion of the specimens. Changes were also produced in segmental coupled rotation in all specimens. The observed changes included completely opposite coupled motion than in the uncoupled specimens, and traditional coupled behavior at one load extreme and the opposite at the other extreme. Constraining C2 during axial rotation to simulate level gaze can produce coupled motion that differs from the classically described flexion and lateral bending to the same side as axial rotation.Statement of Clinical Significance: Activities of daily living that require the head to be kept level during axial rotation of the cervical spine may produce segmental motions that are quite different from the classically described motions with implications for biomechanical experiments and implant designers.

Can Asymmetry in Total Knee Arthroplasty Design Lead to More Normal-Like Postoperative Kinematics? A Multi-Implant Evaluation

BackgroundFew studies have evaluated the effects of symmetrical versus asymmetrical implant designs, more specifically the femoral condyles, trochlear groove, joint line, and bearing surfaces. The objective of this study was to investigate multiple posterior cruciate-retaining (PCR) total knee arthroplasty (TKA) designs influencing factors related to TKA asymmetry, and to investigate whether asymmetry can improve postoperative knee kinematics. MethodsIn vivo tibio-femoral kinematics for 99 subjects was evaluated in this retrospective study. Overall, 10 subjects had a nonimplanted, normal knee, and 89 subjects had 1 of 3 PCR TKAs with varying degrees of asymmetry within their femoral and tibial components (PCR #1 = 30, PCR #2 = 29, PCR #3 = 30). All TKAs were implanted by the same surgeon and were analyzed using fluoroscopy during a deep knee bend. ResultsAt full extension, all 3 PCR TKAs experienced a more posteriorized position of the femoral condyles compared to the normal knee, with the 2 asymmetrical PCR TKAs experiencing more anteriorization compared to the third, symmetrical PCR TKA. Both the normal knee and the PCR TKA with greatest amount of asymmetry experienced statistically more posterior femoral rollback of the lateral condyle than the other 2 PCR TKAs. The PCR TKA with greater asymmetry also experienced statistically greater range of motion than the other 2 PCR TKAs. ConclusionsWith increasing flexion, the design with the most asymmetry also experienced the most posterior femoral rollback, axial rotation, and greatest range of motion. The results in this study seem to suggest that the inclusion of asymmetry in a TKA could be beneficial for achieving more normal-like kinematics and greater weight-bearing knee flexion.

The effects of Core Stability Exercises and Mulligan's mobilization with movement techniques on sacroiliac joint dysfunction.

Sacroiliac joint dysfunction (SIJD), while being the primary contributor to low back pain, is still disregarded and treated as low back pain. Mulligan's Mobilization with Movement (MWM) Techniques and Core Stability Exercises (CSE) are often used to treat low back pain. There is not much evidence that it is effective in SIJD. To evaluate the effectiveness of CSE coupled with MWM (CSE + MWM) in the treatment of SIJD. 39 patients with SIJD were recruited and randomly divided into distinct groups as follows: control group (n = 13), CSE group (n = 13) and CSE + MWM group (n = 13). The Numerical Pain Rating Scale (NPRS), the Roland Morris Disability Questionnaire (RMDQ), the Range of Motion (ROM), the Pressure Pain Threshold (PPT) and the pelvic tilt angle asymmetry ratio in the sagittal plane (PTAR) were used to gauge the intervention's success both before (M0) and after (M1) it. All experimental data were statistically analyzed. The SIJ-related pain metric significantly decreased in both the CSE + MWM group and the CSE group between M0 and M1, as determined by the NPRS and RMDQ. Between M0 and M1, The CSE group's left axial rotation ROM and lumbar flexion ROM were significantly decreased. The CSE + MWM group's extension ROM and left lateral flexion ROM both significantly increased between M0 and M1. In the difference variable (M1-M0), the CSE + MWM group substantially outperformed control group in the left lateral flexion ROM and outperformed the CSE group in the left axial rotation ROM. In individuals with SIJD, CSE + MWM is beneficial in lowering pain, disability, and function. Treatment with CSE and MWM approaches for SIJ appears to boost this efficacy.

The Effects of Cervical Orthoses on Head and Intervertebral Range of Motion.

Prospective Cohort. Quantify and compare the effectiveness of cervical orthoses in restricting intervertebral kinematics during multiplanar motions. Previous studies evaluating the efficacy of cervical orthoses measured global head motion and did not evaluate individual cervical motion segment mobility. Prior studies focused only on the flexion/extension motion. Twenty adults without neck pain participated. Vertebral motion from the occiput through T1 was imaged using dynamic biplane radiography. Intervertebral motion was measured using an automated registration process with validated accuracy better than 1 degree. Participants performed independent trials of maximal flexion/extension, axial rotation, and lateral bending in a randomized order of unbraced, soft collar (foam), hard collar (Aspen), and cervical thoracic orthosis (CTO) (Aspen) conditions. Repeated-measures ANOVA was used to identify differences in the range of motion (ROM) among brace conditions for each motion. Compared with no collar, the soft collar reduced flexion/extension ROM from occiput/C1 through C4/C5, and reduced axial rotation ROM at C1/C2 and from C3/C4 through C5/C6. The soft collar did not reduce motion at any motion segment during lateral bending. Compared with the soft collar, the hard collar reduced intervertebral motion at every motion segment during all motions, except for occiput/C1 during axial rotation and C1/C2 during lateral bending. The CTO reduced motion compared with the hard collar only at C6/C7 during flexion/extension and lateral bending. The soft collar was ineffective as a restraint to intervertebral motion during lateral bending, but it did reduce intervertebral motion during flexion/extension and axial rotation. The hard collar reduced intervertebral motion compared with the soft collar across all motion directions. The CTO provided a minimal reduction in intervertebral motion compared with the hard collar. The utility in using a CTO rather than a hard collar is questionable, given the cost and little or no additional motion restriction.

Determinants of spinal cord stress and strain in degenerative cervical myelopathy: a patient-specific finite element study.

Degenerative cervical myelopathy (DCM) is the commonest cause of spinal cord dysfunction in older adults and is characterized by chronic cervical spinal cord compression. Spinal cord stress and strain during neck motion are also known contributors to the pathophysiology of DCM, yet these factors are not routinely assessed for surgical planning. The aim of this study was to measure spinal cord stress/strain in DCM using patient-specific 3D finite element models (FEMs) and determine whether spinal cord compression is the primary determinant of spinal cord stress/strain. Three-dimensional patient-specific FEMs were created for six DCM patients (mild [n = 2], moderate [n = 2] and severe [n = 2]). Flexion and extension of the cervical spine were simulated with a pure moment load of 2 Nm. Segmental spinal cord von Mises stress and maximum principal strain were measured. Measures of spinal cord compression and segmental range of motion (ROM) were included in a regression analysis to determine associations with spinal cord stress and strain. Segmental ROM in flexion-extension and axial rotation was independently associated with spinal cord stress (p < 0.001) and strain (p < 0.001), respectively. This relationship was not seen for lateral bending. Segmental ROM had a stronger association with spinal stress and strain as compared to spinal cord compression. Compared to the severity of spinal cord compression, segmental ROM is a stronger determinant spinal cord stress and strain. Surgical procedures that address segmental ROM in addition to cord compression may best optimize spinal cord biomechanics in DCM.

Range of motion of the mid-cervical spine: human versus goat

BackgroundThe goat cervical spine represents a promising alternative for human specimen in spinal implant testing, but the range of motion (ROM) of the spine is lacking. We aimed to evaluate and compare the ROMs of fresh goat and human mid-cervical spine specimens.MethodsTen fresh adult healthy male goat cervical spine specimens (G group) and ten fresh frozen adult healthy human cervical spine specimens (average age: 49.5 ± 12.1 years; 6 males, 4 females) (H group) were included. The ROMs of each specimen were biomechanically tested at the C2–3, C3–4, C4–5 and C2–5 levels at 1.5 Nm and 2.5 Nm torque and recorded. The ROMs of different levels of goat cervical samples were compared to those of human cervical samples using an independent sample t test. Significance was defined as a P value of less than 0.05.ResultsAt the C2–3, C3–4 and C4–5 levels, the ROMs of the goat cervical spine were significantly larger than those of the human cervical spine in all directions except extension under 1.5 Nm torque; under 2.5 Nm torque, the ROMs of the goat cervical spine at the C2–3 and C3–4 levels were significantly larger than those of humans in the pure movement of flexion, lateral bending and axial rotation, and the ROMs for axial rotation of the goat specimens and human specimens were comparable. Under both 1.5 Nm and 2.5 Nm torque, the goat cervical spine displayed a much greater ROM in all directions at the C2–5 level.ConclusionsSeveral segmental ROMs of fresh goat and human cervical spine specimens were recorded in this investigation. We recommend using goat cervical specimens as an alternative to fresh human cervical specimens in future studies when focusing only on the ROMs of C2–3, C3–4 and C4–5 in flexion under a torque of 1.5 Nm or the ROMs of C2–3 and C3–4 in flexion and rotation under a torque of 2.5 Nm.

Effects of occipital-atlas stabilization on the upper cervical spine rotation combinations: an in vitro study

The purpose of this study is to compare axial rotation range of motion for the upper cervical spine during three movements: axial rotation, rotation + flexion + ipsilateral lateral bending and rotation + extension + contralateral lateral bending before and after occiput-atlas (C0–C1) stabilization. Ten cryopreserved C0–C2 specimens (mean age 74 years, range 63–85 years) were manually mobilized in 1. axial rotation, 2. rotation + flexion + ipsilateral lateral bending and 3. rotation + extension + contralateral lateral bending without and with a screw stabilization of C0–C1. Upper cervical range of motion and the force used to generate the motion were measured using an optical motion system and a load cell respectively. The range of motion (ROM) without C0–C1 stabilization was 9.8° ± 3.9° in right rotation + flexion + ipsilateral lateral bending and 15.5° ± 5.9° in left rotation + flexion + ipsilateral lateral bending. With stabilization, the ROM was 6.7° ± 4.3° and 13.6° ± 5.3°, respectively. The ROM without C0–C1 stabilization was 35.1° ± 6.0° in right rotation + extension + contralateral lateral bending and 29.0° ± 6.5° in left rotation + extension + contralateral lateral bending. With stabilization, the ROM was 25.7° ± 6.4° (p = 0.007) and 25.3° ± 7.1°, respectively. Neither rotation + flexion + ipsilateral lateral bending (left or right) or left rotation + extension + contralateral lateral bending reached statistical significance. ROM without C0–C1 stabilization was 33.9° ± 6.7° in right rotation and 28.0° ± 6.9° in left rotation. With stabilization, the ROM was 28.5° ± 7.0° (p = 0.005) and 23.7° ± 8.5° (p = 0.013) respectively. The stabilization of C0–C1 reduced the upper cervical axial rotation in right rotation + extension + contralateral lateral bending and right and left axial rotations; however, this reduction was not present in left rotation + extension + contralateral lateral bending or both combinations of rotation + flexion + ipsilateral lateral bending.

Biomechanical behaviour of tension-band-reconstruction titanium plate in open-door laminoplasty: a study based on finite element analysis

ObjectiveTo investigate and evaluate the biomechanical behaviour of tension-band-reconstruction (TBR) and ordinary titanium plates in open-door laminoplasty by finite element (FE) analysis.MethodsTBR titanium plate and ordinary titanium plate were implanted into a validated finite element model of healthy adult cervical vertebrae. Among them, 5 ordinary titanium plate were used in model A, 2 TBR titanium plates and 3 ordinary titanium plates were used in model B, and 5 TBR titanium plates were used in model C. The same loading conditions was applied identically to all models. Range of motion (ROM) of the vertebral body, stress distribution of the titanium plate and intradiscal pressure (IDP) were compared in flexion, extension, lateral bending and rotation.ResultsThe ROM of model B and C was similar in flexion and extension, and both were smaller than that of model A. The highest von Mises stress in the titanium plate appears is in model C. The IDP in C2/3 was significantly higher than that in other segments in flexion. There was no significant difference in IDP among three models in left lateral bending and left axial rotation.ConclusionApplication of TBR titanium plate in open-door laminoplasty can reduced ROM in flexion, extension and axial rotation of the cervical vertebrae. But the increase of stress in TBR titanium plate could lead to higher risk of adverse events such as titanium plate deformation. Moreover, compared with complete TBR titanium plate, the combination of TBR titanium plate for C3 and C7 with ordinary titanium plate for the other vertebrae largely reduce the stress of the titanium plates by ensuring stability. The proposed FE model (C2-T1) exhibits a great potential in evaluating biomechanical behaviour of TBR titanium plate for open-door laminoplasty.

In Vivo Changes in Dynamic Adjacent Segment Motion 1 Year After One and Two-Level Cervical Arthrodesis.

Biomechanical cadaver testing indicates adjacent segment motion increases after one-level anterior cervical spine arthrodesis, and two-level arthrodesis exacerbates these effects. There is little in vivo evidence to support those biomechanical studies. The purpose of this study was to assess the effects of one- and two-level cervical arthrodesis on adjacent segment motion. Fifty patients received either one-level C56 arthrodesis or two-level C456 or C567 arthrodesis and were tested preoperatively (PRE) and 1 year postoperatively (1YR-POST) along with 23 asymptomatic controls. A validated CT model-based tracking technique was used to measure 3D vertebral motion from biplane radiographs collected during dynamic flexion-extension and axial rotation of the cervical spine. Head and adjacent segment intervertebral end-range range of motion (ROM) and mid-range ROM were compared between one-level and two-level arthrodesis patients and controls. Small (2.3° or less) but non-significant increases in adjacent segment end-range ROM were observed from PRE to 1YR-POST. Mid-range flexion-extension ROM in the C67 motion segment inferior to the arthrodesis and mid-range axial rotation ROM in the C45 motion segment superior to the arthrodesis increased from PRE to 1YR-POST (all p < 0.022). This study provides in vivo evidence that contradicts long-held beliefs that adjacent segment end-range ROM increases appreciably after anterior cervical arthrodesis and that two-level arthrodesis exacerbates these effects. Mid-range ROM appears to be more useful than end-range ROM for detecting early changes in adjacent segment motion after cervical spine arthrodesis.

Biomechanical Study on Three Screw-Based Atlantoaxial Fixation Techniques: A Finite Element Study.

This is a finite element study. This study is aimed to compare the biomechanical behaviors of three screw-based atlantoaxial fixation techniques. Screw-based constructs that are widely used to stabilize the atlantoaxial joint come with their own challenges in surgery. Clinical and in vitro studies have compared the effectiveness of screw-based constructs in joint fixation. Nevertheless, there is limited information regarding the biomechanical behavior of these constructs, such as the stresses and strains they experience. A finite element model of the upper cervical spine was developed. A type II dens fracture was induced in the intact model to produce the injured model. The following three constructs were simulated on the intact and injured models: transarticular screw (C1- C2TA), lateral mass screw in C1 and pedicle screw in C2 (C1LM1-C2PD), and lateral mass screw in C1 and translaminar screw in C2 (C1LM1-C2TL). In the intact model, flexion-extension range of motion (ROM) was reduced by up to 99% with C11-C2TA and 98% with C1LM1-C2PD and C1LM1-C2TL. The lateral bending ROM in the intact model was reduced by 100%, 95%, and 75% with C11-C2TA, C1LM1-C2PD, and C1LM1-C2TL, respectively. The axial rotation ROM in the intact model was reduced by 99%, 98%, and 99% with C11-C2TA, C1LM1-C2PD, and C1LM1-C2TL, respectively. The largest maximum von Mises stress was predicted for C1LM1-C2TL (332 MPa) followed by C1LM1-C2PD (307 MPa) and C11-C2TA (133 MPa). Maximum stress was predicted to be at the lateral mass screw head of the C1LM1-C2TL construct. Our model indicates that the biomechanical stability of the atlantoaxial joint in lateral bending with translaminar screws is not as reliable as that with transarticular and pedicle screws. Translaminar screws experience large stresses that may lead to failure of the construct before the required bony fusion occurs.

In vivo 3-Dimensional Kinematics Study of the Healthy Cervical Spine Based on CBCT Combined with 3D-3D Registration Technology.

A cervical biomechanical study. We sought to demonstrate the three-dimensional (3D) intervertebral motion characteristics of the cervical spine in healthy volunteers using cone beam computed tomography (CBCT) combined with 3D-3D registration technology. No previous studies have used CBCT combined with 3D-3D registration technology to successfully documented in vivo 3D intervertebral six-degrees-of-freedom (6-DOF) motions of the cervical spine. Twenty healthy subjects underwent cervical (C1-C7) CBCT scans in seven functional positions. Segmented 3D vertebral body models were established according to the cervical CBCT images. A 3D-to-3D registration was then performed for each vertebral body in the different positions to calculate the 3D segmental motion characteristics in vivo. During flexion-extension, the range-of-motion (ROM) of C1-C2 and C4-C5 was significantly greater than the other segments. The average coupled axial rotation and lateral bending of each segment were between 0.6° and 3.2°. The average coupling translations in all directions were between 0.2 and 2.1 mm. During axial rotation, the ROM of C1-C2 was 65.8 ± 5.9°, which accounted for approximately 70% of all axial rotation. The motion and displacement of C1-C2 coupled lateral bending were 11.4 ± 5.2° and 8.3 ± 1.9 mm, respectively. During lateral bending, the ROM of C3-C4 was significantly greater than C1-C2, C5-C6, and C6-C7. The coupled axial rotation of C1-C2 was 34.4 ± 8.1°, and the coupled lateral translation was 3.8 ± 0.5 mm. The coupled superoinferior and anteroposterior translation of each cervical segment were between 0.1 and 0.6 mm. CBCT combined with 3D-3D registration was used to accurately measure and record the ROMs of lateral bending, axial rotation, and flexion-extension in cervical vertebrae under physiological-load conditions. Our findings may contribute to the diagnosis of cervical spinal disease, the development of new surgical techniques, and the restoration of normal, cervical segmental movement.Level of Evidence: 3.

Biomechanical Analysis of Cervical Artificial Disc Replacement Using Cervical Subtotal Discectomy Prosthesis.

Background: Anterior cervical discectomy and fusion (ACDF) sacrifices segmental mobility, which can lead to the acceleration of adjacent segment degeneration. The challenge has promoted cervical artificial disc replacement (CADR) as a substitute for ACDF. However, CADR has revealed a series of new issues that are not found in ACDF, such as hypermobility, subsidence, and wear phenomenon. This study designed a cervical subtotal discectomy prosthesis (CSDP) consisting of a cervical disc prosthesis structure (CDP structure), cervical vertebra fixation structure (CVF structure), link structure, and locking screw, aiming to facilitate motion control and reduce subsidence. The aim of this study was to assess the biomechanics of the CSDP using finite element (FE) analysis, friction-wear test, and non-human primates implantation study.Study Design: For the FE analysis, based on an intact FE C2-C7 spinal model, a CSDP was implanted at C5-C6 to establish the CSDP FE model and compare it with the Prestige LP prosthesis (Medtronic Sofamor Danek, Minneapolis, MN, United States). The range of motion (ROM), bone-implant interface stress, and facet joint force were calculated under flexion extension, lateral bending, and axial rotation. In addition, CSDP was elevated 1 mm to mimic an improper implantation technique to analyze the biomechanics of CSDP errors in the FE model. Moreover, the friction-wear test was conducted in vitro to research CSDP durability and observe surface wear morphology and total wear volume. Finally, the CSDP was implanted into non-human primates, and its properties were evaluated and verified by radiology.Results: In the FE analysis, the ROM of the CSDP FE model was close to that of the intact FE model in the operative and adjacent segments. In the operative segment, the CSDP error FE model increased ROM in flexion extension, lateral bending, and axial rotation. The maximum stress in the CSDP FE model was similar to that of the intact FE model and was located in the peripheral cortical bone region. The facet joint force changes were minimal in extension, lateral bending, and axial rotation loads in CSDP. In the friction-wear test, after the 150-W movement simulation, both the CVF-link-junction and the CDP-link-junction had slight wear. In the CSDP non-human primate implantation study, no subsidence, dislocation, or loosening was observed.Conclusion: In the FE analysis, the biomechanical parameters of the CSDP FE model were relatively close to those of the intact FE model when compared with the Prestige LP FE model. In terms of CSDP error FE models, we demonstrated that the implantation position influences CSDP performance, such as ROM, bone-implant interface stress, and facet joint force. In addition, we performed a friction-wear test on the CSDP to prove its durability. Finally, CSDP studies with non-human primates have shown that the CSDP is effective.

Evaluation of lumbar spinal fusion utilizing recombinant human platelet derived growth factor-B chain homodimer (rhPDGF-BB) combined with a bovine collagen/β-tricalcium phosphate (β-TCP) matrix in an ovine model.

Background contextWhile the clinical effectiveness of recombinant human Platelet Derived Growth Factor‐B chain homodimer combined with collagen and β‐tricalcium phosphate (rhPDGF‐BB + collagen/β‐TCP) treatment for indications involving hindfoot and ankle is well‐established, it is not approved for use in spinal interbody fusion, and the use of autograft remains the gold standard.PurposeThe purpose of this study was to compare the effects of rhPDGF‐BB + collagen/β‐TCP treatment on lumbar spine interbody fusion in an ovine model to those of autograft bone and collagen/β‐TCP treatments using biomechanical, radiographic, and histological assessment techniques.Study designThirty‐two skeletally mature Columbian Rambouillet sheep were used to evaluate the safety and effectiveness of rhPDGF‐BB + collagen/β‐TCP matrix in a lumbar spinal fusion model. Interbody polyetheretherketone (PEEK) cages contained either autograft, rhPDGF‐BB + collagen/β‐TCP, collagen/β‐TCP matrix, or left empty.MethodsAnimals were sacrificed 8‐ or 16‐weeks post‐surgery. Spinal fusion was evaluated via post‐sacrifice biomechanical, micro‐computed tomography (μCT), and histological analysis. Outcomes were statistically compared using a two‐way analysis of variance (ANOVA) with an alpha value of 0.05 and a Tukey post‐hoc test.ResultsThere were no statistically significant differences between groups within treatment timepoints for flexion‐extension, lateral bending, or axial rotation range of motion, neutral zone, neutral zone stiffness, or elastic zone stiffness. μCT bone volume fraction was significantly greater between treatment groups independent of timepoint where Autograft and rhPDGF‐BB + collagen/β‐TCP treatments demonstrated significantly greater bone volume fraction as compared to collagen/β‐TCP (P = .026 and P = .038, respectively) and Empty cage treatments (P = .002 and P = .003, respectively). μCT mean bone density fraction was most improved in rhPDGF‐BB + collagen/β‐TCP specimens at the 8 week and 16‐week timepoints as compared to all other treatment groups. There were no statistically significant differences in histomorphometric measurements of bone, soft tissue, or empty space between rhPDGF‐BB + collagen/β‐TCP and autograft treatments.ConclusionsThe results of this study indicate that the use of rhPDGF‐BB combined with collagen/β‐TCP promotes spinal fusion comparable to that of autograft bone.Clinical significanceThe data indicate that rhPDGF‐BB combined with collagen/β‐TCP promotes spinal fusion comparably to autograft bone treatment and may offer a viable alternative in large animal spinal fusion. Future prospective clinical studies are necessary to fully understand the role of rhPDGF‐BB combined with collagen/β‐TCP in human spinal fusion healing.

Surgery-related Factors Do Not Affect Short-term Adjacent Segment Kinematics After Anterior Cervical Arthrodesis.

Prospective cohort study. The aim of this study was to identify surgical factors that affect adjacent segment kinematics after anterior cervical discectomy and fusion (ACDF) as measured by biplane radiography. Previous studies investigated the effect of surgical factors on spine kinematics as a potential etiology for adjacent segment disease (ASD). Those studies used static flexion-extension radiographs to evaluate range of motion. However, measurements from static radiographs are known to be unreliable. Furthermore, those studies were unable to evaluate the effect of ACDF on adjacent segment axial rotation. Patients had continuous cervical spine flexion/exten- sion and axial rotation movements captured at 30 images per second in a dynamic biplane radiography system preoperatively and 1 year after ACDF. Digitally reconstructed radiographs generated from subject-specific CT scans were matched to biplane radiographs using a previously validated tracking process. Dynamic kinematics, postoperative segmental kyphosis, and disc distraction were calculated from this tracking process. Plate-to-disc distance was measured on postoperative radiographs. Graft type was collected from the medical record. Multivariate linear regression was performed to identify surgical factors associated with 1-year post-surgery changes in adjacent segment kinematics. A secondary analysis was also performed to compare adjacent segment kinematics between each of the surgical factors and previously defined thresholds believed to be associated with adjacent segment degeneration. Fifty-nine patients completed preoperative and postoperative testing. No association was found between any of the surgical factors and change in adjacent segment flexion/exten- sion or axial rotation range of motion (all P > 0.09). The secondary analysis also did not identify differences between adjacent segment kinematics and surgical factors (all P > 0.07). Following ACDF for cervical spondylosis, factors related to surgical technique were not associated with short-term changes in adjacent segment kinematics that reflect the hypermobility hypothesized to lead to the development of ASD.Level of Evidence: 2.

Differences in trunk range of motion for various flexibility protocol types, particularly in quarterbacks wearing rib protectors

Summary Background It is unclear how rib protectors may affect trunk mobility in American football players. The purposes of the study were: 1) to determine which flexibility protocol (active-assisted, maximal-speed, self-selected) exhibits the highest range of motion for trunk lateral flexion and axial rotation and 2) to determine the effect of rib protectors (hard-rib and soft-rib protectors and control: compression shirt only) on trunk range of motion. Methods Eleven male participants with competitive quarterback experience were recruited. Participants were instructed to rotate the trunk in the lateral flexion and axial rotation directions during each flexibility protocol and rib protector condition. The lower-thoracic range of motion were measured. Results Two-way repeated measures ANOVA (flexibility protocol by rib protector) demonstrated significant main effect of flexibility protocol for lateral flexion, but not axial rotation. The range of motion during self-selected protocol was significantly greater than maximal-speed protocol by approximately 7° (p = .009). Conclusions Self-selected and maximal-speed protocol produced the highest lateral flexion and axial rotation range of motion, respectively, and can be used to test the influence of rib protectors and potentially other sports equipment on thoraco-lumbar range of motion. Additionally, rib protectors likely do not affect trunk range of motion needed to throw long-distance passes or other movements as performed by football quarterbacks.

Age-related gait development in children with autism spectrum disorder

BackgroundA better understanding of gait development and asymmetries in children with autism spectrum disorder (ASD) may improve the development of treatment programs and thus, patient outcomes. Research questionDoes age affect walking kinematics and symmetry in children with ASD? MethodTwenty-nine children (aged 6–14 years old) with mild ASD (level one) were recruited and assigned to one of the three groups based on their ages: 6–8 years (U8), 9–11 years (U11) and 12–14 years (U14). Walking kinematics were captured using an inertia measurement unit system placed bilaterally on participants’ foot, lower leg, upper leg, upper arm, pelvis, and thoracic spine. Joint angles were computed and compared among the age groups. Symmetry angles were used to assess the gait symmetry and were compared among the age groups. ResultsOlder children exhibited less ankle dorsiflexion and knee flexion angles at heel-strike and greater plantarflexion angles at toe-off compared with younger children. In addition, a decreased pelvis and thorax axial rotation range of motion and increased shoulder flexion/extension range of motion were observed for older children. However, no age-related difference in gait symmetry was observed. SignificanceThese findings could suggest that older children with ASD may develop gait kinematics to a more energy-efficient walking pattern.

A Novel Construct Incorporating C2 Unilateral Pedicle and Contralateral Translaminar Screws for Occipitocervical Internal Fixation: An In Vitro Biomechanical Study

Occipitocervical fixation using bilateral C2 pedicle screws (C0-C2BiPS) and occipitocervical fixation using bilateral C2 translaminar screws (C0-C2BiLS) provide satisfactory stability. Bilateral fixation is not feasible for cases of C2 unilateral pedicle morphology abnormality and ipsilateral laminectomy. This study proposed and evaluated novel occipitocervical fixation using C2 unilateral pedicle screw and contralateral translaminar screws (C0-C2PSLS). In 6 human cadaveric specimens, an invitro experiment was performed with 2.0-Nm moment control in flexion-extension, lateral bending, and axial rotation to investigate biomechanical stability. Neutral zone and range of motion (ROM) between the occiput (C0) and C2 were measured in the intact state, after destabilization, and after sequential stabilization using C0-C2BiPS, C0-C2BiLS, and C0-C2PSLS constructs. Flexion-extension ROM of the intact specimens at C0-C2 was 27.4° ± 2.4°. Instrumentation with C0-C2PSLS, C0-C2BiPS, and C0-C2BiLS reduced flexion-extension ROM to 3.7° ± 1.3°, 4.7° ± 1.4°, and 4.5° ± 1.4°, respectively. In lateral bending, ROM values were 7.0° ± 0.6°, 4.5° ± 1.4°, 4.2° ± 1.4°, 2.7° ± 1.0°, respectively. In axial rotation, ROM values were 65.3° ± 5.7°, 2.5° ± 0.5°, 1.4° ± 0.5°, and 0.9° ± 0.6°, respectively. Comparing destabilized and intact specimens, all 3 constructs significantly reduced ROM and neutral zone values in flexion-extension, lateral bending, and axial rotation (P<0.05). Direct comparisons between the 3 constructs revealed no significant difference (P > 0.05). Novel C0-C2PSLS provides similar stabilization effect as C0-C2BiPS and C0-C2BiLS constructs and has potential for clinical use, especially for cases of C2 unilateral pedicle morphology abnormality and ipsilateral laminectomy.

The Role of Transverse Connectors in C1-C2 fixation for Atlantoaxial Instability: Is It Necessary? A Biomechanical Study

To investigate the biomechanical effect of C1 lateral mass-C2 pedicle screw-rod (C1LM-C2PS) fixation with and without transverse connectors (TC) in an atlantoaxial instability (AAI) model. Ten freshly frozen cadaveric specimens were tested using an industrial robot under the following conditions: intact model, AAI model, C1-C2 model, C1-C2 with one TC model, and C1-C2 with two TCs model. Three types of motion, flexion-extension (FE), lateral bending (LB), and axial rotation (AR), were applied (1.5 Nm) to the specimens. The range of motion (ROM) and neutral zone (NZ) between C1 and C2 in all directions were measured. Compared with those of the intact and AAI models, the C1-C2 ROM and NZ of all instrumented groups were decreased significantly in each direction of loading motion (P < 0.05). The mean FE ROM in the no TC, 1 TC, and 2 TC groups was 2.12° ± 0.41°, 2.29° ± 0.42°, and 2.04° ± 0.69°, respectively (P= 0.840, 0.981, 0.628, respectively); the mean LB ROM in the 3 intervention groups was 1.26° ± 0.67°, 1.02° ±0.51° and 1.03° ± 0.57°, respectively (P= 0.489, 0.501, 1.000, respectively). During AR, the ROM and NZ of the no TC group (3.19° ± 0.89° and 1.51° ± 0.42°) were significantly reduced by more than 60% compared with those in the 1 (0.98° ± 0.28° and 0.40° ± 0.11°) and 2 TC groups (1.17° ± 1.69° and 0.42° ± 0.61°) (P < 0.001). Two TCs were equivalent for all loading motions to 1 TC (P > 0.05). Adding TCs to C1LM-C2PS can effectively decrease the axial rotation ROM and enhance the stability of C1-C2 segment. Therefore, it is necessary to use TC-strengthened C1 lateral mass -C2 pedicle screw-rod fixation in patients with instability of C1-C2.

Superior-segment Bilateral Facet Violation in Lumbar Transpedicular Fixation, Part III: A Biomechanical Study of Severe Violation.

This is an in vitro biomechanical study. This study aimed to investigate the biomechanical variations of lumbar spine motor units after bilateral facet joint severe violation in cadaver specimens and analyze the biomechanics under different moments. The incidence of facet joint violation (FJV) is highly variable, and one of the most important factors is the lack of awareness of protection. Until now, the biomechanical effects of FJV remain unclear. Biomechanical testing was performed on 12 human cadaveric spines under flexion-extension, lateral bending, and axial rotation loading. After intact analysis, pedicle screws were inserted at L5, and the biomechanical testing was repeated. Full range of motion (ROM) at the proximal adjacent levels under different moments was recorded and normalized to the intact (100%) noninstrumented spine. The relative ROM changes were compared between the control and severe violation groups. The adjacent-level ROM (flexion-extension, lateral bending, axial rotation) did not change significantly in the control group at each moment (7.5, 6.0, 4.5 Nm) compared with the intact noninstrumented spine. In the severe violation group, the supradjacent-level ROM decreased significantly under all moments relative to the intact noninstrumented spine (P < 0.05) except for the ROM of lateral bending at moments of 7.5 and 6.0 Nm. When comparing the ROM between the two groups, there were significant differences in all movements except lateral bending at 7.5 Nm. When superior-segment bilateral facet joints are severely violated by screws, the flexion-extension and axial rotation ROM of adjacent vertebrae decreases at each moment (7.5, 6.0, 4.5 Nm), and the lateral bending ROM decreases at 4.5 Nm. N/A.