Screw-rod Constructs Research Articles

Sublaminar banding as an adjunct to pedicle screw-rod constructs: a review and technical note on novel hybrid constructs in spinal deformity surgery.

Sublaminar implants that encircle cortical bone are well-established adjuncts to pedicle screw-rod constructs in pediatric deformity surgery. Sublaminar bands (SLBs) in particular carry the advantage of relatively greater bone contact surface area as compared to wires and pullout loads that are independent of bone mineral density, in contrast to pedicle screws. Whereas the relevant technical considerations have been reported for pediatric deformity correction, an understanding of the relative procedural specifics of these techniques is missing for adult spinal deformity (ASD), despite several case series that have used distinct posterior tethering techniques for proximal junctional kyphosis prevention. In this paper, the authors summarize the relevant literature and describe a novel technique wherein bilateral tensioned SLBs are introduced at the nonfused proximal junctional level of long-segment ASD constructs.

'Out with the old and in with the new' - a retrospective review of paediatric craniocervical junction fixation: indications, techniques and outcomes

Background: The paediatric craniocervical junction has anatomical, physiological and biomechanical properties that make this region unique from that of the adult spine, vulnerable to injury, and contribute to the complexity of management. Traditionally, onlay fusion with external halo immobilisation has been used. Instrumented fusion offers intra-operative reduction and immediate stability. Methods: A retrospective review of a single surgeon’s prospectively maintained database was conducted for all cases of paediatric patients that had undergone a fusion involving the occipito-atlanto-axial region. Case notes were reviewed and a radiological analysis was done. Results: Sixteen patients were managed with onlay fusion and external immobilisation, and 27 patients were managed with internal fixation using screw-rod constructs. The fusion rates were 80% and 90.5% respectively. Allograft bone grafting was found to be a significant risk factor for non-union. Conclusion: The screws can be safely and predictably placed as confirmed on radiological follow-up with a high fusion rate and an acceptable complication rate. Uninstrumented onlay fusion with halo immobilisation remains an acceptable alternative. Allograft in the form of bone croutons or demineralised bone matrix is a significant risk factor for non-union, and posterior iliac crest graft should be used preferentially. Level of evidence: Level 4

Surgical, clinical, and radiological outcomes of occipitocervical fusion using the plate-screw-rod system with allograft in craniocervical instability.

Objective:We evaluated surgical, clinical, and radiological outcomes of posterior occipitocervical fusion (OCF) using plate–rod–screw construct supplemented with allograft in cases of occipitocervical instability.Study Design:This was a retrospective analysis of prospective collected data.Methods:Data of 52 patients who underwent posterior OCF using plate–screw–rod construct supplemented with allograft at a single institute from 2009 to 2014 were analyzed. Demographics, clinical parameters (Visual Analog Score [VAS], ODI, and mJOA score), functional status (McCormick scale), radiological parameters – mean atlantodens interval, posterior occipitocervical angle, occipitocervical 2 angle, and surgical parameters (operative time, blood loss, hospital stay, and fusion) with complications were evaluated.Results:The mean age of the patients was 54.56 ± 16.21 years with male: female was 28:24. The mean operative time was 142.2 min (90–185 min) and mean blood loss was 250.8 ml. The mean duration of hospital stay was 6.7 days and mean follow-up period was 65.17 ± 5.39 months. There was significant improvement in clinical parameters (modified JOA score, VAS, and Oswestry Disability Index values) postoperatively. Forty patients showed recovery in neurological status at least in Grade 1 in McCormick scale with no neurological deterioration in any patient. Furthermore, radiological parameters at cervicomedullary junction got into acceptable range. Implant-related complications noted in 1 patient and 1 patient had vertebral artery injury. We had dural tear in 3 patients and infection in 2 patients. Fusion was achieved in 46 cases with mean time for fusion was 11.039 months.Conclusion:Patients with occipitocervical instability can successfully undergo posterior OCF using plate–screw–rod construct supplemented with allograft with high fusion rate, good clinical and functional outcomes, and low complication rate.

Sacral chordoma with degenerative spondylolisthesis and upper lumbar disc herniation

Sacral chordoma is a rare condition requiring multidisciplinary approach for management. Here, we report a 72-year-old male patient who was diagnosed with sacral chordoma with L2–L3 disc herniation and L5–S1 degenerative spondylolisthesis and L1 body fracture. The patient was first managed by discectomy L2–L3 with D12–L3 decompression and fixation. Sacral chordoma excision was done 10 months later. The chordoma was excised by anterior laparoscopic resection and mobilization of tissues from the tumor followed by posterior sacrectomy with L5–S1 decompression and extension of fixation in a single stage. Proline mesh was used to support the colon posteriorly. This was further complicated by proximal junction fracture due to fall which was further managed by proximal extension of the rod-screw construct. The patient became symptom free without any radiotherapy or chemotherapy and is able to walk independently, two years following the primary surgery without recurrence of tumor.

Insights into the Past and Future of Atlantoaxial Stabilization Techniques.

Over the past century, atlantoaxial stabilization techniques have improved considerably. To our knowledge there has been a scarcity of articles published that focus specifically on the history of atlantoaxial stabilization. Examining the history of instrumentation allows us to evaluate the impact of early influences on current modern stabilization techniques. It also provides inspiration to further develop the techniques and prevents repetition of mistakes. This paper reviews the evolution of C1-C2 instrumentation techniques over time and provides insights into the future of these practices.We did an extensive literature search in PubMed, Embase and Google Scholar, using the following search terms: 'medical history', 'atlantoaxial', 'C1/C2', 'stabilization', 'instrumentation', 'fusion', 'arthrodesis', 'grafting', 'neuroimaging', 'biomechanical testing', 'anatomical considerations' and 'future'.Many different entry zones have been tested, as well as different constructs, from initial attempts with use of silk threads to use of hooks and rod-wire techniques, and handling of bone grafts, which eventually led to the development of the advanced screw-rod constructs that are currently in use. Much of this evolution is attributable to advancements in neuroimaging, a wide range of new materials available and an improvement in biomechanical understanding in relation to anatomical structures.

Biomechanical Evaluation of Cervicothoracic Junction Fusion Constructs

We studied the effect of different cervicothoracic construct design variables on biomechanical stability invitro. Six fresh-frozen human cadaveric spines (C5-T4) were used. After intact analysis, each specimen was destabilized and reconstructed, with all groups having 4.0-mm pedicle screws placed at T1-T3. The 2 hook-rod constructs included interlaminar hooks at C6 and C7, with either 3.5-mm or 4.0-mm rods (C6-T3). The 2 screw-rod constructs tested included lateral mass screws at C6 and C7, with either 3.5-mm or 4.0-mm rods (C6-T3). The 2 screw-connector-rod constructs tested included lateral mass screws at C6 and C7, with either 3.5-mm or 4.0-mm rods; 1 rod spanned C6-C7 with a connector to a second rod of the same size spanning T1-T3. Global (C6-T3) and intervertebral (C6-C7, C7-T1, T1-T2, and T2-T3) ranges of motion were compared for each construct. In terms of global (C6-T3) stability, 3.5-mm versus 4.0-mm rod constructs were not significantly different, regardless of whether the construct was hook-rod, screw-rod, or screw-connector-rod. The hook-rod constructs provided less stability compared with the screw-rod and screw-connector-rod constructs in lateral bending (P<0.04) and axial rotation (P < 0.001). The screw-rod constructs demonstrated a similar range of motion to that of the screw-connector-rod constructs, except for significantly less axial rotation at the C6-C7 level with 3.5-mm rods (P= 0.04). We found that the rod diameter of a construct does not appear to significantly influence the biomechanical stability of subaxial constructs. The screw-rod construct resulted in certain biomechanical advantages compared with the screw-connector-rod construct, and both were significantly superior to the hook-rod construct.

Splitting of the semispinalis capitis muscle as a less invasive approach for atlantoaxial fusion – A technical note

PurposeAtlantoxial fusion with screw rod constructs traditionally requires subperiostal dissection of the C1/C2 muscle attachments, which may lead to postoperative axial neck pain and intraoperative blood loss. We evaluate a potentially less invasive, muscle splitting approach for atlantoaxial fusion in a cadaver model. MethodsA technical feasibility study was performed in a human cadaveric specimen with standard surgical instruments and an operating microscope. Surgically relevant anatomical structures as well as final exposure of the C1, C1/C2 and C2 screw entry points are demonstrated. ResultsFollowing a midline skin incision, blunt mobilization and downward retraction of the trapezius and splenius capitis muscle is followed by a longitudinal split of the semispinalis capitis muscle. At the lower border of the rectus capitis posterior major and the obliquus capitis inferior muscle the entry points for C1 lateral mass, C1/C2 transarticular and C2 pedicle screw are exposed. ConclusionMinimal invasive splitting of the semispinalis capitis muscle allows adequate exposure of the screw entry points of C1, C1/C2 and C2 while preserving the intrinsic muscles of the back at the craniocervical junction.

C1 Titanium Cables Combined with C2 Pedicle Screw-Rod Fixation for Atlantoaxial Instability Not Suitable for Placement of C1 Screws

We sought to develop a new posterior fusion technique composed of bilateral C1 titanium cables and C2 pedicle screw-rods for treatment of atlantoaxial instability not suitable for C1 screw placement. A study was conducted of 18 patients with atlantoaxial instability who had C1 broken screw trajectory or anatomic anomalies. All patients underwent posterior fixation with bilateral C1 titanium cables and C2 pedicle screws. The follow-up period was a minimum 1 year. Clinical outcomes measurements included visual analog scale score for neck pain assessment, the American Spinal Injury Association Impairment Scale and Japanese Orthopaedic Association score for neurologic status and function. According to preoperative computed tomography (CT) reconstruction and CT angiography, the patients selected in this study were not suitable for C1 screw placement. Postoperative plain radiographs and CT reconstruction were performed to evaluate the reduction, bony fusion, and implant position. All outcomes were evaluated at each follow-up. The average clinical follow-up period was 24 months (range 12-36 months). All patients had complete neck pain relief at postoperative 6 months. Their neurologic symptoms had improved significantly at 1-year follow-up. Radiologic outcomes indicated good bony fusion and construction stability in all patients without implant failure at the last follow-up. No neural or vascular complications related to this technique were observed. Posterior atlantoaxial fixation using C1 titanium cables and C2 pedicle screw-rod construct appears to be an effective and safe technique for treatment of atlantoaxial instability, which could be an alternative method for cases unsuitable for C1 screw placement when using C1-C2 screw fixation.

Resting Pain Level as a Preoperative Predictor of Success With Indirect Decompression for Lumbar Spinal Stenosis: A Pilot Study.

Study Design:Retrospective review of a single institution.Objective:To determine if resting leg pain level is a predictor of success for indirect decompression in the setting of lumbar spinal stenosis, with lower levels of rest pain correlating with greater likelihood of successful indirect decompression.Methods:Reviewed anterior or lateral lumbar interbody fusions from T12 to L5-S1 patients with a posterior-based pedicle screw-rod construct. Patients were separated into 2 groups based on a preoperative response to Oswestry Disability Index (ODI) Question 7 regarding level of pain at rest in the supine position. Responses of 0 to 2 (minimal rest pain) were group 1 (n = 54) and responses of 3 to 5 (significant rest pain) were group 2 (n = 16).Results:Preoperative difference was detected between groups 1 and 2, in ODI (38 vs 63, P < .001) and Numeric Rating Scale (NRS) back (6.8 vs 7.9, P = .023). Three-month NRS leg and back scores were significantly lower in group 1 (leg, 1.9 vs 4.8, P < .001; back, 3.5 vs 6.4, P = .001). A significant difference was further noted in the percentage decrease in NRS leg and back scores from pre- to 3 months postoperatively between groups 1 and 2 (leg, 68.4% vs 22.7%, P < .001; back, 40.0% vs 7.4%, P = .012). Group 1 reached minimal clinically important difference for leg pain more often than group 2 (83.3% vs 43.8%, P = .001).Conclusion:Preoperative assessment of rest pain level in the supine position has a significant association with reduction in NRS leg and back scores in patients undergoing indirect decompression for lumbar spinal stenosis. This tool may successfully indicate which patients will be candidates for indirect decompression with interbody fusion from an anterior or lateral approach.

Standard versus minimally invasive transforaminal lumbar interbody fusion: A prospective randomized study

Introduction Symptomatic spondylolisthesis patients may benefit from surgical decompression and stabilization. The standard (S) technique is a transforaminal lumbar interbody fusion (TLIF). Newer, minimally invasive (MI) techniques seem to provide similar results with less morbidity. However, prospective studies comparing S versus MI TLIF are rare. Case description Patients with at least 6 months of symptoms and image-confirmed low-grade spondylolisthesis (grade 1 or 2) were enrolled, at a single academic institution, between 2011 and 2015. The patients were randomized to either S or MI TLIF. Iliac crest graft, polyether ether ketone (PEEK) interbody cages, and pedicle screw-rod constructs were used in both groups. The primary outcome measure was the Oswestry Disability Index (ODI) improvement at 1 year. Secondary outcome measures included length of operation, estimated blood loss, length of hospitalization, and fusion rates at 1 year. Complications were also recorded. Results and Conclusions Forty patients were enrolled in each group. There was no crossover between groups. The age was 50.12+/-11.09 years in the S TLIF group and 51.3+/-9.36 years in the MI TLIF group. There were 23 and 24 females in the S and MI TLIF group, respectively. The mean operative time and estimated blood loss in the S versus MI TLIF group were 297+/-101 versus 323 +/-85 minutes and 417+/-211 versus 351+/-198 ml, respectively. There were 4 transfusions in the S TLIF and 3 transfusions in the MI TLIF group. The patients were discharged after surgery at 4.12+/-0.88 days for the S TLIF group and 1.92+/-0.52 days for the MI TLIF group. The ODI improved from 37+/-6 to 11+/-6 in the S TLIF group (ODI difference: 26+/-7) and from 38+/-7 to 11+/-6 in the MI TLIF group (ODI difference: 26+/-8). The fusion was considered solid (Grade I) in 36 (90%) and partial (Grade II) in 4 (10%) patients at 1 year. There were no reoperations for pseudarthrosis or any other postoperative complication. There were 2 superficial wound infections in the standard TLIF group, which resolved with oral antibiotic treatment alone. Take home message In this prospective randomized study, the standard and minimally invasive TLIF in patients with symptomatic spondylolisthesis provided similar clinical and radiological outcomes at 1 year. The patients undergoing MI TLIF had a shorter hospital stay. Both surgical techniques yielded good results at 1 year.

Craniovertebral fixation … a new technique of occipital – cervical fixation

Background: Craniovertebral instability following transoral odontoid excision is usually treated by posterior occipital–cervical fixation using occipital plate and cervical lateral mass fixation with screw rod construct. A patient previously operated for basilar invagination had postoperative infection of both the transoral wound and the posterior implant site which needed removal of the posterior implant earlier.Clinical presentation: The patient presented with severe neck pain, myelopathy, and chronic discharging sinus in the posterior lower aspect the previous neck surgery wound. Reimaging revealed incomplete odontoid excision. He underwent repeat transoral odontoid excision. Treatment of the instability needed occipitocervical fixation avoiding, the atlas, axis (weakened by infection and previous implants), and the infected posterior cervical wound. A new technique using a customized plate rod construct, fixed anteriorly to the mid cervical vertebrae (by a standard mid cervical exposure) with the rods contoured to reach posteriorly through the safe paraspinal corridor and connected with domino connectors to occipital plate rods fixed on either side of midline by additional posterior exposure avoiding the midline scar was planned and executed successfully.Conclusion: This construct transfers the weight of the cranium to the cervical vertebral bodies along the physiological line of weight transmission and can be considered for distraction and reduction of basilar invagination with atlantoaxial dislocation. The technique seems to be safe and reproducible, but will need to tested over time with more cases.

P17 - Biomechanical Comparison of C1 Lateral Mass C2 Pars and C3 Lateral Mass Screw-Rod Construct vs C1 Lateral Mass C2 Pedicle Screw Fixation for Type II Odontoid Fractures

BACKGROUND CONTEXT: Rigid fixation of the atlantoaxial complex in the setting of a type II odontoid fracture is required for successful fusion and fracture healing. The C1 lateral mass—C2 pedicle screw-rod construct (Harms technique) provides excellent C1-C2 fixation and is associated with high rates of fusion. However, C2 pedicle screw placement is challenging due to the risk of vertebral artery injury and is prohibited if the vertebral artery follows an aberrant course. Alternatively, the use of C2 pars screws may be a safer option but may come at the cost of reduced C1-C2 immobilization. Therefore, the hypothesis of this study is that extending the C1 lateral mass—C2 pars screw-rod construct with C3 lateral mass screws will mitigate the risk of vascular injury without compromising C1-C2 fixation.

Safety and efficacy of spinal loop rectangle and sublaminar wires for osteoporotic vertebral compression fracture fixation.

Background:Natural history of osteoporotic vertebral compression fractures (OVCFs), that is, collapse, loads the rigid pedicle screw rod construct in the absence of anterior column reconstruction, often leading to implant back outs. Semi rigid spinal loop rectangle and sublaminar wire construct allows controlled axial collapse and does not require anterior column reconstruction.Materials and Methods:This is a retrospective study of 50 consecutive patients of OVCFs. The immediate and final follow-up safety (neurologic deficit, implant failure/back out, revision surgeries, and infection) and efficacy (visual analog scale [VAS] score, axial collapse of the fracture, fracture union and retaining, and the attempted segmental deformity correction) parameters were compared to describe the utility of spinal loop rectangle and sublaminar wiring as a novel, low cost modality of spinal instrumentation for treating OVCFs.Results:All the twelve patients with Frankel grade D neurologic deficit improved to Frankel grade E and six patients (out of 8) with Frankel grade C improved to Frankel grade E (and remaining two patients improved to Frankel grade D), following surgery. The average preoperative VAS score of 8.98 (ranging from 5 to 10) improved to 2.76 (ranging from 1 to 10) at final follow-up. Controlled collapse of anterior column, union of OVCF nonunion, and retaining of attempted deformity correction by sublaminar wire anchors cephalad and caudal to the transpedicular decompression was seen in each patient at the final follow-up.Conclusion:Spinal loop rectangle and sublaminar wiring construct are viable alternative options for stabilizing OVCFs.

The effect of different screw-rod design on the anti-rotational torque: a biomechanical comparison of three conventional screw-rod constructs

BackgroundScrew-rod constructs have been widely used to correct spinal deformities, but the effects of different screw-rod systems on anti-rotational torque have not been determined. This study aimed to analyze the biomechanical effect of different rod-screw constructs on anti-rotational torque.MethodsThree conventional spinal screw-rod systems (Legacy, RF-F-10 and USSII) were used to test the anti-rotational torque in the material test machine. ANOVA was performed to evaluate the anti-rotational capacity of different pedicle screws-rod constructs.ResultsThe anti-rotational torque of Legacy group, RF-F-10 group and USSII group were 12.3 ± 1.9 Nm, 6.8 ± 0.4 Nm, and 3.9 ± 0.8 Nm, with a P value lower than 0.05. This results indicated that the Legacy screws-rod construct could provide a highest anti-rotation capacity, which is 68% and 210% greater than RF-F-10 screw-rod construct and USSII screw-rod respectively.ConclusionsThe anti-rotational torque may be mainly affected by screw cap and groove design. Our result showed the anti-rotational torque are: Legacy system > RF-F-10 system > USSII system, suggesting that appropriate rod-screw constructs selection in surgery may be vital for anti-rotational torque improvement and preventing derotation correction loss.

Gallie technique versus atlantoaxial screw-rod constructs in the treatment of atlantoaxial sagittal instability: a retrospective study of 49 patients

BackgroundThe objectives of this study are to investigate the clinical curative effect of Gallie technique and atlantoaxial screw-rod constructs (SRC) on atlantoaxial sagittal instability and determine the indication of Gallie technique.MethodsData of 49 patients with atlantoaxial sagittal instability from February 2008 to May 2015 were analyzed retrospectively. The visual analog scale (VAS) score and the neck disability index (NDI) were used to evaluate the curative effect. Postoperative radiological outcomes were used to evaluate the stability of atlantoaxial joint and bone fusion. Perioperative parameters such as blood loss, operation time, radiographic exposure times, and hospital expense were also recorded and analyzed.ResultsForty-nine patients (36 men and 13 women) were included in this study. The mean age was 41.4 ± 8.9 (range from 19 to 64). All patients were followed up for 24–67 months. Among these patients, 25 of these patients underwent Gallie surgery and 24 underwent SRC surgery. The pain in the occipitocervical area of all the patients has been relieved. NDI scores and VAS scores were lower in Gallie group than in SRC group in early postoperative period. The proportion of the patients who achieved good bone fusion within 3 months after operation was 88.0% (22/25) in the Gallie group and 100% (24/24) in the SRC group. The Gallie group is lower than the SRC group in blood loss, operation time, radiographic exposure times, and hospital expense. Statistical difference was observed between the two groups.ConclusionsFor patients with atlantoaxial instability who has (1) the atlantodental interval (ADI) which is bigger than 5 mm on lateral flexion-extension X-ray, or Anderson-D’Alonzo type II odontoid fracture, (2) no asymmetry between odontoid process and lateral mass on open-mouth anterior-posterior X-ray, and (3) no dislocation of lateral mass joint on the CT 3D reconstruction, Gallie technique can be chosen as a safe and effective method if atlantoaxial reduction can be achieved preoperatively. Compared with SRC, Gallie technique can relieve the pain in the occipitocervical area earlier and it can shorten operation time and reduce intraoperative bleeding, radiographic exposure times, and hospital expense effectively. However, for patients with irreducible atlantoaxial dislocation, the Gallie technique should be used with caution.

Biomechanical Evaluation of Unilateral Versus Bilateral C1 Lateral Mass-C2 Intralaminar Fixation.

Study Design:Biomechanical, cadaveric study.Objectives:To compare the relative stiffness of unilateral C1 lateral mass-C2 intralaminar fixation to intact specimens and bilateral C1 lateral mass-C2 intralaminar constructs.Methods:The biomechanical integrity of a unilateral C1 lateral mass-C2 intralaminar screw construct was compared to intact specimens and bilateral C1 lateral mass-C2 intralaminar screw constructs. Five human cadaveric specimens were used. Range of motion and stiffness were tested to determine the stiffness of the constructs.Results:Unilateral fixation significantly decreased flexion/extension range of motion compared to intact (P < .001) but did not significantly affect axial rotation (P = .3) or bending range of motion (P = .3). There was a significant decrease in stiffness in extension for both unilateral and bilateral fixation techniques compared to intact (P = .04 and P = .03, respectively). There was also a significant decrease in stiffness for ipsilateral rotation for the unilateral construct compared to intact (P = .007) whereas the bilateral construct significantly increased ipsilateral rotation stiffness compared to both intact and unilateral fixation (P < .001).Conclusion:Bilateral constructs did show improved biomechanical properties compared to the unilateral constructs. However, unilateral C1-C2 fixation using a C1 lateral mass and C2 intralaminar screw-rod construct decreased range of motion and improved stiffness compared to the intact state with the exception of extension and ipsilateral rotation. Hence, a unilateral construct may be acceptable in clinical situations in which bilateral fixation is not possible, but an external orthosis may be necessary to achieve a fusion.

Is a gradual reduction of stiffness on top of posterior instrumentation possible with a suitable proximal implant? A biomechanical study

Background ContextProximal junctional kyphosis (PJK) is a challenging complication after rigid posterior instrumentation (RI) of the spine. Several risk factors have been described in literature so far, including the rigidity of the cranial aspect of the implant. PurposeThe aim of this biomechanical study was to compare different proximal implants designed to gradually reduce the stiffness between the instrumented and non-instrumented spine. Study Design/SettingThis is a biomechanical study. MethodsEight calf lumbar spines (L2–L6) underwent RI with a titanium pedicle screw rod construct at L4–L6. The proximal transition segment (L3–L4) was instrumented stepwise with different supplementary implants—spinal bands (SB), cerclage wires (CW), hybrid rods (HR), hinged pedicle screws (HPS), or lamina hooks (LH)—and compared with an all-pedicle screw construct (APS). The flexibility of each segment (L2–L6) was tested with pure moments of ±10.0 Nm in the native state and for each implant at L3–L4, and the segmental range of motion (ROM) was evaluated. ResultsOn flexion and extension, the native uninstrumented L3–L4 segment showed a mean ROM of 7.3°. The CW reduced the mean ROM to 42.5%, SB to 41.1%, HR to 13.7%, HPS to 12.3%, LH to 6.8%, and APS to 12.3%. On lateral bending, the native segment L3–L4 showed a mean ROM of 15°. The CW reduced the mean ROM to 58.0%, SB to 78.0%, HR to 6.7%, HPS to 6.7%, LH to 10.0%, and APS to 3.3%. On axial rotation, the uninstrumented L3–L4 segment showed a mean ROM of 2.7°. The CW reduced the mean ROM to 55.6%, SB to 77.8%, HR to 55.6%, HPS to 55.6%, LH to 29.6%, and APS to 37.0%. ConclusionsUsing CW or SB at the proximal transition segment of a long RI reduced rigidity by about 60% in relation to flexion and extension in that segment, whereas the other implants tested had a high degree of rigidity comparable with APS. Clinical randomized controlled trials are needed to elucidate whether this strategy might be effective for preventing PJK.

Spinal column shortening for tethered cord syndrome associated with myelomeningocele, lumbosacral lipoma, and lipomyelomeningocele in children and young adults.

OBJECTIVE Tethered cord syndrome is the clinical manifestation of an abnormal stretch on the spinal cord, presumably causing mechanical injury, a compromised blood supply, and altered spinal cord metabolism. Tethered cord release is the standard treatment for tethered cord syndrome. However, direct untethering of the spinal cord carries potential risks, such as new neurological deficits from spinal cord injury, a CSF leak from opening the dura, and retethering of the spinal cord from normal scar formation after surgery. To avoid these risks, the authors applied spinal column shortening to children and transitional adults with primary and secondary tethered cord syndrome and report treatment outcomes. The authors' aim with this study was to determine the safety and efficacy of spinal column shortening for tethered cord syndrome by analyzing their experience with this surgical technique. METHODS The authors retrospectively reviewed the demographic and procedural data of children and young adults who had undergone spinal column shortening for primary or secondary tethered cord syndrome. RESULTS Seven patients with tethered cord syndrome caused by myelomeningocele, lipomyelomeningocele, and transitional spinal lipoma were treated with spinal column shortening. One patient with less than 24 months of follow-up was excluded from further analysis. There were 3 males and 4 females; the average age at the time was surgery was 16 years (range 8-30 years). Clinical presentations for our patients included pain (in 5 patients), weakness (in 4 patients), and bowel/bladder dysfunction (in 4 patients). Spinal column osteotomy was most commonly performed at the L-1 level, with fusion between T-12 and L-2 using a pedicle screw-rod construct. Pedicle subtraction osteotomy was performed in 6 patients, and vertebral column resection was performed in 1 patient. The average follow-up period was 31 months (range 26-37 months). Computed tomography-based radiographic outcomes showed solid fusion and no instrumentation failure in all cases by the most recent follow-up. Five of 7 patients (71%) reported improvement in preoperative symptoms during the follow-up period. The mean differences in initial and most recent Scoliosis Research Society Outcomes Questionnaire and Oswestry Disability Index scores were 0.26 and -13%, respectively; minimum clinically important difference in SRS-22 and ODI were assumed to be 0.4% and -12.8%, respectively. CONCLUSIONS Spinal column shortening seems to represent a safe and efficacious alternative to traditional untethering of the spinal cord for tethered cord syndrome.

Outcomes Following Arthrodesis for Atlanto-Axial Osteoarthritis.

Retrospective analysis. We set out to evaluate the radiographic and patient-reported outcomes following C1-C2 arthrodesis for atlantoaxial osteoarthritis (AAOA) using modern instrumentation and techniques. Few studies have evaluated outcomes following C1-C2 arthrodesis for AAOA using modern surgical fixation techniques. Retrospective analysis of all patients following C1-C2 arthrodesis with recalcitrant AAOA from a single center, single surgeon from 2002 to 2012. Preoperative, immediate and final follow-up postoperative radiographic images were evaluated. Patient-reported outcomes scores were assessed preoperative, 1-year, and final postoperative follow-up. We found a total of 14 patients (13 female, 1 male) with average follow-up of 2.96 ± 2.26 years and mean age at surgery of 71.8 ± 9.3 years old. The most common construct was posterior C1-C2 bilateral screw-rod construct (SRC) (n = 9), and there were 3 patients with transarticular screw (TAS) constructs, and 2 patients with hybrid fixation (unilateral SRC and contralateral TAS). Mean change from baseline to final follow-up for Numeric Pain Rating Scale (NRS) was -4.7 ± 2.1, and Neck Disability Index (NDI) was -21.0 ± 13.6, with 11 (78.6%) patients demonstrated a substantial clinical benefit (change in NDI ≥ 10). There were no differences from baseline to all follow-up time points for SF-12 Physical and Mental Component Scores. All patients had evidence of solid C1-C2 arthrodesis and stable fixation at final follow-up, with no significant change in subaxial sagittal alignment. There were no perioperative or postoperative complications. We report one of the largest series evaluating patient-reported outcomes in patients following arthrodesis for AAOA using modern C1-C2 fixation techniques. Our study found C1-C2 arthrodesis for AAOA to be safe and effective, with a significant improvement in patient-reported pain and neck disability and most patients reporting substantial clinical benefit. 4.

Biomechanical comparison between cortical screw-rod construct versus pedicle screw-rod construct in transforaminal lumbar interbody fusion.

To compare construct stiffness of cortical screw (CS)-rod transforaminal lumbar interbody fusion (TLIF) construct (G2) versus pedicle screw (PS)-rod TLIF construct (G1) in the standardized porcine lumbar spine. Six porcine lumbar spines (L2-L5) were separated into 12 functional spine units. Bilateral total facetectomies and interlaminar decompression were performed for all specimens. Non-destructive loading to assess stiffness in lateral bending, flexion and extension as well as axial rotation was performed using a universal material testing machine. PS and CS constructs were significantly stiffer than the intact spine except in axial rotation. Using the normalized ratio to the intact spine, there is no significant difference between the stiffness of PS and CS: flexion (1.41 ± 0.27, 1.55 ± 0.32), extension (1.98 ± 0.49, 2.25 ± 0.44), right lateral flexion (1.93 ± 0.57, 1.55 ± 0.30), left lateral flexion (2.00 ± 0.73, 2.16 ± 0.20), right axial rotation (0.99 ± 0.21, 0.83 ± 0.26) and left axial rotation (0.96 ± 0.22, 0.92 ± 0.25). The CS-rod TLIF construct provided comparable construct stiffness to a traditional PS-rod TLIF construct in a 'standardized' porcine lumbar spine model.