Expandable Vertebral Body Replacement Research Articles

Anterior Cervical and Upper Thoracic Column Reconstruction Using an Expandable Poly-Ether-Ether-Ketone Vertebral Body Replacement: A Retrospective Single Center Cohort Analysis

This study aimed to evaluate the safety and efficacy of a novel Poly-Ether-Ether-Ketone (PEEK) expandable vertebral body replacement (VBR) for anterior cervico-thoracic vertebral column reconstruction in patients with metastatic, traumatic, or degenerative diseases. Radiographic and clinical outcomes, as well as complication rates, were analyzed in a retrospective analysis of 28 patients (61 ± 13 years; 64% female) who underwent an anterior cervical corpectomy and fusion (ACCF) with the Expandable Corpectomy Device (ECD) from DePuy/Synthes (2011–2020). Correction of the bisegmental kyphotic angle (BKA) was chosen as the primary outcome. Bony fusion, loss of device height, and implant subsidence were evaluated additionally. Clinical outcome was assessed using Odom’s criteria, the numerical pain rating scale (NRS), the American Spinal Injury Association Impairment Scale (AIS), and the Karnofsky Performance Status Scale (KPSS). Our study found a significant improvement in the BKA (12.3° ± 9.6°; p = 0.0002) at the last follow-up with no statistically relevant loss of device height (p = 0.96) or implant subsidence (p = 0.99). Successful bony fusion was observed in all patients. The KPSS significantly improved in patients with a tumorous disease at the time of discharge (p = 0.0009), and the sensation of pain showed significant improvement at six months post-operatively and at the final follow-up (p = 0.004; p = 0.021). However, four patients needed further secondary posterior stabilization, and one ECD was explanted due to a severe surgical site infection after an accidental esophageal lesion. In conclusion, the ECD proofed the radiographic stability for the anterior column reconstruction of the cervico-thoracic spine with significantly improved clinical outcome.

Anterior Column Reconstruction of Destructive Vertebral Osteomyelitis at the Thoracolumbar Spine with an Expandable Vertebral Body Replacement Implant: A Retrospective, Monocentric Radiological Cohort Analysis of 24 Cases.

Vertebral osteomyelitis (VO) often necessitates surgical intervention due to bone loss-induced spinal instability. Anterior column reconstruction, utilizing expandable vertebral body replacement (VBR) implants, is a recognized approach to restore stability and prevent neurological compromise. Despite various techniques, clinical evidence regarding the safety and efficacy of these implants in VO remains limited. A retrospective cohort analysis, spanning 2000 to 2020, was conducted on 24 destructive VO cases at a Level 1 orthopedic trauma center. Diagnosis relied on clinical, radiological, and microbiological criteria. Patient demographics, clinical presentation, surgical interventions, and radiological outcomes were assessed. The study included 24 patients (62.5% male; mean age 65.6 ± 35.0 years), with 58% having healthcare-associated infections (HAVO). The mean radiological follow-up was 137.2 ± 161.7 weeks. Surgical intervention significantly improved the bi-segmental kyphotic endplate angle (BKA) postoperatively (mean -1.4° ± 13.6°). However, a noticeable loss of correction was observed over time. The study reported a mortality rate of 1/24. Anterior column reconstruction using expandable VBR effectively improved local spinal alignment in destructive VO. However, the study underscores the necessity for prolonged follow-up and continuous research to refine surgical techniques and postoperative care. Addressing long-term complications and refining surgical approaches will be pivotal as the field progresses.

Radiological and mid- to long-term patient-reported outcome after stabilization of traumatic thoraco-lumbar spinal fractures using an expandable vertebral body replacement implant

BackgroundFor the treatment of unstable thoraco-lumbar burst fractures, a combined posterior and anterior stabilization instead of a posterior-only instrumentation is recommend in the current literature due to the instability of the anterior column. Data on restoring the bi-segmental kyphotic endplate angle (BKA) with expandable vertebral body replacements (VBR) and on the mid- to long-term patient-reported outcome measures (PROM) is sparse.MethodsA retrospective cohort study of patients with traumatic thoraco-lumbar spinal fractures treated with an expandable VBR implant (Obelisc™, Ulrich Medical, Germany) between 2001 and 2015 was conducted. Patient and treatment characteristics were evaluated retrospectively. Radiological data acquisition was completed pre- and postoperatively, 6 months and at least 2 years after the VBR surgery. The BKA was measured and fusion-rates were assessed. The SF-36, EQ-5D and ODI questionnaires were evaluated prospectively.ResultsNinety-six patients (25 female, 71 male; age: 46.1 ± 12.8 years) were included in the study. An AO Type A4 fracture was seen in 80/96 cases (83.3%). Seventy-three fractures (76.0%) were located at the lumbar spine. Intraoperative reduction of the BKA in n = 96 patients was 10.5 ± 9.4° (p < 0.01). A loss of correction of 1.0 ± 2.8° at the first follow-up (t1) and of 2.4 ± 4.0° at the second follow-up (t2) was measured (each p < 0.05). The bony fusion rate was 97.9%. The total revision rate was 4.2%. Fifty-one patients (53.1% of included patients; age: 48.9 ± 12.4 years) completed the PROM questionnaires after 106.4 ± 44.3 months and therefore were assigned to the respondent group. The mean ODI score was 28.2 ± 18.3%, the mean EQ-5D VAS reached 60.7 ± 4.1 points. Stratified SF-36 results (ISS < and ≥ 16) were lower compared to a reference population.ConclusionThe treatment of traumatic thoraco-lumbar fractures with an expandable VBR implant lead to a high rate of bony fusion. A significant correction of the BKA could be achieved and no clinically relevant loss of reduction occurred during the follow-up. Even though health related quality of life did not reach the normative population values, overall satisfactory results were reported.

Vertebral Body Replacement With an Anchored Expandable Titanium Cage in the Cervical Spine: A Clinical and Radiological Evaluation.

Expandable cervical cages have been used successfully to reconstruct the anterior spinal column. To perform clinical and radiological evaluation of vertebral body replacement with an anchored expandable titanium cage in the cervical spine after single-level and 2-level corpectomies. Between 2011 and 2017, 40 patients underwent a single-level (N=32) or 2-level (N=8) anterior corpectomy and fusion using an anchored expandable vertebral body replacement cage. Clinical and radiological data at admission, postoperatively, and at 3- and 12-mo follow-up were retrospectively analyzed. Clinical assessment was performed via standardized neurological evaluation, Odom score, and McCormick classification. Radiological assessment was performed via evaluation of sagittal profile, postoperative position, fusion, and subsidence rates. Mean last follow-up was 14.8±7 mo. Overall clinical and myelopathy-related improvements were shown directly after operation and at last follow-up. A stable centralized positioning of cages was achieved in 37 patients (93%). A mild ventral (>1.5 mm) malplacement was noted in 3 patients (7%) without clinical consequences. Sagittal alignment and preoperative cervical kyphosis improved significantly (7.8° gain of lordosis) and remained stable. Mean preoperative height of operated segments increased by 10 mm postoperatively and remained stable. Fusion rate in non-neoplastic patients and subsidence rate at last follow-up comprised 87.5% and 17.8%. With exception of 1 patient suffering from severe osteoporosis and cage subsidence, no patient needed additional secondary stabilization. Anterior corpectomy and fusion by an expandable anchored titanium cage with anchor screws without additional instrumentation resulted in overall clinical improvement and radiological anterior column support, achieving significant and reliable restoration of the physiological sagittal cervical profile.

Anterior column reconstruction of the thoracolumbar spine with a new modular PEEK vertebral body replacement device: retrospective clinical and radiologic cohort analysis of 48 cases with 1.7-years follow-up.

To evaluate whether a new PEEK vertebral body replacement can maintain the sagittal alignment as an anterior column reconstruction device in thoracic and lumbar spinal defects due to trauma or tumor. Retrospective review of 48 patients who underwent a corpectomy between T5 and L5 due to trauma or tumor and were stabilized with the new PEEK vertebral body replacement, between 2013 and 2017. We excluded patients who underwent a corpectomy for infection or degenerative disease and patients without complete follow-up in our institution. The primary outcome was the bi-segmental kyphotic angle (BKA). Secondary outcomes were the assessment of pedicle screw loosening, cage height, and subsidence or tilting of the cage. The clinical outcomes were assessed through the COMI-Score, EuroQol-5D, and Karnofsky indexes. Bony fusion and complications were registered. After the surgery BKA decreased by 12.1° (p < 0.001). At the end of the follow-up, we observed a mean loss of reduction of 1.6° (p = 0.002). This was accompanied by an increase in subsidence of 2.1mm (p < 0.001) and mean tilting of the cage of 1.4° (p = 0.003). The height of the cage and other parameters did not experience any changes. Clinically, the COMI-Score (p = 0.02) and the EuroQol-5D Index (p = 0.012) showed significant improvement, same as Karnofsky-Index (p = 0.015) at final follow-up. The fusion rate according to Bridwell was 92.1%. The 2% late complications were related to implant malpositioning. The new PEEK expandable vertebral body replacement is effective and safe in thoracic and lumbar anterior column reconstruction in tumor and trauma diseases.

Monosegmental anterior column reconstruction using an expandable vertebral body replacement device in combined posterior\u2013anterior stabilization of thoracolumbar burst fractures

IntroductionIn combined posterior–anterior stabilization of thoracolumbar burst fractures, the expandable vertebral body replacement device (VBRD) is typically placed bisegmentally for anterior column reconstruction (ACR). The aim of this study, however, was to assess feasibility, outcome and potential pitfalls of monosegmental ACR using a VBRD. In addition, clinical and radiological outcome of monosegmental ACR was related to that of bisegmental ACR using the same thoracoscopic technique.MethodsThirty-seven consecutive neurologically intact patients with burst fractures of the thoracolumbar junction (T11–L2) treated by combined posterior–anterior stabilization were included. Monosegmental ACR was performed in 18 and bisegmental ACR in 19 patients. Fracture type and extent of vertebral body comminution were determined on preoperative CT scans. Monosegmental and bisegmental kyphosis angles were analyzed preoperatively, postoperatively and at final radiological follow-up. Clinical outcome was assessed after a minimum of 2 years (74 ± 45 months; range 24–154; follow-up rate 89.2%) using VAS Spine Score, RMDQ, ODI and WHOQOL-BREF.ResultsMonosegmental ACR resulted in a mean monosegmental and bisegmental surgical correction of − 15.6 ± 7.7° and − 14.7 ± 8.1°, respectively. Postoperative monosegmental and bisegmental loss of correction averaged 2.7 ± 2.7° and 5.2 ± 3.7°, respectively. Two surgical pitfalls of monosegmental ACR were identified: VBRD positioning (1) onto the weak cancellous bone (too far cranially to the inferior endplate of the fractured vertebra) and (2) onto a significantly compromised inferior endplate with at least two (even subtle) fracture lines. Ignoring these pitfalls resulted in VBRD subsidence in five cases. When relating the clinical and radiological outcome of monosegmental ACR to that of bisegmental ACR, no significant differences were found, except for frequency of VBRD subsidence (5 vs. 0, P = 0.02) and bisegmental loss of correction (5.2 ± 3.7° vs. 2.6 ± 2.5°, P = 0.022). After exclusion of cases with VBRD subsidence, the latter did not reach significance anymore (4.9 ± 4.0° vs. 2.6 ± 2.5°, P = 0.084).ConclusionsThis study indicates that monosegmental ACR using a VBRD is feasible in thoracolumbar burst fractures if the inferior endplate is intact (incomplete burst fractures) or features only a single simple split fracture line (burst-split fractures). If the two identified pitfalls are avoided, monosegmental ACR may be a viable alternative to bisegmental ACR in selected thoracolumbar burst fractures to spare a motion segment and to reduce the distance for bony fusion.

Minimally invasive surgery for thoracolumbar spinal trauma.

The indications for operative intervention after thoracolumbar spine trauma have been well described. Advances in minimally invasive techniques, including percutaneous pedicle screw fixation and mini-open anterolateral retractor-based approaches can improve surgical outcomes when appropriately applied by reducing blood loss, operative duration and post-operative pain. Moreover, they allow for theoretical advantages by preservation of muscular and skeletal blood supply and innervation that is typically lost during the muscular dissection of open approaches. For thoracolumbar spine fractures, percutaneous fixation allows for internal bracing of unstable fractures during healing while maintaining sagittal alignment. In instances of neurological compromise from fracture retropulsion, corpectomies may be required, and mini-open lateral approaches adopted from degenerative disease applications allow for a minimally invasive manner to treat the defect. These further allow for placement of wide rectangular-footprint expandable vertebral body replacement devices to provide anterior column support. We believe this allows for lower rates of subsidence and helps to maintain the biomechanical integrity necessary to prevent post-traumatic malalignment and kyphosis. Together, these minimally invasive techniques combined supply the spine surgeon with a minimally invasive armamentarium to treat nearly all thoracolumbar spine trauma. Surgeons should be comfortable with the strengths and shortcomings of these approaches in order to successfully apply them for this pathology.

Radiological Results and Clinical Patient Outcome After Implantation of a Hydraulic Expandable Vertebral Body Replacement following Traumatic Vertebral Fractures in the Thoracic and Lumbar Spine: A 3-Year Follow-Up.

A prospective monocentric study. The aim of the current study was the analysis of patient outcome and radiological results 3 years after implantation of a hydraulic expandable vertebral body replacement (VBR) system. Around 70% to 90% of all traumatic spinal fractures are located in the thoracic and lumbar spine. Dorso-ventral stabilization is a frequently used procedure in traumatic vertebral body fracture treatment. VBR systems can be used to bridge bony defects. In the current study, a new VBR expanded by water pressure with adjustable endplates is used. All patients who suffered a singular traumatic fracture to a thoracic or lumbar vertebral body (Th 5-L 5) in the period from November 2009 to December 2010 and (i) underwent dorsal instrumentation and (ii) afterwards received the implantation of a hydraulic VBR were included in this study. The clinical outcome (visual analogue scale [VAS] spine score, questionnaire) and radiological findings (sagittal angle, implant subsidence, and implant position) 3 years after implantation were analyzed. The follow-up was successful for n = 47 patients (follow-up rate: 89%). Most of the patients (n = 40) were "generally/very satisfied" with their outcome. The mean rating of the VAS spine score was 65.2 ± 23.1 (range: 20.5-100.0). The analysis of the radiological data showed an average subsidence of the implants of 1.1 ± 1.2 mm (range 0.0-5.0 mm). After the initial operation, the local sagittal angle remained stable in the follow-up 3 years later both for the thoracic spine and lumbar spine. Furthermore, no change in the implant's position was observed. The implantation of a hydraulically expandable VBR allows a permanent stable fixation after traumatic fractures of the thoracic and lumbar spine. 2.

Reconstruction of Vertebral Bone Defects using an Expandable Replacement Device and Bioactive Glass S53P4 in the Treatment of Vertebral Osteomyelitis: Three Patients and Three Pathogens.

Bioactive glass S53P4 is an antibacterial bone substitute with bone-bonding and osteostimulative properties. The bone substitute has been successfully used clinically in spine; trauma; orthopedic; ear, nose, and throat; and cranio-maxillofacial surgeries. Bioactive glass S53P4 significantly reduces the amount of bacteria in vitro and possesses the capacity to kill both planktonic bacteria and bacteria in biofilm. Three patients with severe spondylodiscitis caused by Mycobacterium tuberculosis, Candida tropicalis, or Staphylococcus aureus were operatively treated due to failed conservative treatment. The vertebral defects were reconstructed using bioactive glass S53P4 and an expandable replacement device. Decompression and a posterolateral spondylodesis, using transpedicular fixation, were performed posteriorly in combination with an anterior decompression and reconstruction using an expandable vertebral body replacement device. For patients 1 and 2, the expander was covered with bioactive glass S53P4 only, and for patient 3, the glass was mixed with autograft bone. The patients healed well with complete neurological recovery. Fusion was observed for all patients. The total follow-up was 4 years for patient 1, 1 year and 8 months for patient 2, and 2 years and 2 months for patient 3. No relapses or complications were observed. The antibacterial properties of bioactive glass S53P4 also make it a suitable bone substitute in the treatment of severe spondylodiscitis.

Thoracoscopic Vertebral Body Replacement of Burst Fractures in the Thoracolumbar Spine with a Distractable Titanium Cage

Introduction The treatment of burst fractures in the thoracolumbar spine is controversially discussed. Therapeutic options reach from conservative measures up to the meanwhile established approach through dorsoventral stabilization. Thoracoscopy-assisted operation methods have been applied to restore the anterior column in the ventral spine for a couple of years. This approach helps to avoid invasive thoraco- and laparotomies and prolonged healing periods. These procedures are associated with certain complications such as chronic pain syndrome in over 50% of affected individuals. The Hydrolift (B. Braun Aesculap) is an infinitely variable, expandable vertebral body replacement available for thoracoscopy-assisted implantation. The aim of this study was to evaluate the clinical and radiological outcome, patients' reintegration in the working environment and possible restrictions during athletic and daily-live activities. Materials and Methods We performed a retrospective analysis including 30 patients (m:f = 24:6, average age: 56 years) with fractures of the vertebral bodies Th12 and L1 (3 A3.2, 23 A3.3, 4 B2.3), that have been treated with an infinitely variable, expandable vertebral body replacement (Hydrolift, B. Braun Aesculap) and an axis-stable plate (MACS, B. Braun Aesculap) in the Department of Traumatology of the University Hospital Salzburg, Austria between 03/2009 and 09/2013. A clinical follow-up, an assessment of the impairment through questionnaires (Oswestry Disability Index and VAS Spine) and a radiological evaluation of the position and osseous integration of the cage through CT have been collected after an average of 22 (18–47) months. Results 11 out of 30 patients have the same quality of life as prior to the injury, 13 have low-grade restrictions. After an average recovery period of 5 months, 56,7% of the patients are 100% reintegrated in their previous working life, 36,7% can continue working up to 75%. 1 Patient has changed his profession to a physically less challenging field, 1 patient is unable to work. 5 patients were retired prior to the accident. The outcome of the Oswestry Disability Index shows a low-grade impairment in everyday life with an average of 12,9% (0–40%). The analysis of the VAS Spine shows scores between 47,4% and 96,0%, with an average of 80,5%. A correction of 11,4° could be achieved after dorsoventral stabilization. The correction loss after reconstruction of the ventral spine with Hydrolift amounts to 1,8°. An osseous integration of the implants was observed in 96,7% of the patients. Two cases of a mild dislocation of the Hydrolift into the adjacent vertebral body took place, without any clinical relevance. Conclusion A stable treatment of burst fractures in the thoracolumbar spine can be achieved through a ventral spondylodesis with the Hydrolift and axis-stable MACS plate. The thoracoscopy-assisted operative treatment with Hydrolift is a successful method, due to stability, low additional morbidity, a high reintegration rate in the patients working environment (96%) and a high continuation of their familiar athletic activities.

Outcome after Implantation of a Hydraulic Vertebral Body Replacement in Traumatic Vertebral Fractures

Introduction The dorso-ventral stabilization is a frequently used procedure in traumatic vertebral body fracture treatment. The aim of the study was the analysis of radiological images and clinical outcome 3 years after implantation of an innovative hydraulic vertebral body replacement following a traumatic vertebral body fracture in the thoraco-lumbar spine. Materials and Methods The study includes all patients of our Level I trauma center which suffered a singular traumatic fracture of a thoracic or lumbar vertebral body (Th 5 - L 5) in the period from 11/2009 until 12/2010, that (i) underwent dorsal instrumentation and (ii) afterwards underwent implantation of a hydraulically expandable vertebral body replacement. The following radiological findings of all patients were evaluated (pre- and post-operatively and 3 years after implantation): sagittal angle, implants’ subsidence and implants’ position. Moreover, the clinical outcome 3 years after implantation was analyzed by the VAS spine scoring system. Details about trauma mechanism, current occupation, etc. were also documented. Statistical Analysis was performed with the software SAS 9.2. Results During the above mentioned period, n = 50 patients could be included in the study. The complete follow-up including the data 3 years after implantation of the vertebral body implant was successful for n = 47 (male: 26; female: 21) patients (follow-up rate: 89%). The mean age of all patients was 46.5 ± 17.0 years. The main reasons for spinal trauma were falls ( n = 28) and traffic accidents ( n = 14). The analysis of the radiological data showed an average sintering of the implants of 1.1 ± 1.2 mm (range 0.0 - 5.0 mm). After the initial operation, the local sagittal angle remained stable in the 3-years-follow up at thoracic spine (5.4 ± 4.8 ° versus 5.2 ± 4.8 °; p = 0.451) and lumbar spine (−7.2 ± 6.0 ° versus -7.0 ± 6.0 °; p = 0.451). Furthermore, no change in the implants’ position could be observed. Most of the patients ( n = 40) were “generally satisfied” or “very satisfied” with their outcome. The mean rating of the VAS spine score was 65.2 ± 23.1 (range: 20.5 - 100.0). Activities of daily life are less limited (83.0 ± 21.8) than activities concerning the patients' profession (49.5 ± 37.3). Taking analgesic medication is of clear effect (72.4 ± 27.4) and has a positive correlation ( p = 0.001) to a higher rated VAS spine score. Conclusion In summary, the current study shows that the implantation of that innovative hydraulic vertebral body replacement allows a permanent stable fixation after traumatic fractures of the thoracic and lumbar spine. General complications are rare and the local sagittal angle is fixed after 3 years. Secondary dislocation and serious sintering of the implant were not observed. The clinical outcome after implantation of the hydraulic vertebral body replacement is comparable to the outcome after the ventral stabilization with an iliac crest bone graft. Nevertheless, there is an obvious reduction in the VAS spine score after dorso-ventral stabilization in comparison to the healthy public.

A systematic review of the use of expandable cages in the cervical spine.

Expandable vertebral body replacement cages (VBRs) have been widely used for reconstruction of the thoracolumbar spine following corpectomy. However, their use in the cervical spine is less common, and currently, no expandable cages on the market are cleared or approved by the US Food and Drug Administration for use in the cervical spine. The objective of this study was to perform a systematic review on the use of expandable cages in the treatment of cervical spine pathology with a focus on fusion rates, deformity correction, complications, and indications. A comprehensive Medline search was performed, and 24 applicable articles were identified and included in this review. The advantages of expandable cages include greater ease of implantation with less risk of damage to the end plate, less intraoperative manipulation of the device, and potentially greater control over lordosis. They may be particularly advantageous in cases with poor bone quality, such as patients with osteoporosis or metastatic tumors that have been radiated. However, there is a potential risk of overdistraction, which is increased in the cervical spine, their minimum height limits their use in cases with collapsed vertebra, and the amount of hardware in the expansion mechanism may limit the surface area available for fusion. The use of expandable VBRs are a valuable tool in the armamentarium for reconstruction of the anterior column of the cervical spine with an acceptable safety profile. Although expandable cervical cages are clearly beneficial in certain clinical situations, widespread use following all corpectomies is not justified due to their significantly greater cost compared to structural bone grafts or non-expandable VBRs, which can be utilized to achieve similar clinical outcomes.

Biomechanical analysis of a new expandable vertebral body replacement combined with a new polyaxial antero-lateral plate and/or pedicle screws and rods.

Restoration of the anterior spinal profile and regular load-bearing is the main goal treating anterior spinal defects in case of fracture. Over the past years, development and clinical usage of cages for vertebral body replacement have increased rapidly. For an enhanced stabilization of rotationally unstable fractures, additional antero-lateral implants are common. The purpose of this study was the evaluation of the biomechanical behaviour of a recently modified, in situ distractible vertebral body replacement (VBR) combined with a newly developed antero-lateral polyaxial plate and/or pedicle screws and rods using a full corpectomy model as fracture simulation. Twelve human spinal specimens (Th12-L4) were tested in a six-degree-of-freedom spine tester applying pure moments of 7.5 Nm to evaluate the stiffness of three different test instrumentations using a total corpectomy L2 model: (1) VBR+antero-lateral plate; (2) VBR, antero-lateral plate+pedicle screws and rods and (3) VBR+pedicle screws and rods. In the presented total corpectomy defect model, only the combined antero-posterior instrumentation (VBR, antero-lateral plate+pedicle screws and rods) could achieve higher stiffness in all three-movement planes than the intact specimen. In axial rotation, neither isolated anterior instrumentation (VBR+antero-lateral plate) nor isolated posterior instrumentation (VBR+pedicle screws and rods) could stabilize the total corpectomy compared to the intact state. For rotationally unstable vertebral body fractures, only combined antero-posterior instrumentation could significantly decrease the range of motion (ROM) in all motion planes compared to the intact state.

In vitro biomechanics of an expandable vertebral body replacement with self-adjusting end plates

Background context Unstable burst fractures of the thoracolumbar spine may be treated surgically. Vertebral body replacements (VBRs) give anterior column support and, when used with supplemental fixation, impart rigidity to the injured segments. Although some VBRs are expandable, device congruity to the vertebral end plates is imprecise and may lead to stress risers and device subsidence. Purpose The objective of this study was to compare the rigidity of a VBR that self-adjusts to the adjacent vertebral end plates versus structural bone allograft and with an unsupported anterior column in a traumatic burst fracture reconstruction model. Study design Biomechanical flexibility testing with rod strain measurement. Patient sample Twelve T11–L3 human spine segments. Outcome measures Range of motion, neutral zone, and posterior fixation rod stress (moments). Methods Flexibility testing was performed to±6 Nm in flexion-extension, lateral bending, and axial rotation on 12 intact human T11–L3 specimens. Burst fractures were created in L1, and flexibility testing was repeated in three additional states: subtotal corpectomy with posterior instrumentation (PI) only from T12 to L2, reconstruction with a femoral strut allograft and PI, and reconstruction with a VBR (with self-adjusting end plates) and PI. The PI consisted of pedicle screws and strain gage instrumented rods that were calibrated to measure rod stress via flexion-extension bending moments. Results There was no statistical difference in range of motion or neutral zone between the strut graft and VBR constructs, which both had less motion than the PI-only construct in flexion/extension and torsion and were both less than the intact values in flexion/extension and lateral bending (p<.05). Posterior rod moments were significantly greater for the PI-only construct in flexion/extension relative to the strut graft and VBR states (p=.03). Conclusions This study, which simulated the immediate postoperative state, suggests that a VBR with self-adjusting end plate components has rigidity similar to the standard strut graft when combined with PI. Posterior rod stress was not significantly increased with this type of VBR compared with the strut graft reconstruction. The benefits of burst fracture stabilization using a self-adjusting VBR ultimately will not be known until long-term clinical studies are performed.

TECHNIQUE AND CLINICAL RESULTS OF MINIMALLY INVASIVE RECONSTRUCTION AND STABILIZATION OF THE THORACIC AND THORACOLUMBAR SPINE WITH EXPANDABLE CAGES AND VENTROLATERAL PLATE FIXATION

To evaluate the techniques of minimally invasive single- and multilevel corpectomy and reconstruction of the thoracic and thoracolumbar spine using expandable vertebral body replacement (VBR) cages and ventrolateral plate fixation (VPF) via anterolateral retropleural (ALRA) and combined thoracoabdominal approaches. 38 patients with spondylitis, traumatic or metastatic lesions of thoracic or thoracolumbar vertebrae T4 to L2 underwent spinal decompression and ventral column reconstruction with correction of spinal deformity by VBR and VPF via ALRA or a combined lateral extrapleural/extraperitoneal (extracoelomic) thoracolumbar approach (CLETA). Overall clinical and neurological outcome, operative time, blood loss, reduction of deformity, and postoperative pain were assessed during a mean follow-up period of 22.8 months. VBR and VPF were carried out successfully without conversion to conventional approaches in all patients. Mean operative time (ALRA, 163 +/- 33 min; CLETA, 175 +/- 39 min), mean blood loss (ALRA, 280 +/- 160 ml; CLETA, 420 +/- 250 ml), average correction (19.3 degrees), loss of correction of sagittal deformity (0.9 degrees), and clinical outcome compare favorably to the results reported for open and endoscopic techniques. Postoperative pain levels (mean visual analog scale score at 24 h, 2.7 +/- 0.9) and the incidence of postoperative pulmonary dysfunction (three out of 38 patients) were low. The average length of stay was 7.4 days. ALRA and CLETA obviate routine chest tube insertion, thus allowing for early postoperative ambulation (average, 1.1 d). Minimally invasive VBR and VPF conducted via minimally invasive approaches (ALRA or CLETA) yields favorable clinical results at least equal to conventional open surgery, with significant reductions in perioperative morbidity and pain, expedited ambulation, and early discharge from the hospital.

Secondary Collapse of an Expandable Cage After Vertebral Corpectomy.

Expandable vertebral body replacement systems have been increasingly used for anterior stabilization of spine. We report a secondary collapse of an expandable vertebral body replacement system. This specific complication has not been reported in the literature so far. The most obvious reason for failure was insufficient tightening of a locking screw. This paper emphasizes the importance of correct technical application.

Two in vivo surgical approaches for lumbar corpectomy using allograft and a metallic implant: a controlled clinical and biomechanical study

Both bone graft and metallic implants have been used in combination with the necessary anterior rod or plate instrumentation to fill the voids left by vertebral body removal, with the ultimate goal of restoring stability. One type of device that has recently been introduced is an expandable titanium telescoping cage that is designed to be used as a strut implant to fill corpectomy defects. The use of these devices has met varying success. Acceptance by surgeons and spine biomechanicians has been limited by clinical failure with subsequent loss of reduction and increase in kyphosis. In order to further improve patient care, it is critical to evaluate the use of these implants through biomechanical as well as other modes of testing. To compare and contrast the spinal fusion outcome of using allograft bone versus the expandable vertebral body replacement titanium implant in a lumbar corpectomy procedure. Controlled biomechanical study of lumbar spine fusion using bone graft and the expandable cage in an in vivo bovine model after a 4-month postoperative healing period (n=6). ANIMAL MODEL: Twelve Holstein calves aged 4-6 months with L3 and adjacent discs removed to create a simulated lumbar corpectomy defect. Lumbar spine stability after corpectomy repair was quantified by biomechanical parameters. Strength of fusion was assessed by stiffness of ex vivo spine specimens in flexion-extension, lateral bending, and torsion obtained from biomechanical testing. Uniaxial strain at various positions on the surface of the anterior plate was measured during loading as an additional stability parameter. Loading tests were repeated after removal of the anterior instrumentation (plate and the screws). The calves were randomly allocated to groups for corpectomy defect repair with 1) Allograft metatarsal bone and thoracolumbar spine locking plate, n=6; or 2) Expandable vertebral body replacement device, and thoracolumbar spine locking plate, n=6. After a 4-month postoperative period, anterior-posterior and lateral radiographs were taken of the spine, followed by animal sacrifice and harvesting of the lumbar spine for biomechanical and histological testing. For biomechanical testing, uniaxial strain gauges were applied to the thoracolumbar spine locking plate to measure plate deformation during loading in a custom built fixture for application of flexion-extension, lateral bending, and torsion moments in an Instron materials testing machine. These loading tests were repeated with the thoracolumbar spine locking plate removed, thereby loading solely the fused segment. At 4 months postoperative, the stiffness of the calf spines repaired by the metatarsal allograft and thoracolumbar spine locking plate was significantly greater than that of the spines repaired by the expandable cage and thoracolumbar spine locking plate. This finding was true for all three directions of loading (flexion-extension, left-right lateral bending, and torsion). Concordantly, the neutral zone, elastic zone, and range of motion of the spines repaired with the allograft bone were less than that of the spines repaired with the expandable cage. Greater strain values were observed from the gauges on the thoracolumbar spine locking plate of the spines using the expandable cage than the spines using allograft bone. This finding held for all gauge positions (anterior edge, anterior face, posterior edge, and posterior face at the longitudinal midpoint of the plate). After thoracolumbar spine locking plate removal and a repeat of the loading tests, a decrease in stiffness of the construct and a rise in the motion parameters were observed for both the allograft and cage groups. The use of allograft bone for corpectomy defect repair in the lumbar spine appears to contribute to a stiffer and perhaps more stable spine segment compared with using the expandable cage device for such a repair after a 4-month healing period in this in vivo calf model. These findings thus far are based upon the biomechanical data gathered.

Biomechanical investigations to changes in the stability of the spine after anterior, posterior and combined spondylodeses with a expandable vertebral body replacement after complete corpectomy

Biomechanical investigations to changes in the stability of the spine after anterior, posterior and combined spondylodeses with a expandable vertebral body replacement after complete corpectomy

Expandable vertebral body replacement in patients with thoracolumbar spine tumors

The objectives of surgical interventions for tumoral lesions of the spine include the establishment and improvement of tumor-related symptoms. Anterior tumor resection followed by reconstruction indicated if surgical treatment allowed a marginal removal of the tumor or could extend the individual survival rate in combination with adjuvant therapy options. Sufficient re-stabilization depends on adequate anterior column reconstruction. The purpose of this retrospective study was to present our experiences and results after anterior tumor resection followed by reconstruction with the expandable vertebral body replacement device (VBR, Ulrich, Germany) based on clinical application over 4 degrees years. We carried out an anterior tumor resection followed by reconstruction using an anterior extendable device in 32 patients with different spine tumors between 1996 and 2000. A retrospective evaluation was executed considering the patients medical records and radiological findings. Additionally, a clinical and radiological investigation of still living postoperative patients was carried out. The mean surgical time of all evaluated patients was 317.2 min. The average blood loss was 1,272.5 ml. According to the Tokuhashi score, patients with a postoperative survival time of at least 12 months demonstrated a score value > or = 9 points. According to our evaluated patients group metastatic lesions of the spine represented the largest group (78.1%). The average survival rate of this group amounted to 18.4 months postoperatively. Considering primary tumors the average survival rate at the time of last re-examination amounted to 34.8 months postoperatively. Preoperative neurological pathologies were present in 12 patients (Frankel stage C-D). During the postoperative monitoring period 58.3% of the patients demonstrated an improvement in initial neurological findings. There were no intraoperative complications or perioperative deaths. Implant dislocations were not observed. On account of the underlying, the anterior tumor resection with supplementary instrumentation represented a sufficient procedure in spinal tumor surgery. Adjuvant therapy can influence the postoperative survival period positively in addition to the surgical procedure. Following anterior tumor resection, extendable vertebral body replacements like the VBR device provide immediate spine stability by excellent defect adaptation. With regard to their intraoperative flexibility, expandable cages are more advantageous in contrast to non-expandable implants or bone grafts.