Comparison of multisegment anterior cervical fixation using bone strut graft versus a titanium rod and buttress prosthesis: analysis of outcome with long-term follow-up and interview by independent physician

Anterior cervical transpedicular screw fixation system in subaxial cervical spine: A finite element comparative study

Multilevel cervical corpectomy has raised the concern among surgeons that reconstruction with the anterior cervical screw plate system (ACSPS) alone may fail eventually. As an alternative, the anterior cervical transpedicular screw (ACTPS) has been adopted in clinical practice. We used the finite element analysis to investigate whether ACTPS is a more reasonable choice, in comparison with ACSPS, after a 2-level corpectomy in the subaxial cervical spine. These 2 types of implantation models with the applied 75 N axial pressure and 1 N • m pure moment of the couple were evaluated. Compared with the intact model, the range of motion (ROM) at the operative segments (C4-C7) decreased by 97.5% in flexion-extension, 91.3% in axial rotation, and 99.3% in lateral bending in the ACTPS model, whereas it decreased by 95.1%, 73.4%, 96.9% in the ACSPS model respectively. The ROM at the adjacent segment (C3/4) in the ACTPS model decreased in all motions, while that of the ACSPS model increased in axial rotation and flexion-extension compared with the intact model. Compared to the ACSPS model, whose stress concentrated on the interface between the screws and the titanium plate, the stress of the ACTPS model was well-distributed. There was also a significant difference between the maximum stress value of the 2 models. ACTPS and ACSPS are biomechanically favorable. The stability in reducing ROM of ACTPS may be better and the risk of failure for internal fixator is relatively low compared with ACSPS fixation except for under lateral bending in reconstruction the stability of the subaxial cervical spine after 2-level corpectomy.

Clinicoradiological Outcome of 3 or More Levels of Anterior Cervical Corpectomy and Reconstruction

BACKGROUND

Studies reporting multilevel anterior cervical corpectomy (>2 levels) and reconstruction in patients with long-segment anterior cervical compression are few and surgical outcomes are variable with increased surgical morbidity and a high incidence of graft-related complications. The aim of this study is to evaluate the effectiveness and safety of cervical corpectomy and anterior reconstruction of 3 or more levels in patients with long-segment anterior cervical compression.

METHODS

We retrospectively reviewed patients who had undergone 3 or more levels of anterior cervical corpectomy and reconstruction from 2014 to 2018. Clinical and radiological parameters such as Nurick grading, modified Japanese Orthopedic Association (mJOA) score, cervical segmental angle, cervical sagittal angle, graft subsidence, and fusion rate were evaluated preoperatively and at a 2-year follow-up. Patients were divided into 2 groups according to their anterior reconstruction, either with fibular strut autogenous graft or titanium mesh cage and rigid anterior cervical plating for subgroup analysis. Patients whose bone stock was found to be poor had undergone posterior instrumentation as a staged procedure.

RESULTS

There were 48 patients (mean age: 58.17 years) in the cohort: 42 had undergone 3-level and 6 had undergone 4-level cervical corpectomy with an ossified posterior longitudinal ligament and multilevel cervical spondylotic myelopathy being the main surgical indications. C5 to C7 corpectomy was most common. Of the cohort, 83.4% had standalone anterior reconstruction and only 8 patients (16.6%) had supplementation with posterior instrumentation. Our subgroup analysis showed statistically significant change in Nurick grading, mJOA score, cervical segmental angle, and sagittal angle in both groups at a 2-year follow-up (P < .05). Overall fusion rate was 89.5%. Decreased incidence of graft subsidence, statistically significant less graft subsidence (P = .002) and a higher fusion rate (P = .001) were noted in titanium mesh cage group at 2-year follow-up.

CONCLUSIONS

Multilevel anterior cervical corpectomy and reconstruction is a safe and efficacious procedure. A titanium mesh cage filled with autogenous bone graft and a rigid anterior cervical plate gives best results. Posterior instrumentation should be considered along with a multilevel cervical corpectomy construct in patients with poor bone stock.

LEVEL OF EVIDENCE

4.

Challenge of handling a Charcot spinal arthropathy with a novel hybrid fibular autograft and expandable cage

A 26-year-old man, who was paraplegic for 6 years due to a motor vehicle accident, presented to the authors' clinic following his incapacity to withstand a sitting posture, the frequent sensation of "clicks" in his back, and a complaint of back pain while in his wheelchair. On imaging, his dorsal spine showed a complete arthrodesis of the primarily fused vertebrae. However, distal to this segment, a Charcot spinal arthropathy with subluxation of T12-L1 was evident. Repair of this complex, uncommon, late complication of his paraplegia by the frequently used fusion techniques was shown to be inappropriate. A novel and elaborate surgical procedure is presented by which a complete fusion of the affected spine was secured. A left retrodiaphragmatic approach was used. Complete corpectomy of both the T-12 and L-1 vertebrae to the preserved endplates was performed. Most of the patient's fibula was resected and shaped for engrafting. The segment of the fibula was introduced into a mesh cage, before its intramedullary implantation into the T-12 and L-1 vertebrae. This 2-step procedure combined the hybrid use of a fibular autograft and an expandable mesh cage, incorporated one into the other, in an innovative intramedullary position. This intervention allowed the patient to resume his former condition as an extremely physically active patient with paraplegia. Nine years later, an asymptomatic early-stage Charcot spine was found at L5-S1, but no treatment is planned at this point.

A Novel Anterior Transpedicular Screw Artificial Vertebral Body System for Lower Cervical Spine Fixation: A Finite Element Study

A finite element model was used to compare the biomechanical properties of a novel anterior transpedicular screw artificial vertebral body system (AVBS) with a conventional anterior screw plate system (ASPS) for fixation in the lower cervical spine. A model of the intact cervical spine (C3–C7) was established. AVBS or ASPS constructs were implanted between C4 and C6. The models were loaded in three-dimensional (3D) motion. The Von Mises stress distribution in the internal fixators was evaluated, as well as the range of motion (ROM) and facet joint force. The models were generated and analyzed by mimics, geomagic studio, and ansys software. The intact model of the lower cervical spine consisted of 286,382 elements. The model was validated against previously reported cadaveric experimental data. In the ASPS model, stress was concentrated at the connection between the screw and plate and the connection between the titanium mesh and adjacent vertebral body. In the AVBS model, stress was evenly distributed. Compared to the intact cervical spine model, the ROM of the whole specimen after fixation with both constructs is decreased by approximately 3 deg. ROM of adjacent segments is increased by approximately 5 deg. Facet joint force of the ASPS and AVBS models was higher than those of the intact cervical spine model, especially in extension and lateral bending. AVBS fixation represents a novel reconstruction approach for the lower cervical spine. AVBS provides better stability and lower risk for internal fixator failure compared with traditional ASPS fixation.

Hybrid Decompression Technique Versus Anterior Cervical Corpectomy and Fusion for Treating Multilevel Cervical Spondylotic Myelopathy: Which One Is Better?

BACKGROUND

The hybrid decompression technique (corpectomy combined with discectomy) and anterior cervical corpectomy with fusion (ACCF) both provide good neurological recovery and disease stabilization for the treatment of multilevel cervical spondylotic myelopathy (CSM). However, no single study has been large enough to determine definitively which one is superior for this condition.

OBJECTIVE

A meta-analysis was conducted to compare the clinical efficacy and safety of the hybrid decompression technique versus ACCF for the treatment of multilevel CSM.

METHODS

Electronic databases such as PubMed, MEDLINE, EMBASE, Google Scholar, and the Cochrane Library were selected to search for potentially relevant trials up to April 2015 that compared the outcomes of the hybrid technique with ACCF for the treatment of multilevel CSM. Data extraction and quality assessment were performed according to Cochrane Collaboration guidelines. The outcome assessments were duration of surgery, blood loss, Cobb angle of C2-C7, segment angle, fusion rate, Japanese Orthopedics Association score, Neck Disability Index, and complications. The results were expressed as the odds ratio (OR) for dichotomous outcomes and the mean difference (MD) for continuous outcomes with a 95% confidence interval (CI).

RESULTS

Five controlled clinical trials published between 2009 and 2013, involving 356 patients (hybrid, 196; ACCF, 160) with 3- or 4-level CSM were retrieved in this study. Overall, there were significant differences between the 2 treatment groups for blood loss (MD = -38.69, 95% CI = -54.62 to -22.76, P < 0.01), fusion rate (OR = 2.56, 95% CI = 1.11 to 5.93, P = 0.03), and complications (OR = 0.25, 95% CI = 0.15 to 0.43, P < 0.01). However, no significant differences were found for duration of surgery (MD = -4.50, 95% CI = -22.902 to 13.91, P = 0.63), Cobb angle of C2-C7 after surgery (MD = 3.32, 95% CI = -3.72 to 10.37, P = 0.35), segment angle after surgery (MD = 2.87, 95% CI = -2.47 to 8.21, P = 0.29), Japanese Orthopedics Association score (MD = -0.07, 95% CI = -0.36 to 0.22, P = 0.62), or Neck Disability Index (MD = -0.86, 95% CI = -3.26 to 1.54, P = 0.48).

CONCLUSION

Based on this meta-analysis, both the hybrid technique and ACCF can achieve good results for CSM. However, the hybrid technique is associated with significantly less blood loss, complications, and a higher fusion rate than ACCF.

Analysis of postoperative pain at the anterior iliac crest harvest site: a prospective study of the intraoperative local administration of ropivacaine

Study Design

This was a prospective randomized comparative study.

Purpose

The aim of this study was to objectify donor site-related pain following anterior iliac crest graft harvesting, in patients who have undergone multilevel anterior cervical discectomy and fusion with plating (ACDFP); and to assess the effect of an intraoperative local single injection of ropivacaine on postoperative pain.

Overview of Literature

Multilevel ACDFP can be associated with a high non-union rate. Autogenous iliac bone has been used to increase union rates, although a high incidence of donor site-related pain has been reported.

Methods

Forty consecutive patients who required 3-level or 4-level ACDFP were prospectively assessed for donor site-related pain. Pain levels were assessed daily for five days postoperative using the visual analog scale (VAS). Patients were randomly assigned to group A or B. In group A patients, 7-10 mL of ropivacaine (0.2%) was injected into the iliac crest after iliac crest graft harvesting. Morphine usage via patient controlled analgesia was calculated. At six months postoperative, patient complaints at the harvest site were documented.

Results

Patients were randomly assigned to group A or B. In group A, ropivacaine was locally administered at the site of the iliac crest graft harvest after fascia closure. In group B, no additional treatments were administered. The average patient age in group A was 56±7.6 years, whereas the average age of patients in group B was 52.6±10.4 years. Group A had an average of 0.6±0.7 previous surgeries per patient, whereas group B had an average of 0.8±1.0 previous surgeries per patient. The average number of levels fused in group A was 3.6±0.7, whereas the average number of levels fused in group B was 3.7±0.9 (all p>0.05). In group A, the mean ropivacaine volume administered was 8.4±1.5 mL. No patient complaints regarding chronic pain, were reported six months postoperatively. No complications were encountered from the harvest site, and all patients underwent successful 3-level and 4-level ACDFP. Statistical analysis showed significant differences for VAS on postoperative day 1 (p=0.004) and day 2 (p=0.005).

Conclusions

VAS assessment showed overall moderate perioperative morbidity in terms of donor site-related pain, which was reduced by administering ropivacaine.

Co-registration of isotope bone scan with CT scan and MRI in the investigation of spinal pathology

Image fusion software enables technetium(99m)-methylene diphosphonate (Tc(99m)-MDP) bone scan images to be co-registered with CT scan or MRI, allowing greater anatomical discrimination. We examined the role of bone scan images co-registered with CT scan or MRI in the investigation of patients presenting with axial spinal pain and/or limb pain. One hundred and thirty-nine consecutive patients were examined, and thereafter investigated with CT scan, MRI, and/or dynamic plain films. At this point diagnosis (pathology type and anatomical site) and treatment intention were declared. The co-registered Tc(99m)-MDP bone scan images were then studied, after which diagnosis (pathology type and anatomical site) and treatment intention were re-declared. This data were then analysed to determine whether the addition of co-registered bone scan images resulted in any change in diagnosis or treatment intention. The most significant change in diagnosis was pathology type (10%). Anatomical site changed markedly without overlap of the pre and post-isotope fields in 5%, and with overlap in 10%. Treatment intention had a major change in 3.6% and minor change in 8.6%. In the two groups where there was (i) no obvious pathology after full pre-isotope investigation, or (ii) a spinal fusion under suspicion, addition of the bone scan information led to a major change in the pathology and/or anatomical localisation in 18% and 19%, respectively. The addition of co-registered Tc(99m)-MDP bone scan images offers significant diagnostic assistance, particularly in the difficult diagnostic groups where a failed spinal fusion may be the suspected pain generator, or when no pain generator can otherwise be found.

Construction and accuracy assessment of patient-specific biocompatible drill template for cervical anterior transpedicular screw (ATPS) insertion: an in vitro study

Background

With the properties of three-column fixation and anterior-approach-only procedure, anterior transpedicular screw (ATPS) is ideal for severe multilevel traumatic cervical instabilities. However, the accurate insertion of ATPS remains challenging. Here we constructed a patient-specific biocompatible drill template and evaluated its accuracy in assisting ATPS insertion.

Methods

After ethical approval, 24 formalin-preserved cervical vertebrae (C2–C7) were CT scanned. 3D reconstruction models of cervical vertebra were obtained with 2-mm-diameter virtual pin tracts at the central pedicles. The 3D models were used for rapid prototyping (RP) printing. A 2-mm-diameter Kirschner wire was then inserted into the pin tract of the RP model before polymethylmethacrylate was used to construct the patient-specific biocompatible drill template. After removal of the anterior soft tissue, a 2-mm-diameter Kirschner wire was inserted into the cervical pedicle with the assistance of drill template. Cadaveric cervical spines with pin tracts were subsequently scanned using the same CT scanner. A 3D reconstruction was performed of the scanned spines to get 3D models of the vertebrae containing the actual pin tracts. The deviations were calculated between 3D models with virtual and actual pin tracts at the middle point of the cervical pedicle. 3D models of 3.5 mm-diameter screws were used in simulated insertion to grade the screw positions.

Findings

The patient-specific biocompatible drill template was constructed to assist ATPS insertion successfully. There were no significant differences between medial/lateral deviations (P = 0.797) or between superior/inferior deviations (P = 0.741). The absolute deviation values were 0.82±0.75 mm and 1.10±0.96 mm in axial and sagittal planes, respectively. In the simulated insertion, the screws in non-critical position were 44/48 (91.7%).

Conclusions

The patient-specific drill template is biocompatible, easy-to-apply and accurate in assisting ATPS insertion. Its clinical applications should be further researched.

A new technique for anterior cervical pedicle screw implantation

OBJECTIVE

To introduce and evaluate a new technique, anterior pedicle screw implantation, for anterior cervical reconstruction.

METHODS

Seven patients (five men and two women) with an average age of 65 years were included in this group. After carefully preparation, anterior pedicle screws were implanted under fluoroscopy in all patients. The position of the anterior pedicle screws was evaluated three days postoperatively by X-ray and CT imaging. The mean recovery rate as assessed by the Japanese Orthopaedic Association (JOA) score was recorded at final follow-up.

RESULTS

A total of fourteen anterior pedicle screws were implanted in our group. The average follow up period was 8 months. The mean JOA score was 12.5 preoperatively and 14.8 postoperatively. The mean improvement in the JOA score was 50.5% at final follow-up. The average local alignment improved from 4.0 of kyphosis preoperatively to 6.5 of lordosis at final follow-up. Early bony union was observed in four cases that were followed up for more than 3 months. There were no serious complications. No "pedicle perforation" was observed in any of the fourteen anterior pedicle screws, whereas one screw exposure occurred.

CONCLUSION

Anterior cervical pedicle screw implantation is a feasible method for selected cases. It provides another choice for strong anterior cervical reconstruction.

O que eu não faço mais na cirurgia da coluna vertebral: pesquisa entre cirurgiões de coluna brasileiros

OBJETIVO: Apresentar o resultado de pesquisa realizada entre 257 cirurgiões de coluna sobre os principais procedimentos cirúrgicos que não são mais utilizados para o tratamento das doenças traumáticas, degenerativas e deformidades da coluna vertebral. MÉTODO: Os participantes da pesquisa responderam a um questionário abrangendo o tratamento das diferentes doenças traumáticas, degenerativas e deformidades dos segmentos cervical, torácico e lombar, sendo que cada quesito apresentava três opções de resposta: não faço mais, nunca utilizei e ainda utilizo. RESULTADOS: Os cirurgiões entrevistados eram oriundos de 22 estados brasileiros, 97% eram do sexo masculino com idade variando de 28 a 72 anos de idade (média 43,16 anos ±11,54 anos), e com 0 a 23 anos de atuação na área da cirurgia da coluna vertebral. A formação básica dos cirurgiões entrevistados era Ortopedia em 78,2% e Neurocirurgia em 20,2%. CONCLUSÃO: A avaliação das respostas dos questionários evidencia a mudança de atitude terapêutica e abandono de técnicas classicamente utilizadas no tratamento das doenças da coluna vertebral, influência da formação básica do cirurgião na escolha do tratamento das doenças da coluna vertebral e grande espectro de opções terapêuticas entre os cirurgiões entrevistados considerando o tempo de experiência na área de atuação, idade e formação básica.

The stabilizing potential of anterior, posterior and combined techniques for the reconstruction of a 2-level cervical corpectomy model: biomechanical study and first results of ATPS prototyping

Clinical studies reported frequent failure with anterior instrumented multilevel cervical corpectomies. Hence, posterior augmentation was recommended but necessitates a second approach. Thus, an author group evaluated the feasibility, pull-out characteristics, and accuracy of anterior transpedicular screw (ATPS) fixation. Although first success with clinical application of ATPS has already been reported, no data exist on biomechanical characteristics of an ATPS-plate system enabling transpedicular end-level fixation in advanced instabilities. Therefore, we evaluated biomechanical qualities of an ATPS prototype C4-C7 for reduction of range of motion (ROM) and primary stability in a non-destructive setup among five constructs: anterior plate, posterior all-lateral mass screw construct, posterior construct with lateral mass screws C5 + C6 and end-level fixation using pedicle screws unilaterally or bilaterally, and a 360° construct. 12 human spines C3-T1 were divided into two groups. Four constructs were tested in group 1 and three in group 2; the ATPS prototypes were tested in both groups. Specimens were subjected to flexibility test in a spine motion tester at intact state and after 2-level corpectomy C5-C6 with subsequent reconstruction using a distractable cage and one of the osteosynthesis mentioned above. ROM in flexion-extension, axial rotation, and lateral bending was reported as normalized values. All instrumentations but the anterior plate showed significant reduction of ROM for all directions compared to the intact state. The 360° construct outperformed all others in terms of reducing ROM. While there were no significant differences between the 360° and posterior constructs in flexion-extension and lateral bending, the 360° constructs were significantly more stable in axial rotation. Concerning primary stability of ATPS prototypes, there were no significant differences compared to posterior-only constructs in flexion-extension and axial rotation. The 360° construct showed significant differences to the ATPS prototypes in flexion-extension, while no significant differences existed in axial rotation. But in lateral bending, the ATPS prototype and the anterior plate performed significantly worse than the posterior constructs. ATPS was shown to confer increased primary stability compared to the anterior plate in flexion-extension and axial rotation with the latter yielding significance. We showed that primary stability after 2-level corpectomy reconstruction using ATPS prototypes compared favorably to posterior systems and superior to anterior plates. From the biomechanical point, the 360° instrumentation was shown the most efficient for reconstruction of 2-level corpectomies. Further studies will elucidate whether fatigue testing will enhance the benefit of transpedicular anchorage with posterior constructs and ATPS.

Reconstructive techniques study after anterior decompression of multilevel cervical spondylotic myelopathy

STUDY DESIGN

Retrospectively compared 2 reconstructive techniques after the anterior decompression of multilevel cervical spondylotic myelopathy.

OBJECTIVE

To clinically compare the biomechanical stability and neurologic results of 2 reconstructive techniques after the anterior decompression of multilevel cervical spondylotic myelopathy retrospectively.

SUMMARY OF BACKGROUND DATA

Previous studies comparing different reconstruction techniques after the anterior decompression of multilevel cervical spondylotic myelopathy have yielded mixed results. Some studies have reported a high incidence of graft-plate extrusion when 2 or more corpectomies are performed and reconstructed with a long segmental anterior plate fixation that spans the strut graft without supplemental posterior cervical fixation, a standalone cage and segmental plate fixation after combination 1 level discectomy and 1 level corpectomy used to treat multilevel cervical spondylotic myelopathy were reported have no evidence of late-onset instrumentation-related failure, although 2 techniques have never been directly compared in a consecutive series of patients clinically.

METHODS

A retrospective study of 59 patients with multilevel (3 levels) cervical spondylotic myelopathy treated with 1 of 2 anterior decompression and reconstruction methods were compared. Copectomy method (39 patients) is 2-level corpectomies and long segment end-construct plate fixation; hybrid method (20 patients) is standalone cage and segmental plate fixation after 1-level discectomy combined with 1-level corpectomy.

RESULTS

The follow-up (mean18 mo) results show both methods had similar, satisfactory recovery of neurologic function (P>0.05). There were 7 cases of graft/plate migrations or dislodgments (17.9%) and 4 of these required revision surgery among 39 patients with corpectomy method, as compared with no graft/implant-related complications or nonunion among 20 patients with hybrid method (P<0.001).

CONCLUSIONS

This study clearly demonstrates that, adequate decompression can be achieved for the multilevel cervical spondylotic myelopathy with both methods, and the hybrid method offers better biomechanical stability and fusion results than the corpectomy method, and obviates the need for staged circumferential procedures.

In vitro study of accuracy of cervical pedicle screw insertion using an electronic conductivity device (ATPS part III)

Reconstruction of the highly unstable, anteriorly decompressed cervical spine poses biomechanical challenges to current stabilization strategies, including circumferential instrumented fusion, to prevent failure. To avoid secondary posterior surgery, particularly in the elderly population, while increasing primary construct rigidity of anterior-only reconstructions, the authors introduced the concept of anterior transpedicular screw (ATPS) fixation and plating. We demonstrated its morphological feasibility, its superior biomechanical pull-out characteristics compared with vertebral body screws and the accuracy of inserting ATPS using a manual fluoroscopically assisted technique. Although accuracy was high, showing non-critical breaches in the axial and sagittal plane in 78 and 96%, further research was indicated refining technique and increasing accuracy. In light of first clinical case series, the authors analyzed the impact of using an electronic conductivity device (ECD, PediGuard) on the accuracy of ATPS insertion. As there exist only experiences in thoracolumbar surgery the versatility of the ECD was also assessed for posterior cervical pedicle screw fixation (pCPS). 30 ATPS and 30 pCPS were inserted alternately into the C3-T1 vertebra of five fresh-frozen specimen. Fluoroscopic assistance was only used for the entry point selection, pedicle tract preparation was done using the ECD. Preoperative CT scans were assessed for sclerosis at the pedicle entrance or core, and vertebrae with dense pedicles were excluded. Pre- and postoperative reconstructed CT scans were analyzed for pedicle screw positions according to a previously established grading system. Statistical analysis revealed an astonishingly high accuracy for the ATPS group with no critical screw position (0%) in axial or sagittal plane. In the pCPS group, 88.9% of screws inserted showed non-critical screw position, while 11.1% showed critical pedicle perforations. The usage of an ECD for posterior and anterior pedicle screw tract preparation with the exclusion of dense cortical pedicles was shown to be a successful and clinically sound concept with high-accuracy rates for ATPS and pCPS. In concert with fluoroscopic guidance and pedicle axis views, application of an ECD and exclusion of dense cortical pedicles might increase comfort and safety with the clinical use of pCPS. In addition, we presented a reasonable laboratory setting for the clinical introduction of an ATPS-plate system.

Comparison between anterior cervical discectomy fusion and cervical corpectomy fusion using titanium cages for reconstruction: analysis of outcome and long-term follow-up

Retrospective comparative study of 80 consecutive patients treated with either anterior cervical discectomy fusion (ACDF) or anterior cervical corpectomy fusion (ACCF) for multi-level cervical spondylosis. To compare clinical outcome, fusion rates, and complications of anterior cervical reconstruction of multi-level ACDF and single-/multi-level ACCF performed using titanium mesh cages (TMCs) filled with autograft and anterior cervical plates (ACPs). Reconstruction of the cervical spine after discectomy or corpectomy with titanium cages filled with autograft has become an acceptable alternative to both allograft and autograft; however, there is no data comparing the outcome of multi-level ACDF and single-/multi-level ACCF using this reconstruction. We evaluated 80 consecutive patients who underwent surgery for the treatment of multi-level cervical spondylosis at our institution from 1998 to 2001. In this series, 42 patients underwent multi-level ACDF (Group 1) and 38 patients underwent ACCF (Group 2). Interbody TMCs and local autograft bone with ACPs were used in both procedures. Medical records were reviewed to assess outcome. Clinical outcome was measured by Odom's criteria. Operative time and blood loss were noted. Radiographs were obtained at 6 and 12 weeks, 6 months, 1 year, and 2 years (if necessary). Early hardware failures and pseudarthroses were noted. Cervical sagittal curvature was measured by Ishihara's index at 1 year. Group 1 had a mean age 46.2 years (range 35-60 years). Group 2 had a mean age 50.1 years (range 35-70 years).The operative time was significantly lower (P < 0.001) and blood loss significantly higher (P < 0.001) in Group 2 than in Group 1. At a minimum of 1 year follow up, patients in both groups had equivalent improvement in their clinical symptoms. The fusion rates for Group 1 were 97.6 and 92.1% for Group 2. The rates of early hardware failure were higher in Group 2 (2.6%) than in Group 1 (0%). The fusion rates for Group 1 were not significantly higher than Group 2 (P > 0.28). There was one patient in Group 1 and 2 patients in Group 2 with pseudarthroses. Complication rates in Group 2 were not significantly higher (P > 0.341). Cervical lordosis was well-maintained (80%) in both groups. Both multi-level ACDF and ACCF with anterior cervical reconstruction using TMC filled with autograft and ACP for treatment of multi-level cervical spondylosis have high fusion rates and good clinical outcome. However, there is a higher rate of early hardware failure and pseudarthroses after ACCF than ACDF. Hence, in the absence of specific pathology requiring removal of vertebral body, multi-level ACDF using interbody cages and autologous bone graft could result in lower morbidity.

Correlation between change in graft height and change in segmental angle following central corpectomy for cervical spondylotic myelopathy

Object

This study was undertaken to examine the correlation between change in graft height and change in angulation across grafted segments (segmental angle) in patients undergoing central corpectomy (CC) with autologous bone reconstruction for cervical spondylotic myelopathy (CSM).

Methods

The authors performed a retrospective analysis of 70 cases in which patients with CSM underwent uninstrumented single- or multilevel CC and had evidence of osseous fusion of their grafts at follow-up. The segmental angles and heights of the grafted segments on preoperative, postoperative, and follow-up radiographs were compared.

Results

The mean change in graft height (± standard deviation) was −7.3 ± 3.8 mm (mean duration of follow-up 19.7 ± 5.4 months, range 13–53 months). There was a mean kyphotic change in segmental angle of −7.3 ± 3.8° (p < 0.001). In patients who had a straight or kyphotic cervical spine (28 patients) or a straight or kyphotic segment (32 patients) preoperatively, there was a significant linear correlation between changes in graft height and changes in segmental angle (Pearson correlation, r = 0.40, p = 0.03; r = 0.40, p = 0.02, respectively). Such a correlation was not seen in the patients who had a lordotic cervical spine (42 patients) or a lordotic segment (38 patients) preoperatively (Pearson correlation, r = −0.04, p = 0.81; r = 0.08, p = 0.62, respectively). The change in segmental angle did not influence improvement in Nurick grade (p = 0.8). The degree of agreement between the 2 observers was almost perfect for measurement of graft height (postoperative intraclass correlation coefficient [ICC] = 0.94, follow-up ICC = 0.90) but was significantly lower for measurement of segmental angles (postoperative ICC = 0.71, follow-up ICC = 0.67).

Conclusions

Among patients undergoing uninstrumented CC for CSM, there is a significant correlation between postoperative settling and kyphotic change across fused segments in those who had straight or kyphotic cervical spines or segments preoperatively but not in those who had lordotic cervical spines or segments preoperatively. A more vigorous surgical correction of the segmental kyphosis than achieved in this study might have caused the kyphotic segments to behave like the lordotic segments. Paraspinal muscles and ligaments may play a role in determining the segmental angle as graft settling in patients with lordotic spines or segments is not linearly correlated with angular change.

Cervical anterior transpedicular screw fixation. Part I: Study on morphological feasibility, indications, and technical prerequisites

Multilevel cervical spine procedures can challenge the stability of current anterior cervical screw-and-plate systems, particularly in cases of severe three-column subaxial cervical spine injuries and multilevel plated reconstructions in osteoporotic bone. Supplemental posterior instrumentation is therefore recommended to increase primary construct rigidity and diminish early failure rates. The increasing number of successfully performed posterior cervical pedicle screw fixations have enabled more stable fixations, however most cervical pathologies are located anteriorly and preferably addressed by an anterior approach. To combine the advantages of the anterior approach with the superior biomechanical characteristics of cervical pedicle screw fixation, the authors developed a new concept of a cervical anterior transpedicular screw-and-plate system. An in vivo anatomical study was performed to explore the feasibility of anterior transpedicular screw fixation (ATPS) in the cervical spine. The morphological study was conducted based on 29 cervical spine CT scans from healthy patients and measurements were performed on the pedicle sizes, angulations, vertebral body depth, height and width at C2 to T1. Significant morphologic parameters for the new technique are discussed. These parameters include the sagittal and transverse intersection points of the pedicle axis with the anterior vertebral body wall, as well as the distances between sagittal intersection points from C2 to T1. On the basis of these results, standard spine models were reconstructed and used for the conceptual development of a preclinical release prototype of an anterior transpedicular screw-and-plate system. The morphological feasibility of the new technique is demonstrated, and its indications, biomechanical considerations, as well as surgical prerequisites are thoroughly discussed. In the future, the technique of cervical anterior transpedicular screw fixation might diminish the number of failures in the reconstruction of multilevel and three-column cervical spine instabilities, and avoid the need for supplemental posterior instrumentation.