Vertebral Interbody Fusion Research Articles

Surgical treatment of cervical (C7‐T1) instability caused by discospondylitis in a horse

SummaryDiscospondylitis is an inflammatory condition involving the vertebral bodies and is rarely reported in horses. Clinical signs are associated with neck stiffness and forelimb ataxia. In other species, treatment consists mainly of antibiotics coupled with non‐steroidal analgesics for a period of 3–12 weeks. An inadequate response to conservative treatment requires surgical intervention, but there is limited information in the literature regarding surgical management in large animals. A 3‐year‐old Quarter Horse gelding presented for an approximately 4‐week history of generalised stiffness and reluctance to move. Computed tomography with myelogram revealed abnormalities consistent with discospondylitis at the level of the seventh cervical and first thoracic vertebrae (C7‐T1). The patient underwent cervical vertebral interbody fusion using a combination of compression of the vertebral bodies using cortical screws in lag fashion and a 4‐hole locking compression plate (LCP). The patient was discharged from the hospital with marked improvement. At the time of this report, 4 months after the procedure, the horse continues to show marked improvement in mobility and range of motion.

The Thoracoscopic Approach in Spinal Cord Disease.

Most VATS approaches are from the right side for pathologies involving the middle and upper thoracic spine because there is a greater working spinal surface area lateral to the azygos vein than that lateral to the aorta. Below T-9, a left-sided approach is made possible because the aorta moves away from the left posterolateral aspect of the spine to an anterior position as it passes through the diaphragm. VATS has been used extensively in spinal deformities such as scoliosis. The use of VATS in spine surgery includes the treatment of thoracic prolapsed disk diseases, vertebral osteomyelitis, fracture management, vertebral interbody fusion, tissue biopsy, anterior spinal release, and fusion without or with instrumentation (VAT-I) for spinal deformity correction. As the knowledge and the comfort of using such techniques have expanded, the indications have extended to corpectomy for tumor resections. In the field of minimally invasive surgery, VATS now acts as a keyhole to the thoracic spine and an alternative to open thoracotomy for the treatment of several spinal conditions.Although VATS can be performed in such spine conditions, it is most beneficial in the treatment of scoliotic deformity, which requires taking a multilevel approach, from the upper to the lower thoracic spine.

Use of a nano-hydroxyapatite/polyamide composite in anterior cervical subtotal corpectomy and fusion

This study aimed to explore the safety and efficacy of using nano-hydroxyapatite/polyamide (N-HA/PA) composite in anterior cervical vertebral body subtotal corpectomy and interbody fusion. Total 50 patients with cervical spondylotic myelopathy were enrolled to undergo anterior cervical spondylectomy. Bone graft pedicles were compounded with N-HA/PA and intervertebral body fusion was performed. Study outcomes included surgical efficacy and the degree of fusion. Patients in whom vertebral body fusion was performed with N-HA/PA composite pedicles had significantly improved symptoms. The postoperative Japanese Orthopaedic Association scores increased to 18.56±4.37 from 11.37±3.52, reflecting an improvement rate of 87.3%. The composite pedicle fusion rate was 96.4%. Therefore, N-HA/PA composite pedicle as a bone graft material in fusion surgery provides significant therapeutic efficacy. Moreover, the composite pedicle fusion rate is high, making it ideal for anterior cervical vertebral body subtotal corpectomy and fusion.

Risk factors for cage subsidence and clinical outcomes after transforaminal and posterior lumbar interbody fusion.

Cage subsidence is a very common complication after lumbar interbody fusion. It may compromise vertebral interbody fusion through progressive spinal deformity and consequently cause compression of neural elements. Clinical relevance remains, however, unclear, with few studies on this subject and even less information regarding its correlation with clinical findings. The aim of this study was to identify risk factors for cage subsidence and clinical evaluation after transforaminal (TLIF) and posterior (PLIF) lumbar interbody fusion. A retrospective study in patients submitted to TLIF and PLIF between 2008 and 2017 was conducted. A total of 165 patients were included (123 TLIF and 42 PLIF). Univariate analysis showed an increased risk of cage subsidence in spondylolisthesis comparing with degenerative disk disease (p = 0.007). A higher preoperative lumbar lordosis angle (p = 0.014) and cage placement in L2-L3 (p = 0.012) were associated with higher risk of subsidence. The posterior cage positioning on vertebral endplate was associated with a higher risk of subsidence (p = 0.028) and significant subsidence (p = 0.005), defined as cage migration > 50% of cage height. PLIF presented a higher risk when comparing with TLIF (p = 0.024). Hounsfield unit (HU) values < 135 (OR6; 95% CI [1.95-34]) and posterior positioning (OR7; 95% CI [1.7-27.3]) were independent risk factors for cage subsidence and significant subsidence, respectively, in multivariate analysis. There was a tendency for significant subsidence in degrees ≥ 2 of Meyerding spondylolisthesis (OR4; 95% CI [0.85-21.5]). Significant cage subsidence was not associated with worse clinical results. Other analyzed factors, such as age (p = 0.008), low bone mineral density (BMD) (p = 0.029) and type of surgery (TLIF) (p = 0.004), were associated with worse results. The present study shows that lower BMD and posterior cage positioning are relevant risk factors for lumbar cage subsidence. Low BMD is also a predictor of poor clinical results, so it must be properly evaluated and considered, through HU values measurement in CT scan, a feasible and reliable tool in perioperative planning.

Outcomes after cervical vertebral interbody fusion using an interbody fusion device and polyaxial pedicle screw and rod construct in 10 horses (2015-2019).

Further development of surgical techniques for equine cervical stabilisation is necessary to make the procedure less technically demanding, reduce complications and improve outcomes. To describe clinical outcomes and owner reports in horses undergoing placement of an interbody fusion device and polyaxial pedicle screw and rod construct for cervical vertebral fusion in horses with cervical vertebral compressive myelopathy. Retrospective case series. Data were retrieved from medical records of 10 horses undergoing cervical vertebral fusion (2015-2019). Records were evaluated for signalment, duration of clinical signs, number and location of compression sites, grade of ataxia, duration of hospitalisation and complications. Long-term follow-up was obtained through clinical re-evaluation, postoperative radiographs and owner contact. Breeds were mixed. Median age was 24 (range 12-168) months. There were 2/10 mares, 4/10 geldings and 4/10 stallions. Preoperative grade of ataxia ranged from 1-3/5. Fusion was performed at one (n=3) or two (n=7) sites. Two horses were euthanised within the first year. In 6 of 8 horses with ≥1-year follow-up, ataxia improved by 1-3 grades, with an average improvement of 1.25 grades. In four horses, ataxia improved to grade 0-1. In two horses the gait was unaffected, but neck comfort improved. Complications included seroma formation (n=9), pain (n=5), fever (n=4), upper respiratory tract obstruction (n=2), azotemia (n=2), screw breakage (n=2), progression of neurological signs (n=1), Horner's Syndrome (n=1), dysphagia (n=1), hives (n=1), implant infection (n=1) and nondisplaced fracture (n=1). Small case series, heterogeneous patient population. This technique resulted in ≥1 grade gait improvement in 6/10 cases operated and 6/8 cases for which ≥1-year follow-up was available, similar to other methods. Fatal complications related to implant placement did not occur. This technique may represent a safer alternative to current techniques of ventral interbody fusion with similar outcomes.

Cell and Tissue Response to Polyethylene Terephthalate Mesh Containing Bone Allograft in Vitro and in Vivo.

Extended polyethylene terephthalate mesh (PET, Dacron) can provide containment of compressed particulate allograft and autograft. This study assessed if PET mesh would interfere with osteoprogenitor cell migration from vertebral plates through particulate graft, and its effect on osteoblast differentiation or the quality of bone forming within fusing vertebra during vertebral interbody fusion. The impact of PET mesh on the biological response of normal human osteoblasts (NHOst cells) and bone marrow stromal cells (MSCs) to particulate bone graft was examined in vitro. Cells were cultured on rat bone particles +/- mesh; proliferation and osteoblast differentiation were assessed. The interface between the vertebral endplate, PET mesh, and newly formed bone within consolidated allograft contained by mesh was examined in a sheep model via microradiographs, histology, and mechanical testing. Growth on bone particles stimulated proliferation and early differentiation of NHOst cells and MSCs, but delayed terminal differentiation. This was not negatively impacted by mesh. New bone formation in vivo was not prevented by use of a PET mesh graft containment device. Fusion was improved in sites containing allograft/demineralized bone matrix (DBM) versus autograft and was further enhanced when stabilized using pedicle screws. Only sites treated with allograft/DBM+screws exhibited greater percent bone ingrowth versus discectomy or autograft. These results were mirrored biomechanically. PET mesh does not negatively impact cell attachment to particulate bone graft, proliferation, or initial osteoblast differentiation. The results demonstrated that bone growth occurs from vertebral endplates into graft material within the PET mesh. This was enhanced by stabilization with pedicle screws leading to greater bone ingrowth and biomechanical stability across the fusion site. The use of extended PET mesh allows containment of bone graft material during vertebral interbody fusion without inhibiting migration of osteoprogenitor cells from vertebral end plates in order to achieve fusion. 5.

Comparison of pedicle screw fixation via paraspinal approach and traditional open approach for treatment of thoracolumbar fracture and dislocation

Objective To compare the clinical efficacy of posterior pedicle screw fixation through Wiltse paraspinal approach and posterior traditional open approach in the treatment of thoracolumbar fracture and dislocation. Methods A retrospective case control study was performed based on the clinical data of 40 patients with thoracolumbar fracture and dislocation admitted between January 2013 and January 2016. All the surgeries were performed through posterior midline incision, and they were divided into two groups according to different approaches. Patients in Group A received pedicle screw fixation through Wiltse paraspinal approach while Group B received fixed pedicle screw through open surgery. Group A was composed of 12 males and 8 females, aged 21-60 years [(41.5±9.6)years]. Group B was composed of 13 males and 7 females, aged 18-58 years [(39.1±13.1)years]. The same surgical procedures were adopted in spinal decompression, reduction, and the spinal vertebral interbody bone graft and fusion surgery in the two groups. Operation duration, intraoperative blood loss, postoperative drainage volume, visual analogue scale (VAS), spinal canal patency at the last follow-up, percentage of postoperative injury of vertebral height recovery, and Cobb angle were compared. CT and MRI were used to evaluate postoperative paravertebral muscle atrophy, and American spinal injury association (ASIA) impairment scale was used to evaluate neurological function assessment. Results All patients were followed up for 9-33 months, with (19.3± 5.6)months for Group A and (22.5±4.9)months for Group B (P>0.05). The operation duration was (240.5±38.3)min in Group A and (258.5±43.7)min in Group B (P>0.05). The intraoperative blood loss was (525.0±168.2)ml in Group A, less than (770.0±269.2)ml in Group B (P 0.05). In terms of MRI evaluation score of postoperative paravertebral muscle atrophy, Group A reported better results than Group B [(2.1±0.6)points vs. (1.2±0.6)points] (P 0.05). Within the same group, significant difference was observed between the preoperative data and that at the last follow-up in terms of postoperative VAS score, spinal canal patency, percentage of injury of vertebral height, Cobb angle, and ASIA impairment scale (P<0.05). Conclusion For thoracolumbar fracture and dislocation, compared with traditional open approach, posterior pedicle screw fixation through Wiltse paraspinal approach can effectively restore the vertebral body height and spinal canal patency and can reduce the intraoperative bleeding, postoperative drainage, postoperative back pain, and paravertebral lesion. Key words: Spinal injuries; Thoracic vertebrae; Lumbar vertebrae; Fracture fixation

Characterization of a novel caudal vertebral interbody fusion in a rat tail model: An implication for future material and mechanical testing

BackgroundOf the proposed animal interbody fusion models, rat caudal discs have gained popularity in disc research due to their strong resemblance to human discs with respect to geometry, composition and mechanical properties. The purpose of this study is to demonstrate an efficient, repeatable and easily accessible animal model of interbody fusion for future research into mechanical testing and graft materials. MethodsTwelve 12-week-old female Sprague–Dawley (SD) rats underwent caudal interbody fusion of the third and fourth coccygeal vertebrae of the tail. Serial radiological evaluation, and histological evaluation and manual palpation after sacrifice were performed to assess the fusion quality. Mechanical testing of functional units (FUs) of non-operated and operated segments was compared using a three-point bending test. ResultsAt postoperative 12 weeks, callus formation was observed at the fusion sites in all rats, with the mean radiological evaluations of 2.75/3 according to the Bransford classification. Newly formed bone tissue was also observed in all rats with the mean histological score of 5.85/7, according to the Emery grading system. No palpable gaps and obvious change of bending stiffness was observed in the operated segments. The mean bending stiffness of the FUs was statistically higher than that of the control FUs (26.57 ± 6.71 N/mm vs. 12.45 ± 3.21 N/mm, p < 0.01). ConclusionThe rat caudal disc interbody fusion model proved to be an efficient, repeatable and easily accessible model. Future research into adjuvant treatments like growth factor injection and alternative fusion materials under conditions of osteoporosis using this model would be worthwhile.

Evaluation of Anterior Vertebral Interbody Fusion Using Osteogenic Mesenchymal Stem Cells Transplanted in Collagen Sponge

The study used a rabbit model to achieve anterior vertebral interbody fusion using osteogenic mesenchymal stem cells (OMSCs) transplanted in collagen sponge. We investigated the effectiveness of graft material for anterior vertebral interbody fusion using a rabbit model by examining the OMSCs transplanted in collagen sponge. Anterior vertebral interbody fusion is commonly performed. Although autogenous bone graft remains the gold-standard fusion material, it requires a separate surgical procedure and is associated with significant short-term and long-term morbidity. Recently, mesenchymal stem cells from bone marrow have been studied in various fields, including posterolateral spinal fusion. Thus, we hypothesized that cultured OMSCs transplanted in porous collagen sponge could be used successfully even in anterior vertebral interbody fusion. Forty mature male White Zealand rabbits (weight, 3.5-4.5 kg) were randomly allocated to receive one of the following graft materials: porous collagen sponge plus cultured OMSCs (group I); porous collagen sponge alone (group II); autogenous bone graft (group III); and nothing (group IV). All animals underwent anterior vertebral interbody fusion at the L4/L5 level. The lumbar spine was harvested en bloc, and the new bone formation and spinal fusion was evaluated using radiographic analysis, microcomputed tomography, manual palpation test, and histologic examination at 8 and 12 weeks after surgery. New bone formation and bony fusion was evident as early as 8 weeks in groups I and III. And there was no statistically significant difference between 8 and 12 weeks. At both time points, by microcomputed tomography and histologic analysis, new bone formation was observed in both groups I and III, fibrous tissue was observed and there was no new bone in both groups II and IV; by manual palpation test, bony fusion was observed in 40% (4/10) of rabbits in group I, 70% (7/10) of rabbits in group III, and 0% (0/10) of rabbits in both groups II and IV. These findings suggest that mesenchymal stem cells that have been cultured with osteogenic differentiation medium and loaded with collagen sponge could induce bone formation and anterior vertebral interbody fusion. And the rabbit model we developed will be useful in evaluating the effects of graft materials for anterior vertebral interbody fusion. Further study is needed to determine the most appropriate carrier for OMSCs and the feasibility in the clinical setting.

The clinical effects of atlantoaxial pedicle screw combined with unilateral axial spinous process and lamina screws for atlantoaxial instability

Objective To investigate the clinical effects of the posterior atlantoaxial pedicle screw fixation combined with unilateral axial spinous process and lamina screws and allogeneic bone graft for atlantoaxial instability. Methods From March 2010 to April 2014, data of 10 patients with atlantoaxial instability who had undergone atlanto-axial vertebral pedicle fixation and interbody fusion combined with posterior atlanto-axial spines lamina nails were retrospectively analyzed. There were 6 males and 4 females with an average age of 39 (range, 16-62) years old. The inclusion criteria was atlantoaxial instability together with unilateral vertebral artery segment high cross deformity (7 patients) or atlantoaxial joint break bad involving unilateral pedicle (7 patients). 3 patients have spinal cord disease symptoms and physical signs, both suffered limited neck mobility and pain. The VAS scores were 1-8, with an average of 3.70±2.11. Preoperative X-ray, CT three-dimensional reconstruction and MRI were collected. X-ray and CT examination were performed 7 d and 1, 3, 6, 12 months after operation to evaluate the internal fixation and bone grafting fusion. Results There's no occurrence of cervical spinal cord and vertebral artery injury. Screws were successfully implanted. 1 case's incision occurred infiltration liquid 3 days after operation. For allograft rejection consideration, we changed the plan, and the infiltrating stopped 5 days later. Other incisions were all primary healing. VAS scores were 1.01±0.89 after operation, which was significantly reduced. X-ray showed good recovery of cervical sequence after the operation, and CT revealed 1 patient with atlas pedicle screw in the medial cortex damage. Spinal canal was without infringing, and the other screw positions were normal. 6 months after operation, X-ray or CT examination both showed bony fusion. Conclusion Atlantoaxial pedicle screw fixation combined with unilateral axial spinous process and lamina screws and allograft bone graft fusion for the treatment of atlantoaxial instability can observe good clinical effects. Key words: Cervical atlas; Axis; Joint instability; Internal fixators

Experimental and numerical analysis of the influence of embedding thickness in compressive mechanical testing of vertebral augmentation and spinal interbody fusion

Experimental and numerical analysis of the influence of embedding thickness in compressive mechanical testing of vertebral augmentation and spinal interbody fusion

Unilateral vertebral plate decompression,interbody fusion and pedicle screw fixation in treatment of lumbar disc herniation

Objective:To explore the application and efficiency of unilateral vertebral plate decompression,interbody fusion and pedicle screw fixation in treatment of lumbar disc herniation.Methods:From Feb.2006 to Feb.2008,24 patients underwent unilateral vertebral plate decompression,interbody fusion and pedicle screw fixation.The patients were followed up for one year and the following data were recorded:operation time,estimated blood loss,duration of hospital-stay,short-term and medium-term clinical outcome.Results:All patients had their low back pain and/or lower extremity radicular pain improved during the one year follow-up.The last follow-up showed that the numbers of patients with Oswestry Disability Index(ODI) P0-P5 were 5,11,6,2,0,and 0,respectively.The clinical outcomes determined by modified JOA criteria showed that 18 patients had excellent outcomes,4 had good outcomes,and 2 had fair outcomes,with the excellent and good outcomes occupying 91.67%.Conclusion:The unilateral fixation can be used in patients with lumbar disc herniations who need lumbar spinal fusion.The medium-term outcomes is satisfactory.

Eosinophilic Granuloma of the Pediatric Cervical Spine

Retrospective case review of children with eosinophilic granuloma of the cervical spine. To present the clinical features, radiographic findings, management, and results of 7 pediatric patients with eosinophilic granuloma of the cervical spine. Management of the eosinophilic granuloma of the pediatric cervical spine is challenging, and must be adapted according to the patient, as no level I evidences have been produced. The therapeutic goals in these children are spinal stability, preservation of neurologic function, and relief of pain, always keeping in mind that patients are still growing. The localization in the cervical spine of children is extremely rare, with less than 50 patients reported in literature between 1966 and 2008. We reviewed the 7 pediatric patients with a diagnosis of eosinophilic granuloma of the cervical spine who were managed between 1970 and 1990 by the senior author. All patients presented with isolated cervical spine involvement, and all of them had a histologic diagnosis of eosinophilic granuloma (EG). All had open physes. There were 5 boys and 2 girls (mean age: 10 years; range 4-16). We followed-up patients for 19 years (range 8-29). The symptoms at presentation varied according to the localization of the tumor in the cervical spine. Management of pediatric patients with EG of the cervical spine is challenging, especially when there is neurologic involvement. Observation alone, prolonged immobilization, systemic chemotherapy, curettage with or without bone grafting, corticosteroid injection, and low dose radiation therapy have been proposed for the management of patients with EG. Surgery is required when the child presents neurologic involvement. Children who received a vertebral interbody fusion can show, at long period follow-up, normal shape of the neck, with maintenance of the normal motion of the adjacent segments.

The vertebral interbody grafting site’s low concentration in osteogenic progenitors can greatly benefit from addition of iliac crest bone marrow

The ability of bone substitutes to promote bone fusion is contingent upon the presence of osteoinductive factors in the bone environment at the fusion site. Osteoblast progenitor cells are among these environmental osteoinductive factors, and one of the most abundant and available sources of osteoblastic cells is the bone marrow. As far as biological conditions are concerned, the vertebral interbody space appears as a favorable site for fusion, as it is surrounded by spongy bone, theoretically rich in osteogenic cells. This site may, however, not be as rich in osteogenic precursor cells especially at the time of grafting, because decortication of the vertebral end plates during the grafting process may modify cell content of the surrounding spongy bone. We tested this hypothesis by comparing the abundance of human osteogenic precursor cells in bone marrow derived from the iliac crest, the vertebral body, and the decorticated intervertebral body space. The number of potential osteoblast progenitors in each site was estimated by counting the alkaline phosphatase-expressing colony-forming units (CFU-AP). The results, however, demonstrate that the vertebral interbody space is actually poorer in osteoprogenitor cells than the iliac crest (P<0.001) and vertebral body (P<0.01), especially at the time of graft implantation. In light of our results, we advocate addition of iliac crest bone marrow aspirate to increase the success rate of vertebral interbody fusion.

Thoracoscopic assisted anterior fusion in fractures of the thoracic and lumbar spine

Objectives Using a thoracoscopic approach reduction of vertebral body fractures and interbody fusion of the involved segment after implantation of an autogenous bone graft and plate fixation.

Mechanical strength and bone bonding of a titanium fiber mesh block for intervertebral fusion

We developed a titanium fiber mesh block (TFMB) to use as an alternative to autogenous bone grafts for vertebral interbody fusion. In in vitro tests, we measured the surface pore size and conducted weight loading tests of TFMB with porosities of 50% and 60%. For in vivo testing, we grafted TFMB in 11 mongrel dogs for intervertebral fusion and evaluated bone ingrowth into the grafts and the bonding of TFMB with bone. The mean surface pore size was 375 ± 289µm for 50% porosity TFMB and 445 ± 400µm for 60% porosity TFMB. In the in vitro weight loading test, 60% porosity TFMB showed 50%-60% of the elastic modulus of 50% porosity TFMB, and both materials showed a similar yielding load. After the grafting of 60% porosity TFMB, bone ingrowth occurred to a depth of 2.3mm at 3 months and to a depth of 3.6mm at 6 months; while the values were 0.7mm and 1.5mm, respectively, in 50% porosity TFMB. In a push-out test conducted 6 months after grafting, 50% and 60% porosity TFMB showed similar bone bonding strengths. These results suggest that 60% porosity TFMB implant will be suitable to using for spinal interbody fusion.

Bovine dowels for anterior cervical fusion: experience in 66 patients with a note on postoperative CT and MRI appearance.

Anterior cervical discectomy and vertebral interbody fusion is a widely used technique in the treatment of radicular or cord compression. Instead of using autologous bone removed from the iliac crest, a heterologous bovine dowel was used for fusion. Sixty-six patients presenting with radicular pain or myelopathy were entered into the study retrospectively. Medial herniated, soft or calcified disc, osteophytes with and without herniated disc material, and bony stenosis at one or two levels were shown by CT or MRI studies. Postoperatively, 88% of the patients noted relief of pain and motor improvement. Most of the patients' sensory deficits and myelopathy improved within 6-12 months. No complications occurred and only one re-operation had to be performed at the same level. In the follow-up period between 1-4 years, no cases of instability after surgery were reported. Operating time and postoperative pain were reduced because bone harvest from the iliac crest was not necessary. In postoperatively performed CT and MRI, the bovine dowel was surrounded by a "halo"-like structure and the specific structure of the bovine implant was still present. No real bony fusion occurred, but clinical stability was equivalent to autologous bone fusion reported in the literature. However, there was no MRI evidence of "living bone tissue" within the bovine dowel. This finding is in contrast to the current belief that the bovine implant is replaced or infiltrated by bony growth.

Complications after transpedicular stabilization of the spine. A survivorship analysis of 163 cases.

The authors studied complications of transpedicular stabilization methods. One hundred and sixty-three consecutive transpedicular stabilization procedures were performed between January 1987 and December 1991. The indications for stabilization were trauma (33 cases), metastatic spinal disorder (30 cases), spinal stenosis (33 cases), spondylolisthesis (27 cases), ankylosing spondylitis (6 cases), low back pain (22 cases), and miscellaneous (12 cases). Patients records and the entire series of radiographs for each case were scrutinized by independent observers. All per- and postoperative complications, including implant loosening and fatigue, were recorded. Clinical and radiographic survivorship analyses of the implants were performed. Early complications were unusual and none were associated with permanent morbidity. The probability of not having the implant removed in the first postoperative year was 85%. There was a 40% risk of radiographic failure, defined as loosening or implant fatigue, at 6 months. The outcome was more favorable in cases in which anterior vertebral interbody fusion was also performed. Transpedicular fixation is a safe procedure with a low incidence of serious per- and early postoperative complications. The mechanical durability of transpedicular fixators used alone is a cause for concern.

The Fate of Anterior Vertebral Bone Grafts in Patients Irradiated for Neoplasm

Perioperative irradiation is often used with anterior decompression and vertebral interbody fusion for the treatment of spinal neoplasms, yet little is known regarding the healing potential of these grafts. This review of 25 patients with neoplasm who had anterior vertebrectomy, bone strut insertion, and perioperative irradiation was performed to look specifically for evidence of radiographic fusion as determined by plain radiographs, tomograms, or computed tomography reconstruction. Four of 25 patients (16%) were judged to have a pseudarthrosis. All four pseudarthrosis patients but only four of 21 fusion patients had 4000 cg or more of irradiation, a statistically significant difference. There was a trend for lumbar lesions to have a higher risk for nonunion. Concomitant posterior stabilization did not necessarily prevent pseudarthrosis. Two iliac strut grafts with a pseudoarthrosis developed late fracture and one went on to collapse into kyphosis. The pseudarthrosis rate of anterior vertebral strut grafts in the face of irradiation for tumor is relatively high, and late graft fracture can occur if pseudarthrosis develops. Probable risk factors include irradiation greater than 4000 cg and lumbar lesions. Posterior stabilization to protect the graft may be warranted in the highest-risk patients.

Klippel-Feil syndrome: patterns of bony fusion and wasp-waist sign

Cervical spine radiographs of 33 patients with Klippel-Feil syndrome were studied for patterns of bony fusion and presence of wasp-waist sign. Five patients were found to have the classic features of massive cervical fusion. Two patients with two adjacent levels of bony fusion showed a wasp-waist sign. Fusion at one level of the cervical spine accounted for 26 remaining cases. The wasp-waist sign was observed in 14 of the cases in which there was complete vertebral interbody fusion, making this finding a valuable radiologic sign. Partial anterior or posterior vertebral interbody fusion, or isolated fusion of the neural arch, however, may or may not be associated with the wasp-waist sign. Klippel-Feil syndrome, easy to recognize when presenting with classic features or when associated with the wasp-waist sign, may be confused with a variety of other entities.