Biomedical subjects

Kuniyoshi Abumi

Publications and source records attributed to Kuniyoshi Abumi.

At least 19 recordsLinked to original sources

PubMed2007

Clinical outcome of posterolateral endoscopic surgery for pyogenic spondylodiscitis: results of 15 patients with serious comorbid conditions.

STUDY DESIGN: Clinical results of posterolateral endoscopic debridement and irrigation followed by percutaneous drainage for pyogenic spondylodiscitis were analyzed. OBJECTIVES: To report clinical results of transforaminal endoscopic surgery for pyogenic spondylodiscitis and to evaluate the effectiveness of this procedure in treatment of pyogenic spinal infections. SUMMARY OF BACKGROUND DATA: Pyogenic spinal infections have been increasing due to the development of medical treatment for patients with comorbid medical problems. Common treatments for spinal infections are administration of antibiotics or surgical debridement with bone grafts. There have been no reports, however, regarding the clinical outcome of posterolateral endoscopic treatment for pyogenic spinal infections. METHODS: Fifteen consecutive patients with pyogenic spondylodiscitis in the thoracic or lumbar spine were enrolled. Preoperative antibiotic treatment had failed in all the patients. The procedures consisted of posterolateral endoscopic debridement and irrigation followed by percutaneous drainage through single portal under the combination of local and intravenous anesthesia. Pain response using visual analog scale (VAS, 0-100 mm), inflammation parameters, and duration of antibiotic therapy were investigated. Radiologic evaluation focused on bony fusion, local kyphosis, disc height reduction, and abscess formation. RESULTS: All patients showed immediate pain reduction after surgery. Averaged VAS for pain was 86 before surgery and 25 at postoperative 1 week. Average of CRP was 4.00 mg/dL before surgery and 1.88 mg/dL at postoperative 1 week. Averaged duration of antibiotics therapy was 3.7 weeks. Spinal fusion was obtained in 13 patients. Two patients with neurologic deficits due to epidural abscess returned to normal. Preoperative psoas abscess in 6 patients disappeared after surgery on MRI. CONCLUSIONS: Posterolateral spinal endoscopic debridement and irrigation brought immediate pain reduction and good clinical results to patients who had comorbid medical problems and had pyogenic spondylodiscitis.

Adolescent↗

PubMed2006

Palliative spinal reconstruction using cervical pedicle screws for metastatic lesions of the spine: a retrospective analysis of 32 cases.

STUDY DESIGN: A retrospective study. OBJECTIVES: To evaluate clinical outcomes of palliative spinal reconstruction using cervical pedicle screws in metastatic spine tumors. SUMMARY OF BACKGROUND DATA: No study to date has investigated the effectiveness of cervical pedicle screw fixation in metastatic lesions of the spine. METHODS: A total of 32 patients with metastatic spine tumors who underwent reconstructive surgery using cervical pedicle screws were reviewed. Four patients presented upper cervical lesions and 28 patients had subaxial lesions. All patients had intractable pain, 29 presented myelopathy, and 18 patients were nonambulatory. Combined anterior column reconstruction was considered in cases of life expectancy more than 2 years and anterior spinal cord compression that could not be solved by posterior decompression and kyphosis correction. Posterior fixation alone was performed in 25 patients, and posterior fixation combined with anterior column reconstruction was performed in 7 patients. RESULTS: The average postoperative survival period was 12.2 months. Neck pain was improved in all cases. Twenty-four (83%) of the 29 patients with spinal cord lesions presented neurologic improvement. Of 18 patients who were not ambulatory, 16 patients (89%) became ambulatory. Pain relief, neurologic function, and spinal stability were maintained throughout the survival period in 30 of 32 patients (94%). CONCLUSION: Spinal reconstruction using cervical pedicle screws improved spinal stability, pain, and neurologic function. These improvements were maintained throughout the survival period in 94% of the patients. Anterior column reconstruction could be avoided in 78% of the patients in spite of damaged anterior column.

Adult↗

PubMed2006

Multidirectional flexibility analysis of anterior and posterior lumbar artificial disc reconstruction: in vitro human cadaveric spine model.

The in vitro multidirectional flexibility analysis was conducted to investigate the initial biomechanical effect of biomimetic artificial intervertebral disc replacement from either anterior or posterior approach in a cadaveric lumbosacral spine model. Two designs of anterior total and posterior subtotal artificial discs were developed using bioactive three-dimensional fabric and bioresorbable hydroxyapatite/poly-l-lactide material (3DF disc). Both models were designed to obtain the stable interface bonding to vertebral endplates with maximum surface area occupation. Using seven cadaveric lumbosacral spines, the following three anterior reconstruction methods were sequentially performed at L4-5 level: anterior 3DF disc replacement; anterior BAK cages (BAK); and posterior pedicle screw fixation and anterior BAK cages combined (BAK + PS). The L2-3 level received two methods of posterior reconstructions: subtotal 3DF disc replacement (two implants), and posterior interbody cages and pedicle screw fixation (PLIF). Six unconstrained pure moments were applied and three-dimensional segmental motions were measured with an optoelectronic motion measurement system. The center of rotation (COR) calculation was conducted radiographically using flexion-extension films. Both anterior and posterior 3DF replacements statistically demonstrated equivalent range of motions (ROMs) in all loading modes compared to intact segment. Anterior BAK, BAK + PS, and PLIF demonstrated significantly lower ROMs when compared to intact and 3DF groups (P<0.05). The 3DF reconstruction tended to realign the COR to the posterior third or surrounding position at the operative disc level. The stand-alone lumbar 3DF disc replacement demonstrated biomechanical characteristics nearly equivalent to the intact spinal segments even through anterior or posterior approach in vitro, suggesting an excellent clinical potential.

Absorbable Implants↗

PubMed2006

Radiological risk factors of pseudoarthrosis and/or instrument breakage after PLF with the pedicle screw system in isthmic spondylolisthesis.

OBJECTIVE: Several studies have reported favorable results of posterolateral fusion (PLF) with pedicle screw systems (PSs) for isthmic spondylolisthesis. However, the best indication and limitations of this method still remain unclear. The present study aimed to analyze the radiological risk factors of pseudoarthrosis and/or instrumentation failure after PLF with PSs in isthmic spondylolisthesis, and to determine the limitations of this method. METHODS: The study group comprised of 101 patients with isthmic spondylolisthesis who underwent PLF with PSs. Follow-up was performed for more than 5 years. Statistical analyses with multivariate logistic regression models were used to identify risk factors of pseudoarthrosis and/or instrument failures associated with PLF with PSs. RESULTS: Average follow-up was 8 years. Fusion rate was 95%. There were instrument breakage in 6 patients, and pseudoarthrosis in 5. Statistical analysis with a logistic regression model revealed that preoperative % disc height (odds ratio: 3.60 per 10%, P<0.01) and slip angle (odds ratio: 4.48 per 10 degrees kyphosis, P<0.05) were the most crucial risk factors of pseudoarthrosis and/or instrument breakage when performing PLF for isthmic spondylolisthesis. CONCLUSIONS: In conclusion, PLF with PSs provided satisfactory results with high fusion rate. However, there were complications including pseudoarthrosis or instrument breakage in specific conditions. Preserved disc height and presence of segmental kyphosis were risk factors of these complications. Statistically, % disc height within 20% without segmental kyphosis was the best indication for PLF with PSs.

Adult↗

PubMed2006

Biomechanical study on the effect of five different lumbar reconstruction techniques on adjacent-level intradiscal pressure and lamina strain.

OBJECT: The objectives of this study were to compare the biomechanical effects of five lumbar reconstruction models on the adjacent segment and to analyze the effects of three factors: construct stiffness, sagittal alignment, and the number of fused segments. METHODS: Nondestructive flexion-extension tests were performed by applying pure moments to 10 calf spinal (L3-S1) specimens. One-segment (L5-6) or two-segment (L5-S1) posterior fusion methods were simulated: 1) one-segment posterolateral fusion (PLF); 2) one-segment PLF with interbody fusion cages (one-segment PLIF/PLF); 3) two-segment PLF; 4) two-segment PLIF/PLF; and 5) two-segment PLF in kyphosis (two-segment kyphotic PLF). The range of motion (ROM) of the reconstructed segments, intradiscal pressure (IDP), and lamina strain in the upper (L4-5) adjacent segment were analyzed. The ROM was significantly decreased in the PLIF/PLF models compared with that in the PLF alone models after both the one- and two-segment fusions. If the number of fused segments was increased, the pressure and strains were also increased in specimens subjected to the PLIF/PLF procedure, more so than the PLF-alone procedure. In the one-segment PLIF/PLF model the authors observed a reduced IDP and lamina strain compared with those in the kyphotic two-segment PLF model despite the latter's higher levels of initial stiffness. CONCLUSIONS: If the number of fused levels can be reduced by using PLIF to correct local kyphosis, then this procedure may be valuable for reducing adjacent-segment degenerative changes.

Animals↗

PubMed2006

Long-term follow up of surgical outcomes in patients with cervical disorders undergoing hemodialysis.

OBJECT: As increasing numbers of patients receive long-term hemodialysis, the number of reports regarding hemodialysis-related cervical spine disorders has also increased. However, there have been few reports summarizing the surgical results in patients with these disorders. The objective of this study was to evaluate the long-term follow up and clinical results after surgical treatment of cervical disorders in patients undergoing hemodialysis. METHODS: Seventeen patients in whom surgery was performed for cervical spine disorders while they received long-term hemodialysis therapy were enrolled in this study. Of these, 15 underwent follow-up review for more than 3 years after surgery, and these represent the study population. The remaining two patients died of postoperative sepsis. The average follow-up period was 120 months. Five patients without spinal instability underwent spinal cord decompression in which bilateral open-door laminoplasty was performed. Ten patients with destructive spondyloarthropathy (DSA) underwent reconstructive surgery involving pedicle screw (PS) fixation. In eight patients in whom posterior instrumentation was placed, anterior strut bone grafting was performed with autologous iliac bone to treat anterior-column destruction. Marked neurological recovery was obtained in all patients after the initial surgery. In the mobile segments adjacent to the site of previous spinal fusion, the authors observed progressive destructive changes with significant instability in four patients (40%) who underwent circumferential spinal fusion. No patients required a second surgery after laminoplasty for spinal canal stenosis without DSA changes. CONCLUSIONS: Cervical PS-assisted reconstruction provided an excellent fusion rate and good spinal alignment. During the long-term follow-up period, however, some cases required extension of the spinal fusion due to the destructive changes in the adjacent vertebral levels. Guidelines or recommendations to overcome these problems should be produced to further increase the survival rates of patients undergoing hemodialysis.

Adult↗

PubMed2005

An investigational study on the healing process of anterior spinal arthrodesis using a bioactive ceramic spacer and the change in load-sharing of spinal instrumentation.

STUDY DESIGN: Ceramic anterior lumbar interbody arthrodesis was performed using an in vivo sheep model. Observations of fusion status and the load-sharing of spinal instrumentation were studied at sequential intervals for 1 year after surgery. OBJECTIVES: To elucidate the healing process of spinal arthrodesis performed with a bioactive ceramic spacer and the change in load-sharing of anterior spinal instrumentation. SUMMARY OF BACKGROUND DATA: With the improved development of spinal instrumentation, anterior spinal arthrodesis has become a standard spinal reconstruction technique; however, the mechanistic basis underlying the healing process is not well documented. Moreover, it remains unclear how load-distribution through the fusion mass and spinal instrumentation change throughout the healing process. METHODS: Using 24 sheep, a two-level anterior lumbar interbody fusion (L2-L3, L4-L5) was performed using a smooth surface and a porous surface-modified bioactive ceramic, with each segment instrumented using a one-rod anterior spinal instrumentation system. Four animals each were killed at 2, 4, 8, 12, 24, and 52 weeks after surgery. Postmortem analysis included quantification of anterior rod strain under multidirectional flexibility testing and radiographic and histologic analyses of the arthrodesed segments. RESULTS: From 0 to 8 weeks after surgery, the bending strain of the rod gradually decreased despite no obvious bone formation. From 8 to 24 weeks after surgery, the rod strain markedly decreased with the development of bridging trabeculated bone formation between vertebral bodies. After 24 weeks after surgery, minimal changes were observed in rod strain; however, the fusion mass volumetrically increased with corresponding facet joint atrophy. The porous surface-modification of ceramic did not influence the histologic healing process, despite the improvement of interface osseous union rate. CONCLUSIONS: In anterior spinal arthrodesis, spinal instrumentation is mainly exposed to bending stress, with decreased load-sharing with corresponding development of the spinal fusion. Continuous bone remodeling of the anterior fusion mass results in concurrent decreases in spinal instrumentation and posterior spinal element load-transmission. The principal healing mechanism of ceramic anterior interbody spinal fusion is not an osseous union between the ceramic and vertebral body, but bridging bone formation around the ceramic, which directly connects the vertebral bodies above and below the disc.

Animals↗

PubMed2005

A biomechanical and histological evaluation of a bioresorbable lumbar interbody fusion cage.

Novel spinal interbody fusion cages made of bioactive and bioresorbable composites by a unique forging process were developed. Previous in vitro study demonstrated that these cages marked excellent biomechanical values. The purpose of the present in vivo study was to evaluate the viability and advantage of this forged composite of uncalcined hydroxyapatite/poly L-Lactide (F-u-HA/PLLA) cage radiographically, biomechanically, and histologically, when compared to conventional autologous iliac bone (AIB) and carbon fiber cage (CFC). Twenty-five mature sheep underwent posterior lumbar interbody fusion at L2-3 level with pedicle screws system made of titanium. Three types of interbody fusion implants were grafted: AIB (n = 7), CFCs (n = 9), F-u-HA/PLLA cages (n = 9). Two types of cages were packed with autologous fragmented cancellous bone harvested locally. All animals were euthanized at 120 days after surgery. The fusion scoring using the coronal view CT scans was designed to three-dimensionally evaluate fusion quality within and around cages. The mean CT scores of three groups were 33.3 points, 35.0 points, and 33.6 points in AIB, CFC, and F-u-HA/PLLA cage groups, respectively (full-score: 56 points). Statistical differences were not detected among the three groups. The mean range of motion values among fused groups had no significant difference under all pure loadings. The range of motion showed strong and significant correlation with the CT fusion scores. Histologic results demonstrated that F-u-HA/PLLA cages contacted with the surrounding bone directly, and CFC was encircled with thick fibrous tissue layers without any sign of inflammation around cages. The fusion quality of fused spinal segment using F-u-HA/PLLA cages was equal to that of AIB or CFCs both radiographically and biomechanically. In the histological observation, biocompatibility of F-u-HA/PLLA cage was obviously superior to CFC. It has been confirmed that the novel bioactive and bioresorbable cages had valuable advantages over existing CFC for use in spinal reconstructive surgery.

Absorbable Implants↗

PubMed2005

Multidirectional flexibility analysis of cervical artificial disc reconstruction: in vitro human cadaveric spine model.

OBJECT: This in vitro experimental study was conducted to investigate the initial biomechanical effect of artificial intervertebral disc replacement in the cervical spine. The multidirectional flexibility of replaced and adjacent spinal segments were analyzed using a cadaveric cervical spine model. METHODS: The following three cervical reconstructions were sequentially performed at the C5-6 level after anterior discectomy in seven human cadaveric occipitocervical spines: anterior artificial disc replacement with a bioactive three-dimensional (3D) fabric disc (FD); anterior iliac bone graft; and anterior plate fixation with iliac bone graft. Six unconstrained pure moments were applied with a 6-df spine simulator, and 3D segmental motions at the operative and adjacent segments were measured with an optoelectronic motion measurement system. The 3D FD group demonstrated statistically equivalent ranges of motion (ROMs) when compared with intact values in axial rotation and lateral bending. The 45% increase in flexion-extension ROM was demonstrated in 3D FD group; however, neutral zone analysis did not reach statistical significance between the intact spine and 3D FD. The anterior iliac bone graft and iliac bone graft reconstructions demonstrated statistically lower ROMs when compared with 3D FD in all loading modes (p < 0.05). The adjacent-level ROMs of the 3D FD group demonstrated nearly physiological characteristics at upper and lower adjacent levels. Excellent stability at the interface was maintained during the whole testing without any device displacement and dislodgment. CONCLUSIONS: The stand-alone cervical 3D FD demonstrated nearly physiological biomechanical characteristics at both operative and adjacent spinal segments in vitro, indicating an excellent clinical potential for cervical artificial disc replacement.

Bone Plates↗

PubMed2005

Vertebral osteonecrosis associated with sarcoidosis. Case report.

Sarcoidosis is a systemic disease commonly affecting lung, skin, or eye. Sarcoidosis involved with osseous structures occurs in approximately 5% of patients, usually involving small bones. Spinal sarcoidosis is extremely rare. The authors report on a man in whom examination of a subclavicular lymph node biopsy specimen and its spinal involvement had established a diagnosis of sarcoidosis and who had undergone steroid therapy. Despite intensive conservative treatment, the authors observed progressive collapse of L-2 requiring spinal decompressive and reconstructive surgeries. Histological evaluation of the collapsed vertebra did not show the typical noncaseating granuloma; rather, the authors observed osteonecrosis of the entire L-2 structure without reactive cellular activities. Other potential diagnoses including infectious disease, metastatic spinal tumor, and osteoporotic vertebral collapse were excluded based on laboratory data, imaging studies, and pathological findings. Complete necrosis of the entire L-2 vertebra in this case can be considered as a rare clinical manifestation of spinal sarcoidosis. Because of osteopenia and systemic bone fragility, combined anterior-posterior spinal reconstructive surgery was performed to restabilize the severely damaged spine.

Diagnosis, Differential↗

PubMed2004

Cervical spine injuries associated with lateral mass and facet joint fractures: new classification and surgical treatment with pedicle screw fixation.

To clarify the injury pattern, initial spinal instability, degree of discoligamentous injuries in cervical lateral mass and facet joint fractures, we retrospectively analyzed radiological parameters and introduced a new classification for these injuries. Surgical treatment was performed with cervical pedicle screw fixation (CPS), and overall neurological and radiological outcome was evaluated with a minimum follow-up period of 2 years. Lateral mass fractures were divided into the following four subtypes: separation, comminution, split, and traumatic spondylolysis. The sagittal and frontal alignments were evaluated at both mainly injured and adjacent spinal segments on radiographs. The initial discoligamentous injuries were investigated on magnetic resonance imaging in terms of their frequencies, subtype of injuries, and involved spinal levels. Anterior translation of fractured vertebra was demonstrated in 77% of lateral mass fractures, while 24% of anterior translation was observed, even in cephalad-adjacent vertebrae. On magnetic resonance imaging, signal changes in anterior longitudinal ligament (ALL) and intervertebral disc were demonstrated in 76% of caudal segments and 24% of cephalad segments adjacent to fractured vertebra of lateral mass fractures. The subtype analyses of lateral mass fractures demonstrated high rates of anterior translation in separation, split, and traumatic spondylolisthesis, as well as significant coronal malalignment in comminution and split types (p<0.05). Thirty-one patients underwent surgical treatments using a cervical pedicle screw fixation. The CPS provided the superior capability of deformity correction without pseudoarthrosis, as well as excellent neurological recovery. The average numbers of stabilized segments were minimized without serious complications. In separation, facet joint fracture, and fractures with mild lateral mass comminution, the single level posterior fixation can be considered. The significant unstable injuries of split and comminution type with coronal malalignment can be treated with exclusive two-level posterior stabilization with CPS. The initial evaluation of fracture subtypes helps to successfully minimize the stabilized spinal segment.

Adolescent↗

PubMed2004

Iliac crest reconstruction with a bioactive ceramic spacer.

This study aimed to investigate the long-term clinical results of the apatite wollastonite-containing glass ceramic (AWGC) iliac spacer and to discuss its efficacy in reconstruction of the bone graft donor site at the iliac crest. Thirty-one patients were studied for more than 10 years. All patients underwent anterior spinal fusion using autogenous tricortical iliac bone graft. After harvest of tricortical iliac bone graft, an AWGC iliac spacer ranging from 15 mm to 70 mm in length was press-fitted into the gap. Long-term clinical results were obtained from radiological and blood examinations. Thirty patients (97%) were satisfied with the spacer. There was new bone formation around the spacer on the radiograph. There was no abnormal silicon concentration in blood examinations. AWGC iliac spacer appears to be useful in the reconstruction of harvested iliac crest. New bone formation occurs, reducing the defect size.

Adolescent↗

PubMed2004

A biomechanical analysis of metastatic vertebral collapse of the thoracic spine: a sheep model study.

STUDY DESIGN: This is a biomechanical study using sheep thoracic spine to investigate the probability of mechanical failure of the thoracic spine with various sizes or locations of tumor metastasis. OBJECTIVE: The objectives of this study were to investigate biomechanical effects of not only tumor sizes within the thoracic vertebral body but also its involvement of other spinal components on the probability of mechanical failures of the thoracic spine. SUMMARY OF BACKGROUND DATA: There have been no experimental studies concerning mechanical influences of destruction of costovertebral joint or posterior elements as well as vertebral body on the load-bearing capacity of the thoracic spine. METHODS: Ninety-nine fresh sheep thoracic spine specimens with ribs were used (T7-T9, T10-T12). Within vertebral bodies of 39 specimens, only trabecular defects were created in different sizes. In other 48 specimens, not only vertebral body defects that were 40% to the cross-sectional area of the vertebral body but also additional destruction of costovertebral joint, pedicle, and facet joint were created. All specimens were subjected to destructive biomechanical testing. RESULTS: The failure load decreased as the defect size in the vertebral body increased. A negative linear correlation was observed between the failure load and the size of vertebral body defect (r = 0.782). With 40% cross-sectional defect in the vertebral body, additional costovertebral joint destruction brought 25% reduction of the failure load, which was statistically significant. CONCLUSION: The load-bearing capacity of metastasized vertebrae in the thoracic spine was proportionally decreased when the defect size in the vertebral body increased. Destruction of costovertebral joint significantly increased the probability of vertebral collapse.

Animals↗

PubMed2004

A retrospective radiographic analysis of subaxial sagittal alignment after posterior C1-C2 fusion.

STUDY DESIGN: Subaxial sagittal alignment following atlantoaxial (A-A) posterior fusion was investigated retrospectively in patients with A-A subluxation. OBJECTIVES: To evaluate the association between A-A fusion angle and postoperative subaxial sagittal alignment and to determine the optimal fusion angle for preservation of physiologic subaxial alignment. SUMMARY OF BACKGROUND DATA: A-A posterior fusion has been used for patients with A-A instability and provided satisfactory clinical results. However, there are patients showing unexpected development of subaxial kyphosis after surgery. The reasons for subaxial kyphosis after A-A fusion remain unclear. METHODS: Seventy-six patients with A-A subluxation who underwent several types of posterior A-A fusion were involved. There were 46 women and 30 men. The causes of A-A subluxation were rheumatoid arthritis in 47, trauma in 16, os odontoideum in 8, and unknown in 5. The methods of posterior fusion consisted of Magerl procedure with posterior wiring in 51, Brooks wiring in 18, and Halifax clamp in 7. Angles at C1-C2, C2-C7, and C1-C7 in the neural position were measured before surgery and at the final follow-up to find out any association between postoperative C2-C7 angle and the other radiologic parameters. The association between O-C1 range of motion and C2-C7 angle was also investigated. RESULTS: The mean angles of C1-C2, C2-C7, and C1-C7 before surgery were 18.4 degrees, 14.5 degrees, and 32.9 degrees, respectively. Those at the final follow-up were 26.0 degrees, 5.5 degrees, and 31.5 degrees, respectively. These results indicated that C1-C2 fixation in a hyperlordotic position led to a subaxial kyphosis after surgery. Statistics showed that there was a linear association between the C1-C2 lordotic fixation angle and the C2-C7 kyphotic angle. CONCLUSIONS: Surgical fixation of A-A joint in a hyperlordotic position will lead the lower cervical spine to a kyphotic sagittal alignment after surgery. To maintain the physiologic sagittal alignment of the subaxial cervical spine, C1-C2 should not be fixed in a hyperlordotic position.

Atlanto-Axial Joint↗

PubMed2004

Two-year observation of artificial intervertebral disc replacement: results after supplemental ultra-high strength bioresorbable spinal stabilization.

OBJECT: This 2-year experimental study was conducted to investigate the efficacy of a bioactive three-dimensional (3D) fabric disc for lumbar intervertebral disc replacement. The authors used a bioresorbable spinal fixation rod consisting of a forged composite of particulate unsintered hydroxyapatite/poly-L-lactide acid (HA/PLLA) for stability augmentation. The biomechanical and histological alterations as well as possible device-related loosening were examined at 2 years postoperatively. METHODS: Two lumbar intervertebral discs (L2-3 and L4-5) were replaced with the 3D fabric discs, which were augmented by two titanium screws and a spanning bioresorbable rod (HA/PLLA). The segmental biomechanics and interface bone ingrowth were investigated at 6, 15, and 24 months postoperatively, and results were compared with the other two surgical groups (3D fabric disc alone; 3D fabric disc with additional anterior instrumentation stabilization). The 3D fabric disc and HA/PLLA-spinal segments demonstrated segmental mobility at 15 and 24 months; however, the range of motion (ROM) in flexion-extension decreased to 49 and 40%, respectively, despite statistically equivalent preserved torsional ROM. Histologically there was excellent osseous fusion at the 3D fabric disc surface-vertebral body interface. At 2 years posttreatment, no adverse tissue reaction nor aseptic loosening of the device was observed. CONCLUSIONS: Intervertebral disc replacement with the 3D fabric disc was viable and when used in conjunction with the bioresorbable HA/PLLA spinal augmentation. Further refinements of device design to create a stand-alone type are necessary to obviate the need for additional spinal stabilization.

Animals↗

PubMed2003

Static and dynamic analysis of five anterior instrumentation systems for thoracolumbar scoliosis.

STUDY DESIGN: A nondestructive biomechanical investigation among five anterior spinal instrumentation systems for scoliosis. OBJECTIVES: The purpose of this study is to analyze the static and dynamic biomechanical stability of five different systems. SUMMARY OF BACKGROUND DATA: Although a variety of anterior spinal instrumentation systems for scoliosis are available, very few attempts have been made at comparative biomechanical studies. METHODS: Thirty calf spines were underwent static biomechanical tests, including flexion-extension, axial rotation, and lateral bending loading modes in the multisegmental spinal model. Five anterior instrumentation systems included: 1) Texas Scottish Rite Hospital system; 2) Bad Wildungen Metz; 3) anterior ISOLA; 4) Cotrel-Dubousset Hoph; and 5) Kaneda Anterior Scoliosis System. The initial and postfatigue stability after a cyclic loading test were analyzed by measuring the range of motion at instrumented segments compared to the intact within the same specimen (% to intact). RESULTS: Two-rod systems showed a significant decrease in range of motion compared to one-rod systems in flexion-extension (P < 0.001) and axial rotation (P < 0.05). In lateral bending, all systems demonstrated a significant decrease in range of motion of less than 40% to the intact (P < 0.001). After cyclical loading test, all systems increased in range of motion. In flexion-extension, one-rod systems depicted a significant increase in range of motion, compared to two-rod systems (P < 0.05). CONCLUSIONS: In the initial stability analysis, two-rod systems are superior to one-rod systems. For one-rod systems, repeated physiologic loading may result in reduced stability in flexion-extension.

Analysis of Variance↗

PubMed2003

Types of spinal instability that require interbody support in posterior lumbar reconstruction: an in vitro biomechanical investigation.

STUDY DESIGN: Pedicle screw fixation alone for sequential spinal instabilities was biomechanically compared with pedicle screw fixation using interbody cages. OBJECTIVE: To evaluate biomechanical effects of interbody cages on construct stiffness, pedicle-screw strain, and the adjacent level in posterior lumbar reconstruction using pedicle screw fixation. SUMMARY OF BACKGROUND DATA: It remains undetermined what types of spinal instability require interbody support in posterior lumbar reconstruction. METHODS: For this study, 10 calf spines (L3-L6) were used. Sequential destabilization was performed at L4-L5 followed by posterior reconstruction using pedicle screw fixation (PS) and interbody cages as follows: intact + PS (I-PS), medial facetectomy + PS (MF-PS), total facetectomy + PS (TF-PS), partial discectomy + PS (D-PS), and D-PS + interbody cages (PLIF). Biomechanical testing was performed under flexion and extension loading modes. Construct stiffness (L4-L5), rod-screw bending strain, and range of motion (ROM) at the upper adjacent level (L3-L4) were analyzed. RESULTS: In terms of construct stiffness (L4-L5), all the reconstructions except D-PS demonstrated higher construct stiffness than the intact spine (P < 0.05). The PLIF showed the highest stiffness among all the reconstructions (P < 0.05). In terms of ROM (L3-L4), all the reconstructions increased the ROM, as compared with the intact state (P < 0.05). Importantly, PLIF showed significantly greater ROM than all the other reconstructions except I-PS (P < 0.05). In terms of rod-screw strain, the D-PS resulted in higher strain than the other groups (P < 0.05). The PLIF presented less strain than the other reconstructions (P < 0.05). CONCLUSIONS: For spinal instability with preserved anterior load sharing, pedicle screw fixation alone is biomechanically adequate, and interbody cages should not be used because they further increase segmental motion at the adjacent segment. However, PS alone provides insufficient stability and high implant strain in case of damaged anterior column. In such cases, additional interbody cages significantly increase construct stiffness and decrease hardware strain. However, they increase ROM at the adjacent segment as well.

Animals↗

PubMed2003

Local kyphosis reduces surgical outcomes of expansive open-door laminoplasty for cervical spondylotic myelopathy.

STUDY DESIGN: This retrospective study analyzed the effects of cervical alignment on surgical results of expansive laminoplasty (ELAP) for cervical spondylotic myelopathy (CSM). OBJECTIVE: To determine the limitation of posterior decompression by ELAP for CSM in the presence of local kyphosis. SUMMARY OF BACKGROUND DATA: Several studies have reported that cervical malalignment affected surgical outcomes of ELAP. However, there has been no report to demonstrate crucial determinants of surgical outcomes of ELAP for CSM in relation to cervical sagittal alignment. METHODS: The study group comprised 114 patients who underwent ELAP for CSM. All were followed up for more than 2 years. The Japanese Orthopedic Association (JOA) scoring system for cervical myelopathy (full score, 17 points) was used to evaluate surgical outcomes for each patient 2 years after surgery. Statistical analysis with multivariate logistic regression models was used to ascertain the risk factors affecting postoperative surgical outcomes. RESULTS: The average JOA scores were 9.9 points before surgery and 14 points 2 years after surgery. The recovery rate was 60.2%. Statistical analysis showed that signal intensity change on MRI and local kyphosis were the most crucial risk factors for poor surgical outcomes. Calculated with the logistic regression model, the highest risk of poor recovery was local kyphosis exceeding 13 degrees. CONCLUSIONS: The influence of cervical malalignment on neurologic recovery after ELAP for CSM was shown. When patients have local kyphosis exceeding 13 degrees, anterior decompression or posterior correction of kyphosis as well as ELAP should be considered. Expansive laminoplasty for CSM is best indicated for patients with local kyphosis less than 13 degrees.

Adult↗