A new nomenclature system for the surgical treatment of cervical spine deformity, developing, and validation of SOF system.

PURPOSE: To develop and assess the reliability of new nomenclature system that systematically organizes osteotomy techniques and briefly describes the surgical approach, the surgical sequence, and the fixation technique for cervical spine deformity (CSD). METHODS: We developed a new classification system (SOF system) for CSD surgery that describes the sequence of surgical approach (S), the grade of osteotomy (O), and the information of fixation (F) using alphanumeric codes. Twenty CSD osteotomies (8 anterior osteotomies, 12 posterior osteotomies) were included in this study to evaluate the inter- and intra-observer agreement based on operation records. Six observers performed independent evaluations of the operation records in random order. Each observer described 20 CSD surgeries using the SOF system twice (> 30 days between assessments) based on operation records to validate SOF system. RESULTS: Overall agreement (among all six observers at the initial assessment) on the anterior and posterior osteotomy was ICC = 0.96 and ICC = 0.91, respectively. Overall agreement (repeat observations after at least 30 days) on the anterior and posterior osteotomy was ICC = 0.96 and ICC = 0.91, respectively. This data showed that both inter- and intra-observer agreement revealed 'excellent'. CONCLUSION: This study introduces the SOF system of the CSD surgery to understand the surgical sequence, the type of osteotomy and the fixation techniques. The investigation of the inter- and intra-observer agreement revealed 'excellent agreement' for both anterior and posterior osteotomies. Thus, SOF system can provide a consistent description of the various CSD surgeries and its use will provide a common frame for CSD surgery and help communicate between surgeons.

Cervical myelopathy due to atraumatic odontoid fracture in patients with rheumatoid arthritis: A case series.

To highlight the risk of cervical myelopathy due to occult, atraumatic odontoid fracture in patients with rheumatoid arthritis, we retrospectively reviewed radiographic findings and clinical observations for 7 patients with this disorder. This fracture tends to occur in patients with long-lasting rheumatoid arthritis and to be misdiagnosed as simple atlantoaxial dislocation. Since this fracture causes multidirectional instability between C1 and C2 and is expected to have poor healing potential due to bone erosion and inadequate blood supply, posterior spinal arthrodesis surgery is indicated upon identification of the fracture to prevent myelopathy.

Surgical treatment of double thoracic adolescent idiopathic scoliosis with a rigid proximal thoracic curve.

PURPOSE: There is limited consensus on the optimal surgical strategy for double thoracic adolescent idiopathic scoliosis (AIS). Recent studies have reported that pedicle screw constructs to maximize scoliosis correction cause further thoracic spine lordosis. The objective of this study was to apply a new surgical technique for double thoracic AIS with rigid proximal thoracic (PT) curves and assess its clinical outcomes. METHODS: Twenty one consecutive patients with Lenke 2 AIS and a rigid PT curve (Cobb angle ≥30º on side-bending radiographs, flexibility ≤30 %) treated with the simultaneous double-rod rotation technique (SDRRT) were included. In this technique, a temporary rod is placed at the concave side of the PT curve. Then, distraction force is applied to correct the PT curve, which reforms a sigmoid double thoracic curve into an approximate single thoracic curve. As a result, the PT curve is typically converted from an apex left to an apex right curve before applying the correction rod for PT and main thoracic curve. RESULTS: All patients were followed for at least 2 years (average 2.7 years). The average main thoracic and PT Cobb angle correction rate at the final follow-up was 74.7 and 58.0 %, respectively. The average preoperative T5-T12 thoracic kyphosis was 9.3°, which improved significantly to 19.0° (p < 0.0001) at the final follow-up. Although 71 % patients had preoperative level shoulders or a positive radiographic shoulder height, all patients had mildly imbalanced or balanced shoulders at the final follow-up. The average preoperative main thoracic apical vertebral rotation angle of 20.7° improved significantly after surgery to 16.4° (p = 0.0046), while the average preoperative total SRS questionnaire score of 3.7 improved significantly to 4.4 (p = 0.0012) at the final follow-up. CONCLUSIONS: Radiographic findings and patient outcomes were satisfactory. Thoracic kyphosis can be maintained or improved, while coronal and axial deformities can be corrected using SDRRT for Lenke 2 AIS with a rigid PT curve.

Caspase 3 silencing inhibits biomechanical overload-induced intervertebral disk degeneration.

Intervertebral disk (IVD) degeneration causes debilitating low back pain in much of the worldwide population. No efficient treatment exists because of an unclear pathogenesis. One characteristic event early in such degeneration is the apoptosis of nucleus pulposus (NP) cells embedded in IVDs. Excessive biomechanical loading may also be a major etiology of IVD degeneration. The present study used in vitro and in vivo models of compressive loading to elucidate the underlying mechanism of IVD degeneration. In addition, we investigated whether the inhibition of apoptosis is a potential clinical therapeutic strategy for the treatment of IVD degeneration induced by biomechanical stress. A TUNEL assay showed that NP cell-agarose three-dimensional composite cultures subjected to uniaxial, unconfined, static, compressive loading exhibited a time-dependent increase in apoptosis. Western blot analysis revealed the up-regulation of several extracellular matrix-degrading enzymes and down-regulation of tissue inhibitor of metalloproteinase 1. These responses to compressive loading were all significantly inhibited by caspase 3 siRNA. In the in vivo model of compressive loading-induced IVD degeneration, a single local injection of caspase 3 siRNA significantly inhibited IVD degeneration by magnetic resonance imaging, histological findings, IHC, and TUNEL assay. The present study suggests that caspase 3 siRNA attenuates overload-induced IVD degeneration by inhibiting NP cell apoptosis and the expression of matrix-degrading enzymes.

Cervical spondylotic myelopathy: posterior decompression and pedicle screw fixation.

INTRODUCTION: Posterior decompression by laminoplasty and anterior decompression/fixation have been widely accepted, and they provide sufficient results for cervical spondylotic myelopathy. However, combined procedure of posterior decompression and reconstruction is favorable for some patients accompanying local kyphosis, segmental instability, previously operated conditions on the cervical spine, etc. DISCUSSION: Among posterior cervical instrumentations, pedicle screw fixation is a strong tool of stabilization of unstable segment and correction of deformities in sagittal and/or coronal planes for the patient with cervical spondylotic myelopathy. On the other hand, neurovascular complications including injury to the vertebral artery and nerve root cannot be completely eliminated. Even after surgeons became familiar with placement of cervical pedicle screws, screw malposition rate by freehand technique is high for patients with severe spondylotic condition. Surgeons must especially be careful for inserting pedicle screw in the cervical spine associating marked degenerative changes by spondylosis, and must obtain preoperatively sufficient anatomical information of the pedicle and surrounding structures. CONCLUSION: Combined procedure of posterior reconstructive surgery using a pedicle screw fixation provides better clinical outcomes than laminoplasty alone for cervical spondylotic myelopathy accompanying local kyphosis or segmental instability. Further development of supporting tools for cervical pedicle screw insertion including aiming device, navigation system and neuromonitoring procedure are expected for safer screw insertion.

Subaxial sagittal alignment after atlantoaxial fixation techniques.

STUDY DESIGN: A retrospective clinical case series. OBJECTIVES: To evaluate the association between C1-C2 fixation angle and postoperative C2-C7 alignment in the sagittal plane after C1 lateral mass screw with C2 pedicle screw fixation (C1-LMS) or Magerl with wiring technique. SUMMARY OF BACKGROUND DATA: Various techniques for posterior correction and fusion, such as the Magerl procedure with posterior wiring and C1-LMS procedures, are used for treating atlantoaxial instability. However, only few studies investigating the relationship between postoperative C1-C2 angle and C2-C7 sagittal alignment change after C1-C2 fixation have been reported. METHODS: We retrospectively followed up 42 patients who underwent the C1-LMS (22 patients) or Magerl with wiring procedure (20 patients) to treat C1-C2 instability for >2 years. The atlantodental interval, space available for the spinal cord, and O-C1, C1-C2, C2-C3, and C2-C7 angles were measured. RESULTS: Significant reduction in atlantodental interval and increase in space available for the spinal cord were observed in both groups. Although the preoperative C1-C2 angles were similar, the angle at the final follow-up was higher in the Magerl with wiring group than in the C1-LMS group (P<0.01). The C1-C2 fixation and postoperative C2-C7 angles were negatively correlated in both groups (C1-LMS group, r=-0.55, P<0.01; Magerl with wiring, r=-0.62, P<0.01). CONCLUSIONS: Increased lordotic change in the C1-C2 angle was associated with increased kyphotic changes in the C2-C7 angle after both procedures. The C1-LMS procedure effectively controlled C1-C2 sagittal alignment during surgery. To decrease the risk of postoperative subaxial kyphotic changes, the C1-C2 fixation angle should be carefully determined.

A multicenter study on accuracy and complications of freehand placement of cervical pedicle screws under lateral fluoroscopy in different pathological conditions: CT-based evaluation of more than 1,000 screws.

PURPOSE: To conduct a retrospective multicenter study to investigate the accuracy of pedicle screw (PS) placement in the cervical spine by freehand technique and the related complications in various pathological conditions including trauma, rheumatoid arthritis, degenerative conditions and others. METHODS: 283 patients with 1,065 PSs in the cervical spine who were treated at eight spine centers and finished postoperative CT scan were enrolled. The numbers of placed PSs were 608 for trauma, 180 for rheumatoid arthritis (RA), 199 for spondylosis, and 78 for others. Malposition grades on CT image in the axial plane were defined as grade 0 (G-0) correct placement, grade 1 (G-1): malposition by less than half screw diameter, grade 2 (G-2): malposition by more than half screw diameter. The direction of malposition was classified into four categories: medial, lateral, superior and inferior. RESULTS: Overall malposition rate was 14.8 % (9.6 % in G-1 and 5.3 % in G-2). The highest malposition rate was 26.7 % for RA, followed by 16.6 % for spondylosis, and 11.2 % for trauma. The malposition rate for RA was significantly higher than those for other pathologies. 79.7 % of the malpositioned screws were placed laterally. Though intraoperative vertebral artery injury was observed in two patients with RA, there were no serious complications during a minimal 2-year follow-up. CONCLUSIONS: Malposition rate of PS placement in the cervical spine by freehand technique was high in rheumatoid patients even when being performed by experienced spine surgeons. Any guidance tools including navigation systems are recommended for placement of cervical PSs in patients with RA.

A genome-wide sib-pair linkage analysis of ossification of the posterior longitudinal ligament of the spine.

Ossification of the posterior longitudinal ligament of the spine (OPLL) is a common musculoskeletal disease among people after middle age. The OPLL presents with serious neurological abnormalities due to compression of the spinal cord and nerve roots. The OPLL is caused by genetic and environment factors; however, its etiology and pathogenesis still remain to be elucidated. To determine the susceptibility loci for OPLL, we performed a genome-wide linkage study using 214 affected sib-pairs of Japanese. In stratification analyses for definite cervical OPLL, we found loci with suggestive linkage on 1p21, 2p22-2p24, 7q22, 16q24 and 20p12. Fine mapping using additional markers detected the highest non-parametric linkage score (3.43, P = 0.00027) at D20S894 on chromosome 20p12 in a subgroup that had no complication of diabetes mellitus. Our result would shed a new light on genetic aspects of OPLL.

Mid-term clinical results of minimally invasive decompression and posterolateral fusion with percutaneous pedicle screws versus conventional approach for degenerative spondylolisthesis with spinal stenosis.

INTRODUCTION: In order to minimize perioperative invasiveness and improve the patients' functional capacity of daily living, we have performed minimally invasive lumbar decompression and posterolateral fusion (MIS-PLF) with percutaneous pedicle screw fixation for degenerative spondylolisthesis with spinal stenosis. Although several minimally invasive fusion procedures have been reported, no study has yet demonstrated the efficacy of MIS-PLF in degenerative spondylolisthesis of the lumbar spine. This study prospectively compared the mid-term clinical outcome of MIS-PLF with those of conventional PLF (open-PLF) focusing on perioperative invasiveness and patients' functional capacity of daily living. MATERIALS AND METHODS: A total of 80 patients received single-level PLF for lumbar degenerative spondylolisthesis with spinal stenosis. There were 43 cases of MIS-PLF and 37 cases of open-PLF. The surgical technique of MIS-PLF included making a main incision (4 cm), and neural decompression followed by percutaneous pedicle screwing and rod insertion. The posterolateral gutter including the medial transverse process was decorticated and iliac bone graft was performed. The parameters analyzed up to a 2-year period included the operation time, intra and postoperative blood loss, Oswestry-Disability Index (ODI), Roland-Morris Questionnaire (RMQ), the Japanese Orthopaedic Association score, and the visual analogue scale of low back pain. The fusion rate and complications were also reviewed. RESULTS: The average operation time was statistically equivalent between the two groups. The intraoperative blood loss was significantly less in the MIS-PLF group (181 ml) when compared to the open-PLF group (453 ml). The postoperative bleeding on day 1 was also less in the MIS-PLF group (210 ml) when compared to the open-PLF group (406 ml). The ODI and RMQ scores rapidly decreased during the initial postoperative 2 weeks in the MIS-PLF group, and consistently maintained lower values than those in the open-PLF group at 3, 6, 12, and 24 months postoperatively. The fusion rate was statistically equivalent between the two groups (98 vs. 100%), and no major complications occurred. CONCLUSION: The MIS-PLF utilizing a percutaneous pedicle screw system is less invasive compared to conventional open-PLF. The reduction in postoperative pain led to an increase in activity of daily living (ADL), demonstrating rapid improvement of several functional parameters. This superiority in the MIS-PLF group was maintained until 2 years postoperatively, suggesting that less invasive PLF offers better mid-term results in terms of reducing low back pain and improving patients' functional capacity of daily living. The MIS-PLF utilizing percutaneous pedicle screw fixation serves as an alternative technique, eliminating the need for conventional open approach.

A retrospective study of congenital osseous anomalies at the craniocervical junction treated by occipitocervical plate-rod systems.

PURPOSE: To evaluate the effectiveness of posterior occipitocervical reconstruction using the anchors of cervical pedicle screws and plate-rod systems for patients with congenital osseous anomalies at the craniocervical junction. METHODS: Twenty patients with congenital osseous lesions who underwent posterior occipitocervical fusion using the anchors of cervical pedicle screws and plate-rod systems for reduction and fixation from 1996 to 2009 were reviewed. The lesions included os odontoideum, occipitalization of the atlas, congenital C2-3 fusion, congenital atlantoaxial subluxation, congenital basilar invagination and combined anomalies. The clinical assessment and the measurements of the images were performed preoperatively, postoperatively and at most recent follow-up. RESULTS: The combined deformity of flexion of the occipitoatlantoaxial complex and invagination of the odontoid process associated with congenital osseous lesions at the craniocervical junction was corrected by application of combined forces of extension and distraction between the occiput and the cervical pedicle screws. Preoperative myelopathy improved in 94.7% patients. The mean Ranawat value, Redlund-Johnnell value, atlantodental distance, occiput (O)-C2 angle, and C2-C7 lordosis angle improved postoperatively and was sustained at most recent follow-up. The mean cervicomedullary angle improved from 129.3° preoperatively to 153.3° postoperatively. The mean range of motion at the lower adjacent motion segment remained unchanged at most recent follow-up. The fusion rate was 95%. CONCLUSIONS: The results of the present study indicate that posterior occipitocervical reconstruction using the anchors of cervical pedicle screws and plate-rod systems is an effective technique for treatment of deformities and/or instability caused by congenital osseous anomalies at the craniocervical junction.

Impact of deep extensor muscle-preserving approach on clinical outcome of laminoplasty for cervical spondylotic myelopathy: comparative cohort study.

INTRODUCTION: This study aimed to compare patients undergoing deep extensor muscle-preserving laminoplasty and conventional open-door laminoplasty for the treatment of cervical spondylotic myelopathy (CSM). We specifically assessed axial pain, cervical spine function, and quality of life (QOL) with a minimum follow-up period of 3 years. PATIENTS AND METHODS: Ninety patients were divided into two groups and underwent either conventional open-door laminoplasty (CL group) or laminoplasty using the deep extensor muscle-preserving approach (MP group). The latter approach was undertaken by preserving the multifidus and semispinalis cervicis attachments followed by open-door laminoplasty and resuturing of the bisected spinous processes at each decompression level. The mean follow-up period was 7.7 years (range, 36-128 months). Preoperative and follow-up evaluations included the Japanese Orthopaedic Association (JOA) score, a tentative version of the JOA Cervical Myelopathy Evaluation Questionnaire (JOACMEQ) including cervical spine function and QOL, and a visual analog scale (VAS) for axial pain. Radiological analyses included cervical lordosis and flexion-extension range of motion (C2-7), as well as deep extensor muscle areas on axial magnetic resonance imaging (MRI). RESULTS: The mean number of decompressed laminae was 3.9 and 3.3 in CL and MP groups, respectively, which was statistically equivalent. Japanese Orthopaedic Association recovery was statistically equivalent between the two groups. The MP group demonstrated a superior QOL score (57 vs. 46%) compared with the CL group at final follow-up (p < 0.05). Mean VAS scores at final follow-up were 2.2 and 4.3 in MP and CL groups, respectively (p < 0.05). Cervical lordosis and flexion-extension range of motion were statistically equivalent. The percentage deep muscle area on MRI was significantly lesser in the CL group compared with the MP group (58 vs. 102%; p < 0.01). CONCLUSION: We demonstrated the superiority of deep extensor muscle-preserving laminoplasty in terms of postoperative axial pain, QOL, and prevention of atrophy of the deep extensor muscles over conventional open-door laminoplasty for the treatment of CSM.

Cervical pedicle screw placement using the "key slot technique": the feasibility and learning curve.

STUDY DESIGN: A retrospective study. OBJECTIVES: To present the accuracy and safety of a novel "key slot (KS)" technique for cervical pedicle screw (CPS) placement with the learning curve. SUMMARY OF BACKGROUND DATA: Safety and learning curve are the issues preventing wide acceptance of CPS. On the basis of the local anatomy of the pedicle, the authors modified the conventional technique to increase the accuracy and comfortableness of CPS placement with minimal bone loss. METHODS: A total of 277 subaxial CPS in 50 patients had been inserted using author's technique were reviewed. The KS-shaped entry was created on the medial half of the lateral mass with a 3 mm cutting burr. The shape of entry was a right-angled triangle on the axial plane. The apex of triangle was the virtual pedicle inlet and the oblique side was same as pedicle axis. After making entry, the pedicle was probed with a curved awl along the medial wall. On the postoperative vascular-enhanced computed tomography scan, we analyzed the direction and grade of pedicle perforation (grade 0: no perforation, 1:< 25%, 2: 20% to 50%, 3: > 50% of screw diameter) on the chronological group of consecutive 10 cases. Grade 2 and 3 were considered as incorrect position. RESULTS: The correct position was found in 250 screws (90.3%); grade 0 - 215 screws, 1 - 35 screws and the incorrect position in 27 screws (9.7%); grade 2 - 21 screws, grade 3 - 6 screws. The incidence of incorrect screw position was 18% in the initial 20 cases and 2.7% after that. There was no neurovascular complication related with CPS. CONCLUSIONS: We performed CPS placement using the KS technique and with 90% correct position without clinical complications. After the learning curve, the incidence was 2.7%. This technique could be considered relatively concrete and safe modification of conventional technique with minimal bone loss.

Perioperative complications of anterior cervical decompression with fusion in patients with ossification of the posterior longitudinal ligament: a retrospective, multi-institutional study.

BACKGROUND: Anterior decompression with fusion (ADF) for patients with cervical ossification of the posterior longitudinal ligament (OPLL) is reportedly associated with a higher incidence of complications than is laminoplasty. However, the frequency of perioperative complications associated with ADF for cervical OPLL has not been fully established. The purpose of this study was to investigate the incidence of perioperative complications, especially neurological complications, following ADF performed to relieve compressive cervical myelopathy due to cervical OPLL. METHODS: Study participants comprised 150 patients who had undergone ADF for cervical OPLL at 27 institutions between 2005 and 2008. Perioperative--especially neurological--complications occurring within 2 weeks after ADF were analyzed. Preoperative imaging findings, including Cobb angle, between C2 and C7 and occupying ratio of OPLL were investigated. Multivariate analysis with logistic regression was performed to identify independent risk factors for neurological complications. RESULT: Three patients (2.0 %) showed deterioration of lower-extremity function after ADF. One of the three patients had not regained their preoperative level of function 6 months after surgery. Upper-extremity paresis occurred in 20 patients (13.3 %), five of whom had not returned to preoperative levels 6 months after surgery. Patients with upper-extremity paresis showed significantly higher occupying ratios of OPLL, greater blood loss, longer operation times, fusion of more segments, and higher rates of cerebrospinal fluid leakage than those without paresis. Independent risk factors for upper-extremity paresis were a high occupying ratio of OPLL and large blood loss during surgery. CONCLUSIONS: The incidences of deterioration in upper- and lower-extremity functions were 13.3 % and 2.0 %, respectively. Patients with a high occupying ratio of OPLL are at higher risk of developing neurological deterioration.

Long-Term Clinical Course of Patients After Decompression and Posterior Instrumented Fusion Surgery for Thoracic Ossification of the Posterior Longitudinal Ligament: An Average Follow-Up of 18 years.

STUDY DESIGN: Retrospective observational study. OBJECTIVES: To evaluate the long-term recurrence rates and functional status of patients with thoracic ossification of the posterior longitudinal ligament (OPLL) after decompression and posterior fusion surgery. METHODS: Thirty-seven consecutive patients who underwent posterior thoracic spine surgery at a single institution were retrospectively reviewed. The long-term neurological and functional outcomes of 25 patients who were followed up for ≥10 years after surgery were assessed. Factors associated with the recurrence of myelopathy were also analyzed. RESULTS: The mean preoperative Japanese Orthopaedic Association score was 3.7, which improved to 6.5 at postoperative year 2 and declined to 6.0 at a mean follow-up of 18 years. No patient experienced a relapse of myelopathy due to OPLL within the instrumented spinal segments. However, 15 (60%) patients experienced late neurological deterioration, 10 of whom had a relapse of myelopathy due to OPLL or ossification of the ligamentum flavum (OLF) in the region outside the primary operative lesion, while 4 developed myelopathy due to traumatic vertebral fracture of the ankylosed spine. Young age, a high body mass index, and lumbar OPLL are likely associated with late neurological deterioration. CONCLUSIONS: Decompression and posterior instrumented fusion surgery is a reliable surgical procedure with stable long-term clinical outcomes for thoracic OPLL. However, as OPLL may progress through the spine, attention should be paid to the recurrence of paralysis due to OPLL or OLF in regions other than the primary operative lesion and vertebral fractures of the ankylosed spine after surgery for thoracic OPLL.

A late neurological complication following posterior correction surgery of severe cervical kyphosis.

Though a possible cause of late neurological deficits after posterior cervical reconstruction surgery was reported to be an iatrogenic foraminal stenosis caused not by implant malposition but probably by posterior shift of the lateral mass induced by tightening screws and plates, its clinical features and pathomechanisms remain unclear. The aim of this retrospective clinical review was to investigate the clinical features of these neurological complications and to analyze the pathomechanisms by reviewing pre- and post-operative imaging studies. Among 227 patients who underwent cervical stabilization using cervical pedicle screws (CPSs), six patients who underwent correction of cervical kyphosis showed postoperative late neurological complications without any malposition of CPS (ND group). The clinical courses of the patients with deficits were reviewed from the medical records. Radiographic assessment of the sagittal alignment was conducted using lateral radiographs. The diameter of the neural foramen was measured on preoperative CT images. These results were compared with the other 14 patients who underwent correction of cervical kyphosis without late postoperative neurological complications (non-ND group). The six patients in the ND group showed no deficits in the immediate postoperative periods, but unilateral muscle weakness of the deltoid and biceps brachii occurred at 2.8 days postoperatively on average. Preoperative sagittal alignment of fusion area showed significant kyphosis in the ND group. The average of kyphosis correction in the ND was 17.6° per fused segment (range 9.7°-35.0°), and 4.5° (range 1.3°-10.0°) in the non-ND group. A statistically significant difference was observed in the degree of preoperative kyphosis and the correction angles at C4-5 between the two groups. The diameter of the C4-5 foramen on the side of deficits was significantly smaller than that of the opposite side in the ND group. Late postoperative neurological complications after correction of cervical kyphosis were highly associated with a large amount of kyphosis correction, which may lead foraminal stenosis and enhance posterior drift of the spinal cord. These factors may lead to both compression and traction of the nerves, which eventually cause late neurological deficits. To avoid such complications, excessive kyphosis correction should not be performed during posterior surgery to avoid significant posterior shift of the spinal cord and prophylactic foraminotomies are recommended if narrow neuroforamina were evident on preoperative CT images. Regardless of revision decompression or observation, the majority of this late neurological complication showed complete recovery over time.

Improved bioabsorbability of synthetic hydroxyapatite through partial dissolution-precipitation of its surface.

Even though synthetic hydroxyapatite (HAp) has a chemical composition similar to the mineral phase of bone, it is minimally absorbed and replaced by bone tissue. This could be because HAp is composed of compactly arranged apatite crystals with homogenously large grains. In this study, the surface and non-stoichiometry of the synthetic HAp crystals was modified by partial dissolution and precipitation (PDP) to improve bioabsorbability of HAp. In vitro cell culture demonstrated that more osteoclasts were activated on PDP-HAp compared with HAp. In vivo implantation using a rabbit bone defect model revealed that PDP-HAp was gradually degraded and was replaced by bone tissue. Consistent with the in vitro results, more osteoclasts were activated in PDP-HAp than in HAp, indicating that the former was absorbed through the stimulation of osteoclastic activity. These results suggest that the PDP technique may have clinical utility for modifying synthetic HAp for use as superior bone graft substitutes.

Neurological recovery after surgical treatment of giant cervical pseudomeningoceles extending to lumbar spine associated with previous brachial plexus injury.

The authors describe a case of 28-year-old man who presented with cervical myelopathy and lumbar radiculopathy due to the giant cervical pseudomeningocele extending to the lumbar spine at 10 years after previous brachial plexus injury. To evaluate the communicating tract between pseudomeningocele and subarachnoidal space, the multidetector-row helical CT with simultaneous myelography was performed preoperatively. The surgical treatment in the cervical spine included the resection of pseudomeningocele and the repair of dural defects communicating into the cyst following multi-level laminoplasty and foraminotomies. At 6 years after surgery, the significant neurologic recovery and complete obliteration of cysts in the whole spine area were maintained. This serves as the first report describing the significant neurologic recovery after the surgical treatment of giant cervical pseudomeningocele extending to the lumbar spine after previous brachial plexus injury.

One-stage posterior instrumentation surgery for the treatment of osteoporotic vertebral collapse with neurological deficits.

The number of reports describing osteoporotic vertebral fracture has increased as the number of elderly people has grown. Anterior decompression and fusion alone for the treatment of vertebral collapse is not easy for patients with comorbid medical problems and severe bone fragility. The purpose of the present study was to evaluate the efficacy of one-stage posterior instrumentation surgery for the treatment of osteoporotic vertebral collapse with neurological deficits. A consecutive series of 21 patients who sustained osteoporotic vertebral collapse with neurological deficits were managed with posterior decompression and short-segmental pedicle screw instrumentation augmented with ultra-high molecular weight polyethylene (UHMWP) cables with or without vertebroplasty using calcium phosphate cement. The mean follow-up was 42 months. All patients showed neurologic recovery. Segmental kyphotic angle at the instrumented level was significantly improved from an average preoperative kyphosis of 22.8-14.7 at a final follow-up. Spinal canal occupation was significantly reduced from an average before surgery of 40.4-19.1% at the final follow-up. Two patients experienced loosening of pedicle screws and three patients developed subsequent vertebral compression fractures within adjacent segments. However, these patients were effectively treated in a conservative fashion without any additional surgery. Our results indicated that one-stage posterior instrumentation surgery augmented with UHMWP cables could provide significant neurological improvement in the treatment of osteoporotic vertebral collapse.

Impact of lowest instrumented vertebra tilt and rotation on uninstrumented lumbar curve and L4 tilt in thoracic adolescent idiopathic scoliosis.

OBJECTIVE: Controversy exists regarding the effects of lowest instrumented vertebra (LIV) tilt and rotation on uninstrumented lumbar segments in adolescent idiopathic scoliosis (AIS) surgery. Because the intraoperative LIV tilt from the inferior endplate of the LIV to the superior sacral endplate is not stable after surgery, the authors measured the LIV angle of the instrumented thoracic spine as the LIV angle of the construct. This study aimed to evaluate the effects of the LIV angle of the construct and the effects of LIV rotation on the postoperative uninstrumented lumbar curve and L4 tilt in patients with thoracic AIS. METHODS: A retrospective correlation and multivariate analysis of a prospectively collected, consecutive, nonrandomized series of patients at a single institution was undertaken. Eighty consecutive patients with Lenke type 1 or type 2 AIS treated with posterior correction and fusion were included. Preoperative and 2-year postoperative radiographic measurements were the outcome measures for this study. Outcome variables were postoperative uninstrumented lumbar segments (LIV tilt, LIV translation, uninstrumented lumbar curve, thoracolumbar/lumbar [TL/L] apical vertebral translation [AVT], and L4 tilt). The LIV angle of the construct was measured from the orthogonal line drawn from the upper instrumented vertebra to the LIV. Multiple stepwise linear regression analysis was conducted between outcome variables and patient demographics/radiographic measurements. There were no study-specific biases related to conflicts of interest. RESULTS: Predictor variables for postoperative uninstrumented lumbar curve were the postoperative LIV angle of the construct, number of uninstrumented lumbar segments, and flexibility of TL/L curve. Specifically, a lower postoperative uninstrumented lumbar curve was predicted by a lower absolute value of the postoperative LIV angle of the construct (p < 0.0001). Predictor variables for postoperative L4 tilt were postoperative LIV rotation, preoperative L4 tilt, and preoperative uninstrumented lumbar curve. Specifically, a lower postoperative L4 tilt was predicted by a lower absolute value of postoperative LIV rotation (p < 0.0001). CONCLUSIONS: The LIV angle of the construct significantly affected the LIV tilt, uninstrumented lumbar curve, and TL/L AVT. LIV rotation significantly affected the LIV translation and L4 tilt.