Synovial sarcoma (SS) is a malignant soft tissue tumor characterized by its unique t(X;18)(p11;q11) chromosomal translocation leading to the formation of the SS18-SSX fusion gene. The resulting fusion protein product is considered to play as an aberrant transcription factor and transform target cells by perturbing their gene expression program. However, the cellular origin of SS is highly debated. We herein established two novel human SS cell lines, named Yamato-SS and Aska-SS, and investigated their biological properties. We found the self-renewal ability of these cells to generate sarcospheres, to form tumors in serial xenotransplantation and reconstitute the tumor phenotypes without fractionation by any surface markers. Both SS cells as well as clinical tissue specimens from 15 patients expressed the marker genes-associated stem cell identity, Oct3/4, Nanog, and Sox2. We also found that both SS cells displayed limited differentiation potentials for mesenchymal lineages into osteocytes and chondrocytes albeit with the expression of early mesenchymal and hematopoietic lineage genes. Upon SS18-SSX silencing with sequence-specific siRNAs, these SS cells exhibited morphological transition from spherical growth in suspension to adherent growth in monolayer, additional expression of later mesenchymal and hematopoietic lineage genes, and broader differentiation potentials into osteocytes, chondrocytes, adipocytes, and macrophages in appropriate differentiation cocktails. Collectively, these data suggest that a human multipotent mesenchymal stem cell can serve as a cell of origin for SS and SS is a stem cell malignancy resulting from dysregulation of self-renewal and differentiation capacities driven by SS18-SSX fusion protein.

OBJECTIVE Several biomechanical studies have demonstrated the favorable mechanical properties of the cortical bone trajectory (CBT) screw. However, no reports have examined surgical outcomes of posterior lumbar interbody fusion (PLIF) with CBT screw fixation for degenerative spondylolisthesis (DS) compared with those after PLIF using traditional pedicle screw (PS) fixation. The purposes of this study were thus to elucidate surgical outcomes after PLIF with CBT screw fixation for DS and to compare these results with those after PLIF using traditional PS fixation. METHODS Ninety-five consecutive patients underwent PLIF with CBT screw fixation for DS (CBT group; mean followup 35 months). A historical control group consisted of 82 consecutive patients who underwent PLIF with traditional PS fixation (PS group; mean follow-up 40 months). Clinical status was assessed using the Japanese Orthopaedic Association (JOA) scale score. Fusion status was assessed by dynamic plain radiographs and CT. The need for additional surgery and surgery-related complications was also evaluated. RESULTS The mean JOA score improved significantly from 13.7 points before surgery to 23.3 points at the latest follow-up in the CBT group (mean recovery rate 64.4%), compared with 14.4 points preoperatively to 22.7 points at final follow-up in the PS group (mean recovery rate 55.8%; p < 0.05). Solid spinal fusion was achieved in 84 patients from the CBT group (88.4%) and in 79 patients from the PS group (96.3%, p > 0.05). Symptomatic adjacent-segment disease developed in 3 patients from the CBT group (3.2%) compared with 9 patients from the PS group (11.0%, p < 0.05). CONCLUSIONS PLIF with CBT screw fixation for DS provided comparable improvement of clinical symptoms with PLIF using traditional PS fixation. However, the successful fusion rate tended to be lower in the CBT group than in the PS group, although the difference was not statistically significant between the 2 groups.

OBJECTIVEThe cortical bone trajectory (CBT) screw technique is a new nontraditional pedicle screw (PS) insertion method. However, the biomechanical behavior of multilevel CBT screw/rod fixation remains unclear, and surgical outcomes in patients after 2-level posterior lumbar interbody fusion (PLIF) using CBT screw fixation have not been reported. Thus, the purposes of this study were to examine the clinical and radiological outcomes after 2-level PLIF using CBT screw fixation for 2-level degenerative lumbar spondylolisthesis (DS) and to compare these outcomes with those after 2-level PLIF using traditional PS fixation.METHODSThe study included 22 consecutively treated patients who underwent 2-level PLIF with CBT screw fixation for 2-level DS (CBT group, mean follow-up 39 months) and a historical control group of 20 consecutively treated patients who underwent 2-level PLIF using traditional PS fixation for 2-level DS (PS group, mean follow-up 35 months). Clinical symptoms were evaluated using the Japanese Orthopaedic Association (JOA) scoring system. Bony union was assessed by dynamic plain radiographs and CT images. Surgery-related complications, including symptomatic adjacent-segment disease (ASD), were examined.RESULTSThe mean operative duration and intraoperative blood loss were 192 minutes and 495 ml in the CBT group and 218 minutes and 612 ml in the PS group, respectively (p < 0.05 and p > 0.05, respectively). The mean JOA score improved significantly from 12.3 points before surgery to 21.1 points (mean recovery rate 54.4%) at the latest follow-up in the CBT group and from 12.8 points before surgery to 20.4 points (mean recovery rate 51.8%) at the latest follow-up in the PS group (p > 0.05). Solid bony union was achieved at 90.9% of segments in the CBT group and 95.0% of segments in the PS group (p > 0.05). Symptomatic ASD developed in 2 patients in the CBT group (9.1%) and 4 patients in the PS group (20.0%, p > 0.05).CONCLUSIONSTwo-level PLIF with CBT screw fixation for 2-level DS could be less invasive and result in improvement of clinical symptoms equal to those of 2-level PLIF using traditional PS fixation. The incidence of symptomatic ASD and the rate of bony union were lower in the CBT group than in the PS group, although these differences were not significant.

Using the transverse processes of fresh porcine lumbar spines as an experimental model we evaluated the heat generated by a rotating burr of a high-speed drill in cutting the bone. The temperature at the drilled site reached 174 degrees C with a diamond burr and 77 degrees C with a steel burr. With water irrigation at a flow rate of 540 ml/hr an effective reduction in the temperature was achieved whereas irrigation with water at 180 ml/hr was much less effective. There was a significant negative correlation between the thickness of the residual bone and the temperature measured at its undersurface adjacent to the drilling site (p < 0.001). Our data suggest that tissues neighbouring the drilled bone, especially nerve roots, can be damaged by the heat generated from the tip of a high-speed drill. Nerve-root palsy, one of the most common complications of cervical spinal surgery, may be caused by thermal damage to nerve roots arising in this manner.

This study elucidated symptoms specific to anatomical pathology or compressed segments in thoracic myelopathy. These relationships can be helpful in the initial investigation of thoracic diseases, although additional measures such as MRI or CT are necessary for definitive diagnosis.

Object. This randomized study was designed to elucidate the time course of the perioperative development of intramuscular multifidus muscle pressure after posterior lumbar interbody fusion (PLIF) and to investigate whether the route of pedicle screw insertion affects this pressure and resultant low-back pain. Although several studies have focused on intramuscular pressure associated with posterior lumbar surgery, those studies examined intramuscular pressure generated by the muscle retractors during surgery. No study has investigated the intramuscular pressure after PLIF.Methods. Forty patients with L4-5 degenerative spondylolisthesis were randomly assigned to undergo either the mini-open PLIF procedure with pedicle screw insertion between the multifidus and longissimus muscles (n = 20) or the conventional PLIF procedure via a midline approach only (n = 20). Intramuscular pressure was measured 5 times (at 30 minutes and at 6, 12, 24, and 48 hours after surgery) with an intraoperatively installed sensor. Concurrently, the FACES Pain Rating Scale score for low-back pain and the total dose of postoperative analgesics were recorded.Results. With the patients in the supine position, for both groups the mean pressure values were consistently 40-50 mm Hg, which exceeded the critical capillary pressure of the muscle. With the patients in the lateral decubitus position, the pressure decreased over time (from 14 to 9 mm Hg in the mini-open group and from 20 to 10 mm Hg in the conventional group). Among patients in the mini-open group, the pressure was lower, but the difference was not statistically significant. Postoperative pain and postoperative analgesic dosages were also lower .Conclusions. To the authors' knowledge, this is the first study to evaluate postoperative intramuscular pressure after PLIF. Although the results did not demonstrate a significant difference in the intramuscular pressure between the 2 types of PLIF, mini-open PLIF was associated with less pain after surgery. Clinical trial registration no.: UMIN000010069 (www.umin.ac.jp/ctr/index.htm).

Purpose Adjacent segment disease (ASD) is an increasing problematic complication following lumbar fusion surgeries. ASD requires appropriate treatment, although there are only few reports on surgery for ASD. This study aimed to clarify surgical outcomes of posterior lumbar interbody fusion (PLIF) for ASD. Methods Medical charts of 18 patients who underwent the second (repeat) PLIF for ASD were retrospectively investigated (average follow-up, 40 [27-66] months). Modified Japanese Orthopaedic Association (JOA) score and Whitecloud classification were used as outcome measures. Results Mean modified JOA score improved from 7.7 just before repeat PLIF to 11.4 at maximum recovery and declined to 10.2 at final follow-up. Mean recovery rate of modified JOA score was 52.9 % at maximum recovery and 31.6 % at final follow-up. According to Whitecloud classification, 17 patients (94 %) were excellent or good and only 1 was fair at maximum recovery, whereas 10 (56 %) were excellent or good, 6 were fair, and 2 were poor at final follow-up. Eight patients (44 %) deteriorated again because of recurrent ASD. Two poor patients underwent a third PLIF. Conclusion PLIF is effective for ASD after PLIF in the short term, although it tends to lead to a high incidence of recurrent ASD.

Object Although posterior lumbar interbody fusion (PLIF) is an excellent procedure to attain circumferential decompression, it is technically demanding and can lead to various surgical complications. The authors retrospectively reviewed consecutive patients with nonisthmic spondylolisthesis who underwent PLIF to reveal the incidence and risk factors for perioperative complications of PLIF. Methods A total of 240 patients underwent PLIF. The fusion level was at L4–5 in 220, L3–4 in 18, and L5–S1 in 2. The medial walls of the fusion segment's facet joints were resected, and the VSP Spine System was used for the pedicle screw instrumentation. The operations were performed by 7 surgeons, who were divided into 4 groups according to their level of experience with spinal surgery. Results The average operation time was 175 ± 49 minutes, and the estimated blood loss was 746 ± 489 ml. A total of 90 patients (37.5%) experienced complications; 41 (17%) experienced transient neurological complications, and 18 (7.5%) experienced permanent neurological complications. The mean neurological score according to the Japanese Orthopaedic Association improved from 14.3 ± 3.8 to 24.7 ± 4.0 in the patients without complications and from 14.8 ± 3.6 to 24.0 ± 3.9 in the patients with complications. Multivariate analysis concerning the relationship between complications and risk factors (operation time, estimated intraoperative blood loss, and surgeon experience) revealed that operation time was the only significant risk factor for complications. Conclusions Perioperative complications of PLIF were more frequent in this homogeneous study group than in other studies of various implants. Total excision of the facet joints might preclude neurological complications.