Takashi Fujishiro

Accuracy of Pedicle Screw Placement with Robotic Guidance System: A Cadaveric Study.

Study Design. A cadaveric study. Objective. To investigate the accuracy of pedicle screw placement using a robotic guidance system (RGS). Summary of Background Data. RGS is a unique surgery assistance-apparatus. Although several clinical studies have demonstrated that RGS provides accurate pedicle screw placement, very few studies have validated its accuracy. Methods. A total of 216 trajectories performed with the assistance of the RGS in eight cadavers were evaluated. The RGS was used, with different mounting platforms, to drill pilot holes in the thoracic and lumbosacral spine, using 3-mm diameter fiducial wires as trajectory markers. Deviation between the preoperative plan and executed trajectories was measured at the entry points to the vertebrae and at a depth of 30 mm along the wire. Both the deviation from the preoperative plan and the wire position were evaluated in the axial and sagittal planes using computed tomography (CT). Results. The average deviation from the planned wire placement was 0.64 ± 0.59 mm at the entry point and 0.63 ± 0.57 mm at a depth of 30 mm in the axial plane, and 0.77 ± 0.62 mm and 0.80 ± 0.66 mm, respectively, in the sagittal plane. The magnitude of deviation was not affected by the vertebral level or the platform used. The use of an open approach achieved greater screw placement accuracy at a depth of 30 mm in the sagittal plane, compared with the percutaneous approach. The fiducials were placed completely within the pedicle in 93.9% of trajectories in the axial plane (n = 164 pedicles with a width ≥5 mm) and 98.6% in the sagittal plane (n = 216). Conclusion. In this cadaveric study, RGS supported execution of accurate trajectories that were equal or slightly superior to reports of CT-based navigation systems. Level of Evidence: N/A

Posterior short fusion without neural decompression using pedicle screws and spinous process plates: A simple and effective treatment for neurological deficits following osteoporotic vertebral collapse

BACKGROUND The optimal treatment of neurological deficits following osteoporotic vertebral collapse (OVC) is controversial, owing to complications that result from fragile bone quality. In the present study, we assessed surgical results following posterior spinal fusion without decompression. We achieved stable fusion over a short segment of the spinal column using pedicle screws and spinous process plates, maximizing the use of the preserved posterior elements. METHODS We reviewed surgical data, perioperative complications, clinical outcomes, and radiographic data of 20 consecutively recruited patients with delayed neurological deficits following OVC, who experienced posterior short fusion without neural decompression. The average follow-up period was 24.3 months. The spine was typically stabilized with pedicle screws and spinous process plates from one level above to one level below the collapsed vertebrae, without using neural decompression or considerable correction of kyphosis. RESULTS All patients experienced relief from back pain and neurological improvements of at least one modified Frankel grade. Bone unions of the collapsed vertebrae were achieved in all patients, and spinal fusions of the instrumented segments were achieved in all but one patient. The mean loss of correction was 5.9°, and the average spinal canal compromise by bone fragments was 32.4% before surgery as against 26.0% at the final follow-up time point. Fractures in adjacent or upper instrumented vertebrae were observed in four cases (20%). CONCLUSIONS Rigid augmentation by spinous process plates and an enough bed for the bone grafts were available in patients with severe osteoporosis, without neural decompression. All patients had satisfactory neurological recovery regardless of the extent of spinal canal remodeling, demonstrating that dynamic factors are the primary contributor to neurological deficits following OVC.

The Evaluation of Indirect Neural Decompression After Lateral Lumbar Interbody Fusion Using Intraoperative Computed Tomography Myelogram

BACKGROUND The effect of indirect decompression after lateral lumbar interbody fusion (LLIF) is widely acknowledged; however, its details remain unclear. This study aimed to evaluate the immediate effects of indirect decompression just after LLIF cage placement but just before posterior instrumentation, using intraoperative computed tomography myelogram (iCTM). METHODS Fifty-three levels from 28 patients undergoing LLIF with iCTM, were included in this retrospective study. Radiographic parameters were obtained from preoperative computed tomography myelogram and iCTM. Segmental correction, cross-sectional areas of the spinal canal, and bilateral foramen were compared preoperatively and intraoperatively to assess the neural decompression just after LLIF cage placement. Canal stenosis status during axial computed tomography myelogram was classified into 3 grades according to modified Schizass grading to determine the necessity of additional posterior decompression procedures. The Oswestry Disability Index was obtained before and 3 months after the operation. RESULTS Significant improvements in all radiological parameters of segmental correction, cross-sectional areas of the spinal canal, and bilateral foramen were observed just after LLIF cage placement. However, 11 (21%) levels had insufficient neural decompression status with iCTM grade (10 central canal and 1 lateral recess stenosis), requiring further direct posterior decompression. The difference in the improvement of Oswestry Disability Index between the decompression and nondecompression group was not significant, suggesting the validity of our decision. CONCLUSIONS Detailed evaluation with iCTM revealed that adequate indirect decompression with LLIF was not always obtained, validating the intraoperative decision of further posterior decompression. This procedure, LLIF with iCTM, may reduce the risk of unnecessary direct decompression and reoperation after insufficient indirect decompression.

Risk factors for anterior bone loss in cervical disc arthroplasty

OBJECTIVE The objective of this study was to identify the risk factors of anterior bone loss (ABL) in cervical disc arthroplasty (CDA) and the subsequent effect of this phenomenon. METHODS The authors performed a retrospective radiological review of 185 patients with a minimum 5-year follow-up after CDA (using Bryan, Discocerv, Mobi-C, or Baguera C). Postoperative radiographs were examined and compared to the initial postoperative films to determine the percentage of ABL. The relationship of ABL to potential risk factors was analyzed. RESULTS Complete radiological assessment was available in 145 patients with 193 CDRs and 383 endplates (average age 45 years, range 25-65 years, 54% women). ABL was identified in 63.7% of CDRs (48.7% mild, 11.9% moderate, 3.1% severe). Age (p = 0.770), sex (p = 0.200), postoperative alignment (p = 0.330), midflexion point (p = 0.509), maximal flexion (p = 0.080), and extension (p = 0.717) did not relate to ABL. There was no significant difference in the rate of severe ABL between implants. Multilevel surgery conferred an increased risk of any and severe ABL (p = 0.013 for both). The upper endplate, defined as superior to the CDA, was more commonly involved (p = 0.008), but there was no significant difference whether the endplate was between or not between implants (p = 0.226). The development of ABL did not affect the long-term range of movement (ROM) of the CDA, but did increase the overall risk of autofusion. ABL was not associated with pain or functional deficits. No patients required a reoperation or revision of their implant during the course of this study, and there were no cases of progressive ABL beyond the first year. CONCLUSIONS ABL is common in all implant types assessed, although most is mild. Age, sex, postoperative alignment, ROM, and midflexion point do not relate to this phenomenon. However, the greater the number of levels operated, the higher the risk of developing ABL. The development of ABL has no long-term effect on the mechanical functioning of the disc or necessity for revision surgery, although it may increase the rate of autofusion.

Anterior Bone Loss in Cervical Disc Arthroplasty

Study Design Retrospective, longitudinal observational study. Purpose To describe the natural history of anterior bone loss (ABL) in cervical disc arthroplasty (CDA) and introduce a classification system for its assessment. Overview of Literature ABL has recently been recognized as a complication of CDA, but its cause and clinical effects remain unknown. Methods Patients with non-keeled CDA (146) were retrospectively reviewed. X-rays were examined at 6 weeks, 3, 6, 9, 12, 18, and 24 months, and annually thereafter for a minimum of 5 years. These were compared with the initial postoperative X-rays to determine the ABL. Visual Analog Scale pain scores were recorded at 3 months and 5 years. Neck Disability Index was recorded at postoperative 5 years. The natural history was determined and a classification system was introduced. Results Complete radiological assessment was available for 114 patients with 156 cervical disc replacements (CDRs) and 309 endplates (average age, 45.3 years; minimum, 28 years; maximum, 65 years; 57% females). ABL occurred in 57.1% of CDRs (45.5% mild, 8.3% moderate, and 3.2% severe) and commenced within 3 months of the operation and followed a benign course, with improvement in the bone stock after initial bone resorption. There was no relationship between ABL degree and pain or functional outcome, and no implants were revised. Conclusions ABL is common (57.1%). It occurs at an early stage (within 3 months) and typically follows a non-progressive natural history with stable radiographic features after the first year. Most ABL cases are mild, but severe ABL occurs in approximately 3% of CDAs. ABL does not affect the patients’ clinical outcome or the requirement for revision surgery. Surgeons should thus treat patients undergoing CDA considering ABL.

Identifying the superior and inferior gluteal arteries during a sacrectomy via a posterior approach

Background Identifying the gluteal vessels during a posterior sacrectomy can be challenging. This study defines anatomical landmarks that can be used to approximate the location of the superior and inferior gluteal arteries (SGA and IGA) during a posterior sacrectomy. Methods Cadaveric dissection of six fresh adult pelvises to determine the location of the SGA and IGA in relation to the posterior-inferior aspect of the sacroiliac joint (PISIJ), lateral sacral margin and sacrococcygeal joint (SCJ). Results The anatomical landmarks are easily palpable. The position of the SGA to the PISIJ is relatively constant as it is tethered by a posterior branch of the artery, which runs inferior to the PISIJ. The IGA position is also relatively constant below the mid-point of the PISIJ and SCJ. The vessels are separated from the sacrospinous/sacrotuberous ligament complex (SSTL) in the perisacral region and as a result an anatomical plane exists anterior to the SSTL, which affords protection of the vessels during SSTL transection. The distance between the vessels and the SSTL increases the more medial the dissection. Conclusions The described anatomical landmarks can be used to predict the location of the SGA and IGA during posterior sacrectomy. An anatomical plane exists anterior to the SSTL, which provides protection to the vessels during SSTL transection. Furthermore, the distance between the vessels and the SSTL increases the more medial the dissection, thus, resection of the SSTL as close to the lateral sacral margin as the pathology permits, is advocated.

Spinal nerve root transection caused by spinal instability after osteoporotic vertebral collapse: A case report.

Osteoporotic vertebral compression fractures occur frequently in the elderly, and in most cases, they can be managed well with conservative treatment [1,2]. However, in some cases, the fracture site fails to unite, resulting in vertebral collapse and instability. Surgical treatment is required when delayed neurological deficits occur, which are caused by spinal cord compression resulting from retropulsed bone fragments in the spinal canal, progression of kyphosis, and spinal instability at the fracture site [3,4]. However, there is no consensus on surgical indication when the patients complained of only pain in the back or lower extremities [5]. In the present study, we report our experience of surgery in a patient with osteoporotic vertebral collapse and instability. The patient presented with no motor deficits, and had a long history of conservative treatments. However, the surgery revealed L2 spinal nerve root transection caused by spinal instability. The present case shows the importance of surgical indication and timing in patients with pain as the only symptom of osteoporotic vertebral compression fracture. Informed consent for the publication of this case was obtained from the patient.

Cerebral ischaemia following anterior upper thoracic spinal surgery utilizing a partial manubrial resection

PurposeFirstly, to describe two cases of cerebral ischaemia complicating anterior upper thoracic spinal surgery and define the likely cause of this complication. Secondly, to describe preventative measures and the effect these have had in reducing this complication within our institution.MethodsFirstly, a review of two cases of cerebral ischaemia complicating anterior upper thoracic spinal surgery utilizing a partial manubrial resection. Secondly, cadaveric dissections of the carotid arteries to determine the effect of neck positioning and aortic arch retraction during a simulated procedure. Thirdly, a retrospective review of 65 consecutive cases undergoing this procedure and assessment of the rate of this complication before and after the adoption of preventative measures.ResultsTwo cases of carotid artery territory cerebral ischaemia, without radiographic evidence of carotid or cardiac pathology were identified in 50 consecutive cases prior to the implementation of preventative measures. These patients revealed fluctuating hemodynamic instability after placement of the inferior retractor. Cadaveric dissection reveals significant carotid artery traction particularly with neck extension. Since the adoption of preventative measures, no cases of cerebral ischaemia have been encountered.ConclusionsCerebral ischaemia is a potential complication of anterior upper thoracic spinal surgery requiring retraction of the aortic arch. This most likely occurs from carotid stenosis due to aortic retraction and therefore, may be reduced by positioning the patient with neck flexion. Continuous non-invasive monitoring of cerebral saturation, as well as actively monitoring for hemodynamic instability and reduced carotid pulsation after retractor placement, allows for early detection of this complication. If detected, perfusion can be easily restored by reducing the retraction of aortic arch.

Paraarticular osteochondroma of a lumbar facet joint presenting with radiculopathy.

Conventional osteochondroma is a common benign osteocartilaginous tumor that typically originates near the end of a long bone with an osseous stalk and cartilaginous cap. This type of tumor grows away from the joint and is treated via marginal resection [1,2]. In contrast, “paraarticular osteochondroma” is a rare osteocartilaginous tumor that arises in the soft tissue that is adjacent to a joint, which does not exhibit bone continuity [1,3]. It is reported as a pathological entity which is distinguished from conventional osteochondroma. Several reports describe “paraarticular osteochondroma” existing adjacent to the joints of the extremities, particularly the knee joints [1,3]. However, spinal involvement of this tumor is very rare. To the best of our knowledge, Okamoto et al. have reported the only case of “paraarticular osteochondroma” that existed in the cervical spinal canal, which was adjacent to the facet joint and caused spinal cord compression [4]. In the present report, we describe a case of “paraarticular osteochondroma” in the lumbar spinal canal, which exhibited characteristics that were quite similar to those that were reported by Okamoto et al. The patients were informed