A Universal Strategy for Synthesis of Agropyrenol Family. Total Synthesis of Agropyrenol, Sordarial, and Heterocornol A and B

A divergent strategy for natural polyketides synthesis has been designed. This synthetic route allowed chemical alterations leading to all stereoisomers of the natural agropyrenol 1, sordarial 2, and heterocornol B 4. Key steps involve desymmetrization of divinylcarbinol using asymmetric Sharpless epoxidation and Heck coupling of an easily available aromatic partner and prepared chiral alkene. The versatility of the synthetic method was demonstrated on the preparation of heterocornol A 3 and sordariol 5. The absolute and relative configurations of prepared natural compounds 2·1/3C₆H₁₂ and 4 were confirmed and assigned by single-crystal X-ray analysis.

[Complications in Spine Surgery: Prospective 13-year follow-up of unplanned revision spinal surgeries]

PURPOSE OF THE STUDY Unplanned revision spinal surgeries constitute a complication in the treatment algorithm for the patient, surgeon and the entire treatment team. Any complication leading to an unplanned revision surgery is therefore undesirable. The percentage of complications referred to in publications on this topic focusing on unplanned revision surgeries only varies from 0.7% to 29.8%, with obvious diversity of causes and significant risk factors. The purpose of the submitted paper is to carry out a prospective evaluation of the most serious complications requiring unplanned revision spinal surgeries in the course of 13 years at a single department performing a broad range of spinal surgeries, namely 1300 procedures annually on average. MATERIAL AND METHODS In the period 2006 - 2018, a total of 16872 patients underwent a surgery at our department. During this period, in 556 patients an unplanned revision spinal surgery was performed. In agreement with literature, the patients were categorised by cause for revision: 1/ impaired wound suprafascial (superficial) healing - superficial infection, 2/ impaired wound subfascial (deep) healing - deep infection, 3/ surgical wound hematoma, 4/ deterioration or occurrence of new neurological symptoms, 5/ cerebrospinal fluid leak (liquorrhoea) and 6/ others. The patients operated on for inflammatory diseases of the spine with subsequent infectious complications, primarily treated at another department, and the patients with open spinal injury were excluded from the study. According to these criteria, a cohort of 521 patients was followed up, namely 236 (45.3%) women and 285 (54.7%) men, aged 1 year to 86 years, with the mean age of 55.0 years (median 60 years). Demographic effects, tobacco smoking and comorbidities were followed up in the cohort, together with the effects of surgery, diagnosis, surgical approach and physician. All parameters were statistically evaluated at a p-value below 0.05, including comparison with the control group. RESULTS Of the total number of 16872 operated patients, a group of 521 (3.09%) patients undergoing a revision surgery for complications was analysed in detail. Impaired wound healing - infection (SSI) was found in 199 (1.18%) patients, of whom superficial infection in 124 cases (0.73%) and deep infection in 75 cases (0.44%). Hematoma in a surgical site was detected in 149 (0.88%) patients. In 63 (0.37%) cases, deterioration of the existing neurological finding or occurrence of a new neurological finding were observed, in 68 (0.40%) cases cerebrospinal fluid leak was reported and in 40 (0.24%) cases other complications were identified. As concerns the surgical assistant, the percentage of complications in a board-certified physician is 2.77 (1.14 - 3.29%), in a medical resident it increases to 3.60 (0.00 - 9.38%) (p<0.05). The prevalence of smokers in the group with complications (N=521) was 34.7%. The control group (N=3650) included 30.1% of smokers (p<0.05). The mean age of patients in the group with complications (N=521) was higher, i.e. 55.0 years, with the median age of 60.0 years, than in the primary cohort (N=16872) with the mean age of 49.8 years and the median age of 52.0 years (p<0.05). The mean BMI in the group with complications was (N=521) 27.3, the median BMI was 26.9. In the control group (N=16872), the mean BMI was 27.11, the median BMI was 26.8. In this case the significance (p>0.05) was not confirmed. The complications prevailed strongly in posterior surgical approach, namely in 483 patients (92.7%). As concerns the surgically treated segment, lumber spine dominates with 320 (61.4%) cases. Corticosteroid therapy was used twice as often in women, namely in 13.1% vs. 6.3%. The group of patients with complications (N=521) showed a much higher average length of hospital stay of 12.8 days compared to the average of 4.6 days (N=16872). DISCUSSION In our cohort, the complication rate was 3.09%, of which infections constituted 1.18%, which is in agreement with similarly focused papers. As regards the patient-related factors, in our study the results reported by literature were confirmed with respect to the age, smoking and comorbidities. Moreover, the posterior surgical procedure, lumber spine surgery and presence of a medical resident are essential (p<0.05). No major age difference was observed between women and men (p>0.05). Obesity is one of the key risk factors, especially in infectious complications. In our cohort, a higher BMI did not increase the risk of complications in general (p>0.05). CONCLUSIONS In correlation with current literature, our cohort confirmed a significantly higher risk of complications leading to revision spinal surgery associated with age, smoking, posterior surgical procedure in thoracic or lumber spine, and presence of a medical resident as a surgical assistant. The average length of hospital stay was demonstrably longer in complicated patients, it almost tripled compared to the whole cohort. Contrary to literature, the effect of obesity on the occurrence of complications was not confirmed. Key words: spinal surgery, complications, infection, reoperation, risk factor, hematoma, cerebrospinal fluid leak, screw malposition, smoking, obesity.

Total En Bloc Spondylectomy of C3: A New Surgical Technique and Literature Review

PURPOSE OF THE STUDY

Radical resection of a vertebra is reserved only for specific tumors that invade the surrounding tissues and recur when not removed completely. The vertebra may be removed using a piecemeal technique or en bloc, using only two (in thoracolumbar spine) or more osteotomies (in cervical spine). We present our technique of en bloc resection of subaxial cervical vertebra for Ewing's sarcoma of C3, with preservation of all nerve roots and both vertebral arteries. To our knowledge, this surgical technique has not been reported in the English literature. The aim of this study is to describe the new technique of radical resection of subaxial cervical vertebra.

MATERIAL AND METHODS

A transoral biopsy of tumor tissue anterior to C2-C3 was performed in 8-year old boy, revealing a diagnosis of Ewing's sarcoma. The patient was started on neoadjuvant chemotherapy. After 6 chemotherapy cycles with the VIDE regimen, the soft-tissue component completely regressed, with the only a residual deposit in C3 vertebral body. Based on further multidisciplinary meeting, an en bloc spondylectomy of C3 was recommended, preferably with preservation of nerve roots and vertebral arteries. In August 2014, prior to the planned surgery, we performed another thorough examination of the patient using plain films, CT and MRI. Neither angiography nor embolization was performed. DESCRIPTION OF SURGICAL TECHNIQUE: The first stage of the operation consisted of resection of the posterior structures. We exposed the posterior elements of C2 to C4 by the mid-line incision. The C3 arch was without pathological changes. After partial resection of the C2 inferior and C4 superior articular processes we performed bilateral osteotomy in the region of the pedicle adjacent to the arch with a chisel and removed the whole of the C3 posterior arch. Subsequently we perforated the transverse foramina close to the pedicle, using fine Kerrison rongeurs. The lateral parts around vertebral arteries were left in situ. In the next step we used instrumentation with polyaxial screws to stabilize the C2-C4 section. After 19 days we performed the second stage surgery from an anterior approach with the removal of the anterior and lateral parts of the vertebra. We made a transverse incision anterior to the sternocleidomastoid between the internal carotid artery and the trachea on the right side at the level of C3 to expose the spine. We resected C2-C3 and C3-C4 intervertebral discs and then performed osteotomy with fine Kerrison rongeurs on both sides, again, close to the vertebral body. Subsequently, the vertebral body was released and extracted en bloc. In the next step, both vertebral arteries were mobilized and shifted medially and the lateral portions of the transverse processes were released and removed en bloc. The empty space was filled with solid allograft and the C2-C4 levels were bridged by the cervical plate in 2+1+2 configuration.

RESULTS

There were no complications during both surgeries. The follow-up CT examination 4 months after the operation revealed a clear bone fusion of C2-C4, both anteriorly between vertebral bodies and posteriorly between the arches. Clinically the patient has reached 8 month follow up and had no complaints, both he and his parents were satisfied. Physiotherapy is proceeding according to plan. The patient remains under supervision at our centre.

DISCUSSION

Total en bloc resection of a subaxial cervical vertebra with preservation of neural and vascular structures has been described in the English literature only once. In 2007 was published a total en bloc resection of C5 for chordoma, preserving the above mentioned structures. Authors removed the lamina en bloc after bilateral osteotomy. Transverse foramina were perforated by the Gigli saw and removed in piecemeal fashion, including the posterior tubercle. In the next step, they removed the vertebral body and the anterior tubercle from the anterior approach. However, their treatment differs from the technique described here and does not correspond fully to the principle of en bloc resection. Our surgical technique is based on a similar principle of performing several osteotomies without the use of high speed burr, while preserving all neural and vascular structures. The difference can be particularly seen in the approach to remove lateral parts of the transverse foramen, which are surrounding the vertebral arteries. We consider it as ideal to split the cervical vertebra by smooth cuts into four parts and remove them en bloc.

CONCLUSION

Total en bloc spondylectomy of a subaxial cervical vertebra with preservation of vertebral arteries and nerve roots is a radical surgery that should be used to treat only the most serious conditions. The risk of neurological deficit is outweighed by the benefits of oncological radicality. This new surgical technique has not yet been described and it is clear, that a larger cohort of patients is necessary to assess and potentially modify this technique so that it can be used more frequently in the future.

[Collet-Sicard Syndrome due to Occipital Condyle Fracture. Case Report]

The case of a 63-year-old man diagnosed with Collet-Sicard syndrome due to a fracture of the right occipital condyle is presented. The cause of injury was falling off a bicycle. Dysphonia and dysphagia were present from the moment of injury, with the gradual development of light atrophy of the tongue muscles and right trapezius muscle. The diagnosis was based on examination by CT and MRI methods, the act of swallowing and physical examination by an otorhinolaryngology specialist and a neurologist who confirmed the diagnosis of injury to cranial nerves IX, X and XI on the right side. The patient was treated conservatively with application of a Philadelphia collar. Dysphagia required PEG tube insertion. Skull fracture healing was evident on a CT scan at 3-month follow-up. However, dysphonia with dysphagia and muscle atrophy remained persistent.

[Unstable injuries to the upper cervical spine in children and adolescents]

PURPOSE OF THE STUDY

Injuries to the upper cervical spine in children are rare and account for 0.6 to 9.5% of all cervical spine injuries. We present a detailed analysis of the children and adolescents with unstable upper cervical spine injuries treated at our spinal centre.

MATERIAL

During 16 years of follow-up, unstable injury to the upper cervical spine was recorded in 23 children and adolescents. Two patients (8.7%) were treated conservatively and 21 (91.3%) underwent surgery. The patients were allocated by age to three groups: 0-9 year, 10-14 year and 15-18 year categories. Twenty patients were seen at the final clinical and radiographic follow-up. One patient died at 62 months after surgery and two patients unfit for transport were evaluated on the basis of mailed interviews. The interval between injury and final evaluation ranged from 6 to 137 months, with an average of 53.4 months.

METHODS

The patients treated conservatively first wore a Philadelphia collar, then a custom-made brace, and eventually a soft Schanze cervical collar to finish the healing process. Application of a halo vest was considered a surgical procedure and was used only in very small children. In unstable odontoid fractures, direct osteosynthesis with two cannulated titanium screws was performed from the anterior approach in older children while, in small children, transoral or submandibular retropharyngeal decompression to treat spinal stenosis caused by bone fragments was carried out and a halo vest was applied. Hangman's fractures were treated by anterior cervical discectomy, fusion with bone graft and anterior plate fixation. The other types of unstable fractures were managed from the posterior approach by occipitocervical fixation, atlantoaxial fixation or instrumented fusion extended caudally. The patients characteristics included gender, age, mechanism of injury, type of injury, neurological findings, type of therapy or surgery, complications and treatment outcome. Neurological status was evaluated using the Frankel classification.

RESULTS

The patient group comprised 14 boys (60.9%) and nine girls (39.1%), which gave a gender ratio of 3 : 2. The age of patients at injury ranged from 2 to 18 years, with an average of 11 years and 6 months. The most frequent injuries included rotational or vertical atlantoaxial dislocation in eight (34.8%) and odontoid fractures in seven (30.4%) patients; atlas fracture was recorded in three (13.0%) and hangman's fracture also in three (13.0%) patients; occipitocervical displacement was found in one (4.3%) and complex atlantoaxial fracture also in one patient (4.3%). At the time of injury, 17 patients (73.9%) had no neurological deficit (Frankel grade E), three had Frankel grade A (one paraplegic with a concomitant T5 spinal cord injury) and three had Frankel grade D neurological deficits. Of the six patients with neurological deficit, two showed improvement by one or two Frankel grades. The method of dorsal atlantoaxial fixation was used in eight patients (Magerl fixation in 2 and Harms method in 6). Direct osteosynthesis of an odontoid fracture was performed in four patients, halo fixation was applied in four, C2-C3 discectomy with tricortical bone grafting and plating was carried out in three, occipitocervical fixation was used in three patients, and direct atlas osteosynthesis, simple decompression and simple non-instrumented dorsal spondylodesis each was performed in one patient. Neither intra-operative complications nor post-operative complications related to the surgical technique were recorded. Osteoarthritis or bone non-union, as late post-operative complications, were found in two patients. All other patients showed bone healing by first intention in the desired extent. Superficial or deep wound infections were not recorded.

DISCUSSION

In the first age category, the number of boys and girls with injuries to the upper cervical spine was equal while, in the third one, the boys outnumbered the girls more than twice. Of the 23 patients, 91.3% were surgically treated; the anterior approach was used in approximately one third of the patients and the posterior approach in the rest of them. The high number of surgical interventions is due to the fact that the most serious paediatric spinal injuries are referred to our centre.

CONCLUSIONS

1. Injuries to the upper cervical spine are most frequently found in the youngest children and in adolescents who, however, frequently have injury also to the lower cervical spine. 2. Neurological deficit is relatively frequent but has a better prognosis than in adults. The youngest children with mild deficits have the best prognosis. 3. The mortality rate in young children with upper cervical spine injuries is evidently high, mostly due to associated head, chest and abdomen trauma 4. Therapy, particularly in small children, is strictly individual.

[ProDisc-C Total Disc Replacement. A four-year prospective monocentric study]

PURPOSE OF THE STUDY

To present the results of an independent prospective monocentric study of patients with ProDisc-C Total Disc Replacement (CTDR) followed up for 4 years, and to analyse the most frequent late complications, in particular heterotopic ossification.

MATERIAL

In the period from October 2004 to May 2006, a total of 61 patients underwent ProDisc-C CTDR involving one or two segments at the Department of Spinal Surgery, University Hospital in Motol. This study included 39 patients who were followed up for at least 4 years. With the exception of one patient operated on two segments, the patients were treated by ProDisc-C CTDR at one level.

METHODS

In the study, only the surgical procedure recommended by the implant manufacturer (Synthes, USA) was used and all operations were performed by a team with the same leading surgeon. Clinical assessment. The patients were examined before surgery, immediately after it and at 6 and 12 weeks and 6, 12, 24 and 48 months post-operatively. At each follow-up, responses to the questionnaire were obtained, and the patients' health status was evaluated on the basis of Neck Disability Index (NDI) and Visual Analogue Score (VAS) values for cervical spine and radicular pain, the use of analgesics and personal satisfaction Radiographic assessment. Pre- and post-operative radiographs were taken in antero-posterior and lateral projection, and flexion, extension and lateral bending films were obtained The height of the intervertebral disc space at the affected level was measured and range of motion in flexion and extension was evaluated together with the adjacent levels. In addition, subsidence, loosening, failure or displacement of the implant was assessed, as well as the presence of heterotopic ossification. The results were statistically analysed using Student's t-test.

RESULTS

The clinical results at 1, 2 and 4 years of follow-up were as follows: NDI values, 44.9 pre-operatively, 26.1, 25.8 and 25.1 post-operatively, improvement by 44.1% after 4 years; VAS for cervical spine pain, 5.8 pre-operatively, 3.0, 2.7 and 2.7 postoperatively, improvement after 4 years by 53.7%; VAS for radicular pain, 6.3 pre-operatively, 2.9, 2.9 and 2.7 postoperatively, improvement by 57.1% after 4 years. The radiographic findings showed the average intervertebral disc space height of 3.2 mm at the affected level before and 7.4 mm after surgery, with no significant change in the following period. The average range of disc motion at the affected level was 4.2 degrees before and 11.1 degrees after surgery, with 11.4 degrees at 4 years of follow-up. During that period, heterotopic ossification was recorded in 10 (25%) treated discs, with five of them (12.5%) classified as grade III or IV. Spontaneous fusion across the disc replacement level was found in three cases (7.5%). Two patients (5%) developed kyphosis at the affected disc level. The statistical analysis showed a significant difference between the pre-operative VAS values and those at 6 post-operative weeks for both cervical spine and radicular pain (t = 4.4 and t = 5.3, respectively; p < 0.05). No significant difference in VAS values was found between 6 weeks and 3 months after surgery for either condition (t = 1.69 and t = 0.3; p > 0.05). Changes in VAS values in the following period were minimal and non-significant. The differences in NDI values before surgery and at 6 weeks after it, and between 6 weeks and 3 months post-operatively were significant (t = 11, p < 0.05 and t = 3.8, p < 0.05, respectively). In the following period, changes in the values were minimal and non-significant.

DISCUSSION

Short-term studies on various types of cervical disc replacement have been optimistic and reported good clinical results and few complications. However, with longer follow-ups there has been an increasing incidence of heterotopic ossification as the most frequent late complication. Although the number of patients diagnosed with it is growing, heterotopic ossification influences the patient's clinical problems only little. What are its causes and how to prevent it are questions to be fully answered yet

CONCLUSIONS

Heterotopic ossification is the most frequent late complication of total disc replacement. Many factors may be responsible for its development and therefore its prevention is not clear. The correct indication and appropriate surgical technique are most often recommended, and are considered also by the authors to be most important. Restricted motion at the treated segment/s has no significant effect on the patient's clinical status.

[Kyphotic deformities of the cervical spin]

PURPOSE OF THE STUDY

The development of a cervical kyphotic deformity can be associated with a degenerative disease, trauma, tumour, developmental anomaly and also a surgical procedure. Post-operative kyphosis can develop after both the anterior and posterior surgical approaches. The deformity can also result from systemic diseases, such as ankylosing spondylitis or rheumatoid arthritis. The aim of the study was to make the clinical and radiographic evaluation of a group of patients with kyphotic deformity treated at our department.

MATERIAL

Between May 2005 and April 2010, a total of 102 patients underwent correction of cervical kyphosis at our department. (Center for Spinal Surgery). Of them, 90 patients with complete medical records and post-operative periods longer than 6 months were included in this study. There were 36 men and 54 women ranging in age from 13 to 90 years and with an average of 56.7 years. In six patients cervical kyphosis was caused by an inveterate injury, in 71 by degenerative disease, in six it developed in association with rheumatoid arthritis, and in seven patients it was due to previous surgery. Patients with acute trauma, tumour, infectious disease or congenital anomaly were not included.

METHODS

All patients were examined before surgery by radiography in antero-posterior and lateral projection, including flexion- extension bending films, and by CT scanning of ultrathin cross-sections with sagittal, frontal and recently also 3D reconstructions. Magnetic resonance imaging in three planes was also performed. On the basis of the results and clinical examination, the operative strategy was planned. Surgery was carried out from the anterior or the posterior approach, or the combined approach was used. Three-stage surgery was performed in one patient. The surgical outcome was assessed using the Nurick score and Neck Disability Index (NDI), the Visual Analogue Scale (VAS) was used to evaluate pain intensity or paraesthesia. Statistical analysis was done using the Chi-square test and paired t-test.

RESULTS

The average NDI value was 25.5 before surgery and 14.3 and 14.9 at one and two years after surgery, respectively. Compared with the pre-operative state, improvement or no changes were recorded in 89.7 % of the patients; transient deterioration occurred in 10.3 %. Improvements found were as follows: by one degree in 46.2 % of the patients, by two degrees in 18 %, by three degrees in 5.1 % and by five degrees in 2.6 % of the patients. The condition remained unchanged in 18 % of the patients. The average outcome was an improvement by one degree. The average pre-operative Nurick score was 0.7; an average post-operative value of 0.6 was recorded at both one and two years of follow-up. The average VAS value for neck and radicular pain was 5.7 pre-operatively, and 2.5 and 2.7 at one and two post-operative years, respectively. Out of 90 patients, complete bone union was achieved at 6 months after surgery in 88 patients (97.8 %). The average pre-operative value for the cervical curvature index (Ishihara) was -13.7; the average pre-operative cervical kyphosis was -14.4 degrees, ranging from -2.2 to -44.0 degrees. After surgery, the average Ishihara index was +15.3 and the average lordosis was +13.5 degrees, with a range of -16.0 to + 37.4 degrees.

DISCUSSION

A single/isolated anterior approach can be used for fixed deformities without ankylosing spondylitis. It allows for decompression of the anterior pathology and for correction of cervical kyphosis with use of instrumentation and structural graft. A combined ventral-dorsal approach is appropriate in fixed deformities or deformities involving the cervico-thoracic junction. The main principle of correction is to lengthen the cervical spinal column in the front and to shorten it at the back by anterior decompression with or without instrumentation and by subsequent posterior stabilisation. An isolated/single dorsal correction can be used in the case of successful correction by traction or specific head positioning on the table without anterior nerve compression. In severe fixed deformities such as Bekhterev's disease, the chin can be so close to the chest as to interfere with eating and breathing. The deformity most often develops at the cervico-thoracic junction and requires treatment by osteotomy.

CONCLUSIONS

The results of the study showed a marked improvement in the patients' quality of life after kyphosis correction, improved neurological status and an improved posture seen on radiograms of the cervical spine. The study also revealed a higher number of potential complications associated, in particular, with corrective osteotomy. The best results were achieved with the combined surgical approach; however, the choice of a surgical method was independent of the patient's clinical status.