Bronek M. Boszczyk

Biomechanical evaluation of vertebroplasty and kyphoplasty with polymethyl methacrylate or calcium phosphate cement under cyclic loading.

Study Design. We developed a new method to simulating in vivo dynamic loading as closely as possible, which allows comparison of kyphoplasty and vertebroplasty, as well as augmentation materials. Objective. Special interest was given to calcium phosphate cement, which might fail due to its brittleness. Summary of Background Data. Vertebroplasty and kyphoplasty are, with limitations, 2 promising alternative techniques to augment osteoporotic vertebrae with polymethyl methacrylate or calcium phosphate cements. However, little is known about the fatigue characteristics of the treated vertebrae under cyclic loading. Methods. Twenty-four intact, osteoporotic bi-segmental human specimens were divided into 4 groups: (1) vertebroplasty with polymethyl methacrylate, (2) kyphoplasty with polymethyl methacrylate, (3) kyphoplasty with calcium phosphate cement, and (4) untreated control group. After augmentation of the middle vertebrae, all specimens underwent 100,000 cycles of eccentric loading during which the specimen revolved around its longitudinal axis. Pre-loading and post-loading radiographs, and subsidence measurements at different sites of the vertebrae were taken. The overall height was additionally determined every 20,000 cycles in the material testing machine. Finally, the specimens were cryosectioned to examine the cements. Results. Loss of height progressed with strong individual differences in all groups, with an increasing number of load cycles up to median values of 2.8 mm for both augmented groups and 4.2 mm for the nonaugmented group. At the center of the upper endplate, subsidence in kyphoplasty was greater than in vertebroplasty, with little differences with respect to the kind of cement. The cryosections did not show any signs of fatigue in the polymethyl methacrylate, but small cracks were in the calcium phosphate. Conclusions. Vertebroplasty and kyphoplasty seem to be equivalent methods in strengthening osteoporotic vertebrae. However, these results cannot be transferred to the treatment of fractures with these methods. A “physiologic” loading situation was achieved by complex motion, including all combinations of flexion/extension with lateral bending during eccentric cyclic loading.

Comparative and functional anatomy of the mammalian lumbar spine.

As an essential organ of both weight bearing and locomotion, the spine is subject to the conflict of providing maximal stability while maintaining crucial mobility, in addition to maintaining the integrity of the neural structures. Comparative morphological adaptation of the lumbar spine of mammals, especially in respect to locomotion, has however received only limited scientific attention. Specialised features of the human lumbar spine, have therefore not been adequately highlighted through comparative anatomy. Mathematical averages were determined of 14 measurements taken on each lumbar vertebrae of ten mammalian species (human, chimpanzee, orang‐utan, kangaroo, dolphin, seal, Przewalskis horse, cheetah, lama, ibex). The revealed traits are analysed with respect to the differing spinal loading patterns. All examined mammalian lumbar spines suggest an exact accommodation to specific biomechanical demands. The lumbar spine has reacted to flexion in a predominant plane with narrowing of the vertebral bodies in quadrupeds. Torsion of the lumbar spine is withstood by an increase in the transverse distance between the inferior articular processes in the upper lumbar spine in primates, but lower lumbar spine in humans, quadrupeds and the seal. Sagittal zygapophyseal joint areas resist torsion in the seal and humans. Ventral shear is resisted by frontal zygapophyseal joint areas in humans and primates, and dorsal shear by encompassing joints in the ibex. The human fifth lumbar vertebra is remarkable in possessing the largest endplate surface area and the widest distance between the inferior articular processes, as an indicator of the high degree of axial load and torsion in bipedalism. Anat Rec 264:157–168, 2001.

Kyphoplastik im konventionellen und halboffenen Verfahren

ZusammenfassungDie Kyphoplastie ist ein neuer Therapieansatz, der für die minimal-invasive Augmentation osteoporotischer Wirbelfrakturen entwickelt wurde. Im Gegensatz zur Vertebroplastie erlaubt die Technik der Kyphoplastie eine vom Frakturalter abhängige Reposition durch druckkontrollierte Füllung eines transpedikulär in die Spongiosa des frakturierten Wirbelkörpers eingebrachten Ballons. Zur Retention wird die nach Ballonentfernung verbleibende Kaverne mit hochviskösem Augmentationsmaterial aufgefüllt. Die dabei erreichte niedrige Rate an ernsten Komplikationen, wie beispielsweise ein intraspinaler Materialaustritt, rechtfertigt den Versuch einer Indikationserweiterung auf spezielle traumatische Frakturtypen und neoplastische Wirbeleinbrüche durch osteolytische Metastasen. Neben den Indikationen für die konventionellen perkutanen Zugänge, erlaubt der „halboffene“ mikrochirurgische Zugang die Anwendung der Kyphoplastietechnik auch bei komplexeren Wirbelkörperfrakturen mit Komprimierung der neuralen Strukturen.Die operativen Techniken der Kyphoplastie führen über eine schnell einsetzende Schmerzreduktion zur raschmöglichen Mobilisierung der Patienten durch die sofortige Stabilisierung des betroffenen Wirbelkörpers. Dennoch ist weiterhin ein interdisziplinäres Therapiekonzept gefordert, um neben der operativen Intervention die individuelle medikamentöse und rehabilitative Behandlung der Grunderkrankung zu optimieren.AbstractKyphoplasty is a young method which was developed for the minimally invasive augmentation of osteoporotic vertebral fractures. In contrast to vertebroplasty, the kyphoplasty technique allows an age-dependent fracture reduction through the inflation of a special balloon in the fractured cancellous bone of the vertebral body. The cancellous bone of the fracture zone is compressed by the balloon, so that a cavity remains in the vertebral body after removing the balloon, which is filled with highly viscous augmentation material. The reduced risk of serious complications, for example epidural leakage of augmentation material, justifies progressively expanding the indications for this technique to traumatic fractures with involvement of the posterior vertebral wall and neoplastic vertebral collapse due to osteolytic metastasis. Besides the indications for the conventional percutaneous approaches, the microsurgical interlaminary approach allows the use of kyphoplasty in more complex fractures involving compression of the neural structures.Kyphoplasty induces swift pain relief and allows rapid mobilisation of patients due to the immediate stabilisation of the affected vertebral bodies. Apart from the operative intervention, the medical treatment of the primary disease and the rehabilitation of the individual patient should be optimised through an interdisciplinary approach.

An immunohistochemical study of the dorsal capsule of the lumbar and thoracic facet joints.

Study Design. The molecular composition of the extracellular matrix in the dorsal capsules of lumbar and thoracic facet joints was analyzed immunohisto-chemically. Objectives. To determine whether the immunohistochemical profile of the lumbar joint capsule suggests a role of the capsule in limiting axial rotation of the lumbar motion segment. Summary of Background Data. During axial rotation of the lumbar vertebrae, the axis of rotation shifts toward the facet joints in the direction of rotation. Thus, the capsule of the opposing joint should become tensed and wrap around the inferior articular process. Previous studies suggest that wrap-around ligaments are fibrocartilaginous. However, thoracic joint capsules are largely shielded from such loading and should be purely fibrous. Methods. Dorsal capsules were removed from lumbar and thoracic facet joints of six adult cadavers. Specimens were immunolabeled with monoclonal antibodies for collagens, chondroitin, dermatan and keratan sulfates, versican, tenascin, aggrecan and link protein. Antibody binding was detected using the Vectastain ABC ‘Elite’ peroxidase kit (Vector Laboratories, Inc., Burlingame, CA). Results. Both lumbar and thoracic joint capsules immunolabelled for most glycosaminoglycans and for Type I, III and VI collagens. However, labeling for Type II collagen, chondroitin-6-sulfate, aggrecan, and link protein was restricted to lumbar capsules. Such labeling was constantly seen at entheses and occasionally in the midsubstance. Conclusions. The molecular composition of the lumbar joint capsule suggests that it acts as a fibrocartilaginous, ‘wrap-around’ ligament that withstands compression in addition to tension during torsional movements of the lumbar spine. It wraps around the inferior articular process as rotation occurs and limits further movement.

Minimal-invasive percutaneous reduction and transsacral screw fixation for U-shaped fractures.

Study Design: Technical note and case series. Objective: To introduce an innovative minimal-invasive surgical procedure reducing surgery time and blood loss in management of U-shaped sacrum fractures. Summary of Background: Despite their seldom appearance, U-shaped fractures can cause severe neurological deficits and surgical management difficulties. According to the nature of the injury normally occurring in multi-injured patients after a fall from height, a jump, or road traffic accident, U-shaped fractures create a spinopelvic dissociation and hence are highly unstable. In the past, time-consuming open procedures like large posterior constructs or shortening osteotomies with or without decompression were the method of choice, sacrificing spinal mobility. Insufficient restoration of sacrococcygeal angle and pelvic incidence with conventional techniques may have adverse long-term effects in these patients. Methods: In a consecutive series of 3 patients, percutaneous reduction of the fracture with Schanz pins inserted in either the pedicles of L5 or the S1 body and the posterior superior iliac crest was achieved. The Schanz pins act as lever, allowing a good manipulation of the fracture. The reduction is secured by a temporary external fixator to permit optimal restoration of pelvic incidence and sacral kyphosis. Insertion of 2 transsacral screws allow fixation of the restored spinopelvic alignment. Results: Anatomic alignment of the sacrum was possible in each case. Surgery time ranged from 90 to 155 minutes and the blood loss was <50 mL in all 3 cases. Two patients had very good results in the long term regarding maintenance of pelvic incidence and sacrococcygeal angle. One patient with previous cauda equina decompression had loss of correction after 6 months. Conclusions: Percutaneous reduction and transsacral screw fixation offers a less invasive method for treating U-shaped fractures. This can be advantageous in treatment of patients with multiple injuries.

Interdisciplinary approach to balloon kyphoplasty in the treatment of osteoporotic vertebral compression fractures

Osteoporotic vertebral compression fractures (VCFs) are associated with a series of clinical consequences leading to increased morbidity and even mortality. Early diagnosis and therapeutic intervention is desirable in order to remobilise patients and prevent further bone loss. Not all fractures are, however, sufficiently treatable by conservative measures. Here, vertebroplasty and kyphoplasty may provide immediate pain relief by minimally invasive fracture stabilisation. In cases of acute fractures, kyphoplasty has the potential to reduce kyphosis and restore the normal sagittal alignment of the spine. The complex nature of systemic osteoporosis, coupled with the intricate biomechanics of vertebral fractures, leads to a clinical setting which is ideally treated interdisciplinarily by the rheumatologist and spine surgeon.

Predictors of outcome in head injury: proposal of a new scaling system.

BACKGROUND In a statistical outcome analysis covering 10 years, 554 patients with isolated head trauma were analyzed. The aim of this study was to combine clinical and computed tomographic characteristics in a prognostic scoring system determining outcome after head injury. METHODS After collection of data, mortality and morbidity were determined for each clinical and radiologic parameter; a different grading from 1 to 8 points was then attached to each parameter. The total score for each patient was calculated by adding the individual points from the different parameters. RESULTS Significant differences in outcome (p < 0.01, Mann-Whitney U test) were registered in steps from 0 to 10 points (group I), 11 to 20 points (group II), and > 20 points (group III). Group I had a mortality of 8.3%, and patients in groups II and III died in 51.2% and 80.8%, respectively. Patients in group I had a Glasgow Outcome Scale (GOS) score of 4 and 5 in 19.4% and 56.7%, respectively, whereas group II reached a GOS score of 4 or 5 in only 9.9% and 1.7%, respectively. Patients in group III never reached a GOS score of 4 or 5. CONCLUSION The presented scaling system allows a predictive value in mortality and morbidity to be determined for each patient suffering from brain trauma.

Reduction in late postoperative pain after iliac crest bonegraft harvesting for cervical fusion: a controlled double-blinded study of 100 patients

SummaryBackground. A randomized prospective double-blinded study was conducted in 100 patients suffering from mono- or bisegmental cervical retrospondylosis or disc herniation.Method. In group I, 50 patients were treated by injection of 10 ml Ropivacaine 7,5% at the iliac crest bonegraft donorsite. Local anaesthetic (LA) was injected through the wound drainage after closure of the muscle fascia, the suction drainage was opened after closure of the skin. Group II was treated with 0,9% saline. Operator and patient were blinded to the injected substance. Daily controls of pain intensity were made with the 10 cm visual analog scale from 0 (no pain) to 10 (severe pain) for 5 days. All patients were questioned regarding pain character and movement provoking pain. Additional pain medication was standarized.Findings. Statistical analysis of mean pain intensity over the whole hospital stay showed a significant difference in pain intensity between the two groups (p = 0,017, Chi-Square test). The comparison between pain intensity with LA and without LA showed a gradual increase in statistical significance from day 1 to day 5 (day 1: p = 0,54, not significant; day 2: p = 0,026; day 3: p = 0,008; day 4: p = 0,004; day 5: p = 0,002).Interpretation. This data shows that intra-operative blockage of peripheral nociceptive structures results in decreased pain at later time points. We conclude that wound infiltration with 7,5% Ropivacaine after bonegraft removal at the iliac crest is effective in reducing postoperative pain.

Solid variant of aneurysmal bone cyst on the cervical spine of a child: case report, differential diagnosis and treatment rationale.

IntroductionDespite numerous descriptive publications, the nature, character, differential diagnosis and optimal treatment of aneurysmal bone cysts (ABCs), remain obscure. The authors report a case of the solid variant of aneurysmal bone cyst (S-ABC) occurring in the posterior components and body of C7 vertebra focusing on the differential diagnosis and surgical treatment rationale.Case reportRight shoulder and neck pain were the presenting symptoms of 9-year-old boy. Torticollis developed later on but no neurological deficit was found. Imaging revealed an osteolytic lesion with significant extraosseous extension. Although diagnosis favoured an ABC, imaging studies did not provide clear diagnostic criteria. CT guided biopsy performed preoperatively was also not directly diagnostic. Given that differential diagnoses included S-ABC but also giant cell tumor (GCT) of bone, decision was made to proceed with a staged, back and front, complete resection of the affected bony elements of C7. Preoperative spinal angiography showed supply to the tumor from the right ascending and deep cervical artery territories. Particle embolization was not performed due to the presence of ipsilateral supply to the anterior spinal artery at the C6 level and contralateral supply at the C7 level. Intraoperatively, histology taken from posterior elements, although again not clearly diagnostic, favoured S-ABC variant rather than GCT. Thus, initial plan was revised and anterior surgery was postponed as the extent of the dissection would have been dependent on the presumed diagnosis. The final histological report confirmed the diagnosis of an S-ABC. In view of this, it was decided to embolize the lesion to avoid a second stage anterior surgery. At embolization, repeat spinal angiography showed reduced tumor blush following the surgery. Distal branches of the deep cervical artery were occluded with platinum coils (avoiding the risks associated with the use of particles or liquid embolic agents). No further procedure was planned.ConclusionImaging and histological pattern of this specific type of ABC, differential diagnosis from GCT and the surgical protocol followed with the patient consist of an interesting case of revising the initial plan, according to the upcoming histological reports.

Spine surgery training and competence of European Neurosurgical Trainees

BackgroundLittle is known about the nature of spine surgery training received by European neurosurgical trainees during their residency and the level of competence they acquire in dealing with spinal disorders.MethodsA three-part questionnaire entailing 32 questions was devised and distributed to the neurosurgical trainees attending the EANS (European Association of Neurosurgical Societies) training courses of 2004.ResultsOf 126 questionnaires, 32% were returned. The majority of trainees responding to the questionnaire were in their final (6th) year of training or had completed their training (60.3% of total). Spinal surgery training in European residency programs has clear strengths in the traditional areas of microsurgical decompression for spinal stenosis and disc herniation (77-90% competence in senior trainees). Deficits are revealed in the management of spinal trauma (34-48% competence in senior trainees) and spinal conditions requiring the use of implants and anterior approaches, with the exception of anterior cervical stabilisation.ConclusionsEuropean neurosurgical trainees possess incomplete competence in dealing with spinal disorders. EANS trainees advocate the development of a postresidency spine subspecialty training program.