S. Aunoble

Pelvic parameters: origin and significance

IntroductionThe adoption by humans of an upright position resulted in broadening and verticalisation of the pelvis together with the appearance of characteristic spinal curves, has profoundly modified the structure of the muscles supporting the spine.MaterialIn order to characterise the sagittal balance of the pelvis, it is necessary to define parameters based on notable biomechanical forces involved in the transmission of constraints. The angle of incidence was constructed to enable reproducible analysis of the anatomical characteristics of the pelvis in the sagittal plane. The angle of incidence is the algebraic sum of two complementary angles: pelvic tilt (PT) and sacral slope (SS). Since the value of incidence is fixed for any given patient, the sum of pelvic tilt and sacral slope is a constant value: when one increases, the other necessarily decreases.ResultThe position of the lumbar spine, attached to the sacral plateau, is thus affected by the pelvic tilt and by the sacral slope. Consequently, the pelvic parameters affect the entire underlying sagittal spinal profile.ConclusionGlobal spinal balance involves harmonisation of lumbar lordosis and thoracic kyphosis taking into account the pelvic parameters.

Equilibrium of the human body and the gravity line: the basics.

IntroductionBipedalism is a distinguishing feature of the human race and is characterised by a narrow base of support and an ergonomically optimal position thanks to the appearance of lumbar and cervical curves.MaterialsThe pelvis, adapted to bipedalism, may be considered as the pelvic vertebra connecting the spine to the lower limbs. Laterally, the body’s line of gravity is situated very slightly behind the femoral heads laterally, and frontally it runs through the middle of the sacrum at a point equidistant from the two femoral heads.ResultsAny abnormal change through kyphosis regarding the spinal curves results in compensation, first in the pelvis through rotation and then in the lower limbs via knee flexion. This mechanism maintains the line of gravity within the base of support but is not ergonomic. To analyse sagittal balance, we must thus define the parameters concerned and the relationships between them.ConclusionThese parameters are as follows: for the pelvis: incidence angle, pelvis tilt, sacral slope; for the spine: point of inflexion, apex of lumbar lordosis, lumbar lordosis, spinal tilt at C7; for overall analysis: spino-sacral angle, which is an intrinsic parameter.

Global analysis of sagittal spinal alignment in major deformities: correlation between lack of lumbar lordosis and flexion of the knee.

IntroductionIt has become well recognised that sagittal balance of the spine is the result of an interaction between the spine and the pelvis. Knee flexion is considered to be the last compensatory mechanism in case of sagittal imbalance, but only few studies have insisted on the relationship between spino-pelvic parameters and lower extremity parameters. Correlation between the lack of lumbar lordosis and knee flexion has not yet been established.Materials and methodsA retrospective study was carried out on 28 patients with major spinal deformities. The EOS system was used to measure spinal and pelvic parameters and the knee flexion angle; the lack of lumbar lordosis was calculated after prediction of lumbar lordosis with two different formulas. Correlation analysis between the different measured parameters was performed.ResultsLumbar lordosis correlated with sacral slope (r = −0.71) and moderately with knee flexion angle (r = 0.42). Pelvic tilt correlated moderately with knee flexion angle (r = 0.55). Lack of lumbar lordosis correlated best with knee flexion angle (r = 0.72 and r = 0.63 using the two formulas, respectively).ConclusionKnee flexion as a compensatory mechanism to sagittal imbalance was well correlated to the lack of lordosis and, depending on the importance of the former parameter, the best procedure to correct sagittal imbalance could be chosen.

Vertebroplasty for osteoporotic spine fracture: prevention and treatment.

There is a relatively high prevalence of osteoporotic vertebral compression fractures (VCFs) in the elderly population, especially in women aged 50 or older. The result of these VCFs is increased morbidity and mortality in the short and long term. Medical treatment of these fractures includes bed rest, orthotics, analgesic medication and time. Percutaneous vertebroplasty (PVP) consists of percutaneous injection of biomaterial, such as methylmethacrylate, into the VCF to produce stability and pain relief. Biomechanical testing has shown that PVP can restore strength and stiffness of the vertebral body to the pre-fracture levels. Clinical results show immediate and maintained pain relief in 70–95% of the patients. Possible major complications include cement leakage into the spinal canal or into the venous system. Additionally, percutaneous vertebroplasty may alter the normal loading behavior of the adjacent vertebral body, and there is an increased risk of adjacent segment VCF. Kyphoplasty is a new technique, which introduces a balloon into the vertebral body transpedicularly to reduce the VCF while creating a cavity for the cement injection. This technique has the benefit of kyphosis reduction as well as less cement leakage. Research continues into the development of injectable biomaterials that are resorbable and allow for new bone formation. Vertebroplasty and kyphoplasty are safe and effective in the treatment of osteoporotic VCFs. They may allow for a faster return to function, and thus avoid the morbidity associated with medical treatment.

Evidence showing the relationship between sagittal balance and clinical outcomes in surgical treatment of degenerative spinal diseases: a literature review

The measure of radiographic pelvic and spinal parameters for sagittal balance analysis has gained importance in reconstructive surgery of the spine and particularly in degenerative spinal diseases (DSD). Fusion in the lumbar spine may result in loss of lumbar lordosis (LL), with possible compensatory mechanisms: decreased sacral slope (SS), increased pelvic tilt (PT) and decreased thoracic kyphosis (TK). An increase in PT after surgery is correlated with postoperative back pain. A decreased SS and/or abnormal sagittal vertical axis (SVA) after fusion have a higher risk of adjacent segment degeneration. High pelvic incidence (PI) increases the risk of sagittal imbalance after spine fusion and is a predictive factor for degenerative spondylolisthesis. Restoration of a normal PT after surgery is correlated with good clinical outcome. Therefore, there is a need for comparative prospective studies that include pre- and postoperative spinopelvic parameters and compare complication rate, degree of disability, pain and quality of life.

Minimally invasive endoscopic approach to the cervicothoracic junction for vertebral metastases: report of two cases

The anterior cervicothoracic junction is difficult to expose and many techniques have previously been described. Most of them require an extensile exposure, which can lead to significant morbidity. The aim of this study is to present a less invasive approach, allowing the same exposure on the spine as a larger one. The approach begins with the same incision as the Smith-Robinson technique: a blunt dissection of the posterior face of the manubrium is performed with the finger. An endoscope is inserted through 10-mm trocars, one above the manubrium and the second through the second rib space. The upper mediastinal space is exposed; the dissection is performed on the left side, between the esophagus and trachea medially, between the innominate vein and brachio-cephalic artery distally, and between the left common carotid and internal jugular vein laterally. The recurrent nerve must be protected. Two patients with spine metastases underwent this new approach. A strut graft was fixed anteriorly after decompression of the spinal cord. Levels T1–T3 can be well exposed through this approach, allowing complete vertebral body removal at level T1 or T2. After body removal, the posterior longitudinal ligament is well exposed, allowing complete release of the spinal cord. The use of the endoscope is the key to providing a good view of the spine without an extensile exposure. This new approach is technically feasible. The exposure is sufficient for vertebral body resection and reconstruction by strut graft. The procedure is less aggressive and painful than sternotomy.

Video-assisted Alif With Cage and Anterior Plate Fixation for L5-s1 Spondylolisthesis

Introduction Spondylolysis and spondylolisthesis grade 0, 1, and 2 are mainly asymptomatic but with aging process and different factors some back pain can occur and lead to chronic low back pain. The conservative treatment with physiotherapy and steroid injection is the gold standard but in some cases is not efficient enough and a surgical treatment is proposed. Objectives The goal of this study is to propose a new technique to treat grade 0, 1, and 2 spondylolisthesis with an anterior video-assisted fusion and stabilization. Methods Twenty patients with chronic low back pain since more than 2 years and resistant to conservative therapy were included in this protocol. Clinical signs and radicular pain were noted. They were evaluated preoperatively and postoperatively until the last follow up using Oswestry score and visual analog score (VAS) for leg and back pain. X-rays showed grade 0 (8 cases), 1 (10 cases), and 2 (2 cases) spondylolisthesis according to Meyerding classification with disc collapse (bulging disc). MRI showed in all cases a disc degeneration with at least black disc and/or endplates changes with Modic I or II. All patients were operated using an anterior video-assisted retroperitoneal approach, with discectomy and fusion using an anterior impacted cage filled with autologous cancellous bone from the iliac crest and an anterior fixation with a triangular plate (Pyramid, Medtronic, Memphis). The follow up at 3, 6, 12, and 24 months was done with clinical and radiologic evaluation. In case of problem a computed tomography scan was performed. Results There were 11 women and 9 men, with and average age of 39 years old and a BMI of 25.6. All spondylolistheses occurred at level L5. The average slippage was 19%. All L5S1 discs were black, 8 had a Modic I changes in the endplates and 2 had Modic II. The shape of L5 vertebra was abnormal (trapezoidal) in 7 cases. All anterior approaches were performed without vascular, urologic, or digestive complication. Blood loss was inferior to 100 mL. All patients had a soft brace for 8 weeks postoperatively. There was no retrograde ejaculation for the 9 men and no sexual dysfunction reported by the women. One patient had no pain relief and was reoperated for posterior pedicular screw fixation. It was obvious that there was a pseudarthrosis even after the posterior fixation and an anterior transperitoneal revision was performed with the removal of the interbody device and iliac crest bone graft packing alone. A propioni bacterium acnes germ was found responsible for the anterior nonunion. This revision surgery with antibiotics treatment was successful. One of the patients with grade 2 had an additional posterior screw fixation with a minimally invasive pedicle screw system (Sextant, Medtronic, Memphis). Nineteen patients had a good fusion at 2 years follow-up (95%), mean Oswestry score improved from 74% preoperative to 21% postoperative at the last follow-up. Visual analog score (VAS) for back pain improved from 6.5 to 2.7 and VAS for leg pain improved from 6.2 to 3.4. Satisfaction rate was 90%. All active patients except two, were back to work at an average of 5.5 months (6 wk to 1 y). The 2 patients still not working were the nonunion and a work compensation. Conclusions The results of this technique compare favorably with posterior stabilization and fusion (posterior lumbar interbody fusion and postero-lateral fusion) reported in the literature. Unlike posterior lumbar interbody fusion, however, it seems that the complication rate due to the approach is much lower, the fusion rate is similar. Grade 2 SPL is the limitation of the technique. The main advantage of the technique is to avoid posterior muscle damage and a quick recovery with no blood loss. Preservation of adjacent level disease can be assessed only after long-term follow-up.

Lumbar decompression and fusion in elderly osteoporotic patients: a prospective study using less rigid titanium rod fixation.

Type of study A 2 to 4-year clinical and radiologic prospective study was conducted for 39 patients over the age of 65 treated by lumbar arthrodesis. Objectives Evaluate the quality of lumbar arthrodesis results in elderly patients, in which the bone osteoporosis (poor quality of the spines anatomic components) and general factors (frequent comorbidity) are likely to make this surgery difficult if not dangerous and evaluate a dedicated instrumentation for osteoporotic bone. Materials and Methods Thirty-nine patients over 65 years of age (average 73 y) underwent arthrodesis surgery in 2001and 2002 and were followed for at least 2 years. The instrumentation used (Equation, Medtronic, Memphis, USA) was selected for its mechanical properties adapted for bone of poor mechanical quality. The clinical analysis was based on Oswestry, Visual Analog Scale, and Japanese Orthopaedic Association scores. Radiologic results were evaluated on standard anteroposterior, lateral, and 3/4 radiographs, and computed tomography scans if necessary. Results All the patients were followed for 2 to 4 years. Clinical analysis confirmed a very satisfactory progression of the clinical parameters such as lumbar and radicular pain, and the results were maintained between the first and second years and at last follow-up. No serious general complication or need for reoperation was seen in this series. On x-rays, 35 grafts appear to have fused. The anchors did not come out nor did the instrumentation come apart. On the other hand, 2-year radiographs revealed that 2 screws and 2 rods had failed, but this did not affect correction in the 4 completely asymptomatic patients. These 4 cases are considered stable at last follow-up. Conclusions Arthrodesis for elderly patients will undoubtedly increase in the coming years. The conditions for this surgery are different than those for younger patients and it is desirable to try to provide reliable surgical techniques and solutions regarding options for instrumentation and overall perioperative care for these fragile patients. Dedicated instrumentation for osteoporotic bone seems to allow good clinical outcomes.

Dislocations with intervertebral disc prosthesis: two case reports

To date, only three cases of artificial disc prosthesis dislocation have been reported in the literature. We present in detail two additional cases of prosthesis dislocation and discuss the surgical interventions undertaken that resulted in a good clinical outcome in both patients.

Bone morphogenetic protein use in spine surgery—complications and outcomes: a systematic review

PurposeBecause of significant complications related to the use of autologous bone grafts in spinal fusion surgery, bone substitutes and growth factors such as bone morphogenetic protein (BMP) have been developed. One of them, recombinant human (rh) BMP-2, has been approved by the Food and Drug Administration (FDA) for use under precise conditions. However, rhBMP-2-related side effects have been reported, used in FDA-approved procedures, but also in off-label use.A systematic review of clinical data was conducted to analyse the rhBMP-2-related adverse events (AEs), in order to assess their prevalence and the associated surgery practices.MethodsMedline search with keywords “bone morphogenetic protein 2”, “lumbar spine”, “anterolateral interbody fusion” (ALIF) and the filter “clinical trial”. FDA published reports were also included. Study assessment was made by authors (experienced spine surgeons), based on quality of study designs and level of evidence.ResultsExtensive review of randomised controlled trials (RCTs) and controlled series published up to the present point, reveal no evidence of a significant increase of AEs related to rhBMP-2 use during ALIF surgeries, provided that it is used following FDA guidelines. Two additional RCTs performed with rhBMP-2 in combination with allogenic bone dowels reported increased bone remodelling in BMP-treated patients. This AE was transient and had no consequence on the clinical outcome of the patients. No other BMP-related AEs were reported in these studies.ConclusionsThis literature review confirms that the use of rhBMP-2 following FDA-approved recommendations (i.e. one-level ALIF surgery with an LT-cage) is safe. The rate of complications is low and the AEs had been identified by the FDA during the pre-marketing clinical trials. The clinical efficiency of rhBMP-2 is equal or superior to that of allogenic or autologous bone graft in respect to fusion rate, low back pain disability, patient satisfaction and rate of re-operations. For all other off-label use, the safety and effectiveness of rhBMP-2 have not been established, and further RCTs with high level of evidence are required.