Effect of postural alignment alteration with age on vertebral strength.

EOS biplane radiographs of 117 subjects between 20 and 83 years were analyzed to compute the upper body lever arm over the L1 vertebra and its impact on vertebral strength. Postural sagittal alignment alteration was observed with age and resulted in a greater lever arm causing vertebral strength to decrease. PURPOSE: The purpose of this study was to analyze the impact of postural alignment changes with age on vertebral strength using finite element analysis and barycentremetry. METHODS: A total of 117 subjects from 20 to 83 years were divided in three age groups: young (20 to 40 years, 62 subjects), intermediate (40 to 60 years, 26 subjects), and elderly (60 years and over, 29 subjects). EOS biplane radiographs were acquired, allowing 3D reconstruction of the spine and body envelope as well as spinal, pelvic, and sagittal alignment parameter measurements. A barycentremetry method allowed the estimation of the mass and center of mass (CoM) position of the upper body above L1, relatively to the center of the L1 vertebra (lever arm). To investigate the effect of this lever arm, vertebral strength of a generic finite element model (with constant geometry and mechanical properties for all subjects) was successively computed applying the personalized lever arm of each subject. RESULTS: A combination of an increase in thoracic kyphosis, cervical lordosis, and pelvic tilt with a loss of lumbar lordosis was observed between the young and the older groups. Sagittal alignment parameters indicated a more forward position as age increased. The lever arm of the CoM above L1 varied from an average of 1 mm backward for the young group, to averages of 10 and 24 mm forward, respectively, for the intermediate and elderly group. As a result, vertebral strength decreased from 2527 N for the young group to 1820 N for the elderly group. CONCLUSION: The global sagittal alignment modifications observed with age were consistent with the literature. Posture alteration with age reduced vertebral strength significantly in this simplified loading model. Postural alignment seems essential to be considered in the evaluation of osteoporotic patients.

A systematic approach to the hip-spine relationship and its applications to total hip arthroplasty.

There remains confusion in the literature with regard to the spinopelvic relationship, and its contribution to ideal acetabular component position. Critical assessment of the literature has been limited by use of conflicting terminology and definitions of new concepts that further confuse the topic. In 2017, the concept of a Hip-Spine Workgroup was created with the first meeting held at the American Academy of Orthopedic Surgeons Annual Meeting in 2018. The goal of this workgroup was to first help standardize terminology across the literature so that as a topic, multiple groups could produce literature that is immediately understandable and applicable. This consensus review from the Hip-Spine Workgroup aims to simplify the spinopelvic relationship, offer hip surgeons a concise summary of available literature, and select common terminology approved by both hip surgeons and spine surgeons for future research. Cite this article: Bone Joint J 2019;101-B:808-816.

The influence of spine-hip relations on total hip replacement: A systematic review.

Sagittal pelvic kinematics along with spino-pelvic angular parameters have recently been studied by numerous investigators for their effect on total hip replacement (THR) clinical outcomes, but many issue of spine-hip relations (SHR) are currently unexplored. Therefore, our review aims at clarifying the following questions: is there any evidence of a relationship between articular impingement/dislocation risk in primary THR and (1) certain sagittal pelvic kinematics patterns, (2) pelvic incidence, and (3) types of SHRs? A systematic review of the existing literature utilising PubMed and Google search engines was performed in January 2017. Only clinical or computational studies published in peer-reviewed journals over the last five years in either English or French were reviewed. We identified 769 reports, of which 12 met our eligibility criteria. A review of literature shows that sagittal pelvic kinematics, but not the pelvic incidence, influences the risk of prosthetic impingement/dislocation. We found no study having assessed the relationship between this risk and the types of SHRs. Sagittal pelvic kinematics is highly variable among individuals and certain kinematic patterns substantially influences the risk of prosthetic impingement/dislocation. Recommendations for cup positioning are therefore switching from a systematic to a patient-specific approach, with the standing cup orientation Lewinneck safe zone progressively giving way to a new parameter of interest: the functional orientation of the cup. Based on a recently published classification for SHRs, We propose a new concept of "kinematically aligned THR" for the purposes of THR planning. Further studies are needed to investigate the relevance of such a classification towards the assumptions and hypothesis we have made. Level of evidence,- Level IV, systematic review of level III and IV studies.

Spine-hip relations add understandings to the pathophysiology of femoro-acetabular impingement: A systematic review.

Relationship between hip pathoanatomy and symptomatic FAI has been reported to be weak. This is explained by the reciprocal interaction between proximal femur and acetabular anatomies, but potentially also by the individual spine-hip relations (SHR). The key-answer for a complete understanding of the pathophysiology of FAI might lie in the comprehension of the SHRs, which have not yet been fully addressed. Therefore we conducted a systematic review to answer the subsequent questions: Is there any evidence of a relationship between FAI and (1) sagittal pelvic kinematics, (2) pelvic incidence, and (3) types of SHRs? A systematic review of the existing literature utilizing PubMed and Google search engines was performed in December 2016. Only studies published in peer-reviewed journals over the last ten years in either English or French were reviewed. We identified 90 reports, of which 9 met our eligibility criteria. Review of literature shows Caucasian FAI patients have a pelvis with higher anterior tilt, lesser sagittal mobility, and lower pelvic incidence compared to healthy patients. We found no study having assessed the relationship between SHR and FAI. In order to help further investigations at answering questions 3 and 4, we have developed a classification for SHRs. The classification according spino-pelvic parameters allows identifying patient at risk regarding FAI occurrence. Higher anterior pelvic tilt in standing, sitting and squatting positions and lower pelvic incidence have been found to correlate with symptomatic FAI. Because defining the individual SHR might increase the understanding of the pathophysiology of hip impingement, we have developed a classification for SHRs. LEVEL OF EVIDENCE: Level IV, systematic review of Level III and IV studies.

Degenerative disease supra- and infra-jacent to fused lumbar and lumbo-sacral levels.

Disc degeneration is a normal age-related process. Accelerated degeneration of discs adjacent to fused spinal levels has been observed in numerous case-series studies. The available data document this phenomenon and provide information on its time to occurrence but show huge variations in incidence rates (5% to 70%). The supra-jacent disc is involved more often than the infra-jacent disc. Studies have clarified the underlying biomechanical rationale by showing increased loading of the adjacent discs. Risk factors have been the focus of the most recent studies. They include the number of fused levels, sagittal alignment, level of fusion, stiffness of the construct, and integrity of the posterior structures. Nevertheless, the many published studies have produced somewhat conflicting results. Various radiological criteria have been used to define degeneration of the adjacent disc. Although most patients have no symptoms, adverse effects on the spine and/or nerve roots may occur and, in some cases, require revision surgery. We draw attention to the many sources of bias in the published studies, of which we provide a critical and pragmatic discussion in the light of our personal experience.

Cervical spine surgery in ankylosing spondylitis: Review and current concept.

Ankylosing spondylitis of the cervical spine is associated with stiff kyphosis and increased risk of transversal unstable fracture. A spine surgeon may be involved mainly in the management of trauma cases, but in some situations, corrective surgery of a kyphotic cervical deformity is needed. Both types of cases carry specific aspects and rely on principles that differ from those associated with more common cervical surgery. This paper is a review of the literature regarding cervical surgery in cases of ankylosing spondylitis. It addresses practical technical questions.

Measuring extension of the lumbar-pelvic-femoral complex with the EOS® system.

INTRODUCTION: Sagittal balance of the coxofemoral joint in standing position and its extension capacity determine hip/spine adaptation, especially in relation to pelvic retroversion, which may be age-associated or follow either spinal arthrodesis or vertebral osteotomies. The concept of extension reserve is essential for assessing posterior hip impingement. The global visualization of the lumbar-pelvic-femoral complex obtained by EOS(®) imaging enables this sagittal analysis of both the subpelvic region and lumbar spine by combining the reference standing position and the possibility of dynamic tests. MATERIALS AND METHODS: We studied 46 patients and their 92 hips. The EOS(®) radiography was performed in neutral standing position and with one foot on a step, alternately the right and left feet. Pelvic incidence, sacral slope, pelvic version, and femoral version were measured twice by two operators. The global extension reserve (GER) was defined by the sum of the intrinsic extension reserve (allowed by the hips, IER) and the extrinsic extension reserve (allowed by the spine, EER). The IER for each hip corresponds to the difference in the sacrofemoral angle (SFA) for each of the two positions. The EER was measured by the difference in the sacral slope. A descriptive study was performed, together with studies of inter- and intra-observer reproducibility, right/left symmetry, and an analysis according to age, sex, and BMI. RESULTS: The mean femoral version in the reference position was 11.7° (SD 14.3°). The reproducibility of the SFA measurement was statistically verified. The IER (mean 8.8°), EER (mean -0.7°), and GER (mean 8.2°) all differed significantly between the two sides for each patient and were not associated with age, sex, or BMI. DISCUSSION: The femoral axis is not perpendicular to the ground in neutral position, contrary to the conventional view of this position. The measurements proposed for dynamic sagittal analysis of the hip are reproducible and make it possible to identify the IER within the GER of the spinal-pelvic-femoral complex. CONCLUSION: The assessment of the lumbar-pelvic-femoral complex by EOS imaging makes it possible to define the intrinsic and extrinsic extension reserves to describe the reciprocal adaptive capacities of the hips and spine. LEVEL OF EVIDENCE: IV.

Healthy vs. osteoarthritic hips: a comparison of hip, pelvis and femoral parameters and relationships using the EOS® system.

BACKGROUND: Osteoarthritis is a debilitating disease, for which the development path is unknown. Hip, pelvis and femoral morphological and positional parameters relate either to individual differences or to changes in the disease state, both of which should be taken into account when diagnosing and treating patients. These have not yet been comprehensively quantified. Previous imaging studies have been limited by a number of factors: supine rather than standing measurements; high radiation dose; a limited field of view; and 2D rather than 3D measurements. EOS®, a new radiographic imaging modality that acquires simultaneous frontal and lateral (sagittal) X-ray images of the full body, allows 3D reconstruction of the hip, pelvis and lower limb. The aim of the study was to explore similarities and differences between healthy and osteoarthritis groups. METHODS: Two groups of subjects, 30 healthy and 30 with hip osteoarthritis, were assessed and compared for pelvic, acetabular and femoral parameters in the standing position. FINDINGS: There were not only significant differences between groups but also considerable overlap amongst the individuals. Sacral slope, acetabular angle of Idelberger and Frank, femoral mechanical angle and femoral head eccentricity as well as right-left asymmetries in centre-edge acetabular angle and femoral head diameter were higher on average in osteoarthritic patients compared to healthy subjects, whereas acetabular abduction was lower in the osteoarthritic group (P<0.05). Correlations were identified between key parameters in both groups. INTERPRETATION: Differences between the groups suggest either degenerative changes over time or inherent differences between individuals that may contribute to the disease progression. These data provide a basis for longitudinal and post-surgery studies. Due to the considerable variability amongst individuals and the considerable overlap between groups, patients should be evaluated individually and at multiple joints when planning hip, knee and spine surgery.

Measuring femoral and rotational alignment: EOS system versus computed tomography.

INTRODUCTION: Computed tomography (CT) is currently the reference standard for measuring femoral and tibial rotational alignment. The EOS System is a new biplanar low-dose radiographic device that allows 3-dimensional lower-limb modelling with automated measurements of femoral and tibial rotational alignment (torsion). HYPOTHESIS: Femoral and tibial torsion measurements provided by the EOS System are equivalent to those obtained using CT. MATERIALS AND METHODS: In a retrospective analysis of 43 lower limbs in 30 patients, three senior radiologists measured femoral and tibial torsion on both CT and EOS images. Agreement between CT and EOS values was assessed by computing Pearson's correlation coefficient and interobserver reproducibility by computing the intraclass correlation coefficient (ICC). RESULTS: Femoral torsion was 13.4° by EOS vs. 13.7° by CT (P=0.5) and tibial torsion was 30.8° by EOS vs. 30.3° by CT (P=0.4). Strong associations were found between EOS and CT values for both femoral torsion (P=0.93) and tibial torsion (P=0.89). With EOS, the ICC was 0.93 for femoral torsion and 0.86 for tibial torsion; corresponding values with CT were 0.90 and 0.92. DISCUSSION: The EOS system is a valid alternative to CT for lower-limb torsion measurement. EOS imaging allows a comprehensive evaluation in all three planes while substantially decreasing patient radiation exposure. LEVEL OF EVIDENCE: Level III, case-control.

Trauma of the upper cervical spine: focus on vertical atlantoaxial dislocation.

PURPOSE: Traumatic ligament injuries of the craniovertebral junction, either isolated or associated with bone avulsion or fracture, often lead to death. These injuries are rare and underrated but are increasingly seen in emergency departments due to the improvement in initial on-scene management of accidents. Vertical atlantoaxial dislocation (AAD) is a specific lesion that was barely reported. Based on our experience, our goal was to systematically investigate the prevalence and prognosis of traumatic vertical AAD and discuss its management. METHODS: All cervical CT scans performed at our institution between 2006 and 2010 for cervical trauma in adults were retrospectively reviewed. Based on the measurement of lateral mass index (LMI), defined as the gap between C1 and C2 articular facets, we identified three cases of traumatic vertical AAD in 300 CT scans. Their medical records were investigated. RESULTS: The incidence of vertical AAD was 1% in the exposed population. One case was an isolated vertical AAD and two were associated with a type II odontoid fracture. We report the first case in the literature of unilateral vertical AAD. Two patients died rapidly; the survivor was treated with occipitocervical fixation. Specific maneuvers were used for immobilization and reduction. CONCLUSIONS: This study found a not insignificant incidence of vertical AAD and a high lethality rate. LMI appears to be a relevant radiological criterion for this diagnosis, for which traction is contraindicated. Associated neurological or vascular damage should be suspected and investigated. In our experience, spinal surgical fixation is required because of major instability.

Unstable odontoid fracture: surgical strategy in a 22-case series, and literature review.

Surgical treatment of unstable odontoid fracture (type II OBAR or HTAL) has progressed, with a range of techniques, the specificities of which need to be known so as to determine their respective roles in the therapeutic arsenal now available. A retrospective study of 22 patients operated on in our center for odontoid fracture between 2005 and 2010 examined the operative techniques employed and analyzed results in the light of the literature, so as to construct an updated decision tree. Two populations could be distinguished: elderly victims of simple fall (mean age, 82.1 years), and younger victims of high-energy trauma (mean age, 42.6 years). Surgical techniques comprised: anterior odontoid screwing (n=14), transarticular C1-C2 screwing on the posterior Magerl (n=3) or anterior Vaccaro approach (n=1), Harms' posterior C1-C2 arthrodesis (n=3), and occipitocervical arthrodesis (n=3). The overall complications rate for the series was 28%, including one case of non-union, at a mean 11 months' follow-up. The risk/benefit ratio may be hard to assess in elderly patients. However, anterior screwing restores odontoid anatomy and is the technique of choice in first intention for reducible fracture. In second intention, transarticular C1-C2arthrodesis may be performed on an anterior or posterior approach, depending on local vertebral artery anatomy. Harms' posterior C1-C2 arthrodesis allows fixation of non-reduced fractures. Occipitocervical arthrodesis is a last resort, as the associated morbidity rate is higher.

Lumbar-pelvic-femoral balance on sitting and standing lateral radiographs.

Trunk balance in upright stance expresses an individual postural strategy found on anatomic and functional parameters. The "pelvic vertebra" is an essential transitional region for the coherence of spinal parameters (notably, lumbar lordosis and thoracic kyphosis) and pelvic parameters (sacral slope, pelvic tilt and incidence). Deterioration of this postural harmony is often associated with spinal aging, maladjusted spinal arthrodeses, or mechanical abnormalities of the hip joints. Spinal surgeons are aware of the importance of detecting and analyzing sagittal imbalance, whether compensated or not. The influence of the hip joint, however, is underestimated and poorly objectified on conventional imaging, as are its interrelations with overall lower-limb posture. Currently, hip surgeons focus basically on the pelvis as bone reference in planning implantation, peroperative adjustment and failure analysis. The antero-posterior (AP) pelvic view is the gold standard, with lateral views being little used. Influenced by the classic anatomic attitude in favor of transverse slices in dorsal decubitus, CT is considered the reference method for "horizontal" assessment of the hip joint. The present study draws attention to a more global vision of the pelvic and subpelvic regions in the sagittal balance of the trunk, relying on the sitting as well as the standing posture, as both involve subtle mechanisms of adaptation governed by the pelvic incidence angle.

Salvage technique for postoperative infection and necrosis of the Achilles tendon.

Surgery of the Achilles tendon is associated with postoperative morbidity related to wound healing. Necrotic infection of the tendon is a rare but serious complication that may be associated with increasingly invasive surgical treatments using various free flap transfers proposed in the literature. Dealing with this complication, we prefer the technique of managed wound healing suggested by Dautry. The surgical procedure includes radical debridement of the infected tissue and necrotic Achilles tendon followed by managed wound healing with daily irrigation. Fifteen cases were treated between 1994 and 2003. Healing was achieved after 30 to 100 days. MRI results show scar tissue continuity suggesting a neotendon formation. Function was very satisfactory in 9/15 ankles. The salvage technique presented here for cases of infection and necrosis of the Achilles tendon is simple with low morbidity and results in effective wound and tendon healing with satisfactory functional and anatomical results.

Infections in the operated spine: update on risk management and therapeutic strategies.

UNLABELLED: Among the possible risks of spine surgery, surgical site infection (SSI) is far from negligible. Incidence is higher than in other locomotor system procedures, with more severe local and general impact. Certain broad guidelines can be formulated. The risk of SSI should be taken into account in the choice of treatment options discussed with the patient. Antibiotic prophylaxis, surgical prevention of iatrogenic infection and an SSI surveillance protocol should be implemented. SSI should be suspected in case of any abnormality in postoperative course, and biological and imaging (MRI or CT) measures should be taken. Local sampling for bacteriological identification is mandatory. Treatment strategy should ideally be discussed in a multidisciplinary coordination meeting, and adapted in the light of local bacterial ecology and resistance data. The information provided to the patient should be transparent and adapted to the patient's individual context. LEVEL OF EVIDENCE: Level V.

Pelvis and total hip arthroplasty acetabular component orientations in sitting and standing positions: measurements reproductibility with EOS imaging system versus conventional radiographies.

INTRODUCTION: The literature has recently underlined the interest of pelvic and acetabular component orientation measurements in the standing and sitting position. Radiographic follow-up of total hip arthroplasty (THA) is based on standard AP and lateral X-rays. The use of EOS™ 2D imaging system reduces patient's radiation exposure compared to conventional X-rays. However, using this system, the validity and reproducibility of angular measurements, have not been studied yet for the measurement of pelvic and acetabular parameters in patients with THA. HYPOTHESIS: The EOS™ 2D imaging system offers similar advantages to conventional X-rays in the measurement of pelvic and acetabular orientation parameters which are commonly used. PATIENTS AND METHOD: Five angular parameters characterizing pelvic tilt and acetabular cup orientation were determined using the same digital measurement Imagika™ software based on two series of standard X-rays and EOS™ 2D images acquired in both standing and sitting positions. Radiographs from 50 patients with unilateral THA were measured three times by two observers. Intra- and interobserver reproducibility using each method was independently studied then paired comparison was performed. RESULTS: The ICC and Spearman rank correlation coefficient demonstrated an excellent EOS/conventional X-ray correlation. According to the parameters, the mean difference between these two imaging modalities ranged from 0.30° to 3.43° (P<0.05). The intra- and interobserver variability ranged from ± 2.97° to ± 6.46° using the EOS™ imaging system and from ± 4.26° to ± 10.22° using conventional X-rays (P<0.05). DISCUSSION: The EOS™ 2D imaging system may replace conventional X-rays in the assessment and monitoring of pelvic and acetabular cup orientation in THA. LEVEL OF EVIDENCE: Level III. Prospective diagnostic study.

The EOS imaging system for understanding a patellofemoral disorder following THR.

An aspect of patellofemoral syndrome secondary to total hip replacement (THR) is mainly suggestive of a problem of femoral implant torsion. We here present the first reported case of patellofemoral syndrome secondary to THR relating to limb-length discrepancy, with no abnormality of femoral torsion. The pelvis adapted to the length inequality by axial rotation rather than frontal tilt, and this went undetected on standard X-ray and CT-scan. 3D imaging in upright posture on the EOS system enabled the situation to be clearly described and analyzed, and adapted surgical correction to be indicated.

Pneumorachis: a possible source of traumatic cord compression.

The presence of air within the spinal canal secondary to trauma is a rare condition. These rare cases are generally asymptomatic. We report our first case of closed thoracic trauma with pneumorachis associated with neurological disorders. According to a review of the literature and after personal record analysis, neurologic symptoms can be correlated to the occurrence of intraspinal air. Therefore pneumorachis appears as a possible cause of traumatic spinal cord compression. In this particular case, pneumorachis spontaneously resolved and early outcome was favourable.

Electrical conductivity measurement: a new technique to detect iatrogenic initial pedicle perforation.

Pedicle screw fixation has achieved significant popularity amongst spinal surgeons for both single and multi-level spinal fusion. Misplacement and pedicle cortical violation occurs in over 20% of screw placement and can result in potential complications such as dysthesia, paraparesis or paraplegia. There have been many advances in techniques available for navigating through the pedicle; however, these techniques are not without drawbacks. A new electrical conductivity-measuring device, previously evaluated on the porcine model to detect the pedicle violation, was evaluated amongst nine European Hospitals to be used in conjunction with the methods currently used in that centre. This new device is based on two original principles; the device is integrated in the drilling or screwing tool. The technology allows real-time detection of perforation through two independent parameters, impedance variation and evoked muscle contractions. Data was collected twofold. Initially, the surgeon was given the device and a comparison was made between the devices ability to detect a breech and the surgeon's ability to detect one using his traditional methods of pedicle preparation. In the second module of the study, the surgeon was limited to using the electrical conductivity detection device as their sole guide to detect pedicle breaches. A comparison was made between the detection ability of the device and the other detection possibilities. Post-operative fine cut CT scanning was used to detect the pedicle breaches. Overall, the 11 trial surgeons performed a total of 521 pedicle drillings on 97 patients. Initially there were 147 drillings with 23 breaches detected. The detection rate of these breaches were 22/23 for the device compared to 10/23 by the surgeon. Over both parts of the study 64 breaches (12.3%) were confirmed on post-operative CT imaging. The electrical conductivity detection device detected 63 of the 64 breaches (98.4%). There was one false negative and four false positives. This gives the device an overall sensitivity of 98% and specificity of 99% for detecting a pedicle breach. The negative predictive value was 99.8%, with a positive predictive value of 94%. No adverse event was noted with the use of the electrical conductivity device. Electrical conductivity monitoring may provide a simple, safe and sensitive method of detecting pedicle breech during routine perforation of the pedicle, in the course of pedicle screw placement.

Hip spine relationships: application to total hip arthroplasty.

Lumbo-sacral orientation in the sagittal plane is of utmost importance, as it plays a critical role in the function of the spine and the hip joints. Equilibrium of the trunk influences the tridimensional orientation of the acetabulum and the functional range of motion of the hips. Each patient is characterized by a "morphological" parameter named incidence angle; its sagittal balance is the consequence of a postural adaptation for other functional parameters (pelvic tilt, sacral slope, lumbar lordosis, acetabular sagittal tilt, functional anteversion). Understanding variations of the sacral slope on lateral pelvic X-rays is essential for planning total hip arthroplasty and identifying patients at risk of impingement, as lumbosacral posture influences functional anteversion of the acetabulum. Posterior pelvic version as in sitting position (sacral slope decrease) is linked to the increase of the functional acetabular anteversion. Anterior pelvic version as in standing position (sacral slope increase) is linked to the decrease of the functional acetabular anteversion.