A literature review of biomechanical studies on physiological and pathological sacroiliac joints: Articular surface structure, joint motion, dysfunction and treatments.

BACKGROUND: Sacroiliac joints are affected by mechanical environments; the joints are formed under mechanical stimulation, receive impact of walking between the upper and lower parts of the bodies and can be a cause of pain due to non-physiological loads. However, there are so far very few studies that reviewed biomechanics of physiological and pathological sacroiliac joints. This review article aims to describe the current sacroiliac joint biomechanics. METHODS: Previous original papers have been summarized based on three categories: articular surface structure, sacroiliac joint motion and sacroiliac joint dysfunction and treatments. FINDINGS: Although the articular surface morphologies vary greatly from individual to individual, many researchers have tried to classify the joints into several types. It has been suggested that the surface morphologies may not change regardless of joint dysfunction, however, the relationship between the joint structure and pain are still unclear. The range of sacroiliac joint motion is demonstrated to be less than 1 mm and there is no difference between physiological and pathological joints. The sacroiliac joint absorbs shock within the pelvis by the joint structures of pelvic morphology, ligaments and fat tissues. The morphology and motion of the sacroiliac joints may be optimized for upright bipedal walking. INTERPRETATION: There is no doubt that pelvic mechanical environments affect pain induction and treatment; however, no one has yet provided a concrete explanation. Future research could help develop treatments based on sacroiliac joint biomechanics to support joint function.

Experimental characterization of motion resistance of the sacroiliac joint.

BACKGROUND: The human sacroiliac joint (SIJ) in vivo is exposed to compressive and shearing stress environment, given the joint lines are almost parallel to the direction of gravity. The SIJ supports efficient bipedal walking. Unexpected or unphysiological, repeated impacts are believed to cause joint misalignment and result in SIJ pain. In the anterior compartment of the SIJ being synovial, the articular surface presents fine irregularities, potentially restricting the motion of the joints. OBJECTIVE: To clarify how the SIJ articular surface affects the resistance of the motion under physiological loading. METHODS: SIJ surface models were created based on computed tomography data of three patients and subsequently 3D printed. Shear resistance was measured in four directions and three combined positions using a customized setup. In addition, repositionability of SIJs was investigated by unloading a shear force. RESULTS: Shear resistance of the SIJ was the highest in the inferior direction. It changed depending on the direction of the shear and the alignment position of the articular surface. CONCLUSION: SIJ articular surface morphology is likely designed to accommodate upright bipedal walking. Joint misalignment may in consequence increase the risk of subluxation.

The effects of topping-off instrumentation on biomechanics of sacroiliac joint after lumbosacral fusion.

BACKGROUND: Lumbar/lumbosacral fusion supplemented with topping-off devices has been proposed with the aim of avoiding adjacent segment degeneration proximal to the fusion construct. However, it remains unclear how the biomechanics of the sacroiliac joint (SIJ) are altered after topping-off surgery. The objective of this study was to investigate the biomechanical effects of topping-off instrumentation on SIJ after lumbosacral fusion. METHODS: The validated finite element model of an intact lumbar spine-pelvis segment was modified to simulate L5-S1 interbody fusion fixed with a pedicle screw system. An interspinous spacer, Device for Intervertebral Assisted Motion (DIAM), was used as a topping-off device and placed between interspinous processes of the L4 and L5 segments. Range of motion (ROM), von-Mises stress distribution, and ligament strain at SIJ were compared between fusion (without DIAM) and topping-off (fusion with DIAM) models under moments of four physiological motions. RESULTS: ROM at the left and right SIJs in the topping-off model was higher by 26.9% and 27.5% in flexion, 16.8% and 16.1% in extension, 18.8% and 15.8% in lateral bending, and 3.7% and 7.4% in axial rotation, respectively, compared to those in the fusion model. The predicted stress and strain data showed that under all physiological loads, the topping-off model exhibited higher stress and ligament strain at the SIJs than the fusion model. CONCLUSIONS: Motion, stress, and ligament strain at SIJ increase when supplementing lumbosacral fusion with topping-off devices, suggesting that topping-off surgery may be associated with higher risks of SIJ degeneration and pain than fusion alone.

In-vitro 3D Analysis of Sacroiliac Joint Kinematics: Primary and Coupled Motions.

STUDY DESIGN: An in-vitro biomechanical study of human cadaver sacroiliac joints. OBJECTIVE: Our study aimed to develop a more comprehensive understanding of the native motion of the SIJ within the context of spinal kinematics and spinal implant evaluation. SUMMARY OF BACKGROUND DATA: Increasing attention has been given to the sacroiliac joint (SIJ) as a source of low back pain, despite its limited range of motion. We sought to characterize the rotational and translational motion in each axis utilizing standard pure moment flexion-extension (FE), lateral bending (LB), and axial rotation (AR) testing. METHODS: Sixteen sacroiliac joints were evaluated from eight lumbosacral cadaver specimens (six females, two males) from subjects aged 28 to 57 years (mean age 46.8) with body mass index (BMI) 22 to 36 (mean BMI 30). Single leg stance was modeled by clamping the blocks on one ischium in a vise and letting the contralateral ischium hang freely. Pure moment loading was applied in FE, right/left AR, and right/left LB. Relative motions were collected with infrared markers. RESULTS: The on-axis ratio was significantly lower in LB than in FE (P = 0.012) and in AR (P = 0.017). The rotation deviation angle measured 13.9 ±â€Š9.1° in FE, 17.1 ±â€Š8.7° in AR, and 35.7 ±â€Š25.7° in LB. In LB the rotational deviation angle is significantly higher than both FE and AR (P = 0.003 and P = 0.011, respectively). In-plane translation was significantly higher (P = 0.005) in FE loading than in LB loading. CONCLUSION: A nontrivial amount of rotation and translation occurred out of the expected axis of motion. The largest amount of off-axis rotation was observed in lateral bending. Relative to resultant translation, in-plane translation was lowest in lateral bending. Our results indicate that rotation of the SIJ is not fully described with the in-plane metrics which are normally reported in evaluation of fusion devices. Future studies of the SIJ may need to consider including off-axis rotation measurements when describing SIJ kinematics.Level of Evidence: 5.

Short-Term Effects of Global Pelvic Manipulation on Knee Joint Position Sense in Asymptomatic Participants: A Double-Blind Randomized Controlled Trial.

OBJECTIVE: The purpose of this study was to evaluate short-term effects of the global pelvic manipulation (GPM) on knee joint position sense (JPS). METHODS: This randomized, controlled double-blind trial included 26 asymptomatic participants (X¯± 25.3; standard deviation ± 4.4 years) who were randomly allocated into 2 groups. Sixteen participants were allocated into the experimental group, in which GPM was performed, and the rest of the participants (n = 10) were included in the control group, which received sham ultrasound therapy. Each participant attended 1 session only, and the evaluations were assessed pretreatment and 5 minutes posttreatment through an isokinetic dynamometer (Biodex Medical Systems), in which the data regarding knee JPS ipsilateral to the manipulated sacroiliac joint were collected. Mann-Whitney and Wilcoxon tests were used, with a 95% significance level. RESULTS: There were no statistically significant differences between the groups concerning active and passive JPS at 30° and 60° (P > .05). The results showed a lack of significant differences between the moments in both groups (P > .05). CONCLUSION: This investigation demonstrated that GPM, with high-velocity low-amplitude thrust, has no effect on knee JPS, suggesting that this manipulative technique does not have a relative effect on muscle spindles and Golgi tendon organ activation in asymptomatic participants.

Finite element analysis of load transition on sacroiliac joint during bipedal walking.

The sacroiliac joint (SIJ) is burdened with variant loads. However, no methods have allowed to measure objectively how the SIJ deforms during bipedal walking. In this study, in-vivo walking conditions were replicated in a kinematic model combining the finite element method with 3D walking analysis data divided into five phases in order to visualize the load transition on the SIJ and clarify the role of the SIJ. Both models with and without inclusion of the SIJ were investigated. In models with bilateral SIJs, the displacement differed greatly between the sacrum and both hip bones on the SIJ as the boundary. The movements of the sacrum involved a nutation movement in the stance phase and a counter-nutation in the swing phase relative to the ilium. In models without SIJs, the displacement of the pelvis and loads of pelvic ligaments decreased, and the equivalent stress of the SIJs increased compared to the model with SIJs. The walking loads cause distortion of the entire pelvis, and stress concentration at the SIJ are seen due to the morphology of the pelvic ring. However, the SIJs help dissipate the resulting stresses, and the surrounding ligaments are likewise involved in load transmission.

Quantification of fat in the posterior sacroiliac joint region applying a semi-automated segmentation method.

BACKGROUND AND OBJECTIVE: Fat within the posterior sacroiliac joint region (PSIJ) is thought to compensate for the incongruent surfaces of the sacrum and ilium posteriorly. Knowledge on the presence of fat in the SIJ could provide useful information about joint physiology and clinical kinematic implications of its presence. This study aimed at quantifying fat within the PSIJ, using a semi-automated method, and to compare the results to a manual segmentation method based on data from frozen cadaveric sections and computed tomography (CT). The results may provide a quicker and more objective method for fat volume quantification. METHODS: Seventy-eight cadaveric hemipelves were used. Frozen sections were obtained and photographed and CT data obtained from subsamples. A MATLAB routine was deployed to assess fat in the serial sections and CT scans, using masks derived from color thresholds and Hounsfield units, respectively. Regions of interest were created to isolate the PSIJ region before fat volume was computed. A Friedman test was used for the comparison between all masks and the manual method, a Kruskall-Wallis test for comparing the CT results with all masks and the manual method and Bland-Altman plots were used to express the result differences of these methods. RESULTS: PSIJ fat volume averaged 3.9 ± 2.2, 4.9 ± 2.5, 3.7 ± 2.3 and 7.2 ± 7.3 cm3 for masks 1 (fat mask), 2 (no-fat mask), 3 ('control' fat mask) and CT, respectively. All masks and the CT fat volume were significantly different to the manual segmentation method (p<0.01). Mask 2 differed significantly from masks 1 and 3 (both p<0.01). Bland-Altman plots yielded differences in the measurements between the various methods. CONCLUSIONS: Manual segmentation of PSIJ fat volume may result in a relative underestimation of the total fat compared to semi-automated or CT-based methods, as fat might not be sufficiently distinguished from surrounding structures. However, the CT-based method resulted in vastly higher variation in the results and warrants further study. The semi-automated approach to quantify fat based on color thresholds presented here is more investigator-independent, time efficient and applicable to CT scans, which provides opportunity to use this technique on various tissue types in vivo.

High-velocity, low-amplitude manipulation (HVLA) does not alter three-dimensional position of sacroiliac joint in healthy men: A quasi-experimental study.

The impact of high-velocity, low-amplitude (HVLA) manipulations on the behavior of sacroiliac joint (SIJ) mobility in individuals submitted to an osteopathic intervention has not been sufficiently investigated. Furthermore, there is no standard agreement on the description of the acute effects of HLVA with regards to the mobility of the SIJ through three-dimensional motion analysis. The purpose of this study was to analyse possible alterations in the mobility of the SIJ pre- and post-manipulation of the ilium bone in healthy men. Thirty healthy male patients aged between 18 and 35 years were examined and divided into two groups: manipulation (MN) and placebo (PL) groups. SIJ movement was assessed through a three-dimensional motion analysis system before and after osteopathic manipulation of the anterior ilium bone, during hip flexion. Statistical analysis was performed using the Kolmogorov-Smirnov normality test, and Fisher's exact test was used to observe associations of interest in the mobility of the SIJ. Finally, the t-test was used to analyse values of mobility of the SIJ pre- and post-manipulation (p < 0.05). Non-significant differences were observed in SIJ mobility. In MN the means were pre-manipulation right SIJ 39.98 mm ±â€¯10.82 [CI - 29.16-50.8] and post- 42.85 mm ±â€¯27.17 [CI - 15.68-70.02] with p = 0.61. Pre-manipulation left SIJ 41.73 mm ±â€¯15.34 [CI 10.89-82.99] and post- 39.97 mm ±â€¯14.70 [CI - 24.67-54.07] with p = 0.39. HVLA does not alter the mobility of SIJ under these conditions. Further studies under different conditions, with patients that report pain, are required to fully understand the behavior of the SIJ after HVLA manipulation.

[Pain generator sacroiliac joint : Functional anatomy, symptoms and clinical significance]. / Schmerzquelle Iliosakralgelenk : Funktionelle Anatomie, Symptome und klinische Bedeutung.

BACKGROUND: The sacroiliac joint is a common cause of low back pain. Due to variable symptoms, the diagnosis is often very difficult. For diagnosis, systemic disease, as well as pathologies in the hips and lumbar spine must be excluded. OBJECTIVES: To describe anatomy and function of the joint and underlying pathologies. To present the evidence of actual diagnostic and therapeutic options. MATERIALS AND METHODS: An extensive literature research was carried out on PubMed. RESULTS: The sacroiliac joint is an important and biomechanically complex joint. There are many controversial diagnostic tests to identify the sacroiliac joint as a source of pain. The cause of the dysfunction must be identified in order to treat it correctly and to prevent a chronification of the pain. The gold standard is conservative care. CONCLUSION: The sacroiliac joint must be included in the differential diagnosis in patients with low back pain. Diagnostic tests are often insufficient for the diagnosis of sacroiliac joint pain. Many of the current diagnostic and therapeutic options present weak evidence.

Quantification of fat in the posterior sacroiliac joint region: fat volume is sex and age dependant.

Fat is appreciated as a structural component of synovial joints. It may serve a shock-absorbing function for the incongruent surfaces, vessels and ligaments, but has not been investigated in the posterior sacroiliac joint (PSIJ). Sixty-six cadaveric hemipelves were serially-sectioned and photographed. The amount of visible fat in the PSIJ was quantified using a modified version of Cavalieri's method. Total volume, fat volume and fat percentage of the PSIJ were calculated in predefined sub-regions. Fat is consistently present in the PSIJ (1.9 ± 1.3 cm3). Fat volume correlates with the PSIJ total volume (p < 0.0001; r = 0.73) and age (p = 0.024; r = 0.24), and is smaller in males (1.4 ± 0.8 cm3) than females (2.4 ± 1.5 cm3). Fat volumes in the middle and inferior sub-regions of the PSIJ show side- (p < 0.0001) and sex-differences (p = 0.013 females, middle sub-region). Age and PSIJ total volume correlate between sexes in various sub-regions (p = 0.05 females superior sub-region; males inferior sub-region). Fat percentage differs between sexes and sub-regions (p = 0.018 females, superior sub-region) but is independent of age and sides. The presence of fat within the PSIJ is a normal finding and shows sex-dependant and age-related differences. It is unclear whether fat is linked to age-related degeneration or has a shock-absorbing role in stress- and load-dissipation in the PSIJ.

Posture correctness of young female soccer players.

The objectives of the study were to evaluate the correctness of the body posture of female soccer players in the frontal plane from the back based on selected body points in two static positions (habitual and actively corrected) using a non-contact optical measurement method. Forty-two young women (aged 16-20) playing soccer in a sports club in Poland were examined and compared with controls. The spatial coordinates (x, y, z) of the selected body points were determined. Four points (OcL, OcR, PvL and PvR) were extracted and used to calculate vectors [Formula: see text] and [Formula: see text] for analysis. The results show that median of the pelvic line angle was positive (PvR was lower than PvL) in both groups. For the habitual posture, the absolute value of the difference between the 25th and 75th percentiles in the pelvic line was almost three times greater among the soccer players than the controls (ratio between soccer players and controls: 2.93). Static postural imbalances in female soccer players require diagnosis of the sacroiliac joints with analysis of lumbar-pelvic system support and inhibition in the context of myofascial connection integration. Exercises can be implemented to stabilize the lumbar-pelvis complex as prophylaxis for spinal overload during the training cycle.

In Silico Pelvis and Sacroiliac Joint Motion: Refining a Model of the Human Osteoligamentous Pelvis for Assessing Physiological Load Deformation Using an Inverted Validation Approach.

Introduction. Computational modeling of the human pelvis using the finite elements (FE) method has become increasingly important to understand the mechanisms of load distribution under both healthy and pathologically altered conditions and to develop and assess novel treatment strategies. The number of accurate and validated FE models is however small, and given models fail resembling the physiologic joint motion in particular of the sacroiliac joint. This study is aimed at using an inverted validation approach, using in vitro load deformation data to refine an existing FE model under the same mode of load application and to parametrically assess the influence of altered morphology and mechanical data on the kinematics of the model. Materials and Methods. An osteoligamentous FE model of the pelvis including the fifth lumbar vertebra was used, with highly accurate representations of ligament orientations. Material properties were altered parametrically for bone, cartilage, and ligaments, followed by changes in bone geometry (solid versus 3 and 2 mm shell) and material models (linear elastic, viscoelastic, and hyperelastic isotropic), and the effects of varying ligament fiber orientations were assessed. Results. Elastic modulus changes were more decisive in both linear elastic and viscoelastic bone, cartilage, and ligaments models, especially if shell geometries were used for the pelvic bones. Viscoelastic material properties gave more realistic results. Surprisingly little change was observed as a consequence of altering SIJ ligament orientations. Validation with in vitro experiments using cadavers showed close correlations for movements especially for 3 mm shell viscoelastic model. Discussion. This study has used an inverted validation approach to refine an existing FE model, to give realistic and accurate load deformation data of the osteoligamentous pelvis and showed which variation in the outcomes of the models are attributed to altered material properties and models. The given approach furthermore shows the value of accurate validation and of using the validation data to fine tune FE models.

In-silico pelvis and sacroiliac joint motion-A review on published research using numerical analyses.

BACKGROUND: Computational models of the human pelvis have become highly useful tools to assess mechanisms of injury, diagnostics and treatment options. The purpose of this systematic literature review was to summarize existing pelvic computer models, to assess their comparability and the measures taken for experimental validation. METHODS: Research on virtual simulations of the posterior pelvis and sacroiliac joint available from the ISI Web of Knowledge, PubMed and Scopus databases available until January 2018 were included. FINDINGS: From a total of 3938 articles, 33 studies matched the criteria. Thirteen studies reported on experimental biomechanics, of which seven were parametric. Thirteen studies focused on pelvic injury and surgery, three were clinical case reports. One study assessed the effects of lumbar surgery on the sacroiliac joint, three studies on diagnostics and the non-surgical treatment of the sacroiliac joint. The mode of load application, geometry, material laws and boundary conditions varied vastly between the studies. The majority excluded the lumbosacral transition as part of pelvic biomechanics, and used isotropic linear elastic material properties. Outcomes of the analyses were reported inconsistently with negative impact on their comparability, and validation was commonly conducted by literature with varying agreement of the loading conditions. INTERPRETATION: Comparability and validation are two major issues of present computational biomechanics of the pelvis. These issues diminish the transferability of the in-silico findings into real-life scenarios. In-vitro cadaveric models remain the realistic standard to account for the present computational analyses which simplify the complex nature of musculoskeletal tissues of the pelvis.

Physiological in vitro sacroiliac joint motion: a study on three-dimensional posterior pelvic ring kinematics.

The sacroiliac joint (SIJ) is a well-known source of low back and pelvic pain, of increasing interest for both conservative and surgical treatment. Alterations in the kinematics of the pelvis have been hypothesized as a major cause of SIJ-related pain. However, definitions of both the range and the extent of physiological movement are controversial, and there are no clear baseline data for pathological alterations. The present study combined a novel biomechanical setup allowing for physiological motion of the lumbosacral transition and pelvis without restricting the SIJ movement in vitro, combined with optical image correlation. Six fresh human pelvises (81 ± 10 years, three females, three males) were tested, with bodyweight-adapted loading applied to the fifth lumbar vertebra and both acetabula. Deformation at the lumbopelvises was determined computationally from three-dimensional image correlation data. Sacroiliac joint motion under the loading of 100% bodyweight primarily consisted of a z-axis rotation (0.16°) and an inferior translation of the sacrum relative to the ilium (0.32 mm). Sacroiliac joint flexion-extension rotations were minute (< 0.02°). Corresponding movements of the SIJ were found at the lumbosacral transition, with an anterior translation of L5 relative to the sacrum of -0.97 mm and an inferior translation of 0.11 mm, respectively. Moreover, a flexion of 1.82° was observed at the lumbosacral transition. Within the innominate bone and at the pubic symphysis, small complementary rotations were seen around a vertical axis, accounting for -0.10° and 0.11°, respectively. Other motions were minute and accompanied by large interindividual variation. The present study provides evidence of different SIJ motions than reported previously when exerted by physiological loading. Sacroiliac joint kinematics were in the sub-degree and sub-millimeter range, in line with previous in vivo and in vitro findings, largely limited to the sagittal rotation and an inferior translation of the sacrum relative to the ilium. This given physiological loading scenario underlines the relevance of the lumbosacral transition when considering the overall motion of the lumbopelvis, and how relatively little the other segments contribute to overall motion.

Effects of Cutting the Sacrospinous and Sacrotuberous Ligaments.

The sacrospinous (SS) and sacrotuberous (ST) ligaments form a complex at the posterior pelvis, with an assumed role as functional stabilizers. Experimental and clinical research has yielded controversial results regarding their function, both proving and disproving their role as pelvic stabilizers. These findings have implications for strategies for treating pelvic injury and pain syndromes. The aim of the present simulation study was to assess the influence of altered ligament function on pelvis motion. A finite elements computer model was used. The two-leg stance was simulated, with the load of body weight applied via the fifth lumbar vertebra and both femora, allowing for nutation of the sacroiliac joint. The in-silico kinematics were validated with in-vitro experiments using the same scenario of load application following SS and ST transection in six human cadavers. Modeling of partial or complete ligament failure caused significant increases in pelvis motion. This effect was most pronounced if the SS and ST were affected with 164% and 182%, followed by the sacroiliac and iliolumbar ligaments with 123% and 147%, and the pubic ligaments with 113% and 119%, for partial and complete disruption, respectively. Simultaneous ligament transection multiplied the effects on pelvis motion by up to 490%. Unilateral ligament injury altered the motion at the pelvis contralaterally. The experiments presented here provide strong evidence for the stabilizing role of the SS and ST. A fortiori, the instability resulting from partial or complete SS and ST injury merits consideration in treatment strategies involving these ligaments as important stabilizers. Clin. Anat. 32:231-237, 2019. © 2018 Wiley Periodicals, Inc.

Influence of Sacroiliac Bracing on Muscle Activation Strategies During 2 Functional Tasks in Standing-Tolerant and Standing-Intolerant Individuals.

People who develop low back pain during standing (standing-intolerant) are a subclinical group at risk for clinical low back pain. Standing-intolerant individuals respond favorably to stabilization exercise and may be similar to people with sacroiliac joint dysfunction that respond to stabilization approaches including sacroiliac joint (SIJ) bracing. The purpose was to characterize muscle activation and response to SIJ bracing in standing-tolerant and standing-intolerant individuals during forward flexion and unilateral stance. Trunk and hip electromyography data were collected from 31 participants (17 standing-tolerant and 14 standing-intolerant) while performing these tasks with and without SIJ bracing. Kinematics were captured concurrently and used for movement phase identification. Cross-correlation quantified trunk coactivation and extensor timing during return-to-stand from forward flexion; root mean square amplitude quantified gluteal activity during unilateral stance. The standing-intolerant group had elevated erector spinae-external oblique coactivation without bracing, and erector spinae-internal oblique coactivation with bracing during return-to-stand compared with standing-tolerant individuals. Both groups reversed extensor sequencing during return-to-stand with bracing. Standing-tolerant individuals had higher hip abductor activity in nondominant unilateral stance and increased hip extensor activity with bracing. SIJ bracing could be a useful adjunct to other interventions targeted toward facilitating appropriate muscle activation in standing-intolerant individuals.

Pelvic orthosis effects on posterior pelvis kinematics An in-vitro biomechanical study.

The sacroiliac joint (SIJ) is a well-known source of low back pain, with increasing interest for both conservative and surgical treatment. Alterations in pelvis kinematics are hypothesized as a contributor to SIJ pain and pelvic orthoses one treatment option, but their effects on the pelvis are poorly understood. Alterations in movement patterns induced by the application of pelvic orthoses were determined in five human cadaveric pelvises. Deformations were obtained from the lumbosacral transition and the bilateral SIJ, using digital image correlation and a customized routine to compute the movements within the pelvis. Significant alterations were found for the movements at the SIJ, in particular a vast increase in axial (x-axis) rotation, accompanied by increased inferior (y-) translation of the sacrum relative to the ilium. Movement patterns at the lumbosacral transition changed, causing increases in axial rotation and decreased inferior translation of L5 relative to S1. Using a physiologic mode of load application gives novel insights into the potential effects of pelvic orthoses. The results of these in-vitro experiments vary markedly from previous experiments with loading limited to two or less axes. Furthermore, the influence of pelvic orthoses on the lumbosacral transition warrants further investigation.

Individuals with sacroiliac joint dysfunction display asymmetrical gait and a depressed synergy between muscles providing sacroiliac joint force closure when walking.

Walking is often compromised in individuals with low back and hip disorders, such as sacroiliac joint dysfunction (SIJD). The disorder involves reduced coactivation of the gluteus maximus and contralateral latissimus dorsi, which together provide joint stability during walking. The purpose of our study was to compare the kinematics and contributions of selected muscles to identified synergies during walking between healthy individuals and those with SIJD. Six women with unilateral SIJD and six age-matched healthy controls walked on a force-measuring treadmill at 1 m/s while we recorded kinematics and the activity of 16 muscles with surface EMG. Non-negative matrix factorization was used to identify patterns of EMG activity (muscle synergies). Individuals with SIJD exhibited less hip extension and lower peak vertical ground reaction forces on the affected side than the unaffected side. In contrast to controls, the SIJD group also displayed a depressed muscle synergy between gluteus maximus on the affected side and the contralateral latissimus dorsi. The results indicate that individuals with SIJD exhibited both reduced activation of gluteus maximus during a loading synergy present in walking and greater asymmetry between legs when walking compared with age-matched controls.

Quantifying the force transmission through the pelvic joints during total hip arthroplasty: A pilot cadaveric study.

BACKGROUND: Total hip arthroplasty is one of the most successful and cost effective procedures in orthopedics. The purpose of this study is to investigate force transmission through the sacroiliac joint as a possible source of post-operative pain after total hip arthroplasty through the following three questions: Does the ipsilateral sacroiliac joint, contralateral sacroiliac joint, or pubic symphysis experience more force during placement? Does the larger mallet used to seat the implant generate a higher force? Does the specimen's bone density or BMI alter force transmission? METHODS: A solid design acetabular component was impacted into five human cadaver pelves with intact soft tissues. The pressure at both sacroiliac joints and the pubic symphysis was measured during cup placement. This same procedure was replicated using an existing pelvis finite element model to use for comparison. FINDINGS: The location of the peak force for each hammer strike was found to be specimen specific. The finite model results indicated the ipsilateral sacroiliac joint had the highest pressure and strain followed by the pubic symphysis over the course of the full simulation. The heft of the mallet and bone mineral density did not predict force values or locations. The largest median force was generated in extremely obese specimens. INTERPRETATION: Contrary to previous ideas, it is highly unlikely that forces experienced at the pelvic joints are large enough to contribute post-operative pain during impaction of an acetabular component. These results indicate more force is conveyed to the pubic symphysis compared to the sacroiliac joints.

Participación de los músculos dorsal ancho, glúteo mayor y bíceps femoral en la estabilidad de la articulación sacroíliaca: revisión sistemática / Participation of latissimus dorsi, gluteus maximus and biceps femoris in sacroiliac joint stability: Systematic review

Objetivo: Analizar críticamente la evidencia científica disponible sobre la participación del dorsal ancho, el glúteo mayor y el bíceps femoral en la estabilidad de la articulación sacroilíaca (ASI). Estrategia de búsqueda: Selección de artículos durante abril y junio de 2016 en PubMed, Web of Science, Ovid, ProQuest, Science Direct y Medline. La búsqueda se limitó a estudios en población mayor de 18 años que evaluaran la función de al menos uno de los 3 músculos de interés sobre la estabilidad de la ASI. Selección de estudios: La búsqueda inicial concluyó con 31 estudios; 9 estudios observacionales descriptivos cumplieron los criterios de inclusión y fueron evaluados a través del STROBE. Síntesis de resultados: La puntuación de los estudios incluidos osciló entre 8 y 13 puntos; el 77,77% obtuvo una calidad metodológica aceptable (8-11 puntos) y el 22,22% restante una calidad buena (12-13 puntos). Ningún estudio presenta el cálculo del tamaño de la muestra ni la evaluación de las propiedades psicométricas de los instrumentos utilizados. Las variables empleadas para evaluar la estabilidad de la ASI fueron fuerza, actividad eléctrica muscular, longitud muscular y cinemática de la ASI y la columna lumbosacra. Conclusiones: La literatura revisada permite mostrar la relevancia que tienen los músculos glúteo mayor y bíceps femoral en la estabilidad de la ASI, mientras que presenta al dorsal ancho como estabilizador, principalmente cuando actúa sinérgicamente con el glúteo mayor contralateral. Sin embargo, existe poca evidencia y gran variabilidad metodológica entre los estudios. Se requieren análisis con calidad metodológica que contribuyan con una mejor comprensión de este tema

Purpose: To critically analyse the available scientific evidence on the participation of latissimus dorsi, gluteus maximus and biceps femoris in the stability of the sacroiliac joint (SIJ). Search strategy: Selection of articles during April and June 2016 in PubMed, Web of Science, Ovid, ProQuest, Science Direct and Medline. The search was limited to studies in subjects over the age of 18, and which evaluated the function of at least one of the 3 muscles of interest on SIJ stability. Selection of studies: The initial search obtained 31 studies, and 9 observational descriptive studies met the inclusion criteria and were assessed using the STROBE tool. Synthesis of results: The scores of the included studies ranged from 8 to 13 points. The large majority (77.77%) of them had an acceptable methodological quality (8-11 points) and 22.22% had a good quality (12-13 points). None of them included a sample size calculation or an evaluation of the psychometric properties of the measurement tools used. The variables used to assess the stability of SIJ were strength, muscle electrical activity, muscle length and kinematics of SIJ and lumbosacral spine. Conclusions: The literature analysed suggests the relevance of the gluteus maximus and biceps femoris muscles in the stability of SIJ, while it indicates that latissimus dorsi is a stabilising muscle, mainly when it acts synergistically with the contralateral gluteus maximus muscle. However, the studies analysing the stabilising function of these muscles on SIJ are limited and their methodology varies widely. Studies with better methodological quality and larger sample sizes are needed to improve knowledge on this subject