Introduction and Objective. The human body is designed to walk in an efficient way. As energy can be stored in elastic structures, it is no surprise that the strongest elastic structure of the human body, the iliofemoral ligament (IFL), is located in the lower limb. Numerous popular surgical hip interventions, however, affect the structural integrity of the hip capsule and there is a growing evidence that surgical repair of the capsule improves the surgical outcome. Though, the exact contribution of the iliofemoral ligament in energy efficient hip function remains unelucidated. Therefore, the objective of this study was to evaluate the influence of the IFL on energy efficient ambulation. Materials and Methods. In order to assess the potential passive contribution of the IFL to energy efficient ambulation, we simulated walking using the large public dataset (n=50) from Schreiber in a the AnyBody musculoskeletal modeling environment with and without the inclusion of the IFL. The work required from the psoas, iliacus, sartorius, quadriceps and gluteal muscles was evaluated in both situations. Considering the large uncertainty on ligament properties a parameter study was included. Results. A significant reduction in the active component of all hip flexors was observed when the IFL is intact. The required muscle work was found to be reduced by as much as 48% (CI: 29–62%), 61% (CI: 35–84%) and 38% (CI: 2–69%) for the psoas, iliacus, and sartorius muscle respectively. The IFL inclusion has no major effect on the required work from the quadriceps and the gluteal muscle group. The energy storage in the IFL is largest at maximal hip extension and the contribution to forward motion is the largest at the start of the swing phase. Conclusions. The iliofemoral ligament seems to be a crucial structure in energy efficient walking. The findings support need for meticulous reconstruction of the capsule ligament in case of surgical damage

Abstract. Background. Optimal acetabular component position in Total Hip Arthroplasty is vital for avoiding complications such as dislocation, impingement, abductor muscle strength and range of motion. Transverse acetabular ligament (TAL) and posterior labrum have been shown to be a reliable landmark to guide optimum acetabular cup position. There have been reports of iliopsoas impingement caused by both cemented and uncemented acetabular components. Acetabular component mal-positioning and oversizing of acetabular component are associated with iliopsoas impingement. The Psoas fossa (PF) is not a well-regarded landmark to help with Acetabular Component positioning. Our aim was to assess the relationship of the TAL and PF in relation to Acetabular Component positioning. Methods. A total of 12 cadavers were implanted with the an uncemented acetabular component, their position was initially aligned to TAL. Following optimal seating of the acetabular component the distance of the rim of the shell from the PF was noted. The Acetabular component was then repositioned inside the PF to prevent exposure of the rim of the Acetabular component. This study was performed at Smith & Nephew wet lab in Watford. Results. Out of the twelve acetabular components that were implanted parallel to the TAL, all had the acetabular rim very close or outside to the psoas notch with a potential to cause iliopsoas impingement. Alteration of the acetabular component position was necessary in all cadavers to inside the PF to prevent iliopsoas impingement. It was evident that the edge of PF was not aligned with TAL. Conclusion. Optimal acetabular component position is vital to the longevity and outcome following THA. TAL provides a landmark to guide acetabular component position. We feel the PF is a better landmark to allow appropriate positioning of the acetabular component inside bone without exposure of the component rim and thus preventing iliopsoas impingement at the psoas notch. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Introduction. Adolescent Idiopathic Scoliosis (AIS) is a three-dimensional deformity of the spine with unclear etiology. Due to the asymmetry of lateral curves, there are differences in the muscle activation between the convex and concave sides. This study utilized a comprehensive thoracic spine and ribcage musculoskeletal model to improve the biomechanical understanding of the development of AIS deformity and approach an explanation of the condition. Methods. In this study, we implemented a motion capture model using a generic rigid-body thoracic spine and ribcage model, which is kinematically determinate and controlled by spine posture obtained, for instance, from radiographs. This model is publicly accessible via a GitHub repository. We simulated gait and standing models of two AIS (averaging 15 years old, both with left lumbar curve and right thoracic curve averaging 25 degrees) and one control subject. The marker set included extra markers on the sternum and the thoracic and lumbar spine. The study was approved by the regional Research Ethics Committee (Journal number: H17034237). Results. We investigated the difference between the muscle activation on the right and left sides including erector spinae (ES), psoas major (PS), and multifidus (MF). Results of the AIS simulations indicated that, on average throughout the gait cycle, the right ES, left PS and left MF had 46%, 44%, and 23% higher activities compared to the other side, respectively. In standing, the ratios were 28%, 40%, and 19%, respectively. However, for the control subject, the differences were under 7%, except ES throughout the gait, which was 17%. Conclusion. The musculoskeletal model revealed distinct differences in force patterns of the right and left sides of the spine, indicating an instability phenomenon, where larger curves lead to higher muscle activations for stabilization. Acknowledgement. The project is funded by the European Union's Horizon 2020 program through Marie Skłodowska-Curie grant No. [764644]

Abstract. Purpose. The aim of this study was to assess how biomechanical gait parameters (kinematics, kinetics, and muscle force estimations) differ between patients with camtype FAI and healthy controls, through a systematic search. Methods. A systematic review of the literature from PubMed, Scopus, and Medline and EMBASE via OVID SP was undertaken from inception to April 2020 using PRISMA guidelines. Studies that described kinematics, kinetics, and/or estimated muscle forces in cam-type FAI were identified and reviewed. Results. The search strategy identified 404 articles for evaluation. Removal of duplicates and screening of titles and abstracts resulted in full-text review of 37 articles with 12 meeting inclusion criteria. The 12 studies reported biomechanical data on a total of 173 cam-FAI (151 cam specific, 22 mixed type) patients and 177 healthy age, sex and BMI matched controls. Cam FAI patients had reduced hip sagittal plane ROM (Mean difference −3.00 0 [−4.10, −1.90], p<0.001), reduced hip peak extension angles (Mean Difference −2.05 0[−3.58, −0.53], p=0.008), reduced abduction angles in the terminal phase of stance, and reduced iliacus and psoas muscle force production in the terminal phase of stance compared to the control groups. Cam FAI cohorts walked at a slower speed compared to controls. Conclusions. In conclusion, patients with cam-type FAI exhibit altered sagittal and frontal plane kinematics as well as altered muscle force production during level gait compared to controls. These findings will help guide future research into gait alterations in FAI and how such alterations may contribute to pathological progression and furthermore, how such alterations can be modified for therapeutic benefit

Introduction. Even in localized collapse due to osteonecrosis of the femoral head, a femoral head can be preserved by rotational osteotomy. In addition to anterior rotation, originally described by Sugioka, much more correction can be obtained by posterior rotation. But, transtrochanteric rotational osteotomy needs rather extensive soft tissue release, such as complete capsulotomy and resection of short external rotators and psoas tendons. Many patients tend to complain about the leg length discrepancy and limp due to varus change. We found soft tissue resection and limb shortening could be minimized by doing the osteotomy at the femur neck rather than the trochanteric area following the technique of surgical dislocation. It needs careful dissection of the posterior retinacular artery to preserve circulation to the femoral head. Methods. We have performed 17 cases (14 cases were in men and 3 cases were in women), and average patient age was 45 years old. Osteotomy was applied to cases with collapse or large necrotic region that seemed to be fail by core decompression. All cases showed collapse except one (ARCO 2-B) and 6 cases were ARCO 3-A, 5 cases were ARCO 3-B, 4 cases were ARCO 3-C and one case was ARCO stage 4. Seven cases were rotated anteriorly, and ten cases were rotated posteriorly. Amount of rotation was 63 to 170 degrees in posterior rotation (mean 100.8 degrees) and mean 48 degrees in anterior rotation. The size of the necrotic area was 301 degrees according to the Koo method (combined necrotic angle in mid-coronal and mid-saggital MRI scan). Results. Harris hip scores were improved from 62 to 88 points and VAS was from 8.4 to 2.6 in 13 cases. Conversion to THA was done in 4 cases (23.5%) as pain was persisting and there was one more failed case which was lost to follow-up. Another 2 cases showed insufficient circulation in bone SPECT, but no symptoms until recently. Problems with fixatives were in 4 cases and one case had heterotopic ossification without symptom. Conclusion. In conclusion, the outcome of the operation could be identified much earlier than other procedures. 12 cases (58.8%) showed satisfactory results and 2 cases were in observation due to insufficient circulation, and 5 cases (29.4%) failed. The operative technique will be revised and we are expecting better results

To clarify the pathomechanisms of discogenic low back pain, the sympathetic afferent discharge originating from the L5-L6 disc via the L2 root were investigated neurophysiologically in 31 Lewis rats. Sympathetic afferent units were recorded from the L2 root connected to the lumbar sympathetic trunk by rami communicantes. The L5-L6 discs were mechanically probed, stimulated electrically to evoke action potentials and, finally, treated with chemicals to produce an inflammatory reaction. We could not obtain a response from any units in the L5-L6 discs using mechanical stimulation, but with electrical stimulation we identified 42 units consisting mostly of A-delta fibres. In some experiments a response to mechanical probing of the L5-L6 disc was recognised after producing an inflammatory reaction. This study suggests that mechanical stimulation of the lumbar discs may not always produce pain, whereas inflammatory changes may cause the disc to become sensitive to mechanical stimuli, resulting in nociceptive information being transmitted as discogenic low back pain to the spinal cord through the lumbar sympathetic trunk. This may partly explain the variation in human symptoms of degenerate discs.

A rat model of lumbar root constriction with an additional sympathectomy in some animals was used to assess whether the sympathetic nerves influenced radicular pain. Behavioural tests were undertaken before and after the operation.

On the 28th post-operative day, both dorsal root ganglia and the spinal roots of L4 and L5 were removed, frozen and sectioned on a cryostat (8 μm to 10 μm). Immunostaining was then performed with antibodies to tyrosine hydroxylase (TH) according to the Avidin Biotin Complex method. In order to quantify the presence of sympathetic nerve fibres, we counted TH-immunoreactive fibres in the dorsal root ganglia using a light microscope equipped with a micrometer graticule (10 x 10 squares, 500 mm x 500 mm). We counted the squares of the graticule which contained TH-immunoreactive fibres for each of five randomly-selected sections of the dorsal root ganglia.

The root constriction group showed mechanical allodynia and thermal hyperalgesia. In this group, TH-immunoreactive fibres were abundant in the ipsilateral dorsal root ganglia at L5 and L4 compared with the opposite side. In the sympathectomy group, mechanical hypersensitivity was attenuated significantly.

We consider that the sympathetic nervous system plays an important role in the generation of radicular pain.