Melanopsin retinal ganglion cells mediate light-promoted brain development.

During development, melanopsin-expressing intrinsically photosensitive retinal ganglion cells (ipRGCs) become light sensitive much earlier than rods and cones. IpRGCs project to many subcortical areas, whereas physiological functions of these projections are yet to be fully elucidated. Here, we found that ipRGC-mediated light sensation promotes synaptogenesis of pyramidal neurons in various cortices and the hippocampus. This phenomenon depends on activation of ipRGCs and is mediated by the release of oxytocin from the supraoptic nucleus (SON) and the paraventricular nucleus (PVN) into cerebral-spinal fluid. We further characterized a direct connection between ipRGCs and oxytocin neurons in the SON and mutual projections between oxytocin neurons in the SON and PVN. Moreover, we showed that the lack of ipRGC-mediated, light-promoted early cortical synaptogenesis compromised learning ability in adult mice. Our results highlight the importance of light sensation early in life on the development of learning ability and therefore call attention to suitable light environment for infant care.

Stable Super-Resolution Imaging of Cell Membrane Nanoscale Subcompartment Dynamics with a Buffering Cyanine Dye.

Super-resolution fluorescence imaging is a crucial method for visualizing the dynamics of the cell membrane involved in various physiological and pathological processes. This requires bright fluorescent dyes with excellent photostability and labeling stability to enable long-term imaging. In this context, we introduce a buffering-strategy-based cyanine dye, SA-Cy5, designed to identify and label carbonic anhydrase IX (CA IX) located in the cell membrane. The unique feature of SA-Cy5 lies in its ability to overcome photobleaching. When the dye on the cell membrane undergoes photobleaching, it is rapidly replaced by an intact probe from the buffer pool outside the cell membrane. This dynamic replacement ensures that the fluorescence intensity on the cell membrane remains stable over time. Under the super-resolution structured illumination microscopy (SIM), the cell membrane can be continuously imaged for 60 min with a time resolution of 20 s. This extended imaging period allows for the observation of substructural dynamics of the cell membrane, including the growth and fusion of filamentous pseudopodia and the fusion of vesicles. Additionally, this buffering strategy introduces a novel approach to address the issue of poor photostability associated with the cyanine dyes.

Solvatochromic Buffering Fluorescent Probe Resolves the Lipid Transport and Morphological Changes during Lipid Droplet Fusion by Super-Resolution Imaging.

The varied functions of lipid droplets, which encompass the regulation of lipid and energy homeostasis, as well as their association with the occurrence of various metabolic diseases, are intricately linked to their dynamic properties. Super-resolution imaging techniques have emerged to decipher physiological processes and molecular mechanisms on the nanoscale. However, achieving long-term dynamic super-resolution imaging faces challenges due to the need for fluorescent probes with high photostability. This paper introduces LD-CF, a "buffering probe" for imaging lipid droplet dynamics using structured illumination microscopy (SIM). The polarity-sensitive LD-CF eliminates background fluorescence with a "cyan filter" strategy, enabling wash-free imaging of lipid droplets. In the fluorescent "off" state outside droplets, the probes act as a "buffering pool", replacing photobleached probes inside droplets and enabling photostable long-term SIM imaging. With this probe, three modes of lipid droplet fusion were observed, including the discovery of fusion from large to small lipid droplets. Fluorescence intensity tracking also revealed the direction of lipid transport during the lipid droplet fusion.

MR elastography-based slip interface imaging (SII) for functional assessment of myofascial interfaces: A feasibility study.

PURPOSE: Abnormal adherence at functional myofascial interfaces is hypothesized as an important phenomenon in myofascial pain syndrome. This study aimed to investigate the feasibility of MR elastography (MRE)-based slip interface imaging (SII) to visualize and assess myofascial mobility in healthy volunteers. METHODS: SII was used to assess local shear strain at functional myofascial interfaces in the flexor digitorum profundus (FDP) and thighs. In the FDP, MRE was performed at 90 Hz vibration to each index, middle, ring, and little finger. Two thigh MRE scans were performed at 40 Hz with knees flexed and extended. The normalized octahedral shear strain (NOSS) maps were calculated to visualize myofascial slip interfaces. The entropy of the probability distribution of the gradient NOSS was computed for the two knee positions at the intermuscular interface between vastus lateralis and vastus intermedius, around rectus femoris, and between vastus intermedius and vastus medialis. RESULTS: NOSS map depicted distinct functional slip interfaces in the FDP for each finger. Compared to knee flexion, clearer slip interfaces and larger gradient NOSS entropy at the vastus lateralis-vastus intermedius interface were observed during knee extension, where the quadriceps are not passively stretched. This suggests the optimal position for using SII to visualize myofascial slip interface in skeletal muscles is when muscles are not subjected to any additional force. CONCLUSION: The study demonstrated that MRE-based SII can visualize and assess myofascial interface mobility in extremities. The results provide a foundation for investigating the hypothesis that myofascial pain syndrome is characterized by changes in the mobility of myofascial interfaces.

Improved Interfacial Interactions of Dip Coatings by In Situ Introducing Silica to Enhance Corrosion Resistance and Metal Bonding Strength.

Corrosion is an irreversible phenomenon in nature that has been a major source of metal degradation. We herein provide a unique approach for embedding nanoparticles into epoxy resins via hydrogen bonding adsorption of in situ hydrophilic silica. Based on this adsorption action, a super-anticorrosive epoxy-based Teflon (MEP-PTFE) coating for usage on metals such as aluminum alloys was developed utilizing one-step dip coating, with promising engineering and public applications. It should be noted that the binding strength between the resultant MEP-PTFE coating and the substrate was 13.5 N. This coating had an impedance modulus of over 8 × 109 Ω·cm2 at 0.01 Hz and an impressive corrosion inhibition efficiency of 99.999%. The anticorrosion barrier from the diffusion control to the charge transfer control was revealed for the future good design of resin matrix coatings with excellent corrosion resistance.

Eco-Friendly Superhydrophobic Coupling Conversion Coating with Corrosion Resistance on Magnesium Alloy.

An eco-friendly superhydrophobic conversion coating is fabricated to enhance the corrosion resistance of the AZ31B Mg alloy by combining the deep eutectic solvent pretreatment and electrodeposition. The coral-like micro-nano structure formed by reacting deep eutectic solvent and Mg alloy provides a structural basis for constructing a superhydrophobic coating. Cerium stearate with low surface energy is deposited on the structure, providing the coating's superhydrophobicity and the corrosion inhibition effect. Electrochemical test results demonstrate that the as-prepared superhydrophobic conversion coating (water contact angle at 154.7°) with a 99.68% protection effect significantly improves anticorrosion properties for the AZ31B Mg alloy. The corrosion current density decreases from 1.79 × 10-4 A·cm-2 of Mg substrate to 5.57 × 10-7 A·cm-2 of the coated sample. Besides, the electrochemical impedance modulus reaches the value of 1.69 × 103 Ω·cm2 and increases approximately 23 times in magnitude compared with the Mg substrate. Furthermore, the corrosion protection mechanism is attributed to the coupling effect of water-repellency barrier protection and corrosion inhibition, resulting in excellent corrosion resistance. Results demonstrate a promising strategy for the corrosion protection of Mg alloys by replacing the chromate conversion coating with the superhydrophobic coupling conversion coating.

The Effect of Flexor Carpi Ulnaris Pulley Design on Tendon Gliding Resistance After Flexor Digitorum Superficialis Tendon Transfer for Opposition Transfer.

PURPOSE: The flexor digitorum superficialis (FDS) tendon transfer can be used to restore opposition of the thumb. Several pulley designs have been proposed for this transfer. Gliding resistance is considered to be an important factor influencing the efficiency of the pulley design. Our purpose was to compare the gliding resistance among 4 commonly used pulleys for the FDS oppositional transfer. METHODS: Ten fresh-frozen cadaver specimens were studied. The ring FDS was used as the donor tendon. An oppositional transfer was created using 4 pulley configurations: FDS passed around the flexor carpi ulnaris (a-FCU), FDS passed through a 2.5-cm circumference distally based FCU loop (2.5-FCU), FDS passed through a 3.5-cm circumference distally based FCU loop (3.5-FCU), and FDS passed through a longitudinal split in the FCU tendon (s-FCU). The gliding resistance was measured with the thumb in radial abduction and maximum opposition. RESULTS: In abduction, the average FDS gliding resistance of a-FCU, 2.5-FCU, 3.5-FCU, and s-FCU was 0.66 N (SD, 0.14 N), 0.70 N (SD, 0.14 N), 0.68 N (SD, 0.16 N), and 0.79 N (SD, 0.15 N), respectively. The peak gliding resistance of a-FCU, 2.5-FCU, 3.5-FCU, and s-FCU was 0.75 N (SD, 0.16 N), 0.74 N (SD, 0.15 N), 0.74 N (SD, 0.15 N), and 0.86 N (SD, 0.15 N), respectively. CONCLUSIONS: The average gliding resistance of the s-FCU was found to be significantly higher than that of the a-FCU and 3.5-FCU pulleys. In opposition, there were no differences in average or peak gliding resistance among the different pulley designs. CLINICAL RELEVANCE: In this in vitro cadaveric study, the FDS split pulley produced higher gliding resistance. Consideration of the pulley configuration may improve the overall thumb function by decreasing forces needed to overcome gliding resistance.

Apoptotic Body-Rich Media from Tenocytes Enhance Proliferation and Migration of Tenocytes and Bone Marrow Stromal Cells.

The intrinsic healing following tendon injury is ideal, in which tendon progenitor cells proliferate and migrate to the injury site to directly bridge or regenerate tendon tissue. However, the mechanism determining why and how those cells are attracted to the injury site for tendon healing is not understood. Since the tenocytes near the injury site go through apoptosis or necrosis following injury, we hypothesized that secretions from injured tenocytes might have biological effects on cell proliferation and migration to enhance tendon healing. Tenocyte apoptosis was induced by 24 h cell starvation. Apoptotic body-rich media (T-ABRM) and apoptotic body-depleted media (T-ABDM) were collected from culture media after centrifuging. Tenocytes and bone marrow-derived stem cells (BMDSCs) were isolated and cultured with the following four media: (1) T-ABRM, (2) T-ABDM, (3) GDF-5, or (4) basal medium with 2% fetal calf serum (FCS). The cell activities and functions were evaluated. Both T-ABRM and T-ABDM treatments significantly stimulated the cell proliferation, migration, and extracellular matrix synthesis for both tenocytes and BMDSCs compared to the control groups (GDF-5 and basal medium). However, cell proliferation, migration, and extracellular matrix production of T-ABRM-treated cells were significantly higher than the T-ABDM, which indicates the apoptotic bodies are critical for cell activities. Our study revealed the possible mechanism of the intrinsic healing of the tendon in which apoptotic bodies, in the process of apoptosis, following tendon injury promote tenocyte and stromal cell proliferation, migration, and production. Future studies should analyze the components of the apoptotic bodies that play this role, and, thus, the targeting of therapeutics can be developed.

In Situ Real-Time Nanoscale Resolution of Structural Evolution and Dynamics of Fluorescent Self-Assemblies by Super-Resolution Imaging.

The visualization of self-assembled structure and dynamics at the molecular level has become a powerful method to understand structure-function relationships of self-assembly. Herein, we in situ real-time imaged the dynamic process of benzyl-naphthalimide dyes at the nanoscale and inspected their internal structure with minimum 2.8 nm localization accuracy through single-molecule localization microscopy (SMLM) imaging. We monitored the growth process of three different assemblies in situ, which possessed highly heterogeneous dynamics with different shapes and growth rates. Furthermore, diverse growth rates were also found at different sites in the same assembly. These results highlight the application of super-resolution microscopy techniques for real-time visualization of internal assembled structure and dynamics in situ.

The Impact of Gamification-Induced Users' Feelings on the Continued Use of mHealth Apps: A Structural Equation Model With the Self-Determination Theory Approach.

BACKGROUND: Continued use of mHealth apps can achieve better effects in health management. Gamification is an important factor in promoting users' intention to continue using mHealth apps. Past research has rarely explored the factors underlying the continued use of mobile health (mHealth) apps and gamification's impact mechanism or path on continued use. OBJECTIVE: This study aimed to explore the factors influencing mHealth app users' intention to continue using mHealth apps and the impact mechanism and path of users' feelings induced by gamification on continued mHealth app use. METHODS: First, based on the expectation confirmation model of information system continuance, we built a theoretical model for continued use of mHealth apps based on users' feelings toward gamification. We used self-determination theory to analyze gamification's impact on user perceptions and set the resulting feelings (competence, autonomy, and relatedness) as constructs in the model. Second, we used the survey method to validate the research model, and we used partial least squares to analyze the data. RESULTS: A total of 2988 responses were collected from mHealth app users, and 307 responses were included in the structural equation model after passing the acceptance criteria. The intrinsic motivation for using mHealth apps is significantly affected by autonomy (ß=.312; P<.001), competence (ß=.346; P<.001), and relatedness (ß=.165; P=.004) induced by gamification. The intrinsic motivation for using mHealth apps has a significant impact on satisfaction (ß=.311, P<.001) and continuance intention (ß=.142; P=.045); furthermore, satisfaction impacts continuance intention significantly (ß=.415; P<.001). Confirmation has a significant impact on perceived usefulness (ß=.859; P<.001) and satisfaction (ß=.391; P<.001), and perceived usefulness has a significant impact on satisfaction (ß=.269; P<.001) and continuance intention (ß=.273; P=.001). The mediating effect analysis showed that in the impact path of the intrinsic motivation for using the mHealth apps on continuance intention, satisfaction plays a partial mediating role (ß=.129; P<.001), with a variance accounted for of 0.466. CONCLUSIONS: This study explored the impact path of users' feelings induced by gamification on the intention of continued mHealth app use. We confirmed that perceived usefulness, confirmation, and satisfaction in the classical continued use theory for nonmedical information systems positively affect continuance intention. We also found that the path and mechanism of users' feelings regarding autonomy, competence, and relatedness generated during interactions with different gamification elements promote the continued use of mHealth apps.

Biomechanical effectiveness of tendon transfers to restore active internal rotation in shoulder with deficient subscapularis with and without reverse shoulder arthroplasty.

BACKGROUND: Loss of active shoulder internal rotation can be very disabling. Several tendon transfers have been described for the management of an irreparable subscapularis (SSC) tear. The purpose of this study was to determine and compare the internal rotation moment arm (IRMA) of the sternal head of the pectoralis major (PM), latissimus dorsi (LD), and teres major (TM) when transferred to different insertion sites to restore shoulder internal rotation with and without reverse shoulder arthroplasty (RSA). METHODS: Six fresh-frozen right hemithoraces were prepared and evaluated using a custom tendon transfer model to determine the IRMA of different tendon transfers using the tendon and joint displacement method. Five tendon-transfer pairs were modeled using a single suture and tested before and after implantation of an RSA (Comprehensive; Zimmer-Biomet, Warsaw, IN, USA): PM to the insertion site of the SSC, LD to the anterior insertion site of the supraspinatus (SSP) tendon on the greater tuberosity, LD to SSC, TM to SSP, and TM to SSC. The SSC was not repaired at the end of the RSA procedure to simulate an SSC deficiency. The PM transfer was passed under the conjoined tendon when tested on the intact shoulder and above the conjoined tendon when tested with an RSA. RESULTS: Tendon transfers were shown to have a significant effect on IRMA. The effect of transferred tendons was significantly affected by the position of the humerus. With the humerus adducted, the IRMA of the TM-SSP (14.1 mm ± 3.1 mm) was significantly greater than the other transfers. With the humerus abducted to 90°, the IRMAs of the LD-SSP (30.0 mm ± 5.4 mm) and TM-SSP (28.4 mm ± 6.6 mm) were significantly greater than the IRMAs of other transfer options. The IRMA of the native shoulder differed significantly from that of the RSA state for all tendon transfers. With the humerus adducted to the side of the body, the IRMA of the RSA PM-SSC transfer was significantly greater than that without an RSA (19.0 mm ± 6.4 mm vs. 7.1 mm ± 0.9 mm), demonstrating increased efficiency for internal rotation in the RSA state. CONCLUSION: Tendon transfers to restore shoulder internal rotation differ in effectiveness and may be affected by arm position and by implantation of a lateralized humerus/lateralized glenoid RSA. The LD potentially results in superior restoration of shoulder internal rotation in a native shoulder (given the risk of nerve compression with the TM transfer) compared with PM and should be considered as a potential tendon transfer to restore internal rotation in selected patients. In combination with a lateralized humerus/lateralized glenoid RSA, the fulcrum provided by the biomechanics of the semiconstrained implant allows the PM transfer to become a more efficient tendon transfer to restore active internal rotation.

The effect of fibrin formulation on cell migration in an in vitro tendon repair model.

BACKGROUND: The purpose of this study was to determine the effect of fibrinogen concentration on cell viability and migration in a tissue culture tendon healing model. METHODS: Forty-eight canine flexor digitorum profundus tendons were randomly divided into three groups. In each group the tendons were lacerated and repaired augmented with a canine bone marrow stromal cell seeded fibrin interposition patch using either 5 mg/ml fibrinogen and 25 U/ml thrombin (physiological as a control), 40 mg/ml fibrinogen and 250 U/ml thrombin (low adhesive), or 80 mg/ml fibrinogen and 250 U/ml thrombin (high adhesive). The sutured tendons were cultured for two or four weeks. RESULTS: Failure load was not significantly different among the groups. Cell-labeling staining showed that the stromal cells migrated across the gap in the control and low adhesive groups, but there was no cell migration in the high adhesive group at two weeks. CONCLUSION: A high fibrinogen concentration in a fibrin patch or glue may impede early cell migration. LEVEL OF EVIDENCE: Not applicable because this study was a laboratory study.

Calculation of flexor pollicis longus moment arm for wrist motion in a cadaver model validates the tenodesis effect for therapy.

INTRODUCTION: Synergies of fingers and wrist motion have been incorporated into therapies for finger flexor tendon injuries to improve repair outcomes. Similar synergistic therapy strategies have not been well documented for the thumb. PURPOSE OF THE STUDY: The purpose of this study was to investigate the extent to which wrist motion enables a synergistic effect at the thumb in a cadaveric model by measuring flexor pollicis longus excursion and calculating the moment arm of this tendon at the wrist joint. STUDY DESIGN: This is a basic science research. METHODS: Eight fresh-frozen cadaveric arms were obtained from our anatomical bequest program. The proximal arm was fixed in neutral pronation/supination position, and motion of the wrist was guided through either flexion/extension or radial/ulnar deviation. Fingers were fixed in extension, thumb interphalangeal and metacarpophalangeal joints were fixed in neutral extension, and the carpometacarpal joint was fixed at 30° palmar abduction. The flexor pollicis longus tendon was exposed proximal to the wrist crease and connected to a rotary potentiometer to measure tendon excursion. Optical markers were attached to the hand to capture kinematics. Wrists were moved from a neutral position over the range of flexion and extension and then from the neutral position through the range of radial to ulnar deviation. Moment arms were calculated. RESULTS: Moment arm calculation indicated that the flexor pollicis longus acts as a wrist flexor over the entire motion range and as a weak radial deviator at ulnarly-deviated positions. CONCLUSIONS: This study provides a mechanistic rationale for passive interphalangeal joint motion in varying wrist positions when treating thumb flexor tendon injuries, with benefits seen primarily for wrist extension.

Anchor placement to glenoid rim during Bankart repair recreates contact area of anterior capsulolabral complex on glenoid better than onto articular surface.

PURPOSE: This study aimed to compare the contact areas of Bankart repair with suture anchors placed on the articular surface of the glenoid versus at the rim of the glenoid because it is unclear which technique most effectively restores the footprint after Bankart repair. METHODS: Ten fresh frozen cadaveric shoulders (mean age 70.7 years) were dissected. The attachment site of the capsulolabral complex from the 1 o' clock position to the 6 o'clock position was marked with ink, and the contact area of the anterior-inferior capsulolabral complex on the glenoid neck was measured using imageJ. Bankart lesions were created, and two types of Bankart repair were performed on each specimen. The suture anchors were inserted at the glenoid rim (Rim group) and onto the glenoid articular surface 2 mm from the rim (Surface group). Using pressure-sensitive films, we examined the interface contact area. RESULTS: The Rim group recreated 64.9% of the native surface area, while the Surface group recreated 47.3% of the area. The Rim group recreated significantly greater contact area compared to the Surface group (P = 0.0008). CONCLUSION: The anchor placement to the glenoid rim recreates the footprint of the capsulolabral complex on the anterior inferior glenoid better than the anchor placement onto the articular surface.

Stem Length and Neck Resection on Fixation Strength of Press-Fit Radial Head Prosthesis: An In Vitro Model.

PURPOSE: Various radial head prosthesis designs are currently in use. Few studies compare different prosthetic designs. We hypothesized that increasing a cementless implant stem's length would reduce stem-bone micromotion, with both short and long neck cuts. We also hypothesized that a minimum stem length might be required for the initial fixation strength of a press-fit implant. METHODS: In 16 fresh-frozen cadaveric elbows (8 pairs), the radial head and neck were cut either 10 or 21 mm below the top of the head. Modular cementless stems were inserted and sequentially lengthened in 5-mm increments. Micromotion under eccentric loading was tested after each incremental change. RESULTS: Incremental lengthening of the prosthetic stem and the amount of neck resection (10-mm cut vs 21-mm cut) both had a significant effect on micromotion. After a 10-mm radial head-neck resection, we observed a significant decrease in micromotion with stem lengths of 25 mm or greater, whereas with 21 mm of neck resection there was no further reduction in micromotion with increased stem length. These differences can be explained, at least in part, by the concept of the cantilever quotient: the ratio of the head-neck length outside the bone to the total length of the implant. CONCLUSIONS: The length of the stem affects the initial stability of press-fit radial head prostheses when the level of head and neck resection is at the minimum (ie, 10 mm) for currently available prosthetic designs. At this resection level, stems 25 mm or greater had significantly higher initial stability, but all stem lengths tested had mean micromotion values within the threshold for bone ingrowth. CLINICAL RELEVANCE: The length of a radial head prosthetic stem affects the initial stability of press-fit radial head prostheses when the level of head and neck resection is at the minimum (ie, 10 mm) for currently available prosthetic designs.

Intra-articular injection of a substance P inhibitor affects gene expression in a joint contracture model.

Substance P (SP), a neurotransmitter released after injury, has been linked to deregulated tissue repair and fibrosis in musculoskeletal tissues and other organs. Although SP inhibition is an effective treatment for nausea, it has not been previously considered as an anti-fibrotic therapy. Although there are extensive medical records of individuals who have used SP antagonists, our analysis of human registry data revealed that patients receiving these antagonists and arthroplasty are exceedingly rare, thus precluding a clinical evaluation of their potential effects in the context of arthrofibrosis. Therefore, we pursued in vivo studies to assess the effect of SP inhibition early after injury on pro-fibrotic gene expression and contractures in an animal model of post-traumatic joint stiffening. Skeletally mature rabbits (n = 24) underwent surgically induced severe joint contracture, while injected with either fosaprepitant (a selective SP antagonist) or saline (control) early after surgery (3, 6, 12, and 24 h). Biomechanical testing revealed that differences in mean contracture angles between the groups were not statistically significant (P = 0.27), suggesting that the drug neither mitigates nor exacerbates joint contracture. However, microarray gene expression analysis revealed that mRNA levels for proteins related to cell signaling, pro-angiogenic, pro-inflammatory, and collagen matrix production were significantly different between control and fosaprepitant treated rabbits (P < 0.05). Hence, our study demonstrates that inhibition of SP alters expression of pro-fibrotic genes in vivo. This finding will motivate future studies to optimize interventions that target SP to reduce the formation of post-traumatic joint contractures.

Intramuscular fat infiltration evaluated by magnetic resonance imaging predicts the extensibility of the supraspinatus muscle.

INTRODUCTION: Rotator cuff (RC) tears result in muscle atrophy and fat infiltration within the RC muscles. An estimation of muscle quality and deformation, or extensibility, is useful in selecting the most appropriate surgical procedure. We determined if noninvasive quantitative assessment of intramuscular fat using MRI could be used to predict extensibility of the supraspinatus muscle. METHODS: Seventeen cadaveric shoulders were imaged to assess intramuscular fat infiltration. Extensibility and histological evaluations were then performed. RESULTS: Quantitative fat infiltration positively correlated with histological findings and presented a positive correlation with muscle extensibility (r = 0.69; P = 0.002). Extensibility was not significantly different between shoulders graded with a higher fat content versus those with low fat when implementing qualitative methods. DISCUSSION: A noninvasive prediction of whole-muscle extensibility may directly guide pre-operative planning to determine if the torn edge could efficiently cover the original footprint while aiding in postoperative evaluation of RC repair. Muscle Nerve 57: 129-135, 2018.

Biomechanical effects of metastasis in the osteoporotic lumbar spine: A Finite Element Analysis.

BACKGROUND: Cancer patients are likely to undergo osteoporosis as consequence of hormone manipulation and/or chemotherapy. Little is known about possible increased risk of fracture in this population. The aim of this study was to describe the biomechanical effect of a metastatic lesion in an osteoporotic lumbar spine model. METHODS: A finite element model of two spinal motion segments (L3-L5) was extracted from a previously developed L3-Sacrum model and used to analyze the effect of metastasis size and bone mineral density (BMD) on Vertebral bulge (VB) and Vertebral height (VH). VB and VH represent respectively radial and axial displacement and they have been correlated to burst fracture. A total of 6 scenarios were evaluated combining three metastasis sizes (no metastasis, 15% and 30% of the vertebral body) and two BMD conditions (normal BMD and osteoporosis). RESULTS: 15% metastasis increased VB and VH by 178% and 248%, respectively in normal BMD model; while VB and VH increased by 134% and 174% in osteoporotic model. 30% metastasis increased VB and VH by 88% and 109%, respectively, when compared to 15% metastasis in normal BMD model; while VB and VH increased by 59% and 74% in osteoporotic model. CONCLUSION: A metastasis in the osteoporotic lumbar spine always leads to a higher risk of vertebral fracture. This risk increases with the size of the metastasis. Unexpectedly, an increment in metastasis size in the normal BMD spine produces a greater impact on vertebral stability compared to the osteoporotic spine.

Contribution of the Ligamentum Teres to Hip Stability in the Presence of an Intact Capsule: A Cadaveric Study.

PURPOSE: To determine the contribution of the ligamentum teres (LT) to hip stability in the presence of an intact capsule with special attention to the change in range of motion and femoral head translation. METHODS: Seven fresh-frozen cadaveric pelvises were used. Following visual inspection of the LT at different hip positions, internal rotation angles were measured at 10° of extension and at 0° of flexion, while external rotation was measured at 60°, 90°, and 110° of flexion with different hip abduction angles using electromagnetic motion tracking sensor. Femoral head translations were measured simultaneously. The tests were repeated after resection of the LT. The capsule was left intact for all test conditions. The results were compared between intact and LT resected conditions when torque of 2 and 4 Nm was applied. RESULTS: Compared with the intact hip, the LT resected hip showed no significant difference when 2 Nm torque was applied in all scenarios. With 4 Nm torque application, significant increase in external rotation was found at 60° and at 90° of flexion (1.7° ± 0.8° and 2.1° ± 1.0°, respectively). Significant difference was also noted at 60°, 90°, and 110° of flexion when the hip was in the adducted position while at 90° in the abducted hip. However, LT resection did not show significant change in internal rotation. There was no significant difference in the translation distance of the femoral head in the intact hip compared with the LT resected hip (0.77-1.11 mm vs 0.79-1.29 mm). CONCLUSIONS: Our results indicate that within the physiologic range of motion, LT can minimally limit external rotation when the hip is in the flexed position but does not contribute to translation stability. CLINICAL RELEVANCE: In the hip with intact capsule, LT deficiency can result in a slight increase in range of motion, but its contribution to stability is questionable.

Shear Wave Elastography Can Predict Passive Stiffness of Supraspinatus Musculotendinous Unit During Arthroscopic Rotator Cuff Repair for Presurgical Planning.

PURPOSE: To determine the feasibility of shear wave elastography (SWE) with B-mode ultrasound in predicting the stiffness of the rotator cuff muscle before arthroscopic rotator cuff repair to evaluate the difficulty of the surgical procedure, as well as to compare SWE with the Goutallier stage on magnetic resonance imaging (MRI). METHODS: Thirty-eight patients with a full-thickness supraspinatus tear requiring arthroscopic rotator cuff repair participated. The Goutallier stage of fatty infiltration on MRI was measured before surgery, as was the SWE modulus of the anterior superficial, anterior deep, posterior superficial, and posterior deep (PD) regions of the supraspinatus muscle. To measure the stiffness of the supraspinatus musculotendinous unit during surgery, the supraspinatus tendon was axially stretched until the anatomic insertion site was reached, and force per deformation was recorded. The correlation between stiffness of the supraspinatus and SWE value in each region of the supraspinatus muscle or Goutallier stage was determined. In addition, patients were divided into 2 groups: (1) In the complete footprint coverage group, greater than 50% of the footprint was covered during the stiffness measurement, and (2) in the incomplete footprint coverage group, less than 50% of the footprint was covered during the stiffness measurement. Differences in SWE value and Goutallier stage were measured between the 2 groups. RESULTS: The best correlation of stiffness with the SWE modulus of the PD muscle of the supraspinatus was R = 0.69, and the correlation of stiffness with the Goutallier stage on MRI was R = 0.48. The SWE value of the PD region was greater in the incomplete footprint coverage group than in the complete footprint coverage group, although the Goutallier stage was not significantly different. CONCLUSIONS: The highest correlation with stiffness of the supraspinatus musculotendinous unit was with the SWE modulus of the PD muscle, as compared with SWE evaluation of the other regions or the Goutallier stage on MRI. Ultrasound SWE can predict the stiffness of the supraspinatus musculotendinous unit best. CLINICAL RELEVANCE: Rotator cuff retraction adds difficulty to arthroscopic rotator cuff repair. Ultrasound SWE may be used for presurgical planning.