American Society of Biomechanics Journal of Biomechanics Award 2022: Computer models do not accurately predict human muscle passive muscle force and fiber length: Evaluating subject-specific modeling impact on musculoskeletal model predictions.

Musculoskeletal models are valuable for studying and understanding the human body in a variety of clinical applications that include surgical planning, injury prevention, and prosthetic design. Subject-specific models have proven to be more accurate and useful compared to generic models. Nevertheless, it is important to validate all models when possible. To this end, gracilis muscle-tendon parameters were directly measured intraoperatively and used to test model predictions. The aim of this study was to evaluate the benefits and limitations of systematically incorporating subject-specific variables into muscle models used to predict passive force and fiber length. The results showed that incorporating subject-specific values generally reduced errors, although significant errors still existed. Optimization of the modeling parameter "tendon slack length" was explored in two cases: minimizing fiber length error and minimizing passive force error. The results showed that using all subject-specific values yielded the most favorable outcome in both models and optimization cases. However, the trade-off between fiber length error and passive force error will depend on the specific circumstances and research objectives due to significant individual errors. Notably, individual fiber length and passive force errors were as high as 20% and 37% respectively. Finally, the modeling parameter "tendon slack length" did not correlate with any real-world anatomical length.

Optimal Distal Tendon Insertion Point for Elbow Flexion in Free-Functioning Gracilis Muscle Transfer for Panbrachial Plexus Injuries: A Cadaveric Study.

PURPOSE: Following pan-brachial plexus injuries, restoration of elbow flexion is widely accepted as the reconstructive priority. A gracilis free functioning muscle transfer (FFMT) can be used to restore elbow flexion alone with insertion into the biceps brachii (BIC) or brachioradialis (BRD) tendons or restore combined elbow and finger flexion with a more distal insertion into the flexor digitorum profundus (FDP) tendons. Using cadaveric experiments, we determined the peak instantaneous moment arm for each insertion option. METHODS: Six simulated gracilis transfer surgeries were performed using both arms of three fresh-frozen full body cadaveric specimens (age: 79 + 10 years. 2 female). The gracilis muscles from both legs were harvested and transferred to the contralateral upper extremity. The elbow was manually moved through three flexion-extension cycles while the instantaneous moment arm was calculated from measurements of gracilis excursion and elbow joint angle for the three distal insertion sites. RESULTS: Peak instantaneous moment arm for all three insertions occurred at an elbow angle between 83° to 92° with a magnitude ranging from 33 mm to 54 mm. The more distal (FDP/BRD) insertions produced a significantly greater (∼1.5 times) peak elbow flexion instantaneous moment arm compared to the BIC insertion. CONCLUSIONS: Based on the instantaneous moment arm, the gracilis FFMT distal insertion locations could result in greater reconstructed elbow flexion strength. In addition, direct measurement of the shape and magnitude of the moment arm curve for differing insertion sites allows high resolution surgical planning and model testing. CLINICAL RELEVANCE: This study presents the first direct experimental quantification of the gracilis FFMT instantaneous moment arm. The experimental evidence supports the use of FDP/BRD insertion locations by providing a quantitative explanation for the increased elbow flexion torque observed clinically in patients with a gracilis FFMT and distal FDP insertion.

Direct intraoperative measurement of isometric contractile properties in living human muscle.

Skeletal muscle's isometric contractile properties are one of the classic structure-function relationships in all of biology allowing for extrapolation of single fibre mechanical properties to whole muscle properties based on the muscle's optimal fibre length and physiological cross-sectional area (PCSA). However, this relationship has only been validated in small animals and then extrapolated to human muscles, which are much larger in terms of length and PCSA. The present study aimed to measure directly the in situ properties and function of the human gracilis muscle to validate this relationship. We leveraged a unique surgical technique in which a human gracilis muscle is transferred from the thigh to the arm, restoring elbow flexion after brachial plexus injury. During this surgery, we directly measured subject specific gracilis muscle force-length relationship in situ and properties ex vivo. Each subject's optimal fibre length was calculated from their muscle's length-tension properties. Each subject's PCSA was calculated from their muscle volume and optimal fibre length. From these experimental data, we established a human muscle fibre-specific tension of 171 kPa. We also determined that average gracilis optimal fibre length is 12.9 cm. Using this subject-specific fibre length, we observed an excellent fit between experimental and theorical active length-tension curves. However, these fibre lengths were about half of the previously reported optimal fascicle lengths of 23 cm. Thus, the long gracilis muscle appears to be composed of relatively short fibres acting in parallel that may not have been appreciated based on traditional anatomical methods. KEY POINTS: Skeletal muscle's isometric contractile properties represent one of the classic structure-function relationships in all of biology and allow scaling single fibre mechanical properties to whole muscle properties based on the muscle's architecture. This physiological relationship has only been validated in small animals but is often extrapolated to human muscles, which are orders of magnitude larger. We leverage a unique surgical technique in which a human gracilis muscle is transplanted from the thigh to the arm to restore elbow flexion after brachial plexus injury, aiming to directly measure muscles properties in situ and test directly the architectural scaling predictions. Using these direct measurements, we establish human muscle fibre-specific tension of ∼170 kPa. Furthermore, we show that the gracilis muscle actually functions as a muscle with relatively short fibres acting in parallel vs. long fibres as previously assumed based on traditional anatomical models.

Systematic review of the effectiveness of remifentanil in term breech pregnancies undergoing external cephalic version.

BACKGROUND: External cephalic version (ECV) is a moderately painful procedure used to turn a fetus from a non-vertex to cephalic position. This systematic review and meta-analysis compared intravenous remifentanil with other analgesia or no analgesia or placebo on the success rate and associated pain of ECV. METHODS: Systematic searches for randomised controlled trials using remifentanil during ECV for non-cephalic term singleton pregnancies were conducted in EMBASE, MEDLINE and the Cochrane Library to October 2021. The primary outcomes were successful ECV and maternal pain; secondary outcomes included mode of delivery and adverse effects. The Cochrane Risk of Bias tool was used and meta-analysis undertaken if there were ≥2 comparable studies. RESULTS: Four trials were identified, three placebo-controlled and one vs no analgesia, totalling 482 participants. Comparisons against nitrous oxide or neuraxial anaesthesia were not analysed. Two studies had a low overall risk of bias, and two had some concern for bias. Remifentanil compared with placebo increased the success of ECV by 43% (risk ratio [RR] 1.43; 95% confidence interval [CI] 1.14 to 1.78). Pain scores (0-10) were lower (mean difference -1.97; 95% CI -2.49 to -1.46) whilst there was no impact on caesarean delivery rate (RR 0.97; 95% CI 0.81 to 1.17). Adverse events were rare, with fetal bradycardia observed less often with remifentanil than placebo. CONCLUSIONS: Remifentanil increases the procedural success of ECV and reduces pain compared with placebo. Trials were at low risk of bias and contained a sufficient number of participants to have reasonable confidence in this finding.

Procedures for obtaining muscle physiology parameters during a gracilis free-functioning muscle transfer in adult patients with brachial plexus injury.

A complete understanding of muscle mechanics allows for the creation of models that closely mimic human muscle function so they can be used to study human locomotion and evaluate surgical intervention. This includes knowledge of muscle-tendon parameters required for accurate prediction of muscle forces. However, few studies report experimental data obtained directly from whole human muscle due to the invasive nature of these experiments. This article presents an intraoperative, in vivo measurement protocol for whole muscle-tendon parameters that include muscle-tendon unit length, sarcomere length, passive tension, and active tension in response to external stimulation. The advantage of this protocol is the ability to obtain these rare experimental data in situ in addition to muscle volume and weight since the gracilis is also completely removed from the leg. The entire protocol including the surgical steps for gracilis harvest takes ~ 3 h. Actual testing of the gracilis where experimental data is measured takes place within a 30-min window during surgery.

In vivo human gracilis whole-muscle passive stress-sarcomere strain relationship.

We measured the passive mechanical properties of intact, living human gracilis muscles (n=11 individuals, 10 male and 1 female, age: 33±12 years, mass: 89±23 kg, height: 177±8 cm). Measurements were performed in patients undergoing surgery for free-functioning myocutaneous tissue transfer of the gracilis muscle to restore elbow flexion after brachial plexus injury. Whole-muscle force of the gracilis tendon was measured in four joint configurations (JC1-JC4) with a buckle force transducer placed at the distal tendon. Sarcomere length was also measured by biopsy from the proximal gracilis muscle. After the muscle was removed, a three-dimensional volumetric reconstruction of the muscle was created via photogrammetry. Muscle length from JC1 to JC4 increased by 3.3±1.0, 7.7±1.2, 10.5±1.3 and 13.4±1.2 cm, respectively, corresponding to 15%, 34%, 46% and 59% muscle fiber strain, respectively. Muscle volume and an average optimal fiber length of 23.1±0.7 cm yielded an average muscle physiological cross-sectional area of 6.8±0.7 cm2 which is approximately 3 times that measured previously from cadaveric specimens. Absolute passive tension increased from 0.90±0.21 N in JC1 to 16.50±2.64 N in JC4. As expected, sarcomere length also increased from 3.24±0.08 µm at JC1 to 3.63±0.07 µm at JC4, which are on the descending limb of the human sarcomere length-tension curve. Peak passive muscle stress was 27.8±5.5 kPa in JC4 and muscle modulus ranged from 44.8 MPa in JC1 to 125.7 MPa in JC4. Comparison with other mammalian species indicates that human muscle passive mechanical properties are more similar to rodent muscle than to rabbit muscle. These data provide direct measurements of whole-human muscle passive mechanical properties that can be used in modeling studies and for understanding comparative passive mechanical properties among mammalian muscles.

Measuring and modeling in vivo human gracilis muscle-tendon unit length.

Musculoskeletal models rely heavily on the use of an anatomical dataset and clearly defined assumptions to accurately model the subject being studied. Therefore, it is important to understand the limitations of using musculoskeletal models to study individuals. This paper describes a method of measuring in vivo gracilis muscle-tendon unit length and presents a comparison of experimental data versus predictions from four musculoskeletal models in OpenSim. The largest errors occurred when the knee was fully extended. At this position, the absolute average muscle-tendon unit length error was 7% and the absolute average fiber length error was between 15% and 32%. However, the variability of these errors was significant. Manual linear scaling based on an anthropometric database did not capture the variability observed in subjects. The fiber length errors observed are predicted to have a significant impact on muscle force production that may not represent true subject specific force-length relationship of the gracilis.

Impact of the Spinal Instability Neoplastic Score on Surgical Referral Patterns and Outcomes.

BACKGROUND: The Spinal Instability Neoplastic Score (sins) was developed to identify patients with spinal metastases who may benefit from surgical consultation. We aimed to assess the distribution of sins in a population-based cohort of patients undergoing palliative spine radiotherapy (rt) and referral rates to spinal surgery pre-rt. Secondary outcomes included referral to a spine surgeon post-rt, overall survival, maintenance of ambulation, need for re-intervention, and presence of spinal adverse events. METHODS: We retrospectively reviewed ct simulation scans and charts of consecutive patients receiving palliative spine rt between 2012 and 2013. Data were analyzed using Student's t-test, Chi-squared, Fisher's exact, and Kaplan-Meier log-rank tests. Patients were stratified into low (<7) and high (≥7) sins groups. RESULTS: We included 195 patients with a follow-up of 6.1 months. The median sins was 7. The score was 0 to 6 (low, no referral recommended), 7 to 12 (intermediate, consider referral), and 13 to 18 (high, referral suggested) in 34%, 59%, and 7% of patients, respectively. Eleven patients had pre-rt referral to spine surgery, with a surgery performed in 0 of 1 patient with sins 0 to 6, 1 of 7 with sins 7 to 12, and 1 of 3 with sins 13 to 18. Seven patients were referred to a surgeon post-rt with salvage surgery performed in two of those patients. Primary and secondary outcomes did not differ between low and high sins groups. CONCLUSION: Higher sins was associated with pre-rt referral to a spine surgeon, but most patients with high sins were not referred. Higher sins was not associated with shorter survival or worse outcome following rt.

Las Fan Page de Facebook como medio de difusión de la Enfermería Basada en la Evidencia / Facebook pages for the broadcasting of media on evidenced-based nursing

Desde el cambio que Internet sufrió a principios de este siglo evolucionando hacia la Web 2.0 se ha generado un cambio de paradigma en la manera de gestionar la información. Este hecho no le ha sido indiferente a la enfermería, que está aprendiendo a utilizar las herramientas 2.0 entre otras motivaciones, en beneficio de su difusión científica. A su vez, las redes sociales han cobrado un protagonismo tal que la combinación de redes sociales y herramientas 2.0 forman el escenario actual de la web social. Facebook y sus FanPages forman parte de esta web social y pueden estar al servicio de la ciencia fomentando la difusión de la información y la comunicación. En este estudio descriptivo se muestra la difusión de los contenidos del blog "Enfermería Basada en la Evidencia" a través de la FanPage de su perfil público en Facebook, que ha tenido un alcance rápido y transcultural. Esto nos describe el marco social de la web 2.0 al servicio de la ciencia (AU)

Since the change that the Internet suffered earlier this century evolving into Web 2.0, a change in the model of how to manage information has been generated. This fact has not been indifferent to nurses, who are learning how to use 2.0 tools, among other motivations, for the benefit of scientific broadcasting. In turn, social networks have taken on a role such that the combination of social networks and 2.0 tools are the current scenario of the social web. Facebook and its Fan Pages are part of the social web and can be used by science for promoting the communication of information. This descriptive study shows the spreading of the contents of the blog called "Evidence-Based Nursing" through its Facebook page, which has a rapid and cross-cultural range. This describes the social context of Web 2.0 in the service of science (AU)

Cutting healthcare costs without rationing at the bedside: preserving the doctor-patient fiduciary relationship.

In his essay on bedside rationing, Peter Ubel argues that in an era of rising healthcare costs, it is time to relax the patient-centered ethic of physicians as unconditional patient advocates so they can individualize rationing decisions. This paper raises several concerns with the arguments and the examples he provides to make his case. First, he overlooks cost-effectiveness when making medical spending decisions. Second, his examples of wasteful, unproven and potentially harmful interventions call for physician education, not rationing, as he suggests. Third, informed patients can play a role in lowering costs through shared decision making. Fourth, individualized rationing decisions will worsen already pervasive disparities in medical care. The paper envisions the ideal cost-conscious physician as one who is knowledgeable about cost-effective practices, avoids unproven interventions whenever possible, and facilitates shared decision making through patient education. Such an individual would not, however, withhold interventions of proven benefit except when accommodating a patient's preferences for a particular therapy. The doctor and patient can only work together within the constraints of system-wide rationing if the fiduciary relationship is never violated.

Provision of physiotherapy and occupational therapy in outpatient departments and day hospitals for stroke patients in Nottingham.

The provision of rehabilitation for stroke patients discharged from hospital in Nottingham was determined in three ways: a longitudinal study of consecutive stroke patients discharged from hospital, a cross-sectional survey of stroke patients attending physiotherapy (PT) and occupational therapy (OT) outpatient departments (OPDs), and an observational study of patients attending for rehabilitation at day hospitals (DHs) and PT and OT OPDs. In the longitudinal study 17% of patients went to DHs and 20% to OPDs. During the cross-sectional study patients most commonly attended twice weekly. Twenty-four per cent of DH attenders were 18 months post-stroke. In the observational study, the proportion of time spent in therapy was 22% in DHs, 38% in PT OPDs, 48% in OPD OT, and 51% in those attending both PT and OT OPDs. Day hospitals are now a major facility for the rehabilitation of stroke outpatients. OPDs may deliver rehabilitation more efficiently than DHs, and both OPDs and DHs compare favourably when compared to inpatient rehabilitation in this respect.

[Fixed partial denture on implants. Prosthodontic and biomechanical considerations]. / Prótesis parcial fija sobre implantes. Consideraciones prostodóncicas y biomecánicas.

In this issue are analyzed the factors that support the selection of the partial edentulous patients, for the construction of partial fixed prosthesis implantosupported, and the biomechanical considerations that we have to consider in relation to: relation implant-bone, the use of natural teeth, part of the jaw, length of the space, opponent jaw and materials.

Hydrops foetalis in sheep.

Hydrops foetalis was observed in foetuses from a sheep flock in southern New South Wales over 4 years. Ewes showed marked abdominal distension and most died at parturition, being unable to deliver large affected foetuses. These had birth weights up to 18 kg and exhibited severe generalised oedema of subcutaneous tissues, fluid accumulation in the serous cavities and oedema of the placenta. Microscopically, there was a generalised extramedullary haemopoiesis and massive oedema, consistent with a chronic foetal anaemia. No infectious or environmental factors could be incriminated in the outbreak. The clinical and pathological findings resemble those of the homozygous alpha-thalassaemia in infants associated with haemoglobin Bart's.

Equine herpesvirus abortion in Australia 1977 to 1982.

Until 1977 no case of abortion caused by equine herpesvirus 1 (EHV1) had been recorded in Australia although the virus, called equine rhinopneumonitis virus, had been known to have been present at least since 1962. Outbreaks of EHV1 abortion occurred in New South Wales in 1977 and in 1981. Sporadic cases of EHV1 abortion had been confirmed in some parts of Australia each year since 1975. It was concluded that an abortigenic subtype of EHV1 had been introduced to Australia in 1977 and that the previously endemic respiratory subtype occasionally caused abortion. Virus isolation in a variety of cell cultures and histopathological examination of tissue were shown to be satisfactory methods of diagnosis of EHV1 abortion. Lung proved to be the specimen of choice. Slight serological differences between "abortigenic" and "respiratory" subtypes of EHV1 were found in cross neutralisation tests. A serological survey of 219 Sydney horses of various ages revealed that most yearlings had already acquired neutralising antibody to both subtypes.