Both intrinsic and extrinsic hand muscles contribute to finger flexion; however there are different ways in which individuals can flex their fingers. Due to different muscle insertions, it is possible to distinguish the mechanical effect of intrinsic muscles from extrinsic muscles. The aim of this observational study was to investigate the degree to which individuals in the population rely on either their intrinsic or extrinsic hand muscles. A high frequency camera was used to record the hands of 31 healthy participants, aged between 18 to 40, while they made a fist repeatedly. The hands were placed on a horizontal plane and the video was taken from the ulnar side, aligned horizontally with the hand. The maximum vertical distance between the fingertip and the distal palmer creases (XY) was recorded using WIN analyze 3D software. Three examiners independently analysed the videos and classified them into intrinsic dominant, extrinsic dominant or a mixed pattern. A t-test was performed on the XY values for the three different categories. The XY height difference between the intrinsic and extrinsic groups were statistically significant (P=0.001). The XY of mixed and intrinsic was also statistically significant (p=0.012) but not for mixed and extrinsic (p=0.46). Assessment of time when movement starts at each individual joint showed significant difference with intrinsic predominant moving the MCPJ before IPJ and extrinsic dominant individual moving their IPJ before MCPJ. This study shows that there is a difference in hand muscle dominance between individuals. More importantly it shows that there are individuals who rely on their intrinsic hand muscles more than their extrinsic muscles

Introduction. A 6cm femoral gain requires 5-Y during normal growth, but only 6–8-W surgically (x30–40 faster). In lengthening surgery, losses of muscle force (MF) and circumferences (MC) are major. Recovery is long, preventing sports till bone fusion. Can we maintain MC and strength throughout the entire lengthening and how?. We monitored for over 30 years patients for muscle force (isokinetic), circumferences, activities (including sports) and food intake, and acted on the 5 principles of the Osteostasis. Materials & Methods. Over 750 femoral lengthening with Full WB Nails (FWBN) got Isokinetic testing (≧1991), circumferences measurements (≧2012; 20-15-10-5-0cm above patella, max-calf, mini/max-ankle), food intake (≧2012), using MyFitnessPal App (≧2016), gradually enforced. Preoperative training along with a daily post-operative training are supervised by our trainers. Recommendations for food intake and activities were provided. Patients noted on a specific App all parameters. Compliance was noted. Results. Instead of a traditional 7–9cm circumference loss for 8–10cm gains using Ex-fix or nails, with FWBN and our protocols, no MC loss could be noted in compliant pre-trained patients, intensive early post-op resistance training, high calory intake (M:>4200, F:>3000; 20–25% Proteins) and supplements (no fat pad increase). Bone fusion could be obtained at the end of lengthening or within short weeks (Healing Index down to 8D/cm). Non-compliant patients (or using morphine), lost weight and MC. Conclusions. Increasing by 8–10cm muscle length, even bilaterally, and maintaining MC during lengthening, is possible, with very fast bone fusion. It requires building up several hundred of grams of muscles. The ‘building up equation’ associating resistance bike from the early post-operative phase with sports, strong food intake with increased protein intake, and added supplements with no morphine medication, proved to boost circumferences and bone fusion. It induced fast recovery, walking and sports capacities

Aims. The aticularis genu (AG) is the least substantial and deepest muscle of the anterior compartment of the thigh and of uncertain significance. The aim of the study was to describe the anatomy of AG in cadaveric specimens, to characterize the relevance of AG in pathological distal femur specimens, and to correlate the anatomy and pathology with preoperative magnetic resonance imaging (MRI) of AG. Methods. In 24 cadaveric specimens, AG was identified, photographed, measured, and dissected including neurovascular supply. In all, 35 resected distal femur specimens were examined. AG was photographed and measured and its utility as a surgical margin examined. Preoperative MRIs of these cases were retrospectively analyzed and assessed and its utility assessed as an anterior soft tissue margin in surgery. In all cadaveric specimens, AG was identified as a substantial structure, deep and separate to vastus itermedius (VI) and separated by a clear fascial plane with a discrete neurovascular supply. Mean length of AG was 16.1 cm ( ± 1.6 cm) origin anterior aspect distal third femur and insertion into suprapatellar bursa. In 32 of 35 pathological specimens, AG was identified (mean length 12.8 cm ( ± 0.6 cm)). Where AG was used as anterior cover in pathological specimens all surgical margins were clear of disease. Of these cases, preoperative MRI identified AG in 34 of 35 cases (mean length 8.8 cm ( ± 0.4 cm)). Results. AG was best visualized with T1-weighted axial images providing sufficient cover in 25 cases confirmed by pathological findings.These results demonstrate AG as a discrete and substantial muscle of the anterior compartment of the thigh, deep to VI and useful in providing anterior soft tissue margin in distal femoral resection in bone tumours. Conclusion. Preoperative assessment of cover by AG may be useful in predicting cases where AG can be dissected, sparing the remaining quadriceps muscle, and therefore function. Cite this article: Bone Joint Open 2020;1-9:585–593

Massive posterosuperior cuff tears (mRCT) retracted to the glenoid are surgically challenging and often associated with high retear rates. Primary repair is a less-favourable option and other salvage procedures such as SCR and tendon transfers are used. This study presents clinical and radiological outcomes of muscle advancement technique for repair of mRCT. Sixty-one patients (mean age 57±6, 77% males and 23% females) (66 shoulders) underwent all-arthroscopic rotator cuff repair that included supraspinatus and infraspinatus subperiosteal dissection off scapular bony fossae, lateral advancement of tendon laminae, and tension-free double-layer Lasso Loop repair to footprint. Pre-and post-operative range of motion (ROM), cuff strength, VAS, Constant, ASES, and UCLA scores were assessed. Radiologic assessment included modified Patte and Goutallier classifications. All patients had MRI at 6 months to evaluate healing and integrity of repair was assessed using Sugaya classification with Sugaya 4 and 5 considered retears. Advanced fatty degeneration (Goutallier 3-4) was present in 44% and 20% of supraspinatus and infraspinatus. Tendon retraction was to the level of or medial to glenoid in 22%, and just lateral in 66%. 50.8% mRCT extended to teres minor. Subscapularis was partially torn (Lafosse 1-3) in 46% and completely torn (Lafosse 4-5) in 20%. At mean follow-up (52.4 weeks), a significant increase in ROM, Relative Cuff Strength (from 57% to 90% compared to contralateral side), VAS (from 4 ±2.5 to 1±1.7), Constant (50±17.8 to 74 ±13.0), ASES (52 ±17.5 to 87 ±14.9), and UCLA (16± 4.9 to 30 ±4.9) scores were noted. There were six retears (10%), one failure due to P. acnes infection. 93% returned to pre-injury work and 89% of cases returned to pre-injury sport. Satisfaction rate was 96%. Muscle advancement technique for mRCT is a viable option with low retear rates, restoration of ROM, strength, and excellent functional outcomes

Abstract. Source of Study: London, United Kingdom. This intervention study was conducted to assess two developing protocols for quadriceps and hamstring rehabilitation: Blood Flow Restriction (BFR) and Neuromuscular Electrical Stimulation Training (NMES). BFR involves the application of an external compression cuff to the proximal thigh. In NMES training a portable electrical stimulation unit is connected to the limb via 4 electrodes. In both training modalities, following device application, a standardised set of exercises were performed by all participants. BFR and NMES have been developed to assist with rehabilitation following lower limb trauma and surgery. They offer an alternative for individuals who are unable to tolerate the high mechanical stresses associated with traditional rehabilitation programmes. The use of BFR and NMES in this study was compared across a total of 20 participants. Following allocation into one of the training programmes, the individuals completed training programmes across a 4-week period. Post-intervention outcomes were assessed using Surface Electromyography (EMG) which recorded EMG amplitude values for the following muscles: Vastus Medialis, Vastus Lateralis, Rectus Femoris and Semitendinosus. Increased Semitendinosus muscle activation was observed post intervention in both BFR and NMES training groups. Statistically significant differences between the two groups was not identified. Larger scale randomised-controlled trials are recommended to further assess for possible treatment effects in these promising training modalities

Acute Compartment Syndrome (ACS) is an orthopaedic emergency that can develop after a wide array of etiologies. In this pilot study the MY01 device was used to assess its ease of use and its ability to continuously reflect the intracompartmental pressure (ICP) and transmit this data to a mobile device in real time. This preliminary data is from the lead site which is presently expanding data collection to five other sites as part of a multi-center study. Patients with long bone trauma of the lower or upper extremity posing a possibility of developing compartment syndrome were enrolled in the study. Informed consent was obtained from the patients. A Health Canada licensed continuous compartmental pressure monitor (MY01) was used to measure ICP. The device was inserted in the compartment that was deemed most likely to develop ACS and ICP was continuously measured for up to 18 hours. Fractures were classified according to the AO/OTA classification. Patient clinical signs and pain levels were recorded by healthcare staff during routine in-patient monitoring and were compared to the ICP from the device. Important treatment information was pulled from the patient's chart to help correlate all of the patient's data and symptoms. The study period was conducted from November 2020 through December 2021. Twenty-six patients were enrolled. There were 17 males, and nine females. The mean age was 38 years (range, 17–76). Seventeen patients received the device post-operatively and nine received it pre-operatively. Preliminary results show that post-operative ICPs tend to be significantly higher than pre-operative ICPs but tend to trend downwards very quickly. The trend in this measurement appears to be more significant than absolute numbers which is a real change from the previous literature. One patient pre-operatively illustrated a steep trend upwards with minimal clinical symptoms but required compartment release at the time of surgery that exhibited no muscle necrosis. The trend in this patient was very steep and, as predicted, predated the clinical findings of compartment syndrome. This trend allows an early warning signal of the absolute pressure, to come, in the compartment that is being assessed by the device. Preliminary results suggest that this device is reliable and relatively easy to use within our institutions. In addition it suggests that intracompartmental pressures can be higher immediately post-op but lower rapidly when the patient does not develop ACS. These results are in line with current literature of the difference between pre and post-operative baselines and thresholds of ICP, but are much more striking, as continuous measurements have not been part of the data set in most of past studies. Further elucidation of the pressure thresholds and profiles are currently being studied in the ongoing larger multicenter study and will add to our understanding of the critical values. This data, plus the added value of continuous trends in the pressure, upwards or downwards, will aid in preventing muscle necrosis during our management of these difficult long bone fractures

Many patients who undergo a total knee arthroplasty (TKA) wish to return to a more active lifestyle. The implant must be able to restore adequate muscle strength and function. However, this may not be a reality for some patients as quadriceps and hamstrings muscle activity may remain impaired following surgery. The purpose of this study was to compare muscle activity between patients implanted with a medial pivot (MP) or posterior stabilized (PS) implant and controls (CTRL) during ramp walking tasks. Fifteen patients were assigned to either a MP (n=9) or PS (n=6) TKA operated by the same surgeon. Nine months following surgery, the 15 patients along with nine CTRL patients completed motion and EMG analysis during level, ramp ascent & descent walking tasks. Wireless EMG electrodes were placed on six muscles: vastus medialis (VM), vastus lateralis (VL), biceps femoris (BF), semimembranosus (SM) muscles, gastrocnemius medial head (GM), and gastrocnemius lateral head (GL). Participants completed three trials of each condition. EMG data were processed for an entire gait cycle of the operated limb in the TKA groups, and for the dominant limb in the CTRL group. The maximum muscle activity achieved with each muscle during the level trial was used to normalize the ramp trials. The onset and offset of each muscle was determined using the approximated generalized likelihood ratio. Peak muscle activity (PeakLE), total muscle activity (iEMG), and muscle onsets/offsets were determined for each muscle for the ramp ascent and descent trials. Non-parametric Kruskal Wallace tests were used to test for statistical significance between groups with α=0.05. During the ramp up task, both MP and PS groups had significantly greater PeakLE and iEMG for the hamstring muscles compared to the CTRL, whereas the PS group had significantly greater PeakLE compared with the MP group for the SM muscle. During the ramp down task, both MP and PS groups had significantly greater PeakLE and iEMG for the SM and GL muscles compared to the CTRL. The PS group also had significantly greater iEMG for the BF and VM muscles compared to the CTRL. The MP group had a significantly earlier offset for the SM muscle compared to the CTRL. Stability in a cruciate removing TKA is partially controlled by the prosthetic design. During the ramp up task, the TKA groups compensated the tibial anterior translation by activating their hamstrings more and for a longer duration. The MP group required less hamstrings activation than the PS group. During the ramp down task, TKA patients stiffened their knee in order to stabilize the joint. The quadriceps, hamstrings and GL muscle were activated more and for a longer duration than the CTRL group to protect the tibial posterior translation. The PS group required greater BF and VM iEMG than the MP group. Even if surgery reduced pain, differences in muscle activity exist between TKA patients and healthy controls. The prosthetic design provides some stability to the knee, and the MP implant required less muscle activation than the PS implant to stabilize the knee joint

Musculoskeletal modeling techniques simulate reverse total shoulder arthroplasty (RTSA) shoulders and how implant placement affects muscle moment arms. Yet, studies have not taken into account how muscle-length changes affect force-generating capacity postoperatively. We develop a patient-specific model for RTSA patients to predict muscle activation. Patient-specific muscle parameters were estimated using an optimization scheme calibrating the model to isometric arm abduction data at 0°, 45°, and 90°. We compared predicted muscle activation to experimental electromyography recordings. A twelve-degree of freedom model with experimental measurements created patient-specific data estimating muscle parameters corresponding to strength. Optimization minimized the difference between measured and estimated joint moments and muscle activations, yielding parameters corresponding to subjects' strength that can predict muscle activation and lengths. Model calibration was performed on RTSA patients' arm abduction data. Predicted muscle activation ranged between 3% and 70% of maximum. The maximum joint moment produced was 10 Nm. The model replicated measured moments accurately (R. 2. > 0.99). The optimized muscle parameters produced feasible muscle moments and activations for dynamic arm abduction when using data from isometric force trials. A normalized correlation was found between predicted and experimental muscle activation for dynamic abduction (r > 0.9); the moment generation to lift the arm was tracked (R. 2. = 0.99). Statement of Clinical Significance: We developed a framework to predict patient-specific muscle parameters. Combined with patient-specific models incorporating joint configurations, kinematics, and bone anatomy, they can predict muscle activation in novel tasks and, e.g., predict how RTSA implant and surgical decisions may affect muscle function

Background. Revision total knee arthroplasties (rTKA) are performed with increasing frequency due to the increasing numbers of primary arthroplasties, but very little is known regarding the influence of muscle strength impairments on functional limitations in this population. Objectives. The aim of this study was to assess relationship between muscle strength and functional level in patient with rTKA. Design and Methods. Twenty-three patients (8 males, 15 females) were included in the study with mean age 68.4±10 years. Patients performed 3 performance tests (50-Step Walking Test, 10 Meter Walk Test, 30-Second Chair-Stand Test), and one self-report test (HSS) were preferred to assess patients. The maximum isometric muscle strength of quadriceps femoris and hamstring muscles of all the patients was measured using Hand-Held Dynamometer (HHD). Results. While moderate-to-strong significant correlations was found between quadriceps femoris muscle strength and 30- Second Chair-Stand Test (r=0.390, p=0.049), 50-Step Walking Test (r=−0.530, p=0.005), 10 Meter Walk Test (r=−0.587, p=0.002), there were not significant correlation between HSS knee score and all performance-based tests (p>0.05). Also there were not significant correlation between hamstring muscle strength and all other measurement tests (p>0.05). Conclusion. The moderate-to-strong statistical significant correlation between quadriceps femoris muscle strength and functional performance tests suggests that improved postoperative quadriceps strengthening could be important to enhance the potential benefits of rTKA

Introduction. Current modeling techniques have been used to model the Reverse Total Shoulder Arthroplasty (RTSA) to account for the geometric changes implemented after RTSA [2,3]. Though these models have provided insight into the effects of geometric changes from RTSA these is still a limitation of understanding muscle function after RTSA on a patient-specific basis. The goal of this study sought to overcome this limitation by developing an approach to calibrate patient-specific muscle strength for an RTSA subject. Methods. The approach was performed for both isometric 0° abduction and dynamic abduction. A 12 degree of freedom (DOF) model developed in our previous work was used in conjunction with our clinical data to create a set of patient-specific data (3 dimensional kinematics, muscle activations (), muscle moment arms, joint moments, muscle length, muscle velocity, tendon slack length (), optimal fiber length, peak isometric force)) that was used in a novel optimization scheme to estimate muscle parameters that correspond to the patient's muscle strength[4]. The optimization varied to minimize the difference between measured (“in vivo”) and predicted joint moments and measured (“in vivo”) and predicted muscle activations (). The predicted joint moments were constructed as a summation of muscle moments. The nested optimization was implemented within matlab (Mathworks). The optimization yields a set of muscle parameters that correspond to the subject's muscle strength. The abduction activity was optimized [4,5]. To validate the model we predicted dynamic joint moment and activation for the abduction activity (Figure 1). Results. The muscle activation for the lateral deltoid had a normalized correlation of value of .91(Figure 1 left). The maximum joint moment produced was 18 newton-meters. The joint moments were reproduced to an value of 1 (Figure 1 Right). Muscle parameters were calculated for both isometric and dynamic abduction. The muscle parameters produced provided a feasible solution to reproduce the muscle activation and joint moments seen “in vivo” (Figure 1). Discussion. Current modeling techniques of the upper extremity focus primarily on geometric changes and their effects on shoulder muscle moment arms. In efforts to create patient-specific models we have developed a framework to predict subject-specific strength characteristics. In order to fully understand muscle function we need muscle parameters that correspond to the subject's strength. This effort in conjunction with patient-specific models that incorporate the patient's joint configurations, kinematics and bone anatomy provide a framework to gain insight into muscle tensioning effects after RTSA. This framework describes the relationship between muscle lengthening and muscle performance (recruitment and force generation). With this framework improvements can be made to the surgical implementation and design of RTSA to improve surgical outcomes. Significance. This abstract is the first of its kind to use patient-specific fluoroscopy kinematics, muscle activation and joint moments to create a framework to predict a patients muscle function (activation, force) for RTSA groups. This now allows us to understand how differences in implant design and surgical technique affect each muscle's ability to generate force and function. For any figures or tables, please contact authors directly (see Info & Metrics tab above).

Current modeling techniques have been used to model the Reverse Total Shoulder Arthroplasty (RTSA) to account for the geometric changes implemented after RTSA. Though these models have provided insight into the effects of geometric changes from RTSA these is still a limitation of understanding muscle function after RTSA on a patient-specific basis. The goal of this study sought to overcome this limitation by developing an approach to calibrate patient-specific muscle strength for an RTSA subject. The approach was performed for both isometric 0° abduction and dynamic abduction. A 12 degree of freedom (DOF) model developed in our previous work was used in conjunction with our clinical data to create a set of patient-specific data (3 dimensional kinematics, muscle activations, muscle moment arms, joint moments, muscle length, muscle velocity, tendon slack length, optimal fiber length, peak isometric force)) that was used in a novel optimization scheme to estimate muscle parameters that correspond to the patient's muscle strength[4]. The optimization varied to minimize the difference between measured(“in vivo”) and predicted joint moments and measured (“in vivo”) and predicted muscle activations. The predicted joint moments were constructed as a summation of muscle moments. The nested optimization was implemented within matlab (Mathworks). The optimization yields a set of muscle parameters that correspond to the subject's muscle strength. The abduction activity was optimized. The maximum activation for the muscles within the model ranged between .03–2.4 (Figure 1). The maximum joint moment produced was 11 newton-meters. The joint moments were reproduced to an value of 1. Muscle parameters were calculated for both isometric and dynamic abduction (Figure 2). The muscle parameters produced provided a feasible solution to reproduce the joint moments seen “in vivo” (Figure 3). Current modeling techniques of the upper extremity focus primarily on geometry. In efforts to create patient-specific models we have developed a framework to predict subject-specific strength characteristics. In order to fully understand muscle function we need muscle parameters that correspond to the subject's strength. This effort in conjunction with patient-specific models that incorporate the patient's joint configurations, kinematics and bone anatomy hopes to provide a framework to gain insight into muscle tensioning effects after RTSA. With this framework improvements can be made to the surgical implementation and design of RTSA to improve surgical outcomes

Modern musculoskeletal modeling techniques have been used to simulate shoulders with reverse total shoulder arthroplasty and study how geometric changes resulting from implant placement affect shoulder muscle moment arms. These studies do not, however, take into account how changes in muscle length will affect the force generating capacity of muscles in their post-operative state. The goal of this study was to develop and calibrate a patient-specific shoulder model for subjects with RTSA in order to predict muscle activation during dynamic activities. Patient-specific muscle parameters were estimated using a nested optimization scheme calibrating the model to isometric arm abduction data at 0°, 45° and 90°. The model was validated by comparing predicted muscle activation for dynamic abduction to experimental electromyography recordings. A twelve-degree of freedom model was used with experimental measurements to create a set of patient-specific data (three-dimensional kinematics, muscle activations, muscle moment arms, joint moments, muscle lengths, muscle velocities, tendon slack lengths, optimal fiber lengths and peak isometric forces) estimating muscle parameters corresponding to each patient's measured strength. The optimization varied muscle parameters to minimize the difference between measured and estimated joint moments and muscle activations for isometric abduction trials. This optimization yields a set of patient-specific muscle parameters corresponding to the subject's own muscle strength that can be used to predict muscle activation and muscle lengths for a range of dynamic activities. The model calibration/optimization procedure was performed on arm abduction data for a subject with reverse total shoulder arthroplasty. Muscle activation predicted by the model ranged between 3% and 90% of maximum. The maximum joint moment produced was 20 Nm. The model replicated measured joint moments accurately (R2 > 0.99). The optimized muscle parameter set produced feasible muscle moments and muscle activations for dynamic arm abduction, when calibrated using data from isometric force trials. Current modeling techniques for the upper extremity focus primarily on geometric changes and their effects on shoulder muscle moment arms. In an effort to create patient-specific models, we have developed a framework to predict subject-specific muscle parameters. These estimated muscle parameters, in combination with patient-specific models that incorporate the patient's joint configurations, kinematics and bone anatomy, provide a framework to predict dynamic muscle activation in novel tasks and, for example, predict how joint center changes with reverse total shoulder arthroplasty may affect muscle function

The purpose of this study was to compare lower limb muscle activity in patients who underwent a total knee arthroplasty (TKA) with a medial pivot (MP) implant to healthy controls (CTRL) during a stair ascent task. Seven MP (age: 61.4±6.5 years, BMI: 30.0±4.7 kg/m2, 12.4±3.8 months post-surgery) patients who underwent a TKA performed using either a subvastus or medial parapatellar approach were age- and BMI-matched to seven healthy CTRL participants (age: 62.4±4.2 years, BMI: 26.3±2.7 kg/m2) for comparison in this study. Participants underwent electromyography (EMG) analysis while completing a three-step stairs ascent task. Portable wireless surface EMG probes were placed on the vastus lateralis (VL), rectus femoris (RF), vastus medialis (VM), biceps femoris (BF) and semimembranous (SM) muscles of both lower limbs. Peak linear envelope (peakLE) and total muscle activity (iEMG) were extrapolated and normalised to a maximal voluntary contraction. Nonparametric Kruskal Wallace ANOVA tests were used and Wilcoxon rank sum tests were used to identify where significant (p < 0.05) differences occurred. The operated limb had significantly lower iEMG in the VAL, RF and BF muscles, and significantly lower peakLE in the SM muscle compared to the non-operated limb. The operated-limb of the MP group had significantly lower iEMG in the VAL and BF muscles, and significantly lower peakLE in the VAL, RF and SM muscles compared to the CTRL group. The non-operated limb in the MP group had significantly larger peakLE and iEMG in the RF muscle compared to the CTRL group. Differences in muscle activity between the operated and non-operated limbs in TKA patients with a MP implant demonstrates a compensatory strategy to reduce loading on the operated limb by relying on the non-operated limb. This same strategy has been reported in other studies investigating other functional tasks. This reliance on the non-operated limb resulted by having greater peakLE and iEMG in the RF muscle compared to the healthy CTRLs. These differences between limbs could also result from many years of muscle adaptation waiting to receive a knee replacement. In conclusion, TKA patients exhibit discrepancies in muscle activity compared to healthy knees and differences between operated and non-operated limbs. Post-surgery rehabilitation should rely on unilateral strength exercises of the quadriceps and hamstrings muscles to reduce discrepancies to allow for a more balanced muscle activity between limbs

Purpose. Investigating the effects of femoral stem length on hip and knee muscle strength. Methods. The study included 20 patients having undergone total knee prostheses (TKP) due to coxarthrosis and 10 healthy subjects. Of the 20 patients, 10 underwent conventional TKP and 10 had Thrust Plate Prothesis (TPP). For the assessment of the patients’ muscle strength of operated and non-operated hips (Gl. medius and Gl. Maximus) and knees (Quadriceps Femoris-QF), the Hand-Held Dynamometer (HHD) was used. Results. A significant difference was observed in the muscle strength of Gl. medius in TPP patients and of Gl. maksimus in conventional TKP patients (p <0.05). Compared to the healthy group, only hip muscle strength decreased in TPP patients, but both hip and knee muscle strengths decreased in conventional TKP patients (p <0.05). Conclusion. A decrease in hip and knee muscle strengths was determined in the TPP and conventional THA patients, compared to healthy subjects. Compared to the bone protective prosthetic systems (eg TPP), a significant difference is observed in the QF muscle strength in intramedullary prosthesis applications. This data may be used in planning the treatment of patients with hip arthroplasty

Introduction. The inferior/medial shift in the center of rotation (CoR) associated with reverse shoulder arthroplasty (rTSA) shortens the anterior and posterior shoulder muscles; shortening of these muscles is one explanation for why rTSA often fails to restore active internal/external rotation. This study quantifies changes in muscle length from offsetting the humerus in the posterior/superior directions using an offset humeral tray/liner with rTSA during two motions: abduction and internal/external rotation. The offset and non-offset humeral tray/liner designs are compared to evaluate the null hypothesis that offsetting the humerus in the posterior/superior direction will not impact muscle length with rTSA. Methods. A 3-D computer model was developed to simulate abduction and internal/external rotation for the normal shoulder, the non-offset reverse shoulder, and the posterior/superior offset reverse shoulder. Seven muscles were modeled as 3 lines from origin to insertion. Both offset and non-offset reverse shoulders were implanted at the same location along the inferior glenoid rim of the scapula in 20° of humeral retroversion. Muscle lengths were measured as the average of the 3 lines simulating each muscle and are presented as an average length over each arc of motion (0 to 65° abduction with a fixed scapula and 0 to 40° of internal/external rotation with the humerus in 0° abduction) relative to the normal shoulder. Results. Both the offset and non-offset reverse shoulders shifted the CoR medially by 27.1 mm and inferiorly by 4.5 mm relative to the normal shoulder. The offset humeral tray/liner shifted the humerus posteriorly and superiorly relative to the non-offset reverse shoulder. As depicted in Figures 1–3, the inferior shift in the CoR elongated the anterior, middle, and posterior heads of the deltoid for both the offset and non-offset reverse shoulders during both types of motions. The more superior position of the humerus with the offset tray elongating the deltoid less than did the non-offset tray. As depicted in Figures 2 and 3, the medial shift in the CoR shortened the subscapularis, infraspinatus, teres major, and teres minor for both the offset and non-offset reverse shoulders during both types of motions. However, the more posterior position of the humerus with the offset tray better restored the anatomic muscle length of all 7 muscles during both types of motion. Discussion and Conclusions. Offsetting the humerus in the posterior/superior direction using the offset humeral tray/liner altered muscle lengths and resulted in more anatomic muscle tensioning (e.g. each muscle length approached 0%) relative to the non-offset reverse shoulder. These observations related to muscle shortening may describe the mechanism for instability and poor internal/external rotation with rTSA; and if so, more anatomic muscle tensioning with the offset humeral tray offers the potential for improved internal/external rotation capability. Based upon these results, we reject the null hypothesis and conclude that offsetting the position of the humerus in the posterior/superior direction does impact muscle length with rTSA. Future work should evaluate the clinical significance of these observed changes in muscle length

Background. Loss of muscle mass (sarcopenia) and function in ageing are associated with reduced functional ability, quality of life and reduced life expectancy. In cancer patients, age related muscle loss may be exacerbated by cachexia and poor nutritional intake. Individuals with widespread disseminated disease are most prone to increasing functional decline, increased morbidity and accelerated death. However subjective assessments of physical performance have been shown to be poor indicators of life expectancy in these patients. Aims. To develop an objective measure to aid calculation of life expectancy in cancer by investigating the association between objectively measured lean muscle mass and longevity, in 41 patients with known spinal metastases from all cause primaries. Methods. Lean muscle mass was calculated as total psoas area (TPA)/height (m)2. Two blinded doctors independently calculated TPA from CT images at the L3 level, performed routinely within 7 days of diagnosis of spinal metastases. Time to death was recorded from retrospective analysis of hospital notes. Results. Of patients within the highest tertile for muscle mass 85% were alive at one year, compared with 50% in the lowest tertile. Conclusion. Death within one year in individuals with spinal metastases is significantly higher in patients with low lean muscle mass at presentation

Background:. The balance between the subscapularis muscle and the infraspinatus/teres minor muscles, often referred to as the rotator cuff ‘force couple’, has been proposed to be critical component for glenohumeral stability. Function of these muscles can be estimated with the evaluation of muscle atrophy. In clinical practice, muscle cross-sectional area (CSA) rather than 3D muscle volume measurement have been used because it is less time consuming. Because combined anthropometric measures of length and width more accurately define the muscular volume it seems logical to study the transversal rotator cuff force couple in the transversal plane an not in the sagittal plane of the body because both parameters can be included. But is it not clear which transversal CSA has the best correlation with muscle volume. Purpose:. To determine the optimal transversal CSA that has the best correlation with muscle volume. Material and Methods:. A total of 30 CT images containing the full scapula were used. Using Mimics® and 3-Matic® the correlation between CSA's and volume has been evaluated. Two methods have been evaluated. The first method was the CSA measured on transversal plane without 3D editing. The second method is a CSA measured on a new defined transversal plane using 3D reconstruction and reslice editing techniques. Results. Both techniques showed a very high inter and intraobserver reliability (ICC for single measures in both techniques > 0.97, p < 0.001). Correlation of the muscle volume/CSA of the subscapularis showed a high correlation in both the non-reconstructed (ρ = 0,699, p = 0,002) and reconstructed technique (ρ = 0,842, p < 0,001). Correlation of the muscle volume/CSA of the infraspinatus/teres minor showed a moderate correlation in the non-reconstructed (ρ = 0,591, p = 0,013) and a high correlation in reconstructed technique (ρ = 0,779, p < 0,001). There is a significant higher correlation with the volume with the reconstructed technique compared to the non-reconstructed technique (ρ = 0.638, p < 0.001 for the conventional transversal section versus ρ = 0.818, p < 0.001 for the resliced section). Conclusion. Muscular volume of the rotator cuff force couple can be quantified using a non-reconstructed CSA, but is significant more accurately quantified by a 3D reconstructed technique. In the future, balance of the force couple in different shoulder pathologies can be quantified with this measurement technique

Introduction. Reverse shoulder arthroplasty (rTSA) increases the deltoid abductor moment arm length to facilitate the restoration of arm elevation; however, rTSA is less effective at restoring external rotation. This analysis compares the muscle moment arms associated with two designs of rTSA humeral trays during two motions: abduction and internal/external rotation to evaluate the null hypothesis that offsetting the humerus in the posterior/superior direction will not impact muscle moment arms. Methods. A 3-D computer model simulated abduction and internal/external rotation for the normal shoulder, the non-offset reverse shoulder, and the posterior/superior offset reverse shoulder. Four muscles were modeled as 3 lines from origin to insertion. Both offset and non-offset reverse shoulders were implanted at the same location along the inferior glenoid rim of the scapula in 20° of humeral retroversion. Abductor moment arms were calculated for each muscle from 0° to 140° humeral abduction in the scapular plan using a 1.8: 1 scapular rhythm. Rotation moment arms were calculated for each muscle from 30° internal to 60° external rotation with the arm in 30° abduction. Results. During abduction with the normal shoulder, the subscapularis and infraspinatus act as abductors throughout the range of motion and the teres minor converts from an adductor to abductor at 60°. In the non-offset reverse shoulder, the subscapularis converts from an adductor to abductor at 82°, the infraspinatus converts at 68°, and the teres minor converts at 135°. Because the offset humeral tray shifts the humerus superiorly relative to the non-offset tray, each muscle converts from an adductor to abductor earlier in abduction, where the subscapularis converts at 62°, the infraspinatus converts at 43°, and the teres minor converts at 110°. During rotation (Figures 1–3), both the offset and non-offset reverse shoulders decrease the internal rotation capability of the subscapularis and teres major but increase the external rotation capability of the infraspinatus and teres minor relative to the normal shoulder. Because the offset tray shifts the humerus posteriorly, the internal rotation capability of the subscapularis and teres major is decreased by 7.1 and 9.5 mm while the external rotation capability of the infraspinatus and teres minor is increased by 8.6 and 7.8 mm, respectively. Discussion and Conclusions. Changing humeral position using an offset humeral tray modified the function of each muscle. In abduction, the offset tray caused each muscle to convert from adductors to abductors earlier. Improved abduction capability limits each muscle's antagonistic behavior with the deltoid, potentially reducing the deltoid force required to elevate the arm. In rotation, the offset tray caused the posterior shoulder muscles to be more effective external rotators. Improved external rotation capability is important for patients with external rotation deficiency; as external rotation is required for many activities of daily living, increasing the rotator moment arm lengths of the only two external rotators is advantageous to restore function. Therefore, we reject the null hypothesis and conclude the offset humeral tray does impact muscle moment arms with rTSA. Future work should evaluate the clinical significance of these observed changes in muscle moment arms

The Stanford Upper Extremity Model (SUEM) (Holzbauer, Murray, Delp 2005, Ann Biomed Eng) includes the major muscles of the upper limb and has recently been described in scientific literature for various biomechanical purposes including modeling the muscle behavior after shoulder arthroplasty (Hoenecke, Flores-Hernandez, D'Lima 2014, J Shoulder Elbow Surg; Walker, Struk, Banks 2013, ISTA Proceedings). The initial publication of the SUEM compared the muscle moment arm predictions of the SUEM against various moment arm studies and all with the scapula fixed. A more recent study (Ackland, Pak, and Pandy 2008, J Anat) is now available that can be used to compare SUEM moment arm predictions to cadaver data for similar muscle sub-regions, during abduction and flexion motions, and with simulated scapular motion. SUEM muscle moment arm component vectors were calculated using the OpenSim Analyze Tool for an idealized abduction and an idealized flexion motion from 10° to 90° that corresponded to the motions described in Ackland for the cadaver arms. The normalized, averaged muscle moment arm data for the cadavers was manually digitized from the published figures and then resampled into uniform angles matching the SUEM data. Standard deviations of the muscle moment arms from the cadaver study were calculated from source data provided by the study authors. Python code was then used to calculate the differences, percent differences, and root-mean-square (RMS) values between the data sets. Of the 14 muscle groups in the SUEM, the smallest difference in predicted and measured moment arm was for the supraspinatus during the abduction task, with an RMS of the percent difference of 11.4%. In contrast, the middle latissimus dorsi had an RMS percent difference over 400% during the flexion task. The table presents the RMS difference and the RMS of the percent difference for the muscles with the largest abduction and adduction moment arms (during abduction) and the largest flexion and extension moment arms (during flexion). The moment arm data for the SUEM model and the cadaver data (with 1 standard deviation band) during the motion of the same muscles are provided in Figure 1 for the Abduction motion task and in Figure 2 for the Flexion motion task. It is challenging to simulate the three dimensional, time variant geometries of shoulder muscles while maintaining model fidelity and optimizing computational cost. Dividing muscles in to sub regions and using wrapping line segment approximations appears a reasonable strategy though more work could improve model accuracy especially during complex three dimensional motions

Introduction. Total knee arthroplasty (TKA) is a well proven surgical procedure. Squat and gait motions are common activities in daily life. However, squat motion is known as most dissatisfying motion in activities in daily life after total knee arthroplasty (TKA). Dissatisfaction after TKA might refer to muscle co-contraction between quadriceps and hamstrings. The purposed of this study was to develop squat and gait simulation model and analyses the contact mechanics and quadriceps and hamstring muscle stability. We hypothesized that squat model shows larger contact forces and lower hamstring to quadriceps force ratio than gait model. Materials and Methods. Squat motion and gait model were simulated in musculoskeletal simulation software (AnyBody Modeling System, AnyBody Technology, Denmark). Subject-specific bone models used in the simulation were reconstructed from CT images by Mimics (Materialize, Belgium). The lower extremity model was constructed with pelvis, femur, tibia, foot segments and total knee replacement components: femoral component, tibial insert, tibial tray, and patella component [Fig.1]. The muscle model was consisted of 160 muscle elements. The TKR components used in this study are PS-type LOSPA Primary Knee System (Corentec Co., Ltd, Republic of Korea). Force-dependent kinematics method was used in the simulation. The model was simulated to squat from 15° to 100° knee flexion, in 100 frames. Gait simulation model was based on motion capture and force-plate system. Motion capture and force-plate data were from grand challenge competition dataset. Results / Discussion. Patellofemoral contact forces ranged from 0.18 to 3.78 percent body weight (%BW) and from 0.00 to 1.36 %BW during squat motion and gait cycle, respectively. Patellofemoral contact forces calculated at 30°, 60°, and 90° flexion during squat motion were 0.53, 1.93, and 3.22 %BW, respectively. Wallace et al. also reported patellofemoral contact forces at 30°, 60°, and 90° flexion, which were 0.31, 1.33, 2.45 %BW during squat motion. Our results showed similar results from other studies, however the squat model overestimated the patellofemoral contact forces. Contact stiffness in the simulation model might affected the overestimated contact forces. Hamstring to quadriceps force ratio ranged from 0.32 to 1.88 for squat model, and from 0.00 to 2.54 for gait model. As our hypothesis, squat motion showed larger patellofemoral contact forces. Also, mean hamstring to quadriceps force ratio of squat model were about half than the mean hamstring to quadriceps force ratio of gait model. From the results, possibility exists that unbalanced force of quadriceps and hamstring can affect dissatisfaction after TKA while squat motion is the most dissatisfying motion after TKA. However, muscle stability is not the only factor that can affect dissatisfaction after TKA. In future study, more biomechanical parameters should be evaluated to find meaningful dissatisfying factor after TKA. Conclusion. In conclusion, TKA musculoskeletal models of squat and gait motion were constructed and patellofemoral contact force / hamstring to quadriceps force ratio were evaluated. Patellofemoral mechanics were validated by comparison of previous study. Additional studies are needed to find dissatisfying factor after TKA