Exposure to a workday environment results in an increase in anterior tilting of the scapula in dental hygienists with greater employment experience

Background

Dental hygienists suffer a high incidence of shoulder pathology that seems to increase with job longevity. It has been hypothesized that occupational injuries could be due to local muscle fatigue caused by repetitive low level work and awkward and constrained working postures. In the laboratory, scapular kinematics can be temporarily altered using fatiguing protocols. It is unknown whether or not workday fatigue causes changes to scapular kinematics. The aim of this study was to examine if changes in scapular tilt and rotation occurs after a workday in dental hygienists.

Methods

The pre and post workday scapular kinematics were recorded from dental hygienists using an electromagnetic tracking system. All data were recorded within the place of employment of the dental hygienist.

Results

Following the workday, there was significantly more scapular anterior tilt in dental hygienists (P < 0.05); however, no changes were found for upward or internal rotation. Greater kinematic differences were found for hygienists with greater job longevity.

Interpretation

The increase in scapular anterior tilting could be due to post workday fatigue. Anterior tilting of the scapula may have an influence on the development of subacromial impingement syndrome. Hygienists with greater duration of work experience may be at greater risk for developing shoulder injuries as they have more anterior tilting of the scapula post workday.     

Differences in scapular orientation,subacromial space and shoulder pain between the full can and empty can tests

Background

The empty and full can arm positions are used as diagnostic tests and in therapeutic exercise programs for patients with subacromial impingement syndrome. The adverse effects of these arm positions on the rotator cuff have not been fully described. The purpose of this investigation was to compare the acromio-humeral distance, three-dimensional scapular position, and shoulder pain during maximum isometric contractions in the empty and full can arm positions.

Methods

Subjects with subacromial impingement syndrome (n = 28) and a matched control group without shoulder pain (n = 28) participated. Acromio-humeral distance, scapular/clavicular positions and shoulder pain were measured during maximal isometric contractions in each position.

Findings

No difference was found in acromio-humeral distance (P = 0.314) between the arm positions or between the groups (P = 0.598). The empty can position resulted in greater scapular upward rotation (P < 0.001, difference = 4.9°), clavicular elevation (P < 0.001, difference = 2.7°), clavicular protraction (P = 0.001, difference = 2.5°) and less posterior tilt (P < 0.001, difference = 3.8°) than the full can position. No differences in the scapular positions were found between the groups. Positive correlations were seen between the scapular positions in the control and not in the subacromial impingement group.

Interpretation

Our results did not show a difference in acromio-humeral distance between the arm positions or groups, indicating that the kinematic differences between the positions are not associated with altered acromio-humeral distance. The increased pain in the EC position might be due to the lack of an association amongst the scapular positions rather than the deficiency of a single scapular motion.     

The role of the scapulo-thoracic and gleno-humeral joints in upper-limb motion in children with hemiplegic cerebral palsy

Background

The pathophysiology of abnormal shoulder motion in children with hemiplegic cerebral palsy is not yet well understood. The aim of this study was to compare the motion of the two principle shoulder joints in children with hemiplegic cerebral palsy and typically developing children.

Methods

10 children in each group carried out 6 tasks recorded by an optoelectronic system. The analysis protocol was based on an acromion marker cluster, a functional method to determine the gleno-humeral rotation center and different Euler sequences thus providing three dimensional thoraco-humeral, scapulo-thoracic and gleno-humeral kinematics during upper-limb motion.

Findings

In the children with hemiplegic cerebral palsy, the scapulo-thoracic joint was more protracted (P < 0.05) and tended to be more laterally rotated depending on the tasks and the degree of humeral elevation. The gleno-humeral joint was limited in elevation (P < 0.09), internal rotation (P < 0.05) and plane of elevation (P < 0.05) depending on the task. At rest, the orientation of the arm was more related to the scapular posture than to the gleno-humeral orientation, the latter which appeared to compensate the initial internal arm rotation at the beginning of the motion.

Interpretation

The scapulo-thoracic joint plays a key role in arm posture at rest and during motion but does not seem to limit arm motion. The gleno-humeral joint compensates the scapula orientation at small degrees of humeral elevation but has a reduced total range of motion. Clinical management should focus on both joints taking into account their respective roles in upper-limb motion in this population.     

Quantifying scapula orientation and its influence on maximal hand force capability and shoulder muscle activity

Background

Non-neutral scapular orientations are often implicated as potential causes of shoulder pathologies. However, their specific influence on shoulder functional capabilities is largely unknown. This study objectively measured scapular orientation and quantified its influence on shoulder muscle activity levels and hand force capabilities during vertical and horizontal manual exertions.

Methods

Ten healthy male university students performed 24 exertions in combinations of scapular orientation (protracted, neutral and retracted), exertion direction (up, down, medial, lateral) and intensity (maximal or 40 N). Scapular orientation was quantified using an acromion marker cluster method. An orientation by intensity repeated measures ANOVA identified differences in quantified scapular orientation. A two-way multivariate ANOVA identified the influence of scapular orientation and hand force direction on muscle activity and hand force capability.

Findings

Participants assumed consistent retracted, neutral, and protracted scapular orientations during exertions, and these three orientations were different from each other (F(2, 99) = 158.57; P-value: 0.0001). Scapular orientation and exertion direction influenced muscle recruitment almost universally (P-value: 0.05). Scapular orientation did not influence hand force capability (F(2, 99)=1.34; P-value: 0.05), but a hand force direction effect on force existed (F(3, 99)=144.19; P-value: 0.0001).

Interpretation

These findings support recommendations of health practitioners who advocate neutral scapular orientations to reduce injury risk, as a neutral orientation achieved a balanced overall muscle use pattern between retraction and protraction. Also, lowered muscle activity and higher maximal forces suggest that downward exertion forces may be preferable when possible.     

Mechanical analysis of cuff tear arthropathy during multiplanar elevation with the AnyBody shoulder model

Background

This numerical study analysed the mechanics of cuff tear arthropathy with the AnyBody shoulder model.

Methods

The model simulated three frequent characteristics of cuff tear arthropathy: A supero-posterior massive rotator cuff tear, a proximal and static migration of the humeral head, and a contact between the humeral head and the scapula (glenoid &; acromion) with friction. The mechanics of the cuff tear arthropathy with and without friction were studied by analysing: the mechanics of the deltoid (i.e. length &; strength), the gleno-humeral and acromio-humeral contact forces, the friction moment, and the maximum elevation angle. Elevations in the frontal, scapular and sagittal planes were simulated.

Findings

Compared to an intact condition, the cuff tear arthropathy model without friction estimated a deltoid strength of − 18% (frontal = − 13%, scapular = − 17%, sagittal = − 25%), a gleno-humeral contact force of − 34% (frontal = − 60%, scapular = − 46%, sagittal = + 5%), estimated an acromio-humeral contact force of 240 N (frontal = 213 N, scapular = 184 N, sagittal = 324 N) and a maximum elevation angle of 77° (frontal = 80°, scapular = 87°, sagittal = 65°). Contact friction enhanced this behaviour, decreasing even more the gleno-humeral contact force and the maximum elevation angle, while increasing the acromio-humeral contact force.

Interpretation

This novel cuff tear arthropathy model suggests that friction and plane of elevation greatly influence the mechanics of the shoulder with cuff tear arthropathy. It also shows that the AnyBody simulation tool may be useful to study musculoskeletal pathologies and not only normal conditions.     

Biomechanical effects of joint line elevation in total knee arthroplasty

Background

Inadequate restoration of the knee joint line after total knee arthroplasty may lead to a poor clinical outcome. The purpose of this study was to quantitatively assess the effects of joint line elevation following total knee arthroplasty with increased joint volume on patellofemoral contact kinematics.

Methods

Six cadaveric specimens were tested. Patellofemoral contact area, contact pressure, and kinematics were measured following total knee arthroplasty with an anatomic joint line and after 4 and 8 mm of joint line elevation, at knee flexion angles of 0°, 30°, 60°, 90° and 120°. Repeated measures analysis of variance with a Tukey post hoc test with a significance level of 0.05 was used for statistical analyses.

Findings

There was a decrease in contact area with joint line elevation at flexion angles of 60°, 90° and 120° (P = 0.009–0.04). There was a significant increase in contact pressure only at 30° of knee flexion with 8 mm of joint line elevation (P = 0.004). Three of the six specimens showed inferior edge loading of the patella component following 8 mm of joint line elevation at 120° of knee flexion. The sagittal plane patellofemoral angle increased significantly with joint line elevation except for 0° knee flexion (P = 0.0002–0.02).

Interpretation

Knee joint line elevation with increased knee volume significantly affects patellofemoral contact area and kinematics and produced inferior edge loading/impingement between the patella and tibial components, this may result in loss of knee range of motion, postoperative pain, and premature component wear.     

Hamstrings loading contributes to lateral patellofemoral malalignment and elevated cartilage pressures: an in vitro study

Background

Hamstrings loading has previously been shown to increase tibiofemoral posterior translation and external rotation, which could contribute to patellofemoral malalignment and elevated patellofemoral pressures. The current study characterizes the influence of forces applied by the hamstrings on patellofemoral kinematics and the pressure applied to patellofemoral cartilage.

Methods

Ten knees were positioned at 40°, 60° and 80° of flexion in vitro, and loaded with 586 N applied through the quadriceps, with and without an additional 200 N applied through the hamstrings. Patellofemoral kinematics were characterized with magnetic sensors fixed to the patella and the femur, while the pressure applied to lateral and medial patellofemoral cartilage was measured with pressure sensors. A repeated measures ANOVA with three levels, combined with paired t-tests at each flexion angle, determined if loading the hamstrings significantly (P < 0.05) influenced the output.

Findings

Loading the hamstrings increased the average patellar flexion, lateral tilt and lateral shift by approximately 1°, 0.5° and 0.2 mm, respectively. Each increase was significant for at least two flexion angles. Loading the hamstrings increased the percentage of the total contact force applied to lateral cartilage by approximately 5%, which was significant at each flexion angle, and the maximum lateral pressure by approximately 0.3 MPa, which was significant at 40° and 60°.

Interpretation

The increased lateral shift and tilt of the patella caused by loading the hamstrings can contribute to lateral malalignment and shifts pressure toward the lateral facet of the patella, which could contribute to overloading of lateral cartilage.     

Three-dimensional scapular motion during arm elevation is altered in women with fibromyalgia

Background

The core feature of fibromyalgia is pain, which may play a role in various mechanisms that might lead to alterations in shoulder kinematics. Alterations in muscle activity and presence of tender points in the shoulder girdle have already been described in this population; however there is lack of evidence on three-dimensional scapular motion in women with fibromyalgia.

Methods

Forty women with fibromyalgia and 25 healthy women (control group) matched in terms of age, weight and height, took part in this study. Three-dimensional scapular kinematics of the dominant arm were collected during elevation and lowering of the arm in the sagittal and scapular planes. Pain was evaluated by the Visual Analogue Scale and the Numerical Pain Rating Scale. Group comparisons were performed with one-way ANOVA for pain and two-way ANOVA for the kinematic variables (scapular internal/external rotation, upward/downward rotation and anterior/posterior tilt), with group and humeral elevation angle as categorical factors. Significance level was set at P < 0.05.

Findings

Fibromyalgia women presented higher pain scores (P < 0.001) than the control group. Fibromyalgia women also presented greater scapular upward rotation (P < 0.001, both planes) and greater scapular posterior tilt (P < 0.001, both planes) than the control group.

Interpretation

Women with fibromyalgia present greater scapular upward rotation and posterior tilt in the resting position and during arm elevation and lowering of the arm in sagittal and scapular planes. These alterations may be a compensatory mechanism to reduce pain during arm movement.     

Biomechanical changes accompanying unilateral and bilateral use of laterally wedged insoles with medial arch supports in patients with medial knee osteoarthritis

Background

Laterally wedged insoles have controversial effect in treating medial compartment knee osteoarthritis. This study examined the effects of unilateral and bilateral use of insoles having medial arch supports and of different inclinations on the frontal plane external hip, knee, subtalar moments and pelvic alignment.

Methods

Kinetic and kinematic gait parameters were collected from 21 patients with primary medial knee osteoarthritis. The insoles' inclinations were 0, 6 and 11°, where each of the 6° and 11° was used once unilaterally and another bilaterally while the 0° was used bilaterally as a control.

Findings

The Multivariate Analysis of Variance revealed significant increase in the external subtalar eversion moment using either of the 6° or 11° laterally wedged vs the 0° non-wedged insole conditions (P = 0.003). Moreover, there were significant increases in the external eversion moment using the 11° vs the 6° insole conditions (P < 0.05). However, there were no significant differences for the remaining tested variables (P > 0.05). The bivariate correlations revealed significant negative correlations between the subtalar eversion and knee adduction moments (r = − 0.409, P = 0.000) and the subtalar eversion and hip adduction moments (r = − 0.226, P = 0.049), and positive correlation between the hip and knee adduction moments (r = 0.268, P = 0.019).

Interpretation

The non-significant reduction in the external knee adduction moment may question the efficacy of using wedged insoles having medial arch supports in treating patients with medial knee osteoarthritis. Additionally, using such insoles did not produce appreciable mechanical effects on remote articulations as the hip and pelvis.     

The effects of spinal posture and pelvic fixation on trunk rotation range of motion

Background

Axial rotation of the trunk is important to many vocational tasks and activities of daily living, and may be associated with back injuries. The influence of spinal postures on trunk rotation appears conflicting. This study investigated the influence of forward trunk inclination, spinal posture and pelvic fixation on maximum trunk rotation.

Methods

Twenty male participants were assessed using an optoelectronic motion-analysis system to track trunk movement during maximal trunk rotations in different spinal positions within the sagittal plane. A repeated-measures multivariate analysis of variance investigated the effects of forward trunk inclination, spinal posture and pelvic fixation on trunk and pelvic rotation. Test–retest reliability was determined using interclass correlation coefficients and standard error of measurement.

Findings

Forward trunk inclination at 45° yielded a 19% (6.2°; P < 0.001) increase in trunk rotation and a 40% (25.5°; P < 0.001) decrease in pelvic rotation when compared to standing. When flexing and extending the spine at a forward trunk inclination of 45° there was a 5% (1.9°; P < 0.01) and a 4% (1.6°; P < 0.05) decrease in trunk rotation. Fixing the pelvis increased the trunk rotation by up to 9% (3.3°; P < 0.001).

Interpretation

Inclining the trunk forward and maintaining a neutral spine maximised trunk rotation range of motion (RoM). This has implications for educational programmes intended to maximise sporting performance. Within the clinical setting, unrestricted observation of trunk rotations is considered more appropriate as it may benefit the clinician in determining possible detrimental relative flexibilities that may exist within the body.     

Kinematic patterns in normal and degenerative shoulders. Part II: Review of 3-D scapular kinematic patterns in patients with shoulder pain,and clinical implications

Background

The global range of motion of the arm is the result of a coordinated motion of the shoulder complex including glenohumeral (GH), scapulothoracic, sternoclavicular and acromioclavicular joints.

Effects on tibiofemoral biomechanics from kneeling

Background

Repetitive kneeling in certain occupations, hobbies and cultures is associated with tibiofemoral joint osteoarthritis. The biomechanics of kneeling is therefore of interest. This cadaveric study investigated tibiofemoral joint contact areas, pressures, and kinematics in response to kneeling.

Methods

Five human cadaveric knees were subjected to simulated kneeling at flexion angles of 90°, 105°, 120°, and 135°. Different anterior forces were applied to the knee to simulate crouching (no force), double stance kneeling (339 N of force), and single stance kneeling (678 N of force). Tibiofemoral joint kinematics, contact areas, and pressures were measured.

Findings

Kneeling produced tibial posterior translation and external rotation. Posterior translation was significantly less at 90° than at higher flexion angles (P < 0.05). Posterior translation and external rotation were significantly greater moving from crouching to double stance kneeling when compared to moving from double to single stance kneeling (P < 0.05). Double and single stance kneeling increased contact areas and pressures significantly when compared to crouching (P < 0.05). Pressures also increased significantly moving from double to single stance kneeling (P < 0.05).

Interpretation

Kneeling produces less tibial posterior translation at 90° than at higher flexion angles primarily due to posterior cruciate ligament biomechanics. Tibial external rotation results from posterior cruciate ligament biomechanics and differences between medial and lateral compartment anatomy. Different anatomical constraints allow significantly less posterior translation and external rotation moving from double to single stance kneeling is a result of increased pressure with kneeling likely contributes to the development of tibiofemoral osteoarthritis, and single stance kneeling may be more deleterious than double stance kneeling.     

Influence of test temperature on biomechanical properties of all-inside meniscal repair devices and inside-out meniscus sutures--evaluation of an isolated distraction loading, worst-case scenario

Background

Studies on the biomechanical properties of meniscus repairs are usually performed at room instead of body temperature. However, various all-inside meniscal repair devices include bioabsorbable materials, which are mechanically sensitive to higher environmental temperatures. Therefore, we hypothesize that current test standards may systematically lead to a false overestimation of their performance.

Methods

In 84 cadaveric bovine lateral menisci, an artificial vertical lesion was repaired with different all-inside meniscal repair devices (FasT-Fix, FasT-Fix AB, RapidLoc, Meniscus Arrow, Meniscus Screw) compared to a vertical inside-out Ethibond Excel 2.0 suture loop. Maximum load-to-failure, stiffness, and failure mode were tested in a uniaxial distraction loading at 20 °C and 37 °C.

Findings

Most of the tested implants were not susceptible to the higher environmental test temperature with respect to maximum load-to-failure, stiffness, and failure mode. Only the RapidLoc showed a significantly decreased stiffness (- 28.1%) and a statistical trend to lower maximum load-to-failure (- 20.6%) at 37 °C compared to 20 °C.

Interpretation

20 °C environmental temperature seems to be an acceptable test condition for the most meniscal repair devices. However, if the bioabsorbable part of the implant is the weakest link, body temperature may be considered for testing to prevent false overestimation of the biomechanical properties. For future biomechanical in vitro testing of meniscal repair devices, this study may provide novel insight into biomechanical test protocols for considering the environmental test temperature as an influencing factor of the biomechanical properties of especially bioabsorbable meniscal repair devices.     

Risk of edge-loading and prosthesis impingement due to posterior pelvic tilting after total hip arthroplasty

Background

Proper implant orientation is essential for avoiding edge-loading and prosthesis impingement in total hip arthroplasty. Although cup orientation is affected by a change in pelvic tilt after surgery, it has been unclear whether surgeons can prevent impingement and edge-loading by proper positioning by taking into account any change in pelvic alignment associated with alteration of hip range of motion.

Methods

We simulated implant orientation without edge-loading and prosthesis impingement, even with a change in pelvic tilt and associated change in hip range of motion after surgery, by collision detection using implant models created with computer-aided design.

Findings

If posterior pelvic tilting with a corresponding hyperextension change in hip range of motion after surgery remains within 10°, as occurs in 90% of cases, surgeons can avoid edge-loading and impingement by correctly orienting the implant, even when using a conventional prosthesis. However, if a 20° change occurs after surgery, it may be difficult to avoid those risks.

Interpretation

Although edge-loading and impingement can be prevented by performing appropriate surgery in most cases, even when taking into account postoperative changes in pelvic tilt, it may also be important to pay attention to spinal conditions to ensure that pelvic tilting is not extreme because of increasing kyphosis.     

Alterations in in vivo knee joint kinematics following a femoral nerve branch block of the vastus medialis: Implications for patellofemoral pain syndrome

Background

A potential source of patellofemoral pain, one of the most common problems of the knee, is believed to be altered patellofemoral kinematics due to a force imbalance around the knee. Although no definitive etiology for this imbalance has been found, a weak vastus medialis is considered a primary factor. Therefore, this study's purpose was to determine how the loss of vastus medialis obliquus force alters three-dimensional in vivo knee joint kinematics during a volitional extension task.

Methods

Eighteen asymptomatic female subjects with no history of knee pain or pathology participated in this IRB approved study. Patellofemoral and tibiofemoral kinematics were derived from velocity data acquired using dynamic cine-phase contrast MRI. The same kinematics were then acquired immediately after administering a motor branch block to the vastus medialis obliquus using 3–5 ml of 1% lidocaine. A repeated measures analysis of variance was used to test the null hypothesis that the post- and pre-injection kinematics were no different.

Findings

The null hypothesis was rejected for patellofemoral lateral shift (P = 0.003, max change = 1.8 mm, standard deviation = 1.7 mm), tibiofemoral lateral shift (P < 0.001, max change = 2.1 mm, standard deviation = 2.9 mm), and tibiofemoral external rotation (P < 0.001, max change = 3.7°, standard deviation = 4.4°).

Interpretation

The loss of vastus medialis obliquus function produced kinematic changes that mirrored the axial plane kinematics seen in individuals with patellofemoral pain, but could not account for the full extent of these changes. Thus, vastus medialis weakness is likely a major factor in, but not the sole source of, altered patellofemoral kinematics in such individuals.     

Effects of unloading bracing on knee and hip joints for patients with medial compartment knee osteoarthritis

Background

Osteoarthritis affects the whole body, thus biomechanical effects on other joints should be considered. Unloading knee braces could be effective for knee osteoarthritis, but their effects on the contralateral knee and bilateral hip joints remain unknown. This study investigated the effects of bracing on the kinematics and kinetics of involved and contralateral joints during gait.

Methods

Nineteen patients with medial compartment knee osteoarthritis were analysed. Kinematics and kinetics of the knee and hip joints in frontal and sagittal planes were measured during walking without and with bracing on the more symptomatic knee.

Findings

The ipsilateral hip in the braced condition showed a lower adduction angle by an average of 2.58° (range, 1.05°–4.16°) during 1%–49% of the stance phase, and a lower abduction moment at the second peak during the stance phase than the hip in the unbraced condition (P < 0.05 and P < 0.005, respectively). With bracing, the contralateral hip showed a more marked peak extension moment and lower abduction moment at the first peak (P < 0.05), and the contralateral knee adduction angle increased by an average of 0.32° (range, 0.21°–0.45°) during 46%–55% of the stance phase (P < 0.05), compared to no bracing.

Interpretation

Unloading bracing modified the contralateral knee adduction angle pattern at a specific time point during gait. It also affected the frontal plane on the ipsilateral hip and the frontal and sagittal planes on the contralateral hip joint. Consideration should be provided to other joints when treating knee osteoarthritis.     

Body temperature regulation and outcome after cardiac arrest and therapeutic hypothermia

Objective

Therapeutic temperature modulation is recommended after cardiac arrest (CA). However, body temperature (BT) regulation has not been extensively studied in this setting. We investigated BT variation in CA patients treated with therapeutic hypothermia (TH) and analyzed its impact on outcome.

Methods

A prospective cohort of comatose CA patients treated with TH (32–34 °C, 24 h) at the medical/surgical intensive care unit of the Lausanne University Hospital was studied. Spontaneous BT was recorded on hospital admission. The following variables were measured during and after TH: time to target temperature (TTT = time from hospital admission to induced BT target <34 °C), cooling rate (spontaneous BT − induced BT target/TTT) and time of passive rewarming to normothermia. Associations of spontaneous and induced BT with in-hospital mortality were examined.

Results

A total of 177 patients (median age 61 years; median time to ROSC 25 min) were studied. Non-survivors (N = 90, 51%) had lower spontaneous admission BT than survivors (median 34.5 [interquartile range 33.7–35.9] °C vs. 35.1 [34.4–35.8] °C, p = 0.04). Accordingly, time to target temperature was shorter among non-survivors (200 [25–363] min vs. 270 [158–375] min, p = 0.03); however, when adjusting for admission BT, cooling rates were comparable between the two outcome groups (0.4 [0.2–0.5] °C/h vs. 0.3 [0.2–0.4] °C/h, p = 0.65). Longer duration of passive rewarming (600 [464–744] min vs. 479 [360–600] min, p < 0.001) was associated with mortality.

Conclusions

Lower spontaneous admission BT and longer time of passive rewarming were associated with in-hospital mortality after CA and TH. Impaired thermoregulation may be an important physiologic determinant of post-resuscitation disease and CA prognosis. When assessing the benefit of early cooling on outcome, future trials should adjust for patient admission temperature and use the cooling rate rather than the time to target temperature.     

Heating of gases during neonatal resuscitation: a bench study

Aim

Standard practice within the neonatal unit is to use heated humidified gas as it decreases respiratory complications in neonates requiring respiratory support. Using cold unhumidified gases during resuscitation could potentially cool the baby as well as exacerbate potential lung injury. We aimed to study the temperature and humidity aspects of using heated, humidified gas for neonatal resuscitation.

Methods

A heated patient circuit was connected to a T-piece resuscitator via a humidifier. An oxygen flowmeter was set at 10 L/min. Temperature recordings at the humidifier chamber (T1), distal temperature probe (T2) and T-piece (T3) were taken over 20 min at 30 s intervals. A humidity sensor was placed at T3.

Results

Target temperatures were not reached. Time to 36 °C (mean (sd)): T1 11.1 min (1.71); T3 11.6 min (1.77). T2 took 13.6 min (1.07) to reach 39 °C. T1 and T3 were within ±1 °C at 5.1 min (0.6). A biphasic relationship demonstrated the time lag between the temperatures of the heated patient circuit and the humidifier chamber. T3 strongly correlated to T1 when T1 is ≥28 °C (r² = 0.85). Humidity was difficult to measure and results were inferred from temperature recordings.

Conclusion

This in vitro test showed that heated, humidified gas is possible during neonatal resuscitation. Adequate time must be allowed for the humidifier chamber to warm to near optimal temperature. The patient circuit is initially heated faster than the humidifier chamber. The displayed T1 temperature correlates to the temperature at T3 at ≥28 °C.     

Finite element model of the proximal femur under consideration of the hip centralizing forces of the iliotibial tract

Background

The aim of our investigations was the development of a finite element model of the hip joint under consideration of the hip centralizing forces of the iliotibial tract within different femoral neck angles and its influence to the centralizing of the femoral head to the acetabulum.

Methods

For the development of the finite element model of the femur and the iliotibial tract we utilized the program IDEAS 3D as well as the material/lengthening characteristics of the iliotibial tract. In the following step we developed a hip joint model with different centrum-collum-diaphysis-angles of 115°, 128° and 155° for determination of the IT force and the consequential force on the femoral head.

Findings

With a coxa vara the force on the femoral head in relation to the physiological centrum-collum-diaphysis-angle and the coxa valga decreased (115° = 1601 N, 128° = 2360 N, and 155° = 2422 N). On the other side the hip centralizing forces of the iliotibial tract within a coxa vara increased in comparison to 128° (physiological) and 155° (valga) (115° = 997 N, 128° = 655,5 N, and 155° = 438 N). Within a coxa valga a higher compressive force on the femoral head and with a coxa vara a decreasing compressive force on the femoral head occurred.

Interpretation

The clinical relevance consists in the predictability of an increasing or decreasing band wiring effect of the iliotibial tract in reliance to the centrum-collum-diaphysis-angle of the femoral neck and its importance for the displacement osteotomy of the growing hip.     

Biomechanical evaluation of two intramedullary nailing techniques with different locking options in a three-part fracture proximal humerus model

Background

Osteosynthesis of unstable proximal humerus fractures still remains challenging. The aim of this study was to investigate two intramedullary nailing techniques with different locking options in a three-part fracture model and prove whether two new fixation concepts, introducing additional locking screw-in-screws inserted through the head of the proximal screws, and a calcar screw, provide better stability.

Methods

A biomechanical testing model for three-part proximal humerus fractures including cyclic axial loading with increasing peak load and simultaneous pulling forces at the rotator cuff was used to test 12 pairs of human cadaver humeri, assigned to four groups and instrumented with either Targon PH (T1) or MultiLoc PHN in 3 different configurations (standard M1; two additional screw-in-screw M2; one additional calcar screw and two screw-in-screw M3).

Findings

Initial range of motion in internal–external rotation and mediolateral translation was smallest in M3 (1.82°; 0.11 mm), biggest in T1 (3.63°; 0.51 mm) and significantly different between these two groups (p = 0.02 and p = 0.04, respectively). M3 showed minimum head migration along the nail and varus tilting after 5000 cycles (0.31 mm; 0.20°) and 10000 cycles (1.59 mm; 0.34°). M2 and M3 performed better than M1 and T1 regarding varus collapse. The highest number of cycles to failure was observed for M3 (20733) and the lowest for T1 (10083) with significant difference between these two groups (p = 0.04).

Interpretation

The configuration with two screw-in-screw and a calcar screw was superior in most aspects. The screw-in-screws were found to contribute against varus collapse. Both new fixation concepts could provide better stability in proximal humerus fractures.