Contact Area Pressure Research Articles

Test–retest reliability of the Tekscan® F-Scan® 7 in-shoe plantar pressure system during treadmill walking in healthy recreationally active individuals

In-shoe plantar pressure systems are commonly used in clinical and research settings to assess foot function during functional tasks. Recently, Tekscan® has updated their F-Scan® in-shoe plantar pressure system; however, this system’s test–retest reliability has not been established. Therefore, the purpose of this study was to determine the test–retest reliability of the F-Scan® 7 system in recreationally active individuals during treadmill walking. Seventeen healthy adults completed 2 sessions of treadmill walking. For each session, participants were fitted for shoes and pressure insoles and walked on a treadmill at a self-selected pace for 30 s. Following the sessions, the test–retest reliability peak pressure, pressure time integral, average pressure and pressure contact area over 4 regions of the foot (heel, mid-foot, forefoot and toes) was assessed by calculating intraclass coefficients (ICC 2,k) and coefficient of variation percentage (CoV%). Pressure contact area consistently had the highest ICCs and lowest CoV% (ICCs: 0.91–0.98; CoV%: 2.7–7.8%). Whereas, the forefoot and toe regions had the highest ICCs for all 4 measures (ICCs: 0.83–0.98; CoV%: 3.1–13.4%). During treadmill walking in healthy recreationally active individuals, the reliability of the new Tekscan F-Scan® ranged from poor to high and was dependent on the measure and region of the foot.

Bone plug versus Suture-Only Fixation of Medial Meniscus Allograft Transplantation. Biomechanical Study

Objectives:Our objective was to evaluate the contact load characteristics of medial meniscus allograft transplantation performed by bone-plug versus soft-tissue suture-only fixation in cadaveric knees. Our null hypothesis was that there would not be significant differences between the two fixation groups with regard to load contact pressures and distribution.Methods:Experimental laboratory study in nine fresh-frozen human cadaveric knees (mean age 46.3 years, range 41-50; 5 female). None had cartilage, ligament or meniscal lesions as evaluated by XR and MRI exam. Fresh-frozen, size- and side-matched medial meniscus allografts were obtained based on XR measurements (Pollard method). The knees were secured in a load apparatus where rotation, flexion, extension and tilt were adjusted to ensure correct knee alignment during loading. The tibiofemoral joint surface was oriented parallel to the floor while the femur was placed in three positions: 0, 30 and 60 degrees. A 700N load was applied axially through the knee. Mean and Peak Contact Pressure and contact area were measured with an I-scan pressure sensor-4011 (Tekscan, Boston / MA) placed underneath the medial meniscus through a small capsular incision. The same protocol was applied for each condition: native meniscus, meniscectomy, meniscal allograft transplantation with bone plug (MAT-bone) and with suture-only fixation (MAT-suture). Two measurements were taken under each testing condition. Meniscus transplants were first secured with bone plugs and capsular sutures, and measurements taken. Then, the bone plugs were carefully removed from the meniscal roots and the recipient slots in the tibial plateau filled with cement. The roots were then re-secured with trans-tibial suture-only fixation. The results of mean and peak contact stress and contact area were compared between intact, meniscectomized, MAT-bone and MAT-suture using analysis of variance (ANOVA). The level of significance was set at lower than p0.05.Results:Meniscectomy significantly increased mean contact pressure and the contact area was significant reduced in comparison with the native condition at 0,30 and 60 degrees (p.001). Although the peak contact pressure was higher in the meniscectomy group, it was not statistically significant. Suture-only fixation resulted in slightly higher contact pressure and smaller contact area than bone plug fixation. No significant differences were found for mean and peak contact pressures and contact area between MAT-bone and MAT-suture. Also, regardless of technique, no significant differences were found between transplanted meniscus and native condition. The only exception occurred in 0 degrees of flexion, where MAT-suture demonstrated a statistically significant smaller contact area when compared with the native meniscus (p.016).Conclusion:This study demonstrated that meniscal allograft transplantation can restore load parameters close to the native condition. No significant differences were detected between bone-plug and soft-tissue fixation. This study is unique in utilizing size-matched meniscal transplants and using the same transplant for bone plug and suture-only fixation, thus reducing confounding factors.

FEA of a Double-Point Contact Elastomeric Gasket Considering Corrosion of Counterparts and Tilting during Assembly

The novel geometry of a gasket’s cross-section to optimize the sealing performance was proposed in spite of corrosion of its counterparts or tilted assembly. EPDM was applied for the rubber material and the sealing performance including stress, strain and contact pressure was estimated by finite element analysis (FEA) in both cased of normal and tilted assemblies. If the gaskets were to be normally assembled in the grooves, both gaskets (single-point contact and double-point contact) could be utilized for sealing systems. Even at the tilted assembly, the double-point contact gasket showed two discrete contact pressure areas; thus it could maintain its sealing performance over time at various operating conditions, compared to the single-point gasket.

The influence of water, snow and granular ice on ice failure processes, ice load magnitude and process pressure

This paper describes the outcomes of a series of laboratory ice crushing experiments that was performed (Sopper, 2016) to investigate the effects of external boundary condition and indenter contact geometry on ice load magnitude under crushing conditions. Four boundary conditions were considered: dry cases, submerged cases, and cases with the presence of snow and granular ice material on the indenter surface. Indenter geometries were a flat plate, wedge shaped indenter, (reverse) conical indenter, and a hemispherical indenter. These were impacted with artificially produced ice specimens of conical shape with 20° and 30° cone angles. All indenter – ice combinations were tested in dry and submerged environments at 1mm/s and 100mm/s indentation rates. Additional tests with the flat indentation plate were conducted at 10mm/s impact velocity and a subset of scenarios with snow and granular ice material was evaluated.The tests were performed using a material testing system (MTS) machine located inside a cold room at an ambient temperature of –7°C. Data acquisition comprised time, vertical force, and displacement. In several tests with the flat plate and wedge shaped indenter, supplementary information on local pressure patterns and contact area were obtained using tactile pressure sensors. All tests were recorded with a high speed video camera and still photos were taken before and after each test. Thin sections were taken of some specimens as well.Ice loads were found to strongly depend on contact condition, interrelated with pre-existing confinement and indentation rate. Submergence yielded higher forces, especially at the high indentation rate. This was very evident for the flat indentation plate and spherical indenter, and with restrictions for the wedge shaped indenter. No indication was found for the conical indenter. The presence of snow and granular ice significantly increased the forces at the low indentation rate (with the flat indentation plate) that were higher compared to submerged cases and far above the dry contact condition.Contact area measurements revealed a correlation of higher forces with a concurrent increase in actual contact area that depended on the respective boundary condition. In submergence, ice debris constitution, ice extrusion, as well as crack development and propagation were impeded. Snow and granular ice provided additional material sources for establishing larger contact areas. The dry contact condition generally had the smallest real contact area, as well as the lowest forces. The comparison of nominal and measured contact areas revealed distinct deviations which were dependent on the boundary conditions. The incorporation of those differences in contact process pressures-area relationships indicated that the overall process pressure was not substantially affected by changes in true contact area.

Mammographic compression in Asian women.

ObjectivesTo investigate: (1) the variability of mammographic compression parameters amongst Asian women; and (2) the effects of reducing compression force on image quality and mean glandular dose (MGD) in Asian women based on phantom study.MethodsWe retrospectively collected 15818 raw digital mammograms from 3772 Asian women aged 35–80 years who underwent screening or diagnostic mammography between Jan 2012 and Dec 2014 at our center. The mammograms were processed using a volumetric breast density (VBD) measurement software (Volpara) to assess compression force, compression pressure, compressed breast thickness (CBT), breast volume, VBD and MGD against breast contact area. The effects of reducing compression force on image quality and MGD were also evaluated based on measurement obtained from 105 Asian women, as well as using the RMI156 Mammographic Accreditation Phantom and polymethyl methacrylate (PMMA) slabs.ResultsCompression force, compression pressure, CBT, breast volume, VBD and MGD correlated significantly with breast contact area (p<0.0001). Compression parameters including compression force, compression pressure, CBT and breast contact area were widely variable between [relative standard deviation (RSD)≥21.0%] and within (p<0.0001) Asian women. The median compression force should be about 8.1 daN compared to the current 12.0 daN. Decreasing compression force from 12.0 daN to 9.0 daN increased CBT by 3.3±1.4 mm, MGD by 6.2–11.0%, and caused no significant effects on image quality (p>0.05).ConclusionsForce-standardized protocol led to widely variable compression parameters in Asian women. Based on phantom study, it is feasible to reduce compression force up to 32.5% with minimal effects on image quality and MGD.

Effects of bruxism on the maximum bite force

Background/Aim. Bruxism is a parafunctional activity of the masticatory system, which is characterized by clenching or grinding of teeth. The purpose of this study was to determine whether the presence of bruxism has impact on maximum bite force, with particular reference to the potential impact of gender on bite force values. Methods. This study included two groups of subjects: without and with bruxism. The presence of bruxism in the subjects was registered using a specific clinical questionnaire on bruxism and physical examination. The subjects from both groups were submitted to the procedure of measuring the maximum bite pressure and occlusal contact area using a single-sheet pressure-sensitive films (Fuji Prescale MS and HS Film). Maximal bite force was obtained by multiplying maximal bite pressure and occlusal contact area values. Results. The average values of maximal bite force were significantly higher in the subjects with bruxism compared to those without bruxism (p &lt; 0.001). Occlusal contact area was significantly higher in the subjects suffering from bruxism (p &lt; 0.001), while the maximal bite pressure values did not show a significant difference between the studied groups (p &gt; 0.01). Maximal bite force was significantly higher in the males compared to the females in all segments of the research. Conclusion. The presence of bruxism influences the increase in the maximum bite force as shown in this study. Gender is a significant determinant of bite force. Registration of maximum bite force can be used in diagnosing and analysing pathophysiological events during bruxism.

Comparison of Plantar Pressure and Plantar Contact Area before and after Botulinum Toxin Type A(BoNT-A)Therapy in Stroke Patients with Lower Limb Spasticity

Comparison of Plantar Pressure and Plantar Contact Area before and after Botulinum Toxin Type A(BoNT-A)Therapy in Stroke Patients with Lower Limb Spasticity

Evaluation of the results of arthroscopic double row rotator cuff repair of isolated lesions

Background: Rotator cuff tears are one of the most common soft tissue injuries. The incidence of full thickness tears of the rotators cuff ranges from 5% to 40% of all cuff tears, and increasing in frequency with age. The double row (DR) rotator cuff (RC) repair technique has been developed to optimize healing biology at RC tendon insertion, by increasing pressurized contact area and mean foot print pressure. Patients and Methods: From 2012 to 2014 forty patients with full thickness rotator cuff tear were selected to undergo arthroscopic DR RC repair. All patients were examined clinically and neurologically after history taking. Plain radiography and MRI were done for all patients. All the operations were done under general anesthesia and in beech chair position. Evaluation of the results of this study based on, the University of California, Los Angeles (UCLA) score and Range of motion (ROM). Secondary outcome measures included a Visual Analogue Scale (VAS) for pain. Results: At the end of two years follow up, the average UCLA score was improved from 12 preoperative to 29.8 postoperative. The average abduction was improved from 90 degrees preoperative to 145 degrees postoperative. Secondary outcome measures showed that average Visual Analogue Scale for pain was 2.8.And Visual Analogue Scale for patients satisfaction was 8.8 at the end of follow up. Conclusion: Arthroscopic double row rotator cuff repair is a procedure with good post-operative functional outcome and low complications rate based on a short term follow-up.

Parametric analysis of mixed lubrication characteristics in work zone of strip rolling

A theoretical model for mixed lubrication with more accurate contact length has been developed based on the average volume flow model and asperity flattening model, and the lubricant volume flow rate and outlet speed ratio are determined by integrating differential equations based on rolling parameters. The lubrication characteristics at the roll−strip interface with different surface roughness, rolling speed, reduction and lubricant viscosity are analyzed respectively. Additionally, the average volume flow rates of lubricant under different rolling conditions are calculated and used to explain the change rule of lubrication characteristics. The developed scheme is able to determine the total pressure, lubricant pressure, film thickness and real contact area at any point within the work zone. The prediction and analysis of mixed lubrication characteristics at the interface is meaningful to better control the surface quality and optimize the rolling process.

Comparison of the efficiency of an extra-articular absorber system and high tibial osteotomy for unloading the medial knee compartment: an in vitro study.

The unloading effect of an extra-articular absorber system on the knee joint medial compartment was compared with high tibial osteotomy (HTO) under physiological conditions in vitro. Seven fresh-frozen cadaveric knees were used to test isokinetic flexion-extension motions under physiological loading using a biomechanical knee simulator. Tibiofemoral area contact and peak contact pressures were measured using pressure-sensitive film in the untreated medial compartment. Pressures were measured after KineSpring System implantation and HTO (5° and 10° correction angles) performed with an angular-stable internal fixator (Tomofix). Implantation of the unloading device resulted in significantly decreased medial compartment area contact pressure (Δ0.02±0.01MPa, p=0.001) and peak contact pressure (Δ0.3±0.1MPa, p=0.001) compared with the first test cycle results in the untreated knee. HTO significantly decreased the pressure (p=0.001). Compared with the first test cycle, HTO (5° correction angle) decreased the mean contact pressure by Δ0.03±0.01MPa and peak contact pressure by Δ0.3±0.01MPa. With a 10° correction angle, HTO decreased contact pressure by Δ0.04±0.02MPa and peak contact pressure by Δ0.4±0.1MPa compared with that at the 5° correction angle. Implantation of an extra-capsular unloading device resulted in a significant unloading effect on the medial compartment comparable to that achieved with HTO at 5° and 10° correction angles. Thus, implantation of an extra-articular, extra-capsular absorber could become the method of choice when treating patients with unicompartmental osteoarthritis that cannot be adequately treated by HTO because of their straight-leg axis.

Stratified effect of continuous bi-Gaussian rough surface on lubrication and asperity contact

Continuous bi-Gaussian reconstruction approach is applied to two simulated pure bi-Gaussian and four real worn surfaces. It is compared with segmented bi-Gaussian, ISO 13565-3 bi-Gaussian and Johnson reconstruction approaches in terms of surface property, lubrication and asperity contact. The results show that the continuous approach reproduces a surface in good agreement with the original in terms of maximum fluid pressure, cavitation ratio and lift load, because it serves as a concise way to achieve the high resemblance of surface property with the original surface as similar to the ISO approach. The segmented approach sometimes loses efficiency, and the Johnson approach generates a single-stratum surface with steep valleys, inducing large pressure spikes, large cavitation zone and large lift load. The superiority of the continuous approach can be drawn from the contact mechanics study on contact pressure and real contact area.

Compensatory load redistribution in Labrador retrievers when carrying different weights--a non-randomized prospective trial.

BackgroundRetrievers are dogs particularly bred to retrieve birds or other small game, for the retrieval, the dogs are typically sent to the place where the shot game has fallen or to search the field for the wounded but still live game in order to return them to the hunter as quickly as possible. Examples of game animals are pheasants, mallard ducks and rabbits. For training, dummies with a variety of weights are used to simulate the retrieval of various types of game. The aim of this non-randomized prospective study was to investigate if peak vertical force, vertical impulse and paw pressure contact area are increased in the forelimbs when carrying different weights, and if the symmetrical weight distribution between contralateral limb pairs is disturbed. Ten actively working Labrador retrievers were walked over a pressure plate with or without carrying 0.5, 2.0 and 4.0 kg dummies. The aim of this study was to determine if vertical ground reaction forces and paw pressure contact area are increased in the forelimbs when carrying different weights, and if symmetrical weight distribution is disturbed between contralateral limb pairs.ResultsPeak vertical force and vertical impulse were significantly increased in the forelimbs and decreased in the hindlimbs in all weight carrying conditions.ConclusionsThese results demonstrate the significant effects of carrying weight in the mouth on the ground reaction forces, which likely produce additional stress on the forelimb joints. Carry of game or a dummy is likely to alter the forelimb load distribution.

Patella tracking and patella contact pressure in modular patellofemoral arthroplasty: a biomechanical in vitro analysis.

In the recent years modular partial knee prosthesis with the opportunity to combine unicompartmental tibiofemoral (UKA) and patellofemoral prosthesis (PFJ) were introduced to the clinics. To date, little is known about the biomechanics of these bi-cruciate retaining prosthetic designs. Aim of this study was to evaluate the influence of a PFJ in bicompartmental arthroplasty (UKA+PFJ) on patella tracking and retropatella pressure distribution. A dynamic in vitro knee kinemator simulating an isokinetic extension cycle of the knee was used on eight knee specimen. Patella tracking and patellofemoral contact pressure were evaluated using pressure sensitive films after implantation of a medial UNI and after subsequent implantation of a PFJ. Whereas the area contact pressure remained the same after PFJ implantation, the contact area was reduced significantly and significantly elevated peak pressures were determined in deep flexion and close to extension. The patella tracking was not significantly altered, however, effects of edge loading could be shown. When using PFJ prosthesis, one must be aware of altered pressure introduction on the retropatella surface compared to the physiological situation. The elevated peak pressures and reduced contact area may be an argument for patella resurfacing and the problems of edge loading indicate that care must be taken on the correct implantation of the device with no implant overhang.

Biomechanical response of lumbar facet joints under follower preload: a finite element study.

BackgroundFacet joints play a significant role in providing stability to the spine and they have been associated with low back pain symptoms and other spinal disorders. The influence of a follower load on biomechanics of facet joints is unknown. A comprehensive research on the biomechanical role of facets may provide insight into facet joint instability and degeneration.MethodA nonlinear finite element (FE) model of lumbar spine (L1-S1) was developed and validated to study the biomechanical response of facets, with different values of follower preload (0 N,500 N,800 N,1200 N), under loadings in the three anatomic planes. In this model, special attention was paid to the modeling of facet joints, including cartilage layer. The asymmetry in the biomechanical response of facets was also discussed. A rate of change (ROC) and an average asymmetry factor (AAF) were introduced to explore and evaluate the preload effect on these facet contact parameters and on the asymmetry under different loading conditions.ResultsThe biomechanical response of facets changed according to the loading condition. The preload amplified the facet force, contact area and contact pressure in flexion-extension; the same effect was observed on the ipsilateral facet while an opposite effect could be seen on the contralateral facet during lateral bending. For torsion loading, the preload increased contact area, decreased the mean contact pressure, but had almost no effect on facet force. However, all the effects of follower load on facet response became weaker with the increase of preload. The greatest asymmetry of facet response could be found on the ipsilateral side during lateral bending, followed by flexion, bending (contralateral side), extension and torsion. This asymmetry could be amplified by preload in the bending (ipsilateral), torsion loading group, while being reduced in the flexion group.ConclusionsAn analysis combining patterns of contact pressure distribution, facet load, contact area and contact pressure can provide more insight into the biomechanical role of facets under various moment loadings and follower loads. The effect of asymmetry on facet joint response should be fully considered in biomechanical studies of lumbar spine, especially in post structures subjected to physiological loadings.Electronic supplementary materialThe online version of this article (doi:10.1186/s12891-016-0980-4) contains supplementary material, which is available to authorized users.

Measurement of the Temperature and Pressure Characteristics of the Car Seats - Relationship between Humans&lt;sup&gt;&lt;/sup&gt;

Research of the correlation of the biomechanical characteristic of a sitting human and car seat is based on measurements of several basic parameters, such as value of the area contact pressure, map of contact temperature, contact humidity, etc. So obtained map of surface each parameter which we can compare at a same time and so we can identify correlations between these parameters and biomechanical properties of human, e.g. human anatomy, the body forms, age, sex physique etc. Based on these analyzes is possible to optimize the levels of this parameters for obtaining the ideal seating comfort. The correlation between fatigue for the driver and sitting comfort is described in many publications dealing with this theme. However, a repeatability real experiment in a car is questionable [1]. It is therefore preferable to perform these measurements in the laboratory and simulate the same conditions as in moving car at a constant ambient temperature and humidity, with the same test persons. The most suitable is the use in the measurement of different types of car seats and various human.

Outcomes following arthroscopic transosseous equivalent suture bridge double row rotator cuff repair: a prospective study and short-term results.

Background: The transosseous-equivalent cross bridge double row (TESBDR) rotator cuff (RC) repair technique has been developed to optimize healing biology at a repaired RC tendon insertion. It has been shown in the laboratory to improve pressurized contact area and mean foot print pressure when compared with a double row anchor technique. Pressure has been shown to influence healing between tendon and bone, and the tendon compression vector provided by the transosseous-equivalent suture bridges may enhance healing. The purpose was to prospectively evaluate the outcomes of arthroscopic TESBDR RC repair. Methods: Single center prospective case series study. Sixty-nine patients were selected to undergo arthroscopic TESBDR RC repair and were included in the current study. Primary outcome measures included the Oxford Shoulder Score (OSS), the University of California, Los Angeles (UCLA) score, the Constant-Murley (CM) Score and Range of motion (ROM). Secondary outcome measures included a Visual Analogue Scale (VAS) for pain, another VAS for patient satisfaction from the operative procedure, EuroQoL 5-Dimensions Questionnaire (EQ-5D) for quality of life assessment. Results: At 24 months post-operative, average OSS score was 44, average UCLA score was 31, average CM score was 88, average forward flexion was 145°, average internal rotation was 35°, average external rotation was 79°, average abduction was 150°, average EQ-5D score was 0.73, average VAS for pain was 2.3, and average VAS for patient satisfaction was 9.2. Conclusion: Arthroscopic TESBDR RC repair is a procedure with good post-operative functional outcome and low re-tear rate based on a short term follow-up.

Improving PEM fuel cell performance and effective water removal by using a novel gas flow field

Distribution of reactant gases in polymer electrolyte membrane fuel cells (PEMFCs) plays an important role in current density distribution, temperature distribution, and water concentration. This claim is bound up with the local consumption of reactants and local transport of water through the membrane. Problems like flooding or drying of the membrane which may reduce the life time of the MEA can be associated to the non-uniformity of the above parameters. Optimization of the flow-field design is an applicable idea to prevent these undesired events. Channel to rib ratio is a remarkable factor of flow field design for increasing the performance and life time of PEM fuel cells. It is believed that decreasing the rib width will increase hydrogen concentration at the anode side, but near zero rib width value might crush the MEA layer at high pressure contact areas which is not appropriate. So defining an optimum channel to rib ratio is inevitable in fuel cell design. In this paper seven flow fields are analyzed and fuel cell performance is investigated at the optimum channel to rib ratio. The effects of flow fields on current density, mass fraction of reactant gases, water distribution and flooding are numerically verified. Moreover, the effects of stoichiometry, pressure and temperature on the cell performance are assessed. Ultimately the best flow field design is introduced according to the polarization curve.

Assessment of cartilage contact pressure and loading in the hip joint during split posture.

Given the crucial role of the mechanical behavior in the degenerative process of the hip joint, analyzing the contact mechanics in the articular layers during physical activities could contribute to understanding the pathology. Indeed, the development process of hip osteoarthritis generally evolves over a long time period, and therefore analyzing the mechanical behavior of the hip joint during extreme repetitive movements will be helpful to analyze degeneration causes. The aim of the study was to investigate the link between the excessive movements and the development of hip osteoarthritis. To individualize the analysis, we used a subject-specific and noninvasive approach based on finite element analysis and magnetic resonance imaging (MRI) data. The contact pressure distribution and loading conditions on the acetabular cartilage were assessed on eleven professional dancer subjects performing a split movement. This movement is frequently practiced (repetitive) by dancers during their daily exercises. Moreover, split postures are mostly characterized by high anatomical angles with subluxation (excessive). To ensure the motion accuracy, MRI data of the subjects were acquired in neutral and split positions performed inside the MRI scanner. Based on the reconstructed bone models from the MRI data, a motion tracking approach was used to compute the transformation between the two poses. To evaluate the contact during the split movement and to quantify the role of the labrum in the hip joint mechanics, additional simulations of two daily activities (walking and stand-up) were performed. Finally, a clinical study based on morphological and radiological analysis of the subjects was performed and validated by orthopedic surgeons and radiological experts to evaluate the proposed approach. The reconstructed split movement was characterized by high anatomical angles with a subluxation on the left hip. Consequently, strong deformations and pressures were observed during the simulation. The comparison of the simulation results of split posture and daily activities showed higher pressure and lower contact area during extreme movements. Moreover, the presence of labrum absorbed part of load and consequently decreased the predicted contact pressure and contact area on the acetabular cartilage. The comparison of the simulation results of the split posture and daily activities, as well as the correlation between the results of the analysis on extreme movement results and the clinical analysis performed by medical experts, strongly suggests that repetitive extreme movement could lead to early hip osteoarthritis.

Moberg Osteotomy Shifts Contact Pressure Plantarly in the First Metatarsophalangeal Joint in a Biomechanical Model.

A proximal phalangeal dorsiflexion osteotomy (Moberg osteotomy) is commonly used to treat hallux rigidus, but the mechanical explanation for its effectiveness is unclear. The purpose of our study was to test the effect of a Moberg osteotomy on first metatarsophalangeal joint contact mechanics. Ten cadaveric first ray specimens were dissected, with the medial band of the plantar aponeurosis preserved at its origin, and placed in a custom testing apparatus. Forefoot loads during mid-stance with the first metatarsal positioned at 10 degrees were simulated using a custom-made loading jig while contact mechanics were acquired with a thin pressure-sensitive sensor. A Moberg osteotomy was performed starting 9 mm distal to the proximal phalanx with excision of a 3-mm wedge of bone and fixated with a 2-mm Kirschner wire. The effect of the Moberg osteotomy was tested by reapplying the forefoot loads and acquiring the joint pressures. The center of pressure, peak pressure, and contact area were calculated. Paired t tests were performed to determine if the Moberg osteotomy affected joint contact mechanics. The Moberg osteotomy shifted the center of contact pressure on the proximal phalanx surface more plantarly (P < .01). However, the Moberg osteotomy did not affect the peak pressure (P = .62) or the joint contact area (P = .96). There were no differences in peak pressure or first MTPJ contact area, but a plantar shift in the center of pressure occurred after the Moberg osteotomy. The plantar cartilage, which is often spared from arthritic changes, may be preferentially loaded and the potential edge loading following cheilectomy may be avoided with the Moberg osteotomy secondary to the plantar shift of center of pressure.

Footprint Contact Area and Interface Pressure Comparison Between the Knotless and Knot-Tying Transosseous-Equivalent Technique for Rotator Cuff Repair

To quantify and compare the footprint contact area and interface pressure on the greater tuberosity between knotless and knot-tying transosseous-equivalent (TOE) repair using pressure-sensitive film. We used 11 pairs of fresh-frozen cadaveric shoulders (22 specimens), in which rotator cuff tears were created before repair. Each pair was randomized to either conventional medial knot-tying TOE repair (group A) or medial knotless TOE repair using the modified Mason-Allen technique (group B). Pressure-sensitive film was used to quantify the pressurized contact area and interface pressure between the greater tuberosity and supraspinatus tendon. The mean pressurized contact area was 33.2 ± 2.5 mm(2) for group A and 28.4 ± 2.4 mm(2) for group B. There was a significant difference between groups (P=.005). Although the overall contact configuration of both groups was similar and showed an M shape, group A showed a greater pressurized configuration around the medial row. The mean interface pressure was 0.20 ± 0.02 MPafor group A and 0.17 ± 0.02 MPa for group B. There was a significant difference between groups (P=.001). Contrary to our hypothesis, in this time-zero study, medial knotless TOE repair using a modified Mason-Allen suture produced a significantly inferior footprint contact area and interface pressure compared with conventional medial knot-tying TOE repair. Even though we found a statistically significant difference between the 2 repair methods, it is still unknown if this statistical difference seen in our study has any clinical and radiologic significance.