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Objective@#To evaluate the clinical efficacy of invisible orthodontic appliances without brackets for the distal movement of maxillary molars to improve the ability of orthodontists to predict treatment outcomes.@*Methods@#Web of Science, Cochrane Library, Embase, PubMed, Wanfang Database, CNKI Database, and VIP Database were searched for studies investigating the efficacy of invisible orthodontic appliances for distal movement of maxillary molars in adult patients and published from database inception to August 1, 2023. A total of three researchers screened the studies and evaluated their quality and conducted a meta-analysis of those that met quality standards.@*Results@#This study included 13 pre- and postcontrol trials with a total sample size of 281 patients. The meta-analysis revealed no significant differences in the sagittal or vertical parameters of the jawbone after treatment when compared with those before treatment (P>0.05). The displacement of the first molar was MD=-2.34, 95% CI (-2.83, -1.85); the displacement was MD=-0.95, 95% CI (-1.34, -0.56); and the inclination was MD=-2.51, 95% CI (-3.56, -1.46). There was a statistically significant difference in the change in sagittal, vertical, and axial tilt of the first molar before and after treatment. After treatment, the average adduction distance of the incisors was MD=-0.82, 95% CI (-1.54, -0.09), and the decrease in lip inclination was MD=-1.61, 95% CI (-2.86, -0.36); these values were significantly different from those before treatment (P<0.05).@*Conclusion@#Invisible orthodontic appliances can effectively move the upper molars in a distal direction and control the vertical position of the molars. When the molars move further away, there is some degree of compression and distal tilt movement, which is beneficial for patients with high angles. The sagittal movement of incisors is beneficial for improving the patient's profile.
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Purpose: To evaluate the frequency of facial asymmetry parameters in patients with head tilt versus those with head turn. Methods: This cross-sectional comparative study was performed on 155 cases, including 58 patients with congenital pure head turn due to Duane retraction syndrome (DRS), 33 patients with congenital pure head tilt due to upshoot in adduction or DRS, and 64 orthotropic subjects as the control group. The facial appearance was evaluated by computerized analysis of digital photographs of patients' faces. Relative facial size (the ratio of the distance between the external canthus and the corner of the lips of both face sides) and facial angle (the angular difference between a line that connects two external canthi and another line that connects the two corners of the lips) measured as quantitative facial parameters. Qualitative parameters were evaluated by the presence of one-sided face, cheek, and nostril compression; and columella deviation. Results: The facial asymmetry frequency in patients with head tilt, head turn, and orthotropic subjects was observed in 32 (97%), 50 (86.2%), and 22 (34.3%), respectively (P < 0.001). In patients with head tilt and head turn, the mean facial angle was 1.78º ± 1.01º and 1.19º ± 0.84º, respectively (P = 0.004) and the mean relative facial size was 1.027 ± 0.018 and 1.018 ± 0.014, respectively (P = 0.018). The frequencies of one-sided nostril compression, cheek compression, face compression, and columella deviation in patients with pure head tilt were found in 19 (58%), 21 (64%), 19 (58%), and 19 (58%) patients, respectively, and in patients with pure head turn the frequencies were observed in 42 (72%), 37 (63%), 27 (47%), and 43 (74%), respectively. All quantitative and qualitative facial asymmetry parameters and facial asymmetry frequencies were significantly higher in head tilt and head turn patients as compared to the control group (P < 0.001). Conclusion: All facial asymmetry parameters in patients with head tilt and head turn were significantly higher than orthotropic subjects. The quantitative parameters such as relative facial size and facial angle were significantly higher in patients with pure head tilt than pure head turn. The results revealed that pure head tilt was associated with a higher prevalence of facial asymmetry than pure head turn.
Subject(s)
Facial Asymmetry , Duane Retraction Syndrome , Head-Down TiltABSTRACT
Objective To estimate knee adduction moment (KAM) and knee flexion moment (KFM) under different gait test conditions via an inertial sensor network (ISN). Methods Twelve healthy young male subjects wore eight inertial sensors (located in the trunk, pelvis, both thighs, both shanks, both feet) and walked under different test conditions (changing foot progression angle, trunk sway angle, step width and walking speed). An ISN was used to extract biomechanical features as the input of recurrent neural network (RNN), so as to estimate the KAM and KFM. Results The overall KAM estimation accuracy: relative root mean square error (rRMSE) was 8.54% and r=0.84. The overall KFM estimation accuracy was rRMSE=6.40% and r=0.94. Conclusions The model can be used as the basis for load estimation of knee joints out of the lab and its potential application includes gait training and rehabilitation assessment after knee surgery.
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ABSTRACT Purpose: This study was conducted to further define the specific clinical characteristics of patients with Brown syndrome and evaluate the outcomes of superior oblique tenotomy in its surgical management. Methods: A retrospective analysis of the medical charts of 45 patients with Brown syndrome was performed, which revealed that 11 patients underwent superior oblique tenotomy due to abnormal head posture and/or hypotropia and 1 patient underwent bilateral superior oblique tendon elongation with a silicone band due to abnormal head posture. In the last patient, silicone bands were removed at the postoperative 3rd month due to the lack of improvement in the abnormal head posture and the limitation of elevation in adduction. Simultaneous horizontal rectus muscle surgery was performed in four patients. Results: There was a predominance of female gender, right eye, congenital form, unilaterality, A-pattern, and an abnormal head posture type with a combination of chin up and head tilting. Bilateral form was observed only in female patients. Amblyopia was detected in two patients. Among patients aged >5 years, 40% had reduced stereopsis. Abnormal head posture was found in 60% of patients. More than half of them were diagnosed with a vertical and/or horizontal deviation. Tenotomy procedure eliminated the abnormal head posture in all patients and significantly improved the mean limitation of elevation in adduction and hypotropia (p=0.001, p=0.012). Two patients developed inferior oblique overaction in the operated eye. There was complete spontaneous resolution in two patients. Conclusions: The clinical features of patients with Brown syndrome in our study are considerably consistent with those of previous reports. The present study demonstrated the effectiveness of superior oblique tenotomy with less overcorrection in the surgical treatment of Brown syndrome.(AU)
RESUMO Objetivo: Definir mais detalhadamente as características clínicas específicas de pacientes com síndrome de Brown e avaliar os resultados da tenectomia do músculo oblíquo superior no manejo cirúrgico da síndrome de Brown. Métodos: Prontuários de 45 pacientes com síndrome de Brown foram analisados retrospectivamente. Onze pacientes submetidos à tenectomia do músculo oblíquo superior devido a postura anormal da cabeça ou a hipotropia e um paciente submetido ao alongamento bilateral do tendão do oblíquo superior com uma faixa de silicone devido a postura anormal da cabeça. Neste último paciente, a faixa de silicone foi removida no terceiro mês pós-operatório devido à ausência de melhora na postura anormal da cabeça e à limitação da elevação em adução. Quatro pacientes submeteram-se simultaneamente à cirurgia do músculo reto horizontal. Resultados: Houve predominância de sexo feminino, olho direito, forma congênita, acometimento unilateral, padrão em "A" e um tipo de postura anormal da cabeça combinando queixo elevado e inclinação da cabeça. A forma bilateral foi vista apenas em pacientes do sexo feminino. Foi constatada ambliopia em 2 pacientes. Dentre os pacientes acima de 5 anos de idade, 40% tinham estereopsia reduzida. Postura anormal da cabeça estava presente em 60% dos pacientes. Mais da metade dos pacientes foi diagnosticada com um desvio vertical, horizontal ou ambos. O procedimento de tenectomia eliminou a postura anormal da cabeça em todos os pacientes e melhorou significativamente a limitação média da elevação em adução e a hipotropia (p=0,001 e p=0,012). Dois pacientes desenvolveram hiperação do músculo oblíquo inferior no olho operado. Resolução completa ocorreu espontaneamente em 2 pacientes. Conclusões: O quadro clínico dos pacientes com síndrome de Brown no nosso estudo é bastante consistente com os relatos iniciais na literatura. Este estudo mostrou a eficácia da tenectomia do oblíquo superior, com menor hipercorreção no tratamento cirúrgico da síndrome de Brown.(AU)
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Humans , Tendons/physiopathology , Ocular Motility Disorders/physiopathology , Amblyopia/diagnosis , Retrospective StudiesABSTRACT
Objective To investigate the effects of shoes type (barefoot, ordinary running shoes, minimalist shoes) and walking speed (jogging, walking at normal speed) on biomechanical parameters of knee joint, so as to provide theoretical reference for scientific fitness. Methods Vicon three-dimensional （3D） motion capture system and Kistler 3D force plate were used to collect biomechanical parameters of lower limbs from 10 subjects during walking at different speed with different shoes. Two-way (2 walking conditions × 3 shoe conditions) repeated measures analysis of variance was used to statistically analyze each dependent variable. Results Compared with jogging, the lateral excursion of plantar center of pressure (COP) was greater, the moment arm in frontal plane, the adduction moment and peak loading rate of knee joint were smaller, but the angular impulse of knee joint in frontal plane was greater. Compared with ordinary running shoes, the stride length was decreased, the lateral excursion of COP was greater, and the moment arm of knee joint in frontal plane, the knee adduction moment, the peak load rate and the angular impulse of knee joint in frontal plane were smaller. Conclusions In order to reduce the angular impulse and peak loading rate of knee joint in frontal plane, it is recommended to jog with small strides for ordinary people with minimalist footwear.
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Background: Adhesive Capsulitis usually involves the posterior capsule tightness, which can be stretched either by sleepers or cross-body stretch techniques. The present study aimed to compare and see the effectiveness of two stretching techniques on horizontal adduction and internal rotation range of motion along with pain and disability. Methodology: The study was conducted on 30 subjects diagnosed with adhesive capsulitis (12 females and 18 males) of age group 40-65 years and meeting the inclusion as well as the exclusion criteria. Subjects were divided into three groups- Cross body stretch group (Group 1), Sleeper Stretch group (Group 2), and Control group (Group 3) randomly. Both groups 1 & 2 received the intervention given to group 3 along with the different stretching techniques three times a week for four weeks. Clinical outcome measures were horizontal adduction and internal rotation as measured with a goniometer, pain intensity on a numeric pain rating scale, and shoulder disability with the help of shoulder pain and disability index. Result: Data was collected at baseline and after four weeks of intervention in all three groups. Data were checked for normal distribution. For non-normally distributed data, Kruskal Wallis test-Pain (p-value> 0.419) and Function (p-value>0.665) and for normally distributed data, one-way repeated measure ANOVA-Shoulder Horizontal Adduction (p-value>0.284) and Internal Rotation (p-value>0.334) was used and the p-value was fixed to < 0.05. Conclusion: Both the type of stretches were equally effective for four weeks.
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Objective：The belt-tying movement is of two types. One uses an abduction method in which the scapular on the same side as the upper limb to be moved is touched. The other type uses an adduction method in which the scapular on the opposite side is touched. The purpose of this study was to determine the scapular movement and muscle activity of the periscapular muscle in each method.Methods：Ten healthy men performed abduction and adduction belt-tying movements. The scapular upward rotation, anterior tilt, and internal rotation angles were measured using a three-dimensional operation analysis device. The joint angles were compared between the abduction and adduction methods by using a multiple comparison procedure. In addition, the muscle activities of the trapezius upper, middle, lower, and serratus anterior muscles were measured and analyzed using surface electromyography.Results：The abduction method involved an anterior tilt and upward rotation of the scapular muscle. By contrast, the adduction method involved an upper limb descent at the L5/T12 level, a scapular anterior tilt and upward rotation, and a scapular downward rotation at a level higher than L5/T12. The muscle activity of the upper trapezius muscle fiber was always increased between the ptosis and T7 by the abduction method but was attenuated at a higher level than T12 by the abduction method.Conclusion：Rehabilitation therapy that focuses on scapular anterior tilt and downward rotation, and the muscle activity of the upper trapezius muscle fiber is important for acquiring the belt-tying movement ability using the adduction method.
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Objective：The belt-tying movement is of two types. One uses an abduction method in which the scapular on the same side as the upper limb to be moved is touched. The other type uses an adduction method in which the scapular on the opposite side is touched. The purpose of this study was to determine the scapular movement and muscle activity of the periscapular muscle in each method.Methods：Ten healthy men performed abduction and adduction belt-tying movements. The scapular upward rotation, anterior tilt, and internal rotation angles were measured using a three-dimensional operation analysis device. The joint angles were compared between the abduction and adduction methods by using a multiple comparison procedure. In addition, the muscle activities of the trapezius upper, middle, lower, and serratus anterior muscles were measured and analyzed using surface electromyography.Results：The abduction method involved an anterior tilt and upward rotation of the scapular muscle. By contrast, the adduction method involved an upper limb descent at the L5/T12 level, a scapular anterior tilt and upward rotation, and a scapular downward rotation at a level higher than L5/T12. The muscle activity of the upper trapezius muscle fiber was always increased between the ptosis and T7 by the abduction method but was attenuated at a higher level than T12 by the abduction method.Conclusion：Rehabilitation therapy that focuses on scapular anterior tilt and downward rotation, and the muscle activity of the upper trapezius muscle fiber is important for acquiring the belt-tying movement ability using the adduction method.
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OBJECTIVE@#This study applied the direct orthodontic force system to explore the applicability of the finite element method in the simulation of alveolar bone absorption and analyze periodontal stress distribution and the overall displacement trend.@*METHODS@#The horizontal balanced alveolar bones of model 2, 3 and 4 were reduced by 2, 4, and 6 mm by deleting elements in reference to the established height of the normal alveolar bone model 1. Then, stress distribution on the posterior set of teeth and initial total tooth displacement under the simulated load of 1.47 N of orthodontic force were investigated.@*RESULTS@#The total displacement of posterior teeth increased and parodontium Von Mises stress gradually increased as the alveolar bone height decreased. The total displacement trend and parodontium stress drastically increased when alveolar bone absorp-tion reached the height of 4 mm.@*CONCLUSIONS@#When treating patients with alveolar bone loss, stress should be avoided or drasti-cally reduced to prevent irreversible damage to periodontal tissue and to improve the quality of medical treatment.
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Humans , Computer Simulation , Cuspid , Finite Element Analysis , Maxilla , Periodontal Ligament , Tooth Movement TechniquesABSTRACT
Knee osteoarthritis (KOA) is a common chronic degenerative joint disease. Hip muscle training, with the advantage of convenience and non-invasion, has been attached great importance by people gradually. Hip muscle training may affect keen medial compartment load, the strength and the electromyography signal of the muscle around the knee joint, and strong hip abductor can protect cartilage, which leads to change the load of the knee joint, and alleviate clinical symptoms. This article reviewed the mechanism of hip muscle training for knee osteoarthritis from the views of biomechanical simulation and electromyography.
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Objective To study the effect of lateral wedge insoles with different stiffness on the knee adduction moment (KAM) under walking condition. Methods The gait of 15 healthy males wearing lateral wedge insoles with different stiffness was tested. The kinetics and kinematics data were collected by optical motion capture system and ground reaction force platform. The KAM and its peak values were calculated by Visual 3D software. The differences in peak KAM under 3 walking conditions (shoes only, shoes with softer or harder lateral wedge insoles) were analyzed. Results Compared with walking with the softer lateral wedge insoles, walking with the harder lateral wedge insoles could reduce the 1st and 2nd peak KAM by 9.3% and 9.7%, respectively, with significant statistic differences. Conclusions Increasing some stiffness of lateral wedge insoles can further reduce the pressure and wear on medial compartment of the knee joint, which may relieve the symptom of knee osteoarthritis.
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Objective To study the effect of lateral wedge insoles with different stiffness on the knee adduction moment (KAM) under walking condition.Methods The gait of 15 healthy males wearing lateral wedge insoles with different stiffness was tested.The kinetics and kinematics data were collected by optical motion capture system and ground reaction force platform.The KAM and its peak values were calculated by Visual 3D software.The differences in peak KAM under 3 walking conditions (shoes only,shoes with softer or harder lateral wedge insoles) were analyzed.Results Compared with walking with the softer lateral wedge insoles,walking with the harder lateral wedge insoles could reduce the 1st and 2nd peak KAM by 9.3％ and 9.7％,respectively,with significant statistic differences.Conclusions Increasing some stiffness of lateral wedge insoles can further reduce the pressure and wear on medial compartment of the knee joint,which may relieve the symptom of knee osteoarthritis.
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<p><b>OBJECTIVE</b>To observe the kinetic change that reflects joint loading in different planes during stair climbing in knee osteoarthritis (KOA) after electroacupuncture (EA) by three-dimensional motion analysis, so as to provide reference for its biomechanical mechanism treated with acupuncture.</p><p><b>METHODS</b>Forty KOA patients, in accordance with the random number table, were assigned into an observation group and a control group, 20 cases in each one and finally 18 cases completed. Acupoints in the observation group were Neixiyan (EX-LE 4), Dubi (ST 35), Yanglingquan (GB 34), Yinlingquan (SP 9), Xuehai (SP 10), Liangqiu (ST 34) and Zusanli (ST 36); points in the control groups were located about 2 cm next to the above acupoints with shallow acupuncture. EA was connected at Neixiyan (EX-LE 4) and Yinlingquan (SP 9), Liangqiu (ST 34) and Yanglingquan (GB 34). The frequency was 2 Hz with continuous wave in the observation group and there was no current in the control group for the corresponding points. All the treatment was given for 3 weeks, totally 11 times. Climbing stairs gait was measured before and after treatment. Velocities and kinetic parameters during ascending and descending stairs were analyzed, including flexion and extension peak torques of hip, knee, ankle on the vertical plane, external knee adduction moment on the coronal plane.</p><p><b>RESULTS</b>After treatment in the observation group, velocities during ascending and descending stairs significantly increased (<0.05,<0.01); maximal ankle plantar flexor moments during ascending and descending stairs and the second peak external knee adduction moment (PEKAM2) during ascending stairs significantly increased (<0.05,<0.01). After treatment in the control group, the first peak external knee adduction moment (PEKAM1) and PEKAM2 during descending stairs were less than those before treatment (<0.05,<0.01). In the observation group, the difference value (DV) of velocity before and after treatment was positively correlated to DV in the torque of ankle plantar flexors during ascending stairs in the observation group (=0.598，<0.01). Excluding the impact of velocity, the DV of the maximal torque of ankle plantar flexors during ascending stairs didn't show difference in the observation group (>0.05).</p><p><b>CONCLUSION</b>EA can increase the velocities of ascending and descending stairs of KOA patients. It improves the loading capacity of knee joint on both sagittal and coronary planes. But its effect during ascending may be correlated with the increase of velocity. The mechanism of different effects between EA and minimal acupuncture on joint moments is still unclear and warrants further study.</p>
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BACKGROUND AND OBJECTIVES: In unilateral vocal fold paralysis (VFP), medialization thyroplasty (MT), arytenoid adduction (AA) and injection layrngoplasty (IL) are the most common procedures to correct phonatory problems. There is no consensus that which procedure is superior to the other for correcting the glottal insufficiency. The purpose of this study was to compare the phonatory parameters between MT, AA and AA with IL (AA+IL) in patients with unilateral VFP. MATERIALS AND METHODS: This retrospective study enrolled patients from 2005 to 2016. Total 72 patients (49 male, 23 female, mean age 54.5 years) were classified into three groups ; MT (n=28), AA (n=12), and AA+IL (n=32). GRBAS scales, maximum phonation time (MPT), jitter, shimmer, noise to harmonic ratio (NHR), and voice handicap index (VHI)-10 and VHI-30 were preoperatively and postoperatively collected and compared between the three groups. RESULTS: Age, gender and cause of VFP were not significantly different between the three groups. In MT and AA groups, MPT, VHI, G (overall grade) and B (breathiness) were significantly improved. In AA+IL group, jitter, shimmer, NHR, MPT, VHI, G and B were significantly improved. In analysis of differences (pre-postoperative values), Δ jitter (p < 0.001), Δ shimmer (p=0.031), and Δ NHR (p=0.002) were significantly different and AA+IL group showed the greatest improvement. CONCLUSION: Analysis of voice parameters showed that all the three procedures for patients with unilateral VFP are effective in the improvement of voice ; especially in MPT, VHI-10, G and B scales. Compared to the others, AA+IL provided the better acoustic values including jitter, shimmer and NHR.
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Female , Humans , Male , Acoustics , Consensus , Laryngoplasty , Noise , Paralysis , Phonation , Retrospective Studies , Vocal Cords , Voice , Weights and MeasuresABSTRACT
Objective To investigate the possible effect of fully knee extension in sitting position with or without hip adduction on quadriceps imbalance in patients with patellofemoral pain syndrome (PFPS) by using surface electromyography (sEMG). Methods sEMG signals of vastus lateralis (VL) and vastus medialis oblique (VMO) muscles from 30 patients with PFPS as PFPS group and 30 healthy subjects as control group were collected, during their fully knee extension in sitting position with or without hip adduction. All the EMG data were then analyzed by extracting time domain indexes, namely, the root mean square (RMS) and integrated EMG (IEMG), to compare the balanced relationship between VL and VMO muscles. Results In PFPS group, there were no significant differences in VL time domain indexes during knee extension in sitting position with or without hip adduction, while statistical differences were found in VMO time domain indexes, and values of RMS and IEMG of VMO were higher under hip adduction, which indicated that the VMO muscle recruitment was strengthened. Conclusions Fully knee extension in sitting position with hip adduction can promote EMG activities of VMO muscles in patients with PFPS, which will help to balance the VL and VMO muscles.
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Knee osteoarthritis (KOA) is a common degenerative joint disease. Biomechanics of lower extremity plays an important role in KOA. Foot progression angle, with the advantages of non-invasive, convenience, has been attached great importance by people gradually. Changing foot progression angle may effect the knee adduction torque, tibia rotation, muscle activity, which leads to change the load of the knee joint, and alleviate the pain, improve the function of knee joint and the quality of life of the patients.
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In this report we present a 45 year old man with horizontal diplopia following minor head trauma. Neurological examination was normal except for unilateral adduction paresis of the right eye. Brain magnetic resonance imaging (MRI) revealed a contusion area 7 mm in diameter at the inferiorposterior portion of the mesencephalon. We thought that this contusion affected the sub-nucleus of oculomotor nerve and caused isolated adduction paresis of the right eye. This relatively rare entity is discussed in the light of the available literature.
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Objective To evaluate the effect of double-plate treatment on grade Ⅱsupination adduction ankle frac? tures with impaction of tibial plafond. Methods A total of 17 patients of gradeⅡsupination adduction ankle fractures with impaction of tibial plafond were treated surgically in our hospital. Anteromedial approach to the medial malleolus was taken to expose the tibial plafond and the vertical medial malleolus fractures. One distal radius plate was placed on the anteromei?dal tibial plafond, and another buttress plate was placed on the medial malleolus. Bone grafting was used to restore the height of the collapsed tibia. Lateral malleolus fractures were treated with reconstruction plate. The fracture union after operation was detected by X-ray examination. American Orthopedic Foot and Ankle Society (AOFAS) ankle hind foot score was used to assess the ankle function. Results Sixteen of 17 patients were followed up postoperatively for a mean period of 2.6 ± 0.9 years. CT cross-sectional study found that the collapsed articular surface of 12 (70.6%) patients was mainly located in the an?teromedial one-fourth area, with the worst at anterior margin. Bony fusion was achieved in all patients after an average peri?od of 2.9±0.5 months. No internal fixation loosening or fracture redisplacement was found by X-ray. The average range of an?kle joint activity was 16.4°±2.8° for dorsiflexion, and was 39.2°±5.3° for plantarflexion. According to AOFAS ankle hindfoot scale, ankle function was excellent in 14 patients and good in 2, with excellence rate of 100%. Conclusion The application of double-plate fixation to treat gradeⅡsupination adduction ankle fractures with impaction of tibial plafond can play a key role in reducing fracture redisplacement and osteoarthritis.
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@#Knee osteoarthritis (KOA) is a common degenerative joint disease. Biomechanics of lower extremity plays an important role in KOA. Foot progression angle, with the advantages of non-invasive, convenience, has been attached great importance by people gradually. Changing foot progression angle may effect the knee adduction torque, tibia rotation, muscle activity, which leads to change the load of the knee joint, and alleviate the pain, improve the function of knee joint and the quality of life of the patients.
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Objective To study the biomechanical effect from pulley tissues of extraocular muscles on super adduction of the eye. Methods By the coordinate parameters of extraocular muscles reported in the literature and based on the mechanical equilibrium of eye movement, two mechanical models, active pulley model and non pulley model (as control), were established to simulate eye adduction in the range of 30°-45°. Results For the contribution of medial rectus muscle, the non pulley model produced more force than the active pulley model to control eye adduction, and its corresponding force value increasingly exceeded the physiologically safe threshold (0.5 N). At the maximum simulative adduction of 45°, the force of medial rectus obtained by active pulley model and non pulley model was 0.508 N and 0.782 N, respectively, and the latter was 56% greater than the safe threshold. For controlling eye adduction, the active pulley model consumed much less energy than the non pulley model. Conclusions Due to the existence of pulley tissues, extraocular muscles could control eye adduction by consuming less biological energy and reinforce the ocular derivation. In addition, with the active pulley, the medial rectus muscle could maintain its mechanical advantage under super adduction of the eye.