Orthopaedic medicine has developed and benefited from the advancement of related basic science. Current technologies such as joint replacement and internal fixation of fractures started from research on biocompatible biomaterials and on the understanding of body biomechanics. As ongoing research on life science may dramatically change the appearance of future orthopaedic medicine, it is very important to keep abreast with recent trends of related basic science. This review introduces the realm of basic sciences related to orthopaedic medicine along with comments on future perspectives.
Biocompatible Materials ; Biological Science Disciplines ; Biomechanics ; Joints ; Orthopedics

PURPOSE: The objective of this study was to evaluate the effect of microthreads on removal torque and bone-to-implant contact (BIC). METHODS: Twelve miniature pigs for each experiment, a total of 24 animals, were used. In the removal torque analysis, each animal received 2 types of implants in each tibia, which were treated with sandblasting and acid etching but with or without microthreads at the marginal portion. The animals were sacrificed after 4, 8, or 12 weeks of healing. Each subgroup consisted of 4 animals, and the tibias were extracted and removal torque was measured. In the BIC analysis, each animal received 3 types of implants. Two types of implants were used for the removal torque test and another type of implant served as the control. The BIC experiment was conducted in the mandible of the animals. The P1-M1 teeth were extracted, and after a 4-month healing period, 3 each of the 2 types of implants were placed, with one type on each side of the mandible, for a total of 6 implants per animal. The animals were sacrificed after a 2-, 4-, or 8-week healing period. Each subgroup consisted of 4 animals. The mandibles were extracted, specimens were processed, and BIC was analyzed. RESULTS: No significant difference in removal torque value or BIC was found between implants with and without microthreads. The removal torque value increased between 4 and 8 weeks of healing for both types of implants, but there was no significant difference between 8 and 12 weeks. The percentage of BIC increased between 2 and 4 weeks for all types of implants, but there was no significant difference between 4 and 8 weeks. CONCLUSIONS: The existence of microthreads was not a significant factor in mechanical and histological stability.
Animals ; Biomechanics ; Dental Implants ; Mandible ; Osseointegration ; Swine ; Tibia ; Tooth ; Torque

OBJECTIVE: The offset connector can allow medial and lateral variability and facilitate intralaminar screw incorporation into the construct. The aim of this study was to compare the biomechanical characteristics of C7 intralaminar screw constructs with and without offset connector using a three dimensional finite element model of a C6-7 cervical spine segment. METHODS: Finite element models representing C7 intralaminar screw constructs with and without the offset connector were developed. Range of motion (ROM) and maximum von Mises stresses in the vertebra for the two techniques were compared under pure moments in flexion, extension, lateral bending and axial rotation. RESULTS: ROM for intralaminar screw construct with offset connector was less than the construct without the offset connector in the three principal directions. The maximum von Misses stress was observed in the C7 vertebra around the pedicle in both constructs. Maximum von Mises stress in the construct without offset connector was found to be 12-30% higher than the corresponding stresses in the construct with offset connector in the three principal directions. CONCLUSION: This study demonstrated that the intralaminar screw fixation with offset connector is better than the construct without offset connector in terms of biomechanical stability. Construct with the offset connector reduces the ROM of C6-7 segment more significantly compared to the construct without the offset connector and causes lower stresses around the C7 pedicle-vertebral body complex.
Biomechanics ; Immobilization ; Range of Motion, Articular ; Spine

PURPOSE: The aim of this study was to measure the peri-implant bone length surrounding implants that penetrate the sinus membrane at the posterior maxilla and to evaluate the survival rate of these implants. METHODS: Treatment records and orthopantomographs of 39 patients were reviewed and analyzed. The patients had partial edentulism at the posterior maxilla and limited vertical bone height below the maxillary sinus. Implants were inserted into the posterior maxilla, penetrating the sinus membrane. Four months after implant insertion, provisional resin restorations were temporarily cemented to the abutments and used for one month. Then, a final impression was taken at the abutment level, and final cement-retained restorations were delivered with mutually protected occlusion. The complications from the implant surgery were examined, the number of failed implants was counted, and the survival rate was calculated. The peri-implant bone lengths were measured using radiographs. The changes in initial and final peri-implant bone lengths were statistically analyzed. RESULTS: Nasal bleeding occurred after implant surgery in three patients. No other complications were found. There were no failures of the investigated implants, resulting in a survival rate of 100%. Significantly more bone gain around the implants (estimated difference=-0.6 mm, P=0.025) occurred when the initial residual bone height was less than 5 mm compared to the >5 mm groups. No significant change in peri-implant bone length was detected when the initial residual bone height was 5 mm or larger. CONCLUSIONS: This study suggests that implants penetrating the sinus membrane at the posterior maxilla in patients with limited vertical bone height may be safe and functional.
Biomechanics ; Biostatistics ; Epistaxis ; Humans ; Maxilla ; Maxillary Sinus ; Membranes ; Sinus Floor Augmentation ; Survival Rate

OBJECTIVE: To examine the effect of the posture of immobilization upon the tensile properties in injured Achilles tendon of rat for an initial period of immobilization. METHODS: Forty-two Sprague-Dawley rats were used in the present study. Eighteen rats received a total tenotomy of the right Achilles tendon to mimic total rupture and were divided into three groups comprising of 6 rats each. Ankles of group A were immobilized at 60degrees of plantarflexion. Ankles of group B were immobilized at neutral position. Whereas, those of group C were immobilized at 60degrees of dorsiflexion. Other 18 rats received hemitenotomy to mimic partial rupture and were divided into three groups. The remaining 6 rats were kept free as control. After 14 days, we dissected the tendons and analyzed maximum force, stiffness, and energy uptake during pulling of the tendons until they ruptured. The tendons of 6 rats in each group and control were reserved for histology. Picrosirius staining was done for the analysis of collagen organization. RESULTS: In total tenotomy, tensile properties were significantly different between the control and the intervention groups (p<0.05). Group C showed relatively higher values than the groups A and B with respect to tensile properties (p>0.05). In partial tenotomy, tensile properties were significantly different between the control and the intervention groups (p<0.05). Group C showed significantly higher value than other intervention groups in terms of maximum force and energy uptake (p<0.05). The semiquantitative histologic grading scores were assigned for collagen organization. The scores for dorsiflexion posture were higher than the ones for plantarflexion. CONCLUSION: Dorsiflexion posture in partial ruptured Achilles tendon showed better functional recovery than other immobilized postures. In total ruptured case, the tensile properties showed increasing tendency in dorsiflexion posture.
Achilles Tendon ; Animals ; Ankle ; Biomechanics ; Collagen ; Hydrazines ; Immobilization ; Posture ; Rats ; Rats, Sprague-Dawley ; Rupture ; Tendons ; Tenotomy

BACKGROUND: To determine the influence of lifting speed and type on peak and cumulative back compressive force (BCF) and shoulder moment (SM) loads during symmetric lifting. Another aim of the study was to compare static and dynamic lifting models. METHODS: Ten male participants performed a floor-to-shoulder, floor-to-waist, and waist-to-shoulder lift at three different speeds [slow (0.34 m/s), medium (0.44 m/s), and fast (0.64 m/s)], and with two different loads [light (2.25 kg) and heavy (9 kg)]. Two-dimensional kinematics and kinetics were determined. A three-way repeated measures analysis of variance was used to calculate peak and cumulative loading of BCF and SM for light and heavy loads. RESULTS: Peak BCF was significantly different between slow and fast lifting speeds (p < 0.001), with a mean difference of 20% between fast and slow lifts. The cumulative loading of BCF and SM was significantly different between fast and slow lifting speeds (p < 0.001), with mean differences > or =80%. CONCLUSION: Based on peak values, BCF is highest for fast speeds, but the BCF cumulative loading is highest for slow speeds, with the largest difference between fast and slow lifts. This may imply that a slow lifting speed is at least as hazardous as a fast lifting speed. It is important to consider the duration of lift when determining risks for back and shoulder injuries due to lifting and that peak values alone are likely not sufficient.
Biomechanics ; Humans ; Kinetics ; Lifting* ; Male ; Shoulder

OBJECTIVES: Load carrying tasks are recognized as one of the primary occupational factors leading to slip and fall injuries. Nevertheless, the mechanisms associated with load carrying and walking stability remain illusive. The objective of the current study was to apply local dynamic stability measure in walking while carrying a load, and to investigate the possible adaptive gait stability changes. METHODS: Current study involved 25 young adults in a biomechanics research laboratory. One tri-axial accelerometer was used to measure three-dimensional low back acceleration during continuous treadmill walking. Local dynamic stability was quantified by the maximum Lyapunov exponent (maxLE) from a nonlinear dynamics approach. RESULTS: Long term maxLE was found to be significant higher under load condition than no-load condition in all three reference axes, indicating the declined local dynamic stability associated with load carrying. CONCLUSION: Current study confirmed the sensitivity of local dynamic stability measure in load carrying situation. It was concluded that load carrying tasks were associated with declined local dynamic stability, which may result in increased risk of fall accident. This finding has implications in preventing fall accidents associated with occupational load carrying.
Acceleration ; Biomechanics ; Gait ; Humans ; Lifting ; Nonlinear Dynamics ; Walking ; Young Adult

STUDY DESIGN: An in vitro biomechanical study. PURPOSE: To evaluate the biomechanics of a novel posterior integrated clamp (IC) that extends on an already implanted construct in comparison to single long continuous bilateral pedicle screw (BPS) and rod stabilization system. OVERVIEW OF LITERATURE: Revision surgery in the thoracolumbar spine often necessitates further instrumentation following a failed previous back surgery. Stability of these reconstructed constructs is not known. METHODS: Six osteoligamentous T12-L5 calf spines were tested on a spine motion simulator in the following configurations: intact, four level constructs (T13-L4), three level constructs (L1-L4), and two level constructs (L2-L4), by varying the ratio between BPS and IC. A load control protocol of 8 Nm moments was applied at a rate of 1degrees/sec to establish the range of motion value for each construct in flexion-extension, lateral bending, and axial rotation. Statistical analysis was performed on raw data using repeated measures analysis of variance and significance was set at p<0.05. RESULTS: On an average, the reduction in motion for the four level continuous pedicle screw and rod construct (67%) was similar to those extended with integrated clamps (64%). Furthermore, for three level and two level constructs, no significant difference was observed between continuous pedicle screw constructs and those revised with the integrated clamps (regardless of the ratio between BPS and IC). CONCLUSIONS: The novel posterior IC showed equivalent biomechanical rigidity to continuous pedicle screw rod constructs in revision scenarios. Clinical studies on posterior rod adjunct systems are necessary to confirm these results.
Biomechanics ; Bone Screws ; Range of Motion, Articular ; Reoperation ; Spine

OBJECTIVE: To evaluate the accuracy of the swallowing kinematic analysis. METHODS: To evaluate the accuracy at various velocities of movement, we developed an instrumental model of linear and rotational movement, representing the physiologic movement of the hyoid and epiglottis, respectively. A still image of 8 objects was also used for measuring the length of the objects as a basic screening, and 18 movie files of the instrumental model, taken from videofluoroscopy with different velocities. The images and movie files were digitized and analyzed by an experienced examiner, who was blinded to the study. RESULTS: The Pearson correlation coefficients between the measured and instrumental reference values were over 0.99 (p<0.001) for all of the analyses. Bland-Altman plots showed narrow ranges of the 95% confidence interval of agreement between the measured and reference values as follows: 0.14 to 0.94 mm for distances in a still image, -0.14 to 1.09 mm/s for linear velocities, and -1.02 to 3.81 degree/s for angular velocities. CONCLUSION: Our findings demonstrate that the distance and velocity measurements obtained by swallowing kinematic analysis are highly valid in a wide range of movement velocity.
Biomechanics ; Deglutition ; Epiglottis ; Mass Screening ; Reference Values ; Reproducibility of Results

There are no standard guidelines for treatment of massive rotator cuff tears. In this article, we reviewed the various modalities for treatment of massive rotator cuff tears, especially focusing on arthroscopic treatment. Selection of one of a variety of treatment modalities is essential for understanding pathogenesis, biomechanics and reparability of massive rotator cuff tears. The best clinical results have been reported with arthroscopic complete repair of massive rotator cuff tear. Satisfactory results have also been reported with other various arthroscopic treatment methods, including simple debridement, partial repair, biceps tenotomy or tendesis, and augmentation using a tissue substitution. However few long-term follow up results are available with these salvage options. Treatment of massive rotator cuff tears is difficult due to high incidence of irreparable tears and re-tear rate. Thus, understanding the advantages and disadvantages of various treatment modalities is thought to be helpful to improving the outcome of treatment of massive rotator cuff tears.
Arthroscopy ; Biomechanics ; Debridement ; Follow-Up Studies ; Incidence ; Rotator Cuff ; Tenotomy