Effects of perioperative factors and hip geometry on hip abductor muscle strength during the first 6 months after anterolateral total hip arthroplasty.

[Purpose] The importance and effect of hip joint geometry on hip abductor muscle strength are well known. In addition, other perioperative factors are also known to affect hip abductor muscle strength. This study examined the relative importance of factors affecting hip abductor muscle strength after total hip arthroplasty. [Subjects and Methods] The subjects were 97 females with osteoarthritis scheduled for primary unilateral THA. The following variables were assessed preoperatively and 2 and 6 months after surgery: isometric hip abductor strength, radiographic analysis (Crowe class, postoperative femoral offset (FO)), Frenchay Activities Index, compliance rate with home exercise, Japanese Orthopaedic Association Hip-Disease Evaluation Questionnaire (JHEQ), and demographic data. Factors related to isometric hip abductor muscle strength 2 and 6 months after surgery were examined. [Results] Significant factors related to isometric hip abductor muscle strength at 2 and 6 months after surgery were, in extraction order: 1. isometric hip abductor muscle strength in the preoperative period; 2. BMI; and 3. the JHEQ mental score at 2 and 6 months after surgery. [Conclusion] Preoperative factors and postoperative mental status were related to postoperative isometric hip abductor strength. FO was not extracted as a significant factor related to postoperative isomeric hip abductor strength.

Biomechanical evaluation of the rabbit tibia after implantation of porous hydroxyapatite/collagen in a rabbit model.

PURPOSE: Porous hydroxyapatite/collagen composite (HAp/Col) is an artificial bone substitute with excellent osteoconduction and sponge-like elasticity. However, the porosity of porous HAp/Col is as high as 95% and its mechanical strength is very poor. The aim of this study was to biomechanically analyze sites implanted with porous HAp/Col. METHODS: Rectangular cortical bone defects (3 × 8 mm) were made in the tibia of rabbits and filled with porous HAp/Col or porous ß-tricalcium phosphate or left vacant. The tibia was harvested at 4 or 12 weeks after surgery. The harvested specimens were analyzed using a micro-CT system, and the mechanical strength of the specimens was examined by torsion testing. RESULTS: Quantitative micro-CT analysis of the regenerated bone revealed that both bone substitutes equally facilitated bone regeneration. Biomechanical testing demonstrated that the torsional strength of HAp/Col-implanted sites was higher than that of the control (vs control: p = 0.030 and vs ß-TCP: p = 0.056). CONCLUSIONS: The results indicate that porous HAp/Col implantation is an effective strategy for recovery of the mechanical strength of bone defects.

Pivotal role of Sirt6 in the crosstalk among ageing, metabolic syndrome and osteoarthritis.

Osteoarthritis (OA) is a chronic degenerative joint disorder commonly associated with metabolic syndrome. As ageing and obesity has a great impact on the initiation/severity of OA, herein we sought to investigate the involvement of Sirt6 in the crosstalk between ageing and metabolic syndrome/OA. Sirt6 haploinsufficiency in mice promoted the expression of inflammatory cytokines in the IPFP. Enhanced inflammation of the IPFP in the aged Sirt6 ± HFD group was paralleled with accelerated OA change, including osteophyte growth and chondrocyte hypertrophy. Conversely, mesenchyme-specific Sirt6-deficient mice revealed both attenuated chondrocyte hypertrophy and proteoglycan synthesis, although chondrocyte senescence was enhanced as shown in the aged WT mice. Thus Sirt6 has key roles in the relationship among ageing, metabolic syndrome, and OA.

Incidence of floating toe and its association with the physique and foot morphology of Japanese children.

[Purpose] Physical development, foot morphology, and toe contact of children aged 3 to 5 years were assessed in order to investigate the relationships between body and foot morphology and the incidence of the condition known as "floating toe". [Subjects] A total of 198 children, aged 3 to 5 years old, participated in this study. [Methods] Height and weight were measured for body morphology, and foot length and width were measured for foot morphology. Footprint images were taken to calculate the number of floating toes. Information about the children's height and weight at birth, and the time of starting to walk was obtained from their guardians. [Results] At least one floating toe was observed in 87.7-98.7% of the children depending on their ages. The fifth toe was most commonly affected, occurring in 74.2% of the study population. Among the body and foot morphology parameters, only weight at birth showed a significant but very weak correlation with the number of floating toes. [Conclusion] There was a high incidence of floating toe among the children, with the fifth toe most commonly affected. Floating toe weakly but significantly correlated with weight at birth, but did not correlated with other measures of physique at birth, physical development, or the time of starting to walk.

Comparison of different distal designs of femoral components and their effects on bone remodeling in 1-stage bilateral total hip arthroplasty.

To evaluate the effects of distal design of a proximally coated femoral component on periprosthetic bone remodeling, we prospectively performed 21 one-stage bilateral total hip arthroplasties using a distally tapered and a distally cylindrical stem with the same proximal design, randomized to side. All hips showed good outcomes clinically and radiographically at the final follow-up, average of 7 years postoperatively. Cancellous condensation was always found in Gruen's zones 2 and 6 around the cylindrical stem and in regions between zones 2 and 3 and between zones 6 and 5 around the tapered stem. Bone mineral density of Gruen's zones 2 and 6 was significantly lower around the tapered stem. These results suggested more distal loading in hips with the tapered stem than in those with the cylindrical stem.

Postoperative hip motion and functional recovery after simultaneous bilateral total hip arthroplasty for bilateral osteoarthritis.

BACKGROUND: Simultaneous bilateral total hip arthroplasty (THA) can offer a potential benefit of greater postoperative hip motion without the negative influence of contralateral hip disabilities, compared to two-stage THA. However, postoperative changes in hip motion after simultaneous bilateral THA have rarely been reported. The purpose of this study was to clarify the efficacy of simultaneous procedures on postoperative hip motion and functional recovery. METHODS: We retrospectively compared hip motion in 27 patients treated with simultaneous bilateral THA to those in 11 patients with two-stage bilateral THA, 35 patients with unilateral THA for unilateral disease, and 15 patients with unilateral THA for bilateral disease. We also evaluated the clinical manifestations according to the Japanese Orthopaedic Association (JOA) hip scores and compared the outcomes among the groups. All of the THA surgeries were primarily performed through a posterolateral approach using cement-less prostheses. The diagnosis at surgery was dysplastic osteoarthritis in all patients, and the patients were followed up for at least 4 years. RESULTS: The postoperative improvement of motion in hip flexion was significantly greater in patients treated with simultaneous procedures compared to patients with two-stage THA and unilateral THA for bilateral disease. The differences in improvement of motion in hip abduction were less marked than the improvement in hip flexion among the groups. Although there were no significant differences in pain scores among the groups, the values for activity of daily living were significantly greater in patients treated with simultaneous bilateral THA and patients with unilateral THA for unilateral disease than in patients with unilateral and two-stage bilateral THA for bilateral disease. CONCLUSIONS: The simultaneous procedure was considered to be more effective in patients with bilateral hip osteoarthritis and demonstrated a substantial improvement in hip motion and functional recovery after THA.

The effect of preoperative lateral flexibility of the lumbar spine on perceived leg length discrepancy after total hip arthroplasty.

BACKGROUND: Leg length discrepancy (LLD) after total hip arthroplasty (THA) is a significant factor of patient dissatisfaction. Patients with dissociation between preoperative radiographic LLD and perceived LLD sometimes feel LLD postoperatively even if bilateral leg lengths are equal. There is no publication describing how to decide the amount of leg lengthening in such cases. PURPOSE: By examining the influence of preoperative lumbar lateral flexibility on postoperative perceived LLD, this study aims at creating a guideline for the optimal planning of leg lengthening in THA. METHODS: In 59 cases undergoing primary unilateral THA, radiographic LLD, perceived LLD, pelvic tilting and lumbar lateral flexibility were measured preoperatively. The amount of leg lengthening and the sequential change of the perceived LLD were measured postoperatively. RESULTS: Twelve cases (20%) felt the perceived LLD at two years after surgery. All these cases felt the operative side longer than the non-operative side. In 32 cases with preoperative pelvic inclination to the affected side, postoperative perceived LLD was significantly greater if lumbar spine was rigid. In eight cases with pelvic tilting and rigid lumber spine, the amount of leg lengthening that exceeded preoperative perceived LLD affected the postoperative perceived LLD. CONCLUSIONS: In cases with preoperative pelvic inclination downward to the affected side and with rigid lumbar spine, amount of leg lengthening should not be excessively greater than preoperative perceived LLD. In other cases, lengthening the leg to the same length as the contralateral side rarely results in postoperative perceived LLD.

A proposal for a new definition of the axial rotation angle of the shoulder joint.

The Euler/Cardan angles are commonly used to define the motions of the upper arm with respect to the trunk. This definition, however, has a problem in that the angles of both the horizontal flexion/extension and the axial rotation of the shoulder joint become unstable at the gimbal-lock positions. In this paper, a new definition of the axial rotation angle was proposed. The proposed angle was stable over the entire range of the shoulder motion. With the new definition, the neutral position of the axial rotation agreed with that in the conventional anatomy. The advantage of the new definition was demonstrated by measuring actual complex motions of the shoulder with a three-dimensional motion capture system.

Development of new bone cement utilizing low toxicity monomers.

Acrylic bone cement is self-curing cement comprising of liquid and powder component of methyl methacrylate (MMA). It has been used extensively in orthopedics; however, adverse effects were associated with its use. Hence we investigated in this paper the possibility of new cement utilizing methacrylates with lower toxicity than MMA. LD50s of candidate monomers were determined with administration to the medullary cavity of the rat's femur. 2-Ethylhexyl methacrylate (EHMA) and trimethylolpropane trimethacrylate (TMP) demonstrated greater LD50 values of 187 mg/kg and 380 mg/kg, respectively, than MMA (108 mg/kg); they were selected as the liquid components of the new cement. The copolymer of EHMA and cyclohexyl methacrylate was then selected as the powder component. With this combination, we developed the new cement (EHMA cement).Temperature rise during polymerization of EHMA cement was 9 degrees C-13 degrees C, which was significantly lower than that of conventional cement. The compression strength of the polymerized EHMA cement was 57 MPa without TMP, and 67 MPa with TMP (15 wt%). Thus we concluded that new EHMA cement was slightly inferior in the compression strength than the conventional cement. However, it was characterized by the low toxicity of utilized monomers and the low temperature rise during polymerization.

Small GTPase Ras and Rho expression in rat osteoblasts during spaceflight.

Rat osteoblasts were cultured for 4 and 5 days aboard a space shuttle and solubilized after a 24-h treatment with 1alpha,25 dihydroxyvitamin D(3). The quantitative RT-PCR determined the mRNA levels of signaling molecules upstream and downstream Ras. The small GTPase is activated by guanine nucleotide exchange protein (GEF) and deactivated by GTPase-activating protein (GAP). When external stimuli are transduced into intracellular signals, various pathways are recruited: focal adhesion kinase (FAK) is associated with integrin-beta, and directs tyrosine phosphorylation of downstream substrates, including phospholipase C-gamma (PLC-gamma) and son of sevenless (SOS, a Ras GEF). The mRNA levels of FAK and PLC-gamma1 and -gamma2 in the flight cultures were increased 150% and 250% of the ground controls. The SOS mRNA levels in the flight cultures were increased 520% and 320% of the ground controls. Signals via G protein-coupled receptors are transmitted through PLC-beta and Ras GRF (another Ras GEF). Activated Ras then stimulates Raf, mitogen-activated protein kinase (MAPK) cascades. The mRNA levels of Raf, extracellular signal-regulated protein kinase of MAPK family (ERK-1 and -2), and PLC-beta were increased during spaceflight. Rho GAP expression in the flight cultures was increased twofold of the ground controls. Since Rho GAP deactivates Rho, microgravity may suppress Rho signals, regulating actin filament rearrangement. Microgravity signals may involve two pathways (G protein-coupled receptor-mediated pathway and tyrosine phosphorylation-mediated pathway) that activate Ras, Raf, and MAPK cascades in rat osteoblasts.

Range of motion measurement of an artificial hip joint using CT images.

Total hip arthroplasty (THA) is one of the most effective treatments for osteoarthritis and rheumatoid arthritis. Dislocation of the femoral head from the acetabular socket is a major problem of THA. To prevent dislocation, it is important to know the range of motion (ROM) after THA. Although various studies on the ROM were carried out, there exist only a few reports on ROM evaluation in individual patients. This is because in clinical cases, bone-to-bone and bone-to-component contacts must be considered besides the impingement of components. In this study, a new method for evaluating ROM of internal/external rotation, which takes into account all combinations of contacts between the bones and components, was proposed. A computer simulation demonstrated that the RMS error of the proposed method was approximately 3 degrees . The method was applied to 33 THAs under various conditions of flexion and adduction angles. The method was able to detect any type of impingement. The evaluated ROM was in good agreement with that measured during the THA operation (correlation coefficient = 0.91).

Effect of occlusion status on the time required for initiation of recovery in response to external disturbances in the standing position.

BACKGROUND: To examine whether occlusion status contributes to improvement of postural balance. METHODS: Thirty healthy adolescents (15 males and 15 females; mean age, 20.3; standard deviation (SD) 1.6 years) with no equilibrium or stomatognathic function abnormalities were examined. Occlusion is a term meaning "jaw clenching." Occlusion status was evaluated by measuring masseter activity using the EMG system. Balancing ability was evaluated using the EquiTest system, which measures sway of the center of gravity produced by rapid movement of force plates as an external disturbance (three intensity levels). The time required for initiation of recovery after application of the disturbance was calculated by measuring displacement of the center of foot pressure. Data were compared according to occlusion status. FINDINGS: Little difference in latency was observed following a small disturbances; however, the greater the disturbance the shorter the latency with occlusion, while without occlusion, latency increased with increasing disturbance. A statistically significant interaction (P<0.001) between occlusion and external disturbance was also found. INTERPRETATION: This study suggested that occlusion contributes to maintenance of postural balance and improvement of stability when unexpected sway occurs in the standing position.

Compensation for the effect of soft tissue artefact on humeral axial rotation angle.

Soft tissue artefact (STA) is caused by the relative displacement of markers or sensors mounted on the skin surface with respect to the underlying bones, and is a major source of error in the kinematic measurement of human movement. In particular, the humeral axial rotation (HAR) is affected by STA. The aim of this study was to propose a method for compensating for STA and to validate its effectiveness. In the proposed method, the HAR angle was calculated by a second-order regression using three independent variables converted from the Cardan angles of the shoulder joint. The calculated HAR angle (HAR-r) was compared with the angle calculated from the direction of the longitudinal axis of the forearm (HAR-f). Highly linear correlations were found between HAR-r and HAR-f when the elbow joint was flexed at 90 degrees. The elbow flexion/extension motion had little influence on the HAR-r, whereas HAR-f became unstable when the elbow joint approached its full extension. Because HAR-r effectively compensates for the STA and is independent of the elbow flexion/extension, the regression method is suitable for the movement analysis of the upper limbs.

Intraoperative evaluation of the effects of femoral component offset and head size on joint stability in total hip arthroplasty.

PURPOSE: To evaluate intraoperatively the effects of femoral offset and head size on stability of the hip joints in total hip arthroplasty (THA) via posterior approach. METHODS: Thirty cementless THAs were included in this study. After acetabular shell and femoral broach fixation, trial reduction was repeated using a femoral neck (5- to 8-mm higher or standard offset) and a head (26 mm or 32 mm). To evaluate joint stability, range of internal rotation (IR) in hip flexion prior to posterior subluxation and range of external rotation (ER) in hip extension were measured. RESULTS: The high-offset neck provided significantly (approximately 10°) greater range of IR to subluxation than the standard-offset neck. No hips ended in anterior subluxation by ER. The head size did not have significant effects on the stability. CONCLUSION: Results suggest that the 5- to 8-mm greater femoral offset might be effective in preventing instability in primary THA.

Hip, knee, and ankle kinematics during activities of daily living: a cross-sectional study.

BACKGROUND: Joint angle data from healthy subjects are necessary as baseline information. OBJECTIVE: To analyze the problems of patients who struggle with activities of daily living (ADL) due to restricted range of motion and to provide ADL guidance based on objective data. METHOD: An electromagnetic three-dimensional tracking system (FASTRAK) was used to quantify the hip, knee, and ankle angles of the dominant leg of 26 healthy adults as they performed 22 ADLs related to dressing, using the toilet, bathing, picking up objects, and crouching. For each ADL, the maximum angle was averaged across the 26 subjects. Mean angles of adduction/abduction and internal/external rotation during maximum hip flexion were also measured. RESULTS: The largest mean maximum angle was 101° for hip flexion (trunk rotation during crouching), 17° for hip adduction (putting on shoes), and 149° for knee flexion (trunk rotation during crouching). Analysis of adduction/abduction and internal/external rotation angles during maximum hip flexion showed the largest angle of adduction when putting on shoes, and the largest angle of internal rotation with trunk rotation during crouching. CONCLUSIONS: ADLs such as crouching and putting on pants showed larger joint angles than walking, climbing stairs, and standing up. Results obtained from this study can provide important objective data for ADL guidance for total hip arthroplasty and femoroacetabular impingement patients.

Microgravity signal ensnarls cell adhesion, cytoskeleton, and matrix proteins of rat osteoblasts: osteopontin, CD44, osteonectin, and alpha-tubulin.

Rat osteoblasts were cultured for 4 or 5 days aboard the Space Shuttle and solubilized during spaceflight. Post-flight analyses by quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) determined the relative mRNA levels of matrix proteins, adhesion molecules, and cytoskeletal proteins including osteopontin (OP), osteonectin (ON), CD44, alpha-tubulin, actin, vimentin, fibronectin (FN), and beta1-integrin. The mRNA levels of OP and alpha-tubulin in the flight cultures were decreased by 30% and 50% on day 4 and day 5 of flight, as compared to the ground controls. In contrast, the CD44 mRNA levels in the flight cultures increased by 280% and 570% of the ground controls on day 4 and day 5. The mRNA levels of ON and FN in the flight cultures were slightly increased as compared to ground controls. The mRNA levels of actin, vimentin, or beta1-integrin did not change in spaceflight conditions. The matrix proteins, adhesion molecules, and cytoskeletal proteins may form dynamic network complexity with signaling molecules as an adaptive response to perturbation of mechanical stress under microgravity.

Dynamic imbalance in gait ataxia. Characteristics of plantar pressure measurements.

The present study was designed to evaluate the interaction between disequilibrium and irregular stepping components of ataxic gait. For this purpose, we compared the walking patterns of patients with cerebellar dominant multiple system atrophy (MSAc, n = 8), spinocerebellar ataxia type 6 (SCA6, n = 4) and 16q-linked autosomal dominant cortical cerebellar atrophy (16q-linked ADCA, n = 6), and 6 normal subjects, by measuring toe and heel plantar pressures. In healthy subjects, the heel contacted the floor at step-in followed by an immediate shift of the center of pressure (COP) to the contacted leg. In ataxic gait, however, both the heel and toes simultaneously contacted the floor and the disappearance of the immediate shift of the COP was noted. These changes appeared to be nonspecific compensations for the instability. Examination of two parameters of ataxia-specific changes showed that prolongation of the double support period was associated with proportionate increase in the coefficients of variance of the plantar pressures and the step lengths on walking of patients with SCA6, but not those with MSAc and 16q-linked ADCA. Our results suggest that disequilibrium and irregularity are two separate and independent components of cerebellar ataxic gait.

General endurance in hemiplegic patients: comparison between healthy subjects and hemiplegics using the incremental stand-up exercise-load method.

OBJECTIVES: To evaluate the utility of our newly devised method (incremental stand-up exercise-load) to determine features of general endurance in hemiplegic patients. SUBJECTS/PATIENTS: Participants were 15 healthy adults and 15 hemiplegics, with 13 men and 2 women in each group. METHODS: To evaluate endurance, the subjects were required to assume a sitting position on a bed for 3 minutes and thereafter repeat standing-sitting (SS) movements. Successively increasing loads were imposed by increasing the frequency of repetition of the SS movements. An expired gas analyzer measured the magnitude of general endurance. Results were compared between the two groups using the anaerobic threshold (AT) as an indicator. RESULTS: The AT value was determinable in 80% of subjects in both groups. The AT values in hemiplegics (10.4 +/- 2.0 ml/min/kg) were significantly (p<0.01) less than those (17.3 +/- 3.0 ml/min/kg) in controls. Time of imposition of the load in hemiplegics (11 min 7 s +/- 13 min 45 s) were significantly (p<0.01) less than those (27 min 0 s +/- 7 min 36 s) in controls. CONCLUSION: This newly devised method that does not require special equipment is suitable to examine general endurance in hemiplegic patients.

CAD/CAM evaluation of the fit of trans-tibial sockets for trans-tibial amputation stumps.

The purpose of this study was to objectively evaluate the fit of sockets for trans-tibial stumps in order to establish a guideline for use in the automated production of prosthetic sockets. Subjects were 24 trans-tibial amputees. Using a CAD/CAM system, 11 parameters regarding the 3D shape of the stumps and the sockets were objectively evaluated. A correlation was found between the activity level and the upper and lower volumes of the socket, and between the cause of amputation and the upper volume of the socket. It was considered desirable to make the lower part of the socket looser for patients with lower activity levels, to make the upper part tighter for patients with higher activity levels, and to make the upper part looser for amputation patients with peripheral circulatory diseases.

Effect of Changing the Joint Kinematics of Knees With a Ruptured Anterior Cruciate Ligament on the Molecular Biological Responses and Spontaneous Healing in a Rat Model.

BACKGROUND: The poor healing capacity of a completely ruptured anterior cruciate ligament (ACL) has been attributed to an insufficient vascular supply, cellular metabolism, and deficient premature scaffold formation because of the unique intra-articular environment. However, previous studies have focused on intra-articular factors without considering extra-articular factors, including the biomechanical aspects of ACL-deficient knees. HYPOTHESIS: Changing the joint kinematics of an ACL-ruptured knee will improve cellular biological responses and lead to spontaneous healing through the mechanotransduction mechanism. STUDY DESIGN: Controlled laboratory study. METHODS: A total of 66 skeletally mature Wistar rats were randomly assigned to a sham-operated group (SO), ACL-transection group (ACL-T), controlled abnormal movement group (CAM), and an intact group (IN). The ACL was completely transected at the midportion in the ACL-T and CAM groups, and the CAM group underwent extra-articular braking to control for abnormal tibial translation. The SO group underwent skin and joint capsule incisions and tibial drilling, without ACL transection and extra-articular braking. The animals were allowed full cage activity until sacrifice at 1, 2, 4, 6, and 8 weeks postoperatively for histological, molecular biological, and biomechanical assessment. RESULTS: All injured ACLs in the ACL-T group were not healed, but those in the CAM group healed spontaneously, showing a typical ligament healing response. Regarding the molecular biological response, there was an upregulation of anabolic factors (ie, transforming growth factor-ß) and downregulation of catabolic factors (ie, matrix metalloproteinase). Examination of the mechanical properties at 8 weeks after injury showed that >50% of the strength of the intact ACL had returned. CONCLUSION: Our results suggest that changing the joint kinematics of knees with a ruptured ACL alters the molecular biological responses and leads to spontaneous healing. These data support our hypothesis that the mechanotransduction mechanism mediates molecular responses and determines whether the ACL will heal. CLINICAL RELEVANCE: Elucidating the relationship between the mechanotransduction mechanism and healing responses in knees with completely ruptured ACLs may result in the development of novel nonsurgical treatment that enables the ACL to spontaneously heal in patients who are not suitable for reconstruction.