Efficacy and cost-effectiveness analysis of post-acute care for elderly patients with hip fractures.

BACKGROUND/PURPOSE: Hip fractures are associated with physical dysfunction, and poor quality of life in the elderly. Post-acute care (PAC) would facilitate functional recovery in patients with hip fractures after surgeries. Taiwan has proposed a nationwide PAC program for hip fractures since 2017, but little has been known about its effectiveness. Therefore, this study aimed to evaluate the efficacy and cost-effectiveness of the PAC program for hip fracture patients in Taiwan. METHODS: This was a prospective study. Patients aged ≥ 65 years with hip fractures after surgeries were recruited and divided into home-based, hospital-based, and control groups. Outcome measures included pain, physical function (sit-to-stand test, Barthel Index [BI], and Harris hip score [HHS]), and quality of life (EuroQol instrument [EQ-5D]). Direct medical and non-medical costs were recorded. Cost-effectiveness ratio (CER) was calculated as the amount of New Taiwanese Dollars (NTDs) paid per BI and EQ-5D unit improvement. RESULTS: Forty-one patients participated in this study, with 17, 12, and 12 in the home-based, hospital-based, and control groups, respectively. The home-based group showed significant improvements in BI and HHS compared to the controls (p = 0.018 and p = 0.029, respectively). The hospital-based group demonstrated significant improvement in EQ-5D compared to the controls (p = 0.015). The home-based PAC program demonstrated the best CER for BI (NTD 554) and EQ-5D (NTD 41948). CONCLUSION: Both PAC programs would significantly improve the physical function and quality of life in patients with hip fractures. However, the home-based PAC provided the best CER for BI and EQ-5D.

Stress distribution of the patellofemoral joint in the anatomic V-shape and curved dome-shape femoral component: a comparison of resurfaced and unresurfaced patellae.

PURPOSE: Whether to resurface the patella in knee replacement remains a controversial issue. The geometrical design of the trochlear groove in the femoral component could play an important role in determining the stress distribution on the patellofemoral joint, but this has not been sufficiently reported on. This study attempted to determine the effect of implant design on contact mechanics by means of a finite element method. METHODS: Two designs, an anatomical V-shape design (VSD) and a dome-shape design (DSD), for the anterior trochlear surface in a contemporary femoral component were chosen for examining the contact characteristics. The use and absence of patella resurfacing was simulated. The stress and strain distribution on the patellar bone and the polyethylene component were calculated for comparison. RESULTS: Without patellar resurfacing, the maximal compressive strain in the patellar bone in the VSD model was about 20 % lower than the DSD model. On the other hand, with resurfacing, the maximal strain for the VSD model was 13.3 % greater than for DSD. Uneven stress distribution at the bone-implant interface was also noted for the two designs. CONCLUSION: The femoral component with a V-shape trochlear groove reduced the compressive strain on the unresurfaced patella. If resurfacing the patella, the femoral component with a curved domed-shape design might reduce the strain in the remaining patellar bone. Uneven stress could occur at the bone-implant interface, so design modifications for improving fixation strength and medialization of the patellar button would be helpful in reducing the risk of peg fracture or loosening. LEVEL OF EVIDENCE: III.

Biomechanical evaluation of a new pedicle screw-based posterior dynamic stabilization device (Awesome Rod System)--a finite element analysis.

BACKGROUND: Pedicle-screw-based posterior dynamic stabilization devices are designed to alleviate the rate of accelerated degeneration of the vertebral level adjacent to the level of spinal fusion. A new pedicle-screw-based posterior dynamic stabilization device- the Awesome Dynamic Rod System was designed with curve cuts on the rods to provide flexibility. The current study was conducted to evaluate the biomechanical properties of this new device. METHODS: Finite element models were developed for the intact spine (INT), the Awesome Dynamic Rod Implanted at L4-L5 (AWE), a traditional rigid rod system implanted at L4-L5 along with an interbody cage (FUS), and the Awesome Dynamic Rod System implanted at L4-L5 along with an interbody cage as an adjunct to fusion procedures and extension of dynamic fixation to L3-L4 (AWEFUS). The models were subjected to axial loads and pure moments and evaluated by a hybrid method on range of motion (ROM)s, disc stresses, pedicle screws stresses, and facet joint contact forces. RESULTS: FUS sustained the lowest L4-L5 ROM decrement in flexion and torsion. AWE demonstrated the lowest adjacent level ROM increment in all moments except for extension at L3-L4, and AWEFUS showed the greatest ROM increment at L2-L3. AWE demonstrated lowest adjacent segment disc stress in flexion, lateral bending and torsion at L3-L4. AWEFUS showed the highest disc stress increment in flexion, extension, and lateral bending, and the lowest disc stress decrement in torsion at L2-L3. AWE sustained greater adjacent facet joint contact forces than did FUS in extension and lateral bending at L3-L4, and AWEFUS demonstrated the greatest contact forces concentrating at L2-L3. CONCLUSION: The results demonstrate that the Awesome Dynamic Rod System preserved more bridged segment motion than did the traditional rigid rod fixation system except in extension. However, the Awesome Dynamic Rod System bore a greater facet joint contact force in extension. The Awesome Dynamic Rod System did protect the adjacent level of fusion segments, but led to much greater ROM, disc stresses, and facet joint contact forces increasing at the adjacent level of instrumented segments.

Effects of cord pretension and stiffness of the Dynesys system spacer on the biomechanics of spinal decompression- a finite element study.

BACKGROUND: The Dynesys system provides stability for destabilized spines while preserving segmental motion. However, clinical studies have demonstrated that the Dynesys system does not prevent adjacent segment disease. Moreover, biomechanical studies have revealed that the stiffness of the Dynesys system is comparable to rigid fixation. Our previous studies showed that adjusting the cord pretension of the Dynesys system alleviates stress on the adjacent level during flexion. We also demonstrated that altering the stiffness of Dynesys system spacers can alleviate stress on the adjacent level during extension of the intact spine. In the present study, we hypothesized that omitting the cord preload and changing the stiffness of the Dynesys system spacers would abate stress shielding on adjacent spinal segments. METHODS: Finite element models were developed for - intact spine (INT), facetectomy and laminectomy at L3-4 (DEC), intact spine with Dynesys system (IntDyWL), decompressed spine with Dynesys system (DecDyWL), decompressed spine with Dynesys system without cord preload (DecDyNL), and decompressed spine with Dynesys system assembled using spacers that were 0.8 times the standard diameter without cord pretension (DecDyNL0.8). These models were subjected to hybrid control for flexion, extension, axial rotation; and lateral bending. RESULTS: The greatest decreases in range of motion (ROM) at the L3-4 level occurred for axial rotation and lateral bending in the IntDyWL model and for flexion and extension in the DecDyWL model. The greatest decreases in disc stress occurred for extension and lateral bending in the IntDyWL model and for flexion in the DecDyWL model. The greatest decreases in facet contact force occurred for extension and lateral bending in the DecDyNL model and for axial rotation in the DecDyWL model. The greatest increases in ROMs at L2-3 level occurred for flexion, axial rotation and lateral bending in IntDyWL model and for extension in the DecDyNL model. The greatest increases in disc stress occurred for flexion, axial rotation and lateral bending in the IntDyWL model and for extension in the DecDyNL model. The greatest increases in facet contact force occurred for extension and lateral bending in the DecDyNL model and for axial rotation in the IntDyWL model. CONCLUSIONS: The results reveals that removing the Dynesys system cord pretension attenuates the ROMs, disc stress, and facet joint contact forces at adjacent levels during flexion and axial rotation. Removing cord pretension together with softening spacers abates stress shielding for adjacent segment during four different moments, and it provides enough security while not jeopardizes the stability of spine during axial rotation.

Effect of spacer diameter of the Dynesys dynamic stabilization system on the biomechanics of the lumbar spine: a finite element analysis.

STUDY DESIGN: A finite element analysis to simulate the behavior of lumbar spines implanted with a posterior dynamic neutralization system, Dynesys, under displacement-controlled loading. OBJECTIVE: To investigate whether Dynesys spacers with different diameters would alter the distribution of range of motion, disk stress, and facet contact force at the Dynesys bridging level and the cranial adjacent level. SUMMARY OF BACKGROUND DATA: The Dynesys system is designed to preserve intersegmental motion and reduce loading at adjacent levels, but clinical reports do not support these claims. This system has been shown to be almost as stiff as rigid fixation, which acts to hinder intersegmental motion. Few studies have investigated methods of reducing this stiffness. METHODS: In the finite element study, a previously validated lumbar spine model was used. Five Dynesys constructs with different spacer diameters (0.8, 0.9, 1.0, 1.1, and 1.2 times the original standard size) were implanted into the spine model and bore 4 displacement-controlled loading cases: flexion, extension, torsion, and lateral bending. Resultant range of motions (ROMs), disk stress, and facet contact forces at the bridged level and the cranial adjacent level were compared with the results of a spine model without Dynesys implantation. RESULTS: The results of ROMs, disk stress, and facet contact forces at the bridged levels were all less than those in the intact spine, except for contact forces at the left facet under lateral bending, facet contact forces at the right facet under torsion, and disk stress under torsion. The results of ROMs, disk stress, and facet contact forces at the cranial adjacent levels were all higher than those in the intact spine. CONCLUSIONS: The results of the present study show that changing the diameter of the spacers will alter the stiffness of the Dynesys construct. Dynesys constructs with larger diameters behave stiffer under flexion but behave softer under extension, torsion, and lateral bending. Changing the diameter of the Dynesys spacers does not significantly influence the load distribution at adjacent levels.

Comparison of Highly Intensive Home-Based Post-acute Care to Inpatient Program for Patients With Fragility Fractures After Surgery.

Introduction: Evidence suggests that patients with fragility fractures would benefit from post-acute care (PAC); however, they have been subjected to varying PAC programs. This study aimed to compare the effectiveness of home-based PAC (HPAC) to inpatient PAC (IPAC) programs for patients with fragility fractures in Taiwan. Materials and methods: This is a retrospective study that reviewed the medical records of patients who received HPAC or IPAC within three weeks after hip, knee, or spine fragility fractures in the Taipei City Hospital from September 1, 2017, to August 31, 2018. Results: The mean age (78.9 ± 10.8 years) showed significant difference between the HPAC (age = 80.6 ± 11.1, n = 83) and the IPAC (age = 78.2 ± 10.6, n = 185) groups (P = .049). After PAC, both HPAC and IPAC groups showed improvement on Barthel index, numerical pain rating scale, and Harris hip score (all P < .001). Patients in the HPAC group displayed greater improvement than the IPAC group on Barthel Index for activities of daily living (ADLs) by 5.8 (95% confidence interval, 3.0 to 8.5). The IPAC group had a significant longer length of PAC than the HPAC group (12.4 ± 3.0 vs. 11.1 ± 2.7, P < .001). Conclusion: Both PAC programs could significantly improve functional performance and reduce pain in patients with fragility fractures. Patients treated in the HPAC group had better ADLs, and less length of PAC.

Effect of the cord pretension of the Dynesys dynamic stabilisation system on the biomechanics of the lumbar spine: a finite element analysis.

The Dynesys dynamics stabilisation system was developed to maintain the mobility of motion segment of the lumbar spine in order to reduce the incidence of negative effects at the adjacent segments. However, the magnitude of cord pretension may change the stiffness of the Dynesys system and result in a diverse clinical outcome, and the effects of Dynesys cord pretension remain unclear. Displacement-controlled finite element analysis was used to evaluate the biomechanical behaviour of the lumbar spine after insertion of Dynesys with three different cord pretensions. For the implanted level, increasing the cord pretension from 100 to 300 N resulted in an increase in flexion stiffness from 19.0 to 64.5 Nm/deg, a marked increase in facet contact force (FCF) of 35% in extension and 32% in torsion, a 40% increase of the annulus stress in torsion, and an increase in the high-stress region of the pedicle screw in flexion and lateral bending. For the adjacent levels, varying the cord pretension from 100 to 300 N only had a minor influence on range of motion (ROM), FCF, and annulus stress, with changes of 6, 12, and 9%, respectively. This study found that alteration of cord pretension affects the ROM and FCF, and annulus stress within the construct but not the adjacent segment. In addition, use of a 300 N cord pretension causes a much higher stiffness at the implanted level when compared with the intact lumbar spine.

Influence of Dynesys system screw profile on adjacent segment and screw.

STUDY DESIGN: Displacement-controlled finite element analysis was used to evaluate the mechanical behavior of the lumbar spine after insertion of the Dynesys dynamic stabilization system. OBJECTIVE: This study aimed to investigate whether different depths of screw placement of Dynesys would affect load sharing of screw, range of motion (ROM), annulus stress, and facet contact force. SUMMARY OF BACKGROUND DATA: In clinical follow-up, a high rate of screw complications and adjacent segment disease were found after using Dynesys. The pedicle screw in the Dynesys system is not so easy to implant into the standard position and causes the screw to protrude more prominently from the pedicle. Little is known about how the biomechanical effects are influenced by the Dynesys screw profile. METHODS: The Dynesys was implanted in a 3-dimensional, nonlinear, finite element model of the L1 to L5 lumbar spine. Different depths of screw position were modified in this model by 5 and 10 mm out of the pedicle. The model was loaded to 150 N preload and controlled the same ROMs by 20, 15, 8, and 20 degrees in flexion, extension, torsion, and lateral bending, respectively. Resultant ROM, annulus stress, and facet contact force were analyzed at the surgical and adjacent level. RESULTS: Under flexion, extension, and lateral bending, the Dynesys provided sufficient stability at the surgical level, but increased the ROM at the adjacent level. Under flexion and lateral bending, the Dynesys alleviated annulus stress at the surgical level, but increased annulus stress at the adjacent level. Under extension, the Dynesys decreased facet loading at the surgical level but increased facet loading at the adjacent level. CONCLUSIONS: This study found that the Dynesys system was able to restore spinal stability and alleviate loading on disc and facet at the surgical level, but greater ROM, annulus stress, and facet loading were found at the adjacent level. In addition, profile of the screw placement caused only a minor influence on the ROM, annulus stress, and facet loading, but the screw stress was noticeably increased.

Biomechanical analysis of a new lumbar interspinous device with optimized topology.

Interspinous spacers used stand-alone preserve joint movement but provide little protection for diseased segments of the spine. Used as adjuncts with fusion, interspinous spacers offer rigid stability but may accelerate degeneration on adjacent levels. Our new device is intended to balance the stability and preserves motion provided by the implant. A new interspinous spacer was devised according to the results of topology optimization studies. Four finite element (FE) spine models were created that consisted of an intact spine without an implant, implantation of the novel, the device for intervertebral assisted motion (DIAM system), and the Dynesys system. All models were loaded with moments, and their range of motions (ROMs), peak disc stresses, and facet contact forces were analyzed. The limited motion segment ROMs, shielded disc stresses, and unloaded facet contact forces of the new devices were greater than those of the DIAM and Dynesys system at L3-L4 in almost all directions of movements. The ROMs, disc stresses, and facet contact forces of the new devices at L2-L3 were slightly greater than those in the DIAM system, but much lower than those in the Dynesys system in most directions. This study demonstrated that the new device provided more stability at the instrumented level than the DIAM system did, especially in lateral rotation and the bending direction. The device caused fewer adjacent ROMs, lower disc stresses, and lower facet contact forces than the Dynesys system did. Additionally, this study conducted topology optimization to design the new device and created a smaller implant for minimal invasive surgery.

Biomechanical analysis and design of a dynamic spinal fixator using topology optimization: a finite element analysis.

Surgeons often use spinal fixators to manage spinal instability. Dynesys (DY) is a type of dynamic fixator that is designed to restore spinal stability and to provide flexibility. The aim of this study was to design a new spinal fixator using topology optimization [the topology design (TD) system]. Here, we constructed finite element (FE) models of degenerative disc disease, DY, and the TD system. A hybrid-controlled analysis was applied to each of the three FE models. The rod structure of the topology optimization was modelled at a 39 % reduced volume compared with the rigid rod. The TD system was similar to the DY system in terms of stiffness. In contrast, the TD system reduced the cranial adjacent disc stress and facet contact force at the adjacent level. The TD system also reduced pedicle screw stresses in flexion, extension, and lateral bending.

Biomechanical analysis of foot with different foot arch heights: a finite element analysis.

Clinically, different foot arch heights are associated with different tissue injuries to the foot. To investigate the possible factors contributing to the difference in foot arch heights, previous studies have mostly measured foot pressure in either low-arched or high-arched feet. However, little information exists on stress variation inside the foot with different arch heights. Therefore, this study aimed to implement the finite element (FE) method to analyse the influence of different foot arches. This study established a 3D foot FE model using software ANSYS 11.0. After validating the FE model, this study created low-arched, high-arched and normal-arched foot FE models. The FE analysis found that both the stress and strain on the plantar fascia and metatarsal were higher in the high-arched foot, whereas the stress and strain on the calcaneous, navicular and cuboid were higher in low-arched foot. Additionally, forefoot pressure was increased with an increase in arch height.

Finite element analysis of the scoliotic spine under different loading conditions.

The role of the vertebral body's rotation and the loading conditions of the brace has not been clearly identified in adolescent idiopathic scoliosis. This study aimed to implement a finite element (FE) model of C-type scoliotic spines to investigate the influence of different loading conditions on variations of Cobb's angle and the vertebral rotation. The scoliotic FE model was constructed from C7 to L5, and its geometry was the right thoracic type (37.4°) with an apex over T7. Three loading conditions included a medial-lateral (ML) and anteroposterior (AP) force with a magnitudes of 100-0, 80-20 and 60-40 N. Those forces were respectively applied over the 6th, 7th and 8th ribs. According to an analysis of Cobb's angle, the 100 N ML force that was applied over the 8th rib could achieve the best correction effect. Furthermore, the ML force was dominant in alterations of Cobb's angle, whereas the AP force was dominant in alterations of the axial vertebral rotation. Additionally, the level below the apex was the most appropriate level to apply the force to correct C-type scoliosis.

Using an optimization approach to design an insole for lowering plantar fascia stress--a finite element study.

Plantar heel pain is a commonly encountered orthopedic problem and is most often caused by plantar fasciitis. In recent years, different shapes of insole have been used to treat plantar fasciitis. However, little research has been focused on the junction stress between the plantar fascia and the calcaneus when wearing different shapes of insole. Therefore, this study aimed to employ a finite element (FE) method to investigate the relationship between different shapes of insole and the junction stress, and accordingly design an optimal insole to lower fascia stress.A detailed 3D foot FE model was created using ANSYS 9.0 software. The FE model calculation was compared to the Pedar device measurements to validate the FE model. After the FE model validation, this study conducted parametric analysis of six different insoles and used optimization analysis to determine the optimal insole which minimized the junction stress between plantar fascia and calcaneus. This FE analysis found that the plantar fascia stress and peak pressure when using the optimal insole were lower by 14% and 38.9%, respectively, than those when using the flat insole. In addition, the stress variation in plantar fascia was associated with the different shapes of insole.

Biomechanical comparison of instrumented posterior lumbar interbody fusion with one or two cages by finite element analysis.

STUDY DESIGN: Using finite element models to study the biomechanics of lumbar instrumented posterior lumbar interbody fusion (PLIF) with one or two cages. OBJECTIVE: Analyzing the biomechanics of instrumented PLIF with one or two cages as to evaluate whether a single cage is adequate for instrumented PLIF. SUMMARY OF BACKGROUND DATA: Implantation of a single cage in instrumented PLIF of lumbar spine is still controversial. METHODS: Three validated finite element models of L3-L5 lumbar segment were established [intact model (INT), one cage model (LS-1), and two cages model (LS-2)]. The available finite element program ANSYS 6.0 (Swanson Analysis System Inc., Houston, TX) was applied. To analyze the biomechanics of these models, 10 Nm flexion, extension, rotation, and lateral bending moment with 150 N of preload were respectively imposed on the superior surfaces of the L3. RESULTS: Compared with the INT model, the decrease of ROM in the LS-1 and LS-2 models were exaggerated from 0.67 degrees to 3.73 degrees and ranged from 37.2% to 86.1% in all motions. The mean subsidence was found to be slightly higher in the LS-1 model. Most of the cage dislodgement in both models was less than 0.03 mm. The mean dislodgement was slightly higher in the LS-1 model. The stress of cage was found to be high in the LS-2 model. The mean stress of screw was raised to 4.5% to 9.7% in the LS-1, which was higher than that in the LS-2 model. In general, stress of adjacent disc was more pronounced in the LS-2 model. The most stress distributed at the anterior portion of the adjacent disc, which could be used to interpret the clinical findings of the early adjacent disc degeneration. CONCLUSIONS: A single cage inserted in an instrumented PLIF gains approximate biomechanical stability, slight greater subsidence, and a slight increase in screw stress but less early degeneration in adjacent disc. Adjusting these factors, instrumented PLIF with one cage could be encouraged in clinical practice.