Tuberoplasty reduces resistance force in dynamic shoulder abduction for irreparable rotator cuff tears: a cadaveric biomechanical study.

BACKGROUND: Arthroscopic tuberoplasty is an optional technique for managing irreparable rotator cuff tears. However, there is a lack of studies investigating the resistance force during shoulder abduction in cases of irreparable rotator cuff tears and tuberoplasty. HYPOTHESES: In shoulders with irreparable rotator cuff tears, impingement between the greater tuberosity (GT) and acromion increases the resistance force during dynamic shoulder abduction. Tuberoplasty is hypothesized to reduce this resistance force by mitigating impingement. STUDY DESIGN: Controlled laboratory study. METHODS: Eight cadaveric shoulders, with a mean age of 67.75 years (range, 63-72 years), were utilized. The testing sequence included intact rotator cuff condition, irreparable rotator cuff tears (IRCTs), burnishing tuberoplasty, and prosthesis tuberoplasty. Burnishing tuberoplasty refers to the process wherein osteophytes on the GT are removed using a bur, and the GT is subsequently trimmed to create a rounded surface that maintains continuity with the humeral head. Deltoid forces and actuator distances were recorded. The relationship between deltoid forces and actuator distance was graphically represented in an ascending curve. Data were collected at five points within each motion cycle, corresponding to actuator distances of 20 mm, 30 mm, 40 mm, 50 mm, and 60 mm. RESULTS: In the intact rotator cuff condition, resistance forces at the five points were 34.25 ± 7.73 N, 53.75 ± 7.44 N, 82.50 ± 14.88 N, 136.25 ± 30.21 N, and 203.75 ± 30.68 N. In the IRCT testing cycle, resistance forces were 46.13 ± 7.72 N, 63.75 ± 10.61 N, 101.25 ± 9.91 N, 152.5 ± 21.21 N, and 231.25 ± 40.16 N. Burnishing tuberoplasty resulted in resistance forces of 32.25 ± 3.54 N, 51.25 ± 3.54 N, 75.00 ± 10.69 N, 115.00 ± 10.69 N, and 183.75 ± 25.04 N. Prosthesis tuberoplasty showed resistance forces of 29.88 ± 1.55 N, 49.88 ± 1.36 N, 73.75 ± 7.44 N, 112.50 ± 7.07 N, and 182.50 ± 19.09 N. Both forms of tuberoplasty significantly reduced resistance force compared to IRCTs. Prosthesis tuberoplasty further decreased resistance force due to a smooth surface, although the difference was not significant compared to burnishing tuberoplasty. CONCLUSION: Tuberoplasty effectively reduces resistance force during dynamic shoulder abduction in irreparable rotator cuff tears. Prosthesis tuberoplasty does not offer a significant advantage over burnishing tuberoplasty in reducing resistance force. CLINICAL RELEVANCE: Tuberoplasty has the potential to decrease impingement, subsequently reducing resistance force during dynamic shoulder abduction, which may be beneficial in addressing conditions like pseudoparalysis.

The effect of different posterior inclinations of tibial component on tibiofemoral contact pressures after unicompartmental knee arthroplasty.

BACKGROUND: Different posterior inclinations of tibial component after unicompartmental knee arthroplasty (UKA) may lead to different biomechanical characteristics of the knee joint. This finite element study was designed to investigate the tibiofemoral contact pressures after UKA with different posterior inclinations of tibial component. METHODS: Finite element model of a healthy knee joint was constructed, and mobile-bearing (MB) UKA models with 5 different posterior inclinations (3°, 5°, 7°, 9° and 11°) of tibial components were simulated. The maximum contact pressures of tibial plateau cartilage in the lateral compartment and polyethylene insert in the medial compartment were calculated based on the ground reaction force and the angle of the knee flexion obtained by 3D motion capture system. RESULTS: The loading ratio of medial and lateral compartments during standing stance (medial 54.49%, lateral 45.51%) and tibial anterior displacement (134 N, 3.89 mm) of healthy knee was basically consistent with previous experimental data. The maximum contact pressures of the medial meniscus and lateral tibial plateau cartilage of the healthy knee during standing stance were 2.14 MPa and 1.57 MPa, respectively. At the static standing phase, the maximum contact pressures of the polyethylene insert decreased from 17.90 to 17.29 Mpa, and the maximum contact pressures of the tibial plateau cartilage in the lateral compartment increased from 0.81 to 0.92 Mpa following an increase in the posterior inclination of the tibial component. At the first peak of ground reaction force, the maximum contact pressures of polyethylene insert increased from 22.37 to 25.16 MPa, and the maximum contact pressures of tibial plateau cartilage in the lateral compartment increased from 3.03 to 3.33 MPa, with the increase in the posterior inclination of the tibial component. At the second peak of ground reaction force, the maximum contact pressures of polyethylene insert decreased from 2.34 to 2.22 MPa with the increase in posterior inclination of tibial component. CONCLUSION: The preoperative and postoperative finite element models of MB UKA were well established. The results showed that the maximum contact pressures of the polyethylene insert did not change significantly with the increase in the posterior inclination of the tibial prosthesis, while the maximum contact pressures of the tibial plateau cartilage of the lateral compartment increased when the posterior inclination of the tibial prosthesis was > 7°. Our results also show that the maximum contact pressures were greater with an excessive inclination angle (11°) of the tibial component, and the pressures of the tibial plateau cartilage in the lateral compartment were more concentrated on the posterior area. This study, therefore, proposes that excessive osteotomy should be avoided.

Tibio-Femoral Contact Force Distribution of Knee Before and After Total Knee Arthroplasty: Combined Finite Element and Gait Analysis.

OBJECTIVE: To assess the tibio-femoral contact forces before and after total knee arthroplasty (TKA) in patients with knee osteoarthritis (KOA) by three-dimensional (3D) finite element analysis (FEA) models and gait analysis. METHODS: Two hospitalized patients with Kellgren-Lawrence grade IV varus KOA and two healthy subjects were enrolled in this study. Both patients underwent unilateral TKA. FEA models were established based on CT and MR images of the knees of the patients with KOA and healthy subjects. Gait analysis was performed using a three-dimensional motion capture system with a force plate. Three direction forces at the ankle joints were calculated by inverse dynamic analysis, which provided the load for the FEA models. The total contact forces of the knee joints were also calculated by inverse dynamic analysis to enable comparisons with the results from the FEA models. The total knee contact forces, maximum von Mises stress, and stress distribution of the medial plateau were compared between the patients and healthy subjects. The distributions of the medial plateau force at 2 and 6 months postoperatively were compared with the distributions of the forces preoperatively and those in the healthy subjects. RESULTS: During static standing, the medial plateau bore the most of the total contact forces in the knees with varus KOA (90.78% for patient 1 and 93.53% for patient 2) compared with 64.75 ± 3.34% of the total force in the healthy knees. At the first and second peaks of the ground reaction force during the stance phase of a gait cycle, the medial plateau bore a much higher percentage of contact forces in patients with KOA (74.78% and 86.48%, respectively, for patient 1; 70.68% and 83.56%, respectively, for patient 2) than healthy subjects (61.06% ± 3.43% at the first peak and 72.09% ± 1.83% at the second peak). Two months after TKA, the percentages of contact forces on the medial tibial plateau were 79.65%-85.19% at the first and second peaks of ground reaction forces during the stance phase of a gait cycle, and the percentages decreased to 53.99% - 68.13% 6 months after TKA. CONCLUSION: FEA showed that TKA effectively restored the distribution of tibio-femoral contact forces during static standing and walking, especially 6 months after the surgery. The changes in the gait were consistent with the changes in the contact force distribution calculated by the FEA model.

Intersegmental Coordination in Patients With Total Knee Arthroplasty During Walking.

Precise identification of deficient intersegmental coordination patterns and functional limitations is conducive to the evaluation of surgical outcomes after total knee arthroplasty (TKA) and the design of optimal personalized rehabilitation protocols. However, it is still not clear how and when intersegmental coordination patterns change during walking, and what functional limitations are in patients with TKA. This study was designed to investigate lower limb intersegmental coordination patterns in patients with knee osteoarthritis before and after TKA and identify how intersegmental coordination of patients is altered during walking before and after TKA. It was hypothesized that 6-month after TKA, intersegmental coordination patterns of patients are improved compared with that before TKA, but still do not recover to the level of healthy subjects. Gait analysis was performed on 36 patients before and 6-month after TKA and on 34 healthy subjects. Continuous relative phase (CRP) derived from the angle-velocity phase portrait was used to measure the coordination between interacting segments throughout the gait cycle. Thigh-shank CRP and shank-foot CRP were calculated for each subject. Statistical parametric mapping (SPM), a one-dimensional analysis of the entire gait cycle curve, was performed directly to determine which periods of the gait cycle were different in patients and healthy subjects. Six-month after TKA, thigh-shank CRP was significantly higher during 5-12% of the gait cycle (p = 0.041) and lower during 44-95% of the gait cycle (p < 0.001) compared with healthy subjects, and was significantly higher during 62-91% of the gait cycle (p = 0.002) compared with pre-operation. Shank-foot CRP was significantly lower during 0-28% of the gait cycle (p < 0.001) and higher during 58-94% of the gait cycle (p < 0.001) compared with healthy subjects, and was significantly lower during 3-18% of the gait cycle (p = 0.005) compared with pre-operation. This study found that patients exhibited altered intersegmental coordination during the loading response and swing phase both before and after TKA. Six-month after TKA, the thigh-shank coordination was partially improved compared with pre-operation, but still did not recover to the level of healthy subjects, while there was no improvement in the shank-foot coordination pattern after TKA compared with pre-operation. CRP combined with SPM methods can provide insights into the evaluation of surgical outcomes and the design of rehabilitation strategy.

Coordination of lower limbs in patients with knee osteoarthritis during walking.

BACKGROUND: The movement coordination in patients with knee osteoarthritis may be impaired and the identification of the deficits in lower limb inter-segmental coordination is crucial to understand the effect of knee osteoarthritis on knee function. RESEARCH QUESTION: This study utilizes continuous relative phase to investigate the pattern and variability of lower limb inter-segmental coordination in patients with knee osteoarthritis and in healthy subjects during walking, and to evaluate inter-segmental coordination alterations in patients. METHODS: Gait was measured by a three-dimensional motion capture system for 44 patients with late-stage knee osteoarthritis and 22 healthy subjects. Segmental kinematic parameters, continuous relative phase and its variability were calculated. Independent samples t-tests were used to detect differences between patients and healthy subjects. RESULTS: Thigh-shank continuous relative phase of patients is significantly decreased by 16.04° and 16.18° during late stance and swing phase as compared with healthy subjects (P < 0.05). Shank-foot continuous relative phase of patients is significantly decreased by 6.89° during early stance and significantly increased by 5.49° and 6.39° during late stance and swing phase (P < 0.05). Patients also exhibit increased variability of thigh-shank continuous relative phase during late stance and swing phase by 1.90° and 1.65° respectively, and increased variability of shank-foot continuous relative phase during early stance and swing phase by 0.83° and 0.88° respectively as compared to healthy subjects (P < 0.05). SIGNIFICANCE: Patients with knee osteoarthritis exhibit altered coordination patterns and increased coordination variability of thigh-shank and shank-foot. Knee dysfunction results in altered lower limbs coordination and unstable motor control during walking. Investigation of inter-segmental coordination could therefore provide insights into changes in neuromuscular control of gait in patients with knee osteoarthritis.

The biomechanical effect of different posterior tibial slopes on the tibiofemoral joint after posterior-stabilized total knee arthroplasty.

BACKGROUND: Different posterior tibial slopes (PTS) after posterior-stabilized total knee arthroplasty (PS-TKA) may lead to different biomechanical characteristics of knee joint. This cadaveric study was designed to investigate the tibiofemoral kinematics and contact pressures after PS-TKA with different PTS. METHODS: Nine human cadaveric knee specimens were used for PS-TKA with the PTS of 3°, 6°, and 9°. The tibiofemoral kinematics and contact pressures were measured during knee flexion angle changing from 0 to 120° (with an increment of 10°) with an axial load of 1000 N at each angle. RESULTS: The root mean square (RMS) of the tibiofemoral contact area and the mean and peak contact pressures during knee flexion were 586.2 mm2, 1.85 MPa, and 5.39 MPa before TKA and changed to 130.2 mm2, 7.56 MPa, and 17.98 MPa after TKA, respectively. Larger contact area and smaller mean and peak contact pressures were found in the joints with the larger PTS after TKA. The RMS differences of femoral rotation before and after TKA were more than 9.9°. The posterior translation of the lateral condyle with larger PTS was more than that with smaller PTS, while overall, the RMS differences before and after TKA were more than 11.4 mm. CONCLUSION: After TKA, the tibiofemoral contact area is reduced, and the contact pressure is increased greatly. Approximately 80% of the femoral rotation is lost, and only about 60% of the femoral translation of lateral condyle is recovered. TKA with larger PTS results in more posterior femoral translation, larger contact area, and smaller contact pressure, indicating that with caution, it may be beneficial to properly increase PTS for PS-TKA.

Clinical Gait Evaluation of Patients with Lumbar Spine Stenosis.

OBJECTIVE: The third generation Intelligent Device for Energy Expenditure and Activity (IDEEA3, MiniSun, CA) has been developed for clinical gait evaluation, and this study was designed to evaluate the accuracy and reliability of IDEEA3 for the gait measurement of lumbar spinal stenosis (LSS) patients. METHODS: Twelve healthy volunteers were recruited to compare gait cycle, cadence, step length, velocity, and number of steps between a motion analysis system and a high-speed video camera. Twenty hospitalized LSS patients were recruited for the comparison of the five parameters between the IDEEA3 and GoPro camera. Paired t-test, intraclass correlation coefficient, concordance correlation coefficient, and Bland-Altman plots were used for the data analysis. RESULTS: The ratios of GoPro camera results to motion analysis system results, and the ratios of IDEEA3 results to GoPro camera results were all around 1.00. All P-values of paired t-tests for gait cycle, cadence, step length, and velocity were greater than 0.05, while all the ICC and CCC results were above 0.950 with P < 0.001. CONCLUSIONS: The measurements for gait cycle, cadence, step length, velocity, and number of steps with the GoPro camera are highly consistent with the measurements with the motion analysis system. The measurements for IDEEA3 are consistent with those for the GoPro camera. IDEEA3 can be effectively used in the gait measurement of LSS patients.

(5R)-5-hydroxytriptolide (LLDT-8) prevents collagen-induced arthritis through OPG/RANK/RANKL signaling in a rat model of rheumatoid arthritis.

(5R)-5-hydroxytriptolide (LLDT-8) extracts from Tripterygium have anti-inflammatory, antineoplastic and immunity adjustment functions. The present study used a collagen-induced arthritis (CIA) model to evaluate whether LLDT-8 prevents collagen-induced arthritis, and investigated the signaling underlying this. Male Sprague-Dawley rats were induced to generate CIA, mimicking rheumatoid arthritis (RA). The presence of arthritis was determined using RA progression scores. The inflammatory cytokines interleukin (IL)-1ß, IL-6 and nuclear factor-κB were detected using enzyme-linked immunosorbent assay kits. Induced nitric oxide synthase (iNOS) and matrix metalloprotease (MMP)-13 protein expression were measured using western blot analysis. Lastly, reverse transcription-quantitative polymerase chain reaction was used to evaluate osteoprotegerin (OPG) and receptor activator of nuclear factor κB (RANK) gene expression. LLDT-8 improved RA progression scores and reduced the incidence and severity of CIA. Furthermore, LLDT-8 administration inhibited collagen-induced inflammation and iNOS protein expression in arthritic rats. The current data indicated that MMP-13 production was suppressed and OPG/RANKL expression was increased by LLDT-8 treatment in the arthritic rat. The present results suggest that LLDT-8 attenuates CIA through OPG/RANK/RANK ligand signaling in a rat model of RA.

Increased receptor activator of nuclear factor κß ligand/osteoprotegerin ratio exacerbates cartilage destruction in osteoarthritis in vitro.

Osteoarthritis (OA) is a degenerative joint disease characterized by progressive cartilage destruction, matrix degradation and bony changes. Subchondral bone alterations in osteoarthritis are associated with cartilage destruction. It has previously been demonstrated that osteoprotegerin (OPG) and receptor activator of nuclear factor κß ligand (RANKL) mediate this process. The RANKL/OPG ratio is altered in OA chondrocytes compared with normal chondrocytes. In the pathogenesis of OA, abnormal expression levels of matrix metalloproteinase-13 (MMP-13) are secreted by chondrocytes has a vital role in the progression of cartilage erosion. In the present study, the effect of various RANKL/OPG ratios on MMP-13 expression levels was investigated in interleukin-1ß-stimulated SW1353 human chondrosarcoma cells. Cell viability was assessed by MTT assay and MMP-13 mRNA and protein expression levels were analyzed by quantitative reverse-transcription-quantitative polymerase chain reaction, ELISA and western blot analyses, respectively. The results demonstrated that an increase in MMP-13 mRNA and protein expression levels was observed with increasing RANKL/OPG ratio. These findings suggest that this mechanism may be used as a novel therapeutic strategy against OA.

Finite element analysis of the valgus knee joint of an obese child.

BACKGROUND: Knee valgus and varus morbidity is at the second top place in children lower limb deformity diseases. It may cause abnormal stress distribution. The magnitude and location of contact forces on tibia plateau during gait cycle have been indicated as markers for risk of osteoarthritis. So far, few studies reported the contact stress and force distribution on tibial plateau of valgus knee of children. METHODS: To estimate the contact stresses and forces on tibial plateau of an 8-year old obese boy with valgus knee and a 7-year old healthy boy, three-dimensional (3D) finite element (FE) models of their left knee joints were developed. The valgus knee model has 36,897 nodes and 1,65,106 elements, and the normal knee model has 78,278 nodes and 1,18,756 elements. Paired t test was used for the comparison between the results from the 3D FE analysis method and the results from traditional kinematic measurement methods. RESULTS: The p value of paired t test is 0.12. Maximum stresses shifted to lateral plateau in knee valgus children while maximum stresses were on medial plateau in normal knee child at the first peak of vertical GRF of stance phase. The locations of contact centers on medial plateau changed 3.38 mm more than that on lateral plateau, while the locations of contact centers on medial plateau changed 1.22 mm less than that on lateral plateau for healthy child from the first peak to second peak of vertical GRF of stance phase. CONCLUSIONS: The paired t test result shows that there is no significant difference between the two methods. The results of FE analysis method suggest that knee valgus malalignment could be the reason for abnormal knee load that may cause knee problems in obese children with valgus knee in the long-term. This study may help to understand biomechanical mechanism of valgus knees of obese children.