Effect of bone density on the drill-hole diameter made by a cannulated drill bit in cancellous bone.

BACKGROUND: When a pilot hole is made prior to a screw's insertion into bone, the same drill bit is used irrespective of the bone quality. However, osteoporotic bone is fragile and this may affect the hole diameter, which is of particular concern in cancellous bone. In this study, the relationship between bone density and drill-hole diameter was investigated assuming a pre-drilling process in screw-only osteosynthesis in the metaphysis and epiphysis. METHODS: Two types of drill bit (triple-flute [T] and quadruple-flute [Q]) with different shapes and diameters were prepared: type T bits with 3.5 mm and 4.4 mm diameters, and type Q bits with 3.5 mm and 4.2 mm diameters. Drilling was performed manually in simulated bones with four densities: 5, 10, 15, and 20 pounds per cubic foot. We measured the hole diameters with a coordinate measuring machine and analyzed the relationship between the drill-hole diameters and the densities of the simulated bones. We then compared the screw pull-out strength between the two 3.5-diameter drill bits. RESULTS: In all cases, the diameters of the drill holes were larger than those of the drill bits. The relationship between the drill-hole diameters and the bone densities was a negative linear correlation. Enlarging the hole diameter decreased the screw pull-out strength. CONCLUSIONS: For cannulated drill bits of 3.5, 4.2 and 4.4 mm diameter, the diameter of the drill hole in cancellous bone obtained by the manual drilling technique tends to be larger in low-density (e.g., osteoporotic) compared to high-density (e.g., healthy) bone.

Relationship between thread depth and fixation strength in cancellous bone screw.

BACKGROUND: Clarifying the effect of each parameter of screw design on its fixation strength is critical in the development of any type of screw. The purpose of this study was to clarify the relationship between the thread depth and fixation strength of metal screws for cancellous bone. METHODS: Nine types of custom-made screws with the only changed variable being the thread depth were manufactured. Other elements were fixed at a major diameter of 4.5 mm, a thread region length of 15 mm, a pitch of 1.6 mm, and a thread width of 0.20 mm. The pull-out strength and insertion torque of each screw were measured for each of two foam-block densities (10 or 20 pcf). The correlation between the thread depth of the screw and the mechanical findings were investigated with single regression analysis. RESULTS: Regardless of the foam-block density, the pull-out strength significantly increased as the thread depth increased from 0.1 mm to 0.4 mm; after that, the increase was more gradual (p < 0.01, respectively). The relationship between the thread depth and insertion torque was similar. In addition, the insertion torque tended to be more strongly affected by screw depth than the pull-out strength (2.6 times at 20 pcf and 1.4 times at 10 pcf). CONCLUSIONS: The pull-out strength of 4.5-mm-diameter metal screws in a cancellous bone model was found to be biphasic, although linearly correlated with the change in screw depth in both phases. The boundary of the correlation was 0.4 mm regardless of the density of the bone model, with the effect of screw depth on pull-out strength beyond that being small in comparison.

The clinical outcomes of scaphoid nonunion treated with a precisely processed autologous bone screw: a case series.

INTRODUCTION: Metal implants and bioabsorbable implants are frequently used in orthopaedic surgery, but they have some disadvantages. The usefulness of autologous bone has been described, and a method to precisely process autologous bone into implants such as screws and apply the implants clinically has been desired. We created a new system for manufacturing autologous bone screws during surgery and report five cases of scaphoid nonunion treated with precise autologous bone screws made from the tibial cortex using the new system. PATIENTS AND METHODS: From 2012 through 2017, seven patients were diagnosed with scaphoid nonunion at our hospital and based on the inclusion/exclusion criteria, five of them were analyzed herein. The surgery was performed according to Zaidemberg's technique. The bone screw in each case was made from autologous tibial cortex using a numerically controlled lathe (model MTS4, Nano Co., Yokohama, Japan) under sterile conditions. The change in each patient's modified Mayo wrist score between the preoperative examination and at the final survey was determined, as were complications. RESULTS: The median modified Mayo wrist score improved significantly from 65 to 95 points. All patients who were followed for > 2 years fused at a median duration of 3.5 months. Bone regeneration was confirmed at the donor sites in all cases. One fracture at the donor site occurred as a severe complication. CONCLUSIONS: Precisely shaped autologous bone screws manufactured by a computer-assisted machine, together with a vascularized bone graft, may be a useful technique for treating scaphoid nonunions; these screws had good stability and bone replacement. Careful observation of the donor site is required. LEVEL OF EVIDENCE: IV.

Screening of a Panel of Low Molecular Weight Compounds That Inhibit Synovial Fibroblast Invasion in Rheumatoid Arthritis.

Increased invasion of synovial fibroblasts and their involvement in cartilage damage are characteristic phenotypes of rheumatoid arthritis (RA). To identify low molecular weight compounds that suppress synovial fibroblast invasion, a panel of inhibitors (n = 330) was initially screened using a real-time cell analysis system for human synovial fibroblasts that were enzymatically isolated from surgical samples of RA patients. To evaluate the effects of the inhibitors identified in the screen, synovial fibroblast migration was measured using a wound-healing assay, and phosphorylation of intracellular signaling molecules was determined by immunoblots. Several candidate inhibitors were identified in the screen, including inhibitors against platelet-derived growth factor receptor (PDGFR), Akt, PI3K, and glycogen kinase synthetase 3 (GSK-3). These inhibitors strongly suppressed synovial fibroblast migration after 72 h and downregulated phosphorylation of Akt (Ser473) at 48 h. When the inhibitors were removed from the culture conditions, both migration and phosphorylated Akt (Ser473) levels were restored. Furthermore, all the categories of inhibitors except for PDGFR inhibitor IV decreased cell proliferation as well as IL-6 production in synovial fibroblasts. Interestingly, GSK-3 inhibitors increased anti-inflammatory cytokine IL-10 production but suppressed IL-23 production from LPS-primed macrophages obtained from healthy donors. In conclusion, blocking PDGFR, PI3K, or GSK-3 could have therapeutic value as an RA treatment that targets the invasion/migration of synovial fibroblasts.

Efficacy of duloxetine in patients with knee osteoarthritis or chronic low back pain with early pain reduction: An exploratory post-hoc analysis of Japanese phase 3, 1-year extension studies.

BACKGROUND: Two previous phase 3, double-blind, randomized, placebo-controlled trials showed that duloxetine 60 mg/day for 14 weeks significantly improved pain and quality of life in Japanese patients with knee osteoarthritis or chronic low back pain. In their open-label extension studies, these improvements were maintained for ≥48 weeks. This post-hoc analysis assessed the relationship between initial response to duloxetine and long-term pain reduction and quality of life in patients with knee osteoarthritis or chronic low back pain. METHODS: Patients (knee osteoarthritis: N = 43; chronic low back pain: N = 41) were subdivided based on extent of pain reduction from baseline to Week 4 of duloxetine (≥30%, 10-30%, or <10% reduction in Brief Pain Inventory-Severity average pain score). Outcome measures were changes from baseline for Brief Pain Inventory-Severity and Brief Pain Inventory-Interference at regular intervals up to Week 65. RESULTS: Mean change from baseline in Brief Pain Inventory-Severity was greater in patients with ≥30% early pain reduction than in patients with <10% early pain reduction through Week 27 for both conditions, and also Weeks 47-65 for back pain. Compared with the <10% early pain reduction group, mean change from baseline in the average of seven Brief Pain Inventory-Interference domain scores was greater in the ≥30% or 10-30% early pain reduction groups for knee osteoarthritis (except Weeks 63-65), and in the ≥30% early pain reduction group for chronic low back pain through Week 19. CONCLUSIONS: These results suggest that patients with knee osteoarthritis who respond well to duloxetine in the first month might experience sustained, long-term pain relief with generally greater quality-of-life improvement than patients with poor initial response. Patients with chronic low back pain who had strong initial response may experience a greater long-term pain relief, but not greater quality-of-life improvement, than patients with poor initial response.

Efficacy of duloxetine for multisite pain in patients with knee pain due to osteoarthritis: An exploratory post hoc analysis of a Japanese phase 3 randomized study.

BACKGROUND: Central sensitization, including dysfunction of descending inhibitory pain pathways, may contribute to multisite pain in patients with chronic musculoskeletal conditions. Duloxetine is a centrally acting analgesic that effectively reduces pain in patients with knee osteoarthritis. Here we assessed the efficacy of duloxetine (60 mg/day) in Japanese patients (N = 353) with pain due to knee osteoarthritis based on the number of painful body sites, determined using the Michigan Body Map. METHODS: Post hoc analysis of a phase 3, randomized, placebo-controlled trial (ClinicalTrials.gov; NCT02248480). RESULTS: At Week 14, the change from baseline in Brief Pain Inventory-Severity average pain score ("pain reduction") was significantly greater with duloxetine compared with placebo in patients with 3, 4, or ≥5 painful sites, but not in patients with 1 or 2 painful sites. In patients with ≥3 painful sites (57% of patients), pain reduction was significantly greater with duloxetine (n = 100) compared with placebo (n = 101) throughout the study (least squares mean change from baseline to Week 14: -2.68 vs -1.68). Greater pain reduction with duloxetine (n = 77) than placebo (n = 75) also occurred in patients with ≤2 painful sites, although the between-group difference was significant only at Week 4. CONCLUSIONS: These results are consistent with duloxetine enhancing the activity of descending inhibitory pain pathways that are dysfunctional in patients with central sensitization and multisite pain. In addition, these results suggest that duloxetine may be an effective choice of analgesic for patients with knee osteoarthritis and multisite pain.

Japanese Orthopaedic Association (JOA) clinical practice guidelines on the management of anterior cruciate ligament injury - Secondary publication.

BACKGROUND: This clinical guideline presents recommendations for the management of patients with anterior cruciate ligament (ACL) injury, endorsed by the Japanese Orthopaedic Association (JOA) and Japanese Orthopaedic Society of Knee, Arthroscopy and Sports Medicine (JOSKAS). METHODS: The JOA ACL guideline committee revised the previous guideline based on "Medical Information Network Distribution Service Handbook for Clinical Practice Guideline Development 2014", which proposed a desirable method for preparing clinical guidelines in Japan. Furthermore, the importance of "the balance of benefit and harm" was also emphasized. This guideline consists of 21 clinical questions (CQ) and 23 background questions (BQ). For each CQ, outcomes from the literature were collected and evaluated systematically according to the adopted study design. RESULTS: We evaluated the objectives and results of each study in order to make a decision on the level of evidence so as to integrate the results with our recommendations for each CQ. For BQ, the guideline committee proposed recommendations based on the literature. CONCLUSIONS: This guideline is intended to be used by physicians, orthopedic surgeons, physical therapists, and athletic trainers managing ACL injuries. We hope that this guideline is useful for appropriate decision-making and improved management of ACL injuries.

Reference values for the locomotive syndrome risk test quantifying mobility of 8681 adults aged 20-89 years: A cross-sectional nationwide study in Japan.

BACKGROUND: The locomotive syndrome risk test was developed to quantify the decrease in mobility among adults, which could eventually lead to disability. The purpose of this study was to establish reference values for the locomotive syndrome risk test for adults and investigate the influence of age and sex. METHODS: We analyzed 8681 independent community dwellers (3607 men, 5074 women). Data pertaining to locomotive syndrome risk test (the two-step test, the stand-up test, and the 25-question geriatric locomotive function scale [GLFS-25]) scores were collected from seven administrative areas of Japan. RESULTS: The reference values of the three test scores were generated and all three test scores gradually decreased among young-to-middle-aged individuals and rapidly decreased in individuals aged over 60 years. The stand-up test score began decreasing significantly from the age of 30 years. The trajectories of decrease in the two-step test score with age was slightly different between men and women especially among the middle-aged individuals. The two physical test scores were more sensitive to aging than the self-reported test score. CONCLUSION: The reference values generated in this study could be employed to determine whether an individual has mobility comparable to independent community dwellers of the same age and sex.

Outcomes of surgical treatment for osteochondritis dissecans of the elbow: evaluation by lesion location.

BACKGROUND: For treatment of advanced elbow osteochondritis dissecans (OCD), we have used surgical treatment. Although favorable treatment outcomes have been reported for centrally located OCD, treatment outcomes are generally questionable and the choice of surgical method is controversial for laterally located OCD. Our purpose was to evaluate the treatment outcomes based on lesion location. METHODS: The patients were 30 young (mean age, 14 years) male athletes who underwent surgical treatment of elbow OCD and were monitored for more than 1 year. Osteochondral autografts harvested from the knee were transplanted to centralized (13 patients) or lateral localized (9 patients) OCD lesions. For lateral widespread (8 patients) OCD lesions, a detached osteochondral fragment was fixed using small osteochondral plugs. When the remaining cartilage defect was large after fragment fixation, a large-sized osteochondral plug was transplanted to the defect. Treatment outcomes were evaluated by the Japanese Orthopaedic Association score, elbow range of motion (ROM), and radiographic findings. RESULTS: The Japanese Orthopaedic Association score significantly improved in patients with centralized, lateral localized, and lateral widespread types of OCD. ROM significantly improved in patients with centralized and lateral localized, and they returned to playing sports within 6 months. However, patients with lateral widespread OCD exhibited no significant ROM improvement, and returning to sports was difficult for 3 patients because of poor osseous integration of the fixed osteochondral fragment. CONCLUSIONS: Osteochondral autograft transplantation provided favorable outcomes for centralized and lateral localized elbow OCD lesions. However, for lateral widespread OCD lesions, reconstruction of the entire capitellar lesion area may be necessary.

Efficacy of duloxetine by prior NSAID use in the treatment of chronic osteoarthritis knee pain: A post hoc subgroup analysis of a randomized, placebo-controlled, phase 3 study in Japan.

BACKGROUND: A previously conducted placebo-controlled, randomized, phase 3 study of 353 Japanese patients with knee osteoarthritis (OA) showed significant improvements for duloxetine vs placebo in pain and health-related quality of life (HRQoL) (ClinicalTrials.gov Identifier: NCT02248480). Reported here are post hoc subgroup analyses evaluating the efficacy of duloxetine according to the pattern of prior nonsteroidal anti-inflammatory drug (NSAID) use. METHODS: Patients with knee OA pain received once-daily duloxetine or placebo for 14 weeks. Pain was evaluated using the Brief Pain Inventory (BPI) and HRQoL was evaluated using the Western Ontario McMaster Universities Osteoarthritis Index (WOMAC). Patients were divided into four subgroups based on their prior NSAID use: (i) no prior NSAID use; (ii) low-frequency NSAID use (<14 days/month); (iii) high-frequency transdermal NSAID use (transdermal NSAIDs only; ≥14 days/month for the 3 months before study entry); and (iv) high-frequency other NSAID use (eg, oral NSAIDs only, both oral and transdermal NSAIDs; ≥14 days/month for the 3 months before study entry). RESULTS: In each of the four prior NSAID use subgroups, there were greater reductions in BPI average pain severity score for duloxetine vs placebo at all timepoints during the 14-week treatment period; the treatment*prior NSAID use interaction was not statistically significant. In each subgroup, the proportion of patients achieving a ≥50% reduction in BPI average pain severity score was higher for duloxetine vs placebo. In each subgroup, there were greater reductions in WOMAC total score for duloxetine vs placebo at all timepoints; the treatment*prior NSAID use interaction was not statistically significant. In each subgroup, there were greater reductions at Week 14 in WOMAC pain, stiffness, physical function, and total scores for duloxetine vs placebo. CONCLUSIONS: Duloxetine was consistently effective with respect to pain relief and HRQoL in Japanese patients with knee OA pain, regardless of the pattern of prior NSAID use.

Atraumatic Spontaneous Achilles Tendon Rupture in Patients Receiving Oral Corticosteroids Treated With the Modified Side-Locking Loop Suture Technique.

Atraumatic spontaneous Achilles tendon ruptures sometimes occur in patients receiving oral corticosteroids. In general, these cases are treated surgically; however, delayed postoperative management can lead to impaired activities of daily living. The modified side-locking loop suture (SLLS) technique is a useful suture method for safe and early active mobilization. Three cases of spontaneous Achilles tendon ruptures were treated with the modified SLLS technique with good clinical results. The modified SLLS technique is a useful method with a short rehabilitation period for treating atraumatic spontaneous Achilles tendon rupture in patients undergoing corticosteroid therapy.

Brain Activity Changes in Somatosensory and Emotion-Related Areas With Medial Patellofemoral Ligament Deficiency.

BACKGROUND: Patellar instability with medial patellofemoral ligament (MPFL) deficiency is a common sports injury among young people. Although nonoperative and surgical treatment can provide stability of the patella, patients often have anxiety related to the knee. We speculate that neural dysfunction may be related to anxiety in these patients; however, the mechanism in the brain that generates this anxiety remains unknown. QUESTIONS/PURPOSES: (1) How does brain activity in patients with MPFL deficiency change in the areas related to somatic sensation against lateral shift of the patella? (2) How does patella instability, which can lead to continuous fear or apprehension for dislocation, influence brain activity in the areas related to emotion? METHODS: Nineteen patients with MPFL deficiency underwent surgical reconstruction in our hospital from April 2012 to March 2014. Excluding seven patients with osteochondral lesions, 12 patients (five males and seven females; mean age, 20 years) with MPFL deficiency were sequentially included in this study. Eleven control subjects (four males and seven females; mean age, 23 years) were recruited from medical students who had no history of knee injury. Diagnosis of the MPFL deficiency was made with MR images, which confirmed the rupture, and by proving the instability with a custom-made biomechanical device. Brain activity during passive lateral stress to the patella was assessed by functional MRI. Functional and anatomic images were analyzed using statistical parametric mapping. Differences in functional MRI outcome measures from the detected activated brain regions between the patients with MPFL deficiency and controls were assessed using t tests. RESULTS: Intergroup analysis showed less activity in several sensorimotor cortical areas, including the contralateral primary somatosensory areas (% signal change for MPFL group 0.49% versus 1.1% for the control group; p < 0.001), thalamus (0.2% versus 0.41% for the MPFL versus control, respectively; p < 0.001), ipsilateral thalamus (0.02% versus 0.27% for the MPFL versus control, respectively; p < 0.001), and ipsilateral cerebellum (0.82% versus 1.25% for the MPFL versus control, respectively; p < 0.001) in the MPFL deficiency group than in the control group. In contrast, the MPFL deficiency group showed more activity in several areas, including the contralateral primary motor area (1.06% versus 0.6% for the MPFL versus control, respectively; p < 0.001), supplementary motor area (0.89% versus 0.52% for the MPFL versus control, respectively; p < 0.001), prefrontal cortex (1.09% versus 1.09% for the MPFL versus control, respectively; p < 0.001), inferior parietal lobule (0.89% versus 0.62% for the MPFL versus control, respectively; p < 0.001), anterior cingulate cortex (0.84% versus 0.08% for the MPFL versus control, respectively; p < 0.001), visual cortex (0.86% versus 0.14% for the MPFL versus control, respectively; p < 0.001), vermis (1.18% versus 0.37% for the MPFL versus control, respectively; p < 0.001), and ipsilateral prefrontal cortex (1.1% versus 0.75% for the MPFL versus control, respectively; p < 0.001) than did the control group. CONCLUSIONS: Less activity in the contralateral somatosensory cortical areas suggested that MPFL deficiency may lead to diminished somatic sensation against lateral shift of the patella. In contrast, increased activity in the anterior cingulate cortex, prefrontal cortex, and inferior parietal lobule may indicate anxiety or fear resulting from patellar instability, which is recognized as an aversion similar to that toward chronic pain. CLINICAL RELEVANCE: This study suggests that specific brain-area activity is increased in patients with MPFL deficiency relative to that in controls. Further longitudinal research to assess brain activity and proprioception between patients pre- and postreconstructive knee surgery may reveal more regarding how patella instability is related to brain function. We hope that based on such research, a neural approach to improve patella-instability-related brain function can be developed.

Is being a regular player with fewer teammates associated with musculoskeletal pain in youth team sports? A cross-sectional study.

BACKGROUND: Musculoskeletal pain (MSP) is a commonly reported symptom in youth sports players. Some sports-related risk factors have been reported, but previous studies on extrinsic risk factors did not focus on management of team members (e.g., regular or non-regular players, number of players) for reducing sports-related MSP. This study aimed to examine the association of playing status (regular or non-regular players) and team status (fewer or more teammates) with MSP in youth team sports. METHODS: A total of 632 team sports players (age: 12-18 years) in public schools in Unnan, Japan completed a self-administered questionnaire to determine MSP (overall, upper limbs, lower back, and lower limbs) and playing status (regular or non-regular players). Team status was calculated as follows: teammate quantity index (TQI) = [number of teammates in their grade]/[required number of players for the sport]. Associations between the prevalence of pain and joint categories of playing and team status were examined by multivariable-adjusted Poisson regression. RESULTS: A total of 272 (44.3%) participants had MSP at least several times a week in at least one part of the body. When divided by playing or team status, 140 (47.0%) regular and 130 (41.7%) non-regular players had MSP, whereas 142 (47.0%) players with fewer teammates (lower TQI) and 127 (41.8%) players with more teammates (higher TQI) had MSP. When analyzed jointly, regular players with fewer teammates had a higher prevalence of lower back pain compared with non-regular players with more teammates (21.3% vs 8.3%; prevalence ratio = 2.08 [95% confidence interval 1.07-4.02]). The prevalence of MSP was highest in regular players with fewer teammates for all other pain outcomes, but this was not significant. CONCLUSION: Regular players with fewer teammates have a higher risk of lower back pain. Future longitudinal investigations are required.

Delayed gadolinium-enhanced MRI of cartilage and T2 mapping for evaluation of reparative cartilage-like tissue after autologous chondrocyte implantation associated with Atelocollagen-based scaffold in the knee.

OBJECTIVE: To elucidate the quality of tissue-engineered cartilage after an autologous chondrocyte implantation (ACI) technique with Atelocollagen gel as a scaffold in the knee in the short- to midterm postoperatively, we assessed delayed gadolinium-enhanced magnetic resonance imaging (MRI) of cartilage (dGEMRIC) and T2 mapping and clarified the relationship between T1 and T2 values and clinical results. MATERIALS AND METHODS: In this cross-sectional study, T1 and T2 mapping were performed on 11 knees of 8 patients (mean age at ACI, 37.2 years) with a 3.0-T MRI scanner. T1implant and T2implant values were compared with those of the control cartilage region (T1control and T2control). Lysholm scores were also assessed for clinical evaluation. The relationships between the T1 and T2 values and the clinical Lysholm score were also assessed. RESULTS: There were no significant differences in the T1 values between the T1implant (386.64 ± 101.78 ms) and T1control (375.82 ± 62.89 ms) at the final follow-up. The implants showed significantly longer T2 values compared to the control cartilage (53.83 ± 13.89 vs. 38.21 ± 4.43 ms). The postoperative Lysholm scores were significantly higher than the preoperative scores. A significant correlation was observed between T1implant and clinical outcomes, but not between T2implant and clinical outcomes. CONCLUSION: Third-generation ACI implants might have obtained an almost equivalent glycosaminoglycan concentration compared to the normal cartilage, but they had lower collagen density at least 3 years after transplantation. The T1implant value, but not the T2 value, might be a predictor of clinical outcome after ACI.

Quantitative analysis of glycosaminoglycans, chondroitin/dermatan sulfate, hyaluronic acid, heparan sulfate, and keratan sulfate by liquid chromatography-electrospray ionization-tandem mass spectrometry.

We developed a method using liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) with a selected reaction monitoring (SRM) mode for simultaneous quantitative analysis of glycosaminoglycans (GAGs). Using one-shot analysis with our MS/MS method, we demonstrated the simultaneous quantification of a total of 23 variously sulfated disaccharides of four GAG classes (8 chondroitin/dermatan sulfates, 1 hyaluronic acid, 12 heparan sulfates, and 2 keratan sulfates) with a sensitivity of less than 0.5 pmol within 20 min. We showed the differences in the composition of GAG classes and the sulfation patterns between porcine articular cartilage and yellow ligament. In addition to the internal disaccharides described above, some saccharides derived from the nonreducing terminal were detected simultaneously. The simultaneous quantification of both internal and nonreducing terminal saccharides could be useful to estimate the chain length of GAGs. This method would help to establish comprehensive "GAGomic" analysis of biological tissues.

Implantation of tissue-engineered cartilage-like tissue for the treatment for full-thickness cartilage defects of the knee.

PURPOSE: The purposes of this study were to evaluate early- to midterm clinical results after implantation of tissue-engineered cartilage-like tissue for the treatment for full-thickness cartilage defects of the knee and to identify the factors affecting the final clinical results. METHODS: Tissue-engineered cartilage-like tissue was prepared by culturing autologous chondrocytes in atelocollagen gel for 3-4 weeks. A total of 73 knees of 72 patients with full-thickness cartilage defects were implanted with this tissue-engineered cartilage-like tissue. The follow-up of these patients for >5 years (range 5-11 years, median 8.0 years) is reported. The patients were evaluated clinically using a rating scale, as well as arthroscopically, biomechanically, and histologically. A modified magnetic resonance observation of cartilage repair tissue (MOCART) system was used to quantify the magnetic resonance imaging (MRI) findings of the lesions. The patient or defect factors influencing the final clinical outcomes were also investigated. RESULTS: Clinical rating improved significantly after implantation of tissue-engineered cartilage-like tissue. Arthroscopic findings at 2 years after implantation were graded as normal or nearly normal according to the International Cartilage Repair Society (ICRS) scale in 64 of 73 knees (87.7%). Biomechanically, stiffness of the graft almost equalled the surrounding normal cartilage (87.9-102.5%) at 2 years after implantation. Histologically, overall assessment of the repaired tissue by ICRS Visual Assessment Scale II was 70.4 ± 20.8. The average MOCART score was 13.5 ± 11.3 (0-45) preoperatively, 66.6 ± 16.8 (10-90) at 1 year after implantation, 70.4 ± 16.1 (15-90) at 2 years after implantation, and 72.5 ± 17.4 (15-95) at the final follow-up, indicating that MRI results were maintained. Among the factors investigated, only arthroscopic grade of the repaired lesion at 2 years after implantation was significantly correlated with the final clinical scores. CONCLUSIONS: Implantation of tissue-engineered cartilage-like tissue for the cartilage defects of the knee was effective in short- to midterm post-operatively. This procedure can be proposed as one option for repairing full-thickness cartilage defect of the knee. LEVEL OF EVIDENCE: IV.

Biomechanical comparison of the strength of adhesion of polymethylmethacrylate cement to zirconia ceramic and cobalt-chromium alloy components in a total knee arthroplasty.

PURPOSE: The purpose of this study was to clarify the biomechanical characteristics of cement-material interfaces for the zirconia ceramic and cobalt-chromium (Co-Cr) alloy femoral components used for total knee arthroplasty. METHODS: In the first sub-study, we compared the strength of adhesion of the cement to flat plates, by tensile testing under dry and moistened conditions. In the second sub-study, we compared the maximum load of the cement-component complex by tensile testing. In the third sub-study, we compared the fatigue characteristics of the cement-component complex by use of a dynamic tensile testing machine. RESULTS: Under dry conditions, the maximum strength of adhesion to the zirconia ceramic plate was the same as that to the Co-Cr alloy plate. Under moistened conditions, however, the strength of adhesion to the zirconia ceramic plate was significantly lower (p = 0.0017) whereas the strength of adhesion to the Co-Cr alloy plate was not reduced. Maximum load for the cement-component complexes for zirconia ceramic and Co-Cr alloy was no different under both dry and moistened conditions. Fatigue testing showed that cement-zirconia adhesion was stronger than cement-Co-Cr alloy adhesion (p = 0.0161). CONCLUSIONS: The strength of adhesion of cement to zirconia ceramic is substantially weaker under wet conditions than under dry conditions. The mechanical properties of cement-zirconia ceramic component complexes and cement-Co-Cr alloy component complexes are equivalent.

A genome-wide association study identifies a locus associated with knee extension strength in older Japanese individuals.

Sarcopenia is a common skeletal muscle disease in older people. Lower limb muscle strength is a good predictive value for sarcopenia; however, little is known about its genetic components. Here, we conducted a genome-wide association study (GWAS) for knee extension strength in a total of 3452 Japanese aged 60 years or older from two independent cohorts. We identified a significant locus, rs10749438 which is an intronic variant in TACC2 (transforming acidic coiled-coil-containing 2) (P = 4.2 × 10-8). TACC2, encoding a cytoskeleton-related protein, is highly expressed in skeletal muscle, and is reported as a target of myotonic dystrophy 1-associated splicing alterations. These suggest that changes in TACC2 expression are associated with variations in muscle strength in older people. The association was consistently observed in young and middle-aged subjects. Our findings would shed light on genetic components of lower limb muscle strength and indicate TACC2 as a potential therapeutic target for sarcopenia.