Intra-Articular Injection of Chitin Nanofiber Attenuates Osteoarthritis: An Experimental Study in a Rat Model of Osteoarthritis.

Background: This study aimed to evaluate the effect of chitin nanofibers (CNF) produced from crab shells as a medical material for the knee in an osteoarthritic rat model. Methods: The effect of intra-articular CNF injection was evaluated histologically among three groups: saline, hyaluronic acid (HA), and CNF injection groups. The Osteoarthritis Research Society International (OARSI) cartilage, subchondral bone, synovial, and meniscus scores were used for scoring. Results: At 4 weeks, the CNF group had significantly lower scores than the saline group. The Synovial score was lower in HA and CNF groups at 4 weeks than in the saline group. At 4 weeks post-treatment, the thickening of the subchondral bone plate and angiogenesis were significantly reduced in the CNF treatment group compared to those in the saline treatment group (P = 0.02). Conclusion: The anti-inflammatory effects of CNF on knee osteoarthritis were comparable to that of HA in the early stages.

Factors associated with mortality in patients with extremity necrotizing soft-tissue infections: a single academic center experience.

PURPOSE: Necrotizing soft-tissue infection (NSTI) is a surgical emergency associated with high mortality. This study primarily aimed to identify the factors associated with in-hospital mortality due to NSTI in the extremities at a single institution. Secondarily, we aimed to clarify the effectiveness of the optimal combination of hyperbaric oxygen therapy (HBOT) and surgery for NSTI treatment. STUDY DESIGN: Retrospective observational study. METHODS: This study included all patients newly diagnosed with NSTI in the extremity from 2003 to 2021 in our hospital. Factors associated with mortality, including patient's characteristics, duration from onset to hospitalization, NSTI type, and clinical data at the initial visit; acute disseminated intravascular coagulation (DIC), laboratory risk indicator for necrotizing fasciitis score, and sequential organ failure assessment score; treatment, initial surgery, surgery times, amputation, HBOT, combined surgery with HBOT, and clinical outcomes; amputation rate, mortality rate, and hospitalization duration were examined. RESULTS: A total of 37 cases were treated for NSTIs. The median age was 64 years (range: 22-86). Five cases (13.5%) died during hospitalization. Ten patients were diagnosed with DIC at the initial visit, of whom four died. HBOT combined with surgery was performed in 23 cases, and 16 cases underwent multiple surgeries. Factors associated with mortality included DIC (p = 0.015, 95% confidence interval [CI]: 0.015-0.633) and multiple surgeries combined with HBOT (p = 0.028, 95% CI: 1.302-95.418). CONCLUSION: This study demonstrates that DIC at the initial visit is associated with mortality in extremity NSTI. Additionally, HBOT might improve prognosis when combined with multiple surgeries.

Factors associated with perioperative deep vein thrombosis in arthroscopic anterior cruciate ligament reconstruction.

BACKGROUND: Anterior cruciate ligament reconstruction (ACLR) is reportedly associated with a higher incidence of deep vein thrombosis (DVT) incidence than other arthroscopic surgical procedures. The aim of this study is to retrospectively investigate the incidence and type of DVT and evaluate the relationship between DVT and risk factors among all patients who underwent ACLR under uniform conditions consisting of mechanical prophylaxis, no medical prophylaxis, and preoperative and postoperative lower extremity venous ultrasonography. METHODS: Of the 114 patients who underwent arthroscopic primary ACLR at our hospital who did not have a compound ligament injury or revision surgery, 112 patients were included. Two patients were not examined. DVT evaluation consisted of whole-leg ultrasonography at 1 week after surgery. We evaluated age, sex, body mass index, comorbidities, operative time, tourniquet time, presence of concurrent surgery (meniscus repair/resection or osteochondral column grafting), and non-weight-bearing status at 1 week after surgery as risk factors for DVT. RESULTS: DVT was found in 33 (29.5%) of 112 patients. Of these, 22 (19.6%) had distal DVT and 11 (9.8%) had proximal DVT. Non-weight-bearing status at 1 week after surgery was a statistically significant risk factor for proximal DVT (P = .034). CONCLUSIONS: Non-weight-bearing status is an independent risk factor for DVT, suggesting that early weight bearing may reduce the occurrence of DVT.

A method combining the use of a mobile application and a dedicated pelvic positioner for acetabular cup insertion.

BACKGROUND: We developed a mobile device application and dedicated pelvic positioner with the aim of improving the acetabular cup placement accuracy in patients undergoing total hip arthroplasty (THA). The function of the application was to display the intra-operative cup angle. The accuracy and clinical usefulness of this combined method were verified through comparison with the conventional alignment guide method. METHODS: In total, 60 patients who underwent cementless THA were included in this study. We compared the cup alignment when using this combined method with that when using the conventional alignment guide method. The absolute value error between the intra- and post-operative angles of inclination and anteversion of the cup was calculated. RESULTS: The absolute value error of inclination was 2.4° ± 2.1° in the study group and 4.0° ± 3.3° in the control group (P = 0.107). The absolute value error of anteversion was 2.8° ± 2.6° in the study group and 7.4° ± 5.3° in the control group (P < 0.001). CONCLUSION: Using the application and pelvic positioner is simple and can be introduced at a low cost. The more accurate measurement of the intra-operative cup angle using this combined method has improved the cup insertion accuracy compared with that of the conventional alignment guide method.

Total knee arthroplasty in the past three decades: Trends in patient characteristics and implant survivorship.

OBJECTIVE: To explore the trends in patient characteristics and implant survivorship (IS) for primary total knee arthroplasty (TKA) over the past three decades. METHODS: This retrospective study enrolled a total of 635 knees who underwent TKA from 1985 to 2014. They were divided into three groups: group A, 125 knees in 1985-1994; group B, 203 knees in 1995-2004; and group C, 307 knees A in 2005-2014. The patient characteristics and IS were compared. RESULTS: The mean age of patients undergoing TKA was getting older: 65.3 ± 9.7, 69.1 ± 10.0, and 74.6 ± 8.4 years, in groups A, B, and C, respectively (p = .001). The proportion of patients <60 years old with RA decreased (p < .001), whereas that of patients ≥ 80 years old with OA increased dramatically, it was 7.0%, 14.5%, and 32.0% in groups A, B, and C, respectively (p < .001). The IS free from infection was over 98% in all groups. Alternatively, the IS free from aseptic loosening become better, it was 83.7%, 95.2%, and 98.2% in groups A, B, and C, respectively (p = .014). CONCLUSIONS: From these trends, we can estimate that the number of patients undergoing TKA will further increase in the future in an aging society.

Secreted matrix metalloproteinase-14 is a predictor for antifibrotic effect of IC-2-engineered mesenchymal stem cell sheets on liver fibrosis in mice.

INTRODUCTION: Transplantation of IC-2-engineered bone marrow-derived mesenchymal stem cell (BM-MSC) sheets (IC-2 sheets) was previously reported to potentially reduce liver fibrosis. METHODS: This study prepared IC-2-engineered cell sheets from multiple lots of BM-MSCs and examined the therapeutic effects of these cell sheets on liver fibrosis induced by carbon tetrachloride in mice. The predictive factors for antifibrotic effect on liver fibrosis were tried to identify in advance. RESULTS: Secreted matrix metalloproteinase (MMP)-14 was found to be a useful predictive factor to reduce liver fibrosis. Moreover, the cutoff index of MMP-14 for 30% reduction of liver fibrosis was 0.918 fg/cell, judging from univariate analysis and receiver operating curve analysis. In addition, MMP-13 activity and thioredoxin contents in IC-2 sheets were also inversely correlated with hepatic hydroxyproline contents. Finally, IC-2 was also found to promote MMP-14 secretion from BM-MSCs of elderly patients. Surprisingly, the values of secreted MMP-14 from BM-MSCs of elderly patients were much higher than those of young persons. CONCLUSION: The results of this study suggest that the IC-2 sheets would be applicable to clinical use in autologous transplantation for patients with cirrhosis regardless of the patient's age.

Rheumatoid Arthritis Onset from Shoulder Monoarthritis.

PURPOSE: To investigate the incidence and clinical characteristics of rheumatoid arthritis (RA) presenting with shoulder monoarthritis. PATIENTS AND METHODS: Our study included 113 patients (77 females; mean age, 63.0 ± 13.1 years) whom we newly diagnosed with RA in 2012-2016. We investigated cases with onset from shoulder monoarthritis. Specifically, we examined physical findings, blood test results, radiographic findings, magnetic resonance imaging (MRI) findings, and duration from initial visit to diagnosis. RA was diagnosed based on the 2010 American College of Rheumatology/European League Against Rheumatism (ACR/EULAR) classification criteria. RESULTS: Overall, mean 2010 ACR/EULAR criteria score was 6.8 ± 1.8, and median duration to diagnosis was 3 days (interquartile range: 0-14). Two patients (1.8%) were identified as having RA with onset from shoulder monoarthritis. Both were late middle-aged women with MRI findings of rotator cuff tear and remarkable synovial proliferation. However, neither patient fulfilled the 2010 ACR/EULAR criteria. It took 85 and 98 days to make a definitive diagnosis, respectively. CONCLUSION: Early diagnosis is difficult when RA synovitis develops from shoulder monoarthritis, especially, in elderly patients who have a rotator cuff tear. In addition to MRI, culture-based and pathological examinations may be helpful for early diagnosis of RA.

A Simple Method to Reduce the Incidence of Cyclops Lesion after Anterior Cruciate Ligament Reconstruction.

The purpose of this study is to determine the influence of debridement in and around the bone tunnels on the prevalence of cyclops lesion (CL), after anterior cruciate ligament reconstruction (ACLR) with hamstring grafts. Our hypothesis was that bone tunnel debridement during ACLR would reduce the prevalence of CL. Methods for debridement in and around the bone tunnels after tunnel drilling were standardized and applied to 38 knees undergoing double-bundle ACLR between 2011 and 2014, Group A (debridement group). Group B (nondebridement group) included 56 knees in which bone tunnel debridement was not performed. Postoperative MRI was performed to evaluate the presence of CL and the following three criteria: (1) the intercondylar site of CL (grade 1-3), depending on its anterior extent along the femoral condyle; (2) posterior bowing of the ACL graft; and (3) the positional relationship between the frontmost fiber of ACL graft and Blumensaat's line. If CL caused loss of extension or pain or discomfort during knee extension, it was defined as symptomatic CL (SCL). CL was detected in 8 cases (21.1%) in Group A and 26 cases (46.4%) in Group B. The prevalence of CL was significantly lower in Group A than in Group B (p = 0.010), and the risk ratio of CL was 0.31 (95% confidence interval: 0.12-0.79). Furthermore, 10 patients in Group B had SCL, compared with none in Group A (p = 0.004). In Group A, the intercondylar site of CL was grade 1 in all cases, while in Group B, the CL grades were 1 (n = 17), 2 (n = 7), 3 (n = 2) (p = 0.008). There were no cases of posterior bowing of the ACL in Group A, but six cases in Group B (p = 0.023). Debridement in and around the bone tunnel is a simple and effective method of preventing CL and SCL after ACLR. The level of evidence for the study is 3.

An experimental comparative study of drilling efficiency and temperature elevation with unmodified and modified medical drills in pig tibia bone.

BACKGROUND: There are no medical drill specifications capable of achieving bone drilling in a short time under low-thrust and low-speed drilling. Gekkou-drill® is an industrial drill that enables drilling with low cutting resistance by its characteristic point design. Our aims were to develop Gekkou-modified drills by processing to the points of currently available medical drills and to verify whether these modified drills enable less invasive drilling procedure for bone tissue in thermal exposure compared with unmodified medical drills. MATERIALS AND METHODS: Two commercially available 3.2-mm drills were compared before and after Gekkou modification. Drilling of pig tibias was performed at speeds of 300, 800, and 1,500 rpm and a uniform thrust force of 10 N. Temperature at the entry point for bone drilling was measured using a digital thermometer system. The feed rates were calculated using cortical thickness and monitoring data of the digital force gauge. RESULTS: Two unmodified drills could not penetrate the cortical bone on the near side at 300 rpm, even after 5 min of drilling. The maximum temperatures with modified drills were 54.6 °C and 46.2 °C at 300 rpm. At medium to high speeds, those were statistically significantly lower than with unmodified drills (58.5 °C vs. 90.5 °C at 800 rpm, 62.6 °C vs. 80.8 °C and 73.9 °C vs. 104.6 °C at 1,500 rpm). The feed rates for modified drills were 4.9-6.9 times as high as unmodified drills at 800 rpm, and 3.4 to 4.5 times at 1,500 rpm. On the other hand, the feed rates of modified drills at 300 rpm were equal to or higher than those of unmodified drills at 1500 rpm. CONCLUSION: Gekkou-modified drills clearly suppressed the temperature rise and increased the feed rate compared with conventional drills. Furthermore, it was notable that these modified drills had higher performance even at conditions of low thrust and low speed.

Thermal damage of osteocytes during pig bone drilling: an in vivo comparative study of currently available and modified drills.

OBJECTIVES: The Gekkou-drill® is an industrial drill that is highly efficient due to reduced cutting resistance resulting from its characteristic drill point shape. In this experiment, we compared the degree of thermal damage to bone tissue caused by conventional medical drills and these same drills with Gekkou modifications. METHODS: Holes were created in the tibias of living pigs using two different 3.2-mm diameter drills and their modified versions. Regarding the drilling parameters, the thrust force was 10 N and the drilling speeds were 800 revolutions per minute (rpm) and 1500 rpm. We compared the original and modified drills in terms of the bone temperature around the drill bit and the total time necessary to create each hole, the latter calculated using imaging data captured during drilling. In histopathological examination, the percentages of empty lacunae in osteocytes of the cortical bone beneath the periosteum were evaluated at 400 × magnification with an optical microscope. RESULTS: Compared to the original drills, the modified drills required significantly less time to create each hole and caused a significantly lower temperature rise during bone drilling. With the modified drills, the percentages of empty lacunae around the drilling holes were about 1/2-1/3 of those with the original drills, and were significantly lower for both drilling speeds. CONCLUSIONS: Gekkou-modified medical drills shortened drilling times despite low thrust force, and histopathological assessment demonstrated a significant reduction in osteocyte damage.

Change in the pennation angle of the supraspinatus muscle after rotator cuff tear repair.

BACKGROUND: The pennation angle is an important architectural and functional feature of pennate muscles. The purpose of this study was to investigate the change in the pennation angle of the supraspinatus muscle after rotator cuff tear repair. MATERIALS AND METHODS: The study included 68 patients who underwent arthroscopic rotator cuff repair and magnetic resonance imaging. The size of the tear was measured under arthroscopic visualization. The pennation angle of the supraspinatus both preoperatively and postoperatively and the integrity of the repaired cuff were determined by magnetic resonance imaging. RESULTS: The preoperative pennation angle was significantly greater with enlargement of the tear size (P < .0001, analysis of variance). The retear rate was 29% in patients with medium tears and 59% in patients with large or massive tears. No retear was noted in patients with partial and small tears. The retear rate was 90.9% when the preoperative pennation angle was 20° or greater and was 12.3% when this angle was 19° or less, and the risk ratio for retear was 7.4 when this angle was 20° or greater. For repair-type tears, comparison between the preoperative and postoperative pennation angles showed a significant decrease in the mean value from 11.8° ± 3.7° to 9.9° ± 3.0° in the medium tear group (P = .007, paired t test) but no significant difference in the large or massive tear group (from 15.1° ± 7.0° to 13.3° ± 5.8°) (P = .33). For retear-type tears, no significance was found between groups. CONCLUSION: The preoperative pennation angle is directly correlated with the tear configuration and could be one of the prognostic factors for postoperative cuff integrity. To restore the pennation angle, primary repair is more appropriate in smaller rotator cuff tears than in medium-sized tears.

Conservative treatment for lumbar compartment syndrome shows efficacy over 2-year follow-up: a case report and literature review.

BACKGROUND: Since in all studies of conservative treatment of lumbar compartment syndrome the follow-up duration was less than 6 months, it is difficult to draw firm conclusions. PURPOSE: To report a patient with lumbar paraspinal compartment syndrome who was treated conservatively over a follow-up period of 2 years. STUDY DESIGN: This is a case report of a 23-year-old male college student with lumbar paraspinal compartment syndrome who was treated conservatively. METHODS: We report a case of a 23-year-old male college student with lumbar paraspinal compartment syndrome who was treated conservatively. We repeatedly checked his physical examination, laboratory tests, lumbar compartment pressures, and magnetic resonance imaging, and surgical teams were readily prepared to operate should the patient's condition worsen. To prevent complications of rhabdomyolysis, hydration and alkalization were performed. We followed him up to 2 years after discharge. RESULT: Although the temporal changes on MRI up to the 1-year point, the patient continued to have no symptoms. CONCLUSIONS: Conservative therapy can be recommended if rhabdomyolysis is under control.

Useful ultrasonographic evaluation of the medial meniscus as a feature predicting the onset of radiographic knee osteoarthritis.

OBJECTIVE: Medial radial displacement (MRD) of the medial meniscus is a feature proving a dysfunction in the medial meniscus in osteoarthritis (OA) of the knee. MRD was measured in radiographic pre-OA knee and early osteoarthritis of the knee (early-OA) longitudinally using ultrasound (US) to investigate the characteristics involved in the onset and progression of OA. METHODS: Fifty-five patients with pain on the medial side of the knee participated in the present study. It was possible to follow-up 46 patients for 5 years, and, thus, they were divided into 32 pre-OA patients (female: 59%, mean age: 69.0 years) and 14 early-OA patients (female: 78%, mean age: 74.4 years) based on radiography at the baseline time-point. MRD was measured in standing and supine positions at baseline and after 1 and 5 years using US. MRD corrected with the skeletal size, i.e., the medial displacement index (MDI), was analyzed. The pre- and early-OA groups were divided into subgroups at 5 years: stable and OA progression groups, following the Kellgren/Lawrence classification, and ⊿MDI (gap of the MDI between the standing and supine positions) were retrospectively compared between the subgroups at baseline, 1 and 5 years. RESULTS: In the overall pre-OA group, MDI increased by 7% and 10% at 5 years in the supine and standing position, showing a significant increase (P = 0.044, 0.0147). ⊿MDI was significantly greater in the subgroup with OA progression in the pre- and early-OA groups (P = 0.02 and 0.03, respectively), and was continuously 6-7% in the pre-OA progression group, showing that the displacement rate was 2-fold or higher than in the stable group. CONCLUSION: An increase in ⊿MDI on US may be an important risk factor for the disease stage progression of OA and useful as a feature predicting the onset of radiographic knee OA.

Multifocal localized pigmented villonodular synovitis arising separately from intra- and extra-articular knee joint: case report and literature review.

We present a case of intra- and extra-articular localized pigmented villonodular synovitis (PVNS) of the right knee joint separately. A 14-year-old girl presented with a painful mass over the medial aspect of the right knee. MRI demonstrated nodular masses located in the anteromedial area of the knee joint and on the surface of the deep medial collateral ligament outside the joint. Arthroscopic and open synovectomy were performed for both lesions. Histopathology confirmed diagnosis of localized PVNS and pigmented villonodular bursitis, respectively. Our case highlights that localized PVNS are likely to occur in intra- and extra-articular regions separately.

Ultrasonographic evaluation of medial radial displacement of the medial meniscus in knee osteoarthritis.

OBJECTIVE: To evaluate medial radial displacement (MRD) of the medial meniscus in osteoarthritic (OA) and normal knees, with and without weight bearing, using ultrasonography (US), and to prospectively evaluate the time course of changes in MRD in OA knees. METHODS: The study subjects were 78 patients with OA of the knee (69% female; mean age 66.4 years) and 20 healthy, asymptomatic subjects (70% female; mean age 64.5 years) who served as a control group. The OA stage was determined according to the Kellgren/Lawrence (K/L) radiographic grading system. US measurement of MRD was performed with subjects in the supine and standing positions. With the exception of subjects who dropped out, 58 OA knees (followup rate 74%) were evaluated at baseline and ∼1 year later. RESULTS: The medial meniscus was significantly displaced radially by weight bearing in control knees (P<0.001) and in knees with K/L grades 1-3 OA (P<0.01 for each comparison). MRD in either the supine or the standing position was not significantly different between the control knees and the K/L grade 1 knees, but significant differences were noted between the control knees and K/L grade 2 or more severe OA knees (P<0.01 for each comparison). MRD of the medial meniscus had increased significantly on followup in all knees (P<0.05 for each comparison) excluding K/L grade 4 knees in the standing position. CONCLUSION: MRD of the medial meniscus increased with weight bearing and during followup. These findings suggest a close association between extraarticular displacement of the medial meniscus and progression of OA.

Recent trends in adult-onset septic arthritis of the knee and hip: retrospective analysis of patients treated during the past 50 years.

This study was a retrospective analysis of 53 adult patients with septic arthritis (SA) of the knee or hip treated during the years from 1955 to 2005 in Tottori University Hospital in Japan. Patients with postoperative infection, infection caused by trauma, and periprosthetic infection were excluded. The 50-year period between 1955 and 2005 was divided into five periods: there were 5 patients in the first decade, 9 in the second decade, 11 in the third decade, 10 in the fourth decade, and 18 in the fifth decade. All SA occurred in the knee until the fourth decade. Five cases of septic arthritis in the hip occurred in the fifth decade. In contrast to the decrease in direct infections (post intraarticular injection), hematogenous infections were observed to increase after 1986. The rate of SA caused by Staphylococcus aureus (including methicillin-resistant Staphylococcus aureus, MRSA) had been highest during the 50 years. Infections caused by MRSA, comprising 22% of all staphylococcal infection, occurred in the fifth decade. The numbers of patients with comorbid conditions such as diabetes increased during the 50-year period. This study indicated that patients with SA have been increasing in number. Furthermore, hematogenous SA has been increasing. The increase in occurrence of SA could result from increase in opportunistic infection, occurrence of SA of the hip, and increase in MRSA infection.

Effect of raloxifene on arthritis and bone mineral density in rats with collagen-induced arthritis.

We studied the effect of raloxifene (RAL) on arthritis and bone mineral density (BMD) in rats with collagen-induced arthritis (CIA). Seven-month-old female Sprague-Dawley rats were divided into five groups: rats without CIA (CNT), CIA rats that underwent ovariectomy (OVX) and were treated with RAL (CIA + OVX + RAL), CIA rats that underwent OVX and were treated with vehicle (CIA + OVX + Veh), CIA rats that had sham surgery and were treated with RAL (CIA + sham + RAL), and CIA rats that had sham surgery and were treated with vehicle (CIA + sham + Veh). RAL was orally administered at 10 mg/kg every day for 3 weeks, beginning 1 week after initial sensitization until death at 4 weeks. Every week until death, we evaluated hind paw thickness and arthritis score. BMD was measured by peripheral quantitative computed tomography at the distal metaphysis and the diaphysis of the femur; we also performed histomorphometry of the proximal tibia and histological evaluation of arthritis. RAL administration suppressed hind paw thickness and arthritis score and prevented decreases in BMD and cortical thickness. In the histomorphometric analysis, bone-resorption parameters were significantly lower in the RAL groups than in the Veh groups. RAL significantly inhibited synovial proliferation in CIA rats. RAL effects on arthritis and bone were apparent regardless of whether an animal had undergone OVX. RAL could suppress arthritis and bone loss in estrogen-replete or -depleted rats. These findings, using an animal model, indicate the potential usefulness of RAL as an effective treatment for premenopausal RA patients as well as postmenopausal ones.

Role of subchondral bone in osteoarthritis development: a comparative study of two strains of guinea pigs with and without spontaneously occurring osteoarthritis.

OBJECTIVE: To evaluate the relationships among cartilage and subchondral bone before and after the onset of cartilage degeneration in the Hartley guinea pig model of spontaneous osteoarthritis (OA) as compared with those in Weiser-Maple guinea pigs, which do not develop OA. METHODS: Mice from each strain were used at ages 2, 3, 5, and 8 months (n = 7 at each time point). The region observed was the medial tibial plateau. Cartilage degeneration was evaluated histologically. Subchondral bone structure was evaluated based on subchondral bone plate thickness and subchondral cancellous bone trabecular parameters calculated from the microfocal computed tomography 3-dimensional reconstruction image. The bone mineral density (BMD) of the subchondral cancellous bone as well as levels of urinary N-telopeptide of type I collagen (NTX) and serum osteocalcin (OC) were measured. RESULTS: In Hartley guinea pigs, the number of chondrocytes in the surface layer started to decrease at 3 months. At 8 months, fibrillation expanded to the radial zone. In Weiser-Maple guinea pigs, no cartilage degeneration was noted even at 8 months. Subchondral bone plate thickness was significantly lower in Hartley guinea pigs than in Weiser-Maple guinea pigs at 2 months. The subchondral bone had a rod-like and convex structure at 2 months in Hartley guinea pigs. BMD was significantly lower in Hartley guinea pigs than in Weiser-Maple guinea pigs at 2 months. The serum OC level was significantly higher in Hartley guinea pigs than in Weiser-Maple guinea pigs at 2 months and 3 months, whereas the urinary NTX level was significantly lower in Hartley guinea pigs at 3 months. CONCLUSION: Subchondral bone is fragile, and bone formation may be promoted in subchondral bone before the onset of cartilage degeneration in Hartley guinea pigs. Subchondral bone may be involved in the development of OA.

[Morphological features of articular cartilage and synovial membrane in osteoarthritis and rheumatoid arthritis].

Osteoarthritis (OA) and rheumatoid arthritis (RA) do not show any specific morphological findings. However, there are many morphological findings which are common to each disease. In the current study, we describe morphological changes of articular cartilage and synovial membrane during progression of joint destruction in OA and RA, respectively.