Joint haemorrhage partly accelerated immobilization-induced synovial adhesions and capsular shortening in rats

Development of a novel model for intraarticular adhesion in rat knee joint

In this study, a novel rat model of knee joint adhesion was developed, and its formation was analyzed quantitatively over time. Thirty-nine Wistar rats were randomly divided into intact control (n = 3) and experimental (n = 36) groups. The latter was equally divided into three groups according to the experimental intervention: fixed with deep bending of the knee joint (group I), fixed after incision of the capsule (group II), and fixed after exposure of the patellofemoral joint to artificial patellar subluxation (group III). All rats were subdivided according to their joint immobilization period (1, 2, or 4 weeks). Thereafter, the limited range of motion of the knee joint with (limited knee range of motion) and without (limited knee joint intrinsic range of motion) skin and muscles were measured. The lengths of adhesions of the anterior knee joint and posterior capsules were evaluated histologically. The limited intrinsic range of motion of the knee joint was found to be increased in groups II and III compared to that in group I 4 weeks after immobilization. Adhesions were confirmed within 1 week after immobilization in groups II and III. The length of the adhesions in group III was significantly longer than in other groups at 2 weeks and remained longer than in group I at 4 weeks. This model may contribute to the assessment of the adhesion process and development of new therapeutic avenues following trauma or surgical invasion.

The effects of immobilization duration on joint contracture formation after anterior cruciate ligament reconstruction in rats

BACKGROUND

Both myogenic and arthrogenic factors contribute to contracture formation after anterior cruciate ligament reconstruction surgery. However, effects of immobilization duration on myogenic and arthrogenic contractures after surgery are unknown. We examined the effects of immobilization duration on contracture formation.

METHODS

Rats were divided into groups according to treatment received: untreated control, knee immobilization, anterior cruciate ligament reconstruction, and anterior cruciate ligament reconstruction plus immobilization. Extension range of motion before and after myotomy as well as histomorphological knee changes were assessed two or four weeks after experiment commencement. Range of motion before myotomy mainly represents contractures due to myogenic factors. Range of motion after myotomy represents arthrogenic factors.

FINDINGS

Range of motion before and after myotomy was decreased in the immobilization, reconstruction, and reconstruction plus immobilization groups at both timepoints. In the reconstruction plus immobilization group, range of motion before and after myotomy was significantly smaller than in the immobilization and reconstruction groups. Shortening and thickening of the posterior joint capsule was induced in the immobilization and reconstruction groups. In the reconstruction plus immobilization group, capsule shortening was facilitated via adhesion formation, as compared to the immobilization and reconstruction groups.

INTERPRETATION

Our results indicate that immobilization after anterior cruciate ligament reconstruction surgery facilitates contracture formation via exacerbation of both myogenic and arthrogenic contractures within two weeks. Capsule shortening would be one of the main mechanisms for severe arthrogenic contracture observed in the reconstruction plus immobilization group. Periods of joint immobilization after surgery should be minimized to reduce contracture.

Effects of Joint Immobilization and Treadmill Exercise on Articular Cartilage After ACL Reconstruction in Rats

Background:

The development of osteoarthritis after anterior cruciate ligament (ACL) reconstruction (ACLR) is an important issue. However, the appropriate rehabilitation protocol to prevent cartilage degeneration due to postoperative osteoarthritis is unclear.

Purpose:

To examine the effects of joint immobilization and treadmill exercise on articular cartilage after ACLR.

Study Design:

Controlled laboratory study.

Methods:

A total of 55 rats received unilateral knee ACL transection and reconstruction surgery using tail tendon autografts. After surgery, rats were reared without intervention, with joint immobilization, or with daily treadmill exercise (12 m/minute, 60 minutes/day, 6 days/week). Treadmill exercise was initiated at 3 or 14 days postoperatively. After 2 weeks of immobilization, the fixation device was removed from some of the immobilized rats, and the knee was allowed to move freely for 2 weeks. Untreated, age-matched rats (n = 8) were used as controls. At 2 or 4 weeks after starting the experiment, cartilage degeneration in the medial tibial plateau was histologically assessed using a modified Mankin score, cartilage thickness, chondrocyte density, and immunohistochemistry for cyclooxygenase-2 (COX-2) in the anterior, middle, and posterior regions.

Results:

After ACLR, cartilage degeneration in the anterior region characterized by increased Mankin score, accompanied with increased COX-2 expression, was detected. Joint immobilization after ACLR facilitated cartilage degeneration, which is detected by histological changes such as reductions in cartilage thickness, chondrocyte density, and high Mankin scores. Enhanced COX-2 expression in all degenerated cartilage regions was also detected. It was found that 2 weeks of remobilization could not restore cartilage degeneration induced by 2 weeks of immobilization after ACLR. Treadmill exercise after ACLR did not affect most articular cartilage parameters, regardless of the timing of exercise.

Conclusion:

Our results indicated that (1) immobilization after ACLR accelerates cartilage degeneration, even when applied only for 2 weeks, and (2) mild exercise during early phases after ACLR does not facilitate cartilage degeneration.

Clinical Relevance:

To reduce cartilage degeneration, periods of joint immobilization after ACLR should be minimized. Mild exercise during the early phases after ACLR will not negatively affect articular cartilage.

Effects of Different Static Progressive Stretching Durations on Range of Motion, Myofibroblasts, and Collagen in a Posttraumatic Knee Contracture Rat Model

OBJECTIVE

The purpose of this study was to investigate the effects of different durations of static progressive stretching (SPS) on posttraumatic knee contracture in rats, including range of motion (ROM), gait analysis, myofibroblast proliferation, and collagen regulation.

METHODS

The posttraumatic knee contracture model was established, and male Wistar rats were randomly divided into the 20-minute SPS treatment, 30-minute SPS treatment (S30), 40-minute SPS treatment, untreated, immobilization, and control groups. At Week 1, 2, and 4 of treatment intervention, joint ROM and gait were measured and compared. Knee joint samples stained with hematoxylin and eosin and Masson trichrome were used to observe alterations in pathological structures. Collagen density and cell numbers in the posterior joint capsule were used to assess joint capsule fibrosis and inflammation. Immunohistochemistry was used to detect type I collagen and α-smooth muscle actin expression.

RESULTS

The S30 group improved the most; ROM, stance, mean intensity, print area, and stride length were 115 (SD = 5) degrees, 0.423 (SD = 0.074) seconds, 156.020 (SD = 7.952), 2.116 (SD = 0.078) cm2, and 11.758 (SD = 0.548) cm, respectively. The numbers of myofibroblasts, fibroblasts, and inflammatory cells decreased, and collagen proliferation was significantly suppressed in the S30 group compared with the other groups.

CONCLUSION

S30 significantly improved posttraumatic knee contracture in rats, with reduced type I collagen and α-smooth muscle actin expression, decreased the numbers of myofibroblasts and inflammatory cells, suppressed fibrotic and inflammatory changes in the joint capsule, and increased joint mobility. This study provided basic evidence for an optimal standard-of-care treatment approach for posttraumatic knee joint contracture in rats, which may have significance for humans.

Pleiotropic Long-Term Effects of Atorvastatin on Posttraumatic Joint Contracture in a Rat Model

The antifibrotic effect of atorvastatin has already been demonstrated in several organ systems. In the present study, a rat model was used to investigate the effect of atorvastatin on posttraumatic joint contracture. Forty-eight Sprague Dawley rats were equally randomized into an atorvastatin group and a control group. After initial joint trauma, knee joints were immobilized for intervals of 2 weeks (n = 16) or 4 weeks (n = 16) or immobilized for 4 weeks with subsequent remobilization for another 4 weeks (n = 16). Starting from the day of surgery, animals received either atorvastatin or placebo daily. After euthanasia at week 2, 4 or 8, joint contracture was determined, histological examinations were performed, and gene expression was assessed. The results suggest that the joint contracture was primarily arthrogenic. Atorvastatin failed to significantly affect contracture formation and showed a reduction in myofibroblast numbers to 98 ± 58 (control: 319 ± 113, p < 0.01) and a reduction in joint capsule collagen to 60 ± 8% (control: 73 ± 9%, p < 0.05) at week 2. Gene expression of α-smooth muscle actin (α-SMA), collagen type I, transforming growth factor β1 (TGF-β1) and interleukin-6 (IL-6) was not significantly affected by atorvastatin. Atorvastatin decreases myofibroblast number and collagen deposition but does not result in an improvement in joint mobility.

Effects of Each Phase of Anterior Cruciate Ligament Reconstruction Surgery on Joint Contracture in Rats

BACKGROUND

Although anterior cruciate ligament reconstruction surgery is known to cause joint contracture, the mechanisms of this process are unknown. We aimed to assess the effects of transection of this ligament and each phase of reconstruction surgery on contracture formation.

MATERIALS AND METHODS

Rats were divided into groups according to treatment received: sham (arthrotomy), ligament transection, ligament transection plus bone drilling, and ligament reconstruction. Surgery was performed on the right knee. Untreated left knees in the sham group were used as controls.

RESULTS

At 7 and 28 d post-surgery, range of motion before myotomy, mainly representing myogenic contracture, was restricted in the sham and ligament transection groups, and more so in the bone drilling and reconstruction groups. Restricted range of motion after myotomy, representing arthrogenic contracture, was detected at both timepoints in the bone drilling and reconstruction groups, but not in the sham or ligament transection groups. At 3 d post-surgery, although a large blood clot was observed in all three treatment groups, only the bone drilling and reconstruction groups showed significant joint swelling. At 7 d post-surgery, inflammatory-cell infiltration into the joint capsule was most apparent in the bone drilling and reconstruction groups, and joint capsule fibrosis was also most apparent in these groups at 7 and 28 d post-surgery.

CONCLUSIONS

Our results suggest that (1) myogenic contracture after anterior cruciate ligament reconstruction is caused by arthrotomy and aggravated by bone drilling, and (2) arthrogenic contracture is mostly due to bone drilling, which triggers an inflammation-fibrosis cascade.

Modular reorganization of gait in chronic but not in artificial knee joint constraint

It is currently unknown if modular reorganization does occur if not the central nervous system, but the musculoskeletal system is affected. The aims of this study were to investigate 1) the effects of an artificial knee joint constraint on the modular organization of gait in healthy subjects; and 2) the differences in modular organization between healthy subjects with an artificial knee joint constraint and people with a similar but chronic knee joint constraint. Eleven healthy subjects and eight people with a chronic knee joint constraint walked overground at 1 m/s. The healthy subjects also walked with a constraint limiting knee joint movement to 20°. The total variance accounted (tVAF) for one to four synergies and modular organization were assessed using surface electromyography from 11 leg muscles. The distribution of number of synergies were not significantly different between groups. The tVAF and the motor modules were not significantly affected by the artificial knee constraint. A higher tVAF for one and two synergies, as well as merging of motor modules were observed in the chronic knee constraint group. We conclude that in the short-term a knee constraint does not affect the modular organization of gait, but in the long-term a knee constraint results in modular reorganization. These results indicate that merging of motor modules may also occur when changes in the mechanics of the musculoskeletal system is the primary cause of the motor impairment.NEW & NOTEWORTHY It is currently unknown if modular reorganization does occur if not the central nervous system, but the musculoskeletal system is affected. This study showed that in the short-term a knee constraint does not affect the modular organization of gait, but in the long-term a knee constraint results in modular reorganization. These results indicate that modular reorganization may also occur when changes in the mechanics of the musculoskeletal system is the primary cause of the motor impairment.

Joint hemorrhage accelerates cartilage degeneration in a rat immobilized knee model

Background

Joint hemorrhage is caused by trauma, ligament reconstruction surgery, and bleeding disorders such as hemophilia. Recurrence of hemorrhage in the joint space induces hemosiderotic synovitis and oxidative stress, resulting in both articular cartilage degeneration and arthropathy. Joint immobilization is a common treatment option for articular fractures accompanied by joint hemorrhage. Although joint hemorrhage has negative effects on the articular cartilage, there is no consensus on whether a reduction in joint hemorrhage would effectively prevent articular cartilage degeneration. The purpose of this study was to investigate the effect of joint hemorrhage combined with joint immobilization on articular cartilage degeneration in a rat immobilized knee model.

Methods

The knee joints of adult male rats were immobilized at the flexion using an internal fixator from 3 days to 8 weeks. The rats were randomly divided into the following groups: immobilized blood injection (Im-B) and immobilized-normal saline injection (Im-NS) groups. The cartilage was evaluated in two areas (contact and non-contact areas). The cartilage was used to assess chondrocyte count, Modified Mankin score, and cartilage thickness. The total RNA was extracted from the cartilage in both areas, and the expression of metalloproteinase (MMP)-8, MMP-13, interleukin (IL)-1β, and tumor necrosis factor (TNF)-α was measured by quantitative real-time polymerase chain reaction.

Results

The number of chondrocytes in the Im-B group significantly decreased in both areas, compared with that in the Im-NS group. Modified Mankin score from 4 to 8 weeks of the Im-B group was significantly higher than that of the Im-NS group only in the contact area. The expression of MMP-8 and MMP-13 from 2 to 4 weeks and TNF-α from 2 to 8 weeks significantly increased in the Im-B group compared with those in the Im-NS group, but there was no significant difference in IL-1β expression.

Conclusions

The results showed that joint hemorrhage exacerbated immobilization-induced articular cartilage degeneration. Drainage of a joint hemorrhage or avoidance of loading may help prevent cartilage degeneration during joint immobilization with a hemorrhage.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-020-03795-0.

Effects of arthroscopic pancapsular release for proximal humeral fractures treated with intramedullary nailing: a retrospective study

Background

Proximal humeral fractures are one of the most common fractures in adults. Some patients treated operatively have restriction in range of motion (ROM) after surgery. This study aimed to evaluate arthroscopic pancapsular release in patients with severe stiffness after treatment with intramedullary nailing for proximal humeral fractures.

Methods

This study included 12 patients (7 women and 5 men) who underwent arthroscopic pancapsular release in the beach-chair position between May 2015 and February 2018. Intraoperative findings were recorded, and ordinary (with scapulothoracic motion) and true (without scapulothoracic motion) glenohumeral ROMs were measured with a goniometer. The American Shoulder and Elbow Surgeons shoulder score, Shoulder Rating Scale score of the University of California, Los Angeles scoring system, and Constant score were compared before and after the release. The Wilcoxon signed rank and Mann-Whitney U tests were used to analyze data.

Results

The average age of the patients was 65.1 years (standard deviation, 9.5 years), and the mean follow-up period after the release was 30.6 months (standard deviation, 11.7 months). All ROMs on the affected side after surgery were significantly greater than those before surgery in all directions. However, ROMs in forward flexion, lateral elevation, and external rotation with the arm at the side and at 90° of forward flexion on the affected side postoperatively were significantly lower than those on the unaffected side. All scores were significantly greater after surgery than before surgery.

Conclusion

Arthroscopic pancapsular release is effective for patients with proximal humeral fractures treated with intramedullary nailing.

Mechanisms involved in the arthrofibrosis formation and treatments following bone fracture

Arthrofibrosis is a common complication for patients with bone fracture following external and internal fixation. In this review, we summarize the related factors and significant pathways for joint adhesion following fracture surgery. Moreover, the different types of treatments and related preventive measures are also discussed. Many factors related to the development and treatment of arthrofibrosis are discussed in this review in order to provide possible clues for the prospective targets to develop new medication or treatments for preventing or reducing the joint adhesion following orthopedic surgery.

Effects of losartan and atorvastatin on the development of early posttraumatic joint stiffness in a rat model

BACKGROUND

After a trauma, exuberant tissue healing with fibrosis of the joint capsule can lead to posttraumatic joint stiffness (PTJS). Losartan and atorvastatin have both shown their antifibrotic effects in different organ systems.

OBJECTIVE

The purpose of this study was the evaluation of the influence of losartan and atorvastatin on the early development of joint contracture. In addition to joint angles, the change in myofibroblast numbers and the distribution of bone sialoprotein (BSP) were assessed.

STUDY DESIGN AND METHODS

In this randomized and blinded experimental study with 24 rats, losartan and atorvastatin were compared to a placebo. After an initial joint injury, rat knees were immobilized with a Kirschner wire. Rats received either losartan, atorvastatin or a placebo orally daily. After 14 days, joint angle measurements and histological assessments were performed.

RESULTS

Losartan increased the length of the inferior joint capsule. Joint angle and other capsule length measurements did not reveal significant differences between both drugs and the placebo. At cellular level both losartan and atorvastatin reduced the total number of myofibroblasts (losartan: 191±77, atorvastatin: 98±58, placebo: 319±113 per counting field, p<0.01) and the percentage area of myofibroblasts (losartan: 2.8±1.8% [p<0.05], atorvastatin: 2.5±1.7% [p<0.01], vs control [6.4±4%], respectively). BSP was detectable in equivalent amounts in the joint capsules of all groups with only a trend toward a reduction of the BSP-stained area by atorvastatin.

CONCLUSION

Both atorvastatin and losartan reduced the number of myofibroblasts in the posterior knee joint capsule of rat knees 2 weeks after trauma and losartan increased the length of the inferior joint capsule. However, these changes at the cellular level did not translate an increase in range of motion of the rats´ knee joints during early contracture development.

Endoplasmic reticulum stress-dependent ROS production mediates synovial myofibroblastic differentiation in the immobilization-induced rat knee joint contracture model

Joint contracture is a common complication for people with joint immobility that involves fibrosis structural alteration in the joint capsule. Considering that endoplasmic reticulum (ER) stress plays a prominent role in the promotion of tissue fibrosis, we investigated whether the unfolded protein response (UPR) contributes to the fibrotic development in immobilization-induced knee joint contractures. Using a non-traumatic rat knee joint contracture model, twelve female Sprague-Dawley rats received knee joint immobilization for a period of 8 weeks. We found that fibrosis protein markers (type I collagen, α-SMA) and UPR (GRP78, ATF6α, XBP1s) markers were parallelly upregulated in rat primary cultured synovial myofibroblasts. In the same cell types, pre-treatment with an ER stress inhibitor, 4-phenylbutyric acid (4-PBA), not only abrogated cytokine TGFβ1 stimulation but also reduced the protein level of UPR. Additionally, high reactive oxygen species (ROS) generation was detected in synovial myofibroblasts through flow cytometry, as expected. Notably, TGFβ1-induced UPR was significantly reduced through the inhibition of ROS with antioxidants. These data suggest that ER stress act as a pro-fibrotic stimulus through the overexpression of ROS in synovial fibroblasts. Interestingly, immunohistochemical results showed an increase in the UPR protein levels both in human acquired joint contractures capsule tissue and in animal knee joint contracture tissue. Together, our findings suggest that ER stress contributes to synovial myofibroblastic differentiation in joint capsule fibrosis and may also serve as a potential therapeutic target in joint contractures.

A novel rat model of stable posttraumatic joint stiffness of the knee

Background

Animal models of posttraumatic joint stiffness (PTJS) are helpful in understanding underlying mechanisms, which is important for developing specific treatments and prophylactic therapies. Existing rat models of PTJS in the knee failed to show that the created contracture does not resolve through subsequent remobilization. Our objective was to establish a rat model of persisting PTJS of the knee and compare it to existing models.

Methods

Thirty skeletally immature male Sprague Dawley rats underwent surgical intervention with knee hyperextension, extracartilaginous femoral condyle defect, and Kirschner (K)-wire transfixation for 4 weeks with the knee joint in 146.7° ± 7.7° of flexion (n = 10 per group, groups I–III). After K-wire removal, group I underwent joint angle measurements and group II and group III were allowed for 4 or 8 weeks of free cage activity, respectively, before joint angles were measured. Eighteen rats (n = 6 per group, groups Ic–IIIc) served as untreated control.

Results

Arthrogenic contracture was largest in group I (55.2°). After 4 weeks of remobilization, the contracture decreased to 25.7° in group II (p < 0.05 vs. group I), whereas 8 weeks of remobilization did not reduce the contracture significantly (group III, 26.5°, p = 0.06 vs. group I). Between 4 and 8 weeks of remobilization, no increase in extension (26.5° in group III, p = 0.99 vs. group II) was observed. Interestingly, muscles did not contribute to the development of contracture.

Conclusion

In our new rat model of PTJS of the knee joint, we were able to create a significant joint contracture with an immobilization time of only 4 weeks after trauma. Remobilization of up to 8 weeks alone did not result in full recovery of the range of motion. This model represents a powerful tool for further investigations on prevention and treatment of PTJS. Future studies of our group will use this new model to analyze medical treatment options for PTJS.

Effects of Low-Intensity Pulsed Ultrasound for Preventing Joint Stiffness in Immobilized Knee Model in Rats

The purpose of this study was to examine the effect of low-intensity pulsed ultrasound (LIPUS) in preventing joint stiffness. Unilateral knee joints were immobilized in two groups of rats (n = 6/period/group). Under general anesthesia, the immobilized knee joints were exposed to LIPUS for 20 min/d, 5 d/wk, using an existing LIPUS device (LIPUS group, 1.5-MHz frequency, 1.0-kHz repetition cycle, 200-µs burst width and 30-mW/cm² power output) until endpoints (2, 4 or 6 wk). In the control group, general anesthesia alone was administered in the same manner as in the other group. The variables compared between the groups included joint angles; histologic, histomorphometric and immunohistochemical analyses; quantitative reverse transcription polymerase chain reactions; and tissue elasticity. LIPUS had a preventive effect on joint stiffness, resulting in decreased adhesion, fibrosis and inflammation and hypoxic response after joint immobilization.

Accumulation of advanced-glycation end products (AGEs) accelerates arthrogenic joint contracture in immobilized rat knee

Joint mobility decreases in the elderly and in diabetics, this process is thought to be caused by accumulation of advanced-glycation end products (AGEs). Here, we aimed to elucidate the role of AGEs in joint contracture formation in rat knees. Rats were injected with ribose or saline into the knees twice weekly for 8 weeks. Pentosidine (AGE) levels were measured in the knee-joint tissues. After serial injections, rats were subjected to unilateral knee-joint immobilization in a flexion position for various periods. At day 21, the passive knee ranges of motions (ROMs) were measured. Knee joint histopathology were assessed, and the expression of fibrotic genes in the posterior joint capsules was examined using real-time PCR. Ribose injection induced a 7.0-fold increase in pentosidine levels relative to saline injection. Joint immobilization resulted in equal myogenic ROM restriction in both groups. Arthrogenic ROM restriction was greater with ribose injection in the immobilized joints (p < 0.05), but was not affected in nonimmobilized joints. Type-I (COL1A1) and type-III (COL3A1) collagen gene expression increased significantly in immobilized joints relative to nonimmobilized joints in the ribose group, but was not affected in the saline group. Ribose injection increased COL1A1 expression slightly and COL3A1 expression significantly in immobilized joints. Histologically, inflammatory changes appeared at day 3 of immobilization and peaked at day 7. These responses trended to be more severe and prolonged in the ribose group than in the saline group. Our data provide evidence for a causal relationship between AGEs and joint contracture formation following immobilization. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:854-863, 2018.

Effects of joint immobilization on changes in myofibroblasts and collagen in the rat knee contracture model

The purpose of this study was to examine the time-dependent changes in the development of joint capsule fibrosis and in the number of myofibroblasts in the joint capsule after immobilization, using a rat knee contracture model. Both knee joints were fixed in full flexion for 1, 2, and 4 weeks (immobilization group). Untreated rats were bred for each immobilization period (control group). Histological analysis was performed to evaluate changes in the amount and density of collagen in the joint capsule. The changes in type I and III collagen mRNA were examined by in situ hybridization. The number of myofibroblasts in the joint capsule was assessed by immunohistochemical methods. In the immobilization group, the amount of collagen increased within 1 week and the density of collagen increased within 2 weeks, as compared with that in the control group. Type I collagen mRNA-positive cell numbers in the immobilization group increased at all time points. However, type III collagen mRNA-positive cell numbers did not increase. Myofibroblasts in the immobilization group significantly increased compared with those in the control group at all time points, and they increased significantly with the period of immobilization. These results suggest that joint capsule fibrosis with overexpression of type I collagen occurs and progresses within 1 week after immobilization, and an increase in myofibroblasts is related to the mechanism of joint capsule fibrosis. The findings suggest the need for a treatment targeting accumulation of type I collagen associated with an increase in myofibroblasts. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1998-2006, 2017.

Cyclooxygenase-2 inhibitor celecoxib attenuates joint contracture following immobilization in rat knees

Background

The aim of this study is to clarify the following two points: First, whether a cyclooxygenase-2 mediated pathway is involved in the formation of immobilization-induced joint contracture and, second, the effectiveness of oral administration of non-steroidal anti-inflammatory drug celecoxib (CBX) for the prevention of myogenic and arthrogenic contracture following immobilization in a rat model.

Methods

Thirty male rats were randomly divided into three groups: immobilization (Im), Im + CBX, and control (n = 10 each). External fixation immobilized the right knee joint of Im and Im + CBX groups in flexion for 3 weeks. 50 mg/kg of CBX was administrated daily to the Im + CBX group during this period. The passive range of motion (ROM) of knee joints was measured before and after transection of knee flexor muscles and myogenic and arthrogenic ROM restrictions were calculated. The semitendinosus muscles and knee joints were investigated histologically to elucidate factors responsible for contracture.

Results

Myogenic ROM restrictions were exhibited both in Im and Im + CBX groups (44 ± 5 and 36 ± 8 °, respectively), but restrictions significantly decreased in the Im + CBX group compared to the Im group. Significant reductions of the muscle length ratios (Rt/Lt) and sarcomere number ratios (Rt/Lt) in knee flexor semitendinosus muscle, which are responsible for myogenic contracture, were also seen both in Im group (92 ± 5 and 92 ± 4 %, respectively) and Im + CBX group (97 ± 3 and 97 ± 3 %, respectively), but were inhibited by CBX administration (P < 0.05). Im and Im + CBX groups exhibited arthrogenic ROM restrictions with no significant differences (82 ± 3 and 83 ± 5 °, respectively). Posterior synovial length shortening and pathological changes (hemorrhage in joint cavities and capsule edema) in the knee joints were comparable between Im and Im + CBX groups.

Conclusions

Oral administration of celecoxib partially reduced myogenic ROM restriction concomitantly with knee flexor muscle shortening following immobilization. These results imply that inflammation and nociception are involved in myogenic contracture formation independently of joint immobilization, and that CBX is effective in preventing joint contracture following immobilization in rats.