Comparison of muscular and articular factors in the progression of contractures after spinal cord injury in rats

The effects of weight bearing after ACL reconstruction on joint contracture in rats

PURPOSE

Joint contractures after anterior cruciate ligament (ACL) reconstruction are a serious problem. Given the uncertain effects of weight bearing after ACL reconstruction on contractures, this study was conducted to examine such effects.

MATERIALS AND METHODS

To control the amount of weight bearing, ACL-reconstructed rats were reared with either untreated (small weight bearing; weight bearing during locomotion was 54% of pre-surgery at minimum), hindlimb unloading (non-weight bearing), or sustained morphine administration (large weight bearing; weight bearing during locomotion was maintained at 80% or more of pre-surgery) conditions. Untreated rats were used as controls. Knee extension range of motions (ROMs) before (includes myogenic and arthrogenic factors) and after myotomy (includes arthrogenic factor only) and fibrotic reactions in the joint capsule were assessed 7 and 14 days post-surgery.

RESULTS

ACL reconstruction significantly reduced ROMs both before and after myotomy and induced fibrosis in the joint capsule accompanying upregulation of fibrosis-related genes (i.e., type I and III collagens and transforming growth factor-β1) at both time points. Morphine administration increased the ROM before myotomy, but not after myotomy 7 days post-surgery. Unloading after ACL reconstruction improved ROMs both before and after myotomy at both time points. In addition, unloading after ACL reconstruction attenuated fibrotic reactions in the joint capsule.

CONCLUSIONS

Our results suggest that morphine administration improves myogenic contractures in parallel with an increase in the amount of weight bearing. Unloading after ACL reconstruction is effective in reducing both myogenic and arthrogenic contractures.

Formation process of extension knee joint contracture following external immobilization in rats

BACKGROUND

Current research lacks a model of knee extension contracture in rats.

AIM

To elucidate the formation process of knee extension contracture.

METHODS

We developed a rat model using an aluminum external fixator. Sixty male Sprague-Dawley rats with mature bones were divided into the control group (n = 6) and groups that had the left knee immobilized with an aluminum external fixator for 1, 2, and 3 d, and 1, 2, 3, 4, 6, and 8 wk (n = 6 in each group). The passive extension range of motion, histology, and expression of fibrosis-related proteins were compared between the control group and the immobilization groups.

RESULTS

Myogenic contracture progressed very quickly during the initial 2 wk of immobilization. After 2 wk, the contracture gradually changed from myogenic to arthrogenic. The arthrogenic contracture progressed slowly during the 1^st week, rapidly progressed until the 3^rd week, and then showed a steady progression until the 4^rd week. Histological analyses confirmed that the anterior joint capsule of the extended fixed knee became increasingly thicker over time. Correspondingly, the level of transforming growth factor beta 1 (TGF-β1) and phosphorylated mothers against decapentaplegic homolog 2 (p-Smad2) in the anterior joint capsule also increased with the immobilization time. Over time, the cross-sectional area of muscle fibers gradually decreased, while the amount of intermuscular collagen and TGF-β1, p-Smad2, and p-Smad3 was increased. Unexpectedly, the amount of intermuscular collagen and TGF-β1, p-Smad2, and p-Smad3 was decreased during the late stage of immobilization (6-8 wk). The myogenic contracture was stabilized after 2 wk of immobilization, whereas the arthrogenic contracture was stabilized after 3 wk of immobilization and completely stable in 4 wk.

CONCLUSION

This rat model may be a useful tool to study the etiology of joint contracture and establish therapeutic approaches.

Changes in passive stiffness and length of the semitendinosus muscles in rats with arthritis-induced knee flexion contracture

BACKGROUND

Arthritis-induced joint contracture is caused by arthrogenic and myogenic factors. The arthrogenic factor, localized within the joint, is naturally accepted as the cause of contracture. However, the detailed mechanisms underlying arthritis-induced myogenic contracture are largely unknown. We aimed to elucidate the mechanisms of arthritis-induced myogenic contracture by examining the muscle mechanical properties.

METHODS

Knee arthritis was induced in rats by injecting complete Freund's adjuvant into the right knees, while the untreated contralateral knees were used as controls. After one or four weeks of injection, passive stiffness, length, and collagen content of the semitendinosus muscles were assessed, along with passive knee extension range of motion.

FINDINGS

After one week of injection, flexion contracture formation was confirmed by a decreased range of motion. Range of motion restriction was partially relieved by myotomy, but still remained even after myotomy, indicating the contribution of both myogenic and arthrogenic factors to contracture formation. After one week of injection, the stiffness of the semitendinosus muscle was significantly higher in the injected side than in the contralateral side. After four weeks of injection, the stiffness of the semitendinosus muscle in the injected side returned to levels comparable to the contralateral side, parallel to partial improvement of flexion contracture. Muscle length and collagen content did not change due to arthritis at both time points.

INTERPRETATION

Our results suggest that increased muscle stiffness, rather than muscle shortening, contributes to myogenic contracture detected during the early stage of arthritis. The increased muscle stiffness cannot be explained by excess collagen.

The combined effects of treadmill exercise and steroid administration on anterior cruciate ligament reconstruction-induced joint contracture and muscle atrophy in rats

Rehabilitation protocols to treat joint contracture and muscle atrophy following anterior cruciate ligament (ACL) reconstruction have not been established. In this study, we examined the combined effects of exercise therapy and steroid administration on joint contracture and muscle atrophy following ACL reconstruction. Rats received ACL transection and reconstructive surgery in one knee. After surgery, they were divided into four groups: no intervention, treadmill exercise (started from day three post-surgery, 12 m/min, 60 min/d, 6 d/week), treatment with the steroidal drug dexamethasone (250 μg/kg on days 0-5, 7, and 9 post-surgery), and dexamethasone treatment plus treadmill exercise. Age-matched untreated rats were used as controls. At day 10 or 30 post-surgery, we assessed ACL-reconstruction-induced joint contracture, joint capsule fibrosis, osteophyte formation, and muscle atrophy of the rectus femoris and gastrocnemius. Treadmill exercise after ACL reconstruction improved several indicators of muscle atrophy in both muscles, but it did not have positive effects on joint contracture. Dexamethasone treatment after ACL reconstruction improved joint contracture and joint capsule fibrosis at both timepoints and partially attenuated osteophyte formation at day 10 post-surgery, but delayed recovery from atrophy of the rectus femoris at day 30 post-surgery. The two treatments combined improved both joint contracture and atrophy of the rectus femoris and gastrocnemius. Exercise therapy combined with steroid administration may therefore be a novel therapeutic strategy for joint contracture and muscle atrophy following ACL reconstruction.

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.

Low-level laser therapy attenuates arthrogenic contracture induced by anterior cruciate ligament reconstruction surgery in rats

Therapeutic approaches to treat joint contracture after anterior cruciate ligament (ACL) reconstruction have not been established. Arthrofibrosis accompanied by joint inflammation following ACL reconstruction is a major cause of arthrogenic contracture. In this study, we examined whether anti-inflammatory treatment using low-level laser therapy (LLLT) can prevent ACL reconstruction-induced arthrogenic contracture. Rats underwent ACL transection and reconstruction surgery in their right knees. Unoperated left knees were used as controls. After surgery, rats were reared with or without daily LLLT (wavelength: 830 nm; power output: 150 mW; power density: 5 W/cm2; for 120 s/day). We assessed the passive extension range of motion (ROM) after myotomy at one and two weeks post-surgery; the reduction in ROM represents the severity of arthrogenic contracture. ROM was markedly decreased by ACL reconstruction at both time points; however, LLLT partially attenuated the decrease in ROM. One week after ACL reconstruction, the gene expression of the proinflammatory cytokine interleukin-1beta in the joint capsule was significantly upregulated, and this upregulation was significantly attenuated by LLLT. Fibrotic changes in the joint capsule, including upregulation of collagen type I and III genes, shortening of the synovium, and thickening were caused by ACL reconstruction and seen at both time points. LLLT attenuated these fibrotic changes as well. Our results indicate that LLLT after ACL reconstruction could attenuate the formation of arthrogenic contracture through inhibition of inflammation and fibrosis in the joint capsule. Thus, LLLT may become a novel therapeutic approach for ACL reconstruction-induced joint contracture.

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.

A rat model of arthrofibrosis developed after anterior cruciate ligament reconstruction without rigid joint immobilization

Purpose: Complications including arthrofibrosis have been reported after anterior cruciate ligament reconstruction (ACLR) even under accelerated rehabilitation. To overcome this, we developed an animal model of ACLR-induced arthrofibrosis without immobilization.Materials and Methods: Thirteen male Wistar rats were divided into ACL transection (ACLT) and ACLR groups. Surgery was performed in the right knees and untreated left knees were used as controls. After surgery, rats could move freely without joint immobilization.Results: One week after surgery, flexion contracture represented by passive ROM reduction was 49 ± 5° and 21 ± 6° in ACLR and ACLT groups, respectively. Thereafter, flexion contractures were gradually reduced to 21 ± 8° and 12 ± 6° after 12 weeks, respectively. Fibrosis, which is characterized by significant upregulation of fibrosis-related genes, thickening, and adhesion in the posterior joint capsule, was observed in the ACLR group after 12 weeks of surgery. Nociceptive behavior and joint swelling were more apparent in the ACLR group than in the ACLT group, especially after 1 week of surgery.Discussions: We developed a rat model of ACLR-induced joint contracture due to arthrofibrosis without rigid immobilization. Joint contracture was also observed in the ACLT group, but to a considerably milder degree than in the ACLR group. Thus, signs of inflammation as a result of reconstruction surgery, rather than ACL transection, play an important role in the formation of joint contracture after ACLR. Our animal model is suited to examine the mechanisms and efficacy of therapeutic strategies for arthrofibrosis following ACLR treated without rigid joint immobilization.

Formation process of joint contracture after anterior cruciate ligament reconstruction in rats

Knee joint contracture is often induced by anterior cruciate ligament reconstruction (ACLR). However, the temporal and spatial arthrofibrotic changes following inflammatory events, which occur in parallel with the formation of joint contractures after ACLR, are unknown. This study aimed to reveal: (a) time-dependent changes in myogenic and arthrogenic contractures; and (b) the process of arthrofibrosis development after ACLR. ACLR was performed on knees of rats unilaterally. Passive ranges of motions (ROMs) before and after myotomy, as well as inflammatory and fibrotic reactions, were examined before and after the surgery at various periods up to 56 days. Both ROMs before and after myotomy exhibited their lowest value on day 7 and increased thereafter in a time-dependent manner; nevertheless, significant restrictions remained by day 56. Myotomy partially increased ROMs at all time points, indicating contribution of the myogenic component to ACLR-induced contracture. Inflammatory and fibrotic reactions peaked on day 7. Arthrofibrosis, characterized by the thickening of the joint capsule and the shortening of the synovial length, was established by day 7 and was not completely resolved by day 56. Our results indicate that: (a) both myogenic and arthrogenic contractures generated through ACLR develop maximally by day 7 after surgery and subside thereafter, but persist at least until day 56; and (b) arthrofibrosis is established by day 7 after surgery and is not completely resolved by day 56. These findings suggest that treatment and intervention for preventing joint contracture after ACLR should be performed within the first 7 days after surgery.

Transcutaneous application of carbon dioxide improves contractures after immobilization of rat knee joint

OBJECTIVE

Joint contractures are a major complication following joint immobilization. However, no fully effective treatment has yet been found. Recently, carbon dioxide (CO₂) therapy was developed and verified this therapeutic application in various disorders. We aimed to verify the efficacy of transcutaneous CO₂ therapy for immobilization-induced joint contracture.

METHOD

Twenty-two Wistar rats were randomly assigned to three groups: caged control, those untreated after joint immobilization, and those treated after joint immobilization. The rats were treated with CO₂ for 20 min once a daily either during immobilization, (prevention) or during remobilization after immobilization (treatment). Knee extension motion was measured with a goniometer, and the muscular and articular factors responsible for contractures were calculated. We evaluated muscle fibrosis, fibrosis-related genes (collagen Type 1α1 and TGF-β1) in muscles, synovial intima's length, and fibrosis-related proteins (Type I collagen and TGF-β1) in the joint capsules.

RESULTS

CO₂ therapy for prevention and treatment improved the knee extension motion. Muscular and articular factors decreased in rats of the treatment group. The muscular fibrosis of treated rats decreased in the treatment group. Although CO₂ therapy did not repress the increased expression of collagen Type 1α1, the therapy decreased the expression of TGF-β1 in the treatment group. CO₂ therapy for treatment improved the shortening of the synovial membrane after immobilization and decreased the immunolabeling of TGF-β1 in the joint capsules.

CONCLUSIONS

CO₂ therapy may prevent and treat contractures after joint immobilization, and appears to be more effective as a treatment strategy for the deterioration of contractures during remobilization.

Morphological and biomechanical adaptations of skeletal muscle in the recovery phase after immobilization in a rat

BACKGROUND

Range of motion restriction following immobilization is spontaneously recovered at least in part by remobilization. However, the mechanisms underlying how muscles change with range of motion recovery are poorly understood. This study aimed to reveal morphological and biomechanical changes in the knee flexor semitendinosus muscle that contribute to knee joint contracture following the relief of immobilization.

METHODS

To induce flexion contracture, we immobilized rat right knees by an external fixator at a flexed position for three weeks. After removal of the fixator, the joints were allowed to move freely (remobilization) for up to 14 days. We obtained muscle length and passive stiffness of the isolated semitendinosus muscles after measuring passive knee extension range of motion.

FINDINGS

Three weeks of immobilization induced range of motion reduction, as well as changes in morphological and biomechanical properties of the semitendinosus muscle, such as reduced muscle length and increment of passive stiffness leading to myogenic contracture. Joint immobilization-induced reduction of range of motion, representing flexion contracture, was partially reduced by 14 days of remobilization. Concomitantly, both muscle length and muscle stiffness returned to levels not significantly different from those in the contralateral side during this period.

INTERPRETATION

These results suggest that improvement of myogenic contracture during the early phase of remobilization occurs via both morphological and biomechanical adaptations.

Intra-articular injection of mitomycin C prevents progression of immobilization-induced arthrogenic contracture in the remobilized rat knee

This study tested whether cell cycle inhibitor mitomycin C (MMC) prevents arthrogenic contracture progression during remobilization by inhibiting fibroblast proliferation and fibrosis in the joint capsule. Rat knees were immobilized in a flexed position to generate flexion contracture. After three weeks, the fixation device was removed and rat knees were allowed to freely move for one week. Immediately after and three days after fixator removal, rats received intra-articular injections of MMC or saline. The passive extension range of motion (ROM) was measured before and after myotomy of the knee flexors to distinguish myogenic and arthrogenic contractures. In addition, both cellularity and fibrosis in the posterior joint capsule were assessed histologically. Joint immobilization significantly decreased ROMs both before and after myotomy compared with untreated controls. In saline-injected knees, remobilization increased ROM before myotomy, but further decreased that after myotomy compared with that of knees immediately after three weeks of immobilization. Histological analysis revealed that hypercellularity, mainly due to fibroblast proliferation, and fibrosis characterized by increases in collagen density and joint capsule thickness occurred after remobilization in saline-injected knees. Conversely, MMC injections were able to prevent the remobilization-enhanced reduction of ROM after myotomy by inhibiting both hypercellularity and joint capsule fibrosis. Our results suggest that joint capsule fibrosis accompanied by fibroblast proliferation is a potential cause of arthrogenic contracture progression during remobilization, and that inhibiting fibroblast proliferation may constitute an effective remedy.

Transcutaneous Carbon Dioxide Improves Contractures After Spinal Cord Injury in Rats

BACKGROUND

Joint contractures are a major complication in patients with spinal cord injuries. Positioning, stretching, and physical therapy are advocated to prevent and treat contractures; however, many patients still develop them. Joint motion (exercise) is crucial to correct contractures. Transcutaneous carbon dioxide (CO2) therapy was developed recently, and its effect is similar to that of exercise. This therapy may be an alternative or complementary approach to exercise.

QUESTION/PURPOSES

Using an established model of spinal cord injury in rats with knee flexion contractures, we sought to clarify whether transcutaneous CO2 altered (1) contracture, as measured by ROM; (2) muscular and articular factors contributing to the loss of ROM; (3) fibrosis and fibrosis-related gene expression in muscle; and (4) the morphology of and fibrosis-related protein expression in the joint capsule.

METHODS

Thirty-six Wistar rats were divided into three equal groups: caged control, those untreated after spinal cord injury, and those treated with CO2 after spinal cord injury. The rats were treated with CO2 from either the first day (prevention) or 15th day (treatment) after spinal cord injury for 2 or 4 weeks. The hindlimbs of rats in the treated group were exposed to CO2 gas for 20 minutes once daily. Knee extension ROM was measured with a goniometer and was measured again after myotomy. We calculated the muscular and articular factors responsible for contractures by subtracting the post-myotomy ROM from that before myotomy. We also quantified histologic muscle fibrosis and evaluated fibrosis-related genes (collagen Type 1, α1 and transforming growth factor beta) in the biceps femoris muscle with real-time polymerase chain reaction. The synovial intima's length was measured, and the distribution of fibrosis-related proteins (Type I collagen and transforming growth factor beta) in the joint capsule was observed with immunohistochemistry. Knee flexion contractures developed in rats after spinal cord injuries at all timepoints.

RESULTS

CO2 therapy improved limited-extension ROM in the prevention group at 2 weeks (22° ± 2°) and 4 weeks (29° ± 1°) and in the treatment group at 2 weeks (31° ± 1°) compared with untreated rats after spinal cord injuries (35° ± 2°, mean difference, 13°; 39° ± 1°, mean difference, 9°; and 38° ± 1°, mean difference, 7°, respectively) (95% CI, 10.50-14.86, 8.10-10.19, and 4.73-9.01, respectively; all p < 0.001). Muscular factors decreased in treated rats in the prevention group at 2 weeks (8° ± 2°) and 4 weeks (14°± 1°) and in the treatment group at 2 weeks (14 ± 1°) compared with untreated rats (15° ± 1°, 4.85-9.42; 16° ± 1°, 1.24-3.86; and 17° ± 2°, 1.16-5.34, respectively; all p < 0.05). The therapy improved articular factors in the prevention group at 2 weeks (4° ± 1°) and 4 weeks (6° ± 1°) and in the treatment group at 2 weeks (8° ± 1°) compared with untreated rats (10° ± 1°, 4.05-7.05; 12° ± 1°, 5.18-8.02; and 11° ± 2°, 1.73-5.50, respectively; all p < 0.05). CO2 therapy decreased muscle fibrosis in the prevention group at 2 weeks (p < 0.001). The expression of collagen Type 1, α1 mRNA in the biceps femoris decreased in treated rats in the prevention group at 2 and 4 weeks compared with untreated rat (p = 0.002 and p = 0.008, respectively), although there was little difference in the expression of transforming growth factor beta (p > 0.05). CO2 therapy did not improve shortening of the synovial intima at all timepoints (all p > 0.05). CO2 therapy decreased transforming growth factor beta immunolabeling in joint capsules in the rats in the prevention group at 2 weeks. The staining intensity and Type I collagen pattern showed no differences among all groups at all timepoints.

CONCLUSION

CO2 therapy may be useful for preventing and treating contractures after spinal cord injuries. CO2 therapy particularly appears to be more effective as a prevention and treatment strategy in early-stage contractures before irreversible degeneration occurs, as shown in a rat model.

CLINICAL RELEVANCE

Our findings support the idea that CO2 therapy may be able to improve the loss of ROM after spinal cord injury.

Effects of hypertonia on contracture development in rat spinal cord injury

STUDY DESIGN

Experimental animal study.

OBJECTIVES

Spastic hypertonia is originally believed to cause contractures from clinical observations. Botulinum toxin is effective for the treatment of spasticity and is widely used in patients who have joints with contractures. Using an established rat model with knee contractures after spinal cord injuries, we aimed to verify whether hypertonia contributes to contracture development, and the botulinum toxin improves structural changes in muscles and joint components responsible for contractures.

SETTING

University laboratory in Japan.

METHODS

To evaluate the effect of hypertonia on contracture development, the rats received botulinum toxin injections after spinal cord injuries. Knee extension motion was measured with a goniometer applying a standardized torque under anesthesia, and the contribution by muscle or non-muscle structures to contractures were calculated by measuring joint motion before and after the myotomies. We quantitatively measured the muscle atrophy, muscle fibrosis, and synovial intima length.

RESULTS

Botulinum toxin injections significantly improved contractures, whereas did not completely prevent contracture development. Botulinum toxin was effective in improving the muscular factor, but little difference in the articular factor. Spinal cord injuries induced muscle atrophy, and botulinum toxin significantly accelerated muscle atrophy and fibrosis. The synovial intima length decreased significantly after spinal cord injuries, and botulinum toxin did not improve this shortening.

CONCLUSIONS

This animal study provides new evidence that hypertonia is not the sole cause rather is the partial contributor of contractures after spinal cord injuries. Furthermore, botulinum toxin has adverse effects in the muscle.

Nociceptor-dependent locomotor dysfunction after clinically-modeled hindlimb muscle stretching in adult rats with spinal cord injury

In the course of investigating how common clinical treatments and adaptive technologies affect recovery after spinal cord injury (SCI), we discovered that a clinically-modeled hindlimb stretching protocol dramatically, but transiently, reduces locomotor function. Nociceptive sensory input is capable of altering motor output at the spinal level, and nociceptive neurons are sensitized after SCI. Here we tested the hypotheses that stretch-induced locomotor deficits are dependent on nociceptive afferents by depleting TRPV1+ sensory afferents using capsaicin injections in neonatal rats. Following maturation, animals received 25g-cm contusive SCI at T10. After plateau of locomotor recovery at 6 weeks, daily stretching was performed for 3 weeks, followed by 2 weeks without stretch, and again for two additional weeks. Animals were sacrificed 2 h after the last stretching session for histological assessments. Consistent with previous findings, stretch-induced drops in locomotor function were observed in nociceptor-intact animals but were nearly absent in nociceptor-depleted animals. These functional changes were accompanied by corresponding increases in the number of c-Fos+ nuclei throughout the lumbar enlargement. As expected, nociceptor-depleted animals had very little CGRP+ axonal innervation of the dorsal horn. Nociceptor-intact stretched animals had significantly higher levels of CGRP+ as compared to non-stretched SCI rats, suggesting that stretching promoted intraspinal CGRP+ sprouting. These results indicate that stretch-induced locomotor dysfunction in animals with incomplete SCI involves C-fibers, adding a negative post-SCI role to their adaptive roles (e.g., bladder control), and suggesting that the clinical use of muscle stretching to combat contractures and spasticity may be unintentionally detrimental to locomotor function.

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.

Active exercise on immobilization-induced contractured rat knees develops arthrogenic joint contracture with pathological changes

This study investigated the effects of treadmill walking during remobilization on range of motion (ROM) and histopathology in rat knee joints, which were immobilized for 3 wk in a flexed position. After fixator removal, rats were divided into a no-intervention (RM) group and a group forced to walk on a treadmill daily at 12 m/min for 60 min (WALK group). Passive knee extension ROMs were measured before (m-ROM) and after (a-ROM) knee flexor myotomy on the first and last day of a 7-day remobilization period, with m-ROM mainly reflecting myogenic factors and a-ROM reflecting arthrogenic factors. Knee joints were histologically analyzed and gene expression of inflammatory or fibrosis-related mediators in the posterior joint capsule were examined. m-ROM and a-ROM restrictions were established after immobilization. m-ROM significantly increased following the remobilization period both in RM and WALK groups compared with that of immobilized (IM) group. Conversely, a-ROM decreased following the remobilization period in both RM and WALK groups compared with that of IM group. Importantly, a-ROM was smaller in the WALK group than the RM group. Remobilization without intervention induced inflammatory and fibrotic reactions in the posterior joint capsule after 1 and 7 days. Treadmill walking promoted these reactions and also increased the expression of fibrosis-related TGF-β1 and collagen type I and III genes. While free movement after immobilization improved myogenic contracture, arthrogenic contracture worsened. Treadmill walking further aggravated arthrogenic contracture through amplified inflammatory and fibrotic reactions. Thus active exercise immediately after immobilization may not improve immobilization-induced joint contracture.

NEW & NOTEWORTHY In clinical practice, it is widely accepted that facilitation of joint movements is effective in improving immobilization-induced joint contracture. However, whether active exercises improve arthrogenic contracture is not known. In this study, we revealed that treadmill walking further promoted remobilization-induced progression of arthrogenic contracture. To our knowledge, this is the first study demonstrating no favorable effect of active exercise on immobilization-induced arthrogenic contracture.

Development of arthrogenic joint contracture as a result of pathological changes in remobilized rat knees

This study aimed to elucidate how rats recover from immobilization-induced knee joint contracture. Rats' right knees were immobilized by an external fixator at a flexion of 140° for 3 weeks. After removal of the fixator, the joints were allowed to move freely (remobilization) for 0, 1, 3, 7, or 14 days (n = 5 each). To distinguish myogenic and arthrogenic contractures, the passive extension range of motion was measured before and after myotomy of the knee flexors. Knee joints were histologically analyzed and the expression of genes encoding inflammatory or fibrosis-related mediators, interleukin-1β (1L-1β), fibrosis-related transforming growth factor-β1 (TGF-β1), and collagen type I (COL1A1) and III (COL3A1), were examined in the knee joint posterior capsules using real-time PCR. Both myogenic and arthrogenic contractures were established within 3 weeks of immobilization. During remobilization, the myogenic contracture decreased over time. In contrast, the arthrogenic contracture developed further during the remobilization period. On day 1 of remobilization, inflammatory changes characterized by edema, inflammatory cell infiltration, and upregulation of IL-1β gene started in the knee joint posterior capsule. In addition, collagen deposition accompanied by fibroblast proliferation, with upregulation of TGF-β1, COL1A1, and COL3A1 genes, appeared in the joint capsule between days 7 and 14. These results suggest the progression of arthrogenic contracture following remobilization, which is characterized by fibrosis development, is possibly triggered by inflammation in the joint capsule. It is therefore necessary to focus on developing new treatment strategies for immobilization-induced joint contracture. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1414-1423, 2017.

Stretching After Heat But Not After Cold Decreases Contractures After Spinal Cord Injury in Rats

BACKGROUND

Contractures are a prevalent and potentially severe complication in patients with neurologic disorders. Although heat, cold, and stretching are commonly used for treatment of contractures and/or spasticity (the cause of many contractures), the sequential effects of these modalities remain unclear.

QUESTIONS/PURPOSES

Using an established rat model with spinal cord injury with knee flexion contracture, we sought to determine what combination of heat or cold before stretching is the most effective for treatment of contractures derived from spastic paralyses and investigated which treatment leads to the best (1) improvement in the loss of ROM; (2) restoration of deterioration in the muscular and articular factors responsible for contractures; and (3) amelioration of histopathologic features such as muscular fibrosis in biceps femoris and shortening of the joint capsule.

METHODS

Forty-two adolescent male Wistar rats were used. After spasticity developed at 2 weeks postinjury, each animal with spinal cord injury underwent the treatment protocol daily for 1 week. Knee extension ROM was measured with a goniometer by two examiners blinded to each other's scores. The muscular and articular factors contributing to contractures were calculated by measuring ROM before and after the myotomies. We quantitatively measured the muscular fibrosis and the synovial intima length, and observed the distribution of collagen of skeletal muscle. The results were confirmed by a blinded observer.

RESULTS

The ROM of heat alone (34° ± 1°) and cold alone (34° ± 2°) rats were not different with the numbers available from that of rats with spinal cord injury (35° ± 2°) (p = 0.92 and 0.89, respectively). Stretching after heat (24° ± 1°) was more effective than stretching alone (27° ± 3°) at increasing ROM (p < 0.001). Contrastingly, there was no difference between stretching after cold (25° ± 1°) and stretching alone (p = 0.352). Stretching after heat was the most effective for percentage improvement of muscular (29%) and articular (50%) factors of contractures. Although quantification of muscular fibrosis in the rats with spinal cord injury (11% ± 1%) was higher than that of controls (9% ± 0.4%) (p = 0.01), no difference was found between spinal cord injury and each treatment protocol. The total synovial intima length of rats with spinal cord injury (5.9 ± 0.2 mm) became shorter than those of the controls (7.6 ± 0.2 mm) (p < 0.001), and those of stretching alone (6.9 ± 0.4 mm), stretching after heat (7.1 ± 0.3 mm), and stretching after cold (6.7 ± 0.4 mm) increased compared with rats with spinal cord injury (p = 0.01, p = 0.001, and p = 0.04, respectively). The staining intensity and pattern of collagen showed no difference among the treatment protocols.

CONCLUSIONS

This animal study implies that heat or cold alone is ineffective, and that stretching is helpful for the correction of contractures after spinal cord injury. In addition, we provide evidence that heat is more beneficial than cold to increase the effectiveness of stretching.

CLINICAL RELEVANCE

Our findings tend to support the idea that stretching after heat can improve the loss of ROM and histopathologic features of joint tissues. However, further studies are warranted to determine if our findings are clinically applicable.

Quantitative and temporal differential recovery of articular and muscular limitations of knee joint contractures; results in a rat model

Joint contractures alter the mechanical properties of articular and muscular structures. Reversibility of a contracture depends on the restoration of the elasticity of both structures. We determined the differential contribution of articular and muscular structures to knee flexion contractures during spontaneous recovery. Rats (250, divided into 24 groups) had one knee joint surgically fixed in flexion for six different durations, from 1 to 32 wk, creating joint contractures of various severities. After the fixation was removed, the animals were left to spontaneously recover for 1 to 48 wk. After the recovery periods, animals were killed and the knee extension was measured before and after division of the transarticular posterior muscles using a motorized arthrometer. No articular limitation had developed in contracture of recent onset (≤2 wk of fixation, P > 0.05); muscular limitations were responsible for the majority of the contracture (34 ± 8° and 38 ± 6°, respectively; both P < 0.05). Recovery for 1 and 8 wk reversed the muscular limitation of contractures of recent onset (1 and 2 wk of fixation, respectively). Long-lasting contractures (≥4 wk of fixation) presented articular limitations, irreversible in all 12 durations of recovery compared with controls (all 12 P < 0.05). Knee flexion contractures of recent onset were primarily due to muscular structures, and they were reversible during spontaneous recovery. Long-lasting contractures were primarily due to articular structures and were irreversible. Comprehensive temporal and quantitative data on the differential reversibility of mechanically significant alterations in articular and muscular structures represent novel evidence on which to base clinical practice.

Amount of torque and duration of stretching affects correction of knee contracture in a rat model of spinal cord injury

BACKGROUND

Joint contractures are a common complication of many neurologic conditions, and stretching often is advocated to prevent and treat these contractures. However, the magnitude and duration of the stretching done in practice usually are guided by subjective clinical impressions.

QUESTIONS/PURPOSES

Using an established T8 spinal cord injury rat model of knee contracture, we sought to determine what combination of static or intermittent stretching, varied by magnitude (high or low) and duration (long or short), leads to the best (1) improvement in the limitation in ROM; (2) restoration of the muscular and articular factors leading to contractures; and (3) prevention and treatment of contracture-associated histologic alterations of joint capsule and articular cartilage.

METHODS

Using a rat animal model, the spinal cord was transected completely at the level of T8. The rats were randomly assigned to seven treatment groups (n = 4 per group), which were composed of static or intermittent stretching in combination with different amounts of applied torque magnitude and duration. We assessed the effect of stretching by measuring the ROM and evaluating the histologic alteration of the capsule and cartilage.

RESULTS

Contractures improved in all treated groups except for the low-torque and short-duration static stretching conditions. High-torque stretching was effective against shortening of the synovial membrane and adhesions in the posterosuperior regions. Collagen Type II and VEGF in the cartilage were increased by stretching.

CONCLUSIONS

High-torque and long-duration static stretching led to greater restoration of ROM than the other torque and duration treatment groups. Stretching was more effective in improving articular components of contractures compared with the muscular components. Stretching in this rat model prevented shortening and adhesion of the joint capsule, and affected biochemical composition, but did not change morphologic features of the cartilage.

CLINICAL RELEVANCE

This animal study tends to support the ideas that static stretching can influence joint ROM and histologic qualities of joint tissues, and that the way stretching is performed influences its efficacy. However, further studies are warranted to determine if our findings are clinically applicable.

Joint immobilization induced hypoxic and inflammatory conditions in rat knee joints

The purpose of this study was to examine the hypoxic and inflammatory conditions after immobilization in the joint capsule of rat knees. The unilateral knee joints of adult male rats were immobilized with an internal fixator (Im group) for 1 day, 3 days, and 1, 2, 4, 8, and 16 weeks. Sham-operated animals had holes drilled in the femur and tibia and screws inserted without a plate (control group). The number of cells and blood vessels in the capsule were histologically examined. The hypoxic condition in the capsule was histologically examined with a Hypoxyprobe™-1. The gene expressions related to the hypoxic (hypoxia inducible factor-1α, vascular endothelial growth factor, and fibroblast growth factor 2) and inflammatory conditions [interleukin-6 (IL-6), IL-1α, IL-1β, tumor necrosis factor-α, and tumor necrosis factor-β] were evaluated by quantitative reverse transcription polymerase chain reaction. The number of cells was unchanged at 1 day in the two groups; however, the number significantly increased at 3 days in the Im group. The number of blood vessels in the Im group gradually decreased. Strong immunostaining of Hypoxyprobe™-1 around the blood vessels was observed in the Im group. The gene expressions of hypoxia inducible factor-1α and fibroblast growth factor 2 were significantly higher in the Im group compared with those in the control group. The gene expressions of IL-6, IL-1α, IL-1β, and tumor necrosis factor-β were significantly higher in the Im group compared with those in the control group. These data indicated that joint immobilization induced hypoxic and inflammatory conditions in the joint capsule, which might be an initiating factor for joint contracture.

Remobilization does not restore immobilization-induced adhesion of capsule and restricted joint motion in rat knee joints

Joint immobilization, which is used in orthopaedic treatments and observed in bedridden people, usually causes restricted joint motion. Decreased joint motion diminishes activities of daily living and increases burden of nursing-care. The purpose of this study was to clarify the reversibility of immobilization-induced capsular changes and restricted joint motion in rat knee joints. The unilateral knee joints of adult male rats were immobilized with an internal fixator for 1, 2, 4, 8, and 16 weeks as a model of immobilization after surgery or disuse of the joint. After the fixation devices were removed, the rats were allowed to move freely for 16 weeks. Sham-operated rats were used as controls. Sagittal sections at medial midcondylar regions were made and assessed with histological, histomorphometric, and immunohistochemical methods. Joint motion was measured using a custom-made device under x-ray control after removal of the periarticular muscles. In the 1/16-week and 2/16-week immobilization-remobilization (Im-Rm) groups, cord-like structures connecting the superior and inferior portions of the posterior capsule (partial adhesion) were observed without restricted joint motion. In the 4/16-, 8/16-, and 16/16-week Im-Rm groups, global adhesion of the posterior capsule and restricted joint motion were observed. The restricted joint motion was not completely restored after incision of the posterior capsule. These data indicate that immobilization alone causes irreversible capsular changes and arthrogenic restricted joint motion. Besides the joint capsule, other arthrogenic factors such as ligaments might influence the restricted joint motion. Prolonged immobilization over 4 weeks should be avoided to prevent irreversible joint contracture.

Hindlimb immobilization in a wheelchair alters functional recovery following contusive spinal cord injury in the adult rat

BACKGROUND

Locomotor training of rats with thoracic contusion spinal cord injuries can induce task-specific changes in stepping but rarely results in improved overground locomotion, possibly due to a ceiling effect. Thus, the authors hypothesize that incompletely injured rats maximally retrain themselves while moving about in their cages over the first few weeks postinjury.

OBJECTIVE

To test the hypothesis using hindlimb immobilization after mild thoracic contusion spinal cord injury in adult female rats. A passive stretch protocol was included as an independent treatment.

METHODS

Wheelchairs were used to hold the hindlimbs stationary in an extended position leaving the forelimbs free. The wheelchairs were used for 15 to 18 hours per day, 5 days per week for 8 weeks, beginning at 4 days postinjury. A 20-minute passive hindlimb stretch therapy was applied to half of the animals.

RESULTS

Hindlimb locomotor function of the wheelchair group was not different from controls at 1 week postinjury but declined significantly over the next 4 weeks. Passive stretch had no influence on wheelchair animals but limited functional recovery of normally housed animals, preventing them from regaining forelimb-hindlimb coordination. Following 8 weeks of wheelchair immobilization and stretch therapy, only the wheelchair group displayed an improvement in function when returned to normal housing but retained significant deficits in stepping and coordination out to 16 weeks.

CONCLUSION

Hindlimb immobilization and passive stretch may hinder or conceal the normal course of functional recovery of spinal cord injured rats. These observations have implications for the management of acute clinical spinal cord injuries.

Joint contractures in the intensive care unit: association with resource utilization and ambulatory status at discharge

PURPOSE

The objectives of our study were (1) to explore the link between joint contractures acquired in the ICU and the ambulatory status of patients at discharge home, to determine (2) when and how many patients received physiotherapy services in ICU and on the hospital ward, and (3) the differences in the use of hospital resources in the presence or absence of joint contractures.

METHOD

Data on ICU joint contractures were extracted from an existing contracture database containing information on 155 Canadian patients with a tertiary ICU stay of 14 days or more.

RESULTS

Of 155 patients, 115 (74.2%) received a range of motion assessment in the ICU. The assessment took place a median of 7 days (IQR 0-36) after ICU admission. Significantly fewer patients with joint contractures than without joint contractures were mobilized on the hospital ward (21/38 [55.3%] vs. 27/34 [79.4%], P = 0.03). At discharge home, more patients with joint contractures had a low ambulatory status (38 [64.4%]) compared with patients without joint contractures (26 [51.0%]; P = 0.002).

CONCLUSION

The median delay of 7 days before musculoskeletal assessment in the ICU together with failure to assess 26% of patients may have allowed the development of contractures, which affected the patients' ambulatory status at discharge from hospital.

Expression patterns of collagen types I and III in the capsule of a rat knee contracture model

Our objective was to determine the changes in expression of collagen types I and III in the capsule of a rat knee contracture model. The unilateral knee joints of adult male rats were rigidly immobilized at 150 degrees of flexion using a rigid plastic plate and screws for 3 days, 1, 2, 4, 8, and 16 weeks (immobilized group). Sham-operated animals had holes drilled in the femur and tibia with screws inserted without a plate (control group). The expression patterns of collagen types I and III in the anterior and posterior capsule were evaluated by in situ hybridization (ISH), quantitative real-time polymerase chain reaction (qPCR), immunohistochemistry (IHC), and Western blotting (WB). Expressions of collagen types I and III were decreased after immobilization compared to the control group by ISH and qPCR. The expression was not changed after immobilization compared to the control group by IHC and WB. The expression of mRNA and protein levels of collagen types I and III were not increased after immobilization, which indicated that accumulation of the two types of collagen was not the etiology of joint contracture. Another process, such as capsule and synovial adhesions, may be one possible cause of joint contracture.

Contrasting alteration patterns of different cartilage plates in knee articular cartilage after spinal cord injury in rats

STUDY DESIGN

Experimental, controlled trial, animal study.

OBJECTIVE

To assess morphologic changes in different cartilage plates after spinal cord injury and identify the localization of these alterations.

SETTING

Saitama, Japan.

METHODS

A total of 16 Wistar rats were used. Eight rats underwent a spinal cord injury and eight rats had no intervention as control. The cartilage alterations of the knee joint were evaluated with radiography and histomorphometric analysis. To quantify cartilage alterations, we selected the histologic characteristics: thickness of the articular cartilage, number of chondrocytes, matrix staining to toluidine blue as a reflection of proteoglycan content and surface irregularity.

RESULTS

No differences in knee joints were found between the groups by radiography. In the medial knee joint, cartilage thickness of spinal-cord-injured knees increased at the anterior femoral region and decreased at the tibial and posterior femoral regions; however, in the lateral knee, that of spinal cord injuries did not change compared with control knees. Spinal cord injuries decreased the number of chondrocytes, especially at the anterior femoral regions. Matrix staining increased partially at the tibial regions. Surface irregularity of spinal-cord-injured knees was comparable to that of control knees in all cartilage plates.

CONCLUSION

The present findings exhibit characteristics of the cartilage after spinal cord injury. These alterations were different in nature between the medial and lateral regions. Future studies should assess separately different cartilage plates, to overestimate these severities when the changes at the medial knee were examined and to underestimate when the changes at the lateral knee were examined.

Joint contracture following prolonged stay in the intensive care unit

BACKGROUND

Prolonged immobility during a critical illness may predispose patients to the development of joint contracture. We sought to document the incidence of, the risk factors for and the reversibility of joint contractures among patients who stayed in a tertiary intensive care unit (ICU) for 2 weeks or longer.

METHODS

We conducted a chart review to collect data on the presence of and risk factors for joint contractures in the shoulders, elbows, hips, knees and ankles among patients admitted to the ICU between January 2003 and March 2005.

RESULTS

At the time of transfer out of the ICU, at least 1 joint contracture was recorded in 61 (39%) of 155 patients; 52 (34%) of the patients had joint contractures of an extent documented to impair function. Time spent in the ICU was a significant risk factor for contracture: a stay of 8 weeks or longer was associated with a significantly greater risk of any joint contracture than a stay of 2 to 3 weeks (adjusted odds ratio [OR] 7.09, 95% confidence interval (CI) 1.29-38.9; p = 0.02). Among the variables tested, only the use of steroids conferred a protective effect against joint contractures (adjusted OR 0.35, 95% CI 0.14-0.83; p = 0.02). At the time of discharge to home, which occurred a median of 6.6 weeks after transfer out of intensive care, 50 (34%) of the 147 patients not lost to follow-up still had 1 or more joint contractures, and 34 (23%) of the patients had at least 1 functionally significant joint contracture.

INTERPRETATION

Following a prolonged stay in the ICU, a functionally significant contracture of a major joint occurred in more than one-third of patients, and most of these contractures persisted until the time of discharge to home.

Alteration in articular cartilage of rat knee joints after spinal cord injury

OBJECTIVE

Mechanical forces are crucial for the maintenance of the morphologic and functional integrity of articular cartilage. The alteration of the articular cartilage after spinal cord injury (SCI) has been described in relation to a suppression of mechanical forces, since the joint is unloaded and restricted in movement. However, the morphological and biochemical characteristics of the cartilage after SCI are still poorly understood. We identified the localization of cartilage alterations after SCI and verified the influence of mechanical forces on the articular cartilage.

METHOD

A total of 32 Wistar rats were used. Sixteen animals underwent an SCI and 16 animals served as control. The articular cartilage of the knee joint was assessed, respectively, at 4, 8, 10, and 12 weeks after intervention by histochemical, histomorphometric, immunohistochemical, and biochemical analyses.

RESULTS

Cartilage thickness of spinal cord-injured knees decreased at the tibial and posterior femoral (FP) regions and increased at the anterior femoral (FA) region. Spinal cord injuries decreased the number of chondrocytes at the anterior regions and decreased the cartilage matrix staining only at the tibial regions. Immunolabeling to collagen type II was noted comparably in the superficial layer but noted weakly from the middle to deep layer. Collagen type I existed excessively at the cartilage surface and the pericellular regions.

CONCLUSION

Cartilage alterations after SCI would not be explained by only a suppression of mechanical forces by unloading and immobilization, but there may be influences on the cartilage in addition to the change in mechanical forces.

Progression of an arthrogenic motion restriction after immobilization in a rat experimental knee model

BACKGROUND

Contracture is defined as a decrease in both active and passive ranges of motion after immobilization. A fibrotic change of a capsule is suggested to be one of the main causes of the joint contracture. The goal of this study is to determine the effect of capsule on limiting the range of motion after immobilization.

MATERIALS AND METHODS

We immobilized the knee joint of 35 rats with an internal fixator with the knee joint flexed at 150 degrees. The rats were sacrificed at 1, 2, 4, 6, 8, 12, and 16 weeks after surgery and the lower extremities were disarticulated at the hip joint. After extra-articular myotomies around the tibia and femur, x-rays were taken to measure the angles of extension of the knee joint under 3 different torques. The measurements were repeated after releasing the posterior capsule in order to observe their effects on knee motion.

RESULTS

Joint contracture was rapidly progressed until 8 weeks and advanced slowly after 8 weeks. After releasing the posterior capsule, both the immobilized and the control groups gained the angle of knee extension. The acquired angle in the immobilized group was significantly greater than in the control group after 4 weeks and became plateau after 8 weeks.

CONCLUSION

Joint contracture develops at the early stage of immobilization and progresses over time. The posterior capsule significantly contributes to the limitation in extension.

Alteration of knee joint connective tissues during contracture formation in spastic rats after an experimentally induced spinal cord injury

This study was made to elucidate the changes in the periarticular connective tissue that can underlie the contracture after spasticity development. Sixteen Wistar rats underwent a spinal cord injury and 16 rats were either sham- or nonoperated. The periarticular connective tissue of the knee joint was assessed with histological, histomorphometric, immunohistochemical, and biochemical analyses. Histological results showed a smaller synovial intima, a dense subintimal and posterior joint capsule without fibrosis, and a disarranged posterior capsule in the spinal cord-injured knees with the flexion contracture. The synovial intima length was shortened only at the posterior capsule. Neither the distribution nor expression of type I and III collagen was affected. Contractures after spinal cord injuries are characterized by synovial intima adhesions. A dense and disarranged capsule may lead to joint stiffness. The alteration of periarticular connective tissues exhibits properties characteristic of the contracture after spasticity development.