The influence of a local injection of cortisol on the mechanical properties of tendons and ligaments and the indirect effect on skin

Histological and Biomechanical Effects of Local Anesthetics and Steroids on Achilles Tendon: A Study in Rats

BACKGROUND

Peritendinous injection of local anesthetics, alone or in combination with corticosteroids, is widely used in the treatment of tendinopathies. Toxicity of local anesthetics has been demonstrated in many cells, including myocytes, chondrocytes, and neurons. Bupivacaine and lidocaine are known to have time- and dose-dependent cytotoxicity in these cells. The effects of these agents on the tendon remain unknown.

PURPOSE

To show histological and biomechanical effects after the injection of different local anesthetics and steroids, both single and combined, at different concentrations into the peritendinous sheath of rat Achilles tendon.

STUDY DESIGN

Controlled laboratory study.

METHODS

In the study, 100 rats were divided into 10 groups with equal body weights. Inflammation was induced in both Achilles tendons of each rat by means of the ball drop technique; 7 hours later, injections were made into the peritendinous sheaths of both Achilles tendons using lidocaine, bupivacaine, and dexamethasone as appropriate for the rat's group. At the end of the first week, the right Achilles tendons of the rats were removed for histological study. Left Achilles tendons were evaluated in terms of biomechanics.

RESULTS

Histological findings demonstrated that the group with the most toxicity to the tendon was the group that received injection of dexamethasone alone. The groups with the least toxicity were those receiving dexamethasone combined with low- or high-dose bupivacaine. Biomechanical findings showed that the experimental groups had similar results to each other with the exception of the groups receiving 0.25% bupivacaine alone and dexamethasone alone, in which tendons revealed higher tensile strength.

CONCLUSION

Local anesthetic and steroid applications have different histological and biomechanical effects on the tendon. Although the dexamethasone-injected group was the most affected in terms of histology, these changes could not be demonstrated biomechanically.

CLINICAL RELEVANCE

In future clinical studies, the effect of steroids on the tendon should be investigated more comprehensively. Whether biomechanical results overlap with histological results should be investigated further.

Dexamethasone Enhances Achilles Tendon Healing in an Animal Injury Model, and the Effects Are Dependent on Dose, Administration Time, and Mechanical Loading Stimulation

BACKGROUND

Corticosteroid treatments such as dexamethasone are commonly used to treat tendinopathy but with mixed outcomes. Although this treatment can cause tendon rupture, it can also stimulate the tendon to heal. However, the mechanisms behind corticosteroid treatment during tendon healing are yet to be understood.

PURPOSE

To comprehend when and how dexamethasone treatment can ameliorate injured tendons by using a rat model of Achilles tendon healing.

STUDY DESIGN

Controlled laboratory study.

METHODS

An overall 320 rats were used for a sequence of 6 experiments. We investigated whether the drug effect was time-, dose-, and load-dependent. Additionally, morphological data and drug administration routes were examined. Healing tendons were tested mechanically or used for histological examination 12 days after transection. Blood was collected for flow cytometry analysis in 1 experiment.

RESULTS

We found that the circadian rhythm and drug injection timing influenced the treatment outcome. Dexamethasone treatment at the right time point (days 7-11) and dose (0.1 mg/kg) significantly improved the material properties of the healing tendon, while the adverse effects were reduced. Local dexamethasone treatment did not lead to increased peak stress, but it triggered systemic granulocytosis and lymphopenia. Mechanical loading (full or moderate) is essential for the positive effects of dexamethasone, as complete unloading leads to the absence of improvements.

CONCLUSION

We conclude that dexamethasone treatment to improve Achilles tendon healing is dose- and time-dependent, and positive effects are perceived even in a partly unloaded condition.

CLINICAL RELEVANCE

These findings are promising from a clinical perspective, as the positive effect of this drug was seen even when given at lower doses and in a moderate loading condition, which better mimics the load level in patients with tendon ruptures.

High-energy Flux Density Extracorporeal Shock-wave Therapy Versus Therapeutic Steroid Injection in Costochondritis: A Single-Blind, Randomised Controlled Study

Background This study aims to investigate the effects of extracorporeal shock-wave therapy (ESWT) and intra-articular steroid injection (IASI) on pain, depression, quality of life and pressure pain threshold (PPT) in patients with costochondritis.

Methods A total of 67 patients diagnosed with costochondritis were included. Patients were divided into 2 groups. Group 1 (n=34) received high-energy flux density (H-ESWT) (> 0.28 mJ/mm2) for a total of 7 sessions at 3-day intervals. Group 2 (n=33) received IASI twice at 2-week intervals. At baseline and one month after treatment, Visual Analog Scale (VAS), Short Form-36 (SF-36), Pittsburgh Sleep Quality Index (PSQI), Beck Depression Inventory (BDI) scores and PPT values were compared.

Results There was a statistically significant decrease in VAS scores after treatment compared with baseline scores in both groups. The PPT and SF-36 subscale scores were also statistically significantly higher (p<0.05). After treatment, VAS and PPT showed a significantly better improvement in Group 1 compared to Group 2. There was a significant correlation between VAS and SF-36 physical functioning as well as pain subscales in Group 1 and a significant correlation between VAS and SF-36 physical functioning in Group 2.

Conclusions Our data suggest that both treatments H-ESWT and IASI are effective in costochondritis patients. Of note, H-ESWT has a stronger effect on pain and PPT scores.

Cruciate ligament healing and injury prevention in the age of regenerative medicine and technostress: homeostasis revisited

PURPOSE

This clinical concepts paper discusses the essential elements of cruciate ligament recuperation, micro-trauma repair, and remodeling.

METHODS

Cruciate ligament mechanobiology and tissue heterogeneity, anatomy and vascularity, and synovial membrane and fluid functions are discussed in relationship to deficiency-induced inflammatory responses, nervous and immune system function, recuperation, repair and remodeling, and modern threats to homeostasis.

RESULTS

Cruciate ligament surgical procedures do not appreciate the vital linked functions of the central, peripheral, and autonomic nervous systems and immune system function on knee ligament injury recuperation, micro-trauma repair, and remodeling. Enhanced knowledge of these systems could provide innovative ways to decrease primary non-contact knee injury rates and improve outcomes following reconstruction or primary repair.

CONCLUSIONS

Restoration of knee joint homeostasis is essential to cruciate ligament recuperation, micro-trauma repair, and remodeling. The nervous and immune systems are intricately involved in this process. Varying combinations of high-intensity training, under-recovery, technostress, and environmental pollutants (including noise) regularly expose many athletically active individuals to factors that abrogate the environment needed for cruciate ligament recuperation, micro-trauma repair, and remodeling. Current sports training practice, lifestyle psychobehaviors, and environmental factors combine to increase both primary non-contact knee injury risk and the nervous and immune system dysregulation that lead to poor sleep, increased anxiety, and poorly regulated hormone and cytokine levels. These factors may create a worst-case scenario leading to poor ligament recuperation, micro-trauma repair, and remodeling. Early recognition and modification of these factors may decrease knee ligament injury rates and improve cruciate ligament repair or reconstruction outcomes.

LEVEL OF EVIDENCE

V.

The mechanical and biochemical properties of tail tendon in a rat model of obesity: Effect of moderate exercise and prebiotic fibre supplementation

The worldwide trajectory of increasing obesity rates is a major health problem precipitating a rise in the prevalence of a variety of co-morbidities and chronic diseases. Tendinopathy, in weight and non-weight bearing tendons, in individuals with overweight or obesity has been linked to metabolic dysfunction resulting from obesity. Exercise and dietary fibre supplementation (DFS) are common countermeasures to combat obesity and therefore it seems reasonable to assume that they might protect tendons from structural and mechanical damage in a diet-induced obesity (DIO) model. The purpose of this study was to determine the effects of a DIO, DIO combined with moderate exercise, DIO combined with DFS (prebiotic oligofructose), and DIO combined with moderate exercise and DFS on the mechanical and biochemical properties of the rat tail tendon. Twenty-four male Sprague-Dawley rats, fed a high-fat/high-sucrose diet were randomized into a sedentary, a moderate exercise, a DFS, or a moderate exercise combined with DFS group for 12 weeks. Additionally, six lean age-matched animals were included as a sedentary control group. DIO in combination with exercise alone and with exercise and DFS reduced the Young's Modulus but not the collagen content of the rat tail tendons compared to lean control animals. However, no differences in the mechanical and biochemical properties of the rat tail tendon were detected between the DIO and the lean control group, suggesting that DIO by itself did not impact the tail tendon. It seems that longer DIO exposure periods may be needed to develop overt differences in our DIO model.

Systemic corticosteroids improve tendon healing when given after the early inflammatory phase

Inflammation initiates tendon healing and then normally resolves more or less completely. Unresolved inflammation might disturb the remodeling process. We hypothesized that suppression of inflammation during the early remodeling phase by systemic dexamethasone treatment can improve healing. 36 rats underwent Achilles tendon transection and were randomized to dexamethasone or saline on days 0-4 after surgery (early inflammatory phase), and euthanasia day 7. Another 54 rats received injections days 5-9 (early remodeling phase) and were euthanized day 12 for mechanical, histological and flow cytometric evaluation. Dexamethasone treatment days 0-4 reduced the cross-sectional area, peak force and stiffness by day 7 to less than half (p < 0.001 for all), while material properties (peak stress and elastic modulus) were not significantly affected. In contrast, dexamethasone treatment days 5-9 increased peak force by 39% (p = 0.002) and stiffness by 58% (p < 0.001). The cross-sectional area was reduced by 42% (p < 0.001). Peak stress and elastic modulus were more than doubled (p < 0.001 for both). Semi-quantitative histology at day 12 showed that late dexamethasone treatment improved collagen alignment, and flow cytometry revealed reduced numbers of CD8a+ cytotoxic T cells in the tendon callus. These results suggest that downregulation of lingering inflammation during the early remodeling phase can improve healing.

Effects of corticosteroids and hyaluronic acid on torn rotator cuff tendons in vitro and in rats

Corticosteroids (CS) or hyaluronic acid (HA) is used in subacromial injection for the conservative treatment of rotator cuff tears (RCT); this study addresses the question of how CS and HA affect the tendon tissue and fibroblasts in vitro and in rats. Cell proliferation assays were performed in human tendon fibroblasts from RCT. Rats underwent surgery to create RCT, and the surgical sites were injected with CS or HA. The rotator cuff tendons were subjected to biomechanical testing, microscopic and immunohistochemical analysis of proliferating cell nuclear antigen (PCNA), and ultrastructural analysis. Cell proliferation was significantly decreased with CS in vitro (p < 0.05). Maximal load of CS-treated tendons was significantly decreased compared with that of HA-treated tendons (p < 0.05), as well as PCNA(+) cells at 2 weeks (p < 0.05). Ultrastructural observations of the CS-treated rats detected apoptosis of tendon fibroblasts 24 h after surgery. Histological and biomechanical data 4 weeks after surgery were not significant among the three groups. Unlike HA, CS caused cell death, and inhibition of the proliferation of tendon fibroblasts, leading to a delay of tendon healing involved and a subsequent decrease of biomechanical strength at the surgical site.

Do the presence of pathologic changes and the level of operator experience alter the rate of intra-articular injection of the first metatarsophalangeal joint? A cadaver study

BACKGROUND

Injections, punctures, and aspirations of the first metatarsophalangeal joint are common interventions. Accurate intra-articular placement of the needle is a prerequisite for the achievement of desirable results and the avoidance of complications. We evaluated the rate of successful intra-articular injections and the influence of the degree of operator experience in achieving this success.

METHODS

A total of 106 cadaveric metatarsophalangeal joints were injected with a methylene blue-containing solution and subsequently dissected to distinguish intra-articular from periarticular injections. To evaluate the importance of experience, 38 injections were performed by a student, 38 by a trained resident, and 30 by an experienced surgeon. In the second part of the study, we examined the relation of pathologic findings of the metatarsophalangeal joint and the accuracy of intra-articular injection.

RESULTS

The overall rate of unintentional periarticular injections remained low (9.4%; 10 of 106 joints). The student achieved a successful intra-articular injection in 86.8% of joints (33 of 38), the resident in 92.1% (35 of 38), and the specialist in 93.3% (28 of 30). The number of extra-articular injections increased significantly with the presence of deformity (hallux valgus) and arthritis of the first metatarsophalangeal joint.

CONCLUSIONS

The presence of pathologic changes reduces the rate of successful intra-articular joint puncture. However, the overall frequency of successful intra-articular injections can be improved through experience and the use of imaging.

The risks and benefits of glucocorticoid treatment for tendinopathy: a systematic review of the effects of local glucocorticoid on tendon

OBJECTIVE

Our primary objective was to summarise the known effects of locally administered glucocorticoid on tendon tissue and tendon cells.

METHODS

We conducted a systematic review of the scientific literature using the PRISMA and Cochrane guidelines of the Medline database using specific search criteria. The search yielded 50 articles, which consisted of 13 human studies, 36 animal studies and one combined human/animal study.

RESULTS

Histologically, there was a loss of collagen organisation (6 studies) and an increase in collagen necrosis (3 studies). The proliferation (8 studies) and viability (9 studies) of fibroblasts was reduced. Collagen synthesis was decreased in 17 studies. An increased inflammatory cell infiltrate was shown in 4 studies. Increased cellular toxicity was demonstrated by 3 studies. The mechanical properties of tendon were investigated by 18 studies. Descriptively, 6 of these studies showed a decrease in mechanical properties, 3 showed an increase, while the remaining 9 showed no significant change. A meta-analysis of the mechanical data revealed a significant deterioration in mechanical properties, with an overall effect size of -0.67 (95% CI = 0.01 to -1.33) (data from 9 studies).

CONCLUSIONS

Overall it is clear that the local administration of glucocorticoid has significant negative effects on tendon cells in vitro, including reduced cell viability, cell proliferation and collagen synthesis. There is increased collagen disorganisation and necrosis as shown by in vivo studies. The mechanical properties of tendon are also significantly reduced. This review supports the emerging clinical evidence that shows significant long-term harms to tendon tissue and cells associated with glucocorticoid injections.

The influence of ultrasound guidance in the rate of success of acromioclavicular joint injection: an experimental study on human cadavers

BACKGROUND

Injections of the acromioclavicular joint (ACJ) are performed routinely in patients with ACJ arthritis, both diagnostically and therapeutically. The aim of this prospective controlled study was to estimate the frequency of successful intra-articular ACJ injections with the aid of sonographic guidance versus non-guided ACJ injections.

MATERIALS AND METHODS

A total of 80 cadaveric ACJs were injected with a solution containing methylene blue and subsequently dissected to distinguish intra- from peri-articular injections. In 40 cases the joint was punctured with sonographic guidance, whereas 40 joints were injected in the control group without the aid of ultrasound.

RESULTS

The rate of successful intra-articular ACJ injection was 90% (36 of 40) in the guided group and 70% (28 of 40) in the non-guided group. Ultrasound was significantly more accurate for correct intra-articular needle placement (P = .025).

DISCUSSION

The use of ultrasound significantly improves the accuracy of ACJ injection.

Intra-articular injection of the acromioclavicular joint

Intra-articular punctures and injections are performed routinely on patients with injuries to and chronic diseases of joints, to release an effusion or haemarthrosis, or to inject drugs. The purpose of this study was to investigate the accuracy of placement of the needle during this procedure. A total of 76 cadaver acromioclavicular joints were injected with a solution containing methyl blue and subsequently dissected to distinguish intra- from peri-articular injection. In order to assess the importance of experience in achieving accurate placement, half of the injections were performed by an inexperienced resident and half by a skilled specialist. The specialist injected a further 20 cadaver acromioclavicular joints with the aid of an image intensifier. The overall frequency of peri-articular injection was much higher than expected at 43% (33 of 76) overall, with 42% (16 of 38) by the specialist and 45% (17 of 38) by the resident. The specialist entered the joint in all 20 cases when using the image intensifier. Correct positioning of the needle in the joint should be facilitated by fluoroscopy, thereby guaranteeing an intra-articular injection.

Does the anteromedial or anterolateral approach alter the rate of joint puncture in injection of the ankle?

Injection or aspiration of the ankle may be performed through either an anteromedial or an anterolateral approach for diagnostic or therapeutic reasons. We evaluated the success of an intra-articular puncture in relation to its site in 76 ankles from 38 cadavers. Two orthopaedic surgical trainees each injected methylene blue dye into 18 of 38 ankles through an anterolateral approach and into 20 of 38 through an anteromedial. An arthrotomy was then performed to confirm the placement of the dye within the joint.

Of the anteromedial injections 31 of 40 (77.5%, 95% confidence interval (CI) 64.6 to 90.4) were successful as were 31 of 36 (86.1%, 95% CI 74.8 to 97.4) anterolateral injections. In total 62 of 76 (81.6%, 95% CI 72.9 to 90.3) of the injections were intra-articular with a trend towards greater accuracy with the anterolateral approach, but this difference was not statistically significant (p = 0.25). In the case of trainee A, 16 of 20 anteromedial injections and 14 of 18 anterolateral punctures were intra-articular. Trainee B made successful intra-articular punctures in 15 of 20 anteromedial and 17 of 18 anterolateral approaches. There was no significant difference between them (p = 0.5 and p = 0.16 for the anteromedial and anterolateral approaches, respectively). These results were similar to those of other reported studies. Unintended peri-articular injection can cause complications and an unsuccessful aspiration can delay diagnosis. Placement of the needle may be aided by the use of ultrasonographic scanning or fluoroscopy which may be required in certain instances.

Effect of corticosteroids on the biomechanical strength of rat rotator cuff tendon

BACKGROUND

The effect of corticosteroids on tendon properties is poorly understood, and current data are contradictory and diverse. The biomechanical effect of steroids on rotator cuff tendon has not been studied, to our knowledge. The current study was undertaken to characterize the biomechanical effects of corticosteroid exposure on both uninjured and injured rat rotator cuff tendon.

METHODS

One hundred and twenty-three male Sprague-Dawley rats were randomly assigned to four groups: control (C), tendon injury (I), steroid exposure (S), and tendon injury plus steroid exposure (I+S). Unilateral tendon injuries consisting of a full-thickness defect across 50% of the total width of the infraspinatus tendon were created. Steroid treatment consisted of a single dose of methylprednisolone placed into the subacromial space. At one, three, and five weeks postoperatively, the shoulders were harvested and the infraspinatus tendon was subjected to biomechanical testing. Two specimens from each group were used for histological analysis.

RESULTS

At one week, maximum load, maximum stress, and stiffness were all significantly decreased in Group S compared with the values in Group C. Mean maximum load decreased from 37.9 N in Group C to 27.5 N in Group S (p < 0.0005). Mean maximum stress decreased from 18.1 MPa in Group C to 13.6 MPa in Group S (p < 0.0005). Mean stiffness decreased from 26.3 N/mm in Group C to 17.8 N/mm in Group S (p < 0.0005). At one week, mean maximum stress in Group I+S (17.0 MPa) was significantly decreased compared with the value in Group I (19.5 MPa) (p < 0.0005). At both the three-week and the five-week time point, there were no significant differences between Group C and Group S or between Group I and Group I+S with regard to mean maximum load, maximum stress, or stiffness. Histological analysis showed fat cells and collagen attenuation in Groups S and I+S. These changes appeared to be transient.

CONCLUSIONS

A single dose of corticosteroids significantly weakens both intact and injured rat rotator cuff tendons at one week. This effect is transient as the biomechanical properties of the steroid-exposed groups returned to control levels by three weeks.

The effect of corticosteroid on collagen expression in injured rotator cuff tendon

BACKGROUND

Subacromial corticosteroid injections are commonly used in the nonoperative management of rotator cuff disease. The effects of corticosteroid injection on injured rotator cuff tendons have not been studied. Our aims were to characterize the acute response of rotator cuff tendons to injury through the analysis of the type-III to type-I collagen expression ratio, a tendon injury marker, and to examine the effects of corticosteroid on this response.

METHODS

Sixty Sprague-Dawley rats were randomly assigned to four groups: control, tendon injury, steroid treatment, and tendon injury and steroid treatment. Six rats served as sham controls. Unilateral tendon injuries were created with full-thickness defects across 50% of the total width of the infraspinatus tendon, 5 mm from its humeral insertion. Steroid treatment with a single dose of methylprednisolone (0.6 mg/kg), equivalent to that given to humans, was injected into the subacromial space under direct visualization. Steroid treatment followed the creation of an injury in the rats in the injury and steroid treatment group. At one, three, and five weeks after the injury, the total RNA isolated from tendons was quantified with real-time polymerase chain reaction with use of primers for type-I and type-III collagen and ribosomal 18s RNA.

RESULTS

The type-III to type-I collagen expression ratio remained at baseline at all time-points in the control and sham groups. At one week, the type-III to type-I collagen expression ratio increased more than fourfold above the control level in the tendon injury group (p = 0.017) and the tendon injury and steroid treatment group (p = 0.003). The ratio remained greater than twofold above the control at three weeks in both groups (p = 0.003 and p = 0.037) and returned to baseline at five weeks. Interestingly, the group that had steroid treatment only showed an increase of >4.5-fold (p = 0.001) in the type-III to type-I collagen expression ratio, without structural injury to the tendon. This ratio returned to baseline levels by three weeks.

CONCLUSIONS

A single dose of corticosteroid does not alter the acute phase response of an injured rotator cuff tendon in the rat. However, the same steroid dose in uninjured tendons initiates a short-term response equivalent to that of structural injury.

Glucocorticoids inhibit tenocyte proliferation and Tendon progenitor cell recruitment

Corticosteroid injection is commonly used to treat tendon injuries but is often associated with tendon rupture and impaired tendon healing. The effects of dexamethasone on tenocytes have been studied in vitro but only using high concentrations of dexamethasone in monolayer cultures of tenocytes over short periods of time. We have therefore investigated the effects of physiological and pharmacological concentrations of dexamethasone on monolayer cultures of tenocytes over extended time periods. We have also used fibroblastic-colony forming unit cultures to examine the effects of dexamethasone on a progenitor cell population located in tendons. Culturing tenocytes in the presence of dexamethasone for a period of 24 days resulted in a concentration-related decrease in cell number and collagen synthesis as compared to control cultures. This effect was time dependent with cell number in both dexamethasone-treated and control cultures leveling off after 14 days with the control cultures reaching higher cell densities. In contrast in control cultures, collagen accumulation continued to increase until week 4, whereas in the presence of dexamethasone, this tended to level off after 14 days. To study the role of progenitor cell recruitment, the effects of dexamethasone were investigated using the fibroblastic-colony forming unit assay. Treatment with dexamethasone at concentrations of 0.1 nM to 10 microM leads to a progressive reduction in mean colony size as compared to control cultures. Colony number remained constant at concentrations below 10 nM but fell progressively at concentrations above this. In conclusion, dexamethasone reduces both cell number and collagen synthesis in tenocyte cultures in a concentration-dependent manner by both direct effects on tenocyte proliferation and collagen accumulation, and also by modulating the recruitment of tendon progenitor cells.

Function and biomechanics of tendons

Tendon is a highly organized connective tissue joining muscle to bone, capable of resisting high tensile forces while transmitting forces from muscle to bone. The dense, regularly arranged collagenous tissue is made up of fibers, cells of various shapes and ground substance. The mechanical and physiological characteristics of collagen (nearly 85% of the dry weight of tendon) dictate the qualities of tendon. In addition, tendon is flexible so that it can bend at joints, as well as acting as a damping tissue to absorb shock and limit potential damage to muscle (1). Tendon also shows a degree of extensibility. If the strain used to stretch a tendon could be recovered, a beneficial elastic effect would be achieved. Muscles lengthen and shorten in a cyclical manner. During the lengthening period, elastic energy can be stored and used as elastic recoil. For example, the Achilles tendon is stretched late in the stance phase as the triceps surae muscles contract and the ankle dorsiflexes. Prior to plantarflexion, muscle activation ceases and stored energy helps to initiate planter flexion.

Influence of steroid injection on ligament healing in the rat

The effect of a single local injection of long acting corticosteroid on the healing of acute rat medial collateral ligament injuries was studied. The medial collateral ligaments of 81 adult female rats were exposed surgically. In 32 rats, the ligament was transected sharply, the overlying muscle was closed, and a human equivalent dose of dexamethasone was injected under the muscle layer, bathing the injured ligament. The identical operation with no corticosteroid injection was done in 32 additional rats: in the remaining 17 animals, the incision was closed without ligament transection or injection. The rats were divided into 3 groups of 25. Each group consisted of 10 rats that were injected, 10 that were not injected, and 5 that underwent sham operations. One group was euthanized 6 days after surgery, 1 group after 10 days, and 1 group after 20 days. Histologic evaluation and biomechanical testing were performed for each subgroup. A cellular pathologist examined a smaller group of 6 rats (2 from each group) for histologic changes 40 days after surgery. No histologic differences were noted between the injected and noninjected ligaments 6, 10, or 20 days after injury. At 40 days, the injected specimens showed a slightly more mature crimp pattern than the noninjected specimens. Mechanical testing demonstrated no significant difference in ultimate load or ultimate stress between the injected and noninjected groups. There were no detrimental effects of a single dose administration of dexamethasone on the histologic appearance or biomechanical strength of healing rat medial collateral ligaments.

Effects of local injection of corticosteroids on the healing of ligaments. A follow-up report

One hundred and one skeletally mature New Zealand White rabbits were used to study the long-term effects of a single injection of corticosteroid on the biomechanical, histological, and biochemical properties of ligament-healing. Two steroid doses were studied, as previously described. The injections were made into a fascial pocket immediately after transection of the ligament. The animals were killed forty-two and eighty-four days after the injury. In our previous investigation, in which we examined the early (inflammatory and proliferative) phases of ligament-healing, the specimens that had been injected with a dose of steroids equivalent to that given to humans demonstrated significantly inferior biomechanical properties and histological organization relative to controls that had not received an injection. In the current study, we examined the later (remodeling and maturation) phases of ligament-healing and found that the tensile strength (the ultimate stress) of the specimens that had been injected with the steroids returned to a value that was equal to that of the controls that had not received an injection; however, the peak load of the specimens that had been injected with steroids remained inferior to that of the controls. This was accompanied by a lag in the histological maturation.

Effects of a delayed steroid injection on ligament healing using a rabbit medial collateral ligament model

Corticosteroids are known to inhibit collagen synthesis in vitro as well as having a deleterious effect on ligament healing when applied immediately following injury. An acute injection of betamethasone into a transected rabbit medial collateral ligament significantly impaired the biomechanical and histological properties compared to non-injected transected ligaments. Differences in mechanical, histological and biochemical properties were observed up to 3 months following injury and an acute steroid injection. The present study explored the effects of a corticosteroid (betamethasone) injection 7 days following the initial injury. Biomechanical and histomorphometric analyses were carried determine if the previously observed deleterious effects of a corticosteroid injection immediately following injury can be linked to an interference in the inflammatory phase of healing due to the presence of the corticosteroid.

Healing characteristics of a type I collagenous structure treated with corticosteroids

One hundred twenty-eight skeletally mature New Zealand White rabbits were used to study the effect of a single corticosteroid injection on the biomechanical, biochemical, and histologic aspects of ligamentous healing. Two steroid dosages were used. The amount of the low-dose steroid was calculated by determining the corticosteroid concentration at which fibroblastic synthesis of collagen was inhibited in vitro. A human equivalent dose of betamethasone was used as the high-dose steroid injection. These two steroid doses and a saline control were injected around a transected medial collateral ligament. At 10 days all groups showed significantly inferior biomechanical properties relative to noninjected controls. By 3 weeks the human equivalent steroid dose group continued to demonstrate significantly inferior properties. Histologic and biochemical analyses confirmed the biomechanical results. The clinical relevance of the study was that the delivery of a human equivalent steroid dose into an acutely injured ligament significantly impairs the healing process relative to a noninjected ligament at 10 days and at 3 weeks after injury. This implies that a corticosteroid-treated injured ligament may not be able to withstand the mechanical loads of early vigorous rehabilitation.

Thigh Strains in Competitive Breaststroke Swimmers

Although shoulder and knee injuries are the most common injuries in swimmers, thigh/groin strains have recently been identified as a critical area in elite competitive breaststroke swimmers. A survey of high-level collegiate breaststroke swimmers revealed a 33% incidence of this hip flexor adductor injury. A comprehensive treatment and prevention program is detailed in this paper.

Influence of local steroid injections on traumatized tendon properties. A biomechanical and histological study

We investigated the effects of peritendon injections of hydrocortisone acetate on the separation force required to completely avulse a posttraumatized Achilles tendon of the adult male rat. One hundred thirty-five rats were randomly assigned to 3 groups and subsequently traumatized, treated, and sacrificed. One group was used to examine the effect of trauma; the second to examine effects of trauma and injections of hydrocortisone acetate on the tension to failure strength of tendons; the third group was the control group. Injected animals received one, three, or five injections of 0.10 cc (125 mg/ml) hydrocortisone acetate and were sacrificed 3, 6, or 9 weeks following initial injection. Experimental animals (anesthetized) were traumatized by dropping a weight onto the Achilles tendon. The tendon was tested in tension to failure employing a soft tissue linear disseminator. Histologic analysis using light microscopy was performed. We concluded that hydrocortisone acetate has no deleterious effect on the rat Achilles tendon as measured biomechanically or histologically.

Long term local cortisol treatment of tendons and the indirect effect on skin. An experimental study in rats

The mechanical properties of muscle tendon after long term local cortisol treatment were studied as well as those of skin with regard to possible systemic effects. Rats received cortisol injections 10 mg/kg into each hind limb, around the peroneal tendons every third day for 55 days. A control group was injected in the same way, but with saline. The local cortisol treatment did not alter the mechanical properties of the peroneous longus tendon, even though its dry weight and hydroxyproline content was reduced. A systemic effect on skin from the dorsum was observed. The thickness and hydroxyproline content were reduced, and in spite of that, the strength of the skin specimens increased. The hydroxyproline/nitrogen ratio in purified, insoluble skin collagen was not changed after the cortisol treatment. Two different effects of corticosteroids on collagenous tissues are suggested to act here: (1) within the first one to two weeks corticosteroids induce a relatively fast increase in the stability of the collagenous tissue, (2) followed by a progressive thinning and reduction in collagen of the tissue, caused mainly by an inhibited collagen synthesis. Thus the strength of the muscle tendon is not reduced, even though its collagen content is reduced after local cortisol treatment for 55 days.