Preoperative bone marrow stimulation does not improve functional outcomes in arthroscopic cuff repair: a prospective randomized controlled trial

AIMS

Despite recent advances in arthroscopic rotator cuff repair, re-tear rates remain high. New methods to improve healing rates following rotator cuff repair must be sought. Our primary objective was to determine if adjunctive bone marrow stimulation with channelling five to seven days prior to arthroscopic cuff repair would lead to higher Western Ontario Rotator Cuff (WORC) scores at 24 months postoperatively compared with no channelling.

METHODS

A prospective, randomized controlled trial was conducted in patients undergoing arthroscopic rotator cuff repair. Patients were randomized to receive either a percutaneous bone channelling of the rotator cuff footprint or a sham procedure under ultrasound guidance five to seven days prior to index surgery. Outcome measures included the WORC, American Shoulder and Elbow Surgeons (ASES), and Constant scores, strength, ultrasound-determined healing rates, and adverse events.

RESULTS

Overall, 94 patients were randomized to either bone channelling or a sham procedure. Statistically significant improvements in all clinical outcome scores occurred in both groups from preoperative to all timepoints (p < 0.001). Intention-to-treat analysis revealed no statistical differences in WORC scores between the two interventions at 24 months postoperatively (p = 0.690). No differences were observed in secondary outcomes at any timepoint and healing rates did not differ between groups (p = 0.186).

CONCLUSION

Preoperative bone channelling one week prior to arthroscopic rotator cuff repair was not associated with significant improvements in WORC, ASES, Constant scores, strength, or ultrasound-determined healing rates. Cite this article: Bone Joint J 2021;103-B(1):123-130.

Bone replaces unloaded articular cartilage during knee immobilization. A longitudinal study in the rat

BACKGROUND

Joint immobility results in deleterious changes such as capsule shortening, bone loss and articular cartilage damage. Immobilization of rat knees in flexion for 32 weeks resulted in the distinctive feature of well-established replacement of articular cartilage by bone. Determining the time of onset of bone replacement is critical for the prevention of this likely irreversible complication of joint immobilization.

OBJECTIVES

To determine the onset and progression of bone replacement in the anterior tibial articular cartilage following knee immobilization in flexion.

METHODS

One hundred forty-nine adult male Sprague-Dawley rats were used. The experimental groups had one knee immobilized at 135°of flexion for durations of 2, 4, 8, 16 or 32 weeks and were compared to age-matched controls. The knees were evaluated histologically for the presence and cross-sectional area of bone within the articular cartilage of the tibia. Distance between the anterior aspect of the tibia and intact articular cartilage and cross-sectional bone area of the tibial epiphysis were also measured.

RESULT

Bone replacement in the articular cartilage was observed in 14%, 75%, 95%, 100% and 100% of knees after 2, 4, 8, 16 and 32 weeks of immobilization, respectively. No bone replacement was seen in the control knees. The mean area of bone replacement increased from 0.004 ± 0.007 mm² after 2 weeks to 0.041 ± 0.036 mm²; 0.085 ± 0.077 mm²; 0.092 ± 0.056 mm² and 0.107 ± 0.051 mm² after 4, 8, 16 and 32 weeks of immobilization, respectively, (p < 0.001) largely restricted to the anterior tibial articular cartilage. Mean distance to intact articular cartilage increased from 0.89 ± 0.69 mm at 2 weeks to 1.10 ± 0.35 mm; 1.65 ± 0.77 mm; 1.48 ± 0.63 mm; and 1.78 ± 0.58 mm after 4, 8, 16 and 32 weeks of immobilization, respectively (p = 0.001). Epiphyseal bone cross-sectional area was significantly reduced following 4, 8, and 16 weeks of immobilization compare to controls (all 3 p < 0.05).

CONCLUSION

Knee immobilization in flexion resulted in bone replacement in the anterior tibial articular cartilage that began after 2 weeks and was prevalent after 4 weeks of immobilization. The bone replacement progressed in an anterior-to-posterior direction and stopped at the area of contact between tibia and femur. These findings stress the importance of mobility to maintain joint health.

Supraspinatus tendon transosseous vs anchor repair surgery: a comparative study of mechanical recovery in the rabbit

BACKGROUND

Supraspinatus (SSP) tendon ruptures requiring surgical repair are common. Arthroscopic suture anchor fixation has gradually replaced transosseous repair in supraspinatus tendon tear. Our objective was to compare mechanical properties between transosseous and anchor supraspinatus repair in the first 6 postoperative weeks in a rabbit model.

METHODS

One hundred and fifty-two rabbits had one supraspinatus tendon repaired either with an anchor suture 1 week after detachment or with transosseous sutures. Rabbits were euthanized at 0, 1, 2, 4 or 6 postoperative weeks. Experimental and contralateral tendons (304 tendons) were mechanically tested to failure. Data are expressed as percent of contralateral.

RESULTS

Anchor repair had higher loads to failure compared to transosseous repair, at immediate repair (week 0, 52 ± 21% vs 25 ± 17%, respectively; p = 0.004) and at 1 postoperative week (64 ± 32% vs 28 ± 10%; p = 0.003) with no difference after 2 weeks. There was no difference in stiffness. Transosseous repairs showed higher rates of midsubstance failures compared to anchor repairs at 1 (p = 0.004) and 2 postoperative weeks (p < 0.001). Both transosseous and anchor repairs restored supraspinatus mechanical properties after 4 postoperative weeks.

CONCLUSION

Anchor repair provided better initial tensile strength while transosseous repair led to a faster normalization (namely, midsubstance) of the mode of failure. Research to optimize supraspinatus repair may need to consider the advantages from both surgical approaches.

Reversibility of marrow adipose accumulation and reduction of trabecular bone in the epiphysis of the proximal tibia

Mechanical stimuli play an important role in the homeostasis of trabecular bone and marrow adipose tissue, particularly for the weight-bearing skeleton. Prolonged immobilization and disuse have been shown to reduce trabecular bone content and increase marrow adipose tissue in the bones of lower limb joints such as the knee. However, details on the temporal response of this relationship to prolonged immobilization and its reversibility is limited. Forty rats had one knee immobilized at 45° of flexion for 2, 4, 8, or 16 weeks and subsequently remobilized for 0 or 8 weeks. The contralateral knees were used as controls. Histomorphometric measures of trabecular bone and marrow adipose tissue (MAT) areas were conducted in the epiphysis of the proximal tibia. Knee immobilization for 4, 8, and 16 weeks significantly reduced trabecular bone area by -0.125, -0.139, and -0.161 mm²/mm², respectively, with corresponding 95 % CIs of [-0.012, -0.239], [-0.006, -0.273], and [-0.101, -0.221]. MAT area significantly increased at 2 and 16 weeks by +0.008 and +0.027 mm²/mm², respectively, with 95 % CIs of [0.014, 0.002] and [0.039, 0.016]. Remobilization for 8 weeks restored trabecular bone area compared to the contralateral knee and the magnitude of change was significantly greater for 8 and 16 weeks of immobilization with effect sizes of 1.69 and 1.86, respectively. The difference in MAT area between immobilized and contralateral knees were eliminated with remobilization. These results characterize the temporal response of trabecular bone and MAT in the epiphysis of the proximal tibia to joint immobilization and remobilization.

Hyperplasia and accelerated hypertrophy of marrow adipocytes with knee immobilization were sustained despite remobilization

Skeletal disuse can cause an accumulation of bone marrow adipose tissue (MAT) characterized by a combination of marrow adipocyte hyperplasia and/or hypertrophy. The malleability of MAT accumulation and of the hyperplasia and hypertrophy upon remobilization is unknown. In this study, we showed extensive hyperplasia and accelerated hypertrophy of bone marrow adipocytes in the proximal tibia epiphysis of rat knees immobilized for durations between 1 and 32 wk. Similar histomorphometric measures of adipocytes carried out in unoperated controls allowed distinguishing the effects of immobilization from the effects of aging. Although both knee immobilization and aging led to adipocyte hypertrophy, adipocyte hyperplasia was the hallmark signature effect of immobilization on MAT. Both bone marrow adipocyte hyperplasia and hypertrophy were sustained despite knee remobilization for durations up to four times the duration of immobilization. These results suggest that adipocyte hyperplasia is the predominant mechanism explaining MAT accumulation in skeletal disuse. In this model, the changes were unremitting for the investigated time points. Investigating the cellular and molecular mechanisms of marrow adipocyte mechanoregulation will be important to better understand how adipocytes adapt to changes in mechanical environments.NEW & NOTEWORTHY This longitudinal study elucidates the response of marrow adipose tissue adipocytes in weight-bearing joints to changes in different mechanical environments, and we provide insight on the malleability of the changes over time. In a rat animal model, knee immobilization induced hyperplasia and accelerated the age-dependent hypertrophy of adipocytes. Changes in adipocyte number and size were sustained despite unassisted remobilization. Multimodal distributions of cell size were characteristic of bone marrow adipocytes.

Characterization of Intervertebral Disc Changes in Asymptomatic Individuals with Distinct Physical Activity Histories Using Three Different Quantitative MRI Techniques

(1) Background: Assessments of intervertebral disc (IVD) changes, and IVD tissue adaptations due to physical activity, for example, remains challenging. Newer magnetic resonance imaging techniques can quantify detailed features of the IVD, where T2-mapping and T2-weighted (T2w) and Dixon imaging are potential candidates. Yet, their relative utility has not been examined. The performances of these techniques were investigated to characterize IVD differences in asymptomatic individuals with distinct physical activity histories. (2) Methods: In total, 101 participants (54 women) aged 25–35 years with distinct physical activity histories but without histories of spinal disease were included. T11/12 to L5/S1 IVDs were examined with sagittal T2-mapping, T2w and Dixon imaging. (3) Results: T2-mapping differentiated Pfirrmann grade-1 from all other grades (p < 0.001). Most importantly, T2-mapping was able to characterize IVD differences in individuals with different training histories (p < 0.005). Dixon displayed weak correlations with the Pfirrmann scale, but presented significantly higher water content in the IVDs of the long-distance runners (p < 0.005). (4) Conclusions: Findings suggested that T2-mapping best reflects IVD differences in asymptomatic individuals with distinct physical activity histories changes. Dixon characterized new aspects of IVD, probably associated with IVD hypertrophy. This complementary information may help us to better understand the biological function of the disc.

Translating guidelines to practice: a training session about cancer-related fatigue

Background

Cancer-related fatigue (crf) is the highest unmet need in cancer survivors. The Canadian Association of Psychosocial Oncology (capo) has developed guidelines for screening, assessment, and intervention in crf; however, those guidelines are not consistently applied in practice because of patient, health care provider (hcp), and systemic barriers. Notably, previous studies have identified a lack of knowledge of crf guidelines as an impediment to implementation.

Methods

In this pilot study, we tested the preliminary outcomes, acceptability, and feasibility of a training session and a knowledge translation (kt) tool designed to increase knowledge of the capo crf guidelines among hcps and community support providers (csps). A one-time in-person training session was offered to a diverse sample of hcps and csps (n = 18). Outcomes (that is, knowledge of the capo crf guidelines, and intentions and self-efficacy to apply guidelines in practice) were assessed before and after training. Acceptability and feasibility were also assessed after training to guide future testing and implementation of the training.

Results

After training, participants reported increased knowledge of the capo crf guidelines and greater self-efficacy and intent to apply guidelines in practice. Participant satisfaction with the training session and the kt tool was high, and recruitment time, participation, and retention rates indicated that the training was acceptable and feasible.

Conclusions

The provided training is both acceptable to hcps and csps and feasible. It could increase knowledge of the capo crf guidelines and participant intentions and self-efficacy to implement evidence-based recommendations. Future studies should investigate actual changes in practice and how to optimize follow-up assessments. To promote practice uptake, kt strategies should be paired with guideline development.

Characterizing the effect of exposure to microgravity on anemia: more space is worse

The effects of space travel have renewed importance with space tourism and plans for long-term missions to the moon and Mars. The study of space anemia is limited by the availability of subjects and extreme conditions. An approach using the accumulated data on human space flight may characterize space anemia. A total of 17 336 hemoglobin (Hb) concentration measures from 721 space missions and controls were used to study acute and long-term effects of duration of exposure to space on Hb decrement. Nearly half of astronauts (48%) landing after long duration missions were anemic. Returning to Earth revealed Hb decrements whose magnitude and time to recover were dependent on exposure to space: -0.61 g/dL (4%), -0.82 g/dL (5%) and -1.66 g/dL (11%) of preflight Hb for mean exposure to space of 5.4, 11.5, and 145 days, respectively. Astronauts returning from a mean 5.4 days in space took 24 days to return to preflight Hb while astronauts 11.5 to 145 days in space took 49 days. Negative effects of microgravity on Hb persisted throughout female and male astronauts' terrestrial lives (-0.001 and -0.002 mg/dL Hb respectively) for every day spent in space (both P < .05). The negative effect of exposure to space was not overcome by a statistically significant effect of being an astronaut compared to controls. Exposure to space showed a dose-response relationship with acute and chronic Hb decrements. Space anemia contributes to the deconditioning of astronauts returning to Earth, and needs to be considered for space travel to other planets, space tourism and for the care of bedridden patients who present similar changes as astronauts.

Measuring Human Hemolysis Clinically and in Extreme Environments Using Endogenous Carbon Monoxide Elimination

The measure of hemolysis in humans is clinically important. Here we describe methods using a gas chromatograph equipped with a reduction gas detector to detect the human analyte carbon monoxide (CO) that were developed for the extreme environment of the International Space Station. These methods can be adapted to in-hospital use for clinical care with characteristics that may surpass existing measures of hemolysis. We demonstrate improved performance over previous-generation methods in terms of reproducibility, accuracy, control for physical and intervening factors to quantitatively assess hemolysis rates at unprecedented levels. The presented measure of hemolysis using CO elimination is based on a different physiological approach that can complement and augment existing detection tools. In addition to their suitability for extreme environments, the methods present distinctive advantages over existing markers for the diagnosis, monitoring and response to treatment of hemolytic anemia. These methods have the potential to fulfill a wide range of research and clinical applications.

Adipocyte hyperplasia: the primary mechanism of supraspinatus intramuscular fat accumulation after a complete rotator cuff tendon tear: a study in the rabbit

Intramuscular fat (IMF) accumulates in muscles of the rotator cuff after tendon tear. The number and cross-sectional area of fat clumps and of adipocytes were quantified on osmium tetroxide stained sections of the proximal, middle and distal quarters of SSP muscles 4, 8 and 12 weeks after SSP tendon division in a rabbit model. Linear mixed-effects models were fitted to the data and statistical significance was evaluated by ANOVA. Both the number (P<0.001) and cross-sectional area (P<0.0005) of fat clumps increased after tendon detachment while time had no significant effect (both at P>0.01). IMF accumulation was more important in the distal quarter of detached SSP muscle near tendon sectioning and characterized by increases of the number (P<0.0005) and cross-sectional area of fat clumps (P<0.0005) compared to the proximal quarter. Adipocyte number increased after tendon detachment (P<0.0005) and over time (P<0.01). The cross-sectional area of adipocytes increased in the detached group compared to controls (P<0.01) while time had no significant effect (P>0.01). Interestingly, the number of adipocytes in the distal quarter increased (P<0.0005) but the cross-sectional area was smaller (P<0.0005) compared to adipocytes in the proximal quarter. Adipocyte hyperplasia localized near tendon sectioning was the main contributor to fat accumulation in the detached SSP muscles.

Marrow adipose tissue gradient is preserved through high protein diet and bed rest. A randomized crossover study

Context

Marrow adipose tissue (MAT) has a peripheral to central distribution in adults, higher in peripheral bones. Similarly, the spine has a caudal to cephalad MAT distribution, higher in lumbar vertebras. Diet and the level of physical activities are known modulators of MAT with significant impact on bone; however, whether these can modulate the MAT gradient is unknown.

Objective

To measure the effect of high protein diet and bed rest interventions on the lumbar MAT gradient.

Design participants intervention

In a prospective randomized crossover trial, 10 healthy men participated in 2 consecutive campaigns of 21days head-down-tilt-bed-rest (HDTBR). They received either whey protein and potassium bicarbonate-supplemented or control diet separated by a 4-month washout period.

Main outcome measures

Ten serial MRI measures of lumbar vertebral fat fraction (VFF) were performed at baseline, 10days and 20days of HDTBR and 3 and 28days after HDTBR of each bed rest campaign.

Results

The mean L5-L1 VFF difference of 4.2 ± 1.2 percentage point higher at L5 (p = 0.008) constituted a caudal to cephalad lumbar MAT gradient. High protein diet did not alter the lumbar VFF differences during both HDTBR campaigns (all time points p > 0.05). Similarly, 2 campaigns of 21days of HDTBR did not change the lumbar VFF differences (all time points p > 0.05).

Conclusions

This pilot study established that the lumbar vertebral MAT gradient was not altered by a high protein nor by 2 × 21days bed rest interventions. These findings demonstrated that this lack of mechanical stimulus was not an important modulator of the lumbar MAT gradient. The highly preserved MAT gradient needs to be measured in more situations of health and disease and may potentially serve to detect pathological situations.

Tendon contains more stem cells than bone at the rotator cuff repair site

BACKGROUND

The rotator cuff (RC) repair failure rate is high. Tendon and bone represent sources of mesenchymal stem cells (MSCs), but the number of MSCs from each has not been compared. Bone channeling may increase bone-derived MSC numbers participating in enthesis re-formation at the "footprint" repair site. The effect of preoperative channeling on increasing bone MSC numbers has never been reported. We asked (1) whether bone contains more MSCs than tendon at the time of arthroscopic repair and (2) whether bone preoperative channeling at the RC repair site increases the number of bone-derived MSCs at the time of surgery.

METHODS

In 23 participants undergoing arthroscopic RC repair, bone was sampled from the footprint and tendon was sampled from the distal supraspinatus. We randomized participants to the channeling or no-channeling group 5 to 7 days before surgery. We enumerated MSCs from both tissues using the colony-forming unit-fibroblast (CFU-F) assay (10 per group). We identified MSC identity using flow cytometry and MSC tri-differentiation capacity (n = 3).

RESULTS

Tendon CFU-F per gram exceeded bone CFU-F per gram for both groups (479 ± 173 CFU-F/g vs. 162 ± 54 CFU-F/g for channeling [P = .036] and 1334 ± 393 CFU-F/g vs. 284 ± 88 CFU-F/g for no channeling [P = .009]). Ninety-nine percent of cultured cells satisfied the MSC definition criteria.

CONCLUSIONS

The distal supraspinatus tendon contained more MSCs per gram than the humeral footprint. Tendon may represent an important and overlooked MSC source for postoperative enthesis re-formation. Further studies are needed to evaluate the repair role of tendon MSCs and to recommend bone channeling in RC repair.

Using a Knee Arthrometer to Evaluate Tissue-specific Contributions to Knee Flexion Contracture in the Rat

Normal knee range of motion (ROM) is critical to well-being and allows one to perform basic activities such as walking, climbing stairs and sitting. Lost ROM is called a joint contracture and results in increased morbidity. Due to the difficulty of reversing established knee contractures, early detection is important, and hence, knowing risk factors for their development is essential. The rat represents a good model with which the effect of an intervention can be studied due to the similarity of rat knee anatomy to that of humans, the rat's ability to tolerate long durations of knee immobilization in flexion, and because mechanical data can be correlated with histologic and biochemical analysis of knee tissue. Using an automated arthrometer, we demonstrate a validated, precise, reproducible, user-independent method of measuring the extension ROM of the rat knee joint at specific torques. This arthrometer can be used to determine the effects of interventions on knee joint ROM in the rat.

Hemolysis during and after 21 days of head-down-tilt bed rest

Hemoconcentration is observed in bed rest studies, descent from altitude, and exposure to microgravity. Hemoconcentration triggers erythrocyte losses to subsequently normalize erythrocyte concentration. The mechanisms of erythrocyte loss may involve enhanced hemolysis, but has never been measured directly in bed rest studies. Steady‐state hemolysis was evaluated by measuring two heme degradation products, endogenous carbon monoxide concentration [CO] and urobilinogen in feces, in 10 healthy men, before, during, and after two campaigns of 21 days of 6° head‐down‐tilt (HDT) bed rest. The subjects were hemoconcentrated at 10 and 21 days of bed rest: mean concentrations of hemoglobin (15.0 ± 0.2 g/L and 14.6 ± 0.1 g/L, respectively) and erythrocytes (5.18 ± 0.06E6/μL and 5.02 ± 0.06E6/μL, respectively) were increased compared to baseline (all Ps < 0.05). In contrast, mean hemoglobin mass (743 ± 19 g) and number of erythrocytes (2.56 ± 0.07E13) were decreased at 21 days of bed rest (both Ps < 0.05). Indicators of hemolysis mean [CO] (1660 ± 49 ppb and 1624 ± 48 ppb, respectively) and fecal urobilinogen concentration (180 ± 23 mg/day and 199 ± 22 mg/day, respectively) were unchanged at 10 and 21 days of bed rest compared to baseline (both Ps > 0.05). A significant decrease in [CO] (−505 ppb) was measured at day 28 after bed rest. HDT bed rest caused hemoconcentration in parallel with lower hemoglobin mass. Circulating indicators of hemolysis remained unchanged throughout bed rest supporting that enhanced hemolysis did not contribute significantly to erythrocyte loss during the hemoconcentration of bed rest. At day 28 after bed rest, decreased hemolysis accompanied the recovery of erythrocytes, a novel finding.

Specific Modulation of Vertebral Marrow Adipose Tissue by Physical Activity

Marrow adipose tissue (MAT) accumulation with normal aging impacts the bone, hemopoiesis, and metabolic pathways. We investigated whether exercise was associated with lower MAT, as measured by vertebral marrow fat fraction (VFF) on magnetic resonance imaging. A total of 101 healthy individuals (54 females) aged 25 to 35 years without spine or bone disease but with distinct exercise histories were studied. Long-distance runners (67 km/wk, n = 25) exhibited lower mean lumbar VFF (27.9% [8.6%] versus 33.5% [6.0%]; p = 0.0048) than non-sporting referents (n = 24). In habitual joggers (28 km/wk, n = 30), mean lumbar VFF was 31.3% (9.0%) (p = 0.22 versus referents) and 6.0 percentage points lower than referents at vertebrae T₁₀ , T₁₁ , and T₁₂ (p ≤ 0.023). High-volume road cycling (275 km/wk, n = 22) did not impact VFF. 3D accelerations corresponding to faster walking, slow jogging, and high-impact activities correlated with lower VFF, whereas low-impact activities and sedentary time correlated with higher mean lumbar VFF (all p ≤ 0.05). Given an estimated adipose bone marrow conversion of 7% per decade of life, long distance runners, with 5.6 percentage points lower VFF, showed an estimated 8-year younger vertebral marrow adipose tissue phenotype. Regression analysis showed a 0.7 percentage point reduction in mean lumbar VFF with every 9.4 km/wk run (p = 0.002). This study presents the first evidence in humans or animals that specific volumes and types of exercise may influence the age-determined adipose marrow conversion and result in low MAT. These results identify a potentially modifiable risk factor for prevalent chronic conditions related to bone metabolism, hemopoietic production, and other metabolic functions with potential global health applications. © 2017 American Society for Bone and Mineral Research.

Supraspinatus tendon repair using anchors: a biomechanical evaluation in the rabbit

Background

Arthroscopic rotator cuff repairs are mostly secured with suture anchors and often supplemented by footprint decortication. The objectives of this study were to characterize the strength of bone–tendon healing following anchor repair and assess the effect of channeling the supraspinatus (SSP) humeral footprint 1 week ahead of reattachment surgery.

Methods

One hundred twelve rabbits underwent unilateral detachment of one SSP tendon and were randomly assigned to two groups: channeling the footprint at time of detachment and no channeling. One week later, reattachment was performed using an anchor. The repaired and contralateral shoulders were harvested at 0, 1, 2, or 4 weeks after repair and mechanically tested to failure. Outcome measures included load at failure, stiffness, and site of failure.

Results

Anchor fixation had a mean load at failure of 81 ± 32 N and a stiffness of 27 ± 9 N/mm immediately after repair compared to 166 ± 47 N and 66 ± 13 N/mm in the contralateral (both p < 0.05). Mechanical recovery of the reattached SSP tendon was achieved after 4 weeks (221 ± 73 N, 206 ± 59 N, and 198 ± 49 N in the channeling, no channeling, and contralateral groups, respectively, p > 0.05). The dominant site of failure shifted from the footprint at 0/1 week to bone avulsion/mid-substance tear at 4 weeks (p < 0.05). There were no differences in outcomes between the channeling and no channeling groups.

Conclusions

This study is the first of its kind to provide quantitative data on the mechanical properties of the enthesis following anchor repair in a rabbit model. Anchor repair led to rapid and complete restoration of SSP mechanical properties. Further evidence is needed before recommending channeling ahead of repair surgery.

Bone replaces articular cartilage in the rat knee joint after prolonged immobilization

BACKGROUND

Lost joint range of motion (ROM) is common in chronic osteoarthritis, alters regional weight-bearing across the articular surfaces, and contributes to loss of cartilage and bone alterations. Limited data exist on the regional effects on joints subjected to chronic losses of ROM.

OBJECTIVE

To characterize the regional replacement by bone as part of articular cartilage degeneration after prolonged immobilization.

METHODS

Eleven rat knees were rigidly-immobilized in flexion for 32weeks with contralateral and sham-operated (n=6) knees as controls. Sagittal medial tibial epiphysis histological sections assessed the anterior (non-weight-bearing), middle and posterior (both weight-bearing) regions. We quantified the distribution of collagen I, collagen II, cartilage thickness, glycosaminoglycan (GAG) staining, Mankin scoring, and subchondral bone plate cross-sectional area. Using immunohistochemistry (IHC), we visualized blood vessels, osteoblasts, and mesenchymal stem cells (MSCs).

RESULTS

Immobilized cartilage had increased collagen I content in the anterior tibial region with picrosirius red staining (immobilized=61±20%; contralateral=43±12%, p=0.033; sham=20±10%, p=0.028) and collagen I IHC (immobilized=40±10%; contralateral=11±4%, p=0.003; sham=5±3%, p=0.043). Articular cartilage was thinner anteriorly (18±30μm) in immobilized knees versus contralateral (124±40μm, p<0.001) and sham (125±43μm, p=0.043). GAG staining covered 2±4% of the anterior articular area in immobilized knees versus 28±12% contralaterally (p=0.003) and 26±7% in sham (p=0.043). Mankin scores in immobilized knees were 4.7±1.7 versus 0.2±0.4 and 0±0 for contralateral and sham (p=0.003, p=0.042), respectively. The trabecular bone plate area of anterior and posterior regions showed relative loss of cross-sectional area in immobilized knees compared to controls (immobilized/contralateral area ratios of 0.67 and 0.46 respectively, both p=0.003), while the area in the middle region was preserved. Movat's pentachrome stain and CD31 staining showed chondral vascular ingrowth from subchondral bone. Osteocalcin and CD90 MSC staining were decreased in immobilized knees versus contralateral (p=0.003, p=0.036 respectively).

CONCLUSIONS

Bony replacement characterizes articular cartilage degeneration of knees immobilized for 32weeks in the anterior, non-weight bearing region of the tibia. Replacement of cartilage by bone may have been mediated by chondral vascularization, suggesting irreversible changes. These findings stress the importance of weight-bearing and joint motion to maintain cartilage structure.

Intra-articular collagenase injection increases range of motion in a rat knee flexion contracture model

Objectives

A knee joint contracture, a loss in passive range of motion (ROM), can be caused by prolonged immobility. In a rat knee immobilization flexion contracture model, the posterior capsule was shown to contribute to an irreversible limitation in ROM, and collagen pathways were identified as differentially expressed over the development of a contracture. Collagenases purified from Clostridium histolyticum are currently prescribed to treat Dupuytren’s and Peyronie’s contractures due to their ability to degrade collagen. The potential application of collagenases to target collagen in the posterior capsule was tested in this model.

Materials and methods

Rats had one hind leg immobilized, developing a knee flexion contracture. After 4 weeks, the immobilization device was removed, and the rats received one 50 µL intra-articular injection of 0.6 mg/mL purified collagenase. Control rats were injected with only the buffer. After 2 weeks of spontaneous remobilization following the injections, ROM was measured with a rat knee arthrometer, and histological sections were immunostained with antibodies against rat collagen types I and III.

Results/conclusion

Compared with buffer-injected control knees, collagenase-treated knees showed increased ROM in extension by 8.0°±3.8° (p-value <0.05). Immunohistochemical analysis revealed an increase in collagen type III staining (p<0.01) in the posterior capsule of collagenase-treated knees indicating an effect on the extracellular matrix due to the collagenase. Collagen I staining was unchanged (p>0.05). The current study provides experimental evidence for the pharmacological treatment of knee flexion contractures with intra-articular collagenase injection, improving the knee ROM.

Loss and re-adaptation of lumbar intervertebral disc water signal intensity after prolonged bedrest

The adaptation and re-adaptation process of the intervertebral disc (IVD) to prolonged bedrest is important for understanding IVD physiology and IVD herniations in astronauts. Little information is available on changes in IVD composition. In this study, 24 male subjects underwent 60-day bedrest and In/Out Phase magnetic resonance imaging sequences were performed to evaluate IVD shape and water signal intensity. Scanning was performed before bedrest (baseline), twice during bedrest, and three, six and twenty-four months after bedrest. Area, signal intensity, average height, and anteroposterior diameter of the lumbar L3/4 and L4/5 IVDs were measured. At the end of bedrest, disc height and area were significantly increased with no change in water signal intensity. After bedrest, we observed reduced IVD signal intensity three months (p=0.004 versus baseline), six months (p=0.003 versus baseline), but not twenty-four months (p=0.25 versus baseline) post-bedrest. At these same time points post-bedrest, IVD height and area remained increased. The reduced lumbar IVD water signal intensity in the first months after bedrest implies a reduction of glycosaminoglycans and/or free water in the IVD. Subsequently, at two years after bedrest, IVD hydration status returned towards pre-bedrest levels, suggesting a gradual, but slow, re-adaptation process of the IVD after prolonged bedrest.

Noninflammatory Joint Contractures Arising from Immobility: Animal Models to Future Treatments

Joint contractures, defined as the limitation in the passive range of motion of a mobile joint, can be classified as noninflammatory diseases of the musculoskeletal system. The pathophysiology is not well understood; limited information is available on causal factors, progression, the pathophysiology involved, and prediction of response to treatment. The clinical heterogeneity of joint contractures combined with the heterogeneous contribution of joint connective tissues to joint mobility presents challenges to the study of joint contractures. Furthermore, contractures are often a symptom of a wide variety of heterogeneous disorders that are in many cases multifactorial. Extended immobility has been identified as a causal factor and evidence is provided from both experimental and epidemiology studies. Of interest is the involvement of the joint capsule in the pathophysiology of joint contractures and lack of response to remobilization. While molecular pathways involved in the development of joint contractures are being investigated, current treatments focus on physiotherapy, which is ineffective on irreversible contractures. Future treatments may include early diagnosis and prevention.

Temporal gene expression profiling of the rat knee joint capsule during immobilization-induced joint contractures

Background

Contractures of the knee joint cause disability and handicap. Recovering range of motion is recognized by arthritic patients as their preference for improved health outcome secondary only to pain management. Clinical and experimental studies provide evidence that the posterior knee capsule prevents the knee from achieving full extension. This study was undertaken to investigate the dynamic changes of the joint capsule transcriptome during the progression of knee joint contractures induced by immobilization. We performed a microarray analysis of genes expressed in the posterior knee joint capsule following induction of a flexion contracture by rigidly immobilizing the rat knee joint over a time-course of 16 weeks. Fold changes of expression values were measured and co-expressed genes were identified by clustering based on time-series analysis. Genes associated with immobilization were further analyzed to reveal pathways and biological significance and validated by immunohistochemistry on sagittal sections of knee joints.

Results

Changes in expression with a minimum of 1.5 fold changes were dominated by a decrease in expression for 7732 probe sets occurring at week 8 while the expression of 2251 probe sets increased. Clusters of genes with similar profiles of expression included a total of 162 genes displaying at least a 2 fold change compared to week 1. Functional analysis revealed ontology categories corresponding to triglyceride metabolism, extracellular matrix and muscle contraction. The altered expression of selected genes involved in the triglyceride biosynthesis pathway; AGPAT-9, and of the genes P4HB and HSP47, both involved in collagen synthesis, was confirmed by immunohistochemistry.

Conclusions

Gene expression in the knee joint capsule was sensitive to joint immobility and provided insights into molecular mechanisms relevant to the pathophysiology of knee flexion contractures. Capsule responses to immobilization was dynamic and characterized by modulation of at least three reaction pathways; down regulation of triglyceride biosynthesis, alteration of extracellular matrix degradation and muscle contraction gene expression. The posterior knee capsule may deploy tissue-specific patterns of mRNA regulatory responses to immobilization. The identification of altered expression of genes and biochemical pathways in the joint capsule provides potential targets for the therapy of knee flexion contractures.