Intact Tendon Research Articles

Self-assembling peptide hydrogel scaffold accelerates healing of patellar tendon injury: A histological and biomechanical study.

Although KI24RGDS peptide hydrogel that acts as a cell adhesion has been reported to repair tissue in meniscus injury, its effect on tendon injuries remains unknown. The purpose of this study was to clarify the effect of KI24RGDS for tendon repair based on histological and biomechanical evaluation. After introducing defects (length: 10mm; width: 3mm) at the centers of rabbits' patellar tendons, and the KI24RGDS group was implanted with KI24RGDS and observed for 8 weeks. KI24RGDS implantation resulted in limited tendon elongation and better histological scores with uniformed collagen fiber orientation and early vascularization. The failure load of the patellar tendon was higher in the KI24RGDS group than that in the defect group (p < 0.05) and no significant difference with the control group (intact patellar tendon) at 8weeks postoperatively. In conclusion, KI24RGDS administration might have therapeutic potential for tendon injuries by accelerating collagen remodeling.

Do Intact Rotator Cuff Tendons And Soft Tissue Tensioning Affect Stress Shielding In Reverse Total Shoulder Arthroplasty?

Do Intact Rotator Cuff Tendons And Soft Tissue Tensioning Affect Stress Shielding In Reverse Total Shoulder Arthroplasty?

Deprivation of loading during rat Achilles tendon healing affects extracellular matrix composition and structure, and reduces cell density and alignment.

Tendon healing involves mechanosensitive cells that adapt to mechanical stimuli through mechanotransduction, resulting in increased tissue strength. However, detailed insights into this process in response to different loads remain limited. We aimed to investigate how different loading regimes impact the spatial composition of elastin and collagens during Achilles tendon healing. Histological analysis was conducted on healing rat Achilles tendons exposed to (1) full loading, (2) reduced loading, or (3) minimal loading. Histological analysis included Hematoxylin & Eosin and immunohistochemical staining targeting elastin, Collagen1, Collagen3, and CD31. Our results showed that the impact of mechanical stimuli on healing tendons varied with the degree of loading. Unexpectedly, minimal loading led to higher staining intensity for collagens and elastin. However, tendons exposed to minimal loading appeared thinner and exhibited a less organized matrix structure, with fewer, less aligned, and more rounded cells. Additionally, our findings indicated an inverse correlation between angiogenesis and load level, with more blood vessels in tendons subjected to less loading. Tissue integrity improved by 12 weeks post-injury, but the healing process continued and did not regain the structure seen in intact tendons even after 20 weeks. This study reveals a load-dependent effect on matrix alignment, cell density, and cell alignment.

The Trillat procedure: the man and the technique revisited through the lens of arthroscopy.

The Trillat procedure, initially described by Albert Trillat, is historically one of the first techniques for addressing recurrent anterior shoulder instability, incorporating fascinating biomechanical mechanisms. After lowering, medializing, and fixing the coracoid process to the glenoid neck, the subcoracoid space is reduced, the subscapularis lowered, and its line of pull changed, accentuating the function of the subscapularis as a humeral head depressor centering the glenohumeral joint. Furthermore, the conjoint tendon creates a 'seatbelt' effect, preventing anteroinferior humeral head dislocation. Even though contemporary preferences lean towards arthroscopic Bankart repair with optional remplissage, bone augmentation, and the Latarjet procedure, enduring surgical indications remain valid for the Trillat procedure, which offers joint preservation and superior outcomes in two distinct scenarios: (i) older patients with massive irreparable cuff tears and anterior recurrent instability with an intact subscapularis tendon regardless of the extent of glenoid bone loss; (ii) younger patients with instability associated shoulder joint capsule hyperlaxity without concomitant injuries (glenoid bone loss, large Hill-Sachs lesion). Complications associated with the Trillat procedure include recurrent anterior instability, potential overtightening of the coracoid, leading to pain and a significant reduction in range of motion, risk of subcoracoid impingement, and restriction of external rotation by up to 10°, a limitation that is generally well-tolerated. The Trillat procedure may be an effective alternative technique for specific indications and should remain part of the surgical armamentarium for addressing anterior shoulder instability.

Which muscle is the external rotation compensator after superior capsular reconstruction?

BackgroundSuperior capsular reconstruction (SCR) is a surgical option for massive irreparable rotator cuff tears, particularly involving the supraspinatus and infraspinatus. In this procedure, the torn infraspinatus is not repaired or reconstructed. However, an improvement in postoperative external rotation (ER) angle and strength is observed. There is a lack of studies explaining how ER is restored after SCR. The aim of this study is to identify the ER compensator by assessing the muscle volume of the posterior deltoid and teres minor. MethodsSixty-eight patients with massive rotator cuff tears underwent SCR during 2016-2021. Of these patients, 28 who met the following inclusion criteria were retrospectively reviewed: (1) massive rotator cuff tears including the supraspinatus and infraspinatus; (2) severe muscle atrophy and fatty change; (3) intact or reparable subscapularis tendon; (4) Hamada of grade 3 or lower. Posterior deltoid and teres minor volume were measured by using an open-source medical image processing software preoperatively and 1-year postoperatively. The percentage of the posterior deltoid and teres minor muscle volume change was compared between patients with 1-year postoperative ER manual motor testing (MMT) of grade 5 and of grade < 5. The relationship between grade of fatty change, percentage of the muscle volume change, and ER angle and strength were evaluated. ResultsThere was a significant increase in the 1-year postoperative teres minor volume compared with the preoperative volume (24.6±10.3 cm³ versus 20.9±8.3 cm³, p<0.000), while the posterior deltoid volume remained unchanged (178.1±48.3 cm³ versus 178.8±47 cm³). Patients with ER MMT of grade 5 had a greater teres minor volume compared to those with an ER MMT grade of less than 5 (22.3% versus 9.4%), although this difference was not significant (p=0.074, 95% CI=-1.3–27.0). The posterior deltoid volume showed no significant change. The percentage of teres minor volume change had a weak positive correlation with ER strength (r=0.308, p=0.055, 95% CI=-0.02–1.0). There was a significant negative correlation between ER strength and the severity of both preoperative and postoperative fatty changes in the teres minor (r=-0.258, p=0.065, 95% CI=-1.0–-0.042 and r=-0.323, p=0.028, 95% CI=-1.0–-0.113, respectively). The pre- and postoperative fatty changes in the teres minor were negatively correlated with the percentage of teres minor volume change (r=-0.298, p=0.062, 95% CI=-1.0–0.031 and r=-0.413, p=0.015, 95% CI=-1.0–-0.1, respectively). ConclusionThe teres minor may serve as a potential compensator for ER in patients with massive rotator cuff tears following SCR.

The Biological Effect of Platelet-Rich Plasma on Rotator Cuff Tears: A Prospective Randomized In Vivo Study.

The positive effect of platelet-rich plasma (PRP) on tendon metabolism has been extensively investigated and proven in vitro. Additionally, in vivo animal studies have correlated the application of PRP with the enhancement of tenocyte anabolic activity in the setting of tendon degeneration. However, less is known about its in vivo effect on human tendon biology. The purpose of the current prospective randomized comparative study was to evaluate the effect of PRP on torn human supraspinatus tendon. Twenty consecutive eligible patients with painful and magnetic resonance imaging (MRI)-confirmed degenerative supraspinatus tendon tears were randomized in a one-to-one ratio into two groups. The patients in the experimental group (n = 10) underwent an ultrasound-guided autologous PRP injection in the subacromial space 6 weeks before the scheduled operation. In the control group (n = 10), no injection was made prior to surgery. Supraspinatus tendon specimens were harvested from the lateral end of the torn tendon during shoulder arthroscopy and were evaluated under optical and electron microscopy. In the control group, a mixed cell population of oval and rounded tenocytes within disorganized collagen and sites of accumulated inflammatory cells was detected. In contrast, the experimental group yielded abundant oval-shaped cells with multiple cytoplasmic processes within mainly parallel collagen fibers and less marked inflammation, simulating the intact tendon structure. These findings indicate that PRP can induce microscopic changes in the ruptured tendon by stimulating the healing process and can facilitate a more effective recovery.

Supraspinatus Muscle and Tendon Characteristics 1 Year After Surgical Rotator Cuff Repair Compared With Contralateral Shoulder: Data From the CUT-N-MOVE Trial

Background: It is necessary to better understand the structural characteristics of the supraspinatus tendon and associated muscle after rotator cuff repair and in the event of retear. Purpose: To study structural differences between the repaired and contralateral shoulders 1 year after rotator cuff repair in patients who received either progressive exercise therapy (PR) or usual care (UC) in a randomized controlled trial and to investigate whether there was interaction with tendon retear and limb dominance. Study Design: Cohort study; Level of evidence, 2. Methods: Patients with surgically repaired traumatic full-thickness rotator cuff tears involving the supraspinatus tendon were included. After surgery, they were randomized to PR or UC (active from postoperative week 2 or 6, respectively). The subacromial structures (acromiohumeral distance, supraspinatus tendon thickness, and vascularity) and the supraspinatus muscle thickness were examined with ultrasound at the 1-year follow-up. Results: A total of 79 patients were included. The characteristics of the 2 intervention groups (PR and UC) were comparable, including the Western Ontario Rotator Cuff Index score and number of retears. The authors found significantly thinner supraspinatus tendon (PR, P < .001; UC, P = .003) and reduced acromiohumeral distance (PR, P = .023; UC, P = .025) in the repaired versus the contralateral shoulders in both intervention groups. For neovascularization, there was no interlimb difference in either of the groups or between groups (PR vs UC). In patients with intact tendons, there was no interlimb difference in the muscle thickness, but in patients with tendon retear the muscle was significantly thinner on the repaired side (P = .024 and P < .001, respectively). When the dominant supraspinatus tendon was repaired (both groups), it was significantly thinner than the nondominant healthy tendon, but this difference was not seen when the nondominant supraspinatus tendon was repaired (P = .006). Conclusion: One year after rotator cuff surgery, the repaired supraspinatus tendon was significantly thinner and the corresponding acromiohumeral distance was reduced. In patients with retear, the supraspinatus muscle was significantly thinner on the repaired side and early initiation of tendon-loading exercises did not affect these findings. Registration: NCT02969135 (ClinicalTrials.gov identifier).

Retrospective analysis of the subscapularis-sparing approach for reverse total shoulder arthroplasty.

The influence of the subscapularis tendon on reverse total shoulder arthroplasty (RTSA) has been discussed controversially. The aim of the study was to investigate the subscapularis-sparing approach for RTSA and the effect of the intact subscapularis tendon. This retrospective comparative study included 93 patients. Among these, 55 underwent the deltopectoral subscapularis-sparing approach, and in 38 cases, the standard deltopectoral approach with subscapularis tenotomy was applied. At the final follow-up, representative shoulder scores were measured, radiographs were taken in two planes, and shoulder sonography was performed. The subscapularis-sparing group showed a significantly higher Constant score (71.8 vs. 65.9 points) and adapted Constant score if the subscapularis tendon was shown to be intact in the postoperative sonography (85.2% vs. 78.6%) (p = 0.005; p = 0.041). Furthermore, these patients had improved abduction (128.2 vs. 116.8, p = 0.009) and external rotation (34.6 vs. 27.1, p = 0.047). However, no significant differences were found for the degree of internal rotation and internal rotation strength. No dislocation or infection was observed. The degree of scapular notching was not significantly different between the two groups (p = 0.082). However, independently from the integrity of the subscapularis the subscapularis-sparing approach showed no difference in clinical and radiographic outcome (Constant score scapularis-sparing 70.0 points vs. tenotomy 66.8 points; p = 0.27). The subscapularis-sparing approach RTSA showed improved clinical outcome, abduction, and external rotation, if the subscapularis was shown to be intact at time of follow-up. Both groups showed no difference in internal rotation.

Fractional Lengthening of Forearm Flexor Tendons: A Cadaveric Biomechanical Analysis

Multiple procedures have been described for wrist and finger flexion contractures and spasticity. Fractional lengthening of forearm flexor tendons involves making parallel transverse tenotomies at the musculotendinous junction to elongate the muscle. Currently, there is limited literature to define the biomechanical consequences of this lengthening technique. Forty-eight flexor tendons were harvested from eight paired upper limbs including flexor carpi radialis, flexor carpi ulnaris, flexor pollicis longus, and flexor digitorum superficialis tendons. Each tendon that was lengthened was paired with the contralateral tendon as a control. A pair of transverse tenotomies were completed for the fractional lengthening. The first tenotomy was performed at the musculotendinous junction where the tendon narrowed to 75% of its maximal width. The second tenotomy was made 1 cm distal to the first. Tendon length was measured before and after fractional lengthening at a constant resting tension of 1 N. The maximum load at failure of each tendon and the mechanism of failure were each measured and compared with the contralateral side. After fractional lengthening, the mean increase in resting tendon length was 4 mm. When loaded to failure, the mean maximum load of fractionally lengthened tendons was 42% of the mean maximum load of intact tendons. All lengthened tendons failed at the distal tenotomy site. Fractional lengthening resulted in an increase of 3-6 mm (mean: 4 mm) in tendon length at resting tension. There was a significant loss in tensile strength and load to failure following fractional lengthening compared with an intact musculotendinous unit. The reduction in tensile strength following fractional lengthening results in loads at failure that are, in some cases, lower than the estimated forces required to perform basic tasks. Caution during the healing and rehabilitation period is warranted.

Does the subscapularis repair affect the clinical outcome after primary reverse shoulder arthroplasty?

BackgroundReverse shoulder arthroplasty is an established procedure for patients with rotator cuff tear arthropathy. However, the refixation of the subscapularis tendon remains a controversial and frequently discussed topic. This prospective randomized study was conducted to evaluate the clinical benefit of the subscapularis refixation after reverse shoulder arthroplasty. MethodsFifty patients (f: 36, m:14) were randomized and assigned to either the “repaired” (rep) or the “not repaired” (nrep) cohort. Intraoperatively, the subscapularis tendon was reattached in the rep-cohort with four tendon-to-tendon sutures, whereas no refixation was performed in the nrep-cohort. The Constant-Murley Score (CS) and the range of motion was evaluated preoperatively as well as 12 and 36 months postoperatively. The Subjective Shoulder Value (SSV) and the Lift-off test were performed 36 months postoperatively. The postoperative subscapularis integrity was assessed sonographically. ResultsTwelve months postoperatively the rep-cohort presented better results in the CS (rep: 71 vs. nrep: 66, p: 0.037). The normalized CS was 80% in the rep-cohort and 75% in the nrep-cohort (p: 0.114). At our last follow-up after 36 months we did not find significant differences between the rep-cohort and the nrep-cohort in the CS (rep: 76 vs. nrep: 75, p: 0.285) and normalized CS (rep: 91% vs. nrep: 91%, p: 0.388). Concerning internal rotation (in points) the rep-cohort achieved better results than the nrep-cohort (rep: 7.3 vs. nrep: 6.6, p: 0.040). Flexion (rep: 145° vs. nrep: 151°, p: 0.826), abduction (rep: 135° vs. nrep: 137° p: 0.816), external rotation (rep: 34° vs. nrep: 37°, p: 0.817) and the SSV (rep: 81% vs. nrep: 77%, p: 0.398) presented no significant differences between the cohorts. The ultrasound examination after 36 months displayed an intact tendon in 70%. ConclusionWhile the subscapularis refixation effects the postoperative internal rotation positively, there were no differences in mid-term follow-up concerning the overall results after rTSA. Further, the external rotation is not affected by the refixation of the subscapularis tendon.

Reverse total shoulder replacement versus anatomical total shoulder replacement for osteoarthritis: population based cohort study using data from the National Joint Registry and Hospital Episode Statistics for England

ObjectivesTo answer a national research priority by comparing the risk-benefit and costs associated with reverse total shoulder replacement (RTSR) and anatomical total shoulder replacement (TSR) in patients having elective primary...

The subacromial bursa modulates tendon healing after rotator cuff injury in rats.

Rotator cuff injuries result in more than 500,000 surgeries annually in the United States, many of which fail. These surgeries typically involve repair of the injured tendon and removal of the subacromial bursa, a synovial-like tissue that sits between the rotator cuff and the acromion. The subacromial bursa has been implicated in rotator cuff pathogenesis and healing. Using proteomic profiling of bursa samples from nine patients with rotator cuff injury, we show that the bursa responds to injury in the underlying tendon. In a rat model of supraspinatus tenotomy, we evaluated the bursa's effect on the injured supraspinatus tendon, the uninjured infraspinatus tendon, and the underlying humeral head. The bursa protected the intact infraspinatus tendon adjacent to the injured supraspinatus tendon by maintaining its mechanical properties and protected the underlying humeral head by maintaining bone morphometry. The bursa promoted an inflammatory response in injured rat tendon, initiating expression of genes associated with wound healing, including Cox2 and Il6. These results were confirmed in rat bursa organ cultures. To evaluate the potential of the bursa as a therapeutic target, polymer microspheres loaded with dexamethasone were delivered to the intact bursae of rats after tenotomy. Dexamethasone released from the bursa reduced Il1b expression in injured rat supraspinatus tendon, suggesting that the bursa could be used for drug delivery to reduce inflammation in the healing tendon. Our findings indicate that the subacromial bursa contributes to healing in underlying tissues of the shoulder joint, suggesting that its removal during rotator cuff surgery should be reconsidered.

Rotator Cuff Tendinopathy: Pathways of Apoptosis.

Rotator cuff repair is usually successful, but retear is not uncommon. It has been previously identified that there is a higher incidence of apoptosis in the edges of the torn supraspinatus tendon. A prospective cohort study was conducted with 28 patients-14 rotator cuff tear patients, 5 instability patients, and 9 Anterior cruciate ligament reconstruction patients to determine whether there was any increase in several genes implicated in apoptosis, including Fas receptor (FasR), Fas ligand, Aifm-1, Bcl-2, Fadd, Bax, and caspase-3. There was a significant expression of Bax (P=0.2) and FasR (P=0.005) in the edges of torn supraspinatus tendons, and in intact subscapularis tendons, there was a significant expression of caspase-3 (P=0.02) compared with samples from the torn supraspinatus tendon (P=0.04). The cytochrome c pathway, with its subsequent activation of caspase-3, as well as the TRAIL-receptor signaling pathway involving FasR have both been implicated. The elevated expression of Bax supported the model that the Bax to Bcl-2 expression ratio represents a cell death switch. The elevated expression of Bax in the intact subscapularis tissue from rotator cuff tear patients also may confirm that tendinopathy is an ongoing molecular process.

Fascia Lata Autografts Achieve Interface Healing With the Supraspinatus Muscle Histologically and Mechanically in a Rat Supraspinatus Tendon Reconstruction Model for Massive Irreparable Rotator Cuff Tears

PurposeTo evaluate the histologic healing process and mechanical characteristics of the interface between a fascia lata autograft and supraspinatus muscle by establishing a supraspinatus tendon reconstruction model for chronic massive, irreparable rotator cuff tears (MIRCTs). MethodsA total of 40 rats were studied. Eight rats were sacrificed to establish an intact control group, and the other rats were first established as the chronic MIRCTs model and then developed as the supraspinatus tendon reconstruction model. Histology, fatty infiltration, mechanics and the open field test for the interface between the fascia lata autograft and muscle were assessed at 2, 4, 8 and 16 weeks postoperatively. ResultsHistologically, the interface between the fascia lata autograft and muscle gradually regenerated structural similarities to the normal muscle-tendon interface by 16 weeks postoperatively. The amounts of collagen I and III were both increased significantly during the healing time and stabilized at 8 weeks postoperatively. Fatty infiltration was obvious in the supraspinatus muscle 4 weeks after the MIRCTs model. However, the degree of fatty infiltration in the supraspinatus muscle gradually decreased after supraspinatus tendon reconstruction and stabilized at 8 weeks postoperatively. The ultimate failure force and the ultimate stress gradually increased from 2 to 16 weeks and reached the level of the intact control tendon at 16 weeks postoperatively (P=0.086). The movability of the forepaw returned to normal in the open field test (P=0.907). ConclusionsIn this rat supraspinatus tendon reconstruction model, fascia lata autografts showed good interface healing with the supraspinatus muscle, and fatty infiltration in the supraspinatus muscle was histologically decreased. The interface between the fascia lata autograft and muscle can sustain mechanical strength similar to the anatomical muscle–tendon interface. Clinical RelevanceThe supraspinatus tendon reconstruction technique using fascia lata autografts might be a good histological and biomechanical option for treating MIRCTs.

The influence of rotator cuff tear type and weight bearing on shoulder biomechanics in an ex vivo simulator experiment

Glenohumeral biomechanics after rotator cuff (RC) tears have not been fully elucidated. This study aimed to investigate the muscle compensatory mechanism in weight-bearing shoulders with RC tears and asses the induced pathomechanics (i.e., glenohumeral translation, joint instability, center of force (CoF), joint reaction force).An experimental, glenohumeral simulator with muscle-mimicking cable system was used to simulate 30° scaption motion. Eight fresh-frozen shoulders were prepared and mounted in the simulator. Specimen-specific scapular anthropometry was used to test six RC tear types, with intact RC serving as the control, and three weight-bearing loads, with the non-weight-bearing condition serving as the control. Glenohumeral translation was calculated using instantaneous helical axis. CoF, muscle forces, and joint reaction forces were measured using force sensors integrated into the simulator. Linear mixed effects models (RC tear type and weight-bearing) with random effects (specimen and sex) were used to assess differences in glenohumeral biomechanics.RC tears did not change the glenohumeral translation (p > 0.05) but shifted the CoF superiorly (p ≤ 0.005). Glenohumeral translation and joint reaction forces increased with increasing weight bearing (p < 0.001). RC and deltoid muscle forces increased with the presence of RC tears (p ≤ 0.046) and increased weight bearing (p ≤ 0.042).The synergistic muscles compensated for the torn RC tendons, and the glenohumeral translation remained comparable to that for the intact RC tendons. However, in RC tears, the more superior CoF was close to where glenoid erosion occurs in RC tear patients with secondary osteoarthritis. These findings underscore the importance of early detection and precise management of RC tears.

All-endoscopic approach for distal biceps tendon pathology: analysis of long-term outcomes in partial and complete ruptures

Distal biceps tendon (DBT) pathology is a spectrum that ranges from tendinopathy to complete retracted ruptures, and surgical treatment is usually performed via open approaches. The purpose of this study was to analyze safety and long-term outcomes of all-endoscopic surgery for entire spectrum of primary DBT pathology. The hypothesis was that at an all-endoscopic technique would result in satisfactory clinical outcomes and a low complication rate. Consecutive patients who underwent all-endoscopic surgery for primary isolated DBT pathology (bursitis, partial and acute/chronic complete tears) between January 2013 and December 2021 were assessed and analyzed retrospectively. Refractory bursitis and low-grade partial tears underwent endoscopic débridement, and high-grade partial tears and complete ruptures underwent all-endoscopic repair or graft reconstruction. Preoperative and follow-up assessment included functional assessment using Mayo Elbow Performance Score and a Patient-Reported Distal Biceps Score, and radiological assessment was performed using plain biplanar radiographs and sonography. Pre- and postoperative scores for the overall group, and for partial and complete tears, were compared using a paired t test. Overall, 26 male patients underwent an all-endoscopic surgery for DBT tears; the pathology was classified by endoscopic findings into 6 types, and follow-up period ranged from 21 to 125months (mean 79.4months). Nine chronic partial tears (35%) included predominantly bursitis (type I, n=2) and predominantly partial tears (type IIA and B, n=7). The complete tear group (65%) included isolated short or long head tears (type IIIA and IIIB, n=2) and complete tendon ruptures (types IV, V, and VIA-C, n=15). Endoscopic débridement of the bursitis/low-grade tears and repair of the high-grade and complete ruptures resulted in complete resolution of symptoms and significant improvement in both Mayo Elbow Performance Score and Patient-Reported Distal Biceps Score (P<.001). Autografts were necessary in 35% (6/17) of complete tears, and no significant difference was found in functional scores in this group as compared to those where primary repairs were possible. There were 2 minor complications (7.6%) that involved transient lateral antebrachial cutaneous nerve neuropraxia. Follow-up sonography and radiographs showed an intact tendon and absence of heterotopic ossification or synostosis. An all-endoscopic approach for treating DBT pathology was safe and reliable and was associated with significant improvement in subjective and functional outcomes in the long-term. The dual-anchor onlay repair technique showed long-term radiologically demonstrable structural integrity of the tendon and was associated with a low minor complication rate and absence of heterotopic ossification.

Partially Lacerated Digital Flexor Tendons: A Cadaveric Study Determining the Intact Cross-sectional Area and Biomechanical Analysis.

The extent of injury in partially lacerated tendons has conventionally been expressed as a percentage of the total tendon, to justify surgical repair. We propose a more objective method to estimate the cross-sectional area of the remnant intact tendon and to determine if the remaining tendon fibers can withstand the tensile forces of early active mobilization against resistance. The study was done on 20 cadaveric specimens, which were randomly assigned to receive a laceration of 25%, 50%, or 75% of the measured transverse tendon diameter. The circumference of the remaining intact portion of the partially lacerated tendon was measured and converted using a formula to determine the derived cross-sectional area (D-CSA). These D-CSA values were then validated by comparing them to digitally measured cross-sectional areas using a computer software program (computer-measured cross-sectional area, C-CSA). In addition, the ultimate tensile strength (UTS) of these partially lacerated tendons was analyzed to determine if a threshold exists beyond which surgical repair of a partially lacerated tendon is indicated. We found that the D-CSAs matched moderately with C-CSAs, with 0.622 of Pearson correlation coefficient. The UTSs of tendons with CSAs above 8 mm in circumference were consistently above 150 N. Measurement of the circumference of the partially lacerated tendon to obtain the D-CSA could be an accurate and practical method to benchmark residual tendon strength in the management of partially lacerated tendons.

GLUTAMATE EXPRESSION IN SUBACROMIAL BURSA IS ASSOCIATED WITH ROTATOR CUFF TEAR AND WITH SHOULDER PAIN

Glutamate regulates the expression of apoptosis-related genes and triggers the apoptosis of fibroblasts in rotator cuff tendons. Subacromial bursitis is always accompanied by symptomatic rotator cuff tear (RCT). However, no study has been reported on the presence of glutamate in subacromial bursa and on its involvement of shoulder pain in patients who had RCT. The purposes of this study were to determine whether the glutamate expression in subacromial bursa is associated with the presence of RCT and with the severity of shoulder pain accompanying RCT.Subacromial bursal tissues were harvested from patients who underwent arthroscopic rotator cuff tendon repair or glenoid labral repair with intact rotator cuff tendon. Glutamate tissue concentrations were measured, using a glutamate assay kit. Expressions of glutamate and its receptors in subacromial bursae were histologically determined. The sizes of RCT were determined by arthroscopic findings, using the DeOrio and Cofield classification. The severity of shoulder pain was determined, using visual analog scale (VAS). Any associations between glutamate concentrations and the size of RCT were evaluated, using logistic regression analysis. The correlation between glutamate concentrations and the severity of pain was determined, using the Pearson correlation coefficient. Differences with a probability &lt;0.05 were considered statistically significant.Glutamate concentrations showed significant differences between the torn tendon group and the intact tendon group (P = 0.009). Concentrations of glutamate significantly increased according to increases in tear size (P &lt; 0.001). In histological studies, the expressions of glutamate and of its ionotropic and metabotropic receptors have been confirmed in subacromial bursa. Glutamate concentrations were significantly correlated with pain on VAS (Rho=0.56 and P =0.01).The expression of glutamate in subacromial bursa is significantly associated with the presence of RCT and significantly correlated with its accompanying shoulder pain.Acknowledgements: This research was supported by the Basic Science Research Program, through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (NRF-2015R1D1A3A01018955 and 2017R1D1A1B03035232).

The effects of zinc sulfate mineral supplementation on Achilles tendon healing in rats.

The Achilles tendon is the most commonly injured and ruptured tendon in the body and typically occurs during participation in sports or recreational activities in men between 30 and 50 years of age. Treatment options for Achilles tendon rupture include conservative and surgical approaches. Conservative treatment is associated with a higher risk of rerupture, while surgical treatment carries a risk of wound site complications. Generally, both methods result in a prolonged tendon healing time. Studies are ongoing to identify biomolecules that aid tendon repair. The main objective of our study is to investigate the effects of zinc sulfate (ZnSO4) mineral supplementation on Achilles tendon healing in rats. Forty-eight female Sprague-Dawley rats were divided into four equal groups (C-15, C-30, ZnSO4-15, and ZnSO4-30) after standard Achilles tendon repair surgery. The ZnSO4-15 and ZnSO4-30 groups received an oral zinc sulfate monohydrate solution (50 mg/kg/day) for 15 and 30 days, respectively. The C-15 and C-30 groups were given 1 mL of distilled water per day orally during the experimental periods. Rats were sacrificed on the 15th and 30th day depending on their groups, and the healing of the operated tendons was evaluated using Movin and Bonar histopathologic scoring. For biomechanical analyses, the operated and intact Achilles tendons of all groups were removed, and tensile tests were performed to determine the tensile strength and toughness values for each tendon. Movin and Bonar scores were significantly lower in the ZnSO4-15 group than in the C-15 group and in the ZnSO4-30 group than in the C-30 group (p<0.05). Although we did not find the biomechanical results statistically significant, the intact tendons of the ZnSO4-15 group exhibited higher toughness than those of the C-15 group, and the tensile strength and toughness values of the operated and intact tendons of the ZnSO4-30 group were also higher than those of the C-30 group. Zinc sulfate monohydrate mineral supplementation had histopathologically positive effects on the proliferation and remodeling stages of Achilles tendon healing and may biomechanically benefit both operated and intact tendons.

Achilles Tendon Rupture Treated with Flexor Digitorum Lateralis Tendon Transposition and Transarticular External Skeletal Fixator in Ouessant Sheep

Abstract Objective To describe the appositional augmentation of a complete Achilles tendon rupture in Ouessant sheep, using the intact flexor digitorum lateralis tendon, and immobilization with a type II transarticular external skeletal fixator. Clinical Report A 1-year-old neutered male Ouessant sheep was presented for Achilles tendon rupture and multiple bite wounds, secondary to a dog attack. The Achilles tendon was torn entirely, and a significant 3-cm gaping defect was present. The remnants of the Achilles tendon were debrided and attached using locking-loop and epitendinous sutures. The intact flexor digitorum lateralis tendon was then transposed and secured over the tendinous repair to increase the tendon strength. The bite wounds were closed with a primary repair. Finally, a type II transarticular external skeletal fixator was used to immobilize the tarsocrural joint for 6 weeks. Results A mild lameness, associated with a decreased range of motion of the tarsocrural joint, was present at the time of external skeletal fixator removal. Four months postoperatively, the lameness had completely resolved. A slight decrease in the range of motion of the tarsocrural joint was conserved. Clinical Significance In a small ruminant, transposition of the flexor digitorum lateralis was successful for the repair of an Achilles tendon rupture with a large musculotendinous gap and infected open wounds. To the authors' knowledge, this is the first such case described in sheep.