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PubMed2003

Repair strength of tendons of varying gliding curvature: a study in a curvilinear model.

PURPOSE: This study was done to investigate changes in the strength of the repaired tendons by different curvatures of tendon motion arcs. METHOD: Forty-two fresh-frozen digital flexor tendons were divided into 4 groups and were repaired by the modified Kessler method with a running peripheral suture. The tendons were pulled over pulleys with tension at a fixed angle of 90 degrees, but radii of gliding curvature of the pulleys were set at 2.0, 1.5, and 1.0 cm in 3 groups, respectively. The tendons in the other group were subjected to linear tension. These tendons were tested in an Instron tensile machine to determine the 2-mm gap formation force and ultimate strength of the repairs. RESULTS: The 2-mm gap formation force of the tendons pulled over the curvature of a 2.0-, 1.0-, and 0.5-cm radius was, respectively, 69%, 61%, and 49% of that pulled linearly. The ultimate strength of the tendons over curvatures of 2.0-, 1.5-, and 1.0-cm radius was, respectively, 77%, 73%, and 63% of that of tendons pulled with linear tension. The gap formation force and ultimate strength were statistically the lowest in the tendons with a gliding radius of curvature of 1.0 cm. Both the gap formation force and the ultimate strength of tendon repairs decreased as the radius decreased. CONCLUSIONS: The curvature of tendon motion arcs affects the repair strength of the tendons. The findings suggest an increased likelihood of repair ruptures in the tendons that glide along curvatures over the sheaths, pulleys, or joints.

Analysis of Variance↗
PubMedDate not supplied

A new clamping technique for biomechanical testing of tendons in small animals. aprobst@uni-muenster.de.

When biomechanical properties of tendons are studied, the technique of clamping the tendons in the testing machine presents a methodological challenge, especially when murine tendons are examined. These short tendons tend to rupture at the transition line to the fixation, leading to false interpretations. Therefore a new clamping technique for investigation of healthy murine Achilles tendons (n = 50) was developed, in which the intramuscular tendon fibers were fixed between two paper strips and the calcaneus was wedged into a conical slot in a wooden block and then mounted in the testing machine (n = 20). This technique was compared with the conventional clamping technique that fixes both ends of the tendon by clamps (n = 15) and an earlier described method that used glue or plastic cement for the fixation of the intramuscular tendon fibers and calcaneus in the testing machine (n = 15). When tested by the new clamping technique, 17 tendons ruptured intratendinously at a mean tensile force of 8.4 +/- 1.1 N. Three Achilles tendons (17%) tore at the site of paper fixation and had to be excluded from investigation. Data from 73% of the measurements fixed by gluing had to be excluded because slippage of the proximal tendon fibers and contamination of the tendon with glue occurred. All the conventionally clamped tendons ruptured at the site of fixation at a mean tensile force of 6.1 +/- 2.3 N (p < .05). This was 30% lower than with the new clamping technique. Thus, the newly developed clamping technique enables investigators to obtain more valid biomechanical studies of the murine Achilles tendon.

Achilles Tendon↗
PubMed2000

In vivo gene transfer into tendon by recombinant adenovirus.

Recombinant adenovirus mediated Escherichia coli lacZ gene transfer into chicken tendon and tendon sheath has been reported in the current study. The constructed recombinant virus carrying lacZ gene was injected between tendon and tendon sheath to conduct in vivo gene transfer. During the course of the study, each tendon received a 10 uL injection containing 10(5) plaque forming units of recombinant adenovirus with beta-galactosidase gene. The samples were harvested at 3 days, 30 days, and 75 days after injection. For the virus dose-transduction rate study, five different doses were injected to groups of chicken tendons. LacZ gene transfer was detected for its coding product beta-galactosidase by staining with X-gal solution. Results showed that the tendon and tendon sheath received the gene transfer with blue staining. The transferred lacZ gene remained stable for 75 days in the tendon and tendon sheath. A virus dose-dependent pattern of transduction rate was observed in the gene transferred tendons. The area of tendon transduction was approximately 2% for 3 x 10(6) plaque forming units recombinant adenovirus with beta-galactosidase versus 40% for 6 x 10(7) plaque forming units recombinant adenovirus with beta-galactosidase gene. The data suggested that functional exogene could be transferred into the tendon and tendon sheath by the same strategy to improve healing and avoid adhesion.

Adenoviridae↗
PubMed1999

In vivo human tendon mechanical properties.

1. The aim of the present study was to measure the mechanical properties of human tibialis anterior (TA) tendon in vivo. 2. Measurements were taken in five males at the neutral ankle position and involved: (a) isometric dynamometry upon increasing the voltage of percutaneous electrical stimulation of the TA muscle, (b) real-time ultrasonography for measurements of the TA tendon origin displacement during contraction and tendon cross-sectional area, and (c) magnetic resonance imaging for estimation of the TA tendon length and moment arm. 3. From the measured joint moments and estimated moment arms, the values of tendon force were calculated and divided by cross-sectional area to obtain stress values. The displacements of the TA tendon origin from rest to all contraction intensities were normalized to tendon length to obtain strain values. From the data obtained, the tendon force-displacement and stress-strain relationships were determined and the tendon stiffness and Young's modulus were calculated. 4. Tendon force and stress increased curvilinearly as a function of displacement and strain, respectively. The tendon force and displacement at maximum isometric load were 530 N and 4.1 mm, and the corresponding stress and strain values were 25 MPa and 2.5 %, respectively. The tendon stiffness and Young's modulus at maximum isometric load were 161 N mm-1 and 1.2 GPa, respectively. These results are in agreement with previous reports on in vitro testing of isolated tendons and suggest that under physiological loading the TA tendon operates within the elastic 'toe' region.

Adult↗
PubMed1996

Prevalence and possible pathological significance of calcium phosphate salt accumulation in tendon matrix degeneration.

OBJECTIVES: To investigate the prevalence of calcium phosphate mineral salt accumulation in degenerative supraspinatus 'tendinitis' compared with a normal sample of human tendons, and to determine whether there is an association of calcium salt deposition with pathological changes in the tendon extracellular matrix. METHODS: Cadaver tendons (supraspinatus and common biceps tendons, n = 96) and fragments of supraspinatus tendons obtained during shoulder surgery (n = 31) were analysed for calcium content by atomic absorption spectroscopy, phosphorous content using a spectrophotometric assay, and matrix composition (collagen, glycosaminoglycans and DNA) using standard biochemical techniques. RESULTS: We established baseline values of calcium concentration in macroscopically normal cadaver tendons (mean 1.1 (SD 0.35) micrograms/mg dry wt, n = 60) and found that 33% (nine of 27) of ruptured tendons from patients with 'degenerative tendinitis' contained an excess of calcium (more than 2SD greater than the normal sample mean). Five of these specimens had increased concentrations of phosphorous and calcium:phosphorous (molar) ratios consistent with a variety of possible calcium crystals, including calcium pyrophosphate, hydroxyapatite, and tricalcium phosphate, in addition to mixed or amorphous calcium phosphate deposits. Four of these specimens contained normal concentrations of phosphorous, consistent with deposits of calcium oxalate or calcium carbonate, although this was not confirmed biochemically. In contrast, surgical specimens (n = 4) from patients with 'calcifying tendinitis' (radiographically detected calcium deposits) all contained salts with a mineral composition consistent with hydroxyapatite. The presence and identity of crystal deposits was subsequently confirmed in five specimens by radiographic microanalysis. Analysis of the tendon matrix demonstrated a number of significant differences between normal and degenerate (ruptured) tendons, including a reduction in collagen content, an increase in sulphated glycosaminoglycans (predominantly dermatan sulphate) and an increase in DNA (cellular) content. However, there were no significant differences between degenerate tendons that were 'calcified' and those degenerate specimens that contained normal concentrations of calcium. CONCLUSIONS: Although there was a relatively high prevalence of calcium salts in degenerate tendons, which might contribute to the pathological process (such as increased matrix collagen degradation), these data are consistent with the hypothesis that 'dystrophic calcification' of degenerate tendon matrix is a pathological entity distinct from cell mediated 'calcifying tendinitis'. Calcification is probably one possible outcome (or end point) of chronic tendon injury, although the possibility exists that in many cases, the presence of calcium salts may contribute to the tendon matrix degeneration.

Adolescent↗
PubMed2004

Eccentric training in patients with chronic Achilles tendinosis: normalised tendon structure and decreased thickness at follow up.

OBJECTIVE: To prospectively investigate tendon thickness and tendon structure by ultrasonography in patients treated with eccentric calf muscle training for painful chronic Achilles tendinosis located at the 2-6 cm level in the tendon. METHODS: The patients were examined with grey scale ultrasonography before and 3.8 years (mean) after the 12 week eccentric training regimen. At follow up, a questionnaire assessed present activity level and satisfaction with treatment. RESULTS: Twenty six tendons in twenty five patients (19 men and six women) with a mean age of 50 years were followed for a mean of 3.8 years (range 1.6-7.75). All patients had a long duration of painful symptoms (mean 17.1 months) from chronic Achilles tendinosis before treatment. At follow up, 22 of 25 patients were satisfied with treatment and active in Achilles tendon loading activities at the desired level. Ultrasonography showed that tendon thickness (at the widest part) had decreased significantly (p<0.005) after treatment (7.6 (2.3) v 8.8 (3) mm; mean (SD)). In untreated normal tendons, there was no significant difference in thickness after treatment (5.3 (1.3) mm before and 5.9 (0.8) mm after). All tendons with tendinosis had structural abnormalities (hypoechoic areas and irregular structure) before the start of treatment. After treatment, the structure was normal in 19 of the 26 tendons. Six of the seven patients with remaining structural abnormalities experienced pain in the tendon during loading. CONCLUSIONS: Ultrasonographic follow up of patients with mid-portion painful chronic Achilles tendinosis treated with eccentric calf muscle training showed a localised decrease in tendon thickness and a normalised tendon structure in most patients. Remaining structural tendon abnormalities seemed to be associated with residual pain in the tendon.

Achilles Tendon↗
PubMed1996

Peroneus longus and brevis tendon tears: MR imaging evaluation.

PURPOSE: To evaluate magnetic resonance (MR) findings of surgically proved peroneal tendon tears. MATERIALS AND METHODS: MR images, medical records, and surgical findings were retrospectively reviewed in the cases of 12 patients who underwent surgery because of suspected peroneal tendon tear (14 tendons). Sagittal and oblique axial T1-weighted spin-echo and T2-weighted fast spin-echo images were obtained in all patients. RESULTS: At surgery, isolated peroneus longus tendon tears were seen in four patients, isolated peroneus brevis tendon tears in five, and both peroneus brevis and peroneus longus tendon tears in two. When correlated with surgical findings, findings at MR imaging were correct in 12 tendons. Findings were false-positive in two patients and false-negative in one, who underwent surgery anyway because unrelated abnormal MR findings were present. The most common MR finding was increased intra-substance signal intensity on T1- and T2-weighted images (11 tendons), in linear or rounded areas on oblique axial images (n = 11) and in linear areas along the longitudinal axis of the tendons on sagittal images (n = 7). Tendon distortion was noted in severe cases (five tendons). The most frequent surgical finding was a longitudinal tendon tear (split) (10 tendons). CONCLUSION: MR imaging enabled detection of peroneus brevis and peroneus longus tendon tears.

Adolescent↗
PubMed2005

Suture plication, thermal shrinkage, and sclerosing agents: effects on rat patellar tendon length and biomechanical strength.

BACKGROUND: Shortening or tightening of dense, collagenous tissues is often desirable in the treatment of laxity. PURPOSE: To compare the effect of stress-protection suture, radiofrequency thermal shrinkage combined with stress-protection suture, and a 5% sodium morrhuate sclerosing injection on the length and biomechanical strength of the rat patellar tendon. HYPOTHESIS: Sclerosing agents will increase tendon mechanical strength. Thermal shrinkage combined with stress-protection suture and stress-protection suture only will cause a short-term decrease in tendon strength. All 3 methods will produce equivalent shortening of the tendon. STUDY DESIGN: Controlled laboratory study. METHODS: Forty-six female retired breeder rats were split into 4 groups, each receiving 1 of the 3 aforementioned treatments plus a control group that received a saline injection. After 4 weeks' survival, the length and biomechanical properties of the patellar tendons were measured and compared to the contralateral untreated tendon. RESULTS: Rats treated with stress-protection suture had shorter tendons. Radiofrequency thermal shrinkage combined with stress-protection suture yielded tendons that were both shorter and stronger than were the untreated contralateral tendons. The sodium morrhuate-injected tendons were stronger whereas the saline-treated tendons were weaker than were their respective untreated contralateral tendons. CONCLUSION: Surgical stress-protection suture without radiofrequency shrinkage is most effective at shortening the length of the rat patellar tendon, whereas radiofrequency thermal shrinkage combined with stress-protection suture as well as sodium morrhuate are effective at increasing the strength of rat patellar tendons. CLINICAL RELEVANCE: Judicious use of thermal shrinkage in combination with stress protection may improve ligament strength and decrease laxity.

Animals↗
PubMed1998

Muscle and tendon morphogenesis in the avian hind limb.

The proper development of the musculoskeletal system in the tetrapod limb requires the coordinated development of muscle, tendon and cartilage. This paper examines the morphogenesis of muscle and tendon in the developing avian hind limb. Based on a developmental series of embryos labeled with myosin and tenascin antibodies in whole mount, an integrative description of the temporal sequence and spatial pattern of muscle and tendon morphogenesis and their relationship to cartilage throughout the chick hind limb is presented for the first time. Anatomically distinct muscles arise by the progressive segregation of muscle: differentiated myotubes first appear as a pair of dorsal and ventral muscle masses; these masses subdivide into dorsal and ventral thigh, shank and foot muscle masses; and finally these six masses segregate into individual muscles. From their initial appearance, most myotubes are precisely oriented and their pattern presages the pattern of future, individual muscles. Anatomically distinct tendons emerge from three tendon primordia associated with the major joints of the limb. Contrary to previous reports, comparison of muscle and tendon reveals that much of their morphogenesis is temporally and spatially closely associated. To test whether reciprocal muscle-tendon interactions are necessary for correct muscle-tendon patterning or whether morphogenesis of each of these tissues is autonomous, two sets of experiments were conducted: (1) tendon development was examined in muscleless limbs produced by coelomic grafting of early limb buds and (2) muscle development was analyzed in limbs where tendon had been surgically altered. These experiments demonstrate that in the avian hind limb the initial morphogenetic events, formation of tendon primordia and initial differentiation of myogenic precursors, occur autonomously with respect to one another. However, later morphogenetic events, such as subdivision of muscle masses and segregation of tendon primordia into individual tendons, do require to various degrees reciprocal interactions between muscle and tendon. The dependence of these later morphogenetic events on tissue interactions differs between different proximodistal regions of the limb.

Animals↗
PubMed1994

Tears of the anterior portion of the rotator cuff (the subscapularis tendon): MR imaging findings.

OBJECTIVE: Tears of the most anterior portion of the rotator cuff, the subscapularis tendon, are reported to be uncommon and rarely occur in isolation. The MR findings of subscapularis tendon tears have received little attention in radiologic publications. Accordingly, the objective of this study was to describe the MR imaging findings in the shoulders of patients with tears of the subscapularis tendon. MATERIALS AND METHODS: Preoperative MR images of nine patients with surgically confirmed rotator cuff tears that predominantly or exclusively involved the subscapularis tendon were analyzed. RESULTS: In all patients, MR imaging showed the contours of the subscapularis tendon to be poorly defined and the tendon itself to be of abnormally high signal intensity on T2- or T2*-weighted images. Discontinuity and frank retraction of the tendon were evident in seven patients (78%). Thickening of the distal portion of the tendon (n = 3) and calcification (n = 1) were seen less frequently. Associated abnormalities of the biceps tendon were common, seen in seven patients (78%), five of whom had medial dislocation of the tendon. Bone and labral injuries were uncommon. CONCLUSION: Tears of the subscapularis tendon can be identified on MR images as areas of disorganized tendon morphology and abnormal high signal intensity on T2- or T2*-weighted images. Abnormalities of the biceps tendon also are seen commonly. When subscapularis tears are recognized, the long head of the biceps tendon should be scrutinized for associated injury or malposition.

Humans↗
PubMed2001

Association of posterior tibial tendon injury with spring ligament injury, sinus tarsi abnormality, and plantar fasciitis on MR imaging.

OBJECTIVE: The purpose of this study was to investigate the frequency of abnormalities of the spring ligament, sinus tarsi, and plantar fascia revealed on MR imaging in a group of patients with advanced injury of the posterior tibial tendon. MATERIALS AND METHODS; MR images from 25 patients with advanced posterior tibial tendon injury were retrospectively examined for spring ligament, sinus tarsi, and plantar fascia abnormalities. These images were randomly compared with those obtained from 25 control patients with normal-appearing posterior tibial tendons. RESULTS: The spring ligament was abnormal in 23 (92%) of 25 patients with a posterior tibial tendon injury and seven (28%) of 25 patients with a normal posterior tibial tendon (p < 0.0001). The sinus tarsi was abnormal in 18 (72%) of 25 patients with posterior tibial tendon injury and nine (36%) of 25 patients with a normal posterior tibial tendon (p < 0.0132). The plantar fascia was abnormal in seven (32%) of 22 patients with posterior tibial tendon injury and two (9%) of 22 patients with a normal posterior tibial tendon (p < 0.0768). Two or more associated abnormalities were present in 20 (80%) of 25 patients with posterior tibial tendon injury and four (16%) of 25 patients with a normal posterior tibial tendon (p < 0.0001). CONCLUSION: Advanced posterior tibial tendon injury has a high association with spring ligament and sinus tarsi abnormalities on MR imaging. There was a low association between advanced posterior tibial tendon injury and plantar fascia abnormality. Patients with posterior tibial tendon injury often have abnormalities of two or more associated structures.

Adult↗
PubMed1995

Ultrasonographic cross-sectional area and mean echogenicity of the superficial and deep digital flexor tendons in 50 trained thoroughbred racehorses.

Fifty Thoroughbred horses were examined. All horses had been in race training for a minimum of 4 months before examination and had worked at racing speed; 24 horses had raced. All horses were clinically sound at the time of examination. Ultrasonography was performed, using a 7.5-MHz transducer with built-in fluid offset. Videotaped images of the palmar soft tissue structures were obtained at 4, 8, 12, 16, 20 and 24 cm distal to the base of the accessory carpal bone (DACB). Images were digitized, and each image was calibrated. Values for cross-sectional area (CSA) and mean echogenicity (ME) were then determined from the cross-sectional images of the superficial digital flexor (SDF) and the deep digital flexor (DDF) tendons, using an image-analysis program. The SDF tendons were compared between right and left forelimbs at each level, and from proximal to distal on each limb, as were the DDF tendons. The relation between the SDF and DDF tendons for the same forelimb was determined at each level. There were no significant differences in CSA or ME at equivalent levels of the left and right SDF tendons. Mean (+/- SD) CSA was 1.01 +/- 0.12) cm2 at 4 cm DACB, 0.95 (+/- 0.14) cm2 at 12 cm DACB, and 1.12 (+/- 0.15) cm2 at 24 cm DACB. Adjusted ME was 2.34 (+/- 0.34) at 4 cm DACB, 2.03 (-/+- 0.38) at 12 cm DACB, and 2.04 (+/- 0.35) at 24 cm DACB. The left and right DDF tendons did not have significant differences in CSA or ME at any level. Cross-sectional area was 1.13 (+/- 0.18) cm2 at 4 cm DACB, 1.01 (+/- 0.12) cm2 at 12 cm DACB, and 1.75 (+/- 0.29) cm 2 at 24 cm DACB. Adjusted ME was 2.60 (+/-0.46) at 4 cm DACB, 2.49 (+/- 0.49) at 12 cm DACB, and 2.50 (+/- 0.44) at 24 cm DACB. At all levels, the left and right SDF tendons were smaller and less echoic than the DDF tendons of the same limb. The SDF and DDF tendons had an hour glass shape, with smallest CSA at 12 cm DACB. Mean echogenicity generally decreased for the SDF and DDF tendons from proximal to distal on the limb. These results indicate that for clinically normal trained Thoroughbred racehorses, there should be no significant difference in CSA or echogenicity between the left and right SDF tendons at equivalent distances DACB. There should be no significant differences in the left and right DDF tendons at equivalent levels DACB. The SDF tendon is usually smaller and less echoic than the corresponding DDF tendon at each level.

Animals↗
PubMed2000

MR imaging of the Achilles tendon: overlap of findings in symptomatic and asymptomatic individuals.

OBJECTIVE: To differentiate MR imaging characteristics of symptomatic as compared with asymptomatic Achilles tendons. DESIGN: 1.5 T MR images of 94 feet (88 patients) with "abnormal" MR examinations were retrospectively evaluated and clinically correlated. Two masked, independent observers systematically evaluated for intratendon T2 signal, tendon thickness, presence of peritendonitis, retrocalcaneal bursal fluid volume, pre-Achilles edema, bone marrow edema at the Achilles insertion, and tears (interstitial, partial, complete). These findings were correlated with symptoms (onset and duration) and physical examination results (tenderness, palpable defects, increased angle of resting dorsiflexion). RESULTS: Of the 94 ankles, 64 ankles (32 females, 29 males) were clinically symptomatic. No relationship between Achilles tendon disorders and age or gender was identified. Asymptomatic Achilles tendons frequently demonstrated mild increased intratendon signal (21/30), 0.747 cm average tendon thickness, peritendonitis (11/30), pre-Achilles edema (12/30), and 0.104 ml average retrocalcaneal bursal fluid volume. Symptomatic patients had thicker tendons (0.877 cm), greater retrocalcaneal fluid volume (0.278 ml), more frequent tears (23/64), a similar frequency of peritendonitis (22/64) but less frequent pre-Achilles edema (18/64). Sixty-four percent of the Achilles tendon tears were interstitial. Except for two interstitial tears in control patients, the majority of Achilles tears were in symptomatic patients (14/16). Only symptomatic tendons demonstrated partial or complete tendon tears. In addition, calcaneal edema was found almost exclusively in actively symptomatic patients. Thicker tendons were associated more often with chronic symptoms and with tears. When present in symptomatic patients, peritendonitis was usually associated with acute symptoms. The presence of pre-Achilles edema, however, did not distinguish acute from chronic disorders. CONCLUSION: There is significant overlap of MR findings in symptomatic and asymptomatic Achilles tendons. Furthermore, there is apparently a spectrum of disease in symptomatic tendons ranging from subtle intratendinous and peritendinous signal to partial and complete tendon tear.

Achilles Tendon↗
PubMed1999

[Lesional pattern and clinical symptoms in rheumatoid flexor tendon disease].

OBJECTIVES: To assess complaints and clinical findings of rheumatoid hand flexor tendon disease in relationship to the anatomical site and the type of lesion in order to improve the diagnosis and enable early operative treatment with preservation of hand function. METHODS: 123 patients of the hands of 78 patients (66 female, 12 male) with a mean age of 57 years were analyzed retrospectively. Preoperative complaints and clinical findings were recorded according to their frequency. Three different types of flexor tendon disease were distinguished intraoperatively: isolated tenosynovitis, tenosynovitis with tendon lesion, and complete tendon rupture. RESULTS: 188 tendons showed isolated synovitis, 208 had a tendon lesion with synovitis, and 30 tendons a rupture. Tenosynovitis was found in the palm and wrist mainly. The 2nd, 3rd and 4th finger were most frequently involved. 81 tendon adhesions, 12 nodules, 63 superficial lesions and 52 defects were detected. These lesions were found mainly in the palm and the second and third ray. The profundus tendon was affected most often. Ruptures were detected most often in the wrist caused by bony spurs and tenosynovitis. A clinical difference between tenosynovitis with and without tendon lesion was not found. However, complaints and findings were different in the digit, palm, wrist and forearm. Ruptures had characteristic clinical findings. CONCLUSIONS: Rheumatoid flexor tendon disease is common. Tenosynovitis is often accompanied by tendon lesions. Ruptures occur as disease progresses. Exact assessment of complaints and clinical findings is mandatory to diagnose and localize flexor tendon disease. Early operative intervention helps to preserve the function of the hand.

Adult↗
PubMed2004

Correlations between mean echogenicity and material properties of normal and diseased equine superficial digital flexor tendons: an in vitro segmental approach.

The objective of this study was to test the hypothesis that tendon echogenicity is associated with the material properties of the corresponding tendon site, especially in case of lesions, due to local changes in tendon matrix composition. Four normal and nine spontaneously injured equine superficial digital flexor tendons (SDFT) were isolated then ultrasonographically examined under tension, in a special device placed in a water bath. Ultrasonographic transversal images (7.5MHz linear transducer) of five segments along each tendon were digitized, and analyzed in order to measure the mean cross-sectional area (MCSA) and mean echogenicity (ME) of each segment. The tendons were then tested in traction until rupture in a testing machine. For each segment, stress and strain were determined throughout the test, and the elastic modulus (EM) was evaluated. The tendon lesions were also documented by histology. No correlation was found between ME and the material properties of normal tendon segments. At the rupture sites of the nine diseased tendons, ME was positively correlated with maximal stress and EM, whereas no correlation was demonstrated with maximal strain. Besides, a positive correlation was demonstrated between ME and both MCSA and EM, when the three metacarpal segments of the diseased tendons were considered. Although ME gives only rough information about tendon matrix structure, it does show, under these in vitro conditions, significant correlations with material properties of pathological tendon segments, which may improve the functional significance and therefore the prognostic value of the ultrasonographic examination of tendon lesions.

Animals↗
PubMed1999

Wrist and digital joint motion produce unique flexor tendon force and excursion in the canine forelimb.

The force and excursion within the canine digital flexor tendons were measured during passive joint manipulations that simulate those used during rehabilitation after flexor tendon repair and during active muscle contraction, simulating the active rehabilitation protocol. Tendon force was measured using a small buckle placed upon the tendon while excursion was measured using a suture marker and video analysis method. Passive finger motion imposed with the wrist flexed resulted in dramatically lower tendon force (approximately 5 N) compared to passive motion imposed with the wrist extended (approximately 17 N). Lower excursions were seen at the level of the proximal interphalangeal joint with the wrist flexed (approximately 1.5 mm) while high excursion was observed when the wrist was extended or when synergistic finger and wrist motion were imposed (approximately 3.5 mm). Bivariate discriminant analysis of both force and excursion data revealed a natural clustering of the data into three general mechanical paradigms. With the wrist extended and with either one finger or four fingers manipulated, tendons experienced high loads of approximately 1500 g and high excursions of approximately 3.5 mm. In contrast, the same manipulations performed with the wrist flexed resulted in low tendon forces (4-8 N) and low tendon excursions of approximately 1.5 mm. Synergistic wrist and finger manipulation provided the third paradigm where tendon force was relatively low (approximately 4 N) but excursion was as high as those seen in the groups which were manipulated with the wrist extended. Active muscle contraction produced a modest tendon excursion (approximately 1 mm) and high or low tendon force with the wrist extended or flexed, respectively. These data provide the basis for experimentally testable hypotheses with regard to the factors that most significantly affect functional recovery after digital flexor tendon injury and define the normal mechanical operating characteristics of these tendons.

Animals↗
PubMed2002

Remodeling of the gliding surface after flexor tendon repair in a canine model in vivo.

Maintaining a smooth lubricated surface between the flexor tendon and sheath after tendon repair is very important for restoration of digit function. We studied the tendon surface after tendon repair mechanically in a canine model in vivo by measuring frictional force. One hundred and twenty flexor digitorum profundus (FDP) tendons were lacerated to 80% of their cross-section and repaired with either a modified Kessler (MK) or Becker (MGH) repair. The postoperative therapeutic regimen was either synergistic wrist and digit motion (SWM) or passive digit flexion and extension with the wrist fixed in 45 degrees of flexion (FIX). The dogs were sacrificed at one, three, or six weeks postoperatively. Thirty six FDP tendons from normal paws served as the control group, with each control tendon tested in two different conditions: intact and immediately after partial laceration and repair (0 time), making a total of five different timing points (intact, 0 time, one week, three weeks, and six weeks) for each repair type and each postoperative therapy. Frictional force between tendon and proximal pulley was evaluated after breaking any adhesions. Compared to intact tendons, friction was significantly increased immediately after tendon repair. The friction of the MK repair was significantly less than that of the MGH repair at all time and therapy groups, except at six weeks in the SWM group. For the MGH repair, at six weeks friction in the SWM group was significantly less than friction in the FIX group. This study showed that postoperative tendon gliding depends on the method of tendon repair and the postoperative therapy regimen. Furthermore, we have demonstrated that the gliding surface after tendon repair remodels with time.

Animals↗
PubMed2004

The effect of overuse activity on Achilles tendon in an animal model: a biomechanical study.

Musculoskeletal soft tissue injuries from athletic activities are common in the rotator cuff tendons, lateral epicondyle of the elbow, the patella tendon, and the Achilles tendon. Despite the fact that the Achilles tendon is the largest and strongest tendon in the human body, it is frequently injured in the athletic setting. To study the etiology and pathogenesis of Achilles tendon injuries, our goal was to develop a model of Achilles tendon overuse by evaluating the Achilles tendons from animals subjected to the exercise protocol previously described as overuse for the supraspinatus tendon. We hypothesized that the same exercise protocol would produce injuries to the Achilles tendon as demonstrated by changes in the cross-sectional area and biomechanical properties. While a significant injury was induced into the supraspinatus tendon, we found no changes in the Achilles tendons of these exercised animals based on gross observation, geometric measurements, and mechanical testing analyses. Although surprising, there are many possible explanations for these findings including differences in potential injury mechanisms, functional capabilities of the differing tendons, and other factors.

Achilles Tendon↗