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PubMed1985

Prevention of spastic paralytic dislocation of the hip.

In a retrospective review of 99 children with spastic cerebral palsy, the efficacy of soft-tissue procedures alone in reducing early subluxation of the hip and preventing further subluxation and dislocation was determined. The indication for surgery was early subluxation of one or both hips. Surgery was either adductor tenotomy with or without anterior branch obturator neurectomy, or adductor tenotomy in combination with iliopsoas recession. Results were poor for 64 per cent after adductor tenotomy and anterior branch obturator neurectomy. For patients who also had iliopsoas recession the success rate was 72 per cent. Radiographic analysis showed that uncovering of the femoral head had halted or improved in 80 per cent of patients following iliopsoas recession.

Adolescent↗
PubMed2006

Angiogenic effect of intramuscular administration of basic fibroblast growth factor in atrophied muscles: an experimental study in the rat.

BACKGROUND: Although angiogenic therapy using recombinant growth factors holds much hope for the treatment of ischaemic diseases, there are still many unanswered questions, including its effectiveness on atrophic muscles. OBJECTIVE: To evaluate the angiogenic effects of intramuscularly administered basic fibroblast growth factor (b-FGF) on normal gastrocnemius muscles of rats and atrophic gastrocnemius muscles after tenotomy. METHODS: Forty rats were divided into groups as follows: group A, controls; group B, injected with 1 microg b-FGF; group C, tenotomy performed on the right gastrocnemius muscle; group D, tenotomy and 1 microg b-FGF. Mouse anti-rat CD31 antibody was used to evaluate the number of blood vessels present in histological preparations. RESULTS: There was a significant (p<0.01) decrease in the number of blood vessels compared with the controls in the atrophic muscles of group C. This was similar to the decrease in muscle weight in this group. However, there was a significant (p<0.01) increase in the number of blood vessels compared with the controls in groups B and D. Similarly, there was a significant (p<0.01) increase in the number of blood vessels in group D compared with the atrophic muscles in group C. CONCLUSION: Intramuscular administration of b-FGF increases angiogenesis in both normal and atrophic rat gastrocnemius muscles at the injection area.

Angiogenesis Inducing Agents↗
PubMed1995

Operative repair of the mallet toe deformity.

Over a 14-year period, 60 patients (86 toes) underwent resection arthroplasty of the proximal interphalangeal joint for a mallet toe deformity. During the same period, 788 hammertoe corrections were performed, for a ratio of 9:1 hammertoe to mallet toe corrections. Fifty patients (72 toes) were evaluated at an average 55-month follow-up. In 53 toes (73%), the involved toe was longer than the adjacent toes. The second, third, and fourth toes were almost equally involved with a mallet toe deformity. With a resection arthroplasty technique, an arthrodesis of the PIP joint occurred in 52 toes (72%) and a fibrous union occurred in the remaining 20 toes (28%). Overall, 86% of the toes were rated as satisfactory by the patient (P < .001). A slightly lower satisfaction rate (75%) was noted in those toes with a fibrous union. A flexor tenotomy was performed in 22 toes along with the mallet toe repair. Acceptable alignment was noted in 96% of toes with a flexor tenotomy, and in 90% where a mallet toe repair was performed without a flexor tenotomy [corrected]. Pain was relieved (97%), correction was well maintained (91%), and patient subjective satisfaction was high (86%) with this procedure. Minor complications occurred in 14% of cases; however, one fourth of these patients still noted a satisfactory result.

Adolescent↗
PubMed2001

Morphological changes and recovery process in the tenotomized soleus muscles of the rat.

Tenotomized soleus muscles of adult rats were analyzed morphologically and biochemically with special reference to the recovery process. Light microscopic observations of semi-thin sections showed that the characteristic central core lesion was most extensive at 1 week after tenotomy and began to diminish in extent at 2 weeks until no trace of lesion could be seen by 6th week, as confirmed by thin-section electron microscopy. Three phases of changes in the cross-sectional area of muscle fibers after tenotomy were demonstrated by morphometry: phase I designated as the initial increase up to the 3rd day, phase II as the progressive decrease until the 4th week, and phase III as the recovery to normal or even hypertrophy. In electron microscopy, the earliest alteration of myofibrils was recognized at 3 days after tenotomy. The Z discs showed a wavy or zigzag profile with frequent longitudinal splitting of myofibrils. From the 2nd week on, muscle fibers underwent a process of recovery, replacing the central core lesion with new myofibrils in which a reassembly of thick filaments into bundles of thin filaments took place, with Z discs being aligned adjacent to the peripheral complete myofibrils. In SDS-polyacrylamide gel electrophoresis, the molar ratio of myosin to actin diminished markedly as the central core lesion developed and gradually returned to normal with time, correlating well with the loss and subsequent reassembly of thick filaments.

Actins↗
PubMed1999

Distraction osteogenesis for lengthening of the tibia in patients who have limb-length discrepancy or short stature.

BACKGROUND: This study was performed to determine the safety and effectiveness of lengthening of the tibia, in patients who have a limb-length discrepancy or a short stature, with use of distraction osteogenesis, a technique based on the principle of distracting the callus that is formed after a subperiosteal osteotomy of the proximal portion of the diaphysis of a long bone. METHODS: A total of 230 tibial lengthening procedures were done in 150 patients. Seventy procedures were performed because of a limb-length discrepancy, which was secondary to trauma (thirty limbs), congenital fibular hemimelia (twenty-six), poliomyelitis (ten), or infection (four). The remaining 160 procedures were performed because of a short stature, which was secondary to achondroplasia (fifty-eight limbs), Turner syndrome (thirty-four), an idiopathic etiology (twenty-two), hypochondroplasia (twenty), achondroplasia (ten), Ellis-van Creveld syndrome (six), rickets (four), or adrenogenital syndrome, Laron syndrome, or pseudoachondroplasia (two limbs each). The age of the patients at the time of the operation was 18.4+/-6.2 years (average and standard deviation), with a range of six to forty-one years. The procedures were performed according to one of three protocols. In Group A (ninety procedures), an Orthofix telescopic fixator and a variable number of screws were used and the tibiofibular syndesmosis was not stabilized; in Group B (ninety-six procedures), an Orthofix reconstruction system was used, the syndesmosis was stabilized, and a tenotomy of the Achilles tendon was performed; and in Group C (forty-four procedures), an Orthofix Garches lengthening device was used, the syndesmosis was stabilized, and a tenotomy of the Achilles tendon was performed. RESULTS: At the time of the latest follow-up (average, five years; range, two to seven years), the average gain in length after the seventy procedures performed because of a limb-length discrepancy was 4.0+/-1.98 centimeters (range, 2.5 to 9.5 centimeters), or 14 percent (range, 7 to 45 percent). The average gain in length after the 160 procedures that were performed because of a short stature was 7.8+/-2.28 centimeters (range, 2.5 to fifteen centimeters), or 33 percent (range, 10 to 78 percent). Ten (14 percent) of the seventy procedures performed because of a limb-length discrepancy and forty-six (29 percent) of the 160 performed because of a short stature were associated with a complication. There was only one permanent sequela in the entire series. CONCLUSIONS: Although the three operative protocols resulted in similar healing indices, the rates of complications differed significantly among the groups (p<0.0001). Group C (the Garches device) had the lowest rate of complications (7 percent). It is important to be aware of potential complications as well as the need for additional procedures in order to avoid predictable problems. These procedures include percutaneous tenotomy of the Achilles tendon and fixation of the distal segment of the fibula to the tibia to maintain the integrity of the tibiotalar articulation and the alignment of the foot.

Achilles Tendon↗
PubMed2005

Repair of tears of the subscapularis.

BACKGROUND: Rotator cuff tears involving the subscapularis are less common than those involving the superior aspect of the rotator cuff. The purpose of the present study was to report the results of repair of isolated tears of the subscapularis. METHODS: The records on eighty-four shoulders that had undergone open repair of the subscapularis tendon were reviewed. The mean age of the patients at the time of surgery was 53.2 years. The mean interval from the onset of symptoms to the time of surgery was 12.5 months. Fifty-seven tears were traumatic, and twenty-seven were degenerative. Twenty-three tears involved the superior one-third of the subscapularis tendon, forty-one tears involved the superior two-thirds, and twenty tears were complete. Fifty-four shoulders had a dislocation or subluxation of the long head of the biceps tendon, and ten shoulders had a rupture of the long head of the biceps tendon. Forty-eight shoulders underwent concomitant biceps tenodesis, thirteen shoulders underwent concomitant biceps tenotomy, and four shoulders underwent concomitant recentering of the biceps. Patients were evaluated clinically and radiographically at a mean of forty-five months (range, twenty-four to 132 months) postoperatively. RESULTS: The mean Constant score increased from 55.0 points preoperatively to 79.5 points postoperatively. Seventy-five patients were satisfied or very satisfied with the result. Preoperatively, four shoulders had mild glenohumeral arthritis. Postoperatively, twenty-five shoulders had mild glenohumeral arthritis and two shoulders had moderate glenohumeral arthritis. Tenodesis or tenotomy of the biceps tendon at the time of subscapularis repair was associated with improved subjective and objective results, independent of the preoperative condition of the biceps tendon. CONCLUSIONS: Repair of isolated subscapularis tears yields acceptable improvement in shoulder function in selected patients. Additionally, the results of the present study support routine tenodesis or tenotomy of the long head of the biceps tendon at the time of subscapularis repair.

Adult↗
PubMed2006

Early results of a new method of treatment for idiopathic congenital vertical talus.

BACKGROUND: The treatment of idiopathic congenital vertical talus has traditionally consisted of manipulation and application of casts followed by extensive soft-tissue releases. However, this treatment is often followed by severe stiffness of the foot and other complications. The purpose of this study was to evaluate a new method of manipulation and cast immobilization, based on principles used by Ponseti for the treatment of clubfoot deformity, followed by pinning of the talonavicular joint and percutaneous tenotomy of the Achilles tendon in patients with idiopathic congenital vertical talus. METHODS: The cases of eleven consecutive patients who had a total of nineteen feet with an idiopathic congenital vertical talus deformity were retrospectively reviewed at a minimum of two years following treatment with serial manipulations and casts followed by limited surgery consisting of percutaneous Achilles tenotomy (all nineteen feet), fractional lengthening of the anterior tibial tendon (two) or the peroneal brevis tendon (one), and percutaneous pin fixation of the talonavicular joint (twelve). The principles of manipulation and application of the plaster casts were similar to those used by Ponseti to correct a clubfoot deformity, but the forces were applied in the opposite direction. Patients were evaluated clinically and radiographically at the time of presentation, immediately postoperatively, and at the time of the latest follow-up. Radiographic measurements obtained at these times were compared. In addition, the radiographic data at the final evaluation were compared with normal values for an individual of the same age as the patient. RESULTS: Initial correction was obtained both clinically and radiographically in all nineteen feet. A mean of five casts was required for correction. No patient underwent extensive surgical releases. At the final evaluation, the mean ankle dorsiflexion was 25 degrees and the mean plantar flexion was 33 degrees . Dorsal subluxation of the navicular recurred in three patients, none of whom had had pin fixation of the talonavicular joint. At the time of the latest follow-up, there was a significant improvement (p < 0.0001) in all of the measured radiographic parameters compared with the pretreatment values, and all of the measured angles were within normal values for the patient's age. CONCLUSIONS: Serial manipulation and cast immobilization followed by talonavicular pin fixation and percutaneous tenotomy of the Achilles tendon provides excellent results, in terms of the clinical appearance of the foot, foot function, and deformity correction as measured radiographically at a minimum two years, in patients with idiopathic congenital vertical talus.

Ankle Joint↗
PubMed2006

Repair of tears of the subscapularis. Surgical technique.

BACKGROUND: Rotator cuff tears involving the subscapularis are less common than those involving the superior aspect of the rotator cuff. The purpose of the present study was to report the results of repair of isolated tears of the subscapularis. METHODS: The records on eighty-four shoulders that had undergone open repair of the subscapularis tendon were reviewed. The mean age of the patients at the time of surgery was 53.2 years. The mean interval from the onset of symptoms to the time of surgery was 12.5 months. Fifty-seven tears were traumatic, and twenty-seven were degenerative. Twenty-three tears involved the superior one-third of the subscapularis tendon, forty-one tears involved the superior two-thirds, and twenty tears were complete. Fifty-four shoulders had a dislocation or subluxation of the long head of the biceps tendon, and ten shoulders had a rupture of the long head of the biceps tendon. Forty-eight shoulders underwent concomitant biceps tenodesis, thirteen shoulders underwent concomitant biceps tenotomy, and four shoulders underwent concomitant recentering of the biceps. Patients were evaluated clinically and radiographically at a mean of forty-five months (range, twenty-four to 132 months) postoperatively. RESULTS: The mean Constant score increased from 55.0 points preoperatively to 79.5 points postoperatively. Seventy-five patients were satisfied or very satisfied with the result. Preoperatively, four shoulders had mild glenohumeral arthritis. Postoperatively, twenty-five shoulders had mild glenohumeral arthritis and two shoulders had moderate glenohumeral arthritis. Tenodesis or tenotomy of the biceps tendon at the time of subscapularis repair was associated with improved subjective and objective results, independent of the preoperative condition of the biceps tendon. CONCLUSIONS: Repair of isolated subscapularis tears yields acceptable improvement in shoulder function in selected patients. Additionally, the results of the present study support routine tenodesis or tenotomy of the long head of the biceps tendon at the time of subscapularis repair.

Humans↗
PubMed2002

[Electron microscopic analysis of expression of NMDA-R1 in the developmental process of visual cortex in strabismic amblyopic cat].

OBJECTIVE: To investigate the expression and distribution of N-methyl-D-aspartate receptor subunit 1 (NMDA-R1) in neuronal ultrastructure in visual cortex of strabismic amblyopic cat during development. METHODS: Eleven kittens were used for this study. Esotropia in six kittens had been made monocularly by tenotomy at two weeks of age. Two pairs of normal and strabismic kittens were sacrificed in three weeks of age, one week after tenotomy. Another two pairs of normal and strabismic kittens were sacrificed in five weeks of age, three weeks after tenotomy. One normal and two strabismic amblyopic cats were sacrificed after 6 months of age. Animals were deeply anaesthetized and perfused transcardially with 4% paraformaldehyde. Cryostat sections of frontal central area P5-P0 were cut to 25 micro m thickness. The mouse anti-NMDA-R1 monoclonal antibody (mAb54.1, PharMingen) was used. After stained, a light microscope was used to select regions of layer II-III, layer IV and layer V-VI of visual cortex area 17 for re-embedding. HITACHI H-7000 transmission electron microscope at magnifications ranging from 30 000 - 300 000 X was used for observation. RESULTS: Three hundred and twenty-eight neurons of strait cortex were observed. NMDA-R1 receptor was located at the nuclei, Nissl body, cytoplasm, plasma membrane and the postsynaptic element of axons and dendrites. The ultrastructural morphology, including the mitochondrion, smooth endoplasmic reticulum, rough endoplasmic reticulum, and the Golgi apparatus, was not significantly different in the comparison between the cells in visual cortex of normal and strabismic groups. In the entire normal group, the percentage density of NMDA-R1 labeled cells was higher than that of strabismic groups (chi(2) = 4.280, 4.41, 4.89; P < 0.05). One thousand and three hundred and twenty NMDA-R1 immunopositive synapses were counted. The NMDA-R1 immunopositive synapses were dominated in layer II-III of visual cortex and increased during the development of normal kittens (F = 3.28, P < 0.05). There was no significant difference of NMDA-R1 immunopositive synapse distribution between the normal and strabismic kitten at 3 weeks (one week after operation) of age (F = 0.17, P > 0.05). The reduction of NMDA-R1 immunopositive synapse of plasma membrane in visual cortex of strabismic kitten was started at 5 weeks (threes weeks after surgery) of age. It was decreased significantly in strabismic amblyopic cat compared with that of the normal cat (F = 26.94, 47.01; P < 0.001). The ratios of nuclear membrane invagination of cells in visual cortex of normal and strabismic cat were higher than those of normal and squint kittens (chi(2) = 36.24, P < 0.01), but the ratio was not significantly different between the normal and strabismic group. CONCLUSION: (1) In the normal developmental process of cat, the plasticity of the neuronal synapsis in II and III layer of visual cortex is relatively great. (2) In the strabismus amblyopia occurring in the plastic critical period of visual development, no pathological changes of neuronal organelle in the visual cortex are found, but there are changes at molecular level in the neuronal synapsis.

Amblyopia↗
PubMed2003

[Entrapment of the long head of the biceps: the "hourglass biceps". Another cause of pain and locking of the shoulder].

PURPOSE OF THE STUDY: We describe a mechanical condition affecting the long head of the biceps tendon (LHBT) causing potentially unrecognized entrapment within the joint and subsequent pain and locking. This is caused by a hypertrophic intra-articular portion of the tendon that is unable to slide into the bicipital groove during elevation of the arm. MATERIALS AND METHODS: Twenty one patients were identified, during open (14 cases) or arthroscopic (7 cases) surgery, with a so called "hourglass biceps" i.e., hypertrophic intraarticular portion of the LHBT and incarceration of the tendon during elevation. All cases occurred in conjunction with a rotator cuff rupture except one who had a partial deep tear. All patients were treated by excision of the biceps, after tenodesis or bipolar tenotomy, and appropriate treatment of the concomitant lesions. RESULTS: All patients presented with anterior shoulder pain and loss of passive elevation averaging 10-20 degrees. A dynamic intraoperative test involving forward elevation with the elbow extended demonstrated entrapment of the tendon within the joint in each case. This test creates a characteristic "buckling" of the tendon and "squeezing" of the tendon between the humeral head and the glenoid ("hourglass test"). Excision of the tendon allowed immediate restoration of complete elevation. Mean Constant score increased from 38 points to 76 points postoperatively. DISCUSSION: The "hourglass biceps" is caused by a hypertrophic intraarticular portion of the tendon that is unable to slide into the bicipital groove during elevation of the arm. Loss of 10-20 degrees of passive elevation, bicipital groove tenderness, and radiographic findings of a hypertrophied tendon can aid in diagnosis. The "hourglass biceps" should not be misdiagnosed for a frozen shoulder. Definitive diagnosis is made at surgery with the "hourglass test": incarceration and squeezing of the tendon within the joint during forward elevation of the arm with the elbow extended. Simple tenotomy cannot resolve this mechanical block. Either tenotomy with excision of the intraarticular portion of the LHBT or tenodesis must be performed. The "Hourglass" biceps is an addition to the familiar pathologies of the long head of the biceps tendon (tenosynovitis, prerupture, rupture, instability), and should be considered in any case of chronic anterior shoulder pain associated with a loss of shoulder elevation.

Aged↗
PubMedDate not supplied

Heterotopic ossification after hip surgery in cerebral palsy.

Heterotopic ossification is a post-surgery complication occasionally observed in patients with infantile cerebral palsy. In the majority of the cases such lesions are found at the hip after surgery on the skeleton and the soft tissues. At our Institute in the last five years, this complication has been observed four times, in 39 patients, who underwent mainly soft tissue releases because of flexion and adduction contracture of the hip. In these cases, as in a further patient with myelomeningocele, the periarticular heterotopic ossification appeared in the hip after tenotomy of the ilio-psoas at the lesser tronchater associated to other surgical procedures. Conversely, no cases of ossification have been found after tenotomy of the adductors or the gracilis or selective tenotomy of the psoas at the pelvic brim. The exact causes of this complication are still unclear, but after an analysis of the literature and patient history it can be hypothesised that it may be related to the surgical procedures carried out.

Adolescent↗
PubMed2006

[The effect of weakening the overaction superior oblique muscles on the status of ocular torsion].

OBJECTIVE: To investigate the effect of weakening the superior oblique muscles on the status of ocular torsion. METHODS: Twenty-nine patients (58 eyes) underwent tenotomy or partial ectomy of bilateral superior oblique muscles for treatment of superior oblique overacting. Objective cyclodeviations were assessed by fundus photograph before and 7 days after the surgery. The photographs were transferred to a computer and then the fovea-disc angle was measured by a software for drawing pictures. Subjective cyclodeviations and binocular vision function were assessed by synoptophore. RESULTS: Fundus photography before surgery revealed that the intorsion was 10.48 degrees +/- 6.01 degrees for the right eye and was 9.37 degrees +/- 5.88 degrees for the left eye. The reduction of the cyclodeviations by weakening the superior oblique muscle for the right and left eye was 9.11 degrees +/- 7.09 degrees and 7.94 degrees +/- 4.76 degrees respectively. The comparisons of objective ocular torsion for both eyes showed high significant differences (P < 0.01) pre- and post-operatively. There were no significant differences (P > 0.05) between the effects of tenotomy or partial ectomy of bilateral superior oblique muscles. All patients showed no cyclotropia and normal binocular vision function was obtained with synoptophore before and after surgery. CONCLUSIONS: Weakening the overaction superior oblique could correct ocular incyclodeviation. Both tenotomy and partial ectomy of bilateral superior oblique muscles can treat ocular incyclodeviation effectively. The changes of subjective and objective cyclodeviations are inconsistent with each other.

Adolescent↗
PubMed1987

Overwork-induced axonal hypertrophy in the soleus nerve of the rat.

Effect of overwork, induced by synergistic tenotomy (bilateral tenotomy of the gastrocnemius and the plantaris muscles) of the soleus muscle, was evaluated on areas of the large myelinated axons (LMA) (greater than 19.5 micron 2), in the soleus nerve (the tibial nerve branch innervating the soleus muscle) of the rat. Three lots (n = 12-16) of young adult male (body weight of 275 to 325 g), Sprague-Dawley rats were used. One lot of 16 animals was kept as normal, while the other two underwent bilateral L4 or L5 spinal nerve sectioning. Six to seven animals each from the normal, L4-, and L5 neurectomized animals underwent bilateral synergistic tenotomy of the soleus so that the soleus was retained as the sole plantar-flexor of the ankle joint. The remaining animals were kept as normal or neurectomized control groups. Thus, the six groups studied were normal control (n = 9); normal synergistically tenotomized (n = 7); L4 neurectomized control (n = 8); L4 neurectomized and synergistically tenotomized (n = 6); L5 neurectomized control (n = 8); and L5 neurectomized and synergistically tenotomized (n = 7). Seven days after surgery, the soleus muscles were used to evaluate the muscle weights. The soleus nerves were evaluated for the number plus areas of the LMA by computerized planimetric procedures. The data revealed a 13.9% (p less than 0.05) increase in areas of the LMA in the L5 neurectomized control group; whereas the L5 neurectomized and synergistically tenotomized group showed a 39.6% (p less than 0.01) increase in areas of the LMA.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

[History of strabismus surgery].

The history of strabismus surgery starts from the end of the eighteenth century. The first surgical trials consisted of performing myotomies of the medial rectus. Although Taylor from Great Britain could be one of the first to be mentioned, it was Dieffenbach from Germany who accomplished the first official myotomy in 1839. He is followed by many authors as Roux, Velpeau in Paris, and Bonnet in Lyon, the latter performing tenotomy instead of myotomy. In 1849 Guerin performed muscular advancement. In 1883, de Wecker described the muscular pleating, and Blascowiczs the muscular resection. Thus, by the end of the nineteenth century, the surgical treatment of esodeviations was supported by methods aimed to weaken the medial rectus (tenotomies, myotomies) and to strengthen the lateral rectus (advancement, pleating and resection). During twentieth century, progress achieved in anesthesiology and the quality of suture material led Jameson (1922) to substitute tenotomy by muscular recession. Since then, the surgery of squint has never been modified basically up to 1970 when Cuppers created the retro-equatorial myopexy. Thus, two kinds of surgical technics are currently available to surgeons: classic surgery, recession, resection and their variants, dealing with the static component of the deviation angle, and the Faden Operation of Cuppers struggling against the dynamic or innervational component.

Adult↗
PubMed1980

The target phenomenon in tenotomized rat gastrocnemius muscle. A comparative electrophysiological and morphological study.

In ten female rats electrophysiological recordings and subsequent histological and histochemical examinations were performed at different time intervals and in different parts of the gastrocnemius muscle, following tenotomy and following combined tenotomy and neurotomy. Repetitive motor action potentials were more easily evoked during the period and at the sites of occurrence, of target fibres in tenotomized gastrocnemius muscle with an intact nerve supply. Both phenomena, the electrophysiological as well as the morphological one, were strongly inhibited by the simultaneous neurotomy. This study suggested that the target phenomenon is a morphological expression of an increased irritability of the muscle, following tenotomy.

Achilles Tendon↗
PubMed1993

Ultrastructural changes of myotendinous junctions in tenotomized soleus muscles of the rat.

The effects of tenotomy on the ultrastructure of myotendinous junctions in the rat soleus muscle were studied by thin-section electron microscopy. When the soleus muscle was tenotomized at both distal and proximal ends, virtually all muscle fibers showed a characteristic alteration called central core lesion in their middle portions. The similar alteration was also found in the end portions of each muscle fiber. As early as 5 days after tenotomy, myofibrils at the fiber end were extensively disoriented and disintegrated with thickening of the Z-discs. The surface specializations, sarcoplasmic processes and invaginations of the fiber end were also altered in such a way that the sarcoplasmic processes retracted. The disintegration of myofibrils was most extensive at one week after tenotomy, often losing their association with the sarcolemma. The thickening and rod formation of the Z-discs at the fiber ends were prominent at 1 and 2 weeks. The thickened Z-discs and rod structures were never closely associated with the sarcolemmal undercoats, which were not significantly thickened. This suggests that the Z-disc and the sarcolemmal undercoat are discrete entities. Interestingly, the basal laminae were frequently seen to be separated from the sarcolemma forming free sheets, as the sarcoplasmic processes retracted. In the space surrounded by such free basal lamina were seen many vesicular or granular materials. At 3 and 4 weeks the fiber end showed a recovery process forming new myofibrils, as the sarcoplasmic processes grew long. Thus, the surface specializations of the fiber end were much more elaborate than those in the control muscle. At 5 and 6 weeks the myotendinous junctions returned to normal ultrastructure except that the surface specializations were still elaborated. These findings demonstrated that the myotendinous junction underwent a series of characteristic alterations and recovery of the surface specializations as well as myofibrils.

Animals↗
PubMed1998

Non-myotendinous force transmission in rat extensor digitorum longus muscle

The extensor digitorum longus muscle (EDL) of the rat hindleg consists of four heads. The heads are named after their insertions on the digits of toes II, III, IV and V. The EDL heads share a proximal tendon and aponeurosis, but have separate distal aponeuroses and tendons. By cutting the distal tendons of selected heads, direct myotendinous force transmission within these heads is prevented. Therefore, force exerted by the muscle would be expected to decrease according to the physiological cross-sectional area disconnected if myotendinous force transmission were the only mechanism of force transmission. The results indicate that EDL force production remained at high levels after acute tenotomy: muscle length-force curves did not alter significantly following cutting of the tendons of heads II and III. Cutting the tendon of head IV as well leaves only head V in its original condition. After tenotomy of head IV, length-force characteristics were altered significantly, but optimum force was maintained at 84 % of that of the intact muscle. After separation of head IV from head V intramuscularly for some distance along their interface, the force dropped to much lower levels, with optimum force approaching 50 % of that of the intact muscle. The length of active proximal fibres (located within head II) did not remain constant but increased with increasing muscle lengths after tenotomy as well as after partial separation of heads IV and V. The amount of length change decreased after intramuscular separation of the heads, indicating declining reactive forces. It is concluded that force transmission occurred from tenotomized heads to their intact neighbours and vice versa . The magnitude of the force transmitted from head to head was dependent on the degree of integrity of the connective tissue at the interface between heads.

Journal Article↗
PubMed1998

Non-myotendinous force transmission in rat extensor digitorum longus muscle.

The extensor digitorum longus muscle (EDL) of the rat hindleg consists of four heads. The heads are named after their insertions on the digits of toes II, III, IV and V. The EDL heads share a proximal tendon and aponeurosis, but have separate distal aponeuroses and tendons. By cutting the distal tendons of selected heads, direct myotendinous force transmission within these heads is prevented. Therefore, force exerted by the muscle would be expected to decrease according to the physiological cross-sectional area disconnected if myotendinous force transmission were the only mechanism of force transmission. The results indicate that EDL force production remained at high levels after acute tenotomy: muscle length-force curves did not alter significantly following cutting of the tendons of heads II and III. Cutting the tendon of head IV as well leaves only head V in its original condition. After tenotomy of head IV, length-force characteristics were altered significantly, but optimum force was maintained at 84% of that of the intact muscle. After separation of head IV from head V intramuscularly for some distance along their interface, the force dropped to much lower levels, with optimum force approaching 50% of that of the intact muscle. The length of active proximal fibres (located within head II) did not remain constant but increased with increasing muscle lengths after tenotomy as well as after partial separation of heads IV and V. The amount of length change decreased after intramuscular separation of the heads, indicating declining reactive forces. It is concluded that force transmission occurred from tenotomized heads to their intact neighbours and vice versa. The magnitude of the force transmitted from head to head was dependent on the degree of integrity of the connective tissue at the interface between heads.

Animals↗