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Biomedical subjects

P Renström

Publications and source records attributed to P Renström.

At least 19 recordsLinked to original sources
PubMed2000

[Risk factors in leisure sports. Early and late sequelae].

Risk factors for sports injuries result from extrinsic factors such as footgear, playing field surfaces, and crash helmets as well as intrinsic factors such as muscle imbalances, chronic injuries, and deficiencies in coordination. To prevent sports injuries, the incidence and severity of sports injuries must be identified and described. Then the mechanisms of injury and the risk factors must be determined accordingly. Only thereafter can consideration be given to measures that reduce the risk and severity of sports injuries. To be able to conclusively establish the total benefit of preventive measures, this process must be continually monitored for its efficacy.

Ankle Injuries↗
PubMed1998

Subtalar instability of the foot. A review and results after surgical treatment.

Most subtalar ligamentous injuries occur in combination with ankle ligament injuries, but the exact aetiology and the true incidence remain unknown. The aim of this study was to review the problem, propose a definition and to analyze the results of an anatomic reconstructive surgical technique in the treatment of subtalar instability. Twenty-two patients suffering from chronic subtalar instability of the foot were operated with anatomical reconstruction. The cervical, the lateral talo-calcaneal and the calcaneo-fibular ligaments were imbricated and reinforced with the lateral root of the inferior extensor retinaculum. After a minimum of 2 years follow-up the functional results were excellent or good in 18 of 22 (82%) patients and fair or poor in 4 of 22 (18%). All of the patients with unsatisfactory results suffered from residual ankle pain, two of whom also had residual instability. No reoperations have been performed. Surgical complications were seen in three patients, all minor nerve injuries of the lateral branch of the superficial peroneal nerve. These complications had no bearing on the functional results, however. This procedure was found to be feasible in patients with chronic subtalar instability.

Adult↗
PubMed1995

Patellofemoral pain syndrome in young women. I. A clinical analysis of alignment, pain parameters, common symptoms and functional activity level.

Clinical alignment, pain variables, common symptoms and functional activity level associated with patellofemoral pain syndrome (PFPS) were evaluated in 40 women with PFPS and 20 healthy controls. No significant difference could be found neither between the patients' most symptomatic knee and least symptomatic knee, nor between the patients and controls regarding clinical lower extremity alignment, such as Q-angle and leg-heel alignment measurements. There were no radiographic signs of malalignment. The patients were significantly more involved competitively in sports but had a significantly lower pain free activity level than the controls. Pain was associated with increased activity. It is suggested that chronic overloading and temporary overuse of the patellofemoral joint, rather than malalignment, contribute to patellofemoral pain.

Activities of Daily Living↗
PubMed1995

Patellofemoral pain syndrome in young women. II. Muscle function in patients and healthy controls.

Muscle function was evaluated in 40 patients with patellofemoral pain syndrome (PFPS) and 20 healthy controls. Patients with PFPS had a significantly lower knee extensor strength in the most symptomatic knee compared to the least symptomatic knee. Further, the patients had less vertical jumping ability and were weaker in the most symptomatic knee compared to the controls, with the largest differences in eccentric knee extension. There were lower strength and EMG activity, in the patients compared to the controls, in the range closer to full extension and significant differences in muscle activity between the vastus medialis and the rectus femoris muscle. The results can be explained by inhibition selective to knee angles and to the vastus medialis muscle.

Adolescent↗
PubMed1995

Effect of anterior cruciate ligament reconstruction with patellar tendon or prosthetic ligament on the morphology of the other ligaments of the knee joint. An experimental study in dogs.

The effect of anterior cruciate ligament replacement on the other ligaments of the knee, including the medial or lateral collateral and posterior cruciate ligaments, was studied histologically in the canine knee. The anterior cruciate ligament was replaced either with the medial third of the patellar tendon or with a prosthetic ligament. Histologic analysis was performed 3 months after prosthetic ligament implantation and 1 year after patellar ligament reconstruction. In all ligaments, numerous pathologic alterations were found. Degenerative changes such as glycosaminoglycan accumulation, metachromasia, collagenolysis, collagen necrosis, and lipomatosis were similar after 3 months and after 1 year. Granulation tissue, a sign that characterizes tissue repair, was seen only in those ligaments taken 3 months after anterior cruciate ligament surgery. Similar degenerative changes also were found in the ligaments of the knees with only a large medial arthrotomy (sham). In the contralateral control knees, the pathologic alterations were rare. Thus, open arthrotomy alone or with anterior cruciate ligament reconstruction seems to result in longstanding degenerative changes in all ligaments of the canine knee joint.

Animals↗
PubMed1994

Determination of a zero strain reference for the anteromedial band of the anterior cruciate ligament.

The objective of this study was to verify a method previously used to determine a reference length for calculations of anterior cruciate ligament strain. In nine knee specimens, an arthroscopic force probe and a Hall effect transducer were placed in the anteromedial band of the ligament. Anteroposterior-directed shear loads then were applied to the knee joint with the knee flexed to 30 degrees. From the sigmoidal curve for shear load versus displacement of the anterior cruciate ligament midsubstance, the length of the transducer at the inflection point was determined graphically by two independent examiners. Previous studies suggested that the inflection point corresponds to the slack-taut transition of the anteromedial band. The force probe was used to determine the actual length of the transducer when the anteromedial band became load bearing. No significant differences were found between the reference lengths determined by the inflection point method and the force probe. The force probe demonstrated that the anterior cruciate ligament became load bearing when an anterior shear load of 8.8 N was applied to the tibia with the knee at 30 degrees of flexion. Furthermore, multiple cycles of anteroposterior shear loading did not influence these values. The force probe verified that the inflection method provides a reasonable estimate of the absolute strain reference (within 0.7% strain).

Adult↗
PubMed1992

Effect of one-legged exercise on the strength, power and endurance of the contralateral leg. A randomized, controlled study using isometric and concentric isokinetic training.

The purpose of this investigation was to study the effect of one-legged exercise on the strength, power and endurance of the contralateral leg. The performance of the knee extensor and flexor muscle of 20 healthy young adults (10 men and 10 women) was first tested by Cybex II+ and 340 dynamometers. Then 10 subjects were chosen at random to train using one leg three times a week for 7 weeks whilst the other 10 served as controls. During the 8th week, the tests were repeated. Both quadriceps and hamstring muscles of the trained subjects showed a cross-transfer effect from the trained limb to the untrained side. This concerned the strength and power, as well as endurance characteristics of these muscles. The average change in peak torque of the quadriceps muscle was +19% (P less than 0.001) in the trained limb, +11% (P less than 0.01) in the untrained limb and 0% in the control limbs. In hamstring muscles the changes were +14% (P less than 0.01), +5% and -1%, respectively. Concerning muscle endurance (work performed during the last 5 contractions in the 25-repetition test) the corresponding changes were +15% (P less than 0.01), +7% (P less than 0.01), and -1% in quadriceps muscle, and +17% (P less than 0.05), +7%, and -3% in hamstring muscles. The average strength benefit in the untrained limb was +36% (hamstring muscles) and +58% (quadriceps muscle) of that achieved in the trained limb. Untrained hamstring muscle showed better benefits in the endurance parameters than in strength or power parameters, while in the quadriceps muscle this effect was reversed. A positive relationship was observed between the changes (greater improvement in the trained limb resulted in greater improvement in the untrained limb) (hamstring muscles: r = 0.83, P less than 0.001, quadriceps muscle: r = 0.53, P less than 0.001). In endurance parameters, this relationship was almost linear while in the strength and power parameters the results were more in favour of a curvilinear relationship with limited benefit.

Adult↗
PubMed1992

Function after through-knee compared with below-knee and above-knee amputation.

Fifty-nine amputees, 24 below-knee (BK), 17 through-knee (TK) and 18 above-knee (AK) who had prosthetic replacements, were evaluated using a questionnaire which provided a quantitative and qualitative assessment scale for the prosthetic function. The ability to apply or don the prosthesis was noted in 100% of the BK, 70% of the TK and 56% of the AK amputations (p < 0.001). Daily use of the prosthesis was recorded in 96% of the BK, 76% of the TK and 50% of the AK amputations (p < 0.001). A higher level of amputation resulted in a significantly lower degree of rehabilitation (p < 0.05). The qualitative evaluation shows that the higher the level of amputation, the lower the usefulness of the prosthesis. Four percent of the BK, 12% of the TK and 39% of the AK amputees had no use whatsoever of their prosthesis (p < 0.01). From a functional standpoint, TK amputation should always be considered as the primary alternative to AK amputation when a BK amputation is not feasible.

Aged↗
PubMed1991

Injuries to the posterior cruciate ligament of the knee.

The posterior cruciate ligament (PCL) is the strongest ligament about the knee and is approximately twice as strong as the anterior cruciate ligament. Its main function is to prevent the posterior dislocation of the tibia in relation to the femur, providing 95% of the strength to resist the tibial posterior displacement. Along with the anterior cruciate ligament (ACL) the PCL controls the passive 'screw home' mechanism of the knee in terminal knee extension. It also provides mechanical support for the collateral ligaments during valgus or varus stress of the knee. PCL ruptures are uncommon apparently due to its strong fibre structure. The most frequent injury mechanism in isolated PCL tears is a direct blow on the anterior tibia with the knee flexed thus driving the tibia posteriorly. Automobile accidents (in which the knee hits the dashboard) and soccer injuries (in which an athlete receives a blow to the anterior surface of the tibia during knee flexion) characteristically produce this type of injury. In other PCL injury mechanisms (hyperextension, hyperflexion or rotational injuries with associated valgum/varum stress), other knee structures are also often damaged. The most characteristic diagnostic finding in a knee with a PCL rupture is the 'posterior sag sign' meaning the apparent disappearance of the tibial tubercle in lateral inspection when the knee is flexed 90 degrees. This is due to gravity-assisted posterior displacement of the tibia in relation to the femur. A positive posterior drawer test performed at 90 degrees of flexion and a knee hyperextension sign are sensitive but nonspecific tests. False negative findings are frequent, especially in acute cases. If necessary, the clinical diagnosis of the PCL tear can be verified by magnetic resonance imaging, examination under anaesthesia, arthroscopy, or a combination of these modalities. If a PCL avulsion fragment has been dislocated, surgical treatment is recommended. In isolated, complete midsubstance tears of the PCL the majority of the recent studies recommend conservative treatment, since abnormal residual posterior laxity1 in most of these knees is consistent with functional stability and minimal symptoms. This has been the case even in athletes. In isolated PCL tears, the outcome seems to depend more on the muscular (quadriceps) status of the knee than on the amount of residual posterior laxity. Therefore, the conservative treatment protocol emphasises intensive quadriceps exercises, and only a short (under 2 weeks) immobilisation period followed by early controlled activities and early weightbearing.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1991

Sports traumatology today. A review of common current sports injury problems.

Increasing participation and training intensity in sports and physical activity has resulted in an increasing number of injuries as well as recognition of "new" injuries. Improved diagnostic techniques such as MRI, CT scan, scintigraphy and ultrasound have proven to be valuable in the diagnosis of especially soft tissue injuries. Surgery is today generally accepted as the treatment of choice for anterior cruciate ligament injuries in the active population. Arthroscopic reconstruction using the bone-patellar tendon-bone graft is considered to be the "gold standard". Alternative grafts such as semitendinosus and gracilis can also be used. The use of artificial ligaments and allografts is still experimental. Most posterior cruciate ligament injuries are today treated conservatively, and so are ankle ligament injuries. There is still no final solution how to treat articular cartilage lesions although interest is being focussed on cartilage resurfacing. Overuse tendon injuries often become chronic and are then associated with persistent structural alteration. Chronic overuse injuries are characterized by a failure to develop adequate scar tissue restoration. The reason for this delayed healing is still unclear. The treatment of these injuries include, today, early strength and stretching training, but the main concepts are still controversial due to lack of scientific evidence. Our understanding of shoulder injuries in athletes has developed enormously during the last few years. The use of arthroscopy when performing subacromial decompression and surgery of labral tears have allowed more athletes to return early to sports than before. Laboratory studies have increased our understanding of muscle injuries and they show the importance of early mobilization. Prevention will be a major issue for research within the next decade. It is the author's opinion that within the next decade, sports traumatology will take a leading role in orthopaedic and sports medicine research.

Athletic Injuries↗
PubMed1990

Anterior cruciate ligament repair with and without augmentation. A prospective 7-year study of 51 patients.

A prospective comparison was made of the 7-year results of repair of the acutely ruptured anterior cruciate ligament with and without augmentation using the longitudinal patellar retinaculum. The knee stability was evaluated by clinical tests and by a specially constructed testing device. In the repair group, 6/22 had unchanged activity and intensity levels compared with 24/29 in the augmentation group. Lysholm's functional score was higher in the augmentation group. All the clinical tests and all the objective measurements except Lachman's test showed better stability in the augmentation group.

Adolescent↗
PubMed1990

Anatomy and biomechanics of the menisci.

The shape of the menisci and the orientation of the collagen fibers are optimal for weight bearing and shock absorption. The menisci are of clinical importance to knee biomechanics as they function to maintain knee joint stability and congruity, resist capsular and synovial impingement during knee motion, support the screw home mechanism, and distribute load over a large area of the articular surface. Because of these vital roles, an attempt should be made to save viable meniscus when performing knee surgery.

Biomechanical Phenomena↗
PubMed1990

Isokinetic strength training in below-knee amputees.

Eight below-knee amputees performed isokinetic training of knee extensor- and knee-flexor muscles for a period of 8-12 weeks at angular velocities of 60 degrees/s, 180 degrees/s and 240 degrees/s. Before and after training isokinetic and isometric knee extensor/flexor strength was measured. Muscle biopsies were taken from the vastus lateralis and the cross-sectional area of the thigh muscles was measured with computerized tomography. Peak torque of the amputated leg increased significantly in all knee-extension tests and in knee-flexion at 180 degrees/s, and in the non-amputated leg in extension at 180 degrees/s, 240 degrees/s and for isometric strength at 60 degrees knee angle. Knee-flexion strength increased at 240 degrees/s. The cross-sectional area of the muscle fibers increased in the amputated leg in all patients except one. There was no significant increase in the non-amputated leg which also was trained. The quotient between the cross-sectional areas of type II and type I fibers increased from 1.04 to 1.20 in the amputated leg, demonstrating an increase specially in the type II fibers. There was no difference in the non-amputated leg. The cross-sectional area of the thigh muscles did not show any significant change in either leg. The patients estimated their ability to walk after training to more than double the distance compared to before training. They could also manage better without walking aids. The increase in strength and the synchronous increase in the size of type II (fast twitch) fibers indicate that the training model has activated also these motor units which probably have not been given as much training earlier.

Adult↗
PubMed1988

Effects of electrical muscle stimulation combined with voluntary contractions after knee ligament surgery.

The aim of the present study is to compare the effect of electrical muscle stimulation combined with voluntary muscle contractions with a program only with voluntary muscle contractions during immobilization in casts after anterior cruciate ligament surgery. Twenty-three patients, 7 women and 16 men with a mean age of 28 yr, were randomized into two groups: an experimental group (13 patients) and a control group (10 patients). Post-operatively, the patients were immobilized for 3 wk in a full leg cast with the knee flexed at an angle of 20 degrees to 30 degrees and then in a knee cast for another 3 wk. All patients had a standard program with quadriceps muscle contractions. In addition, the experimental group received electrical stimulation of the quadriceps muscle 4 X 10 min, 3 times.wk-1, at a frequency of 30 Hz. During each stimulation, the patients were requested to contract the quadriceps muscle voluntarily as well. When pre-operative measurements were compared with those at the end of the immobilization period (6 wk after the operation), a significantly larger reduction in the knee extension isometric muscle strength was found for the control group than for the experimental group. In comparisons of the data of the male subjects only, this difference was still seen to be significant. The cross-sectional area of the quadriceps muscle measured with computed tomography was significantly less reduced during the immobilization period in the experimental group than in the control group.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1984

Health and aging characteristics of highly physically active 65-year-old men.

Eighteen highly physically active men aged 65 years, training since youth, were compared to 67-year-old men from the general population. Body fat was low in the well-trained men, particularly in the central regions of the body. They smoked less. They characterized themselves as being in a general state of good health and well-being. Plasma insulin values were remarkably low. Blood pressure and resting heart rate were lower and ventilatory capacity better than in controls, and they had less heart diseases. The "juvenile" traits in their energy metabolism as well as in blood pressure and in their own perception of being highly energetic were not associated with less aging characteristics of hair, skin, or function of senses. The results obtained in this selected group suggest that physical activity protects against several age-dependent conditions as well as obesity, also at a fairly advanced age. These findings as well as the observations of differences in ventilatory function, smoking habits, and well-being between the group of highly physically active men and the control group deserve further studies.

Aged↗
PubMed1984

Health and ageing characteristics of highly physically active 65-year-old men.

Eighteen highly physically active men at mean age of 65 years, and who had training since youth, were compared with men from the general population at 67 years of age (N = 644). Body fat was low in the well-trained men, particularly in central regions of the body. They smoked less and characterized themselves as being in a general state of good health and well-being. Plasma insulin values were remarkably low and blood pressure and resting heart rate were lower and ventilatory capacity better than in controls. The 'juvenile' traits in their energy metabolism, as well as in blood pressure and in their own perception of being highly energetic were not associated with less ageing characteristics of hair, skin or function of senses. The results obtained in this highly selected group suggest that physical activity might retard the rate of decline of some age-dependent factors, also at a fairly advanced age.

Aged↗