RESUMEN

Equipment which measure femorotibial motions indirectly by using a patellar pad are reported to have errors caused by deformation of soft tissues and slippage of the device. For the purpose of validation, the tibial translation in relation to the femur per degree of knee extension was estimated from the slope coefficients of the flexion-displacement curve, obtained by both fluoroscopic and electrogoniometric tests, in the knee of the dominant limb in healthy subjects and in both knees of patients with unilateral anterior cruciate ligament (ACL) deficiency. In addition, the anterior and posterior static knee laxity limits and the tibial resting position were evaluated. Within all knee groups, the tibia moved posteriorly in relation to the femur during extension. The measured movement was similar both with the electrogoniometer and with fluoroscopy thereby indicating that sagittal plane knee translation measurements with the CA-4000 electrogoniometer are reliable and in good agreement with the X-ray measurements, even though the measurements were made separately. The ACL injured knees showed approximately 20% smaller posterior movement of tibia in relation to femur per degree change of knee extension than the non-injured or control knees (p < 0.05) and a more anterior resting position of the tibia relative to femur as compared to the contralateral healthy knee during knee laxity testing (p = 0.002).

Asunto(s)

Asunto(s)

RESUMEN

PURPOSE: The purpose of this study was to describe the sagittal tibial translation and EMG activity of muscles v. medialis and lateralis, gastrocnemius, and hamstrings, during common locomotion, in patients with an anterior cruciate ligament deficiency (ACL-def) and uninjured controls. METHODS: In 12 ACL-def patients and 17 controls, sagittal tibial translation was registered with the CA-4000 electrogoniometer during level walking, cutting, and stair walking. Tibial position at each flexion angle was expressed relative to the femuro-tibial position at passive knee extension. EMG activity, measured with ME-4000, was normalized to the individual maximum isometric voluntary contraction for each muscle. RESULTS: During the weight-bearing phase of motion, the tibia was anteriorly positioned in all legs. In the injured leg, the tibia translated more rapidly to an anterior position that was maintained for a longer time during the gait cycle. In the noninjured knees, motions with increased load lead to an increased anterior tibial translation in contrast to the injured knees, where the maximum displacement was already reached during level walking. The quadriceps and gastrocnemius muscles were simultaneously active during stance phase. Hamstrings were mainly active when the knee was close to extension and translation increased in spite of this activity. CONCLUSIONS: The mechanism of the anterior positioning of tibia is qualitatively similar in the normal and the injured knee, but that position is obtained much further forward in the ACL deficient knee. Quadriceps and gastrocnemius muscles seem to work synergistically to stabilize the knee by maintaining the anterior position of tibia during weight-bearing motion. The role of hamstrings to restrict anterior translation is questioned.

Asunto(s)

RESUMEN

STUDY DESIGN: Factorial quasi-experimental design. OBJECTIVES: To quantify the effect of different levels of isokinetic concentric and eccentric knee extensor torques on the anterior tibial translation in subjects with anterior cruciate ligament (ACL) deficiency. Electromyogram (EMG) activity of 4 leg muscles was recorded in order to detect any co-activation of extensors and flexors. BACKGROUND: The rehabilitation after an ACL injury is of importance for the functional outcome of the patient. In order to construct a rehabilitation program after that injury, it is important to understand the in vivo relationships between muscle force and tibial translation. METHODS AND MEASURES: Twelve patients with unilateral ACL injury and 11 uninjured volunteers performed 36 repetitions of a quadriceps contraction at different isokinetic concentric and eccentric torque levels, on a KinCom machine (60 degrees x s(-1)), with simultaneous recordings of tibial translation (CA-4000) and EMG activity from quadriceps and hamstrings muscles. Tibial translations and EMG levels were normalized to the maximum of each subject. RESULTS: The individual anterior tibial translation increased with increased quadriceps torque in a similar manner in both quadriceps contraction modes in all legs tested. During concentric mode, translation was similar in all groups, but during eccentric mode, the mean translation was 38% larger in the ACL injured knees. No quadriceps-hamstrings co-activation occurred in any test or group. CONCLUSIONS: An ACL deficient knee can limit the translation within a normal space during concentric muscle activity but not during eccentric activity. That limitation depends on other mechanisms than hamstrings co-activation.

Asunto(s)

RESUMEN

Using electrogoniometry and electromyography, we measured tibial translation and muscle activation in 12 patients with unilateral anterior cruciate ligament injury and in 12 control subjects. Measurements were made during an active extension exercise with 0-, 4-, and 8-kg weights and during squats on two legs and on one leg where the projection of the center of gravity was placed over, behind, and in front the feet. In the uninjured subjects, tibial translation increased with increasing load except during the squat with the center of gravity behind the feet, which produced the smallest translation. For the active extension exercises, translation was greater during eccentric activity. In the anterior cruciate ligament-injured knees, all squats resulted in similar translation, which was smaller than that during the active extension exercise. The highest muscle activation was seen during squats. Hamstring muscle activity was low. Increased static laxity in the anterior cruciate ligament-deficient knee can be controlled during closed but not during open kinetic chain exercises. Coactivation of the quadriceps and gastrocnemius muscles seems to be important for knee stability, whereas hamstring muscle coactivation was insignificant. To minimize sagittal translation during nonoperative management of anterior cruciate ligament-deficient knees, closed kinetic chain exercises are preferable to open kinetic chain exercises, and importance should be attached to the spontaneous coactivation of the quadriceps and gastrocnemius muscles.

Asunto(s)

RESUMEN

We have followed for 13 years a consecutive series of 31 patients who had open repair of a torn meniscus. They were between 13 and 43 years of age at the time of operation and all had intact stabilising ligaments. Comparison was made with a matched group of normal subjects of similar age and level of activity. The total rate of failure after meniscal repair was 29%; three of the repaired menisci did not heal and six reruptured during the follow-up period. At follow-up 80% of the patients had normal knee function for daily activities. Radiological changes were found in seven. Two had reduction of the joint space (Ahlbäck grade 1), one with successful and one with failed repair. In the control group of uninjured subjects one knee showed Fairbank changes but none had changes according to Ahlbäck. The incidence of radiological changes did not differ between the group with meniscal repair and the control group but knee function was reduced after meniscal repair (p < 0.001). We conclude that the long-term results of meniscal repair in stable knees are good with nearly normal function and a low incidence of low-grade radiological changes.

Asunto(s)

RESUMEN

We report short-term data from 82 consecutive patients with arthroscopic meniscectomy 1995-1998 in stable knees and without severe cartilage changes. All patients were treated as outpatients, the operating time was, on average, 23 SD12 minutes and 3 of 4 patients were back at work within 1 week. Almost half of the patients still had some knee problems 3 months after surgery, but thereafter a substantial improvement was seen. We also report original data from a consecutive series of patients having arthroscopic meniscectomy 1980-81. In that series, the frequency of total meniscectomies was higher, the operating time longer, but the time to recovery was shorter than in 1995-98. In contrast to 1995-98, most of the patients in 1980-81 were followed by the doctor and had supervised rehabilitation. However, sick leave was similar in the two series. The total costs for an arthroscopic meniscectomy in 1998 was less than half the costs in 1980-81. We conclude that the improved technique for arthroscopic meniscectomy during the last 15-20 years and less supervised rehabilitation have reduced the costs, but not the recovery time.

Asunto(s)

RESUMEN

Three-month-old male rats were subjected 3 times weekly for 1 h to eccentric exercise of one triceps surae muscle (30 stimulations/min) under general anesthesia in order to induce Achilles tendon disorder corresponding to paratenonitis and tendinosis in man. Net muscle work during the sessions ranged between 0.67 and 4.37 mJ (mean 1.72, SD 0.77). After 9 and 13 sessions, respectively, 2 rats started to show gait alterations during the functional test which was performed 2-3 times weekly. These rats were killed after additional sessions which showed a worsening of the limp. The other trained rats and controls did not limp and were killed after 7-11 weeks. Histologic evaluation of the Achilles tendons from the exercised limb showed in the majority of the cases hypervascularization, increased number of nerve filaments and increased immunoreactivity for substance P and calcitonin gene-related peptide. The tendons from the nonstimulated limb looked normal. The distribution of collagen types I and II appeared normal in the tendon and its insertion to the calcaneus. Inflammation of the epi- and paratenon could be provoked in the rat, but tendon changes corresponding to chronic tendinosis did not develop within 11 weeks with the used training regime. The clinical relevance of this model for chronic tendon disease needs to be evaluated further.

Asunto(s)

RESUMEN

The effect of increasing isokinetic, eccentric quadriceps torques on sagittal translation of the tibia was examined in six healthy volunteers and compared to the translation at 20 degrees of knee flexion during a drawer test with 90 N force. The tibial translation increased in a linear fashion with a mean of 0.5 mm per 20% torque increase. In 20 degrees of knee flexion, 10% of eccentric quadriceps peak torque consumed 80% of the anterior tibial translation induced by the 90 N Lachman test while eccentric quadriceps peak torque utilized 100% of the translation at the same test. The in vivo relation between muscle force and tibial translation is of importance in the treatment of patients with injury to the cruciate ligaments. The results indicate that an already low eccentric quadriceps torque causes a tibial translation that reaches the limit of the passive knee joint displacement where strain is assumed to develop in the anterior cruciate ligament. Already low eccentric quadriceps torque levels may therefore be harmful during rehabilitation after anterior cruciate ligament surgery.

Asunto(s)

RESUMEN

Knee ligament injuries are common in sport. A rupture of the anterior cruciate ligament (ACL) is the most serious of these injuries because it may cause long term disability. In this literature review, the frequency of post-traumatic gonarthrosis is examined. There are few long term prospective studies but a number of retrospective studies with follow-up times between 5 and 20 years have been published. These studies show that radiographic gonarthrosis is significantly increased after all knee injuries compared with the uninjured joint of the same patient. Isolated meniscus rupture and subsequent repair, or partial or total ruptures of the ACL without major concomitant injuries, seem to increase the risk 10-fold (15 to 20% incidence of gonarthrosis) compared with an age-matched, uninjured population (1 to 2%). Meniscectomy in a joint with intact ligaments further doubles the risk of gonarthrosis (30 to 40%), and 50 to 70% of patients with complete ACL rupture and associated injuries have radiographic changes after 15 to 20 years. Thus, an ACL rupture combined with meniscus rupture or other knee ligament injuries results in gonarthrosis in most patients. Ten to 20 years after ACL injury, gonarthrosis often presents as a slight joint space reduction or, occasionally, joint space obliteration (Ahlbäck grades I to II), but is usually not associated with major clinical symptoms. According to the few longitudinal studies, the progress of gonarthrosis is slow, and in some cases the condition seems to remain stable. Time is an important determinant for the degree of gonarthrosis and problems demanding treatment may be encountered only at > 30 years after the initial accident.

Asunto(s)

RESUMEN

With an electrogoniometer system, we made bilateral measurements of the maximal sagittal plane anterior-posterior knee translations in 15 healthy subjects (controls) and 14 patients with arthroscopically confirmed unilateral anterior cruciate ligament deficiency during two types of ascents and descents (straight and side). In both groups, during the ascent cycle the tibia moved anteriorly in relation to the femur, whereas during the descent cycle it moved posteriorly. There was wide individual variation in maximal translation in both the control and anterior cruciate ligament-deficient groups (range, 1 to 12 mm; mean, 7 mm). The maximal translations were similar in both groups (P > 0.05), but they occurred at a significantly smaller flexion angle in the injured knees (38 degrees +/- 8 degrees) than in the control and non-injured knees (44 degrees +/- 8 degrees) (P < 0.05). The translation during step ascent and descent did not differ between the injured and control knees. These findings indicate that patients with anterior cruciate ligament injuries are able to control abnormal anterior translation during normal activity.

Asunto(s)

RESUMEN

In this prospective study we investigated 70 patients with chronic anterior instability who underwent anterior cruciate ligament reconstruction with a Dacron prosthesis. Fifty-five (79%) patients could be followed up at a mean of 9 years. Within the follow-up time, 44% (29 of 66) of the prostheses were diagnosed as ruptured; the annual rupture frequency was 5%. Second reconstructions were performed for 20 patients (29%), 5 patients had third reconstructions, and 9 patients wanted no further surgical treatment. Fifty-two patients (74% of the original group) underwent radiographic examination. Eighty-three percent (43) of these patients had radiographic changes in the operated knee, and 40% (21 of 52) had joint space reduction up to 50%. The rate of radiographically detected osteoarthritis was increased 10 times compared with the normal knee. Patients with medical instability and patients older than 30 years at the initial operation had more severe osteoarthritic changes. Based on the functional results of the patients with a ligament in place after 9 years, only 14% (10) of the original group had acceptable stability and knee function.

Asunto(s)

RESUMEN

Static anterior-posterior (AP) laxity is one of the commonly used criteria in selecting patients for cruciate ligament reconstructions, but in reality dynamic AP laxity plays a more important role. The aim of this in vivo study was to compare the sagittal translation of the knee during active and passive motion, signifying dynamic AP laxity, with static AP laxity in healthy subjects (controls) and patients with anterior cruciate ligament deficiency. The sagittal plane knee translations were recorded and compared in both knees of nine healthy subjects (Controls) and seven patients with confirmed unilateral ACL deficiency during dynamic and static situations with an electrogoniometer system. In all groups during the ascents the tibia moved anteriorly in relation to the femur, whereas during the descents it moved posteriorly. The static anterior-posterior translation was significantly smaller in the control knee than in both healthy and injured knees of the ACL deficient group (P < 0.05). The injured knee showed the same laxity (92%) as the uninjured knee during dynamic activities, but it was 46% of static laxity. Also in the injured knees, the dynamic active laxity was larger during descents than ascents (P < 0.05). The results indicate that there is also a change in mechanics of the noninjured knee following injury to the contralateral knee and that this population of patients with ACL deficiency had good control over their abnormal anterior-posterior laxity.

Asunto(s)

Asunto(s)

RESUMEN

Sixty patients with stable knees and arthroscopic menisectomy were matched into two groups according to the presence of early degenerative changes at the operation. Patients with severe cartilage changes were excluded. The patients were between 20 and 40 years of age at the operation and no patient had previous surgery on the involved knee. The intraarticular findings were documented at surgery and the patients were re-examined 12 to 15 years after the meniscectomy. Pre-existing cartilage fibrillation at the meniscectomy did not seem to influence the long-term results. At the follow-up no difference was found between the groups at the physical examination, in subjective complaints, in knee function and activity or in radiographic findings. In the total group 62% had early signs of arthrosis (Fairbank changes) and 42% narrowing of the joint space (Ahlbäck grade 1-2) in the operated knee. No one had more severe changes. Radiographic signs of arthrosis were 4 times commoner in the operated knee compared to the non-operated knee after partial meniscectomy and 7 times commoner in the operated knee after subtotal meniscectomy. Arthrosis at the follow-up was seen three times more often in patients older than 30 years of age at surgery than in younger patients. The functional outcome was good and 70% were still active in sports compared to 90% before the operation.

Asunto(s)

Asunto(s)

RESUMEN

The rabbit knee is a common model for meniscus replacement, but data on the failure load of its meniscal attachments are not available. Therefore we determined the tensile failure load of the normal attachment of the rabbit meniscus. Both knee joints of five adolescent New Zealand white rabbits were dissected, leaving only the menisci intact on the tibia. Both menisci were sectioned at the midpoint along the circumference, and the anterior attachment of the lateral meniscus and the anterior and posterior attachments of the medial meniscus were tested on a MTS 858 machine. In the rabbit, the posterior attachment of the lateral meniscus inserts on the femur and thus was not tested. All failures occurred within the soft tissue of the attachment. The anterior attachments had significantly different failure loads (lateral, 158 +/- 28N; medial, 108 +/- 25N), and both were stronger than the posterior attachment of the medial meniscus (75 +/- 23N, p < 0.05). There were no differences between left and right knees. The relatively high failure loads in the meniscus attachments may be indicative of the normal tensile loads developed in these structures and the demands on the fixation of a meniscal substitute.

Asunto(s)

RESUMEN

Lipoma of the knee joint is a rare disease and most cases are lipoma arborescens within the joint. Here we report a case of true extraarticular lipoma of the knee.

Asunto(s)

RESUMEN

Maximal sagittal plane knee translation during stair walking was investigated in 5 healthy male subjects without any previous history of knee joint trauma during 2 types of ascents and descents (straight and side) using an electrogoniometer system (CA-4000, OS Inc., Hayward CA, USA). During the ascents, the tibia moved anteriorly in relation to femur, whereas during the descents it moved posteriorly. The maximum translations occurred within the range of 39 degrees to 51 degrees of knee flexion and were significantly larger during the ascents than during descents, but there was no difference between straight and side activities. There were significant interindividual differences in the maximum translations during the ascent or descent cycles but no differences between trials or the right or left limbs. The mean difference between repeated trials was 1.2 mm and the 95% confidence interval was +/- 0.6 mm.

Asunto(s)