Inga Arvidsson

The biomechanics of anterior cruciate ligament rehabilitation and reconstruction

The rehabilitation of knee injuries involving the anterior cruciate ligament (ACL) is controversial. This paper describes strain in the normal and reconstructed ACL during a series of passive and active tests of knee flexion with and without varus, valgus, and axial rotation torques on the tibia. Strain in the human knee ACL was significantly different depending on whether the knee flexion angle was changed passively or via simulated quadriceps contraction. The knee joint capsule was found to be important for strain protection of the ACL. Quadriceps activity did not strain the normal or recon structed ACL when the knee was flexed beyond 60°, but significantly strained the tissue from 0 to 45° of knee flexion. Immobilization may not protect the ACL if isometric quadriceps contractions are allowed to occur. Properly placed reconstructions exhibited strain behav ior which closely followed the anteromedial band of the ACL.

Diagnostic and operative arthroscopy of the hip.

Diagnostic and operative arthroscopies of the hip joint have been performed from an anterior approach after extension of the joint. The force needed to achieve a sufficient visualization of the hip joint was studied. In an anesthetized patient 300 Newtons (N) to 500 N was required, whereas up to 900 N was needed in an unanesthetized subject to achieve sufficient joint extension. Hip arthroscopy has been performed with a standard 5 mm Storz arthroscope. Alternatively, fluid and gas was used. It was possible to achieve good visualization of the anterior parts of the hip. Gas gave better information about the degree of degenerative arthritis while fluid was preferable for operative arthroscopy, eg, arthroscopic synovectomy. Synovial biopsies, removal of loose bodies, and partial arthroscopic synovectomy have been performed. The advantage was a very short time of rehabilitation. No serious complications occurred.

Stabilizing training compared with manual treatment in sub-acute and chronic low-back pain.

The present aim was to compare the effects of stabilizing training with those of manual treatment in patients with sub-acute or chronic low-back pain (LBP). Forty-seven patients were randomized to a stabilizing training group (ST group) or a manual treatment group (MT group). The patients underwent a 6-week treatment programme on a weekly basis. Pain, health and functional disability level at the start of treatment, after treatment, and at 3- and 12-month follow-ups were assessed. In the ST group all assessed variables improved significantly (P<0.05) after the treatment period and were maintained long term. After the treatment period there was a significant difference between the groups in assessed function (P<0.05). More individuals in the ST group had improved than in the MT group. At the 3-month follow-up significantly more improved individuals were evident in the ST group regarding pain, general health and functional disability levels. In the long term, significantly more (P<0.05) patients in the MT group reported recurrent treatment periods. The study did not indicate any clear short-term differences between the groups in the accessed outcome measures. In the long term, however, stabilizing training seemed to be more effective than manual treatment in terms of improvement of individuals and the reduced need for recurrent treatment periods.

Reliability of EMG spectral parameters in repeated measurements of back muscle fatigue.

The change in median frequency of the power spectrum of the electromyographic (EMG) signal may be used as a measure of muscle fatigue. The reliability of the median frequency parameters was investigated for EMG-recording sites at L1 and L5 right and left on the erector spinae. The reliability of subjective fatigue ratings of the back muscles (Borg CR-10 scale) and of maximal trunk extension torque (MVC) was also investigated. Eleven subjects with healthy backs performed a 45-s isometric trunk extension at 80% of MVC twice a day, on three different days. Two-factor analysis of variance was made to obtain the different variances from which the standard error of measurement (SEM) and the intra class correlation coefficient (ICC) were calculated. The SEM within-day was somewhat lower than that between-days. Both were about the same at all four electrode sites. The 95% confidence interval for the studied variables was for the initial median frequency +/- 10 Hz, for the slope +/- 0.4-0.5%/s, for the MVC +/- 36 Nm and for the Borg ratings +/- 1.6. We conclude that, with the presently used method, changes or differences within these limits should be regarded as normal variability. The slope may be of limited value because of its large variability. Whether the low intraclass correlation coefficient for the EMG parameters in the presently studied test group implies a low potential in discriminating subjects with back pain can not be decisively concluded.

Reduction of Pain Inhibition on Voluntary Muscle Activation by Epidural Analgesia

The influence of postoperative pain on muscle function, and the possible effect of local anesthetics on the normal muscle function are discussed. The integrated EMG (IEMG) during maximum voluntary contraction of the quadriceps muscle was registered in ten patients the day after undergoing reconstruction of the anterior cruciate ligament. Recordings were taken before, 5, 12, and 20 min to 25 min after epidural injection of 20 ml of 0.25% lidocaine with adrenaline (2.5 micrograms/ml). As pain gradually subsided, IEMG increased a mean of 2,728% 20 min to 25 min after injection (range 425% to 10,068%), compared to initial recordings before anesthesia. This indicates that pain relief plays a significant role in the ability to normally activate the quadriceps muscle after open knee surgery. Neither the Hoffman (H-)reflex, nor maximum voluntary isokinetic muscle torque was appreciably affected by epidural injection of dilute local anesthetics, as tested on two healthy volunteers. Infiltrations of local anesthetics into the distal part of the quadriceps muscle did not affect maximum voluntary isokinetic knee extension torque. From the experiments performed we conclude that it is possible to selectively block pain by injections of local anesthetics into the epidural space, without interfering with normal muscle function. It might thus be possible to prevent some of the postoperative muscle atrophy by using a continuous epidural analgesia for two to three days following surgery, and starting an early active physical therapy program.

Prevention of Quadriceps Wasting After Immobilization: An Evaluation of the Effect of Electrical Stimulation

Eighteen male and 20 female patients who underwent reconstruction of their anterior cruciate ligament (ACL) with a flap from the patellar tendon were randomly assigned into either closed cast, isometric muscle training and electric stimulation (ES group), or closed cast and isometric training alone (control group). The degree of quadriceps wasting was determined from computerized tomographic scans (CT) before and 6 weeks after surgery. Electrical stimulation was given with a battery operated stimulator that produced a rectangular asymmetric balanced biphasic pulse shape. The pulse rate was 40 Hz and the pulse width 300 microseconds. Patients received 30 min of stimulation three times daily during 5.5 weeks. Female control patients showed a larger decrease in quadriceps area on CT than male control patients (P less than .001). No significant difference was found between male electrically stimulated patients and control patients. In female patients, there was on the contrary, a highly significant difference in favor of electrical stimulation (P less than .001) When the different parts of the quadriceps were studied, a significantly lower degree of atrophy of the vastus medialis was found after electrical stimulation. Vastus lateralis did not show any difference. Measurements of CT attenuation, pre- and post-operatively, showed a decrease in attenuation of 17% for the vastus medialis and lateralis of the operated leg after immobilization, indicating an increase in fat content. In the rectus femoris, however, there was an increase in attenuation of 14.6%. Percutaneous muscle biopsies from the vastus lateralis obtained before, one week after, and 6 weeks after surgery revealed that the cross-sectional area of the individual muscle fibers decreased less in the electrically stimulated than in controls, but the difference was not significant. There were no differences between the two groups in the activity of an oxidative enzyme, citrate synthase, or a glycolytic enzyme, phosphofructokinase (PFK). We conclude that females reacted more favorably than males to electrical stimulation of quadriceps during an immobilization period after knee surgery.

Electrical stimulation of vastus medialis and stretching of lateral thigh muscles in patients with patello-femoral symptoms

Thirty patients with unilateral patello-femoral symptoms and a hypotrophic vastus medialis muscle were treated with transcutaneous electrical stimulation of the vastus medialis obliquus and stretching of the lateral thigh muscles twice daily for 10 weeks. Before and after treatment the position of the patella at fixed knee flexion angles and the area of the vastus medialis and vastus lateralis muscles were studied by computed tomography. Isokinetic quadriceps torque was registered with a Cybex II Dynamometer. An evaluation with a functional knee score was carried out. The healthy contralateral leg served as control in all the examinations. Clinically two-thirds of the patients had improved after 10 weeks of treatment and this improvement remained at follow-up 3.5 years later. The area of the vastus medialis and the quadriceps torque of the treated leg increased significantly, while the area of the vastus lateralis and the position of patella did not change. We conclude that transcutaneous electrical muscle stimulation of the vastus medialis and stretching of the lateral thigh muscles might be of benefit in patients with patello-femoral symptoms and a hypotrophic vastus medialis. An improvement after 10 weeks of treatment seems to predict a good long-term result.

Graded Exercise for Recurrent Low-Back Pain : A Randomized, Controlled Trial With 6-, 12-, and 36-Month Follow-ups

Study Design. The study was a randomized controlled trial. Treatment was for 8 weeks, with follow-up posttreatment and at 6-, 12-, and 36- months. Objective. The purpose was to evaluate the effect of a graded exercise intervention emphasizing stabilizing exercises in patients with nonspecific, recurrent low back pain (LBP). Summary of Background Data. Exercise therapy is recommended and widely used as treatment for LBP. Although stabilizing exercises are reportedly effective in the management of certain subgroups of LBP, such intervention protocols have not yet been evaluated in relation to a more general exercise regimen in patients with recurrent LBP, all at work. Methods. Seventy-one patients recruited consecutively (36 men, 35 women) with recurrent nonspecific LBP seeking care at an outpatient physiotherapy clinic were randomized into 2 treatment groups; graded exercise intervention or daily walks. The primary outcome was perceived disability and pain at 12-month follow-up. Secondary outcomes included physical health, fear-avoidance, and self-efficacy beliefs. Results. Of the participants, 83% provided data at the 12-month follow-up and 79% at 36 months. At 12 months, between-group comparison showed a reduction in perceived disability in favor of the exercise group, whereas such an effect for pain emerged only immediately postintervention. Ratings of physical health and self-efficacy beliefs also improved in the exercise group over the long term, though no changes were observed for fear-avoidance beliefs. Conclusion. A graded exercise intervention, emphasizing stabilizing exercises, for patients with recurrent LBP still at work seems more effective in improving disability and health parameters than daily walks do. However, no such positive results emerged for improvement regarding pain over a longer term, or for fear-avoidance beliefs.

Back muscle fatigue in healthy men and women studied by electromyography spectral parameters and subjective ratings.

To obtain reference data for future studies of patients with low back pain, back muscle fatigue was studied by surface electromyography at L1 and L5 lumbar levels in 55 healthy subjects exerting 80% of maximal voluntary contraction of the back extensors in a sitting position. Reference data were the initial value and rate of decrease (slope) of the median frequency during the contraction. The aim was also to study the effects of contraction time, gender differences, electrode locations and correlations with torque, age and subjective ratings. Initial median frequency was 52 Hz +/- 7.5, with no difference between electrode locations; steeper slopes were found at L5 level (-0.44%/s +/- 0.25) than at L1 (-0.36%/s +/- 0.26). No right-left differences and no gender differences were found for these parameters. A correlation was observed between slope and initial median frequency, higher for men (r approximately -0.7) than for women (r approximately -0.5). Intersubject coefficient of variation for the slope was smallest for the longest (45 seconds) recording time (60-70%), but still much higher than for the initial median frequency (14%). The torque and the subjective ratings of fatigue showed no correlation with the electromyography variables. We conclude that the same reference values can be used for men and women. Owing to the large intersubject range of the slope, the clinical use of this variable may, however, be impeded.

Factors predicting clinical outcome 12 and 36 months after an exercise intervention for recurrent low-back pain

Purpose: The aim of this cohort study was to identify early predictive factors for a poor outcome of disability and pain 12- and 36-months after an intervention in patients with recurrent low-back pain, currently at work. Method: Seventy-one patients with recurrent low-back pain, all at work, seeking care in a primary health care setting were included. Predictive indicators including demographic data and health-related variables were derived from questionnaires pre- and post intervention over eight weeks. The dependent outcome variables were perceived disability and present pain at 12- and 36-months. Results: Multivariate regression analyses show that early data on poor self-efficacy for physical activity, greater disability, and higher level of pain-ratings emerged as independent predictors of a poor outcome of disability at 12 and 36 months. Higher ratings of pain and poor self-efficacy appeared again as independent predictors of a poor outcome of pain at the 12-month follow-up. Pain frequency ratings predicted a poor outcome of pain at 36 months. Conclusions: Our results suggest that ratings of poor self-efficacy for physical activity, greater disability, and pain-ratings, are the most consistent independent predictors of long-term poor outcome of disability and pain. This indicates the importance of screening for such factors to optimize the management of low-back pain. However, larger studies in similar patient populations are needed to confirm these results. Implications for Rehabilitation Patients ratings of self-efficacy for physical activities, disability and pain predict long-term poor outcome of perceived disability and pain in subjects with recurrent low-back pain. Prognostic information about self-efficacy for physical activity may be used to tailor intervention to prevent future disablement resulting from further episodes of recurrent low-back pain. It is important to implement knowledge of predictive factors in the clinical work.