Malcolm H. Pope

A survey was done on 1221 men between the ages of eighteen and fifty-five years who had been seen in a family-practice facility between 1975 and 1978 Each patient completed a questionnaire concerning any history of low-back pain, associated symptoms in the lower limbs, resultant disability, types of health care utilized, certain occupational characteristics, exposure to vehicular vibration, and sports activities. We found that 368 patients (30. 1 per cent) had never experienced low-back pain, 565 (46.3 per cent) had or were having moderate low-back pain, and 288 (23.6 percent) had or were having severe low-back pain. Patients with severe low-back pain had significantly more complaints in the lower limbs, sought more medical care and treatment for the low-back pain, and had lost more time from work for this reason. Risk factors associated with severe low-back pain included jobs requiring repetitive heavy lifting, the use of jackhammers or machine tools, and the operation of motor vehicles. Patients with severe pain were more likely to be cigarette-smokers and had a greater tobacco consumption as measured by both the number of cigarettes smoked per day and the number of years of exposure. Patients with moderate low-back pain were more often joggers and cross-country skiers when compared with the asymptomatic men and the men with severe low back pain. Otherwise, there were no identifiable differences related to sports activity.

The objectives of this study were to measure strain in the ACL during simulated: hamstring activity alone, quadriceps activity alone, and simultaneous quadriceps and hamstring activity. Seven knee specimens removed from cadavers were studied. Heavy sutures applied to load cells were attached to the hamstring and quadriceps tendons. Loads were then applied manually (hamstrings) and/or with an Instron testing machine (quadriceps) to simulate isometric contractions of the various muscle groups. Strain was measured using a Hall effect transducer. Acting alone, the isometric hamstring activity decreased ACL strain relative to the passive normal strain at all positions tested. Thus, hamstring exercises are not detrimental to ACL repairs or reconstruction and can be included early in the rehabilitation program after ACL surgery. Acting alone, at flexion angles of 0 degree to 45 degrees, the quadriceps significantly increased the strain within the ACL relative to the passive normal strain. Strain in the ACL during simultaneous hamstring and quadriceps activity was significantly higher than that during passive normal motion from full extension to 30 degrees of flexion. The hamstrings are not capable of masking the potentially harmful effects of simultaneous quadriceps contraction on freshly repaired or reconstructed ACLs unless the knee flexion angle exceeds 30 degrees.

The records of 3920 patients (2068 females, 1852 males) entering a model family practice unit between 1975 and 1978 have been analyzed. Eleven percent of males and 9.5% of females reported an episode of low-back pain during that 3-year interval. The complaint of medically reported low-back pain was significantly related to occupational factors such as truck driving (p < 0.001), lifting, carrying, pulling, pushing, and twisting (P < 0.001 for all variables) as well as nondriving vibrational exposure (P < 0.001). Patients reporting low-back pain also reported more episodes of anxiety (P < 0.001) and depression (P < 0.001) and had more emotionally stressful occupations (P < 0.001). The mean number of pregnancies was greater in women with low-back pain (2.6) than in those without (1.6) (P < 0.001). The low-back pain sufferers were more likely to be cigarette smokers (P < 0.001), particularly when smoking was accompanied by a chronic cough (P < 0.001). This population is currently under prospective study to define the relevance of each of these risk factors to the complaint of low-back pain.

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 reconstructed ACL when the knee was flexed beyond 60 degrees, but significantly strained the tissue from 0 to 45 degrees of knee flexion. Immobilization may not protect the ACL if isometric quadriceps contractions are allowed to occur. Properly placed reconstructions exhibited strain behavior which closely followed the anteromedial band of the ACL.

Before studying the biomechanical effects of rehabilitation exercises on the reconstructed knee, it is important to understand their effects on the normal anterior cruciate ligament. The objective of this investigation was to measure the strain behavior of this ligament during rehabilitation activities in vivo. Participants were patient volunteers with normal anterior cruciate ligaments instrumented with the Hall effect transducer. At 10 degrees and 20 degrees of flexion, ligament strain values for active extension of the knee with a weight of 45 N applied to a subject's lower leg were significantly greater than active motion without the weight. Isometric quadriceps muscle contraction at 15 degrees and 30 degrees also produced a significant increase in ligament strain, while at 60 degrees and 90 degrees of knee flexion there was no change in ligament strain relative to relaxed muscle condition. Simultaneous quadriceps and hamstrings muscles contraction at 15 degrees produced a significant increase in ligament strain compared with the relaxed state but did not strain the ligament at 30 degrees, 60 degrees, and 90 degrees of flexion. Isometric contraction of hamstrings muscles did not produce change in ligament strain at any flexion angle. Exercises that produce low or unstrained ligament values, and would not endanger a properly implanted graft, are either dominated by the hamstrings muscle (isometric hamstring), involve quadriceps muscle activity with the knee flexed at 60 degrees or greater (isometric quadriceps, simultaneous quadriceps and hamstrings contraction), or involve active knee motion between 35 degrees and 90 degrees of flexion.