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Forces at the knee-joint
Volume 2 Number I
ABSTRACTS
Bacteria in Suction Machines Some apparatus draws what may be septic discharge into a chamber in which the inlet tube ends some way above the contained disinfectant in order to prevent bubbling and frothing. In these conditions a contaminated aerosol can form above the disinfectant and be drawn out to contaminate first the pump and then the environment. The apparatus was found to be sterile after it had sucked air through 1 litre of formaldehyde for 1 hour and then been cleared by drawing air through it for another 2 hours. Contamination can be prevented by placing a cotton-wool filter between the aspiration chamber and the pump. REES, T. A. (1970), ' Bacteria in Suction Machines ', Lancet, 1,240. Penicillin Penicillin remains the most effective antibiotic available against several micro-organisms; it is nontoxic, easily administered, and inexpensive. Between 5 and 10 per cent of patients treated with penicillin develop sensitivity to the drug. ErnTORIAL (1969), ~Penicillin ', J. Am. reed. Ass., 209, 1520. PATHOLOGY AND EXPERIMENTAL WORK
Forces at the Knee-joint Forces at the knee in ordinary walking rise to about three times body-weight, a large part being taken by the medial condyles. Muscle contraction force rises to 4001b. The collateral and cruciate ligaments variously sustain forces of 14-74 lb., the posterior cruciate being the one taking the largest force. MORRmON, J. B. (1970), ' T h e Mechanics of the Knee Joint in Relation to Normal Walking', J. Biomech., 3, 51. Double-contrast Arthrography of the Knee This technique of arthrography is preferred to the conventional contrast techniques because better delineation of the menisci and articular cartilages may be obtained. All the patients were examined under television fluoroscopic control with spot-filming of the menisci in various projections. This requires a small focus under-couch tube with a low kV. technique. This enables the entire meniscus to be visualized and the resilience to be assessed under manipulation. Tears, degeneration, and cysts of the meniscus may be shown with fractures, erosion, or osteocbondritis dissecans from the articular cartilage. Collateral and cruciate ligament tears, villosynovitis, cysts, and tears of the synovium may also be shown. A breakdown of the age-distribution of the arthrograms showed that peripheral separations and undisplaced vertical tears occur in younger patients, that buckethandle tears and flap tears are generally distributed throughout the age-range and that meniscus degeneration, maceration, and articular erosion occur at later ages, and that patellar chondromalacia is a disease of older persons. Ten per cent of all meniscus tears were associated with a tear of the other meniscus in the same knee and this was often clinically unrecognized. Baker's cysts occurred in 10 per cent of patients with tears of the menisci, particularly in those with peripheral separation of the posterior horn of the
81
medial meniscus. In a series of 142 verified diagnoses of meniscus lesions there was 1 false positive in which a fracture of the articular cartilage with a detached fragment was misdiagnosed as a flap tear of the medial meniscus. There were 4 false negative meniscus diagnoses in which even on retrospective examination a lesion was not evident. Arthrography was not found to be particularly reliable in demonstrating articular cartilage erosion and fracture and tears of the anterior cruciate ligament. The latter can be diagnosed with some confidence, however, if instead of appearing as a taut strut it is lax both on anterior traction of the tibia and with the knee in full extension. It was found that a combined injection of air and carbon dioxide allowed the patient to return home without swelling of the knee or significant after-effects. Boa-r, W. P., and MCINTYRE,J. L. (1969), ' Double Contrast Arthrography of the Knee ', Radiology, 92, 487.
Direct Motor Nerve Implantation This is an interesting account of a successful direct implantation of a motor branch of the ulnar nerve to the denervated flexor carpi radialis muscle in the dog, with the formation of new motor end-plates. Quantitative comparisons of the muscle by measuring the four muscle parameters--volume, myoneural delay, rate of contraction, and greatest developed tension--showed that direct implantation of a new motor nerve restored denervated muscle volume in 20 weeks, and at least 50 per cent of its original strength was recovered. The length of time a muscle can be left deprived of nerve-supply and yet recover after nerve implantation is yet to be determined. The authors suggest that clinical application for direct nerve implantation should await further experiments which will be repeated in the monkey, but if these show an equal response to direct implantation the technique may have advantages over the tendon transfer or direct end-to-end suture. SORBIE, C., and PORTER, P. T. L. (1969), ' Reinnerration of Paralysed Muscles by Direct Motor Nerve Implantation ', J. Bone .It Surg., 51B, 156. The Mast Cell in Callus This paper is a study of the role of the mast cell in callus formation of healing fractures. Histological samples were taken from the periosteal callus of 400 fractures in adult white rats, using Holmgren's toluidine blue staining technique. Counts were made with a light microscope and high-power fields were screened systematically. A progressive increase in the mast-cell count in fibrous parts of the periosteal callus continued until the thirteenth day, after which there was a progressive decrease. Cortisone, BAPN intoxication (lathyrism), peripheral denervation, and radiation sickness were found to be features inhibiting bone formation. Following the administration of a combination of growth hormone and thyrotropin known to be the most active accelerator of the healing process, the mast cell appeared considerably earlier, but the administration of androgens and oestrogens was not associated with appreciable alteration in the count. This experience suggests that mast cells are far more numerous in cases of delayed healing and the disturbance of the process of mineralization of the callus.
ABSTRACTS
Bacteria in Suction Machines Some apparatus draws what may be septic discharge into a chamber in which the inlet tube ends some way above the contained disinfectant in order to prevent bubbling and frothing. In these conditions a contaminated aerosol can form above the disinfectant and be drawn out to contaminate first the pump and then the environment. The apparatus was found to be sterile after it had sucked air through 1 litre of formaldehyde for 1 hour and then been cleared by drawing air through it for another 2 hours. Contamination can be prevented by placing a cotton-wool filter between the aspiration chamber and the pump. REES, T. A. (1970), ' Bacteria in Suction Machines ', Lancet, 1,240. Penicillin Penicillin remains the most effective antibiotic available against several micro-organisms; it is nontoxic, easily administered, and inexpensive. Between 5 and 10 per cent of patients treated with penicillin develop sensitivity to the drug. ErnTORIAL (1969), ~Penicillin ', J. Am. reed. Ass., 209, 1520. PATHOLOGY AND EXPERIMENTAL WORK
Forces at the Knee-joint Forces at the knee in ordinary walking rise to about three times body-weight, a large part being taken by the medial condyles. Muscle contraction force rises to 4001b. The collateral and cruciate ligaments variously sustain forces of 14-74 lb., the posterior cruciate being the one taking the largest force. MORRmON, J. B. (1970), ' T h e Mechanics of the Knee Joint in Relation to Normal Walking', J. Biomech., 3, 51. Double-contrast Arthrography of the Knee This technique of arthrography is preferred to the conventional contrast techniques because better delineation of the menisci and articular cartilages may be obtained. All the patients were examined under television fluoroscopic control with spot-filming of the menisci in various projections. This requires a small focus under-couch tube with a low kV. technique. This enables the entire meniscus to be visualized and the resilience to be assessed under manipulation. Tears, degeneration, and cysts of the meniscus may be shown with fractures, erosion, or osteocbondritis dissecans from the articular cartilage. Collateral and cruciate ligament tears, villosynovitis, cysts, and tears of the synovium may also be shown. A breakdown of the age-distribution of the arthrograms showed that peripheral separations and undisplaced vertical tears occur in younger patients, that buckethandle tears and flap tears are generally distributed throughout the age-range and that meniscus degeneration, maceration, and articular erosion occur at later ages, and that patellar chondromalacia is a disease of older persons. Ten per cent of all meniscus tears were associated with a tear of the other meniscus in the same knee and this was often clinically unrecognized. Baker's cysts occurred in 10 per cent of patients with tears of the menisci, particularly in those with peripheral separation of the posterior horn of the
81
medial meniscus. In a series of 142 verified diagnoses of meniscus lesions there was 1 false positive in which a fracture of the articular cartilage with a detached fragment was misdiagnosed as a flap tear of the medial meniscus. There were 4 false negative meniscus diagnoses in which even on retrospective examination a lesion was not evident. Arthrography was not found to be particularly reliable in demonstrating articular cartilage erosion and fracture and tears of the anterior cruciate ligament. The latter can be diagnosed with some confidence, however, if instead of appearing as a taut strut it is lax both on anterior traction of the tibia and with the knee in full extension. It was found that a combined injection of air and carbon dioxide allowed the patient to return home without swelling of the knee or significant after-effects. Boa-r, W. P., and MCINTYRE,J. L. (1969), ' Double Contrast Arthrography of the Knee ', Radiology, 92, 487.
Direct Motor Nerve Implantation This is an interesting account of a successful direct implantation of a motor branch of the ulnar nerve to the denervated flexor carpi radialis muscle in the dog, with the formation of new motor end-plates. Quantitative comparisons of the muscle by measuring the four muscle parameters--volume, myoneural delay, rate of contraction, and greatest developed tension--showed that direct implantation of a new motor nerve restored denervated muscle volume in 20 weeks, and at least 50 per cent of its original strength was recovered. The length of time a muscle can be left deprived of nerve-supply and yet recover after nerve implantation is yet to be determined. The authors suggest that clinical application for direct nerve implantation should await further experiments which will be repeated in the monkey, but if these show an equal response to direct implantation the technique may have advantages over the tendon transfer or direct end-to-end suture. SORBIE, C., and PORTER, P. T. L. (1969), ' Reinnerration of Paralysed Muscles by Direct Motor Nerve Implantation ', J. Bone .It Surg., 51B, 156. The Mast Cell in Callus This paper is a study of the role of the mast cell in callus formation of healing fractures. Histological samples were taken from the periosteal callus of 400 fractures in adult white rats, using Holmgren's toluidine blue staining technique. Counts were made with a light microscope and high-power fields were screened systematically. A progressive increase in the mast-cell count in fibrous parts of the periosteal callus continued until the thirteenth day, after which there was a progressive decrease. Cortisone, BAPN intoxication (lathyrism), peripheral denervation, and radiation sickness were found to be features inhibiting bone formation. Following the administration of a combination of growth hormone and thyrotropin known to be the most active accelerator of the healing process, the mast cell appeared considerably earlier, but the administration of androgens and oestrogens was not associated with appreciable alteration in the count. This experience suggests that mast cells are far more numerous in cases of delayed healing and the disturbance of the process of mineralization of the callus.