The effect of medial collateral ligament repair tension on elbow joint kinematics and stability.

PURPOSE: Medial collateral ligament (MCL) repair is commonly performed for the management of acute or subacute instability after elbow dislocations and fracture-dislocations. The effectiveness of transosseous repair of the MCL, as is typically performed clinically, in restoring the normal kinematics and stability of the elbow is of interest as is the effect of MCL tensioning on the initial stability of the elbow. The purpose of this study was to determine whether suture repair of the MCL is able to restore the normal kinematics and stability of the elbow and to determine the optimal initial MCL repair tension. METHODS: Six cadaveric upper extremities were mounted in an upper limb joint simulator. Simulated active and passive elbow flexion was generated while the kinematics were measured with the arm in the dependent and the valgus gravity-loaded orientations. After testing the intact elbow, the MCL was released at its humeral attachment and repaired using a transosseous suture technique at three different repair tensions: 20, 40, and 60 N. RESULTS: Medial collateral ligament repair using a transosseous suture technique restored the kinematics and stability of the MCL-deficient elbow. Motion pathways were affected by the magnitude of initial MCL tension. For all arm orientations and forearm positions, the 20-N and 40-N repairs were not statistically different from each other or from the intact MCL. The 60-N repairs, however, were often statistically different than the other groups, suggesting an overtightening that tended to pull the ulna into a varus position-especially in the midrange of flexion. CONCLUSIONS: These data suggest that MCL repair using transosseous sutures provide adequate joint stability to permit early motion. There is a broad range of acceptable tensions for MCL repair, which is a favorable, clinically relevant finding. Clinical studies are needed to validate these in vitro results.

Design for a constant peak current defibrillator.

A damped sine wave defibrillator that is capable of delivering a constant peak discharge current over a wide range of patient thoracic impedance is shown to be theoretically possible. This is realized in practice by the technique of storing an amount of energy above that required for delivery, and dumping the excess charge when the discharge current has reached a predetermined level, the dumping being triggered by a current sensor. A larger than normal inductance assists in swamping the effect of varying impedance and produces a smooth waveform. The preselected peak current can be delivered with a variation of about +/- 6% to 95% of a normal patient population. The energy expended in a simulated patient circuit is somewhat lower than for conventional defibrillators.

Fatty acids in the milk of goats after cessation of lactation.

Regular hand milking of six goats was discontinued after 32-35 weeks of lactation. A few days after milking out ceased, the concentration of triglyceride in peripheral blood plasma increased. Over a period of weeks, the concentration of triglyceride in small samples of fluid taken from the teat canal fell gradually. Lipase activity of the milk fluid was temporarily reduced shortly after milking out ended, but, despite this, its concentration of free fatty acids increased. It is suggested that free fatty acids are released during clearance of milk triglyceride from residual fluid in the mammary gland after cessation of lactation.

Prepartum milking and the onset of secretion of milk fat in the goat.

Late-pregnant goats were separated into two groups. A control group of four goats had small (approximately 3 ml) volumes of secretion expelled from one mammary gland at infrequent intervals between day 130 of gestation and parturition. An experimental group of five goats had as much secretion as possible removed from both glands twice daily beginning on day 137 of gestation and continuing until parturition. After parturition, both groups were milked twice daily. Regular 'milking out' before parturition stimulated secretion of triglyceride by the mammary gland, and most of the fatty acids secreted in the triglyceride before parturition had a chain length of 18 carbons. Secretion of 6-14-carbon chain-length fatty acids in the milk triglycerides increased after parturition. There was no evidence that the onset of secretion of medium-chain and long-chain fatty acids occurred at different times in the control animals. It is concluded that the onset of secretion of medium-chain and long-chain fatty acids in milk triglycerides can be dissociated, although both are normally synchronized with parturition. Removal of secretion by the offspring at parturition may be a stimulus for the onset of secretion of long-chain fatty acids, but the onset of secretion of medium-chain fatty acids is brought about by some other mechanism.