Ankle injuries in the young athlete.

Ankle injuries in the young athlete are quite different from those of an adult. Because the epiphyseal plates of the distal tibia and fibula are significantly weaker than surrounding ligaments, failure on stress occurs through the growth plates rather than through soft tissue. Growth-plate injuries can assume a distinct pattern based on the maturity of the physis. Leg length inequality and angular deformity are potential sequelae from significant injury to the ankle in the skeletally immature but, fortunately, occur infrequently. Soft-tissue injuries about the ankle are rare, but with advanced, rigorous training techniques a new pattern of overuse injuries appears to be emerging.

Effect of optimization of hemodynamics on fibrinolytic activity and antithrombotic efficacy of external pneumatic calf compression.

External pneumatic calf compression is effective but imperfect for antithrombotic prophylaxis in surgical patients. In preliminary studies, sequential filling of multisegmented leggings with graded pressure decreasing from ankle to knee increased venous flow velocity and wall shear stress, decreased residual venous volume, and enhanced postoperative fibrinolysis more than uniform compression. To determine if improved hemodynamics also increased antithrombotic activity, we performed a prospective randomized trial in neurosurgical patients comparing sequential application of graded pressure with uniform pressure applied to either a segmented bladder or to a single bladder. Deep vein thrombosis was diagnosed by leg scanning and impedance plethysmography and confirmed by phlebography. Venous thrombosis developed in 3 of 45 patients with graded-sequential filling, 6 of 50 with uniform compression-multiple compartments, and 3 of 41 with uniform pressure single bladder (differences not significant). These results suggest either that uniform compression offers all that can be expected of external pneumatic calf compression in prevention of venous thrombosis, or that even if a study with greater statistical power showed graded-sequential filling to be superior, the benefit/cost ratio of the more complex latter system is not likely to be large.

Crosslinked polyether/polysiloxane networks for blood-interfacing applications.

The interaction of blood with new artificial surfaces is an area of continual medical interest. In this study, a series of polyether/polysiloxane networks were synthesized, characterized in terms of both bulk and surface compositions, and evaluated for blood compatibility. The crosslinked networks were produced by reacting the epoxy groups of polyglycidoxy propyl methyl siloxane (PGPMS) with the hydroxyl end groups of polypropylene glycol (PPG). Blood compatibility was evaluated using an in vitro platelet retention test and fibrinogen adsorption experiments from human plasma and buffered saline. The PPG/PGPMS networks exhibit low fibrinogen adsorption and low platelet activation. Such properties make the networks potentially attractive as materials for blood-interfacing applications.

Does the conformation of adsorbed fibrinogen dictate platelet interactions with artificial surfaces?

Platelet activation by polymer surfaces is thought to require preliminary adsorption of fibrinogen and perhaps changes in fibrinogen conformation. We measured fibrinogen adsorption by a series of polymers by two methods, using either 125I-labeled fibrinogen or 125I-labeled antifibrinogen antibodies, and correlated the results with platelet reactivity (retention and secretion) in columns of beads coated with the polymers. For polyalkyl methacrylates with 1 to 4 carbon side chains, platelet reactivity varied directly with increasing length of the alkyl side chain and with the quantity of bound fibrinogen recognizable by antifibrinogen antibody but not with the total quantity of fibrinogen adsorbed. The same pattern of results was seen with five antibody preparations, including affinity-purified Fab fragments against the D or E domain of fibrinogen. Tests of platelet retention and fibrinogen binding to four polyalkyl acrylates and to three unrelated polymers (polystyrene, polymethyl methacrylate, and a polyether polyurethane) indicated that platelet retention correlated positively with both total fibrinogen binding and with the amount of antibody-recognizable fibrinogen bound. Drugs that block platelet aggregation, but not adhesion, did not alter the hierarchy of platelet retention to the polyalkyl methacrylates. These data suggest that, contrary to previous views, platelet adhesion to artificial surfaces increases with increasing surface coverage of adsorbed fibrinogen if the bound fibrinogen maintains a conformation such that its functional domains remain recognizable by antibody probes.

Platelet aggregation by fibrinogen polymers crosslinked across the E domain.

There is evidence that platelet interactions with artificial surfaces are mediated by plasma proteins, especially fibrinogen, adsorbed on the surfaces. Multiple site interactions between fibrinogen molecules adsorbed in high concentration and receptors in the unactivated platelet may be sufficient for platelet adhesion and subsequent activation. To examine this hypothesis, we prepared soluble polymers of fibrinogen. Polymers produced by interaction of fibrinogen with Fab'2 fragments of antibodies against fibrinogen's E (central) domain (Fg-Fab'2(E] induced, in gel-filtered platelets, aggregation and serotonin release, which were blocked by monoclonal antibodies against the GPIIb/IIIa complex, by Fab fragments against the D domain, and by metabolic inhibitors; aggregation was attenuated but not abolished by enzymatic removal of ADP (with CP/CPK) or by blockage of ADP binding sites (with FSBA), and when secretion was inhibited by aspirin. Fg-Fab'2(E) also induced a dose-dependent elevation in cytoplasmic Ca2+ (measured by Aequorin luminescence) which was attenuated by CP/CPK and by FSBA, and was eliminated by metabolic inhibitors and by anti-IIb/IIIa antibody. Fibrinogen complexes crosslinked with dimethylsuberimidate or Factor XIII neither aggregated gel-filtered platelets nor inhibited platelet aggregation by ADP and fibrinogen, probably because of inaccessibility of lysine residues in the D (terminal) domain of fibrinogen, which are thought to be required for platelet binding. Thus, soluble complexes of fibrinogen having multiple available platelet receptor recognition sites activate gel-filtered platelets and may provide a useful model for platelet-surface interactions mediated by adsorbed fibrinogen.

The surgical treatment of osteochondritis of the capitellum.

This paper reviews 14 patients who underwent elbow arthrotomy for osteochondritis of the capitellum. The etiology in 7 of the 14 cases appears to be the result of repeated trauma from throwing sports. Five of the 14 described a singular significant traumatic episode, and in 2 of the 14, a clear etiology is uncertain. The diagnostic features including signs, symptoms, and elbow range of motion are examined. The operative findings are correlated with plain x-ray films of the elbow in all cases and with an elbow arthrogram in 11 out of 14 cases. The average length of followup was 24 months. The postoperative range of motion was increased an average of 18 degrees. Eighty-six percent (12 out of 14) patients returned to organized, competitive athletic activity without restrictions. The Little League background of those patients with apparent repetitive microtrauma to the elbow is examined in terms of length of pitching experience and types of pitches thrown. In addition, the throwing mechanism of these patients is evaluated with respect to the type of delivery at possible risk for the development of osteochondritis. We conclude that after a failure of conservative therapy, surgical treatment, including removal of the intraarticular loose bodies, excision of capitellar lesions, and curettage to bleeding bone can be expected to produce pain relief and improvement in joint motion. A return to organized competitive sport activities can be expected.

Dimethylsulfoxide-treated, cryopreserved venous allografts in the arterial and venous systems.

Autologous saphenous vein is the preferred conduit for most vascular reconstructive procedures; however, many authorities have emphasized the need for a reliable alternate. This study was designed to assess the short-term patency of dimethylsulfoxide-treated, cryopreserved saphenous vein allografts in both high- and low-flow states. An early patency rate of 58.3% was found for such allografts interposed in the arterial system. No instance of aneurysm formation was noted. Allografts interposed in the venous system uniformly occluded within 5 weeks. However, in animals treated with aspirin and dipyridamole there was an 83% early patency rate for cryopreserved allografts in the venous system. These studies suggest that dimethylsulfoxide cryopreservation is a viable technique for venous allograft preservation as demonstrated by satisfactory short-term patency of grafts implanted in the arterial system. The results also suggest that treatment with aspirin and dipyridamole has a beneficial effect on the early patency of such grafts placed in the venous system.

Semitendinosus tenodesis for recurrent subluxation or dislocation of the patella.

In 26 knees treated by semitendinosus tenodesis, there was no recurrence of dislocation, but fair and poor results totaled 38% due to persistent pain because of chondromalacia of the patella. Poor results are also more common in the patients with generalized ligamentous laxity. Postoperative complications in wound healing suggest that the medial parapatellar skin incision is less than adequate. Semitendinosus tenodesis with or without modifications is a useful procedure to prevent recurrent dislocations and subluxation during the growth period.