Biomedical subjects
Publications and source records attributed to M Merle.
Scapholunate dissociation is well documented as a condition occurring in adult patients. We report it in a 14-year-old female patient. Persistent wrist pain 9 months after a well healed fracture of the distal radius triggered further investigation. Dynamic clinical and radiological studies demonstrated the instability.
Wrist arthroscopy performed on 78 patients showed 35 lunates of Type I (44.9%) i.e., having only one facet on their distal (midcarpal) aspect, and 43 lunates of Type II (55.1%), i.e., having two facets on this aspect. Chondral defects and/or arthritic lesions of the ulnar portion of the midcarpal joints were observed in 22.8% of Type I lunates and in 30.2% of Type II lunates. Chondral lesions of the midcarpal joints in Type I lunates were always associated with other ligamentous and/or osteochondral lesions, whereas the same lesions could be found isolated in Type II lunates. The observed association of lesions seemed to point to a trauma as the cause of some chondral lesions. The results of our clinical study were compared with anatomical studies by Viegas, all which showed no hamate pathologic conditions in Type I lunates.
The maximum longitudinal tension that can be applied to the stumps of a divided peripheral nerve during surgical repair is not precisely defined. Uncertainty about the threshold of unacceptable nerve tension may be due to the lack of studies on isolated and reproducible stretch, i.e., on quantified elongation without concomitant compression, crush, or transection. The authors devised a simple method for producing isolated, long-term static loading of the nerve in vivo without concomitant compression, crush, or transection. Tension was applied to intact and crushed sciatic nerves in the rat, stretching them by 15 or 30 percent of their initial length, and the corresponding functional consequences were evaluated. Results showed that no measurable functional deficit resulted from stretching a segment of intact nerve to a length 30 percent greater than its initial length. In contrast, a significant delay in functional recovery resulted from stretching a crushed nerve by the same amount. A practical conclusion may be that the site of application of stretch forces during surgical repair, i.e., the location of coapting stitches, could play an important role in clinical practice.
Technical advances in revascularization and in skin cover have resulted in increases in the possibilities of digital replantation. In cases of multiple digital lesions and isolated avulsions of the thumb, all attempts to ensure recovery of basic pinch capacity are justified. On the other hand, in cases of proximal amputations with extensive avulsion or crush injury such attempts should be abandoned if results on function are important. Primary and secondary surgery must confront two difficult problems namely, repair of the avulsed flexor tendons and resensibilization. But in the field of replantation one should not be too dogmatic because for cosmetic reasons, some patients may find even a stiff or insensitive finger satisfactory. Distal and very distal replantations yield the best results in all fields. This information should be brought to the attention of all trauma teams that tend to consider such replantations useless. These replantations are both rapid and simple, requiring only mastery of suturing vessels 0.5 mm in diameter. The surgeon responsible for replantation should weigh the indications after assessing the patient's needs and explaining the advantages and drawbacks of this type of surgery and its results on function.
A mathematical model of the citric acid cycle devoted to the analysis of 13C-NMR data was developed for determining the relative flux of molecules through the anaplerotic versus oxidative pathways and the relative pyruvate carboxylase versus pyruvate dehydrogenase activities. Different variants of the model were considered depending on the reversibility of the conversion of fumarate into malate and oxaloacetate. The model also included the possibility of orientation-conserved transfer of the four-carbon citric acid cycle intermediates, leading to conversion of succinyl-CoA C1 into either malate C1 or C4. It was used to analyse NMR data from glutamine isotopomers produced by cerebellar astrocytes incubated with [1-13C]glucose. Partial cycling (39%) between oxaloacetate and fumarate was evident from the analysis. Application of the model to glutamate isotopomers from granule cells incubated with [1-13C]glucose [Martin, M.. Portais, J.C.. Labouesse. J., Canioni. P, & Merle, M. (1993) Eur. J. Biochem. 217, 617-625] indicated that total cycling of oxaloacetate into fumarate was, in this case, required to get the best fit. The results emphasized some important differences in carbon metabolism between cerebellar astrocytes and granule cells concerning the sources of carbon fuelling the citric acid cycle and the carbon fluxes on different pathways.
The question as to whether glutamine and glucose are both required for optimal growth of glioma cells is studied through the role of these substrates on the metabolism of the cells. C6 rat glioma cells grow only very slowly when glutamine is omitted from the culture medium. The rates of glucose consumption and lactate production on confluent cells in glutamine-free medium were 0.88 +/- 0.09 and 1.06 +/- 0.25 mumol/h/mg protein, respectively. In the presence of 4 mM glutamine, glucose utilization increase to 60% leading to a 45% increase of lactate production. We have studied the kinetics of enrichment of intracellular glutamate at C2, C3 and C4 positions on cells incubated with 5 mM 99% enriched [1-(13)C]glucose in the presence or the absence of glutamine in the incubation medium. The specific enrichments at metabolic steady state of all carbon positions were the same under both conditions, but we observed a significantly reduced rate of 13C incorporation in the presence of glutamine, showing an isotopic dilution of tricarboxylic acid cycle intermediates and indicating the use of this amino acid as an anaplerotic substrate. The fact that no dilution occurred at the level of pyruvate suggests strongly the lack of glutaminolysis in these cells. The main conclusion from this work is that glutamine metabolism in C6 cells appears complementary to that of glucose as far as energy production and carbon sources for the growing of the cells are concerned: glutamine is mainly utilized for anaplerosis as carbon donor to replenish the tricarboxylic acid cycle; it is not a substrate for energy metabolism. In contrast, glucose is poorly anaplerotic and is essentially used as energetic fuel by the C6 cells.
The arterial system of the palmar subcutaneous fatty tissue of fingers was studied by injecting a coloured silicone polymer into the vessels of 12 fresh human cadaver hands. Arterial vascularisation of these tissues is ensured by small palmar branches arising from the main digital arteries: there were an average of 7 branches on each side varying between 4 and 12 in the specimens studied. Three anatomical patterns could be distinguished: an I-shaped configuration in 64% of cases, a narrow V-shape in 23%, and a Y-shape in 13%. An accompanying venous network was always present and drained into either the superficial or deep venous network. These anatomical findings confirm the vascular reliability of the homodigital subcutaneous flap described by the authors.
We analyzed the glutamine isotopomers released into the extracellular medium by cerebellar astrocytes incubated with [1-13C]glucose. We developed a mathematical model of the tricarboxylic acid (TCA) cycle to determine the relative flux of molecules through the anaplerotic versus oxidative pathways and the relative pyruvate carboxylase versus pyruvate dehydrogenase activities. As glutamine C2 and C3 exhibited unequivalent enrichments, we examined the possibility of: (1) both the entry of the label into the TCA cycle from pyruvate and the conversion of the oxaloacetate into citrate before equilibration with fumarate, and (2) the occurrence of an orientation-conserved transfer of the symmetrical 4-carbon intermediates. The best fit required partial cycling between oxaloacetate and fumarate, whereas the occurrence of any orientation-conserved transfer was rejected. On the other hand, the analysis of glutamate isotopomers from perchloric acid extracts of granule cells incubated with [1-13C]glucose indicated that total cycling of oxaloacetate into fumarate occurred in these cells.
The loss of a thumb is traumatic on the functional, cosmetic and psychological level. If immediate replantation cannot be successfully accomplished, the surgeon must plan to treat the patient within the first days or, at the latest, within the first weeks following the injury. If the patient is left to "mourn" his lost thumb, he will find it difficult to incorporate his new thumb into his body image and this will compromise the results of a late reconstruction. There is a vast range of therapeutic options, even for cases of severe injury. The most classic treatments include lengthening the first metacarpal, osteoplasty, pollicization of long fingers or stump. These techniques were very common up until the late 1970's at which time microsurgical techniques of partial or total toe transfer became popular. For a short time, there was some opposition between proponents of classic techniques and microsurgeons. In fact, there was a role for each method and classic and microsurgical techniques became complementary. Since 1976, we have performed 196 thumb reconstructions in our department; it is interesting to note that classic techniques were used in 14.1% of cases and microsurgical techniques in 85.7% of cases. Very early on, we decided against the use of the big toe because of the resulting plantar sequelae and preferred use of the second toe (50% of cases). Our experience with the reliability of dissection of big toes has led us to prefer partial toe transfer especially the wrap-around technique of Morrison. The failure rate for microsurgical transfer is 3.6%.
Dorsal skin defects of proximal interphalangeal joint (PIP) of fingers are a common situation in hand surgery. Skin grafting is contraindicated in the absence of extensor peritendon. The choice of flap depends on the site and surface area of the skin defect and the injuries of adjacent digits. Homodigital flaps, such as Smith's sliding flap, advancement-rotation or advancement-recession flaps and dorsal V-Y advancement flap, are the first choices for small defects. In case of larger dorsal skin defects, flaps must be raised on the dorsal aspect of the hand, such as reverse dorsal metacarpal flaps, distally based dorsal hand flaps and dorsocommisural flaps. Cross-finger flaps are only used when the previous options are not feasible. Descriptions of the dorsal vascular network have led to the loss of indications for venous flaps, with the exception of the Tsai's venous free flap. In case of multidigital dorsal skin defect, flaps, such as radial forearm flap, pediculed groin flap or free lateral arm flap, used for temporary syndactylisation of the fingers.
Rat cerebellar and cortical astrocytes cultured for 15 or 35 days were incubated with [1-13C]glucose in the presence or absence of 4 mM exogenous glutamine and the release of 13C-enriched metabolites into cell media was studied by 13C-NMR spectroscopy. In the presence of exogenous glutamine, both cerebellar and cortical astrocytes consumed the amino acid. In contrast, a net production of glutamine occurred in the absence of the amino acid. Simultaneously, a release of 13C-enriched glutamine into cell media was observed and was higher in the presence than in the absence of exogenous glutamine. This demonstrated the occurrence of an isotopic-exchange process which may involve a futile cycle at the level of glutamine synthetase and glutaminase activities. The 13C-enrichment ratio between glutamine carbons C2 and C3 was close to 1 in the presence of exogenous glutamine whereas it was higher than 1 in its absence, indicating that pyruvate carboxylase was more active in the absence of glutamine. In addition to glutamine, alanine was synthesized and exported into the medium of both cerebellar and cortical astrocytes. In contrast, citrate was specifically produced by cortical astrocytes. Slight increases in alanine and glutamine productions were observed for cortical astrocyte cultures between 15 and 35 days, whereas the amino acid production by cerebellar astrocytes increased several-fold after 35 days compared with that at 15 days of culture.
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A method of surgical correction is described for Wartenberg's sign, or persistent abduction of the little finger, using a slip of the extensor digitorum communis of the ring finger. The transferred component can be either the central slip, or the ulnar slip extended by the connexus intertendineus to the little finger. This technique maintains the integrity of the extensor mechanism of the little finger, avoiding loss of active extension, which is frequently observed when extensor digiti minimi is used. The donor site is dependable since the extensor digitorum communis tendon of the ring finger is always composed of several slips. This technique should be considered only in cases of isolated persistent abduction of the little finger, when there is no claw deformity.
We report results on the use of bioabsorbable pins and intramedullary rods made of high-molecular-weight polylactic acid in both experimental and clinical conditions. In the experimental study, bioabsorbable rods were implanted in rabbit femora. Histologic assessment on nondecalcified bone showed that resorption of the material began at 4 months after implantation and gradually fragmented over a period of 3 years. In 12 patients 13 metacarpophalangeal joints of the thumb were arthrodesed by using one bioabsorbable intramedullary rod with one or two oblique pins. All joints fused within 6 to 8 weeks. During that period there was no sign of inflammation, and there were no nonunions. Postoperative magnetic resonance imaging assessment was done in all rabbits and eight patients. This modality is a useful tool in postoperative evaluation of the position and shape of the rod but is not sufficiently sensitive to assess the presence of local inflammation and the rate of resorption of the rods.
The authors propose the use of the metallic trocar used for venous catheter introduction as a pin guide and protector. These trocars are available in several internal diameters, allowing the use of 8/10 mm to 15/10 mm Kirschner pins. This technique has the following advantages: easy guiding of the pins and protection of subcutaneous neurovascular structures. The disadvantages are related to overheating and its consequences due to metal-on-metal friction.
The stumps of divided rat sciatic nerves were coapted by suturing the epineurium to a small rectangular device made of a sheet of polylactic acid. One month later, significant degradation of the implanted material was observed. At that time, the local condition of the nerve was excellent, and the precise location of the initial injury could not be determined by examination under the operating microscope. Histology confirmed that there was no visible reaction to the biodegradable substance or its metabolites, and that neurotization of the distal stump was satisfactory. These findings were in agreement with those of other studies, and indicated that polylactic-acid devices affixed to divided nerves have no adverse effect on regeneration.
PURPOSE OF THE STUDY: The authors present 13 cases of delayed or non-union of the distal phalanx of the long fingers treated surgically. MATERIAL AND METHODS: The patients were all men aged from 41 years to 60 years. The involved digits were 4 second, 2 long, 5 ring, and 2 little fingers. The operated side was the right side 5 times, the left one 8 times, the dominant one 4 times. Ten cases were due to inadequate treatment of the initial fracture. The three others cases had no clear explanation. Three types of incisions were used: transverse distal, lateral or an extended one combining the two previous. Bone stabilisation was made either, by longitudinal K wires or with a small cancellous screw. In 7 cases, bone grafting was needed. RESULTS: Bone healing was obtained in 9 cases in an average time of 9 weeks. Further procedures included: 2 distal amputations after septic conditions, 2 removals of distal bone fragment and 2 fusions of the distal interphalangeal joint. Overall results evaluated by the patients themselves were fair, including 2 excellent, 6 good (but 2 after distal interphalangeal joint arthrodesis), 2 mild (1 after distal interphalangeal joint arthrodesis), 1 poor and 2 failures. DISCUSSION: The type of skin incision was chosen according to the bone condition; distal in cases of fibrous nonunion when fibrous tissue removal and bone grafting were needed. Neither the type of bone stabilisation (pinning or screwing) nor the donor site of bone grafting influenced the final result. CONCLUSION: The authors would like to stress the importance of an adequate treatment of finger injuries in a emergency situation, considering the difficulties to restore secondarily a satisfactory functional outcome.