TREPANNING. 



proceeding neccffary, and conceive that, as more of the 

 pericranium mud always be removed than what is abfolutely 

 intended, it may fometimes be tTie caufe of exfohations. 

 We advife it, therefore, to be rcjefted, as well as the old 

 plan of fcraping the periofteum off the bones which are to 

 be fawn in amputations. The rugine, which is kept in moil 

 cafes of trephining inftruments for the purpofe of fcraping 

 off the pericranium, would be no real lofs if omitted. 



Now, on firft beginning to work either with the trephine 

 or trepan, the praftitioner would find that it would flip 

 about and not Iteadily divide the bone, were it not for a 

 particular contrivance. This is the centre-pin, which admits 

 of being pufhed down a little below the level of the teeth, 

 and being very fharply pointed, immediately fixes itfelf in 

 the mid-point of the circle of bone which is to be removed. 

 Asfoon, however, as the teeth of the trephine have made a 

 fufficient furrow, the centre-pin fhould be withdrawn, as it 

 would otherwife wound the dura mater before the fawing 

 of the bone were completed. 



In making the incifion through the fcalp, when there is 

 a frafture, the knife mud be ufed with fome degree of 

 caution, left it fliould deprefs the fragments of bone againft 

 the cerebrum, or be carried too deeply, fo as to injure the 

 dura mater. In certain inftances, it will be advifeable to 

 make the requifite incifion with a direftor and curved 

 biftoury. 



The trephine is worked by being rotated backward and 

 forward ; the trepan is turned round continually in one 

 direftion. In trepanning upon a fimple frafture, or fiffure, 

 the crown of the inftrument (hould be fo placed as to include 

 an equal portion of the bone on each fide. But when there 

 are portions of bone depreffed and moveable, it is cuftomary 

 to apply the trepan upon an adjacent folid part of the 

 cranium, which will ferve after the operation as a fulcrum 

 for the elevation or extraftion of the depreffed fragments. 

 We muft obferve, however, that this method, if praftifed 

 indifcriminately, will often lead to an unneceffary removal 

 of bone ; a circumftance which it is always defirous to 

 avoid. Loofe depreffed pieces of bone (hould conftantly 

 be taken away with a pair of forceps, whenever it can be 

 done ; and then no trepanning will be needed. Alfo, when 

 the frafture is fliaped fomewhat like the letter V, or when 

 it is of an oblong form, the depreffed piece of bone may 

 frequently be entirely removed by fawing through the part 

 which connefts it with the reft of the cranium, and no 

 circle of bone will ftand in need of being fawn out. For 

 the performance of fuch operation, Mr. Hey's faws (repre- 

 fented in the furgical plates) will be found exceedingly 

 advantageous. 



The furgeon ftiould not prefs too heavily with the trephine, 

 or trepan, w>hen he is in the aft of fawing the bone ; but 

 execute the bufinefs with as light a hand as poffible. As 

 ioon as a fufficient groove is formed for the teeth of the 

 crown, the centre-pin is to be taken out. The firft part 

 of the fawing may be done bnilily. Afterwards, the oper- 

 ation is to proceed flowly and cautioufly. With a bit of 

 quill, the furgeon muft examine the depth of the circular 

 groove, in order to be fure that he has not fawn through 

 at any particular point. When one fide feems to be more 

 cut than another, the faw muft not be allowed to aft upon 

 it fo much ; and if there be any part of the circle which is 

 completely fawn through, the inftrument muft not be ap- 

 plied to that point any longer. While the furgeon examines 

 tlie depth of the groove with a piece of quill, an affjftant 

 takes care to clean the teeth of the faw with a fmall brufh 

 made for the purpofe, by which means the aftion of the 

 inftrument will not be obftrufted by the particles of bone. 



10 



When thefe become tinged with blood, the teeth of the faw 



are known to have reached the diploe ; but the praftitiower 

 muft remember, that the diploe is not a criterion which will 

 be met with in every inftance, as in fome fubjefts it is fo 

 inconfiderable, that it does not give any tinge of blood to the 

 bone-duft. It is of importance to be aware of this faft ; 

 for were a furgeon to faw boldly on in all cafes until he 

 fees marks of his having arrived at the diploe, he would fre- 

 quently be apt to injure the dura mater and brain. When 

 he knows that he is fawing the internal table, he is to pro- 

 ceed with great flownefs aiid circumfpeftion, making re- 

 peated examinations of the groove with the pointed quill. 

 When the portion of bone to be taken out appears to be 

 connefted with the reft of the fkuU principally on one fide 

 of the groove, the trephine is to be inchned to that fide. 

 Immediately the circle is loofe enough, it is to be taken 

 out with a pair of forceps conftrufted for this objeft, or 

 with the elevator. (See furgical plates.) But rather 

 than run a hazard of fawing too deeply with the trephine, 

 we would always recommend the furgeon to prefer breaking 

 the few laft fibres of bone which impede the circle from 

 being taken out. 



When there ai-e any inequalities round the margin of the 

 perforation, they muft be carefully removed by means of 

 the lenticular knife. (See plates.) In doing this part of 

 the operation, care muft be taken not to let the lenticular 

 knife make improper preffure upon the dura mater, a thing 

 which might have the worft conlequences. 



The circle of bone having been fawn out, the furgeon is 

 to keep in mind the grand objeft of the operation ; viz. that 

 of relieving the brain from the preffure, which is the caufe 

 of the alarming fymptoms. All depreffed fragments of 

 bone are to be raifed, and, if quite detached, they ought to 

 be entirely removed. All fpicula; of bone, penetrating the 

 dura mater and fubftance of the brain, are to be extrafted 

 without delay. If there be blood or matter upon the fur- 

 face of the dura mater, it now efcapes, being expelled by 

 the pulfatory movement of the cerebrum. 



When the extravafation is under the dura mater, a punc- 

 ture may be cautioufiy made through this membrane with J 

 the point of a biftoury, or lancet. There muft be, however, " 

 a manifefl: ele ration and tcnfion of the dura mater, arifing 

 from the lodgment of a fluid below it, to juftify the pre- 

 ceding praftice. If blood ftiould be found in the fufpefted 

 fituation, the punfture may be enlarged into a crucial 

 incifion. ■ 



According to furgical writers, if, after dividing the dura ' 

 mater, the furface of the brain appears fmooth and flabby, 

 with a fluftuation, there is an abfcefs in its fubftance. They 

 then fanftion the method of carrying the point of the bif- 

 toury to the depth of an inch, if circumftances render fo 

 deep a punfture neceffary. But, fays Richerand, prudence 

 forbids us to go further. Cutting the furface of the brain 

 caufes no pain, and it produces lefs danger than one could 

 prefume to expeft ; but experience and obfei"v3tion have 

 proved, that the effential pai-ts of this organ are fituated 

 near its bafe, and that its furface may be removed without 

 danger or pain. Nofogr. Chir. t. ii. p. 301. edit. 3. 



After the operation of trephining, the divided fcalp is 

 to be placed as nearly as poffible in its natural fituation, 

 and lightly dreffed with a fimple pledget of any common 

 unirritating ointment. In applying the di-effings, the fur- 

 geon ftiould invariably keep in view thefe objefts ; namely, 

 to let whatever is put on the wound be as light as poffible, 

 not apt to make preffure on the brain, and of a nature 

 wliich cannot excite irritation. All ftimulants are to be 

 ftriftly avoided ; nor will any bandage be better than an 



ordinary 



