US 3540447 A
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Description (OCR text may contain errors)
United States Patent Inventor Wesley J. Howe Franklin Lakes, New Jersey Appl. No. 671,635 Filed Sept. 29, 1967 Patented Nov. 17, 1970 Assignee Becton, Dickinson and Company,
East Rutherford, New Jersey a corporation of New Jersey SPINAL NEEDLE 1 Claim, 4 Drawing Figs.
U.S. Cl 128/221', 128/347 Int. Cl A6lm 5/32, A6lb 17/34 Field of Search 128/2l4.4,
Primary Examiner-Dalton L. Truluck Attorney-Kane, Dalsimer, Kane, Sullivan and Kurucz I ABSTRACTi A spinal needle having two portions of different diameter, and which is accurately dimensioned to facilitate entry and positioning in the spinal cord. The needle is hollow and has a sharpened point section of reduced diameter connected by a tapering intermediate portion to an enlarged portion which extends to a hub member. A stylet is also provided which has an external configuration identical to internal configuration of the hollow needle.
//5 gym/2% SPINAL NEEDLE BACKG ROUND AND SUMMARY OF THE INVENTION mediately adjacent dura mater, the latter of which is the.
thickest and most substantial of the variouslayers surrounding the spine. The dura and the arachnoid are usually closely adjacent to each other, and both are penetrated by-the spinal needle as if they were a single membrane.
In giving spinal injections, the needle and stylet must penetrate the dura and arachnoid, and enter the subarachnoid space which contains the spinal fluid. Usually, the distinct scnsation is imparted to the fingers of the doctor as'the needle penetrates the dura. However, this sensation is not always apparent, especially when a smaller diameter needle is used. Therefore; it has been current practice to interrupt the ad vancement of theneedle and frequent intervals, to withdraw the stylet,.and observe whether or not fluidappears in the hub of the needle; the presence of fluid indicating that the needle has entered the subarachnoid space.
When the fluid indicates that. the needle is properly posi- Y tioned, a syringe containing the selecteddosc of anesthetic or other solution is carefully attached to thehub. An attempt is then made to aspirate the fluid into the syringe by-drawing on the plunger to once again make certain that the tip of the needle is still in the subarachnoid space. lffluid-again appears, the injection is made.
The presently used injection proccdures'havemany disadvantages. First, the interruption of the insertion of the needle to check for penetration of the dura is most uncomfortable to the patient. Also, the resulting time delay increases the opportunity for a sudden movement by the patient which may tear the puncture opening or break the needle.
Second, the needle may be advanced. too far through the dura such that it may strike or even pierce the posteriorsurface. If this occurs, the needle must be retracted and there exists the possibility that part of-the injection may exit through the perforation.
Third, a small diameter needle may lack the degree of stiffness necessary to properly control its direction during insertion and is easilybroken.
Fourth, the use of a larger diameter needle toirnprove the;
stiffness will result in increased trauma and may cause excess coring of the body tissue into the boreof the needle. Also, a larger needle will increase the sizeof the puncture opening through the. dura which will permit the loss ofspinal fluid from the subarachnoid space upon withdrawal of the needle. This loss of fluid is a major cause of-spinal headache.
In general, the invention relatcsto a spinal needle comprising an initial portion having a precise outside diameter; a rear portion having a precise outside diameter somewhat larger than that of theinitial portion, and a-tapered portion joining the initial and rear portions.
lt isan object of the present invention to provide a spinal needle which may be advanced to its final position by a con-.
tinuous uninterrupted insertion operation. lt-is-a further object.
to provide a needle which gives a distinct sensation to the doctor when it enters a proper distance into the subarachnoid space ofthe spinal column.-
lt is another object of this invention to provide a spinal nee dle which has a high degree of stiffness and strength, but at the same time may be inserted with a minimum of trauma and coring.
. adjacent the taper 13. It has been found that if the length A is Additional objects and advantages of the present invention will become apparentto one skilled in the art from the following detailed description.
BRlEF DESCRIPTION OF THE DRAWINGS FIG. 1 is aside view of the needle and mating stylet'of the present invention;
DESCRIPTION 05 THE PREFERRED EMBODIMENT Referring to the drawings, the needle of the subjectinvention is generally designated at 10', and its mating stylet at 20.
The needle 10 includes a forward portion 11, a rear portion l2 of greater diameter, and a conical or tapered connectingportion 13. The tip of the needle is'beveled, as at 14, in any con ventional manner. The needle is joined to a standard hub 15',
.such as the Luer-Lok hub, which maybe either metallic or plastic. The hub --is provided with a slot 16- in its outer periphery for the purpose hereinafter set forth.
The foru'ardportion H of the needle is of relatively large gage (11s.. small diameter) to minimize the incision or puncture. For purposes of example, a needle having an outside diameter of approximately ,02 inches and a bore diameter of .Ol inches (commonly called 25 gage in the industry) has been found to be very satisfactory.
The rear portion 12 is of relatively small gage to add the required stiffness to the structure and eliminate the need for a needle guide or other external means of support against bending during insertion. For example. if the rear portion has an outside diameter of approximately .035 inches and a bore diameter ofapproximately .023 inches (20 gage) very satisfactory results are obtained.
It is thus apparent that the needle of the present invention retains the advantageous features of both the large gage and small gage needle, yet retains none of their disadvantages. The enlarged diameter rear portion has the effect of adding stiffness to the needle, while the smaller forward portion has the effect of minimizing the incision or puncture.
The transition from the forward to the rear portions is accomplished by a tapered or conical portion 13 which is smoothly blended into the adjacent surfaccsto minimize the resistance to insertion.
Animportant feature of the present invention is the particular length of the forward portion 11, designated A in FIG. 4. In use, the forward portion 11 pierces the dura and enters the subarachnoi'd space of the'spine. When the tapered portion 13 reaches the dura, the increased resistance gives a distinct sensation to the hands of the doctor such that he will be aware of the needles exact position. By design, the length A of the portion 11 is such that the tip of the needle-will beat the most favorable depth in the subarachnoid space when the dura is seven thirty-seconds of'an inch (or approximately .22 inches) very satisfactory results are obtained. The particular length'A is also critical by reason of the fact that a needle having a forward portionof a length greater than seven thirty-seconds of an inch will tend to bend or break at point l7'during the insertion operation. This dimension may otherwise vary to a slight extent depending on the age and size of the patient, as well as the exact portion of the spine to be entered.
The angle of taper B as seen in FIG. 2 should be in the order of 35 for optimum penetration characteristics. Also. an angle. of this order has been found to be sufficient to give the required distinct sensation to the hands of the doctor upon reaching the dura.
The overalllength C of the needle varies'considerablyaccording to the specific use ofthe spinal tap, but typically is in the order of} /2 inches.
In the preferred embodiment, the stylet or obdurator 20 includes a forward portion 21 of a diameter closely conforming to the bore diameter of portion ll, a rear portion 22 of a diameter closely conforming to the bore diameter of portion 12, and a conical connecting portion 23. The tip of the stylet-is beveled at an angle corresponding to the angle at 14. The stylet'is joined to'a handle 25 in a conventional manner, the handle including a key 26 adapted to engage the slot 16 of the hub to effect alignment of the beveled surfaces l4 and 24 when assembled as shown in FIG. 4.
The stylet could of course be of constant diameter throughout its length. However, it is preferred to have its external shape closely conform to the shape of the bore of the needle to provide extra strength for the needle. Similarly, the bore of the needle could be of constant diameter throughout. It is preferred however to utilize a larger bore diameter in the rear portion 12 since this improves the flow characteristics no sense limited thereby and its scope is to be determined byv that of the appended claims.
i. In combination, an accurately dimensioned tubular integral spinal needle having a distal end portion, an intermediate portion. a proximal end portion and a bore therethrough, a hub mounted on the rear end of the proximal end portion, the forward end of the proximal end portion terminating at the rear end of the intermediate portion and the forward end of the intermediate portion terminating at the rear end of the distal portion, the forward tip of the distal portion being beveled, the distal portion having a precisely determined outside diameter in the order of .02 inches and precisely determined length in the order of .22 inches to minimize the size of the puncture made by the needle upon insertion and to assure that insertion is at the proper depth, the proximal end portion having a precisely determined outside diameter in the order of .035 inches to provide a needle of desired stiffness. the intermediate portion being tapered and joining the distal and proximal end portions with the angle of taper in the order of 3.5" so as to join said distal and proximal end portions in a smoothly blended manner to minimize resistance to insertion of the needle, the bore ofsaid needle having a surface configuration approximating the outer configuration of said needle, a stylet removably inserted in the bore otthe needle and having an outer configuration and diameter substantially conforming to the surface configuration and diameter of the bore of the needle so asito substantially fill the bore ofthe needle when inserted therein. and said stylet having a beveled distal tip which may be aligned with the beveled distal tip of said needle when said stylet is positioned within the bore of said needle to facilitate proper insertion ofsaid combination.