the surgical approach for the minimally invasive hip replacement begins with an incision over the postero - lateral area of the hip approximately 3 to 5 cm . distal to the greater trochanter . the exact position of the incision depends upon the anatomical location of the trochanter in relation to the acetabulum . the incision extends approximately 2½ to 3 inches in a postero - superior direction , in line with the fibers of the gluteus maximus . the surgical field is increased exposing the posterior capsule of the hip . the hip is dislocated by internal rotation providing lateral access and view of the acetabulum , along with the trochanter , neck of the femur and ball . the exposed hip joint is evaluated to determine necessary repair . an osteotomy of the femoral neck may be performed and the head and neck of the femur removed and replaced with an artificial ball supported by a femoral rod , as part of the total hip replacement . of course , other procedures may be indicated and performed . the acetabular alignment guide 10 , shown in fig1 is then used to determine the location of the insertion point of the guide wire . the leading end 11 is placed in the acetabulum . the leading end 11 has a dome shaped attachment 50 similar to the shape of the acetabulum and fits in the acetabulum . the leading end 11 is of a length to extend from the center of the acetabulum outwardly to a docking port 19 located within the surgical incision . the trailing end 12 of acetabular alignment guide 10 is then adjusted to obtain the desired angle used for preparation of the acetabulum by reaming , trialing , and , finally , impacting the acetabular prosthesis and liner . depending on the size of the patient , the handle 16 attaching the leading end 11 and the trailing end 12 can be adjusted to accommodate the patient . as shown in fig1 the height and length of the acetabular alignment guide is adjustable by couplings 21 and 23 . the leading end 11 and the trailing end 12 of the guide 10 are separated by a space approximating the distance from the acetabulum and a point where an imaginary line from the acetabulum would exit the body and have a common longitudinal axis . in surgery , soft tissue occupies this space between the surgical field and the point on the skin where the imaginary line would exit . both the leading end and the trailing end of the acetabular alignment guide have a bore or channel extending through the longitudinal axis 13 . leading end 11 has a channel 14 terminating in the docking port 19 and trailing end 12 has a through channel 15 in line with each other . the handle portion 16 , extending between the leading end and the trailing end , is strong and rigid enough to maintain the alignment of the channels 14 and 15 . further , the handle 16 may be used by the surgeon to secure the guide 10 once the final alignment is accomplished . the specific shape of the handle 16 is important only to the extent that it is displaced from the trailing and leading ends to allow movement of the trailing end over the patient &# 39 ; s body to orient the channels with the mouth of the acetabulum and locate the exit point . to this end the handle may be arched or angled . it may be integral with the leading and trailing ends or made of assembled parts . it may be made in different sizes and / or it may be adjustable in length . the entire guide 10 may be made of materials acceptable for repeated surgeries or it may be disposable after a single use . once the acetabular alignment guide 10 has been manipulated to the proper position , the trailing end contacts the patient &# 39 ; s skin in line with the optimum angle for reaming the patient &# 39 ; s acetabulum . a small incision , e . g . one inch , may be made through the skin at the forward edge of the trailing end 12 . a guide wire 20 or steinman pin is inserted into the channel 15 through the small incision , through the intervening tissue and into channel 14 of the leading end . the resistance to farther insertion indicates the leading end of the guide wire 20 is in contact with the docking port 19 of the channel 14 . this establishes the proper angle for reaming the acetabulum . the channels 14 and 15 have an opening 17 and 18 along the bottom wall opposite the handle 16 . alternatively , the channels may be formed as bores with a removable lower wall portion , e . g . a telescoped lower wall to be removed after insertion of the guide wire or a laterally retractable partition . in any event , the guide wire 20 exits the guide 10 through the longitudinal openings 17 and 18 in the channels 14 and 15 as the handle is lifted from the patient &# 39 ; s body leaving the guide wire in place . the common shaft 30 , shown in fig2 is inserted along the path of the guide wire between the surgical field and the exit point and small incision , if there is one . once the shaft 30 is in place the guide wire 20 may or may not be removed , as desired by the surgeon . on the outside of the patient &# 39 ; s body the shaft 30 may be connected to a power source or may be manually operated . the leading end 31 of the shaft appears in the surgical field . the surgeon fits a particular sized reamer , suitable to the patient &# 39 ; s acetabulum size , to the shaft within the surgical field . the attachments 22 are conventional hudson or trinkle fittings . as shown in fig3 the reamer or other working head , may be provided with a short shaft 41 for ease of connection with the elongated shaft 30 . alternatively , each working head could be supplied with its own shaft or the shaft 30 could be connected directly to the working head . as the acetabulum is progressively cleaned , larger reamers may be exchanged through the surgical field , without changing shafts , until the a suitable size is obtained . at this point , a trial artificial acetabulum 42 is placed on the end of the shaft 30 , in the incision , for ascertaining the best union with the pelvic bone . several different trials 42 may be needed before an acceptable fit . once selected , the properly sized artificial acetabulum is then driven into place by the impactor 45 attached to the shaft 30 . the acetabulum liner is then inserted and attached . the artificial acetabulum may require bone screws for additional support . in that case , the shaft 30 is attached to a screw driver 44 inserted to tighten the screws . the screw driver shaft 41 may be fitted with a hinge 43 to accommodate different screw angles . once the acetabulum is securely in place , the guide wire is withdrawn through the minor incision and it is closed . the remaining procedures of the total hip replacement may be accomplished in the major surgical field . upon completion , it is closed . this procedure obviates the need for lengthy incision to properly position an instrument to ream , trial , and impact an acetabular prosthesis and liner . this invention improves subsequent hospital care and patient rehabilitation . the instruments of this invention may be supplied individually or as a kit . it is to be understood that while a certain form of the invention is illustrated , it is not to be limited to the specific form or arrangement of parts herein described and shown . it will be apparent to those skilled in the art that various changes may be made without departing from the scope of the invention and the invention is not to be considered limited to what is shown and described in the specification and drawings .
a surgical kit for minimally invasive total hip replacement includes a guide for inserting a guide wire into the body at the appropriate angle for reaming an acetabulum . a shaft is inserted along the path of the guide wire . working heads are sequentially attached to the shaft . the working heads of the reamers , impactors , trials and screw drivers are changed in the primary surgical incision thereby reducing the size of the incision and the trauma .