MINI-INCISION TOTAL HIP SURGERY &
COMPUTER ASSISTED SURGERY
Statement by the American Association of Hip and Knee Surgeons (2005)
for more detailed description of advantages and disadvantages of MIS
There is more than one surgical technique how to carry out a mini-incision (MIS) total hip surgery.
The latest improvement of the MIS technique has been attained by the use of computer assisted surgery. Computer assisted placement of the components of total hip increases the precision of the operation enormously,
Picture : Conventional and minimally invasive THR Click on the icon for a full size picture.
This schematic picture shows the patient lying supine. The surgeon uses the so called anterior approach to the hip joint, he approaches the joint from the front.
The MIS surgery uses an incision (cut) that is between 7 and 12 cm long (usually), depending on the patient's body proportions. In this picture you see (dotted line) also the extension of the conventional incision, which is somewhere between 15 and 25 cm long (usually); thus, the MIS is done through about a half as long incision as the conventional surgery.
In the picture you see also the additional stab wounds used during MIS approach in obese patients to get the instruments in place.
Picture : Conventional and minimally invasive THR. Adapted from: Kaggi Orthopaedic Foundation, Waterbury, CT, USA
The surgeon can move the incision through the skin up and down, front and back. Through this "movable window", the surgeon may see successively all important landmarks of the hip joint. In theory at least.
Pictures: How much does the surgeon see. Reaming of the hip socket in theory.
In this obese patient, the surgeon made additional stab wound to get the reamer's axis through the skin. You see the reamer placed in the correct position in the socket. In theory, this operation step is easy.
Reaming of the hip socket in theory. Adapted from: Kaggi Orthopaedic Foundation, Waterbury, CT, USA
In practice it is, however, difficult / impossible to visualize the whole hip's socket (acetabulum) from this small cut. Without the visualization of the rim of the whole hip socket it is very difficult to place the cup component in right position.
Reaming of the hip socket, praxis. The assistant keeps the soft tissues away from the reamer. Do you believe that the surgeon can see enough of the reamer's head through this limited exposure? How sure can the surgeon be about the right position of the reamer's head in the socket?
Reaming of the hip socket, praxis. Adapted from: Kaggi Orthopaedic Foundation, Waterbury, CT, USA
Here comes the computer assisted technique to help. Computer program guides the surgeon's hands and instruments into precise position for inserting total hip components, (theoretical error limits of this methods are 1 mm and 1 degree).
Picture: The computer-assisted placement of total hip components
Click on the icon for a full size picture.
The computer assisted operation may be used also in conventional surgical approaches. The technique presented here has three stages.
A. Before the operation, the patient's hip joint is CT scanned (special X-ray examination). The CT scan is then put in the computer program. Before the operation, the surgeon selects the proper size of the cup component with the help of the computer program.
B. At operation the surgeon places beacons in the patient's pelvis and on the instruments. These beacons send infrared light signals. The signals are registered by the infrared cameras placed above the patients body. The information about the position of the patient's hip and the surgeon's instruments is put into the computer program, where is already the CT picture of the patient's hip joint. With help of this information the computer program produces a map of the position of the cup component, together with the jig that holds it, relative to the patient's pelvis on an interactive screen.
Note in this schematic picture that the surgeon holds the jig that places the cup component, but he looks on the screen and not in the minimal wound. One infrared beacon is on the patient's pelvis skeleton, the other one is placed on the handle of the jig. Some computer programs use up to 14 such infrared beacons. The computer program produces a real time picture of the position of the cup component. The surgeons sees the position of the cup component on the screen both in frontal plane and in sideview (profile-view). With help of this computer program the surgeon can choose the precise position of the cup component, although he does not see the whole hip socket.
C. After placement of the cup, the surgeon assesses the precision of the cup placement. Recent programs provide also measurement of the patient's leg length before and when the femoral component has been put in place. These programs also present a "safe" range of motion of the prosthesis (the range within which there is no danger of impingement and dislocation of the hip joint). The surgeon can choose "stable" position of total hip components that minimizes the risk of dislocation of the total hip joint.
Who is the candidate:
Usually not too obese patients and patients without severe deformation of the hip skeleton.
The surgeon selects himself the patients suitable for this operation. Consult always your surgeon.
This operation needs a set of special instruments and a special training of the surgeon.
Note, however, that the total hip joint components inserted at mini-incision operations are those used with normal total hip operations. All other restrictions apply, postoperative complications are the same as those after the "normal" THR.
The advantages are: less bleeding, less surgical trauma, quicker rehabilitation.
The disadvantages are not known as yet, as no comprehensive, long term follow up reports have been published as yet.
The first reports, however, demonstrate that there is less bleeding and quicker return to normal hip function in patients operated on with the mini-incision, computer-assisted technique (Digioia 2003).
Remember: It is not the aesthetic look (short and "nice" scar) that is important, the important thing is what the surgeon has done beneath the skin.
Remember that patients for MIS are selected, otherwise healthy patients. The MIS operation technique is only one component of a whole set of special adaptations:
The anesthesia is specialized so that the patient may leave the bed / and the hospital the operation day or the next day.
The rehabilitation procedures are rehearsed before the surgery so that the patient will be able to continue with them early at home.
The pain management drugs are specially selected; the patient should not be drowsy after their use.
In short: If you are a candidate for MIS, see too it that you are perfectly prepared and informed.
Minimally invasive surgery has quickly attained a status of some exceptional surgery. Actually, some surgeons believe that this term should be abandoned because the term "minimally invasive surgery" is today used for purely commercial purposes by many surgeons, not only in total hip surgery.
If the skillful surgeon can really carry out the surgery without damage of the muscles, tendons and other soft tissues through a short cut (incision), then minimally invasive surgery is a great benefit to the patient.
If the surgeon makes a short cut and then damages the muscles and tendons by forceful pressure on the retractors and places the total hip in wrong position, then a short cut is a big price to pay for faulty operation.
It is useful to cite the debate in the renown Journal of Bone and Joint Surgery. Doctor Huo published there a report "What is new in hip arthroplasty". Two Australian surgeons were criticizing Doctor Huo's paper by not mentioning the minimally invasive total hip surgery. Doctor Huo says that he and his colleague were unable to find some reliable reports on this technique in peer reviewed journals. They conclude "The clinical efficacy and reproducibility of this technique remain to be fully substantiated by studies of larger patient populations and by wider use in more centers".(Huo 2002)
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References:
Digioia et al.: J Arthroplasty 2003; 18: 123 -8
Huo MH, Cook SM.: J Bone Joint Surg-Am 2002; 84-A: 1481-2
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