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RISKS 11 |
| ROBOTIC SURGERY 12 |
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GOAL OF THE OPERATION |
The goal of total hip replacement is to replace the destroyed hip joint with an artificial hip joint. The operation relieves pain from the damaged hip and gives the patient a good range of motion, good stability, and equal leg length. After successful total hip replacement, the patient can return to everyday activities, sports (except high impact sports), and to normal social life.
The Principle
The principle of the operation is simple:
Show Picture: The principle of the total hip replacement operation
A) The hip joint with joint surfaces destroyed by disease is stiff and painful and needs to be removed and replaced.
B) During the replacement operation, the surgeon removes the destroyed surfaces of the hip joint: the whole damaged femoral head and the damaged surface of the hip socket
C) The surgeon puts a new artificially made hip joint in place of the removed hip joint.
This is the total removal of the destroyed hip joint followed by the total replacement of the destrroyed hip joint with an artificial hip joint=
= TOTAL HIP REPLACEMENT OPERATION
Replacing the destroyed hip joint surfaces with artificially made joint surfaces is today the only way to produce a pain-free, well functioning new hip joint.
WHY?
Why is the total replacement of the destroyed hip joint surfaces the only treatment available today to relieve pain and restore function in the hip? Because the joint cartilage cannot renew itself!
Show Picture: Healthy joint cartilage tolerates big loads well
The joint cartilage functions as a sophisticated hydraulic bumper that follows simple physical laws for liquids.
The pressure spreads in liquids equally in all directions. In this picture, the pressure on every square centimeter inside the ball on this picture is distributed equally. That is why a ball filled with a liquid can bear the weight of an elephant. On every place of the ball, either directly under the elephant’s foot or on the buckling sides of the ball, the load per area unit is equal.
The joint cartilage that covers the healthy hip joint’s surfaces is a very sophisticated structure that can sustain even big loads without damage. The joint cartilage exploits the same hydraulic principle that allows the ball to bear the weight of an elephant.
It contains an ingenious system of small balls, in reality hydraulic bumpers, distributed inside the cartilage’s microscopic structure. Every “ball” is actually a large protein molecule binding huge amounts of water inside the molecule.
These small balls change their form and release a part of their water content when loaded. When the load ceases the bumpers restore their round form and take in the lost water. They change their form equally well as the ball on the picture does when the elephant tramps on it.
As long as the cartilage is not damaged all is well, the sparse cartilage cells produce continually new “balls” – protein molecules called aggregans – to keep the elastic resilience of the cartilage unchanged.
Once damaged, however, the bearing capacity of the cartilage vanishes.
Cartilage has namely no vessels nourishing it; thus, once damaged the cartilage cannot repair itself, it cannot repair the small hydraulic bumpers; there are no medicines either that can do it.
Show Picture: Covering denuded raw bone surface with artificial surfaces– only possibility to create a new pain-free hip joint
The destruction of the damaged joint cartilage thus continues successively until the raw bone is revealed at the bottom of the joint. Once the raw bone surface is denuded at the bottom of the joint surface, the dull unending pain and stiffness start. It is impossible to manage these symptoms successfully with medicines or simple operations.
Covering the denuded raw bone surface with an artificial surface (made from metal, or ceramic) stops the pain and gives the joint the motion again. The total replacement of whole joint surfaces is thus the only available operation to restore the pain-free function in the joint.
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OPERATION ROOM |
Show Picture: Conventional operation room; two views
A) The people believe that modern operation rooms are free of bacteria as is shown of this idealized picture of the operation room. Note that the people assembled the operation table are wearing operation suits leaving large areas of the neck uncovered, operation caps and operation face masks covering faces and hairs only partially. The operation room on this picture is clean and neat and light.
B) This is a lie! Every person spreads his / her bacteria around him / herself continually. Where more people are assembled in a room the air there is crammed with their own bacteria. In closer spaced rooms, such as operation rooms, the air would be filled with bacteria soon. Thus, modern operation rooms have advanced ventilation systems.
In spite of advanced ventilation systems on conventional modern operation rooms
which
are producing copious quantities of clean air ( about 20 air changes/hour), a cubic meter of air on a modern operation room still contains about
100
to
500 bacterial
colonies.
The
risk
that
some
of
them
crash-land
in
the
operation
wound
is
high.
This air cleanliness is sufficient for general surgery and for general orthopedic and fracture operations. The body takes care of these bacteria if they crash-land (sediment) from the air into the operation wound.
But such air is too dirty for the total joint operations. These operations (the total joint devices) can be infected even if only one bacterial colony crash-lands in the wound from the air!
Thus, the total joint operations need special operation rooms with so called laminar air flow ventilation. The operation staff there is dressed in special “astronaut” dresses that prohibit escape of people’s own bacteria into the clean air. One cubic meter of air in these super-sterile operation rooms should preferably not contain any bacterial colonies (less than 3) at all.
Even this is not enough and all total joint patients are receiving prophylactic antibiotics directly before the surgery.
For more information see the chapter Bacteria characteristics
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ANATOMY of THE HIP JOINT |
Show Picture: Anatomy of the hip joint
A) The hip joint is a typical ball and socket joint. In the hip joint the upper end of the long thigh-bone –the head of femur - articulates with a hole (socket) – acetabulum - in the pelvis. This is a “whole view” from the outside.
B) On the cross-section view of the hip joint one sees the femoral head as a round ball that is well fitted within the socket (acetabulum). The femoral head is attached to the thighbone (femur) with a “neck” of the thighbone or “collum femoris”
A structure called poetically “tear drop” and formed by the cross section of the pelvic bone indicates the lower end of the hip joint. “Tear drop” is seen on x-ray pictures only and it is a very important landmark.
Note that the bottom of the hip socket is only a thin layer of bone dividing the hip joint from the pelvic organs (bowels, uro-genital organs).
C) The “usual” x-ray picture of the hip joint actually shows a cross section view of the hip joint. Such picture is also called “frontal x-ray view” of the hip joint.
On this x-ray picture you see the round femoral head seated securely within the hip socket (acetabulum) as white contours on the black background. The femoral head sits on the femoral neck (collum). Note the “tear drop” that is well distinguishable on this picture.
Show Picture: "Tear Drop" and the placement of the cup component.
The surgeon uses the tear drop as a landmark to see if the cup component is placed in the right height. The tear drop marks the lower end of the hip joint, so obviously also the cup component's lower end should lie level with the lower end of the tear drop. Note in this picture the tear drop which is level with the lower end of the cemented cup; that means that the position of the cup component (its height) in this patients is right.
The x-ray assessment of the place of the cup component in relation to the tear drop is especially important for patients who feel that their operated on leg became too short after surgery. See also the chapter: Too long leg
For more anatomical details about the hip joint, its ligaments and muscles see the chapter Details of hip joint anatomy
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PLANNING OF THE OPERATION |
Preoperative planning should help the surgeon to choose the right model and right size of the total hip device (prosthesis) and place it in the right position.
Show Picture: Preoperative planning of the size of the total hip on an x-ray picture
A) The surgeon plans the choice of the right size and the right position of the total hip device already before the surgery. The planning includes the decision how much of the damaged skeleton to remove so that the operation will result in a stable total hip and the patient will have equally long legs. In this picture the surgeon sketched the place of the chosen total hip device directly into the patient’s x-ray picture as sketched contours.
The manufacturer also provided the surgeon with large choice of different sizes of the total hip device made from different materials to combine together, also shown on the picture. The surgeon has thus good opportunity to choose the right size of the total hip device. The possibilities of different combination of modular devices are large – in some modular total hip systems there are about 250 possible combinations of different total hip devices to be made from the modular parts.
The manufacturer provided the surgeon with special templates that make it possible to draw these pictures on the x-ray films and make the right choices.
Show Picture: Preoperative templates for planning the total hip replacement
Upper row: Left picture shows the celluloid templates for the old Charnley total hip, (Thackray). The templates have the contours of total hip devices of different sizes imprinted on their surfaces. (The sizes of the contours on the templates are magnified with 20%. This is so because the “usual” frontal x-ray picture of the hip joint magnifies the x-rayed hip with about 20%, depending on the distance of the hip and of the film from the x-ray tube.
Right picture shows the x-ray picture with the overlaid template (Charnley, later Elite total hip system, Thackrays)
The surgeon places successively templates of different sizes directly on the x-ray picture (film) until he finds the right size of the total hip component that fits with the x-ray picture. This is a tedious process. At operation the surgeon then uses the chosen size of the total hip device (prosthesis) for the replacement of the destructed hip joint.
Lower row: In modern radiology the x-ray films have been replaced by digital plates and computer screens. The x-ray picture appears directly on the computer screen. There are now computer programs that allow preoperative planning on the computer screen picture directly. The computer program has pictures of different models of total hip components with appropriate magnifications enclosed and the surgeon makes the preoperative planning directly on the computer screen. This is a new application of the well known CAD (computer aided design) system in orthopaedic surgery. Elegant and easy system which needs, however, learning.
TOP I QUIT the PICTURE I NEXT
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APPROACHES to THE HIP JOINT |
Hip joint is situated deep under a layer of large muscles, with important nerves and vessels passing the joint both in the front and on the back side of it.
Show Picture: Muscles covering back side of the hip joint
On this picture you see two muscle layers that cover the back and outside of the hip joint, as well as an important nerve (sciatic nerve that passes the back area of the hip joint. The outer muscle layer is divided and retracted and on the bottom of the wound you see four small muscles that rotate the leg outwards. Behind them is the capsule of the hip joint.
The surgeon who approaches the hip joint should cause minimum trauma to any of these muscles and tendons and no damage to the nerves and vessels.
For this purpose the surgeons developed, explored and evaluated special ways how to approach the hip joint and still avoid any damage to the muscles, nerves and vessels around it. These ways are called surgical approaches.
You and your PT should know which approach the surgeon used in your total hip replacement because
· The surgical approach directs the speed and the conditions of the postoperative rehabilitation.
· The surgical approach is related to the postoperative limp
· The surgical approach may be related to the (in-) stability of the total hip
This is so because the muscles and tendons that the surgeon severed during the operation and then restored need to be taken special care during the postoperative muscle training.
The two most used surgical approaches (with many personal modifications by individual surgeons) are A) the antero-lateral and B) the postero-lateral approaches.
Show Picture: Surgical approaches to the hip joint
A) Approaches coming obliquely from the front, so called antero-lateral approaches. The patient is usually lying supine on the operation table. The surgeon has in this position (theoretically) the possibility to palpate patient’s both legs and assess and compare their lengths during the surgery.
The disadvantages of this approach are two:
First, there is a risk of the damage of the many small nerves that cross this area subcutaneously (close to the skin). See the chapter Details of the anatomy of the hip joint
Second, the surgeon must cut partially into the tendon of the middle gluteus (middle) muscle which results in a longer period of postoperative limp.
B) Approaches coming obliquely from the back, so called postero-lateral approaches. The patient is lying on his healthy side on the operation table.
These approaches have actually only one disadvantage. They approach the hip joint through a naturally weaker part of the joint capsule (back part of the hip joint capsule). The surgeon is thus obliged to suture thoroughly all cut structures at the end of the operation thoroughly; otherwise there will be risk that the femoral ball component will dislocate through the not restored soft tissues.
A - Posterior (backside) side of the hip joint capsule is covered by four small muscles that the surgeon must divide to gain the access to the joint capsule and the joint itself. These muscles help to rotate the leg outside. They arise at the back pelvis' skeleton and attach at the trochanter area.
These muscles together with hip joint capsule are important for the stability of the hip joint and also for the stability of the total hip joint.
B - Shows the situation of the operation wound, the muscles cross the bottom of the wound.
Why do I mention these muscles? For only one reason: It is obvious that these muscles must be repaired at the end of the total hip surgery to have a stable total hip; the need to restore these muscles’ insertions has not been, however, obvious for many surgeons.
Earlier statistics demonstrated that patients operated on through the posterior (backside) approach suffered much more often total hip dislocations than patients operated on through the anterior (frontal) approach. That was so because up to the mid 1990’s, the surgeons who used the posterior approach did not repair the posterior joint capsule and the divided muscles at the end of the total hip operation. (These surgeons, even those working at respectful institutions, believed that it was an unnecessary delay!)
Some more cautious patients will still ask their surgeons who use the posterior access to their hip joints: “Will you repair the insertion of my hip muscles at the end of surgery?”
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MINIMAL INCISION |
Ordinary total hip replacement is a big surgery which carries with it a long operation wound, big operation trauma, large blood loss and long recovery time.
The surgeons must always balance the size of the operation wound against the magnitude of the operation trauma. The “ordinary” operation wound (about 25 centimeters long) produces good vision and accessibility of the hip joint but carries with it also a large operation trauma. A small operation wound produces small operation trauma and makes postoperative rehabilitation much quicker, but it makes the orientation inside the operation wound difficult.
Show Picture: Length of scar: minimal incision surgery (MIS) vs general surgical approach.
Surgical textbooks recommend a skin incision 15 to 25 centimeters (6 to 10 in) long for ordinary total hip replacement operation (the upper scar in the picture).
It is possible, however, to carry out the total hip replacement through shorter (10 cm) incisions (The lower scar in the picture). This access got the name Minimal Incision Surgery (MIS).
The patients operated on with the MIS must have special preoperative preparation, special form of operation anesthesia, and specially modified postoperative rehabilitation if the operation should succeed.
IT is important what is under the skin surface not what you can see on the skin surface.
This MIS operation approach is appropriate for certain patients, but its more general use is still hotly discussed. For more details see the chapter MINI INCISION and COMPUTER ASSISTED Surgery
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SURFACE REPLACEMENT |
At the total hip operation the surgeon removes and replaces the whole hip joint. On the femoral side the surgeon removes the whole femoral head, neck, and the contents of the femoral bone marrow cavity.
Show Picture: Surface vs. Total hip replacement
A) In reality, in many patients only the joint surfaces of the femoral head were destructed and needed replacement. For these patients it would suffice to remove only the destructed surfaces of the femoral head and cover the chamfered femoral head with a smooth and small artificial surface.
Such operation would keep the skeleton of the femoral bone intact and produce less operation trauma. It is actually possible to carry out such “minimal” replacement operation and yet render the patient pain-free with a well functioning hip joint. Such operation is called surface replacement of the hip joint.
B) For fixation of the conventional femoral shaft component, the surgeon must remove the whole femoral head and much of the femoral neck and then make a hole through the shaft of the thighbone. All this widespread removal of the skeleton is done only to make place for the somehow clumsy femoral shaft device that carries the femoral ball.
Many surgeons believe that this total removal of the head and neck of femoral bone is not necessary in many young patients.
Please note, that the surface replacement operation spares only the skeleton of the thighbone; the quantity of the removed pelvic skeleton is equal for both operation types, total and surface replacement.
Read more about it in the chapter Surface hip replacement .
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OPERATION – HOW IS IT DONE? |
This is only a schematic picture tour that will give you the idea how the total replacement operation is done. After reading it you will be able to comprehend better the different recommendations, rehabilitation advices, and restrictions you will receive from your surgeon and your PT after the total hip surgery.
At the early stage of the operation (before the removal of the femoral head) many surgeons also make markings of the distance between the leg and the pelvis. In this way they can keep the appropriate leg length during insertion of the total hip joint.
Show Picture: Avoiding leg length discrepancy
A) This schematic picture shows that the surgeon, who has approached the hip joint through one of the approach ways has placed two landmarks – two pins- in the hip joint skeleton as a first step before removing the damaged skeleton. One pin sits in the superior rim of the pelvis (a) and the second pin in the thigh bone’s greater trochanter (b). The distance between them is l, and the surgeon measured it with a ruler. The surgeon then proceeds with removal of the femoral head as usually.
B) The surgeon who wishes to keep the leg length unchanged chooses for the replacement of the resected (removed) femoral head the femoral component of such length so that the distance “l” remains unchanged after insertion of the trial total hip device. In the picture “l = l* “
Similarly, if the surgeon wishes to make the leg longer (or shorter) he chooses a femoral component with longer (or shorter) neck.
See also the chapter Too long leg
After the surgeon secured the measurement of the proper leg length, the surgeon starts with resection (removal) of the femoral head.
Show Picture: Resection of the destructed femoral head
A) The upper picture shows that the surgeon must rotate forcefully the leg which dislocates the femoral head and neck into the wound. This is necessary to make these structures easily accessible for the vibrating saw.
B) With the femoral head and neck well visible in the wound, the surgeon is now able to divide the neck with reciprocating saw at the predestined place and remove the whole femoral head. The surgeon chose the place for sawing off the femoral head at the preoperative planning.
With femoral head gone the surgeon has now place to ream up the acetabulum (hip joint socket) to make place for the up component
Show Picture : Reaming acetabulum and inserting cup component
A - Removed femoral head leaves easy access to the hip socket (acetabulum).
B - With special reamer the surgeon removes the damaged joint surfaces of the acetabulum and deepens it to make place for the artificial cup component.
C - There are many types of cup components, this picture shows a cementless cup component: the polyethylene inner layer (“the liner”) is embedded in a metallic back up that has the form of screw – the cup will be screwed directly into the walls of the acetabulum.
D - The cup component is inserted (screw in) in the walls of the acetabulum. The polyethylene liner is seen to reach over the rim of the metallic back up.
The right position of the cup is very important. The stability of the total hip and the length of the patient’s leg depends also on the right position of the cup component.
Then follows inserting of the shaft component in place.
Show Picture: Inserting the shaft component of the total hip
When the cup component is in place the surgeon continues with insertion of the shaft component.
A - With a special reamer the surgeon opens the marrow hole of the thigh and makes place there for the shaft component.
When the hole is clean and dry the surgeon places first a trial shaft component in the marrow hole first, replaces it into the cup and examines the stability, mobility, and leg length of the future total hip with this trial component.
B - When the surgeon sees that the total hip would have the desired good function and stability the surgeon removes the trial component and replaces it with a definite femoral shaft device of the same dimensions. The fixation of the shaft component in the marrow cavity is either with cement or press-fit. When the shaft component is stably placed in the marrow hole the surgeon replaces the ball of the shaft component back into the cup component. The stable, mobile total hip is now in place and the surgeon then sutures all divide soft tissues and the skin.
How does the surgeon fix the components of the total hip device to the skeleton?
Show Picture : cemented and cementless fixation..
The surgeon has two possibilities how to fix the total hip components to the skeleton, the cementless and the cemented option.
A) The surgeon can either make the bedding holes in the skeleton slightly greater, put bone cement dough into them and then press the components into this doughy bone cement. This fixation is called cemented fixation. When the bone cement gets stiff it fixes the components in place. The bone tissue is in direct contact with the bone cement.
On this schematic picture you see the cement layer as gray layer between the skeleton and the total hip device. The cement layer is also apparent as a distinct layer on an x-ray picture.
B) Or the surgeon can either make the bedding holes in the skeleton for the components slightly smaller and blow the components directly into the prepared holes; this fixation is called “cementless fixation” – sometimes also called “press-fit fixation”. The surfaces of the components are in direct contact with the raw bone tissue. The bone tissue successively grows into the porous surface of the cementless total hip device.
On this picture you see the cementless total hip (shaft component) removed from the body of an automobile accident victim. You see that the bone tissue is penetrating the porous surface of this component.
In the circle you see the porous surface magnified. The surface consists of small sintered metallic balls. The bone tissue is spreading in the space between these balls. In this way the shaft component is firmly fixed to the skeleton.
See more details in the chapter Cemented and cementless total hips.
Whatever fixation the surgeon uses, the total hip device must sit "rock-stably" in the skeleton at the end of surgery. The patients where the surgeon achieved rocky stable fixation of the total hip on the operation table may theoretically put the whole body weight on their total hips already from the first postoperative day. (The surgeon call it “bear weight as tolerated”). Only the healing of the soft tissues decides the pace of weight bearing then. This applies on all cemented total hips. When the bone cement layer hardens (about 15 minutes after inserting the components into it) the components are solidly fixated to the skeleton and tolerate full weight bearing.
Absolutely stable fixation in cementless total hips is of course an ideal too; there are, however, cases - such as revision operations or operations on patients with defects in their hip skeleton - where the surgeon must compromise and accept less then perfect stable fixation of the cementless total hip device in the skeleton at the end of operation and hope that the ingrowth of the bone tissue will eventually produce the "rock-stable fixation".
These patients are then urged to restrict the loading of their operated on hips for 6 – 12 weeks, or even longer. It is supposed that during this time the bone tissue will grow into the surface of the cementless total hips and render them stably fixated to the skeleton.
Only your surgeons knows how stably fixed your total hip is. Follow his advices to the point!
X- RAY CONTROL OF THE NEW HIP.
Show Picture: X-ray picture of the total hip joint
It is, actually, an inseparable part of the total hip operation, although it is done after the finished operation. It will tell the surgeon –and you – if the operation succeeded in the way your surgeon and you planned it.
On this x- ray picture you see a cementless total hip joint. The cup component has additional fixation with two screws. I chose this x-ray picture because it shows so clearly all components of a total hip device in place: the cup with its metallic back up and the two fixation screws, and the shaft component, which is composed from two modular parts. The ball is seated on the shaft's neck and itself well placed inside the cup. It is not always one can see such a clear x-ray picture of a total hip device.
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STABILITY OF THE TOTAL HIP |
The stability of the hip joint is its resistance against dislocation.
The stability of the total hip depends on several factors: the right position of the total hip components, their right size, the right tension in the soft tissues around the total hip. The stability of the total hip is always less than the stability of the healthy hip joint.
Show Picture: Cross section view on soft tissues around the healthy hip joint and around an artificial total hip joint
A) The healthy hip joint (cross-section):. The articulating joint surfaces (head and socket) are surrounded by strong muscles, by strong joint ligaments, and by a strong joint capsule. The elasticity and the tension of these structures create a strong force that keeps the femoral head inside and in close contact with the hip joint socket during all movements in the hip joint.
Moreover, inside the healthy hip joint is negative pressure. Thus, in the healthy hip joint the strong joint ligaments and joint capsule do the most of the work to keep the hip joint stable, whereas the muscle force comes as second.
Note also the large diameter of the femoral head. The large diameter of the healthy femoral head and the strong and elastic capsule allows great range of motion in the hip joint in all directions and prevent the dislocation.
B) The total hip joint: During total hip replacement operation the surgeon divided a portion of the muscles, ligaments, and joint capsule to have easier access to the hip joint. Even if the surgeon restored at the end of surgery the divided tendons, joint ligaments and capsule by a careful suture, there is usually some imbalance and weakness of all soft tissues left. The divided and sutured soft tissues are weak and need protection against overuse while healing is ongoing. Thus, the patients after total hip surgery are urged to restrict their activity during the first 4 -6 postoperative weeks to leave time for healing of the sutured soft tissues. In the artificial hip joint there is “a loose space” between the cup and ball components and the restored (sutured) joint capsule. The sutured soft tissues make always a weaker spot when the hip joint is flexed (bent) too much. In the artificial joint strong muscles are necessary to compensate for weakness of joint ligaments and joint capsule. Thus, you should work hard on the improvement of the force of muscles around your operated on total hip joint.
The artificial hip joint’s ball has much smaller diameter then the natural femoral head. Thus, the small artificial ball is much less stable inside the socket during extreme motions in the artificial hip joint. Thus, the patients are usually urged to avoid extreme range of motion during the first 4 -6 weeks after total hip surgery and sometimes even later to let the sutured joint capsule to heal.
Note that the ball of the artificial total hip joint does not sit always in the centre of the cup. During walking it moves up and down, making small “piston-like” movements. See more in the chapter Function of a total hip prosthesis.
To create a stabile total hip joint the surgeon must carefully restore the tension in the divided tendons, joint ligaments and joint capsule, to place the total hip components in the right position, and to choose the right size of the total hip device.
See also the chapter Hip dislocation.
| MOTION IN THE TOTAL HIP JOINT |
The hip joint is a typical socket and ball joint. As such it moves in all three planes.
Show Picture: Function of the healthy hip joint
In the healthy hip joint the leg moves forward and backward, to the side (out and in), and it rotates. This big range of motion is nicely demonstrated on this more than 100 years old illustration of “globographic recording” of the hip joint motion.
The hip joint disease makes the hip joint stiff. Movements in all three directions are restricted in the diseased hip joint. For the patient the most noticeable is the restricted full extension (stretching), restricted rotation, and restricted motion to the side (abduction) in the hip joint. It is usually not possible (and not even desirable) to achieve full range of motion in all directions in the total hip joint.
Show Picture: Full extension and abduction in the total hip joint:
For comfortable everyday life the patient needs flexion in the total hip from 0 to 70 -90 degrees and abduction (pushing the leg to the side) from 0 to 30 degrees. It is thus important for the surgeon to restore this range of motion at the operation. The final range will, however, depend on the preoperative range of motion.
To achieve full extension and good abduction in the total hip joint the surgeon may be forced to divide some muscle attachments (iliopsoas and adductor muscle tendons) that are shriveled and don’t allow full extension and abduction. Usually this procedure does not leave noticeable functional deficit.
For more details about motion of the total hip joint see the chapter Function of the total hip prosthesis
| RISKS WITH THE TOTAL HIP OPERATION |
As with all big surgeries, there is certain, although very small risk to die and to catch some postoperative complications after total hip surgery.
The risk to die immediately (“immediately” means within 90 days) after total hip surgery depends on the patient’s age.
It is practically zero for all patients younger than 70 years but for older patients the risk raises steeply; for people 80 years and older the risk to die “immediately” after total hip surgery is 2.4%. The patients with the so called “commorbidity” = patients with diseases of heart, lung, kidneys, and like are at increased risk. The main cause of “postoperative” death is heart infarct and stroke, whereas the so much spoken about lung emboli death is a very rare complication (0.1%). (A. Blom: Acta Orthopaedica 2006: 77: 351 – 8)
For information about other postoperative complications see the chapter General complications after THR surgery.
| ROBOTIC SURGERY |
Usually, the surgeon prepares the cavity for the prosthetic shaft in the thigh bone with drills, saws, and templates that look like instruments carpenters use
Although these instruments are high precision tools, they are manually driven. Some surgeons try to improve the precision of the cutting and drilling procedures to make the hole for the prosthetic stem more precise. These surgeons replaced the surgeon's hand with a computer steered milling tool. This is the known principle of the computer aided milling machine. This machine drills a hole through the marrow cavity after data put into the computer by the surgeon. The patient is fastened to the operation board and the milling machine too. Once the computer "aided" milling starts the surgeon has no control about the milling process. In rare case can the sharp milling tool go the wrong way and may destruct the thigh bone's shaft.
The milling operation makes only a small part (about 10%) of the total hip operation. Yet, with the use of the Computer aided milling machine, this is is an elaborate procedure that needs extensive preparations with placing of special target wires in the thigh and taking several X-rays, all done at a separate operation one or more days before the total hip replacement operation proper.
Advantages: better shape of the hole for the prosthetic stem milled in the femoral shaft. (This is still discussed)
Disadvantages: Expensive and time consuming procedure, still largely experimental not in general use. More complications.
