LOOSENING OF TOTAL HIP JOINTS
"I have had my second full hip replacement 3 years ago, and now I have extreme pain again. I would like to hear some reasons why a second full hip replacement can come loose already after 3 years. According to my Doctor, after Bone Scans and X-rays, the hip is loose where it goes into the leg."
CONTENTS
The radiological signs of a loose total hip
Two forms of osteolysis / bone cysts
The treatment of loose total hip
Results of revision operations
Complications of revision operations
What is it:
Loosening of a total hip occurs when a total hip prosthesis loses adequate fixation to the bone. Usually, loosening of a total hip prosthesis is accompanied by increasing pain, and by distinct radiological changes.
There is, however, confusion concerning the meaning of the term "loosening". This is so because there are many patients with radiologically loose total hips that function surprisingly well. Moreover, with loose total hip the surgeon means an aseptic loosening, i.e. loosening not caused by bacterial infection.
What is a failed loose total hip replacement?
A painful total hip which restricts the patient’s daily activities severely and lost its fixation is a failed loose total hip. A failed total hip involves also a severe psychical burden for the patient. The pain and other symptoms from a failed total hip are lasting and / or increasing.
The majority of loose failed total hip joints have also distinct changes apparent on the X-ray pictures. There are, however, limits to the ability of plain radiographs to detect early signs of loosening.
Because of this lack of precision, there are patients with loose painful and stiff hip joints who do not have signs of loosening on plain radiographs in the early phases of the loosening process and
there are patients with well functioning total hips that have signs of loosening.
How will I know the failed loose total hip?
The surest sign of a loose failed total hip is increasing and lasting pain and stiffness in the total hip accompanied by typical radiological changes.
The pain in loose total hips:
The patient will usually notice increasing pain in and around the artificial joint, difficulty to put weight on the joint, and diminished motion in the joint. The discomfort and pain usually develop slowly, years after the operation that was initially successful. In the minority of patients, however, the new artificial joint was never functioning well, and the pain and other discomfort only increased steadily since the operation.
The pain is usually in the whole hip area and in the thigh when both components of the total hip are loose.
Patients with only the femoral component loose experience mainly thigh pain.
The radiological signs
There are two radiological signs of a total hip loosening :
change of the position of the prosthesis
radiolucent lines
Change of the position of the prosthesis
the prosthesis may change its position on two successive X-ray pictures taken months or years apart. This is a definitive sign that the prosthesis (or some of its components) is loose.
There is a special X-ray method called X-ray stereofotogrammetry that can measure the changes in the position of the total joint relative to the skeleton very accurately. This method can discover incipient loosening of a total joint very early, already within two years after the operation. Unfortunately, this method is technically difficult and it is used only on special clinics for research purposes.
Radiolucent lines
development of radiolucent lines around the total hip prosthesis is another sign of total hip loosening. Whereas the change of the position of the prosthesis are unequivocal, the "radiolucent lines" that are apparent on the radiograms must be "interpreted".
The radiologist must distinguish between "innocent" radiolucent lines and the radiolucent lines that are characteristic for loose total hips.
The innocent radiolucent lines are thin, less than 2 millimeters thick. They are apparent already on the early X-ray pictures and they do not change.
The radiolucent lines that are associated with loosening develop successively around some or all prosthetic components. The thickness of these lines increases successively, from 2 to 3 and more millimeters. The lines are expanding and the whole prosthesis may be eventually enshrouded in radiolucent lines several millimeters thick.
The more poetic surgeons sometimes speak about "ominous" radiolucent lines around a total hip prosthesis if they observe increasing thickness of radiolucent lines and describe such X-ray picture as an "imminent" loosening of the total hip joint.
Picture: Loose total hip.
(Click on the icon for a full size picture)
In this schematic picture the left side shows a firmly seated total hip. The prosthesis surface has direct contact with the skeleton. The X-ray picture shows direct contact of the white shadows of the prosthesis with the white shadow of the skeleton.
On the right side picture, both components of the total hip prosthesis are loose. They lie in a large cavity of the skeleton and are surrounded with areas of loose connective tissue. The connective tissue contains cells that are dissolving the skeleton. The connective tissue is pervious for X-rays, so that on the (negative) X-ray picture, the white shadows of the prosthesis are surrounded by a dark line called "radiolucent" line or zone.
Moreover, the shaft of the femoral component changed position- it is tilted. This is a sure sign of loosening of the shaft component of the total hip.
Picture: X-ray picture of loose total hip
Click on the icon for a full size picture
The stem component of the total hip is enclosed in a white envelope of bone cement.
The white shadows of the skeleton have been "eaten up" by the dark shadows of the connective tissue that dissolved the skeleton around the prosthesis. The shaft of the thighbone (the so called corticalis bone tissue) is very thin and ballooning. Between the corticalis and the bone cement is a dark area filled with soft tissue that dissolves the skeleton. The surgeon enforced the thighbone with four wire cerclages.
In the lower part of the picture there is a model of the changes in the thighbone. You can see the thin bone layer that enclosed as a balloon the stem component. There is a hole (an opening in the cortical bone made by the soft tissue.
The radiolucent lines are signs of a bone dissolving process called osteolysis. The dark area of these lines is in reality a space between the prosthesis and the skeleton that is filled with soft tissue that dissolved the skeleton.
Plain X-ray pictures provide, however, only limited information on the amount and location of osteolysis after total hip arthroplasty. One recent study demonstrated that plain radiographs were inaccurate to find osteolysis in 88% of all patients who had the osteolysis discovered with the use of CT scans. (Puri 2002)
See also Diagnostic methods of hip diseases
Other methods for diagnosis of total hip loosening, such as a technetium bone scan are less precise and less specific.
Two forms of osteolysis:
Picture: Two forms of osteolysis -schematic x-ray picyure
(Click on the icon for a full size picture)
1) Linear osteolysis
The radiolucent lines form and expand around the periphery of the whole prosthesis. Successively, the lines become more thick. The lines correspond to the osteolytic process. The loose tissue that dissolves the skeleton expands successively around the whole surfaces of the total hip components. Eventually all surfaces of the prosthesis are in contact with soft connective tissue only, all fixation between the prosthesis and the skeleton is lost. The prosthesis is loose.
2) Expansile osteolysis:
("polyethylene bone cysts")
With the advent of cementless prostheses operated on young, active patients, there appeared another form of osteolysis called expansile osteolysis. The bone dissolving process starts on a small area, on the spot, of the skeleton and spreads into the skeleton, away from the surface of the prosthesis, not along the surface of the prosthesis. (Zicat 1995)
The skeleton may bulge outward under the pressure of the bone dissolving tissue, thus the name "expansile".
Note that large areas of the prosthesis are still in immediate contact with the skeleton, the prosthesis is not loose.
Sometimes, these changed are called "polyethylene bone cysts".
The increased production of small polyethylene particles and the pumping of the fluid into the into the osteolysis cavities is the process that keeps the osteolytic process going:
Picture: The mechanisms of expansile osteolysis.
(Click on the icon for a full size picture).
The expansile osteolysis needs two condition for its development:
1) Joint fluid with many small particles of preferably polyethylene
2) repeated movements that pump this fluid into the space between the prosthesis and the bone
The movements in the total hip are creating a large volume of very small polyethylene particles. Note also that the ball component is not longer in the center of the cup, it moved upward. The ball dug a hole in the polyethylene cup, and moved upwards in this tract. This is a sign of increased wear of the polyethylene liner, that documents the production of many polyethylene wear particles.
Every step is creating yet more polyethylene wear particles that are continuously pumped into the bulging osteolysis spot. One may describe the osteolytic spot also as a cyst in the bone.
The screw hole in the metallic back-up allows the escape of the joint fluid, which comes into direct contact with the raw bone around the outer surface of the metallic back-up.
The rhythmically increasing fluid pressure during every step in combination with polyethylene particles in the fluid eventually leads to the formation of inflammatory tissue that destruct the bone and creates a bone cavity - an expansile osteolytic cavity, i.e. an osteolytic bone cyst filled with loose tissue mixed with polyethylene particles.
Expansile osteolysis is not identical with loose failed total hip. But the bone destruction may continue so that the whole total hip joint becomes eventually loose.
Expanasile osteolysis may destructs large volumes of the skeleton. Because the bone dissolving expands away from the surface of the prosthesis and not around the surface, the prosthetic component may be still well attached to the skeleton at its periphery, whereas in the centrum there is no contact between the prosthesis and the skeleton. Thus, the prosthesis is not loose in spite of this lesion and the patients are usually without pain. The surgeons speak about "silent osteolysis".
Unfortunately, this form of osteolysis may destruct larger areas of skeleton before it is detected. Sometimes it results in a sudden fracture through the attenuated skeleton.
The frequency of the expansile osteolysis decreases with the patient’s age: According to statistics based on conventional X-ray pictures, patients up to 50 years of age have had 22 % of expansile osteolysis changes, whereas this percentage was only 8 % for patients between 50 and 70 years of age.
When the osteolytic focus is situated " behind" the acetabulum it may not appear on plain X-ray pictures of the hip joint and pelvis.The surgeon may order special projection X-ray pictures to unveil the hidden osteolytic focus of the silent osteolysis. Such examination may be difficult and incomplete if the patient has difficulty to move under the X-ray examination.
The expansile osteolysis may be discovered with a special radiological technique called helical computer tomography, using a Metal Artifact Suppression (MARS) program. (Puri 2002)
Because the silent expansile osteolysis develops usually after >6 years after the operation with a cementless cup, some surgeons recommend that all patients with the cementless cups should be screened radiographically 6 to 10 years after the index operation.
The treatment of the failed loose total hip
depends on several factors:
severity of pain
extent and progress of osteolysis
risk of fracture
Non-operative treatment
Not all patients with radiological signs of loosening and osteolysis need revision operation
Loosening of a total hip prosthesis with moderate changes in the skeleton, without progress of osteolysis, and with mild symptoms may be treated by "watchful observance", That means reduced weight bearing and repeated controls including X-ray pictures, while you and the surgeon wait with the decision to operate on your total hip.
Patients with grave medical condition that precludes a new operation of the loose total hip joint are left without a revision operation. Usually, the grave medical condition restricts the mobility of these patients substantially so that the risk of the skeleton fracture is lower in these patients
The optimal treatment of patients with silent expansile osteolysis in young patients is still discussed. Some surgeons are advocating operative treatment of all such lesions once discovered. Other surgeons maintain that as long as the lesion is small, does not present a risk for fracture, and does not progress, a regime of watchful observation is appropriate
When is a revision operation for a loose total hip necessary?
Reasons for a revision operation of a failed loose total hip are
unbearable pain
loss of function
progress of osteolysis with risk of fracture
The progress of osteolysis is of overriding importance for the decision to have revision operation, especially for the young patients with silent osteolysis. The progress of the osteolysis is namely unpredictable. There is always the risk that osteolysis will destruct large areas of the skeleton around the total hip joint if you will wait too long.
Management of patients with silent osteolysis
according to Puri and colleagues
Young patients ( < 50 years)
Do routinely a CT scan in all active patients 6 -7 years after operation with cementless cup component.
If the 6-7 year CT scan is negative follow the patient only with conventional X-rays controls as necessary. Follow the signs of increased wear of the polyethylene liner in the cup.
If the 6- 7 year CT scan shows small areas of expansive osteolysis only, inform the patient and repeat the CT scan in one year
If the CT scan shows moderate extension of osteolysis discuss with the patient the possibility of treatment with drugs such as Fosamax that are used to stop bone destruction. Repeat the CT scan in one year.
If the CT scan shows severe bone loss discuss revision operation: exchange of the worn out liner, bone graft of the destructed bone.
In older patients with cementless cups
take conventional X - ray pictures and look for signs of increased polyethylene wear and osteolysis. If there are signs of increased PE wear or signs of osteolysis follow the above schema.
What happens if I will not have a revision operation of my loose total hip?
There is always a risk that the loosening process will destruct large parts of the skeleton if you wait too long. The revision operation may then be more difficult. So if you will wait, you should have a careful monitoring of the progress of the skeletal changes around your total joint.
Studies demonstrate (Britton 1997) that
50 % of all patients with increasing moderate pain waited between two to four years and
87% of patients with severe pain waited one year for the revision operation
Replacement of only one or both total hip joint components?
The total hip joint consists of two components and only one of them ( the femoral stem or the pelvic cup) may become loose,
When only one component is loose, the surgeon may decide to replace only the loose component if the other component is stable. This proceeding shortens the operation time, diminishes the operation trauma, diminishes the need for blood transfusion, and shortens the postoperative recovery.
Studies also showed that the results of this procedure were equally good as in revision operations where both components have been replaced. About 95 % of all such components were still in function 5 years after the revision operation.
Operative treatment
The main goal of a revision operations of a failed loose total hip joint is to put in a new total hip prosthesis that will be anchored stable to the remaining skeleton.
The biggest problem challenging the surgeon is to reconstitute the severe bone loss caused by bone destruction around the failed total hip prosthesis. The total mass of the skeleton lost by osteolysis also determines the operation method.
Techniques for revision operations and the results
Use of special revision total hip prostheses
In total hips where there is enough of the skeleton left for secure anchoring of the revision prosthesis, the surgeon may use special revision prostheses to fill the bone defects and to attach the revision prostheses to the healthy parts of the skeleton
Picture: Total hip prostheses for revision operation of a loose total hip
(Click on the icon for a full size picture)
The failed loose total hip prosthesis produces large skeleton destructions. The revision prosthesis must fill this lost volume and be stable.
The shaft components of a revision prostheses are bulkier to fill the void after the destructed thigh bone skeleton. These prostheses also have a longer shaft for stable anchorage of the shaft in the yet healthy bone marrow cavity beneath the failed total hip joint
The cup component is large. Usually it is a metal backed polyethylene cup. The metal backing has two or more plates attached to it. These plates are placed on the surface of the pelvic bones around the destructed acetabulum and attached there with screws. The whole cup is thus fixated to the skeleton with these screws.
Cementless revision prostheses rely on ingrowth of the patient’s bone tissue for lasting fixation of the prosthesis. For this purpose, the outer surface of the revision prostheses is rough, covered with porous coating. ( for more details see the chapter Cemented and cementless THP)
If the prosthesis has been implanted without bone cement, the patient will be usually put on a partial weight bearing regime (touch-down eight bearing) for six weeks followed by weight bearing as tolerated with two crutches or a walker for further six weeks. Restricted weight bearing should improve the chances for the patient’s own skeleton to grow into the surface of these revision prostheses if the prosthesis was implanted without the bone cement.
If the prosthesis has been implanted with bone cement, the patient is usually put on two crutches and allowed to bear weight as tolerated in 6 weeks and then successively go without support.
(6A) The results of revision operations with revision prostheses
According to the available statistics, more than 90 % of all revision prostheses operated on this way have been in function 10 years after the operation. The skeleton defects around the stable revision prostheses often improved spontaneously, or with the transplantation of small amounts of the patient’s own bone.
The results of revision operation with special revision prostheses were rated as excellent and good in 79% , fair in 15% and poor in 6%.
The pain relief has been most impressive, whereas improvement in the walking capacity has been often only moderate in these patients.
(Böhm 2001)
The results of revision operations demonstrate that the expectations of patients awaiting revision hip operation are high. Improvement of the function in the hip joint , especially the walking capacity, is often less than expected by the patients. The patients should discuss thoroughly their expectations with the surgeon (Eisle 2002)
Bone transplantation in revision of loose total hip joints
Use of bulkier and longer revision prostheses do not solve one important problem: How to replace the large defects in the skeleton with a new bone. Moreover, the surgeon may not wish to engage new, as yet untouched parts of the skeleton with the very large and the very long revision prosthesis.
Only a strong living bone tissue has the necessary characteristics to guarantee the long term stability of the revision total hip prosthesis attached to it; consequently, transplantation of a new bone tissue in the defects around the revision prosthesis seems to be a lasting solution of the problem..
The patient’s own bone may be used to fill the defect, the autografts (pieces of own bone) are usually taken from the pelvic skeleton. Patients own bone tissue has the best capacity to heal completely and replace the bone defect. However, the sources of patient’s bone are very limited and the quantity usually is insufficient to fill the large bone defects. Moreover, the procedure with taking the autograft adds to the surgical trauma and produces a second wound.
Bone allograft. The replacement of the lost skeleton with a bone graft taken from another person (bone allograft) may partially solve these problems. ( Bone transplants coming from other individuals are called bone allografts.)
The bone tissue in the bone allografts is dead. It serves only as a scaffold for successive ingrowth of the patient’s own bone The transplanted bone, especially if it is crushed into small bone chips, may contain, however, not only dead bone tissue but also hormones (morphogenetic bone proteins) that entice the ingrowth of the host’s own bone tissue. The patient's own bone growths successively into the dead bone chips, dissolves them and replaces them with the patient's own skeleton.This is a slow process called accordingly "creeping substitution".
The surgeon may use many small pieces of bone or one large bone graft to fill the defect in the skeleton, or to use massive chunks of the whole skeleton. It depends on the form of the skeletal defect.
Impaction bone grafting
Many small pieces of bone are pressed, impacted, into the skeletal defect.
Picture: Principle of the bone impact grafting operation of the defect in the thigh bone
Click on the icon for a full size picture
The thawed femoral head (allograft) from the bone bank is ground, nipped and chipped into small chips. The surgeon speaks about morselled bone allografts . These chips are packed tightly into the cavity left after the failed total hip (in this picture it is the cavity in the thigh bone).
Into this stable bed of crushed bone chips the surgeon then cements the shaft of a total hip prosthesis in the usual way.
Note that the walls of the defect in the thigh bone are very thin, yet still retained.
The surgeon may also use patient's own bone (autograft) and mix it with the allograft chips from the bone bank bone to improve the chances of incorporation of the mass of bone into the patients own skeleton
The femoral heads used for production of bone chips are stored in deep frozen state in special bone banks. The bone banks take different measures, such as irradiation, to guarantee that this bone tissue does not contain any blood borne infection such as AIDS and hepatitis, but also no conventional bacteria.
According to the available statistics about one third of all total hip revision operations use impaction graft method.
After the operation the patients are usually put on a " toe touch" weight bearing regime for 6 - 12 weeks followed by weight bearing as tolerated with two crutches. In some clinics the patients are kept in bed for up to two weeks, although the exercise of the operated on hip starts already the day after the surgery.
Results of the impaction bone graft revision operations
After 4 years, 92% of the impacted total hip prostheses were in function and 91 % of all patients said the result of the revision operation was good to excellent.
96% have had none or slight pain, 97% had limp, 39% used crutches
X-ray pictures indicated that between 30 and 70 % of the bone chips were replaced by the patient’s own bone after 4 years.
Complications of the impaction grafting method
The complications of impaction grafting are similar to the complications occurring after other forms of revision operations: Fracture through the thin bone shell during the operation is relatively frequent (0 to 6%). Such fracture is usually recognized during the revision operation. It is treated by cerclages and other fixation devices that stabilize the fracture. It implies only that the patient will be put on non-weight bearing program until the fracture heals. (Leopold 1999)
Transplantation of massive bone allografts
In some patients the osteolysis has destructed a large part of the skeleton entirely, there are no walls remaining around the defect in the skeleton.
Picture: Use of massive bone allograft
Click on the icon for a full size picture
In this picture the middle upper part of the thigh bone is lacking, instead there is a gaping defect in the wall of the thigh bone. The surgeon must repair this large defect in the thigh bone. Moreover, the surgeon cannot use small bone chips to repair the defect, they will fall out of the defect into the soft tissues.
For repair of such large defects the surgeon may use large pieces of skeleton, for example pieces of the femoral shaft bone that have similar form as the defect.. These bone allografts are taken from corpses, are stored and controlled in special bone banks before the delivery to the surgeon.
The surgeon places such large bone allograft over the defect and fixes it to the patient’s thigh bone with wire cables or wire cerclages.
After the repair of the bone defect with the allograft, the surgeon then implants a revision total hip prosthesis. These are very large surgical procedures, demanding blood transfusion, and lasting several hours.
The allograft is not a living bone, but a piece of a dead skeleton. The allograft will be successively resorbed and replaced by the patient’s own bone tissue. The "creeping substitution" of large chunks of bone is a very slow process, only about 5 mm of the allografts is rebuilt during the ten years after the revision operation!
These operations are done on large orthopedic centers because the surgeon must collaborate with a well functioning bone bank, anesthesiologist, and other specialists.
The complication rate after these highly specialized revision operations is usually higher than after the "usual" revision operations.
There is still discussion ongoing among the surgeons whether these large allografts are as useful as the use of large revision prostheses.
Cemented total hip prostheses in revision operations of loose total hip joints?
Revised cup components implanted with bone cement have a greater risk of failure than cementless cup components.
Use of bone cement for fixation of revised femoral components, on the other hand, has equally good results as the use of cementless components
Operation for silent expansile osteolysis
If the prosthesis component is stable, the surgeon opens only the lesion, removes its content of soft tissue and may place bone grafts in the cavity. If the polyethylene cup is worn out, it should be exchanged.
It is not necessary to move the stable prosthetic component. The majority of such lesions heal and the osteolysis process does not return even if the surgeon did not succeed to remove all soft tissue content of the cavity. This is a relatively modest operation. After this operations, the patients are allowed weight bearing as tolerated with crutches for six weeks and then full weight bearing.
If the component is not stable, the surgeon must remove all soft tissue in the defect, fill the cavity with bone graft and then place a larger component in the defect and anchor it reliably in the remaining skeleton. . Patients are placed on protected weight bearing with crutches for six to twelve weeks after such operation. This is a big operation. The majority of the lesions treated in this way also heal, but the complication rate and the necessity of blood transfusion is higher in these operations.(Maloney 1997)
The main complications
that might occur after revision operation of a failed loose total hip prosthesis are
fracture of the thigh bone (0-6%)
damage to the nerves (0-3%)
dislocation of the revised total hip joint (0-3%)
postoperative infection (0- 2%).
All these complications are treatable.
Risk factors for failure of a revision operation
Early failure of the first total hip prosthesis:
If the primary total hip prosthesis failed during the first year after the operation, the risk of a second revision operation is almost doubled compared with total hip prostheses that failed five and more years after the first revision operation
Previous revision operation:
every successive new revision operation increases the risk that the revision operation will fail
FAILURE RATES OF REVISION OPERATIONS of TOTAL HIPS (Swedish statistics)
REVISION OPERATION FAILURE RATE First revision operation failed in 12,5 % Second re-operation failed in 17 % Third revision operation failed in 20 %
What do the patients expect from the new revision operation of the failed total hip.
Of course, all patients with failed total hips expect the disappearance of the troubles with their hip: Statistics show that 92 % of all patients expected pain-free hip joint and 82% of them expected return of good walking ability.
The revision operation relieves the pain in the failed hip but the improvement of the function after the revision operation is lesser than the improvement after the first total hip joint operation.
Satisfaction After primary surgery (% of all patients)
After revision surgery (% of all patients)
overall satisfaction 84% 61 % with pain relief 95 % 69 % with walking capacity 85 % 55 %
See also the chapter Expectations and satisfaction with THR
Conclusion:
The lower rate of satisfied patients after revision operations of the failed loose total hips has two reasons
First, the objective improvement of the function after the revision operation is usually less than the improvement of the hip function after the first operation.
Second, the patients awaiting the revision operation have often unrealistically high preoperative expectations, engendered often by insufficient or incorrect information. (Eisler 2002, Haddad 2001)
For more details on aseptic loosening of total hip joints
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References:
Böhm et al J Bone Joint Surg-Am 2001;83-A: 1023- 31,( Wagner revision prosthesis)
Eisler et al J Arthroplasty 2002; 17: 457 -62
Haddad et al J Arthroplasty 2001;16:87-91
Fitzpatrick WO, J Arthroplasty , 2002;17:165 -71
Leopold et al J Bone Joint Surg-Am, 1999, 81-A;1080-92)
Maloney WJ et al J Bone Joint Surg-Am 1997;79-A: 1628- 34
Zicat B et al. J Bone Joint Surg-Am 1995;77-A: 432 - 39
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