OVERALL MANAGEMENT OF INFECTIONS AROUND TOTAL KNEE AND HIP ARTHROPLASTIES

Transcription

1 OVERALL MANAGEMENT OF INFECTIONS AROUND TOTAL KNEE AND HIP ARTHROPLASTIES I would like to share our experience in managing 51 infected total hips and 6 infected total knees between 1970 and 001. In a survey of all Orthopaedic Surgeons in South Africa, aimed at determining the frequency of total joint replacement, it was found that the ratio of primary total hips to primary total knees performed in the country was ½ to 1. The ratio of infected arthroplasties is 1.85 total hips to 1 total knee. The incidence of infection in knee arthroplasties is therefore about 5% higher. The presentation, management and prognosis of infected total hips and total knees differs somewhat. Early infection around a total knee arthroplasty usually presents as either acute inflammation or wound dehiscence or necrosis or haematoma or synovial fistula. There are several conditions that mimic or predispose to infection so one must establish firmly whether there is indeed superficial soft tissue infection or deep infection in the joint. When these complications present within six weeks after total knee I prefer to immobilise the knee and prescribe a narrow spectrum antibiotic while establishing the exact nature of the pathology. Early and vigorous mobilisation of the joint after replacement arthroplasty can itself initiate and encourage wound break down and inflammation. Where infection threatens a wound a plaster cast has the added advantage of limiting the opportunity to peer at the wound. I believe that every exposure invites colonisation by bacteria particularly if there is a joint fistula pumping synovial fluid. The antibiotic selected should have a narrow spectrum targeted at gram-positive cocci, because these are the most common pathogens initially encountered. When necrosis is limited to the skin and is clearly demarcated it should be excised and repaired urgently before infection spreads deeper into the joint itself. The diagnosis of infection is not always easy to establish. Inflammation, swelling and fever have many causes, apart from infection. On the other hand infection may exist with an intact wound. Laboratory investigations and radiological examinations do not always give clear answers in the early stages. If the swelling is due to effusion and not soft tissue thickening, aspiration can be helpful. When examining fluid aspirated from the joint, besides microscopic examination, bacterial culture and antibiotic sensitivity, I also pay particular attention to the number and type of white cells infiltrating the fluid and I look for a low synovial sugar to help me overcome the high incidence of falsely negative bacterial cultures. These amount to 1 in 3. Early infection around Total Hip Replacements As with total knee replacements cellulitis and oedema may be seen soon after total hip replacement. The management is precisely the same. Haematoma and seroma is more likely to cause early problems after total hip than skin sloughing or dehiscence. Although wound dehiscence and visible skin necrosis is an unusual complication of total hip arthroplasty one should remember the hidden soft tissue necrosis which may be present beneath the skin. Sonar can determine the existence and the depth of fluid collections and differentiate them from oedema. Up to one third of haematomata and seromata may go on to deep infection so 1

2 there may be good reason to evacuate these early. In doing so one gets a second chance to debride tissue which may have been permanently injured by prolonged and powerful retraction or tight sutures or devices used to fix the trochanter. Tissues which have been dissected and divided by cautery may be injured for a considerable distance away from the point of application. These damaged tissues will offer a fertile medium if any bacteria arrive on the scene. When I do so I advocate the use of local instillation of antibiotics and suction drainage to prevent the development of infection. It takes only a small shower of passing bacteria to take advantage of such compromised tissue. When this happens there is a race between the bacteria and the normal defences of the host. If the host succeeds the bacteria are eliminated but if the bacteria prevail they attach themselves to the prosthesis or devitalised tissue and then cover themselves with a protective layer of biofilm which will protect them from antibiotics, antibodies and other natural defence mechanisms and even the manipulations of surgical interventions. In my experience one has a better chance to prevent or abort infection within the first six weeks after surgery. After that the hope of successfully eradicating infection diminishes. Early Synovectomy It would seem logical to consider radical debridement, including synovectomy, without removing a knee or hip prosthesis when one finds infection penetrating down to the prosthesis but not yet apparently intruding into the bone cement interface. When I do so I like to follow this with local antibiotic instillations and suction drainage. EARLY SYNOVECTOMY Good Fair Poor 19 TKR 9 Infected 5 % 55% % 11 THR 11 Infected % 45% 7% We performed debridement and synovectomy in 19 patients after total knee. Infection was confirmed in 9 at operation. Of these were cured and 5 were relieved of their infection. We also debrided 11 hips in which all were confirmed to be infected.3 of these were cured and 5 were relieved of their infection. There are two risks that we gamble with in these circumstances. One is that we really have no way of assessing accurately with the naked eye whether infection has already penetrated that tiny microscopic gap between bone and cement. The main reason for failure however is probably the invisible layer of glycocalyx or biofilm on the implant. Antibiotics such as Clindamycin or Linezolid are said to be able to penetrate biofilm.

3 EVALUATION OF DEGREE OF OUTCOME Points Clinical Laboratory Radiological 5 Pyrexia Exudate Neutrophilia Positive bacterial Cultures New bone loss Sequestrum 4 Inflammation Oedema Decreasing PCV Hb MCV MCH 3 Lymphadenopathy Baseline Blood Count & Iron Local warmth Improving Blood Count & Iron 1 Nothing abnormal Ferritin:Iron Ratio Less than 5:1 New periosteal Reaction No change Sclerosis Persists Trabecula normal Negative isotope Points Scoring Good Fair Poor Assessing control of infection after treatment: Clinical, laboratory and radiological parameters are used to assess the result. The intensity of infection can be divided into five grades in each of the three modes of examination according to the features expressed. Five points for the most obvious features of infection and one point for normality. In all three modes a score of 5 indicates definite failure to eradicate infection while a score of 1 indicates definite success in curing the infection. A score of 3 in all areas would be the condition to be found immediately after surgery. This would give a total of 9 points. From this central score further points are gained or lost according to improvement or deterioration. At the time of evaluation a total score from 3 to 6 signifies a cure or good result; 7 to 11 a fair result and 1 to 15 a poor score or failure to control infection. CONSERVATIVE MANAGEMENT High surgical risk Very ill patient Advanced age Tolerable pain Acceptable disability Low functional demand Good bone stock Depleted bone stock Unwilling patient Unrealistic hopes Very well patient Uncertain diagnosis Conservative Management: Once infection is established conservative management becomes an option. It may seem odd to advocate conservative management for a condition which we know has no hope of spontaneous resolution, but if one makes a careful audit of the advantages and disadvantages of surgery, one can actually find a host of good reasons for masterly inactivity. Conservative management may be the best option when one is confronted by high risks compared to the reasonably expected gains of surgery. This option may also be attractive when one compares the degree of disability to the demands of the patient s lifestyle. One can afford to wait if the 3

4 patient has good bone stock provided one monitors this regularly and is prepared to act as soon as bone begins to melt away before your eyes. On the other hand if the bone is already so destroyed that one s chances of reconstructing the limb are seriously compromised, it is better to be wise than to be brave. We find conservative management acceptable to about one third of our patients with established infection around a knee arthroplasty and one quarter of the infected hip arthroplasties. The most persuasive reason to follow this course is if the intensity of pain is acceptable. PAIN ASSOCIATED WITH JOINT REPLACEMENT (A) SOFT TISSUE ABSCESS PAIN ASSOCIATED WITH JOINT REPLACEMENT (B) INTERFACE INECTION Cause Fluid under tension in soft tissues Provocation Direct pressure Cause Fluid under pressure inside a bone Provocation Nothing special Perhaps wt bearing Pain Constant Relief Drainage Pain Constant & persistent Relief When fluid escapes The character of pain provides a valuable clue to the underlying pathology causing that pain. Where there is acute inflammation this may become particularly severe when an abscess develops under tension in the soft tissues. This pain is constant and unaffected by movement and weight bearing. It is tender to pressure and relieved by incision and drainage in order to release the tension. Pressure inside the bone may cause pain, particularly when fluid is bottled up within the confines of the interface between bone and cement or in the medullary canal beyond the prosthesis. Such pain is constant and persistent. It may not be aggravated by weight bearing if the prosthesis is firmly fixed. However, if a cloaca or a defect occurs spontaneously in the bone, or if the fluid can escape through a defect between bone and cement this provides a perfect release valve and thus pain may be relieved or averted. PAIN ASSOCIATED WITH JOINT REPLACEMENT (C) LOOSENING PAIN ASSOCIATED WITH JOINT REPLACEMENT (D) IN RESPONSE TO HEAVY ACTIVITY Cause Fluctuating hydraulic pressure in bone Provocation On weight bearing Or movement Cause Inflammatory oedema Mechanical irritation Provocation Excessive activity Pain On initiating activity Relief Dissipation of pressure on resting Pain Only on provocation Relief Rest and passage of time or steady activity Loosening causes pain because the movement of the loose prosthesis which generates fluctuating hydraulic pressures during pistoning movement and particularly during weight bearing. The fluid under pressure may disperse after a few paces and then this initiation pain disappears. It is absent at rest. Later it may return after sustained activity because of inflammation due to mechanical irritation. 4

5 One may encounter an obviously infected knee arthroplasty with loss of bone between the implant and joint surface but because the stems of the two components are well fixed in bone the patient does not complain of pain. So we find many people who can get by even with a draining sinus because this prevents the build up of tension or because there is no significant loosening of their prosthesis in spite of the infection. This is more so if they are able to accept some limitation of activity or they can get more comfortable with a walking aid. Low-grade musculo skeletal infection presents little or no threat to health, let alone life in the majority of cases. Ultimately the plan of management is based on a decision arrived at by consensus between the doctor, the patient and the family. The bottom line is there is no escaping the fact that each successive revision becomes more compromised than the previous one and the durability or survival of the arthroplasty falls off markedly after each operation. At the same time the risk of persistent infection rises steeply with each operation. Exchange Arthroplasty: A quarter of our patients with infected total knee replacements and half of those with infected total hip replacements had an exchange arthroplasty. In the literature good functional results are reported in on average about out of 3 revisions of total knee replacement when infection is not a factor. For total hip revision the figure is more like 3 out of 4 on average. Exchange arthroplasty is not to be taken lightly when there is infection. It can be technically extremely difficult to preserve bone while removing all the cement. It can be brutally traumatic to remove every speck of infected tissue. The duration of surgery may be as little as two and a half hours for the removal of an easy knee arthroplasty, or up to eight hours for a well fixed hip arthroplasty surrounded by extensive fibrous and calcified scar tissue around the hip. The blood loss will be at least litres for a total knee replacement and up to twenty units or 10 litres for a tough hip. Auto transfusion is generally not considered to be a safe option in the presence of infection. Spectacular complications such as injuries to the iliac, femoral and popliteal vessels and the sciatic and femoral nerves are fortunately rare, but not unknown. This kind of surgery is not for the faint hearted. Success is directly related to uncompromising thoroughness and shrewd familiarity with the anatomy. Such surgery can only be justified by significant pain or instability, sufficient bone stock, technical feasibility and a healthy patient. A one-stage exchange is indicated for milder and less extensive infections, especially if it is difficult to distinguish between pure loosening or granuloma given the fact that any combination of these three pathologies can exist in any one patient. My policy is to treat all such patients as though they were infected although I will occasionally spare a securely fixed component. I send many tissue specimens for bacterial culture and then set up an irrigation and suction system which I will maintain for about a week by which time I should have received the results of the cultures on the biopsy material. If these are negative I simply abort the irrigation, having lost nothing but gained excellent prophylaxis against new infection anyway. 5

6 ONE STAGE EXCHANGE For milder less extensive uncertain infection Loosening polythene granuloma and infection may be in combinations and difficult to distinguish In doubt treat all as septic until proven otherwise then abort irrigation valuable prophylaxis 17 of our total knees suspected of infection were revised in one stage. Only 9 were confirmed infected. 50 patients had their total knee arthroplasties revised in two stages. 65 of our total hips were revised in one stage while 198 were revised in two stages. A single operation has some obvious advantages. The costs are halved and the period of hospitalisation or recumbency is halved for knees and reduced to one third for hips. The less obvious advantages of one-stage exchanges of knees are the greatly reduced incidence of wound morbidity and in both hips and knees there is a lower incidence of thrombo-embolic disease a potentially fatal complication. Naturally post-operative rehabilitation will be expedited. The most important advantage of a two-stage programme is a better chance of curing infection. It may take longer to rehabilitate after a two stage programme but at the end of the day there is little difference in the final level of pain and function between one and two stage exchanges of hips and knees. Among the advantages of a two stage programme is the fact that one hasn t burnt one s bridges because if the operation fails to bring the infection under control one can either repeat the debridement or switch to arthrodesis in the case of a failed knee arthroplasty or leave the hip as an excision arthroplasty in which the levels of pain and infection have a far greater chance of settling down than in the presence of an arthroplasty. 1 Stage Knee Stage Knee 1 Stage Hip Stage Hip Please note PERCENTAGE PERSISTENT INFECTION Good Fair Poor % Only the most favourable qualify for one stage programme (55.5) () (4) (14) The most important difference between the two is the rate of cure of infection. 44% of our knee arthroplasties and 58% of our hips are successfully cured of infection after a single operation or one stage exchange. 78% of patients with infected knee arthroplasties and 86% of patients with infection around hip arthroplasties are cured of infection after a two-stage procedure. When making comparisons one should not lose sight of the fact that only the most favourable cases are selected for a one-stage exchange. 6

7 Salvage Procedures: When the extent of infection and soft tissue pathology is so extensive or when the loss of bone does not permit reconstruction by arthroplasty, a salvage procedure has to be considered. These mutilating procedures undoubtedly leave the patient considerably disabled but their attraction is they offer the best possibility for cure or durable remission from infection and freedom from pain. For knees this usually means arthrodesis and for hips an excision arthroplasty. RESULTS OF 77 KNEE ARTHRODESES Good Fair Poor Failed % 1 Stage external fixator (33.3) Stage closed nail (80) Stage open nail (36.4) Stage external fixation (THR on same side) (33.3) 77 (47.%) of our patients with infected knee arthroplasties had an arthrodesis using either a long intramedullary nail or an external fixator. If the patient is young with good hard bone we perform an arthrodesis in one stage using an external fixator, especially if there are skin defects resulting from destructive sinuses. If the bone is osteopaenic and soft or if there are large bone defects, giving poor coaption of bone, an intramedullary nail is preferred. This requires better control of infection and therefore a two-stage programme. Many patients had removal of their knee arthroplasties and debridement hoping to replace the arthroplasty at a second procedure but when control of infection proved to be unsuccessful after the first debridement, the second procedure was changed to arthrodesis. Remember that many such patients required an intramedullary nail in the face of dubious fascio cutaneous flaps or gastrocnemius flaps and poor general resistance to infection. 9 Patients were suitable for arthrodesis of the knee following removal of a total knee arthroplasty in one stage using an external fixator. 6 had good results and 3 poor. In an attempt to avoid the terrible wound complications associated with a two-stage programme I fixed 10 knees by driving a nail down the leg without opening the knee joint. Only of these had a good result and 8 a poor one. I think this was because of all the tissue that was stripped and sequestrated to die inside during reaming and insertion of the nail. I now prefer to open and debride the knee when fixing it with a long intramedullary nail. A good result was achieved in 34 of 55 patients thus treated. In 3 patients I fixed the knee with an external fixator in a two-stage procedure. We were obliged to do this because of a total hip replacement present in the same femur. Although were cured of their infection, none of them achieved bony ankylosis. 7

8 RESULTS OF 108 EXCISION ARTHROPLASTIES 87 (75%) cured at first procedure 98 (93.5%) cured after further attempt 10 (6.5%) infected but comfortable Excision Arthroplasty: We left 108 of our patients with an excision arthroplasty either because they had insufficient bone stock to support another arthroplasty or because they were too sick for the prolonged immobilisation. Most however suffered this fate because we could not control their infection with an arthroplasty in place. 81 (75%) were cured of their infection at the first attempt and another 17 achieved this happy result after a further procedure bringing the cure rate of infection to 93.5%. Drastic Cures: 5 of our patients ended up with an above knee amputation after failing to control infection after total knee arthroplasty and three had a disarticulation for a similar problem with a total hip replacement. Serious Complications: Two of our patients died during the second stage of total hip exchange and one had a serious vascular accident in the first stage after such a procedure. One patient died soon after having an excision arthroplasty and one had a serious vascular accident. One patient had a serious vascular accident during the second procedure of a two-stage exchange total knee and one patient died during a one-stage exchange of knee. Pulmonary embolism was the commonest cause of death followed by myocardial infarction. SUMMARY OF OVERALL MANAGEMENT Knees % Hips % No operation 94 (36.0) 131 (8.4) Synovectomy 19 ( 7.3) 11 (.1) 1 Stage exchange 17 ( 6.5) 65 (1.6) Stage exchange 50 (19.1) 198 (38.4) Excision arthroplasty 108 (0.9) Arthrodesis 78 (9.9) Amputation 3 61 ( 1.1) ( 0.6) This presentation is clearly a retrospective audit. We are not looking at an academic prospective double blind random selection trial. I don t believe that would be ethical or moral in these circumstances. We did have some patients who went on to exchange arthroplasty after failed synovectomy or who went on to arthrodesis or excision arthroplasty after a failed exchange. In the end the selection of a procedure was based on what we thought was best for the patient or what the patient thought was best for them based on our experience. It is most obvious that we tended to replace more hips (50%) than knees (5%) because our experience was that we were slightly more successful with hips than with knees. 8

9 SURGICAL RESULTS 166 TOTAL KNEES Good Fair Poor % Synovectomy 19 (9) 5 () 1 Stage exchange 17 (9) 5 (55) Stage exchange () Arthrodesis: 1 Stg XFX Stg XFX Stg closed nail Stg open nail (33.3) (33.3) (80) (36.4) Gaiter 1 1 (0) Amputation 3 1 (33.3) Surgical outcome of infected total knees We failed to control infection in % of total knees treated by synovectomy and irrigation and 55% of total knees treated by one-stage exchange. We were tempted to adopt this programme because we thought it would be advantageous to shorten the programme and thus have a better chance of ending up with a mobile knee. However the high failure rate caused us to treat such patients with a two-stage exchange where we had only % failure. We went through a learning curve with arthrodesis. External fixation was generally not effective in gaining bony ankylosis except in a few selected young patients with good bone stock and minimal body fat. There we failed to control the infection in one third but all achieved bony ankylosis. We used intramedullary rodding to fix the majority of our patients who had poor bone stock. When this rodding was done blind we failed to gain control of the infection in the vast majority. This caused us to revert back to open nailing with debridement but we still failed to gain control of infection in 36%. This is not terrible because we can remove the nail when the knee is fused and finally eradicate the infection. One patient amazed us when his knee fused after the initial debridement and he wore a long brace. Our earlier experience suggested that fusion was not that readily achieved. Those who had amputation were desperate. They all had terrible loss of bone and severe infection. 9

10 SURGICAL RESULT 385 TOTAL HIPS Good Fair Poor % Synovectomy (7.3) 1 Stage exchange 65 (43) (41.9) Stage exchange (14.1) Excision first go repeat (5.0) (7.4) Disarticulation Hindquarter amputation 1 1 (100) Serious vascular injury Deaths 4 Surgical outcome of infected total hips Compared to the management of total knees we had the same success with simple synovectomy and only slightly better luck with a one-stage exchange of arthroplasty. We were tempted to employ this method particularly when we thought that only one of the two components of the arthroplasty was involved in the infection. I think this is a dangerous assumption. We also include, in this group, patients who had both components exchanged in one operation. Exchange arthroplasty of a total hip in two stages can be very satisfying. The failure rate is much smaller than with two-stage total knee (14%). The cure rate of infection after excision arthroplasty is far better than arthrodesis of the knee as a salvage procedure. This is simply because we leave no foreign body behind after excision arthroplasty whereas when arthrodesing a knee, using a long intramedullary nail, we leave behind a very large foreign body implant. The two patients who had disarticulation of their hips suffered widespread infiltrating infection into the soft tissues around the hip along with such severe loss of bone that the vestigial remaining would have been quite useless. I recall our patient whose infection was not brought under control even by hindquarter amputation. This unfortunate patient had had the area extensively irradiated for malignancy, which made tissue healing and control of the infection pretty much impossible. 10