Septic arthritis

This is another disease in which failure to drain pus early is a real disaster[md]a severe and probably painful disability for the rest of the patient's life. If you don't drain his infected joint early, it will be destroyed and may ultimately ankylose. If he is a child, the epiphyses near it may displace, or dislocate. As soon as you have made the diagnosis, drainage is urgent[md]this is not an operation to leave until tomorrow!

Bacteria can reach a joint: (1) Before the age of 6 months from osteomyelitis in the metaphyses of any long bone. After this age the epiphyseal plates prevent spread like this. (2) At any age in the hip, because the proximal metaphysis of the femur is partly within the capsule of the hip joint. This anatomical peculiarity makes septic arthritis of the hip and osteomyelitis of the neck of the femur, virtually the same disease. (3) Through the blood from a distant septic focus. This is haematogenous septic arthritis, which involves the knee, hip, shoulder, and ankle in this order of frequency. (4) Through a penetrating joint wound of a joint, especially of the fingers or knee.

The first sign of septic arthritis is that a patient cannot use his limb. One of his joints, commonly his hip or his knee, becomes so painful that moving it even a little in any direction causes him great pain. Sometimes, several of his joints are involved at the same time. He is usually febrile. The combination of fever and a limb which is too painful to move is either osteomyelitis, or septic arthritis, until you have proved it is not. Later, if the infected joint is near the surface, you will be able to feel that it is warm and swollen with fluid. Unfortunately, the shoulder and the hip are so deep that you cannot easily detect fluid, so that the only local sign is acutely painful limitation of movement.

If septic arthritis always ran a typical course, it would be easier to diagnose. Unfortunately, it often runs a very atypical one. Here are some of the difficulties: (1) If a patient is very old or very young, he may have few general signs of infection, and his effusion may not even appear to be inflammatory. There is only one way to be sure[md]aspirate all joint effusions, and examine them. (2) In the spine, the sacroiliac joints, and the hips, pain may be the only presenting symptom. (3) Only half the patients have a fever or a leucocytosis. (4) You can easily confuse tuberculous arthritis with the subacute type of suppurative arthritis. To distinguish them rely on the X-ray, and your findings on aspiration (pus or caseous tissue). If you are still in doubt, treat the patient for both diseases. Review his progress at 3 and 6 weeks, when suppurative arthritis should show much improvement, whereas it is still too early for tuberculosis to show much change.

The diagnosis is particularly difficult in babies as this case shows.

AHMED (1 year) was brought by his mother saying he had fever and was drawing up his left hip in pain. This in itself was unusual, because, if a baby does this, he usually draws up both of them. He was found to have suppurative arthritis of his right hip, which was too painful to move. It was aspirated, chemotherapy was started within 24 hours, and he recovered. LESSON The diagnosis was made early and treatment started immediately. Remember the risk factors[md]some patients have several: (1) As with infections of other kinds, septic arthritis is more common in the disadvantaged and malnourished. (2) Infancy and old age. (3) Systemic diseases which affect the body's response such as diabetes, chronic renal failure, liver disease, malignancy, the arthritides, intravenous drug abuse, alcoholism, and immunosuppression, especially by AIDS. (4) Local joint-damage due to earlier earlier surgery or osteoarthritis.

Although Staphylococcus aureus is the dominant organism, each risk group has its own characteristic infective organisms, patterns of joint involvement, and clinical response. If the patient has sickle-cell disease, you may find E. coli or salmonellae in his joint. Haemophilus influenzae is the most frequent organism in newborns, but is seldom seen in older patients. Other organisms include streptococci, brucellae, and gonococci. The gonococcus often affects young healthy adults without any obvious risk factor except sexual activity. With other organisms there is usually a risk factor.

When infection is well established, antibiotics seldom help. Occasionally, if you are fortunate, and are able to give the right one early enough, a patient may be lucky and recover without any other treatment.

The X-ray signs of septic arthritis are: (1) Widening of the joint space. (2) The signs of early osteitis (7.4). You may see the first signs of new bone formation as early as the 5th day in an infant, but it will not appear before the 10th day in an older child, and may take longer.

The critical investigation is to aspirate the joint as soon as you suspect infection. Frank pus in the syringe, or even slightly cloudy synovial fluid, confirms the diagnosis. You may get a false negative result, but apart from contaminants in the culture, you will never get a false positive one. Aspiration alone is not enough; it only tells you that pus is present, so incise the joint and wash out the pus. Then insert a corrugated drain, or (in the knee) leave the incision open.

Aspirating the more superficial joints is usually easy, but you may fail to aspirate the shoulder, or the hip. If aspiration succeeds or fails, you must incise and drain the infected joint. The results of not doing so are so serious, that the dangers of attempting it are well worthwhile. If you allow pus to accumulate under pressure in a patient's hip, it may impair the blood supply to the head of his femur within 24 hours, so that it necroses. Pus can also damage a joint, even if the blood supply is not impaired.

If, when you incise an infected joint and wash out the pus, you feel that its surfaces are smooth, he has a good chance of having a normal or a nearly normal limb. His prognosis is worse if cartilage has been lost, if the joint surfaces are rough, if the bone is soft, or if the X-ray shows severe joint destruction. Even so, he still has some hope of a movable joint, especially if he is young[md]a child's epiphysis may appear to be largely destroyed on an X-ray, and yet regenerate considerably.

Several things can happen to a severely damaged joint: (1) It can dislocate. (2) An epiphysis can slip, either immediately, or several weeks later, as with the patient Hasina in Fig. 7-14. Prevent this happening by splinting the joint or applying skin traction. (3) A painless stable bony ankylosis can form in the position of function. Provided it really is stable and is in the position of function, this may be only a minor disability. (4) The patient may get a painful unstable fibrous ankylosis, which can be a serious disability. If ankylosis fails, and his symptoms are severe enough, you may be able to refer him to have his joint fused.

If the patient is a child, and is lucky, he will have a painless joint with a useful range of movement. If he is unlucky he will have a painful joint that will ultimately need operative fusion, but meanwhile his limb will have had time to grow. Fusing a joint is difficult in a child, and is rarely necessary; if it is done too early, there will be growth problems. The decision to fuse an adult's painful joint can be taken much earlier.

If movement in a joint is going to be absent or limited, the position in which it lies is critical. This is described in the next section.

HASINA (17 years) was admitted with pain in her left hip and inability to walk for 3 days. She was given physiotherapy, nursed on a fracture bed for 3 weeks, and discharged on crutches. Some weeks later she was readmitted, febrile, and with a swelling of her right thigh extending from her knee to her iliac crest. Three litres of yellow-green pus were aspirated. Her X-rays are shown in Fig. 7-14.]] MARIAMU (12 years) was admitted with osteomyelitis of her tibia. This was settling nicely when she developed pain in her left hip and became febrile. The X-rays of her hip were normal, septic arthritis was diagnosed, and she was given large doses of the latest broad-spectrum antibiotic. Her pain improved slowly but her fever continued. Later, X-rays showed destruction of the head of her femur. Traction was applied. Sinuses developed, and she was never able to walk again. Two years later her pain was so severe that she had to have her hip disarticulated. All this happened in a ''good' hospital. LESSONS (1) The early diagnosis of septic arthritis of Hasina's hip was not made, although the history and signs were obvious. (2) Rest in bed on traction would have prevented her epiphysis slipping. At best she will have a painful hip, either for life, or until her hip has ankylosed spontaneously, or been fused surgically.(3) Explore a hip on the [f10]suspicion [f09]of septic arthritis. Fig. 7-15 ASPIRATING A JOINT may confirm the diagnosis, if pus is thin enough to come out of the needle. It is not effective treatment because it does not provide enough drainage, and pus may reform. [f10]So always open and drain an infected joint. [f11]A, the shoulder and elbow. B, the wrist. C, the posterior approach to the hip. D, the anterior and anterolateral approach to the hip. E, the knee, and F, the ankle. G, and H, the anterior and posterior approach to the shoulder. A, to F, after ''Hamilton Bailey's Emergency Surgery', edited by HAF Dudley. John Wright, with kind permission. G, and H, kindly contributed by Jack Lange. ASPIRATE AND EXAMINE ALL JOINT EFFUSIONS DRAIN ALL INFECTED JOINTS

SEPTIC ARTHRITIS If possible take several blood cultures from the patient.

ANAESTHESIA. (1) Ketamine (A 8.1). (2) General anaesthesia (A 10.1). (3) To aspirate his joints sedate him and use local anaesthesia.

ASPIRATION. This is diagnostic only: follow it immediately by operative drainage. Push a large (1.2 mm) needle down into the joint, and aspirate as in Fig. 7-15.

SPECIAL TESTS. Culture of the synovial fluid isolates the organism in 30% of cases and blood culture in another 14%. A leucocytosis of [lt]20 000 [gm]l makes the diagnosis unlikely but does not exclude it, especially if the gonococcus is responsible.

ANTIBIOTICS. Give the appropriate antibiotic. If you cannot isolate the organism, chloramphenicol is likely to be the most suitable one (2.9). In acute cases give it for 2 to 3 weeks. In chronic cases give it for up to 6 weeks.

EXPLORATION. Open his infected joint by the methods described in the next section. Operate under a tourniquet where possible, and if his hand is involved, watch out for its nerves. Irrigate the interior of the joint forcefully using a syringe and a litre or two of Ringer's lactate or 0.9% saline. Do this until the fluid comes back clear. Feel the surfaces of the joint.

Leave the wound open. The linear incision you have just made will become elliptical, and you will see the cartilage underneath. If the joint is superficial, it needs no drain. If it is deep, as in the hip and shoulder, insert a rubber drain. The wound will heal spontaneously as the infection subsides.

If his joint surfaces feel smooth, his prognosis is good. After 10 days of rest start gradual active movements.

If his joint surfaces feel rough but some cartilage still covers the bones, he may still have useful function in his joint. If all its cartilage has been destroyed, his prognosis is bad. His best hope is a stable ankylosis in the position of function (7-16).

If there is any danger of his joint ankylosing, make sure it does so in the position of function. If his hip or knee are involved, apply temporary skin traction.

If, later, he has a persistently painful joint with limited movement, refer him for operative fusion. In a child, delay this as long as possible.