UNCEMENTED TOTAL HIP ARTHROPLASTY USING ANATOMIC-SIZED METAL ON METAL BEARINGS

Abstract

On hundred and ninety unselected patients, mean age 62(SD12.8) were operated upon by one surgeon, using same approach.

HSS improved from 33 to 75 post-operatively, the low figures reflecting a high percentage of Charnley C patients (71%). There was a 5% mortality rate from unrelated causes. Early complications included a 2.97% femoral fracture rate within 4–8 weeks of surgery (analysis showed no relation between implant position, BMI, age or Charnley classification, but there was correlation between high level of satisfaction and early weight bearing). There was one infection and one dislocation. Late complications included 3 periprosthetic fractures, 3 dislocations and 2 aseptic cup failures. However, 30% of patients developed groin pain, increasing stiffness and clunking at 1–2 years following surgery. These patients were investigated with an ultrasound scan. 28 patients (14%) had an effusion and were aspirated. Chrome and cobalt levels in synovial fluid, blood and urine were very high. 13 patients have been revised. 1 showed infection, 10 showed metal allergy and 2 a mixed picture of allergy and foreign body reaction.

In our MOM database (762 hips including the current study) a total of 35 patients were revised for similar problems. Two distinct histological finding were observed. Metal allergy occurred independently of cup angle. The implants were well fixed; there was tissue necrosis and histological evidence of ALVAL. There was no infection or metalosis.

FB reaction occurred more frequently when the cup was open. The Implants were loose; there was naked eye evidence of metalosis and metallic particles seen on light microscopy. We concluded that Birmingham/Freeman Hybrid had high complication rate without significant functional superiority, and other MoM devises shared similar complication. Both Metal allergy and FB reaction can occur in MOM THR. Ultra sound is a good screening tool in symptomatic patients.