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Deep infection after total knee arthroplasty is a rare, but serious complication. The gold standard in the treatment of an infected total knee arthroplasty involves a two-stage protocol with implantation of a temporary spacer. Different types of spacers are used: non-articulating spacers and articulating spacers. The non-articulating spacer causes a temporary arthrodesis of the joint with various complications like deep vein thrombosis, knee stiffness and pain. Further, soft tissue contracture and muscle atrophy complicate the reimplantation and limit the postoperative function of the joint. In order to solve these problems, articulating spacers were developed. They allow for a certain range of motion until the spacer is removed and a revision arthroplasty is performed.
37 patients were included in this retrospective study. They all were treated with a two-stage revision after infected total knee arthroplasty in the Hospital for Orthopedics in Marburg between 2001 and 2008. All patients, with massive bone loss prior to revision, were excluded from this study, because the implantation of an articulating spacer would not have been possible. It was the surgeons decision, which type of spacer was implanted in each patient. In 16 cases an articulating spacer and in 21 cases a non-articulating spacer was implanted.
With implantation of the articulating spacer the fluid bone cement was filled into different sized, preformed molds. After setting of the cement the spacers were implanted in the joint. In 21 cases where a non-articulating spacer was used, firm metal rods were implanted in the medullary canal of femur and tibia. The bone cement was formed manually to a single block and implanted in the joint. In both types of spacers, Gentamycin loaded bone cement was used.
All patients received early mobilisation under supervision of physical therapists. In both groups, no weight bearing of the afflicted leg was allowed. In the group of articulating spacers, the patients were allowed to passively bend the knee until 60°. In the group of the non-articulating spacer, no knee movement was possible. To compare the knee function between both groups, the range of motion (ROM) was evaluated at different times prior to revision of the infected total knee arthroplasty, after reimplantation of the new total knee arthroplasty and at three follow ups: at an average of 11, 19 and 34 weeks after reimplantation.
The eradication of the deep infection was successful in all patients. So all patients were treated with a second stage procedure with removal of the spacer and implantation of a new total knee arthroplasty.
One recurrence of infection was found in the group treated with non-articulating spacers and three cases were found in the group treated with a non-articulating spacer until the last evaluated follow-up. A single case of intraoperative injury of the quadriceps tendon and one single case with pulmonal embolism were the only complications found in this study, each in the group with non-articulating spacers.
The average ROM was 98° in the group of articulating spacer (group A) and 79° for the group of non-articulating spacer (group B) before revision of the infected total knee arthroplasty. At the time of discharge from the hospital after reimplantation of the new total knee arthroplasty the average ROM was 85° for group A and 74° for group B. There was an improvement of the average ROM in both study groups until the last follow up. At this point of time, 34 weeks after reimplantation, the average ROM was 102° for group A and 79° for group B.
Both groups approached the preoperative ROM. There was a significant difference in the ROM between both study groups, at the time prior to revision and at the last follow up. The patients who were treated with an articulating spacer had a better ROM. No significant change in ROM within each group was found between the last follow-up and the preoperative investigation.
In this study the ROM and the infection eradication rates between the two different types of spacers were compared. Although the patients who were treated with an articulating spacer were allowed to move the joint, their infection eradication rate was similar to the one in the non-articulating spacer group. The recurrence of the infection, as well as the rate of complications were low in both groups. The use of an articulating spacer in two-stage revision for infected total knee arthroplasty is a safe alternative to non-articulating spacers.
Patients of both study groups achieved a good level of ROM until the last follow up. A significant improvement of the knee joint mobility by use of articulating spacers could not be demonstrated.
In conclusion, it was shown that the treatment with articulating spacers in two-stage revision for infected total knee arthroplasty is a safe alternative to non-articulating spacers with good knee function and equal infection eradication rates.