J A Rand

From 1971 through 1987, 9200 total knee arthroplasties were performed at the Mayo Clinic. Actuarial analysis was used to estimate cumulative rates of survival. Use of a proportional-hazard, general linear model led to the identification of four independent variables that were associated with a significantly lower risk of failure: primary total knee arthroplasty, a diagnosis of rheumatoid arthritis, an age of sixty years or more, and use of a condylar prosthesis with a metal-backed tibial component. When all four of these favorable variables were present (without regard for radiographic changes and non-disabling symptoms), the probability of an implant being in situ was 97 per cent at both five and ten years.

Of 168 consecutive knees (118 patients) that had been treated with an arthroplasty with use of a kinematic total condylar prosthesis that allowed retention of the posterior cruciate ligament, 119 knees (eighty-four patients) were available for review at a mean of 10.0 +/- 0.7 years after the operation. The Hospital for Special Surgery knee score improved significantly, from a mean of 55 +/- 12 points preoperatively to a mean of 81 +/- 9 points at ten years (p < 0.0001). Radiolucent lines about the patellar component, present in thirty-five of eighty-three knees at the latest follow-up examination, were related to malpositioning of the tibial and femoral components. Six revisions were performed, and four of them were for a loose patellar component. The rate of deep infection was 1 per cent (one knee). Complications occurred in twenty-six knees (22 per cent). With revision as the end point, the rate of survival of the prostheses was estimated to be 96 per cent at ten years. The knee scores, the rate of survival of the implants, and the range of motion of the knees in the current study were similar to those reported previously for patients who had insertion of a total condylar prosthesis with sacrifice of the posterior cruciate ligament and for those who had substitution of the posterior cruciate ligament with a posterior stabilized prosthesis. A prosthesis that has a metal-backed tibial component and that allows preservation of the posterior cruciate ligament provides durable results, but loosening of the patellar component remains a major problem.

Pelvic fractures are often the result of high-energy trauma and can result in significant morbidity. Initial management is focused on patient resuscitation and stabilization given the potential for life-threatening hemorrhage that is associated with these injuries. Radiographic evaluation and classification of the pelvic injury guides initial management, provisional stabilization, and preoperative surgical planning. Definitive reduction and fixation of the posterior and anterior pelvic ring is sequentially performed to restore stability and allow for mobilization and healing. Open techniques are commonly used for the pubic symphysis and displaced anterior and posterior ring injuries for which an acceptable reduction is unable to be obtained with closed or indirect techniques. Percutaneous fixation has become increasingly more common for both the anterior and posterior ring and utilizes screw placement within the osseous fixation pathways of the pelvis.

Eighty-six patients with 89 infected total knee arthroplasties were treated with insertion of another prosthesis. Treatment was not according to an established protocol for parameters, such as delay between removal of the infected prosthesis and insertion of the new prosthesis, duration of antibiotics, use of antibiotic-impregnated cement spacers or beads, and use of antibiotic-impregnated cement for prosthetic fixation at revision surgery. Final followup averaged 52 months (range, 6-126 months). Complications occurred in 30 (33.7%) knees, with recurrent deep infection developing in 10 (11.24%) knees. Patient age, medical diagnosis, type of microorganism, duration of parenteral antibiotics, delay between the resection and revision surgery, and use of antibiotic-impregnated cement spacers or beads were not correlated with the cure rate of infection. Use of antibiotic-impregnated bone cement for prosthesis fixation at revision surgery was the only variable that correlated with the cure rate of deep infection. Seven (28%) of the 25 knees without antibiotic-impregnated cement for prosthesis fixation developed recurrent infection compared with 3 (4.7%) of 64 knees with antibiotic-impregnated cement for prosthesis fixation. This difference was statistically significant (p = 0.0025, log-rank test).

We retrospectively reviewed the results in fourteen patients in whom salvage of an acutely infected total knee arthroplasty was attempted between 1970 and 1981 by the implantation of a new prosthesis within two weeks of removal of the infected one. Salvage was successful in six of the seven patients with a low-virulence infection but in only two of the seven patients with a high-virulence infection. Of the eight patients for whom the result was a functioning prosthesis, two had significant restriction of motion and one had moderate pain. If these three patients are eliminated from analysis, the over-all success rate is only 35 per cent (five of fourteen patients). We concluded that the implantation of another prosthesis for the treatment of infection of a total knee arthroplasty should be done with caution, and preferably when the infection has been caused by a low-grade organism and after a waiting period of longer than two weeks.