Deborah J. Ammeen

Revision of failed unicompartmental knee arthroplasty.

Little information has been published on the salvage of failed unicompartmental knee arthroplasty. The current authors examined the failure mechanisms, complexity of surgery, and complications in such revisions. Of 39 consecutive unicompartmental knee revisions, two patients died within 2 years of surgery, four had inadequate followup, and one was excluded because of infection before revision. Therefore, 30 patients (32 knees) were followed up a mean 53 months. The patients were a mean age of 59 years at the time of unicompartmental knee arthroplasty and were predominantly male (60%). Revisions were done 9 to 204 months after the unicompartmental knee arthroplasty. The predominant failure mechanism was polyethylene wear; however, nine failed because of loosening. The mean polyethylene thickness of the failed arthroplasties was 7.3 mm. Revision procedures were straightforward. Ten patients required local autograft but no allografts were used. Primary femoral components were used in all patients; 25 were cruciate-retaining. Fourteen patients had stemmed tibial components; eight had wedge augments. The mean range of motion after revision was 111°. Six patients had complications not requiring intervention. Three patients had rerevision surgery for polyethylene wear at 76, 77, and 102 months, respectively, two of whom required polyethylene insert and patellar component revision. The third patient also required tibial component revision for osteolysis. Although this is a small series, the simplicity of the procedure and the complications encountered compare favorably with those of total knee revision.

Wear and Osteolysis Around Total Knee Arthroplasty

Osteolysis induced by wear debris of ultra-high-molecular-weight polyethylene has emerged as a significant problem after total knee arthroplasty. The generation of polyethylene wear and the development of osteolysis around total knee arthroplasty are caused by a combination of patient, implant, and surgical factors. Activity level over time may be the most important patient factor affecting the loads placed on a total knee replacement, but it is the most difficult to manage. Multiple factors related to the manufacturing of the polyethylene implant influence the extent of wear, and surgeons should be cautious in considering enhanced polyethylenes pending results of further investigations. The optimal design of the articular bearing surface remains controversial but needs to be considered with respect to the stresses imparted on component-bone and modular tibial backside interfaces. Surgical factors, including restoration of alignment and ligament balance, are important for long-term durability of the implant. Methods of measuring the wear of total knee implants are still evolving. Thus, when confronted with a worn total knee implant and developing osteolysis, the surgeon should consider each of these factors in selecting the best management option to eliminate the source of debris and minimize the potential for wear and osteolysis following revision.

Use of structural allograft in revision total knee arthroplasty in knees with severe tibial bone loss.

BACKGROUND Tibial bone loss is frequently encountered at the time of revision total knee arthroplasty, and the outcome of the revision often depends on the management of this bone deficiency. We examined the clinical and radiographic outcomes of a series of revision total knee arthroplasties in which a structural allograft had been used to reconstruct a tibial bone defect encountered at the time of the revision procedure. METHODS From January 1985 through September 1999, one surgeon performed revision arthroplasty in forty-nine knees (forty-seven patients) with a severe tibial bone defect. The reasons for the revisions included polyethylene wear and osteolysis in twenty-four knees, aseptic loosening in seventeen knees, infection in five knees, and failure for another reason for three knees. Structural allograft was used alone in thirty-five knees and in conjunction with a tibial augment in fourteen knees. The mean age of the patients at the time of the revision arthroplasty with the allograft was sixty-seven years. The patients were assessed clinically with use of the Knee Society score and radiographically. RESULTS The status of the implant was known for forty-six of the forty-nine knees in this study. It was unknown for one patient (one knee) who was lost to follow-up and for two patients (two knees) who died less than five years postoperatively. Four revision procedures in four patients failed and required a reoperation. Two of the failures were due to infection. At a mean of ninety-seven months postoperatively, the mean Knee Society clinical score was 84 points for the knees that had not had a reoperation due to failure. The mean arc of motion improved from 87 degrees preoperatively to 103 degrees at the most recent follow-up evaluation. Histological evaluation of specimens retrieved at two autopsies demonstrated graft union to host bone. CONCLUSIONS A structural allograft provides a stable and durable reconstruction of a tibial bone deficiency. At a mean of ninety-five months postoperatively, we found no instance of graft collapse or aseptic loosening associated with the structural allograft. We recommend the use of a structural allograft for the management of severe tibial bone deficiency at the time of revision total knee arthroplasty.

CLASSIFICATION AND PREOPERATIVE RADIOGRAPHIC EVALUATION: KNEE

Preoperative radiographic planning for revision total knee arthroplasty begins with obtaining excellent quality AP and lateral radiographs that permit: 1. Evaluation of the extent of bone loss in the metaphyseal region of the femur and tibia. 2. Full visualization of the patients intramedullary canal for determining appropriate stem size and length. The surgeon should then determine the appropriate bone defect classification, keeping in mind the provisions needed to address Type 2 and 3 defects. These provisions include any augments or allografts, stemmed components, and the degree of component constraint needed in the patients revision surgery. Through preoperative templating, the surgeon can determine whether a particular implant system provides the options necessary to achieve an optimal surgical result. Whenever templating leaves unanswered questions regarding the extent of bone damage or the degree of knee instability, the surgeon must prepare for the worst case scenario to ensure that the appropriate components and graft material are made available.

Rapid Polyethylene Failure of Unicondylar Tibial Components Sterilized with Gamma Irradiation in Air and Implanted After a Long Shelf Life

Background: The mechanical toughness of polyethylene that has been sterilized by gamma irradiation in air decreases after a long shelf life. The purpose of the present study is to report the high failure rate after unicondylar knee replacements performed with polyethylene bearings that had been sterilized with gamma irradiation in air and implanted after a shelf life of ⩽4.4 years. Methods: Between December 1997 and January 2000, seventy-five unicondylar knee replacements were performed in sixty-two patients. All patients were followed both clinically and radiographically. A revision operation was offered when the patient had pain, swelling, and radiographic evidence of rapid polyethylene wear. The effect of aging of the polyethylene during storage was evaluated by dividing the knees into three groups on the basis of shelf life and comparing them with regard to the rate of revision and the observed wear of the polyethylene. Four retrieved components were examined for the presence of oxidation. Results: At a mean of eighteen months after the arthroplasty, thirty knees had been revised and seven were scheduled for revision. The rate of polyethylene wear increased as the shelf life increased. There was a significant inverse linear correlation between the shelf life of the polyethylene and the time to revision (p < 0.01, r2 = 0.64). All retrieved components had greater-than-expected wear with pitting and delamination of the surface. Seven components had fractured, and ten had both fractured and fragmented. Analysis of four components confirmed severe oxidation of the polyethylene. Conclusion: The present study demonstrated early, severe wear of tibial polyethylene bearings that had been sterilized by gamma irradiation in air and stored for ⩽4.4 years. This risk can be minimized by ensuring that implants have not been sterilized with gamma irradiation in air and stored for several years.

Influence of surgical approach on lateral retinacular releases in total knee arthroplasty.

The rate of lateral retinacular releases in 2 groups of patients who underwent knee surgery performed by the senior author is compared and the factors that contribute to these differing rates are discussed. The first group of subjects consists of 88 patients who had total knee arthroplasties performed with a standard medial parapatellar approach between August 1987 and August 1988. The second group is comprised of 88 patients who had total knee arthroplasties through a midvastus surgical arthrotomy that splits the fibers of the vastus medialis muscle. This method is used by the senior author for all primary total knee arthroplasties. Lateral retinacular releases were performed in 50% of the cases in the medial parapatellar group versus only 3% of the cases in the midvastus group. Patellofemoral instability occurs as a consequence of incising the quadriceps tendon in the medial parapatellar approach and results in the need to perform lateral retinacular releases. The reduction in lateral retinacular releases is attributed to the fact that the midvastus approach leaves the connection of the vastus medialis to the quadriceps tendon intact.

Results of total knee arthroplasty with medial epicondylar osteotomy to correct varus deformity.

The clinical results of using medial epicondylar osteotomies to correct varus deformities in total knee arthroplasties were investigated. Unlike the traditional method of subperiosteal stripping of tibial ligaments, this alternative does not damage ligaments. Between 1991 and 1996, the senior author performed medial epicondylar osteotomies in 80 patients (93 knees) with primary total knee arthroplasty; of these, 60 patients (70 knees) were available for 2- to 4-year followup. At followup, no patients reported knee instability. Mean varus and valgus stability measured 14.2 points (Knee Society scale, 0-15 points). The Knee Society clinical score was 93 points, compared with a preoperative score of 42 points. The mean range of motion at followup was 111 degrees, compared with a preoperative mean of 101 degrees. The postoperative tibiofemoral angle on full limb radiographs taken with the patient weightbearing averaged 7 degrees valgus, compared with an average 6 degrees varus preoperative angle. Ninety-five percent of the patients were satisfied and reported less pain and improved knee function. Bone union occurred in 54% of the knees and fibrous union occurred in 46%. Focal tenderness, restricted motion, or other symptoms were not associated with fibrous union. The results show that epicondylar osteotomy for varus knee deformity provides excellent patient satisfaction, knee stability, motion, and deformity correction.

Learning Curve With Minimally Invasive Unicompartmental Knee Arthroplasty

This study examined 445 consecutive minimally invasive unicompartmental knee arthroplasties (UKAs) from one institution to determine whether revision and reoperation rates would decrease as the number of cases performed increased, indicating the presence of a learning curve with this procedure. At a mean of 3.25 years, 26 knees required revision yielding an overall revision rate of 5.8%; survivorship at 2 years with revision as an end point was 96% +/- 1.7%. Both revisions and reoperations decreased over time but not significantly. For the first half of UKA cases performed vs the second half, revision rates fell from 5.0% to 2.5%, and reoperation rates fell from 8.1% to 5.4%. These data demonstrate that despite modifications made to improve surgical technique across time, a substantial complication rate with this procedure persists.

Synovial entrapment: A complication of posterior stabilized total knee arthroplasty

Background: We observed a complication of posterior stabilized total knee arthroplasty involving hypertrophy of tissue proximal to the patella associated with pain during active knee extension from 90° of flexion. The purpose of this paper was to describe synovial entrapment and to determine if design features of the prosthesis predispose patients to the complication.Methods: Between April 1990 and June 1999, we performed 459 consecutive posterior stabilized primary total knee arthroplasties using three prosthetic designs with different femoral intercondylar geometries. We identified twenty-six patients (twenty-seven knees) in whom arthroscopic débridement of the knee or open arthrotomy with débridement of the knee had been subsequently performed because of a diagnosis of synovial entrapment. We reviewed the records of these patients to identify the knee components that had been used and the symptoms and conditions that necessitated additional treatment.Results: Symptoms (grating, crepitation, and pain with active knee extension from 90°) necessitating subsequent débridement occurred in 13.5% (nineteen) of 141 knees treated with the Anatomic Modular Knee-Congruency implant, 3.8% (eight) of 212 treated with the Anatomic Modular Knee-Posterior Stabilized implant, and none of the 106 treated with the Press Fit Condylar Sigma-Posterior Stabilized implant. All patients had difficulty rising from a chair and climbing stairs; however, none had symptoms when standing or walking. No patient had a patellar clunk. The symptoms occurred at a mean of seven months after the arthroplasty in the patients with an Anatomic Modular Knee-Congruency implant and at a mean of twenty months after the arthroplasty in those with an Anatomic Modular Knee-Posterior Stabilized implant. Débridement of the frond-like hypertrophic synovial tissue at the distal aspect of the quadriceps tendon alleviated symptoms in all patients. No nodules were identified during the arthroscopy.Conclusions: Synovial entrapment is characterized by hypertrophic synovial tissue at the superior pole of the patella. Use of a posterior stabilized femoral component with a proximally positioned or wide femoral box is more likely to result in this complication.

Outcome of knee arthroplasty in patients with poor preoperative range of motion

In the current study, 27 consecutive total knee arthroplasties in 21 patients were assessed. All patients had a preoperative range of motion of less than 50°, severe debilitation, and a minimum clinical and radiographic followup of 2 years (mean, 6 years; range, 2.3–11.8 years). The mean preoperative arc of motion was 30° (range, 0°–50°) and improved to a mean 74° (range, 15°–110°) postoperatively. Preoperative flexion contracture was corrected from a mean 28° (range, 0°–60°) to a mean postoperative flexion contracture of 4.4° (range, −5°–30°). In this series, the overall complication rate was 41% and the revision rate was 18.5%. The clinical significance of this study is that patients with stiff knees who are debilitated severely can have an improved quality of life after total knee arthroplasty, reflected by an increased walking tolerance, increased functional abilities, and decrease in pain, but in association with a high risk of complications and subsequent revisions.