Thomas K. Fehring

Early failures in total knee arthroplasty.

Total knee arthroplasty is a predictable operation. Unfortunately, there is a subset of patients who do not do well and require revision surgery within the first 5 years. The purpose of the current study was to analyze the mechanisms of failure in patients who had revision surgery within 5 years of their index arthroplasty. Between 1986 and 1999, 440 patients with total knee arthroplasties were referred for revision surgery. An analysis of patients in whom the arthroplasties failed within 5 years of the index arthroplasty and the reasons for early failure were documented. Of the 440 patients who had revision surgery, 279 (63%) had revision surgery within 5 years of their index arthroplasty: 105 of the 279 patients with early failures (38%) had revision surgery because of infection; 74 (27%) had revision surgery because of instability; 37 (13%) had revision surgery because of failure of ingrowth of a porous-coated implant; 22 (8%) had revision surgery because of patellofemoral problems; and 21 (7%) had revision surgery because of wear or osteolysis. Only eight of the 279 patients with early failures (3%) had revision surgery because of aseptic loosening of a cemented implant. The remaining 12 patients had revision surgery because of miscellaneous problems. Host factors may prevent infection from ever being eradicated totally. The two other major patterns of failure in this series were failure of cementless fixation and instability. If all of the arthroplasties in the patients in this early failure group would have been cemented routinely and balanced carefully, the total number of early revisions would have decreased by approximately 40%, and the overall failures would have been reduced by 25%.

Articulating Versus Static Spacers in Revision Total Knee Arthroplasty for Sepsis

Antibiotic laden spacer blocks frequently are used to treat an infected total knee arthroplasty. Static spacer blocks make exposure at reimplantation difficult secondary to quadriceps shortening. Unexpected bone loss attributable to migration of the spacer block also has been reported. To avoid these problems, a temporary articulating molded implant made of antibiotic cement was used in a consecutive series. The authors sought to determine whether its use would affect the reinfection rate, improve functional results, or prevent bone loss compared with static spacers. Twenty-five patients were treated with static nonarticulating spacers. Since 1996, 30 patients have been treated with tobramycin-laden articulating spacers. The knee arthroplasties in three patients treated with a static spacer became reinfected (12%). The knee arthroplasty in one patient with an articulating spacer became reinfected (7%). Fifteen of the 25 patients with static spacers had unexpected bone loss between stages. No appreciable bone loss could be measured in the patients who received articulating spacers. The average Hospital for Special Surgery score was 83 points in the patients with static spacers and 84 points for the patients with articulating spacers. Range of motion at final followup averaged 98° in the patients who received static spacers and 105° in the patients who received articulating spacers. Articulating spacers seem to facilitate reimplantation of infected total knee arthroplasty without additional risk of infection. Unexpected bone loss is no longer a concern with this two-stage technique. Articulating spacers offered no functional advantage over static spacers in this study group.

Rotational malalignment of the femoral component in total knee arthroplasty.

Ligamentous balancing is a crucial part of total knee arthroplasty. To ensure proper kinematics, balance must be achieved in flexion and extension. Failure to do so may result in limited range of motion, premature polyethylene wear, or patellofemoral tracking problems. Balancing in extension is dependent on the type and extent of correctional ligamentous release. Flexion balance is dependent on proper femoral rotation. There are two methods to determine femoral rotation. In the classic method, the knee is tensed in flexion after ligamentous release in extension. The anteroposterior cut then is made parallel to the cut tibial surface. Alternatively, the anteroposterior cut can be based off fixed femoral landmarks. The purpose of the current study was to determine the variance between balancing the flexion gap with the classic method versus the technique of using fixed femoral landmarks to determine rotation. One hundred consecutive posterior stabilized knee arthroplasties were performed using the classic method. The resected posterior condyles in each case were measured. The actual difference between the resected condyles using the classic method was compared with the calculated difference of resected bone using bony landmarks to determine rotation. A variance analysis then was performed. Compared with classically balanced knees, rotational errors of at least 3° occurred in 45% of patients when rotation was determined from fixed bony landmarks. These patients had trapezoidal rather than rectangular flexion gaps. Such errors may have implications regarding polyethylene wear, range of motion, and long-term clinical results.

Two-Stage Reimplantation for Periprosthetic Knee Infection Involving Resistant Organisms

BACKGROUND Two-stage reimplantation is the most accepted mode of treatment for patients with a periprosthetic infection following total knee arthroplasty. Most studies, however, do not stratify their results on the basis of the type of infecting organism. The purpose of this study was to determine the outcomes for patients who had two-stage reimplantation for the treatment of infection with a resistant organism, methicillin-resistant Staphylococcus aureus or methicillin-resistant Staphylococcus epidermidis, at the site of a total knee replacement. METHODS A multicenter study was performed to review the cases of all patients treated between 1987 and 2003 because of an infection with methicillin-resistant Staphylococcus aureus or methicillin-resistant Staphylococcus epidermidis organisms at the site of a total knee replacement. The prevalence of reinfection following two-stage reimplantation was determined. Variables that may influence the outcome, such as the duration and type of intravenous antibiotics administered, previous surgery, and comorbidities of the host, were analyzed. RESULTS We identified thirty-seven patients who had an infection with a resistant organism. All patients had negative cultures at the time of reimplantation. Four of the thirty-seven patients had a reinfection with the same organism, while five had a reinfection with a different organism. None of the variables noted above were found to be significantly associated with reinfection, on the basis of the numbers available. CONCLUSIONS Reports in the literature have discouraged reimplantation for the treatment of an infection with a resistant organism at the site of a total knee replacement. While 24% of the patients in this series had a reinfection, 14% had a reinfection with a different organism. We believe that two-stage reimplantation remains a viable treatment option for patients who have an infection with a resistant organism at the site of a total knee replacement. LEVEL OF EVIDENCE Therapeutic Level IV.

The Fate of Acute Methicillin-Resistant Staphylococcus aureus Periprosthetic Knee Infections Treated by Open Debridement and Retention of Components

The success of open irrigation and debridement with component retention (ODCR) for acute periprosthetic knee joint infection varies widely. The species and virulence of the infecting organism have been shown to influence outcome. This multicenter, retrospective study identified 19 cases of acute periprosthetic methicillin-resistant Staphylococcus aureus (MRSA) knee infections managed by ODCR and at least 4 weeks of postoperative intravenous vancomycin therapy. At minimum follow-up of 2 years, the treatment failed to eradicate the infection in 16 cases (84% failure rate). Of those 16 failures, 13 patients required a 2-stage exchange arthroplasty, 2 patients required repeat incision and debridement with antibiotic suppression, and 1 patient died of MRSA sepsis. In addition, a systematic review of the literature revealed failure to eradicate infection in 10 of 13 patients managed with a similar protocol. The total success rate of ODCR in acute periprosthetic MRSA knee infection was 18%.

Core Decompression of the Osteonecrotic Femoral Head

The results in 114 hips of ninety-two patients who had osteonecrosis of the femoral head were assessed after treatment with core decompression. The average duration of follow-up was three years and four months (range, two years to six years and six months). The average age of the patients was forty-one years (range, fifteen to sixty-seven years). The presumed risk factors were the use of corticosteroids (thirty-seven hips), excessive use of alcohol (thirty-two hips), trauma (seven hips), and various other factors (seven hips). No specific risk factor was identified for thirty-one hips, and the osteonecrosis was considered to be idiopathic. The preoperative evaluation consisted of clinical assessment, magnetic resonance imaging, and radiographic staging according to a modification of the system of Ficat. Thirty-two hips were in stage I; thirty-eight, in stage IIA; twenty-five, in stage IIB (transition stage, with a crescent sign); and nineteen, in stage III. Clinical failure was defined as the performance of a subsequent operation. Over-all, sixty-four hips (56 percent) failed clinically. Fifty-seven were treated with a hip replacement; four, with a femoral osteotomy; and three, with a vascularized fibular graft. Clinical failure was seen in five (16 percent) of the thirty-two hips in stage I, twenty (53 percent) of the thirty-eight hips in stage IIA, twenty (80 percent) of the twenty-five hips in stage IIB, and in all nineteen of the hips in stage III.(ABSTRACT TRUNCATED AT 250 WORDS)

The Chitranjan Ranawat Award: Fate of Two-stage Reimplantation After Failed Irrigation and Débridement for Periprosthetic Knee Infection

BackgroundIrrigation and débridement is an attractive low morbidity solution for acute periprosthetic knee infection. However, the failure rate in the literature is high, averaging 68% (range, 61%–82%). Patients who fail subsequently undergo two-stage reimplantation after a prolonged period of illness. This leads to higher surgical risk and further delays in rehabilitation and may contribute to failure of subsequent revision surgery.Questions/purposesWe determined the rerevision rate due to infection after two-stage reimplantation performed for failed irrigation and débridement of infected TKA.MethodsWe performed a multicenter retrospective review of periprosthetic knee infections treated with a two-stage procedure from 1994 to 2008. Selection criteria for the study included initial treatment with irrigation and débridement and subsequent two-stage revision surgery. Failure of two-stage revision was defined as the need for any additional surgery due to infection.ResultsOf the 83 knees that had undergone previous irrigation and débridement, 28 (34%) failed subsequent two-stage revision and required reoperation for persistent infection.ConclusionsThe failure rate in this series of two-stage revisions for periprosthetic knee infection in patients treated with previous irrigation and débridement is considerably higher than previously reported failure rates of two-stage revision. Factors affecting the failure rate may include host quality, thoroughness of débridement, and organism virulence. Patients and surgeons must understand that irrigation and débridement, while initially attractive, may lead to high failure rates of subsequent two-stage reimplantation.Level of EvidenceLevel III, therapeutic study. See the guidelines online for a complete description of level of evidence.

The Value of White Blood Cell Counts Before Revision Total Knee Arthroplasty

A white blood cell count (WBC) of >50000 cell/mm(3) from a knee aspirate with >or=80% polymorphonuclear cells (PMNCs) is suggestive of infection. This study sought to determine if these same criteria were applicable when interpreting aspirates from a total knee. Of 440 revision total knee arthroplasties, 86 patients had preoperative aspirations of the knee before revision. Fifty-five aspirates were from aseptic failures; 31 aspirates were from patients determined to have septic failure. The mean white blood cell (WBC) count in aspirates from the aseptic group was 645 cells/mm(3) (SD = 878). The mean WBC count in the septic group was 25951 cells/mm(3) (SD = 34994; P=<.001). The mean percentage of PMNCs was statistically higher in the septic group compared with the aseptic group (72.8% vs 27.3%; P=<.001). The synovial fluid WBC count differential analysis is a statistically relevant indicator of the presence or absence of infection in revision knee arthroplasty. Aspirates with a WBC count of 2500 per milliliter and 60% PMNCs are highly suggestive of infection.

Knee instability after total knee arthroplasty

From 1986 to the present, 126 total knee revisions were performed by the authors. Twenty-five cases (20%) were revised for instability of the tibiofemoral articulation. Patellofemoral instability and those patients treated conservatively were excluded from this subset of patients. All patients were clinically evaluated using the Hospital for Special Surgery knee rating system and radiographically rated using The Knee Society scoring system. The average follow-up period was 28 months. Preoperative synovial fluid analysis showed a predominance of red blood cells (average, 64,000). Reasons for instability were ligamentous imbalance and incompetence, malalignment and late ligamentous incompetence, a deficient extensor mechanism, inadequate prosthetic design, and surgical error. All patients currently have stable knees with an overall improvement in clinical and radiographic scores. When evaluating a patient with a painful knee after total knee arthroplasty, this diagnosis should be considered. Careful physical examination, dynamic radiographs, and synovial fluid analysis should help to make a proper diagnosis. Treatment should aim to correct the cause of instability. The prosthesis chosen should compensate for the specific ligamentous deficiency present.

Stem Fixation in Revision Total Knee Arthroplasty: A Comparative Analysis

Methods of stem fixation are a controversial aspect of revision TKA. We sought to determine which technique was superior by reviewing 475 revision TKAs done between 1986 and 2000. Of these 475 revisions, 286 major component revisions were done using 484 extended stems for fixation. Patients who died, patients who had less than 2 years followupm, or patients who had diaphyseal engaging stems were excluded from the study. The final data set included 113 revision TKAs with 202 metaphyseal engaging stems. Of the 202 stems, 107 were cemented whereas 95 were press-fit metaphyseal engaging stems. One hundred one of these were femoral stems and 101 were tibial stems. Using a modified Knee Society radiographic scoring system, 100 (93%) of the 107 implants with cemented stems were considered stable, seven (7%) were categorized as possibly loose requiring close followup, and none were loose. Of the 95 implants placed with cementless stems, only 67 (71%) were categorized as stable. Eighteen (19%) were possibly loose requiring close followup and 10 (10%) were loose (two tibial and eight femoral implants). We currently would urge caution in using cementless metaphyseal engaging stems for fixation in revision TKA.