A Randomized Clinical Trial of Static Versus Articulating Antibiotic Spacer for Treatment of Periprosthetic Joint Infection in Total Knee Arthroplasty
Phase: NA
Conditions: Prosthetic Joint Infection of the Knee
Sponsor: Mayo Clinic

 
 
A Randomized Clinical Trial of 
Static versus Articulating 
Antibiotic Spacer for Treatment 
of Periprosthetic Joint Infection 
in Total Knee Arthroplasty 
 
NCT 02547129  
 
Version date of the document: 
04/05/2018 

RCT – Static vs. Articulating Spacer  PJI TKA 
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A Randomized Clinical Trial of Static versus Articulating Antibiotic Spacer for 
Treatment of Periprosthetic Joint Infection in Total Knee Arthroplasty  
Michael J Taunton, MD -- Principal Investigator 
Matthew P. Abdel, MD, -Co-Investigator 
Tad M. Mabry, MD – Co- Investigator 
Arlen D. Hanssen, MD – Co- Investigator 
Kevin I. Perry, MD – Co-Investigator 

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Abstract 
Choice of treatment for periprosthetic joint infection for total knee arthroplasty has 
provided significant controversy in the orthopedic literature. A prospective randomized 
clinical trial is proposed to compare directly compare a randomized cohort of patients 
treated at a single institution by a single group of surgeons with expertise in the 
management of the infected total knee replacement. This study is designed to address the 
major clinically important issues between the two types of procedures with emphasis on 
functional outcome and survivorship free of infection. Patients will be randomized to 
receive resection knee arthroplasty with either a static or an articulating antibiotic spacer, 
followed by reimplantation total knee arthroplasty. Twenty-Eight cases will be assigned 
to each arm of the study (10% drop out rate) for a total of 50 cases to complete the trial.  
The principal outcome measures include early functional outcome as assessed by 
the Mayo Knee Sheet, and SF-12 score. In-hospital and perioperative complications such 
as mortality, deep vein thrombosis, pulmonary embolus, neurovascular complications, 
and infection will be recorded.  Satisfaction with surgery will also be assessed. 
Survivorship techniques will be used to evaluate time-to-event outcomes such as the need 
for revision surgery. 

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Potential impact of study results 
 
To our knowledge, there is no published prospective randomized trial that 
critically compares the results of treatment of infected total knee arthroplasty with static 
and articulating antibiotic spacers. Currently, there remains only personal bias for 
choosing one surgical procedure over another. Both procedures are widely accepted and 
performed in the medical community.  The findings from this work will be treated as 
valuable information to guide clinical practice.   
Specific Aims 
                Choice of treatment for periprosthetic joint infection for total knee arthroplasty 
has provided significant controversy in the orthopedic literature. The purpose of this 
study would be to directly compare the results of a randomized cohort of patients treated 
with either with static or articulating antibiotic spacers.  This will be performed at a 
single institution by a single group of surgeons with expertise in the management of the 
infected total knee replacement.   
We hope to shed some light on the actual benefits of one procedure over the other. 
The remainder of the treatment of the knee infection in both approaches will be the same 
utilizing standard clinical practice for treatment of PJI in order to make both groups 
comparable with respect to outcome.  
Background 
Deep infection following total knee replacement presents a relatively rare, but 
devastating complication.  The risk for deep infection hovers around 2 percent for a 
primary total knee replacement and increases in the setting of revision surgery.  As the 

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number of total knee replacements performed annually continues to rise exponentially, 
the burden of treatment for the infected total knee replacement will rise accordingly.  
 
It is important to consider not only the burden of treatment that applies to the 
patient, but also to the health care system.  Managing the patient with an infected total 
knee replacement consumes an inordinate amount of healthcare resources.  It is also a 
substantial cause of lost work and potential institutionalization during the treatment 
phase.  For these reasons it will become more important over time that we establish the 
best possible treatments for the infected total knee replacement.   
The infected total knee replacement is categorized by the timing of the infection.  
This will typically guide treatment.   
Acute infections, including infections that occur in the first three or four weeks 
postoperatively (acute postoperative infection) and infections in the setting of bacteremia 
with a short duration of symptoms (acute hematogenous infection) are often treated with 
irrigation and debridement with component retention.  Following surgery, these patients 
are treated with a course of IV antibiotics followed by a prolonged course of oral 
antibiotics. 
In the setting of a more chronic infection the gold standard for treatment in the 
United States is a two-stage exchange.  The first stage is characterized by resection of all 
components, foreign material and necrotic tissue.  At the time of the first stage it is 
typical practice to place some type of high dose antibiotic cement spacer. The high-dose 
antibiotic-loaded cement spacer has shown to be clinically safe[1]  In general terms, the 
purpose of the spacer is to stabilize the soft-tissue envelope in order to facilitate later 

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reimplantation.  It is also a mechanism for the delivery of high-dose local antibiotics into 
the infected field.   
 
There are two basic types of spacers that can be placed at the time of the first 
stage resection.  These are the static antibiotic spacer and the articulating antibiotic 
spacer. Utilizing a static spacer in a two-stage exchange protocol for infected total knee 
arthroplasty, Haleem, et al[2] found  survivorship free of implant removal for any reason 
was 90% at 5 years and 77.3% at 10 years. The survivorship free of implant removal for 
reinfection was 93.5% at 5 years and 85% at 10 years. These results suggest that the high 
likelihood of early success after two-stage reimplantation with a static spacer is 
maintained throughout long-term follow-up, with a modest rate of late recurrent infection 
or mechanical implant failure. 
A study by Fehring et al[3] retrospectively reviewed  25  patients treated with 
static nonarticulating spacers and 30 patient with articulating spacers.  Survivorship of 
the static spacer was 88% at 36 months f/u.   The survivorship of the articulating spacers 
at 27 months was 93%.  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 follow-up, was an average of 98 degrees in the patients who 
received static spacers and 105degrees in the patients who received articulating spacers.  
Similarly, Chiang, et al[4] found similar results with equivalent rates of eradication of 
infection in both groups. They did find superior satisfaction in the articulating group 
(21/23) vs 7/23 in the static group. 

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There has never been a randomized, head-to-head comparison of these two types 
of spacers.  Prior studies have been retrospective analyses.  Both studies by Fehring, et al 
[3]and Chiang et al[4]were retrospective series when techniques were evolving.  There 
was no classification of bone loss, or consideration of severity of infection or bone loss 
between the cases, making it difficult to make any real conclusions on both eradication of 
infection, and postoperative function.  Assessments of “satisfaction” and range of motion 
in non-comparable groups gives little guidance for treatment.  
Hypotheses 
 
1. The 1-year post-operative range of motion and Knee Society score will be 
superior after reimplantation Total Knee Arthroplasty performed after articulating 
spacer than TKA reimplantation after a static spacer. 
2. Patient satisfaction is higher after articulating cement spacer when compared to 
static cement spacers. 
3. The rate of repeat infection after reimplantation Total Knee Arthroplasty 
performed after articulating spacer will be equal to TKA reimplantation after a 
static spacer. 
4. The survivorship of Total Knee Arthroplasty (TKA) reimplantation performed 
after articulating spacer will be equal to TKA remplantation after a static spacer. 
 
 
Materials and Methods 
Basic Study Plan 

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A prospective randomized clinical trial is proposed to compare the results of 
treatment of infected total knee arthroplasty with static or articulating antibiotic 
spacers.  This study is designed to address the major short-term clinically important 
issues between the two types of procedures with special emphasis on survivorship and 
clinical outcomes. A research coordinator will supervise the running of the study.  The 
patient and the surgeon will not be blinded to the operation performed.   
Surgical Technique 
        All procedures will be performed by the principle investigators (TMM, ADH, 
MJT, MPA, KIP) with a subspecialty interest in total knee arthroplasty. All bone loss will 
be classified both for the femur and tibia, and recorded in the operative report.  
Resection Total Knee Arthroplasty with placement of static Antibiotic Spacer 
The technique for use of the static spacer would include complete resection and 
debridement at the time of initial resection.  The antibiotic cement would contain 3 grams 
of Vancomycin and 3 grams of Gentamicin per 40 gram batch of cement.  The technique 
would involve the creation of two intramedullary antibiotic cement dowels followed by 
capping the distal femur and proximal tibia in a standardized fashion.  The remaining 
space in the tibiofemoral joint would be filled with antibiotic cement in a standard 
technique.  The leg would be casted, at least until the time of wound healing.  After the 
first cast change and suture removal the leg could be placed into a cast or knee 
immobilizer at the surgeon’s discretion.  The weightbearing would be allowed 40 to 60 
pounds of weight (partial weightbearing).  When feasible, the patient would receive 
erythropoietin between stages where possible.  The patients would be screened and 
decolonized for colonization with staphylococcus aureus as indicated.  The patients 

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would receive six weeks of organism-specific antibiotics in coordination with Orthopedic 
Infectious Disease.  The patients should be scheduled for reimplantation between 8 and 
12 weeks following knee resection.  The final decision regarding reimplantation versus 
repeat debridement and spacer exchange would be based on the surgeon’s evaluation of 
the soft tissues, laboratory studies, radiographs and intraoperative evaluation at the time 
of planned reimplantation which would include both the gross and microscopic 
appearance of the peri-articular tissues. 
Resection Total Knee Arthroplasty with placement of articulating Antibiotic Spacer. 
The technique with the articulating antibiotic cement spacer would be very 
similar.  The main difference would be, instead of filling the tibiofemoral space with a 
static spacer, we would utilize a modular posterior stabilized femoral component and a 
modular polyethylene liner.  We would utilize a standard technique for the placement of 
this articulating spacer, which would include high-dose antibiotic cement of the femoral 
component into an appropriate position as well as modifying the counter surface of the 
modular posterior stabilized liner for cementation.  As in the static spacer technique, the 
limb would be placed into a cast or knee immobilizer full time until wound healing.  The 
patient would be allowed partial weight bearing.  However, in contrast to the static spacer 
protocol, once the wound  has been found to heal in a satisfactory fashion, the patient 
would perform self-directed physical therapy to include quad sets and active range of 
motion two to three times daily within the range of comfort.  The patient would be 
instructed to wear the immobilizer or other type of knee orthosis locked in extension 
when not performing the active range of motion exercises.  The remainder would be the 
same between techniques. 

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Hospitalization 
                Patients will come into the hospital on the day of their surgery, unless medical 
problems dictate earlier admission.  Hospitalization of 3 nights is routine for these 
patients, although complications may prolong that time.  The patient will receive one 
preoperative dose of antibiotics if the organism is known preoperatively Antibiotics are 
typically held preoperatively if infection is highly suspected, but no organism has been 
identified by prior pre-operative studies.  All patients will receive appropriate antibiotics 
postoperatively which will be tailored to the infection. All patients will receive 
appropriate anticoagulation for deep venous thrombosis prophylaxis. 
 
Postop Physical Therapy 
            Both treatment groups will have similar postoperative care.  Structured physical 
therapy will begin the day after surgery and continued during the 
hospitalization.  Patients are encouraged to sit up at the bedside the evening of their 
surgery.  A home therapy program will be given to the patient although formal physical 
therapy will not continue on an outpatient basis. 
            a.  Post-op Day 1, use of walker or personnel to assist with transfer from bed to 
chair. 
            b.  No Range of motion in the affected knee. 
            c.  Weight bearing status 40-60 lbs. 
Progression 
•     Progress ambulation utilizing walker to crutches. 

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•     Patients should be encouraged to maximize independent ambulation and increase 
distance ambulated daily under the above listed restrictions. 
 
Discharge Criteria (home going) 
• Independent and safe with aids 
• Transfer out of and into bed from a standing position 
• Rise to and from a chair to a standing position 
• Ambulate 100 feet 
Study Procedures Summary 
Data Collection (obtained via the research assistant and prospectively entered into a 
computerized data base (RedCap)) 
Visit #1           Preoperative:  Aspiration of knee (Send synovial fluid for cell count, 
culture).  Labs: Erythrocyte sedimentation Rate, C-Reactive Protein, 
Complete Blood Count with differential. Consent.   
Visit #2           Preoperative:  Radiographs of the knee, Mayo Knee Sheet, SF-12 Version 
1, measurement of clinical parameters, Range of motion, Knee Society 
Score: Pre-Op.   
Operative #1:      Radiographs of the knee, complications. Classification of bone loss. 
Visit #3           Two Weeks: Mayo Knee Sheet, SF-12 Version 1, measurement of clinical 
parameters, Wound Examination, Knee Society Score: Post-Op. 

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Visit #4           Preoperative 2nd Stage (typically 8 weeks) Mayo Knee Sheet, SF-12 
Version 1, measurement of clinical parameters, Wound Examination. 
Range of motion for articulating group. Knee Society Score: Post-Op . 
Labs: Erythrocyte sedimentation Rate, C-Reactive Protein, Complete 
Blood Count with differential. 
Operative #2: Radiographs of the knee, complications. 
Visit #5           Two Weeks: Mayo Knee Sheet, SF-12 Version 1, measurement of clinical 
parameters, Wound Examination. Range of motion (both groups). Knee 
Society Score: Post-Op. 
Visit #6          Two Months: Mayo Knee Sheet, SF-12 Version 1, measurement of clinical 
parameters, Wound Examination. Range of motion (both groups). Knee 
Society Score: Post-Op Labs: Erythrocyte sedimentation Rate, C-Reactive 
Protein, Complete Blood Count with differential. 
Visit #7 
One Year: Mayo Knee Sheet, SF-12 Version 1, measurement of clinical 
parameters, Wound Examination. Range of motion (both groups). Knee 
Society Score: Post-Op.  Labs: Erythrocyte sedimentation Rate, C-
Reactive Protein, Complete Blood Count with differential.  
 
 
Preop 
visit 
#1 
Preop 
visit #2 
(Listing) 
Operative 
#1 
Postop 
2 week 
(#3) 
Pre-op 
Stage 
2 (#4) 
Operative 
#2 
Postop 
2 week 
(#5) 
Postop 
2 month 
(#6) 
Postop 
1 year 
(#7) 
Consent 
x 
 
 
 
 
 
 
 
 
Knee Radiograph 
 
x 
x 
 
x 
x 
 
x 
x 
Identify 
Complications 
 
 
x 
x 
x 
x 
x 
x 
x 
Mayo Knee Sheet 
 
x 
 
x 
x 
 
x 
x 
x 

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SF-12 Version 1 
 
x 
 
x 
x 
 
x 
x 
x 
Range Motion 
 
x 
 
x(artic.) 
x 
 
x 
x 
x 
KSS Pre-Op 
 
x 
 
 
 
 
 
 
 
KSS Post-Op 
 
 
 
x 
x 
 
x 
x 
x 
Assess Clinical 
Parameters 
 
 
 
x 
x 
 
x 
x 
x 
Satisfaction 
 
 
 
x 
x 
 
x 
x 
x 
Labs 
x 
 
 
 
x 
 
 
x 
x 
 
 
 
Measurement Tools 
At the time of reimplantation the surgeon would record whether the implant used would 
be a posterior stabilized design versus a varus valgus constrained condylar knee, versus 
hinged total knee. 
Laboratory Parameters 
Data points to be collected would include laboratory studies from the initial 
diagnosis, at the time of antibiotic stop date and immediately prior to reimplantation.  
This would include the Erythrocyte Sedimentation Rate and C-Reactive Protein at a 
minimum.  We would also gather a complete blood count with differential prior to knee 
resection and, again, prior to reimplantation.  We would analyze the microbiologic 
culture data from the time of resection and reimplantation.  We would analyze the 
histopathology from the time of resection and the time of reimplantation.  
Intraoperative Data 
  
Surgical data collected would include surgical time as measured from the time of 
the skin incision to the time of final wound closure.  The type of exposures needed 
(standard versus extensile, such as quadriceps snip, tibial tubercle osteotomy or other), 

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the level of prosthetic constraint required, intraoperative range of motion following 
capsular closure, complications between stages such as fracture, progressive bone loss, 
tendon or ligament injury, antibiotic complications, intraoperative blood loss, transfusion 
data. Classification of bone loss at 1st and 2nd stages. Classification will be done at the 
two surgical stages by the Anderson Orthopedic Institute classification [5]  Which is a 
validated and  reliable system of measuring bone loss which facilitates planning of total 
knee arthroplasty revision and rehabilitation and meaningful comparisons between 
different series of patients and treatment protocols. 
Surgical Difficulty 
Surgical difficulty will be assessed by a survey of the treating surgeons to rate 
from 1 to 10 the ease of surgery at the time of reimplantation. 
Radiographic Parameters 
            Knee radiographs including an anterior-posterior view and true lateral view, and 
merchant view will be recorded preoperative, postoperatively after the resection, prior to 
the reimplantation, postoperatively after the reimplantation, at two months after 
reimplantation, and at the 1 year follow-up appointment.  The radiographs will be 
evaluated for component fixation, component position, and alignment.   
Mayo Knee Sheet 
           This is a clinical standard for rating efficiency of total knee replacement.  It is a 
disease-specific test that has been validated and is used widely (presently the standard for 
current practice at the Mayo Clinic). This data will be collected at the time of diagnosis, 
prior to the knee reimplantation, at the time of Total Joint Registry follow up, 2 weeks, 8 
weeks, and one year. 

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Knee Society Score 
 
This is a clinical standard for rating the outcome of total knee replacement.[6, 7] 
It is a disease-specific test that has been validated and is used widely.  The data can be 
obtained directly from the Mayo Knee Sheet. This data will be collected at the time of 
diagnosis, prior to the knee reimplantation, at the time of Total Joint Registry follow up, 
2 weeks, 8 weeks, and one year. 
 
SF-12 Version 1 
            This self-administered questionnaire has been validated for measuring and 
monitoring health status in large group studies.  It has been published as the best measure 
for assessing general health for arthroplasty patients as noted in the analysis of the 
Swedish Registry. 
Complications/Lost to Follow-up Form 
            Any serious complications that occur from the surgery will be 
documented.  Sepsis, embolism, failure of primary wound healing, hemorrhage, 
prosthesis loosening, , skin necrosis, hematoma, approach extension, or periprosthetic 
fracture are possible complications.  If for any reason a patient is lost to follow-up (will 
not return for office visits) there must be a form completed to indicate this event. 
  
Satisfaction 
This data will be available from the Mayo Knee Scoring sheet. 
            

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Medical Device 
        The revision total knee system, which will be used for both groups, has been 
FDA approved.  
PARTICIPANT POPULATION 
 
Inclusion Criteria 
1. Male or female age 18 to 100. 
2. Preoperative diagnosis of bacterial infection by culture which would include a 
preoperative aspiration and at least three intraoperative cultures.  The preoperative 
aspiration would also be sent for a cell count with differential.  All patients would 
have an ESR and CRP drawn in the preoperative phase.  Patients with a negative 
preoperative aspiration, but an actively draining wound or draining sinus tract, 
would be considered as infected.  Intraoperative histopathology would also be 
obtained in all cases of infected total knee replacement at the time of the 
resection.   
3. Intact extensor mechanism. 
4. Adequate soft tissue envelope (no requirement for soft tissue coverage such as a 
muscle flap or skin graft) 
5. Adequate bone stock for knee reconstruction 
6. Medical fitness for staged knee reconstruction  
 
 
Exclusion Criteria  
1. Known Atypical infection (mycobacterial or fungal) 

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2. Extensor mechanism disruption 
3. Inadequate soft tissue envelope requiring muscle flap or skin grafting 
4. Inadequate bone stock (T3 or F3 by the AORI classification) 
5. Medical status precluding staged knee reconstruction 
6. Requirement for hinged knee reconstruction at the time of reimplantation 
7. Pregnant women – for women of child bearing age, a negative pregnancy test will 
be needed prior to enrollment to the study. 
Recruitment 
            This will be carried out by the investigator.  The study will be described to the 
patient, and a form of consent that states clearly the background and reasoning will be 
given to the patient.   
We would plan to keep a running log of patients diagnosed with a chronic total 
knee infection who:  
1) Refuse to enter the study. 
2) Were not deemed to be appropriate candidates for the study and for which 
reason. 
3) Have an Intraoperative conversion aside from the randomization to a different 
type of spacer or planned reconstruction design. 
 
 
Competency 
                Study participants must be able to give informed consent. 
 

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Gender and Racial/Ethnic Distribution 
            No gender or racial/ethnic group will be intentionally excluded from this study. 
 
Risks 
                Participation in this study poses no increased risk to patients undergoing 2 stage 
treatment of infected total knee arthroplasty.  With any knee replacement, there is a 
possibility that the prosthesis will need to be removed and replaced and that the 
procedure may involve unforeseeable risks.  Some of the known risks include failure to 
achieve firm attachment of the implant to the bone, fracture of bone during implantation, 
infection, deep vein thrombosis, neurovascular injury, wound problems, and anesthetic 
problems.  In a some of cases, the knee prosthesis will loosen over years of use and pain 
and decreased mobility will occur.   
             
Randomization of the Study Patients 
                In order to assign patients to specific treatment groups in an unbiased manner, 
randomization will occur prior to surgery.  The assigned treatment codes for patients in 
each group will be generated by a computerized randomization program developed by the 
Division of Biostatistics.  After the patient has met the entrance criteria, and given their 
full informed consent to participate in the study, they will be assigned to the treatment 
group.  Patient randomization will be performed at the time of consent. 
            The randomization will be stratified on four variables with potential confounding 
effects on the outcomes of interest.  Specifically, separate strata will be created by 

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surgeon (TMM, MJT, MPA, ADH, and KIP), gender (male vs female), age  (<60 years vs 
≥60 years), and BMI (<30 vs ≥30).  
 
Statistical Methods and Sample Size 
                Several factors determine the appropriate sample size for a scientific clinical 
investigation.  The following criteria are believed to be relevant for this study:   
1. Selection of the level of difference between treatment results, if it exists, that the 
study desires to detect 
2. A sample of sufficient size to provide statistical validity at a power level of 80 
percent and an alpha level of 0.05.  
3. A study and database size that is manageable to insure good data quality.  
4. Consideration of expected subject attrition.  
The two patient cohorts will be followed prospectively and evaluated with 
specific functional, clinical and radiographic outcome measures at 2 weeks, 2months and 
at a year from surgery. The principal outcomes include the treatment of infection, and the 
clinical result of the reimplantation, specifically pain and range of motion.   
 
 
Power Analysis 
 
For this study, we hypothesized that the articulating and static spacers would be 
equally efficacious at eradicating infection[4, 8].  A study by Haleem et al(CORR 2004) 
[2] The preoperative pain scores improved(p</=0.001) from a median of 49 points  
to a median of 89 points  postoperatively. Preoperative functional scores improved 

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(p,/=0.001) from a median of 5 points  to a median of 50 points (range, 0–100 points) 
postoperatively. The preoperative range of motion (ROM) in the 81 knees that did not 
have major surgery had a median of 85° (range 30°–125°), and the ROM at last follow-up 
had a median of 90° (range 30°–120°). The median change was an improvement (p < 
0.01) of 10°, ranging from a loss of 55° to a gain of 80°. Using this data to generate 
estimates of variability, we calculated the sample sizes required to detect differences in 
ROM and also Knee Society scores, with 80% power.  If we enroll 28 per group, and 
after 10% attrition end up with 25 per group, we will have 80% power to detect 
differences of at least 15 degrees in ROM, 10.5 points in knee pain score, and 17 points 
in knee function score.  Any observed differences smaller than these will likely not be 
detected as significantly different.  Therefore, the goal of the study would be to 
randomize a total of 56 patients with 28 patients in each arm of the study.  
The participating surgeons would be TMM, MJT, MPA, ADH, and KIP.  All of 
the surgeries would be performed at the Mayo Clinic in Rochester, Minnesota at either 
the Rochester Methodist or St. Marys Hospital campuses.   
We expect to be able to enroll between 1-2 patients per month for this study from 
5 surgeons (MJT, TMM, ADH, MPA, KIP). We expect to see at least 3 to 6 patients per 
month who would be candidates for the study.  The total enrollment period is anticipated 
to be approximately 1 year, with an additional 15 months needed for performance of the 
procedure and follow-up. 
The sample size feasible for this study is not adequate to be able to detect a 
statistically significant difference between the literature-estimated joint survival times of 

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revision total knee arthroplasty.  The focus on joint survival in this study will instead be 
estimation with confidence intervals. 
            Patient demographics and outcomes will be described using mean ± standard 
deviation if continuous and distributed approximately Gaussian, or median (25th 
percentile, 75th percentile) if continuous but not Gaussian.  Categorical variables will be 
described as count (percent).  Outcomes of primary interest will include the range of 
motion, quality of life as measured by the SF-12, and Knee Society scores, at 2 weeks 
after resection, prior to reimplantation, 2 weeks after reimplantation, 2 months, and 12 
months. The two treatment groups will be compared on these outcomes using two-sample 
t-tests if the data are approximately Gaussian. If the data are not sufficiently normal, 
Wilcoxon rank sum tests will be used.  In-hospital and perioperative complications such 
as periprosthetic fracture (intraoperative and postoperative), deep vein thrombosis, 
pulmonary embolus, neurovascular complications, infection and mortality will be 
compared using chi-square tests or Fisher’s exact tests if necessary and appropriate. 
Analysis of time to event outcomes such as fracture, complications related to the surgical 
procedure, the need for revision surgery and survival will utilize survival techniques such 
as the method of Kaplan and Meier and Cox proportional hazards models. All statistical 
tests will be two-sided and p-values less than 0.05 will be considered statistically 
significant.  SAS v9.1 (SAS Institute INC, Cary, NC) will be utilized. 
                 
 
 

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POTENTIAL CONFLICT OF INTEREST FOR INVESTIGATOR 
            The principal investigators (MJT, TMM, MPA, ADH, and KIP) of this study do 
not have a direct financial interest in the study implants or the surgical techniques. 

RCT – Static vs. Articulating Spacer  PJI TKA 
Taunton, Abdel, Mabry, Hanssen, Perry 
 
 
 
 
4/5/2018 
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REFERENCES 
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2. 
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two-stage reimplantation for infected total knee arthroplasty. Clinical 
Orthopaedics & Related Research, 2004(428): p. 35-9. 
3. 
Fehring, T.K., et al., Articulating versus static spacers in revision total knee 
arthroplasty for sepsis. The Ranawat Award. Clinical orthopaedics and related 
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4. 
Chiang, E.R., et al., Comparison of articulating and static spacers regarding 
infection with resistant organisms in total knee arthroplasty. Acta Orthopaedica, 
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total knee arthroplasty system. Journal of Orthopaedic Surgery, 2005. 13(3): p. 
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Hofmann, A.A., et al., Treatment of infected total knee arthroplasty using an 
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