Open vs Arthroscopic Treatment of Septic Arthritis in the Adult Native Knee: A Prospective Trial
Phase: NA
Conditions: Septic Arthritis
Sponsor: Texas Tech University Health Sciences Center, El Paso

Open vs Arthroscopic Treatment of Septic Arthritis in the Adult Native Knee:         
A Prospective Trial 
 
“Study Protocol and Statistical Analysis Plan” 
 
Document Date: 02.19.2021 
 
University Medical Center of El Paso 
 
4815 Alameda Ave, El Paso TX 79905 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

PROTOCOL 
Study Title: Open vs Arthroscopic Treatment of Septic Arthritis in the Adult Native 
Knee: A Prospective Trial 
Name, title, department of Principal Investigator (PI) 
 
Dr. Ahmed Hagag-Thabet, MD PHD 
Assistant Professor 
Department of Orthopaedic Surgery and Rehabilitation 
Texas Tech University Health Sciences Center El Paso 
 
 
Name, title, department affiliation of any co-investigators 
(1) Dr. Adam Adler, MD 
Assistant Professor and Program Director 
Department of Orthopaedic Surgery and Rehabilitation  
Texas Tech University Health Sciences Center El Paso  
 
(2) Dr. Matthew Wells, DO 
Orthopaedic Surgery Resident, PGY-2 
Department of Orthopaedic Surgery and Rehabilitation  
Texas Tech University Health Sciences Center El Paso  
 
(3) Dr. Benjamin Childs, MD 
Orthopaedic Surgery Resident, PGY-2 
Department of Orthopaedic Surgery and Rehabilitation  
Texas Tech University Health Sciences Center El Paso  
 
(4) Dr. Isaac Fernandez, MD 
Orthopaedic Surgery Resident, PGY-2 
Department of Orthopaedic Surgery and Rehabilitation  
Texas Tech University Health Sciences Center El Paso  

 
Version: 1.0 
Abstract: 
Septic arthritis is defined as a pathologic inoculation of a joint by direct or hematogenous 
means rather than an immunologic response to pathogens as that seen inflammatory 
arthropathies.1 The gold standard for diagnosis of septic arthritis is a positive gram stain 
or subsequent positive cultures from arthrocentesis.2 Cultures may require multiple days 
in order to result in growth of the causative organism and delay in treatment can result in 
degenerative joint changes, osteonecrosis, or joint instability.3, 4 The pathogenesis begins 
as the bacteria induces synovial cells to secrete proteolytic enzymes5 that can result in 
cartilage damage as early as 8 hours after infection6 with subsequent proteoglycan and 
collagen destruction.7 As the infection progresses, the intra-articular pressure rises with 
further compression and thrombosis of the synovial vasculature thus enhancing cartilage 
damage.8 Therefore, prompt establishment of diagnosis and providing early intervention 
is paramount for treatment outcomes.      
 
The typical signs and symptoms of adult septic arthritis include an edematous 
joint with surrounding erythema that is warm and tender to palpation. Some common risk 
factors include, but are not limited to: rheumatoid arthritis, diabetes, renal disease, or 
recent bacteremia.1, 2, 9-11 The classic modality to diagnose septic arthritis in patients with 
suspected septic arthritis is to perform an arthrocentesis. A synovial white blood cell 
count of 50,000 cells/mm2 is highly suggestive of septic arthritis12, although lower 
numbers have been cited as well.13 Other laboratory values can be utilized in conjunction 
such as serum procalcitonin14, IL-615, or lactate.16 Ultimately a summation of the 
patient’s overall clinical presentation, risk factors, and laboratory values is the best way 
to establish a diagnosis of septic arthritis.17 
 
Surgical excisional debridement is the main stay of management with necessary 
decompression, lavage, debridement, and partial synovectomy.17 However, there has been 
considerable debate over the optimal modality. Most surgeons perform an open 
arthrotomy or arthroscopic debridement, although serial aspiration can be considered as 
an option in very limited circumstances with patients who cannot tolerate surgery.18, 19 
While open arthrotomy has been often utilized, there has been an increasing number of 
proponents for arthroscopic treatment citing lower re-infection rates and better functional 
outcomes.20-23 However, there has been a lack of well-designed prospective studies 
comparing surgical treatment modalities for native knee septic arthritis. The goals of this 
present study are to determine if arthroscopic management of septic arthritis in the native 
knee resulted in lower number of surgeries and shorter length of stay compared to open 
arthrotomy. Secondary outcomes included differences in functional outcome and overall 
patient satisfaction.  
 
 
 
References: 
 
1. 
Mathews CJ, Kingsley G, Field M, et al. Management of septic arthritis: a 
systematic review. Ann Rheum Dis. Apr 2007;66(4):440-5. doi:10.1136/ard.2006.058909 

2. 
Hunter JG, Gross JM, Dahl JD, Amsdell SL, Gorczyca JT. Risk factors for failure 
of a single surgical debridement in adults with acute septic arthritis. J Bone Joint Surg 
Am. Apr 2015;97(7):558-64. doi:10.2106/JBJS.N.00593 
3. 
Choi IH, Pizzutillo PD, Bowen JR, Dragann R, Malhis T. Sequelae and 
reconstruction after septic arthritis of the hip in infants. J Bone Joint Surg Am. Sep 
1990;72(8):1150-65.  
4. 
Wada A, Fujii T, Takamura K, Yanagida H, Urano N, Surijamorn P. Operative 
reconstruction of the severe sequelae of infantile septic arthritis of the hip. J Pediatr 
Orthop. Dec 2007;27(8):910-4. doi:10.1097/bpo.0b013e31815a606f 
5. 
Dingle JT. The role of lysosomal enzymes in skeletal tissues. J Bone Joint Surg 
Br. Feb 1973;55(1):87-95.  
6. 
Smith RL, Schurman DJ, Kajiyama G, Mell M, Gilkerson E. The effect of 
antibiotics on the destruction of cartilage in experimental infectious arthritis. J Bone Joint 
Surg Am. Sep 1987;69(7):1063-8.  
7. 
McCarthy JJ, Dormans JP, Kozin SH, Pizzutillo PD. Musculoskeletal infections 
in children: basic treatment principles and recent advancements. Instr Course Lect. 
2005;54:515-28.  
8. 
Morrey BF, Bianco AJ, Rhodes KH. Suppurative arthritis of the hip in children. J 
Bone Joint Surg Am. Apr 1976;58(3):388-92.  
9. 
Mathews CJ, Coakley G. Septic arthritis: current diagnostic and therapeutic 
algorithm. Curr Opin Rheumatol. Jul 2008;20(4):457-62. 
doi:10.1097/BOR.0b013e3283036975 
10. 
Sharff KA, Richards EP, Townes JM. Clinical management of septic arthritis. 
Curr Rheumatol Rep. Jun 2013;15(6):332. doi:10.1007/s11926-013-0332-4 
11. 
Kaandorp CJ, Van Schaardenburg D, Krijnen P, Habbema JD, van de Laar MA. 
Risk factors for septic arthritis in patients with joint disease. A prospective study. 
Arthritis Rheum. Dec 1995;38(12):1819-25. doi:10.1002/art.1780381215 
12. 
Carpenter CR, Schuur JD, Everett WW, Pines JM. Evidence-based diagnostics: 
adult septic arthritis. Acad Emerg Med. Aug 2011;18(8):781-96. doi:10.1111/j.1553-
2712.2011.01121.x 
13. 
Margaretten ME, Kohlwes J, Moore D, Bent S. Does this adult patient have septic 
arthritis? JAMA. Apr 2007;297(13):1478-88. doi:10.1001/jama.297.13.1478 
14. 
Hügle T, Schuetz P, Mueller B, et al. Serum procalcitonin for discrimination 
between septic and non-septic arthritis. Clin Exp Rheumatol. 2008 May-Jun 
2008;26(3):453-6.  
15. 
Lenski M, Scherer MA. The significance of interleukin-6 and lactate in the 
synovial fluid for diagnosing native septic arthritis. Acta Orthop Belg. Mar 
2014;80(1):18-25.  
16. 
Lenski M, Scherer MA. Diagnostic potential of inflammatory markers in septic 
arthritis and periprosthetic joint infections: a clinical study with 719 patients. Infect Dis 
(Lond). Jun 2015;47(6):399-409. doi:10.3109/00365548.2015.1006674 
17. 
Elsissy JG, Liu JN, Wilton PJ, Nwachuku I, Gowd AK, Amin NH. Bacterial 
Septic Arthritis of the Adult Native Knee Joint: A Review. JBJS Rev. 01 
2020;8(1):e0059. doi:10.2106/JBJS.RVW.19.00059 

18. 
Manadan AM, Block JA. Daily needle aspiration versus surgical lavage for the 
treatment of bacterial septic arthritis in adults. Am J Ther. 2004 Sep-Oct 2004;11(5):412-
5. doi:10.1097/01.mph.0000087296.80768.1e 
19. 
Goldenberg DL, Brandt KD, Cohen AS, Cathcart ES. Treatment of septic 
arthritis: comparison of needle aspiration and surgery as initial modes of joint drainage. 
Arthritis Rheum. 1975 Jan-Feb 1975;18(1):83-90. doi:10.1002/art.1780180116 
20. 
Peres LR, Marchitto RO, Pereira GS, Yoshino FS, de Castro Fernandes M, 
Matsumoto MH. Arthrotomy versus arthroscopy in the treatment of septic arthritis of the 
knee in adults: a randomized clinical trial. Knee Surg Sports Traumatol Arthrosc. Oct 
2016;24(10):3155-3162. doi:10.1007/s00167-015-3918-8 
21. 
Böhler C, Dragana M, Puchner S, Windhager R, Holinka J. Treatment of septic 
arthritis of the knee: a comparison between arthroscopy and arthrotomy. Knee Surg 
Sports Traumatol Arthrosc. Oct 2016;24(10):3147-3154. doi:10.1007/s00167-015-3659-8 
22. 
Wirtz DC, Marth M, Miltner O, Schneider U, Zilkens KW. Septic arthritis of the 
knee in adults: treatment by arthroscopy or arthrotomy. Int Orthop. 2001;25(4):239-41. 
doi:10.1007/s002640100226 
23. 
Aïm F, Delambre J, Bauer T, Hardy P. Efficacy of arthroscopic treatment for 
resolving infection in septic arthritis of native joints. Orthop Traumatol Surg Res. Feb 
2015;101(1):61-4. doi:10.1016/j.otsr.2014.11.010 
 
Hypothesis: There is a significant difference in hospital length of stay and the number of 
surgeries required to provide clinical resolution of septic arthritis in an adult native knee 
when treated with arthroscopic versus open irrigation and debridement.  
 
Background (literature review): Please see abstract  
 
Specific Aims: To determine if there is an overall difference in hospital length of stay 
and number of surgeries required to provide clinical resolution of septic arthritis of an 
adult native knee. Secondary outcomes will evaluate differences in knee range of motion, 
post operative pain levels, and overall patient satisfaction.  
 
Significance of this study (why is it important, what new information will it 
provide?) 
Currently the recommended treatment for septic arthritis is surgical irrigation and 
debridement in an urgent manner (<24 hours from presentation). However, with the 
increasing utilization of arthroscopic approaches to orthopedic cases, there has not been 
an established optimal surgical approach to intra articular knee irrigation and 
debridement. Surgeons most often rely on their own preference (i.e. arthroscopic versus 
open approaches), however there has not been an established optimal surgical approach. 
Ultimately all patients undergo operative management (and repeated trips to the operating 
room, if needed). However, newer retrospective studies have shown clinical benefit with 

shorter hospital stays, lower number of repeated trips to the operating room, and overall 
improved patient satisfaction when treated with arthroscopic surgical management of 
septic arthritis of the knee.  
 
This study would help solidify in a randomized control trial the most appropriate surgical 
approach to septic arthritis of the adult native knee.  
 
Study Design & Methods (include the following information):  
Human Study Subjects: 
A.) Informed consent process and timing of obtaining consent 
 
Study recruitment will take place in the emergency department. All adult patients (>18 
years) who have a clinically established diagnosis of septic arthritis in the emergency 
department based on the following will be considered for study inclusion and approached 
for offering participation in our study: 
 
 
• Arthrocentesis with synovial WBC > 50,000 with left shift (85% PMNs) 
 
• Acrystalline (without gout crystals) elevated synovial WBC >25,000 
with high clinical suspicion 
 
• Willingness to participate in this research study 
 
Once the arthrocentesis results have confirmed the above inclusion criteria, the orthopedic 
resident who is managing the patient's care will contact one of the study investigators. In 
the meantime, the orthopedic resident managing the patient's care will obtain consent for 
surgery and book the patient for the operating room to ensure there is not a delay in patient 
care.  
 
One of the study investigators will perform a face to face introduction of the study to the 
patient in the emergency department prior to the operative management. Their diagnosis 
of septic arthritis of the knee will be explained in thorough detail with the assistance of a 
Language Line Solutions certified translator if the patient is Spanish speaking. Informed 
consent for study inclusion will be obtained if the patient meets the above inclusion 
criteria.  
 
It must be emphasized that the patient's care is not to be delayed in order to obtain 
consent for study inclusion. The study investigators include multiple orthopedic attending 
surgeons and residents. However, a situation may arise in which the study investigators are 
NOT available to explain the study and obtained informed consent. In this case, the 
patient's care is not to be delayed in order to ensure their inclusion in this study. They will 
be treated promptly to ensure appropriate patient care and will not be included in this study. 
 

B.) If non-English speaking persons will be enrolled, state the informed consent process 
for enrolling the subjects, including who will conduct the consent interview, translated 
documents, etc.  Exclusion of non-English speaking subjects from research requires ethical 
and scientific justification 
 
All non-english speaking persons will be offered study inclusion. Informed consent will be 
obtained utilizing a Spanish-translated consent form (after IRB approval). There are 
multiple Spanish speaking members of the research personnel and they will be obtaining 
Spanish consents. If one is not available, then a certified hospital interpreter will be utilized. 
If none are available, since UMC does not allow language line solutions to be used for 
research purposes, the patient will not be able to be consented and thus will not be included 
in the study.  
 
C.) Indicate the population of subjects potentially able to participate in this study 
 
All adult patients (>18 years) who have a clinically established diagnosis of septic arthritis 
in the emergency department based on the following will be considered for study inclusion 
and approached for offering participation in our study: 
 
-Arthrocentesis with synovial WBC > 50,000 with left shift (85% PMNs) 
-Acrystalline (without gout crystals) elevated synovial WBC >25,000 with 
high clinical suspicion 
-Willingness to participate in this research study 
 
These patients are all indicated with formal operative irrigation and debridement of their 
knee, regardless of study inclusion. However, they will be excluded from study inclusion 
if they meet one of the following exclusion criteria: 
 
• Recently treated septic arthritis (within past 3 months) 
• If they have a prosthetic joint replacement to the affected knee 
• Refusal to participate in the study  
 
 
D.) Indicate the number needed 
 
Our power analysis (beta =0.80, alpha = 0.05) shows the optimal sample size to be a 
minimum of 40 patients.  
 
E.) List the inclusion/exclusion criteria 
 
All adult patients (>18 years) who have a clinically established diagnosis of septic arthritis 
in the emergency department based on the following will be considered for study inclusion 
and approached for offering participation in our study: 
 
-Arthrocentesis with synovial WBC > 50,000 with left shift (85% PMNs) 
-Acrystalline (without gout crystals) elevated synovial WBC >25,000 with 

high clinical suspicion 
-Willingness to participate in this research study 
 
These patients are all indicated with formal operative irrigation and debridement of their 
knee, regardless of study inclusion. However, they will be excluded from study inclusion 
if they meet one of the following exclusion criteria: 
 
• Recently treated septic arthritis (within past 3 months) 
• If they have a prosthetic joint replacement to the affected knee 
• Refusal to participate in the study  
 
 
F.) Vulnerable populations 
 
Patients with altered mental status at the time of presentation. In accordance with current 
guidelines, a legally authorized representative may provide consent for inclusion in this 
study. If a legally authorized representative is unavailable, the patient will not be 
considered for inclusion in this study.  
 
G.) Describe the method of identifying and recruiting subjects and any screening 
 
All adult patients (>18 years) who have a clinically established diagnosis of septic arthritis 
in the emergency department based on the following will be considered for study inclusion 
and approached for offering participation in our study: 
 
-Arthrocentesis with synovial WBC > 50,000 with left shift (85% PMNs) 
-Acrystalline (without gout crystals) elevated synovial WBC >25,000 with 
high clinical suspicion 
-Willingness to participate in this research study 
 
These patients are all indicated with formal operative irrigation and debridement of their 
knee, regardless of study inclusion. However, they will be excluded from study inclusion 
if they meet one of the following exclusion criteria: 
 
• Recently treated septic arthritis (within past 3 months) 
• If they have a prosthetic joint replacement to the affected knee 
• Refusal to participate in the study  
 
 
 
H.) Define how long each subject will be studied 
 
Approximately 6 weeks after discharge (the hospital length of stay will be variable 
depending on patient comorbidities). 
 
I.) Describe any compensation given to subjects 

 
This study will NOT be offering compensation to any subjects. 
Describe the following aspects of the study design: 
 
A.) Proposed study groups with number/group and treatments/group 
 
Group 1: patients who undergo open surgical incision and drainage with debridement and 
irrigation (>20 patients) 
 
Group 2: patients who undergo arthroscopic incision and drainage with debridement and 
irrigation (>20 patients) 
 
 
B.) Describe the method used to determine the number of subjects needed 
 
Power analysis utilized to determine a difference in the number of surgeries required to 
display apparent clinical resolution between open versus arthroscopic treatments (beta 
=0.80, alpha = 0.05) shows the optimal sample size to be a minimum of 40 patients.  
 
C.) Describe how you determined that this number of subjects could be recruited 
 
Power analysis. Additionally, Dani Joyner (CHRC/Research Manager MC EP 
Compliance) was contacted and was able to find a preliminary potential of 1,851 unique 
patient records from the year 2000 to the present who had septic arthritis. Even if only 
20% of these patients met study inclusion/exclusion criteria, approximately 20 patients a 
year would be included. This would require 2-3 years of data collection in order to meet 
appropriate power analysis.  
 
Anecdotally, the attending physicians serving as principal- and co-investigators believe 
they treat a minimum of 20 adult patients each per year with septic arthritis of the native 
knee.   
 
D.) Method of randomization 
 
Patients with medical record numbers ending in an EVEN number will undergo open 
surgical irrigation and debridement.  
 
Patients with medical record numbers ending in an ODD number will undergo 
arthroscopic surgical irrigation and debridement.  
 
E.) Schedule of events (i.e. control vs. treatment, number of visits) 
 
All patients who present to the emergency department with a painful knee and clinical 
suspicion for septic arthritis undergo appropriate workup by the emergency department 
staff members. If there is a clinical suspicion for septic arthritis, the standard workup 
includes the following: 

 
-assessment of vitals 
-obtaining a history of the present illness 
-performing an appropriate physical examination 
 
If a provider determines that septic arthritis is part of their differential diagnosis, a basic 
serum laboratory workup is to be ordered. There will be a template created on the Cerner 
application to assist providers with a convenient, expedited manner of ordering these 
labs. These will include the following blood serum values: 
 
-complete blood count with differential (CBC w/ diff) 
-complete metabolic panel (CMP) 
-erythrocyte sedimentation rate (ESR) 
-c-reactive protein (CRP)  
-total protein  
-blood cultures 
 
Septic arthritis is destruction to the chondrocytes and places patients at risk for 
accelerated degenerative arthritis, abscess formation, and osteonecrosis. Therefore, 
establishing a timely diagnosis and initiating definitive management (i.e. surgical 
debridement) is of utmost importance. If the clinical suspicion is high enough, providers 
may perform an arthrocentesis of the knee prior to waiting for the aforementioned labs to 
return with results from the lab. Otherwise they should await results and determine if 
infectious etiology should be included. When providers perform arthrocentesis, the 
following laboratory markers will be included in the synovial fluid analysis (also through 
a templated order set on Cerner): 
 
-cell count with differential  
-gram stain 
-crystal analysis (for gout) 
-aerobic cultures x3 
-anaerobic cultures x3 
-fungal cultures x3 
-acid fast bacilli 
 
The gold standard method to establish the diagnosis of septic arthritis is positive bacterial 
growth on cultures. However, this may take days and ultimately delays treatment. 
Thankfully there is a plethora of research for predictive blood serum and synovial fluid 
laboratory markers, which have been included above. 
 
At any point during the initial emergency department presentation the emergency 
department may consult orthopaedic surgery, in which an orthopaedic surgery resident 
may continue the appropriate workup.  
 
All adult patients (>18 years) who have a clinically established diagnosis of septic 
arthritis based on the following will be considered for study inclusion: 

 
• Arthrocentesis with synovial WBC > 50,000 with left shift (85% PMNs) 
• Acrystalline (without gout crystals) elevated synovial WBC >25,000 with high 
clinical suspicion  
• Willingness to participate in this research study  
 
These patients are all indicated with formal operative irrigation and debridement of their 
knee, regardless of study inclusion. However, they will be excluded from study inclusion 
if they meet one of the following exclusion criteria: 
 
• Recently treated septic arthritis (within past 3 months) 
• If they have a prosthetic joint replacement to the affected knee 
• Refusal to participate in the study  
 
 
If the diagnosis of septic arthritis has been established, the diagnosis, pathogenesis and 
treatment options will be discussed with the patient. The current standard of care for the 
management of septic arthritis in the knee is operative incision and drainage of the joint 
with debridement and irrigation, obtaining intra operative cultures, then initiating 
antibiotic therapy. Non operative management would consist of antibiotic treatment 
alone. Should the patient decide to proceed with surgical intervention, an informed 
consent for surgery in the presence of a witness will be obtained, as per standard 
guidelines. At that time, the patient will be asked to participate in this study. If they 
agree, then the patient will be randomized into one of two groups: 
 
1. Open surgical incision and drainage with debridement and irrigation 
2. Arthroscopic incision and drainage with debridement and irrigation 
 
An informed consent will be performed by one of the participating research investigators 
in the setting of a witness, as per standard guidelines. The surgical consent will be 
obtained at that time in a similar manner. If the patient declines to participate in this 
study, they will still be offered surgical intervention based on physician preference and 
their surgical ability.  
 
All patients will be admitted after surgery for continued intravenous antibiotics and 
infectious disease consultation. Additionally, they will be followed for signs/symptoms 
that indicated a second surgery is required. The specific criteria for recurrence and failure 
of initial irrigation and debridement will be the following: 
 
-persistent purulent discharge from a drain or incisional site 
-increasing pain 
-decreasing range of motion 
-persistent fevers 
-persistent elevation of serologic inflammatory markers 
 

Patients showing steady clinical improvement after 72 hours post operatively will be 
discharged with continued antibiotic therapy targeted to bacteria if positive growth on 
cultures. If delayed growth occurs after patient discharge, they will be individually 
contacted for change to antibiotics if deemed appropriate, as is standard clinical practice. 
All study participants will have regularly 2-week and 6-week post-operative 
appointments where functional outcomes will be assessed in include physical exam, knee 
Lysholm scores and basic laboratory evaluation. 
 
Vitals, physical exam findings, and laboratory markers will be recorded in the clinical 
record and maintained within the patient’s electronic medical record. The principal 
investigator will utilize the electronic medical record to record and maintain pertinent 
physical examination findings, laboratory markers, and treatments on a private, secured 
device. The only individuals who will be granted access to the device are co-investigators 
participating in this research study.  
 
F.) List of Key Variables or Measurements to be done 
 
-initial presenting arthrocentesis labs as well as serum lab values  
-physical examination findings  
-time from presentation to operative management 
-type of surgical approach performed  
-total operative time  
-reason for necessity to return to operating room  
-number of operative procedures required in order to establish clinical 
improvement  
-bacterial growth from arthrocentesis and operative cultures  
-length of antibiotic course as deemed by infectious disease specialist  
-hospital length of stay  
-Lysholm knee scores  
 
 
G.) Assessment of subject safety and development of a data and safety monitoring plan 
 
All data will be stored on a password locked external hard drive device. The password 
will only be provided to primary investigators of this study. The information recorded 
will be maintained on this device and stored in accordance with TTUHSC policies. The 
principal investigator will be responsible for version control and will ensure the study 
data are shared among team members in a secure fashion in accordance with 
TTUHSC/UMC guidelines (e.g., encrypted email, restricted-access share portal). The 
original email communications will be permanently deleted from the principle 
investigator’s email inbox, outbox, and deleted folders.  
 
Any unanticipated problems or other adverse events will be reported to the TTUHSC 
Human Protections Administrator. All unanticipated problems involving risk to subjects 
or others, adverse events, and all concerns related or possibly related to the study will be 
reported promptly to the TTUHSC Human Research Protections Office by providing 

initial notification of the event as quickly as possible after the research team’s knowledge 
of the event, but within five (5) business days.  
 
H.) Create and attach your data collection form 
 
 
This has been completed and filed with the IRB submission.  
 
 
I.) Methods of data analysis (statistical analysis) 
 
 
Both Dr. Childs and Dr. Fernandez have served as statisticians in their previous roles 
as research assistants and have advanced training in statistical analysis. Regardless, the 
finalized data will be submitted to Texas Tech statisticians for validation and 
confirmation. Some of the anticipated statistical analysis tests are as follows: 
Independent samples t-tests will be used to compare means of continuous and ordinal 
variables and p values less than 0.05 will be considered to represent a significant 
difference. For variables with Levene's Test for Equality of Variances greater than 0.05, 
equal variance is assumed. Pearson Chi-Square test p-values less than 0.05 will be 
considered to represent a significant difference in categorical variables. Fischer’s exact 
test less will not be utilized as NCDB groups with n<10 are not to be included. ANOVA 
will be used to calculate significant differences in continuous and ordinal variables that 
have more than two categories. Paired samples t test and repeated measures ANOVA will 
be used to determine the progression of individual patients over time for continuous and 
ordinal variables respectively. Wilk’s Lambda p-value less than 0.05 will be considered 
significant for repeated measures ANOVA and pairwise comparison will be used to 
determine the location of significance. Binary logistic regressions will be used to 
calculate odds ratios. Multivariate binary logistic regression may be attempted for all 

significant variables. Receiver Operator Characteristic (ROC) may be calculated for 
significant continuous variables to determine the existence of a threshold that maximized 
sensitivity and specificity. All analysis will likely be performed by Dr. Childs on SPSS 
version 25 (IBM Corp. Released 2018. IBM SPSS Statistics for Macintosh, Version 25.0. 
Armonk, NY: IBM Corp).   
 
 
Sites where study will be done 
University Medical Center of El Paso  
4815 Alameda Ave 
El Paso, TX 79905 
 
Risks 
We do not anticipate any unexpected risks, as patients will be receiving appropriate care 
regardless of surgical approach to which they are randomized.  
  
Possible benefits to subjects 
None. Again, they will all undergo appropriate operative management of septic arthritis 
of the knee in an urgent manner. However, they will be part of a study that (possibly) 
establishes the most appropriate surgical approach.  
 
Confidentiality measures 
This study requires collecting patient medical record numbers (MRNs) and patient ages 
over 89, both of which are considered private health information (PHI). Therefore, a 
separate master list containing PHI will be established in order to assign patients a 
“subject identification number (ID).” This subject ID variable will serve as an added 
measure of confidentiality.  No patient PHI will be reported in the manuscript of this 
study nor any of the tables/figures included. The final manuscript will be provided to the 
appropriate Texas Tech University Health Sciences Center research committees for 
review prior to submission to a peer-reviewed journal.