Aim

While metagenomic (microbial DNA) sequencing technologies can detect the presence of microbes in a clinical sample, it is unknown whether this signal represents dead or live organisms. Metatranscriptomics (sequencing of RNA) offers the potential to detect transcriptionally “active” organisms within a microbial community, and map expressed genes to functional pathways of interest (e.g. antibiotic resistance). We used this approach to evaluate the utility of metatrancriptomics to diagnose PJI and predict antibiotic resistance.

Persistent wound drainage after total joint arthroplasty (TJA) has been associated with a higher incidence of superficial and deep periprosthetic infection but the predictors for prolonged drainage and its outcome have not been thoroughly studied.

A consecutive series of 7,153 TJA cases performed between 2000 and 2006 at our institute, were recruited into this study. There were 301 cases (4.2%) of persistent wound drainage, defined as discharge from the wound for > 48 hours. The cases were matched in a 2:1 ratio for type of surgery, joint replaced, and date of surgery.

This study identified higher BMI (p< 0.005), malnutrition as defined by serum albumin< 3.4g/dl (p< 0.04), longer operative time (p< 0.01), and higher medical comorbidities, in particular diabetes (p< 0.001) as important risk factors for persistent wound drainage. In addition, patients in the drainage group were more likely to have a peak INR of > 1.5 (p< 0.001) during their hospital stay. Patients with wound drainage had a significantly lower hemoglobin postoperatively (p< 0.01) that necessitated greater number of postoperative allogenic transfusions (p=0.004). The hospital length of stay for the drainage group was also significantly higher (p< 0.005). One of the major risk factors for development of deep infection was prolonged drainage (> 7 days). In the deep hematoma and periprosthetic subgroups, the mean of delay in treatment was 6 days in those with retention of the prosthesis and successful outcome, and 9.5 days for those with failure of incision and drainage leading to resection arthroplasty (p= 0.03).

72% of the patient were successfully treated by oral or intravenous antibiotics. 27% required at least one re-operation for deep hematoma and 13% developed deep periprosthetic infection, resulting in 6% rate of resection arthroplasty. 1.5% of those with drainage remained in girdlestone status.

This study suggests early surgery for persistent drainage and avoidance of aggressive anticoagulation.

The differential diagnosis of pain after total knee arthroplasty (TKA) should always include periprosthetic infection (PPI). The current diagnostic tools vary in sensitivity, specificity, and predictive value. Currently there is no test with an absolute accuracy for diagnosis of PPI. Furthermore, cost effectiveness of investigations has become an important issue in recent years as increased expenses can place an unnecessary heavy burden on the medical system.

We retrospectively evaluated 296 patients who underwent revision TKA at our institution during 2000–2005 and had preoperative erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) performed. The criteria used for diagnosing infection were a positive intraoperative culture on solid media, presence of an abscess or sinus tract that communicated with the joint, positive preoperative aspiration culture, and/or elevated fluid cell count and neutrophil differential of the aspirated fluid. The sensitivity, specificity, and predictive values of ESR and CRP were determined. Combinations were performed in parallel that necessitate both tests to be negative to rule out infection. The cost of each serological test was compared to that of other commonly used screening modalities.

One hundred and sixteen patients (39%) were classified as infected and 180 patients (61%) were considered non-infected. The sensitivity, specificity, positive predictive value, and negative predictive value for the ESR were: 91%, 72%, 68%, and 93%. The sensitivity, specificity, positive predictive value, and negative predictive value for the CRP were: 94%, 74%, 70%, and 95%. The sensitivity and negative predictive value for the combined studies were 96% and 95%, respectively. However, five infected patients (4%) had a normal

ESR and CRP. An organism was cultured on solid media in 4 of the 5 cases. ESR and CRP were the least costly of all the preoperative tests including radionuclide imaging and joint fluid analysis. ESR and CRP are important preoperative tests in diagnosis of PPI and their ability to clench the diagnosis in the majority of cases should not be underestimated. When combined, these simple serological tests have improved sensitivity and negative predictive value to rule out infection.

Currently two-stage resection arthroplasty is the preferred method for surgical treatment of periprosthetic infection in North America. However, the success of this treatment strategy has varied from 54% to 98% based on previous reports. The exact reason for this variation in outcome is not known. The purpose of this study was to determine the efficacy of this treatment modality and delineate patient risk factors that result in recurrent infection and failure.

During the period of this study (2000–2005) 77 patients with an infected THA were treated at our institution. Fifty-four patients underwent two-stage exchange arthroplasty while the remaining 22 failed to have the second stage reimplantation due to ill health. The latter 22 were excluded from the analysis. All patients were followed up prospectively for at least two years after reimplantation. Detailed data including demographics, comorbidities, surgical history, and medication intake was collected. Intraoperative data, organism profile, and complications were also documented. Failure was defined as patient requiring additional surgical procedure for control of infection or loosening.

Two-stage exchange arthroplasty successfully eradicated infection in 36 patients (67%) without need for further treatment. Seven patients (13%) had recurrent infection that necessitated resection arthroplasty. Eleven (20%) patients required irrigation and debridement for postoperative purulent drainage which successfully treated infection in 8 of the cases. The remaining 3 patients failed and required resection arthroplasty. Three additional patients had early loosening of components and required revision arthroplasty. The exact cause of loosening in these patients could not be determined and despite lack of isolation of organisms infection was suspected. Multivariate analysis identified previous medical comorbidity and postoperative allogenic transfusion as risk factors for failure.

Current strategies to treat periprosthetic infection remain imperfect. Two-stage exchange arthroplasty with all its inherent problems and inconveniences imparted a modest success in treatment of PPI at our high volume specialized center. With the increase in the number of virulent and resistant organisms, and the rise in arthroplasties being performed in infirm patients with medical comorbidities the success of this procedure is likely to be jeopardized. Novel treatment modalities to combat this dreaded condition is needed.

The differential diagnosis of pain after total knee arthroplasty (TKA) should always include periprosthetic infection (PPI). The current diagnostic tools vary in sensitivity, specificity, and predictive value. Currently, there is no test with an absolute accuracy for diagnosis of PPI. Furthermore, cost effectiveness of investigations has become an important issue in recent years as increased expenses can place an unnecessary heavy burden on the medical system.

We retrospectively evaluated 296 patients who underwent revision TKA at our institution during 2000–2005 and had preoperative erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) performed. The criteria used for diagnosing infection were a positive intraoperative culture on solid media, presence of an abscess or sinus tract that communicated with the joint, positive preoperative aspiration culture, and/or elevated fluid cell count and neutrophil differential of the aspirated fluid. The sensitivity, specificity, and predictive values of ESR and CRP were determined. Combinations were performed in parallel that necessitate both tests to be negative to rule out infection. The cost of each serological test was compared to that of other commonly used screening modalities.

One hundred sixteen patients (39%) were classified as infected and 180 patients (61%) were considered non-infected. The sensitivity, specificity, positive predictive value, and negative predictive value for the ESR were: 91%, 72%, 68%, and 93%. The sensitivity, specificity, positive predictive value, and negative predictive value for the CRP were: 94%, 74%, 70%, and 95%. The sensitivity and negative predictive value for the combined studies were 96% and 95% respectively. However, five infected patients (4%) had a normal ESR and CRP. An organism was cultured on solid media in 4 of the 5 cases.

ESR and CRP were the least costly of all the preoperative tests including radionuclide imaging and joint fluid analysis. ESR and CRP are important preoperative tests in the diagnosis of PPI and their ability to clench diagnosis in the majority of cases should not be underestimated. When combined, those simple serological tests have improved sensitivity and negative predictive value to rule out infection.

Background: Vascular injuries associated with total joint arthroplasty are the most feared complication. The arterial and venous injury can occur due to direct or indirect trauma. A high index of suspicion, recognition of the injury and prompt treatment, with the immediate availability of a vascular surgeon is vital for good outcome.

Methods: Using prospectively collected data on 13624 patients undergoing total joint arthroplasty at our institution, all incidences of vascular injury were identified. Detailed data regarding the mode of presentation, the type and the outcome of intervention delivered, and the eventual functional outcome of the total joint arthroplasty were determined.

Results: There were a total of 17 vascular injuries (0.1%). Majority (16/17) of these vascular injuries were detected in the postoperative recovery area. 9 injuries occurred after TKA and 8 occurred after THA. Indirect injury was the mechanism in TKA patients with popliteal artery thrombosis being the mechanism. In contrast direct injury was the mechanism in THA patients. Fasciotomy was performed in all TKA patients and none were needed in the THA patients. One patient died of complications related to vascular injury. 12 of 17 patients (70%) had launched a legal suit against the operating surgeon.

Conclusions: After more than 80 years of accumulated experience and more than 35000 joint replacements performed by 5 surgeons in our center, the vascular complication still continues to occur. Patient awareness regarding this real problem may play a role in defraying the extremely high likelihood of legal suits associated with this complication.

Introduction: The use of coumadin for prophylaxis against thromboembolism (TE) following total joint arthroplasty is the standard of care. In light of recent publication of the American College of Chest Physicians (ACCP), we altered our anticoagulation protocol to be compliant with the recommendations. This study evaluates the incidence of TE and bleeding complications following TJA when low dose coumadin vs. regular dose coumadin was administered.

Methods: 987 consecutive patients undergoing total joint arthroplasty by a single surgeon between the years of 2004–2005 were included. 446 patients operated on during the 2004 received low dose coumadin (intended INR 1.5–1.7) whilst 541 patients undergoing TJA during 2005 were given regular dose coumadin (intended INR 2–2.5).

Results: The mean INR for patients operated during the year 2005 was significantly higher than the INR for patients receiving TJA in 2004. There were more complications in 2005. There were 13 PE, 44 wound drainage, 4 DVT, and 11 hematoma formation (requiring surgical evacuation) during the year 2005 compared to 10 PE, 26 wound drainage, 6 DVT, and 5 hematoma formation in 2004. The difference for all complications except DVT was significant.

Conclusion: This study confirms the commonly held belief that aggressive anticoagulation does carry a higher incidence of complications such as wound drainage and bleeding. It appears that administering higher dose coumadin increased the bleeding complications without conferring additional protection against thromboembolic disease.

Purpose: Periprosthetic infection (PPI) is a devastating complication. Surgical intervention to treat PPI is often required. The objective of this prospective study is to determine if there is any difference in functional improvement following revision TKA in patients with infected and non-infected failures.

Methods: 123 consecutive patients undergoing revision TKA at our institution were prospectively recruited into this study. The indication for revision TKA was PPI in 37 cases and aseptic failure in 86 cases. Detailed patient demographics and functional outcome using SF-36, KSS, Womac, lower extremity functional outcome score were collected at base line and at various time points after revision TKA. The baseline and two year follow up functional scores were calculated and compared. The functional score at the time of diagnosis of PPI (prosthesis in place) were used for baseline comparisons

Results: All baseline functional scores, and their individual elements, for the infected cases were worse than the non-infected cases. The functional scores at the two-year follow-up were not different between the infected and non-infected cases. Hence, there was a more impressive improvement (Δ) in functional outcome for the infected cases following revision TKA compared to non-infected cases. However, the general health perception as determined by the patients themselves appeared to deteriorate after revision TKA in both groups.

Discussion: It appears that patients with PPI are markedly more disabled at base line than the non-infected cases. These patients, however, benefit the most from surgical intervention compared to the non-infected cases. It appears that the patients’ perception of improvement in functional scores is less optimistic than physician measured parameters.

Introduction: Intraoperative tissue culture remains the “gold standard” in diagnosing periprosthetic infection (PPI). However, an organism is not always cultured and this has been attributed to the fact that preoperative antibiotics were administered. This study intends to examine if preoperative antibiotics prevent isolation of intraoperative organisms.

Methods: 91 total joint arthroplasty patients diagnosed with PPI during (1999–2005) and who had positive aspiration culture were included in the study. All intravenous antibiotics that were given to the patient within seven days of surgery were documented. The total number of positive intraoperative fluid and tissue samples of patients who did and did not receive antibiotics was calculated. Susceptibility of the organism(s) to antibiotics was determined by antibiogram of the preoperative and intraoperative culture.

Results: 60 out of 91 patients received preoperative antibiotics within seven days of surgery. Antibiotics prevented isolation of an intraoperative organism in 6 out of the 60 (10%) cases. All of the 31 patients who did not receive any preoperative antibiotics had positive intraoperative cultures. Chi-square analysis revealed no significant difference between giving preoperative antibiotics within 7 days and isolating an intraoperative organism (p=0.068). Giving antibiotics that specifically targets the culprit organism did not significantly affect the fluid (p=0.585) or tissue culture yield (p=0.152) either.

Discussion: Although, giving preoperative antibiotics can prevent isolation of intraoperative organisms in 10% of cases, this is not statistically or clinically significant in patients with positive aspiration cultures because the organism is known beforehand. However, it is clinically and medicolegally relevant to withhold antibiotics in patients with negative aspiration cultures since the postoperative treatment antibiotic is tailored according to the organism cultured.

Introduction: A small, yet not uncommon, problem following total joint arthroplasty (TJA) is post-operative ileus (POI). The purpose of this study was two-fold. First the study sought to determine the incidence of POI after TJA in a consecutive series of patients receiving regional anesthesia and an aggressive postoperative rehabilitation protocol. Second, the influence of narcotic medications, including intrathecal medications, in the incidence of POI was examined.

Methods: 5,262 patients underwent total joint replacements, including primary and revision surgery, at our institution from 2004 to 2005. All surgeries were performed at a university-affiliated institution where complications, if any, are prospectively recorded in a comprehensive database. Demographic, clinical, surgical, and radiographic details were obtained and examined.

Results: 26 (0.5%) patients developed ileus. There were 17 males and 9 female patients, who had a mean age of 67.7 years (range, 52.7 to 91.2 years). The mean BMI was 30.2 kg/m2. The index procedures included 15 primary hip, 4 primary knee, 4 revision hip, and 3 revision knee procedures. Of the patients who developed ileus, intrathecal narcotics were administered in 16 patients (62%).

Discussion: There is a very low incidence of postoperative ileus and gastrointenstinal hypomobility following joint arthroplasty. Early patient ambulation, a reduction in the use of postoperative narcotics, supplementation of analgesia with non-narcotic drugs, and reduced length of hospital stay may all have an important role in reducing this complication. Based on our findings, it seems unlikely that intrathecal narcotics have an adverse effect on gastrointestinal motility.

Background: Total joint arthroplasty (TJA) is a successful procedure. With the demographic tendency towards an elderly society and a relatively high prevalence of arthritis, the number of joint replacement in the US will increase dramatically in the upcoming years. The orthopaedic surgeons need to be aware of the various types of complications in the early hospital setting associated with elective TJA.

Methods: This prospective study reviewed the systemic and local early complications occurring after 13133 TJA which included 7,438 hip arthroplasties (6,010 primary and 1,428 revisions) and 5,695 knee replacements (4,944 primary and 751 revisions). A standardized and detailed form intended to capture all medical and orthopedic complications was devised, plus a full-time research fellow was dedicated to this study. The hospital course of every patient was followed on a daily basis closely. The circumstances leading to the complications and the details of the therapeutic intervention for each complication were recorded.

Results: In general the incidences of complications were higher following TKA compared to THA. There was 26(0.19%) deaths in the cohort that occurred within 10 days after surgery. 329 major (life threatening) complications occurred in the cohort that included myocardial infarction (36), hypotensive crisis (11), pulmonary embolus (145), tachyarrhythmia (93), pulmonary edema (10), acute renal failure (24), stroke (6), bowel obstruction or perforation (3), and pneumothroax (1). There were 37 major local complications. 301 (91%) of these complications occurred within 4 days of index surgery. There were 453 minor systemic complications, mostly related to anemia, and 99 minor local complications in this cohort.

Conclusions: Total joint arthroplasty despite its success can be associated with serious and life threatening complications. The introduction of MIS surgery and the potential for very early discharge of patients undergoing arthroplasty needs to be scrutinized in light of these findings.

Introduction: Management of bone loss during revision total knee arthroplasty (TKA) can be challenging. The degree and location of bone loss often dictates the type of prosthesis that can be utilized during revision surgery. The aim of this prospective study was to determine if plain radiographs are adequate in assessing the degree of bone loss around TKA and identify the limitations of plain radiographs for this purpose, if any.

Methods: 205 patients undergoing revision TKA at our institution were included. The indication for revision was aseptic failure in 120 patients and septic failure in the remaining patients. The plain radiographs were evaluated by a research fellow and the attending surgeon. The degree and the location of bone loss around the TKA was determined using the UPenn Bone Loss chart. The degree of real bone loss was then determined intraoperatively.

Results: The predicted amount of bone loss for the tibia based on the AP (p=0.136) and lateral (p=0.702) radiographs correlated well with the intraoperative findings. However, plain radio-graphs underestimated the degree of bone loss around femur, particularly the condyles (p=0.005).

Discussion: Reconstructive surgeons performing revision TKA need to be aware of the limitations of routine radiographs in assessing the degree of bone loss around the femoral component. Hence, patients undergoing revision TKA with suspected bone loss may need to be evaluated by additional imaging techniques and/or alternative reconstructive options need to be available to deal with greater than expected degree of bone loss intraoperatively.