Early Postoperative Pain Predicts 2-Year Functional Outcomes following Knee Arthroplasty.

Pain control following knee arthroplasty is extremely important to both patients and surgeons to improve the perioperative experience; however, the implication of early pain control on long-term outcomes following knee arthroplasty remains poorly understood. We hypothesized that poor early pain control results in poor functional outcomes 2 years following total (TKA) and unicondylar knee arthroplasty (UKA). This retrospective study reviewed 242 TKA and 162 UKA performed at a single institution by two surgeons. Mean visual analog scale (VAS) pain scores were collected for first 3 postoperative days. Patients were prospectively evaluated using short form (SF-12), the Western Ontario and McMaster University osteoarthritis index (WOMAC), and the Knee Society functional score (KSFS) questionnaires. Pearson's correlation coefficients were calculated between mean VAS pain scores and functional outcome scores at 2 years. In the TKA group, poorly controlled perioperative pain correlated with poorer functional scores at 2 years. There was a significant negative correlation between early mean VAS pain scores (mean, 3.2 ± 2.0) and most 2-year functional outcomes including SF-12 physical score (r = -0.227, p ≤ 0.01), WOMAC pain scores (r = -0.268, p ≤ 0.01), WOMAC stiffness scores (r = -0.224, p < 0.01), WOMAC function score (r = -0.290, p 0.01), and KSFS (r = -0.175, p = 0.031). Better control of early pain was associated with improved functional outcomes at 2 years following TKA. We also found significant negative correlations between preoperative functional scores and early postoperative pain scores. Collectively, using preoperative and early postoperative pain scores, we identified an "at-risk" patient group that manifested an inferior functional outcome at 2 years; these patients may benefit from closer surveillance and a multidisciplinary approach to pain and function to optimize their clinical outcome following knee arthroplasty.

Robotic-assisted unicompartmental knee replacement offers no early advantage over conventional unicompartmental knee replacement.

PURPOSE: Unicompartmental knee arthroplasty (UKA) is effective for treating degenerative joint disease in a single compartment. Robotic-arm-assisted arthroplasty (RAA) has gained popularity and has theoretical benefits of improved outcomes over conventional (CONV) UKA due to the technical precision of bone preparation. This study compares the short-term clinical outcomes, including survivorship and patient-reported functional outcomes, for a series of medial UKAs performed with RAA and CONV. METHODS: One hundred seventy-six consecutive fixed-bearing medial UKAs were retrospectively identified with a minimum follow-up of 2 years. One hundred and eighteen CONV and 58 RAA were performed. Pre- and post-operative SF12, WOMAC, and KSS Functional Questionnaires were available for all patients. RESULTS: At 2 years, both groups improved in all functional outcomes, with no significant difference between the RAA and CONV cohorts. However, the RAA cohort had a significantly longer operative time (p < 0.001) and a higher early revision rate than the CONV group (7 [12.0%] vs. 7 [6.8%]; p < 0.05). CONCLUSIONS: These results demonstrate that at short-term follow-up of 2 years, RAA was not superior to CONV in terms of functional scores and instead was associated with greater operative time and cost and lower survivorship. Therefore, at this time usage of RAA in UKA is not recommended compared to conventional UKA. Longer term studies are necessary to draw conclusions about the overall outcomes of RAA compared to CONV. LEVEL OF EVIDENCE: III.

Has the risk of dislocation after total hip arthroplasty performed for displaced femoral neck fracture improved with modern implants?

BACKGROUND: Displaced femoral neck fractures (DFNF) in the elderly can be treated with hemiarthroplasty or total hip arthroplasty (THA). One concern with utilizing THA in this setting is post-operative dislocation. The purposes of this study were to determine the incidence of hip dislocation following THA for DFNF and to identify risk factors for dislocation. METHODS: The charts of 66 posterior-approach THA cases performed for DFNF with mean post-operative follow-up of 4.4 years were retrospectively reviewed. Pre-operative patient demographic data and intra-operative clinical data were recorded including age, race, gender, height, weight, body mass index (BMI), femoral head diameter, acetabular cup diameter, use of an elevated liner, and cementing of femoral component. For patients with available post-operative pelvis radiographs, acetabular cup inclination and version angles were also calculated. RESULTS: Four dislocation (4/66, 6%) events occurred at an average of 51 days after surgery. No specific risk factors for dislocation were identified but the use of a cemented femoral stem did approach significance (p = 0.06). 47% of the acetabular cups were located outside of the Lewinnek safe zone. Although the dislocation rate of THAs with acetabular cups outside of the safe zone was higher than the dislocation rate for THAs with cups in the safe zone (12.5% vs 0%), placement of acetabular cups outside of the safe zone was not a risk factor for dislocation. CONCLUSIONS: Posterior THA with proper cup positioning and meticulous soft tissue repair is an effective treatment option for DFNF with low dislocation risk.

Which do patients prefer, unicompartmental or total knee arthroplasty?

OBJECTIVE: Unicompartmental knee arthroplasty (UKA) is a viable option for relieving pain and improving function in patients with isolated compartment knee osteoarthritis (OA). Certain surgeons prefer total knee arthroplasty (TKA) over UKA even when patients are candidates for UKA. Therefore, the decision to perform a UKA or a TKA when both are indicated is not straightforward. The goal of this study was to compare pre-operative and post-operative patient-reported outcome (PRO) scores for patients who underwent both a UKA and a contralateral TKA. METHODS: In this study, 17 patients were identified who underwent UKA in one knee and TKA in the contralateral knee either simultaneously or at different time points between 2003 and 2014. All procedures were performed by one of two fellowship trained surgeons at a large academic medical center. Patients were evaluated pre-operatively and then post-operatively using the validated PRO measurements Short Form 12 (SF12), Knee Society Functional Score (KSS), and the Western Ontario and McMaster University Osteoarthritis Index (WOMAC) questionnaires. Student's paired t-tests were conducted to compare PRO scores for UKA and TKA pre-operatively and post-operatively. RESULTS: Post-operatively, mean follow-up was 2.5 years (range, 3 months to 9 years). There was no significant difference in PRO scores between pre-operative values for UKA and TKA, and no significant difference between post-operative values for UKA and TKA (e.g. SF12 pre-operative difference between UKA and TKA mean = 1.6, p = 0.57; SF12 post-operative difference between UKA and TKA mean = 1.9, p = 0.51). CONCLUSION: UKA and TKA are comparable in terms of PROs at mid-term follow-up. When choosing between UKA and TKA, the surgeon should expect similar PROs for each, and can therefore take into account other considerations when making a selection.

Adductor Canal Block Compared with Periarticular Bupivacaine Injection for Total Knee Arthroplasty: A Prospective Randomized Trial.

BACKGROUND: In the last decade, the widespread use of regional anesthesia in total knee arthroplasty has led to improvements in pain control, more rapid functional recovery, and reductions in the length of the hospital stay. The aim of this study was to compare the efficacy of adductor canal blocks (ACB) and periarticular anesthetic injections (PAI), both with bupivacaine, for pain management in total knee arthroplasty. METHODS: One hundred and fifty-five patients undergoing primary total knee arthroplasty under spinal anesthesia were randomized to 1 of 3 groups: ACB alone (15 mL of 0.5% bupivacaine), PAI alone (50 mL of 0.25% bupivacaine with epinephrine), and ACB+PAI. The primary outcome in this study was the visual analog scale (VAS) pain score in the immediate postoperative period. Secondary outcomes included postoperative opioid use, activity level during physical therapy, length of hospital stay, and knee range of motion. RESULTS: The mean VAS pain score was significantly higher after use of ACB alone, compared with the score after use of ACB+PAI, on postoperative day 1 (POD1) (3.9 versus 3.0, p = 0.04) and POD3 (4.2 versus 2.0, p = 0.02). Total opioid consumption through POD3 was significantly higher when ACB alone had been used (131 morphine equivalents [ME]) compared with PAI alone (100 ME, p = 0.02) and ACB+PAI (98 ME, p = 0.02). Opioid consumption in the ACB-alone group was significantly higher than that in the ACB+PAI group on POD2 and POD3 and significantly higher than that in the PAI-alone group on POD2. There was no significant difference in opioid consumption between the patients treated with PAI alone and those who received ACB+PAI. The activity level during physical therapy on POD0 was significantly lower after use of ACB alone (26 steps) than after use of PAI alone (68 steps, p < 0.001) or ACB+PAI (65 steps, p < 0.001). CONCLUSIONS: This randomized controlled clinical trial demonstrated significantly higher pain scores and opioid consumption after total knee arthroplasty done with an ACB and without PAI, suggesting that ACB alone is inferior for perioperative pain control. There were no significant differences between PAI alone and ACB+PAI with regard to pain or opioid consumption. LEVEL OF EVIDENCE: Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.

Risk factors for conversion surgery to total hip arthroplasty of a hemiarthroplasty performed for a femoral neck fracture.

INTRODUCTION: The purpose of this study was to determine risk factors for conversion to total hip arthroplasty (THA) in patients originally treated with hemiarthroplasty (HA) for displaced femoral neck fractures. METHODS: In this case-controlled study, we identified 54 patients who were treated with HA for femoral neck fracture (FNF) who subsequently underwent conversion to THA at our institution between 2003 and 2013. We randomly selected 142 control patients who underwent HA for a displaced FNF without conversion surgery during the same time period. We compared demographic data, implant parameters, and radiographic data between the groups to identify risk factors for conversion surgery. RESULTS: In the univariate analysis, younger age at index surgery (mean 75 vs. 80 years, p = 0.006), higher body mass index (26.1 vs. 23.7, p = 0.031), bipolar prosthesis (20% vs. 36%, p = 0.024), absence of dementia (6% vs. 23%, p = 0.01), increased leg length compared to contralateral limb (6.5 mm vs. 0.2 mm, p<0.001), and increased HA femoral head size compared to the contralateral femoral head (2.7 mm vs. 1.5 mm, p = 0.02) were associated with a significantly increased risk of conversion surgery. In the multivariate logistic regression, decreased age at index surgery, no dementia, use of a bipolar head, and increased leg length discrepancy (LLD) were associated with risk of conversion. CONCLUSIONS: Patient characteristics, including younger age, increased BMI, and absence of dementia can lead to increased risk for conversion of HA to THA. Intraoperative considerations of head size and increase in ipsilateral LLD may increase the risk of conversion surgery. These factors should be considered by surgeons who employ HA for displaced FNFs.

Treatment of Periprosthetic Knee Infection With Concurrent Rotational Muscle Flap Coverage Is Associated With High Failure Rates.

BACKGROUND: Soft-tissue deficiency is a potentially devastating complication of the infected total knee arthroplasty (TKA). Rotational muscle flaps are commonly used to address these defects. However, reported success rates vary widely. METHODS: We reviewed 26 consecutive patients who underwent rotational muscle flap surgery for full-thickness anterior soft-tissue defect during treatment of an infected TKA. Twenty-four cases used a medial gastrocnemius rotational flap, 1 used a lateral gastrocnemius flap, and 1 used a rectus femoris-vastus intermedius flap. Implant survival, recurrence of infection, and limb survival were reported. Patient and procedural characteristics were tested for association with failure using χ2 and Student t-test. Kaplan-Meier analysis was used to estimate the failure-free survival function. RESULTS: Mean follow-up time was 3.3 years. Eighteen of 26 patients (69.2%) experienced recurrent infection requiring an average of 5.3 additional operations (range, 1-20). Five (19.2%) required arthrodesis while 6 (23.1%) eventually underwent above-the-knee amputation. Two patients (7.7%) died due to complications of revision surgery or persistent infection. Eleven patients (42.3%) were infection free with a retained prosthesis after treatment at a mean follow-up of 5.3 years (range, 0.7-18.0 years). CONCLUSION: Rotational muscle flap coverage of soft-tissue defects in the setting of the infected TKA remains a viable salvage option. However, despite adequate tissue coverage, many patients experience recurrent infection requiring additional surgical treatment. Patients and surgeons should be aware of the potential high failure rates observed when treating these complex problems.

Tranexamic acid increases early perioperative functional outcomes after total knee arthroplasty.

BACKGROUND: The purpose of this study was to investigate the influence of tranexamic acid (TXA) on functional outcomes in the immediate postoperative period after total knee arthroplasty (TKA). We hypothesized that the known benefits of TXA would confer measurable clinical improvements in physical therapy (PT) performance, decrease pain, and decrease hospital length of stay (LOS). METHODS: We retrospectively analyzed 560 TKA patients, including 280 consecutive patients whose surgery was performed before the initiation of a standardized TXA protocol and the first 280 patients who received TXA after protocol initiation. Outcome measurements included postoperative changes in hemoglobin and hematocrit, LOS, pain scores, destination of discharge, and steps ambulated with PT over 5 sessions. RESULTS: TXA administration resulted in less overall drops in hemoglobin (P < .001) and hematocrit levels (P < .001). Moreover, patients administered TXA ambulated more than their counterparts during every PT session, which was statistically significant during the second (P = .010), third (P = .011), and fourth (P = .024) sessions. On average, the TXA cohort ambulated 20% more per PT session than patients who did not receive TXA (P < .001). TXA administration did not influence pain levels during PT, hospital LOS, or discharge destination in this investigation. CONCLUSIONS: It is well known that TXA reduces postoperative anemia, but this study also demonstrates that it confers early perioperative functional benefits for TKA patients. Potential mechanisms for this benefit include reduced rates of postoperative anemia and reduced rates of hemarthroses.

Step-wise medial collateral ligament needle puncturing in extension leads to a safe and predictable reduction in medial compartment pressure during TKA.

PURPOSE: Medial soft tissue release in a varus deformity knee during total knee arthroplasty is essential for accurate balancing of the reconstruction. This study attempts to quantify the effect of sequential needle puncturing of the medial collateral ligament (MCL) using a pressure sensor insert (Verasense by OrthoSensor) and gap measurement under tension. METHODS: Cruciate-retaining arthroplasties were placed in 14 cadaveric knees. The MCL was elongated by step-wise perforation, in five sets of five perforations, with the use of an 18-gauge needle, followed by valgus stress. Following the fifth set of needle perforations, blade perforation was performed on the remaining tense fibers of the MCL. Following each step-wise perforation, corresponding medial compartment pressures and gap measurements under tension were recorded. RESULTS: Sensor measurements correlated closely with step-wise tissue release (R = 0.73, p < 0.0001), and a significant decrease in pressure was found in early needle puncturing (mean 49 N after 5, 83 N after 15, p values < 0.05), although changes diminished at later stages of needle perforation (90 N after 20). Gap measurement demonstrated small gradual changes with early puncturing, but showed significant opening in the later stages of release. There was minimal variation in pressure or gap measurements in flexion versus extension. This finding suggests that MCL needle puncture will not lead to unequal gaps between flexion and extension. There were no cases of MCL over-release after 15 punctures, one case after 20 punctures, and three after blade perforation. CONCLUSION: Needle puncturing of the MCL in extension for up to 15 punctures can be a safe and predictable way to achieve medial opening when balancing a varus knee during TKA as demonstrated in this cadaveric model. Blade perforation should be used with caution to avoid over-release. The needle puncture method can be used by surgeons to achieve reliable reductions in medial compartment pressures, to help achieve a balanced TKA, with minimal risk of over-release.

Risk factors for conversion surgery to total hip arthroplasty of a hemiarthroplasty performed for a femoral neck fracture.

INTRODUCTION: The purpose of this study was to determine risk factors for conversion to total hip arthroplasty (THA) in patients originally treated with hemiarthroplasty (HA) for displaced femoral neck fractures. METHODS: In this case-controlled study, we identified 54 patients who were treated with HA for femoral neck fracture (FNF) who subsequently underwent conversion to THA at our institution between 2003 and 2013. We randomly selected 142 control patients who underwent HA for a displaced FNF without conversion surgery during the same time period. We compared demographic data, implant parameters, and radiographic data between the groups to identify risk factors for conversion surgery. RESULTS: In the univariate analysis, younger age at index surgery (mean 75 vs. 80 years, p = 0.006), higher body mass index (26.1 vs. 23.7, p = 0.031), bipolar prosthesis (20% vs. 36%, p = 0.024), absence of dementia (6% vs. 23%, p = 0.01), increased leg length compared to contralateral limb (6.5 mm vs. 0.2 mm, p<0.001), and increased HA femoral head size compared to the contralateral femoral head (2.7 mm vs. 1.5 mm, p = 0.02) were associated with a significantly increased risk of conversion surgery. In the multivariate logistic regression, decreased age at index surgery, no dementia, use of a bipolar head, and increased leg length discrepancy (LLD) were associated with risk of conversion. CONCLUSIONS: Patient characteristics, including younger age, increased BMI, and absence of dementia can lead to increased risk for conversion of HA to THA. Intraoperative considerations of head size and increase in ipsilateral LLD may increase the risk of conversion surgery. These factors should be considered by surgeons who employ HA for displaced FNFs.

Simultaneous ipsilateral knee arthroscopy and unicondylar knee arthroplasty is effective for bicompartmental symptoms.

BACKGROUND: Patients with unicompartmental radiographic arthritis but bicompartmental symptoms pose a clinical challenge. Some surgeons may perceive it as a contraindication for unicondylar knee arthroplasty (UKA). We investigated patient outcomes 2 years after simultaneous ipsilateral arthroscopy and UKA as compared to a similar group of patients who had total knee replacement (TKA) for a similar clinical presentation. METHODS: We identified 9 patients with simultaneous ipsilateral arthroscopy and UKA between 2004 and 2013, and 12 clinically similar patients treated with TKA. RESULTS: At 1- and 2-years, SF-12 physical scores were significantly improved in the UKA-scope group than in the TKA group (47.2 vs 40.3, p = 0.042; 48.3 vs 32.6, p = 0.026). WOMAC pain score, WOMAC stiffness score, WOMAC function and KSFS were significantly improved in the UKA-scope group at 2 years as compared to the TKA group (98.7 vs 63.8, p = 0.030), (90.1 vs 43.8, p = 0.013), (92.3 vs 55.2, p = 0.027 and (92.3 vs 55.2, p = 0.027), respectively). Change in score from baseline for KSFS, SF-12 physical and WOMAC stiffness were significantly improved in the UKA-scope group at 2 years compared to TKA, (28.3 vs -5, p = 0.041), (13.6 vs 3.0, p = 0.026), (52.6 vs -6.3, p = 0.025), respectively. CONCLUSION: This study shows that patients with isolated compartment radiographic disease but with bicompartmental symptoms can benefit from UKA and simultaneous arthroscopy. Further, TKA for isolated compartment radiographic disease in this limited series had poorer outcomes. We obtain MRI selectively when physical exam and radiographic findings suggest isolated arthritic disease in patients with bicompartmental symptoms.

Acute Kidney Injury After First-Stage Joint Revision for Infection: Risk Factors and the Impact of Antibiotic Dosing.

BACKGROUND: Scarce literature exists regarding risk factors associated with postoperative acute kidney injury (AKI) after first-stage revision procedures. The purpose of this study was to determine risk factors for AKI and the efficacy of intra-articular antibiotics in infection eradication. METHODS: We retrospectively identified 247 patients who underwent a 2-stage revision procedure for the treatment of hip or knee periprosthetic joint infection. We applied previously published diagnostic criteria for AKI to determine its incidence and risk factors for its development. RESULTS: A 26% incidence of AKI was found after first-stage joint revision for infection. Higher body mass index (odds ratio [OR], 1.07; 95% confidence interval [CI], 1.01-1.13; P = .02), lower baseline hemoglobin level (OR, 0.70; 95% CI, 0.51-0.96; P = .03), and existence of a comorbid condition (OR, 2.67; 95% CI, 1.26-5.64; P = .01) were significant risk factors for AKI. Neither a higher dose of vancomycin (OR, 0.99; 95% CI, 0.88-1.11; P = .83) nor tobramycin (OR, 0.89; 95% CI, 0.77-1.04; P = .15) used in the cement spacer increased the risk of AKI. Each unit increase in vancomycin dose in the cement spacer decreased the odds of failing to clear the infection at 1 and 2 years by a factor of 0.82 (95% CI, 0.70-0.95; P = .01). CONCLUSION: AKI after first-stage revision procedures for periprosthetic joint infection occurs more commonly than previously reported. Patients with identified risk factors should be managed carefully with attention paid to hemoglobin levels, to avoid AKI after this procedure. Further research is needed to determine the optimal local antibiotic type and dosing to maximize infection clearance and minimize potential side effects.

The Use of Electronic Sensor Device to Augment Ligament Balancing Leads to a Lower Rate of Arthrofibrosis After Total Knee Arthroplasty.

BACKGROUND: Total knee arthroplasty (TKA) is a highly successful surgery shown to improve quality of life. One of the more common known complications of TKA is early arthrofibrosis requiring manipulation under anesthesia (MUA). This investigation evaluates the incidence of arthrofibrosis before and after the implementation of an electronic sensor device used to assist with ligament balancing. METHODS: Six hundred ninety TKAs performed without sensor use were compared to a cohort of 252 TKAs performed with sensor usage. RESULTS: Prior to usage, there was a 5% rate of MUA after TKA, while after implementation, the MUA rate went down to 1.6% (P = .004). Ligament balancing using sensor assistance led to a statistically significant decrease in MUA in this cohort of patients. An odds ratio analysis also demonstrated that non-sensor patients had a 3.2× higher likelihood of requiring MUA than the sensor patients. CONCLUSION: The use of an electronic sensor device during trialing of TKA with resultant improved ligamentous balancing led to a statistically significant reduction in the rate of MUA in this cohort of patients. This type of approach to ligamentous balancing may continue to show evidence of improved clinical outcomes.

Chronic Pain and Obesity Within a Pediatric Interdisciplinary Pain Clinic Setting: A Preliminary Examination of Current Relationships and Future Directions.

OBJECTIVES: Pediatric obesity and chronic pain are 2 of the most significant public health crises affecting youth today. Despite the high number of youth experiencing both chronic pain and obesity, little research has been done examining their relationship. This study aims to both replicate and extend this research base. METHODS: A retrospective chart review of 99 patients presenting for evaluation in a pediatric pain clinic was conducted. Demographic information, including patient weight status, and self-report measures completed by both patients and their parents, including the Pain Frequency-Severity-Duration scale, the Functional Disability Inventory, and the Pain Catastrophizing Scale were examined. RESULTS: Abdominal pain was the most frequently reported primary pain diagnosis category, with headache, diffuse musculoskeletal, localized musculoskeletal, and back pain categories reported from greatest to least frequency. Results show that 29% of our sample was obese. Age was related to weight status such that older children were more likely to have a higher body mass index. Among school-aged children, a higher body mass index percentile was associated with greater parent-reported pain catastrophizing. Obese youth had higher parent-reported Functional Disability Inventory scores than those in the normal weight group. Post hoc comparisons identified that this finding was only significant for girls. Further, obese youth were more likely to have a longer pain duration than those classified as normal weight. DISCUSSION: The results of this study add to the growing literature regarding the importance of taking weight status into account when intervening with youth with chronic pain.

Hemiarthroplasty for Displaced Femoral Neck Fractures in the Elderly Has a Low Conversion Rate.

BACKGROUND: Hemiarthroplasty (HA) has been a mainstay treatment for displaced femoral neck fractures for many years. The purpose of this study was to report the conversion rate of HA to total hip arthroplasty (THA) for displaced femoral neck fractures and compare outcomes between implant constructs (bipolar vs unipolar), fixation options (cemented vs cementless stems), and age groups (<75 years vs ≥75 years). METHODS: We retrospectively reviewed the results of a consecutive cohort of 686 patients who underwent HA for the treatment of femoral neck fractures at our institution between 1999 and 2013 with a minimum of 2-year follow-up. RESULTS: The overall component revision rate, including conversion to THA, revision HA, revision with open reduction internal fixation, and Girdlestone procedure, was 5.6% (39/686). Seventeen patients (2.5%) were converted from HA to THA at an average of 1.9 years after index procedure. A significantly lower conversion rate of 1.4% (7/499 patients) was found in the older patient cohort (≥75 years old) compared to 5.3% (11/187) in the younger cohort. The most common causes for conversion surgery to THA were acetabular wear (5 patients), aseptic loosening (4 patients), and periprosthetic fracture (3 patients). There was a significantly lower rate of periprosthetic fracture (0.4% vs 2.5%, P value .025) in the cemented implant group compared to the cementless group. We observed a higher rate of dislocations in the bipolar vs unipolar group (3.8% vs 1%, P value .02) and no other significant differences between these groups. CONCLUSION: We observed a low reoperation rate for this cohort of patients, relatively higher conversion rates for the younger population, fewer periprosthetic fractures with the use of cemented stems, and no advantage of bipolar over unipolar prostheses.

Silver-Impregnated Occlusive Dressing Reduces Rates of Acute Periprosthetic Joint Infection After Total Joint Arthroplasty.

BACKGROUND: Commercial silver-impregnated occlusive dressings (such as AQUACEL® Ag SURGICAL Cover Dressing) have been touted as antimicrobial dressings to be used following total joint arthroplasty. Given the increased cost of an AQUACEL® Ag SURGICAL Cover Dressing over a standard dressing for total joint arthroplasty, the objective of this study was to determine whether AQUACEL® Ag SURGICAL Cover Dressing is effective in reducing the rates of acute periprosthetic joint infection (PJI) compared to standard sterile dressing. METHODS: We retrospectively reviewed the charts of 1173 consecutive patients who underwent a total knee or total hip arthroplasty between 2007 and 2015 by 1 surgeon. The surgeon switched from using a standard xeroform/gauze dressing to an AQUACEL® Ag SURGICAL Cover Dressing in June 2011, with no other major changes in antimicrobial management. Charts were reviewed for evidence of acute PJI (within 3 months of surgery). RESULTS: There were a total of 11 cases of acute PJI in this patient cohort (0.94%). The incidence of acute PJI for patients managed with a sterile xeroform dressing was 1.58% (9 of 568 patients), compared to 0.33% (2 of 605 patients) with the use of AQUACEL® Ag SURGICAL Cover Dressing. Univariate analysis showed this to be statistically significant (P = .03), and a multiple logistic regression model supported AQUACEL® Ag SURGICAL Cover Dressing as a protective factor with an odds ratio of 0.092 (95% confidence interval, 0.017-0.490; P = .005). CONCLUSION: This 4-fold decrease in acute PJI with the use of AQUACEL® Ag SURGICAL Cover Dressing supports the use of silver-impregnated occlusive dressings for the reduction of acute PJI.

Prospective Comparison of Blood Culture Bottles and Conventional Swabs for Microbial Identification of Suspected Periprosthetic Joint Infection.

BACKGROUND: Early, accurate detection of infection is vital to successful treatment of periprosthetic joint infection (PJI). Currently, no "gold standard" diagnostic testing exists. The goal of this prospective study was to compare the efficacy of a blood culture bottle system (BCBS) to commonly used culture swabs in confirming PJI in patients with high clinical suspicion. METHODS: Patients were selected for enrollment based on Musculoskeletal Infection Society guidelines for PJI. erythrocyte sedimentation rate and C-reactive protein were obtained before aspiration. Aspirated fluid was divided between BCBS, swab, and synovial fluid analysis. Forty-nine samples were analyzed. RESULTS: BCBS yielded 41 positive cultures vs 19 with swab (P < .0001), particularly with respect to Staphylococcus epidermidis. There were no false positive results in the BCBS group, using strict Musculoskeletal Infection Society guidelines. CONCLUSION: BCBS increased identification of pathogens in lower extremity PJI, providing clinicians with a low-cost, broadly-applicable test.

Redefining the Acetabular Component Safe Zone for Posterior Approach Total Hip Arthroplasty.

BACKGROUND: Acetabular component orientation influences joint stability in total hip arthroplasty (THA). The purpose of this study was to evaluate the effect of cup orientation and other variables on hip dislocation risk and to define a posterior approach specific safe zone. METHODS: A cohort of 1289 posterior approach primary THA cases was prospectively followed and component position measured radiographically. RESULTS: Cup malposition, with respect to the Lewinnek safe zone, was an independent risk factor for dislocation (OR1.88). Modifying the anteversion safe zone limits to 10-25° strongly predicted increased dislocation risk (OR2.69). No dislocations occurred within a zone defined by a circle centered at 41.4° abduction and 17.1° anteversion, radius 4.3°. CONCLUSION: Utilizing a posterior approach specific safe zone of 10-25° anteversion and 30-50° abduction may minimize THA dislocations. LEVEL OF EVIDENCE: Level III.