In Vitro Inflammatory Cell-Induced Corrosion Using a Lymphocyte and Macrophage Co-Culture.

INTRODUCTION: Cobalt-chromium-molybdenum (CoCrMo) and titanium alloys have been used for orthopaedic implants for decades. However, recent evidence has shown that inflammatory cell-induced corrosion (ICIC) can damage these metal alloys. This study aimed to investigate the mechanisms of ICIC by co-culturing macrophages with lymphocytes. We hypothesized that macrophages would be able to alter the surface oxide layer of CoCrMo and titanium alloy (Ti6Al4V) disks, with greater oxide layer damage occurring in groups with a co-culture compared to a macrophage monoculture and in groups with inflammatory activators compared to nonactivated groups. METHODS: Murine macrophages were cultured on American Society for Testing and Materials (ASTM) F1537 CoCrMo and ASTM F136 Ti6Al4V disks for 30 days and activated with interferon gamma and lipopolysaccharide. Interferon gamma and lipopolysaccharide were added to the culture medium to simulate local inflammation. Macrophages were either cultured alone or in a co-culture with T helper lymphocytes. After the 30-day experiment, scanning electron microscopy was used to examine the disk surfaces, and oxide levels were found using energy dispersive x-ray spectroscopy. RESULTS: Pitting features consistent with previous reports of ICIC were found on disks cultured with cells. Both CoCrMo and Ti6Al4V disks had significantly lower oxide levels in all groups with cells compared to control groups with no cells (P < 0.01). Additionally, CoCrMo disks had significantly lower oxide levels when cultured with activated macrophages and lymphocytes compared to nonactivated macrophages alone (P < 0.001), activated macrophages alone (P < 0.01), and nonactivated macrophages and lymphocytes (P < 0.05). No differences in the oxide levels were found among the Ti6Al4V groups. CONCLUSION: This study demonstrates the ability of macrophages to alter the surface chemistry of commonly used orthopaedic alloys. We found that the addition of lymphocytes and a simulated local inflammatory response may contribute to the ICIC of CoCrMo implants.

Muscle activation patterns during active external rotation after reverse total shoulder arthroplasty: an electrophysiological study of the teres minor and associated musculature.

BACKGROUND: Preoperative teres minor insufficiency has been identified as a risk factor for poor restoration of external rotation (ER) after reverse total shoulder arthroplasty (RTSA). However, there has been little investigation regarding muscle activation patterns generating ER. This prospective study sought to determine the timing and activation levels of the shoulder girdle musculature during ER in well-functioning RTSAs with an intact teres minor using a lateralized design. METHODS: Patients who underwent RTSA ≥1 year previously with functional ER, an American Shoulder and Elbow Surgeons (ASES) score >70, superior rotator cuff deficiency, and an intact teres minor were identified. Electrophysiological and kinematic analyses were performed during ER in the modified neutral position (arm at side with 90° of elbow flexion) and in abduction (AB) (shoulder abducted 90° with 90° of elbow flexion). Dynamometer-recorded torque and position were pattern matched to electromyography during ER. The root-mean-square and integrated electromyography (in microvolts × milliseconds with standard deviation [SD]), as well as median frequency (MF) (in hertz with SD), were calculated to determine muscle recruitment. Pair-wise t test analysis compared muscle activation (P < .05 indicated significance). RESULTS: After an a priori power analysis, 16 patients were recruited. The average ASES score, visual analog scale pain score, and ASES subscore for ER in AB ("comb hair") were 87.7, 0.5, and 2.75 of 3, respectively. In AB, muscle activation began with the upper trapezius, middle trapezius, and latissimus dorsi, followed by the anterior deltoid activating to neutral. With ER beyond neutral, the teres major (9.6 µV × ms; SD, 9.2 µV × ms) initiated ER, followed by the teres minor (14.1 µV × ms; SD, 18.2 µV × ms) and posterior deltoid (11.1 µV × ms; SD, 9.3 µV × ms). MF analysis indicated equal contributions of the teres major (1.1 Hz; SD, 0.5 Hz), teres minor (1.2 Hz; SD, 0.4 Hz), and posterior deltoid (1.1 Hz; SD, 0.4 Hz) in ER beyond neutral. In the modified neutral position, the upper trapezius and middle trapezius were not recruited to the same level as in AB. For ER beyond neutral, the teres major (9.5 µV × ms [SD, 9 µV × ms]; MF, 1.1 Hz [SD, 0.5 Hz]), teres minor (11.4 µV × ms [SD, 15.1 µV × ms]; MF, 1.1 Hz [SD, 0.5 Hz]), and posterior deltoid (8.5 µV × ms [SD, 8 µV × ms]; MF, 1.2 Hz [SD, 0.3 Hz]) were activated in similar sequence and intensity as AB. No differences in muscle activation duration or intensity were noted among the teres major, teres minor, and posterior deltoid (P > .05). CONCLUSION: Active ER after RTSA is complex and is not governed by a single muscle-tendon unit. This study establishes a sequence, duration, and intensity of muscle activation for ER in well-functioning RTSAs. In both tested positions, the teres major, teres minor, and posterior deltoid function equally and sequentially to power ER.

United States Experience With a Femoral Neck Retaining Total Hip Arthroplasty Stem: A Retrospective Study With Control Comparison From the Literature.

BACKGROUND: Femoral neck retaining prostheses have gained popularity in Europe, but the United States has not seen the same trends occurring. Previous reports demonstrate high survivorship for these implants, but to our knowledge, there are no reports examining US data. METHODS: After institutional review board approval, 824 primary total hip arthroplasties utilizing a femoral neck-retaining prosthesis were examined for femoral component survivorship rates. European studies were systematically reviewed to determine survivorship rates. The data were used to formulate a Kaplan-Meier survivorship curve and compare US data to that of the European studies. RESULTS: European studies demonstrated survivorship rates for all causes of 97.7 and 99.0% for aseptic loosening at an average of 6 years (range, 4.5 to 10). The current study demonstrated an all-cause 94% Kaplan-Meier survivorship estimate at 5 years and when aseptic loosening only was considered, survivorship increased to 99.4% at 5 years and 98.4% at 11 years. CONCLUSION: This femoral neck-retaining prosthesis demonstrated excellent survivorship that is comparable to the rates seen in European studies as well as the rates of standard and mid-stem prostheses in the United States.

Spinal Versus General Anesthesia for Outpatient Total Hip and Knee Arthroplasty in the Ambulatory Surgery Center: A Matched-Cohort Study.

BACKGROUND: Spinal anesthesia is the predominant regimen in outpatient total joint arthroplasty (TJA), but induction often is unsuccessful, unobtainable, or against patient preference. We compared outcomes of same-day discharge (SDD) TJA with spinal versus general anesthesia in a free-standing ambulatory surgery center (ASC). METHODS: We took 105 general anesthesia TJA and one-to-one nearest-neighbor matched them to 105 spinal anesthesia TJA over 7 years at 1 ASC. The rate of successful SDD, minutes to discharge, postoperative pain and nausea, and 90-day complications were compared. Postanesthesia care unit outcomes were additionally stratified by spinal anesthetic (mepivacaine versus bupivacaine). RESULTS: All spinal anesthetic patients underwent SDD compared with 103 (98%) general anesthetic patients (P = .498). Mepivacaine spinal anesthesia patients spent the fewest minutes in postanesthesia care unit prior to discharge from the facility (206), followed by general anesthesia (227), and bupivacaine spinal anesthesia (291; P < .001). General anesthesia patients had the highest levels of pain at 1 hour (5.2 versus 1.5 versus 1.5) and 2 hours (3.2 versus 2.0 versus 1.3) postoperatively, and rates of nausea (48 versus 22 versus 28%) compared with mepivacaine and bupivacaine spinal anesthesia, respectively. The 90-day complications (6 versus 7), admissions (1 versus 3), and reoperations (5 versus 2) were similar among spinal and general anesthesia, respectively (P ≥ .445). CONCLUSIONS: Both spinal and general anesthesia led to reliable SDD with similar 90-day complication rates. General anesthesia facilitated faster discharge from the ASC compared with bupivacaine spinal anesthesia but led to higher levels of pain and incidence of nausea postoperatively. LEVEL OF EVIDENCE: Level 3, Retrospective Cohort Comparison.

Body Habitus Impact on Success of Cryoneurolysis for Postoperative Total Knee Arthroplasty Pain Control: A Retrospective Cohort Study.

Background: Cryoneurolysis utilizes temperatures below -20°C for nonpermanent analgesia to control pain in total knee arthroplasty (TKA). There is concern that body habitus could limit pain control because of accuracy of cryoneurolysis to subcutaneous nerves. This study aimed to determine the relationship between body habitus and effectiveness of cryoneurolysis on postoperative pain control. Methods: A retrospective chart review was performed on patients undergoing cryoneurolysis before primary TKA from 2017 to 2019. Included were 114 patients (58 control group and 56 treatment group). Cryoneurolysis patients were divided into 3 groups (small, medium, and large) based on the soft tissue to femoral diaphysis ratio of 7 cm proximal to superior pole of the patella. Postoperative outcome measures were morphine equivalents, numerical rating score for pain, range of motion, and Knee Injury and Osteoarthritis Outcome Score Joint Replacement. Results: The small cryoneurolysis group showed decreased opioid consumption at the 2, 6, and 12 weeks compared with control group, with morphine equivalents significantly decreased at 2 weeks for small compared with medium groups (54.3 vs 142.9, P = .0097). Numerical rating score for pain decreased significantly between small and medium groups (3.4 vs 4.0, P = .012) and between medium and large groups (4.0 vs 2.4, P = .012). Range of motion increased at 12 weeks for small group compared with medium group (118 vs 112, P = .042). There were no differences in any outcome measure between small and large groups. Conclusions: Body habitus does not appear to affect efficacy of cryoneurolysis in controlling postoperative pain following TKA. Cryoneurolysis remains a useful tool for multimodal pain management.

The Association of Total Knee Arthroplasty With Weight Loss in the Look AHEAD (Action for Health in Diabetes) Clinical Trial.

BACKGROUND: Patients who have obesity seldom lose weight after total knee arthroplasty (TKA). The Look AHEAD (Action for Health in Diabetes) trial randomized patients with type 2 diabetes who were overweight or had obesity to a 10-year intensive lifestyle intervention (ILI) or diabetes support and education (DSE). METHODS: Of the total 5,145 participants enrolled who had a median 14-year follow-up, a subset of 4,624 met inclusion criteria. The ILI aimed at achieving and maintaining a 7% weight loss and included weekly counseling the first 6 months, with decreasing frequency thereafter. This secondary analysis was undertaken to determine what effects a TKA had on patients participating in a known successful weight loss program and specifically if there was a negative impact on weight loss or their Physical Component Score. RESULTS: The analysis suggests that the ILI remained effective for maintaining or losing weight after TKA. Participants in ILI had significantly greater percent weight loss than those in DSE both before and after TKA (ILI-DSE before TKA: -3.6% (-5.0, -2.3); after TKA: -3.7% (-4.1, -3.3); both P < .0001). When comparing percent weight loss before to after TKA, there was no significant difference within either the DSE or ILI group (least square means ± standard error ILI: -0.36% ± 0.3, P = .21; DSE: -0.41% ± 0.29, P = .16). Physical Component Scores improved after TKA (P < .001), but no difference was found between TKA ILI and DSE groups before or after surgery. CONCLUSION: Participants who had a TKA did not have an altered ability to adhere to intervention goals to maintain weight loss or obtain further weight loss. The data suggest patients who have obesity can lose weight after TKA on a weight loss program.

Changes in Neuraxial Anesthesia Protocols and Improved Efficiency of Same-Day Discharge Total Knee Arthroplasty in an Ambulatory Surgery Center: A Retrospective Cohort Study.

INTRODUCTION: This study evaluated the effect of bupivacaine versus mepivacaine spinal anesthesia and preoperative adductor canal block (ACB) on recovery, length of stay, pain, and complications of same-day discharge total knee arthroplasty (TKA) at a free-standing ambulatory surgery center. METHODS: We performed a retrospective review of patients who underwent TKA between March 2018 and September 2019. The patients were grouped based on the neuraxial anesthetic regimen: bupivacaine with ACB, bupivacaine without ACB, and mepivacaine without ACB. Preoperative ACBs were discontinued in December 2018, and use of mepivacaine spinal anesthesia was initiated in March 2019. Length of stay in the postanesthesia care unit (PACU), time to controlled void and ambulation, postoperative pain, morphine milligram equivalents (MME), and transient neurologic symptoms were compared. RESULTS: Ninety consecutive patients who underwent TKA were identified. Fifty patients received bupivacaine with ACB, 20 received bupivacaine without ACB, and 20 received mepivacaine without ACB. Mepivacaine spinal anesthesia led to a 93-minute shorter PACU stay (P < 0.001), 115-minute quicker time to void (P < 0.001), 60-minute earlier ambulation (P = 0.024), and 109-minute shorter total facility time (P = 0.003) but increased total MME (P = 0.049) despite nonsignificant difference in pain at discharge (P = 0.908) compared with bupivacaine. Patients receiving bupivacaine with and without ACB had a nonsignificant difference in pain scores at discharge, time to ambulation, and time to discharge (P ≥ 0.1). No transient neurologic symptoms or overnight stays were observed. DISCUSSION: Mepivacaine spinal anesthesia for TKA safely facilitated more rapid same-day discharge through decreased times to controlled void and ambulation but with a slight increase in MME requirements. Discontinuing preoperative ACBs did not negatively affect PACU outcomes.

Hip Arthroplasty Femoral Stem Designs and Their Association With Early Postoperative Periprosthetic Femoral Fractures.

BACKGROUND: Periprosthetic femoral fractures (PFFs) in total hip arthroplasty (THA), especially those in contact with the diaphyseal stem, carry high morbidity. This study evaluated how stem design influences the risk of early Vancouver B PFF or other PFF requiring operative intervention after THA. METHODS: A multicenter, retrospective study of 3,433 primary cementless THAs performed from 2014 to 2021 included 2,302 single-taper (micro M/L [n = 1,169]; M/L [n = 1,133]) and 1,131 double-taper (fit-and-fill [n = 420]; compaction-collared [n = 711]) stems. Mean follow-up was 2.2 years (range, 0.3 to 6.5 years). Primary outcomes were Vancouver B and surgically treated postoperative PFFs among differing femoral stems. Secondary outcomes included rates of intraoperative and postoperative Vancouver A and C PFFs. RESULTS: Forty five postoperative PFFs (1.3%) occurred within 8.8 weeks (median), 25 of which were Vancouver B (0.7%) and 20 total PFFs that required operative intervention (0.6%). Compaction-collared stems had a decreased risk of Vancouver B (hazard ratio 0.18, 95% confidence interval: 0.03-0.97 P = .044) and any surgically treated PFF (hazard ratio 0.10, 95% confidence interval: 0.01-0.95; P = .037). Intraoperative PFFs were most common with fit-and-fill stems (3.6%, P < .001) and Vancouver A with compaction-collared stems (1.8%, P < .001). The cohort with PFF had a higher Charlson comorbidity index (P = .004), more women (P = .001), more Dorr A or C femora (P = .013), and more posterior or lateral surgical approaches compared to those without PFF (P ≤ .001). CONCLUSION: After controlling for confounding variables, compaction-collared stems had a significantly lower risk of postoperative Vancouver B and PFF requiring operative treatment than single-taper and double-taper stems.

Endurance Behavior of Cemented Tibial Tray Fixation Under Anterior Shear and Internal-External Torsional Shear Testing: A New Methodological Approach.

BACKGROUND: Early total knee arthroplasty failures continue to surface in the literature. Cementation technique and implant design are two of the most important scenarios that can affect implant survivorship. Our objectives were to develop a more suitable preclinical test to evaluate the endurance of the implant-cement-bone interface under anterior shear and internal-external (I/E) torsional shear testing condition in a biomechanical sawbones. METHODS: Implants tested included the AS VEGA System PS and the AS Columbus CR/PS (Aesculap AG, Germany), with zirconium nitride (ZrN) coating. Tibial implants were evaluated under anterior shear and I/E torsional shear conditions with 6 samples in 4 test groups. For the evaluation of the I/E torsional shear endurance behavior, a test setup was created allowing for clinically relevant I/E rotation with simultaneous high axial/tibio-femoral load. The test was performed with an I/E displacement of ±17.2°, for 1 million cycles with an axial preload of 3,000 N. RESULTS: After the anterior shear test an implant-cement-bone fixation strength for the AS VEGA System tibial tray of 2,674 ± 754 N and for the AS Columbus CR/PS tibial tray of 2,177 ± 429 N was determined (P = .191). After I/E rotational shear testing an implant-cement-bone fixation strength for the AS VEGA System PS tray of 2,561 ± 519 N and for the AS Columbus CR/PS tray of 2,824 ± 515 N was resulted (P = .39). CONCLUSION: Both methods had varying degrees of failure modes from debonding to failure of the sawbones foam. These two intense biomechanical loading tests are more strenuous and more representative of clinical activity.

Effect of deltoid volume on range of motion and patient-reported outcomes following reverse total shoulder arthroplasty in rotator cuff-intact and rotator cuff-deficient conditions.

BACKGROUND: Deltoid muscle function is paramount to the success of reverse total shoulder arthroplasty. The purpose of this study was to investigate the role of deltoid volume on shoulder range of motion and patient-reported outcomes following reverse total shoulder arthroplasty in rotator cuff-intact and rotator cuff-deficient conditions. METHODS: Retrospective review of records identified 107 patients who met inclusion criteria. The rotator cuff integrity was evaluated by two musculoskeletal-trained radiologists. Volumetric deltoid measurements were calculated from preoperative computed tomography or magnetic resonance imaging scans. Satisfactory outcomes were defined as forward elevation of at least 135°, external rotation of at least 35°, and American Shoulder and Elbow Surgeons and Single Assessment Numerical Evaluation scores of at least 70. RESULTS: Mean total deltoid muscle volume was significantly higher in patients with satisfactory forward elevation (57.8 ± 18.1 cm³) versus unsatisfactory forward elevation (48.6 ± 19.5 cm³) (p = 0.013). When separated by rotator cuff integrity, total deltoid volume was significantly higher (p = 0.030) in patients who achieved satisfactory forward elevation in the rotator cuff-deficient group but not the rotator cuff-intact group (p = 0.533). DISCUSSION: Preoperative deltoid volume directly correlated with achieving satisfactory forward elevation after reverse total shoulder arthroplasty in rotator cuff-deficient conditions and may be one factor in determining the ability to achieve satisfactory outcomes in the rotator cuff-deficient patient.

In-Vitro Cell-Induced Corrosion by Macrophages on Cobalt-Chromium-Molybdenum Alloy.

BACKGROUND: Patients have received cobalt-chromium-molybdenum (CoCrMo) implants for their joint replacement for decades. There have been reports of inflammatory cell-induced corrosion (ICIC) of these implants from retrieval studies. The goal of this study is to see if we could recreate ICIC in vitro and whether electrocautery damage to alloy surfaces may hasten this process. METHODS: Murine macrophages were cultured on CoCr disks with and without damage from a monopolar electrocautery. Culture medium was replaced every 12 hours and supernatant was collected every 4 days. After 30 days, cells were removed, counted, and digested. The metal concentrations in the supernatant and within cells were assessed using inductively coupled plasma spectrometry for comparison. RESULTS: The Co supernatant concentration was higher in the undamaged disks with activated macrophages. Higher concentrations of Co and Mo were found in the supernatant of the undamaged disks vs the electrocautery (EC) corrosion damaged disks. There was a significantly higher intracellular Co and Mo concentration with activated cells on CoCrMo disks vs the control group and no difference compared to EC damaged disk group. Scanning electron microscopy displayed microscopic pitting on the surfaces exposed to macrophages without EC damage. CONCLUSION: We found that macrophages could reproduce findings of ICIC pits on the surface of CoCrMo alloy and that the addition of EC damage to the surface did not increase the process. The clinical significance of these findings should be further investigated to determine if this could explain a small number of poor total knee arthroplasty reported outcomes.

Necrotizing Soft-Tissue Infections After Hip Arthroplasty.

Necrotizing soft-tissue infections are a rare complication following hip arthroplasty procedures. These rapidly spreading infections have a high mortality rate and must be diagnosed and treated in an expeditious manner. This article discusses the epidemiology, classification, diagnosis, and treatment of these conditions and describes 2 related case reports.

The Influence of Mathematical Definitions on Patellar Kinematics Representations.

A correlation between patellar kinematics and anterior knee pain is widely accepted. However, there is no consensus on how they are connected or what profile of patellar kinematics would minimize anterior knee pain. Nevertheless, answering this question by merging existing studies is further complicated by the variety of ways to describe patellar kinematics. Therefore, this study describes the most frequently used conventions for defining patellar kinematics, focusing on the rotations. The similarities and differences between the Cardan sequences and angles calculated by projecting axes are analyzed. Additionally, a tool is provided to enable the conversion of kinematic data between definitions in different studies. The choice of convention has a considerable impact on the absolute values and the clinical characteristics of the patello-femoral angles. In fact, the angles that result from using different mathematical conventions to describe a given patello-femoral rotation from our analyses differ up to a Root Mean Squared Error of 111.49° for patellar flexion, 55.72° for patellar spin and 35.39° for patellar tilt. To compare clinical kinematic patello-femoral results, every dataset must follow the same convention. Furthermore, researchers should be aware of the used convention's implications to ensure reproducibility when interpreting and comparing such data.

Risk Factors for Prolonged Time to Discharge in Total Hip Patients Performed in an Ambulatory Surgery Center due to Complaints of the Inability to Void.

BACKGROUND: Postoperative urinary retention (POUR) is among the reasons for delay in discharge after outpatient total hip arthroplasty (THA), occurring in 2%-46% of patients. We hypothesized that the frequency of POUR following outpatient THA in the ambulatory surgery center (ASC) is low compared to previously reported rates and that management can be effective in the perioperative period when it is encountered. METHODS: Three hundred seventy-seven THA patients (409 hips) who had arthroplasties in the ASC over a 5-year period were identified. Preoperatively, appropriate demographic information and medical comorbidities were collected from patient health history questionnaires completed during clinic visits. Intraoperatively, albumin volume administered and estimated blood loss were recorded. Postoperatively, post-anesthesia care unit medications, patients who reported an inability to urinate, and those who required urinary catheterization were recorded. RESULTS: POUR occurred in only 2 patients but complaints of the inability to void occurred in 38 others for an incidence of 9.8%. Factors associated with POUR and the inability to urinate included older age, time spent in the ASC, and intraoperatively albumin volume administered. No significant differences were found in body mass index, preoperative hematocrit, estimated blood loss, surgical time, or operating time. CONCLUSION: POUR was infrequent but the reported inability to urinate was not (9.8%) and can be safely managed when it does occur and we found that increased age and albumin volume over 500 mL may increase the risk for a prolonged length of stay due to the inability to urinate.

Blood Management in Outpatient Total Hip Arthroplasty.

Based on a series of 407 outpatient total hip arthroplasties performed by a single surgeon, a standardized protocol for blood loss management in outpatient arthroplasty was developed consisting of a presurgical hematocrit of greater than 36%, administration of tranexamic acid, prophylactic introduction of albumin, hypotensive epidural anesthesia, monopolar electrocautery, and bipolar sealer. This protocol uses techniques that alone are not novel but together create a standardized and reproducible pathway that when implemented can increase the safety of outpatient hip arthroplasty.

Anterior Supine Intermuscular Total Hip Arthroplasty at an Ambulatory Surgery Center Versus Hospitalization: Cost and Adverse Events.

This study compares anterior supine intermuscular total hip arthroplasty performed at an ambulatory surgery center with the same procedure performed in a hospital setting in regard to complications and costs. The ambulatory surgery center had significantly shorter postoperative stays and superior visual analog pain scores at 3 months. No differences were noted in operative time, blood loss, or complications. Costs were significantly different between groups, with significant cost savings noted in the ambulatory surgery center group.

Opioid Use Patterns After Primary Total Knee Replacement.

Orthopedic surgeries are associated with the prescription of more narcotics than any other surgical specialty, particularly for total knee replacement (TKR) surgery. The authors examined controlled substance prescriptions following TKR surgery in a sample of 560 TKR patients. Results indicated that of all the 5164 prescriptions documented on the controlled substance monitoring database, 64% were for opioid medications. More than half of the patients received controlled substances from both the surgery site provider and a nonsurgery site provider in the year following surgery. The authors recommend that providers consider the possibility of outside prescribing when prescribing opioid analgesic.

Electrocautery Induced Damage of Total Knee Implants.

BACKGROUND: Pitting damage on implants has been reported and attributed to the use of electrocautery. This study aimed to determine how different total knee arthroplasty bearing surfaces are susceptible to this type of damage and whether surgeons are aware that this damage can occur. METHODS: A survey was sent to Hip and Knee Society members to determine what percentage of adult reconstructive surgeons use electrocautery after implantation of components. Three bearing surfaces for total knee arthroplasty were selected: cobalt chromium, Oxinium, and zirconium nitride to be damaged by electrocautery with a monopolar (MP) and bipolar (BP) electrocautery with 3 different energy settings. A comparison of surface damage using scanning electron microscopy and elemental differences using energy dispersion spectroscopy was performed. Average roughness (Ra), maximal peak-to-valley height (Rz), kurtosis (Rk), and skewness (Rsk) were recorded for comparison using a profilometer was performed. RESULTS: Median Rz and Ra measurements were larger for BP damaged areas compared to MP for all bearing surfaces. The Oxinium surface had the greatest increase in roughness parameters. Survey results indicate that a significant percentage of adult reconstructive surgeons use the electrocautery after implants are in place and are not aware of this type of damage. Backscatter scanning electron microscopy analysis found significant changes for BP damage compared to MP. CONCLUSION: Surface damage caused by electrocautery can have significant effects on the bearing surfaces of implants but further study needs to be performed to determine if this is a clinical issue. Our survey determined that many arthroplasty experts are unaware that this damage can occur.

Defining Outpatient Hip and Knee Arthroplasties: A Systematic Review.

INTRODUCTION: The term "outpatient" has a variety of meanings regarding the location of arthroplasty and the duration of stay postoperatively. The purpose of this systematic review was to evaluate the literature and more accurately define the term "outpatient." METHODS: A PubMed search (2014 to 2019) using the terms "outpatient AND arthroplasty" identified 76 studies; 35 studies that met the inclusion criteria were assessed to determine the definition of "outpatient." The level of evidence, type of arthroplasty, location of surgery (hospital or ambulatory surgery center [ASC]), approach used for hip arthroplasty, number of patients, number of surgeons, and length of time the patients were kept at the location after surgery were evaluated. RESULTS: Arthroplasties analyzed were total hip (11), total knee (seven), unicompartmental knee (five), and hip and knee (12). Only 16.8% of surgeries defined as outpatient hip or knee arthroplasty were done in a freestanding ASC, and 44.2% of patients defined as outpatients were kept overnight for the 23-hour observation. DISCUSSION: We propose "DASH" (Discharge from ASC to Home) as a new term to define arthroplasties done in an outpatient setting with the patient discharged home the same day.