Nicholas B. Frisch

Rivaroxaban Versus Enoxaparin for Venous Thromboembolism Prophylaxis after Hip and Knee Arthroplasty

The oral Factor Xa inhibitor rivaroxaban (Xarelto) has been the pharmacologic agent used for venous thromboembolism (VTE) prophylaxis after primary hip and knee arthroplasty (THA/TKA) at our institution since February 2012. The purpose of our study was to compare rates of VTE and major bleeding between rivaroxaban and our previous protocol of enoxaparin after THA/TKA. A retrospective cohort study was performed including 2406 consecutive patients at our institution between 1/1/11 and 9/30/13. Patients who did not have unilateral primary THA/TKA or who received other anticoagulants were excluded. Of the 1762 patients included, 1113 patients (63.2%) received enoxaparin and 649 patients (36.8%) received rivaroxaban. This study found no demonstrable differences between these two anticoagulants in rates of VTE, infection, reoperation, transfusion, or major bleeding. Therapeutic, Retrospective comparative study, Level III.

Effect of body mass index on blood transfusion in total hip and knee arthroplasty

Perioperative blood management remains a challenge during total hip arthroplasty (THA) and total knee arthroplasty (TKA). The purpose of this study was to systematically examine the relationship between body mass index (BMI) and perioperative blood transfusion during THA and TKA while attempting to resolve conflicting results in previously published studies. The authors retrospectively evaluated 2399 patients, 896 of whom underwent THA and 1503 of whom underwent TKA. Various outcome variables were assessed for their relationship to BMI, which was stratified using the World Health Organization classification scheme (normal, <25 kg/m(2); overweight, 25-30 kg/m(2); obese, >30 kg/m(2)). Among patients undergoing THA, transfusion rates were 34.8%, 27.6%, and 21.9% for normal, overweight, and obese patients, respectively (P=.002). Among patients undergoing TKA, transfusion rates were 17.3%, 11.4%, and 8.3% for normal, overweight, and obese patients, respectively (P=.002). Patients with an elevated BMI have decreased rates of blood transfusion following both THA and TKA. This same cohort also loses a significantly decreased percentage of estimated blood volume. No trends were identified for a relationship between BMI and deep venous thrombosis, pulmonary embolism, myocardial infarction, discharge location, length of stay, 30-day readmission rate, and preoperative hemoglobin level. Elevated BMI was significantly associated with increased estimated blood loss in patients undergoing THA and those undergoing TKA. There was a statistically significant trend toward increased deep surgical-site infection in patients undergoing THA (P=.043). Patients with increased BMI have lower rates of blood transfusion and lose a significantly smaller percentage of estimated blood volume following THA and TKA. [Orthopedics.2016; 39(5):e844-e849.].

Intraoperative Hypothermia in Total Hip and Knee Arthroplasty.

Total hip arthroplasty (THA) and total knee arthroplasty (TKA) are common and successful orthopedic procedures, and as their frequency continues to increase substantially, the focus on limiting perioperative complications heightens. Intraoperative normothermia is recommended to minimize additional complications, but limited evidence exists regarding the effect of hypothermia on orthopedic patients. The purpose of this retrospective study was to determine the incidence of perioperative hypothermia in the setting of TKA and THA, and to evaluate its impact on complications and outcomes. The clinical records of 2580 consecutive patients who underwent TKA or THA at a single institution between January 1, 2011, and December 31, 2013 were reviewed. After excluding patients with complex or revision procedures, a total of 2397 patients comprised the study population. Patient demographic data, surgery-specific data, postoperative complications, length of hospital stay, and 30-day readmission were recorded. Patients with a mean intraoperative temperature less than 36°C were identified as hypothermic. Statistical analysis evaluated associations with hypothermia and the effect on complications and outcomes. The incidence of mean intraoperative hypothermia was 37%, 43.9%, and 32.6% for arthroplasty, THA, and TKA, respectively. General anesthesia was significantly associated with hypothermia (P<.001). Women and THA patients were at higher risk for hypothermia. In the arthroplasty and THA cohorts, longer operating room time and re-warmer use were associated with hypothermia (P=.010). Overall, hypothermia was associated with increased estimated blood loss, but no increase in associated transfusion was demonstrated (P=.006). Hypothermia was not associated with postoperative complications. [Orthopedics. 2017; 40(1):56-63.].

The Effect of Impact Location on Force Transmission to the Modular Junctions of Dual-Taper Modular Hip Implants

BACKGROUND The purpose of this study was to investigate the effect that off-axis impaction has on stability of dual-taper modular implants as measured by forces delivered to and transmitted through the head-neck and neck-stem tapers, respectively. METHODS One hundred forty-four impact tests were performed using 6 different directions: one on-axis and five 10° off-axes. Four different simulations were performed measuring the head-neck only and 3 different neck angulations: 0°, 8°, and 15°. A drop tower impactor delivered both on- and off-axis impaction from a constant height. Load cells positioned in the drop mass and at the head-neck (HN) or neck-stem (NS) junction measured the impact and joint forces, respectively. RESULTS Impact force of the hammer on the head ranged from 3800-4500 N. Greatest impact force delivered to the head was typically with axial impact. However, greatest force transmission to the neck-stem junction was not necessarily with axial impacts. There was limited variability in the force measured at the NS junction for all impaction directions seen in the 8° neck, whereas the 15° neck had greater forces transmitted to the NS junction with off-axes impactions directed in the proximal and posterior-proximal directions. CONCLUSION The location of the impact significantly influences the force transmitted to the head-neck and neck-stem junctions in dual-taper modular hip implants. Although axial impacts proved superior to off-axis impacts for the straight 0° neck, greater force transmission with off-axis impacts for the angled necks suggests that off-axis impacts may potentially compromise the stability of dual-taper components.

Short Versus Long Cephalomedullary Nails for Pertrochanteric Hip Fracture

This study compared patients who underwent treatment with short or long cephalomedullary nails with integrated cephalocervical screws and linear compression. Patients with AO/OTA 31-A2 or A3 pertrochanteric fractures treated with either short (n=72) or long (n=97) InterTAN (Smith & Nephew, Memphis, Tennessee) cephalomedullary nails were reviewed. Information on perioperative measures (estimated blood loss, surgical time, and fluoroscopy time) and postoperative orthopedic complications (infection, implant failure, screw cutout, and periprosthetic femur fracture) was included. Estimated blood loss (short nail, 161 mL; long nail, 208 mL; P=.002) and surgical time (short nail, 64 minutes; long nail, 83 minutes; P=.001) were lower in the short nail group. There were no differences in fluoroscopy time (short nail, 90 seconds; long nail, 142 seconds; P=.071) or rates of infection (short nail, 1.4%; long nail, 3.1%; P=.637) or overall orthopedic complications (short nail, 11.1%; long nail, 9.3%; P=.798) between the 2 groups. The long nail group had a trend toward more screw cutouts (long nail, 5.2%; short nail, 0.0%; P=.134) but fewer periprosthetic femur fractures (short nail, 8.3%; long nail, 0.0%; P=.013). This study found a similar overall rate of orthopedic complications between short and long nails with integrated cephalocervical screws and linear compression. These results confirm the suspected advantages of short nails, including faster surgery and less blood loss; however, the rate of periprosthetic femur fracture remains high, despite changes to implant design. [Orthopedics. 2017; 40(2):83-88.].

Intraoperative chlorhexidine irrigation to prevent infection in total hip and knee arthroplasty

Background Surgical site irrigation during total hip (THA) and total knee (TKA) arthroplasty is a routine practice among orthopaedic surgeons to prevent periprosthetic joint infection. The purpose of this study was to evaluate the effect of chlorhexidine gluconate (CHG) irrigation on infection rates following THA and TKA. Methods Arthroplasties performed before September 2014 served as controls. THA performed before September 2014 (N = 253) underwent intraoperative irrigation with 0.9% saline followed by a 2-minute soak with <2% dilute povidone-iodine. TKA (N = 411) patients underwent only intraoperative saline irrigation. After October 2014, all patients (248 TKA and 138 THA) received intraoperative irrigation with 0.9% saline and periodic 0.05% CHG solution followed by a final 1-minute soak in CHG with immediate closure afterward. Results In this 2:1 comparison of consecutive patients, there were no differences in patient demographics between the 2 groups. No difference was noted in wound healing concerns subjectively, and no statistically significant association in nonsurgical site infections, superficial surgical site infection, and deep surgical site infection rates between the 2 groups (nonsurgical site infections [THA: P = .244, TKA: P = .125]; superficial surgical site infection [THA: P = .555, TKA: P = .913]; and deep surgical site infection [THA: P = .302, TKA: P = .534]). Conclusions We were unable to discern a difference in infection rates between chlorhexidine irrigation and our prior protocols using dilute Betadine for THA and 0.9% saline for TKA. The theoretic advantages of dilute CHG retention during closure appear to be safe without infectious concerns.

Intraoperative Periprosthetic Femur Fracture: A Biomechanical Analysis of Cerclage Fixation

Intraoperative periprosthetic femur fracture is a known complication of total hip arthroplasty (THA) and a variety of cerclage systems are available to manage these fractures. The purpose of this study was to examine the in situ biomechanical response of cerclage systems for fixation of periprosthetic femur fractures that occur during cementless THA. We compared cobalt chrome (CoCr) cables, synthetic cables, monofilament wires and hose clamps under axial compressive and torsional loading. Metallic constructs with a positive locking system performed the best, supporting the highest loads with minimal implant subsidence (both axial and angular) after loading. Overall, the CoCr cable and hose clamp had the highest construct stiffness and least reduction in stiffness with increased loading. They were not demonstrably different from each other.

The stability of dual-taper modular hip implants: a biomechanical analysis examining the effect of impact location on component stability

Background The purpose of this study was to investigate the stability of dual-taper modular implants following impaction forces delivered at varying locations as measured by the distraction forces required to disassemble the components. Methods Distraction of the head-neck and neck-stem (NS) tapers of dual-taper modular implants with 0°, 8°, and 15° neck angles were measured utilizing a custom-made distraction fixture attached to a servohydraulic materials test machine. Distraction was measured after hand pressing the components as well as following a simulated firm hammer blow impaction. Impacts to the 0°, 8°, 15° necks were directed axially in line with the neck, 10° anterior, and 10° proximal to the axis of the neck, respectively. Results Impaction increased the range of NS component distraction forces when compared to hand pressed components (1125-1743 N vs 248-302 N, respectively). Off-axis impacts resulted in significantly reduced mean (±95% confidence interval) distraction forces (8° neck, 1125 ± 117 N; 15° neck, 1212 ± 73 N), which were up to 35% lower than the mean distraction force for axial impacts to the 0° neck (1743 ± 138 N). Conclusions Direction of impaction influences stability of the modular interface. The greatest stability was achieved with impaction directed in line with the longitudinal axis of the taper junction. Off-axis impaction of the 8° and 15° neck led to significantly reduced stability at the NS. Improving stability of dual-taper modular hip prostheses with appropriately directed impaction may help to minimize micromotion, component settling, fretting corrosion, and subsequent failure.

Short-term Medical Complications Following Short Versus Long Cephalomedullary Nails

The purpose of this retrospective cohort study was to evaluate whether there is an increased rate of short-term medical complications following short vs long cephalomedullary nails for the treatment of intertrochanteric hip fractures. A total of 899 patients treated surgically with cephalomedullary nails from January 1, 2005, to September 1, 2014, were included. Patients who received short nails (n=334) were older and had a higher incidence of coronary artery disease and diabetes mellitus compared with patients who received long nails (n=565). The incidences of 30-day medical complications, including myocardial infarction, stroke, deep venous thrombosis, pulmonary embolism, blood transfusion, non-surgical site infection, surgical site infection, and mortality, were recorded. The orthopedic complications of periprosthetic fracture of the ipsilateral hip and implant failure through the latest outpatient follow-up were recorded. No significant difference was found between nails for any studied medical complication (63.5% short vs 66.0% long, P=.4393) or mortality (6.9% short vs 5.3% long, P=.3322). There was also no significant difference in the incidence of orthopedic complications (P=.70). Longer operating room time was associated with superficial surgical site infection. [Orthopedics. 2018; 41(5):e636-e642.].

Use of MicroRNA biomarkers to distinguish enchondroma from low-grade chondrosarcoma

ABSTRACT Establishing a definitive diagnosis between benign enchondroma versus low-grade chondrosarcoma presents a potential challenge to both clinicians and pathologists. microRNAs (small non-coding RNAs) have proven to be effective biomarkers for the identification of tumors and tumor progression. We present analysis, both array and quantitative PCR, that shows consistently and substantially increased expression of two microRNAs, miRs-181a and -138, in low-grade chondrosarcomas compared with enchondromas. The data suggest these microRNAs would provide an analytical distinction between the chondrosarcoma and benign neoplasms that can be performed in formalin-fixed paraffin-embedded specimens. Together with recent publications, these data indicate that miRs-181a and -138 also play a role in tumor development and homeostasis and may provide new targets for the development of much needed therapeutic intervention.