Comparison of postoperative clinical outcome in medial-pivotal and gradually reducing radius design cruciate-retaining total knee arthroplasty-A multicenter analysis of propensity-matched cohorts.

Purpose: To clarify differences in surgery duration, postoperative knee range of motion (ROM), anterior and posterior (AP) laxity, and Forgotten Joint Score (FJS) in patients undergoing medial-pivot (MP) and GRADIUS cruciate-retaining (CR) total knee arthroplasty (TKA) surgeries. Methods: We examined patients who underwent either MP or CR TKA at six different Japanese centres. Patients were propensity score matched for age, sex, and preoperative hip-knee angle (HKA). We compared the groups' average surgery duration, postoperative knee ROM, AP laxity, and FJS 1 year after surgery. Results: There were 86 study patients: 43 MP and 43 CR TKA matched for age, sex, and preoperative HKA. The MP group enjoyed a significantly shorter surgery duration (89.1 ± 10.9 mins vs. 95.7 ± 12.0 mins, p = 0.0091) and significantly better postoperative knee flexion than the CR group (123.7 ± 9.1° vs. 115.3 ± 12.4°, p < 0.001). The MP had significantly smaller postoperative AP laxity with 30° of knee flexion than the CR group (3.4 ± 1.3 vs. 5.6 ± 2.2 mm, p < 0.001). Conversely, postoperative AP laxity with 90° of knee flexion was significantly larger for the MP group (3.6 ± 1.3 vs. 2.7 ± 1.9 mm, p = 0.0098). There were no between-group differences in postoperative FJS. Conclusions: The MP group showed better postoperative knee flexion, midrange AP knee stability, and shorter surgery duration. Level of Evidence: Level III, retrospective comparative study.

Predeposited Autologous Blood Transfusion in Single-Anesthetic Bilateral Total Knee Arthroplasty with Modern Blood Conservation Strategy.

This study was performed to examine the hypothesis that the rate of allogeneic blood transfusion in patients who did not predeposit an autologous blood transfusion before single-anesthetic bilateral total knee arthroplasty (TKA) would be noninferior to that in patients who did predeposit blood. Methods: We assessed the number of allogeneic transfusions required in 338 patients undergoing single-anesthetic bilateral TKA with a preoperative hemoglobin level of ≥11.0 g/dL. All TKAs were performed by a single surgeon according to the same operative and postoperative protocol. All patients received a combination of intravenous and intra-articular tranexamic acid. Neither a pneumonic tourniquet nor a drain was used. The difference in the risk of allogeneic transfusion between patients without and with autologous blood predeposit was compared with a noninferiority margin of 10 percentage points. Results: Allogeneic transfusion was required in 1 (0.5%) of 194 patients who predeposited autologous blood and 3 (2.1%) of 144 patients who did not predeposit blood. The difference in risk was -1.6 percentage points (95% confidence interval, -4.1 to 1.0 percentage points); the confidence interval did not include the noninferiority margin and included zero. Conclusions: In single-anesthetic bilateral TKA, allogeneic transfusion requirements in patients who did not predeposit autologous blood were noninferior to those in patients who predeposited blood. Level of Evidence: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Augmented reality-aided unicompartmental knee arthroplasty.

PURPOSE: To illustrate a surgical technique for augmented reality (AR)-assisted unicompartmental knee arthroplasty (UKA) and report preliminary data. METHODS: We developed an AR-based navigation system that enables the surgeon to see the tibial mechanical axis superimposed on the patient's leg in addition to the tibial cutting angle. We measured the tibial resection angle in 11 UKAs using postoperative radiographs and calculated the absolute difference between preoperative target angle and postoperative measured angle. The target angle was determined for each patient: mean values were 0.7° ± 1.0° varus in coronal alignment and 5.3° ± 1.4° posterior slope in sagittal alignment. RESULTS: The angles measured on postoperative radiographs were 2.6° ± 1.2° varus in the coronal plane and 4.8° ± 2.5° posterior slope in the sagittal plane. The absolute differences between the target and measured angles were 1.9° ± 1.5° in coronal alignment and 2.6° ± 1.2° in sagittal alignment. No patients experienced complications, including surgical site infection and periprosthetic fracture. CONCLUSION: The AR-based portable navigation system may provide passable accuracy in terms of proximal tibial resection during UKA. LEVEL OF EVIDENCE: IV.

Augmented Reality- vs Accelerometer-Based Portable Navigation System to Improve the Accuracy of Acetabular Cup Placement During Total Hip Arthroplasty in the Lateral Decubitus Position.

BACKGROUND: There have been no studies regarding the effectiveness of augmented reality (AR)-based portable navigation systems compared with accelerometer-based portable navigation systems in total hip arthroplasty (THA). METHODS: We retrospectively compared THAs performed using an AR-based portable navigation system (n = 45) and those performed using an accelerometer-based portable navigation system (n = 42). All THAs were performed with the patient in the lateral decubitus position. The primary outcome was the absolute difference between cup placement angles displayed on the navigation screen and those measured on postoperative X-ray. RESULTS: The mean absolute differences were significantly smaller in the AR-based portable navigation system group than the accelerometer-based portable navigation system group in radiographic inclination (2.5° ± 1.7° vs 4.6° ± 3.1°; 95% confidence interval 1.1°-3.2°, P < .0001). Similarly, the mean absolute differences were significantly better in the AR-based portable navigation system group in radiographic anteversion (2.1° ± 1.8° vs 6.4° ± 4.2°; 95% confidence interval 3.0°-5.7°, P < .0001). Neither hip dislocation, surgical site infection, nor other complications associated with use of the navigation system occurred in either group. CONCLUSION: The AR-based portable navigation system may provide more precise acetabular cup placement compared with the accelerometer-based portable navigation system in THA.

Augmented Reality-Assisted Femoral Bone Resection in Total Knee Arthroplasty.

An augmented reality (AR)-based navigation system allows visualization of the center of the femoral head and femoral mechanical axis superimposed on the surgical field during total knee arthroplasty (TKA) and may help surgeons to improve the accuracy of distal femoral resection. METHODS: First, we resected 10 femoral Sawbones specimens using the AR-based navigation system and performed computed tomography (CT) to measure the resection angle of the distal part of the femur. We calculated the absolute values of the differences between angles measured using CT images and angles displayed on the smartphone screen of the navigation system. Second, we measured coronal alignment using standing long-leg radiographs for 72 patients undergoing TKA and compared the error in the resection angle between TKA using the AR-based navigation system and that using a conventional intramedullary guide. RESULTS: In the experimental study, the absolute values of the differences between angles measured on CT images and angles displayed using the AR-based navigation system were 0.8° ± 0.5° (range, 0.3° to 1.9°) in the coronal plane and 0.6° ± 0.5° (range, 0.0° to 1.4°) in the sagittal plane. In the clinical study, the mean absolute value of the error in coronal alignment was significantly smaller in the AR-based navigation group than the intramedullary-guide group (1.1° ± 1.0° [range, 0.0° to 3.2°] compared with 2.2° ± 1.6° [range, 0.0° to 5.5°], respectively; 95% confidence interval, 0.5° to 1.8°; p < 0.001). CONCLUSIONS: The AR-based navigation system may enable surgeons to perform distal femoral resection more accurately than with the conventional intramedullary guide during TKA. CLINICAL RELEVANCE: This study validates the use of AR technology to enhance the precision of bone resection in TKA.

Addition of corticosteroid to periarticular injections reduces postoperative pain following total hip arthroplasty under general anaesthesia: a double-blind randomized controlled trial.

AIMS: Although periarticular injection plays an important role in multimodal pain management following total hip arthroplasty (THA), there is no consensus on the optimal composition of the injection. In particular, it is not clear whether the addition of a corticosteroid improves the pain relief achieved nor whether it is associated with more complications than are observed without corticosteroid. The aim of this study was to quantify the safety and effectiveness of cortocosteroid use in periarticular injection during THA. METHODS: We conducted a prospective, two-arm, parallel-group, randomized controlled trial involving patients scheduled for unilateral THA. A total of 187 patients were randomly assigned to receive periarticular injection containing either a corticosteroid (CS group) or without corticosteroid (no-CS group). Other perioperative interventions were identical for all patients. The primary outcome was postoperative pain at rest during the initial 24 hours after surgery. Pain score was recorded every three hours until 24 hours using a 100 mm visual analogue scale (VAS). The primary outcome was assessed based on the area under the curve (AUC). RESULTS: The CS group had a significantly lower AUC postoperatively at 0 to 24 hours compared to the no-CS group (AUC of VAS score at rest 550 ± 362 vs 392 ± 320, respectively; mean difference 158 mm; 95% confidence interval (CI) 58 to 257; p = 0.0021). In point-by-point evaluation, the CS group had significantly lower VAS scores at 12, 15, 18, 21, 24, and 48 hours. There were no significant differences in complication rates, including surgical site infection, between the two groups. CONCLUSION: The addition of corticosteroid to periarticular injections reduces postoperative pain without increasing complication rate following THA. Cite this article: Bone Joint J 2020;102-B(10):1297-1302.

Intraoperative Intravenous and Intra-Articular Plus Postoperative Intravenous Tranexamic Acid in Total Knee Arthroplasty: A Placebo-Controlled Randomized Controlled Trial.

BACKGROUND: Combined intraoperative intravenous and intra-articular tranexamic acid (TXA) is 1 of the most effective administration routes to decrease the amount of perioperative blood loss during total knee arthroplasty (TKA). However, the additive effect of postoperative intravenous TXA administration remains unclear. We hypothesized that the postoperative repeated-dose intravenous administration of TXA would provide lower perioperative blood loss. METHODS: We performed a double-blinded, placebo-controlled trial involving patients undergoing primary TKA. A total of 100 patients who were managed with combined intraoperative intravenous and intra-articular TXA were randomly assigned to receive 3 postoperative 1,000-mg doses of intravenous TXA (TXA group) or 3 postoperative doses of intravenous normal saline solution (placebo group) in a 1:1 ratio. The prespecified primary outcome was perioperative blood loss calculated from patient blood volume and the difference in hemoglobin from preoperatively to postoperative day 3. A post hoc power analysis showed that the number of patients allocated to either the TXA group (n = 46) or the placebo group (n = 54) possessed >80% power to detect a 200-mL difference in perioperative blood loss. RESULTS: In the intention-to-treat analysis, we found no significant differences in perioperative blood loss between the TXA group and the placebo group through postoperative day 3 (578 ± 229 compared with 640 ± 276 mL, respectively; 95% confidence interval for the difference, -40 to 163 mL; p = 0.23). The prevalence of postoperative thrombotic events did not differ between the 2 groups (4.3% compared with 3.7%, respectively; p > 0.99). CONCLUSIONS: Postoperative intravenous TXA had no additive effect in reducing perioperative blood loss in patients receiving intraoperative combined intravenous and intra-articular TXA. LEVEL OF EVIDENCE: Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.

Comparison of Early-Stage and Late-Stage Periarticular Injection for Pain Relief After Total Hip Arthroplasty: A Double-Blind Randomized Controlled Trial.

BACKGROUND: No randomized controlled trial has investigated a more optimal timing of periarticular injection for pain relief after total hip arthroplasty. METHODS: The study included 140 patients, and these patients were randomly allocated to the early-stage (periarticular injection was performed just before arthrotomy, and placebo was injected after implantation) or late-stage (placebo was injected just before arthrotomy, and periarticular injection was performed after implantation) injection groups. Other perioperative interventions were similar in all participants. The prespecified primary outcome was postoperative pain score at the recovery room. RESULTS: The visual analog scale score at the recovery room of the early-stage injection group was significantly lower than that of the late-stage injection group (30 ± 28 vs 46 ± 30 mm; 95% CI, -25 to -5 mm; P = .0022), and this difference reaches a minimal clinically important difference level of 10 mm. No differences were observed with regard to complication rate. CONCLUSION: Early-stage periarticular injection during total hip arthroplasty provided better postoperative pain relief than late-stage periarticular injection without elevating complication rate. LEVEL OF EVIDENCE: Level I, randomized controlled trial.

Intraoperative loose flexion gap may restrict postoperative knee flexion after J-curve design posterior-stabilized total knee arthroplasty.

INTRODUCTION: Although soft tissue tension during total knee arthroplasty (TKA) has been targeted to achieve equal flexion and extension gaps, such a perfect gap is not always obtained. This study was performed to investigate the impact of difference between flexion and extension gaps on postoperative knee flexion angle. MATERIALS AND METHODS: We reviewed 107 consecutive TKAs using a J-curve design posterior-stabilized prosthesis. Soft tissue tension was measured intraoperatively using an offset-type tensor under 30 lb force of joint distraction with the patella reduced. All TKAs were performed in a uniform manner including the subvastus approach and without use of a pneumatic tourniquet. We assessed the association between knee flexion angle 1 year after TKA and the difference between flexion and extension gaps using Pearson's product-moment correlation and multiple regression analysis with age, sex, body mass index, diagnosis, history of diabetes mellitus, preoperative flexion angle, and gap difference as explanatory variables. RESULTS: The difference between flexion and extension gaps showed a slight negative correlation with postoperative knee flexion angle in univariate analysis (r = - 0.20, 95% CI, - 0.38 to - 0.01, p = 0.04). Multiple regression analysis showed that the gap difference was an independent factor associated with postoperative knee flexion angle (ß = - 0.89, 95% CI, - 1.60 to - 0.18, p = 0.01). CONCLUSIONS: The difference between flexion and extension gaps was negatively correlated with postoperative knee flexion angle. Looser flexion gap compared with extension gap should be avoided in J-curve design posterior-stabilized TKA.

Augmented reality-based navigation system applied to tibial bone resection in total knee arthroplasty.

BACKGROUND: This pilot study was performed to examine the accuracy of the AR-KNEE system, an imageless navigation system using augmented reality (AR) technology for total knee arthroplasty. The AR-KNEE system enables the surgeon to view information from the navigation superimposed on the surgical field on a smartphone screen in real time. METHODS: Using the AR-KNEE system, one surgeon resected 10 tibial sawbones with viewing the tibial axis and aiming varus/valgus, posterior slope, internal/external rotation angles, and resection level superimposed on the surgical field. We performed computed tomography of the resected sawbones and measured the varus/valgus, posterior slope, and internal/external rotation angles using a designated computer software. The thickness of the resected bone was measured using digital calipers. RESULTS: The absolute differences between the values displayed on the smartphone screen and the measurement values for varus/valgus, posterior slope, internal/external rotation angles, and thickness of the resected bone were 0.5° ± 0.2°, 0.8° ± 0.9°, 1.8° ± 1.5°, and 0.6 mm ± 0.7 mm, respectively. CONCLUSIONS: This pilot study using sawbones suggested that the AR-KNEE system may provide reliable accuracy for coronal, sagittal, and rotational alignment in tibial bone resection during total knee arthroplasty.

A Strategy of Continued Antiplatelet Agents, Vitamin K Antagonists, and Direct Oral Anticoagulants Throughout the Perioperative Period of Total Knee Arthroplasty in Patients Receiving Chronic Antithrombotic Therapy.

Although continuing antithrombotic therapy is desirable to prevent perioperative cardiovascular and cerebrovascular diseases, perioperative blood loss remains a concern in patients undergoing total knee arthroplasty. The purpose of this study was to assess the impact of continuing chronic antithrombotic therapy on blood loss and major bleeding events. METHODS: We classified 201 consecutive patients undergoing total knee arthroplasty into 2 groups: (1) patients taking antiplatelet agents, vitamin K antagonists, and/or direct oral anticoagulants, referred to as the continuing antithrombotic therapy group (n = 32); and (2) patients not receiving these agents, referred to as the no antithrombotic therapy group (n = 169). During the study period, antithrombotic agents were continued perioperatively in all patients receiving antithrombotic therapy. Surgical procedures were performed without the use of a pneumatic tourniquet or drain. Screening for deep vein thrombosis was routinely performed before and after total knee arthroplasty. The total perioperative blood loss was calculated from blood volume and change in hemoglobin from preoperatively to postoperative days 1, 3, and 7. RESULTS: The perioperative blood loss after total knee arthroplasty did not differ significantly between the continuing antithrombotic therapy group and the no antithrombotic therapy group at 1 day postoperatively (448 ± 213 compared with 495 ± 345 mL [95% confidence interval (CI) of the difference, -172 to 77 mL]; p = 0.45), 3 days postoperatively (841 ± 308 compared with 826 ± 328 mL [95% CI, -108 to 139 mL]; p = 0.81), and 7 days postoperatively (855 ± 313 compared with 861 ± 245 mL [95% CI, -122 to 108 mL]; p = 0.91). No patients in the continuing antithrombotic therapy group and 2 patients (1.2%) in the no antithrombotic therapy group had allogeneic blood transfusion (p = 1). No major bleeding events occurred in the continuing antithrombotic therapy group. CONCLUSIONS: Perioperative blood loss in patients continuing chronic antithrombotic therapy during total knee arthroplasty was not significantly different from that in patients receiving no chronic antithrombotic therapy. LEVEL OF EVIDENCE: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Intra-articular tranexamic acid as an adjunct to intravenous tranexamic acid for simultaneous bilateral total knee arthroplasty: a randomized double-blind, placebo-controlled trial.

BACKGROUND: Intra-articular tranexamic acid (TXA) as an adjunct to intravenous TXA was reported to decrease perioperative blood loss during unilateral total knee arthroplasty (TKA). However, there have been no randomized controlled trials comparing intravenous versus combined intravenous and intra-articular TXA administration in patients undergoing simultaneous bilateral TKA. METHODS: We randomly assigned 77 patients with 154 involved knees undergoing simultaneous bilateral TKA to the intravenous TXA group (intra-articular placebo for each knee) or combined TXA group (1000 mg of intra-articular TXA for each knee) with 1:1 treatment allocation. In both groups, 1000 mg of TXA was given intravenously twice, just before surgery and 6 h after the initial administration. Other perioperative medications, surgical procedures, and blood management strategies were the same for all patients. The primary outcome was perioperative blood loss calculated from blood volume and change in hemoglobin from preoperative to postoperative day 3. RESULTS: Intention-to-treat analysis showed no statistically significant differences in perioperative blood loss until postoperative day 3 (1067 ± 403 mL in the intravenous TXA group vs. 997 ± 345 mL in the combined TXA group [95% CI, - 240 to 100 mL], P = 0.42). No patients required allogenic blood transfusion. The incidence of thrombotic events did not differ between groups (12% in the intravenous TXA group vs. 9% in the combined TXA group; P = 0.73). CONCLUSIONS: The addition of intra-articular TXA did not reduce perioperative blood loss in patients undergoing simultaneous bilateral TKA compared with placebo. TRIAL REGISTRATION: University Hospital Medical Information Network UMIN000026137 . Registered 14 February 2017.

Early stage periarticular injection during total knee arthroplasty may provide a better postoperative pain relief than late-stage periarticular injection: a randomized-controlled trial.

PURPOSE: This study was performed to determine whether periarticular injection performed in the early stage of total knee arthroplasty (TKA) could provide a better postoperative pain relief than periarticular injection performed in the late stage of TKA. The hypothesis was based on the concept that analgesic intervention before the onset of noxious stimuli would be associated with less postoperative pain. METHODS: A total of 105 participants were randomly assigned to receive superficial injection just prior to arthrotomy (early stage periarticular injection group) or superficial injection after implanting the prosthesis (late-stage periarticular injection group) in patients undergoing unilateral TKA with 1:1 treatment allocation. In both groups, deep injection was performed according to the same schedule (just prior to implanting prosthesis). The solution consisted of 300 mg of ropivacaine, 8 mg of morphine, 40 mg of methylprednisolone, 50 mg of ketoprofen, and 0.3 mg of epinephrine mixed with normal saline to a final volume of 60 mL. All surgeries were managed under general anesthesia without any regional blocks. Registry-specified primary outcome was postoperative pain score at rest measured at the recovery room using a 100-mm visual analog scale (VAS). The VAS score was compared between two groups and assessed to reach the reported threshold values for the minimal clinically important difference (MCID) of 10 mm for the postoperative VAS score. RESULTS: The VAS score at the recovery room was significantly lower in the early stage periarticular injection group than the late-stage periarticular injection group (23 ± 25 mm versus 39 ± 34 mm, respectively; 95% confidence interval 4-28 mm; p = 0.0078). The mean difference in the primary outcome fulfilled the MCID value. CONCLUSIONS: Bringing forward the timing of periarticular injection may provide significant and clinically meaningful improvement in pain following TKA under general anesthesia. LEVEL OF EVIDENCE: I.

Cutaneous Hypesthesia and Kneeling Ability After Total Knee Arthroplasty: A Randomized Controlled Trial Comparing Anterolateral and Anteromedial Skin Incision.

BACKGROUND: Anterolateral skin incision can preserve the skin sensory of the anterior aspect of the knee and may improve kneeling ability after total knee arthroplasty (TKA). METHODS: This is a prospective, 2-arm, parallel-group, randomized, controlled trial involving patients scheduled for TKA. A total of 118 patients (162 knees) were randomly assigned to receive anterolateral skin incision or anteromedial skin incision with 1:1 treatment allocation. The surgical techniques other than skin incision were identical in both groups. The area of cutaneous hypesthesia was measured by a nonblinded assessor, and kneeling ability was evaluated by 2 blinded assessors at 12 months after surgery. RESULTS: The area of cutaneous hypesthesia was significantly smaller in the anterolateral skin incision group than the anteromedial skin incision group (3.0 ± 8.7 cm2 vs 10.6 ± 18.6 cm2; 95% confidence interval, 2.8-12.3 cm2; P = .0019). The rates of patients judged to be able to kneel were significantly higher in the anterolateral skin incision group by both assessors (81% vs 60%; P = .025 and 81% vs 59%; P = .015, respectively) with almost perfect agreement between the 2 assessors (kappa value = 0.94). There were no significant differences in terms of complication rate, including wound complications, between the 2 groups (P > .05). CONCLUSION: Compared with anteromedial skin incision, anterolateral skin incision may provide less cutaneous hypesthesia and better kneeling ability after TKA without increasing complication rate.

No Clinically Important Difference in Pain Scores After THA Between Periarticular Analgesic Injection and Placebo: A Randomized Trial.

BACKGROUND: Periarticular analgesic injection (PAI) is being used more commonly for pain relief after orthopaedic surgeries. However, there is conflicting evidence regarding the effectiveness of PAI for post-THA pain relief. QUESTIONS/PURPOSES: In a double-blind, randomized, controlled trial among patients undergoing same-day bilateral THA, with each patient serving as his or her own control, we asked: (1) Did the pain score as measured on a 100-mm VAS differ between the hips that received PAI versus placebo? (2) Were there differences in complications between the treatment and control hips in these patients? METHODS: Over a 1-year period at one center, 45 patients underwent same-day bilateral THA; three were excluded for prespecified reasons, and two declined participation in this randomized, controlled trial, leaving 40 patients (80 THAs) in the study. Patients randomly received PAI in one hip and placebo in the contralateral hip; patients, surgeons, and nurses were blinded in terms of which hip received the PAI and which hip received a placebo saline injection. The PAI solution included ropivacaine, morphine hydrochloride hydrate, methylprednisolone, ketoprofen, and epinephrine. The primary outcome was the VAS for pain at rest 24 hours after THA, measured using a 100-mm horizontal VAS. The VAS score was compared between two groups and assessed to reach the reported threshold values for the minimum clinically important difference (MCID) of 20 mm for the postoperative VAS score. No patients were lost to followup, and there were no missing data for the primary outcome. Complications that occurred during the trial were recorded prospectively with emphasis on infection, wound complications, nerve palsy and allergic reactions to the injections. RESULTS: There were no clinically important differences between hips treated with the PAI and those treated with the placebo injection at any point. The hips that received PAI had less pain than those receiving placebo 24 hours after THA (16 ± 17 mm versus 22 ± 20 mm; mean difference, 6 mm; 95% confidence interval [CI], 2-9 mm; p = 0.006), but this effect size was below the MCID of 20 mm and thus is unlikely to be clinically important. The hips that received PAI also had better VAS scores in the recovery room (38 ± 29 mm versus 52 ± 33 mm; mean difference 14 mm; 95% CI, 5-23 mm; p = 0.004) and 3 hours after THA than placebo controls (28 ± 22 mm versus 37 ± 24 mm; mean difference 9 mm; 95% CI, 2-16 mm; p = 0.010). Neither of these differences exceeded the MCID and likewise were unlikely to be clinically important. No complications, including surgical site infections, were observed in either group. CONCLUSIONS: Periarticular analgesic injection for pain control after THA did not result in a clinically important reduction in pain at any point examined. Given the expense associated with this PAI mixture and the lack of effectiveness outside this timeframe, we cannot recommend its use. Other mixtures or concentrations of drugs may be helpful in short-stay admissions for THA, but this will require further research. LEVEL OF EVIDENCE: Level I, therapeutic study.