Varus Collapse in Total Knee Arthroplasty: Does Fixation or Bone Fail First?

INTRODUCTION: Aseptic tibial loosening is now considered the most common reason that total knee arthroplasties (TKA) fail long term. There are unique subsets of patients that fail into varus alignment of the tibial tray with collapse of the medial proximal tibia. It is currently unknown if the implant fixation fails first or if the proximal medial tibia collapses first. MATERIALS: We performed a retrospective analysis of 88 patients that were revised at our institution secondary to aseptic varus collapse of the proximal tibia. Two fellowship-trained arthroplasty surgeons performed a retrospective analysis on sequential precollapse radiographs in each patient to determine which failed first: the implant fixation (implant-cement or cement-bone interface) or the medial proximal tibia. DISCUSSION: 36/88 (40.9%) patients had a series of precollapse radiographs that could be reviewed. Failure at the implant-cement interface before varus collapse in 23 vs 22 patients, failure at the implant-cement and cement-bone interface before varus collapse in two patients, and contemporaneous failure at the implant-cement interface and varus collapse in 11 vs 12 patients were identified by reviewers one and two, respectively. CONCLUSION: The most frequent mechanism of failure identified was failure of the implant-cement interface followed by subsequent medial tibial varus collapse. Improving implant fixation may decrease the incidence of this unique failure mechanism. We advocate the use of supplemental stem fixation in high-risk patients and optimal cement techniques for all patients as methods of potentially avoiding tibial varus collapse, one of the most frequent modes of long-term failure.

Chitranjan S. Ranawat Award: Motion During Total Knee Cementing Significantly Decreases Tibial Implant Fixation Strength.

BACKGROUND: Aseptic tibial loosening following primary total knee arthroplasty persists despite technique and device-related advancements. The mechanisms for this mode of failure are not well understood. We hypothesized that knee movement while the cement was curing dispersed lipids at the implant-cement interface and would result in decreased tibial fixation strength. METHODS: A cadaveric study was performed utilizing 32 torso-to-toe specimens (64 knees). Four contemporary total knee arthroplasty designs were evaluated. Each implant design was randomly assigned to a cadaveric specimen pair with side-to-side randomization. Specimen densitometry was recorded. Each tibial implant was cemented using a standard technique. On one side, the tibial component was held without motion following impaction until complete cement polymerization. The contralateral knee tibial implant was taken through gentle range of motion and stability assessment 7 minutes after cement mixing. Axial tibial pull-out strength and interface failure examination was performed on each specimen. RESULTS: The average pull-out strength for the no motion cohort (5,462 N) exceeded the motion cohort (4,473 N) (P = .001). The mean pull-out strength between implant designs in the no motion cohort varied significantly (implant A: 7,230 N, B: 5,806 N, C: 5,325 N, D 3,486 N; P = .007). Similarly, the motion cohort inter-implant variance was significant (P ≤ .001). Intra-implant pull-out strength was significantly higher in implant A than D. The average pull-out strength was significantly lower in specimens that failed at the implant-cement interface vs bone failures (4,089 ± 2,158 N vs 5,960 ± 2,010 N, P < .0025). CONCLUSION: Knee motion during cement polymerization is associated with significant decreases in tibial implant fixational strength. Reduction in implant pull-out strength was identified with each implant design with motion and varied between designs. Across all tested designs, we recommend limiting motion while cementing the tibial implant to improve fixation strength.

The Efficacy and Safety of Corticosteroids in Total Joint Arthroplasty: A Direct Meta-Analysis.

BACKGROUND: Corticosteroids are commonly used intraoperatively to treat pain and reduce opioid consumption and nausea associated with primary total joint arthroplasty (TJA). The purpose of this study was to evaluate the efficacy and safety of corticosteroids in primary TJA to support the combined clinical practice guidelines of the American Association of Hip and Knee Surgeons, American Academy of Orthopaedic Surgeons, Hip Society, Knee Society, and the American Society of Regional Anesthesia and Pain Management. METHODS: The MEDLINE, Embase, and Cochrane Central Register of Controlled Trials databases were searched for studies published before February 2020 on corticosteroids in TJA. All included studies underwent qualitative and quantitative homogeneity testing followed by a systematic review and direct comparison meta-analysis to assess the efficacy and safety of corticosteroids. RESULTS: Critical appraisal of 1,581 publications revealed 23 studies regarded as the best available evidence for analysis. Intraoperative dexamethasone reduces postoperative pain, opioid consumption, and nausea and vomiting. Multiple doses lead to further reduction in pain, opioid consumption, nausea and vomiting. There is insufficient evidence on the risk of adverse events with perioperative dexamethasone in TJA. CONCLUSION: Strong evidence supports the use of a single dose or multiple doses of intravenous dexamethasone to reduce postoperative pain, opioid consumption, nausea and vomiting after primary TJA. There is insufficient evidence on perioperative dexamethasone in primary TJA to determine the optimal dose, number of doses, or risk of postoperative adverse events.

Where Is the "Weak Link" of Fixation in Contemporary Cemented Total Knee Replacements?

BACKGROUND: Aseptic tibial loosening is a frequent cause of long-term failure following primary cemented total knee replacement. Failure of the tibial implant can occur at the implant-cement interface or at the cement-bone interface. Currently, it is unknown at which interface failure occurs in cases of aseptic tibial loosening. The following study was designed to determine which interface represents the "weak link" for tibial implant fixation. METHODS: We performed a retrospective analysis of 149 patients who were revised secondary to aseptic tibial loosening at our institution from 2005 to 2017. Operative reports and radiographs were reviewed on each patient to determine the location and pattern of fixation failure. RESULTS: Implant failure was more prevalent at the implant-cement than cement-bone interface, 140/149 (94.0%) vs 9/149 (6.0%). Additionally, we noted 2 distinct patterns of failure in patients that loosened at the implant-cement interface. Ninety of 140 (64.3%) patients developed varus collapse pattern of failure. Forty-nine of 140 (35.0%) patients developed failure between the implant-cement interface without angulation. All 149 patients had heterotopic bone formation anterior to the tibial baseplate, which was consistent regardless of which interface failed. CONCLUSION: The most frequent interface failure identified in our study was at the implant-cement interface, 140/149 (94.0%). This finding has substantial clinical ramifications. Because failure was predominantly at the implant-cement interface there may be design opportunities for increasing implant fixation to cement. Implants with improved undersurface tibial tray features may be necessary to mitigate the risk of failure at this interface, especially in overly active patients or those with elevated body mass indices.

Acetabular Revision via Direct Anterior Approach-Technical Considerations.

Acetabular implant revision is commonly performed during revision total hip arthroplasty (THA).1 With recent significant increase in the utilization of direct anterior approach for primary THA,2,3 many surgeons familiar with this approach are exploring the direct anterior for revision THA (r-THA) applications. This chapter will specifically address acetabular implant revision via direct anterior approach. The exposure techniques for the acetabulum are described elsewhere in this lecture series. Instead, attention to the mechanics and techniques of acetabular implant revision via direct anterior approach will be stressed.

Kinematic Performance of Gradually Variable Radius Posterior-Stabilized Primary TKA During Various Activities: An In Vivo Study Using Fluoroscopy.

BACKGROUND: Posterior-stabilized total knee arthroplasty (TKA) with gradually variable radii (G-curve) femoral condylar geometry is now available. It is believed that a G-curve design would lead to more mid-flexion stability leading to reduced incidence of paradoxical anterior slide. The objective of this study was to assess the in vivo kinematics for subjects implanted with this type of TKA under various conditions of daily living. METHODS: Tibiofemoral kinematics of 35 patients having posterior-stabilized TKA with G-curve design were analyzed using fluoroscopy while performing three activities: weight-bearing deep knee bend, gait, and walking down a ramp. The subjects were assessed for range of motion, condylar translation, axial rotation, cam-spine engagement, and condylar lift-off. RESULTS: The average weight-bearing flexion during deep knee bend was 111.4°. On average, the subjects exhibited 5.4 mm of posterior rollback of the lateral condyle and 2.0 mm of the medial condyle from full extension to maximum knee flexion. The femur consistently rotated externally with flexion, and the average axial rotation was 5.2°. Overall movement of the condyles during gait and ramp-down activity was small. No incidence of condylar lift-off was observed. CONCLUSION: Subjects in this study experienced consistent magnitudes of posterior femoral rollback and external rotation of the femur with weight-bearing flexion. The variation is similar to that previously reported for normal knee where the lateral condyle moves consistently posterior compared to the medial condyle. Subjects experienced low overall mid-flexion paradoxical anterior sliding and no incidence of condylar lift-off leading to mid-flexion stability.

Systemic Safety of Liposomal Bupivacaine in Simultaneous Bilateral Total Knee Arthroplasty.

BACKGROUND: Intraoperative periarticular injections (PAIs) with local anesthetic are an important component of multimodal pain control in total joint arthroplasty. Liposomal bupivacaine is an extended-release formulation of bupivacaine designed to provide extended pain relief, approved for use in a single surgical site. The systemic safety profile for use in simultaneous bilateral TKA (bTKA) with a full dose in each knee has not been evaluated. The purpose of this study was to determine the safety and pharmacokinetics of bilateral full-dose PAI liposomal bupivacaine in the blood collected in patients undergoing simultaneous bTKA. METHODS: In this prospective study, patients had an identical PAI consisting of 20 cc of liposomal bupivacaine (266 mg), 30 cc of 0.25% bupivacaine (75 mg) with epinephrine, and 10 cc of normal saline injected into each knee during bTKA. Blood samples were collected at predefined intervals until patient discharge. No exogenous bupivacaine was administered. Pharmacokinetic evaluations were subsequently performed and compared to bupivacaine toxicity levels. Patients were monitored for adverse events related to anesthetic toxicity (cardiac and neurologic). RESULTS: Fifteen patients (mean age, 60.7 years; range, 57-64 years) were enrolled in the study. The mean peak level (Cmax) was 0.8 µg/mL (range, 0.4-1.2 µg/mL). All patients were well below the reported systemic cardiac and toxicity levels reported as 2-4 µg/mL. There were no reported cardiac and neurotoxic events in any patients. CONCLUSION: The use of full-dose PAI with liposomal bupivacaine placed into each knee during simultaneous bTKA is safe with systemic bupivacaine levels well below reported cardiac and neurotoxic levels.

Early Failure of Primary Total Hip Arthroplasty: Is Surgical Approach a Risk Factor?

BACKGROUND: In an era of innovation in surgical approaches for total hip arthroplasty (THA), there is concern for increasing trends of early failure. The purpose of this study is to evaluate the incidence of early failure of primary THA stratified by surgical approach. METHODS: A retrospective review was performed on consecutive primary THAs completed from 2007 to 2014 at a high-volume center. THAs were stratified by surgical approach. Only the direct anterior (DAA) and posterior approaches (PA) were included. The primary outcome measure was early revision (<5 years). Descriptive statistics were performed using SAS software. RESULTS: In total, 6894 primary THAs performed between 2007 and 2014 were included. Across 2431 DAA THAs and 4463 PA THAs, there were 103 revisions overall. There was no difference in the overall revision rate for DAA THAs (1.69%) compared to PA THAs (1.39%) (P = .33). The DAA had a higher rate of early revisions for femoral component loosening compared to the PA (P = .0003). About 35.7% of DAA THAs were revised for femoral loosening compared to 8% for the PA (P = .0003). Early failure by femoral loosening occurred more often via the DAA in Dorr A bone (P = .03). The PA had a higher incidence of revision for instability (P = .04). There was no difference in modes of failure with regards to time to failure, acetabular loosening, early periprosthetic fracture, or infection. CONCLUSION: The DAA had a higher incidence of femoral loosening while PA had a higher mode of failure due to instability. Overall revision rates were not statistically different between approaches.

Primary Total Hip Arthroplasty: Everything You Need to Know.

Total hip arthroplasty is an extremely successful procedure that relieves pain and improves function. Orthopaedic surgeons should understand how to improve outcomes of patients who undergo primary total hip arthroplasty. Orthopaedic surgeons can enhance the outcomes of total hip arthroplasty by optimizing preoperative and perioperative management, improving surgical techniques, and selecting an appropriate femoral component and bearing surface.

Radiation Exposure During Fluoro-Assisted Direct Anterior Total Hip Arthroplasty.

BACKGROUND: Utilization of the direct anterior approach (DAA) for total hip arthroplasty (THA) has increased in the last decade with fluoroscopy often used to confirm implant position, leg length, and offset. Radiation exposure thresholds around 800 mGy are published for the risk of cataracts. We hypothesized that surgeon eye exposure during fluoro-assisted DAA total hip arthroplasty would be well below these published thresholds. METHODS: Three experienced orthopedic surgeons performed 30 consecutive fluoro-assisted DAA THAs. During each procedure, the surgeon wore a helmet-mounted dosimeter. After 30 consecutive cases, the dosimeters were analyzed. A chart review was then completed to obtain fluoroscopic data saved for each individual case including fluoroscopic time, total radiation dose, and radiation tech experience. RESULTS: Fluoroscopic data were available for 89 of 90 cases (98.8%). Surgeon 1 had an average fluoroscopic time of 18.51 seconds, radiation dose of 2.396 mGy, and tech experience of 13.06 years. Surgeon 2 had an average fluoroscopic time of 15.63 seconds, radiation dose of 2.139 mGy, and tech experience of 23.69 years. Surgeon 3 had an average fluoroscopic time of 11.06 seconds, radiation dose of 1.462 mGy, and tech experience of 16.03 years. The dosimeter results were 8, 5, and <1 mrem, respectively, for each surgeon. The mean total radiation dose per case for all surgeons was 2.00 mGy (±1.31), and there was no correlation between radiation dose and radiologic tech experience (0.089, P > .05) or radiation dose and patients' body mass index (0.260, P = .014). CONCLUSIONS: Each surgeon would need to perform >300,000 DAA THAs to exceed the 800-mGy cataract threshold dose. The decision to wear protective glasses should be at the surgeon's discretion; however, the findings in this study show a very low radiation dose to the surgeon's eye regardless of radiologic tech experience or patient's body mass index.

Femoral Vessel Blood Flow Is Preserved Throughout Direct Anterior Total Hip Arthroplasty.

Posterolateral and anterolateral approach THA disrupts femoral vessel blood flow, however, this has not been established for the direct anterior (DA) approach. Ten patients undergoing primary DA THA had peak vascular flow rates for the femoral artery and vein calculated via Doppler ultrasound at specified points: incision, acetabular preparation, femoral preparation and final reduction. Peak femoral arterial and venous flow decreased over baseline, but not significantly, during acetabular preparation (P=0.88, P=0.98) and femoral preparation (P=0.97, P=0.97). At final reduction, arterial peak flow was restored (P=1) with an increase in venous flow (P=0.55). Although there were alterations to peak flow, no vessel occlusion occurred at any point during DA THA.

Direct anterior total hip arthroplasty yields more rapid voluntary cessation of all walking aids: a prospective, randomized clinical trial.

This study sought to prospectively examine the clinical and radiographic differences between direct anterior (DA-THA) and mini-posterior approach total hip arthroplasty (MPA-THA). Fifty-four patients were prospectively randomized to either MPA or DA-THA. Patient recorded diaries were collected. Radiographs were reviewed. SF-36, WOMAC and HHS scores were tabulated. Time to ambulation without any assistive device favored DA-THA (22 vs. 28 days, P=0.04). Three week SF mental scores favored MPA-THA (60.66 vs. 58.43, P=0.01). In a randomized prospective trial, patients undergoing DA-THA voluntarily quit use of all walking aids on average 6 days earlier than patients with a MPA-THA. Little additional clinical or radiographic benefit was seen between the cohorts.