Distal femoral resection in conventional total knee arthroplasty (TKA) utilizes an intramedullary guide to determine coronal alignment, commonly planned for 5° of valgus. However, a standard 5° resection angle may contribute to malalignment in patients with variability in the femoral anatomical and mechanical axis angle. The purpose of the study was to leverage deep learning (DL) to measure the femoral mechanical-anatomical axis angle (FMAA) in a heterogeneous cohort. Patients with full-limb radiographs from the Osteoarthritis Initiative were included. A DL workflow was created to measure the FMAA and validated against human measurements. To reflect potential intramedullary guide placement during manual TKA, two different FMAAs were calculated either using a line approximating the entire diaphyseal shaft, and a line connecting the apex of the femoral intercondylar sulcus to the centre of the diaphysis. The proportion of FMAAs outside a range of 5.0° (SD 2.0°) was calculated for both definitions, and FMAA was compared using univariate analyses across sex, BMI, knee alignment, and femur length.Aims
Methods
Mid-level constraint designs for total knee arthroplasty (TKA) are intended to reduce coronal plane laxity. Our aims were to compare kinematics and ligament forces of the Zimmer Biomet Persona posterior-stabilized (PS) and mid-level designs in the coronal, sagittal, and axial planes under loads simulating clinical exams of the knee in a cadaver model. We performed TKA on eight cadaveric knees and loaded them using a robotic manipulator. We tested both PS and mid-level designs under loads simulating clinical exams via applied varus and valgus moments, internal-external (IE) rotation moments, and anteroposterior forces at 0°, 30°, and 90° of flexion. We measured the resulting tibiofemoral angulations and translations. We also quantified the forces carried by the medial and lateral collateral ligaments (MCL/LCL) via serial sectioning of these structures and use of the principle of superposition.Aims
Methods
Accurate identification of the ankle joint centre is critical for estimating tibial coronal alignment in total knee arthroplasty (TKA). The purpose of the current study was to leverage artificial intelligence (AI) to determine the accuracy and effect of using different radiological anatomical landmarks to quantify mechanical alignment in relation to a traditionally defined radiological ankle centre. Patients with full-limb radiographs from the Osteoarthritis Initiative were included. A sub-cohort of 250 radiographs were annotated for landmarks relevant to knee alignment and used to train a deep learning (U-Net) workflow for angle calculation on the entire database. The radiological ankle centre was defined as the midpoint of the superior talus edge/tibial plafond. Knee alignment (hip-knee-ankle angle) was compared against 1) midpoint of the most prominent malleoli points, 2) midpoint of the soft-tissue overlying malleoli, and 3) midpoint of the soft-tissue sulcus above the malleoli.Aims
Methods
Navigation devices are designed to improve a surgeon’s accuracy in positioning the acetabular and femoral components in total hip arthroplasty (THA). The purpose of this study was to both evaluate the accuracy of an optical computer-assisted surgery (CAS) navigation system and determine whether preoperative spinopelvic mobility (categorized as hypermobile, normal, or stiff) increased the risk of acetabular component placement error. A total of 356 patients undergoing primary THA were prospectively enrolled from November 2016 to March 2018. Clinically relevant error using the CAS system was defined as a difference of > 5° between CAS and 3D radiological reconstruction measurements for acetabular component inclination and anteversion. Univariate and multiple logistic regression analyses were conducted to determine whether hypermobile (Aims
Methods
Pulmonary embolism (PE) complicates up to 1% of total joint arthroplasties (TJA). Many PE treatment guidelines call for immediate initiation of therapeutic anticoagulation. Options include Xa inhibitors, Enoxaparin, and Warfarin. Deciding between these is a balance of the efficacy and the risks. Little data exists regarding the risks of each of these treatment options for treating PE in arthroplasty patients. We examined the records of 29,270 patients who underwent a primary total joint arthroplasty (TJA), defined as a unilateral total knee arthroplasty (TKA) (18,987) or total hip arthroplasty (THA) (10,283), between 2/2016 and 12/2018 at our institution and identified 338 (242 TKA, 96 THA) patients who developed an in-hospital PE treated with therapeutic anticoagulation. The patients were treated with therapeutic doses of Xa inhibitors, enoxaparin or warfarin. The type and frequency of complications were determined and classified as major or minor. Major complication included: bleeding requiring surgery, GI bleed requiring treatment, >2 unit transfusion and mortality. Minor complications included wound drainage, bleeding not requiring surgery, and thrombocytopenia.Introduction
Methods
Surgeons commonly resect additional distal femur during primary total knee arthroplasty (TKA) to correct a flexion contracture. However, the effect of joint line proximalization on TKA kinematics is unclear. Thus, our goal was to quantify the effect of additional distal femoral resection on knee extension and mid-flexion laxity. Six computational knee models with TKA-specific capsular and collateral ligament properties were implanted with a contemporary posterior-stabilized TKA. A 10° flexion contracture was modeled to simulate a capsular contracture. Distal femoral resections of +2 mm and +4 mm were simulated for each model. The knees were then extended under standardized torque to quantify additional knee extension achieved. Subsequently, varus and valgus torques of ±10 Nm were applied as the knee was flexed from 0° to 90° at the baseline, +2 mm, and +4 mm distal resections. Coronal laxity, defined as the sum of varus and valgus angulation with respective torques, was measured at mid-flexion.Introduction
Methods
Up to 15 % of patients report anterior knee pain (AKP) after a total knee arthroplasty (TKA). The correlation of radiographic patellar measurements and post-operative AKP remains controversial. The purpose of this study was to determine whether any radiographic measurements can predict anterior knee pain after TKA. We performed a retrospective analysis of data on 343 patients who underwent a primary unilateral TKA between 2009–2012 at a single institution. Post-operative radiographs were evaluated with standing anteroposterior, lateral, and merchant views. Radiographic assessment was performed to assess posterior offset, Insall Salvati ratio, Blackburne, PP angle, Patella thickness, Congruence angle, Patella tilt, and patella displacement. Clinical function was assessed by the Kujala anterior knee pain scale at a minimum of 5 years. Patients were asked if they currently had anterior knee pain post-operatively by responding “yes” or “no.” There were 264 females and 79 males; the mean age at surgery was 64.2 ± 9.7 (range, 42–92 years) years; the mean BMI 31±5.8 kg/m2 (range, 18.8–49 kg/m2).Introduction
Methods
Patients undergoing primary total hip arthroplasty (THA) with prior lumbar spine fusion (LSF) are at high risk for instability with reported incidence of dislocation as high as 8.3%. The use of dual mobility cups in patients undergoing revision THA, another high risk group, has demonstrated decreased incidence of instability. Purpose of this study was to evaluate the risk of instability in patients undergoing primary THA with a history of prior LSF using dual mobility cups. This was a multi-center retrospective study with 93 patients undergoing primary THA using a dual mobility cup with prior history of instrumented LSF. The primary outcome investigated was instability. Secondary variables investigated included number of levels fused, approach, length of stay, and other complications. The minimum follow-up time was 1 year since the majority of dislocations occur during first year following the primary THA.Introduction
Methods
One of the more common complaints from patients in their post-operative total knee arthroplasty (TKA) is the perceived feeling of the operative leg feeling longer than the non-operative leg. Studies have shown that the leg length discrepancies may occur in up to 80% of patients following unilateral TKA patients. The purpose of this study was to determine the incidence of leg length discrepancy (LLD) after primary TKA as well as determine the correlation between deformity and incidence of LLD. We retrospectively reviewed 1108 patients who underwent a primary unilateral TKA at a single institution. 97 patients were excluded for lack of imaging, prior total hip replacement or body mass index greater than 40 kg/m2. Hip to ankle biplanar radiographs were obtained pre-operative and 6 weeks postoperatively for all patients. Two independent observers measures leg length, femur length, tibia length, overall alignment and deformity present for all radiographs.Introduction
Methods
The anatomic dual mobility (ADM) technology utilized a monoblock cobalt chromium acetabular component. However, design limitations conferred difficulties controlling orientation during component insertion and inability to confirm full implant seating; the solution resulted in the creation of the modular dual mobility (MDM). The modular implant combines a standard titanium acetabular component and a cobalt chromium liner insert. Due to the metal-on-metal interface on MDM implants, fretting and corrosion releasing metal ions like previous metal-on-metal THA implants, were a concern. This study prospectively reviewed metal ions (cobalt, chromium and titanium) on patients who were at least 1 year post MDM implantation and compared them to patients with an ADM implant and evaluated radiographic seating of the components. All patients with ADM and MDM implants underwent evaluation of metal ions (cobalt, chromium and titanium) at their one year follow-up appointment. Radiographic evaluation for acetabular polar gaps was performed. Elevated metal ions were determined using standard laboratory ranges. Differences in baseline demographics were assessed using the Mann Whitney-U test and Fishers's exact test. Differences in metal ions and implant type were compared using the Fisher's exact tests.Introduction
Methods
Computer-assisted hip navigation offers the potential for more accurate placement of hip components, which is important in avoiding dislocation, impingement, and edge-loading. The purpose of this study was to determine if the use of computer-assisted hip navigation reduced the rate of dislocation in patients undergoing revision THA. We retrospectively reviewed 72 patients who underwent computer-navigated revision THA [Fig. 1] between January 2015 and December 2016. Demographic variables, indication for revision, type of procedure, and postoperative complications were collected for all patients. Clinical follow-up was performed at 3 months, 1 year, and 2 years. Dislocations were defined as any episode that required closed or open reduction or a revision arthroplasty. Data are presented as percentages and was analyzed using appropriate comparative statistical tests (z-tests and independent samples t- tests).Introduction
Methods and Materials
Whether anterior referencing (AR) or posterior referencing (PR) are optimal to position and size the femoral component in Total Knee Arthroplasty (TKA) remains controversial. This controversy stems, in part, from a lack of understanding of whether one technique more consistently balances the medial/lateral collateral ligaments (MCL & LCL) in flexion and extension. Therefore, our goal was to compare AR and PR in terms of: (1) maximum MCL and LCL forces in passive flexion, and (2) medial and lateral gaps at full extension and 90‖ of flexion. In addition, we identified geometric landmarks that could help predict the ligament forces during flexion. Computational models of six knees were virtually implanted with TKAs based on our previously-developed framework. AR and PR were simulated in each of the six models. A Posterior Stabilized implant was utilized. Standard AR and PR cuts and component positioning were simulated with the femoral component aligned parallel to the transepicondylar axis. In both AR and PR models, the distal femoral cut and the proximal tibial cut were perpendicular to the femoral and tibial mechanical axis, respectively. The amount of posterior bone resected with AR knees ranged from 4.2 to 10.8 mm, and with PR knees ranged from 4.2 to 8 mm. Ligament properties were standardized to reflect a balanced knee at full extension. Passive flexion under 500 N of compression was applied and the MCL and LCL forces were predicted. A new measure, the MCL ratio, that incorporated the femoral insertion of the anterior fiber of MCL relative to the posterior and distal femoral cuts was estimated (Fig. 1). A varus/valgus moment of 6 Nm was applied at full extension and 90‖ of flexion, and the corresponding lateral and medial gaps were measured.Introduction
Methods
Over the past few decades, opioid abuse has become a major threat to public health. In 2013 alone, enough opioid prescriptions were written in the United States for every American adult to have their own bottle of pills. Since then, opioid prescribing rates and opioid related deaths have continued to grow, with over 46 people dying on average each day from prescription opioid overdoses in 2016. Orthopaedic surgeons are among the top 5 specialties in the number of opioid prescriptions written. For many common surgeries, such as total knee arthroplasty (TKA), post-discharge prescriptions are based on prescriber habits and opinion. There exists limited data-driven protocols to guide post-operative opioid prescribing practices. The purpose of this prospective study was to determine the average postoperative opioid consumption in patients undergoing primary TKA using a novel mobile text messaging platform. We hypothesized that majority of patients undergoing TKA do not properly dispose of left over pills after surgery. 95 patients undergoing primary unilateral TKA with one of nine arthroplasty surgeons at a single orthopaedic specialty hospital were prospectively enrolled. Daily pain levels and opioid consumption, and quantity and disposal patterns for left over medications were collected for six weeks following surgery using a novel mobile phone text messaging system. This system automatically queried patients twice a day, storing responses on a secure third-party host that investigators monitored and used to generate data reports in real-time.Introduction
Methods
Acetabular component position is considered a major factor affecting the etiology of hip dislocation. The ‘Lewinnek safe zone’ has been the most widely accepted range for component position to avoid hip dislocation, but recent studies suggest that this safe zone is outdated. We used a large prospective institutional registry to ask: 1) is there a ‘safe zone’ for acetabular component position, as measured on an anteroposterior radiograph, within which the risk of hip dislocation is low?, and 2) do other patient and implant factors affect the risk of hip dislocation? From 2007 to 2012, 19,449 patients (22,097 hip procedures) were recorded in an IRB approved prospective total joint replacement registry. All patients who underwent primary THA were prospectively enrolled, of which 9,107 patients consented to participate in the registry. An adverse event survey (80% compliance) was used to identify patients who reported a dislocation event in the six months after hip replacement surgery. Postoperative AP radiographs of hips that dislocated were matched with AP radiographs of stable hips, and acetabular position was measured using Ein Bild Röntgen Analyse software. Dislocators in radiographic zones (± 5°, ± 10°, ± 15° boundaries) were counted for every 1° of anteversion and inclination angles.Introduction
Materials and Methods
Pelvic flexion and extension in different body positions can affect acetabular orientation after total hip arthroplasty, and this may predispose patients to dislocation. The purpose of this study was to evaluate functional acetabular component position in total hip replacement patients during standing and sitting. We hypothesize that patients with degenerative lumbar disease will have less pelvic extension from standing to sitting, compared to patients with a normal lumbar spine or single level spine disease. A prospective cohort of 20 patients with primary unilateral THR underwent spine-to-ankle standing and sitting lateral radiographs that included the lumbar spine and pelvis using EOS imaging. Patients were an average age of 58 ± 12 years and 6 patients were female. Patients had (1) normal lumbar spines or single level degeneration, (2) multilevel degenerative disc disease or (3) scoliosis. We measured acetabular anteversion (cup relative to the horizontal), sacral slope angle (superior endplate of S1 relative to the horizontal), and lumbar lordosis angles (superior endplates of L1 and S1). We calculated the absolute difference in acetabular anteversion and the absolute difference in lumbar lordosis during standing and sitting (Figure 1).Introduction
Methods
Tranexamic acid (TXA) has been shown to reduce post-operative blood loss, but the dosage and method of administration remains controversial. The purpose of our study was to study the effectiveness of topical TXA in a cohort of patients (n=224) undergoing TKA by a single surgeon. Two groups of patients who received topical TXA were compared to patients who did not receive TXA. Patients that received topical TXA had the least early postoperative blood loss, with patients that received topical TXA with a tourniquet and a drain having the least. Patients receiving TXA required fewer transfusions than patients who did not receive TXA and there was no difference in the rate of symptomatic DVT/PE. Our results support the use of topical TXA during TKA.
Digital templating is a critical part of preoperative planning for total hip arthroplasty (THA) that is increasingly used by orthopaedic surgeons as part of their preoperative planning process. Digital templating has been used as a method of reducing hospital costs by eliminating the need for acetate films and providing an accurate method of preoperative planning. Pre-operative templating can help anticipate and predict appropriate component sizes to help avoid postoperative leg length discrepancy, failure to restore offset, femoral fracture, and instability. A preoperative plan using digital radiographs for surgical templating for component size can improve intraoperative accuracy and precision. While templating on conventional and digital radiographs is reliable and accurate, the accuracy of templating on digital images acquired with a novel biplanar imaging system (EOS Imaging Inc, Cambridge, MA, USA) remains unknown. EOS imaging captures whole body images of a standing patient without stitching or vertical distortion, less magnification error and exposes patients to less radiation than a pelvis AP radiograph. Therefore, the purpose of this study was to compare EOS imaging and conventional anteroposterior (AP) xrays for preoperative digital templating for THA, and compare the results to the implant sizes used intraoperatively. Forty primary unilateral THA patients had preoperative supine AP xrays and standing EOS imaging. The mean age for patients was 61 ± 8 years, the mean body mass index 29 ± 6 kg/m2 and 21 patients were female. All patients underwent a THA with the same THA system (R3 Acetabular System and Synergy Cementless Stem, Smith & Nephew, TN, USA) by a single surgeon. Two blinded observers preoperatively templated using both AP xray and EOS imaging for each patient to predict acetabular size, femoral component size, and stem offset. All templating was performed by two observers with standard software (Ortho Toolbox, Sectra AB, Linköping, Sweden) [Figure 1] one week prior to surgery, and were compared using the Cronbach's alpha (∝) coefficient of reliability. The accuracy of templating was reported as the average percent agreement between the implanted size and the templated size for each component.Background
Methods
Obesity is a risk factor for acetabular malposition when total hip arthroplasty (THA) is performed with manual orientation techniques. However, conflicting evidence exists regarding the usefulness of computer-assisted surgery for performing THA in obese patients. The purpose of this study was to compare the precision and accuracy of imageless navigation for acetabular component placement in obese versus non-obese patients. After institutional review board approval, 459 THA performed for primary hip osteoarthritis were reviewed retrospectively. The same imageless navigation system was used for acetabular component placement in all THA. During surgery the supine anterior pelvic plane was referenced superficially. THA was performed via posterolateral approach in the lateral position. A hemispherical acetabular component was used, with target inclination of 40° and target anteversion of 25°. Computer software was used to determine acetabular orientation on postoperative anteroposterior pelvic radiographs. Obese patients (BMI ≥ 30 kg/m2) were compared to non-obese patients. A 5° difference in mean orientation angles was considered clinically significant. Orientation error (accuracy) was defined as the absolute difference between the target orientation and the measured orientation. Student's t test was used to compare means. Hartley's test compared variances of the mean differences (precision). Fisher exact tests examined the relationship between obesity and component placement in the target zone (target ± 10°) for inclination and version. All statistical tests were two-sided with a significance level of 0.05. Differences in mean inclination and anteversion between obese and non-obese groups were 1.1° (p=0.02 and p=0.08, respectively), and not clinically significant. Inclination accuracy trended toward improvement for non-obese patients (p=0.06). Inclination precision was better for non-obese patients (p=0.006). Accuracy and precision for anteversion were equal between the two groups (p=0.19 and p=0.95, respectively). There was no relationship between obesity and placement of the acetabulum outside of the target ranges for inclination (p=0.13), anteversion (p=0.39) or both (p=0.99), with a trend toward more inclination outliers in obese patients versus non-obese patients (7.3% versus 3.9%). The observed differences in mean acetabular orientation angles were not clinically significant (< 5°), although inclination orientation was less accurate and precise for obese patients. In contrast to existing literature, we found no difference in the accuracy and precision with regard to anteversion in obese and non-obese patients. We propose that accurate superficial registration of landmarks in obese patients is achievable, and the use of imageless navigation likely improves acetabular positioning in obese and non-obese patients.
Surgeons often target the Lewinnek zone (40°±10° of inclination; 15°±10° of anteversion) for acetabular orientation during total hip arthroplasty (THA). However, matching native anteversion (20°-25°) may achieve optimal stability. The purpose of this study was to (1) determine incidence of early dislocation with increased target acetabular anteversion, and (2) report the accuracy of imageless navigation for achieving target acetabular position in a large, single-surgeon cohort. A posterolateral approach with soft tissue repair was performed in the 553 THA meeting the inclusion criteria. The same imageless navigation system was used for acetabular component placement in all THA. Target acetabular orientation was 40° ± 10° of inclination and 25° ± 10° of anteversion. Computer software was used to measure acetabular positioning on 6-week postoperative anteroposterior pelvic radiographs. Incidence of dislocation within 6 months of surgery was determined. Repeated measures multiple regression using the Generalised Estimating Equations approach was used to identify baseline patient characteristics (age, gender, BMI, primary diagnosis, and laterality) associated with component positioning outside of the targeted ranges for inclination and anteversion. Fisher exact tests were used to examine the relationship between dislocation and component placement in either the Lewinnek safe zone or the targeted zone. All tests were two-sided with a significance level of 0.05. Mean inclination was 42.2° ± 4.9°, and mean anteversion was 23.9° ± 6.5°. 82.3% of cups were placed within the target zone. Variation in anteversion accounted for 67.3% of outliers. Only body mass index was associated with inclination outside the target range (p = 0.017), and only female gender was associated with anteversion outside the target range (p = 0.030). Six THA (1.1%) experienced early dislocation, and 3 THA (0.54%) were revised for multiple dislocations. There was no relationship between dislocation and component placement in either the Lewinnek zone (p = 0.224) or the target zone (p = 0.287). This study demonstrates that increasing target acetabular anteversion using the posterolateral approach does not increase the incidence of early THA dislocation. However, the long-term effects on bearing surface wear and stability must be elucidated. The occurrence of instability even in patients within our target zone emphasises the importance of developing patient-specific targets for THA component alignment.
Conventional, extramedullary (EM) tibial alignment guides are only 65%–88% accurate in creating a tibial resection within 2° of perpendicular to the tibial mechanical axis in total knee arthroplasty (TKA). The purpose of this study was to compare the overall, tibial component alignment, and the surgeon's ability to achieve a specific, intraoperative goal for alignment between a portable, navigation system (KneeAlign™) and conventional, EM alignment guides. One hundred patients were enrolled in a prospective, randomized controlled study. Fifty patients received a TKA using the KneeAlign™ to perform the tibial resection, and 50 patients an EM alignment guide. Standing AP hip-to-ankle radiographs and lateral knee-to-ankle radiographs were obtained at the first, postoperative visit.Background:
Methods:
