Automatic annotation of hip anatomy in fluoroscopy for robust and efficient 2D/3D registration.

PURPOSE: Fluoroscopy is the standard imaging modality used to guide hip surgery and is therefore a natural sensor for computer-assisted navigation. In order to efficiently solve the complex registration problems presented during navigation, human-assisted annotations of the intraoperative image are typically required. This manual initialization interferes with the surgical workflow and diminishes any advantages gained from navigation. In this paper, we propose a method for fully automatic registration using anatomical annotations produced by a neural network. METHODS: Neural networks are trained to simultaneously segment anatomy and identify landmarks in fluoroscopy. Training data are obtained using a computationally intensive, intraoperatively incompatible, 2D/3D registration of the pelvis and each femur. Ground truth 2D segmentation labels and anatomical landmark locations are established using projected 3D annotations. Intraoperative registration couples a traditional intensity-based strategy with annotations inferred by the network and requires no human assistance. RESULTS: Ground truth segmentation labels and anatomical landmarks were obtained in 366 fluoroscopic images across 6 cadaveric specimens. In a leave-one-subject-out experiment, networks trained on these data obtained mean dice coefficients for left and right hemipelves, left and right femurs of 0.86, 0.87, 0.90, and 0.84, respectively. The mean 2D landmark localization error was 5.0 mm. The pelvis was registered within [Formula: see text] for 86% of the images when using the proposed intraoperative approach with an average runtime of 7 s. In comparison, an intensity-only approach without manual initialization registered the pelvis to [Formula: see text] in 18% of images. CONCLUSIONS: We have created the first accurately annotated, non-synthetic, dataset of hip fluoroscopy. By using these annotations as training data for neural networks, state-of-the-art performance in fluoroscopic segmentation and landmark localization was achieved. Integrating these annotations allows for a robust, fully automatic, and efficient intraoperative registration during fluoroscopic navigation of the hip.

Correction to: Mechanically Induced Periprosthetic Osteolysis: A Systematic Review.

[This corrects the article DOI: 10.1007/s11420-018-9641-5.].

Pose Estimation of Periacetabular Osteotomy Fragments With Intraoperative X-Ray Navigation.

OBJECTIVE: State-of-the-art navigation systems for pelvic osteotomies use optical systems with external fiducials. In this paper, we propose the use of X-ray navigation for pose estimation of periacetabular fragments without fiducials. METHODS: A two-dimensional/three-dimensional (2-D/3-D) registration pipeline was developed to recover fragment pose. This pipeline was tested through an extensive simulation study and six cadaveric surgeries. Using osteotomy boundaries in the fluoroscopic images, the preoperative plan was refined to more accurately match the intraoperative shape. RESULTS: In simulation, average fragment pose errors were 1.3 ° /1.7 mm when the planned fragment matched the intraoperative fragment, 2.2 ° /2.1 mm when the plan was not updated to match the true shape, and 1.9 ° /2.0 mm when the fragment shape was intraoperatively estimated. In cadaver experiments, the average pose errors were 2.2  ° /2.2 mm, 3.8 ° /2.5 mm, and 3.5  ° /2.2 mm when registering with the actual fragment shape, a preoperative plan, and an intraoperatively refined plan, respectively. Average errors of the lateral center edge angle were less than 2 ° for all fragment shapes in simulation and cadaver experiments. CONCLUSION: The proposed pipeline is capable of accurately reporting femoral head coverage within a range clinically identified for long-term joint survivability. SIGNIFICANCE: Human interpretation of fragment pose is challenging and usually restricted to rotation about a single anatomical axis. The proposed pipeline provides an intraoperative estimate of rigid pose with respect to all anatomical axes, is compatible with minimally invasive incisions, and has no dependence on external fiducials.

Mechanically Induced Periprosthetic Osteolysis: A Systematic Review.

BACKGROUND: Peri-prosthetic bone loss can result from chemical, biological, and mechanical factors. Mechanical stimulation via fluid pressure and flow at the bone-implant interface may be a significant cause. Evidence supporting mechanically induced osteolysis continues to grow, but there is no synthesis of published clinical and basic science data. QUESTIONS/PURPOSES: We sought to review the literature on two questions: (1) What published evidence supports the concept of mechanically induced osteolysis? (2) What is the proposed mechanism of mechanically induced osteolysis, and does it differ from that of particle-induced osteolysis? METHODS: A systematic review was performed of the PubMed and Web of Science databases. Additional relevant articles were recommended by the senior authors based on their expert opinion. Abstracts were reviewed and the manuscripts pertaining to the study questions were read in full. Studies showing support of mechanically induced osteolysis were quantified and findings summarized. RESULTS: We identified 49 articles of experimental design supporting the hypothesis that mechanical stimulation of peri-prosthetic bone from fluid pressure and flow can induce osteolysis. While the molecular mechanisms may overlap with those implicated in particle-induced osteolysis, mechanically induced osteolysis appears to be mediated by distinct and parallel pathways. CONCLUSIONS: The role of mechanical stimuli is increasingly recognized in the pathogenesis of peri-prosthetic osteolysis. Current research aims to elucidate the molecular mechanisms to better target therapeutic interventions.

Ceramic Femoral Heads for All Patients? An Argument for Cost Containment in Hip Surgery.

Trunnionosis and taper corrosion have recently emerged as problems in total hip arthroplasty (THA). No longer restricted to metal-on-metal bearings, these phenomena now affect an increasing number of metal-on-polyethylene THAs and are exacerbated by modularity. Resulting increases in metal toxicity and patient morbidity, and the added costs of toxicity surveillance and revision surgery, will place a substantial economic burden on many health systems. Although they are more expensive than cobalt-chrome heads, ceramic femoral heads make metal toxicity a nonissue. In this article, we provide a theoretical framework for debating whether use of ceramic femoral heads in all THA patients could represent a more cost-effective option.

Anteroposterior Radiographs Are More Accurate than Cross-Table Lateral Radiographs for Acetabular Anteversion Assessment: a Retrospective Cohort Study.

BACKGROUND: Measuring acetabular anteversion is relevant to routine follow-up of total hip arthroplasties (THAs) and for malfunctioning THAs. Imageless navigation facilitates acetabular component orientation relative to the anterior pelvic plane (APP) or to the APP adjusted for sagittal pelvic tilt (PT). The optimal plain radiographic method for the postoperative assessment of anteversion is not agreed upon. QUESTIONS/PURPOSES: (1) Do anteversion measurements on plain radiographs correlate more with APP anteversion or PT-adjusted anteversion? (2) Do measurements of anteversion performed on supine anteroposterior (AP) radiographs more accurately reflect intraoperative anteversion values for navigated THA compared to anteversion measured on cross-table lateral (CL) radiographs? METHODS: Seventy patients receiving primary navigated THA were included. APP and PT-adjusted anteversion were recorded; the latter defined the intraoperative target for anteversion. Postoperative anteversion was measured on supine AP pelvis radiographs with computer software and CL radiographs with conventional methods. Intraoperative measurements were used as the reference standards for comparisons. RESULTS: Mean intraoperative APP anteversion was 20.6° ± 5.6°. Mean intraoperative PT-adjusted anteversion was 22.9° ± 4.5°. Mean anteversion was 22.7° ± 4.7° on AP radiographs and 27.2° ± 4.2° on CL radiographs (p < 0.001). Only correlations between PT-adjusted anteversion and radiographic assessments of anteversion were significant. The mean difference between PT-adjusted anteversion and anteversion on AP radiographs was -0.2° ± 4.3°, while the mean difference between the PT-adjusted anteversion and anteversion measured on CL radiographs was 4.3 ± 5.1° (p < 0.001). CONCLUSION: Plain film assessment of anteversion was more accurate on supine AP radiographs than on CL radiographs, which overestimated acetabular anteversion.

Radiation Exposure during Fluoroscopic Guided Direct Anterior Approach for Total Hip Arthroplasty.

Fluoroscopic guidance is commonly utilized during direct anterior total hip arthroplasty (DA THA). The purpose of this study was to measure patient and surgeon exposure utilizing this technique. Fifty-one consecutive patients who underwent primary DA THA by a single surgeon were prospectively studied. Fluoroscopic guidance was utilized according to an established protocol. Dose-area product (DAP) (Gy-cm(2)) and fluoroscopy time were recorded for each case. Surgeon exposure was recorded by a dosimeter. The median DAP was 0.716 Gy-cm(2) (range 0.251-1.81). Mean fluoroscopy time was 0.59 minutes. Dosimeter results were 10 mrem for all procedures combined. DAP and fluoroscopy times were comparable to published values for other fluoroscopically guided hip procedures. This information may aid in setting reference dose levels for this procedure.

Acetabular component orientation in total hip arthroplasty: the impact of obesity.

INTRODUCTION: Acetabular component position can be an important determinant of joint stability and bearing surface wear after THA. Nonetheless, the incidence of malpositioning is high. Patient obesity, low surgeon volume, and minimally invasive approaches are known risk factors for malposition. As the incidence of obesity continues to increase, it is important to recognise its effect on intraoperative component positioning in THA. OBJECTIVES: Our goal was to assess the impact of obesity on component position for a high-volume surgeon using a standard postero-lateral approach. METHODS: A consecutive series of 120 obese (BMI >30, mean BMI 34.4) and 120 non-obese patients (mean BMI 25.4), who had undergone primary THA by a single surgeon, were included in our retrospective study. AP pelvis and cross-table radiographs obtained at the first postoperative visit were analysed using EBRA software to determine inclination and anteversion angles. Optimal position was defined as 30-45º of inclination and 5-25º of anteversion. RESULTS: Mean inclination and anteversion were 40.6 (+/-5.4º) and 16.6 (+/-5.5º) respectively, in the obese group and 39º (+/-5.0º) and 16.2º (+/-7.5º) in the non-obese group. In the obese group 89 (74%) patients were within the desired range for both measurements, 31 (26%) were out of range in at least one, compared to 91 (76%) and 29 (24%) in the non-obese group, respectively. The overall incidence of malpositioning was 25% for both groups. Among outliers, mean deviation from the optimal range was ≤3.8º in both groups. CONCLUSIONS: The risk of component malpositioning in THA may be reduced when surgery is performed by an experienced, high volume surgeon utilising a standard posterolateral approach. In this setting the deleterious effect of obesity may be overcome.

Results of custom-fit, noncemented, semiconstrained total elbow arthroplasty for inflammatory arthritis at an average of eighteen years of follow-up.

BACKGROUND: The literature available on the results after noncemented total elbow arthroplasty (TEA) in inflammatory arthritis is limited. METHODS: Ten patients (7 women, 3 men; 14 elbows total) who underwent custom, noncemented TEA from 1988 to 1995 were retrospectively reviewed. The average age was 28 years (range, 17-45 years). Four patients (4 elbows) had rheumatoid arthritis, and 6 patients (10 elbows) had juvenile rheumatoid arthritis. The mean follow-up was 18 years. All patients underwent a custom, noncemented, semiconstrained TEA with a plasma spray surface designed from preoperative computed tomography scan to achieve metaphyseal fit. The primary outcome was the Mayo Elbow Performance Score, and secondary outcomes were flexion and rotation arc of motion. Intraoperative and postoperative complications and revisions performed were also recorded. Radiographs taken at final follow-up were evaluated for evidence of loosening. RESULTS: The Mayo Elbow Performance Score improved from a mean of 35 preoperatively to a mean of 91 postoperatively. Flexion arc of motion improved from 50° preoperatively to 111° postoperatively, and rotation arc improved from 75° preoperatively to 145° postoperatively. Four patients underwent bushing revision at 8, 8, 22, and 22 years (29%), respectively, and there was 1 deep infection (7%). One patient had an intraoperative fracture in the humerus that did not require further treatment. On final radiographic follow-up at a mean of 18 years, all the components were fully ingrown, and there was no evidence of loosening or loss of fixation. CONCLUSION: In the younger population with inflammatory arthritis, noncemented TEA has reliable outcomes clinically and radiographically at long-term follow-up.

The management of extensor mechanism complications in total knee arthroplasty. AAOS exhibit selection.

Complications involving the knee extensor mechanism and patellofemoral joint occur in 1% to 12% of patients following total knee arthroplasty and have major negative effects on patient outcomes and satisfaction. The surgeon must be aware of intraoperative, postoperative, and patient-related factors that can increase the rate of these problems. This review focuses on six of the most commonly encountered problems: patellar tendon disruption, quadriceps tendon rupture, patellar crepitus and soft-tissue impingement, periprosthetic patellar fracture, patellofemoral instability, and osteonecrosis of the patella. The goals of this report are to (1) review the relevant anatomy of the knee extensor mechanism, (2) present risk factors that may lead to extensor mechanism complications, (3) provide a diagnostic and treatment algorithm for each of the aforementioned problems, and (4) review the specific surgical techniques of Achilles tendon allograft reconstruction and synthetic mesh augmentation. Extensor mechanism disorders following total knee arthroplasty remain difficult to manage effectively. Although various surgical techniques have been used, the results in patients with a prior total knee arthroplasty are inferior to the results in the young adult without such a prior procedure. Surgical attempts at restoration of the knee extensor mechanism are usually warranted; however, the outcomes of treatment of these complications are often poor, and management of patient expectations is important.

Dual-mobility acetabular components in total hip arthroplasty.

With dislocation being one of the most serious complications of total hip arthroplasty, prevention of recurrent instability has been the driving force behind several implant designs, including large-diameter heads, metal-on-metal bearing surfaces, and constrained acetabular components. Dual-articulation acetabular component design was similarly conceived in an effort to reduce postoperative dislocation risk. This design, developed in France in 1975 and popularized in Europe, was recently approved in the United States and represents a new surgical option for United States orthopedic surgeons performing total hip arthroplasty. In this article, we review the dual-articulation design in terms of its history, biomechanical concepts, published indications, contraindications, outcomes, and complications based on more than 20 years of largely French clinical experience.

Long term safety, efficacy, and patient acceptability of hyaluronic acid injection in patients with painful osteoarthritis of the knee.

The increasing prevalence of painful knee osteoarthritis has created an additional demand for pharmacologic management to prevent or delay surgical management. Viscosupplementation, via intraarticular injection of hyaluronic acid (HA), aims to restore the favorable milieu present in the nonarthritic joint. The safety profile of intraarticular HA injections for painful knee osteoarthritis is well established, with the most common adverse effect being a self-limited reaction at the injection site. Although acceptance of the early literature has been limited by publication bias and poor study quality, more recent and rigorous meta-analysis suggests that intraarticular HA injection is superior to placebo injection for pain relief and matches, if not surpasses, the effect size of other nonoperative treatments, such as nonsteroidal anti-inflammatory medication. Intraarticular HA injection is effective in providing temporary pain relief in patients with painful knee osteoarthritis. Future investigations should focus on optimizing the composition and administration of HA agents to provide prolonged relief of painful osteoarthritis in the knee and other joints.

Patient-specific instrumentation in total knee arthroplasty: a review.

Recently, patient-specific approaches to total knee arthroplasty (TKA) have been introduced, in which preoperative imaging (plain radiographs, computed tomography, and magnetic resonance imaging) are used to manufacture cutting blocks specific to a patient's anatomy. Proposed benefits of patient-matched cutting blocks include a decrease in operative time, instrument trays required, and the ability to preoperatively plan a patient's component size, position, and alignment. In addition, an improvement in postoperative mechanical alignment is expected, without violation of the intramedullary canal. However, questions remain regarding patient outcomes and the cost-effectiveness associated with patient-specific cutting block technology. This article will review the evolution of surgical techniques in TKA, the development of patient-specific cutting blocks, surgical considerations, and the literature associated with this new technology.

Preoperative templating and its intraoperative applications for hip resurfacing arthroplasty.

Hip resurfacing arthroplasty (HRA) is a viable alternative to total hip arthroplasty (THA) in the younger, active adult with degenerative hip disease. However, hip resurfacing has proven to be technically demanding, as accurate component positioning is crucial for success, yet difficult to obtain. Risks of malpositioning of the femoral head include femoral neck notching, varus/valgus malalignment, and femoral neck fracture, while malpositioning of either component may lead to increased edge loading and metal ion levels. A thorough preoperative plan, including a review of clinical findings, radiographic studies, and surgical templating for component size and positioning improves intraoperative accuracy and precision. Key aspects of formulating a methodical preoperative plan for HRA are reviewed. Pertinent aspects of the clinical and radiographic examinations, the technique of preoperative templating, its intraoperative application, clinical outcomes of various preoperative templating systems and intraoperative alignment guides, and the senior author's (EPS) preferred technique are presented.