Gavin C. Pereira

Fracture of Fully Coated Echelon Femoral Stems in Revision Total Hip Arthroplasty

Three cases of fractured uncemented, fully porous Echelon femoral stems (Smith & Nephew, Memphis, Tenn) are examined. Fracture of these components, an uncommon complication of revision hip surgery, is thought to result from cantilever bending after distal bony ingrowth. The stems in these cases fractured at 11, 22, and 28 months after revision surgery. Risk factors include increased body weight, excessive activity, an undersized stem, varus alignment, inadequate proximal femoral bone stock, and metallurgic defects. Extraction can be difficult and is often accomplished with the use of multiple trephines or via tamping through a distal cortical window.

Identification of the landmark registration safe zones during total knee arthroplasty using an imageless navigation system

Incorrect registration during computer assisted total knee arthroplasty (CA-TKA) leads to malposition of implants. Our aim was to evaluate the tolerable error in anatomic landmark registration. We incorrectly registered the femoral epicondyles, femoral and tibial centers, as well as the malleoli and documented the change in angulation or rotation. We found that the distal femoral epicondyles were the most difficult anatomic landmarks to register. The other bony landmarks were more forgiving. Identification of the distal femoral epicondyles has a high inter-observer and intra-observer variability. Our observation that there is less than 2mm of safe zone in the anterior or posterior direction during registration of the medial and lateral epicondyles may explain the inability of CA-TKA to improve upon the outcomes of conventional TKA.

Kinematics of the Stiff Total Knee Arthroplasty

The kinematics of 10 total knee replacements with poor flexion (<90 degrees ) were compared with 11 replacements with good flexion (>110 degrees ) at a mean of 3 years from surgery using optical calibration with implant shape-matching techniques from radiographs taken in standing, early-lunge, and late-lunge positions. There were no significant differences between groups in anteroposterior translation of the medial and lateral femoral condyles or tibial rotation during standing and early lunge. Groups differed in amount of posterior translation of the femoral condyles during late lunge because of the poor-flexion groups inability to achieve the same amount of flexion as the good-flexion group. Poor flexion after total knee arthroplasty, we conclude, is not associated with abnormal kinematics in the setting of well-aligned, well-fixed implants.

Calculating the Position of the Joint Line of the Knee Using Anatomical Landmarks

Restoration of the joint line of the knee during primary and revision total knee arthroplasty is a step that directly influences patient outcomes. In revision total knee arthroplasty, necessary bony landmarks may be missing or obscured, so there remains a lack of consensus on how to accurately identify and restore the joint line of the knee. In this study, 50 magnetic resonance images of normal knees were analyzed to determine a quantitative relationship between the joint line of the knee and 6 bony landmarks: medial and lateral femoral epicondyles, medial and lateral femoral metaphyseal flares, tibial tubercle, and proximal tibio-fibular joint. Wide variability was found in the absolute distance from each landmark to the joint line of the knee, including significant differences between the sexes. Normalization of the absolute distances to femoral or tibial diameters revealed reliable spatial relationships to the joint line of the knee. The joint line was found to be equidistant from the lateral femoral epicondyle and the proximal tibio-fibular joint, representing a reproducible point of reference for joint line restoration. The authors propose a simple 3-step algorithm that can be used with magnetic resonance imaging, computed tomography, or radiography to reliably determine the anatomical location of the joint line of the knee relative to the surrounding bony anatomy. [Orthopedics. 2016; 39(6):381-386.].

Metal in total hip arthroplasty: Wear particles, biology, and diagnosis

Total hip arthroplasty (THA) has been performed for nearly 50 years. Between 2006 and 2012, more than 600,000 metal-on-metal THA procedures were performed in the United States. This article reviews the production of metal wear debris in a metal-on-metal articulation and the interaction of cobalt and chromium ions that ultimately led to a dramatic decline in the use of metal-on-metal THA articulations. Additionally, the article reviews mechanisms of metal wear, the biologic reaction to cobalt and chromium ions, the clinical presentation of failing metal-on-metal articulations, and current diagnostic strategies. Further, the article discusses the use of inflammatory markers, metal ion levels, radiographs, metal artifact reduction sequence magnetic resonance imaging, and ultrasound for failed metal-on-metal THA procedures. When adopting new technologies, orthopedic surgeons must weigh the potential increased benefits against the possibility of new mechanisms of failure. Metal-on-metal bearings are a prime example of the give and take between innovation and clinical results, especially in the setting of an already successful procedure such as THA. [Orthopedics. 2016; 39(6):371-379.].

Effects of fondaparinux on wound drainage after total hip and knee arthroplasty

Background The purpose of this investigation was to determine the effects of fondaparinux on postoperative wound drainage, length of hospital stay (LOS) and rate of surgical site infection in total joint patients. Methods 117 patients undergoing total joint arthroplasty treated with fondaparinux for venous thromboembolism (VTE) prophylaxis were prospectively studied. Results The average time to a dry wound was 3.4 days, with an average LOS of 3.77 days. Perioperative complications included 2 cases each of superficial cellulitis, deep vein thrombosis, and pulmonary embolism; there were no cases of deep infection. Multi-variate analysis showed increased patient BMI increased LOS (p = 0.0169). Conclusion Fondaparinux is an effective drug for VTE prophylaxis in total joint arthroplasty with wound drainage and LOS comparable to historical controls of enoxaparin, warfarin, and rivaroxaban.

Local bio-absorbable antibiotic delivery in calcium sulfate beads in hip and knee arthroplasty

Antibiotic-impregnated calcium sulfate (AICS) beads have been used for prevention and treatment of periprosthetic joint infections. We evaluated post-operative complications following the use of AICS beads. 56 patients undergoing complex primary or revision hip or knee arthroplasty received antibiotic calcium sulfate beads. Primary outcomes were wound complication rates. Secondary outcomes included reoperation and reinfection rates. One case (1.7%) of persistent wound drainage occurred requiring surgical irrigation and a poly-exchange. No post-operative infections were seen. Use of 100% pure calcium sulfate AICS beads may help reduce post-operative wound complications. AICS appears to be a safe adjunct tool in local antibiotic delivery.

Self-Resolution of a Draining Sinus Tract in a Patient with Chronic Periprosthetic Hip Infection

We report a novel case of a patient who had a draining sinus soon after a total hip arthroplasty that spontaneously resolved. The patient voluntarily discontinued antibiotic suppressive therapy (AST) after 10 years of treatment and paradoxically experienced full resolution of signs of chronic prosthetic joint infection (PJI), including recovery of his left-sided draining sinus tract. Now 8 years after discontinuing AST, the patient has no pain, good function, and no major or minor criteria of joint infection according to the Musculoskeletal Infection Society (MSIS) workgroup. The authors have not identified literature describing a similar resolution of draining sinus tracts from around a prosthetic joint after discontinuing AST. Despite the resolution of this patients sinus tract, the authors do not advocate for discontinuing AST in patients with a draining sinus tract. However, in spite of the fact that the MSIS consensus statement suggests that a draining sinus is a sure sign of PJI and that the assumption is that the infection will not go away until explant, this case was different.

Warfarin-induced skin necrosis after total knee arthroplasty: A case report

Skin and soft-tissue necrosis is a known, but rare, complication of warfarin administration. The diagnosis is usually guided by clinical suspicion, possible biopsy, and the exclusion of other diagnoses. The treatment is cessation of warfarin, local and/or surgical wound care, and medical therapy. Regardless of the treatment, the disease can lead to substantial morbidity or even death. We report the case of a patient who underwent total knee arthroplasty and developed tissue necrosis localized to the area of surgery. To the best of our knowledge, this complication previously has been reported only twice in the orthopaedic literature1,2. In these cases, the tissue necrosis occurred in multiple locations of the patient’s body. The patient was informed that data concerning the case would be submitted for publication, and he provided consent. An eighty-three-year-old man with multiple medical comorbidities, including atrial fibrillation, underwent a primary right total knee arthroplasty. A tourniquet was used only during the cementing portion. No drain was used. There were no perioperative complications. Preoperatively, the patient had been on chronic warfarin therapy for the atrial fibrillation, but the warfarin had been stopped for six days before the procedure. In the five months prior to stopping the warfarin, the international normalized ratio (INR) ranged from 1.7 to 2.1. After surgery, the patient was treated with enoxaparin while hospitalized, and warfarin therapy was resumed. On postoperative day three, the skin around the incision appeared slightly swollen and ecchymotic but was within normal expectations, and the patient was discharged home. On postoperative day four, the patient presented to the emergency room because of increased pain and inability to mobilize, and he was admitted to the hospital. The knee was swollen and mildly erythematous and had some new hemorrhagic blisters. On postoperative day five, blisters were noted on the …