Early to midterm results of "low-friction" articulating antibiotic spacers for septic total knee arthroplasty.

BACKGROUND: Infection of total knee arthroplasty is a complex problem often resulting in multiple surgeries for the patient. We examined the early to midterm results of a retained cemented "low-friction" metal-on-polyethylene articulating antibiotic spacer in total knee arthroplasty. METHODS: We retrospectively reviewed patients with a total knee cemented articulating antibiotic spacer performed for joint sepsis. Patients were allowed full weight bearing and normal activities after eradication of the infection at 6 weeks postop. Two months later, patients were given the option of conversion to a revision implant vs retention of the spacer. We examined infection cure rate, mechanical failure, Knee Society Scores, range of motion, and patient factors associated with spacer retention. RESULTS: Fifty-five knees were studied with average follow-up of 1.8 years (0.2-8.4). Among patients choosing spacer retention (40%), the average follow-up time of the spacer was 3.3 years (0.6-8.4). Five patients (9.1%) required a repeat spacer for recurrent infection. CONCLUSIONS: Usage of articulating cement antibiotic spacers with a metal-on-polyethylene bearing couple provides excellent infection eradication, while also resulting in good functional outcomes. Early evidence suggests that use of the implant can be extended beyond typical timeframes and, in certain patient populations, may be suitable for a single-stage procedure.

Squeaking in third- and fourth-generation ceramic-on-ceramic total hip arthroplasty: meta-analysis and systematic review.

Postoperative squeaking in ceramic-on-ceramic total hip arthroplasty is a recently emerging phenomenon. We performed a meta-analysis of published data to examine patient and procedural risk factors. Twelve studies (6137 patients, total) were analyzed, with 150 patients (2.4%) complaining of squeaking. The only significant patient risk factor was increasing body mass index (P = .03, n = 2957). There was no significance found with patient age, sex, height, weight, or procedural laterality for squeak incidence. For implant type, the presence of a Stryker Accolade femoral stem (beta-titanium; Stryker Orthopedics, Mahwah, NJ) was significantly found to increase squeak (P < .0001, n = 4654). The presence of a raised metallic lip on the acetabular component was not found to be associated with squeak. Acetabular cup position was also not found to have a significant bearing on the incidence of squeaking.

Catastrophic polyethylene failure diagnosed with magnetic resonance imaging in a painful total knee arthroplasty.

Determining the etiology of a painful knee after arthroplasty can be extremely challenging. Traditionally, orthopedists relied mainly on physical examination, laboratory results, serial radiographs, and 3-phase bone or indium-labeled white blood cell scans; however, recent advances in magnetic resonance imaging (MRI) software have given orthopedists another powerful tool in their diagnostic armamentarium. We provide the MRI software modification technique for metallic artifact reduction as well as present a novel case in which MRI was used to diagnose catastrophic polyethylene postfailure in a posterior cruciate ligament substituting knee. Although the role for MRI in the postarthroplasty knee has yet to be clearly defined, its utility in working up a painful arthroplasty when history, physical examination, and other diagnostic utilities fail to provide answers is clearly demonstrated in this case.

Use of the Gartland classification system for treatment of pediatric supracondylar humerus fractures.

The extension-type pediatric supracondylar humerus fracture accounts for nearly two-thirds of all pediatric hospitalizations due to elbow trauma. The Gartland classification guides the standard of care for treatment of this entity. Type I injuries are treated with cast immobilization while type II and III injuries are treated operatively. The reported interobserver reliability ranges from moderate to full agreement, which is on par with other frequently referenced classification systems such as Lauge-Hansen for adult ankle fractures. In this study, 4 fellowship-trained pediatric orthopedic surgeons reviewed radiographs of 72 pediatric supracondylar fractures and classified them based on Gartland's system. They recommended their preferred treatment of cast immobilization for type I fractures and of closed reduction and pinning in the operating room for type II and type III fractures. The interobserver and intraobserver reliability for each set of radiographs was then analyzed. There was moderate agreement comparing all fractures and comparing types I and II fractures, while there was full agreement for type III fractures. There was full agreement for the intraobserver reliability. The preferred treatment (casting vs operative intervention) differed in 35% of patients, if based on the fracture classification.

Posterior thigh compartment syndrome as a result of a basketball injury.

Acute compartment syndrome of the thigh is a serious although rare occurrence that was sparsely documented in the orthopedic literature until Schwartz et al reported on a series of 21 cases. Although classically associated with high-energy femur fracture, thigh contusion, or the use of military anti-shock trousers, compartment syndrome of the thigh has recently been diagnosed in seemingly low-energy injuries. A complete hamstring avulsion from its ischial origin during routine ambulation and rupture of the quadriceps tendon after a low-energy fall have been shown to result in compartment syndrome. In light of the potential medicolegal ramifications surrounding the diagnosis of compartment syndrome, emergency room consultations to rule out compartment syndrome are on the rise. Specifically, the time to fasciotomy was found to be linearly related to indemnity payment, and a fasciotomy performed within 8 hours was uniformly associated with a successful defense. This article describes a case of a 29-year-old healthy man who developed posterior thigh compartment syndrome as a result of an intrasubstance tear of the biceps femoris muscle sustained while attempting a lay-up during a recreational basketball game. His posterior thigh compartment pressure measured 70 mm Hg and he required emergent posterior thigh compartment fasciotomy.

Characterization of the inhibitory effects of erythromycin and clarithromycin on the HERG potassium channel.

Both erythromycin and clarithromycin have been reported to cause QT prolongation and the cardiac arrhythmia torsade de pointes in humans, however direct evidence documenting that these drugs produce this effect by blocking human cardiac ion channels is lacking. The goal of this study was to test the hypothesis that these macrolide antibiotics significantly block the delayed rectifier current (IKr) encoded by HERG (the human ether-a-go-go-related gene) at drug concentrations, temperature and ionic conditions mimicking those occurring in human subjects. Potassium currents in HEK 293 cells stably transfected with HERG were recorded using a whole cell voltage clamp method. Exposure of cells to erythromycin reduced the HERG encoded potassium current in a concentration dependent manner with an IC50 of 38.9 +/- 1.2 microM and Hill Slope factor of 0.4 +/- 0.1. Clarithromycin produced a similar concentration-dependent block with an IC50 of 45.7 +/- 1.1 microM and Hill Slope factor of 1.0 +/- 0.1. Erythromycin (25-250 microM) and clarithromycin (5 or 25 microM) also produced a significant decrease in the integral of the current evoked by an action potential shaped voltage clamp protocol. The results of this study document that both erythromycin and clarithromycin significantly inhibit the HERG potassium current at clinically relevant concentrations.