High Failure Rates for Unicompartmental Knee Arthroplasty in Morbidly Obese Patients: A Two-Year Minimum Follow-Up Study.

BACKGROUND: Several recent studies have recommended offering unicompartmental knee arthroplasty (UKA) to all patients regardless of body mass index (BMI). The aim of this investigation was to evaluate the proposition that UKA can indeed be offered to the morbidly-obese and super-obese (morbidly-obese, BMI ≥ 40 kg/m2) without compromising results or survivorship. METHODS: We retrospectively reviewed mobile-bearing medial UKA procedures performed at our facility from January 2012 to May 2015 with a minimum of 2-year follow-up. The study cohort was divided into patients with morbid obesity (BMI ≥ 40 kg/m2) and those without morbid obesity (BMI < 40 kg/m2). A detailed medical record review was performed. Extracted outcome data included the frequency of (1) major revision procedures (components revised), (2) minor secondary procedures (components not revised), (3) infection procedures, and (4) recommendations for revision. RESULTS: We found 152 patients (190 knees) who met criteria for inclusion. Mean follow-up duration was 3.4 years (range: 2.0-6.8 years). Major revision surgery occurred more frequently in the morbid-obesity UKA group (15.7% vs 3.0%, P < .01). Rates of minor secondary surgery and infection were comparable for both groups. Most failures in the morbid-obesity UKA group (85.7%) were due to disease progression involving other compartments or mobile-bearing instability. CONCLUSION: We found the rate of early major revision surgery in morbidly-obese patients undergoing UKA to be over 5-times greater than that of other patients. Failure was predominantly due to disease progression in other compartments or mobile-bearing instability. Further study is warranted and needed before expanding UKA indications to the morbidly-obese population.

Dual-Agent Antibiotic Prophylaxis Using a Single Preoperative Vancomycin Dose Effectively Reduces Prosthetic Joint Infection Rates With Minimal Renal Toxicity Risk.

BACKGROUND: We performed this study to compare prosthetic joint infection (PJI) and renal toxicity rates following hip and knee total joint arthroplasty (TJA) when a first-generation cephalosporin was administered either alone or in combination with a single preoperative vancomycin dose, whether vancomycin administration timing potentially influenced dual-antibiotic PJI prophylaxis approach effectiveness, and whether single-dose vancomycin use increased risk of renal impairment. METHODS: This was a retrospective study of 1997 consecutive primary TJAs (1871 patients) treated with cefazolin alone (1044 TJAs) or cefazolin with single-dose vancomycin (953 TJAs). The vancomycin group included 476 TJAs (450 patients) with infusion started at least 45 minutes before the skin incision and 477 TJAs (464 patients) with infusion started less than 45 minutes before the skin incision. RESULTS: The addition of a single dose of vancomycin did not significantly reduce PJI rates when compared with cefazolin alone (1.6% vs 2.1%, P = .32). However, the PJI rate was significantly lower following primary TJA when vancomycin administration was initiated at least 45 minutes before incision (0.2%) when compared with other TJA procedures performed using cefazolin and vancomycin (2.9%, P < .01) or cefazolin alone (2.1%, P < .01). We observed no difference in renal toxicity between treatment groups. CONCLUSION: In our institution, the addition of vancomycin to cefazolin at least 45 minutes before incision reduced PJI infection rates in primary hip and knee TJA with a low risk of renal impairment.

Correlation between radiographic measures of acetabular morphology with 3D femoral head coverage in patients with acetabular retroversion.

BACKGROUND AND PURPOSE: Acetabular retroversion may result in anterior acetabular over-coverage and posterior deficiency. It is unclear how standard radiographic measures of retroversion relate to measurements from 3D models, generated from volumetric CT data. We sought to: (1) compare 2D radiographic measurements between patients with acetabular retroversion and normal control subjects, (2) compare 3D measurements of total and regional femoral head coverage between patients and controls, and (3) quantify relationships between radiographic measurements of acetabular retroversion to total and regional coverage of the femoral head. PATIENTS AND METHODS: For 16 patients and 18 controls we measured the extrusion index, crossover ratio, acetabular angle, acetabular index, lateral center edge angle, and a new measurement termed the "posterior wall distance". 3D femoral coverage was determined from volumetric CT data using objectively defined acetabular rim projections, head-neck junctions, and 4 anatomic regions. For radiographic measurements, intra-observer and inter-observer reliabilities were evaluated and associations between 2D radiographic and 3D model-based measures were determined. RESULTS: Compared to control subjects, patients with acetabular retroversion had a negative posterior wall distance, increased extrusion index, and smaller lateral center edge angle. Differences in the acetabular index between groups approached statistical significance. The acetabular angle was similar between groups. Acetabular retroversion was associated with a slight but statistically significant increase in anterior acetabular coverage, especially in the anterolateral region. Retroverted hips had substantially less posterior coverage, especially in the posterolateral region. INTERPRETATION: We found that a number of 2D radiographic measures of acetabular morphology were correlated with 3D model-based measures of total and regional femoral head coverage. These correlations may be used to assist in the diagnosis of retroversion and for preoperative planning.

Total knee arthroplasty in osteopetrosis using patient-specific instrumentation.

Osteopetrosis is an uncommon endocrine disease characterized by defective osteoclast resorption of bones. This causes a hard, sclerotic, and brittle bone throughout the skeleton. Fractures and unforgiving subchondral bone are common in this condition, both of which can lead to osteoarthritis. Total knee arthroplasty is often the treatment of choice but presents challenges due to the hard and sclerotic bone present throughout the metaphysis and diaphysis of the femur and the tibia. We present a case of knee osteoarthritis in a patient with osteopetrosis who underwent total knee arthroplasty using patient-specific instrumentation. This technique eliminates intramedullary alignment and minimizes drilling, reaming, and saw passes, making it attractive in the setting of diseases such as osteopetrosis to decrease operative time and potential complications.

The Rottinger approach for total hip arthroplasty: technique and review of the literature.

The surgical approach utilized in total hip arthroplasty has been identified as a factor that may affect surgical outcomes. There have been many different approaches and modifications used since the procedure was popularized by Sir John Charnley. The popular approaches today can be grouped by their relationship to the trochanter (anterior or posterior), patient position, leg position for dislocation/femoral preparation, and treatment of the abductors and short external rotators. The Rottinger approach is an anterior approach which utilizes the muscle interval between the tensor fascia lata and abductor musculature. The abductor attachments are preserved and the femur is prepared in extension, adduction, and external rotation. This approach has been shown in literature to be safe with some studies showing improved outcomes both in terms of reduced complications and better function than other standard approaches.

Piezoelectric-nanowire-enabled power source for driving wireless microelectronics.

Harvesting energy from irregular/random mechanical actions in variable and uncontrollable environments is an effective approach for powering wireless mobile electronics to meet a wide range of applications in our daily life. Piezoelectric nanowires are robust and can be stimulated by tiny physical motions/disturbances over a range of frequencies. Here, we demonstrate the first chemical epitaxial growth of PbZr(x)Ti(1-x)O(3) (PZT) nanowire arrays at 230 °C and their application as high-output energy converters. The nanogenerators fabricated using a single array of PZT nanowires produce a peak output voltage of ~0.7 V, current density of 4 µA cm(-2) and an average power density of 2.8 mW cm(-3). The alternating current output of the nanogenerator is rectified, and the harvested energy is stored and later used to light up a commercial laser diode. This work demonstrates the feasibility of using nanogenerators for powering mobile and even personal microelectronics.

Hybrid nanogenerator for concurrently harvesting biomechanical and biochemical energy.

Harvesting energy from multiple sources available in our personal and daily environments is highly desirable, not only for powering personal electronics, but also for future implantable sensor-transmitter devices for biomedical and healthcare applications. Here we present a hybrid energy scavenging device for potential in vivo applications. The hybrid device consists of a piezoelectric poly(vinylidene fluoride) nanofiber nanogenerator for harvesting mechanical energy, such as from breathing or from the beat of a heart, and a flexible enzymatic biofuel cell for harvesting the biochemical (glucose/O2) energy in biofluid, which are two types of energy available in vivo. The two energy harvesting approaches can work simultaneously or individually, thereby boosting output and lifetime. Using the hybrid device, we demonstrate a "self-powered" nanosystem by powering a ZnO nanowire UV light sensor.