A high Q piezoelectric resonator as a portable VLF transmitter.

Very low frequency communication systems (3 kHz-30 kHz) enable applications not feasible at higher frequencies. However, the highest radiation efficiency antennas require size at the scale of the wavelength (here, >1 km), making portable transmitters extremely challenging. Facilitating transmitters at the 10 cm scale, we demonstrate an ultra-low loss lithium niobate piezoelectric electric dipole driven at acoustic resonance that radiates with greater than 300x higher efficiency compared to the previous state of the art at a comparable electrical size. A piezoelectric radiating element eliminates the need for large impedance matching networks as it self-resonates at the acoustic wavelength. Temporal modulation of this resonance demonstrates a device bandwidth greater than 83x beyond the conventional Bode-Fano limit, thus increasing the transmitter bitrate while still minimizing losses. These results will open new applications for portable, electrically small antennas.

Does the femoral offset affect replacements? The results from a National Joint Registry.

BACKGROUND: Femoral component offset influences the torque forces exerted on a femoral stem and may therefore adversely affect femoral component survival. This study investigated the influence of femoral component offset on revision rates for primary total hip replacements (THR) registered on the New Zealand Joint Registry (NZJR). METHODS: There were 106,139 primary THRs registered, resulting in 4960 revisions for any cause. There were 46,242 THRs performed using the five commonest femoral components listed on the NZJR. A total of 41,100 were done for primary osteoarthritis of which 40,548 had all the offset information available for analysis. We defined low offset as < 42 mm, standard as 42-48 mm and high offset as > 48 mm offset and examined revision rates according to the reasons for revision. We performed survival analyses for both cemented and uncemented femoral components grouped by the different offsets. RESULTS: The all-cause revision rate was 0.54/100 component years (cys). Stems with < 42 mm offset had a revision rate of 0.58/100 cys (mean 0.58; 95% confidence interval (CI) 0.53-0.63), 42-48 mm offset 0.47 (95% CI 0.43-0.52) and > 48 mm offset 0.67 (95% CI 0.57-0.79). There was no significant difference in all-cause revision rates between varying stem offsets in uncemented stems adjusting for age and gender. In cemented stems both high and low offset stems were more likely to be revised. Uncemented stems of all offsets were more likely to undergo revision for femoral fracture. CONCLUSIONS: Femoral component offset affects the overall all-cause revision rate of the most commonly used cemented stem, but not uncemented stem designs. In cemented stems offset influences the rate of revision for loosening and periprosthetic fractures.

Does overstuffing of the patellofemoral joint in total knee arthroplasty have a significant effect on postoperative outcomes?

BACKGROUND: There is ongoing debate in the literature as to whether or not patellofemoral joint overstuffing has a clinically significant effect on postoperative outcomes following total knee arthroplasty (TKA). This study investigates the effect of patellofemoral joint overstuffing on patient-reported outcomes using novel methods of radiographic measurement. METHODS: The study population consisted of a prospective cohort of 266 patients receiving a Triathlon® (Stryker, Kalamazoo, MI, USA) TKA between 2006 and 2009. Participants completed the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) questionnaire preoperatively and at 12 months postoperatively. Pre- and postoperative radiographic measurements were taken according to a defined protocol to assess for patellofemoral overstuffing. Measurement reproducibility was assessed using inter-observer intraclass correlation coefficients. Associations between radiographic measurements and patient-reported outcomes were analysed using linear regression analysis. RESULTS: A total of 107 patients had adequate images and were included in the analysis for this study. Three different radiographic measurements were used to identify patellofemoral overstuffing all with good intra- and inter-observer reliability. There was no association identified between combined (patella and trochlea) patellofemoral overstuffing measurements and WOMAC scores. However, a statistically significant association was identified between an increase in anterior trochlear offset and worse knee pain and function scores (P < 0.05). CONCLUSIONS: There is no identifiable association between true patellofemoral overstuffing and clinical outcome; however, there is a small association with the anterior trochlear offset though further studies are warranted to confirm the clinical significance of this finding.

The Use of Routine Postoperative Microscopy and Culture Screening Following Elective Hip and Knee Arthroplasty: An Unnecessary Cost With No Effect on Clinical Management?

BACKGROUND: The use of microscopy and culture screening to detect pathogenic microorganisms followed by a decolonization protocol is a widely performed practice prior to elective hip and knee arthroplasty. In our center, the routine care of hip and knee arthroplasty also involves postoperative screening including direct culture of the surgical site. The aim of this study was to assess the frequency of pathogen detection following these tests and to determine whether routine postoperative screening, with particular reference to postoperative surgical site culture, led to any change in clinical management of these patients. METHODS: A series of 1000 patients undergoing hip or knee arthroplasty at The Mater Hospital between January 2014 and December 2015 were identified from our arthroplasty database. Results of preoperative and postoperative microscopy and culture screening were reviewed by 2 independent researchers. RESULTS: Of the 1000 subjects, positive microscopy and culture results were identified in 88 patients (8.8%) preoperatively and 5 patients (0.5%) postoperatively. None of the 1000 postoperative surgical site swabs had a positive microscopy and culture screen. All the 5 positive postoperative microscopy and culture screen results were in patients who had positive cultures preoperatively. There were no positive postoperative microscopy and culture screen results in patients who had had negative preoperative results. Postoperative screening was performed at a cost of AUS$213 per patient. CONCLUSION: Routine postoperative surgical site culture following hip and knee arthroplasty does not alter clinical management, has a significant associated financial cost, and has the potential to expose the patient to a risk of surgical site infection and is therefore not supported.

Avulsion of the perforating branch of the peroneal artery secondary to an ankle sprain: a cause of acute compartment syndrome in the leg.

In this report, we describe the case of an adult male who developed an acute compartment syndrome localized to the anterior compartment of the leg following an ankle sprain. Compartment syndrome in association with ankle sprain is unusual, and has been previously described in association with avulsion of the perforating peroneal artery. Because of the potential for severe morbidity, we feel that it is important to make foot and ankle surgeons aware of this unusual injury.

Functional and oncological outcome following marginal excision of well-differentiated forearm liposarcoma with nerve involvement.

PURPOSE: Liposarcoma is one of the most common soft tissue sarcomas in adults. It is often low-grade and can occasionally involve neurovascular structures. We present the functional and oncological outcome resulting from planned marginal excision of a series of forearm low-grade liposarcomas with nerve involvement. METHODS: The Oxford tumor registry was used to identify cases of histologically proven, well-differentiated liposarcoma of the forearm, with nerve involvement, treated surgically between 1997 and 2006. Nerve involvement was identified clinically with symptoms or signs of nerve compression, or by images showing direct contact of the tumor with a nerve on magnetic resonance imaging. This was then further defined at the time of surgery as tumor abutting (capsular involvement) or encasing a peripheral nerve. Demographic and clinical data were collected and oncological outcome was assessed by noting local and distant recurrence during follow-up. Postoperative functional outcome was assessed using the Toronto Extremity Salvage Scores. RESULTS: Eight cases were identified, 6 with preoperative neurological symptoms. The total group comprised 6 men and 2 women with a mean age of 61 (range, 30-71) years. At surgery, all had their tumors successfully excised, with preservation of the involved nerves. In those with preoperative neurological symptoms, complete recovery occurred by 18 months after surgery. The average follow-up was 5 years (range, 3-9 y). There were no cases of either local or distant recurrence of disease, with a mean Toronto Extremity Salvage Score of 99%. CONCLUSIONS: Planned marginal excision of a well-differentiated liposarcoma, arising in the forearm and involving nerve, can result in excellent functional and oncological outcome. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic IV.