Prepatellar Friction Syndrome: a common cause of knee pain in the elite cyclist.

BACKGROUND: Although anterior knee pain is extremely common in high-level road cyclists, the exact etiology still remains unclear. METHODS: A group of 28 professional male elite cyclists diagnosed with Prepatellar Friction Syndrome (PPFS) were retrospectively reviewed with specific attention for the typical history, clinical findings and treatment modalities. RESULTS: A traumatic onset of the complaints was reported by 10 athletes, while the complaints were caused by chronic overuse in the remaining 18 subjects. Conservative treatment delivered poor results and all cases were eventually treated surgically. Surgery confirmed macroscopic damage to at least one prepatellar fascial layer in all patients, after which partial fasciectomy was performed through a mini incision. CONCLUSION: PPFS is a new clinical entity of the triple-layered prepatellar fascial structures. Correct diagnosis is critical and based on the typical history and clinical findings. Partial prepatellar fasciectomy is the treatment of choice in order to regain the pre-injury performance level.

Characterized chondrocyte implantation in the patellofemoral joint: an up to 4-year follow-up of a prospective cohort of 38 patients.

BACKGROUND: Autologous chondrocyte implantation (ACI) is an accepted treatment option for selected condylar cartilage defects in the knee. Results for patellofemoral chondral defects have been less favorable. HYPOTHESIS: Autologous chondrocyte implantation with characterized chondrocytes will result in clinically relevant improvement in patellofemoral lesions. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: Patients with symptomatic patellofemoral full-thickness cartilage lesions were treated with ACI using characterized chondrocytes (ChondroCelect) covered with a collagen type I membrane. Clinical outcome was assessed using the Knee Injury and Osteoarthritis Outcome Score (KOOS) and a visual analog scale (VAS) for pain. Responders were defined using 5 categories (≥10 points and ≥20%, 30%, 50%, 70%) based on the KOOS and VAS. Treatment failure was defined as partial loosening of more than 20% of the graft with subsequent procedures to the subchondral bone. RESULTS: Thirty-eight patients, with a mean defect size of 4.89 cm(2) (range, 1.5-11 cm(2)), were treated for a patellar defect (n = 28), trochlear defect (n = 7), or a kissing lesion (trochlea and patella; n = 3). The minimum follow-up period was 24 months (mean, 37 months; range, 24-72 months). Treated patients showed statistically significant improvements in the KOOS (at 12, 18, 24, 36, and 48 months) and VAS (at the same time points) compared with pretreatment for each time point. Responder analysis identified approximately 84% of patients with a clinically relevant improvement greater than 10 points at 3 years. Treatment failure was observed in 5 patients. The most commonly reported adverse events were joint crepitation (n = 18) and arthrofibrosis (n = 7). No relationship could be found between clinical outcome and anatomic characteristics of the patellofemoral joint, lesion size and site, time since onset, or age. Nine patients required additional surgery: 6 because of persistent symptoms and 3 for hardware removal. CONCLUSION: Characterized chondrocyte implantation resulted in statistically significant and clinically relevant improvement over time. These results add to the evidence demonstrating that ACI is a valuable cartilage repair technique for patellofemoral lesions.

Wide tuning of silicon-on-insulator ring resonators with a liquid crystal cladding.

Wide electrical tuning of silicon-on-insulator ring resonators is demonstrated using a top cladding layer of nematic liquid crystals. A tuning range of 31 nm is demonstrated for ring resonators guiding the TM mode, covering nearly the entire C-band of optical communications. Ring resonators guiding the TE mode can be tuned over 4.5 nm. The combination of a liquid crystal director calculation and a fully anisotropic mode solver confirms the interpretation of these experimental results. The realization of broad and low-power tuning in silicon-on-insulator opens up new opportunities in the field of tunable lasers, filters, and detectors.

Vernier-cascade label-free biosensor with integrated arrayed waveguide grating for wavelength interrogation with low-cost broadband source.

Recently, cheap silicon-on-insulator label-free biosensors have been demonstrated that allow fast and accurate quantitative detection of biologically relevant molecules for applications in medical diagnostics and drug development. However, whereas the sensor chip can be made cheaply, an expensive tunable laser is typically required to accurately monitor spectral shifts in the sensor's transmission spectrum (wavelength interrogation). To address this issue, we integrated a very sensitive Vernier-cascade sensor with an arrayed waveguide grating spectral filter that divides the sensor's transmission spectrum in multiple wavelength channels and transmits them to spatially separated output ports, allowing wavelength interrogation with a much cheaper broadband light source. Experiments show that this sensor can monitor refractive index changes of watery solutions in real time with a detection limit (1.6·10(-5) RIU) competitive with more expensive interrogation schemes, indicating its applicability in low-cost label-free biosensing. The relaxation on the complexity of the source, moreover, offers the prospect to integrate the source and detectors to further reduce the device cost and to increase its portability.

Experimental characterization of a silicon photonic biosensor consisting of two cascaded ring resonators based on the Vernier-effect and introduction of a curve fitting method for an improved detection limit.

We studied a refractive index sensor that consists of two cascaded ring resonators and that works analogously to a Vernier-scale. We implemented it in silicon-on-insulator and experimentally determined its sensitivity to be as high as 2169 nm/RIU in aqueous environment. We derived formulas describing the sensor's operation, and introduced a fitting procedure that allows to accurately detect changes in the sensor response. We determined the detection limit of this first prototype to be 8.310(-6)RIU.