Tracking forest phenology and seasonal physiology using digital repeat photography: a critical assessment.

Digital repeat photography is becoming widely used for near-surface remote sensing of vegetation. Canopy greenness, which has been used extensively for phenological applications, can be readily quantified from camera images. Important questions remain, however, as to whether the observed changes in canopy greenness are directly related to changes in leaf-level traits, changes in canopy structure, or some combination thereof. We investigated relationships between canopy greenness and various metrics of canopy structure and function, using five years (2008­2012) of automated digital imagery, ground observations of phenological transitions, leaf area index (LAI) measurements, and eddy covariance estimates of gross ecosystem photosynthesis from the Harvard Forest, a temperate deciduous forest in the northeastern United States. Additionally, we sampled canopy sunlit leaves on a weekly basis throughout the growing season of 2011. We measured physiological and morphological traits including leaf size, mass (wet/dry), nitrogen content, chlorophyll fluorescence, and spectral reflectance and characterized individual leaf color with flatbed scanner imagery. Our results show that observed spring and autumn phenological transition dates are well captured by information extracted from digital repeat photography. However, spring development of both LAI and the measured physiological and morphological traits are shown to lag behind spring increases in canopy greenness, which rises very quickly to its maximum value before leaves are even half their final size. Based on the hypothesis that changes in canopy greenness represent the aggregate effect of changes in both leaf-level properties (specifically, leaf color) and changes in canopy structure (specifically, LAI), we developed a two end-member mixing model. With just a single free parameter, the model was able to reproduce the observed seasonal trajectory of canopy greenness. This analysis shows that canopy greenness is relatively insensitive to changes in LAI at high LAI levels, which we further demonstrate by assessing the impact of an ice storm on both LAI and canopy greenness. Our study provides new insights into the mechanisms driving seasonal changes in canopy greenness retrieved from digital camera imagery. The nonlinear relationship between canopy greenness and canopy LAI has important implications both for phenological research applications and for assessing responses of vegetation to disturbances.

Function and quality of life following medial unicompartmental knee arthroplasty in patients 60 years of age or younger.

INTRODUCTION: UKA is an appropriate bone-sparing solution for focal advanced knee osteoarthritis in young patients. As the expectations of patients younger than 60 years of age are different from those in an older population, we aimed to evaluate quality of life and the quality of sports activity after UKA in this population. PATIENTS AND METHODS: Sixty-five UKAs in 62 patients younger than 60 (mean age: 54.7 years; mean BMI: 28 kg/m(2)) performed between 1989 and 2006 were included. At last follow-up (minimum 2 years), before the objective evaluation, patients were asked to fill in a KOOS questionnaire and a specific sports questionnaire including the UCLA score and questions from the Mohtadi score. RESULTS: With a mean follow-up of 11.2±5 years (range, 2-19 years), the KOOS score was higher than 75 points in 90% of the patients for the quality-of-life categories but also for the score's four other categories: 83.4% of the patients had resumed their sports activities and the mean UCLA score was 6.8 (range, 4-9); 90% of the patients reported no or slight limitation during sports activities. The function KSS improved from 52±4 to 95±3 points postoperatively and the Knee KSS from 50±4 to 94±4 points. With three patients undergoing revision for an isolated insert exchange, one for septic loosening and three for osteoarthritis in the external compartment, the 12-year Kaplan-Meier survivorship was 94%. DISCUSSION AND CONCLUSION: These results confirmed that UKA can provide good patient-rated outcomes, which is very important in this demanding population. As for TKA, wear remains a problem in this active population. LEVEL OF EVIDENCE: Therapeutic study, level IV.

Child pectus excavatum: correction by minimally invasive surgery.

INTRODUCTION: Pectus excavatum (PE) is a congenital deformity essentially responsible for an unattractive aspect, much more rarely for compression problems. The classical treatments consist either in filling the excavation or in open thoracic reconstruction (the Ravitch technique). Alternatively, the treatment described by Nuss raises the sternum with a retrosternal metallic bar placed under thoracoscopic guidance. We present the preliminary results of a series of 25 children operated on using this technique. HYPOTHESIS: The minimally invasive procedure described by Nuss is a valid surgical strategy to treat PE. MATERIALS AND METHODS: Twenty-five patients were operated on between February 2004 and April 2007 by the same surgeon. Nineteen of these patients presented a purely cosmetic indication. The six other patients were considered to have a more severe form of PE, with cardiorespiratory repercussions. In this group, there were two cases of Marfan syndrome and two patients presenting a history of previous cardiothoracic surgery. The technique has always consisted in placing a retrosternal bar through two lateral incisions. The surgery was always performed with right lung exclusion and was guided by thoracoscopy in 21 cases. In four particularly severe cases, a subxiphoid approach was required, making endoscopic guidance unnecessary. The severity of the lesion was evaluated by the Haller Index. All the patients had regular clinical follow-up (at three weeks, three months, and then every six months); assessment of pain, satisfaction with the cosmetic results, and perceived improvement in respiratory function were the criteria used for this follow-up. RESULTS: The cosmetic result was judged to be positive by 24 patients. One patient was dissatisfied (because of the asymmetrical shape resulting from the use of a single implant). Five patients presented minor complications with no repercussions on the cosmetic or functional result. One case of secondary bar displacement required revision on day 15. Following this revision evolution was uncomplicated (discharge on day 7 and activities resumed at three weeks). Finally, the hardware was removed at a delay after implantation ranging from one to two years. As of today, 13 patients have had their hardware removed with no complications or loss of the initial result. DISCUSSION: The original indication of the Nuss technique remains symmetrical PE in seven to 14-year-old children. The insubstantial scarring makes the technique valuable in the purely cosmetic forms of the condition. Based on this series, our technique has evolved toward certain adjustments depending on the severity and the etiology of the lesion. The most reported complication in the literature is secondary displacement of the bars. This problem is easily controlled by attaching the bar to a rib. Over the years, we have modified the implant design so as to improve its tolerance and stability. In asymmetrical forms of PE, implanting two bars has provided better efficacy. When a major form is present or when there is a history of cardiorespiratory problems, we recommend a short subxiphoid incision to release the pleural and pericardial adherences, precluding the need for thoracoscopic guidance. With these simple adjustments, this technique gains in reliability for cosmetic indications and its use can be extended to specific forms such as collagenosis or postoperative deformities. LEVEL OF EVIDENCE: Level IV. Therapeutic Study.