Dense point cloud acquisition with a low-cost Velodyne VLP-16

This study develops a low-cost terrestrial lidar system (TLS) for dense point cloud acquisition. Our system consists of a VLP-16 lidar scanner produced by Velodyne, which we have placed on a motorized rotating platform. This allows us to continuously change the direction and densify the scan. Axis correction is performed in post-processing to obtain accurate scans. The system has been compared indoors with a high-cost system, showing an average absolute difference of ±2.5 cm. Stability tests demonstrated an average distance of ±2 cm between repeated scans with our system. The system has been tested in abandoned mines with promising results. It has a very low price (approximately USD 4000) and opens the door to measuring risky sectors where instrument loss is high but information valuable.

Patellar Height Is Not Altered When the Knee Axis Correction Is Less than 15 Degrees and Has Good Short-Term Clinical Outcome

The objectives of our study were to evaluate (1) patellar height changes when the knee axis correction was < 15 degrees and (2) the clinical effect after open wedge high tibial osteotomy (OWHTO). Sixty-nine patients (69 knees) undergoing OWHTO between January 2016 and June 2017 were enrolled in this prospective study. All patients underwent OWHTO using a three-dimensional (3D)-printed patient-specific instrument. We used X-ray and lower-limb computed tomography scan to measure the osteotomy angle, patellar height, and other patellofemoral joint indices. We used the hospital for special surgery knee (HSS), Western Ontario and McMaster Universities Arthritis Index (WOMAC), and Kujala's scores to evaluate the clinical outcome. All knee axis corrections were less than 15 degrees. The change in posterior tibial slope (PTS) did not show a statistically significant difference. We observed that the patellar height was not altered when we used femur referenced measurement method. The change in modified Miura–Kawamura index (MKI) and Femoral patellar height index (FPHI) did not show a statistically significant difference. The differences in Blackburne–Peel index (BPI) and Caton–Deschamps index (CDI) were statistically significant, decreasing from 0.91 ± 0.12 and 1.06 ± 0.11 preoperatively to 0.79 ± 0.13 and 0.95 ± 0.11 postoperatively, respectively. In the axial plane, we did not observe a change in lateral patellar shift (LPS), but we found that lateral patellar tilt (LPT) showed a significant decrease from 8.67 ± 2.60 degrees preoperatively to 6.13 ± 2.30 postoperatively, respectively. The tuberositas tibae–trochlear groove (TT–TG) distance showed a significant decrease after OWHTO from 14.30 ± 4.10 mm preoperatively to 11.52 ± 3.63 mm postoperatively. The clinical score showed a significant increase after OWHTO, and all patients were satisfied with the outcome. After OWHTO, the patellar height was not altered when the knee axis correction was < 15 degrees. It was also found that there was still lateral displacement of the patella. Internal rotation of the distal tibia is an important cause of LPT reduction. After OWHTO, all patients achieved satisfactory clinical outcomes. At 1-year short-term follow-up, patients did not report discomfort in the patellofemoral joint. The Level of Evidence for this study was IV.

Vector Analysis of the Effects of FS-LASIK and Toric ICL for Moderate to High Astigmatism Correction

Purpose. To estimate the treatment effectiveness of femtosecond-assisted laser in situ keratomileusis (FS-LASIK) and Toric implantable collamer lens (Toric ICL) for moderate and high astigmatism via vector analysis.Materials and Methods. The study involved 44 eyes from 44 patients who had a preoperative refractive cylinder ≥1.0 diopters (D) and underwent bilateral FS-LASIK or Toric ICL surgery. The examinations included corrected distance visual acuity measurement and subjective refraction before and 3 months after surgery. The astigmatic changes were estimated using vector analysis.Results. No statistically significant differences were found in cylindrical refraction and percentage of spherical equivalent within 0 D, ±0.50 D, ±1.00 D, and ±1.50 D between the FS-LASIK and Toric ICL groups at 3 months after surgery. The parameters of the vector analysis included intended refractive correction, surgically induced refractive correction, error vector, correction ratio, error ratio, error of magnitude, and error of angle, with no significant differences between the groups. However, error ratio the of the off-axis correction in the FS-LASIK and Toric ICL groups was 4.11 ± 3.02 and 8.11 ± 3.82, respectively, and the difference was significant (t = −2.46,p=0.02).Conclusion. Both FS-LASIK and Toric ICL were effective for correcting moderate and high astigmatism, although Toric ICL might produce a larger error of angle than FS-LASIK when an off-axis correction occurs.

Influence of postoperative alignment on clinical outcome following medial open-wedge osteotomy for medial gonarthrosis in patients with underlying varus deformity

Aims and Objectives: High tibial osteotomy (HTO) has gained more and more importance in the treatment of cartilage damage of the medial compartment with concurrent varus deformity. Concerning the extent of axis correction, various different views exist. The aim of this study was to evaluate the effect of the degree of axis correction on the functional outcome in patients suffering from cartilage damage of the medial compartment and undergoing a valgus HTO. Materials and Methods: From January 2005 to December 2013 there were 156 patients suffering from cartilage damage of the medial compartment and an underlying varus deformity who were treated by a biplanar valgus HTO. According to the degree of axis correction - mirrored by the position of the intersection point of the weight bearing line and the tibial plateau - patients were allocated to different groups. For this purpose 3 adjacent areas respectively comprising 5% of the tibial plateau were defined. Limits of those areas were set as follows: with the medial border representing the 0%-point and the lateral border representing the 100%-point, the 3 areas were separated according to their intersection point (group 1 50-55%, group 2 55-60%, group 3 > 60%). For comparison of the functional outcomes, standardized measures and scores were used (pre-OP: VAS, Lysholm; post-OP: VAS, Lysholm, KOOS, IKDC). Analysis of the pre- and post-operatively recorded X-Rays was effected by means of a planning software (mediCAD\, Hectec GmbH, Germany), statistical analysis was carried out with the aid of SPSS Statistics 21.0 (IBM Corp., Armonk, USA.). A p-value of 0.05 was considered statistically significant. Results: 39 patients were allocated to group 1, 49 patients to group 2, 68 to group 3. Concerning mean follow up, age, gender, height, weight and pre-operative VAS there were no statistically significant differences (p>0,05). Thus, patients in each group were of a homogenous constitution. Regarding outcome parameters, group 1 showed significantly higher results. They reached statistical significance when comparing results of the Lysholm score (83,50±15,41 vs. 68,64±23,31 vs. 61,36±30,58), KOOSpain (89,93±9,62 vs. 77,15±15,37 vs. 74,24±21,05), KOOS (81,25±9,20 vs. 72,63±17,38 vs. 66,45± 19,29), KOOS4 (77,89±10,69 vs. 69,56±18,21 vs. 63,28±19,35) and VAS post-OP (1,88±1,73 vs. 2,36±0,92 vs. 3,45±2,84). A positive correlation between height and KOOSpain (Pearson correlation 0,181) KOOSadl (PC 0,239), KOOSsport (PC 0,213) and KOOS5 (0,196)was calculated . A negative correlation existed between age and Lysholm Post (PC -0,207), KOOSpain (PC 0,190), KOOSadl (PC -0,231) and KOOSges (PC -0,161) Conclusion: Valgus HTO of varus deformity in patients with concomitant cartilage damage of the medial compartment is highly efficient regarding functional outcome. Precise preoperative planning regarding individual factors in each patient is mandatory as correction to a neutral weight bearing axis or only mild overcorrection seem to be beneficial in comparison to larger correction angles.