Long-Term Evaluation and Calibration of Low-Cost Particulate Matter (PM) Sensor.

Low-cost light scattering particulate matter (PM) sensors have been widely researched and deployed in order to overcome the limitations of low spatio-temporal resolution of government-operated beta attenuation monitor (BAM). However, the accuracy of low-cost sensors has been questioned, thus impeding their wide adoption in practice. To evaluate the accuracy of low-cost PM sensors in the field, a multi-sensor platform has been developed and co-located with BAM in Dongjak-gu, Seoul, Korea from 15 January 2019 to 4 September 2019. In this paper, a sample variation of low-cost sensors has been analyzed while using three commercial low-cost PM sensors. Influences on PM sensor by environmental conditions, such as humidity, temperature, and ambient light, have also been described. Based on this information, we developed a novel combined calibration algorithm, which selectively applies multiple calibration models and statistically reduces residuals, while using a prebuilt parameter lookup table where each cell records statistical parameters of each calibration model at current input parameters. As our proposed framework significantly improves the accuracy of the low-cost PM sensors (e.g., RMSE: 23.94 → 4.70 µ g/m 3 ) and increases the correlation (e.g., R 2 : 0.41 → 0.89), this calibration model can be transferred to all sensor nodes through the sensor network.

Anatomical reconstruction of the fourth brachymetatarsia with one-stage iliac bone and cartilage cap grafting.

BACKGROUND: We present a one-stage procedure for lengthening the fourth brachymetatarsia with autogenous iliac bone and cartilage cap grafting for the anatomical reconstruction of the metatarsophalangeal (MTP) joint METHODS: During the last 8 years, 56 feet in 41 patients with congenital brachymetatarsia of the fourth toe were corrected with a one-stage operation to reposition the articular cartilage cap to the distal part of interpositional iliac bone graft at the metatarsal epiphysis. RESULTS: The length of the harvested iliac bone graft was 22.9 mm on average. The mean fixation period was 58.5 days, and the mean gain in length and percentage increase was 20.9 mm and 39%, respectively. MRI showed a stable MTP joint over viable cartilage cap in 83.3% of the cases. Mean postoperative American Orthopedic Foot and Ankle Society lesser MTP-interphalangeal score was 82.0. Neither neurovascular impairment nor recurrence of brachymetatarsia occurred in the mean follow-up period of 43.6 months. All patients were satisfied with the postoperative cosmetic results. Thirteen patients (23.2%) complained of limited active dorsiflexion of the fourth toe, and extensor adhesion was released by extensor tenolysis in only one patient. In a single case of nonunion at the bone graft site, additional surgery was not necessary. CONCLUSIONS: Anatomical reconstruction of the fourth brachymetatarsia with one-stage interpositional iliac bone and cartilage cap grafting resulted in excellent cosmetic results and a physiologic MTP joint, providing the benefits of one-stage lengthening with a low complication rate. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, IV.

Hemicallotasis for correction of varus deformity of the proximal tibia using a unilateral external fixator.

BACKGROUND: Gradual correction of varus deformity of the proximal tibia is generally accepted and produces good results. However, most studies have used circular external fixators, which are complex and cause patient discomfort. This study was undertaken to determine the efficacy of hemicallotasis with a unilateral external fixator for correction of varus deformity of the proximal tibia. METHODS: Thirteen patients (21 legs, 8 bilateral) were included in this study: 6 with constitutional bowing, 3 with a malunion, 2 with Blount's disease, and 2 with Turner syndrome. There were 7 males and 6 females of mean age 21 years (range 13-40). With an oblique osteotomy on the proximal tibia, a unilateral external fixator was placed on the medial side. Using a distraction of 1 mm/day, the external fixator was removed after consolidation of the callus. RESULTS: Surgery corrected medial proximal tibia angle from a preoperative average of 75.1° (64°-81°) to 88.6° (86°-90°) at final follow-up. Average tibiofemoral angle improved from -7° to 6.8°. The duration of external fixation averaged 101.3 days and the external fixation index was 70 days/cm. No patient had a limited ambulation, and all recovered preoperative range of knee motion (mean 130.1°) at final follow-up. Seven minor complications (pin tract infection, clamp loosening) and 1 major complication (uncorrected genu procurvatum) were observed. CONCLUSIONS: Hemicallotasis using a unilateral external fixator was found to be a safe and simple corrective procedure for varus deformity of the proximal tibia, with few complications.

Malignant fibrous histiocytoma arising in the area of total hip replacement.

A patient developed a rapidly progressive and extensive periprosthetic osteolysis after a cemented total hip arthroplasty for postradiation necrosis of pelvic bone and femoral head. Malignant tumor is one of the causes of periprosthetic bone loss. The biopsy confirmed the malignant fibrous histiocytoma (MFH). However, majority of periprosthetic bone loss is due to wear debris induced osteolysis. Usually, wear debris induced periprosthetic osteolysis is developed later and the progression is much slower than there of malignant tumor. Also wear debris induced osteolysis is confirmed by chronic inflammation with macrophages containing wear particles. When there is a rapidly progressive and extensive osteolysis a prosthesis following hip replacement arthroplasty, the physician should suspect the possibility of malignant tumor.

Percutaneous plate stabilization of proximal tibial fractures.

BACKGROUND: Despite various treatment methods, proximal tibial fractures are common injuries associated with poor outcomes and high rates of complications. To improve this, a percutaneous plating technique was performed to treat proximal tibial fractures. METHODS: Twenty-four proximal tibial fractures (17 proximal fractures [AO 41] and 7 proximal shaft fractures [AO 42]) were treated using percutaneous plating with either or both sides without bone graft. One was an open fracture. RESULTS: All fractures healed. The average time for fracture healing was 16.5 weeks (range, 8-24 weeks). Complications included one case of shortening (1 cm) and two cases of malalignments; one valgus of 6 degrees and one varus of 5 degrees. There was one case of superficial infection that was healed after removal, but no patient showed deep infection. Results were evaluated by the modified Rasmussen scoring system. Most patients had excellent or good results; only one patient had fair results. CONCLUSION: Minimally invasive percutaneous plating can provide favorable results in the treatment of proximal tibial fractures.

Femoral lengthening over an intramedullary nail using the external fixator: risk of infection and knee problems in 22 patients with a follow-up of 2 years or more.

BACKGROUND: The time for femoral lengthening is shortened if external fixation is combined with intramedullary nailing. However, several complications have been reported with this procedure. PATIENTS AND METHODS: We retrospectively reviewed the outcome of femoral lengthening performed over an intramedullary nail using external fixation in 22 patients. These patients were followed for a mean of 3.2 (2-5.2) years. The mean age was 22 (13-35) years at the time of the index procedure. The mean lengthening was 5 (2.7-8.1) cm and the external fixator was removed after median 20 (8-30) weeks. The mean external fixation index was 24 (11-35) days/cm and the mean consolidation index was 43 (26-55) days/cm of lengthening. RESULTS: 3 patients who had a past history of infection or open trauma developed osteomyelitis which required removal of the nail. There were 4 knee joint complications when the lengthening was over 20%, including posterior knee subluxation and patella subluxation. In 1 patient, the lengthened segment collapsed with breakage of locking screws. INTERPRETATION: Although lengthening over a nail can reduce the duration of external fixation, caution is required to prevent major complications.

Minimally invasive percutaneous plating of distal femoral fractures using the dynamic condylar screw.

BACKGROUND: In distal femoral fractures, conventional open reduction and internal fixation causes complications because of excessive soft-tissue stripping. To prevent this, minimally invasive percutaneous plating was performed in distal femoral fractures. METHODS: Sixteen supracondylar or intercondylar femoral fractures were treated by minimally invasive percutaneous plating with the dynamic condylar screw without bone graft. Five (31%) were open fractures. RESULTS: All fractures healed except one. The average time for fracture healing was 17 weeks (range, 14-22 weeks). Complications included one nonunion related to early full weight bearing. No patient showed malunion or deep infection. Results were evaluated by modified Neer rating, and all patients had excellent or good results. Intra-articular fractures showed less favorable range of motion and clinical scores than extra-articular fractures. CONCLUSION: Minimally invasive percutaneous plating with the dynamic condylar screw can provide favorable results in the treatment of distal femoral fractures.

Treatment of femoral shaft fractures in young children: comparison between conservative treatment and retrograde flexible nailing.

Outcomes of pediatric femoral fractures treated with traction followed by cast (conservative treatment) were compared with flexible nailing treatment. Fifty-one femoral fractures (24 conservative, 27 nail) from 46 patients were studied retrospectively. Four cases of angular deformities greater than 10 degree were observed from the conservative treatment and none from the nailing group. Conservative treatment showed a wider variance of leg length discrepancy (LLD) and four cases showed severe LLD greater than 10 mm. The nailing group had no discrepancy. Retrograde flexible nailing may result in more reliable outcomes than conservative treatment for femoral fractures.

Injected calcium sulfate for consolidation of distraction osteogenesis in rabbit tibia.

This study investigated the effects of calcium sulfate powder injection in a rabbit tibial distraction model. There was one experimental group and two control groups. The calcium sulfate powder, suspended in carboxymethylcellulose (CMC) medium, was injected into the distracted tissue in the experimental rabbit group, whereas only CMC medium was injected into the one control group. The other control group did not undergo any intervention. On radiography and bone mineral density tests, the amount of newly formed bone was greater in the distracted zone of the experimental group than in the two control groups, which showed incomplete bone deposition and calcification. The application of calcium sulfate to distracted tissue increased the rate of osteogenesis and calcification.

Fourth brachymetatarsia treated with distraction osteogenesis.

BACKGROUND: This study investigated metatarsal lengthening by distraction osteogenesis for fourth brachymetatarsia in 22 metatarsals (16 patients). METHODS: From May 1997 to May 2000, lengthening was performed with a monoexternal fixator, and distraction was started at a rate of 0.5 mm per day after a latency period of approximately 7-10 days. RESULTS: The average gain in length was 16.5 mm (range, 13-21 mm), equivalent to an increase of 39% (range, 28-51%), and the average healing index was 72.9 days/cm (range, 51.7-95.7 days/cm). The American Orthopaedic Foot and Ankle Society (AOFAS) average score for lesser toe was 86.3 (range, 47-100). The most common residual complication was subluxation of metatarsophalangeal (MTP) joint in five cases, with partial or total stiffness of the MTP joint. These complications happened in the group of metatarsals excessively lengthened more than 40% and made the AOFAS score poorer. The other complications were three cases of angular deformity in the lengthened bone, and two cases of pin-tract infection. CONCLUSION: Although distraction osteogenesis is an effective method to address fourth brachymetatarsia, stiffness or subluxation of the MTP joint was not uncommon. To avoid complications that can happen as a result of excessive lengthening, careful preoperative radiographic measurement to calculate the optimal amount of lengthening may help us to avoid overlengthening and the complications that accompany it.

Percutaneous plating for unstable tibial fractures.

Twenty-four unstable tibial fractures were stabilized with a narrow limited contact-dynamic compression plate inserted using a percutaneous plating technique under fluoroscopic guidance. The major indication for this technique was a tibial fracture for which intramedullary nailing would be difficult. There were 16 proximal or distal metaphyseal fractures and 5 segmental fractures in adults and 3 mid-shaft fractures in adolescents who still had an open physis. Of the 24 fractures, 22 healed without a second procedure; the two failures included one that required an early bone graft for severe comminution and another with a superficial infection that healed after early removal of the plate. There were no other infections. There were three cases of screw breakage, but they did not require a further procedure. At the final follow-up, one patient had healed with 5 degrees varus alignment and another with 10 degrees external rotation. All the patients had good knee or ankle function. We are confident that the percutaneous plating technique to treat unstable tibial fractures for which intramedullary nailing would be difficult will prove to be an alternative stabilization method, as it avoids the risk of infection or soft tissue compromise.

Tendon-to-bone tunnel healing in a rabbit model: the effect of periosteum augmentation at the tendon-to-bone interface.

We examined whether periosteum enhances the healing process of a tendon in a bone tunnel and leads to better biomechanical fixation in a shorter period of time. The effect of the periosteum-wrapped tendon on tendon-to-bone healing was analyzed in 20 New Zealand white rabbits. The animals were divided into two groups, a periosteum-wrapped group and a control group. The two legs were operated on in the same manner. The long digital extensor tendon was harvested and transplanted into the proximal tibial tunnel. One limb was transplanted with the tendon wrapped with periosteum, while the other was without periosteum. The healed tendon-bone attachment was evaluated after 3 and 6 weeks by histological examination and biomechanical testing. At all time points histological examination demonstrated more extensive bone formation around the tendon with closer apposition of new bone to the tendon in the periosteum-wrapped limb than in the control limb. Biomechanical testing demonstrated higher tendon pullout strength in the periosteum-wrapped limb at all time points, with statistically significant differences between the periosteum-wrapped limb and the control limb after 3 and 6 weeks. Histological and biomechanical data suggest superior healing at the periosteum-wrapped side. These findings demonstrate that periosteum enhances the healing process when a tendon graft is transplanted into a bone tunnel.

Retrograde flexible intramedullary nailing in children's femoral fractures.

We treated 31 femoral shaft fractures in 28 children with a mean age of 6.7 (5-10) years with retrograde flexible intramedullary nailing. There were 16 isolated fractures, while 12 children had associated injuries. The average time for union was 10.5 weeks and there were no delayed unions. There was one broken nail requiring change of treatment, but no infection or refractures. At follow-up after a mean time lapse of 27 months there was no limb-length inequality exceeding 1 cm and no malunion. We feel that femoral fractures in patients aged 5-10 years can be safely treated with retrograde flexible intramedullary nailing with minimal risk of surgical complications.