Investigation of Ionization Chamber Characteristics for Ultrahigh-dose-rate Scanned Carbon-ion Beams.

BACKGROUND/AIM: There are only a few studies on dosimetry with ultrahigh-dose-rate (uHDR) scanned carbon-ion beams. This study investigated the characteristics of four types of ionization chambers for the uHDR beam. MATERIALS AND METHODS: We employed a newly developed large-plane parallel chamber to monitor a 208.3-MeV/u uHDR scanned carbon-ion beam with a 110-Gy/s average dose rate. The ionization chambers used were the Advanced Markus chamber (AMC), PinPoint 3D chamber (PPC), Farmer chamber (FC), and large-plane parallel chamber (StingRay). The AMC and StingRay surfaces and the PPC and FC geometric centers were aligned to the radiation isocenter using treatment room lasers. Using the voltage range stated in the instruction manuals, we obtained the saturation curves of the chambers. From these curves, we obtained the ion recombination correction factors using the two-voltage and three-voltage linear methods. The dose linearity was evaluated using five measurement points, and the chamber repeatability was verified by conducting repeated measurements for different dose values. RESULTS: Although all chambers, except for AMC, reached saturation when specified voltages were applied, they exhibited excellent linearity for different dose values. The ion recombination correction factors of the AMC obtained using the aforementioned linear methods were nearly 1. Additionally, all chambers exhibited excellent repeatability. Although the standard deviation of the PPC for the lowest dose was ~1.5%, those of all the other chambers were <1.0%. CONCLUSION: All ionization chambers can be used for measuring the relative dose, and absolute dose can be conveniently measured using the AMC with an uHDR carbon-ion scanned beam.

Development and characterization of a dedicated dose monitor for ultrahigh-dose-rate scanned carbon-ion beams.

The current monochromatic beam mode (i.e., uHDR irradiation mode) of the scanned carbon-ion beam lacks a dedicated dose monitor, making the beam control challenging. We developed and characterized a dedicated dose monitor for uHDR-scanned carbon-ion beams. Furthermore, a simple measurable dose rate (dose rate per spot (DRspot)) was suggested by using the developed dose monitor and experimentally validating quantities relevant to the uHDR scanned carbon-ion beam. A large plane-parallel ionization chamber (IC) with a smaller electrode spacing was used to reduce uHDR recombination effects, and a dedicated operational amplifier was manufactured for the uHDR-scanned carbon-ion beam. The dose linearity of the IC was within ± 1% in the range of 1.8-12.3 Gy. The spatial inhomogeneity of the dose response of the IC was ± 0.38% inside the ± 40-mm detector area, and a systematic deviation of approximately 2% was measured at the edge of the detector. uHDR irradiation with beam scanning was tested and verified for different doses at the corresponding dose rates (in terms of both the average dose rate and DRspot). We confirmed that the dose monitor can highlight the characteristics (i.e., dose, dose rate, and dose profile) of uHDR-scanned carbon-ion beams at several dose levels in the monochromatic beam mode.

Validity of a preoperative scoring system for surgical management of periprosthetic hip infection: one-stage vs. two-stage revision.

INTRODUCTION: There are no widely accepted algorithms for determining optimal treatment for periprosthetic joint infection (PJI). Our study aimed to confirm the validity of a previously published scoring system in a larger number of patients to support a rational surgical treatment strategy for periprosthetic hip infection. MATERIALS AND METHODS: Between February 2001 and December 2020, we performed 155 consecutive revision total hip arthroplasties (THAs) for PJI, with mean follow-up of 6 years. One-stage revision THA was performed in 56 hips and two-stage revision THA in 99 hips. Prosthesis survival from recurrent infection was determined by Kaplan-Meier analysis, using implant removal as the endpoint. The pre-operative scoring system (full score of 12 points), including 6 essential elements, was retrospectively evaluated. RESULTS: The 10-year survival rates were 98% for one-stage (95% confidence interval [CI], 94-100) and 87% (95% CI, 79-96) for two-stage revision THA. Multivariate Cox regression analysis provided a total preoperative score as an independent risk factor for implant removal (hazard ratio, 0.17; 95% CI, 0.06-0.49; p < 0.001). The sensitivity and specificity at the cut-off of 4 points on the scoring system were 80% and 91%, respectively. The average score for one-stage revision THA in successful and failed cases were 8.9 and 6.0, and for two-stage revision THA were 6.5 and 3.9, respectively. We found significant differences between successful cases in one- and two-stage revision THA (p < 0.05). CONCLUSIONS: The preoperative scoring system was useful for managing PJI. One-stage revision THA is recommended in patients scoring ≥ 9 points, and meticulously performed two-stage revision THA is encouraged for patients scoring ≥ 4 points.

Can serum C-reactive protein determine the timing of reimplantation in two-stage revised arthroplasty for periprosthetic hip infection?

BACKGROUND: There are no definitive guides to determine the timing of reimplantation in two-stage revision total hip arthroplasties (THA) for periprosthetic joint infection (PJI). This study was to design to support a rational strategy of surgical treatment using serum C-reactive protein (CRP). METHODS: We analyzed a total of 75 hips for PJI in the process of performing two-stage and multiple-stage revision THAs. CRP level was retrospectively evaluated every week and transformed to log2 (CRP) using a logistic regression model. Prosthesis survival from recurrent infection was determined by Kaplan-Meier analysis, using implant removal as the endpoint. Receiver operating characteristic curves were calculated using each log2 (CRP) to assess predictions of recurrent infection. RESULTS: The 10-year survival rates were 85% (95% confidence interval, 76-95) and 100% for two-stage and multiple-stage revision THAs, respectively. Preoperatively, at 1, 2, 3, and 5 weeks, log2 (CRP) was not associated with recurrent infection. In failed two-stage revision THAs, log2 (CRP) at 3 weeks divided by that at 2 weeks showed a significant difference. Failure was associated with a ratio of >4.0 for the CRP level between 3 and 2 weeks. CONCLUSION: In two-stage revision THA for PJI, patients with CRP elevation from 2 weeks to 3 weeks, especially 4-fold elevation, suggests the need for further debridement and postponement of second-staged reimplantation.

Treatment strategies for recurrent dislocation following total hip arthroplasty: relationship between cause of dislocation and type of revision surgery.

BACKGROUND: There are many therapeutic options for dislocation following total hip arthroplasty (THA). The aim of this study was to evaluate the results of revision surgery for dislocated hips. METHODS: Between November 2001 and December 2020, 71 consecutive revision hip surgeries were performed at our institution for recurrent dislocation following THA. We conducted a retrospective study of all 65 patients (71 hips), who were followed for a mean of 4.7 ± 3.2 years (range, 1-14). The cohort included 48 women and 17 men, with a mean age of 71 ± 12.3 years (range, 34-92). The mean number of previous surgeries was 1.6 ± 1.1 (range, 1-5). From intraoperative findings, we created six categories of revision hip surgery for recurrent dislocation following THA: open reduction and internal fixation (2 hips); head change or liner change only (6 hips); cup change with increased head size only (14 hips); stem change only (7 hips); cup and stem change (24 hips); and conversion to constrained cup (18 hips). Prosthesis survival was analyzed by the Kaplan-Meier method, with repeat revision surgery for re-dislocation or implant failure as the endpoint. A cox proportional hazards model was used for risk factors of re-revision surgery. RESULTS: Re-dislocation occurred in 5 hips (7.0%) and implant failure in 1 hip (1.4%). The 10-year survival rate was 81.1% (95% confidence interval, 65.5-96.8). A Dorr classification of "positional" was a risk factor for re-revision surgery due to re-dislocation. CONCLUSION: Clear understanding of the cause of dislocation is essential for optimizing revision procedures and improving the rate of successful outcomes.

Endofemoral Shooting Technique for Removing Well-fixed Cementless Stems.

Background: The removal of a well-fixed cementless stem poses technical challenges. The aim of this study was to evaluate the outcomes of our endofemoral extraction technique established in 2001. Methods: Between January 2001 and December 2016, 118 consecutive revisions following bipolar or total hip arthroplasty, which required cementless femoral stem removal, were performed at our institution. This retrospective study evaluated 106 patients (108 hips) who were followed up for a mean of 9.2 years (range, 5-20 years). The patients included 15 men and 91 women with a mean age of 65 years (range, 33-87 years). Endofemoral extracted stem removal was performed as follows. Multiple Kirschner wires were sequentially inserted into the interface between the implant and cortical bone, after which the implant was detached using a thin chisel. After the cementless stem was removed, it was replaced with a cemented stem using an autograft, as needed. Radiological loosening of the femoral stem was defined as definite or probable loosening, based on the criteria of Harris et al. Prosthesis survival was analyzed using the Kaplan-Meier method, with the endpoint set as repeat revision surgery for stem loosening or femoral fracture. Results: Re-revision surgery was performed in 7 hips. Stem loosening was observed in 4 hips, and the mean subsidence was 0.3 mm (0-3 mm). The 10-year survival rate was 97.7% (95% confidence interval, 93.2-100). Conclusions: Our technique for removing well-fixed cementless stems yielded successful results.

Technical Obstacles for Low-Volume Surgeons in Primary Anterior Cruciate Ligament Reconstruction.

A longer surgical time will lead to postoperative complications in orthopaedic surgery. According to previous reports, surgeon volume affects a surgical time in anterior cruciate ligament (ACL) reconstruction. However, little attention has been paid to difference of a surgical time between high- and low-volume surgeons in ACL reconstruction. The purpose of the present study was to investigate the surgical time for both high- and low-volume surgeons and to clarify technical obstacles as well as the important technique to reduce the surgical time in ACL reconstruction. A total of 103 knees in 103 patients with ACL tear were enrolled. All the procedures were performed by 13 different surgeons. The surgeons were divided into two surgeon groups (high- and low-volume groups) based on the number of annual cases. The operative technique was divided into the same five steps to perform comparisons of step-by-step surgical time between the surgeon groups of different volumes. The statistical comparison was done between high- and low-volume groups in terms of surgical time in each step. Total operation times were 87.8 ± 17.6 and 129.9 ± 42.9 minutes in high- and low-volume group, respectively. Low-volume surgeons took much time in tendon harvesting and bone tunnel creation using arthroscopy. Low-volume surgeons took more time for primary ACL reconstruction, especially in tendon harvesting, compared with high-volume surgeons. Tendon harvesting was extremely important, as well as bone tunnel creation, for low-volume surgeons to reduce surgical time in primary ACL reconstruction.

Arthroscopic Treatment of Tibial Eminence Avulsion Fracture With Suture Tensioning Technique.

Although a tibial eminence avulsion fracture is a rare knee injury, it can result in some complications such as nonunion, limited range of motion, and anterior instability of the knee if the displaced fracture is not well reduced. Arthroscopic procedures for this fracture have been commonly performed in recent years. In patients with small fragments, a pullout operation is usually performed, but arthroscopic suture reduction is technically difficult. In addition, anterior instability of the knee may remain even if the fragment is well reduced at the time of the surgical procedure. Generally, surgeons are concerned about anatomic reduction compared with appropriate tensioning during surgery. Therefore, one of the key points to avoid remaining anterior instability of the knee is to obtain and maintain appropriate tensioning. The purpose of this article is to present an easy and safe technique for acquisition of appropriate tensioning using a tensioning device for tibial eminence avulsion fractures. Although it has limitations, this technique can facilitate the reduction of tibial eminence avulsion fractures and appropriate tensioning of the anterior cruciate ligament.

Self-flip Technique of the TightRope RT Button for Soft-Tissue Anterior Cruciate Ligament Reconstruction.

The TightRope RT (Arthrex, Naples, FL) is a suspensory device for anterior cruciate ligament reconstruction. However, there is a potential risk of the button being pulled too far off the lateral femoral cortex into the soft tissue because the adjustable loop is long. The purpose of this article is to present an easy and safe technique for self-flip. As to the preparation of the graft, we draw the first line in the loop of the TightRope RT at the same length as the femoral tunnel, and we draw the second line 7 mm longer than the length of the femoral tunnel as a self-flip line. Concerning passing of the graft, the side sutures are pulled from the lateral side. We stop pulling the sutures just at the self-flip line by holding the graft at the tibial end. The side suture is inclined to the medial side with strong pulling of the suture at full extension of the knee. Then the surgeon pulls the tibial end of the graft to feel a secure positioning of the button on the lateral femoral cortex. Although it has limitations, the present technique is easy and certainly helps surgeons achieve appropriate positioning of the button.

Stereospecific synthesis of cyclobutylboronates through copper(I)-catalyzed reaction of homoallylic sulfonates and a diboron derivative.

A copper(I)-catalyzed stereospecific reaction for the preparation of cis- and trans-1-silyl-2-borylcyclobutanes as well as 1-phenyl-2-borylcyclobutanes is reported. (Z)- and (E)-Homoallylic methanesulfonates were converted to the corresponding trans- and cis-cyclobutane derivatives, respectively, in the presence of a CuCl/dppp catalyst, bis(pinacolato)diboron, and K(O-t-Bu)/THF. Stereospecific derivatizations of the cis- and trans-borylcyclobutanes were carried out to demonstrate the utility of the borylcyclobutanes.

Cyclic straining of cell-seeded synthetic ligament scaffolds: development of apparatus and methodology.

Cyclic tensile strains acting along a ligament implant are known to stimulate cells that colonize it to proliferate and to synthesize an extracellular matrix (ECM), which will then remodel and form a new ligament structure. However, this process of tissue induction is poorly understood. As a first step toward elucidating this process, we aimed to investigate the effect of cyclic tensile strain on the proliferation of, and possible ECM synthesis by, cells colonizing ligament scaffolds. Because there was no commercially available apparatus to undertake such investigation the objectives of this study were to develop an apparatus for the application of cyclic tensile strains on cell-seeded synthetic ligament scaffolds and to develop and validate (through preliminary data obtained using the apparatus) methodology for studying the effect of cyclic strain on cell proliferation. We designed a multi-station test apparatus that operated inside an incubator. It allowed the application of tensile cyclic strains of between 0.5% and 5% at a frequency of 1 Hz on cell-seeded polyester ligament scaffolds immersed in culture medium. Test stations with windows in their bases could be easily de-coupled from the apparatus. This allowed monitoring of cell proliferation and morphology, with inverted light microscopy, through the transparent glass bases of the culture wells. Preliminary experiments lasting for 1 day or 9 weeks examined the effect of selected aspects of the cyclic strain on proliferation of cells seeded onto ligament scaffolds. Tests lasting for 1 day showed that the application of cyclic tensile strain of 5% for 4 h increased cell proliferation 24% above that observed in unstrained controls (p < .05). Scanning electron microscopy data from tests lasting for 9 weeks demonstrated further the dependency of cell proliferation and possible ECM synthesis on the magnitude of the strain. The larger the amplitude, the greater was the coverage of the scaffold with cells and ECM. Transmission electron microscopy of the ECM observed at 9 weeks showed evidence of collagen fibrils aligned in the direction of load in strained scaffolds, whereas the tissue on the control scaffolds was random.

Hydrostatic pressure modulates mRNA expressions for matrix proteins in human meniscal cells.

There have been few reports describing the effects of mechanical loading on the metabolism of meniscal cells. The aim of this study was to investigate the effects of hydrostatic pressure on meniscal cell metabolism. Human meniscal cells were cultured in alginate beads for 3 days. They were then subjected to 4 MPa hydrostatic pressure for 4 hours in either a static or cyclic (1 Hz) mode using a specially designed and constructed system. Immediately after the pressure application, the messenger RNA levels for aggrecan, type I collagen, matrix metalloproteinases (MMP) -1, -3, -9, -13 and tissue inhibitors of metalloproteinases (TIMP) -1 and -2 were measured. It was found that the application of static hydrostatic pressure caused a significant decrease in mRNA expression for MMP-1 and -13 (p<0.05). In contrast, the application of cyclic hydrostatic pressure was associated with a significant increase in type I collagen (p<0.01), TIMP-1 and -2 mRNA expression (p<0.01). These results would suggest that hydrostatic pressure in isolation can modulate mRNA expressions for matrix proteins in meniscal cells.

Clinical features of hematological disorders caused by copper deficiency during long-term enteral nutrition.

OBJECTIVE: Copper deficiency has been reported to cause hematological disorders. However, its clinical and hematological characteristics are not fully understood. Therefore, we investigated bedridden patients suffering from copper deficiency and tried to clarify the clinical features of hematological disorders caused by this condition. PATIENTS AND METHODS: Five patients with typical copper deficiency who had been dependent upon enteral nutrition for a long period of time due to various diseases were investigated. We measured hematological parameters and observed the response to copper supplementation therapy and the recovery process of hematological disorders. RESULTS: Their mean age was 82.6+/-10.4 years and the mean duration of enteral nutrition was 16.4+/-5.2 months. Their serum copper concentration was extremely decreased (range, 3 to 8 microg/dl). All five patients had anemia and neutropenia. On the other hand, platelet count remained within the normal range. After copper supplementation therapy, hemoglobin concentration increased from 6.8+/-0.7 g/dl to 9.9+/-0.7 g/dl within a few months (p<0.01). Neutrophil count also increased from 750+/-370/microl to 3,690+/-1,210/microl in a few weeks (p<0.01). Mean corpuscular volume (MCV) decreased from 94.3+/-7.3 fl to 86.0+/-4.8 fl (p<0.05). Elevated serum ferritin and erythropoietin (EPO) levels were normalized after the improvement of anemia. CONCLUSION: Bicytopenia (anemia and neutropenia) with normal platelet count is a feature of hematological disorders caused by copper deficiency. MCV tends to indicate macrocytic anemia. Serum ferritin and EPO levels are elevated. These hematological abnormalities are improved within a few months after copper supplementation therapy.

Hydrostatic pressure modulates proteoglycan metabolism in chondrocytes seeded in agarose.

OBJECTIVE: To investigate the effect of isolated hydrostatic pressure on proteoglycan metabolism in chondrocytes. METHODS: Bovine articular chondrocytes cultured in agarose gels were subjected to 5 MPa hydrostatic pressure for 4 hours in either a static or a pulsatile (1 Hz) mode, and changes in glycosaminoglycan (GAG) synthesis, hydrodynamic size, and aggregation properties of proteoglycans and aggrecan messenger RNA (mRNA) levels were determined. RESULTS: The application of 5 MPa static pressure caused a significant increase in GAG synthesis of 11% (P < 0.05). Column chromatography showed that this increase in GAG synthesis was associated with large proteoglycans. In addition, semiquantitative reverse transcriptase-polymerase chain reaction showed a 4-fold increase in levels of aggrecan mRNA (P < 0.01). CONCLUSION: Hydrostatic pressure in isolation, which does not cause cell deformation, can affect proteoglycan metabolism in chondrocytes cultured in agarose gels, indicating an important role of hydrostatic pressure in the regulation of extracellular matrix turnover in articular cartilage.

Heterotopic ossification after total knee arthroplasty.

The incidence of heterotopic ossification (HO) after total knee arthroplasty (TKA) and its effect on the postoperative range of motion (ROM) were assessed in 63 primary TKAs. Twenty-five of 63 knees (39%) showed postoperative HO, most of which were found in the region anterior to the distal femur. The incidence of HO was significantly higher (P <.05) in the osteoarthritic knees than in the rheumatoid knees. Significant positive correlation was seen between the preoperative grade of osteophyte formation and the incidence of postoperative HO. The ROM in the knees with HO was not significantly different than that in the knees without HO at 1 year after surgery. Thus, we concluded that HO after TKA is a self-limiting condition and its pathogenesis is completely different from that of myositis ossificance.

Upregulation of aggrecan and type II collagen mRNA expression in bovine chondrocytes by the application of hydrostatic pressure.

The aim of this study was to investigate the effect of hydrostatic pressure on the expression of messenger ribonucleic acid (mRNA) for specific extracellular matrix proteins in chondrocytes. Chondrocytes obtained from bovine metatarsophalangeal joints were embedded in cylindrical 2% agarose gels. A novel experimental system was used to apply 5 MPa of static hydrostatic pressure to these chondrocytes for 4 hours. The application of hydrostatic pressure caused a significant increase in the level of aggrecan mRNA by almost four fold (p<0.01) as well as a 50% increase in the level of type II collagen mRNA (p<0.05). However, there was no significant change in the level of TIMP-1 mRNA. It was suggested that the application of hydrostatic pressure, in the absence of cell deformation, can bring about changes in the matrix components which may play an important role in the homeostasis and mechanical properties of articular cartilage.