Volumetry of simulated bone grafts in the edentulous maxilla by computed tomography: an experimental study.

OBJECTIVE: To determine the precision of CT for calculating the volume of bone grafts to the maxilla. METHODS: Plaster of Paris was used to simulate bone as onlay and inlay grafts to the maxillary alveolus and sinus in a dry skull. Two mm thick axial CT scans were obtained. The area of the graft on each slice was measured and volumes calculated according to the formula V(graft)=Sigma of areas x the thickness of each section. Scans were repeated with the skull at approximately +5 degrees and -5 degrees to the horizontal plane and the calculations repeated. The real volume was calculated by the displaced water technique. Precision was estimated as reliability coefficient. RESULTS: The reliability coefficients for the right and left inlay and the onlay grafts were 0.97, 0.6 and 0.96 respectively. CONCLUSION: Calculations of the volume of both inlay and onlay grafts to the maxilla from axial CT is precise.     

MRI for the display of autologous onlay bone grafts during early healing—an experimental study

Objectives:Autologous bone grafts are the gold standard to augment deficient alveolar bone. Dimensional graft alterations during healing are not known as they are not accessible to radiography. Therefore, MRI was used to display autologous onlay bone grafts in vivo during early healing.Methods and materials:Ten patients with alveolar bone atrophy and autologous onlay grafts were included. MRI was performed with a clinical MR system and an intraoral coil preoperatively (t0), 1 week (t1), 6 weeks (t2) and 12 weeks (t3) postoperatively, respectively. The graft volumes were assessed in MRI by manual segmentation by three examiners. Graft volumes for each time point were calculated and dimensional alteration was documented. Cortical and cancellous proportions of bone grafts were assessed. The intraobserver and interobserver variability were calculated. Statistical analysis was performed using a mixed linear regression model.Results:Autologous onlay bone grafts with cortical and cancellous properties were displayed in vivo in eight patients over 12 weeks. The fixation screws were visible as signal voids with a thin hyperintense fringe. The calculated volumes were between 0.12–0.74 cm³ (t1), 0.15–0.73 cm³ (t2), and 0.17–0.64 cm³ (t3). Median changes of bone graft volumes of −15% were observed. There was no significant difference between the examiners (p = 0.3).Conclusions:MRI is eligible for the display and longitudinal observation of autologous onlay bone grafts. Image artifacts caused measurements deviations in some cases and minimized the precise assessment of graft volume. To the knowledge of the authors, this is the first study that used MRI for the longitudinal observation of autologous onlay bone grafts.     

A biomechanical comparison of posterior cruciate ligament reconstruction techniques

Most posterior cruciate ligament reconstruction techniques use both tibial and femoral bone tunnels for graft placement. Because of the acute angle the graft must make to gain entrance into the tibial tunnel, abnormal stresses are placed on the graft that could lead to graft failure. An alternative technique for posterior cruciate ligament reconstruction involves placement of the bone plug from the graft anatomically on the back of the tibia (inlay), preventing formation of an acute angle at the tibial attachment site. We used six pairs of human cadaver knees to compare the biomechanical properties of these two techniques. One knee from each pair underwent tunnel reconstruction while the other knee underwent inlay reconstruction. There was significantly less anterior-posterior laxity in the inlay group when compared with the tunnel group from 30 degrees to 90 degrees of knee flexion and after repetitive loading at 90 degrees of knee flexion. Evaluation of the grafts revealed evidence of mechanical degradation in the tunnel group but not in the inlay group. The inlay technique resulted in less posterior translation with less graft degradation than did the tunnel technique for posterior cruciate ligament reconstruction.     

Spatial and temporal registration of CT and SPECT images: development and validation of a technique for in vivo three-dimensional semiquantitative analysis of bone.

The combined use of postoperative 3-dimensional CT and SPECT imaging provides a means of relating anatomy and physiology for the semiquantitative in vivo analysis of bone. This study focuses on the development and validation of a technique that accomplishes this through the registration of SPECT data to a 3-dimensional volume of interest (VOI) interactively defined on CT images. METHODS: Five human cadaver heads served as anthropomorphic models for all experiments. Four cranial defects were created in each specimen with inlay and onlay split-skull bone grafts reconstructed to skull and malar recipient sites. To acquire all images, each specimen was landmarked with 1.6-mm ball bearings and CT scanned. Bone surfaces were coated with 99mTc-doped paint. The locations of the ball bearings were marked with paint doped with 111In. Separate SPECT scans were acquired using the energy windows of 99mTc and 111In. RESULTS: Serial SPECT images aligned with an average root-mean-square (RMS) error of 3.8 mm (i.e., <1 pixel). CT-to-SPECT volume matching aligned with an RMS error of 7.8 mm. Total counts in CT-defined VOIs applied to SPECT data showed a strong linear correlation (r2 = 0.86) with true counts obtained from a dose calibrator. CONCLUSION: The capability of this multimodality registration technique to anatomically localize and quantify radiotracer uptake is sufficiently accurate to warrant further assessment in an in vivo trial.     

A matched-pair comparison of inlay and onlay trochlear designs for patellofemoral arthroplasty: no differences in clinical outcome but less progression of osteoarthritis with inlay designs

Purpose

To compare clinical and radiographic results after isolated patellofemoral arthroplasty (PFA) using either a second-generation inlay or onlay trochlear design. The hypothesis was that an inlay design will produce better clinical results and less progression of tibiofemoral osteoarthritis (OA) compared to an onlay design.

Methods

Fifteen consecutive patients undergoing isolated PFA with an onlay design trochlear component (Journey? PFJ, Smith & Nephew) were matched with 15 patients after isolated PFA with an inlay design trochlear component (HemiCAP^® Wave, Arthrosurface). Matching criteria were age, gender, body mass index, and follow-up period. An independent observer evaluated patients prospectively, whereas data were compared retrospectively. Clinical outcome was assessed using WOMAC, Lysholm score, and pain VAS. Kellgren–Lawrence grading was used to assess progression of tibiofemoral OA.

Results

Conversion to total knee arthroplasty was necessary in one patient within each group, leaving 14 patients per group for final evaluation. The mean follow-up was 26 months in the inlay group and 25 months in the onlay group (n.s.). Both groups displayed significant improvements of all clinical scores (p < 0.05). No significant differences were found between the two groups with regard to the clinical outcome and reoperation rate. No significant progression of tibiofemoral OA was observed in the inlay group, whereas 53 % of the onlay group showed progression of medial and/or lateral tibiofemoral OA (p = 0.009).

Conclusion

Isolated PFA using either a second-generation inlay or onlay trochlear component significantly improves functional outcome scores and pain. The theoretical advantages of an inlay design did not result in better clinical outcome scores; however, progression of tibiofemoral OA was significantly less common in patients with an inlay trochlear component. This implant design may therefore improve long-term results and survival rates after isolated PFA.

Level of evidence

III.

     

Lateral cephalometric radiograph for the planning of maxillary implant reconstruction

OBJECTIVE: To present a simple and objective method for the planning of maxillary implant reconstruction with autogenous bone graft in maxilla atrophy. METHODS: Lateral cephalometric radiographs were performed with a metallic marker placed inside an acrylic-coated model, followed by cephalometric studies, to predict the most adequate grafting method for maxillary reconstruction in 13 edentulous patients (2 males and 11 females) whose age ranged from 27 to 47 years (mean age 37.9 years). RESULTS: It was possible to predict the type of maxillary reconstruction in all patients. Onlay graft was used in 12 patients. One patient was submitted to LeFort I reconstruction with interpositional graft. After 8 months, the patients received a total of 95 standard implants. The success rate was 94.7% with loss of five implants. Rehabilitation was performed with protocol-type prostheses. All patients have been followed for more than 18 months since osseointegration. CONCLUSIONS: This simple and objective method provided a useful contribution to maxillary reconstruction, and to the functional and aesthetic rehabilitation of the patients.     

Age-related expansion and reduction in aeration of the sphenoid sinus: volume assessment by helical CT scanning

BACKGROUND AND PURPOSE: Aeration of the sphenoid sinus expands with the development of the sphenoid bone, but scant detailed volumetric data regarding this process, as it evolves from childhood to old age, exist. Using helical CT scanning, we assessed age-related volumetric changes of the sphenoid sinus. METHODS: We used CT data obtained from 214 patients (age range, 1 to 80 years; 111 male and 103 female subjects) with middle or inner ear disease to assess the extent of sphenoid aeration. We also determined volumes of the sphenoid sinuses on 1.0- or 1.5-mm reformatted images by integrating the sinus air (< or = -900 HU) area. RESULTS: Sphenoid sinus aeration began as a doublet in the anterior boundary of the sphenoid bone by the age of 5 years, with patients more than 6 years old exhibiting varying degrees of aeration. The aeration on both sides continued to expand until the third decade of life. The maximum average volume was 8.2 +/- 0.5 cm3. Thereafter, the volume decreased gradually, with the average volume in the seventh decade of life being 71% of the maximum level. The aeration of the peripheral portions of the sphenoid bone, such as the pterygoid process, anterior clinoid process, and dorsum sella, occurred predominantly after closure of the spheno-occipital suture, and showed a tendency to recede during aging. CONCLUSION: Volumetric assessment of the sphenoid sinus by helical CT scanning revealed age-related expansion and reduction in aeration.     

不同修复方式对下颌第一磨牙牙体组织影响的有限元分析

目的探讨下颌第一磨牙经根管治疗后,不同修复方式对牙体组织受力的影响。方法模拟右侧下颌第一磨牙的三维有限元模型,分别以近中--远中(MOD)嵌体,全冠,MOD高嵌体修复,观察不同牙体组织的应力大小及分布。结果高嵌体修复后,牙釉质的最大主应力(εMax)在垂直载荷下较嵌体降低了88.94%,在舌颊向载荷下较嵌体降低了77.92%。垂直载荷下三种修复体的牙本质εMax都出现在根分叉处,全冠修复比嵌体和高嵌体分别高出18.35%和18.16%;而在舌颊向载荷下,全冠修复的牙本质εMax较嵌体和高嵌体分别降低19.63%和17.96%,位置转移至牙根中上1/3处,此时嵌体和高嵌体的牙本质εMax位于髓室底部。结论在生物力学方面,全瓷MOD高嵌体和全瓷冠均可以对牙体组织起到较好的保护作用,其中全冠优于MOD高嵌体。     

Radiographic and scintigraphic courses of union in cervical interbody fusion: hydroxyapatite grafts versus iliac bone autografts.

This study investigated the radiographic and scintigraphic courses of union in cervical interbody fusion using hydroxyapatite (HA) grafts or iliac bone autografts. METHODS: Twelve patients underwent both serial plain radiography and bone scintigraphy during the 12 mo after surgery. Serial plain radiographs were obtained every month until the end of the study period. Bone scintigrams with 99mTc-hydroxymethylene diphosphonate (HMDP) were obtained at 2 wk and at 1, 2, 3, and 6 mo. Uptake of 99mTc-HMDP in the graft was expressed as a ratio of the counts in the graft to those in the axis. RESULTS: In the HA graft group, the plain radiographs of all patients showed a radiolucent stripe that disappeared 7.3 +/- 1.5 (mean +/- SD) months after surgery. In the autograft group, a radiolucent stripe around the graft was not seen for any patient, and union was confirmed by follow-up radiographs within 6 mo after surgery. The serial changes in the 99mTc-HMDP uptake ratio showed no difference between the 2 groups. The 99mTc-HMDP uptake ratio peaked 1 mo after surgery and decreased rapidly to a plateau within 2 mo. CONCLUSION: In the HA graft group, despite the presence of a radiolucent stripe around the graft for more than 6 mo, the scintigraphic course of union was not different from that in the autograft group. The likelihood is that the presence of a radiolucent stripe around the HA graft in the early months after surgery is not always a sign of pseudoarthrosis.     

Scaphoid nonunions treated with vascularised bone grafts: MRI assessment

Purpose: To assess the value of MR imaging (MRI) with regard to union, graft viability and proximal pole bone marrow status, after use of vascularized bone grafts for treating scaphoid nonunions. Materials and methods: Vascularized bone grafts from the distal radius were used to treat 47 scaphoid nonunions resulting from fractures or enchondromas. Clinical and imaging evaluation was used for the pre- and postoperative assessment of all patients. Apart of conventional radiographs obtained in all cases, 15 patients were also assessed postoperatively with MRI at 3 months. From these 15 patients, eight were assessed preoperatively with MRI whereas nine had serial MRI evaluations at 6 and 12 months. The clinical follow-up time of this subgroup of 15 patients ranged from 6 to 27 months. Results: All patients showed clinical signs of union within 12 weeks form the procedure and at the latest follow-up they experienced complete (10 cases) or almost complete (five cases) relief from pain. Both plain and contrast-enhanced MRI obtained at 3 months showed viability of the bone graft in all cases. At 3 months union was established with plain radiographs in 12 patients at both sides of the graft and in three patients between the graft and proximal pole. At 3 months plain MRI showed nonunion in four patients (two between graft and proximal pole, two between graft and distal pole and one at both sides of the graft) whereas contrast-enhanced MRI revealed only one case of nonunion between graft and proximal pole. Four patients were considered to have osteonecrosis of the proximal pole intraoperatively. Two of them showed necrosis of the proximal pole with preoperative and postoperative plain radiographs and three of them with plain postoperative MRI. Contrast-enhanced MRI at 3 months showed postoperative reversal of necrotic changes in all four scaphoids. MRI also revealed bone marrow oedema of the carpal bones surrounding the scaphoid in 14 cases. Serial MRI at 6 and 12 months, obtained in nine patients, revealed resolution of the bone marrow oedema of the surrounding bones and full graft incorporation in all cases. Conclusion: Contrast-enhanced MRI is able to demonstrate the early union after treatment of scaphoid nonunions with vascularised bone grafts allowing thus earlier mobilisation. In addition, MRI can assess the viability of the proximal pole and the graft as well as the postoperative bone marrow oedema-like lesions of the surrounding bones.     

A biomechanical comparison of posterior cruciate ligament reconstructions using single- and double-bundle tibial inlay techniques

BACKGROUND: The efficacy of using a double-bundle versus single-bundle graft for posterior cruciate ligament reconstruction has not been demonstrated. HYPOTHESIS: A double-bundle graft restores knee kinematics better than a single-bundle graft does in tibial inlay PCL reconstructions. STUDY DESIGN: Controlled laboratory study. METHODS: Eight cadaveric knees were subjected to 6 cycles from a 40-N anterior reference point to a 100-N posterior translational force at 10 degrees , 30 degrees , 60 degrees , and 90 degrees of flexion. Testing was performed for the intact and posterior cruciate deficient knee as well as for both reconstructed conditions. Achilles tendons, divided into 2 equal sections, were prepared as both single-bundle and double-bundle grafts. Both grafts were employed in the same knee, and the order of graft reconstruction was randomized. RESULTS: There were no statistical differences in translation between the intact state and either of the reconstructions (P > .05) or between either of the reconstructions at any flexion angle (P > .05). CONCLUSION: No differences in translation between the 2 graft options were identified. CLINICAL RELEVANCE: The use of a double-bundle graft may not offer any advantages over a single-bundle graft for tibial inlay posterior cruciate reconstructions.     

Influence of basal support and early loading on bone cartilage healing in press-fitted osteochondral autografts

Purpose

The influence of basal graft support combined to early loading following an osteochondral autograft procedure is unclear. It was hypothesized that bottomed grafts may allow for early mobilization by preventing graft subsidence and leading to better healing.

Methods

Osteochondral autografts were press fitted in the femoral condyles of 24 sheep (one graft per animal). In the unbottomed group (n = 12), a gap of 2 mm was created between graft and recipient bone base. In the bottomed group (n = 12), the graft firmly rested on recipient bone. Animals were allowed immediate postoperative weightbearing. Healing times were 3 and 6 months per group (n = 6 per subgroup). After killing, histological and histomorphometric analyses were performed.

Results

Unbottomed grafts at 3 months showed significantly more graft subsidence (P = 0.024), significantly less mineralized bone (P = 0.028) and significantly worse cartilage and subchondral bone plate healing (P = 0.034) when compared to bottomed grafts. At 6 months, no differences were seen. Compared to the native situation, unbottomed grafts showed significantly more graft subsidence (P = 0.024), whereas bottomed grafts did not. Cystic lesions were seen in both groups. Osteoclasts were closely related to the degree of bone remodelling.

Conclusion

In the animal model, in the case of early loading, bottomed osteochondral autografts have less chance of graft subsidence. Evident subsidence negatively influences the histological healing process. In the osteochondral autograft procedure, full graft support should be aimed for. This may allow for early mobilization, diminish graft subsidence and improve long-term integration.     

Evaluation of vascularized graft reconstruction of the mandible with Tc-99m MDP bone scintigraphy

AIM: The aim of this study was to evaluate the value of bone scintigraphy for the assessment of graft viability following vascularized bone grafts in patients with mandibular reconstruction. METHODS: We investigated 16 patients with vascularized grafts from the fibula (13 patients) and iliac crest (3 patients) in the last 8 years. For the follow up of all these patients, Tc-99m MDP bone scintigraphy was performed between 2-10 days postoperatively. SPECT study was included in 5 patients. For the evaluation of the grafts, a six-grade scoring system was used. The grading system was based on a comparison of tracer uptake between graft and the cranium. The uptake was defined as increasing from grade 6 to grade 1. RESULTS: Thirteen of the 16 grafts had an uncomplicated clinical course. Complications in the graft occurred in three patients. In the analysis of planar scintigrams, patients with uncomplicated healing showed increased uptake in 12 of the 13 grafts (grade 1-3) and 1 showed the same level tracer uptake compared to cranium (grade 4). In the failed 3 grafts, decreased uptake was observed (grade 5 and 6). In 5 patients, SPECT was performed in addition to planar imaging. In these patients, 4 of the 5 grafts had an uncomplicated clinical course and 1 had a complicated one. In the analysis of SPECT images, while all the grafts with an uncomplicated clinical course exhibited increased uptake (grade 1-3), the failed graft showed decreased uptake (grade 6). CONCLUSION: Three-phase bone scintigraphy performed within 10 days after the mandibular reconstruction is a useful tool to monitor the viability and early complications of vascularized mandibular bone grafts. SPECT is also recommended. It may contribute to interpretation of the bone scans and to precise assessment of graft viability.     

The effect of length on the structural properties of an Achilles tendon graft as used in posterior cruciate ligament reconstruction

BACKGROUND: The clinical outcomes of posterior cruciate ligament reconstruction are varied. No previous studies have investigated the effect of graft length on the structural properties of the graft. HYPOTHESIS: Graft length significantly affects the structural properties of posterior cruciate ligament grafts. STUDY DESIGN: Controlled laboratory study. METHODS: Eight Achilles tendon grafts were tested under tensile loads up to 400 N at 3 different lengths: long (75 mm), medium (48 mm), and short (34 mm). These 3 lengths represent midtunnel fixation, inlay fixation, and fixation near the ligament insertions. RESULTS: Shortening the graft from both long to medium and from medium to short increased the stiffness by approximately 25%. Long and medium grafts displaced significantly more than medium and short grafts, respectively. CONCLUSION: The effective length of a graft, which is determined by where it is fixed, should be considered an important variable in posterior cruciate ligament reconstruction.     

Living donor right liver lobes: preoperative CT volumetric measurement for calculation of intraoperative weight and volume

PURPOSE: To prospectively develop equations for the calculation of expected intraoperative weight and volume of a living donor's right liver lobe by using preoperative computed tomography (CT) for volumetric measurement. MATERIALS AND METHODS: After medical ethics committee and state medical board approval, informed consent was obtained from eight female and eight male living donors (age range, 18-63 years) for participation in preoperative CT volumetric measurement of the right liver lobes by using the summation-of-area method. Intraoperatively, the graft was weighed, and the volume of the graft was determined by means of water displacement. Distributions of pre- and intraoperative data were depicted as Tukey box-and-whisker diagrams. Then, linear regressions were calculated, and the results were depicted as scatterplots. On the basis of intraoperative data, physical density of the parenchyma was calculated by dividing weight by volume of the graft. RESULTS: Preoperative measurement of grafts resulted in a mean volume of 929 mL +/- 176 (standard deviation); intraoperative mean weight and volume of the grafts were 774 g +/- 138 and 697 mL +/- 139, respectively. All corresponding pre- and intraoperative data correlated significantly (P < .001) with each other. Intraoperatively expected volume (V(intraop)) in millilliters and weight (W(intraop)) in grams can be calculated with the equations V(intra)(op) = (0.656 . V(preop)) + 87.629 mL and W(intra)(op) = (0.678 g/mL . V(preop)) + 143.704 g, respectively, where preoperative volume is V(preop) in milliliters. Physical density of transplanted liver lobes was 1.1172 g/mL +/- 0.1015. CONCLUSION: By using two equations developed from the data obtained in this study, expected intraoperative weight and volume can properly be determined from CT volumetric measurements.     

颈椎体间植骨骨针固定稳定性的试验研究

 目的 为了减少颈椎前路手术后植骨块脱出,设计一种植骨块被自体骨针固定的手术方法;并证实其植骨块增加骨针固定后,其稳定性明显增加。方法 采用10根成年羊脊柱,把它们平均分成两组,一组采用常规植骨。之后分别进行屈伸及旋转活动,并采用相同测量方法得到植骨块脱出的数据;同时将植骨块向外拉至完全脱出,记录其牵引力的大小。结果 植骨块加骨针组经活动后其脱出程度明显减轻,其抗牵引力平均增加1.5kg。结论颈椎体间植骨块骨针固定后其稳定型明显增加。     

前交叉韧带重建术后三维MRI表现

目的 探讨前交叉韧带(ACL)重建术后ACL移植物和骨隧道的3D MRI表现和演变规律.方法 回顾性分析26例双束ACL重建和16例单束ACL重建患者行3D MRI术后随访56例次的资料,用多平面重组法显示和评价移植物、骨隧道、固定器及并发症,计算术后不同时期低信号及高信号移植物的比例和骨隧道周围骨髓水肿的出现率.结果 发现低信号移植物24例次,高信号移植物32例次.移植物固定2例股骨端采用横杆,1例股骨端使用纽扣,其余部位使用可吸收螺钉.术后3个月、6～9个月和12个月及以上低信号移植物比例分别为20/25、0/14和4/10,高信号移植物比例分别为5/25、14/14和6/10,骨隧道周围骨髓水肿出现比例分别为54/54、10/32和4/26.发现1例移植物撕裂,4例胫骨隧道偏前伴ACL移植物髁间窝顶撞击,3例股骨隧道偏前,2例可吸收螺钉与骨隧道不匹配.结论 3D MRI可准确显示ACL重建术后移植物、骨隧道和固定器的状态及并发症信息,移植物信号在术后呈先增高再恢复低信号的过程.     

Assessment of maxillary sinus volume for the sinus lift operation by three-dimensional magnetic resonance imaging

OBJECTIVES: To calculate sinus and bone graft volumes and vertical bone heights from sequential magnetic resonance imaging (MRI) examinations in patients undergoing a sinus lift operation. METHODS: MRI scans were obtained pre-operatively and at 10 days and 10 weeks post-operatively, using a 0.95 tesla MRI scanner and a three-dimensional (3D) magnetisation prepared, rapid acquisition gradient-echo (MP-RAGE) sequence. RESULTS: Estimates of the bone graft volumes required for a desired vertical bone height were made from the pre-operative MRI scan. Measurements of the graft volumes and bone heights actually achieved were made from the post-operative scans. The MRI appearance of the graft changed between the 10 day and 10 week scans. CONCLUSIONS: We have proposed a technique which has the potential to give the surgeon an estimate of the optimum volume of graft for the sinus lift operation from the pre-operative MRI scan alone and demonstrated its application in a single patient. Changes in the sequential MRI appearance of the graft are consistent with replacement of fluid by a matrix of trabecular bone.     

Brachytherapy for the prevention of stenosis in a canine hemodialysis graft model: preliminary observations.

PURPOSE: To determine whether gamma brachytherapy can prevent in-stent stenosis in hemodialysis grafts. MATERIALS AND METHODS: Six-millimeter polytetrafluoroethylene arteriovenous grafts were created bilaterally in six dogs. After 1 month, Wallstents spanning the venous anastomosis were placed to accelerate restenosis. Gamma irradiation (12 Gy) was delivered endoluminally to one of the two grafts by using an iridium 192 source; thus, each animal served as its own control. Fistulography was performed monthly for 10 months or until graft thrombosis, with measurement of stenosis at each time point. At the conclusion of the study period, the treated area was examined histologically, and a computer model was used to calculate the volume of intimal hyperplasia. RESULTS: Delayed stent migration resulted in exclusion of one dog. In the remaining five dogs; maximum stenosis across all time intervals was less for the treated side (P < .04), and the volume of intimal hyperplasia was less for the treated side (P < .045). In one animal studied at 1 year, this trend reversed in terms of percentage stenosis but not total neointimal volume. CONCLUSION: Brachytherapy with 192Ir (gamma) delivered at the time of stent placement reduces restenosis in this hemodialysis graft model, but, depending on the parameter evaluated (stenosis vs total volume of neointima), the benefit may wane or even reverse with time.     

Evaluation of the incorporation of bone grafts used in maxillofacial surgery with [18F]fluoride ion and dynamic positron emission tomography

This study investigates the incorporation of bone grafts used in maxillofacial surgery by means of [¹⁸F]fluoride ion and positron emission tomography (PET). It considers patients who received pedicle grafts for mandibular reconstruction or onlay grafts for alveolar ridge augmentation. Dynamic PET images and arterialized venous blood samples were obtained within a 1-h period after i.v. injection of [¹⁸F-]fluoride. Assuming a three-compartment model and applying multilinear least squares fitting, bone blood flow (K ₁) and fluoride influx (K _mlf) were determined. Additionally Patlak plot analysis was used to calculate fluoride influx (K _pat). In cervical vertebral bodies as the reference region, mean values for flow ofK ₁ = 0.1162±0.0396 ml/min/ml and influx ofK _mlf = 0.0508±0.0193 andK _pat = 0.0385±0.0102 ml/min/ml were found. Essentially these figures are comparable with physiological values in animal and man reported in the literature. Early after surgery a significant increase in flow and influx compared to vertebral bodies was observed in the regions of osteosyntheses between grafts used for reconstruction and recipient bone (K ₁ = 0.2181,K _mlf = 0.1000 andK _pat = 0.0666 ml/min/ml) and in onlay grafts (K ₁ = 0.2842,K _mlf = 0.1637 andK _pat = 0.0827 ml/min/ml). At the same time pedicle grafts showed a significant increase in flow but not in influx (K ₁ = 0.2042,K _mlf = 0.0774 andK _pat = 0.0529 ml/ min/ml). FurthermoreK _pat was significantly lower in pedicle grafts than in onlay grafts. In follow-up studies a significant decrease in flow occurred in pedicle grafts and the regions of osteosyntheses. Moreover the latter showed a significant decrease inK _mlf as well. It is concluded that [¹⁸F-] PET depicted increased blood flow and osteoblastic activity in onlay grafts and regions of osteosyntheses, indicating bone repair in the graft and adjacent host bone early after surgery. For the regions of osteosyntheses the decrease in both parameters corresponded to uncomplicated healing. The lack of increased influx, although flow was increased in pedicle grafts, most likely indicates that some necrosis occurred in these grafts despite patency of anastomoses. It may be concluded that [¹⁸F-] PET provides further insight into the biology of graft incorporation.