In vivo detection of acute rat renal allograft rejection by MRI with USPIO particles

BACKGROUND: Magnetic resonance imaging (MRI) for non-invasively detecting renal rejection was developed by monitoring the accumulation of macrophages labeled with dextran-coated ultrasmall superparamagnetic iron oxide (USPIO) particles at the rat renal allografts during acute rejection. METHODS: Five groups of male rats with DA-->BN renal allografts and one group with BN-->BN renal isografts were investigated by MRI before, immediately after, and 24 hr after intravenous infusion with different doses of USPIO particles. All infusions were done on post-operative day 4. MRI experiments were carried out in a 4.7-Tesla instrument using a gradient echo sequence. RESULTS: MR signal intensity (MRSI) of the cortex was found to decrease with higher dosages of USPIO particles. In the absence of USPIO infusion, a decrease in MRSI was seen in the medulla region, presumably due to hemorrhage associated with renal graft rejection, while no significant change was observed in the cortex. The optimal dose of USPIO particles for visualizing rejection-associated changes in our rat kidney model appears to be 6 mg Fe/kg body weight. Iron staining results correlated with the MRSI data, indicating that the signal reduction in the MR images was due to the presence of iron. Immunohistochemical results indicated that USPIO particles were mostly taken up by infiltrating macrophages in the rejecting grafts. CONCLUSIONS: Our results suggest that MRI with intravenous administration of dextran-coated USPIO particles appears to be a valuable and promising tool that can be used as a non-invasive and sensitive method to detect graft rejection in renal transplantation.     

L5/S1椎间孔内韧带的形态和分布规律

目的:探讨L5/S1椎间孔内韧带的形态、分布规律并评价其临床意义。方法:取5具防腐和5具新鲜冰冻正常成人腰骶部标本(年龄42~80岁,平均51岁)。仔细剔除脊柱周围的软组织,从正中矢状位锯开脊柱。找出L5/S1神经根并沿椎间孔小心去除周围脂肪和筋膜等软组织。在肉眼及手术显微镜下观察韧带的形态、走行、起始位置及分布特点,用游标卡尺在手术显微镜下测量其长度、宽度及直径或厚度。用HE染色和Masson三色染色法分析对比不同类型韧带的组织学类型。结果:在20个L5/S1椎间孔内共发现215条韧带,其中条带形90条,条索形125条;连接神经根到横突或椎间孔内壁的放射状韧带181条(84.2%),连接椎间孔周围组织横跨在椎间孔内的横跨状韧带34条(15.8%);放射状韧带出现率与横跨状韧带出现率的比较有统计学差异(Z=-3.928,P=0.000)。在L5/S1椎间孔内口(73条,34.0%)、中间(102条,47.4%)及外口(40条,18.6%)区域均有分布。韧带长度多变,为1.43~19.01mm;厚度最厚处达3.46mm。光镜下,HE染色提示椎间孔内韧带由纤维结缔组织构成且部分韧带内包含小血管组织,Masson三色法染色提示椎间孔内韧带由大量的胶原纤维和少量的弹性纤维构成。放射状韧带与横跨状韧带组织学表现无明显差异。结论:L5/S1椎间孔内韧带主要分为条带形和条索形两种形状。椎间孔内放射状韧带比横跨状韧带出现率高。经骶骨裂孔硬膜外腔导管粘连松解术前应掌握其分布规律并在术中辨别并予以正确松解,以减少并发症的发生。     

Ganglion cysts of the cruciate ligaments detected by MRI

 Eight patients with ganglion cysts arising from the cruciate ligaments of the knee joint underwent arthroscopic excision after the MR examination. The MR findings, clinical features and arthroscopic findings were evaluated comparatively.

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Résumé  Après un examen IRM, huit patients présentant des kystes se développant à partir des ligaments croisés du genou, ont subi une excision arthroscopique. Les résultats de l’examen IRM, de l’examen clinique et de l’examen arthroscopique ont été comparés.

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Accepted: 4 March 1998     

In vivo strain patterns in the four major canine knee ligaments

Using mercury gauges, we measured strains in vivo in the four major ligaments of the canine knee joint as the tibia was loaded in valgus or varus at fixed angles of knee flexion. Free axial rotation of the tibia on the femur was allowed. Forces up to 78.4 N were applied to the tibia, producing moments of approximately 9 N-m. We found that with valgus loading, significant strains were observed in the medial collateral ligament at extension. At 45 degrees of flexion, the medial collateral, posterior cruciate, and anterior cruciate were strained. At 90 degrees of flexion, all four ligaments were strained. With varus loading, significant strains were found in the lateral collateral and anterior cruciate at extension. The lateral collateral and anterior cruciate ligaments were strained at 45 degrees of flexion. At 90 degrees of flexion, the lateral collateral, anterior cruciate, and posterior cruciate ligaments were strained. With valgus loading, the tibia rotated internally and the degree of axial rotation increased with flexion. External rotation of the tibia resulted from varus loading, and was relatively constant through the range of flexion. Thus when axial rotation is allowed, stability of the knee in response to valgus and varus loads is maintained by the cruciates as well as the collaterals, and the role of the cruciates increases with flexion and axial rotation.     

Neurohistology of lumbar spine ligaments

A study was conducted to identify neural elements in the posterior ligaments of the lumbar spine by using a modified gold-chloride method. Three morphologic types of mechanoreceptors were identified: Ruffini corpuscles, Ruffini end organs, and pacinian corpuscles. Free nerve endings, which are thought to be responsible for pain production, were also demonstrated within the ligaments.     

Neurohistology of lumbar spine ligaments

A study was conducted to identify neural elements in the posterior ligaments of the lumbar spine by using a modified gold-chloride method. Three morphologic types of mechanoreceptors were identified: Ruffini corpuscles, Ruffini end organs, and pacinian corpuscles. Free nerve endings, which are thought to be responsible for pain production, were also demonstrated within the ligaments.     

In vivo range of motion of the lumbar spinous processes

The study design included an in vivo laboratory study. The objective of the study is to quantify the kinematics of the lumbar spinous processes in asymptomatic patients during un-restricted functional body movements with physiological weight bearing. Limited data has been reported on the motion patterns of the posterior spine elements. This information is necessary for the evaluation of traumatic injuries and degenerative changes in the posterior elements, as well as for improving the surgical treatment of spinal diseases using posterior procedures. Eight asymptomatic subjects with an age ranging from 50 to 60 years underwent MRI scans of their lumbar segments in a supine position and 3D models of L2–5 were constructed. Next, each subject was asked to stand and was positioned in the following sequence: standing, 45° flexion, maximal extension, maximal left and right twisting, while two orthogonal fluoroscopic images were taken simultaneously at each of the positions. The MRI models were matched to the osseous outlines of the images from the two orthogonal views to quantify the position of the vertebrae in 3D at each position. The data revealed that interspinous process (ISP) distance decreased from L2 to L3 to L4 to L5 when measured in the supine position; with significantly higher values at L2–3 and L3–4 compared with L4–5. These differences were not seen with weight-bearing conditions. During the maximal extension, the ISP distance at the L2–3 motion segment was significantly reduced, but no significant changes were detected at L3–4 and L4–5. During flexion the ISP distances were not significantly different than those measured in the MRI position at all segments. Going from the left to right twist positions, the L4–5 segment had greater amounts of ISP rotation, while all segments had similar ranges of translation in the transverse plane. The interspinous process distances were dependent on body posture and vertebral level.     

In vivo facet joint loading of the canine lumbar spine.

This study describes a technique to measure in vivo loads and the resultant load-contact locations in the facet joint of the canine lumbar spine. The technique is a modification of a previously described in vitro method that used calibrated surface strains of the lateral aspect of the right L3 cranial articular process. In the present study, strains were measured during various in vivo static and dynamic activities 3 days after strain gage implantation. The in vivo recording technique and its errors, which depend on the location of the applied facet loads, is described. The results of applying the technique to five dogs gave the following results. Relative resultant contact load locations on the facet tended to be in the central and caudal portion of the facet in extension activities, central and cranial in standing, and cranial and ventral in flexion or right-turning activities. Right-turning contact locations were ventral and cranial to left-turning locations. Resultant load locations at peak loading during walking were in the central region of the facet, whereas resultant load locations at minimum loading during walking were relatively craniad. This resultant load-contact location during a walk gait cycle typically migrated in an arc with a displacement of 4 mm from minimum to maximum loading. Static tests resulted in a range of facet loads of 0 N in flexion and lying to 185 N for two-legged standing erect, and stand resulted in facet loads of 26 +/- 15 N (mean +/- standard deviation [SD]). Dynamic tests resulted in peak facet loads ranging from 55 N while walking erect to 170 N for climbing up stairs. Maximum walk facet loads were 107 +/- 27 N. The technique is applicable to in vivo studies of a canine facet joint osteoarthritis model and may be useful for establishing an understanding of the biomechanics of low-back pain.     

Three-dimensional quantitative morphology of lumbar spinal ligaments.

The three-dimensional (3-D) morphology of lumbar spinal ligaments was studied using 22 functional spinal units. A specially constructed 3-D morphometer instrument was used for quantitative measurements of each ligament's attachment point locations, origins and insertions, and attachments to the lower and upper vertebral bodies, respectively. Lengths and orientations of the ligaments according to the vertebral level were then computed and presented in reference to a local anatomic coordinate system. Associated cross-sectional areas are also obtained.     

In vivo and in vitro cellular ingrowth into a new generation of artificial ligaments

Artificial ligaments are a useful tool in ligament reconstruction. Although the new generation of artificial ligaments shows encouraging clinical results, in contrast to earlier generations studies on the biological properties are lacking. Biopsies were taken from a ligament advancement reinforcement system (LARS) 6 months after implantation and investigated by histochemistry. An in vitro study seeding human fibroblasts or osteoblast-like cells (up to 10(6) cells for 21 days) on ligament pieces (5 x 5 mm) was conducted and analyzed by histochemistry. The biopsies showed complete cellular and connective tissue ingrowth in the LARS ligament. In vitro fibroblasts and osteoblast-like cells encapsulated the fibers by building a cellular net around them. To our knowledge, these findings demonstrate for the first time the cellular ingrowth into the LARS ligament. This mechanism might explain the strength and the inert behavior of the ligament without the synovialitis shown in clinical studies.     

Study of the innervation of the spinal ligaments at the lumbar level

The authors studied the innervation of the human lumbar spinal ligaments on cadaver or surgical specimens. In the ligaments annexed to the neural arch and in the posterior longitudinal ligament were found free-ending fibers and amyelinic perivascular fibers. In the anterior longitudinal ligament, coexisting with perivascular fibers were found encapsulated corpuscular formations on the ventrolateral aspect of the junction between the intervertebral disc and vertebral body. These findings comfort the role of the anterior longitudinal ligament in proprioception essential both in static and dynamic function of the spine.     

In vivo detection of the Christiansen-Douglas-Haldane effect in clinical conditions

The Christiansen-Douglas-Haldane effect, also termed Haldane effect, describes the dependence of CO2 absorption by blood on the degree of hemoglobin oxygenation. Under the physiological condition of an "open" system between blood and alveolus, the arterial partial pressure of CO2 (paCO2; mmHg) must range below the mixed-venous (pvCO2; mmHg) value. During the nonphysiological situation of a "closed" system, e.g. hyperoxic apnea after adequate pre-oxygenation (O2 uptake with lack of CO2 delivery), paCO2 can assimilate to pvCO2 and even exceed it. The remainder has often been termed a "paradoxical phenomenon". It was the aim of this study to prove the Haldane effect in vivo in the "closed" system of hyperoxic apnea. Eighty patients (ASA II-IV, NYHA II-III) scheduled for coronary surgery gave written informed consent and were examined. Following the preparations for induction (venous and arterial cannulas, pulmonary artery catheter), they were pre-oxygenated with 6 l O2/min until induction of anesthesia was achieved. Pre-oxygenation was maintained actively/passively until intubation. At the onset and the end of intubation the arterial (a) and mixed-venous (v) blood gas status (pHa, pHv, saO2 and svO2 (%), paO2 and pvO2, paCO2 and pvCO2 were determined using the Corning 170 pH/blood gas analyzer and the Corning 2500 CO-oximeter. Statistical analysis of the data was based on Student's t-test for paired samples. Periods of apnoea ranged between 60 and 180 s. The data were allocated to three groups, depending on the duration of apnea: Group I: 60-100 s; Group II: 101-140 s; Group III: 141-180 s.(ABSTRACT TRUNCATED AT 250 WORDS)     

Ossification of the posterior longitudinal and yellow ligaments on the lumbar spine

Ossification of the posterior longitudinal ligament and ossification of the yellow ligament are the main causes of spinal canal stenosis. This article describes a case of ossification of the posterior longitudinal and yellow ligaments on the lumbar spine. The patient presented with gradually worsening left lower-extremity ache and pain. The deep tendon reflex was hyperreflexia in the lower extremities. Disturbances existed in the blade and bowel. The ossified lesion of ossification of the posterior longitudinal ligament was observed at L5-S1, and plain lateral radiographs and computed tomography revealed ossification of the yellow ligament on L3, which occupied a large part of the spinal canal. Because of the findings on the preoperative radiographs, we performed posterior approach decompression and bone grafting and excisied the ossified lesion. Pedicle screws were inserted from L3 to S1. The patient's symptoms disappeared postoperatively, and his Japanese Orthopaedic Association score was 25 two weeks postoperatively. No standard surgical procedure exists for the treatment of lumbar ossification of the posterior longitudinal ligament, but it is important to select a surgical procedure according to individual patient conditions. Many factors, such as local mechanic stress, tissue metabolism, high glucose, and genetics, contribute to the progression of ossification of the posterior longitudinal and yellow ligaments on the lumbar spine. However, the mechanism is unclear. Further study and long-term follow-up on lumbar ossification of the posterior longitudinal ligament is needed.     

Surgical treatment of intraforaminal/extraforaminal lumbar disc herniations: Many approaches for few surgical routes

Acta Neurochirurgica - Several disc disease nomenclatures and approaches for LDH exist. The traditional midline bone-destructive procedures together with approaches requiring extreme muscular...