Re: a radiostereometric analysis of the movements of the sacroiliac joints in the reciprocal straddle position.
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Humans↗
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Lumbosacral stability of consolidated anteroposterior fusion after instrumentation removal determined by roentgen stereophotogrammetric analysis and direct surgical exploration.
STUDY DESIGN: The intervertebral stability of bony consolidated anteroposterior lumbosacral spondylodesis is evaluated by roentgen stereophotogrammetric analysis and direct surgical exploration before and after removal of the internal fixator. OBJECTIVES: To determine the remaining in vivo stability of spinal arthrodesis solely retained by a bony integrated carbon fiber cage. SUMMARY OF BACKGROUND DATA: Roentgen stereophotogrammetric analysis studies on posterolateral lumbar fusions demonstrate primary spinal stability after additional dorsal instrumentation, which is retained during bony fusion healing. Animal models show a persistent stabilizing effect of the fixator despite the presence of bony fusion. Although direct surgical inspection is the most reliable method to evaluate fused vertebrae, roentgen stereophotogrammetric analysis has also proven to be a highly accurate method to evaluate spinal stability. METHODS: In 10 patients lumbosacral fusion was performed using carbon interbody implants and an internal fixator. Ten months after initial surgery (range 7-15 months) the internal fixation was removed to reduce local soft tissue impingement as soon as bony fusion was achieved. Fusion site exploration in the course of instrumentation removal was performed by applying distraction, compression, and torque to the grafted area under fluoroscopic control. Any motion indicated a pseudarthrosis. Lumbosacral stability was evaluated by serial roentgen stereophotogrammetric analysis after fusion and after instrumentation removal. RESULTS: During instrumentation removal the mechanical stress test under fluoroscopic control did not indicate pseudarthrosis. After instrumentation removal, roentgen stereophotogrammetric analysis measurements revealed a nonsignificant increase in lumbosacral micromotions within the fused segment with 0.14, 0.31, and 0.44 mm in the transverse, vertical, and sagittal axes, respectively. CONCLUSIONS: The internal fixator could be removed without endangering the stability of the fusion. Direct surgical exploration confirmed the adequacy of roentgen stereophotogrammetric analysis as a reliable in vivo method to evaluate lumbosacral stability after anteroposterior fusion.
Adult↗
Differences by quadrant of retinal nerve fiber layer thickness in healthy eyes.
PURPOSE: The purpose of this study was to determine the distribution of retinal nerve fiber layer thickness by quadrant in healthy eyes. PATIENTS AND METHODS: Forty subjects with healthy eyes were included in the study. A complete ophthalmic examination was performed, including determination of visual fields by automated perimetry. The subjects had no family history of retinal disease or glaucoma. Forty right eyes and 40 left eyes were measured. Retinal nerve fiber layer thickness was measured using simultaneous stereophotographs with stereophotogrammetry at the disc margin. For the total disc and four quadrants, absolute retinal nerve fiber layer thickness and optic disc area was determined using a magnification correction formula. RESULTS: Comparison of the quadrants showed that the retinal nerve fiber layer thicknesses of the superior, inferior, and nasal quadrants were significantly thicker than the temporal quadrant (P = 0.00006 for right and left eyes). No significant differences were observed between the superior, inferior, and nasal quadrants in the right eye. In the left eye, the superior retinal nerve fiber layer thickness was significantly greater than the inferior (P = 0.028) and nasal retinal nerve fiber layer thicknesses (P = 0.00006), while the inferior was not significantly different from the nasal. No significant difference in quadrant retinal nerve fiber layer thickness was noted between eyes. CONCLUSIONS: Measurements of retinal nerve fiber layer thickness in healthy eyes show the thinnest quadrant to be the temporal, with the other three quadrants having similar thicknesses. This pattern corresponds to the histologic measurements of retinal nerve fiber layer thickness.
Adult↗
Comparison of 2 wound volume measurement methods.
OBJECTIVE: To compare 2 wound volume measurement techniques, the Kundin device and stereophotogrammetry, on 2 wound shapes. DESIGN: Using 2 wound measurement techniques, the interrater and intrarater reliability and the bias and standard error of measurement of an L-shaped and a pear-shaped plaster of paris wound model were assessed. SETTING: A clinical laboratory of a school of nursing. PARTICIPANTS: Twenty-four raters, all but 2 being registered nurses, measured each of the wounds using both techniques. INTERVENTIONS: Each rater measured each wound twice using each method in a randomly assigned order defined on a card that was drawn from a box. Measurements were recorded on a researcher-designed data collection form, which included some demographic data related to each participant. MAIN OUTCOME MEASURES: The study hypothesis was that there would be no significant difference in accuracy between the 2 wound volume measurement methods. RESULTS: The least biased and most accurate technique was stereophotogrammetry, with the smallest standard of error of measurement. Interrater reliability of average ratings was identical for both methods at 0.98. For single ratings, stereophotogrammetry was slightly higher than the Kundin device. Intrarater reliability was higher on the pear-shaped wound for the Kundin device, which had lower interrater reliability, suggesting that nurses were consistent in the direction and size of personal error. Intrarater reliability for stereophotogrammetry was identical to that of the Kundin device for the L-shaped wound and lower for the pear-shaped wound. CONCLUSIONS: Although both techniques have acceptable accuracy, stereophotogrammetry is more accurate and has more clinical applications.
Adult↗
More than one way to measure a wound: an overview of tools and techniques.
PURPOSE: To improve clinical practice and the quality of patient care by providing a learning opportunity that enhances the participant's understanding of the tools and techniques available for wound measurement. TARGET AUDIENCE: This CME/CE activity is intended for physicians and nurses with an interest in learning about tools and techniques available for wound measurement. OBJECTIVES: After reading the article and taking the test, the participant will be able to: Identify advantages and disadvantages of various dimensional methods used to measure wounds. Identify advantages and disadvantages of visual and photographic assessment methods. Identify advantages and disadvantages of vascular and pressure assessment methods.
Blood Pressure↗
Sizing up wounds accurately.
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Anthropometry↗
Fixation of total knee arthroplasty improved by mobile-bearing design.
We examined the in vivo displacement of mobile-bearing polyethylene and its effect on prosthesis-bone fixation. Thirty-five patients with the Interax ISA mobile platform total knee arthroplasties were examined by roentgen stereophotogrammetric analysis. Our protocol included weightbearing to measure the range of motion of the mobile platform in relation to the tibial component. We also studied the micromotions of the tibial component in relation to the tibia during a 2-year followup. The analysis of micromotion (maximum total motion mean, 0.5 mm; subsidence mean, 0.15 mm) showed this mobile platform design is stable and improves fixation at the prosthesis-bone interface. Longitudinal rotations of the mobile platform occurred in all patients and followed a homogeneous pattern of motion, depending on the examination. However, anteroposterior translations did not show any patterns with specific examination. This suggests the meniscal movement adapts itself to different weightbearing conditions. We measured the in vivo mobile-bearing displacement under static loading conditions. We also observed improved fixation at the bone-prosthesis interface.
Adult↗
The history and future of radiostereometric analysis.
Roentgen stereophotogrammetry allows one to localize the position of an object in space using roentgen rays. For orthopaedic purposes it was developed 35 years ago by Göran Selvik, and since that time many investigators have refined the radiostereometric calculations and evaluative software. Many uses and mathematical algorithms have been developed, and advancements in computer programs and digital radiography continue to expand its capabilities. Despite these advances, improvements in the technical accuracy and type of kinematic analyses possible have been relatively modest. However, radiostereometric analysis is now easier and less time consuming to use, with a resolution in clinical practice almost equal to what could only previously be obtained under ideal laboratory conditions. The ability to measure skeletal and implant movements with high resolution in vivo images was an important progressive step for the orthopaedic community. Radiostereometric analysis has helped develop new fields in clinical orthopaedic research and continues to improve advancements in orthopaedic health care.
History, 20th Century↗
RSA-measured inducible micromotion and interface modeling with finite element methods.
Osteolysis is the main cause of aseptic loosening and stem failure. The mechanism that leads to osteolysis is poorly understood; pressure generation caused by reversible stem micromotion may play an important role. We aimed to determine whether dynamically inducible micromotion occurs in vivo at the prosthesis-cement interface and to use these data to develop and confirm a finite element representation of this interface. Dynamically inducible micromotion was measured using radiostereometric analysis in 21 hips implanted with an Exeter stem, at 3 months and 12 months postoperatively, by changing loading from double-leg stance to single-leg stance. Dynamically inducible micromotion occurred at 3 and 12 months; similar micromotion was observed at both time points. At 3 months the head of the stem was displaced posteriorly (0.10 +/- 0.16 mm) and inferiorly (0.08 +/- 0.12 mm) on loading. A Coulomb friction nonbonded representation of the stem-cement interface was used to fit the clinically measured dynamically inducible micromotion. The final finite element model predicted gap opening and closing between the implant and the mantle. This may be a mechanism for generating pressure and distributing wear debris, which are believed to important contributors to failure.
Aged↗
Assessment of fragment micromotion in distal femur fracture fixation with RSA.
To assess fragment micromotion in three fracture fixation constructs 18 composite femur models were sectioned to create AO-C3 fractures and fixed using the Less Invasive Stabilization System (LISS), Dynamic Condylar Screw (DCS), or the Condylar Buttress Plate (CBP). Tantalum beads were attached to each fracture fragment. The constructs were tested for permanent deformation after cyclical loading (amplitude = 242.2N) and elastic deformation during static loading with 490.5N. Radiographs were taken before loading and then after unloading to determine permanent deformation or during loading to determine elastic deformation. We used RSA to quantify the six degrees of freedom interfragmentary maximum total motion, strain, and stress. For maximum total motion the CBP had more permanent deformation and two failures, whereas the LISS underwent the greatest elastic deformation. LISS and CBP had the highest strain conditions in the fracture gap and LISS had the greatest stress movements between fragments, all of which exceeded the upper limits for bone healing. LISS and CBP may not be indicated for comminuted fractures due to the high degree of flexibility of the LISS, resulting in high stress and strain conditions and susceptibility to catastrophic failure and high strain conditions with the CBP.
Elasticity↗
Model-based RSA of a femoral hip stem using surface and geometrical shape models.
Roentgen stereophotogrammetry (RSA) is a highly accurate three-dimensional measuring technique for assessing micromotion of orthopaedic implants. A drawback is that markers have to be attached to the implant. Model-based techniques have been developed to prevent using special marked implants. We compared two model-based RSA methods with standard marker-based RSA techniques. The first model-based RSA method used surface models, and the second method used elementary geometrical shape (EGS) models. We used a commercially available stem to perform experiments with a phantom as well as reanalysis of patient RSA radiographs. The data from the phantom experiment indicated the accuracy and precision of the elementary geometrical shape model-based RSA method is equal to marker-based RSA. For model-based RSA using surface models, the accuracy is equal to the accuracy of marker-based RSA, but its precision is worse. We found no difference in accuracy and precision between the two model-based RSA techniques in clinical data. For this particular hip stem, EGS model-based RSA is a good alternative for marker-based RSA.
Arthroplasty, Replacement, Hip↗
Standing versus supine radiographs in RSA evaluation of femoral head penetration.
Evaluation of polyethylene acetabular component wear in total hip arthroplasties commonly is performed using serial radiographs of the hip by measuring the change in the location of the center of the femoral head in relation to the acetabular component. Of the different methods currently used for this purpose, radiostereometric analysis (RSA) is considered the most accurate and precise. In all such radiographic studies, it is assumed the femoral head is seated into the deepest portion of the acetabular component during all radiographic examinations. Although most radiographs used for wear measurements are taken with the patient supine, we questioned whether standing radiographs, with substantial joint load, are better suited for these measurements. We evaluated two groups of patients having total hip arthroplasty who had radiostereometric radiographs taken in supine and standing positions. The average femoral head penetration that occurred between the 6-month and 2-year time interval was measured with radiographs taken in the standing or supine position. We found no difference between the average total femoral head penetration when using supine or standing radiographs.
Arthrography↗
RSA can measure ACL graft stretching and migration: development of a new method.
UNLABELLED: We describe the development of a method using radiostereometric analysis to measure fixation slippage and graft stretching after anterior cruciate ligament reconstruction. Initial development used a glass phantom object, then a series of laxity measurements of cadaveric knees. After this, we prospectively studied 14 patients after anterior cruciate ligament reconstruction using bone-patellar tendon-bone and hamstrings grafts. Tantalum markers were inserted into the femur, the tibia, and the graft. Radiostereometric analysis was used to measure sagittal laxity, graft stretching, and fixation slippage postoperatively and at intervals up to 1 year after surgery. The cadaveric knee laxity measured by RSA correlated with clinically-accepted KT2000 measurements. A steady increase in total anteroposterior laxity was found in both clinical groups during the year of followup. Migration of the bony fixations and stretching of the grafts tended to be higher in the hamstrings group. This method of anterior cruciate ligament graft analysis provides a new way to ascertain laxity changes in the reconstruction after surgery. LEVEL OF EVIDENCE: Diagnostic Level II. See Guidelines for Authors for a complete description of levels of evidence.
Adolescent↗
Comparison of femoral head penetration using RSA and the Martell method.
UNLABELLED: Radiostereometry has high precision and accuracy measuring polyethylene wear in total hip arthroplasty but requires a specialized setup. The Martell method is simpler and can be used on larger populations. The hypothesis that the radiostereometry analysis and the Martell analysis would yield comparable wear data from the same group of patients having total hip arthroplasty was tested. A group of twenty-five total hip arthroplasty patients who had both radiostereometry and standard anterior-posterior pelvic and cross-table lateral radiographs of sufficient quality for analysis were identified. The films were taken at postoperative periods of 6 weeks, 1 year, 2 years, and 5 years. Femoral head penetration was measured by both methods at each time point. The median penetration rates measured by each method decreased over time. Penetration results were affected by method of analysis, time, and dimension, with greater penetration for Martell compared with radiostereometry at each time point, greater penetration with increasing time for each method, and larger three-dimensional magnitude compared with two-dimensional analysis. LEVEL OF EVIDENCE: Case series Level IV. See Guidelines for Authors for a complete description of levels of evidence.
Arthrography↗
Shoulder kinematics in 25 patients with impingement and 12 controls.
UNLABELLED: We used dynamic radiostereometry to study the three-dimensional kinematics of the shoulder joint during active abduction. Twenty-five patients experiencing shoulder symptoms (Neer Stage 2) for more than 18 months, without total rotator cuff tears, participated. Eight men and four women without shoulder symptoms constituted controls. The rotation of the humeral head relative to a fixed scapula and the absolute rotation of the humerus (caused by humeral, scapular, and trunk motion) were measured. The rotations were calculated in the order of abduction/adduction (anteroposterior axis), internal/external rotation (longitudinal axis), and flexion/extension (transverse axis). The absolute abduction of the humerus in our patients did not differ from controls, nor did the abduction in the glenohumeral joint. During abduction, the humeral centre displaced medially, proximally, and anteriorly. In the patient group, slightly more (1-1.5 mm) proximal translation was observed. Presence of impingement syndrome was associated with increased proximal translation of the humeral head center, which occurred in the early phase of the arc of motion. LEVEL OF EVIDENCE: Diagnostic Level I. See Guidelines for Authors for a complete description of Levels of Evidence.
Adult↗
Biomechanical comparison of anterolateral plate, lateral plate, and pedicle screws-rods for enhancing anterolateral lumbar interbody cage stabilization.
STUDY DESIGN: A repeated measures in vitro flexibility experiment was performed in calf spines. OBJECTIVES: To determine the biomechanical differences among three techniques for augmenting stability of an anterolateral lumbar threaded interbody cage. BACKGROUND: Stand-alone interbody cages are known to inadequately stabilize the spine. Surgeons often add supplementary instrumentation for a more stable construct. METHODS: Six L2-L5 calf spines (L3-L4 level instrumented) were tested: 1) intact; 2) with a single anterolateral interbody cage; 3) with cage plus anterolateral plating; 4) with cage plus lateral plating; and 5) with cage plus pedicle screw fixation. Specimens were loaded in each anatomic plane quasistatically (maximum 5.0 Nm). Angular motion was measured stereophotogrammetrically. RESULTS: The stand-alone interbody cage allowed significantly less range of motion than normal during all loading modes except axial rotation. Addition of pedicle screws-rods, anterolateral plate, or lateral plate significantly further reduced range of motion in all planes. Pedicle screws slightly outperformed the anterolateral plate during extension and lateral bending and slightly outperformed the lateral plate during flexion, extension, and left axial rotation (range of motion differences <0.65 degrees, P < 0.05). The anterolateral plate outperformed the lateral plate during flexion and extension, whereas the lateral plate outperformed the anterolateral plate during lateral bending (range of motion difference <0.57 degrees, P < 0.05). CONCLUSION: Anterolateral or lateral lumbar plating increases stability significantly compared to stand-alone interbody cage fixation. These findings support anterolateral or lateral plate fixation as a potential clinical alternative to pedicle screws-rods in this role and may obviate the need for combined anterior and posterior approaches when spinal instability exists.
Animals↗
Stereolithography in oral implantology: a comparison of surgical guides.
This article presents the use of stereolithography in oral implantology. Stereolithography is a new technology that can produce physical models by selectively solidifying an ultraviolet-sensitive liquid resin using a laser beam, reproducing the true maxillary and mandibular anatomic dimensions. With these models, it is possible to fabricate surgical guides that can place the implants in vivo in the same places and same directions as those in the planned computer simulation. A 70-year-old woman, in good health, with severe mandibular bone atrophy was rehabilitated with an over-denture supported by 2 Branemark implants. Two different surgical planning methods were considered: 1) the construction of a surgical guide evaluating clinical aspects, and 2) the surgical guide produced by stereolithographic study. The accuracy of surgical planning can reduce the problems related to bone density and dimensions. Furthermore, the stereolithographic study assured the clinicians of a superior location of fixtures in bone. Surgical planning based on stereolithographic technique is a safe procedure and has many advantages. This technologic advance has biologic and therapeutic benefits because it simplifies anatomic surgical management for improved implant placement.
Aged↗
Update in three-dimensional imaging in facial plastic surgery.
PURPOSE OF REVIEW: Facial plastic surgeons have always relied on photography for preoperative and postoperative analysis, medicolegal documentation, and communication. The current standards for analysis and documentation of facial structures have been determined by obtaining measurements and parameters from two-dimensional photographs or radiographs. However, the face and neck are three-dimensional structures and require manipulation in three planes within the constraints of esthetics, stability, and function. Recent advances in technology have made three-dimensional imaging and analysis possible. RECENT FINDINGS: The ability to capture images in three dimensions has opened up new avenues for observation and has increased the ability to analyze changes after surgery. Whereas only linear distances, angles, and areas can be determined by use of two-dimensional images, soft tissue volumetric data and surface topography can also be measured accurately; this can be helpful in validating changes in patients undergoing aging facial or orthognathic procedures. Recent studies have focused on descriptions of imaging techniques, validation of measurements, and the creation of normative data and its applications in surgery. SUMMARY: The availability of three-dimensional imaging and software systems presents new opportunities for the facial cosmetic surgeon to plan, execute, and assess the outcomes in patients undergoing surgery of the face and neck.
Cephalometry↗