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PubMed1993

Effect of reconstruction of the anterior cruciate ligament on proprioception of the knee and the heel strike transient.

Abnormal proprioception of the knee joint has been documented after rupture of the anterior cruciate ligament (ACL) and may result in the loss of muscular reflexes. Excessive loading from the lack of muscular control may predispose the joint to osteoarthrosis. To investigate this problem, 10 patients were studied at an average of 31.6 months after ACL reconstruction. Three tests of joint proprioception and measurements of the vertical component of heel strike force during normal gait were used. A normal control group also was studied. For two of the proprioception tests (reproduction of passive motion and relative reproduction), there were no statistical differences among the uninjured (control) limbs, the normal contralateral limb of patients with a reconstructed ACL, and the extremity with a reconstructed ACL. In the third test (threshold of detection of motion), which previously has been shown to be adversely affected by ACL injury, the measurements for both extremities of patients with a reconstructed ACL were more accurate than those for the control group. The reconstructed extremity performed less accurately than the contralateral extremity (p < 0.05). The heel strike transient (vertical component of ground reaction force at heel strike) for uninjured and ACL-reconstructed limbs was not significantly different. In fact, the extremity with the reconstructed ACL had a lower transient than the uninjured extremity. Heel strike transients in patients with a reconstructed ACL were higher than those in the controls, but the differences were significant only when corrected for velocity of gait.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed2006

Breast reconstruction with the TRAM flap: pedicled and free.

BACKGROUND: Breast cancer is a ubiquitous disease affecting one in seven women. While breast conservation techniques are available for local control of the disease for many patients, not all patients are good candidates for these techniques. Mastectomy, therefore, remains a common method of breast cancer treatment. Methods of reconstruction include implant reconstruction and autogenous reconstruction. The advantages of autogenous reconstruction include the creation of a soft, ptotic breast mound, which tends to match a native contralateral breast both in and out of bra support. Autogenous reconstructions do not tend to change with time and usually do not require periodic revision as seen in implant reconstructions. METHODS: The most common method of autogenous reconstruction is the TRAM flap, either pedicled or free. The TRAM flap employs the redundant excess lower abdominal tissue typically removed during a cosmetic abdominoplasty. This tissue is brought to the mastectomy defect as a pedicled flap, passing subcutaneously from the upper abdomen and into the defect site. The pedicled flap is based upon the superior epigastric vessels. A free TRAM is harvested with the overlying muscle and the attached inferior epigastric vessels. This flap is completely separated from the abdomen and brought to the chest defect where it is anastomosed to either the thoracodorsal or internal mammary vessels. The donor defect within the abdominal wall is repaired with an inlay mesh with both the pedicled and free techniques. RESULTS: Patient selection criteria usually help determine which technique is used. The advantage of the free flap technique is improved blood supply to the skin island. The free flap, therefore, is used in patients at higher risk for partial flap loss with the pedicled technique. Such high-risk patients include smokers, the obese, patients with significant medical comorbidities, and patients with prior abdominal surgery. Patients without these risk factors can be expected to achieve good results with either the pedicled or free flap technique. CONCLUSION: Autogenous breast reconstruction with the TRAM flap achieves long lasting satisfactory results in most patients with the creation of a soft, naturally ptotic breast mound, which typically matches well a contralateral native breast.

Anastomosis, Surgical↗

PubMed2001

Direct reconstruction of non-Cartesian k-space data using a nonuniform fast Fourier transform.

An algorithm of Dutt and Rokhlin (SIAM J Sci Comput 1993;14:1368-1383) for the computation of a fast Fourier transform (FFT) of nonuniformly-spaced data samples has been extended to two dimensions for application to MRI image reconstruction. The 2D nonuniform or generalized FFT (GFFT) was applied to the reconstruction of simulated MRI data collected on radially oriented sinusoidal excursions in k-space (ROSE) and spiral k-space trajectories. The GFFT was compared to conventional Kaiser-Bessel kernel convolution regridding reconstruction in terms of image reconstruction quality and speed of computation. Images reconstructed with the GFFT were similar in quality to the Kaiser-Bessel kernel reconstructions for 256(2) pixel image reconstructions, and were more accurate for smaller 64(2) pixel image reconstructions. Close inspection of the GFFT reveals it to be equivalent to a convolution regridding method with a Gaussian kernel. The Gaussian kernel had been dismissed in earlier literature as nonoptimal compared to the Kaiser-Bessel kernel, but a theorem for the GFFT, bounding the approximation error, and the results of the numerical experiments presented here show that this dismissal was based on a nonoptimal selection of Gaussian function.

Algorithms↗

PubMed1996

Three-dimensional structure of nucleotide-bearing crossbridges in situ: oblique section reconstruction of insect flight muscle in AMPPNP at 23 degrees C.

We have explored the three-dimensional structure of myosin crossbridges in situ in order to define the structural changes that occur when nucleotide binds to the myosin motor. When AMPPNP binds to rigor insect flight muscle, each half sarcomere lengthens by approximately 2.0 nm and tension is reduced by approximately 70% without a reduction in stiffness, suggesting partial reversal of the power stroke. We have obtained averaged oblique section three-dimensional reconstructions of mechanically monitored insect flight muscle in AMPPNP that permit simultaneous examination of all myosin crossbridges within the unit cell and direct comparison of calculated transforms with X-ray diagrams of the native fibers. Transforms calculated from the oblique section reconstruction of AMPPNP insect flight muscle at 23 degrees C show good agreement with native X-ray diagrams, suggesting that the average crossbridge forms in the reconstruction reflect the native structure. In contrast to the rigor lead and rear crossbridges in the double chevrons, the averaged reconstruction of AMPPNP fibers show only one crossbridge class, in the position of the rigor lead bridge. The portion of the crossbridge close to the thick filament appears broader than in rigor, and shows a small 0.5 to 1.0 nm M-ward shift of the regulatory domain region of myosin. In transverse view, AMPPNP "lead" crossbridges are less azimuthally bent than rigor. Fitting the atomic model of actomyosin subfragment 1 to the averaged crossbridges shows that the detectable differences between rigor bridges and between rigor and AMPPNP bridges occur in the alignment and angles of the regulatory domains and suggests that rear bridges are more strained than lead crossbridges. The apparent absence of rear bridges in AMPPNP in averaged reconstructions indicates detachment of a number of force-bearing bridges, which conflicts with the maintained stiffness of the fibers used for the reconstruction. This conflict may be explained if rigor rear bridges become distributed irregularly over more actin sites in AMPPNP, so that their average density is too low to appear in the averaged reconstructions. The reconstructions indicate that in insect flight muscle the response of in situ rigor crossbridges to AMPPNP binding is not uniform. Lead bridges persist but have altered structure in the light chain domain, whereas rear bridges detach and possibly redistribute. Shape changes in attached myosin heads within the myofibrillar lattice are in the appropriate direction and of the appropriate magnitude needed to explain the sarcomere lengthening. This could be a direct response to nucleotide binding, a passive response to rear bridge detachment, or a combination of both.

Adenosine Triphosphate↗

PubMed2002

Skin-sparing mastectomy and immediate breast reconstruction: a prospective cohort study for the treatment of advanced stages of breast carcinoma.

BACKGROUND: Recent published series demonstrate the safety and effectiveness of skin-sparing mastectomy (SSM) with immediate reconstruction for the treatment of early-stage breast carcinoma. Although several reports have retrospectively evaluated outcomes after breast reconstruction for locally advanced disease (stages IIB and III), no study has specifically considered immediate breast reconstruction after SSM for locally advanced disease. METHODS: From 1996 to 1998, 67 consecutive patients with breast carcinoma underwent SSM with immediate reconstruction and were prospectively observed. From this group of patients, those with locally advanced disease (stage IIB, n = 12; stage III, n = 13) were analyzed separately. Tumor characteristics, adjuvant therapy, type of reconstruction, operative time, complications, hospital stay, and incidence of local recurrence and distant metastasis were noted. RESULTS: Breast reconstruction consisted of a transverse rectus abdominis myocutaneous flap (n = 22) or a latissimus flap plus an implant (n = 4). The median operative time was 5.5 hours; the average hospital stay was 5.2 days. Complications required reoperation in three patients (12%): partial skin flap necrosis in two and partial abdominal skin necrosis in one. Surgery on the opposite breast for symmetry was required in one patient (4%). Postoperative adjuvant therapy was not significantly delayed (median interval, 32 days). With a median length of follow-up of 49.2 months (range, 33-64 months), local recurrence was present in only one patient (4%), with successful local salvage treatment, and distant metastasis was present in four patients (16%). CONCLUSIONS: SSM with immediate reconstruction seems safe and effective and has a low morbidity for patients with advanced stages of breast carcinoma. Local recurrence rates and the incidence of distant metastasis are not increased compared with those of patients who have had modified radical mastectomies without reconstruction.

Adult↗

PubMed2003

Preliminary evaluation of image reconstruction by ordered-subset expectation maximization in thallium-201 lung scintigraphy.

OBJECTIVES: We observed whether clearer tumor delineation and greater tumor to non-tumor (T/N) count ratios could be obtained using an iterative ordered-subsets expectation maximization (OSEM) algorithm than conventional filtered-back projection algorithm (FBP) in the image reconstruction of thallium-201 (201Tl) lung scintigraphy. METHODS: In 29 patients with lung cancer and phantom studies, tomograms were reconstructed using FBP and OSEM algorithms, with and without a prefilter (Butterworth filter: BW), whose cut-off frequencies were 0.10 cycles/pixel for FBP and 0.10 and 0.17 cycles/pixel for OSEM. Visual interpretation and tumor to non-tumor (T/N) count ratios were obtained and compared. RESULTS: Without a prefilter, T/N ratios from OSEM and FBP were 1.89 +/- 0.31 (early) and 2.00 +/- 0.54 (late) for OSEM, 1.90 +/- 0.33 (early) and 2.05 +/- 0.59 (late) for FBP, respectively. The OSEM reconstruction without prefiltering showed clearer tumor contours than FBP without a prefilter. Incorporation of BW showed visually low-noised images but decreased T/N ratios in both reconstructions with BW (0.10 cycles/pixel). No greater T/N ratios were obtained by OSEM than FBP, with or without prefiltering. With BW with a cut-off frequency of 0.17 cycles/pixel, the same T/N ratios as those without BW were obtained. The tumor model sized 0.9 cm in the phantom study was invisible in both OSEM and FBP reconstructions without a prefilter, but visible with a prefilter. The influence of prefiltering on T/N ratios was also observed in phantom studies. CONCLUSIONS: Visually improved tumor delineation could be obtained in OSEM reconstruction without a prefilter as compared to FBP reconstruction without a prefilter for tumors greater than 2 cm. Prefiltering should be incorporated into OSEM reconstruction in diagnosing small tumors. However, the influence of prefilter (BW) setting on semi-quantitative interpretation needs further discussion.

Adult↗

PubMed1997

Direct reconstruction of single-photon emission computed tomography images using retained matrix elements.

In clinical applications, two methods of single-photon emission computed tomography (SPECT) reconstruction are widely used. These are filtered backprojection and iterative reconstruction. Filtered backprojection is fast and produces acceptable images. Iterative reconstruction is slow, but produces images of greater accuracy than backprojection. The authors sought to develop a method of SPECT reconstruction that would have the advantages of both established methods: close in speed to backprojection and with the accuracy of iterative reconstruction. This was accomplished by computing a direct solution to the set of linear equations governing SPECT reconstruction. We tested this method of SPECT reconstruction using a set of projections from a cold rod and sphere phantom. Direct reconstruction produced images having equivalent resolution to backprojected images, but with double the contrast ratio. The direct method required 10 seconds of computation per slice on a Macintosh Quadra 950 (Apple Computer; Cupertin, CA), significantly faster than most iterative methods.

Image Processing, Computer-Assisted↗

PubMed2006

Arthroscopic anterior cruciate ligament reconstruction with quadriceps tendon autograft: clinical outcome in 4-7 years.

Surgical reconstruction of the anterior cruciate ligament (ACL) is indicated in the ACL-deficient knee with symptomatic instability and multiple ligaments injuries. In the present study, we describe the clinical results of quadriceps tendon-patellar bone autograft for ACL reconstruction. From 1996 to 1998, the graft has been used in 38 patients. Thirty-four patients with complete final follow-up for 4-7 years were analyzed. The average follow-up time was 62 (48-84) months. Thirty-two patients (94%) achieved good or excellent results by Lysholm knee rating. Twenty-six patients (76%) could return to moderate or strenuous activity after reconstruction. Twenty-eight patients (82%) had ligament laxity of less than 2 mm. Finally; 31 patients (91%) were assessed as normal or nearly normal rating by IKDC guideline. Twenty-five patients (73%) had less than 10 mm difference in thigh girth between their reconstructed and normal limbs. Thirty-two (94%) and 31 (91%) patients could achieve recovery of the extensor and flexor muscle strength in the reconstructed knee to 80% or more of normal knee strength, respectively. A statistically significant difference exists in thigh girth difference, extensor strength ratio, and flexor strength ratio before and after reconstruction. Tunnel expansion with more than 1 mm was identified in 2 (6%) tibial tunnels. Our study revealed satisfactory clinical subjective and objective results at 4-7 years follow-up. Quadriceps tendon autograft has the advantage of being self-available, relatively easier arthroscopic technique, and having a suitable size, making it an acceptable graft choice for ACL reconstruction. There is little quadriceps muscle strength loss after quadriceps harvest. A quadriceps tendon-patellar autograft is an adequate graft choice to ACL reconstruction.

Adolescent↗

PubMed2006

Quantification of FDG PET studies using standardised uptake values in multi-centre trials: effects of image reconstruction, resolution and ROI definition parameters.

PURPOSE: Standardised uptake values (SUVs) depend on acquisition, reconstruction and region of interest (ROI) parameters. SUV quantification in multi-centre trials therefore requires standardisation of acquisition and analysis protocols. However, standardisation is difficult owing to the use of different scanners, image reconstruction and data analysis software. In this study we evaluated whether SUVs, obtained at three different institutes, may be directly compared after calibration and correction for inter-institute differences. METHODS: First, an anthropomorphic thorax phantom containing variously sized spheres and activities, simulating tumours, was scanned and processed in each institute to evaluate differences in scanner calibration. Secondly, effects of image reconstruction and ROI method on recovery coefficients were studied. Next, SUVs were derived for tumours in 23 subjects. Of these 23 patients, four and ten were scanned in two institutes on an HR+ PET scanner and nine were scanned in one institute on an ECAT EXACT PET scanner. All phantom and clinical data were reconstructed using iterative reconstruction with various iterations, with both measured (MAC) and segmented attenuation correction (SAC) and at various image resolutions. Activity concentrations (AC) or SUVs were derived using various ROI isocontours. RESULTS: Phantom data revealed differences in SUV quantification of up to 30%. After application-specific calibration, recovery coefficients obtained in each institute were equal to within 15%. Varying the ROI isocontour value resulted in a predictable change in SUV (or AC) for both phantom and clinical data. Variation of image resolution resulted in a predictable change in SUV quantification for large spheres/tumours (>5 cc) only. For smaller tumours (<2 cc), differences of up to 40% were found between high (7 mm) and low (10 mm) resolution images. Similar differences occurred when data were reconstructed with a small number of iterations. Finally, no significant differences between MAC and SAC reconstructed data were observed, except for tumours near the diaphragm. CONCLUSION: Standardisation of acquisition, reconstruction and ROI methods is preferred for SUV quantification in multi-centre trials. Small unavoidable differences in methodology can be accommodated by performing a phantom study to assess inter-institute correction factors.

Algorithms↗

PubMed2002

Reconstructive procedure after distal gastrectomy for gastric cancer that best prevents duodenogastroesophageal reflux.

Billroth I and II reconstructions are commonly performed after distal gastrectomy. Both may cause duodenogastric and duodenogastroesophageal reflux, conditions reported to have carcinogenetic potential. The aim of this study was to investigate which reconstructive procedure would most effectively prevent bile reflux into the gastric remnant and esophagus after distal gastrectomy. A group of 92 patients who underwent curative distal gastrectomy for gastric cancer were subjected and classified into three groups retrospectively by the reconstructive procedure undertaken: group A, Roux-en-Y (Roux-Y) reconstruction (n = 29); group B, Billroth I reconstruction (n = 41); group C, Billroth II reconstruction (n = 22). The bile reflux periods (percent time) for the gastric remnant and esophagus were measured with the Bilitec 2000 under standardized conditions. The percent time for the gastric remnant was significantly less in group A than in group B or C. In 61% of all patients, bile reflux into the esophagus was found to be more than 5.0% of the time; it was less in group A than in group B or C (p = 0.057). A questionnaire revealed a good correlation between the incidence of reflux symptoms and the percent time for the gastric remnant and esophagus. Roux-Y reconstruction is superior to either Billroth I or II reconstruction for preventing bile reflux into the gastric remnant and esophagus after distal gastrectomy.

Adult↗

PubMed1998

Arterial reconstruction: justified for patients with intermittent claudication?

The objective of this study was to evaluate the effects of arterial reconstruction in patients with intermittent claudication. A total of 243 patients (305 limbs) underwent lower extremity vascular reconstruction at our institution from 1979 to 1995. They were assessed by physical examination, pulse volume recordings, segmental pressure, Duplex ultrasonography, and intravenous subtraction arteriography to evaluate the effects of arterial reconstruction. Surviving patients (220 limbs) were enrolled for evaluation of outcome during the follow-up period. There were 59 deaths during the follow-up period. The cumulative life-table 5-year patency rates were 90% +/- 3%, 73% +/- 6%, and 74% +/- 10% for aortoiliac, infrainguinal, and aortofemorodistal arterial reconstructions, respectively. Among 129 repairs in the aortoiliac region, Fontaine stages I, II, and III were found in 109 limbs (84.5%), 17 limbs (13.2%), and 2 limbs (1.5%), respectively. There was one (0.7%) minor amputation. There was Fontaine stage I in 50 limbs (76.9%), Fontaine stage II in 14 limbs (21.5%), and Fontaine stage III in 1 limb (1.5%) for repairs in the infrainguinal region. Among the 26 aortofemorodistal repairs, there was Fontaine stage I in 21 limbs (81%) and Fontaine stage II in 5 limbs (19%). There was a statistically significantly higher incidence of Fontaine stage I than Fontaine stage II or III in aortofemoral, infrainguinal, and aortofemorodistal arterial reconstructions (p < 0.0001). Arterial reconstruction for patients at Fontaine stage II offered benefits and improved quality of life at follow-up. Arterial reconstruction for patients at Fontaine stage II offers benefits and improved quality of life at follow-up. It was concluded that the significant improvement in quality of life after arterial reconstruction warrants continued use of the procedure in patients with intermittent claudication.

Adult↗

PubMed2003

Primary ACL reconstruction with fresh-frozen patellar versus Achilles tendon allografts.

BACKGROUND: In recent years, there has been an interest in the use of allografts as an alternative graft for anterior cruciate ligament (ACL) reconstruction to reduce potential donor-site morbidity resulting from the harvest of autogenous tissue. Nevertheless, in the literature, the use of allografts for primary ACL reconstruction is controversial due to a higher failure rate and the potential risk of disease transmission. METHOD: In this retrospective study, we evaluated the clinical outcome of 251 fresh-frozen patellar vs Achilles tendon allografts for primary ACL reconstruction. Patients (average age 39 years) were operated on between 1993 and 1998, and the mean follow-up was 37.7 months (range 24-74 months). We were able to follow up 225 patients (89.6%). According to the different types of allograft, we divided the patients into two groups: group P with patellar bone-tendon-bone allograft (BTB; n=183) and group A with Achilles bone-tendon allograft ( n=42). Clinical evaluation consisted of a history, an examination, IKDC Score, Cincinnati Knee Score (CKS), Cincinnati Sports Activity Scale (CSAS), KT-1000 testing, and standardized X-rays. RESULTS: According to the IKDC, the outcome was normal or nearly normal in 75.3% in group P and 76.2% in group A. Overall rating according to the CKS was an average of 85 in group P and 82.9 in group A. CSAS was 79.6 in group P and 84.8 in group A. The objective stability measured with the KT-1000 showed an average side-to-side difference of 2.1 mm in group P and 2.0 mm in group A. 4.4% of group P and 2.5% of group A were considered a laxity failure, and 10.4% of group P and 4.8% of group A re-ruptured the reconstructed ACL. In summary, there was a significantly higher failure rate ( p<0.001) in group P compared with group A. CONCLUSION: Satisfactory clinical results can be achieved with the use of allografts for primary ACL reconstruction. Comparing Achilles tendon and patellar BTB allografts, the Achilles tendon-bone allograft seems to be advantageous for ACL reconstruction as the failure rate was significantly lower. Nevertheless, the total failure rate appears to be much higher compared with autogenous ACL reconstruction, indicating that the use of an allograft for routine uncomplicated primary ACL reconstruction offers few advantages. Therefore, autograft tissue remains our graft of first choice for this procedure. We advise reserving allografts for revision procedures where suitable autogenous tissues have been previously compromised, where a contraindication for autogenous tissue harvest exists, or for multiple ligament surgery.

Achilles Tendon↗

PubMed2006

Intraoperative assessment of reconstructed vessels in living-donor liver transplantation, using a novel fluorescence imaging technique.

BACKGROUND/PURPOSE: In living-donor liver transplantation (LDLT), hepatic arterial thrombosis and portal venous thrombosis are critical problems that can result in graft loss. Only intraoperative Doppler ultrasound (IDUS) is able to evaluate blood flow in the reconstructed vessels. The aim of this study was to evaluate the utility of a newly developed fluorescence imaging technique using indocyanine green (ICG) for visualizing reconstructed vessels. METHODS: In three patients who had undergone LDLT, IDUS was performed after reconstruction of the portal vein and hepatic artery. Fluorescence images were then recorded, using a SPY system (Novadeq Technologies), which employs ICG as a fluorescent imaging medium activated by light. The ICG (3.75 mg) was injected intravenously, then, 10 s later, the images were recorded for 30 s (first photographic recording). Two minutes later, the same procedure was repeated (second photographic recording), and 40 min later, images were obtained without injection of ICG (third photographic recording). RESULTS: After portal venous reconstruction, IDUS demonstrated a nonphasic and continuous waveform, with a mean velocity of 52.1 cm/s and a mean portal blood flow volume of 69.5 ml/s per kg. After hepatic arterial reconstruction, a pulsatile waveform with a mean peak systolic velocity of 52.4 cm/s and a mean resistance index of 0.76 was obtained. The first photographic recording clearly visualized the blood flow in the reconstructed hepatic artery, without kinking or stenosis, in all three patients. The second photographic recording visualized the flow in the portal vein without stenosis, kinking, or stagnation. The third photographic recording demonstrated the excretion of ICG into bile, thus confirming bile production by the grafts. CONCLUSIONS: Fluorescence imaging can clearly visualize the reconstructed hepatic artery and portal vein and demonstrate the production of bile by a transplanted liver graft. A combination of IDUS and the new system can guarantee the patency of the reconstructed vessels.

Blood Flow Velocity↗

PubMed2006

Endoscopic anterior cruciate ligament reconstruction using a computer-assisted fluoroscopic navigation system.

BACKGROUND: During anterior cruciate ligament (ACL) reconstruction, placement of the reconstructed ligament affects the clinical results. To accomplish accurate and reproducible placement of the tibial bone tunnel, we employed a fluoroscopic navigation system for endoscopic ACL reconstruction. In this study, preciseness of the tibial tunnel placement was evaluated, and the advantages and disadvantages of this navigation system for endoscopic ACL reconstruction are discussed. METHODS: Altogether, 16 knees of 16 patients who had undergone ACL reconstruction using this system (navi group) were evaluated regarding the positioning of the tibial tunnel against Blumensaat's line using X-p and the route of the graft by magnetic resonance imaging (MRI). Another 16 knees of 16 patients who underwent endoscopic ACL reconstruction without the navigation system were the controls (control group). RESULTS: At the 1-year follow-up, maximally extended lateral knee X-p revealed that the anterior edge of the tibial tunnel and Blumensaat's line were almost aligned and that roof impingement was avoided; the T2-weighted MR images showed that the graft was placed close to and parallel to the intercondylar roof in all the knees of the navi group. The ratio of the distance between Blumensaat's line and the anterior edge of the tibial tunnel at the level of the tibial plateau to the anteroposterior width in fully extended true lateral radiographs was 2.7% +/- 3.4% in the navi group and 8.4% +/- 7.4% in the control group. CONCLUSIONS: The computer-assisted fluoroscopic navigation system improves accuracy and decreases dispersion of the tibial tunnel placement against Blumensaat's line in single-bundle ACL reconstruction. This innovative device renders the reconstruction procedure more reliable, eliminating the problem of skeletal variation among patients. However, the function of this navigation system for femoral tunnel placement is insufficient at present. Further refinement of the system is necessary, and the method of application requires improvement.

Adolescent↗

PubMed2003

Vascular reconstruction in limbs associated with resection of tumors.

Patients with tumors in limbs who undergo surgical treatment may present involvement of major vessels. The artery must be reconstructed for limb salvage and the vein may be reconstructed to avoid the onset of venous hypertension. The objective of this study was to analyze the results from surgical treatment of tumors associated with vascular reconstruction in limbs. A prospective follow-up was made of 17 patients with tumors involving major vessels in limbs who underwent vascular reconstruction. Arterial and venous reconstructions were performed in nine patients, arterial reconstruction was performed in six, and venous reconstruction in two patients. The vascular substitutes used were greater saphenous vein (19), expanded polytetrafluoroethylene prosthesis (5), and Dacron prosthesis (2). Vascular complications occurred in seven patients: one arterial graft rupture, three venous graft occlusions, and lymphedema in five patients. The following nonvascular complications occurred in 10 patients: pulmonary metastasis (7), local recurrence (2), neurological deficit (2), infection (2), partial necrosis of the flap (1), and enteric fistula (1). Six patients with pulmonary metastasis died. One patient underwent transfemoral amputation. Major vessel reconstruction in limbs associated with resection of neoplasms is a safe procedure. Venous revascularization should be performed using an autologous substitute.

Adult↗

PubMed1995

Loss of viable neuronal units in the proximal stump as possible cause for poor function recovery following nerve reconstructions.

Function recovery after nerve reconstructions is often poor. Could this be caused by a loss of viable neuronal units proximal to the nerve reconstruction? The number of neuronal units (i.e., a motor or sensory neuron, including its axon and axonal branches) in the proximal segments of reconstructed peripheral nerves were studied using a novel magnetic recording technique. In five rabbits a common personal nerve was transected and microsurgically reconstructed. After 8 weeks regeneration time the nerve compound action signals were recorded magnetically from the reconstructed as well as from the healthy contralateral peroneal nerve and from peroneal nerves of five unoperated control animals. The amplitudes of the recorded signals were compared and the diameter distribution histograms were calculated. These calculations were based on the conduction distance between the stimulator and the sensor and the conduction velocities of 30 different axon diameter classes ranging from 3 to 18 microns. Our results indicate that there is a reduction of approximately 50% in the number of viable neuronal units at 10 mm proximal to a simple nerve reconstruction after 8 weeks regeneration time. The number of neuronal units innervating a hand is strongly correlated with clinical function in a healthy hand. The reduction in viable neuronal units after a reconstruction, demonstrated in our experiments, corresponds with a frequently clinically observed decrease in function after nerve reconstructions. Therefore, we suggest that the number of viable neuronal units may be a good indicator of final functional recovery.

Action Potentials↗

PubMed1989

Biomechanical analysis of finger flexor pulley reconstruction.

Fifty cadaver digits were used to study the mechanical properties of five different methods of pulley reconstruction and the effectiveness of three different pulley reconstructive arrangements in restoring a normal relationship between tendon excursion and joint motion. All reconstructed pulleys showed less stiffness and more displacement before failure than normal intact pulleys. Although reconstruction using a length of another tendon woven through the remaining fibrous rim of the pulley and both double and triple tendon graft loops around bone absorbed more energy to failure than a normal pulley, only the triple loop around bone could withstand as much load before failure as a normal pulley. No reconstruction restored a normal tendon excursion/joint motion relationship, but reconstruction of the A2 and A4 pulleys restored a more normal relationship than either the "belt loop" reconstruction or a combination belt loop, A2 and A4 reconstruction.

Biomechanical Phenomena↗

PubMed1988

The reconstruction of helical particles with variable pitch.

In the reconstruction of helical particles, it is normally assumed that translation along the length of a particle is coupled to rotation about its axis. This assumption is not valid for particles whose pitch varies along the particle length (e.g. actin, HbS fibers), and application of the usual algorithms results in significant errors in both the shape and coordinates of subunits in the reconstructed density map. We have developed an iterative procedure for reconstructing particles with variable pitch. The goal of this procedure is to obtain an accurate estimate of the local pitch of the particle which can then be incorporated into the reconstruction algorithm. This involves synthesis of trial model structures which have constant pitch. The local pitch is derived from a cross-correlation analysis between these trial models and the variable pitch particles. The constant pitch models are constructed using coordinates measured from the reconstructed density maps. Each iteration of the procedure provides an improved estimate of the pitch which is incorporated into the succeeding iteration. The fidelity of the reconstruction is determined from cross-correlation between the original micrograph and a variable pitch model. The iterations are continued until the cross-correlation coefficient between the variable pitch model and the micrograph of the particle is maximized. The implementation of the iterative procedure is described and its behavior is evaluated using model structures which incorporate variations in pitch similar to those actually occurring in sickle hemoglobin fibers. The results indicate that the iterative reconstruction procedure considerably reduces the errors associated with constant pitch reconstructions. These tests provide a basis for applying this procedure in the structural analysis of micrographs of helical particles which display variable pitch. Application to sickle hemoglobin fibers resulted in an improvement in the accuracy with which the hemoglobin S molecules can be located in the density maps.

Algorithms↗