Resonant Ultrasound Spectroscopy for Irregularly Shaped Samples and Its Application to Uranium Ditelluride

Resonant ultrasound spectroscopy (RUS) is a powerful technique for measuring the full elastic tensor of a given material in a single experiment. Previously, this technique was practically limited to regularly shaped samples such as rectangular parallelepipeds, spheres, and cylinders [W. M. Visscher et al. J. Acoust. Soc. Am. 90, 2154 (1991)JASMAN0001-496610.1121/1.401643]. We demonstrate a new method for determining the elastic moduli of irregularly shaped samples, extending the applicability of RUS to a much larger set of materials. We apply this new approach to the recently discovered unconventional superconductor UTe_{2} and provide its elastic tensor at both 300 and 4 kelvin.

Quantum Oscillations in Graphene Using Surface Acoustic Wave Resonators

Surface acoustic waves (SAWs) provide a contactless method for measuring wave-vector-dependent conductivity. This technique has been used to discover emergent length scales in the fractional quantum Hall regime of traditional, semiconductor-based heterostructures. SAWs would appear to be an ideal match for van der Waals heterostructures, but the right combination of substrate and experimental geometry to allow access to the quantum transport regime has not yet been found. We demonstrate that SAW resonant cavities fabricated on LiNbO_{3} substrates can be used to access the quantum Hall regime of high-mobility, hexagonal boron nitride encapsulated, graphene heterostructures. Our work establishes SAW resonant cavities as a viable platform for performing contactless conductivity measurements in the quantum transport regime of van der Waals materials.

Rapid method for computing the mechanical resonances of irregular objects

A solid object's geometry, density, and elastic moduli completely determine its spectrum of normal modes. Solving the inverse problem-determining a material's elastic moduli given a set of resonance frequencies and sample geometry-relies on the ability to compute resonance spectra accurately and efficiently. Established methods for calculating these spectra are either fast but limited to simple geometries, or are applicable to arbitrarily shaped samples at the cost of being prohibitively slow. Here, we describe a method to rapidly compute the normal modes of irregularly shaped objects using entirely open-source software. Our method's accuracy compares favorably with existing methods for simple geometries and shows a significant improvement in speed over existing methods for irregular geometries.

Weyl Fermion magneto-electrodynamics and ultralow field quantum limit in TaAs

Topological semimetals are predicted to exhibit unconventional electrodynamics, but a central experimental challenge is singling out the contributions from the topological bands. TaAs is the prototypical example, where 24 Weyl points and 8 trivial Fermi surfaces make the interpretation of any experiment in terms of band topology ambiguous. We report magneto-infrared reflection spectroscopy measurements on TaAs. We observed sharp inter-Landau level transitions from a single pocket of Weyl Fermions in magnetic fields as low as 0.4 tesla. We determine the W2 Weyl point to be 8.3 meV below the Fermi energy, corresponding to a quantum limit—the field required to reach the lowest LL—of 0.8 tesla—unprecedentedly low for Weyl Fermions. LL spectroscopy allows us to isolate these Weyl Fermions from all other carriers in TaAs, and our result provides a way for directly exploring the more exotic quantum phenomena in Weyl semimetals, such as the chiral anomaly.

Remarkably Weak Anisotropy in Thermal Conductivity of Two-Dimensional Hybrid Perovskite Butylammonium Lead Iodide Crystals

Two-dimensional (2D) hybrid organic-inorganic perovskites consisting of alternating organic and inorganic layers are a new class of layered structures. They have attracted increasing interest for photovoltaic, optoelectronic, and thermoelectric applications, where knowing their thermal transport properties is critical. We carry out both experimental and computational studies on thermal transport properties of 2D butylammonium lead iodide crystals and find their thermal conductivity is ultralow (below 0.3 W m^-1 K^-1) with very weak anisotropy (around 1.5) among layered crystals. Further analysis reveals that the unique structure with the preferential alignment of organic chains and complicated energy landscape leads to moderately smaller phonon lifetimes in the out-of-plane direction and comparable phonon group velocities in in-plane and out-of-plane directions. These new findings may guide the future design of novel hybrid materials with desired thermal conductivity for various applications.

Extent of Fermi-surface reconstruction in the high-temperature superconductor HgBa2CuO4+δ

High magnetic fields have revealed a surprisingly small Fermi surface in underdoped cuprates, possibly resulting from Fermi-surface reconstruction due to an order parameter that breaks translational symmetry of the crystal lattice. A crucial issue concerns the doping extent of such a state and its relationship to the principal pseudogap and superconducting phases. We employ pulsed magnetic-field measurements on the cuprate [Formula: see text]Cu[Formula: see text] to identify signatures of Fermi-surface reconstruction from a sign change of the Hall effect and a peak in the temperature-dependent planar resistivity. We trace the termination of Fermi-surface reconstruction to two hole concentrations where the superconducting upper critical fields are found to be enhanced. One of these points is associated with the pseudogap endpoint near optimal doping. These results connect the Fermi-surface reconstruction to both superconductivity and the pseudogap phenomena.

One-component order parameter in URu2Si2 uncovered by resonant ultrasound spectroscopy and machine learning

The unusual correlated state that emerges in URu2Si2 below T HO = 17.5 K is known as "hidden order" because even basic characteristics of the order parameter, such as its dimensionality (whether it has one component or two), are "hidden." We use resonant ultrasound spectroscopy to measure the symmetry-resolved elastic anomalies across T HO. We observe no anomalies in the shear elastic moduli, providing strong thermodynamic evidence for a one-component order parameter. We develop a machine learning framework that reaches this conclusion directly from the raw data, even in a crystal that is too small for traditional resonant ultrasound. Our result rules out a broad class of theories of hidden order based on two-component order parameters, and constrains the nature of the fluctuations from which unconventional superconductivity emerges at lower temperature. Our machine learning framework is a powerful new tool for classifying the ubiquitous competing orders in correlated electron systems.

Spatial control of heavy-fermion superconductivity in CeIrIn5

Although crystals of strongly correlated metals exhibit a diverse set of electronic ground states, few approaches exist for spatially modulating their properties. In this study, we demonstrate disorder-free control, on the micrometer scale, over the superconducting state in samples of the heavy-fermion superconductor CeIrIn5. We pattern crystals by focused ion beam milling to tailor the boundary conditions for the elastic deformation upon thermal contraction during cooling. The resulting nonuniform strain fields induce complex patterns of superconductivity, owing to the strong dependence of the transition temperature on the strength and direction of strain. These results showcase a generic approach to manipulating electronic order on micrometer length scales in strongly correlated matter without compromising the cleanliness, stoichiometry, or mean free path.

Thermodynamic Signatures of Weyl Fermions in NbP

We present a high magnetic field study of NbP—a member of the monopnictide Weyl semimetal (WSM) family. While the monoarsenides (NbAs and TaAs) have topologically distinct left and right-handed Weyl fermi surfaces, NbP is argued to be “topologically trivial” due to the fact that all pairs of Weyl nodes are encompassed by a single Fermi surface. We use torque magnetometry to measure the magnetic response of NbP up to 60 tesla and uncover a Berry paramagnetic response, characteristic of the topological Weyl nodes, across the entire field range. At the quantum limit B^* (≈32 T), τ/B experiences a change in slope when the chemical potential enters the last Landau level. Our calculations confirm that this magnetic response arises from band topology of the Weyl pocket, even though the Fermi surface encompasses both Weyl nodes at zero magnetic field. We also find that the magnetic field pulls the chemical potential to the chiral n = 0 Landau level in the quantum limit, providing a disorder-free way of accessing chiral Weyl fermions in systems that are “not quite” WSMs in zero magnetic field.

Magnetoresistance Scaling Reveals Symmetries of the Strongly Correlated Dynamics in BaFe_{2}(As_{1-x}P_{x})_{2}

The phenomenon of T-linear resistivity commonly observed in a number of strange metals has been widely seen as evidence for the breakdown of the quasiparticle picture of metals. This study shows that a recently discovered H/T scaling relationship in the magnetoresistance of the strange metal BaFe_{2}(As_{1-x}P_{x})_{2} is independent of the relative orientations of current and magnetic field. Rather, its magnitude and form depend only on the orientation of the magnetic field with respect to a single crystallographic axis: the direction perpendicular to the magnetic iron layers. This finding suggests that the magnetotransport scaling does not originate from the conventional averaging or orbital velocity of quasiparticles as they traverse a Fermi surface, but rather from dissipation arising from two-dimensional correlations.

Resonant torsion magnetometry in anisotropic quantum materials

Unusual behavior in quantum materials commonly arises from their effective low-dimensional physics, reflecting the underlying anisotropy in the spin and charge degrees of freedom. Here we introduce the magnetotropic coefficient k = ∂²F/∂θ², the second derivative of the free energy F with respect to the magnetic field orientation θ in the crystal. We show that the magnetotropic coefficient can be quantitatively determined from a shift in the resonant frequency of a commercially available atomic force microscopy cantilever under magnetic field. This detection method enables part per 100 million sensitivity and the ability to measure magnetic anisotropy in nanogram-scale samples, as demonstrated on the Weyl semimetal NbP. Measurement of the magnetotropic coefficient in the spin-liquid candidate RuCl₃ highlights its sensitivity to anisotropic phase transitions and allows a quantitative comparison to other thermodynamic coefficients via the Ehrenfest relations.

Scale-invariant magnetoresistance in a cuprate superconductor

The anomalous metallic state in the high-temperature superconducting cuprates is masked by superconductivity near a quantum critical point. Applying high magnetic fields to suppress superconductivity has enabled detailed studies of the normal state, yet the direct effect of strong magnetic fields on the metallic state is poorly understood. We report the high-field magnetoresistance of thin-film La_2-x Sr _x CuO₄ cuprate in the vicinity of the critical doping, 0.161 ≤ p ≤ 0.190. We find that the metallic state exposed by suppressing superconductivity is characterized by magnetoresistance that is linear in magnetic fields up to 80 tesla. The magnitude of the linear-in-field resistivity mirrors the magnitude and doping evolution of the well-known linear-in-temperature resistivity that has been associated with quantum criticality in high-temperature superconductors.

Nonzero Berry phase in quantum oscillations from giant Rashba-type spin splitting in LaTiO3/SrTiO3 heterostructures

The manipulation of the spin degrees of freedom in a solid has been of fundamental and technological interest recently for developing high-speed, low-power computational devices. There has been much work focused on developing highly spin-polarized materials and understanding their behavior when incorporated into so-called spintronic devices. These devices usually require spin splitting with magnetic fields. However, there is another promising strategy to achieve spin splitting using spatial symmetry breaking without the use of a magnetic field, known as Rashba-type splitting. Here we report evidence for a giant Rashba-type splitting at the interface of LaTiO₃ and SrTiO₃. Analysis of the magnetotransport reveals anisotropic magnetoresistance, weak anti-localization and quantum oscillation behavior consistent with a large Rashba-type splitting. It is surprising to find a large Rashba-type splitting in 3d transition metal oxide-based systems such as the LaTiO₃/SrTiO₃ interface, but it is promising for the development of a new kind of oxide-based spintronics.

Rashba-type splitting is an effective way to manipulate the spin degrees of freedom in a solid without external magnetic field. Here, the authors demonstrate a strong Rashba-type splitting at the interface of LaTiO₃ and SrTiO₃ which is promising for the development of oxide-based spintronics.

Robust spin correlations at high magnetic fields in the harmonic honeycomb iridates

The complex antiferromagnetic orders observed in the honeycomb iridates are a double-edged sword in the search for a quantum spin-liquid: both attesting that the magnetic interactions provide many of the necessary ingredients, while simultaneously impeding access. Focus has naturally been drawn to the unusual magnetic orders that hint at the underlying spin correlations. However, the study of any particular broken symmetry state generally provides little clue about the possibility of other nearby ground states. Here we use magnetic fields approaching 100 Tesla to reveal the extent of the spin correlations in γ-lithium iridate. We find that a small component of field along the magnetic easy-axis melts long-range order, revealing a bistable, strongly correlated spin state. Far from the usual destruction of antiferromagnetism via spin polarization, the high-field state possesses only a small fraction of the total iridium moment, without evidence for long-range order up to the highest attainable magnetic fields.The complex antiferromagnetic orders observed in the honeycomb iridates prevent access to a spin-liquid ground state. Here the authors apply extremely high magnetic fields to destroy the antiferromagnetic order in γ-lithium iridate and reveal a bistable, strongly correlated spin state.

Magnetic field tuning of an excitonic insulator between the weak and strong coupling regimes in quantum limit graphite

The excitonic insulator phase has long been predicted to form in proximity to a band gap opening in the underlying band structure. The character of the pairing is conjectured to crossover from weak (BCS-like) to strong coupling (BEC-like) as the underlying band structure is tuned from the metallic to the insulating side of the gap opening. Here we report the high-magnetic field phase diagram of graphite to exhibit just such a crossover. By way of comprehensive angle-resolved magnetoresistance measurements, we demonstrate that the underlying band gap opening occurs inside the magnetic field-induced phase, paving the way for a systematic study of the BCS-BEC-like crossover by means of conventional condensed matter probes.

Hydrogel coated mesh decreases tissue reaction resulting from polypropylene mesh implant: implication in hernia repair

PURPOSE

Use of polypropylene mesh (PPM) in hernia repair is associated with tissue reactivity. We examined, in a rat model, a novel non-biodegradable hydrogel coated PPM which may allow for decreased inflammation and a decreased foreign body reaction.

METHODS

Through a dorsal midline incision, a 2 cm × 2 cm section of PPM (either coated or uncoated) was placed on the fascial surface 1.5 cm from the incision on the dorsal wall of Sprague-Dawley rats. At 2 and 12 weeks after placement, the PPM and surrounding tissue were harvested. A board-certified dermatopathologist examined H&E stained slides for fibrosis and foreign body reaction. In addition, tissues were stained for apoptotic cells, oxidative damage, macrophages, fibroblasts, neovascularization and metalloproteases.

RESULTS

At 2 and 12 weeks, there was a greater than 95 % decrease in foreign body giant cells in coated PPM samples compared to uncoated; fibrosis was decreased by 50 %. At 2 and 12 weeks, oxidative damage, fibroblast accumulation, apoptosis and macrophages were significantly decreased in coated PPM samples compared to uncoated PPM.

CONCLUSION

These results demonstrate that a non-biodegradable hydrogel coating of PPM led to significant reduction in foreign body reaction, oxidative stress and apoptosis compared to uncoated PPM in vivo, and suggest that this coating could be clinically useful in hernia repair.

Nodal bilayer-splitting controlled by spin-orbit interactions in underdoped high-Tc cuprates

The highest superconducting transition temperatures in the cuprates are achieved in bilayer and trilayer systems, highlighting the importance of interlayer interactions for high Tc. It has been argued that interlayer hybridization vanishes along the nodal directions by way of a specific pattern of orbital overlap. Recent quantum oscillation measurements in bilayer cuprates have provided evidence for a residual bilayer-splitting at the nodes that is sufficiently small to enable magnetic breakdown tunneling at the nodes. Here we show that several key features of the experimental data can be understood in terms of weak spin-orbit interactions naturally present in bilayer systems, whose primary effect is to cause the magnetic breakdown to be accompanied by a spin flip. These features can now be understood to include the equidistant set of three quantum oscillation frequencies, the asymmetry of the quantum oscillation amplitudes in c-axis transport compared to ab-plane transport, and the anomalous magnetic field angle dependence of the amplitude of the side frequencies suggestive of small effective g-factors. We suggest that spin-orbit interactions in bilayer systems can further affect the structure of the nodal quasiparticle spectrum in the superconducting phase. PACS numbers: 71.45.Lr, 71.20.Ps, 71.18.+y.

Evidence for a small hole pocket in the Fermi surface of underdoped YBa2Cu3Oy

In underdoped cuprate superconductors, the Fermi surface undergoes a reconstruction that produces a small electron pocket, but whether there is another, as yet, undetected portion to the Fermi surface is unknown. Establishing the complete topology of the Fermi surface is key to identifying the mechanism responsible for its reconstruction. Here we report evidence for a second Fermi pocket in underdoped YBa2Cu3Oy, detected as a small quantum oscillation frequency in the thermoelectric response and in the c-axis resistance. The field-angle dependence of the frequency shows that it is a distinct Fermi surface, and the normal-state thermopower requires it to be a hole pocket. A Fermi surface consisting of one electron pocket and two hole pockets with the measured areas and masses is consistent with a Fermi-surface reconstruction by the charge-density-wave order observed in YBa2Cu3Oy, provided other parts of the reconstructed Fermi surface are removed by a separate mechanism, possibly the pseudogap.

Direct measurement of the upper critical field in cuprate superconductors

In the quest to increase the critical temperature Tc of cuprate superconductors, it is essential to identify the factors that limit the strength of superconductivity. The upper critical field Hc2 is a fundamental measure of that strength, yet there is no agreement on its magnitude and doping dependence in cuprate superconductors. Here we show that the thermal conductivity can be used to directly detect Hc2 in the cuprates YBa2Cu3Oy, YBa2Cu4O8 and Tl2Ba2CuO6+δ, allowing us to map out Hc2 across the doping phase diagram. It exhibits two peaks, each located at a critical point where the Fermi surface of YBa2Cu3Oy is known to undergo a transformation. Below the higher critical point, the condensation energy, obtained directly from Hc2, suffers a sudden 20-fold collapse. This reveals that phase competition-associated with Fermi-surface reconstruction and charge-density-wave order-is a key limiting factor in the superconductivity of cuprates.

Bounding the pseudogap with a line of phase transitions in YBa2Cu3O6+δ

Close to optimal doping, the copper oxide superconductors show 'strange metal' behaviour, suggestive of strong fluctuations associated with a quantum critical point. Such a critical point requires a line of classical phase transitions terminating at zero temperature near optimal doping inside the superconducting 'dome'. The underdoped region of the temperature-doping phase diagram from which superconductivity emerges is referred to as the 'pseudogap' because evidence exists for partial gapping of the conduction electrons, but so far there is no compelling thermodynamic evidence as to whether the pseudogap is a distinct phase or a continuous evolution of physical properties on cooling. Here we report that the pseudogap in YBa2Cu3O6+δ is a distinct phase, bounded by a line of phase transitions. The doping dependence of this line is such that it terminates at zero temperature inside the superconducting dome. From this we conclude that quantum criticality drives the strange metallic behaviour and therefore superconductivity in the copper oxide superconductors.

Incisional hernia recurrence through genomic profiling: a pilot study

PURPOSE

Although situational risk factors for incisional hernia formation are known, the methods used to determine who would be most susceptible to develop one are unreliable. We hypothesized that patients with recurrent incisional hernias may possess unique gene expression profiles.

METHODS

Skin and intact fascia were collected from 15 normal control (NC) patients with no hernia history and 18 patients presenting for recurrent incisional hernia (RH) repair. Microarray analysis was performed using whole genome microarray chips on NC (n = 8) and RH (n = 9). These samples were further investigated using a pathway-specific PCR array containing fibrosis-related genes.

RESULTS

Microarray data revealed distinct differences in the gene expression profiles between RH and NC patients. One hundred and sixty-seven genes in the skin and 7 genes in the fascia were differentially expressed, including 8 directly involved in collagen synthesis. In particular, GREMLIN1, or bone morphogenetic protein antagonist 1, was under expressed in skin (fold = 0.49, p < 10(-7), q = 0.0009) and fascia (fold = 0.23, p < 10(-4), q = 0.095) of RH patients compared with NC. The PCR array data supported previous reports of decreased collagen I/III ratios in skin of RH versus NC (mean = 1.51 ± 0.73 vs. mean = 2.26 ± 0.99; one-sided t test, p = 0.058).

CONCLUSION

To our knowledge, this is the first microarray-based analysis to show distinct gene expression profiles between the skin and fascia of RH and NC patients and the first report of an association between GREMLIN1 and incisional hernia formation. Our results suggest that gene expression profiles may act as surrogate markers that stratify patients into different groups at risk for hernia development prior to their initial surgery.

Conjugation of gold nanoparticles to polypropylene mesh for enhanced biocompatibility

Polypropylene mesh materials have been utilized in hernia surgery for over 40 years. However, they are prone to degradation due to the body's aggressive foreign body reaction, which may cause pain or complications, forcing mesh removal from the patient. To mitigate these complications, gold nanomaterials were attached to polypropylene mesh in order to improve cellular response. Pristine samples of polypropylene mesh were exposed to hydrogen peroxide/cobalt chloride solutions to induce formation of surface carboxyl functional groups. Gold nanoparticles were covalently linked to the mesh. Scanning electron microscopy confirmed the presence of gold nanoparticles. Differential scanning calorimetry and mechanical testing confirmed that the polypropylene did not undergo any significantly detrimental changes in physicochemical properties. A WST-1 cell culture study showed an increase in cellularity on the gold nanoparticle-polypropylene mesh as compared to pristine mesh. This study showed that biocompatibility of polypropylene mesh may be improved via the conjugation of gold nanoparticles.

Assessment of the biocompatibility of two novel, bionanocomposite scaffolds in a rodent model

Two novel, bionanocomposite scaffolds were evaluated in a rodent model over the course of three months to determine whether these scaffolds possessed adequate biocompatibility characteristics to warrant further evaluation as possible tissue reconstruction scaffolds. These bionanocomposite scaffolds were comprised of amine-functionalized gold nanoparticles (AuNP) or silicon carbide nanowires (SiCNW) crosslinked to an acellular porcine diaphragm tendon. It was hypothesized that the addition of nanomaterials to the porcine tendon would also improve its biocompatibility by imparting a nanostructured surface. As early as seven days after implantation, both types of bionanocomposite scaffolds displayed evidence of granulation tissue and the beginning of scaffold remodeling with new collagen deposited by the host, and by ninety-seven days the bionanocomposite scaffolds were completely remodeled with no evidence of any adverse host tissue reaction or scar tissue formation. The AuNP bionanocomposite scaffolds exhibited accelerated scaffold remodeling compared to the SiCNW scaffolds.

Method of preparing a decellularized porcine tendon using tributyl phosphate

Extracellular matrix (ECM) materials are currently utilized for soft tissue repair applications such as vascular grafts, tendon reconstruction, and hernia repair. These materials are derived from tissues such as human dermis and porcine small intestine submucosa, which must be rendered acellular to prevent disease transmission and decrease the risk of an immune response. The ideal decellularization technique removes cells and cellular remnants, but leaves the original collagen architecture intact. The tissue utilized in this study was the central tendon of the porcine diaphragm, which had not been previously investigated for soft tissue repair. Several treatments were investigated during this study including peracetic acid, TritonX-100, sodium dodecyl sulfate, and tri(n-butyl) phosphate (TnBP). Of the decellularization treatments investigated, only 1% TnBP was effective in removing cell nuclei while leaving the structure and composition of the tissue intact. Overall, the resulting acellular tissue scaffold retained the ECM composition, strength, resistance to enzymatic degradation, and biocompatibility of the original tissue, making 1% TnBP an acceptable decellularization treatment for porcine diaphragm tendon.

Nernst and Seebeck coefficients of the cuprate superconductor YBa2Cu3O6.67: a study of Fermi surface reconstruction

The Seebeck and Nernst coefficients S and nu of the cuprate superconductor YBa{2}Cu{3}O{y} (YBCO) were measured in a single crystal with doping p=0.12 in magnetic fields up to H=28 T. Down to T=9 K, nu becomes independent of field by H approximately 30 T, showing that superconducting fluctuations have become negligible. In this field-induced normal state, S/T and nu/T are both large and negative in the T-->0 limit, with the magnitude and sign of S/T consistent with the small electronlike Fermi surface pocket detected previously by quantum oscillations and the Hall effect. The change of sign in S(T) at T approximately 50 K is remarkably similar to that observed in La2-xBaxCuO4, La{2-x-y}Nd{y}Sr_{x}CuO{4}, and La{2-x-y}Eu{y}Sr{x}CuO{4}, where it is clearly associated with the onset of stripe order. We propose that a similar density-wave mechanism causes the Fermi surface reconstruction in YBCO.

Characterization of heavyweight and lightweight polypropylene prosthetic mesh explants from a single patient

Although polypropylene has been used as a hernia repair material for nearly 50 years, very little science has been applied to studying the body's effect on this material. It is possible that oxidation of mesh occurs as a result of the chemical structure of polypropylene and the physiological conditions to which it is subjected; this leads to embrittlement of the material, impaired abdominal movement, and chronic pain. It is also possible that lightweight polypropylene meshes undergo less oxidation due to a reduced inflammatory reaction. The objective of this study was to characterize explanted hernia meshes using techniques such as scanning electron microscopy, differential scanning calorimetry, thermogravimetric analysis, and compliance testing to determine whether the mesh density of polypropylene affects the oxidative degradation of the material. The hypothesis was that heavyweight polypropylene would incite a more intense inflammatory response than lightweight polypropylene and thus undergo greater oxidative degradation. Overall, the results support this theory.

Laparoscopic ventral hernia repair (LVHR) in morbidly obese patients

OBJECTIVE

The aim of this study was to evaluate our experience with LVHR in morbidly obese patients (BMI >40) and to compare their outcomes to those of patients with lower BMI.

METHODS

Data on adult (>18 years old) patients who underwent LVHR with mesh over the last 13 years performed by four experienced surgeons were collected retrospectively and from a previously collected database. Of the 1,071 patients, 901 had completed LVHR and were available for follow-up. One hundred and thirty-four patients (group A) met BMI criteria for morbid obesity (>or=40, mean 46), 767 patients had BMI < 40, mean 30 (group B). The follow-up time ranged from 1 to 91 months. The Wilcoxon rank sum test was used for nonparametric data analysis. Outcomes were stratified on the follow up time and analyzed using Cochran-Mantel-Haenszel methodology.

RESULTS

The groups did not differ in terms of ASA score, previous surgery and conversion rate (p=0.22, 0.32 and 0.23). Morbidly obese patients were younger (48.3 vs. 54; p<0.01) and were more often female (p=0.02), but this did not correlate with outcome. Group A also had longer operative time (154 vs. 119 min, p<0.01) and hospital stay (3.6 vs. 2.4 days, p=0.03). Mesh size was significantly larger in group A (449 vs. 349 cm(2), p=002). During mean follow-up time of 19 months hernia recurrence was 8.3% in group A and 2.9% in group B (p=0.003), with an odds ratio of 4.3 (95% CI 1.9-9.9). However, there was no significant difference in the rate of complications (19.7 vs. 15.3%; p=0.46).

CONCLUSIONS

LVHR in the morbidly obese population is both safe and feasible, although there is a higher, but still acceptable recurrence rate. Despite the increased risk for recurrence, LVHR in morbidly obese patients minimizes the potential wound and mesh complications that frequently occur for open mesh repair in this group of patients.

Laparoscopic parastomal hernia repair using a nonslit mesh technique

BACKGROUND

The management of parastomal hernia is associated with high morbidity and recurrence rates (20-70%). This study investigated a novel laparoscopic approach and evaluated its outcomes.

METHODS

A consecutive multi-institutional series of patients undergoing parastomal hernia repair between 2001 and 2005 were analyzed retrospectively. Laparoscopy was used with modification of the open Sugarbaker technique. A nonslit expanded polytetrafluoroethylene (ePTFE) mesh was placed to provide 5-cm overlay coverage of the stoma and defect. Transfascial sutures secured the mesh, allowing the stoma to exit from the lateral edge. Five advanced laparoscopic surgeons performed all the procedures. The primary outcome measure was hernia recurrence.

RESULTS

A total of 25 patients with a mean age of 60 years and a body mass index of 29 kg/m2 underwent surgery. Six of these patients had undergone previous mesh stoma revisions. The mean size of the hernia defect was 64 cm2, and the mean size of the mesh was 365 cm2. There were no conversions to open surgery. The overall postoperative morbidity was 23%, and the mean hospital length of stay was 3.3 days. One patient died of pulmonary complications; one patient had a trocar-site infection; and one patient had a mesh infection requiring mesh removal. During a median follow-up period of 19 months (range, 2-38 months), 4% (1/25) of the patients experienced recurrence.

CONCLUSION

On the basis of this large case series, the laparoscopic nonslit mesh technique for the repair of parastomal hernias seems to be a promising approach for the reduction of hernia recurrence in experienced hands.

Use of porcine dermal collagen as a prosthetic mesh in a contaminated field for ventral hernia repair: a case report

Chronic infection of a prosthetic mesh implant is a severe complication of ventral hernia repair, and mesh explantation is usually required in these cases. Biologic mesh implants have a possible role in ventral hernia repair in this setting. Here we present a case of chronic mesh infection following ventral hernia repair and the use of a biologic mesh to repair the existing defect following explantation of the infected mesh. Analysis of the explant material demonstrated possible oxidative degradation of the original polypropylene. A review of the literature follows.

Materials characterization of explanted polypropylene hernia meshes

Hernia repair with prosthetic mesh significantly decreases the rate of recurrence compared with traditional, primary suture repair by reducing the tension on the edges of the wound. However, there are several complications associated with the use of mesh that may be due to the chronic inflammatory reaction to the mesh or a loss of compliance after degradation of the material. Mesh contraction and migration can also occur, sometimes resulting in a recurrent hernia. Based on the chemical structure of the polypropylene mesh material and the physiological conditions to which it is subjected, it is possible that oxidation is responsible for these changes in material properties. Oxidation would result in surface cracking, decreased melting temperature, loss of mass, and reduced compliance of the material. The objective of this study was to identify physiochemical changes in the surface and bulk properties of explanted polypropylene hernia meshes compared to pristine polypropylene mesh materials. Several characterization techniques were utilized, including scanning electron microscopy, differential scanning calorimetry, thermogravimetric analysis, and compliance testing. Overall, the results supported our hypothesis that oxidation is involved with the degradation of polypropylene hernia mesh materials.

What happens to the rectus abdominus fascia after laparoscopic ventral hernia repair?

BACKGROUND

One criticism of laparoscopic ventral hernia repair (LVH) is that the rectus muscles are not re-approximated to the midline, and the effect of LVH repair on the fascial edges is unclear. Progressive migration of the fascial edges toward the midline has been observed anecdotally, but objective evidence remains limited. The purpose of this study is to observe the effect of LVH repair on the rectus abdominus fascia.

METHODS

Patients undergoing LVH repair with defects > 10 cm in horizontal diameter were identified prospectively and enrolled. All were repaired laparoscopically with intraperitoneal placement of mesh (DualMesh, W.L. Gore and Associates) using a standard approach. Radio-opaque clips were placed at the fascial edges intraoperatively to mark the defect, and plain abdominal films were taken postoperatively (Time 1) to establish the initial distance between clips (measured in cm). A subsequent follow-up film was taken (Time 2), and the difference in clip distance per patient was recorded. Results were analyzed using a chi-squared test.

RESULTS

Twelve patients qualified for analysis and their results were compared. Mean fascial defect size was 15.1 cm (range 8.3-22.0). With respect to change in clip distance from Times 1 to 2, three events were observed: (1) Diminished (i.e. medialized), (2) Enlarged, or (3) No Change. Ten patients (83%) medialized, one patient enlarged, and one patient showed no change (chi2 (d.f. = 2) 9.17, p < 0.0023).

CONCLUSIONS

Medialization of the rectus abdominus fascia occurs in the majority of patients undergoing LVH repair. Causes for this phenomenon are unclear: however eliminating intrabdominal pressure with intraperitoneal mesh placement likely plays a role.

Laparoscopic palliative surgery for complicated colorectal cancer

BACKGROUND

The aim of this study was to evaluate the feasibility and outcomes of the laparoscopic approach for the palliation of advanced complicated colorectal cancer (CRC).

METHODS

We reviewed 21 laparoscopic palliative procedures for emergent complications of advanced CRC between 1994 and 2002. Intraoperative complications, estimated blood loss, transfusions, operative times, time to first bowel movement, length of hospital stay, and postoperative complications were assessed.

RESULTS

Indications for surgery included perforation (n = 10), bleeding (n = 7), and obstruction (n = 4). A proximal diverting procedure was performed in all patients, and a concomitant colon resection was performed in 18 patients (86%). The mean operative time was 181 +/- 22 min. Estimated blood loss was 283 +/- 48 cc, with three patients (14%) requiring transfusions. The average length of hospital stay was 8.6 +/- 2 days, and time to first bowel movement was 61 +/- 9 h. The complication rate and the 30-day mortality rate were 33% and 0%, respectively.

CONCLUSION

A laparoscopic approach to address advanced CRC is safe and effective and should be considered part of the surgeon's armamentarium for the palliation of advanced complicated CRC.

Resistance to adhesion formation: A comparative study of treated and untreated mesh products placed in the abdominal cavity

BACKGROUND

New materials have been devised to prevent postoperative adhesions when placing a prosthesis in contact with abdominal contents.

METHODS

Eighty rats underwent laparotomy and denudation of the serosa of the cecum and peritoneal covering of the abdominal wall. Five treated mesh products (Parietex Composite, Parietene Composite, Bard Composix E/X, Sepramesh, and Gore-Tex Dual Mesh) and one untreated mesh product (untreated Parietene) were randomly placed between the cecum and abdominal wall. A group without mesh was used as control. The animals were sacrificed at 21 days following surgery and analyzed for the presence of adhesions.

RESULTS

The incidence of adhesion formation, mean adhesion area, maximum adhesion length, and strength of adhesion separation were similar between Parietex Composite, Parietene Composite, and Bard Composix E/X, and they were significantly less than with Sepramesh, untreated Parietene, and the control group. Gore-Tex Dual Mesh resulted in less adhesions, adhesion area, mean strength of separation, and work of separation than the untreated Parietene group and the control group. Sepramesh resulted in less strength and work of separation compared to the control group.

CONCLUSIONS

The incidence of adhesions and work and strength of adhesion separation are reduced when using a treated mesh, compared to the untreated mesh and the control group without mesh. Parietex Composite, Parietene Composite, Bard Composix E/X, and Gore-Tex Dual Mesh were superior to Sepramesh, untreated Parietene, and the control group in the prevention of adhesion formation.

Laparoscopic vs open resection for the treatment of diverticular disease

INTRODUCTION

The aim of this study was to evaluate whether laparoscopic colon resection (LCR) offers any advantages over open colon resection (OCR) in the treatment of diverticular disease.

METHODS

Between 1992 and 2002, 95 patients underwent LCR and 80 patients underwent OCR for the treatment of diverticular disease. Demographics, details of operative procedure, outcome, and pathology were compared.

RESULTS

Patients in both groups were matched for age, sex, body mass index, history of previous abdominal operations, comorbidities, location of the disease, and presence of complications. LCR resulted in significantly less estimated blood loss and postoperative complications, shorter time to first bowel movement, and shorter length of stay than the OCR. There was no difference in operative time, intraoperative complications, mortality rates between groups.

CONCLUSIONS

LCR is a safe and effective approach for the treatment of patients with diverticular disease. It results in less estimated blood loss, shorter time to first bowel movement, less postoperative complications, and shorter length of hospital stay.

After 10 years and 1903 inguinal hernias, what is the outcome for the laparoscopic repair?

BACKGROUND

The procedure of choice for inguinal hernia repair has remained controversial for decades. The laparoscopic approach has now been utilized for more than 10 years, and a significant volume of patient outcomes is now available for review.

METHODS

The hospital and office records of 1388 patients who underwent 1903 laparoscopic inguinal hernia repairs at Atlanta Medical Center during the past 10 years were retrospectively reviewed in order to determine demographics, recurrence rate, and complications. In addition, 123 hernia repairs were prospectively studied in 71 patients during this time period in order to accurately evaluate postoperative pain and return to activity.

RESULTS

Two hundred fifty-five (13.4%) hernias were recurrent and 1648 (86.6%) were primary. Five hundred and fifteen (37.1%) hernias were bilateral. The total extraperitoneal approach was utilized for 1561 (82.0%) of the 1903 repairs. The average operative time was 75.4 (14-193) minutes. Estimated blood loss was 22.0 (0-250) ml. Seventeen patients (1.2%) were converted to an open form of hernia repair. Minor complications occurred in 83 (6.0%) patients and major complications occurred in 18 (1.3%) patients.

CONCLUSIONS

The laparoscopic approach is a safe form of inguinal hernia repair that offers the patient a shorter and less painful recovery with an extremely low recurrence rate.

The role of multimedia interactive programs in training for laparoscopic procedures

BACKGROUND

The application of minimally invasive techniques to the performance of abdominal surgery by general surgeons has been perhaps the greatest advance in the history of general surgery. The safe adoption of many of these procedures, however, has been hampered by significant obstacles, mainly due to the problem of providing adequate training for surgeons. Outside of animal and cadaver labs, most training has been didactic in nature, and adoption rates after completion of these courses are discouraging. Multimedia interactive training has been used in a number of high-tech industries with great success. A >60% improvement in the learning curve after multimedia interactive training, as compared to traditional didactic training, has been reported. Multimedia interactive training programs for surgeons that use content and input from multiple experts in laparoscopic procedures have now been developed.

METHODS

Residents from a general surgery residency program who used these programs were asked to rate their effectiveness in increasing their knowledge and comfort level prior to their participation in a real procedure as the primary surgeon or first assistant. A comparison to other traditional training techniques was also made. Eleven residents completed 41 programs designed to teach one of five different laparoscopic procedures-cholecystectomy, fundoplication, appendectomy, colon resection, or hernia repair.

RESULTS

On a scale of 1 to 10, with 10 being the highest, the residents reported that the multimedia interactive training programs raised their knowledge level of the procedure from 6.0 to 8.7 (+2.7 point value increase after using the multimedia interactive program). The programs increased their comfort level when actually called on to perform or assist with the procedure from 5.3 to 8.1 (+2.8 point value increase after using the multimedia interactive program). In comparing the value of training methods for learning laparoscopic procedures, the residents rated text, lectures, videos, and animal labs at 4.7, 5.1, 6.0 and 7.3, respectively. By comparison, the residents rated the multimedia interactive training program at 8.8.

CONCLUSION

The use of multimedia interactive training programs in addition to current laparoscopic training courses may help to increase the safe adoption of laparoscopic procedures. These programs may be a beneficial adjunct to residency training programs.

Laparoscopic ventral and incisional hernia repair in 407 patients

BACKGROUND

Recurrence rates after primary repair of ventral and incisional hernias range from 25% to 52%. Recurrence after open surgery is less likely if mesh is used, but the wide fascial dissection and required flap creation increase complication rates. Laparoscopic techniques offer an alternative.

STUDY DESIGN

To assess the safety and efficacy of laparoscopic ventral and incisional herniorrhaphy, we reviewed the records of all our patients who underwent such a procedure from November 1993 to August 1999. A laparoscopic approach was attempted in all patients considered to require a mesh repair. Patient demographic characteristics, operative details, and outcomes were recorded.

RESULTS

Of 415 patients scheduled to undergo laparoscopic ventral or incisional herniorrhaphy, conversion to an open procedure was necessary in 8. All the remaining 407 patients (205 men and 202 women; mean age 53.2 years; range 13 to 88 years) were included in the study. Mean fascial defect size was 100.1 cm2 (range 1 to 480 cm2). In 97% of patients, expanded polytetrafluoroethylene mesh was used. Mean operating time was 97 minutes (range 11 to 270 minutes). Mean estimated blood loss was 35 mL (range 10 to 150 mL). Average hospital stay was 1.8 days (range 0 to 17 days). There were 53 complications (13.0%), including cellulitis of a trocar site, infection requiring mesh removal, prolonged suture pain, persistent seroma, intestinal injury, hematoma or postoperative bleeding, prolonged ileus, urinary retention, respiratory distress, fever, intraabdominal abscess, and trocar site herniation. There were no deaths. During a mean followup time of 23 months (range 1 to 60 months), there were 14 hernia recurrences (3.4%), 6 in patients in whom only a stapling device (no sutures) had been used to secure the mesh to the abdominal wall.

CONCLUSIONS

Laparoscopic repair was completed in 98.1% of patients in whom it was attempted. The complication rate was acceptable. A short hospital stay and minimal blood loss were documented. The recurrence rate was 3.4%. Laparoscopic ventral and incisional hernia repair appear to be safe and effective.

Laparoscopic ventral hernia repair: a report of 100 consecutive cases

INTRODUCTION

Effective surgical therapy for ventral and incisional hernias is problematic. Recurrence rates following primary repair range as high as 25-49%, and breakdown following conventional treatment of recurrent hernias can exceed 50%. As an alternative, laparoscopic techniques offer the potential benefits of decreased pain and a shorter hospital stay. This study evaluates the efficacy of the laparoscopic approach for ventral herniorrhaphy.

METHODS

A retrospective review was performed for 100 consecutive patients with ventral hernias who underwent laparoscopic repair at our institutions between November 1995 and May 1998. All patients who presented during this period and were candidates for a mesh hernia repair were treated via an endoscopic approach.

RESULTS

One hundred patients underwent a laparoscopic ventral hernia repair. There were 48 men and 52 women. The patients were typically obese, with a mean body mass index (BMI) of 31 kg/m(2). Each had undergone an average of 2.5 (range; 0-8) previous laparotomies. Forty-nine repairs were performed for recurrent hernias. An average of two patients (range; 1-7) had previously failed open herniorhaphies; in 20 cases, intraabdominal polypropylene mesh was present. There were no conversions to open operation. The mean size of the defects was large at 87 cm(2) (range; 1-480). In all cases, the mesh (average, 287 cm(2)) was secured with transabdominal sutures and metal tacks or staples. Operative time and estimated blood loss averaged 88 min (range; 18-270) and 30 cc (range; 10-150). Length of stay averaged 1. 6 days (range; 0-4). There were 12 minor and (two) major complications: cellulitis of the trocar site (two), seroma lasting >4 weeks (three), postoperative ileus (two), suture site pain > 2 weeks (two), urinary retention (one), respiratory distress (one), serosal bowel injury (one), and skin breakdown (one) and bowel injury (one). Both of the latter complications required mesh removal. With an average follow-up of 22.5 months (range; 7-37), there have been (three) recurrences.

CONCLUSION

The laparoscopic approach to the repair of both primary and recurrent ventral hernias offers a low conversion rate, a short hospital stay, and few complications. At 23 months of follow-up, the recurrence rate has been 3%. Laparoscopic repair should be considered a viable option for any ventral hernia.

Laparoscopic repair of bilateral and recurrent hernias

The optimal inguinal hernia repair has been controversial for decades. Since the advent of minimally invasive surgery, laparoscopic techniques have added to the controversy. Laparoscopic hernia repair has been advocated by many experts for the repair of bilateral and recurrent inguinal hernias. This study reviews the experience of a single community-based teaching hospital using the total extraperitoneal (TEP)-approach laparoscopic hernia repair for treating patients with bilateral and/or recurrent inguinal hernias. Since the TEP approach was adopted in June 1993, a total of 457 patients were treated for bilateral (322 patients) and/or recurrent (175) inguinal hernias (40 patients had recurrent and bilateral hernias). A total of 779 hernias were repaired with this technique. The average age of this patient group was 47 years, and there were 413 males and 44 females. Operative time averaged 68.3 minutes per patient, and there were 26 (5.7%) minor complications. There were 2 (0.4%) major complications, an enterotomy and a cystotomy, both early in the series and both in patients with previous lower abdominal surgery. There have been no deaths. With an average follow-up of 30 months (range, 1-60 months), there have been three (0.2%) recurrences. These recurrences were due to technical problems (inadequate mesh coverage), and each was repaired with a laparoscopic transabdominal approach or an anterior open approach. The use of the TEP-approach laparoscopic hernia repair is safe and effective in patients with recurrent and/or bilateral inguinal hernias.

Comparison of laparoscopic and open ventral herniorrhaphy

The repair of large and/or recurrent ventral hernias is associated with significant complications and a recurrence rate that can be more than 50 per cent. Laparoscopic ventral herniorrhaphy, a recent development, has been shown to be safe and effective in the repair of ventral hernias. This study retrospectively reviews all ventral hernia repairs over a 3-year period, November 1995 through December 1998, at a community-based teaching hospital. The purpose of the study was to compare open and laparoscopic repairs. A total of 253 ventral hernia repairs were performed during this time, 174 open and 79 laparoscopic. The age, weight, and sex distribution was similar for each group. The hernias in the open group averaged 34.1 cm2 in size, and mesh used averaged 47.3 cm2. In the laparoscopic group, the hernia defect averaged 73.0 cm2, and the mesh size averaged 287.4 cm2. Operative time was longer in the open group, 82.0 versus 58.0 minutes. In the open group, there were 38 (21.8%) minor and 8 (4.6%) major complications, compared with 13 (16.5%) minor and 2 (2.5%) major complications in the laparoscopic group. Hospital stay was shorter for the laparoscopic group, 1.7 versus 2.8 days. At an average follow-up of 21 months (range, 2-40 months), there have been 36 recurrences in the open group (20.7%) compared with 2 recurrences in the laparoscopic group (2.5%). In this series, laparoscopic ventral herniorrhaphy compares favorably to open ventral herniorrhaphy with respect to wound complications, hospital stay, operative time, and recurrence rate.

Laparoscopy for diagnosis and staging of malignancy

The use of minimally invasive surgery for abdominal pathology, including malignancy, has increased significantly within the past decade. Despite the advances in radiographic imaging, the use of laparoscopy for diagnosing and staging abdominal malignancy has become an important tool in the overall care of these patients. A review of published series for a variety of abdominal malignancies is presented. With the growing experience in this technique, some preliminary conclusions and ongoing issues are discussed.

Laparoscopic surgery for cancer patients

Laparoscopy is an effective tool for diagnosis and staging of malignancies. Laparoscopic resection of abdominal tumors has been performed rarely, with two exceptions: laparoscopic adrenalectomy and laparoscopic resection of colorectal cancer. One of the best applications of minimally invasive surgery is the use of laparoscopic techniques for palliation of abdominal cancer. Requiring thorough training and preparation of surgeons and mandating their strict credentialing will reduce the risk of complications from laparoscopic surgery.

500 total extraperitoneal approach laparoscopic herniorrhaphies: a single-institution review

At Georgia Baptist Medical Center, a community-based, university-affiliated hospital, we adopted the total extraperitoneal approach (TEPA) to laparoscopic herniorrhaphy due to potential complications in entering the abdominal cavity reported previously with the transabdominal preperitoneal technique (Am Surg 1996;62:69-72). We have also employed regional anesthesia (epidural) in 108 patients in whom the TEPA was utilized. In our institution, the TEPA has compared favorably to the transabdominal preperitoneal technique, with lower complication and recurrence rates. In patients with previous lower abdominal surgery, the TEPA is considered a relative contraindication due to the increased risk of complications (Am Surg 1997, in press). Since June 1993, we have performed 503 laparoscopic herniorrhaphies using the TEPA, with encouraging early results. To date, two recurrences have been reported, one with previous lower abdominal surgery and another whose recurrence was noted to be secondary to incomplete reapproximation of the mesh with staples around the cord structures. Four major complications include two bowel perforations and two cystotomies noted during balloon dissection of the preperitoneal space. Three of these patients had previous lower abdominal surgery. Epidural anesthesia was used in 108 patients, 4 of whom required conversion to general anesthesia due to peritoneal tears and pain associated with pneumoperitoneum. All four of these patients had previous lower abdominal surgery. In summary, the TEPA remains a viable technique for laparoscopic herniorrhaphy with acceptable complication and recurrence rates. Epidural anesthesia is well tolerated by the patients undergoing this particular repair. We feel that lower abdominal surgery may be a mitigating factor in selection of the TEPA. Continued re-evaluation of the procedure is warranted before definitive conclusions can be made.

The effect of previous lower abdominal surgery on performing the total extraperitoneal approach to laparoscopic herniorrhaphy

At Georgia Baptist Medical Center in Atlanta, GA, we adopted the total extraperitoneal approach (TEPA) to laparoscopic herniorrhaphies because of the concerns of potential early and late complications associated with entering the abdominal cavity. In our institution, the TEPA has compared favorably with the transabdominal approach, with lower complication and recurrence rates. There has been concern, however, in performing the TEPA in patients with previous lower abdominal surgery. The question has been raised that there is increased risk of complications in these patients. From June 1993 to May 1994, we performed 247 laparoscopic herniorrhaphies in 192 patients using the TEPA. Of these, 55 hernias were repaired in 45 patients with previous lower abdominal surgery. Overall retrospective results showed a slightly higher complication rate (23.1% vs 11.3%) and slightly higher recurrence rate (1.8% vs 0%) in the patients with previous surgery over those without. Although these differences are not statistically significant, it is important to keep these risks in mind when selecting the appropriate hernia repair for each patient.

A comparison of the approaches to laparoscopic herniorrhaphy

BACKGROUND

There are a variety of accepted techniques for herniorrhaphy. With the advent of laparoscopic general surgery, new endoscopic techniques using the transabdominal and total extraperitoneal approaches have been added to the many options for the repair of inguinal hernia. The purpose of this study was to compare the early results of these approaches at a single institution.

METHODS

Between May 1991 and August 1994, 600 laparoscopic herniorrhaphies were performed on 493 patients. Three hundred hernias were repaired using the transabdominal preperitoneal approach and 300 were repaired using the total extraperitoneal approach. A retrospective review was performed with emphasis on the comparison of recurrence rates and complication rates between these two approaches to laparoscopic herniorrhaphy.

RESULTS

The recurrence rates were 2.0% (6/300) for the transabdominal approach and 0.3% (1/300) for the total extraperitoneal approach. The complication rate for the transabdominal approach was 10.7% and included thigh paresthesias (6), inferior epigastric artery injuries (4), enterotomy (1), bowel obstruction (1), bladder injury (1), and urinary retention (14). The complication rate for the total extraperitoneal approach was 3.7% and included enterotomies (2), bladder injury (1), paresthesia (1), and urinary retention (6). The recurrence, the enterotomies, and the bladder injury in the total extraperitoneal group were all in patients who had previous lower abdominal operations.

CONCLUSIONS

Although both the transabdominal preperitoneal and total extraperitoneal approaches to laparoscopic herniorrhaphy have acceptable recurrence and complication rates, there were significant advantages to the total extraperitoneal approach in our institution. Previous lower abdominal surgery may be a relative contraindication to the total extraperitoneal approach.