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PubMed2004

Biomechanical evaluation of cervical lateral mass fixation: a comparison of the Roy-Camille and Magerl screw techniques.

OBJECT: The purpose of this study was to assess human cervical spine pullout force after lateral mass fixation involving two different techniques: the Roy-Camille and the Magerl techniques. Although such comparisons have been conducted previously, because of the heterogeneity of results and the importance of this procedure in clinical practice, it is essential to have data derived from a prospective and randomized biomechanical study involving a sufficient sample of human cervical spines. The authors also evaluated the influence of the sex, the vertebral level, the bone mineral density (BMD), the length of bone purchase, and the thickness of the anterior cortical purchase. METHODS: Twenty-one adult cervical spines were harvested from fresh human cadavers. Computerized tomography was performed before and after placing 3.5-mm titanium lateral mass screws from C-3 to C-6. Pullout forces were evaluated using a material testing machine. The load was applied until the pullout of the screw was observed. A total of 152 pullout tests were available, 76 for each type of screw fixation. The statistical analysis was mainly performed using the Kaplan-Meier survival method. The mean pullout force was 266 +/- 124 N for the Roy-Camille technique and 231 +/- 94 N for the Magerl technique (p < 0.025). For the C3-4 specimen group, Roy-Camille screws were demonstrated to exert a significantly higher resistance to pullout forces (299 +/- 114 N) compared with Magerl screws (242 +/- 97 N), whereas no difference was found between the two techniques for the C5-6 specimen group (Roy-Camille 236 +/- 122 N and Magerl 220 +/- 86 N). Independent of the procedure, pullout strengths were greater at the C3-4 level (271 +/- 114 N) than the C5-6 level (228 +/- 105 N) (p < 0.05). No significant correlation between the cancellous BMD, the thickness of the anterior cortical purchase, the length of bone purchase, and maximal pullout forces was found for either technique. CONCLUSIONS: The difference between pullout forces associated with the Roy-Camille and the Magerl techniques was not as significant as has been previously suggested in the literature. It was interesting to note the influence of the vertebral level: Roy-Camille screws demonstrated greater pullout strength (23%) at the C34 vertebral level than Magerl screws but no significant difference between the techniques was observed at C5-6.

Biomechanical Phenomena↗

PubMed2005

The role of graft materials in suture augmentation for tendon repairs and reattachment.

Various biomaterials have been used to augment sutures for the repair and reattachment of tendons. This study examined four different graft materials in a simple and reproducible model using chicken Achilles tendons to determine the strength and mechanism of suture reinforcement of tendon repairs. The graft materials tested were Gore-Tex(R) Soft Tissue Patch, Graftjacket, bovine pericardium, and an experimental graft material from Xylos Corporation. Testing was performed in shear to simulate forces on a torn tendon repair and pull-off to simulate those on a tendon reattachment to bone. Compared to unaugmented suture, grafts increased suture fixation strength from 10% to 60% in shear and from 0% to 36% in pull-off with the bovine pericardium graft, providing significant improvement in both tests. In no cases (even unaugmented) did the suture pull directly through the tendon, but instead sliced along it, demonstrating that the interface between the suture and the tendon determines fixation strength. Grafts function by increasing the area, friction, and nature of this interface, not by acting as a barrier for suture pull-through.

Achilles Tendon↗

PubMed1996

Augmentation of femoral neck fracture fixation with an injectable calcium-phosphate bone mineral cement.

The first goal of this study was to determine if augmentation with an injectable, in situ setting, calcium-phosphate cement that is capable of being remodeled and was designed to mimic bone mineral significantly improved the strength and stiffness of fixation in a cadaveric femoral neck fracture model. The second goal was to determine if greater increases in fixation strength were achieved as the bone density of the specimen decreased. Sixteen pairs of fresh cadaveric human femora with a mean age of 70.9 years (SD = 17.2 years) were utilized. The bone density of the femoral neck was measured with dual-energy x-ray absorptiometry. The femoral head was impacted vertically with the femoral shaft fixed in 12 degrees of adduction using a materials testing machine to create a fully displaced fracture. Following fracture, 30% inferior comminution was created in each specimen. One randomly chosen femur from each pair underwent anatomic reduction and fixation with three cannulated cancellous bone screws, 7 mm in diameter, in an inverted triangle configuration. The contralateral femur underwent the same fixation augmented with calcium-phosphate cement. Specimens were preconditioned followed by 1.000 cycles to one body weight (611.6 N) at 0.5 Hz to simulate single-limb stance loading. The stiffness in the first cycle was observed to be significantly greater in cement-augmented specimens compared with unaugmented controls (p < 0.05). After cycling, each specimen was loaded at 10 mm/min until complete displacement of the fracture surface and failure of fixation occurred. Specimens augmented with bone mineral cement failed at a mean of 4,573 N (SD = 1,243 N); this was significantly greater (p < 0.01) than the mean for controls (3,092 N, SD = 1,258 N). The relative improvement in fixation strength (augmented/control x 100%) was not inversely correlated to femoral neck bone density (p = 0.25, R2 = 0.09), was weakly correlated to the volume of cement injected (p = 0.07, R2 = 0.22), and was inversely related to the fixation failure load of the control specimen (p = 0.001, R2 = 0.54). There was a mean relative improvement in fixation strength of 169.6% (SD = 77.5). These findings suggest that calcium-phosphate cement provides initial beneficial augmentation to fixation of femoral neck fractures.

Adult↗

PubMed2001

An experimental study on the interface strength between titanium mesh cage and vertebra in reference to vertebral bone mineral density.

STUDY DESIGN: Using human cadaver spines, the authors investigated mechanical properties of the interface between titanium mesh cage and vertebra in respect to vertebral bone mineral density. OBJECTIVES: The objective of this study is to examine the effects of the size of the mesh cage and an internal end ring system on interface mechanical properties in reference to vertebral bone mineral density. SUMMARY OF BACKGROUND DATA: A titanium mesh cage has recently been developed for anterior spinal reconstruction. The cage provides immediate postoperative stability and facilitates bony union with cancellous bone packed in the cage itself. Mechanical properties of the interface between the cage and vertebra, however, are yet to be clarified in osteoporotic spine. METHODS: Twenty-five lumbar vertebrae harvested from embalmed human cadavers (n = 20) were used. The vertebrae were divided into four experimental groups according to the applied cage conditions: Phi25 mm cage without internal end ring (L-), Phi19 mm cage without internal end ring (S-), Phi25 mm cage with internal end ring (L+), and Phi19 mm cage with internal end ring (S+). Bone mineral density of whole vertebral body was measured by dual energy radiograph absorptiometer (DXA). Peripheral quantitative computed tomography was used to determine local bone mineral density of subchondral cancellous bone of vertebral body. Each cage was compressed on vertebral endplate via a specially designed device connected to a material testing machine. Maximum load and stiffness of the interface between the cage and vertebra were measured from load-deformation data in quasi-static compression loading with a loading rate of 0.5 mm/min. Relationships between the mechanical properties and vertebral bone mineral densities were evaluated. In 11 specimens acoustic emission during compression loading was measured and simultaneously recorded in load-deformation data. After the mechanical test microradiograms of midsagittal sections of the vertebrae were taken to observe failure patterns of endplate or trabecular bone. RESULTS: Vertebrae compressed with large cages (group: L- or L+) showed greater maximum load than those compressed with small cages (group: S- or S+). The internal end ring contributed to higher maximumload. The size of the cage or the internal end ring, however, did not have any effect on stiffness. Maximum load and stiffness were positively correlated with whole vertebral bone mineral density measured by dual energy radiograph absorptiometer or local cancellous bone mineral density of subchondral bone measured by peripheral quantitative computed tomography. Correlation coefficient and P value were more significant in the association of the mechanical properties and subchondral bone mineral density measured by peripheral quantitative computed tomography than in the association of the parameters and whole vertebral bone mineral density measured by DXA. A load-deformation curve with an acoustic emission event count rate showed that significant acoustic emission signals were generated around maximum load. On microradiographic study most vertebrae compressed with the cage showed encroachment of the cage spikes into the endplate or trabecular structure, preserving structures of the most central portion of the vertebrae. CONCLUSION: A titanium mesh cage with larger diameter and/or augmentation of internal end ring produces a significant increase of the interface strength between the cage and the vertebra. A positive correlation between the interface strength and vertebral bone mineral density suggests that vertebral bone mineral density is an important parameter for successful spinal reconstruction, and also implies that in severe osteoporotic spine the stability of the cage is declined, and other instrumentation should be combined.

Aged↗

PubMedDate not supplied

Primary stability with tibial press-fit fixation of patellar ligament graft: An experimental study in ovine knees.

PURPOSE: To investigate the initial fixation strength and to assess the value of tibial press-fit fixation of the bone-tendon-bone graft in anterior cruciate ligament reconstruction. TYPE OF STUDY: Nonrandomized control trial. METHODS: For tibial press-fit fixation, the tibial bone block of the bone-tendon-bone graft is countersunk in a bony groove at the distal tunnel outlet and fixed over a bone bridge with 2 No. 6 Ethibond sutures. The bone cylinder harvested from the tibial tunnel using an oscillating hollow saw is plugged into the tibial tunnel parallel to the graft, thus providing for additional anchoring of the graft by tibial press-fit fixation. In a comparative experimental study in 46 ovine knees, this fixation method was assessed for its value in anterior cruciate ligament reconstruction. A tibial bone tunnel was placed in routine manner in each ovine tibia using a target drill unit and an oscillating hollow saw. The complete patellar ligament, proximally attached to the patella and distally to a cylindrical bone block (20 x 8.4 mm), served as graft. Tibial fixation in group A (n = 10) was done using a titanium interference screw (20 x 8 mm), in group B (n = 10) using a titanium staple, in group C (n = 12) using suture fixation over a bone bridge, and in group D (n = 14) using the press-fit fixation described above. In a materials testing machine, all specimens were subjected to continuously increasing load until failure at a velocity of 1 mm/second. Ultimate failure load, stiffness, stress-strain characteristics, and failure mode were evaluated. RESULTS: Ultimate load to failure was 572 N (range, 473 to 680 N) in group A, corresponding to a fixation stiffness of 17.68 N/mm. For group B, ultimate load to failure was 608.4 N (range, 511 to 727 N) and stiffness of 19.92 N/mm. Bone block dislocation was the failure mode in groups A and B. Group C with exclusive suture fixation showed an ultimate load to failure of 304.5 N (range, 120 to 327 N) and a stiffness of only 6.96 N/mm. The mode of failure was suture cutout caused by the bone block in 9 of the cases and untying of the suture knot in 3 cases. Group D with press-fit fixation showed a significantly higher primary stability of 758 N (range, 513 to 993 N) relative to group C, with a corresponding stiffness of 25.12 N/mm (P <.02). In this group, the mode of failure was ligamentous rupture from the bone block. Regarding mechanical properties, no significant differences were seen between groups A, B, and D. CONCLUSIONS: Tibial press-fit fixation allows for metal-free fixation with high primary stability. By refilling the bone tunnel, the ligament (with a rather small cross-sectional diameter compared with hamstrings) is safely fixed within the bone tunnel to prevent potential postoperative tunnel enlargement due to movement of the graft within the tunnel. Anchoring the graft at the entrance into the joint, it provides for reduced graft length and adequate elasticity and accomplishes the requirements of fixation at the correct anatomic insertion site.

Animals↗

PubMed2001

Evaluation of metallic and polymeric biomaterial surface energy and surface roughness characteristics for directed cell adhesion.

Directed cell adhesion remains an important goal of implant and tissue engineering technology. In this study, surface energy and surface roughness were investigated to ascertain which of these properties show more overall influence on biomaterial-cell adhesion and colonization. Jet impingement was used to quantify cellular adhesion strength. Cellular proliferation and extracellular matrix secretion were used to characterize colonization of 3T3MC fibroblasts on: HS25 (a cobalt based implant alloy, ASTM F75), 316L stainless steel, Ti-6Al4V (a titanium implant alloy), commercially pure tantalum (Ta), polytetrafluoroethylene (PTFE), silicone rubber (SR), and high-density polyethylene (HDPE). The metals exhibited a nearly five-fold greater adhesion strength than the polymeric materials tested. Generally, surface energy was proportional to cellular adhesion strength. Only polymeric materials demonstrated significant increased adhesion strength associated with increased surface roughness. Cellular adhesion on metals demonstrated a linear correlation with surface energy. Less than half as much cellular proliferation was detected on polymeric materials compared to the metals. However the polymers tested demonstrated greater than twice the amount of secreted extracellular matrix (ECM) proteins on a per cell basis than the metallic materials. Thus, surface energy may be a more important determinant of cell adhesion and proliferation, and may be more useful than surface roughness for directing cell adhesion and cell colonization onto engineered tissue scaffoldings.

3T3 Cells↗

PubMed1995

Do porous calcium hydroxyapatite ceramics cause porosis in bone? A bone densitometry and biomechanical study on cortical bones of rabbits.

Porous calcium hydroxyapatite (CHA) ceramics are biocompatible and present osteoconductive properties. These ceramics are widely used in orthopaedic surgery; however, it is not yet known whether they have some adverse effects on bone and bone marrow healing. Our previous radiological study revealed possible local porosis at the adjacent sites of the CHA ceramic. Histological findings of the same study revealed bone marrow swelling and depletion at the implantation site. Osteoclasts removed particles of the implant that may be the cause of local porosis. In the present study, possible local osteoporosis was evaluated by bone densitometry analyses, and compression and three-point bending tests. CHA particles were implanted into the left limbs and a sham operation was utilized on the right limbs of 75 white rabbits. The animals were followed up for 23 weeks for bone mineral density and for 6 months for biomechanical analyses. The CHA implanted area and its distal or proximal adjacent areas were evaluated with a Hologic QDR-2000 bone densitometer. Three-point bending and compression tests were performed with an M-30 K material testing device. The results revealed a time-dependent bone density increase at the CHA implantation site and no significant porosis at adjacent areas of the implant. The stiffness of CHA-implanted bones in three-point bending is larger than that of the control group. CHA-implanted rabbit bones presented a different fracture pattern from the control group. The stiffness of the control and CHA-implanted bones generally increased with time indicating no adverse effects of porous CHA ceramics in bone and bone marrow healing. The clinical relevance of this work is that porous CHA ceramics do not cause local porosis at adjacent areas when implanted into osseous sites.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1987

Adherence of Streptococcus mutans to implant materials.

The adherence of Streptococcus mutans OMZ-176 to six implant materials (poly-crystal alumina, single-crystal alumina, titanium alloy, cobalt-chromium-molybdenum alloy, hydroxyapatite, and heat-curing polymethylmethacrylate resin) was studied in vitro. The change of free energy, which corresponds to the adherence process, was also evaluated for hydrophobic interaction. Adherence of S. mutans to poly-crystal alumina was lower than adherence to other materials. The adherence of S. mutans to the test materials was highly correlated with the change of free energy, which suggests that hydrophobic interaction plays an important role in the adherence of S. mutans to the implant materials.

Alloys↗

PubMed1989

The chick chorioallantoic membrane as test system for biocompatible materials.

Biologic and non-biologic materials clinically used as hemostyptica, as vascular prostheses, or as temporary skin substitutes were implanted to the chick chorioallantoic membrane (CAM) during days 9-14 of incubation. The histological study revealed an intact CAM after application of cellulose gauze (Tabotamp). The fibrin tissue adhesive (Tissucol), the collagen sponge (Tachotop), or the gelatin sponge (Gelfoam) induced different amounts of connective tissue. Some fibroblasts were about to grow into the fibrin adhesive. Fibroblasts and capillaries filled the interstices of the collagen sponge poorly, and in the case of the gelatin sponge markedly. Neutrophils and giant cells of the foreign body type occurred more often in the gelatin sponge than in the collagen sponge. With regard to the non-biologic materials, expanded polytetrafluorethylene induced squamous metaplasia of the chorionic epithelium. Dacron caused ulceration with the onset of connective tissue ingrowth, based on a reaction of giant cells of the foreign body type. Polyurethane foam (SYSpur-derm) showed bleeding into the implant due to spikes of the material. Eosinophilic granulocytes were absent in all materials studied. The results are related to different clinical findings. The correlation allows consideration of the CAM as an in vivo model in screening materials for their biocompatibility and their connective tissue reaction.

Allantois↗

PubMed2004

Stiffness characteristics of hamstring tendon graft fixation methods at the femoral site.

In ACL reconstruction, stiffness and strength of a tendon graft complex are important features for knee stability and rehabilitation. The fixation between tendon and bone is known to be one of the weakest components of the graft complex. We examined the tensile load-displacement characteristics of looped semitendinosus tendons in a porcine femoral tunnel. Two groups of six cadaveric semitendinosus tendons and porcine femurs were tested, secured with either an aperture or non-aperture fixation method. Constructs were tested at 1 mm/s until failure in a materials testing machine, which allowed force and displacement data to be recorded. The non-aperture fixation group was significantly less stiff for the first 4 mm of displacement and had significantly higher ultimate failure loads. Provided that adequate ultimate strength can be achieved, stiffness properties of a tendon graft will be improved by using aperture fixation in femoral-site ACL reconstruction.

Animals↗

PubMed2006

Repair of articular cartilage lesions in aged chickens by allogeneic transplantation of fresh embryonic epiphyses.

INTRODUCTION: The potential of fresh whole chick epiphyses of embryonic origin to serve as implant material for cartilage defects of aged chicken was tested. MATERIALS AND METHODS: Fresh epiphyses of 11-day-old embryos were collected from 24 animals and transplanted into defects created in the weight-bearing areas of tibiotarsal joint cartilage of 2-year-old chicks. Upon sacrifice, samples were examined macroscopically and microsections were prepared for histology. RESULTS: Macroscopically, control defects remained empty at all the time intervals. Defects of the experimental group were, on the other hand, filled with cartilaginous tissue as early as 2 weeks posttransplantation, although individual epiphyses could still be noted in the implant tissue. At 4 weeks and later, defects were filled with cartilaginous material indistinguishable from hyaline cartilage. Histologically, all grafts remained within the defect's pits, showing mitotic and metabolic activity typical to proliferating hyaline cartilage. The engrafted epiphyses showed a partial incorporation and integration with the surrounding host tissues already at 2 weeks. At 4 weeks and later, the integration was complete. CONCLUSIONS: It is concluded that a chick embryonic epiphyseal cartilage is suitable as a graft source for articular cartilage transplantation. The embryonic epiphyses provide immediate inherent stability to the graft and supply a good mix of mesenchymal progenitor cells responsible for the high rate of cell proliferation and adhesion to the differentiated committed chondrocytes of the host that create the typical favorable chondrogenic milieu. Based on the present findings, it is postulated that human embryonic epiphyses may, in the future, represent an alternative source to the commonly used techniques of hyaline cartilage repair.

Animals↗

PubMed1990

Redefining cooling rate in terms of ice front velocity and thermal gradient: first evidence of relevance to freezing injury of lymphocytes.

A freezing process and the resulting injury or survival of biological cells is commonly characterized in terms of the cooling rate, B. Under certain circumstances, the cooling rate can be expressed as B = G.v, where G denotes the thermal gradient at the ice-liquid interface and v its velocity, respectively. To determine the influence of G and v on the morphology of the ice-liquid interface and on cell survival, a gradient freezing stage was designed. Flat capillaries could be pushed with constant velocity from a warm to a cold heat reservoir. With this setup both parameters, G and v, are independently adjustable and the resulting process of directional solidification can be observed dynamically in a light microscope. Human lymphocytes in phosphate-buffered saline with 10 vol% of dimethyl sulfoxide were used as biological test material. Viability was assessed by a membrane integrity test with fluorescein diacetate and ethidium bromide. All cells were cooled down to a final temperature of -196 degrees C and then rapidly thawed. The results obtained with this technique show that the viability determined after freezing and thawing with a certain cooling rate, B = G.v, may vary considerably depending on the imposed values of the thermal gradient, G, and the ice front velocity, v. In addition, the data seem to suggest that, first, the maximum viability which can be reached is governed by the cooling rate, and, second, this maximum for a given cooling rate could be achieved by establishing small temperature gradients and high interface velocities (about 30 degrees K/cm and 500 microns/sec, respectively, for the range of values of G and v tested).

Cell Membrane↗

PubMed1986

Comparison of three epoxy die materials.

Sixty MOD inlay and 60 complete crown castings were fabricated on three epoxy die materials. The castings were evaluated with a specific criteria for fit, retention, and margin adaptation. Of the three materials tested, the castings fabricated on the Unitek die material had consistently higher ratings on the master die with the exception of unacceptable ratings in retention for the MOD inlay.

Crowns↗

PubMed1989

Wear of dental restorative and prosthetic materials in vitro.

The aim of this study was to evaluate the wear of some modern materials for fixed crown and bridge restorations and fillings in vitro. Eighteen commercial materials (8 composites, 4 alloys, 4 façade materials, and 2 denture-base resins) were tested. Enamel was used as the control. Test specimens were abraded on abrasion discs under water or in artificial saliva. There was a great variation in the wear rates of the tested materials. The greatest wear was shown by resins used for base material and the smallest by gold and Cr-Co alloys and porcelain. Most of the composites had a wear rate near that of enamel. The wear for amalgam was slightly greater than for most of the composites. When one is using several different materials for reconstructing occlusion, differences in wear resistance should be taken into account.

Dental Materials↗

PubMed1984

Teratological evaluation of gamma-glycidoxypropyltrimethoxysilane in rats.

The embryotoxic and teratogenic potential of gamma- glycidoxypropyltrimethoxysilane ( GPTS ) was evaluated in rats. Pregnant Sprague-Dawley rats were administered 0, 50, 500, or 1,000 mg/kg/day of GPTS by gavage on days 6 through 15 of gestation. No treatment related signs of toxicity, behavioral alterations or mortalities were observed in any of the pregnant animals. There was no evidence of adverse effects in mean maternal body weight, liver weight or food consumption of the treated females. The number of implantation sites, number of live fetuses per litter, the mean litter size, the sex ratio, the fetal body weight or the crown-rump length were not affected by treatment. The incidence of resorptions among the total fetal population was not altered by the administration of GPTS to pregnant rats, indicating that the test material is not embryolethal in rats at the tested dose levels. Few scattered incidences of fetal alterations in the external, soft tissue or skeletal examinations were seen both among treated and untreated litters, however, no single alteration was observed in treated litters at an incidence which was significantly different from the control. In conclusion GPTS was not embryotoxic or teratogenic in rats at dose levels up to 1000 mg/kg/day.

Abnormalities, Drug-Induced↗

PubMed1994

Effects of pretwist on biomechanical properties of canine patellar tendon.

The purpose of this study was to measure the effect produced on canine patellar tendon of a 90 degree pretwist on the following mechanical properties: failure stress, failure strain, average elastic modulus, and strain energy density. Forty adult mongrel dog cadavers, killed for other studies, were used. Paired patellar tendons were isolated with patellar and tibial bone and the central 4.0-4.6 mm of tendon used for testing. Specimens were elongated to failure using a Materials Testing System (MTS). Only those paired specimens both failing in substance were analyzed. Eight paired specimens were analyzed, both with 0 degree twist, for right-left reproducibility. Thirty-two paired specimens were randomly assigned to four groups: right 0 degree/left 90 degree clockwise pretwist; right 0 degree/left 90 degree counterclockwise; left 0 degree/right 90 degree clockwise; left 0 degree/right 90 degree counterclockwise. No statistically significant differences were present between the paired untwisted specimens in any mechanical property. In the pretwisted specimens, there were statistically significant differences between the group left/clockwise and right/counterclockwise and the group left/counterclockwise and right/clockwise with respect to the mechanical properties failure stress, average elastic modulus, and strain energy density. No statistically significant differences were observed between the two groups for failure strain. For the canine patella-patellar tendon-tibia complex (PPTTC), the mechanical properties failure stress, average elastic modulus, and strain energy density are sensitive to both side (left/right) of PPTTC and direction (clockwise/counterclockwise) of pretwist. Pretwist of patellar tendon grafts in anterior cruciate ligament reconstruction may produce significant changes in their mechanical properties that vary with the direction of twist.

Animals↗

PubMed2001

Optimization of stacked half-hitch knots for arthroscopic surgery.

PURPOSE: This study was conducted to determine the optimal configuration of stacked half-hitch knots that would give the maximum knot-holding capacity (KHC). TYPE OF STUDY: Mechanical testing study. METHODS: The 2 types of suture materials tested were No. 1 PDS II monofilament and No. 2 Ethibond braided (Ethicon, Somerville, NJ) because these are the 2 most commonly used sutures in arthroscopic surgery. Twelve configurations of stacked half-hitch knots including 2 versions of the Revo knot were tested. Knots were tied between 2 steel hooks 7 mm apart on a manual knot-testing machine. The steel hooks were spread apart to break the knot and the KHC was determined by the peak load recorded on the digital force transducer. Maximum KHC was achieved for No. 1 PDS II sutures by locking the knot with 2 RHAPs (reversing half-hitch on alternate post) and, for No. 2 Ethibond sutures, by locking the knot with 3 RHAPs. Because of the possibility of PDS II sutures unraveling, it is recommended for both No. 1 PDS II and No. 2 Ethibond sutures, that all stacked half-hitches be locked with 3 RHAPs. By adding 1 RHAP to the Revo knot, failure by slippage can be eliminated. RESULTS: The recommended knots tied with braided No. 2 Ethibond sutures were 1.5 times stronger than knots tied with No. 1 PDS II sutures. Although there was variability in the KHC of the recommended knots tied by different surgeons using different knot tiers, the greatest difference in the mean KHC was less than 10%. CONCLUSIONS: Stacked half-hitch knots locked with 3 RHAPs are unlikely to fail by slippage.

Arthroscopy↗

PubMed2001

The influence of cross-sectional area on the tensile properties of flexor tendons.

Clinicians have long noted substantial variation in the cross-sectional size of flexor tendons in the hand; however, data indicating that surgical repair techniques of lacerated flexor tendons should be altered according to size are unavailable. Our objectives were to evaluate the cross-sectional size differences among tendons within the same hand and to correlate tendon size with tensile mechanical properties after suture repair. Fifty human cadaver flexor digitorum profundus tendons were measured with digital calipers to determine radioulnar and volardorsal diameters. Twenty tendons were used to measure resistance to suture pull-through; tendons were transected at the A2 pulley, and a transverse double-stranded 4-0 Supramid suture (S. Jackson, Inc, Alexandria, VA) was passed through the radioulnar plane of the tendon 1 cm from the transection site. The remaining tendons were transected and repaired by using a modified Kessler repair with double-stranded 4-0 Supramid suture. Both tendon repairs and tendon-suture pull-through specimens were tested to failure in tension by using a material testing machine. Dorsovolar tendon height and tendon cross-sectional area varied significantly between digits, with an average difference of approximately 40% between the values of the smallest (fifth) and largest (third) fingers. Yield and ultimate force determined by pull-through tests of the simple transverse suture correlated positively with tendon radioulnar width. Tensile properties of tendons repaired with a double-stranded modified Kessler repair, however, did not depend significantly on tendon size. These results indicate that the strength of the commonly used Kessler suture technique is not dependent on tendon cross-sectional size within the clinically relevant range of tendons evaluated.

Humans↗