Assessment of knee laxity using a robotic testing device: a comparison to the manual clinical knee examination.

PURPOSE: The purpose of this study was to collect knee laxity data using a robotic testing device. The data collected were then compared to the results obtained from manual clinical examination. METHODS: Two human cadavers were studied. A medial collateral ligament (MCL) tear was simulated in the left knee of cadaver 1, and a posterolateral corner (PLC) injury was simulated in the right knee of cadaver 2. Contralateral knees were left intact. Five blinded examiners carried out manual clinical examination on the knees. Laxity grades and a diagnosis were recorded. Using a robotic knee device which can measure knee laxity in three planes of motion: anterior-posterior, internal-external tibia rotation, and varus-valgus, quantitative data were obtained to document tibial motion relative to the femur. RESULTS: One of the five examiners correctly diagnosed the MCL injury. Robotic testing showed a 1.7° larger valgus angle, 3° greater tibial internal rotation, and lower endpoint stiffness (11.1 vs. 24.6 Nm/°) in the MCL-injured knee during varus-valgus testing when compared to the intact knee and 4.9 mm greater medial tibial translation during rotational testing. Two of the five examiners correctly diagnosed the PLC injury, while the other examiners diagnosed an MCL tear. The PLC-injured knee demonstrated 4.1 mm more lateral tibial translation and 2.2 mm more posterior tibial translation during varus-valgus testing when compared to the intact knee. CONCLUSIONS: The robotic testing device was able to provide objective numerical data that reflected differences between the injured knees and the uninjured knees in both cadavers. The examiners that performed the manual clinical examination on the cadaver knees proved to be poor at diagnosing the injuries. Robotic testing could act as an adjunct to the manual clinical examination by supplying numbers that could improve diagnosis of knee injury. LEVEL OF EVIDENCE: Level II.

The AdLMP-1 transfection in two different cells; AF cells, chondrocytes as potential cell therapy candidates for disc degeneration.

BACKGROUND: LMP-1 is known to increase proteoglycan production through the upregulating the BMPs and it is also known that BMP-2 acts on anulus fibrosus cells and chondrocytes to increase proteoglycan production. METHOD: We carried out an experiment, the effect of AdLMP-1 transfection on AF cells and chondrocytes in the production of sulfated-glycosaminoglycans, mRNA expression (aggrecan, type I, II collagen, LMP-1, BMP-2, and BMP-7), and immunofluorescence staining. AF cells and chondrocytes were grown in monolayer and treated for 6 days with AdLMP1-green fluorescence protein (GFP) (10, 20, and 30 multiplicity of infection [MOI]). After 6 days, the sGAG content in the media was quantified using 1,9-dimethylmethylene blue staining. The mRNA expression was measured with real-time PCR after 20 MOI infection of AdLMP1-GFP. The each cells treated with 20 MOI infection of AdGFP was used as a control group for the mRNA expression. The each cell group was immunofluorescence stained with each antibodies in the chamber slide at 3 x 10(4) cells/chamber. FINDINGS: 1) The sGAG production was maximum in 20 MOI AdLMP1-GFP infection on the AdLMP-1 treatment for both of AF cells and chondrocytes. 2) The mRNA expression of aggrecan, type I collagen, type II collagen, LMP-1, BMP-2, and BMP-7 is increased in both AF cells and chondrocytes in 20 MOI AdLMP1-GFP infection. 3) On the immunofluorescence staining results, the positive immunofluorescence stained cell numbers are increased after 20 MOI AdLMP1-GFP infection concordant with upregulation of mRNA expression. CONCLUSIONS: The AdLMP-1 treatments in AF cells and chondrocytes may be useful for cell transplantation therapy in disc degeneration.

Molecular dynamics of the local anesthetic tetracaine in phospholipid vesicles.

Upon introduction into phosphatidylcholine vesicles, the 13C magnetic resonance peaks of the aromatic resonances of tetracaine are broadened while the T1 relaxation times show little change. Addition of tetracaine to vesicles containing 30% cholesterol produces a similar broadening in the 13C NMR spectrum of tetracaine. Nuclear magnetic resonance parameters of phosphatidylcholine in vesicles which are unchanged by the addition of equimolar tetracaine include 13C T1 relaxation time and 31P linewidth, T1 relaxation time, and nuclear Overhauser effect enhancement. These results are interpreted as indicating a hydrophobic interaction between hydrocarbon portions of the anesthetic and phospholipid bilayer. The rotational correlation time of tetracaine about its long axis in the vesicles has been calculated from the 13C NMR spin lattice relaxation times to be about 10(-10.3) s and is unchanged by incorporation into the phospholipid bilayer. The positively charged ammonium group of tetracaine interacts with the negatively charged phosphate group of the vesicle lipids. Using shift reagents and 31P NMR, tetracaine has been shown to displace cations from the bilayer surface, and does not undergo fast flip-flop across the vesicle bilayer.

The structure of vesicular stomatitis virus membrane. A phosphorus nuclear magnetic resonance approach.

The proton decoupled 40.48 M Hz 31P NMR spectrum of intact and unperturbed membrane-enclosed vesicular stomatitis virus (sterotype Indiana) exhibited two distinct maxima. These can be resolved into a narrow, symmetric line and a broad asymmetric line. The 31P NMR spectrum of a multilamellar (unsonicated) preparation of the extracted viral lipids exhibited a line shape similar to that of the intact virus. A sonicated vesicle preparation of the extracted viral lipids exhibited a narrow symmetric line. The narrow component in the intact virus spectrum may be attributed to small membrane fragments. Phospholipase C digestion of the intact virus resulted in substantial reduction in intensity of both components which suggests that much of the contribution to both peaks is due to phosphate in the phospholipid polar head groups. The phospholipid phosphates in both sonicated and unsonicated preparations of the extracted viral lipids exhibited substantially longer relaxation times than did those in the intact virus. The short relaxation time emanating from the intact virus preparation is caused by immobilization of the phospholipid head groups which could be due to lipid-protein interactions. Trypsin treatment of vesicular stomatitis virions, which results in complete removal of the exterior hydrophilic segment of the membrane glycoprotein, increased the 31P relaxation time to a value similar to that observed in the protein-free total lipid extracts; this finding provides supporting evidence for the role of virus glycoprotein in shortened relaxation times. A reversible temperature-dependent change in apparent line width and absence of an effect of cholesterol on the 31P phospholipid spectrum were also demonstrated.

The effect of flexor digitorum profundus tendon shortening on jersey finger surgical repair: a cadaveric biomechanical study.

Delayed diagnosis of jersey finger injuries often results in retraction of the flexor digitorum profundus tendon. Current practice recommends limiting tendon advancement to 1 cm in delayed repairs. The purpose of this study was to investigate the biomechanical consequences of tendon shortening on the force required to form a fist. The flexor digitorum profundus muscle was isolated in ten cadaveric forearms and the force required to form a fist was recorded. Simulated jersey finger injuries to the ring finger were then created and repaired. The forces required to pull the fingertips to the palm after serial tendon advancements were measured. There was a near linear increase in the force required for making a fist with shortening up to 2.5 cm. The force required to make a fist should be taken into account when considering the limit of 'safe' tendon shortening in delayed repair of jersey finger injuries.

A method of in vivo measurement of the elastic properties of skin in radiotherapy patients.

A portable apparatus which measures the force-displacement or elastic characteristics of skin in vivo has been constructed. A displacement transducer between two arms measures the extension of the skin as the arms are driven apart by means of a lead screw, and the force exerted on the skin is measured by means of two electrical resistance strain gauges attached at a reduced section on each of the arms. The apparatus was designed for compactness and lightness to enable it to be hand held. Illustrative results obtained on patients during and after courses of radiotherapy are presented.

Conformationally restricted polysubstituted biphenyl derivatives with angiotensin II receptors antagonist properties.

The synthesis and in vitro activity of new nonpeptide angiotensin II antagonists is presented. Compared to previously reported biphenyl compounds, the new analogues 8 and 9 have reduced conformational freedom derived from steric hindrance. Methyl 4'-methyl-2',6'-dimethoxy[1,1'-biphenyl]-2-carboxylate 4 has been synthesized by a Von Pechmann condensation of orcinol with oxocyclohexane-2-carboxylate followed by dehydrogenation. This scheme provided the carbon skeleton of the biphenyl potentially substituted on the 2-, 2'-, 4'-, and 6'-positions. Elaboration of the subsituents led to a biphenyl derivative used to alkylate a 2-n-butyl-4-chloro-5-(hydroxymethyl)imidazole. After coupling with the imidazole two regioisomers were separated and identified by 1H NMR. NOESY experiments were useful to establish regiochemistry of the final products that have angiotensin II blocking activity. Their affinity for angiotensin II receptors was established in a binding assay experiment and in an isolated organ test. The presence of 2',6'-dimethoxy substituent on the biphenyl moiety of the antagonist was found to significantly decrease affinity for the receptor.

The interaction of lanthanide and calcium salts with phospholipid bilayer vesicles: the validity of the nuclear magnetic resonance method for determination of vesicle bilayer phospholipid surface ratios.

Contrary to a recent report (B. Sears et al., Biochemistry 15 (1976) 1635), it has been determined that the ratio of the number of phospholipids on the inner and outer surfaces of phospholipid bilayer vesicles can be accurately determined by NMR paramagnetic ion shift reagent studies of vesicles. It is concluded that the metal interacts with all of the phospholipid on the exposed bilayer surface. A ratio of outer phospholipid to inner surface phospholipid of 2.1 +/- 0.1 is obtained regardless of the nucleus studied, position of the nucleus relative to the metal ion binding site, molar ratio of metal to phospholipid over three orders of magnitude, or location of the metal ion of the inside or outside of the vesicle. Additionally, P-31 NMR studies using LaC13 and CaC12 indicate that Ca2+ weakly interacts with egg PC vesicles and that the lanthanides are adequate substitutes for Ca2+ since neither metal is found to perturb measurably the average polar head group conformation.

The effects of split dose radiations on the mechanical properties of the skin.

A series of split dose experiments in which the interval between doses was varied from 1 to 7 d is reported. In vitro measurements of the mechanical properties of skin are made 50 and 120 d after the first irradiation. The variation of the skin thickness, load at rupture, extension at rupture, stress at rupture and skin stiffness with dose and with time interval between doses is examined. The results suggest that after the highest doses of irradiation the skin is matted in structure and the fractionation pattern is insignificant. Different fractionation patterns only influence the radiation effects at lower doses where the skin retains an open mesh structure. The experiments indicate that a maximum skin sparing effect is obtained with a two day interval between the split doses.

The effects of x-irradiation on the mechanical properties of skin.

The elastic properties of rat skin previously irradiated with single doses form 1000 to 3000 rad have been studied. The measurements were made 50 and 120 d after irradiation on skin specimens immersed in saline at 37 degrees c. The tests were carried out on a tensile testing machine. The load extension curve, which was plotted to the point of rupture, exhibits two portions which are identified with the aligment of the collagen fibres and then their subsequent stretching. The elastic properties associated with fibre alignment are little affected by these doses of radiation but the stiffness of the collagen itself tends to decrease with increasing dose, exhibiting a shoulder in the dose response curve.

Lumbar intertransverse-process spinal arthrodesis with use of a bovine bone-derived osteoinductive protein. A preliminary report.

The use of a bovine bone-derived osteoinductive protein extract as a bone-graft substitute was evaluated in a rabbit model of intertransverse process arthrodesis of the lumbar spine. Forty-five adult New Zealand White rabbits had arthrodesis between the fifth and sixth lumbar vertebrae with use of one of three graft materials: autogenous iliac-crest bone, osteoinductive protein delivered in an allogeneic demineralized bone matrix/collagen carrier, or demineralized bone matrix/collagen carrier or demineralized bone matrix/collagen carrier without osteoinductive protein. Fusion was assessed by manual palpation, radiography, biomechanical testing, and light microscopy at two and five weeks after the operation. At two weeks, light microscopic analysis of the arthrodesis site in which osteoinductive protein had been used showed that most of the demineralized bone matrix was still present, with small amounts of membranous and endochondral bone formation at the peripheral margins of the implant. Light microscopic analysis of the five-week specimens showed increased new-bone formation and a more homogeneous and mature fusion mass with the osteoinductive bone protein than with the autogenous bone graft. At five weeks, the fusions with the osteoinductive protein extract were characterized by more secondary spongiosa, with formation of bone marrow centrally and a cortical rim peripherally. Of the thirty-five rabbits that were examined at five weeks, all ten in the group that had received osteoinductive bone protein had a solid fusion, but the rate of fusion was significantly less in the other two groups: eight of thirteen rabbits (p = 0.05) in the group that had received autogenous bone graft and two of twelve rabbits (p = 0.0001) in the group that had received demineralized bone matrix/collagen carrier without osteoinductive bone protein. The use of osteoinductive bone protein resulted in stronger (p = 0.02) and stiffer (p = 0.005) fusions compared with those obtained with the use of autogenous iliac-crest graft.

Increase of motion between lumbar vertebrae after excision of the capsule and cartilage of the facets. A cadaver study.

Seventeen fresh segments of cadaveric lumbar spines were tested in flexion, extension, and axial rotation. The resulting angular rotations were measured with the use of a goniometer and a three-dimensional system of video analysis. Measurements of flexibility were made, in order, in the intact spine; after decompression (bilateral total laminectomies, partial medial facetectomies, and foraminotomies); after excision of the capsule and cartilage of the facets; and after cancellous bone had been packed into the facet defects. Decompression resulted in a slight increase in the sagittal and axial ranges of motion. Subsequent excision of the capsule and cartilage of the facets, as in preparation for an arthrodesis of the facets, resulted in a significant increase in both the sagittal (5.7 +/- 2.9 degrees, mean and standard deviation) (p < 0.001) and the axial (1.4 +/- 0.9 degrees) (p < 0.01) ranges of motion compared with the motion in the intact specimen and with the motion in the specimen after only decompression had been done (p < 0.01 and p < 0.05, respectively). Packing of bone in the facets did not significantly reduce motion. It was calculated that the increase in the sagittal range of motion after excision of the capsule and cartilage of the facets would increase the tensile strain in a graft between the transverse processes of the fourth and fifth lumbar vertebrae (18 +/- 1 per cent tensile strain [mean and 95 per cent confidence interval] for the intact vertebrae and 25 +/- 1 per cent for the vertebrae in which the facets had been excised).

Adenoviral delivery of LIM mineralization protein-1 induces new-bone formation in vitro and in vivo.

BACKGROUND: The LIM mineralization protein-1 (LMP-1) gene encodes for an intracellular protein that induces the expression of several bone growth factors. The purpose of the present study was to determine the feasibility and the optimal dose of adenoviral delivery of the LMP-1 cDNA to promote spinal fusion. METHODS: A replication-deficient human recombinant adenovirus was constructed with the LMP-1 cDNA driven by a cytomegalovirus promoter. In phase 1, an in vitro dose-response experiment was performed to determine the optimal adenovirus-LMP-1 (AdLMP-1) concentration and infection time. In phase 2, nine rabbits had a single-level posterolateral arthrodesis of the lumbar spine with implantation of a carrier matrix loaded with bone-marrow-derived buffy-coat cells that had been infected for ten minutes with adenovirus containing the cDNA for LMP-1 (AdLMP-1) or beta-galactosidase (AdBgal). In phase 3, posterolateral arthrodesis of the spine was performed with implantation of cells infected with AdLMP-1 (ten rabbits) or cells infected with an empty adenovirus that did not contain LMP-1 cDNA (ten rabbits) and the results were compared. In this phase, peripheral-blood-derived buffy-coat cells were used instead of bone-marrow-derived cells and a collagen-ceramic-composite sponge was used as the carrier. RESULTS: In phase 1, the in vitro dose-response experiment showed that a multiplicity of infection of 0.25 plaque-forming units per cell was the most efficient dose. In phase 2, the implants that had received cells infected with AdLMP-1 induced a solid, continuous spinal fusion mass at five weeks. In contrast, the implants that had received cells infected with AdBgal or a lower dose of AdLMP-1 induced little or no bone formation. In phase 3, a solid spinal fusion was observed at four weeks in all ten rabbits that had received cells infected with AdLMP-1 and in none of the ten rabbits that had received cells infected with the empty adenovirus. Biomechanical and histological testing of the AdLMP-1-treated specimens revealed findings that were consistent with a high-quality spinal fusion. CONCLUSIONS: Adenoviral delivery of LMP-1 cDNA promotes spinal fusion in immune-competent rabbits.

A comparison of different treatment regimes on the visual appearance and mechanical properties of mouse skin.

Four different regimes of radiotherapy employed in the treatment of basal cell epitheliomas were compared in order to assess their effect on the visual appearance and mechanical properties of skin. Three groups of mice received exposures identical to those given in the radiotherapy treatments; three months after completion of the radiation the visual and mechanical properties of the skin and its appendages were examined. The skin scarring, coat condition, greying of hair, skin, thickness, load at rupture, extension at rupture, mechanical stress at rupture and stiffness were used as cirteria for comparing the four treatments. The treatment regime which caused the least damage to normal skin was identified.

Effects of radiation on the visual appearance and mechanical properties of mouse skin.

A study of the long term effects of radiation on the visual appearance and mechanical properties of mouse skin is presented. The effects associated with the hair follicle (greying and alopecia) increase monotonically with exposure. Other effects (load, extension and stress at rupture and scarring of the skin) all show a reversal at the highest exposures. The skin thickness changes little with exposure, while the skin stiffness exhibits a shoulder on the response curve. Possible mechanisms underlying these effects are discussed.

The mechanical function of the lumbar apophyseal joints.

Experiments were carried out on cadaveric lumbar spines to determine the mechanical function of the apophyseal joints. It was found that they resist most of the intervertebral shear force and share in resisting the intervertebral compressive force, but only in lordotic postures. They prevent excessive movement from damaging the discs: the posterior annulus is protected in torsion by the facet surfaces and in flexion by the capsular ligaments.

Variations in the amount and distribution of cortical bone across the partes interarticulares of L5. A predisposing factor in spondylolysis?

The possible role of the physical and mechanical properties of the neural arch as contributing factors in the etiology of spondylolysis was tested by comparing two groups of vertebral specimens obtained at necropsy. Group I specimens had been subjected to repetitive cyclic force which they withstood without fracturing. Group II specimens were randomly selected. The cross-sectional distribution of cortical and cancellous bone in the partes interarticulares were measured, and the two groups compared. The previously stressed group was found to have a greater percentage of cortical bone than the random group. The data are interpreted to suggest that thin partes interarticulares may predispose to spondylolysis through the mechanism of fatigue failure.

Articular tropism and stability of the lumbar spine.

Lumbar intervertebral joints were subjected to compressive and shear forces calculated to simulate walking with a heavy pack on the back. The joints with articular tropism were found to rotate toward the side of the more oblique facet. The mechanics relating the orientation of the articular facets with joint forces and stability of the lumbar spine are discussed.

The relevance of torsion to the mechanical derangement of the lumbar spine.

Cadaveric lumbar intervertebral joints were loaded simultaneously in torsion and compression, and load-deformation curves were obtained. These were repeated after each of the following structures were cut through in turn: the supra/interspinous ligaments, the apophyseal joint in compression, and the apophyseal joint in tension. From the differences in the curves, it was possible to deduce the role of each structure and of the intervertebral disc in resisting and limiting torsion. The results show that torsion of the lumbar spine is resisted primarily by the apophyseal joint that is in compression, although the intervertebral disc does play a major role. The capsular ligaments of the tension facet and the supra/interspinous ligaments are unimportant. The compression facet is the first of rotation in joints with nondegenerated intervertebral discs. Much greater angles are required to damage the intervertebral disc, so torsion seems unimportant in the etiology of disc degeneration and prolapse.

Can the lumbar spine be crushed in heavy lifting?

Cadaveric lumbar intervertebral joints were wedged to simulate forward flexion and then compressed to failure. The compressive strengths of the young male specimens tested were compared with the forces calculated to act when average young men perform maximum lifts from the flexed posture. It is concluded that the spine has a considerable margin of safety when such lifts are performed.