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 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.

The 2.5 mm PushLock suture anchor system versus a traditional suture anchor for ulnar collateral ligament injuries of the thumb: a biomechanical study.

We compared the biomechanical strength of the 2.5 mm PushLock suture anchor with a traditional Bio-SutureTak suture anchor in repair of ulnar collateral ligament injuries. Iatrogenic ulnar collateral ligament injuries in 18 cadaveric thumbs were repaired and used to test for load to failure and cyclic loading. The average force required to generate a 2 mm gap was 7.7 N for the 2.5 mm PushLock and 6.3 N for the Bio-SutureTak (p = 0.04). The ultimate load to failure was 28.0 N for the 2.5 mm PushLock and 18.8 N for the Bio-SutureTak (p = 0.16). There were no statistical differences between the two suture anchors under cyclic loading. The 2.5 mm PushLock suture anchor provides significantly stronger resistance to 2 mm gap formation at the repair site and is less likely to fail at the suture-ligament interface. However, there was no difference in the load to failure between the two suture anchors.

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.

Do the intervertebral disc cells respond to different levels of hydrostatic pressure?

OBJECTIVE: To test the hypothesis that hydrostatic pressure directly affects the synthesis of collagen and proteoglycan by intervertebral disc cells. DESIGN: By the use of pressure vessels, hydrostatic pressure was applied to intervertebral disc cells cultured in alginate. BACKGROUND: The influence of compression (both hydrostatic and axial) on chondrocyte metabolism was examined in a number of earlier studies. However, in most of these studies, articular cartilage, not intervertebral disc was used, and in none of these was hydrostatic pressure applied to intervertebral disc cells cultured in alginate. METHODS: Fresh cells were harvested from the lumbar intervertebral discs of dogs. Before their suspension in an alginate gel system, the cells were plated and expanded until they reached confluence. Then, by use of the alginate gel system, the cells were exposed (for up to 9 days) to specific values of hydrostatic pressure inside two stainless steel pressure vessels. One vessel was kept at 0.35 MPa and the other at atmospheric pressure (approximately 0.1 MPa). The effects of 0.35 MPa were compared against atmospheric pressure by measuring the incorporation of [3H]-proline and [35S]-sulfate into collagen and proteoglycans, respectively, for the anulus cells and nucleus cells separately, and by determining whether this incorporation was reflected by changes in the levels of mRNA for aggrecan and Types I and II collagen. RESULTS: Proteoglycan synthesis was inhibited at 0.35 MPa as compared to atmospheric pressure for both the nucleus and anulus cells, whereas collagen synthesis was stimulated in the nucleus cells, but inhibited in the anulus cells. The mRNA levels of collagen 1A and collagen 2A decreased in the anulus but showed a differential response in the nucleus (collagen 1A increased, while collagen 2A decreased). The mRNA levels for aggrecan core protein decreased in the anulus and increased in the nucleus. CONCLUSIONS: Hydrostatic pressure directly affects the synthesis of collagen and proteoglycan by the intervertebral disc cells. RELEVANCE: This in vitro study reveals the direct effect of hydrostatic pressure on disc cells, in the absence of other factors. However, circumspection must be applied when comparisons between these results, from in vitro experiments on dog disc cells, are extrapolated and applied to the whole discs of humans.

Anterior lumbar interbody fusion using a barbell-shaped cage: a biomechanical comparison.

There are drawbacks to using threaded cylindrical cages (e.g., limited area for bone ingrowth and metal precluding radiographic visualization of bone healing). To somewhat offset these drawbacks, a barbell-shaped cage has been designed. The central core of the barbell can be wrapped with collagen sheets infiltrated with bone morphogenetic protein. The obvious theoretical advantages of a barbell cage have to be weighed against potential biomechanical disadvantages. Our purpose was to compare the biomechanical properties of an anterior lumbar interbody reconstruction using 18-mm-diameter threaded cylindrical cages, with a reconstruction using barbell cages (18-mm diameter and 6 mm wide at both cylindrical ends, with a round 4-mm-diameter bar joining the two ends). Twelve cadaveric lumbar motion segments were tested. Three L5-S1 segments received two threaded cylindrical cages, and three L5-S1 segments received two barbell cages. Three L3-L4 segments received one threaded cylindrical cage, and three L3-L4 segments received one barbell cage. A series of biomechanical loading sequences were carried out on each motion segment, and stiffness curves were obtained. After the biomechanical testing, an axial compressive load was applied to the motion segments until failure. They were then radiographed and bisected through the disc, and the subsidence (or penetration) of the cage(s) in the cancellous bone of the vertebral bodies was measured. There was no difference in terms of stiffness between the motion segments with the threaded cylindrical cage(s) inserted and those with the barbell cage(s) inserted (p > 0.15). The average values of subsidence was 0.96 mm for the threaded cylindrical cage group and 0.80 mm for the barbell cage group (difference not significant: p = 0.38). The results suggest that a reconstruction using barbell cages is a biomechanically acceptable alternative to one using threaded cylindrical cages.

Anterior lumbar interbody fusion using two standard cylindrical threaded cages, a single mega-cage, or dual nested cages: a biomechanical comparison.

Our purpose was: (1) to compare the biomechanical properties of an interbody reconstruction using two standard threaded cages (18-mm diameter), a reconstruction using a single mega-cage (24-mm diameter), and a reconstruction using dual nested cages (22-mm diameter); and (2) to quantify the surface area of the cancellous bone bed exposed by reaming for the cages. Each motion segment was tested according to a nondestructive biomechanical loading sequence (compression, flexion, extension, lateral bending, axial torsion). Load was applied first to the intact motion segment and again after the insertion of cages, and stiffness values were calculated at each step. After the testing, each specimen was bisected through the disc and the surface area of the vascular bed was calculated. Comparison of the biomechanical properties of the three reconstructions showed that the dual nested cages produced the stiffest reconstruction. However, when the standard cages were compared with the nested cages, there was no significant difference, and compared with the mega-cage, the only difference was in flexion. The surface area of cancellous bone exposed by reaming for each of the three reconstructions showed the greatest value with the dual nested cages. These findings, together with the improved safety afforded by the nested or mega-cage, suggest that they are appropriate alternatives to the standard dual threaded cage reconstruction.

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.

Cervical spine pedicle screws: a biomechanical comparison of two insertion techniques.

STUDY DESIGN: Biomechanical testing of the pullout strengths of pedicle screws placed by two different techniques in adult human cadaveric cervical spines. OBJECTIVES: To determine whether there is a significant difference in screw purchase of two commonly proposed methods of cervical pedicle screw insertion. SUMMARY OF BACKGROUND DATA: Wiring techniques remain the gold standard for posterior cervical fixation. However, absent or deficient posterior elements may dictate the use of alternative fixation techniques. Cervical pedicle screws have been shown to have significantly higher pullout strength than lateral mass screws. METHODS: Fifty fresh disarticulated human vertebrae (C3-C7) were evaluated with computed tomography for anatomic disease and pedicle morphometry. The right and left pedicles were randomly assigned to either a standard method or the Abumi insertion method. In the latter technique the cortex and cancellous bone of lateral mass are removed with a high-speed burr, which provides a direct view of the pedicle introitus. The pedicle is then probed and tapped and a 3.5-mm cortical screw inserted. Each screw was subjected to a uniaxial load to failure. RESULTS: There was no significant difference in the mean pullout resistance between the Abumi (696 N) and standard (636.5 N) insertion techniques (P = 0.41). There was no difference in pullout resistance between vertebral levels or within vertebral levels. Two (4%) minor pedicle wall violations were observed. CONCLUSION: In selected circumstances pedicle screw instrumentation of the cervical spine may be used to manage complex deformities and patterns of instability. Surgeons need not be concerned about reduced screw purchase when deciding between the Abumi method and its alternatives.

Coaxial portals for posterior ankle arthroscopy: An anatomic study with clinical correlation on 29 patients.

PURPOSE: The authors performed a cadaveric study on 10 ankles and retrospectively reviewed 29 arthroscopic synovectomies to determine the trajectory, minimal safe distances, and complications using a new approach for posterior ankle arthroscopy. TYPE OF STUDY: Anatomic study and case series. MATERIALS AND METHODS: A posterolateral portal was established immediately posterior to the peroneal tendon sheath. While staying within the posterior ankle capsule, an inside-out technique was then used to establish the posteromedial portal directly behind the medial malleolus adjacent to the posterior tibial tendon. The cadaveric ankles were frozen, sectioned, and photographed to measure the proximity of neurovascular structures to these coaxial portals. From 1988 to 1994, arthroscopic synovectomy was performed on 23 patients (29 ankles) with hemophilia using these modified portals. RESULTS: Results of the anatomic study showed that the posterior tibial nerve and posterior tibial artery were located a mean distance of 5.7 mm (SEM, 0.6 mm) and 6.4 mm (SEM, 0.7 mm) from the edge of the cannula, respectively. Neither penetration nor contact of nerve or vessel was observed at either posterior portal. In the 29 clinical cases, posterior capsular synovectomy was achieved arthroscopically with no detectable complications at an average 45-month follow-up. CONCLUSIONS: Our anatomic data show that the coaxial portals described here are essentially equidistant to the neurovascular structures compared with conventional portals. Our clinical results suggest that his technique for posteromedial and posterolateral portals is safe, effective, and reproducible.

Bone loss during simulated weightlessness: a biomechanical and mineralization study in the rat model.

BACKGROUND: Astronauts exposed to weightlessness for extended periods experience significant decreases in bone mineral density. The clinical implications of this demineralization are not entirely clear, and the biomechanics involved are not completely understood. HYPOTHESIS: Local (rather than global) measurements of geometry and calcium concentration effectively predict femur strength in adult rats exposed to a hind-limb suspension model of weightlessness. METHODS: Female Fischer rats (6-mo-old) were divided into groups of control and hind-limb-suspended animals. Animals were sacrificed after 2 or 4 wk of hind-limb suspension, and both femurs removed from each animal. The 3-point bending strength and total bone mineralization were determined for one femur from each animal, and the mid-shaft cross-sectional geometrical properties and distribution of calcium were determined for the contralateral femur. RESULTS: Although suspension led to significant decreases in total bone mineralization, the concentration of calcium at the anterior periosteal surface was unaffected. Total bone percent mineralization was not well correlated with structural properties, but bone geometrical properties (particularly cross-sectional moment of inertia and length) correlated strongly with ultimate bending strength (r2 = 0.81). Differences in bone geometry due to suspension were consistent with a distribution of bone material closer to the axis of the femur. CONCLUSIONS: Structural properties of bone are predicted well by bone geometry and poorly by total bone percent mineralization. Decreased bone mechanical strength in this model of weightlessness is primarily due to a distribution of bone material nearer the axis of the bone.

The biomechanical relationship between the tendoachilles, plantar fascia and metatarsophalangeal joint dorsiflexion angle.

We carried out an experiment to measure the relationship between tensile force in the tendoachilles and plantar fascia strain, and how this relationship is affected by the metatarsophalangeal joint dorsiflexion angle. Eight cadaver lower extremity specimens underwent biomechanical testing. Using a servo-hydraulic testing machine, a tensile force up to 500 N was applied to the tendoachilles while the strain on the plantar fascia was measured using an extensometer. The experiment was repeated at four different metatarsophalangeal joint dorsiflexion angles (0 degrees, 5 degrees, 30 degrees, and 45 degrees). Measurements and calculations showed that dorsiflexion of the toes tightens the plantar fascia (the windlass effect) and increases the effect that a tensile force in the tendoachilles has on the tensile strain and tensile force in the plantar fascia.

Achilles tendon rupture repair: biomechanical comparison of the triple bundle technique versus the Krakow locking loop technique.

This study was designed to compare the tensile strength of ruptured Achilles tendons repaired using either the triple bundle technique or the Krakow locking loop technique. Eight pairs of fresh frozen cadaveric Achilles tendons were harvested. A simulated "Achilles tendon rupture" was created 4 cm from the calcaneal insertion in all sixteen tendons by transversely cutting the tendon with a scalpel. One Achilles tendon "rupture" of a pair was repaired using the triple bundle technique, while the other tendon of the pair was repaired using the Krakow locking loop technique. Then, using a servohydraulic testing machine, each tendon was tested to failure in tension at a displacement rate of 2.54 cm/sec. The average rupture load for the triple bundle technique was 453 N (range 397 n 549 N), while the average rupture load for the Krakow locking loop technique was 161 N (range 121 n 216 N). This difference in averages represents a statistically significant superiority of 2.8 to 1 (p < 0.001) in favor of the triple bundle technique.

Purification of a jojoba embryo wax synthase, cloning of its cDNA, and production of high levels of wax in seeds of transgenic arabidopsis.

Wax synthase (WS, fatty acyl-coenzyme A [coA]: fatty alcohol acyltransferase) catalyzes the final step in the synthesis of linear esters (waxes) that accumulate in seeds of jojoba (Simmondsia chinensis). We have characterized and partially purified this enzyme from developing jojoba embryos. A protein whose presence correlated with WS activity during chromatographic fractionation was identified and a cDNA encoding that protein was cloned. Seed-specific expression of the cDNA in transgenic Arabidopsis conferred high levels of WS activity on developing embryos from those plants. The WS sequence has significant homology with several Arabidopsis open reading frames of unknown function. Wax production in jojoba requires, in addition to WS, a fatty acyl-CoA reductase (FAR) and an efficient fatty acid elongase system that forms the substrates preferred by the FAR. We have expressed the jojoba WS cDNA in Arabidopsis in combination with cDNAs encoding the jojoba FAR and a beta-ketoacyl-CoA synthase (a component of fatty acid elongase) from Lunaria annua. (13)C-Nuclear magnetic resonance analysis of pooled whole seeds from transgenic plants indicated that as many as 49% of the oil molecules in the seeds were waxes. Gas chromatography analysis of transmethylated oil from individual seeds suggested that wax levels may represent up to 70% (by weight) of the oil present in those seeds.

Does long-term compressive loading on the intervertebral disc cause degeneration?

STUDY DESIGN: Coil springs were stretched and attached to produce a compressive force across the lumbar intervertebral discs of dogs for up to 53 weeks. OBJECTIVE: To test the hypothesis that compressive forces applied to the intervertebral disc for a long period of time cause disc degeneration in vivo in a dog model. SUMMARY OF BACKGROUND DATA: It is a commonly held belief that high forces applied to the intervertebral disc, and to joints in general, play a role in causing degeneration. METHODS: Coil springs were stretched and attached to produce a compressive force across the lumbar intervertebral discs (L3/L4) of 12 dogs. After up to a year, the dogs were killed, and their lumbar spines were removed and radiographed. The L3/L4 disc and the controls (T13/L1 and L4/L5) were excised and examined for visible signs of degeneration. The discs then were assessed using immunohistochemical analysis and enzyme-linked immunosorbent assay. Disc chondrocytes also were assayed for apoptosis. RESULTS: No obvious signs of degeneration in the discs (L3/L4) that had been under compression for up to a year could be observed. There was no disc bulging, anular fissures, or disc space narrowing. Some changes were observed at the microscopic level, although no thickening of the endplate was apparent. The enzyme-linked immunosorbent assay analysis provided significant data for all three regions of the disc (nucleus, inner anulus, and outer anulus). When comparing the compressed disc (L3/L4) with either of the control discs (T13/L1 and L4/L5), in the compressed disc: 1) the nucleus contained less proteoglycan and more collagen I and II; 2) the inner anulus contained less proteoglycan and collagen I; and 3) the outer anulus contained more proteoglycan and less collagen I. The collagen II differences for the inner and outer anulus were not significant. CONCLUSION: Compression applied to the lumbar intervertebral discs of dogs for up to a year does not produce degeneration in any visible form. It does produce microscopic changes and numerical changes, however, in the amounts of proteoglycan and collagen in the nucleus, inner anulus, and outer anulus. The present results add no credence to the commonly held belief that high compressive forces play a causative role in disc degeneration.

Cervical transfacet versus lateral mass screws: a biomechanical comparison.

The authors directly the compared biomechanical pullout strength of screws placed in the cervical lateral masses to that of screws placed across the facet joints. Posterior cervical fixation with lateral mass plates is an accepted adjunctive technique for cervical spine fusions. Altered anatomy resulting from congenital malformation, tumor, trauma, infection, or failed lateral mass fixation may limit traditional screw placement options. Transfacet screw placement, which has been studied extensively in the lumbar spine, may offer an alternative when posterior cervical fusion is required. Ten fresh human cadaveric cervical spines (postmortem age range, 69 to 91 years) were harvested. On one side, transfacet screws were placed at the C3-4, C5-6, and C7-T1 levels. On the other side, lateral mass screws were placed at the C3, C5, and C7 levels. The screw insertion technique at each level was randomized for right or left. After screw placement, each set of vertebral bodies were dissected and mounted in a custom jig for axial pullout testing using a servohydraulic testing machine. The load-displacement curves were obtained for each screw pullout. The mean pullout strength for the screws placed across the facets was 467 N (range, 192 to 1,176 N). This compares with 360 N (range, 194 to 750 N) for the lateral mass screws (p = 0.008). At each level, transfacet screws exhibited greater pullout resistance compared with the lateral mass placement, but the difference was most pronounced at the C7-T1 level (lateral mass = 373 N, transfacet = 539 N, p = 0.042). Cervical transfacet screw placement provides pullout resistance that is comparable to, if not greater than, lateral mass placement. This type of placement, although technically difficult, may be an alternative to lateral mass screws in cases with unusual anatomy, stripped screws, or when additional intermediate points of fixation are desired.

Enzymatic synthesis of 4-amino-3,5-diethylphenyl sulfate, a rodent metabolite of alachlor.

Rat liver tissue homogenates were utilized for in vitro enzymatic conversion of 2,6-diethylaniline (DEA) to the important alachlor metabolite 4-amino-3,5-diethylphenyl sulfate (ADEPS), which was also generated as a radiolabeled standard for use in metabolism studies. ADEPS formation in rodents is associated with the production of other reactive metabolites implicated in alachlor rodent carcinogenesis, making dependable access to an ADEPS standard highly desirable. (14)C-DEA was oxidized by rat liver microsomes to (14)C-4-amino-3,5-diethylphenol, which was further converted to ADEPS via addition of the phosphosulfate transferase cofactor adenosine-3'-phosphate-5'-phosphosulfate. Microprobe NMR was used in conjunction with high-resolution mass spectrometry to fully characterize the resulting (14)C-ADEPS and confirm its structure. Because microgram quantities sufficed for full characterization, the enzymatic transformation provides a viable alternative to radiosynthesis of (14)C-ADEPS.

Correlation of medial/lateral rotation of the humerus with glenohumeral translation.

OBJECTIVES: To correlate glenohumeral translation in the anterior/posterior direction with medial and lateral rotation of the humerus. In addition, the length of the anterior and posterior component of the glenohumeral capsuloligamentous complex was varied in order to gain insight into the contribution of each component to limiting translation. All measurements were made with the humerus positioned at 90 degrees of abduction and 0 degrees of flexion/ extension. METHODS: Six fresh cadaveric shoulders were used. Each scapula was mounted in a cement pot to rest it in its correct anatomical position. Seven tests were carried out on each shoulder. A series of measurements of translation of the humerus in the anterior direction and posterior direction were taken at 20 degrees intervals of lateral rotation and then at 20 degrees intervals of medial rotation until the limit of lateral or medial rotation had clearly been reached (test 1). The capsuloligamentous complex was then incised and a beaded chain and catches were sutured across the joint to mimic the capsuloligamentous complex at different lengths (tests 2 to 7). RESULTS/CONCLUSIONS: (a) When the glenohumeral capsuloligamentous complex is intact, the humerus translates maximally in the glenoid (between 20 and 30 mm) when the humerus is between 40 degrees and 100 degrees of lateral rotation. (b) As the glenohumeral capsuloligamentous complex increases in length, so does the extent of translation. (c) In medial rotation, the length of the posterior capsule, rather than the length of the anterior capsule, has the greater effect on anterior/posterior translation. (d) In lateral rotation the length of the anterior capsule, rather than the length of the posterior capsule, has the greater effect on anterior/posterior translation. (e) The glenohumeral ligamentous complex acts more as a cuff, enclosing the joint, rather than as a sling, as is commonly thought.

The effect of hydrostatic pressure on intervertebral disc metabolism.

STUDY DESIGN: By the use of pressure vessels, hydrostatic pressure was applied to intervertebral disc cells cultured in an alginate. OBJECTIVE: To test the hypothesis that hydrostatic pressure directly affects the synthesis of collagen and proteoglycan by the intervertebral disc cells. SUMMARY OF BACKGROUND DATA: The influence of compression (both hydrostatic and mechanical) on chondrocyte metabolism was examined in a number of earlier studies. However, in most of these studies, articular cartilage, not intervertebral disc, was used, and in none of these was hydrostatic pressure applied to intervertebral disc cells cultured in alginate. METHODS: Fresh cells were harvested from the lumbar intervertebral discs of dogs. Before their suspension in an alginate gel system, the cells were plated and expanded until they reached confluence. Then, by use of the alginate gel system, the cells were exposed (for up to 9 days) to specific values of hydrostatic pressure inside two stainless steel pressure vessels. One vessel was kept at 1 MPa and the other at atmospheric pressure. The effects of 1 MPa were compared against atmospheric pressure by measuring the incorporation of [3H]-proline and [35S]-sulfate into collagen and proteoglycans, respectively, for the anulus cells and nucleus cells separately, and by determining whether this incorporation was reflected by changes in the levels of mRNA for aggrecan and Types I and II collagen. RESULTS: Comparisons with atmospheric pressure yielded the following findings: 1) In the incorporation studies, the nucleus and anulus cells exhibited a differential response to a hydrostatic pressure of 1 MPa. Collagen and proteoglycan syntheses were stimulated in the nucleus cells and inhibited in the anulus cells. 2) There was no significant increase in cell proliferation, as measured by DNA content, at 1 MPa for either the anulus or nucleus cells. 3) The mRNA levels of collagen (Col 1A1 and Col 2A1) and aggrecan increased at 1 MPa in both the nucleus and anulus cells. CONCLUSIONS: Hydrostatic pressure directly affects the synthesis of collagen and proteoglycan by the intervertebral disc cells.

An in vivo magnetic resonance imaging study of changes in the volume (and fluid content) of the lumbar intervertebral discs during a simulated diurnal load cycle.

STUDY DESIGN: Magnetic resonance imaging was used to measure the changes in volume of the lumbar intervertebral disc in vivo during a load cycle. OBJECTIVES: To measure changes in volume of the lumbar intervertebral disc during a load cycle and relate these changes to changes in fluid content. SUMMARY OF BACKGROUND DATA: There have been very few experiments conducted to measure the volume and fluid changes in intervertebral discs in vivo. METHODS: Five healthy subjects were recruited (aged 27, 29, 31, 34, and 52 years) in a study using magnetic resonance imaging to measure the changes in volume of the lumbar intervertebral disc in vivo, during a load cycle. The experiment was designed to simulate a diurnal load cycle, but over less time. The load cycle consisted of bed rest, followed by walking with a 20-kg backpack for 3 hours, followed by bed rest for 3 hours. Magnetic resonance imaging scans of the lumbar spine were obtained 10 times during this load cycle. The disc volume was calculated by summing the disc area contained in each slice of the scan. The changes in volume of the discs (L2-L3, L3-L4, and L4-L5) recorded at the 10 times were then related to the fluid changes. RESULTS: Load-induced changes in disc volume can be detected and measured using MR imaging. The average volume increase 3 hours after removing a highly compressive load was 5.4%. The water content of the nucleus and anulus in the disc of the young human is said to be approximately 80% and 70%, respectively. If the disc gained 5.4% of its initial total volume, and assuming that the initial fluid content was approximately 75%, then it gained approximately 7% (i.e., 5.4%/75% x 100% approximately 7%) of its fluid. CONCLUSIONS: Load-induced changes in disc volume can be detected and measured using magnetic resonance imaging.