bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanical characteristics of proximal femoral reconstruction after 50% resection
Authors: Markel Mark D. , Gottsauner‐Wolf Florian , Rock Michael G. , Frassica Frank J. , Chao Edmund Y. S.
Published: February 2005

Six techniques of proximal femoral replacement were compared in vitro with the use of compression, bending, and torsional testing in a canine model. One femur of each pair was osteotomized in the midshaft region, and the proximal portion was replaced with one of six techniques. These techniques included (a) a segmental proximal femoral endoprosthesis cemented into the distal femur with no allograft (technique Es); (b) a long‐stem endoprosthesis press‐fit into an allograft and cemented into the distal femur with a transverse osteotomy (technique AT); (c) the same construct as technique AT, but with a step‐cut at the osteotomy (technique AS); (d) a long‐stem endoprosthesis interlocked into an allograft and cemented into the distal femur with a transverse osteotomy (technique AI); (e) a short‐stem endoprosthesis cemented into an allograft combined with one plate laterally stabilizing the allograft to the distal femur with a transverse osteotomy (technique AP1); and (f) the same construct as technique AP1, but with an additional plate cranially (technique AP2). A long‐stem endoprosthesis cemented into the contralateral intact femur served as the control. Techniques that involved a long‐stem endoprosthesis and cementing distally (AT, AS, and AI) were more resistant in torsion than the plated replacement techniques (AP1 and AP2). The segmental replacement construct (ES) was equal to or stronger than all other techniques under each testing condition. In torsion, the addition of a step‐cut (AS) significantly lowered angular displacement of the reconstruction when compared with the reconstruction with a transverse osteotomy (AT) (p ≤ 0.05). Bones with one‐plate fixation (AP1) were significantly weaker in torsional stiffness and maximum torque and in mediolateral bending (p ≤ 0.05) than all other techniques. The addition of a second plate (AP2) increased the mechanical properties of the construct so that it was greater than the one‐plate method and was equal to (bending and compression) or still weaker (torsion) than the other techniques. The results indicate that segmental replacement methods and allograft/endoprosthetic composites that involve long‐stem endoprostheses fixed with cement are mechanically superior to methods that involve short‐stem endoprostheses with single or double plating at the osteotomy sites.
Distribution of integrins and their matrix ligands in osteogenic sarcomas
Authors: Kawaguchi Satoshi , Uede Toshimitsu
Published: February 2005

We studies the expression of the members of the β1 integrin family and extracellular matrix ligands in osteosarcoma tissues. Immunostaining of primary osteosarcomas with use of specific antibodies for α1‐α6 integrin subunits, fibronectin, type‐I collagen, and laminin gave characteristic patterns: despite the diffuse expression of type‐I collagen in all 16 osteosarcomas, collagen receptors were detected in only one. Laminin and laminin receptors were expressed poorly. In contrast, the α4 and α5 fibronectin receptors were found in 100 and 75%, respectively, which correlates very well with the strong expression of fibronectin in the stroma. The other ligand for α4, vascular cell adhesion molecule‐1, was not expressed in the seven specimens tested. Therefore, primary osteosarcomas closely interact with fibronectin through α4 and possibly α5 subunits of the β1 integrin. We also examined the expression the expression was detected in all six specimens, however, the change varied. In contrast, osteosarcoma cells obtained from invasive portions of tumors exhibited new and augmented expression of certain integrins in two of the three cases in which their ligands were also expressed.
Adrenergic control mechanisms of blood flow in a vascularized canine tibial allograft
Authors: Moran Christopher G. , McGrory Brian J. , Roorda Jan , Wood Michael B.
Published: February 2005

A vascularized canine tibial allograft was used to study the alpha‐adrenoreceptor subtypes of the microcirculation of bone. Bone transplantation was performed on six dogs, and the bone blood flow was estimated with the use of serial injections of radiolabeled 15 μm microspheres. After microvascular anastomosis, the mean cortical blood flow in the allografted tibia was 3.6 ± 2.1 ml/100 g/min. Alpha1‐adrenoreceptor blockade, with prazosin, caused an increase in normalized blood flow in five allografts and a slight decrease in one allograft. The mean increase was 32 ± 48%, but this was not statistically significant (p ≤ 0.2). The addition of an alpha2‐adrenoreceptor blockade, with rauwolszin, resulted in a significant increase (132 ± 88%) in normalized blood flow in all allografts (p ≤ 0.02). This ex vivo experiment confirms that both alpha1 and alpha2 adrenergic mechanisms play a role in controlling bone blood flow in centrally denervated allografts.
Comparison of demineralized allogeneic bone matrix grafting (the Urist procedure) and the Ilizarov procedure in large diaphyseal defects in sheep
Authors: Ehrnberg Anders , De Pablos Julio , Martinez‐Lotti Gabriel , Kreicbergs Andris , Nilsson Olle
Published: February 2005

The bone inductive capability of the Urist and Ilizarov procedures was compared in the repair of large diaphyseal defects in sheep. In 30 animals, a 4 cm segmental defect was created in the middle portion of the right femur and was stabilized with an external fixator. The sheep were divided into four groups according to the type of reconstruction of the defect. In group 1, a demineralized allogeneic bone matrix (DABM) cylinder was used; in group 2, DABM chips; and in group 3, gradual transport of a piece of bone detached from the proximal femoral fragment was used to fill the defect. Group 4 served as a control (the defect was left empty). New bone formation was assessed by serial radiographs until the time of death at 2 or 4 months. Postmortem specimens were analyzed with respect to bone mineral content, uptake of isotopes (45Ca and 3H‐proline), and histology. The first signs of new bone formation were radiographically evident at 4 weeks. In the two groups in which reconstruction involved DABM (Urist procedures), new bone failed to form in eight of the 13 animals. Full bridging of the defect was observed at 8 weeks in one animal with a DABM cylinder and two with DABM chips. No decisive difference in bone yield could be demonstrated between the two Urist procedures. In the group treated with the Ilizarov procedure, new bone formation consistently occurred at a high rate; full bridging of the defect was observed in seven of the eight animals. Bone mineral scanning and histologic analysis essentially confirmed the radiographic results. Uptake of isotopes was selectively analyzed in two sheep from each experimental group in which new bone formation was exhibited in the defect; new bone formation was increased compared with that in the contralateral femur but was equal among the three experimental groups. Our study shows that gradual transport of a detached piece of autogeneic bone (Ilizarov procedure) is more effective than implantation of DABM (Urist procedure) in eliciting new bone formation in large diaphyseal defects in sheep. The variable bone induction by DABM may be explained by differences in host immune responses to the implants.
A mechanical comparison of gluteus medius attachment methods in a canine model
Authors: Markel Mark D. , Rock Michael G. , Bergenthal D. Stephanie , Young David R. , Vanderby Ray , Chao Edmund Y. S.
Published: February 2005

Seven techniques of gluteus medius attachment were compared in vitro in a canine model. Four methods were used for tendon to tendon attachment: (a) two modified Bunnell‐Mayer stutures, (b) two Kessler locking loop sutures, (c) two horizontal mattress sutures, and (d) two sutures with a looped suture technique. The two methods of tendon to bone attachment were repair with a 1 cm spiked staple and repair with a spiked washer and screw, and the method of bone to bone attachment involved two figure‐eight cerclage wires. The colitralateral limb served as a control. Compared with the bone to bone attachment, the four tendon to tendon attachments and the two tendon to bone attachments had significantly less strength (31 and 30% of the ultimate load for bone to bone repair, respectively) and tensile stiffness (24 and 39% of the tensile stiffness for bone to bone attachment, respectively) (p ≤ 0.0001). The control specimens were significantly stronger and stiffer than all specimens (p ≤ 0.05) except those that had bone to bone fixation. There were no significant differences among the four tendon to tendon suture repairs with regard to either strength or stiffness; the values ranged from 28–45% of those of the controls. Among the tendon to bone repairs, fixation with a spiked washer and screw was significantly stronger than that with a spiked staple (p = 0.032), but there was no difference between these two techniques with regard to stiffness.
Pleiotrophin is an abundant protein in dissociative extracts of bovine fetal epiphyseal cartilage and nasal cartilage from newborns
Authors: Neame Peter J. , Young Carmen N. , Brock Charles W. , Treep James T. , Ganey Timothy M. , Sasse Joachim , Rosenberg Lawrence C.
Published: February 2005

An abundant protein that is identical to the growth‐associated protein pleiotrophin (PTN) has been isolated from dissociative extracts of bovine nasal and fetal epiphyseal cartilage. The yield from these tissues was at least 15 μg/g wet weight of cartilage. PTN was absent or was present only in trace amounts in mature articular cartilage. An analysis of tryptic fragments of PTN, held together with disulfide bonds, did not indicate any set pattern of cystine cross‐links, which suggests a propensity for rapid refolding of the protein. PTN could not be isolated from thin (10 μm) slices of nasal cartilage in physiological extraction buffers, which indicates that it was tightly associated with the cell surface, was tightly associated with nonextractable matrix, or was an intracellular protein. Its appearance in various extraction media parallels that of histone H2b, a nucleosomal protein; this suggests a possible intracellular location for the protein. Immunohistochemical analysis of its distribution in fetal epiphysis indicated that it is associated with chondrocytes.
In vivo quantification of proteoglycan synthesis in articular cartilage of different topographical areas in the murine knee joint
Authors: van Osch G. J. V. M. , van der Kraan P. M. , van den Berg W. B.
Published: February 2005

We developed a method of quantitative measurement of the synthesis of proteoglycans in different areas of the patella and the tibial plateau of the mouse. After incorporation of radioactive sulfate in vivo, the patella was divided with a punch into a central and a peripheral part. A central medial and a central lateral part were taken from the tibial plateau to measure the synthesis of proteoglycans. The synthesis was determined in normal joints and at different intervals after intra‐articular injection of sodium iodoacetate and was compared with autoradiographs of whole joint sections. Although considerable variation in sulfate incorporation was found within a group on particular days after induction of osteoarthritis, the variation among experiments was low. Comparison with autoradiographs showed that this new method makes it possible to quantify proteoglycan synthesis by incorporation of radioactive sulfate in different topographical areas of the murine knee joint.
Changes in bone in a model of spinal cord injury
Authors: Hill Esther L. , Martin R. Bruce , Gunther Elizabeth , Morey‐Holton Emily , Holets Vicky R.
Published: February 2005

Bone calcium, histomorphometry, and mechanical strength were evaluated in a model of spinal cord injury. Cortical bone area and rates of formation and apposition at the tibiofibular junction (TFJ) and midshaft of the humerus were measured at 35–42, 42–77, and 77–94 days after transection of the spinal cord. All comparisons were between the animals with a spinal lesion and control animals. A 0.34% difference in the length of the tibia of the two groups of animals was observed, the dry weight of the tibia was 28.4% less in rats with a lesion, and there was no significant difference in the amount of calcium per milligram of bone. At 35 days after surgery, the cortical area in the midshaft of the humerus was slightly less (11%) in rats with a lesion, but by 94 days there was no difference in cortical or medullary area. The final (day 94) cortical area at the TFJ in rats with a lesion was less than that in the controls. Bone formation at the TFJ was similar in both groups in the period of 35–42 days and was similar at 77–94 days in the animals with a lesion, and rates of formation and apposition were greater in the humerus of rats with a lesion; the rates did not differ significantly between groups at either site. At 94 days, trabecular bone area in the tibial metaphysis was 41% less in rats with a lesion. Mechanical parameters were significantly less in the femora, but not the humeri, of rats with a lesion.
Effect of controlled local release of sodium fluoride on bone formation: Filling a defect in the proximal femoral cortex
Authors: McCormack A. P. , Anderson P. A. , Tencer A. F.
Published: February 2005

To assess the effect of sodium fluoride (NaF) in the healing of a defect in cortical bone, an experimental model was created by the drilling of 5.0 mm holes in the proximal ends of both femora of 12 adult male New Zealand White rabbits. An interlocking intramedullary implant constructed of poly(d,l‐lactic acid) containing NaF was placed in the right femur and an identical implant without NaF (sham), in the left. The implant in the right femur was designed to release NaF in a controlled manner over the duration of the experiment. Ten weeks after implantation, the specimens were removed and were tested in torsion. The mechanical properties were not significantly different between the groups. The femora exposed to NaF had an 18.6% increase in intact cortex near the defect (p = 0.023), however, the deposition of mineralized bone within the defect was not significantly greater. In fact, healing appeared to be impaired by the presence of NaF. There was complete closure of the defect in all but one of the femora with a sham implant, but the tissue had not yet calcified. In contrast, only one femoral defect exposed to NaF had closed. Examination of the material filling the defects of the femora exposed to NaF showed that it was predominantly uncalcified osteogenic mesenchymal tissue.
In vitro pharmacokinetics of antibiotic release from locally implantable materials
Authors: Miclau Theodore , Dahners Laurence E. , Lindsey Ronald W.
Published: February 2005

Local deposition of antibiotics has became increasingly popular in the management of open fractures or osteomyelitis, and several substances have been employed as the vehicle for delivery. Although the elution characteristics of some substances have been documented, a comparative study of the characteristics of the commonly used substances could establish the clinical indications for particular vehicles. Cylindrical pellets of uniform size (6 × 4 mm) were prepared from bone graft (BG), demineralized bone matrix (DBM), plaster of Paris (POP), or polymethylmethacrylate (PMMA), with 25 mg of tobramycin/g of substance in each pellet. The pellets were suspended in phosphate buffered saline, and the antibiotic concentration in the buffer was determined at various time intervals by an enzyme immunoassay. BG and DBM eluted 70 and 45% of their antibiotic load by 24 h, and negligible amounts were detected at 1 week; POP released 17% of its load by 24 h, with trace amounts detected at 3 weeks; and PMMA eluted 7% at 24 h, with trace amounts detected for as long as 14 days. These findings suggest that the optimal vehicle for local deposition of antibiotic depends on the clinical setting. BG and DBM may be best employed when brief antibiotic coverage is required (as for acute contaminated open fractures), whereas POP and PMMA may be better suited for long‐term coverage (such as for established osteomyelitis).
Effects of ascorbic acid, calcitriol, and retinoic acid on the differentiation of preosteoblasts
Authors: Choong Peter F. M. , Martin T. John , Ng Kong Wah
Published: February 2005

The responses of the immortalized rat preosteoblast UMR‐201‐10B to ascorbic acid (AA), 1,25(OH)2D3 (calcitriol), and retinoic acid (RA) were examined. UMR‐201‐10B cells have an undetectable basal alkaline phosphatase (ALP) activity that is induced after 24 h of treatment with 10−6 M RA (4.64 ± 0.06 μmol/h/mg of protein). The addition of 10−8 M calcitriol resulted in a slight induction of ALP activity after 72 h (0.43 ± 0.07 μmol/h/mg of protein). When calcitriol was added to RA, however, over the same period ALP activity was enhanced significantly compared with treatment with RA alone (RA and calcitriol, 12.29 ± 0.86 μmol/h/mg of protein). Treatment with AA (50 μg/ml) alone had no effect on ALP activity but increased RA‐induced ALP activity to 6.78 ± 0.28 μmol/h/mg of protein at 24 h. In contrast, AA inhibited calcitriol‐induced ALP activity after 7 days of combined treatment with calcitriol (calcitriol, 7.73 ± 0.16 μmol/h/mg of protein; AA and calcitriol, 1.44 ± 0.06 μmol/h/mg of protein). Individually, RA and calcitriol induced mRNA expression for ALP, matrix‐gla protein (MGP), and osteopontin (OP). The steady state level of pro‐α1(I) collagen mRNA also was increased significantly by treatment with RA and AA individually. The combination of RA and calcitriol had a synergistic effect on ALP, OP, and especially MGP mRNA expression but significantly reduced the expression of pro‐α1(I) collagen mRNA. AA enhanced the effect of RA on the expression of pro‐α1(I) collagen, MGP, and ALP mRNAs as well as the effect of calcitriol on OP and MGP. The addition of AA to RA resulted in a decrease in the steady state level of OP, whereas its cotreatment with calcitriol caused a decrease in pro‐α1(I) collagen and ALP mRNA. In conclusion, these studies identify RA, calcitriol, and AA as regulators of differentiated osteoblast function.
Associations and dissociations between serum bone gla protein and alkaline phosphatase in skeletal metabolism
Authors: Parthemore J. G. , Burton D. W. , Deftos L. J.
Published: February 2005

Serum bone Gla protein (BGP) and alkaline phosphatase (AP) activity were compared for the assessment of skeletal status in 11 normal pregnant women, 12 normal women on days 3 and 13 of the menstrual cycle, five postmenopasual women before and after 1 month of treatment with ethinyl estradiol (20 μg/day), five patients with cancer and hypercalcemia during treatment with calcitonin, and one patient with Paget disease during treatment with Plicamycin. BGP and AP correlated with each other only in the pregnant women. In all other circumstances, there was no correlation between these two serum osteoblast products. Furthermore, there were condisitions in which the two measurements became discordant. These studies demonstrate that BGP and AP commonly are dissociated when used as measurements of skeletal status. Although both are osteoblast products, BGP and AP probably reflect different aspects of osteoblast differentiation and function.
Effect of compressive loading and unloading on the synthesis of total protein, proteoglycan, and fibronectin by canine cartilage explants
Authors: Burton‐Wurster Nancy , Vernier‐Singer Margaret , Farquhar Tony , Lust George
Published: February 2005

Full‐thickness canine articular cartilage explants were subjected to compressive loads equivalent to a uniaxial stress of 0.025–1.2 MPa. A single cycle (18 h) of unconfined compression resulted in inhibition of total protein, proteoglycan, and fibronectin synthesis. The inhibition of fibronectin synthesis followed that of total protein synthesis. The magnitude of inhibition increased nonlinearly with increasing load levels. The signal that depressed synthesis remained effective for several hours after removal of load, but by 24 h proteoglycan synthesis had partially recovered and fibronectin and protein synthesis had fully recovered and sometimes exceeded the rate of synthesis in free‐swelling controls. Forty‐eight hours after five cycles of intermittent unconfined compression with similar loads, proteoglycan content and synthesis did not differ in loaded disks and in disks that were never loaded in vitro. Interestingly, the percentage of water in disks that had never been loaded in vitro increased significantly after 10 days in culture, relative to the percentage of water in free‐swelling disks on the day of harvest. Intermittent compressive loading in the range of 0.5–1.2 MPa partially prevented this increase. Our results confirmed the previously reported inhibition of biosynthesis with static loading but also suggested that exposure to intermittent compressive loading may help to maintain the normal ratio of dry to wet weight in the explant.
Preservation of bone graft vascularity with the University of Wisconsin cold storage solution
Authors: Moran Christopher G. , Adams Mary L. , Wood Michael B.
Published: February 2005

The preservation of the microcirculation of bone has been evaluated with use of an in vitro canine tibia perfusion model. The production of relaxing factors by the osseous vascular endothelium was used as a metabolic marker for viability. This endothelial eccrine function was preserved for 5 days (120 h) by cold storage without continuous perfusion after a washout with the University of Wisconsin (UW) solution. This synthetic perfusate was superior to Krebs Ringer solution (p < 0.05), but storage without perfusion failed to prevent a significant rise in vascular resistance. Two techniques were effective for the preservation of bone vascularity for 24 h: washout with UW solution followed by nonperfusion cold (4°C) storage, and vascular washout with mannitol solution followed by continuous hypothermic (5°C) microperfusion (0.03 ml/min) with UW solution. The most consistent, and lowest, vascular resistance was produced by the microperfusion technique. However, UW solution does not consistently prevent an increase in vascular resistance with hypothermic ischemia. This technique may prove useful for the preservation of vascularized bone grafts, but it needs to be evaluated in a transplantation model.
Localized hyperthermic treatment of experimental bone tumors with ferromagnetic ceramics
Authors: Ikenaga Minoru , Ohura Kouichiro , Yamamuro Takao , Kotoura Yoshihiko , Oka Masanori , Kokubo Tadashi
Published: February 2005

Localized hyperthermic treatment was carried out with use of a metastatic bone tumor model in rabbits. The experimental bone tumor was created by transplantation of pieces of tumor line VX2 into the medullary canal of rabbit tibiae. Two weeks after the transplantation, a ferromagnetic ceramic pin was inserted in the medullary canal. Then, hyperthermia (HT) of the tumor was accomplished with use of an alternating magnetic field for 50 min. All the rabbits were killed 5 weeks after tumor transplantation, and the therapeutic effect was evaluated histologically and roentgenographically. Almost all the tumor cells within the bone marrow were killed by the procedure. The area of the tumor necrosis in the HT group was significnatly larger than in the control group. The pathological fracture rate and displacement rate were reduced significantly by this treatment (38.5 and 0%) compared with the controls (92.3 and 92.3%). Therefore, HT with the use of ferromagnetic ceramics was effective for local control of malignant bone tumors and seems to be a promising new method of treatment.
Low intensity ultrasound treatment increases strength in a rat femoral fracture model
Authors: Wang Shyu‐Jye , Lewallen David G. , Bolander Mark E. , Chao Edmund Y. S. , Ilstrup Duane M. , Greenleaf James F.
Published: February 2005

Bilateral closed femoral shaft fractures were made in 22 male Long‐Evans rats. In 16 animals, ultrasound was applied to one limb for 15 minutes daily 10 times within the first 14 postoperative days. The treated limbs received a 200 μsec burst of 1.5 or 0.5 MHz sine waves repeated at 1.0 KHz at a spatial average and temporal average intensity of 30 mW/cm2. The contralateral limb of each animal served as a nontreated control. Six remaining animals with fractures and six additional animals without fractures received sham ultrasound treatment to control for the effects of anesthesia and handling. Fracture repair was evaluated on postoperative day 21 by radiography, mechanical testing in torsion, and histology. Five of 16 ultrasound‐treated fractures showed obliteration of the fracture gap on radiographs, whereas none of the 28 controls did. The average maximum torque of fractures treated with either signal was 22% greater than that of the contralateral controls (p < 0.05). The stiffness of treated fractures was greater than that of control fractures, but the difference was significant only in animals treated with the 1.5 MHz signal (p < 0.02). Sham treatment did not affect repair in the control group. These results indicate that low‐intensity pulsed ultrasound at either 0.5 or 1.5 MHz can accelerate fracture repair at 21 days in this highly controlled model.
Decreased microvascular perfusion in the rabbit ear after six hours of ischemia
Authors: Pollock F. Edward , Smith Thomas L. , Andrew Koman L. , Holden Martha B. , Smith Beth P.
Published: February 2005

The cellular injury produced by reperfusion of ischemic tissue with oxygen‐rich blood has been studied in numerous tissues but has not been investigated extensively in thermoregulatory tissue. This study was designed (a) to compare 4 and 6 hours of ischemia to document the evidence of impaired capillary perfusion after resumption of blood flow (reperfusion injury) in a thermoregulatory end organ (the rabbit ear), and (b) to examine, with use of vital capillaroscopy (VC) and laser Doppler flowmetry (LDF), the altered microvascular blood flow in the rabbit ear after ischemia and reperfusion. One ear from each of five rabbits underwent warm ischemia for 4 hours. VC showed no deficits of capillary perfusion in these ears after reperfusion; LDF measurements in both ears also demonstrated no significant difference between control and reperfusion blood flow. One ear from each of eight additional rabbits underwent 6 hours of warm ischemia. LDF values were significantly reduced in the ischemic ear after reperfusion as compared with baseline measurements for that ear and as compared with the control ear. VC showed arrested perfusion and static plasma gaps within three to five capillaries per high‐power field (an area of 300 × 500 μm) in the ischemic ear and good perfusion of all vessels in the contralateral control ear. This evidence of reperfusion injury in a thermoregulatory end organ may help to explain the poor functional result that often occurs after replantation of an amputated digit.
Collagens in the injured porcine intervertebral disc
Authors: Kääpä E. , Holm S. , Han X. , Takala T. , Kovanen V. , Vanharanta H.
Published: February 2005

Spinal pain often is thought to be due to degeneration and mechanical failure of the intervertebral disc. Since the mechanical strength of the tissue depends on collagen fibers, the present study was designed to investigate the reactions in collagen metabolism after an experimentally induced disc injury. Five domestic pigs underwent an incision in the anterior part of the annulus fibrosus of disc L4‐L5 through a retroperitoneal approach. The animals were killed 3 months postoperatively, and the injured discs and intact discs (controls) from different animals were removed for chemical analysis. Slices were cut from seven different parts across the disc. The concentration of total collagen (hydroxyproline [Hyp]), the activities of the two key enzymes in collagen biosynthesis (prolyl 4‐hydroxylase [PH] and galactosylhydroxylysyl glucosyltransferase [GGT]), and the concentration of mature collagen crosslinks (hydroxypyridinium [HP]) were determined. In all experimental discs, the morphology had changed considerably: the nucleus pulposus was small, fibrous, and yellowish. The annular lamellar structure was partially destroyed and had been replaced by granulation tissue in the region of the injury. Large osteophytes had formed at the ventral edges of the vertebral bodies. In the nucleus pulposus, the Hyp concentration and the activities of PH and GGT were significantly increased, whereas the water content had decreased. The concentration of HP crosslinks was decreased in the anterior annulus fibrosus.
Mechanical evaluation of a canine intervertebral disc spacer: In situ and In vivo studies
Authors: Vuono‐Hawkins M. , Zimmerman M. C. , Lee C. K. , Carter F. M. , Parsons J. R. , Langrana N. A.
Published: February 2005

An elastomeric intervertebral disc spacer with hydroxyapatite ingrowth surfaces was implanted in a canine model. We studied (a) the mechanical behavior of motion segments at time 0 and at 3, 6, and 12 months and (b) the effect of the interface between the spacer and vertebral bone on implant stability and bone ingrowth. A polymeric spacer was designed with compressive and torsional properties similar to those of the isolated canine lumbar disc. Implantation of the spacer in canine cadaver motion segments permitted in situ biomechanical evaluation at time 0. An in vivo study permitted continuous neurological monitoring of animals, with evaluation of mechanical behavior, stability, and ingrowth at 3, 6, and 12 months. Mechanical testing of cadaver motion segments with the spacer in situ resulted in decreased compressive and torsional stiffnesses, averaging 25 and 42%, respectively. This decrease was due to a combination of the surgical insult to the annulus and decortication of adjacent vertebral endplates. In the in vivo study, all 12 animals tolerated the surgery well and none had permanent neurological impairment. The measured parameters indicated that behavior of the spacer‐motion segment composite appeared to return to normal within 3‐6 months. However, despite use of a porous hydroxyapatite on the implant surface, there was no significant bone ingrowth. Instead, a layer of dense fibrous connective tissue was formed at the spacer‐vertebral bone interface. Early migration of five of the 12 spacers resulted in eccentric loading patterns with consistent reactive osteophyte formation.
Intraosseous incorporation of composite collagen prostheses designed for ligament reconstruction
Authors: Dunn Michael G. , Maxian Suzanne H. , Zawadsky Joseph P.
Published: February 2005

Composite collagen prostheses are potentially useful for reconstruction of the anterior cruciate ligament (ACL). We evaluated the intraosseous response to composite collagen prostheses to determine if “biological fixation” could be used to secure the prostheses within surgical bone tunnels. The rate of degradation of the prosthesis and the response of the tissue were evaluated, as a function of collagen crosslinking agent and time, in nonloaded bone tunnels in rabbits. Prostheses were fabricated by the alignment of 200 reconstituted type‐I collagen fibers (60 μm in diameter) and the embedding of the fibers within a collagen matrix. The prostheses degraded rapidly within the bone tunnels in comparison with soft‐tissue implantation sites. Dehydrothermal‐cyanamide crosslinked collagen fibers were completely degraded by 8 weeks. Only 10% of glutaraldehyde crosslinked collagen fibers remained intact at 12 weeks. Fibrous tissue and inflammatory cells rapidly infiltrated the prostheses, and new bone surrounded the circumference of the prostheses, advancing toward the center at longer times. At the lateral cortex, where fibrous tissue emerged, the bone/soft‐tissue interface was delineated by a tidemark, similar to that observed in a normal ligament insertion site. Preliminary pull‐out testing of the soft tissue; this suggests rapid incorporation of the prostheses within the bone tunnels. Composite collagen prostheses designed for ACL reconstruction degrade rapidly in bone and induce rapid ingrowth of fibrous tissue and bone. These results suggest that tissue ingrowth in the bone tunnels might provide biological fixation for collagen prostheses used for ACL reconstruction.
Structural differences between two populations of articular cartilage proteoglycan aggregates
Authors: Buckwalter Joseph A. , Pita Julio C. , Muller Francisco J. , Nessler Julie
Published: February 2005

To determine if articular cartilage contains structurally distinct populations of proteoglycan aggregates, we extracted and purified proteoglycans from canine knee cartilage under associative conditions. Equilibrium density gradient centrifugation separated three proteoglycan populations, on the basis of differences in sedimentation velocity, into groups of 21, 106, and 270 S. Electron microscopic examination showed that the 21 S samples contained free aggrecan molecules and clusters of aggrecan molecules, with a mean of five aggrecan molecules per cluster. The 106 and 270 S samples contained proteoglycan aggregates consisting of central hyaluronan filaments with multiple attached aggrecan molecules. The two populations of aggregates did not differ in mean aggrecan length or in the spacing of aggrecan molecules along the hyaluronan filaments, but the slower sedimenting aggregates (106 S) had significantly shorter hyaluronan filaments as measured by electron microscopy (mean hyaluronan length, 400 compared with 1,162 nm) and one‐third as many aggrecan molecules per aggregate (mean number of aggrecan molecules per aggregate, 15 compared with 44). This study shows that articular cartilage contains aggrecan clusters and two structurally distinct populations of proteoglycan aggregates. The differences between the two types of aggregate, in particular the number of aggrecan molecules per aggregate, may reflect differences in their assembly, stability, or turnover and give them different mechanical and biological properties.
Serial kinematic analysis of the unstable knee after transection of the anterior cruciate ligament: Temporal and angular changes in a canine model of osteoarthritis
Authors: Vilensky Joel A. , O'Connor Brian L. , Brandt Kenneth D. , Dunn Elizabeth A. , Rogers Pamela I. , Delong Cynthia A.
Published: February 2005

Transection of the anterior cruciate ligament in the dog leads to osteoarthritis. This study defines the kinematic changes in the unstable knee after transection of the cruciate ligament (six dogs) and after a sham operation (four dogs). In the dogs that were anterior cruciate ligament‐deficient (ACL‐D), the duration of stance 1 week postoperatively decreased 38% from the preoperative value, but only a 4% decrease was seen at 6 weeks. The duration of double hindlimb support increased from 6 to 19% of the entire cycle 1 week after surgery but returned to the baseline value by 18 weeks. As the unstable limb contacted the treadmill belt, the initial flexion (yield) and subsequent extension (propulsive) phases were not evident or were markedly attenuated in every ACL‐D dog throughout the 26‐week period of observation. The angular velocity patterns were characterized by a slight extension velocity at touchdown (compared with a zero value preoperatively) and a decrease in the peak velocities (both flexion and extension) during the remainder of the stance phase. None of these changes was observed in the animals that had a sham operation. These data indicate that, in the dog, the nervous system compensates for instability of the knee by altering angular, but not temporal, parameters. The extension velocity at touchdown and the reduction in peak flexion velocity during the yield component of the stance phase may reduce the ability of the limb to absorb impact forces and lead to the development of osteoarthritis of the knee. Alternatively, the reductions in flexion and extension of the knee during the stance phase and in the values for peak velocity presumably reflect protective muscular reflexes that may slow the rate of progression of joint breakdown.
Fibronectin in the tendon‐synovial complex: Quantitation In vivo and In vitro by elisa and relative mRNA levels by polymerase chain reaction and northern blot
Authors: Brigman Brian E. , Hu Peiqui , Yin Hongliang , Tsuzaki Mari , Thomas Lawrence W. , Banes Albert J.
Published: February 2005

An enzyme‐linked immunosorbent assay was used to quantitate fibronectin (Fn) levels in the outer synovia (epitenon) and internal fibrous portion (endotenon) of chicken flexor tendon and sheath. Primary cell cultures from these tissues and their secretions also were assayed for Fn levels. The polymerase chain reaction (PCR) was used to determine relative steady‐state levels of Fn mRNA in primary cultures of synovial and internal fibroblasts from chicken tendon, and Northern blot analysis was performed to verify relative levels of the Fn message. The epitenon contained 3.8‐fold more Fn than did the endotenon, and the sheath synovium contained 21‐fold more Fn than did the internal fibrous portion of sheath. Cells cultured from the epitenon produced 9.3 and 13‐fold more cell‐associated and secreted Fn, respectively, than did cultured endotenon fibroblasts. Sheath synovial cells produced 17 and 3.2‐fold more cell‐associated and secreted Fn, respectively, than did sheath internal fibroblasts. Levels of Fn mRNA, as measured by PCR and Northern blot, were 1.6 and 1.8‐fold greater, respectively, in tendon synovial cells compared with tendon internal fibroblasts. The biologic reason for increased Fn in tendon synovium is not known. We theorize that Fn may stabilize tendon synovium to shear stress and may play a role in the modulation of synovial rheology in the normal tendon. In the injured tendon, Fn may be involved in the organization of collagen deposition or may act through association with growth factors to aid healing.
Effect of capacitively coupled electric fields on an experimental model of delayed union of fracture
Authors: Rijal Kiran Prasad , Kashimoto Osamu , Sakurai Minoru
Published: February 2005

To evaluate the effect of capacitively coupled electric fields (CCEF) on delayed union of fractures, an experimental model of delayed union was produced in the radius of rabbits, and the process of healing was investigated by radiography, bone mineral density (BMD) measured with dual energy x‐ray absorptiometry, and histological survey. It was confirmed radiographically and histologically that callus formation was enhanced in the group treated with CCEF. After stimulation, the average BMD increased more than 18% compared with the controls. Our experiment on a delayed union model suggests that CCEF is effective for the treatment of delayed union of fractures.
Bone response to hydroxyapatite‐coated and commercially pure titanium implants in the human arthritic knee
Authors: Carlsson L. , Regnér L. , Johansson C. , Gottlander M. , Herberts P.
Published: February 2005

Rough and smooth commercially pure (c.p.) titanium implants and hydroxy‐apatite‐coated (HA‐C) implants were inserted in arthritic human knees and left in situ in order to compare the response of bone to these three implants. Radiographic examination alone could not determine if bone apposition had occurred. After 3 and 6 months, histomorphometric analyses of undecalcified sections, 10 μm thick, revealed a statistical significance in the amount of bone apposition to rough‐surfaced and HA‐C implants as compared with smooth uncoated implants. Most of the rough‐surfaced c.p. titanium implants and the HA‐C implants had achieved bone apposition on the order of 50%. No statistically significant differences in apposition were seen between the rough‐surfaced and HA‐C implants. The smooth c.p. titanium implants were mostly encapsulated in fibrous tissue.
Particle‐induced synthesis of collagenase by synovial fibroblasts: An immunocytochemical study
Authors: Greis P. E. , Georgescu H. I. , Fu F. H. , Evans C. H.
Published: February 2005

The response of synoviocytes to wear particles has been implicated in several orthopaedic pathologies, including the synovitis associated with the failure of synthetic anterior cruciate ligament (ACL) replacements. To study the interactions of particles with synovial fibroblasts at the level of the individual cell, we employed immunocytochemistry, with use of antiserum, to lapine interstitial collagenase. Cultures of the HIG‐82 lapine synovial cell line showed only weak immunofluorescence under resting conditions. Incubation with phorbol myristate acetate or autocrine factors known as cell‐activating factors (CAFs) induced marked changes in morphology and intense immunofluorescence. This technique then was used to study the effects of standard particles of latex and of particles generated from two prosthetic ACL materials, Dacron and carbon. Internalized particles of latex, Dacron, and carbon all induced collagenase. Particles of latex that were too large for endocytosis failed to induce collagenase, whereas particles of carbon and, in particular, Dacron that remained extracellular, still provoked considerable synthesis of collagenase. Thus, both the size and the physical properties of these materials influence their ability to activate synoviocytes. Certain cells that appeared by visual inspection to contain no particles nevertheless produced collagenase when in co‐culture with cells that did contain particles. This is consistent with earlier biochemical data showing that phagocytosis, in addition to inducing collagenase, also provokes the release of CAFs, which then activate additional cells in the culture. More rarely, cells were identified which, although containing particles, did not stain positively for collagenase. Since carbon and Dacron are the major components of certain prosthetic ligament replacements, the cellular responses to their wear particles and to debris generated from other prosthetic materials merit further close attention.
Mathematical model for the mineralization of bone
Authors: Martin Bruce
Published: February 2005

A mathematical model is presented for the transport and precipitation of mineral in refilling osteons. One goal of this model was to explain calcification “halos,” in which the bone near the haversian canal is more highly mineralized than the more peripheral lamellae, which have been mineralizing longer. It was assumed that the precipitation rate of mineral is proportional to the difference between the local concentration of calcium ions and an equilibrium concentration and that the transport of ions is by either diffusion or some other concentration gradient‐dependent process. Transport of ions was assumed to be slowed by the accumulation of mineral in the matrix along the transport path. The model also mimics bone apposition, slowing of apposition during refilling, and mineralization lag time. It was found that simple diffusion cannot account for the transport of calcium ions into mineralizing bone, because the diffusion coefficient is two orders of magnitude too low. If a more rapid concentration gradient‐driven means of transport exists, the model demonstrates that osteonal geometry and variable rate of refilling work together to produce calcification halos, as well as the primary and secondary calcification effect reported in the literature.
Restoration of tissue components after insertion of absorbable fracture fixation devices of polyglycolide through the articular surface: An experimental study in the distal rabbit femur
Authors: Böstman Ole , Päivärinta Unto
Published: February 2005

Absorbable implants for fracture fixation do not require a secondary removal procedure, a fact that could make them particularly suitable for intra‐articular fixation, provided the degree of regeneration of the articular surface is acceptable. To determine the restoration pattern in distal rabbit femurs after the intra‐articular insertion of absorbable fixation devices, polyglycolide pins and screws were implanted through the articular surface of the intercondylar portion of the bone in adult animals. The polymer was known to have a degradation time of approximately 20 weeks. At follow‐up times of 3–48 weeks, the restoration of the tissue components was examined histomorphometrically and microradiographically. The intact contralateral femur served as an internal control. The first signs of degradation of the implants were seen at 6 weeks. The mean fractional osteoid formation surface of the bone trabeculae within the sample fields showed significantly increased values until 6 weeks but thereafter approached the level of the control femur. In the 36‐week and 48‐week specimens, the polyglycolide had been absorbed and the intra‐articular entrance of the implant channel had become filled either with firm whitish tissue resembling mature articular cartilage or with soft undifferentiated mesenchymal tissue only. Good restoration of the trabecular bone archtecture corresponding to the original subchondral bone was a prerequisite for the regeneration of the articular cartilage. The causes of the dichotomous pattern of restoration could not be identified, but possibly it represented a normal biologic variation. Since instability associated with fracture fixation, not an issue of this study, could affect the quality of tissue restoration, the present findings call for caution if large‐diameter absorbable devices are to be inserted through articular surfaces in clinical practice.
Role of fibronectin in staphylococcal adhesion to metallic surfaces used as models of orthopaedic devices
Authors: Delmi M. , Vaudaux P. , Lew D. P. , Vasey H.
Published: February 2005

Staphylococcal infection of various prosthetic and internal fixation devices is a major complication associated with orthopaedic surgery. This study investigated the role of the host protein fibronectin in promoting adhesion of Staphylococcus aureus and Staphylococcus epidermidis to metallic surfaces representing materials used for orthopaedic devices. Pure human fibronectin was adsorbed in vitro onto coverslips (0.8 × 0.8 cm) of stainless steel, pure titanium, or titanium‐aluminum‐niobium alloy. In vitro bacterial adhesion was promoted more strongly by the metallic surfaces coated with fibronectin than by albumin‐coated controls for two strains of S. aureus and one strain of S. epidermidis. Furthermore, with the fibronectin‐coated coverslips, bacterial adhesion to titanium alloy was significantly greater than adhesion to stainless steel. Adhesion of the three staphylococcal strains was promoted more strongly by coverslips explanted from the subcutaneous space of guinea pigs and tested under similar conditions than by albumin‐coated controls. Incubation of either in vitro fibronectin‐coated or explanted metallic coverslips with anti‐fibronectin antibodies produced a significant decrease in staphylococcal adhesion. These results suggest that the presence of fibronectin on the surface of implanted metallic devices is an important determinant of colonization of orthopaedic biomaterials by staphylococi.
Histomorphometric analysis of the repair of a segmental diaphyseal defect with ceramic and titanium fibermetal implants: Effects of bone marrow
Authors: Wolff David , Goldberg Victor M. , Stevenson Sharon
Published: February 2005

We used a rat femoral diaphyseal defect/implant model to quantify the ingrowth of bone, cartilage, and fibrous connective tissue in a comparative study of woven sintered titanium fibermetal and porous hydroxyapatite/tricalcium phosphate ceramic implanted with and without the addition of syngeneic bone marrow cells. The patterns of tissue growth into the implants were analyzed with respect to time, type of implant, and the presence or absence of syngeneic marrow. Significantly more bone was found in ceramic implants than in fibermetal implants, with the addition of syngeneic marrow than without it, and at 4 months than at 2 months. Significantly more bone was found at both time periods in ceramic implants with bone marrow than in any other combination studied. We hypothesize that these findings resulted from interactions between the implanted material and its surroundings, specifically its ability to serve as a substratum for cell attachment, and cells in and around the defect, whether surgically implanted or arising from the soft‐tissue bed.