A porous metal coating applied to a solid substrate implant has been shown, in vivo, to offer advantages over current polymethylmethacrylate cement fixation in orthopedic devices. These advantages may be lost, however, in devices requiring a sintering heat treatment to apply the coating since these treatments may have a detrimental effect on the substrate material mechanical properties. In addition, more biocompatible interface coating materials have come of interest with recent literature reports of metal ion release. These coatings may be of particular use in porous-coated systems since the surface area of implant in contact with the surrounding tissues is greatly increased. This study investigated the effects that both a porous Ti- 6Al -4V alloy coating and a ULTI carbon coating have on the fatigue properties of a Ti- 6Al -4V alloy substrate system. The fatigue properties of uncoated as-received, uncoated sinter heat treated and notched Ti- 6Al -4V material were also investigated. The results of this study revealed endurance limits for Ti- 6Al -4V alloy tested with a rotating beam system of 617 MN/m2 (uncoated as-received), 624 MN/m2 ( ULTI carbon-coated), 377 MN/m2 ( sinter heat treated), 220 MN/m2 (notched) and 138 MN/m2 (porous-coated). No effects on fatigue properties were observed when testing the material in saline compared with air. The slight increase in fatigue strength for the carbon-coated material is thought to be due to the increase in surface hardness resulting from the formation of titanium carbides on the surface. The low-endurance limit of the porous-coated material is due to both the transition from the as-received equiaxed microstructure to a lamellar microstructure upon sintering and to the notch effect created by the porous coating.

Alloys↗

PubMedDate not supplied

A histologic and mechanical evaluation of carbon-coated polyester suture.

Ultra low temperature isotropic (ULTI) carbon-coated polyester suture material was evaluated histologically and mechanically in dogs. These results were compared to those obtained for uncoated polyester and polybutylate coated polyester. The suture materials were used in the repair of the surgically incised medial collateral ligament and subcutaneous tissues to evaluate the potential of the carbon-coated system for ligamentous repairs. Following surgery, the dogs were sacrificed at periods of 1-48 weeks postoperatively for evaluation of tissue biocompatibility and mechanical strength of the materials. The polybutylate-coated polyester suture broke at lower force levels than did comparable sizes of uncoated or carbon-coated polyester. All three types showed a high retention (greater than 98%) of mechanical strength at 48 weeks, often exhibiting an increase in tensile strength due to tissue ingrowth. The histologic response to carbon-coated polyester was equal to or better than the response to either the uncoated polyester or polybutylate-coated polyester. A greater degree of tissue growth into the carbon-coated material was evident at most time periods following an initial acute inflammatory response which was also present in the other materials.

Animals↗

PubMedDate not supplied

Functional performance of the knee after intraarticular anesthesia.

Ten healthy young volunteers underwent gait analysis and tests of knee joint position sense. Gait analysis included determination of stride characteristics (velocity, cadence, gait cycle, stride length, and single limb support time), force plate analysis, and motion analysis of the knee. The tests of joint position sense examined the ability of the subject to reproduce passive positioning of the knee and the ability to detect change in angle at the knee joint. In a double-blind manner, 10 cc of sterile fluid were injected into the left knee of each volunteer. Five received 2% lidocaine, the other five received sterile saline. All tests were then repeated. No statistically significant difference was observed in any measurement before and after injection in either test group. It is concluded that intraarticular anesthesia has no effect on gait pattern or joint proprioception as measured. Intraarticular local anesthesia is used in sports medicine to alleviate pain during arthroscopy of the knee under local anesthetic. The possibility of permitting damage in the early postoperative period due to loss of joint position sense is addressed in this paper. The results of this study suggest that injection of local anesthetic into a joint with an intact joint capsule does not compromise joint position sense as measured in this study. Furthermore, no change in gait parameters was observed in the functional task of ambulation. It must be noted that no conclusions regarding the loss of pain sensation can be made from the results of this study. Also, no conclusions regarding competitive activity can be drawn from this study.

Arthroscopy↗

PubMedDate not supplied

Conditions of the talus in the runner.

The anatomy and biomechanics of the talus in its relationship with ankle and subtalar joints expose it to increased stresses and forces in the runner. Many injuries to the talus, such as stress fractures, anterolateral compression syndromes, osteochondral Stage I and II lesions, and posterior compartment fractures can be treated with consecutive methods initially. Surgical treatment is indicated if these problems become chronic or in the conditions of osteochondral Stage III and IV lesions, anterior impingement syndrome, or symptomatic or trigonum fractures.

Athletic Injuries↗

PubMedDate not supplied

Biomechanical evaluation of superficial transfer of the biceps femoris tendon.

The biomechanics of the biceps femoris tendon transfer were determined from four fresh, frozen extremities. All transfers involved the proximal and anterior advancement of a selected portion of the tendon to a position superficial to the lateral collateral ligament. The rotational torque and flexion force were measured before and after the transfer with the knee positioned at 10 degrees, 20 degrees, 30 degrees, and 45 degrees of flexion, in neutral and 5 degrees internal rotation. Although more specimens need to be tested for statistical confirmation, the transfer of the superficial portion of the biceps tendon resulted in average decreases of 2% and 15% in the rotational and flexion capacity of the biceps, respectively. Biomechanically, the functional lever arm of the transferred tendon about the longitudinal (internal-external rotation) axis was essentially unchanged, while the functional lever arm about the sagittal (flexion-extension) axis was decreased slightly. The total transfer of the biceps tendon resulted in an increase of 28% in the rotational capacity, while the flexion capability was decreased an average of 75%. In addition, the total transfer resulted in the biceps becoming an extensor at 10 degrees and 20 degrees of flexion, which could actually worsen the instability. Thus, following the total transfer, the functional level arm about the sagittal axis was decreased, while the functional lever arm about the longitudinal axis was increased. In summary, neither the partial nor the total transfer of the biceps femoris tendon superficial and anterior to the fibular collateral ligament appeared to be a biomechanically effective ancillary for the treatment of anterolateral rotatory instability.

Biomechanical Phenomena↗

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Trabecular bone density and menstrual function in women runners.

Osteoporosis results in decreased bone mineral mass and reduced trabecular bone density. Although its etiology remains unknown, studies have revealed differential changes in the bone mineral densities of postmenopausal women, anorexic women, and amenorrheic female athletes. Correlations have also been made between estrogen deficiency and osteoporosis in both premenopausal and postmenopausal women. In order to examine the possibility of osteopenia, a group of 36 female runners between the ages of 15 and 44 years were evaluated for bone mineral density, menstrual function, and dietary habits. Serum calcium, phosphorus, and parathyroid hormone (PTH) levels were also determined for each participant, as were complete blood counts. Using dual photon absorptiometry, all participants underwent a 20 minute scan of the lumbar spine with specificity to the L1-14 vertebrae. The 36 subjects included 19 oligomenorrheic and 17 eumenorrheic women. Results of bone density analyses revealed that the oligomenorrheic runners had significantly lower calibrated bone mineral density (CBMD) than their eumenorrheic counterparts (P less than or equal to 0.01). Likewise, the PTH levels of the oligomenorrheic runners were also significantly lower (P less than or equal to 0.01). Analysis of dietary logs revealed no significant differences between the dietary habits, the calcium intake, or the caloric intake of the two groups. The data from this study indicate that there is a relationship between reduced serum PTH levels and the oligomenorrheic state. The loss of the protective effect of estrogen in the oligomenorrheic runners possibly contributed to their reduced bone mineral densities and could be a contributing factor in osteopenia.

Adolescent↗

PubMedDate not supplied

The simple bunion: anatomy at the metatarsophalangeal joint of the great toe.

The pathomechanics for the development of the hallux valgus deformity takes place at the first metatarsophalangeal joint--the sesamoid complex. The sesamoid complex consists of seven muscles, eight ligaments, and two sesamoid bones. When the first metatarsal escapes the complex and drifts medially, the sesamoids remain twisted in situ, several of the ligaments "fail," and others contract. The authors propose reduction of the metatarsus primus varus by first metatarsal osteotomy and appropriate ligament releases and plications to restore alignment. A detailed understanding of the pathomechanics is essential for proper interpretation of the problems and anticipated lasting surgeries.

Hallux Valgus↗

PubMedDate not supplied

Fretting corrosion in orthopaedic alloys.

Fretting corrosion, a mechanical-chemical phenomenon, most often occurs at screwhead-plate countersink junctions of internal fixation devices. An apparatus was constructed which would simulate the conditions of fretting corrosion in vivo. Fretting corrosion was studied as a function of the number of cycles and the solution in which the fretting occurred. The solutions studied were 0.9% physiological saline and a saline plus 0.5% albumin solution. The implant materials tested were Co-Cr-Mo alloy, 316L stainless steel, and Ti-6A1-4V alloy. The results demonstrated that weight loss increased with the number of fretting cycles but reached a plateau where further weight loss was negligible. Co-Cr-Mo alloy showed less weight loss than 316L stainless steel at any number of cycles. Weight loss for Ti-6A1-4V alloy was similar to Co-Cr-Mo alloy although marked abrasion was noted. All of the materials showed a marked decrease in weight loss when tested in the saline plus albumin solution as compared to the saline only solution.

Alloys↗

PubMedDate not supplied

Sickle-cell disease involvement of the hip and its surgical treatment.

Explore the source record for details and available documents.

Adolescent↗

PubMedDate not supplied

An evaluation of skeletal attachment to LTI pyrolytic carbon, porous titanium, and carbon-coated porous titanium implants.

Porous titanium, carbon-coated porous titanium, and low-temperature isotropic (LTI) pyrolytic carbon transcortical implants were placed in the femora of mongrel dogs. Mechanical and histologic analyses were performed in specimens that remained in situ for six months. Qualitative histologic results indicated that the bone formed a direct appositional interface with as-deposited LTI carbon. The bone tissue response to the two systems with porous coatings was similar. Both systems showed little fibrous tissue interposition and a high degree of mineralized bone ingrowth. The ingrown bone was well organized. However, there was some evidence that the ingrown bone mineral differed significantly from the bulk bone mineral. The only difference between carbon-coated and uncoated porous systems was a significant increase in the percentage of bone ingrowth, with carbon-coated specimens having a 4% increase in bone volume. The strength of appositional attachment to LTI carbon was shown to be at least one order of magnitude weaker than bone ingrowth attachment to the porous systems. The interface shear stiffness of the two porous systems was equivalent; however, the attachment shear strength of bone growth into carbon-coated porous titanium was significantly increased compared with that of bone growth into the uncoated porous titanium. Correlation of the percentage of bone ingrowth and pushout strength was also found to be statistically significant, suggesting that the presence of the carbon coating enhanced bone ingrowth, which resulted in significantly increased shear strengths.

Animals↗