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At least 1,081 records · Page 60Linked to original sources
PubMed2000

Anthropometric measurements to design total knee prostheses for the Indian population.

An anthropometric computed tomography scan study was undertaken to design femoral components in 86 knees (47 osteoarthritic Indians-21 men, 26 women) who matched standards suggested by the Indian Council of Medical Research, 1990. Patients were classified into 3 random groups based on anteroposterior diameter (<55 mm, 55-59 mm, >59 mm). Most Indian men (86.8%) could have the femoral component satisfactorily replaced by available designs. A statistically significant number of women (60.4%, P < .001) had femoral anteroposterior diameters smaller than the smallest available (55 mm) femoral component. Splaying in mediolateral dimension (> 10 mm) in a given anteroposterior size was noted in all 3 groups. This pilot study representative of the Indian population can be used to manufacture prosthetic inventories suitable for most of the Asian-Pacific population having smaller anthropometric measurements than Western populations.

Anthropometry↗
PubMed2000

The anatomic basis for the concept of lateralized femoral stems: a frontal plane radiographic study of the proximal femur.

We determined the range of sizes for a system of monoblock femoral prostheses that would provide adequate (a term defined in the text) fill in the frontal plane and restore femoral offset and leg length. We performed an anatomic study, based on measurements in 200 anteroposterior pelvic radiographs. If diaphyseal filling implants are to be used, 9 sizes are sufficient to obtain excellent canal filling and restoration of femoral offset in >80% of cases, assuming that the level of neck osteotomy can vary over a 1-cm range. When using metaphyseal filling implants, only a limited adjustment can be obtained from the level of neck osteotomy. A system limited to 8 sizes approximates the anatomy of the femoral canal with satisfactory precision in 73% of cases. If such a system is provided with only a single neck shaft angle for each stem size, it does not allow restoration of the biomechanical center of the hip in >67% of cases. A system of 8 sizes of 1 neck/shaft angle and a 22-mm modular head restores the anatomy in only 49% of cases. Approximating the frontal anatomy of 85% of femora with an implant filling the metaphysis requires at least 15 sizes distributed in 3 metaphyseal configurations, each supplied with 2 different neck shalt angles.

Aged↗
PubMed1998

Intraoperative assessment of tibiofemoral contact stresses in total knee arthroplasty.

The production of polyethylene wear debris in total knee arthroplasty (TKA) is due to multiple factors. In particular, inadequate implant alignment and high bearing surface contact stresses are associated with polyethylene failure. Optimal implant placement and soft tissue balancing may contribute to reducing wear and the production of polyethylene particles. We present a case in which a quantitative technique was used to measure tibiofemoral contact stresses during implantation of a total knee prosthesis in vivo. In a knee with preoperative varus and fixed flexion deformity, medial compartment contact stresses after initial resection were reduced from 14.3 MPa to 11.3 MPa in neutral alignment by additional bone resection. Posterior cruciate release was required to reduce contact stresses further and to provide satisfactory balance between medial and lateral compartments, as determined by the operating surgeon, and was confirmed by the measurement system (3.8 MPa medially; 3.0 MPa laterally). This technique has potential to fine-tune implant positioning and ligament balancing during TKA.

Aged↗
PubMed2003

Magnetically adjustable intraocular lens.

PURPOSE: To provide a noninvasive, magnetic adjustment mechanism to the repeatedly and reversibly adjustable, variable-focus intraocular lens (IOL). SETTING: University of Missouri-Rolla, Rolla, and Eggleston Adjustable Lens, St. Louis, Missouri, USA. METHODS: Mechanically adjustable IOLs have been fabricated and tested. Samarium and cobalt rare-earth magnets have been incorporated into the poly(methyl methacrylate) (PMMA) optic of these adjustable lenses. The stability of samarium and cobalt in the PMMA matrix was examined with leaching studies. Operational force testing of the magnetic optics with emphasis on the rotational forces of adjustment was done. RESULTS: Prototype optics incorporating rare-earth magnetic inserts were consistently produced. After 32 days in solution, samarium and cobalt concentration reached a maximum of 5 ppm. Operational force measurements indicate that successful adjustments of this lens can be made using external magnetic fields with rotational torques in excess of 0.6 ounce inch produced. Actual lenses were remotely adjusted using magnetic fields. CONCLUSIONS: The magnetically adjustable version of this IOL is a viable and promising means of handling the common issues of postoperative refractive errors without the requirement of additional surgery. The repeatedly adjustable mechanism of this lens also holds promise for the developing eyes of pediatric patients and the changing needs of all patients.

Biocompatible Materials↗
PubMed2003

Development of a repeatedly adjustable intraocular lens.

PURPOSE: To provide a variable-focus intraocular lens (IOL) that is able to adjust repeatedly and reversibly. SETTING: University of Missouri-Rolla, Rolla, and Eggleston Adjustable Lens, St. Louis, Missouri, USA. METHODS: An adjustable IOL based on a mechanically adjustable design has been developed. Prototypes were fabricated from traditional Perspex CQ poly(methyl methacrylate) (PMMA) provided off the shelf by a current IOL manufacturer. The prototypes have undergone proof-of-concept testing per the requirements of National Institutes of Health grant 1 R41 EY13482-01, with specific attention to the feasibility and safety of continuing development of the lens with in vivo trials. The experimental results presented focus on operational force measurements. RESULTS: Prototype lenses were produced consistently. Operational force measurements indicated that use of the mechanical adjustment mechanism is viable for an adjustable IOL and provides repeated adjustments over time. Turning forces exhibited by the prototypes were low enough to suggest that operation of this adjustable IOL will not damage the capsular bag or ciliary body of the eye, a potential concern in using this design. Biocompatibility and optical quality of the prototype lenses are ensured by use of traditional Perspex CQ PMMA. CONCLUSIONS: The mechanically adjustable IOL provides a feasible and promising means of confronting postoperative refractive errors and the changing desires of patients. The viability of this IOL design has been proven, and results suggest that operation of the lens is safe enough to pursue in vivo trials. Evaluation of the biocompatibility of the lens architecture as well as the ultimate goal of noninvasive adjustment using this model are reported in a companion article.

Biocompatible Materials↗
PubMed1998

Peripheral radial incisions to treat inferior contact lens edge lift after penetrating keratoplasty for keratoconus.

A patient with marked corneal astigmatism and inferior contact edge lift after penetrating keratoplasty for keratoconus had corneal relaxing incisions (CRIs) on the donor button and radial incisions on the host cornea. Results were evaluated by computerized videokeratography and by refitting the contact lens. Two pairs of CRIs decreased astigmatism from 11.00 to 4.25 diopters but did not alleviate the contact lens edge lift, which was caused by excessive steepness in the keratoconic host cornea. After 6 radial incisions were made to flatten the inferior host cornea, the peripheral cornea flattened and the patient was successfully refitted with a contact lens.

Astigmatism↗
PubMed2003

The correction of astigmatism with soft contact lenses.

Soft contact lens correction for astigmatism has made significant advances over the last 20 years. Soft toric tinted lenses, disposables lenses, and bifocal lenses are now available at lower costs with greater reproducibility, enhanced parameters, and better comfort. Because of these innovations and significant design changes, a greater percentage of astigmatic patients are being treated with soft toric lenses than before.

Astigmatism↗
PubMed2003

Correction of astigmatism with rigid gas permeable lenses.

Comparison of the results of keratometry and refraction usually suggests the appropriate contact lens for a patient's eye. Specialized rigid toric contact lenses include bitoric and back toric RGP lenses, front toric RGP lenses, and bitoric RGP lenses with prism ballast. Each lens has specific indications.

Astigmatism↗
PubMed2003

Disposable and frequent replacement contact lenses.

Disposable and frequent replacement contact lenses dominate the marketplace. They are available in a wide variety of parameters for use in refractive errors, including myopia, hyperopia, astigmatism, and presbyopia. They are convenient and affordable and lend themselves to most wearing modalities, including daily wear, flexible wear, and extended wear for up to 30 days. In addition, they have been shown to be the most trouble-free contact lens wear modality for daily wear or extended wear. They are an appropriate choice for patients who desire occasional contact lens wear and have gained wide acceptance as therapeutic bandage contact lenses. Disposable and frequent replacement lenses will remain important modalities for some time to come as the variety of contact lenses and contact lens parameters that are offered continue to expand. New contact lens varieties, such as the high-Dk silicone hydrogel lenses, will further expand the role of these contact lenses in vision correction.

Contact Lenses↗
PubMed2003

Contact lens management following corneal refractive surgery.

Corneal refractive surgery has enjoyed considerable success and popularity in recent years; LASIK has become the surgical procedure of choice. The incidence of visually significant complications varies widely, but is inversely related to surgeon experience. Visual complaints include multifocal images, shadows, ametropias, anisometropia, night vision difficulties, decreased contrast sensitivity and loss of BCVA. Contact lenses offer an option to rehabilitate patients when visually symptomatic following refractive surgery. RGP lenses provide the best postoperative visual rehabilitation following refractive surgery.

Contact Lenses↗
PubMed2006

Kinematic navigation in total knee replacement--experience from the first 50 cases.

BACKGROUND/PURPOSE: Proper alignment of the prosthesis is critical in total knee replacement (TKR) to minimize long-term wear, risk of osteolysis, and loosening of the prosthesis. This study examined the accuracy of lower limb alignment obtained using a kinematic navigation system for TKR, and the extra time needed to adopt this system. METHODS: From August 2002 to April 2003, 71 patients with knee osteoarthritis underwent 79 primary TKR operations by the same surgical team. Fifty of these operations were performed with the aid of the CT-free kinematic navigation system, and the remaining 29 were performed with conventional manual methods. Results, including operation time, radiographic alignment of the prosthesis and complications, for the two groups were compared. RESULTS: Patients in the kinematic navigation group achieved better accuracy in the coronal plane than the conventional group in terms of postoperative mechanical axis (1.89 +/- 0.63 degrees vs. 3.38 +/- 1.07 degrees ). Less variation was noted in the navigation group (femur: SD 1.88 degrees vs. 7.12 degrees ; tibia: SD 1.54 degrees vs. 2.99 degrees ), although the difference in the mean values was not significant (p = 0.475 and 0.55, respectively). The operation time (from skin to skin) in the navigation group (100.6 +/- 4.3 minutes) was longer than that in the conventional group (92.7 +/- 5.1 minutes; p = 0.027). Two perioperative fractures occurred in the navigation group, both of which were attributed to patient factors as opposed to operation procedures. No major complications such as infection or pulmonary embolism occurred during this study. CONCLUSION: Use of a kinematic navigation system in TKR provides better accuracy than conventional manual methods. The technique is easy to use, has a short learning curve, and requires an additional operation time of less than 10 minutes. Precise alignment can be achieved with the aid of navigation in most cases.

Aged↗
PubMed2002

Energy expenditure and biomechanical characteristics of lower limb amputee gait: the influence of prosthetic alignment and different prosthetic components.

In this study, the influence of different prosthetic alignments and components on oxygen consumption and the important biomechanical characteristics of the normal gait pattern of leg amputees was investigated. With 15 transtibial and 12 transfemoral amputees, the oxygen consumption during walking on a treadmill was analyzed and biomechanical parameters during walking on even ground at a self-selected speed were defined. The amputation of all patients was caused by trauma. Variations of the prosthetic alignment affect the energy consumption of transfemoral amputees more significantly than that of transtibial amputees. Comparison of different prosthetic feet worn by transtibial amputees did not show significant differences regarding metabolic parameters. Compared with conventional hydraulic knee controls, the oxygen consumption of transfemoral amputees provided with an electronically controlled hydraulic knee joint is reduced. All investigated variations can be clearly characterized by the sagittal moments acting on the joints of the prosthetic limb during gait.

Adolescent↗
PubMed2003

Adjustments in gait symmetry with walking speed in trans-femoral and trans-tibial amputees.

The effect of increased walking speed on temporal and loading asymmetry was investigated in highly active trans-femoral and trans-tibial amputees. With increasing walking speed, temporal gait variables reduced in duration, particularly on the prosthetic limb, while vertical ground reaction force (vGRF) increased in magnitude, particularly on the intact limb. Thus, temporal asymmetry reduced and loading asymmetry increased with walking speed. The greater force on the intact limb may reflect the method by which the amputees achieve greater temporal symmetry in order to walk fast, and could possibly account for greater instances of joint degeneration in the intact limb reported in the literature.

Adaptation, Physiological↗
PubMed2002

Stent-graft design: the good, the bad and the ugly.

10 years of experience with endovascular AAA repair has yielded important information regarding the relationship between stent-graft design and stent-graft performance. Commercially available systems differ in important ways. General conclusions regarding endovascular AAA repair need to be qualified by reference to a specific system, or systems. Nevertheless, one can draw conclusions regarding the observed effects of certain design features, some of which are common to several devices. For example: tapered, trackable delivery systems (< or =20 French in diameter) rarely fail to traverse tortuous iliac arteries: transmural barbs provide the most secure means of proximal attachment, column strength is of little value; proximal stent migration is becoming the primary late failure mode; modular stent-grafts are more versatile than unibody stent-grafts; fully-stented graft limbs are less prone to thrombosis than unstented graft limbs, iliac implantation and low porosity are associated with lower rates of aneurysm dilatation in the absence of endoleak (endotension); any movement between the angle of a stent and the overlying fabric will lead to graft erosion; unpolished (black) Nitinol is prone to fracture; and a long trunk/short limb combination is more stable than a short trunk/long limb combination.

Aortic Aneurysm, Abdominal↗
PubMed2003

The effect of component malalignment on the clinical and radiological outcome of the Kinemax total knee replacement.

Component angles of 198 Kinemax total knee replacements were measured from standard short leg radiographs. An ideal tibio-femoral angle of between 4 and 10 degrees of valgus was achieved in 64.6% of patients. After an average follow-up of 6.5 years (range 4.5 to 9.5), there was no significant difference between knees in acceptable and suboptimal alignment in terms of pre- and post-operative knee and function scores and prevalence of radiolucent lines. Varus placement of the tibial component was significantly more common by trainee surgeons (P<0.001).

Aged↗
PubMed2003

Symmetrical vs asymmetrical total knee replacement--a medium term comparative analysis.

Modifications of established implants can result in deleterious effects, as with the Capitol and the matt coated Exeter hips. In 1991 the Kinemax plus modification of the Kinematic knee was introduced in Bristol, the design changes having been made to reduce patello-femoral complications. We carried out a comparative analysis of the prospective recorded data on a consecutive series of 182 total knee replacements (95 Kinematic and 87 Kinemax plus knees) performed between 1991 and 1993. The same instrumentation and surgical technique was used. Since the design had introduced a broader trochlear, offset patella and had changed from an asymmetrical to a symmetrical femoral component, particular attention was paid to tracking and range of movement. All patients were reviewed at 5 years using the Bristol knee score and radiographs. There was no difference in the overall score (both prosthesis scoring 85-86) but the Kinemax plus group with a symmetrical trochlear had a significantly greater improvement in the range of movement (14 degrees as opposed to 4 degrees; P<0.05). In addition, secondary intervention for mal-tracking was significantly less in the Kinemax group. No deleterious effect of the changed geometry was observed. It is concluded that the introduction of a symmetrical femoral component with an offset patella reduced patello-femoral complications without detectable disadvantages.

Aged↗
PubMed1995

Use of the palatal mucosal graft for reconstruction of the eye socket.

Hard palate mucosa is thick and rigid. Grafted with its periosteal layer, it can be a supportive material. Simultaneously, wound healing of the palatal donor site is very rapid and the patient does not experience any pain. Such characteristics of the palatal mucosal graft have led to its use in reconstruction of the eyelids, including the tarsal plate. Nevertheless, there have been very few reports on its use in this are of the face. Herein we report the use of the palatal mucosal graft in reconstruction of the eye sockets.

Adult↗