Fibroblast cell attachment and growth on nanoengineered sculptured thin films.

Nanoengineered parylene-C sculptured thin films (STFs) are deposited on glass and silicon substrates using a direct one-step growth technique. The deposited STFs support fibroblast cell attachment and proliferation in vitro, which is an early indication of biocompatibility and bioactivity of this emerging class of biomaterials. Surface modification of endoprostheses of the small joints of the hand, which heal with fibrous stabilization, may be greatly enhanced by such nanoengineered biomaterials.

Influence of metacarpophalangeal joint position on basal joint-loading in the thumb.

BACKGROUND: Conventional wisdom holds that hyperextension of the metacarpophalangeal joint of the thumb is secondary to degenerative subluxation of the trapeziometacarpal joint as occurs in osteoarthritis. We propose that a hypermobile metacarpophalangeal joint may have a causative role in the development of primary osteoarthritis at the base of the thumb by concentrating forces on the palmar aspect of the trapeziometacarpal joint. METHODS: Twenty fresh-frozen cadaveric forearm specimens were obtained post mortem from donors with no history of connective-tissue disease. Each specimen was categorized by its passive range of metacarpophalangeal joint motion. Testing was conducted with Fuji ultra-low-pressure-sensitive film while the hand was in the lateral-pinch mode with the metacarpophalangeal joint in each of the following positions: unrestrained, pinned in neutral, pinned in 30 degrees of flexion, and pinned in maximal hyperextension. Quantitative analysis of the trapezial contact surface at each of the metacarpophalangeal joint positions was performed, and the center of pressure was determined. Each specimen was then classified according to the extent of arthritic disease (nonarthritic, moderately arthritic, or affected by end-stage arthritis). RESULTS: In specimens affected by end-stage osteoarthritis, the center of pressure on the trapeziometacarpal joint moved dorsally by 56.8% of the length of the trapezial surface with metacarpophalangeal joint flexions of 30 degrees (p < 0.01), whereas the corresponding values were 28.2% and 40.9% in the hyperextended and neutral metacarpophalangeal joint positions, respectively. In specimens with moderate osteoarthritis, 30 degrees of metacarpophalangeal joint flexion also produced the most dorsal trapeziometacarpal center of pressure (44.8%); however, this center of pressure was not significantly different from the centers of pressure at the other metacarpophalangeal joint positions. In nonarthritic specimens, the center of pressure was again significantly more dorsal with metacarpophalangeal joint flexion of 30 degrees than it was at the other positions (p < 0.01). CONCLUSION: Metacarpophalangeal joint flexion effectively unloaded the most palmar surfaces of the trapeziometacarpal joint regardless of the presence or severity of arthritic disease in this joint.

Median nerve function in patients undergoing carpal tunnel release: pre- and post-op nerve conductions.

Patients undergoing surgery for carpal tunnel decompression may improve clinically, however it is not well known as to how median nerve neurophysiology is altered following surgery. Fifty patients who underwent open carpal tunnel release were prospectively studied. Each patient underwent nerve conduction studies pre-op and at 6 months post-op. Patients were also asked to answer several questions regarding their clinical symptoms to see how they improved. 48/50 patients had clinical improvement based on their response (resolution of nocturnal paresthesias, decreased sensory complaints and pain). Average pre- and post-op parameters were as follows: distal motor latency (DML) (msec) 5.24/4.42; distal motor amplitude (mV) 8.28/8.64; sensory conduction velocity (m/sec) 38.9/41.0; sensory amplitude (uV) 10.94/15.61. We conclude that the DML and sensory amplitude showed significant improvement following surgery; the sensory conduction velocity remains slow.

Initial stability of a modular uncemented, porous-coated femoral stem: a mechanical study.

A versatile modular hip system was used to evaluate the initial stability of a cementless femoral stem in anatomically consistent composite bones. Four implant bone configurations of varying proximal and distal fit/fill were tested. The implanted femurs were tested on an Instron 1331 materials testing machine in neutral loading and flexion loading; both translational micromotions and rotations of the implant relative to the bone were recorded on all three axes of motion, accounting for all 6 degrees of freedom of joint motion. Implants were then sectioned, and both endosteal canal fit and intramedullary canal fill were measured. Results indicate that (1) loading the implant in flexion by out-of-plane forces significantly increases both relative translation and rotation at the interface, (2) increasing the proximal fit reduces implant rotation about its longitudinal axis in flexion loading and (3) increasing the distal canal fit and fill increases prosthesis rotation about its longitudinal axis in flexion loading. These results indicate that the femoral stem is more unstable in out-of-plane loading, such as during stair climbing, and that increasing the proximal fit may enhance the initial rotational stability of an uncemented femoral stem.

Compartment syndrome of the forearm and hand.

Compartment syndrome in the hand and forearm is a serious and debilitating complication of crush injury. Pain with passive motion is the most reliable physical finding; however, compartment pressure measurement is the only truly reliable method of diagnosis. Immediate and adequate decompression will prevent the development of Volkmann's ischemic contracture and its associated severe loss of function in the affected extremity.

Orderly oriented wire mesh: a novel porous coating.

As an alternative to commercially available porous beads and fiber metal mesh, a new porous coating, orderly oriented wire mesh (OOWM), was developed. Rectangular plugs, 10 x 5 x 5 mm with porous-coated beads, and four different OOWM configurations were inserted into bilateral femoral condyles of adult beagles. Dogs were sacrificed immediately after implantation, and at 4 weeks, 8 weeks, and 12 weeks postimplantation. Mechanical pullout strength of plugs revealed that porous beads are equivalent to the simplest OOWM at 12 weeks postimplantation. Of the four OOWMs tested, the 25 x 25 single layer was significantly more stable than others at 4 weeks postimplantation. These results indicate that in an in vivo unloaded model, OOWM is just as effective as the porous beads in achieving early bone ingrowth and stability.

Radiation-induced physical changes in UHMWPE implant components.

Post-irradiation aging of ultra-high molecular weight polyethylene (UHMWPE) is not well understood. Retrieval studies and in vitro aged specimens have shown oxidative changes along with increases in crystallinity. Critical analysis and review of the polymer science and polymer physics literature shows that while oxidation may be important during the first year post-irradiation, subsequent aging occurs because of initial gamma radiation-induced chain scission leading to eventual isothermal crystallization of polymer chains in the amorphous regions of the UHMWPE bulk. Mechanical properties of aged UHMWPE are not as yet clear and, until such data become available, gamma irradiation sterilization must be used with caution.

Percutaneous pinning of proximal humerus fractures: a biomechanical study.

Mechanical testing of two-part surgical neck fractures fixed with four different pin configurations was performed. Ten fresh, frozen, unembalmed humeri stripped of all soft tissues were used; the surgical neck was osteotomized perpendicular to the humerus long axis. Terminally threaded 2.5-mm AO pins were used to fix the fracture. Humeri then were tested in both torsion and bending on a custom-made jig using Instron 1331 to assess the rigidity of pinning constructs. In torsion, two lateral pin construct was significantly less rigid than all other pin configurations. The addition of an anterior pin to two lateral pins did not increase bending rigidity, but significantly increased torsional stiffness. The addition of two bicortical tuberosity pins or two bicortical tuberosity pins and one anterior pin to two lateral pins significantly increased rotational and bending rigidity. Results confirm clinical data, and the authors conclude that multiplanar pins are needed to augment torsional stiffness, and that the addition of two bicortical tuberosity pins enhances bending rigidity.

Varicella-associated acute supraglottitis.

Acute bacterial supraglottitis is a well-recognized pediatric entity. There are reports in the literature of numerous supraglottic infections not limited to the usual organism, Haemophilus influenzae type b. We present a case of acute supraglottitis that is associated with varicella infection.

Pre- and postimplantation dynamic mechanical properties of silastic HP-100 finger joints.

Dynamic mechanical properties of Silastic HP-100 finger joint implants were studied. Sixteen sections of unimplanted and 14 sections of retrieved implants were analyzed with standard thermal analysis techniques. Results show that implantation does not alter the viscoelastic properties of Silastic HP-100 elastomers. The authors conclude that fracture of Silastic HP-100 implants cannot be attributed to changes in rheologic properties of the implanted elastomer.

Isolated digital swelling as the initial presentation of juvenile rheumatoid arthritis.

Juvenile rheumatoid arthritis (JRA) is an inflammatory condition that affects children under 16 years of age. The cases of 7 patients with isolated finger swelling as the initial manifestation of JRA are reviewed. In these children, the diagnosis was significantly delayed (t-test, p < .0076) for up to 14 months (mean, 8 months) when compared to a mean of 3.4 months in the JRA patients with a typical onset. Of the patients with the initial presentation of isolated digital swelling, +/7 (57%) had disease that became polyarticular, whereas only 15% of the patients with the initial presentation of large-joint disease experienced progression to polyarticular disease (Fisher's exact test, p < .0307). This presentation of JRA should be recognized so that appropriate management can be instituted promptly.

Mechanical stamping: a cause of fatigue fracture.

Failure analysis of a retrieved flexible intramedullary nail was performed by standard optical and scanning electron microscopy. Results show that the corrosion fatigue at the stamped label caused the nail fracture. The authors strongly recommend that the American Society for Testing of Materials standard F86-91 be modified to exclude mechanical stamping from the repertoire for labeling implants. Surgeons also must avoid using mechanically stamped hardware that will be subject to cyclic loads in vivo.

Relationships between clinical symptom severity scales and nerve conduction measures in carpal tunnel syndrome.

This study examined the severity of symptoms in carpal tunnel syndrome (CTS) in relation to nerve conduction measures of the median nerve. Clinical symptom severity and nerve conduction studies were evaluated for 64 hands with CTS in 45 patients. We found the following: (1) significant relationships identified among the clinical scales resulted in a dichotomous symptom classification scheme into primary and secondary symptoms, with the former being more specific for those symptoms usually seen in association with nerve injury; (2) there were significant relationships between symptom severity and nerve conduction abnormality; (3) the primary symptom scale correlated more strongly with the electrodiagnostic measures of nerve injury than did the secondary symptom scale. Based on these findings, we believe that these clinical scales have biological significance and reflect median nerve injury. This would support their potential utility for evaluating the outcome of CTS treatment and developing a model for exposure-severity relationship.

Lightning injury: management of a case with ten-day survival.

A boy, injured by lightning, had cardiopulmonary arrest. Following resuscitation and during the course of hospitalization, he developed further cardiac arrhythmia, cerebral edema, generalized seizures, and upper gastrointestinal bleeding. Despite efforts to combat these complications, the patient's condition deteriorated, and he died on the tenth day of hospitalization. The pathologic findings are described and the treatment discussed.

Percutaneous pinning of distal radius fractures: a biomechanical study.

Mechanical testing of extra-articular distal radius fractures stabilized with percutaneous pins was performed. Twelve fresh-frozen unembalmed radii stripped of all soft tissues were used. An osteotomy with dorsal comminution was made 2.5 cm proximal to the radial styloid. Three pin sizes and four pin configurations were used to fix the fracture, and the constructs were mechanically tested. Results show that at least a .062-inch pin was required for any significant changes in rigidity of the four pin configurations tested to be discerned. Cross-pinning with two radial styloid pins and placement of a pin from the ulnar corner of the radius as the most rigid construct in both torsion and cantilever bending.

In vivo inflammatory response to silicone elastomer particulate debris.

Silicone elastomer particles (Silastic silicone elastomer, Dow Corning, Midland, MI), polymethylmethacrylate particles, and monosodium urate particles smaller than 10 microns were injected into a rat subcutaneous air pouch lined with synovial membrane-like cells. Inflammatory exudate from the air pouch was retrieved at 6 hours, 24 hours, 48 hours, and 72 hours after injection. White blood cell count, tumor necrosis factor, and prostaglandin E2 were measured in the exudate. White blood cell and tumor necrosis factor levels in the exudate were the highest for the silicone group at 6 and 24 hours. Prostaglandin E2 was also significantly higher in the silicone group at 24 hours. We conclude that the acute inflammation is particle-type specific and that Silicone elastomer particles are acutely inflammatory.