Biomedical subjects

J R Parsons

Publications and source records attributed to J R Parsons.

76 records · Page 5Linked to original sources

PubMedDate not supplied

Micromechanical properties of epiphyseal trabecular bone and primary spongiosa around the physis: an in situ nanoindentation study.

The elastic modulus and hardness of the mineralized bone around the growth plate was measured to determine its regional micromechanical properties. Multiple nanoindentation tests, >10 sessions, with depths ranging from 100 to 1,000 nm at loading rates of 12.5 and 750 microN/s, were performed on the trabecular bone in the epiphysis, trabecular bone at the junction of the physis and epiphysis, primary spongiosa in the metaphysis, and surrounding cortical bone of the distal femur of 300-gm Sprague-Dawley rats. The indentation load-displacement data obtained in these tests were analyzed to determine the elastic modulus and hardness of the tissues. The nanoindentation results highlighted the regional variations in the material properties of the mineralized tissues around the growth plate. The primary spongiosa had a lower elastic modulus and hardness than both epiphyseal trabecular and cortical bone (p < 0.01). A relatively well-defined thick trabecular band at the physeal-epiphyseal junction had modulus and hardness values comparable to those of cortical bone (p > 0.05). These findings support the hypothesis that the primary spongiosa has micromechanical properties that are significantly lower than the epiphyseal trabecular bone. On this basis, it is speculated that the fracture patterns commonly seen in patients with physeal injuries are influenced by the micromechanical properties of these tissues, as well as by the nature and direction of the applied force.

Analysis of Variance↗

PubMedDate not supplied

Medial collateral ligament replacement with a partially absorbable tissue scaffold.

The medial collateral ligaments and medial capsular structures of canines were resected and replaced with a carbon fiber-polylactic acid polymer tissue scaffold or allowed simply to "scar-in." After 4, 8, 12, and 26 weeks in vivo, the stability of the knees was quantitatively evaluated and the mechanical properties of the regrown structures determined. Histological sections of the regrown structures were examined after 26 weeks in vivo. At all time periods, the knees receiving tissue scaffold ligaments were significantly more stable than those knees allowed to stabilize with scar tissue. Initial strength, rapid ingrowth, and benign tissue reaction suggest this new composite material may be useful in the treatment of joint instability.

Animals↗

PubMedDate not supplied

The biomechanics and histopathology of chemically processed patellar tendon allografts for anterior cruciate ligament replacement.

A study was initiated to examine chemically processed patellar tendon allografts in sheep anterior cruciate ligament repairs, both mechanically and histologically. One group of animals received frozen, untreated allografts, one group received frozen grafts that were processed with a chloroform-methanol solvent extraction technique, and one group received frozen tendons treated with a permeation-enhanced extraction technique. All animals were operated on unilaterally, with the contralateral knee acting as a normal, intact control. Histologic analysis after 2 months of implantation revealed similar enhanced cellular repopulation in both chemically treated ligament allografts compared with the more hypocellular, untreated grafts. At 6 months the chloroform-methanol group demonstrated a more aggressive chronic cellular response with numerous thick-walled vessels relative to the untreated and permeation-enhanced grafts. Mechanical testing after 6 months of implantation showed statistically similar anterior drawer resistance in all grafted knees, yet the two chemically extracted grafts had significantly less stiffness than untreated anterior cruciate ligament grafts. Both treatment groups also tended to be weaker than the untreated allografts. All anterior cruciate ligament reconstructions showed excessive anterior drawer laxity and, regardless of treatment, had lower strength and less stiffness than normal anterior cruciate ligament tissue at the 6-month period.

Animals↗

PubMedDate not supplied

Achilles tendon repair with an absorbable polymer-carbon fiber composite.

Twenty-seven patients were surgically treated for Achilles tendon rupture using a composite implant. The implant is ribbon-like in configuration and composed of filamentous carbon fiber coated with an absorbable polymer. When used to secure an Achilles repair, the implant acts as a scaffold for the regrowth of collagenous tissue. Rapid attachment of host tissue assures good, early repair strengths which allows for a more vigorous rehabilitation program. Fourteen patients have at least 9 months of follow-up (average follow-up, 14.4 months) and have been objectively and subjectively evaluated on a temporal basis for return of function. To date, complications have been minimal. Results have been very encouraging with 90% return of function at 18 months.

Achilles Tendon↗