Biomedical subjects

L L Malcom

Publications and source records attributed to L L Malcom.

4 recordsLinked to original sources

PubMed1985

The measurement of anterior knee laxity after ACL reconstructive surgery.

An objective clinical instrument known as a knee ligament Arthrometer was developed. The instrumentation system was applied to measurements of knee ligament laxity in the operating room with the patients under anesthesia. Prereconstruction and immediate postreconstruction measurements were made with the patient still on the operating table. The change in laxity of the patient's operated knee as compared to the opposite nonoperated control knee was documented for 19 chronic and 24 acute patients. Four separate reconstruction types were studied in the operating room. The immediate postreconstruction measurements documented that all four of the reconstruction types were equally effective in the immediate restoration of normal laxity in the ACL-deficient knees. The Arthrometer proved to be a useful tool for confirming that each patient's normal knee laxity was reestablished in the O.R. by its reconstruction.

Humans↗

PubMed1985

Instrumented measurement of anterior laxity of the knee.

We performed instrumented measurement of anterior-posterior laxity of the knee in thirty-three cadaver specimens, 338 normal subjects, and eighty-nine patients with unilateral disruption of the anterior cruciate ligament. The test instrument was the Medmetric knee arthrometer, model KT-2000. We measured total anterior-posterior laxity, produced by anterior and posterior loads of eighty-nine newtons (twenty pounds), and the anterior compliance index. The total anterior-posterior laxity is composed of an anterior displacement and a posterior displacement; these are measured from a testing reference position, defined as the resting position of the knee after applying and then releasing a posterior load of eighty-nine newtons. The anterior compliance index is defined as the anterior displacement between an anterior load of sixty-seven newtons and one of eighty-nine newtons. All tests were performed with the knee held on a thigh support that placed the knee in 20 +/- 5 degrees of flexion. The mean anterior displacement at eighty-nine newtons was 5.7 millimeters in a group of normal subjects and 13.0 millimeters in a group of patients with a disrupted anterior cruciate ligament. Ninety-two per cent of the normal subjects had a left knee-right knee difference in anterior displacement of no more than two millimeters, while 96 per cent of the patients with a unilateral disruption of the anterior cruciate ligament had an injured knee-normal knee difference in anterior displacement of more than two millimeters. Ninety-three per cent of the normal subjects had a difference in the left-right compliance index of no more than 0.5 millimeter, and 85 per cent of the patients with unilateral disruption of the anterior cruciate ligament had a difference in the compliance index of the injured and normal sides of more than 0.5 millimeter.

Adolescent↗

PubMed1980

The spherocentric knee: a re-evaluation and modification.

The purpose of this study was to assess prospectively the initial results of total knee replacement with the standard spherocentric component and to identify retrospectively the pathogenesis of any unsatisfactory results. As a consequence of this study, the femoral component was modified. Thirty-six knees were reviewed twenty-two to fifty-two months after a standard spherocentric total knee replacement, with a mean follow-up of thirty-five months. Twenty-five (70 per cent) of the knees had significant relief of pain and improved function. Eleven knees were not improved because of confirmed loosening in five, supracondylar fracture in two, infection in one, and suspected loosening in three. Ten of these eleven complications became manifest within the first postoperative year. Alignment in the coronal plane was not consistently precise and hyperextension was a recurrent problem in twelve of the thirty-six knees. A modification in the femoral component was made: the stem was lengthened to 10.0 centimeters and the body was reoriented so that there was 5 degrees of valgus and 15 more degrees of posterior rotation than the original design. This modified prosthesis was used in twenty-five additional knees, with definite improvement in alignment, but the follow-up was insufficient to ascertain the effect of the modification on lossening and fracture.

Adult↗

PubMedDate not supplied

Experimental hemarthrosis in the knee of the mature canine.

The knee joints of 14 skeletally mature mongrel dogs were subjected to a continuous hemarthrosis. Minimal morphologic changes of the articular cartilage did not occur until after 16 weeks. As early as 4 weeks, biochemical analyses showed a significant decrease in glycosaminoglycans (GAG) that became progressively more severe with time, whereas total collagen was not significantly altered until after 12 and 16 weeks. Bioengineering measurements of the experimental cartilage surfaces showed that the tissue becomes more deformable as well as less resistive to shear than the control at 8 weeks. These differences increased as the duration of hemarthrosis increased.

Animals↗