Analysis of three-dimensional computerized representations of articular cartilage lesions.

RATIONALE AND OBJECTIVES: The authors assess the accuracy of three-dimensional (3D) computer representations based on magnetic resonance images of articular cartilage lesions, using actual cartilage lesions as reference standards. METHODS: Grade 2 and grade 3 articular lesions were created on articular surfaces of five porcine knee joints. The knees were then imaged using 3D fat-suppressed SPGR acquisition at four different slice thicknesses. Magnetic resonance imaging data sets were transferred to a computer workstation for image processing and 3D reconstruction. Lesion dimensions (length, width, and depth) based on the 3D reconstructed image were compared with the dimensions measured using actual lesions. RESULTS: The average percent error of lesion length, width, and depth based on the 3D images ranged from approximately 8% to 12% when using the thinnest magnetic resonance slice thickness (0.7 mm). CONCLUSIONS: Three-dimensional reconstructed images derived from thin-slice magnetic resonance imaging can provide reasonable representations of true articular cartilage lesion dimensions.

Hyperalimentation for superior mesenteric-artery (cast) syndrome following correction of spinal deformity.

The cast syndrome, recently called the superior mesenteric-artery syndrome, is a well recognized complication that can occur after a body cast has been applied. We are reporting the cases of three patients who had this syndrome following surgical correction of spinal deformity. The complication failed to resolve with the usual non-operative measures but did resolve with treatment by total parenteral nutrition.

Knee joint accessory motion following anterior cruciate ligament allograft reconstruction: a preliminary report.

Early in the postoperative period, changes in tibial translation have been noted in patient populations following anterior cruciate ligament reconstructive surgery. Deformation due to a lengthening of the ligament graft has been the most widely accepted reason for the change in tibial translation. Treatment techniques have not been proven successful in the abatement or reversal of this graft lengthening. The purpose of this study was to investigate the effect of functional bracing on tibial translation during the first year postoperatively in a group of patients with early changes in tibial translation. Three consecutive patients with early increases in KT-2000 manual maximum total drawer following bone-patellar tendon-bone allograft reconstruction were identified as subjects in the control group. Five consecutive anterior cruciate ligament bone-patellar tendon-bone allografts with early increases in KT-2000 manual maximum total drawer were identified as subjects in the treatment group. These patients were followed monthly during the first year postoperatively by manual maximum total drawer KT-2000 testing. Criteria for inclusion in the treatment and control groups included KT-2000 testing, with an increase in translation of greater than or equal to 2 mm when compared with the uninvolved knee during the first year postoperatively. The treatment group was required to wear a functional knee brace during all weight-bearing activities until KT-2000 displacement measures were stabilized for 3 consecutive months. Treatment with the functional brace resulted in a mean 2.3-mm decrease in tibial translation in the manual maximum total drawer KT-2000 when comparing the involved and uninvolved knee prebracing with posttreatment. All five subjects in the treatment group had a decrease in tibial translation. A Median Test comparing the control and treatment group's KT-2000 scores was significant at the p < .05 level. Patients who experience early increases in tibial translation with anterior cruciate ligament reconstructions may be assisted in a reduction of the displacement by the use of a functional brace.

A measurement of anterior tibial displacement in the closed and open kinetic chain.

Anterior displacement of the tibia during knee extension movement has been identified as a possible factor in anterior cruciate ligament (ACL) reconstruction failure due to the increased stress placed on the graft, leading to a creep response in the healing graft. Nineteen healthy subjects with a unilateral ACL deficiency were evaluated in an open and closed kinetic chain. A KT-1000 was used to measure anterior displacement of the tibia on the femur during isometric open and closed kinetic chain exercise at 30 and 60 degrees. An analysis of variance for repeated measures followed by Newman-Keuls multiple comparison tests were performed to determine the differences between the open and closed kinetic chain for the involved and uninvolved knee. Statistically significant differences were found when comparing the amount of anterior displacement between the open and closed kinetic chain for the involved and uninvolved knee at 30 and 60 degrees. Clinicians utilizing isometric exercise in rehabilitation of the anterior-cruciate-deficient and the anterior-cruciate-reconstructed patient should be aware of the increased amount of anterior tibial displacement when comparing open and closed kinetic chain exercise.

Effects of pretwist on biomechanical properties of canine patellar tendon.

The purpose of this study was to measure the effect produced on canine patellar tendon of a 90 degree pretwist on the following mechanical properties: failure stress, failure strain, average elastic modulus, and strain energy density. Forty adult mongrel dog cadavers, killed for other studies, were used. Paired patellar tendons were isolated with patellar and tibial bone and the central 4.0-4.6 mm of tendon used for testing. Specimens were elongated to failure using a Materials Testing System (MTS). Only those paired specimens both failing in substance were analyzed. Eight paired specimens were analyzed, both with 0 degree twist, for right-left reproducibility. Thirty-two paired specimens were randomly assigned to four groups: right 0 degree/left 90 degree clockwise pretwist; right 0 degree/left 90 degree counterclockwise; left 0 degree/right 90 degree clockwise; left 0 degree/right 90 degree counterclockwise. No statistically significant differences were present between the paired untwisted specimens in any mechanical property. In the pretwisted specimens, there were statistically significant differences between the group left/clockwise and right/counterclockwise and the group left/counterclockwise and right/clockwise with respect to the mechanical properties failure stress, average elastic modulus, and strain energy density. No statistically significant differences were observed between the two groups for failure strain. For the canine patella-patellar tendon-tibia complex (PPTTC), the mechanical properties failure stress, average elastic modulus, and strain energy density are sensitive to both side (left/right) of PPTTC and direction (clockwise/counterclockwise) of pretwist. Pretwist of patellar tendon grafts in anterior cruciate ligament reconstruction may produce significant changes in their mechanical properties that vary with the direction of twist.