Biomedical subjects

Christof Hurschler

Publications and source records attributed to Christof Hurschler.

24 records · Page 2Linked to original sources

PubMed2003

Scanning electron microscopic characterization of healing and normal rat ligament microstructure under slack and loaded conditions.

The objective of this study was to observe and compare behavior of the collagen fiber microstructure in normal and healing ligaments, both in situ and ex vivo, in order to add insight into the structure-function relationship in normal and healing ligaments. Fifty-two ligaments from 26 male rats were investigated. Eleven animals underwent surgical transection of both medial collateral ligaments (MCLs) (22 ligaments), which were allowed to heal for a period of 2 weeks. An additional 15 animals (30 ligaments) were used as normals. Ligaments were placed into six groups: Slack (n = 6 control, n = 6 healing), Reference (n = 4 control, n = 4 healing), Loaded (n = 4 control, n = 4 healing), 15 degrees Flexion (n = 4 control, n = 4 healing), 120 degrees Flexion (n = 4 control, n = 4 healing), and Tissue Strain vs. Flexion Angle (n = 8 normals). All ligaments, except those in the Tissue Strain vs. Flexion Angle group, were prepared for scanning electron microscopy. Tissues were harvested, mounted in a load frame, and chemically fixed in one of five states: (1). slack, (2). reference (onset of loading), (3). loaded, (4). 15 degrees knee flexion, or (5). 120 degrees knee flexion. After fixation the tissues were prepared for electron microscopy (SEM). The micrographs from the slack, reference, and loaded groups show fiber straightening with loading in normal ligaments as well as in both scar and "retracted" regions of healing ligaments. Collagen fibers' diameter and crimp patterns were dramatically changed in the scar region of healing ligaments: Width decreased from 19.4 +/- 1.7 microm to 6.5 +/- 2.1 microm (p <.000001), period from 51.4 +/- 15.1 microm to 11.0 +/- 2.4 microm (p <.000001), and amplitude from 9.8 +/- 0.8 microm to 3.9 +/- 0.8 microm (p <.000001). Normal ligaments fixed in situ show wavy regions at 120 degrees but less so at 15 degrees flexion. Healing ligaments fixed in situ show regions of fiber waviness in the scar region at 120 degrees and also at 15 degrees flexion, indicating ligament laxity persists toward both extremes of the range of motion. The data suggest that straightening of crimped fibers is a functionally relevant phenomenon, not only in normal but also in healing ligaments.

Animals↗

PubMed2002

Tibiofemoral contact stress after total knee arthroplasty: comparison of fixed and mobile-bearing inlay designs.

We measured tibiofemoral contact stresses and the load-bearing contact area of fixed and mobile-bearing inlay knee prostheses under dynamic loading conditions. An electronic resistive pressure-measuring sensor was used to detect contact stresses and contact area in five cadaver knees. Stresses were measured with the tibial component aligned normally, as well as in internally- and externally-rotated positions. The average peak contact stresses measured on the fixed inlay were greater (medial 21 MPa and lateral 21 MPa) than those on the mobile inlay (medial/lateral 7.7/5.3 MPa, p = 0.04). Although the average peak contact stresses of the fixed standard inlay greatly exceeded the contact stresses of the other two inlay designs in each malrotated position tested, no statistically significant differences were seen. The data suggest that the ability of the inlay to translate on the tibial baseplate permits the inlay to align itself on the femoral component so that the contact surface area is maximized and contact stresses are reduced.

Aged↗

PubMed2002

Cavus foot correction in adults by dorsal closing wedge osteotomy.

Twelve patients (13 feet) who underwent dorsal closing wedge osteotomy for cavus foot deformity were re-examined clinically and radiographically 46 months after surgery (range, 24 to 80 months). A dorsally based bone wedge, sized according to the deformity on the preoperative radiographs, was excised between the Lisfranc and Chopart joint lines. Eight patients (nine feet) were satisfied with the procedure. Although significant improvement of both symptoms and foot alignment was achieved, most patients continued to experience mild to moderate pain postoperatively. The outcome seems not to be directly related to the achieved surgical correction.

Adult↗

PubMedDate not supplied

Evaluation of the lag sign tests for external rotator function of the shoulder.

Rotator cuff lesions pose a serious clinical challenge. The objective of this study was to verify the biomechanical basis for the lag sign clinical tests for rotator cuff dysfunction. The lag sign tests were simulated in vitro by a sensor-guided robotic simulator configured to reproduce in vivo testing conditions. The ability of the test to isolate supraspinatus and/or infraspinatus dysfunction was investigated from 20 degrees to 90 degrees of scapular plane arm elevation. The test was 100% sensitive for lack of all infraspinatus-teres minor force at all elevations tested (6/6 specimens at 20 degrees, 30 degrees, and 60 degrees elevation; 5/5 at 90 degrees elevation). The test was less sensitive to complete loss of supraspinatus force (1/6 specimens testing positive at 20 degrees, 0/6 at 30 degrees, 3/6 at 60 degrees, and 3/5 at 90 degrees elevation). The results of this biomechanical study suggest the lag sign tests to be highly sensitive only for infraspinatus-teres minor muscle dysfunction.

Adult↗

PubMedDate not supplied

The influence of arthroscopic subscapularis tendon and anterior capsular release on glenohumeral translation: a biomechanical model.

The effect of an arthroscopic release of the intraarticular portion of the subscapularis tendon and the anterior capsule on glenohumeral translation was investigated in a cadaveric model. Ten human cadaveric shoulders with a mean age of 63.5 years (range, 52-79 years) were tested in a robot-assisted shoulder simulator. Joint translation was measured before and after an arthroscopic release of the intraarticular portion of the subscapularis tendon and a subsequent release of the anterior capsule at 0 degrees , 30 degrees , 60 degrees , and 90 degrees of glenohumeral elevation. Translation was measured in the anterior, anterior-inferior, and inferior directions under 20 N of applied load. Testing of the specimen revealed that the release of the intraarticular portion of the subscapularis tendon and the anterior capsule increased translation in all directions. Significant increases in translation were observed after release of the intraarticular portion of the subscapularis tendon in the midrange of motion. The influence of the arthroscopic capsular release, in conjunction with the release of the subscapularis tendon, was very high above 60 degrees of elevation. The study indicates that the intraarticular component of the subscapularis tendon functions as a restraint to anterior-inferior translation primarily in the midrange of glenohumeral motion, whereas the anterior capsule adds anterior-inferior stability to the glenohumeral joint mainly above 60 degrees of elevation.

Aged↗

PubMedDate not supplied

Femoral press-fit fixation of the hamstring tendons for anterior cruciate ligament reconstruction.

BACKGROUND: Press-fit fixation of patellar tendon-bone anterior cruciate ligament autografts is an interesting technique because no hardware is necessary. For hamstring tendon grafts, no biomechanical data exist of a press-fit procedure. HYPOTHESIS: Press-fit femoral fixation of hamstring tendons is mechanically equivalent to press-fit patellar tendon-bone fixation. STUDY DESIGN: Controlled laboratory study. METHODS: Patellar and hamstring tendons of 30 human cadavers (age, 53.8 +/- 18.0 years) were used. An outside-in press-fit fixation with a knot in the semitendinosus and gracilis tendons and an inside-out and outside-in fixation with the tendons wrapped around a bone block were compared with patellar tendon-bone press-fit fixation in 30 ovine femora. Constructs were cyclically strained and then loaded until failure. Maximum load to failure, stiffness, and elongation during failure testing and cyclical loading were investigated. RESULTS: The maximum load to failure was 561 +/- 309 N for the patellar tendon, 599 +/- 234 N for the semitendinosus/gracilis tendons knot construct, 678 +/- 231 for the semitendinosus/gracilis tendons bone construct inserted outside in, and 339 +/- 236 for the semitendinosus/gracilis tendons bone construct inserted inside out (inferior to the others; analysis of variance, Dunn test, P < .01). Stiffness of the constructs averaged 134 +/- 32 N/mm for the patellar tendon, 124 +/- 21 N/mm for the knot construct, 118 +/- 27 N/mm for the outside-in fixation, and 117 +/- 23 N/mm for inside-out fixation. Elongation during initial cyclical loading was 0.7 +/- 0.6 mm for the patellar tendon, 1.6 +/- 0.5 mm for the knot construct, 1.9 +/- 1.2 mm for the outside-in fixation, and 1.9 +/- 0.9 mm for the inside-out fixation (significantly larger for all semitendinosus/gracilis tendon techniques, P < .05). CONCLUSIONS: Failure loads for the semitendinosus/gracilis tendons bone construct inserted outside in and the semitendinosus/ gracilis tendons knot construct were within the confidence interval of the patellar tendon press-fit fixation. All semitendinosus/ gracilis tendon graft techniques exhibited larger elongation during initial cyclical loading than the patellar tendon graft. There was no difference in stiffness between all techniques. CLINICAL RELEVANCE: Two of the 3 hamstring press-fit fixation techniques showed loads to failure similar to the patellar tendon fixation. Preconditioning of the constructs is critical. These results must be interpreted with care because of high standard deviations.

Adolescent↗