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Biomedical subjects

H U Stäubli

Publications and source records attributed to H U Stäubli.

At least 19 recordsLinked to original sources
PubMed2001

Design and evaluation of a cryogenic soft tissue fixation device -- load tolerances and thermal aspects.

Mechanical studies of soft connective tissues often encounter methodological difficulties, particularly in the secure fixation of the tissues. A simple, inexpensive technique which allowed stable cryofixation of soft tissues in uniaxial loading machines was developed. The cryogenic fixation device was evaluated in terms of its fixation strength and the temperature gradients within the tested tissues. Human patellar ligaments and quadriceps tendons were tested successfully to an average failure load of 2219N (S.D. 448N) with mid-substance failures occurring in 90% of the specimens. The temperature gradients within porcine flexor and extensor tendons were determined and found to exhibit a typical diffusion profile. The fixation quality was dependent upon the initial block temperature and the desired testing time. In summary, the cryofixation device presented here is an effective tool for soft tissue fixation but the effect of this type of fixation on internal tissue temperatures and possible testing times must be acknowledged.

Adult↗
PubMed2000

The point of view of the clinician: a prospective study of the mechanism of accidents and the morphology of tibial and fibular shaft fractures.

In a prospective study of 210 tibial shaft fractures, the accident mechanisms and the resultant fracture morphologies were analyzed. 86 fractures occurred due to indirect impact. The fracture morphology in this group consisted of short and long spiral fractures resulting from rotational injuries complicated by anterior torsion butterfly fragments if the person fell forward, posterior torsion butterfly fragments if they fell backwards and complicated by multiple torsion butterfly fragments if it was a high velocity injury. 124 fractures occurred due to direct impact. The fracture morphology in this group consisted of transverse, oblique segmental or crush fractures, complicated by one or more butterfly fragments due to bending, the injury depending on whether it was pure, one-point, three-point, or four-point-bending and on additional axial loading and velocity. In the indirect impact group, there were a few soft tissue injuries and fibular fractures at a different level to the tibial fracture. In the direct group, a large number of soft tissue injuries and fibular fractures at the level of impact were found.

Accidents↗
PubMed1999

Anatomy and surface geometry of the patellofemoral joint in the axial plane.

We studied the anatomy of the patellofemoral joint in the axial plane on cryosections from a cadaver knee and on MR arthrotomograms from 30 patients. The cryosections revealed differences in the geometry and anatomy of the surface of the articular cartilage and corresponding subchondral osseous contours of the patellofemoral joint. On the MR arthrotomograms the surface geometry of the cartilage matched the osseous contour of the patella in only four of the 30 knees. The articular cartilaginous surface of the intercondylar sulcus and corresponding osseous contour of the femoral trochlea matched in only seven knees. Since MR arthrotomography can distinguish between the surface geometry of the articular cartilage and subchondral osseous anatomy of the patellofemoral joint, it allows the surgeon and the radiologist to appraise the true articulating surfaces. We therefore recommend MR arthrotomography as the imaging technique of choice.

Adult↗
PubMed1998

Effect of cyclic preconditioning on the tensile properties of human quadriceps tendons and patellar ligaments.

Preconditioning of soft tissues has become a common procedure in tensile testing to assess the history dependence of these viscoelastic materials. To our knowledge, this is the first study comparing tensile properties of soft tissues-before and after cyclic preconditioning with high loads. Sixteen quadriceps tendon-bone (QT-B) complexes and 16 patellar ligament-bone (PL-B) complexes from a young population (mean age 24.9 +/- 4.4 years) were loaded to failure with a deformation rate of 1 mm/s. Half of the QT-B and the PL-B complexes underwent 200 uniaxial preconditioning cycles from 75 to 800 N at 0.5 Hz before ultimate failure loading. High-load preconditioning was made possible by the development of a highly reliable and easy-to-use cryofixation device to attach the free tendon end. PL-B complexes were more influenced by preconditioning than the QT-B complexes. Ultimate failure load, stiffness at 200 N and stiffness at 800 N were significantly higher for PL-B complexes after preconditioning, while the structural properties of QT-B complexes exhibited no significant alterations. The values of the mechanical properties like Young's modulus at 200 N and 800 N were much higher for both preconditioned specimen groups. In addition, ultimate stress was augmented by preconditioning for PL-B complexes. Hysteresis and creep effects were highest during the first few loading cycles. More than 160 cycles were needed to reach a steady state. Beyond 160 cycles there was no further creep, and hysteresis was almost constant. Creep values were 2.2% of the initial testing length for the QT-B and 3.2% of the initial testing length for the PL-B complexes. The effect of cyclic preconditioning seems to be caused by progressive fiber recruitment and by alterations of the interstitial fluid milieu.

Anterior Cruciate Ligament↗
PubMed1996

Quadriceps tendon and patellar ligament: cryosectional anatomy and structural properties in young adults.

Structural tensile properties analyses of 10-mm-wide central sections of quadriceps tendon-bone (QT-B) and bone-patellar ligament (B-PL) complexes from young male donors (mean age 24.9 years, range 19-32 years) were complemented by a cryosectional analysis: each QT-B complex was composed of the segment of the quadriceps tendon with the proximal half of the patella attached, each B-PL complex was composed of the distal half of the patella with the patellar ligament attached. A servohydraulic materials testing machine was used to assess ultimate failure load of 16 unconditioned and 16 preconditioned QT-B and B-PL complexes at an extension rate of 1 mm/s. Ligaments/tendons were preconditioned during 200 cycles from 50 to 800 N at 0.5 Hz. On cryosections the quadriceps tendons were significantly longer and thicker and exhibited a significantly larger bony attachment area than the patellar ligaments. Cross-sectional areas of 10-mm-wide, full-thickness, central parts of unconditioned quadriceps tendons were significantly greater and measured 64.6 +/- 8.4 mm2 with respect to the cross-sectional area of patellar ligaments, measuring 36.8 +/- 5.7 mm2 (P < 0.0025). Ultimate failure loads for unconditioned complexes resulted at 2173 +/- 618 N for QT-B complexes and at 1953 +/- 325 N for B-PL complexes (P = 0.43). Ultimate failure load values measured 2353 +/- 495 N for preconditioned QT-B complexes and 2376 +/- 152 N for preconditioned B-PL complexes, respectively (P = 0.77). Despite the fact that initial testing length, thickness, cross-sectional shape and area of unconditioned QT-B and B-PL complexes were significantly different, displacement at ultimate load, energy to failure and total energy were not. In terms of ultimate tensile strength, the 10-mm-wide central part of the QT-B complex compared favourably to the tensile properties of the human femur-anterior cruciate ligament-tibia complex from a comparable young age group. The evidence from anatomic, cryosectional and structural properties analyses suggests that the QT-B complex may be a valuable and versatile adjunct to the surgeon's armamentarium in reconstructive cruciate ligament surgery.

Adult↗
PubMed1994

Tibial attachment area of the anterior cruciate ligament in the extended knee position. Anatomy and cryosections in vitro complemented by magnetic resonance arthrography in vivo.

Knowledge of the anatomy of the anterior cruciate ligament (ACL), including its course and orientation in relation to the roof of the intercondylar fossa, is a prerequisite for successful intra-articular ACL reconstruction. To attain precision placement of the tibial attachment site and to avoid graft/roof conflict in the extended knee position, we assessed the anteroposterior tibial insertion of the ACL in the midsagittal plane of the extended knee. We measured the anterior-posterior (AP) limits and the center of the tibial attachment area of the ACL from the anterior tibial margin. The inclination angle of the intercondylar fossa roof was measured with respect to the shaft axis of the femur. The tibial attachment area of the ACL was determined in ten cadaveric knees. Using the cryoplaning technique, we determined the tibial attachment of the ACL in five knees. Using contrast magnetic resonance arthrography (MRA), we measured the tibial insertion of the ACL in 35 patients (23 male and 12 female) with intact ACLs. The total AP midsagittal diameter of the tibia averaged 51.0 +/- 5.8 mm in the cadaveric knees, 49 mm on cryosections, and 53.7 mm in men and 49.0 mm in women with MRA. The average anterior limit of the ACL, measured from the anterior tibial margin, was 14 +/- 4.2 mm in the cadaveric knees, 12.1 mm at cryosectional anatomy, and 15.2 mm in men and 13.4 mm in women with MRA.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

[Knee injuries in alpine sports].

Knowledge of functional anatomy and cryo-sectional microanatomy are prerequisites for successful intra-articular arthroscopy, assisted ACL reconstruction in documented anterior subluxation of the tibia.

Anterior Cruciate Ligament↗
PubMed1993

Evaluation of knee ligament injuries with the IKDC form.

Various scoring systems have been proposed to quantify the disability caused by knee ligament injuries and to evaluate the results of treatment. None of these systems has found worldwide acceptance, mainly because all scoring systems attribute numerical values to factors that are not quantifiable, and then the arbitrary scores are added together for parameters not comparable with each other. For these reasons a group of knee surgeons from Europe and America met in 1987 and founded the International Knee Documentation Committee (IKDC). A common terminology and an evaluation form was created. This form is the standard form for all publications on results of treatment of knee ligament injuries. It is a concise one-page form. It includes a documentation section, a qualification section and a evaluation section. For evaluation there are four problem areas (subjective assessment, symptoms, range of motion and ligament examination). These are supplemented with four additional areas that are only documented but not included in the evaluation (compartmental findings, donor site pathology, X-ray findings and functional tests). The form can be used pre- and post-operatively and at follow-up. It has been specified that in any publication the minimum follow-up time for short-term results should be 2 years, for medium-term results 5 years and for long-term results 10 years. The largest part of the sheet is the qualification section. It is called "qualification" section rather than "scoring" section because no scores are given. Each parameter is qualified as "normal", "nearly normal", "abnormal" or "severely abnormal". This qualification is less subjective and emotional than "very good", "good", "fair" and "poor".(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation Studies as Topic↗
PubMed1990

The popliteus tendon and its fascicles at the popliteal hiatus: gross anatomy and functional arthroscopic evaluation with and without anterior cruciate ligament deficiency.

Gross anatomical dissection of the popliteus muscle, the popliteus tendon and its fascicles, and their relation to the lateral meniscus was carried out in 14 human adult cadaver knees. Videoarthroscopy through an anterolateral portal was then used to assess and document the functional integrity of the popliteus tendon and its fascicles forming the popliteal hiatus in vivo. A control group of cruciate ligament intact knees (n = 107) was compared with an anterior cruciate ligament (ACL)-deficient group (n = 68). The incidence of structural lesions of the popliteus system was 18.7% in the control knees, 95% in 40 acute ACL disruptions, and 85.7% in 28 chronic ACL-deficient knees. Functional arthroscopic evaluation of the popliteus tendon and its fascicles blending into the lateral meniscus was a valuable adjunct in assessing secondary posterolateral restraints in acute and chronic ACL-incompetent knees.

Adult↗
PubMed1990

Posterior instability of the knee near extension. A clinical and stress radiographic analysis of acute injuries of the posterior cruciate ligament.

We evaluated the accuracy of six clinical tests for posterior instability in 24 knees with acute surgically-proven posterior cruciate ligament injuries and intact anterior cruciate ligaments. We also performed stress radiography under anaesthesia. The gravity sign and the posterior drawer test in near extension and its passive reduction were diagnostic in 20 of the 24 knees, and the active reduction of posterior subluxation was diagnostic in 18. The reversed pivot shift sign helped to diagnose severe posterior and posterolateral subluxations, but the external rotation recurvatum test was negative in all 24 knees. Stress radiography in near extension revealed a highly significant increase in posterior tibial subluxation in the injured knees.

Acute Disease↗
PubMed1988

[Critical study of the repair of the anterior cruciate ligament of the knee using a pediculated flap to the Hoffa pad taken from the middle 3d of the patellar tendon. 50 surgical knees with a 2-to-4-year follow-up].

A reconstruction of the anterior cruciate ligament of the knee has been devised on the anatomical principle of an intra-articular flap taken from the middle third of the patellar tendon and based on the sub-patellar fat pad. Fifty knees have been treated and assessed after a follow-up of two to four years to provide a critical analysis of the method. The technique of the operation is described in detail in relation to the isometric reconstruction of the course of the anterior cruciate ligament. With a mean follow-up of 33 months (minimum 24 and maximum 48 months), 98 per cent of the patients had a good result as regards stability together with a good anatomical result, with complete or almost complete elimination of the anterior drawer sign and the jerk test in 96 per cent. The subjective result described by the patient was good in 92 per cent but only 54 per cent returned to the same sporting activity. The main problem encountered with this method was loss of 10 degrees of extension in 40 per cent of patients and loss of more than 10 degrees in 22 per cent. This loss of extension arose on the one hand from an impingement of the fatty pedicle in a narrow intercondylar notch and on the other from an associated postero-lateral laxity which resulted in an intra-articular transplant which was too short despite its anatomical attachments. The pedicled transplant has not given better results than free transplants and has given rise to additional iatrogenic problems even with a meticulous operative technique.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗
PubMed1988

OAK knee evaluation. A new way to assess knee ligament injuries.

The Orthopädische Arbeitsgruppe Knie (OAK) documentation is based on clinical evaluation during functional knee stability testing near extension and near flexion. Increased compartmental translations and rotations, which result from structural defects because of anatomic lesions in a given knee injury, are clinically evaluated. The synopsis of the clinically detectable abnormal knee motion is graphically documented. A clinically applicable grading system of the true and reversed pivot shift phenomena completes the assessment of compartmental knee instability. Important contributing factors such as the constitutional laxity, the morphotype, and the range of motion are registered on the documentation form. The evaluation form presents four categories that represent subjective, objective, and functional criteria reflecting the overall results of repaired ligaments. This evaluation format establishes selected criteria to compare results from different centers.

Documentation↗
PubMed1987

Grading the pivot shift. Objective tests with implications for treatment.

A logical, objective and reproducible grading system for the pivot shift test is proposed. The rationale is based on performing the examination in varying positions of rotation of the tibia, allowing the type and degree of the different laxities to be defined and quantified. The system has been assessed against a new "unblocked" test for anterior subluxation and against radiographic measurements, operative findings and results. This grading system can be valuable in pre-operative assessment and planning and its use in postoperative evaluation would enable results from different centres and different procedures to be compared more accurately.

Humans↗