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Biomedical subjects

Christian Gerber

Publications and source records attributed to Christian Gerber.

At least 37 records · Page 2Linked to original sources
PubMed2004

Glenoid version and rotator cuff tears.

The purpose of this study was to determine the relationship between rotator cuff (RC) tear and the orientation of the glenoid. Ninety-six shoulders (94 patients) that underwent open RC repair were grouped according to the type of tear. We measured on MRI the acromio-glenoid angle (AG) and the supraspinatus fossa glenoid angle on the anterior-posterior (SGAP) and axial (SGAX) views. RC patients had a smaller AG angle (76+/-7 degrees vs. 86+/-10 degrees ) and a larger SGAP angle (112+/-6 degrees vs. 102+/-7 degrees ) compared to controls (p<0.001). We also found a highly significant difference (p<0.001) in glenoid version measured by SGAX between anterior cuff tears (-5+/-4 degrees ) and posterior cuff tears (3+/-3 degrees ). Furthermore, we identified an association between RC tear and the orientation of the glenoid relative to the axis of the supraspinatus fossa. Greater retroversion is predictive of an anterior cuff injury and greater anteversion is predictive of a posterior cuff injury.

Humans↗
PubMed2004

The effect of capsular tightening on humeral head translations.

UNLABELLED: Idiopathic or surgical tightening of the glenohumeral joint capsule may cause displacement of the humeral head relative to the glenoid fossa and favor the development of instability and/or osteoarthritis. In the present investigation the relative position of the humerus to the glenoid fossa was determined at the end of the ranges of eight different passive movements before and after selective capsular plication in eight cadaveric shoulders to study the effects of selective capsular plications on the kinematics of the shoulder. While the capsule was in its unaltered state, translation of the humeral head was 3.8 mm superiorly in abduction, 7.3 mm antero-superiorly in flexion. In internal rotation in 0 degrees, 45 degrees and 90 degrees of abduction the head moved 6.1, 8.0 and 12.0 mm antero-inferiorly. In external rotation at 0 degrees of abduction the translation was 0.9 mm antero-inferiorly, at 45 degrees and 90 degrees of abduction it was 4.3 and 5.6 mm postero-inferiorly, respectively. Plications of the anterior part of the capsule reproducibly and significantly either increased or decreased translations during flexion (up to 5.9 mm anteriorly and up to 3.8 mm inferiorly), external rotation (up to 2.9 mm posteriorly and 1 mm inferiorly) and internal rotation (from 5.5 mm posteriorly to 2 mm anteriorly and up to 2.2 mm superiorly). Posterior plications had only little effect on translations (mainly a decrease of anterior translation during flexion of 2.8 mm). CLINICAL RELEVANCE: The 'obligate' glenohumeral translations which occur towards the end of passive shoulder movements are altered in a reproducible fashion by tightening specific parts of the glenohumeral joint capsule, as often carried out in treatment of shoulder instability. These alterations of the kinematics of the glenohumeral joint may be relevant for the development of static subluxation and osteoarthitis as seen after too tight plication in the treatment of instability [Int. Orthop. (SICOT) 67-B (1985) 709; J. Bone Joint Surg. Am. 72 (1990) 1193; J. Bone Joint Surg. Am. 66-A (1984) 169; J. Bone Joint Surg. Am. 65 (1983) 456].

Humans↗
PubMed2004

Assessment of fat content in supraspinatus muscle with proton MR spectroscopy in asymptomatic volunteers and patients with supraspinatus tendon lesions.

PURPOSE: To evaluate proton magnetic resonance (MR) spectroscopy in the assessment of lipid content of the supraspinatus muscle in asymptomatic volunteers and patients with supraspinatus tendon lesions. MATERIALS AND METHODS: Single-voxel proton MR spectroscopy was used to assess lipid content of the supraspinatus muscle in asymptomatic volunteers (n = 30) and patients with partial-thickness supraspinatus tendon tears (n = 30), newly diagnosed full-thickness supraspinatus tendon tears (n = 30), and chronic full-thickness supraspinatus tendon tears (n = 30). The apparent lipid content of the supraspinatus muscle measured with proton MR spectroscopy was related to its appearance on sagittal-oblique T1-weighted spin-echo MR images (grades 0-4). One-way analysis of variance was performed to test for significant differences, and the Tukey honestly significant difference procedure was performed for post hoc comparisons. RESULTS: Mean apparent lipid content was 13.7% (95% confidence interval [CI]: 11.5%, 15.8%) for asymptomatic volunteers, 29.5% (95% CI: 25.1%, 34.0%) for patients with partial-thickness tears, 48.6% (95% CI: 41.3%, 55.9%) for patients with full-thickness tears, and 66.1% (95% CI: 57.7%, 74.5%) for patients with chronic tears. Values were significantly different (analysis of variance, P <.001; P <.001-.002 for all post hoc pairwise comparisons). Mean apparent lipid content for the supraspinatus muscle was as follows: grade 0, 19.6% (95% CI: 16.7%, 22.6%); grade 1, 36.8% (95% CI: 33.2%, 40.4%); grade 2, 53.6% (95% CI: 43.1%, 64.2%); grade 3, 67.5% (95% CI: 52.6%, 82.3%); and grade 4, 79.2% (95% CI: 73.2%, 85.3%). With analysis of variance (P <.001), all post hoc pairwise comparisons were significant (P </=.001) except between grades 2 and 3 (P =.112) and between grades 3 and 4 (P =.261). In 14 (25%) subjects who had grade 0 appearance on T1-weighted images, lipid content values were greater than the upper range of values in the volunteers. CONCLUSION: Proton MR spectroscopy is suitable in the assessment of apparent lipid content of rotator cuff muscles.

Adult↗
PubMed2004

Influence of humeral prosthesis height on biomechanics of glenohumeral abduction. An in vitro study.

BACKGROUND: During shoulder replacement surgery, the normal height of the proximal part of the humerus relative to the tuberosities frequently is not restored because of differences in prosthetic geometry or problems with surgical technique. The purpose of the present study was to determine the effect of humeral prosthesis height on range of motion and on the moment arms of the rotator cuff muscles during glenohumeral abduction. METHODS: Tendon excursions and abduction angles were recorded simultaneously in six cadaveric specimens during passive glenohumeral abduction in the scapular plane. Moment arms were calculated for each muscle by computing the slope of the tendon excursion-versus-glenohumeral abduction angle relationship. The experiments were carried out with the intact joint and after replacement of the humeral head with a prosthesis that was inserted in an anatomically correct position as well as 5 and 10 mm too high. RESULTS: Insertion of the prosthesis in positions that were 5 and 10 mm too high resulted in significant and marked reductions of the maximum abduction angle of 10 degrees (range, 5 degrees to 18 degrees ) and 16 degrees (range, 12 degrees to 20 degrees ), respectively. In addition, the moment arms of the infraspinatus and subscapularis decreased by 4 to 10 mm. This corresponded to a 20% to 50% decrease of the abduction moment arms of the infraspinatus and an approximately 50% to 100% decrease of the abduction moment arms of the subscapularis, depending on the abduction angle and the part of the muscle being considered. CONCLUSIONS: If a humeral head prosthesis is placed too high relative to the tuberosities, shoulder function is impaired by two potential mechanisms: (1) the inferior capsule becomes tight at lower abduction angles and limits abduction, and (2) the center of rotation is displaced upward in relation to the line of action of the rotator cuff muscles, resulting in smaller moment arms and decreased abduction moments of the respective muscles. CLINICAL RELEVANCE: In patients managed with shoulder replacement surgery, limitation of range of motion, loss of abduction strength, and overload with long-term failure of the supraspinatus tendon are potential consequences of positioning the humeral head of the prosthesis proximal to the anatomic position.

Analysis of Variance↗
PubMed2003

Mechanical testing of absorbable suture anchors.

PURPOSE: Absorbable suture anchors offer great advantages but are made of mechanically weak material. The weakest link in the fixation of soft tissue to bone may therefore be the anchor itself. In this study, several commercially available anchors were mechanically tested in vitro. TYPE OF STUDY: Biomechanical bench study. METHODS: Twelve absorbable suture anchor models were implanted into an artificial test bone according to the recommended technique. Testing temperature was 37 degrees C +/- 1 degrees C. The anchors were loaded with an Instron testing machine with the suture material (USP No. 2, Ethibond, Ethicon, Somerville, NJ) in line with the anchor axis, with and without previous abrasion of the suture at the eyelet. Tensile load at failure and failure mode were recorded. To test creep behavior, a permanent load of 100 N was applied to the anchors, and time to failure was recorded. Suture anchor weight and crystallinity were analyzed. RESULTS: Mean failure load on tensile testing using a cross-head speed of 60 mm/min ranged from 124 to 244 N. Failure modes were eyelet failure in 5 cases, suture failure in 6 cases, and anchor pullout in 1 case. In creep testing, eyelet failure occurred in 8 anchor models after a mean duration of 0.5 to 99 hours; 3 anchor models remained intact after 300 hours, and 1 anchor model failed by pullout of the test sample. Crystallinity ranged from 0% (amorphous) to 57.2%; anchor weight ranged from 0.036 to 0.161 g. Mechanical properties did not correlate with crystallinity but with anchor weight. Abrasion of the suture material at the eyelet had little effect on failure load. CONCLUSIONS: At 37 degrees C, structural failure (breaking) of absorbable suture anchors may occur if loaded to the mechanical limit. Absorbable anchors are particularly sensitive to static, long-term loading.

Absorbable Implants↗
PubMed2003

Outcome of pectoralis major transfer for the treatment of irreparable subscapularis tears.

BACKGROUND: Chronic tears of the subscapularis tendon with or without associated tears of the supraspinatus and infraspinatus tendons may lead to pain and dysfunction of the shoulder. If conservative treatment fails and repair of the musculotendinous unit is impossible, transfer of the pectoralis major tendon can be attempted to substitute for lost subscapularis function. METHODS: Twenty-eight patients underwent a total of thirty consecutive pectoralis major transfers at an average age of fifty-three years. There were twelve isolated subscapularis tears and eighteen subscapularis tears associated with a tear of the supraspinatus or the supraspinatus and infraspinatus. All patients were examined clinically and with standard radiographs. RESULTS: The mean relative Constant score increased from 47% preoperatively to 70% at an average of thirty-two months postoperatively (p < 0.0001). The mean Constant scores for pain (p = 0.0009) and activities of daily living (p < 0.0001), the range of forward flexion (p < 0.05), and abduction strength (p = 0.001) also improved. Thirteen patients (14 shoulders) were very satisfied, ten patients (eleven shoulders) were satisfied, two patients (two shoulders) were disappointed, and three patients (three shoulders) were dissatisfied with the result. The average subjective shoulder value increased from 23% preoperatively to 55% postoperatively (p = 0.0009). In patients with a massive tear, the outcome was less favorable when the torn supraspinatus tendon was irreparable, as determined preoperatively or intraoperatively, than when it was reparable (average relative Constant scores, 49% and 79%, respectively; p = 0.002). CONCLUSIONS: Pectoralis major transfer results in improvement for patients with an irreparable subscapularis tear with or without an associated reparable supraspinatus tear. If an irreparable subscapularis tear is associated with an irreparable supraspinatus tear, the results are less favorable, and pectoralis major transfer may not be warranted.

Adult↗
PubMed2002

Classification of glenohumeral joint instability.

Shoulder instabilities have been classified according to the etiology, the direction of instability, or on combinations thereof. The current authors describe a classification system, which distinguishes between static instabilities, dynamic instabilities, and voluntary dislocation. Static instabilities are defined by the absence of classic symptoms of instability and are associated with rotator cuff or degenerative joint disease. The diagnosis is radiologic, not clinical. Dynamic instabilities are initiated by a trauma and may be associated with capsulolabral lesions, defined glenoid rim lesions, or with hyperlaxity. They may be unidirectional or multidirectional. Voluntary dislocation is classified separately because dislocations do not occur inadvertently but under voluntary control of the patient.

Chronic Disease↗
PubMed2002

Evaluation of complex joint motion with computer-based analysis of fluoroscopic sequences.

RATIONALE AND OBJECTIVES: To develop a computer-assisted analysis of complex joint motion based on standard fluoroscopic sequences. MATERIALS AND METHODS: Fluoroscopic sequences of 10 normal shoulders and 20 patients after total shoulder arthroplasty were recorded during abduction and adduction. The analysis of the shoulder motion was based on automated tracking of selected components (models) of the shoulder joint. After processing the digitized images with an edge-detection procedure, visible edges were defined as base models. These models were tracked frame by frame. Several automated postprocessing evaluation procedures were developed and tested. RESULTS: The amounts of rotation and translation of the glenohumeral joint can be quantified and related. The mean translation parallel to the glenoid in the normal shoulder joints was 2.8 mm and 1.9 mm in joints after shoulder arthroplasty. The mean translation perpendicular to the glenoid was 0.9 mm and 0.8 mm, respectively. In complex motion patterns (ie, combined glenohumeral and thoracoscapular motion), electronic stabilization of an object (ie, stabilization of scapula) and, thus, separate analysis of each component. CONCLUSION: Computer assisted analysis allows automated evaluation of complex joint motion based on standard fluoroscopic sequences.

Algorithms↗
PubMed2002

Mechanical strength of arthroscopic rotator cuff repair techniques: an in vitro study.

BACKGROUND: Retears after rotator cuff repairs occur relatively frequently and may compromise the functional result. The goal of this study was to analyze the mechanical properties following arthroscopic techniques for rotator cuff repair and to evaluate possible alternative techniques. METHODS: In the first part, five different bone anchors (the Revo screw; Mitek Rotator Cuff anchor, 5.0-mm Statak, PANALOK RC absorbable anchor, and 5.0-mm Bio-Statak) were tested in vitro under cyclic loading on five pairs of cadaveric shoulders. Then five types of arthroscopic tendon suturing instruments were tested on rotator cuff tendons. Finally, the arthroscopically performed mattress and modified Mason-Allen stitches, fixed with either the Revo screw or the Bio-Statak, were evaluated on ten pairs of human cadaveric shoulders. RESULTS: The holding strengths of the various anchors were similar, ranging from 130 to 180 N, and approximated the holding strength of knotted number-2 suture materials. The fixation of the tested anchors yielded comparable values of stiffness except for one anchor, which showed significantly greater subsidence under cyclic load (p = 0.003). All tested, commercially available arthroscopic suturing devices were unsuitable for performing a modified Mason-Allen stitch on normal supraspinatus tendons. Modification of a commercially available suture punch with a longer needle allowed us to consistently perform a modified Mason-Allen stitch. The modified Mason-Allen stitch, which has shown favorable mechanical properties in open repairs of the rotator cuff, was not found to be stronger than the mattress stitch when performed arthroscopically and used with bone anchors. When the modified Mason-Allen stitch was fixed to one anchor, it was even weaker than a mattress stitch repaired with another anchor (168 versus 228 N). Unequal loading of the two suture branches due to the more rigid modified Mason-Allen stitch may be the reason for this difference. CONCLUSIONS: Arthroscopic techniques for rotator cuff repair with use of the mattress stitch and bone anchors allow for a relatively solid fixation. The holding strength is not improved with use of the modified Mason-Allen stitch. Although a direct comparison with previous in vitro studies is not possible, the holding strength of open fixation techniques seems to be stronger. If rotator cuffs are subjected to high postoperative loading, open repair might be preferred to reduce the risk of a retear, until stronger arthroscopic fixation techniques are developed.

Arthroscopy↗
PubMedDate not supplied

Association of osteopenia of the humeral head with full-thickness rotator cuff tears.

Rotator cuff tendon repair may fail for various reasons. Although the role of repair techniques and of the musculotendinous unit has been studied, there is little information on the quality of the bone to which the tendon is to be repaired. Therefore, 14 cadaveric humeral heads, 7 specimens without and 7 with a full-thickness rotator cuff tendon tear, were quantitatively assessed by use of high-resolution micro-computed tomography. Bone density is higher below the articular surface than in the greater tuberosity (40% vs 10%-20%), and tendon tears are associated with a reduction in cancellous bone density of greater than 50%, leading to a virtually hollow greater tuberosity, with intact cortical bone. The results found suggest that in long-standing rotator cuff tears, creating a deep trough should be avoided to achieve reliable tendon-to-bone contact. For optimal suture fixation to bone, sutures or anchors should be positioned subcortically or medially under the articular surface.

Aged↗
PubMedDate not supplied

Functional analysis of shoulder arthrodesis.

The goal of this study was to determine the optimal position of shoulder arthrodesis for functional outcome and pain. Twenty patients who had undergone shoulder arthrodesis were interviewed and examined clinically and with standard radiographs. In addition, computed tomography (CT) scans were used to determine the exact position of the humerus relative to the scapula in all three planes. The average position observed was 14 degrees of flexion (humerus to longitudinal body axis), 55 degrees of abduction (humerus to lateral scapular border), and 23 degrees of internal rotation (forearm to sagittal body plane). Clinical evaluation showed functional advantages for tasks above waist level with increasing flexion but at the cost of more pain. Increasing abduction improved upper limb function above waist level but compromised complex movements below waist level. Higher degrees of abduction tended to improve the result expressed by the overall score and furnished better pain relief. Higher degrees of internal rotation resulted in improved function below waist level but also in more pain. Our results show that there is no single optimal position but suggest that a clinically estimated position of 15 degrees to 30 degrees of flexion, 35 degrees to 45 degrees of abduction, and 30 degrees to 40 degrees of internal rotation is desirable. This corresponds to CT-measured angles of 15 degrees to 30 degrees for flexion, 55 degrees to 65 degrees for abduction, and 0 degrees of internal rotation (humeral epicondylar axis to scapular plane).

Adult↗
PubMedDate not supplied

The Constant score in normal shoulders.

Relative Constant-Murley shoulder scores are based on an age- and sex-matched normal population from Constant's original research. The purpose of this study was to determine normal Constant scores in a contemporary population and compare these values with those originally established by Constant. Two subject groups were analyzed. The first group comprised 1620 clinic patients whose normal shoulders were scored by resident physicians instructed on the Constant scoring technique. The second group comprised 115 healthy volunteers whose normal shoulders were scored by 1 experienced physician-researcher. There were no significant score differences between the two groups, indicating that, after instruction, scoring did not depend on tester experience. In both groups, there were significant score differences between sex and age groups. Similar to Constant's study, age-related declines in scores and strength existed for both sexes but were less pronounced. Using Constant's original values to calculate relative scores can overestimate shoulder function in women aged over 40 years and men aged over 60 years. If relative Constant scores are used, absolute scores should be concurrently reported to allow comparisons with different populations.

Adolescent↗
PubMedDate not supplied

Biomechanical relevance of glenoid component positioning in the reverse Delta III total shoulder prosthesis.

The presence of a notch at the inferior part of the scapular neck is a common radiographic finding in patients treated with a reverse Delta III shoulder prosthesis. It is thought that this notch is a result of mechanical contact between the polyethylene cup of the humeral implant and the inferior glenoid pole during adduction of the arm. This in vitro study assessed the effect of glenoid component positioning on glenohumeral range of motion in 8 shoulder specimens. Four different positions of the glenosphere were tested: glenosphere centered on the glenoid, leaving the inferior glenoid rim uncovered (configuration A); glenosphere flush with the inferior glenoid rim (configuration B); glenosphere extending beyond the inferior glenoid rim (configuration C); and glenosphere tilted downward 15 degrees (configuration D). The respective mean adduction and abduction angles in the scapular plane were -25 degrees and 67 degrees for configuration A, -14 degrees and 68 degrees for configuration B, -1 degrees and 81 degrees for configuration C, and -9 degrees and 75 degrees for configuration D. Placing the glenosphere distally (test configuration C) significantly improved adduction and abduction angles compared with all other test configurations (P < .001).

Biomechanical Phenomena↗
PubMedDate not supplied

The effect of cementing technique on structural fixation of pegged glenoid components in total shoulder arthroplasty.

Although loosening of cemented glenoid components is one of the major complications of total shoulder arthroplasty, there is little information about factors affecting initial fixation of these components in the scapular neck. This study was performed to assess the characteristics of structural fixation of pegged glenoid components, if inserted with two different recommended cementing techniques. Six fresh-frozen shoulder specimens and two types of glenoid components were used. The glenoids were prepared according to the instructions and with the instrumentation of the manufacturer. In 3 specimens, the bone cement was inserted into the peg receiving holes (n = 12) and applied to the back surface of the glenoid component with a syringe. In the other 3 specimens, the cement was inserted into the holes (n = 15) by use of pure finger pressure: no cement was applied on the backside of the component. Micro-computed tomography scans with a resolution of 36 microm showed an intact cement mantle around all 12 pegs (100%) when a syringe was used. An incomplete cement plug was found in 7 of 15 pegs (47%) when the finger-pressure technique was used. Cement penetration into the cancellous bone was deeper in osteopenic bone. Application of bone cement on the backside of the glenoid prosthesis improved seating by filling out small spaces between bone and polyethylene resulting from irregularities after reaming or local cement extrusion from a drill hole. The fixation of a pegged glenoid component is better if the holes are filled with cement under pressure by use of a syringe and if cement is applied to the back of the glenoid component than if cement is inserted with pure finger pressure and no cement is applied to the back surface of the component.

Arthroplasty, Replacement↗
PubMedDate not supplied

Subacromial pressures in vivo and effects of selective experimental suprascapular nerve block.

Subacromial impingement has been related to increased subacromial pressures. High subacromial pressures may, therefore, have a negative effect on tendon healing after rotator cuff repair, but avoidance of high pressures during healing is only possible if pressures in different positions of the arm are known. The purpose of this study was to determine the subacromial pressures for different positions of active shoulder movement and to determine the effects of supraspinatus and infraspinatus failure on subacromial pressures, as it is currently held that rotator cuff weakness might increase subacromial pressures. Subacromial pressures were statistically significantly altered by arm position (P = .001). There was an increase in pressure from 17.5 mm Hg at rest up to more than 60 mm Hg during abduction and flexion. Subacromial pressure decreased in external rotation and increased in internal rotation. Generally, patients with strong external rotation (arm at the side) had lower subacromial pressures. Conversely, paralysis of the supraspinatus or infraspinatus muscles had no statistically significant effect on subacromial pressures at rest or during active movements of the shoulder. High subacromial pressures can be prevented by avoiding active abduction, flexion, and internal rotation of the arm. External rotation does not need to be limited to reduce subacromial pressure.

Humans↗
PubMedDate not supplied

Effects of glenoid component version on humeral head displacement and joint reaction forces: an experimental study.

The purpose of this study was to determine whether changes in glenoid version are associated with humeral head displacement and changes in the joint reaction forces, as these might contribute to instability or loosening in total shoulder replacement. A total shoulder prosthesis was implanted in neutral version in 6 cadaveric shoulders. Glenoid version was then changed in steps of 4 degrees toward more anteversion and retroversion. An increase in anteversion resulted in anterior translation of the humeral head and in eccentric loading of the anterior part of the glenoid. Retroversion was associated with posterior displacement and posterior loading of the glenoid. A change in rotation of the humeral component did not compensate for altered version of the glenoid component. These results suggest that both instability and glenoid component loosening may be related to the version of the glenoid component. Therefore, assessment of loosening and instability justifies precise assessment of glenoid component version.

Arthroplasty, Replacement↗
PubMedDate not supplied

The biomechanical role of the subscapularis in latissimus dorsi transfer for the treatment of irreparable rotator cuff tears.

Inferior functional results of latissimus tendon transfer for the treatment of irreparable rotator cuff tears have been reported in the presence of a subscapularis tendon tear. A biomechanical or experimental explanation for the necessity of an intact subscapularis is unavailable. It was, therefore, the purpose of this investigation to study the biomechanical role of the subscapularis in the treatment of a posterosuperior rotator cuff tear with latissimus dorsi transfer. A biomechanical cadaveric model was developed to reproduce glenohumeral motion patterns created by loading of the transferred latissimus dorsi tendon with and without simultaneous action of the subscapularis muscle. Significant differences could be demonstrated not only for translation but also for rotation of the humeral head depending on subscapularis action. In the neutral and in the abducted/externally rotated position of the arm, anterior translation and dislocation of the joint were encountered without subscapularis action. Our results provide evidence that motion patterns of the humeral head are significantly altered in the absence of the stabilizing effect of the subscapularis muscle. The inferior functional results of latissimus dorsi transfer in the presence of subscapularis dysfunction are explained by the loss of centering of the humeral head upon abduction and elevation if subscapularis function is deficient.

Aged↗