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Biomedical subjects

A G Schneeberger

Publications and source records attributed to A G Schneeberger.

At least 19 recordsLinked to original sources
PubMed2004

Effect of tendon release and delayed repair on the structure of the muscles of the rotator cuff: an experimental study in sheep.

BACKGROUND: Ruptures of the tendons of the rotator cuff lead to profound and possibly irreversible changes in the structure and physiological properties of the rotator cuff muscles. Muscle atrophy and fatty infiltration are important prognostic factors that affect the natural history and outcome of treatment. The purpose of this study was to examine the amount of muscle atrophy and fatty infiltration in an animal model and to determine whether the repair of a long-standing tendon tear can reverse these changes. METHODS: The infraspinatus tendon in six sheep was released and encased in a silicone tube to prevent spontaneous healing. The musculotendinous unit was allowed to retract for forty weeks. Throughout this period, the muscular changes were studied with use of computed tomography, histological analysis, and electron microscopy. At forty weeks, the elasticity, intramuscular pressure, and perfusion were measured intraoperatively and a tendon repair was carried out. The structural changes of the muscle were studied for thirty-five weeks after the repair. The animals were then killed, and the musculotendinous units were examined macroscopically and by computed tomography, histological analysis, and electron microscopy. RESULTS: At the time of the tendon release, the infraspinatus showed no fatty changes. The force needed to cause a tendon excursion of 1 cm was a mean (and standard deviation) of 6.8 +/- 1 N. The application of tension on the tendon did not alter the perfusion and decreased the intramuscular pressure. After the tendon release, muscular atrophy developed and there was a significant increase (p < 0.001) in interfascicular and intrafascicular fat, representing fatty infiltration rather than fatty degeneration. Furthermore, there was an increase of interstitial connective tissue. At the time of the tendon repair, between forty and forty-two weeks after the release, there was a sevenfold poorer elasticity of the musculotendinous unit but preserved muscle perfusion. The structural changes increased six weeks after the repair and then recovered partially at twelve and thirty-five weeks thereafter but only to the amount demonstrated before the repair. CONCLUSIONS: Musculotendinous retraction induced by tendon release is associated with profound changes in the structure and function of the affected muscle. Vascularization, intramuscular pressure, and individual fiber composition are not markedly affected, and muscle fibers do not appear to degenerate. However, muscle atrophy, infiltration by fat cells, and an increase of interstitial connective tissue lead to impairment of the physiological properties of the muscle. These changes were irreversible under the conditions of this experiment with the repair technique used.

Adipose Tissue↗
PubMed2002

[Endoprosthesis implantation in the elbow joint].

Previously used total elbow prostheses were mainly constrained hinged implants. Their early clinical results were favourable but they failed due to a high rate of loosening already a few years after implantation. The cause for the early loosening was the great forces across the elbow joint which were directly transmitted to the prosthesis-bone interface in these implants. Therefore, these implants were abandoned. Afterwards, unlinked, semiconstrained or non-constrained resurfacing devices were introduced. In these devices, the soft tissues constrain the joint and therefore absorb part of the transmitted forces. The rates of loosening were significantly improved and rarely the cause of early failure. But resurfacing implants require intact condyles and collateral ligaments. These implants can, therefore, only be used in a limited number of indications, and postoperative instabilities are known complications. The currently most frequently used device is the semiconstrained Coonrad-Morrey prosthesis. It is a floppy hinge which allows valgus-varus and rotational laxities. Therefore, a part of the forces across the elbow joint are absorbed by the soft tissues. The loosening rate is not a clinical problem any more, and is with 4% 10 years after implantation (rheumatoid arthritis) similar to that of total hip or knee replacement. Furthermore, this device is stabilised with a small anterior flange to the anterior cortex of the humeral shaft. Condyles and collateral ligaments are therefore not necessary neither for short nor for long-term stability. The Coonrad-Morrey total elbow prosthesis can therefore be used for almost every indication, such as severe destruction of the elbow joint and even in case of complete loss of the distal humerus. The long-term outcome with this prosthesis for the treatment of rheumatoid arthritis is favourable with 96% of very good and good results. Function is restored with an average flexion of 131 degrees, a mean loss of extension of 28 degrees, and an unrestricted pronation and supination. The rate of complications for patients with rheumatoid arthritis is 10%. Similarly, the results for Coonrad-Morrey total elbow replacement for posttraumatic arthrosis are favourable with 83% of satisfactory results. Most patients consider their elbow as improved compared to preoperatively, but pain relief is obtained only in three quarters of the patients. The rate of complications is high with 30%, indicating the total elbow replacement is contraindicated for strenuous labour and sports activities.

Arthritis, Rheumatoid↗
PubMed2001

Edge deepithelialization: a method to prevent leakage when tubed free skin flap is used for pharyngoesophageal reconstruction.

BACKGROUND: Anastomosis leakage remains a major source of morbidity and mortality in patients who receive pharyngoesophageal reconstruction, especially when a free skin flap is used as the substitute. This makes free skin flaps less favored than other substitutes in pharyngoesophageal reconstruction. However, a free skin flap provides many advantages for pharyngoesophageal reconstruction and, in some circumstances, may be the only choice. To reduce the incidence of postoperative leakage, we developed a technical modification called edge-deepithelialization for skin flap to ensure a more secure anastomosis. METHODS: Twenty-four patients who received tubed free skin flaps for cervical esophagus or hypopharynx reconstruction during a 7-year period were included in this study. Group 1 (n = 12) received flap edge-deepithelialization before undergoing the anastomosis, and Group 2 (n = 12) received the conventional anastomosis method. Preoperative nutritional status was evaluated by serum albumin level. All the patients were followed up for at least 1 year (1 approximately 14 years; mean, 7.3 years). Postoperative leakage was detected by clinical symptoms and signs or by routine esophagography. RESULTS: Postoperative anastomosis leakage developed in 1 patient in Group 1 (8.3%) and 5 patients in Group 2 (41.67%). The difference in the leakage rate between these groups was of statistical significance (P =.0001). There were no significant differences in the preoperative serum albumin level noted between these 2 groups (t test, P >.05). Older age was not associated with a higher leakage rate. Among the 6 leakage cases, 1 was treated conservatively, and the other 5 needed an additional 1 to 5 procedures for the management of leakage. All the leakages were cured during the follow-up period. CONCLUSIONS: With the flap edge deepithelialized, a more secure and reliable anastomosis can be obtained. This makes the free skin flap an easier and safer alternative in pharyngoesophageal reconstruction, especially when laparotomy and enteric flaps are contraindicated.

Adult↗
PubMed1999

Experimental rotator cuff repair. A preliminary study.

BACKGROUND: The repair of chronic, massive rotator cuff tears is associated with a high rate of failure. Prospective studies comparing different repair techniques are difficult to design and carry out because of the many factors that influence structural and clinical outcomes. The objective of this study was to develop a suitable animal model for evaluation of the efficacy of different repair techniques for massive rotator cuff tears and to use this model to compare a new repair technique, tested in vitro, with the conventional technique. METHODS: We compared two techniques of rotator cuff repair in vivo using the left shoulders of forty-seven sheep. With the conventional technique, simple stitches were used and both suture ends were passed transosseously and tied over the greater tuberosity of the humerus. With the other technique, the modified Mason-Allen stitch was used and both suture ends were passed transosseously and tied over a cortical-bone-augmentation device. This device consisted of a poly(L/D-lactide) plate that was fifteen millimeters long, ten millimeters wide, and two millimeters thick. Number-3 braided polyester suture material was used in all of the experiments. RESULTS: In pilot studies (without prevention of full weight-bearing), most repairs failed regardless of the technique that was used. The simple stitch always failed by the suture pulling through the tendon or the bone; the suture material did not break or tear. The modified Mason-Allen stitch failed in only two of seventeen shoulders. In ten shoulders, the suture material failed even though the stitches were intact. Thus, we concluded that the modified Mason-Allen stitch is a more secure method of achieving suture purchase in the tendon. In eight of sixteen shoulders, the nonaugmented double transosseous bone-fixation technique failed by the suture pulling through the bone. The cortical-bone-augmentation technique never failed. In definite studies, prevention of full weight-bearing was achieved by fixation of a ten-centimeter-diameter ball under the hoof of the sheep. This led to healing in eight of ten shoulders repaired with the modified Mason-Allen stitch and cortical-bone augmentation. On histological analysis, both the simple-stitch and the modified Mason-Allen technique caused similar degrees of transient localized tissue damage. Mechanical pullout tests of repairs with the new technique showed a failure strength that was approximately 30 percent of that of an intact infraspinatus tendon at six weeks, 52 percent of that of an intact tendon at three months, and 81 percent of that of an intact tendon at six months. CONCLUSIONS: The repair technique with a modified Mason-Allen stitch with number-3 braided polyester suture material and cortical-bone augmentation was superior to the conventional repair technique. Use of the modified Mason-Allen stitch and the cortical-bone-augmentation device transferred the weakest point of the repair to the suture material rather than to the bone or the tendon. Failure to protect the rotator cuff post-operatively was associated with an exceedingly high rate of failure, even if optimum repair technique was used. CLINICAL RELEVANCE: Different techniques for rotator cuff repair substantially influence the rate of failure. A modified Mason-Allen stitch does not cause tendon necrosis, and use of this stitch with cortical-bone augmentation yields a repair that is biologically well tolerated and stronger in vivo than a repair with the conventional technique. Unprotected repairs, however, have an exceedingly high rate of failure even if optimum repair technique is used. Postoperative protection from tension overload, such as with an abduction splint, may be necessary for successful healing of massive rotator cuff tears.

Animals↗
PubMed1999

Anterior cervical interbody fusion with plate fixation for chronic spondylotic radiculopathy: a 2- to 8-year follow-up.

In retrospectively analyzing 35 consecutive patients with chronic spondylotic radiculopathy treated by nerve root decompression, interbody fusion (Robinson technique), and plating, we studied the perioperative complication rate as well as the long-term clinical and radiologic outcomes of an additional plate fixation in degenerative cervical disorders. After an average of 54 months (range 24-102 months), all cases were reviewed for the purpose of this study. There were no perioperative or postoperative complications related to the plate fixation. In particular, there was no infection, graft extrusion, or neurologic deterioration. A solid fusion was obtained in all cases with a single-level fusion and in 87% of the cases with a multilevel fusion. The overall fusion rate was 94%. The clinical outcome of the patients with chronic radiculopathy was comparable with that in the literature, with only three patients (8.6%) having a poor result. This study demonstrated that plate fixation can be a useful adjunct in patients undergoing interbody fusion for cervical spondylotic radiculopathy. Plate fixation seems to reduce the rate of nonunion without additional hazards for the patient. This report should form the basis for a prospective randomized trial to answer the question more conclusively of whether an additional plate fixation is superior to uninstrumented cervical fusion in degenerative disorders.

Adult↗
PubMed1998

Blood loss in total hip arthroplasty. Lateral position combined with preservation of the capsule versus supine position combined with capsulectomy.

The intraoperative blood loss of 40 uncomplicated primary total hip arthroplasties was studied in a retrospective, matched pair analysis. Half of them were implanted in the supine position after complete excision of the capsule and the other half in the lateral position with preservation of the capsule. The patients were matched for mono- or bilateral procedure. Only one surgeon carried out the operations using the same operative technique and identical prosthesis in both groups. The intraoperative blood loss associated with the lateral position and preservation of the capsule averaged 830 ml and was significantly lower (P = 0.01) than 1165 ml with the supine position and complete capsulectomy. Thus, the intraoperative blood loss can be significantly reduced in primary total hip arthroplasty by choosing the lateral position and preserving the capsule.

Adult↗
PubMed1998

Posterior interosseous flap and its variations for coverage of hand wounds.

BACKGROUND: Conventional posterior interosseous flap has the disadvantage of partial or even complete necrosis of the flap when there is anatomical variation or contusion around its distal pedicle. To make it a more reliable flap, three types of auxiliary procedures were designed. METHODS: (1) When there is congestion after inset of the distally based flap, an additional venous anastomosis was carried out. (2) When there is anatomical variation so that a distally based flap could not be raised without compromising the nerve branches, or when contusion was found around the distal pedicle, the flap was changed into a free flap. This design is also indicated for coverage of the distal fingers. (3) When the patient is elderly with possible peripheral arterial disease, the flap was raised with a wide base, incorporating the branches of both the anterior and posterior interosseous arteries. There were eight, 36, and five patients in each group, respectively. RESULTS: There was only one failure in the free flap group. No partial necrosis of the flap was found. Other complications were analyzed. CONCLUSION: With these backup procedures, the posterior interosseous flap can be more widely used with safety. By combining various reconstructive armaments, the result of a conventional procedure can be improved.

Adolescent↗
PubMed1998

[Classification and therapy of the unstable shoulder].

Instability of the shoulder can be classified as uni- or multidirectional with or without general hyperlaxity. Instability of a shoulder without hyperlaxity is often caused by a single traumatic event for the unidirectional instability and by two or several different events for the rarer multidirectional instability. The diagnosis of unidirectional instability is made with a positive apprehension test. For multidirectional instabilities, the anterior and posterior apprehension tests are positive. The treatment consists of surgical repair of the labrum-capsule complex for both the uni- and the multidirectional instabilities without hyperlaxity. For shoulders with a concomitant hyperlaxity, uni- or multidirectional instability is often caused by only minor trauma. Hyperlaxity itself is not a disease but represents a risk factor of instability. The typical feature of hyperlaxity is the positive "sulcus sign". Unidirectional instability with hyperlaxity is characterised by a positive apprehension test combined with a positive sulcus sign. Multidirectionally unstable shoulders with hyperlaxity have a positive anterior and posterior apprehension test as well as a positive sulcus sign. The unidirectional instability with hyperlaxity is best treated surgically whereas conservative treatment is recommended for the multidirectional instability with hyperlaxity. The voluntary instability without loss of control of position of the shoulder is not a real instability and has an excellent prognosis without treatment.

Chronic Disease↗
PubMed1997

[The trochanteric flip osteotomy.].

GOAL OF SURGERY: Easy access to the posterior, superior and anterior joint capsule through an osteotomy which reduces the risk of complications and the incidence of non-union. INDICATIONS: Hip joint revision with or without intertrochanteric osteotomy, periarticular ossifications, difficult total hip procedures, exchange procedures. CONTRAINDICATIONS: Absolute: None Relative: Distal transfer of the trochanter. PREOPERATIVE WORK UP: Radiographs in 2 planes (anterior-posterior pelvis+"false profile" hip). POSITIONING AND ANAESTHESIA: Lateral decubitus. General anaesthesia. SURGICAL TECHNIQUE: In lateral decubitus the greater trochanter will be osteotomized from posterior leaving a 1 to 1.5 cm thick bony wafer uniting the insertion of the gluteus medius and minimus with the origin of the vastus lateralis. The trochanteric crest remains untouched. After refixation with nonresorbable sutures #3 the fragment is not subjected to a unidirectional tension by the abductors which could interfere with the consolidation. POSTOPERATIVE MANAGEMENT: Bed rest with lower limb in neutral position. Mobilization with 2 canes on the 2nd postoperative day. The timing of partial weight bearing depends on the type of surgery. Abductor exercises after 6 weeks. POSSIBLE COMPLICATIONS: Bony wafer too thin or too thick. Inadequate refixation. Delayed consolidation. Cranial migration of the greater trochanter. RESULTS: Between 1991 and 1994 41 patients were operated. Diagnoses, see Table 1. Method of refixation: see Table 2. After 21+/-9 months 39 patients could be reexamined clinically, and radiological after 17+/-11 months: 38 osteotomies consolidated. Cranial migration varied between 0 and 8 mm. 25 patients were free of symptoms, 12 had slight and 2 moderate pain over the trochanter. Avulsion of wire cerclage: 2, foreign body irritation: 2 necessitating implant removal.

English Abstract↗
PubMed1997

Semiconstrained total elbow replacement for the treatment of post-traumatic osteoarthrosis.

Forty-one consecutive patients were managed for post-traumatic osteoarthrosis or dysfunction of the elbow with use of a non-customized semiconstrained Coonrad-Morrey total elbow prosthesis. The average age at the time of the operation was fifty-seven years (range, thirty-two to eighty-two years). The patients were followed for an average of five years and eight months (range, two to twelve years). Radiographs were made at least two years postoperatively (average, five years and one month; range, two to twelve years) for thirty-nine of the forty-one patients. According to the Mayo elbow performance score, sixteen patients (39 per cent) had an excellent result, eighteen (44 per cent) had a good result, five (12 per cent) had a fair result, and two (5 per cent) had a poor result. Thirty-six (95 per cent) of the thirty-eight patients who had a functioning implant at the time of follow-up considered the outcome to be satisfactory. Preoperatively, thirty-seven patients (90 per cent) had moderate or severe pain; postoperatively, thirty (73 per cent) had no or only mild discomfort. Motion improved from an average arc of flexion of 40 to 118 degrees preoperatively to an average arc of flexion of 27 to 131 degrees postoperatively. All thirty-eight functioning implants rendered the elbow stable. Eleven patients (27 per cent) had a major complication. Nine of them (22 per cent of the series) needed an additional operation. There was no aseptic loosening, and most of the complications were primarily due to so-called mechanical failure. The ulnar component fractured in five patients (12 per cent), and the polyethylene bushings wore out in two (5 per cent). These complications were attributed principally to the performance of strenuous physical labor, such as lifting more than ten kilograms on a regular basis, against the advice of the surgeon; excessive preoperative deformity of the joint; or an unstable traumatic injury. Two patients (5 per cent) had an infection. Semiconstrained joint replacement of the elbow can be a reliable form of treatment, and frequently is the only viable option, for the difficult problems encountered with post-traumatic destruction of a joint. Restoration of function, relief of pain, and patient satisfaction can be achieved even when a patient is less than sixty years old if that patient has low demands and a low level of activity. However, the mechanical failures underscore the fact that this procedure is relatively contraindicated in patients who anticipate strenuous physical activity or who are not expected to comply with the postoperative protocol. This observation reflects the tendency for increased and excessive use of a previously functionless joint, after it has been rendered stable and pain-free, to lead to mechanical failure.

Adult↗
PubMed1995

[In-vitro stability of rotator cuff repair techniques].

Rotator cuff repair techniques were examined in vitro. First, the mechanical properties of nine different tendon-grasping techniques were compared using 159 normal infraspinatus sheep tendons. The clinically most frequently used simple stitch and mattress suture failed at low-to-moderate loads (two stitches, 184 N and 269 N) with the sutures pulling out of the tendons. A modification of the Mason-Allen grasping technique improved the ultimate tensile strength to 359 N (two stitches) without allowing relevant gap formation. Augmentation with synthetic materials did not improve the mechanical properties of the tendon-grasping techniques tested. The mechanical properties of different anchoring techniques to bone were assessed using osteoporotic bone specimens with mechanical properties comparable to those of proximal humeri with long-standing cuff defects. Single as well as double transosseous suture fixation (139 N and 146 N) and suture anchor fixation (142 N) were weak. Tying the knots over a plate-like cortical bone augmentation device improved the failure strength to 329 N. Some of these data were presented in the English literature in 1994. Considering the excellent preliminary experience in the clinical application of the modified Mason-Allen grasping technique and cortical augmentation, it seemed appropriate to present them in German as well.

Animals↗
PubMed1994

Mechanical strength of repairs of the rotator cuff.

We have studied the mechanical properties of several current techniques of tendon-to-bone suture employed in rotator-cuff repair. Non-absorbable braided polyester and absorbable polyglactin and polyglycolic acid sutures best combined ultimate tensile strength and stiffness. Polyglyconate and polydioxanone sutures failed only at high loads, but elongated considerably under moderate loads. We then compared the mechanical properties of nine different techniques of tendon grasping, using 159 normal infraspinatus tendons from sheep. The most commonly used simple stitch was mechanically poor: repairs with two or four such stitches failed at 184 N and 208 N respectively. A new modification of the Mason-Allen suture technique improved the ultimate tensile strength to 359 N for two stitches. Finally, we studied the mechanical properties of several methods of anchorage to bone using typically osteoporotic specimens. Single and even double transosseous sutures and suture anchor fixation both failed at low tensile loads (about 140 N). The use of a 2 mm thick, plate-like augmentation device improved the failure strength to 329 N. The mechanical properties of many current repair techniques are poor and can be greatly improved by using good materials, an improved tendon-grasping suture, and augmentation at the bone attachment.

Animals↗
PubMed1990

The arterial vascularization of the humeral head. An anatomical study.

In twenty-nine specimens from fresh cadavera, we performed an anatomical study of the arteries of the humeral head to determine their intraosseous distributions. A radiopaque suspension was injected into the anterior circumflex, posterior circumflex, suprascapular, thoracoacromial, or subscapular artery and then the specimens were dissected and were analyzed macroscopically, and radiographs were made in three mutually perpendicular projections. In addition, sixteen of the specimens were cut into four-millimeter slices and were studied microradiographically. The humeral head was shown to have been perfused by the anterolateral ascending branch of the anterior circumflex artery in all specimens. That vessel ran parallel to the lateral aspect of the tendon of the long head of the biceps and entered the humeral head where the proximal end of the intertubercular groove met the greater tuberosity. When the intraosseous (terminal) part of the anterolateral branch, the so-called arcuate artery, had been perfused, almost the entire epiphysis was radiopaque. The posterior circumflex artery vascularized only the posterior portion of the greater tuberosity and a small posteroinferior part of the head. Anastomoses between the different arteries were abundant, but vascularization of all of the humeral head was possible only through the anterolateral branch of the anterior circumflex artery.

Adult↗
PubMedDate not supplied

Defects of camera covers after arthroscopic surgery.

Arthroscopic cameras are used either sterilized or in an unsterile manner enveloped in a sterile cover. The goal of this investigation was to determine the integrity of camera covers after arthroscopic procedures, as defects of camera covers have been occasionally observed by us. Such defects might be a potential cause of infection. Six different types of camera covers were tested in a prospective randomized study involving 90 consecutive shoulder arthroscopies. After surgery, the covers were tested by filling them with water up to a level of 20 cm. Any water leaks were recorded. Of all tested camera covers, 74% had 1 to 9 holes involving all types of covers. Of the holes, 17% were larger than 1 mm. In addition, 37% of the covers leaked at the junction between the cover and the arthroscope. The type of cover with the lowest number of leaks had the largest diameter of all tested covers and included an arthroscope adapter, in contrast to the others, which were only sealed off from the arthroscope by adhesive tape. One cover with tape sealing leaked more frequently than the others at the junction (93% of cases, P < .003). The tested camera covers are fragile and tend to leak. This might be a potential risk factor for infection. Mechanically more resistant camera covers or sterilized cameras without the need for covers should be used instead.

Arthroscopes↗
PubMedDate not supplied

Reduction of triceps muscle force after shortening of the distal humerus: a computational model.

Bone deficiency resulting in shortening of the distal humerus may occur after fractures, treatment of nonunions, or revision of total elbow arthroplasty. A biomechanical model of the triceps muscle and tendon was used to investigate the effect of distal humeral shortening on triceps force production. The analysis indicated that shortening of the distal humerus primarily influences the media head of the triceps, which contributes most to elbow extension strength in extended elbow positions. In a posture of 30 degrees elbow flexion, shortening the distal humerus by 1, 2, and 3 cm reduced the extension strength by 17%, 40%, and 63%, respectively. At 90 degrees of flexion, strength was reduced by 11%, 15%, and 21%, respectively. This result suggests that shortening the humerus by 1 cm may be well tolerated, but shortening by 2 or more cm may cause a significant reduction in triceps force. This would be particularly important in patients requiring terminal extension strength for weight bearing.

Arm↗
PubMedDate not supplied

Structural changes of the rotator cuff caused by experimental subacromial impingement in the rat.

Subacromial impingement of the infraspinatus tendon was experimentally created in 28 young adult rats by thickening the undersurface of the acromion with either one or two platelike bony transplants of the ipsilateral scapular spine. Nine nonoperated and eight shoulders that had undergone a sham operation served as control groups. The rats were killed after 2 days and after 1, 2, 4, 8, 16, and 32 weeks for histologic evaluation. All rats with experimental subacromial impingement showed an infraspinatus tear on the bursal side of the tendon. An isolated tear on the articular side or within the tendon was not seen. Two plates caused larger tears than one (P = .04), and more long-standing impingement was associated with larger lesions (P = .002). Multiple chondrocytes were observed within the tendon adjacent to the bony transplants. No calcium deposits were found. In the subacromial space rapid thickening of the bursa was observed. The undersurfaces of the bony transplants showed no evidence of abrasion or remodeling caused by the tendon. The shoulders of the control groups were found intact without any alteration. Experimental subacromial impingement in the rat caused bursal side rotator cuff tears. The type of partial tears that are most frequently observed in clinical practice, that is, intratendinous and articular side tears, were not seen in this experimental model.

Acromioclavicular Joint↗