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Biomedical subjects

M A Wirth

Publications and source records attributed to M A Wirth.

At least 19 recordsLinked to original sources
PubMed2001

Complications of metallic suture anchors in shoulder surgery: A report of 8 cases.

PURPOSE: Metallic suture anchors are widely used in open and arthroscopic operations about the shoulder. We report the cases of 8 patients who were referred to our institution with complications following shoulder surgery in which metallic suture anchors were used. TYPE OF STUDY: Retrospective case series. METHODS: There were 7 male patients and 1 female patient with an average age of 36 years (range, 18 to 76 years). The initial operation was open anterior reconstruction for anterior instability of the glenohumeral joint in 5 patients, open rotator cuff tear repair in 2 patients, and an open posterior capsular reconstruction for posterior instability in 1 patient. All patients were referred for evaluation after a failed index reconstructive procedure. RESULTS: On average, 5.5 suture anchors (range, 3 to 8) per shoulder were used. Of 4 patients undergoing reconstruction with glenoid anchors only, 3 patients had an extraosseously positioned device. In this subset of glenoid-sided reconstructions, when more than 3 anchors were used, at least 1 anchor was inserted in an extraosseous position. In 2 of 3 patients with isolated humeral anchors, there was evidence of migration over time (1 intra-articular, 2 bursal). Three patients (38%) developed severe articular damage that was directly caused by a loose or intra-articular metal suture anchor. One patient developed a wound infection after reconstructive surgery. In all 8 patients, the index procedure failed and required subsequent surgery. CONCLUSIONS: The use of metallic suture anchors about the shoulder is commonplace and useful, but, as with other hardware used about the shoulder, there are significant risks if the anchors are improperly placed or if the index procedure fails.

Adult↗
PubMed2001

Shoulder arthrodesis.

Current indications for shoulder arthrodesis include posttraumatic brachial plexus injuries, paralysis of the deltoid muscle and rotator cuff, chronic infection, failed revision arthroplasty, severe refractory instability, and bone deficiency following resection of a tumor in the proximal aspect of the humerus. The trapezius, levator scapulae, serratus anterior, and rhomboid muscles must be functional to optimize the functional result following shoulder arthrodesis. A consensus has not been reached concerning the ideal position of the shoulder arthrodesis, although excessive abduction or flexion has been associated with chronic postoperative pain. Decortication of both the acromiohumeral and the glenohumeral surfaces to increase the surface area available for arthrodesis is the most common means for obtaining successful fusion. Although there are numerous methods for stabilization of a shoulder arthrodesis, the most popular method today is probably the AO technique with either a single plate or double plates.

Arthrodesis↗
PubMed2001

The often overlooked posterior dislocation of the shoulder.

Unlike most shoulder dislocations, the posterior dislocation is truly a diagnostic challenge to the treating physician because it may be missed more often than it is recognized. In fact, more than 60% of posterior dislocations are misdiagnosed initially by the treating orthopedic surgeon, and the correct diagnosis is often delayed for months or years. A history of seizures, electroshock, or a fall onto a flexed, adducted arm should alert the physician to the possibility of posterior dislocation. A careful physical examination with comparison to the unaffected arm must be performed with particular attention given to subtle posterior fullness and anterior flatness of the shoulder, along with a lack of external rotation and abduction. A radiographic trauma series made in the scapular plane must always be obtained in cases of shoulder trauma to rule out posterior dislocation. A computed tomographic scan may also be necessary. The correct diagnosis of this injury will facilitate proper orthopedic evaluation and treatment and will reduce the incidence of missed posterior shoulder dislocation and its associated morbidity.

Casts, Surgical↗
PubMed2000

Knot security in simple sliding knots and its relationship to rotator cuff repair: how secure must the knot be?

We sought to determine which simple sliding knot configurations would have adequate strength for rotator cuff repair. Four knot configurations were tied with both No. 1 polydioxanone suture and No. 2 Ethibond suture (Ethicon, Somerville, NJ) using 3 different tying techniques: hand-tie, standard knot pusher, and cannulated double-diameter knot pusher. The knots were then tested to failure on a materials testing system. The weakest standard knot configuration was S=S=S=S. The other 3 knot configurations (S//S//S//S, SxSxSxS, and S//xS//xS//xS) generally failed in the 35 to 50 N range. Ultimate strength in this range can be shown to be adequate to withstand, without suture failure, a maximal contraction of a repaired rotator cuff tear within the rotator crescent, assuming certain conditions are met (suture anchors placed 1 cm apart, 2 sutures per anchor). More complex knots are not necessary for adequate knot security. However, the same configuration with only 1 suture per anchor will not be strong enough because the suture will fail under maximum physiological load. This study shows that we can predict the adequacy of a given knot configuration under maximum physiological loading conditions.

Arthroscopy↗
PubMed1999

Isolation and characterization of polyethylene wear debris associated with osteolysis following total shoulder arthroplasty.

We evaluated the interface membranes surrounding three total shoulder prostheses that had been removed because of progressive aseptic loosening associated with osteolysis. The mean time between the uncomplicated initial arthroplasty and the revision procedure was twelve years (10.5, 10.5, and 16.0 years). Membranes from around both the humeral and the glenoid component were obtained from all three shoulders and were studied histologically to determine the biological response involved in the development of aseptic loosening. For the purpose of comparison, periprosthetic tissue was also obtained from the sites of four failed total hip prostheses that were associated with osteolysis. Polyethylene particles were retrieved with an enzymatic digestion technique that involved the use of papain. Raman vibrational spectroscopy verified that the particles were ultra-high molecular weight polyethylene. The particles were isolated from the tissue, and a computerized image-analysis system characterized 582 of them in terms of size and morphology. Each particle was defined with the use of six shape descriptors: equivalent circle diameter, roundness, form factor, aspect ratio, elongation, and outline fractal dimension. The particles from the hips had a mean equivalent circle diameter (and standard error of the mean) of 0.62 +/- 0.03 micrometer, were predominantly globular in shape, and had low mean values for aspect ratio (1.46 +/- 0.02) and elongation (1.85 +/- 0.03) and relatively high values for roundness (0.74 +/- 0.01) and form factor (0.87 +/- 0.01). In contrast, the particles from the shoulders had a mean equivalent circle diameter of 1.04 +/- 0.03 micrometers. In addition, they had relatively high values for aspect ratio (2.36 +/- 0.07) and elongation (4.96 +/- 0.23) and correspondingly low values for roundness (0.54 +/- 0.01) and form factor (0.67 +/- 0.01), indicating that they were more fibrillar in shape. The particles from the shoulders and those from the hips were significantly different (p < 0.0001) with respect to all of the descriptors except outline fractal dimension. The particles from the shoulders, in general, were larger and more fibrillar than the particles from the hips.

Aged↗
PubMed1998

Loop security as a determinant of tissue fixation security.

Secure arthroscopic repair of rotator cuff tears and Bankart lesions requires tight knots (knot security). Equally important, but usually overlooked, is the tightness of the suture loop (loop security). This study compared loop security in knots tied with No. 1 PDS suture using three different methods: (1) hand-tied, (2) single-hole standard knot pusher, and (3) cannulated double-diameter knot pusher. The results of this study show that the double-diameter knot pusher maintained tight suture loops that were equivalent in circumference to hand-tied loops and were significantly tighter than suture loops tied with a standard single-hole knot pusher. This study highlights the fact that loop security is equally important to knot security in tissue fixation.

Arthroscopy↗
PubMed1998

Neuropathic arthropathy of the shoulder.

We retrospectively reviewed the records of six men (seven shoulders) with neuropathic arthropathy of the shoulder who were referred to our shoulder service during a twenty-eight-year period (from 1969 through 1997). The etiology of the neuropathic condition was syringomyelia in five patients (six shoulders) and chronic alcoholism in one patient. Five patients (six shoulders) were initially misdiagnosed, and seven operative procedures that were unrelated to the etiology of the neuropathic condition were performed in four of these patients. Radiographs revealed destruction of the shoulder joint and marked resorption of the humeral head in all patients. Magnetic resonance images revealed a syrinx of the central cord in all of the patients except for the one who had chronic alcoholism.

Adult↗
PubMed1998

Capsulorrhaphy through an anterior approach for the treatment of atraumatic posterior glenohumeral instability with multidirectional laxity of the shoulder.

Between June 1983 and March 1992, we performed a capsular reconstruction procedure through an anterior approach in ten patients (ten shoulders) who had multidirectional laxity of the shoulder and symptomatic atraumatic posterior glenohumeral instability. The procedure included closure of the capsule in the rotator interval and imbrication of the anterior, inferior, and posteroinferior aspects of the capsule by a double-breasting technique that decreases the overall capsular volume. The mean duration of follow-up was sixty months (range, twenty-four to 103 months). According to the system of Rowe and Zarins, the result was graded as excellent for five shoulders, good for four, and poor for one. On the basis of our results, we recommend capsular reconstruction through an anterior approach only in patients who have persistent multidirectional laxity and symptomatic atraumatic posterior instability of the shoulder despite participation in an intensive rehabilitation program.

Adolescent↗
PubMed1998

Reconstruction of chronic and complete dislocations of the acromioclavicular joint.

The authors report on a technique for the treatment of symptomatic, chronic complete dislocations of the acromioclavicular joint. The coracoacromial ligament is substituted for the coracoclavicular ligaments, and a special temporary coracoclavicular lag screw is used to stabilize the clavicle to the coracoid during ligament healing. The technique has been used on 23 patients who were observed for an average of 5.2 years. Good to excellent results were obtained in 19 of 23 patients. The four patients with fair or poor results had one or more resections of the distal clavicle before the reconstruction. Subjectively, 22 of 23 patients reported improvement in their shoulder.

Acromioclavicular Joint↗
PubMed1997

Nonoperative management of full-thickness tears of the rotator cuff.

Rotator cuff tendonopathies are among the most common disorders encountered in the shoulder. There is an abundance of literature on the operative management of these lesions, but only a small amount devoted to nonoperative treatment of full-thickness tears of the rotator cuff. The purpose of this article is to review the literature pertaining to full-thickness tears as well as our results with expectant management.

Female↗
PubMed1997

Cyclic loading of anchor-based rotator cuff repairs: confirmation of the tension overload phenomenon and comparison of suture anchor fixation with transosseous fixation.

Previous experimental studies of failure of rotator cuff repair have involved single pull to ultimate load. Such an experimental design does not represent the cyclic loading conditions experienced in vivo. We created 1 x 2 cm rotator cuff defects in 16 cadaver shoulders, repaired each defect with three Mitek-RC suture anchors (Mitek Surgical Products, Inc, Westwood, MA) using simple sutures of No. 2 Ethibond, and cyclically loaded the repairs by a servohydraulic materials test system actuator at physiological rates and loads (rate of 33 mm/s, load 180 N). A progressive gap was noted in each specimen, for a 100% rate of failure of the repairs. The central suture always failed first and by the largest magnitude, confirming tension overload centrally. One specimen exhibited combined bone and tendon failure, but the other 15 specimens failed through the tendon. Overall, the repairs failed to 5 mm and 10 mm at an average of 61 cycles and 285 cycles, respectively. Half the specimens were less than 45 years of age and had a 5-mm and 10-mm failure at an average of 107 and 478 cycles, respectively. The other half were over 45 years of age and failed to 5 mm and 10 mm at an average of 17 and 91 cycles, respectively, indicating more rapid failure of the rotator cuff tendons in the older group, and this was statistically significant (P < or = .02). Comparison of suture anchor fixation in this study with transosseous bone tunnel fixation in a previous cyclic loading study at this institution indicates that bone fixation by suture anchors is significantly less prone to failure than bone fixation through bone tunnels (P = .0008). Changing the bone fixation from bone tunnels to suture anchors effectively transferred the weak link from bone to tendon.

Adolescent↗
PubMed1997

Cyclic loading of transosseous rotator cuff repairs: tension overload as a possible cause of failure.

Previous experimental studies of failure of rotator cuff repair have involved a single pull to ultimate load. Such an experimental design does not represent the cyclic loading conditions experienced in vivo. We created 1 cm x 2 cm rotator cuff defects in 16 cadaver shoulders, repaired each defect with transosseous simple sutures, and cyclically loaded the repairs by a servohydraulic materials test system actuator at physiologic rates and loads (rate of 33 mm/sec to a load of 180 N.). A progressive gap was noted in each specimen, for a 100% rate of failure of the repairs. A 5 mm gap developed at an average of 25 cycles, and a 10 mm gap developed at an average of 188 cycles. The central suture always failed first and by the largest magnitude. This study suggests that rotator cuff tears that are repaired with a "tension overload" of a portion of the muscle-tendon units will undergo gradual failure with physiologic cyclic loading until the normal resting lengths of the muscle-tendon units are restored. This "controlled failure" of the repairs may explain residual defects that have been demonstrated by ultrasonography and by arthrography in patients with "successful" rotator cuff repairs. Clinical implications are that: 1) rotator cuff tears should be repaired without tension if possible; and 2) transosseous bone tunnels should ideally extend distal to the weak metaphysical bone so that purchase is obtained into cortical bone for greater fixation strength.

Adolescent↗
PubMed1997

Morphology of the axillary nerve in an anteroinferior shoulder arthroscopy portal.

An anteroinferior portal can be safely used in arthroscopic shoulder surgery but requires an in-depth knowledge of axillary nerve anatomy. The purpose of this report is to present the qualitative and spatial anatomy of the axillary nerve and to describe patterns of arborization that may affect safe anteroinferior arthroscopic portal placement. Measurements were taken in 42 embalmed cadaveric shoulders (20 male, 22 female). The distance from the acromioclavicular (AC) joint to the axillary nerve averaged 7.90 cm (range, 7.2 to 9.1 cm) in males and 6.37 cm (range, 5.2 to 8.1 cm) in females. We describe the axillary nerve index (distance of nerve from the AC joint/length of deltoid from AC joint) which can be used to predict the location of the axillary nerve along the anterior clavicular line (ACL). The axillary nerve index averaged 0.48 (range, 0.42 to 0.57) in males and 0.41 (range, 0.31 to 0.57) in females. Four types of morphology were noted in the axillary nerve: (1) main trunk with superior and inferior branches, (2) main trunk with superior branches, (3) main trunk with inferior branches, and (4) main trunk only. Our work supports the traditional operable safe zone for the axillary nerve.

Aged↗
PubMed1997

Resection arthroplasty of the sternoclavicular joint.

The results of resection of the medial end of the clavicle to treat a painful sternoclavicular joint in fifteen patients were retrospectively reviewed. The patients fell into two groups: eight patients who had had a primary arthroplasty of the sternoclavicular joint in which the costoclavicular ligament was left intact (group I), and seven patients who had had revision of a failed arthroplasty of the sternoclavicular joint and in whom the costoclavicular ligament had to be reconstructed (group II). The results for these two groups were compared at an average of 7.7 years postoperatively. All eight patients in group I had an excellent result. In sharp contrast, three patients in group II had an excellent result, three had a fair result, and one had a poor result. We conclude that preservation or reconstruction of the costoclavicular ligament is essential at the time of resection of the medial portion of the clavicle in order to obtain a satisfactory result.

Adolescent↗
PubMed1997

Operative treatment of irreparable rupture of the subscapularis.

Between 1980 and 1994, 221 shoulders with recurrent anterior glenohumeral subluxation or dislocation were reconstructed at our institution. At the time of the operation, thirteen shoulders were found to have an irreparable injury of the subscapularis muscle, which we believed to be a contributing factor to the ongoing instability. All but three of the thirteen patients had had two to six previous reconstructions. Operative treatment of the irreparable rupture included a dynamic muscle transfer using the pectoralis major in seven shoulders, the pectoralis minor in five, and both of these muscles in one. According to a modification of the grading system of Neer and Foster, the result was satisfactory for ten shoulders and unsatisfactory for three at a mean of five years after the operation. All shoulders with a satisfactory result demonstrated active contraction of the transferred pectoralis muscle and diminished anterior glenohumeral translation. On the basis of our analysis, we concluded that transfer of the pectoralis muscle is effective for reconstruction of the shoulder in patients who have loss of the subscapularis muscle.

Adult↗
PubMed1997

Repair of soft tissue to bone using a biodegradable suture anchor.

The medial collateral ligaments of 18 New Zealand rabbits were surgically detached from bone. In one knee, the ligament was repaired using a biodegradable suture anchor composed of a co-polymer of lactic and glycolic acid. The contralateral medial collateral ligament was not repaired. Animals were sacrificed at 4, 8, and 12 weeks after the operation, and the knee that had the ligament repair was compared with the contralateral control knee. All knees were tested manually tested for stability to valgus stress and then prepared for histologic examination. Medial collateral ligaments repaired using the biodegradable suture anchor demonstrated stability to valgus stress and anatomic healing at the bone-tendon junction. Resorption of the implant was virtually complete by 12 weeks. All specimens demonstrated less inflammatory reaction to the suture anchor than to the attached Vicryl suture. This contrasts with the control group, which was grossly unstable and demonstrated scarring in this nonanatomic position. These results demonstrate efficacy of this particular material of biodegradable implant and justify further investigative efforts.

Animals↗