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Michael A Wirth

Publications and source records attributed to Michael A Wirth.

13 recordsLinked to original sources
PubMed2006

Shoulder arthroplasty in cases with avascular necrosis of the humeral head.

Avascular necrosis (AVN) is a relatively uncommon cause of glenohumeral arthritis. Previous retrospective reviews of shoulder arthroplasty for AVN have shown very good results in small numbers of patients. This study prospectively evaluated a consecutive series of 21 shoulders in 19 patients treated with the same modular prosthesis at a single institution. Of the shoulders, 8 developed AVN after a proximal humeral fracture, 1 was associated with a massive rotator cuff tear, 10 developed after corticosteroid therapy, and 2 were idiopathic. The patients, 14 women and 5 men, with a mean age of 54 years, were followed up for a mean of 4.7 years (range, 2 to 8 years). Hemiarthroplasty was performed in 15 shoulders, whereas 6 required total shoulder arthroplasty. Assessment included visual analog scales, the Simple Shoulder Test, and the American Shoulder and Elbow Surgeons Shoulder Score Index (SSI). Physical examination was performed, and radiographs were obtained. The visual analog scale scores for pain and function improved significantly after surgery (P < .01). The mean SSI score rose from 36 to 81 (where 0 indicates the worst outcome and 100 indicates the best outcome). The mean number of positive responses on the Simple Shoulder Test increased from 3 to 10. Mean active elevation increased from 88 degrees to 123 degrees . External rotation improved from 7 degrees to 34 degrees , and internal rotation improved from L4 to T12. No difference in outcome was noted based on age or sex. Patients with steroid-related or idiopathic AVN had greater pain and functional impairment preoperatively (mean SSI score, 26) than those with prior fracture or rotator cuff tear (mean SSI score, 49) (P < .01). Postoperatively, however, these groups fared equally well (mean SSI score, 78 vs 82). Shoulder arthroplasty for AVN produces good pain relief and function, although a concurrent series with osteoarthritis yielded better results. Forward elevation did not approach normal as had been previously reported.

Adult↗
PubMed2006

Treatment of glenohumeral arthritis with a hemiarthroplasty: a minimum five-year follow-up outcome study.

BACKGROUND: Glenohumeral hemiarthroplasty is well established as a method to treat glenohumeral arthritis. This study was designed to report longer-term results and to provide a decision model to assist surgeons in achieving successful outcomes. Our selection strategy for hemiarthroplasty included shoulders with (1) a concentric glenoid with eburnated bone, (2) a nonconcentric glenoid that could be converted to a smooth concentric surface, and (3) a humeral head centered within the glenoid after soft-tissue balancing. METHODS: Fifty-seven consecutive patients (sixty-four shoulders) who had osteoarthritis of the glenohumeral joint, without advanced disease in the glenoid, were treated with hemiarthroplasty. In each instance, a modular prosthesis was implanted. Clinical assessment was performed preoperatively and at one-year intervals postoperatively for at least five years with use of patient self-assessment instruments, including the American Shoulder and Elbow Surgeons questionnaire, the Simple Shoulder Test, and a visual analog pain scale. A detailed radiographic analysis was performed to determine the presence of glenohumeral subluxation, periprosthetic radiolucency, and glenoid bone loss. RESULTS: Forty-three patients (fifty shoulders) were followed for a minimum of five years (mean, 7.5 years). Of the remaining fourteen patients (fourteen shoulders), ten were lost to follow-up, three had died, and one was excluded. For the Simple Shoulder Test, and for every visual analog scale measure, the results at the final follow-up evaluation were significantly better than the preoperative results (p < 0.0001 for each). The mean Simple Shoulder Test score at the time of the final follow-up was 9.4 positive responses compared with 9.7 positive responses at the two-year evaluation (p = 0.32), and the mean visual analog scale score for pain was 18.6 points compared with 14.9 points at two years (p = 0.45). Radiographic analysis showed the majority of stems had either no lucency or lucencies only near the tip of the stem. Glenoid bone loss and subluxation improved postoperatively, and the results were maintained at the final follow-up evaluation. CONCLUSIONS: Shoulder hemiarthroplasty provides sustained good-to-excellent pain relief and functional improvement at five to ten years postoperatively in carefully selected patients with osteoarthritis.

Adult↗
PubMed2005

Performance evaluation of image processing algorithms in CADe.

One of the key limitations of existing image processing algorithms for computer-aided detection (CADe) is that they are often designed and evaluated in an ad hoc manner. This paper characterizes some of the issues and shortcomings in existing performance evaluation paradigms for image processing algorithms in breast cancer screening, particularly in the context of computer aided detection. We present the framework for establishing a performance evaluation process using standardized criteria. We conclude with some specific recommendations to improve the infrastructure for evaluation the performance of image processing algorithms.

Algorithms↗
PubMed2005

Decision making in contemporary shoulder arthroplasty.

Clinical experience with humeral implants has evolved over the past decade, along with a better understanding of shoulder anatomy and function. There is no question that surgeons are getting better at restoring normal anatomic relationships than in preceding decades. Whether or not this impacts implant longevity will only be known with time and further follow-up. Even over the short term, it is difficult to ascertain whether new prosthetic designs have improved patient function as well as has been implied by the related biomechanical studies. Most surgeons with experience using old and new systems realize a greater sense of predictability in achieving their surgical goals when using more modern implants. Concerns over the durability of prosthetic systems with multiple moving parts and hand-tightened locking mechanisms have almost been forgotten in shoulder arthroplasty, but time will also reveal their importance. New glenoid designs have been less exciting, the major problem being one of developing appropriate materials. Polyethylene does not behave like normal cartilage, and its wear is constant and unforgiving. Surgeons now better understand how to reconstruct the normal glenoid position and achieve more secure early fixation than in the past, but this does not promise long-term durability and freedom from complications.

Arthroplasty, Replacement↗
PubMed2004

Shoulder arthroplasty for the treatment of inflammatory arthritis.

BACKGROUND: Prosthetic replacement of the glenohumeral joint can relieve pain and improve shoulder function for patients with end-stage inflammatory arthritis. The purpose of this study was to prospectively analyze the clinical, functional, and radiographic outcomes of shoulder reconstruction with hemiarthroplasty or total shoulder arthroplasty. METHODS: In this multicenter prospective study, clinical history, physical examination, and self-assessment tools including a visual analogue scale, the Simple Shoulder Test, and an activities questionnaire were used to measure comfort, quality of life, and function. Radiographic outcome was determined by assessing the severity of the disease, the adaptation of the prosthesis to the anatomy, the implant position and relationships, and the restoration of glenohumeral alignment. RESULTS: At the time of follow-up, at a minimum of twenty-four months (mean, thirty-nine months), the thirty-six shoulders treated with a hemiarthroplasty and the twenty-five treated with a total shoulder arthroplasty showed significant improvement (p < 0.0001) as demonstrated by the visual analogue scale and the Simple Shoulder Test as well as improvements in the components of the activities questionnaire. Active forward elevation was significantly better (p < 0.004) after the total shoulder arthroplasties than after the hemiarthroplasties. The presence of extremely severe disease did not affect the clinical outcome. Prosthetic adaptation to the anatomy and restoration of glenohumeral alignment resulted in significant improvement in certain motion parameters and were associated with one another (p < 0.001). Restoration of glenohumeral alignment resulted in significant improvements in overall quality of life (p = 0.038), use of the arm for work and play (p = 0.014), and range of motion (p = 0.0004) compared with those parameters when alignment had not been restored. Glenoid erosion occurred in four of the shoulders treated with hemiarthroplasty. Two of the glenoid components used in the total shoulder arthroplasties loosened. CONCLUSIONS: Patients with inflammatory arthritis treated with hemiarthroplasty or total shoulder arthroplasty can be expected to have improved comfort, range of motion, and function. Restoration of glenohumeral alignment appears to lead to even greater improvement in these clinical parameters.

Adult↗
PubMed2003

Late sequelae of proximal humerus fractures.

Proximal humerus fractures, both minimally displaced and complex, are subject to the development of complications. Late sequelae of such injuries include refractory shoulder stiffness, osteonecrosis, malunion, nonunion, and heterotopic bone formation. A prompt, accurate diagnosis and proper treatment protocol can decrease the occurrence and severity of such complications. When complications do occur, treatment options to improve outcome should be implemented.

Fracture Fixation↗
PubMed2002

Standardized analysis of UHMWPE wear particles from failed total joint arthroplasties.

Periprosthetic tissue obtained at revision surgery from eight total hip replacement cases was hydrolyzed, and polyethylene debris particles were isolated from each case. Individual particles were analyzed by scanning electron microscopy (SEM) and computerized image analysis in accordance with ASTM F1877-98, a standard for quantitative description of wear debris. For comparison, periprosthetic tissues from eight total knee revision and four total shoulder revision cases were processed and analyzed with identical methods. A total of 2599 hip, 4345 knee, and 1200 shoulder particles were analyzed. The morphologies of the isolated polyethylene particles from the total hip specimens were distinctly different from the total knee and total shoulder particles. The mean equivalent circle diameter (ECD) for hip particles was 0.694 microm +/- 0.005; knee particles measured 1.190 microm +/-0.009; and shoulder particles 1.183 microm +/- 0.017. The ECD was significantly different between hip particles and those from the shoulder and knee. The mean aspect ratio (AR) for the hip particles was 1.626 +/- 0.015, compared to the knee particles at 1.935 +/- 0.015 and shoulder particles at 2.082 +/- 0.033. The AR was statistically different among all three groups. Other descriptors from the ASTM standard, elongation (E), form factor (FF), and roundness (R) were all significantly different among the three groups of joints. This study demonstrates the utility of ASTM F1877-98 in differentiating wear debris particles from different sources.

Adult↗
PubMed2002

Ipsilateral combination Monteggia and Galeazzi injuries in an adult patient: a case report.

Monteggia fractures represent approximately 1 to 2 percent of forearm fractures, whereas Galeazzi fractures represent 3 to 6 percent. The combination of these injuries in the same extremity is an exceedingly rare occurrence. We report a case of ipsilateral combination Monteggia and Galeazzi fractures in an adult patient. The patient was treated with anatomic reduction and rigid internal fixation. The radius was stabilized with a 3.5-millimeter dynamic compression plate (Synthes USA, Paoli, PA, U.S.A.) and the olecranon with tension band fixation. The radiocapitellar and distal radioulnar joint relationships were restored; the fractures healed; and the patient proceeded to obtain a satisfactory functional result at one year.

Adult↗
PubMedDate not supplied

A prospective functional outcome study of shoulder arthroplasty for osteoarthritis with an intact rotator cuff.

Prospective pain relief and functional outcome data were obtained on 65 shoulder arthroplasties in 55 patients. Thirty-seven total shoulder arthroplasties (TSAs) and twenty-eight hemiarthroplasties were followed up for a mean of 4.3 years (range, 2-8 years). The mean age was 63 years. Pain scores on a visual analog scale improved from a preoperative mean of 64 to 12 postoperatively. TSA and hemiarthroplasty postoperative scores did not differ significantly, but TSA patients started with a worse preoperative score and improved more. Five other visual analog scale scores improved, including function and quality of life. There were similar relationships between TSAs and hemiarthroplasties in each instance (poorer preoperative scores and more improvement). The American Shoulder and Elbow Surgeons Shoulder Score Index improved from 39 to 88 with surgery. The hemiarthroplasty group improved from a mean of 42 to 84, and the TSA group improved from 37 to 91. Although the numerical differences were small, the superiority of TSAs with regard to final score and rate of improvement was statistically significant. Patients with the poorest preoperative scores improved the most, regardless of prosthesis type. Mean active forward elevation improved from 100 degrees to 147 degrees, external rotation improved from a mean of 7 degrees to 39 degrees, and internal rotation improved by a mean of 3 spinal segments. These measures did not differ between TSA and hemiarthroplasty patients. One implant failure was treated with revision from TSA to hemiarthroplasty. Radiographic parameters characterizing component position and offset were measured, but none was found to predict outcome. The results suggest a modest superiority of TSA over hemiarthroplasty in the medium term. Because both TSA and hemiarthroplasty provide considerable and nearly comparable improvement, the long-term risks of glenoid wear and loosening need to be clearly defined before a definitive conclusion can be reached regarding the differential indications for these two procedures.

Aged↗
PubMedDate not supplied

Observation on retrieved Hylamer glenoids in shoulder arthroplasty: problems associated with sterilization by gamma irradiation in air.

Hylamer is an ultra-high molecular weight polyethylene that was used in the glenoid prosthesis of the Global Shoulder. It was developed from a joint venture with DePuy Orthopaedics, Inc, and E.I. DuPont Company. In presterilization evaluations it was noted to have improved mechanical strength with superior creep and wear resistance. However, after sterilization was performed with gamma irradiation in an air environment from 1990 to 1993, the Hylamer glenoids were affected by oxidation, which altered the mechanical properties, and they became brittle and eroded. From 1993 to 1995 Hylamer glenoids were sterilized by gamma irradiation in a nitrogen environment. From 1995 to 1998 sterilization was by gas plasma processes, which do not create the oxidation problem. Since 1998 the glenoid prosthesis of the Global Shoulder has been made exclusively of Enduron and is gas sterilized. The primary purpose of this article is to provide orthopaedic surgeons the best information available about Hylamer glenoids. We make suggestions concerning the diagnosis and treatment of the patients who had a Hylamer glenoid inserted between 1990 and 1993.

Arthroplasty, Replacement↗