Stephen B Gunther | Search PubMed

PubMed2002

Retrieved glenoid components: a classification system for surface damage analysis.

There have been many reports describing modes of damage in retrieved total hip and total knee arthroplasty components. The most common mechanism in total hip arthroplasties has been shown to be surface wear. Fatigue failure shown as pitting and delamination are observed more often in total knee components. There has been no previous analysis of retrieved polyethylene glenoid components. This study evaluated the wear mechanisms contributing to failure of total shoulder glenoid components. Polyethylene glenoid components from 10 consecutive total shoulder arthroplasties have been retrieved and analyzed. Wear mechanisms were analyzed under low-power magnification, and a classification system was designed for total shoulder arthroplasties. This classification system is an adaptation of previous models of hip and knee surface damage. The severity of each damage mode was graded in 4 separate quadrants. The most prevalent damage modes were abrasion, pitting, and delamination. These data show a combination of abrasive wear and fatigue in retrieved total shoulder specimens. Surface wear and subsurface fatigue failure mechanisms both contribute to glenoid implant failure.

Aged↗

PubMed2002

Interactive computer simulations of knee-replacement surgery.

OBJECTIVE: Current surgical training programs in the United States are based on an apprenticeship model. This model is outdated because it does not provide conceptual scaffolding, promote collaborative learning, or offer constructive reinforcement. Our objective was to create a more useful approach by preparing students and residents for operative cases using interactive computer simulations of surgery. Total-knee-replacement surgery (TKR) is an ideal procedure to model on the computer because there is a systematic protocol for the procedure. Also, this protocol is difficult to learn by the apprenticeship model because of the multiple instruments that must be used in a specific order. We designed an interactive computer tutorial to teach medical students and residents how to perform knee-replacement surgery. We also aimed to reinforce the specific protocol of the operative procedure. Our final goal was to provide immediate, constructive feedback. DESCRIPTION: We created a computer tutorial by generating three-dimensional wire-frame models of the surgical instruments. Next, we applied a surface to the wire-frame models using three-dimensional modeling. Finally, the three-dimensional models were animated to simulate the motions of an actual TKR. The tutorial is a step-by-step tutorial that teaches and tests the correct sequence of steps in a TKR. The student or resident must select the correct instruments in the correct order. The learner is encouraged to learn the stepwise surgical protocol through repetitive use of the computer simulation. Constructive feedback is acquired through a grading system, which rates the student's or resident's ability to perform the task in the correct order. The grading system also accounts for the time required to perform the simulated procedure. We evaluated the efficacy of this teaching technique by testing medical students who learned by the computer simulation and those who learned by reading the surgical protocol manual. Both groups then performed TKR on manufactured bone models using real instruments. Their technique was graded with the standard protocol. The students who learned on the computer simulation performed the task in a shorter time and with fewer errors than the control group. They were also more engaged in the learning process. DISCUSSION: Surgical training programs generally lack a consistent approach to preoperative education related to surgical procedures. This interactive computer tutorial has allowed us to make a quantum leap in medical student and resident teaching in our orthopedic department because the students actually participate in the entire process. Our technique provides a linear, sequential method of skill acquisition and direct feedback, which is ideally suited for learning stepwise surgical protocols. Since our initial evaluation has shown the efficacy of this program, we have implemented this teaching tool into our orthopedic curriculum. Our plans for future work with this simulator include modeling procedures involving other anatomic areas of interest, such as the hip and shoulder.

Arthroplasty, Replacement, Knee↗

PubMedDate not supplied

Internal fixation of symptomatic os acromiale: a series of twenty-six cases.

Twenty-six patients who presented to our shoulder service with a symptomatic meso-os acromiale were reviewed. All had been initially treated for impingement symptoms. Nonoperative treatment had failed in all patients. One patient had also undergone an arthroscopic acromioplasty without benefit. The diagnosis of symptomatic os acromiale was made on the basis of radiographs and point tenderness over the acromion coupled with signs of rotator cuff pathology. We assessed these patients after treatment by internal fixation and bone grafting. Fixation was achieved with either K-wires or screws and tension banding with either wire or suture. Fifteen patients had associated rotator cuff tears. The clinical and radiologic results are reported. The rate of union was 96% (25/26), and 24 of 26 patients (92%) were satisfied with their results. The mean time to union was 4 months. There were two postoperative fractures. Eight patients (thirty-one percent) had postoperative pain that was subsequently relieved by wire or screw removal. Seventeen patients had concomitant rotator cuff tears. Eleven cuff tears were repaired, and six were irreparable. One of these six was extensively debrided. We conclude that open reduction-internal fixation of the symptomatic meso-acromion yields satisfactory results, and with the exception of hardware discomfort necessitating removal, minimal complications arise in the majority of cases.

Adolescent↗