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Biomedical subjects

Gerard A Engh

Publications and source records attributed to Gerard A Engh.

32 records · Page 2Linked to original sources
PubMed2004

Treatment of the unstable total knee arthroplasty.

Instability is one of the leading causes of clinical failure after total knee arthroplasty. Instability can be categorized according to three basic patterns: AP or flexion space instability, varus/valgus or extension space instability, and global instability. Surgical options for treating instability include polyethylene exchange of a modular component, revision to a more constrained component, or revision to a hinged component. The results achieved with these surgical options vary for each type of instability. In general, the use of more constrained components to manage unstable knees is favored.

Arthroplasty, Replacement, Knee↗
PubMed2004

Epidemiology of osteolysis: backside implant wear.

Osteolysis is an emerging problem in patients who undergo total hip arthroplasty and total knee arthroplasty (TKA). Before the introduction of modular components, osteolysis was not as prevalent in patients who underwent TKA. Although polyethylene wear and the generation of small-particle debris were linked to the presence of osteolysis in patients who have undergone total hip arthroplasty, the fatigue-type wear and larger wear particles often seen with TKA were not thought to invoke the cellular response that causes osteolysis. Despite the lack of an identifiable cause for the osteolysis, the number of knees that developed lesions continued to increase. Therefore, modular components were examined to determine whether this innovation in TKA was actually contributing to the manifestation of osteolysis.

Arthroplasty, Replacement, Knee↗
PubMed2003

Constraint in total knee arthroplasty: when and what?

Tibiofemoral instability is increasingly recognized as a common mode of failure in total knee arthroplasty. Despite this, there are few published guidelines concerning treatment options, component selection, and expected results. In the treatment of the unstable total knee arthroplasty, cruciate-retaining designs can be considered only in the presence of well-balanced ligaments, including the posterior cruciate ligament. More predictable results are obtained with the use of cruciate-substituting components, but they provide no varus-valgus stability and cannot compensate for severe flexion laxity. Varus-valgus constrained designs cannot provide long-term stability in cases of varus-valgus instability or severe flexion laxity. Such cases are most reliably treated with a linked implant.

Algorithms↗
PubMed2003

Responsibilities when confronting a defective surgical implant.

The senior author shares lessons from his experience with faulty knee implants that resulted in severe polyethylene wear and 51% failure of 73 unicondylar knee arthroplasties within 2 years after implantation. Ensuing research showed that the components had been sterilized by gamma irradiation in air and had shelf lives ranging from 4.5 years to 6.5 years. It was learned that gamma-irradiated components with more than 5-year shelf lives remain in inventories without information showing their sterilization dates. This experience reiterated the importance of staying abreast of the literature and reports concerning products and of being alert to unexpected patient outcomes relatively soon after implantation. If a surgeon suspects a faulty prosthetic device, he or she should contact the manufacturer and the United States Food and Drug Administration, so that an investigation can begin. In such situations, the physician's primary responsibility lies with the patient, and it is necessary to arrange extra time and staff resources to give the affected patients information, compassion, added clinical monitoring, and treatment. Because the potential exists for gamma-irradiated in air implants with lengthy shelf lives to remain undetected in inventories, the current authors recommend that surgeons select implants sterilized by a different process.

Humans↗
PubMed2003

The difficult knee: severe varus and valgus.

To correct severe varus or valgus deformity, the surgeon must have clear knowledge of the location, orientation, and physical characteristics of the soft tissue structures that provide stability to the knee. Correct ligament balance restores proper load transfer across the knee and minimizes polyethylene wear. The failure to adequately release contracted ligaments or the overzealous release of ligaments will result in instability and secondary accelerated wear of a total knee implant. I describe several methods of selective ligament release of the contracted soft tissues that contribute to fixed varus and valgus deformity.

Arthroplasty, Replacement, Knee↗
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

Orthopaedic crossfire--can we justify unicondylar arthroplasty as a temporizing procedure? in the affirmative.

In 1972, unicondylar knee arthroplasty (UKA) was introduced, along with total knee arthroplasty (TKA), as an option for managing gonarthrosis. Although the early clinical results with the first generation of implants were equivalent to those of total knee arthroplasty, little interest in UKA was sustained. If unicondylar arthroplasty is to realize a role in the management of degenerative arthritis, even as a temporizing procedure, the results must be predictable and reproducible. Patient satisfaction must be equivalent to or better than that of TKA. Finally, the conversion of UKA to TKA must be uncomplicated, avoiding complex reconstructive procedures and the use of revision implants. As documented in the literature, UKA achieves these goals. Therefore, we cannot only justify UKA as a temporizing procedure, but also as a definitive procedure with long-term results that are comparable to TKA for gonarthrosis.

Arthritis↗
PubMed2002

Outcome of knee arthroplasty in patients with poor preoperative range of motion.

In the current study, 27 consecutive total knee arthroplasties in 21 patients were assessed. All patients had a preoperative range of motion of less than 50 degrees, severe debilitation, and a minimum clinical and radiographic followup of 2 years (mean, 6 years; range, 2.3-11.8 years). The mean preoperative arc of motion was 30 degrees (range, 0 degrees -50 degrees) and improved to a mean 74 degrees (range, 15 degrees -110 degrees) postoperatively. Preoperative flexion contracture was corrected from a mean 28 degrees (range, 0 degrees -60 degrees) to a mean postoperative flexion contracture of 4.4 degrees (range, -5 degrees -30 degrees). In this series, the overall complication rate was 41% and the revision rate was 18.5%. The clinical significance of this study is that patients with stiff knees who are debilitated severely can have an improved quality of life after total knee arthroplasty, reflected by an increased walking tolerance, increased functional abilities, and decrease in pain, but in association with a high risk of complications and subsequent revisions.

Adult↗
PubMed2002

Rapid polyethylene failure of unicondylar tibial components sterilized with gamma irradiation in air and implanted after a long shelf life.

BACKGROUND: The mechanical toughness of polyethylene that has been sterilized by gamma irradiation in air decreases after a long shelf life. The purpose of the present study is to report the high failure rate after unicondylar knee replacements performed with polyethylene bearings that had been sterilized with gamma irradiation in air and implanted after a shelf life of < or = 4.4 years. METHODS: Between December 1997 and January 2000, seventy-five unicondylar knee replacements were performed in sixty-two patients. All patients were followed both clinically and radiographically. A revision operation was offered when the patient had pain, swelling, and radiographic evidence of rapid polyethylene wear. The effect of aging of the polyethylene during storage was evaluated by dividing the knees into three groups on the basis of shelf life and comparing them with regard to the rate of revision and the observed wear of the polyethylene. Four retrieved components were examined for the presence of oxidation. RESULTS: At a mean of eighteen months after the arthroplasty, thirty knees had been revised and seven were scheduled for revision. The rate of polyethylene wear increased as the shelf life increased. There was a significant inverse linear correlation between the shelf life of the polyethylene and the time to revision (p < 0.01, r (2) = 0.64). All retrieved components had greater-than-expected wear with pitting and delamination of the surface. Seven components had fractured, and ten had both fractured and fragmented. Analysis of four components confirmed severe oxidation of the polyethylene. CONCLUSION: The present study demonstrated early, severe wear of tibial polyethylene bearings that had been sterilized by gamma irradiation in air and stored for < or = 4.4 years. This risk can be minimized by ensuring that implants have not been sterilized with gamma irradiation in air and stored for several years.

Arthroplasty, Replacement, Knee↗
PubMed2002

Tibial interface wear in retrieved total knee components and correlations with modular insert motion.

BACKGROUND: Wear occurring at the interface between the polyethylene insert and metal baseplate of a modular tibial component has become an increasingly common finding at the time of revision total knee arthroplasty. Although this so-called backside wear on retrieved polyethylene inserts has been evaluated in prior studies, wear on retrieved metal baseplates has not been described, to our knowledge. The purposes of the present study were to characterize backside wear on retrieved polyethylene inserts and on the mating surfaces of their corresponding baseplates and to investigate if there is a relationship between backside wear and relative motion of the modular elements. METHODS: Twenty-nine retrieved modular tibial components of twelve fixed-bearing designs were analyzed in vitro with regard to backside wear and relative motion between the polyethylene insert and the metal baseplate. We graded the backside of each polyethylene insert and the mating surface of the metal baseplate for wear with use of a scoring system that consisted of three modes of wear and three levels of severity of wear. Relative motion between the insert and the baseplate was measured in the transverse plane with use of a mechanical testing machine. These measurements were used to compute the insert motion index, which served to quantify unrestricted motion of the insert with respect to the baseplate. RESULTS: The mean insert motion index for the tibial components was 416 micro m (range, 104 micro m to 760 micro m). On a wear-grading scale ranging from 0 to 54 (with 0 indicating no wear), the mean backside wear score was 30 (range, 12 to 48) for the inserts and 28 (range, 7 to 51) for the baseplates. Insert motion was positively correlated with backside polyethylene wear (p = 0.003) and baseplate wear (p < 0.001). Baseplate wear was strongly correlated with backside polyethylene wear (p < 0.001). CONCLUSIONS: Backside wear was correlated with the relative motion between the polyethylene insert and the metal baseplate. New locking mechanism designs directed toward better methods of securing the polyethylene insert to the tibial tray are needed to minimize the generation of particulate wear debris at the modular interface.

Adult↗
PubMed2002

Synovial entrapment: a complication of posterior stabilized total knee arthroplasty.

BACKGROUND: We observed a complication of posterior stabilized total knee arthroplasty involving hypertrophy of tissue proximal to the patella associated with pain during active knee extension from 90 degrees of flexion. The purpose of this paper was to describe synovial entrapment and to determine if design features of the prosthesis predispose patients to the complication. METHODS: Between April 1990 and June 1999, we performed 459 consecutive posterior stabilized primary total knee arthroplasties using three prosthetic designs with different femoral intercondylar geometries. We identified twenty-six patients (twenty-seven knees) in whom arthroscopic débridement of the knee or open arthrotomy with débridement of the knee had been subsequently performed because of a diagnosis of synovial entrapment. We reviewed the records of these patients to identify the knee components that had been used and the symptoms and conditions that necessitated additional treatment. RESULTS: Symptoms (grating, crepitation, and pain with active knee extension from 90 degrees) necessitating subsequent débridement occurred in 13.5% (nineteen) of 141 knees treated with the Anatomic Modular Knee-Congruency implant, 3.8% (eight) of 212 treated with the Anatomic Modular Knee-Posterior Stabilized implant, and none of the 106 treated with the Press Fit Condylar Sigma-Posterior Stabilized implant. All patients had difficulty rising from a chair and climbing stairs; however, none had symptoms when standing or walking. No patient had a patellar clunk. The symptoms occurred at a mean of seven months after the arthroplasty in the patients with an Anatomic Modular Knee-Congruency implant and at a mean of twenty months after the arthroplasty in those with an Anatomic Modular Knee-Posterior Stabilized implant. Débridement of the frond-like hypertrophic synovial tissue at the distal aspect of the quadriceps tendon alleviated symptoms in all patients. No nodules were identified during the arthroscopy. CONCLUSIONS: Synovial entrapment is characterized by hypertrophic synovial tissue at the superior pole of the patella. Use of a posterior stabilized femoral component with a proximally positioned or wide femoral box is more likely to result in this complication.

Aged↗