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Gerard A Engh

Publications and source records attributed to Gerard A Engh.

At least 19 recordsLinked to original sources
PubMed2007

Wear and osteolysis around total knee arthroplasty.

Osteolysis induced by wear debris of ultra-high-molecular-weight polyethylene has emerged as a significant problem after total knee arthroplasty. The generation of polyethylene wear and the development of osteolysis around total knee arthroplasty are caused by a combination of patient, implant, and surgical factors. Activity level over time may be the most important patient factor affecting the loads placed on a total knee replacement, but it is the most difficult to manage. Multiple factors related to the manufacturing of the polyethylene implant influence the extent of wear, and surgeons should be cautious in considering enhanced polyethylenes pending results of further investigations. The optimal design of the articular bearing surface remains controversial but needs to be considered with respect to the stresses imparted on component-bone and modular tibial backside interfaces. Surgical factors, including restoration of alignment and ligament balance, are important for long-term durability of the implant. Methods of measuring the wear of total knee implants are still evolving. Thus, when confronted with a worn total knee implant and developing osteolysis, the surgeon should consider each of these factors in selecting the best management option to eliminate the source of debris and minimize the potential for wear and osteolysis following revision.

Arthroplasty, Replacement, Knee↗
PubMed2006

Relationship between product demand, tibial polyethylene insert shelf age, and total knee arthroplasty survival: retrospective review of total knees of one design.

Shelf aging of gamma-irradiated-in-air polyethylene tibial components has been associated with increased articular surface wear and an elevated risk for revision. Nine hundred fifty cruciate-retaining inserts of one design were implanted between 1987 and 1996 (shelf age, 1.0 +/- 1.2 years). Less frequently used inserts (smallest/largest sizes, thicker thicknesses, supplemental articular constraint) had longer shelf ages (means ranged from 1.2 to 2.6 years). Survival analysis showed that shelf age (P < .01) and gamma-sterilization in air (P = .01) elevated the risk for revision. Surgeons must remain attentive to identify the shelf-aged gamma-irradiated-in-air polyethylene tibial component while following designs from the era when this sterilization method was used. Recognition is expedited by understanding how shelf life is related to product demand and can be of aid when diagnosing the painful knee.

Arthroplasty, Replacement, Knee↗
PubMed2006

What would you do? Case challenges in knee surgery.

Six cases representing a variety of orthopedic issues were presented to a panel of senior surgeons. These included the following: (1) developmental patella baja with degenerative arthritis, (2) high valgus knee with attenuated medial collateral ligament, (3) degenerative arthritis with near-ankylosis, (4) depressed tibial plateau fracture with degenerative arthritis, (5) degenerative arthritis with laterally dislocating patella, and (6) degenerative arthritis with distal femoral malunion.

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PubMed2006

Patient, implant, and alignment factors associated with revision of medial compartment unicondylar arthroplasty.

The investigators reviewed 245 fixed-bearing unicondylar arthroplasties that one surgeon performed as treatment of medial compartment osteoarthritis between 1988 and 1997 using a variety of cemented metal-backed tibial components and gamma-irradiated-in-air polyethylene bearings. Multivariate statistical analysis was used to evaluate how the event of revision was influenced by 3 patient factors, 3 implant factors, and 7 factors assessed from preoperative and early postoperative radiographs. Five factors were statistically associated with revision: (younger) patient age, (thinner) tibial component initial thickness, (longer) polyethylene shelf age, (lesser) angular reduction of medial tibial plateau varus, and (more varus) postoperative hip-knee-ankle angle. Besides illustrating deleterious consequences of using gamma-irradiated-in-air polyethylene in medial unicompartmental arthroplasty, our results support reducing varus angulation of the medial tibial plateau and knee at surgery.

Age Factors↗
PubMed2006

Incidence and reasons for reoperation after minimally invasive unicompartmental knee arthroplasty.

The goal of this report is to review reoperations undertaken on the initial 221 unicompartmental arthroplasties performed using a minimally invasive technique. A comparison was then performed between these cases and the previous 514 open medial unicompartmental arthroplasties performed at our institution. In the minimally invasive group, 9 (4.1%) of 221 knees were revised (8 for component loosening, 1 for deep infection). Of 212 unrevised knees, 16 have required a total of 18 nonrevision reoperations. Overall, 25 of 221 knees required at least 1 reoperation (total reoperation rate, 11.3%). Despite an accelerated recovery and decreased hospital stay in our minimally invasive unicompartmental arthroplasties, the rate of revision due to aseptic loosening (3.7% vs 1.0%) and the overall reoperation rate (11.3% vs 8.6%) compare unfavorably with those performed with an open technique.

Adult↗
PubMed2006

Radiographic prediction of intraoperative bone loss in knee arthroplasty revision.

UNLABELLED: A key challenge for orthopaedic surgeons performing revision total knee arthroplasty is the management of bone loss. The goal of our study was to test the validity of predicting bone loss from preoperative radiographs using two commonly utilized bone loss assessments: the Anderson Orthopaedic Research Institute and University of Pennsylvania systems and secondarily to assess the frequency and severity of bone loss in a prospective study of total knee arthroplasty revisions. Ninety-eight total knee arthroplasty revision patients were assessed and bone loss was detected in 76 (77.6%) patients preoperatively and intraoperatively. The validity of both systems was established. Agreement between preoperative and intraoperative Anderson Orthopaedic Research Institute classification was fair for the femur and good for the tibia. All University of Pennsylvania preoperative measures were correlated with intraoperative measures. Establishing valid and reliable preoperative systems of measuring bone loss facilitates planning of total knee arthroplasty revision and rehabilitation and meaningful comparisons between different series of patients and treatment protocols. LEVEL OF EVIDENCE: Diagnostic study, level I (prospective testing of previously developed diagnostic criteria on consecutive patients [with universally applied reference "gold" standard]). See Author Guidelines for a complete description of levels of evidence.

Adult↗
PubMed2006

Survival of medial unicondylar arthroplasties placed by one surgeon 1984-1998.

Unicondylar arthroplasty survival rates have varied widely. Implant- and patient-specific factors may be contributory. One surgeon placed 411 medial compartment arthroplasties of 12 designs from 1984 to 1998. In most cases, the fixed bearing tibial component was placed with cement and featured gamma-sterilized-in-air polyethylene and a metal backing. Tibial component initial thickness averaged 8.5 +/- 1.4 mm. Polyethylene shelf age averaged 1.3 +/- 1.2 years. Age and weight at arthroplasty averaged 67 +/- 8 years and 83 +/- 15 kg, respectively. Survival (no revision) at 9 years was 80%. Revision was more common in younger patients, in those with a thinner tibial component or longer polyethylene shelf age, and when some designs were used rather than others; weight and gender were not associated with revision. Nine-year survival improved to 94% when tibial component thickness was > 7 mm and polyethylene shelf age was < 1 year (154 knees). Per our experience, placement of a thin or shelf-aged gamma-irradiated-in-air polyethylene bearing into a young or active subject could explain most failures of unicondylar arthroplasties done in the 1980s and 1990s. Unicondylar patients of that era who were fortunate enough to avoid a thin or aged oxidation-prone polyethylene bearing probably have enjoyed superior outcomes.

Aged↗
PubMed2005

Augments and allografts in revision total knee arthroplasty: usage and outcome using one modular revision prosthesis.

Sixty-five consecutive Coordinate (DePuy, Warsaw, Ind) revision total knee arthroplasties were eligible for minimum 5-year follow-up. Nine patients died and 2 patients were lost. Therefore, 54 knees (51 patients) had a known outcome. Nine knees failed and required either revision or component removal. Eight additional knees were considered clinical failures. Despite the use of metallic augmentation in 89% of the knees, large structural allografts were required in 48% of the knees. Revisions with bone loss that required bulk allograft failed less often (19.2%) than revisions managed without bulk allografts (42.9%). Of 24 knees originally revised for osteolysis/polyethylene wear, only 1 required rerevision for the same mechanism of failure. Modular augments did not effectively address the bone loss and instability encountered in many instances at revision surgery. Survivorship of this implant was 79.4% +/- 13.7% at 8 years.

Adult↗
PubMed2005

Isolated revision of failed metal-backed patellar components: outcome with minimum 4-year follow-up.

Several reports document high failure rates of metal-backed patellar components, but few report the outcome of revising these components to all-polyethylene, cemented implants. At a mean 87.2-month follow-up, we describe a series of 36 patients (40 knees) who underwent isolated metal-backed patellar revision to a cemented, all-polyethylene patellar component. After the patellar revision, 5 patients (6 knees) underwent additional surgery, but no patellar components required revision. The additional surgeries were performed at an average of 77.6 months after patellar revision and included 3 tibial insert exchanges for polyethylene wear, 2 revisions of femoral and tibial components for osteolysis, and 1 realignment procedure for recurrent subluxation of the patella. We conclude that revision of a failed metal-backed patellar component to a cemented, all-polyethylene patella is a durable, successful procedure.

Arthroplasty, Replacement, Knee↗
PubMed2005

Osteolysis after total knee arthroplasty: influence of tibial baseplate surface finish and sterilization of polyethylene insert. Findings at five to ten years postoperatively.

BACKGROUND: Debris displaced from the articular and backside surfaces of the polyethylene inserts of modular tibial components is considered a chief cause of osteolysis at the sites of total knee arthroplasties. One design of total knee replacement featured changes, over time, in the proximal surface roughness of the tibial baseplate and the method of sterilization of the polyethylene insert. We hypothesized that polishing the baseplate surface and sterilizing the insert with means other than gamma radiation in air had reduced the prevalence of osteolysis. METHODS: Three hundred and sixty-five posterior cruciate ligament-retaining Anatomic Modular Knee primary total knee arthroplasties were performed in 300 patients from 1987 to 1998. Anteroposterior and lateral radiographs of the knees were made within a five to ten-year postoperative interval. Two arthroplasty specialists independently examined the radiographs for evidence of osteolysis (defined as any nonlinear region of cancellous bone loss with delineable margins). RESULTS: Osteolysis was identified in 34% (eighty-two) of 242 knees treated with an insert that had been gamma-irradiated in air and affixed to a rough baseplate surface, and it was identified in 9% (nine) of ninety-eight knees treated with an insert that had been gamma-irradiated in an inert gas, or had not been irradiated, and joined to a polished surface. Osteolysis was associated with six factors, including one related to the patient (male gender), one related to the tibial baseplate (the proximal surface finish), three related to the polyethylene insert (the material from which it was machined, the sterilization method, and the shelf age), and one related to the technique (hyperextension of the femoral component relative to the tibial component). CONCLUSIONS: In this design of a total knee prosthesis, polishing the tibial baseplate counterface and implementing a more contemporary sterilization practice (as opposed to gamma radiation in air) noticeably diminished but did not eliminate osteolysis.

Aged↗
PubMed2004

Proprioceptive deficits are comparable before unicondylar and total knee arthroplasties, but greater in the more symptomatic knee of the patient.

The clinical importance of the known proprioceptive deficit in patients with osteoarthritis of the knee is unclear. Attention to the factors that influence proprioception is needed to better understand the role that proprioception plays in the disease process and to assess how these deficits influence clinical outcomes of various treatment options for osteoarthritis. We hypothesized that preoperative proprioception would be poorer in knees with greater symptoms and that knees considered candidates for unicompartmental arthroplasty would have superior proprioception to those in which a total knee arthroplasty was indicated because of the less extensive disease process in the former group. Proprioceptive thresholds were measured in 119 patients with osteoarthritis and no prior knee arthroplasties who were scheduled for unicondylar or total knee arthroplasty. Proprioception examinations consisted of passively flexing and extending each of the bilateral knees in patients independently, from 45 degrees flexion until the blinded patient identified motion. Proprioceptive thresholds for flexion and extension were computed from the angular delays that elapsed before the patient recognized the stimulus. Multiple regression analysis was done to assess the association that these proprioceptive thresholds had with patient factors (age, gender, body mass index, activity level, functional capacity) and knee factors (surgical history, osteoarthritis severity, angular deformity, instability, range of motion). Patient age was the strongest predictor of proprioceptive thresholds, with older patients tending to respond slower to stimulus. Comparison of the right and left knees of each patient showed that proprioception was significantly poorer in the more symptomatic of the two knees. Preoperative thresholds did not differ between knees that received a total knee arthroplasty and those that received a unicondylar arthroplasty.

Adult↗
PubMed2004

Is an intact anterior cruciate ligament needed in order to have a well-functioning unicondylar knee replacement?

Controversy exists about whether a functional anterior cruciate ligament is necessary to achieve success with unicompartmental knee arthroplasty. When the anterior cruciate ligament was deficient, higher failure rates were reported with mobile-bearing implants and with the Lotus implant, a relatively flat, fixed-bearing component. Most failures were secondary to wear. In contrast, the absence of an anterior cruciate ligament did not lead to failure with the St. Georg and Marmor implants. Theoretically, an absent anterior cruciate ligament would increase the sliding motion that caused accelerated polyethylene wear in laboratory studies. Hypothetically, such motion could lead to accelerated wear of unicompartmental arthroplasty in an ACL deficient knee. Currently, unicompartmental knee arthroplasties should not be done in patients with symptoms of anterior cruciate ligament instability and should judiciously be done in older patients without a functional anterior cruciate ligament but with no symptoms of instability.

Anterior Cruciate Ligament↗
PubMed2004

Shelf age of the polyethylene tibial component and outcome of unicondylar knee arthroplasty.

BACKGROUND: A recent report linked shelf-aging of unicondylar polyethylene tibial components with accelerated fatigue wear and rapid failure. We retrospectively reviewed our experiences with another unicondylar knee system to investigate the relationship between the shelf age of the polyethylene components and clinical outcome. METHODS: One hundred Single Compartment Replacement unicompartmental knee arthroplasties were performed with cement between 1990 and 1996. The median shelf age for the polyethylene inserts was 1.7 years. At the time of the review, four knees had been lost to follow-up, sixteen were in patients who had died, and nineteen had been revised. Sixty-one knee replacements remained in situ at a mean and standard deviation of 8 +/- 2 years postoperatively. RESULTS: With revision as the end point, Kaplan-Meier survivorship analysis demonstrated a six-year rate of survival of 96% when the shelf age of the insert was less than the median shelf age but only 71% when the median shelf age was exceeded. Fatigue wear was identified on all retrieved components except for two that had shelf ages under one year and had been revised within three years. At four to six years of clinical follow-up, the group of knees in which the median shelf age had been exceeded also had poorer Knee Society knee scores and function scores. CONCLUSIONS: Aging on the shelf accelerated fatigue failure of polyethylene inserts sterilized with gamma irradiation in air and compromised our intermediate-term clinical outcomes with this unicondylar knee replacement system. Attention to the relationship between the shelf age and the clinical performance of the polyethylene component continues to be warranted with unicondylar knee arthroplasty implants.

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