Douglas E. Padgett

Revision total knee arthroplasty for failed unicompartmental replacement.

The results in nineteen patients (twenty-one knees) who had a failed unicompartmental knee replacement followed by a revision total knee arthroplasty were evaluated. There were twelve excellent, four good, one fair, and two poor results. The interval between the unicompartmental replacement and the revision total knee arthroplasty ranged from eight months to eight years. At the time of the revision, a major osseous defect was found in sixteen knees (76 per cent). The duration of follow-up after the revision ranged from two to ten years. At the most recent follow-up examination, radiographs revealed at least one radiolucent line in thirteen knees (62 per cent). The technical difficulties associated with the revision operation are evidence that unicondylar arthroplasty is not a conservative procedure that allows a total knee arthroplasty to be done easily later. The results also do not support the argument that a revision performed after failure of a unicondylar arthroplasty is less technically demanding than one performed after a failed primary total knee arthroplasty.

The International Consortium of Orthopaedic Registries: Overview and Summary

FDA Post-Market Efforts and Interest in Orthopaedics The United States Food and Drug Administration (FDA) Center for Devices and Radiological Health (CDRH) monitors both mandatory and voluntary post-market reporting to identify adverse events and problems associated with medical devices. Although the manufacturers of medical devices are required to report deaths, injuries, and malfunctions directly to the FDA, the device users are required to report these events to the manufacturer and are required to report only deaths to the FDA. Voluntary reporting systems such as the MedWatch program, the MAUDE (Manufacturer and User Facility Device Experience) database, and the MedSun (Medical Product Safety Network) enhanced surveillance network provide nationwide medical device surveillance in the U.S. However, these reporting systems have important weaknesses, such as incomplete, inaccurate, or nonvalidated data, reporting biases related to event severity, concerns that reporting may result in adverse publicity or litigation, and general underreporting of events. Most importantly, denominator data are missing, which makes evaluation of the incidence or prevalence of a safety-related event impossible. The FDA’s interest in orthopaedic device safety and in the development of infrastructure for enhanced safety monitoring is natural and timely; the lack of such safety evidence is particularly troubling for the most commonly used implants. Over 700,000 joint replacements involving implantable devices are conducted annually in the U.S. alone, and the annual volume is projected to increase twofold for hip joint replacements and sevenfold for knee joint replacements, to a total of more than 3 million annually, in just the next twenty years. Moreover, these surgical procedures are expected to become more expensive, with costs tripling in just the next five years. Despite remarkable advancements in orthopaedics, including new devices and improved surgical techniques, the value of many therapeutic devices has not been established in clinical trials or in real-world settings. Several factors contribute to this shortcoming: (1) rapidly changing device technology coupled with an enormous number of devices on the market; (2) the need for large numbers of patients and long-term follow-up to adequately evaluate the primary safety end point, which is longterm device failure or need for revision; and (3) the need for prospective data collection, planning, and substantial funding to evaluate short and long-term patient-reported outcomes, which are the primary effectiveness end points. The poor state of research and the resulting inability to learn about a device’s benefits, its potential harms, and the balance between them hinder decision-making by the FDA and other stakeholders such as the Centers for Medicare & Medicaid Services (CMS) and commercial insurers.

Taper Design Affects Failure of Large-head Metal-on-metal Total Hip Replacements

BackgroundLarge-head metal-on-metal (MoM) hip arthroplasties have demonstrated poor survival. Damage at the taper-trunnion junction is a contributing factor; however, the influence of junction design is not well understood.Questions/purposes(1) Does taper type affect fretting, corrosion, and volumetric wear at the junction? (2) Do taper types have different wear patterns? (3) Does larger offset or head diameter increase fretting, corrosion, and wear? (4) Is the extent of fretting and corrosion associated with earlier failure?MethodsTaper damage in 40 retrieved heads was subjectively graded for fretting and corrosion, and wear was determined with high-resolution confocal measurement. Taper types (11/13, 12/14, and Type 1) differed by angle, distal diameter, and contact length; Type 1 were thinnest and 11/13 had longer contact lengths.ResultsFretting scores were higher in 11/13 than in Type 1 tapers. Volumetric wear and wear rates did not differ among types. Uniform, circumferential, and longitudinal wear patterns were observed in all types, but fretting, corrosion, and wear did not differ among the patterns. Head diameter and lateral offset did not correlate with fretting, corrosion, or wear. No correlation was found between fretting, corrosion, or wear and length of implantation.ConclusionsIn general, thicker tapers with longer contact lengths were associated with greater fretting scores, whereas no relationship was found among the three designs for corrosion scores or volumetric wear. This finding suggests that trunnion diameter and engagement length are important factors to consider when improving taper-trunnion junction design.Level of EvidenceLevel III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

The unstable total hip replacement.

Instability after total hip arthroplasty (THA) is not a rare occurrence. Numerous factors have been associated with dislocation including surgical approach, implant design, failure to restore proper hip mechanics and soft tissue restraints, and patient variables such as early postoperative compliance, soft tissue integrity, and neurologic conditions such as poor proprioception. A thorough understanding of the mechanism of dislocation, timing, and direction of dislocation is mandatory in formulating an approach toward treatment. The radiographic evaluation should evaluate hip mechanics including component orientation, adequacy of leg lengths, and restoration of offset in the frontal and sagittal planes. The treatment of the unstable total hip replacement is based on numerous variables including the timing of instability, direction, and mechanism. Instability in the early postoperative period in the hip with proper orientation and restored mechanics often is treated successfully with patient reeducation and use of adjunctive bracing. The treatment of the recurrent dislocator can be more difficult. Although reestablishing proper mechanics and orientation can be successful in many instances, some patients continue to have dislocation. Constrained acetabular liners have significantly improved the success rate of reducing the incidence of dislocation, but problems related to premature wear and dislodgement are a major concern. The use of larger articulating bearing surfaces used with the newer cross-linked polyethylene may provide the solution to instability minimizing the concerns related to constrained components.

Thrombosis prevention after total hip arthroplasty: a prospective, randomized trial comparing a mobile compression device with low-molecular-weight heparin.

BACKGROUND Thromboembolic disease is a common complication of total hip arthroplasty. The purpose of this study was to compare a new mobile compression device with low-molecular-weight heparin with regard to their safety and effectiveness for the prevention of venous thromboembolic disease. METHODS Patients who had a total hip arthroplasty were randomized to receive prophylaxis with a mobile compression device or low-molecular-weight heparin for ten days. Use of the compression device began intraoperatively, and the patients in this group could receive 81 mg of aspirin daily after the surgery. The first injection of the low-molecular-weight heparin began between twelve and twenty-four hours after the surgery. After ten to twelve days, all patients underwent bilateral lower-extremity duplex ultrasonography to screen for deep venous thrombi in the calf and thigh. Any clinical symptoms of pulmonary embolism were evaluated with spiral computed tomography lung scans. Bleeding events and utilization of (i.e., compliance with) prophylactic treatment in both groups were documented. Clinical evaluation to look for evidence of deep venous thrombi and pulmonary emboli was performed at twelve weeks postoperatively. RESULTS Four hundred and ten patients (414 hips) were randomized; 392 of these patients (395 of the hips) were evaluable with regard to the safety of the intervention and 386 patients (389 hips) were evaluable with regard to its efficacy. Demographics were similar clinically between the groups. The rate of major bleeding events was 0% in the compression group and 6% in the low-molecular-weight heparin group. The rates of distal and proximal deep venous thrombosis were 3% and 2%, respectively, in the compression group compared with 3% and 1% in the heparin group. The rates of pulmonary embolism were 1% in the compression group and 1% in the heparin group, and there were no fatal pulmonary emboli. Within the twelve-week follow-up period, two events (one deep venous thrombosis and one pulmonary embolus) occurred in one patient in the compression group following negative findings on duplex ultrasonography on the twelfth postoperative day. There was no difference between the groups with regard to the prevalence of venous thromboembolism. CONCLUSIONS When compared with low-molecular-weight heparin, use of the mobile compression device for prophylaxis against venous thromboembolic events following total hip arthroplasty resulted in a significant decrease in major bleeding events.

MRI Predicts ALVAL and Tissue Damage in Metal-on-Metal Hip Arthroplasty

BackgroundAdverse local tissue reactions (ALTR) around metal-on-metal (MOM) hip arthroplasties are increasingly being recognized as a cause of failure. These reactions may be associated with intraoperative tissue damage and complication rates as high as 50% after revision. Although MRI can identify ALTR in MOM hips, it is unclear whether the MRI findings predict those at revision surgery.Questions/purposesWe therefore (1) identified which MRI characteristics correlated with histologically confirmed ALTR (using the aseptic lymphocytic vasculitis-associated lesions [ALVAL] score) and intraoperative tissue damage and (2) developed a predictive model using modified MRI to detect ALVAL and quantify intraoperative tissue damage.MethodsWe retrospectively reviewed 68 patients with failed MOM hip arthroplasties who underwent preoperative MRI and subsequent revision surgery. Images were analyzed to determine synovial volume, osteolysis, and synovial thickness. The ALVAL score was used to grade tissue samples, thus identifying a subset of patients with ALTR. Intraoperative tissue damage was graded using a four-point scale. Random forest analysis determined the sensitivity and specificity of MRI characteristics in detecting ALVAL (score ≥ 5) and intraoperative tissue damage.ResultsMaximal synovial thicknesses and synovial volumes as determined on MRI correlated with the ALVAL score and were higher in cases of severe intraoperative tissue damage. Our MRI predictive model showed sensitivity and specificity of 94% and 87%, respectively, for detecting ALVAL and 90% and 86%, respectively, for quantifying intraoperative tissue damage.ConclusionsMRI is sensitive and specific in detecting ALVAL and tissue damage in patients with MOM hip implants. MRI can be used as a screening tool to guide surgeons toward timely revision surgery.Level of EvidenceLevel III, diagnostic study. See Guidelines for Authors for a complete description of levels of evidence.

Total knee arthroplasty for patients younger than 55 years

There are few reports in the literature that deal with the results of total knee arthroplasty in the younger patient. The present study was undertaken to evaluate the results of total knee arthroplasty in patients under the age of 55 years. Ninety-three knee arthroplasties in 62 patients were performed between 1974 and 1982. The preoperative diagnosis was rheumatoid arthritis in 76 knees and osteoarthritis in 17 knees. The total condylar knee prosthesis was used in all knees. Defects in the tibial plateau were noted in 13 knees, and supplemental support was required. Ninety knees (17 with osteoarthritis and 73 with rheumatoid arthritis) were available for follow-up study at a mean of 6.1 years. The knee rating for the entire group was 87.1. The subgroup scores for the osteoarthritis and rheumatoid arthritis groups were also 87.1. Roentgenographic evaluation revealed a lucency rate of 30%. Two implants were found to have global radiolucencies and were considered loose. Survivorship analysis resulted in a cumulative survivorship rate of 96% at ten years for the entire group. These results are comparable to the long-term results of total knee arthroplasty in the older patient and better than the results of total hip arthroplasty in the younger patient. Total knee arthroplasty in the younger patient is a reliable and durable procedure but should be used with caution despite the excellent results reported here.

Efficacy of Intraoperative Cultures Obtained During Revision Total Hip Arthroplasty

The purpose of this study was to determine the incidence of positive intraoperative cultures, correlate the findings of the permanent histopathology with the results of culture, and determine the natural history and predictive value of the positive intraoperative culture in a consecutive series of 138 revision total hip arthroplasties. The incidence of positive cultures was 30% (42 hips). Of these 42 hips, only 1 ultimately developed sepsis, requiring a second surgical procedure. After a mean follow-up period of 48 months, the remaining 41 culture-positive hips show no evidence of sepsis and are considered clinical successes. The histologic appearance of the infected case was characterized by polymorphonuclear leukocyte infiltration suggestive of acute inflammation. The remaining hips demonstrated findings of chronic inflammation consistent with a diagnosis of aseptic loosening. With the development of sepsis as an endpoint, the positive predictive value of a positive intraoperative culture is 2.4%. The results demonstrate that intraoperative cultures are an unreliable predictor of sepsis and that permanent histologic sectioning is a more useful tool in determining sepsis at the time of revision surgery.

Influence of total hip design on dislocation: a computer model and clinical analysis.

Dislocation following hip arthroplasty remains problematic. While the etiology of dislocation may be multifactorial, implant system design may play a role. Using a computer aided design program, virtual range of motion of several commonly implanted designs was performed with prosthetic interference representing impingement used as an endpoint. Implants with small diameter head size (22mm) and a larger trunion geometry (type II taper) demonstrated impingement in flexion at less than 90°, suggesting an increased risk for dislocation. To investigate this clinically, we performed a review of a consecutive series of 254 primary hip arthroplasties performed by a single surgeon using an implant with a type II taper (Biomet™, Warsaw, IN). At a minimum 2 year followup, 12 patients with 12 hips (4.8%) had at least one episode of dislocation. Stratified by head size, the dislocation rates were 3.6% for 28 mm, 4.8% for 26 mm, and 18.8% for 22mm bearings. These findings support the notion that computer aided design modeling of implant systems is useful in evaluating range of motion and this technique could be employed during the design of any new implant system.Level of Evidence: Therapeutic study, level IV (case series). See Guidelines for Authors for a complete description of levels of evidence.

A mobile compression device for thrombosis prevention in hip and knee arthroplasty.

BACKGROUND Venous thromboembolic events, either deep venous thrombosis or pulmonary embolism, are important complications in patients undergoing knee or hip arthroplasty. The purpose of this study was to evaluate the effectiveness of a mobile compression device (ActiveCare+S.F.T.) with or without aspirin compared with current pharmacological protocols for prophylaxis against venous thromboembolism in patients undergoing elective primary unilateral arthroplasty of a lower-extremity joint. METHODS A multicenter registry was established to capture the rate of symptomatic venous thromboembolic events following primary knee arthroplasty (1551 patients) or hip arthroplasty (1509 patients) from ten sites. All patients were eighteen years of age or older with no known history of venous thromboembolism, coagulation disorder, or solid tumor. Use of the compression device began perioperatively and continued for a minimum of ten days. Patients with symptoms of deep venous thrombosis or pulmonary embolism underwent duplex ultrasonography and/or spiral computed tomography. All patients were evaluated at three months postoperatively to document any evidence of deep venous thrombosis or pulmonary embolism. RESULTS Of 3060 patients, twenty-eight (0.92%) had venous thromboembolism (twenty distal deep venous thrombi, three proximal deep venous thrombi, and five pulmonary emboli). One death occurred, with no autopsy performed. Symptomatic venous thromboembolic rates observed in patients who had an arthroplasty of a lower-extremity joint using the mobile compression device were noninferior (not worse than), at a margin of 1.0%, to the rates reported for pharmacological prophylaxis, including warfarin, enoxaparin, rivaroxaban, and dabigatran, except in the knee arthroplasty group, in which the mobile compression device fell short of the rate reported for rivaroxaban by 0.06%. CONCLUSIONS Use of the mobile compression device with or without aspirin for patients undergoing arthroplasty of a lower-extremity joint provides a noninferior risk for the development of venous thromboembolism compared with current pharmacological protocols.