Background
Numerous factors influence total hip arthroplasty (THA) stability including surgical approach and soft tissue tension, patient compliance, and component position. One long-held tenet ...regarding component position is that cup inclination and anteversion of 40° ± 10° and 15° ± 10°, respectively, represent a “safe zone” as defined by Lewinnek that minimizes dislocation after primary THA; however, it is clear that components positioned in this zone can and do dislocate.
Questions/purposes
We sought to determine if these classic radiographic targets for cup inclination and anteversion accurately predicted a safe zone limiting dislocation in a contemporary THA practice.
Methods
From a cohort of 9784 primary THAs performed between 2003 and 2012 at one institution, we retrospectively identified 206 THAs (2%) that subsequently dislocated. Radiographic parameters including inclination, anteversion, center of rotation, and limb length discrepancy were analyzed. Mean followup was 27 months (range, 0–133 months).
Results
The majority (58% 120 of 206) of dislocated THAs had a socket within the Lewinnek safe zone. Mean cup inclination was 44° ± 8° with 84% within the safe zone for inclination. Mean anteversion was 15° ± 9° with 69% within the safe zone for anteversion. Sixty-five percent of dislocated THAs that were performed through a posterior approach had an acetabular component within the combined acetabular safe zones, whereas this was true for only 33% performed through an anterolateral approach. An acetabular component performed through a posterior approach was three times as likely to be within the combined acetabular safe zones (odds ratio OR, 1.3; 95% confidence interval CI, 1.1–1.6) than after an anterolateral approach (OR, 0.4; 95% CI, 0.2–0.7; p < 0.0001). In contrast, acetabular components performed through a posterior approach (OR, 1.6; 95% CI, 1.2–1.9) had an increased risk of dislocation compared with those performed through an anterolateral approach (OR, 0.8; 95% CI, 0.7–0.9; p < 0.0001).
Conclusions
The historical target values for cup inclination and anteversion may be useful but should not be considered a safe zone given that the majority of these contemporary THAs that dislocated were within those target values. Stability is likely multifactorial; the ideal cup position for some patients may lie outside the Lewinnek safe zone and more advanced analysis is required to identify the right target in that subgroup.
Level of Evidence
Level III, therapeutic study.
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FZAB, GEOZS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UL, UM, UPUK, VKSCE, ZAGLJ
Current techniques for the identification of the infecting organism in prosthetic-joint (e.g., hip or knee) infection remain insensitive. In this study of 331 surgeries involving prosthetic joint ...replacement, a new technique that sonicates the removed artificial joint is found to be more sensitive in identifying the infecting organism than are standard culture techniques.
In surgeries involving prosthetic joint replacement, a new technique that sonicates the removed artificial joint is found to be more sensitive in identifying the infecting organism than are standard culture techniques.
In the United States, 638,000 patients underwent hip or knee replacement in 2003.
1
Although they may improve the quality of life, these procedures are associated with complications, including aseptic failure and prosthetic-joint infection.
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It is important to distinguish prosthetic-joint infection from other causes of joint failure, because its management is different.
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Nonmicrobiologic methods developed for diagnosing native-joint infection use different criteria from those used to diagnose prosthetic-joint infection.
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Microbiologic diagnosis of prosthetic-joint infection may also require different criteria from those used for the microbiologic diagnosis of native-joint infection.
Most clinicians and laboratory workers culture periprosthetic tissue (hereafter referred to as . . .
Abstract The purpose of this study was to calculate the risk of revision secondary to aseptic tibial loosening correlated with increased BMI in 5088 primary TKAs. The mean age was 69 years, with a ...mean follow-up of 7 years. Fifty-two (1.0%) revision TKAs were performed due to aseptic tibial loosening, with the 15-year risk being 2.7%. Patients with a BMI ≥ 35 kg/m2 were significantly more likely to undergo revision due to aseptic tibial failure (HR = 1.9; P < 0.05). Coronal alignment was equivalent between those who did and did not experience tibial loosening. Given that the risk of revision TKA due to aseptic tibial component failure is 2-fold greater in those with a BMI of ≥ 35 kg/m2 , consideration should be given to additional fixation. Therapeutic Level III. See Instructions to Authors for a complete description of levels of evidence.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
BACKGROUND:Severe metaphyseal and meta-diaphyseal bone loss poses important challenges in revision total knee arthroplasty. The best strategy for addressing massive tibial bone loss has not been ...determined. The purpose of this study was to assess the intermediate-term clinical and radiographic results of porous tibial cone implantation.
METHODS:Sixty-six porous tantalum tibial cones (sixty-three patients) were reviewed at a mean follow-up time of seventy months (range, sixty to 106 months). According to the Anderson Orthopaedic Research Institute bone defect classification, twenty-four knees had a Type-3 defect, twenty-five knees had a Type-2B defect, and seventeen knees had a Type-2A defect.
RESULTS:The mean age at the time of the index revision was sixty-seven years (range, forty-one to eighty-three years), and 57% of patients were female. The mean American Society of Anesthesiologists Physical Status was 2.4 (range, 2 to 3), and the mean body mass index was 33 kg/m (range, 25 to 53 kg/m). Fifteen patients (24%) were on immunosuppressant medications, and eight patients (13%) were current smokers. The patients underwent a mean number of 3.4 prior knee surgical procedures (range, one to twenty procedures), and 49% of patients (thirty-one patients) had a history of periprosthetic infection. The mean Knee Society Scores improved significantly from 55 points preoperatively (range, 4 to 97 points) to 80 points (range, 28 to 100 points) at the time of the latest follow-up (p < 0.0001). One patient had progressive radiolucencies about the tibial stem and cone on radiographs. One patient had complete radiolucencies about the tibial cone, concerning for fibrous ingrowth. Three other cones were revisedone for infection, one for aseptic loosening, and one for periprosthetic fracture. Revision-free survival of the tibial cone component was >95% at the time of the latest follow-up.
CONCLUSIONS:Porous tantalum tibial cones offer a promising management option for severe tibial bone loss. At the intermediate-term follow-up (five to nine years), porous tantalum tibial cones had durable clinical results and radiographic fixation. The biologic ingrowth of these implants offers the potential for successful long-term structural support in complex knee reconstruction.
LEVEL OF EVIDENCE:Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.
This study applies metagenomic shotgun sequencing to identify prosthetic joint pathogens from infected and uninfected prostheses. This single approach detects potential pathogens in 94.8% of ...culture-positive infections and 43.9% of culture-negative infections, demonstrating utility in difficult-to-diagnose infections.
Abstract
Background
Metagenomic shotgun sequencing has the potential to change how many infections, particularly those caused by difficult-to-culture organisms, are diagnosed. Metagenomics was used to investigate prosthetic joint infections (PJIs), where pathogen detection can be challenging.
Methods
Four hundred eight sonicate fluid samples generated from resected hip and knee arthroplasties were tested, including 213 from subjects with infections and 195 from subjects without infection. Samples were enriched for microbial DNA using the MolYsis basic kit, whole-genome amplified, and sequenced using Illumina HiSeq 2500 instruments. A pipeline was designed to screen out human reads and analyze remaining sequences for microbial content using the Livermore Metagenomics Analysis Toolkit and MetaPhlAn2 tools.
Results
When compared to sonicate fluid culture, metagenomics was able to identify known pathogens in 94.8% (109/115) of culture-positive PJIs, with additional potential pathogens detected in 9.6% (11/115). New potential pathogens were detected in 43.9% (43/98) of culture-negative PJIs, 21 of which had no other positive culture sources from which these microorganisms had been detected. Detection of microorganisms in samples from uninfected aseptic failure cases was conversely rare (7/195 3.6% cases). The presence of human and contaminant microbial DNA from reagents was a challenge, as previously reported.
Conclusions
Metagenomic shotgun sequencing is a powerful tool to identify a wide range of PJI pathogens, including difficult-to-detect pathogens in culture-negative infections.
BACKGROUND:For patients undergoing 2-stage exchange for the treatment of periprosthetic joint infection (PJI) following total knee arthroplasty, the long-term risk of reinfection and mechanical ...failure and long-term clinical outcomes are not well known. The purpose of our study was to determine the long-term clinical results of 2-stage exchange for PJI following total knee arthroplasty.
METHODS:We identified 245 knees that had undergone total knee arthroplasty and were subsequently treated with 2-stage exchange due to infection during the period of 1991 to 2006; the cohort had no prior treatment for PJI. Major, or 4 of 6 minor, Musculoskeletal Infection Society (MSIS) diagnostic criteria were fulfilled by 179 (73%) of the knees. The cumulative incidence of reinfection and of aseptic revision, accounting for the competing risk of death, were calculated. Risk factors for reinfection were evaluated using Cox proportional hazards regression. Knee Society Score (KSS) values were calculated. The mean age at spacer insertion was 68 years; 50% of the patients were female. The mean follow-up was 14 years (range, 2 to 25 years) following reimplantation.
RESULTS:The cumulative incidence of reinfection was 4% at 1 year, 14% at 5 years, 16% at 10 years, and 17% at 15 years. Factors that were predictive of reinfection included a body mass index of ≥30 kg/m (hazard ratio HR, 3.1; p < 0.01), previous revision surgery (HR, 2.8; p < 0.01), and a McPherson host grade of C (HR, 2.5; p = 0.04). The cumulative incidence of aseptic revision for loosening was 2% at 5 years, 5% at 10 years, and 7% at 15 years. Femoral (HR, 5.0; p = 0.04) and tibial (HR, 6.7; p < 0.01) bone-grafting at reimplantation were predictive of aseptic failure. The most common complications were wound-healing issues, requiring reoperation in 12 (5%) of the knees. The rate of death at 2 years following reimplantation was 11%. The mean KSS improved from 45 at PJI diagnosis to 76 at 10 years following reimplantation (p < 0.01).
CONCLUSIONS:Long-term reinfection rates following 2-stage exchange for PJI after total knee arthroplasty were similar to those of shorter-term reports and were maintained out to 15 years. Mechanical failure rates were low if bone loss was addressed at the time of reimplantation. Improvements in clinical outcomes were maintained at long-term follow-up.
LEVEL OF EVIDENCE:Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.
Background. Culture-negative (CN) prosthetic joint infection (PJI) has not been well studied. We performed a retrospective cohort study to define the demographic characteristics and determine the ...outcome of patients with CN PJI. Methods. All cases of CN total hip arthroplasty and total knee arthroplasty infections (using a strict case definition) treated at our institution from January 1990 through December 1999 were analyzed. Kaplan-Meier survival methods were used to determine the cumulative probability of success. Results. Of 897 episodes of PJI during the study period, 60 (7%) occurred in patients for whom this was the initial episode of CN PJI. The median age of the cohort was 69 years (range, 36–87 years). Patients had received a prior course of antimicrobial therapy in 32 (53%) of 60 episodes. Of the 60 episodes, 34 (57%), 12 (20%), and 8 (13%) were treated with 2-stage exchange, debridement and retention, and permanent resection arthroplasty, respectively. The median duration of parenteral antimicrobial therapy was 28 days (range, 0–88 days). Forty-nine (82%) of 60 episodes were treated with a cephalosporin. The 5-year estimate of survival free of treatment failure was 94% (95% confidence interval, 85%–100%) for patients treated with 2-stage exchange and 71% (95% confidence interval, 44%–100%) for patients treated with debridement and retention. Conclusions. CN PJI occurs infrequently at our institution. Prior use of antimicrobial therapy is common among patients with CN PJI. CN PJI treated at our institution is associated with a rate of favorable outcome that is comparable to that associated with PJI due to known bacterial pathogens.
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BFBNIB, NUK, PNG, UL, UM, UPUK
INTRODUCTION:Contemporary failure etiologies of primary total hip arthroplasties (THAs) have not been precisely defined because of heterogeneity of referral practices.
METHODS:A single-institution ...registry of 4,555 primary, noncemented THAs performed by subspecialty trained arthroplasty surgeons between 2000 and 2012 was analyzed. Only revision surgeries and revisions that occurred after THAs initially performed at the institution were included.
RESULTS:The estimated 10-year survivorships free from THA revision surgery, modular implant revision, and nonmodular implant revision were 98.2%, 98.1%, and 96.3%, respectively. The most common reasons for revision surgeries were wound-related complications (49%), periprosthetic fracture (25%), and pain (18%). Hip instability (53%) and acute periprosthetic joint infection (26%) were the most common etiologies of revision procedures with isolated exchange of at least one modular implant. The most common reasons for replacement or removal of nonmodular implant were periprosthetic fracture (32%), aseptic loosening (22%), and adverse tissue reaction (17%).
DISCUSSION:Focusing on primary THAs initially performed by a contemporary, subspecialty practice allowed an accurate determination of etiologies and rates of failure (defined by revision surgery or revision) after THA.
LEVEL OF EVIDENCE:Level IV
BACKGROUND:Two-stage exchange arthroplasty after a previous, failed 2-stage exchange procedure is fraught with difficulties, and there are no clear guidelines for treatment or prognosis given the ...heterogeneous group of patients in whom this procedure has been performed. The Musculoskeletal Infection Society (MSIS) staging system was developed in an attempt to stratify patients according to infection type, host status, and local soft-tissue status. The purpose of this study was to report the results of 2-stage exchange arthroplasty following a previous, failed 2-stage exchange protocol for periprosthetic knee infection as well as to identify risk factors for failure.
METHODS:We retrospectively identified 45 patients who had undergone 2 or more 2-stage exchange arthroplasties for periprosthetic knee infection from 2000 to 2013. Patients were stratified according to the MSIS system, and risk factors for failure were analyzed. The minimum follow-up was 2 years (mean, 6 years; range, 24 to 132 months).
RESULTS:At the time of follow-up, twenty-two (49%) of the patients had undergone another revision due to infection and 28 (62%) had undergone another revision for any reason. The infection recurred in 6 (75%) of 8 substantially immunocompromised hosts (MSIS type C) and in 3 (30%) of 10 uncompromised hosts (type A) following the second 2-stage exchange arthroplasty (p = 0.06). The infection recurred in 4 (80%) of 5 patients with compromise of the extremity (MSIS type 3) and 3 (33%) of 9 patients with an uncompromised extremity (type 1) (p = 0.27). Both extremely compromised hosts with an extremely compromised extremity (type C3) had recurrence of the infection whereas 3 (30%) of the 10 uncompromised patients with no or less compromise of the extremity (type A1 or A2) did. Five patients in the failure group underwent a third 2-stage exchange arthroplasty following reinfection, and 3 of them were infection-free at the time of the latest follow-up.
CONCLUSIONS:Uncompromised hosts (MSIS type A) with an acceptable wound (MSIS type 1 or 2) had a 70% rate of success (7 of 10) after a repeat 2-stage exchange arthroplasty, whereas type-B2 hosts had a 50% success rate (10 of 20). The repeat 2-stage exchange procedure failed in both type-C3 hosts; thus, alternative salvage procedures should be considered for such patients.
LEVEL OF EVIDENCE:Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.
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