Hypersensitivity to metals in metal-on-metal hip arthroplasty: a prospective study of one hundred and thirty five lymphocyte transformation tests.

BACKGROUND: Metal allergy remains a controversial topic in the orthopaedic community. It is not known if or to what degree metal sensitivity contributes to inflammatory soft tissue failures, unexplained residual pain, or clinical complications after total joint replacement with metal prostheses. METHODS: We investigated the efficacy of the lymphocyte transformation test (LTT) in predicting adverse outcomes in patients after receiving a metal joint replacement. Our study cohort consists of 135 metal-on-metal hip resurfacing arthroplasty cases performed between 2013 and 2015. All study patients had an LTT preoperatively. We retrospectively analyzed clinical outcomes and failures for our cohort. RESULTS: There was no difference in LTT reactivity between men and women. Of the 135 patients tested, 46 (34.1% of cohort) tested positive to at least one of the materials comprising their implant, and 78 patients (57.8%) had at least one reactive score to any component of the LTT. After a minimum follow-up of two years, we did not observe an allergic response to the implant in any patients. There were no failures requiring revision. We observed a 2.2% rate of moderate residual pain; no patients with residual pain tested positive for metal sensitivity. When patients with moderate-high LTT reactivity (30.4% of cohort) were compared to the remainder of the study group, there was no difference in HHS or UCLA activity score. There was no correlation between blood metal ion levels and LTT reactivity. CONCLUSION: We were unable to prove any predictive value of the LTT. We failed to identify hypersensitivity to metals in patients with metal-on-metal hip resurfacing arthroplasty.

Long-term clinical outcomes of the Biomet M2a-38: a retrospective review of 335 total hip arthroplasty cases.

BACKGROUND: At the turn of the century, over one-third of total hip arthroplasties comprised metal-on-metal bearings. As this patient population and their implants age, it is crucial to understand associated late failure modes and expected long-term functional outcomes. We report the long-term results of a large metal-on-metal uncemented total hip arthroplasty system with unique design characteristics compared to others that have been reported with high failure rates. METHODS: We retrospectively analyze our prospective clinical database to determine overall implant survivorship and functional outcomes. Further, we compare these results to the clinical outcomes reported in orthopedic registries and in other published studies with similar metal-on-metal total hip arthroplasty cohorts. RESULTS: Implant survivorship at 10 years was 99.1% and continued to 97.6% survivorship at 20 years. Implant survivorship at 20 years did not vary significantly between sexes (Male: 98.3%, Female: 97.2%; log-rank p-value = 0.46). Mean whole blood cobalt levels were 2.6 µg/L in unilateral cases, 5.3 µg/L in bilateral patients, and 3.4 µg/L for the combined cohort. Average blood chromium levels were 1.4 µg/L in unilateral patients, 2.9 µg/L in bilateral patients, and 1.8 µg/L for group combined. We observed a 0.9% rate of failure due trunnion corrosion at a mean of 13.1 years postoperatively (10.6-15.6 years) but had no bearing wear failures. CONCLUSIONS: Our 20-year implant survivorship of 97.6% with the M2a-38 bearing surpassed registry benchmarks for THA. This large-bearing (38 mm), full hemisphere coverage metal-on-metal system had no bearing wear failures, one failure of instability, one failure of fixation, and three trunnion failures, perhaps suggesting an optimum balance between stability of the joint and the trunnion.

Antibiotic Delivery via Hickman Catheter for the Treatment of Prosthetic Joint Infection.

Infection rates for total joint arthroplasty range from 1% to 2%, and infection carries significant risk. The traditional course of treatment is irrigation and debridement, but historically, success rates have been variable. The goals of this study were to evaluate the safety and efficacy of Hickman catheterization in the treatment of prosthetic joint infection and to assess its value as an alternative to irrigation and debridement. The authors retrospectively analyzed 26 Hickman catheterizations in the treatment of acute early, acute late, and chronic late infections of primary and revision hip and knee arthroplasty. Initial arthroplasty procedures were performed between 2006 and 2018, with all cases followed for a minimum of 1 year postoperatively. The authors evaluated surgical data, clinical outcomes, and success rates, and they compared their success rates with reported values for cases treated with irrigation and debridement. The authors' success rate was 100% for acute early hip infection, 100% for chronic knee infection, and 80.0% for chronic hip infection. They reported a 75.0% success rate in the treatment of acute late infection for hip arthroplasty and a rate of 62.5% for knee arthroplasty. Postoperative clinical outcomes were significantly improved for both hips and knees for all infection types. The success rates for the treatment of acute early prosthetic joint infection and chronic late prosthetic knee infection were superior to available reported rates on irrigation and debridement. The authors also reported the highest success rate for the treatment of acute late infection. The current data suggest that Hickman catheterization is a promising safe and effective alternative to irrigation and debridement for the treatment of prosthetic joint infection. [Orthopedics. 2021;44(3):e395-e401.].

Optimizing Acetabular Component Bone Ingrowth: The Wedge-Fit Bone Preparation Method.

We investigate the efficacy of a modified acetabular bone-preparation technique in reducing the incidence of two clinical problems identified in hip resurfacing arthroplasty. The first issue is failure due to lack of bone ingrowth into the acetabular component. The second is a newly recognized phenomenon of early cup shift. We hypothesize that these issues might be resolved by using a "wedge-fit method", in which the component wedges into the peripheral acetabular bone rather than bottoming out and potentially toggling on the apex of the cup. Prior to November 2011, all acetabula were reamed 1 mm under and prepared with a press-fit of the porous coated acetabular component. After November 2011, we adjusted reaming by bone density. In "soft bone" (T-score <-1.0), we underreamed acetabula by 1 mm less than the outer diameter of the cup, as was previously done in all cases. For T-scores greater than -1.0, we reamed line-to-line. Additionally, we began performing an "apex relief" starting June 2012 in all cases by removing 2 mm of apex bone with a small reamer after using the largest reamer. Failure of acetabular ingrowth occurred in 0.5% of cases before the wedge-fit method and <0.1% after. Rate of cup shift was reduced from 1.1% to 0.4%. The rate of unexplained pain between 2 and 4 years postoperatively also declined significantly from 2.6% to 1.3%. Our evidence suggests that wedge-fit acetabular preparation improves initial implant stability, leading to fewer cases of early cup shift, unexplained pain, and acetabular ingrowth failure.

Femoral Fixation Methods in Hip Resurfacing Arthroplasty: An 11-Year Retrospective Comparison of 4013 Cases.

BACKGROUND: The optimal femoral fixation method remains unclear. To evaluate the role of femoral fixation techniques in hip resurfacing, we present a comparison of 2 consecutive groups: group 1 (739 hips) with cemented femoral components; group 2 (3274 hips) with uncemented femoral components. METHODS: We retrospectively analyzed our clinical database to compare failures, reoperations, complications, clinical results, and radiographic measurements. Groups were consecutive, so cemented cases had longer follow-up. However, all patients from both groups were at least 2 years out from surgery. Two-year clinical and radiographic data were compared. Longer-term comparison data as well as Kaplan-Meier implant survivorship curves specifically focusing on femoral failure modes were analyzed. RESULTS: Kaplan-Meier 10-year implant survivorship using nontraumatic femoral failure as an end point was 98.9% for the cemented and 100% for the uncemented femoral component. The uncemented, group 2 cases showed a significantly lower raw failure rate (1.1% vs 4.6%), 2-year failure rate (0.8% vs 2.8%), 2-year femoral failure rate (0.4% vs 0.9%), and a lower combined rate of femoral complications and failures (0.6% vs 1.8%). In cases that did not fail, patient mean clinical scores, pain scores, and combined range of motion were all significantly better for group 2. CONCLUSION: We have demonstrated that in the fully porous-coated ReCap device, uncemented femoral fixation is superior to cemented fixation at 11 years follow-up (0.0% vs 1.1% late femoral loosening) in this single-surgeon cohort. Early femoral fractures also reduced from 0.8% to 0.3%, but this may be partially or completely due to a new bone density management program. This study demonstrates better femoral implant survivorship for the uncemented device compared to the cemented femoral resurfacing component for this implant design.

Acetabular Debonding: An Investigation of Porous Coating Delamination in Hip Resurfacing Arthroplasty.

BACKGROUND: To date, there have been no published investigations on the cause of acetabular debonding, a rare failure phenomenon in metal-on-metal hip resurfacing where the acetabular porous coating delaminates from the implant while remaining well fixed to the pelvic bone. PURPOSES: This study aims to summarize the current understanding of acetabular debonding and to investigate the discrepancy in rate of debonding between two implant systems. PATIENTS AND METHODS: To elucidate potential causes of debonding, we retrospectively analyzed a single-surgeon cohort of 839 hip resurfacing cases. Specifically, we compared rate of debonding and manufacturing processes between two implant systems. RESULTS: Group 1 experienced significantly more cases of debonding than Group 2 cases (4.0% versus 0.0%, p value<0.0001). Implant manufacturing processes differed in surface coating, heat treatment, postmanufacturing treatment, and apex thickness. Debonded implants were more likely to have missed RAIL guidelines (p=0.04). CONCLUSIONS: We identified implant system, postoperative time, and acetabular component placement as variables contributing to rate of debonding. We recommend minimizing acetabular inclination angle according to RAIL guidelines. Further, we evaluated manufacturing differences between the two implant systems but did not have access to proprietary data to identify the cause of debonding. Both implants met ASTM standards, yet only the Group 1 implant debonded. This suggests the second implant had greater fatigue shear strength. Because the Group 2 implant achieved a more durable interface that did not debond, we suggest the ASTM F1160 standard for fatigue shear strength be increased to that achieved by its manufacturer. LEVEL OF EVIDENCE II: A retrospective evaluation of prospectively collected data.

Intravascular ultrasound as a novel tool for the diagnosis and targeted treatment of functional popliteal artery entrapment syndrome.

Functional popliteal artery entrapment syndrome can be difficult to diagnose, as the imaging modalities presently employed are designed to detect anatomic entrapment. We describe a novel imaging technique to aid in diagnosis in this cohort. A 22-year-old cyclist presented with exercise-limiting claudication. Magnetic resonance angiography with provocative maneuvers was nondiagnostic. Digital subtraction angiography revealed long-segment occlusion of the popliteal artery with plantar flexion; however, the specific site of compression remained unclear. Intravascular ultrasound allowed specific localization of compression and further confirmed the diagnosis. Thus, we report this as an adjunctive imaging modality to definitively diagnose functional popliteal artery entrapment syndrome and to assist in operative planning.

Specialized vascular floors after open aortic surgery: cost containment while preserving quality outcomes.

BACKGROUND: Postoperative care of open abdominal aortic surgery (OAAS) traditionally involves the intensive care unit (ICU). We hypothesized that in patients without an indication for postoperative ICU admission, admission to a specialized vascular floor unit (hemodynamic monitoring, 2:1 nursing) offers cost savings to both payer and institution without compromising care. METHODS: The electronic medical record was used to collect perioperative data for patients who underwent OAAS between July 2007 and July 2011. The university's cost accounting system provided information on revenue, total margin, and professional billing. Patients with ICU indications (spinal drain, Swan-Ganz monitoring, vasopressors, intubation, or blood product resuscitation) were excluded. Comparative cost and outcome analysis was performed on vascular ward and ICU admissions using the Fisher's exact test for dichotomous categorical variables and the Student's t-test for continuous variables. Long-term survival comparison was calculated using Kaplan-Meier survival estimates. RESULTS: One hundred thirty of 215 patients were included for analysis (85 excluded, 51 floor, 79 ICU). Perioperative data amongst the floor and ICU cohorts were similar. Day of operation professional billing fees were comparable (ICU $13,365 vs. floor $12,626; P = 0.18); however, postoperative professional fees were significantly higher in the ICU cohort (ICU $3,258 vs. floor $2,101; P = 0.001) primarily because of intensivist billing. The hospital generated an average of 8.7% more revenue from the ICU cohort (ICU $37,770 vs. floor $34,756; P = 0.023). This was offset by greater expenses in the ICU cohort (ICU $30,756 vs. floor $25,144; P = 0.02), yielding a hospital profit margin of 107.5% favoring floor admission (ICU $2,858 vs. floor $5,931; P = 0.19). Duration of stay was similar (ICU 8.0 days vs. floor 7.8 days; P = 0.86). Kaplan-Meier survival analysis was not significantly different between cohorts (ICU 10.1%, median follow-up, 1,070 days vs. floor 0%, median follow-up, 405 days; P = 0.13). CONCLUSIONS: Postoperative admission to the ICU is not always necessary after OAAS. Specialized vascular floors offer a financial savings to both payer and institution, which allows for simultaneous cost containment while preserving quality outcomes.