Faculty Bibliography

OBJECTIVE: To perform a general literature review of dysbaric osteonecrosis (DON) to describe its pathophysiology, prevalence in scuba divers, prognosis, and treatment options. DATA SOURCES: A literature search on PubMed was performed using the term "dysbaric osteonecrosis" yielding 67 results. There was no exclusion based on dates. Articles that mainly dealt with decompression sickness secondary to tunnel work, mining, or airplane travel were not selected. An additional search on PubMed using the terms "(osteonecrosis diving) NOT dysbaric" was performed to identify other publications not picked up in the initial search. MAIN RESULTS: Dysbaric osteonecrosis is associated with prolonged hyperbaric exposure and rapid decompression that cause nitrogen bubbles to enter the fatty marrow-containing shafts of long bones leading to reduction in blood flow and subsequent osteonecrosis. Patients may present asymptomatically, and typical radiographic findings of DON include: decalcification of bone, cystic lesions, osteosclerotic patterns, nontraumatic fractures, bone islands, and a subchondral crescent sign. Surgical treatment options are comprised of core decompression and free vascularized fibular graft, whereas nonsurgical treatment options consist of monitoring, physical therapy, and bisphosphonate therapy. CONCLUSIONS: Although the incidence of DON has decreased significantly over the past 2 decades, the lack of timely diagnosis and optimal management keeps DON relevant in the orthopedic and sport medicine community.

INTRODUCTION: With this growing demand, the length of stay for total hip arthroplasty (THA) procedures has decreased, and as a trade-off, we have seen a higher utilization of extended care facilities (ECFs). Both trends have significant economic implications on the health care system, and predicting the discharge destinations of THA patients would help policy makers plan for future health expenditures. We performed a retrospective data analysis of a large patient database to determine which variables are significant in predicting discharge destinations of THA patients. METHODS: We used the California Hospital Discharge data set of the year 2010, collected and provided by the Office of Statewide Health Planning and Development. The data set includes information about patient demographics, insurance type, diagnoses and procedures, and patient disposition. The study cohort included 14 326 patients. Discharge to home was the reference category. Discharge to ECF and discharge to home with home care were the 2 additional alternatives. RESULTS: In all, 46.9% of patients were discharged home with home health care, followed by 29.6% to ECF, and 23.5% to home without care. Discharge to ECF was more likely for patients with more comorbidities and a higher age. The strongest predictors were Medicaid and black or Asian race. Medicare relative to private payer was a strong predictor of ECF discharge. Male gender was the only factor that lowered the risk of discharge to ECF. The strongest predictor for discharge to home with home care was black race relative to whites. Medicaid lowered the risk of home care, and gender did not matter. CONCLUSION: This study serves to provide insight on which patient characteristics influence discharge destination after THA. Race, insurance, and morbidity were highly significant factors on patient discharge destination to a subacute nursing facility.

Posterior cruciate ligament (PCL) release may be required to balance the flexion gap in PCL retaining TKA. This study examines the incidence and functional consequences of PCL release in both fixed and mobile bearing TKA. A consecutive series of 1388 TKAs with 1014 fixed bearing, and 374 mobile bearing implants were reviewed for prevalence of partial PCL release, restoration of potential flexion and objective knee stability at minimum one-year follow-up. Patients receiving mobile bearing inserts were more likely to need partial PCL release (42% versus 17.5%). The occurrence of partial PCL release did not have a significant impact on knee range of motion and subjective knee stability. The need for a partial PCL release appears to be greater in mobile than in fixed bearing. Knees that required a release in both groups demonstrated no difference in restoration of flexion compared with unreleased knees and no adverse effects on flexion stability.

Intranasal carrier status of Methicillin-sensitive Staphylococcus aureus (MSSA), and Methicillin-resistant Staphylococcus aureus (MRSA) has been shown to be a significant risk factor for developing surgical site infections. To determine if current treatment protocol for positive nasal screen was effective at decolonizing carriers 289 consecutive patients undergoing primary or revision total joint arthroplasty were screened preoperatively. Those patients with positive cultures were treated with a 5-day course of intranasal mupirocin. Preoperatively 44 (15.2%) patients tested positive for MSSA colonization, and 12 (4.2%) patients for MRSA. Testing on the day of surgery revealed 15 (5.2%) patients with MSSA positive cultures, and 1 (0.35%) patient with a MRSA positive culture. Reduction of MSSA and MRSA colonization was statistically significant (P=0.0341, P=0.0073 respectively). Our overall results indicate that our current decolonization protocol with nasal mupirocin was effective in reducing MSSA and MRSA colonization, although a significant number of patients remained positive for MSSA.

PURPOSE: To create standard T2 map profiles from the entire femoral cartilage of healthy volunteers in order to assess regional variations using an angular and layer-dependent approach. MATERIALS AND METHODS: Twenty healthy knees were evaluated using 3T sagittal images of a T2 mapping sequence. Manual segmentation of the entire femoral cartilage was performed slice-by-slice by two raters using MatLab. Inter- and intrarater reliabilities were calculated using intraclass correlation coefficient (ICC) and Bland-Altman analysis. T2 values were analyzed with respect to specific locations (medial condyle, trochlea, and lateral condyle), angles to B0 , and layers of cartilage (whole, deep, and superficial). RESULTS: Inter- and intrarater reliability obtained from the entire femoral cartilage was excellent (ICC = 0.84, 0.86, respectively). The ICCs around the trochlea were lower than those of the medial and lateral condyle. Both the inter- and intrarater Bland-Altman plots indicated larger differences in pixel count are seen as the size of the angular segment becomes larger. T2 values were significantly higher in the superficial layer compared to the deep layer at each femoral compartment (P < 0.001). A magic angle effect was clearly observed, especially within the whole and deep layer over the medial and lateral femoral condyles, except for the superficial layer at the medial condyle. CONCLUSION: The normal T2 map profiles of the entire femoral cartilage showed variations in ICCs by location and in T2 values by angles and layers. These profiles can be useful for diagnosis of early cartilage degeneration in a specific angle and layer of each condyle and trochlea. J. MAGN. RESON. IMAGING 2015.

Pelvic discontinuity is an uncommon condition that usually presents in the revision total hip arthroplasty population. However, its incidence will most likely increase due to the increasing number of primary and revision total hip arthroplasties (THA) done in recent years. Pelvic discontinuity (acetabular disassociation) is perhaps one of the more challenging cases for the hip arthroplasty surgeon to manage. Historically, the management of pelvic discontinuity has been wrought with many challenges. What follows is a review of the current techniques and outcomes for acetabular reconstruction in patients with acetabular disassociation including: porous metal components, internal fixation with acetabular reconstruction, acetabular distraction with jumbo cups, cup and cage construct, and the use of custom triflange.The complexity of pelvic discontinuity and with the myriad of options available to the hip arthroplasty surgeon to address this particular issue, preoperative planning becomes all the more essential.

INTRODUCTION: Real-time monitoring of blood loss is critical in fluid management. Visual estimation remains the standard of care in estimating blood loss, yet is demonstrably inaccurate. Photometric analysis, which is the referenced "gold-standard" for measuring blood loss, is both time-consuming and costly. The purpose of this study was to evaluate the efficacy of a novel tablet-monitoring device for measurement of Hb loss during orthopaedic procedures. METHODS: This is a prospective study of 50 patients in a consecutive series of joint arthroplasty cases. The novel System with Feature Extraction Technology was used to measure the amount of Hb contained within surgical sponges intra-operatively. The system's measures were then compared with those obtained via gravimetric method and photometric analysis. Accuracy was evaluated using linear regression and Bland-Altman analysis. RESULTS: Our results showed a significant positive correlation between Triton tablet system and photometric analysis with respect to intra-operative hemoglobin and blood loss at 0.92 and 0.91, respectively. DISCUSSION: This novel system can accurately determine Hb loss contained within surgical sponges. We believe that this user-friendly software can be used for measurement of total intraoperative blood loss and thus aid in a more accurate fluid management protocols during orthopaedic surgical procedures.

This meta-analysis reviewed 12 studies comparing patient-specific instrumentation (PSI) with standard instrumentation (SI) for total knee arthroplasty in terms of postoperative coronal alignment and operation time. There is no significant difference between PSI and SI in terms of hip-knee-ankle angle (overall coronal alignment or mechanical axis), tibial coronal alignment, and operation time.

BACKGROUND: Tranexamic acid is a safe and effective antifibrinolytic agent used systemically and topically to reduce blood loss and transfusion rate in patients having TKA or THA. As the hip does not have a defined capsule, topical application of tranexamic acid may entirely envelop the sciatic nerve during THA. Accidental application of tranexamic acid onto the spinal cord in spinal anesthesia has been shown to produce seizures; therefore, we sought to investigate if topical application of tranexamic acid on the sciatic nerve has a deleterious effect. QUESTIONS/PURPOSES: We explored whether there were any short- or long-term alterations in (1) electrophysiologic measures, (2) macrophage recruitment, or (3) blood-nerve barrier permeability. Our hypothesis was that local application of tranexamic acid would have a transient effect or no effect on histologic features and function of the sciatic nerve. METHODS: We used a rat protocol to model sciatic nerve exposure in THA to determine the effects of tranexamic acid on neural histologic features and function. We evaluated 35 rats by the dorsal gluteal splitting approach to expose the sciatic nerve for topical use of control and tranexamic acid. We evaluated EMG changes (distal latency, amplitude, nerve conduction velocity), histologic signs of nerve injury via macrophage recruitment, and changes in blood-nerve barrier permeability at early (4 days) and late (1 month) times after surgery, after application of subtherapeutic (1 mg/kg body weight [1.6 mg]), therapeutic (10 mg/kg [16 mg]), and supratherapeutic (100 mg/kg [160 mg]) concentrations of tranexamic acid. Differences in blood-nerve barrier permeability, macrophage recruitment, and EMG between normal and tranexamic acid-treated nerves were calculated using one-way ANOVA, with Newman-Keuls post hoc analyses, at each time. A post hoc power calculation showed that with the numbers available, we had 16% power to detect a 50% difference in EMG changes between the control, 1 mg/kg group, 10 mg/kg group, and 100 mg/kg group. RESULTS: At the early and late times, with the numbers available, there were no differences in EMG except for distal latency at 4 days, macrophage recruitment, or changes in blood-nerve barrier between control rats and those with tranexamic acid-treated nerves. The distal latency in the 1 mg tranexamic acid-treated animals at 4 days was 1.06 +/- 0.15 ms (p = 0.0036 versus all other groups, 95% CI, 0.89-1.25), whereas the distal latencies in the control, the 10 mg/kg, and 100 mg/kg tranexamic acid-treated animals were 0.83 +/- 0.11, 0.89 +/- 0.05, and 0.87 +/- 0.13, respectively. Distal latencies were not increased in any of the groups at 1 month with the numbers available (0.81 +/- 0.10, 0.89 +/- 0.03, 0.81 +/- 0.06, and 0.83 +/- 0.08 ms, respectively, for controls; 1 mg/kg, 10 mg/kg, and 100 mg/kg for the tranexamic acid-treated groups). CONCLUSION: In our in vivo rat model study, tranexamic acid did not appear to have any clinically relevant effect on the sciatic nerve resulting from topical administration up to 1 month. However, because our statistical power was low, these data should be considered hypothesis-generating pilot data for larger, more-definitive studies. CLINICAL RELEVANCE: Topical tranexamic acid is effective in decreasing patient blood loss during THA, and results from our in vivo rat model study suggest there may be no electrophysiologic and histologic effects on the sciatic nerve, with the numbers available, up to 1 month.

BACKGROUND: Metal hypersensitivity is an uncommon complication after total knee arthroplasty (TKA) that can lead to significant functional impairment and aseptic prosthesis failure. CASE REPORT: We describe a 70-year-old patient who presented with persistent pain, swelling, and instability 2 years after a primary TKA. The patient had a history of metal hypersensitivity following bilateral metal-on-metal total hip arthroplasty (THA) that was revised to ceramic-on-polyethylene implants. Knee radiographs showed severe osteolysis with implant loosening. Serum cobalt was elevated and serum chromium was significantly elevated, while joint aspiration and inflammatory marker levels ruled out a periprosthetic infection. Revision TKA was performed, with intraoperative tissue pathology and postoperative leukocyte transformation testing confirming metal hypersensitivity as the cause for aseptic implant failure. CONCLUSIONS: This case report demonstrates the clinical and laboratory signs that suggest metal hypersensitivity in total knee arthroplasty and the potential for joint function restoration with revision surgery.