Synovial fluid pH sensor for early detection of prosthetic hip infections.

We describe an implantable sensor developed to measure synovial fluid pH for noninvasive early detection and monitoring of hip infections using standard-of-care plain radiography. The sensor was made of a pH responsive polyacrylic acid-based hydrogel, which expands at high pH and contracts at low pH. A radiodense tantalum bead and a tungsten wire were embedded in the two ends of the hydrogel in order to monitor the change in length of the hydrogel sensor in response to pH via plain radiography. The effective pKa of the hydrogel-based pH sensor was 5.6 with a sensitivity of 3 mm/pH unit between pH 4 and 8. The sensor showed a linear response and reversibility in the physiologically relevant pH range of pH 6.5 and 7.5 in both buffer and bovine synovial fluid solutions with a 30-minute time constant. The sensor was attached to an explanted prosthetic hip and the pH response determined from the X-ray images by measuring the length between the tantalum bead and the radiopaque wire. Therefore, the developed sensor would enable noninvasive detection and studying of implant hip infection using plain radiography.

Noninvasively Imaging pH at the Surface of Implanted Orthopedic Devices with X-ray Excited Luminescence Chemical Imaging.

Implanted medical device-associated infections are a leading cause of fixation failure, and early diagnosis is the key to successful treatment. During infection, acidosis near the implant plays a role in antibiotic resistance and low pH is a potential infection indicator. Herein, we describe a pH sensor which attaches to the implants to noninvasively image local pH with high spatial resolution. The sensor has two layers: a scintillator layer which emits 620 and 700 nm light upon X-ray irradiation and a pH indicator layer containing bromocresol green dye that absorbs 620 nm luminescence in neutral/basic pH and passes 700 nm light at all pHs. We also developed a dedicated imaging system capable of scanning relatively large specimens through thick tissues. A focused X-ray beam irradiates one spot on the sensor, and the 620 to 700 nm peak ratio is measured to determine the local pH; images are acquired by scanning the X-ray beam across the surface and measuring the pH point-by-point. The sensor was covered with varying thickness slices of chicken breast tissue (0-19 mm) to evaluate how the tissue affects the peak intensity and ratio. Thick tissues attenuated both 620 and 700 nm light, with more attenuation at 620 nm than 700 nm. Although this spectral distortion shifted the pH calibration curve, the effect could be corrected for using a scintillator film region with no pH indicator layer as a spectral reference. The sensor was attached to an orthopedic plate affixed to a human cadaveric tibia and imaged through tissue. This approach provides both high spatial resolution from focused X-ray excitation and surface chemical specificity from the indicator dye, providing a tool for imaging local pH through tissue.

An implanted pH sensor read using radiography.

A biomedical sensor was developed to measure local pH near orthopedic implants to detect and study implant-associated infection. The sensor is read using plain radiography, a technique which is noninvasive, inexpensive, ubiquitously available in medical facilities, and routinely used in diagnosis and follow-up. The sensor comprises a radiopaque tungsten indicator pin embedded within a chemically responsive hydrogel that exhibits a pH-dependent swelling. A stainless steel well holds this hydrogel and attaches to an orthopedic plate. The local pH may be determined from the extent of hydrogel swelling by radiographically measuring the indicator position relative to the well. We calibrated the sensor in a series of standard pH buffers and tested it during bacterial growth in culture. The sensor was robust: its response was negligibly affected by changes in temperature, ionic strength within the normal physiological range, or long-term incubation with reactive oxygen species generated from hydrogen peroxide and copper. Pooled data from several sensors fabricated at different times and tested in different conditions had a root-mean-square deviation from a pH electrode reading of 0.24 pH units. Radiographic measurements were also performed in cadaveric tissue with the sensor attached to an orthopedic plate fixed to a tibia. Pin position readings varied by 100 µm between observers surveying the same radiographs, corresponding to 0.065 pH units precision in the range pH 4-8. The sensor was designed to augment standard radiographs of tissue, bony anatomy, and hardware by also indicating local chemical concentrations.

Rates of osteoporosis screening and treatment following vertebral fracture.

BACKGROUND CONTEXT: Osteoporosis remains an underrecognized and undertreated disease entity in the orthopaedic setting, accounting for substantial long-term morbidity and mortality. Osteoporosis is often not diagnosed or treated until multiple fractures have occurred. Vertebral compression fractures are the most common sentinel fracture, providing an opportunity to intervene with antiresorptive therapy before more debilitating fractures occur. Little data has been published on osteoporosis screening and treatment following vertebral fractures. Further elucidation of the osteoporosis care gap in these patients is warranted. PURPOSE: To demonstrate the current state of post vertebral fracture osteoporosis management at a large tertiary care center with no established secondary fracture prevention program. STUDY DESIGN: Retrospective cohort study. SETTING: A large tertiary care hospital or one of its affiliated community hospitals. PATIENT SAMPLE: All 2,933 patients, 50 years of age or older, who presented to an emergency department with a new vertebral fracture between 2008 and 2014. OUTCOME MEASURES: The physiological measures are rates of new fractures within 2 years following first vertebral fracture. PATIENT CARE METRICS: Post vertebral fracture rates of dual energy X-ray absorptiometry (DXA) testing, calcium and vitamin D supplementation, and pharmacotherapy for osteoporosis within 1 year postfracture, and more than 1 year postfracture. Linear trend of the rate of new antiosteoporosis pharmacotherapy among previously antiosteoporosis medication naive patients within 1 year of fracture over time from 2008 to 2014. METHODS: All patients aged 50 years or older presenting to an emergency department with a vertebral fracture between 2008 and 2014 were included. Only an individual's first documented vertebral fracture was considered. Individuals were assessed for DXA screening, calcium and vitamin D supplementation, treatment with an antiosteoporosis medication, and additional fractures following incident vertebral fracture. Statistical analyses included descriptive statistics and a simple logistic regression. No specific funding was provided for this study. The authors of this study report no relevant financial conflicts of interests or associated biases. RESULTS: Between 2008 and 2014, 2,933 unique patients were seen at an included emergency department for one or more vertebral fracture encounters. Ninety-eight percent did not receive a DXA scan within the preceding 2 years or 1 year following fracture. Seven percent of patients were started on antiresorptive therapy after their fracture, with 341 (5%) starting within 1 year of fracture and 211 (2%) starting thereafter. Twenty-one percent (n=616) had taken an antiresorptive medication before their fracture. Seventy three percent (n=2,128) were never prescribed antiresorptive therapy. Treatment rates slightly decreased over time. Thirty eight percent of patients presenting with a vertebral fracture (n=1,115) went on to develop a second fragility fracture within 2 years. CONCLUSIONS: In the absence of a specific local program to improve secondary fracture prevention following minimal trauma spinal fractures, recognition and treatment of osteoporosis in patients at this institution remained dismal over time despite numerous calls to action on the topic in the orthopaedic literature and elsewhere. Undertreatment of osteoporosis puts patients at increased risk of incurring additional fractures. Within 2 years, 38% of the patients in this sample developed an additional fragility fracture. This study demonstrates a profound post vertebral fracture osteoporosis care gap.

Unilateral S2 alar-iliac screws for spinopelvic fixation.

BACKGROUND: This study compared the clinical complications, radiographic measurements of deformity, and quality of life outcomes for patients with de novo scoliosis undergoing thoracolumbar fusions for spinopelvic fixation (SPF) utilizing unilateral S2 alar-iliac (S2AI) screw or unilateral iliac bolt fixation. METHODS: This retrospective review was performed in 29 patients who underwent SPF at one institution; 10 patients received unilateral S2AI screws, and 19 patients received unilateral iliac bolts. The following variables were studied: reoperation rates, pseudarthrosis, sacral insufficiency fracture, hardware prominence, infection, proximal junctional kyphosis (PJK), deformity correction (radiographs), windshield wipering, hardware fracture, and hardware removal. Outcomes were analyzed utilizing both the visual analog scale (VAS) and Oswestry Disability Index (ODI). The mean follow-up period was 27 months. RESULTS: The reoperation rate for unilateral S2AI screws was 30% vs. 53% for unilateral iliac bolts (P = 0.43); reoperations were performed with a 1:5 ratio for infection, a 1:4 ratio for pseudarthrosis, and 1:1 a ratio for PJK comparing S2AI screws to iliac bolts, respectively. CONCLUSION: There were no significant differences in postoperative complications and reoperation rates between unilateral S2AI screws and unilateral iliac bolts utilized for SPF. For the S2AI screw group, there were no instances of hardware prominence or need for removal. The use of unilateral S2AI screws resulted in adequate fixation and comparably low complication rates.

X-ray excited luminescent chemical imaging (XELCI) for non-invasive imaging of implant infections.

X-ray excited luminescent chemical imaging (XELCI) uses a combination of X-ray excitation to provide high resolution and optical detection to provide chemical sensing. A key application is to detect and study implant-associated infection. The implant is coated with a layer of X-ray scintillators which generate visible near infrared light when irradiated with an X-ray beam. This light first passes through a pH indicator dye-loaded film placed over the scintillator film in order to modulate the luminescence spectrum according to pH. The light then passes through tissue is collected and the spectral ratio measured to determine pH. A focused X-ray beam irradiates a point in the scintillator film, and a pH image is formed point-by-point by scanning the beam across the sample. The sensor and scanning system are described along with preliminary results showing images in rabbit models.

Implantable strain sensor to monitor fracture healing with standard radiography.

Current orthopaedic clinical methods do not provide an objective measure of fracture healing or weight bearing for lower extremity fractures. The following report describes a novel approach involving in-situ strain sensors to objectively measure fracture healing. The sensor uses a cantilevered indicator pin that responds to plate bending and an internal scale to demonstrate changes in the pin position on plain film radiographs. The long lever arm amplifies pin movement compared to interfragmentary motion, and the scale enables more accurate measurement of position changes. Testing with a human cadaver comminuted metaphyseal tibia fracture specimen demonstrated over 2.25 mm of reproducible sensor displacement on radiographs with as little as 100 N of axial compressive loading. Finite element simulations determined that pin displacement decreases as the fracture callus stiffens and that pin motion is linearly related to the strain in the callus. These results indicate that an implanted strain sensor is an effective tool to help assess bone healing after internal fixation and could provide an objective clinical measure for return to weight bearing.

Prevention and Management of Postoperative Delirium in Elderly Patients Following Elective Spinal Surgery.

STUDY DESIGN: This study is a systematic review. OBJECTIVE: Propose an evidence-based algorithm for prevention, diagnosis, and management of postoperative delirium in geriatric patients undergoing elective spine surgery. SUMMARY OF BACKGROUND DATA: Delirium is associated with longer stays after elective surgery, increased risk of readmission, and $6.9 billion annually in medical costs. Early diagnosis and treatment of delirium can reduce length of stay (LOS), in-hospital morbidity, and health care costs. After spinal surgery, postoperative delirium increases average LOS to >7 days and is diagnosed in 12.5%-24.3% of geriatric patients. Currently, studies for management of postoperative delirium after elective spinal procedures are not available. METHODS: A literature review was performed for observational studies, randomized controlled trials, and systematic reviews between 1990 and 2015. RESULTS: Risk factors for delirium after elective spinal surgery include age, functional impairment, preexisting dementia, general anesthesia, surgical duration >3 hours, intraoperative hypercapnia and hypotension, greater blood loss, low hematocrit and albumin, preoperative affective dysfunction, and postoperative sleep disorders. Postoperatively, decreasing the use of methylprednisolone and promoting movement with an appropriate orthosis can reduce delirium incidence (P=0.0091). Polypharmacy is an independent risk factor for delirium (P=0.01) and decreasing use of delirium-inducing medications may reduce incidence. The delirium observation screening scale diagnoses and monitors delirium and is rated by nurses as easier to use than the NEECHAM Confusion Scale (P<0.003). Haloperidol is used widely to treat postoperative delirium. Randomized controlled trials show that adding quetiapine results in delirium resolution an average of 3.5 days faster than haloperidol alone (P=0.001) and decreases agitation and LOS (P=0.02; P=0.05). CONCLUSIONS: An evidence-based algorithm is proposed to prevent, diagnose, and manage postoperative delirium that can be used clinically for geriatric patients undergoing elective spine surgery. Prevention and diagnosis involve efforts from the anesthesiologist and postoperative clinical care team. Treatment may include a therapeutic regimen of low-dose neuroleptic medications as needed. LEVEL OF EVIDENCE: Level II.

Maximum pain on visual analog scales in spinal disorders.

BACKGROUND CONTEXT: Determining pain intensity is largely dependent on the patient's report. PURPOSE: The objective of this study was to test the hypothesis that patients initially reporting a pain score of 10 out of 10 on the visual analog scale (VAS) would experience symptom improvement to a degree similar to patients reporting milder pain. STUDY DESIGN: This study is a retrospective chart review. PATIENT SAMPLE: A total of 6,779 patients seeking care for spinal disorders were included in the study. OUTCOME MEASURES: The outcome measures used in the study were pain scores on the VAS pain scale, smoking status, morbid depression, gender, and the presence of known secondary gain. MATERIALS AND METHODS: Patients with lumbar degenerative disk disease with or without spinal stenosis who reported a VAS pain score of 10 out of 10 were identified. Changes in reported VAS pain, patient age, smoking status, morbid depression, gender, and the presence of known secondary gain were examined. RESULTS: A total of 160 individuals (2.9%) reported a maximum pain score of 10 out of 10 on a VAS at their initial presentation. The patients had a median improvement of 3 points in reported VAS pain between the first visit and the last follow-up appointment. The odds to improve by at least 40% on the VAS were 1.500 (95% confidence interval 1.090-2.065) compared with patients reporting submaximal pain. The proportion of patients with identifiable secondary gain was higher (p=.001) than that of patients with submaximal pain. Patients whose pain scores improved dramatically (ie, at least 4 points on the VAS) tended to be older (p=.001), to less often have secondary gain from their disease (p=.007), and to have a negative current smoking status (p=.002). Patients whose pain remained 10 out of 10 during the course of treatment smoked more frequently (p=.016). CONCLUSIONS: Our analysis supports the need to consider the influence of secondary gain on the patients' reported VAS pain scores. Maximum pain seems to be a more acute phenomenon with some likelihood to significantly improve.

Symptomatic sacrococcygeal joint dislocation treated using closed manual reduction: A case report with 36-month follow-up and review of literature.

Dislocation of the sacrococcygeal joint is a rare injury from trauma to the buttocks, most often from falling backwards. Standard of care for this injury has not been determined because it is rare. Left untreated this can cause coccydynia in the long-term. Here we present a case report to describe the treatment of an anterior sacrococcygeal dislocation with closed manual reduction. A 13-year-old female presented to the emergency department with buttock pain after slipping backwards down the stairs. On X-ray the coccyx was in bayonette apposition to the anterior distal sacrum and shortened by 6 mm. To manage the injury, closed manual reduction of the sacrococcygeal joint was performed. To our knowledge, this is the first successful case of sacrococcygeal dislocation treated with closed manual reduction, resulting in complete relief of symptoms at 36 months follow-up. Sacrococcygeal dislocations can be treated with closed manual reduction, resulting in lower morbidity and faster recovery compared to surgical treatment.

Incidence, Positional Distribution, Severity, and Time Missed in Medial Collateral Ligament Injuries of the Knee in NCAA Division I Football Athletes.

INTRODUCTION: We studied injury to the medial collateral ligament (MCL) in National Collegiate Athletic Association (NCAA) Division I football players, their incidence, magnitude of injury, distribution by position, and missed time, which has not previously been described in a consecutive series. METHODS: The knee injuries sustained in 163 consecutive NCAA Division I collegiate football players at our institution were evaluated over a span of 6 years. RESULTS: The incidence of MCL injuries with any knee injury was 29% (47 of 163). Of 47 MCL injuries, 34% occurred in defensive linemen and 29% in offensive linemen. The average days missed by linemen were 14.65 compared with 4.5 by nonlinemen (P = 0.07). The MCL injuries in linemen were more severe than nonlinemen (0.018). DISCUSSION: MCL injuries occur most commonly in linemen in whom the magnitude of injury is also more significant than nonlinemen. Linemen miss more days than do nonlinemen to MCL injury. STUDY DESIGN: Descriptive Epidemiology Study.

C1-2 Fixation Approach for Patients With Vascular Irregularities: A Case Report.

In posterior spinal fusion (PSF), the vertebral artery is most vulnerable to injury at C1-2. C2 pedicle screws are often placed into the dorsomedial isthmus of C2. Alternative techniques include C2 laminar screws and wiring techniques. A 67-year-old male underwent PSF for persistent severe intractable neck pain and degeneration at C1-2. The patient had an enlarged left vertebral artery with midline migration into the C2 body. This pattern was within one standard deviation of normal; however, it rendered typical placement of a C2 pedicle screw unsafe. As a salvage, a C2 laminar screw was placed on the left to avoid risk of vertebral artery injury. The operation and recovery were without complication. C2 laminar screws can be viable alternatives to C2 pedicle screws in cases of midline vertebral artery migration or other vascular anomalies preventing normal safe placement of C2 pedicle screws.

Nonsurgical Management of Early-onset Scoliosis.

Early-onset scoliosis is potentially fatal if left untreated. Although surgical management with growing instrumentation may be necessary, this is not a panacea and is associated with high complication rates. Recent evidence has demonstrated that nonsurgical treatment can be an effective early management strategy in delaying or even precluding the need for surgery, especially surgery with growing instrumentation. The goal of both nonsurgical and surgical management is to control or correct the spinal curve to allow appropriate pulmonary development while delaying definitive fusion until an appropriate skeletal age. Although more commonly used to delay surgery, serial cast correction using the Cotrel and Morel elongation-derotation-flexion technique may result in complete correction in patients with infantile idiopathic scoliosis and smaller curve magnitudes.