Treatment Options for Distal Radioulnar Joint Arthritis: Balancing Functional Demand and Bony Resection

The distal radioulnar joint is a complex anatomic structure that allows for a combination of rotation and translation with extrinsic and intrinsic stabilizers that maintain stability through a delicate equilibrium. Traumatic, congenital, inflammatory, and degenerative processes can disturb this sensitive balance, resulting in distal radioulnar joint arthritis. We discuss the joint's anatomy and biomechanics and the clinical approach to the patient. We review the surgical treatment options, expected outcomes, and their shortcomings. Selecting the best surgical intervention often means choosing the procedure with the set of complications and limitations best suited for the specific patient.

Point-of-care antimicrobial coating protects orthopaedic implants from bacterial challenge

Implant related infections are the most common cause of joint arthroplasty failure, requiring revision surgeries and a new implant, resulting in a cost of $8.6 billion annually. To address this problem, we created a class of coating technology that is applied in the operating room, in a procedure that takes less than 10 min, and can incorporate any desired antibiotic. Our coating technology uses an in situ coupling reaction of branched poly(ethylene glycol) and poly(allyl mercaptan) (PEG-PAM) polymers to generate an amphiphilic polymeric coating. We show in vivo efficacy in preventing implant infection in both post-arthroplasty infection and post-spinal surgery infection mouse models. Our technology displays efficacy with or without systemic antibiotics, the standard of care. Our coating technology is applied in a clinically relevant time frame, does not require modification of implant manufacturing process, and does not change the implant shelf life.

Evading the host response: Staphylococcus "hiding" in cortical bone canalicular system causes increased bacterial burden

Extremity reconstruction surgery is increasingly performed rather than amputation for patients with large-segment pathologic bone loss. Debate persists as to the optimal void filler for this "limb salvage" surgery, whether metal or allograft bone. Clinicians focus on optimizing important functional gains for patients, and the risk of devastating implant infection has been thought to be similar regardless of implant material. Recent insights into infection pathophysiology are challenging this equipoise, however, with both basic science data suggesting a novel mechanism of infection of Staphylococcus aureus (the most common infecting agent) into the host lacunar-canaliculi network, and also clinical data revealing a higher rate of infection of allograft over metal. The current translational study was therefore developed to bridge the gap between these insights in a longitudinal murine model of infection of allograft bone and metal. Real-time Staphylococci infection characteristics were quantified in cortical bone vs metal, and both microarchitecture of host implant and presence of host immune response were assessed. An orders-of-magnitude higher bacterial burden was established in cortical allograft bone over both metal and cancellous bone. The establishment of immune-evading microabscesses was confirmed in both cortical allograft haversian canal and the submicron canaliculi network in an additional model of mouse femur bone infection. These study results reveal a mechanism by which Staphylococci evasion of host immunity is possible, contributing to elevated risks of infection in cortical bone. The presence of this local infection reservoir imparts massive clinical implications that may alter the current paradigm of osteomyelitis and bulk allograft infection treatment.

Nonmechanical Revision Indications Portend Repeat Limb-Salvage Failure Following Total Femoral Replacement

BACKGROUND

There is scant evidence to guide decision-making for patients considering total femoral replacement (TFR). We aimed to identify the indication, patient, disease, and surgical technique-related factors associated with failure. We hypothesized that failure occurs more frequently in the setting of revision surgical procedures, with infection as the predominant failure mode.

METHODS

We performed a retrospective cohort study of patients receiving total femoral endoprostheses for oncological and revision arthroplasty indications; 166 patients met these criteria. Our primary independent variable of interest was TFR for a revision indication (arthroplasty or limb salvage); the primary outcome was failure. Analyses were performed for patient variables (age, sex, diagnosis group, indication), implant variables (model, decade, length, materials), and treatment variables. We analyzed TFR failures with respect to patient factors, operative technique, and time to failure. We conducted bivariate logistic regressions predicting failure and used a multivariate model containing variables showing bivariate associations with failure.

RESULTS

Forty-four patients (27%) had treatment failure. Failure occurred in 24 (23%) of 105 primary TFRs and in 20 (33%) of 61 revision TFRs; the difference was not significant (p = 0.134) in bivariate analysis but was significant (p = 0.044) in multivariate analysis. The mean age at the time of TFR was 37 years in the primary group and 51 years in the revision group (p = 0.0006). Of the patients who had mechanical failure, none had reoccurrence of their original failure mode, whereas all 8 patients from the nonmechanical cohort had reoccurrence of the original failure mode; this difference was significant (p = 0.0001).

CONCLUSIONS

TFR has a high failure rate and a propensity for deep infection, especially in the setting of revision indications and prior infection. All failed TFRs performed for revision indications for infection or local recurrence failed by reoccurrence of the original failure mode and resulted in amputation.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Novel in vivo mouse model of shoulder implant infection

BACKGROUND

Animal models are used to guide management of periprosthetic implant infections. No adequate model exists for periprosthetic shoulder infections, and clinicians thus have no preclinical tools to assess potential therapeutics. We hypothesize that it is possible to establish a mouse model of shoulder implant infection (SII) that allows noninvasive, longitudinal tracking of biofilm and host response through in vivo optical imaging. The model may then be employed to validate a targeting probe (1D9-680) with clinical translation potential for diagnosing infection and image-guided débridement.

METHODS

A surgical implant was press-fit into the proximal humerus of c57BL/6J mice and inoculated with 2 μL of 1 × 103 (e3), or 1 × 104 (e4), colony-forming units (CFUs) of bioluminescent Staphylococcus aureus Xen-36. The control group received 2 μL sterile saline. Bacterial activity was monitored in vivo over 42 days, directly (bioluminescence) and indirectly (targeting probe). Weekly radiographs assessed implant loosening. CFU harvests, confocal microscopy, and histology were performed.

RESULTS

Both inoculated groups established chronic infections. CFUs on postoperative day (POD) 42 were increased in the infected groups compared with the sterile group (P < .001). By POD 14, osteolysis was visualized in both infected groups. The e4 group developed catastrophic bone destruction by POD 42. The e3 group maintained a congruent shoulder joint. Targeting probes helped to visualize low-grade infections via fluorescence.

DISCUSSION

Given bone destruction in the e4 group, a longitudinal, noninvasive mouse model of SII and chronic osteolysis was produced using e3 of S aureus Xen-36, mimicking clinical presentations of chronic SII.

CONCLUSION

The development of this model provides a foundation to study new therapeutics, interventions, and host modifications.

In vivo Mouse Model of Spinal Implant Infection

Spine implant infections portend poor outcomes as diagnosis is challenging and surgical eradication is at odds with mechanical spinal stability. The purpose of this method is to describe a novel mouse model of spinal implant infection (SII) that was created to provide an inexpensive, rapid, and accurate in vivo tool to test potential therapeutics and treatment strategies for spinal implant infections. In this method, we present a model of posterior-approach spinal surgery in which a stainless-steel k-wire is transfixed into the L4 spinous process of 12-week old C57BL/6J wild-type mice and inoculated with 1 x 103 CFU of a bioluminescent strain of Staphylococcus aureus Xen36 bacteria. Mice are then longitudinally imaged for bioluminescence in vivo on post-operative days 0, 1, 3, 5, 7, 10, 14, 18, 21, 25, 28, and 35. Bioluminescence imaging (BLI) signals from a standardized field of view are quantified to measure in vivo bacterial burden. To quantify bacteria adhering to implants and peri-implant tissue, mice are euthanized and the implant and surrounding soft tissue are harvested. Bacteria are detached from the implant by sonication, cultured overnight and then colony forming units (CFUs) are counted. The results acquired from this method include longitudinal bacterial counts as measured by in vivo S. aureus bioluminescence (mean maximum flux) and CFU counts following euthanasia. While prior animal models of instrumented spine infection have involved invasive, ex vivo tissue analysis, the mouse model of SII presented in this paper leverages noninvasive, real time in vivo optical imaging of bioluminescent bacteria to replace static tissue study. Applications of the model are broad and may include utilizing alternative bioluminescent bacterial strains, incorporating other types of genetically engineered mice to contemporaneously study host immune response, and evaluating current or investigating new diagnostic and therapeutic modalities such as antibiotics or implant coatings.

Progress not panacea: vancomycin powder efficacy and dose evaluated in an in vivo mouse model of spine implant infection

BACKGROUND

Intrawound vancomycin powder (VP) has been rapidly adopted in spine surgery with apparent benefit demonstrated in limited, retrospective studies. Randomized trials, basic science, and dose response studies are scarce.

PURPOSE

This study aims to test the efficacy and dose effect of VP over an extended time course within a randomized, controlled in vivo animal experiment.

STUDY DESIGN/SETTING

Randomized controlled experiment utilizing a mouse model of spine implant infection with treatment groups receiving vancomycin powder following bacterial inoculation.

METHODS

Utilizing a mouse model of spine implant infection with bioluminescent Staphylococcus aureus, 24 mice were randomized into 3 groups: 10 infected mice with VP treatment (+VP), 10 infected mice without VP treatment (No-VP), and 4 sterile controls (SC). Four milligrams of VP (mouse equivalent of 1 g in a human) were administered before wound closure. Bioluminescence imaging was performed over 5 weeks to quantify bacterial burden. Electron microscopy (EM), bacterial colonization assays (Live/Dead) staining, and colony forming units (CFU) analyses were completed. A second dosing experiment was completed with 34 mice randomized into 4 groups: control, 2 mg, 4 mg, and 8 mg groups.

RESULTS

The (+VP) treatment group exhibited significantly lower bacterial loads compared to the control (No-VP) group, (p<.001). CFU analysis at the conclusion of the experiment revealed 20% of mice in the +VP group and 67% of mice in the No-VP group had persistent infections, and the (+VP) treatment group had significantly less mean number of CFUs (p<.03). EM and Live/Dead staining revealed florid biofilm formation in the No-VP group. Bioluminescence was suppressed in all VP doses tested compared with sterile controls (p<.001). CFU analysis revealed a 40%, 10%, and 20% persistent infection rate in the 2 mg, 4 mg, and 8 mg dose groups, respectively. CFU counts across dosing groups were not statistically different (p=.56).

CONCLUSIONS

Vancomycin powder provided an overall infection prevention benefit but failed to eradicate infection in all mice. Furthermore, the dose when halved also demonstrated an overall protective benefit, albeit at a lower rate.

CLINICAL SIGNIFICANCE

Vancomycin powder is efficacious but should not be viewed as a panacea for perioperative infection prevention. Dose alterations can be considered, especially in patients with kidney disease or at high risk for seroma.

An Early Look at Operative Orthopaedic Injuries Associated with Electric Scooter Accidents: Bringing High-Energy Trauma to a Wider Audience

BACKGROUND

There is a new method of transportation that started in our community in late 2017- rideshare electric scooters (e-scooters). These scooters have proven immensely popular and can now be found in many cities around the world. Despite the pervasiveness of e-scooters, their associated injury patterns are poorly understood. The purpose of this study was to describe our department's experience at the epicenter of the e-scooter phenomenon that is sweeping the globe and to characterize operative orthopaedic injuries that are related to e-scooter accidents.

METHODS

We performed a retrospective chart review of all of the operative orthopaedic cases and trauma consults at 2 trauma centers (a level-I center and a level-II center) between September 2017 and August 2019. We identified all operative injuries in which the cause of injury was an e-scooter accident. Data that included demographics, mechanism of injury, diagnosis, and treatment were collected.

RESULTS

Seventy-five operative injuries were identified in 73 patients during the study period. The mean patient age was 35.4 years (range, 14 to 74 years), and the median age was 32 years. There were 4 pediatric patients (14, 15, 15, and 17 years old). Thirty-two patients (43.8%) sustained upper-extremity injuries, and 42 patients (57.5%) sustained lower-extremity injuries; 1 of these patients had both upper and lower-extremity injuries. Nine patients (12.3%) had open fractures. There were 7 hip fractures in patients with an average age of 42.4 years (range, 28 to 68 years). Seventy-one (97.3%) of 73 patients were e-scooter riders, and 2 (2.7%) were pedestrians who were struck by e-scooter riders.

CONCLUSIONS

E-scooters can cause serious injury. Seventy-three patients required operative treatment in just the first 2 years of e-scooter use in our community. Operative injuries occurred throughout the skeletal system, and several were injuries that are typically associated with high-energy trauma. Although, as a rule, e-scooter use is limited to adults and banned in high pedestrian-traffic areas in our city, the inclusion of 4 underage riders and 2 pedestrians in our cohort suggests that these rules are not always followed. As e-scooters continue to increase in popularity, additional steps should be taken to regulate their use and protect riders and the public.

Multimodal imaging guides surgical management in a preclinical spinal implant infection model

Spine implant infections portend disastrous outcomes, as diagnosis is challenging and surgical eradication is at odds with mechanical spinal stability. Current imaging modalities can detect anatomical alterations and anomalies but cannot differentiate between infection and aseptic loosening, diagnose specific pathogens, or delineate the extent of an infection. Herein, a fully human monoclonal antibody 1D9, recognizing the immunodominant staphylococcal antigen A on the surface of Staphylococcus aureus, was assessed as a nuclear and fluorescent imaging probe in a preclinical model of S. aureus spinal implant infection, utilizing bioluminescently labeled bacteria to confirm the specificity and sensitivity of this targeting. Postoperative mice were administered 1D9 probe dual labeled with 89-zirconium (89Zr) and a bars represent SEM dye (NIR680) (89Zr-NIR680-1D9), and PET-CT and in vivo fluorescence and bioluminescence imaging were performed. The 89Zr-NIR680-1D9 probe accurately diagnosed both acute and subacute implant infection and permitted fluorescent image-guided surgery for selective debridement of infected tissue. Therefore, a single probe could noninvasively diagnose an infection and facilitate image-guided surgery to improve the clinical management of implant infections.

A Comparison of Defense and Plaintiff Expert Witnesses in Orthopaedic Surgery Malpractice Litigation

BACKGROUND

According to the American Academy of Orthopaedic Surgeons (AAOS) Standards of Professionalism, the responsible testimony of expert witnesses in orthopaedic surgery malpractice lawsuits is important to the public interest. However, these expert witnesses are recruited and compensated without established standards, and their testimony can potentially sway court opinion, with substantial consequences. The objective of this study was to characterize defense and plaintiff expert orthopaedic surgeon witnesses in orthopaedic surgery malpractice litigation.

METHODS

Utilizing the WestlawNext legal database, defense and plaintiff expert witnesses involved in orthopaedic surgery malpractice lawsuits from 2013 to 2017 were identified. Each witness's subspecialty, mean years of experience, involvement in academic or private practice, fellowship training, and scholarly impact, as measured by the Hirsch index (h-index), were determined through a query of professional profiles, the Scopus database, and a PubMed search. Statistical comparisons were made for each parameter among defense and plaintiff expert witnesses.

RESULTS

Between 2013 and 2017, 306 expert medical witnesses for orthopaedic cases were identified; 174 (56.9%) testified on behalf of the plaintiff, and 132 (43.1%) testified on behalf of the defense. Orthopaedic surgeons who identified themselves as general orthopaedists comprised the largest share of expert witnesses on both the plaintiff (n = 61) and defense (n = 25) sides. The plaintiff witnesses averaged 36 years of experience versus 31 years for the defense witnesses (p < 0.001); 26% of the plaintiff witnesses held an academic position versus 43% of the defense witnesses (p = 0.013). Defense witnesses exhibited a higher proportion of fellowship training in comparison to plaintiff expert witnesses (80.5% versus 64.5%, respectively, p = 0.003). The h-index for the plaintiff group was 6.6 versus 9.1 for the defense group (p = 0.04). Two witnesses testified for both the plaintiff and defense sides.

CONCLUSIONS

Defense expert witnesses held higher rates of academic appointments and exhibited greater scholarly impact than their plaintiff counterparts, with both sides averaging >30 years of experience. These data collectively show that there are differences in characteristics between plaintiff and defense witnesses. Additional study is needed to illuminate the etiology of these differences.

Long-term outcomes of cement in cement technique for revision endoprosthesis surgery

BACKGROUND AND OBJECTIVE

Cemented endoprosthetic reconstruction after resection of primary bone sarcomas has been a standard-of-care option for decades. With increased patient survival, the incidence of failed endoprostheses requiring revision surgery has increased. Revision of cemented endoprotheses by cementing into the existing cement mantle (CiC) is technically demanding.

METHODS

This is a retrospective review of our endoprosthesis database of 512 consecutive cemented endoprosthetic reconstructions performed for oncologic diagnoses between 1980 and 2014. A total of 54 implants (mean patient age 32 years, range 13-81) were revised with a CiC technique. Outcomes evaluated were prosthesis survival, revision surgery categorized according to the Henderson Failure Mode Classification, complications, and functional scores.

RESULTS

Fifteen-year Kaplan-Meier survival rate was 34% for initial revision and 39% for subsequent revision implants. Mean revised Musculoskeletal Tumor Society (MSTS) Score was 27 at latest follow-up. Infection rate was 2%, 9%, and 13% for primary endoprostheses, initial revisions, and subsequent revisions, respectively. Limb salvage rate was 87%.

CONCLUSIONS

At long-term follow up, endoprostheses revised with the CiC technique showed consistent 15-year survival from initial (34%) to subsequent (39%) revision. Despite a relatively high failure rate, these results are encouraging and demonstrate that this is a conservative, repeatable technique.

Single-Dose, Preoperative Vitamin-D Supplementation Decreases Infection in a Mouse Model of Periprosthetic Joint Infection

BACKGROUND

Despite recent advances, infection remains the most common etiology of arthroplasty failure. Recent work suggests that 25-hydroxyvitamin D (25D) deficiency correlates with the frequency of periprosthetic joint infection (PJI). We endeavored to examine whether 25D3 deficiency leads to increased bacterial burden in vivo in an established mouse model of PJI and, if so, whether this effect can be reversed by preoperative 25D3 supplementation.

METHODS

Mice (lys-EGFP) possessing fluorescent neutrophils were fed a vitamin D3-sufficient (n = 20) or deficient (n = 40) diet for 6 weeks. A group of 25D3-deficient mice (n = 20) were "rescued" with 1 intraperitoneal dose of 25D3 at 3 days before surgery. A stainless steel implant was inserted into the knee joint and the joint space was inoculated with bioluminescent Staphylococcus aureus (1 × 10 colony forming units [CFUs]). In vivo imaging was used to monitor bacterial burden and neutrophil infiltration. Blood was drawn to confirm 25D3 levels 3 days before surgery and on postoperative days (PODs) 0 and 14. Mice were killed at POD 21, and CFUs were quantified after culture. Myeloperoxidase (MPO) and β-N-acetylglucosaminidase (NAG) were assayed to look at neutrophil infiltration and activated tissue macrophage recruitment, respectively.

RESULTS

Serum values confirmed 25D3 deficiency and repletion of the 25D3-rescued group. Bacterial bioluminescence and neutrophil fluorescence were significantly greater (p < 0.05) in the 25D3-deficient group. CFU counts from the joint tissue and implant were also significantly greater in this group (p < 0.05). Rescue treatment significantly decreased bacterial burden and neutrophil infiltration (p < 0.05). Compared with the 25D3-sufficient and 25D3-rescued groups, MPO activity was higher (p < 0.02) and NAG activity was lower (p < 0.03) in the 25D3-deficient group.

CONCLUSIONS

This study demonstrated in vivo in a mouse model of PJI that (1) 25D3 deficiency results in increased bacterial burden and neutrophil infiltration, and (2) this effect can be reversed with preoperative repletion of 25D3.

CLINICAL RELEVANCE

Considering that >65% of patients undergoing arthroplasty have insufficient or low levels of total 25D and that 25D levels can be replenished with ease using a U.S. Food and Drug Administration (FDA)-approved, oral 25D3 product, 25D deficiency may be an important modifiable risk factor in humans undergoing joint replacement.

Staged reconstruction of diaphyseal fractures with segmental defects: Surgical and patient-reported outcomes

INTRODUCTION

Two-stage limb reconstruction is an option for patients with critical size segmental bone defects following acute trauma or non-union. Reconstruction is technically demanding and associated with a high complication rate. Current protocols for limb reconstruction have well-documented challenges, and no study has reported on patient outcomes using a validated questionnaire. In this study, we aimed to examine the clinical and patient-centered outcomes following our surgical protocol for two-stage limb reconstruction following critical size segmental defects.

PATIENTS AND METHODS

A single surgeon performed reconstruction of long bone defects using antibiotic impregnated cement spacers and intramedullary cancellous bone autograft. A retrospective chart review was performed. Three reviewers independently measured time to union based on radiographs. The Lower Extremity Functional Scale (LEFS) survey was administered to patients after most recent follow-up.

RESULTS

Ten limbs representing nine patients were included. All patients sustained a lower extremity injury, and one patient had bilateral lower extremity injuries. Average clinical follow-up was 18.3 months (range 7-33) from final surgical intervention, and follow-up to questionnaire administration was 28 months (range 24-37). The mean time between stages was 3.1 months. Average time to unrestricted weight-bearing was 7.9 months from Stage 1 (range 3.4-15.9) and 4.5 months from Stage 2 (range 1.1-11.6). Average time to full union was 16.7 months from Stage 1 (range 6.4-28.6) and 13.5 months from Stage 2 (range 1.8-27). Eight patients (nine limbs) participated in the LEFS survey, the average score was 53.1 (range 30-67), equating to 66% of full functionality (range 38%-84%). Complications included 5 infections, 3 non-unions, and one amputation. There was a moderate positive correlation between infection at any time point and non-union (R=0.65, p=0.03).

DISCUSSION AND CONCLUSIONS

Outcomes in this small patient cohort were good despite risks of complication. There is an association between infection and non-union. Further studies addressing clinical and functional outcomes will help to guide expectations for future surgeons and patients.

The Relationship Between OREF Grants and Future NIH Funding Success

BACKGROUND

The Orthopaedic Research and Education Foundation (OREF) is the leading specialty-specific nongovernmental organization providing orthopaedic funding in the United States. As extramural research funding has become increasingly difficult to acquire, one mission of the OREF is to support investigators to generate data needed to secure larger extramural funding from agencies such as the National Institutes of Health (NIH). The objectives of this study were to evaluate the rate of translating OREF faculty-level grants into subsequent NIH funding and to determine if there are identifiable factors that increase the rate of converting an OREF grant into NIH funding.

METHODS

This is a retrospective review of OREF grants awarded to full-time faculty orthopaedic surgeons between 1994 and 2014. Grants were analyzed on the basis of award type and were categorized as basic science, clinical, or epidemiological. Sex, individual scholarly productivity, and publication experience were evaluated. All awardees were assessed for subsequent NIH funding using the NIH RePORTER web site.

RESULTS

One hundred and twenty-six faculty-level OREF grants were awarded to 121 individuals. Twenty-seven OREF grant awardees (22%) received NIH funding at a mean of 6.3 years after OREF funding. Nineteen (46%) of 41 Career Development Grant winners later received NIH funding compared with 10 (12%) of 85 other award winners. OREF grants for basic science projects were awarded more often (58%) and were more than 4 times as likely to result in NIH funding than non-basic science projects (odds ratio, 4.70 [95% confidence interval, 1.66 to 13.33]; p = 0.0036). Faculty who later received NIH funding had higher scholarly productivity and publication experience (p < 0.05).

CONCLUSIONS

The OREF grant awardee conversion rate of 22% and, particularly, the 46% for Career Development Grant winners compares favorably with the overall NIH funding success rate (18% in 2014). Faculty-level OREF grants appear to achieve their purpose of identifying and supporting researchers who aim to secure subsequent federal funding.

CLINICAL RELEVANCE

The goal of this study is to examine how successful faculty who have obtained OREF grants have been in securing NIH funding later in their careers. Although subsequent accrual of NIH funding is not the only goal of OREF funding, it can be used as an important benchmark to assess the development of orthopaedic clinician-scientists.

Regression of Disc-Osteophyte Complexes Following Laminoplasty Versus Laminectomy with Fusion for Cervical Spondylotic Myelopathy

BACKGROUND

Laminectomy with fusion (LF) and laminoplasty are two posterior-based surgical approaches for the surgical treatment of cervical spondylotic myelopathy (CSM). The decompressive effect of these approaches is thought to be primarily related to the dorsal drift of the spinal cord away from ventral compressive structures. A lesser known mechanism of spinal cord decompression following cervical LF is regression of the ventral disc osteophyte complexes which is postulated to result from the alteration of motion across the fused motion segment. The goal of this study was to determine whether regression of the ventral disc-osteophyte complexes occur following laminoplasty and compare the magnitude of this occurrence to cervical laminectomy and fusion.

METHODS

Seventy patients with CSM who underwent pre- and postoperative magnetic resonance imaging (MRI) and were treated with either laminoplasty or LF. The size of the disc-osteophyte complex at all operative levels were measured on pre- and postoperative MRI using digital calipers.

RESULTS

The laminoplasty group consisted of 25 patients with an average age of 54.9 and a mean of 3.24 surgical levels while the LF group consisted of 45 patients with an average age of 65.4 and a mean of 3.44 surgical levels (age, p < 0.0001; levels, p= 0.46). The average time interval between pre- and post-operative MRI was 16.2 and 15.6 months in the laminoplasty and LF groups, respectively (p = 0.91). The average time interval between surgery and post-operative MRI was 10.1 and 10.7 months in the laminoplasty and LF groups, respectively (p = 0.86). When comparing pre- and post-operative MRI, there was a 9.59% decrease in disc-osteophyte complex size from 3.84mm ± 0.74 to 3.47mm ± 0.86 in the laminoplasty group compared to a 35.4% decrease in disc-osteophyte complex size from 4.60mm ± 1.06 to 2.98mm ± 1.33 in LF group (laminoplasty, p < 0.0001; LF, p = 0.0067). Using logistic regression analysis, LF, increased time interval between surgery and post-operative MRI, high cobb angle, and straight sagittal alignment were all independently associated with increased disc-osteophyte complex regression (p < 0.05). No differences in functional outcomes (as defined by mJOA scores) was found between the two surgical techniques.

CONCLUSIONS

In patients with CSM that had a posterior surgical approach, LF is associated with a larger interval regression in disc-osteophyte complex size compared to laminoplasty. This is likely related to the loss of motion of the cervical spine after surgery as governed by Wolff's law and the Heuter-Volkmann's principle. Although the decompressive effect of LF and laminoplasty is primarily related to the dorsal drift of the spinal cord away from ventral compressive structures, disc-osteophyte complex regression likely provides another mechanism of spinal cord decompression.

Combinatory antibiotic therapy increases rate of bacterial kill but not final outcome in a novel mouse model of Staphylococcus aureus spinal implant infection

Background

Management of spine implant infections (SII) are challenging. Explantation of infected spinal hardware can destabilize the spine, but retention can lead to cord compromise and biofilm formation, complicating management. While vancomycin monotherapy is commonly used, in vitro studies have shown reduced efficacy against biofilm compared to combination therapy with rifampin. Using an established in vivo mouse model of SII, we aim to evaluate whether combination therapy has increased efficacy compared to both vancomycin alone and infected controls.

Methods

An L-shaped, Kirschner-wire was transfixed into the L4 spinous process of 12-week-old C57BL/6 mice, and inoculated with bioluminescent Staphylococcus aureus. Mice were randomized into a vancomycin group, a combination group with vancomycin plus rifampin, or a control group receiving saline. Treatment began on post-operative day (POD) 7 and continued through POD 14. In vivo imaging was performed to monitor bioluminescence for 35 days. Colony-forming units (CFUs) were cultured on POD 35.

Results

Bioluminescence peaked around POD 7 for all groups. The combination group had a 10-fold decrease in signal by POD 10. The vancomycin and control groups reached similar levels on POD 17 and 21, respectively. On POD 25 the combination group dropped below baseline, but rebounded to the same level as the other groups, demonstrating a biofilm-associated infection by POD 35. Quantification of CFUs on POD 35 confirmed an ongoing infection in all three groups.

Conclusions

Although both therapies were initially effective, they were not able to eliminate implant biofilm bacteria, resulting in a rebound infection after antibiotic cessation. This model shows, for the first time, why histologic-based, static assessments of antimicrobials can be misleading, and the importance of longitudinal tracking of infection. Future studies can use this model to test combinations of antibiotic therapies to see if they are more effective in eliminating biofilm prior to human trials.

Traumatic brain injury in pediatric patients: evidence for the effectiveness of decompressive surgery

Traumatic brain injury (TBI) is the current leading cause of death in children over 1 year of age. Adequate management and care of pediatric patients is critical to ensure the best functional outcome in this population. In their controversial trial, Cooper et al. concluded that decompressive craniectomy following TBI did not improve clinical outcome of the analyzed adult population. While the study did not target pediatric populations, the results do raise important and timely clinical questions regarding the effectiveness of decompressive surgery in pediatric patients. There is still a paucity of evidence regarding the effectiveness of this therapy in a pediatric population, and there is an especially noticeable knowledge gap surrounding age-stratified interventions in pediatric trauma. The purposes of this review are to first explore the anatomical variations between pediatric and adult populations in the setting of TBI. Second, the authors assess how these differences between adult and pediatric populations could translate into differences in the impact of decompressive surgery following TBI.

Characterization and taxonomic validity of the ciliate Oxytricha trifallax (Class Spirotrichea) based on multiple gene sequences: limitations in identifying genera solely by morphology

Oxytricha trifallax - an established model organism for studying genome rearrangements, chromosome structure, scrambled genes, RNA-mediated epigenetic inheritance, and other phenomena - has been the subject of a nomenclature controversy for several years. Originally isolated as a sibling species of O. fallax, O. trifallax was reclassified in 1999 as Sterkiella histriomuscorum, a previously identified species, based on morphological similarity. The proper identification of O. trifallax is crucial to resolve in order to prevent confusion in both the comparative genomics and the general scientific communities. We analyzed nine conserved nuclear gene sequences between the two given species and several related ciliates. Phylogenetic analyses suggest that O. trifallax and a bona fide S. histriomuscorum have accumulated significant evolutionary divergence from each other relative to other ciliates such that they should be unequivocally classified as separate species. We also describe the original isolation of O. trifallax, including its comparison to O. fallax, and we provide criteria to identify future isolates of O. trifallax.

Variation in a locus linked to platelet aggregation phenotype predicts intraparenchymal hemorrhagic volume

OBJECTIVE

Alteration in platelet aggregation has been shown to promote bleeding and affect outcome after intracerebral hemorrhage (ICH).We investigated the influence of genetic variants of platelet aggregation, and their effects on admission ICH volume and clinical outcome.

METHODS

Our prospective study analyzed selected candidate single-nucleotide polymorphisms (SNPs) previously associated with platelet aggregation phenotype in previous genome-wide association studies, with regards to outcome and ICH volume. Patients were assessed at the Columbia University Medical Center Neuro-Intensive Care Unit. Exclusion criteria included age <18 years, ICH following trauma, hemorrhagic transformation, or tumor, no consent for genetic analysis, or incomplete data. Radiological variables (location and volume of acute ICH, presence of intraventricular extension, midline shift, and hydrocephalus) and clinical variables (mortality and modified Rankin score at discharge) were prospectively recorded.

RESULTS

One hundred and twenty-two patients with spontaneous ICH between February 2009 and May 2011 diagnosed via clinical assessment and admission computed tomography scan were included. The median admission Glasgow coma scale score (GCS) was 11·5. Univariate predictors of mortality at discharge included systolic blood pressure, presence of intraventricular hemorrhage, anticoagulant use, and GCS, the only independent predictor of discharge mortality (P<0·001). Age, intraventricular hemorrhage, and GCS were associated with poor functional outcome; age (P = 0·001) and GCS (P<0·001) were significant in the multivariate model. Admission GCS (P<0·01), antiplatelet use, and rs342286 (PIK3CG; P = 0·04; R(2) = 0·247) had univariate associations with hematoma volume.

DISCUSSION

We identified SNP rs342286 as an independent predictor of admission hematoma volume. Our findings suggest that PIK3CG function, which is previously linked to this SNP and affects platelet aggregation, impacts the severity of the intraparenchymal bleed.