In Vivo Assessment of Phage and Linezolid Based Implant Coatings for Treatment of Methicillin Resistant S. aureus (MRSA) Mediated Orthopaedic Device Related Infections

Staphylococcus comprises up to two-thirds of all pathogens in orthopaedic implant infections with two species respectively Staphylococcus aureus and Staphylococcus epidermidis, being the predominate etiological agents isolated. Further, with the emergence of methicillin-resistant S. aureus (MRSA), treatment of S. aureus implant infections has become more difficult, thus representing a devastating complication. Use of local delivery system consisting of S.aureus specific phage along with linezolid (incorporated in biopolymer) allowing gradual release of the two agents at the implant site represents a new, still unexplored treatment option (against orthopaedic implant infections) that has been studied in an animal model of prosthetic joint infection. Naked wire, hydroxypropyl methylcellulose (HPMC) coated wire and phage and /or linezolid coated K-wire were surgically implanted into the intra-medullary canal of mouse femur bone of respective groups followed by inoculation of S.aureus ATCC 43300(MRSA). Mice implanted with K-wire coated with both the agents i.e phage as well as linezolid (dual coated wires) showed maximum reduction in bacterial adherence, associated inflammation of the joint as well as faster resumption of locomotion and motor function of the limb. Also, all the coating treatments showed no emergence of resistant mutants. Use of dual coated implants incorporating lytic phage (capable of self-multiplication) as well as linezolid presents an attractive and aggressive early approach in preventing as well as treating implant associated infections caused by methicillin resistant S. aureus strains as assessed in a murine model of experimental joint infection.

Racial Disparities in Lower Extremity Arthroplasty Outcomes and Use

Race-associated disparities often occur in patients who undergo lower extremity total joint arthroplasty (TJA). Although it is imperative to elucidate and describe the disparities in race and ethnicity that may influence patient perception, satisfaction, and surgical outcomes, there is a paucity of reports detailing the nature of potential racial disparities in TJA. Therefore, the purpose of this review was to examine racial and ethnic disparities in the (1) physician-patient relationship; (2) use of TJA; (3) intraoperative and 30-day postoperative complications; and (4) patient-reported outcomes. Although there are limited studies that evaluated this topic, it has been shown that there are race-specific differences in physician-patient relationships. Specifically, African American patients report lower satisfaction rates in communication with their physician than their Caucasian counterparts and physicians were more apt to describe African Americans as less "medically cooperative." The majority of the studies the authors found regarding TJA use indicated that African Americans and Hispanics were less likely to undergo lower extremity TJA than Caucasians. Furthermore, racial minorities may have higher 30-day readmission and intra- and postoperative complication rates compared with Caucasians. Despite these compelling findings, concrete conclusions are difficult to make due to the presence of multiple confounding patient factors, and more studies examining the racial and ethnic disparities in patients with TJA are needed.

Repair of massively defected hemi-joints using demineralized osteoarticular allografts with protected cartilage

Surgical replacement of massively defected joints necessarily relies on osteochondral grafts effective to both of bone and cartilage. Demineralized bone matrix (DBM) retains the osteoconductivity but destroys viable chondrocytes in the cartilage portion essential for successful restoration of defected joints. This study prepared osteochondral grafts of DBM with protected cartilage. Protected cartilage portions was characterized by cellular and molecular biology and the grafts were allogenically used for grafting. Protected cartilage showed similar histomorphological structure and protected proteins estimated by total proteins and cartilage specific proteins as in those of fresh controls when DBMs were generated in bone portions. Such grafts were successfully used for simultaneously repair of bone and cartilage in massively defected osteoarticular joints within 16 weeks post-surgery. These results present an allograft with clinical potential for simultaneous restoration of bone and cartilage in defected joints.

Human mesenchymal stem cells as a tool for joint repair in rheumatoid arthritis

Rheumatoid arthritis (RA) is characterised with chronic inflammatory synovitis and progressive joint. Because damaged and/or deformed joints cannot be repaired, a novel treatment strategy aimed at both anti-inflammation and bone regeneration is a prerequisite. Mesenchymal stem cells (MSCs) can be easily isolated from various organs and possess multipotent capacity and exhibit immunoregulatory properties. Using human MSC derived from bone marrow and adipose tissue, we have clarified the following novel findings in vitro. 1) MSCs differentiated into osteoblasts or osteocytes under osteoblast-conditioned medium including the inflammatory stimuli such as IL-1. 2) The combination of IL-6 and soluble IL-6 receptor induced differentiation of MSCs to chondrocyte. 3) MSCs produced osteoprotegerin and inhibited osteoclastogenesis. Furthermore, we developed a local delivery system of MSCs by using nano-fibre scaffold. MSCs seeded on nano-fibre scaffold suppressed arthritis and joint destruction by inhibiting systemic inflammatory reaction and immune response through the induction of regulatory T cells and subsequent reduction in the production of anti-type II collagen antibody in vivo. Thus, our data may serve as a new strategy for MSC-based therapy in inflammatory diseases and an alternative delivery method for the treatment of damaged joints in RA.

Comparison of limited-contact dynamic compression plate and locking compression plate constructs for proximal interphalangeal joint arthrodesis in the horse

This study compared in vitro monotonic and cyclic mechanical properties of equine proximal interphalangeal joint arthrodeses stabilized using an open or closed technique combined with axial 4.5 mm narrow limited-contact dynamic compression plate (LC-DCP) or 4.5 mm narrow locking compression plate (LCP). Ten forelimb pairs were randomly assigned to LCP or LC-DCP groups. One limb in each pair was assigned to either open or closed technique. Limbs were tested for cyclic fatigue at 20 000 cycles and then single-cycle to failure under 3-point dorsopalmar bending. There was no significant difference in stiffness of constructs during cyclic fatigue testing or on force or stiffness at failure in single cycle to failure testing between open and closed techniques or between plate types. Both implants, surgical technique, or combinations thereof are suitable for clinical use. More work is necessary to define the interaction between implant type and surgical technique.

Development of a Cadaveric Model for Arthrocentesis

This article reports the development of a novel cadaveric model for future use in teaching arthrocentesis. In the clinical setting, animal safety is essential and practice is thus limited. Objectives of the study were to develop and compare a model to an unmodified cadaver by injecting one of two types of fluids to increase yield. The two fluids injected, mineral oil (MO) and hypertonic saline (HS), were compared to determine any difference on yield. Lastly, aspiration immediately after (T1) or three hours after (T2) injection were compared to determine any effect on diagnostic yield. Joints used included the stifle, elbow, and carpus in eight medium dog cadavers. Arthrocentesis was performed before injection (control) and yield measured. Test joints were injected with MO or HS and yield measured after range of motion (T1) and three hours post injection to simulate lab preparation (T2). Both models had statistically significantly higher yield compared with the unmodified cadaver in all joints at T1 and T2 (p<.05) with the exception of HST2 carpus. T2 aspiration had a statistically significant lower yield when compared to T1HS carpus, T1HS elbow, and T1MO carpus. Overall, irrespective of fluid volume or type, percent yield was lower in T2 compared to T1. No statistically significant difference was seen between HS and MO in most joints with the exception of MOT1 stifle and HST2 elbow. Within the time frame assessed, both models were acceptable. However, HS arthrocentesis models proved appropriate for student trial due to the difficult aspirations with MO.

Adapting Scott and Bruce's General Decision-Making Style Inventory to Patient Decision Making in Provider Choice

OBJECTIVE

Research testing the concept of decision-making styles in specific contexts such as health care-related choices is missing. Therefore, we examine the contextuality of Scott and Bruce's (1995) General Decision-Making Style Inventory with respect to patient choice situations.

METHODS

Scott and Bruce's scale was adapted for use as a patient decision-making style inventory. In total, 388 German patients who underwent elective joint surgery responded to a questionnaire about their provider choice. Confirmatory factor analyses within 2 independent samples assessed factorial structure, reliability, and validity of the scale.

RESULTS

The final 4-dimensional, 13-item patient decision-making style inventory showed satisfactory psychometric properties. Data analyses supported reliability and construct validity. Besides the intuitive, dependent, and avoidant style, a new subdimension, called "comparative" decision-making style, emerged that originated from the rational dimension of the general model.

CONCLUSIONS

This research provides evidence for the contextuality of decision-making style to specific choice situations. Using a limited set of indicators, this report proposes the patient decision-making style inventory as valid and feasible tool to assess patients' decision propensities.

[Continuous passive motion in joint rehabilitation after injury and surgery]

Devices for continuous passive motion, also known as motor-driven splints, are widely used in rehabilitation therapy following injuries and surgery. They present an adjunct method substituting the physical work of a physiotherapist. The method is indicated in early post-injury or post-operative periods. It is expected to increase blood drainage and remove haemarthrosis and synovial fluid exudate which precede an undesired development of granulation and fibrous tissues. However, continuing such an intensive therapy after 3 to 4 post-operative weeks lacks its raison d'être. The only exceptions include conditions after autologous chondrocyte transplantation and a supplementary therapy to active rehabilitation programmes for releasing muscle hypertonia which restricts movement. Values for the range of motion set up on the device cannot be considered the real values pertinent to the exercised joint; these are usually considerably lower. Key words: continuous passive motion, motor-driven splint.

Biomechanical evaluation of an interfacet joint decompression and stabilization system

A majority of the middle-aged population exhibit cervical spondylosis that may require decompression and fusion of the affected level. Minimally invasive cervical fusion is an attractive option for decreasing operative time, morbidity, and mortality rates. A novel interfacet joint spacer (DTRAX facet screw system, Providence Medical) promises minimally invasive deployment resulting in decompression of the neuroforamen and interfacet fusion. The present study investigates the effectiveness of the device in minimizing intervertebral motion to promote fusion, decompression of the nerve root during bending activity, and performance of the implant to adhere to anatomy during repeated bending loads. We observed flexion, extension, lateral bending, and axial rotation resonant overshoot mode (ROM) in cadaver models of c-spine treated with the interfacet joint spacer (FJ spacer) as stand-alone and supplementing anterior plating. The FJ spacer was deployed bilaterally at single levels. Specimens were placed at the limit of ROM in flexion, extension, axial bending, and lateral bending. 3D images of the foramen were taken and postprocessed to quantify changes in foraminal area. Stand-alone spacer specimens were subjected to 30,000 cycles at 2 Hz of nonsimultaneous flexion-extension and lateral bending under compressive load and X-ray imaged at regular cycle intervals for quantitative measurements of device loosening. The stand-alone FJ spacer increased specimen stiffness in all directions except extension. 86% of all deployments resulted in some level of foraminal distraction. The rate of effective distraction was maintained in flexed, extended, and axially rotated postures. Two specimens demonstrated no detectable implant loosening (<0.25 mm). Three showed unilateral subclinical loosening (0.4 mm maximum), and one had subclinical loosening bilaterally (0.5 mm maximum). Results of our study are comparable to previous investigations into the stiffness of other stand-alone minimally invasive technologies. The FJ spacer system effectively increased stiffness of the affected level comparable to predicate systems. Results of this study indicate the FJ spacer increases foraminal area in the cervical spine, and decompression is maintained during bending activities. Clinical studies will be necessary to determine whether the magnitude of decompression observed in this cadaveric study will effectively treat cervical radiculopathy; however, results of this study, taken in context of successful decompression treatments in the lumbar spine, are promising for the continued development of this product. Results of this biomechanical study are encouraging for the continued investigation of this device in animal and clinical trials, as they suggest the device is well fixated and mechanically competent.

Incorporating population-level variability in orthopedic biomechanical analysis: a review

Effectively addressing population-level variability within orthopedic analyses requires robust data sets that span the target population and can be greatly facilitated by statistical methods for incorporating such data into functional biomechanical models. Data sets continue to be disseminated that include not just anatomical information but also key mechanical data including tissue or joint stiffness, gait patterns, and other inputs relevant to analysis of joint function across a range of anatomies and physiologies. Statistical modeling can be used to establish correlations between a variety of structural and functional biometrics rooted in these data and to quantify how these correlations change from health to disease and, finally, to joint reconstruction or other clinical intervention. Principal component analysis provides a basis for effectively and efficiently integrating variability in anatomy, tissue properties, joint kinetics, and kinematics into mechanistic models of joint function. With such models, bioengineers are able to study the effects of variability on biomechanical performance, not just on a patient-specific basis but in a way that may be predictive of a larger patient population. The goal of this paper is to demonstrate the broad use of statistical modeling within orthopedics and to discuss ways to continue to leverage these techniques to improve biomechanical understanding of orthopedic systems across populations.

Selection of tendon grafts for distal radioulnar ligament reconstruction and report of a modified technique

PURPOSE

To investigate the graft length necessary to complete a distal radioulnar ligament reconstruction and assess the suitability of several tendon graft sources.

METHODS

We measured the graft length needed to complete the distal radioulnar ligament reconstruction in 7 fresh-frozen cadaver specimens. The pure tendon lengths of 7 tendon graft sources were measured: palmaris longus, extensor indicis proprius, slips of extensor digiti minimi and abductor pollicis longus, and portions of flexor carpi ulnaris, flexor carpi radialis, and extensor carpi ulnaris. A modified technique that allows for a shorter length of graft is also described, and the suitability of each graft source for this technique was assessed.

RESULTS

The mean graft lengths needed to complete the original and modified reconstructions were 138 mm and 89 mm, respectively. The average length of the tendon graft when measured as pure tendon was: palmaris longus (127 mm), slip of extensor digiti minimi (112 mm), extensor indicis proprius (100 mm), partial flexor carpi radialis (87 mm), slip of abductor pollicis longus (69 mm), partial flexor carpi ulnaris (67 mm), and partial extensor carpi ulnaris (67 mm). The palmaris longus was too short for the original technique in the majority of specimens but was sufficient to complete the modified technique in every specimen that had a palmaris longus. Six specimens also had an extensor indicis proprius of suitable length for the modified technique.

CONCLUSIONS

The length of donor graft required for the modified reconstruction was significantly less than that needed for the original reconstruction. Three specimens had no donor tendons sufficiently long to complete the original technique if a pure tendon graft were used, whereas the modified technique could be completed in all specimens.

CLINICAL RELEVANCE

Many tendon graft sources in the upper extremity are of insufficient length to complete the distal radioulnar ligament reconstruction as described. A modified technique using suture anchors may be a useful alternative in such cases.

Prosthetic joint infections due to methicillin-resistant and methicillin-susceptible staphylococci treated with open debridement and retention of the prosthesis

OBJECTIVES

To compare the specific characteristics, the outcome and the predictors of failure of prosthetic joint infections (PJI) due to methicillin-resistant (MRS) and methicillin- susceptible staphylococci (MSS) treated with open debridement and retention of the implant.

MATERIAL AND METHODS

PJI due to MRS or MRS prospectively registered in a database from 1999 to 2009 were retrospectively reviewed.

RESULTS

During the study period, 96 patients met the inclusion criteria of the study. The mean follow-up period was 3.9 years and at least 2 years in all patients. The failure rate was 25%. The only variable significantly associated with failure in the global cohort was polymicrobial infection (59.3% vs. 40.7%, p=0.036). Thirty-four (35.4%) patients had an infection due to MRS and 62 (63.6%) due to MSS. Among MSS infections, 95.2% corresponded to primary arthroplasties while 29.4% of PJI due to MRS were after revision arthroplasties (p=0.001). CRP was significantly higher in PJI due to MSS (5.2 mg/dl vs 9.1 mg/dL, p=0.02).The failure rate (20% vs 27%, p=0.62) was very similar in MSS and MRS groups.

CONCLUSION

PJI due to MRS were mainly coagulase-negative staphylococci, more frequent after revision arthroplasties, had a lower inflammatory response, and had a similar failure rate than MSS infections.

[Surgical reconstruction of joint function]

In recent years a concept of "treat to target" is introduced into a medical treatment of RA, and tight control is recommended from the early stage of the disease. However, it is difficult to relieve all patients in a true remission. Nowadays, disease activity is controlled well and a reconstructive surgery is performed at a limited number of the damaged joints in a state of good remaining of bone and soft tissue structures. The patients are highly motivated, and a newly developed disorder at the non-surgically treated joints is uncommon. Therefore, an aggressive rehabilitation is possible. Combined with a medical treatment of RA, a surgical intervention enables to acquire a higher level of ADL and an improved QOL (Japanese T2T).

Joint-preserving tumor resection and reconstruction using image-guided computer navigation

BACKGROUND

Joint-preserving surgery is performed in select patients with bone sarcomas of extremities and allows patients to retain the native joint with better joint function. However, recurrences may relate to achieving adequate margins and there is frequently little room for error in tumors close to the joint surface. Further, the tumor margin on preoperative CT and/or MR images is difficult to transpose to the actual extent of tumor in the bone in the operating room.

QUESTIONS/PURPOSES

We therefore determined whether joint-preserving tumor surgery could be performed accurately under image-guided computer navigation and determined local recurrences, function, and complications.

METHODS

We retrospectively studied eight patients with bone sarcoma of extremities treated surgically by navigation with fused CT-MR images. We assessed the accuracy of resection in six patients by comparing the cross sections at the resection plane with complementary prosthesis templates. Mean age was 17 years (range, 6-46 years). Minimum followup was 25 months (mean, 41 months; range, 25-60 months).

RESULTS

The achieved resection was accurate, with a difference of 2 mm or less in any dimension compared to that planned in patients with custom prostheses. We noted no local recurrence at latest followup. The mean Musculoskeletal Tumor Society score was 29 (range, 28-30). There were no complications related to navigation planning and procedures. There was no failure of fixation at the remaining epiphysis.

CONCLUSIONS

In selected patients, the computer-assisted approach facilitates precise planning and execution of joint-preserving tumor resection and reconstruction. Further followup assessment in a larger study population is required in these patients.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See Instructions for Authors for a complete description of levels of evidence.

Subject-specific analysis of joint contact mechanics: application to the study of osteoarthritis and surgical planning

Advances in computational mechanics, constitutive modeling, and techniques for subject-specific modeling have opened the door to patient-specific simulation of the relationships between joint mechanics and osteoarthritis (OA), as well as patient-specific preoperative planning. This article reviews the application of computational biomechanics to the simulation of joint contact mechanics as relevant to the study of OA. This review begins with background regarding OA and the mechanical causes of OA in the context of simulations of joint mechanics. The broad range of technical considerations in creating validated subject-specific whole joint models is discussed. The types of computational models available for the study of joint mechanics are reviewed. The types of constitutive models that are available for articular cartilage are reviewed, with special attention to choosing an appropriate constitutive model for the application at hand. Issues related to model generation are discussed, including acquisition of model geometry from volumetric image data and specific considerations for acquisition of computed tomography and magnetic resonance imaging data. Approaches to model validation are reviewed. The areas of parametric analysis, factorial design, and probabilistic analysis are reviewed in the context of simulations of joint contact mechanics. Following the review of technical considerations, the article details insights that have been obtained from computational models of joint mechanics for normal joints; patient populations; the study of specific aspects of joint mechanics relevant to OA, such as congruency and instability; and preoperative planning. Finally, future directions for research and application are summarized.

Calcium sulfate cement in contained traumatic metaphyseal bone defects

The aim of this study was to evaluate prospective patients with periarticular fractures where a meta physeal bone defect was grafted with high compressive calcium sulfate cement. The calcium sulfate cement MIIG X3, (Wright Medical Technology, Inc, Arlington, TN) was used in 45 patients with periarticular fractures--distal radial, tibial plateau, humeral head, and calcaneal fractures--to fill the metaphyseal defect. All fractures were treated either with open or closed reduction, fracture fixation, and the cement was applied openly or closed. Radiographs were evaluated for fracture reduction, joint line gap, and step, as well as for rate of graft replacement by bone. All fractures united without an additional procedure. There were no wound infections or other complications attributed to the graft. At three-month follow-up, a complete graft replacement by bone was observed in all fractures. Joint line step was not developed in any patient, but a joint line gap of 3 mm was observed postoperatively in one patient with a tibial plateau fracture. Loss of reduction occurred in one patient with an extra-articular distal radial fracture treated with closed reduction and k-wire fixation. Cement that escaped into the joint or the surrounding soft tissues was not visible at the six-week follow-up. In conclusion, the results of this study confirm the safety and the efficacy of this cement when it is used as graft with the appropriate fixation method in traumatic metaphyseal bone defects.

[Prostheses, a surgical answer to the wear and tear of joints due to osteoarthritis]

The joints of patients with osteoarthritis suffer constant and irreversible wear and tear resulting in pain and functional incapacity. Prostheses are an appropriate response for improving quality of life.

Role of Newman's classification in predicting outcomes in patients with crystal arthritis

PURPOSE

The aim of the study was to evaluate the utility of Newman's classification in predicting outcomes in patients presenting with crystal arthritis.

METHODS

Between January and December 2009, all patients who presented to our institution with acute crystal arthritis and were investigated with microbiological assessment of their synovial fluid were included in the study. Patients were divided into two groups depending on the fulfilment of Newman's criteria for culture-negative septic arthritis. Group 1 included patients that fulfilled Newman's B criteria. Group 2 included patients that fulfilled Newman's C criteria. A database looking at the demographics, mode of presentation, investigations, treatment and outcomes was then established and the results compared between the two groups.

RESULTS

A total of 58 patients were identified (group 1: n = 13; group 2: n = 45). The average age was 71 years (range 33-96). The joint most commonly involved was the knee followed by the wrist. Clinical findings at presentation were comparable in both groups; however, WBC and C-reactive protein (CRP) were more likely to be raised in group 1. Although most patients in group 1 were treated with antibiotics (62%) there was still a higher rate of morbidity, greater use of supportive therapy and a longer hospital stay (22.3 days, SD 17.4) in comparison with group 2, where most patients were treated by observation only (76%, mean hospital stay 3.5 days, SD ± 4.4). The difference in length of hospital stay was statistically significant (p < 0.0001).

CONCLUSIONS

Newman's criteria are a good indicator for prognosis in patients with crystal arthritis. However, the presence of crystals in an acutely inflamed joint does not exclude the need for supportive therapy and long hospital stay even in the absence of positive synovial fluid culture.