Percutaneous pars interarticularis screw fixation: a technical note.

PURPOSE: A conventional midline posterior approach is used for most of the described surgical techniques. We describe a technique of percutaneous fixation of the pars interarticularis, augmented where necessary by grafting the defect, which minimises muscle injury. METHOD: A 4.5 mm partially threaded dynamic compression screw is placed over a wire inserted percutaneously across the pars interarticularis defect. Compression is achieved across the pars interarticularis defect on placement of the screw. The screw is locked in a compressed state. RESULTS: The patient is mobilised the same day with a corset for comfort and discharged the following day. Aerobic fitness is maintained for 3 months; then, focused rehabilitation performed until a CT scan confirms healing at 5-6 months, at which stage full (sports) activity is resumed. CONCLUSIONS: The minimal tissue injury and small incision used allow for the minimising of complications and for a rapid recovery and discharge from hospital. With adolescents, we have the opportunity to treat symptomatic pars interarticularis defects with minimal disruption to their academic and physical development.

Pars interarticularis injury in elite athletes - The role of imaging in diagnosis and management.

Injuries of the lumbar neural arch, in particular the pars interarticularis, are widely considered to be due to abnormal bone stress secondary to repetitive loading/shearing, and are a common pathology and a main cause of lower back pain in elite athletes across a range of sports. Medical imaging plays a pivotal role in the diagnosis, monitoring and prognostication of neural arch injury. Early detection is highly desirable in the young elite athlete, as early injuries have been shown to require shorter recovery time and have a higher potential of full healing, whilst accurate grading of injury allows appropriate rehabilitation planning. Various imaging modalities are used in the diagnosis and management of pars stress injury, each with their strengths and weaknesses. There is currently a lack of general consensus over the most appropriate imaging pathway for neural arch injury in this specific group of patients. In this review article, we present an overview of neural arch injury, the various imaging modalities used and their imaging appearances with a brief pictorial review, and a proposed imaging algorithm with special considerations in the young elite athletes.

Comparative performance of three ceramic bone graft substitutes.

BACKGROUND CONTEXT: A number of different synthetic calcium-based bone graft substitutes (BGS) are currently available for clinical use. There is, however, a lack of comparative performance data regarding the relative efficacy of these materials when placed in an osseous defect site. PURPOSE: To compare the rate, quality, and extent of osseous healing in a standard rabbit defect model for three commercially available BGS materials by measuring early bone formation and completion of defect healing and to identify whether rapid scaffold resorption stimulated or impaired bone healing. STUDY DESIGN: Osteochondral defects, 4.8 mm in diameter and 6 to 7 mm deep, were made through the articular surface into the subchondral bone of the femoral condyle of New Zealand White rabbits and filled with cylindrical pellets of one of three commercially available BGS materials: dense calcium sulfate (DCaS), ultraporous tricalcium phosphate (beta-TCP), and porous silicated calcium phosphate (Si-CaP). The repair response was examined at 1, 3, 6, and 12 weeks after surgery (n=4 per BGS per time point). METHOD: Qualitative histological and quantitative histomorphometric (% new bone, % bone graft substitute, capillary index, and mineral apposition rates) analysis. RESULTS: Rapid resorption of D-CaS, primarily through dissolution, elicited a mild inflammatory response that left the defect site empty before significant quantities of new bone were formed. Both beta-TCP and Si-CaP scaffolds supported early bone apposition (<1 week). However, beta-TCP degradation products subsequently provoked an inflammatory response that impaired and reversed bone apposition within the defect site. The Si-CaP scaffolds appeared to be more stable and supported further bone apposition, with the development of an adaptive bone-scaffold composite; cell-mediated resorption of scaffold and new bone were observed in response to local load and contributed to the production of a functional repair within the defect site. CONCLUSIONS: Rapid BGS resorption impaired the regenerative ability of local bone via three pathways: 1) insufficient persistence of an osteoconductive scaffold to encourage bone apposition, 2) destabilization of early bony apposition through scaffold disintegration, and 3) stimulation of an inflammatory response by elevated levels of particulate degradation products. This had a significant impact on the ultimate rate of healing. D-CaS did not stimulate early bone apposition, but bone repair was more advanced in D-CaS-treated defects at 12 weeks as compared with those treated with beta-TCP, despite the beta-TCP supporting direct bone apposition at 1 week. Si-CaP appeared to provide a more stable osteoconductive scaffold, which supported faster angiogenesis and bone apposition throughout the defect site, with the development of a functionally adaptive trabecular structure through resorption/remodelling of both scaffold and new bone. There was rapid formation of mineralized tissue at week 1 within the center of the defect and complete infiltration with dense, predominantly mature bone by weeks 3 to 6. The progressive remodeling of bone ingrowth and scaffold to reflect the distribution of local host tissue, combined with histological evidence of targeted osteoclastic resorption of both scaffold and bone, suggest that bone adaptation within the scaffold could be in response to Wolff's law. Although this model may not directly translate to a spinal fusion model and the products may vary according to the environment, these results suggest that, in patients in whom bone regeneration may be compromised, the degradation observed with some resorbable bone grafts may contribute to the decoupling of bone regeneration and resorbtion within the graft site, which may ultimately lead to incomplete bone repair.

Neurological complications using a novel retractor system for direct lateral minimally invasive lumbar interbody fusion.

We describe our experience using the RAVINE retractor (K2M, Leesburg, VA, USA) to gain access to the lateral aspect of the lumbar spine through a retroperitoneal approach. Postoperative neurological adverse events, utilising the mentioned retractor system, were recorded and analysed. We included 140 patients who underwent minimally invasive lateral lumbar interbody fusion (MI-LLIF) for degenerative spinal conditions between 2011 and 2015 at two major spinal centres. A total of 228 levels were treated, 35% one level, 40% two level, 20% three level and 5% 4 level surgeries. The L4/5 level was instrumented in 28% of cases. 12/140 patients had postoperative neurological complications. Immediately after surgery, 5% of patients (7/140) had transient symptoms in the thigh ranging from sensory loss, pain and paraesthesia, all of which recovered within 12weeks following surgery. There were five cases of femoral nerve palsy (3.6% - two ipsilateral and three contralateral), all of which recovered completely with no residual sensory or motor deficit within 6months. MI-LLIF done with help of the described retractor system has proved a safe and efficient way to achieve interbody fusion with minimal complications, mainly nerve related, that recovered quickly. Judicious use of the technique to access the L4/5 level is advised.

Effectiveness of Broad-Spectrum Chemical Produce Sanitizers against Foodborne Pathogens as In Vitro Planktonic Cells and on the Surface of Whole Cantaloupes and Watermelons.

Over the past few years, foodborne disease outbreaks linked to enteric pathogens present on cantaloupe and watermelon surfaces have raised concerns in the melon industry. This research evaluated the effectiveness of commercially available produce sanitizers against selected foodborne pathogens, both in cell suspensions and on the outer rind surface of melons. The sanitizers (65 and 200 ppm of chlorine, 5 and 35% hydrogen peroxide, 5 and 50 ppm of liquid chlorine dioxide, various hydrogen peroxide-acid combinations, 0.78 and 2.5% organic acids, and 300 ppm of quaternary ammonium) were tested against Escherichia coli O157:H7, Listeria monocytogenes, Salmonella, and non-O157 Shiga toxin-producing E. coli (O26, O45, O103, O111, O121, and O145). The cell suspension study revealed the ability of all tested sanitizers to reduce all selected pathogens by 0.6 to 9.6 log CFU/ml in vitro. In the melon study, significant differences in pathogen reduction were observed between sanitizers but not between melon types. The most effective sanitizers were quaternary ammonium and hydrogen peroxide-acid combinations, with 1.0- to 2.2-log CFU/g and 1.3- to 2.8-log CFU/g reductions, respectively, for all pathogens. The other sanitizers were less effective in killing the pathogens, with reductions ranging from 0.0 to 2.8 log CFU/g depending on pathogen and sanitizer. This study provides guidance to the melon industry on the best produce sanitizers for use in implementing a broad-spectrum pathogen intervention strategy.