Tularemia Proximal Interphalangeal Joint Septic Arthritis: A Case Report.

CASE: A case of Francisella tularensis finger proximal interphalangeal joint septic arthritis secondary to feral cat bite is presented. The patient underwent operative debridement on presentation. On postoperative day 5, a gram-negative rod resembling F. tularensis was identified. The patient received 4 weeks of gentamicin for culture-confirmed ulceroglandular tularemia. At the final follow-up, the infection had resolved, and full function of the digit had been regained. CONCLUSION: Francisella tularensis septic arthritis secondary to a feral cat bite is exceedingly rare but should be considered in the appropriate clinical context. Proper identification and treatment with antibiotics is essential for a positive outcome.

Is pin-plate overlap in tibial plateau fractures associated with increased infection rates?

INTRODUCTION: Despite advances in the treatment of high energy proximal tibia fractures, including the utilization of staged management with external fixation, the infection rate remains high. Overlap between external fixator pin sites and definitive internal fixation has been proposed as a risk factor for infection. METHODS: This retrospective study reviews 244 patients with staged knee-spanning external fixation followed by delayed definitive internal fixation at two separate level one trauma centers. Presence of pin-plate overlap as well as several other known risk factors for infection were recorded and measured to include open fractures, compartment syndrome, operative time and number of incisions. Development of deep infection was the primary outcome. Both univariate and multivariate statistics were applied to determine differences in rates of infection. RESULTS: 65 (26.6%) patients had presence of pin-plate overlap while 179 (73.4%) patients had no overlap. There were no differences between overlapping and non-overlapping groups with respect to other infectious risk factors. Deep infection occurred in 34 (13.9%) total patients, 18 (27.7%) were in patients with pin-plate overlap and 16 (8.9%) in those without overlap. (P = 0.003; RR 3.01, 95% CI 1.51-4.76). DISCUSSION: This large, multicenter study demonstrated a statistically significant association between pin-plate overlap and the development of deep infection in tibial plateau fractures. On multivariate analysis, pin-plate overlap was identified as an independent risk factor for infection. When treating these complex injuries, surgeons should consider the definitive fixation construct when placing external fixation pins.

Biomechanics of prophylactic tethering for proximal junctional kyphosis: effects of cyclic loading on tether strength and failure properties.

STUDY DESIGN: Biomechanical evaluation of woven polyester tethers. OBJECTIVES: To quantify changes in tether elongation, stiffness, and failure characteristics after cyclic loading. Ligamentous augmentation is gaining interest as a technique to prevent proximal junctional kyphosis (PJK) in adult spinal fusions. There are a lack of data regarding the effects of cyclic loading on polyester tether mechanical properties. Tether stretch may lead to loss of stabilization and increased risk of tether failure. Biomechanical data are needed to determine the effects of cyclic loading on tether integrity. METHODS: Testing was done in two materials: (1) a synthetic cortical bone composite to determine baseline mechanical properties, and (2) nine cadaveric L1 spinous processes. 5 mm woven polyester tethers were looped through 2.5 mm holes drilled in each material. First, five tethers were tested directly to failure in the synthetic bone to establish baseline failure properties. Next, tethers were tested at one of the three cyclic load ranges [5%, 25%, and 50% (n = 5 each) of baseline failure] for 1000 cycles and then loaded to failure. Cadaveric tests were done at the 25% range and compared to synthetic bone tests at the same range. Cadaveric failure tests were classified as either tether failure or spinous process bone failure. RESULTS: Greater cyclic loading range had a significant effect on tether loop elongation, increased stiffness, and decreased ultimate tensile force. Among the cadaveric failure tests, 56% resulted in tether failure and the remaining 44% resulted in bone failure. CONCLUSIONS: Polyester tethers stretch significantly when loaded to physiological ranges. Anticipation of tether stretch may be an important consideration for a tethering strategy to prevent PJK. Improved understanding of tether material properties can provide guidance for the evaluation of clinical outcomes associated with techniques to reduce the risk of PJK caused by ligamentous laxity. LEVEL OF EVIDENCE: Biomechanical study.

Biomechanics of Prophylactic Tethering for Proximal Junctional Kyphosis: Characterization of Spinous Process Tether Pretensioning and Pull-Out Force.

STUDY DESIGN: Biomechanical evaluation of cadaver functional spinal units (FSUs). OBJECTIVES: Demonstrate the effect of increasing spinous process (SP) tether pretension on FSU flexion range of motion (ROM), intervertebral disc (IVD) pressure, and SP force. Quantify SP tether pull-out forces and relate them to SP forces generated at maximum flexion. SUMMARY OF BACKGROUND DATA: There has been recent interest in the use of SP tethering for prophylactic treatment of proximal junctional kyphosis (PJK). There is currently no consensus on standard tethering technique and no biomechanical data on the effect of tether pretension. METHODS: Nine T11-T12 FSUs were tested to 5 Nm of flexion-extension bending. A strain gauge was applied at the base of the T11 SP to measure force. Two custom pressure sensors were inserted into the anterior and posterior thirds of the IVD. Motion kinematics were measured by a motion capture system. An untethered test was done to describe baseline behavior. A 5-mm polyester tether was looped through holes drilled at the base of each SP and pretensioned to five different pretensions ranging from 0 to 88 N. Following ROM testing, specimens were dissected into individual vertebra and then SP pull-out testing was done at each level. RESULTS: Increasing pretension significantly reduced flexion ROM, reduced IVD pressures, and increased SP force. All pretensions, including the minimum, significantly reduced flexion ROM. SP pull-out forces were significantly greater than SP forces generated at maximum flexion. CONCLUSIONS: Tether pretension significantly affects segmental FSU biomechanics. Pretension should be considered an integral factor in the overall success of a tethering strategy. Efforts should be made to control and record pretension intraoperatively. LEVEL OF EVIDENCE: Level V, biomechanical study.