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"Gardner, Michael J"
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Treatment of critical-sized bone defects: clinical and tissue engineering perspectives
Critical-sized bone defects are defined as those that will not heal spontaneously within a patient’s lifetime. Current treatment options include vascularized bone grafts, distraction osteogenesis, and the induced membrane technique. The induced membrane technique is an increasingly utilized method with favorable results including high rates of union. Tissue engineering holds promise in the treatment of large bone defects due to advancement of stem cell biology, novel biomaterials, and 3D bioprinting. In this review, we provide an overview of the current operative treatment strategies of critical-sized bone defects as well as the current state of tissue engineering for such defects.
Journal Article
Mortality After Distal Femur Fractures in Elderly Patients
Background
Hip fractures in the elderly are associated with high 1-year mortality rates, but whether patients with other lower extremity fractures are exposed to a similar mortality risk is not clear.
Questions/purposes
We evaluated the mortality of elderly patients after distal femur fractures; determined predictors for mortality; analyzed the effect of surgical delay; and compared survivorship of elderly patients with distal femur fractures with subjects in a matched hip fracture group.
Patients and Methods
We included 92 consecutive patients older than 60 years with low-energy supracondylar femur fractures treated between 1999 and 2009. Patient, fracture, and treatment characteristics were extracted from operative records, charts, and radiographs. Data regarding mortality were obtained from the Social Security Death Index.
Results
Age-adjusted Charlson Comorbidity Index and a previous TKA were independent predictors for decreased survival. Congestive heart failure, dementia, renal disease, and history of malignant tumor led to shorter survival times. Patients who underwent surgery more than 4 days versus 48 hours after admission had greater 6-month and 1-year mortality risks. No differences in mortality were found comparing patients with native distal femur fractures with patients in a hip fracture control group.
Conclusions
Periprosthetic fractures and fractures in patients with dementia, heart failure, advanced renal disease, and metastasis lead to reduced survival. The age-adjusted Charlson Comorbidity Index may serve as a useful tool to predict survival after distal femur fractures. Surgical delay greater than 4 days increases the 6-month and 1-year mortality risks. Mortality after native fractures of the distal femur in the geriatric population is high and similar to mortality after hip fractures.
Level of Evidence
Level II, prognostic study. See the guidelines online for a complete description of evidence.
Journal Article
Biomechanical analysis of recently released cephalomedullary nails for trochanteric femoral fracture fixation in a human cadaveric model
BackgroundRecently, two novel concepts for intramedullary nailing of trochanteric fractures using a helical blade or interlocking dual screws have demonstrated advantages as compared to standard single-screw systems. However, these two concepts have not been subjected to a direct biomechanical comparison so far. The aims of this study were to investigate in a human cadaveric model with low bone quality (1) the biomechanical competence of nailing with the use of a helical blade versus interlocking screws, and (2) the effect of cement augmentation on the fixation strength of the helical blade.MethodsTwelve osteoporotic and osteopenic human cadaveric femoral pairs were assigned for pairwise implantation using either a short TFN-ADVANCED Proximal Femoral Nailing System (TFNA) with a helical blade head element or a short TRIGEN INTERTAN Intertrochanteric Antegrade Nail (InterTAN) with interlocking screws. Six osteoporotic femora, implanted with TFNA, were augmented with bone cement. Four groups were created: group 1 (TFNA) paired with group 2 (InterTAN), both consisting of osteopenic specimens, and group 3 (TFNA augmented) paired with group 4 (InterTAN), both consisting of osteoporotic specimens. An unstable trochanteric AO/OTA 31-A2.2 fracture was simulated and all specimens were tested until failure under progressively increasing cyclic loading.ResultsStiffness in group 3 was significantly higher versus group 4, p = 0.03. Varus (°) and femoral head rotation around the femoral neck axis (°) after 10,000 cycles were 1.9 ± 1.0/0.3 ± 0.2 in group 1, 2.2 ± 0.7/0.7 ± 0.4 in group 2, 1.5 ± 1.3/0.3 ± 0.2 in group 3 and 3.5 ± 2.8/0.9 ± 0.6 in group 4, being significantly different between groups 3 and 4, p = 0.04. Cycles to failure and failure load (N) at 5° varus or 10° femoral head rotation around the neck axis in groups 1–4 were 21,428 ± 6020/1571.4 ± 301.0, 20,611 ± 7453/1530.6 ± 372.7, 21,739 ± 4248/1587.0 ± 212.4 and 18,622 ± 6733/1431.1 ± 336.7, being significantly different between groups 3 and 4, p = 0.04.ConclusionsNailing of trochanteric femoral fractures with use of helical blades is comparable to interlocking dual screws fixation in femoral head fragments with low bone quality. Bone cement augmentation of helical blades provides significantly greater fixation strength compared to interlocking screws constructs.
Journal Article
circadian oscillator gene GIGANTEA mediates a long-term response of the Arabidopsis thaliana circadian clock to sucrose
Circadian clocks are 24-h timing devices that phase cellular responses; coordinate growth, physiology, and metabolism; and anticipate the day-night cycle. Here we report sensitivity of the Arabidopsis thaliana circadian oscillator to sucrose, providing evidence that plant metabolism can regulate circadian function. We found that the Arabidopsis circadian system is particularly sensitive to sucrose in the dark. These data suggest that there is a feedback between the molecular components that comprise the circadian oscillator and plant metabolism, with the circadian clock both regulating and being regulated by metabolism. We used also simulations within a three-loop mathematical model of the Arabidopsis circadian oscillator to identify components of the circadian clock sensitive to sucrose. The mathematical studies identified GIGANTEA (GI) as being associated with sucrose sensing. Experimental validation of this prediction demonstrated that GI is required for the full response of the circadian clock to sucrose. We demonstrate that GI acts as part of the sucrose-signaling network and propose this role permits metabolic input into circadian timing in ARABIDOPSIS:
Journal Article
Short versus long cephalomedullary nailing of intertrochanteric fractures: a meta-analysis of 3208 patients
ObjectivesThe purpose of the study was to compare treatment outcomes after short or long cephalomedullary nailing for intertrochanteric femur fractures.Data sourcesA systematic review of perioperative outcomes after short or long cephalomedullary nailing for intertrochanteric femur fractures was performed. The following databases were used: using the Cochrane Database of Systematic Reviews, the Cochrane Central Register of Controlled Trials, PubMed (1980–2019), and MEDLINE (1980–2019). The queries were performed in June 2019.Study selectionThe following search term query was used: “Intramedullary Nail AND Intertrochanteric Fracture OR “Long OR Short Nail AND intertrochanteric Fracture.” Studies were excluded if they were “single-arm” studies (i.e., reporting on either long or short CMN but not both), or did not report at least one of the outcomes being meta-analyzed. Furthermore, cadaveric studies, animal studies, basic science articles, editorial articles, surveys and studies were excluded.Data extractionTwo investigators independently reviewed abstracts from all identified articles. Full-text articles were obtained for review if necessary, to allow further assessment of inclusion and exclusion criteria. Additionally, all references from the included studies were reviewed and reconciled to verify that no relevant articles were missing from the systematic review.Data synthesisShort nails were associated with statistically significantly less estimated blood loss and operative time compared to long nails. There were no significant differences in transfusion rates, implant failures or overall re-operation rates between implant lengths. Similarly, there was no significant difference in peri-implant fracture between implant lengths.ConclusionsOverall, the available clinical evidence supports the use of short cephalomedullary nails for the majority of intertrochanteric femur fractures.Study design/level of evidenceMeta-analysis; Level III, therapeutic.
Journal Article
Osteoinductive 3D printed scaffold healed 5 cm segmental bone defects in the ovine metatarsus
Autologous bone grafts are considered the gold standard grafting material for the treatment of nonunion, but in very large bone defects, traditional autograft alone is insufficient to induce repair. Recombinant human bone morphogenetic protein 2 (rhBMP-2) can stimulate bone regeneration and enhance the healing efficacy of bone grafts. The delivery of rhBMP-2 may even enable engineered synthetic scaffolds to be used in place of autologous bone grafts for the treatment of critical size defects, eliminating risks associated with autologous tissue harvest. We here demonstrate that an osteoinductive scaffold, fabricated by combining a 3D printed rigid polymer/ceramic composite scaffold with an rhBMP-2-eluting collagen sponge can treat extremely large-scale segmental defects in a pilot feasibility study using a new sheep metatarsus fracture model stabilized with an intramedullary nail. Bone regeneration after 24 weeks was evaluated by micro-computed tomography, mechanical testing, and histological characterization. Load-bearing cortical bridging was achieved in all animals, with increased bone volume observed in sheep that received osteoinductive scaffolds compared to sheep that received an rhBMP-2-eluting collagen sponge alone.
Journal Article
Controversies in Fracture Healing: Early Versus Late Dynamization
Dynamization of fracture fixation constructs provides early rigidity for primary bone healing and late motion for secondary healing. A review of laboratory, animal, and clinical studies investigating the impact, and optimal timing, of dynamization is limited by lack of standardization across studies. However, in animal models, dynamization improves histologic and biomechanical properties compared with statically rigid or flexible controls. In animals, dynamization at 3 to 4 weeks showed improved histologic results. In clinical studies, it showed faster, stronger, and stiffer bone healing. Clinical success dynamizing external fixators and intramedullary nails suggests a role for late dynamization in other fixation types, such as bridge plating. [
Orthopedics
. 2020;43(3):e125–e133.]
Journal Article
Biomechanics of sacroiliac joint fixation using lag screws: a cadaveric study
Background
Iliosacral screw placement is ubiquitous and now part of the surgeon’s pelvic trauma armamentarium. More recent evidence supports sacroiliac arthrodesis for treating sacroiliac joint (SIJ) dysfunction in select patients. Regardless of the surgical indication, there are currently no studies examining lag screw compression biomechanics across the SIJ. The objective of this biomechanical investigation was to quantify iliosacral implant compressive loads and to examine the insertion torque and compressive load profile over time.
Methods
Eight human cadaveric pelvic specimens underwent SIJ fixation at S1 and S2 using 11.5 and 10.0 mm iFuse-TORQ Lag implants, respectively, and standard 7.3 mm trauma lag screws. Load decay analysis was performed, and insertion and removal torques were measured.
Results
For both implants at S1 and S2 levels, the load relaxed 50% in approximately 67 min. Compressive load decay was approximately 70% on average occurring approximately 15 h post-insertion. Average insertion torque for the 11.5 mm TORQ implant at S1 was significantly greater than the trauma lag screw. Similarly, at S2, insertion torque of the 10.0 mm TORQ implant was greater than the trauma lag screw. At S1, removal torque for the 11.5 mm TORQ implant was higher than the trauma lag screw; there was no significant difference in the removal torque at S2.
Conclusions
In this study, we found that a novel posterior pelvic implant with a larger diameter, roughened surface, and dual pitch threads achieved improved insertion and removal torques compared to a standard screw. Load relaxation characteristics were similar between all implants.
Journal Article
Limb position affects intraoperative assessment of condylar width
Purpose
We sought to define how changes in position and rotation of fluoroscopic imaging may affect the assessment of condylar widening intraoperatively.
Methods
Thirty-three patients with tibial plateau fractures were prospectively identified and included in this study. Fluoroscopic images of the uninjured tibial plateau were obtained in (1) full extension and (2) slight flexion on foam ramp. Beginning with a plateau view, additional views of the tibial plateau were then obtained by rotating the fluoroscope around the knee in 5 degree increments up to 15 degrees in both internal and external rotation. Measurements of distal femoral condylar width (DFW), distal femoral articular width (FAW), proximal tibial articular width (TAW) and lateral plateau width (LPW) were performed.
Results
LPW was decreased in flexion compared to extension at all degrees of rotation (
p
= 0.04–0.00001). There was a trend toward increasing LPW with increasing degrees of internal rotation which reached significance at 15˚ of internal rotation when the knee was flexed. On ANOVA, there was a significant difference of LPW with increasing degree of internal rotation when the knee was in flexion (
p
= 0.008), but not in extension. There were no differences in DFW, FAW, TAW and DFW/TAW at any point though LPW was decreased in flexion at all degrees of rotation. The FAW/TAW ratio was increased in flexion at all degrees of rotation.
Discussion
The knee in flexion will underestimate the measurement of condylar width compared to the knee in full extension, by ~ 2 mm. Rotation of the knee, in comparison, did not have a significant effect on condylar width assessment.
Level of evidence
Diagnostic II.
Journal Article