Impact of the mandibular divergence on the position of the inferior alveolar nerve and mylohyoid nerve: a computed tomography study and its relevance to bilateral sagittal split osteotomy

Purpose

Bilateral sagittal split osteotomy (BSSO) is the most common procedure used to treat mandibular deformities. BSSO procedures include the Epker technique and the Dal Pont technique which are the most frequently used. Because of the intramandibular pathway of the inferior alveolar nerve (IAN), neurosensory disturbance of the lower lip and chin is the most common complication of BSSO. This study performed quantitative measurements from computed tomographic (CT) data obtained on dry human mandibles. The main aim of the study was to evaluate if mandibular divergence can predict the position of the IAN and the mylohyoid nerve (MHN) to prevent nerve injury.

Methods

After CT and 3D reconstruction of 65 dry mandibles, 30 measurements were made on 3 planes for each hemi-mandible. This allowed analysis of the IAN and MHN pathways. Three groups of hemi-mandibles were created depending on their divergence, and a statistical analysis was performed.

Results

Eight out of the 30 measurements showed a significant difference among the 3 groups. There was no significant difference for the remaining 22 measurements.

Conclusions

The IAN seems to have a more superior position in the groups of mandibular hypo- and hyper-divergence. Orthognathic surgeons should use a more superficial retromolar bone incision in these cases. Finally, the Epker technique would be safer for preserving the MHN in normo- and hypo-divergent patients.     

Low total haemoglobin mass, blood volume and aerobic capacity in men with type 1 diabetes

Blood O₂ carrying capacity affects aerobic capacity (VO_2max). Patients with type 1 diabetes have a risk for anaemia along with renal impairment, and they often have low VO_2max. We investigated whether total haemoglobin mass (tHb-mass) and blood volume (BV) differ in men with type 1 diabetes (T1D, n = 12) presently without complications and in healthy men (CON, n = 23) (age-, anthropometry-, physical activity-matched), to seek an explanation for low VO_2max. We determined tHb-mass, BV, haemoglobin concentration ([Hb]), and VO_2max in T1D and CON. With similar (mean ± SD) [Hb] (144 vs. 145 g l^?1), T1D had lower tHb-mass (10.1 ± 1.4 vs. 11.0 ± 1.1 g kg^?1, P < 0.05), BV (76.8 ± 9.5 vs. 83.5 ± 8.3 ml kg^?1, P < 0.05) and VO_2max (35.4 ± 4.8 vs. 44.9 ± 7.5 ml kg^?1 min^?1, P < 0.001) than CON. VO_2max correlated with tHb-mass and BV both in T1D (r = 0.71, P < 0.01 and 0.67, P < 0.05, respectively) and CON (r = 0.54, P < 0.01 and 0.66, P < 0.001, respectively), but not with [Hb]. Linear regression slopes were shallower in T1D than CON both between VO_2max and tHb-mass (2.4 and 3.6 ml kg^?1 min^?1 vs. g kg^?1, respectively) and VO_2max and BV (0.3 and 0.6 ml kg^?1 min^?1 vs. g kg^?1, respectively), indicating that T1D were unable to reach similar VO_2max than CON at a given tHb-mass and BV. In conclusion, low tHb-mass and BV partly explained low VO_2max in T1D and may provide early and more sensitive markers of blood O₂ carrying capacity than [Hb] alone.     

Free and pedicle flaps in lower extremity trauma

Improvements in microsurgical techniques and perioperative management have led to more attempts at limb salvage surgery after severe extremity trauma. Although some microsurgery-trained orthopedic surgeons will perform extremity soft tissue reconstruction, many rely on plastic surgeons or hand surgeons. However, the orthopedic trauma surgeon often remains the principle decision maker in the follow-up of these patients. Therefore, orthopedic surgeons should have a clear understanding of the planning and execution of flap reconstruction of the traumatized extremities. Collaboration with the microsurgery team will also improve planning of orthopedic procedures and facilitate a better understanding of the expected outcomes after tissue transfer. This becomes especially important when considering, debridement, early amputation versus extensive soft tissue reconstruction and when discussing these alternatives with patients and family as well as postoperative course. The goals of this article are to provide orthopedic trauma surgeons with an understanding of the selection, planning, and execution of tissue transfers for posttraumatic extremity reconstruction and to review their successes and outcomes in the literature. Communication between teams involved in reconstruction of the traumatized extremity and an understanding of limitations are paramount to successful outcomes after reconstruction.Level of Evidence: Not ratable.     

Cyclin-dependent kinase 5 is a mediator of dopaminergic neuron loss in a mouse model of Parkinson's disease

Recent evidence indicates that cyclin-dependent kinases (CDKs, cdks) may be inappropriately activated in several neurodegenerative conditions. Here, we report that cdk5 expression and activity are elevated after administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), a toxin that damages the nigrostriatal dopaminergic pathway. Supporting the pathogenic significance of the cdk5 alterations are the findings that the general cdk inhibitor, flavopiridol, or expression of dominant-negative cdk5, and to a lesser extent dominant-negative cdk2, attenuates the loss of dopaminergic neurons caused by MPTP. In addition, CDK inhibition strategies attenuate MPTP-induced hypolocomotion and markers of striatal function independent of striatal dopamine. We propose that cdk5 is a key regulator in the degeneration of dopaminergic neurons in Parkinson's disease.     

Direct Agglutination of Weak D Red Cells by Tetramolecular Complexes Containing Monoclonal IgG Anti-D

The capacity of blood group antibodies to agglutinate red cells suspended in saline is largely dependent on the antibody isotype. The immunological cross-linking of IgG antibodies has previously been described as a means to increase the reactivity of IgG in many situations. We have prepared anti-D-containing complexes by blending a human IgG anti-D monoclonal antibody (mAb) and a murine anti-human IgG mAb. In standard red cell serology assays, the anti-D complexes exhibited a very high avidity and could agglutinate weak D-positive red cells in direct saline testing. These results indicate that potent saline hemagglutinating reagents of RhD and eventually of other blood group specificities can be prepared from IgG mAbs.     

Physiological Demands of Simulated Off-Road Cycling Competition

The purpose of the study was to measure the demands of off-road cycling via portable spirometry, leg-power output (PO), heart rate (HR) and blood lactate (BLa) concentration. Twenty-four male competitive cyclists (age: 29±7.2 yrs, height: 1.79 ± 0.05 m, body mass: 70.0 ± 4.9 kg, VO_2peak: 64.9 ± 7.5 ml·kg^-1·min^-1) performed simulated mountain bike competitions (COMP) and laboratory tests (LabT). From LabT, we determined maximal workload and first and second ventilatory thresholds (VT1, VT2). A high-performance athlete (HPA) was used for comparison with three groups of subjects with different sport-specific performance levels. Load profiles of COMP were also investigated during uphill, flat and downhill cycling. During the COMP, athletes achieved a mean oxygen uptake (VO_2COMP) of 57.0 ± 6.8 ml·kg^-1·min^-1 vs. 71.1 ml·kg^-1·min^-1 for the HPA. The PO_COMP was 2.66±0.43 W·kg^-1 and 3.52 W·kg^-1 for the HPA. PO_COMP, VO_2COMP and HR_COMP were compared to corresponding variables at the VT2 of LabT. LabT variables correlated with racing time (RT_COMP) and PO_COMP (p < 0.01 to <0.001; r-0.59 to -0.80). The VO_2peak (LabT) accounted for 65% of variance of a single COMP test. VO_2COMP, PO_COMP and also endurance variables measured from LabTs were found as important determinants for cross-country performance. The high average VO_2COMP indicates that a high aerobic capacity is a prerequisite for successful COMP. Findings derived from respiratory gas measures during COMPs might be useful when designing mountain bike specific training.

Key points

• Cross- country cycling is characterized by high oxygen costs due to the high muscle mass simultaneously working to fulfill the demands of this kind of sports.
• Heart rate and blood lactate concentration measures are not sensitive enough to assess the energy requirements of COMP. Therefore, respiratory gas and power output measures are helpful to provide new information to physiological profile of cross- country cycling.
• An excellent cycling-specific capacity is a prerequisite for successful off-road cycling.
• Data determined from LabT might be utilized to describe semi-specific abilities of MB- athletes on a cycle ergometer, while data originating from COMP might be useful when designing a mountain bike specific training.

Key words: Off-road cycling, mountain biking, oxygen uptake, power output, lactate, heart rate