Andreas H. Weiglein

Histology and intramandibular course of the inferior alveolar nerve

The morphology of the inferior alveolar nerve is a very important factor for all surgical procedures in the mandibular region. The aim of this anatomical and histological study was to describe the intramandibular course and the microscopic histology of the inferior alveolar nerve in the dissected human cadaver. Twenty partially dentulous hemimandible specimens from human cadavers were dissected and embalmed, and the findings were interpreted by standard and histological imaging. The result of this study showed that the inferior alveolar nerve comprises two larger nerves that are separately wrapped in perineural sheaths and spirally twisted around each other. The mental nerve exits through the mental foramen in the premolar region and the dental nerve continues from the premolar region as the incisive nerve in the incisive canal. These findings provide relevant data for clinical dentistry, especially when planning oral and dental operative treatment procedures in the mandibular region.

Position of the mental foramen: an anatomical study.

ZusammenfassungDie Kenntnis der Lage des Foramen mentale ist bei allen chirurgischen Eingriffen von großer Bedeutung, so auch vor jedem operativen Eingriff im Unterkieferbereich. Ziel dieser Studie war es, die Lage des Foramen mentale anatomisch darzustellen und zu analysieren. Vierhundert hemimandible Proben von Kadavern wurden seziert und nach der Lage des Foramen mentale analysiert. Die häufigste Position des Foramen mentale war zwischen ersten und zweitem unteren Prämolaren. Die Ergebnisse dieser Studie liefern relevante Daten bezüglich der klinischen Anatomie, insbesondere bei der Planung von operativen Eingriffen im Prämolaren Bereich.SummaryKnowledge of the position of the mental foramen is very important during all surgical procedures and it needs to be considered before all surgical procedures in the mandible region. The aim of this study was to determine the position of the mental foramen in the dissected human cadaver specimens. Four hundred hemimandible specimens from human cadavers were dissected and analyzed for the position of the mental foramen. The most common position of the mental foramen investigated – using anatomical dissection – was between the first and second mandibular premolars. These investigations provide relevant data for clinical anatomy, especially when planning oral operative treatment in the premolar area.

The risk injury to the posterior interosseous nerve in standard approaches to the proximal radius: a cadaver study

PurposeThe aim of this study was to provide guidance on the safe zones for the exposure of the proximal radius by measuring the distance from the PIN to various anatomical landmarks in the proximal forearm in pronation and supination.MethodsTwenty cadaveric arms were used for this study. On the anterior aspect of the forearm, the distance between insertion of the biceps tendon and the arcade of Frohse as well as the shortest distance between the PIN and the ulnar aspect of the radial neck were measured. On the posterior aspect of the forearm, the shortest distance between the PIN and the ulnar border of the interosseous membrane was measured at 30 and 50xa0mm distal to the articular surface of the radial head.ResultsThe distance between the PIN and ulnar aspect of the radial neck had a mean of 21.6xa0mm in supination and 13.3xa0mm in pronation. The distance between the radial tuberosity and the arcade of Frohse was 18.6xa0mm. The mean distance between the PIN and the radial border of ulna at 30xa0mm distal to the articular surface of the proximal radius was 12.3xa0mm in supination and 22.3xa0mm in pronation. At 50xa0mm distal to the articular surface of the proximal radius the mean distance was 8xa0mm in supination and 16.2xa0mm in pronation.ConclusionsThe course of this nerve is variable as it winds around the radial neck within the belly of the supinator muscle. Safe distances for dissection have been presented in our study.

Arterial blood architecture of the maxillary sinus in dentate specimens.

Aim To describe vascular anatomy of the maxillary sinus in dentate specimens dissected from human cadavers. Methods Twenty dentate maxillary specimens were dissected, anatomically prepared, and injected with liquid latex for a better visualization of the maxillary sinus artery. Results We found an intraosseous anastomosis in 100% and an extraosseous anastomosis in 90% of the cases. The anterior lateral wall of the maxillary sinus was transversed by two anastomoses between the posterior superior alveolar artery (PSAA) and the infraorbital artery (IOA). The PSAA was divided into a gingival and dental branch. The gingival branch anastomosed with the terminal extraosseous branch of the extraosseous anastomosis (EOA) and the dental branch with the intraosseous branch of the intraosseous anastomosis (IOA). The mean distances from the alveolar ridge to the extraosseus anastomosis were 16 mm for the second maxillary molar, 12.3 mm for the first maxillary molar, and 13.1 mm for the second maxillary premolar. The mean distances from the intraosseous anastomosis to the alveolar ridge were 17.7 mm for the second maxillary molar, 14.5 mm for the first maxillary molar, and 14.66 mm for the second maxillary premolar. Conclusion These findings provide relevant data for clinical dentistry in order to avoid bleeding complications and minimize the risk of injury to the arterial network of the maxillary sinus during surgical procedures in the dentate maxilla region.

Sensory nerve supply of the distal radio-ulnar joint with regard to wrist denervation

The objective of this study was to determine the precise departure points of the articular branches innervating the distal radio-ulnar joint from the anterior and posterior interosseous nerves. The study sample consisted of 116 upper limbs from adult human cadavers. The articular branches were prepared under the dissection microscope to take measurements using the radial styloid process as point of reference. The articular branch departed from the anterior interosseous nerve at a mean distance of 2.9u2009cm proximal to the styloid for a radius length of 20.5u2009cm, and 3.7u2009cm for a radius length of 26.5u2009cm, respectively. For the posterior interosseous nerve, the departure point was at a mean distance of 3.1u2009cm (radius length of 20.5u2009cm) and at 4.0u2009cm (radius length of 26.5u2009cm). Apart from a single branch from the posterior interosseous nerve, all articular branches were located distal to the proximal border of the pronator quadratus. Results indicate that wrist denervation from the volar approach, if performed at the proximal border of the pronator quadratus, or from the dorsal approach at a distance of 4.8u2009cm (for a radius length of 20.5u2009cm) or 6.2u2009cm (for a radius length of 26.5u2009cm) proximal to the radial styloid process, will eliminate the nerve supply to the distal radio-ulnar joint in the majority of cases.

Minimally invasive approach to the radial nerve – A new technique

PURPOSEnTo describe a minimally invasive approach to find the radial nerve (RN) simply and safely by tracing the posterior antebrachial cutaneous nerve (PACN) without damaging muscles, using only the surgeons hand to define a window for the skin incision.nnnBACKGROUNDnAlthough it is absolutely necessary to locate the radial nerve during osteosynthesis of the humerus, the literature lacks guidelines on how to do so.nnnMETHODSnWe have dissected the upper extremities of 54 adult human cadavers, embalmed using Thiels method. After the PACN was identified in a defined space, its course was traced proximally by incising the lateral intermuscular septum (LIS) of the upper arm and thereby reaching the radial nerve (RN). Subsequently, using the lateral epicondyle (LE) of the humerus as a reference point, the distances to the points where the PACN perforated the LIS, and where the RN was identified, were measured. These individual data were related to the total length of the humerus.nnnRESULTSnThe results indicate that with this approach and without harming musculature, the RN can be reached by tracing the PACN at a height of 11.1-13.0 cm (females) and 11.9-14.0 cm (males) starting from the LE.nnnCONCLUSIONnOur examination shows the PACN to be a convenient guide to the RN.

Safe zone for the posterior interosseous nerve with regard to the lateral and posterior approaches to the proximal radius

PurposeThe posterior interosseous nerve (PIN) is at risk during the posterior and lateral approaches to the proximal radius. We aimed to define a safe zone for these approaches to avoid injury of the PIN and to evaluate their close and changing relationship to the nerve during forearm rotation.MethodsThe study collective consisted of 50 upper limbs. After performance of the lateral approach, the distance between the tip of the radial head and the PIN’s exit point from the supinator (=u2009distance 1) and the shortest interval between the nerve’s exit to the radial margin of the ulna (=u2009distance 2) were measured in maximum pronation and supination. Then, the dorsal approach was conducted and again distance 1 and the interval between the distal margin of the anconeus and the nerve’s exit point (distance 2) were evaluated (pronation and supination).ResultsThere were significantly shorter distances during supination in comparison to pronation. Regarding the lateral approach, distance 1 changed from a mean of 60.3xa0mm (supination) to 62.7xa0mm in pronation (pu2009<u20090.001). For the dorsal approach, distance 1 decreased significantly (pu2009<u20090.001) from 62.9xa0mm (pronation) to 60.2xa0mm (supination).ConclusionSupination during the lateral and dorsal approaches to the proximal radius needs to be avoided to protect the PIN. Furthermore, the nerve appeared at an interval between 45 and 84.1xa0mm (lateral approach) and 47.5–93.8xa0mm (dorsal approach), respectively. Therefore, care must be taken at this height during extension of the approaches in a distal direction.

Prevalence of the distal oblique bundle of the interosseous membrane of the forearm: an anatomical study:

A study was undertaken to examine the presence of the distal oblique bundle of the forearm in a large sample in order to describe its true prevalence. The study sample consisted of 200 cadaveric forearms. Fifteen were excluded due to defects in the distal interosseous membrane. In the remaining 185 specimens, the distal interosseous membrane was examined following removal of soft tissue, to determine whether a distal oblique bundle was present and whether there were connecting fibres to the distal radio–ulnar joint. The distal oblique bundle was observed in 53 specimens (29%). In 45 of these forearms (85%), one or more connecting fibres to the distal radio–ulnar joint were identified. The presence of a distal oblique bundle in 29% is less frequent than that reported in previous literature. The presence of the distal oblique bundle should be noted and may be of importance in the management of disorders of the distal radio–ulnar joint.

Anatomy of the Le Fort I segment: Are arterial variations a potential risk factor for avascular bone necrosis in Le Fort I osteotomies?

PURPOSEnOsteotomies of the Le Fort I segment are routine operations with low complication rates. Ischemic complications are rare, but can have severe consequences that may lead to avascular bone necrosis of the Le Fort I segment. Therefore the aim of this study was to investigate the blood supply and special arterial variants of the Le Fort I segment responsible for arterial hypoperfusion or ischemic avascular necrosis after surgery.nnnMATERIAL AND METHODSnThe arterial anatomy of the Le Fort I segments blood supply using 30 halved human cadaver head specimens was analyzed after complete dissection until the submicroscopic level. In all specimens the arterial variants of the Le Fort I segment and also the arterial diameters measured at two points were evaluated.nnnRESULTSnThe typical known vascularization pattern was apparent in 90% of all specimens, in which the ascending palatine (D1: 1,2xa0mmxa0±xa00,34xa0mm; D2: 0,8xa0mmxa0±xa00,34xa0mm) and ascending pharyngeal artery (D1: 1,3xa0mmxa0±xa00,58xa0mm; D2: <0,4xa0mm) were both supplying the Le Fort I segment. However in 10% of all specimens, the Le Fort I segment was dependent on the ascending pharyngeal artery alone and the missing ascending palatine artery was replaced with the anterior branch of the ascending pharyngeal artery (D1: 1,9xa0mmxa0±xa00,32; D2: 1,0xa0mmxa0±xa00,3xa0mm).nnnCONCLUSIONnThis study is the first description of a special type of arterial variation of the Le Fort I segment. The type of this arterial variation, its clinical relevance and potential consequences are explained. Individuals with this special arterial anatomy may clinically be at a high risk for hypoperfusion and avascular segment necrosis after surgery. An individualized operation plan may prevent ischemic complications in at-risk patients.

Straight proximal humeral nailing: Risk of iatrogenic tendon injuries with respect to different entry points in anatomical specimens

BACKGROUNDnThe purpose of the study was to evaluate the relationship of implant-related injuries to the adjacent anatomical structures in a newer generation straight proximal humeral nail (PHN) regarding different entry points. The proximity of the proximal lateral locking-screws of the MultiLoc proximal humeral nail (ML PHN) may cause iatrogenic tendon injuries to the lateral edge of the bicipital humeral groove (BG) as reference point for the tendon of the long head of biceps brachii (LBT) as well as the lateral insertion of the infraspinatus tendon (IST).nnnMATERIALS AND METHODSnThe study comprised nu202f=u202f40 upper extremities. Nail application was performed through a deltoid approach and supraspinatus tendon (SSP) split with a ML PHN. All tests were performed in three different entry points. First nail (N1) - standard position in line with the humeral shaft axis; second nail (N2) - a more lateral entry point; third alternative (N3) - medial position, centre of the humeral head. After nail placement, each specimen was screened for potential implant-related injuries or worded differently hit rates (HR) to the BG and the IST. The distances to the anatomical structures were measured and statistically interpreted.nnnRESULTSnThe observed iatrogenic IST injury rate was 17.5% (nu202f=u202f7/40) for N1, 5% (nu202f=u202f2/40) for N2 and 62.5% (nu202f=u202f25/40) for N3, which was statistically significantly higher (pu202f<u202f0.001). Regarding the BG, the evaluated HR was 7.5% (nu202f=u202f3/40) for both N1 and N2. Only the nail placed in the head centre (N3) showed an iatrogenic injury rate of 20% (nu202f=u202f8/40) (pu202f<u202f0.062). No statistically significant association between humeral head size and the HR could be observed (head diameter: IST: pu202f=u202f0.323, BG: pu202f=u202f0.621; head circumference: IST: pu202f=u202f0.167; BG: pu202f=u202f0.940). For the IST and BG, all distances in nail positions N1 and N2 as well as N2 and N3 differ statistically significant (pu202f<u202f0.001).nnnCONCLUSIONSnAn entry point for nail placement in line or slightly laterally to the humeral shaft axis - but still at the cartilage - should be advocated.