Background: The Inferior Glenohumeral Ligament (IGHL) has a well known mechanical and propioceptive relevance in shoulder stability. The interrelation of the IGHL anatomical disposition and innervation has not actually been described. The studys purpose was to determine the IGHL innervation patterns and relate them to dislocation.

Material & methods: Forty-five embalmed and 16 fresh-frozen human cadaveric shoulders were studied. Massons Trichrome staining was used to detail the intra-ligamentous nerve fibre arrangements. Neural behaviour of the articular nerves was studied dynamically at the apprehension position and while anteroinferior dislocation of the shoulder joint was performed.

Results: The anatomy of the IGHL was clearly defined. However, in 7 out of 61 cases the anterior band was only a slight thickening of the ligament. It averaged 34 mm (range, 28 to 46 mm) in length. The posterior band was only seen in 40.98 % of the cases. The axillary nerve provided IGHL innervation in 95.08 % of the cases. We found two distinct innervation patterns originating in the axillary nerve. In Type 1 (29.5 % of the cases), one or two collaterals later diverged from the main trunk to enter the ligament. Type 2 (65.57%) showed innervation to the ligament provided by the posterior branch for three to four neural branches. In both cases, these branches enter the ligament near the glenoid rim and at 7 oclock position (right shoulder). The shortest distance to the glenohumeral capsule was noted at 5 oclock position. The radial nerve (Type 3 innervation pattern) provided IGHL innervation in 3.28 % (2 specimens). Microscopic analysis revealed wavy intraligamentous neural branches. The articular branches relaxed and separated from the capsule at external rotation and abduction and stayed intact after dislocation.

Conclusions: The current results showed the IGHL to have three different innervation patterns. The special neural anatomy of the IGHL suggested it was designed to avoiding denervation when dislocated. This might contribute to understand why the neural arch remains unaffected after most dislocations. To our knowledge this is the first work that clearly describes specimens in which the main innervation of the IGHL is provided by the radial nerve.

Knowledge of the neural anatomy of the shoulder will clearly help in avoiding its injury in surgical procedures.

Introduction and purpose: Different neurovascular structures may be damaged when making arthroscopic portals to the shoulder joint. The description of new portals poses new challenges. The goal of the present study is to provide an update on the anatomic vasculonervous responses of the current approaches to shoulder arthroscopy.

Materials and methods: 16 fresh cadavers were systematically dissected. The most usual arthroscopic portals were marked and, then, the dissection started on a plane-to-plane basis. Relationships were identified and distances were measured to the most important neurovascular elements with a standard caliber (accuracy: 0.5mm).

Results: The portals studied and the structures at risk were the following:

* Posterior portal: anterior branch of the axillary nerve and posterior circumflex artery 3.4 cm (range: 1.4 – 5); cutaneous branch of the axillary nerve 6.3 cm (range: 3.8 – 8.3), suprascapular nerve 2.8 cm (range: 2.1–3.3).

Conclusions: Although the crucial elements at risk when performing a shoulder arthroscopy are multiple, the axillary and suprascapular nerves were the most vulnerable structures to the different approaches. In spite of the presence of the “safe areas” described above, the neurovascular bundle was frequently affected by passage through the anteroinferior subaxillary portal. The results suggest that the use of this portal is not safe for routine arthroscopic practice.