Abstract
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.
Theses abstracts were prepared by Professor Roger Lemaire. Correspondence should be addressed to EFORT Central Office, Freihofstrasse 22, CH-8700 Küsnacht, Switzerland.
