In the middle-age group with a population in the ages between 25 and 50, it is important to distinguish between an active population with a high demand on shoulder activity and the ones with less pretense. The incidence rate reported for traumatic anterior shoulder dislocation in the United States within NEISS (National Electronic Injury Surveillance System) was 47.76, 25.69 and 17.59 per 100,000 persons/year at risk within the age groups 20–29, 30–39, and 40–49, with a higher risk for young age and male sex [17] and an overall prevalence of 2% [6] with a less common posterior instability (2–10% of all shoulder instabilities) [1, 2, 10]. The risk for recurrent anterior shoulder dislocation is mostly depending on age, sex, time of initial dislocation, and damage to the capsule-labral complex or the bony anatomy and decreased with time from the initial dislocation [13]. Compared to young population (<20 years), the recurrence rate of shoulder dislocation is much lower in the age between 23 and 29 with 56% and even lower in patients over 30 years with a rate of 27–30% [7, 14]. Through aging and changes in static and dynamic shoulder stabilizers, there is a certain stiffening, due to collagen changes in the capsular complex and changes in daily life and sports activities. This may be an explanation for decreasing recurrence rate in the aging population. Due to this loosening of elastic characteristics, the impact of a traumatic shoulder event may have more effect on the static stabilizers with glenoid and humeral bony deficiency and fractures. Patients with recurrent instability and dislocation with a total time-out of the joint (cumulative time from dislocation to reduction) of more than 5 h will have a significant glenoid bone loss [3, 5]. Therefore, it is important to differentiate between the high-active person in the middle and late 20s with a higher recurrence rate and the less-active patients at the end of their 40s. It has been proposed that the active group may benefit from early surgical intervention due the increasing risk to suffer from bony deficiency resulting in a chronic instability with a degenerative arthropathy as the final result [8]. The incidence of humeral and glenoidal cartilage lesions in unstable shoulders is reported to be 24% (acute instability), 25% (chronic instability) [4], and 57% [16], respectively. There is no association between the direction of instability and the degree of cartilage damage and no specific defect location, neither on the humeral side nor on the glenoidal side. The results in the study from Cameron et al. showed a more severe osteoarthritis (OA) the longer the shoulder was unstable with a higher prevalence for OA [4], and it is undoubted that there is an increased risk for glenohumeral OA development after shoulder stabilization [11, 12, 15, 18].

The less-active and older patient population may benefit from a first-line conservative treatment, unless bony deficiency and fractures on glenoid and humeral side do not substantially increase the risk of recurrent dislocation. It has been shown that the older population suffers more from nerve lesions and fractures of the proximal part of the humerus due to the tendency to dislocate the shoulder by falling on the outstretched arm apart from a blow against the shoulder [9]. As a consequence of this finding, soft tissue repair is becoming less important compared to fracture treatment.

In conclusion the following chapters will focus on treatment of shoulder instability in the middle-age patient, aimed to point out the specifics of this population in regard to their activity level.