Bone Loss in the Upper Extremity

Introduction

Bone loss is a serious problem that can affect any part of the body, both anatomically and functionally, and it must be considered and addressed appropriately. When examining the upper extremity specifically, an area that must be considered extensively is the glenoid and humerus that combine to create the glenohumeral joint. Hantes and Raoulis describe the shoulder as an inherently unstable ball and socket joint that is liable to a multitude of injuries, which makes it highly susceptible to dislocation. In fact, the incidence rate of shoulder dislocations in the United States has been documented to be 23 injuries per 100,000 people. The main cause of the primary shoulder dislocation events is almost always trauma related, due to the traumatic force causing the humeral head to slide out of the glenoid articular arc.

The difficult aspect of glenohumeral dislocation lies in the predisposition for these injuries to become recurrent and lead to an unstable shoulder. Recurrent instability compounds upon itself by creating further attritional bone loss. There are many factors, in addition to trauma, that lead to recurrent glenohumeral instability, such as age, hyperlaxity, glenoid bone loss, humeral head bone loss, and sex. Oftentimes, there are multiple of these factors occurring simultaneously leading to recurrent instability, instead of one isolated factor causing a problem. When determining how to manage shoulder instability several things should be taken into consideration including, osseous defects, experience of the surgeon, and patient-related factors such as participation in athletics and work demands.

Glenoid

The glenoid’s main function is to form a rimmed barrier constraining the humeral head from dislocating. Bony lesions of the glenoid are problematic because they shorten the glenoid arc length and lessen the stability of the joint by reducing the glenoid surface contact area and its concavity ( Fig. 8.1 ). Burkhart and de Beer were able to determine that there was a 4% failure rate for patients not containing a significant glenoid defect, while there was a 67% failure rate in patients with a significant lesion. For the overall prevalence of glenoid defects in cases of recurrent anterior shoulder instability, the rate has been as high as 90%. Of the 90%, 50% of the documented injuries were bony Bankart lesions and 40% were due to erosions from chronic recurrent traumatic anterior instability.

Evaluating the significance of glenoid bone loss has been controversial and indecisive as far as definitive preoperative measurements. The two most commonly used methods for measuring a glenoid defect today are the Pico method and the usage of a preinjury diameter for comparison. The Pico method determines the degree of bone loss by first creating a “normal glenoid circle” from three reference points along the intact rim of the uninjured glenoid. Then, the normal circle is placed on the pathologic glenoid, and the missing part of the normal circle can be divided by area of the inferior glenoid circle to determine the defect as a percent of the entire circle. To find defect size using diameter comparison, the anterioposterior diameter of the injured glenoid is subtracted from the estimated preinjury diameter of the glenoid. Then, that number is divided by the estimated preinjury diameter. A descriptive way of describing a significant glenoid defect, as written by Lo and Burkhart, is to refer to it as an “inverted-pear” shape when viewed arthroscopically from a superior-to-inferior perspective.

The general accepted numerical value for glenoid bone loss is a lesion spanning greater than 25% of the glenoid surface area. However, Gottschalk et al. conducted a systematic review recently and found that 44.7% of the recurrently unstable shoulders studied had glenoid bone loss between 5% and 20%. This means that a large number of shoulders in the past may have been overlooked for potential surgical glenoid augmentation.

Surgical Management

There are several different surgical procedures to stabilize the shoulder, and the correct choice of procedure for each specific patient remains a polarizing topic in the literature. The most common debate in shoulder stabilization surgery is the comparison of the efficacy of arthroscopic and open procedures. In the 1900s and early 2000s, open procedures were thought to be the “gold” standard, but now there is proof in the literature that there are many cases where arthroscopy offers its own advantages.

Arthroscopic Bankart repair is an extremely successful technique for treating soft tissue injuries in the shoulder in conjunction with minimal to zero glenoid bone loss. However, when the glenoid presents a bony defect encompassing 20%–25% of the diameter of the inferior glenoid, the osseous defect must be addressed for a successful surgical outcome. This is because progressive anteroinferior bone loss leads to an increased mean contact pressure and peak pressure. The neglect of the bone loss by performing solely a soft tissue Bankart repair would lead to the bone–soft tissue repair interface having to resist the extra overload, leading to a greater likelihood of repair failure.