Sunday, June 12, 2016

Glenoid dysplasia

Glenoid Dysplasia Pathophysiology, Diagnosis, and Management

These authors present a current concepts review on 'glenoid dysplasia'.  Their bullet points are reproduced here:

➤ Subtle forms of glenoid dysplasia may be more common than previously thought and likely predispose some patients to symptomatic posterior shoulder instability. Severe glenoid dysplasia is a rare condition with characteristic radiographic findings involving the posteroinferior aspect of the glenoid that often remains asymptomatic.

➤ Instability symptoms related to glenoid dysplasia may develop over time with increased activities or trauma. Physical therapy focusing on rotator cuff strengthening and proprioceptive control should be the initial management.

➤ Magnetic resonance imaging and computed tomographic arthrograms are useful for detecting subtle glenoid dysplasia by revealing the presence of an abnormally thickened or hypertrophic posterior part of the labrum, increased capsular volume, glenoid retroversion, and posteroinferior glenoid deficiency.

➤ Open and arthroscopic labral repair and capsulorrhaphy procedures have been described for symptomatic posterior shoulder instability. Glenoid retroversion of >10° may be a risk factor for failure following soft-tissue-only procedures for symptomatic glenoid dysplasia.

➤ Osseous procedures are categorized as either glenoid reorientation (osteotomy) or glenoid augmentation (bone graft), and no predictable results have been demonstrated for any surgical strategy. Glenoid osteotomies have been described for increased retroversion, with successful results, although others have noted substantial complications and poor outcomes.

➤ In severe glenoid dysplasia, the combination of bone deficiency and retroversion makes glenoid osteotomy extremely challenging. Bone grafts placed in a lateralized position to create a blocking effect may increase the risk of the development of arthritis, while newer techniques that place the graft in a congruent position may decrease this risk.

Comment: This article does a nice job of summarizing what is known about the evaluation and management of glenoid dysplasia. As the authors point out, "a variety of terms and definitions have been used to describe abnormal glenoid morphology, including dysplasia, hypoplasia, glenoid cleft, and retroversion, which contribute to confusion regarding diagnosis and management." Dysplasia (from the Greek δυσ- dys-, "bad" or "difficult" and πλάσις plasis, "formation").  As such glenoid dysplasia should be used to refer to abnormal glenoid development.

This got a bit confused when a type C glenoid shape was defined (see this link) as " a glenoid retroversion of more than 25 degrees, regardless of erosion; retroversion was primarily of dysplastic origin and explained the early event of osteoarthritis. In primary GHOA, this classification of the glenoid can discriminate retroversion between posterior erosion and dysplasia." It is important to distinguish glenoid 'bad formation' from glenoid retroversion that is acquired from osteoarthritis or capsulorrhaphy arthropathy. Likewise in cases of glenoid dysplasia it is important to distinguish symptoms of painful stiffness without arthritis or instability from dysplasia + instability or dysplasia + arthritis.

The most clinically important form of glenoid 'bad formation', is that shown below where the posterior osseous elements of the glenoid do not form. This brings the posterior soft tissues (labrum and capsule and cartilage)  into a role usually served by bone.

The result can be failure of these soft tissues leading to posterior instability and / or bone on bone arthritis.

Reports of successful surgical management are few. Soft tissue repairs are not durable. There is not enough bone to enable an osteotomy. Secure fixation of a bone graft is difficult and the loads on a posterior graft can be overwhelming. Prosthetic glenoid arthroplasty (either anatomic or reverse) is challenged by the difficulty in achieving secure fixation.

In our hands, the best approach seems to be to use stretching and strengthening external rotation to avoid an internal rotation contracture and to optimize posterior stability.

Should non-opeartive management fail, consideration can be given to an arthroplasty. In our hands the safest and most successful is a well balanced hemiarthroplasty.

Interested readers should check out our prior posts on this important entity here, here, here, and here.