Key Points and Surgical Pearls for Managing B2 Glenoids
Jason C. Ho, MD; Joseph P. Iannotti, MD PhD; and Eric T. Ricchetti, MD
- Preoperative 3D planning/templating is helpful to define the preoperative pathology and determine the amount of reaming necessary for the glenoid implant of choice (standard or augmented).
- Choosing a standard implant or augmented component that is too small may lead to incomplete pathologic correction, while choosing an augment that is too large may lead to excessive posterior bone removal that results in peg perforation and inadequate bone support for the implant.
- Reaming the high side or leaving the glenoid in retroversion may lead to increased risk of component loosening using standard components.
- The use of step and wedge augments in B2 glenoids is supported by biomechanical and clinical data.
- Appropriate glenoid exposure is crucial to achieving optimal preparation of the glenoid for placement of an augmented glenoid component. Release of the anterior and inferior joint capsule of the humerus and glenoid is key in achieving this exposure, as it allows for increased posterior retraction of the humeral head. We routinely resect the anterior and inferior joint capsule. This can be performed without concern for injury to the axillary nerve with appropriate identification of the nerve and protection with retractors. Proper retractor placement is also important for appropriate glenoid exposure (Figure 1).
- Inadequate glenoid exposure may lead to poor glenoid preparation and poor seating of the augmented glenoid component.
- When preparing the sclerotic posterior glenoid for the augmented glenoid component, under-reaming will cause the implant to not fully seat.
- The use of a high-speed burr is helpful in the initial shaping of the posterior glenoid and removal of bone when using a stepped augmented component, followed by use of the manufacturer’s reamer to finish the step cut and ensures adequate seating of the implant.
- Release of the posterior capsule can be performed in a B2 glenoid when an augmented glenoid component is used to restore anatomic version without medialization of the native joint line. Posterior instability of the humeral head may occur if the posterior capsule is released and there is residual glenoid retroversion or medialization of the joint line.
- Excessive reaming of the posterior glenoid should also be avoided to prevent inadequate bone support for the augmented component. For a stepped augment, very little or no bone is removed from the posterior glenoid rim, with the majority of the bone removed more centrally in creating the posterior step.
- When removing the posterior retractor from the posterior inferior glenoid after glenoid implantation, the surgeon must be careful not to catch the implant in the retractor, as it can be pulled out or loosened.
- A glenoid rim fracture can occur during excessive posterior glenoid reaming or with excessive pathologic bone loss. Preoperative 3D planning is helpful in avoiding this scenario, as it shows how much glenoid is available for reaming, if an augmented component is feasible, and the appropriate size and location of the augment. There are 3 ways to address this issue: (1) If the rim fracture is large enough, the fragment can be fixed with 1 or 2 small fragment screws. (2) If there is sufficient, stable glenoid remaining, an anatomic TSA may still be performed. (3) However, if after fixation there is poor glenoid stability and bone stock, or if the rim fracture is not repairable or both, then a conversion to hemiarthroplasty or reverse TSA is indicated.
- A posterior capsulorraphy can be considered if there is posterior instability of the humeral head after placing the glenoid component. Three purse string sutures are placed and tied in the mid portion of the posterior capsule. These sutures are placed 1 cm apart from superior to inferior. Use of an external rotation brace is usually needed for 4 weeks postoperatively. The surgeon can also consider use of a larger or offset humeral head to gain stability. A larger head can result in tightening of the anterior soft tissues and over stuffing of the joint.
Figure 1. Bovie mark showing glenoid biconcavity, demonstrating the typical posterior inferior wear pattern seen in B2 glenoids (A). Guide pin placement prior to reaming, again showing the guide pin placed posterior to the glenoid biconcavity (B). Glenoid after anterior reaming and prior to reaming of the posterior glenoid (C). Glenoid with step reaming guide sitting flush on reamed anterior glenoid surface (D). Prepared glenoid with posterior step cut and peripheral peg holes drilled (E). Implanted glenoid component (F). Oblique view of the augmented component with reamings in the central anchor peg (G).
Jason C. Ho, MD, is a resident in the Department of Orthopaedic Surgery, Orthopaedic & Rheumatologic Institute, at the Cleveland Clinic, Cleveland, Ohio. Joseph P. Iannotti, MD, PhD, is chairman of the Orthopaedic and Rheumatologic Institute at the Cleveland Clinic, Cleveland, Ohio. Eric T. Ricchetti, MD, is director of the Shoulder Service of the Orthopaedic and Rheumatologic Institute at the Cleveland Clinic Cleveland, Ohio.
Dr. Ho has no disclosures relevant to this article. Dr. Iannotti has disclosed that he receives royalties from Depuy Synthes and has stock or stock options in Custom Orthopaedic Solutions. Dr. Ricchetti has no disclosures relevant to this article.