Glenoid Bone Loss in Reverse Shoulder Arthroplasty Treated with Bone Graft Techniques

Modern methods for determining glenoid version, medialization, and eccentric bone wear include 3-D reconstruction and patient-specific instruments. For many years, version determination has been confirmed at surgery with subscapularis elevation, palpating the glenoid center point along Friedman’s line, and then inserting a Steinmann pin as a guide to restore version and the lateral joint line at the time of bone grafting. An example of this is demonstrated in Figures 3A-3E.⁹

All grafts are harvested with a hole saw from the humeral head. The inner diameter is 29 mm, the same as that of the base plate. Originally, the hole saw and mandrel were obtained from the hardware store, but Pascal Boileau upgraded the hole saw quality when he had industry develop a stainless-steel hole saw and published his results with the BIO-RSA (Wright Medical).¹⁰ In an unpublished study, Harmsen reviewed our 220 consecutive humeral head bone grafts for use of this technique with successful and reproducible results. In a separate evaluation, 29 shaped humeral head bone grafts for B2, B3, and C glenoid bone deficits showed 100% healing.¹¹ This technique has good reproducibility when performed with an autogenous bone graft from a local donor source.

The more challenging cases involve glenoid bone loss from polyethylene osteolysis and, in some revision cases, concomitant sepsis.¹² The humeral head is no longer available, and the distal clavicle or humeral metaphysis are often insufficient to restore the glenoid vault and joint line. Gunther and associates at the UC Berkeley biomaterials laboratory have made many contributions to our understanding of polyethylene wear and the factors leading to its loosening that result in massive glenoid bone loss.¹³

Antuna and colleagues¹⁴ classified these cases as having a central vault cavitary defect, or one combined with a peripheral glenoid wall bone loss of either the anterior or posterior glenoid. Newton and colleagues¹⁵ described the structural tricortical iliac crest bone graft as a 2-stage reconstruction. The second stage could be performed 4 to 6 months later after graft incorporation. With the excellent Association for Osteosynthesis (AO) type fixation using the base plate with compression and locking screws, it was reasonable to perform this in 1 stage, assuming that adequate fixation could be obtained with the iliac bone graft to the glenoid.¹⁶ This worked well with the cavitary glenoid defects and those in which either the anterior or posterior wall was absent.^17-19

EXCEPTIONS TO THE 1-STAGE FIXATION TECHNIQUE

Fixation could still be obtained medially, but more severe cases were encountered with loss of both the anterior and posterior walls. In these more advanced cases, the vault was no longer present after removal of the polyethylene, cement, and rubbery osteolytic tissue that replaced the bone. To account for this, a simplified 3-stage classification was proposed.²⁰ The cavitary vault defect is designated as type 1 bone loss. Type 2A includes the cavitary central defect plus loss of the anterior glenoid wall, and 2B is similar with loss of the posterior wall (Figures 4A-4F). Type 3 involves loss of the glenoid vault and both anterior and posterior walls with erosion down to the medial juncture of the base of the scapular spine, coracoid, and pillar of the scapula.

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