Monday, June 5, 2017

Reverse total shoulder - glenoid bone grafting

Midterm outcomes of bone grafting in glenoid defects treated with reverse shoulder arthroplasty

These authors reviewed 20 patients with glenoid bone loss who underwent primary or revision surgery using a glenoid bone allo or autograft.

The majority of grafts incorporated.  There was a 20% postoperative complication rate: 1 case of aseptic glenoid component loosening, 1 surgical wound hematoma, 1 acromial fracture, and a symptomatic grade 3 scapular notching.

Comment : Several key factors deserve consideration before proceeding with a bone graft reconstruction. (1) Is the patient a suitable candidate for a major and potentially complex surgery? (2) Is a bone graft necessary or can the glenosphere be stabilized in the residual glenoid bone (see technique described later in this post)? (3) Can the very strong construct shown in the figure above be securely fixed to the often weak bone of the residual scapula? (4) How worried to we need to be about graft resorption? The answers to these questions are individualized for each patient and each surgeon. To put this small series in perspective, we've reposted some previous posts on the subject below.

As an aside, it is of interest that the case shown in this article demonstrates a revision of a failed metal back glenoid and a platform humeral component. The former resulted in severe glenoid bone loss and the 'promise' of easy conversion using a platform prosthesis was not realized as shown by the postoperative film below.

Here is some previously posted content on this topic:

Glenoid bone grafting in primary reverse total shoulder arthroplasty

These authors sought to determine results, complications, and rates of failure of glenoid bone grafting in 41 shoulders having primary reverse shoulder arthroplasty.

These surgeons used bone grafting to achieve between 30% and 50% contact  between the implant and bone. In specific instances of superior bone loss, graft was used to promote inferior tilt of the implant. In the setting of posterior or anterior defects, graft was used to  restore glenoid version. Cancellous graft was used in the setting of  lesser defects. In larger glenoid deficiencies, the use of structural grafts was considered.

Thirty-four received corticocancellous grafts and 7 structural grafts. At a minimum follow-up of 2 years, they found that preoperative severe glenoid erosion and increasing body mass index were significantly associated with worse American Shoulder and Elbow Surgeons scores.

Two sets of x-rays were presented.

On radiographic evaluation, 7 patients had grade 1 or grade 2 glenoid lucency. Glenoid bone graft incorporation was observed in 31 patients. Twelve patients suffered from grade 1 or grade 2 scapular notching. All of the patients with structural grafts showed graft incorporation and no signs of glenoid lucency. None of the patients needed revision surgery. 

Comment: As the authors point out, major glenoid erosion is an indication of severe disease. Patients with severe disease are more likely to have poor outcomes.

The decision to graft and what type of graft to use depends on a number of factors, including the type of baseplate fixation of the particular implant, the experience of the surgeon, the pathoanatomy, and the quality of the residual bone.

In our practice, we use a small drill inserted into the central glenoid vault as a 'dip stick' to determine the adequacy of the extant bone. If a bone depth of approximately 3 cm is present, we conclude that there is sufficient bone to stabilize the implant and ream around a tap placed along the path of this drill.

The use of bone grafting in reverse total shoulder is also discussed in this link.

Our standard reverse technique is shown in this link.

A bit more about bone grafting is detailed in the articles and discussion below

Management of glenoid bone loss in primary and revision reverse total shoulder arthroplasty

These authors reviewed the literature on the management of glenoid defects in reverse shoulder arthroplasties and presented their approach.

They present a classification system:

 For contained defects, they have used impaction allografting beneath the base plate

For eccentric defects, they have used structural grafts

or allograft composites.

If there is concern about the stability of the construction, the authors consider a two stage procedure in which the  glenoid augmentation is performed without implanting the base plate combined with a humeral hemiarthroplasty. The reverse arthroplasty is done as a secondary procedure after confirming graft incorporation with CT scans.

The system used by the authors includes a central bone ongrowth peg. For cases of glenoid deficiency they use an extended length peg.

Comment: This is a useful review of the challenges posed by defects in glenoid bone when performing a reverse total shoulder.

It can be compared to anther recent publication:

These authors point out that large glenoid defects pose difficulties in shoulder arthroplasty. They reviewed 44 patients (20 men and 24 women; mean age, 69 years) having a bulk structural graft behind the baseplate of a reverse total shoulder to manage structure defects.  The grafts consisted of a humeral head autograft in 29, iliac crest autograft in 1, or femoral head allograft in 14.

These cases used a prosthesis with a bone ingrowth stem on the baseplate

inserted over the bone graft as shown below.

Postoperative scores for the bone graft cohort were significantly lower than those in a cohort without grafting. Complete or partial incorporation was shown radiographically in 81% of grafts. 

Six baseplates were considered loose. The major (clinically significant) complication rate was 13.6%. There were 2 graft failures that caused clinical loosening of the baseplate and required revision. Two infections occurred (1 autograft and 1 allograft). One was revised in a 2-stage procedure, and 1 elected to retain the antibiotic spacer. One patient with clinical humeral loosening required revision (autograft). One postoperative dislocation (autograft) occurred. The patient was treated with a closed reduction in the operating room and immobilized for 6 weeks. No further dislocations occurred. Other minor (not clinically significant) complications included 6 patients with scapular notching of grades 1 or 2, and 4 patients with radiolucent lines of 2 mm around the humeral stem but without evidence of gross loosening. This resulted in a total complication rate of 36%.

Comment: There is no question that bone deficiency complicates shoulder arthroplasty. The question is when to use a graft and when to work with the bone stock available. That is a decision that can be made only by the operating surgeon based on the glenoid, the prosthesis used and the surgical technique.

We prefer to avoid structural grafts whenever possible because of uncertainty regarding quality, healing, and resistance to resorption. As pointed out in this paper, bone graft failures can cause clinical loosening of the baseplate.

Our preferred method for reverse total shoulder arthroplasty uses a central screw on the baseplate that provides immediate purchase in glenoid cortical bone without having to depend on bone ingrowth into a central peg and that provides lateral offset of the glenosphere to make up for bone deficiency.

In cases of glenoid bone deficiency, we use a small drill as a 'dip stick' to probe the glenoid to find the appropriate area that offers the best bone stock.  The depth of solid bone is then verified with the tap: 30 mm is ideal.

The baseplate is then screwed into position, assuring that it locks securely in place when tightened.

Here is a recent case of failed shoulder hemiarthroplaty with severe glenoid deficiency.

Secure baseplate and glenosphere fixation was achieved by the method described.

This method may be considered instead of bone grafting when there is sufficient remaining bone of quality.


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