Monday, May 8, 2017

Reverse total shoulder - how to fix the stem

Radiographic changes and clinical outcomes associated with an adjustable diaphyseal press-fit humeral stem in primary reverse shoulder arthroplasty

These authors evaluated the minimum two year radiographic and clinical outcomes of an adjustable diaphyseal press-fit humeral stem in 232 primary reverse total shoulders.

Radiographic evidence of loosening was identified in 1 RSA (0.4%) associated with deep infection. Aseptic loosening was not observed. No stems were identified as being at high risk for loosening.
Internal stress shielding was observed proximal to the coated diaphyseal component in 226 shoulders (97.4%). This finding was often visible at 3 months (92.7%) and predictably progressed on subsequent radiographs. Progression beyond the 2-year period was rarely seen (4.4%). No external stress shielding or osteolysis was observed. Example post operative films are show below. Arrows added to show the progressive change in the bony increased offset bone graft used between the glenoid component and the glenoid bone. 

Immediate post op

3 months post op

22 mo post op

46 mo post op

At an average follow-up of 36.6 months, significant improvements were identified in all measured clinical outcomes (P < .001).

Thirty-six complications occurred in 33 patients (15.1%). These complications included acromial/scapular spine stress fracture (n = 7), deep infection (n = 7), baseplate failure (n = 6), dislocation (n = 5), transient neuropathy (n = 4), superficial infection (n = 3), postoperative periprosthetic Vancouver C humeral shaft fracture (n = 1), humeral shaft fracture during implant removal (n = 1), baseplate malposition (n = 1), and retained drill fragment (n = 1). 

Failures, defined as requiring revision surgery, were documented in 17 RSAs. In 11 of these shoulders, the diaphyseal component was retained and used for revision RSA. These included 6 baseplate failures and 1 baseplate malposition that required revision. In some of these revisions, the metaphyseal component was exchanged without the need for humeral stem removal. Segmental stacking inserts were available to adjust component height in the management of instability.

One stem was left in place during stage 1 of a 2-stage revision RSA for treatment of a deep infection.
Six stems were removed for treatment of deep infection. One of these stems was loose and was easily removed. The other 5 stems were well fixed and were explanted using various stem removal techniques. An iatrogenic humeral shaft fracture occurred in 1 patient. No other complications occurred during stem removal.

Comment: This is a large and interesting series of primary reverse total shoulders performed by an individual highly experienced surgeon. The overall good patient results are presented along with a candid report of the complications. It is of note that this series did not include patients treated for failed primary arthroplasty - a cohort in which the complication rate is predictably higher.

With respect to the management of infection, it is always a challenge to decide if a well fixed stem needs to be removed (to increase the chance that the biofilm has been eliminated). Here one stem was retained and six were removed.

With this implant the goal is to customize the implant to fit the diaphysis.

We use an alternative approach that fits the internal anatomy of humerus to the implant.

The goal is to achieve secure fixation without creating a stress riser at the tip of the component and to reduce the risk of stress shielding. Impaction grafting enables us to use a prosthetic humeral stem that is smaller in diameter than the humeral diaphysis so that diaphyseal loading is avoided. The medullary canal is conservatively reamed to remove cancellous but retain cortical bone. The humeral metaphysis is reamed to 42 mm to accommodate the metaphyseal aspect of the humeral component 

A trial component is inserted to assure that reduction can be accomplished, that the joint is stable, and that there is no unwanted contact between the prosthesis and the scapula. Impaction grafting is carried out with an impactor of the same size and shape of the monoblock humeral component.

Drill holes are placed in the lesser tuberosity for reattachment of the subscapularis if sufficient tendon is available. The wound is thoroughly irrigated. The humeral prosthesis is driven into the impaction grafted canal, assuring a snug fit and rotational stability.

The joint is reduced; range of motion and stability are again verified. The subscapularis is repaired to the previously placed sutures. A standard wound closure is followed by the application of dry sterile dressings. 

Postoperative rehabilitation consists of the use of a sling for comfort and support for 6 weeks. Gentle activities of daily living are allowed during this period. After six weeks progressive increase in active use of the shoulder is encouraged; stretching exercises are usually unnecessary.

Here are the post operative radiographs from two case examples of the technique. 


Note also the use of a glenosphere with a short neck on it rather that the use of bone graft to offset the glenosphere.


This approach is bone preserving. By using a single piece (monoblock) component) and avoiding a tight diphyseal fit, ingrowth surfaces, cement, and modularity, the technique is simplified and revision is facilitated.

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