Group
Type of infection
Clinical signs of infection
Number of positive samples
I
Certain
Present
≥ 2
II
Probable
Present
1
III
Possible
Absent
≥ 1
Number of positive samples | Number of associated signs | Including |
|---|---|---|
≥2 | +1 | • ≥ 2 local surgeries • Presence of orthopedic implant • Local signs of infection • Loosening |
1 | +3 | • ≥ 2 local surgeries • Presence of orthopedic implant • Local signs of infection • Inflammatory syndrome • Loosening |
Treatment strategies in chronic infection vary from a scheduled implant replacement (one, two or three stage) [34] to resection arthroplasty. In a patient with good functional status, scheduled replacement is the best choice. In most of the published series, there is no difference between one-stage or sequential replacement in terms of eradication of infection.
In a series published by Sevelda et al. [35], 93% of 14 cases were free of infection at 5-years follow-up. The authors performed a preoperative study obtaining cultures of articular fluid or synovium. If cultures were negative, a one-stage procedure was performed. In a recent systematic review, a one-stage procedure was reported as the best procedure (in comparison with staged revision, permanent cement spacers and resection arthroplasty) in terms of function [36, 37].
A staged procedure usually includes two phases: (1) explantation, debridement, cement spacer implantation and directed antibiotherapy and (2) reimplantation once biological markers have returned to normal values with absence of clinical signs of infection. With this protocol, Assenmacher et al. [38] reported an 85% of survival free of infection after 5-years follow-up, which is in line with the literature [39].
Tseng et al. [34] reported 100% of survival free of infection in 28 cases at 32 months follow-up after a three-staged procedure. This protocol consists of (1) explantation, debridement, implantation of cement spacer and parenteral antibiotics, (2) open biopsy and debridement and (3) reimplantation, if cultures were negative.
However, in a series by Stone et al. [40], they reported no differences in infection eradication after the one- or two-stage procedure. These authors concluded that revision for infection has an increased risk of infection compared with primary procedures. As a general rule, a staged procedure is indicated in case of history of previous surgery or if the bacteria is unknown or multiresistant [8].
9.3.3 Implant Loosening and Bone Loss
9.3.3.1 Humeral Side
Initially, the glenoid side was thought to be more prone to failure after RSA but the constrained nature of this design produces increased stress and forces on the humeral side [8].
Humeral bone loss is frequent in posttraumatic and tumor surgery or in cases of proximal bone resorption. In this context, the stem is only stabilized distally in the humeral diaphysis. Forces are concentrated at this point, especially with rotational movements. Polyethylene and metal debris may also contribute to loosening, especially in case of scapular notching [8].
Contained defects can be managed using morcellized bone graft or cement. Stephens reported good results with the use of cemented with or without bone grafting in case of proximal humeral defects of less than 5 cm [41].
Uncontained defects or those in which humeral resection compromises deltoid function can be managed with an allograft prosthetic composite (APC) or a megaprosthesis [8]. APC is a good option in massive defects with a reoperation-free survival rate varying from 88% to 96% at 5 years-follow-up [42, 43].
Another cause of humeral defects is intraoperative fractures. Previous prosthesis instability, HA revision or being a female are risk factors for these fractures. However, Wagner et al. demonstrated that if the fracture is properly addressed final outcomes are not significantly affected [4].
9.3.3.2 Glenoid Side
As a rule, aseptic glenoid loosening is rare. In these cases, infection should always be suspected [44]. Aseptic loosening is almost always due to a technical error. A glenoid implant placed high or with superior inclination is associated with increased rates of notching. Severe cases of notching may increase the likelihood of developing aseptic glenoid loosening in RSA [8].
Cavitary glenoid defects can be managed with allograft impaction or structural iliac crest autograft. Both are useful, but in these cases, allograft works well and allows avoiding the morbidity associated with iliac crest harvest [45, 46]. In uncontained and complex glenoid defect, an autograft is preferable because of biological properties for incorporation. In primary cases, the resected humeral head can be utilized, but in revisions, the humeral head is not present, and iliac crest or allograft must be used [47, 48]. There are multiple ways to harvest the bone, and it can be adapted to the defect once addressed. One way is to harvest it as a wedge and fix it directly on the remnant bone of the glenoid. Norris et al. proposed a technique using iliac crest in which the glenoid implant was directly prepared in the crest with the help of prosthesis reamers and instrumentation. Once the metaglene is implanted on the iliac crest, it is harvested and fixed with screws or a long-peg baseplate to the original glenoid [49].
Boileau [7] proposed an algorithm to treat glenoid bone loss in one or two stages. One-stage reimplantation can be afforded if the following conditions are present: (1) enough graft stability after impaction, (2) central peg or screw has, at least, 5 mm implanted in the native scapular bone and (3) additional fixation to the scapula can be obtained with screws. If these conditions are not present or it is advisable to have too much tension after reimplantation, it is preferable not to reimplant and let the graft consolidate properly. After 6 months, reimplantation is performed.
In case of massive bone loss, hemiarthroplasty as a salvage procedure is an option [50].
9.4 Conclusions
Reverse shoulder arthroplasty has become a common procedure to address multiple shoulder surgeries. Improvements in prosthetic designs and surgical technique have dramatically decreased complications in the last decade. However, the global rate of complications remains high. Most of complications leading to revision surgery, with prosthetic exchange, are addressed with an RSA. Instability incidence has dramatically decreased with new prosthetic designs. Closed reduction can be an option for instability in <3 months after primary surgery. However, the revision rate in this case is still high. In the chronic setting, it is better managed with implant exchange. In case of severe and recurrent instability, deltoid function should be carefully examined and HA can be used as a salvage procedure. Infection is a very severe complication. Lavage and debridement in acute infections has a low rate of success (about 20%). If it fails, or in the chronic setting, implant exchange is used. Several protocols have been proposed, but there is a lack of strong evidence. The one-stage procedure seems to provide better function in comparison with sequential treatment. However, multiresistant or unknown bacteria before revision surgery are better managed with staged procedures. Bone loss deficiency can be present on either the humeral or glenoid side. On the humeral side, impacted bone graft or cement is useful in contained defects. In uncontained defects compromising implant stability, megaprosthesis or a allograft prosthetic composite is used. On the glenoid side, contained defects can be addressed with an impacted graft. Complex defects can be managed with a structural graft. In these cases, implantation of a definitive baseplate should be only performed if the attachment to the scapular remnant is stable.
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