Patients’ selection
Between 2008 and 2018, 208 ATSAs were performed at a single institution. Among these, 20 patients underwent revision of failed ATSA with RSA. Primary and revision procedures were performed by the senior author (PV) and were available for follow up. The patients’ characteristics are described in table 1. (Table 1) Patients’ inclusion criteria consisted of 1) ATSA to RSA revision surgeries using a completely convertible RSA implant and 2) minimal clinical follow-up of 2 years. Exclusion criteria consisted of 1) revision of full PE of ATSA to a metal-backed ATSA (one case), 2) revision of full PE cemented ATSA to an hemiarthoplasty (one case), 3) deltoid palsy, 4) prosthetic infection, 5) revision with additional soft tissue procedure (3 cases).
This study was classified as observational (non-interventional) by our local ethics committee. Statutory and ethical obligations of observational (non-interventional) studies in our country: According to the past Huriet law on biomedical research, and to the current regulation that went into effect in August 2006 (law n°2004-806), such studies do not require prior submission or approval to/from an IRB, and they do not require written consent. This observational research on data fulfils current local regulatory and ethical obligations.
The study cohort was divided into two groups based on the glenoid implant type that was used at the primary ATSA procedure. Group A (10 cases) consisted of failed ATSAs that were primarily treated with MB glenoid convertible implant (FIGURE 1) and group B (10 cases) represented failed ΑTSA treated primarily with PE cemented glenoid (PE CG) implants (FIGURE 2). Data regarding the etiologies for primary ΑTSA surgeries and revision RSA surgeries are summarized in Table 1 (Table 1).
For the primary ATSAs a convertible shoulder prosthesis (Arrow; FH Orthopedics, Mulhouse, France) that facilitates ATSA to RSA revision surgeries was used for most of the cases (FIGURE 1). The system offers a universal humeral stem and either a MB glenoid convertible or a cemented full PE glenoid implant. The MB component was preferred by the senior author if there are cysts in the glenoid, if there was a B1 or B2 glenoid and in case of rheumatoid arthritis. Conversion to a reverse prosthesis allows the surgeon to replace the humeral head metallic tray (ATSA) with a polyethylene insert (RSA) without removing the humeral stem. In case the glenoid implant is a MB device (all cases in group A), polyethylene shell removal exposes a well-fixed glenoid baseplate, which supports a glenosphere insertion. In 2 cases of group B, the PE cemented glenoid implant was part of ATSA with no convertible platform humeral stem implant (DePuy Synthes, J&J MedTech, MA, USA).
Surgical technique and intraoperative findings
All revisions were performed under general anesthesia and interscalene block for a better postoperative pain relief with the patient in a semi beach chair position and the arm in lying position on a support to relax the deltoid. A Reverse Arrow system (FH orthopedics, Mulhouse, France) was implanted in all cases. The previous deltopectoral approach was used, which could also allow for distal extension of the exposure in case of stem replacement. Adhesions at the deep part of the deltoid and the conjoint tendon were carefully released. Previous biceps tenodesis to the aponeurosis of pectoralis major was verified. In case of thin, fibrotic or considered as non-functional rotator cuff tear, or tear of the subscapularis or supraspinatus muscle, or both, causing instability, a conversion from an anatomic to an RSA was performed. When the subscapularis tendon could be retained, it was peeled off from the medial border of the bicipital groove to obtain sufficient length for a tension-free reinsertion. The RSA that was used (Arrow; FH Orthopedics, Mulhouse, France) allows lateralization in both components (glenosphere and humerus) and the subscapularis tendon was frequently medialized during transosseous reinsertion in order to maintain 30º of external rotation. Before implantation of the new prosthesis five tissue biopsies were collected systematically to search germs even in the absence of local or general infectious signs. The Arrow convertible system is a dual platform system, with a convertibility on both sides (humeral stem and the glenoid MB baseplate). Therefore, the system allows shifting from ATSA to RSA without any humeral stem and/or glenoid MB revision making surgery less demanding, less invasive and less time consuming (FIGURE 1). Nevertheless, the humeral stem had to be revised in cases of loosening or malposition (excessive retroversion/anteversion and/or too proud stem) (FIGURES 2,3). There were 10 cases with MB glenoid component (group A) and 10 cemented PE glenoid components (group B). In group A, the baseplate with a convex back covered with hydroxyapatite, a central keel and an anterior winglet is fixed with two cortical divergent screws. A 4mm thickness polyethylene is impacted into the baseplate. In group B the polyethylene component was pegged (four pegs). During conversion, the anatomic head of the humeral implant was disconnected from the stem and removed. In case of a MB glenoid component, the PE glenoid onlay was removed from the baseplate. No baseplate was loosened, and no baseplate has been removed in this group A (FIGURE 1). In the case of a cemented PE glenoid component, its replacement with a MB glenoid component was performed (FIGURES 2,3). After removing the PE glenoid component and cement, bone defects were reconstructed with cancellous graft (iliac crest bone autograft in one case, synthetic bone graft in one case, and humeral autograft from the humeral re-cut in one case). A metallic long-peg baseplate was used in 6 cases with 10 mm into the native bone. Inferior tilt and perforation of the anterior fossa of the scapula improved the press fit of the base plate. The shape and the lateralization of the metal back glenoid component (thickness 8.5 mm) allowed to decrease the necessity, or the amount of bone graft needed. The metallic long peg (FH orthopedics, Mulhouse, France) improves the primary stability of the glenoid component in glenoid deficiency (FIGURE 4). A glenosphere was impacted on the baseplate. Humeral stems were removed in 7 cases: 5 cases in group A (1 for humeral loosening and 4 to be placed in lower position because the stem was too proud and rendered the RSA irreducible) and 2 cases in group B (the stem was not convertible, DePuy Synthes, J&J MedTech, MA, USA). In all cases except from 1, removal of the stem was possible without osteotomy and, hence, was replaced with a new cemented stem in the correct high. For 1 case (group B) cortical osteotomy of the metaphyseal part was performed to change the humeral stem. A new cemented humeral stem was placed lower to facilitate the reduction of the prosthesis and wire cerclage was used for the fixation of the humerus (FIGURE 3). The metaphyseal part was re-cut and cancellous and chips bone graft allowed to obtain a press fit metaphyseal stem and cement into the diaphysis. A standard polyethylene humeral insert was implanted on the humeral stem in all cases.
Postoperative rehabilitation
All the patients were immobilized with a brace in neutral rotation maintained for four weeks. Passive ROM in forward elevation and external rotation begun immediately after the operation until pain limits. Active ROM and hydrotherapy were initiated at 6 weeks post-operatively and muscular strengthening of the external rotators and the depressor muscles represented the last step of rehabilitation that was initiated 3 months post-operatively.
Patient assessment
Pre- and post-operative clinical evaluation was performed by the senior author and included evaluation of functional scores: absolute Constant–Murley score (CMS), subjective shoulder value (SSV), Simple Shoulder Test (SST) and active ROM assessment including forward elevation (FE) at scapular level, external rotation with the arm at the side (ER1), external rotation in 90º of abduction (ER2) and internal rotation (IR). Subjective pain evaluation was recorded with the visual analogue scale (VAS) pain score from one to ten. Strength was measured with the arm in abduction of 90° in the plane of the scapula, with a resistance during five seconds against a hand-held dynamometer fixed at the level of the wrist. In addition, at the last follow up visit patients were asked to evaluate their degree of satisfaction from the final outcome using the following scale: very satisfied, satisfied, or fair. True antero-posterior (neutral, external and internal rotation) and scapular lateral radiographs were routinely performed pre- and post-operatively at the latest follow-up examination. Pre-operative computed tomography (CT) scans were performed to analyze bone deformity, glenoid bone stock, muscle trophicity and degree of fatty infiltration (according to Goutallier classification) [17]. We looked for evidence of glenoid component loosening (radiolucent lines around the PE cemented or the base plate, medialization of the PE component, hardware breakage and migration of base plate or PE) or scapular notching (graded according to the Sirveaux-Nerot classification) [18]. Intra- and post-operative complications were recorded.
Statistical analysis
The analysis was performed with the statistical battery provided by STATA® (version 11.0 for Mac OS; StataCorp, Texas, USA.). The Shapiro-Wilk test was used to assess the normal distribution of the results, according to the different groups. The Student’s t test or Mann–Whitney test were used to compare the preoperative and postoperative results for all values in the distinct groups, and between groups. Statistical significance was determined at a p-value < 0.05.