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Comparative Study
. 2019 Dec 5;90(12-S):54-63.
doi: 10.23750/abm.v90i12-S.8983.

Onlay versus Inlay humeral steam in Reverse Shoulder Arthroplasty (RSA): clinical and biomechanical study

Alessandro Beltrame  1 , Paolo Di Benedetto, Chiara Cicuto, Vanni Cainero, Renato Chisoni, Araldo Causero
Affiliations
Comparative Study

Onlay versus Inlay humeral steam in Reverse Shoulder Arthroplasty (RSA): clinical and biomechanical study

Alessandro Beltrame et al. Acta Biomed. .

Abstract

Background and aim of the work: Reverse shoulder arthroplasty (RSA) is becoming treatment of choice in glenohumeral arthropathies with massive lesion of the rotator cuff, due to a gradual extension of indications and new designs that provide better outcome. In this study we compared two different reverse shoulder prosthesis designs, defined as Inlay (or typical Grammont type) and a relatively new model defined as Onlay (that preserves tuberosity bone stock). We analyzed clinical, biomechanical and radiological outcomes, as well as complications of RSA in these two groups.

Methods: We performed a prospective study on a population of 42 patients undergoing Reverse Shoulder Replacement by a single expert surgeon. We consider 21 patients (group A) who underwent to reverse shoulder replacement with a curved onlay steam with 145° inclination (Ascend Flex group, Wright medical, Memphis, TN, USA) and 21 patients who underwent to reverse shoulder replacement with a traditional Inlay Grammont steam (Modular Shoulder System SMR, Systema Multiplana Randelli; Lima-LTO, San Daniele del Friuli, Italy) between August 2010 and October 2018. We studied the following items: active range of motion (AROM), radiological parameters (lateralization shoulder angle LSA, Distalization Shoulder Angle DSA), functional scale (Constant-Murley Score), post-operative complications (infection, aseptical implant mobilitazion, residual pain, scapular notching, fractures, tuberosity reabsorbtion, dislocation, bleedings, nerve palsy, pulmonary embolus).

Results: A significant improvement in ROM and functional score (Constant Shoulder Score) were observed in both groups. Group A (Onlay design 145°, medial tray) provides improvement in adduction, extension and external rotation compared to group B. No significant differences were found in abduction, external rotation and forward flexion. At 6 months follow-up, pain relief was detected in all patients. Although complications occur in a high percentage of patients in literature, no postoperative complications were observed in our cases series.

Conclusions: Our results showed how RSA is a real solution to improve quality of life and to restore pain-free shoulder ROM in patients where cuff tear arthropathy occurs. Onlay design 145° may provides better active external rotation, extension, adduction: it is necessary to continue follow up and include more cases to prove these data.

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Conflict of interest statement

Each author declares that he or she has no commercial associations (e.g. consultancies, stock ownership, equity interest, patent/licensing arrangement etc.) that might pose a conflict of interest in connection with the submitted article

Figures

Figure 1.
Figure 1.
“Cuff tear arthropathy” (CTA) characterized by a massive rotator cuff tear that gradually leads to Eccentric Osteoarthrosis
Figure 2.
Figure 2.
Pre-operative planning. The red spot on inferior scapular neck shows the Notching point
Figure 3.
Figure 3.
Reverse Shoulder Arthoplasty (P.Grammont, 1991, Delta III, DePuy)
Figure 4.
Figure 4.
a. Inlay steam; b. Onlay curved steam
Figure 5.
Figure 5.
Onlay Aequalis Ascend Flex curved steam: bone stock preservation zones
Figure 6.
Figure 6.
Active Internal Rotation: each image has a corresponding vertebral range. Vertebral levels are converted to points for analysis purposes (Triplets et al. (22)
Figure 7.
Figure 7.
Constant-Murley Score
Figure 8.
Figure 8.
DSA and LSA angle in Inlay RSA (28)
Figure 9.
Figure 9.
DSA and LSA angle in Onlay RSA (28)
Figure 10.
Figure 10.
Distal humerus fracture with complete lesion of radial nerve occurred 1 year after shoulder replacement
Figure 11.
Figure 11.
Scapular Notching, grade 1, at six month follow up
See this image and copyright information in PMC

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