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Prosthesis design and placement in reverse total shoulder arthroplasty.

Ackland DC, Patel M, Knox D - J Orthop Surg Res (2015)

Bottom Line: Patient selection, surgical approach and post-operative management are factors vital to successful outcome of RSA, with implant design and component positioning having a significant influence on the ability of the shoulder muscles to elevate, axially rotate and stabilise the humerus.Clinical and biomechanical studies have revealed that component design and placement affects the location of the joint centre of rotation and therefore the force-generating capacity of the muscles and overall joint mobility and stability.Furthermore, surgical technique has also been shown to have an important influence on clinical outcome of RSA, as it can affect intra-operative joint exposure as well as post-operative muscle function.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical Engineering, University of Melbourne, Parkville, Victoria, 3010, Australia. dackland@unimelb.edu.au.

ABSTRACT
The management of irreparable rotator cuff tears associated with osteoarthritis of the glenohumeral joint has long been challenging. Reverse total shoulder arthroplasty (RSA) was designed to provide pain relief and improve shoulder function in patients with severe rotator cuff tear arthropathy. While this procedure has been known to reduce pain, improve strength and increase range of motion in shoulder elevation, scapular notching, rotation deficiency, early implant loosening and dislocation have attributed to complication rates as high as 62%. Patient selection, surgical approach and post-operative management are factors vital to successful outcome of RSA, with implant design and component positioning having a significant influence on the ability of the shoulder muscles to elevate, axially rotate and stabilise the humerus. Clinical and biomechanical studies have revealed that component design and placement affects the location of the joint centre of rotation and therefore the force-generating capacity of the muscles and overall joint mobility and stability. Furthermore, surgical technique has also been shown to have an important influence on clinical outcome of RSA, as it can affect intra-operative joint exposure as well as post-operative muscle function. This review discusses the behaviour of the shoulder after RSA and the influence of implant design, component positioning and surgical technique on post-operative joint function and clinical outcome.

No MeSH data available.


Related in: MedlinePlus

Inferior angulation of the glenoid component to mitigate scapular notching
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Fig5: Inferior angulation of the glenoid component to mitigate scapular notching

Mentions: Inferior angulation of the metaglene is an alternative technique that may reduce scapular notching [57] (Fig. 5). Suggested by Sirveaux et al. [20], this method is combined with inferior placement of the metaglene and was a response to poor clinical outcome in cases of superior glenoid wear (Favard classification 2 and 3). Cadaveric and computer model studies have suggested a potential benefit [54, 56], but in neither investigation was inferior angulation the most important factor in mitigating notching. In a prospective randomised clinical trial involving 42 Aequalis implants followed for a minimum of 1 year, 10° of inferior tilt actually provided no protection against notching as compared to neutral glenoid reaming [58]. A retrospective cohort trial reviewing 71 Delta III implants again revealed no mechanical benefit [59]. Inferior inclination has the disadvantage of requiring additional reaming in order to generate tilt, resulting in loss of glenoid bone stock and further medialisation of the joint centre of rotation. Inferior inclination combined with a lateralised design will ultimately reduce the amount of lateralisation obtained. The effect of inferior tilt may thus show a design-dependent effect, which is also true of the contact forces at the baseplate-bone interface. Inferiorly shifted eccentric glenospheres may generate an uneven distribution of glenohumeral joint force across the metaglene when placed in an inferior tilt. This may produce a ‘rocking horse’ effect at the glenoid, not seen in concentric implants. While this has only been demonstrated in a computer model to date [60], it is another example of important consequences of design variations within the family of reversed anatomy prosthetic joint components.Fig. 5


Prosthesis design and placement in reverse total shoulder arthroplasty.

Ackland DC, Patel M, Knox D - J Orthop Surg Res (2015)

Inferior angulation of the glenoid component to mitigate scapular notching
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4493953&req=5

Fig5: Inferior angulation of the glenoid component to mitigate scapular notching
Mentions: Inferior angulation of the metaglene is an alternative technique that may reduce scapular notching [57] (Fig. 5). Suggested by Sirveaux et al. [20], this method is combined with inferior placement of the metaglene and was a response to poor clinical outcome in cases of superior glenoid wear (Favard classification 2 and 3). Cadaveric and computer model studies have suggested a potential benefit [54, 56], but in neither investigation was inferior angulation the most important factor in mitigating notching. In a prospective randomised clinical trial involving 42 Aequalis implants followed for a minimum of 1 year, 10° of inferior tilt actually provided no protection against notching as compared to neutral glenoid reaming [58]. A retrospective cohort trial reviewing 71 Delta III implants again revealed no mechanical benefit [59]. Inferior inclination has the disadvantage of requiring additional reaming in order to generate tilt, resulting in loss of glenoid bone stock and further medialisation of the joint centre of rotation. Inferior inclination combined with a lateralised design will ultimately reduce the amount of lateralisation obtained. The effect of inferior tilt may thus show a design-dependent effect, which is also true of the contact forces at the baseplate-bone interface. Inferiorly shifted eccentric glenospheres may generate an uneven distribution of glenohumeral joint force across the metaglene when placed in an inferior tilt. This may produce a ‘rocking horse’ effect at the glenoid, not seen in concentric implants. While this has only been demonstrated in a computer model to date [60], it is another example of important consequences of design variations within the family of reversed anatomy prosthetic joint components.Fig. 5

Bottom Line: Patient selection, surgical approach and post-operative management are factors vital to successful outcome of RSA, with implant design and component positioning having a significant influence on the ability of the shoulder muscles to elevate, axially rotate and stabilise the humerus.Clinical and biomechanical studies have revealed that component design and placement affects the location of the joint centre of rotation and therefore the force-generating capacity of the muscles and overall joint mobility and stability.Furthermore, surgical technique has also been shown to have an important influence on clinical outcome of RSA, as it can affect intra-operative joint exposure as well as post-operative muscle function.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical Engineering, University of Melbourne, Parkville, Victoria, 3010, Australia. dackland@unimelb.edu.au.

ABSTRACT
The management of irreparable rotator cuff tears associated with osteoarthritis of the glenohumeral joint has long been challenging. Reverse total shoulder arthroplasty (RSA) was designed to provide pain relief and improve shoulder function in patients with severe rotator cuff tear arthropathy. While this procedure has been known to reduce pain, improve strength and increase range of motion in shoulder elevation, scapular notching, rotation deficiency, early implant loosening and dislocation have attributed to complication rates as high as 62%. Patient selection, surgical approach and post-operative management are factors vital to successful outcome of RSA, with implant design and component positioning having a significant influence on the ability of the shoulder muscles to elevate, axially rotate and stabilise the humerus. Clinical and biomechanical studies have revealed that component design and placement affects the location of the joint centre of rotation and therefore the force-generating capacity of the muscles and overall joint mobility and stability. Furthermore, surgical technique has also been shown to have an important influence on clinical outcome of RSA, as it can affect intra-operative joint exposure as well as post-operative muscle function. This review discusses the behaviour of the shoulder after RSA and the influence of implant design, component positioning and surgical technique on post-operative joint function and clinical outcome.

No MeSH data available.


Related in: MedlinePlus