A review of shoulder replacement surgery.
Abstract: Shoulder replacement surgery is employed in the treatment of severe shoulder arthritis and following some proximal humeral fractures. Three different replacements are available: hemiarthroplasty (HAS), total shoulder replacement (TSR) and reverse shoulder replacement (RSR). HAS and TSR are indicated in patients with intact rotator cuffs and RSR for cuff deficient older patients. Outcomes are favourable, with the majority of patients having improvements in shoulder pain and function.

KEYWORDS Shoulder / Replacement / Arthroplasty / Orthopaedics
Article Type: Report
Subject: Fractures
Orthopedic surgery
Authors: Wand, RJ
Dear, KEA
Bigsby, E.
Wand, JS
Pub Date: 11/01/2012
Publication: Name: Journal of Perioperative Practice Publisher: Association for Perioperative Practice Audience: Academic Format: Magazine/Journal Subject: Health; Health care industry Copyright: COPYRIGHT 2012 Association for Perioperative Practice ISSN: 1750-4589
Issue: Date: Nov, 2012 Source Volume: 22 Source Issue: 11
Accession Number: 309315445
Full Text: Introduction

Shoulder replacement surgery came into common usage in the 1990s for patients with severe joint pain associated with destructive joint disease. Initially, there were two types of implant: hemiarthroplasty (replacement of the humeral head only) and total shoulder replacement (replacement of the humeral head and glenoid). More recently, a reverse (inverse) shoulder replacement has been developed for situations where the rotator cuff is deficient. In this situation, the ball (glenosphere) of the shoulder is attached to the glenoid (articular surface of the scapula) and the socket to the humerus.

This review provides a background of shoulder replacement surgery, together with an insight into the decision making process with regard to implant selection. It concludes with an overview of common complications and outcomes following surgery.

History

The first shoulder replacement was performed in Paris in 1893 by the French surgeon Jules-EmilesPean (Pean1894), preceding the first hip replacement by more than 25 years. The shoulder prosthesis was made of rubber and platinum and was implanted into a 37 year old baker with tuberculous arthritis. The prosthesis functioned well for two years, but became infected and required removal. Koenig performed the second shoulder replacement operation in 1914 using an ivory prosthesis, however the procedure was not attempted again for almost 40 years (Foruria et al 2008).

Between 1951 and 1952, resin (Boron, Sevin, Judet) and vitallium (Krueger) prostheses were produced, while Charles S Neer II developed the modern monoblock (single piece) prosthesis. Later, in Europe (Scales & Lettin in 1969, Reeves & Jobbins in 1971, Kolbel in 1972, Zippel in 1972 and Kessel in 1973) and in the United States (Neer) different shoulder prostheses were developed. However, due to high rates of loosening (more than 50%), interest in this type of implant diminished.

Shoulder prostheses only became mainstream following Neer's unconstrained designs (first generation), which mimicked the natural shoulder anatomy. Second generation implants also termed 'modular prostheses' were developed at the end of the 1980s (e.g. Biomet, Cofield and Global models). These consisted of an independent segment for the head and stem, allowing for a greater choice and a more anatomic implant. The first third generation implants introduced variable neck angles and eccentric heads which recreated the tridimensional measurements of the bone, allowing the natural anatomy of the shoulder to be mimicked more closely. More recently, fourth generation implants have been developed, allowing for variable head positions in three axes and in situ positioning of the head.

Anatomy

The shoulder is comprised of three bones (Figure 1): scapula, humerus and clavicle, and two synovial joints: the glenohumeral joint and acromioclavicular joint. The glenohumeral joint, often referred to as 'the shoulder joint', is a synovial ball and socket joint, where the hemi-spherical head of the humerus articulates with the lateral aspect of the scapula (the glenoid fossa). The glenoid fossa is shallow, with a small surface area, allowing a wide range of movement in all three planes. It is the most mobile joint in the body.

[FIGURE 1 OMITTED]

The main muscles moving the shoulder are the rotator cuff muscles. This is a group of four muscles consisting of supraspinatus, infraspinatus, subscapularis and teres minor, which work together with the deltoid muscle (a non-rotator cuff muscle). The rotator cuff (specifically supraspinatus) together with the deltoid is responsible for abducting the arm (lifting it up from the side of the body). The deltoid muscle covers the outer aspect of the shoulder originating from the outer part of the clavicle and acromion and inserting onto the proximal part of the humerus. In rotator cuff deficient patients the deltoid is solely responsible for abducting the arm. This is of particular significance for reverse shoulder replacements (see below).

Types of replacement

There are three distinct types of shoulder replacement: hemiarthroplasty (HAS), total shoulder replacement (TSR), and reverse shoulder replacement (RSR). The type of implant selected depends upon the patient as well as the underlying pathology (Figure 2).

[FIGURE 2 OMITTED]

Hemiarthroplasty

A hemiarthroplasty (HAS) involves replacing only the humeral head. It articulates with the native glenoid. This group includes surface replacements, also called resurfacings (Figure 3) and stemmed prostheses (Figure 4). Surface replacements are used to treat focal arthritis, avascular necrosis where there is still adequate supporting bone, and cartilage damage on the humeral head (Jensen 2007). This procedure preserves bone stock while attempting to restore the normal anatomy (Levy & Copeland 2004). Stemmed HAS are used for patients with humeral head fractures, pathological fractures, focal cartilage damage or avascular necrosis of the humeral head (Brown 2008).

[FIGURE 3 OMITTED]

[FIGURE 4 OMITTED]

Whilst HAS allows for good pain management, some have reported poor performance in return of function (DiGiovanni et al 1998). It is however, technically an easier and less invasive operation than a TSR since glenoid exposure is not required. It obviates the potential long-term problem of loosening of the glenoid component, but may be associated with glenoid erosion with subsequent bone loss.

Total shoulder replacement

Total shoulder replacements (TSR) (Figure 5) are performed when there is disease of both the humeral head and the glenoid (Brown 2008), be it primary osteoarthritis or post-traumatic arthritis (Ricchetti & Williams 2011). However, sufficient glenoid bone stock is needed to ensure solid fixation of the glenoid component. For good function, the rotator cuff needs to be intact whether a TSR or a HAS is performed. TSR is often used for inflammatory arthropathies such as rheumatoid arthritis, where the bone is soft, and thus the risk of glenoid erosion from HAS would be high. However this is not an absolute indication.

[FIGURE 5 OMITTED]

Although TSR can provide a better medium term functional outcome (Edwards et al 2003, Bishop & Flatow 2005), there are concerns about loosening of the glenoid component (Gonzalez et al 2011, Bohsali et al 2006) and so they have traditionally been implanted into an older, less physically demanding population.

Reverse shoulder replacement

The semi-constrained reverse shoulder prosthesis was designed by Grammont in the late 1980s (Zumstein et al 2011). As the name implies, there is a reversal of the anatomic shoulder, with the ball being fitted to the glenoid (glenosphere) and the cup being inserted into the humerus. The modern designs (Figure 6) are based on Grammont's principles, that in order to improve biomechanics, the centre of rotation of the joint must be medialised and distalised (Figure 7). In RSR this increases the tension in the deltoid muscle, which increases its functional strength while decreasing the mechanical torque at the glenoid. It is intended that this should reduce the risk of glenosphere loosening.

[FIGURE 6 OMITTED]

[FIGURE 7 OMITTED]

Reverse shoulder replacements are usually indicated for elderly patients with massive irreparable rotator cuff tears. Other indications for RSR have included revision TSR (when glenoid reconstruction with bone graft would be required), four part displaced proximal humeral fractures, and tumours requiring resection of the greater tuberosity (Smithers et al 2011). In recent years, the indications for RSR have expanded to include proximal humeral malunion and non-union, acute fractures, revision surgery after failed hemiarthroplasty (Boileau et al 2006, Wall & Walch 2007), reconstruction after tumour resection of the proximal humerus (de Wilde et al 2003), and pseudoparesis of the shoulder (Werner et al 2005). In order to have good function, there needs to be a functional and powerful deltoid. The operation is contra-indicated in the presence of an axillary nerve palsy (i.e. a denervated deltoid).

Operative procedure

The procedure for a shoulder replacement varies both with surgeon preference and with the type of implant used. The description below is an outline of the main steps rather than a 'how to' guide of the operation.

Anaesthetic

Typically a general anaesthetic is used. However, regional anaesthesia can be used, often supplemented by sedation. Many anaesthetists favour inter-scalene blocks performed under ultrasound control. There is an incidence of about 1 in 5000 of nerve damage following this type of regional anaesthetic.

Patient positioning

Patients are often positioned in a beach chair position on the operating table with the operative arm free to allow for extensive shoulder movements. Prior to surgery, a gentle manipulation is usually performed to assess the arc of shoulder movements.

Approach

The shoulder is commonly approached through an incision of approximately 10-15 cm extending from the coracoid process to the distal insertion of the deltoid muscle. This varies depending on surgeon preference and the shoulder replacement being implanted. The deltoid muscle is retracted laterally and the subscapularis tendon (if present) identified. Stay sutures are used to hold the subscapularis before it is divided or detached from the lesser tuberosity, exposing the joint capsule. An incision is then made in the joint capsule and the glenohumeral (shoulder) joint entered. This is the delto-pectoral approach. Some surgeons favour the direct lateral approach of McKenzie, with splitting of the deltoid, when performing an RSR.

Dislocation

The humerus is dislocated anteriorly from the glenoid, providing access to both the humeral head and the glenoid. Many surgeons perform a biceps tenodesis whereby the intra-articular portion of the long head of biceps is excised and the biceps tendon attached to the proximal humerus. In order to expose the glenoid, an extensive capsular release is needed, the head resected and the humeral head dislocation posteriorly. Satisfactory access to the glenoid can be difficult to achieve.

Head preparation

The humeral head is prepared first by removing osteophytes (abnormal bony growths). A humeral neck cut is then made in a plane to simulate the plane of the anatomic neck of the humerus. This can be done with the aid of cutting jigs depending on the implant.

In a stemmed HAS, TSR and RSR the humerus is then prepared for the insertion of the component by reaming of the bone canal with successively larger reamers. The humeral component is then sized appropriately to fit, and inserted either with or without cement, into the humeral canal.

Soft tissue releases are required to balance the shoulder and to allow a full arc of movement. Often the shoulder has been immobile for a number of years prior to surgery with concomitant stiffness of the adjacent soft tissues. If these tissues are not released the shoulder movements will always be restricted, irrespective of the implant used.

In shoulder resurfacings there is no need for any preparation of the humeral canal as there is no intramedullary stem. They are simply attached to the top of the humerus via a central peg or corona (crown) once the humeral head has been drilled or reamed (depending on the implant).

Glenoid preparation

For TSR and RSR the glenoid is exposed and reamed to accept the glenoid component. This is attached to the bone with either screws or cement. In uncemented designs, the implant is often coated with hydroxyapatite to encourage bone ingrowth.

Stability testing

Although stability testing is carried out throughout the operation, once the final implants are in situ, the stability of the shoulder is again tested to ensure that the appropriate tension is present, and that it is stable i.e. not likely to dislocate. While some implant systems allow adjustments in the sizes of the head to improve stability, others rely on the initial bone cuts.

Closure

The wound is closed in layers with either clips or subcuticular sutures to skin. Many surgeons favour leaving a drain in situ for 24 hours.

Postoperative recovery

The postoperative recovery phase is tailored to the individual patient, and depends on patient factors (pre-operative state, muscle function, bone quality, general functional demands), operative factors (intra-operative fractures, the requirement for rotator cuff repair) and the type of prosthesis implanted. However, generally patients are placed in a collar and cuff or sling for comfort for the first few days and thereafter physiotherapy commences. The main restriction post-operatively is to avoid forced external rotation for the first month to prevent damaging the subscapularis repair.

Physiotherapy aims to prevent shoulder and elbow stiffness through encouraging movement, and improve shoulder muscle function through exercise. An aggressive postoperative rehabilitation program is needed for the best clinical results. Sometimes a manipulation under anaesthetic is needed to stretch any adhesions that may have formed and to improve the arc of movements. Generally, any manipulation, if indicated, is performed within two months of surgery.

Complications

For any patient undergoing an operation the decision to proceed is a balance between the potential benefits and the risks. The risk of adverse events is dependent on the patient, the complexity of the surgery and the prosthesis used. Potential complications of all shoulder replacement surgery are shown in Box 1. Implant specific complications include: glenoid erosion (HAS only), loosening of the glenoid component (mainly TSR), scapular notching (RSR only) and rotator cuff tear or dysfunction (HAS and TSR only).

Outcomes

The aim of shoulder replacement surgery is to restore shoulder function and relieve pain. Various studies have been undertaken to assess whether this is indeed the case. Gartsman et al (2000) reported significant improvements in subjective patient scoring systems at an average of 35 months, for both HAS and TSR, although TSR significantly outperformed HAS in terms of pain relief and improvement in internal rotation. Others have also reported good results for both HAS and TSR in the short and medium term (Edwards et al 2003, Radnay et al 2007). In the long-term (10 year review) Haines et al (2006) showed both HAS and TSR improved shoulder assessment scores, with no significant difference in outcomes between the procedures.

While there is little long-term data on RSR, in the short and medium term most patients who received a RSR reported being satisfied or very satisfied, and had significant improvements in their functional assessment scores (Sirveaux et al 2004, Werner et al 2005, Boileau et al 2006, Frankle et al 2006, Wall et al 2007, Young et al 2009).

Summary

Shoulder replacement surgery is a good option for patients with a number of shoulder pathologies and can give a pain free shoulder with a good function. However, complications can and do occur. The decision to go ahead with surgery is one that is taken following discussion between surgeon and patient and the choice of implant used is based on both patient factors and the underlying pathology being treated.

* Anaesthetic complications

* Bleeding

* Nerve damage (axillary and musculo-cutaneous nerves)

* Fracture (during or after operation)

* Infection (superficial or deep)

* Dislocation

* Loosening

* Need for revision (redo) surgery

Box 1. Potential complications of all shoulder replacement surgery

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by RJ Wand, KEA Dear, E Bigsby and JS Wand

Correspondence address: RJ Wand, Department of Trauma and Orthopaedic Surgery, Cheltenham General Hospital, Sandford Road, Cheltenham, GL53 7AN. Email: rw7706@bristol.ac.uk

About the authors

Richard J Wand

BSc

Medical Student, University of Bristol

Katherine EA Dear

BSc

Medical Student, University of Bristol

Ewan Bigsby

MRCS, DPhil

SpR in Trauma and Orthopaedic Surgery, Cheltenham General Hospital

Jonathan S Wand

BSc, MBBS, FRCS

Consultant Orthopaedic Surgeon, Cheltenham General Hospital

No competing interests declared

Provenance and Peer review: Unsolicited contributed; Peer reviewed; Accepted for publication June 2012.
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