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Reverse shoulder arthroplasty current concepts
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Reverse shoulder arthroplasty current concepts
prosthesis was introduced. The aim of this paper is to review the biomechanics, technical considerations, indications, clinical results and complications of reverse shoulder arthroplasty.
Current designs
Nawfal Al-Hadithy
Grammont’s first prosthesis10 consisted of two components: a metallic or ceramic glenoid ball which, although positioned medially, still sat proud of the native glenoid surface, and a concave humeral polyethylene socket, both of which were cemented. Although all of the initial eight patients were painfree, they had limited function and revision surgery was required in three cases. The Delta III prosthesis has been available since 1991 and consists of five components: the hydroxyapatite coated glenoid baseplate (metaglene), which has divergent peripheral screws and a central peg/screw, the glenosphere, polyethylene lateralized humeral cup, humeral neck (epiphysis) and stem (diaphysis). Although the De Puy Delta III prosthesis has the largest number of published trials, other implants are also available including the Aequalis Reversed Shoulder Prosthesis (Tournier, Inc, Edina, MN) and the reversed polar, linked BayleyeWalker Implant (Stanmore Implants, Elstree, UK).
Adam P Rumian
Abstract The reverse shoulder arthroplasty (RSA) was introduced in 1987 for cuff tear arthropathy. Over time the prostheses have evolved and its indications have increased. RSA is a semi-constrained reverse ball and socket prosthesis with several key biomechanical advantages, including a fixed centre of rotation which allows the deltoid to function. In this review, the history, key principles, indications, surgical tips and complications are discussed. RSA can provide excellent results with significant improvements in pain and function but is a technically demanding procedure.
Keywords cuff tear arthropathy; reverse shoulder arthroplasty
Introduction
Biomechanics
Although the first prosthetic shoulder arthroplasty was performed in 18931 by a French surgeon, Jules Emile Pean, there was little progression thereafter until 1955, when Neer2 developed a stemmed, non-constrained total shoulder replacement (TSR) for the treatment of 4-part proximal humerus fractures. Neer published a further study in 19743 describing the results of a hemiarthroplasty prosthesis. There has since been a considerable number of studies since then, showing that both TSR and hemiarthroplasty are effective at relieving pain and improving function for widening indications, including trauma, osteoarthritis and rheumatoid arthritis.4e6 However, the initial success of these procedures was not replicable in the cuff deficient shoulder, with Neer3 noting slow recovery and poor strength and he suggested that the use of shoulder prostheses in these patients should be expected to have limited functional goals. In subsequent studies, other surgeons noted the use of TSR in cuff arthropathy to have unpredictable and poor outcomes.7 Total shoulder arthroplasty in the cuff deficient shoulder has now been abandoned due to the “rocking horse” effect causing eccentric loading of the glenoid component due to superior migration of the humeral head component and thereby early loosening and failure.8,9 The reverse shoulder arthroplasty was introduced by Paul Grammont10 in 1987 in an attempt to improve outcomes in cuff deficient shoulders. It has subsequently undergone several revisions and modifications, and in 1991, the Delta IIIÒ
The cuff-deficient shoulder The shoulder is a complex joint and to allow its great range of motion, static and dynamic stabilizers work to keep the humeral head in place. The rotator cuff is a key dynamic stabilizer and causes compression at the glenohumeral joint, ensuring that the humeral head remains central and stable within the glenoid fossa11 throughout the range of shoulder movement. Severe deficiency of the rotator cuff can lead to a muscle imbalance such that the humeral head is no longer held centrally in the glenoid fossa when the deltoid contracts. Instead, the unopposed deltoid contractions cause proximal migration of the humeral head over time, leading to impingement of the greater tuberosity on the acromion and cartilage damage in the glenohumeral joint, ie a “cuff tear arthropathy”.12 Biomechanics of the reverse shoulder prosthesis Early attempts at implanting a reverse shoulder prosthesis design failed due to it having a lateralized glenoid component with a centre of rotation lateral to the glenoid bonestock, resulting in excessive torque and shear forces on the glenoid component fixation and causing early catastrophic loosening (Figure 1). However, Grammont developed a semi-constrained reverse ball and socket prosthesis with key biomechanical advantages13 (Figure 2): Stable fulcrum of rotation with congruent joint surfaces Compensates for deficient rotator cuff by providing a “semi-constrained” arrangement, conferring inherent stability that is no longer reliant on compression from the rotator cuff Stable fulcrum of rotation allows deltoid contractions to produce functional elevation and the remaining cuff muscles to produce functional rotation Medialized centre of rotation and medialized humerus Increases deltoid lever arm, therefore improving elevation & abduction
Nawfal Al-Hadithy BSc MSc MRCS Orthopaedic Registrar, East and North Herfordshire NHS Trust, Lister Hospital, Stevenage, UK. Conflict of interest: none. Adam P Rumian MD FRCS(Tr & Ortho) Consultant Orthopaedic Surgeon, East and North Herfordshire NHS Trust, Lister Hospital, Stevenage, UK. Conflict of interest: none.
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rheumatoid arthritis with rotator cuff deficiency proximal humeral fractures: there has been a recent trend to use RSA for complex three- and four- part proximal humeral fractures in more elderly patients where the results of a hemiarthroplasty would be expected to be poor or if successful reconstruction of the fractured tuberosities is not anticipated. Anatomical reduction and healing of the tuberosities has been shown to be one of the main prognostic factors influencing recovery of the shoulder.14 Examples of this are patients with severe osteoporosis, comminuted fractures of the greater tuberosity, preexisting rotator cuff tears or co-existing glenoid fractures. post-traumatic reconstruction: operative treatment of shoulder fracture sequelae is one of the most challenging problems in shoulder surgery. RSA has been used successfully in certain patterns of severe malunion or nonunion. revision shoulder arthroplasty: RSA is being used increasingly for revision shoulder arthroplasty where either soft tissue or bony deficiencies preclude the use of an anatomical prosthesis osteoarthritis with associated rotator cuff tear: primary osteoarthritis is distinct from cuff tear arthropathy, in that the latter is an end-stage result of cuff tear deficiency. The rotator cuff is usually intact in primary osteoarthritis but RSA has been used in those cases associated with a rotator cuff tear as an alternative to hemiarthroplasty where there are concerns that implanting an anatomical glenoid component may be at risk from loosening from the “rocking-horse” effect osteoarthritis with particular glenoid morphology: the results of anatomical total shoulder replacement is poorer in cases where the humeral head is subluxed posteriorly and the glenoid is biconcave and eroded posteriorly (Walch type B2), or dysplastic with excess retroversion (Walch type C). Recent reports suggest more favourable outcomes with RSA. tumour surgery: RSA is indicated for shoulder reconstruction where resection of the rotator cuff has been performed.
Figure 1 Schematic diagram revealing excessive torque in the glenoid component which was the cause of failure in early reverse shoulder prosthesis designs.
Reduces torque and shearing forces on the glenoid component, thus reducing the risk of loosening Lowering of humerus A non-anatomical humeral inclination (155 ) lowers the humerus, increasing the mechanical advantage of the deltoid.
Indications The use of RSA was initially restricted to patients with an established cuff tear arthropathy, ie degenerative changes in the glenohumeral joint caused by proximal migration of the humeral head due to chronic cuff deficiency. However the indications for RSA have gradually expanded as experience and confidence with the prosthesis has increased. Potential indications now include: cuff tear arthropathy massive irreparable cuff tear: RSA has been used in patients with severe functional deficit as a result of a massive irreparable rotator cuff tear, but without degenerative change of the glenohumeral joint.
Figure 2 Biomechanics of (a) normal shoulder showing compression at glenohumeral joint and balance between ascending force of the deltoid and descending forces of the rotator cuff muscles (b) cuff tear arthropathy e superior migration of the humeral head and a slack deltoid causing an unstable centre of rotation (c) reverse shoulder arthroplasty with an inferiorly titled & hanging glenoid sphere and non-anatomical humeral inclination, lowering the deltoid and increasing mechanical advantage & (d) failure to have an inferior overhang predisposes to scapular notching when the arm is adducted.
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Absolute contra-indications to RSA include active infection, axillary nerve palsy/complete deltoid insufficiency, inadequate glenoid bone stock to support the glenoid component (unless bone grafting is considered) and patient non-compliance. Relative contra-indications include young age (<70) and isolated anterior deltoid insufficiency. Caution should be exercised when contemplating RSA in patients that may be at high risk of subsequent prosthetic instability, such as wheelchair users using their arms extensively for transfers.
Pre-operative assessment As is standard for all patients for whom an arthroplasty is considered, a thorough patient assessment should be performed including plain radiographs of the shoulder (anteroposterior, scapular lateral and axillary views). A computerized tomography (CT) scan is necessary to evaluate the glenoid bone stock and retroversion. The glenoid vault should ideally be more than 2 cm in depth to provide adequate primary fixation of the glenoid component. Inadequate pre-operative bone stock may warrant glenoid augmentation with bone grafting.15 The glenoid and humeral shaft diameters should be assessed to confirm that standard implant sizes can be used. Magnetic resonance imaging may be used to confirm the status and quality of the remaining rotator cuff, especially the remaining external rotators, which impact on the eventual outcome. In complex cases, scaled radiographs of both humeri may be required to allow accurate restoration of humeral length. Patients who have undergone previous surgery may require exclusion of underlying infection by a combination of inflammatory markers and joint aspiration/tissue biopsy.
Figure 3 Top 2 cm of pectoralis major is divided.
glenoid. The middle glenohumeral ligament and anterior capsule lying on the deep surface of subscapularis are then easily seen and incised and the rotator interval tissue is excised. The axillary nerve runs over the anterior surface of the subscapularis tendon and courses posteriorly through the quadrilateral space and is therefore potentially at risk during an inferior capsular release. The inferior capsular release can be safely and reliably performed by retracting the subscapularis tendon slightly medially and downwards so that the inferior capsule is identified. A pair of dissecting scissors is then passed between the capsule and the subscapularis tendon until it reaches the glenoid surface. Cutting down onto the scissors incises the capsule without the risk of damage to the subscapularis tendon and axillary nerve (Figure 4). The deltopectoral approach is reported to be associated with a higher dislocation rate than when the superolateral approach is used, which is thought to be due to the detachment of the subscapularis that is required in the deltopectoral approach, but which can be preserved in the superolateral approach.16 However, the higher dislocation rate may also reflect the fact that more complex cases such as revision cases, rather than simple primary arthroplasties, are performed using the deltopectoral approach, as this can be extended to give access to the humeral shaft. Although the superolateral approach allows easier visualization of the glenoid surface itself, it can be more difficult to achieve accurate glenoid component placement inferiorly or with
Surgical technique Approach Both the superolateral and deltopectoral approaches have been used. For the deltopectoral approach, the cephalic vein identifies the interval between the deltoid and pectoralis major muscles, which may often by seen as a stripe of fat. The interval is easiest to identify proximally, overlying the palpable coracoid process and is exploited distally until the pectoralis major tendon insertion is identified. The top 2 cm of pectoralis major can be released, by incision 1 cm medial to its insertion (Figure 3). This allows better exposure for the rest of the procedure, especially in a tight shoulder, and is repaired at the end. To expose the glenohumeral joint, the remaining subscapularis tendon is either tenotomized 1 cm medial to its insertion or released directly off its insertion on the lesser tuberosity, the latter preserving the tendon length and making it more likely that it can be repaired at the end of the procedure. Capsular releases are often essential in obtaining adequate exposure and can be approached in a reproducible and sequential manner. First, the capsule is released off its humeral insertion around the inferior border of the humeral head. This release should be continued all the way around the humeral neck to include the posterior band of the inferior glenohumeral ligament. Once the humeral head is retracted posteriorly and laterally with a retractor, the capsule overlying the superior border of the subscapularis tendon is incised along the tendon border up to the
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Figure 4 Safe incision of inferior capsule.
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inferior tilt. Levigne et al suggested that there is a higher incidence of scapular notching in the superolateral position and the component tends to be placed with superior tilt.17 Table 1 summarizes the advantages/disadvantages of each approach. Humeral preparation The humerus is dislocated and the head is resected using a guide after removing any large osteophytes. Generally, but dependent on the prosthesis being used, the head is resected to a nonanatomic inclination of 155 . The amount of bony resection is often surprisingly small. The humerus is then reamed and rasped to accept the trial prosthesis (Figure 5). The anatomical retroversion of the humeral head has a mean value of 30 , but the RSA humeral stem is usually placed in a non-anatomical retroversion of 0e20 . Favre et al.18 evaluated the effect of humeral component version on stability and found that placing it in neutral or anteversion of up to 20 improved stability. Placing the prosthesis in lesser retroversion will increase eventual internal rotation and decrease external rotation, and vice-versa. To ensure correct retroversion a guide wire attached to the jigs in may instrument sets from different manufacturers of both reverse and total shoulder can be aligned with the forearm (Figure 6).
Figure 5 Reaming of the humeral head.
Glenoid exposure/preparation A Kolbel forked lever retractor is positioned on the anterior glenoid neck to expose the anterior glenoid rim (Figure 7). The labrum can then be resected and the capsule released off the glenoid up to the 7 o’clock position. Care must be taken to release the capsule directly off the bone around the inferior rim of the glenoid to avoid axillary nerve injury. Once capsular releases are performed, this should allow sufficient posterior retraction of the humeral head to expose the glenoid fully. The arm should be positioned in slight abduction with either internal or external rotation together with some elbow flexion. To expose the glenoid, anterior, posterior, inferior and superior glenoid retractors are used. Drawing the transverse and horizontal equators on the glenoid allows identification of the central point. Drawing a second line inferior and parallel to the horizontal equator identifies the correct point of entry for a guide wire for reaming. This ensures the correct inferior positioning of the baseplate (Figure 8). Nyffeler et al19 found that placing the glenosphere
Figure 6 Retroversion guide.
such that it extends beyond the inferior glenoid rim provides significantly (p < 0.001) improved adduction and abduction compared with a flush prosthesis. They ensured that the glenoid baseplate was flush with the inferior glenoid to facilitate this. Levigne et al also found that a 4 mm inferior overhang provided the best outcomes.17,20 Kelly et al21 showed, in their cadaveric study of 10 shoulders, that the ideal location of the drill hole for the baseplate was 12 mm above the inferior glenoid rim and should provide excellent fixation in most cases. Most studies
Summary of advantages/disadvantages of deltopectoral/superolateral approach
Exposure
Notching Deltoid Dislocation
Deltopectoral
Superolateral
Excellent exposure of lower pole of glenoid with inferior capsular release Additional procedures can be performed (humeral osteotomy in revisions/Lat dorsi transfer) Reduced incidence
Easier visualization of glenoid surface
Deltoid preserved Increased e interrupts subscapularis tendon Requires extended capsular release
Higher incidence Tendency to place baseplate with superior tilt and higher Disruption to deltoid fibres Reduced e subscapularis muscle left in tact
Table 1
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Figure 9 Glenoid positions. (a) Central and neutral (b) flush and neutral (c) inferior overhand and neutral (d) flush and inferior tilt (e) Superior and neutral (f ) central and superior tilt.
Figure 7 Forked anterior Kolbel retractor exposes the anterior glenoid rim.
suggest that the glenosphere should be tilted inferiorly to avoid scapular notching and early loosening.22 The ideal position is still under investigation. A biomechanical study performed by Gutierrez et al23 found that 15 of inferior tilt provided the most even distribution of compressive forces. They also found that altering glenosphere version had little effect on stability and suggested that its spherical surface caused an unchanged angle of incidence. Figure 9 shows different glenoid positions. Once the glenoid is prepared, the glenoid baseplate can be impacted (Figure 10). The central peg has been shown to provide about 15% of the primary stability of the glenoid baseplate,24 with the peripheral screws contributing substantially more. Although the ideal number of screws is unknown, there has been considerable research into ideal screw position and size. DiStefano et al25 performed high resolution CT scans with 3D reconstruction and found increased cortical thickness in the lateral aspects of suprascapular notch, scapular spine base, anterior/superior aspect of inferior pillar and junction of glenoid neck. Humphreys et al26 described a three-column concept and suggest that screws at the coracoid base, within the spine and within the pillar provided the best fixation and was easily reproducible. Harman et al27 found that using peripheral screws of 5 mm diameter reduced micromotion by 21%e35% compared with screws of 3.5 mm. A subsequent study has found locked 5 mm screws to provide the most stable fixation.28 The Tornier Aequalis baseplate has four screwholes. The anterior and
posterior holes are for compression screws and are inserted and tightened first to compress the baseplate against the glenoid bone. Additional fixation is provided by the superior and inferior multidirectional locking screws that are directed into the coracoid base and scapular pillar, respectively. The glenosphere is then impacted onto the baseplate and secured with a screw to prevent dissociation. The size of the polyethylene humeral insert is decided after trial reduction and soft tissue tension assessment. Reduction of the humerus can be difficult and a “tyre-lever” technique can be used to lever the humerus into its correct articulating position. Deltoid tensioning can be affected by inferior positioning of the glenoid component, the size of polyethylene insert and level of humeral cut. Increasing deltoid length improves function by providing a stable fulcrum, essential for active elevation and prosthesis stability, undertensioning consistently leads to poor function. Although overtensioning does not affect function, it increases the chance of neurological injury, permanent arm abduction, acromial fracture and loss of the normal deltoid contour.13,29 Correct deltoid tensioning is difficult to establish perioperatively and Boileau13 suggested that it largely depends on surgical experience. Smith et al30 suggest that it is most easily corrected by altering the length of the polyethylene spacer and with correct tightness noted that the trial reduction and dislocation are quite difficult to perform, with no visible gap being
Figure 8 Central point of glenoid.
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Figure 10 Impacted glenoid baseplate.
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Results
present when the components are forcibly distracted. Various other indicators of correct component positioning and soft tissue tension have been suggested, including a tight conjoint tendon with the elbow extended, no abutment in adduction, no acromial impingement, and stability in abduction and external rotation.
The most common use of reverse shoulder arthroplasty is for the treatment of glenohumeral osteoarthritis in the presence of a cuff tear. Sirveaux31 et al reviewed 77 shoulders with glenohumeral
Summary of clinical outcomes Author
Pat no
Indication
Follow-up
Outcome
ROM
Rittmeister37 Sirveaux31
8 77
RA & Cuff tear CTA
54 m 44 m
CS: 17e63 CS: 22.6e65.6
FF: 73 e138
Naveed33
50
CTA
39 m
ASES: 19e65
FF: 55 e105
Guery34
62
53 e CTA 6 e RA 3 e Fracture
69.6 m
If CS<30 e 58% survival at 120 m
Ekelund35
33
RA
56 m
CS: 13e52
FF: 33 e115
Young36
18
RA
45.6 m
CS: 22.5e64.9
FF: 77.5 e138.6
Boileau47
71
Fracture
19 m
CS: 26e65
FF: 74 e102
Bufquin48
41
Fracture
22 m
CS: 69
FF-97
Levy38
25
Revision (hemiarthroplasty)
w60 m
ASES: 22.3e52.1
FF38.1 e72.7
Cuff28
22
Infection
43 m
ASES: 31.9e57
FF43.1 e79.5
Complication 1 e Septic loosening 5 e Glenoid aseptic loosening 7 e Glenoid disassociation 2 e # acromium 2 e Deep infection 1 e Instability 3 e Deep infection 1 e Dislocation 3 e Glenoid dissociation 1 e Glenoid loosening 1 e Glenoid rim # 1 e Loosening 1 e Screw breakage 1 e # Acromium 1 e # Acromial spine 1 e Coracoid process # 1 e GT # 1 e Axillary nerve injury 4 e Perioperative # 9 e GT displacement/ non-union/osteolysis 1 e Dislocation 1 e Radial nerve palsy 2 e Deep infection 5 e Neurological complications 1 e Anterior dislocation 19 e GT displacement 1 e PP# 1 e Deep infection 2 e Dislocation 1 e Screw breakage 1 e Dissociation 1 e Aseptic loosening 1 e Scapular # 1 e Polyethlene # 1 e Dislocation 1 e Humeral loosening 1 e Humeral # 1 e Neurological 1 e Poly dissociation
ASES ¼ American Shoulder and Elbow Score. CS ¼ Constant Score. GT ¼ Greater tuberosity. PP ¼ Peri-prosthetic. # ¼ Fracture.
Table 2
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reverse shoulder arthroplasties, 9 were unstable. Instability of an RSA can have several causes that need to be considered before contemplating any revision surgery. These include inadequate humeral length (from implanting the humeral component too distally), incorrect humeral retroversion and inadequate soft tissue tension (from component mal-position or wrong size of polyethylene insert). Gallo et al41 found superiorly inclined or positioned metaglenes were the cause in 5 (56%). In all cases, an incompetent subscapularis tendon was seen, and detachment in the deltopectoral approach has been considered the most significant risk factor for dislocation.16 This has been confirmed by a study showing no dislocations in 40 patients using subscapularis sparing approaches.41 Laderman et al42 also found a strong correlation between humeral length and dislocation. In all cases of dislocation, humeral length was reduced significantly compared with the contralateral side. Exchanging a glenosphere and humeral metaphyseal component for one of a larger diameter can sometimes restore stability in cases of recurrent instability without an obvious technical error. Scapular notching is most likely caused by mechanical impingement of the medial rim of the humeral cup against the scapular neck in adduction, causing erosion of the inferior glenoid neck.17 In a series of 448 patients,20 scapular notching was seen in 68% of cases at a mean time of 51 months and although in some patients notching remained static, they most often progressed with time and may be associated with loosening and early failure. The authors suggested that notching may be underreported in other studies due to obscuring of the zone of notching by the glenoid hemisphere, which may be partially avoided by precisely aligning the X-ray beam with the flat side of the baseplate. As previously discussed the glenoid hemisphere is usually placed and aimed inferiorly, and the authors found that mal-position of the component with a superiorly tilted base plate allows for erosion of the scapular rim by the medial surface of the humeral component and should therefore be avoided. Surgeons may choose to preferentially ream the inferior aspect the glenoid to ensure that the glenoid baseplate is either placed in neutral or tilted inferiorly. A classification system for scapular notching has been made by Sirveaux et al31 (Table 3) based on the size of the defect, and although they suggest that it corresponds with outcomes, this has not been validated yet. Apart from inferomedial impingement, a medialized glenohumeral joint may also restrict internal rotation due to mechanical impingement of tuberosities on the coracoid process and scapular spine in external rotation.43 To overcome this, several authors have attempted to increase the offset by
osteoarthritis and massive cuff ruptures that underwent Grammont inverted shoulder arthroplasty. He noted improved Constant shoulder scores (from 22.6 pre-operatively to 65.6 postoperatively) and improvements in active forward flexion (from 73 to 138 ), with all patients having mild or no pain. The current alternative therapy is hemiarthroplasty, Sanchez-Sotelo32 found similar relief in pain, but significantly reduced functional outcomes at 5 years, with forward flexion improving marginally, from 72 to 91 . Naveed et al33 stressed the importance of patient selection on successful outcomes, and found those with cuff tears secondary to arthritis had better functional outcomes and lower complication rates than other authors found for other indications. Despite these early improvements, Guery et al34 found that although loss of fixation and revision surgery remained low at 8 years in patients with massive cuff tear, functional outcomes deteriorated progressively after 6 years, which may have been attributed to ageing of the patients or loosening not visible on radiographic evaluation. The outcomes in patients with rheumatoid arthritis have been encouraging, with several studies showing significant improvements in pain and function, albeit less than seen in the osteoarthritic group.35,36 Despite the recent trend of RSA for proximal humeral fractures and its theoretical advantages, there is still considerable debate about whether it provides superior outcomes compared to conventional hemiarthroplasty. As may be expected, the use of reverse shoulder arthroplasty in revision surgery yields poorer functional results and a higher number of complications. Levy et al38 investigated the use of reverse shoulder arthroplasty for failed hemiarthroplasty in cuff arthropathy in 19 shoulders as a salvage procedure in the presence of moderateesevere glenoid erosions (68%), making stable fixation of the glenoid baseplate particularly challenging. Poor glenoid stock has been such a problem that other authors15 have investigated the role of augmenting the glenoid surface with bone grafting in either 1 or 2 stage procedures. Although there were significant gains in functional and pain scores, at 44 months, it was not without complications. six patients (32%) had prosthesis-related complications, including peri-prosthetic scapular fractures (2), baseplate loosening (1), failure of polyethylene (2) requiring revision, and one patient had severe proximal humeral bone loss requiring revision. Boileau et al13 had similar results, with 42% of patients (8 of 19) requiring revision surgery after conversion of failed hemiarthroplasty to reverse prosthesis. A summary of clinical outcomes is shown in Table 2.
Complications Complications of reverse shoulder arthroplasty include infection, instability, scapular notching, haematoma, glenoid loosening, humeral loosening, component dissociation, acromial fracture, other fractures and neurovascular injury. Treatment options for deep infection include prolonged antibiotic therapy, debridement with antibiotic therapy with retention of the prosthesis, revision or in salvage cases arthrodesis, resection arthroplasty or amputation.39 Implant retention has high rates of recurrence of infection, up to 63%,40 and salvage procedures have poor functional outcomes. Dislocation rates can be as high as 9% and represent one of the most significant complications of RSA.16 In a series 57
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Sirveaux classification of scapular notching Grade Grade Grade Grade
1 2 3 4
Defect Defect Defect Defect
confined to the pillar reaches lower screw crosses the lower screw extends under the baseplate
Table 3
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metallic lateralization (augmenting the lateral length of the glenosphere itself during manufacture) or grafting the glenoid surface. The main disadvantage of metallic lateralization is the increased torque on the glenoid component and the increased risk of subsequent loosening.27 To avoid this, Boileau et al43 have recently advocated using autologous bone graft from the humeral head to increase offset whilst maintaining the prosthetic centre of rotation at the implant-glenoid bone interface, and showed significant improvement in rotation with no failures at 24 months (Figure 11). A guide wire is inserted into the humeral head and a circular bell saw is used to cut a disc of bone. After the articular surface is reamed off (Figure 12), it is resected from the humeral head. This provides a size matched bone graft disc (Figure 13) that is impacted together with a specific baseplate that has a long central peg. Zumstein et al performed a systematic review44 of all reoperations (procedures not altering or replacing the components) and revisions (procedures with partial or total exchange or removal of components) in 21 studies. 84 patients underwent 26 re-operations and 79 revisions, representing 3.3% and 10.1% respectively. Interestingly, although the incidence of reoperation was almost equal in revision of TSR surgery (REV) and primary arthroplasty groups, revisions were twice as common in the REV group. Reverse shoulder arthroplasty is considered a difficult procedure even for experienced surgeons, and there is a learning curve. Complication rates are significantly higher in the first 10 patients compared with the second 10 patients with the majority of complications in the early phase arising from glenoid preparation and baseplate insertion.45
Figure 12 Articular surface reamed away.
Recent concepts The results of RSA have been shown to be inferior when the teres minor muscle is deficient. This can be explained by considering the normal shoulder, where there is a natural predominance of internal rotator muscles (subscapularis, pectoralis major, latissimus dorsi and teres major) over external rotator muscles (infraspinatus and teres minor). This predominance is even more pronounced in rotator cuff-deficient shoulders when the rotator cuff tear extends posteriorly. The teres minor is a key shoulder muscle, providing 40% of the strength of external rotation. When both the infraspinatus and teres minor are absent or fatty infiltrated, there is no other muscle to provide active external rotation: any attempt at shoulder elevation results in the forearm swinging in towards the trunk and such patients can no longer control the spatial positioning of their upper limb. From a biomechanical and surgical standpoint, patients with massive irreparable rotator cuff tears, may be categorized into three groups: those with an isolated loss of active elevation (i.e. pseudoparalyzed shoulder e PPS), those with an isolated loss of active external rotation (ILER), and those with a combined loss of active elevation and external rotation (CLEER). In the first group (PPS) there is a muscular imbalance in the vertical plane between the intact deltoid muscle and the non-functional rotator cuff muscles. A reverse shoulder arthroplasty (RSA) solves this problem of vertical muscle imbalance, by providing a fixed
Figure 11 Lateralized glenoid component using bone graft reveals no scapular notching even in an adducted arm.
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Figure 13 Impaction of bone graft onto baseplate.
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centre of rotation and increasing the deltoid tension to compensate for the weak/torn rotator cuff muscles. In the second group (ILER) there is a muscular imbalance in the horizontal plane between the intact internal rotator muscles (remaining subscapularis, pectoralis major, latissimus dorsi and teres major) and the absent or atrophied infraspinatus and teres minor; there are thus four functional muscles providing internal rotation with no functional muscles providing external rotation, i.e. four against zero. This definitive loss of active external rotation is a rare but disabling condition which results from posterior extension of the rotator cuff tear to the teres minor, as described above.1,2 Since active elevation is conserved (because the vertical muscle balance is conserved), a RSA is not indicated; a latissimus dorsi/teres major (LD/TM) transfer (modified l’Episcopo procedure) can rebalance the shoulder in the horizontal plane. The latissimus dorsi and teres major tendons are transferred laterally and posteriorly on the humerus, which changes their function from internal rotators to external rotators, resulting in two internal and two external rotators, i.e. two against two. In the third group (CLEER) there is both a vertical and horizontal muscle imbalance. The RSA can address the problem of vertical muscle imbalance but it cannot rebalance the shoulder in the horizontal plane. When both the infraspinatus and teres minor are absent or fatty infiltrated, prosthetic lateralization alone is not sufficient to provide active external rotation5,16; this is why, in this subgroup of patients, a RSA combined with the modified L’Episcopo have been used,46 Boileau et al improved active elevation and external rotation by 75 and 34 respectively using a single deltopectoral incision.46
7 8
9
10 11
12 13
14
15
16
Conclusion
17
RSA is a valuable option that can give excellent results in the absence of other suitable alternatives. However, it is a technically demanding procedure with a significant learning curve, even for the experienced surgeon, and a relatively high complication rate. Its use should therefore be reserved for patients with severe preoperative functional deficits and pain. Concerns about the longevity of the prosthesis and deterioration in function observed after 7 years mean that its use is recommended to be restricted to those patients over the age of 70 years. A
18
19
20
21
22
REFERENCES 1 Lugli T. Artificial shoulder joint by Pean (1893): the facts of an exceptional intervention and prosthetic method. Clin Orthop Relat Res 1978; 133: 215e8. 2 Neer 2nd CS. Articular replacement for the humeral head. J Bone Joint Surg Am 1955; 37: 215e28. 3 Neer 2nd CS. Replacement arthroplasty for glenohumeral osteoarthritis. J Bone Joint Surg Am 1974; 56-A. 4 Torchia ME, Cofield RH, Settergren CR. Total shoulder arthroplasty with the Neer prosthesis: long-term results. J Shoulder Elbow Surg 1997 Nov-eDec; 6: 495e505. 5 Barrett WP, Franklin JL, Jackins SE, Wyss CR, Matsen 3rd FA. Total shoulder arthroplasty. J Bone Joint Surg Am 1987 Jul; 69: 865e72. 6 Robinson CM, Page RS, Hill RM, Sanders DL, Court-Brown CM, Wakefield AE. Primary hemiarthroplasty for treatment of
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proximal humeral fractures. J Bone Joint Surgy Am 2003 Jul; 85-A: 1215e23. Marmor L. Hemiarthroplasty for the rheumatoid shoulder joint. Clin Orthop Relat Res 1977; 37: 215e8. Franklin JL, Barrett WP, Jackins SE, Matsen 3rd FA. Glenoid loosening in total shoulder arthroplasty. Association with rotator cuff deficiency. J Arthroplasty 1988; 3: 39e46. Pollock RG, Deliz ED, McIlveen ST, Flatow EL, Bigliani LU. Prosthetic replacement in rotator cuff-deficient shoulders. J Shoulder Elbow Surg 1992 Jul; 1: 173e86. Grammont P, Trouilloud P, Laffay P, Deries X. Etude et realisation d’une nouvelle prothese d’epuale. Rheumatologie 1987; 39: 407e18. Lippitt S, Vanderhooft E, Harris SL. Glenohumeral stability from concavity-compression: a quantitative analysis. J Shoulder Elbow Surg 1993; 2: 27e35. Walker M, Brooks J, Willis M, Frankle M. How reverse shoulder arthroplasty works. Clin Orthop Relat Res 2011; 469: 2440e51. Boileau P, Watkinson DJ, Hatzidakis AM, Balg F. Grammont reverse prosthesis: design, rationale, and biomechanics. J Shoulder Elbow Surg 2005 JaneFeb; 14(1 suppl S). 147Se61S. Kralinger F, Schwaiger R, Wambacher M, et al. Outcome and primary hemiarthroplasty for fracture of the head of the humerus: a retrospective multicentre study of 167 patients. J Bone Joint Surg Br 2004; 86-B: 217e9. Neyton L, Boileau P, Nove-Josserand L, Edwards B, Walch G. Glenoid bone grafting with a reverse design prosthesis. J Shoulder Elbow Surg 2007 MayeJune; 16: S71e8. Edwards BT, Williams MD, Labriola JE, Elkousy HA, Gartsman GM, O’Connor DP. Subscapularis insufficiency and the risk of shoulder dislocation after reverse shoulder arthroplasty. J Shoulder Elbow Surg 2009; 18: 892e6. Levigne C, Boileau P, Favard L, et al. Scapular notching in reverse shoulder arthroplasty. J Shoulder Elbow Surg 2008; 17: 925e35. Favre P, Sussmann PS, Gerber C. The effect of component positioning on intrinsic stability of reverse shoulder arthroplasty. J Shoulder Elbow Surg 2010; 19: 550e6. Nyffeler RW, Werner CM, Gerber C. Biomechanical relevance of glenoid component positioning in the reverse Delta III total shoulder prosthesis. J Shoulder Elbow Surg 2005 SepeOct; 14: 524e8. Levigne C, Garret J, Boileau P, Alami G, Favard L, Walch G. Scapular notching in reverse shoulder arthroplasty: is it important to avoid and how? Clin Orthop Relat Res 2011 Sep; 469: 2512e20. Kelly J, Humphrey S, Norris TR. Optimizing glenosphere position and fixation in reverse shoulder arthroplasty, Part One: the twelve-mm rule. J Shoulder Elbow Surg 2008 July-Aug; 17: 589e94. Mole D, Favard L. Excentered scapulohumeral osteoarthritis. Rev Chir Orthop Reparatrice Appar Mot Oct 2007; 93(6 suppl): 37e94. Gutierrez S, Walker M, Willis M, Pupello DR, Frankle MA. Effects of tilt and glenosphere eccentricity on baseplate/bone interface forces in a computational model, validated by a mechanical model, of reverse shoulder arthroplasty. J Shoulder Elbow Surg 2005; 14: 162Se7. Codsi MJ, Iannotti JP. The effect of screw position on the initial fixation of a reverse total shoulder prosthesis in a glenoid with cavitary bone defect. J Shoulder Elbow Surg 2008 May-June; 17. DiStefano JG, Park AY, Nguyen TQ, Diederichs G, Buckley JM, Montgomery 3rd WH. Optimal screw placement for base plate fixation in reverse total shoulder arthroplasty. J Shoulder Elbow Surg 2011 Apr; 20: 467e76. Humphreys CS, Kelly 2nd JD, Norris TR. Optimizing glenosphere position and fixation in reverse shoulder arthroplasty. Part two:
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38 Levy JC, Virani N, Pupello D, Frankle M. Use of the reverse shoulder prosthesis for the treatment of failed hemiarthroplasty in patients with glenohumeral arthritis and rotator cuff deficiency. J Bone Joint Surg Br 2007; 89-B: 189e95. 39 Cuff DJ, Virani NA, Levy J, et al. The treatment of deep shoulder infection and glenohumeral instability with debridement, reverse shoulder arthroplasty and post-operative antibiotics. J Bone Joint Surg Br 2008; 90-B: 336e42. 40 Coste JS, Reig S, Trojani C, et al. The management of infection in arthroplasty of the shoulder. J Bone Joint Surg Br 2004; 86-B: 65e9. 41 Gallo RA, Gamradt SC, Mattern CJ, et al. Instability after reverse total shoulder replacement. J Shoulder Elbow Surg 2011; 20: 584e90. 42 Ladermann A, Lubbeke A, Melis B, Stern R, Hoggmeyer P, Walch G. Objective evaluation of lengthening in reverse shoulder arthroplasty. J Shoulder Elbow Surg 2009; 18: 588e95. 43 Boileau P, Moineau G, Roussanne Y, O’Shea K. Bony increased-offset reversed shoulder arthroplasty. Minimising scapular impingement whilst maximising glenoid fixation. Clin Orthop Relat Res 2011; 469: 2558e67. 44 Zumstein MA, Pinedo M, Old J, Boileau P. Problems, complications, reoperations and revisions in reverse total shoulder arthroplasty: a systematic review. J Shoulder Elbow Surg 2011; 20: 146e57. 45 Wierks C, Skolasky RL, Ji JH, McFarland EG. Reverse total shoulder replacement. Intraoperative and early postoperative complications. Clin Orthop Relat Res 2009; 467: 225e34. 46 Boileau P, Chuinard C, Roussanne Y, Neyton L, Trojani C. Modified latissimus dorsi and teres major transfer through a single deltopectoral approach for external rotation deficit of the shoulder: as an isolated procedure or with a reverse arthroplasty. J Shoulder Elbow Surg 2007 NoveDec; 16: 671e81. 47 Boileau P, Trojani C, Walch G, Krishnan SG, Romeo A, Sinnerton R. Shoulder arthroplasty for the treatment of the sequelae of fractures of the proximal humerus. J Shoulder Elbow Surg 2001 JuleAug; 10: 299e308. 48 Bufquin T, Hersan A, Hubert L, Massin P. Reverse shoulder arthroplasty for the treatment of three- and four-part fractures of the proximal humerus in the elderly: a prospective review of 43 cases with a shortterm follow-up. J Bone Joint Surg Br 2007 Apr; 89: 516e20.
the three column concept. J Shoulder Elbow Surg 2008 JuleAug; 17: 595e601. Harman M, Frankle M, Vasey M, Banks S. Initial glenoid component fixation in “reverse” total shoulder arthroplasty: a biomechanical evaluation. J Shoulder Elbow Surg 2005; 14: 162Se7. Cuff P, Pupello D, Virani N, Levy J, Frankle M. Reverse shoulder arthroplasty for the treatment of rotator cuff deficiency. J Bone Joint Surg Am 2008; 90: 1244e51. Ladermann A, Walch G, Lubbeke A, et al. Influence of arm lengthening in reverse shoulder arthroplasty. J Shoulder Elbow Surg 2012; 21: 336e41. Smith CD, Guyver P, Bunker TD. Indications for reverse shoulder replacement. A systematic review. J Bone Joint Surg Br 2012; 94-B: 577e83. Sirveaux F, Favard L, Oudet D, Huquet D, Walch G, Mole D. Grammont inverted total shoulder arthroplasty in the treatment of glenohumeral osteoarthritis with massive rupture of the cuff. J Bone Joint Surg Br 2004 Apr; 86: 388e95. Sanchez-Sotel J, Cofield R, Rowland C. Shoulder hemiarthroplasty for glenohumeral arthritis associated with severe rotator cuff deficiency. J Bone Joint Surg [Am] 2001; 83-A: 1814e22. Naveed MA, Kitson J, Bunker TD. The Delta II reverse shoulder replacement for cuff tear arthropathy. J Bone Joint Surg Br 2011; 93B: 57e61. Guery J, Favard L, Sirveaux F, Oudet D, Mole D, Walch G. Reverse total shoulder arthroplasty. Survivorship analysis of eighty replacements followed for five to ten years. J Bone Joint Surg Am 2006 Aug; 88: 1742e7. Ekelund A, Nyberg R. Can reverse shoulder arthroplasty be used with few complications in rheumatoid arthritis. Clin Orthop Relat Res 2011; 469: 2483e8. Young AA, Smith MM, Bacle G, Moraga C, Walch G. Early results of reverse shoulder arthroplasty in patients with rheumatoid arthritis. J Bone Joint Surg Am 2011 Oct 19; 93: 1915e23. Rittmeister M, Kerschbaumer F. Grammont reverse total shoulder arthroplasty in patients with rheumatoid arthritis and nonreconstructible rotator cuff lesions. J Shoulder Elbow Surg 2001 JaneFeb; 10: 17e22.
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Reverse shoulder arthroplasty current concepts
prosthesis was introduced. The aim of this paper is to review the biomechanics, technical considerations, indications, clinical results and complications of reverse shoulder arthroplasty.
Current designs
Nawfal Al-Hadithy
Grammont’s first prosthesis10 consisted of two components: a metallic or ceramic glenoid ball which, although positioned medially, still sat proud of the native glenoid surface, and a concave humeral polyethylene socket, both of which were cemented. Although all of the initial eight patients were painfree, they had limited function and revision surgery was required in three cases. The Delta III prosthesis has been available since 1991 and consists of five components: the hydroxyapatite coated glenoid baseplate (metaglene), which has divergent peripheral screws and a central peg/screw, the glenosphere, polyethylene lateralized humeral cup, humeral neck (epiphysis) and stem (diaphysis). Although the De Puy Delta III prosthesis has the largest number of published trials, other implants are also available including the Aequalis Reversed Shoulder Prosthesis (Tournier, Inc, Edina, MN) and the reversed polar, linked BayleyeWalker Implant (Stanmore Implants, Elstree, UK).
Adam P Rumian
Abstract The reverse shoulder arthroplasty (RSA) was introduced in 1987 for cuff tear arthropathy. Over time the prostheses have evolved and its indications have increased. RSA is a semi-constrained reverse ball and socket prosthesis with several key biomechanical advantages, including a fixed centre of rotation which allows the deltoid to function. In this review, the history, key principles, indications, surgical tips and complications are discussed. RSA can provide excellent results with significant improvements in pain and function but is a technically demanding procedure.
Keywords cuff tear arthropathy; reverse shoulder arthroplasty
Introduction
Biomechanics
Although the first prosthetic shoulder arthroplasty was performed in 18931 by a French surgeon, Jules Emile Pean, there was little progression thereafter until 1955, when Neer2 developed a stemmed, non-constrained total shoulder replacement (TSR) for the treatment of 4-part proximal humerus fractures. Neer published a further study in 19743 describing the results of a hemiarthroplasty prosthesis. There has since been a considerable number of studies since then, showing that both TSR and hemiarthroplasty are effective at relieving pain and improving function for widening indications, including trauma, osteoarthritis and rheumatoid arthritis.4e6 However, the initial success of these procedures was not replicable in the cuff deficient shoulder, with Neer3 noting slow recovery and poor strength and he suggested that the use of shoulder prostheses in these patients should be expected to have limited functional goals. In subsequent studies, other surgeons noted the use of TSR in cuff arthropathy to have unpredictable and poor outcomes.7 Total shoulder arthroplasty in the cuff deficient shoulder has now been abandoned due to the “rocking horse” effect causing eccentric loading of the glenoid component due to superior migration of the humeral head component and thereby early loosening and failure.8,9 The reverse shoulder arthroplasty was introduced by Paul Grammont10 in 1987 in an attempt to improve outcomes in cuff deficient shoulders. It has subsequently undergone several revisions and modifications, and in 1991, the Delta IIIÒ
The cuff-deficient shoulder The shoulder is a complex joint and to allow its great range of motion, static and dynamic stabilizers work to keep the humeral head in place. The rotator cuff is a key dynamic stabilizer and causes compression at the glenohumeral joint, ensuring that the humeral head remains central and stable within the glenoid fossa11 throughout the range of shoulder movement. Severe deficiency of the rotator cuff can lead to a muscle imbalance such that the humeral head is no longer held centrally in the glenoid fossa when the deltoid contracts. Instead, the unopposed deltoid contractions cause proximal migration of the humeral head over time, leading to impingement of the greater tuberosity on the acromion and cartilage damage in the glenohumeral joint, ie a “cuff tear arthropathy”.12 Biomechanics of the reverse shoulder prosthesis Early attempts at implanting a reverse shoulder prosthesis design failed due to it having a lateralized glenoid component with a centre of rotation lateral to the glenoid bonestock, resulting in excessive torque and shear forces on the glenoid component fixation and causing early catastrophic loosening (Figure 1). However, Grammont developed a semi-constrained reverse ball and socket prosthesis with key biomechanical advantages13 (Figure 2): Stable fulcrum of rotation with congruent joint surfaces Compensates for deficient rotator cuff by providing a “semi-constrained” arrangement, conferring inherent stability that is no longer reliant on compression from the rotator cuff Stable fulcrum of rotation allows deltoid contractions to produce functional elevation and the remaining cuff muscles to produce functional rotation Medialized centre of rotation and medialized humerus Increases deltoid lever arm, therefore improving elevation & abduction
Nawfal Al-Hadithy BSc MSc MRCS Orthopaedic Registrar, East and North Herfordshire NHS Trust, Lister Hospital, Stevenage, UK. Conflict of interest: none. Adam P Rumian MD FRCS(Tr & Ortho) Consultant Orthopaedic Surgeon, East and North Herfordshire NHS Trust, Lister Hospital, Stevenage, UK. Conflict of interest: none.
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rheumatoid arthritis with rotator cuff deficiency proximal humeral fractures: there has been a recent trend to use RSA for complex three- and four- part proximal humeral fractures in more elderly patients where the results of a hemiarthroplasty would be expected to be poor or if successful reconstruction of the fractured tuberosities is not anticipated. Anatomical reduction and healing of the tuberosities has been shown to be one of the main prognostic factors influencing recovery of the shoulder.14 Examples of this are patients with severe osteoporosis, comminuted fractures of the greater tuberosity, preexisting rotator cuff tears or co-existing glenoid fractures. post-traumatic reconstruction: operative treatment of shoulder fracture sequelae is one of the most challenging problems in shoulder surgery. RSA has been used successfully in certain patterns of severe malunion or nonunion. revision shoulder arthroplasty: RSA is being used increasingly for revision shoulder arthroplasty where either soft tissue or bony deficiencies preclude the use of an anatomical prosthesis osteoarthritis with associated rotator cuff tear: primary osteoarthritis is distinct from cuff tear arthropathy, in that the latter is an end-stage result of cuff tear deficiency. The rotator cuff is usually intact in primary osteoarthritis but RSA has been used in those cases associated with a rotator cuff tear as an alternative to hemiarthroplasty where there are concerns that implanting an anatomical glenoid component may be at risk from loosening from the “rocking-horse” effect osteoarthritis with particular glenoid morphology: the results of anatomical total shoulder replacement is poorer in cases where the humeral head is subluxed posteriorly and the glenoid is biconcave and eroded posteriorly (Walch type B2), or dysplastic with excess retroversion (Walch type C). Recent reports suggest more favourable outcomes with RSA. tumour surgery: RSA is indicated for shoulder reconstruction where resection of the rotator cuff has been performed.
Figure 1 Schematic diagram revealing excessive torque in the glenoid component which was the cause of failure in early reverse shoulder prosthesis designs.
Reduces torque and shearing forces on the glenoid component, thus reducing the risk of loosening Lowering of humerus A non-anatomical humeral inclination (155 ) lowers the humerus, increasing the mechanical advantage of the deltoid.
Indications The use of RSA was initially restricted to patients with an established cuff tear arthropathy, ie degenerative changes in the glenohumeral joint caused by proximal migration of the humeral head due to chronic cuff deficiency. However the indications for RSA have gradually expanded as experience and confidence with the prosthesis has increased. Potential indications now include: cuff tear arthropathy massive irreparable cuff tear: RSA has been used in patients with severe functional deficit as a result of a massive irreparable rotator cuff tear, but without degenerative change of the glenohumeral joint.
Figure 2 Biomechanics of (a) normal shoulder showing compression at glenohumeral joint and balance between ascending force of the deltoid and descending forces of the rotator cuff muscles (b) cuff tear arthropathy e superior migration of the humeral head and a slack deltoid causing an unstable centre of rotation (c) reverse shoulder arthroplasty with an inferiorly titled & hanging glenoid sphere and non-anatomical humeral inclination, lowering the deltoid and increasing mechanical advantage & (d) failure to have an inferior overhang predisposes to scapular notching when the arm is adducted.
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Absolute contra-indications to RSA include active infection, axillary nerve palsy/complete deltoid insufficiency, inadequate glenoid bone stock to support the glenoid component (unless bone grafting is considered) and patient non-compliance. Relative contra-indications include young age (<70) and isolated anterior deltoid insufficiency. Caution should be exercised when contemplating RSA in patients that may be at high risk of subsequent prosthetic instability, such as wheelchair users using their arms extensively for transfers.
Pre-operative assessment As is standard for all patients for whom an arthroplasty is considered, a thorough patient assessment should be performed including plain radiographs of the shoulder (anteroposterior, scapular lateral and axillary views). A computerized tomography (CT) scan is necessary to evaluate the glenoid bone stock and retroversion. The glenoid vault should ideally be more than 2 cm in depth to provide adequate primary fixation of the glenoid component. Inadequate pre-operative bone stock may warrant glenoid augmentation with bone grafting.15 The glenoid and humeral shaft diameters should be assessed to confirm that standard implant sizes can be used. Magnetic resonance imaging may be used to confirm the status and quality of the remaining rotator cuff, especially the remaining external rotators, which impact on the eventual outcome. In complex cases, scaled radiographs of both humeri may be required to allow accurate restoration of humeral length. Patients who have undergone previous surgery may require exclusion of underlying infection by a combination of inflammatory markers and joint aspiration/tissue biopsy.
Figure 3 Top 2 cm of pectoralis major is divided.
glenoid. The middle glenohumeral ligament and anterior capsule lying on the deep surface of subscapularis are then easily seen and incised and the rotator interval tissue is excised. The axillary nerve runs over the anterior surface of the subscapularis tendon and courses posteriorly through the quadrilateral space and is therefore potentially at risk during an inferior capsular release. The inferior capsular release can be safely and reliably performed by retracting the subscapularis tendon slightly medially and downwards so that the inferior capsule is identified. A pair of dissecting scissors is then passed between the capsule and the subscapularis tendon until it reaches the glenoid surface. Cutting down onto the scissors incises the capsule without the risk of damage to the subscapularis tendon and axillary nerve (Figure 4). The deltopectoral approach is reported to be associated with a higher dislocation rate than when the superolateral approach is used, which is thought to be due to the detachment of the subscapularis that is required in the deltopectoral approach, but which can be preserved in the superolateral approach.16 However, the higher dislocation rate may also reflect the fact that more complex cases such as revision cases, rather than simple primary arthroplasties, are performed using the deltopectoral approach, as this can be extended to give access to the humeral shaft. Although the superolateral approach allows easier visualization of the glenoid surface itself, it can be more difficult to achieve accurate glenoid component placement inferiorly or with
Surgical technique Approach Both the superolateral and deltopectoral approaches have been used. For the deltopectoral approach, the cephalic vein identifies the interval between the deltoid and pectoralis major muscles, which may often by seen as a stripe of fat. The interval is easiest to identify proximally, overlying the palpable coracoid process and is exploited distally until the pectoralis major tendon insertion is identified. The top 2 cm of pectoralis major can be released, by incision 1 cm medial to its insertion (Figure 3). This allows better exposure for the rest of the procedure, especially in a tight shoulder, and is repaired at the end. To expose the glenohumeral joint, the remaining subscapularis tendon is either tenotomized 1 cm medial to its insertion or released directly off its insertion on the lesser tuberosity, the latter preserving the tendon length and making it more likely that it can be repaired at the end of the procedure. Capsular releases are often essential in obtaining adequate exposure and can be approached in a reproducible and sequential manner. First, the capsule is released off its humeral insertion around the inferior border of the humeral head. This release should be continued all the way around the humeral neck to include the posterior band of the inferior glenohumeral ligament. Once the humeral head is retracted posteriorly and laterally with a retractor, the capsule overlying the superior border of the subscapularis tendon is incised along the tendon border up to the
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Figure 4 Safe incision of inferior capsule.
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inferior tilt. Levigne et al suggested that there is a higher incidence of scapular notching in the superolateral position and the component tends to be placed with superior tilt.17 Table 1 summarizes the advantages/disadvantages of each approach. Humeral preparation The humerus is dislocated and the head is resected using a guide after removing any large osteophytes. Generally, but dependent on the prosthesis being used, the head is resected to a nonanatomic inclination of 155 . The amount of bony resection is often surprisingly small. The humerus is then reamed and rasped to accept the trial prosthesis (Figure 5). The anatomical retroversion of the humeral head has a mean value of 30 , but the RSA humeral stem is usually placed in a non-anatomical retroversion of 0e20 . Favre et al.18 evaluated the effect of humeral component version on stability and found that placing it in neutral or anteversion of up to 20 improved stability. Placing the prosthesis in lesser retroversion will increase eventual internal rotation and decrease external rotation, and vice-versa. To ensure correct retroversion a guide wire attached to the jigs in may instrument sets from different manufacturers of both reverse and total shoulder can be aligned with the forearm (Figure 6).
Figure 5 Reaming of the humeral head.
Glenoid exposure/preparation A Kolbel forked lever retractor is positioned on the anterior glenoid neck to expose the anterior glenoid rim (Figure 7). The labrum can then be resected and the capsule released off the glenoid up to the 7 o’clock position. Care must be taken to release the capsule directly off the bone around the inferior rim of the glenoid to avoid axillary nerve injury. Once capsular releases are performed, this should allow sufficient posterior retraction of the humeral head to expose the glenoid fully. The arm should be positioned in slight abduction with either internal or external rotation together with some elbow flexion. To expose the glenoid, anterior, posterior, inferior and superior glenoid retractors are used. Drawing the transverse and horizontal equators on the glenoid allows identification of the central point. Drawing a second line inferior and parallel to the horizontal equator identifies the correct point of entry for a guide wire for reaming. This ensures the correct inferior positioning of the baseplate (Figure 8). Nyffeler et al19 found that placing the glenosphere
Figure 6 Retroversion guide.
such that it extends beyond the inferior glenoid rim provides significantly (p < 0.001) improved adduction and abduction compared with a flush prosthesis. They ensured that the glenoid baseplate was flush with the inferior glenoid to facilitate this. Levigne et al also found that a 4 mm inferior overhang provided the best outcomes.17,20 Kelly et al21 showed, in their cadaveric study of 10 shoulders, that the ideal location of the drill hole for the baseplate was 12 mm above the inferior glenoid rim and should provide excellent fixation in most cases. Most studies
Summary of advantages/disadvantages of deltopectoral/superolateral approach
Exposure
Notching Deltoid Dislocation
Deltopectoral
Superolateral
Excellent exposure of lower pole of glenoid with inferior capsular release Additional procedures can be performed (humeral osteotomy in revisions/Lat dorsi transfer) Reduced incidence
Easier visualization of glenoid surface
Deltoid preserved Increased e interrupts subscapularis tendon Requires extended capsular release
Higher incidence Tendency to place baseplate with superior tilt and higher Disruption to deltoid fibres Reduced e subscapularis muscle left in tact
Table 1
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Figure 9 Glenoid positions. (a) Central and neutral (b) flush and neutral (c) inferior overhand and neutral (d) flush and inferior tilt (e) Superior and neutral (f ) central and superior tilt.
Figure 7 Forked anterior Kolbel retractor exposes the anterior glenoid rim.
suggest that the glenosphere should be tilted inferiorly to avoid scapular notching and early loosening.22 The ideal position is still under investigation. A biomechanical study performed by Gutierrez et al23 found that 15 of inferior tilt provided the most even distribution of compressive forces. They also found that altering glenosphere version had little effect on stability and suggested that its spherical surface caused an unchanged angle of incidence. Figure 9 shows different glenoid positions. Once the glenoid is prepared, the glenoid baseplate can be impacted (Figure 10). The central peg has been shown to provide about 15% of the primary stability of the glenoid baseplate,24 with the peripheral screws contributing substantially more. Although the ideal number of screws is unknown, there has been considerable research into ideal screw position and size. DiStefano et al25 performed high resolution CT scans with 3D reconstruction and found increased cortical thickness in the lateral aspects of suprascapular notch, scapular spine base, anterior/superior aspect of inferior pillar and junction of glenoid neck. Humphreys et al26 described a three-column concept and suggest that screws at the coracoid base, within the spine and within the pillar provided the best fixation and was easily reproducible. Harman et al27 found that using peripheral screws of 5 mm diameter reduced micromotion by 21%e35% compared with screws of 3.5 mm. A subsequent study has found locked 5 mm screws to provide the most stable fixation.28 The Tornier Aequalis baseplate has four screwholes. The anterior and
posterior holes are for compression screws and are inserted and tightened first to compress the baseplate against the glenoid bone. Additional fixation is provided by the superior and inferior multidirectional locking screws that are directed into the coracoid base and scapular pillar, respectively. The glenosphere is then impacted onto the baseplate and secured with a screw to prevent dissociation. The size of the polyethylene humeral insert is decided after trial reduction and soft tissue tension assessment. Reduction of the humerus can be difficult and a “tyre-lever” technique can be used to lever the humerus into its correct articulating position. Deltoid tensioning can be affected by inferior positioning of the glenoid component, the size of polyethylene insert and level of humeral cut. Increasing deltoid length improves function by providing a stable fulcrum, essential for active elevation and prosthesis stability, undertensioning consistently leads to poor function. Although overtensioning does not affect function, it increases the chance of neurological injury, permanent arm abduction, acromial fracture and loss of the normal deltoid contour.13,29 Correct deltoid tensioning is difficult to establish perioperatively and Boileau13 suggested that it largely depends on surgical experience. Smith et al30 suggest that it is most easily corrected by altering the length of the polyethylene spacer and with correct tightness noted that the trial reduction and dislocation are quite difficult to perform, with no visible gap being
Figure 8 Central point of glenoid.
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Figure 10 Impacted glenoid baseplate.
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Results
present when the components are forcibly distracted. Various other indicators of correct component positioning and soft tissue tension have been suggested, including a tight conjoint tendon with the elbow extended, no abutment in adduction, no acromial impingement, and stability in abduction and external rotation.
The most common use of reverse shoulder arthroplasty is for the treatment of glenohumeral osteoarthritis in the presence of a cuff tear. Sirveaux31 et al reviewed 77 shoulders with glenohumeral
Summary of clinical outcomes Author
Pat no
Indication
Follow-up
Outcome
ROM
Rittmeister37 Sirveaux31
8 77
RA & Cuff tear CTA
54 m 44 m
CS: 17e63 CS: 22.6e65.6
FF: 73 e138
Naveed33
50
CTA
39 m
ASES: 19e65
FF: 55 e105
Guery34
62
53 e CTA 6 e RA 3 e Fracture
69.6 m
If CS<30 e 58% survival at 120 m
Ekelund35
33
RA
56 m
CS: 13e52
FF: 33 e115
Young36
18
RA
45.6 m
CS: 22.5e64.9
FF: 77.5 e138.6
Boileau47
71
Fracture
19 m
CS: 26e65
FF: 74 e102
Bufquin48
41
Fracture
22 m
CS: 69
FF-97
Levy38
25
Revision (hemiarthroplasty)
w60 m
ASES: 22.3e52.1
FF38.1 e72.7
Cuff28
22
Infection
43 m
ASES: 31.9e57
FF43.1 e79.5
Complication 1 e Septic loosening 5 e Glenoid aseptic loosening 7 e Glenoid disassociation 2 e # acromium 2 e Deep infection 1 e Instability 3 e Deep infection 1 e Dislocation 3 e Glenoid dissociation 1 e Glenoid loosening 1 e Glenoid rim # 1 e Loosening 1 e Screw breakage 1 e # Acromium 1 e # Acromial spine 1 e Coracoid process # 1 e GT # 1 e Axillary nerve injury 4 e Perioperative # 9 e GT displacement/ non-union/osteolysis 1 e Dislocation 1 e Radial nerve palsy 2 e Deep infection 5 e Neurological complications 1 e Anterior dislocation 19 e GT displacement 1 e PP# 1 e Deep infection 2 e Dislocation 1 e Screw breakage 1 e Dissociation 1 e Aseptic loosening 1 e Scapular # 1 e Polyethlene # 1 e Dislocation 1 e Humeral loosening 1 e Humeral # 1 e Neurological 1 e Poly dissociation
ASES ¼ American Shoulder and Elbow Score. CS ¼ Constant Score. GT ¼ Greater tuberosity. PP ¼ Peri-prosthetic. # ¼ Fracture.
Table 2
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reverse shoulder arthroplasties, 9 were unstable. Instability of an RSA can have several causes that need to be considered before contemplating any revision surgery. These include inadequate humeral length (from implanting the humeral component too distally), incorrect humeral retroversion and inadequate soft tissue tension (from component mal-position or wrong size of polyethylene insert). Gallo et al41 found superiorly inclined or positioned metaglenes were the cause in 5 (56%). In all cases, an incompetent subscapularis tendon was seen, and detachment in the deltopectoral approach has been considered the most significant risk factor for dislocation.16 This has been confirmed by a study showing no dislocations in 40 patients using subscapularis sparing approaches.41 Laderman et al42 also found a strong correlation between humeral length and dislocation. In all cases of dislocation, humeral length was reduced significantly compared with the contralateral side. Exchanging a glenosphere and humeral metaphyseal component for one of a larger diameter can sometimes restore stability in cases of recurrent instability without an obvious technical error. Scapular notching is most likely caused by mechanical impingement of the medial rim of the humeral cup against the scapular neck in adduction, causing erosion of the inferior glenoid neck.17 In a series of 448 patients,20 scapular notching was seen in 68% of cases at a mean time of 51 months and although in some patients notching remained static, they most often progressed with time and may be associated with loosening and early failure. The authors suggested that notching may be underreported in other studies due to obscuring of the zone of notching by the glenoid hemisphere, which may be partially avoided by precisely aligning the X-ray beam with the flat side of the baseplate. As previously discussed the glenoid hemisphere is usually placed and aimed inferiorly, and the authors found that mal-position of the component with a superiorly tilted base plate allows for erosion of the scapular rim by the medial surface of the humeral component and should therefore be avoided. Surgeons may choose to preferentially ream the inferior aspect the glenoid to ensure that the glenoid baseplate is either placed in neutral or tilted inferiorly. A classification system for scapular notching has been made by Sirveaux et al31 (Table 3) based on the size of the defect, and although they suggest that it corresponds with outcomes, this has not been validated yet. Apart from inferomedial impingement, a medialized glenohumeral joint may also restrict internal rotation due to mechanical impingement of tuberosities on the coracoid process and scapular spine in external rotation.43 To overcome this, several authors have attempted to increase the offset by
osteoarthritis and massive cuff ruptures that underwent Grammont inverted shoulder arthroplasty. He noted improved Constant shoulder scores (from 22.6 pre-operatively to 65.6 postoperatively) and improvements in active forward flexion (from 73 to 138 ), with all patients having mild or no pain. The current alternative therapy is hemiarthroplasty, Sanchez-Sotelo32 found similar relief in pain, but significantly reduced functional outcomes at 5 years, with forward flexion improving marginally, from 72 to 91 . Naveed et al33 stressed the importance of patient selection on successful outcomes, and found those with cuff tears secondary to arthritis had better functional outcomes and lower complication rates than other authors found for other indications. Despite these early improvements, Guery et al34 found that although loss of fixation and revision surgery remained low at 8 years in patients with massive cuff tear, functional outcomes deteriorated progressively after 6 years, which may have been attributed to ageing of the patients or loosening not visible on radiographic evaluation. The outcomes in patients with rheumatoid arthritis have been encouraging, with several studies showing significant improvements in pain and function, albeit less than seen in the osteoarthritic group.35,36 Despite the recent trend of RSA for proximal humeral fractures and its theoretical advantages, there is still considerable debate about whether it provides superior outcomes compared to conventional hemiarthroplasty. As may be expected, the use of reverse shoulder arthroplasty in revision surgery yields poorer functional results and a higher number of complications. Levy et al38 investigated the use of reverse shoulder arthroplasty for failed hemiarthroplasty in cuff arthropathy in 19 shoulders as a salvage procedure in the presence of moderateesevere glenoid erosions (68%), making stable fixation of the glenoid baseplate particularly challenging. Poor glenoid stock has been such a problem that other authors15 have investigated the role of augmenting the glenoid surface with bone grafting in either 1 or 2 stage procedures. Although there were significant gains in functional and pain scores, at 44 months, it was not without complications. six patients (32%) had prosthesis-related complications, including peri-prosthetic scapular fractures (2), baseplate loosening (1), failure of polyethylene (2) requiring revision, and one patient had severe proximal humeral bone loss requiring revision. Boileau et al13 had similar results, with 42% of patients (8 of 19) requiring revision surgery after conversion of failed hemiarthroplasty to reverse prosthesis. A summary of clinical outcomes is shown in Table 2.
Complications Complications of reverse shoulder arthroplasty include infection, instability, scapular notching, haematoma, glenoid loosening, humeral loosening, component dissociation, acromial fracture, other fractures and neurovascular injury. Treatment options for deep infection include prolonged antibiotic therapy, debridement with antibiotic therapy with retention of the prosthesis, revision or in salvage cases arthrodesis, resection arthroplasty or amputation.39 Implant retention has high rates of recurrence of infection, up to 63%,40 and salvage procedures have poor functional outcomes. Dislocation rates can be as high as 9% and represent one of the most significant complications of RSA.16 In a series 57
ORTHOPAEDICS AND TRAUMA 27:5
Sirveaux classification of scapular notching Grade Grade Grade Grade
1 2 3 4
Defect Defect Defect Defect
confined to the pillar reaches lower screw crosses the lower screw extends under the baseplate
Table 3
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metallic lateralization (augmenting the lateral length of the glenosphere itself during manufacture) or grafting the glenoid surface. The main disadvantage of metallic lateralization is the increased torque on the glenoid component and the increased risk of subsequent loosening.27 To avoid this, Boileau et al43 have recently advocated using autologous bone graft from the humeral head to increase offset whilst maintaining the prosthetic centre of rotation at the implant-glenoid bone interface, and showed significant improvement in rotation with no failures at 24 months (Figure 11). A guide wire is inserted into the humeral head and a circular bell saw is used to cut a disc of bone. After the articular surface is reamed off (Figure 12), it is resected from the humeral head. This provides a size matched bone graft disc (Figure 13) that is impacted together with a specific baseplate that has a long central peg. Zumstein et al performed a systematic review44 of all reoperations (procedures not altering or replacing the components) and revisions (procedures with partial or total exchange or removal of components) in 21 studies. 84 patients underwent 26 re-operations and 79 revisions, representing 3.3% and 10.1% respectively. Interestingly, although the incidence of reoperation was almost equal in revision of TSR surgery (REV) and primary arthroplasty groups, revisions were twice as common in the REV group. Reverse shoulder arthroplasty is considered a difficult procedure even for experienced surgeons, and there is a learning curve. Complication rates are significantly higher in the first 10 patients compared with the second 10 patients with the majority of complications in the early phase arising from glenoid preparation and baseplate insertion.45
Figure 12 Articular surface reamed away.
Recent concepts The results of RSA have been shown to be inferior when the teres minor muscle is deficient. This can be explained by considering the normal shoulder, where there is a natural predominance of internal rotator muscles (subscapularis, pectoralis major, latissimus dorsi and teres major) over external rotator muscles (infraspinatus and teres minor). This predominance is even more pronounced in rotator cuff-deficient shoulders when the rotator cuff tear extends posteriorly. The teres minor is a key shoulder muscle, providing 40% of the strength of external rotation. When both the infraspinatus and teres minor are absent or fatty infiltrated, there is no other muscle to provide active external rotation: any attempt at shoulder elevation results in the forearm swinging in towards the trunk and such patients can no longer control the spatial positioning of their upper limb. From a biomechanical and surgical standpoint, patients with massive irreparable rotator cuff tears, may be categorized into three groups: those with an isolated loss of active elevation (i.e. pseudoparalyzed shoulder e PPS), those with an isolated loss of active external rotation (ILER), and those with a combined loss of active elevation and external rotation (CLEER). In the first group (PPS) there is a muscular imbalance in the vertical plane between the intact deltoid muscle and the non-functional rotator cuff muscles. A reverse shoulder arthroplasty (RSA) solves this problem of vertical muscle imbalance, by providing a fixed
Figure 11 Lateralized glenoid component using bone graft reveals no scapular notching even in an adducted arm.
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Figure 13 Impaction of bone graft onto baseplate.
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centre of rotation and increasing the deltoid tension to compensate for the weak/torn rotator cuff muscles. In the second group (ILER) there is a muscular imbalance in the horizontal plane between the intact internal rotator muscles (remaining subscapularis, pectoralis major, latissimus dorsi and teres major) and the absent or atrophied infraspinatus and teres minor; there are thus four functional muscles providing internal rotation with no functional muscles providing external rotation, i.e. four against zero. This definitive loss of active external rotation is a rare but disabling condition which results from posterior extension of the rotator cuff tear to the teres minor, as described above.1,2 Since active elevation is conserved (because the vertical muscle balance is conserved), a RSA is not indicated; a latissimus dorsi/teres major (LD/TM) transfer (modified l’Episcopo procedure) can rebalance the shoulder in the horizontal plane. The latissimus dorsi and teres major tendons are transferred laterally and posteriorly on the humerus, which changes their function from internal rotators to external rotators, resulting in two internal and two external rotators, i.e. two against two. In the third group (CLEER) there is both a vertical and horizontal muscle imbalance. The RSA can address the problem of vertical muscle imbalance but it cannot rebalance the shoulder in the horizontal plane. When both the infraspinatus and teres minor are absent or fatty infiltrated, prosthetic lateralization alone is not sufficient to provide active external rotation5,16; this is why, in this subgroup of patients, a RSA combined with the modified L’Episcopo have been used,46 Boileau et al improved active elevation and external rotation by 75 and 34 respectively using a single deltopectoral incision.46
7 8
9
10 11
12 13
14
15
16
Conclusion
17
RSA is a valuable option that can give excellent results in the absence of other suitable alternatives. However, it is a technically demanding procedure with a significant learning curve, even for the experienced surgeon, and a relatively high complication rate. Its use should therefore be reserved for patients with severe preoperative functional deficits and pain. Concerns about the longevity of the prosthesis and deterioration in function observed after 7 years mean that its use is recommended to be restricted to those patients over the age of 70 years. A
18
19
20
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22
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