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Reverse geometry configuration total shoulder replacements are in widespread use for the treatment of patients with rotator cuff deficient shoulders associated with significant arthritic change, known as cuff tear arthropathy. Such implants have also been used in the management of patients with irreparable proximal humeral fractures, a technique which has been described elsewhere in Orthoracle.
The design rationale in placing a prosthetic ball on the glenoid (the glenosphere) and a socket on the humeral side in a semi-constrained construct, is to medialise the joints centre of rotation and so increase the moment arm of the large deltoid muscle. This potentially optimises its function in the absence of the deficient rotator cuff tendons.
Many companies have developed such shoulder replacement implant systems. In this case, I am using the stemmed reverse geometry system, known as SMR from the Italian company Lima. The patient in this case is a female in her 70s, who presented with pain and disfunction in her non dominant left shoulder. Clinical assessment and investigations revealed a rotator cuff tear arthropathy. She had exhausted conservative measures and felt that her shoulder was bad enough to consider major arthroplasty surgery. During her history, she revealed that she had a significant allergy to nickel. Whilst there is little evidence that patients with nickel allergies or sensitivities have significant reaction to orthopaedic implants containing nickel, this is a risk to which the patient does not need to be exposed.
In the standard Lima shoulder replacement implants, the cobalt chrome components do contain nickel, although this is less than 1%. The Lima system does have options to avoid using any nickel and the implants used in this case are titanium, with a polyethylene humeral insert.
INDICATIONS
Cuff tear arthropathy is the prime indication for this operation. Whilst such reverse geometry arthroplasty has historically been reserved for an older population, I would consider using it in any patient over the age of 60.
SYMPTOMS & EXAMINATION
Patients will present with gradual insidious deterioration in shoulder function and increasing pain. The dysfunction usually manifests as an inability to raise their arm and weakness with any lifting or loading in the shoulder. They will often describe deep-seated pain within the shoulder girdle, perhaps radiating down their arm. On occasion there may be some swelling in comparison with the opposite shoulder. They may describe a previous history of injury to the shoulder but often there is a complete absence of a trauma. Usually the symptoms have come on gradually over a number of months or even years. Debilitating night pain is often a feature and they may describe a crunching or clicking within the shoulder.
Clinical examination is important, to compare both shoulders looking for symmetry, with respect to swelling and muscle wasting. Active and passive range of motion should be assessed and it is most likely that a clinical assessment of rotator cuff strength will reveal marked weakness. Neurological status in the upper limb is particularly important with documentation of axillary nerve sensory function and the motor function in the deltoid muscle. I assess this by asking the patient to actively abduct the flexed elbow away from their side, whilst palpating over the deltoid muscle to feel for adequate contraction. It is important to assess range of motion of the cervical spine, as well as elbow, wrist and hand function on the effected side. As with any patients considered for any surgical management, their past medical history and co-morbidities, including medication, should be taken into consideration and carefully documented.
IMAGING
Plain X-rays are mandatory and ideally these should be 3 views: an A-P, lateral and an axillary (or modified axial views). I recommend MRI scanning in all patients undergoing shoulder replacement and I use this to confirm my clinical findings, with respect to the rotator cuff deficiency. It is in particular important to look at the subscapularis muscle and compare this with clinical findings. I will try to preserve the subscapularis or certainly repair it if it needs to be taken down to gain access to the shoulder. The adequacy of bone stock can be well assessed on the MRI images, particularly within the glenoid.
ALTERNATIVE OPERATIVE TREATMENT
Patients with rotator cuff deficiency and minimal arthritis could be considered for arthroscopic assessment of the shoulder, with a view to rotator cuff repair. Such repair surgery could also be performed as an open operation. If repair of the rotator cuff tear is technically not possible, then surgeons have described arthroscopic debridement, tuberoplasty of the exposed greater tuberosity, in combination with long headed bicep tenotomy, or release of the suprascapular nerve.
More recently, some surgeons have had success with interposition patch grafting of rotator cuff deficiencies, or more recently described techniques, such as superior capsular reconstruction or insertion of an absorbable balloon spacer to the subacromial space to depress the humeral head into the glenoid (which can facilitate physiotherapy strengthening of the deltoid muscle). Traditionally, a hemi-arthroplasty of the proximal humerus would be considered in patients with arthritis but in absence of rotator cuff tendons, though this has had notoriously poor outcomes. Extended humeral heads on such implants (either stemmed or resurfacing) were also developed to allow prosthetic material to articulate with the undersurface of the acromion . These were known as cuff tear arthropathy(CTA) implants.
NON-OPERATIVE MANAGEMENT
As with all patients considered for any joint replacement surgery, conservative non-operative management should have been exhausted. Such treatment includes education of the patient as to their condition, suitable oral analgesia or anti-inflammatory medication (taking into account their medical comorbidities) and physiotherapy to optimise their function. Therapists will concentrate on an anterior deltoid strengthening program, which can be very successful in a motivated patient, to improve range of motion, function, strength and hence reduce pain. Some doctors will consider steroid and local anesthetic injection to the shoulder, which can certainly help with acute inflammatory synovitis or arthritis. In my practice, we use ultrasound guided suprascapular nerve blocks with local anesthetic, instilled into the suprascapular notch around the suprascapular nerve. This can be very beneficial in helping shoulder pain and then allowing deltoid function to improve. In combination with physiotherapy exercise program, this can be very effective. If patients get good transient benefit from guided local anaesthetic blockade of the suprascapular nerve, then they can be considered for percutaneous ablation of the nerve, using either a radio-frequency or cryoablation probe. Studies are ongoing as to the effectiveness of such treatment but should be considered in the non-operative management of such patients.
CONTRAINDICATIONS
As with any patient treated surgically for arthritic conditions, their general medical health and comorbidities must be taken into consideration. Patients must be able to comply with relatively straightforward physiotherapy in the post-operative period and ongoing rehabilitation instructions to optimise their function. In patients with significant medical comorbidities then a multidisciplinary approach with a pre-operative assessment team, often lead by a senior anesthetist, is recommended. Dysfunction of the deltoid muscle due to complete axillary nerve palsy is a contraindication to reverse geometry shoulder, as the bio-mechanics of the implant are reliant on function of the deltoid muscle. Relative contraindications are lack of bone stock within the glenoid and scapula but this can be addressed with either a bone grafting techniques or augmented implants. Such technique is not described here.
The procedure is performed under general anesthetic usually supplemented with interscalene local anaesthetic nerve block performed by the anaesthetist. The patient is placed in the semi-sitting beach chair position, with the arm on a moveable narrow armboard. This is often appropriate to perform a social wash of the affected shoulder and axilla prior to routine skin preparation. Unless there are contraindications, I use Flowtron intermittent calf compression during surgery to reduce the risk of thromboembolic disease. Intravenous antibiotics are administered by anaesthetist. The skin is prepared using Chlorhexidine solution, starting at the hand and preparing the whole of the upper limb and shoulder, across to the patient’s midline. Standard adhesive drapes are used to protect the patient’s airway tubing and to allow adequate exposure for approach to the shoulder from anterior incision. With the help of a company representative, the nurses should be familiarised with the sets required for shoulder arthroplasty. I also use a standard set of shoulder retractors which significantly facilitate the operation.
General points
• The surgery is primarily performed for pain relief, function can improve but it is often secondary to a reduction in pain –allowing improved Deltoid function.
• Patient progress and outcome will ultimately depend on the condition of the joint and soft tissue pre-operatively.
• Improvement can continue for 18-24 month’s post-operatively, it is therefore important to encourage patient to continue with rehabilitation until no further improvement.
• Aim of rehabilitation is good quality of movement, and maximal function, however in this group of patients increased scapula motion is to be expected and maybe encouraged,
• Don’t sacrifice quality of movement and function for ROM
• The principles of the Deltoid Rehabilitation Programme for irreparable rotator cuffs should be utilised.
Precautions
The underlying pathology is one of chronic degenerative rotator cuff rupture; it varies from patient to patient as to what if any rotator cuff remains intact. If any tendons were repaired then this will be stated in the op notes and the rehabilitation will be guided by this.
Repetitive overhead activities and loaded activities above shoulder height may be limited long term and should not be forced with rehabilitation.
Lifting weights above shoulder height with more than 2-4 kg should be avoided unless otherwise instructed by the surgeon.
Hand behind back (HBB) should not be forced and may not be regained There is likely to be a chronic deficit in rotator cuff strength, particularly in ER
Immobilisation
• Patient to wear sling for 3 weeks 24 hours a day, only removing for physiotherapy exercises • At 3 weeks, start to wean out of sling but to continue wearing at night for a further 3 weeks
• Total sling usage – 6 weeks
Post-Operative
0-6 weeks: Pendular exercises; Active assisted ER to neutral (ONLY IF THERE IS NO SUBSCAPULARIS REPAIR); Active assisted elevation in supine as comfort allows – consider use of table slides or walk backs
3 weeks: Gradually wean out of sling – light activities only (weight of a cup of tea within the field of vision, short lever)
6 weeks: Start to increase ER, as ER increases gradually increase elevation ROM; Active assisted exercises progressing to active exercises – utilise short lever, supine & CKC if appropriate; Don’t force HBB position; No long lever open chain exercises until 8 weeks
8 weeks: Consider use of the principles of the Deltoid Rehabilitation programme Sub maximal isometrics in neutral – avoiding any repaired tendons
12 weeks+: Isometrics in variable starting positions; Progressing to resisted through range strengthening – consider weight of arm, varied starting position & functional weights as well as theraband. REMEMBER FUNCTIONAL GOAL and the underlying pathology is massive irreparable rotator cuff tear
The Ultimate Aim is Function rather than anatomical normal movement.
Nickel sensitivity and the implantation of orthopaedic prostheses. D Gawkrodger. Contact Dermatitis. 1993;28:257-259
Intolerance reactions to knee arthroplasty in patients with nickel/cobalt allergy and disappearance of symptoms after revision surgery with titanium-based endoprostheses. K Dietrich, F Mazoochian, B Summer, M Reinert, T Ruzicka, P Thomas. J German Soc Dermatology. 2009 May;7(5):410-412
The SMR reverse shoulder prosthesis in the treatment of cuff-deficient shoulder conditions. S Young, N Everts, C Ball, T Astley, P Poon. J Shoulder Elbow Surg. 2009 July;18(4):622-626
Mid-term results of a metalbacked glenoid component in total shoulder replacement. A Castagna, M Randelli, R Garofalo, L Maradei, A Giardella, M Borroni. J Bone Joint Surg [Br] 2010;92(10):1410-1415
Biomechanical evaluation of different designs of glenospheres in the SMR reverse shoulder prosthesis: micromotion of the baseplate and risk of loosening. P Poon, J Chou, D Young, S Malak, I Anderson. Shoulder & Elbow. 2010.2:94-99
Shoulder arthroplasty in the patient with metal hypersensitivity. M Morwood, G Garrigues. J Shoulder Elbow Surg. 2015 May;24:1156-1164
Reference
- orthoracle.com
