Overview
It is notoriously difficult to achieve a good functional outcome in older patients with displaced comminuted proximal humerus fractures managed surgically. In recent years shoulder surgeons have considered that this injury should be treated as a fracture with rotator cuff deficiency and hence have been using reverse geometry total shoulder replacements with a prosthetic ball on the glenoid (the glenosphere) and socket on the humeral side of a semi-constrained construct. This medialises the centre of rotation and increases the moment arm on which the large deltoid muscle can work in the absence of the rotator cuff tendons which normally insert around the proximal humerus. The main design remit for reverse shoulder arthroplasty was to address the difficult problem of arthritis in the rotator cuff deficient shoulder so called cuff tear arthropathy which presents as a chronic condition. Such implants have been in widespread use over the last 30 years gaining in popularity such that they have overtaken the number of anatomical shoulder replacements performed.
More recently the same implants have been used to treat comminuted displaced fractures of the proximal humerus. Traditionally such fractures have been associated with relatively poor outcomes when managed either conservatively or with internal fixation. The latter has been made significantly easier with contoured proximal humeral locking plates but still such surgery in osteoporotic bone is technically difficult and often associated with poor outcomes. A significant risk is avascular necrosis of the humeral head and resorption of the tuberosities with consequent rotator cuff dysfunction mimicking cuff tear arthropathy hence the adoption of reverse geometry arthroplasty.
An alternative would be to consider hemiarthroplasty reconstruction of the proximal humerus using a stemmed hemiarthroplasty prosthesis with reconstruction of the tuberosities around the implant. In such cases the significant problem is that the tuberosities resorb and the patient is left with a metal spacer and a rotator cuff deficient shoulder.
Implant companies have developed fracture specific reverse geometry implants which are tailored to the task. The Lima SMR is one of these as part of the spectrum of options available on their platform system. It uses the same glenosphere and humeral stem (cemented or uncemented) as their cuff tear arthropathy stemmed prosthesis but has a module trauma body added to the humeral stem which incorporates holes for passage of sutures to repair residual small fragments of bone and rotator cuff remnants.
Whilst there is some evidence in sporadic publications we are yet to have good hard level 1 evidence that reverse geometry arthroplasty in such cases is reliably and significantly better than either conservative management, internal fixation or hemiarthroplasty reconstruction, however there are trials ongoing to try and address the issue. Anecdotally most shoulder surgeons will have many examples of good outcomes from reverse geometry arthroplasty in such cases.
Indication
INDICATIONS
Comminuted displaced fractures of the proximal humerus involving the lesser and greater tuberosities. Typically an older age group would be considered for such surgery where the bone will be of poorer quality risking tuberosity resorption with either internal fixation or hemiarthroplasty reconstruction.
SYMPTOMS & EXAMINATION
Patients will usually present having had a fall from standing height injuring their shoulder. They will have pain and dysfunction. Clinical assessment will confirm swelling, bruising and tenderness. It is important to ascertain the neurological and vascular status of the upper limb. Assessment of distal perfusion is important and if there is any concern then angiography should be performed in close liaison with local vascular surgeons.
Neurological status of the upper limb particularly documenting the axillary nerve sensory function is important. Within the history taking pre-fracture shoulder function and status should be ascertained particularly whether the patient has had any previous surgical intervention. As with any patients considered for surgical management of acute fractures their past medical history and co-morbidities including medications should be taken into consideration.
IMAGING
Plain X-rays are mandatory and ideally these should be 3 views: AP, lateral and axillary or modified axial views. CT scanning, if logistically possible in the acutely injured patient, is also useful in pre-operative planning to assess the fracture fragments and looking for concurrent bony injury of the glenoid which may affect glenoid component fixation.
ALTERNATIVE OPERATIVE TREATMENT
Such fractures could be considered for internal fixation with plate and screws. Current practice would usually involve using a specific proximal humeral locking plate which is contoured to the proximal humerus anatomy. Techniques have been described for percutaneous wire fixation or even suture fixation of such fractures but these are technically challenging. Classically the approach in the older patient would have been to use a stemmed hemiarthroplasty implant reconstructing the tuberosities around the proximal aspect of the prosthesis.
NON-OPERATIVE MANAGEMENT
In a patient who is not suitable for surgical fixation then it is entirely reasonable to treat this fracture conservatively using a sling for comfort and prescribing oral analgesia. As the pain begins to settle then graduated physiotherapy rehabilitation can be adopted to try and optimise the function and in a significant proportion of patients this is acceptable to both patient and treating surgeon. Function is likely to be limited but often this is pain free.
CONTRAINDICATIONS
As with any patient treated surgically for acute fractures, their general medical health and co-morbidities must be taken in to consideration. Patients must be able to comply with relatively straight forward physiotherapy in the post-operative period and ongoing rehabilitation instruction to optimise their function
Operation
Exposure
Glenoid Prosthetic Arthroplasty
Humeral Prosthetic Arthroplasty
Post-operative
Imaging
Postop Protocol
The patient’s arm is rested in a polysling for the first two weeks. During this time they can actively mobilise elbow wrist and hand and are encouraged to maintain underarm hygiene. They can start early active assisted elevation exercises below shoulder height and typically lying supine.
Post-operative X-rays are taken in the first 24 hours following surgery and prior to discharge from hospital. Routine post-operative blood tests are taken and the patient is discharged home with the polysling and physiotherapy instruction when they are safe to do so typically in the first 48 hours following surgery.
Outpatient physiotherapy rehabilitation is arranged to concentrate on graduated range of motion initially active assisted. Fracture clinic review is typically undertaken at two weeks for a wound check, removal of the paper Steristrips, trim ends of the absorbable sutures and further check radiographs. The sling can be weaned by four weeks and ongoing rehabilitation to optimise function is established with regular post-operative physiotherapy.
The patient should be reviewed with repeat radiographs at six months, one year, two years and five years following surgery.
References
- Crowther, M. (n.d.). Lima SMR Reverse Total Shoulder Replacement for proximal humeral fracture. OrthOracle. Retrieved July 23, 2021, from https://www.orthoracle.com/library/lima-smr-reverse-total-shoulder-replacement-for-proximal-humeral-fracture/
