1 Principles top
Hemiarthroplasty is indicated in all cases where a stable osteosynthesis is not achievable especially in situations with poor bone quality like severe osteoporosis or significant comminution. In the elderly, the indication might be extended to head-splitting fractures and situations with a probably ischemic humeral head (eg, a displaced anatomical neck fracture with no capsular attachment remaining).
In these fractures it is necessary to mobilize greater and lesser tuberosity fragments so they can be correctly reconstructed under the prosthetic humeral head.
The reverse shoulder prosthesis may have a role for arthroplasty in elderly patients with comminuted proximal humerus fractures. Tuberosity healing is less predictable in the elderly. Their function may be improved by using this type of prosthesis.
Keys to successful hemiarthroplasties
- Correct determination of the surgical landmarks
- Proper determination of prosthesis size and version
- Proper height of the prosthesis with correct soft-tissue tensions
- Anatomical reduction of the tuberosities
- Stable fixation of the tuberosities (with cables or other stout sutures) to promote their union to the proximal humerus
- Autologous bone grafting underneath the tuberosities
2 Evaluation of the fracture topenlarge
It is crucial to evaluate the fracture. Identify the fracture lines, the long head of the biceps and the condition of the rotator cuff.
3 Suture insertion topenlarge
Place rotator cuff sutures
Insert sutures into the subscapularis tendon (1) and the supraspinatus tendon (2). Place these sutures just superficial to the tendon’s bony insertions. These provide anchors for reduction, and temporary fixation of the greater and lesser tuberosities.
4 Tenotomy of the long head of the bicipital tendon topenlarge
Temporarily attach the bicipital tendon to the superior border of the major pectoralis. Perform a tenotomy of the long head of the bicipital tendon close to the rotator interval.
Pearl: move the stump of the bicipital tendon out of the surgical field.
5 Retrieval of the humeral head topenlarge
Extend the exposure
In order to retrieve the humeral head it is necessary to achieve a proper exposure. To do this, divide the soft tissues over the fracture, and extend this incision along supraspinatus muscle fibers as shown.
Note: If a cranial extension is needed, it should be carried into the supraspinatus tendon (A) and not into the rotator interval (B). This is because the typical “intertuberosity” fracture line of a four-part fracture is actually lateral to the bicipital groove, and thus through the greater tuberosity.
Retrieve the humeral head
Any remaining medial capsular attachment to the head should be carefully released with special attention not to damage the axillary nerve medial to the proximal humerus.
Be sure that all loose small fragments are removed.
Keep the humeral head for later measurements and bone grafting.
Inspect the glenoid fossa
Resect the tendon of long head of the biceps at its labral origin and retrieve the intermediate tendon.
Inspect the glenoid fossa in order to rule out any injury.
If there is a glenoid fracture, osteosynthesis should be performed now.
Remove any bony fragments.
6 Suture insertion into the infraspinatus tendon topenlarge
Insert a suture into the infraspinatus tendon.
To protect its distal periosteal sleeve, the greater tuberosity is pushed gently into the shoulder cavity instead of being retracted laterally.
Pitfall: use of forceps or clamps in osteoporotic bone
Grabbing bone fragments with a forceps or clamp will typically increase comminution of osteoporotic bone. This should be avoided by using sutures as “handles” for manipulation and reduction.
7 Measurement of the humeral head topenlarge
The correct prosthesis head size can be measured on the retrieved humeral head. In cases of comminution an x-ray of the contralateral humeral head will be used to determine the appropriate size.
Note: The humeral head is not spherical. Measure the smallest diameter.
Note: If an x-ray is used to determine the size of the humeral head use a marker ball in order to compensate for any radiological magnification.
The correct size of the humeral head can also be assessed by direct comparison with a trial head.
Determine the posteromedial metaphyseal extension
The posteromedial metaphyseal extension (h) determines the implantation height of the prosthesis. It can be measured easily with a ruler.
8 Preparation of the greater tuberosity topenlarge
Prepare the greater tuberosity for later suture fixation
If there is cartilage attached to the tuberosities, this needs to be resected.
In general, the reattachment of the tuberosities can be performed with sutures or cables. We will demonstrate the use of cables through the holes in the prosthesis.
Passing the cables is easier if two 2.0 mm drill holes are first placed through the greater tuberosity. Pass the cables with a wire or cable passer, if needed.
Pearl: use a passing instrument
Pass the cables through the bone with an appropriate instrument. A standard catheter 14G can be bent in a hockey-stick shape and used as a cable passer.
9 Preparation of the humeral shaft topenlarge
Open the humeral shaft
Expose the humeral shaft by extending and adducting the shoulder. Open the medullary canal and gently enlarge the humeral canal with rasps of increasing sizes.
Correct rasp size
Insert rasps of increasing size until the end of the rasp protrudes above the bone an amount equal to the previously measured posteromedial metaphyseal extension (h). If the rasp fits snugly in this position, the optimal size has been found. If not, increase the rasp size and progress until you reach the appropriate height. Be careful not to exert too high of a force as the shaft is at risk of fracturing.
Size of the humeral shaft component
The correct size of the humeral shaft component equals the last rasp size used.
Pearl: cancellous bone removal
In order to insert the maximal size of suitable rasps, it is often helpful to remove some of the medial cancellous bone as illustrated. Use a curette or rongeur.
Determine humeral head retroversion
The humeral head should be retroverted approximately 25° relative to the distal humeral epicondylar axis. As illustrated, the retroversion guide shows the perpendicular to the humeral head axis. The forearm is perpendicular to the epicondylar axis. The angle between the guide and the forearm equals the retroversion of the humeral head.
The humeral head retroversion can additionally be checked using the distance between the deepest point of the bicipital groove and the centerline of the rasps or prosthesis. This distance should be approximately 8 mm.
Pearl: Prosthesis with pronounced calcar design
If a prosthesis with a pronounced calcar design is used, this type of prosthesis will center itself if the maximal stem size is used.
This technique acknowledges the patients individual retroversion.
10 Implantation of prosthesis topenlarge
Insert the prosthesis, respecting the proper insertion height (posteromedial metaphyseal extension), and the retroversion.
For detailed surgical steps please refer to the technical guide of the specific prosthesis chosen.
Depending on the prosthesis type and the remaining bony situation, bone cement may be necessary to fix the implant. Certainly it is wise to use cement if the prosthesis does not fit securely in the humerus.
11 Fixation of the tuberosities topenlarge
Pass the tuberosity cables through the corresponding holes in the prosthesis.
Fix the lesser tuberosity
Drill two 2.0 mm holes through the lesser tuberosity and pass the cables through them. An appropriate passing device is used, if necessary.
Glenohumeral reduction and reduction of the tuberosities
Reduce the glenohumeral joint and preliminarily reduce the tuberosities under the flange of the prosthetic humeral head.
Retrieve cancellous bone from the humeral head and pack it beneath the tuberosities. This will increase the primary stability of the tuberosities, particularly in osteoporotic bone.
Final reduction of the tuberosities
By pulling the stay sutures inserted through the subscapularis and the infraspinatus tendons, the tuberosities are reduced beneath the humeral head.
Then tighten the stay sutures and tie them securely.
Confirmation of reduction
After preliminary fixation of the reduced tuberosities, the reduction has to be confirmed by visual, tactile, and x-ray control.
There should be no gap and no step-off between the tuberosities underneath the humeral head prosthesis. The tuberosities must be under the humeral head.
The inferior spike of the greater tuberosity should fit snugly into the fracture gap. This would be revealed by visual control.
Close the supraspinatus split
Close the supraspinatus split with a running suture.
12 Tenodesis of the long head of the bicipital tendon topenlarge
Place the bicipital tendon into the bicipital groove and preliminarily fix it with sutures.