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Author

Jörg Auer

Executive Editor

Jörg Auer

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Screw fixation

1. Principles

Anatomic reduction of the fracture and fixation by means of three 5.5mm cortex screws inserted in lag fashion associated with a tension band fixation. The tension band is a necessity in cases where the biceps tendon was not transected because the biceps muscle is extremely powerful and the screws being inserted parallel to the tension forces created by the biceps tendon will be pulled out if not secured by a tension band.

supraglenoid tubercle

Transection of the biceps tendon allows anatomic reduction of the fracture and fixation by means of two to three 5.5mm cortex screws inserted in lag fashion without a tension band fixation.

screw fixation

The image shows an immediate postoperative radiographic view depicting good reduction of the supraglenoid tubercle fracture by means of two cortex screws. The tension band was not applied because the biceps tendon was transected.

screw fixation

Complications and patient prognosis

Read more about possible complications and patient prognosis.

2. Preparation and approach

This procedure is performed with the patient placed in lateral recumbency through the craniolateral approach to the shoulder.

craniolateral approach to the shoulder

3. Reduction and Fixation with resection of the biceps tendon

The biceps tendon is transected in the region of its origin at the supraglenoid tubercle facilitating fragment reduction.

screw fixation

A stab incision is prepared through the tendon stump cranial to the tubercle and the drill bit, protected by its drill sleeve, is passed through it down to the bone. The orientation of the 5.5mm drill bit is almost perpendicular relative to the fracture plane.

The glide hole is prepared across the fragment in the non-reduced position to allow immediate recognition of the drill bit entering the fracture plane. Ideally, the drill bit is left in place.

screw fixation

A second stab incision is prepared approximately 1cm distal to the first one, and a second 5.5 mm glide hole is drilled across the fracture, at a slightly different angle relative to the proximal glide hole diverging in the axial plane.

The same procedure is repeated once more further distally. This is the most difficult aspect of the surgery.

The drill bits left in the glide holes serve as aiming aid for the drilling of the next glide hole.

screw fixation

The proximal most drill guide is removed and replaced by a smaller Steinmann pin over which the 4.0mm insert drill sleeve is placed and secured in the fragment.

screw fixation

The fracture is reduced with the help of the insert drill sleeve and maintained in reduction with large pointed reduction forceps.

The proximal thread hole is drilled into the parent portion of the scapula.

screw fixation

After determining the length of the drill hole and tapping the thread hole, a 5.5mm cortex screw 4mm shorter than the measured depth of the hole is inserted and solidly tightened.

The addition of a washer through which the screw can be inserted is optional.

screw fixation

The remaining two 5.5mm cortex screws are inserted one after the other applying identical technique.

The use of self-tapping 5.5mm cortex screws is encouraged in this procedure.

screw fixation

The image shows an immediate postoperative radiographic view depicting a supraglenoid tubercle fracture repaired by means of two 5.5mm cortex screws.

Note: The most proximal screw is inserted through a washer.

screw fixation

4. Reduction and fixation with biceps tendon intact

Fracture fixation is achieved as described above, except that the proximal incision has to be prepared across the intact biceps tendon.

craniolateral approach to the shoulder

If the biceps tendon is intact, reduction of the fragment is more difficult, but it can be achieved by pulling the entire forelimb forward, reducing tension on the fragment by doing so.

Additionally compression of the fracture site is achieved by application of the large pointed reduction forceps across the fracture.

screw fixation

Stab incisions have to be prepared through the intact biceps tendon to allow access to the cranial rim of the scapula. The glide holes are prepared across the non-reduced fragment in the non-reduced position to appreciate penetration of the fracture plane. Identical technique is applied as described above.

screw fixation

The proximal most 5.5mm cortex screw is inserted as described before.

screw fixation

The remaining two 5.5mm cortex screws are inserted one by one, applying identical technique as described before.

screw fixation

A lateral to medial 2.5mm drill hole is prepared through the neck of the scapula, approximately 2-3cm caudal to the fracture line. Access for the drill hole may require additional dissection or transcutaneous/muscular drilling.

Note: Care must be taken to prevent any (additional) injury to the suprascapular nerve and vascular bundle.

screw fixation

The proximal most screw is slightly loosened and the washer displaced away from the bone.

Subsequently the 1.25mm diameter cerclage wire (or cable) is fed through the drill hole, applied in figure-of-8 fashion underneath the washer and tightened at the dorsal aspect of the scapula.

The screw is subsequently solidly tightened again.

screw fixation

A second figure-of-eight tension band is applied through an additional 2.5mm drill hole, prepared across the parent portion of the scapula and the fragment.

screw fixation

Preoperative image of a supraglenoid tubercle fracture.

plate fixation

The image shows a supraglenoid tubercle fracture attached by means of three 5.5mm cortex screws (two of which through washers) and two tension bands.

screw fixation

5. Closure

The soft tissues are closed in several layers. A simple continuous suture is placed in subcutaneous tissues, followed simple interrupted sutures in the skin covered by a stent bandage.

screw fixation

6. Aftercare

Horses are restricted to stall rest for 60 days to allow time for the dead space to fill with fibrous tissue and the biceps tendon to reattach. A carefully controlled rehabilitation program is important for these horses to regain strength and coordination in their shoulder joints.

Percutaneous stimulation of the shoulder muscles during rehabilitation to minimize muscle atrophy should be considered.

plate fixation

Typically, physical therapy begins with range-of-motion exercises and hand-walking for 5 minutes per day, followed by walking over ground poles and gradual increases in duration of exercise each day. Horses are not usually ready to return to training or to be turned out into a paddock for 6 to 12 months after surgery.

plate fixation