1 Principles topenlarge
Acute and pathological fractures can be nailed.
For nailing, the fracture must be situated between the humeral neck and 5 cm above the olecranon fossa. The fracture type is of no importance.
Retrograde nailing offers the possibility of axial compression. This is recommended in fracture distraction, and for transverse and short oblique fracture types.
There are many different nails on the market, including some which are designed specifically for retrograde nailing. The main difference between them relates to their locking systems. Some nails allow compression at the fracture site.
To demonstrate the principles, the illustrations below show the use of a Synthes nail. Some details may not be applicable with other nailing systems.
2 Determining nail diameter and length topenlarge
Use the radiographic ruler
Use a radiographic ruler to determine the correct diameter and length of the nail to be inserted.
The ruler is placed posteriorly on the arm and in line with the medullary canal.
Determine nail diameter
Visualize the medullary canal under image intensification in AP view and compare with the diameters of the marks on the ruler.
The correct size of the humeral nail corresponds to the diameter of the mark that fits completely into the medullary canal.
Look carefully at the distal humeral canal. It may be narrower than the rest.
In our example, a 7.5 mm nail diameter is chosen.
Determine nail length
First, provisionally reduce the humeral fracture. Next, the ruler is placed parallel to the arm, with the top-of-nail mark at the level of the upper edge of the insertion site.
Take an AP image intensifier view of the proximal humerus together with the ruler, as above.
The humeral nail should be long enough to just enter into the humeral head. Determine this length with the aid of the ruler.
In our example a nail of 240 mm length is chosen.
3 Entry portal topenlarge
A central triangle with a proximal apex is defined between the medial and the lateral supracondylar ridges and the olecranon fossa.
Three holes are drilled at the points of this triangle, in the dorsal humeral cortex.
First use the 3.2 mm drill bit, then enlarge the 3 holes with the 4.5 mm drill bit.
During the drilling process, the drill direction is changed from its initial perpendicular orientation, through about 30° towards the long axis of the humerus.
The 3 drill holes are joined to form a single insertion portal by using the 8.5 mm burr.
The burr is directed almost in line with the long axis of the medullary canal.
The goal of this procedure is to create a central supracondylar entry portal, 2 cm long and 1 cm wide, that will allow gentle insertion of the medullary nail obliquely to the bone surface. It may be necessary to enlarge the opening proximally, using a bone nibbler, to obtain adequate length.
4 Nail insertion topenlarge
Use of the compression device
If the fracture type indicates the application of interfragmentary compression (eg, transverse, or short oblique), the compression device must be mounted onto the nail, together with the insertion handle/aiming guide, at this stage.
Mount the insertion handle/aiming guide on the nail base with the connection screw.
Ensure that the convexity of the nail curvature points away from the insertion handle.
Gently insert the nail tip into the entry portal. If there is any resistance, consider enlarging the entry portal as there is a very real risk of iatrogenic supracondylar fracture when the nail flexes the distal fragment forwards during insertion.
Do not use a hammer, as this may increase the risk of fissure or fracture at the insertion site.
Advance the nail as far as the fracture site.
Use the nail tip as a reduction aid.
After passing the fracture site, adjust humeral shaft alignment, rotation and length.
Control under image intensification in two different planes.
The nail is then advanced gently until it has reached the desired position.
Avoid fracture distraction.
Ensure correct position
The nail should be inserted completely into the entry hole with its distal end located at the proximal margin of the entry portal.
The Synthes system has a hole in the aiming jig through which a K-wire may be passed to indicate the end of the nail.
5 Interlocking: General considerations topenlarge
Static interlocking with two screws on each side of the fracture is recommended. When distal interlocking is performed first, rotation can be adjusted before proximal interlocking.
When axial compression is used, static interlocking at the distal end of the nail is performed as the last step.
The sequence of interlocking as shown below is the only way to enable axial compression. A different sequence can be chosen in other cases.
6 Distal dynamic interlocking topenlarge
If dynamic locking is available, place the sleeve system through the hole in the insertion handle/aiming guide corresponding to the dynamic slot of the nail, and if necessary make a stab skin incision.
Drill a hole for the dynamic interlocking screw through both cortices.
Measure the length of the hole.
The selected screw is inserted through the outer sleeve to engage both cortices.
7 Proximal interlocking top
For proximal interlocking, all three interlocking holes can be used. The insertion of at least two interlocking screws is recommended. For better purchase, placement of the screws in the metaphysis, or diaphysis, is preferable.
Do not damage the axillary nerve.
Position of the skin incision
Use the image intensifier and, by gentle rotatory movements of the arm, ensure that the selected interlocking hole appears as a perfect circle.
A sharp skin incision is made just over this circle.
Soft tissue dissection
Use a small clamp to prepare a track for insertion of the drill bit.
Blunt dissection of the soft tissues helps to protect the axillary nerve.
The positioning of the drill tip, its fine adjustment, and the drilling procedure are performed under image intensification. Many surgeons prefer a radiolucent drill attachment if it is available.
The radioopaque circles of the radiolucent drill should be centered on the locking hole.
Drill a hole through the hole in the nail and both cortices.
The length of the required screw is measured with a depth gauge.
Insertion of interlocking screw
Insert the interlocking screw and subsequently check for correct position and length under image intensification in two planes.
Further locking screws
Further interlocking screws are inserted as described above.
Pearl: Place an absorbable suture around the screw
To avoid losing the screw in the soft tissues during insertion and tightening, an absorbable suture is fastened around the screw’s head beforehand.
8 Distal static interlocking topenlarge
Finally, place the static locking screw.
Place the sleeve system through the corresponding hole in the insertion handle/aiming guide, make a stab skin incision, and advance the sleeve system through this incision onto the humeral shaft. Sometimes the sleeve can be placed in the proximal edge of the larger skin incision made for the entry portal.
Drill a hole for the static interlocking screw.
Measure the depth of the hole. The screw tip should just protrude through the far cortex.
The selected screw is inserted through the sleeve.
Should axial compression not be used, distal dynamic and static interlocking are performed together before or after proximal interlocking.
9 Fracture compression topenlarge
Use of the compression device
If the nailing system in use has a compression device, this allows controlled axial compression.
If the fracture type indicates the application of axial compression (eg, transverse or short oblique), mount this device onto the nail with the insertion handle/aiming guide before insertion, and replace the connecting screw.
Measuring device to indicate gap closure
Before tightening the screw on the compression device, make sure that distal dynamic and proximal static interlocking have been performed.
At the top of the compression device there is a millimeter scale which indicates that a fracture gap up to 8 mm can be closed by tightening the screw.
Apply fracture compression
Apply fracture compression by turning the screw on the compression device in a clockwise direction.
Check gap closure under image intensification and monitor the scale on the compression device.
Static distal interlocking
The static distal interlocking screw is required for maintaining interfragmentary compression.
Insert this screw through the insertion handle/aiming guide as previously described.
Check under image intensification.
When interlocking is completed, the definitive position of the implant is checked under image intensification in two planes. Take particular notice of the position of the proximal end of the nail and the location and length of all interlocking screws.
10 Nail capping and wound closure topenlarge
Cap the end of the nail
Remove the insertion handle/aiming guide and its connecting screw (with or without the compression device).
Insert an end cap in order to prevent ingrowth of bony tissue.
End caps of different lengths may be available and may add as much as 15 mm to the overall length of the nail. Our example shows a 0 mm end cap, which fits completely into the nail.
Finally, the wounds are irrigated and cleaned.
One drainage tube may be inserted into the main wound.
The different layers of the main wound are closed separately. For the stab incisions, skin closure only is performed.