IOHC Screws

A surgeon has written a procedure for how they use these screws which may be of interest:

• Pre-op planning- Humeral trans condylar / transcortical distance – this is can be taken from a CT or a well centered and positioned CrCa or CaCr radiograph of the elbow. If using a radiograph, be sure to place a calibration marker level with and adjacent to your area of anatomical interest. It can also be very helpful to study your radiographs alongside an anatomical model to help ‘visualize’ these landmarks when you later palpate them though soft tissue.
• Surgery- Once the appropriate lateral and medial landmarks are determined and soft tissue gently retracted and protected, drill a 1.1mm tunnel across the humeral condyle. The use of a universal drill aiming guide can be helpful. A scrubbed assistant will help maintain the position of the guide, as will drilling a 1.5mm diameter hole at the ideal trans cortex exit point, to anchor the drill aiming guide.
• Remove the aiming guide, (if used). Slide a cannulated 3.2 mm drill bit over the K-wire, protect the soft tissue at the cis-cortex and steadily over drill the 1.1mm K-wire in situ. Lavage and patience are crucial- Cannulated drill bits are not as efficient and can generate considerable heat. You may have to exit one or two times to lavage debris around the K-wire via a 21G needle on a 20ml syringe, from the hole. (Exercise caution when pulling the drill bit out- placing wire forceps on the trans cortex end of the K-wire can help prevent inadvertent pull out of the K-wire)
• Use a counter sink or 2mm curette to widen the caudal aspect of the entrance hole on the lateral condyle to help facilitate the seating of the threaded-head portion of the screw. Judicious slow speed use of a 4.5 mm drill bit and drill stop may also help widen the first 3-4mm of the hole at the cis-cortex.
• Measure the length of the appropriate screw with a depth gauge. As a final check, review the length of the chosen screw against the exposed length of your depth gauge. Be sure to check that the trans cortex threaded portion of your chosen screw is less than half of your depth gauge distance to ensure a lagged compression.
• Steadily insert the screw by hand in a traditional tapping motion- half to 3/4 turn clockwise, quarter turn back, to facilitate the passage of the screw in the bone stock that is often sclerotic.
• Finally- palpate your transcortical landmarks- you should JUST be able to feel the screw tip almost level with your lateral/ medial humeral epicondyle depending on your preferred screw placement direction.
• Consider carrying a spare screw of each length in case of accidental droppage.