Pre-drilling or Self Drilling External Fixation Pins

Background

The application of external fixation is a commonly performed emergency procedure in orthopaedics for temporary stabilization as well as definitive treatment of fractures. External fixation requires that metal pins be placed into the bone on either side of the fracture. The pins are then connected to an external frame, thus stabilizing the fracture. There is debate over the optimal technique for the insertion of these pins in regards to the need to pre-drill a pilot hole prior to pin insertion.

The technology behind external fixation has evolved greatly over the past thirty years. The original external fixation pins, "Shanz pins," were essentially metal rods with threads and a trocar point. A pilot hole was needed because these pins did not have the capability to create their own hole or path in the bone. Recent advances have lead to the creation of self-drilling/self-tapping pins, which have decreased the number of steps necessary to place the pins and thereby decreased operative time. The external fixators are usually placed as a temporary measure to allow for improvement of soft tissue condition before definitive open reduction and internal fixation. Since many external fixation devices are placed in patients who are critically ill, decreasing operative time is very important.

While saving operative time is essential it is also important that the device serves its purpose without leading to complications in the short term. The major complications related to external fixation are pin site infection and pin loosening. The literature is clear that high temperatures created during pin insertion leads to bone necrosis surrounding the pin, increased infection, and increased rates of loosening. It is unclear if the new generation self-drilling pins create the same amount of necrosis as the older generation of pins. Lab studies have shown increased temperatures with direct drilling with these pins as compared to pin insertion after drilling pilot holes with dedicated drill bits. It is unclear if this increased temperature results in increased rate of loosening or pin site infection in clinical practice.

A thorough literature search has revealed no randomized controlled studies to support the use of these pins without drilling pilot holes before insertion. The current standard of care is undefined and left to surgeon preference. Our study aims to provide guidelines for schanz pin insertion for external fixator application, which may help to reduce the number of pin tract infections suffered by patients and improve outcomes.

Study Design and Treatment Plan

This will be a prospective, randomized, within-subject, single-blind trial to be conducted at Temple University Hospital. Patients who are determined to require an external fixation procedure of the lower extremities due to fracture or dislocation will be considered for enrollment according to the above inclusion criteria. Standard of care for treatment of their fractures will be provided. Once patients have provided informed consent for enrollment in the study, their pins will be randomized in a paired design according to a computer generated randomization schedule. There will be two types of pins, pre-drilled and non pre-drilled. A standard external fixation device requires two pins on each side of the fracture. Each pair of pins will have one each of pre-drilled and not pre-drilled pins, according to the randomization schedule. Therefore, each patient will have two pre-drilled pins and two pins inserted without pre-drilling. Some surgeons may prefer three pins on each side of the fracture/dislocation that is to be immobilized. We will have a randomization protocol for these situations as well.

The computer generated randomization algorithm will be placed in a secure location in sealed opaque envelopes. The operating surgeon will open the envelope prior to pin insertion and follow the randomization schedule as prescribed in the envelope.

A standard technique will be followed. IV antibiotics will be administered within 60 minutes of the starting skin incision. Pin insertion will be done by standard techniques. This involves a 1 cm incision, and blunt dissection. 4.0 mm (calcaneal or metatarsal), 5.0 mm (tibia) or 6.0 mm (femur) pins will be inserted by one of two techniques: (1) self drilling pins are inserted with a power drill directly into the bone; (2) a standard twist drill bit is utilized with a power drill to create a pilot hole, followed by insertion of the self-drilling pin by power drill.

Soft tissue relaxation incisions are made according to standard technique after external fixation assembly, as needed. The pin care protocol will consist of daily pin site cleaning using dilute hydrogen peroxide and dry dressings. Patients with suspected pin site infection will be treated with Keflex 500mg po q 6hr. Patients with an allergy to Keflex will receive Clindamycin 300mg po q 6hr.