Indications for external fixation
Conditions treated with external fixation
Nonunion/Malunion
Joint distraction
Callus distraction/lengthening of bone
Off-loading of wound/flap
Osteotomy
Arthrodesis
Infection/Osteomyelitis
Soft tissue/skin contracture
Fracture
Extensive scarring/contracture/burns
Previous infection
Osteopenia/osteoporosis
Charcot neuroarthropathy
Poor soft tissue quality
Large deformity
Open wounds
Patient unable to maintain non-weight bearing
Immune compromised host
Complications of External Fixation: Pin Site Infections
Pin site infections are the most common complication of circular external fixation . It is important to maintain a stable construct throughout the course of treatment because loosening of the fixation can lead to inflammation of the surrounding soft tissue. An unstable external fixator can result in a higher likelihood of a pin site infection. Paley developed a simple grading system for pin site associated problems : Grade 1, soft tissue inflammation (Fig. 30.1); Grade 2, soft tissue infection (Fig. 30.2); Grade 3, bone infection (Fig. 30.3) [6]. As long as Grade 1 and 2 problems are addressed (usually with a 10-day course of orally administered antibiotics), progression of serious infection to Grade 3 usually does not occur. The recalcitrant infections that infect a joint or have prominent cellulitis might require pin removal in the office or in the operating room, with additional wire placement as needed to maintain stability. Pin site infections that fail to respond to oral antibiotics should be treated with intravenous antibiotics. Prompt action is required to prevent premature removal secondary to deep infection.
Fig. 30.1
Grade 1 pin site infection with soft tissue inflammation due to edema of the lower extremity. Treatment was successful with oral antibiotics and edema management (Reprinted with permission from the Rubin Institute for Advanced Orthopedics, Sinai Hospital of Baltimore)
Fig. 30.2
Grade 2 pin site infection in a brachymetatarsia lengthening . Prompt pin care and oral antibiotics resolved this pin site infection (Reprinted with permission from the Rubin Institute for Advanced Orthopedics, Sinai Hospital of Baltimore)
Fig. 30.3
Grade 3 pin site infection with radiographic evidence of proximal half-pin loosening and osteomyelitis formation in a neuropathic patient undergoing calcaneal-tibial arthrodesis for limb salvage (Reprinted with permission from the Rubin Institute for Advanced Orthopedics, Sinai Hospital of Baltimore)
Patients and their families should be well educated before and after the application of the fixator that infection may occur more than once during treatment. It is important to clean the pins with saline daily and keep them dry. The authors allow non-neuropathic patients to shower daily as long as attention is made to dry the pin sites thoroughly. Neuropathic patients have a higher likelihood of pin tract infections, and therefore as long as the pin sites are stable, we do not recommend showering or daily care. However, if the pin sites become inflamed, infected and/or draining, we recommend daily saline cleansing of the pin sites with Q-tips and wrapping gauze on the affected sites to stabilize the soft tissue. Oral antibiotics are prescribed for pin site infections, along with advising the patient to limit weight-bearing activity until the infection resolves. Persistent pin site infections are treated with removal of the affected pin/wire. If proper care is initiated immediately upon the discovery of a pin site infection, the progression to osteomyelitis is rare.
Classification of Pin Site Infections
Problem—Pin site infection requiring removal of the half-pin or wire in the office and treatment with wound care and orally administered antibiotics.
Obstacle—Pin site infection requiring removal of the half-pin or wire and addition of a new half-pin performed in the operating room.
Complication—Bone infection resulting from pin or wire site infection. Treatment of osteomyelitis consists of bone debridement and intravenously administered antibiotics.
Nerve and Vascular Injury
Injury to the major nerves and vessels of the lower extremity with the insertion of thin wire fixation and half-pin fixation is relatively rare. The surgeon must have intimate knowledge of the cross-sectional anatomy of the extremity and the safe zones for transosseous fixation. Nerve lesions manifest as pain in the anatomic distribution of the nerve. This is caused by nerve impingement from the percutaneous insertion of a wire or pin or during gradual deformity correction as a nerve becomes stretched or tethered. The best treatment is to remove the offending wire or pin and monitor the patient for improvement in symptoms. If symptoms do not improve, exploration of the nerve may be warranted.
Entrapment of the posterior tibial nerve can occur with external fixation during distal tibial/ankle deformity correction, especially when combined with lengthening. Prophylactic tarsal tunnel release should be considered for acute varus, equinus, or procurvatum ankle correction greater than 10° and gradual correction of deformity greater than 20° (Fig. 30.4) [8]. It is important to ensure complete decompression of the posterior tibial nerve, including the distal medial and lateral plantar nerve tunnels at the porta pedis. If tarsal tunnel decompression is not done prophylactically, it is important to monitor the patient closely for signs and symptoms of posterior tibial nerve entrapment postoperatively. Prompt intervention if symptoms arise will prevent irreversible nerve damage.
Fig. 30.4
Tarsal tunnel decompression performed prophylactically in a case of varus ankle deformity correction with ankle distraction. This was done prior to application of the multiplanar external fixator for correction of the deformity. Note the vertical nature of the incision so as not to disrupt healing during deformity correction (Reprinted with permission from the Rubin Institute for Advanced Orthopedics, Sinai Hospital of Baltimore)
Classification of Neurological Injury
Problem—Distraction and/or deformity correction results in numbness to the ankle/foot/toe. Decreasing the rate of correction allows the nerve compromise to resolve before the end of treatment.
Obstacle—Distraction results in numbness to the ankle/foot/toe; however, decreasing the rate of distraction does not resolve the numbness. Nerve decompression is then performed, and the nerve recovers before the end of treatment.
Complication—Intraoperative nerve injuries that result in slight numbness of the ankle/foot/toe but are not painful and do not affect the patient’s function are minor complications. A major complication is a residual nerve insult that creates a neuropathic ankle/foot/toe that remains well after treatment and affects function.
Vascular injury is typically caused by a wire or pin introduced directly into a vessel. Bleeding will be noted with a vascular injury. The treatment is removal of the pin or wire and compression. Angiography may be necessary to determine what vessel has been injured and elucidate the sequelae. Edema throughout the treatment course is common as patients are often weight bearing as tolerated. To reduce edema, gauze is wrapped tightly around the pin sites between the skin and external fixator. Venous thromboembolism is uncommon in foot and ankle surgery; however, in patients with external fixation, proper prophylaxis should be considered based on the patient’s risk factors.
Classification of Vascular Injury
Problem—Edema that is controlled with daily gauze wrapping. The daily gauze wrapping allows the edema to resolve before the end of treatment.
Obstacle—Vascular insult because of a misplaced pin/wire. The offending pin/wire should be removed and adjusted during a second surgery, which will allow the vascular insult to repair. This obstacle resolves before the end of treatment.
Complication—Non-repairable intraoperative vascular insult that affects vascularity to the foot is a minor complication. Intraoperative vascular insult, deep vein thrombosis, pulmonary embolism, and compartment syndrome are major complications.
Thermal Necrosis
Prevention of thermal necrosis is extremely important when placing wires and pins. Techniques used to reduce thermal necrosis include predrilling for half-pins and inserting by hand, use of sharp and non-cannulated drill bits, use of “on-off” drilling technique of pins and wires, tapping the wire through the soft tissues, deflation of the tourniquet to allow blood flow to cool the wires, and use of saline irrigation around the wires/pins during insertion. All cortical wires should be avoided due to rapid generation of heat during drilling. The prevention of thermal necrosis is vital because this can potentially lead to a stress riser and stress fracture in the bone or place the site at increased risk for developing later infection due to formation of a ring sequestrum.
Classification of Thermal Necrosis
Problem—Dense bone is noted during predrilling of half-pin. The drill bit is removed and flutes are cleaned. Drilling is continued with “on-off” technique to prevent further heat generation.
Obstacle—Pin/wire becomes loose postoperatively due to bone resorption from thermal necrosis. Pin/wire should be removed and replaced in a second surgery.
Complication—Thermal necrosis during pin insertion results in loosening of pin and forms a sequestrum leading to osteomyelitis. This is a minor complication if treatment leads to resolution prior to end of treatment. This is a major complication if it remains after treatment ends.
Stress Fractures/Fractures
Stress fractures and fractures can occur during treatment or following frame removal. The use of half-pins in neuropathic patients can increase the risk of this complication [9]. If this occurs during the treatment course, it is necessary to return to the operating room to extend the frame or increase the stability of the external fixation (Fig. 30.5). If this occurs following frame removal and the fracture is non-displaced, cast immobilization can be utilized. Most often, this does not affect the final result as long as the fracture heals. However, it is important to adhere to proper principles of building a stable frame to reduce the stress placed on the lower extremity. The authors recommend the use of all wire fixation and avoiding fixation in the isthmus of the tibia in patients whenever possible. The tibial ring block fixation should be utilized to diminish the amount of stress placed on the fixation.
Fig. 30.5
Tibial diaphyseal fracture in a neuropathic patient (a), which required modification of external fixator for reduction and stabilization (b) (Reprinted with permission from the Rubin Institute for Advanced Orthopedics, Sinai Hospital of Baltimore)
Classification of Stress Fracture/Fracture
Problem—Intraoperative stress fracture/fracture noted. Frame bridged across the fracture to stabilize.
Obstacle—Postoperative stress fracture/fracture necessitates return to surgery for modification of frame to bridge and stabilize fracture. Fracture healing does not prolong treatment course.
Complication—Stress fracture/fracture after removal of external fixator that necessitates return to surgery for fixation or further immobilization in cast. This is a minor complication if the fracture heals without residual functional loss. This is a major complication if results in residual deformity or loss of function.
Joint Subluxation
Subluxation or dislocation of the ankle joint or metatarsophalangeal (MTP) joint can be seen with gradual correction of ankle equinus (Fig. 30.6) and gradual lengthening of the metatarsals for brachymetatarsia, respectively. This adverse result is due to preexisting muscle imbalance, joint incongruity, or improper external fixation construct. In order to prevent joint subluxation/dislocation, it is important to plan for this preoperatively. Correctly applying hinges at the axis of ankle joint motion and using two points of fixation in the talus will maintain ankle joint congruity while gradually correcting for equinus deformity. Relocation of the MTP joint and bridging of the external fixator across the MTP joint to the digit allows for maintenance of alignment during lengthening of the metatarsal. Pinning of the MTP joint with a Kirschner wire to maintain alignment has also been described, but in our experience, this causes a great amount of joint stiffness once the pin is removed. Treatment options for joint subluxation include physiotherapy, splinting, adjustment/modification of external fixation, revision surgery, decreasing the distraction rate, and isolated capsular release [7].
