Stepwise Approach to Midfoot and Hindfoot Elective and Reconstructive Surgery with External Fixation

John J. Stapleton

Thomas Zgonis

Introduction

External fixation for elective and reconstructive arthrodesis of the midfoot and hindfoot offers a versatile alternative when internal fixation is not feasible. The utilization of circular external fixation with transosseous smooth wires provides increased stability with compression of the desired osteotomy and/or joint(s) to achieve bone healing while allowing immediate partial or full weight bearing status in certain cases. The inherent stabilization provided with external fixation is also advantageous in preventing of internal fixation failure when used in combination. This chapter focuses on the technical aspects of appropriately applying a circular external fixation construct and utilizing the pre-bent transosseous wire technique for continuous compression across a single or multiple midfoot and/or hindfoot joint(s). This technique has improved the surgeon’s ability to correct severe multiplane foot deformities and address primary or posttraumatic arthritic joints. High-risk patients with multiple comorbidities or local characteristics that increase the likelihood of failed internal fixation, malunion, nonunion, and/or deep infection may benefit from the utilization of advanced circular external fixation techniques.

Indications/Contraindications

External fixation for elective midfoot and hindfoot arthrodesis has shown prevalence among surgeons treating patients with end-stage arthritic conditions and deformities that are further complicated with severe osteoporotic bone, bone deficiency, and/or poor soft tissue envelope. The main indications for selecting external fixation in these conditions may include and are not limited to osteoporosis, segmental bone loss, chronic osteomyelitis, Charcot neuroarthropathy (CN), previous ulcerations, and complicated failed arthrodesis.

Poor bone stock and osteoporosis pose obvious challenges when internal fixation is utilized. In patients with severe disuse and osteopenia, internal screw purchase may not be adequate to ensure osseous healing at the arthrodesis site and nonunion may result. Circular external fixation with transosseous wire compression and stabilization is indicated as an alternative to screw fixation since it is not dependent on the structural integrity of the osteoporotic bone. Half pins utilized with uniplane monolateral external fixation constructs are advantageous for certain conditions but are not usually chosen for patients with severe osteoporosis since stability is dependent on the cortical integrity. Half pins are commonly combined with transosseous wires in hybrid or circular external fixation constructs to provide adequate stability in this patient population.

Segmental bone loss in the midfoot and hindfoot can be quite challenging and various external fixation constructs can be utilized that are typically procedure dependent. Delta and uniplane monolateral external fixation configurations are usually utilized to stabilize the foot and ankle while maintaining length to the area of bone loss. Large structural bone grafts may also be required to manage the osseous defects in the midfoot and hindfoot and the time frame for these defects to heal may be prolonged in certain cases. The utilization of combined external with internal fixation is advantageous for these case scenarios in order to prevent hardware failure, osseous collapse, or malpositioning of the structural bone graft. Circular external fixation constructs are usually utilized to perform shortening and primary arthrodesis of the midfoot and hindfoot when structural bone grafting with internal fixation is not performed. The capability of stabilizing a difficult-to-heal arthrodesis may be accomplished with a multiplane circular external fixator as opposed to a delta or unilplane monolateral external fixator.

Elective midfoot and hindfoot arthrodesis to salvage chronic infected nonunions with osteomyelitis is another indication for external fixation. All necrotic and infected bone is surgically debrided or resected and an external fixator is utilized to stabilize the arthrodesis while avoiding the inherent risk of persistent infection with internal fixation. Retained fixation in these cases can present as a nidus for chronic deep infections and loosening of the hardware is likely to develop. External fixation may also be indicated in these reconstructive cases since the soft tissue envelope is usually compromised and may limit an open extensive surgical incisional approach.

Other indications for external fixation in midfoot and hindfoot elective and reconstructive cases include diabetic patients with CN. Surgical intervention is usually required in patients who present with an unstable deformity or ulceration. In patients in whom the ulcer remains open at the time of surgical reconstruction, internal fixation is relatively contraindicated. Typically, the ulcer is surgically excised and cultures are obtained to guide appropriate antibiotic therapy. External fixation can be utilized to perform corrective joint alignment and arthrodesis after resection of any osseous prominences. Circular external fixation can also further stabilize the lower extremity to prevent an equinus deformity while simultaneously compressing the midfoot and/or hindfoot arthrodesis sites.

External fixation is also indicated in previous failed attempted midfoot and hindfoot arthrodesis sites with internal fixation. Any retained internal fixation or broken hardware are surgically removed, the joints are prepared again with or without the use of bone grafting and external fixation is utilized for providing progressive compression until osseous healing is present. External fixation will also allow for early protective partial weight bearing status in selected patients without dense peripheral neuropathy.

Severe arterial insufficiency not amenable to revascularization is a contraindication to elective midfoot and hindfoot arthrodesis with circular external fixation. Poor edema control as a result of venous insufficiency or lymphedema may need to be addressed prior to these types of procedures with external fixation. The utilization of a wound care team or lymphedema clinic is beneficial on providing edema control and patient education to prevent any soft tissue compromise during the external fixation utilization.

Chronic smoking, recreational drugs and severe alcohol abuse may have a major effect on wound and osseous healing. Smoking cessation programs and counseling may be required before these types of surgery along with a patient and family understanding of prompt compliance with treatment throughout the patient’s recovery.

Preoperative Considerations

A detailed history, physical examination, gait analysis and necessary laboratory, radiographic and medical imaging are necessary during the preoperative period. Plain weight bearing radiographic views of the foot, ankle, and lower extremity are needed in order to evaluate for any deformity. Computed tomography may demonstrate extensive bone destruction and malalignment and its utilization is beneficial for surgical planning of complex nonunions, diseased bone, and broken hardware. Nuclear imaging and magnetic resonance imaging are useful to determine if a deep infection and osteomyelitis is present. If osteomyelitis is presumed, then intraoperative bone biopsy and cultures may need to be obtained to guide not only the antibiotic therapy but also the staging of reconstructive procedures required to perform a successful midfoot and hindfoot arthrodesis.

Elective and reconstructive cases in the diabetic population require optimum glycemic control by the internist and/or endocrinologist before and after the surgical procedure. Hyperglycemia may have significant effects in delaying osseous and wound healing. In addition, any vascular testing abnormalities may necessitate a vascular surgery consultation and intervention if necessary.

External fixation in rheumatoid patients will also require medical and rheumatology consultations to further address the poor bone quality, antirheumatic pharmacologic use, and anesthesia precautions. Wound and osseous complications may also be increased in this patient population and external fixation offers an alternative method for compression and stabilization across the midfoot and hindfoot joints.

Detailed Surgical Technique

Circular External Fixation for Midfoot and/or Hindfoot Arthrodesis

After the selected joints are prepared for arthrodesis, provisional fixation with Steinmann pins maintains the necessary alignment across the joint(s) until the external fixator can be applied. A static circular external fixation construct that consists of one or two tibia rings with a foot plate can be utilized for the majority of midfoot and hindfoot arthrodesis. If one tibia ring is to be utilized, the ring is positioned 10 to 15 cm proximal to the ankle joint and is secured with two crossing smooth wires and/or additional half-pins for further stability. Once the half-pins are inserted, the transosseous smooth wires can then be tensioned to approximately 110 to 130 kg of force. A second tibia ring with two crossing smooth wires can be placed as an alternative to the half-pins. A foot plate should then be placed slightly superior to the plantar surface of the foot if early weight bearing will be permitted after the surgery. The foot plate is connected to the tibial block with threaded rods and/or hinges. At this time, the calcaneus is stabilized with two opposing olive wires that are usually tensioned between 70 and 90 kg of force unless the bone is very osteopenic in which case the olive wires are tensioned or tightened manually. It is imperative that a surgical assistant maintains the foot in a neutral position during this portion of the procedure in order to avoid an iatrogenic equinus deformity within the external fixator.

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