Tips for performing MIS beaming for Charcot foot reconstruction
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Charcot foot arthropathy is a complex disease process that most often presents in patients with diabetes who have severely compromised perfusion and sensory feedback.
The combination of poor-quality bone and repetitive microtrauma can lead to significant midfoot, hindfoot and ankle deformity resulting in increased loads in plantar weight-bearing surfaces (Figures 1 and 2). The development of soft tissue ulcers and infection is often the sequela of this insidious process. The mainstay of nonoperative treatment is to achieve a plantigrade foot through which weight-bearing can be performed using total contact casts, commercially available diabetic controlled ankle motion (CAM) boots and/or custom Charcot restraint orthotic walker boots. When nonoperative treatment fails with progression of deformity, surgical reconstruction is recommended to restore the bony alignment and redistribute loads to normal weight-bearing plantar structures.
Source: Justin C. Haghverdian, MD; and Andrew R. Hsu, MD
Traditional surgical reconstruction for Charcot foot is often done through large, open, medial approaches, requiring extensive soft tissue dissection, bony resection and plates and screws to maintain deformity correction. For patients who have active infection, ulceration or cannot tolerate the morbidity of extensive dissection, circular static ring fixation is an alternative treatment strategy. Although circular ring fixation is a powerful correction tool, it necessitates specialized surgical technique, reliable patient compliance with frame maintenance and frequent follow-up appointments, which are often not feasible. Unfortunately, high infection and wound complication rates are often reported in the literature with traditional open Charcot foot surgery.
In recent years, minimally invasive surgical techniques in foot and ankle reconstruction have gained consistent interest. The use of low-speed, high-torque burrs cooled with saline are employed in a variety of foot and ankle procedures, such as cheilectomy, bunion correction, calcaneus osteotomy and now fusion procedures. Advancements in technique and instrumentation have allowed for percutaneously performed bony correction and arthrodesis safely and reproducibly, especially in high-risk diabetic cases.
New MIS techniques have recently emerged in Charcot foot reconstruction that combines percutaneous deformity correction and fusion with intramedullary beaming to restore coronal and sagittal alignment with significantly reduced soft tissue dissection. Similar to MIS bunion surgery, a steep learning curve is involved with MIS Charcot foot surgery, with a case volume of 20 to 40 as an approximate number to become proficient. In this article, we present surgical tips and tricks for performing MIS Charcot foot beaming.
Surgical technique
The patient is brought to the OR and placed supine on a regular radiolucent table. The foot is positioned off the end of the bed to allow for sufficient space for the mini-C arm image intensifier, axial alignment views and placement of subtalar screws (Figure 3). A small bump is placed under the hip of the operative extremity to maintain neutral foot alignment. A nonsterile tourniquet is applied at the level of the thigh. The extremity is positioned over a foam leg ramp ensuring that the foot hangs freely and out of the way of the contralateral extremity.
The mini-C arm is wrapped in several layers of Coban (3M) so the foot can be securely positioned on the receiver of the image intensifier. The surgeon is seated so one foot can operate the burr pedal while the other can simultaneously run the mini-C arm pedal (Figure 4).
In the first steps of Charcot foot reconstruction, the Achilles tendon is assessed for contracture, which is often a contributing factor of midfoot and hindfoot collapse. A percutaneous Achilles tendon lengthening is performed using three separate hemi-section stab incisions spaced 2 cm apart and closed with 3-0 nylon sutures.
Under fluoroscopic guidance, a small K-wire is used to mark out the subtalar, talonavicular and midfoot joints along with the longitudinal axis of the medial column. In Charcot foot deformity, the midfoot tarsometatarsal joints are often abducted and dorsiflexed resulting in a rocker bottom foot with plantar ulceration due to cuboid collapse. Similar collapse often occurs at the talonavicular joint with navicular fragmentation. For rigid deformities, the apex of the midfoot and hindfoot deformity is identified and a biplanar osteotomy is planned. The biplanar osteotomy consists of a medial-based closing wedge osteotomy and a dorsal-based plantarflexion osteotomy to achieve a plantigrade foot.
Separate 5-mm dorsal, medial and longitudinal stab incisions are made using an 11-blade knife or Beaver blade centered over the apex of the deformity. Soft tissue dissection is performed down to bone using a small hemostat and periosteal elevator. The MIS fusion burrs (3 mm or 4 mm; PROstep MIS Console, Stryker) are introduced through the incisions and the osteotomies are performed such that the cut converges laterally and dorsally, and the limbs of the osteotomy are perpendicular to the long axis of the medial column.
Some surgeons may find it helpful to place two K-wires from medial to lateral under fluoroscopic guidance to assist as a cutting guide and reference. The burrs are continuously run, and the osteotomy is complete once the bone is turned into a paste-like material and the midfoot-hindfoot can be manually manipulated and reduced.
Next, a separate 5-mm incision is made over the talonavicular joint. A straight burr is used to denude the remaining cartilage and prepare the talonavicular joint for arthrodesis. With involvement of the peri-navicular joints, a talonavicular arthrodesis is supplemented with a subtalar arthrodesis to increase construct stability. Through a separate stab incision centered over the posterior facet of the subtalar joint on the lateral aspect of the foot, the burr is introduced and the subtalar joint is denuded of remaining cartilage and confirmed on multiple fluoroscopic views. The cartilage and bone debris is flushed out with normal saline using an angiocath or 18 gauge needle and syringe. Injectable bone allograft (Augment, Stryker) can then be used through the stab incisions to assist with bony healing and fusion. Radiopaque bone grafts are particularly useful in MIS fusion procedures as their location of delivery can be visualized on fluoroscopy to ensure proper placement.
Guidewires are then placed across the subtalar joint, over-drilled and one or two 7-mm fully threaded beams (Salvation Fusion Bolts and Beams, Stryker) are placed to secure the subtalar fusion (Figure 5). Multiple axial foot, lateral foot and anteroposterior ankle views are checked to ensure the subtalar screw(s) are central and fully contained within bone. The decision to place the subtalar or medial column beams first depends on individual patient deformity correction and surgeon preference.
Next, the medial column is prepared for reduction and fixation. If adequate adduction and plantarflexion of the medial column cannot be performed, separate lateral stab incisions are made to further burr and free up the bony deformity. A stab incision is then made over the lateral aspect of the calcaneocuboid joint and a straight burr is used to remove the remaining cartilage. Next, a 7-mm fully threaded beam is inserted in a retrograde fashion beginning at the base of the fourth metatarsal and driven across the calcaneocuboid joint into the lateral body of the calcaneus (Figures 6 and 7). A separate, more plantar stab incision can be used with the burr to remove any residual plantar exostosis along the plantar aspect of the cuboid.
A 5-mm stab incision is then made over the plantar aspect of the hallux metatarsophalangeal (MTP) joint. Compared with traditional dorsal MTP joint incisions, we have found that small plantar MTP stab incisions require less soft tissue dissection and joint manipulation and allow for a more direct path along the longitudinal axis of the medial column. The hallux is held in slight dorsiflexion, while the guidewire for the 7-mm fully threaded beam is placed in a retrograde fashion from the head of first metatarsal to the back of the talus to maximize construct length. The medial column is held in a reduced position using plantar and medial manual manipulation while the medial column is over-drilled, and the 7-mm beam is inserted to compress the osteotomy and fusion sites (Figures 6 and 8). The result is creation of a “power triangle” of the medial column, subtalar joint and lateral column for maximal construct strength and stability.
An additional beam can be inserted through the second MTP joint across the midfoot into the talus if there is enough bony space and if the second metatarsal is aligned with the axis of the talus. Alternatively, partially threaded 7-mm beams or solid 5-mm vs. 6.5-mm bolts can be used in place of or in addition to the 7-mm fully threaded beams based on surgeon preference. It is our preference to use 7-mm fully threaded beams across all the osteotomy and fusion sites to maximize bony purchase and prevent beam migration.
The stab incisions are then thoroughly irrigated to remove any remaining bone paste and closed with 3-0 nylon mattress sutures (Figures 9 to 11). The incisions are covered in a well-padded soft dressing followed by a posterior mold splint in neutral dorsiflexion.
Postoperative protocol
Postoperatively, patients are made non-weight-bearing in a short-leg splint for 2 weeks. Sutures are removed 2 to 4 weeks after surgery depending on soft tissue healing and swelling, and radiographs are obtained (Figures 12 and 13).
Patients are then transitioned to a tall diabetic CAM boot and made non-weightbearing for 8 weeks after surgery. When there are signs of fusion on follow-up radiographs, progressive weight-bearing is then initiated in the CAM boot from weeks 8 to 14 followed by gradual transition to a supportive diabetic shoe with arch support insole.
Conclusion
MIS techniques in foot and ankle surgery continue to evolve from forefoot to midfoot, hindfoot and ankle procedures. The risk of soft tissue complications with traditional open Charcot foot reconstruction is high and infection and wound dehiscence are common complications. With low-speed, high-torque burrs, percutaneous deformity correction can be achieved along with intramedullary beaming for Charcot foot reconstruction. In carefully selected patients without active infection and sufficient bone stock, MIS correction can provide a significant clinical improvement from a soft tissue perspective while still maximizing construct stability.
We believe MIS Charcot foot and ankle reconstruction will continue to develop and progress to a new potential standard of care similar to MIS bunion surgery as techniques and clinical studies continue in the future.
Technical tips
- Position the patient with the foot off the end of the bed, allowing for placement of the foot onto the Coban wrapped detector of the mini-C arm.
- Percutaneous Achilles tendon lengthening assists with deformity correction and achieving a plantigrade foot.
- Carefully mark out the planned burr entry locations, joint surfaces and osteotomy site at the apex of the deformity using fluoroscopy.
- For deformities that are not reducible after performing the biplanar osteotomy, consider addressing the lateral column though additional stab incisions. If the lateral column is not addressed with a beam across the calcaneocuboid joint, a second beam can be placed through the second MTP joint in addition to the medial column beam.
- Radiopaque injectable bone grafts are particularly useful to visualize correct graft placement.
- Plantar hallux and second MTP stab incisions for beam placement allow for a more direct path of the beam across the medial column into the talus.
- Beams are placed across the subtalar joint, medial column and calcaneocuboid joint to create a “power triangle” configuration to maximize construct stability.
- References:
- Jones CP. Foot Ankle Int. 2015;doi:10.1177/1071100715588637.
- Lausé GE, et al. J Am Acad Orthop Surg. 2023;doi:10.5435/JAAOS-D-22-00608.
- Miller R. Foot Ankle Clin. 2022;doi10.1016/j.fcl.2022.05.001.
- Miller RJ. Foot Ankle Clin. 2016;doi:10.1016/j.fcl.2016.04.012.
- Pinzur MS. J Am Acad Orthop Surg. 2023;doi:10.5435/JAAOS-D-22-00365.
- For more information:
- Justin C. Haghverdian, MD, and Andrew R. Hsu, MD, can be reached at the department of orthopedic surgery at the University of California-Irvine in Orange, California. Hsu’s email: hsuar@hs.uci.edu.
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