Bradley M. Lamm, Shine John, John E. Herzenberg, and Dror Paley
BACKGROUND
Ankle arthrodesis remains the gold standard for ankle arthritis.
Ankle arthrodesis is indicated for painful arthroses, instability, malalignment, and joint sepsis.
Regardless of the method of arthrodesis, complications are not uncommon and include nonunion, malunion, infection, osteoarthrosis of contiguous joints, neurovascular injury, wound healing issues, and limb-length discrepancy.6
Rates of nonunion and other complications alone have been reported to be as high as 30% and 60%, respectively.
Malunion may be among the most consequential and detrimental complications because of its effect on functional outcome.
Sequelae of a malaligned ankle arthrodesis include subtalar degeneration, reduced foot flexibility, compensatory foot deformities, and pain with ambulation. Correction of malaligned ankle fusion is thus critical to preserve the functional mobility of neighboring joints.
Revision of a malaligned ankle arthrodesis can be both technically demanding and traumatic to previously operated bone and soft tissue.
Preservation of compromised soft tissue structures, including the periosteum, is also a critical consideration when revising the failed ankle arthrodesis.
The amount of bone resection required to obtain apposition of viable bony surfaces can create an even greater limblength discrepancy (larger than the expected 1 cm).
Malunion ankle deformities are typically multiplanar and therefore are not easily corrected acutely.
The literature is sparse in regard to rates and management of the malpositioned ankle fusion. At our institution, we address these complex deformities through a minimally invasive osteotomy with gradual external fixation correction.
In addition to presenting our technique and results, we will objectively define the optimal clinical and radiographic position for an ankle realignment arthrodesis.7,10
SURGICAL MANAGEMENT
Our minimally invasive technique uses a four-incision percutaneous Gigli saw osteotomy with gradual external fixation correction of the ankle malunion.
The subperiosteal Gigli saw osteotomy through a prior malaligned fusion site limits soft tissue compromise while optimizing soft tissue and bone healing.
External fixation provides gradual accurate multiplanar (rotation, angulation, and translation) realignment, while simultaneously correcting limb length. In addition, obtaining proper alignment of an ankle fusion is paramount.
Positioning
Under general anesthesia, the patient is positioned supine on the radiolucent table with an ipsilateral hip bump so as to place the foot in a foot-forward position.
A nonsterile thigh tourniquet is placed, and sterile prep of the entire leg to the level of the tourniquet is performed.
Under video fluoroscopy, a marking pen is used to indicate the desired level of the osteotomy on both the anteroposterior (AP) and lateral views. The thigh tourniquet is then inflated.
TECHNIQUES
PERCUTANEOUS OSTEOTOMY
The first incision is made transversely, just medial to the tibialis anterior tendon (TECH FIG 1A–C).
Subperiosteal dissection with a periosteal elevator is performed across the anterior tibia.
This subperiosteal dissection creates a subperiosteal tunnel that protects the tendons and neurovascular bundle along the anterior aspect of the ankle.
Along the desired level of the osteotomy, the periosteal elevator is then maneuvered in a rocking motion against the bone and across the entire anterior ankle to the lateral aspect of the ankle malunion.
A vertical second incision is made where the skin is tented by the extension of the periosteal elevator, and the elevator is removed.
A no. 2 Ethibond suture is clasped with a curved tonsil hemostat and passed through the previously created subperiosteal tunnel from the medial incision to the lateral incision (TECH FIG 1D).
Once the suture is passed, the Gigli saw is tied to the suture and also pulled from medial to lateral through the same subperiosteal tunnel (TECH FIG 1E).
The position of the Gigli saw is then checked by image intensifier to ensure that the desired level of osteotomy has been properly maintained.
Through the lateral incision, the periosteal elevator is passed posterior subperiosteally to exit just on the posterolateral corner of the ankle malunion.
A vertical third incision is made posterolaterally, where the elevator tents the skin (TECH FIG 1F).
The curved tonsil is then passed subperiosteally from the third incision to the second incision to clasp the Ethibond suture, and the suture with the Gigli saw is passed through the third incision (TECH FIG 1G).
Again the elevator is extended from the third incision subperiosteally posterior to the ankle malunion deep to the flexor tendons to exit medially at the level just anterior to the posterior tibialis tendon (TECH FIG 1H).
A transverse fourth incision is made where the elevator tents the medial skin.
From the fourth incision to the third incision, the curved tonsil is used to grasp the suture attached to the Gigli saw and pull them through the fourth incision.
The Gigli saw is now circumferentially around the ankle malunion (TECH FIG 1I).
Care must be taken during the passage of the Gigli saw to maintain the correct level of the planned osteotomy.
The two Gigli saw handles are now attached, and, using a reciprocating motion, the ankle is cut from lateral to medial.
To avoid injury to the medial skin, cutting is stopped just before the medial bone is exited, a periosteal elevator is placed between the fourth and first incisions crossing the Gigli saw, and then the cut is continued (TECH FIG 1J).
When the cut is complete, the elevator will block further progression of the saw, thereby preventing medial soft tissue damage (TECH FIG 1K,L).
The completion of the osteotomy is confirmed with the image intensifier.
Then the Gigli saw is cut and removed (TECH FIG 1M,N).
The tourniquet is deflated, and the incisions are closed.
TECH FIG 1 • Percutaneous Gigli saw osteotomy of a malunited ankle arthrodesis. A. A Gigli saw can be passed percutaneously at the level of a previous ankle fusion. Four small incisions are used to pass the saw: two longitudinal medial and two transverse lateral incisions. B.Because of the square-shaped fusion mass, four incisions are used to safely pass the Gigli saw. The Gigli saw is passed subperiosteally starting anteromedial (1) and ending posteromedial (4). C. The medial longitudinal incision (1) is made just medial to the tibialis anterior tendon. Through the anterior medial incision, a periosteal elevator is passed subperiosteally across the anterior aspect of the fusion mass at the desired level. D. The second incision, which is transverse lateral (2), is made where the periosteal elevator tents the lateral skin. A suture is passed through the same subperiosteal tunnel from medial to lateral (the reverse can also be done). E. The suture with the attached Gigli saw is passed from medial to lateral anterior to the ankle fusion mass. F. Through the second incision, the lateral periosteum is elevated, and a third incision is made posterolateral (3). G. The suture and attached Gigli saw are passed through the third incision. H. The posterior periosteum is elevated. Care must be taken to avoid extra periosteal dissection. I. A fourth incision is made at the posterior medial corner of the ankle fusion mass. The suture and Gigli saw are passed around the malunited ankle fusion. Care must be taken to protect the peroneal tendons as the Gigli saw is being passed from the third to fourth incision. J. The medial periosteum is then elevated from the fourth incision to the first incision. K. The Gigli saw osteotomy is performed halfway through the fusion mass. L. The periosteal elevator is then inserted in the previously created tunnel, crossing the Gigli saw so as to protect the medial soft tissues. M. The osteotomy is completed. N. The Gigli saw is cut and removed. (Copyright 2008, Rubin Institute for Advanced Orthopedics, Sinai Hospital of Baltimore.)
EXTERNAL FIXATION APPLICATION
The tourniquet is inflated only while passing the Gigli saw but is released before the fixator application.
External fixation allows for gradual correction of deformity and lengthening, which can be accomplished by using the Ilizarov external fixator or the Taylor spatial frame (TECH FIG 2).
The frame is built according to the deformity, with the proximal fixation block fixing the tibia and the distal fixation block fixing the talus, calcaneus, and foot.
The goal is to achieve stable fixation proximal and distal to the osteotomy.
Smooth wire (1.8 mm) or half-pin (6 mm) fixation is used per the surgeon's preference.
The proximal ring is mounted perpendicular to the tibia in both the AP and lateral fluoroscopic views.
The distal ring is mounted parallel to the plantar aspect of the foot. By using this mounting technique, at the end of correction, the foot and tibial rings will be parallel, confirming a plantigrade foot position.
The proximal ring (full ring) is mounted on a lateralto-medial smooth wire crossing the distal tibia perpendicular to the AP long axis of the tibia and tensioned.
Then an anterior half-pin (6 mm) is inserted on this ring and two additional half-pins are inserted proximal or distal in a delta fashion. These half pins are placed perpendicular to the tibia in the sagittal plane.
The foot ring is fixed in place with 1.8-mm tensioned smooth wires (two crossing calcaneal wires, two talar wires, and two forefoot wires) parallel to the plantar aspect of the foot.
A foot board (an intraoperative rigid board that stimulates weight bearing) is used to ensure a plantigrade foot ring mounting.
An oblique (posterolateral to anteromedial) talar wire and medial to lateral talar wires are placed for increased stability.
Occasionally talar half-pins are used. Distraction of the subtalar joint is performed by rotating both talar wire fixation bolts using the Russian technique.
The Russian tensioning technique provides compression of the osteotomy site by pushing proximally on the talus.
Six struts are added between the distal tibial and foot rings to complete the Taylor spatial frame.
Computer planning on an Internet-based program is then performed, which generates a daily patient turn schedule.
Patients are followed biweekly during the gradual correction to ensure accurate final realignment.
TECH FIG 2 • A. Lateral intraoperative radiographic view shows a malunion of the ankle (equinus of 15 degrees and the foot anteriorly translated) in an adult patient. The Gigli saw has been passed at the level of the ankle malunion. B. Lateral radiographic view showing opening posterior wedge of regenerate bone formation and posterior translation of the foot during distraction treatment with the Taylor spatial frame. (Copyright 2008, Rubin Institute for Advanced Orthopedics, Sinai Hospital of Baltimore.)
OUTCOMES
The subperiosteal Gigli saw osteotomy through a prior malaligned fusion site limits soft tissue compromise while optimizing soft tissue and bone healing.
External fixation provides gradual accurate multiplanar (rotation, angulation, and translation) realignment, while simultaneously correcting limb length.
In addition, obtaining proper alignment of an ankle fusion is paramount (FIG 1).
Using this technique we have successfully realigned more than a dozen of these ankle malunions.
COMPLICATIONS
Complications can occur (pin site infection, residual leg-length discrepancy, wound problems, premature or delayed consolidation, tarsal tunnel syndrome, and pin failure).
FIG 1 • Final weight-bearing AP radiographic view of the patient in Techniques Figure 2 shows full correction of the equinus deformity. (Copyright 2008, Rubin Institute for Advanced Orthopedics, Sinai Hospital of Baltimore.)
A well-aligned ankle arthrodesis with a plantigrade foot was achieved in all patients using the described technique.
Therefore, patients with a malunited ankle fusion, with or without a limb-length discrepancy, can be successfully treated with minimally invasive Gigli saw osteotomy and gradual external fixation correction.
ACKNOWLEDGMENTS
The authors thank Joy Marlowe, MA, for her excellent illustrative artwork, and Alvien Lee for his photographic expertise.
REFERENCES
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