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Use of a Magnetic Intramedullary Nail for TTC Arthrodesis
Editors’ Note: Please note that the authors describe certain off-label approaches in this piece, which they disclose in the body of the article.
The primary goal of a tibiotalocalcaneal (TTC) joint fusion is to alleviate pain, eliminate deformity, and provide a stable and functional foot and ankle complex. Overall, we have found the procedure has shown promising outcomes in terms of pain reduction, improvement in function, and patient satisfaction in a definitive, durable, and lasting way. Success rates vary depending on the specific surgical technique, patient characteristics, and the underlying condition being treated. This procedure has been used to treat a multitude of conditions such as end-stage osteoarthritis, post-traumatic arthritis, acute ankle fragility fractures, avascular necrosis, Charcot neuroarthropathy, and after failed primary ankle fusion and total ankle arthroplasty.1
The procedure was first described in the 1970s as an open procedure and the 1980s brought its description arthroscopically. It is generally accepted as a successful procedure with published studies showing high union rates ranging from 86 to 100%.2
Regardless of fixation choices, TTC joint fusion may result in some degree of shortening and an often-predictable limb length discrepancy. The amount of shortening can vary depending on the preoperative condition, the extent of deformity correction and bone loss, and the surgical technique employed. Studies have reported an average shortening ranging from a few millimeters to approximately 2 cm.3 In some instances, for example, it may be necessary to remove the talus and backfill the resultant defect to prevent overshortening.
Another alternative, which we will present here, is a single-staged approach with docking fusions and lengthening over a nail (LON). We also present another concept, compression-lengthening over nail (C-LON), previously not possible within the hindfoot nail market of devices. We aim to introduce a magnetic intramedullary nail (MIN) technique to obtain TTC fusion in the ankle and hindfoot when retrograde hindfoot nailing is indicated.
A limb length discrepancy may lead to significant gait abnormalities, although the extent of its impact will vary based on the amount of discrepancy and the patient's adaptability. It is also important to mention that a purposeful small limb length discrepancy is desirable in order to assist the fused ankle and hindfoot through the swing phase of gait when normal dorsiflexory ankle movement is not possible.
In a recent retrospective radiographic analysis, authors evaluated the change in height following TTC fusion in patients with Charcot, arthritis, and pes planus conditions. They found the Charcot group had an average change in height of -12.0mm anteriorly and -7.6mm posteriorly. The arthritis group had an average change of -6.9 mm anteriorly and -3.8 mm posteriorly. The pes planus interestingly had an average increase in height of +0.5 mm anteriorly and +2.9mm posteriorly after correcting the deformity.3
The technical aspect of how to perform a TTC fusion has been described via a multitude of approaches. We highlight the utility of the lateral trans-fibular approach to the ankle joint with detachment and morselization of the distal fibula for autografting. In addition to the various surgical techniques, there are also various options in terms of fixation. Internal fixation with screws, plates, staples, and procedure specific retrograde intramedullary nails have been described as well as external fixation. It is also fairly well accepted that a combination of internal and external fixation may be helpful, especially in patients with neuropathy or obesity, or when non-adherence is suspected. In addition, external fixation has been utilized when concurrent lengthening is indicated during a fusion case. In a systematic review, the average union rate following open fusion techniques was 89%, with a range of 64–100%, and arthroscopic fusion was 94% with a range of 70–100%.4
Various forms of retrograde intramedullary fixation exist, including both static and dynamic nails. A multitude of nail shapes, other than straight, have also been proposed in order to best match the anatomy (valgus bend nails) or improve biomechanical strength (posterior bend nails).
Insights on the Magnetic Dynamic Nail
Our presentation focuses on a magnetic dynamic nail, which differs in mechanical properties and its unique ability to compress or lengthen up to several centimeters as per the surgeon’s discretion. We propose that this unique intra- and postoperative ability will positively affect union rates. The time to union and union rates contrast between nails according to studies and literature review. Please add references It is known that dynamic intramedullary nails allow for some continued compression across the arthrodesis site as fusions remodel. This is difficult to measure and determine quantitatively and is generally something that “runs out” as the elastic memory metals which provide the benefit eventually have no further elasticity to compress with.
Further complicating this evaluation is that the elastic compressive element runs out during the perioperative period in my experience. Ideally, a positive compressive environment is maintained up until arthrodesis is achieved but this is nearly impossible to guarantee in any predictable fashion with semi-elastic metals. A question exists as to whether the time to union and union rate of the ankle joint is superior in the dynamic nails versus static nails. Both types of intramedullary nail options have shown advantages in biomechanical properties compared to other methods for ankle arthrodesis due to the load sharing characteristics if IM nailing in long bones.5 This is secondary to their increased load sharing, bending stiffness, rotational stability, and ability to achieve compression and stability due to large areas of cortical contact.
Static locking of an intramedullary nail is said to resist natural compression of the fusion site as the bone remodels. Several authors have presented that dynamically locking the proximal end of a retrograde TTC nail allows for both rotational stability at the fusion site and axial compression.6
A study by Dujela and colleagues compared two groups of 30 patients, one static and one dynamic nail group with similar body mass indices (BMIs).7 Results revealed a mean time to fusion in the static group was 111.6 days versus 97.2 days in the dynamic group. The static group had a union rate of 83.3% and nonunion rate of 16.6% while the dynamic group had a union rate of 86.6% and nonunion rate of 13.3%. All reported nonunions were asymptomatic.
We propose a novel technique using a magnetic intramedullary nail and present our case series of 10 patients. This nail was initially designed for femoral and tibial lengthening cases and in more recent years has been described in retrograde rearfoot and ankle cases. The innate ability of this nail to compress and lengthen allows for our innovative, compression-lengthening over nail (C-LON) technique to apply active, dynamic compression/distraction during the initial and postoperative period following placement.
Unlike the nitinol nail offerings that allow less predictable compression following implantation, we present a calculated postoperative protocol that we believe may have an effect on the arthrodesis site's ability to consolidate robustly. Research has shown retrograde TTC intermetatarsal nails have a high limb salvage rate of over 88% across a variety of indications and comorbidities.8 Diabetes has been shown to carry the most notable risk factor for amputation, followed by revision surgery, ulcer preoperatively, and age.8
Given the risks associated with a failed surgery and the relatively high risk for major amputation following this procedure, we propose an innovative, although currently off-label approach, to advance the medicine and research with retrograde hindfoot intramedullary nailing. Additionally, based on our experience, we believe that an osteotomy with secondary bone healing immediately adjacent to an arthrodesis with internal fixation and primary bone healing may create an environment of osseous healing synergistically more powerful than either alone. This is currently only a hypothesis, but likely warrants focused dedicated research.
A Closer Look at the Surgical Technique
Patients are placed supine on the OR table with an ipsilateral hip bump to internally rotate their operative limb, as well as blankets beneath the limb to avoid radiographic interference when obtaining intraoperative lateral X-rays.
A lateral curvilinear incisional approach is utilized to take down the fibula, which is later morselized and used as an autograft. The ankle joint and subtalar joint are exposed and distracted, and denuded of cartilage using osteotomes, curettes, and rasps. The fusion site is irrigated and fenestrated. Additional adjuvants to the fusion sites include biologics (rh-BMP2) and autogenous bone.
After provisional fixation with guide pins and once optimal positioning is obtained, a linear incision is made on the plantar heel to allow for the guide wire and tissue protector for the intramedullary nail (IMN). The guidewire is oriented anterior to the weight-bearing surface of the calcaneus superiorly in line with the tibia anatomic axis and the calcaneus is medialized to reduce the foot under the leg.
Prior to advancing the guidewire, in cases where lengthening was performed, the location for the osteotomy was chosen in the distal tibia about 6–10 cm proximal to the plafond. We follow the technique put forth by Paley and colleagues.9 The osteotomy is performed by creating multiple drill hotels with a 3.5 mm drill bit through the anterior tibia and then completed carefully with a 6 or 8 mm osteotome.
Next, the wire is advanced and sequentially reamed for placement of the IMN. The authors routinely ream 1.5 to 2 mm over the outer diameter of the chosen nail. The jig system is utilized and two proximal locking bolts are placed through the nail in the proximal tibia. Manual compression is placed across the heel and then 2 distal locking screws are placed with jig assistance across the calcaneus and talus. Intraoperative compression via magnetic assistance is achieved with direct visualization until satisfactory. This is carefully performed 1 mm at a time to avoid overcompression.
Patients with standard TTC arthrodesis were compressed in the office with use of the external magnetic remote device at specific time periods. Compression was performed at weeks 1, 3, and 6 postoperatively, usually between 1 and 1.5 mm but never more.
In patients with C-LON, a latency period of 3 weeks was followed by a distraction period at weeks 3, 6, and 9 postoperatively. Also, 0.5 mm of daily tibial lengthening was broken into distraction periods of 0.16 mm 3 times daily using the Precice Intramedullary Limb Lengthening System (NuVasive Specialized Orthopedics) and the patient followed every 2 weeks for radiographs until optimal length and consolidation achieved. In cases of isolated TTC arthrodesis, loading of the foot in a controlled ankle motion (CAM) walker was started at 6 weeks. In cases of tibial corticotomy, weight-bearing in CAM boot was limited to 50 pounds until 3 cortices of callus and bone bridging achieved at the corticotomy and regenerate site. In cases of ankle fusion where additional postoperative compression is planned for, all extraneous screws placed across the TTC fusion site are placed colinear or nearly colinear with the long axis of the hindfoot nail. Only partially threaded screws are used to avoid friction points during compression.
All patients receive 1 gram of vancomycin powder placed within the surgical site and are closed in layers and splinted. Surgical prophylaxis IV antibiotics are routinely given and VTE prophylaxis-initiated postop day #1. Drains are placed and pulled within 24–48 hours postoperatively and patients are all monitored inpatient until discharge home with home health care aid or until safe transfer to skilled nursing facilities. Standard wound care and offloading tactics are employed until the patient is healed.
Case Examples
We present 3 of our 10 cases; one patient with a standard TTC arthrodesis CON, 1 with C-LON, and 1 patient with a talectomy and a talocalcaneal docking arthrodesis with C-LON. All 10 patients utilizing this lengthening IMN achieved successful union without significant complications.
Case 1: TTC Arthrodesis CON (Compression Over Nail)
A 35-year-old female presented with post-traumatic right ankle arthritis with bony block equinus, dystonias, and hemiparesis. A decision for ankle and subtalar joint fusion was made to allow for a definitive, durable, and lifelong plantigrade foot position. Preop (Figure 1) and 6-month follow-up (Figure 2) photos shown.
Case 2: TTC Arthrodesis C-LON
The second case is a 78-year-old man with four decades of post-traumatic ankle arthritis secondary to open ankle fracture with muscle flap in his early 30s. He had a preoperative limb length discrepancy of ~ 1.5 inches short on the injured left limb. Preop (Figure 3) and 9-month follow-up (Figure 4) photos are shown.
Case 3: Talectomy + TC Arthrodesis C-LON
A 78-year-old male presented with Charcot neuroarthropathy, subtalar joint dislocation, advanced degenerative joint disease and avascular necrosis of the talus. Preop (Figure 5) and 5-month follow-up (Figure 6) photos are shown.
From our series of 10 cases, we report:
10/10 (100%) union
0/10 (0%) non-union, deep infection, or venous thromboembolism
0/10 (0%) hardware failure
1/10 (10%) 1 case of unscheduled return to due to development of hematoma which resolved uneventfully.
*No ancillary bone stimulation was used to achieve fusion
**Hardware removal at 1 year is performed on a case-by-case basis
In Conclusion
We report a series of 10 cases of an innovative, albeit currently off-label approach to retrograde hindfoot nailing with greater than 1 year follow-up. If the surgeon desires to dial in postoperative compression whilst allowing the ability to lengthen via corticotomy and regenerate bone without the need for external fixator devices or a secondary surgery, this technique remains unique. We are aware of only 1 other publication evaluating technique similar to this with magnetic intramedullary nailing.8
Dr. Sebag is a Diplomate of the American Board of Foot and Ankle Surgery. He holds additional board-qualification in reconstructive rearfoot and ankle surgery. He practices at Coastal Orthopaedic & Sports Medicine Center in Florida.
Dr. Breitenbach is
a Foot/Ankle Reconstructive Surgical Fellow at Certified Foot and Ankle Specialists in Florida.
Dr. Adler is a Foot and Ankle Surgical Fellow at Certified Foot and Ankle Specialists in Florida.
References
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2. Raikin SM, Moncman TG, Raikin J. Improved pain and function after TTC Fusion with a custom cage. Foot Ankle Int. 2022;43(11):1410-1418. doi:10.1177/10711007221115182
3. Vesely BD, LeSavage LK, King MA, Evans JK, Scott AT. Change in height following tibiotalocalcaneal arthrodesis: retrospective radiographic analysis. J Foot Ankle Surg. 2023 May-Jun;62(3):465-468. doi: 10.1053/j.jfas.2022.11.009. Epub 2022 Nov 20. PMID: 36504137.
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5. Chaudhary M. Limb lengthening over a nail can safely reduce the duration of external fixation. Indian J Orthop. 2008 Jul;42(3):323-9. doi: 10.4103/0019-5413.41857. PMID: 19753160; PMCID: PMC2739482.
6. Dujela MD, Berlet GC, Houng BE, Hyer CF. Comparison of dynamic versus static locked retrograde tibiotalocalcaneal arthrodesis with intramedullary nail fixation: evaluation of the RAIN Database. J Foot Ankle Surg. 2023 Jul-Aug;62(4):657-660. doi: 10.1053/j.jfas.2023.02.002. Epub 2023 Feb 16. PMID: 36941141.
7. Dujela MD, Berlet GC, Houng BE, Hyer CF. Comparison of dynamic versus static locked retrograde tibiotalocalcaneal arthrodesis with intramedullary nail fixation: Evaluation of the RAIN database. J Foot Ankle Surg. 2023;62(4):657-660. https://www.sciencedirect.com/science/article/pii/S1067251623000327. doi: 10.1053/j.jfas.2023.02.002.
8. DeVries JG, Berlet GC, Hyer CF. Predictive risk assessment for major amputation after tibiotalocalcaneal arthrodesis. Foot Ankle Int. 2013;34(6):846-850. doi:10.1177/1071100712472488.
9. Paley D, Lamm BM, Robbins C, et al. Simultaneous limb lengthening with ankle fusion using an internal lengthening nail. J Foot Ankle Surg. 2022 Jul-Aug;61(4):e15-e20. doi: 10.1053/j.jfas.2021.11.020. Epub 2021 Dec 4. PMID: 34969598.
109. Vogt B, Roedl R, Gosheger G, et al. Tibial lengthening using a retrograde magnetically driven intramedullary lengthening device in 10 patients with preexisting ankle and hindfoot fusion. Acta Orthop. 2020 Dec;91(6):761-769. doi: 10.1080/17453674.2020.1807222. Epub 2020 Aug 24. PMID: 32835564; PMCID: PMC8023964.
11. Sherman AE, Mehta MP, Nayak R, et al. Biologic augmentation of tibiotalocalcaneal arthrodesis with allogeneic bone block is associated with high rates of fusion. Foot Ankle Int. 2022;43(3):353-362. doi:10.1177/10711007211041336
12. Tellisi N, Fragomen AT, Ilizarov S, Rozbruch SR. Limb salvage reconstruction of the ankle with fusion and simultaneous tibial lengthening using the Ilizarov/Taylor spatial frame. HSS Journal. 2008;4(1):32-42. doi:10.1007/s11420-007-9073-0
