Literature ReviewSubtalar distraction arthrodesis, originally described by Gallie (1), is a common treatment modality for subtalar joint (STJ) depression. This condition is often the sequela of calcaneal fractures (with posterior facet collapse) or a nonunion from a failed attempt at a STJ arthrodesis (2-5). STJ depression is diagnosed radiographically by a decrease in both the talar declination angle as well as the lateral talocalcaneal angle (Fig. 5). Clinically, the patient may experience anterior tibiotalar impingement, subfibular impingement, and an apropulsive gait due to a reduction in the lever arm of the Achilles tendon (2). It has been suggested that indications for surgical management include >8mm of STJ depression, radiographic or clinical evidence of tibiotalar impingement, talar declination angle <20 degrees in patients with ankle pain, and patients with ankle pain and <10 degrees of ankle dorsiflexion (5-6).

Traditionally, structural autograft has been the gold standard for subtalar distraction arthrodesis; however, this is associated with donor site morbidity, limitations in size and shape, and graft collapse (7-9). Allograft is also used, but it is associated with a higher rate of nonunion as it is less osteogenic than autograft with the added risk of disease transmission and higher rates of late collapse (8,10,11). Overall, traditional methods have proven to have good results with increase in the talocalcaneal angle in the sagittal plane, but the results are varied from study to study (2,12-14). Pollard and Schuberth reported a 91% success rate for these procedures; however, of the two failed cases, one was due to non-union and the other was due to graft subsidence (2). Trnka reported an 86% union rate with this method, yet there were also reported cases where subtalar joint height was not restored, attributed to settling of the posterior graft (13).

MethodologyA retrospective review of patients that underwent subtalar joint distraction arthrodesis using a tantulum wedge from 2014 to 2016 at our institution by the senior surgeon (BH) was conducted. Six patients were identified that met the inclusion criteria. Patient demographics, comorbidities, indications, time to weightbearing, amount of STJ elevation, residual symptomology, and complications were reviewed. Lateral ankle radiographs were evaluated

References

Revision of Subtalar Joint Arthrodesis with Trabecular Wedge Cage: A Case SeriesAnthony Romano, DPM, PGY-21; David Larson, DPM, AACFAS2; Byron Hutchinson, DPM, FACFAS1

1Franciscan Foot & Ankle Institute, Federal Way, WA; 2Orthopedic Foot & Ankle Center, Westerville, OH

Statement of PurposeFoot and ankle surgeons are often faced with the difficult case of a depressed subtalar joint (STJ) as a sequelae of failed subtalar joint arthrodesis or collapse due to a past intraarticular calcaneal fracture. This case series presents an option to correct the loss of STJ height following calcaneal fracture (Fig. 1) or failed STJ arthrodesis (Fig. 2) using an allograft packed trebecular wedge cage (Figs. 3 & 4). This allows for restoration of joint height with the added benefit of load sharing through its design. This is particularly important with patients that are noncompliant or unable to be fully non-weightbearing. It allows for earlier loading with less concern for the subsidence, disease transmission, and donor site morbidity seen in traditional bone grafting techniques.

ProceduresSTJ distraction arthrodesis with a trabecular cage was performed on 6 patients with pathologies including failed subtalar joint arthrodesis, STJ depression following calcaneal fracture, and STJ arthritis with los of height and tarsal coalition. Pre operative symptomology included STJ pain with ambulation or ROM, decreased ankle ROM (leading to apropulsive gait), and peroneal impingement under the lateral malleolus. All correction was done acutely. The procedure was performed via a lateral extensile incision as viewed in Fig. 4. A cancellous graft filled trabecular cage was placed across the posterior articular surface or non-union site of the subtalar joint (Figs. 3 &4). The senior surgeon was able to increase the subtalar joint height with the cage to a more anatomical position. Internal fixation was then placed across the arthrodesis site (Fig. 5b). Bone marrow aspirate from the tibia was used in all cases. In one case, external fixation superconstruct was also used. Pre- and postoperative assessment of subtalar joint height as well as ankle range of motion was noted to be increased.

Figure 3: Allograft packed trabecular wedge cage Figure 4: Placement of trabecular cage across posterior articular surface of STJ

As a result, tantalum structural grafts have gained popularity for this procedure after their successful use in hip and knee surgery (15-20). The use of a tantalum wedge cage provides a strong construct for joint elevation and arthrodesis. It allows for earlier weightbeariing as the trabecular cage acts as a truss that allows for load sharing. Literature has shown full incorporation and bony trabeculation within the tantalum truss as seen in Figure 7 (21). Furthermore, there is no donor site (iliac crest, tibia, etc.) morbidity which has been reported in up to 41% of cases (12). Papadelis et al in a study of 18 patients undergoing STJ distraction arthrodesis with a trabecular cage showed CT verified arthrodesis in all patients as well as marked increase in AOFAS scores and a decrease in VAS scores. Few complications were reported. Radiographically, talocalcaneal angle, talocalcaneal height, talar declination angle had all increased, and the intraoperatively achieved correction was maintained for a mean follow-up period of 18 months thus proving to be a viable option for STJ arthrodesis revision (12). Figure 2. Failed STJ Arthrodesis as part of

failed TTC Arthrodesis

both pre- and postoperatively to evaluate sagittal plane increase in STJ height. Measurements were made using talocalcaneal angle which is the angle between the calcaneal inclination angle and talar declination angle (Fig. 5). Time to weightbearing was determined radiographically and correlated with absence of any clinical signs of non-union.

Results The study included 5 males and 1 female with an average age of 56.5 years old. Preoperative diagnoses included 4 patients with failed STJ arthrodesis (1 patient had failed STJ fusion as part of failed TTC fusion), 1 patient with STJ arthritis status post calcaneal open reduction internal fixation, and 1 patient with primary arthritis of the STJ with a tarsal coalition. Two patients were current tobacco users. Comorbidities were remarkable for morbid obesity in 3 of the 6 patients in the study. Of those 3, 2 had diabetes mellitus as well. It should also be noted that one patient had a documented vitamin D deficiency that was diagnosed after the original attempt at STJ fusion. All patients went on to radiographic and clinical fusion (Fig. 6). Patients were weightbearing in a CAM boot in an average of 61.6 days. All patients were able to ambulate postoperatively with or without the use of a brace. The average increase in talocalcaneal angle on lateral radiographs was 10 degrees. This increase in talocalcaneal angle (posterior STJ height loss) allowed for resolution of all preoperative symptomology. Complications were minor and included a forefoot varus and one DVT that was successfully treated. No major complications occurred. Average follow up time for all patients was 11.2 months. Results are seen below (Table 1).

Analysis & Discussion

Figure 1: STJ depression, late sequelae of calcaneal fractures

This study details our technique of successful STJ arthrodesis revision utilizing a trabecular wedge cage. Although it has been well documented in the literature that revisional STJ arthrodesis for STJ depression can be performed with the use of auto or allograft, this procedure may ultimately fail and is associated with higher rates of donor site morbidity, graft collapse, and disease transmission. The method described in this study allows the surgeon to restore the lost subtalar joint height, and also maintain this height in a revisonal procedure with a high union rate. The technique addresses and corrects the biomechanical problems associated with STJ depression including anterior tibiotalar impingement as well as apropulsive gait.

The results of this study not only show that height can be restored to a depressed subtalar joint, but also that there is a relatively short time to weightbearing (Table 1). Furthermore there was complete elimination of the preoperative symptoms that were experienced. The outcomes present the ability to provide consistent neutral alignment with high rates of fusion. There is not only bony trabeculation and incorporation with in the truss as seen in Fig. 7, the trabecular wedge allows for earlier weightbearing in patients with the added benefit of load sharing in patients that are noncompliant or unable to be fully non-weightbearing.

Finally, the complication profile displayed minimal complications. When compared to the preoperative states, patients saw significant improvement in overall hindfoot alignment as well. Overall, STJ distraction arthrodesis was found to be effective in reaching the goals of revisional STJ fusion.

Figure 7: Histologic evidence of full incorporation and bony trabeculation within the tantalum truss

Figure 6. Lateral radiograph of patient 12 months status post revisional TTC arthrodesis with trabecular STJ Cage showing bony consolidation across the tantulum cage as well as maintenece of STJ height

Table 1: Patient demographics, comorbidities, procedure details, complications and results

Figures 5a & b. Pre- & postoperative lateral radiographs showing the increase in the lateral talo-calcaneal angle after insertion and fixation of tantulum wedge cage, representing increased posterior STJ height

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