SLR - October 2023 - Anjum
Title: Factors influencing successful bone union of isolated subtalar arthrodesis for posttraumatic subtalar arthritis: a multicenter case series.Reference: Kim HN, Choi YR, Kim BS, et al. Factors influencing successful bone union of isolated subtalar arthrodesis for posttraumatic subtalar arthritis: a multicenter case series. J Orthop Surg Res. 2023;18(1):559.
Level of Evidence: IV, retrospective case series
Reviewed By: Hozaifa M. Anjum, DPM
Residency Program: Inova Fairfax Medical Campus, Falls Church, VA
Podiatric Relevance: Non-union is a significant complication of subtalar joint arthrodesis. Avascularity and bony sclerosis are seen following calcaneal fractures. These features are generally understood to impede osseous union. Hardware and graft choice approximate two of the most important factors affecting union – mechanical stability and biologic factors that promote healing. As such, it is prudent to investigate whether these choices can help mitigate this debilitating complication of subtalar arthrodesis.
Methods: This is a multicenter, multi-surgeon retrospective case series. 119 cases of post traumatic subtalar joint arthritis treated with isolated subtalar arthrodesis following calcaneal fracture were included. Patients who underwent concomitant ankle arthrodesis, ankle arthroplasty, or triple arthrodesis were excluded. Patients with Charcot arthropathy, uncontrolled diabetes mellitus, or infection were also excluded. Patients were categorized based on type of fixation used including number of screws and use of fully threaded vs partially threaded screws. The use of graft vs no graft as well as graft type (bone substitute, allograft, cancellous autograft, structural autograft) was also examined. The primary outcome measure was radiographic osseous union.
Results: There was a 64.7% rate of successful bony union defined as trabecular bridging over 50% of the posterior facet on plain film radiographs or CT within 6 months of surgery without evidence of hardware loosening. There were 9.2% cases of delayed union defined as adequate trabecular bridging after 6 months post-op. They found a 6.7% rate of “questionable union” with significant clinical pain despite radiographic evidence of osseous bridging noted. The overall non-union rate was 19.3%. Factors predicting increased likelihood of union were found to be the use of fully threaded screws, the use of two screws, and the use of autograft. Use of fully threaded screws was 5.9 times more likely to yield successful union. Two-screw fixation was 82% less likely to develop nonunion compared to single screw. Autograft use was 79% less likely to develop non-union compared to the use of no graft.
Conclusions: In the setting of calcaneal fractures where there is often a wedge of avascular bone from prior elevation of the posterior facet, it can be difficult to achieve full contact between the talus and calcaneus. The authors propose that the use of partially threaded screws in this situation decreases the level of engagement of screw threads with bone and potentially allows for motion at the smooth part of the screw shaft. Additionally, double screw fixation constructs are known to increase resistance to rotational forces, which could potentially explain the higher rate of non-union with single screw fixation. Finally, the use of autograft may help counteract the deficit of vascularity and presence of sclerosis after elevation of depressed posterior facet during calcaneal fracture reduction.
In challenging cases of subtalar joint arthrodesis with prior traumatic insult, optimizing stability and biological potential for healing are crucial. The use of two fully threaded screws and autograft bone are two surgeon-controlled choices that may increase the chance of successful union in STJ arthrodesis following calcaneal fracture.