Effects of Parallax and Distortion in Total Ankle Arthroplasty.

BACKGROUND: Surgeons rely on intraoperative fluoroscopy to assist in placement of implant components during total ankle arthroplasty (TAA). Parallax alters the direction of an object when viewed from two different points, resulting in image distortion. The purpose of this study was to evaluate parallax/distortion in intraoperative fluoroscopic images during TAA. METHODS: A retrospective review of all TAAs performed by two surgeons (R.W.M. and B.S.) from August 2019 to April 2023 were reviewed. Intraoperative fluoroscopic anteroposterior (AP) ankle views were evaluated for any obvious parallax image distortion. Cases with obvious parallax distortion were included for angular evaluation of AP intraoperative fluoroscopic and first postoperative plain films. The tibia was marked at 2-centimeter intervals to create zones from the proximal stem of the implant. The anatomical axis of the tibia (AAT) was drawn at the mid-diaphysis. The anatomic lateral distal tibial angle (aLDTA) and anatomic axis deviation (AAD) were measured for each zone. RESULTS: A total of 22 TAAs were performed during the study period. Four cases were excluded due to inadequate imaging, leaving a total of 18 TAAs for review. We found 6 of 18 (33.3%) cases had obvious parallax distortion. We found the average aLDTA was 90.9° (84°-101°). At the most proximal tibial zone, the average aLDTA was 94° (91°-101°). We found the average AAD was 4.7 (0.5-17.2) mm. The AAD ranged from 0.5 to 17.2 mm lateral to 0.8 to 8.2 mm medial. Postoperative plain film radiographs displayed a normal aLDTA and an AAT centered within the ankle joint. CONCLUSION: Parallax can distort the appearance of the tibia on fluoroscopic images. Deviation from the normal aLDTA and anatomical axis should be anticipated. Surgeons should be aware of the potential impact of parallax and ways to mitigate these effects.

Traumatic Periprosthetic Fractures Following Total Ankle Replacement A Systematic Review and Proposed Classification.

Total ankle replacements (TAR) are increasingly utilized, but postoperative traumatic periprosthetic fractures remain a rare yet challenging complication. This systematic review aims to address the gap in literature by proposing a comprehensive classification system for these fractures, considering implant stability, fracture location, and surrounding bone quality. A systematic review identified 13 cases from 9 studies meeting inclusion criteria. Fractures were categorized using the proposed Hill-Brown classification: Type A (talus or fibula), Type B (distal tibial component), and Type C (diaphysis/proximal tibial metaphysis). Implant stability was a key factor, with Type B fractures further classified as B1 (stable), B2 (unstable with adequate bone stock), and B3 (unstable with poor bone stock). Most fractures occurred at or near the distal tibial component (Type B), with implant stability largely dependent on fracture location and bone quality. Surgical fixation, particularly minimally invasive plate osteosynthesis (MIPO) with locking plates, was the preferred treatment for stable implants, showing low complication rates. Unstable implants often required revision TAR or conversion to arthrodesis. Surgical intervention is recommended following all traumatic periprosthetic fractures in the setting of a TAR. Bone quality, particularly in patients with rheumatoid arthritis or osteoporosis, significantly impacted treatment decisions. Our findings emphasize the importance of fracture location, implant stability, and bone quality in managing these fractures. Future multicenter studies are necessary to validate this classification system and refine treatment protocols.Level of Evidence: Level III.

Does the Subtalar or Tibiotalar Joint Need Fused in Primary Retrograde Tibiotalocalcaneal Nailing for Fragility Ankle Fractures?

BACKGROUND: As an alternative to traditional open reduction internal fixation of ankle fragility fractures, primary retrograde tibiotalocalcaneal (TTC) nailing has been investigated as a treatment option. These results suggest that this treatment is an acceptable alternative treatment option for these injuries. There are still questions about the need for formal joint preparation at the subtalar or tibiotalar joint when performing primary TTC nailing for fragility fractures. METHODS: In this study, we retrospectively evaluated 32 patients treated with primary retrograde TTC nail without subtalar or tibiotalar joint preparation for a mean of 2.4 years postoperatively. We specifically reviewed the charts for nail breakages at either joint, patients developing subtalar or tibiotalar joint pathology requiring additional treatment, including return to the operating room for formal joint preparation. RESULTS: Fracture union occurred in 100% of patients. There were 3 cases (10.0%) of hardware failure, and 2 of these cases were asymptomatic and did not require any treatment. One patient (3.3%) developed hardware failure with nail breakage at the subtalar joint. This patient developed progressive pain and symptoms requiring revision surgery with formal arthrodesis of the subtalar and tibiotalar joint. CONCLUSIONS: This study shows that retrograde hindfoot nailing without formal subtalar or tibiotalar joint preparation is an acceptable potential treatment option in ankle fragility fractures. Mid-term follow-up demonstrates favorable outcomes without the need for formal joint preparation in this high-risk population. Comparative studies with higher patient numbers and long-term follow-up are needed to confirm the results of this study.Levels of Evidence: Level IV.

Parallax and Distortion in Fluoroscopy Units.

BACKGROUND: Parallax is an imaging phenomenon where an object appears to be at different positions when viewed from different angles. Distortion can occur secondary to internal fluoroscopic, or external environmental, factors. Fluoroscopy is a vital tool to assist surgeons intraoperatively. However, parallax and distortion can lead to inaccuracy, potentially leading to incorrect surgical decisions. The purpose of this study was to investigate the prevalence of parallax/distortion in large fluoroscopy units at a level-1 trauma center. METHODS: Two types of C-arm models were evaluated, including (1) round image intensifiers, and (2) flat plate detectors (FPD). A square plexiglass grid with embedded wire at ½-in intervals was created, with a round metal washer secured centrally. The grid was placed 16 in from the image intensifier. A metal ball bearing (BB) was secured to the center of the x-ray tube. Fluoroscopic images were obtained until the BB and washer were "center-center." A straight blade served as a fiducial marker to ensure there was no off-axis angulation. Standard anterior-posterior and lateral views were obtained. External factors were considered, tested, and limited. Images were printed and the patterns of parallax/distortion were identified. RESULTS: All 11/11 (100%) of fluoroscopy units had some degree of parallax and/or distortion. We noted 3 different patterns, including sigmoidal, converging, and diverging. The FPD units had less apparent distortion overall; however, two-thirds (66%) were off-axis in the x- and y-axes in relation to the fiducial marker. CONCLUSION: All fluoroscopy units had varying degrees and patterns of parallax/distortion. We noted less overall distortion in FPDs. However, some of these units may produce images that are off-axis. This research has important implications for improving the accuracy of intraoperative fluoroscopy. Musculoskeletal surgeons should understand the limitations of fluoroscopy and how to combat parallax distortion to improve surgical outcomes and reduce patient morbidity. LEVEL OF EVIDENCE: Level V.