Introduction: Auto-generated 3-dimensional (3D) measurements based on weightbearing cone-beam computed tomography (CT) scan technology may allow for a more accurate hind- and midfoot assessment. The current study evaluated the reliability and clinical relevance of such measurements in patients with posttraumatic end-stage ankle osteoarthritis. Methods: Seventy-two patients treated at our institution for posttraumatic end-stage ankle osteoarthritis, with available weightbearing conventional radiographs and a cone-beam CT scan, were analyzed. Twenty healthy individuals aged between 40 and 70 years served as controls. Seven variables were measured on weightbearing conventional radiographs (2D) and compared to 3D measurements that were based on reconstructions from weightbearing cone-beam CT scans. The reliability of each measurement was calculated and subgroups formed according to commonly observed deformities. Results: Inter- and intraobserver reliability was superior for 3D compared to 2D measurements. The accuracy of 3D measurements performed on osteoarthritic ankles was similar to 3D measurements performed on healthy individuals. Thirty-three of the 72 included patients (46%) evidenced an inframalleolar compensation of a supramalleolar/intra-articular ankle deformity (78% = varus compensation; 22% = valgus compensation), whereas 24 of those 72 patients (33%) showed no compensation or a further increase of a supramalleolar/intra-articular ankle deformity (67% = varus deformity; 33% = valgus deformity). Conclusion: Auto-generated 3D measurements of the hind- and midfoot were found to be reliable in both healthy individuals and patients with posttraumatic end-stage ankle osteoarthritis. Such measurements may be crucial for a detailed understanding of the location and extent of hindfoot deformities, possibly impacting decision making in the treatment of end-stage ankle osteoarthritis. Level of Evidence: Level III, comparative study.

Background: A challenge in treating acquired flatfoot deformities is the collapse of the medial arch at the level of the naviculocuneiform (NC) joint. Triple fusions, being a treatment option, may lead to problems such as increased foot stiffness. We thus established a method that combines subtalar (ST) fusion with NC fusion while preserving the Chopart joint. We analyzed the radiographic correction, fusion rate, and patient satisfaction with this procedure. Methods: 34 feet in 31 patients (female, 23; male, 8; age 67 [45-81] years) were treated with a ST and NC joint fusion. In 15 cases, a medial sliding-osteotomy was additionally necessary to fully correct hindfoot valgus. The following radiographic parameters were measured on weightbearing radiographs preoperatively and at 2 years: talo-first metatarsal angle, talocalcaneal angle, calcaneal pitch, talonavicular coverage angle and calcaneal offset. Fusion was radiologically confirmed. Results: All parameters, except the calcaneal pitch, showed a significant improvement. Fusion was observed after 1 year in all but 2 cases (94.1%). One nonunion each occurred at the ST and NC joint without needing any subsequent treatment. One patient developed avascular necrosis of the lateral talus with need for total ankle replacement after 1 year. All patients were satisfied with the obtained results. Conclusion: Our data suggest that a combined fusion of the ST and NC joint was effective and safe when treating adult acquired flatfoot with collapse of the medial arch at the level of the NC joint. Although the talonavicular joint was not fused, its subluxation was significantly reduced. Level of Evidence: Level IV, case series.

Category: Midfoot/Forefoot Introduction/Purpose: A conflicting problem in treating acquired flatfoot deformities is the break-down of the arch at the naviculocuneiform (NC) joints. After having encountered problems with extended triple fusion, in particular increased stiffness of the foot, we established a rational to combine subtalar (ST) fusion with NC I-III fusion while preserving the talonavicular (TN) and calcaneo-cuboidal (CC) joint. Our hypothesis was that the break-down of the arch at the NC joint can be specifically addressed while sparing the Chopart Joint (TN and CC joint). This, in turn, will allow the patient to accommodate better to the ground while walking. The aim of the study was to analyze the radiographic correction and fusion rate, and to determine patient’s satisfaction with this procedure. Methods: Between 2009 and 2015, a consecutive series of 34 feet in 31 patients (female, 23; male, 8; age 67 [45-81] years) were treated by combining a fusion of the subtalar joint with a NC fusion. Both joints were exposed through a medial approach. Two 7.5mm-screws were used for ST fusion, and two 5.5mm-screws were used for NC fusion. In addition an anatomically contoured plate was used as a medio-plantar tension bending support of the NC joint. In 15 patients, an additional medial sliding-osteotomy was done to fully correct valgus misalignment of the hindfoot. The following measures were taken on standard weight-bearing radiographs including hindfoot alignment view preoperatively and at 2 years: the talus-first metatarsal angle, the talocalcaneal angle, the calcaneal pitch, the talonavicular coverage angle, the talus-first metatarsal angle, and calcaneal offset. Bony fusion was confirmed on plain radiographs. If no trabeculation was visible, a CT scan was performed. Results: All radiographic parameters, except the calcaneal pitch, showed a statistically significant improvement (Table 1). Solid fusion at the arthrodesis site was observed between 8 and 12 weeks in all but 2 cases (94.1%). One nonunion occurred at the ST joint and one at the NC joint. No interventions were necessary as both cases were asymptomatic. One patient developed an avascular necrosis of the lateral talus with need for a total ankle replacement after one year. All patients were satisfied with the results of this procedure and stated that they would undergo the surgery again. All patients were able to wear normal shoes without insoles. Conclusion: Our results show that a combined fusion of the subtalar and NC joint is an effective and safe technique in treating the adult acquired flatfoot with collapse of the medial arch at the level of the NC joint. The deformity was corrected in all three planes. Even though the TN joint was not fused, its subluxation was significantly reduced. Although our radiographic results are promising, a clinical follow-up study is necessary to quantify the clinical benefit of this procedure.

Category: Ankle; Ankle Arthritis; Hindfoot Introduction/Purpose: While correction of varus alignment at the level of the ankle joint has been investigated extensively after supramalleolar osteotomy (SMOT), the effect on the hindfoot alignment remains unclear. This can be attributed to the limitations of former 2-dimensional radiographic measurements used to quantify the complex 3-dimensional subtalar joint alignment. Therefore, we aimed to determine both the ankle and subtalar joint alignment before and after SMOT using a weightbearing CT and autogenerated 3-dimensional measurements. Methods: Twenty-seven patients with a mean age of 53 years (SD=10.1; range=25-73) were retrospectively analyzed in a pre- post study design using weightbearing CT images. Inclusion criteria were correction of ankle varus deformity by either an opening wedge (N=19) or dome osteotomy (N=8). Exclusion criteria consisted of an additional inframalleolar bony correction, i.e. calcaneal osteotomy or subtalar arthrodesis. Corresponding three-dimensional bone models were reconstructed to compute the autogenerated measurements: tibial anterior surface (TAS) -, tibiotalar surface (TTS)-, talar tilt (TT) - and talocalcaneal (TC) angle. Results: The pre-operative (TAS=86.9°, SD=4.9; TTS=79.8°, SD=5.6; TT=8.8°, SD=4.3) radiographic parameters of the ankle joint alignment improved significantly compared to the post-operative parameters (TAS=92.4°, SD=4.9; TTS=87.1°, SD=6.3; TT=5.1°, SD=2.7; P<0.05). (Fig. 1A) Radiographic parameters to assess the subtalar joint alignment improved significantly from preoperatively (TCax =42.8°, SD=9.3; TCsag=42.3°,SD=10.9; TCcor =29.5°,SD=11.8) to post-operatively (TCax =37.8°, SD=8.8; TCsag=39.1°, SD=10.6; TCcor=24.6°,SD=9.1; P<0.05). (Fig. 1B) Conclusion: A supramalleolar osteotomy is able to correct both the ankle and subtalar joint alignment. However, correction at the level of the subtalar joint accounted for only 3 to 4 degrees, which was less than found for the ankle joint alignment. For cases where a higher correction at the subtalar joint is necessary, we thus suggest adding a calcaneal osteotomy or subtalar arthrodesis to the SMOT.