The amino acid-polyamine-organocation (APC) superfamily has been shown to include five recognized families, four of which are specific for amino acids and their derivatives. Recent high-resolution X-ray crystallographic data have shown that four additional transporter families (BCCT, TC No. 2.A.15; SSS, 2.A.21; NSS, 2.A.22; and NCS1, 2.A.39), transporting a wide range of solutes, exhibit sufficiently similar folds to suggest a common evolutionary origin. We have used established statistical methods, based on sequence similarity, to show that these families are, in fact, members of the APC superfamily. We also identify two additional families (NCS2, 2.A.40; SulP, 2.A.53) as being members of this superfamily. Repeat sequences, each having five transmembrane α-helical segments and arising via ancient intragenic duplications, are demonstrated for all of these families, further strengthening the conclusion of homology. The APC superfamily appears to be the second largest superfamily of secondary carriers, the largest being the major facilitator superfamily (MFS). Although the topology of the members of the APC superfamily differs from that of the MFS, both families appear to have arisen from a common ancestral 2 TMS hairpin structure that underwent intragenic triplication followed by loss of a TMS in the APC family, to give the repeat units that are characteristic of these two superfamilies.

Background: The Salto Talaris is a fixed-bearing implant first approved in the US in 2006. While early surgical outcomes have been promising, mid- to long-term survivorship data are limited. The aim of this study was to present the survivorship and causes of failure of the Salto Talaris implant, with functional and radiographic outcomes. Methods: Eighty-seven prospectively followed patients who underwent total ankle arthroplasty with the Salto Talaris between 2007 and 2015 at our institution were retrospectively identified. Of these, 82 patients (85 ankles) had a minimum follow-up of 5 (mean, 7.1; range, 5-12) years. The mean age was 63.5 (range, 42-82) years and the mean body mass index was 28.1 (range, 17.9-41.2) kg/m2. Survivorship was determined by incidence of revision, defined as removal/exchange of a metal component. Preoperative, immediate, and minimum 5-year postoperative AP and lateral weightbearing radiographs were reviewed; tibiotalar alignment (TTA) and the medial distal tibial angle (MDTA) were measured to assess coronal talar and tibial alignment, respectively. The sagittal tibial angle (STA) was measured; the talar inclination angle (TIA) was measured to evaluate for radiographic subsidence of the implant, defined as a change in TIA of 5 degrees or more from the immediately to the latest postoperative lateral radiograph. The locations of periprosthetic cysts were documented. Preoperative and minimum 5-year postoperative Foot and Ankle Outcome Score (FAOS) subscales were compared. Results: Survivorship was 97.6% with 2 revisions. One patient underwent tibial and talar component revision for varus malalignment of the ankle; another underwent talar component revision for aseptic loosening and subsidence. The rate of other reoperations was 21.2% ( n = 18), with the main reoperation being exostectomy with debridement for ankle impingement ( n = 12). At final follow-up, the average TTA improved 4.4 (± 3.8) degrees, the average MDTA improved 3.4 (± 2.6) degrees, and the average STA improved 5.3 (± 4.5) degrees. Periprosthetic cysts were observed in 18 patients, and there was no radiographic subsidence. All FAOS subscales demonstrated significant improvement at final follow-up. Conclusions: We found the Salto Talaris implant to be durable, consistent with previous studies of shorter follow-up lengths. We observed significant improvement in radiographic alignment as well as patient-reported clinical outcomes at a minimum 5-year follow-up. Level of Evidence: Level IV, retrospective case series.

Recommendation: There is evidence supporting medial soft tissue reconstruction, such as spring and deltoid ligament reconstructions, in the treatment of severe progressive collapsing foot deformity (PCFD). We recommend spring ligament reconstruction to be considered in addition to lateral column lengthening or subtalar fusion at the initial operation when those procedures have given at least 50% correction but inadequate correction of the severe flexible subluxation of the talonavicular and subtalar joints. We also recommend combined flatfoot reconstruction and deltoid reconstruction be considered as a joint sparing alternative in the presence of PCFD with valgus deformity of the ankle joint if there is 50% or more of the lateral joint space remaining. Level of Evidence: Level V, expert opinion.

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Recommendation: There is evidence that the use of WEIGHTBEARING imaging aids in the assessment of progressive collapsing foot deformity (PCFD). The following WEIGHTBEARING conventional radiographs (CRs) are necessary in the assessment of PCFD patients: anteroposterior (AP) foot, AP or mortise ankle, and lateral foot. If available, a hindfoot alignment view is strongly recommended. If available, WEIGHTBEARING computed tomography (CT) is strongly recommended for surgical planning. When WEIGHTBEARING CT is obtained, important findings to be assessed are sinus tarsi impingement, subfibular impingement, increased valgus inclination of the posterior facet of the subtalar joint, and subluxation of the subtalar joint at the posterior and/or middle facet. Level of Evidence: Level V, consensus, expert opinion.

Background: Assessment of operative correction of adult-acquired flatfoot deformity (AAFD) has been traditionally performed by clinical evaluation and conventional radiographic imaging. Previously, a 3-dimensional biometric weightbearing computed tomography (WBCT) tool, the foot ankle offset (FAO), has been developed and validated in assessing hindfoot alignment. The purpose of this study was to investigate the role of FAO in evaluating operative deformity correction in AAFD. Methods: In this prospective comparative study, 19 adult patients (20 feet) with stage II (flexible) flatfoot deformity underwent preoperative and postoperative standing WBCT examination at mean 19 months (range, 6-24) after surgery. Three-dimensional coordinates of the foot tripod and center of the ankle joint were acquired by 2 independent and blinded observers. These coordinates were used to calculate the FAO using dedicated software, and subsequently compared pre- and postoperatively. The FAO is a previously validated biometric measurement that represents centering of the foot tripod as well as hindfoot alignment, with a normal mean FAO of 2.3% ± 2.9%. In addition, Patient Reported Outcomes Measurement Information System (PROMIS) clinical outcomes scores were compared pre- and postoperatively with a mean follow-up of 22.6 months (range, 14-37). Results: There was significant correction of flatfoot deformity from a mean preoperative FAO of 9.8% to a mean postoperative value of 1.3% ( P < .001). Additionally, there was statistically significant improvement in all PROMIS domains ( P < .05), except depression, at an average follow-up of 22.6 months. Spring ligament reconstruction was the only procedure associated with a significant correction in FAO ( P = .0064). Conclusion: The FAO was a reliable and sensitive tool that was used to evaluate preoperative deformity as well as postoperative correction, with patients demonstrating both significant improvement in FAO as well as patient-reported outcomes. These findings demonstrate the role for biometric 3-dimensional WBCT imaging in assessing operative correction after flatfoot reconstruction, as well as the potential role for operative planning to address preoperative deformity. Level of Evidence: Level II, prospective comparative study.

Recommendation: In the treatment of progressive collapsing foot deformity (PCFD), the combination of bone shape, soft tissue failure, and host factors create a complex algorithm that may confound choices for operative treatment. Realignment and balancing are primary goals. There was consensus that preservation of joint motion is preferred when possible. This choice needs to be balanced with the need for performing joint-sacrificing procedures such as fusions to obtain and maintain correction. In addition, a patient’s age and health status such as body mass index is important to consider. Although preservation of motion is important, it is secondary to a stable and properly aligned foot. Level of Evidence: Level V, consensus, expert opinion.

Background: In 2016, the US Food and Drug Administration (FDA) approved the use of a polyvinyl alcohol (PVA) hydrogel implant for the surgical management of hallux rigidus. Though recent studies have evaluated the safety and efficacy of the implant, no study has compared outcomes following PVA implantation with those following traditional joint-preserving procedures for hallux rigidus, such as cheilectomy with Moberg osteotomy. The purpose of this study was to compare clinical and patient-reported outcomes for patients undergoing cheilectomy and Moberg osteotomy, with or without PVA implant, at a single multisurgeon academic center. Our hypothesis was that the addition of the PVA implant would result in superior clinical and patient-reported outcomes. Methods: In total, 166 patients were identified who underwent cheilectomy and Moberg osteotomy with (PVACM; n = 72) or without (CM; n = 94) a PVA implant between January 2016 and December 2018 by 1 of 8 foot and ankle fellowship-trained orthopedic surgeons at our institution. Of these patients, 60 PVACM and 73 CM patients had both baseline and minimum 1-year postoperative Patient-Reported Outcomes Measurement Information System (PROMIS) scores. The average time to survey follow-up was 14.5 months for PVACM patients and 15.6 months for CM patients. Retrospective chart review was performed to assess the incidence of postoperative complications and reoperations, with an average clinical follow-up of 27.7 (range, 16.0-46.4) months for PVACM patients and 36.6 (range, 18.6-47.8) months for CM patients. Results: Both PVACM and CM cohorts demonstrated significant improvement in the PROMIS Physical Function, Pain Interference, Pain Intensity, and Global Physical Health domains when comparing preoperative and postoperative scores within each group ( P < .01). When comparing scores between the PVACM and CM cohorts, preoperative scores were similar, while CM patients demonstrated significantly higher postoperative Physical Function (51.8 ± 8.7 vs 48.8 ± 8.0; P = .04) and significantly lower Pain Intensity (39.9 ± 8.3 vs 43.4 ± 8.7; P = .02) scores. The pre- to postoperative change in Physical Function was also significantly greater for CM patients (7.1 ± 8.5 vs 3.6 ± 6.2; P = .011). In the PVACM group, there were 3 revisions (5%), 1 reimplantation, 1 conversion to arthrodesis, and 1 revision to correct hyperdorsiflexion. In the CM group, there was 1 revision (1.4%), a conversion to arthrodesis ( P = .21). Other postoperative complications included persistent pain (7 out of 60 PVACM patients [11.7%] and 8 out of 73 CM patients [11.0%]; P = .90) and infection in 3 PVACM patients (5%) and no CM patients ( P = .05). Conclusion: Though our results generally support the safety and utility of the PVA implant as previously established by the clinical trial, at 1 to 2 years of follow-up, CM without a PVA implant may provide equivalent or better relief compared with a PVACM procedure, while avoiding potential risks associated with the implant. Level of Evidence: Level III, retrospective comparative study.