Advertisement

Inconclusive Evidence That Arthroscopic Techniques Yield Better Outcomes Than Open Techniques For Subtalar Arthrodesis - A Systematic Review

Open AccessPublished:November 08, 2022DOI:https://doi.org/10.1016/j.jisako.2022.10.006

      Abstract

      Importance

      Open in situ subtalar arthrodesis (ISTA) has been a standard procedure for treating subtalar arthritis for varied etiologies with good outcomes. There has been a paradigm shift from ISTA to arthroscopic sub-talar arthrodesis (ASTA) over the past two decades due to increase in number of surgeons performing arthroscopy worldwide. However, there is only limited evidence in the existing literature to substantiate the benefit of this change with regards to patient benefit. To our knowledge there are also no systematic reviews comparing the results of the two techniques for subtalar arthrodesis (STA).

      Aim

      Our systematic review aims to determine the superior technique for performing STA by comparing the outcomes, union rates and complications between open and arthroscopic approach for in situ STA. We hypothesized that both procedures would have similar outcomes, union rates, time to union & complication rate for in-situ STA.

      Evidence review

      Three databases: MEDLINE/PubMed’, ‘the Cochrane library’ & ‘Google scholar’ were searched using predefined inclusion & exclusion criteria to compare the two procedures. Risk of bias assessment was done using- The Risk of Bias in Non-randomized Studies of Interventions (ROBINS-I) tool for assessing risk of bias in the included studies. Weighted mean averages were computed for all parameters and tabulated separately for ASTA & ISTA.

      Findings

      We included a total of 22 studies with a total of 978(ASTA-310, ISTA-668) patients in the review. The most common indication for both techniques was post traumatic subtalar arthritis due to malunited calcaneal fracture in both groups (54.5%). The AOFAS score was better in the ASTA group with a weighted average improvement of 43.4 while the weighted average improvement was 31.1 in the ISTA group respectively. Patients undergoing ASTA, had a weighted average union rate of 95.5%(SD-3.6) with a weighted average time to union of 12.2 weeks (SD-2.4) while the ISTA group reported 90.7% (SD-6) union rate with a weighted average time to union of 15.5 weeks (SD-8.4). The weighted overall average complication rate was 13.1%(SD-8.9) in ASTA group & 20.3%(SD-16.2) in the ISTA group with hardware related complications being the most common in both the groups.

      Conclusion

      From the existing literature, our review suggests that both ASTA and ISTA techniques are effective procedures for STA. However, there is no conclusive evidence to recommend one technique over another. High quality randomised studies may be further required to clearly define the superiority of one technique over another

      Level of Evidence: Level III

      What is already known?
      • Previously done retrospective studies indicate similar outcomes and union rates with shorter time to union and return to sports and activities of daily living with arthroscopic subtalar arthrodesis (ASTA) in comparison to open in situ arthrodesis (ISTA).
      What are the new findings?
      • This is the first systematic review to compare data on arthroscopic versus open approach for performing in-situ subtalar arthrodesis.
      • From the existing literature, our review suggests that both ASTA and ISTA techniques are effective procedures for STA. However, there is no conclusive evidence to recommend one technique over another. High quality randomised studies may be further required to clearly define the superiority of one technique over another

      Introduction

      Subtalar arthritis is a commonly encountered problem in the outpatient clinic that can be secondary to malunited calcaneal fractures most commonly while inflammatory joint disease, tarsal coalitions & primary osteoarthritis are less common causes[
      • Rajasekaran S.
      • Sundararajan S.R.
      • Ramakanth R.
      • Shreeram V.
      • Joseph J.B.
      Is Distraction Bone Block Arthrodesis better than Subtalar Arthrodesis for Malunited Calcaneal Fractures with Subtalar Arthritis? A Retrospective Case Series.
      ] [
      • Rungprai C.
      • Phisitkul P.
      • Femino J.E.
      • Martin K.D.
      • Saltzman C.L.
      • Amendola A.
      Outcomes and complications after open versus posterior arthroscopic Subtalar Arthrodesis in 121 patients.
      ]. Open In- situ subtalar arthrodesis (ISTA) is an effective strategy in managing subtalar arthritis that relieves pain and improves function of the affected hindfoot though gross malalignment & significant bone loss at talus/calcaneum may limit its use in all cases of subtalar joint pathologies [
      • Mann R.A.
      • Beaman D.N.
      • Horton G.A.
      Isolated subtalar arthrodesis.
      ] [
      • Tuijthof G.J.M.
      • Beimers L.
      • Kerkhoffs G.M.M.J.
      • Dankelman J.
      • van Dijk C.N.
      Overview of subtalar arthrodesis techniques: options, pitfalls and solutions.
      ]. Over the past two decades there has been a paradigm shift from ISTA to arthroscopic sub-talar arthrodesis (ASTA) as the preferred technique for performing subtalar arthrodesis (STA) due to advantages like preservation of blood supply of the involved bones & proprioceptive input for the foot & also due to lesser perioperative morbidity due to its minimal invasive nature [
      • Amendola A.
      • Lee K.-B.
      • Saltzman C.L.
      • Suh J.-S.
      Technique and early experience with posterior arthroscopic subtalar arthrodesis.
      ]. However, there is only limited evidence in existing literature to substantiate the benefit of this change with regards to patient outcomes, union rates & complications. To our knowledge there are also no systematic reviews comparing the results of the two techniques for STA. Our systematic review aims to determine the superior technique for performing STA by comparing the outcomes, union rates and complications between open and arthroscopic approach for in situ STA. We hypothesized that both procedures would have similar outcomes, union rates, time to union & complication rate for in-situ STA.

      Methodology

      A literature search was conducted as per the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines [
      • Moher D.
      • Liberati A.
      • Tetzlaff J.
      • Altman D.G.
      • Altman D.
      • Antes G.
      • et al.
      Preferred reporting items for systematic reviews and meta-analyses: The PRISMA statement.
      ]. A comprehensive search was conducted for studies related STA in 3 databases including ‘MEDLINE/PubMed’, ‘the Cochrane library’ & ‘Google scholar’. Search terms were broad to encompass all studies involving STA & included the following combination of keywords and Boolean operators: ‘talocalcaneal’ OR ‘subtalar’ AND ‘arthrodesis’ OR ‘fusion’. All studies in English language reporting functional outcomes or union rates of isolated in-situ subtalar fusion were included.

      Screening

      The search results were exported to the systematic review software Rayyan[
      • Ouzzani M.
      • Hammady H.
      • Fedorowicz Z.
      • Elmagarmid A.
      Rayyan-a web and mobile app for systematic reviews.
      ], to eliminate duplicates & to screen the title & abstracts for relevant studies applying the inclusion & exclusion criteria. The screening process included two reviewers (Author2) (Author 4) with initial Blind-on for individual assessment and with Blind-off subsequently for collaboration & sorting conflicted articles.

      Inclusion & Exclusion criteria

      Patients with post-traumatic subtalar arthritis, primary arthritis, infective/inflammatory arthritis, talocalcaneal coalitions, isolated STA for pes planovalgus were included in the review. Distraction arthrodesis, primary arthrodesis for displaced intra-articular calcaneal fractures, arthrodesis in combination of other procedures or adjacent joint fusions, skeletally immature patients with extra-articular STA, fusions for deformities in cerebral palsy, polio & Charcot’s arthropathy were excluded from the review. Cadaveric & biomechanical studies, animal studies, review articles, technical notes, conference proceedings & case reports were also excluded.

      Risk of bias (ROB)assessment

      ROB assessment was done using ROBINS-I tool [
      • Sterne J.A.C.
      • Hernán M.A.
      • Reeves B.C.
      • Savović J.
      • Berkman N.D.
      • Viswanathan M.
      • et al.
      The Risk Of Bias In Non-randomized Studies of Interventions ( ROBINS-I ).
      ] as advocated by the Cochrane group for assessing risk of bias in non-randomized studies of interventions by (Author2) (Author3) (Author 4). This is a tool comprising of 7 domains assessing bias from confounding(D1), selection of participants(D2), classification of intervention(D3), deviations from intended intervention(D4), missing data(D5), measurement of outcomes & reporting results (D6 &D7). Each domain & eventually overall risk of bias was graded as low, moderate, serious, critical & no information.

      Data extraction & analysis

      Each article was analysed in detail by (Author1) (Author 2) (Author 3) (Author 4) and the data was tabulated systematically by (Author2) (Author 4). Author followed by year of publication, Level of evidence (LOE), Portals/Approach for STA, number of patients/feet included in the study, duration to surgery(months), age, sex ratio, follow-up(months) was tabulated for ASTA, ISTA & for comparative studies under demographic details (Table I). Functional scores, union rates, time to union, modality used for assessment of union were tabulated for all studies (Table II). Complications were classified under hardware related; non-union, wound healing/infection & nerve related complications & analysed separately (Table III). Weighted mean values were calculated by multiplying the average mean value of a parameter with number of patients in that study. Values from each study were then added and divided by the total number of patients.
      Table 1Demographic details.
      Author(year)LOEPortals/ApproachNo. of PatientsNo. of feetMean Age (years)Sex Ratio (M:F)Duration to surgery (months)Follow-up (m)
      ASTA
      1. coulomb2019(20)IVP2P222249.516:667.7(8-468)24.1(12-38)
      2. aldahshan2018(21)IVP2P15153813:224(6-36)36(30-38)
      3. walter2018(26)IVSinus tarsi/lateral 2 portals747753.444:30NR15.3
      4. rico2017(22)IIIP2P65655038:27NR57.5(24-105)
      5. oliva2017(23)IVP2P191950.912:7NR42.9(15.5-68)
      6. albert2011(24)IVP2P101037.86:4NR21.5(12-31)
      7. lee2010(25)IVP2P16164416:0NR30(20-46)
      8. el shazly2009(13)IVLateral- 3portal1010428:2NR28.4(24-32)
      9. amendola2007(5)IVP3P1011415:545(11-168)34(24-48)
      ISTA
      10. paiva2019(32)IIILateral808047.663:17NR23.2(14.8-54.1)
      11. jangir2019((9)IVLateral1212399:3NR22(20-24)
      12. perez2015(28)IIILateral3333-Total

      17(screws), 16(staples)
      5726:7NR43(24.5-84.3)
      13. Romeo2015(29)IIILateral333341.522:11NR44(14-70)
      14. yuan2014(27)IIIA: Lateral,

      B: Sinus tarsi,

      C: Posterolateral
      10210243.264:3838(1-360)NR
      15. joveneaux2010(30)IVLateral26284819:16NRNR
      16. decarbo2010(33)IVLateral1131134954:59NR24
      17. diezi2008(31)IVLateral121545.36:6NR33(24-47)
      18. haskell2004(34)IIILateral1001015248:52NRNR
      19. mann1998(3)IIILateral44484118:2642(12-156)59.5(24-177)
      20. kitaoka1997(35)IVLateral21216018:3NR36(24-60)
      21. mangone1997(42)IVLateral32345316:16NR30.8(16-55)
      ASTA VERSUS ISTA
      22. rungprai2016 (ASTA/Open) (2)IIIPASTA/Lateral69/6060/6947.667:5466.8(6-126)23.7(6-126)
      Abbreviations: ASTA-Arthroscopic subtalar arthrodesis, ISTA-open in situ subtalar arthrodesis, LOE-Level of evidence,P2P-Posterior two portal, P3P-Posterior three portal, NR- Not Reported
      Table 2Functional Outcomes & Union Rates.


      Author(year)
      ScoringPre-operative AOFASPost-operative AOFASImprovementUnion rate (%)Time to union (weeks)Modality used for assessmentReturn to ADL/Work/Sports
      ASTA
      1. coulomb2019)(20)AOFAS,SF-12, VAS46.476.43090.9NRCTNR
      2. aldahshan2018(21)AOFAS, VAS43.489.245.81008.6XRAYNR
      3. walter2018(26)NRNRNRNR97.415.3XRAY & CT-if doubtNR
      4. rico2017(43)AOFAS51.581.935.495.412.1XRAY & CT-if doubtNR
      5. oliva2017(23)AOFAS,VAS,

      SF-12
      42.48037.694.79.8XRAY & CT-if doubtNR
      6. albert2011(24)AOFAS4778311006.8XRAY & CT-if doubtNR
      7. lee2010(25)AOFAS, Angus & Cowell3584499411XRAY & CT-if doubtNR
      8. el shazly2009(13)AOFAS38743610011.4XRAYNR
      9. amendola2007(5)AOFAS36744890.910XRAYNR
      ISTA
      10. paiva2019(36)NRNRNRNR91.3NRXRAY & CT-if doubtNR
      11. jangir2019((9)AOFASNRNRNR93.714XRAYNR
      12. perez2015(28)AOFAS54843088NRXRAY & CT-if doubtNR
      13. Romeo2015(29)AOFAS,FFI, SF3637.679.842.2NRNRXRAY25% returned to sports in 3 months, 91.6% returned to sports in 12 months, high impact sports like soccer and jogging showed decreased participation.
      14. yuan2014(27)AOFAS5785.628.6A=97, B=100, C=100.8.5XRAY & CT-if doubtNR
      15. joveneaux2010(30)AOFAS4976.527.510013XRAYNR
      16. decarbo2010(33)NRNRNRNR83.224XRAYNR
      17. diezi2008(31)AOFAS55883393.333XRAYNR
      18. haskell2004(34)NRNRNRNR9812XRAYNR
      19. mann1998(44)AOFASNR89NR100NRXRAY25/36 pre injury recreational sports
      20. kitaoka1997(35)OTHERSNRNRNR100NRXRAYNR
      21. mangone1997(42)AOFASNR77NRNRNRNRNR
      ASTA VERSUS ISTA
      22. rungprai2016 (ASTA/Open) (2)SF-36;

      FFI IMPORVEMENT AT 2 YEARS
      NRPCS: 24.5/24.8

      MCS:16/15.8;

      FFI:32.7/32.5
      NR94/9015/11XRAY & CT-if doubtADL(wks): 15.5/10.9;

      RTW(wks): 14/17.4

      RTS(wks): 30.8/24
      Abbreviations: ASTA-Arthroscopic subtalar arthrodesis, ISTA-open in-situ subtalar arthrodesis, AOFAS-American Orthopaedic Foot & Ankle Society ankle-hindfoot scoring system, FFI-Foot Function Index, SF(Short Form)-36, 12, NAS-Numerical analogue scale, VAS-visual analog scale, PCS-Physical component summary, MCS-mental component summary, ADL-activities of daily living, RTW-return to work, RTS-return to sports.
      Table 3Complications.


      Author(year)
      Complication RateHardware RelatedNon UnionWound Healing/InfectionNerve RelatedOthers
      ASTA
      1. coulomb2019(20)8/28(36%)NIL2(9%)NIL2(7%)Impingement(2)
      2. aldahshan2018(21)NRNRNILNRNRNR
      3. walter2018(26)13/74(17.5%)7(9.4%)2(2.7%)1(1%)NILCRPS(1),FHL rupture(1),DVT(1)
      4. rico2017(43)9/65(13.8%)5(7.6%)3(4.6%)1(1.5%)NILNIL
      5. oliva2017(23)4/19(21%)2(10%)1(5.2%)NIL1(5.2%)NIL
      6. albert2011(24)2/10(20%)NILNILNILNIL2- lateral impingement
      7. lee2010(25)2/16(12.5%)NIL1(6.25%)1(6%)NILNIL
      8. el shazly2009(13)1/10(10%)NILNILNIL1(10%)NIL
      9. amendola2007(5)2/10(20%)1(10%)1NILNILNIL
      ISTA
      10. paiva2019(35)7/80(8.7%)NIL7(9%)NILNILNIL
      11. jangir2019((9)1/11(9%)NIL1(8.3%)NILNILNIL
      12. perez2015(28)4/33(11%)NIL4(12.1%)NILNILNIL
      13. Romeo2015(29)2/33(6%)NILNRNILNILNIL
      14. yuan2014(27)15/102(14%)NIL1(1%)NIL14(13.7%)NIL
      15. joveneaux2010(30)11/28(39%)NILNIL1(3.5%)4(14%)1-varus malunion, 1-DVT, 4- RSD
      16. decarbo2010(33)47/113(41%)23(20.3%)19(16.8%)5(4.4%)NILNIL
      17. diezi2008(31)5/12(41.6%)4(33.3%)1(6.6%)NILNILNIL
      18. haskell2004(34)15/101(15%)13(13%)2(2%)NILNILNIL
      19. mann1998(44)30/44(68%)16(36%)NILNIL14(32%)NIL
      20. kitaoka1997(35)1/21(5%)NILNIL1(5%)NILNIL
      21. mangone1997(42)2/32(6%)2(6.2%)NRNILNILNIL
      ASTA VERSUS ISTA
      22. rungprai2016(21) ASTA

      ISTA
      20/69(29%)

      27/60(45%)
      9(13%)

      5(8%)
      4/69(5.8%)

      6/60(10%)
      0

      1(1.7%)
      4(6%)

      8(13.3%)
      Painful scar:2/6,

      CRPS1/1
      Abbreviations: ASTA-Arthroscopic subtalar arthrodesis, ISTA-open in situ subtalar arthrodesis, FHL-flexor hallucis longus, DVT-Deep vein thrombosis, RSD-reflex sympathetic dystrophy.

      Results

      Screening Process

      The initial search identified 800 articles, all of which were screened to exclude duplicates(n=294). Among the 506 patients, the title & abstracts were screened by two reviewers to exclude those not relevant to the review(n=463), leaving 43 articles for detailed analysis. Full text retrieval was attempted for these filtered 43 articles. 21 articles were excluded due to non-availability of full text/ other language(n=2), those including distraction arthrodesis/primary arthrodesis/combination of other procedures, extra-articular arthrodesis(n=12), STA using minimally invasive techniques/using trephine(n=4), duplicates(n=2) & one being a Level -V study, which left a total of 22 articles(9- ASTA, 12- ISTA & one retrospective study comparing both the techniques) for this systematic review with a total of 978(ASTA-310, ISTA-668) patients. The PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) flowchart depicting the results of screening & selection has been outlined in Fig 1. The highlight of the screening process was a lack of Level I & Level II studies between the two methods for STA.
      Fig1
      Fig1Flow chart depicting the results of screening & selection.

      Risk Of Bias Assesment & Critical Appraisal

      ROB assessment revealed majority studies included were prospective/retrospective level III/IV studies. 12 studies had only moderate ROB in at least one domain making them comparable to a well conducted non randomized study. One study by Jangir et al[
      • Jangir N.K.
      • Sharma M.
      • Meena M.
      • Jhanwar P.
      Functional outcome of subtalar arthrodesis in posttraumatic arthritis.
      ], was analyzed to have serious bias in measuring outcomes & reporting results. 9 out of 22 studies had a low risk of bias, making them comparable to a well conducted randomized trial. These results were plotted graphically as “traffic light” plots for each study using the Robvis tool[
      • McGuinness L.A.
      • Higgins J.P.T.
      Risk-of-bias VISualization (robvis): An R package and Shiny web app for visualizing risk-of-bias assessments.
      ] (Fig 2).
      Fig 2
      Fig 2Risk of bias Assessment using ROBINS-I (Risk of bias in non-randomized studies of interventions) & ROBVIS TOOL (Visualization tool for risk of bias assessments in a systematic review)
      There were no randomised studies comparing the two techniques. None of the studies had a comparative group except one study by Rungprai et al[
      • Rungprai C.
      • Phisitkul P.
      • Femino J.E.
      • Martin K.D.
      • Saltzman C.L.
      • Amendola A.
      Outcomes and complications after open versus posterior arthroscopic Subtalar Arthrodesis in 121 patients.
      ]. Both techniques included patients undergoing isolated STA for varied indications without additional procedures. American Orthopaedic Foot & Ankle Society (AOFAS) ankle-hindfoot scoring system[
      • Kitaoka H.B.
      • Alexander I.J.
      • Adelaar R.S.
      • Nunley J.A.
      • Myerson M.S.
      • Sanders M.
      Clinical rating systems for the ankle-hindfoot, midfoot, hallux, and lesser toes.
      ], Foot Function Index (FFI)[
      • Budiman-Mak E.
      • Conrad K.J.
      • Roach K.E.
      The Foot Function Index: a measure of foot pain and disability.
      ], Short Form (SF)-36[
      • Brazier J.
      • Roberts J.
      • Deverill M.
      The estimation of a preference-based measure of health from the SF-36.
      ], SF-12[
      • Forero C.G.
      • Vilagut G.
      • Adroher N.D.
      • Alonso J.
      Multidimensional item response theory models yielded good fit and reliable scores for the Short Form-12 questionnaire.
      ], Angus and Cowell rating scale scores[
      • Angus P.D.
      • Cowell H.R.
      Triple arthrodesis. A critical long-term review.
      ], Numerical analogue scale(NAS)[
      • Rungprai C.
      • Phisitkul P.
      • Femino J.E.
      • Martin K.D.
      • Saltzman C.L.
      • Amendola A.
      Outcomes and complications after open versus posterior arthroscopic Subtalar Arthrodesis in 121 patients.
      ], visual analogue scale (VAS)[
      • Rungprai C.
      • Phisitkul P.
      • Femino J.E.
      • Martin K.D.
      • Saltzman C.L.
      • Amendola A.
      Outcomes and complications after open versus posterior arthroscopic Subtalar Arthrodesis in 121 patients.
      ] were the outcome measures reported across the studies. However, AOFAS modified with a maximum score of 94(compensation for loss of subtalar joint function)[
      • Coulomb R.
      • Hsayri E.
      • Nougarede B.
      • Marchand P.
      • Mares O.
      • Kouyoumdjian P.
      • et al.
      Do clinical results of arthroscopic subtalar arthrodesis correlate with CT fusion ratio?.
      ] was the most commonly used scoring system for reporting the outcomes.However, both preoperative & postoperative AOFAS scores were reported only in 12 studies[
      • Amendola A.
      • Lee K.-B.
      • Saltzman C.L.
      • Suh J.-S.
      Technique and early experience with posterior arthroscopic subtalar arthrodesis.
      ] [
      • Coulomb R.
      • Hsayri E.
      • Nougarede B.
      • Marchand P.
      • Mares O.
      • Kouyoumdjian P.
      • et al.
      Do clinical results of arthroscopic subtalar arthrodesis correlate with CT fusion ratio?.
      ] [
      • Aldahshan W.
      • El-Sherief F.
      • Abdelaziz A.M.
      Arthroscopic subtalar arthrodesis in malunited fracture calcaneus.
      ] [
      • Vilá y Rico J.
      • Jiménez Díaz V.
      • Bravo Gimenez B.
      • Mellado Romero M.Á.
      • Ojeda Thies C.
      Results of arthroscopic subtalar arthrodesis for adult-acquired flatfoot deformity vs posttraumatic arthritis.
      ] [
      • Oliva X.M.
      • Falcão P.
      • Cerqueira R.F.
      • Rodrigues-Pinto R.
      Posterior arthroscopic subtalar arthrodesis: clinical and radiologic review of 19 cases.
      ] [
      • Albert A.
      • Deleu P.A.
      • Leemrijse T.
      • Maldague P.
      • Devos Bevernage B.
      Posterior arthroscopic subtalar arthrodesis: Ten cases at one-year follow-up.
      ] [
      • Lee K.B.
      • Park C.H.
      • Seon J.K.
      • Kim M.S.
      Arthroscopic Subtalar Arthrodesis Using a Posterior 2-Portal Approach in the Prone Position.
      ] [
      • El Shazly O.
      • Nassar W.
      • El Badrawy A.
      Arthroscopic subtalar fusion for post-traumatic subtalar arthritis.
      ] [
      • Herrera-Pérez M.
      • Andarcia-Bañuelos C.
      • Barg A.
      • Wiewiorski M.
      • Valderrabano V.
      • Kapron A.L.
      • et al.
      Comparison of cannulated screws versus compression staples for subtalar arthrodesis fixation.
      ] [
      • Romeo G.
      • Martinelli N.
      • Bonifacini C.
      • Bianchi A.
      • Sartorelli E.
      • Malerba F.
      Recreational Sports Activities After Calcaneal Fractures and Subsequent Subtalar Joint Arthrodesis.
      ] [
      • Yuan C.
      • Tan X.
      • Zhou B.-H.
      • Liu J.
      • Tao X.
      • Tang K.-L.
      Differential efficacy of subtalar fusion with three operative approaches.
      ] [
      • Diezi C.
      • Favre P.
      • Vienne P.
      Primary isolated subtalar arthrodesis: Outcome after 2 to 5 years follow-up.
      ].
      There was a lack of single modality for analysing union with plain radiographs being employed most commonly with the use of CT scans utilized when in doubt of union.

      ASTA

      The ASTA technique is broadly categorized depending on the portals employed for STA. The initial approach was by using anterolateral-posterolateral (AL/PL) portals as described by Tasto in 1992 [
      • Tasto J.P.
      Arthroscopy of the subtalar joint and arthroscopic subtalar arthrodesis.
      ] while later on van Djik et al in 2000[

      van Dijk CN. Subtalar Arthrodesis. In: Ankle Arthroscopy. Springer; 2014. p. 309–15. doi: https://doi.org/10.1007/978-3-642-35989-7

      ] popularized the posterolateral-posteromedial (PL/PM) approach/ posterior arthroscopic STA(PASTA) technique. We had two studies [
      • El Shazly O.
      • Nassar W.
      • El Badrawy A.
      Arthroscopic subtalar fusion for post-traumatic subtalar arthritis.
      ] [
      • Walter R.P.
      • Walker R.W.
      • Butler M.
      • Parsons S.
      Arthroscopic subtalar arthrodesis through the sinus tarsi portal approach: A series of 77 cases.
      ] that employed the lateral approach while rest employed the PASTA technique for STA.
      310 patients were included in the ASTA group with weighted mean age of 48(SD-5.8) years with a mean duration of symptoms of 59.5(21.9) months. The most common indication was post traumatic arthritis following malunited calcaneum fracture(n=146) (62%) followed by primary arthritis(n=3) (13%), adult acquired flat foot(n=28) (11.8%), Talocalcaneal coalitions(n=18) (7.6%) & inflammatory arthritis(n=9) (3.8%) respectively among 9 studies with 236 patients that reported the indications [
      • Rungprai C.
      • Phisitkul P.
      • Femino J.E.
      • Martin K.D.
      • Saltzman C.L.
      • Amendola A.
      Outcomes and complications after open versus posterior arthroscopic Subtalar Arthrodesis in 121 patients.
      ] [
      • Amendola A.
      • Lee K.-B.
      • Saltzman C.L.
      • Suh J.-S.
      Technique and early experience with posterior arthroscopic subtalar arthrodesis.
      ] [
      • Coulomb R.
      • Hsayri E.
      • Nougarede B.
      • Marchand P.
      • Mares O.
      • Kouyoumdjian P.
      • et al.
      Do clinical results of arthroscopic subtalar arthrodesis correlate with CT fusion ratio?.
      ,
      • Aldahshan W.
      • El-Sherief F.
      • Abdelaziz A.M.
      Arthroscopic subtalar arthrodesis in malunited fracture calcaneus.
      ,
      • Vilá y Rico J.
      • Jiménez Díaz V.
      • Bravo Gimenez B.
      • Mellado Romero M.Á.
      • Ojeda Thies C.
      Results of arthroscopic subtalar arthrodesis for adult-acquired flatfoot deformity vs posttraumatic arthritis.
      ,
      • Oliva X.M.
      • Falcão P.
      • Cerqueira R.F.
      • Rodrigues-Pinto R.
      Posterior arthroscopic subtalar arthrodesis: clinical and radiologic review of 19 cases.
      ,
      • Albert A.
      • Deleu P.A.
      • Leemrijse T.
      • Maldague P.
      • Devos Bevernage B.
      Posterior arthroscopic subtalar arthrodesis: Ten cases at one-year follow-up.
      ,
      • Lee K.B.
      • Park C.H.
      • Seon J.K.
      • Kim M.S.
      Arthroscopic Subtalar Arthrodesis Using a Posterior 2-Portal Approach in the Prone Position.
      ,
      • El Shazly O.
      • Nassar W.
      • El Badrawy A.
      Arthroscopic subtalar fusion for post-traumatic subtalar arthritis.
      ]. Subtalar instability & Talus fracture were other indications for ASTA. Additional procedures for flat foot deformity correction per say have not been mentioned among studies that included STA for adult acquired flat foot(AAFD)[
      • Rungprai C.
      • Phisitkul P.
      • Femino J.E.
      • Martin K.D.
      • Saltzman C.L.
      • Amendola A.
      Outcomes and complications after open versus posterior arthroscopic Subtalar Arthrodesis in 121 patients.
      ] [
      • Vilá y Rico J.
      • Jiménez Díaz V.
      • Bravo Gimenez B.
      • Mellado Romero M.Á.
      • Ojeda Thies C.
      Results of arthroscopic subtalar arthrodesis for adult-acquired flatfoot deformity vs posttraumatic arthritis.
      ].In patients undergoing ASTA in 8 studies which reported AOFAS scores[
      • Amendola A.
      • Lee K.-B.
      • Saltzman C.L.
      • Suh J.-S.
      Technique and early experience with posterior arthroscopic subtalar arthrodesis.
      ] [
      • Coulomb R.
      • Hsayri E.
      • Nougarede B.
      • Marchand P.
      • Mares O.
      • Kouyoumdjian P.
      • et al.
      Do clinical results of arthroscopic subtalar arthrodesis correlate with CT fusion ratio?.
      ,
      • Aldahshan W.
      • El-Sherief F.
      • Abdelaziz A.M.
      Arthroscopic subtalar arthrodesis in malunited fracture calcaneus.
      ,
      • Vilá y Rico J.
      • Jiménez Díaz V.
      • Bravo Gimenez B.
      • Mellado Romero M.Á.
      • Ojeda Thies C.
      Results of arthroscopic subtalar arthrodesis for adult-acquired flatfoot deformity vs posttraumatic arthritis.
      ,
      • Oliva X.M.
      • Falcão P.
      • Cerqueira R.F.
      • Rodrigues-Pinto R.
      Posterior arthroscopic subtalar arthrodesis: clinical and radiologic review of 19 cases.
      ,
      • Albert A.
      • Deleu P.A.
      • Leemrijse T.
      • Maldague P.
      • Devos Bevernage B.
      Posterior arthroscopic subtalar arthrodesis: Ten cases at one-year follow-up.
      ,
      • Lee K.B.
      • Park C.H.
      • Seon J.K.
      • Kim M.S.
      Arthroscopic Subtalar Arthrodesis Using a Posterior 2-Portal Approach in the Prone Position.
      ,
      • El Shazly O.
      • Nassar W.
      • El Badrawy A.
      Arthroscopic subtalar fusion for post-traumatic subtalar arthritis.
      ], weighted pre-operative scores improved from 45.4(SD-5.8) to 93.5(SD-7.8) post-operatively with a mean improvement of 43.4. Majority i.e., 5/9 studies [
      • Vilá y Rico J.
      • Jiménez Díaz V.
      • Bravo Gimenez B.
      • Mellado Romero M.Á.
      • Ojeda Thies C.
      Results of arthroscopic subtalar arthrodesis for adult-acquired flatfoot deformity vs posttraumatic arthritis.
      ,
      • Oliva X.M.
      • Falcão P.
      • Cerqueira R.F.
      • Rodrigues-Pinto R.
      Posterior arthroscopic subtalar arthrodesis: clinical and radiologic review of 19 cases.
      ,
      • Albert A.
      • Deleu P.A.
      • Leemrijse T.
      • Maldague P.
      • Devos Bevernage B.
      Posterior arthroscopic subtalar arthrodesis: Ten cases at one-year follow-up.
      ,
      • Lee K.B.
      • Park C.H.
      • Seon J.K.
      • Kim M.S.
      Arthroscopic Subtalar Arthrodesis Using a Posterior 2-Portal Approach in the Prone Position.
      ] [
      • Walter R.P.
      • Walker R.W.
      • Butler M.
      • Parsons S.
      Arthroscopic subtalar arthrodesis through the sinus tarsi portal approach: A series of 77 cases.
      ] employed plain radiographs to assess union and in doubtful cases used CT (computerized tomography). Patients undergoing ASTA, had a weighted average union rate of 95.5% (10 studies, 305 patients) with a weighted average time to union of 12.2 weeks (9 studies,288 patients). The overall weighted average complication rate was 13.1. Hardware related complications were the most common complication in patients undergoing ASTA with a weighted average of 8% followed by non-union( weighted average of 4.5%). Wound healing problems/ infection(weighted average-1%), nerve injury( weighted average of 1%), FHL rupture, Complex regional pain syndrome(CRPS) were other reported complications.

      ISTA

      The open technique of arthrodesis can be broadly divided into the traditional lateral approach using a skin incision between the tip of lateral malleolus and the base of 4th metatarsal, the sinus tarsi approach using a parallel incision along the sinus tarsi & a posterolateral L approach employing an incision from the base of the 5th metatarsal curving upward along the lateral border of tendoachilles[
      • Yuan C.
      • Tan X.
      • Zhou B.-H.
      • Liu J.
      • Tao X.
      • Tang K.-L.
      Differential efficacy of subtalar fusion with three operative approaches.
      ].Most studies in our review employed the traditional lateral approach while one study by yuan et al[
      • Yuan C.
      • Tan X.
      • Zhou B.-H.
      • Liu J.
      • Tao X.
      • Tang K.-L.
      Differential efficacy of subtalar fusion with three operative approaches.
      ].,described the differential efficacy of three approaches.
      668 patients underwent ISTA with weighted average age of 50.2(SD-6.5) years & a weighted average symptom duration of 45.4 months. The most common indication was post traumatic arthritis following malunited calcaneum fracture (n=347) (52%) followed by primary arthritis (n=117) (17.5%), adult acquired flat foot(n=64) (9.5%), talocalcaneal coalition(n=30) (4%) & inflammatory arthritis(n=24) (3.5%) respectively among 13 studies with 668 patients. Infection including tuberculosis, Osteochondral lesions of talus & calcaneum, Subtalar joint instability & Talus fracture were other indications for ASTA.
      In 6 studies that included 206 patients that reported the pre-operative & post-operative AOFAS scores, the pre-operative scores improved from a weighted average of 52.2(SD-4.8) to 84.3(SD-5.1) post-operatively with a mean improvement of 31.1[
      • Rungprai C.
      • Phisitkul P.
      • Femino J.E.
      • Martin K.D.
      • Saltzman C.L.
      • Amendola A.
      Outcomes and complications after open versus posterior arthroscopic Subtalar Arthrodesis in 121 patients.
      ] [
      • Herrera-Pérez M.
      • Andarcia-Bañuelos C.
      • Barg A.
      • Wiewiorski M.
      • Valderrabano V.
      • Kapron A.L.
      • et al.
      Comparison of cannulated screws versus compression staples for subtalar arthrodesis fixation.
      ,
      • Romeo G.
      • Martinelli N.
      • Bonifacini C.
      • Bianchi A.
      • Sartorelli E.
      • Malerba F.
      Recreational Sports Activities After Calcaneal Fractures and Subsequent Subtalar Joint Arthrodesis.
      ,
      • Yuan C.
      • Tan X.
      • Zhou B.-H.
      • Liu J.
      • Tao X.
      • Tang K.-L.
      Differential efficacy of subtalar fusion with three operative approaches.
      ,
      • Diezi C.
      • Favre P.
      • Vienne P.
      Primary isolated subtalar arthrodesis: Outcome after 2 to 5 years follow-up.
      ] [
      • Joveniaux P.
      • Harisboure A.
      • Ohl X.
      • Dehoux E.
      Long-term results of in situ subtalar arthrodesis.
      ]. Among 11 studies that reported the union rates [
      • Rungprai C.
      • Phisitkul P.
      • Femino J.E.
      • Martin K.D.
      • Saltzman C.L.
      • Amendola A.
      Outcomes and complications after open versus posterior arthroscopic Subtalar Arthrodesis in 121 patients.
      ] [
      • Mann R.A.
      • Beaman D.N.
      • Horton G.A.
      Isolated subtalar arthrodesis.
      ] [
      • Jangir N.K.
      • Sharma M.
      • Meena M.
      • Jhanwar P.
      Functional outcome of subtalar arthrodesis in posttraumatic arthritis.
      ] [
      • Herrera-Pérez M.
      • Andarcia-Bañuelos C.
      • Barg A.
      • Wiewiorski M.
      • Valderrabano V.
      • Kapron A.L.
      • et al.
      Comparison of cannulated screws versus compression staples for subtalar arthrodesis fixation.
      ] [
      • Yuan C.
      • Tan X.
      • Zhou B.-H.
      • Liu J.
      • Tao X.
      • Tang K.-L.
      Differential efficacy of subtalar fusion with three operative approaches.
      ] [
      • Diezi C.
      • Favre P.
      • Vienne P.
      Primary isolated subtalar arthrodesis: Outcome after 2 to 5 years follow-up.
      ] [
      • Joveniaux P.
      • Harisboure A.
      • Ohl X.
      • Dehoux E.
      Long-term results of in situ subtalar arthrodesis.
      ,
      • Paiva J.
      • Mansur H.
      • Moreira I.
      • Junior D.C.
      Subtalar arthrodesis : does a second screw increase the fusion rate.
      ,
      • DeCarbo W.T.
      • Berlet G.C.
      • Hyer C.F.
      • Smith W.B.
      Single-screw fixation for subtalar joint fusion does not increase nonunion rate.
      ,
      • Haskell A.
      • Pfeiff C.
      • Mann R.
      Subtalar joint arthrodesis using a single lag screw.
      ,
      • Kitaoka H.B.
      • Patzer G.L.
      Subtalar arthrodesis for posterior tibial tendon dysfunction and pes planus.
      ] majority i.e., 6 studies employed only plain radiographs for assessing bony union. The weighted average union rate in patients undergoing ISTA was 90.7% (11 studies, 603 patients). Among the 7 studies[
      • Rungprai C.
      • Phisitkul P.
      • Femino J.E.
      • Martin K.D.
      • Saltzman C.L.
      • Amendola A.
      Outcomes and complications after open versus posterior arthroscopic Subtalar Arthrodesis in 121 patients.
      ] [
      • Jangir N.K.
      • Sharma M.
      • Meena M.
      • Jhanwar P.
      Functional outcome of subtalar arthrodesis in posttraumatic arthritis.
      ] [
      • Yuan C.
      • Tan X.
      • Zhou B.-H.
      • Liu J.
      • Tao X.
      • Tang K.-L.
      Differential efficacy of subtalar fusion with three operative approaches.
      ] [
      • Diezi C.
      • Favre P.
      • Vienne P.
      Primary isolated subtalar arthrodesis: Outcome after 2 to 5 years follow-up.
      ] [
      • Joveniaux P.
      • Harisboure A.
      • Ohl X.
      • Dehoux E.
      Long-term results of in situ subtalar arthrodesis.
      ] [
      • DeCarbo W.T.
      • Berlet G.C.
      • Hyer C.F.
      • Smith W.B.
      Single-screw fixation for subtalar joint fusion does not increase nonunion rate.
      ] [
      • Haskell A.
      • Pfeiff C.
      • Mann R.
      Subtalar joint arthrodesis using a single lag screw.
      ] reporting the time to union, the weighted average time to union was 15.5 weeks. The overall weighted average complication rate was 20.3%. Hardware related complications were the most common complications as in patients undergoing ASTA with weighted average of 9.3%. Wound healing problems/ infection(weighted average - 1%), nerve injury(weighted average - 5.9%), Complex regional pain syndrome(CRPS) & painful scar were other reported complications. The Weighted mean average values for all parameters in both procedures have been summarized in Table IV.
      Table 4Weighted average mean Values.
      ParametersNumber of patients included for the pooled outcome

      ASTA:ISTA
      ASTA

      Mean(SD)
      ISTA

      Mean(SD)
      Age(years)

      Duration to surgery(months)

      Follow up(months)

      Pre-operative AOFAS

      Post-operative AOFAS

      Improvement in AOFAS scores

      Union rate(%)

      Time to fusion(weeks)

      Complication rate(%)
      310:668

      116:210

      310:466

      167:206

      145:330

      145:206

      310: 651

      288:425

      295:668
      48(5.8)

      59.5(21.9)

      31.7(12.5)

      45.4(5.8)

      93.5(7.8)

      43.4

      95.5(3.6)

      12.2(2.4)

      13.1(8.9)
      50.2(6.5)

      45.4(14.2)

      32.7(13.2)

      52.2(4.8)

      84.3(5.1)

      31.1

      90.7(6)

      15.5(8.4)

      20.3(16.2)
      Abbreviations: ASTA-Arthroscopic subtalar arthrodesis, ISTA-open in situ subtalar arthrodesis, SD(Standard deviation)
      Both staples[
      • Herrera-Pérez M.
      • Andarcia-Bañuelos C.
      • Barg A.
      • Wiewiorski M.
      • Valderrabano V.
      • Kapron A.L.
      • et al.
      Comparison of cannulated screws versus compression staples for subtalar arthrodesis fixation.
      ] and cannulated cancellous screws with diameter ranging from 5.5-8mm[
      • Rungprai C.
      • Phisitkul P.
      • Femino J.E.
      • Martin K.D.
      • Saltzman C.L.
      • Amendola A.
      Outcomes and complications after open versus posterior arthroscopic Subtalar Arthrodesis in 121 patients.
      ] have been used in the studies included for STA. Regarding the fixation methods, Perez et al [
      • Herrera-Pérez M.
      • Andarcia-Bañuelos C.
      • Barg A.
      • Wiewiorski M.
      • Valderrabano V.
      • Kapron A.L.
      • et al.
      Comparison of cannulated screws versus compression staples for subtalar arthrodesis fixation.
      ] found no difference in outcomes, union rates & complications between staples & cannulated screws for STA in their series of 33 patients. The use of a second screw did not increase fusion rates in two studies[
      • Paiva J.
      • Mansur H.
      • Moreira I.
      • Junior D.C.
      Subtalar arthrodesis : does a second screw increase the fusion rate.
      ] [
      • DeCarbo W.T.
      • Berlet G.C.
      • Hyer C.F.
      • Smith W.B.
      Single-screw fixation for subtalar joint fusion does not increase nonunion rate.
      ]. Though posterior-anterior (PA) screw insertion has been the most prevalent method for fixation across studies two studies employed the anterior-posterior fixation(AP)[
      • Yuan C.
      • Tan X.
      • Zhou B.-H.
      • Liu J.
      • Tao X.
      • Tang K.-L.
      Differential efficacy of subtalar fusion with three operative approaches.
      ] [
      • DeCarbo W.T.
      • Berlet G.C.
      • Hyer C.F.
      • Smith W.B.
      Single-screw fixation for subtalar joint fusion does not increase nonunion rate.
      ].Three studies reported the surgical time[
      • Rungprai C.
      • Phisitkul P.
      • Femino J.E.
      • Martin K.D.
      • Saltzman C.L.
      • Amendola A.
      Outcomes and complications after open versus posterior arthroscopic Subtalar Arthrodesis in 121 patients.
      ] [
      • Aldahshan W.
      • El-Sherief F.
      • Abdelaziz A.M.
      Arthroscopic subtalar arthrodesis in malunited fracture calcaneus.
      ] [
      • Albert A.
      • Deleu P.A.
      • Leemrijse T.
      • Maldague P.
      • Devos Bevernage B.
      Posterior arthroscopic subtalar arthrodesis: Ten cases at one-year follow-up.
      ] while 4 studies reported the length of hospital stay[
      • Rungprai C.
      • Phisitkul P.
      • Femino J.E.
      • Martin K.D.
      • Saltzman C.L.
      • Amendola A.
      Outcomes and complications after open versus posterior arthroscopic Subtalar Arthrodesis in 121 patients.
      ] [
      • Aldahshan W.
      • El-Sherief F.
      • Abdelaziz A.M.
      Arthroscopic subtalar arthrodesis in malunited fracture calcaneus.
      ] [
      • Albert A.
      • Deleu P.A.
      • Leemrijse T.
      • Maldague P.
      • Devos Bevernage B.
      Posterior arthroscopic subtalar arthrodesis: Ten cases at one-year follow-up.
      ] [
      • Walter R.P.
      • Walker R.W.
      • Butler M.
      • Parsons S.
      Arthroscopic subtalar arthrodesis through the sinus tarsi portal approach: A series of 77 cases.
      ]. The reported surgical time for ASTA in our review varied from 50-160 mins[
      • Rungprai C.
      • Phisitkul P.
      • Femino J.E.
      • Martin K.D.
      • Saltzman C.L.
      • Amendola A.
      Outcomes and complications after open versus posterior arthroscopic Subtalar Arthrodesis in 121 patients.
      ] [
      • Aldahshan W.
      • El-Sherief F.
      • Abdelaziz A.M.
      Arthroscopic subtalar arthrodesis in malunited fracture calcaneus.
      ] depending on the experience of the surgeon. Rungprai et al[
      • Rungprai C.
      • Phisitkul P.
      • Femino J.E.
      • Martin K.D.
      • Saltzman C.L.
      • Amendola A.
      Outcomes and complications after open versus posterior arthroscopic Subtalar Arthrodesis in 121 patients.
      ] reported a mean surgical time of 100 mins( range, 65-160) for PASTA as compared to 93.4 mins(range, 47-139) for open in situ STA, that was statistically significant. The weighted average hospital stay in our review was 1.73 days in the ASTA group among 4 studies [
      • Amendola A.
      • Lee K.-B.
      • Saltzman C.L.
      • Suh J.-S.
      Technique and early experience with posterior arthroscopic subtalar arthrodesis.
      ] [
      • Aldahshan W.
      • El-Sherief F.
      • Abdelaziz A.M.
      Arthroscopic subtalar arthrodesis in malunited fracture calcaneus.
      ] [
      • Albert A.
      • Deleu P.A.
      • Leemrijse T.
      • Maldague P.
      • Devos Bevernage B.
      Posterior arthroscopic subtalar arthrodesis: Ten cases at one-year follow-up.
      ] [
      • Walter R.P.
      • Walker R.W.
      • Butler M.
      • Parsons S.
      Arthroscopic subtalar arthrodesis through the sinus tarsi portal approach: A series of 77 cases.
      ] while Rungprai et al[
      • Rungprai C.
      • Phisitkul P.
      • Femino J.E.
      • Martin K.D.
      • Saltzman C.L.
      • Amendola A.
      Outcomes and complications after open versus posterior arthroscopic Subtalar Arthrodesis in 121 patients.
      ] reported a range of 0-1 day of hospital stay for ASTA group versus 0.4-4.3 days of hospital stay for ISTA group. One study reported the time to return to activities of daily living as 15.5(SD-2.9) weeks for ASTA & 10.9(SD- 2.5) weeks for ISTA [
      • Rungprai C.
      • Phisitkul P.
      • Femino J.E.
      • Martin K.D.
      • Saltzman C.L.
      • Amendola A.
      Outcomes and complications after open versus posterior arthroscopic Subtalar Arthrodesis in 121 patients.
      ]. Time to return for sports was 24(SD-3.4) weeks & 30.8(SD-7.7) for ASTA & ISTA respectively [
      • Rungprai C.
      • Phisitkul P.
      • Femino J.E.
      • Martin K.D.
      • Saltzman C.L.
      • Amendola A.
      Outcomes and complications after open versus posterior arthroscopic Subtalar Arthrodesis in 121 patients.
      ]. Romeo et al [
      • Romeo G.
      • Martinelli N.
      • Bonifacini C.
      • Bianchi A.
      • Sartorelli E.
      • Malerba F.
      Recreational Sports Activities After Calcaneal Fractures and Subsequent Subtalar Joint Arthrodesis.
      ] reported that sports participation reached pre-surgery levels, however there was a shift from high to low impact activities post ISTA.

      Discussion

      The most important finding of our review is that ASTA results in a better functional outcome, union rate, faster time to union with less complication rate than ISTAAnother striking finding is the lack of level I and level II studies & systematic reviews/ metanalyses comparing the two procedures previously.
      There was a significant improvement in AOFAS scores post ASTA and ISTA, however the mean weighted difference between post-operative and pre-operative scores was 43.4 in ASTA & 31.21in ISTA groups respectively. Patients undergoing STA have been previously reported to have a high satisfaction rate with almost 90% of them recommending the procedure to friends and family [
      • Hollman E.J.
      • van der Vliet Q.M.J.
      • Alexandridis G.
      • Hietbrink F.
      • Leenen L.P.H.
      Functional outcomes and quality of life in patients with subtalar arthrodesis for posttraumatic arthritis.
      ]. Our review included STA for various indications that have employed different outcome measures for assessment of functional outcome at varied intervals. Though better functional outcomes were observed in patients undergoing ASTA, a conclusive opinion cannot be based on existing evidence due to lack of statistical analysis. Though the outcomes were not analysed based on etiology in most studies, mann [
      • Mann R.A.
      • Beaman D.N.
      • Horton G.A.
      Isolated subtalar arthrodesis.
      ] et al reported better functional outcomes when STA is done for patients with primary arthritis followed by patients with posterior tibialis tendon dysfunction followed by those undergoing STA for malunited calcaneal fracture. Malunited calcaneal fractures maybe associated with problems such as varus malunion, loss of heel height, lateral calcaneofibular impingement, ankle impingement which maybe better addressed by distraction arthrodesis than in situ subtalar arthrodesis(36). Hence careful patient selection especially while dealing with post-traumatic arthritis for ASTA or ISTA is necessary to obtain a high satisfaction rate.
      The overall fusion rate & time to fusion was also better in the ASTA group than in the ISTA group. Jones et al[
      • Jones C.P.
      • Coughlin M.J.
      • Shurnas P.S.
      Prospective CT scan evaluation of hindfoot nonunions treated with revision surgery and low-intensity ultrasound stimulation.
      ] concluded that CT scans were a better modality to assess fusion and that non-unions would be picked up only half the time on plain radiographs. Dorsey et al devised the CT fusion ratio and divided non-union as < 33% fusion, incomplete fusion as 34-66% and complete fusion as 67-100%[
      • Dorsey M.L.
      • Liu P.T.
      • Roberts C.C.
      • Kile T.A.
      Correlation of arthrodesis stability with degree of joint fusion on MDCT.
      ]. 11 studies in our review have employed plain radiographs, using CT scans only in case of doubt to assess union. This result could have been validated better if there was uniformity in the usage of plain radiographs or CT scans across the studies for reporting union. Union rate was not affected by using an additional screw as probably this decreased the contact surface for fusion that neutralized the actual mechanical superiority gained without any real benefit[
      • Paiva J.
      • Mansur H.
      • Moreira I.
      • Junior D.C.
      Subtalar arthrodesis : does a second screw increase the fusion rate.
      ]. Staples and cannulated screws resulted is similar fusion rates when employed for STA[
      • Herrera-Pérez M.
      • Andarcia-Bañuelos C.
      • Barg A.
      • Wiewiorski M.
      • Valderrabano V.
      • Kapron A.L.
      • et al.
      Comparison of cannulated screws versus compression staples for subtalar arthrodesis fixation.
      ].
      A direct comparison of the PASTA and lateral portal technique for STA was not possible, due to paucity of studies employing the lateral approach in our review [
      • El Shazly O.
      • Nassar W.
      • El Badrawy A.
      Arthroscopic subtalar fusion for post-traumatic subtalar arthritis.
      ] [
      • Walter R.P.
      • Walker R.W.
      • Butler M.
      • Parsons S.
      Arthroscopic subtalar arthrodesis through the sinus tarsi portal approach: A series of 77 cases.
      ]. 7/9 studies employed a posterior two portal technique for ASTA. A recently published systematic review of Level III/IV studies by Banerjee et al [
      • Banerjee S.
      • Gupta A.
      • Elhence A.
      • Choudhary R.
      Arthroscopic Subtalar Arthrodesis as a treatment strategy for Subtalar Arthritis–A Systematic Review.
      ], reported a better functional outcome, lower complication rate with a lower union rate with PASTA compared to lateral portal approach to STA. In the open in situ STA group, one study by yuan et al [
      • Yuan C.
      • Tan X.
      • Zhou B.-H.
      • Liu J.
      • Tao X.
      • Tang K.-L.
      Differential efficacy of subtalar fusion with three operative approaches.
      ] studied the differential efficacy of open in-situ STA with three approaches & found that surgical area exposed was least in sinus tarsi approach while time for exposure, intra op bleeding volume & complications are higher in PL approach while there was no difference in fusion rate/ time to fusion with the three approaches.
      The overall complication rate was more in patients undergoing ISTA than ASTA. Majority of the complications were due to the screws used for fixation irrespective of the technique. Wound related complications were 1% in both techniques, indicating that wound healing problems are not an actual concern in patients undergoing ISTA. Nerve related numbness/paresthesia due to either sural nerve/superficial peroneal nerve involvement were more in patients undergoing ISTA than ASTA probably due to the more invasive nature of the technique.
      Though the weighted average mean of the pooled data is better for ASTA than ISTA with respect to functional outcome, time to union & overall complications, conclusive recommendation to prefer one technique over another cannot be made due to lack of statistical analysis. It should be noted that ASTA can only be used in cases of isolated STA without significant deformities/malalignment. Also, most of the studies have included patients with varied indications consisting of post-traumatic and non-traumatic cases. Thus, a careful patient selection is recommended for achieving optimal outcomes especially while employing ASTA for in-situ subtalar arthrodesis.

      Limitations

      This review has taken level III/IV studies into consideration due to paucity of prospective randomized studies. As only one study had a comparative analysis [
      • Rungprai C.
      • Phisitkul P.
      • Femino J.E.
      • Martin K.D.
      • Saltzman C.L.
      • Amendola A.
      Outcomes and complications after open versus posterior arthroscopic Subtalar Arthrodesis in 121 patients.
      ] while others were either retrospective or prospective studies/series studying either of the techniques separately, variable reporting of data, variable lengths of follow up, different modalities used for analysis of union made direct comparison & statistical analysis difficult. Future directives for research would be to include large scale randomized studies comparing both the techniques with utilization of CT for assessing union with standardized outcomes measures.

      Conclusion

      From the existing literature, our review suggests that both ASTA and ISTA techniques are effective procedures for STA. However, there is no conclusive evidence to recommend one technique over another. High quality randomised studies may be further required to clearly define the superiority of one technique over another.

      Declaration of interests

      The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

      Uncited References

      • Fletcher A.N.
      • Liles J.L.
      • Steele J.J.
      • Pereira G.F.
      • Adams S.B.
      Systematic Review of Subtalar Distraction Arthrodesis for the Treatment of Subtalar Arthritis.
      .

      References

        • Rajasekaran S.
        • Sundararajan S.R.
        • Ramakanth R.
        • Shreeram V.
        • Joseph J.B.
        Is Distraction Bone Block Arthrodesis better than Subtalar Arthrodesis for Malunited Calcaneal Fractures with Subtalar Arthritis? A Retrospective Case Series.
        J Foot Ankle Surg (Asia Pacific). 2021; 8: 3-7
        • Rungprai C.
        • Phisitkul P.
        • Femino J.E.
        • Martin K.D.
        • Saltzman C.L.
        • Amendola A.
        Outcomes and complications after open versus posterior arthroscopic Subtalar Arthrodesis in 121 patients.
        J Bone Jt Surg - Am. 2016; 98: 636-646https://doi.org/10.2106/JBJS.15.00702
        • Mann R.A.
        • Beaman D.N.
        • Horton G.A.
        Isolated subtalar arthrodesis.
        Foot ankle Int. 1998; 19: 511-519https://doi.org/10.1177/107110079801900802
        • Tuijthof G.J.M.
        • Beimers L.
        • Kerkhoffs G.M.M.J.
        • Dankelman J.
        • van Dijk C.N.
        Overview of subtalar arthrodesis techniques: options, pitfalls and solutions.
        Foot ankle Surg. 2010; 16: 107-116https://doi.org/10.1016/j.fas.2009.07.002
        • Amendola A.
        • Lee K.-B.
        • Saltzman C.L.
        • Suh J.-S.
        Technique and early experience with posterior arthroscopic subtalar arthrodesis.
        Foot ankle Int. 2007; 28: 298-302https://doi.org/10.3113/FAI.2007.0298
        • Moher D.
        • Liberati A.
        • Tetzlaff J.
        • Altman D.G.
        • Altman D.
        • Antes G.
        • et al.
        Preferred reporting items for systematic reviews and meta-analyses: The PRISMA statement.
        PLoS Med. 2009; 6https://doi.org/10.1371/journal.pmed.1000097
        • Ouzzani M.
        • Hammady H.
        • Fedorowicz Z.
        • Elmagarmid A.
        Rayyan-a web and mobile app for systematic reviews.
        Syst Rev [Internet. 2016; 5 (Available from:): 1-11https://doi.org/10.1186/s13643-016-0384-4
        • Sterne J.A.C.
        • Hernán M.A.
        • Reeves B.C.
        • Savović J.
        • Berkman N.D.
        • Viswanathan M.
        • et al.
        The Risk Of Bias In Non-randomized Studies of Interventions ( ROBINS-I ).
        Bmj. 2016; 355: i4919https://doi.org/10.1136/bmj.i4919
        • Jangir N.K.
        • Sharma M.
        • Meena M.
        • Jhanwar P.
        Functional outcome of subtalar arthrodesis in posttraumatic arthritis.
        J Orthop Traumatol Rehabil. 2019; 11: 6
        • McGuinness L.A.
        • Higgins J.P.T.
        Risk-of-bias VISualization (robvis): An R package and Shiny web app for visualizing risk-of-bias assessments.
        Res Synth Methods. 2021; 12: 55-61https://doi.org/10.1002/jrsm.1411
        • Kitaoka H.B.
        • Alexander I.J.
        • Adelaar R.S.
        • Nunley J.A.
        • Myerson M.S.
        • Sanders M.
        Clinical rating systems for the ankle-hindfoot, midfoot, hallux, and lesser toes.
        Foot Ankle Int. 1994 Jul; 15: 349-353https://doi.org/10.1177/107110079401500701
        • Budiman-Mak E.
        • Conrad K.J.
        • Roach K.E.
        The Foot Function Index: a measure of foot pain and disability.
        J Clin Epidemiol. 1991; 44 (PMID: 2037861): 561-570https://doi.org/10.1016/0895-4356(91)90220-4
        • Brazier J.
        • Roberts J.
        • Deverill M.
        The estimation of a preference-based measure of health from the SF-36.
        J Health Econ. 2002; 21: 271-292https://doi.org/10.1016/s0167-6296(01)00130-8
        • Forero C.G.
        • Vilagut G.
        • Adroher N.D.
        • Alonso J.
        Multidimensional item response theory models yielded good fit and reliable scores for the Short Form-12 questionnaire.
        J Clin Epidemiol [Internet]. 2013; 66 (Available from:): 790-801https://doi.org/10.1016/j.jclinepi.2013.02.007
        • Angus P.D.
        • Cowell H.R.
        Triple arthrodesis. A critical long-term review.
        J Bone Joint Surg Br. 1986 Mar; 68: 260-265https://doi.org/10.1302/0301-620X.68B2.3958012
        • Coulomb R.
        • Hsayri E.
        • Nougarede B.
        • Marchand P.
        • Mares O.
        • Kouyoumdjian P.
        • et al.
        Do clinical results of arthroscopic subtalar arthrodesis correlate with CT fusion ratio?.
        Orthop Traumatol Surg Res. 2019; 105: 1125-1129https://doi.org/10.1016/j.otsr.2019.01.017
        • Aldahshan W.
        • El-Sherief F.
        • Abdelaziz A.M.
        Arthroscopic subtalar arthrodesis in malunited fracture calcaneus.
        Egypt Orthop J. 2017; 52: 184https://doi.org/10.4103/eoj.eoj_51_17
        • Vilá y Rico J.
        • Jiménez Díaz V.
        • Bravo Gimenez B.
        • Mellado Romero M.Á.
        • Ojeda Thies C.
        Results of arthroscopic subtalar arthrodesis for adult-acquired flatfoot deformity vs posttraumatic arthritis.
        Foot ankle Int. 2016; 37: 198-204https://doi.org/10.1016/j.fas.2015.11.007
        • Oliva X.M.
        • Falcão P.
        • Cerqueira R.F.
        • Rodrigues-Pinto R.
        Posterior arthroscopic subtalar arthrodesis: clinical and radiologic review of 19 cases.
        J Foot Ankle Surg. 2017; 56: 543-546https://doi.org/10.1053/j.jfas.2017.01.021
        • Albert A.
        • Deleu P.A.
        • Leemrijse T.
        • Maldague P.
        • Devos Bevernage B.
        Posterior arthroscopic subtalar arthrodesis: Ten cases at one-year follow-up.
        Orthop Traumatol Surg Res [Internet]. 2011; 97 (Available from:): 401-405https://doi.org/10.1016/j.otsr.2011.02.005
        • Lee K.B.
        • Park C.H.
        • Seon J.K.
        • Kim M.S.
        Arthroscopic Subtalar Arthrodesis Using a Posterior 2-Portal Approach in the Prone Position.
        Arthrosc - J Arthrosc Relat Surg [Internet]. 2010; 26 (Available from:): 230-238https://doi.org/10.1016/j.arthro.2009.07.008
        • El Shazly O.
        • Nassar W.
        • El Badrawy A.
        Arthroscopic subtalar fusion for post-traumatic subtalar arthritis.
        Arthrosc J Arthrosc Relat Surg. 2009; 25: 783-787https://doi.org/10.1016/j.arthro.2008.12.017
        • Herrera-Pérez M.
        • Andarcia-Bañuelos C.
        • Barg A.
        • Wiewiorski M.
        • Valderrabano V.
        • Kapron A.L.
        • et al.
        Comparison of cannulated screws versus compression staples for subtalar arthrodesis fixation.
        Foot ankle Int. 2015; 36: 203-210https://doi.org/10.1177/1071100714552485
        • Romeo G.
        • Martinelli N.
        • Bonifacini C.
        • Bianchi A.
        • Sartorelli E.
        • Malerba F.
        Recreational Sports Activities After Calcaneal Fractures and Subsequent Subtalar Joint Arthrodesis.
        J Foot Ankle Surg. 2015; 54: 1057-1061https://doi.org/10.1053/j.jfas.2015.05.003
        • Yuan C.
        • Tan X.
        • Zhou B.-H.
        • Liu J.
        • Tao X.
        • Tang K.-L.
        Differential efficacy of subtalar fusion with three operative approaches.
        J Orthop Surg Res. 2014; 9 ([Internet]) (Available from:doi: 10.1186/s13018-014-0115-2): 115https://doi.org/10.1186/s13018-014-0115-2
        • Diezi C.
        • Favre P.
        • Vienne P.
        Primary isolated subtalar arthrodesis: Outcome after 2 to 5 years follow-up.
        Foot Ankle Int. 2008; 29: 1195-1202https://doi.org/10.3113/FAI.2008.1195
        • Tasto J.P.
        Arthroscopy of the subtalar joint and arthroscopic subtalar arthrodesis.
        Instr Course Lect. 2006; 55 (PMID: 16958488): 555-564
      1. van Dijk CN. Subtalar Arthrodesis. In: Ankle Arthroscopy. Springer; 2014. p. 309–15. doi: https://doi.org/10.1007/978-3-642-35989-7

        • Walter R.P.
        • Walker R.W.
        • Butler M.
        • Parsons S.
        Arthroscopic subtalar arthrodesis through the sinus tarsi portal approach: A series of 77 cases.
        Foot Ankle Surg. 2018; 24: 417-422https://doi.org/10.1016/j.fas.2017.04.006
        • Joveniaux P.
        • Harisboure A.
        • Ohl X.
        • Dehoux E.
        Long-term results of in situ subtalar arthrodesis.
        Int Orthop. 2010; 34: 1199-1205https://doi.org/10.1007/s00264-010-1041-5
        • Paiva J.
        • Mansur H.
        • Moreira I.
        • Junior D.C.
        Subtalar arthrodesis : does a second screw increase the fusion rate.
        Artrodese subtalar : um segundo parafuso aumenta a taxa de consolidação ?. 2019; 13: 28-34
        • DeCarbo W.T.
        • Berlet G.C.
        • Hyer C.F.
        • Smith W.B.
        Single-screw fixation for subtalar joint fusion does not increase nonunion rate.
        Foot Ankle Spec. 2010; 3: 164-166https://doi.org/10.1177/1938640010368992
        • Haskell A.
        • Pfeiff C.
        • Mann R.
        Subtalar joint arthrodesis using a single lag screw.
        Foot ankle Int. 2004; 25: 774-777https://doi.org/10.1177/107110070402501103
        • Kitaoka H.B.
        • Patzer G.L.
        Subtalar arthrodesis for posterior tibial tendon dysfunction and pes planus.
        Clin Orthop Relat Res. 1997; 345 (PMID: 9418639): 187-194
        • Hollman E.J.
        • van der Vliet Q.M.J.
        • Alexandridis G.
        • Hietbrink F.
        • Leenen L.P.H.
        Functional outcomes and quality of life in patients with subtalar arthrodesis for posttraumatic arthritis.
        Injury. 2017; 48: 1696-1700https://doi.org/10.1016/j.injury.2017.05.018
        • Fletcher A.N.
        • Liles J.L.
        • Steele J.J.
        • Pereira G.F.
        • Adams S.B.
        Systematic Review of Subtalar Distraction Arthrodesis for the Treatment of Subtalar Arthritis.
        Foot ankle Int. 2020; 41: 437-448https://doi.org/10.1177/1071100719899050
        • Jones C.P.
        • Coughlin M.J.
        • Shurnas P.S.
        Prospective CT scan evaluation of hindfoot nonunions treated with revision surgery and low-intensity ultrasound stimulation.
        Foot Ankle Int. 2006; 27: 229-235https://doi.org/10.1177/107110070602700401
        • Dorsey M.L.
        • Liu P.T.
        • Roberts C.C.
        • Kile T.A.
        Correlation of arthrodesis stability with degree of joint fusion on MDCT.
        Am J Roentgenol. 2009; 192: 496-499https://doi.org/10.2214/AJR.08.1254
        • Banerjee S.
        • Gupta A.
        • Elhence A.
        • Choudhary R.
        Arthroscopic Subtalar Arthrodesis as a treatment strategy for Subtalar Arthritis–A Systematic Review.
        J Foot Ankle Surg. 2021 Sep-Oct; 60: 1023-1028https://doi.org/10.1053/j.jfas.2021.04.006