Osteotomies Around the Knee Interfere with Alignment of the Hindfoot: A Systematic Review of Biomechanical and Clinical Studies

Category: Hindfoot; Ankle Introduction/Purpose: Several emerging reports suggest an important involvement of the hindfoot alignment in the outcome of knee osteotomy. At present these studies are scattered across the literature and lack a comprehensive overview. Therefore, we aimed to systematically review all biomechanical and clinical studies investigating the role of the hindfoot alignment in the setting of osteotomies around the knee. Methods: A systematic literature search was conducted on following databases: Pubmed, EMBASE, Cochrane Library and Web of Science. Search terms consisted of 'knee osteotomy' combined with 'hindfoot/ankle alignment'. Inclusion criteria were all English language studies analyzing the association between knee osteotomy and hindfoot alignment comprising biomechanical or clinical outcomes. Exclusion criteria consisted of knee osteotomy performed in conjunction with total knee arthroplasty and level V studies. A quality assessment was conducted using the Quality Appraisal for Cadaveric Studies (QUACS) - and modified methodologic index for non-randomized studies (MINORS) scales. This protocol was performed according to the PRISMA guidelines and registered on PROSPERO (CRD42021277189). Results: Eighteen studies were confirmed eligible and consisted of a cadaveric (n=3) -, retrospective cohort (n=14) - and case- control (n=2) study design. Following knee osteotomy, biomechanical hindfoot characteristics were also positively affected (n=4), except in rigid subtalar joint (n=1) or talar tilt (n=1) deformity. Patient symptoms and/or radiographic alignment (Fig. 1a) at the level of the hindfoot did also improve after knee osteotomy (n=13). However this did not apply in case of a small pre-operative lateral distal tibia- and hip knee ankle (HKA) angulation (Fig. 1b) or in case of a large HKA correction (>14.5°). Additionally, a pre- existent hindfoot deformity (>15.9°) was associated with undercorrection of lower limb alignment following knee osteotomy. The mean QUACS score was 61.3% (range: 46-69%) and mean MINORS score was 9.2 out of 16 (range 6-12) for non-comparative and 16.5 out of 24 (range 15-18) for comparative studies. Conclusion: Osteotomies performed to correct knee deformity have also an impact on biomechanical and clinical outcomes of the hindfoot. In general, these are reported to be beneficial, but several parameters were identified that are associated with newly onset - or deterioration of hindfoot symptoms following knee osteotomy. These results should be interpreted in light of the moderate methodological quality of the included studies. Therefore, further prospective studies are warranted to assess how diagnostic and therapeutic algorithms based on the identified criteria could be implemented to optimize the overall outcome of knee osteotomy in relation to the foot and ankle.