Nail-to-bicondylar ratio, but not CPAK classification, is associated with arthrosis and deformity progression after retrograde fixator-assisted nailing for distal femoral deformity in metabolic bone disease.
retrospective_cohort · Level III
Where this comes from
- Record sourced from PubMed, PMID 42247862.
- Also identified by DOI 10.1016/j.knee.2026.104520.
- No licence information is recorded for this record.
- Because redistribution is not established, this page shows the abstract only. Follow the links below for the full text.
Abstract
Distal femoral deformities are common in metabolic bone disease and often require surgical correction. Retrograde Fixator-Assisted Nailing(r-FAN) stabilizes the femoral axis, yet the influence of nail-to-bicondylar ratio (NBR) and coronal-plane knee alignment patterns(CPAK) on deformity and osteoarthritis(OA) progression remains unclear. We retrospectively evaluated 30 limbs from 17 patients with distal femoral deformities treated with r-FAN, with a mean follow-up of 10.5 ± 4.6 years. Pre- and postoperative radiographs were analyzed for mechanical lateral distal femoral angle (mLDFA), arithmetic hip-knee-ankle angle (aHKA), joint line obliquity (aJLO), and CPAK classification. NBR and osteotomy-to-nail ratio (ONR) were measured. Predictors of mLDFA progression were assessed using Elastic Net and Ordinary Least Squares (OLS) regression, while Bayesian ordinal regression was applied to determine predictors of OA progression (KL grades). Postoperative alignment improved in both varus (mLDFA 111.88° → 96.32°) and valgus knees (71.14° → 94.00°), with aHKA approaching physiological ranges (valgus 19.50° → -3.50°, varus -24.32° → -7.14°). aJLO progression was more pronounced in valgus knees (3.23° vs -1.54°, p = 0.018). CPAK types shifted postoperatively, reflecting variable coronal alignment, but were not significant predictors of deformity or OA progression. Elastic Net and OLS regression identified NBR as the only significant predictor of mLDFA progression (β = -2.550 per 0.02-unit increase; 95%CI -3.962 to -1.136; p = 0.001; R<sup>2</sup> = 0.535). Bayesian ordinal regression confirmed its protective effect on KL progression (OR = 0.967 per 0.02-unit increase; 95%CrI 0.932-0.998). Other demographic and surgical variables, including sex, etiology, preoperative alignment, and osteotomy count, were not significant. In patients with metabolic bone disease undergoing r-FAN, higher NBR was associated with less radiographic deformity progression and lower odds of OA progression. In contrast, single time-point CPAK assessments were not associated with progression outcomes in this cohort. Level IV.