Does retrograde entry in femoral lengthening over nail allow greater lengthening without increasing complications? A single-surgeon cohort study

Background Despite advances in motorized internal lengthening nails, the lengthening over an intramedullary nail (LON) technique remains relevant in selected clinical scenarios. In femoral LON, both antegrade and retrograde nailing directions may be considered according to osteotomy level, deformity characteristics, and planned lengthening. Although antegrade entry is more commonly preferred, retrograde entry may offer technical advantages in selected cases. This study compared outcomes and complications between antegrade and retrograde femoral LON in a single-surgeon cohort. Methods A retrospective cohort of 44 femoral lengthening procedures between 1997 and 2018 was analyzed. Patients were divided into antegrade ( n = 18) and retrograde ( n = 26) groups based on nail entry direction. Demographic characteristics, lengthening parameters, consolidation indices, callus quality, outcome scores, and complications, which were classified using a standardized system, were compared between groups. Statistical significance was set at p < 0.05. Results The mean lengthening amount and percentage were higher in the retrograde group. The consolidation index and regenerate quality were comparable between groups. No statistically significant difference was observed between groups in overall complication rates or Grade 3 complications. Outcome scores were significantly higher in the antegrade group. Difficulty level was positively correlated with Grade 3 complications and poor callus quality. Conclusions In this retrospective single-surgeon cohort, retrograde entry in femoral LON was associated with a higher amount of achieved lengthening and percentage compared with antegrade entry, without an observed increase in overall complication rates. However, these findings should not be interpreted as evidence that retrograde entry independently permits greater lengthening or carries no additional risk, because entry direction was likely influenced by preoperative case selection, planned lengthening amount, osteotomy location, deformity characteristics, and surgeon-specific decision-making. Retrograde entry may be considered a viable option in carefully selected femoral LON cases, but larger prospective studies are needed to clarify its indications, complication profile, and comparative effectiveness.