STRYDE versus PRECICE magnetic internal lengthening nail for femur lengthening

INTRODUCTION: Magnetic internal lengthening nails (MILNs) have been used for femoral lengthening to avoid complications associated with external fixation. The titanium version of the MILN (PRECICE(®)) has been in use since 2011 but had limitations (50–75 lb) in post-operative weight bearing. A new stainless-steel version of the MILN (STRYDE(®)) allows 150–250 lb of post-operative weight bearing. The aim is to compare the outcomes of using these two different MILNs for both unilateral and bilateral femoral lengthening. METHODS: A single-center, retrospective cohort study was conducted in which patients’ records were reviewed from the period from January 2017 to March 2020. A total of 66 femoral lengthening procedures were included in the study and were divided into two groups: STRYDE(®) group (30 femora) and PRECICE(®) group (36 femora). Outcomes assessed were the 6-months post-operative Limb Deformity-Scoliosis Research Society (LD-SRS) Score, adjacent joint range of motion (ROM), average distraction rate, bone healing index (BHI), and complications. RESULTS: No statistically significant difference was found between the two groups in regard to the (LD-SRS) score, hip ROM, or knee ROM. Statistically significant differences were found between the two groups in regard to BHI (average of 0.84 months/cm and 0.67 months/cm for STRYDE(®) and PRECICE(®), respectively) and distraction rate (average of 0.6 mm/day and 0.9 mm/day for STRYDE(®) and PRECICE(®), respectively). No mechanical nail complications were reported in the STRYDE(®) group compared to three events of nail failure in the PRECICE(®) group. One femur in the PRECICE(®) group needed BMAC injection for delayed healing compared to four femurs in the STRYDE(®) group. CONCLUSION: The STRYDE(®) MILN yields comparable functional results to those of PRECICE(®) MILN and shows fewer mechanical nail complications. However, STRYDE(®) MILN requires a slower distraction rate and yields slower healing (larger BHI). LEVEL OF EVIDENCE: Level III, Therapeutic study. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00402-021-03943-8.