Long-term effects of retrograde approach on the knee after motorized femoral limb lengthening

Background and purpose - The retrograde femoral approach is an established technique for implantation of nails for leg lengthening and correction and in cases of distal femoral fractures. The purpose of this study was to deter-mine the 10-year outcome of this technique by analyzing the clinical long-term effects and radiological status of the knee after leg lengthening via a retrograde femoral approach.Patients and methods - This retrospective single -center study included 13 patients (median age at surgery 17 [range 15-20] years) who underwent unilateral, retrograde, femoral lengthening with a motorized nail. Outcome mea-surements were graded variables of the SF-36, ISKD score, and Lysholm score. MRI of both knees was performed in all patients. MRI was evaluated for the presence of degenerative changes and compared with the healthy contralateral knee. Cartilage condition was graded according to the Interna-tional Cartilage Repair Society (ICRS) scoring system.Results - All patients were pain-free and had a full range of motion 10 (range 10.0-12.2) years after surgery. All postoperative knees showed fibrosis of Hoffa's fat pad and moderate to severe cartilage defects (ICRS Grade 2-4) of the trochlear groove (nail entry site). 6 out of 13 operated knees exhibited retropatellar cartilage defects. Conclusion - Our study showed that patients were pain -free, but cartilage defects at the entry point and arthrofibro-sis at Hoffa's fat pad were observed without causing clinical impairment.