Surgical treatment of insufficiency fractures after primary total knee arthroplasty

Insufficiency periprosthetic fractures after total knee arthroplasty are uncommon, typically nontraumatic events; however, clinical outcome data on their surgical management remain limited. We retrospectively reviewed 21 patients (18 women, 3 men; mean age = 76 years) who sustained femoral or tibial insufficiency periprosthetic fractures between November 2016 and January 2022 and underwent revision total knee arthroplasty with stemmed components augmented by bulk femoral-head allografts and autologous bone graft. Five patients with preoperative valgus alignment presented medial condylar fractures, whereas sixteen patients with varus deformity exhibited ten lateral and 6 medial condylar fractures. At a mean follow-up of 25 months (range, 17-36 months), allograft-to-host union was achieved in 15 ± 4 weeks. The postoperative mechanical axis averaged 1° of varus (range, 7.8° varus to 4.5° valgus) At the latest follow-up, the mean Knee Society knee score was 88 points (72-95), the Knee Society function score was 60 points (35-75), and the range of knee motion was 116° (95°-145°). One periprosthetic infection occurred, and no cases of implant loosening, allograft fracture, or nonunion were observed. Three IPF patterns and their putative mechanisms were identified. Femoral-head allografts in conjunction with a stemmed component and autogenous bone graft may be a good alternative for this situation. Most patients had satisfactory clinical outcomes and graft healing, although longer-term surveillance is warranted to clarify graft behavior and late complications.