The "Sandwich Phenomenon": A Rare Complication in Adjacent, Double-Level X-Stop Surgery Report of Three Cases and Review of the Literature

Study Design. Case reports. Objective. To report the atraumatic fracture of the intervening (L4) spinous process (SP) in patients treated with X-Stop at 2 adjacent levels and discuss the potential underlying causes. Summary of Background Data. Limited evidence on complications in double-level X-Stop surgery is available. Methods. Three men, 47, 63, and 75 years old, respectively, underwent surgery with insertion of X-Stop at L3-L4 and L4-L5 because of low back pain and neurogenic claudication due to degenerative lumbar spine conditions. Two 10 mm devices were implanted in the first patient and two 16 mm distractors in the second man. One 10 mm X-Stop at L3-L4 and one 12 mm at L4-L5, respectively, were implanted in the third patient. No intraoperative complications occurred and the postoperative course was uneventful, with symptoms relief. Results. The first 2 patients presented because of recurrent symptoms 4 and 6 months after surgery, respectively. Imaging revealed "spontaneous" fracture of the L4 SP in both of them. Revision surgery was required, with removal of the interspinous devices, decompression and fixation. In the third patient the L4 SP fracture was detected when the patient presented because of recurrent back pain 18 months after the index surgery, but revision surgery was not consented. Conclusion. To our knowledge this is the first report describing the "sandwich phenomenon," i.e., the atraumatic fracture of the intervening SP in patients with adjacent, double-level X-Stop. Possible underlying theories and anatomic peculiarities which may predispose to this rare event are discussed.