Role of femoral ring allograft in anterior interbody fusion of the spine.

A review was carried out on 59 patients (10 males and 49 females) who had anterior interbody fusion performed with femoral ring allograft packed with autograft bone chips with a minimum follow up of 2 years. The average age at the time of surgery was 49.1 year old (26 to 75). The total number of levels grafted was 141. The diagnosis consisted of multiple degenerative disease in 6, degenerative change below the long segment of fusion for scoliosis in 9, osteoporosis with collapsed fracture in 3, pseudarthrosis after posterior laminectomy and fusion in 35, congenital scoliosis in 3, scoliosis in 2 and paralytic scoliosis due to multiple sclerosis in one. The distribution of levels fused was T12-L1 in 6, L1-2 in 12, L2-3 in 17, L3-4 in 22, L4-5 in 35 and L5-S1 in 39. The remaining 10 levels were in the lower thoracic areas (T7-T12). The operations were performed as anterior fusion alone in 13 patients, one-stage anterior and posterior fusion in 26 patients and two-stage surgery in 20 patients. Anterior instrumentation was used in all 141 levels. At average follow-up (33.7 months) there was no significant change in allograft angles (average = 1.6 degrees ). Fusion of the allograft was classified by Bridwell's grading system. At 24 months of the follow up, 97 % of the allografts were in grade I (fully incorporated) and 3% were in grade II (partially incorporated). Compared to 12 months follow-up only 76.2% of the grafts were in grade I, 28 % were in grade II and 0.8% were in grade III. Two patients had deep posterior infections which required further surgery (without resorption of the allograft anteriorly). One patient had a screw migration anteriorly which required removal. Three patients had persistence of radiolucent line at one of the vertebral end plates - graft interfaces but no subsidence of the graft or pain. In conclusion, the femoral ring allograft appeared to benefit the anterior interbody fusion in complex spinal surgery.