Scoliosis surgery with hybrid system in osteogenesis imperfecta (OI) National Hospital Organization Kobe Medical Center, Japan Thank you, // Mr. Chairman. /// Koki Uno Teppei Suzuki

Introduction Spinal surgery in OI is difficult due to the extreme bone fragility. The application of the pedicle screws (PS) to the weak and fragile vertebrae in OI was still unclear. Although, spine surgery in OI is difficult due to the extreme bone fragility. The application of the pedicle screws in OI was still unclear.

Purpose The retrospective analysis of the spinal surgery with hybrid system and the accuracy of PS placement in OI. The purpose of this study was to evaluate the spinal surgery with hybrid system and the accuracy of PS placement in OI.

Methods 12 8 : 4 23.4±11.0 y.o. 3.3±1.5 yrs 8 cases 4 cases Between 2006 and 2011, single institution No. of patients 12 Gender (F:M) 8 : 4 Age at surgery 23.4±11.0 y.o. Duration of follow-up　　 3.3±1.5 yrs Sillence type 1 type 3 8 cases 4 cases 12 cases, 8 female and 4 male, were examined. The mean age at surgery was 23 years old and the mean follow-up was 3.3 years. Of the 12 cases, Sillence type 1 was in 8 cases, and type 3 in 4 cases.

Accuracy of PS Acceptable <2mm from the pedicle We defined the displacement from the pedicle more than 2mm as perforation in postoperative CT scan. To evaluate the accuracy of PS, we defined the displacement from the pedicle more than 2mm as deviation in postoperative CT scan. Acceptable <2mm from the pedicle Medial perforation>2mm Lateral perforation>2mm

Surgical procedures 12 cases 9 cases Anterior release(AR) + 6 cases Posterior fusion(PF); 9 cases Halo-gravity traction(HGT) ; 6 cases Without HGT; 3 cases PF only; 2 cases HGT; 1 case Without HGT; 1 case Dual growing rod surgery; 1 case Surgeries performed were anterior release followed by posterior fusion in 9 cases, posterior only in 2 cases. 7 cases were underwent 4 weeks preoperative halo-gravity traction. One case was performed dual growing rod surgery.

Cobb angles of Main curve Degree mean Scoliosis was corrected from 100degrees to 67.8 degrees post operation and 69.1 degrees at final FU. Correction rate was 33% at post operation, and loss of correction was only 1.8% at final follow up. Mean degree 100.4±19.2 67.8±23.3 69.1±19.3 Degree ＊ ＊ : p<0.01 ＊ Correction rate was 33% at post OP. Loss of correction rate was 1.8% at final f/u.

Cobb angles of Kyphosis Degree mean Kyphosis was maintained from mean 45 degrees to 37 degrees at post operation, and no significant change at final f/u. Mean degree 45.1±39.8 37.3±31.1 37.3±29.9 n.s. n.s.: not significant

Accuracy of pedicle screws medial perforation rate 5.3% 23.5% Total 148 PS were inserted in these cases. In Sillence type 1, 6 screws out of 114 were medially perforated, whereas in Sillence type 3, 8 screws out of 34 were medially perforated. Medially perforation rates of type 3 were much higher than of type 1.

Complications disturbance : 2 cases Deep infection : 2 cases Treated with antibiotics and debridement. Transient neurological disturbance : 2 cases Complications related to spinal surgery included 2 deep infections and 2 transient neurological disturbances. One case related to the medially perforation of PS.

Discussion Janus GJ et al. Spine2000 Our study No. of patients 20 cases 12 cases Follow up time 4.8 years 3.3 years Operation method CD instrument or Harrington rod Hybrid system (pedicle screws) Correction rate at Post OP 35.5% 33.3% Failure of instrumentation 4 cases none Loss of correction rate at final f/u 8.9% 1.8% Complications rate 30% 33% No implant dislodgement and loosening were observed in our series. Discussion Janus et al. reported 20 OI cases underwent surgiery with hooks. In their cases, failure of instrumentation was found in four cases postoperatively. On the other hand, no implant dislodgement and loosening were observed in our series. In addition to this, loss of correction rate was lower than that of theirs. It is therefore considered that hybrid system including pedicle screw may provide better results in this very challenging pathological condition.

Summary We reviewed 12 cases of OI who underwent spinal surgery with hybrid system including PS. There were no significant loss of correction and no dislodgement of the implants at final f/u. Hybrid system including PS may provide better results in this very challenging pathological condition. In summary, We reviewed 12 cases of OI who underwent spinal surgery with hybrid system including PS. There were no significant loss of correction and no dislodgement of the implants at final f/u. Hybrid system including PS may provide better results in this very challenging pathological condition.