Skipping Two-level Transpedicular Wedge Osteotomy For Correction Of Severe Kyphosis In Ankylosing Spondylitis: Surgical Strategies, Clinical Outcomes And Complications

Objective To evaluate the clinical outcomes and complications of skipping two-leveltranspedicular wedge osteotomy (TWO) for correction of severe kyphotic deformity inankylosing spondylitis (AS) and investigate the strategies of the surgical procedure.Methods From Jan2003to Dec2009, a total of38consecutive patients with AS andfixed severe kyphosis (chin-brow vertical angle (CBVA) or global thoraco-lumbarkyphosis angle (TLKA) over70°) including32males and6females with the mean age of38years(range,22-65) were respectively reviewed in our institution. All38patientsunderwent a one stage intermittent skipping two-level transpedicular wedge osteotomywith the mean follow-up periods of32months (range,24-78months).The preoperative C7L1S1angle, TLKA, T11-L2kyphotic angle, L1-S1lordosic angle,sagittal imbalance and CBVA were obtained from the Standing lateral total spine X-ray or3-D CT and clinical lateral photograph． The surgical goal was to restore spinal alignment,correct sagittal imbalance and CBVA. According to the characteristic curves of the patients,the normal spinal alignment, TLKA and CBVA, osteotomy location and angle weredetermined and confirmed by computer simulations (L1/L3in22cases, T12/L2in13cases,T12/L3in2cases and L2/L4in1case). Wake-up testing was performed during closure.Intra-operative sensory and motor evoked potentials was used routinely in later procedures.Improvement of post-operative and last follow-up of the same indicators were observedand treatment outcomes was evaluated through SRS-22scores (18Patients in the laterstage answered the same SRS–22Outcome questionnaire at final follow-up).Complications were also analyzed prospectively for the entire group of consecutiveskipping two-level PSO done at our institution to date (n=54).Results The average operating time was309min(range,185-420min), and averageblood loss was2050ml (range,850-4600ml). The C7L1S1angle, TLKA, T11-L2kyphotic angle and L1-S1lordosic angle improved from preoperative77.6±13.5,101.0°±21.3°,45.2°±13.6°,-28.2°±23.3°to postoperative24.1±9.3,26.0°±12.1°,2.8°±11.6°,28.9°±13.3°, respectively (P <0.01), and the average correction rates were69.12%,74.32%,93.75%and180.71%, respectively. The CBVA improved from79.4°±15.9°to13.6°±10.9°(P <0.01), and the improvement rate was82.34%. Thesagittal imbalance distance improved from (49±13) cm to (15±7) cm (P <0.01), and thecorrection rate of was70.49%. The average follow-up was32months (range,2-6.6years).All patients could walk with orthophoria and lie horizontally postoperatively. The patients'waist and back symptoms were totally or partly relieved. Fusion of the osteotomy wasachieved in all patients and no loss of correction or implant failure were noted. TheSRS-22total scores improved from1.8to4.2(P <0.01).The complications of the54patients were as follows: no permanent neurologicdeficits except one with Andersson lesion were directly referable to the osteotomies, nofatalities and aortic injury or catastrophic bleeding was found. Cerebrospinal fluid leakageoccurred in8patients, suturation and drainage were performed. One patient with stiffcervical spine suffered a spinal fracture at C5/6,hard collar was used and bony fusion wasachieved at the6th month follow-up.2patients suffered a spinal fracture just proximal tothe uppermost instrumented vertebra and required extension of instrumentation.4casesoccurred with compressive fracture of the anterior structures of the osteotomy vertebralbody.2patients suffered from pulmonary infection and recovered after anti-inflammatorytreatment. Paralytic ileus and superior mesenteric artery syndrome in1case respectively.15cases occurred gastrointestinal distensions, all had recovered uneventfully. Transientneurologic deficits ocurred in6cases,2patients had a weak quadriceps on one side, andrecovered3months after operation.1patient with preoperative pseudarthrosis underwentsingle-level PSO who had nonunion and a broken pedicle screw at the osteotomy siteunderwent revision and healed uneventfully. Superficial infection occurred in1case, andrecovered without adverse effect on the final result through local wound care andantibiotics.2patients had proximal junctional kyphosis at2years after surgery, butrequired no repeat operation at follow-up. Only one patient with Andersson lesion suffered from incomplete paraplegia(ASIA B)on the left side caused directly by sagittal translationreferable to the osteotomies ultimately need additional central canal enlargement andrecovering. All other patients recovered uneventfully.Conclusions Skipping two-level transpedicular wedge osteotomy is a satisfactoryand reliable technique for correction of severe fixed kyphotic deformity in AS andimproved appearance and function significantly.All the parameters in this study are simple and reliable indicators and highlycorrelated with spinal sagittal alignment and pelvic parameters. All the parameters areessential and valuable reference in the outcome evaluating and surgical planning of theprocedures.Given its technically demanding features, its potential risk of significantcomplications should be paid more attention, so to enhance the efficacy of the proceduressafely.