Running Head: Accuracy of Multilevel RegistrationAccuracy of Single-time, Multilevel Registration MINI ABSTRACTAccuracy of multilevel registration for skip pedicle screw placement during image-guided, computer-assisted spine surgery, in adolescent idiopathic scoliosis was assessed. Mean surgical time: 310 min. Pedicle violation observed in only 4/265 screws (1.5%). Mean registration error after point merge: 1.69±0.52: after surface merge 0.51±0.16. Multilevel registration may decrease operative time without compromising accuracy of pedicle screw placement. Accuracy of Multilevel Registration KEY POINTS Multilevel registration employs more than 6 registration points for two, three or four consecutive vertebra to shorten the surgical time.  Pedicle violation was observed in 1.5% of inserted screws.  Multilevel registration may decrease operative time without compromising accuracy of pedicle screw placement afforded by this technique in the setting of adolescent idiopathic scoliosis.  Mean correction rate of skip pedicle screw instrumentation was 66.2%. Accuracy of Multilevel Registration STRUCTURED ABSTRACTStudy Design: Retrospective clinical study. Objective: To assess the accuracy of multilevel registration for skip pedicle screw placement during image-guided, computer-assisted spine surgery, in the setting of adolescent idiopathic scoliosis (AIS). Summary of background data: Computerized frameless stereotactic image-guidance has been used recently to improve pedicle screw placement accurately and safety during spine surgery. Because of possible intervertebral motion and usual difference in patients' position between preoperative imaging and surgery, the imaging model and the surgically exposed spine may be significantly discordant. Consequently, current protocols suggested separate registration of each spinal level (single-level registration) before respective pedicle screw placement, a timeconsuming process. Moreover, although multilevel registration for lumbar spine has been reported, that for thoracic spine has not. Methods: Nineteen patients (1 male, and 18 females; mean age, 13.9 years) with AIS who underwent multilevel registration for skip pedicle screw placement were included. Variables including surgical time, blood loss, preoperative and 2-year post-operative Cobb angle, correction rate, and post-operative screw position by CT image were evaluated. Mean registration error (MRE) after point merge and again after surface merge were recorded for each consecutive vertebra of each case. Results: Mean surgical time was 310 min. (range, 168-420 min.). Mean blood loss 1138 g (range, 300-2300 g). Cobb angle before operation and at 2 years post-operation was 62.4 (43-100) degrees and 21.6 (9-42) degrees, respectively. Mean correction rate 66.2% (39.7-84.5%). Total 265 screws were inserted with CT-based navigation system. Pedicle violation was observed in only 4 screws (1.5%). No neurovascular complication occurred. After point merge, average MRE of all cases was 1.69±0.52mm, and after surface merge was 0.51...

The LSH concept can measure with high reliability and concurrent or discriminant validity, and it is a different concept from outdoor life-space mobility. Life-space mobility at home may be an important factor associated with physical functions related to mobility and functional status, and measuring LSH may be useful to assess current indoor life-space activity in older adults who have difficulty performing outdoor activities.

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Careful insertion of pedicle screws is necessary, especially at C3 to C5, even when using a CT-based navigation system. Pedicle screws tend to be laterally perforated.

Study DesignMulticenter analysis of two groups of patients surgically treated for degenerative L4 unstable spondylolisthesis.PurposeTo compare the clinical and radiographic outcomes of posterolateral fusion (PLF) and posterior lumbar interbody fusion (PLIF) for degenerative L4 unstable spondylolisthesis.Overview of LiteratureSurgery for lumbar degenerative spondylolisthesis is widely performed. However, few reports have compared the outcome of PLF to that of PLIF for degenerative L4 unstable spondylolisthesis.MethodsPatients with L4 unstable spondylolisthesis with Meyerding grade II or more, slip of >10° or >4 mm upon maximum flexion and extension bending, and posterior opening of >5 degree upon flexion bending were studied. Patients were treated from January 2008 to January 2010. Patients who underwent PLF (n=12) and PLIF (n=19) were followed-up for >2 years. Radiographic findings and clinical outcomes evaluated by the Japanese Orthopaedic Association (JOA) score were compared between the two groups. Radiographic evaluation included slip angle, translation, slip angle and translation during maximum flexion and extension bending, intervertebral disc height, lumbar lordotic angle, and fusion rate.ResultsJOA scores of the PLF group before surgery and at final follow-up were 12.3±4.8 and 24.1±3.7, respectively; those of the PLIF group were 14.7±4.8 and 24.2±7.8, respectively, with no significant difference between the two groups. Correction of slip estimated from postoperative slip angle, translation, and maintenance of intervertebral disc height in the PLIF group was significantly (p<0.05) better than those in the PLF group. However, there was no significant difference in lumbar lordotic angle, slip angle and translation angle upon maximum flexion, or extension bending. Fusion rates of the PLIF and PLF groups had no significant difference.ConclusionsThe L4–L5 level posterior instrumented fusion for unstable spondylolisthesis using both PLF and PLIF could ameliorate clinical symptoms when local stability is achieved.