Comparison of intraoperative fluoroscopy and postoperative CT measurement of mounting parameters for Taylor Spatial Frame

Objective To investigate the accuracy and postoperative efficacy of fluoroscopy and CT in measuring the mounting parameters of Taylor Spatial Frame. Methods Data of patients with peripheral knee deformities who were treated by Taylor Spatial Frame from June 2006 to December 2017 were retrospectively analyzed. According to different measurement methods of mounting parameters, they were divided into fluoroscopy group (mounting parameters were obtained by intraoperative fluoroscopy) and CT group (mounting parameters were obtained by postoperative CT). There were 33 patients (35 segments) in the fluoroscopy group, 23 males (23 segments) and 10 females (12 segments), with an average age of 36.4±11.6 years old. In CT group, there were 30 patients, 19 males and 11 females, with an average age of 36.9±13.8 years. There were 22 cases (24 segments) of high tibial osteotomy, 5 cases (5 segments) of distal femur osteotomy, and 6 cases (6 segments) of both distal femur and high tibial osteotomy. Operation time, external fixation time, the number of electronic prescription and deformity correction time, mechanical axis deviation (MAD), medial proximal tibia angle (MPTA), mechanical lateral distal femoral angle (mLDFA), range of motion (ROM) andhospital for special surgery (HSS) knee functional scores were compared between the two groups. Results All the 63 patients were followed up for 21.9 months (range, 12-60 months). In fluoroscopy group, operating time was 100.9±9.1 min, electronic prescription number 1.4±0.6, and deformity correction time was 19.4±3.6 days. In CT group, operating time was 79.2±10.8 min, electronic prescription number 1.2±0.4, and deformity correction time was 16.0±4.4 days. The difference of the above indexes between the two groups was statistically significant (t=8.803, 2.042, 3.440, all P 0.05). In the fluoroscopy group, 22 segmental deformities were corrected by one electronic prescription, and 13 segmental deformities were corrected by two or more electronic prescriptions. In CT group, 25 segmental deformities were corrected by one electronic prescription, and 5 segmental deformities were corrected by two electronic prescriptions. There was no incision infection and no neurovascular injury in the two groups. Conclusion Both fluoroscopy and CT scan can obtain the mounting parameters of the Taylor Spatial Frame, and the results of correction of the peripheral deformities of the knee joint are satisfactory. However, CT measurement of the mounting parameters is more accurate which could achieve shorter operation time, and less times of electronic prescriptions. Key words: Knee joint; Musculoskeletal abnormalities; Fluoroscopy; Tomography, spiral computed; External fixators