Minimum ten-year outcome of a triple-tapered femoral stem implanted with line-to-line cementing technique

Background A triple-tapered polished femoral stem was implanted with line-to-line cementing technique. The purpose of this study was to determine the survivorship, loosening rate, stem subsidence, radiologic changes and clinical outcomes in the minimum 10-year follow-up. Methods This was a retrospective study done in three institutes. Finally, 118 hips in 97 patients could be followed-up at the mean follow-up period of 126.3 months. The survivorship, radiological and clinical outcomes were investigated. Results Radiologically, 107 hips (90.7%) were categorized to Barrack cementing grade A, and 108 stems (91.5%) were inserted in neutral position. All hips were not loose and were not revised due to any reason. Survival with revision for any reason as the endpoint was 100% after 10 years. At the last follow-up, the mean subsidence was 0.43 mm, and the subsidence was less than 1 mm in 110 hips (93.2%). JOA hip score improved from 42.7 ± 8.9 points preoperatively to 92.8 ± 6.8 points at the last follow-up. No patient complained thigh pain. Conclusions Line-to-line cementing technique with use of a triple-tapered polished stem was effective to achieve good cementation quality and centralization of the stem. The subsidence was small, and the minimum 10-year results were excellent without any failures related to the stem. Trial registration Retrospectively registered.

Minimum Ten-Year Outcome of a Triple-Tapered Femoral Stem Implanted With Line-To-Line Cementing Technique

Background A triple-tapered polished femoral stem was implanted with line-to-line cementing technique. The purpose of this study was to determine the survivorship, loosening rate, stem subsidence, radiologic changes and clinical outcomes in the minimum ten-year follow-up. Methods This was a retrospective study done in three institutes. Finally, 118 hips in 97 patients could be followed-up at the mean follow-up period of 126.9 months. The survivorship, radiological and clinical outcomes were investigated. Results Radiologically, 107 hips (90.7%) were categorized to Barrack cementing grade A, and 108 stems (91.5%) were inserted in neutral position. All hips were not loose and were not revised due to aseptic loosening. Survival with revision for any reason as the endpoint was 100% after 10 years. At the last follow-up, the mean subsidence was 0.41 mm, and the subsidence was less than 1 mm in 110 hips (93.2%). JOA hip score improved from 42.7 ± 9.2 points preoperatively to 92.9 ± 6.8 points at the last follow-up. No patient complained thigh pain. Conclusions Line-to-line cementing technique with use of a triple-tapered polished stem was effective to achieve good cementation quality and centralization of the stem. The subsidence was small, and the minimum ten-year results were excellent without any failures related to the stem.Trial registration: Retrospectively registered

Hounsfield units of the vertebral body and pedicle as predictors of pedicle screw loosening after degenerative lumbar spine surgery

OBJECTIVEThe authors aimed to compare the efficacy of lumbar vertebral body Hounsfield units (HUs) and pedicle HUs at predicting pedicle screw loosening.METHODSThe authors retrospectively assessed 143 patients with L3–5 instrumentation. The patients were classified into one of two groups based on the status of their L3 screws (a screw loosening group or a control group). The pedicle HUs and vertebral HUs of L3 were measured using preoperative lumbar CT scans, and the pedicle HUs were measured in two ways: by excluding or by including cortical bone.RESULTSThe screw loosening rate was 20.3% (n = 29/143) at the 12-month follow-up. The vertebral body HUs and pedicle HUs in the screw loosening group were lower than those in the control group (vertebral body group: 98.6 HUs vs 121.4 HUs, p < 0.001; pedicle excluding cortical bone: 208.9 HUs vs 290.5 HUs, p = 0.002; pedicle including cortical bone: 249.4 HUs vs 337.5 HUs, p < 0.001). The pedicle HUs tended to have a higher area under the receiver operating characteristic curve value in predicting screw loosening, compared with that of vertebral body HUs, but the difference was not statistically significant (p > 0.05). Among patients with low vertebral body HUs of ≤ 130, the loosening rate was much lower in patients with pedicle HUs of ≤ 340 than in those with pedicle HUs of > 340 (31.0% vs 13.0%, respectively; p < 0.05).CONCLUSIONSVertebral body HUs alone are insufficient to accurately evaluate the risk of pedicle screw loosening. Therefore, it is important to collect both the pedicle HU and vertebral body HU measurements for surgical planning.

Radiographic Evaluation of Minimally Invasive Instrumentation and Fusion for Treating Unstable Spinal Column Injuries

Study Design: Retrospective cohort. Objective: Facet fusion in minimally invasive spine surgery (MISS) may reduce morbidity and promote long-term construct stability. The study compares the maintenance of correction of thoracolumbar (TL) trauma patients who underwent MISS with facet fusion (FF) and without facet fusion (WOFF) and evaluates instrumentation loosening and failure. Methods: TL trauma patients who underwent MISS between 2006 and 2013 were identified and stratified into FF and WOFF groups. To evaluate progressive kyphosis and loss of correction, Cobb angles were measured at immediate postoperative, short-term, and long-term follow-up. Evidence of >2 mm of radiolucency on radiographs indicated screw loosening. If instrumentation was removed, postremoval kyphosis angle was obtained. Results: Of the 80 patients, 24 were in FF and 56 were in WOFF group. Between immediate postoperative and short-term follow-up, kyphosis angle changed by 4.0° (standard error [SE] 1.3°) in the FF and by 3.0° (SE 0.4°) in the WOFF group. The change between immediate postoperative and long-term follow-up kyphosis angles was 3.4° (S.E 1.1°) and 5.2° (S.E 1.6°) degrees in the FF and WOFF groups, respectively. Facet fusion had no impact on the change in kyphosis at short term ( P = .49) or long term ( P = .39). The screw loosening rate was 20.5% for the 80 patients with short-term follow-up and 68.8% for the 16 patients with long-term follow-up. There was no difference in screw loosening rate. Fifteen patients underwent instrumentation removal—all from the FF group. Conclusion: FF in MISS does not impact the correction achieved and maintenance of correction in patients with traumatic spine injuries.

Decompression and Instrumentation without Fusion for Spinal Metastases: Loosening Rate and Consequences

Background/Purpose For patients with spinal metastases, decompression surgery was usually followed by instrumentation without fusion. Over time, mechanical stress would lead to loosening of implants. Yet, there is a lack of studies concerning the loosening rate, or the impact on patients when the implants are loosened. We aim at finding the postoperative loosening rate of implant, postoperative survivorship of patients, as well as their correlation with the mode of instrumentation. Methods A retrospective study including patients with metastatic spinal cord compression, who received decompression and instrumentation without fusion in a local hospital in Hong Kong from 2007 to 2014 was carried out. Patients with primary spinal tumour or prior spinal fusion were excluded. Demographics, tumour characteristics, mode of instrumentation, loosening rate of implants, as well as survivorship of patients were retrieved. Radiographs at 1 year postoperation were counter-examined by 2 Orthopaedic specialists on the Electronic Patient Record System. Results Total of 65 operations were retrieved. The age ranged from 27 to 84 years old. The most frequent primary source of malignancy was lung (26.5%), followed by breast (24.62%). Thoracic level (60%) was the most frequent site of spinal metastases. The survivorship at 1 year postoperation was 61.54%. The overall loosening rate of implants was 44.44%, with the Luque rods and sublaminar wire system being the most (70%). None of the cases required revision or removal of implants at 1 year postoperation. Conclusion The loosening rate of implants was high, and it is expected to grow even higher as oncological patients continue to improve in their survivorship with the medical advances such as target therapy. Yet there is still no definite evidence on how the implant loosening would affect patients’ quality of life and clinical performance.

Some factors affecting the loosening failure of bolted joints under vibration using finite element analysis

Finite element analysis has been regarded as an effective research method for analyzing the loosening failure of bolted joints under vibration. However, there exist some factors, which influence the accuracy and reliability of loosening results, thus determining the explanations of the loosening mechanism. In this study, a 3D finite element model of a typical bolted joint was built to investigate the effects of several different factors on the loosening under transverse vibration loading. These influencing factors include preload generation, vibration parameter, and material model. Based on the simulation results, it was found that applying the method of pretension element to generate preload instead of the actual method of torque was reliable and efficient. For the vibration parameter, it showed that the decrease rate in preload was higher for a larger vibration amplitude. But once the bearing surface reached complete slip, the loosening rate would keep constant. This was because the thread surface at that time reached a sticking state. Vibration frequency was proved to have no effect on the loosening behavior. This result demonstrated that the quasi-static assumption for vibration frequency was reasonable. Additionally, it also indicated that plastic material models only affected the preload loss in the initial several vibration cycles and had no influence on the loosening rate of preload after several vibration cycles. Finally, experiments were conducted to confirm qualitatively the results obtained based on finite element analysis.