Effects Induced by Osteophytes on the Strain Distribution in the Vertebral Body Under Different Loading Configurations

The mechanical consequences of osteophytes are not completely clear. We aimed to understand whether and how the presence of an osteophyte perturbs strain distribution in the neighboring bone. The scope of this study was to evaluate the mechanical behavior induced by the osteophytes using full-field surface strain analysis in different loading configurations. Eight thoracolumbar segments, containing a vertebra with an osteophyte and an adjacent vertebra without an osteophyte (control), were harvested from six human spines. The position and size of the osteophytes were evaluated using clinical computed tomography imaging. The spine segments were biomechanically tested in the elastic regime in different loading configurations while the strains over the frontal and lateral surface of vertebral bodies were measured using digital image correlation. The strain fields in the vertebrae with and without osteophytes were compared. The correlation between osteophyte size and strain alteration was explored. The strain fields measured in the vertebrae with osteophytes were different from the control ones. In pure compression, we observed a mild trend between the size of the osteophyte and the strain distribution (R2 = 0.32, p = 0.15). A slightly stronger trend was found for bending (R2 = 0.44, p = 0.075). This study suggests that the osteophytes visibly perturb the strain field in the nearby vertebral area. However, the effect on the surrounding bone is not consistent. Indeed, in some cases the osteophyte shielded the neighboring bone, and in other cases, the osteophyte increased the strains.

A Rare Case of Proximal Junctional Failure with Delayed Infection after Adult Spinal Deformity Surgery: A Report of Two Cases

Proximal junctional failure (PJF) is one of the most devastating complications that develop after adult spinal deformity (ASD) surgery. Here, we report 2 rare cases of PJF accompanied by delayed infection after ASD surgery with a review of the relevant literatures. Late-onset infection is an infrequent complication despite acute postoperative infection is common after posterior spinal instrumentation and fusion. Among them, delayed onset pyogenic spondylitis of the adjacent vertebra to the instrumented vertebrae is an extremely rare phenomenon. We do not have a clear explanation for this pathology. Since the delayed infections developed not in the fused segments but in the adjacent vertebra, the cause of the first case can be speculated as stimulation of low-virulent organisms to fester and hematogenous seeding and that of the second case as metal fretting and a sterile inflammatory response causing hematogenous microbial seeding, respectively. Additional studies on this phenomenon are warranted to elucidate the pathogenesis of this complication.

Can relative rotation angle serve as a sensitive predictor for the development of adjacent segment degeneration after single-segment PLIF?

Background: Adjacent segment degeneration (ASD) is a major issue after posterior lumbar interbody fusion (PLIF). Several studies have reported the potential causes of ASD based on radiography. However, the postoperative dynamic changes in the adjacent segments are not clear. This study aimed to determine the effect of PLIF on ASD using a formetric 4D system and to compare the effectiveness of this system with that of traditional radiography for the prediction of ASD. Methods: Eighty-five consecutive patients who underwent PLIF of a single-segmen t were included. The formetric 4Dsystem was used to calculate the relative rotation angle between the fusion segment and the upper and lower adjacent vertebrae preoperatively and at 6, 12 and 24 months postoperatively. The range of motion (ROM) and disc height (DH) of the adjacent segments were measured using radiography preoperatively and at 24 months postoperatively. At the final follow-up, the visual analogue scale (VAS) and Oswestry disability index (ODI) were used to evaluate the surgical outcome. The patients were divided into two groups according to the occurrence of radiographic ASD: the ASD group with progression of degeneration and the N-ASD group without progression of degeneration. The clinical outcomes and measurement data between the two groups were compared and analyzed. Results: The index fusion segments included L2-3 to L5-S1. Preoperatively, the relative rotation angles between the fused segment and the upper and lower adjacent vertebrae were 5.1°±2.2°and 3.3°±2.0°,respectively, and both angles increased significantly at all time-points after surgery ( p <0.05). The angles changed most significantly during L2-3 fusion . Radiographic ASD was noted in 13 of 85 patients (15.3%) at 24 months. There was no significant difference in the DH, ROM, or clinical outcome between the two groups ( p >0.05), while the relative rotation angle with the upper adjacent vertebra was greater in the ASD group than in the N-ASD group ( p <0.05). Conclusion: The relative rotation angle with the adjacent vertebra increased significantly after lumbar fusion surgery. It may be a more sensitive predictor for the development ofradiographic ASD than flexion-extension ROM and DH.

Comparison of the clinical outcomes of percutaneous vertebroplasty vs. kyphoplasty for the treatment of osteoporotic Kümmell’s disease:a prospective cohort study

Background Percutaneous vertebroplasty (PVP) and percutaneous kyphoplasty (PKP) are widely used in the treatment of Kümmell's disease. The purpose of this article is to investigate the clinical efficacy of PVP and PKP for Kümmell's disease. Methods The clinical data that 56 cases of OVCF treated with either PVP (28 cases) or PKP (28 cases) and met the selection criteria from December 2015 to December 2017 were prospectively analyzed. Gender, age, course of disease, injury segment, BMD, VAS, ODI, imaging measurement indexes before surgery between the two groups showed no significant difference (all P>0.05). The bone cement leakage rate, bone cement injection amount, operation time, VAS, ODI, the rate of vertebral compression, correction rate of kyphosis and refracture rate of adjacent vertebra in 2 years were compared between the two groups to calculate clinical efficacy. Results The two groups were followed up for 24-48 months. There was no significant difference in the follow-up time, amount of bone cement injected, incidence of bone cement leakage and refracture rate of adjacent vertebra between the two groups (all P > 0.05). The operation time, intraoperative blood loss and fluoroscopy times of the PVP group were significantly lower than those of the PKP group (all P = 0.000). VAS score and ODI of the two groups were significantly lower at 1 d, 1 year and 2 years after surgery than before surgery (all P <0.05), but there was not statistically significant difference between the two groups at each time point after surgery (all P> 0.05). The rate of vertebral compression and kyphosis correction in the two groups were significantly corrected (P <0.05, respectively) and decreased significantly with time (all P <0.05), But there was not significant difference between the two groups at any time point (all P> 0.05). Conclusion Both PVP and PKP can achieve similar effects in the treatment of Kümmell's disease. Because the cost, operation time, blood loss, radiation exposure and surgical procedure of PVP are less than those of PKP, PVP has more clinical priority value.

Prophylactic adjacent-segment vertebroplasty following kyphoplasty for a single osteoporotic vertebral fracture and the risk of adjacent fractures: a retrospective study and clinical experience

OBJECTIVE This study investigated the benefit of prophylactic vertebroplasty of the adjacent vertebrae in single-segment osteoporotic vertebral body fractures treated with kyphoplasty. METHODS All patients treated with kyphoplasty for osteoporotic single-segment fractures between January 2007 and August 2012 were included in this retrospective study. The patients received either kyphoplasty alone (kyphoplasty group) or kyphoplasty with additional vertebroplasty of the adjacent segment (vertebroplasty group). The segmental kyphosis with the rate of adjacent-segment fractures (ASFs) and remote fractures were studied on plain lateral radiographs preoperatively, postoperatively, at 3 months, and at final follow-up. RESULTS Thirty-seven (82%) of a possible 45 patients were included for the analysis, with a mean follow-up of 16 months (range 3–54 months). The study population included 31 women, and the mean age of the total patient population was 72 years old (range 53–86 years). In 21 patients (57%), the fracture was in the thoracolumbar junction. Eighteen patients were treated with additional vertebroplasty and 19 with kyphoplasty only. The segmental kyphosis increased in both groups at final follow-up. A fracture through the primary treated vertebra (kyphoplasty) was found in 4 (22%) of the vertebroplasty group and in 3 (16%) of the kyphoplasty group (p = 0.6). An ASF was found in 50% (n = 9) of the vertebroplasty group and in 16% (n = 3) of the kyphoplasty group (p = 0.03). Remote fractures occurred in 1 patient in each group (p = 1.0). CONCLUSIONS Prophylactic vertebroplasty of the adjacent vertebra in patients with single-segment osteoporotic fractures as performed in this study did not decrease the rate of adjacent fractures. Based on these retrospective data, the possible benefits of prophylactic vertebroplasty do not compensate for the possible risks of an additional cement augmentation.