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Objective: To investigate the biomechanical effect of different intervertebral reconstructive heights on adjacent segments following C5/C6 anterior cervical discectomy and fusion (ACDF) through finite element analysis. Methods: A finite element model of intact C4–C7 segments was developed and validated for the present study. Five additional C4–C7 postoperative models were constructed with 100%, 125%, 150%, 175%, and 200% of the benchmark height of C5/C6 on the basis of the intact model. The changes in intradiscal pressure (IDP) and range of motion (ROM) of adjacent segments before and after reconstruction of C5/C6 were analyzed. Results: For the upper adjacent segment (C4/C5), the IDPs under the different loading conditions all increased after reconstruction. The maximum IDPs were 0.387, 0.489, 0.491, and 0.472 MPa under flexion, extension, axial rotation, and lateral bending, respectively, observed at the reconstructive height of 200%. The minimum IDPs were observed at 150% reconstructive height under all loading conditions except extension, and were 57, 86 and 81% of the maximum IDPs under flexion, axial rotation, and lateral bending, respectively. The minimum IDP under extension occurred when the reconstructive height is 125% of the benchmark height. For the lower adjacent segment (C6/C7), the IDPs of postoperative models under all loading conditions also increased compared to the preoperative model. The maximum IDPs after reconstruction under flexion, extension, axial rotation, and lateral bending were 0.402, 0.411, 0.461, and 0.497 MPa, respectively, when the height of the reconstruction was 200% of the benchmark. The minimum IDPs were observed after a reconstruction at 150% of the benchmark, and were 59%, 85%, 82%, and 81% of the maximum IDPs under flexion, extension, axial rotation, and lateral bending loading conditions. Conclusions: The reconstructive height is an important factor affecting the IDP and the ROM of adjacent segments after ACDF. To delay the adjacent segment disease, an intervertebral reconstructive height of 150% is an appropriate height in C5/C6 ACDF. [ABSTRACT FROM AUTHOR]

Objective: To compare the preventive effects of teriparatide and alendronate on the progression of vertebral body collapse in postmenopausal single‐level Kümmell's disease (KD). Methods: From March 2013 to December 2020, the medical records for 53 postmenopausal single‐level KD patients who received conservative treatment with teriparatide (25 patients, teriparatide group) or alendronate (28 patients, alendronate group) were retrospectively reviewed. Midsagittal computed tomography (CT) images were analyzed by ImageJ to assess the intravertebral bone formation (mineralized bone) by calculating the ratio of area of intravertebral mineralized bone (AIMB) to the area of fractured vertebral body (AFVB). The changes in radiological parameters of the fractured vertebral body including kyphosis angle (KA), anterior and posterior border heights (ABH and PBH) and spinal canal diameter (SCD), bone turnover biomarkers (BTMs), and bone mineral density (BMD) were analyzed to evaluate the therapeutic effect. Results: At month 12, the ratio of AIMB to AFVB was significantly greater in teriparatide group (54.28% ± 15.30%) than in alendronate group (35.57% ± 17.61%) (P < 0.001). Sagittal CT substantiated the formation of bone bridge in 16 patients in teriparatide group. No bone bridge was detected in alendronate group. The KA was significantly smaller and the ABH, PBH, and SCD was greater in teriparatide group than in alendronate group (all P < 0.001). The KA increments were significantly smaller in teriparatide group (3.98° ± 1.30°) than in alendronate group (11.43° ± 3.73°) (P < 0.001). The ABH and PBH decrement were significantly lower in teriparatide group (11.96% ± 1.93% and 2.80% ± 2.52%) than in alendronate group (37.04% ± 8.00% and 19.50% ± 8.22%) (both P < 0.001). The BTMs and BMD were significantly greater in the teriparatide group than in the alendronate group. In teriparatide group, KA increment was negatively correlated with the change in PINP (r = −0.781, P < 0.001) and the ratio of AIMB to AFVB (r = −0.592, P = 0.002) from baseline to month 12. The ABH decrement was negatively correlated with the change in PINP (r = −0.612, P = 0.001) and the ratio of AIMB to AFVB (r = −0.806, P < 0.001) from baseline to month 12. Conclusions: In postmenopausal single‐level KD patients, conservative treatment with teriparatide was better than alendronate at preventing the progressive vertebral collapse. [ABSTRACT FROM AUTHOR]