Background. The mechanisms and risk factors for proximal junctional kyphosis of elderly patients may differ from those of non-elderly patients. The risk factors for PJK in the elderly population remain unclear.
Methods. The present study enrolled elderly DSD patients over 65 years of age who underwent thoracolumbar fusion with no less than 3 levels fused. All patients underwent CT and MRI scans preoperatively, and full spine standing X-ray preoperatively, postoperatively and during follow-up with a minimum follow-up of 18 month. Paraspinal muscle cross-sectional area(CSA) and paraspinal muscle fatty infiltration(FI) of erector spinae(ES) and multifidus muscle(MF), LL, PI, PT, SS, PI-LL and vertebra CT HU value were measured. Radiological PJK was defined as a sagittal Cobb angle between the UIV and the two levels above the UIV (UIV+2) of 10° or greater and at least 10° greater than the preoperative measurement. Parameters were compared between PJK and Non-PJK patients.
Result. A total of 259 patients were enrolled. The prevalence of PJK was 35.9%. Compared with Non-PJK group, PJK group had significantly older age at surgery, greater BMI, lower vertebra CT value and greater PI and a larger PI-LL mismatch. Both erector spinae(ES) and multifidus muscle(MF) relative cross-sectional area(rCSA) of PJK patients were significantly smaller, the ES and MF fatty infiltration(FI) were significantly greater than the Non-PJK patients. Older age at surgery, greater BMI, greater PI, smaller MF rCSA, greater ES and MF FI and smaller CT value were independent risk factors for PJK in elderly patient population.
Conclusions. For elderly patients with DSD, PJK is a commonly seen complication. Higher age at surgery, larger BMI, significant paraspinal muscle degeneration and low bone mineral density are risk factors for PJK. Appropriate preoperative and postoperative measures are beneficial for reducing the risk of PJK in the elderly.

Figure 1
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Posted 16 Feb, 2021
Received 30 Mar, 2021
On 30 Mar, 2021
Received 27 Mar, 2021
Received 21 Mar, 2021
On 17 Mar, 2021
On 15 Mar, 2021
On 09 Mar, 2021
Invitations sent on 08 Mar, 2021
On 09 Feb, 2021
On 09 Feb, 2021
On 09 Feb, 2021
On 25 Jan, 2021
Posted 16 Feb, 2021
Received 30 Mar, 2021
On 30 Mar, 2021
Received 27 Mar, 2021
Received 21 Mar, 2021
On 17 Mar, 2021
On 15 Mar, 2021
On 09 Mar, 2021
Invitations sent on 08 Mar, 2021
On 09 Feb, 2021
On 09 Feb, 2021
On 09 Feb, 2021
On 25 Jan, 2021
Background. The mechanisms and risk factors for proximal junctional kyphosis of elderly patients may differ from those of non-elderly patients. The risk factors for PJK in the elderly population remain unclear.
Methods. The present study enrolled elderly DSD patients over 65 years of age who underwent thoracolumbar fusion with no less than 3 levels fused. All patients underwent CT and MRI scans preoperatively, and full spine standing X-ray preoperatively, postoperatively and during follow-up with a minimum follow-up of 18 month. Paraspinal muscle cross-sectional area(CSA) and paraspinal muscle fatty infiltration(FI) of erector spinae(ES) and multifidus muscle(MF), LL, PI, PT, SS, PI-LL and vertebra CT HU value were measured. Radiological PJK was defined as a sagittal Cobb angle between the UIV and the two levels above the UIV (UIV+2) of 10° or greater and at least 10° greater than the preoperative measurement. Parameters were compared between PJK and Non-PJK patients.
Result. A total of 259 patients were enrolled. The prevalence of PJK was 35.9%. Compared with Non-PJK group, PJK group had significantly older age at surgery, greater BMI, lower vertebra CT value and greater PI and a larger PI-LL mismatch. Both erector spinae(ES) and multifidus muscle(MF) relative cross-sectional area(rCSA) of PJK patients were significantly smaller, the ES and MF fatty infiltration(FI) were significantly greater than the Non-PJK patients. Older age at surgery, greater BMI, greater PI, smaller MF rCSA, greater ES and MF FI and smaller CT value were independent risk factors for PJK in elderly patient population.
Conclusions. For elderly patients with DSD, PJK is a commonly seen complication. Higher age at surgery, larger BMI, significant paraspinal muscle degeneration and low bone mineral density are risk factors for PJK. Appropriate preoperative and postoperative measures are beneficial for reducing the risk of PJK in the elderly.

Figure 1
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