The measurement of Hounsfield Units (HU) by computed tomography (CT) has been reported as a technique for determining Bone Mineral density (BMD). The BMD of the UIV was useful for surgical planning for surgeons considering a revision lumbar fusion. On the other hand, a metal artifact from the apparatus was a potential confounder, and previous research hasn’t verified HU readings in the scenario. For a study, the researchers sought to see if HU can be reliably measured at the lumbar fusion’s supra-adjacent and upper instrumented levels. An observational cohort in retrospect was conducted. After an instrumented posterior lumbar fusion, patients obtained lumbar CT scans. At the upper instrumented vertebra and levels proximal, Hounsfield Units were used. Researchers compared pre-and postoperative CT scans of 50 patients who had L2 and distal instrumented lumbar fusion and had scans no more than a year apart, obtaining HU measurements of analogous axial cuts at the upper instrumented level (immediately caudal to the pedicle screw halo), as well as additional control levels above the construct. The HU at pre-and post-operative UIV, as well as 1 (r=0.887, p<0.001) and 2 (r=0.853, p<0.001) levels above the UIV, showed a substantial connection (r=0.917, p<0.001). At 1 (-9.0±26.2) and 2 (-12.2±30.2) levels above UIV, as well as T12 (-13.9±42.2), there were large but predictable reductions in the postoperative HU compared to preoperative. At UIV (4.6±34.1), there was no significant change in HU. The postoperative HU at the UIV was well linked with the preoperative HU and did not differ significantly. Although the HU in the vertebrae closest to the UIV was somewhat lower after surgery, the change could be predicted using a correction factor.