CT-defined sarcopenia and early ambulation after transforaminal lumbar interbody fusion: a retrospective cohort study

Abstract Background Early ambulation is an important indicator of immediate functional recovery after transforaminal lumbar interbody fusion (TLIF). Whether CT-defined sarcopenia is associated with delayed early ambulation after TLIF, and whether osteoporosis modifies this association, remain unclear. Methods We retrospectively analyzed 223 patients who underwent TLIF for degenerative lumbar disease between August 2022 and October 2024. CT-defined sarcopenia was determined using the L3-level psoas muscle index, and osteoporosis was defined as a bone mineral density T-score of ≤ − 2.5. The primary outcome was ambulation within 24 h after surgery. Secondary outcomes included operative time, estimated blood loss, postoperative pain, length of stay, MMT, analgesic use, the modified MacNab score, complications, and cage subsidence. Multivariable regression models were adjusted for age, sex, body mass index, osteoporosis status, and number of operated levels. Results Among 223 patients, 46 had CT-defined sarcopenia and 177 served as controls. Ambulation within 24 h was less frequent in patients with CT-defined sarcopenia than in controls (28/46 [60.9%] vs 143/177 [80.8%]; risk difference, − 19.9%; 95% CI, − 35.2 to − 5.7; P = 0.004). After adjustment, CT-defined sarcopenia remained associated with lower odds of early ambulation (adjusted OR, 0.34; 95% CI, 0.16–0.73; P = 0.006). This association was stronger among patients with osteoporosis, with a significant interaction between CT-defined sarcopenia and osteoporosis ( P for interaction = 0.032). No statistically significant between-group differences were observed in the secondary outcomes. Conclusions CT-defined sarcopenia was associated with lower odds of ambulation within 24 h after TLIF. Exploratory analyses suggested that this association may be stronger in patients with osteoporosis. Because sarcopenia was defined using CT-derived muscle mass rather than functional criteria, these findings should be interpreted as an association between an imaging-defined low muscle mass phenotype and early postoperative recovery.