Objective To explore the relationship between ultrasonic multi-parameter changes and hand function in

patients with carpal tunnel syndrome （CTS） before and after small incision surgery， and its prognostic value， so as to provide basis for early diagnosis and accurate treatment of CTS. Methods From January 2019 to April 2025，120 patients with unilateral CTS were selected， and all of them underwent ultrasound-guided small incision release of transverse carpal ligament. According to Kelly criteria， the patients were divided into two groups： good prognosis group （n=87） and poor prognosis group （n=33）. Evaluation indexes： ultrasonic multi-parameters including cross-sectional area of lentiform horizontal median nerve （CSA）， thickness of transverse carpal ligament （TTCL） and anteroposterior diameter of horizontal median nerve of hooked bone （D）； Electrophysiological indexes including terminal motor latency （DML）， sensory nerve conduction velocity （SCV） and sensory nerve action potential amplitude （SNAP）； Functional scores including visual analogue scale （VAS）， Boston carpal tunnel scale （BCTQ） and Mayo wrist function score. Multiple linear regression analysis was used to analyze the correlation between ultrasonic multi-parameter changes and patient′s hand function. Multivariate Logistic regression was used to analyze the influencing factors of poor prognosis of CTS patients. The restricted cubic spline （RCS） and threshold effect were used to analyze the relationship between ultrasonic multi-parameters and poor prognosis. Results The group with poor prognosis had higher values in age， BMI， duration of disease， proportion of severe CTS， affected side distribution， proportion of wrist loading>6 hours/day， and WBC， compared to the group with good prognosis （P<0.05）. Compared with the poor prognosis group， the good prognosis group exhibited significantly lower postoperative CSA， TTCL， D， and DML values， and significantly higher SCV and SNAP values （P<0.05）， with a more pronounced improvement trend （between-group×time interaction，P< 0.05）. Compared to the poor prognosis group， the post-operative VAS， BCTQ scores were significantly lower in the good prognosis group， while the Mayo score was higher （P<0.001）. The changes in ultrasonic multi-parameters （ΔCSA/ ΔTTCL/ΔD） were positively correlated with ΔVAS and ΔBCTQ （β=2.082~3.574，P<0.05）， and negatively correlated with ΔMayo score （β=−1.032~−1.986，P<0.05）. Age， BMI， course of disease， severe CTS，ΔCSA，ΔTTCL， and ΔD were influencing factors for poor prognosis （P<0.05）. RCS analysis showed that ΔCSA，ΔTTCL and ΔD had a nonlinear relationship with poor prognosis， and the inflection points were 0.45 mm²，1.02 mm and 0.94 mm respectively （the risk increased significantly after exceeding the inflection point，P<0.05）. Conclusion The dynamic changes of ultrasonic multi-parameters （CSA， TTCL， D） can effectively evaluate the recovery of nerve structure and the improvement of hand function in patients with CTS， and the range of changes is closely related to the prognosis. ΔCSA≥0.45 mm²，ΔTTCL≥ 1.02 mm and ΔD≥0.94 mm are the early warning thresholds of poor prognosis， which can provide objective basis for individualized treatment.

Ultrasonic multi-parameters, Small incision, Carpal tunnel syndrome, Hand function, Prognosis