Association of the preoperative MRI LAMBDA sign with long-term patient-reported outcomes after isolated ATFL surgery: a ten-year retrospective cohort study.

BACKGROUND

The LAMBDA sign has been reported to be associated with syndesmotic-region injury on MRI, but its relationship with long-term outcomes after isolated ATFL surgery remains unclear.

OBJECTIVE

To evaluate the association between the preoperative MRI LAMBDA sign and long-term patient-reported outcomes in patients undergoing isolated anterior talofibular ligament (ATFL) repair or reconstruction.

METHODS

We retrospectively reviewed patients who underwent ATFL repair or reconstruction at a single institution between 2014 and 2016. A transparent cohort flow was documented, comparing included and excluded patients to assess for selection bias. The primary endpoint was the Foot and Ankle Outcome Score (FAOS) at final follow-up. At surgery, all patients were diagnosed clinically as having isolated ATFL injuries without chondral lesions, and the syndesmosis was not examined. Preoperative MRIs were reanalyzed, and patients were classified according to the presence or absence of the LAMBDA sign. LAMBDA-positive patients were additionally stratified by distal tibiofibular joint effusion height (DTJEH ≥ 8 mm vs. < 8 mm). Baseline characteristics and long-term patient-reported outcomes (FAOS, Karlsson, Tegner, VAS, satisfication) were collected. Adjusted effects, along with 95% confidence intervals (CIs), were reported. Rater reliability (ICC/κ) for LAMBDA and DTJEH was assessed with CIs and exact methods.

RESULTS

Seventy-nine patients were included (mean follow-up, 112.2 ± 8.0 months): 46 LAMBDA-positive and 33 LAMBDA-negative. LAMBDA-positive patients had significantly higher preinjury Tegner scores compared with the negative group (6.0 [6.0-7.0] vs. 5.0 [4.5-6.5]; P < 0.05), but worse long-term outcomes. Specifically, FAOS was lower in the LAMBDA-positive group (80.0 [75.0-85.0] vs. 86.0 [81.5-88.0]; mean difference, -6.1; 95% CI, -9.3 to -3.0; P < 0.001), as were Karlsson scores (80.0 [75.0-85.0] vs. 85.0 [84.0-90.0]; mean difference, -6.1; 95% CI, -9.5 to -2.7; P = 0.001). Additionally, LAMBDA-positive patients showed greater decline in Tegner activity levels (2.0 [1.0-3.0] vs. 1.0 [0.5-2.0]; P < 0.05). However, despite these statistically significant differences, they did not exceed established minimal clinically important difference (MCID) thresholds for FAOS and Karlsson scores (FAOS: 11.7; Karlsson: 10.0).

CONCLUSION

A preoperative MRI LAMBDA sign was associated with slightly inferior long-term patient-reported outcomes after isolated ATFL surgery. Given the limitations of static MRI and the lack of intraoperative syndesmotic evaluation, these findings should be viewed as associations rather than causal relationships. Further studies incorporating dynamic or intraoperative assessments are warranted.

LEVEL OF EVIDENCE: III (retrospective cohort).