Ultrasound screening of lateral hinge fracture after medial open wedge proximal tibial osteotomy.

BACKGROUND

Open wedge proximal tibial osteotomy includes open wedge high tibial osteotomy (OWHTO) and open wedge distal tuberosity tibial osteotomy (OWDTO). These techniques differ in fixation stability and risks, including lateral hinge fracture (LHF), which is a known factor in delayed bone healing. Early detection of LHF is crucial for optimizing bone union. This study evaluated the accuracy of LHF assessment using a non-invasive ultrasound device.

HYPOTHESIS: We hypothesized that (1) ultrasound would detect lateral hinge fractures with high diagnostic accuracy compared with CT, and (2) greater dynamic widening at the hinge site measured by ultrasound would be associated with delayed bone union.

PATIENTS AND

METHODS

We analyzed 61 knees (33 OWDTO, 28 OWHTO) in 33 women (mean age 60 years, range 27-78). LHF was assessed using radiographs, CT scans, and ultrasound. On ultrasound, LHF was defined as discontinuity of the lateral cortical bone at the hinge site. Ultrasound was used to measure lateral hinge widening under non-weight-bearing and full-weight-bearing conditions, and its relationship with time to bone union was examined. Lower limb alignment was evaluated using radiographs, and bone union was assessed using radiographs and CT scans. Clinical outcomes included the visual analogue scale (VAS), range of motion (ROM), and the Knee injury and Osteoarthritis Outcome Score (KOOS).

RESULTS

The incidence of LHF was similar between OWHTO and OWDTO. Ultrasound showed 100% sensitivity and 93.9% specificity, with two false positives in which anterior lateral cortical continuity was lost on CT while posterior cortical continuity at the hinge was preserved. Type I LHF showed greater widening in OWDTO (0.40 mm) than in OWHTO (0.20 mm) (p < 0.05), and widening distance correlated positively with time to union (r = 0.56, p < 0.01). Type I LHF delayed bone union in OWDTO (p < 0.01) but not in OWHTO.

CONCLUSION

Ultrasound provided high diagnostic accuracy for detecting LHF after open wedge proximal tibial osteotomy. Dynamic assessment of hinge instability was associated with delayed bone union, particularly in OWDTO, and may help tailor postoperative rehabilitation.

LEVEL OF EVIDENCE: IV; retrospective observational study.