Study assesses if anterior lip displacement predicts complications in patients with tibial spine fractures

Young patients who undergo surgery for displaced tibial spine fractures and who had both an extension and flexion contracture, had 2.2 times the odds of having a complication compared to patients who did not have any contractures, according to research presented today at the American Orthopaedic Society for Sports Medicine's 2022 Annual Meeting.

Tibial spine fracture is a break at the top of the tibia bone in the lower leg near the knee. This type of injury is most common in children between the ages eight to 14. A flexion contracture is a bent (flexed) joint that cannot be straightened actively or passively. Surgery for displaced tibial spine fractures consists of suture or screw fixation to reduce the fragment in addition to restoring tension of the anterior cruciate ligament. But, it is unknown whether this surgery impacts healing, range of motion, or looseness of the limb (laxity).

To investigate this further, Shannon A. McGurty, Boston Children's Hospital in Boston, created a study to determine if residual displacement of the anterior portion of a tibial spine fragment affects the range of motion or laxity in post-operative and non-operatively treated tibial spine patients and to assess if anterior lip displacement (ALD) predicts complications in these patients.

McGurty and colleagues gathered data on 578 patients treated for tibial spine fractures from an institutional review board-approved multicenter retrospective cohort of patients treated for tibial spine fractures between January 1, 2000, and January 31, 2019, at 10 institutions.

The researchers examined range of motion and anterior lip displacement measurements and compared these from pre-treatment to the patient's final visit. Anterior lip displacement measurements were categorized into four groups: 0 to <1 mm, excellent; 1 to <3 mm, good; 3 to 5mm, fair; and >5mm, poor.

Of the 578 patients reviewed, 82 % (474/578) had an operative treatment while only 18% of patients (104/578) had a non-operative treatment. There was a higher proportion of patients who had a positive Lachman test in the non-operative group (12%; 12/104) compared to the operative group (4%; 18/474; p=0.001). The surgical group had a median time of 3.4 months from surgery (range, 0.10 to 91.86 months) to final displacement measurement, while the non-operative group had a median time of 2.6 months from initial treatment to final displacement measurement (range, 0.07 to 61.37 months). Overall, there was no significant difference in the final range of motion measurements between these groups. The median anterior lip displacement measurement prior to treatment was 6.1mm and decreased to 0.7mm after treatment (p<0.001).

At the final visit for patients, over half (52%; 248/477) were categorized in the excellent group for the anterior lip displacement measurement compared to only 4% (18/434) pre-treatment. Total range of motion prior to treatment was 75 degrees and it increased to 140 degrees after treatment (p<0.001). Patients categorized as having a good final anterior lip displacement measurement had a 3 degree decrease in their final range of motion compared to patients categorized in the excellent group (β=-6.4; 95% CI=-11.36, -1.52; p=0.01). Patients categorized as having a fair final anterior lip displacement measurement had a 7.5 degree decrease in their final range of motion compared to patients categorized in the excellent group (β=-9.3; 95% CI=-13.77, -4.75; p<0.001). Patients categorized as having a poor final anterior lip displacement measurement had a 10 degree decrease in their final range of motion compared to patients categorized in the excellent group (β=-10.9; 95% CI=-18.26, -3.47; p=0.004).

There were no associations detected between final anterior lip displacement category and laxity. Focusing on the operative group, there were no significant differences detected in laxity among the four different final anterior lip measurements (p=0.76). Post-hoc tests determined that the median total range of motion was larger for the excellent group (140 degrees) compared to the fair group (132.5 degrees; p<0.001). Similarly, there were significant differences detected between the excellent and fair group for flexion and extension measurements (p<0.001 and p=0.001, respectively). Overall, the study cohort had a 12% arthrofibrosis rate, with 11% in the non-operative group and 16% in the operative group. Thirty-seven patients had to return to the operating room for treatment of arthrofibrosis, which was independent of final anterior lip displacement.

Operative patients who had both an extension and flexion contracture had 2.2 times the odds of having a complication compared to patients who did not have any contractures, this was independent of final ALD. Operative patients demonstrated greater ACL stability than the non-operative group, but had more complications and reoperations, independent from ALD. While ALD measurements of 'fair', 'good', and 'poor' all resulted in some loss of range of motion, this was of minimal clinical significance in patients at final follow up. This study provides evidence that patients are able to return to full range of motion with stable knees without an ideal reduction of the anterior lip, suggesting that anatomic reduction may not be mandatory."

Shannon A. McGurty, Boston Children's Hospital, Boston

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