Arthroscopy - 2026-09-12 - Journal Article
Increased Risk of Fixation Failure With Two 3.5 Versus 4.5 Millimeter Solid Bicortical Screws for Tibial Tubercle Osteotomy.
Varady NH, Neijna AG, Terry HL, Reddy RP, Gomoll AH, Strickland SM
Topics
Key Takeaway
Two 3.5 mm bicortical screws for tibial tubercle osteotomy carry a 7.9% fixation failure rate versus 1.4% with 4.5 mm screws (OR 8.1, 95% CI 1.1–59.8).
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Summary
This study compared fixation failure rates after TTO fixed with two 3.5 mm versus two 4.5 mm solid bicortical screws across 398 patients treated by two patellofemoral surgeons from 2015–2024. Fixation failure (fracture, nonunion, or symptomatic delayed union requiring reoperation) occurred in 7.9% of the 3.5 mm group versus 1.4% of the 4.5 mm group (P=.03), with the disparity widening in the female subgroup (7.9% vs 0.78%, P=.02). On multivariable analysis controlling for age, sex, smoking, concomitant procedures, and distalization, 3.5 mm screws remained independently associated with failure (OR 8.1, 95% CI 1.1–59.8); no other factor reached significance.
Key Limitation
The wide confidence interval (OR 8.1, 95% CI 1.1–59.8) reflects a small absolute number of failure events (n=8 total), limiting precision of the effect estimate.
Original Abstract
PURPOSE
To assess the association between screw size and fixation failure after tibial tubercle osteotomy (TTO).
METHODS
Patients undergoing primary TTO from 2015 to 2024 by 2 patellofemoral surgeons fixed with two 3.5 mm or two 4.5 mm solid bicortical screws were compared. The primary outcome was fixation failure (i.e., fracture, nonunion, or symptomatic delayed union requiring operative intervention) by 6 months. Patient demographic and surgical factors were collected. Univariate and multivariable adjusted analyses controlling for known and/or theoretical risk factors for overall complications after TTO were performed. Secondary analysis assessed the association between other patient/surgical factors and fixation failure.
RESULTS
There were 398 patients with a mean follow-up of 2.2 years (mean age 28.3 ± 9.6 years; 74.4% women). The overall rate of fixation failure was 2.0%, occurring at a mean of 3.3 ± 1.8 months postoperatively. Patients undergoing TTO with 3.5 mm screws were significantly more likely to experience fixation failure than patients undergoing TTO with 4.5 mm screws (7.9% vs 1.4%, P = .03); results were even more pronounced when limiting analysis to the 296 female patients (7.9% vs 0.78%, P = .02). Results held in all adjusted analyses, including when controlling for age, sex, smoking, concomitant procedures, and TTO distalization (which was more common in the 3.5 mm group), among other factors (odds ratio 8.1, 95% confidence interval 1.1-59.8, P = .04). No other patient or surgical factor, including distalization, was associated with fixation failure (P ≥ .15 for all).
CONCLUSIONS
Compared with two 4.5 mm screws, two 3.5 mm screws were associated with a significantly increased risk of fixation failure after TTO, even after adjusting for patient and surgical factors. Although fixation failure overall remains rare after TTO, screw size may be a modifiable risk factor to reduce the risk of this devastating complication.
LEVEL OF EVIDENCE
Level III, retrospective comparative case series.