Summary

Tibial tubercle osteotomy (TTO) fixation using two 5.0mm fully-threaded headless compression screws led to significantly lower rates of hardware removal than standard fixation without compromising safety and efficacy.

Abstract

Purpose

Hardware removal is a common reason for re-operation after tibial tubercle osteotomy (TTO), with prior literature reporting rates up to 59%. Superficial hardware-related pain is the most common reason for re-operation after osteotomy union. There is no clear solution for symptomatic hardware requiring removal following TTO. This study investigates the risk of hardware removal after TTO fixation using two 5.0mm fully-threaded, headless, titanium, cannulated compression screws. We hypothesized that the use of headless compression screws would lead to a decreased incidence of hardware removal when compared to traditional fixation techniques.

Methods

The study included 42 consecutive TTO surgeries conducted at a single institution between October 2019 and August 2022. Patients with a minimum of 2 years’ follow-up were included. All patients met clinical criteria for TTO surgery. Each TTO was fixed with two 5.0mm fully-threaded, headless, titanium, cannulated compression screws. Osteotomy union was evaluated with serial radiographs. Hardware removal was offered to all symptomatic patients after radiographic evidence of complete osteotomy healing or sooner if clinical situation warranted. The study rate of hardware removal was then compared to a representative literature value using a two-proportion Z-test. Patient-reported outcome measures were collected and analyzed using Wilcoxon Signed-Rank tests and Mann-Whitney tests.

Results

Forty-two knees were examined across 39 patients. Among these patients, 69% (n = 29) were female, while 31% (n = 13) were male. Average participant age was 29 years (range 16-69) with an average follow-up period of 39 months (range 24-58). Surgical procedures included anteriorization (n = 5), anteromedialization (AMZ) (n = 22), medialization + distalization (n = 3), AMZ + distalization (n = 5) and AMZ + proximalization ( n=3). One patient (2.8%) developed arthrofibrosis and underwent arthroscopic arthrolysis with concomitant hardware removal at 7 months post-op. There was no radiographic evidence of screw complication prior to removal and no additional complications following hardware removal. The remaining osteotomies healed uneventfully, and no other cases required symptomatic hardware removal or re-operation due to fracture, non-union, or revision TTO. The results of a two-proportion Z-test (Z = -4.48, p < 0.001) indicate a statistically significant reduction in the rate of hardware removal at the α=0.05. There were also statistically significant improvements in patient-reported Knee SANE, KOOS Symptom, KOOS Sport and Recreation, and KOOS QOL measures (p < 0.05).

Conclusion

TTO fixation using two 5.0mm fully-threaded, headless compression screws led to significantly lower rates of hardware removal at two-year follow up compared to literature-reported values using classic fixation techniques. The use of headless screws demonstrated an excellent safety profile, including radiographic union in all patients, without fracture or non-union requiring re-operation. Although preliminary data are promising, studies that directly compare various fixation strategies would be beneficial in the future.

KEYWORDS: Tibial tubercle osteotomy, TTO, hardware removal, headless screw, complication