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BACKGROUND
Increased external tibial torsion and tibial tuberosity-trochlear
groove distance (TTTG) affect patellofemoral instability and can be
corrected by tibial rotational osteotomy and tibial tuberosity
transfer. Thus far, less attention has been paid to the combined
correction of tibial torsion and TTTG by supratuberositary
osteotomy.
PURPOSE
To quantify the effect of a supratuberositary torsional osteotomy on
TTTG.
STUDY DESIGN
Descriptive laboratory study.
METHODS
Seven patients who underwent supratuberositary osteotomy to treat
patellofemoral instability and an additional 13 patients with
increased TTTG were included (N = 20). With 3-dimensional (3D)
surface models, supratuberositary rotational osteotomies were
simulated with predefined degrees of rotation. Concomitant 3D TTTG
was measured by a novel and validated measurement method. In
addition, all operated patients underwent 2-dimensional (2D)
radiographic evaluation with pre- and postoperative computed
tomography data. Absolute differences among simulated, predicted,
and achieved postoperative corrections were compared.
RESULTS
A total of 500 supratuberositary osteotomies were simulated. The
linear regression estimate yielded a change of -0.68 mm (95% CI,
-0.72 to -0.63; < .0001) in 3D TTTG per degree of tibial
rotation, and 2D and 3D TTTG measurements in the operated patients
were comparable in pre- and postoperative measurements
(preoperative, 19.8 ± 2.5 mm and 20.0 ± 2.4 mm;
postoperative, 13.6 ± 3.8 mm and 14.6 ± 3.4 mm,
respectively). Postoperative 2D TTTG deviated in absolute terms from
predicted (regression) and simulated TTTG by 1.4 ± 1.0 mm and
1.5 ± 0.6 mm. Inter- and intrarater reliability (intraclass
correlation coefficient) for radiological and simulated measurements
ranged between 0.883 and 0.996 and were almost perfect.
CONCLUSION
In supratuberositary osteotomy, TTTG changes by -0.68 mm per degree
of internal tibial rotation. The absolute mean difference between
postoperative predicted TTTG and 2D TTTG was only 1.4 mm. Thus, TTTG
correction can be successfully predicted by the degree of tibial
rotation.
CLINICAL RELEVANCE
TTTG correction can be successfully predicted by the degree of
tibial rotation. Therefore, in selected cases, tibial torsional
deformity and TTTG can be corrected by 1 osteotomy. However,
isolated rotations have been performed, and unintended translational
movements during tibial rotation may alter the postoperative
results.
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