tibial tuberosity to trochlear groove (TTTG) is a well-known orthopaedic
radiographic measurement around the knee joint. This measurement in the western
population is a well-recognized entity and widely studied through various
modalities such as X-rays, computerized tomography (CT) and magnetic resonance
imaging (MRI) 1-3. However no literature is
currently present to indicate that the TTTG distance has been studied in the
Black African population.
measurement is of clinical significance due to its relevance in patella
instability4. It plays a pivotal role when deciding on the need for
currently know that the normal TTTG measurement is less than 15mm. The
literature also suggests that anything above 20mm needs to be considered for a
bony surgical procedure (e.g. medializing osteotomy of tibial tuberosity) 5-7.
purpose of this comparative study was to measure the TTTG measurement in the
Black African population and compare it to the Western quoted norms in the
study does not aim to assess patella instability as a pathology but rather
scrutinize the measurement in isolation.
TTTG measurement was first described by Goutallier and Bernageau in 1978 8 based on x-ray
et al then adapted the same measurement to the CT scan in 1987 9. His set of patients with patella instability and his
control group were derived from the French population. His control group had an
average measurement of 12.7mm +-3.4mm and showed that a measurement of >20mm
was present in pathological cases.
et al, in a Level 1 study, reported that a large variation may even be present
in asymptomatic patients10. This study found normal
TTTG values of 13.6 +- 8.8mm.
T.K. et al reported in a systematic review about the morphological differences
that exist in certain anatomical features and measurements around the knee11. Tse et al suggested that
actually the threshold for tibial tuberosity transfer should
rather be lower in Chinese patients12. Koerner et al has also queried the variations of “normal”
femoral versions amongst genders and ethnicities13. This in turn brings
about the discussion of a range of possible ethnic differences when it comes to
anatomical structure and previously believed to be normal TTTG measurements.