New surgical treatment for sliding calcaneal osteotomy; retrospective case-series

Sliding calcaneus osteotomy may be indicated to restore the natural congruency
of the ankle joint and thereby preventing progression of symptoms and prevent
progression of degenerative changes. The ankle joint has a high congruency. A
decrease in joint congruence will increase contact pressure per area. More
displacement corresponds to increasing contact pressure. Clinical and basic
scientific investigations have shown that loading and motion of the joint can
influence the healing of articular cartilage and joints. Malalignment may also
increase the contact pressure of the ankle. Biomechanical experiments have
demonstrated that in varus and supination the maximum pressure is located on
the medial border of the talus, while in valgus and pronation the maximum
pressure is located on the lateral talar border. It is therefore important to
correct malalignment in patients with degenerative changes in the ankle.
Sliding calcaneus osteotomy is an established procedure for treatment of an
acquired adult flatfoot, correct hindfoot valgus after recurrent pronation
trauma and deltoid ligament insufficiency, uncompartimental osteoarthritis,
cavovarus foot deformity, osteochondral defects, and correction of a malaligned
ankle.
Currently, cannulated screw*fixation is used for sliding calcaneus osteotomy.
This method fixation is achieved by inserting one or two compressive screws
from posterior. The stability of the osteotomy allows a rapid mobilization of
the ankle and weight bearing after 4 weeks. Radiographically, consolidation is
complete after approximately 8 weeks. Nonunion of the osteotomy is rare because
of the extensive spongy surface tissue which always remains in contact.
However, fixation with screws has some disadvantages. Separate incisions have
to be made for introduction of the screws. Patients may develop pain on walking
when prominence of the screw heads on the plantar surface of the calcaneus. A
fluoroscope has to be used during surgery, to determine the exact size and
control the position of the screws. The osteomized area where screws can be
placed is small. Furthermore, it is difficult to maintain and check the desired
amount of calcaneal displacement since the screws are inserted from a different
position. This may lead to over- and under-correction after calcaneus
osteotomy. Recently, a stepplate-fixation technique was developed in order to
overcome these problems. This study will be the first study to assess the
results of this new surgical technique.

The primary objective of the study is to determine the patient satisfaction and
assess objectively the clinical outcome at a minimum of one year follow-up
after surgical intervention.
The secondary objective is to determine whether the osteotomy heals in the
correct way and to evaluate the calcaneus displacement and fixation.

This study is designed as a retrospective descriptive study with postoperative
follow- up. All patients will be asked to come to our outpatient clinic for one
visit. During this visit conventional radiographs of the ankle (lateral and AP)
and of the calcaneus (axial) will be taken.

All patients will receive three routine weight bearing radiographs, which is an
exposure to radiation. This study does not provide immediate advantage for the
participating patient. For future patients however this study is beneficial as
it will evaluate the effectiveness of a new surgical procedure for sliding
calcaneal osteotomies at the AMC.