To assess the accuracy of patient-specific instruments (PSIs) CT scans were obtained from five female cadaveric pelvises. Five osteotomies were designed using Mimics software: sacroiliac, biplanar supra-acetabular, two parallel iliopubic and ischial. For cases of the left hemipelvis, PSIs were designed to guide standard oscillating saw osteotomies and later manufactured using 3D printing. Osteotomies were performed using the standard manual technique in cases of the right hemipelvis. Post-resection CT scans were quantitatively analysed. Student’s Objectives
Methods
We report our experience of using a computer
navigation system to aid resection of malignant musculoskeletal tumours
of the pelvis and limbs and, where appropriate, their subsequent
reconstruction. We also highlight circumstances in which navigation
should be used with caution. We resected a musculoskeletal tumour from 18 patients (15 male,
three female, mean age of 30 years (13 to 75) using commercially
available computer navigation software (Orthomap 3D) and assessed
its impact on the accuracy of our surgery. Of nine pelvic tumours,
three had a biological reconstruction with extracorporeal irradiation,
four underwent endoprosthetic replacement (EPR) and two required
no bony reconstruction. There were eight tumours of the bones of
the limbs. Four diaphyseal tumours underwent biological reconstruction.
Two patients with a sarcoma of the proximal femur and two with a
sarcoma of the proximal humerus underwent extra-articular resection
and, where appropriate, EPR. One soft-tissue sarcoma of the adductor
compartment which involved the femur was resected and reconstructed
using an EPR. Computer navigation was used to aid reconstruction
in eight patients. Histological examination of the resected specimens revealed tumour-free
margins in all patients. Post-operative radiographs and CT showed
that the resection and reconstruction had been carried out as planned
in all patients where navigation was used. In two patients, computer
navigation had to be abandoned and the operation was completed under
CT and radiological control. The use of computer navigation in musculoskeletal oncology allows
accurate identification of the local anatomy and can define the
extent of the tumour and proposed resection margins. Furthermore,
it helps in reconstruction of limb length, rotation and overall
alignment after resection of an appendicular tumour. Cite this article:
We evaluated the oncological and functional outcome
of 18 patients, whose malignant bone tumours were excised with the
assistance of navigation, and who were followed up for more than
three years. There were 11 men and seven women, with a mean age
of 31.8 years (10 to 57). There were ten operations on the pelvic
ring and eight joint-preserving limb salvage procedures. The resection
margins were free of tumour in all specimens. The tumours, which
were stage IIB in all patients, included osteosarcoma, high-grade
chondrosarcoma, Ewing’s sarcoma, malignant fibrous histiocytoma
of bone, and adamantinoma. The overall three-year survival rate
of the 18 patients was 88.9% (95% confidence interval (CI) 75.4
to 100). The three-year survival rate of the patients with pelvic malignancy
was 80.0% (95% CI 55.3 to 100), and of the patients with metaphyseal
malignancy was 100%. The event-free survival was 66.7% (95% CI 44.9
to 88.5). Local recurrence occurred in two patients, both of whom
had a pelvic malignancy. The mean Musculoskeletal Tumor Society
functional score was 26.9 points at a mean follow-up of 48.2 months
(22 to 79). We suggest that navigation can be helpful during surgery for
musculoskeletal tumours; it can maximise the accuracy of resection
and minimise the unnecessary sacrifice of normal tissue by providing
precise intra-operative three-dimensional radiological information.
