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Orthopaedic Proceedings
Vol. 103-B, Issue SUPP_6 | Pages 47 - 47
1 May 2021
Gigi R Gorrtzak Y Golden E Gabay R Rumack N Yaniv M Dadia S Segev E
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Introduction

Patient-specific instruments (PSI) and surgical-guiding templates are gaining popularity as a tool for enhancing surgical accuracy in the correction of oblique bone deformities Three-dimensional virtual surgical planning technology has advanced applications in the correction of deformities of long bones and enables the production of 3D stereolithographic models and PSI based upon a patient's specific deformity. We describe the implementation of this technology in young patients who required a corrective osteotomy for a complex three-plane (oblique plane) lower-limb deformity.

Materials and Methods

Radiographs and computerized tomographic (CT) scans (0.5 mm slices) were obtained for each patient. The CT images were imported into post-processing software, and virtual 3D models were created by a segmentation process. Femoral and tibial models and cutting guides with locking points were designed according to the deformity correction plan as designed by the surgeon. The models were used for preoperative planning and as an intraoperative guide. All osteotomies were performed with the PSI secured in the planned position.


Orthopaedic Proceedings
Vol. 99-B, Issue SUPP_5 | Pages 71 - 71
1 Mar 2017
Owyang D Dadia S Jaere M Auvinet E Brevadt MJ Cobb J
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Introduction

Clear operative oncological margins are the main target in malignant bone tumour resections. Novel techniques like patient specific instruments (PSIs) are becoming more popular in orthopaedic oncology surgeries and arthroplasty in general with studies suggesting improved accuracy and reduced operating time using PSIs compared to conventional techniques and computer assisted surgery. Improved accuracy would allow preservation of more natural bone of patients with smaller tumour margin.

Novel low-cost technology improving accuracy of surgical cuts, would facilitate highly delicate surgeries such as Joint Preserving Surgery (JPS) that improves quality of life for patients by preserving the tibial plateau and muscle attachments around the knee whilst removing bone tumours with adequate tumour margins. There are no universal guidelines on PSI designs and there are no studies showing how specific design of PSIs would affect accuracy of the surgical cuts.

We hypothesised if an increased depth of the cutting slot guide for sawblades on the PSI would improve accuracy of cuts.

Methods

A pilot drybone experiment was set up, testing 3 different designs of a PSI with changing cutting slot depth, simulating removal of a tumour on the proximal tibia (figure 1)

A handheld 3D scanner (Artec Spider, Luxembourg) was used to scan tibia drybones and Computer Aided Design (CAD) software was used to simulate osteosarcoma position and plan intentioned cuts (figure 1). PSI were designed accordingly to allow sufficient tumour. The only change for the 3 designs is the cutting slot depth (10mm, 15mm & 20mm). 7 orthopaedic surgeons were recruited to participate and perform JPS on the drybones using each design 2 times. Each fragment was then scanned with the 3D scanner and were then matched onto the reference tibia with customized software to calculate how each cut (inferior-superior-vertical) deviated from plan in millimetres and degrees (figure 3). In order to tackle PSI placement error, a dedicated 3D-printed mould was used.


Orthopaedic Proceedings
Vol. 99-B, Issue SUPP_3 | Pages 88 - 88
1 Feb 2017
Dadia S Jaere M Sternheim A Eidelman M Brevadt MJ Gortzak Y Cobb J
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Background

Dislocation is a common complication after proximal and total femur prosthesis reconstruction for primary bone sarcoma patients. Expandable prosthesis in children puts an additional challenge due to the lengthening process. Hip stability is impaired due to multiple factors: Resection of the hip stabilizers as part of the sarcoma resection: forces acts on the hip during the lengthening; and mismatch of native growing acetabulum to the metal femoral head. Surgical solutions described in literature are various with reported low rates of success.

Objective

Assess a novel 3D surgical planning technology by use of 3D models (computerized and physical), 3D planning, and Patient Specific Instruments (PSI) in supporting correction of young children suffering from hip instability after expandable prosthesis reconstruction following proximal femur resection. This innovative technology creates a new dimension of visualization and customization, and could improve understanding of this complex problem and facilitate the surgical decision making and procedure.


Orthopaedic Proceedings
Vol. 98-B, Issue SUPP_8 | Pages 58 - 58
1 May 2016
Brevadt M Manning V Wiik A Aqil A Dadia S Cobb J
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Introduction

Femoral component design is a key part of hip arthroplasty performance. We have previously reported that a hip resurfacing offered functional improved performance over a long stem. However resurfacing is not popular for many reasons, so there is a growing trend towards shorter femoral stems, which have the added benefit of ease of introduction through less invasive incisions. Concern is also developing about the impact of longer stems on lifetime risk of periprosthetic fracture, which should be reduced by the use of a shorter stem. For these reasons, we wanted to know whether a shorter stem offered any functional improvement over a conventional long stem. We surmised that longer stems in hip implants might stiffen the femoral shaft, altering the mechanical properties.

Materials and Methods

From our database of over 800 patients who have been tested in the lab, we identified 95 patients with a hip replacement performed on only one side, with no other lower limb co-morbidities, and a control group:

19 with long stem implant, age 66 ± 14 (LONG)

40 with short stem implant, age 69 ± 9 (SHORT)

26 with resurfacing, age 60 ± 8 (RESURF)

43 healthy control with no history of arthroplasty, age 59 ± 10 (CONTROL)

All groups were matched for BMI and gender.

Participants were asked to walk on an instrumented treadmill. Initially a 5 minute warm up at 4 km/h, then tests at increasing speed in 0.5 km/h increments. Maximum walking speed was determined by the patients themselves, or when subjects moved from walking to running.

Ground reaction forces (GRF) were measured in 20 second intervals at each speed. Features were calculated based on the mean GRF for each trial, and on symmetry measures such as first peak force (heel strike), second peak force (toe-off), the rate at which the foot was loaded and unloaded, and step length.