Methods

We retrospectively analysed the gait of 33 controls and 50 patients with a unilateral hip replacement, operated by the same surgeon. Follow-up ranged from 9–68 months. In 27 hips a small femoral head size was used (≤ 36mm); in 23 hips a large head size (>36mm). The small size group consisted of 11 long femoral stem THA and 16 short-stem THA and the large group of 5 long-stem THA, 8 short-stem THA and 10 HRA patients. There were 14 females/19 males in the control group; 22 females/5 males in the small size group; 13 females/10 males in the large size group.

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.

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.

Method

After informed consent each subject was allowed a 5 minute acclimatisation period at 4km/hr on the instrumented treadmill (Kistler Gaitway, Amherst, NY). Their gait performance on an increasing incline at 5, 10 and 15%. At all 0.5km incremental intervals of speed, the vertical component of the ground reaction forces, center of pressure and temporal measurements were collected for both limbs with a sampling frequency of 100Hz over 10sec.

They were also asked to log onto our JointPRO website and report their function using Oxford, EQ5D, and Imperial scores.

Owing to current restrictions in indications, the patient groups selected were not comparable. However, from our database of over 800 patients who have been through the gait lab. 82 subjects were tested from 2 diagnostic groups (29 conventional THR, 27 hip resurfacing) and compared with a slightly younger group of 26 healthy controls. Patients were excluded if less than 12 months postop, or with any other documented joint disease or medical comorbidities which might affect gait performance.

Body weight scaling was also applied to the outputted mechanical data to correct for mass differences. All variables for each subject group were compared to each other using an analysis of variance (ANOVA) with Tukey post hoc test with significance set at α=0.05.

Method

110 subjects were tested on an instrumented treadmill (Kistler Gaitway), 4 groups (short-stem THR, long-stem THR, hip resurfacing and healthy controls) of 28, 29, 27, and 26 respectively. The new short femoral stem patients (Furlong Evolution, JRI) were taken from the ongoing Evolution Hip trial that have been tested on the treadmill minimum 12months postop. The long stem total hip replacements and hip resurfacing groups were identified from our 800+ patient treadmill database, and only included with tests minimum 12 months postop and had no other joint disease or medical comorbidities which would affect gait performance.

All subjects were tested through their entire range of gait speeds and incline after having a 5 minute habituation period. Speed were increased 0.5kmh until maximum walking speed achieved and inclines at 4kmh for 5,10,15%. At all incremental intervals of speed 10seconds ere collected, including vertical ground reaction forces (normalized to body mass), center of pressure and temporal measurements were for both limbs (fs=100Hz). Symmetry Index(SI) were calculated on a range of features comparing leg with implanted hip to the contralateral normal hip. Group means for each feature for each subject group were compared using an analysis of variance (ANOVA) with Tukey post-hoc test with significance set at α=0.05.

Patients and Methods

145 participants (121 healthy controls, 12 patients with cruciate-retaining TKA, and 12 with mobile-bearing medial UKA) were recruited. The TKA and UKA patients were a minimum of 12 months post-operative, and matched for pattern and severity of arthrosis, age, and body mass index.

Participants walked on an instrumented treadmill until their maximum walking speed was reached. Temporospatial gait parameters, and vertical ground reaction force data, were captured at each speed. Oxford knee scores (OKS) were also collected. An ensemble of trees algorithm was used to analyse the data: 27 gait variables were used to train classification trees for each speed, with a binary output prediction of whether these variables were derived from a UKA or TKA patient. Healthy control gait data was then tested by the decision trees at each speed and a final classification (UKA or TKA) reached for each subject in a majority voting manner over all gait cycles and speeds. Top walking speed was also recorded.