The Effect of Hip Arthroplasty on Osteoarthritic Gait: A Blinded, Prospective and Controlled Gait Study at Fast Walking Speeds.

Background: Painful unilateral cox arthrosis results in excessive forces passing through the "good leg." The impact of hip arthroplasty on contralateral leg gait has not been fully explored. We measured patients gait before and after arthroplasty, to answer 3 questions: (1) Are peak forces for the good legs outside the normal range? (2) Does arthroplasty protect contralateral limbs by reducing peak forces? and (3) Does arthroplasty result in a more symmetric and normal gait at fast walking speeds?

Methods: This prospective, controlled study, assessed ground reaction forces before and 13 months (range, 6-21 months) after hip arthroplasty.

Resurfacing head size and femoral fracture: Are registry conclusions on head size justified?

Background: Joint registries report that peri-prosthetic fractures are the most common reason for early revision of a hip resurfacing arthroplasty (HRA) and are twice as likely with small implant sizes. However, a national survey found peri-prosthetic fracture to be strongly associated with surgical accuracy. We therefore asked whether the force required to induce a peri-prosthetic fracture: (1) was significantly lower when using smaller implants and (2) correlated to the size of implant used, when surgery was performed accurately.

Birmingham Mid-Head Resection Periprosthetic Fracture.

Total hip arthroplasty in the young leads to difficult choices in implant selection. Until recently bone conserving options were not available for younger patients with deficient femoral head bone stock. The novel Birmingham Mid-Head Resection (BMHR) device offers the option of bone conserving arthroplasty in spite of deficient femoral head bone stock.

Does cam osteochondroplasty compromise proximal femur strength?

Little is known about the effect on load bearing ability of cam-type femurs following osteochondroplasty. The aim of this study was to compare the change in deformation undergone by cam-type femoral acetabular impingement femur models after resection of different volumes. Dry-bone replicas (N = 10) of two cam-type femurs (cam A and B) underwent resections of increasing volume (Surgery I, II and III) representing conservative, adequate and radical resections.

Validation of the 'FeMorph' software in planning cam osteochondroplasty by incorporating labral morphology.

Impingement resulting from a cam deformity may cause pain, limit the hip joint range of motion (RoM) and lead to osteoarthritis. We have previously developed FeMorph software to quantify and plan corrective surgery and predict hip RoM post surgery. This study aimed to validate the software and evaluate the influence of the acetabular labrum on hip RoM.

The knee adduction angle of the osteo-arthritic knee: a comparison of 3D supine, static and dynamic alignment.

Background: End-stage knee osteoarthritis (OA) commonly results in knee arthroplasty. Three dimensional (3D) supine imaging is often used for pre-operative planning to optimise post-operative knee adduction angles (KAA). However, supine imaging may not represent loaded knee alignment.

A local reference frame for describing the proximal human femur: application in clinical settings.

Objective: The conventional reference frame for the femur has limited relevance for the planning of hip surgery as the femoral neck axis, a crucial reference for surgeons, has to be independently derived. The purpose of this study is to develop and validate a reliable frame of reference for the proximal femur that can be applied in clinical settings.

Materials And Methods: Ten three-dimensional models of femurs were obtained.

Unicompartmental knee arthroplasties: robot vs. patient specific instrumentation.

Background: The technical reliability demonstrated by semi active robots in implant placement could render unicompartmental knee arthroplasties (UKAs) more favourable than they are currently. The relatively untested method using patient specific instrumentation (PSI), however, has the potential to match the accuracy produced by robots but without the barriers that have prevented them from being used more widely in clinical practice, namely operative time. Therefore this study took a step towards comparing the accuracy and time taken between the two technologies.

Protocol for evaluation of robotic technology in orthopedic surgery.

In recent years, robots have become commonplace in surgical procedures due to their high accuracy and repeatability. The Acrobot Sculptor is an example of such a robot that can assist with unicompartmental knee replacement. In this study, we aim to evaluate the accuracy of the robot (software and hardware) in a clinical setting.

Dynamic analysis of the upper limb during activities of daily living: comparison of methodologies.

Often researchers use kinematics and kinetics to evaluate the effect of limb pathology. The net forces and moments that cause motion depend on kinematics, body segment parameters and the external loads applied. This study aimed to evaluate the discrepancies caused by different methods and assumptions of kinetic analysis.

Robotic assistance enables inexperienced surgeons to perform unicompartmental knee arthroplasties on dry bone models with accuracy superior to conventional methods.

Robotic systems have been shown to improve unicompartmental knee arthroplasty (UKA) component placement accuracy compared to conventional methods when used by experienced surgeons. We aimed to determine whether inexperienced UKA surgeons can position components accurately using robotic assistance when compared to conventional methods and to demonstrate the effect repetition has on accuracy. Sixteen surgeons were randomised to an active constraint robot or conventional group performing three UKAs over three weeks.

Musculoskeletal shoulder models: a technical review and proposals for research foci.

Musculoskeletal shoulder models allow non-invasive prediction of parameters that cannot be measured, particularly the loading applied to morphological structures and neurological control. This insight improves treatment and avoidance of pathology and performance evaluation and optimisation. A lack of appropriate validation and knowledge of model parameters' accuracy may cause reduced clinical success for these models.

Mathematical representation of the normal proximal human femur: application in planning of cam hip surgery.

Precise modelling of the proximal femur can be used for detecting and planning corrective surgery for subjects with deformed femurs using robotic technology or navigation systems. In this study, the proximal femoral geometry has been modelled mathematically. It is hypothesised that it is possible to fit a quadratic surface or combinations of them onto different bone surfaces with a relatively good fit.

The gait of patients with one resurfacing and one replacement hip: a single blinded controlled study.

Purposes: Post arthroplasty gait analysis has up till now been performed on subjects walking slowly on flat ground rather than challenging them at faster speeds or walking uphill. We therefore asked: (1) Is there a measurable difference in the performance of hip resurfacing arthroplasty (HRA) and total hip arthroplasty (THA) limbs at patients' self-determined fastest walking speeds and steepest inclines? and (2) Is there a relationship between the observed differences between the gait of HRA and THA implanted limbs and patient walking speeds and inclines.

Methods: In an ethically approved study we recruited patients with bilateral hip arthroplasties: one HRA and one THA.

Use of robotic technology in cam femoroacetabular impingement corrective surgery.

Background: Cam type femoroacetabular impingement (FAI) is an anatomical disorder that can lead to osteoarthritis (OA) of the hip joint. With existing surgical options there is invariably a tendency for under-resection or over-resection of the cam lesion, both having dire consequences. This study assessed the application of robotic technology in the surgical management of cam FAI.

A method of assessing the severity of cam type femoro-acetabular impingement in three dimensions.

Femoroacetabular impingement is caused by abnormal morphology of either the femur or acetabulum or both. Diagnostic criteria currently include an alpha angle of over 50° on a lateral radiograph. In this study, CT scans of symptomatic hips (n = 37) were compared with normal hips (n = 34) obtained from CT colonoscopy procedures.

Cam type femoro-acetabular impingement: quantifying the diagnosis using three dimensional head-neck ratios.

Objective: Cam hips are commonly quantified using the two-dimensional α angle. The accuracy of this measurement may be affected by patient position and the technician's experience. In this paper, we describe a method of measurement that provides a quantitative definition of cam hips based upon three-dimensional computed tomography (CT) images.

Comparison of range of motion and function of subjects with reverse anatomy Bayley-Walker shoulder replacement with those of normal subjects.

Patients with rotator cuff tear and degenerative shoulder joint disease commonly experience severe pain and reduced performance during activities of daily living. A popular way to treat these patients is by means of reverse anatomy shoulder prosthesis. Studying the kinematics of subjects with reverse anatomy implant would be useful in order to gain knowledge about functionality of different designs.

Glenohumeral contact forces in reversed anatomy shoulder replacement.

A major requirement to design an implant is to develop our understanding of the applied internal forces during everyday activities. In the absence of any basic apparatus for measuring forces directly, it is essential to rely on modelling. The major aim of this study was therefore to understand the biomechanical function of subjects with the reversed anatomy Bayley-Walker prosthesis, using an inverse dynamic shoulder model.