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Orthopaedic Proceedings
Vol. 101-B, Issue SUPP_4 | Pages 74 - 74
1 Apr 2019
Giles J Broden C Tempelaere C Rodriguez-Y-Baena F
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PURPOSE

To validate the efficacy and accuracy of a novel patient specific guide (PSG) and instrumentation system that enables minimally invasive (MI) short stemmed total shoulder arthroplasty (TSA).

MATERIALS AND METHODS

Using Amirthanayagam et al.'s (2017) MI posterior approach reduces incision size and eliminates subscapular transection; however, it precludes glenohumeral dislocation and the use of traditional PSGs and instruments. Therefore, we developed a PSG that guides trans-glenohumeral drilling which simultaneously creates a humeral guide tunnel/working channel and glenoid guide hole by locking the bones together in a pre-operatively planned pose and drilling using a c-shaped drill guide (Figure 1). To implant an Affinis Short TSA system (Mathys GmbH), novel MI instruments were developed (Figure 2) for: humeral head resection, glenoid reaming, glenoid peg hole drilling, impaction of cruciform shaped humeral bone compactors, and impaction of a short humeral stem and ceramic head.

The full MI procedure and instrument system was evaluated in six cadaveric shoulders with osteoarthritis. Accuracy was assessed throughout the procedure: 1) PSG physical registration accuracy, 2) guide hole accuracy, 3) implant placement accuracy. These conditions were assessed using an Optotrak Certus tracking camera (NDI, Waterloo, CA) with comparisons made to the pre-operative plan using a registration process (Besl and McKay, 1992).


Orthopaedic Proceedings
Vol. 99-B, Issue SUPP_20 | Pages 40 - 40
1 Dec 2017
Giles J Rodriguez y Baena F
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Patient Specific Instruments (PSIs) are becoming increasingly common in arthroplasty but have only been used with highly invasive surgical approaches that can result in significant complications. We have previously described a novel PSI for minimally invasive total shoulder arthroplasty and shown that it can accurately guide the creation of guide holes in the humerus and scapula. However, conducting shoulder replacement in a minimally invasive environment precludes the use of traditional instruments. In this work, we describe and evaluate the efficacy of a set of novel instruments that, in conjunction with our PSIs, enable accurate minimally invasive total shoulder arthroplasty to be achieved for the first time.

The key components of this surgical procedure are: 1) a new minimally invasive posterior surgical approach that avoids the need for muscle transection; 2) a novel PSI that enables accurate guide tunnels to be simultaneously created in the humerus and scapula using a c- shaped drill guide that mates to the PSI; 3) a custom humeral head resection guide that uses the humeral guide tunnel; 4) a novel reamer and 3D metal printed gear mechanism for radial displaced drilling both powered by a central driver placed through the humeral head; and 5) custom impactors for glenoid and humeral implantation – the latter is achieved using a modular slap hammer that is guided by the central humeral drill hole. Accuracy of this system was assessed at each surgical step using an optical tracking camera and an iterative closest point registration method to map measurements to the pre-operative plan.

The accuracy results for the physical PSI registration and guide hole drilling were found to be in line with our previously reported results: the intra-articular guide hole locations were 2.2mm and 3.9mm for the humerus and glenoid with angular errors of 2.8° and 8°, respectively. After humeral resection, the humeral cut plane had an angular error of 10.1°. The final humeral implant location had an error of 12.1° and 1.9mm. For the glenoid implant, the positional error was 3.8mm with angular errors of 3.3° ante-retroversion and 8.6° supero- inferior inclination.

We believe that these initial results demonstrate that this minimally invasive PSI and instrumentation system can accurately guide total shoulder replacement while avoiding the complications of open surgery. A full cadaveric testing series is currently being completed.


Orthopaedic Proceedings
Vol. 99-B, Issue SUPP_20 | Pages 58 - 58
1 Dec 2017
Liu H Bowyer S Auvinet E Rodriguez y Baena F
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In robot-assisted orthopaedic surgery, registration is a key step, which defines the position of the patient in the robot frame so that the preoperative plan can be performed. Current registration methods have their limitations, such as the requirement of immobilisation of the limbs or the line of sight (LOS) issues. These issues cause inconvenience for the surgeons and interrupt the surgical workflow in the operating room.

Targetting these issues of current registration methods, we propose a camera-robot registration system for joint replacement. The bone geometry, which is measured directly by a depth camera, is aligned to a preoperatively obtained bone model to calculate the pose of the target. Simultaneously, in order to avoid registration failure caused by LOS interruptions, the depth camera tracks objects that may occlude the target bone, and a robot manipulator is used to move the camera away from the nearest obstacle. The optimal camera motion is calculated based on the position and velocity of the obstacle, which avoids the occlusion efficiently without changing the target position in the camera frame. Inverse kinematics of the robot is used to project the Cartesian velocity of the end-effector into the joint space, with kinematic singularities considered for stable robotic control. An admittance controller is designed as the human-robot interface so that the surgeon can directly set the robot configuration by hand according to the actual environment.

Simulations and experiments were conducted to test the performance. The results show that the proposed obstacle avoidance method can effectively increase the distance between the obstacle and the LOS, which lowers the risk of registration failure due to obstacle occlusion. This pilot study is promising in reducing distractions to the surgeon and can help achieve a fluent and surgeon-centred workflow.


Orthopaedic Proceedings
Vol. 99-B, Issue SUPP_3 | Pages 20 - 20
1 Feb 2017
Athwal K El Daou H Lord B Davies A Manning W Rodriguez-Y-Baena F Deehan D Amis A
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Introduction

There is little information available to surgeons regarding how the lateral soft-tissue structures prevent instability in knees implanted with total knee arthroplasty (TKA). The aim of this study was to quantify the lateral soft-tissue contributions to stability following cruciate retaining (CR) TKA.

Methods

Nine cadaveric knees with CR TKA implants (PFC Sigma; DePuy Synthes Joint Reconstruction) were tested in a robotic system (Fig. 1) at full extension, 30°, 60°, and 90° flexion angles. ±90 N anterior-posterior force, ±8 Nm varus-valgus and ±5 Nm internal-external torque were applied at each flexion angle. The anterolateral structures (ALS, including the iliotibial band, anterolateral ligament and anterolateral capsule), the lateral collateral ligament (LCL), the popliteus tendon complex (Pop T) and the posterior cruciate ligament (PCL) were then sequentially transected. After each transection the kinematics obtained from the original loads were replayed, and the decrease in force / moment equated to the relative contributions of each soft-tissue to stabilising the applied loads.


Orthopaedic Proceedings
Vol. 98-B, Issue SUPP_8 | Pages 36 - 36
1 May 2016
Henckel J Rodriguez-y-Baena F Jakopec M Harris S Barrett A Gomes M Alsop H Davies B Cobb J
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Introduction

We report 10-year clinical outcomes of a prospective randomised controlled study on uni-compartmental knee arthroplasty using an active constraint robot.

Measuring the clinical impact of CAOS systems has generally been based around surrogate radiological measures with currently few long-term functional follow-up studies reported. We present 10 year clinical follow up results of robotic vs conventional surgery in UKA.

Material and methods

The initial study took place in 2004 and included 28 patients, 13 in the robotic arm and 15 in the conventional arm. All patients underwent medial compartment UKA using the ‘OXFORD’ mobile bearing knee system. Clinical outcome at 10 years was scored using the WOMAC scoring system.


Orthopaedic Proceedings
Vol. 98-B, Issue SUPP_8 | Pages 1 - 1
1 May 2016
Giles J Amirthanayagam T Emery R Amis A Rodriguez-Y-Baena F
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Background

Total Shoulder Arthroplasty (TSA) has been shown to improve the function and pain of patients with severe degeneration. Recently, TSA has been of interest for younger patients with higher post-operative expectations; however, they are treated using traditional surgical approaches and techniques, which, although amenable to the elderly population, may not achieve acceptable results with this new demographic. Specifically, to achieve sufficient visualization, traditional TSA uses the highly invasive deltopectoral approach that detaches the subscapularis, which can significantly limit post-operative healing and function. To address these concerns, we have developed a novel surgical approach, and guidance and instrumentation system (for short-stemmed/stemless TSA) that minimize muscle disruption and aim to optimize implantation accuracy.

Development

Surgical Approach: A muscle splitting approach with a reduced incision size (∼6–8cm) was developed that markedly reduces muscle disruption, thus potentially improving healing and function. The split was placed between the infraspinatus and teres-minor (Fig.1) as this further reduces damage, provides an obvious dissection plane, and improves access to the retroverted articular surfaces. This approach, however, precludes the use of standard bone preparation methods/instruments that require clear visualization and en-face articular access. Therefore, a novel guidance technique and instrumentation paradigm was developed.

Minimally Invasive Surgical Guidance: 3D printed Patient Specific Guides (PSGs) have been developed for TSA; however, these are designed for traditional, highly invasive approaches providing unobstructed access to each articular surface separately. As the proposed approach does not offer this access, a novel PSG with two opposing contoured surfaces has been developed that can be inserted between the humeral and scapular articular surfaces and use the rotator cuff's passive tension to self-locate (Fig.2). During computer-aided pre-operative planning/PSG design, the two bones are placed into an optimized relative pose and the PSG is constructed between and around them. This ensures that when the physical PSG is inserted intra-operatively, the bones are locked into the preoperatively planned pose.

New Instrumentation Paradigm: With the constraints of this minimally invasive approach, a new paradigm for bone preparation/instrumentation was required which did not rely on en-face access. This new paradigm involves the ability to simultaneously create glenoid and humeral guide axes – the latter of which can guide humeral bone preparation and be a working channel for tools – by driving a short k-wire into the glenoid by passing through the humerus starting laterally (Fig.3). By preoperatively defining the pose produced by the inserted PSG as one that collinearly aligns the bones’ guide axes, the PSG and an attached c-arm drill guide facilitate this new lateral drilling technique. Subsequently, bone preparation is conducted using novel instruments (e.g. reamers and drills for creating holes radial to driver axis) powered using a trans-humeral driver and guided by the glenoid k-wire or humeral tunnel.


Orthopaedic Proceedings
Vol. 95-B, Issue SUPP_28 | Pages 90 - 90
1 Aug 2013
Hawke T Jakopec M Rodriguez y Baena F
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In computer assisted orthopaedic surgery, intraoperative registration is commonly performed by fitting features acquired from the exposed bone surface to a preoperative virtual model of the bone geometry. In cases where the acquired spatial measurements are unreliable or have been inappropriately chosen, the registration result can degenerate. Current performance indicators, such as the root mean squared (RMS) error and the spatial distribution of the registered feature errors may not be sufficient to warn the surgeon of such a case.

In this study, statistical analysis is applied to the registration outcomes of perturbed variants of a collected point set. In this way, it is possible to assess the ability of the original set to represent the underlying surface, taking into account the distribution of the points as well as errors introduced during the acquisition process. Confidence measures are calculated to predict the reliability of the original registration result and therefore the robustness of the point set itself.

For proof of concept, this method has been tested in simulation with a CT-generated tibia model. The algorithm was used to identify the 10 best performing of a population of 1000 randomly generated point sets. All registration outcomes produced by these point sets were found to be superior to those resulting from sets of the same size produced manually using an optimised point-acquisition protocol. Preliminary results suggest that this method, alongside the standard RMS and residual point error distribution, may be used to provide the surgeon with a reliable indication of registration outcome in the operating room.