Abstract

High tibial osteotomy (HTO) is a joint preserving alternative to knee replacement for medial tibiofemoral osteoarthritis in younger, more active patients. The procedure is technically challenging and limited also by ‘one size fits all’ plates which can result in patient discomfort necessitating plate removal.

This clinical trial evaluated A novel custom-made HTO system – TOKA (3D Metal Printing LTD, Bath, UK) for accuracy of osteotomy correction and improvements in clinical outcome scores.

The investigation was a single-arm single-centre prospective clinical trial (IRCCS Istituto Ortopedico Rizzoli; ClinicalTrials.gov NCT04574570), with recruitment of 25 patients (19M/6F; average age: 54.4 years; average BMI: 26.8), all of whom received the TOKA HTO 3D planning and surgery. All patients were predominantly diagnosed with isolated medial knee osteoarthritis and with a varus deformity under 20°. Patients were CT scanned pre- and post-operatively for 3D virtual planning and correctional assessment. All surgeries were performed by the lead clinical investigator – a consultant knee surgeon with a specialist interest in and clinical experience of HTO.

On average, Knee Society Scores (KSS) improved significantly (p<0.001) by 27.6, 31.2 and 37.2 percentage points respectively by 3-, 6- and 12-months post-surgery respectively. Other measures assessed during the study (KOOS, EQ5D) produced similar increases.

Our early experience using custom implants is extremely promising. We believe the reduced profile of the plate, as well as the reduced invasiveness and ease of surgery contributed to faster patient recovery, and improved outcome scores compared to conventional techniques. These clinical outcome results compare very favourably other case-series with published KOOS scores using different devices.

Conventional proximal tibial osteotomy is a widely successful joint-preserving treatment for osteoarthritis; however, conventional procedures do not adequately control the posterior tibial slope (PTS). Alterations to PTS can affect knee instability, ligament tensioning, knee kinematics, muscle and joint contact forces as well as range of motion.

This study primarily aimed to provide a comprehensive investigation of the variables influencing PTS during high tibial osteotomy using a 3D surgical simulation approach. Secondly, it aimed to provide a simple means of implementing the findings in future 3D pre-operative planning and /or clinically.

The influence of two key variables: the gap opening angle and the hinge axis orientation on PTS was investigated using three independent approaches: (1) 3D computational simulation using CAD software to perform virtual osteotomy surgery and simulate the post-operative outcome. (2) Derivation of a closed-form mathematical solution using a generalised vector rotation approach (3) Clinical assessment of synthetically generated x-rays of osteoarthritis patients (n=28; REC reference: 17/HRA/0033, RD&E NHS, UK) for comparison against the theoretical/computational approaches.

The results from the computational and analytical assessments agreed precisely. For three different opening angles (6°, 9° and 12°) and 7 different hinge axis orientations (from −30° to 30°), the results obtained were identical. A simple analytical solution for the change in PTS, ΔP_s, based on the hinge axis angle, α, and the osteotomy opening angle, θ, was derived:

ΔP_s=sin^-1(sin α sin θ)

The clinical assessment demonstrated that the absolute values of PTS, and changes resulting from various osteotomies, matched the results from the two relative prediction methods.

This study has demonstrated that PTS is impacted by the hinge axis angle and the extent of the osteotomy opening angle and provided computational evidence and analytical formula for general use.

High tibial osteotomy (HTO) is an effective surgical treatment for isolated medial compartment knee osteoarthritis; however, widespread adoption is limited due to difficulty in achieving the planned correction, and patient dissatisfaction due to soft tissue irritation. A new HTO system – Tailored Osteotomy Knee Alignment (TOKA®, 3D Metal Printing Ltd, Bath, UK) could potentially address these barriers having a custom titanium plate and titanium surgical guides featuring a unique mechanism for precise osteotomy opening as well as saw cutting and drilling guides. The aim of this study was to assess the accuracy of this novel HTO system using cadaveric specimens; a preclinical testing stage ahead of first-in-human surgery according to the ‘IDEAL-D’ framework for device innovation.

Local ethics committee approval was obtained. The novel opening wedge HTO procedure was performed on eight cadaver leg specimens. Whole lower limb CT scans pre- and post-operatively provided geometrical assessment quantifying the discrepancy between pre-planned and post-operative measurements for key variables: the gap opening angle and the patient specific surgical instrumentation positioning and rotation - assessed using the implanted plate.

The average discrepancy between the pre-operative plan and the post-operative osteotomy correction angle was: 0.0 ± 0.2°. The R2 value for the regression correlation was 0.95.

The average error in implant positioning was −0.4 ± 4.3 mm, −2.6 ± 3.4 mm and 3.1 ± 1.7° vertically, horizontally, and rotationally respectively.

This novel HTO surgery has greater accuracy and smaller variability in correction angle achieved compared to that reported for conventional or other patient specific methods with published data available. This system could potentially improve the accuracy and reliability of osteotomy correction angles achieved surgically.

Abstract

Abstract

The screw fastening torque applied during bone fracture fixation has a decisive influence on subsequent bone healing. Insufficient screw tightness can result in device/construct instability; conversely, excessive torques risk damaging the bone causing premature fixation failure. This effect is even more prominent in osteoporotic bone, a condition associated annually with almost 9 million fractures worldwide. During fracture fixation, screw tightening torque is applied using subjective feel. This approach may not be optimal for patient”s recovery, increasing risk of fixation failure, particularly in osteoporotic bone, and potentially require revision surgical interventions.

Besides bone density, various factors influence the performance of screw fixation. These factors include bone geometry, cortical thickness and time-dependant relaxation behaviour of the bone. If the influence of screw fastening torque on the bone and relationships between these factors was better understood, the surgical technique could be optimised to reduce the risk of complications.

Within this study, we developed an axisymmetric finite element (FE) model of bone screw tightening incorporating viscoelastic behaviour of the cortical bone such as creep and stress relaxation. The model anticipated time-dependent behaviour of the bone for different bone thickness and density after a typical bone fixation screw had been inserted. The idealised model has been developed based on CT scans of bones with varying densities and inserted screws. The model was validated through a series of experiments involving bovine tibiae (4–5 months) to evaluate the evolution of surface strains with time (Ncorr v1.2). Stress distribution was assessed in photoelastic experiments using acrylic analogues. Relaxation tests have been performed in aqueous environment for up to 48 hours to ensure the relaxation would be complete. The creep behaviour (maximum principal strain) was compared against computational predictions. Our early simulations predicted relaxation strains on the surface of the bone to be 1.1% within 24 hours comparing favourably to 1.3% measured experimentally. Stress distribution patterns were in agreement with photoelastic results.

Using experimentally derived viscoelastic properties, the model has the potential to predict creep and stress relaxation patterns after screw insertion with different fastening torques for bones with varying density and geometry. We aim to develop this into a planning tool providing guidance to surgeons for optimal tightening when using screw fixation, particularly in reduced quality bone.

Objectives

Secondary fracture healing is strongly influenced by the stiffness of the bone-fixator system. Biomechanical tests are extensively used to investigate stiffness and strength of fixation devices. The stiffness values reported in the literature for locked plating, however, vary by three orders of magnitude. The aim of this study was to examine the influence that the method of restraint and load application has on the stiffness produced, the strain distribution within the bone, and the stresses in the implant for locking plate constructs.

Background

The Nottingham Hip Fracture Score (NHFS) is a risk stratifying score that estimates the 30-day and 12-month mortality rates of hip fracture patients. To date, it has only been validated in few centres in the UK. Our study aims to see how our mortality rates compare with those predicted by the NHFS.

Background

A large proportion of the expense incurred due to hip fractures arises due to secondary factors such as duration of hospital stay and additional theatre time due to surgical complications. Studies have shown that the use of intramedullary (IM) nail fixation presents a statistically higher risk of re-fracture than plating, which has been attributed to the stress riser at the end of the nail. It is not clear, however, if this situation also applies to unstable fractures, for which plating has a higher fixation failure rate. Moreover, biomechanical studies to date have not considered newer designs of IM nails which have been specifically designed to better distribute weight-bearing loads. This aim of this experimental study was to evaluate the re-fracture risk produced by a newer type of nailing system compared to an equivalent plate.

Background

Numerical modelling using Finite Element (FE) Analysis has become ubiquitous in orthopaedic biomechanics, with both commercial and freely available packages widely used. Three FE packages in particular have gained popularity: Abaqus (Simulia); Ansys (ANSYS, Inc.) and FEBio (University of Utah). Although FEBio is now well established, its developers advise that comparisons should be made against more extensively tested software before trusting its results for specific problems. The aim of the study to conduct a comparison of mesh convergence and to provide validated open-source models of the femur for use all three FE packages.

Femoral head collapse is a possible complication after surgical treatment of femoral neck fractures. The purpose of this study was to examine whether implantation of a Sliding Hip Screw (SHS) or an X-Bolt could increase the risk of femoral head collapse. Similar to traditional hip screws, the X-Bolt is implanted through the femoral neck; however, it uses an expanding cross-shape to improve rotational stability. The risk of collapse was investigated alongside patient factors, such as osteonecrosis.

This numerical study assessed the risk of femoral head collapse using linear eigenvalue buckling (an established method [1]), and also from the maximum von Mises stress within the cortical bone. The femoral head was loaded using the pressures reported by Yoshida et al. for a patient sitting down (reported to put the femoral head at greatest risk of collapse [2]), with a peak pressure of 9.4 MPa and an average pressure of 1.59 MPa. The femur was fixed in all degrees of freedom at a plane through the femoral neck. The X-Bolt and SHS were implanted in accordance with the operative techniques. The femoral head and implants were meshed with quadratic tetrahedral elements, and cortical bone was meshed with triangular thin shell elements. A converged mesh seeding density of 1.2 mm was used. All models were create and solved using ABAQUS finite element software (version 6.12, Simulia, Dassault Systèmes, France). The influence of implant type and presence was examined alongside a variety of patient factors:

Osteonecrosis, modelled as a cone of bone of varying angle, and varying modulus values

Twenty-two finite element models were run for each implant condition (intact; implanted with the X-Bolt; implanted with a SHS), resulting in a total of 66 models. The finite element models were validated using experimental tests performed on five 4^th generation composite Sawbones femurs (Malmö, Sweden), and verified against previously published results [1].

No significant difference was found between the X-Bolt and the SHS, for either critical buckling pressure (p=0.964), or the maximum von Mises stress (p=0.274), indicating no difference in the risk of femoral head collapse. The maximum von Mises stress (and therefore the risk of collapse) within the cortical bone was significantly higher for the intact femoral head compared to both implants (X-Bolt: p=0.048, SHS: p=0.002). Of the factors examined, necrosis of the femoral head caused the greatest increase in risk.

The study by Volokh et al. [1] concluded that deterioration of the cancellous bone underneath the cortical shell can greatly increase the risk of femoral head collapse, and the results of the present study support this finding. Interestingly the presence of either an X-Bolt or SHS implant appeared to reduce the risk of femoral head collapse.

Introduction

The majority of primary total hip arthroplasty (THA) procedures performed throughout the world use modular junctions, such as the trunnion-head interface; however, the failure of these press-fit junctions is currently a key issue that may be exacerbated by the use of large diameter heads. Several factors are known to influence the strength of the initial connection, however, the influence of different head sizes has not previously been investigated. The aim of the study was to establish whether the choice of head size influences the initial strength of the trunnion-head connection.

Finite element modelling is being extensively used to evaluate the biomechanical behaviour of fractured bone treated with fixation devices. Appropriate modelling of the bone-implant interface is key to quality biomechanical prediction.

The present study considers this interface modelling in the context of locking plates. A majority of previous studies assume the interface to be represented by a tied constraint or a fully bonded interface. Many other studies incorporate a frictional interface but ignore screw threads. This study compares the various interface modelling strategies. An interface with screw threads explicitly included is also considered.

The study finds that interface modelling has significant impact on both the global and local behaviour. Globally, the load-deflection behaviour shows considerable difference depending on the interface model. Locally, the stress-strain environment within the bone close to the screws is significantly altered.

The results show that the widely used tie constraint can overestimate stiffness of a construct which must be correctly predicted to avoid non-union or periprosthetic re-fracture, especially in osteoporotic bone. In addition, the predictions of screw loosening, bone damage and stress shielding are very different when screw threads are included in the model.

Humerus non-unions are difficult to treat, especially those with infected non-unions, bone loss, deformity, previous multiple surgeries and/or broken hardware. This paper presents our experience with the use of the Ilizarov frame with humerus non- unions.

Eight consecutive humerus non-unions were treated using the Ilizarov frame. Only loose or infected hardware was removed. The Ilizarov frame was applied using safe zones principles of Ilizarov, Catagni and Paley.

Aspetic non-unions were treated with deformity correction, sequential compression and distraction, bone grafting and intramedullary stabilisation for diaphyseal nonunions. Infected diaphyseal non-unions were treated intra-medullary reaming with or without excision of infected necrotic bone segment, followed by insertion of antibiotic cement rod and compression.

Elbow spanning frames were avoided for supracondylar non-unions. Fine wire fixation of the distal fragment was preferred instead. Free elbow movement was allowed.

There were two infected (diaphyseal) and six aseptic non-unions (four diaphyseal and two supracondylar) treated with this technique. Broken hardware was left in-situ in five cases.

The average time from the index injury was 14 months, with each case having had an average of 3.2 procedures, prior to the application of the Ilizarov frame.

Union was obtained in all cases. The average humerus shortening was 1.5 cm. There was no residual angular or rotational deformity. Infection was eliminated in both the infected non-unions.

Primary bone grafting was used in all aseptic nonunions. Additional bone grafting was needed as a secondary procedure in four cases prior to frame removal. T he average time spent in the frame was 4.5 months. The Ilizarov method is a useful option for the management of complex humerus non-unions. Patients learn to tolerate the fixator and can achieve functional shoulder and elbow range with the fixator.

Podiatrists have an important role in providing care in a Foot and Ankle clinic. Most Foot and Ankle Surgeons welcome the assistance they can provide – in a supervised role. Most Trusts should have one Foot and Ankle Surgeon but there are a limited number of trained specialists. Some Trusts have been appointing ‘Consultant Podiatric Surgeons’ – perhaps as a way of addressing this shortfall.

There are potentially a number of concerns amongst Foot and Ankle Surgeons: the public perception of title ‘consultant’; a Non supervised role; Potential to be used as a more cost effective option

We therefore undertook a Questionnaire assessment of patients attending a Foot and Ankle Clinic. Over a six week period 148 patients attended the specialist clinic. Of those 76% responded. 64% were females. The average age range was 45-64. Most patients assumed the Consultant in charge of their care was a qualified medical practitioner (93%) and regulated by the GMC (92%) and who had completed a recognised higher surgical training scheme (93%). Irrespective of suitable experience 2 out of 3 patients stated they would object if the Consultant in charge of their care did not meet the above criteria.

If the patient required surgery 80% stated they would object if the supervising Consultant was not a medically qualified doctor (this was more important in female patients) Interestingly 78% stated they would refuse surgery unless they were under the care of a medically qualified doctor. Very few patients understood the title Consultant Podiatric Surgeon (with those responding assuming they were medical doctors)

This potentially has significant implications in those Trusts employing Consultant Podiatric Surgeons as opposed to Foot and Ankle (Orthopaedic) Surgeons. Unless this differential is clearly explained to the patients there is an issue with informed consent and the potential for litigation.

Introduction: Lesser metatarsophalangeal instability is a common cause of forefoot pain. Previous studies were small and there is little data comparing surgical with non-surgical treatment.

Patients and Methods: Metatarsophalangeal instability was diagnosed and staged with the draw test. We recorded the clinical presentation, involved toes, severity of instability, presence of toe deformity and management. Patients were followed-up in clinic or by telephone interview with visual analogue pain and satisfaction scores and AOFAS lesser metatarsophalangeal scores. Outcomes were assessed by an independent observer.

Results: We studied 154 patients: 127 (82%) female and 27 (18%) male. The median age was 56 years (range 33–85). One foot was affected in 107 patients (69%) and both feet in 47 (31%). The second toe only was affected in 99 patients (64%) and multiple toes in 52 (34%). Seventy-three patients (47%) had a complaint of generalised forefoot pain. Sixty-eight (44%) had pain and deformity localised to the second toe. Thirteen patients (8%) had toe deformity with significant MTPJ instability. 150 toes (52%) had grade 1 instability, 108 (37%) grade 2 instability and 21 (7%) grade 3 instability. Twelve toes (4%) presented dislocated with a history of instability. Ninety-nine patients (64%) were treated conservatively, using functional taping, shoe modifications, insoles and injections. Fifty-five patients (36%) had surgery, including lesser toe straightening, flexor-extensor transfer, plantar plate repair, Weil and Stainsby procedures. 79% of patients were reviewed at a mean of 65 months (range 14 to 138). Mean pain score was 31mm ± 23.7mm for the conservative group and 23mm ± 24.1mm in the surgical group. Mean AOFAS score was 69 ± 16.3 for the conservative group and 67 ± 17.8 in the surgical group. 39 (52%) conservatively treated patients were either satisfied or very satisfied compared to 31 (66%) surgically treated patients. No differences were statistically significant.

Anterior cruciate ligament reconstruction has been traditionally performed as an inpatient due to post-operative analgesic requirements.

Increased patient demands and pressures of bed shortages have led to the development of day case surgery.

Day case anterior cruciate ligament (ACL) reconstruction surgery using an analgesic pump was assessed.

24 consecutive ACL reconstructions using arthroscopic hamstring technique were performed as day case procedures.

All received a standard anaesthetic of propofol, fentanyl, tenoxicam, and morphine. And an intra-articular administration of 10mls 0. 75% Ropivicaine Hydrochloride at the end of surgery.

0. 2% Ropivicaine at a rate of 2mls/hr was infused over 48hrs using a compression spring infusion pump (Pain Control Infusion Pump – Sgarlato Labs) via an intraarticular catheter.

Post operative pain was assessed by a Visual Analogue Score (VAS) recorded by the patient onto an unmarked 1 Ocin line (0 – no pain ; 1 0 – maximum pain)

For the 48hrs the pump was infusing the average VAS was 2. 7 with minimal additional analgesia required.

Following pump removal by a District Nurse, the average VAS score was 1. 9 with similar analgesia requirements

All patients were satisfied with their care; none had problems related to the use of or removal of the pump; none required re-admission or review from their GP; or suffered post-operative complications.

The cost for day case surgery was 260 (including theatre time; pump and drug costs; District Nurse costs) compared to 1072 for an average in-patient stay of 4 days (both exclude ACL specific implants, surgeon and anaesthetist costs).

The intra-articular infusion of local anaesthetic has been shown to be well received by patients with no additional risks.

It is an effective and cost-effective means of providing post-operative analgesia allowing day case ACL Reconstruction surgery to be performed.

This study has demonstrated that there are no requirements for additional resources from primary care.

The aim of this trial was to assess the clinical examination findings commonly used for the ACL deficient knee.

For reliability testing and criterion validation 102 patients with ACL injuries were assessed by a single observer, 35 by a second observer and 47 again by the initial observer. For construct and criterion validation 30 patients were assessed pre-operatively and a mean of 1.7 years after ACL reconstruction. The Lysholm 11, Tegner and Cincinnati outcome measures were assessed along with instrumented knee laxity (Stryker test), the one hop test (OHT) and graded tests (including anterior draw, Lachman test, quality of end point, and pivot shift test).

The outcome measures were found to be reliable except the Cincinnati system. All examination findings were of unsatisfactory reliability, with the exception of the OHT and the Stryker test. Construct validation revealed a significant improvement in all outcome measure scores and examination findings following ACL reconstruction. Criterion validation revealed that of the examination findings only the OHT had a satisfactory correlation with the symptom of giving way and the Lysholm/Tegner measures. Comparison of the difference between the desired and actual Tegner activity levels with the examination findings revealed an improvement in all levels of correlation.

With the exception of the OHT, the clinical examination findings used for the ACL deficient knee are unreliable and correlate poorly with the functional outcome of the patient. They may, however, have some benefit in assessment of deficiency of the anatomical structures and the findings should be presented individually, rather than forming part of the functional assessment of the patient.