The recruitment drive, investment and collaboration within Betsi Cadwaladr University Health Board (BCUHB) sites providing specialist lower limb arthroplasty and trauma service has evolved over last few years with aims to improve patient care and reduce reliance on tertiary referral centres. Through our service-evaluation project, we reviewed the results of treatment provided for periprosthetic femur fractures (PPFFs) presenting to BCUHB sites over last 4 years. We retrospectively reviewed consecutive PPFFs admitted at three BCUHB sites from January’20 to June’23 with mean follow-up of 20.8 ± 13.2 (8–49) months [n=161; Mean age: 82.2 ± 8.5 (59–101) years, Females:107]. Over the review period we noted a 23% increase in service demand for care of PPFFs. Majority were managed surgically [132/161] [38 revision arthroplasties; 94 ORIFs] at BCUHB sites and two patients were referred to tertiary centre. Average time to surgery was 3.5 days. 90% of the PPFFs were managed successfully with 10% (16/159) having orthopaedic complications needing further intervention. 6.3 (10/159) had medical complications and did not need orthopaedic re-intervention. In our series, 12-month re-operation rate was 6.1% (8/132) and 1-month, 3-month and 1-year mortality rate was 6.3%, 11.3% and 21.4% respectively. These results are comparable to the published results of PPFF management at tertiary centres. Potential cost savings compared to transfer to tertiary centre for PPFF management was £2.31 million. Thus, it is possible to successfully provide adequate care for PPFFs at DGHs and efforts should be made to appropriately equip and adequately staff DGHs, to provide service for local PPFF care.
Posterior column plating through the single anterior approach reduces the morbidity in acetabular fractures that require stabilization of both the columns. The aim of this study is to assess the effectiveness of posterior column plating through the anterior intrapelvic approach (AIP) in the management of acetabular fractures. We retrospectively reviewed the data from R G Kar Medical College, Kolkata, India, from June 2018 to April 2023. Overall, there were 34 acetabulum fractures involving both columns managed by medial buttress plating of posterior column. The posterior column of the acetabular fracture was fixed through the AIP approach with buttress plate on medial surface of posterior column. Mean follow-up was 25 months (13 to 58). Accuracy of reduction and effectiveness of this technique were measured by assessing the Merle d’Aubigné score and Matta’s radiological grading at one year and at latest follow-up.Aims
Methods
The Oxford Unicompartmental Knee Replacement's (OUKR's) fully-congruent design minimises polyethylene wear. Consequently, wear is a rare failure mechanism. Phase-3 OUKR linear wear at 5 years was higher than previous OUKR phases, but very low compared to fixed-bearing UKRs. This study aimed to measure OUKR bearing wear at 10 years and investigate factors that may affect wear. Bearing thickness for 39 OUKRs from a randomised study was calculated using radiostereometric analysis at regular intervals up to 10 years. Data for 39 and 29 OUKRs was available at 5 and 10 years, respectively. As creep occurs early, wear rate was calculated using linear regression between 6 months and 10 years. Relationships between wear and patient factors, fixation method, Oxford Knee Score (OKS), bearing position, and component position were analysed.Abstract
Introduction
Methodology
This presentation discusses the experience at our Centre with treating traumatic thoracolumbar fractures using percutaneous pedicle screw fixation and also looks at clinical and radiological outcomes as well as complications. This is a retrospective study reviewing all cases performed between Jan 2013 and June 2019Objectives
Design
Venous thromboembolism (VTE) is a serious complication after total hip and knee arthroplasty. There is still no consensus regarding the best mode of thromboprophylaxis after lower limb arthroplasty. The aim of this study was to ascertain the efficacy, safety profile and rate of adverse thromboembolic events of aspirin as extended out of hospital pharmacological anticoagulation for elective primary total hip and knee arthroplasty patients and whether these rates were comparable with published data for low molecular weight heparin (LMWH). Data was extracted from a prospective hospital acquired thromboembolism (HAT) database. The period of study was from 1st Jan 2013-31st Dec 2016 and a total of 6078 patients were treated with aspirin as extended thromboprophylaxis after primary total hip and knee arthroplasty. The primary outcome measure of deep vein thrombosis and pulmonary embolism within 90 days postoperatively was 1.11%. The secondary outcome rates of wound infection, bleeding complications, readmission rate and mortality were comparable to published results after LMWH use. The results of this study clearly show that Aspirin, as part of a multimodal thromboprophylactic regime, is an effective and safe regime in preventing VTE with respect to risk of DVT or PE when compared to LMWH. It is a cheaper alternative to LMWH and has associated potential cost savings.
Total hip arthroplasty (THA) in patients with congenital dysplasia of the hip (CDH) is complex and challenging. The Crowe and Hartofilakidis classification systems are the most commonly used. However, neither encompasses the whole spectrum of disease and deformity and therefore does not guide modern surgical options. We present a new classification system which aims to guide surgical strategy by focusing on the three main areas of disease and deformity: The aim of this study is to assess the reliability of this new adult CDH classification system in the setting of THA. A sample size calculation showed 28 evaluations were required to reach a power of 85% (based on a kappa value of 0.4). The anterior-posterior pelvis and lateral hip radiographs of 30 hips, in 26 patients were evaluated by three Consultant Orthopaedic Surgeons using the classification detailed in table 1. A second evaluation, with the case order randomised, was performed after a minimum period of 1month. Randolph's free multi-rater Kappa co-efficient was used to assess for inter and intra- observer reliability and 95% confidence intervals were calculated.Background
Study design and Methods
Uncemented porous coated acetabular components have gained more research emphasis in recent years compared to their cemented counterparts, largely owing to the natural biological fixation they offer. Nevertheless, sufficient peri-prosthetic bone ingrowth is essential for long-term fixation of such uncemented acetabular components. The phenomenon of bone ingrowth can be predicted based on mechanoregulatory principles of primary bone fracture healing. Literature review reveals that the surface texture of implant plays a major role in implant-bone fixation mechanism. A few The 3-D microscale model [Fig.1] of implant-bone interface was developed using CATIA® V5R20 software (DassaultSystèmes, France) and was modelled in ANSYS V15.0 FE software (Ansys Inc., PA, USA) using coupled linear elastic ten-noded tetrahedral finite elements. The model consists of cast-inbeaded mesh textured implant having finely meshed inter-bead spacing. Linear, elastic and isotropic material properties considering Young's modulus of 210 GPa and Poisson's ratio of 0.3 for stainless steel implant were employed in the model. Boundary of bone was assumed to be rich in Mesenchymal Stem Cells(MSC) with periodic boundary conditions at contralateral surfaces. The linear elastic material properties in the model were updated iteratively through a tissue differentiation algorithm that works on the principle of mechanotransduction driven by local mechanical stimuli, e.g. hydrostatic pressure and equivalent deviatoric strain.Introduction
Materials/Methods
Bone fracture toughness is an important parameter in resistance of bone to monotonic and fatigue failure. Earlier studies on bone fracture toughness were focused on either cortical or cancellous bone, separately [1, 2]. Reported fracture toughness values indicated that cortical bone is tougher to break as compared to cancellous bone. In order to understand complete fracture of a whole bone, the interface between cortical and cancellous bone (named as corticellous bone) might play a crucial role and is interesting topic of research. The goal of this study was to identify fracture toughness in terms of J integral and fracture mechanism of the corticellous bone. Corticellous bone samples (single edge notch bend specimen or SENB) were prepared from bovine proximal femur according to ASTM E399-90 standard (Fig.1). For corticellous bone, samples were prepared in such way that approximately half of the sample width consist of cortical bone and another half is cancellous bone. Precaution was taken while giving notch and pre-crack to corticellous bone that pre-crack should not enter from cortical to cancellous portion. All specimens were tested using a universal testing machine (Tinius Olsen, ± 100 N) under displacement rate of 100 µm/min until well beyond yield point. The fracture toughness parameter in terms of critical stress intensity (KIC) was calculated according to ASTM E399-90 as given by,
Where, P = applied load in kN, S = loading span in cm, B = specimen thickness in cm, W = specimen width in cm, a = total crack length, f(a/W) = geometric function. After the fracture test the J integral of each specimen was calculated using following equation. [ASTM E1820].
Where, Jel is J integral of the elastic deformation, Jpl is J integral of the plastic deformation, E′=E for plane stress condition and E′= E/(1−ν2) for plane strain condition (E is elastic modulus; ν is Poisson's ratio), bo = W−ao, height of the un-cracked ligament, and Apl is the area of the plastic deformation part in the load–displacement curve.Introduction
Material and Methods
In the young and highly active population of military patients, femoroacetabular impingement can be a source of serious disability as well as a threat to their career. This morbidity can be treated with hip arthroscopy with debridement of cam lesion, and excision or repair of a corresponding labral tear. We report on the long term outcomes (>1 year) of 26 military cases who underwent hip arthroscopy for femoroacetabular impingement, in a single surgeon's series. Twenty two patients (four bilateral cases) underwent hip arthroscopy as a day case procedure during the period February 2013 to October 2014. Non-Arthritic Hip Scores (NAHS) were obtained from patients pre-operatively, at two months, four months and at least one year post-operatively. There was a significant improvement in NAHS at two months (75.6)(p<0.05), four months (85.1)(p<0.001) and one year (84.8)(p<0.001), compared to pre-operative NAHS (65.8). There was no significant change in NAHS beyond four months. Only three out of the 22 patients were medically discharged secondary to persistent hip symptoms. Hip arthroscopy for femoroacetabular impingement is an effective, viable procedure for military patients. Mobility, pain and function is significantly improved after surgery. This improvement is sustained in the long term up to and beyond one year.
Our aim was to compare the biomechanical strength modified side-to-side repair with modified pulvertaft technique keeping overlap length, anchor points, type of suture, suture throw and amount of suture similar. In our study, we have used turkey tendons. Two investigators performed 34 repairs during one summer month. All mechanical testing was carried out using the tensile load testing machine. Variables measured were maximum load, load to first failure, modulus, load at break, mode of failure, site of failure, tensile strain, and tensile stress. The statistical comparison was carried by Levene's test and T test for means. The mean maximum load tolerated by modified side-to-side repair was 50.3N(S.D13.7) and that by modified pulvertaft 46.96N(S.D: 16.4), overall it was 48.29 N (S.D: 14.57). The tensile stress at maximum load for modified pulvertaft and modified side-to-side repair was 4.2MPa(S.D: 3.1) and 4.7 MPa (S.D: 3.8) respectively {Overall 4.3MPa(S.D: 3.5)}. The tensile stress at yield was 4.01 MPa (S.D: 3.1) and 5.5 MPa (S.D: 3.7) respectively for modified pulvertaft and modified side-to-side repair {overall 4.44 MPa (S.D: 3.45)}. The tensile strain at maximum load respectively for side-to-side and modified pulvertaft repair was 7.87%(S.D: 33.3) and 7.84%(S.D: 34.02) respectively. We found no statistical difference between 2 repairs in terms of strength, load to first failure, and maximum load to failure. The suture cut through was the commonest mode of failure. Our study uniquely compares two techniques under standard conditions, and contrary to existing evidence found no difference.
Dislocation is a major complication post total hip replacement (THR) and a common cause for revision. Jameson et al (2012) studied 35,000 cemented Exeter (Stryker) THRs demonstrating the risk of revision was significantly influenced by the acetabular component design. This led 3 surgeons in a single hospital group to make a mass move from using the hooded Exeter Low Profile (LP) cup to the better performing Contemporary Flanged (CF) component. The purpose of this study was to show whether this change was associated with a fall in dislocation rates. Locally held National Joint Registry data between 2010 and 2015 was used to ascertain implants used in all primary THRs by 3 experienced high volume surgeons. This was linked to local Hospital Episode Statistics to identify patients who had undergone closed or open reduction of a dislocated hip replacement in theatre.INTRODUCTION
PATIENTS/MATERIALS & METHODS
Long-term success of the cementless acetabular component has been depends on amount of bone ingrowth around porous coated surface of the implant, which is mainly depends on primary stability, i.e. amount of micromotion at the implant-bone interface. The accurate positioning of the uncemented acetabular component and amount of interference fit (press-fit) at the rim of the acetabulum are necessary to reduce the implant-bone micromotion and that can be enhancing the bone ingrowth around the uncemented acetabular component. However, the effect of implant orientations and amount of press-fit on implant-bone micromotion around uncemented acetabular component has been relatively under investigated. The aim of the study is to identify the effect of acetabular component orientation on implant-bone relative micromotion around cementless metallic acetabular component. Three-dimensional finite element (FE) model of the intact and implanted pelvises were developed using CT-scan data [1]. Five implanted pelvises model, having fixed antiversion angle (25°) and different acetabular inclination angle (30°, 35°, 40°, 45° and 50°), were generated in order to understand the effect of implant orientation on implant-bone micromotion around uncemented metallic acetabular component. The CoCrMo alloy was chosen for the implant material, having 54 mm outer diameter and 48 mm bearing diameter [1]. Heterogeneous cancellous bone material properties were assigned using CT-scan data and power law relationship [1], whereas, the cortical bone was assumed homogeneous and isotropic [1]. In the implanted pelvises models, 1 mm diametric press-fit was simulated between the rim of the implant and surrounding bone. Six nodded surface-to-surface contact elements with coefficient of friction of 0.5 were assigned at the remaining portion of the implant–bone interface [1]. Twenty-one muscle forces and hip-joint forces corresponds to peak hip-joint force of a normal walking cycle (13%) were used for the applied loading condition. Fixed constrained was prescribed at the sacroiliac joint and pubis-symphysis [1]. A submodelling technique was implemented, in order to get more accurate result around implant-bone interface [1].Introduction
Materials and Method
Total hip arthroplasty (THR) with non-cemented or hybrid fixation remains one of the most successful procedures performed today. The aim of this study was to assess the safety and efficacy of a hydroxyapatite (HA) coated, hemispherical cup. Between 2003 and 2007, 223 THAs (210 patients) with peripheral self-locking (PSL) cup and highly cross-linked polyethylene (Crossfire, Stryker, Mahwah, NJ) with minimum 5 years clinical and radiographic follow-up (5–9 years) were analyzed. The mean age was 62.5 years ± 10.8 (range, 32.7 – 86.3) at the time of surgery and the predominant preoperative diagnoses was osteoarthritis (97.8%). 72% were solid cups without screw augmentation and 28% were multi-hole with screw. Clinical analysis included Hospital for Special Surgery (HSS) hip scores at latest follow-up. Detail radiographic analysis was carried out on anteroposterior and false profile views for evidence of osseointegration in all Charnley's zones. Osseointegration was assessed based on presence of Stress Induced Reactive Cancellous Bone (SIRCaB) with trabecular bone hypertrophy 5–15mm extending from the cup, and absence of radiolucency or demarcation. EBRA software was used to assess cup positioning.Introduction
Material and Methods
Difficulties arise when counselling younger patients on the long-term sequelae of a minor knee chondral defect. This study assesses the natural history of patients with grade 2 Outerbridge chondral injuries of the medial femoral condyle at arthroscopy. We reviewed all arthroscopies performed by one surgeon over 12 years with Outerbridge grade 2 chondral defects. Patients aged 30 to 59 were included. Meniscal injuries found were treated with partial menisectomy. All patients had five-year follow up minimum. Primary outcome measure was further interventions of total or unicondylar arthroplasty or high tibial osteotomy. We analysed 3,344 arthroscopies. Average follow up was 10 years (Range 5–17 years). A total of 357 patients met inclusion criteria of which 86 had isolated medial femoral condyle disease. Average age was 50 at the time of arthroscopy. Average BMI at surgery was 31.7 and average chondral defect area was 450 mm2. Isolated MFC chondral disease had a 10.5% intervention rate. Intervention occurred at a mean of 8.5 years post primary arthroscopy. In young patients Outerbridge II chondral injuries affecting ≥2 compartments have a high rate of further intervention within a decade. This information is crucial in counselling young patients on long-term sequelae of benign chondral lesions.
The MediShoe (Promedics Orthopaedics Ltd, Glasgow) is a specific post-operative foot orthosis used by post-operative foot and ankle patients designed to protect fixations, wounds and maximise comfort. The use of rigid-soled shoes has been said to alter joint loading within the knee and with the popular use of the MediShoe at our centre in post operative foot and ankle surgery patients, it is important to ascertain whether this is also true. An analysis of the knee gait kinetics in healthy subjects wearing the MediShoe was carried out. Ten healthy subjects were investigated in a gait lab both during normal gait (control) and then with one shoe orthosis worn. Force plates and an optoelectronic motion capture system with retroreflective markers were used and placed on the subjects using a standardised referencing system. Three knee gait kinetic parameters were measured:- knee adduction moment; angle of action of the ground reaction force with respect to the ground in the coronal plane as well as the tibiofemoral angle. These were calculated with the Qualisys software package (Gothenburg, Sweden). A two-tailed paired t-test (95% CI) showed no significant difference between the control group and the shoe orthosis-fitted group for the knee adduction moment (p = 0.238) and insignificant changes with respect to the tibiofemoral angle (p = 0.4952) and the acting angle of the ground reaction force (p = 0.059). The MediShoe doesn't significantly alter knee gait kinetics in healthy patients. Further work, however is recommended before justifying its routine use.
Instability is reported to account for around 20% of early TKR revisions. The concept of restoring the “Envelope of Laxity” (EoL) mandates a balanced knee through a continuous arc of functional movement. We therefore hypothesised that a single radius (SR) design should confer this stability since it has been proposed that the SR promotes normal medial collateral ligament (MCL) function with isometric stability throughout the full arc of motion. Our aim was to characterise the EoL and stability offered by a SR cruciate retaining (CR)-TKR, which maintains a SR from 10–110° flexion. This was compared with that of the native knee throughout the arc of flexion in terms of anterior, varus/valgus and internal/ external laxity to assess whether a SR CR-TKR design can mimic normal knee joint kinematics and stability. Eight fresh frozen cadaveric lower limbs were physiologically loaded on a custom jig. The operating surgeon performed anterior drawer, varus/ valgus and internal/external rotation tests to determine ‘maximum’ displacements in 1) native knee and 2) single radius CR-TKR (Stryker Triathlon) at 0°, 30°, 60°, 90° and 110° flexion. Displacements were recorded using computer navigation. Significance was determined by linear modelling (p≤0.05). The key finding of this work was that the EoL offered by the SR CR-TKR was largely equivalent to that of the native knee from 0–110°. The EoL increased significantly with flexion angle for both native and replaced knees. Overall, after TKR anterior laxity was comparable with the native knee, whilst total varus-valgus and internal-external rotational laxities reduced by only 1°. However, separated varus and valgus laxities at 110° significantly increased after TKR as did anterior laxity at 30° flexion. In conclusion, the overall EoL offered by the SR CR-TKR is comparable to that of the native knee. In the absence of soft tissue deficiency, the implant appears to offer reliable and reproducible stability throughout the functional range of movement, with exception of anterior laxity at 30° and varus and valgus laxity when the knee approaches high flexion. These shortcomings should offer scope for future work.
The Lubinus SP2 femoral stem has a 10 year survivorship of 96%. Curiosity lies in that force-closed stem designs such as the Exeter appear to be more superior to that of the composite-beam like the Lubinus which performs best compared with all other stem types. Biomechanical comparisons of the stress distributions between native and implanted human femora with a cemented Lubinus stem simulating an everyday clinical activity were made. Rosette strain gauges were placed onto fourth generation composite cortical sawbone femora and placed within a hemipelvis rig simulating the dynamic position of the femur during single-legged stance. The femora were then implanted with the Lubinus and principal strain measurements calculated for both intact and implanted femora. These values correlate directly with stress. Statistical calculations were carried out including a two-way ANOVA and Student's unpaired t-test so as to ascertain any relationship between the intact and implanted femora strain values. There were significant decreases (p<0.05) in principal tensile and principal compressive strains upon implantation in the proximal and distal areas of the femur. However, there were insignificant changes (p>0.05) in principal tensile strains at the mid-stem and insignificant changes (p>0.05) in principal compressive strains at both the mid-stem and distal areas. This is the largest biomechanical study to be carried out on this stem and the first in the English language. Changes in principal stresses were not significant in all aspects of the femur upon implantation which appears to give some biomechanical explanation to its clinical success.
Despite the generally inferior clinical performance of acetabular prostheses as compared to the femoral implants, the causes of acetabular component loosening and the extent to which mechanical factors play a role in the failure mechanism are not clearly understood yet. The study was aimed at investigating the load transfer and bone remodelling around the uncemented acetabular prosthesis. The 3-D FE model of a natural right hemi-pelvis was developed using CT-scan data. The same bone was implanted with two uncemented hemispherical acetabular components, one metallic (CoCrMo alloy) and the other ceramic (Biolox delta), with 54 mm outer diameter and 48 mm bearing diameter. The FE models of the implanted pelvis (containing ∼116000 quadratic tetrahedrals) were generated using a submodelling approach, which were based on an overall full model of implanted pelvis (containing ∼217600 quadratic tetrahedrals) acted upon by hip joint force and twenty one muscle forces. The apparent density (ρ in g cm−3) of each cancellous bone element was calculated using linear calibration of CT numbers of bone, from which the Young's modulus (E in MPa) was determined using the relationship, E = 2017.3 ρ2.46 [1]. Implant-bone interface conditions, fully bonded and debonded with friction coefficient μ = 0.5, were simulated using contact elements. Applied loading conditions consist of two load cases during a gait cycle, corresponding to 13% and 52% of the walking cycle. Fixed constraints were prescribed at the pubis and at the sacroiliac joint. The bone remodelling algorithm was based on strain energy based site-specific formulation [2]. The FE analysis, in combination with the bone remodelling simulation, was performed using ANSYS FE software. The predicted changes in peri-prosthetic bone density were similar for the metallic and the ceramic implant. For debonded implant-bone interface, stress shielding led to ∼20% reductions in bone density at supero-anterior, infero-anterior and posterior part of the acetabulum (Fig. 1). However, bone apposition was observed at the supero-posterior part of the acetabulum, where implantation led to ∼60% increase in bone density (Fig. 1). The effect of bone resorption was higher for the fully bonded implant-bone interface, wherein bone density reductions of 20–50% were observed in the cancellous bone underlying the implant (Fig. 1), which is indicative of implant loosening over time. However, implantation led to an increase in bone density around the acetabular rim for both the interface conditions (Fig. 1). These results are well corroborated by the earlier studies [3, 4]. Implantation with a ceramic component resulted in 2–7% increase in bone density at supero-posterior part of the acetabulum as compared to the metallic component, for the debonded interface condition. Considering better wear resistant properties and absence of metal ion release, results of this study suggest that the ceramic component might be a viable alternative to the metallic prosthesis.
Uncemented total hip replacement is on the rise worldwide. Latest studies from various European and other developed country joint registers are clearly showing that it is taking preference over the cemented joint replacements. These figures were discussed most recently at the London hip meeting. Our study is related to one single make of implant the Exceed hip (Biomet) at two hospitals in Northamptonshire, Kettering UK. Our series includes 256 cases of Exceed uncemented total hip replacement done in 236 patients with a minimum follow up of 6 months and maximum of 5 years. The study included 126 female and 110 male patients. Out of this number 121 cases were done at Kettering General Hospital and 135 cases were performed at Woodlands Hospital private limited in Kettering. The cases were performed by 2 senior consultants and one junior consultant. The total number of cases was 317 but 73 cases were lost to follow up and 2 patients had expired at the time of the study. In all cases pre operative and post operative Harris hip scores were measured. Patients were asked to fill up the scores in retrospect through post. The range of motion parameter and range of motion scale were measured and added from clinical notes. The average age of patients in our study was 71.2 years with the oldest patient being 90 years old and the youngest being 34 years old. Most common cause for replacement was primary osteoarthritis in 202 cases. In 52 cases it was done for secondary osteoarthritis due to rheumatoid arthritis or post traumatic osteoarthritis following dislocation and acetabular fractures. In 2 cases it was done for fracture neck of femur. All the cases were done through posterior approach. One senior surgeon used bone grafts in the acetabular floor harvested from the femoral head at time of surgery in all of his cases. The ABT ringloc shell, polyethylene liner was used in all cases. The average pre operative Harris hip score was 43.15 and average post operative Harris hip score was 78.32. In 4 cases peri prosthetic fractures occurred per operatively and needed fixation. In 3 cases dislocation occurred but only one case needed revision due to recurrent dislocation.INTRODUCTION
MATERIAL & METHODS
Creating cement keyholes (i.e. drilling simple holes in cancellous bone to allow cement filling) is a practice used in multiple scenarios in orthopaedic surgery to ensure improved fixation between the bone-cement interface and as such between bone and prosthesis. It is most commonly used in hip arthroplasty to secure fixation of the cup to the acetabulum by drilling keyholes in acetabulum. However very little research has been conducted into what the dimensions of such cement keyholes should be. The following laboratory based research was performed to provide insight into the optimum dimensions of cement keyholes. The investigator designed a novel arrangement to enable testing of keyholes. Beechwood block models were then made to this design testing keyholes of varying diameters and depths. These were cemented with acrylic bone cement and then loaded to failure. A finite system analysis was also performed. Results show that stresses are concentrated at the base of the keyhole. As such increasing diameter of keyhole infers greater strength, but there is no relationship between depth and strength. This has been further confirmed with finite element analysis. We suggest the width of cement keyholes bears more importance than the depth and propose drilling wide but shallow keyholes.
