Aims. Surgical treatment of young femoral neck fractures often requires an open approach to achieve an anatomical reduction. The application of a calcar plate has recently been described to aid in femoral neck fracture reduction and to augment fixation. However, application of a plate may potentially compromise the regional vascularity of the femoral head and neck. The purpose of this study was to investigate the effect of calcar femoral neck plating on the vascularity of the femoral head and neck. Methods. A Hueter approach and capsulotomy were performed bilaterally in six cadaveric hips. In the experimental group, a one-third tubular plate was secured to the inferomedial femoral neck at 6:00 on the clockface. The contralateral hip served as a control with surgical approach and capsulotomy without fixation. Pre- and post-contrast MRI was then performed to quantify signal intensity in the femoral head and neck. Qualitative assessment of the terminal arterial branches to the femoral head, specifically the inferior retinacular artery (IRA), was also performed. Results. Quantitative MRI revealed a mean reduction of 1.8% (SD 3.1%) of arterial contribution in the femoral head and a mean reduction of 7.1% (SD 10.6%) in the femoral neck in the plating group compared to non-plated controls. Based on femoral head quadrant analysis, the largest mean decrease in arterial contribution was in the inferomedial quadrant (4.0%, SD 6.6%). No significant differences were found between control and experimental hips for any femoral neck or femoral head regions. The inferior retinaculum of Weitbrecht (containing the IRA) was directly visualized in six of 12 specimens. Qualitative MRI assessment confirmed IRA integrity in all specimens. Conclusion. Calcar femoral neck plating at the 6:00 position on the clockface resulted in minimal decrease in femoral head and neck vascularity, and therefore it may be considered as an adjunct to laterally-based fixation for reduction and fixation of femoral neck fractures, especially in younger patients. Cite this article: Bone Jt Open 2021;2(8):611–617

Aims. The aim of this study was to explore why some calcar screws are malpositioned when a proximal humeral fracture is treated by internal fixation with a locking plate, and to identify risk factors for this phenomenon. Some suggestions can be made of ways to avoid this error. Methods. We retrospectively identified all proximal humeral fractures treated in our institution between October 2016 and October 2018 using the hospital information system. The patients’ medical and radiological data were collected, and we divided potential risk factors into two groups: preoperative factors and intraoperative factors. Preoperative factors included age, sex, height, weight, body mass index, proximal humeral bone mineral density, type of fracture, the condition of the medial hinge, and medial metaphyseal head extension. Intraoperative factors included the grade of surgeon, neck-shaft angle after reduction, humeral head height, restoration of medial support, and quality of reduction. Adjusted binary logistic regression and multivariate logistic regression models were used to identify pre- and intraoperative risk factors. Area under the curve (AUC) analysis was used to evaluate the discriminative ability of the multivariable model. Results. Data from 203 patients (63 males and 140 females) with a mean age of 62 years (22 to 89) were analyzed. In 49 fractures, the calcar screw was considered to be malpositioned; in 154 it was in the optimal position. The rate of malpositioning was therefore 24% (49/203). No preoperative risk factor was found for malpositioning of the calcar screws. Only the neck-shaft angle was found to be related to the risk of screw malpositioning in a multivariate model (with an AUC of 0.72). For the fractures in which the neck-shaft angle was reduced to between 130° and 150°, 91% (133/46) of calcar screws were in the optimal position. Conclusion. The neck-shaft angle is the key factor for the appropriate positioning of calcar screws when treating a proximal humeral fracture with a locking plate. We recommend reducing the angle to between 130° and 150°. Cite this article: Bone Joint J 2020;102-B(12):1629–1635

Aims. This study aimed to determine whether lateral femoral wall thickness (LWT) < 20.5 mm was associated with increased revision risk of intertrochanteric fracture (ITF) of the hip following sliding hip screw (SHS) fixation when the medial calcar was intact. Additionally, the study assessed the association between LWT and patient mortality. Methods. This retrospective study included ITF patients aged 50 years and over treated with SHS fixation between 2019 and 2021 at a major trauma centre. Demographic information, fracture type, delirium status, American Society of Anesthesiologists grade, and length of stay were collected. LWT and tip apex distance were measured. Revision surgery and mortality were recorded at a mean follow-up of 19.5 months (1.6 to 48). Cox regression was performed to evaluate independent risk factors associated with revision surgery and mortality. Results. The cohort consisted of 890 patients with a mean age of 82 years (SD 10.2). Mean LWT was 27.0 mm (SD 8.6), and there were 213 patients (23.9%) with LWT < 20.5 mm. Overall, 20 patients (2.2%) underwent a revision surgery following SHS fixation. Adjusting for covariates, LWT < 20.5 mm was not independently associated with an increased revision or mortality risk. However, factors that were significantly more prevalent in LWT < 20.5 mm group, which included residence in care home (hazard ratio (HR) 1.84; p < 0.001) or hospital (HR 1.65; p = 0.005), and delirium (HR 1.32; p = 0.026), were independently associated with an increased mortality risk. The only independent factor associated with increased risk of revision was older age (HR 1.07; p = 0.030). Conclusion. LWT was not associated with risk of revision surgery in patients with an ITF fixed with a SHS when the calcar was intact, after adjusting for the independent effect of age. Although LWT < 20.5 mm was not an independent risk factor for mortality, patients with LWT < 20.5 mm were more likely to be from care home or hospital and have delirium on admission, which were associated with a higher mortality rate. Cite this article: Bone Jt Open 2024;5(2):123–131

Aims. The aim of this study was to estimate the 90-day risk of revision for periprosthetic femoral fracture associated with design features of cementless femoral stems, and to investigate the effect of a collar on this risk using a biomechanical in vitro model. Materials and Methods. A total of 337 647 primary total hip arthroplasties (THAs) from the United Kingdom National Joint Registry (NJR) were included in a multivariable survival and regression analysis to identify the adjusted hazard of revision for periprosthetic fracture following primary THA using a cementless stem. The effect of a collar in cementless THA on this risk was evaluated in an in vitro model using paired fresh frozen cadaveric femora. Results. The prevalence of early revision for periprosthetic fracture was 0.34% (1180/337 647) and 44.0% (520/1180) occurred within 90 days of surgery. Implant risk factors included: collarless stem, non-grit-blasted finish, and triple-tapered design. In the in vitro model, a medial calcar collar consistently improved the stability and resistance to fracture. Conclusion. Analysis of features of stem design in registry data is a useful method of identifying implant characteristics that affect the risk of early periprosthetic fracture around a cementless femoral stem. A collar on the calcar reduced the risk of an early periprosthetic fracture and this was confirmed by biomechanical testing. This approach may be useful in the analysis of other uncommon modes of failure after THA. Cite this article: Bone Joint J 2019;101-B:779–786

Aims. In recent years, the use of a collared cementless femoral prosthesis has risen in popularity. The design intention of collared components is to transfer some load to the resected femoral calcar and prevent implant subsidence within the cancellous bone of the metaphysis. Conversely, the load transfer for a cemented femoral prosthesis depends on the cement-component and cement-bone interface interaction. The aim of our study was to compare the three most commonly used collared cementless components and the three most commonly used tapered polished cemented components in patients aged ≥ 75 years who have undergone a primary total hip arthroplasty (THA) for osteoarthritis (OA). Methods. Data from the Australian Orthopaedic Association National Joint Replacement Registry from 1 September 1999 to 31 December 2022 were analyzed. Collared cementless femoral components and cemented components were identified, and the three most commonly used components in each group were analyzed. We identified a total of 11,278 collared cementless components and 47,835 cemented components. Hazard ratios (HRs) from Cox proportional hazards models, adjusting for age and sex, were obtained to compare the revision rates between the groups. Results. From six months postoperatively onwards, patients aged ≥ 75 years undergoing primary THA with primary diagnosis of OA have a lower risk of all-cause revision with collared cementless components than with a polished tapered cemented component (HR 0.78 (95% confidence interval 0.64 to 0.96); p = 0.018). There is no difference in revision rate prior to six months. Conclusion. Patients aged ≥ 75 years with a primary diagnosis of OA have a significantly lower rate of revision with the most common collared cementless femoral component, compared with the most common polished tapered cemented components from six months postoperatively onwards. The lower revision rate is largely due to a reduction in revisions for fracture and infection. Cite this article: Bone Joint J 2024;106-B(3 Supple A):121–129

Abstract. Objective. To estimate the effect of calcar collar separation on the likelihood of calcar collar contact during in vitro periprosthetic fracture. Methods. Three groups of six composite femurs were implanted with a collared cementless femoral stem. Neck resection was increased between groups (group 1 = normal, group 2 = 3mm additional, group 3 = 6mm additional), to simulate failure to obtain calcar collar contact. Prior to each trial, the distances between anterior (ACC) and posterior (PCC) collar and the calcar were measured. Periprosthetic fractures of the femur were simulated using a previously published technique. High speed video recording identified when collar to calcar contact (CCC) occurred. The ACC and PCC were compared between trials where the CCC was and was not achieved. Regression estimated the odds of failing to achieve CCC for a given ACC or PCC. Results. CCC was achieved prior to fracture in all cases in group one, 50% in group two and 0% in group three. The median (range) ACC for those trials where CCC was achieved was 0.40 (0.00, 3.37) mm versus 6.15 (3.06 to 6.88) mm, where CCC was not achieved (p <0.01). The median (range) PCC for those trials where CCC was achieved was 0.85 (0.00 to 3.71) mm versus 5.97 (2.23 to 7.46) mm, where CCC was not achieved (p <0.01). Binomial logistic regression estimated risk of failure to obtain CCC increased 3.8 fold (95% confidence interval 1.6 to 30.2, p <0.05) for each millimetre of PCC. Conclusions. Increased separation between collar and calcar reduced the likelihood of calcar collar contact during a simulated periprosthetic fracture of the femur. Surgeons should aim to achieve a calcar-collar distance of less than 1mm following implantation to ensure calcar collar contact during periprosthetic femoral fracture and to reduce the risk of fracture. Declaration of Interest. (a) fully declare any financial or other potential conflict of interest

The calcar femorale is a vertical plate of bone lying deep to the lesser trochanter and is formed as a result of traction of the iliopsoas which separates the femoral cortex into two distinct layers, the calcar femorale and the medial femoral cortex. They fuse together proximally to form the medial femoral neck. A stem placed centrally will abut against the calcar femorale with little or no space for cement. Clearing of the calcar will offer space for a cement layer, which will support the stem proximally on the posterior aspect. We compared two consecutive groups of Charnley low-friction arthroplasties, with and without clearing of the calcar. In 330 patients who had an arthroplasty without clearing the calcar, there were ten revisions for aseptic loosening of the stem and six other stems were considered ‘definitely loose’, giving a rate of failure of 4.8%. In 111 patients in whom the calcar was cleared there was only one revision for aseptic loosening and no stems were classed as ‘definitely loose’, giving a rate of failure of 0.9%. Survivorship analysis has again shown the need for long-term follow-up; the differences became clear after ten years but because of the relatively small numbers, statistical analysis is not yet applicable. We now clear the calcar femorale routinely and advocate optimal access to the medullary canal and insertion of the stem in the area of the piriform fossa

Aims. Fixation of osteoporotic proximal humerus fractures remains challenging even with state-of-the-art locking plates. Despite the demonstrated biomechanical benefit of screw tip augmentation with bone cement, the clinical findings have remained unclear, potentially as the optimal augmentation combinations are unknown. The aim of this study was to systematically evaluate the biomechanical benefits of the augmentation options in a humeral locking plate using finite element analysis (FEA). Methods. A total of 64 cement augmentation configurations were analyzed using six screws of a locking plate to virtually fix unstable three-part fractures in 24 low-density proximal humerus models under three physiological loading cases (4,608 simulations). The biomechanical benefit of augmentation was evaluated through an established FEA methodology using the average peri-screw bone strain as a validated predictor of cyclic cut-out failure. Results. The biomechanical benefit was already significant with a single cemented screw and increased with the number of augmented screws, but the configuration was highly influential. The best two-screw (mean 23%, SD 3% reduction) and the worst four-screw (mean 22%, SD 5%) combinations performed similarly. The largest benefits were achieved with augmenting screws purchasing into the calcar and having posteriorly located tips. Local bone mineral density was not directly related to the improvement. Conclusion. The number and configuration of cemented screws strongly determined how augmentation can alleviate the predicted risk of cut-out failure. Screws purchasing in the calcar and posterior humeral head regions may be prioritized. Although requiring clinical corroborations, these findings may explain the controversial results of previous clinical studies not controlling the choices of screw augmentation

Total hip arthroplasty (THA) allows patients to return to an active lifestyle. Unfortunately one of the more common complications of cementless THA is a fracture of the greater trochanter (GT) or the calcar. These may compromise the outcomes of THA, but there are no large studies looking into this hypothesis. Between September 1998 and August 2005 the Hamilton Arthroplasty group performed 2282 THA operations. Demographic and outcome data on these patients was collected and tabulated in a prospective database. Radiographs were available on a picture archiving system for 1075 of the patients, 85% of which were primary THAs. GT and calcar fractures were identified. Statistical comparisons on the normal distributed outcome data were made using the Student’s T-test comparing repaired and missed fractures. A total of 60 GT fractures were found in the review of 1075 radiographs, giving an incidence of 5.6%. This included 19 isolated GT fractures and 10 GT fractures with associated calcar fractures that were found in primary hip arthroplasties, 48% of the total. Revision hip surgeries had 14 isolated GT fractures and 17 GT fractures with associated calcar fracture. We found that 23 (40%) of all GT fractures were missed intra-operatively and did not receive any fixation. All calcar fractures were noted and repaired, even if the associated GT fracture was not. 106 isolated calcar fractures were noted, 10% of all arthroplasties, only one of which did not receive fixation. Of this, 85 (80%) were from primary total hip arthroplasty and 21 (20%) from revision hip arthroplasty. Evaluation of the outcome data showed no significant difference between repaired and missed GT fractures. Reported outcomes compared favourably with the average for all THA in that time period. Adoption of cementless total hip arthroplasty in North America undoubtedly increases the rate of GT and calcar fractures. Most calcar fractures were noted and fixed but only 50% of GT fractures were discovered intraoperatively, an area of potential improvement. Greater trochanter and recognized calcar fractures may not have long-term detrimental effects

Introduction. Segmental defects of the femur present a major problem during revision hip arthroplasty. In particular, calcar segmental defects may compromise initial and long-tem femoral stem stability. Objective. The objective of the present study is to assess mid-term clinical and radiographic follow-up results at least two years after femoral revision comprising reconstruction for calcar segmental defect using metal wire mesh and impacted morcellised allograft. Methods. We performed 26 femoral revisions with calcar reconstruction in 24 patients between 2002 and 2010. The average age was 69.7 years, and the average follow-up period was 5 years and 1 month. All surgeries were performed using a cemented polished collarless tapered stem. The segmental calcar defect was reconstructed with metal wire mesh with doubled stainless wires. Large sized morcellised cancellous allograft was tightly impacted into the cavity between the phantom stem and the metal wire mesh. Nineteen hips were reconstructed with impaction bone grafting of the femur, and 7 hips with cement-in-cement technique except for the reconstructed calcar region.ã�� For clinical assessment, Merle d'Aubigné and Postel hip scores were recorded. For radiological assessment, antero-posterior hip radiographs were analyzed pre-operatively, and post-operatively at one month, 6 months and every 6 months thereafter. Clear lines around the femoral component using Gruen zone classification, stem subsidence in cement mantle, and change of stem axis were recorded. Kaplan-Meier survival analyses were performed with any re-operation of the femoral component or aseptic loosening as end points. In one case, the histological appearance of a biopsy specimen of the most proximal part of the reconstructed calcar, which was obtained at a later surgery for infection at 4 years after the revision, is described. Results. For clinical assessment, the mean Merle d'Aubigné and Postel hip scores improved from 10.4 points before the operation to 14.7 points at the final follow-up. For radiological assessment, no clear lines at the cement-bone interface and no stem axis changes were detected. Twenty-five of 26 hips showed less than 2 mm of stem subsidence at the final follow-up and one hip showed 2.2 mm stem subsidence. Both hips of one female patient underwent a one stage stem exchange because of an infection that occurred 48 months after revision. No cases showed aseptic loosening up to and including the last follow-up. The Kaplan-Meier survival analysis revealed that the survival rate at five years after revision was 88.0% with any type of re-operation on the femoral side as the endpoint and 100% with aseptic stem loosening as the endpoint, respectively. A biopsy specimen taken from the most proximal part of the reconstructed calcar region at 4 years after surgery in the infected case showed almost complete regeneration of viable bone with normal marrow spaces with partially formed granulation tissue. Conclusion. Reconstruction using metal wire mesh and tightly impacted morcellised allograft is a favorable method for the correction a calcar segmental defect. The procedure is simple and reliable, achieving initial and mid-term stem stability even for femurs with a complete calcar defect

The calcar femorale or ‘true neck’ of the femur has a role in transmitting load from the cantilevered neck to the femoral shaft (Zhang 2009). It can appear as a distinct condensation in clinical CT images because its structure is very similar to compact bone (Aspden 1998). Harty (1957) proposed that the calcar acts as a ‘spike’ in certain fall situations, contributing to splitting of the trochanter. We hypothesised that among elderly fallers, the size of the calcar would influence whether fractures occurred in the trochanteric (TR) or femoral neck (FN) site. We also asked whether patients who sustained a fracture had more or less calcar bone than frailty-matched controls that fell but didn't fracture. The FEMCO study is designed to investigate male (M) and female (F) patients with acute hip fracture with multi-detector CT, before they undergo surgery. It includes an age, sex and frailty-matched control group (who have sustained at least one injurious fall without hip fracture). The fractured hip is reconstructed in 3D for classification of fracture type (FN or TR). For the present pilot study, there were 14 cases (5TR, 9FN mean 80+/−8.5yrs. 7M, 7F) and 11 controls (83+/−7.0yrs. 3M, 8F). Axial CT slices where a calcar was visible were opened in Stradwin 4.1 software (Treece 2011). The calcar femorale was semi-automatically selected with the flood fill tool. Each axial image that contained a visible calcar was included in the analysis, so that for each femur a single calcar volume was generated. Results were examined using ANOVA. Combining male and female results, there was a non-significant trend towards a higher calcar volume in patients sustaining trochanteric rather than femoral neck fractures (0.73cm3 +/− 0.26 vs 0.61cm3 +/−0.14, p=0.27) but no difference between cases and controls. Males had a significantly higher calcar volume than females (mean 0.82cm3 +/− 0.24 vs 0.59cm3 +/− 0.13, p=0.005). Further studies are now planned in larger samples of each sex, to examine the role of the calcar in fracture mechanics. Three-dimensional visualisations provide a novel insight into the damage patterns and resultant fragment locations

Background. Post-operative periprosthetic femoral fractures (PFF) are a devastating complication associated with high mortality and are costly. Few risk factors are modifiable apart from implant choice. The design features governing risk of PFF are unknown. We estimated the 90-day risk of revision for PFF associated with design features of cementless femoral stems and to investigate the effect of a collar on early PFF risk using a biomechanical in-vitro model. Patients, materials and methods. 337 647 primary THAs from the National Joint Registry (UK) were included in a multivariable survival and regression analysis to identify the adjusted hazard of PFF revision following primary THA using cementless stems. The effect of a collar in cementless THA on early PFF was evaluated in an in-vitro model using paired fresh frozen cadaveric femora. Results. Prevalence of PFF revision was 0.34% (1180/337647) and 44.0% occurred (520/1180) within 90 days of surgery. Implant risk factors included: collarless stem, non grit-blasted finish and triple tapered design. In the in-vitro PFF model a medial calcar collar consistently improved construct stability and fracture resistance. Discussion. During rotational injury the collar can load the calcar in compression increasing the force required for a fracture. This increases the force required to cause a PFF around a collared implant versus collarless implants. The calcar possibly acts as a check-rein which prevents excessive peri-prosthetic trabecular deformation in rotational injuries and may improve the resistance to loosening after high energy injuries which do not cause cortical fracture. Conclusion. Analysis of stem design features in registry data is a useful method to identify implant characteristics which affect the risk of early PFF around cementless femoral stems. Calcar collar reduced early PFF risk and this was confirmed by biomechanical testing. This approach may be useful in the analysis of other uncommon arthroplasty failure modes

Metal meshes are used in revision surgery of the hip to contain impacted bone grafts in cases with cortical or calcar defects in order to provide rotational stability to the stem. However, the viability of bone allografts under these metal meshes has been uncertain. We describe the histological appearances of biopsies obtained from impacted bone allografts to the calcar contained by a metal mesh in two femoral reconstructions which needed further surgery at 24 and 33 months after the revision procedure. A line of osteoid and viable new bone was observed on the surface of necrotic trabeculae. Active bone marrow between these trabeculae showed necrotic areas in some medullary spaces with reparative fibrous tissue and isolated reactive lymphocytes. This is interpreted as reparative changes after revascularisation of the cancellous allografts. These pathological findings are similar to those reported in allografts contained by cortical host bone and support the hypothesis that incorporation of morcellised bone under metal meshes is not affected by these devices

Background: The Calcaneus is the largest of the tarsal bones. 2% of all adult and 60 % of all tarsal fractures involve the Calcaneus. A true consensus regarding the management of these fractures still eludes orthopaedic surgeons. While operative treatment for displaced fractures has gained more acceptance in the last decade, surgical morbidity still remains high. Aim: A retrospective review of the early complications and radiological outcomes following open reduction and internal fixation of displaced calcaneal fractures in our unit over the last 15 months. Methods: A consecutive series of 33 patients who underwent surgical fixation of the Calcaneus was selected. Patient records, X rays and scans were reviewed. Mode and nature of injury, life style factors, surgical complications and Bohler’s angles were analysed. Results: 37 fractures in 33 patients underwent operative fixation. 81 % were male. Mean age at surgery was 37yrs (range19–59). 35 % were operated within 1 week of the injury and 13% after 2 weeks of injury. 43% were Sanders’ type III, 18% type II and 13% tuberosity avulsion fractures. 63% of patients had a reversed or zero Bohler’s angle. Mean post-op Bohler’s angle was 32 degrees. Overall complication rate was 32%, with a combined deep infection rate of 8%. All patients with infection were male, and 70% were smokers. 86% were above 40yrs of age (mean 47yrs). The deep infection rate for intra-articular fractures was 3% and for tuberosity avulsion fractures 40%. Majority of patients with wound complications had been operated within 7 days of injury. 4 patients had persisting pain requiring removal of metal work. Discussion: Our study highlights that there are significant risks associated with operative management of calcaneal fractures. Male patients over the age of 40yrs who are smokers seem to be at most risk of wound complications. Time to surgery or delay in surgery up to 2 weeks did not seem to have any adverse consequences. Complications increase with fracture complexity, and avulsion fractures have a high risk of wound breakdown. Near anatomical restoration of the articular surface is possible in most cases

Resorption of the calcar below the collar of a titanium femoral prosthesis was observed. Biopsies of these lesions showed concentrations of polyethylene. We assessed the size of the resorption, correlating it with the size of the femoral prosthesis and the time since implantation. The age and the weight of the patient was also linked to the size of the prosthesis. We conducted a finite element analysis (FEA) of the femoral component-femur complex in both the loaded and unloaded situation. FEA demonstrated changing pressure under the collar. This can be translated into micro-bending, with the degree of movement dependent on the size of the prosthesis, the material of the prosthesis and the weight of the patient. We postulate the existence of a ‘polyethylene pump’ owing to the bending motion of the collared prosthesis, and that calcar resorption is due to the resultant polyethylene granulomatous lesions

Resorption of the calcar below the collar of a titanium femoral prosthesis was observed. Biopsies of these lesions showed concentrations of polyethylene. We assessed the size of the resorption and correlated this with the size of the femoral prosthesis and the time since implantation. The age and the weight of the patient were also linked to the size of the prosthesis. We conducted a finite element analysis (FEA) of the femoral component-femur complex in both the loaded and unloaded situation. The FEA study demonstrated changing pressure under the collar that can be translated into microbending motions, with the degree of the movement dependent on the size of the prosthesis, the material of the prosthesis and the weight of the patient. We hypothesise that the existence of a ‘polyethylene pump’ due to the bending movements of the collared prosthesis concentrates polyethylene particles under the collar. We therefore postulated that the calcar resorption is due to the polyethylene granulomatous lesions, resulting from the micromotion of the collar of the prosthesis

Between January 1990 and October 2000, 108 total hip arthroplasties using a cemented polished titanium stem and a cemented ultra-high molecular weight polyethylene (UHMWP) cup were performed at our hospital. Because during routine follow-up visits we noted instances of resorption of the calcar, we decided to assess whether this was a problem. We were able to assess 85 of the original 108 hips. Calcar resorption was observed in 43 hips. The extent of calcar resorption varied from 1 mm to over 15 mm. In one patient a biopsy showed typical polyethylene granuloma. Because there is a risk of long-term failure, we concluded that it is inadvisable to use a cemented polished titanium stem when UHMWP is one of the bearing surfaces

We have previously reported on early lytic lesions occurring when collared titanium prostheses are used. Previous finite element analysis studies (FEAs) showed that lytic lesions of the calcar were due to concentration of polyethylene wear particles under the collar by a ‘pumping action’. Further follow-up of these calcar lytic lesions showed that their rate of increase in size progressively slowed down. Further FEAs were performed to determine why this was so. An FEA mesh construct was developed, incorporating the new parameters of no contact between the collar and the calcar bone. A mechanical model to determine displacement parameters was also developed. These FEA studies demonstrated that the pumping action of the collar became less efficient as the size of the lytic lesions increased. This led to less concentration of polyethylene particles under the collar and fewer granulomatous reactions. The change in the proximal prosthesis-cement-bone construct may lead to cement mantle deterioration and earlier failure. We still recommend caution when a collared prosthesis is used, and the material and geometry of the prosthesis remain important

Aims

The aim of this retrospective study was to assess the incidence of early periprosthetic femoral fracture (PFF) associated with Charnley-Kerboull (CK) femoral components cemented according to the ‘French paradox’ principles through the Hueter anterior approach (HAA) in patients older than 70 years.