Aims. Periprosthetic femoral fracture (PPF) is a major complication following total hip arthroplasty (THA). Uncemented femoral components are widely preferred in primary THA, but are associated with higher PPF risk than cemented components. Collared components have reduced PPF rates following uncemented primary THA compared to collarless components, while maintaining similar prosthetic designs. The purpose of this study was to analyze PPF rate between collarless and collared component designs in a consecutive cohort of posterior approach THAs performed by two high-volume surgeons. Methods. This retrospective series included 1,888 uncemented primary THAs using the posterior approach performed by two surgeons (PKS, JMV) from January 2016 to December 2022. Both surgeons switched from collarless to collared components in mid-2020, which was the only change in surgical practice. Data related to component design, PPF rate, and requirement for revision surgery were collected. A total of 1,123 patients (59.5%) received a collarless femoral component and 765 (40.5%) received a collared component. PPFs were identified using medical records and radiological imaging. Fracture rates between collared and collarless components were analyzed. Power analysis confirmed 80% power of the sample to detect a significant difference in PPF rates, and a Fisher’s exact test was performed to determine an association between collared and collarless component use on PPF rates. Results. Overall, 17 PPFs occurred (0.9%). There were 16 fractures out of 1,123 collarless femoral components (1.42%) and one fracture out of 765 collared components (0.13%; p = 0.002). The majority of fractures (n = 14; 82.4%) occurred within 90 days of primary THA. There were ten reoperations for PPF with collarless components (0.89%) and one reoperation with a collared component (0.13%; p = 0.034). Conclusion. Collared femoral components were associated with significant decreases in PPF rate and reoperation rate for PPF compared to collarless components in uncemented primary THA. Future studies should investigate whether new-generation collared components reduce PPF rates with longer-term follow-up. Cite this article: Bone Joint J 2024;106-B(3 Supple A):115–120

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. The aim of this study was to determine both the incidence of, and the reoperation rate for, postoperative periprosthetic femoral fracture (POPFF) after total hip arthroplasty (THA) with either a collared cementless (CC) femoral component or a cemented polished taper-slip (PTS) femoral component. Methods. We performed a retrospective review of a consecutive series of 11,018 THAs over a ten-year period. All POPFFs were identified using regional radiograph archiving and electronic care systems. Results. A total of 11,018 THAs were implanted: 4,952 CC femoral components and 6,066 cemented PTS femoral components. Between groups, age, sex, and BMI did not differ. Overall, 91 patients (0.8%) sustained a POPFF. For all patients with a POPFF, 16.5% (15/91) were managed conservatively, 67.0% (61/91) underwent open reduction and internal fixation (ORIF), and 16.5% (15/91) underwent revision. The CC group had a lower POPFF rate compared to the PTS group (0.7% (36/4,952) vs 0.9% (55/6,066); p = 0.345). Fewer POPFFs in the CC group required surgery (0.4% (22/4,952) vs 0.9% (54/6,066); p = 0.005). Fewer POPFFs required surgery in males with a CC than males with a PTS (0.3% (7/2,121) vs 1.3% (36/2,674); p < 0.001). Conclusion. Male patients with a PTS femoral component were five times more likely to have a reoperation for POPFF. Female patients had the same incidence of reoperation with either component type. Of those having a reoperation, 80.3% (61/76) had an ORIF, which could greatly mask the size of this problem in many registries. Cite this article: Bone Joint J 2024;106-B(2):144–150

Aims. Hydroxyapatite (HA)-coated collars have been shown to reduce aseptic loosening of massive endoprostheses following primary surgery. Limited information exists about their effectiveness in revision surgery. The aim of this study was to radiologically assess osteointegration to HA-coated collars of cemented massive endoprostheses following revision surgery. Methods. Retrospective review of osseointegration frequency, pattern, and timing to a specific HA-coated collar on massive endoprostheses used in revision surgery at our tertiary referral centre between 2010 to 2017 was undertaken. Osseointegration was radiologically classified on cases with a minimum follow-up of six months. Results. In all, 39 patients underwent radiological review at mean 43.5 months; 22/39 (56.4%) showed no osseointegration to the collar. Revision endoprostheses for aseptic loosening were less likely to show osseointegration compared with other indications for revision. Oncological cases with previous or current infection were more likely to show osseointegration to ≥ 1 collar side than those without evidence of prior infection. Conclusion. This seven-year review identified osseointegration of HA-coated collars after revision surgery is less likely (43.6%, 17/39) than after primary surgery. Young patients who undergo revision surgery following initial oncological indication may benefit the most from this collar design. Use in revision oncological cases with a history of infection may be beneficial. HA-coated collars showed limited benefit for patients undergoing revision for failed arthroplasty with history of infection. Cite this article: Bone Jt Open 2021;2(6):371–379

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

Aims. The direct anterior (DA) approach has been associated with rapid patient recovery after total hip arthroplasty (THA) but may be associated with more frequent femoral complications including implant loosening. The objective of this study was to determine whether the addition of a collar to the femoral stem affects implant migration, patient activity, and patient function following primary THA using the DA approach. Methods. Patients were randomized to either a collared (n = 23) or collarless (n = 26) cementless femoral stem implanted using the DA approach. Canal fill ratio (CFR) was measured on the first postoperative radiographs. Patients underwent a supine radiostereometric analysis (RSA) exam postoperatively on the day of surgery and at two, four, six, 12, 26, and 52 weeks postoperatively. Patient-reported outcome measures (Western Ontario and McMaster Universities Osteoarthritis (WOMAC) Index, the 12-item Short Form Health Survey Mental and Physical Score, and University of California, Los Angeles (UCLA) Activity Score) were measured preoperatively and at each post-surgery clinic visit. Activity and function were also measured as the weekly average step count recorded by an activity tracker, and an instrumented timed up-and-go (TUG) test in clinic, respectively. Results. Comparing the RSA between the day of surgery baseline exam to two weeks postoperatively, subsidence was significantly lower (mean difference 2.23 mm (SD 0.71), p = 0.023) with collared stems, though these patients had a greater CFR (p = 0.048). There was no difference (p = 0.426) in subsidence between stems from a two-week baseline through to one year postoperatively. There were no clinically relevant differences in PROMs; and there was no difference in the change in activity (p = 0.078) or the change in functional capacity (p = 0.664) between the collared stem group and the collarless stem group at any timepoint. Conclusion. Presence of a collar on the femoral stem resulted in reduced subsidence during the first two postoperative weeks following primary THA using the DA approach. However, the clinical implications are unclear, and larger studies examining patient activity and outcomes are required. Cite this article: Bone Joint J 2020;102-B(12):1654–1661

Aims. Massive endoprostheses rely on extra-cortical bone bridging (ECBB) to enhance fixation. The aim of this study was to investigate the role of selective laser sintered (SLS) porous collars in augmenting the osseointegration of these prostheses. Materials and Methods. The two novel designs of porous SLS collars, one with small pores (Ø700 μm, SP) and one with large pores (Ø1500 μm, LP), were compared in an ovine tibial diaphyseal model. Osseointegration of these collars was compared with that of a clinically used solid, grooved design (G). At six months post-operatively, the ovine tibias were retrieved and underwent radiological and histological analysis. Results. Porous collars provided a significantly greater surface (p < 0.001) for the ingrowth of bone than the standard grooved design. Significantly greater extracortical pedicle formation was seen radiologically around the grooved design (length p = 0.002, thickness p < 0.001, surface area p = 0.002) than around the porous collars. However, the ingrowth of bone occurred from the transection site into the porous structure of both types of collar. A fivefold increase in integration was seen with the SP and a threefold increase in the LP design when compared with G (p < 0.001). Conclusion. SLS porous collars allow the direct ingrowth of more bone and are better than current designs which rely on surface ongrowth and ECBB. Cite this article: Bone Joint J 2017;99-B:276–82

Introduction. Cervical orthoses are commonly used to regulate the motion of cervical spines for conservative treatment of injuries and for post-operative immobilization. Previous studies have reported the efficacy of orthoses for 2D flex-extension or 3D motions of the entire cervical spine. However, the ability of cervical orthoses to reduce motion might be different at each intervertebral level and for different types of motion (flexion-extension, rotation, lateral bending). The effectiveness of immobilizing orthoses at each cervical intervertebral level for 3D motions has not been reported. The purpose of this study is to evaluate the effectiveness of the Philadelphia collar to each level of cervical spines with 3D motion analysis under loading condition. Patients & Methods. Patient Sample Four asymptomatic volunteer subjects were recruited and provided informed consent. Approval of the experimental design by the institutional review board was obtained. These 4 individuals were without any history of cervical diseases or procedures. The presence of any symptoms, spinal disorders and anatomical abnormalities in fluoroscopic images or CT was a criterion of exclusion from this study. Outcome Measures To evaluate the efficacy of the Philadelphia collar, ANOVA was used to compare the range of motion with and without collar at the C3/4, C4/5, C5/6 and C6/7 intervertebral levels for each motion. The level of statistical significance was set at p < 0.05. When a statistical difference was detected, post hoc Tukey tests were performed. Methods. Three-dimensional models of the C3–C7 vertebrae were developed from CT scans of each subject using commercial software (see Figure 1). Two fluoroscopy systems were positioned to acquire orthogonal images of the cervical spine. The subject was seated within the view of the dual fluoroscopic imaging system (see Figure 2). Pairs of images were taken in each of 7 positions: neutral posture, maximum flexion and extension, maximum left and right lateral bending, and maximum left and right rotation. The images and 3D vertebral models were imported into biplane 2D-3D registration software, where the vertebral models were projected onto the pair of digitized images and the 3D bone pose was adjusted to match its radiographic projection in each image (see Figure 3). Relative motions between each vertebral body were calculated from body-fixed coordinate systems using a flexion-lateral bending-axial rotation Cardan angle sequence. Results. Flexion range was significantly reduced with the collar at each cervical level. Extension range was significantly reduced at the C3/4 level. Rotation and lateral bending were reduced for C3/4, C4/5, C5/6 levels with the collar. Discussion/Conclusion. The Philadelphia Collar significantly reduces cervical motion at C3/4, C4/5 and C5/6 levels in almost all motions (except for extension). At the C6/7 level, this type of collar has limited effectiveness reducing cervical motion. We used 3D radiographic measurements to quantify the effectiveness of the Philadelphia collar for reducing cervical motion. Bi-plane 2D-3D registration method is useful technique to evaluate 3D motion of cervical spines

Introduction: A collar can be defined as any projection from the surface of the proximal third of the femoral stem that interferes with the capacity of the stem to move distally within the cement mantle and provide optimal load distribution along the calcar area. Contraversy exists concerning the usage of a collared or collarless prosthesis and the ability of the collar to perform its effect on the medial femoral neck. The purpose of this study is to compare the proximal femoral bone resorption and aseptic loosening in cases that had poor or good contact between the collar and the proximal medial femoral neck. Materials& Methods: 102 hybrid total hip arthroplasties which were done for severe hip joint disease were analyzed radiographically in the current study. Pre-operative, immediate post operative and the last follow-up anteroposterior and lateral pelvis radiographies were examined. The medial femoral neck-collar contact was considered to be ideal if the medial femoral neck was fully covered by the prosthesis (group A). Contact was deamed to be poor if the medial femoral neck was partially uncovered (group B) or there was cement interposition between the bone and the prosthesis (group C) Cortical femoral bone thickness of the femoral neck was measured on the immediate post-operative and the latest follow-up radiograph as well as the thicker area of bone in Gruen Zone 7. The medial femoral neck height was measured from the superior border of the lesser trochanter. Results: The mean follow up was 4.86 years. The good contact between the collar and the medial femoral neck was achieved for most of the patients. 55 hips were in group A. 30 hips were in group B and 17 hips were in group C at the latest follow-up. The mean loss in the height of the medial femoral neck was 4.21 mm for group A, 4.26mm for group B and 3.05mm for group C. The difference among the groups was not statiscally significant (p=0.545). As we evaluate the relation between the transverse bone loss in the Gruen Zone 7; the loss was 2.49 for group A, 2.26 for group B and 1.58 for group C. The difference among the groups was not statistically significant (p=0.246). Discussion: Unloading of the proximal femur leads resorption of the medial femoral neck and the proximal support of the prosthesis can be lost ultimately leading to aseptic failure due to excessive stresses on the proximal cement and debonding. Although the main purpose of using a collared femoral stem is to transfer load to the medial femoral neck and to prevent bone resorption, in the current study the collar did not prevent calcar resorption even when ideal contact was achieved between the collar and proximal medial femoral neck. Revision rate seems to be unchanged whether the collar had good or bad contact

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

Introduction. Aseptic loosening is the most common mode of failure of massive endoprostheses. Introduction of Hydroxyapatite coated collars have reduced the incidence of aseptic loosening. However bone growth is not always seen on these collars. Objectives. The aims of our study were to determine the extent of osseous integration of Hydroxyapatite coated collars, attempt a grading system for bone growth and to determine the effect of diagnosis, surgical technique and adjuvant therapy on bone growth. Methods. We reviewed the records and radiographs of 58 patients who had a massive endoprosthesis implanted by two surgeons in our unit over the last five years. Revision surgeries were recorded separately. Bone growth was graded 1–4 based on appearance in antero-posterior and lateral radiographs. Results. Three groups were identified. Group 1-Resections for primary bone tumours (33 patients), Group 2-resections for metastatic bone disease (22 patients) and Group 3- Resections for non tumour indications (3 patients). Overall, 60% of patients had grade 1, 12% had grade 2, 19% had grade 3 and 9% had grade 4 osteointegration. Grade 3 or 4 Collar osteointegration was found in 37% of patients in Group 1, 9% in group 2 and 67% in group 3. 5% of patients with grade 1 integration, 100% patients with grade 2 integration and none of the patients with grade 3 or 4 integration underwent revision for aseptic loosening. Appearance or widening of a gap between the resected bone end and the collar indicated loosening and impending revision. Proximal humeral replacements had the lowest rate of osteointegration (12%). Adjuvant therapy did not affect osteointegration. Conclusion. Osteointegration of collars is seen more often after resection of primary bone tumours. The role of collars in metastatic tumour surgery is questionable. Our radiographic grading system of bone growth predicted aseptic loosening

Introduction. The value of collared stems for uncemented implants remains controversial. Some comparative studies have demonstrated advantages of collared stems regarding the potential for subsidence. Other studies with longer follow-up have shown no adverse effect of the use of a collar regarding the femoral component survivorship. To date, the adequate size of the collar with regards to the anatomy of the proximal femur has never been studied. The goal of this study was to assess whether the size of the collar needs to be adjusted according to the size of the femoral component used, and according to the use of a standard or a lateralized component. Materials and Method. 102 CT of normal femurs have been divided into 2 groups of 51 femurs each. Each group has been analysed by 2 independant surgeons. Each CT view passed through the axis of the proximal diaphysis and the center of the femoral head. The scale was 100%. Templates of femoral components have been set in order to reproduce the center of rotation and an optimal filling of the proximal femoral canal. Sizes of the femoral components as well as the need for standard or lateralized implants have been recorded. In order to determine the ideal size of the collar, the distance between the medial edge of the prothesis and the medial edge of the femur (so-called P-C distance) at the level of the neck cut (calcar) has been measured. Results. The inter-observer concordance for the selection of the implant type (i.e. standard or lateralized), size, and P-C distance measurement was satisfactory (kappa 0.7). 56% of the selected implants were standard. The mean size was 5 (1 to 10). The mean P-C distance was 9.9mm (5 to 16mm). It was 8.8mm for standard implants and 11.3mm for lateralized implants, with significant difference (p<0.0001). The size of the selected implant was significantly related to the P-C distance (r=0.27; p<0.005). Conclusion. These results suggest that the size of the collar should increase with larger sizes, and that the use of a longer collar with lateralized implants should be advocated

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

Background/Aims. The development of extendable prostheses has permitted limb salvage surgery in paediatric patients with bone tumours in proximity to the physis. Prostheses are extended to offset limb length discrepancy as the child grows. Aseptic loosening (AL) is a recognised complication. The implant stem must fit the narrow paediatric medullary canal and remain fixed while withstanding growth and increasing physical demands. Novel designs incorporate a hydroxyapatite (HA) coated collar that manufacturers claim improves bony ongrowth and stability, providing even stress distribution in stem and shoulder regions and providing a bone-implant seal, resulting in decreased AL and prolonged survival. This study aims to assess whether there is a relationship between bony ongrowth onto a HA collar and AL. Hypothesis: Bone ongrowth onto the HA collar of extendable prostheses is associated with more stable fixation and less AL despite patient growth. Methods. Retrospective review of 51 primary partial femoral extendable prostheses implanted over 12 years from 1994–2006 (followed up to death at a mean of 2.5±2.2 years or last clinical encounter at a mean of 8.6 years) and 24 subsequent revisions, to ascertain failure rate and mode, together with a cohort study reviewing bony ongrowth onto the HA coated collar in 10 loose and 13 well fixed partial femoral, humeral and tibial implants. Patient growth was measured as a change in bone:implant-width ratio. Results. 21 (41.2%) primary femoral implants failed at a mean 42.8 months, 5 through AL. 1 secondary implant was revised for AL. 2 implants displayed evidence of progressive AL but had not failed at last follow-up. 5 of 11 tibial component revisions in distal femoral replacement were due to AL. 1 major complication occurred after revision surgery for AL in a primary implant: deep infection requiring 2 stage revision. Bony collar ongrowth was significantly higher in all 4 quadrants (anterior, posterior, medial and lateral) in the well-fixed as opposed to loose group, demonstrating a strong negative relationship in each quadrant between bony ongrowth and AL (p0.001) in the presence of patient growth as shown by increased bone:implant width ratio. In both groups, collar ongrowth was greatest in the posterior quadrant. Summary and Conclusions: AL has been confirmed as a common cause of failure in massive extendable endoprostheses. Revision surgery is difficult and may cause serious complications. For the first time, a significant relationship between a well fixed implant stem and bony ongrowth onto a HA coated collar in the context of massive implants used in tumour surgery has been demonstrated. This newly-proven relationship may result in longer-term implant survival and thus a reduced need for revision surgery. It is hoped that this study will provide the basis for further study of this relationship

Purpose: Hinged knee prostheses are mainly used for reconstruction after major tumour resection. Aseptic loosening is the main problem with these implants. One of the solutions proposed to reduce the rate of loosening is to add a hydroxyapatite collar on the shaft stems. This work was conducted to study bone ingrowth with a new hinged implant with a hydroxyapatite collar at the junction between the zone of resection and the shaft. Material and methods: Twenty-nine massive prostheses with a hydroxyapatite collar were implanted between 1998 and 2001. Nine patients were excluded from the analysis because follow-up was less than two years. This retrospective analysis thus compared twenty massive prostheses with twenty matched hinged GUEPAR prostheses without a collar. Bony ingrowth was measured on plain x-rays (two orthogonal views) at 6, 12, 24, and 36 months. Filling of the gap between the bone and the implant was also assessed. Signs of loosening were noted. Results: Mean bony ingrowth in implants with a hydroxyapatite collar was 6.58 mm at 6 months 9.84 mm at 12 months, 12.3 mm at 24 months and 13.25 mm at 36 months. Mean bony ingrowth in the implants without a hydroxyapatite collar was 1.65 mm at 6 months, 3.31 mm at 12 months, 4.8 mm at 24 months and 4.35 mm at 36 months. In the implants with a collar, gap filling was partial in five cases and total in 15. In implants without a collar, there was no gap filling in eight cases, partial filling in two cases and total filling in fifteen cases. Discussion: Prostheses with a hydroxyapatite collar enable better radiological bony ingrowth than observed in implants without a hydroxyapatite collar. Gap filling is better for prostheses with a collar. There was no case of loosening at last follow-up for implants with a hydroxyapatite collar. Conclusion: In light of these results, shaft anchorage appears to be better with implants with a hydrosyapatite collar. Confirmation of improvement in clinical outcome and lower rate of aseptic loosening will require longer follow-up

Cervical spine collars are applied in trauma situations to immobilise patients' cervical spines. Whilst movement of the cervical spine following the application of a collar has been well documented, the movement in the cervical spine during the application of a collar has not been. There is universal agreement that C-spine collars should be applied to patients involved in high speed trauma, but there is no consensus as to the best method of application. The clinical authors have been shown two different techniques on how to apply the C-spine collars in their Advanced Life Support Training (ATLS). One technique is the same as that recommended by the Laerdal Company (Laerdal Medical Ltd, Kent) that manufactures the cervical spine collar that we looked at. The other technique was refined by a Neurosurgeon with an interest in pre-hospital care. In both techniques the subjects' head is immobilised by an assistant whilst the collar is applied. We aimed to quantify which of these techniques caused the least movement to the cervical spine. There is no evidence in the literature quantifying how much movement in any plane in the unstable cervical spine is safe. Therefore, we worked on the principle: the less movement the better. The Qualisys Motion Capture System (Qualisys AB, Gothenburg, Sweden) was used to create an environment that would measure movement on the neck during collar application. This system consisted of cameras that were pre-positioned in a set order determined by trial and error initially. These cameras captured reflected infra-red light from markers placed on anatomically defined points on the subject's body. As the position of the cameras was fixed then as the patients moved the markers through space, a software package could deduce the relative movement of the markers to each camera with 6 degrees of freedom (6DOF). Six healthy volunteers (3 M, 3 F; age 21-29) with no prior neck injuries acted as subjects. The collar was always applied by the same person. Each technique was used 3 times on each subject. To replicate the clinical situation another volunteer would hold the head for each test. The movements we measured were along the x, y, and z axes, thus acting as an approximation to flexion, extension and rotation occurring at the C-spine during collar application. The average movement in each axis (x, y and z) was 8 degrees, 8 degrees and 5 degrees respectively for both techniques. No further data analysis was attempted on this small data set. However this pilot study shows that our method enables researchers to reproducibly collect data about cervical spine movement whilst applying a cervical collar

The purpose of this study was to determine whether the low rate of mechanical loosening of the SMILES rotating hinge distal femoral endoprosthesis relates to the hydroxyapatite (HA)-coated, grooved collar of the femoral component. A database was used to identify two groups of cases of primary distal femoral replacement with a custom-designed and manufactured SMILES endoprosthesis at our unit; those with the collared femoral component (“collar group”), and those without a collar (“non-collargroup”). From these two groups, patients were pair-matched for age and length of bone resection. A retrospective review of serial biplanar pairs of radiographs of each patient, assessing radiolucent lines and extracortical bone pedicle. 11 matched pairs were identified, (14 females, 8 males), with a mean age of 36 years, (range 16–66). The pathology was primary bone tumour in 20 cases, (17 malignant, 3 benign), and metastatic disease in 2 cases. Mean length of follow-up was 85 months, (range 27–122). Radiolucent line score (RLS) progression over time was significantly lower in the collar group, (0.01 vs 0.73, p=0.001) (fig. 1 & 2), as was the mean final RLS, (2.72 vs 7.81, p=0.02). Mean RLS per radiographic quadrant was 0.56 in cases in which a bony pedicle was ingrown onto the prosthesis, (exclusively in the collared-group), 2.41 in cases in which the pedicle was not ingrown, (most prevalent in the non-collared group), and 1.02 in those cases without any pedicle formation, (ANOVA analysis, p=0.0002). This study demonstrates that the HA-coated, grooved collar significantly reduces the progression of radiolucent lines, and consequently the overall RLS, explaining the reduced rate of mechanical loosening of the collared endoprosthesis. A bony pedicle that does not incorporate onto the prosthesis surface may be associated with an increase in radiographic loosening

Purpose: The purpose of this study was to determine whether the low rate of mechanical loosening of the SMILES rotating hinge distal femoral endoprosthesis relates to the hydroxyapatite (HA)-coated, grooved collar of the femoral component. Methods and results: A database was used to identify two groups of cases of primary distal femoral replacement with a custom-designed and manufactured SMILES endoprosthesis at our unit; those with the collared femoral component (“collar group”), and those without a collar (“non-collar group”). From these two groups, patients were pair-matched for age and length of bone resection. We performed a retrospective review of serial biplanar pairs of radiographs of each patient, assessing radiolucent lines and extracortical bone pedicle. 11 matched pairs were identified, (14 females, 8 males), with a mean age of 36 years, (range 16–66). The pathology was primary bone tumour in 20 cases, (17 malignant, 3 benign), and metastatic disease in 2 cases. Mean length of follow-up was 85 months, (range 27–122). Radiolucent line score (RLS) progression over time was significantly lower in the collar group, (0.01 vs 0.73, p=0.001) (fig. 1 & 2), as was the mean final RLS, (2.72 vs 7.81, p=0.02). Mean RLS per radiographic quadrant was 0.56 in cases in which a bony pedicle was ingrown onto the prosthesis, (exclusively in the collared-group), 2.41 in cases in which the pedicle was not ingrown, (most prevalent in the non-collared group), and 1.02 in those cases without any pedicle formation, (ANOVA analysis, p=0.0002). Conclusion: This study demonstrates that the HA-coated, grooved collar significantly reduces the progression of radiolucent lines, and consequently the overall RLS, explaining the reduced rate of mechanical loosening of the SMILES prosthesis. A bony pedicle that does not incorporate onto the prosthesis surface may be associated with an increase in radiographic loosening

Cervical extrication collars are frequently used in pre hospital stabilization and in the definitive treatment for lesions of the cervical spine. The control of extensionflexion, lateral bending, and rotation given to individual segments is variable with different designs. Objective: To highlight the patient satisfaction and reported pain perception with immobilization of cervical injury with the extrication collar. Method: We present prospective cohort of fourteen patients with median age of 28 years with suspected C-spine injury waiting for CT scan. Unreliable patients were defined as those with admission Glasgow Coma Scale score < 15. They were treated with extrication collar immobilization. The initial diagnosis was made by supine cross-table lateral radiograph and then by computed tomographic scan as early as possible. All had no apparent neurologic deficit attributed to the C-spine at admission. Results: All reported increased level of pain despite administering adequate analgesia. Most patients reported increased pain at the pressure point of the collar. Conclusion: These cases demonstrate the limitations of current management techniques of suspected cervical fractures in unreliable trauma patients and highlight the lack of appropriate orthosis for cervical immobilization in our institution