Aims. Congenital pseudarthrosis of the tibia (CPT) has traditionally been a difficult condition to treat, with high complication rates, including nonunion, refractures, malalignment, and leg length discrepancy. Surgical approaches to treatment of CPT include intramedullary rodding, external fixation, combined intramedullary rodding and external fixation, vascularized fibular graft, and most recently cross-union. The current study aims to compare the outcomes and complication rates of cross-union versus other surgical approaches as an index surgery for the management of CPT. Our hypothesis was that a good index surgery for CPT achieves union and minimizes complications such as refractures and limb length discrepancy. Methods. A multicentre study was conducted involving two institutions in Singapore and China. All patients with CPT who were surgically managed between January 2009 and December 2021 were included. The patients were divided based on their index surgery. Group 1 included patients who underwent excision of hamartoma, cross-union of the tibia and fibula, autogenic iliac bone grafting, and internal fixation for their index surgery. Group 2 included patients who underwent all other surgical procedures for their index surgery, including excision of hamartoma, intramedullary rodding, and/or external fixation, without cross-union of the tibia and fibula. Comparisons of the rates of union, refracture, limb length discrepancy, reoperations, and other complications were performed between the two groups. Results. A total of 36 patients were included in the study. Group 1 comprised 13 patients, while Group 2 comprised 23 patients. The mean age at index surgery was four years (1 to 13). The mean duration of follow-up was 4.85 years (1.75 to 14). All patients in Group 1 achieved bony union at a mean of three months (1.5 to 4), but ten of 23 patients in Group 2 had nonunion of the pseudarthrosis (p = 0.006). None of the patients in Group 1 had a refracture, while seven of 13 patients who achieved bony union in Group 2 suffered a refracture (p = 0.005). None of the patients in Group 1 had a limb length discrepancy of more than 2 cm, while ten of 23 patients in Group 2 have a limb length discrepancy of more than 2 cm (p = 0.006). In Group 1, four of 13 patients had a complication, while 16 of 23 patients in Group 2 had a complication (p = 0.004). Excluding removal of implants, four of 13 patients in Group 1 had to undergo additional surgery, while 18 of 23 patients in Group 2 had to undergo additional surgery following the index surgery (p = 0.011). Conclusion. A good index surgery of excision of hamartoma, cross-union of the tibia and fibula, autogenic iliac bone grafting, and internal fixation for CPT achieves union and minimizes complications such as refractures, limb length discrepancy, and need for additional surgeries

Femoral Impaction allografting is now an established method in revision hip arthroplasty where there is a deficiency in bone stock. Most experience of this technique has been in conjunction with a cemented collarless, polished, tapered (CPT) stem. We conducted a retrospective study into the clinical and radiological results of 67 consecutive patients with an average of 62 months (36–108 months) follow-up. In all cases, Impaction bone grafting was performed using a transtrochanteric approach and cemented Charnley and Elite Plus stems. In our series no femoral component has been revised. The overall subsidence was 2.2 mm. 57 hips (85%) showed subsidence of 4 mm or less. However two patients showed massive subsidence of greater than 10mm, both with associated osteolysis and radiolucent lines. In addition, one stem showed a progressive varus position and debonding of the cement-metal interface. Analysis of the bone allograft showed evidence of incorporation in 56 (84%) of patients. The Merle D’Aubigne-Postal clinical score increased from an average of 8.3 pre-operatively to 15.3 at the last review. 60 patients (89.5%) complained of no or slight pain. There was a 10% re-operation rate due to complications. Three patients sustained periprosthetic fractures around the tip of the prosthesis, all successfully treated with a plate. Three patients suffered recurrent dislocation, two needed revision of the acetabula component. Two patients needed trochanteric wires removed for persistent pain. Direct comparison of different prostheses is difficult due to many confounding variables. However the medium term results of our study are comparable to the results reported using the Exeter and CPT stems

We prospectively followed 191 consecutive collarless polished tapered (CPT) femoral stems, implanted in 175 patients who had a mean age at operation of 64.5 years (21 to 85). At a mean follow-up of 15.9 years (14 to 17.5), 86 patients (95 hips) were still alive. The fate of all original stems is known. The 16-year survivorship with re-operation for any reason was 80.7% (95% confidence interval 72 to 89.4). There was no loss to follow-up, with clinical data available on all 95 hips and radiological assessment performed on 90 hips (95%). At latest follow-up, the mean Harris hip score was 78 (28 to 100) and the mean Oxford hip score was 36 (15 to 48). Stems subsided within the cement mantle, with a mean subsidence of 2.1 mm (0.4 to 19.2). Among the original cohort, only one stem (0.5%) has been revised due to aseptic loosening. In total seven stems were revised for any cause, of which four revisions were required for infection following revision of the acetabular component. A total of 21 patients (11%) required some sort of revision procedure; all except three of these resulted from failure of the acetabular component. Cemented acetabular components had a significantly lower revision burden (three hips, 2.7%) than Harris Galante uncemented components (17 hips, 21.8%) (p < 0.001). The CPT stem continues to provide excellent radiological and clinical outcomes at 15 years following implantation. Its results are consistent with other polished tapered stem designs

Aims. Periprosthetic hip fractures (PPFs) after total hip arthroplasty are difficult to treat. Therefore, it is important to identify modifiable risk factors such as stem selection to reduce the occurrence of PPFs. This study aimed to clarify differences in fracture torque, surface strain, and fracture type analysis between three different types of cemented stems. Methods. We conducted biomechanical testing of bone analogues using six cemented stems of three different types: collarless polished tapered (CPT) stem, Versys Advocate (Versys) stem, and Charnley-Marcel-Kerboull (CMK) stem. Experienced surgeons implanted each of these types of stems into six bone analogues, and the analogues were compressed and internally rotated until failure. Torque to fracture and fracture type were recorded. We also measured surface strain distribution using triaxial rosettes. Results. There was a significant difference in fracture torque between the three stem types (p = 0.036). Particularly, the median fracture torque for the CPT stem was significantly lower than that for the CMK stem (CPT vs CMK: 164.5 Nm vs 200.5 Nm; p = 0.046). The strain values for the CPT stem were higher than those for the other two stems at the most proximal site. The fracture pattern of the CPT and Versys stems was Vancouver type B, whereas that of the CMK stem was type C. Conclusion. Our study suggested that the cobalt-chromium alloy material, polished surface finish, acute-square proximal form, and the absence of a collar may be associated with lower fracture torque, which may be related to PPF. Cite this article: Bone Joint Res 2022;11(5):270–277

Background. Periprosthetic femoral fractures following total hip arthroplasty are relatively uncommon but are associated with significant morbidity. With an increasing number of total hip arthroplasties being carried out in an aging population we need to ensure correct implants are chosen for our patients. A recent review of NJR data suggested a significantly higher revision risk for the Zimmer CPT stems due to periprosthetic fractures when compared to the Stryker Exeter stems. Objectives. Our aim was to compare the biomechanics of periprosthetic fractures around the CPT and Exeter V40 stems in a composite saw bone model to identify if a difference in fracture risk exists between the two stems. We also compared the engineering design of the two implants in order to analyse the possible effect this may have on fracture risk. Study Design & Methods. Fourteen composite femurs were divided into two groups and cemented using Palacos R cement with either the CPT or Exeter V40 stem by a single surgeon. The implanted femurs were then mounted onto an Instron machine and were axially loaded and torqued to fracture with an axial compressive force of 2000N over 10 seconds followed by a rotation of 40 degrees applied over 1 second. A power calculation from a previous composite saw bone model study suggested that a minimum of 6 implanted femurs would be required in each group. Results. The implanted femurs invariably sustained fracture patterns similar to the Vancouver B2 periprosthetic fracture which are commonly seen in clinical practice. Implanted femurs with CPT stems suffered periprosthetic fractures with less rotation when compared to those femurs with the Exeter V40 stem (20.10 versus 33.60, p<0.01). We also found that CPT implanted femurs were fracturing at significantly lower torque values when compared to the Exeter V40 implanted femurs (124Nm Versus 174Nm, p<0.01). The energy release rate (G111) for CPT stems was 21.8Nm compared to 61.2Nm for Exeter V40 stems. The higher energy release with Exeter stems led to more comminuted fractures in Exeter implanted femurs when compared to the CPT femurs, which fractured earlier, but with simpler fracture patterns. Finite element method (FEM) simulation analysis showed that fractures initiated between the prosthesis and cement at the proximal end of the femur. Two dimensional sections at the same height showed a difference in bone-cement-implant geometrics at the critical point of failure suggesting that a design cause may be the reason for the higher risk of periprosthetic fractures in CPT implanted femurs. Conclusions. Our observations may explain the higher revision risk secondary to periprosthetic fractures that has been observed with the CPT stem when compared to the Exeter V40 stem

There is little evidence on the cost effectiveness of different brands of hip prostheses. We compared lifetime cost effectiveness of frequently used brands within types of prosthesis including cemented (Exeter V40 Contemporary, Exeter V40 Duration and Exeter V40 Elite Plus Ogee), cementless (Corail Pinnacle, Accolade Trident, and Taperloc Exceed) and hybrid (Exeter V40 Trilogy, Exeter V40 Trident, and CPT Trilogy). We used data from three linked English national databases to estimate the lifetime risk of revision, quality-adjusted life years (QALYs) and cost. . For women with osteoarthritis aged 70 years, the Exeter V40 Elite Plus Ogee had the lowest risk of revision (5.9% revision risk, 9.0 QALYs) and the CPT Trilogy had the highest QALYs (10.9% revision risk, 9.3 QALYs). Compared with the Corail Pinnacle (9.3% revision risk, 9.22 QALYs), the most commonly used brand, and assuming a willingness-to-pay of £20 000 per QALY gain, the CPT Trilogy is most cost effective, with an incremental net monetary benefit of £876. Differences in cost effectiveness between the hybrid CPT Trilogy and Exeter V40 Trident and the cementless Corail Pinnacle and Taperloc Exceed were small, and a cautious interpretation is required, given the limitations of the available information. However, it is unlikely that cemented brands are among the most cost effective. Similar patterns of results were observed for men and other ages. The gain in quality of life after total hip arthroplasty, rather than the risk of revision, was the main driver of cost effectiveness. Cite this article: Bone Joint J 2015;97-B:762–70

Introduction. Natural population variation in femoral morphology results in a large range of offsets, anteversion angles and lengths. During total hip arthroplasty, accurate restoration of hip biomechanics is essential to achieve good functional results. One option is to restore the anatomic hip rotation center. Alternatively, medializing the rotation center and compensating by increasing the femoral offset, reduces acetabular contact forces and increases the abductor lever arm. We investigated the ability of two cemented stem systems to restore hip biomechanics in an anatomic and medialized way. We compared an undersized “Exeter-type” of stem with three offset options and 18 sizes (CPT, Zimmer), to a line-to-line “Kerboul-type” of stem with proportional offset and 12 sizes (Centris, Mathys). Methods. Thirty CT scans of whole femora were segmented and the hip rotation center, proximal femoral axis and femoral length were determined with Mimics and 3-matic (Materialise). Using scripting functionality in the software, CAD design files of both stems were automatically sized and aligned along the proximal femoral axis to restore an anatomical and a 5 mm medialized hip rotation center. Stem size and position could be fine-tuned manually. The maximum distances between the prosthetic (PRC), the anatomic (ARC) and the medialized hip rotation center (MRC) were calculated (Fig. 1). Variations in femoral offset (ΔFO), anteroposterior (ΔAP) and proximodistal distance (ΔPD) were analyzed. Finally, the number of cases where the hip rotation center could be restored within 5 mm was reported. Results. Both implants allowed restoring the ARC accurately (mean distance PRC-ARC: CPT 0.97±0.88 mm, Centris 1.66±1.59 mm; mean difference ΔFO: CPT 0.09±0.19 mm, Centris 0.11±0.29 mm; mean difference ΔAP: CPT 0.12±1.22°, Centris 0.27±1.78 mm, mean difference ΔPD: CPT 0.04±0.44 mm, Centris 0.49±1.35 mm). The CPT stem allowed restoring the PRC within 5 mm of the ARC in all cases (max. 4.31 mm), whereas the Centris stem achieved this in only 28/30 hips (max. 6.72 mm) (Fig. 2). Aiming for a MRC was less satisfactory with both stems (mean distance PRC-MRC: CPT 1.38±1.63 mm, Centris 3.61±2.73 mm; mean difference ΔFO: CPT 0.09±0.10 mm, Centris 0.06±0.35 mm; mean difference ΔAP: CPT 0.17±2.02 mm, Centris 2.58±2.68 mm, mean difference ΔDP; CPT 0.28±0.67 mm, Centris 1.98±1.66 mm). The CPT stem allowed restoring the PRC within 5 mm of the MRC in 29/30 cases (max. 8.09 mm), whereas the Centris stem achieved this in only 25/30 cases (max. 11.15 mm) (Fig. 3). Discussion. Although both stem systems allowed restoring hip biomechanics accurately in most cases, the CPT system was superior to the Centris stem for achieving both ARC and MRC. This could be explained by more implant sizes (18 vs. 12) and undersized stems offering more freedom to correct version. Although medializing the hip rotation center offers biomechanical advantages, both stems had more difficulties achieving this. In some cases, differences between aimed and planned rotation centers were close to 1 cm which might negatively impact on clinical outcome. As such, to avoid suboptimal reconstructions with the available implants, templating is mandatory especially when aiming at a medialized reconstruction strategy

Introduction. The French paradox regarding cemented femoral components has not been resolved, so we compared the mechanical behavior of a French stem, the CMK stem (Biomet, Warsaw, IN, USA), with a collarless, polished, tapered stem (CPT, Zimmer, Warsaw, IN, USA) using an original biomechanical instrument. Materials and Methods. Two size-3 CPT stems and two size-302 CMK stems stems were fixed with bone cement into a composite femur soaked in vegetable oil to simulate wet condition. The composite femur was attached to a biomechanical testing instrument after stem implantation, and a 1-Hz dynamic sine wave load (3000 N) was applied to the stems for a total of 1 million cycles. An 8-hour unload period was set after every 16 hours of load. Femur temperature was maintained at 37°C during testing. The femoral canal was prepared for the CPT stems by standard rasping; for the CMK stems, however, the French method was used, in which cancellous bone was removed with a reamer. One CMK stem (CMK-1) was inserted into a femur without collar contact (>2 mm above the calcar), and the other (CMK-2) was inserted into a femur with collar contact. Stem subsidence was measured at the stem shoulder. Compressive force and horizontal cement movement were measured via rods set at the cement–bone interface on the medial, lateral, anterior, and posterior sides of the proximal and distal portions of the composite femurs. Results. Subsidence was as follows: 0.521 mm and 0.629 mm for the CPT stems, 0.46 mm for CMK-1, and 0.36 mm for CMK-2. Compressive force at the cement–bone interface was at the maximum level at the proximomedial portion of all stems. These forces increased gradually until the one-millionth loading. Maximum compressive forces were 183 N and 107 N for the CPT stems, 180 N for CMK-1, and 215 N for CMK-2. There was a strong positive correlation between stem subsidence and compressive force in all stems. Radial cement creep at the proximomedial portion was 90 μ for one of the CPT stems, 184 μ for CMK-1, and −636 μ for CMK-2. Discussion. We previously reported our findings of a positive correlation between stem subsidence and compressive force in CPT stems. In the current study, CMK stems also subsided even when there was stem collar contact with bone. Subsidence was less in CMK stems than in CPT stems, but the values were close. In addition, compressive force and radial cement creep in CMK stems were also similar to or greater than in CPT stems. Conclusion. The two different concept stems demonstrated similar behavior in relation to bone cement, a finding that may present a solution to the French paradox

Aims. Periprosthetic fracture (PF) after primary total hip arthroplasty (THA) is an uncommon but potentially devastating complication. This study aims to investigate the influence of cemented stem designs on the risk of needing a revision for a PF. Patients and Methods. We analysed data on 257 202 primary THAs with cemented stems and 390 linked first revisions for PF recorded in the National Joint Registry (NJR) of England, Wales and Northern Ireland to determine if a cemented femoral stem brand was associated with the risk of having revision for a PF after primary THA. All cemented femoral stem brands with more than 10 000 primary operations recorded in the NJR were identified. The four most commonly used cemented femoral stems were the Exeter V40 (n = 146 409), CPT (n = 24 300), C-Stem (n = 15 113) and Charnley (n = 20 182). We compared the revision risk ratios due to PF amongst the stems using a Poisson regression model adjusting for patient factors. Compared with the Exeter V40, the age, gender and ASA grade adjusted revision rate ratio was 3.89 for the cemented CPT stem (95% confidence interval (CI) 3.07 to 4.93), 0.89 for the C-Stem (95% CI 0.57 to 1.41) and 0.41 for the Charnley stem (95% CI 0.24 to 0.70). Conclusions. The limitations of the study include incomplete data capture, analysis of only PF requiring revision and that observation does not imply causality. Nevertheless, this study demonstrates that the choice of a cemented stem may influence the risk of revision for PF. Cite this article: Bone Joint J 2016;98-B:1347–54

Introduction. This is a report of the outcome of management of congenital pseudoarthrosis of the tibia (CPT) at skeletal maturity. Materials and Methods. Retrospective study. Inclusion criteria:. CPT Crawford IV. Skeletally maturity. Availability of radiographs and medical records. Outcome: union rate, healing time, residual deformities, ablation and refracture. Results. 23 patients who reached maturity were analysed. Time to union was 7.6 months. Union rate 70%. External fixation group: 7 patients, age 6.1 years, all united, 1 needed Bone graft. Average union time 8.2 months, no residual mal-alignment, no amputations, 2/7 needed corrective osteotomies and residual LLD in 2/7 < 1 cm. Numbers of surgery was 3. Vascularized fibular graft was done in 3 cases; all had failed previous attempts. Union time was 7 months. 2/3 united, 1 had amputation due to extensive disease. All patients had residual mal-alignment. Rodding group included 13 patients, age 3.2 years, union rate 61%, union time 8.3 months. Average LLD 1 cm with 1 patient LLD > 2 cm. Residual knee mal-alignment in 2/13, 4 had procurvatum and 55% of patients had ankle valgus. Fibula pseudoarthrosis. Refracture was reported in 53% of the rodding group. The causes of refracture were mal-alignment in 3, traumatic in 2 and idiopathic in 2. Total surgeries no 5. 2 patients had amputations after an unsuccessful 1. st. attempt. Our current trend of treatment was applied on 8 patients. They are not skeletally mature yet. the treatment combined excision of hamartoma, tibial rodding, wrapped periosteal graft with/out neutralization frame, and fibular fixation. Average age 3.8 years, union time was 10 months, Union rate 80%, no residual deformities. Conclusions. Our study shows the evolution of the treatment of CPT with increasing union rate, fewer residual deformities, and numbers of surgeries with more recent techniques

The Masquelet technique, also known as the ‘induced membrane technique’ has been utilised in adult reconstruction with varied success. However, there is limited literature on its use in children and this study aims to share our experience. Materials & Methods. Between 2014 and 2022, 7 children underwent bone defect/infection reconstruction using Masquelet technique, four for complications of Congenital Pseudoarthrosis of Tibia (CPT) treatment, two with chronic osteomyelitis and one for Osteogenesis imperfecta with infected nonunion. The length of the defect relative to the length of the bone (index of reconstruction expressed as a percentage), time to union and complications were evaluated with standard radiographs and from electronic medical records. Results. The mean age was 11 years and the procedure was done in five tibiae, one femur and a metatarsal. The mean time interval was 7.1 weeks between the first and second stage surgery. The mean index of reconstruction was 25.8% and the mean follow up period was 17 months. Though six patients achieved union with a mean time to union of 6.5 months (range 4.5 to 10), two patients with multiple previous surgeries for CPT decided to have ablation despite union. The interosseous Masquelet technique of cross synostosis between the tibia and fibula is being highlighted. Conclusions. The Masquelet technique is a reliable method in complex aetiologies and complications that require methodical planning to achieve good results especially in rescue situations of the tibia

Periprosthetic joint infections (PJIs) centers are garnering the attention of different arthroplasty surgeons and practices alike. Nonetheless, their value has yet to be proven. Therefore, we evaluated weather PJI centers produce comparable outcomes to the national average of THA PJIs on a national cohort. We performed a retrospective review of patient data available on PearlDiver from 2015 – 2021. PJI THA cases were identified through ICD-10 and CPT codes. Patients treated by 6 fellowship trained arthroplasty surgeons from a PJI center were matched based on age, gender, Charlson Comorbidity Index and Elixhauser comorbidity index at a 1:1 ratio to patients from the national cohort. Compared outcomes included LOS, ED visits, number of patients readmitted, total readmissions. Sample sized did not allow the evaluation of amputation, fusion or explantation. Normality was tested through the Kolmogorov-Smirnov test. And comparisons were made with Students t-tests and Chi Square testing. A total of 33,001 THA PJIs and were identified. A total of 77 patients were identified as treated by the PJI center cohort and successfully matched. No differences were noted in regard to age, gender distribution, CCI or ECI (p=1, 1, 1 and 0.9958 respectively). Significant differences were noted in mean LOS (p<0.43), number of patients requiring readmissions (p=0.001) and total number of readmission events (p<0.001). No difference was noted on ED visits. Our study demonstrates that a PJI for THA cases may be beneficial for the national growing trend of arthroplasty volume. Future data, that allows comparison of patient's specific data will allow for further validation of PJI centers and how these can play a role in helping the national PJI growing problem

To investigate predictors of periprosthetic fracture level (around stem (Vancouver B) or distal to stem (Vancouver C/D) in cemented polished tapered femoral stems. Retrospective cohort study of 188 patients (mean age 79 (range 30–91); 99 (53%) male) with unilateral periprosthetic femoral fractures associated with CPT stems. Medical notes were reviewed and the following recorded: patient demographics, past medical history, drug history, date of prosthesis insertion, and date of injury. Radiographs analysis included Vancouver classification, cement restrictor type, cement mantle to implant tip distance, cortical thickness, femoral diameter and DORR classification. Univariate, multivariate and ROC curve analysis was performed. Fractures occurred at mean 7.5 years following primary procedure: 152 (83%) were B fractures; and 36 (19%) C/D. On univariate analysis female gender, lower BMI, osteoporosis, NSAID use, Bisphosphonate therapy, cortical thickness, distal cement mantle length and distal cement mantle length:femoral diameter ratio were significantly associated with C level fractures (p<0.05). Distal cement mantle lengths of >19.6mm (AUC 0.688, p<0.001) were associate with C level fractures. Multivariate analysis demonstrated female gender and distal cement mantle length:femoral diameter ratio to be independent predictors of C level periprosthetic fractures. Though female sex is the largest independent predictor of periprosthetic fractures distal to a CPT femoral stem, the relationship between cortical thickness and distal cement mantle length appears significant. As fractures distal to the stem are invariably managed by ORIF, whereas fractures around the stem frequently require revision arthroplasty, this has relevance at primary surgery in osteoporotic females to reduce the need for complex revisions

Introduction. In cemented total hip arthroplasty (THA), proper cement mantle thickness in the femoral canal is still controversial subject. It is widely accepted that the cement mantle around a femoral stem should be at least 2 mm in thickness. But articles from France reported good long-term result with thin cement mantle. It is so called “The French paradox”. We have already reported that the greater compressive force at the cement-bone interface was seen in collarless polished tapered (CPT, Zimmer, USA) stem with thick cement mantle than that with thin cement mantle. However, the stem with thick cement mantle subsided more than with thin mantle. It may have a possibility to cause an early mechanical failure of cemented THA. We compared to stem and cement subsidence in various cement mantles using tantalum ball into cement in this study. Methods. A cemented stem model was used for this study with a CPT stem into composite femur. Three sizes of CPT stems (No. 1, No. 2 and No. 3) and one size composite femur were prepared for this study. We inserted two stems for each size, for a total of six stems. Composite femurs were reamed with a No. 3 rasp, and various size of stem was fixed with cement in each composite femur to make a various thicknesses of cement mantle. Two to three tantalum marker balls were injected into the cement in each femur before cement was hardened. 1-Hz dynamic load applied to the stems for half a-million cycles. Each 16 hours of loading was followed by 8 hours without loading. We used micro-CT before and after loading to measure the movement of the tantalum balls in three dimensions. And we analyzed occupation ratio of stem in the femoral canal by computed reconstructed three dimensional model of bone cement and stem. Results. We were able to detect a total of 13 balls in the cement for the 6 stems. The range of cement thickness in the CT slice on balls was 1.52 to 5.32 mm. Stem subsidence showed a significantly positive correlation to the thickness of cement mantle. In the horizontal plane, 8 of these 13 balls moved in an outside direction and five moved in an inside direction. The horizontal/perpendicular ratio for the tantalum balls showed a significant negative correlation to the thickness of the cement mantle. The subsidence rate (ratio of stem subsidence to ball subsistence) showed a significant negative correlation to the stem occupation ratio. The effective radial cement creep was also detected when the cement mantle was less than 2.5 mm thick and more than 60% in the occupation ratio. Conclusions. Stem subsistence was more commonly associated with cement subsidence in the thicker cement mantles and with a low stem occupation rate in CPT stems

Objectives. Favourable results for collarless polished tapered stems have been reported, and cement creep due to taper slip may be a contributing factor. However, the ideal cement thickness around polished stems remains unknown. We investigated the influence of cement thickness on stem subsidence and cement creep. Methods. We cemented six collarless polished tapered (CPT) stems (two stems each of small, medium and large sizes) into composite femurs that had been reamed with a large CPT rasp to achieve various thicknesses of the cement mantle. Two or three tantalum balls were implanted in the proximal cement in each femur. A cyclic loading test was then performed for each stem. The migration of the balls was measured three-dimensionally, using a micro-computed tomography (CT) scanner, before and after loading. A digital displacement gauge was positioned at the stem shoulder, and stem subsidence was measured continuously by the gauge. Final stem subsidence was measured at the balls at the end of each stem. Results. A strong positive correlation was observed between mean cement thickness and stem subsidence in the CT slices on the balls. In the small stems, the balls moved downward to almost the same extent as the stem. There was a significant negative correlation between cement thickness and the horizontal:downward ratio of ball movement. Conclusion. Collarless polished tapered stems with thicker cement mantles resulted in greater subsidence of both stem and cement. This suggests that excessive thickness of the cement mantle may interfere with effective radial cement creep. Cite this article: E. Takahashi, A. Kaneuji, R. Tsuda, Y. Numata, T. Ichiseki, K. Fukui, N. Kawahara. The influence of cement thickness on stem subsidence and cement creep in a collarless polished tapered stem: When are thick cement mantles detrimental? Bone Joint Res 2017;6:–357. DOI: 10.1302/2046-3758.65.BJR-2017-0028.R1

CPT is a uniquely difficult condition, often associated with Neurofibromatosis (NF1), where bone healing is compromised. Although rare, the severity of this condition and the multiple procedures often entailed in treating it, warrant research attention. As study material is limited, animal models of the disorder are desirable for testing new treatments. We sought to create a model of CPT where both copies of the NF1 gene were ablated at the fracture site, as has been found in some clinical specimens. NF1 floxed mice had fracture surgery; both closed fracture and open osteotomy were performed. Either a Cre- or control GFP-adenovirus was injected into the fracture site at day zero. Recombination was confirmed in ZAP reporter mice. Additionally, cell culture studies were used to examine the possible responses of NF1+/+ (wild type) NF1+/− or NF1−/− to drugs which may rescue the dysregulated Ras/MAPK pathway in NF1. In closed fractures, radiographic bridging was 100% in NF1+/+ calluses and <40% in NF1−/− calluses (P<0.05). In open fractures, radiographic bridging was 75% in NF1+/+ calluses and <30% in NF1−/− calluses (P<0.05). In both fracture repair models the NF1−/− state was associated with a significant up to 15-fold increase in fibrotic tissue invading the callus by week 3. In NF1−/− fractures, large numbers of TRAP+ cells were observed histologically in the fibrotic tissue. Closed fractures also showed a significant increase in BRDU labelled proliferating cells in the callus. In cell culture models of NF1 deficient osteogenesis, NF1−/− progenitors were found to be significantly impaired in their capacity to form a calcified matrix as measured by Alizarin Red S staining and osteogenic markers (Runx2, Osteocalcin, Alp expression). However, when differentiated calvarial NF1 floxed osteoblasts were treated with Cre adenovirus, mineralization was not affected, suggesting that NF1 impacts on osteogenic differentiation rather than mature cell function. Treatment with MEK inhibitor PD0325901 was found to rescue the NF1−/− progenitor differentiation phenotype and permit robust mineralization. Treatment with the JNK inhibitor SP600125 was also able to improve ALP activity and mineralization in NF1+/− osteoprogenitors compared to control cells. This model of NF1 −/− induction at a fracture or osteotomy site closely replicates the clinical condition of CPT, with lack of bone healing and fibrous tissue invasion. Underlying defects in bone cell differentiation in NF1 deficiencies can be at least partially rescued by JNK and MEK inhibitors

Thumb carpometacarpal (CMC) arthritis is a common and disabling condition that can be treated with an operative procedure. Before operative measures, patients typically undergo conservative treatment utilizing methods such as physical therapy and injections. This study aims to determine what clinical modalities are being used for preoperative evaluation and nonoperative therapy and the associated cost prior to operative intervention. We queried Truven Market Scan, a large insurance provider database to identify patients undergoing CMC arthroplasty from 2010 to 2017. Patients were identified by common Current Procedural Terminology (CPT) codes for CMC arthroplasty. All associated CPT codes listed for each patient during the 1 year period prior to operative intervention were collected and filtered to only include those codes associated with the ICD-9/10 diagnosis codes relating to CMC arthritis. The codes were then categorized as office visits, x-ray, injections, physical therapy, medical devices, and preoperative labs. The frequency and associated cost for each category was determined. There were 44,676 patients who underwent CMC arthroplasty during the study period. A total of $26,319,848.36 was charged during the preoperative period, for an average of $589.13 per patient. The highest contributing category to overall cost was office visits (42.1%), followed by injections (13.5%), and then physical therapy (11.1%). The most common diagnostic modality was x-ray, which was performed in 74.7% of patients and made up 11.0% of total charges. Only 49% of patients received at least one injection during the preoperative period and the average number of injections per patient was 1.72. Patients who were employed full time were more likely to receive two or more injections prior to surgery compared to patients who had retired (47% of full-time workers; 34% of retirees). The modalities used for the preoperative evaluation and conservative treatment of CMC arthritis and the associated cost are important to understand in order to determine the most successful and cost-effective treatment plan for patients. Surprisingly, despite the established evidence supporting clinical benefits, many patients do not undergo corticosteroid injections. With office visits being the largest contributor to overall costs, further inquiry into the necessity of multiple visits and efforts to combine visits, can help to reduce cost. Also, with the advent of telemedicine it may be possible to reduce visit cost by utilizing virtual medicine. Determining the best use of telemedicine and its effectiveness are areas for future investigation

Aim. Intracellular persistence of S. aureus is believed to be one of the major mechanisms leading to bone and joint infection (BJI) chronicity and relapses. Despite its poor intracellular activity, daptomycin (DAP) is increasingly used in the treatment of staphylococcal BJI. The well-known in vitro synergy of daptomycin with various betalactam antibiotics consequently led us to investigate whether these combinations enhance the activity of daptomycin against the intracellular reservoir of methicillin-susceptible (MSSA) and -resistant (MRSA) S. aureus in an ex-vivo model of human osteoblast infection. Method. Osteoblastic MG63 cells were infected for 2h with MSSA strain or its isogenic MRSA. After killing the remaining extracellular bacteria with lysostaphin, infected cells were then incubated for 24h with DAP, oxacillin (OXA) or ceftaroline (CPT) alone or in combination, at the intraosseous concentrations reached with standard human therapeutic doses. Intracellular bacteria were then quantified by plating cell lysates. Minimum inhibitory concentrations (MICs) of these molecules alone and in combination were determined using the checkerboard method at pH7, but also at pH5 to mimic intracellular conditions. Results. Compared to untreated cells, DAP reduced significantly intracellular inoculum for MRSA only (p<10–3). OXA and CPT were active on MSSA and MRSA (p<0.05 for all). The OXA-DAP combination reduced the intracellular inoculum of MSSA and MRSA more efficiently than antibiotic alone (p<0,05). In contrast, no synergy was observed with the association DAP-CPT. Decrease of the intracellular inoculum compared to untreated cells. In vitro, an important increase in DAP MICs was observed at acidic pH for the two strains (0.3 (pH7) to 2mg/L (pH5)). On the contrary, decreasing pH from 7 to 5 led to a drop in OXA MICs from 0.5 to 0.1mg/L for MSSA and from 128 to 0.5mg/L for MRSA. Conclusions. Our results confirm the low activity of DAP against intra-osteoblastic S. aureus, probably due to its inactivation by acidic pH condition encountered in lysosomes. On the opposite, betalactams are still active in intracellular compartment, including OXA on MRSA due to an acidic pH-related activity restauration. The OXA-DAP combination allows amplifying the intracellular effect of DAP on MSSA and MRSA. This synergy is not observed with CPT

An analysis of the cement mantle obtained with the Exeter impaction allografting system at one centre showed that it was either deficient or absent in almost 47% of Gruen zones. We therefore examined the mantle obtained using this system at another hospital and compared the results with those from the CPT and Harris Precoat Systems at other centres. The surgical indications for the procedure and the patient details were broadly similar in all four hospitals. There was some variation in the frequency of use of cortical strut allografts, cerclage wires and wire mesh to supplement the impaction allograft. Analysis of the cement mantles showed that when uncertain Gruen zones were excluded, the incidence of zones with areas of absence or deficiency of the cement was 47% and 50%, respectively, for the two centres using the Exeter system, 21% for the CPT system and 18% for the Harris Precoat system. We measured the difference in size between the proximal allograft impactors and the definitive prosthesis for each system. The Exeter system impactors are shorter than the definitive prosthesis and taper sharply so that the cavity created is inadequate, especially distally. The CPT proximal impactors are considerably longer than the definitive prosthesis and are designed to give a mantle of approximately 2 mm medially and laterally and 1.5 mm anteriorly and posteriorly. The Harris Precoat proximal impactors allow for a mantle with a circumference of 0.75 mm in the smaller sizes and 1 mm in the larger. Many reports link the longevity of a cemented implant to the adequacy of the cement mantle. For this reason, femoral impaction systems require careful design to achieve a cement mantle which is uninterrupted in its length and adequate in its thickness. Our results suggest that some current systems require modification

Functional evaluations using the Harris hip scoring system and the delayed Trendelenberg test were performed on fifty randomly selected patients who had undergone cemented primary CPT total hip replacements (Zimmer UK) at least 12 months previously using Hardinge approach. The prosthesis used increases offset with femoral stem diameter but did not allow separate correction of neck offset. Patients were grouped according to whether hip offset had been accurately reconstructed, increased or decreased. Their functional outcomes were compared. There was no significant difference (p value 0.57) in the final functional outcome between the three groups. Reconstruction of the hip using a standard cemented CPT prosthesis produced considerable variation in the reconstructed hip arthroplasty offset. This resulted in no functionally significant effect. Accurate reconstruction of the hip joint offset in total hip arthroplasty may therefore not be as important in the early functional outcome as recently advocated