Objectives. Intramedullary fixation is considered the most stable treatment for pertrochanteric fractures of the proximal femur and cut-out is one of the most frequent mechanical complications. In order to determine the role of clinical variables and radiological parameters in predicting the risk of this complication, we analysed the data pertaining to a group of patients recruited over the course of six years. Methods. A total of 571 patients were included in this study, which analysed the incidence of cut-out in relation to several clinical variables: age; gender; the AO Foundation and Orthopaedic Trauma Association classification system (AO/OTA); type of nail; cervical-diaphyseal angle; surgical wait times; anti-osteoporotic medication; complete post-operative weight bearing; and radiological parameters (namely the lag-screw position with respect to the femoral head, the Cleveland system, the tip-apex distance (TAD), and the calcar-referenced tip-apex distance (CalTAD)). Results. The incidence of cut-out across the sample was 5.6%, with a higher incidence in female patients. A significantly higher risk of this complication was correlated with lag-screw tip positioning in the upper part of the femoral head in the anteroposterior radiological view, posterior in the latero-lateral radiological view, and in the Cleveland peripheral zones. The tip-apex distance and the calcar-referenced tip-apex distance were found to be highly significant predictors of the risk of cut-out at cut-offs of 30.7 mm and 37.3 mm, respectively, but the former appeared more reliable than the latter in predicting the occurrence of this complication. Conclusion. The tip-apex distance remains the most accurate predictor of cut-out, which is significantly greater above a cut-off of 30.7 mm. Cite this article: G. Caruso, M. Bonomo, G. Valpiani, G. Salvatori, A. Gildone, V. Lorusso, L. Massari. A six-year retrospective analysis of cut-out risk predictors in cephalomedullary nailing for pertrochanteric fractures: Can the tip-apex distance (TAD) still be considered the best parameter?. Bone Joint Res 2017;6:481–488. DOI: 10.1302/2046-3758.68.BJR-2016-0299.R1

Objectives. Because of the contradictory body of evidence related to the potential benefits of helical blades in trochanteric fracture fixation, we studied the effect of bone compaction resulting from the insertion of a proximal femoral nail anti-rotation (PFNA). . Methods. We developed a subject-specific computational model of a trochanteric fracture (31-A2 in the AO classification) with lack of medial support and varied the bone density to account for variability in bone properties among hip fracture patients. Results. We show that for a bone density corresponding to 100% of the bone density of the cadaveric femur, there does not seem to be any advantage in using a PFNA with respect to the risk of blade cut-out. On the other hand, in a more osteoporotic femoral head characterised by a density corresponding to 75% of the initial bone density, local bone compaction around the helical blade provides additional bone purchase, thereby decreasing the risk of cut-out, as quantified by the volume of bone susceptible to yielding. Conclusions. Our findings indicate benefits of using a PFNA over an intramedullary nail with a conventional lag screw and suggest that any clinical trial reporting surgical outcomes regarding the use of helical blades should include a measure of the femoral head bone density as a covariable

Aims. Proximal femur fractures treatment can involve anterograde nailing with a single or double cephalic screw. An undesirable failure for this fixation is screw cut-out. In a single-screw nail, a tip-apex distance (TAD) greater than 25 mm has been associated with an increased risk of cut-out. The aim of the study was to examine the role of TAD as a risk factor in a cephalic double-screw nail. Methods. A retrospective study was conducted on 112 patients treated for intertrochanteric femur fracture with a double proximal screw nail (Endovis BA2; EBA2) from January to September 2021. The analyzed variables were age, sex, BMI, comorbidities, fracture type, side, time of surgery, quality of reduction, pre-existing therapy with bisphosphonate for osteoporosis, screw placement in two different views, and TAD. The last follow-up was at 12 months. Logistic regression was used to study the potential factors of screw cut-out, and receiver operating characteristic curve to identify the threshold value. Results. A total of 98 of the 112 patients met the inclusion criteria. Overall, 65 patients were female (66.3%), the mean age was 83.23 years (SD 7.07), and the mean follow-up was 378 days (SD 36). Cut-out was observed in five patients (5.10%). The variables identified by univariate analysis with p < 0.05 were included in the multivariate logistic regression model were screw placement and TAD. The TAD was significant with an odds ratio (OR) 5.03 (p = 0.012) as the screw placement with an OR 4.35 (p = 0.043) in the anteroposterior view, and OR 10.61 (p = 0.037) in the lateral view. The TAD threshold value identified was 29.50 mm. Conclusion. Our study confirmed the risk factors for cut-out in the double-screw nail are comparable to those in the single screw. We found a TAD value of 29.50 mm to be associated with a risk of cut-out in double-screw nails, when good fracture reduction is granted. This value is higher than the one reported with single-screw nails. Therefore, we suggest the role of TAD should be reconsidered in well-reduced fractures treated with double-screw intramedullary nail. Cite this article: Bone Jt Open 2024;5(6):457–463

Lag screw cut-out is a serious complication of dynamic hip screw fixation in trochanteric hip fractures. Lag screw position is recognised as a crucial factor influencing the occurrence of lag screw cut-out. We propose a modification of the Tip Apex Distance (TAD) and hypothesize that it could enhance the reliability of predicting lag screw cut-out in these injuries. A retrospective study of hip fracture cases was conducted from January 2018 to July 2022. A total of 109 patients were eligible for the final analysis. The modified TAD was measured in millimetres, based on the sum of the traditional TAD in the lateral view and the net value of two distances in the anteroposterior (AP) view. The first distance is from the lag screw tip to the opposite point on the femoral head along the lag screw axis, while the second distance is from that point to the femoral head apex. The first distance is a positive value, whereas the second distance is positive if the lag screw is superior and negative if it is inferior. Receiver operating characteristic (ROC) curve analysis was used to assess the reliability of various parameters for evaluating the lag screw position within the femoral head. Factors such as reduction quality, fracture pattern according to the AO/OTA classification, TAD, Calcar-Referenced TAD, Axis Blade Angle, Parker’s ratio in the AP view, Cleveland Zone 1, and modified TAD were statistically associated with lag screw cut-out. Among the tested parameters, the novel parameter exhibited 90.1% sensitivity and 90.9% specificity for predicting lag screw cut-out at a cut-off value of 25 mm, with a p-value < 0.001. The modified TAD demonstrated the highest reliability in predicting lag screw cut-out. A value of 25 mm may potentially reduce the risk of lag screw cut-out in trochanteric hip fractures

Introduction. The purpose of the present study was to identify risk factors for lag-screw cut-out following osteosynthesis of intertrochanteric fractures. Materials and methods. The study was a case-control study using a sex and age matched control group. The fractures were classified according to Evans and OTA/AO classifications. Operative treatment was performed using dynamic hip-screw or cephalomedullary nailing systems. All patients were followed for at least 3–4 months postoperatively. The following risk factors were assessed: fracture type, quality of reduction by blinded assessment using a visual analogue scale, tip-apex distance (TAD) according to Baumgaertner, lag-screw positioning and other relevant additional risk factors in terms of walking ability, osteoporosis, cardio-vascular disease, neurological disease, diabetes, obesity, alcohol consumption and smoking. Results. 35 cases with lag-screw cut-out and 122 controls without cut-out, 124 women with a mean age of 84.9 (range: 51–95) years and 33 men with a mean age of 82.3 (range: 67–94) years were identified. Cut-out were significantly more frequent in OTA/AO type 31-A3 fractures (odds ratio (OR) 4.13; 95% CI: 1.50–11.36). The quality of reduction was significantly related to the risk of cut-out. The mean TAD was 26.5 mm in the case group and 21 mm in the control group. This difference was significant (chi square test p=0.046). Assessment of the lag-screw positioning showed that a central/central (OR 0.18; 95 % CI: 0.11–0.30) or central/inferior (OR 0.14; 95 % CI: 0.03–0.63) position was associated with a reduced risk for cut-out. None of the additional risk factors included in this study seemed to have any influence on the results. Conclusion. This study showed that fracture type, quality of reduction, TAD and lag-screw positioning were the most important risk factors for cut-out

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

Introduction: Lag screw cut-out in gamma nailing is reported between 1,1% and 7.1% in the literature. Searching for predictive factors we performed a retrospective study, and we analyzed our cut-out cases. Material & Methods: We reviewed our first 1000 gamma nailings. A detailed analysis of the cut-out cases was performed. We focused on fracture type and the technical failures of the primary surgery. Fractures were classified according to AO. Timing of surgery, implant type and an estimated value of osteoporosis on x-ray was investigated. Distance of the tip of the lag screw from the cortical bone, from the ideal central line of the neck and head in AP and lateral view, and precision of reduction was measured and classified. We recorded the direction of cut-out and the occurrence of secondary varus displacement. Results: We had 29/1000 (2,9%) cut-outs. Average age was: 76 years. 14/29 (48%) AO A2.2 type and 8/29 (28%) A3.3 type fractures were found in the cut out group. Normal collo-diaphyseal angle was achieved in all cases primarily. In 21/29 (72%) the gap between main fragments was narrower than 5 mm, and in 8/29 (28%) it was bigger. The subjective evaluation of the reduction was 2/29 excellent, 9/29 good, 12/29 satisfactory and 6/29 bad. Primary position of the lag screw tip was caudal in 13/29, central in 10/29 and cranial in 6/29 cases. The distance of the lag screw from the central line in frontal/dorsal direction was 0–4 mm in 5/29, 5–9 mm in 12/29, 10–14 mm in 7/29 and 15–19 mm in 5/29 cases. The numbers of too short or too long lag screws were not high in this patient group. The cut out was cranial in 24/29 (83%) cases and central at 5/29 (17%) patients. We recorded 20/29 (68%) secondary varus displacement. We found 2/29 (7%) patients where none of the above mentioned technical problems could be justified. Conclusion: AO A2.2 and A3.3 fracture type is a predisposing factor. Cut-out appears relatively early. Correct positioning of the lag screw in both views is essential. Leaving the fracture in a significantly displaced position increases the risk of cut out, too. The lag screw migrates mainly cranial with a secondary varus dislocation. With adequate technique the majority of cut-outs can be avoided, but there is a little percentage of the cases when the primary mistake is not obvious. A possible explanation could be osteoporosis, but further investigation is necessary to clarify these unknown factors

Purpose: Purpose of the study is to compare the changing Tip Apex Distance (TAD) and therefore the cut out development risk during fracture healing in two different types of implant. Materials and Methods: 166 patients with intertrochanteric femur fracture were operated with proximal femoral nail between the years 1999 and 2006 in our clinic. 117 patients with avaible radiological data were studied. Group I defined as PFN, had 90 patients. Median age was 74.2 (25–93) years, 44 female and 46 male. Grup II defined as PFN-A had 27 patients. Median age was 75 (33–88) years, 18 females, 9 males. The mean of following time of patients was 48 months (12–84 months). We measured in AP radiograph the tip-apex distance (TAD) both of early postop and fracture healing time. Results: In group I change in TAD was observed in 70 (%77.7) patients. Average TAD change rate was %29 (%4–%230). In group II, change in TAD was observed in 15 (%55.6) patients, and the average TAD change rate was %12 (%5–%40). Among Group I, 3 patients had a revision surgery with cut-out complications (%3.3). Among Group II no patient had cut out complication. Discussion: While cut out was developed in 3 PFN patients, no cut-out was observed in any of PFN-A patients. Among the patients without cut-out development, 77.7 % of PFN patients and 55.6 % of PFN-A were under cut out risk. Average TAD change rate was 29% in PFN Group whereas 12% in PFN-A Group. When TAD change rates are considered, no cut-out was determined in PFN-A Group while its development risk was lower. When we investigate the cut out complication, the 3 cut out complications (%3.3) was seen in PFN. PFN-A group had no cut out complications

The failure rate of peritrochanteric fracture implants ranges from 5 to 20 % The aim of the present preliminary study is to evaluate the relationship between Singh index (SI), and failure of internal fixation (cut-out), examining bone mechanical properties from ex-vivo human femoral heads.

The failure rate of peritrochanteric fracture implants ranges from 5 to 20 % The aim of the present preliminary study is to evaluate the relationship between Singh index (SI), and failure of internal fixation (cut-out), examining bone mechanical properties from ex-vivo human femoral heads.

From a methodological point of view we decided to use SI on the basis of previous literature,, our data seems not to be influenced by the use of this methodological approach. > Three load speeds were set: 3, 10, 500 mm/min resulting values of BW/s were compared with Davy and Bergmann ones (obtained with instrumented prosthesis), and test validity was confirmed. In conclusion our data demonstrated that: cut out phenomenon occurs for lower mechanical load in femoral heads of patients with lower SI.

Aim. The most frequent mechanical failure in the osteosynthesis of intertrochanteric fractures is the cut-out. Fracture pattern, reduction quality, tip-apex distance or the position of the cervico-cephalic screw are some of the factors that have been associated with higher cut-out rates. To date, it has not been established whether underlying bacterial colonization or concomitant infection may be the cause of osteosynthesis failure in proximal femur fractures (PFF). The primary objective of this study is to assess the incidence of infection in patients with cut-out after PFF osteosynthesis. Method. Retrospective cohort study on patients with cut-out after PFF osteosynthesis with endomedullary nail, from January 2007 to December 2020. Demographic data of patients (such as sex, age, ASA), fracture characteristics (pattern, laterality, causal mechanism) and initial surgery parameters were collected (time from fall to intervention, duration of surgery, intraoperative complications). Radiographic parameters were also analyzed (tip-apex distance and Chang criteria). In all cut-out cases, 5 microbiological cultures and 1 anatomopathological sample were taken and the osteosynthesis material was sent for sonication. Fracture-related infection (FRI) was diagnosed based on Metsemakers et al (2018) and McNally et al (2020) diagnostic criteria. Results. Of the 67 cut-out cases, 16 (23.9%) presented clinical, analytical or microbiological criteria of infection. Of these sixteen patients, only in 3 of them the presence of an underlying infection was suspected preoperatively. A new osteosynthesis was performed in 24 cases (35.8%) and a conversion to arthroplasty in the remaining 43 (64.2%). A comparative analysis was performed between cases with and without infection. The groups were comparable in terms of demographic data and postoperative radiological data (using Chang criteria and tip-apex distance). Patients with underlying infection had a higher rate of surgical wound complication (56.3% vs 22%, p = 0.014), higher rates of leukocytes counts (11.560 vs 7.890, p = 0.023) and time to surgery (5.88 vs 3.88 days, p = 0.072). Conclusions. One out of four osteosynthesis failure in PFF is due to underlying FRI and in almost 20% were not unsuspected before surgery. In PFF osteosynthesis failures, underlying infection should be taken into account as a possible etiological factor and thus a preoperative and intraoperative infection study should be always performed

Objectives. The Sliding Hip Screw (SHS) is commonly used to treat trochanteric hip fractures. Fixation failure is a devastating complication requiring complex revision surgery. One mode of fixation failure is lag screw cut-out which is greatest in unstable fracture patterns and when the tip-apex distance of the lag screw is > 25 mm. The X-Bolt Dynamic Hip Plating System (X-Bolt Orthopaedics, Dublin, Ireland) is a new device which aims to reduce this risk of cut-out. However, some surgeons have reported difficulty minimising the tip-apex distance with subsequent concerns that this may lead to an increased risk of cut-out. Patients and Methods. We measured the tip-apex distance from the intra-operative radiographs of 93 unstable trochanteric hip fractures enrolled in a randomised controlled trial (Warwick Hip Trauma Evaluation, WHiTE One trial). Participants were treated with either the sliding hip screw or the X-Bolt dynamic hip plating system. We also recorded the incidence of cut-out in both groups, at a median follow-up time of 17 months. Results. There was a significantly increased tip-apex distance with the use of the X-Bolt (mean difference 3.7mm (95% confidence interval 1.58 to 5.73); SHS mean 17.1 mm, X-Bolt mean 20.8; p = 0.001. However, this was not associated with an increased incidence of cut-out at a median follow-up time of 17 months, with three cut-outs (6%) in the SHS group and 0 (0%) in the X-Bolt group. Conclusion. The X-Bolt is a safe implant with no increased risk for cut-out. Concerns about minimising the tip-apex distance may be justified but do not appear to be clinically important. Cite this article: M. A. Fernandez, A. Aquilina, J. Achten, N. Parsons, M. L. Costa, X. L. Griffin. The tip-apex distance in the X-Bolt dynamic plating system. Bone Joint Res 2017;6:–207. DOI: 10.1302/2046-3758.64.BJR-2015-0016.R2

This study compares outcomes of fixation of subtrochanteric femoral fractures using a single lag screw (Gamma3 nail, GN) with a dual lag screw device (InterTAN nail, IN). The primary outcome was mechanical failure, defined as lag screw cut-out, back-out, nail breakage or peri-implant fracture. Technical factors associated with mechanical failure were also identified. All adult patients (>18yrs) with a subtrochanteric femoral fracture treated in a single centre were retrospectively identified using electronic records. Included patients underwent surgical fixation using either a long GN (2010–2017) or IN (2017–2022). Cox regression analysis was used to determine the risk of mechanical failure and technical predictors of failure. The study included 587 patients, 336 in the GN group (median age 82yrs, 73% female) and 251 in the IN group (median age 82yrs, 71% female). The IN group exhibited a higher prevalence of osteoporosis (p=0.002) and CKD□3 (p=0.007). There were no other baseline differences between groups. The risk of any mechanical failure was increased two-fold in the GN group (HR 2.51, p=0.020). Mechanical failure comprising screw cut-out (p=0.040), back-out (p=0.040) and nail breakage (p=0.51) was only observed in the GN group. The risk of peri-implant fracture was similar between the groups (HR 1.10, p=0.84). Technical predictors of mechanical included varus >5° for cut-out (HR 15.61, p=0.016), TAD>25mm for back-out (HR 9.41, p=0.020) and shortening >1cm for peri-implant fracture (HR 6.50, p=<0.001). Dual lag screw designs may reduce the risk of mechanical complications for patients with subtrochanteric femoral fractures

Failure of cephalomedullary fixation for proximal femur fractures is an uncommon event associated with significant morbidity to the patient and cost to the healthcare system. This institution changed nailing system from the PFNA (DePuy Synthes) to InterTan (Smith and Nephew) in February 2020. To assess for non-inferiority, a retrospective review was performed on 247 patients treated for unstable proximal femur fractures (AO 31 A2; A3). Patients were identified through manual review of fluoroscopic images. Stable fracture patterns were excluded (AO 31 A1). Pre/post operative imaging, demographic data, operative time and ASA scores assessed. Internal/external imaging and national joint registry data were reviewed for follow up. No significant difference was found in overall failure rate of PFNA vs InterTan (4.84% vs 3.23%; p = 0.748). Overall, short nails were more likely to fail by cut-out than long nails (7.5% vs 1.2%; p = 0.015). Nails which failed by varus cut-out had a higher tip/apex distance (TAD) (26.2mm vs 17.0mm; p < 0.001). Of concern, varus cut-out occurred in two InterTan nails with TAD of <25mm. The PFNA enjoyed a shorter operative time for both the short (59.1 vs 71.8 mins; p = 0.022) and long nails (98.8 vs 114.3 mins; p = 0.016) with no difference in 120-day survival rate. Overall failure rates of the PFNA and InterTan nailing systems were comparable. However, the failure rate of short nails in this study is concerning. Using long nails with a lag screw design for unstable intertrochanteric femoral fractures may reduce failure rates. Cumulative frequency analysis suggests stringent tip-apex distances of less than 21mm may reduce failure rates in lag-screw design cephulomedullary nails. This dataset suggests that unstable intertrochanteric fractures may be more reliably managed with a long cephalomedullary device

Subtrochanteric femoral fractures are a subset of hip fractures generally treated with cephalomedullary nail fixation\[1\]. Single lag screw devices are most commonly-used, but integrated dual screw constructs have become increasingly popular\[2,3\]. The aim of this study was to compare outcomes of fixation of subtrochanteric femoral fractures using a single lag screw (Gamma3 nail, GN) with a dual screw device (InterTAN nail, IN). The primary outcome was mechanical failure, defined as lag screw cut-out, back-out, nail breakage or peri-implant fracture. Consecutive adult patients (18yrs) with subtrochanteric femoral fracture treated in a single centre were retrospectively identified using electronic records. Patients that underwent surgical fixation using either a long GN (2010–2017) or IN (2017–2022) were included. Medical records and radiographs were reviewed to identify complications of fixation. Cox regression analysis was used to determine the risk of mechanical failure and secondary outcomes by implant design. Multivariable regression models were used to identify predictors of mechanical failure. The study included 622 patients, 354 in the GN group (median age 82yrs, 72% female) and 268 in the IN group (median age 82yrs, 69% female). The risk of any mechanical failure was increased two-fold in the GN group (HR 2.44 \[95%CI 1.13 to 5.26\]; _p=0.024_). Mechanical failure comprising screw cut-out (_p=0.032_), back-out (_p=0.032_) and nail breakage (_p=0.26_) was only observed in the GN group. Technical predictors of failure included varus >5° for cut-out (OR 19.98 \[2.06 to 193.88\]; _p=0.01_), TAD;25mm for back-out (8.96 \[1.36 to 58.86\]; p=0.022) and shortening 1cm for peri-implant fracture (7.81 \[2.92 to 20.91\]; _p=<0.001_). Our results demonstrate that an intercalated screw construct is associated with a lower risk of mechanical failure compared with the a single lag screw device. Intercalated screw designs may reduce the risk of mechanical complications for patients with subtrochanteric femoral fractures

Introduction. Current treatments of rotational deformities of long bones in children are osteotomies and fixations. In recent years, the use of guided growth for correction of rotational deformities has been reported in several pre-clinical and clinical studies. Various techniques have been used, and different adverse effects, like growth retardation and articular deformities, have been reported. We tested a novel plate concept intended for correction of rotational deformities of long bones by guided growth, with sliding screw holes to allow for longitudinal growth, in a porcine model. Method. Twelve, 12-week-old female porcines were included in the study. Surgery was performed on the left femur. The right femur was used as control. Plates were placed distally to induce external rotation, as longitudinal growth occurred. CT-scans of the femurs were processed to 3-D models and used for measuring rotation. Result. The plates rotated as intended in all 12 porcines. One porcine was excluded due to congenital deformity of the proximal part of the femurs. Two porcines had cut-out of the proximal screw on the lateral side, observed at the end of the intervention. These two porcines were included in the results. We observed a Δrotation of 5.7° ± 2° in external direction (CI: 3.7°– 7.7°). ΔFemur length was -0.4 cm [-0.7 cm – 0 cm] equal to 1.5% shortening of the operated femur. No significant difference was observed in coronal or sagittal plane. Conclusion. Significant external rotation was achieved with minimal effect on longitudinal growth. While the use of guided growth for correction of rotational deformities is already being used clinically, it is still to be considered an experimental procedure with sparse evidence. This study shows promising results for the feasibility of the method in a large animal model and is an important first step in validating the technique and detecting possible adverse effects, before future clinical studies

Despite past advances of implant technologies, complication rates of fixations remain high at challenging sites such as the proximal humerus [1]. These may not only be owed to the implant itself but also to dissatisfactory surgical execution of fracture reduction and implant positioning. Therefore, the aim of this study was to quantify the instrumentation accuracy of a highly standardised and guided procedure and its influence on the biomechanical outcome and predicted failure risk. Preoperative planning of osteotomies creating an unstable 3-part fracture and fixation with a locking plate was performed based on CT scans of eight pairs of low-density proximal humerus samples from elderly female donors (85.2±5.4 years). 3D-printed subject-specific guides were used to osteotomise and instrument the samples according to the pre-OP plan. Instrumentation accuracies in terms of screw lengths and orientations were evaluated by comparing post-OP CT scans with the pre-OP plan. The fixation constructs were biomechanically tested until cyclic cut-out failure [2]. Failure risks of the planned and the post-OP configurations were predicted using a validated sample-specific finite element (FE) simulation approach [2] and correlated with the experimental outcomes. Small deviations were found for the instrumented screw trajectories compared to the planned configuration in the proximal-distal (0.3±1.3º) and anterior-posterior directions (-1.7±1.8º), and for screw tip to joint distances (-0.3±1.1 mm). Significantly higher failure risk was predicted for the post-OP compared to the planned configurations (p<0.01) via FE. When incorporating the instrumentation inaccuracies, the biomechanical results could be predicted well with FE (R. 2. =0.70). Despite the high instrumentation accuracy achieved using sophisticated subject-specific 3D-printed guides, even minor deviations from the pre-OP plan significantly increased the FE-predicted risk of failure. This underlines the importance of intraoperative guiding technology [3] in tandem with careful pre-OP planning to assist surgeons to achieve optimal outcomes. Acknowledgements. This study was performed with the assistance of the AO Foundation via the AOTRAUMA Network

Introduction. Cephalomedullary nailing (CMN) is commonly used for unstable pertrochanteric fracture. CMN is relatively safe method although various complications can potentially occur needing revision surgery. Commonly used salvage procedures such as renailing, hemiarthroplasty, conservative treatment or total hip arthroplasty (THA) are viable alternatives. The aim was to investigate the rate of THA after CMN and evaluate the performance on conversion total hip arthroplasty (cTHA) after failure of CMN. Method. Collected data included patients from two orthopedic centers. Data consisted of all cTHAs after CMN between 2014-2020 and primary cementless THA operations between 2013-2023. Primary THA operations were treated as a control group where Oxford Hip Score (OHS) was the main compared variable. Result. From 2398 proximal femoral hip procedures 1667 CMN procedures were included. Altogether 46/1667 (2.8%) CMNs later received THA. Indications for THA after CMN failure were 13 (28.3%) cut-outs, nine (19.6%) cut-throughs, eight (17.4%) nail breakages, seven (15.2%) post traumatic arthrosis, seven (15.2%) nonunions, one (2.2%) malunion and one (2.2%) collum screw withdrawal. Mean (SD) time to complication after CMN operation is 5.9 (6.8) months. Mean (SD) time from nail procedure to THA was 10.4 (12.0) months. Total complication rate for cTHA after CMN was 17.4%. Reported complications were infection with seven (15.2%) cases and one (2.2%) nerve damage. Mean (SD) time to cTHA complication was 3.6 (6.1) months. One-sample T-test showed OHS to be significantly better (P<.001) for primary cementless THA compared to cTHA after one year. Conclusion. Altogether 2.8% of CMN were converted to THA. Nearly half (47.8%) of the cTHA procedures were due to CMN cut-out or cut-through. OHS was significantly better in primary cementless THA compared to cTHA. Prosthetic joint infection was the most frequent complication related to cTHA

Introduction. Lag screw cut-out following fixation of unstable intertrochanteric fractures in osteoporotic bone remains an unsolved challenge. A novel new device is the X-Bolt which is an expanding type bolt that may offer superior fixation in osteoporotic bone compared to the standard DHS screw type device. Aims. The aim of this study was to test if there was a difference in cut-out using the X-Bolt implant compared with the standard DHS system. Methods. Specimens of low density surrogate bone (5pcf) were inserted into a simplified biomechanical fracture model and had either an X-Bolt or DHS implant inserted. There were eight samples in each group. The fracture model was tested with an incremental cyclical loading programme in a Material Test System. Displacement, cycle count and force exerted were continuously recorded until cut-out of the implant. Results. All of the specimens failed by varus collapse with superior cut-out and resulted in an automatic stop of the MTS. Specimens with the X-Bolt implant inserted lasted longer on cyclical count and withstood a greater force at cut-out compared with DHS specimens. The mean number of cycles to cutout in the DHS specimens was 4345 and in specimens with the X-Bolt inserted was 6898. The mean force at which cutout occurred in the DHS group was 1.025kN and in specimens with the X-Bolt inserted was 1.275kN. A statistically significant difference was observed with a P-value of 0.005 and a power of 87.2% with respect to cycle count and a P-value of 0.008 and power 84.8% with respect to force exerted at failure when comparing between the two groups. Conclusion. This study shows that the X-Bolt device demonstrated superior cut-out resistance and withstood greater loads compared to the DHS in low density surrogate bone in an unstable fracture model under cyclical axial loading

Objectives. The paradoxical migration of the femoral neck element (FNE) superomedially against gravity, with respect to the intramedullary component of the cephalomedullary device, is a poorly understood phenomenon increasingly seen in the management of pertrochanteric hip fractures with the intramedullary nail. The aim of this study was to investigate the role of bidirectional loading on the medial migration phenomenon, based on unique wear patterns seen on scanning electron microscopy of retrieved implants suggestive of FNE toggling. Methods. A total of 18 synthetic femurs (Sawbones, Vashon Island, Washington) with comminuted pertrochanteric fractures were divided into three groups (n = 6 per group). Fracture fixation was performed using the Proximal Femoral Nail Antirotation (PFNA) implant (Synthes, Oberdorf, Switzerland; n = 6). Group 1 was subjected to unidirectional compression loading (600 N), with an elastomer (70A durometer) replacing loose fracture fragments to simulate surrounding soft-tissue tensioning. Group 2 was subjected to bidirectional loading (600 N compression loading, 120 N tensile loading), also with the elastomer replacing loose fracture fragments. Group 3 was subjected to bidirectional loading (600 N compression loading, 120 N tensile loading) without the elastomer. All constructs were tested at 2 Hz for 5000 cycles or until cut-out occurred. The medial migration distance (MMD) was recorded at the end of the testing cycles. Results. The MMDs for Groups 1, 2, and 3 were 1.02 mm, 6.27 mm, and 5.44 mm respectively, with reliable reproduction of medial migration seen in all groups. Bidirectional loading groups showed significantly higher MMDs compared with the unidirectional loading group (p < 0.01). Conclusion. Our results demonstrate significant contributions of bidirectional cyclic loading to the medial migration phenomenon in cephalomedullary nail fixation of pertrochanteric hip fractures. Cite this article: G. W. Law, Y. R. Wong, A. K-S. Yew, A. C. T. Choh, J. S. B. Koh, T. S. Howe. Medial migration in cephalomedullary nail fixation of pertrochanteric hip fractures: A biomechanical analysis using a novel bidirectional cyclic loading model. Bone Joint Res 2019;8:313–322. DOI: 10.1302/2046-3758.87.BJR-2018-0271.R1

The aim of this study was to establish any association between implant cut-out and a Tip Apex Distance (TAD), ≥25mm, in proximal femoral fractures, following closed reduction and stabilisation, with either a Dynamic Hip Screw (DHS) or Intramedullary Hip Screw (IMHS) device. Furthermore, we investigated whether any difference in cut-out rate was related to fracture configuration or implant type. WE conducted a retrospective review of the full clinical records and radiographs of 65 consecutive patients, who underwent either DHS or IMHS fixation of proximal femoral fractures. The TAD was measured in the standard fashion using the combined measured AP and lateral radiograph distances. Fractures were classified according to the Muller AO classification. 35 patients underwent DHS fixation and 30 patients had IMHS fixation. 5 in each group had a TAD≥25mm. There were no cut-outs in the DHS group and 3 in the IMHS group. 2 of the cut-outs had a TAD≥25mm. The 3 cut-outs in the IMHS group had a fracture classification of 31-A2, 31-A3 and 32-A3.1 respectively. In addition, the fractures were inadequately reduced and fixed into a varus position. A TAD<25mm would appear to be associated with a lower rate of cut-out. The cut-out rate in the IMHS group was higher than the DHS group. Contributing factors may have included an unstable fracture configuration and inadequate closed fracture reduction at the time of surgery