The lordosis distribution index (LDI) describes distribution of lumbar lordosis, measured as the % of lower lumbar lordosis (L4-S1) compared to global lordosis (L1-S1) with normal value 50–50%. Maldistributed LDI is associated with higher revision in short lumbar fusions, 4 vertebrae1. We hypothesise maldistributed LDI is also associated with mechanical failure in longer fusions. Retrospective review of 29 consecutive ASD patients, aged 55+, undergoing long lumbar fusion, 4 levels, with >3-years follow-up. LDI, pelvic incidence (PI) and sagittal vertical axis (SVA) were measured on pre- and post-op whole spine standing X-rays (Fig A and B). Patients were categorized according to their pelvic incidence (PI) and postoperative LDI: Normal (LDI 50 80), Hypolordotic (LDI < 50), or Hyperlordotic (LDI > 80) and assessed for failure rate compared to normal LDI and PI <60. Mean follow-up 4.5 years. 19 patients had mechanical failures including junctional failure and metalware fracture. PI >60o was associated with higher mechanical failure rates (Chi^2 p<0.05). Hypolordotic LDI was associated with 82% mechanical failure (Chi^2 p<0.001), Hyperlordotic 88% mechanical failure (Chi^2 p<0.001) and Normal 8% mechanical failure (Table 1). Maldistributed LDI, whether Hyperlordotic or Hypolordotic, correlated with 10× greater mechanical failure rate compared to Normal LDI in long fusions. LDI is a useful measurement that should be considered, especially in high PI patients

Aims. We evaluated a large database with mechanical failure of a single uncemented modular femoral component, used in revision hip arthroplasty, as the end point and compared them to a control group treated with the same implant. Patient- and implant-specific risk factors for implant failure were analyzed. . Methods. All cases of a fractured uncemented modular revision femoral component from one manufacturer until April 2017 were identified and the total number of implants sold until April 2017 was used to calculate the fracture rate. The manufacturer provided data on patient demographics, time to failure, and implant details for all notified fractured devices. Patient- and implant-specific risk factors were evaluated using a logistic regression model with multiple imputations and compared to data from a previously published reference group, where no fractures had been observed. The results of a retrieval analysis of the fractured implants, performed by the manufacturer, were available for evaluation. Results. There were 113 recorded cases with fracture at the modular junction, resulting in a calculated fracture rate of 0.30% (113/37,600). The fracture rate of the implant without signs of improper use was 0.11% (41/37,600). In 79% (89/113) of cases with a failed implant, either a lateralized (high offset) neck segment, an extralong head, or the combination of both were used. Logistic regression analysis revealed male sex, high body mass index (BMI), straight component design, and small neck segments were significant risk factors for failure. Investigation of the implants (76/113) showed at least one sign of improper use in 72 cases. Conclusion. Implant failure at the modular junction is associated with patient- and implant-specific risk factors as well as technical errors during implantation. Whenever possible, the use of short and lateralized neck segments should be avoided with this revision system. Implantation instructions and contraindications need to be adhered to and respected. Cite this article: Bone Joint J 2020;102-B(5):573–579

7–20 % of the patients with a total knee arthroplasty (TKA) are dissatisfied without an indication for revision. Therapeutic options for this patient population with mostly a lack of quadriceps strength are limited. The purpose of this study is to evaluate the effect of six weeks low load resistance training with blood flow restriction (BFR) on the clinical outcome in these unhappy TKA patients. Thirty-one unhappy TKA patients (of the scheduled fifty patients) without mechanical failure were included in this prospective study since 2022. The patients participate in a supervised resistance training combined with BFR, two times a week during nine weeks. Patients were evaluated by the Knee Osteoarthritis Outcome Score (KOOS), Knee Society Score: satisfaction (KSSs) and the Pain Catastrophizing Scale (PCS). Functionality was tested using the Six Minute Walk Test (6MWT) and the 30-Second Chair Stand Test (30CST). Follow-up took place at six weeks, three months and six months after the start. Six weeks training with BFR provided statistically significant improvements in all the KOOS subscales compared to the baseline, especially for symptoms (55.1 (±15.4) versus 48.0 (±16.5); p<0.001), activities in daily living (50.3 (±21.1) versus 43.7 (±17.2); p<0.00) and quality of life (24.6 (±18.5) versus 17.3 (±13.0); p<0.001). The PCS reduced from 27.4 (±11.0) to 23.2 (±11.4) at six weeks (p<0.01), whereas the KSSs increased from 11.8 (±6.5) to 14.9 (±7.6) (p=0.021). Both the 6MWT and the 30CST improved statistically significant from respectively 319.7 (±15.0) to 341.6m (±106.5) (p<0.01) and 8.6 (±3.9) to 9.3 times (±4.5) (p<0.01). Blood flow restriction appears to enhance the quality of life and functional performance of unhappy TKA patients. Based on these preliminary results, BFR seems to be a promising and valuable alternative for these TKA patients with limited therapeutic options

In a prospective study we assessed the causes of mechanical failure in a series of 230 intertrochanteric femoral fractures which had been internally fixed with either a sliding hip screw or a Kuntscher Y-nail. The overall rate of mechanical failure was 16.5%; cutting-out of the implant from the femoral head was the cause in three-quarters of the instances. Implants placed posteriorly in the femoral head cut out more often (27%) than those placed centrally (7%). The cut-out rate was also determined by the quality of the fracture reduction, but age, walking ability and bone density (assessed by the Singh grade and metacarpal indices) had no significant influence. We conclude that these fractures should be reduced as accurately as possible and it is imperative that the implant is placed centrally within the femoral head

Between October 2001 and September 2009 we lengthened 242 lower-limb segments in 180 patients using the Intramedullary Skeletal Kinetic Distractor (ISKD). Mechanical failure was defined either as breakage of the ISKD or failure of the internal mechanism to activate. Retrieved nails which failed mechanically were examined by the manufacturer for defects. In all, 15 ISKDs in 12 patients (13 limbs) failed mechanically representing an overall failure rate of 6.2%, with fracture of the device occurring in ten of the 15 failures. Two nails in one patient failed to lengthen and had to be replaced. The manufacturer detected an error in the assembly of the nail, which prompted a wide recall. One nail jammed after being forcefully inserted, and two nails failed to lengthen fully. Lengthening was achieved in all 12 patients, although three required a second operation to exchange a defective nail for a new, functioning device. The ISKD is a complex mechanical device which lengthens by the oscillation of two telescopic sections connected by a threaded rod. The junction between these sections is surrounded by a keyring collar. This keyring collar is the weakest part of the device

Purpose: Massive endoprostheses have become the mainstay of treatment for reconstruction after resection of primary bone tumours. The Kotz Modular Femoral Tibial Replacement (KMFTR, Kotz prosthesis, Stryker Inc.) system has been one of the most widely utilized uncemented modular systems. Although this prosthesis has excellent bone ingrowth characteristics and a low aseptic loosening rate, we have identified a significant incidence of mechanical failure and breakage of the prosthesis. The purpose of this investigation is to review the outcomes after prosthetic revision for a broken Kotz prosthesis. Method: A retrospective review was undertaken of our institutional database from the years 1989, when we first utilized the Kotz prosthesis, until present. We identified all patients who had undergone a revision of the prosthesis for mechanical failure or prosthetic breakage. Periprosthetic fractures and revisions for polyethylene bushing wear were excluded. Results: 119 distal femoral, 55 proximal tibial and 47 proximal femoral Kotz endoprostheses (221 in total) have been implanted in our center since 1989. There were 21 revisions (9.5% of total prostheses) for mechanical failure. Of these, 16 were in the distal femur, four in the proximal tibia and one in the proximal femur. Mechanical failures occurred at a mean of 77 months (range 24–170). Of the 21 metal failures, 8 stems broke at the junction of the stem and body, 8 fractured through screw holes in the stem, 3 fractured the derotation lug, one fractured the tibial housing and one lateral side-plate failed. Of these failures only three implants had associated definite loosening and two of these three were cemented. Broken stems initially required extraction whilst preserving as much of the longitudinal and transverse bone stock as possible in order to facilitate osseo-mechanical integration of the revision prosthesis. This was accomplished using trephines to core the ingrown broken stem out of the bone. Over the last 20 years, the 16 broken stems have been revised in 5 patients to larger Kotz uncemented stems, 2 to cemented GMRS stems with an adaptor to the KMFTR system, 3 to Restoration uncemented revision hip stems with a custom adaptor to the KMFTR system, 2 to custom GMRS uncemented stems with an adaptor to the KMFTR system, and 4 to total femurs. All except one patient was alive with no evidence of disease. Post-revision, 14 patients had TESS, MSTS87, MSTS93 scores of 80.5, 25.5 and 70 respectively. Conclusion: Despite very low aseptic loosening rates, mechanical failure of the Kotz prosthesis continues to be a significant clinical problem even several years after implantation. Fatigue failure often leads to the difficult scenario of removing a well-ingrown uncemented stem. Our data illustrates that these prostheses can often be successfully revised by trephining out the broken stem and inserting new uncemented stems. Functional outcome continues to be good and is comparable to pre-revision levels

Aims. The risk of mechanical failure of modular revision hip stems is frequently mentioned in the literature, but little is currently known about the actual clinical failure rates of this type of prosthesis. The current retrospective long-term analysis examines the distal and modular failure patterns of the Prevision hip stem from 18 years of clinical use. A design improvement of the modular taper was introduced in 2008, and the data could also be used to compare the original and the current design of the modular connection. Methods. We performed an analysis of the Prevision modular hip stem using the manufacturer’s vigilance database and investigated different mechanical failure patterns of the hip stem from January 2004 to December 2022. Results. Two mechanical failure patterns were identified: fractures in the area of the distal fluted profile (distal stem fracture) and failure of the modular taper (modular fracture). A failure rate of 0.07% was observed for distal stem fracture, and modular fracture rates of 1.74% for the original and 0.013% for the current taper design. Conclusion. A low risk of mechanical failure for both fracture types was observed compared to other known complications in revision hip arthroplasty. In addition, the data show that a design change did significantly reduce the risk of a modular fracture. Cite this article: Bone Joint J 2024;106-B(2):151–157

Background. The Kotz Modular Femoral Tibial Replacement system has been one of the most widely utilised uncemented modular systems for bone and joint reconstruction after tumour resection. We have identified a significant incidence of mechanical failure and breakage of the prosthesis. The purpose of this investigation is to review the modes of implant failure and the outcomes after prosthetic revision for a broken Kotz prosthesis. Methods. Over 20 years there were 121 distal femoral, 55 proximal tibial, 47 proximal femoral and 12 total femoral replacements performed. Results. Out of 180 currently living patients there were 27 implant fractures in 23 patients (13%) with 22 distal femoral and five proximal tibial implant failures. Mechanical failures occurred at a mean of 77 months (range 24-170). There were 21 stem fractures. Five fractured at the derotation lug and one fractured the tibial housing. Lug fracture is an unreported mode of failure of these implants. The implant design selected for revision was very much dependent on when the fractured implant was revised. Eleven patients had new KMFTR stems inserted; 4 Restoration stems (one of which was cemented), 3 GMRS stems (one of which was cemented), two total femora and one Compress (Biomet) implants have been utilised, all with custom adaptors between the stem and the KMFTR system. There were 12 complications (44%), seven infections, three implant re-fractures, one vascular insufficiency necessitating amputation and one per-prosthetic fracture. The mean pre-implant fracture and post-revision TESS scores were 80.9 (Range 54.2-98.3) and 79.1 (50-96.7). The MSTS87 pre- and post- scores were 26.8 (14-33) and 26.1 (15-33) respectively. The MSTS93 also demonstrated no differences in the pre-fracture and post-revision scores with 75.4 (50-93) and 74.8 (40-100). Conclusion. Our data illustrate that these prostheses can often be successfully revised by trephining out the broken stem and inserting new uncemented stems. Functional outcome continues to be good and is comparable to pre-revision levels, despite a 44% complication rate

Introduction. One of the major concerns in the use of modular hip prostheses is the structural failure of one or more components of the prosthesis, with total mechanical failure. In literature there are sporadic cases of breakage of the prosthetic neck in patients with high functional demand. Material and methods. In our experience we have implanted a model of modular hip prostheses in 38 patients. In 17 of these patients it was implanted a neck made of titanium alloy, while in the remaining 21 was utilised a CrCo neck. In 5 of the 17 patients with neck titanium it has been a spontaneous rupture of the neck in a time ranging from 12 to 24 months. We proceeded with the replacement of the titanium neck with similar neck made of CrCo alloy in 5 patients with failed neck, and we decided to call the remaining 12 patients with titanium neck, offering them the revision of the system. All patients accepted the revision surgery. Results. implants explanted and subject to breakage of the neck were analyzed by an independent metallurgical laboratory which has produced a document in which were found the main signs of wear which led to the deterioration of metal involved. Conclusions. The rupture of the modular hip prostheses is a possible event both because of the high functional loads required by some types of patients, that of the building materials and design of the modular components. In this study we are presented the results of the laboratory tests that allow us to pose hypotheses about the causes and failure mechanisms of modular hip prostheses

Aims. The timing of when to remove a circular frame is crucial; early removal results in refracture or deformity, while late removal increases the patient morbidity and delay in return to work. This study was designed to assess the effectiveness of a staged reloading protocol. We report the incidence of mechanical failure following both single-stage and two stage reloading protocols and analyze the associated risk factors. Methods. We identified consecutive patients from our departmental database. Both trauma and elective cases were included, of all ages, frame types, and pathologies who underwent circular frame treatment. Our protocol is either a single-stage or two-stage process implemented by defunctioning the frame, in order to progressively increase the weightbearing load through the bone, and promote full loading prior to frame removal. Before progression, through the process we monitor patients for any increase in pain and assess radiographs for deformity or refracture. Results. There were 244 frames (230 patients) included in the analyses, of which 90 were Ilizarov type frames and 154 were hexapods. There were 149 frames which underwent single-stage reloading and 95 frames which underwent a two-stage reloading protocol. Mechanical failure occurred after frame removal in 13 frames (5%), which suffered refracture. There were no cases of change in alignment. There was no difference between refracture patients who underwent single-stage or two-stage reloading protocols (p = 0.772). In all, 14 patients had failure prevented through identification with the reloading protocol. Conclusion. Our reloading protocol is a simple and effective way to confirm the timing of frame removal and minimize the rate of mechanical failure. Similar failure rates occurred between patients undergoing single-stage and two-stage reloading protocols. If the surgeon is confident with clinical and radiological assessment, it may be possible to progress directly to stage two and decrease frame time and patient morbidity. Cite this article: Bone Jt Open 2022;3(5):359–366

Between January 1998 and December 2002, 418 hip revisions were performed. Of these, 45 hips were diagnosed as infected and two-stage revisions were done six weeks apart. These were excluded from the study, leaving 373 revisions for mechanical failure. In 310 cases both components were exchanged, in 59 the acetabular prostheses only and in three the stem only. One permanent resection arthroplasty was done for bone loss. Where necessary bone graft was used liberally. In 83 patients (22%) specimens taken at surgery cultured positive. A first generation cephalosporin was given as systemic prophylaxis. Routine usage of Gentamycin was reinforced by Vancomycin or fucidic acid in the cement and bone grafts. Double lumen irrigation was inserted in only 5% of cases on the basis of operative findings. Gram stains done intraoperatively in suspected cases were non-contributory. Seventy-six percent of cultures were gram positive, with a preponderance of coagulase negative staphylococcus. Twelve percent were gram negative and 12% were mixed cultures of gram positive and gram negative organisms. One methicillin-resistant Staphylococcus aureus and one fungus were identified. As most of these patients were referred from elsewhere, we did not know whether or not Gentamycin had been used in the cement during previous surgery. Implant failure due to low-grade infection was under-diagnosed in this series. Because of the relatively low number of failures caused by infection in this group, we recommend, with some improvements, the revision protocol presented. The expense of more detailed preoperative evaluation should be weighed against the success of the protocol

Aims. Registry studies on modified acetabular polyethylene (PE) liner designs are limited. We investigated the influence of standard and modified PE acetabular liner designs on the revision rate for mechanical complications in primary cementless total hip arthroplasty (THA). Methods. We analyzed 151,096 primary cementless THAs from the German Arthroplasty Registry (EPRD) between November 2012 and November 2020. Cumulative incidence of revision for mechanical complications for standard and four modified PE liners (lipped, offset, angulated/offset, and angulated) was determined using competing risk analysis at one and seven years. Confounders were investigated with a Cox proportional-hazards model. Results. Median follow-up was 868 days (interquartile range 418 to 1,364). The offset liner design reduced the risk of revision (hazard ratio (HR) 0.68 (95% confidence interval (CI) 0.50 to 0.92)), while the angulated/offset liner increased the risk of revision for mechanical failure (HR 1.81 (95% CI 1.38 to 2.36)). The cumulative incidence of revision was lowest for the offset liner at one and seven years (1.0% (95% CI 0.7 to 1.3) and 1.8% (95% CI 1.0 to 3.0)). No difference was found between standard, lipped, and angulated liner designs. Higher age at index primary THA and an Elixhauser Comorbidity Index greater than 0 increased the revision risk in the first year after surgery. Implantation of a higher proportion of a single design of liner in a hospital reduced revision risk slightly but significantly (p = 0.001). Conclusion. The use of standard acetabular component liners remains a good choice in primary uncemented THA, as most modified liner designs were not associated with a reduced risk of revision for mechanical failure. Offset liner designs were found to be beneficial and angulated/offset liner designs were associated with higher risks of revision. Cite this article: Bone Joint J 2022;104-B(7):801–810

The relative advantages and disadvantages of two-stage versus one-stage management of infected total hip arthroplasties are the current subject of intense debate. To understand the merits of each approach detailed information on the short and, importantly, longer-term outcomes of each must be known. The purpose of this study was to assess the long-term results of two-stage exchange arthroplasty for THAs in one of the largest series to date.

We identified 331 infected THAs treated with a two-stage exchange arthroplasty between 1993 and 2021 at a single institution. Patients were excluded if they had prior treatment for infection. Mean age at reimplantation was 66 years, 38% were female, and mean BMI was 30 kg/m². PJI diagnosis was based on the 2011 MSIS criteria. A competing risk model accounting for death was utilized. Mean follow up was 8 years.

The cumulative incidence of reinfection was 7% at 1 year and 11% at 5 and 10 years. Factors predictive of reinfection included BMI>30 kg/m² (HR 2; p=0.049), and need for a spacer exchange (HR 3.2; p=0.006). The cumulative incidence of any revision was 13% at 5 and 10 years. The cumulative incidence of aseptic revision was 3% at 1 year, 7% at 5 years, and 8% at 10 years. Dislocation occurred in 33 hips (11% at 10 years; 45% required revision). Factors predictive of dislocation were female sex (HR 2; p=0.047) and BMI<30 kg/m² (HR 3; p=0.02). The mean HHS improved from 54 to 75 at 10 years.

In this series of 331 two-stage exchange arthroplasties performed for infected hips, we found a low aseptic revision rate (8%) and a low rate of reinfection (11%) at 10 years. These long-term mechanical and infection data must be kept in mind when considering a paradigm shift to one-stage exchanges.

Level of Evidence: Level III

Aims. Endoprosthetic reconstruction with a distal femoral arthroplasty (DFA) can be used to treat distal femoral bone loss from oncological and non-oncological causes. This study reports the short-term implant survivorship, complications, and risk factors for patients who underwent DFA for non-neoplastic indications. Methods. We performed a retrospective review of 75 patients from a single institution who underwent DFA for non-neoplastic indications, including aseptic loosening or mechanical failure of a previous prosthesis (n = 25), periprosthetic joint infection (PJI) (n = 23), and native or periprosthetic distal femur fracture or nonunion (n = 27). Patients with less than 24 months’ follow-up were excluded. We collected patient demographic data, complications, and reoperations. Reoperation for implant failure was used to calculate implant survivorship. Results. Overall one- and five-year implant survivorship was 87% and 76%, respectively. By indication for DFA, mechanical failure had one- and five-year implant survivorship of 92% and 68%, PJI of 91% and 72%, and distal femur fracture/nonunion of 78% and 70% (p = 0.618). A total of 37 patients (49%) experienced complications and 27 patients (36%) required one or more reoperation. PJI (n = 16, 21%), aseptic loosening (n = 9, 12%), and wound complications (n = 8, 11%) were the most common complications. Component revision (n = 10, 13.3%) and single-stage exchange for PJI (n = 9, 12.0 %) were the most common reoperations. Only younger age was significantly associated with increased complications (mean 67 years (SD 9.1)) with complication vs 71 years (SD 9.9) without complication; p = 0.048). Conclusion. DFA is a viable option for distal femoral bone loss from a range of non-oncological causes, demonstrating acceptable short-term survivorship but with high overall complication rates. Cite this article: Bone Jt Open 2022;3(3):173–181

The case reports of four patients with breakage of the intramedullary nail of the femur are presented. In all four patients the nail broke after consolidation of the fracture of the femoral shaft. All the nails broke at the same place: the junction between the round cross-section and the cloverleaf cross-section.

Introduction

Cementless acetabular fixation in total hip replacement (THA) is reliable and has been the fixation method of choice in the United States for decades. While revision for failure of osseointegration or early loosening is relatively rare, recurrent dislocation remains a leading cause of early revision. Novel acetabular implants and those offered by smaller companies often lack constrained or dual mobility liners, which may result in revision of well-fixed, well-positioned cups in cases of recurrent dislocation.

The purpose of this study was to compare outcomes of THA with three different acetabular cups with differing fixation surfaces. One hydroxyapatite (HA)-coated cup (Trident, Stryker, Kalamazoo, MI, USA) offered dual mobility or constrained liner options. The other cups were a novel highly porous cup (Restoris PST, Stryker, Kalamazoo, MI, USA), and a Calcium Phosphate (CaP)-coated cup (Trinity, Corin, Cirincester, UK), neither of which offered dual mobility or constrained options at the time of investigation. Endpoints of interest were: clinical and radiographic outcomes including evidence of osseointegration, overall reoperations, reoperations for acetabular fixation failure, and reoperations to address dislocation in which a well-positioned shell was revised due to the lack of dual mobility or constrained options.

Aims: To evaluate the results of a novel modular press-þt acetabular cup in primary total hip arthroplasty (THA) for osteoarthrosis (OA) and inßammatory arthritis (IA). Methods: From February 1996 to June 1999 in 324 patients (249 women, 75 men) 355 THA using a novel cup has been carried out. The shell is non-hemispherical on cross-section and has a hydroxyapatite coating on porous titanium for osseointegration. Diagnosis was: osteoarthrosis (OA) 236, developmental dysplasia (DDH) 21, post-traumatic arthrosis 27, avascular necrosis 6, IA 65 Ð mainly rheumatoid arthritis (RA). Average age at operation was 65.8 years. The patients were studied prospectively using Harris Hip Score (HHS), by measuring any radiolucency around the cup and by looking for signs of migration. Results: Median follow-up was 4.5 years. At follow-up, 21 patients had deceased. Revision for deep infection was carried out in 5 hips (3 low-grade infections). No septic loosening occurred with low-grade infection. Recurrent dislocations required revision of 1 cup and exchange of 2 inserts. Only 1 cup in a RA patient with severe superior bone loss became unstable after a fall 4 months postoperatively. Survival with aseptic loosening of the cup as endpoint was 1 in OA and 0.98 in IA. In all 290 patients with 318 THA in follow-up the cup was functioning well, both clinically and radiographically. HHS increased from 44.5 to 90.3. Conclusion: Press-þt þxation using a modern acetabular component is an excellent treatment option in primary total hip arthroplasty for all diagnostic groups.

Purpose

Two-stage re-implantation after infection of Total Knee Arthroplasty (TKA), remains the gold standard to which other forms of treatment should be compared. The primary purpose of this study was to determine the rates of failure and functional outcome of two stage revision TKA for treatment of infection comparing cemented posterior stabilized compared to constrained condylar implants.

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

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