Atypical Subtrochanteric Femoral Fractures Research Articles

Surgical management and outcomes following atypical subtrochanteric femoral fractures − results from a matched-pair analysis of the registry for geriatric trauma of the German Trauma Society

Background and objectivesThe outcomes of patients with atypical subtrochanteric fractures (ASFs) remain unclear. Data from a large international geriatric trauma registry were analysed to examine the outcome of patients with ASFs compared to patients with typical osteoporotic subtrochanteric fractures (TSFs).Materials and methodsData from the Registry for Geriatric Trauma of the German Trauma Society (Deutsche Gesellschaft für Unfallchirurgie [DGU]) (ATR-DGU) were analysed. All patients treated surgically for ASFs or TSFs were included in this analysis. Across both fracture types, a paired matching approach was conducted, where statistical twins were formed based on background characteristics sex, age, American Society of Anesthesiologists (ASA) score and walking ability. In-house mortality and mortality rates at the 120-day follow-up, as well as mobility at 7 and 120 days, the reoperation rate, hospital discharge management, the hospital readmission rate at the 120-day follow-up, health-related quality of life, type of surgical treatment and anti-osteoporotic therapy at 7 and 120 days, were assessed as outcome measures using a multivariate logistic regression analysis.ResultsAmongst the 1,800 included patients, 1,781 had TSFs and 19 had ASFs. Logistic regression analysis revealed that patients with ASFs were more often treated with closed intramedullary nailing (RR = 3.59, p < 0.001) and had a higher probability of vitamin D supplementation as osteoporosis therapy at 120 days (RR = 0.88, p < 0.002). Patients with ASFs were also more likely to live at home after surgery (RR = 1.43, p < 0.001), and they also tended to continue living at home more often than patients with TSFs (RR = 1.33, p < 0.001). Accordingly, patients with TSFs had a higher relative risk of losing their self-sufficient living status, as indicated by increased rates of patients living at home preoperatively and being discharged to nursing homes (RR = 0.19, p < 0.001) or other hospitals (RR = 0.00, p < 0.001) postoperatively.ConclusionsSurgical treatment of ASFs was marked by more frequent use of closed intramedullary fracture reduction. Furthermore, patients with ASFs were more likely to be discharged home and died significantly less often in the given timeframe. The rate of perioperative complications, as indicated by nonsignificant reoperation rates, as well as patient walking abilities during the follow-up period, remained unaffected.

Does the Nonunion Rate of Atypical Femoral Fractures Differ According to Fracture Site?: A Meta-Analysis.

The nonunion rate for atypical femoral fractures (AFF) is known to be higher than that for typical fractures of the femur. We performed a meta-analysis to determine the incidence of nonunion necessitating reoperation following fixation for AFF and compare the rates according to the fracture site (subtrochanter or midshaft). A total of 742 AFFs from 29 studies were included. A proportion meta-analysis utilizing a random-effects model was conducted to estimate the prevalence of nonunion. The outcomes were the incidence of reoperations that included osteosynthesis. To determine the association of nonunion with patient mean age or average duration of bisphosphonate use, meta-regression analysis was done. In proportion meta-analysis, the estimated pooled prevalence of nonunion was 7% (95% confidence interval [CI], 5%-10%) from all studies. There was a significant difference in nonunion rate between the 2 groups (I2 = 34.4%, p = 0.02); the estimated prevalence of nonunion was 15% (95% CI, 10%-20%) in subtrochanteric AFFs and 4% (95% CI, 2%-6%) in midshaft AFFs. From meta-regression analysis, significant correlations were identified between nonunion rate and patient mean age (coefficient: -0.0071, p = 0.010), but not in the average duration of bisphosphonate use (coefficient: -0.0024, p = 0.744). A notable disparity existed in the nonunion rate among subtrochanteric AFFs and midshaft AFFs group. Therefore, it is critical for orthopedic surgeons to consider the complexity and challenges associated with AFF and to estimate the proper possibility of nonunion according to the fracture site.

Atypical Versus Typical Subtrochanteric Femoral Fractures: Disparate Patient Profiles, Similar Outcomes.

The purpose of the present study was to evaluate differences in demographic features and clinical outcomes between patients who sustained a typical versus atypical subtrochanteric femoral fracture. We reviewed the records for a cohort of consecutive patients who had undergone operative treatment of a subtrochanteric femoral fracture. Fractures were classified as either "typical" or "atypical" on the basis of the criteria of the American Society for Bone and Mineral Research (ASBMR). All patients were treated with a similar surgical algorithm and postoperative protocol. Groups were compared on the basis of demographic features, injury characteristics, operative quality measures, postoperative complications and outcomes, and radiographic time to healing. Comparative analyses were performed to compare the typical and atypical cohorts. Of 220 subtrochanteric fractures, 165 (75.0%) were classified as typical and 55 (25.0%) were classified as atypical. The atypical cohort was predominately female and more likely to have bisphosphonate usage (odds ratio [OR], 7.975; [95% confidence interval (CI), 3.994-15.922]; p < 0.001) and fractures with lower-energy mechanisms (p < 0.001). Patients in the atypical cohort were more likely to be treated with a 10-mm cephalomedullary nail (CMN) (OR, 2.100 [95% CI, 1.119-3.939]; p = 0.020), whereas patients in the typical cohort were treated more frequently with an 11-mm CMN (OR, 0.337 [95% CI, 0.168-0.674]; p = 0.002). There were no differences between the groups in terms of other operative parameters; however, anatomic fracture reduction in neutral lateral alignment was achieved more frequently in the typical cohort (OR, 0.438 [95% CI, 0.220-0.875]; p = 0.018). There were no differences between the groups in terms of hospital quality measures, mortality rates, readmission rates, or complication rates (including implant failure [broken screw or nail] and fracture nonunion) (p = 1.00). Interestingly, there was no significant difference between the groups in terms of time to radiographic healing (260.30 ± 187.97 days in the typical group, compared with 246.40 ± 116.33 days in the atypical group) (OR, 0.999 [95% CI, 0.997-1.002]; p = 0.606). Despite differences in terms of demographic and injury characteristics, patients who sustain a subtrochanteric femur fracture can expect similar outcome profiles regardless of fracture type. Prognostic Level III . See Instructions for Authors for a complete description of levels of evidence.

Frequency and pathogenesis of periprosthetic atypical femoral fractures associated with total knee arthroplasty: A multicenter prospective study with complementary histopathological and biomechanical analysis

IntroductionAlthough the diagnostic criteria for atypical femoral fracture (AFF) exclude periprosthetic fractures, reports of periprosthetic femoral fractures with characteristics of AFF are rapidly increasing. In this study, we investigated the frequency and pathogenesis of periprosthetic AFF associated with total knee arthroplasty (TKA) based on a theory of AFF subtypes that divides AFFs into two main types: fragility stress fractures of the bowed femoral shaft in the mid-shaft and “typical” subtrochanteric AFFs due to suppression of bone turnover (e.g., by bisphosphonates). Patients and MethodsThis multicenter prospective study of AFFs was conducted from 2015 through 2022. Clinical, pathological, and morphological characteristics were investigated in patients with periprosthetic AFFs associated only with non-stem TKA. Then, biomechanical investigation of the periprosthetic AFF was performed by computer tomography-based finite element analysis (CT/FEA) using two models with different load axes to examine how the correction of lower limb alignment by TKA influences the tensile stress distribution of the femur and the location of the AFF. ResultsFour of 61 AFFs (6.6%) were identified to be periprosthetic AFF (1 mid-shaft; 3 subtrochanteric). Periprosthetic AFFs had characteristics including mechanical stress due to bowing deformity and potentially suppressed bone turnover due to long-term exposure to specific drugs (e.g., bisphosphonates and glucocorticoids). Although 2 periprosthetic AFFs appeared to involve a bowed femur, one with both of the aforementioned characteristics occurred in the subtrochanteric region, which would be an unusual site for a bowed AFF, and it was demonstrated histologically to have biological activity at the fracture site, suggesting a stress fracture. Furthermore, CT/FEA revealed that tensile stress distribution changed proximally as load axis was shifted laterally according to correction of lower limb alignment by TKA. ConclusionOrthopedic surgeons should recognize the presence of TKA-associated periprosthetic AFF caused by various factors including specific drugs, bowing deformity, and lower limb alignment. X-rays of the full-length femurs should be checked regularly after TKA, especially in patients with bowed femurs or long-term exposure to specific drugs.

The role of an augmentative plating in the management of femoral subtrochanteric nonunion.

Owing to its distinct biomechanical properties, nonunion is common (7-20%) after intramedullary (IM) nailing of subtrochanteric femoral fractures. Unlike diaphyseal nonunion, it is difficult to provide sufficient stability by exchanging nailing alone in subtrochanteric nonunion. This study investigated the clinical outcomes of femoral subtrochanteric nonunion initially treated with an IM nail and subsequently managed with minimally invasive augmentative plate fixation. Nineteen patients were enrolled retrospectively. The mechanisms of initial injury were traffic accidents in 8, falls from a height in seven, and slipping in two patients. Two patients with atypical subtrochanteric femoral fractures without a specific trauma history were further included. All patients underwent IM nailing as the index operation. Nonunion surgery was performed an average of 45.2weeks after the initial surgery. In cases of hardware damage and/or atrophic nonunion, exchange nailing and bone grafting were performed in addition to augmentative plating, as necessary. Conversely, augmentative plating alone was performed in cases of hypertrophic nonunion without any failure of the preexisting IM nail or malalignment. A narrow locking compression plate was fixed after contouring according to the shape of the proximal femur. The mean follow-up period was 36.1months. Bony union was achieved in 18/19 patients (94.7%), at an average of 19.8weeks after nonunion surgery. In the case that did not heal even after exchange nailing, additional plating and bone grafting, further autogenous bone grafting was required after 11months, which healed uneventfully. There were 2 cases of soft tissue irritation over the plate, but no major complications were observed. Additional plate augmentation over a retained IM nail yields satisfactory outcomes in terms of the bony union in subtrochanteric nonunion. Given its expected biomechanical superiority and relatively easy surgical technique, it may be a reasonable option for the management of femoral subtrochanteric nonunion.

Medialized Trochanteric Entry Nailing Is a Safe and Effective Method for High-Energy Subtrochanteric Femur Fracture Treatment.

Fixation of subtrochanteric femur fractures using intramedullary nails can provide high rates of osseous union. However, a lateral starting point or a medial trajectory can result in varus alignment, typically seen with trochanteric entry nails. Even with piriformis nails, medial comminution can result in secondary malalignment and varus. Varus can predictably result in nonunion and need for repeat operations. Medialized trochanteric entry nailing has been reported previously as a method to prevent varus alignment in low-energy, atypical subtrochanteric femur fractures in association with bisphosphonate use. We present a surgical technique using a medialized trochanteric nail entry point to provide proper alignment and avoidance of varus malreduction in 24 patients with a subtrochanteric femur fracture after a high-energy traumatic event.

Functional and Radiological Outcome in Atypical Subtrochanteric Femur Fracture After Surgical Fixation: A Retrospective Observational Study.

Background: Treatment for osteoporosis can have catastrophic side effects, including the uncommon fracture known as an atypical femur fracture (AFF), which is related to the long-term usage of antiresorptive agents. Bisphosphonate therapy may lead to significant and chronic suppression of bone turnover, impairing the bone's remodelling property and finally leading to incomplete or complete atypical femur fracture. AFF was defined by the American Society for Bone and Mineral Research (ASBMR) Task Force in 2010 and is far less prevalent than proximal femur (hip) fracture, with an incidence of 2 to 78 per 100,000 patients per year following two to eight years of bisphosphonate therapy, respectively. Due to the rarity of the fracture, it is still not clear what the functional and radiological outcome will be after surgery.Aim: To identify the functional and radiological outcomes of surgical fixation of atypical femur fractures.Methods: The study was conducted in a tertiary healthcare centre after scientific and ethical clearance from the competent authority. Between January 2018 and December 2021, individuals who were diagnosed with an atypical subtrochanteric femoral fracture associated with the use of bisphosphonates and treated surgically were retrospectively evaluated. The study's inclusion and exclusion criteria were used to include 20 patients. The features of an atypical subtrochanteric fracture were congruent with the radiographic findings. Most of the patients were treated with internal fixation with intramedullary osteosynthesis in standard with or without plate osteosynthesis. They were then followed up for a year to look at the functional and radiological outcomes.Results: All of the 20 patients who were included had an atypical subtrochanteric fracture, with 15 of them being female and 5 of them being male. The patients' mean age at surgery was 65.12 (range 49 to 82) years, and their average history of bisphosphonate use was 3 (range 2.5 to 5) years. All patients were treated surgically. We found that five months was the mean period for bone union (p = 0.990). Within six months, bone union was achieved in 11 patients (55 %) (p = 0.884). Five patients (about 25%) had implant failure and non-union, requiring two to three revision surgeries. At three, six, and nine months, the mean visual analogue score (VAS) was 4.14, 3.12, and 1.85, respectively. The modified Hip Harris Score had a mean of 72.66 and 15 patients (about 75% of them) could walk normally again after a fracture. The mean of the modified HHS was 72.66, and the VAS at three, six, and nine months was 4.14, 3.12, and 1.85, respectively.Conclusion: AFFs are rare fractures that must be treated effectively, and most of them require surgery. Successful treatment of AFF is possible by the use of intramedullary fixation, which enhances axial stability, serves as an internal splint, and lessens the likelihood of implant failure. A good functional and radiological prognosis can come from a stable fixation and a fracture that has been reduced anatomically.

Metastatic Fracture Femur in Subtrochanteric Region Misdiagnosed as Bisphosphonate Fracture - A Case Report of a Very Unusual Presentation of Metastatic Fracture Femur

There is a gradual increase in atypical subtrochanteric femur fractures which are related to bisphosphonate administration. Atypical femoral fractures are difficult to manage and need a great deal of care.

The importance of reconstruction nailing for diaphyseal atypical femoral fractures: a comparative study with standard nailing

Subtrochanteric atypical femoral fractures (AFFs) usually require long cephalomedullary or reconstruction nailing to achieve satisfactory healing. Recently, this type of nailing has also been recommended to fix diaphyseal AFFs and prevent fragility fractures around the proximal femur, although standard antegrade nailing seems sufficient from a biomechanical perspective. This study aimed to compare treatment outcomes and complications between reconstruction and standard nailing for diaphyseal AFFs. A retrospective comparative study of 48 female patients with diaphyseal AFFs who underwent surgical treatment with either reconstruction or standard nailing was conducted. The reconstruction nailing group comprised 23 patients with a mean age of 74.4years and included 16 complete and 7 incomplete AFFs. The mean follow-up period was 30months. The standard nailing group comprised 25 patients with a mean age of 71.1years and included 16 complete and 9 incomplete AFFs. The mean follow-up period was 57.8months. The healing rate, time to union, and complications were analyzed and compared between the two groups. Bony union was achieved in all 23 cases (100%) of the reconstruction nailing group by a mean of 19.3weeks postoperative. In the standard nailing group, 23 of 25 cases healed (92%) by a mean of 16weeks postoperative. The standard nailing group included two delayed fragility fractures of the femoral neck (5 and 10years after the initial surgery), four cases of newly developed subtrochanteric AFFs at the distal screw of the proximal interlocking screws of the nail (one complete and three incomplete fractures), and two cases of nonunion. Complications only occurred in the standard nailing group (p = 0.01, Fisher's exact test). In diaphyseal AFFs, reconstruction nailing may achieve a satisfactory outcome and can also decrease delayed peri-implant fragility fractures of the hip, newly developed subtrochanteric AFFs, and nonunion.

Bilateral Atypical Femoral Fracture(AFF) After Teriparatide and Subsequent Anti-Resorptive Therapy: A Management Dilemma

Introduction: Femoral fractures carry devastating morbidity for long term ambulation. Atypical femoral fractures (AFF) are uncommon, and bilateral AFFs are more rare with added post-fracture limitations. We report two patients with bilateral AFFs despite receiving teriparatide (TPTD). Case 1: A 72 y.o. Filipino lady with osteoporosis since late 1990 was treated with bisphosphonates (BP) intermittently over 25 years with drug holidays for dental work. She stopped alendronate in mid-2013 and continued raloxifene. She suffered a spontaneous left mid-femur AFF in June, 2015 that was treated with intramedullary (IM) rod and nailing. In July, 2015 she started TPTD 20 mcg daily for 23 months until May, 2017. Alendronate was restarted weekly. In December, 2018 she developed right thigh and hip prodromal pain without x-ray changes. In April, 2019 (46 months after the left AFF and 23 months after TPTD), she sustained a spontaneous right sub-trochanteric AFF. BP was stopped. After IM rod and nailing, she began a second course of TPTD. Case 2: 72 y.o Caucasian lady with osteoporosis since 2000 was treated with alendronate until April, 2006. She was switched to daily TPTD for 22 months from May, 2006 to March, 2008. Oral BP was resumed in April, 2008. She suffered a left AFF in November, 2009; BP was stopped in March, 2010. In July, 2010 she sustained a right AFF (9 months after the left AFF and 28 months post-TPTD). Each spontaneous AFF occurred after prodromal pain, and each was treated with IM rod placement with nailing. She received BP infusion in 2011 and TPTD from March, 2012 to March, 2014. DXA scan in 2020 showed lumbar spine osteopenia. She currently takes calcium and Vit D supplementation. Discussion: TPTD is reported as a potential treatment for enhancing AFF healing, bone mineral density and pain resolution. The expectation is that it might prevent contralateral AFF. No randomized studies of prevention of AFF with TPTD exist. Available reports show variable results. Prolonged presence of BP in bone may contribute to this variation. We identified 7 reported AFF patients treated with TPTD who then developed a contralateral AFF. We found 2 patients with new AFF after TPTD as in our Case 2. In all cases there was previous exposure to BP. Perhaps the 28–30% risk of a contralateral AFF within 4 years in the setting of BP is irremediable. Conclusion: TPTD increases healing of AFF in some reports, but prevention of an initial or further AFF has not been well documented. Our 2 patients and 9 others reported suggest a possible subset with increased sensitivity to the effect of BP and increased AFF risk. The best choice after TPTD is unclear, but it may include permanent removal of anti-resorptive agents. The anti-sclerostin antibody romosozumab also has been associated with AFF. Choices are limited for these patients other than excellent surgical care, adequate calcium/vitamin D intake, and periodic imaging as symptoms dictate.

Differences in subtrochanteric and diaphyseal atypical femoral fractures in a super-aging prefectural area: YamaCAFe Study.

Atypical femoral fractures (AFFs) have been correlated with long-term use of bisphosphonates (BPs), glucocorticoids (GCs), and femoral geometry. We investigated the incidence and characteristics of subtrochanteric (ST) and diaphyseal (DP) AFFs in all institutes in a super-aging prefectural area. We performed a blinded analysis of radiographic data in 87 patients with 98 AFFs in all institutes in Yamagata prefectural area from 2009 to 2014. Among the 98 AFFs, 57 AFFs comprising 11 ST fractures in 9 patients and 46 DP fractures in 41 patients with adequate medical records and X-rays were surveyed for time to bone healing and geometry. Of the 87 patients, 67 received BPs/denosumab (77%) and 10 received GCs (11%). Surgery was performed in 94 AFFs. Among 4 AFFs with conservative therapy, 3 required additional surgery. In univariate regression analyses for ST group versus DP group, male-to-female ratio was 2/7 versus 1/40, mean age at fracture was 58.2 (37-75) versus 78 (60-89) years, rheumatic diseases affected 55.5% (5/9) versus 4.9% (2/41), femoral lateral bowing angle was 1.7 (0-6) versus 11.8 (0.8-24)°, GC usage was 67% (6/9) versus 4.9% (2/41), and bone healing time was 12.1 (6-20) versus 8.1 (3-38) months (p < 0.05). In multivariate analyses, higher male-to-female ratio, younger age, greater proportion affected by rheumatic diseases, and higher GC usage remained significant (p < 0.05). The incidence of AFFs in our prefectural area was 1.43 cases/100,000 persons/year. This study suggeststhat theonset of ST AFFs have greater correlation with the worse bone quality, vice versa, the onset of DP AFFs correlatedwith the bone geometry. The developmental mechanisms of AFFs may differ significantly between ST and DP fractures.

Histopathological Finding of Microdamage Accumulation in Atypical Subtrochanteric Femoral Fracture

Atypical femoral fracture is a low-energy stress fracture in the subtrochanteric region or the femoral shaft and is a complication of the long-term use of bisphosphonates. Histopathological findings of atypical femoral fractures have not been clarified. Herein, we report the case of a 61-year-old woman who fell while walking, which prompted her to visit our facility. She had a 7-year history of alendronate use to treat osteoporosis. A radiograph showed an atypical subtrochanteric femoral fracture, following which she underwent a primary surgery, where an intramedullary femoral nail was used. Implant breakage was discovered 8 weeks after the primary surgery. The patient underwent a revision surgery in which the entry point for the revised intramedullary hole was created to prevent varus position. The lag screw was successfully inserted into the center of the femoral head. Cancellous bone, isolated from the right ilium, was autogenously implanted into the fracture site. Fracture healing was promoted using low-intensity pulse ultrasonography. Callus formation was detected on a radiograph, and full weight-bearing was advised 12 weeks after the revision surgery. The fracture had healed completely at 13 months after the revision surgery. The patient was able to walk without support and could independently perform activities of daily life. Laboratory findings suggested that the concentrations of her bone formation markers were normal, while those of bone resorption markers were elevated. Iliac bone histomorphometry did not reveal severely suppressed bone turnover. In the cortex of fracture site, the lacunar density was markedly lower than the osteocyte density, and microcracks were detected, suggesting impaired osteocyte function and a low potential for fracture healing. This case is notable because it helps to clarify the histopathological findings of atypical femoral fractures.

Femoral Bowing and Femoral Neck-Shaft Angle Evaluation Can Reduce Atypical Femoral Fractures in Osteoporotic Patients: A Scientific Report.

Bisphosphonates (BPs) are the mainstay of osteoporosis treatment due to their safety and efficacy. There is evidence that BPs medication may be complicated by atypical femoral fractures (AFFs). Prolonged administration of BPs is even more strongly associated with AFFs. AFF is a relatively rare complication of BPs when taking into account the huge population worldwide that benefits from this pharmacotherapy. AFF is, however, a serious complication of BPs treatment, which includes prolonged healing time and high revision rate when operative treatment is required. Less frequently, AFFs occur even without BPs administration, while these fractures have all the characteristics of “stress” or “insufficiency” fractures. The critical point of view in AFFs pathogenesis seems to be not only the biology of cortical bone, but also the mechanical issue. It has been proven that BPs, glucocorticoids and proton pump inhibitors (PPIs) can cause bone turnover suppression and affect the biological parameter of AFFs pathogenesis. Specific mechanical femoral bone properties predispose to AFFs pathogenesis. Several studies have already reported that increased femoral bowing > 5.250 degrees or decreased femoral neck-shaft angle <125 degrees, are associated with increased risk for diaphyseal and subtrochanteric AFFs respectively, regardless of BPs uptake. If these two parameters are simultaneously present, the probability for AFFs occurrence increases dramatically. Our scientific report, which is based on the current evidence about AFFs, is that if both femoral bowing angle and femoral neck-shaft angle are evaluated before BPs administration, this intervention may reduce the incidence of AFFs. Thus, in cases with excessive lateral femoral shaft bowing or very small femoral neck-shaft angle, the prescription of another anti-osteoporotic treatment than BPs should be recommended. If, however, BPs can’t be avoided, clinicians should be aware of the fact that long-term administration may be implicated with AFFs occurrence. In these cases, short term BPs administration with timely drug holiday between three and five years may be reasonable. Finally, roentgenographic evaluation of both femurs every six months and medical reference in case of any emerging thigh pain are also logical interventions to prevent and reduce AFFs.

Evaluation of factors affecting the occurrence of second atypical fracture after bone union of the first atypical fracture.

Teriparatide is sometimes used in the treatment of atypical femoral fracture (AFF). Even if bone union is achieved, orthopedic physicians must consider the risk of relapse. This study aimed to investigate the factors affecting AFF recurrence, and to determine the appropriate treatment for osteoporosis after bone union. One hundred thirty-one consecutive AFFs in 113 Japanese patients were included. Eleven patients had AFF in the unaffected limb (9 patients) after the first AFF or re-fracture at the original fracture site (2 patients) after bone union of the first AFF was confirmed. We divided all patients into two groups: the second fracture group (22 AFFs in 11 patients) and non-second fracture group (109 AFFs in 102 patients). We compared clinical information between the 2 groups and investigated the factors affecting AFF recurrence using the Student t-, Welch t-, and chi-square tests. Although there was no significant difference in clinical characteristics between the 2 groups, multivariate analysis of factors associated with AFF recurrence identified short duration of treatment with teriparatide and active vitamin D3 (p=0.0408 and 0.0366, respectively) as risk factors. Even in the analysis excluding subtrochanteric AFF, short periods of teriparatide and active vitamin D3 administration were observed as risk factors (p=0.0484 and 0.0346, respectively). The administration of teriparatide for as long as possible after occurrence first AFF and the use of active vitamin D3 after completion of teriparatide therapy may be the most effective strategy to prevent the recurrence of AFF.

Biological activity is not suppressed in mid-shaft stress fracture of the bowed femoral shaft unlike in "typical" atypical subtrochanteric femoral fracture: A proposed theory of atypical femoral fracture subtypes.

We have investigated mid-shaft stress fractures of the bowed femoral shaft (SBFs), well before the first report of an association between suppression of bone turnover and atypical femoral fractures (AFFs). Although all cases of SBF meet the criteria for AFF, SBFs can also occur in patients with no exposure to bone turnover suppression-related drugs (e.g., bisphosphonates). Using bone morphometry and biomechanical analyses, we devised a theory of AFF subtypes, dividing AFFs into fragility SBFs in the mid-shaft and "typical" subtrochanteric AFFs caused by suppressed bone turnover. The aim of this multicenter prospective study was to provide evidence for this novel concept in terms of biological activity. The study was conducted at 12 hospitals in Japan from 2015 through 2019. Thirty-seven elderly women with AFF were included and classified according to location of the fracture into a mid-shaft AFF group (n=18) and a subtrochanteric AFF group (n=19). Patient demographics and clinical characteristics were investigated to compare the two groups. The main focus was on histological analysis of the fracture site, and bone metabolism markers were evaluated to specifically estimate biological activity. All patients in the subtrochanteric AFF group had a history of long-term (>3years) exposure to specific drugs that have been reported to cause AFF, but 5 of the 18 patients in the mid-shaft AFF group had no history of exposure to such drugs. Femoral bowing was significantly greater in the mid-shaft AFF group (p<0.001). In the histological analysis, active bone remodeling or endochondral ossification was observed in the mid-shaft AFF group, whereas no fracture repair-related biological activity was observed in the majority of patients in the subtrochanteric AFF group. Levels of tartrate-resistant acid phosphatase-5b and undercaroxylated osteocalcin were significantly lower in the subtrochanteric AFF group (p<0.05). The possibility of our devised AFF subtype theory was demonstrated. Biological activity tends not to be suppressed in mid-shaft SBFs unlike in "typical" subtrochanteric AFFs involving bone turnover suppression. Although validation of the proposed theory in other populations is needed, we suggest that the pathology and treatment of AFFs be reconsidered based on its subtype.

O01 Hypophosphatasia in adults at a specialist centre in the UK: the spectrum of musculoskeletal disease

Abstract Background Hypophosphatasia (HPP) is a condition arising due to mutations in the gene encoding the tissue-non-specific alkaline phosphatase (TNSALP) isoenzyme (ALPL), leading to deficient activity of TNSALP. It can be inherited as an autosomal dominant or recessive disorder. There are over 300 known mutations in the ALPL gene associated with HPP, leading to varying degrees of deficiency in the activity of TNSALP. There are six clinical forms of HPP, with a great degree of heterogeneity in clinical presentation. The adult form is generally milder than perinatal and infantile forms, which may be fatal. Estimates of the prevalence of HPP range from 0.3/100,000 (more severe forms), to 1/6370 (less severe forms). Diagnosis is based on clinical features, biochemical abnormalities (low serum alkaline phosphatase (ALP), raised serum pyridoxal-5’-phosphate and raised urinary phosphoethanolamine), and genetic testing. The dentition and musculoskeletal system are often affected. Low trauma, metatarsal and atypical subtrochanteric femoral fractures may be seen, often with poor healing. However in some cases, individuals may present with calcium pyrophosphate deposition disease (CPPD) or non-specific musculoskeletal features. Under-recognition of HPP and diagnostic delay are therefore common. This retrospective observational study, performed at a specialist centre, aimed to characterise the spectrum of musculoskeletal manifestations in adults with HPP. Methods Patient records of adults with a confirmed diagnosis of HPP seen in the Rheumatology department at St George’s Hospital, London, were consulted. Clinical features at presentation and those developed subsequently were recorded, with a focus on musculoskeletal manifestations. Biochemical, genetic and radiographic data were also obtained. Results Fifteen individuals (two male, thirteen female) with a confirmed diagnosis of HPP were identified. Average delay to diagnosis was 21 years. The commonest presenting feature for the whole cohort was joint pain or swelling, followed by dental caries. The commonest presenting musculoskeletal feature in childhood was fracture (often low trauma and recurrent); in adults it was joint pain followed by poor mobility. There were eight diagnoses of osteoarthritis, five cases of tendinopathy and three of bursitis. Four patients had previously been diagnosed with psoriatic arthritis and three with pseudogout. Other musculoskeletal diagnoses included patellofemoral dysfunction, hypermobility and musculoskeletal tumours (two individuals). The upper limb joints were most commonly affected; some individuals reported back and knee pain. Musculoskeletal morbidity was high: eight individuals had poor mobility or abnormal gait, and three were unable to work through ill health. Conclusion There is a long delay to diagnosis of HPP. The condition may present in adults with non-specific musculoskeletal or dental features. It is therefore important to consider the diagnosis in individuals with a low ALP and musculoskeletal features which may suggest HPP, such as fractures or CPPD. Earlier recognition may avoid potential harm through inappropriate bisphosphonate or high-dose vitamin D therapy. Disclosures J. Kotecha None. S. Mansour None. C. Hall None. K.E. Moss None.

Atypical subtrochanteric and diaphyseal femoral fractures associated with a bisphosphonate therapy

Atypical subtrochanteric and diaphyseal femoral fractures associated with a bisphosphonate therapy

Is Full-Length Intramedullary Nail Necessary for Atypical Subtrochanteric Femoral Fracture Associated with Bisphosphonate?

BackgroundAmerican Society for Bone and Mineral Research recommend the use of intramedullary reconstruction of full length-nail for atypical subtrochanteric femoral fracture (ASFF). However, there is no study on the incidence of the ipsilateral femoral fracture after index operation of ASFF, and full-length nail has disadvantage as iatrogenic fracture and leg length discrepancy (LLD). The aim of this study was to investigate the incidence of ipsilateral secondary fracture after using partial-length nail, and to compare the outcomes on surgery of ASFF between partial length-nails and full length-nails.MethodsForty-five consecutive fractures with ASFFs which had undergone intramedullary fixation using cephalomedullary nail between 2011 and 2018 were enrolled. The 45 cases were grouped based on nail length into the partial-length nail group (n=26) and the full-length nail group (n=19). Ipsilateral secondary fracture, time to union, intra-operative iatrogenic fracture, metal failure, LLD, operative duration, and post-operative 24-hr blood loss were investigated.ResultsThere was no ipsilateral secondary fracture after index operation. There were no statistically significant differences between the partial-length nail and full-length nail groups in the time to union, LLD, and post-operative 24-hr blood loss (P=0.427, 0.478, and 0.228, respectively). Operative duration showed statistically significant difference between 2 groups (P=0.034). Metal failure were occurred in 1 (3%) case of the partial-length nail group and 2 (10%) cases of the full-length nail group. Iatrogenic fractures during nail insertion occurred in 2 (7%) cases of the partial-length-nail group and 3 cases (15%) of the full-length nail group.ConclusionsAlthough large scale studies are required, our study indicate that full-length nails are not usually required for the treatment of ASFF.

Corrigendum: Failure of Intramedullary Nailing for Subtrochanteric Atypical Femoral Fractures Caused by Endosteal Cortical Thickening

Corrigendum: Failure of Intramedullary Nailing for Subtrochanteric Atypical Femoral Fractures Caused by Endosteal Cortical Thickening

Potential bone fragility of mid-shaft atypical femoral fracture: Biomechanical analysis by a CT-based nonlinear finite element method

IntroductionThe authors previously reported a CT-based nonlinear finite element analysis (nonlinear CT/FEA) model to investigate loading stress distribution in the femoral shaft of patients with atypical femoral fractures (AFFs). This showed that stress distribution, influenced primarily by femoral bowing, may determine the location of AFF. Here, we demonstrate the locational characteristics associated with AFFs in an Asian, specifically Japanese, population regarding bone strength. This is the second report from our multicentre research project suggesting a possible new concept of diagnostic criteria or treatment according to AFF subtype. Patients and methodsA multicentre prospective study was conducted at 12 hospitals in Japan from August 2015 through June 2018. We recruited three study groups composed of elderly females over the age of 60 years—the mid-shaft AFF group (n = 14; 80.0 ± 6.5 years), the subtrochanteric AFF group (n = 15; 73.9 ± 6.8 years), and the control group who had sustained unilateral hip fracture (n = 21; 82.1 ± 7.1 years)—and analysed femoral neck bone density and strength. Bone strength of the femoral neck was predicted with an evaluation method using nonlinear CT/FEA in both standing and falling configuration. ResultsFemoral neck bone density and strength were significantly higher in the subtrochanteric AFF group compared with the mid-shaft AFF and control groups (p < 0.0001). No significant difference was seen in bone strength between the mid-shaft AFF and control groups (standing, p = 0.7616; falling, p = 0.3803). ConclusionsAFF has different features, in terms of bone strength, depending on fracture location. At the very least, Japanese patients with mid-shaft AFF could be at high risk of hip fracture because of bone fragility, in contrast to the firm bone of subtrochanteric AFF. For internal fixation of mid-shaft AFF using an IM nail, cervical screw insertion toward the femoral head might be recommended to prevent possible hip fracture.