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The aim of this study was to investigate the relationship between acetabular labral length and symptoms in patients with acetabular dysplasia. In a retrospective medical record review, 218 patients with acetabular dysplasia who had undergone rotational acetabular osteotomy were identified. After implementing the inclusion and exclusion criteria, 53 patients were analyzed for preoperative symptoms measured by the Japanese Orthopaedic Association Hip Disease Evaluation Questionnaire (JHEQ), acetabular bone morphology parameters by anteroposterior pelvic radiographs and labral parameters by radial magnetic resonance imaging. Spearman’s correlation coefficients were calculated among JHEQ scores, bone morphologic parameters and labral parameters. Multiple linear regression models to determine the predictive variables of JHEQ score and labral length were obtained. There was no correlation between bone morphologic parameters and JHEQ scores. Labral length measured anteriorly correlated with JHEQ pain {r [95% confidence interval (CI)] = −0.335 (−0.555, −0.071), P = 0.014}, movement subscale [r (95% CI) = −0.398 (−0.603, −0.143), P = 0.003], mental subscale [r (95% CI) = −0.436 (−0.632, −0.188), P = 0.001] and total JHEQ score [r (95% CI) = −0.451 (−0.642, −0.204), P = 0.001]. The multiple linear regression results showed that anterior labral length was independently associated with JHEQ subscales in some models. Meanwhile, age, acetabular head index and total JHEQ score were independently associated with anterior labral length in all models. Labral length, notably in anterosuperior area, in patients with symptomatic acetabular dysplasia was related to patient’s symptom. Labral length may be an important objective image finding that can be used to assess the severity of cumulative hip instability.

The acetabular morphology varies greatly among individuals, and hypoplasia is more common in Asia than in Europe. Dislocation after bipolar hip arthroplasty (BHA) for femoral neck fracture occurs at a constant rate, and is affected by the acetabular morphology. This study aimed to clarify individual differences in the acetabula of Asian patients with displaced femoral neck fractures.Fifty patients with displaced femoral neck fractures were assessed (50 fractured hips, 50 non-fractured hips). On CT corrected by the anterior pelvic plane, the 100 hips were assessed regarding acetabular coverage (six parameters), acetabular depth (two parameters), and acetabular opening angle (four parameters). Additional parameters related to the fracture and sex were examined. The percentile of each parameter was shown for all hips.There was no patient with hip dysplasia defined as superior acetabular sector angle (SASA) less than 110° Compared with men, women had a significantly smaller anterior acetabular sector angle (AASA) (p = 0.016), and significantly larger acetabular inclination angle (p = 0.006) and acetabular index angle (p = 0.034). In the group with a normal SASA, seven hips (7.3%) had an anterior wall defect (AASA50°) and five hips (5.2%) had a posterior wall defect (posterior acetabular sector angle90°).Older adults with femoral neck fractures can have anterior wall and posterior wall defects, even if their SASA is normal. Hidden acetabular dysplasia may be related to post-BHA dislocation. So, our results suggest that is important to accurately evaluate the acetabulum of patients with femoral neck fracture before surgery.

Avoiding stem subsidence is crucial for achieving better outcome for cementless total hip arthroplasty (THA). The aim of this study was to develop a prediction model for the incidence of post-operative stem subsidence using full quantitative acoustic parameters in hammering sound during the broaching procedure and to assess the accuracy of this prediction model.The acoustic parameters of the hammering sounds during a broaching procedure for 55 hips in 49 patients who underwent THAs with cementless taper-wedged stem were analysed. The stem subsidence was assessed at one month post-operatively, and the relationship between the acoustic parameters and the value of stem subsidence was investigated.The average stem subsidence was 2.15 ± 2.91 mm. The subsidence 3 mm or more was observed in eleven hips (20%), and 5 mm or more was observed in seven hips (12.7%). Basic patient's characteristics, preoperative femoral morphology and immediate post-operative canal fill ratio and stem alignment were not significantly related to the volume of stem subsidence. Nine acoustic parameters were significantly correlated with the value of subsidence. The prediction model for post-operative subsidence using only acoustic parameters during broaching procedure was established, and this model showed a positive prediction value of 100% and a negative prediction value of 90.6% for post-operative stem subsidence at 5 mm or more.Post-operative stem subsidence can be predicted by using acoustic parameters of the hammering sound during the broaching procedure. Our results suggest that we are at the start of a new era in which novel and innovative smart technologies can be used to assist in orthopaedic surgery.

Acoustic analysis has recently been applied to cementless total hip arthroplasty (THA). The aim of this study was to develop a machine learning algorithm to predict post-operative subsidence with high accuracy.The acoustic parameters of the hammering sounds during a broaching procedure for 62 hips in 55 patients who underwent THAs with cementless taper-wedged stem were analysed. The patient's basic background such as age, sex, height, weight and body mass index, the femoral morphological parameters and the hammering sound characteristics of 24 features of normalised sound pressure (nSP) in 24 frequency ranges were applied to binary classification using a support vector machine using the following models with different features: model A, nSP only; model B, nSP + patients' basic background features; model C, nSP + patients' basic background features + femoral morphological parameters.In 62 hips with 310 hammering sounds, 12 hips (19.4%) showed ≥ 3 mm of post-operative subsidence; hence, 60 hammering sounds were set as positive examples and 250 hammering sounds were set as negative examples. The AUC was very high in all models. The accuracy (AUC/sensitivity/specificity/positive predictive value/negative predictive value/accuracy rate) of each model was as follows: model A, 0.963/0.656/0.996/0.980/0.925/0.934; model B, 0.9866/0.675/1.000/1.000/0.928/0.937 and model C, 0.998/0.750/1.000/1.000/0.950/0.957.In this study, we developed a high-accuracy machine learning algorithm for post-operative subsidence using acoustic parameters and additional pre-operative features. Our results represent a step toward the realisation of acoustic monitoring to avoid the complication in cementless THA.

Background: This study aims to investigate the clinical outcome of unstable femoral trochanteric fractures treated by hip arthroplasty through direct anterior approach (DAA). Methods: The subjects were patients with unstable femoral trochanteric fractures who were independently ambulatory before injury. Twenty-two patients who underwent hip replacement between 2019 and 2021 (arthroplasty group), and 22 patients treated by osteosynthesis between 2016 and 2018 (osteosynthesis group) were compared. Results: Regarding complications, reoperation, dislocation, or infection did not occur, but over telescoping of the lag screw larger than 10 mm was noted in 4 patients (18.2%) in the osteosynthesis group. No significant difference was noted in the mean Barthel Index score on admission, but it was significantly different at discharge (arthroplasty group: 71.4±17.3, osteosynthesis group: 48.0±23.1, PConclusion: Hip arthroplasty through DAA did not cause postoperative dislocation. For unstable trochanteric fractures, patients who underwent hip arthroplasty through DAA had a higher Barthel index at discharge and a higher maintenance rate of walking ability at 1 year after surgery than those who underwent osteosynthesis. Hip arthroplasty through DAA is effective for the treatment of unstable femoral trochanteric fractures considering functional recovery of the hip joint.

The diagnosis of and decision-making for early revision surgery to treat failure of biological fixation with a proximally coated cementless stem are challenging. A 73-year-old woman was referred to our hospital with thigh pain 2 years after the initial total hip arthroplasty. Although a plain radiograph showed no signs indicating biological fixation failure, digital tomosynthesis showed a highly radiodense line along the proximal part, and bone scintigraphy showed uptake at the distal part. With the diagnosis of biological fixation failure due to the proximal-distal mismatch, the cementless stem was revised to a cemented stem, and the thigh pain was improved after the revision surgery. Digital tomosynthesis and bone scintigraphy can be helpful for the diagnosis of biological fixation failure due to proximal-distal mismatch.

Corrosion of stem-cobalt/chromium (Co/Cr) head interface and subsequent systemic Co ion complication have been a clinical concern after total hip arthroplasty (THA). The aim of this study is to investigate correlation between type of femoral head and blood Co ion level.One hundred four patients with THA using accolade TMZF and Co/Cr femoral head (32-mm; 55 cases, 36-mm; 20 cases, dual mobility system (DM) with 22.2 or 28-mm inner head; 29 cases) participated in this study, and blood Co ion concentration test was performed in patients a minimum of four years after THA.DM group was significantly older than 32-mm and 36-mm group (DM: 73.9 ± 4.6, 32-mm: 63.3 ± 8.5, 36-mm: 66.8 ± 10.5). The median (interquartile range) blood Co concentration of each group was 32-mm group 0.26 µg/L (0.69), 36-mm group; 0.21 µg/L (0.30); and DM group 0.21 µg/L (0.13). There was a significant difference of Co concentration between DM and 32-mm group (p = 0.023). Abnormal values of the blood Co concentration ( 1 µg/L) were observed in the 32-mm group; 12 cases (21.8%), 36-mm group; 2 cases (10.0%); and DM group; 0 case (0%) (p = 0.018).Co blood concentration differed among the different sizes of Co/Cr femoral head. THA using DM is a safe option with low risk of complication from cobalt ion if it is used for elderly patients.

Postoperative over-telescoping (OT) with lag screws is often observed in reverse oblique intertrochanteric fractures. This study aimed to clarify the risk factors of OT in patients with reverse oblique intertrochanteric fractures.Electronic medical records of patients diagnosed with reverse oblique intertrochanteric fractures using plain radiography who underwent operative fixation with an intramedullary nail between August 2013 and December 2019 were reviewed. Patients were classified into two groups according to the Futamura classification: lateral wall pattern (LW) and reverse oblique pattern (RO). The incidence of OT in the LW and RO groups was compared. Also, we compared the incidence of OT for each reduction type in the LW group.Twenty patients had LW, and nine had RO. OT was observed in eight fractures (42.1%) in the LW group but not in the RO group. The incidence of OT was significantly higher in the LW group than in the RO group (P = 0.0261). Among the 19 fractures with LW, OT was observed in 7 of 10 and 1 of 9 fractures with postoperative reduction in the intramedullary and extramedullary or anatomical types, respectively. In the LW group, the incidence of OT was significantly higher in fractures with postoperative reduction in the intramedullary type than in those of the extramedullary or anatomical type (P = 0.0198).Our study showed that the incidence of OT was significantly higher in LW than in RO and that postoperative reduction in the intramedullary type in LW was a risk factor for OT.

In nanocomposites, improved mechanical performance is critically linked to understanding and controlling interfacial properties. In the work reported here, ion implantation is introduced as a new method for tailoring the complex nanoscale interfaces between multiwall carbon nanotubes (MWCNTs) and a ceramic matrix. The results show that surface layers of the nanocomposite with high toughness can be created with C2+ ions. This enhanced toughening due to ion implantation is associated with large compressive stresses in the MWCNTs and with significant changes in the carbon structure. These observations are consistent with molecular dynamics (MD) simulations, which indicate that partial amorphization of the MWCNTs is enhanced by the compressive stress and confinement within the ceramic matrix. This work opens up new opportunities for using ion implantation to create a new class of exceptionally tough ceramic nanocomposites.

Along with the accumulating reports of autologous concentrated bone marrow (CBM) grafting for osteonecrosis of the femoral head (ONFH), the related medical device, a "point-of-care device" has also been recently developed. However, no study has confirmed the feasibility, safety, and efficiency of CBM grafting using a specific point-of-care device.We designed this phase I, prospective clinical study to evaluate the feasibility and safety of autologous CBM grafting processed using a point-of-care device, the BioCUE system, in patients with ONFH. The primary outcomes were the safety and adverse event (AE), the secondary outcomes included pain score; hip function score; ONFH stage using X-ray; and the volume of the osteonecrotic area on 3T MRI. Besides, safety quality tests on the final product of concentrated bone marrow were performed.Two patients (a 34-year-old man and a 33-year-old woman; three hips) with systemic lupus erythematosus were included. The incidence of AEs was 100% such as pain or transient fever after the operation, but all AEs were nonserious. No peri-operative complications were observed. Pain and hip function score remained unchanged from the preoperative to the postoperative observational periods. Safety quality test demonstrated were all negative or under the threshold.The feasibility and safety of grafting of concentrated autologous CBM in patients with ONFH using a point-of-care device were confirmed. A further clinical study aiming for the authorization of this procedure should be conducted in the future.

Purpose Currently, sacroiliac joint dislocations, including crescent fracture–dislocations, are treated using several techniques that have certain issues. We present the technical details and clinical outcomes of a new technique, anterior sacroiliac stabilisation (ASIS), performed using spinal instrumentation. Methods ASIS is performed with the patient in a supine position via the ilioinguinal approach. The displacements are reduced and fixed by inserting cancellous screws from the sacral ala and iliac brim; the screw heads are bridged using a rod and locked. We performed a retrospective review of patients with iliosacral disruption who underwent ASIS between May 2012 and December 2020 at two medical facilities. The patients were assessed for age, sex, injury type, associated injuries, complications, functional outcome by evaluating the Majeed pelvic score after excluding the sexual intercourse score and fracture union. Results We enrolled 11 patients (median age: 63 years). The median operative time was 195 min, median blood loss was 570 g, and eight patients (72.3%) required blood transfusion. The sacral and iliac screws had a diameter of 6.0–8.0 mm and 6.2–8.0 mm, and a length of 50–70 mm and 40–80 mm, respectively. Bone union was achieved with no marked loss of reduction in the median follow-up period of 12 months in all cases. The median Majeed score at the final follow-up was 85/96. Conclusion ASIS is a rigid internal fixation method that provides angular stability. Despite invasiveness issues compared to iliosacral screw fixation, this method is easy to confirm and achieves precise reduction.

Background A large-diameter femoral head is effective in preventing dislocation after total hip arthroplasty. However, although rare, catastrophic stem tribocorrosion may occur at the head-stem junction. Case presentation A 70-year-old woman underwent revision surgery 7.5 years after total hip arthroplasty because of catastrophic stem corrosion with dissociation of the metal head (cobalt/chromium) and stem (TiMo12Zr6Fe2). Abnormal levels of cobalt were found in the intra-articular fluid, capsule, hip muscle, and blood. Revision surgery was performed via the direct anterior approach. The well-fixed femoral stem was explanted, and a cemented stainless stem with stainless head was implanted. Three months after the revision surgery, the cobalt concentration in the blood had decreased to normal. Conclusions Stem dissociation in the present case might have been caused by synergistic combination of a 36-mm-diameter femoral head and long neck length offset with high frictional torque, a cobalt-chromium head with a high risk of galvanic corrosion, and a TMZF (TiMo12Zr6Fe2) alloy stem with a low Young’s modulus of elasticity. The combination of these factors must be avoided.

It is difficult to investigate clinical features in a single-center study because atypical periprosthetic femoral fracture (APFF) is rare. This study aims to perform a nationwide survey of APFF to investigate the characteristics of this fracture and compare the clinical outcome with that of typical periprosthetic femoral fracture (typical PFF). A nationwide survey was performed asking for cooperation from 183 councilors of the Japanese Society for Fracture Repair. The subjects were patients with APFF injured between 2008 and 2017. The control group was comprised of patients with typical PFF of our facility injured in the same period. A total of 43 patients met the APFF definition. The control group was comprised of 75 patients with typical PFF. The rate of bisphosphonate use was significantly higher in the APFFs group than in the typical PFF group (62.8% and 32%, p p p = 0.045). However, no significant association between PFF and APFF was observed in the patients with arthroplasty for other hip diseases. The risk of complications was higher in the APFF group than in the typical PFF group in the patients with arthroplasty for fracture. When AFPP after arthroplasty for the fracture is suspected, it may be necessary to add not only internal fixation with a normal plate but also some additional treatment.

Recent studies have focused on hammering sound analysis during insertion of the cementless stem to decrease complications in total hip arthroplasty. However, the nature of the hammering sound is complex to analyse and varies widely owing to numerous possible variables. Therefore, we performed a preliminary feasibility study that aimed to clarify the accuracy of a prediction model using a machine learning algorithm to identify the final rasping hammering sound recorded during surgery. The hammering sound data of 29 primary THA without complication were assessed. The following definitions were adopted. Undersized rasping: all undersized stem rasping before the rasping of the final stem size, Final size rasping: rasping of the final stem size, Positive example: hammering sound during final size rasping, Negative example A: hammering sound during minimum size stem rasping, Negative example B: hammering sound during all undersized rasping. Three datasets for binary classification were set. Finally, binary classification was analysed in six models for the three datasets. The median values of the ROC-AUC in models A–F among each dataset were dataset a: 0.79, 0.76, 0.83, 0.90, 0.91, and 0.90, dataset B: 0.61, 0.53, 0.67, 0.69, 0.71, and 0.72, dataset C: 0.60, 0.48, 0.57, 0.63, 0.67, and 0.63, respectively. Our study demonstrated that artificial intelligence using machine learning was able to distinguish the final rasping hammering sound from the previous hammering sound with a relatively high degree of accuracy. Future studies are warranted to establish a prediction model using hammering sound analysis with machine learning to prevent complications in THA.

Background; An incision for total hip arthroplasty (THA) via the direct anterior approach (DAA) is generally made outside of the space between sartorius and tensor fasciae lataea muscles to prevent lateral femoral cutaneous nerve (LFCN) injury. Recent anatomical studies have revealed that the LFCN not only courses between the sartorius and tensor fasciae latae muscles, but it also branches radially while distributing in the transverse direction from the sartorius muscle to the tensor fasciae latae muscle. The latter is called the fan type, and studies suggest that damage to the fan type LFCN is unavoidable by conventional fasciotomy. We previously demonstrated that injury to non-fan type LFCN occurred in 28.6% of patients who underwent THA by fasciotomy performed 2 cm away from the intermuscular space. This suggests that the conventional approach also poses a risk of LFCN injury for non-fan type LFCN. LFCN injury is rarely reported in the anterolateral approach (ALA), which involves incision of fascia further away than DAA. The purpose of this study is to investigate how the position of fasciotomy in DAA affects the risk of LFCN injury. Methods; This is a prospective, randomized, controlled study. All patients are divided into the fan type and non-fan type using ultrasonography before surgery. Patients with the non-fan type LFCN will be performed by the conventional fasciotomy and the lateral fasciotomy in the order specified in the allocation table created in advance by our clinical trial center. The primary endpoint is the presence of LFCN injury. The secondary endpoints will be assessed based on patient-reported outcomes (PROs) at 3 months after surgery in an outpatient setting using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), the Japanese Orthopaedic Association Hip-Disease Evaluation Questionnaire (JHEQ), and the Forgotten-Joint Score-12 (FJS-12). Discussion; We hypothesize that the incidence of LFCN injury due to DAA-THA can be reduced by making the incision further away from where it is typically made in conventional fasciotomy. If our hypothesis is confirmed, it will reduce the disadvantages of DAA, improve patient satisfaction. Trial registration; UMIN Clinical Trials Registry, UMIN000035945.Registered on 20 Feburary 2019.

Cortical hypertrophy (CH) after total hip arthroplasty (THA) is thought as a process of femoral cortical functional adaptation against the stem. However, no study has been performed to investigate the association between CH and femoral head size. The purpose of this study is to investigate the factors related to femoral CH around the cementless stem after THA. THAs in 31 patients using 36-mm metal head and as a control, age-matched 62 THAs with 32-mm metal head have been analyzed. Radiographs were reviewed at four years to determine cortical thickness change from immediate post-operative one. Pre-operative and immediate post-operative radiographs were used to calculate the femoral morphology, canal fill ratio, stem alignment, and femoral and acetabular offset. Univariate and multivariate logistic regression analyses were performed to identify the risk factors for CH. Patients with a 36-mm metal head had a significantly higher rate of severe CH (P = 0.001) than those with a 32-mm metal head. The multivariate logistic regression analysis with dependent variables of CH showed that the use of a 36-mm metal head had a significantly positive effect on CH. The odds ratio of a 36-mm metal head in mild CH was 2.517 (95% confidence interval, 1.032–6.143; P = 0.043), and that in severe CH was 8.273 (95% confidence interval, 2.679–25.551; P = 0.000). Age and the canal flare index were weakly and negatively influenced by mild CH. The use of a 36-mm metal head was the dominant risk factor for CH.

The aim of this study was to evaluate the role of Charlson comorbidities index (CCI) and cofactors on 2-year mortality in older patients with intertrochanteric fractures. 60 cases with unilateral intertrochanteric fracture were retrospectively analyzed and divided into Low-CCI group (CCI: 1-4) or high-CCI groups (CCI: 5-6). All the patients’ electronic hospital records were reviewed. The preoperative situations (demographic data, comorbidities and fracture conditions), perioperative situations (wait time, operation time, implant choice, blood loss, transfusion or not) and postoperative situations (complications, first time out of bed, function about 1-/2- week and 2-year mortality) were recorded. 51.67% were in low-CCI group and 48.33% in high-CCI group. The survival rates in low- and high-CCI group were 93.5% and 86.2 % respectively. According to the functional results of 1- or 2- week after operation, no significant difference was found (P=0.955, 0.140). Log-rank analysis showed that the main prognostic factors were blood loss, first time out of bed and complication (P

The aim of this study was to evaluate how the Charlson Comorbidity Index (CCI) scores contribute to early recovery and 2-year mortality in elderly patients undergoing surgical treatment of inter-trochanteric fractures. 60 cases with unilateral intertrochanteric fracture were retrospectively analyzed and divided into Low-CCI group (CCI: 1–4) or high-CCI groups (CCI: 5–6). All the patients’ electronic hospital records were reviewed. The preoperative situations (demographic data, comorbidities and fracture conditions), perioperative situations (wait time, operation time, implant choice, blood loss, transfusion or not) and postoperative situations (complications, first time out of bed, function about 1-/2- week and 2-year mortality) were recorded. 51.67% were in low-CCI group and 48.33% in high-CCI group. The survival rates in low- and high-CCI group were 93.5% and 86.2% respectively. According to the functional results of 1- or 2- week after operation, no significant difference was found (P = 0.955, 0.140). Log-rank analysis showed that the main prognostic factors were blood loss, first time out of bed and complication (P

Full-quantitative characterization has not been performed to analyze changes in the hammering sound in cementless hip arthroplasty. We analyzed the frequency spectrum of the hammering sound during stem insertion for 20 cases of uncomplicated cementless total hip arthroplasty for osteoarthritis using a proximal-coated stem. The absolute sound pressure (Pa) and normalized sound pressure of each frequency bands in early and late stage of femoral stem insertion were determined by the Fast Fourier Transform analysis. The absolute sound pressures (Pa) of a majority of frequency bands was significantly higher in the late-stage stem insertion than in the early stage The 1.0–1.5-kHz frequency band showed a significant change in normalized sound pressure in all cases between the early and late stages of stem insertion (p=0.000). The femoral morphology and canal fill ratio were correlated with late stage normalized sound pressure in specific frequency bands. In the 5.0–5.5 kHz band, the Dorr A femoral morphology was significantly higher normalized sound pressure than those in the Dorr B (p=0.004). This study revealed the hammering sound frequency with full-quantitative value altered during cementless stem insertion. Frequency bands of 1.0–1.5 kHz, 5.0–5.5 kHz were the key bands for predicting stem fixation.

Background Although the antidislocation effect of total hip arthroplasty (THA) via the direct anterior approach (DAA) with dual mobility cup (DMC) for displaced femoral neck fracture (FNF) has already been reported, the clinical result of DMC-DAA-THA for displaced FNF in terms of mortality, complications, and walking ability are still unclear. Methods 106 cases with DMC-DAA-THA for displaced FNF were investigated of dislocation; perioperative complications; 3-, 6-, and12-month mortality rate; and pre/early postoperative walking ability. The walking ability was stratified into the following four categories: (1) use of a wheelchair (no walking), (2) walking alongside a support (including walkers designed for the elderly), (3) walking using one stick, and (4) unaided walking. Results There was no dislocation withing one-year postoperative. The 3-, 6-, and 12-month mortality rate was 2.8%, 4.7%, and 5.7%. Total complications occurred in 14 cases (14.7%). Although there was no revision surgery, two cases (1.9%) of intraoperative fracture treated without additional fixation, and one case of postoperative fracture was occurred. Among patients with preinjury walking category 2, 3, and 4 (total 94 cases), the number of patients who recovered same walking category at two-week postoperation was 56 cases (59.6%). Conclusions Our study demonstrated that DMC-DAA-THA for displaced FNF offered quick recovery of walking ability with no dislocation and low one-year mortality rate. We believe that the combination of early postoperative recovery due to the minimal invasiveness of the DAA and decreased dislocation rate due to increased range of motion by DMC and adequate soft tissue tension by DAA contributed to null dislocation.

Background An incision for total hip arthroplasty (THA) via the direct anterior approach (DAA) is generally made outside of the space between the sartorius and tensor fasciae latae muscles to prevent lateral femoral cutaneous nerve (LFCN) injury. Anatomical studies have revealed that the LFCN courses between the sartorius and tensor fasciae latae muscles. When the LFCN branches radially while distributing in the transverse direction from the sartorius muscle to the tensor fasciae latae muscle, it is called the fan type. Studies suggest that damage to the fan type LFCN is unavoidable during conventional fasciotomy. We previously demonstrated that injury to non-fan variation LFCN occurred in 28.6% of patients who underwent THA by fasciotomy performed 2 cm away from the intermuscular space. This suggests that the conventional approach also poses a risk of LFCN injury to non-fan variation LFCN. LFCN injury is rarely reported in the anterolateral approach, which involves incision of fascia further away than the DAA. The purpose of this study is to investigate how the position of fasciotomy in DAA affects the risk of LFCN injury. Methods We will conduct a prospective, randomized, controlled study. All patients will be divided into a fan variation and a non-fan variation group using ultrasonography before surgery. Patients with non-fan variation LFCN will receive conventional fasciotomy and lateral fasciotomy in the order specified in the allocation table created in advance by our clinical trial center. The primary endpoint will be the presence of LFCN injury during an outpatient visit using a patient-based questionnaire. The secondary endpoints will be assessed based on patient-reported outcomes at 3 months after surgery in an outpatient setting using the Western Ontario and McMaster Universities Osteoarthritis Index, the Japanese Orthopaedic Association Hip-disease Evaluation Questionnaire, and the Forgotten-Joint Score-12. Discussion We hypothesize that the incidence of LFCN injury due to DAA-THA is reduced by making the incision further away from where it is typically made in conventional fasciotomy. If our hypothesis is confirmed, it will reduce the disadvantages of DAA and improve patient satisfaction. Trial registration UMIN Clinical Trials Registry, UMIN000035945. Registered on 20 February, 2019.

Background; Lateral cutaneous nerve (LFCN) injury is one of the complication specific to total hip arthroplasty via the direct anterior approach. Recent anatomical studies have revealed that the LFCN not only courses between the sartorius and tensor fasciae latae muscles, but it also branches radially while distributing in the transverse direction from the sartorius muscle to the tensor fasciae latae muscle. The latter is called the fan type, in which injury of the LFCN is almost unavoidable using the conventional site for incision of the fascia. In order to reduce LFCN injury in the fan type, we devised a new approach of incising the fascia at a side 2 cm medial from the conventional site of incision. The purpose of this study is to examine how the site of incision of the fascia influences LFCN injury.Methods; This is a prospective, randomized, controlled study. All patients are divided into the fan type and non-fan type using ultrasonography before surgery. Patients with the fan type LFCN will be performed by the conventional approach and the medial approach in the order specified in the allocation table created in advance by our clinical trial center. The conventional approach involves incision of the skin, followed by incision of the fascia just below the site of skin incision. The medial approach proceeds medially from the site of skin incision, and involves incision of the fascia at a site 2 cm medial from the conventional site of incision. The primary endpoint is the presence of LFCN injury. The secondary endpoints will be assessed based on PROs at 3 months after surgery in an outpatient setting using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), the Japanese Orthopaedic Association Hip-Disease Evaluation Questionnaire (JHEQ), and the Forgotten-Joint Score-12 (FJS-12).Discussion; We hypothesize that the fan type LFCN can be protected from injury by incising the fascia at a more medial site than conventional site. If the usefulness of this surgical procedure is confirmed, the disadvantages of the DAA will be eliminated, potentially being highly beneficial to patients.Trial registration; UMIN Clinical Trials Registry, UMIN000035944.Registered on 20 Feburary 2019.

Background Total hip arthroplasty (THA) via the direct anterior approach (DAA) using dual mobility cup (DMC) is considered to effectively prevent postoperative dislocation. However, the dislocation and reduction procedure using a trial implant during the surgery is difficult because of high soft tissue tension. Thereby, leg length discrepancy (LLD) is difficult to assess when using DM via the DAA. Purpose To compare the LLD between cases using conventional SM and those using DMC in THA via the DAA with fluoroscopy. Patients and methods We retrospectively investigated 34 hips treated with DMC (DMC-DAA group) and 31 hips treated with SM (SM-DAA group). The LLD was defined as the difference in the distance from the teardrop to the medial-most point of the lesser trochanter between the operative and nonoperative sides at immediate postoperative X-ray. Results The mean LLD in the DMC-DAA group and SM-DAA group was 0.68 ± 7.7 mm and 0.80 ± 5.5, respectively, with no significant difference. The absolute value of the LLD in the DMC-DAA group and SM-DAA group was 6.3 ± 4.4 mm and 5.9 ± 5.5, respectively, with no significant difference. Conclusion Despite the difficulty in assessment of the LLD during THA via the DAA using DMC, this technique does not increase the LLD compared with the use of SM. Level of evidence III, matched case-control study.

Introduction: Loss of reduction after operative fixation of volarly unstable distal radius fractures with a volar lunate facet fragment (VLF) is considered problematic because it results in carpal subluxation or dislocation and subsequent impaired function. We hypothesized that the indicator of loss of reduction of the VLF after fixation is plate coverage of the bony fragment. We investigated the relationship between the plate coverage of the VLF and loss of reduction after fixation, and calculated the plate coverage that was associated with failure of fixation of the VLF. Materials and methods: We conducted a retrospective review. We included patients with surgically treated volarly unstable distal radius fractures with VLF with a volar locking plate who had a minimum follow-up of 6 months. A total of 33 patients (35 wrists) met criteria for inclusion into the study. The patients were divided into a displacement group and a non-displacement group. We calculated and compared longitudinal dimension and plate coverage of the VLF between the two groups to reveal the risk factors for loss of reduction. Results: At final follow-up, 25 fractures maintained radiographic alignment and 10 (28.6%) lost reduction. Univariate analysis between the two groups showed that plate coverage against the transverse and longitudinal dimension of the VLF was correlated with loss of reduction after operative fixation. In multivariate logistic regression analysis, only plate coverage against the longitudinal dimension of the VLF remained a significant predictor of failure. With 64.7% as the cut-off point for plate coverage against the longitudinal dimension of the VLF, the sensitivity and specificity of the prediction were 96% and 80%, respectively. Conclusion: The predictor of loss of reduction after fixation of volarly unstable distal radius fractures with a VLF was plate coverage against the longitudinal dimension of the VLF.