Use of a Helicopter Emergency Medical Service Hangar as a Staging Care Unit in a Disaster-Affected Area.

OBJECTIVE: There are a few reports regarding the use of a hangar as a temporal medical facility (staging care unit [SCU]) during large-scale disasters. The aim of this study was to describe the activities performed by disaster medical assistance teams (DMATs) at the hangar of the eastern Shizuoka physician-staffed helicopter as an SCU in the 2022 Shizuoka Prefecture disaster drill. METHODS: We selected the narrative method for this study. RESULTS: Four DMATs helped manage the SCU at the hangar. During the training period, there were 3 instances of a mock doctor helicopter landing and takeoff and 1 actual eastern Shizuoka doctor helicopter landing and takeoff while transporting a mock burn patient. Four DMATs treated 3 mock patients in addition to receiving training regarding medical materials. Such an SCU was able to reduce the burden on the disaster base hospital because many severely ill or traumatized mock patients were transported to the hospital. However, an evaluation meeting held after the drill revealed problems with lifelines, safety management, stock, and quality management of materials in an actual disaster situation. CONCLUSION: We reported our experience with a training exercise using a hangar of the eastern Shizuoka doctor helicopter as an SCU in the 2022 Shizuoka Prefecture disaster drill. There are advantages and disadvantages to using the hangar of a doctor helicopter in this way, so further investigation will be necessary.

Paradoxical Embolization of the Bilateral Subclavian Arteries After High Tibial Osteotomy.

A patent foramen ovale provides a portal through which a thrombus might pass from the right side of the circulation to the left. A 65-year-old man underwent high tibial osteotomy after the diagnosis of the right knee osteoarthritis. On postoperative day 12, he developed bilateral arm paresthesia. Enhanced CT revealed emboli in the bilateral pulmonary and subclavian arteries and deep vein thrombosis in the left lower limb. Transesophageal echocardiography after treatment revealed a patent foramen ovale during the Valsalva maneuver. It was thought that bilateral arm paresthesias were caused by the arterial emboli in the bilateral subclavian arteries.

Total hip arthroplasty for a woman with hemophilia A -case report.

Hemophilia A is a congenital bleeding disorder caused by an X-linked hereditary pattern. Female hemophilia A carriers are usually asymptomatic, although some have far lower levels of clotting factor because more X chromosomes with the normal gene are switched off, a phenomenon referred to as "lyonization." During a medical checkup at our hospital, a 56-year-old Japanese woman with coxalgia was also diagnosed as an obligate hemophilia A carrier based on World Federation of Hemophilia criteria. She underwent total hip arthroplasty using blood product coagulation factor VIII to address her hemophilia. Immediate female relatives (mother, sisters, daughters) of a person with hemophilia should have their clotting factor levels checked, especially prior to any invasive intervention or childbirth, or if any symptoms occur.

Preservation of the articular capsule and short lateral rotator in direct anterior approach to total hip arthroplasty.

INTRODUCTION: In total hip arthroplasty via a direct anterior approach, the femur must be elevated at the time of femoral implant placement. For adequate elevation, division of the posterior soft tissues is necessary. However, if we damage and separate the posterior muscle tissue, we lose the benefits of the intermuscular approach. Furthermore, damage to the posterior soft tissue can result in posterior dislocation. We investigate that protecting the posterior soft tissue increases the joint stability in the early postoperative period and results in a lower dislocation rate. METHODS: We evaluated muscle strength recovery by measuring the maximum width of the internal obturator muscle on CT images (GE-Healthcare Discovery CT 750HD). We compared the maximum width of the muscle belly preoperatively versus 10 days and 6 months postoperatively. As clinical evaluations, we also investigated the range of motion of the hip joint, hip joint function based on the Japanese Orthopaedic Association hip score (JOA score), and the dislocation rate 6 months after surgery. RESULTS: The width of the internal obturator muscle increased significantly from 15.1 ± 3.1 mm before surgery to 16.4 ± 2.8 mm 6 months after surgery. The JOA score improved significantly from 50.8 ± 15.1 points to 95.6 ± 7.6 points. No dislocations occurred in this study. CONCLUSIONS: We cut only the posterosuperior articular capsule and protected the internal obturator muscle to preserve muscle strength. We repaired the entire posterosuperior and anterior articular capsule. These treatments increase joint stability in the early postoperative period, thus reducing the dislocation rate. LEVEL OF EVIDENCE: Therapeutic, Level IV.

"Within ring"-based sacroiliac rod fixation may overcome the weakness of spinopelvic fixation for unstable pelvic ring injuries: technical notes and clinical outcomes.

PURPOSE: Spinopelvic fixation and triangular osteosynthesis give firm internal fixation for unstable pelvic ring injuries (UPRI), but with sacrifice of mobility of the lumbar spine. Here, we describe the procedure and outcomes of a new approach, which we refer to as "within ring"-based sacroiliac rod fixation (SIRF). METHODS: The patient was placed in a prone position and longitudinal skin incisions were made at the medial margins of the bilateral posterior superior iliac spines (PSIS). After reduction of fracture, a pedicle screw was inserted into the first sacral vertebra on the injured side and iliac screws inserted through the bilateral PSIS were bridged using rods. RESULTS: SIRF was performed in 15 patients. The AO/OTA classification was 61-B2.3 in 1, C1.3 in 4, C2.3 in 7, C3.3 in 1, and H-type spinopelvic dissociation in two cases. The mean operative time was 179 (110-298) minutes, mean blood loss was 533 (100-2700) cc. One patient died during hospitalization and three patients stopped outpatient treatment. The other 11 patients achieved bone union without major loss of reduction in a mean post-operative follow-up period of 23.8 (4-50) months. The mean Majeed score at final follow-up was 86.7 (73-96) out of 96, excluding scoring sexual intercourse. CONCLUSIONS: "Within ring"-based SIRF not including the lumbar spine in the fixation range is a simple, safe, and low-invasive internal fixation method for UPRI.

A study of the blood flow restriction pressure of a tourniquet system to facilitate development of a system that can prevent musculoskeletal complications.

BACKGROUND: After an emergency or disaster, subsequent trauma can cause severe bleeding and this can often prove fatal, so promptly stopping that bleeding is crucial to preventing avoidable trauma deaths. A tourniquet is often used to restrict blood flow to an extremity. In operation and hospital, the tourniquet systems currently in use are pneumatically actuated by an air compressor, so they must have a steady power supply. These devices have several drawbacks: they vibrate and are noisy since they are pneumatically actuated and they are far from portable since they are large and heavy. INTRODUCTION: Presumably, the drawbacks of pneumatic tourniquets could be overcome by developing a small, lightweight, vibration-free, quiet, and battery-powered tourniquet system. The current study built a small, vibration-free electrohydrodynamic (EHD) pump and then used that pump to restrict blood flow to the leg of rats in an experiment. This study explored the optimal conditions for effective restriction of blood flow by assessing biochemical and musculoskeletal complications following the restriction of blood flow, and this study also examined whether or not an EHD pump could be used to actuate a tourniquet system. METHODS: A tourniquet cuff (width 12 mm × length 150 mm, material: polyolefin) was placed on the thigh of Wistar rats and pressure was applied for 2 hours by a device that uses EHD phenomena to generate pressure (an EHD pump). Animals were divided into four groups based on how much compressive pressure was applied with a tourniquet: 40 kPa (300 mm Hg, n = 13), 30 kPa (225 mm Hg, n = 12), 20 kPa (150 mm Hg, n = 15), or 0 kPa (controls, n = 25). Tissue oxygen saturation (regional oxygen saturation, denoted here as rSO2) was measured to assess the restriction of blood flow. To assess behavior once blood flow resumed, animal activity was monitored for third day and the amount of movement was counted with digital counters. Body weight was measured before and after the behavioral experiment, and changes in body weight were determined. Blood was sampled after a behavioral experiment and biochemically assessed and creatine kinase (CK) levels were measured. RESULTS: Tissue oxygen saturation decreased significantly in each group. When a tourniquet was applied at a pressure of 30 kPa or more, tissue oxygen saturation decreased significantly. The amount of movement (the count) over third day decreased more when a tourniquet was applied at a higher pressure. The control group resumed the same amount of movement per day second after blood flow resumed. Animals to which a tourniquet was applied at a pressure of 20 or 30 kPa resumed the same amount of movement third day after blood flow resumed. In contrast, animals to which a tourniquet was applied at a pressure of 40 kPa did not resume the same amount of movement third day after blood flow resumed. After the behavioral experiment, animals to which a tourniquet was applied at a pressure of 40 kPa had a significantly lower body weight in comparison to the control group. After the behavioral experiment, animals to which a tourniquet was applied at a pressure of 40 kPa had significantly elevated CK levels in comparison to the control group. DISCUSSION AND CONCLUSION: A relationship between blood flow restriction pressure and tissue oxygen saturation was noted. rSO2 measurement can be used to assess the restriction of blood flow during surgery. On the basis of the decrease in rSO2, blood flow was effectively restricted at a pressure of 30 kPa or more. When, however, blood flow was restricted at a pressure of 40 kPa, weight loss and decreased movement were noted and CK levels increased after the behavioral experiment. Thus, complications had presumably developed due to damage to muscle tissue. These findings indicate that blood flow was effectively restricted in this experiment and they also indicate the existence of an optimal blood flow restriction pressure that does not cause musculoskeletal complications. The pressure in question was around 30 kPa. The tourniquet system that was developed here is actuated with an EHD pump that is still in the trial stages. That said, its pressure can readily be controlled and this pump could be used in a tourniquet system since it is quiet, vibration-free, and small. The pressure of this pump can be finely adjusted to prevent musculoskeletal complications.

Intraoperative dislocation of the trial bipolar cup into the pelvis during bipolar hip arthroplasty - A case report.

INTRODUCTION: Bipolar hip arthroplasty is a good option for treating femoral neck fractures, although some contraindications have been indicated. We report a case of intraoperative dislocation of the trial bipolar cup into the pelvis during bipolar hip arthroplasty. CASE PRESENTATION: A 74-year-old woman underwent bipolar hip arthroplasty for a femoral neck fracture (AO31-B2). She was placed in a lateral decubitus position, and a direct lateral approach was used. During intraoperative trial reduction, the trial bipolar cup became disengaged and dislocated into the anterior space of hip joint. Several attempts to retrieve it failed. The permanent femoral component was inserted, and the wound was closed. The patient was repositioned supine to allow an ilioinguinal approach, and the component was easily removed. She had an uneventful, good recovery. DISCUSSION: Several cases of intraoperative dislocation of the femoral trial head during total hip arthroplasty have been reported, this is the first report of dislocation of a bipolar trial cup. A previous report described difficulty retrieving a trial cup. CONCLUSION: We easily removed our trial cup using another approach. It is vital to plan systematically for this frustrating complication.

Malreduction of syndesmosis injury associated with malleolar ankle fracture can be avoided using Weber's three indexes in the mortise view.

PURPOSE: Malalignment of syndesmosis is generally associated with a poor outcome, yet occurs at a high rate in malleolar ankle fractures. In this study, we examine whether malreduction of syndesmosis injury associated with malleolar ankle fracture can be avoided using Weber's three indexes in the mortise view. MATERIALS AND METHODS: Of 156 patients with malleolar ankle fracture who underwent surgery from December 2012 to March 2016 at two medical facilities, 24 patients who received syndesmotic screw fixation were included in the study. Fractures were Danis-Weber types B and C in 8 (8/134, 6.0%) and 16 (16/22, 72.7%) patients, respectively. Using axial computed tomography (CT), we calculated the difference between injured and non-injured sides for each of three parameters: tibiofibular clear space (TFCS), anterior tibiofibular interval (ATF), and fibular rotation (θfib). Malreduction was diagnosed if one or more of the three parameters had an abnormal value. Weber's three indexes in the mortise view on the injured side were used to determine whether reduction of syndesmosis was performed successfully. Consistency between the evaluation of reduction of syndesmosis in axial CT images and reevaluation of mortise views was examined by calculation of sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV). RESULTS: The rate of malreduction of syndesmosis in axial CT images was 29.2% (7/24). Re-evaluation in the mortise view confirmed malreduction of syndesmosis in six of the seven subjects, all of whom also had malreduction based on axial CT images. The one subject in whom malreduction could not be detected in a mortise view showed an abnormal value only for ATF. Use of the mortise view for perioperative diagnosis had a sensitivity of 0.857, specificity of 1.000, PPV of 1.000, and NPV of 0.944. CONCLUSION: The results of our study show that malreduction of syndesmosis can be avoided by careful interpretation of intraoperative perspective mortise views based on Weber's three indexes. To increase the diagnostic accuracy further, it is important to detect anteroposterior deviation of the fibula in intraoperative lateral views.

Acoustic pattern evaluation during cementless hip arthroplasty surgery may be a new method for predicting complications.

BACKGROUND: Although surgeons must perform implantation of the cementless stem during total hip arthroplasty (THA) without complications, assessment is left to the surgeon's intuitive judgement, which could contain inter/intra-observer bias variety. We therefore asked (1) whether the sound created during the stem implantation could be evaluated objectively and (2) whether those sounds are correlate to the complication specific to the cementless stems. Our hypothesis is that the sounds produced during stem insertion could be quantified and related to the complications. PATIENTS AND METHOD: In 71 THAs, we quantified the sound produced during stem insertion and investigated the relationship between these sounds and the occurrence of intraoperative fracture and subsidence. RESULTS: The sound data were divided into two patterns: Patterns A and B. The difference between the peak value (dB) at the most common frequency (near 7 kHz) and the second most common frequency (near 4 kHz) of strikes during the final phase of implantation in Patterns A and B showed a significant difference. Adverse events on intraoperative fracture and subsidence were significantly less common in patients with Pattern A than in those with Pattern B (six of 42 hips with Pattern A and 13 of 29 hips with Pattern B, p = 0.004). Pattern A in predicting a clinical course without those adverse events was 69.2% and the specificity was 68.4%. Positive and negative predictive values were 85.7% and 44.8%, respectively. CONCLUSION: The sound generated during stem insertion was quantified. Those sound patterns were associated with complications.

Treatment of postoperative sciatic nerve palsy after total hip arthroplasty for postoperative acetabular fracture: A case report.

Acetabular fracture is usually treated with osteosynthesis. However, in the case of an intra-articular fracture, osteosynthesis can result in arthropathy of the hip joint and poor long-term results, hence, total hip arthroplasty is required. However, in total hip arthroplasty for postoperative acetabular fracture, sciatic nerve palsy tends to develop more commonly than after primary total hip arthroplasty. This is a case report of a 57-year-old Japanese male who had internal skeletal fixation for a left acetabular fracture that had occurred 2 years earlier. One year later, he developed coxarthrosis and severe pain of the hip joint and total hip arthroplasty was performed. After the second surgery, he experienced pain along the distribution of the sciatic nerve and weakness of the muscles innervated by the peroneal nerve, indicating sciatic nerve palsy. We performed a third operation, and divided adhesions around the sciatic nerve. Postoperatively, the anterior hip joint pain and the buttocks pain when the hip was flexed were improved. Abduction of the fifth toe was also improved. However, the footdrop and sensory disturbance were not improved. A year after the third operation, sensory disturbance was slightly improved but the footdrop was not improved. We believe the sciatic nerve palsy developed when we dislocated the hip joint as the sciatic nerve was excessively extended as the hip joint flexed and internally rotated. Sciatic nerve adhesion can occur easily in total hip replacement for postoperative acetabular fracture; hence, adhesiotomy should be conducted before performing hip dislocation to prevent injury caused by nerve tension. The patient agreed that the details of this case could be submitted for publication. The work has been reported in line with the CARE criteria and cite.

New classification focusing on the relationship between the attachment of the iliofemoral ligament and the course of the fracture line for intertrochanteric fractures.

PURPOSE: There are various types of intertrochanteric fractures that are unstable pertrochanteric fractures of the hip. The aim of this study was to develop a systematic and comprehensive classification of intertrochanteric fractures. MATERIALS AND METHODS: This study enrolled 74 patients with intertrochanteric fractures treated by us between 2012 and 2015. The fractures were classified using 3D-CT images taken immediately after the fractures occurred based on the course of the lateral fracture line (LFL) that extends through the lateral femoral cortex distal to the vastus ridge of the greater trochanter in the intertrochanteric area. Furthermore, the presence or absence of additional typical fractures was also studied. Then, 4 orthopedic specialists examined the 3D-CT images of 20 patients randomly selected from the 74 patients to evaluate both the inter-rater and intra-rater agreement levels. RESULTS: Intertrochanteric fractures were classified into three types according to the LFL patterns. Type I (41.9%), the Lateral Wall Pattern, has a LFL that extends towards the lateral fiber bundle attachment area of the iliofemoral ligament. Type II (24.3%), the Transverse Pattern, has a LFL that extends towards the medial bundle attachment area. Type III (33.8%), the Reverse Oblique Pattern, has a LFL that extends between the lateral and medial fiber bundle area of the iliofemoral ligament. Each type showed characteristic displacement and was associated with various combinations of typical fractures (fracture across the intertrochanteric line, posteromedial fragment, including the lesser trochanter, posterolateral fragment posterior to the femoral greater trochanter, and banana-shaped big fragment, including both the greater trochanter and the lesser trochanter). The mean κ values for the interobserver and intraobserver agreement levels were 0.77 (0.70-0.85) and 0.76 (0.70-0.85), respectively, which were considered substantial agreement levels. CONCLUSION: We believe our new classification is a useful communication tool for medical professionals in the diagnosis of fractures.

Iliopsoas impingement after revision total hip arthroplasty treated with iliopsoas muscle transection.

INTRODUCTION: Iliopsoas tendinitis after revision total hip arthroplasty (THA) is rare and its etiology and optimal treatment are still unclear. We report a case of iliopsoas impingement after revision THA with a Kerboull acetabular reinforcement device requiring two-level iliopsoas muscle transection. PRESENTATION OF CASE: A 70-year-old woman presented to our hospital complaining of debilitating right groin pain after revision THA with a Kerboull reinforcement device. She had undergone multiple hip operations after experiencing a pelvic fracture in a motor vehicle accident. A lidocaine nerve block at the level of the Kerboull device resulted in temporary but marked reduction in pain and a diagnosis of psoas impingent. We performed surgery via an anterior approach to release the iliopsoas muscle from the lesser trochanter. After iliopsoas tenotomy was performed, the muscle was still under high tension because of dense adhesions. Repeat transection of the iliopsoas muscle at the level of the anterior branch of the Kerboull device resulted in loosening of the iliopsoas muscle and resolution of impingement. Postoperatively, the patient's groin pain completely disappeared, and she can now walk with a single cane and is satisfied with her result. DISCUSSION: Adhesions around the iliopsoas muscle likely contributed to the patient's groin pain. Open surgery to perform complete release of iliopsoas muscle impingement should be considered in patients with pain after revision THA. CONCLUSION: We reported a patient with Iliopsoas tendinitis after revision THA requiring two-level iliopsoas muscle transection.

Total Hip Arthroplasty Using a Polished Tapered Cemented Stem in Hereditary Multiple Exostosis.

A 61-year-old Japanese man underwent right total hip arthroplasty for hereditary multiple exostosis. At first presentation, he had suffered from coxalgia for a long time. On radiographic images, there was a gigantic femoral head, increased shaft angle, and large diameter of the femoral neck. He had also developed coxarthrosis and severe pain of the hip joint. The transformation of the proximal femur bone causes difficulty in setting a cementless total hip prosthesis. Therefore, total hip arthroplasty using a cemented polished tapered stem was performed via a direct lateral approach. Using a cemented polished tapered stem allowed us to deal with the femoral bone transformation and bone substance defectiveness due to exostosis and also minimized the invasiveness of the operation.

A 42-year-old patient presenting with femoral head migration after hemiarthroplasty performed 22 years earlier: a case report.

INTRODUCTION: Treatment of femoral neck fractures in young adults may require total hip arthroplasty or hip hemiarthroplasty using a bipolar cup. The latter can, however, result in migration of the femoral head and poor long-term results. CASE PRESENTATION: We report a case of femoral head migration after hemiarthroplasty performed for femoral neck fracture that had occurred 22 years earlier, when the patient (a Japanese man) was 20 years old. He experienced peri-prosthetic fracture of the femur, subsequent migration of the prosthesis, and a massive bone defect of the pelvic side acetabular roof. After bone union of the femoral shaft fracture, the patient was referred to our hospital for reconstruction of the acetabular roof. Intra-operatively, we placed two alloimplants of bone from around the transplanted femoral head into the weight-bearing region of the acetabular roof using an impaction bone graft method. We then implanted an acetabular roof reinforcement plate and a cemented polyethylene cup in the position of the original acetabular cup. Eighteen months post-operatively, X-rays showed union of the transplanted bone. CONCLUSIONS: Treatment of femoral neck fractures in young adults is usually accomplished by osteosynthesis, but it may be complicated by femoral head avascular necrosis or by infection or osteomyelitis. In such cases, once an infection has subsided, either hip hemiarthroplasty using a bipolar cup or total hip arthroplasty may be required. However, if the acetabular side articular cartilage is damaged, a bipolar cup should not be used. Total hip arthroplasty should be performed to prevent migration of the implant.

New classification focusing on implant designs useful for setting therapeutic strategy for periprosthetic femoral fractures.

PURPOSE: In periprosthetic femoral fractures, our hypothesis was that when the bone and implant are stable, the fracture does not occur at the biologic or cement fixation regions but occurs at the no fixation region. The aim of this study was to investigate the validity of our new classification for periprosthetic femoral fractures and compare reliability of radiographic evaluation for implant stability between our classification and the Vancouver classification. PATIENTS AND METHODS: Sixty-six patients with periprosthetic femoral fracture were operatively treated by us between 2005 and 2013. We investigated the sensitivity and specificity of our new classification with actual implant stability. Twenty patients were randomly selected from 66 patients. After fully explaining the Vancouver and our new classification to four orthopaedic surgeons, plain radiographs acquired in two directions at the time of injury were presented, and the interobserver reliability based on the two classifications and accuracy rates of stem stability were investigated. RESULTS: The specificity of the new classification was 89%, and sensitivity was 94%. The positive and negative predictive values were 84% and 96%, respectively. Interobserver agreement was separately assessed among all possible pairs of orthopaedic surgeons. The κ values for the Vancouver and the new classification were 0.36 (0.19-0.49) and 0.76 (0.66-1.0), respectively. CONCLUSIONS: Our classification is based on a completely new concept and was prepared to overcome periprosthetic femoral fracture failures by objective evaluation. We believe this new classification is useful to establish a therapeutic strategy for femoral fractures around the stem.

Introduction of a physician-staffed helicopter emergency medical service in eastern Shizuoka prefecture in Japan.

OBJECTIVE: To analyze the operating situation of a physician-staffed helicopter emergency medical service in eastern Shizuoka prefecture. METHODS: A retrospective analysis was performed using the conveyance records reported by staff members of the physician-staffed helicopter. A comparison between 2007 (n = 619) and 2012 (n = 678) was performed. RESULTS: There were no significant differences between the 2 groups with regard to the sex, ratio of cardiopulmonary arrest, and survival ratio. In contrast, the duration from the request of dispatch to arrival at the hospital in 2007 was significantly longer than that in 2012 (53.7 vs 48.2 minutes, P < 0.0001). The average age in 2007 was significantly younger than in 2012 (55.7 vs 59.4 years, P < 0.01). The ratio of trauma case in the 2012 was higher than that in 2007 (47 vs 37%, P < 0.001). The ratio of severe cases in 2007 was higher than in 2012 (45 vs 39%, P < 0.05). CONCLUSION: Japan is an aging society. In eastern Shizuoka prefecture, the increase in the number of trauma and minor injury cases may have increased due to the emphasis on the importance of early medical intervention by the fire department.

The Massive Bleeding after the Operation of Hip Joint Surgery with the Acquired Haemorrhagic Coagulation Factor XIII(13) Deficiency: Two Case Reports.

Two women, aged 81 and 61, became haemorrhagic after surgery. Their previous surgeries were uneventful with no unexpected bleeding observed. Blood tests prior to the current surgeries indicated normal values including those related to coagulation. There were no problems with the current surgeries prior to leaving the operating room. At 3 hours after the surgery, the 81-year-old patient had an outflow of the drain at 1290 grams and her blood pressure decreased. She had disseminated intravascular coagulation (DIC). The 61-year-old woman had repeated haemorrhages after her current surgery for a long time. Their abnormal haemorrhages were caused by a deficiency of coagulation factor XIII(13). The mechanism of haemorrhagic coagulation factor XIII(13) deficiency is not understood, and it is a rare disorder. The only diagnostic method to detect this disorder is to measure factor XIII(13) activity in the blood. In this paper, we used Arabic and Roman numerals at the same time to avoid confusion of coagulation factor XIII(13) with coagulation factor VIII(8) that causes hemophilia A.

Limitation of total hip arthroplasty of the acetabular roof by press-fit without screw fixation: discussion of a biomechanical study.

In total hip arthroplasty of the acetabular roof fixed by press-fit without screw fixation, there is little possibility for loosening to occur, because it is difficult for wear debris to enter between the cup and the acetabular roof, as screw holes are not present. However, stability is provided only by contact. In the case of acetabular dysplasia, it is not well understood whether sufficient initial fixation power is provided. We performed a torsion test and a lever-out test. In the torsion test, in the case of a normal hip joint, as the cup grew bigger, the fixation power tended to increase in strength. In the acetabular dysplasia model, with cups of each size, as the protrusion angle increased, the fixation power of the cup tended to become weak. When the protrusion angle approaches 15 degrees, we must use a cup that is 4 mm larger than the original cup to achieve the same initial fixation power. Furthermore, when the protrusion angle is 15 degrees in cups that are over 48 mm in size, we obtain fixation power that is theoretically adequate, but when small cups, for example, 46 mm in size are set with protrusion, the initial fixation power decreases significantly, and we cannot obtain a fixation power that is theoretically adequate.