Surgical Correction of Ischiopagus Tripus Conjoined Twins with Fused Pelvis: Enhancing Quality of Life through Orthopedic Intervention.

BACKGROUND The rarity of ischiopagus tripus conjoined twins complicates the surgical separation, owing to the lack of cases and high complexity. We aim to report our experience in performing orthopedic correction for ischiopagus tripus twins. CASE REPORT A pair of 3-year-old conjoined boys presented with a fused body at the pelvis region and only 1 umbilicus. There were 2 legs separated by shared genitalia and an anus at the midline, and 1 fused leg, which could be felt and moved by both of the patients. The twins also shared internal organs of the bladder, intestine, and rectum, as visualized through angiography computerized tomography scan. After several team discussions with the institutional review board, the hospital ethics committee, and both parents, it was agreed to perform disarticulation of the fused third limb, followed by correction of the trunk alignment by pelvic closed wedge osteotomy and internal fixation. We successfully reconstructed the pelvis using locking plates and additional 3.5-mm cortical screws and 1.2-mm stainless steel wire. CONCLUSIONS This report describes the presentation and surgical management of a case of ischiopagus tripus conjoined twins. It highlights the challenges involved in surgery and the importance of investigating these infants for other congenital abnormalities. Although surgical approaches for different sets of twins should be individually tailored, interventions aimed to provide optimal outcomes should consider ethical issues and parental/patient expectations. Even in situations in which the twins are inseparable, there is still room for surgical correction to be performed.

Transiliac-Shortening Osteotomy to Treat Ischial Pressure Injury due to Fixed Pelvic Obliquity: A Case Report.

CASE: A 17-year-old adolescent boy with Gross Motor Function Classification System 5 cerebral palsy and neuromuscular scoliosis underwent posterior spinal fusion and segmental spinal instrumentation from T3 to the pelvis. He developed a right ischial pressure injury a few months postoperatively, which persisted despite nonoperative measures. He subsequently underwent an ipsilateral transiliac-shortening osteotomy 16 months after spinal surgery to treat his residual pelvic obliquity and the ischial pressure injury, which healed completely. At the 1-year follow-up visit, there were no further signs of pressure injury. CONCLUSION: This case report describes transiliac-shortening osteotomy as a viable treatment option for non-healing ischial pressure injuries secondary to fixed pelvic obliquity.

Anatomical study of the modified direct posterior gluteal splitting approach for acetabular fractures.

BACKGROUND: In this study, we investigated the area that can be addressed with an approach in which the skin incision is made directly above the dorsal column with Thiel cadaveric specimens. METHODS: Six Thiel cadaveric specimens were prepared. A skin incision was made directly above the dorsal column. The accessible proximal end from the proximal part of the greater sciatic notch to the gluteal ridge and the accessible distal end of the ischium were marked with a flat chisel. A molded 8-hole reconstruction plate was placed from the base of the ischium toward the gluteal ridge and fixed with 3 screws proximally and 2 screws distally. The length of the skin incision and the distance from each reference point on the bone to the reachable markings were assessed after the muscles were removed. RESULTS: Mean skin incision length was 9.3 ± 0.7 (range, 8.0-10.0) cm. In 3 of 6 cases, proximal screws were inserted through different spaces between muscle fibers. In all cases, we were able to reach at least the greater sciatic notch, the gluteal ridge at the level of superior border of the acetabulum, and the base of the ischial tuberosity. In all cases, an 8-hole plate could be placed from the gluteal ridge to the base of the ischium. There were no superior gluteal artery or sciatic nerve injuries in any of the cases. CONCLUSION: We anatomically investigated the area that can be addressed with an approach in which the skin incision was made directly above the dorsal column. In all cases, we were able to access the areas needed to reduce the fracture and place the plates necessary to stabilize the fracture through a 9.3 ± 0.7 cm skin incision. This approach can be a useful minimally invasive posterior approach for acetabular fractures.

Making the cut: a technical note and literature review of Bernese periacetabular osteotomy techniques with special attention to ischial osteotomy initiation and completion with an inside to anterior curved osteotomy.

Periacetabular osteotomy includes a fluoroscopy-guided ischial cut without direct visualization. Previously described techniques include a mediolateral ischial cortex cut, which is associated with the risk of injuring nearby nerves. Another drawback of that technique is the difficulty connecting an ischial cortex cut with a retroacetabular cut due to orthogonal nature of the osteotomy. In general, an additional cut from medial to lateral is required. The present study aimed to describe a technique that eliminates those problems due to use of only a central cut of the ischium and the curved nature of the osteotomy.

Colgajo DIEP pediculado para reconstrucción de úlceras isquiáticas y trocantéricas sin opción a colgajo local / DIEP pedicled flap for reconstruction of ischial and trochanteric ulcers without local flap option

Introducción y objetivo: El colgajo DIEP pediculado ofrece una alternativa reproducible en el manejo de úlceras isquiáticas y trocantéricas en las que no hay tejido sano periférico disponible para la realización de un colgajo local. Describimos la técnica quirúrgica y presentamos 2 casos clínicos en los que empleamos este procedimiento. Material y método: Previo rastreo con ultrasonido doppler de las arterias perforantes periumbilicales, trazamos una isla cutánea vertical de 10 x15 cm, disecamos el pedículo hasta la unión con la arteria epigástrica inferior profunda que disecamos lo más proximal posible. Realizamos un túnel subcutáneo hasta el área a tratar para el paso sin tensión del pedículo vascular y colocamos el colgajo en su área receptora, suturándolo en dos planos. Resultados: Describimos 2 casos en los que obtuvimos excelentes resultados funcionales con baja morbilidad del área donadora. Conclusiones: En nuestra experiencia, el colgajo DIEP pediculado fue una adecuada opción reconstructiva en pacientes con úlceras isquiáticas y trocantéricas en quienes los tejidos periféricos no permitían reconstrucción con colgajos locales, ya que presenta una baja morbilidad en la zona donadora y un pedículo relativamente largo que le permite alcanzar la zona del defecto.(AU)

Background and objective: The pedicled DIEP flap offers a reproducible alternative in the management of ischial and trochanteric ulcers where healthy peripheral tissue is not available for the realization of a local flap. We describe the surgical technique and present 2 clinical cases in which this procedure has been used, offering a reproducible alternative in the treatment of these conditions. Methods: A doppler ultrasound scan of the periumbilical perforating arteries is carried out, tracing a 10 x 15 cm vertical skin island. The pedicle is dissected down to the junction with the deep inferior epigastric artery, which is dissected as proximal as possible. A subcutaneous tunnel is made to the area to be treated for the passage without tension of the vascular pedicle and the flap is placed in its receiving area, suturing it in two planes. Results: We present 2 clinical cases in which we obtained excellent functional results and low morbidity in the donor area. Conclusions: In our experience, the pedicled DIEP flap was an adequate reconstructive option in patients with ischial and trochanteric ulcers in whom peripheral tissues do not allow reconstruction with local flaps, since it has low morbidity in the donor area and a relatively long pedicle that allows it to reach the defect area.(AU)

Bilateral pubic and ischial osteotomy in cats offers good exposure for resection of large vaginal masses with minimal postoperative complications.

OBJECTIVE: To describe the clinical presentation, diagnostic imaging findings, surgical technique, histopathological diagnosis, and postoperative outcome in 3 cats with extensive vaginal masses. ANIMALS: Medical records of cats diagnosed with vaginal masses that had a bilateral pubic and ischial osteotomy and vaginectomy between 2004 and 2022 were retrospectively reviewed. Three cats met the inclusion criteria. CLINICAL PRESENTATION: Histopathological diagnosis included T-cell-rich B-cell lymphoma (n = 1), mycetoma (1), and vaginal polyp (1). Diagnostic imaging included CT (n = 2) and MRI (1), and tumor length/width/height percentages in relation to the pelvic dimensions were 53% X 62% X 63% (case 1), 50% X 100% X 60% (case 2), and 150% X 120% X 120% (case 3). A bilateral pubic and ischial osteotomy was performed in all 3 cases. RESULTS: All 3 cases developed mild pelvic-limb splaying postoperatively; all resolved within 8 weeks, and 2 cases fully resolved within 14 days. Two of the 3 cases presented with mild stranguria postoperatively, which resolved fully in both cases. CLINICAL RELEVANCE: Vaginal neoplasia, either malignant or benign, is infrequently reported in cats in the veterinary literature. Bilateral pubic and ischial osteotomy for resection of vaginal masses in cats is a successful surgical approach, offering good exposure for resection of large vaginal masses, with minimal postoperative complications.

Endoscopic Ischial Tuberosity Osteophyte Resection for Treatment of Ischiofemoral Impingement: A Case Report.

ABSTRACT: Ischiofemoral impingement is a distinct pathologic finding with abnormal osseous contact between the ischium and the lesser trochanter of the femur. Lesser trochanter excision has been recommended for recalcitrant ischiofemoral impingement through an open or endoscopic approach; however, no study has included ischial tuberosity osteophyte resection and refixation of the hamstring tendon. We report an endoscopic procedure involving ischial tuberosity osteophyte resection with refixation of the partially detached hamstring insertion through a posterior approach in the prone position. Using this technique, it is easier to reach the lesion and less likely to injure the sciatic nerve. The postoperative pain score (visual analogy score) was significantly decreased, the modified Harris hip score increased from 39 preoperatively to 86 postoperatively, and there was no adverse effect on the hamstring tendon.

Ischiofemoral impingement syndrome: a case report and review of literature.

INTRODUCTION: The etiology of ischiofemoral impingement (IFI) syndrome, an unusual and uncommon form of hip pain, remains uncertain. Some patients demonstrate narrowing of the space between the ischial tuberosity and lesser trochanter from trauma or abnormal morphology of the quadratus femoris muscle. Combined clinical and imaging aid in the diagnosis. CASE REPORT: A 32-year-old female presented with a 3 years history of pain over the lower aspect of the right buttock, aggravated by movements of the right hip, and partially relieved with rest and medications. The right hip showed extreme restriction of abduction and external rotation. MRI of the right hip showed reduced ischiofemoral space and quadratus femoris space when compared to the left hip. The patient underwent endoscopic resection of the right lesser trochanter, with no recurrence of pain at 2 years. CONCLUSION: An unusual cause of hip pain, IFI syndrome, should be suspected when hip pain at extremes of movement is associated with signal abnormality of quadratus femoris muscle. Management is tailored to address the inciting factors that precipitated the IFI syndrome.

Defining the canal for ischial and pubic screws in cup revision surgery.

PURPOSE: When revising acetabular cups, it is often necessary to provide additional stabilisation with screws. In extensive defect situations, the placement of screws caudally in the ischium and/or pubis is biomechanically advantageous. Especially after multiple revision operations, the surgeon is confronted with a reduced bone stock and unclear or altered anatomy. In addition, screw placement caudally is associated with greater risk. Therefore, the present study aims to identify and define safe zones for the placement of caudal acetabular screws. METHODS: Forty-three complete CT datasets were used for the evaluation. Sixty-three distinctive 3D points representing bone landmark of interests were defined. The coordinates of these points were then used to calculate all the parameters. For simplified visualisation and intra-operative reproducibility, an analogue clock was used, with 12 o'clock indicating cranial and 6 o'clock caudal. RESULTS: A consistent accumulation was found at around 4.5 ± 0.3 hours for the ischium and 7.9 ± 0.3 hours for the pubic bone. CONCLUSIONS: The anatomy of the ischium and pubis is sufficiently constant to allow the positioning of screws in a standardised way. The interindividual variation is low - regardless of gender - so that the values determined can be used to position screws safely in the ischium and pubis. The values determined can provide the surgeon with additional orientation intra-operatively when placing caudal acetabular screws.

Avulsion fractures of the ischial tuberosity in the pediatric athlete: a systematic review and return to sport analysis.

Apophyseal avulsion fractures of the ischial tuberosity (AFIT) in pediatric athletes are relatively uncommon injuries with treatment and return to sport (RTS) outcomes being largely unknown. The purpose of this review is to perform a systematic review analyzing RTS and predictors of successful RTS for pediatric athletes sustaining AFIT. Studies reporting on athletes strictly under the age of 18 years sustaining an AFIT with reported RTS status were included. RTS was analyzed based on injury acuity, mechanism, and management, whereas the incidence of any complications was recorded. A total of 33 studies comprising 90 cases of AFIT were identified. The mean age of athletes sustaining injuries was 14.7 + 1.4 years (range, 9-17 years), most commonly participating in soccer ( n = 25), sprinting ( n = 21), and gymnastics ( n = 7). Acute trauma during sporting activities was responsible for 74.4% ( n = 77/90) of injuries. A total of 82% ( n = 74/90) of athletes reported successful RTS at an average of 7.0 + 5.0 months. Athletes undergoing surgery had a significantly higher RTS rate ( n = 36/38, 94.7%) compared with athletes treated nonoperatively (n = 38/52, 73.08%; P = 0.008). When reported, a high rate of misdiagnosis was reported (39.4%, n = 28/71). Complications were reported in 15.8% ( n = 7/38) and 32.7% ( n = 17/52) of athletes managed surgically and conservatively, respectively. As such, the high rate of misdiagnosis and subsequent high rate of complications and poor rate of RTS highlight the importance of accurate diagnosis and treatment. Future prospective studies evaluating patient outcomes based on fracture displacement, sporting activity, and management strategies are warranted to better treat pediatric athletes. Study design: Level IV, systematic review.

Incidental finding of hereditary multiple osteochondroma causing ischiofemoral impingement.

Ischiofemoral impingement (IFI) has been described in the medical literature as a cause of hip pain. IFI occurs due to an abnormal contact or reduced space between the lesser trochanter and the lateral border of the ischium and is an often unrecognised cause of pain and snapping in the hip. Association of multiple exostoses and a skeletal dysplasia characterised by an abnormal modelling of bone metaphysis and osseous deformities is highly characteristic of this disease. Consequently, multiple exostoses may narrow the ischiofemoral space and cause impingement and pain, even in the absence of malignant transformation. Surgical excision of exostosis of the lesser trochanter is a safe and effective method of treatment for patients with IFI. We present a case of left hip pain with incidental finding of hereditary multiple osteochondroma causing IFI and discuss the predisposing factors and review of literature.

Delayed proximal hamstring tendon repair after ischial tuberosity apophyseal fracture in a professional volleyball athlete: a case report.

BACKGROUND: Ischial tuberosity apophyseal fractures are avulsion fractures of the anatomic footprint of the proximal hamstring tendons. Generally, these injuries are rare and frequently occur in skeletally immature, active patients due to incomplete ossification. Depending on the fragment displacement, non-operative or operative treatment approaches are used. CASE PRESENTATION: We report a case of a 29-year-old professional volleyball athlete who has suffered from a nonunion avulsion fracture for 14 years. Isolated suture anchor fixation was performed after open excision of a large bony fragment followed by excellent clinical and functional outcome at 1 year postoperatively. CONCLUSION: In conclusion, avulsion fractures of the ischial tuberosity with large fragments and restrictions to activities of daily living due to pain can, in individualized cases, be treated with an open excision of the fragment followed by repair of the proximal hamstring tendons using suture anchors.

The ischiofemoral space of the hip is influenced by the frontal knee alignment.

PURPOSE: The ischiofemoral distance (IFD), defined as the distance between the ischial tuberosity and the lesser trochanter of the femur, is gaining recognition as an extra-articular cause of hip pain. It is unknown whether the IFD is influenced by the frontal knee alignment. The aim of this study was to determine the influence of realignment surgery around the knee on the IFD. It was hypothesized that valgisation osteotomy around the knee is associated with reduction of the IFD. METHODS: A consecutive series of 154 patients undergoing frontal realignment procedures around the knee in 2017 were included in this study. Long-leg standing radiographs were obtained before surgery and postoperatively. The IFD was measured between the ischium and the lesser trochanter at three different levels (proximal, middle and distal margins of the lesser trochanter parallel to the horizontal orientation of the pelvis) on standardized long-leg radiographs with the patient in upright standing position. The knee alignment was determined by measuring the hip knee ankle angle, mechanical lateral distal femur angle and the medial mechanical proximal tibia angle. Linear regression was performed to determine the influence of the change of frontal knee alignment on the IFD. RESULTS: Linear regression showed a direct influence of the overall change in frontal knee alignment on the IFD of the hip, regardless of the site of the osteotomy (ß-0.4, confidence-interval - 0.5 to - 0.3, p < 0.001). Valgisation osteotomy around the knee induced a significant reduction of the ipsilateral IFD (p < 0.001), while varisation osteotomy induced a significant increase (p < 0.001). The amount of ISD change was 0.4 mm per corresponding degree of change in frontal knee alignment. CONCLUSION: These findings are relevant to both the hip and knee surgeons when planning an osteotomy or arthroplasty procedure. Correction of a malalignment of the knee may resolve an ischiofemoral conflict in the hip. The concept deserves inclusion in the diagnostic workup of both the hip and knee joints. LEVEL OF EVIDENCE: IV.

Surgical repair techniques, functional outcome, and return to sports after apophyseal avulsion fractures of the ischial tuberosity in adolescents.

PURPOSE: Among juvenile apophyseal avulsion injuries of the pelvis in adolescents, fractures of the ischial tuberosity are rare but sustainably debilitating. Also because informations on surgical repair options are very sparse and so far limited to general reviews, reports of individual cases or heterogeous small case series, practitioners, patients and their parental environment still feel a comprehensible hesitation regarding operative treatment. Therefore we intended to investigate patient related outcome measurements and return to sports rates after different types of surgical intervention in an own case series, so far unprecendented in its size. METHODS: Patient data of adolescents that underwent surgical intervention for a displaced apophyseal avulsion fracture of the ischial tuberosity between 01/2015 and 12/2019 in our institution were gathered. Patients were then evaluated using the hamstring injury specific Perth Hamstring Assessment Tool (PHAT). Furthermore the return to sports level in comparison to the particular pre-injury level was rated. RESULTS: Eleven adolescents with an acute or chronic mean fragment dislocation of 3.3 cm (SD ± 1.7) underwent surgical intervention in the assigned period. The mean post-operative PHAT score was 86.9 (0-100, SD ± 11.9) and thus good to excellent. The majority of adolescents (10/11) was able to return to their pre-injury sports, whereas 63.6% achieved full or nearly full level. CONCLUSIONS: Surgical refixation or restoration of aphoyseal avulsion fractures of the ischial tuberosity result in good to excellent outcomes and return to sport rates, irrespective of the type of intervention. Here prompt diagnosis with a timely intervention seems more promising than delayed interventions in chronic cases. Beyond 1.5 cm of fragment displacement affected patients should be counselled for surgical intervention.

Pelvic Avulsion Injuries in the Adolescent Athlete.

Pelvic avulsion fractures are common in youth athletes; many of these injuries can be treated conservatively. This article reviews the etiology, presentation, and management of the more common pelvic avulsion fractures, including anterior superior iliac spine, anterior inferior iliac spine, ischial tuberosity, and iliac crest avulsions. Adolescent pelvic avulsion fractures rely on the amount of fracture displacement to guide treatment. Conservative management includes rest and avoiding use of the muscle(s) that attach to the avulsed fragment. Operative treatment is reserved for widely displaced fractures or symptomatic nonunions. With appropriate treatment, young athletes frequently return to their same level of sport.

Infra-acetabular screw exited between ischial tuberosity and ischial spine is more suitable for Asian population: a 3D morphometric study.

BACKGROUND: Recently, the infra-acetabular screw has been proposed for use in treatment of acetabular fractures as a part of a periacetabular fixation frame. Biomechanical studies have shown that an additional infra-acetabular screw placement can enhance the fixation strength of acetabular fracture internal fixation. Currently, the reported exit point of the infra-acetabular screw has been located at the ischial tuberosity (Screw I). However, our significant experience in placement of the infra-acetabular screw has suggested that when the exit point is located between the ischial tuberosity and the ischial spine (Screw II), the placement of a 3.5 mm infra-acetabular screw may be easier for some patients. We conducted this study in order to determine the anatomical differences between the two different IACs. METHODS: The raw datasets were reconstructed into 3D models using the software MIMICS. Then, the models, in the STL format model, were imported into the software Geomagic Studio to delete the inner triangular patches. Additionally, the STL format image processed by Geomagic Studio was imported again into MIMICS. Finally, we used an axial perspective based on 3D models in order to study the anatomical parameters of the two infra-acetabular screw corridors with different exit points. Hence, we placed the largest diameter virtual screw in the two different screw corridors. The data obtained from this study presents the maximum diameter, length, direction, and distances between the entry point and center of IPE. RESULTS: In 65.31% males and 40.54% females, we found a screw I corridor with a diameter of at least 5 mm, while a screw II corridor was present in 77.55% in males and 62.16% in females. Compared to screw I, the length of screw II is reduced, the angle with the coronal plane is significantly reduced, and the angle with the transverse plane is significantly increased. CONCLUSIONS: For East Asians, changing the exit point of the infra-acetabular screw can increase the scope of infra-acetabular screw use, especially for females.

Safety and efficacy of ischial spine fascia and sacrospinous ligament fixation for symptomatic stage 2 and 3 apical prolapse.

OBJECTIVE: To compare safety, efficacy, and impact on quality of life (QoL) between ischial spine fascia fixation (ISFF) and sacrospinous ligament fixation (SSLF) for stage 2-3 pelvic organ prolapse (POP). METHOD: A prospective cohort study among women with POP attending a national referral university hospital in Beijing, China, between May 2007 and May 2015. Women underwent either ISFF or SSLF. Primary end point was objective success rates at 3 months after surgery. Exploratory outcomes included perioperative parameters, complications, subjective satisfaction rates and QoL at 1 year. RESULTS: There was no difference in baseline characteristics between the groups (all P>0.05). After ISFF and SSLF, the objective success rate at 3 months was 100% and 98.1% (P>0.99), the recurrence rate at 1 year was 5.3% and 8.3% (P=0.266), and the subjective satisfaction rate at 1 year was 97.8% and 97.9%, respectively. Pelvic Organ Prolapse/Urinary Incontinence Sexual Questionnaire-12 scores improved significantly after ISFF. De novo urinary incontinence occurred for 5.3% and 6.3% of women, respectively, and de novo dyspareunia for approximately 14% of women in both groups. CONCLUSION: ISFF was found to be a safe and effective alternative to SSLF for women with symptomatic stage 2 and 3 POP.

Periacetabular osteotomy for hip dysplasia treatment through a mini-invasive technique. Our results at mid-term in 131 cases. / Osteotomía periacetabular en el tratamiento de displasia de cadera mediante técnica mini-invasiva. Nuestros resultados a medio plazo en 131 casos.

BACKGROUND AND OBJECTIVE: Periacetabular osteotomy (PAO) is an accepted and worldwide technique recognized for residual dysplasia treatment and even in unstable hips with limited acetabular coverage. The aim of this study is to analyse the functional, radiological and complication results in patients treated with mini-invasive PAO. MATERIAL AND METHODS: We performed a retrospective study in which we analysed 131 cases undergoing mini-invasive PAO at our centre. The degree of joint degeneration was evaluated with Tönnis scale, Wiberg angle, acetabular index (AI), anterior coverage angle (AC), joint space, complications and functional outcome with the Non-Arthritic Hip Score (NAHS) were analysed preoperatively and at the end of follow-up. RESULTS: The average age was 32.3±9.5 (SD) years, 102 (77.9%) were female and 29 (22.1%) were male. 7.7±2.8 (SD) years follow up. The radiological parameters improved between the pre-surgical phase and the end of follow-up, Wiberg angle+18.5° (18.3° versus 36.8°, 95% CI 17.3 to 19.7), AC angle+13.5° (26.2° versus 39.7°, 95%CI 11.6 to 15.4) and the AI -11.1° (19.5° versus 8.4°; 95%CI -12.1 to -10,1). In addition, the functional results, with the NAHS scale, improved+31.3 points (60.7 pre-surgical versus 92 at the end of follow-up, 95% CI 28.7 to 33.8). The most common complication was transient lateral femoral cutaneous nerve hypoaesthesia in 10 cases (7%). CONCLUSION: The mini-invasive PAO approach is a reproducible technique, it allows restoration of acetabular coverage and provides an improvement in functional scales as confirmed by our series.

Inferior extended fixation utilizing porous titanium augments improves primary anti-rotational stability of the acetabular component.

BACKGROUND: The primary anti-rotational stability is critical to preventing cup tilting failure following revision total hip arthroplasty, but is frequently compromised by severe ischial bone loss. A novel technique of "inferior extended fixation" was introduced by securing a porous metal augment into the deficient ischium. This study evaluated the effect of this technique on primary anti-rotational stability in revision total hip arthroplasty. METHODS: Composite hemipelvis specimens, acetabular components and "lotus" augments were used to simulate total hip arthroplasty surgeries. Three different cementless operative settings of cup implantation were simulated: (1) native ischium without defects; (2) ischium with a defect not reconstructed; (3) ischial defect reconstructed with inferior extended fixation using a lotus augment. Lever-out testing was used to examine primary anti-rotational stability, which was measured as interface stiffness and yield moment. FINDINGS: Compared with the native ischium setting, the mean interface stiffness decreased by 53.1% in the ischial defect setting (p < 0.001). In the inferior extended fixation setting, the mean value was 110% greater than that in the ischial defect setting (p = 0.014), and comparable to that in the native ischium setting (p = 1). Similar results were observed for the yield moment (declined by 63.1%, p < 0.001; 200% higher, p < 0.001; and p = 0.395; respectively). INTERPRETATION: In revision total hip arthroplasty with severe ischial defects, inferior extended fixation with a lotus porous titanium augment restores anti-rotational stability of the acetabular component to the level of that with a native ischium, which provides the mechanical environment for bone ingrowth and prevents cup tilting failure.