Rigid fixation of pelvic tracker essential for accurate cup placement in CT-based navigation total hip arthroplasty.

Research is lacking on the effect of intraoperative pelvic tracker displacement relative to the pelvis on cup orientation accuracy in computed tomography (CT)-based navigation (CTN) or multivariable analysis to detect factors associated with CTN accuracy. Here, we asked: (1) how pelvic tracker displacement influences the CTN accuracy of cup orientation in total hip arthroplasty (THA)? and (2) what factors are associated with CTN accuracy on multivariable analysis? Regarding cup orientation in 446 THA procedures using CTN, we evaluated clinical error defined as the difference between postoperative measurement and preoperative planning and measurement error defined as the difference between postoperative and intraoperative measurements. Multivariable regression analyses detected the associated factors. Subjects with an intraoperative tracker displacement of < 2 mm were classified in the verified group. Mean absolute clinical and measurement errors were < 1.5° in the verified group, whereas the measurement error of 2.6° for cup inclination and 1.3° for anteversion was larger in the non-verified versus verified group. Tracker displacement and screw fixation were associated with larger clinical errors, while tracker displacement and surgeon inexperience were associated with larger measurement errors. Clinical and measurement accuracies were high for CTN cup placement with rigid pelvic tracker fixation.

Use of artificial intelligence to identify data elements for The Japanese Orthopaedic Association National Registry from operative records.

BACKGROUND: The Japanese Orthopaedic Association National Registry (JOANR) was recently launched in Japan and is expected to improve the quality of medical care. However, surgeons must register ten detailed features for total hip arthroplasty, which is labor intensive. One possible solution is to use a system that automatically extracts information about the surgeries. Although it is not easy to extract features from an operative record consisting of free-text data, natural language processing has been used to extract features from operative records. This study aimed to evaluate the best natural language processing method for building a system that automatically detects some elements in the JOANR from the operative records of total hip arthroplasty. METHODS: We obtained operative records of total hip arthroplasty (n = 2574) in three hospitals and targeted two items: surgical approach and fixation technique. We compared the accuracy of three natural language processing methods: rule-based algorithms, machine learning, and bidirectional encoder representations from transformers (BERT). RESULTS: In the surgical approach task, the accuracy of BERT was superior to that of the rule-based algorithm (99.6% vs. 93.6%, p < 0.001), comparable to machine learning. In the fixation technique task, the accuracy of BERT was superior to the rule-based algorithm and machine learning (96% vs. 74%, p < 0.0001 and 94%, p = 0.0004). CONCLUSIONS: BERT is the most appropriate method for building a system that automatically detects the surgical approach and fixation technique.

Does a computed tomography-based navigation system reduce the risk of dislocation after total hip arthroplasty in patients with osteonecrosis of the femoral head? A propensity score analysis.

This study aimed to investigate whether use of a computed tomography (CT)-based navigation system reduce the risk of dislocation after total hip arthroplasty (THA) in patients with osteonecrosis of the femoral head (ONFH). A total of 271 hips from 192 consecutive patients that underwent primary THA for ONFH were included. There were 110 hips in non-navigation group, and 161 hips in navigation group. After applying exclusion criteria, 209 hips from 149 patients were selected for analysis. Clinical outcomes and complication rates were evaluated, and implant alignments were also calculated. To identify whether the navigation system was useful to prevent dislocation, the inverse probability of treatment-weighted Cox regression analysis using a propensity score in relationship to sex, age at surgery, body mass index, and femoral head size was performed. No significant difference was observed in clinical scores between both groups. Dislocation was significantly lower in the navigation group (3 hips, 2.7%) than in the non-navigation group (11 hips, 11.2%; p = 0.012), whereas periprosthetic joint infection and aseptic loosening did not differ between the groups. Variance of cup inclination and anteversion angles was smaller in the navigation group than in the non-navigation group (p < 0.001). Use of the CT-based navigation system (hazard ratio; 0.26, 95% confidence interval, 0.07-0.98; p = 0.047) turned out to be the predictor for preventing dislocation. In conclusion, use of the CT-based navigation system provided a precise placement of components, and thus helps to prevent dislocation in patients with ONFH in the propensity score analysis.

Asymptomatic Deep Venous Thrombosis After Elective Hip Surgery Could Be Allowed to Remain in Place Without Thromboprophylaxis After a Minimum 2-Year Follow-Up.

BACKGROUND: It is not clear how to treat asymptomatic deep venous thromboses (DVTs) following elective hip arthroplasty because the natural course of DVTs is unclear. It is therefore valuable to understand the natural course of DVTs and their relation to thromboprophylactic methods. METHODS: We followed 742 consecutive patients who underwent elective hip arthroplasty followed by mechanical or chemical prophylaxis of a DVT. All patients underwent preoperative and postoperative duplex ultrasonography of both limbs. Patients who developed postoperative DVT in the popliteal or calf vein were followed without thromboprophylaxis. DVT-positive patients were prospectively followed up with duplex ultrasonography at 3, 6, 12, and 24 months postoperatively. RESULTS: Incidences of preoperative and postoperative DVTs were 3.9% and 33.0%, respectively. Nonfatal pulmonary embolism (PE) occurred in 1 patient after negative echography. All DVTs that developed in the calf vein postoperatively and without anticoagulation remained benign, and 93% of the DVTs ultimately disappeared. CONCLUSION: These results confirmed that the natural course of asymptomatic distal DVTs is benign, with no risk of leading to PE. Thus, distal DVTs could be allowed to remain untreated without chemical prophylaxis to prevent PE in Asian populations.

Risk of injury to the femoral blood vessels based on the extent of acetabular dysplasia in total hip arthroplasty.

We evaluated the course of the femoral blood vessels of patients with acetabular dysplasia. Patients were divided into five groups: those with Crowe type I, II, III, and IV dysplastic hips and those with normal hips. A computed tomography-based hip navigation software was used to measure the distance between the femoral blood vessels and the anterior pelvic wall in four axial planes located 10-40 mm proximal to the pelvic teardrop. In Crowe Groups I through IV, the distance was shortest at a point 20 mm proximal to the pelvic teardrop. Furthermore, the distance decreased as the Crowe classification grade increased. Because the femoral blood vessels pass close to the pelvis in many patients in Crowe III and IV hips, caution is required during surgery in these patients.

Differences in activities of daily living after hip arthroplasty among hip resurfacing, anterolateral THA, and posterolateral THA: a propensity score matched analysis.

The aim was to elucidate the differences in activities of daily living (ADL) after hip arthroplasty among hip resurfacing (HRA), anterolateral total hip arthroplasty (AL-THA), and posterolateral THA (PL-THA) patients after age, sex, body mass index, bilateral/unilateral hip arthroplasty, and postoperative duration were matched using propensity scores. A total of 673 hips from 540 consecutive patients who underwent hip arthroplasty were included. A self-completed questionnaire on preoperative and postoperative ADLs was administered during postsurgical visits at least ≥ 4 years postoperatively. Between HRA and PL-THA patients, the numbers of patients who performed heels-down squatting was significantly more in HRA than in PL-THA. Between AL-THA and PL-THA patients, there were significant differences in postoperative ADLs including bathing in a bathtub, riding on a train/bus, cutting toenails, bowing while straight sitting, heels-up/down squatting, riding on a bicycle, driving a car, and domestic travel. There were no significant differences in postoperative ADLs between ≥ 36 mm head and ≤ 32 mm head PL-THA patients, and between AL-THA and HRA patients. This propensity score matched study indicated that AL-THA and HRA patients were more active postoperatively than PL-THA patients.

Does Robotic Milling For Stem Implantation in Cementless THA Result in Improved Outcomes Scores or Survivorship Compared with Hand Rasping? Results of a Randomized Trial at 10 Years.

BACKGROUND: Robotic-assisted THA has been promoted as potentially advantageous due to the precision it may afford when machining the proximal femur. However, few reports have compared the long-term clinical results of robotic techniques for femoral component insertion during THA regarding clinical outcomes scores or loosening. QUESTIONS/PURPOSES: The purpose of this study was to compare results from a randomized clinical trial (RCT) at a minimum followup of 10 years between robot-assisted and hand-rasped stem implantation techniques with regard to (1) Japanese Orthopaedic Association (JOA) clinical outcomes scores, and (2) aseptic loosening, revision surgery, and heterotopic ossification. METHODS: This is a concise followup of a previously reported RCT. In that trial, robot-assisted primary THA was performed on 75 hips (69 patients), and a hand-rasping technique was used on 71 hips (61 patients). Five experienced surgeons at two institutions participated in this trial; all THAs were performed through the posterolateral approach and the patients were treated similarly apart from the method used to prepare the femur. In all, 115 of 130 (88%) of patients initially randomized were available for followup at a minimum of 10 years (mean, 135 months; range, 120-152 months). There was no differential loss to followup between the study groups, and the final study groups here included 64 hips in 59 patients in the robotic group, and 64 hips in 56 patients in the hand-milling group. There were no differences between the study groups in terms of age, sex, diagnosis, body-mass index, or baseline JOA scores. The primary study endpoint was the JOA score, which is scored from 0 to 100, with higher scores representing better function and less pain. Secondary outcomes were revision surgery, and radiographic signs of aseptic loosening and heterotopic ossification as assessed using the four-grade Brooker scale by individuals other than the operating surgeon. RESULTS: At a minimum of 10 years postoperatively, there were no differences between patients treated with robot-assisted surgery or hand rasping in JOA scores (97 ± 5 versus 96 ± 7, mean difference 1.4; p = 0.159). No stems in either group developed aseptic loosening, and there were no revisions in either group. There was no difference between the groups in heterotopic ossification (19 of 64 [30%] in the robot-assisted group versus 12 of 64 [19%] in the hand-rasping group; p = 0.186), severe heterotopic ossification was uncommon in both groups, and no hips developed Grade 4 heterotopic ossification in either group. CONCLUSIONS: Clinically and radiographically, THAs performed with robotic milling for stem implantation did not result in better 10-year clinical outcomes scores, or a lower risk of loosening or revision, compared with hand-rasping. We recommend against widespread adoption of robotic milling for stem implantation in primary cementless THAs. LEVEL OF EVIDENCE: Level II, therapeutic study.

Characteristics of bone turnover markers in rapidly destructive coxopathy.

The purpose of this study was to clarify bone turnover marker levels in rapidly destructive coxopathy (RDC). Twenty patients with RDC (mean age, 72 ± 11 years; 3 men, 17 postmenopausal women), 111 with osteoarthritis (OA) (age, 60 ± 10 years; 15 men, 13 premenopausal women, 83 postmenopausal women), and 18 with osteonecrosis of femoral head (ON) (55 ± 14 years; 11 men, 3 premenopausal women, 4 postmenopausal women), and 100 patients with femoral neck fracture (FNF) (81 ± 10 years; 27 men, 73 postmenopausal women) were included. Serum tartrate-resistant acid phosphatase 5b (TRACP-5b), bone alkaline phosphatase (BAP), matrix metalloproteinase-3 (MMP-3) levels, and bone mineral density (BMD) of proximal femur and lumbar spine were investigated. TRACP-5b levels were significantly higher in RDC than in OA and ON, whereas BAP levels were higher in RDC than in OA (P < 0.05). MMP-3 levels were higher in RDC and ON than in OA (P < 0.05). TRACP-5b were higher in RDC than OA (P < 0.05) and FNF (P < 0.05) in performing propensity score matching; there were no differences in BMD between RDC and OA. TRACP-5b showed the largest area under the curve (AUC, 0.82) according to receiver operating characteristic (ROC) curve analysis for diagnosing RDC against OA and ON. AUCs of BAP and MMP-3 were 0.78 and 0.74. The respective sensitivities and specificities were 70.0 % and 85.3 % for TRACP-5b (cutoff, 623 mU/dl), 95.0 % and 57.1 % for BAP (13.8 U/l), and 70.0 % and 76.4 % for MMP-3 (52.7 ng/ml). The lack of differences in BMD suggested that high bone turnover marker levels may reflect osteoclast cell activation in RDC hips. Serum TRACP-5b and BAP could be RDC markers.

Improvement of activities of daily living after total hip arthroplasty using a computed tomography-based navigation system.

The purpose of this study was to evaluate the outcome improvements after total hip arthroplasty (THA) using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) in patients who underwent THA with a navigation system in our institutions. The subjects were 219 patients. All patients had adequate data to allow complete scoring of the WOMAC for a 1-year postoperative follow-up. CT-based navigation was used in all THAs. Postoperatively, no restrictions were imposed on patients' ADL. One year after surgery, the average WOMAC pain subscale score was 1.8 ± 2.9, the stiffness subscale score was 1.1 ± 1.6, and the physical function subscale score was 7.5 ± 11.6 points. The number of patients whose score for the WOMAC physical function score was 0 points was 61 (27.9%). A lower WOMAC score usually represents a better status. In some of the most difficult functions, such as ascending stairs, bending to the floor, putting on socks/stockings, and heavy domestic duties, the scores tended to be higher than the other scores postoperatively. These results show that THA using navigation can improve patients' postoperative QOL.

Thrombophylaxis with low-dose, short-term fondaparinux after elective hip surgery.

Some studies have cautioned about the possibility of bleeding complications with routine use of anticoagulants like fondaparinux (FPX) for thrombophylaxis after elective hip surgery. Overdosing or prolonged periods of anticoagulant use should be avoided. We trialed a new regimen using FPX and tranexamic acid (TA) to reduce the risk of bleeding complications while maintaining efficacy in preventing deep vein thrombosis (DVT). The present study evaluated the effectiveness and safety of this regimen in 391 consecutive patients. Each patient was assigned either the FPX group, administered a once-daily subcutaneous injection of 1.5 mg of FPX on postoperative days 2, 3, and 4; or the intermittent pneumatic compression (IPC) group, which used an IPC device continuously for 1-2 days with no administration of any anticoagulant drugs. Ultrasonography was performed to diagnose DVT in all patients. No cases of fatal or symptomatic pulmonary embolism were encountered in either group, but six patients (3.1 %) in the FPX group and nine patients (6.0 %) in the IPC group showed asymptomatic distal DVT. The incidence of DVT tended to be lower (p = 0.19), volumes of intraoperative (p < 0.01) and postoperative (p < 0.01) blood loss were significantly smaller, and hemoglobin level was significantly higher in the FPX group than in the IPC group (p < 0.01). Our new thrombophylactic regimen using FPX and TA appears effective and safe for use after elective hip surgery.

The Accuracy of a Mechanical Cup Alignment Guide in Total Hip Arthroplasty (THA) Through Direct Anterior and Posterior Approaches Measured with CT-Based Navigation.

The purpose of this study was to compare the accuracy of a mechanical cup alignment guide using CT-based navigation between a direct anterior approach (DAA) in both supine and lateral positions and a posterior approach (PA) in the lateral position. A trial cup was placed with a mechanical guide that aimed at 47° of radiographic inclination and 14° of anteversion. The average cup inclination and anteversion were measured using CT-based navigation. The average radiographic anteversion in the DAA supine and lateral group was larger, and that in the PA group was smaller than the target angle. In conclusion, there are no differences in the accuracy or precision of cup angles among the DAA supine, DAA lateral position, and PA groups using a mechanical guide.

Difference in Stem Alignment Between the Direct Anterior Approach and the Posterolateral Approach in Total Hip Arthroplasty.

The purpose of this study was to investigate the effects of different surgical approaches, the posterolateral approach (PLA) and the direct anterior approach (DAA), on postoperative femoral anteversion and stem coronal and sagittal alignment in total hip arthroplasty (THA), and to identify the factors related to postoperative femoral anteversion and stem alignment. A total of 209 hips of 181 patients were evaluated. THA was performed through the PLA in 80 hips and through the DAA in 129 hips. Femoral anteversion and stem alignment were measured on postoperative computed tomography images. The factor related to postoperative anteversion change was preoperative femoral anteversion, and the surgical approaches did not affect the postoperative anteversion change, while surgical approach did have an effect on stem sagittal alignment.

Synovial joint fluid cytokine levels in hip disease.

OBJECTIVE: The purpose of this study was to evaluate cytokine level characteristics in the hip joint fluid, including rapidly destructive coxopathy (RDC), OA, osteonecrosis (ON) of the femoral head and RA. METHODS: Thirty-three hips with RDC, 57 with OA, 36 with ON and 10 with RA were included in the study. OA hips were divided into two groups: 20 hips with early OA without joint space narrowing and 37 hips with terminal OA. ON hips were divided into three groups: 13 hips with <3 mm collapse, 14 hips with >3 mm collapse and 9 hips with terminal ON. Joint fluid was collected during surgery. Cytokine levels including IL-1ß, IL-6, IL-8 and TNF-α were measured using homogeneous time-resolved fluorescence. RESULTS: All measured cytokine levels in RDC were significantly higher than those in OA (P < 0.05). Terminal OA showed higher cytokine levels than those in early OA (P < 0.05). IL-6 and TNF-α levels in the ON group with >3 mm collapse were higher than those found in the ON group with <3 mm collapse. In comparing cytokine levels between RDC, terminal OA, RA and terminal ON, RDC showed significantly higher IL-8 levels than terminal OA and RA (P < 0.05). CONCLUSION: IL-8 levels in RDC were higher than in the other hip diseases. The IL-8 level may reflect the aggressiveness of joint destruction in RDC, and IL-6 and TNF-α levels may also reflect ongoing destruction in OA and ON.

Accuracy of femoral component anteversion in robotic total hip arthroplasty.

Aims: Femoral component anteversion is an important factor in the success of total hip arthroplasty (THA). This retrospective study aimed to investigate the accuracy of femoral component anteversion with the Mako THA system and software using the Exeter cemented femoral component, compared to the Accolade II cementless femoral component. Methods: We reviewed the data of 30 hips from 24 patients who underwent THA using the posterior approach with Exeter femoral components, and 30 hips from 24 patients with Accolade II components. Both groups did not differ significantly in age, sex, BMI, bone quality, or disease. Two weeks postoperatively, CT images were obtained to measure acetabular and femoral component anteversion. Results: The mean difference in femoral component anteversion between intraoperative and postoperative CT measurements (system accuracy of component anteversion) was 0.8° (SD 1.8°) in the Exeter group and 2.1° (SD 2.3°) in the Accolade II group, respectively (p = 0.020). The mean difference in anteversion between the plan and the postoperative CT measurements (clinical accuracy of femoral component anteversion) was 1.2° (SD 3.6°) in the Exeter group, and 4.2° (SD 3.9°) in the Accolade II group (p = 0.003). No significant differences were found in acetabular component inclination and anteversion; however, the clinical accuracy of combined anteversion was significantly better in the Exeter group (0.6° (SD 3.9°)) than the Accolade II group (3.6° (SD 4.1°)). Conclusion: The Mako THA system and software helps surgeons control the femoral component anteversion to achieve the target angle of insertion. The Exeter femoral component, inserted using Mako THA system, showed greater precision for femoral component and combined component anteversion than the Accolade II component.

Altered coronary flow velocity reserve and left ventricular wall motion dynamics: a phenomenon in hypertensive patients with ECG strain.

BACKGROUND: The inner-half layer of the left ventricular (LV) wall is primarily affected by ischemia and increased LV afterload. We hypothesized that LV wall thickening of inner-half layer and coronary microvascular function are impaired in hypertensive patients, especially in those with electrocardiographic (ECG) strain, which is a marker of LV hypertrophy and adverse prognosis. Therefore, the aim of this study is to investigate the association of the ratio of inner- to outer-half layer of the LV myocardial deformation and coronary microvascular function with ECG strain in hypertensive patients. METHODS: We studied 98 hypertensive patients and 13 controls. Hypertensive patients were divided into 2 groups, with (S+) and without (S-) ECG strain. Coronary flow velocity reserve (CFVR) of the left anterior descending artery was evaluated using transthoracic echocardiography. Circumferential and radial strains of the LV wall were analyzed by two-dimensional echocardiographic speckle tracking method, and the inner- to outer-half layer ratio (in/out ratio) was assessed. RESULTS: Coronary flow velocity reserve of S+ (2.06 ± 0.65) was significantly smaller than those in S- and controls (3.03 ± 0.65 and 3.38 ± 0.51, respectively). In/out ratio in both circumferential and radial strains were decreased as well as in S+ patients. Furthermore, in/out ratio was directly proportional to CFVR. CONCLUSIONS: Hypertensive patients with ECG strain possessed severely impaired CFVR and inner-half myocardial deformation. Moreover, the more severe the LV hypertrophy progresses, the greater is the impairment of coronary microvascular and LV inner-half myocardial deformation. Thus, CFVR and in/out ratio are useful quantitative markers that can render sensitive assessment of physiological changes in hypertensive heart disease.

Application of computed tomography-based navigation for revision total hip arthroplasty.

The usefulness of navigation systems for revision total hip arthroplasty (THA) remains unclear. The purpose of this study was to evaluate the accuracy of cup positioning using a navigation system in revision THA. Cup alignment of thirty revision cases was evaluated. Data were also compared with those of 30 navigated primary THA cases. In the revision THA group, mean difference in postoperative measurement from preoperative plan was 0.5 ± 4° (range, -9° to 8°) for inclination and -0.07° ± 5° (-14° to 13°) for anteversion. Mean difference in postoperative measurement from intraoperative record was 0.7° ± 3° (-5° to 8°) for inclination and -0.7° ± 3° (-12° to 5°) for anteversion. Compared with the primary THA group, none of these parameters were significantly different. This navigation system was useful even in revision THA.

Modular acetabular reconstructive cup in acetabular revision total hip arthroplasty at a minimum ten year follow-up.

PURPOSE: Modular acetabular reconstructive cups have been introduced in an attempt to offer initial rigid fixation by iliac lag screws and ischial pegs, to support bone grafts with a flanged metal socket, and to restore original hip center in acetabular revision. The purpose of this study was to clarify minimum ten year follow-up results of this cup system with morsellised allografts in revision cases. METHODS: We retrospectively investigated 54 acetabular revisions at a mean of 11 years (range, ten to 14 years). The indications were Paprosky's type 2B (eight hip), 2C (eight hips), 3A (23 hips), 3B (nine hips), and 4 (six hips). RESULTS: Using aseptic loosening as the endpoints, the survival rate was 89.3 % (95 % CI 81-98). Radiographically, one type 3A hip, three type 3B hips and one type 4 hip showed aseptic loosening while no type 2 hips or no cemented cups showed loosening. CONCLUSIONS: The modular reconstructive cups for acetabular revision showed bone stock restoration and stable implantation.

Management and outcomes of suction loss during LASIK flap creation with a femtosecond laser.

PURPOSE: To evaluate risk factors, management, and outcomes in patients who experienced suction loss during LASIK flap creation with a femtosecond laser (Intra-Lase FS 60, Abbott Medical Optics Inc). METHODS: Pre- and postoperative visual outcomes and refractions for 71 eyes of 70 patients after suction loss during flap creation with the IntraLase FS60 femtosecond laser were analyzed and studied. RESULTS: In patients requiring a second or third lamellar flap cut immediately after suction loss, 97.2% of eyes achieved uncorrected distance visual acuity of 0.00 logMAR (20/20) or better and 100% of eyes achieved corrected distance visual acuity of 0.00 logMAR (20/20) or better at most recent follow-up. CONCLUSIONS: Our study suggests that excellent visual outcomes can be achieved if an immediate lamellar recut is performed after suction loss with a femtosecond laser.

Dynamic measurements of hip movement in deep bending activities after total hip arthroplasty using a 4-dimensional motion analysis system.

Although deep hip bending activities are often required in Asian populations because of traditional lifestyles and religious practices, few have examined the required hip range of motion (ROM) in these activities after total hip arthroplasty (THA). We performed postoperative motion analysis to evaluate the differences in required ROMs between Japanese-style and Western-style deep hip bending activities, to investigate whether prosthetic impingement would occur during these activities and to clarify the necessity for precautions in these activities after THA. Japanese-style activities did not require larger hip ROMs than Western-style ones, and all required hip flexion angles were less than 120°. Prosthetic impingement was not observed, with a safety margin 10° or higher until impingement in any directions of flexion, adduction, or internal rotation for any activities. Thus, particular postoperative precautions for Japanese-style activities are not required.

Is the transverse acetabular ligament a reliable cup orientation guide?

BACKGROUND AND PURPOSE: It is controversial whether the transverse acetabular ligament (TAL) is a reliable guide for determining the cup orientation during total hip arthroplasty (THA). We investigated the variations in TAL anatomy and the TAL-guided cup orientation. METHODS: 80 hips with osteoarthritis secondary to hip dysplasia (OA) and 80 hips with osteonecrosis of the femoral head (ON) were examined. We compared the anatomical anteversion of TAL and the TAL-guided cup orientation in relation to both disease and gender using 3D reconstruction of computed tomography (CT) images. RESULTS: Mean TAL anteversion was 11° (SD 10, range -12 to 35). The OA group (least-square mean 16°, 95% confidence interval (CI): 14-18) had larger anteversion than the ON group (least-square mean 6.2°, CI: 3.8 - 7.5). Females (least-square mean 20°, CI: 17-23) had larger anteversion than males (least-square mean 7.0°, CI: 4.6-9.3) in the OA group, while there were no differences between the sexes in the ON group. When TAL was used for anteversion guidance with the radiographic cup inclination fixed at 40°, 39% of OA hips and 9% of ON hips had more than 10° variance from the target anteversion, which was 15°. INTERPRETATION: In ON hips, TAL is a good guide for determining cup orientation during THA, although it is not a reliable guide in hips with OA secondary to dysplasia. This is because TAL orientation has large individual variation and is influenced by disease and gender.