Background: Preoperative templating is an essential step in hip arthroplasty (HA), guiding implant selection and reducing surgical complications. It is typically performed using acetate templates or digital software. These methods, however, depend on the surgeon’s experience and may be limited by cost and availability. This study aimed to develop and validate a deep learning (DL) model using plain radiographs to predict implant sizes in HA. Methods: This retrospective study included patients who underwent primary HA using a cementless CORAIL® femoral stem and PINNACLE® acetabular cup. The DL model was trained on 688 preoperative anteroposterior (AP) hip radiographs and validated temporally on 98 additional cases. Implant sizes predicted by the DL model were compared with on-screen templating (acetate templates overlaid on digital images). The actual implanted size was used as the reference standard. Accuracy, mean absolute error (MAE), and root mean square error (RMSE) were calculated. Logistic regression was performed to identify factors influencing prediction accuracy. Results: The DL model showed higher accuracy than the on-screen templating for the acetabular cup (88.9% [77.4% to 95.8%] vs. 83.3% [70.7% to 90.2%]) and femoral stem components (85.7% [77.2% to 92.0%] vs. 81.6% [72.5% to 88.7%]), while the on-screen method performed better for the bipolar head (93.2% [81.3% to 98.6%] vs. 72.7% [57.2% to 85.0%]). MAE and RMSE were comparable between the methods for acetabular and femoral stem components (all p > 0.05), with statistically significant differences observed only in the bipolar head (p < 0.01 and 0.02, respectively). Although logistic regression analysis showed trends toward higher accuracy in acetabular size prediction among women and those with shorter height, no demographic factors were statistically significant predictors of accuracy. Conclusions: A DL model using only plain radiographs can accurately predict implant sizes in HA, particularly for the acetabulum and femoral stem. These findings suggest that the DL-based model could be a useful tool in preoperative planning. With further refinement to improve generalizability, this approach could be useful in a routine clinical setting in the future.

Introduction: Elderly individuals frequently suffer from hip fractures, particularly femoral neck intracapsular fractures, which can cause serious morbidity. Bipolar hip hemiarthroplasty is a preferred treatment for displaced fractures, but accurate preoperative templating is essential to predict acetabular component size and to improve surgical outcomes. Aim: To assess the accuracy of preoperative digital radiographs in predicting acetabular component size for bipolar hip hemiarthroplasty, thereby improving surgical planning and implant selection. Materials and Methods: A hospital-based prospective study was conducted at SMS Hospital, Jaipur, Rajasthan, India, involving 50 patients undergoing bipolar hip hemiarthroplasty from November 2017 to December 2019. The primary inclusion criteria included age over 20, a diagnosis of hip arthrosis or femoral neck fracture, skeletal maturity, no significant concomitant disorders, and informed consent to participate. The demographic parameters included age, gender, Body Mass Index (BMI), diagnosis (hip arthrosis or femoral neck fracture according to Garden's classification), side of hip involvement, and ethnicity/race (if applicable) for anatomical variations. Preoperative digital radiographs were analysed using templating software to predict the acetabular component size. Intraoperatively, the actual implant size was determined and compared with the predicted size. Accuracy, deviations, and influencing factors were assessed using statistical analysis. A paired t-test was used to compare the predicted acetabular component sizes with the actual intraoperative sizes and to evaluate the reliability of digital radiographs for preoperative sizing. A p-value of &lt; 0.05 was considered statistically significant for all tests. Results: The predicted acetabular size ranged between 40 and 53 mm, with an accuracy of 14 (28%) for the exact size and 42 (84%) within one size including the most accurate ones. Accuracy was slightly higher in female patients at 24 (90%) compared to males at 18 (78.3%). The inconsistencies were attributed to the limited availability of prosthesis sizes and the quality of radiography. Conclusion: Digital templating improves preoperative planning for bipolar hip hemiarthroplasty, but it is less accurate than for Total Hip Arthroplasty (THA). To improve the templating outcomes in clinical practice, it is advised to implement better radiography techniques, calibration protocols, and surgeon training.

Certain implant combinations change leg length and offset in primary total hip arthroplasty (THA). Poor restoration of leg biomechanics is a frequently cited reason for patient dissatisfaction following primary THA. A pure high-offset stem should provide direct lateralization without affecting femoral length when compared to a standard stem. However, clinical experience with preoperative planning software based on computed tomography-based three-dimensional-models reveals that using pure high-offset stems in THA may cause a difference between expected (no change in femoral length) and actual (small increase) in postoperative femoral length. To elucidate the causes of these femoral length discrepancies using preoperative planning software. Preoperative templating for 43 robotic-assisted THAs, optimizing acetabular size and orientation, center of rotation, stem size and offset, and prosthetic head diameter were obtained. The preoperative planning software was used to calculate differences between preoperative and postoperative femoral length for standard and pure high-offset stems, unique to each patient. Whilst the increase in femoral length between standard and high-offset stems was not significant (P = 0.93), 35 femurs (81.4%) experienced a 1-mm increase, and 3 (7.0%) experienced a 2-mm increase in femoral length while using high-offset stem compared to the standard stem. The incidence of femoral length increase was lower for patients with shorter femurs (18/22; 81.8%) compared to patients with longer femurs (20/21; 95.2%). When pure high-offset stems were used in preoperative planning software, we demonstrated an unexpected increase in leg length between 1-2-mm in 88.4% of patients. This unexpected increase in femoral length is due to a function of the preoperative planning software's planned stem alignment with the anatomical axis, and not an inherent fault in the stem design. With expanding accessibility of robotic-assisted THA platforms, all potential sources of postoperative leg length discrepancy should be identified during preoperative templating and necessary alterations to the surgical plan should be made to accommodate this unexpected difference when using a pure high-offset stem.

Purpose of the studyTotal hip replacements (THRs) are a standard and effective surgical procedure that benefits from preoperative planning. Despite this, no consensus exists on the best preoperative templating tool for THRs. In this study, we compare the single marker to the KingMark™ double-templating system for predicting the size of implants used intraoperatively.MethodsThis retrospective study compares two cohorts of 50 consecutively selected patients who underwent primary THR under the care of two orthopaedic surgeons. All patients had preoperative anteroposterior (AP) pelvic radiographs to facilitate templating by one of the two methods. The first cohort had surgery with single-marker templated THRs from August to December 2021. The second cohort had THRs templated using the KingMark™ system and underwent surgery between January and April 2022. For both groups, the templated size of the acetabular and femoral implants was compared to the definitive acetabular and femoral implants, respectively. Any patients with a history of previous hip surgery, with developmental abnormality affecting hip anatomy, or requiring bespoke implants were excluded.ResultsSingle-marker templating accurately predicted the femoral implant size in 32% of cases. KingMark™ correctly predicted femoral implant size in 54% of cases, a statistically significant improvement (p=0.04). The mean templated acetabular cup size for the single-marker cohort templated acetabular size was 52.5±4.1, and the definitive acetabular size was 53.6±3.5. The mean templated acetabular cup size for the KingMark™ cohort was 52.0±3.7, and the definitive acetabular cup size was 53.2±4.8. The absolute difference between templated and definitive acetabular implants was 2.3±2.4 and 2.2±2.6, respectively, which was not statistically significant (p=0.84). This is consistent with the rate of accurate acetabular implant prediction for both templating methods (32% for single marker and 30% for KingMark™) with no significant difference (p=0.83).ConclusionThe KingMark™ system showed superior accuracy in predicting the femoral stem size in THR over the conventional single mark. However, it's important to note that there was no significant difference between the two methods in predicting the cup size, a key finding of our study.

Abstract Purpose: Mixed type FAI is common in both sexes, however isolated pincer-type FAI disproportionately affects females. There is limited data on sex-specific pincer lesion characteristics. The aims of this study are twofold: 1) to test the hypothesis that absolute pincer lesion size will be larger in male patients, but there will be no sex differences in pincer lesion size relative to femoroacetabular size 2) to test the hypothesis that maximum pincer lesion depth will be greatest around the 2 o’clock region of the acetabulum in both sexes with mixed-type FAI. Methods: Participant demographics: Females (n=74, Age: 34±9 years, BMI 25.4±4.6, Height 1.67±0.07 meters, Weight 71.1±14.8 kg) Males (n=74, Age: 35±10 years, BMI 26.6±4.5, Height 1.8±0.08 meters, Weight 86.4±16.5 kg). The study cohort consisted of patients presenting with symptomatic mixed-type FAI without signs of dysplasia. A CT-based analysis software was used to determine pincer lesion depth and location, along with femoroacetabular morphological measurements. Chi-Square tests were used to compare pincer lesion depth as a categorical variable between sexes at all acetabular clockface locations. Independent t-tests were performed to compare the following measurements between sexes: Acetabular coverage, acetabular surface area (ASA), acetabular version (AV) at 12-3 o’clock locations, femoral torsion (FT), and lateral center edge angle (LCEA). Results: Pincer lesion depth was significantly greater in males across the 1-3 acetabular clockfaces (p≤0.0009) and was not different between sexes at all other clockface locations (p&amp;gt;0.05). The greatest areas of pincer lesion depth were the 1.5-2 o’clock positions among females and the 2-2.5 o’clock positions among males. AV at the 12, 2, and 3 o’clock locations was higher in females (p&amp;lt;0.002), while ASA was significantly greater in males (4715 mm2 vs. 3854 mm2, p&amp;lt;0.0001). Acetabular coverage, LCEA, and FT were not different between sexes (p&amp;gt;0.05). Conclusions: These preliminary findings suggest that males with mixed-type FAI have larger absolute pincer lesions, along with larger absolute acetabular size, indicating that relative lesion size may not be different between sexes. Additionally, both sexes were shown to have maximum pincer lesion depth around the 2 o’clock acetabular region, with a greater depth magnitude in males at this location.

Salvage arthroplasty for failed proximal femoral fracture fixation is a complex procedure. This involves the removal of the primary failed or broken implant followed by a hip joint replacement procedure. The complications and technical difficulties associated with these surgeries are often difficult to anticipate. Initially, to further understand the position in the literature with regardto salvage arthroplasty, we completed an informative scoping review. Search terms were selected, and databases Embase and PubMed were utilised to form a literature search. Relevant articles were selected by two independent researchers, with a final list of nine studies reviewed and tabulated for themes to be identified and analysed. Subsequently, we retrospectively studied the notes of all the patients who underwent complex conversion arthroplasty in the same district hospitals in a span of 16 years (August 2002 to August 2018) and presented the results. Seventy-one patients underwent complex salvage arthroplasty following a failed fixation of proximal femoral fracture under the care of three different surgeons. All surgeries were carried out by the posterior approach. The demographics, intraoperative events, and postoperative follow-up have been presented through clinical and radiological assessments. With a mean age being 73.6, female patients were almost twice the number of male patients. The left hip was the more common surgical site. Implant cutout was the most common cause of failure of the primary implant. Most of these surgeries were either uncemented (31 cases, 43.66%) or hybrid (29 cases, 40.84%). The most common acetabular size to be used was 50 mm, and the most common head size used was 32 mm. A majority of the surgeries were metal on poly bearings (64 cases, 90.14%). The mean surgical time, including anesthetic,was four hours and 13 minutes. A total of 31 (44%)patients needed blood transfusion postoperatively. The infection rate was 21.13% (15 cases), being the most common surgical complication. The mean follow-up of the patients was 27.2months with the maximum follow-up being 125 months. The one-year mortality was found to be 14% (10 cases). The mean limb length discrepancy was shortening by an average of 3.84 mm. A total of 66.2% (47 cases) of patientswere shortened postoperatively. The average cup abduction and anteversion angles were 35° and 24.25°, respectively. The average position of the femoral stem was 0.31° in the varus with 40.85% (29 cases) of patients having a slightly varus stem. Upon drawing comparisons with primary hip arthroplasty for primary osteoarthritis through data available in the literature, it is obvious that salvage arthroplasty is a complex procedure with longer surgical times and onerous rehabilitation. Whilst it is not the same as revision arthroplasty, many of the characteristics in terms of surgical planning and outcomes are similar. Therefore, it is our recommendation that salvage hip arthroplasty procedures should be categorised, listed, and studied separately from primary arthroplasty in the National Joint Registry database.

Selecting the optimal size of components is crucial when performing a primary total hip arthroplasty. Implanting the accurate size of the acetabular component can occasionally be exacting, chiefly for surgeons with little experience, whilst the complications of imprecise acetabular sizing or over-reaming can be potentially devastating. To assist clinicians intraoperatively with a simple and repeatable tip in elucidating the ambivalence when determining the proper acetabular component size is not straightforwardly achieved, specifically when surgeons are inexperienced or preoperative templating is unavailable. This method was employed in 263 operations in our department from June 2021 to December 2022. All operations were performed by the same team of joint reconstruction surgeons, employing a typical posterior hip approach technique. The types of acetabular shells implanted were: The Dynasty® acetabular cup system (MicroPort Orthopedics, Shanghai, China) and the R3® acetabular system (Smith & Nephew, Watford, United Kingdom), which both feature cementless press-fit design. The mean value of all cases was calculated and collated with each other. We distinguished as oversized an implanted acetabular shell when its size was > 2 mm larger than the size of the acetabular size indicator reamer (ASIR) or when the implanted shell was larger than 4 mm compared to the preoperative planned cup. The median size of the implanted acetabular shell was 52 (48-54) mm, while the median size of the preoperatively planned cup was 50 (48-56) mm, and the median size of the ASIR was 52 (50-54) mm. The correlation coefficient between ASIR size and implanted acetabular component size exhibited a high positive correlation with r = 0.719 (P < 0.001). Contrariwise, intraoperative ASIR measurements precisely predicted the implanted cups' size or differed by only one size (2 mm) in 245 cases. In our study, we demonstrated that the size of the first acetabular reamer not entering freely in the acetabular rim corroborates the final acetabular component size to implant. This was also corresponding in the majority of the cases with conventional preoperative templating. It can be featured as a valid tool for avoiding the potentially pernicious complications of acetabular cup over-reaming and over-sizing in primary total hip arthroplasty. It is a simple and reproducible technical note useful for confirming the predicted acetabular cup size preoperatively; thus, its application could be considered routinely, even in cases where preoperative templating is unavailable.

Comparison of three-versus two-dimensional pre-operative planning for total hip arthroplasty

BackgroundIn recent years, ‘Get It Right First Time (GIRFT)’ have advocated cemented replacements in femoral part of Total hip arthroplasty (THA) especially in older patients. However, many studies were unable to show any difference in outcomes and although cemented prostheses may be associated with better short-term pain outcomes there is no clear advantage in the longer term. It is not clear when and why to do cemented instead of cementless.AimTo assess differences in patient reported outcomes in uncemented THAs based on patient demographics in order to decide when cementless THA can be done safely.MethodProspective data collection of consecutive 1079 uncemented THAs performed for 954 patients in single trust between 2010 and 2020. Oxford Hip Score (OHS) and complications were analysed against demographic variables (age, sex, BMI, ASA) and prosthesis features (femoral and acetabular size, offset and acetabular screws).ResultsThe mean pre-operative OHS was 14.6 which improved to 39.0 at 1 year follow up (P Value=0.000). There was no statistically significant difference between OHS outcome in patients aged over 70 versus younger groups. With a small number of revisable complications increase with age from 50s upwards. Male patients’ OHS score was on average 2.4 points higher than women. Men, however were 2.9 times more likely to experience fractures and high offset hips were 2.5 times more likely to experience dislocations. DAIR, intraoperative calcar fractures, post-operative fractures and dislocations were not associated with worse OHS. Patients with increased BMI had worse pre and post-operative hip functions yet, there was a significant multivariate association between increased BMI and increased improvement in OHS from pre-op to 1 year in women aged 55–80 and men under the age of 60. Femoral stem size increases with age but decreases in male patients over 80. There was no difference found in OHS between bilateral hip replacements and unilateral, nor was there any change found with laterality side of the replacement.ConclusionsThis study suggests that ageing &gt;70 is not associated with poorer outcomes despite small number of revisable complication rates that increase with age from 50 upwards. Men had marginally higher average OHS than women At 1 year. Higher BMI or ASA scores are associated with worse pre-operative hips and worse final outcome score. Despite this, the Delta OHS increases with increased BMI shown in the 55–80 year old female patients and male patients under 60.Key Words: THR, Uncemented, Oxford hip score, outcome.

Periacetabular osteotomy (PAO) is an effective technique to treat symptomatic hip dysplasia. However, following PAO, some patients still experience persistent pain or development of hip arthritis, requiring total hip arthroplasty (THA). Issues such as whether patients with PAO are necessarily at increased risk of post-THA complications and revision of the prosthesis remain debatable. The purpose of this study was to evaluate the biomechanical influence of PAO on the acetabulum after THA by finite element analysis. Eight patients with developmental dysplasia of the hip (DDH) diagnosed in the Fourth Medical Center of the PLA General Hospital were enrolled in this research. Patient-specific hip joint models were reconstructed from computed tomography scans, and the hip prosthesises, were established via computer-aided design (CAD) modeling technology. The finite element analysis was conducted to compare the surface and internal stress through the process mapping of the model due to the THA. Compared with the THA after PAO, the position of the high-stress area of the acetabular fossa of patients without PAO decreased, and the high-stress area developed toward the lower edge of the acetabulum. Although the high-stress area of the suprapubic branch did not change significantly, the peak stress was higher (t=.00237). The analysis of the section plane showed that the high-stress area of cancellous bone had a large distribution. The acetabular size and vertical distance of rotation center (VDRC) were significantly correlated with the maximum postoperative acetabular equivalent stress (p=.011, p=.001). In the Post group, both the horizontal distance of rotation center (HDRC) and A-ASA were significantly correlated with postoperative maximal acetabular equivalent stress, with a significance of 0.014 and 0.035, respectively. The risk of postoperative prosthetic revision following THA is not increased by PAO, although the risk of postoperative suprapubic branch fracture is increased.

Demographic Data Reliably Predicts Total Hip Arthroplasty Component Size

BackgroundThere is a common conception held by patients with a high body mass index (BMI) that they have “big bones”. Some people hold the assumption that their weight is attributed to larger bone stock rather than adipose tissue. It was the suspicion of the surgeons at our unit that this is often not the case. We therefore conducted a study investigating if there is any association between BMI and acetabular bone size.MethodsWe conducted a retrospective chart review of all patients undergoing total hip arthroplasty using the Trident acetabular system from Stryker at our tertiary level 1 trauma centre between September 2016 and August 2020. Patient demographic and surgical data were collected, and the association of BMI, height, and weight, with acetabular cup size was investigated using Pearson’s correlation coefficient and chi-square test for independence.ResultsA total of 418 patients were included in this study (52.4% female; age: 20-93 years; mean age: 62.51 years), with a mean BMI of 29.55 kg/m2(range: 14.95-52.32 kg/m2). A weak positive association between BMI and cup size, which was statistically significant (r = 0.107; n = 418; p = 0.02). The chi-square test for independence was used to study the association between obesity and cup size (large vs small), which demonstrated no significant difference (p = 0.08). There was a moderately strong positive association between height and cup size (r = 0.551; n = 418; p < 0.01). There was a weak positive association between weight and cup size, which was statistically significant (r = 0.355; n = 418; p < 0.01).ConclusionOur study suggests that there is indeed a weakly positive linear association between BMI and cup size among total hip arthroplasty patients. This effect was, however, more significant for height and weight, and there was no significant association between obese and non-obese groups with small versus large cup size implanted. We therefore conclude that clinically there is no significant relationship between obesity and acetabular bone size and that the “big bones” claim is indeed fallacious.

Hominin pelvic form differs dramatically from that of other primates by having more laterally facing iliac blades, a wider sacrum and a larger, transversely broad pelvic inlet. Acetabular orientation may differ as well, plausibly related to differences in load transmission during habitual bipedal posture and locomotion. Here, we test the hypothesis that hominin acetabular orientation differs from that of other anthropoids using two approaches. First, we performed a 3D geometric morphometric analysis of landmarks collected on the acetabula of 220 specimens representing 30 extant taxa, humans, A. afarensis (AL 288-1), and a Neandethal (Kebara 2). Second, we measured the 3D orientation of the acetabulum on in silico models of individual hipbones that were aligned to the median plane by registering models to landmark coordinates that had been collected on articulated pelves. We fit a plane to the acetabular rim and measured its orientation relative to the median plane, a “transverse” plane fit to the lumbosacral joint, and a “coronal” plane orthogonal to the median and lumbosacral planes. Angles between the acetabular plane and reference planes are 3D angles, measured as the angle between the normal vectors of the acetabular and selected reference plane in the plane containing both normal vectors. The sample for this analysis included 77 specimens from 22 extant anthropoid taxa, humans, Kebara 2, A. afarensis (AL 288-1), and A. sediba (MH 2). Results of the geometric morphometric analysis do demonstrate differences between hominins and non-hominins, but results are confounded by variation in acetabular size. Analysis of angular relationships between the acetabulum and reference planes, though, support the hypothesis that hominin acetabula indeed are more anteriorly and inferiorly oriented than those of other anthropoids. Other taxa are generally similar, although African apes exhibit slightly more anteriorly oriented acetabula than other anthropoids. Results suggest that the orientation of the acetabulum is a key component in the suite of pelvic characteristics related to habitual bipedality in hominins and should be considered in future analyses of hominin pelvic morphology.

The acetabular fossa is thought to be located in the center of the acetabulum, and acetabular reaming in total hip arthroplasty is conventionally performed in the center of the fossa. However, the actual location of the fossa and the influence that hypoplasia or deformity may have on the position of the fossa are unknown. We hypothesized that the fossa is located in the center of the acetabulum, regardless of hypoplasia or deformity. Fifty patients with normal hips (normal hip group), 50 patients with dysplasia who underwent rotational acetabular osteotomy (dysplastic hip group), and 46 patients with osteoarthritis who underwent total hip arthroplasty (osteoarthritic hip group) were evaluated by computed tomography (CT) imaging. On the horizontal plane that passes through the center of the femoral head, the center line of the acetabulum was defined as the perpendicular bisector of the anterior and posterior rims of the acetabulum. The angle and distance of the center of the acetabular fossa in relation to the center line of the acetabulum were evaluated; furthermore, the center position of the fossa from the anterior margin of the acetabulum was calculated as a ratio relative to acetabular size. A 1-way analysis of variance was performed to compare measurements among the 3 groups. The center of the acetabular fossa was positioned anteriorly to the center line of the acetabulum in all 3 groups. The mean center angle of the acetabular fossa was 14.0° ± 3.8°, 15.2° ± 5.6°, and 14.9° ± 5.5° in the normal, dysplastic, and osteoarthritic hip groups, respectively (p = 0.33). The mean center distance of the acetabular fossa was 5.6 ± 1.8, 5.8 ± 2.3, and 6.1 ± 2.2 mm, respectively (p = 0.55). The mean center position of the acetabular fossa was 38.8% ± 3.3%, 38.5% ± 4.2%, and 38.3% ± 3.9%, respectively (p = 0.71). The center of the acetabular fossa is positioned anteriorly to the center of the acetabulum, and the positioning is affected by neither dysplasia nor osteoarthritis. The preconception that the center of the acetabulum corresponds to the center of the acetabular fossa may risk eccentric reaming, possibly damaging the anterior wall. Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Early results of 500 primary total hip arthroplasties with a large diameter bearing ceramic monoblock acetabular components

L’usage de calques sur des radiographies digitales calibrées en orthostatisme améliore la précision de la planification des arthroplasties totales de hanche

Acetate templating on calibrated standing digital radiograph improves accuracy of preoperative templating for total hip arthroplasty

Femoral head size provides important information on body size in extinct species. Although it is well-known that femoral head size is correlated with acetabular size, the precision with which femoral head size can be estimated from acetabular size has not been quantified. The availability of accurate 3D surface models of fossil acetabular remains opens the possibility of obtaining accurate estimates of femoral head size from even fragmentary fossil remains [Hammond et al.,: Am J Phys Anthropol 150 (2013) 565-578]. Here we evaluate the relationship between spheres fit to surface models of the femoral head and acetabulum of a large sample of extant anthropoid primates. Sphere diameters are tightly correlated and scale isometrically. In spite of significant taxonomic and possibly functional differences in the relationship between femoral head size and acetabulum size, percent prediction errors of estimated femoral head size remain low regardless of the taxonomic composition of the reference sample. We provide estimates of femoral head size for a series of fossil hominins and monkeys.

Only one study to date has explored the potential of innominate measurements for the estimation of stature in forensic contexts. The acetabulum, however, is among the skeletal regions most resistant to the processes of destruction and often survives intact. In this investigation, diameter, area and perimeter dimensions of the acetabulum were recorded from digital photographs in a documented French sample, consisting of 36 males and 33 females. Linear regression equations for estimating stature were then generated for each dimension in both males and females. Correlation coefficients for the models ranged from r = 0.401 to r = 0.474, and standard error of the estimate (SEE) values were between 5.7 cm and 6.1 cm. The highest correlation coefficients in both sexes were observed for the diameter of the acetabulum. These results indicate that acetabular dimensions should only be used for stature estimation when more accurate bones are unavailable for analysis.

Floriparicapitus n. gen. (Cestoda: Lecanicephalidea), with Floriparicapitus euzeti n. gen., n. sp. as its type, is erected to house 3 new tapeworm species and 2 known species that are transferred to the new genus, all parasitizing sawfishes and guitarfishes (order Rhinopristiformes) in Indo-Pacific waters. The new genus differs from the 21 valid lecanicephalidean genera in its possession of a large scolex bearing a laterally expanded apical organ in the form of a rugose sheet in combination with a cirrus conspicuously armed with spinitriches and 3 pairs of excretory vessels. It most closely resembles Lecanicephalum, but differs conspicuously in its possession of 3, rather than 1, pair of excretory vessels. Two new species are described from sawfishes: Floriparicapitus euzeti n. sp., from Pristis clavata and Floriparicapitus juliani n. sp. from Pristis pristis, both from Australia. Floriparicapitus plicatilis n. sp. is described from the guitarfish Glaucostegus typus in Australia and the guitarfish Glaucostegus thouin in Malaysian Borneo. Two species formerly assigned to Cephalobothrium are transferred to the new genus; Floriparicapitus variabilis ( Southwell, 1911 ) n. comb. from the sawfish Anoxypristis cuspidata in Sri Lanka and Floriparicapitus rhinobatidis ( Subhapradha, 1955 ) n. comb. from the guitarfish Glaucostegus granulatus in India. The species from guitarfish differ conspicuously from those parasitizing sawfish in their possession of only 4 ( F. plicatilis n. sp.) or 5 (F. rhinobatidis n. comb.) testes per proglottid versus 9 or more in the 3 sawfish-parasitizing species. The latter 3 species differ from one another in scolex width, acetabular size, number of proglottids, and cirrus sac size. As it stands, the new genus appears to be restricted to a subclade of the Rhinopristiformes consisting of the sawfishes and species of Glaucostegus.