The management of femoral bone loss is challenging during revision hip arthroplasty. In patients with Paprosky grade IIIB and IV defects, obtaining fixation and rotational stability using traditional surgical constructs is difficult. The use of a custom-made internal proximal femoral replacement prostheses has been proposed as a solution in patients, with severe femoral bone stock loss. However, there is a paucity in the literature on their use and long-term outcomes. We report on the clinical and radiological results of our cohort. We retrospectively reviewed all patients who underwent internal proximal femoral replacement for revision hip arthroplasty between April 1996 and April 2019. All patients had at least 2 years of follow-up time. 160 patients underwent limb salvage at our institution using internal proximal femoral replacement. The mean follow-up was 79.7 months (S.D 41.3). Indications for revision included periprosthetic fractures, aseptic loosening, and deep infection. The mean Oxford hip score increased from 13.8 (0–22) to 31.5 (18–43) (paired t-test, p < 0.001). Kaplan-Meier prosthesis survival analysis with revision as the endpoint was 87% at 5 years. None required revision of the femoral stem. There were four dislocations (5%) and there was failure to eradicate the deep infection in four. This technique allows instant distal fixation, allowing for early mobilisation. Long-term clinical and radiological outcomes are encouraging and the complication rates are acceptable for this patient group

The incidence of hip fractures in the elderly is increasing. Minimally displaced and un-displaced hip fractures can be treated with either internal fixation or hemiarthroplasty. The aim was identifying the revision rate of internal fixation and hemiarthroplasty in patients 60 years or older with Garden I or II hip fractures and to identify risk factors associated with each method. A retrospective analysis was conducted from 2 Major Trauma Centres and 9 Trauma Units between 01/01/2015 and 31/12/2020. Patients managed conservatively, treated with a total hip replacement and missing data were excluded from the study. 1273 patients were included of which 26.2% (n=334) had cannulated hip fixation (CHF), 19.4% (n=247) had a dynamic hip screw (DHS) and 54.7% (n=692) had a hemiarthroplasty. 66 patients in total (5.2%) required revision surgery. The revision rates for CHF, DHS and hemiarthroplasty were 14.4%, 4%, 1.2% (p<0.001) respectively. Failed fixation was the most common reason for revision with the incidence increasing by 7-fold in the CHF group [45.8% (n=23) vs. 33.3% (n=3) in DHS; p<0.01]. The risk factors identified for CHF revision were age >80 (p<0.05), female gender (p<0.05) and smoking (p<0.05). The average length of hospital stay was decreased when using CHF compared to DHS and hemiarthroplasty (12.6 days vs 14.9 days vs 18.1 days respectively, p<0.001) and the 1 year mortality rate for CHF, DHS and hemiarthroplasty was 2.5%, 2% and 9% respectively. Fixation methods for Garden I and II hip fractures in elderly patients are associated with a higher revision rate than hemiarthroplasty. CHF has the highest revision rate at 14.4% followed by DHS and hemiarthroplasty. Female patients, patients over the age of 80 and patients with poor bone quality are considered high risk for fixation failure with CHF. When considering a fixation method in such patients, DHS is more robust than a screw construct, followed by hemiarthroplasty

In 2005, we demonstrated that the polished triple-tapered C-stem at two years had migrated distally and rotated internally. From that series, 33 patients have now been followed radiologically, clinically and by radiostereometric analysis (RSA) for up to ten years. The distal migration within the cement mantle had continued and reached a mean of 2 mm (0.5 to 4.0) at ten years. Internal rotation, also within the cement mantle, was a mean 3.8° (external 1.6° to internal 6.6°) The cement mantle did not show any sign of migration or loosening in relation to the femoral bone. There were no clinical or radiological signs indicating that the migration or rotation within the cement mantle had had any adverse effects for the patients. Cite this article: Bone Joint J 2014;96-B:604–8

The treatment algorithms for displaced fractures of the femoral neck need to be improved if we are to reduce the need for secondary surgery. We have studied 102 patients of mean age 80 years, with an acute displaced fracture of the femoral neck. They were randomly placed into two groups, treated either by internal fixation (IF) with two cannulated screws or total hip replacement (THR). None showed severe cognitive dysfunction, all were able to walk independently, and all lived in their own home. They were reviewed at four, 12 and 24 months after surgery. Outcome measurements included hip complications, revision surgery, hip function according to Charnley and the health-related quality of life (HRQoL) according to EuroQol (EQ-5D). The failure rate after 24 months was higher in the IF group than in the THR group with regard to hip complications (36% and 4%, respectively; p < 0.001), and the number of revision procedures (42% and 4%, p < 0.001). Hip function was significantly better in the THR group at all follow-up reviews regarding pain (p < 0.005), movement (p < 0.05 except at 4 months) and walking (p < 0.05). The reduction in HRQoL (EQ-5D . index. score) was also significantly lower in the THR group than in the IF group, comparing the pre-fracture situation with that at all follow-up reviews (p < 0.05). The results of our study strongly suggest that THR provides a better outcome than IF for elderly, relatively healthy, lucid patients with a displaced fracture of the femoral neck

Aims

The optimal management of intracapsular fractures of the femoral neck in independently mobile patients remains open to debate. Successful fixation obviates the limitations of arthroplasty for this group of patients. However, with fixation failure rates as high as 30%, the outcome of revision surgery to salvage total hip arthroplasty (THA) must be considered. We carried out a systematic review to compare the outcomes of salvage THA and primary THA for intracapsular fractures of the femoral neck.

Aims

The objective of this study was to investigate bone healing after internal fixation of displaced femoral neck fractures (FNFs) with the Dynamic Locking Blade Plate (DLBP) in a young patient population treated by various orthopaedic (trauma) surgeons.

Dual Mobility (DM) Total Hip Replacements (THRs) were introduced to reduce dislocation risk, which is the most common cause of early revision. The in-vivo mechanics of these implants is not well understood, despite their increased use in both elective and trauma settings. Therefore, the aim of this study was to comprehensively assess retrieved DM polyethylene liners for signs of damage using visual inspection and semi-quantitative geometric assessment techniques. Retrieved DM liners (n=20) were visually inspected for the presence of seven established modes of polyethylene damage. If embedded debris was identified on the external surface, its material composition was characterised using energy-dispersive x-ray analysis (EDX). Additionally, each liner was geometrically assessed for signs of wear/deformation using a validated methodology. Visual inspection of the liners revealed that scratching and pitting were the most common damage modes on either surface. Burnishing was observed on 50% and 15% of the internal and external surfaces, respectively. In addition, embedded debris was identified on 25% of the internal and 65% of the external surfaces. EDX analysis of the debris identified several materials including iron, titanium, cobalt-chrome, and tantalum. Geometric analysis demonstrated highly variable damage patterns across the liners. The results of this study provide insight into the in-vivo mechanics of DM bearings. For example, the results suggest that the internal bearing (i.e., between the head and liner) acts as the primary articulation site for DM-THRs as evidenced by a higher incidence of burnishing and larger, more concentrated regions of penetration across the liners’ internal surfaces. Furthermore, circumferential, and crescent-shaped damage patterns were identified on the articulating surfaces of the liners thus providing evidence that these components can rotate within the acetabular shell with varying degrees of mobility. The mechanics of DM bearings are complex and may be influenced by several factors (e.g., soft tissue fibrosis, patient activities) and thus further investigation is warranted. Finally, the results of this study suggest that DM liners may be susceptible to ex-vivo surface damage and thus caution is advised when handling and/or assessing these types of components

Aims. The aims of this study were to validate the Forgotten Joint Score-12 (FJS-12) in the postoperative evaluation of periacetabular osteotomy (PAO), identify factors associated with joint awareness after PAO, and determine the FJS-12 threshold for patient-acceptable symptom state (PASS). Methods. Data from 686 patients (882 hips) with hip dysplasia who underwent transposition osteotomy of the acetabulum, a type of PAO, between 1998 and 2019 were reviewed. After screening the study included 442 patients (582 hips; response rate, 78%). Patients who completed a study questionnaire consisting of the visual analogue scale (VAS) for pain and satisfaction, FJS-12, and Hip disability and Osteoarthritis Outcome Score (HOOS) were included. The ceiling effects, internal consistency, convergent validity, and PASS thresholds of FJS-12 were investigated. Results. The median follow-up was 12 years (interquartile range 7 to 16). The ceiling effect of FJS-12 was 7.2%, the lowest of all the measures examined. FJS-12 correlated with all HOOS subscales (ρ = 0.72 to 0.77, p < 0.001) and pain and satisfaction-VAS (ρ = -0.63 and 0.56, p < 0.001), suggesting good convergent validity. Cronbach’s α was 0.95 for the FJS-12, which indicated excellent internal consistency. The median FJS-12 score for preoperative Tönnis grade 0 hips (60 points) was higher than that for grade 1 (51 points) or 2 (46 points). When PASS was defined as pain-VAS < 21 and satisfaction-VAS ≥ 77, the FJS-12 threshold that maximized the sensitivity and specificity for detecting PASS was 50 points (area under the curve (AUC) = 0.85). Conclusion. Our results suggest that FJS-12 is a valid and reliable assessment tool for patients undergoing PAO, and the threshold of 50 points may be useful to determine patient satisfaction following PAO in clinical settings. Further investigation of the factors influencing postoperative joint awareness may enable improved prediction of treatment efficacy and informed decision-making regarding the indication of PAO. Cite this article: Bone Joint J 2023;105-B(7):760–767

Hip precautions following total hip arthroplasty (THA) limits flexion, adduction and internal rotation, yet these precautions cause unnecessary psychological stress. This study aims to assess bony and implant impingement using virtual models from actual patient's bony morphology and spinopelvic parameters to deduce whether hip precautions are necessary with precise implant positioning in the Asian population. Individualized sitting and standing sacral slope data of robotic THAs performed at two tertiary referral centers in Hong Kong was inputted into the simulation system based on patients’ pre-operative sitting and standing lumbar spine X-rays. Three-dimensional dynamic models were reconstructed using the Stryker Mako THA 4.0 software to assess bony and implant impingement both anteriorly and posteriorly, with default cup placement at 40° inclination and 20° anteversion. Femoral anteversion followed individual patient's native version. A 36mm hip ball was chosen for all cups equal or above 48mm and 32mm for those below. Anterior impingement was assessed by hip flexion and posterior impingement was assessed by hip extension. 113 patients were included. At neutral rotation and adduction, no patients had anterior implant impingement at hip flexion of 100°. 1.7% had impingement at 110°, 3.5% had impingement at 120°, 9.7% had impingement at 130°. With 20° of internal rotation and adduction, 0.8% had anterior implant impingement at hip flexion of 90°, 7.1% had impingement at 100° and 18.5% had impingement at 110°. With the hip externally rotated by 20°, 0.8% of patients had posterior implant impingement, and 8.8% bony impingement at 0° extension. With enabling technology allowing accurate component positioning, hip precautions without limiting forward flexion in neutral position is safe given precise implant positioning and adequate osteophyte removal. Patients should only be cautioned about combined internal rotation, adduction with flexion

Aims. We aimed to compare the implant survival, complications, readmissions, and mortality of Vancouver B2 periprosthetic femoral fractures (PFFs) treated with internal fixation with that of B1 PFFs treated with internal fixation and B2 fractures treated with revision arthroplasty. Methods. We retrospectively reviewed the data of 112 PFFs, of which 47 (42%) B1 and 27 (24%) B2 PFFs were treated with internal fixation, whereas 38 (34%) B2 fractures underwent revision arthroplasty. Decision to perform internal fixation for B2 PFFs was based on specific radiological (polished femoral components, intact bone-cement interface) and clinical criteria (low-demand patient). Median follow-up was 36.4 months (24 to 60). Implant survival and mortality over time were estimated with the Kaplan-Meier method. Adverse events (measured with a modified Dindo-Clavien classification) and 90-day readmissions were additionally compared between groups. Results. In all, nine (8.01%) surgical failures were detected. All failures occurred within the first 24 months following surgery. The 24-month implant survival was 95.4% (95% confidence interval (CI) 89.13 to 100) for B1 fractures treated with internal fixation, 90% (95% CI 76.86 to 100) for B2 PFFs treated with osteosynthesis-only, and 85.8% (95% CI 74.24 to 97.36) for B2 fractures treated with revision THA, without significant differences between groups (p = 0.296). Readmissions and major adverse events including mortality were overall high, but similar between groups (p > 0.05). The two-year patient survival rate was 87.1% (95% CI 77.49 to 95.76), 66.7% (95% CI 48.86 to 84.53), and 84.2% (95% CI 72.63 to 95.76), for the B1 group, B2 osteosynthesis group, and B2 revision group, respectively (p = 0.102). Conclusion. Implant survival in Vancouver B2 PFFs treated with internal fixation was similar to that of B1 fractures treated with the same method and to B2 PFFs treated with revision arthroplasty. Low-demand, elderly patients with B2 fractures around well-cemented polished femoral components with an intact bone-cement interface can be safely treated with internal fixation. Cite this article: Bone Joint J 2021;103-B(7):1222–1230

Aims. Our primary aim was to assess reoperation-free survival at one year after the index injury in patients aged ≥ 75 years treated with internal fixation (IF) or arthroplasty for undisplaced femoral neck fractures (uFNFs). Secondary outcomes were reoperations and mortality analyzed separately. Methods. We retrieved data on all patients aged ≥ 75 years with an uFNF registered in the Swedish Fracture Register from 2011 to 2018. The database was linked to the Swedish Arthroplasty Register and the National Patient Register to obtain information on comorbidity, mortality, and reoperations. Our primary outcome, reoperation, or death at one year was analyzed using restricted mean survival time, which gives the mean time to either event for each group separately. Results. Overall, 3,909 patients presenting with uFNFs were included. Of these patients, 3,604 were treated with IF and 305 with primary arthroplasty. There were no relevant differences in age, sex, or comorbidities between groups. In the IF group 58% received cannulated screws and 39% hook pins. In the arthroplasty group 81% were treated with hemiarthroplasty and 19% with total hip arthroplasty. At one year, 32% were dead or had been reoperated in both groups. The reoperation-free survival time over one year of follow-up was 288 days (95% confidence interval (CI) 284 to 292) in the IF group and 279 days (95% CI 264 to 295) in the arthroplasty group, with p = 0.305 for the difference. Mortality was 26% in the IF group and 31% in the arthroplasty group at one year. Reoperation rates were 7.1% in the IF group and 2.3% in the arthroplasty group. Conclusion. In older patients with a uFNF, reoperation-free survival at one year seems similar, regardless of whether IF or arthroplasty is the primary surgery. However, this comparison depends on the choice of follow-up time in that reoperations were more common after IF. In contrast, we found more early deaths after arthroplasty. Our study calls for a randomized trial comparing these two methods. Cite this article: Bone Jt Open 2024;5(2):86–92

Aims. The objectives of this study were to investigate the patient characteristics and mortality of Vancouver type B periprosthetic femoral fractures (PFF) subgroups divided into two groups according to femoral component stability and to compare postoperative clinical outcomes according to treatment in Vancouver type B2 and B3 fractures. Methods. A total of 126 Vancouver type B fractures were analyzed from 2010 to 2019 in 11 associated centres' database (named TRON). We divided the patients into two Vancouver type B subtypes according to implant stability. Patient demographics and functional scores were assessed in the Vancouver type B subtypes. We estimated the mortality according to various patient characteristics and clinical outcomes between the open reduction internal fixation (ORIF) and revision arthroplasty (revision) groups in patients with unstable subtype. Results. The one-year mortality rate of the stable and unstable subtype of Vancouver type B was 9.4% and 16.4%. Patient demographic factors, including residential status and pre-injury mobility were associated with mortality. There was no significant difference in mortality between patients treated with ORIF and Revision in either Vancouver B subtype. Patients treated with revision had significantly higher Parker Mobility Score (PMS) values (5.48 vs 3.43; p = 0.00461) and a significantly lower visual analogue scale (VAS) values (1.06 vs 1.94; p = 0.0399) for pain than ORIF in the unstable subtype. Conclusion. Among patients with Vancouver type B fractures, frail patients, such as those with worse scores for residential status and pre-injury mobility, had a high mortality rate. There was no significant difference in mortality between patients treated with ORIF and those treated with revision. However, in the unstable subtype, the PMS and VAS values at the final follow-up examination were significantly better in patients who received revision. Based on postoperative activities of daily life, we therefore recommend evision in instances when either treatment option is feasible. Cite this article: Bone Jt Open 2023;4(1):38–46

Aims. We assessed the long-term outcomes of a large cohort of patients who have undergone a periacetabular osteotomy (PAO), and sought to validate a patient satisfaction questionnaire for use in a PAO cohort. Methods. All patients who had undergone a PAO from July 1998 to February 2013 were surveyed, with several patient-reported outcome measures (PROMs) and radiological measurements of preoperative acetabular dysplasia and postoperative correction also recorded. Patients were asked to rate their level of satisfaction with their operation in achieving pain relief, restoration of activities of daily living, ability to perform recreational activity, and their overall level of satisfaction with the procedure. Results. A total of 143 PAOs were performed between 1998 and 2013. Of those, 90 postoperative surveys were returned. Only 65 patients (73 hips) had both pre- and postoperative radiographs available for measurement. The mean time to follow-up was 15 years (6.5 to 20). Most patients were female (91%), with a mean age of 26.4 years (14.9 to 48.3) at the time of their surgery. A statistically significant improvement in radiological correction was detected in all hips (p < 0.001). A total of 67 patients (92.3%) remained either very satisfied or satisfied with their PAO. The internal consistency of the patient satisfaction questionnaire, measured using Cronbach’s α, ranged from 0.89 to 0.94 indicating ‘good’ to ‘excellent’ reliability. Conclusion. Outcomes of importance to patients undergoing a PAO include several key domains: pain relief, improve activities of daily living, and improve recreational ability. Our study demonstrates high rates of long-term patient satisfaction in all domains, and found the patient satisfaction questionnaire to be a valid and reliable instrument for use in this cohort. Cite this article: Bone Jt Open 2023;4(12):964–969

Aims. Post-traumatic periprosthetic acetabular fractures are rare but serious. Few studies carried out on small cohorts have reported them in the literature. The aim of this work is to describe the specific characteristics of post-traumatic periprosthetic acetabular fractures, and the outcome of their surgical treatment in terms of function and complications. Methods. Patients with this type of fracture were identified retrospectively over a period of six years (January 2016 to December 2021). The following data were collected: demographic characteristics, date of insertion of the prosthesis, details of the intervention, date of the trauma, characteristics of the fracture, and type of treatment. Functional results were assessed with the Harris Hip Score (HHS). Data concerning complications of treatment were collected. Results. Our series included 20 patients, with a mean age of 77 years (46 to 90). All the patients had at least one comorbid condition. Radiographs showed that 75% of the fractures were pure transverse fractures, and a transverse component was present in 90% of patients. All our patients underwent surgical treatment: open reduction and internal fixation, revision of the acetabular component, or both. Mean follow-up was 24 months, and HHS at last follow-up was 75.5 (42 to 95). The principal complications observed were dislocations of the prosthesis (30%) and infections (20%). A need for revision surgery was noted in 30% of patients. No dislocation occurred in patients undergoing osteosynthesis with acetabular reconstruction. We did not note either mechanical loosening of the acetabular component nor thromboembolic complications. In all, 30% of patients presented acute anemia requiring transfusion, and one death was reported. Conclusion. Post-traumatic periprosthetic acetabular fractures frequently have a transverse component that can destabilize the acetabular implant. The frequency of complications, principally dislocations, led to a high rate of revision surgery. Improvements in preoperative planning should make it possible to codify management to reduce this high rate of complications. The best results were obtained when the surgical strategy combined osteosynthesis with acetabular reconstruction. Cite this article: Bone Jt Open 2024;5(1):28–36

Aims. The aim of this study was to determine both the incidence of, and the reoperation rate for, postoperative periprosthetic femoral fracture (POPFF) after total hip arthroplasty (THA) with either a collared cementless (CC) femoral component or a cemented polished taper-slip (PTS) femoral component. Methods. We performed a retrospective review of a consecutive series of 11,018 THAs over a ten-year period. All POPFFs were identified using regional radiograph archiving and electronic care systems. Results. A total of 11,018 THAs were implanted: 4,952 CC femoral components and 6,066 cemented PTS femoral components. Between groups, age, sex, and BMI did not differ. Overall, 91 patients (0.8%) sustained a POPFF. For all patients with a POPFF, 16.5% (15/91) were managed conservatively, 67.0% (61/91) underwent open reduction and internal fixation (ORIF), and 16.5% (15/91) underwent revision. The CC group had a lower POPFF rate compared to the PTS group (0.7% (36/4,952) vs 0.9% (55/6,066); p = 0.345). Fewer POPFFs in the CC group required surgery (0.4% (22/4,952) vs 0.9% (54/6,066); p = 0.005). Fewer POPFFs required surgery in males with a CC than males with a PTS (0.3% (7/2,121) vs 1.3% (36/2,674); p < 0.001). Conclusion. Male patients with a PTS femoral component were five times more likely to have a reoperation for POPFF. Female patients had the same incidence of reoperation with either component type. Of those having a reoperation, 80.3% (61/76) had an ORIF, which could greatly mask the size of this problem in many registries. Cite this article: Bone Joint J 2024;106-B(2):144–150

Aims. In computer simulations, the shape of the range of motion (ROM) of a stem with a cylindrical neck design will be a perfect cone. However, many modern stems have rectangular/oval-shaped necks. We hypothesized that the rectangular/oval stem neck will affect the shape of the ROM and the prosthetic impingement. Methods. Total hip arthroplasty (THA) motion while standing and sitting was simulated using a MATLAB model (one stem with a cylindrical neck and one stem with a rectangular neck). The primary predictor was the geometry of the neck (cylindrical vs rectangular) and the main outcome was the shape of ROM based on the prosthetic impingement between the neck and the liner. The secondary outcome was the difference in the ROM provided by each neck geometry and the effect of the pelvic tilt on this ROM. Multiple regression was used to analyze the data. Results. The stem with a rectangular neck has increased internal and external rotation with a quatrefoil cross-section compared to a cone in a cylindrical neck. Modification of the cup orientation and pelvic tilt affected the direction of projection of the cone or quatrefoil shape. The mean increase in internal rotation with a rectangular neck was 3.4° (0° to 7.9°; p < 0.001); for external rotation, it was 2.8° (0.5° to 7.8°; p < 0.001). Conclusion. Our study shows the importance of attention to femoral implant design for the assessment of prosthetic impingement. Any universal mathematical model or computer simulation that ignores each stem’s unique neck geometry will provide inaccurate predictions of prosthetic impingement. Cite this article: Bone Joint Res 2021;10(12):780–789

Aims. The aim of this study was to compare open reduction and internal fixation (ORIF) with revision surgery for the surgical management of Unified Classification System (UCS) type B periprosthetic femoral fractures around cemented polished taper-slip femoral components following primary total hip arthroplasty (THA). Methods. Data were collected for patients admitted to five UK centres. The primary outcome measure was the two-year reoperation rate. Secondary outcomes were time to surgery, transfusion requirements, critical care requirements, length of stay, two-year local complication rates, six-month systemic complication rates, and mortality rates. Comparisons were made by the form of treatment (ORIF vs revision) and UCS type (B1 vs B2/B3). Kaplan-Meier survival analysis was performed with two-year reoperation for any reason as the endpoint. Results. A total of 317 periprosthetic fractures (in 317 patients) with a median follow-up of 3.6 years (interquartile range (IQR) 2.0 to 5.4) were included. The fractures were type B1 in 133 (42.0%), B2 in 170 (53.6%), and B3 in 14 patients (4.4%). ORIF was performed in 167 (52.7%) and revision in 150 patients (47.3%). The two-year reoperation rate (15.3% vs 7.2%; p = 0.021), time to surgery (4.0 days (IQR 2.0 to 7.0) vs 2.0 days (IQR 1.0 to 4.0); p < 0.001), transfusion requirements (55 patients (36.7%) vs 42 patients (25.1%); p = 0.026), critical care requirements (36 patients (24.0%) vs seven patients (4.2%); p < 0.001) and two-year local complication rates (26.7% vs 9.0%; p < 0.001) were significantly higher in the revision group. The two-year rate of survival was significantly higher for ORIF (91.9% (standard error (SE) 0.023%) vs 83.9% (SE 0.031%); p = 0.032) compared with revision. For B1 fractures, the two-year reoperation rate was significantly higher for revision compared with ORIF (29.4% vs 6.0%; p = 0.002) but this was similar for B2 and B3 fractures (9.8% vs 13.5%; p = 0.341). The most common indication for reoperation after revision was dislocation (12 patients; 8.0%). Conclusion. Revision surgery has higher reoperation rates, longer surgical waiting times, higher transfusion requirements, and higher critical care requirements than ORIF in the management of periprosthetic fractures around polished taper-slip femoral components after THA. ORIF is a safe option providing anatomical reconstruction is achievable. Cite this article: Bone Joint J 2023;105-B(2):124–134

Aims. Cam and pincer morphologies are potential precursors to hip osteoarthritis and important contributors to non-arthritic hip pain. However, only some hips with these pathomorphologies develop symptoms and joint degeneration, and it is not clear why. Anterior impingement between the femoral head-neck contour and acetabular rim in positions of hip flexion combined with rotation is a proposed pathomechanism in these hips, but this has not been studied in active postures. Our aim was to assess the anterior impingement pathomechanism in both active and passive postures with high hip flexion that are thought to provoke impingement. Methods. We recruited nine participants with cam and/or pincer morphologies and with pain, 13 participants with cam and/or pincer morphologies and without pain, and 11 controls from a population-based cohort. We scanned hips in active squatting and passive sitting flexion, adduction, and internal rotation using open MRI and quantified anterior femoroacetabular clearance using the β angle. Results. In squatting, we found significantly decreased anterior femoroacetabular clearance in painful hips with cam and/or pincer morphologies (mean -11.3° (SD 19.2°)) compared to pain-free hips with cam and/or pincer morphologies (mean 8.5° (SD 14.6°); p = 0.022) and controls (mean 18.6° (SD 8.5°); p < 0.001). In sitting flexion, adduction, and internal rotation, we found significantly decreased anterior clearance in both painful (mean -15.2° (SD 15.3°); p = 0.002) and painfree hips (mean -4.7° (SD 13°); p = 0.010) with cam and/pincer morphologies compared to the controls (mean 7.1° (SD 5.9°)). Conclusion. Our results support the anterior femoroacetabular impingement pathomechanism in hips with cam and/or pincer morphologies and highlight the effect of posture on this pathomechanism. Cite this article: Bone Jt Open 2021;2(11):988–996

Aims. Computer-assisted 3D preoperative planning software has the potential to improve postoperative stability in total hip arthroplasty (THA). Commonly, preoperative protocols simulate two functional positions (standing and relaxed sitting) but do not consider other common positions that may increase postoperative impingement and possible dislocation. This study investigates the feasibility of simulating commonly encountered positions, and positions with an increased risk of impingement, to lower postoperative impingement risk in a CT-based 3D model. Methods. A robotic arm-assisted arthroplasty planning platform was used to investigate 11 patient positions. Data from 43 primary THAs were used for simulation. Sacral slope was retrieved from patient preoperative imaging, while angles of hip flexion/extension, hip external/internal rotation, and hip abduction/adduction for tested positions were derived from literature or estimated with a biomechanical model. The hip was placed in the described positions, and if impingement was detected by the software, inspection of the impingement type was performed. Results. In flexion, an overall impingement rate of 2.3% was detected for flexed-seated, squatting, forward-bending, and criss-cross-sitting positions, and 4.7% for the ankle-over-knee position. In extension, most hips (60.5%) were found to impinge at or prior to 50° of external rotation (pivoting). Many of these impingement events were due to a prominent ischium. The mean maximum external rotation prior to impingement was 45.9° (15° to 80°) and 57.9° (20° to 90°) prior to prosthetic impingement. No impingement was found in standing, sitting, crossing ankles, seiza, and downward dog. Conclusion. This study demonstrated that positions of daily living tested in a CT-based 3D model show high rates of impingement. Simulating additional positions through 3D modelling is a low-cost method of potentially improving outcomes without compromising patient safety. By incorporating CT-based 3D modelling of positions of daily living into routine preoperative protocols for THA, there is the potential to lower the risk of postoperative impingement events. Cite this article: Bone Jt Open 2023;4(6):416–423

Aims. In the native hip, the hip capsular ligaments tighten at the limits of range of hip motion and may provide a passive stabilizing force to protect the hip against edge loading. In this study we quantified the stabilizing force vectors generated by capsular ligaments at extreme range of motion (ROM), and examined their ability to prevent edge loading. Methods. Torque-rotation curves were obtained from nine cadaveric hips to define the rotational restraint contributions of the capsular ligaments in 36 positions. A ligament model was developed to determine the line-of-action and effective moment arms of the medial/lateral iliofemoral, ischiofemoral, and pubofemoral ligaments in all positions. The functioning ligament forces and stiffness were determined at 5 Nm rotational restraint. In each position, the contribution of engaged capsular ligaments to the joint reaction force was used to evaluate the net force vector generated by the capsule. Results. The medial and lateral arms of the iliofemoral ligament generated the highest inbound force vector in positions combining extension and adduction providing anterior stability. The ischiofemoral ligament generated the highest inbound force in flexion with adduction and internal rotation (FADIR), reducing the risk of posterior dislocation. In this position the hip joint reaction force moved 0.8° inbound per Nm of internal capsular restraint, preventing edge loading. Conclusion. The capsular ligaments contribute to keep the joint force vector inbound from the edge of the acetabulum at extreme ROM. Preservation and appropriate tensioning of these structures following any type of hip surgery may be crucial to minimizing complications related to joint instability. Cite this article: Bone Joint Res 2021;10(9):594–601