Introduction. The correct anteversion of the acetabular cup is critical to achieve optimal outcome after total hip arthroplasty. While number of method has been described to measure the anteversion in plane anteroposterior and lateral radiograph, it is still controversial which method provides best anteversion measurement. While many of the previous studies used CT scan to validate the anteversion measured in plane anteroposterior radiograph, this may cause potential bias as the anteversion measured in CT scan reflects true anteversion while the anteversion measurement methods in plane radiograph are design to measure the planar anteversion. Thus, in the current study, we tried to find the optimal anteversion measurement method free from the previously described bias. Material and method. Custom made cup model was developed which enables change in anteversion and inclination. Simple radiograph was taken with the cup in 10° to 70° degree of inclination at 10° increments and for each inclination angle, anteversion was corrected from 0° to 30° at 5° increments. The radiograph was taken with the beam directed at the center of the cup (mimicking hip centered anteroposterior radiograph) and at 9cm medial to the cup (mimicking pelvis anteroposterior radiograph). The measurements were done by two orthopaedic surgeons using methods described by 1) Pradhan et al, 2) Lewinak et al, 3) Widmer et al, and 4) Liaw et al. For each measurements, the anteversion were compared with the actual anteversion. Result. Interoverver correlation (kappa value) were high in all measurements ranging 0.988 to 0.998. Regardless of how the radiograph was taken, Pradhan method was the most accurate measurement method showing difference of 2.17° ± 1.69° and −2.5° ± 1.93° compare to the actual anteversion respectively for hip centered radiograph and pelvis anteroposterior radiograph. The Widmer method showed the least accuracy (pelvis AP : −6.75° ± 4.62°, hip centered AP : −14.84° ± 4.36°). However, when the anteversion were measured in the safe zone with the inclination in 30° to 50° Liaw's method in hip centered radiograph showed the highest accuracy (1.63° ± 1.4°). Conclusion. The study indicates that the Pradhan's method may provide the most accurate anteversion measurement. However, with the hip in 30° to 50° inclination, Liaw's method measured from hip centred radiograph will provide most accurate anteversion measurement

In 100 patients the fulcrum axis which is the line connecting the anterior tip of the coracoid and the posterolateral angle of the acromion, was used to position true anteroposterior radiographs of the shoulder. This method was then compared with the conventional radiological technique in a further 100 patients. Three orthopaedic surgeons counted the number of images without overlap between the humeral head and glenoid and calculated the amount of the glenoid surface visible in each radiograph. The analysis was repeated for intraobserver reliability. The learning curves of both techniques were studied. The amount of free visible glenoid space was significantly higher using the fulcrum-axis method (64 vs 31) and the comparable glenoid size increased significantly (8.56 vs 6.47). Thus the accuracy of the anteroposterior radiographs of the shoulder is impaired by using this technique. The intra and interobserver reliability showed a high consistency. No learning curve was observed for either technique

In total hip replacement, orientation of the cup is critical to the stability of the prosthesis. A new method to determine the angle of planar anteversion is described. A simple mathematical formula uses the measurements taken from anteroposterior radiographs to calculate the planar anteversion without reference to tables or charts. An experimental study in vitro has shown the efficacy of the formula in giving results which are within a clinically acceptable range

Aim: To evaluate the radiographs of proximal humeral fractures in an attempt to define a diagnostic sign as a predictor of four-part fracture. Diagnostic sign: The normal humeral head articular surface points towards the glenoid. We describe our ‘sunset’ sign as ‘articular surface of humeral head pointing away from the glenoid and tilted upwards, in the presence of a displaced greater tuberosity fracture’. We postulate that a patient with proximal humerus fracture showing this sign has four-part fracture until proved otherwise. Materials and Methods: Between 2002 and 2006, 80 consecutive patients underwent open reduction and internal fixation of their proximal humeral fractures in our Shoulder unit. We reviewed their preoperative radiographs and operative notes retrospectively. 79 patients were included in the study as one patient’s pre-operative radiograph was not available. The AP radiograph was evaluated independently by three observers who were blinded to the identity of the patients and their operative diagnosis. The presence of ‘sunset’ sign was recorded. There was 90% inter-observer agreement. In the remaining 10%, a consensus review was performed as to the presence of sign for evaluation purpose. The findings were then correlated with the operative findings to confirm whether they were four-part fractures or not. With 95% confidence interval we calculated the sensitivity, specificity, and positive and negative predictive values for our diagnostic sign. Results: 30 out of 79 patients displayed ‘sunset’sign in their preoperative radiograph. Of these 28 had confirmed four-part fractures operatively. The positive predictive value of ‘sunset’ sign in diagnosis the four-part fracture was 93%. The specificity and sensitivity were 95% and 78% respectively. The sensitivity was affected by 8 patients with four part fractures with displaced articular head fragment which had dropped either medially or posteriorly. Conclusion: Our results suggest that in patients with proximal humeral fractures, the presence of ‘sunset’sign in the anteroposterior radiograph is a reliable indicator of four-part fracture

Destruction of the articular cartilage is the first change seen on gross examination of the knee in osteoarthritis. Weight-bearing radiographs are conventionally taken with the knee in full extension. Biomechanical studies have shown, however, that the major contact stresses in the femorotibial articulation occur when the knee is flexed about 28 degrees. Arthroscopy has confirmed that cartilage loss occurs in a more posterior portion of the femoral condyles than is revealed by radiographs taken in full extension. The 'standing tunnel view' is a weight-bearing postero-anterior radiograph taken with the knee in 30 degrees of flexion. The radiographs of 64 patients have been used to compare the conventional with the standing tunnel view. In 10 knees in which the conventional view suggested normal cartilage the standing tunnel view revealed severe degeneration.

Introduction

When performing a total hip arthroplasty (THA), some surgeons routinely perform an intraoperative anteroposterior (AP) pelvis radiograph to assess components. The purpose of this study was to evaluate the reliability of the intraoperative radiograph to accurately reflect acetabular inclination, leg length, and femoral offset as compared to the immediate postoperative supine AP radiograph.

BACKGROUND:. Although most radiographs used for polyethylene wear measurements have been taken with the patient in the supine position in order to assess penetration by the femoral head into the acetabular polyethylene socket, we have questioned the effect of weight-bearing on the position of the head within the socket. The current study aimed to determine the effect of weight bearing, i.e. standing on the two-dimensional radiographic position of the femoral head within the socket. PATIENTS AND METHODS:. A total of three hundred and fifty patients (three hundred and eighty three hips) who had had a total hip arthroplasty had digital radiographs made a set of anteroposterior radiographs for each patient: one radiograph was made with the patient supine and one was made with the patient standing in full weight bearing on the replaced hip. The patients were divided into the following two groups: 1) seventy-five patients (eighty-three hips) with conventional polyethylene (CON) (group-1); 2) two hundred and seventy-five patients (three hundred hips) with highly cross-linked polyethylene (XPL) (group-2). The set of radiograph was taken at three weeks postoperatively and at the time of semiannual follow-up. The average ceramic femoral head penetration was measured with radiographs taken in the standing or supine position at the final follow-up and compared with those of three weeks postoperatively. A single researcher with use of a computerized measurement system performed all measurements on the radiographs of the two-dimensional position of the head. Follow-up period were 13.5 ± 1.0 (range. 11.0–15.5) years in group-1 and 7.6 ± 2.1 (range. 5.0–12.6) years in group-2. RESULTS:. Linear penetration rates in group-1 were 0.172 ± 0.069 mm/year in supine position and 0.178 ± 0.069 mm/year in standing position (p < 0.05, paired t-test; r. 2. = 0.88), and the rates in group-2 were 0.029 ± 0.024 mm/year and 0.035 ± 0.027 mm/year respectively (p < 0.0005, paired t-test; r. 2. = 0.16). The mean ceramic head penetration rate in XPL socket showed 80 to 83% reduction compared with those in CON. CONCLUSIONS:. We found significant difference between the average total ceramic femoral head penetration between supine and standing radiographs in using both CON and XPL socket. Standing radiographs were useful and recommended for polyethylene socket wear measurements. Figure legend. Fig. Wear measurement: With use of a computerized measurement system, the thickness of the polyethylene socket (a) was measured along a line connecting the center of the ceramic femoral head to the outer border of the socket at its shortest distance. The wear rate was determined by comparing the thickness in the latest follow up radiograph with the thickness in the initial postoperative radiograph at the same location. Each radiographically measured value was corrected for magnification by a factor derived from comparing the diameter of the ceramic head on the radiograph (b) with its known diameter of 22.225 mm

This study aimed to assess the effect of flexion and external rotation on measurement of femoral offset (FO), greater trochanter to femoral head centre (GT-FHC) distance, and neck shaft angle (NSA). Three-dimensional femoral shapes (n=100) were generated by statistical shape modelling from 47 CT-segmented right femora. Combined rotations in the range of 0–50° external and 0–50° flexion (in 10° increments) were applied to each femur after they were neutralised (defined as neck and proximal shaft axis parallel with detector plane). Each shape was projected to create 2D images representing radiographs of the proximal femora.

As already known, external rotation resulted in a significant error in measuring FO but flexion alone had no impact. Individually, neither flexion nor external rotation had any impact on GT-FHC but, for example, 30° of flexion combined with 50°of external rotation resulted in an 18.6mm change in height. NSA averaged 125° in neutral with external rotation resulting in a moderate increase and flexion on its own a moderate decrease. However, 50° degrees of both produced an almost 30 degree increase in NSA.

In conclusion, although the relationship between external rotation and FO is appreciated, the impact of flexion with external rotation is not. This combination results in apparent reduced FO, a high femoral head centre and an increased NSA. Femoral components with NSAs of 130° or 135° may historically have been based on X-ray misinterpretation. This work demonstrates that 2D to 3D reconstruction of the proximal femur in pre-op planning is a challenge.

Femoral stem version has a major influence on impingement and early post-operative stability after total hip arthroplasty (THA).

The main objective of this study was to evaluate the validity of a novel radiological method for measuring stem version. Anteroposterior (AP) radiographs and three-dimensional CT scans were obtained for 115 patients (female/male 63/72, mean age 62.5 years (50 to 75)) who had undergone minimally invasive, cementless THA. Stem version was calculated from the AP hip radiograph by rotation-based change in the projected prosthetic neck–shaft (NSA*) angle using the mathematical formula ST = arcos [tan (NSA*) / tan (135)]. We used two independent observers who repeated the analysis after a six-week interval. Radiological measurements were compared with 3D-CT measurements by an independent, blinded external institute.

We found a mean difference of 1.2° (sd 6.2) between radiological and 3D-CT measurements of stem version. The correlation between the mean radiological and 3D-CT stem torsion was r = 0.88 (p < 0.001). The intra- (intraclass correlation coefficient ≥ 0.94) and inter-observer agreement (mean concordance correlation coefficient = 0.87) for the radiological measurements were excellent.

We found that femoral tilt was associated with the mean radiological measurement error (r = 0.22, p = 0.02).

The projected neck–shaft angle is a reliable method for measuring stem version on AP radiographs of the hip after a THA. However, a highly standardised radiological technique is required for its precise measurement.

Cite this article: Bone Joint J 2015; 97-B:306–11.

The Unified Classification System (UCS), or Vancouver system, is a validated and widely used classification system to guide the management of periprosthetic femoral fractures. It suggests that well-fixed stems (type B1) can be treated with fixation but that loose stems (types B2 and B3) should be revised. Determining whether a stem is loose can be difficult and some authors have questioned how to apply this classification system to polished taper slip stems which are, by definition, loose within their cement mantle. Recent evidence has challenged the common perception that revision surgery is preferable to fixation surgery for UCS-B periprosthetic fractures around cemented polished taper slip stems. Indications for fixation include an anatomically reducible fracture and cement mantle, a well-fixed femoral bone-cement interface, and a well-functioning acetabular component. However, not all type B fractures can or should be managed with fixation due to the risk of early failure. This annotation details specific fracture patterns that should not be managed with fixation alone.

Cite this article: Bone Joint J 2023;105-B(5):481–486.

Aims. To evaluate whether low-intensity pulsed ultrasound (LIPUS) accelerates bone healing at osteotomy sites and promotes functional recovery after open-wedge high tibial osteotomy (OWHTO). Methods. Overall, 90 patients who underwent OWHTO without bone grafting were enrolled in this nonrandomized retrospective study, and 45 patients treated with LIPUS were compared with 45 patients without LIPUS treatment in terms of bone healing and functional recovery postoperatively. Clinical evaluations, including the pain visual analogue scale (VAS) and Japanese Orthopaedic Association (JOA) score, were performed preoperatively as well as six weeks and three, six, and 12 months postoperatively. The progression rate of gap filling was evaluated using anteroposterior radiographs at six weeks and three, six, and 12 months postoperatively. Results. The pain VAS and JOA scores significantly improved after OWHTO in both groups. Although the LIPUS group had better pain scores at six weeks and three months postoperatively, there were no significant differences in JOA score between the groups. The lateral hinge united at six weeks postoperatively in 34 (75.6%) knees in the control group and in 33 (73.3%) knees in the LIPUS group. The progression rates of gap filling in the LIPUS group were 8.0%, 15.0%, 27.2%, and 46.0% at six weeks and three, six, and 12 months postoperatively, respectively, whereas in the control group at the same time points they were 7.7%, 15.2%, 26.3%, and 44.0%, respectively. There were no significant differences in the progression rate of gap filling between the groups. Conclusion. The present study demonstrated that LIPUS did not promote bone healing and functional recovery after OWHTO with a locking plate. The routine use of LIPUS after OWHTO was not recommended from the results of our study. Cite this article: Bone Jt Open 2022;3(11):885–893

The current standard of practice following knee arthroplasty is to demonstrate the appropriate alignment of knee replacements using knee radiographs. Recent studies have suggested that standard knee radiographs provide adequate accuracy for tibial prosthesis alignment assessment as compared with long knee view radiographs which are more technically demanding and carry greater radiation exposure. In this study, we aim to address whether alignment measured on standard knee radiographs are reliable and reproducible over time. We examined a cohort of 80 patients 37 male (46%), 43 females (54%), mean age = 68 years) who underwent total knee arthroplasty (TKA). Standard knee anteroposterior radiographs performed within 2 days following surgery were compared to standard knee anteroposterior radiographs taken 1 year following the surgery in patients with well-functioning prosthesis. Tibial prosthesis alignment angles between the longitude of the tibial shaft and the tibial baseplate were calculated using Centricity Enterprise Web V3.0 software. The data was examined using R software. In well-functioning primary knee arthroplasties, tibial prosthesis alignment angles measured in the 1-year follow-up standard view knee radiographs were found to deviate from measurements obtained with the same radiographic specifications in the immediate post-operative period. A significant mean percentage difference was found between the two radiographs. Long knee view radiographs may be required in order to accurately assess tibial prothesis alignment following total knee arthroplasty

Aims. Temporary hemiepiphysiodesis (HED) is applied to children and adolescents to correct angular deformities (ADs) in long bones through guided growth. Traditional Blount staples or two-hole plates are mainly used for this indication. Despite precise surgical techniques and attentive postoperative follow-up, implant-associated complications are frequently described. To address these pitfalls, a flexible staple was developed to combine the advantages of the established implants. This study provides the first results of guided growth using the new implant and compares these with the established two-hole plates and Blount staples. Methods. Between January 2013 and December 2016, 138 patients (22 children, 116 adolescents) with genu valgum or genu varum were treated with 285 flexible staples. The minimum follow-up was 24 months. These results were compared with 98 patients treated with 205 two-hole plates and 92 patients treated with 535 Blount staples. In long-standing anteroposterior radiographs, mechanical axis deviations (MADs) were measured before and during treatment to analyze treatment efficiency. The evaluation of the new flexible staple was performed according to the idea, development, evaluation, assessment, long-term (IDEAL) study framework (Stage 2a). Results. Overall, 79% (109/138) of patients treated with flexible staples achieved sufficient deformity correction. The median treatment duration was 16 months (interquartile range (IQR) 8 to 21). The flexible staples achieved a median MAD correction of 1.2 mm/month/HED site (IQR 0.6 to 2.0) in valgus deformities and 0.6 mm/month/HED site (IQR 0.2 to 1.5) in varus deformities. Wound infections occurred in 1%, haematomas and joint effusions in 4%, and implant-associated complications in 1% of patients treated with flexible staples. Valgus AD were corrected faster using flexible staples than two-hole plates and Blount staples. Furthermore, the median MAD after treatment was lower in varus and valgus AD, fewer implant-associated complications were detected, and reduced implantation times were recorded using flexible staples. Conclusion. The flexible staple seems to be a viable option for guided growth, showing comparable or possibly better results regarding correction speed and reducing implant-associated complications. Further comparative studies are required to substantiate these findings. Cite this article: Bone Joint J 2023;105-B(3):331–340

Radiological investigations are essential in the work-up of patients presenting with non-arthritic hip pain, to allow close review of the complex anatomy around the hip and proximal femur. The aim of this study is to quantify the radiation exposure associated with common radiological investigations performed in assessing young adult patients presenting with non-arthritic hip pain. A retrospective review of our UK tertiary hip preservation centre institutional imaging database was performed. Data was obtained for antero-posterior, cross-table lateral and frog-lateral radiographs, along with data for the low dose CT hip protocol and the Mako CT Hip protocol. The radiation dose of each imaging technique was measured in terms of dose-area product (DAP) with units of mGycm2, and the effective doses (ED, mSv) calculated. The mean effective radiation dose for hip radiographs was in the range 0.03 to 0.83mSv (mean DLP 126.7–156.2 mGycm2). The mean effective dose associated with the low-dose CT hip protocol was 3.04mSv (416.8 mGycm2) and for the Stryker Mako CT Hip protocol was 8.4mSv (1061 mGycm2). The radiation dose associated with use of CT imaging was significantly greater than plain radiographs (p<0.005). Investigation of non-arthritic hip pain can lead to significant ionising radiation exposure for patients. In our institution, the routine protocol is to obtain an anteroposterior radiograph and then a specific hip sequence 3 Tesla MRI including anteversion views. This provides the necessary information in the majority of cases, with CT scanning reserved for more complex cases where we feel there is a specific indication. We would encourage the hip preservation community to carefully consider and review the use of ionising radiation investigations

Aims. Limited implant survival due to aseptic cup loosening is most commonly responsible for revision total hip arthroplasty (THA). Advances in implant designs and materials have been crucial in addressing those challenges. Vitamin E-infused highly cross-linked polyethylene (VEPE) promises strong wear resistance, high oxidative stability, and superior mechanical strength. Although VEPE monoblock cups have shown good mid-term performance and excellent wear patterns, long-term results remain unclear. This study evaluated migration and wear patterns and clinical and radiological outcomes at a minimum of ten years’ follow-up. Methods. This prospective observational study investigated 101 cases of primary THA over a mean duration of 129 months (120 to 149). At last follow-up, 57 cases with complete clinical and radiological outcomes were evaluated. In all cases, the acetabular component comprised an uncemented titanium particle-coated VEPE monoblock cup. Patients were assessed clinically and radiologically using the Harris Hip Score, visual analogue scale (pain and satisfaction), and an anteroposterior radiograph. Cup migration and polyethylene wear were measured using Einzel-Bild-Röntgen-Analyze software. All complications and associated treatments were documented until final follow-up. Results. Clinical assessment showed persistent major improvement in all scores. On radiological assessment, only one case showed a lucent line (without symptoms). At last follow-up, wear and migration were below the critical thresholds. No cup-related revisions were needed, indicating an outstanding survival rate of 100%. Conclusion. Isoelastic VEPE cups offer high success rates and may prevent osteolysis, aseptic loosening, and the need for revision surgeries in the long term. However, longer follow-up is needed to validate our findings and confirm the advantages offered by this cup. Cite this article: Bone Jt Open 2024;5(10):825–831

The primary treatment goal for patients with femoroacetabular impingement syndrome, a common hip condition in athletes, is to improve pain and function. In selected patients, in the short term following intervention, arthroscopic hip surgery is superior to a pragmatic NHS- type physiotherapy programme. Here, we report the three-year follow-up results from the FemoroAcetabular Impingement Trial (FAIT), comparing arthroscopic hip surgery with physiotherapy in the management of patients with femoroacetabular impingement (FAI) syndrome. Two-group parallel, assessor-blinded, pragmatic randomised controlled study across seven NHS England sites. 222 participants aged 18 to 60 years with FAI syndrome confirmed clinically and radiologically were randomised (1:1) to receive arthroscopic hip surgery (n = 112) or physiotherapy and activity modification (n = 110). We previously reported on the hip outcome score at eight months. The primary outcome measure of this study was minimum Joint Space Width (mJSW) on Anteroposterior Radiograph at 38 months post randomisation. Secondary outcome measures included the Hip Outcome Score and Scoring Hip Osteoarthritis with MRI (SHOMRI) score. Minimum Joint Space Width data were available for 101 participants (45%) at 38 months post randomisation. Hip outcome score and MRI data were available for 77% and 62% of participants respectively. mJSW was higher in the arthroscopy group (mean (SD) 3.34mm (1.01)) compared to the physiotherapy group (2.99mm (1.33)) at 38 months, p=0.017, however this did not exceed the minimally clinically important difference of 0.48mm. SHOMRI score was significantly lower in the arthroscopy group (mean (SD) 9.22 (11.43)) compared to the physiotherapy group (22.76 (15.26)), p-value <0.001. Hip outcome score was higher in the arthroscopy group (mean (SD) 84.2 (17.4)) compared with the physiotherapy group (74.2 (21.9)), p-value < 0.001). Patients with FAI syndrome treated surgically may experience slowing of osteoarthritisprogression and superior pain and function compared with patients treated non- operatively

Aims. The aim of this study is to evaluate whether acetabular retroversion (AR) represents a structural anatomical abnormality of the pelvis or is a functional phenomenon of pelvic positioning in the sagittal plane, and to what extent the changes that result from patient-specific functional position affect the extent of AR. Methods. A comparative radiological study of 19 patients (38 hips) with AR were compared with a control group of 30 asymptomatic patients (60 hips). CT scans were corrected for rotation in the axial and coronal planes, and the sagittal plane was then aligned to the anterior pelvic plane. External rotation of the hemipelvis was assessed using the superior iliac wing and inferior iliac wing angles as well as quadrilateral plate angles, and correlated with cranial and central acetabular version. Sagittal anatomical parameters were also measured and correlated to version measurements. In 12 AR patients (24 hips), the axial measurements were repeated after matching sagittal pelvic rotation with standing and supine anteroposterior radiographs. Results. Acetabular version was significantly lower and measurements of external rotation of the hemipelvis were significantly increased in the AR group compared to the control group. The AR group also had increased evidence of anterior projection of the iliac wing in the sagittal plane. The acetabular orientation angles were more retroverted in the supine compared to standing position, and the change in acetabular version correlated with the change in sagittal pelvic tilt. An anterior pelvic tilt of 1° correlated with 1.02° of increased cranial retroversion and 0.76° of increased central retroversion. Conclusion. This study has demonstrated that patients with symptomatic AR have both an externally rotated hemipelvis and increased anterior projection of the iliac wing compared to a control group of asymptomatic patients. Functional sagittal pelvic positioning was also found to affect AR in symptomatic patients: the acetabulum was more retroverted in the supine position compared to standing position. Changes in acetabular version correlate with the change in sagittal pelvic tilt. These findings should be taken into account by surgeons when planning acetabular correction for AR with periacetabular osteotomy. Cite this article: Bone Joint J 2024;106-B(2):128–135

Aims. Conflicting clinical results are reported for the ATTUNE Total Knee Arthroplasty (TKA). This randomized controlled trial (RCT) evaluated five-year follow-up results comparing cemented ATTUNE and PFC-Sigma cruciate retaining TKAs, analyzing component migration as measured by radiostereometric analysis (RSA), clinical outcomes, patient-reported outcome measures (PROMs), and radiological outcomes. Methods. A total of 74 primary TKAs were included in this single-blind RCT. RSA examinations were performed, and PROMs and clinical outcomes were collected immediate postoperatively, and at three, six, 12, 24, and 60 months’ follow-up. Radiolucent lines (RLLs) were measured in standard anteroposterior radiographs at six weeks, and 12 and 60 months postoperatively. Results. At five-year follow-up, RSA data from 61 patients were available and the mean maximum total point motion (MTPM) of the femoral components were: ATTUNE: 0.96 mm (95% confidence interval (CI) 0.79 to 1.14) and PFC-Sigma 1.37 mm (95% CI 1.18 to 1.59) (p < 0.001). The PFC-Sigma femoral component migrated more in the first postoperative year, but stabilized thereafter. MPTM of the tibial components were comparable at five-year follow-up: ATTUNE 1.12 mm (95% CI 0.95 to 1.31) and PFC-Sigma 1.25 mm (95% CI 1.07 to 1.44) (p = 0.438). RLL at the medial tibial implant-cement interface remained more prevalent for the ATTUNE at five-year follow-up compared to the PFC-Sigma (20% vs 3%). RLL did not progress over time, and varied between patients at different timepoints for both TKA systems. Clinical outcomes and PROMs improved compared with preoperative scores, and were not different between groups. Conclusion. MTPM migration at five-year follow-up of the femoral and tibial component of the ATTUNE were similar and as low as that of the PFC-Sigma. MTPM migration of both knee implants did not significantly change from one year post-surgery, indicating stable fixation. Long-term ATTUNE performance may be expected to be comparable to the clinically well-performing PFC-Sigma. We have not found evidence of increased tibial component migration as measured by RSA to support concerns about cement debonding and a higher risk of aseptic loosening with the ATTUNE TKA. Cite this article: Bone Joint J 2023;105-B(11):1168–1176

Introduction. Wolff's Law proposes that trabecular bone adapts in response to mechanical loading and that trabeculae align with the trajectory of predominant loads. The current study is aimed to investigate trabecular orientation in the tibia in patients with osteoarthritis of the knee. Consistent with Wolff's Law, it was hypothesised that orientation would reflect the mechanical loading of the joint and hence that there would be a correlation between the trabecular orientation and the mechanical axis of the lower limb. Methods. 51 anonymised radiographs from patients with osteoarthritis were analysed using ImageJ (National Institute of Health). Each patient had both a standard anteroposterior radiograph of the knee and a long leg view taken while weight bearing. For each anteroposterior radiograph, the angle of the femoral shaft and tibial shaft were measured. The femoral shaft – tibial shaft (FS -TS) angle was then calculated as the difference between the two, as described by Sheehy et al. (2011). A medial rectangle was selected with the top, bottom, medial and lateral borders being the sclerotic bone, the growth line, the bone edge and the centre of the medial tibial spine. Corresponding measurements were done on the lateral side. Trabecular orientation of both areas was measured using OrientationJ (an ImageJ plugin). In all cases the medial and lateral orientation angles were expressed relative to the angle of the tibial shaft. The mechanical axis of the lower limb was measured from the full length radiographs by calculating the angle formed by the femoral and tibial axes, as described by Goker and Block. All measurements were done independently by two observers, SAS and SL. Results. Except where indicated, the results are based on analysis of 51 radiographs. Inter-tester analysis indicated excellent reliability (ICC = 0.99) for the mechanical axis measurement and preliminary inter-tester analysis (based on 25 radiographs) indicated good reliability for the orientation measurements (ICC = 0.76). The FS-TS angle calculated from the anteroposterior radiographs was significantly correlated with the mechanical axis calculated from the full-leg views (r = 0.96, p < 0.01), with an average offset of 5.7°, which is consistent with previous research. There was a significant correlation between the lateral trabecular orientation and both the FS-TS angle measured from the anteroposterior radiographs (r = −0.48, p < 0.01) (Figure) and the mechanical axis measured from the long leg views (r = −0.39, p < 0.01). There was also a significant correlation between the medial trabecular orientation and the FS-TS angle (r = 0.35, p = 0.01). Discussion. There were significant correlations between leg alignment (both the mechanical axis and the FS − TS angle) and trabecular orientation in the human tibia. These findings were consistent with Wolff's Law, which proposes that trabecular bone adapts in response to mechanical loading. To the best of our knowledge, the current study is the first to investigate in vivo trabecular orientation in the human tibia and to establish a correlation with the mechanical axis of the lower limb. The findings also suggest that inspection of the trabecular orientation might provide valuable information on leg alignment and mechanical loading prior to surgery