Aims. Highly cross-linked polyethylene (HXLPE) greatly reduces wear in total hip arthroplasty, compared to conventional polyethylene (CPE). Cross-linking is commonly achieved by irradiation. This study aimed to compare the degree of cross-linking and in vitro wear rates across a cohort of retrieved and unused polyethylene cups/liners from various brands. Methods. Polyethylene acetabular cups/liners were collected at one centre from 1 April 2021 to 30 April 2022. The trans-vinylene index (TVI) and oxidation index (OI) were determined by Fourier-transform infrared spectrometry. Wear was measured using a pin-on-disk test. Results. A total of 47 specimens from ten brands were included. The TVI was independent of time in vivo. A linear correlation (R. 2. = 0.995) was observed between the old and current TVI standards, except for vitamin E-containing polyethylene. The absorbed irradiation dose calculated from the TVI corresponded to product specifications for all but two products. For one electron beam-irradiated HXLPE, a mean dose of 241% (SD 18%) of specifications was determined. For another, gamma-irradiated HXLPE, a mean 41% (SD 13%) of specifications was determined. Lower wear was observed for higher TVI. Conclusion. The TVI is a reliable measure of the absorbed irradiation dose and does not alter over time in vivo. The products of various brands differ by manufacturing details and consequently cross-linking characteristics. Absorption and penetration of electron radiation and gamma radiation differ, potentially leading to higher degrees of cross-linking for electron radiation. There is a non-linear, inverse correlation between TVI and in vitro wear. The wear resistance of the HXLPE with low TVI was reduced and more comparable to CPE. Cite this article: Bone Joint Res 2024;13(11):682–693

Aims

The aim of this study was to evaluate the suitability of the tapered cone stem in total hip arthroplasty (THA) in patients with excessive femoral anteversion and after femoral osteotomy.

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.

Aims

The primary objective of this study was to develop a validated classification system for assessing iatrogenic bone trauma and soft-tissue injury during total hip arthroplasty (THA). The secondary objective was to compare macroscopic bone trauma and soft-tissues injury in conventional THA (CO THA) versus robotic arm-assisted THA (RO THA) using this classification system.

In total hip arthroplasty (THA), cementless cup without screw holes has the putative benefits of maximizing host bone contact and reducing osteolysis by eliminating channels to backside wear particles. However, supplemental trans-acetabular screws cannot be used.

74 hips in 60 patients receiving same model of cementless cup without screw holes (Depuy Duraloc 100 HA cup) from 6/1999 to 3/2003 were prospectively followed up. All patients were allowed to have immediate full weight bearing. Age at THA was 53 ± 13 (range 24–74) years. Osteonecrosis was the leading hip disease (45% of hips). Survivorship was assessed using revision of the cup as the end point. Radiological parameters, including lateral opening angle, vertical and horizontal migration distances of the cups were measured. Paired t-test was used to compare between the measurements in early postoperative period and at final follow up.

51 hips were assessed at minimum 20 years follow-up. The mean follow-up was 22.6 (range 21 – 25) years. All the cups were well fixed. There were two cup revisions. Conventional polyethylene (PE) was used in both hips; osteolysis occurred 17 and 18 years later. Both cups were well fixed but were revised, one due to cup mal-positioning, one due to need in upsizing the articulation. 14 other hips were revised but these cups were well fixed and not revised; 9 loosened stems (most were cemented Elite plus stems), 5 PE wear and osteolysis (all were conventional PE). At 20 years, the survivorship of cups was 96.1%. Changes in lateral opening angle, vertical and horizontal migration distances were 0.44±1.59°, 0.01±1.52mm and -0.32±1.47mm respectively, without statistical significance.

This study provided evidence of excellent long-term survivorship of cementless cup without screw holes. Immediate postoperative weight-bearing also did not lead to cup migration in the long-term.

Hip resurfacing arthroplasty (HRA) is a bone conserving alternative to total hip arthroplasty. We present the early 2-year clinical and radiographic follow-up of a novel ceramic-on-ceramic (CoC) HRA in an international multi-centric cohort. Patients undergoing HRA between September 2018 and January 2021 were prospectively included. Patient-reported outcome measures (PROMS) in the form of the Forgotten Joint Score (FJS), HOOS Jr, WOMAC, Oxford Hip Score (OHS) and UCLA Activity Score were collected preoperatively and at 1- and 2-years post-operation. Serial radiographs were assessed for migration, component alignment, evidence of osteolysis/loosening and heterotopic ossification formation. 200 patients were identified to have reached 2-year follow-up. Of these, 185 completed PROMS follow-up at 2 years. There was significant improvement in HOOS (p< 0.001) and OHS (p< 0.001) and FJS (p< 0.001) between the pre-operative and 2-year outcomes. Patients reported improved pain (p<0.001), function (p<0.001) and reduced stiffness (p<0.001) as measured by the WOMAC score. Patients had improved activity scores on the UCLA Active Score (P<0.001) with 53% reporting return to impact activity at 2 years. There was no osteolysis and the mean acetabular cup inclination angle was 41deg and the femoral component shaft angle was 137deg. No fractures were reported over but there was one sciatic nerve palsy with partial recovery. Two patients were revised; one at 3 months for pain due to a misdiagnosed back problem and another at 33 months for loosening of the acetabular component with delamination of the titanium ingrowth surface. CoC resurfacing at 2-years post-operation demonstrate promising results with satisfactory PROMS

The direct superior approach (DSA) is a modification of the posterior approach (PA) that preserves the iliotibial band and short external rotators except for the piriformis or conjoined tendon during total hip arthroplasty (THA). The objective of this study was to compare postoperative pain, early functional rehabilitation, functional outcomes, implant positioning, implant migration, and complications in patients undergoing the DSA versus PA for THA. This study included 80 patients with symptomatic hip arthritis undergoing primary THA. Patients were prospectively randomised to receive either the DSA or PA for THA, surgery was undertaken using identical implant designs in both groups, and all patients received a standardized postoperative rehabilitation programme. Predefined study outcomes were recorded by blinded observers at regular intervals for two-years after THA. Radiosteriometric analysis (RSA) was used to assess implant migration. There were no statistical differences between the DSA and PA in postoperative pain scores (p=0.312), opiate analgesia consumption (p=0.067), and time to hospital discharge (p=0.416). At two years follow-up, both groups had comparable Oxford hip scores (p=0.476); Harris hip scores (p=0.293); Hip disability and osteoarthritis outcome scores (p=0.543); University of California at Los Angeles scores (p=0.609); Western Ontario and McMaster Universities Arthritis Index (p=0.833); and European Quality of Life questionnaire with 5 dimensions scores (p=0.418). Radiographic analysis revealed no difference between the two treatment groups for overall accuracy of acetabular cup positioning (p=0.687) and femoral stem alignment (p=0.564). RSA revealed no difference in femoral component migration (p=0.145) between the groups at two years follow-up. There were no differences between patients undergoing the DSA versus PA for THA with respect to postoperative pain scores, functional rehabilitation, patient-reported outcome measurements, accuracy of implant positioning, and implant migration at two years follow-up. Both treatment groups had excellent outcomes that remained comparable at all follow-up intervals

The purpose of this study was to assess the variability in implant position between sides in patients who underwent staged, bilateral THA and whether variation from one side to the other affected patient-reported outcomes. A retrospective review was conducted on 207 patients who underwent staged, bilateral THA by the same surgeon from 2017–2022. Leg length, acetabular height, cup version, and coronal and sagittal stem angles were assessed radiographically and compared to the contralateral THA. Surgical approach and technology utilization were further assessed for their impact on variability. Linear regression was used to model the relationship between side-to-side variability and patient-reported outcome measures (PROMS). Between sides, mean radiographic leg length varied by 4.6mm (0.0–21.2), acetabular height varied by 3.3mm (0.0–13.7), anteversion varied by 8.2° (0.0 to 28.7), coronal stem alignment varied by 1.1° (0.0 to 6.9), and sagittal angulation varied by 2.3° (0.0 to 10.5). The anterior approach resulted in more variability in stem angle position in both the coronal (1.3° vs. 1.0°, p=0.036) and sagittal planes (2.8° vs. 2.0° p=0.012) compared to the posterior approach. The posterior approach generally led to more anteversion than the anterior approach. Use of robotics or navigation for acetabular positioning did not increase side-to-side variability in cup-related position or leg length. Despite considerable side-to-side variability, Hip dysfunction and osteoarthritis outcome scores (HOOS JR) were not affected by higher levels of position inconsistency. Staged, bilateral THA results in considerable variability in component position between sides. The anterior approach leads to more side-to-side variability in sagittal stem angle and cup anteversion than the posterior approach. Navigation and robotics do not improve the consistency of component position in bilateral THA. Variation in implant position was not associated with differences in PROMs, suggesting that despite variability, patients can tolerate these differences between sides

The painful hip without obvious clinical or radiographic signs of complications is a well-known scenario for surgeons. The clinical tools we have access to currently lack a dynamic test for detecting early signs of motion between implant and bone. A new software, Sectra IMA, has a potential to facilitate diagnosis of early implant loosening by analysis of paired CT exams. In clinical practise the two scans are acquired by endpoint of a possible motion, “a provocation CT”, for example maximal external and internal rotation in a CT hip examination. 20 years of research by Olivecrona and Weidenhielm is the scientific background for the technique. Early results are presented by Sandberg et al 2022. To further validate and create clinical evidence more extensive clinical studies is needed. A proposal for a multicentric, global clinical study will be presented for further discussion. A new technique for diagnosis of acetabular cup loosening using computed tomography: preliminary experience in 10 patients. Henrik Olivecrona, Lotta Olivecrona, Lars Weidenhielm, Marilyn E Noz, Jocelyn Kardos, Gerald Q Maguire Jr, Michael P Zeleznik, Peter Aspelin. Acta Orthop. 2008 Jun;79(3):346-53. doi: 10.1080/17453670710015247. Inducible displacement CT increases the diagnostic accuracy of aseptic loosening in primary total hip arthroplasty. Sandberg O, Carlsson S, Harbom E, Cappelen V, Tholén S, Olivecrona H, Wretenberg P. Acta Orthop. 2022 Oct 31;93:831-836. doi: 10.2340/17453674.2022.5240.PMID: 36314542

There remains concern with the use of constrained liners (CL) implanted at the time of acetabular cup revision in revision total hip replacement (rTHA). The aim of this study was to determine the implant survival in rTHA when a CL was implanted at the same time as acetabular cup revision. We reviewed our institutional database to identify all consecutive rTHAs where a CL was implanted simultaneously at the time acetabular cup revision from 2001 to 2021. One-hundred and seventy-four revisions (173 patients) were included in the study. Mean follow-up of 8.7 years (range two – 21.7). The most common indications for rTHA were instability (35%), second-stage periprosthetic joint infection (26.4%), and aseptic loosening (17.2%). Kaplan Meier Analysis was used to determine survival with all-cause re-revision and revision for cup aseptic loosening (fixation failure) as the endpoints. A total of 32 (18.3%) patients underwent re-revision at a mean time of 2.9 years (range 0.1 – 14.1). The most common reasons for re-revision were instability (14), periprosthetic joint infection (seven), and loosening of the femoral component (four). Three (1.7%) required re-revision due to aseptic loosening of the acetabular component (fixation failure) at a mean of two years (0.1 – 5.1). Acetabular component survival free from re-revision due to aseptic loosening was 98.9% (95% CI 97.3 – 100) at five-years and 98.1% (95% CI 95.8 – 100) at 10-years. There were no acetabular component fixation failures in modern highly porous shells. CLs implanted at the time acetabular cup revision in rTHA have a 98.1% 10-year survival free from acetabular cup aseptic loosening (fixation failure). There were no cup fixation failures in modern highly porous shells. Thus, when necessary, implanting a CL during revision of an acetabular component with stable screw fixation is safe with an extremely low risk of cup fixation failure

Dislocation after total hip replacement (THR) is a devastating complication. Risk factors include patient and surgical factors. Mitigation of this complication has proven partially effective. This study investigated a new innovating technique to decrease this problem using rare earth magnets. Computer simulations with design and magnetic finite element analysis software were used to analyze and quantitate the forces around hip implants with embedded magnets into the components during hip range of motion. N52 Neodymium-Iron-Boron rare earth magnets were sized to fit within the existing acetabular shells and the taper of a hip system. Additionally, magnets placed within the existing screw holes were studied. A 50mm titanium acetabular shell and a 36mm ceramic liner utilizing a taper sleeve adapter were modeled which allowed for the use of a 12mm × 5mm magnet placed in the center hole, an 18mm × 15mm magnet within the femoral head, and 10mm × 5mm magnets in the screw holes. Biomechanical testing was also performed using in-vitro bone and implant models to determine retention forces through a range of hip motion. The novel system incorporating magnets generated retentive forces between the acetabular cup and femoral head of between 10 to 20 N through a range of hip motion. Retentive forces were stronger at the extreme position hip range of motion when additional magnets were placed in the acetabular screw holes. Greater retentive forces can be obtained with specially designed femoral head bores and acetabular shells specifically designed to incorporate larger magnets. Mechanical testing validated the loads obtained and demonstrated the feasibility of the magnet system to provide joint stability and prevent dislocations. Rare earth magnets provide exceptional attractive strength and can be used to impart stability and prevent dislocation in THR without the complications and limitations of conventional methods

Aims

Periprosthetic fracture and implant loosening are two of the major reasons for revision surgery of cementless implants. Optimal implant fixation with minimal bone damage is challenging in this procedure. This pilot study investigates whether vibratory implant insertion is gentler compared to consecutive single blows for acetabular component implantation in a surrogate polyurethane (PU) model.

Polymethylmethacrylate (PMMA) bone cement is strong in compression, however it tends to fail under torsion. Sufficient pressurisation and subsequent interdigitation between cement and bone are critical for the mechanical interlock of cemented orthopaedic implants, and an irregular surface on the acetabular cup is necessary for reasonable fixation at the cup-cement interface. There is limited literature investigating discrepancies in the failure mechanisms of cemented all-polyethylene acetabular cups with and without cement spacers, under torsional loading. In vitro experimental comparison of three groups of polyethylene acetabular prosthesis (PAP) cemented into prepared sawbone hemipelvises:. * PAP without PMMA spacers maintaining an equal cement mantle circumferentially. (Group 1 n=3). * PAP without PMMA spacers cemented deliberately ‘bottoming-out’ the implant within the acetabulum. (Group 2 n=3). * PAP with PMMA spacers. (Group 3 n=3). The constructs were tested to torstional failure on a custom designed setup, and statistical analysis done by a one-way ANOVA and Tukey-Welsh test. Group 3 demonstrated superior torsional resistance with a statistically significant torque of 145Nm (SD±12Nm) at failure, compared to group 2 (109Nm, SD±7Nm) and group 1 (99Nm, SD±8Nm). Group 3 experienced failure predominantly at the bone-cement interface, in contrast, Groups 1 and 2 exhibited failure predominantly at the cup-cement interface. There was no significant difference between Group 1 and 2. Qualitative analysis of the failure mode indicates the efficient redistribution of stress throughout the cement mantle, consistent with the greater uniformity of cement. PMMA spacers increase the resistance to torsional failure at the implant-cement interface. Acetabular components without spacers (Groups 1 and 2) failed at the implant-cement interface before the cement-bone interface, at a statistically significantly lower level of torque to failure. Although the PMMA spacers may reduce cement interdigitation at the cement-bone interface the torsional forces required to fail are likely supraphysiological

Dual Mobility (DM) Total Hip Replacements (THRs), are becoming widely used but function in-vivo is not fully understood. The aim of this study was to compare the incidence of impingement of a modular dual mobility with that of a standard cup. A geometrical model of one subject's bony anatomy \[1\] was developed, a THR was implanted with the cup at a range of inclination and anteversion positions (Corail® stem, Pinnacle® cup (DePuy Synthes)). Two DM variants and one STD acetabular cup were modelled. Joint motions were taken from kinematic data of activities of daily living associated with dislocation \[2\] and walking. The occurrence of impingement was assessed for each component combination, orientation and activity. Implant-implant impingement can occur between the femoral neck and the metal or PE liner (DM or STD constructs respectively) or neck-PE mobile liner (DM only). The results comprise a colour coded matrix which sums the number of impingement events for each cup position and activity and for each implant variant. Neck-PE mobile liner impingement, occurred for both DM sizes, for all activities, and most cup placement positions indicating that the PE mobile liner is likely to move at the start of all activities including walking. For all constructs no placement positions avoided neck-metal (DM) or neck-PE liner (STD) impingementevents in all activities. The least number of events occurred at higher inclination and anteversion component positions. In addition to implant-implant impingement, some instances of bone-bone and implant-bone impingement were also observed. Consistent with DM philosophy, neck-PE mobile liner impingement and liner motion occurred for all activities including walking. Neck-liner impingement frequency was comparable between both DM sizes (metal liner) and a standard cup (PE liner)

Aims

Isolated acetabular liner exchange with a highly crosslinked polyethylene (HXLPE) component is an option to address polyethylene wear and osteolysis following total hip arthroplasty (THA) in the presence of a well-fixed acetabular shell. The liner can be fixed either with the original locking mechanism or by being cemented within the acetabular component. Whether the method used for fixation of the HXLPE liner has any bearing on the long-term outcomes is still unclear.

Aims

Pelvic discontinuity is a challenging acetabular defect without a consensus on surgical management. Cup-cage reconstruction is an increasingly used treatment strategy. The present study evaluated implant survival, clinical and radiological outcomes, and complications associated with the cup-cage construct.

Aims. Manual impaction, with a mallet and introducer, remains the standard method of installing cementless acetabular cups during total hip arthroplasty (THA). This study aims to quantify the accuracy and precision of manual impaction strikes during the seating of an acetabular component. This understanding aims to help improve impaction surgical techniques and inform the development of future technologies. Methods. Posterior approach THAs were carried out on three cadavers by an expert orthopaedic surgeon. An instrumented mallet and introducer were used to insert cementless acetabular cups. The motion of the mallet, relative to the introducer, was analyzed for a total of 110 strikes split into low-, medium-, and high-effort strikes. Three parameters were extracted from these data: strike vector, strike offset, and mallet face alignment. Results. The force vector of the mallet strike, relative to the introducer axis, was misaligned by an average of 18.1°, resulting in an average wasted strike energy of 6.1%. Furthermore, the mean strike offset was 19.8 mm from the centre of the introducer axis and the mallet face, relative to the introducer strike face, was misaligned by a mean angle of 15.2° from the introducer strike face. Conclusion. The direction of the impact vector in manual impaction lacks both accuracy and precision. There is an opportunity to improve this through more advanced impaction instruments or surgical training. Cite this article: Bone Joint Res 2024;13(4):193–200

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This study reports the results of 38 total hip arthroplasties (THAs) in 33 patients aged less than 50 years, using the JRI Furlong hydroxyapatite ceramic (HAC)-coated femoral component.

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Oxidized zirconium (OxZi) and highly cross-linked polyethylene (HXLPE) were developed to minimize wear and risk of osteolysis in total hip arthroplasty (THA). However, retrieval studies have shown that scratched femoral heads may lead to runaway wear, and few reports of long-term results have been published. The purpose of this investigation is to report minimum ten-year wear rates and clinical outcomes of THA with OxZi femoral heads on HXLPE, and to compare them with a retrospective control group of cobalt chrome (CoCr) or ceramic heads on HXLPE.

Aims

Mechanical impingement of the iliopsoas (IP) tendon accounts for 2% to 6% of persistent postoperative pain after total hip arthroplasty (THA). The most common initiator is anterior acetabular component protrusion, where the anterior margin is not covered by anterior acetabular wall. A CT scan can be used to identify and measure this overhang; however, no threshold exists for determining symptomatic anterior IP impingement due to overhang. A case-control study was conducted in which CT scan measurements were used to define a threshold that differentiates patients with IP impingement from asymptomatic patients after THA.