Roentgen Stereophotogrammetric Analysis (RSA) is the gold standard for measuring implant micromotion thereby predicting implant loosening. Early migration has been associated with the risk of long-term clinical failure. We used RSA to assess the stability of the Australian designed cementless hip stem (Paragon TM) and now report our 5-year results. Fifty-three patients were prospectively and consecutively enrolled to receive a Paragon hip replacement. Tantalum beads were inserted into the bone as per RSA protocol and in the implant. RSA x-rays were taken at baseline 1–4 days post-surgery, at 6 weeks, 6 months, 12 months, 2 years, and 5 years. RSA was completed by an experienced, independent assessor. We reported the 2-year results on 46 hips (ANZJS 91 (3) March 2021 p398) and now present the 5-year results on 27 hips. From the 2-year cohort 5 patients had died, 8 patients were uncontactable, 1 patient was too unwell to attend, 5 patients had relocated too far away and declined. At 5 years the mean axial subsidence of the stem was 0.66mm (0.05 to 2.96); the mean rotation into retroversion was 0.49˚ (−0.78˚ to 2.09˚), rotation of the stem into valgus was −0.23˚ (−0.627˚ to 1.56˚). There was no detectable increase in subsidence or rotation between 6 weeks and 5 years. We compared our data to that published for the Corail cementless stem and a similar pattern of migration was noted, however greater rotational stability was achieved with the Paragon stem over a comparable follow-up period. The RSA results confirm that any minor motion of the Paragon cementless stem occurs in the first 6 weeks after which there is sustained stability for the next 5 years. The combination of a bi-planar wedge and transverse rectangular geometry provide excellent implant stability that is comparable to or better than other leading cementless stems

Introduction. There have been many attempts to reduce the risk of femoral component loosening. Using a tapered stem having a highly polished stem surface results in stem stabilization subsequent to debonding and stem-cement taper-lock and is consistent with force-closed fixation design. Purpose. In this study, we assessed the subsidence of two different polished triple tapered stems and two different cements in primary THA. Materials and methods. From March 2013 to March 2014, two kinds of polished triple tapered cemented stem were applied in 74 primary THA. 12 male, 62 female, mean age at surgery was 68 years old, mean F/U time was 12months. When they were compared by stems, this study comprises 35 THA with Trilliance stem(Aesculap, Germany) and 39 THA with SC stem (Kyocera, Japan), and when they were compared by cements, this study comprises 36 Simplex cement (Stryker, USA) cases and 38 Cobalt cement(Biomet, USA) cases. Using digitized x-ray, we measured the subsidence of each implants. Measurements were taken from initial postoperative radiographs to the final follow-up. We also evaluated the existence of radiolucent line between cement and stem and also evaluated calcar resorption. Results. The mean subsidence of Trilliance stem was 0.26mm and of SC stem was 0.44mm at 12months.(P<0.0001) Statistic significance was observed between the stems. When compared between 2 cements, the mean subsidence of Simplex cement was 0.25mm and of Cobalt cement was 0.48mm.(P=0.0563). No statistic significance was observed. There was no case of stem loosening and calcar resorption. Conclusion. 2 different designed cemented triple taper stems showed significantly different degree of subsidence after THA. No difference of subsidence was observed between two cements

Corail implants have shown to give good results in elective total hip replacements (THR) and in hemi-arthroplasties. Pre-operative planning to identify the correct size of the Corail implant is vital for good post-operative outcomes. An undersized implant can lead to subsidence. The aim of the study was to review the incidence of subsidence. Post-operative radiographs of trauma patients (n=39) and elective (n=45) patients who had Corail femoral implants were reviewed. The implant-to-canal (I:C) ratio were calculated at the given 50% and 70% levels of the Corail implant. Follow up radiographs were reviewed to identify subsidence. The average age of patients was 80.3 years (range 66–93 years) in hemi-arthroplasties and 61 years (range 18–88) in elective THRs. The implant to canal (I:C) ratio at the 50% and 70% levels in trauma patients were 0.77 (range 0.54 – 0.97) and 0.81 (range 0.59 – 0.94) respectively. In elective patients, the ratios at the 50% and 70% marks were 0.77 (range 0.57 – 0.98) and 0.81 (0.56 – 0.95). One case of subsidence was seen in a collarless implant and I:C ratios at 50% and 70% were 0.57 and 0.56. A larger study is required to determine the reliability of this novel ‘implant:canal’ ratio to predict incidence

Increasing pressure to use rapid recovery care pathways when treating patients undergoing total hip arthroplasty (THA) is evident in current health care systems for numerous reasons. Patient autonomy and health care economics has challenged the ability of THA implants to maintain functional integrity before achieving bony union. Although collared stems have been shown to provide improved axial stability, it is unclear if this stability correlates with activity levels or results in improved early function to patients compared to collarless stems. This study aims to examine the role of implant design on patient activity and implant fixation. The early follow-up period was examined as the majority of variation between implants is expected during this time-frame. Patients (n=100) with unilateral hip OA who were undergoing primary THA surgery were recruited pre-operatively to participate in this prospective randomized controlled trial. All patients were randomized to receive either a collared (n=50) or collarless (n=50) cementless femoral stem. Patients will be seen at nine appointments (pre-operative, < 2 4 hours post-operation, two-, four-, six-weeks, three-, six-months, one-, and two-years). Patients completed an instrumented timed up-and-go (TUG) test using wearable sensors at each visit, excluding the day of their surgery. Participants logged their steps using Fitbit activity trackers and a seven-day average prior to each visit was recorded. Patients also underwent supine radiostereometric analysis (RSA) imaging < 2 4 hours post-operation prior to leaving the hospital, and at all follow-up appointments. Nineteen collared stem patients and 20 collarless stem patients have been assessed. There were no demographic differences between groups. From < 2 4 hours to two weeks the collared implant subsided 0.90 ± 1.20 mm and the collarless implant subsided 3.32 ± 3.10 mm (p=0.014). From two weeks to three months the collared implant subsided 0.65 ± 1.54 mm and the collarless implant subsided 0.45 ± 0.52 mm (p=0.673). Subsidence following two weeks was lower than prior to two weeks in the collarless group (p=0.02) but not different in the collared group. Step count was reduced at two weeks compared to pre-operatively by 4078 ± 2959 steps for collared patients and 4282 ± 3187 steps for collarless patients (p=0.872). Step count increased from two weeks to three months by 6652 ± 4822 steps for collared patients and 4557 ± 2636 steps for collarless patients (p=0.289). TUG test time was increased at two weeks compared to pre-operatively by 4.71 ± 5.13 s for collared patients and 6.54 ± 10.18 s for collarless patients (p=0.551). TUG test time decreased from two weeks to three months by 7.21 ± 5.56 s for collared patients and 8.38 ± 7.20 s for collarless patients (p=0.685). There was no correlation between subsidence and step count or TUG test time. Collared implants subsided less in the first two weeks compared to collarless implants but subsequent subsidence after two weeks was not significantly different. The presence of a collar on the stem did not affect patient activity and function and these factors were not correlated to subsidence, suggesting that initial fixation is instead primarily related to implant design

Introduction:. Subsidence of cementless femoral stems in total hip arthroplasty (THA) has been associated with poor initial fixation and subsequent risk of aspectic loosening. There is limited literature on how subsidence of cementless, proximally porous coated, tapered wedge femoral stems impacts the patient clinically. The aim of our study was to assess whether subsidence with these stems is associated with a decline in clinical function. Method:. A review of a prospectively collected database of THAs performed by a single surgeon at one institution using two cementless, tapered wedge stem designs from January 2006 to June 2010 was performed. Radiographic analysis using Picture Archiving and Communications System (PACS) was used to identify patients with greater than 1.5 mm of subsidence, and to document osseointegration. Preoperative and postoperative pain and Harris hip scores were recorded; and analyzed to identify if the clinical recovery pattern of the subsidence versus no subsidence groups differed. Protected weight bearing was recommended to all patients with subsidence. Results:. 264 hips were reviewed clinically and radiographically at a mean follow-up of 29 months. 10 hips had subsidence greater than 1.5 mm at last follow up. There were 6 males and 3 females with a mean age of 62.1 years in the subsidence group. Subsidence was noted at the 6 week visits in all 10 patients. Mean Harris Hip scores and pain scores were significantly diminished at 6 weeks in the subsidence group (Mean 67.6) as compared to the none subsidence group (82.2) (Figure 1). The two groups had similar scores preoperatively, at 1 year and 2 years postoperatively. In the subsidence group 9 of 10 hips had no further progression of subsidence, and showed radiographic evidence of osseointegration. Persistent thigh pain was noted in 2 patients in the subsidence group. One underwent successful femoral revision for failure of osseointegration and the other continues to have pain with radiographic signs of osseointegration. All 254 hips in the control group had evidence of osseointegration. Conclusion:. Subsidence of tapered wedge stems which occurs at the 6 week mark may be associated with a transient decline in clinical function. Early modification in the rehabilitation regimen may help improve clinical outcome scores in these patients

The fully hydroxyappatite (HA) coated tapered collarless femoral stem has been available worldwide for more than 20 years. However, in Thailand this design became available in 2007. In uncemented collarless tapered and HA coated designs, axial subsidence is a sign of early failure of the implant. This leads to stem instability, loosening and dislocation. To achieve vertical stability, the surgeon should use the correct surgical technique, accurate instrumentation, appropriate stem size and fill in the femoral canal before biologic fixation occurs. This study addresses the axial subsidence of the design. Methods. 46 consecutive total hip arthroplasties with fully HA coated tapered collarless femoral stem (Corail, DePuy) were performed between July 2007-November 2009 by a single surgeon. Patients with at least 6 months follow-up were included in this study. This involved 39 stems. The average follow-up was 11.86 months (6–24 months). The average age at the time of surgery was 58.6 years (37–83 years). Results. 25 stems (64%) had no evidence of subsidence. 14 stems (36%) had some subsidence. The average axial subsidence was 0.68 mm. The femoral canal shape was identified by canal flare index and classified to stovepipe in 12 cases, normal in 20 cases and Champagne –flute in 7 cases. The average axial subsidences at the end of the follow-up period were 0.67 mm, 0.8 mm and 0.25 mm respectively. All cases had no signs of loosening. All subsidences occurred on the first 3 months and no further subsidence was detected at 6 months or more. 12 cases (30%) were aged 60 years or older at time of surgery. In this group, 6 cases (50%) had stovepipe femoral stems (canal flare index <3.0). Conclusion. The fully hydroxyappatite coated tapered femoral stem design shows minimal axial subsidence within the first 3 months after full stability after 6 months

Uncemented femoral components of hip arthroplasty are believed to have a higher risk of subsidence in older patient groups. This has not been conclusively related to a poorer outcome of the arthroplasty over time. Our aim is to measure prevalence of subsidence in uncemented femoral components in a population of patients over 75 years of age and correlate with clinical outcome measures. Patients over 75 years of age from Jan 2002 to Aug 2009 had uncemented THJR at the discretion of the senior surgeon (RF). Pre-operative Charnley Hip Classification and Harris Hip Scores were recorded, as were HHS at 6 weeks and 1 year post-operatively for all patients. Post-operative radiographs were retrospectively reviewed and presence of subsidence quantified at 1 year and subsequent follow-ups. 83 patients had 92 uncemented THJR in the designated time frame. 5 pts were lost to follow-up or died within 12 months after operation leaving 78 patients and 87 hips for assessment. Average pre-op HHS 40.6 (13.1–64.6) and Charnley Classification noted (A 55.4 %: B 30.4%: C 14.1%). 12/87 (13.8%) hips had subsidence > 2mm (2 – 18mm) noted at 1 year radiographs. Average HHS for those with >2mm subsidence was 89.4 (69.7–100; median 93.9) compared to 90.7 (64.7 – 100; median 91.9) for those with < 2mm subsidence. 4 patients underwent revision procedures during follow-up period, all for periprosthetic fracture following falls. In appropriately selected patients over 75 years of age, the presence of subsidence in uncemented femoral components does not seem to result in poorer outcome measures

Introduction:. Although cementless total hip arthroplasty (THA) is well accepted, the optimal femoral component design remains unknown. Among early complications, loosening and periprosthetic fracture persist and are related to implant design. The purpose of this study is to compare the anatomic fit and early subsidence of two different stem designs: a modern, short taper-wedge design and a traditional fit-and-fill design. Methods:. A retrospective cohort study of 129 consecutive cementless THAs using two different femoral stems was performed. A modern taper-wedge stem was used in 65 hips and a traditional proximal fit-and-fill stem was used in 64 hips. Radiographic analysis was performed at preoperative, immediate postoperative and 1-month postoperative intervals. The radiographic parameters of bone morphology via the canal-flare index, implant subsidence at 1 month, sagittal alignment, and the “anatomic fit” metrics of canal fill and associated gaps were measured and recorded. Results:. There were no differences between groups in patient demographics (p > 0.4), and in bone morphology via the canal-flare index (p = 0.6) with numbers available. The mean subsidence was less in the taper-wedge design at 0.27 mm compared to 1.1 mm in the fit-and-fill stem (p < 0.0001). Subsidence greater than 2 mm occurred in 26 of 64 fit-and-fill stems (41%) compared to 1 of 65 taper-wedge implants (1.5%). The percentage fill at all levels measured was greater in the taper-wedge design (p < 0.0001). The taper-wedge design was inserted a mean of 2.7° sagittal extension compared to 0.4° in the fit-and-fill design (p < 0.0001). Conclusion:. Despite being shorter in length, the taper-wedge design demonstrates greater axial stability and less subsidence compared to a traditional fit-and-fill stem. The optimized proximal femoral fit inherent in this anatomic-based taper-wedge design is likely responsible for the minimal subsidence. The clinical implication of greater extension in the sagittal plane is unknown and longer-term clinical follow up is warranted

Introduction. In cemented total hip arthroplasty (THA), proper cement mantle thickness in the femoral canal is still controversial subject. It is widely accepted that the cement mantle around a femoral stem should be at least 2 mm in thickness. But articles from France reported good long-term result with thin cement mantle. It is so called “The French paradox”. We have already reported that the greater compressive force at the cement-bone interface was seen in collarless polished tapered (CPT, Zimmer, USA) stem with thick cement mantle than that with thin cement mantle. However, the stem with thick cement mantle subsided more than with thin mantle. It may have a possibility to cause an early mechanical failure of cemented THA. We compared to stem and cement subsidence in various cement mantles using tantalum ball into cement in this study. Methods. A cemented stem model was used for this study with a CPT stem into composite femur. Three sizes of CPT stems (No. 1, No. 2 and No. 3) and one size composite femur were prepared for this study. We inserted two stems for each size, for a total of six stems. Composite femurs were reamed with a No. 3 rasp, and various size of stem was fixed with cement in each composite femur to make a various thicknesses of cement mantle. Two to three tantalum marker balls were injected into the cement in each femur before cement was hardened. 1-Hz dynamic load applied to the stems for half a-million cycles. Each 16 hours of loading was followed by 8 hours without loading. We used micro-CT before and after loading to measure the movement of the tantalum balls in three dimensions. And we analyzed occupation ratio of stem in the femoral canal by computed reconstructed three dimensional model of bone cement and stem. Results. We were able to detect a total of 13 balls in the cement for the 6 stems. The range of cement thickness in the CT slice on balls was 1.52 to 5.32 mm. Stem subsidence showed a significantly positive correlation to the thickness of cement mantle. In the horizontal plane, 8 of these 13 balls moved in an outside direction and five moved in an inside direction. The horizontal/perpendicular ratio for the tantalum balls showed a significant negative correlation to the thickness of the cement mantle. The subsidence rate (ratio of stem subsidence to ball subsistence) showed a significant negative correlation to the stem occupation ratio. The effective radial cement creep was also detected when the cement mantle was less than 2.5 mm thick and more than 60% in the occupation ratio. Conclusions. Stem subsistence was more commonly associated with cement subsidence in the thicker cement mantles and with a low stem occupation rate in CPT stems

Introduction. Aligning the tibial tray is a critical step in total knee arthroplasty (TKA). Malalignment, (especially in varus) has been associated with failure and revision surgery. While the link between varus malalignment and failure has been attributed to increased medial compartmental loading and generation of shear stress, quantitative biomechanical evidence to directly support this mechanism is incomplete. We therefore constructed and validated a finite element model of knee arthroplasty to test the hypothesis that varus malalignment of the tibial tray would increase the risk of tray subsidence. Methods. Cadaver Testing. Fresh human knees (N = 4) were CT scanned and implanted with TKA cruciate-retaining tibial tray (Triathlon CR, Stryker Orthopaedics, New Jersey). The specimens were subjected to ISO-recommended knee wear simulation loading for up to 100,000 cycles. Micromotion sensors were mounted between the tray and underlying bone to measure micromotion. In two of the specimens, the application of vertical load was shifted medially to generate a load distribution ratio of 55:45 (medial:lateral) to represent neutral varus-valgus alignment. In the remaining two specimens, a load distribution ratio of 75:25 was generated to represent varus alignment. Finite element analysis. qCT scans of the tested knees were segmented using MIMICS (Materialise, Belgium). Material properties of bone were spatially assigned after converting bone density to elastic modulus. A finite element model of the tibia implanted with a tibial tray was constructed (Abaqus 6.8, Simulia, Dassault Syst`mes). Boundary conditions were applied to simulate experimental mounting conditions and the tray was subjected to a single load cycle representing that applied during cadaver loading. Results. The two cadaver specimens tested at 55:45 medial:lateral (M:L) force distribution survived the 100,000 cycle test, while both cadaver specimens tested at 75:25 M:L force distribution failed. The finite element model generated distinct differences in compressive strain distribution patterns in the proximal tibia. A threshold of 2000 microstrain was used for fatigue damage in bone under cyclic loading. Both specimens loaded under 75:25 M:L distribution demonstrated substantially larger cortical bone volumes in the proximal tibial cortex that were greater than this fatigue threshold. Discussion & Conclusion. We validated a finite element model of tibial loading after TKA. Local compressive strains directly correlated with subsidence and failure in cadaver testing. A significantly greater volume of proximal tibial cortical bone was compressed to a strain greater than the fatigue threshold in the varus alignment group, indicating an increased risk for fatigue damage. This model is extremely valuable in studying the effect of surgical alignment, loading, and activity on damage to proximal bone. Emerging techniques that customize tibial tray placement to the individual patient's pre-arthritic alignment run counter to the traditional recommendations for coronal alignment to the mechanical axis of the knee. A method that determines the risk of bone damage in a patient-specific manner can provide the surgeon with a safe range for component alignment and may even be applicable in preoperative planning

Introduction. Component and limb alignment (especially varus >3°) have been associated with soft-tissue imbalance, increased polyethylene wear, and tibial tray subsidence. However, not all clinical outcome studies have found significant correlation between tibial varus and revision surgery. While the link between limb alignment and failure has been attributed to increased medial compartmental loading and generation of shear stress, quantitative biomechanical evidence to directly support this mechanism is incomplete. In this study, we analyzed the effect of limb alignment and tibial tray alignment on the risk for bone damage and subsequent risk for tray loosening. Methods. A finite element model of knee arthroplasty previously validated with in vitro cadaver testing was used. Models of four subjects were constructed with tibial resections simulating a 0°, 3°, 5°, and 7° varus alignment with respect to the mechanical axis of the tibia and the tray implanted at the corresponding angles. Tibial tray orientation was simulated without change in limb alignment (i.e. maintaining the mechanical axis of the knee at 0°) and with limb alignment ranging from 3° valgus to 7° varus (Fig 1). A static load equivalent to three times the bodyweight of the subject was applied in line with the mechanical knee axis. Relative motion between the tibial tray and tibial bone was calculated. Elements with an equivalent von Mises strain >0.4% were selected and assigned an elastic modulus of 5 MPa to reflect damaged bone. Simulation was repeated and after-damage micromotion recorded. Results. At neutral limb alignment, average tray micromotion was <10 μm and did not increase significantly with increasing tray varus (Fig 2). The after-damage micromotion also did not increase significantly. However, limb alignment had a more substantial effect on before- and after-damage micromotion (Fig 3). The magnitude of micromotion increased with increasing varus limb alignment. Discussion. We did not find significant increase in micromotion with increased tray varus (of up to 7°) as long as neutral limb mechanical axis was maintained by compensating for tibial varus with femoral valgus. The volume of bone at risk also did not increase significantly with increasing tray varus. Removing the damaged bone did little to affect after-damage micromotion. This suggests that the “damaged” bone was not an important factor and likely did not contribute to the stability of the tray under the loading conditions analyzed in this report. Changes in limb alignment significantly offset the net axial load vector resulting in damage in a greater volume of elements due to overloading. This is due to the shift in Mechanical axis and load vector with subsequent increase in moment applied to the model. The micromotion was also substantially increased after the damage indicating that the damaged bone was providing structural support to the tray. This emphasizes the effects of increasing the static coronal loading in this model. Consequently, it identifies the benefit of neutral limb alignment in this loading scenario. This model is an extremely valuable tool in studying the effect of surgical alignment, loading, and activity on damage to proximal bone

Shoulder arthroplasty humeral stem design has evolved to accommodate patient anatomy characteristics. As a result, stems are available in numerous shapes, coatings, lengths, sizes, and vary by fixation method. This abundance of stem options creates a surgical paradox of choice. Metrics describing stem stability, including a stem's resistance to subsidence and micromotion, are important factors that should influence stem selection, but have yet to be assessed in response to the diametral (i.e., thickness) sizing of short stem humeral implants. Eight paired cadaveric humeri (age = 75±15 years) were reconstructed with surgeon selected ‘standard’ sized short-stemmed humeral implants, as well as 2mm ‘oversized’ implants. Stem sizing conditions were randomized to left and right humeral pairs. Following implantation, an anteroposterior radiograph was taken of each stem and the metaphyseal and diaphyseal fill ratios were quantified. Each humerus was then potted in polymethyl methacrylate bone cement and subjected to 2000 cycles of 90º forward flexion loading. At regular intervals during loading, stem subsidence and micromotion were assessed using a validated system of two optical markers attached to the stem and humeral pot (accuracy of <15µm). The metaphyseal fill ratio did not differ significantly between the oversized and standard stems (0.50±0.06 vs 0.50±0.10; P = 0.997, Power = 0.05); however, the diaphyseal fill ratio did (0.52±0.06 vs 0.45±0.07; P < 0.001, Power = 1.0). Neither fill ratio correlated significantly with stem subsidence or micromotion. Stem subsidence and micromotion were found to plateau following 400 cycles of loading. Oversizing stem thickness prevented implant head-back contact in all but one specimen with the least dense metaphyseal bone, while standard sizing only yielded incomplete head-back contact in the two subjects with the densest bone. Oversized stems subsided significantly less than their standard counterparts (standard: 1.4±0.6mm, oversized: 0.5±0.5mm; P = 0.018, Power = 0.748;), and resulted in slightly more micromotion (standard: 169±59µm, oversized: 187±52µm, P = 0.506, Power = 0.094,). Short stem diametral sizing (i.e., thickness) has an impact on stem subsidence and micromotion following humeral arthroplasty. In both cases, the resulting three-dimensional stem micromotion exceeded, the 150µm limit suggested for bone ingrowth, although that limit was derived from a uniaxial assessment. Though not statistically significant, the increased stem micromotion associated with stem oversizing may in-part be attributed to over-compacting the cancellous bed during broaching, which creates a denser, potentially smoother, interface, though this influence requires further assessment. The findings of the present investigation highlight the importance of proper short stem diametral sizing, as even a relatively small, 2mm, increase can negatively impact the subsidence and micromotion of the stem-bone construct. Future work should focus on developing tools and methods to support surgeons in what is currently a subjective process of stem selection

This study used model-based radiostereometric analysis (MBRSA) to compare migration of a recently introduced cementless hip stem to an established hip stem of similar design. Novel design features of the newer hip stem included a greater thickness of hydroxyapatite coating and a blended compaction extraction femoral broach. Fifty-seven patients requiring primary total hip arthroplasty (THA) were enrolled at a single centre. Patients were randomized to receive either an Avenir collarless stem and Trilogy IT cup (ZimmerBiomet) or a Corail collarless stem and Pinnacle cup (DePuy Synthes) via a posterior or lateral approach. Both stems are broach-only femoral bone preparation. RSA beads (Halifax Biomedical) were inserted into the proximal femur during surgery. Patients underwent supine RSA imaging a 6 weeks (baseline), 6, 12, and 24 months following surgery. The primary study outcome was total subsidence of the hip stem from baseline to 24 months as well as progression of subsidence between 12 and 24 months. These values were compared against published migration thresholds for well-performing hip stems (0.5mm). The detection limit, or precision, of MBRSA was calculated based on duplicate examinations taken at baseline. Patient reported outcome measures were collected throughout the study and included the Oxford-12 Hip Score (OHS), EuroQoL EQ-5D-5L, Hip Osteoarthritis Score (HOOS) as well as visual analogue scales (VAS) for thigh pain and satisfaction. Analysis comprised of paired and unpaired t-tests with significance set at p≤0.05. Forty-eight patients (30 males) were included for analysis; 7 patients received a non-study hip stem intra-operatively, 1 patient suffered a traumatic dislocation within three weeks of surgery, and 1 patient died within 12 months post-surgery. RSA data was obtained for 45 patients as three patients did not receive RSA beads intra-operatively. Our patient cohort had a mean age of 65.9 years (±;7.2) at the time of surgery and body mass index of 30.5 kg/m2 (±;5.2). No statistical difference in total stem migration was found between the Avenir and Corail stems at 12 months (p=0.045, 95%CI: −0.046 to 0.088) and 24 months (p=0.936, 95% CI: −0.098 to 0.090). Progression of subsidence from 12-24 months was 0.011mm and 0.034mm for the Avenir and Corail groups which were not statistically different (p=0.163, 95%CI: −0.100 to 0.008) between groups and significantly less than the 0.5mm threshold (pNo statistically significant differences existed between study groups for any pre-operative function scores (p>0.05). All patients showed significant functional improvement from pre- to post-surgery and no outcome measures were different between study groups with exception of EQ-5D-5L health visual analogue scale at 12 months which showed marginally superior (p=0.036) scores in the Avenir group. This study was not powered to detect differences in clinical outcomes. This study has demonstrated no statistical difference in subsidence or patient-reported outcomes between the Corail hip stem and the more recently introduced Avenir hip stem. This result is predictable as both stems are of a triple-tapered design, are coated with hydroxyapatite, and utilize a broach-only bone preparation technique. Both stem designs demonstrate migration below 0.5mm suggesting both are low-risk for aseptic loosening in the long-term

Clinical success of prostheses in joint arthroplasty is ultimately determined by survivorship and patient satisfaction. The purpose of this study was to compare (non-inferiority) a new morphometric designed stem for total hip arthroplasty (THA) against an established comparator. A prospective randomised multi-centre study of 144 primary cementless THA performed by nine experienced orthopaedic surgeons was completed (70 received a fully coated collarless tapered stem and 74 received a morphometric designed proximally coated tapered stem). PROMs and blood serum markers were assessed preoperatively and at intervals up to 2-years postoperatively. In addition, measures of femoral stem fit, fill and subsidence at 2-years post-operatively were measured from radiographs by three observers, with an intra-class correlation coefficient of 0.918. A mixed effects model was employed to compare the two prosthesis over the study period. A p-value <0.05 was considered statistically significant. Demographics, Dorr types and blood serum markers were similar between groups. Both stems demonstrated a significant improvement in PROMs between the pre- and post-operative measurements, with no difference at any timepoint (p > 0.05). The fully coated tapered collarless femoral stem had a non-significantly higher intra-operative femoral fracture rate (5.8% vs 1.4%, p = 0.24), with all patients treated with cable fixation and partial weight bearing. The mean subsidence at 2-years was 2.5mm +/- 2.3mm for the morphometric stem and 2.4mm +/- 1.8mm for the fully coated tapered collarless femoral stem (p = 0.879). There was one outlier in each group with increased subsidence (fully coated tapered collarless femoral stem 6.9mm, morphometric wedge stem 7.4mm), with both patients reporting thigh pain at 2 years. When compared with an established stem, the newer designed morphometric wedge stem performed well with comparable radiological and PROM outcomes at 2 year follow up. Continued follow-up is required for long term benchmarking

Clinical success of prostheses in joint arthroplasty is ultimately determined by survivorship and patient satisfaction. The purpose of this study was to compare (non-inferiority) a new morphometric designed stem for total hip arthroplasty (THA) against an established comparator. A prospective randomised multi-centre study of 144 primary cementless THA performed by nine experienced orthopaedic surgeons was completed (70 received a fully coated collarless tapered stem and 70 received a morphometric designed proximally coated tapered stem). PROMs and blood serum markers were assessed preoperatively and at intervals up to 2-years postoperatively. In addition, measures of femoral stem fit, fill and subsidence at 2-years post-operatively were measured from radiographs by three observers, with an intra-class correlation coefficient of 0.918. A mixed effects model was employed to compare the two prostheses over the study period. A p-value <0.05 was considered statistically significant. Demographics and Dorr types were similar between groups. Both stems demonstrated a significant improvement in PROMs between the pre- and post-operative measurements, with no difference at any timepoint (p > 0.05). The fully coated tapered collarless femoral stem had a non-significantly higher intra-operative femoral fracture rate (5.8% vs 1.4%, p = 0.24), with all patients treated with cable fixation and partial weight bearing. The mean subsidence at 2-years was 2.5mm +/- 2.3mm for the morphometric stem and 2.4mm +/- 1.8mm for the fully coated tapered collarless femoral stem (p = 0.879). There was one outlier in each group with increased subsidence (fully coated tapered collarless femoral stem 6.9mm, morphometric wedge stem 7.4mm), with both patients reporting thigh pain at 2 years. When compared with an established stem, the newer designed morphometric wedge stem performed well with comparable radiological and PROM outcomes at 2 year follow up. Continued follow-up is required for long term benchmarking

Introduction. Comparative studies examining Fixed-Bearing (FB) and Mobile-Bearing (MB) Total Ankle Replacement (TAR) designs have demonstrated similar results and successful long-term outcomes for both. To date there has been no study directly comparing FB and MB designs of the same prosthesis. We present the first prospective randomised trial comparing patient satisfaction, functional outcomes and radiographic results of the Salto Talaris Fixed-Bearing and the Salto Mobile-Bearing Total Ankle Replacement in the treatment of end-stage ankle arthritis. Methods. A total of 108 adult patients with end-stage ankle arthritis were enrolled in the study between November 2014 and October 2021 with similar demographic comparison. Prospective patient-reported outcomes and standardised weightbearing ankle radiographs were performed preoperatively, at 6 weeks, 6 months and 12 months post-operatively, followed by yearly intervals. All surgeries were performed by a single non-design orthopaedic foot and ankle specialist with experience in over 200 Salto and Salto Talaris TAR prior to the study. Radiographs were examined independently by two clinicians. Complete patient data and radiographs were available for 103 patients with an average follow up of 2 years. Results. Both groups demonstrated statistically significant improvement from preoperative evaluation to most recent follow up with no statistically significant difference between the two groups in all outcome measures. Radiographic incidence of subchondral cyst formation was 8.9% and 38.2% for FB and MB, respectively. Talar subsidence occurred in 2.2% and 5.5% of FB and MB, respectively. Discussion. Our study demonstrates a higher than previously reported rate of cyst formation in the MB TAR and comparatively higher talar subsidence in the MB TAR vs FB however this did not correlate with clinical outcome measures which were favourable for both groups. Conclusion. Fixed-Bearing and Mobile-Bearing Total Ankle Replacement demonstrate comparable favourable

Introduction. Femoral component loosening is one of the most common failure modes in cementless total hip arthroplasty (THA). Patient age, weight, gender, osteopenia, stem design and Dorr-C bone have all been proposed as risk factors for poor fixation and subsequent stem subsidence and poor outcome. With the increased popularity of CT-based assistive technologies in THA, (Stryker MAKO and Corin OPSTM), we sought to develop a technique to predicted femoral stem fixation using pre-operative CT. Methods. Fourteen patients requiring THA were randomly selected from a previous study investigating component alignment. Mean age was 64 (53 to 76), and 57% were female. All patients received pre-operative CT for 3D dynamic templating (OPSTM), and a TriFit stem and Trinity cup (Corin, UK) implanted through a posterior approach. Post-operatively, patients received an immediate CT and AP x-ray prior to leaving the hospital, and a 1-year follow-up x-ray. On both the immediate post-op x-ray and 1-year follow-up x-ray, the known cup diameter was used to scale the image. On both images, the distance between the most superior point of the greater trochanter and the shoulder of the stem was measured. The difference was recorded as stem subsidence. Subsidence greater than 4mm was deemed clinically relevant. The post-operative CT was used to determine the precise three-dimensional placement of the stem immediately after surgery by registering the known 3D implant geometry to the CT. For each patient, the achieved stem position from post-op CT was then virtually implanted back into the pre-operative OPSTM planning software. The software provides a colour map of the bone density at the stem/bone interface using the Hounsfield Units (HU) of each pixel of the CT [Fig. 1]. Blue represents low density bone transitioning through to green and then red (most dense). Results. Mean stem subsidence was 2.1mm (0.2mm to 11.1mm). Two patients had clinically relevant subsidence. The first stem in a 68M subsided 11.1mm. The second in a 58M subsided 5.0mm. Both density colour plots had significant areas of blue (low density bone) around the proximal portion of the stem, with minimal medium/high density fixation when compared to the stems with minimal subsidence. Discussion. Using the Hounsfield units of the CT scan as an indicator for bone density, we were able to predict poor implant fixation and subsequent subsidence in a taper wedge stem. This new technology might have pre-operative value in providing a more quantitative measure of fixation and resultant stem choice. For any figures or tables, please contact the authors directly

When removing femoral cement in revision hip surgery, creating an anterior femoral cortical window is an attractive alternative to extended trochanteric osteotomy. We describe our experience and evolution of this technique, the clinical and radiological results, and functional outcomes. Between 2006 and 2021 we used this technique in 22 consecutive cases at Whanganui Hospital, New Zealand. The average age at surgery was 74 years (Range 44 to 89 years). 16 cases were for aseptic loosening: six cases for infection. The technique has evolved to be more precise and since 2019 the combination of CT imaging and 3-D printing technology has allowed patient-specific (PSI) jigs to be created (6 cases). This technique now facilitates cement removal by potentiating exposure through an optimally sized anterior femoral window. Bone incorporation of the cortical window and functional outcomes were assessed in 22 cases, using computer tomography and Oxford scores respectively at six months post revision surgery. Of the septic cases, five went onto successful stage two procedures, the other to a Girdlestone procedure. On average, 80% bony incorporation of the cortical window occurred (range 40 −100%). The average Oxford hip score was 37 (range 22 – 48). Functional outcome (Oxford Hip) scores were available in 11 cases (9 pre-PSI jig and 2 using PSI jig). There were two cases with femoral component subsidence (1 using the PSI jig). This case series has shown the effectiveness of removing a distal femoral cement mantle using an anterior femoral cortical window, now optimized by using a patient specific jig with subsequent reliable bony integration, and functional outcomes comparable with the mean score for revision hip procedures reported in the New Zealand Joint Registry

Anterior cervical discectomy and fusion (ACDF) is a well-established spinal operation for cervical disc degeneration disease with neurological compromise. The procedure involves an anterior approach to the cervical spine with discectomy to relieve the pressure on the impinged spinal cord to slow disease progression. The prosthetic cage replaces the disc and can be inserted stand-alone or with an anterior plate that provides additional stability. The literature demonstrates that the cage-alone (CA) is given preference over the cage-plate (CP) technique due to better clinical outcomes, reduced operation time and resultant morbidity. This retrospective case-controlled study compared CA versus CP fixation used in single and multilevel anterior cervical discectomy and fusion for myelopathy in a tertiary centre in Wales. A retrospective clinico-radiological analysis was undertaken, following ACDF procedures over seven years in a single tertiary centre. Inclusion criteria were patients over 18 years of age with cervical myelopathy who had at least six-month follow-up data. SPSS was used to identify any statistically significant difference between both groups. The data were analysed to evaluate the consistency of our findings in comparison to published literature. Eighty-six patients formed the study cohort; 28 [33%] underwent ACDF with CA and 58 [67%] with CP. The patient demographics were similar in both groups, and fusion was observed in all individuals. There was no statistical difference between the two constructs when assessing subsidence, clinical complication (dysphagia, dysphonia, infection), radiological parameters and reoperations. However, a more significant percentage [43% v 61%] of patients improved their cervical lordosis angle with CP treatment. Furthermore, the study yielded that surgery to upper cervical levels results in a higher incidence of dysphagia [65% v 35%]. Finally, bony growth across the cage was observed on X-ray in 12[43%] patients, a unique finding not mentioned in the literature previously. Our study demonstrates no overall difference between the two groups, and we recommend careful consideration of individual patient factors when deciding what construct to choose

Introduction. The Oxford Unicompartmental Knee Replacement (OUKA) is the most popular unicompartmental knee replacement (UKR) in the New Zealand Joint Registry with the majority utilising cementless fixation. We report the 10-year radiological outcomes. Methods. This is a prospective observational study. All patients undergoing a cementless OUKA between May 2005 and April 2011 were enrolled. There were no exclusions due to age, gender, body mass index or reduced bone density. All knees underwent fluoroscopic screening achieving true anteroposterior (AP) and lateral images for radiographic assessment. AP assessment for the presence of radiolucent lines and coronal alignment of the tibial and femoral components used Inteliviewer radiographic software. The lateral view was assessed for lucencies as well as sagittal alignment. Results. 687 OUKAs were performed in 641 patients. Mean age at surgery was 66 years (39–90yrs), 382 in males and 194 right sided. 413 radiographs were available for analysis; 92 patients had died, 30 UKRs had been revised and 19 radiographs were too rotated to be analysed the remainder were lost to follow-up. Mean radiograph to surgery interval was 10.2 years (7.1–16.2yrs). RLLs were identified in zone 1 (3 knees), zone 2 (2 knees), zone 3 (3 knees), zone 5 (3 knees), zone 6 (2 knees) and zone 7 (42 knees). No RLL had progressed, and no case had any osteolysis or prosthesis subsidence. Alignment in the coronal plane: mean 2.90° varus (9.30° varus - 4.49° valgus) of the tibial component to the tibial anatomic axis and the femoral component in mean 4.57° varus (17.02° varus - 9.3° valgus). Sagittal plane posterior tibial slope was a mean 6.30° (0.44° -13.60° degrees) and mean femoral component flexion of 8.11° (23.70° flexion – 16.43° extension). Conclusion. The cementless OUKA demonstrates stable fixation with low revision rates at our centre supporting results earlier published by the design centre