Inverse kinematic total knee arthroplasty using conventional instrumentation restores constitutional coronal alignment.

PURPOSE: Restricted inverse kinematic alignment (iKA) is a contemporary alignment strategy for total knee arthroplasty (TKA), commonly performed with robotic assistance. While superior clinical results are reported for kinematic-type alignment strategies, registry data indicate no survivorship benefit for navigation or robotic assistance. This study aimed to determine the efficacy of an instrumented, restricted iKA technique for achieving patient-specific alignment. METHODS: Seventy-nine patients undergoing 84 TKAs (five bilateral procedures) using an iKA technique were included for preoperative and postoperative lower limb alignment analysis. The mean age was 66.5 (range: 43-82) with 33 male and 51 female patients. Artificial intelligence was employed for radiographic measurements. Alignment profiles were classified using the Coronal Plane Alignment of the Knee (CPAK) system. Preoperative and postoperative alignment profiles were compared with subanalyses for preoperative valgus, neutral and varus profiles. RESULTS: The mean joint-line convergence angle (JLCA) reduced from 2.5° to -0.1° postoperatively. The mean lateral distal femoral angle (LDFA) remained unchanged postoperatively, while the mean medial proximal tibial angle (MPTA) increased by 2.5° (p = 0.001). By preservation of the LDFA and restoration of the MPTA, the mean hip knee ankle angle (HKA) moved through 3.5° varus to 1.2° valgus. The CPAK system was used to visually depict changes in alignment profiles for preoperative valgus, neutral and varus knees; with 63% of patients observing an interval change in classification. CONCLUSION: Encouraged by the latest evidence supporting both conventional instrumentation and kinematic-type TKA strategies, this study describes how a restricted, conventionally instrumented iKA technique may be utilised to restore constitutional lower limb alignment. LEVEL OF EVIDENCE: Level III.

Conventionally instrumented inverse kinematic alignment for total knee arthroplasty: How is it done?

Purpose: For primary total knee arthroplasty (TKA), there is an increasing trend towards patient-specific alignment strategies such as kinematic alignment (KA) and inverse kinematic alignment (iKA), which by restoring native joint mechanics may yield higher patient satisfaction rates. Second, the most recent Australian joint registry report describes favourable revision rates for conventionally instrumented TKA compared to technology-assisted techniques such as those using navigation, robotics or custom-cutting blocks. The aim of this technique article is to describe in detail a surgical technique for TKA that: (1) utilises the principles of iKA and (2) uses conventionally instrumented guided resections thereby avoiding the use of navigation, robotics or custom blocks. Methods: A TKA technique is described, whereby inverse kinematic principles are utilised and patient-specific alignment is achieved. Additionally, the patellofemoral compartment of the knee is restored to the native patellofemoral joint line. The sequenced technical note provided may be utilised for cemented or cementless components; cruciate retaining or sacrificing designs and for fixed or rotating platforms. Results: An uncomplicated, robust and reproducible technique for TKA is described. Discussion: Knee arthroplasty surgeons may wish to harness the emerging benefits of both a conventionally instrumented technique and a patient-specific alignment strategy. Level of Evidence: Level V.

Mechanical outcomes of the TFNA, InterTAN and IMHS intramedullary nailing systems for the fixation of proximal femur fractures.

INTRODUCTION: Hip fractures have become a major public health priority due to their increasing incidence. Intramedullary (IM) nailing has gained popularity as a surgical technique for managing these fractures. However, comparative studies with extramedullary devices indicate potentially increased mechanical complications associated with IM nailing. Specifically, there have been recent reports of early implant fracture associated with the TFNA system. This study compares the rate of mechanical complications between 3 implants. Secondarily, we analysed the factors associated with implant fracture and all other mechanical complications. METHODS: This retrospective study included 803 IM nails performed between 2008-2021 for the fixation of proximal femur fractures at a level 1 trauma centre. We recorded patient demographics, AO fracture classification, implant specification and intra-operative parameters such as tip-apex distance, Cleveland index, reduction quality, presence of medial calcar integrity, neck-shaft angle. The outcomes analysed included implant fracture, lag screw cut-out, >10 mm backing out, autodynamisation, periprosthetic fracture, non-union at 6 months and time to revision surgery. RESULTS: The overall implant fracture rate was 3.1 % (25/803), with no statistically significant difference between the three devices (p = 0.51). The TFNA group included 183 patients with a median follow-up of 1.6 years. The TFNA fracture rate was 2.2 % (4/183) which occurred at 207 +/- 16.66 days post-operatively. The rate of all mechanical complications was 4.9 % in the TFNA group, 12.9 % in the InterTAN group and 17 % in the IMHS group. Non-union (p < 0.001) and increasing lag screw length (p < 0.02) were identified as risk factors for implant fracture and other mechanical complications. The reverse oblique fracture pattern (AO 31 A3.1) was associated with mechanical complications only (p < 0.01). The cumulative survival rates without revision for the TFNA, InterTAN, IMHS groups were 97.8 %, 95.5 % and 87.9 % respectively at 2.5 years. DISCUSSION: The rates of implant fracture were comparable between the three nailing systems. The TFNA provides effective fixation for proximal femur fractures using a traditional screw without cement augmentation. The TFNA was associated with an overall reduction in mechanical complications compared to the InterTAN and IMHS. Previously reported mechanical complications associated with IM Nails may relate to older device designs.

Pilot study of micromotion nailing for mechanical stimulation of tibial fracture healing.

AIMS: The study objective was to prospectively assess clinical outcomes for a pilot cohort of tibial shaft fractures treated with a new tibial nailing system that produces controlled axial interfragmentary micromotion. The hypothesis was that axial micromotion enhances fracture healing compared to static interlocking. METHODS: Patients were treated in a single level I trauma centre over a 2.5-year period. Group allocation was not randomized; both the micromotion nail and standard-of-care static locking nails (control group) were commercially available and selected at the discretion of the treating surgeons. Injury risk levels were quantified using the Nonunion Risk Determination (NURD) score. Radiological healing was assessed until 24 weeks or clinical union. Low-dose CT scans were acquired at 12 weeks and virtual mechanical testing was performed to objectively assess structural bone healing. RESULTS: A total of 37 micromotion patients and 46 control patients were evaluated. There were no significant differences between groups in terms of age, sex, the proportion of open fractures, or NURD score. There were no nonunions (0%) in the micromotion group versus five (11%) in the control group. The proportion of fractures united was significantly higher in the micromotion group compared to control at 12 weeks (54% vs 30% united; p = 0.043), 18 weeks (81% vs 59%; p = 0.034), and 24 weeks (97% vs 74%; p = 0.005). Structural bone healing scores as assessed by CT scans tended to be higher with micromotion compared to control and this difference reached significance in patients who had biological comorbidities such as smoking. CONCLUSION: In this pilot study, micromotion fixation was associated with improved healing compared to standard tibial nailing. Further prospective clinical studies will be needed to assess the strength and generalizability of any potential benefits of micromotion fixation. Cite this article: Bone Jt Open 2021;2(10):825-833.

Nontraumatic Tibial Polyethylene Insert Cone Fracture in Rotating-Platform Total Knee Arthroplasty.

We report a case of a fracture through the polyethylene (PE) insert cone in a rotating-platform (RP) primary total knee arthroplasty (TKA) implant. This is the first reported case of cone fracture with this particular implant. This case highlights a 65-year-old female presenting with a 4-month history of knee pain and symptoms of instability 10 years after primary RP TKA. At the time of revision surgery, the PE insert cone was found to be fractured 10 mm from the inferior surface of the PE liner. Analysis suggests that the cone fracture occurred by fatigue failure which caused loosening of the tibial tray. Clinicians should be aware that this is a potential cause of failure with an RP TKA in the setting of symptoms including instability and pain.

The decline of hip fracture incidence rates over a 10-year period: A single centre experience.

AIMS: Accurate epidemiological hip fracture data is essential for healthcare planning and targeted prevention strategies. Limited reports of hip fracture incidence rates in the Republic of Ireland (ROI) exist. The aim is to calculate the current age- and gender-specific incidence of hip fractures in a level 1 Trauma Centre in the ROI, and the difference in these rates over a 10 year period. MATERIALS AND METHODS: This was a retrospective, population-based, observational study. The local Hospital In-Patient Enquiry (HIPE) database was used to generate data for analysis; capturing all patients admitted for hip fracture in three time periods over 10 years. Patients < 55 years old, pathological fractures, and periprosthetic fractures were excluded. Age- and gender-specific incidence rate was calculated using HIPE and national census data. RESULTS: Absolute number of hip fractures rose by 8.5% between 2008/09 (n = 800) and 2018/19 (n = 868) time periods. Cervical hip fractures dominated in all 3 time periods. The average age of patients remained at 80 years but length of stay for patients was reduced by 16% 5 years later and by 21% 10 years later from the initial study point. Both the entire and susceptible (> 55 years) population numbers increased by 13% and 30%, respectively, yet overall hip fracture incidence rate declined 10 years on. Hip fracture incidence rate in the entire population fell by 3.23 per 100,000 population, and by 65.11 per 100,000 population in the susceptible population. The majority of both male and female age groups exhibited declining annual incidence rates over the 10 year study period. CONCLUSION: Results are consistent with the global experience of declining overall incidence rate of hip fractures, despite rising susceptible population numbers. This report adds to the sparse hip fracture incidence data available in the ROI which can be applied in future healthcare planning strategies.

Trabecular Metal Augments for Severe Acetabular Defects in Revision Hip Arthroplasty: A Long-Term Follow-Up.

BACKGROUND: Paprosky type IIIa and IIIb acetabular defects remain technically challenging during revision hip arthroplasty. Numerous surgical options exist to counter extensive acetabular bone loss with high postoperative complication and revision rates reported. Our aim was to report comprehensive long-term outcomes of our experience with Trabecular Metal (TM) augments for these difficult cases. METHODS: 38 patients underwent revision total hip arthroplasty at our institution from 2009 to 2014 where a TM augment was used for acetabular deficiency. Prospective radiographic and Patient-Reported Outcome Measures were recorded and analyzed to a mean of 7.3 years (range: 5.4 to 10.8). RESULTS: No patient was excluded or lost to follow-up. Complications included 3 intraoperative fractures, 1 early infection requiring washout with implant retention, 1 early revision due to allograft resorption, and 6 patients who required late repeat revision surgery: 3 for late infection, 2 for aseptic loosening with augment fracture or dislocation, and 1 for recurrent dislocation. The estimated mean implant survivorship was 8.99 years. 93.5% of augments remaining were well osseointegrated while 97% of the acetabular shells were osseointegrated. Hip center of rotation was restored by a mean of 14 mm inferiorly without significant medialization. Short Form-12 (SF-12) and Western Ontario and McMaster Universities Arthritis Index (WOMAC) scores were significantly reduced postoperatively to a level comparable to the average individual. CONCLUSION: This long-term study details our experience of TM augments for the most severe acetabular defects. For such cases, no excellent surgical solution exists; in comparison to alternative methods, we advocate that this technique is reasonably safe and effective.

Patellar stabilization surgeries in cases of recurrent patellar instability: a retrospective clinical and radiological audit.

BACKGROUND: Patellar instability is a disabling condition that limits the functional ability and physical aspirations of patients. There are multiple anatomical structures which stabilize the patella and surgical treatment is tailored to repair the underlying aetiology. AIMS: To evaluate the clinical and radiological outcome of patellar stabilization procedures in patients with recurrent patellar instability. METHODS: We analysed 34 patients (36 knees) (mean age, 26.6) with recurrent patellar instability who underwent patellar stabilization surgery from June 2009 to September 2014. Type of procedure was dependent on the concomitant aetiological factors; tibial tuberosity osteotomy (61.76%), medial patellofemoral ligament reconstruction (67.64%), lateral release (5.88%) and trochleoplasty (2.94%). Mean follow-up was 3 years (range 9 months-6 years). RESULTS: At follow-up, 77% of patients were satisfied with the overall outcome of the procedure. The mean IKDC was 66.7, Lysholm 74.9. Mean patellar height decreased significantly (P < .05) to anatomical values. Pre-operatively, the mean tibial tuberosity-trochlear groove distance was 14.66 mm (55.6% at borderline/abnormal level) and 81% showed evidence of trochlear dysplasia. Complications were found in 3 patients (8.33%), 2 of which had further episodes of instability. CONCLUSIONS: Patellar stabilization surgery is an effective method of treating patellar instability, resulting in stability of the knee in 94.4%. Despite this, patient dissatisfaction rates are quite high suggesting that this patient group, whilst mostly stable, remains significantly symptomatic from their knee. These positive results which are reflected in the recent literature represent a strong case for consideration of primary surgical stabilization in cases of patellar instability.

Pediatric Trauma and the COVID-19 Pandemic: A 12-Year Comparison in a Level-1 Trauma Center.

BACKGROUND: The effect of COVID-19 on pediatric trauma rates is still largely under investigation. With the potential need to reallocate human and financial resources at this challenging time, it will be useful to have detailed descriptions of the rates of pediatric trauma and understanding of how the pandemic affects these rates. QUESTIONS/PURPOSES: We sought to describe the effect of the COVID-19 pandemic on the number of acute pediatric trauma admissions and procedures performed in a level-I trauma center in Cork University Hospital, Ireland. METHODS: We compared the number of acute traumatic pediatric admissions and procedures that occurred during the first 4 weeks of a nationwide lockdown due to COVID-19 with that of the same 4-week period in each of the preceding 11 years. Seasonal variables were measured and controlled for using multivariate regression analysis. RESULTS: A total of 545 pediatric patients (under 16 years of age) were included. Over 12 years, the lowest number of acute traumatic pediatric admissions and procedures was recorded during the 2020 pandemic. There was a significant correlation between the number of school days and the number of acute traumatic admissions, as well as the procedures performed. The relationship between the number of school days and the number of trauma procedures was evident even when controlling for confounder variables of seasonal variation. CONCLUSION: The COVID-19 pandemic significantly reduced the number of acute traumatic pediatric admissions and procedures performed in our level-I trauma center, likely because of a reduction in school days. With the reopening of schools, playgrounds, and sporting events, an increase in pediatric trauma admissions is anticipated. The results of this study can help prepare institutions and regulatory bodies to plan appropriately for this new phase.

Polyethylene spinout in the Attune® Cruciate-Retaining Rotating-Platform (CR RP) total knee arthroplasty performed with a cruciate-sacrificing and measured-resection technique.

INTRODUCTION: Polyethylene (PE) spinout is a known but uncommon complication when using a mobile-bearing (MB) total knee arthroplasty (TKA) design. Sacrificing the posterior cruciate ligament (PCL) is within the manufacturer's recommendations for the Attune® Cruciate-Retaining Rotating-Platform (CR RP) knee design. AIM: To discuss the potential aetiology and prevention of spinout in the Attune® CR RP knee. METHODS: We used a retrospective radiological review from two centres reporting a higher rate of spinout in the Attune® CR RP knee using a cruciate-sacrificing and measured-resection technique when compared to a gap-balancing technique. Three hundred and thirty-two patients were evaluated over a 3-year period. RESULTS: There were 8 out of 279 (2.86%) cases of spinout in our first cohort of patients using a measured-resection technique. There were 0 out of 53 cases of spinout in our second cohort of patients where a gap-balancing technique was used. One spinout was reduced closed, the other seven were initially revised to a thicker RP insert of the same design. Of these seven, three underwent a further revision TKA and one patient required a knee fusion/arthrodesis. CONCLUSIONS: This study reports a higher incidence of PE spinout in the Attune® CR RP TKA when a measured-resection technique in combination with PCL resection is performed. We recommend a gap-balancing technique with conservative soft-tissue release if the surgeon is planning to sacrifice the PCL in the Attune® CR RP.

Follow-up study on transphyseal ACL reconstruction in Irish adolescents with no cases of leg length discrepancy or angular deformity.

BACKGROUND: The rate of ACL injury in adolescents has been rising in recent years. Surgical options include transphyseal and physeal-sparing ACL reconstruction. AIMS: In this study, we performed a transphyseal ACL reconstruction and followed up patients to assess functional outcomes and to assess for growth disturbance. METHOD: There were 22 patients seen at follow-up between the age of 12 and 16. Skeletal age assessment was performed using an MRI atlas with an average skeletal age of 14.7 (range 12-16). The mean follow-up time was 36 months (range 14-63 months). Clinical examination was performed to assess for leg length discrepancy, and leg length radiographs were used to assess for angular deformity. Patients' post-surgery functionality was assessed with the IKDC score and the Tegner Lysholm score. RESULTS: The mean IKDC and Lysholm scores at follow-up were found to be 91 and 94, respectively. The median Tegner score prior to injury was 8.5 and postoperatively was 7.5. There were no cases of leg length discrepancy found on clinical examination, and there were no cases of significant angular deformity. Four patients ruptured again and went on to have repeat ACL reconstruction. CONCLUSIONS: Midterm results at an average follow-up of 3 years after the surgery showed good functional outcomes using the transphyseal ACL reconstruction technique with good return to activity. There were no cases of leg length discrepancy or angular deformity. Transphyseal ACL reconstruction is a viable method of treatment for adolescent ACL tears.

Bicortical Contact Predicts Subsidence of Modular Tapered Stems in Revision Total Hip Arthroplasty.

BACKGROUND: We describe the intraoperative parameters that affect stem subsidence rates in tapered modular femoral stems for revision total hip arthroplasty (THA). We also determine the effect of the stem bicortical contact on subsidence rates and whether there is a minimum threshold bicortical contact that must be achieved to avoid the complication of subsidence. METHODS: This is a retrospective cohort study consisting of 109 hips in 105 patients (53 males and 52 females) at a minimum of 2 years of follow-up. All revisions were carried out for Paprosky type 3A and 3B femoral deficits. Clinical outcomes included the indication for revision, aseptic re-revision surgery, specifications of the stem inserted, and specifications of the femoral head and acetabular components implanted. Radiographic outcome measures included subsidence (mm) and bicortical contact (mm). RESULTS: Using multivariate regression analysis, 3 parameters were associated with an increased rate of stem subsidence. A reduced bicortical contact distance (P < .001) and a stem length of ≤155 mm (P < .001) were both associated with higher subsidence rates. We also demonstrated a novel threshold of 20-mm bicortical contact which must be achieved to significantly reduce subsidence rates in these modular femoral stems for revision THA. CONCLUSION: Subsidence rates of modular tapered femoral stems for revision THA can be significantly reduced by increasing the initial bicortical contact of the stem within the diaphysis and the overall length of the femoral stem >155 mm. We describe a minimum threshold bicortical contact distance of 20 mm that should ideally be exceeded to significantly reduce the risk of stem subsidence within the femoral canal.

Arthroplasty and global research output: A bibliometric analysis.

INTRODUCTION: Peer-reviewed research helps to advance many aspects of medical and surgical practice. This paper determines the main contributors tos joint arthroplasty research in terms of quantity and quality. METHODS: A search of the Web of Science™ platform was conducted to identify arthroplasty articles published between 2001 and 2016. The number of articles and citations per article were analysed to assess the quantity and quality of research from individual countries. Results were standardised according to the country's populations and Gross Domestic Product (GDP). RESULTS: In total, 43,470 arthroplasty articles were published worldwide from January 2001 through December 2016. There was a 4.5-fold increase in global output during this time period. Twenty-two countries contributed at least 1% to the total number of publications. The United States of America published the most articles (35.40%), followed by England (10.31%) and Germany (10.03%). The USA had the highest absolute number of citations (50,777). Denmark had the highest average citation per item (8.76). When number of articles was normalized to population, Switzerland ranked the highest. When adjusted by GDP, Scotland ranked highest. When standardised according to GDP per capita, the People's Republic of China rated highest. The Journal of Arthroplasty produced the highest number of publications related to arthroplasty with 10.9% of total volume. CONCLUSION: There has been a substantial increase in worldwide publications relating to arthroplasty. The USA has produced the largest volume whilst Denmark has produced the highest quality publications. When output was normalized according to population and GDP, Switzerland and Scotland ranked highest.

Virtual Mechanical Testing Based on Low-Dose Computed Tomography Scans for Tibial Fracture: A Pilot Study of Prediction of Time to Union and Comparison with Subjective Outcomes Scoring.

BACKGROUND: Quantitative outcomes assessment remains a persistent challenge in orthopaedic trauma. Although patient-reported outcome measures (PROMs) and radiographic assessments such as Radiographic Union Scale for Tibial Fractures (RUST) scores are frequently used, very little evidence has been presented to support their validity for measuring structural bone formation or biomechanical integrity. METHODS: In this pilot study, a sequential cohort of patients with a tibial shaft fracture were prospectively recruited for observation following standard reamed intramedullary nailing in a level-I trauma center. Follow-up at 6, 12, 18, and 24 weeks included radiographs and completion of PROMs (EuroQol 5-Dimension [EQ-5D] and pain scores). Low-dose computed tomography (CT) scans were also performed at 12 weeks. Scans were reconstructed in 3 dimensions (3D) and subjected to virtual mechanical testing via the finite element method to assess torsional rigidity in the fractured limb relative to that in the intact bone. RESULTS: Patients reported progressive longitudinal improvement in mobility, self-care, activity, and health over time, but the PROMs were not correlated with structural bone healing. RUST scoring showed moderate intrarater agreement (intraclass coefficient [ICC] = 0.727), but the scores at 12 weeks were not correlated with the time to union (R = 0.104, p = 0.193) and were only moderately correlated with callus structural integrity (R = 0.347, p = 0.010). In contrast, patient-specific virtual torsional rigidity (VTR) was significantly correlated with the time to union (R = 0.383, p = 0.005) and clearly differentiated 1 case of delayed union (VTR = 10%, union at 36 weeks) from the cases in the normally healing cohort (VTR > 60%; median union time, 19 weeks) on the basis of CT data alone. CONCLUSIONS: PROMs provide insight into the natural history of the patient experience after tibial fracture but have limited utility as a measure of structural bone healing. RUST scoring, although reproducible, may not reliably predict time to union. In contrast, virtual mechanical testing with low-dose CT scans provides a quantitative and objective structural callus assessment that reliably predicts time to union and may enable early diagnosis of compromised healing. LEVEL OF EVIDENCE: Therapeutic Level IV. Please see Instructions for Authors for a complete description of levels of evidence.

Virtual structural analysis of tibial fracture healing from low-dose clinical CT scans.

Quantitative assessment of bone fracture healing remains a significant challenge in orthopaedic trauma research. Accordingly, we developed a new technique for assessing bone healing using virtual mechano-structural analysis of computed tomography (CT) scans. CT scans from 19 fractured human tibiae at 12 weeks after surgery were segmented and prepared for finite element analysis (FEA). Boundary conditions were applied to the models to simulate a torsion test that is commonly used to access the structural integrity of long bones in animal models of fracture healing. The output of each model was the virtual torsional rigidity (VTR) of the healing zone, normalized to the torsional rigidity of each patient's virtually reconstructed tibia. This provided a structural measure to track the percentage of healing each patient had undergone. Callus morphometric measurements were also collected from the CT scans. Results showed that at 12 weeks post-op, more than 75% of patients achieved a normalized VTR (torsional rigidity relative to uninjured bone) of 85% or above. The predicted intact torsional rigidities compared well with published cadaveric data. Across all patients, callus volume and density were weakly and non-significantly correlated with normalized VTR and time to clinical union. Conversely, normalized VTR was significantly correlated with time to union (R2 = 0.383, p = 0.005). This suggests that fracture scoring methods based on the visual appearance of callus may not accurately predict mechanical integrity. The image-based structural analysis presented here may be a useful technique for assessment of bone healing in orthopaedic trauma research.

Acetabular Revision Using Trabecular Metal Augments for Paprosky Type 3 Defects.

BACKGROUND: Trabecular Metal (TM) augments are one option when reconstructing bone loss during acetabular side revision surgery. METHODS: We studied 38 consecutive patients with Paprosky type 3 defects that were revised using a TM shell and one or more augments over a 6-year period. There were 29 Paprosky type 3A defects and 9 Paprosky type 3B defects. The mean age of the patients at the time of surgery was 68.2 years (range 48-84). The mean length of follow-up was 36 months (range 18-74). RESULTS: The mean preoperative short form 12 health survey improved from 27.7 before operation to 30.1 at the time of final follow-up (P = .001). The mean Western Ontario and McMaster Universities Osteoarthritis Index score improved from 53 preoperatively to a mean of 78.8 at final follow-up (P < .0001). There was evidence of radiographic loosening in 7 of the cup-augment constructs. One patient developed a deep infection requiring re-revision. Two patients required revision for aseptic loosening. CONCLUSION: The use of TM in complex acetabular reconstruction is associated with good outcome in the short to medium term.

The impact of trabecular metal on hip centre of rotation in revision and complex primary hip arthroplasty, a radiological review.

INTRODUCTION: Total hip arthroplasty (THA) is a very successful procedure. Revision THA is becoming increasingly common. Recent developments to improve outcomes include the development of large trabecular metal (TM) acetabular cups and augments. There is a paucity of data on the benefit of these new techniques. METHODS: A single-centre retrospective review consisting of a radiological review of post-op revision THA anteroposterior pelvis. Data collection was performed using the Irish National Orthopaedic Register (INOR) and from a previous project. We used a technique developed by Fessy et al in 1999 to measure the centre of rotation (COR) of the hip. We then compared our study to that of a study measuring the COR of healthy native hips. RESULTS: 127 revision THA analysed. Native COR calculated by Fessy et al showed a mean horizontal (x) axis 33.6 mm (standard deviation [SD] 5.74) and a vertical (y) axis 16.4 mm (SD 4.67). Non-TM revisions showed a mean x axis of 29 mm (SD 3.9) and y axis 17.9 (SD 5.9). TM Augments had a mean x axis 29.2 mm (SD 7.9) and y axis of 21.5 (SD 8.4). TM Cups alone had a mean x axis 27 mm (SD 6.9) and y axis 22 mm (SD 10.18). CONCLUSIONS: COR of TM implants showed considerable deviation from the norm. Non-TM implants showed a COR within acceptable physiological range. TM components consistently failed to restore a natural COR in our cohort. The implications of this remain uncertain but must be considered in any decision to use TM.

Role of the fibula in the stability of diaphyseal tibial fractures fixed by intramedullary nailing.

BACKGROUND: For tibial fractures, the decision to fix a concomitant fibular fracture is undertaken on a case-by-case basis. To aid in this clinical decision-making process, we investigated whether loss of integrity of the fibula significantly destabilises midshaft tibial fractures, whether fixation of the fibula restores stability to the tibia, and whether removal of the fibula and interosseous membrane for expediency in biomechanical testing significantly influences tibial interfragmentary mechanics. METHODS: Tibia/fibula pairs were harvested from six cadaveric donors with the interosseous membrane intact. A tibial osteotomy fracture was fixed by reamed intramedullary (IM) nailing. Axial, torsion, bending, and shear tests were completed for four models of fibular involvement: intact fibula, osteotomy fracture, fibular plating, and resected fibula and interosseous membrane. FINDINGS: Overall construct stiffness decreased slightly with fibular osteotomy compared to intact bone, but this change was not statistically significant. Under low loads, the influence of the fibula on construct stability was only statistically significant in torsion (large effect size). Fibular plating stiffened the construct slightly, but this change was not statistically significant compared to the fibular osteotomy case. Complete resection of the fibula and interosseous membrane significantly decreased construct torsional stiffness only (large effect size). INTERPRETATION: These results suggest that fixation of the fibula may not contribute significantly to the stability of diaphyseal tibial fractures and should not be undertaken unless otherwise clinically indicated. For testing purposes, load-sharing through the interosseous membrane contributes significantly to overall construct mechanics, especially in torsion, and we recommend preservation of these structures when possible.

Automated measurement of fracture callus in radiographs using portable software.

The development of software applications that assist the radiographic evaluation of fracture healing could advance clinical diagnosis and expedite the identification of effective treatment strategies. A radiographic feature regularly used as an outcome measure for basic and clinical fracture healing research is new bone growth, or fracture callus. In this study, we developed OrthoRead, a portable software application that uses image-processing algorithms to detect and measure fracture callus in plain radiographs. OrthoRead utilizes an optimal boundary tracking algorithm to semi-automatically segment the cortical surface, and a novel iterative thresholding selection algorithm to then automatically segment the fracture callus. The software was validated in three steps. First, algorithm accuracy and sensitivity were analyzed using surrogate models with known callus size. Second, the callus area of distal femur fractures measured using OrthoRead was compared to callus area manually outlined by orthopaedic surgeons. Third, the callus area of ovine tibial fractures was measured using OrthoRead and compared to callus volume measured from micro-CT. The software had less than a 5% error in measuring surrogate callus, and was insensitive to changes in image resolution, image rotation, and the size of the analyzed region of interest. Strong positive correlations existed between OrthoRead and clinicians (R(2) = 0.98), and between 2D callus area and 3D callus volume (R(2) = 0.70). The average run time for OrthoRead was 3 s when using a 2.7 GHz processor. By being accurate, fast, and robust, OrthoRead can support prospective and retrospective clinical studies investigating implant efficacy, and can assist research on fracture healing mechanobiology. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1224-1233, 2016.