A Polished Cobalt-Chrome Baseplate is not Associated With a Lower Revision Rate Than Matt Titanium in a Single Total Knee Arthroplasty Implant System With Identical Baseplate Design.

BACKGROUND: Polished baseplates were introduced into total knee arthroplasty (TKA) systems to reduce the incidence of backside wear. In 2004, a fixed-bearing knee arthroplasty system underwent a change in baseplate material from matt titanium to polished cobalt-chrome (CoCr) with the intention to reduce backside wear. Other design aspects were left unchanged. The aim of this study was to compare these implants with each baseplate using data from the Australian Orthopaedic Association National Joint Replacement Registry. METHODS: Primary TKA procedures performed between January 2010 and December 2021 for osteoarthritis, using a single design with cross-linked polyethylene inserts and matt titanium or polished CoCr baseplates, were analyzed. The primary outcome was all-cause revision, summarized using Kaplan-Meier estimates, with age- and sex-adjusted hazard ratios estimated from Cox proportional hazards models. In total, there were 2,091 procedures with matt titanium and 2,519 procedures with polished CoCr baseplates. RESULTS: The 9-year cumulative percent revision was 2.5% (95% confidence interval [CI] 1.8 to 3.5%) and 4.2% (95% CI 3.1 to 5.6%) for the matt titanium and CoCr groups, respectively. Compared to matt titanium, the revision rate of CoCr baseplates was not significantly higher (hazard ratio 1.44; 95% CI 0.96 to 2.15; P = .076). CONCLUSIONS: Polished CoCr baseplates in a single TKA system were not associated with reduced all-cause revision rates compared to matt titanium up to 11 years post-TKA. Our results suggest that the predicted reduction in wear particle debris production from polished CoCr baseplates may not correlate with reduced revision rates in vivo, but further evaluation is required.

Atypical femur fractures associated with bisphosphonate therapy: post-operative outcomes.

PURPOSE: Bisphosphonates are commonly used medication for the treatment of osteoporosis, and a well-established complication of this medication is bisphosphonate-associated atypical femur fractures (BAAFFs). The aim of this study was to assess the post-operative functional and radiographic outcomes of surgically treated BAAFFs. METHODS: An analysis of patients treated at a university-affiliated institution was performed. Patients who had undergone surgical fixation for a subtrochanteric or shaft of femur fracture which had been classified as atypical and treated with bisphosphonate therapy at the time of fracture were included. The outcome measures assessed included post-operative complications, length of stay, discharge destination, post-operative function, independence in activities of daily living (ADLs) and fracture union. RESULTS: Twenty patients were included in this study with a mean age of 75.2 years. The cohort was predominantly female. The average duration of bisphosphonate therapy was 7.35 years. Nine patients had contralateral bisphosphonate-related stress reactions at the time of their initial fracture and underwent prophylactic surgical intervention. The majority of patients received cephalomedullary nail fixation (95%) with more than half (65.0%) of the cohort experiencing one or more post-operative complications. The median length of stay was 6.5 days and 50% of the cohort required inpatient rehabilitation. At final review, independent mobilisation was recorded in only 10.0% of patients, and 70% of patients were dependent with their ADLs at their latest follow-up. Average follow-up was 8 months, and only six cases demonstrated union at the six-month review, with delayed union between 9 and 12 months being common. CONCLUSION: Patients with BAAFFs experience high rates of complications, record poor post-operative functional outcomes, and demonstrate a delayed time to union. Nearly half of our cohort had radiographic evidence of bilateral pathology.

Radiolucent line assessment in cemented stemmed total knee (RISK) arthroplasty: validation of a modernized classification system.

BACKGROUND: This study aims to implement and assess the inter- and intra-reliability of a modernized radiolucency assessment system; the Radiolucency In cemented Stemmed Knee (RISK) arthroplasty classification. Furthermore, we assessed the distribution of regions affected by radiolucency in patients undergoing stemmed cemented total knee arthroplasty. METHODS: Stemmed total knee arthroplasty cases over 7-year period at a single institution were retrospectively identified and reviewed. The RISK classification system identifies five zones in the femur and five zones in the tibia in both the anteroposterior (AP) and lateral planes. Post-operative and follow-up radiographs were scored for radiolucency by four blinded reviewers at two distinct time points four weeks apart. Reliability was assessed using the kappa statistic. A heat map was generated to demonstrate the reported regions of radiolucency. RESULTS: 29 cases (63 radiographs) of stemmed total knee arthroplasty were examined radiographically using the RISK classification system. Intra-reliability (0.83) and Inter-reliability (0.80) scores were both consistent with a strong level of agreement using the kappa scoring system. Radiolucency was more commonly associated with the tibial component (76.6%) compared to the femoral component (23.3%), and the tibial anterior-posterior (AP) region 1 (medial plateau) was the most affected (14.9%). CONCLUSION: The RISK classification system is a reliable assessment tool for evaluating radiolucency around stemmed total knee arthroplasty using defined zones on both AP and lateral radiographs. Zones of radiolucency identified in this study may be relevant to implant survival and corresponded well with zones of fixation, which may help inform future research.

Is the Survivorship of Birmingham Hip Resurfacing Better Than Selected Conventional Hip Arthroplasties in Men Younger Than 65 Years of Age? A Study from the Australian Orthopaedic Association National Joint Replacement Registry.

BACKGROUND: The Birmingham Hip Resurfacing (BHR) prosthesis is the most commonly used metal-on-metal hip resurfacing arthroplasty device. The current manufacturer-recommended target demographic for the BHR is male patients, younger than 65 years requiring a femoral head size of ≥ 50 mm. Female patients, older patients, and individuals with smaller femoral-head diameter (≤ 50 mm) are known to have higher revision rates. Prior studies suggest that the survivorship of the BHR when used in the target demographic is comparable with that of primary conventional THA, but comparing survivorship of the most durable hip resurfacing arthroplasty device to the survivorship of all conventional THA prostheses is not ideal because the THA group comprises a large number of different types of prostheses that have considerable variation in prosthesis survival. A more informative comparison would be with the THA implants with the best survivorship, as this might help address the question of whether survivorship in the BHR target population can be improved by using a well-performing conventional THA. QUESTIONS/PURPOSES: We compared the difference in cumulative percent revision, reasons for revision and types of revision for procedures reported to the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) using the BHR prosthesis (femoral-head size > 50 mm) and three conventional THA prostheses identified as having the lowest 10-year cumulative percent revision in the currently recommended BHR target population to ask: (1) Does the BHR have a lower cumulative revision rate than the group of three conventional THA prostheses? (2) Is there a difference in the revision diagnosis between the BHR and the three best conventional THA prostheses? (3) What is the difference in the components used for a revision of a BHR compared with the three best conventional THA prostheses? METHODS: Data reported to the AOANJRR between September 1, 1999 and December 31, 2018 was used for this analysis. This study period includes almost the entire use of the BHR in Australia. The AOANJRR is a large national joint registry with almost 100% completeness, high accuracy, rigorous validation, and little to no loss to follow-up. The study population included males younger than 65 years that had received one hip replacement procedure for osteoarthritis. All patients with bilateral procedures, no matter the time interval between hips, were excluded. Only BHR prostheses with a femoral-head size ≥ 50 mm and conventional THA prostheses with femoral head sizes ≥ 32 mm and either ceramic-on-ceramic or metal, ceramic, ceramicized metal-on-crosslinked polyethylene (XLPE) bearings were included. These femoral head sizes and bearings were selected because they reflect modern conventional THA practice. There is no difference in the revision rate of these bearings in the AOANJRR. There were 4790 BHR procedures and 2696 conventional THA procedures in the study group. The mean (± SD) age for BHR procedures was 52 ± 7.8 years and 56 ± 7.1 years for conventional THA procedures. All comparative analyses were adjusted for age. Other demographics data including American Society Anesthesiologists (ASA) score and BMI were only included in AOANJRR data collection since 2012 and 2015, respectively, and have not been included in this analysis because of the low use of BHR in Australia since that time. The maximum follow-up was 18.7 years for both groups and mean follow-up of 11.9 years for the BHR and 9.3 years for the conventional THA group. Revision rates were determined using Kaplan-Meier estimates of survivorship to describe the time to the first revision, with censoring at the time of death or closure of the database at the time of analysis. A revision was defined as removal, replacement or addition of any component of a joint replacement. Revisions can be further classified as major revisions (removal of a component articulating with bone-usually the stem and/or the shell) or minor revisions (removal of other components-usually the head and/or the liner). The unadjusted cumulative percent revision after the primary arthroplasty (with 95% confidence intervals) was calculated and compared using Cox proportional hazard models adjusted for age. RESULTS: The BHR prosthesis had a statistically higher rate of all-cause revision at 17 years than the selected conventional THA prostheses (HR 2.77 [95% CI 1.78 to 4.32]; p < 0.001). The revision diagnoses differed between the groups, with the BHR demonstrating a higher revision rate for loosening after 2 years than the conventional THA protheses (HR 4.64 [95% CI 1.66 to 12.97]; p = 0.003), as well as a higher fracture rate during the entire period (HR 2.57 [95% CI 1.24 to 5.33]; p = 0.01). There was a lower revision rate for infection for the BHR compared with the THA group in the first 5 years, with no difference between the two groups after this time. All revisions of the BHR were major revisions (such as, removal or exchange of the femoral and/or acetabular components) and this occurred in 4.5% of the primary BHR procedures. Major revision was the most common type of revision for primary THA accounting for 1.7% of all primary THA procedures. Minor revisions (head, inset or both) were undertaken in a further 0.6% of primary THA procedures. CONCLUSIONS: Given the increasing revision risk of the BHR compared with better-performing conventional THA prostheses in the target population, we recommend that patients be counseled about this risk. We suggest that a THA with proven low revision rates might be the better choice, particularly for patients who are concerned about implant durability. Well-controlled prospective studies that show appreciable clinically important differences in patient-reported outcomes and functional results favoring the BHR over conventional THA prostheses using modern bearings are needed to justify the use of the BHR in view of this revision risk. LEVEL OF EVIDENCE: Level III, therapeutic study.

Knee Arthroplasty Component Malrotation Does Not Affect Function or Quality of Life in the Short to Medium Term.

BACKGROUND: Component rotation in total knee arthroplasty is thought to affect patella tracking, flexion gap, and balancing and hence is hypothesized to affect function, pain, and longevity. Few studies have directly correlated post-operative component rotation to function and quality of life in the short to medium term post-operatively, with findings in the current literature conflicting. METHODS: A retrospective study of prospectively collected data was used to determine the effect of femoral, tibial, and combined component rotation in primary total knee arthroplasty with primary outcomes being function as measured by the Knee Society Score, pain and quality of life as measured by the Short-Form 12 score, and secondary outcome being prosthesis failure. Malrotation was defined using the current literature as being internally rotated from neutral, or externally rotated greater than 5° for the femoral component, internally rotated greater than 6° for the tibial component, or internally rotated from neutral for the 2 components combined. RESULTS: No clinically relevant correlation between function or quality of life and component rotation could be found at 5 years. However, it was noted that those patients with combined component malrotation (femoral rotation added to tibial rotation resulting in overall component internal rotation) improved less in overall pain scores than those that were not malrotated. CONCLUSION: In the mid-term, component malrotation may result in a decreased level of improvement from pain compared to pre-operative results. However, component malrotation does not make a significant difference to function or quality of life. LEVEL OF EVIDENCE: Level III: Therapeutic Study.

Gap Balancing Sacrifices Joint-Line Maintenance to Improve Gap Symmetry: 5-Year Follow-Up of a Randomized Controlled Trial.

BACKGROUND: Gap balancing (GB) has been noted to sacrifice joint-line maintenance to improve gap symmetry. This study aims to determine whether this change affects function or quality of life in the midterm. METHODS: A prospective blinded randomized controlled trial was completed with 103 patients randomized to measured resection (n = 52) or GB (n = 51). Primary outcome measured was femoral component rotation. Secondary outcomes measured were joint-line change, gap symmetry, and function and quality-of-life outcomes. RESULTS: At 5 years, 83 of 103 patients (85%) were assessed. There was no significant difference between groups in terms of functional or quality of life outcomes. A subgroup analysis revealed that there was no significant association between those with asymmetrical flexion and/or extension or medial and/or lateral gaps during knee replacement and subsequent functional outcomes. No significant difference was detected with those with an elevated joint line and postoperative function. CONCLUSION: In the midterm, the resultant change in joint-line and maintained gap symmetry noted with GB does not result in significant change to function or quality of life.

Gap balancing sacrifices joint-line maintenance to improve gap symmetry: a randomized controlled trial comparing gap balancing and measured resection.

A total knee arthroplasty can be completed using two techniques; measured resection or gap balancing. A prospective blinded randomized controlled trial was completed with 103 patients randomized to measured resection (n = 52) or gap balancing (n = 51). Primary outcome measure was femoral component rotation. Secondary outcome measures were joint-line change, gap symmetry and function and quality-of-life outcomes. Gap balancing resulted in a significantly raised joint-line compared to measured resection. Gap symmetry was significantly better using gap balancing. Functional outcomes and quality-of-life were not significantly different at 24 months. Using computer navigation, gap balancing significantly raises the joint-line in order to improve gap symmetry. This does not result in a clinical difference in function or quality of life at 24 months.

Effect of Intravenous Zoledronic Acid on Total Knee Replacement in Patients With Symptomatic Knee Osteoarthritis and Without Severe Joint Space Narrowing: A Prespecified Secondary Analysis of a Two-Year, Multicenter, Double-Blind, Placebo-Controlled Clinical Trial.

OBJECTIVE: To determine the effect of zoledronic acid (ZA) on the risk of total knee replacement (TKR) in patients with symptomatic knee osteoarthritis and without severe joint space narrowing (JSN). METHODS: We included 222 participants (mean age 62 years, 52% female) from the two-year Zoledronic Acid for Osteoarthritis Knee Pain trial (113 received 5 mg of ZA annually and 109 received placebo) conducted between November 2013 and October 2017. Primary TKR were identified until February 22, 2022. The effect of ZA on TKR risk was evaluated using Cox proportional hazard regression models. Because the treatment effect failed the proportional hazards assumption, a time-varying coefficients analysis for treatment was conducted by splitting the study into two periods (ie, within and after two years of randomization). RESULTS: Over a mean follow-up of seven years, 39% and 30% of participants had any TKR in the ZA and placebo groups, and 28% and 18% had TKR in the study knee, respectively. Use of ZA was associated with a higher risk of TKR in any knee (hazard ratio [HR] 4.2, 95% confidence interval [CI] 1.2-14.7) and showed a trend in the study knee (HR 6.8, 95%CI 0.9-53.9) during the trial. In the posttrial period, the risk of TKR was similar in the ZA and the placebo groups for any knee (HR 1.2, 95%CI 0.5-1.8) and the study knee (HR 1.4, 95%CI 0.5-2.2). CONCLUSION: These results suggest that ZA is not protective against TKR in patients with symptomatic knee osteoarthritis and without severe JSN.

The effect of tibio-femoral over-distraction in primary knee arthroplasty.

PURPOSE: Overstuffing the patellofemoral joint has been associated with poor post-operative outcomes. No study has assessed the effect of over-distracting the tibio-femoral joint in the vertical plane and its effects on function and quality of life. The purpose of this study is to assess the effect of tibio-femoral joint distraction on function and quality of life after total knee arthroplasty. METHODS: Measurements of knee joint distraction were devised using long-leg alignment radiographs. Seventy-three patients were prospectively recruited and their joint distraction measured post-operatively. A comparison was made between the level of joint distraction and functional outcomes as measured by the International Knee Society score and its components, such as pain and flexion, and the Knee injury and Osteoarthritis Outcome Score and quality of life as measured by the Short-Form 12 score. Twelve-month follow-up was achieved. RESULTS: Knee joint over-distraction post-arthroplasty correlated significantly with Knee Society score (p = 0.041), flexion (p = 0.005) and pain (p = 0.002). Those knees that were over-distracted post-operatively suffered more pain, less flexion and a lower International Knee Society score compared with their counterparts. No correlation was found between over-distracting the knee joint and quality of life. CONCLUSION: Over-distracting the tibio-femoral joint during arthroplasty is a significant predictor of reduction in function and increase in pain in the short to medium term. When between sizes of tibial inserts, the surgeon should consider using the thinner option.

Obesity is associated with an increased risk of undergoing hip replacement in Australia.

BACKGROUND: Obesity is a known risk factor for the development of hip osteoarthritis. The aim of this study was to investigate whether obesity is associated with the risk of undergoing total hip replacement (THR) in Australia. METHODS: A cohort study was conducted comparing data from the Australian Bureau of Statistics and the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) from 2017 to 2018. Body mass index (BMI) data for patients undergoing primary total hip replacement and resurfacing for osteoarthritis were obtained from the AOANJRR. The distribution of THR patients by BMI category was compared to the general population, in age and sex sub-groups. RESULTS: During the study period, 32 495 primary THR were performed for osteoarthritis in Australia. Compared to the general population, there was a higher prevalence of Class I, II and III obesity in patients undergoing THR in both sexes aged 35-74 years. Class III obese females and males aged 55-64 years were 2.9 and 1.7 times more likely to undergo THR, respectively (P < 0.001). Class III obese females and males underwent THR on average 5.7 and 7.0 years younger than their normal weight counterparts, respectively. CONCLUSION: Obese Australians are at increased risk of undergoing THR, and at a younger age.

Coronal alignment correlates with outcome after total knee arthroplasty: five-year follow-up of a randomized controlled trial.

In a prospective randomized control trial comparing computer-assisted vs conventional total knee arthroplasty, we previously reported that patients with coronal alignment within 3° of neutral had superior international knee society and Short-Form 12 (SF-12) physical scores at 6 weeks, 3 months, 6 months, and 12 months after surgery. Computer-assisted total knee arthroplasty achieved greater accuracy in implant alignment, and this correlated with better knee function and quality of life. At 5 years, 90 of 111 patients assessed in our original study were reviewed. Coronal alignment within 3° of neutral continued to be correlated with superior International Knee Society and SF-12 scores. Coronal alignment greater than 3° was associated with a significant decline in SF-12 mental health scores.

A Comparison of Revision Rates and Dislocation After Primary Total Hip Arthroplasty with 28, 32, and 36-mm Femoral Heads and Different Cup Sizes: An Analysis of 188,591 Primary Total Hip Arthroplasties.

UPDATE: This article was updated on August 17, 2022, because of previous errors, which were discovered after the preliminary version of the article was posted online. On page 1462, in the first sentence of the Abstract section entitled "Results," the phrase that had read "and 36-mm heads had fewer dislocations than 28-mm (HR = 0.33 [95% CI, 0.16 to 0.68]; p = 0.003), but more dislocations than 32-mm heads (HR for >2 weeks = 2.25 [95% CI, 1.13 to 4.49]; p = 0.021)" now reads "and 36-mm heads had fewer dislocations than 28-mm (HR = 0.33 [95% CI, 0.16 to 0.68]; p = 0.003) and 32-mm heads (HR for ≥2 weeks = 0.44 [95% CI, 0.22 to 0.88]; p = 0.021)." On page 1468, in the last sentence of the section entitled "Acetabular Components with a Diameter of <51 mm," the phrase that had read "and HR for ≥2 weeks = 2.25 [95% CI, 1.13 to 4.49; p = 0.021]) ( Fig. 3 )" now reads "and HR for ≥2 weeks = 0.44 [95% CI, 0.22 to 0.88; p = 0.021]) ( Fig. 3 )." Finally, on page 1466, in the upper right corner of Figure 3 , under "32mm vs 36mm," the second line that had read "2Wks+: HR=2.25 (1.13, 4.49), p=0.021" now reads "2Wks+: HR=0.44 (0.22, 0.88), p= 0.021."

The acetabular component diameter can influence the choice of femoral head size in total hip arthroplasty (THA). We compared the rates of revision by femoral head size for different acetabular component sizes. Data from the Australian Orthopaedic Association National Joint Replacement Registry were analyzed for patients undergoing primary THA for a diagnosis of osteoarthritis from September 1999 to December 2019. Acetabular components were stratified into quartiles by size: <51 mm, 51 to 53 mm, 54 to 55 mm, and 56 to 66 mm. Femoral head sizes of 28 mm, 32 mm, and 36 mm were compared for each cup size. The primary outcome was the cumulative percent revision (CPR) for all aseptic causes and for dislocation. The results were adjusted for age, sex, femoral fixation, femoral head material, year of surgery, and surgical approach and were stratified by femoral head material. For acetabular components of <51 mm, 32-mm (hazard ratio [HR] = 0.75 [95% confidence interval (CI), 0.57 to 0.97]; p = 0.031) and 36-mm femoral heads (HR = 0.58 [95% CI, 0.38 to 0.87]; p = 0.008) had a lower CPR for aseptic causes than 28-mm heads; and 36-mm heads had fewer dislocations than 28-mm (HR = 0.33 [95% CI, 0.16 to 0.68]; p = 0.003), and 32-mm heads (HR for ≥2 weeks = 0.44 [95% CI, 0.22 to 0.88]; p = 0.021). For 51 to 53-mm, 54 to 55-mm, and 56 to 66-mm-diameter acetabular components, there was no difference in the CPR for aseptic causes among head sizes. A femoral head size of 36 mm had fewer dislocations in the first 2 weeks than a 32-mm head for the 51 to 53-mm acetabular components (HR for <2 weeks = 3.79 [95% CI, 1.23 to 11.67]; p = 0.020) and for the entire period for 56 to 66-mm acetabular components (HR = 1.53 [95% CI, 1.05 to 2.23]; p = 0.028). The reasons for revision differed for each femoral head size. There was no difference in the CPR between metal and ceramic heads. There is no clear advantage to any single head size except with acetabular components of <51 mm, in which 32-mm and 36-mm femoral heads had lower rates of aseptic revision. If stability is prioritized, 36-mm femoral heads may be indicated. Therapeutic Level III . See Instructions for Authors for a complete description of levels of evidence.

Obesity is associated with an increased risk of undergoing knee replacement in Australia.

BACKGROUND: Obesity is associated with the development of knee osteoarthritis (OA). The aim of this study was to examine the incidence of obesity in patients undergoing knee replacement (KR) for OA in Australia compared to the incidence of obesity in the general population. METHODS: A cohort study was conducted, comparing data from the Australian Bureau of Statistics (ABS) 2017-2018 National Health Survey with data from the National Joint Replacement Registry. The distribution of patients who underwent KR from July 2017 to June 2018 by BMI category was compared to the distribution of the general population, in age and gender sub-groups. RESULTS: During the study period, 35.6% of Australian adults were overweight and 31.3% were obese. Of the 56 217 patients who underwent primary KR for OA, 31.9% were overweight and 57.7% were obese. The relative risk of undergoing KR for OA increased with increasing BMI category. Class 1, 2 and 3 obese females aged 55-64 years were 4.7, 8.4 and 17.3 times more likely to undergo KR than their normal weight counterparts, respectively. Males in the same age and BMI categories were 3.4, 4.5 and 5.8 times more likely to undergo KR, respectively. Class 3 obese patients underwent KR 7 years younger, on average, than normal weight individuals. CONCLUSION: Obesity is associated with an increased risk of undergoing KR, and at a younger age, particularly for females. There is an urgent need for a societal level approach to address the prevalence of obesity, to reduce the burden of obesity related KR.

Periprosthetic bone remodeling using a triple-taper polished cemented stem in total hip arthroplasty.

The triple-taper cemented femoral stem was developed to promote proximal femoral and calcar loading to minimize periprosthetic bone loss and aseptic loosening. Periprosthetic changes in bone mineral density in Gruen zones 1 to 7 were analyzed in 103 patients over a 2-year period using dual x-ray absorptiometry. There was a statistically significant decrease in bone mineral density in all Gruen zones, but was most marked in zones 1 and 7. Periprosthetic bone density was reduced significantly in the first 3 to 9 months, after which recovery of bone density occurred. Greater calcar bone loss was seen in women, patients with a low preoperative bone density, and patients with poor postoperative mobility. Age at surgery did not effect calcar bone loss.

Does accurate anatomical alignment result in better function and quality of life? Comparing conventional and computer-assisted total knee arthroplasty.

This is a randomized prospective controlled trial comparing the alignment, function, and patient quality-of-life outcomes between patients undergoing conventional (CONV) and computer-assisted (CAS) knee arthroplasty. One hundred and fifteen patients (60 CAS, 55 CONV) underwent cemented total knee arthroplasty. Three patients were lost to follow-up. Eighty-eight percent (CAS) vs 61% (CONV) of knees achieved a mechanical axis within 3 degrees of neutral (P = .003). Aligning femoral rotation with the epicondylar axis was accurately achieved in CAS and CONV with no significant difference. Patients with coronal alignment within 3 degrees of neutral had superior International Knee Society and Short-Form 12 physical scores at 6 weeks, 3 months, 6 months, and 12 months after surgery. Computer-assisted total knee arthroplasty achieves greater accuracy in implant alignment and this correlates with better knee function and improved quality of life.

The long leg radiograph is a reliable method of assessing alignment when compared to computer-assisted navigation and computer tomography.

BACKGROUND: The mechanical alignment of the knee is an important factor in planning for, and subsequently assessing the success of a knee replacement. It is most commonly measured using a long-leg anteroposterior radiograph (LLR) encompassing the hip, knee and ankle. Other modalities of measuring alignment include computer tomography (CT) and intra-operative computer navigation (Cas). Recent studies comparing LLRs to Cas in measuring alignment have shown significant differences between the two and have hypothesized that Cas is a more accurate modality. This study aims to investigate the accuracy of the above mentioned modalities. METHODOLOGY: A prospective study was undertaken comparing alignment as measured by long-leg radiographs and computer tomography to intra-operative navigation measurements in 40 patients undergoing a primary total knee replacement to test this hypothesis. Alignment was measured three times by three observers. Intra- and inter-observer correlation was sought between modalities. RESULTS: Intra-observer correlation was excellent in all cases (>0.98) with a coefficient of repeatability <1.1°. Inter-observer correlation was also excellent measuring >0.960 using LLRs and >0.970 using CT with coefficient of repeatability <2.8°. Inter-modality correlation proved to be higher when comparing LLRs and CT (>0.893), than when comparing either of these modalities with Cas (>0.643 and >0.671 respectively). Pre-operative values had the greatest variability. CONCLUSION: Given its availability and reduced radiation dose when compared to CT, LLRs should remain the mainstay of measuring the mechanical alignment of the lower limb, especially post-operatively. LEVEL OF EVIDENCE: II.

Prospective randomized comparison of endobutton versus cross-pin femoral fixation in hamstring anterior cruciate ligament reconstruction with 2-year follow-up.

BACKGROUND: To determine if there is a different clinical outcome after TransFix versus endobutton femoral fixation in hamstring anterior cruciate ligament (ACL) reconstruction. METHODS: Twenty-nine patients were randomized into either Endobutton (Smith & Nephew, Andover, MA, USA) (n= 13) or TransFix (Arthrex, Naples, FL, USA) (n= 16) femoral fixation in hamstring ACL reconstruction. The distal fixation was with a bioabsorbable interference screw. The evaluation methods were clinical history and examination, KT1000 arthrometry for laxity as well as the International Knee Documentation Committee (IKDC) scores over a 2-year time frame. RESULTS: There were no significant differences between the study groups preoperatively. For the 2-year follow-up, 11 patients in the Endobutton group and 13 patients in the TransFix group were available (greater than 80%). No statistical differences between the two groups were found at the 1- or 2-year follow-up examinations. At the 2-year follow-up, 72.7% of the Endobutton and 84.6% of the TransFix group patients were in the IKDC A or B categories. Additional procedures postoperatively occurred more frequently in the TransFix group. CONCLUSIONS: There were no significant differences in the results for either technique of femoral fixation.