Survey of New Zealand Arthroplasty Surgeons on Surgeon-Level Outcome Reporting.

BACKGROUND: Surgeon-specific outcome monitoring has become increasingly prevalent over the last 3 decades. The New Zealand Orthopaedic Association monitors individual surgeon performance through 2 mechanisms: arthroplasty revision rates derived from the New Zealand Joint Registry and a practice visit program. Despite remaining confidential, surgeon-level outcome reporting remains contentious. The purpose of this survey was to evaluate the opinions of hip and knee arthroplasty surgeons in New Zealand on the perceived importance of outcome monitoring, current methods used to evaluate surgeon-specific outcomes, and potential improvements identified through literature review and discussion with other registries. METHODS: The survey consisted of 9 questions on surgeon-specific outcome reporting, using a five-point Likert scale, and 5 demographic questions. It was distributed to all current hip and knee arthroplasty surgeons. There were 151 hip and knee arthroplasty surgeons who completed the survey, a response rate of 50%. RESULTS: Respondents agreed that monitoring arthroplasty outcomes is important and that revision rates are an acceptable measure of performance. Reporting risk-adjusted revision rates and more recent timeframes were supported, as was including patient-reported outcomes when monitoring performance. Surgeons did not support public reporting of surgeon-level or hospital-level outcomes. CONCLUSION: The findings of this survey support the use of revision rates to confidentially monitor surgeon-level arthroplasty outcomes and suggest that concurrent use of patient-reported outcome measures would be acceptable.

The Strongest Oxford Knee Score Predictors of Subsequent Revision are "Overall Pain," "Limping When Walking," and "Knee Giving Way".

BACKGROUND: The Oxford Knee Score (OKS) is used to measure knee arthroplasty outcomes; however, it is unclear which questions are more relevant. Our aims were to (1) identify which OKS question(s) were the strongest predictors of subsequent revision and (2) compare the predictive ability of the "pain" and "function" domains. METHODS: All primary total knee arthroplasties (TKAs) and unicompartmental knee arthroplasties (UKAs) in the New Zealand Joint Registry between 1999 and 2019 with an OKS at 6 months (TKA n = 27,708; UKA n = 8,415), 5 years (TKA n = 11,519; UKA n = 3,365) or 10 years (TKA n = 6,311; UKA n = 1,744) were included. Prediction models were assessed using logistic regressions and receiver operating characteristic analyses. RESULTS: A reduced model with 3 questions ("overall pain," "limping when walking," "knee giving way") showed better diagnostic ability than full OKS for predicting UKA revision at 6 months (area under the curve [AUC]: 0.80 versus 0.78; P < .01) and 5 years (0.81 versus 0.77; P = .02), and comparable diagnostic ability for predicting TKA revision at all time points (6 months, 0.77 versus 0.76; 5 years, 0.78 versus 0.75; 10 years, 0.76 versus 0.73; all not significant), and UKA revision at 10 years (0.80 versus 0.77; not significant). The pain domain had better diagnostic ability for predicting subsequent revision for both procedures at 5 and 10 years. CONCLUSION: Questions on "overall pain", "limping when walking", and "knee giving way" were the strongest predictors of subsequent revision. Attention to low scores from these questions during follow-up may allow for prompt identification of patients most at risk of revision.

Surgical Helmet Systems Are Associated With a Lower Rate of Prosthetic Joint Infection After Total Knee Arthroplasty: Combined Results From the New Zealand Joint Registry and Surgical Site Infection Improvement Programme.

BACKGROUND: This study aimed to identify the risk factors, in particular the use of surgical helmet systems (SHSs), for prosthetic joint infection (PJI) after total knee arthroplasty (TKA). Data recorded by the New Zealand Surgical Site Infection Improvement Programme (SSIIP) and the New Zealand Joint Registry (NZJR) were combined and analyzed. METHODS: Primary TKA procedures performed between July 2013 and June 2018 that were recorded by both the SSIIP and NZJR were analyzed. Two primary outcomes were measured: (1) PJI within 90 days as recorded by the SSIIP and (2) revision TKA for deep infection within 6 months as recorded by the NZJR. Univariate and multivariate analyses were performed to identify risk factors for both outcomes with results considered significant at P < .05. RESULTS: A total of 19,322 primary TKAs were recorded by both databases in which 97 patients had a PJI within 90 days as recorded by the SSIIP (0.50%), and 90 patients had a revision TKA for deep infection within 6 months (0.47%) as recorded by the NZJR. An SHS was associated with a lower rate of PJI (adjusted odds ratio [OR] = 0.50, P = .008) and revision for deep infection (adjusted OR = 0.55, P = .022) than conventional gowning. Male sex (adjusted OR = 2.6, P < .001) and an American Society of Anesthesiologists score >2 were patient risk factors for infection (OR = 2.63, P < .001 for PJI and OR = 1.75, P = .017 for revision for deep infection). CONCLUSION: Using contemporary data from the SSIIP and NZJR, the use of the SHS was associated with a lower rate of PJI after primary TKA than conventional surgical gowning. Male sex and a higher American Society of Anesthesiologists score continue to be risk factors for infection.

Ballistic trauma caused by military rifles: experimental study based on synthetic skull proxies.

Rifles are often involved in violent deaths such as homicide and suicide. Consequently, expert knowledge and experimental forensic investigations are important to clarify the nature of ballistic trauma when applied to the human head and neurocranium. This study investigated differences in entrance wound morphology with Synbone® spheres which are described as being comparable to human flat bones. A series of ballistic experiments were conducted using two different rifle calibers (5.56 × 45 mm and 7.62 × 39 mm Full Metal Jacket (FMJ)). Synbone® spheres were used for close-range 0.3 m simulated executions as well as at 25 m and 35 m to simulate urban and military engagements. Results were compared with previously published experimental studies using similar military ammunition. In our study, entry wound morphology closely resembles real forensic cases compared to exit wound and overall shape morphology independently of the distance and the caliber. Circumferential delamination was clearly visible with full metal jacket (FMJ) rounds, yielding similar damage pattern morphology to the human crania. This study documented the presence of hydraulic burst or shock in all ten rounds from all three distances. Krönlein shots were also observed in some cases. Synbone® spheres constitute an acceptable synthetic surrogate for ballistic experiments. The present study offers new initial data on the behavior of Synbone® proxies in ballistic testing of military ammunitions; FMJ gunshot injuries to the human head, for distances that have not previously been published, suggesting that efficient tests can take place under these conditions. Further research on experimental ballistics with a larger number of controlled factors and multiple repetitions is recommended to verify the results of this pilot study before applied in forensic simulations.

Associations between comorbidity and quality of life outcomes after total joint replacement.

PURPOSE: We examined associations between self-reported and clinician-assessed comorbidity and quality of life (QOL) outcomes after hip and knee replacement. METHODS: This is a cross-sectional, questionnaire-based national survey. Participants aged 45 years or older (n = 409) were recruited from the New Zealand Joint Registry six months after a total hip (THR), total knee (TKR) or unicompartmental knee replacement (UKR). The main outcome QOL was measured using an 8-item short form of the World Health Organisation Quality of Life (WHOQOL-Bref) questionnaire six months following joint replacement surgery. The WHOQOL is a generic and non-health condition specific measure of QOL. RESULTS: Participants were on average 68 years of age, with more men (54%) than women (46%). Number of coexisting conditions and body mass index were correlated with age, pain and function scores, and QOL (p < 0.01), but not with each other. Linear regression analyses showed that comorbidities such as number of comorbid conditions and BMI had moderate associations with QOL outcomes. CONCLUSION: This study showed that general QOL outcomes following hip and knee joint replacement, while generally high, were associated with comorbidity burden and BMI. Future prospective research examining change in QOL before and following surgery would help to advance understandings of the various factors that contribute to patient satisfaction with their joint replacement.

Are Lipped Polyethylene Liners Associated with Increased Revision Rates in Patients with Uncemented Acetabular Components? An Observational Cohort Study.

BACKGROUND: Recurrent dislocation after THA remains a serious complication that carries with it a high risk of revision surgery. Previous studies have shown reduced dislocation rates with the use of lipped polyethylene (PE) liners in modular uncemented acetabular components, but there may be increased wear because of impingement, which may lead to aseptic loosening in the longer term; whether the aggregate benefit of lipped PE liners outweighs the risks associated with their use remains controversial. QUESTIONS/PURPOSES: We used data from the New Zealand Joint Registry to (1) compare Kaplan-Meier survival rates, (2) rates of revisions for dislocation between neutral and lipped PE liners, and (3) revision rates for aseptic loosening for the four most commonly used modular uncemented cups. METHODS: We used data from the New Zealand Joint Registry (NZJR) to identify 31,247 primary THAs using the four most commonly used uncemented modular acetabular implants from January 1, 1999 to December 31, 2018. The lipped liner group comprised 49% males (9924 of 20,240) compared with 42% (4669 of 11,007) in the neutral group (p < 0.001); 96% (19,382 of 20,240) of patients in the liner group had OA versus 95% (10,450 of 11,007) in the neutral group (p < 0.001). There was no difference in other patient characteristics such as age (mean 66.9 years), BMI (mean 29 ± 6 kg/m) and American Society of Anesthesiologists grade. The mean follow-up was 5.1 years (SD 3.9) and longest follow-up 19.3 years. The NZJR has more than 96% capture rate and data entry is a mandatory requirement of members of the New Zealand Orthopaedic Association. Kaplan-Meier survival rates were compared between 20,240 lipped and 11,007 neutral PE liners. Highly cross-linked polyethylene was used in 99% of lipped liner cups and 85% of neutral liner cups. Associated hazard ratios were calculated using a Cox regression analysis with a Kaplan-Meier revision-free estimates plot. RESULTS: The Kaplan-Meier survival at 10 years for lipped PE liners was 96% (95% confidence interval 95.4 to 96.2) and for neutral liners 95% (95% CI 94.7 to 95.9). After controlling for age, gender approach, femoral head size, and the use of image guidance, the all-cause revision risk was greater for neutral PE liners than that for lipped PE liners (HR 1.17 [95% CI 1.06 to 1.36]; p = 0.032). There was a higher risk of revision for dislocation in those with neutral PE liners than in those with lipped liners (HR 1.84 [95% CI 1.41 to 2.41]; p < 0.001) but no difference in the revision rate for aseptic acetabular component loosening (HR 0.85 [95% CI 0.52 to 1.38]; p = 0.511). CONCLUSIONS: The use of a lipped PE liner is not associated with a higher rate of aseptic loosening in patients who undergo primary THA compared with a neutral PE liner. Lipped PE liners are associated with lower rates of dislocation and lower all-cause revision rates without any increased association with revision rates for wear and aseptic loosening. LEVEL OF EVIDENCE: Level III, therapeutic study.

Despite Improved Survivorship of Uncemented Fixation in Total Knee Arthroplasty for Osteoarthritis, Cemented Fixation Remains the Gold Standard: An Analysis of a National Joint Registry.

BACKGROUND: Total knee arthroplasty (TKA) numbers are increasing worldwide. While cement fixation for both femoral and tibial components is commonly used, alternatives include hybrid and uncemented TKAs. This study aimed to evaluate survivorship, revision rates, and patient-reported outcomes for cemented, hybrid, and uncemented TKAs using New Zealand Joint Registry (NZJR) data. METHODS: NZJR data relating to all TKAs performed during the 19 years up to the end of December 2017 were analyzed. Outcomes were assessed using prosthesis survivorship data (including reasons for revision) and Oxford scores at 6 months, 5 years, and 10 years postoperatively. RESULTS: A total 96,519 primary TKAs were performed during the period examined. Most (91.5%) were fully cemented with 4.8% hybrid and 3.7% uncemented. Mean Oxford scores at 6 months were highest in cemented and lowest in uncemented TKAs (P < .001). However, this was not clinically significant. There was no difference at 5 or 10 years. Ten-year survival rates were 97%, 94.5%, and 95.8% for cemented, uncemented, and hybrid TKAs, respectively. Revision rates were 0.47, 0.74, and 0.52 per 100 component years for cemented, uncemented, and hybrid prostheses, respectively. The revision rate for uncemented prostheses compared with cemented was higher (P < .001). When stratified by age group, there were differences in survival rates between cemented and uncemented groups (P = .001) and hybrid and uncemented groups (P = .038) in patients aged <55 years; between cemented and uncemented groups in those aged 55-64 years (P = .031); and between cemented and hybrid groups in those aged >75 years (P = .004). CONCLUSION: Uncemented TKAs had similar patient-reported outcomes but higher revision rates and worse survivorship compared with hybrid or fully cemented TKAs.

Growth Factor Delivery Systems for Tissue Engineering and Regenerative Medicine.

Growth factors (GFs) are often a key component in tissue engineering and regenerative medicine approaches. In order to fully exploit the therapeutic potential of GFs, GF delivery vehicles have to meet a number of key design criteria such as providing localized delivery and mimicking the dynamic native GF expression levels and patterns. The use of biomaterials as delivery systems is the most successful strategy for controlled delivery and has been translated into different commercially available systems. However, the risk of side effects remains an issue, which is mainly attributed to insufficient control over the release profile. This book chapter reviews the current strategies, chemistries, materials and delivery vehicles employed to overcome the current limitations associated with GF therapies.

Untangling chronic pain and post-concussion symptoms: the significance of depression.

OBJECTIVES: Post-concussion-like symptoms (PCS) are common in patients without a history of brain injury, such as those with chronic pain (CP). This exploratory study examined neuro-cognitive and psychological functioning in patients with PCS following mild traumatic brain injury (mTBI) or CP, to assess unique and overlapping phenomenology. METHODS: In this case-control study, participants (n = 102) with chronic symptoms after mTBI (n = 45) were matched with mTBI recovered (n = 31) and CP groups (n = 26), on age, gender, ethnicity and education. Psychological status, cognitive functioning, health symptoms, beliefs and behaviours were examined. RESULTS: Participants who had not recovered from an mTBI and participants with CP did not differ in terms of PCS symptoms, quality of life, distress or illness behaviours, however, the CP group endorsed fewer subjective cognitive problems, more negative expectations about recovery and more distress (p < 0.05). On cognitive testing participants who had not recovered from an mTBI demonstrated greater difficulties with attention (p < 0.01) although differences disappeared when depression was controlled in the analyses. CONCLUSIONS: Unique patterns associated with each condition were evident though caution is required in attributing PCS and cognitive symptoms to a brain injury in people with mTBI presenting with chronic pain and/or depression. Psychological constructs such as illness and recovery beliefs appear to be important to consider in the development of treatment interventions.

The Impact of Patient and Surgical Factors on the Rate of Postoperative Infection After Total Hip Arthroplasty-A New Zealand Joint Registry Study.

BACKGROUND: Periprosthetic joint infection (PJI) is a devastating complication after total hip arthroplasty (THA). The potential to define and modify risk factors for infection represents an important opportunity to reduce the incidence of PJI. This study uses New Zealand Joint Registry data to identify independent risk factors associated with PJI after primary THA. METHODS: Data on 91,585 THAs performed between 2000 and 2014 were analyzed. Factors associated with revision for PJI within 12 months were identified using univariate and multivariate analyses. RESULTS: Revision rates for PJI were 0.15% and 0.21% at 6 and 12 months, respectively. Multivariate analysis showed significant associations with the American Society of Anesthesiologists grade (odds ratio [OR] 6.13, 95% confidence interval [CI] 1.28-29.39), severe or morbid obesity (OR 2.15, CI 1.01-4.60 and OR 3.73, CI 1.49-9.39), laminar flow ventilation (OR 1.98, CI 1.38-2.85), consultant-supervised trainee operations (OR 1.94, CI 1.22-3.08), male gender (OR 1.68, CI 1.23-2.30) and anterolateral approach (OR 1.62, CI 1.11-2.37). Procedures performed in the private sector were protective for revision for infection (OR 0.68, CI 0.48-0.96). CONCLUSIONS: The PJI risk profile for patients undergoing THA is constituted of a complex of patient and surgical factors. Several patient factors had strong independent associations with revision rates for PJI. Although surgical factors were less important, these may be more readily modifiable in practice.

Quantitative imaging of excised osteoarthritic cartilage using spectral CT.

OBJECTIVES: To quantify iodine uptake in articular cartilage as a marker of glycosaminoglycan (GAG) content using multi-energy spectral CT. METHODS: We incubated a 25-mm strip of excised osteoarthritic human tibial plateau in 50 % ionic iodine contrast and imaged it using a small-animal spectral scanner with a cadmium telluride photon-processing detector to quantify the iodine through the thickness of the articular cartilage. We imaged both spectroscopic phantoms and osteoarthritic tibial plateau samples. The iodine distribution as an inverse marker of GAG content was presented in the form of 2D and 3D images after applying a basis material decomposition technique to separate iodine in cartilage from bone. We compared this result with a histological section stained for GAG. RESULTS: The iodine in cartilage could be distinguished from subchondral bone and quantified using multi-energy CT. The articular cartilage showed variation in iodine concentration throughout its thickness which appeared to be inversely related to GAG distribution observed in histological sections. CONCLUSIONS: Multi-energy CT can quantify ionic iodine contrast (as a marker of GAG content) within articular cartilage and distinguish it from bone by exploiting the energy-specific attenuation profiles of the associated materials. KEY POINTS: • Contrast-enhanced articular cartilage and subchondral bone can be distinguished using multi-energy CT. • Iodine as a marker of glycosaminoglycan content is quantifiable with multi-energy CT. • Multi-energy CT could track alterations in GAG content occurring in osteoarthritis.

Evaluating quality of life outcomes following joint replacement: psychometric evaluation of a short form of the WHOQOL-Bref.

PURPOSE: Reducing participant burden is important in health research and clinical assessment. We examined the psychometric properties of the EUROHIS-QOL 8-item index, a short version of the 26-item World Health Organisation Quality of Life questionnaire (WHOQOL-Bref), in a sample of people receiving joint replacement surgery. METHODS: Participants (n = 1008) completed the WHOQOL-Bref at either 6, 12, 24 or 60 months after hip or knee replacement. The factor structure, differential item functioning (DIF) and unidimensionality of the EUROHIS-QOL 8-item index were examined using exploratory and confirmatory factor analyses and Rasch analyses. Convergent validity was examined using correlations with the parent measure and other patient-reported outcome measures (Oxford scores, Western Ontario and McMaster Universities Osteoarthritis Index). Discriminant validity was assessed between groups reporting high versus low pain and function, and by joint replaced. RESULTS: The measure demonstrated high internal consistency (α = 0.86), adequate convergent (r = 0.47-0.82, p < 0.001) and discriminant validity (p < 0.001). Factor and Rasch analyses supported a unidimensional structure. However, there were also indications of multidimensionality, with support for a two-factor model focusing on general health and function, and psychosocial aspects of QOL. There was minimal evidence of DIF, with just one item evaluating energy level showing DIF for age. CONCLUSIONS: The EUROHIS-QOL 8-item index demonstrated adequate properties as a unidimensional scale and as a two-factor scale evaluating general health and function, and psychosocial aspects of quality of life. It is low on clinical and participant burden, showed minimal ceiling effects and showed good concurrent and discriminant validity.

Do larger femoral heads improve the functional outcome in total hip arthroplasty?

Use of larger diameter femoral heads has been popularised in total hip arthroplasty (THA). Recent studies have implicated larger femoral heads in early failure. We evaluated what effect the size of the femoral head had on the early functional outcome in order to determine the optimal head size for the maximal functional outcome. There were 726 patients who underwent elective THA and were divided into 3 groups according to head size then compared with respect to functional outcome scores and dislocation rates. This study failed to show that increasing the size of the femoral head significantly improved the functional outcome at 1 year after total hip arthroplasty but that the use of a 36 mm or greater femoral head did reduce the dislocation rate.

Does computer-assisted total knee arthroplasty improve the overall component position and patient function?

PURPOSE: There remains controversy as to whether computer-navigated total knee replacement (TKR) improves the overall prosthesis alignment and patient function. The aim of this study was to determine whether computer-assisted total knee arthroplasty provides superior prosthesis positioning when compared to a conventional jig-assisted total knee replacement and whether this affected the functional outcome. METHODS: This prospective, randomised controlled study compared computer navigated and conventional jig-assisted total knee replacement in 37 patients who underwent bilateral TKR. A quantitative assessment of the spatial positioning of the implant in the 74 total knee replacements was determined using a low-dose dual-beam CT scanning technique. This resulted in six parameters of alignment that were compared. Functional outcomes using the high activity arthroplasty score and Knee Society score were assessed pre-operatively, postoperatively, at three years and at five years. Patients also indicated which knee they felt was subjectively the best. RESULTS: There was no statistically significant difference in the prosthesis alignment between both groups and the number of outliers was not decreased with navigation. All function scores improved from pre-operative to postoperative but there was no statistically significant difference between the groups at five years. At five years, 40.6% of patients thought their jig-assisted knee was the better knee compared with 21.9% their computer assisted knee and 37.5% of patients who felt they were the same. CONCLUSION: Computer-assisted implantation of total knee replacements does not offer a significant advantage in prosthesis alignment. There was no difference in functional outcome or subjective "best knee" between the computer-assisted or jig-assisted knee.

Effect of surgeon-specific feedback on surgical outcomes: a systematic review of the literature.

BACKGROUND: Surgeon-specific outcome reporting provides an opportunity for quality assurance and improved surgical results. It is becoming increasingly prevalent and remains contentious amongst surgeons. The purpose of this systematic review was to evaluate the extent to which published literature supports the concept that feedback of surgeon-level outcomes reduces morbidity and/or mortality. No systematic reviews have previously been completed on this subject. METHODS: Medline and Embase were systematically searched for studies published prior to the 1st of January 2022. Feedback was defined as a summary of clinical performance over a specified period of time provided in written, electronic or verbal format. Studies were required to provide surgeon-specific feedback to multiple individual consultant surgeons with the primary purpose being to determine if feedback improved outcomes. Primary outcome(s) needed to relate to surgical outcomes as opposed to process measures only. All surgical specialties and procedures were eligible for inclusion. RESULTS: Seventeen studies were included in the review, traversing a wide range of specialties and procedures. Sixteen were non-randominsed and one randomized. Fifteen were before and after studies. The balance of the non-randomized studies support the concept that provision of surgeon-specific feedback can improve surgical outcomes, while the single randomized study suggests feedback may not be effective. CONCLUSIONS: This systematic review supports the use of surgeon-level feedback to improve outcomes. The strength of this finding is limited by reliance on before and after studies, further randomized studies on this subject would be insightful.

A comparison of clinical thresholds for revision following total and unicompartmental knee arthroplasty.

Unicompartmental knee arthroplasty (UKA) has higher revision rates than total knee arthroplasty (TKA). As revision of UKA may be less technically demanding than revision TKA, UKA patients with poor functional outcomes may be more likely to be offered revision than TKA patients with similar outcomes. The aim of this study was to compare clinical thresholds for revisions between TKA and UKA using revision incidence and patient-reported outcomes, in a large, matched cohort at early, mid-, and late-term follow-up. Analyses were performed on propensity score-matched patient cohorts of TKAs and UKAs (2:1) registered in the New Zealand Joint Registry between 1 January 1999 and 31 December 2019 with an Oxford Knee Score (OKS) response at six months (n, TKA: 16,774; UKA: 8,387), five years (TKA: 6,718; UKA: 3,359), or ten years (TKA: 3,486; UKA: 1,743). Associations between OKS and revision within two years following the score were examined. Thresholds were compared using receiver operating characteristic analysis. Reasons for aseptic revision were compared using cumulative incidence with competing risk. Fewer TKA patients with 'poor' outcomes (≤ 25) subsequently underwent revision compared with UKA at six months (5.1% vs 19.6%; p < 0.001), five years (4.3% vs 12.5%; p < 0.001), and ten years (6.4% vs 15.0%; p = 0.024). Compared with TKA, the relative risk for UKA was 2.5-times higher for 'unknown' reasons, bearing dislocations, and disease progression. Compared with TKA, more UKA patients with poor outcomes underwent revision from early to long-term follow-up, and were more likely to undergo revision for 'unknown' reasons, which suggest a lower clinical threshold for UKA. For UKA, revision risk was higher for bearing dislocations and disease progression. There is supporting evidence that the higher revision UKA rates are associated with lower clinical thresholds for revision and additional modes of failure.

Associations of the Oxford Knee Score and knee arthroplasty revision at long-term follow-up.

BACKGROUND: Self-reported outcome measures are increasingly being collected for healthcare evaluation therefore it is prudent to understand their associations with patient outcomes. Our aims were to investigate: (1) if Oxford Knee Score (OKS) is associated with impending revision at long-term (5 and 10 years) follow-up, and (2) if decreased OKS at subsequent follow-ups is associated with higher risk of revision. PATIENTS AND METHODS: All total knee (TKAs) and unicompartmental knee arthroplasties (UKAs) between 1999 and 2019 in the New Zealand Joint Registry with an OKS at 6 months (TKA n = 27 708, UKA n = 8415), 5 years (TKA n = 11 519, UKA n = 3365) or 10 years (TKA n = 6311, UKA n = 1744) were included. Logistic regression determined associations of the OKS with revision within 2 years of each score. Change in OKS between timepoints were compared with revision risk. RESULTS: For every one-unit increase in OKS, the odds of TKA and UKA revision decreased by 10% and 11% at 6 months, 10% and 12% at 5 years and 9% and 5% at 10 years. For both procedures a decrease of seven or more OKS points from previous follow-up was associated with higher risk of revision (5 years: TKA 4.7% versus 0.5%, UKA 8.7% versus 0.9%; 10 years: TKA 4.4% versus 0.7%, UKA 11.3% versus 1.5%; all P < 0.01). CONCLUSION: The OKS had a strong negative association with risk of impending TKA and UKA revision from early to long-term (10+ years) follow-up. A decrease of seven or more points when compared with the previous follow-up was also associated with higher revision risk.

Similar Survivorship but Different Revision Reasons for Uncemented Mobile-Bearing and Cemented Fixed-Bearing Medial UKA: A Long-Term Population-Based Cohort Study of 2,015 Patients.

BACKGROUND: Long-term survivorship and accurate characterization of revision reasons in unicompartmental knee arthroplasty (UKA) are limited by a lack of long-term data and standardized definitions of revision. The aim of this study was to identify survivorship, risk factors, and reasons for revision in a large cohort of medial UKAs with long-term follow-up (up to 20 years). METHODS: Patient, implant, and revision details for 2,015 primary medial UKAs (mean follow-up, 8 years) were recorded following systematic clinical and radiographic review. Survivorship and risk of revision were analyzed using Cox proportional hazards. Reasons for revision were analyzed using competing-risk analysis. RESULTS: Implant survivorship at 15 years was 92% for cemented fixed-bearing (cemFB), 91% for uncemented mobile-bearing (uncemMB), and 80% for cemented mobile-bearing (cemMB) UKAs (p = 0.02). When compared with cemFB, the risk of revision was higher for cemMB implants (hazard ratio [HR] = 1.9, 95% confidence interval [CI] = 1.1 to 3.2; p = 0.03). At 15 years, cemented implants had a higher cumulative frequency of revision due to aseptic loosening (3% to 4%, versus 0.4% for uncemented; p < 0.01), cemMB implants had a higher cumulative frequency of revision due to osteoarthritis progression (9% versus 2% to 3% for cemFB/uncemMB; p < 0.05), and uncemMB implants had a higher cumulative frequency of revision due to bearing dislocation (4% versus 2% for cemMB; p = 0.02). Compared with the oldest patients (≥70 years), younger patients had a higher risk of revision (<60 years: HR = 1.9, 95% CI = 1.2 to 3.0; 60 to 69 years: HR = 1.6, 95% CI = 1.0 to 2.4; p < 0.05 for both). At 15 years, there was a higher cumulative frequency of revision for aseptic loosening in these younger groups (3.2% and 3.5% versus 2.7% for ≥70 years; p < 0.05). CONCLUSIONS: Implant design and patient age were risk factors for revision of medial UKA. The findings from this study suggest that surgeons should consider using cemFB or uncemMB designs because of their superior long-term implant survivorship compared with cemMB designs. Additionally, for younger patients (<70 years), uncemMB designs had a lower risk of aseptic loosening than cemFB designs at the expense of a risk of bearing dislocation. LEVEL OF EVIDENCE: Prognostic Level III . See Instructions for Authors for a complete description of levels of evidence.

Enhanced bone formation in locally-optimised, low-stiffness additive manufactured titanium implants: An in silico and in vivo tibial advancement study.

A tibial tuberosity advancement (TTA), used to treat lameness in the canine stifle, provides a framework to investigate implant performance within an uneven loading environment due to the dominating patellar tendon. The purpose of this study was to reassess how we design orthopaedic implants in a load-bearing model to investigate potential for improved osseointegration capacity of fully-scaffolded mechanically-matched additive manufactured (AM) implants. While the mechanobiological nature of bone is well known, we have identified a lower limit in the literature where investigation into exceedingly soft scaffolds relative to trabecular bone ceases due to the trade-off in mechanical strength. We developed a finite element model of the sheep stifle to assess the stresses and strains of homogeneous and locally-optimised TTA implant designs. Using additive manufacturing, we printed three different low-stiffness Ti-6Al-4 V TTA implants: 0.8 GPa (Ti1), 0.6 GPa (Ti2) and an optimised design with a 0.3 GPa cortex and 0.1 GPa centre (Ti3), for implantation in a 12-week in vivo ovine pilot study. Static histomorphometry demonstrated uniform bone ingrowth in optimised low-modulus Ti3 samples compared to homogeneous designs (Ti1 and Ti2), and greater bone-implant contact. Mineralising surfaces were apparent in all implants, though mineral apposition rate was only consistent throughout Ti3. The greatest bone formation scores were seen in Ti3, followed by Ti2 and Ti1. Results from our study suggest lower stiffnesses and higher strain ranges improve early bone formation, and that by accounting for loading environments through rational design, implants can be optimised to improve uniform osseointegration. STATEMENT OF SIGNIFICANCE: The effect of different strain ranges on bone healing has been traditionally investigated and characterised through computational models, with much of the literature suggesting higher strain ranges being favourable. However, little has been done to incorporate strain-optimisation into porous orthopaedic implants due to the trade-off in mechanical strength required to induce these microenvironments. In this study, we used finite element analysis to optimise the design of additive manufactured (AM) titanium orthopaedic implants for different strain ranges, using a clinically-relevant surgical model. Our research suggests that there is potential for locally-optimised AM scaffolds in the use of orthopaedic devices to induce higher strains, which in turn encourages de novo bone formation and uniform osseointegration.

Osteotomy and unicompartmental knee arthroplasty converted to total knee arthroplasty: data from the New Zealand Joint Registry.

We reviewed the revision rate and functional outcome of all patients who had a total knee arthroplasty (TKA) after an osteotomy or unicompartmental knee arthroplasty (UKA) on the New Zealand Joint Registry. We used these data to compare the results with primary TKA scores, including comparison of age-matched subgroups. There were 711 patients who had undergone TKA as salvage for a failed osteotomy with a revision rate of 1.33 per 100 component years and a mean 6-month Oxford Knee Score (OKS) of 36.9. There were 205 patients who had a failed UKA converted to TKA with a revision rate of 1.97 per 100 component years and a mean OKS of 29.1. The revision rates of TKA for both failed osteotomy and failed UKA were significantly poorer than after primary TKA (0.48 per 100 component years). The mean OKS after revision of a UKA was significantly poorer than both primary TKA and TKA for a failed osteotomy. There was no significant difference in mean OKS between primary TKA and TKA for a failed osteotomy, even among patients younger than 65 years. Revision of a failed osteotomy to a TKA has improved functional results compared with revision of a failed UKA. However, both yield poorer survivorship rates compared with primary TKA.