Accuracy and completeness of registry-reported unicompartmental knee arthroplasty revision

INTRODUCTION

The key outcome of joint registries is revision events, which inform clinical practice and identify poor-performing implants. Registries record revision events and reasons, but accuracy may be limited by a lack of standardized definitions of revision. Our study aims to assess the accuracy and completeness of unicompartmental knee arthroplasty (UKA) revision and indications reported to the New Zealand Joint Registry (NZJR) with independent clinical review.

METHODS

Case record review of 2272 patients undergoing primary UKA at four large tertiary hospitals between 2000 and 2017 was performed, identifying 158 patients who underwent revision. Detailed review of clinical findings, radiographs and operative data was performed to identify revision cases and the reasons for revision using a standardized protocol. These were compared to NZJR data using chi-squared and Fisher exact tests.

RESULTS

The NZJR recorded 150 (95%) of all UKA revisions. Osteoarthritis progression was the most common reason on the systematic clinical review (35%), however, this was underreported to the registry (8%, P < 0.001). A larger proportion of revisions reported to the registry were for 'pain' (30% of cases vs. 5% on clinical review, P < 0.001). A reason for revision was not reported to the registry for 10% of cases.

CONCLUSION

The NZJR had good capture of UKA revisions, but had significant differences in registry-reported revision reasons compared to our independent systematic clinical review. These included over-reporting of 'pain', under-reporting of osteoarthritis progression, and failing to identify a revision reason. Efforts to improve registry capture of revision reasons for UKA could be addressed through more standardized definitions of revision and tailored revision options for UKA on registry forms.

International Expert-Based Consensus Definition, Staging Criteria, and Minimum Data Elements for Osteoradionecrosis of the Jaw: An Inter-Disciplinary Modified Delphi Study

Purpose

Osteoradionecrosis of the jaw (ORNJ) is a severe iatrogenic disease characterized by bone death after radiation therapy (RT) to the head and neck. With over 9 published definitions and at least 16 diagnostic/staging systems, the true incidence and severity of ORNJ are obscured by lack of a standard for disease definition and severity assessment, leading to inaccurate estimation of incidence, reporting ambiguity, and likely under-diagnosis worldwide. This study aimed to achieve consensus on an explicit definition and phenotype of ORNJ and related precursor states through data standardization to facilitate effective diagnosis, monitoring, and multidisciplinary management of ORNJ.

Methods

The ORAL Consortium comprised 69 international experts, including representatives from medical, surgical, radiation oncology, and oral/dental disciplines. Using a web-based modified Delphi technique, panelists classified descriptive cases using existing staging systems, reviewed systems for feature extraction and specification, and iteratively classified cases based on clinical/imaging feature combinations.

Results

The Consortium ORNJ definition was developed in alignment with SNOMED-CT terminology and recent ISOO-MASCC-ASCO guideline recommendations. Case review using existing ORNJ staging systems showed high rates of inability to classify (up to 76%). Ten consensus statements and nine minimum data elements (MDEs) were outlined for prospective collection and classification of precursor/ORNJ stages.

Conclusion

This study provides an international, consensus-based definition and MDE foundation for standardized ORNJ reporting in cancer survivors treated with RT. Head and neck surgeons, radiation, surgical, medical oncologists, and dental specialists should adopt MDEs to enable scalable health information exchange and analytics. Work is underway to develop both a human- and machine-readable knowledge representation for ORNJ (i.e., ontology) and multidisciplinary resources for dissemination to improve ORNJ reporting in academic and community practice settings.

Progressive submaximal effort hamstring muscle endurance is reduced after reconstruction of the anterior cruciate ligament

BACKGROUND

Endurance capability in the muscles controlling the knee is poorly understood post anterior cruciate ligament (ACL) reconstruction, despite many sporting activities requiring notable muscle endurance. The hamstring muscles, when active, provide important anatomical support to protect the reconstructed graft. In the absence of good hamstring endurance, fatigue may predispose individuals to re-injury.

OBJECTIVE

To assess whether ACL reconstruction (ACLR) with a hamstring graft leads to reduced hamstring endurance 9-13 months post-surgery.

STUDY DESIGN

A cross-sectional inter-limb comparison study was undertaken with participants 9-13 months after an ACLR with a hamstring graft, and a group of age, sex, and activity-matched controls. There were 22 participants in each group.

METHOD

Submaximal hamstring endurance was measured using a progressive fatigue test on an isokinetic dynamometer at a joint angular velocity of 120°/second. The dependant variable was the maximum number of repetitions performed. Statistical comparisons were made across injured, uninjured and control group limbs.

RESULTS

There was a significant (p < 0.05) deficit in hamstring endurance observed between the injured leg (mean: 111 repetitions, SD 49) and uninjured leg (mean: 136 repetitions, SD 67) of the ACL group, but not between the uninjured and control group legs (mean: 124 repetitions, SD 50).

CONCLUSION

The 18% deficit in submaximal hamstring endurance across the ACL-reconstructed individual's limbs is indicative of a notable loss in muscle performance at 9-13 months post-surgery. These results provide initial evidence for supporting further research examining the inclusion of hamstring endurance training in ACL rehabilitation programmes post-surgery.

Risk factors for reoperation for arthrofibrosis following primary anterior cruciate ligament reconstruction

PURPOSE

The purpose of this study is to identify the rate and risk factors for a reoperation for arthrofibrosis following primary anterior cruciate ligament (ACL) reconstruction.

METHODS

Prospective data recorded in the New Zealand ACL Registry were cross-referenced with data from the Accident Compensation Corporation (ACC). Primary ACL reconstructions performed between April 2014 and May 2021 were analysed. The ACC database was used to identify patients who underwent a reoperation for a diagnosis of arthrofibrosis. Multivariable survival analysis was performed to compute adjusted hazard ratios (aHR) and 95% confidence intervals.

RESULTS

A total of 12,296 primary ACL reconstructions were analysed, of which 230 underwent a reoperation for arthrofibrosis (1.9%) at a mean follow-up of 3.6 years. A higher risk of arthrofibrosis was observed in females (aHR = 1.76, p = 0.001), patients with a history of previous knee surgery (aHR = 1.82, p = 0.04) and when a transtibial drilling technique was used (aHR = 1.53, p = 0.03). ACL reconstruction >6 months after injury had the lowest rate of arthrofibrosis (1.3%, aHR = 0.45, p = 0.01). There was no difference in risk between early surgery within 6 weeks versus delayed surgery between 6 weeks and 6 months after injury (2.9% versus 2.1%, aHR = 0.78, not significant).

CONCLUSION

Female sex, previous knee surgery and a transtibial drilling technique increased the risk of reoperation for arthrofibrosis. Early surgery within 6 weeks of injury was not associated with an increased risk when compared with surgery between 6 weeks and 6 months after injury.

LEVEL OF EVIDENCE

Level III.

Intraosseous regional prophylaxis in total knee arthroplasty

Prophylactic antibiotics are important in reducing the risk of periprosthetic joint infection (PJI) following total knee arthroplasty. Their effectiveness depends on the choice of antibiotic and the optimum timing of their administration, to ensure adequate tissue concentrations. Cephalosporins are typically used, but an increasing number of resistant organisms are causing PJI, leading to the additional use of vancomycin. There are difficulties, however, with the systemic administration of vancomycin including its optimal timing, due to the need for prolonged administration, and potential adverse reactions. Intraosseous regional administration distal to a tourniquet is an alternative and attractive mode of delivery due to the ease of obtaining intraosseous access. Many authors have reported the effectiveness of intraosseous prophylaxis in achieving higher concentrations of antibiotic in the tissues compared with intravenous administration, providing equal or enhanced prophylaxis while minimizing adverse effects. This annotation describes the technique of intraosseous administration of antibiotics and summarizes the relevant clinical literature to date.

Comparison of Knee Pain and Difficulty With Kneeling Between Patellar Tendon and Hamstring Tendon Autografts After Anterior Cruciate Ligament Reconstruction: A Study From the New Zealand ACL Registry

BACKGROUND

The bone-patellar tendon-bone (BTB) autograft is associated with difficulty with kneeling after anterior cruciate ligament (ACL) reconstruction; however, it is unclear whether it results in a more painful or symptomatic knee compared with the hamstring tendon autograft.

PURPOSE

To identify the rate and risk factors for knee pain and difficulty with kneeling after ACL reconstruction.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Primary ACL reconstruction procedures prospectively recorded in the New Zealand ACL Registry from April 2014 to May 2021 were analyzed. The Knee injury and Osteoarthritis Outcome Score (KOOS) was used to identify patients reporting consequential knee pain (CKP), defined as a KOOS Pain subscore of ≤72 points, and severe kneeling difficulty (SKD), defined as a self-report of "severe" or "extreme" difficulty with kneeling. Absolute values of the KOOS Pain and Symptoms subscales were also compared.

RESULTS

A total of 10,999 patients were analyzed. At 2-year follow-up, 9.3% (420/4492) reported CKP, and 12.0% (537/4471) reported SKD. The most important predictor of CKP at 2-year follow-up was having significant pain before surgery (adjusted odds ratio, 4.10; P < .001). The most important predictor of SKD at 2-year follow-up was the use of a BTB autograft rather than a hamstring tendon autograft (21.3% vs 9.4%, respectively; adjusted odds ratio, 3.12; P < .001). There was no difference between the BTB and hamstring tendon grafts in terms of CKP (9.9% vs 9.2%, respectively; P = .494) or in absolute values of the KOOS Pain (mean, 88.7 vs 89.0, respectively; P = .37) and KOOS Symptoms (mean, 82.5 vs 82.1, respectively; P = .49) subscales.

CONCLUSION

At 2-year follow-up after primary ACL reconstruction, 9.3% of patients reported CKP, and 12.0% reported SKD. The BTB autograft was associated with difficulty with kneeling, but it did not result in a more painful or symptomatic knee compared with the hamstring tendon autograft.

Better post-operative outcomes at 1-year follow-up are associated with lower levels of pre-operative synovitis and higher levels of IL-6 and VEGFA in unicompartmental knee arthroplasty patients

PURPOSE

Osteoarthritis (OA) is associated with inflammation, and residual inflammation may influence outcomes following knee arthroplasty. This may be more relevant for patients undergoing unicompartmental knee arthroplasty (UKA) due to larger remaining areas of native tissue. This study aimed to: (1) characterise inflammatory profiles for medial UKA patients and (2) investigate whether inflammation markers are associated with post-operative outcomes.

METHODS

This prospective, observational study has national ethics approval. Bloods, synovial fluid, tibial plateaus and synovium were collected from medial UKA patients in between 1 January 2021 and 31 December 2021. Cytokine and chemokine concentrations in serum and synovial fluid (SF) were measured with multiplexed assays. Disease severity of cartilage and synovium was assessed using validated histological scores. Post-operative outcomes were measured with Oxford Knee Score (OKS), Forgotten Joint Score (FJS-12) and pain scores.

RESULTS

The study included 35 patients. SF VEGFA was negatively correlated with pre-operative pain at rest (r - 0.5, p = 0.007), and FJS-12 at six-week (r 0.44, p = 0.02), six-month (r 0.61, p < 0.01) and one-year follow-up (r 0.63, p = 0.03). Serum and SF IL-6 were positively correlated with OKS at early follow-up (serum 6 weeks, r 0.39, p = 0.03; 6 months, r 0.48, p < 0.01; SF 6 weeks, r 0.35, p = 0.04). At six weeks, increased synovitis was negatively correlated with improvements in pain at rest (r - 0.41, p = 0.03) and with mobilisation (r - 0.37, p = 0.047).

CONCLUSION

Lower levels of synovitis and higher levels of IL-6 and VEGFA were associated with better post-operative outcomes after UKA, which could be helpful for identifying UKA patients in clinical practice.

LEVEL OF EVIDENCE

Level IV case series.

Meniscal repair failure following concurrent primary anterior cruciate ligament reconstruction: results from the New Zealand ACL Registry

PURPOSE

This study aimed to identify the risk factors for meniscal repair failure following concurrent primary anterior cruciate ligament (ACL) reconstruction.

METHODS

Prospective data recorded by the New Zealand ACL Registry and the Accident Compensation Corporation were reviewed. Meniscal repairs performed during concurrent primary ACL reconstruction were included. Repair failure was defined as a subsequent reoperation involving meniscectomy of the repaired meniscus. Multivariate survival analysis was performed to identify the risk factors for failure.

RESULTS

A total of 3,024 meniscal repairs were analysed with an overall failure rate of 6.6% (n = 201) at a mean follow-up of 2.9 years (SD 1.5). The risk of medial meniscal repair failure was higher with hamstring tendon autografts (adjusted HR [aHR] = 2.20, 95% CI 1.36-3.56, p = 0.001), patients aged 21-30 years (aHR = 1.60, 95% CI 1.30-2.48, p = 0.037) and in patients with cartilage injury in the medial compartment (aHR = 1.75, 95% CI 1.23-2.48, p = 0.002). The risk of lateral meniscal repair failure was higher in patients aged ≤ 20 years (aHR = 2.79, 95% CI 1.17-6.67, p = 0.021), when the procedure was performed by a low case volume surgeon (aHR = 1.84, 95% CI 1.08-3.13, p = 0.026) and when a transtibial technique was used to drill the femoral graft tunnel (aHR = 2.30, 95% CI 1.03-5.15, p = 0.042).

CONCLUSION

The use of a hamstring tendon autograft, younger age and the presence of medial compartment cartilage injury are risk factors for medial meniscal repair failure, whereas younger age, low surgeon volume and a transtibial drilling technique are risk factors for lateral meniscal repair failure.

LEVEL OF EVIDENCE

Level II.

Success of Debridement, Antibiotics, and Implant Retention in Prosthetic Joint Infection Following Primary Total Knee Arthroplasty: Results from a Prospective Multicenter Study of 189 Cases

BACKGROUND

This study aimed to identify the success rate of debridement, antibiotics, and implant retention (DAIR) for prosthetic joint infection (PJI) in a large prospective cohort of patients undergoing total knee arthroplasty (TKA). The ability for different PJI classification systems to predict success was assessed.

METHODS

Prospective data recorded in the Prosthetic Joint Infection in Australia and New Zealand Observational (PIANO) study was analyzed. 189 newly diagnosed knee PJIs were managed with DAIR between July 2014 and December 2017. Patients were prospectively followed up for 2 years. A strict definition of success was used, requiring the patient being alive with documented absence of infection, no ongoing antibiotics and the index prosthesis in place. Success was compared against the Coventry (early PJI = ≤1 month), International Consensus Meeting (early = ≤90 days), Auckland (early = <1 year), and Tsukayama (early = ≤1 month, hematogenous = >1 month with <7 days symptoms, chronic = >1 month with >7 days symptoms) classifications.

RESULTS

DAIR success was 45% (85/189) and was highest in early PJIs defined according to the Coventry (adjusted odds ratio [aOdds Ratio (OR)] = 3.9, P=0.01), the ICM (aOR = 3.1, p=0.01), and the Auckland classifications (aOR = 2.6, P=0.01). Success was lower in both hematogenous (aOR = 0.4, P=0.03) and chronic infections (aOR = 0.1, P=0.003).

CONCLUSION

Time since primary TKA is an important predictor of DAIR success. Success was highest in infections occurring <1 month of the primary TKA and progressively decreased as time since the primary TKA increased.

The Effect of Minor Adjustments to Tibial and Femoral Component Position on Soft Tissue Balance in Robotic Total Knee Arthroplasty

BACKGROUND

Ideal goals for alignment and balance in total knee arthroplasty (TKA) remain controversial. We aimed to compare initial alignment and balance using mechanical alignment (MA) and kinematic alignment (KA) techniques, and to analyze the percentage of knees that could achieve balance using limited adjustments to component position.

METHODS

Prospective data on 331 primary robotic TKAs (115 MA and 216 KA) were analyzed. Medial and lateral virtual gaps were recorded in both flexion and extension. A computer algorithm was used to calculate potential (theoretical) implant alignment solutions to achieve balance within 1 millimeter (mm) without soft tissue release given an alignment philosophy (MA or KA), angular boundaries (±1, ±2, or ±3°), and gap targets (equal gaps or lateral laxity allowed). The percentage of knees that could theoretically achieve balance was compared.

RESULTS

Less than 5% of TKAs were initially balanced. Limited adjustments to component position increased the percentage of TKAs that could be balanced in a graduated manner, with no difference between MA and KA start points: adjustments of ±1 (10 vs 6% P=0.17), or ±2 (42 vs 39% P=0.61) or of ±3 (54 vs 51% P=0.66). A higher percentage of TKAs could be balanced when a greater range for lateral gap laxity was allowed. Balancing from KA resulted in increased joint line obliquity in the final implant alignment.

CONCLUSION

A high percentage of TKAs can be balanced without soft-tissue release using minor adjustments to component position. Surgeons should consider the relationship between alignment and balance goals when optimizing component positioning in TKA.

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 predictive ability of the 'pain' and 'function' domains.

PATIENTS AND METHODS

All primary total (TKAs) and unicompartmental knee arthroplasties (UKAs) in the New Zealand Joint Registry between 1999 and 2019 with an OKS at six months (TKA n=27,708, UKA n=8,415), five years (TKA n=11,519, UKA n=3,365) or ten 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 three questions ('overall pain,' 'limping when walking,' 'knee giving way') showed better diagnostic ability than full OKS for predicting UKA revision at six months (area under the curve (AUC): 0.80 vs. 0.78; P<0.01) and five years (0.81 vs. 0.77; P=0.02), and comparable diagnostic ability for predicting TKA revision at all timepoints (6 months, 0.77 vs. 0.76; 5 years, 0.78 vs. 0.75; 10 years, 0.76 vs. 0.73; all not significant (NS)), and UKA revision at 10 years (0.80 vs. 0.77; NS). The pain domain had better diagnostic ability for predicting subsequent revision for both procedures at five and ten 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.

Comparative Study of ACL Reconstruction With Hamstring Versus Patellar Tendon Graft in Young Women: A Cohort Study From the New Zealand ACL Registry

BACKGROUND

Young female athletes are a specific population that is at high risk of primary anterior cruciate ligament (ACL) rupture and subsequent graft failure. Despite large numbers of ACL reconstructions being carried out in young women, there is limited analysis of outcomes in this group, leading to low levels of evidence for graft choice.

PURPOSE

To assess the effect of graft choice on ACL reconstruction failure rates among young women in New Zealand.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

Prospective data captured by the New Zealand ACL Registry between April 2014 and March 2022 were reviewed. Young women aged 15 to 20 years were included. The primary outcome measure was ACL graft failure during the study period, with the key independent variable being graft type, either patellar or hamstring tendon autograft. This is presented as the rate per 100 patient-years and is compared between the 2 groups using the hazard ratio generated from a Cox proportional hazards regression. Secondary outcome measures were Marx activity scores and the Knee injury and Osteoarthritis and Outcome Score patient-reported outcome measure.

RESULTS

A total of 1261 primary ACL reconstructions in young women aged 15 to 20 years were reviewed. Hamstring tendon grafts were used in 797 (63%) reconstructions and patellar tendon graft in 464 (37%) reconstructions. Patients with a hamstring tendon graft had a graft failure rate of 7.7% compared with 1.1% in patients with a patellar tendon graft (hazard ratio, 6.1; 95% CI, 2.4-15.1; P < .001). The number of failures per 100 person-years was significantly higher in the hamstring group (2.05) compared with the patellar tendon group (0.37). No difference was noted at final follow-up between the hamstring tendon and patellar tendon groups when comparing patient-reported outcome measures during the follow-up period.

CONCLUSION

In the young female population of this study, the use of a patellar tendon graft was associated with reduced risk of graft failure and was not associated with an increase in knee morbidity. This highlights the importance of informed decision-making in this high-risk population when considering ACL reconstruction graft type.

Robotic-arm assisted unicompartmental knee arthroplasty system has a learning curve of 11 cases and increased operating time

PURPOSE

UKA has higher revision risk, particularly for lower volume surgeons. While robotic-arm assisted systems allow for increased accuracy, introduction of new systems has been associated with learning curves. The aim of this study was to determine the learning curve of a UKA robotic-arm assisted system. The hypothesis was that this may affect operative times, patient outcomes, limb alignment, and component placement.

METHODS

Between 2017 and 2021, five surgeons performed 152 consecutive robotic-arm assisted primary medial UKA, and measurements of interest were recorded. Patient outcomes were measured with Oxford Knee Score, EuroQol-5D, and Forgotten Joint Score at 6 weeks, 1 year, and 2 years. Surgeons were grouped into 'low' and 'high' usage groups based on total UKA (manual and robotic) performed per year.

RESULTS

A learning curve of 11 cases was found with operative time (p < 0.01), femoral rotation (p = 0.02), and insert sizing (p = 0.03), which highlighted areas that require care during the learning phase. Despite decreased 6-week EQ-5D-5L VAS in the proficiency group (77 cf. 85, p < 0.01), no difference was found with implant survival (98.2%) between phases (p = 0.15), or between 'high' and 'low' usage surgeons (p = 0.23) at 36 months. This suggested that the learning curve did not lead to early adverse effects in this patient cohort.

CONCLUSION

Introduction of a UKA robotic-arm assisted system showed learning curves for operative times and insert sizing but not for implant survival at early follow-up. The short learning curve regardless of UKA usage indicated that robotic-arm assisted UKA may be particularly useful for low-usage surgeons.

LEVEL OF EVIDENCE

Level III, Retrospective cohort study.

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.

Stability and compatibility of admixtures containing bupivacaine hydrochloride and ketorolac tromethamine for parenteral use

OBJECTIVE

Bupivacaine hydrochloride (BH) and ketorolac tromethamine (KT) are commonly used in parenteral admixtures to manage postoperative pain. However, stability and compatibility data for these admixtures applicable to current practice are limited, posing the patient to potential risk.

METHODS

The stability of BH/KT admixtures in commonly used parenteral fluids was studied in Eppendorf tubes and glass vials at ambient room temperature using a newly developed and validated stability-indicating high-performance liquid chromatography (HPLC) method capable of the simultaneous quantification of both drugs. The chemical compatibility of BH/KT was assessed using Fourier transform infrared spectroscopy (FTIR) and thermal analysis. Additionally, the validity of the developed HPLC method for the quantification of BH/KT in human plasma was evaluated.

RESULTS

BH and KT demonstrated <10% loss of their initial concentrations when prepared in Ringer, normal saline or dextrose solution at ambient temperature for up to 4 weeks. FTIR and thermal analysis demonstrated mild intermolecular interactions between BH and KT in solution, with no evidence of incompatibility. The developed HPLC method demonstrated satisfactory accuracy and precision for the simultaneous quantification of BH and KT in human plasma over the range of 0.2-3.2 µg·mL-1.

CONCLUSION

BH/KT parenteral admixtures are chemically stable for a period of 4 weeks when stored at room temperature. The stability-indicating HPLC method is valid for BH/KT simultaneous determination in human plasma, facilitating pharmacokinetics studies.

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.

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.

Safety and efficacy of intraosseous ropivacaine in lower extremity (SORE) study

BACKGROUND

Day stay surgery for anterior cruciate ligament (ACL) reconstructions is an increasingly common practice and has driven clinicians to develop postoperative pain regimes that allow same day mobilization and a safe and timely discharge. There is a paucity of literature surrounding the use of intraosseous (IO) ropivacaine used as a Bier's block to provide both intraoperative and postoperative analgesia in lower limb surgery.

METHODS

This patient blinded, pilot study randomized 15 patients undergoing ACL reconstruction to receive either IO ropivacaine 1.5 or 2.0 mg/kg; or 300 mg of ropivacaine as local infiltration. The primary outcome for this study was arterial plasma concentration of ropivacaine. Samples were taken via an arterial line at prespecified times after tourniquet deflation. Secondary outcomes included immediate postoperative pain scores using the visual analogue scale and perioperative opioid equivalent consumption.

RESULTS

All patients in the intervention group receiving IO ropivacaine had plasma concentrations well below the threshold for central nervous system (CNS) toxicity (0.60 μg/mL). The highest plasma concentration was achieved in the intervention group receiving 1.5 mg/kg dose of ropivacaine reaching 2.93 mg/mL. This would equate to 0.18 μg/mL of free plasma ropivacaine. There were no differences across the three groups regarding pain scores or perioperative opioid consumption.

CONCLUSIONS

This study demonstrates that IO ropivacaine is both safe and effective in reducing perioperative pain in patients undergoing ACL reconstruction. There may be scope to increase the IO dose further or utilize other analgesics via the IO regional route to improve perioperative pain relief.

Early manipulation under anaesthesia for stiffness following total knee arthroplasty is associated with a greater gain in knee flexion

PURPOSE

This study aimed to identify the risk factors for manipulation under anaesthesia (MUA) following total knee arthroplasty (TKA) and whether performing an 'early' MUA within 3 months leads to a greater improvement in range of motion.

METHODS

Primary TKAs performed between 2013 and 2018 at three tertiary New Zealand hospitals were reviewed with a minimum follow-up of 1 year. Clinical details of patients who underwent MUA were reviewed to identify the knee flexion angle prior to and following MUA. Multivariate analysis identified the risk factors for undergoing MUA and compared flexion angles between 'early' (< 3 months) and 'late' MUA (> 3 months).

RESULTS

A total of 7386 primary TKAs were analysed in which 131 underwent an MUA (1.8%). Patients aged < 65 years were two times more likely to undergo MUA compared to patients aged ≥ 65 years (2.5 versus 1.3%, p < 0.001; adjusted HR = 2.1, p < 0.001). There was no difference in the final flexion angle post-MUA between early and late MUA (104.7° versus 104.1°, p = 0.819). However, patients who underwent early MUA had poorer pre-MUA flexion (72.3° versus 79.6°, p = 0.012), and subsequently had a greater overall gain in flexion compared to those who underwent late MUA (mean gain 33.1° versus 24.3°, p < 0.001).

CONCLUSION

Younger age was the only patient risk factor for MUA. Patients who underwent early MUA had similar post-MUA flexion, but had poorer pre-MUA flexion compared to those who underwent late MUA. Subsequently, a greater overall gain in flexion was achieved in those who underwent early MUA.

LEVEL OF EVIDENCE

III.

A combination of high preoperative pain and low radiological grade of arthritis is associated with a greater intensity of persistent pain 12 months after total knee arthroplasty

Aims

Despite new technologies for total knee arthroplasty (TKA), approximately 20% of patients are dissatisfied. A major reason for dissatisfaction and revision surgery after TKA is persistent pain. The radiological grade of osteoarthritis (OA) preoperatively has been investigated as a predictor of the outcome after TKA, with conflicting results. The aim of this study was to determine if there is a difference in the intensity of pain 12 months after TKA in relation to the preoperative radiological grade of OA alone, and the combination of the intensity of preoperative pain and radiological grade of OA.

Methods

The preoperative data of 300 patients who underwent primary TKA were collected, including clinical information (age, sex, preoperative pain), psychological variables (depression, anxiety, pain catastrophizing, anticipated pain), and quantitative sensory testing (temporal summation, pressure pain thresholds, conditioned pain modulation). The preoperative radiological severity of OA was graded according to the Kellgren-Lawrence (KL) classification. Persistent pain in the knee was recorded 12 months postoperatively. Generalized linear models explored differences in postoperative pain according to the KL grade, and combined preoperative pain and KL grade. Relative risk models explored which preoperative variables were associated with the high preoperative pain/low KL grade group.

Results

Pain 12 months after TKA was not associated with the preoperative KL grade alone. Significantly increased pain 12 months after TKA was found in patients with a combination of high preoperative pain and a low KL grade (p = 0.012). Patients in this group were significantly more likely to be male, younger, and have higher preoperative pain catastrophizing, higher depression, and lower anxiety (all p ≤ 0.05).

Conclusion

Combined high preoperative pain and low radiological grade of OA, but not the radiological grade alone, was associated with a higher intensity of pain 12 months after primary TKA. This group may have a more complex cause of pain that requires additional psychological interventions in order to optimize the outcome of TKA. Cite this article: Bone Joint J 2022;104-B(11):1202–1208.

Robotic-arm assisted total knee arthroplasty has a learning curve of 16 cases and increased operative time of 12 min

BACKGROUND

Robotic-arm assisted systems are increasingly used for knee arthroplasty, however introduction of new systems can involve a learning curve. We aimed to define the learning curve in terms of operative time and component placement/sizing of a robotic system for total knee arthroplasty (TKA) in a team of experienced surgeons, and to investigate mid-term patient outcomes.

METHODS

A total of 101 consecutive patients underwent primary robotic-arm assisted TKA by three surgeons (mean 2 year follow-up). Operative times, component placement, implant sizing and reoperations were recorded. Cumulative Summation (CUSUM) was used to analyse learning curves. Patient outcomes were compared between learning and proficiency phases.

RESULTS

The learning curve was 16 cases, with a 12-min increase in operative time (P < 0.01). Once proficiency was achieved, the greatest time reductions were seen for navigation registration (P = 0.003) and bone preparation (P < 0.0001). A learning curve was found with polyethylene (PE) insert sizing (P = 0.01). No differences were found between learning and proficiency groups in terms of implant survival (100% and 97%, respectively, NS) or patient-reported outcome measures at 2 years (NS).

CONCLUSION

Introduction of a robotic-arm assisted system for TKA led to increased operative times for navigation registration and bone preparation, and a learning curve with PE insert sizing. No difference in patient outcomes between learning and proficiency groups at 2 years was found. These findings can inform surgeons' expectations when starting to use robotic-assisted systems.

No Difference in Revision Rate Between Low Viscosity and High Viscosity Cement Used in Primary Total Knee Arthroplasty

BACKGROUND

Loosening remains one of the most common reasons for revision total knee arthroplasty (TKA). Cement viscosity has a potential role in reducing revision rates for loosening. The aim of this study was to assess the outcome for loosening of the 5 most used cemented knee prostheses by constraint type, based on the cement viscosity type used.

METHODS

There were 214,708 TKA procedures performed between 1999 and 2020 for a diagnosis of osteoarthritis using the 5 most commonly used minimally stabilized, posterior stabilized, and medial pivot design cemented tibial components. Only procedures with a cemented tibial component were included. Outcomes for two different cement viscosities, 140,060 high viscosity and 74,648 low viscosity cement, were compared for each fixation type within each of the three stability groups.

RESULTS

There was no difference in a risk of all-cause revision when high viscosity cement was used compared to low viscosity cement for minimally stabilized prostheses (hazards ratio [HR] 1.07 [95% CI 0.99-1.15], P = .09), posterior stabilized prostheses (HR 1.03 [95% CI 0.95-1.11], P = .53), and medial pivot design prostheses (HR 1.06 [95% CI 0.80-1.41], P = .67). No difference was observed between cement viscosity types for any of the prosthesis constraint types when aseptic loosening was assessed.

CONCLUSIONS

We found no difference in the risk of revision for any reason, or for loosening, with cement viscosity for the most commonly used minimally stabilized, posterior stabilized, and medial pivot TKA. The role of cement viscosity in the risk of TKA revision remains unclear and further research is required.

LEVEL OF EVIDENCE

Level III Retrospective comparative study.

Disease progression, aseptic loosening and bearing dislocations are the main revision indications after lateral unicompartmental knee arthroplasty: a systematic review

IMPORTANCE

Lateral unicompartmental knee arthroplasty (UKA) is a surgical option for patients with isolated lateral osteoarthritis however, the procedure has higher revision rates than medial UKA. The reason for this remains unclear; therefore, a better understanding of the indications for lateral UKA revision is needed.

AIM

The primary aim of this systematic review was to identify revision indications for lateral UKA. Secondary aims were to further investigate if revision indications were influenced by implant design and time from surgery.

EVIDENCE REVIEW

A systematic literature review was performed according to the PRISMA 2020 guidelines. Search was performed in January 2022 in MedLine, EMBASE, CINAHL and the Cochrane Library using the keywords "knee arthroplasty", "unicompartmental", "reoperation", synonyms and abbreviations. Articles published in 2000-2021 that were at least level III retrospective cohort studies with at least 10 lateral UKAs and reported all failure modes were included. Risk of bias was assessed using the ROBINS-I tool. Revision indications, patient characteristics, study design, implant types and time to failure were extracted from the selected studies. Collated data were tabulated and differences were tested using Chi-square or Fisher's exact test.

FINDINGS

A total of 29 cohort and 4 registry studies that included 7,668 UKAs met the inclusion criteria. Studies were judged as having moderate or severe risk of bias; this was associated with the retrospective nature of studies required to investigate long-term outcomes of knee arthroplasty. The main indications for lateral UKA revision were OA progression (35%), aseptic loosening (17%) and bearing dislocation (14%). The incidence of revision was similar for mobile-bearing implants (7.6%) and fixed-bearing (6.4%). For mobile-bearing implants, there was introduction of bearing dislocations as an additional mode of failure (24% cf. 0%, p < 0.001). For fixed-bearing implants, the incidence of revision was higher for all-poly-ethylene (13.9%) than metal-backed (1.8%) tibial components. Early lateral UKA failures were associated with bearing dislocations (sequential decrease from 69% under 6 months to 0% 10+ years, p < 0.001), whereas late failures were associated with OA progression (sequential increase from 0% under 6 months to 100% > 10+ years, p < 0.01). Compared with medial UKA, OA progression (41% cf. 30%, p = 0.004), malalignment (2.7% cf. 0.8%, p = 0.02), instability (4% cf. 1%, p = 0.02) and bearing dislocations (20% cf. 10%, p < 0.001) were more common for lateral UKA.

CONCLUSIONS AND RELEVANCE

OA progression, aseptic loosening and bearing dislocation were the three main revision indications for lateral UKA. Compared to medial UKA, OA progression, malalignment, instability and bearing dislocations were more common revision indications for lateral UKA. Higher survivorship of metal-backed fixed-bearing implants was found. The findings suggest that the outcomes of lateral UKA may be improved with more optimal alignment, gap balancing and patient selection.

LEVEL OF EVIDENCE

Level III systematic review.

A prospective randomised controlled trial of mechanical axis with soft tissue release balancing vs functional alignment with bony resection balancing in total knee replacement-a study using Stryker Mako robotic arm-assisted technology

Background

Improving the functional outcome following total knee arthroplasty (TKA) by using different alignment techniques remains controversial. The surgical techniques and technologies used so far to obtain these alignments have all suffered from inaccuracies. The use of robotic technology to plan and execute the bony resection provides increased accuracy for these various alignment techniques and may determine which will deliver superior function. Functional alignment (FA) is a newer surgical technique that aims to position the prosthesis with respect to each patients’ specific bony anatomy whilst minimising disruption to the soft tissue envelope. This trial aims to compare the patient and surgical outcomes of FA to the current gold standard surgical technique, mechanical alignment (MA), under randomised and blinded conditions.

Methods

Patients with symptomatic knee osteoarthritis will be prospectively recruited. Following informed consent, 240 patients will be randomised to either a MA surgical technique (the control group) or a FA surgical technique (the intervention group) at a ratio of 4:1 using a random number generator. All patients will undergo computer tomography (CT) based robotic arm-assisted surgery to execute planned implant positioning and alignment with high levels of accuracy. The primary outcome is the forgotten joint score (FJS) at 2 years post-operation. Secondary outcome measures include patient reported outcome measures of post-operative rehabilitation, pain, function and satisfaction, as well as limb alignment, implant revisions and adverse events. Intention-to-treat and per-protocol population analysis will also be conducted. Standardisation of the surgical system and care pathways will minimise variation and assist in both patient and physiotherapist blinding. Ethical approval was obtained from the Northern B Health and Disability Ethics Committee (20/NTB/10).

Discussion

Currently, MA remains the gold standard in knee replacement due to proven outcomes and excellent long-term survivorship. There are many alternative alignment techniques in the literature, all with the goal of improving patient outcomes. This study is unique in that it leverages an advanced analytics tool to assist the surgeon in achieving balance. Both alignment techniques will be executed with high precision using the CT-based robotic arm-assisted surgery system which will minimise surgical variation. This trial design will help determine if FA delivers superior outcomes for patients.

Trial registration

Australia and New Zealand Clinical Trials Registry (ANZCTR), ACTRN12620000009910. Registered on 9 January 2020. ClinicalTrials.gov, NCT04600583. Registered on 29 September 2020.

Optimal Graft Choice in Athletic Patients with Anterior Cruciate Ligament Injuries: Review and Clinical Insights

Anterior cruciate ligament (ACL) rupture is a common sporting-related knee injury with a potentially detrimental impact on the athlete’s career, yet there is no formal consensus on the optimal graft choice for reconstructing the ruptured ACL in this specific population. Options for reconstruction include autograft, allograft, and artificial grafts. However, each has associated failure risk and donor site morbidity. Our operational definition of the athlete is a skeletally mature individual participating in high level activity with the expectation to return to pre-injury level of activity. The athlete has unique injury characteristics, post-operative expectations, and graft demands that differ to the general population. Long-term outcomes are of particular importance given on-going mechanical demands on the reconstructed knee. Therefore, the purpose of this review is to consolidate current literature on the various ACL reconstruction graft options, with a focus on the optimal graft for returning the athlete to activity with the lowest rate of re-injury.

The lifetime revision risk of unicompartmental knee arthroplasty

AIMS

Unicompartmental knee arthroplasty (UKA) has a higher risk of revision than total knee arthroplasty (TKA), particularly for younger patients. The outcome of knee arthroplasty is typically defined as implant survival or revision incidence after a defined number of years. This can be difficult for patients to conceptualize. We aimed to calculate the 'lifetime risk' of revision for UKA as a more meaningful estimate of risk projection over a patient's remaining lifetime, and to compare this to TKA.

METHODS

Incidence of revision and mortality for all primary UKAs performed from 1999 to 2019 (n = 13,481) was obtained from the New Zealand Joint Registry (NZJR). Lifetime risk of revision was calculated for patients and stratified by age, sex, and American Society of Anesthesiologists (ASA) grade.

RESULTS

The lifetime risk of revision was highest in the youngest age group (46 to 50 years; 40.4%) and decreased sequentially to the oldest (86 to 90 years; 3.7%). Across all age groups, lifetime risk of revision was higher for females (ranging from 4.3% to 43.4% vs males 2.9% to 37.4%) and patients with a higher ASA grade (ASA 3 to 4, ranging from 8.8% to 41.2% vs ASA 1 1.8% to 29.8%). The lifetime risk of revision for UKA was double that of TKA across all age groups (ranging from 3.7% to 40.4% for UKA, and 1.6% to 22.4% for TKA). The higher risk of revision in younger patients was associated with aseptic loosening in both sexes and pain in females. Periprosthetic joint infection (PJI) accounted for 4% of all UKA revisions, in contrast with 27% for TKA; the risk of PJI was higher for males than females for both procedures.

CONCLUSION

Lifetime risk of revision may be a more meaningful measure of arthroplasty outcomes than implant survival at defined time periods. This study highlights the higher lifetime risk of UKA revision for younger patients, females, and those with a higher ASA grade, which can aid with patient counselling prior to UKA. Cite this article: Bone Joint J 2022;104-B(6):672-679.

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.

Higher Tissue Concentrations of Vancomycin Achieved With Low-Dose Intraosseous Injection Versus Intravenous Despite Limited Tourniquet Duration in Primary Total Knee Arthroplasty: A Randomized Trial

BACKGROUND

Vancomycin use has been suggested in high risk patients undergoing total knee arthroplasty (TKA). Previous literature has shown that a lower dose (500 mg) of vancomycin given by intraosseous regional administration (IORA) achieves tissue concentrations 4-10 times higher than intravenous (IV) administration. There is increasing interest in performing TKA with limited tourniquet inflation time. The purpose of this study is to evaluate whether IORA of vancomycin can achieve effective tissue concentrations with limited tourniquet inflation time.

METHODS

Based on prior power calculations, 24 patients undergoing primary TKA were randomized into 2 groups. Group IV-Systemic received weight-based (15 mg/kg) vancomycin with the tourniquet inflated for cementation only. Group IORA received 500 mg vancomycin via IORA after tourniquet inflation which remained inflated for 10 minutes, then reinflated for cementation only. Vancomycin concentrations from tissue, serum, and drain fluid were compared between the 2 groups.

RESULTS

Median vancomycin concentrations in tissue were significantly higher (5-15 times) at all time points in the IORA group. Concentrations in fat at the time of wound closure, after the tourniquet had been deflated for most of the procedure, were 5.2 μg/g in Group IV-Systemic and 33.1 μg/g in Group IORA (P < .001). Median bone concentrations taken just prior to cementation were 7.9 μg/g in Group IV-Systemic and 21.8 μg/g in Group IORA (P = .006). There were no complications related to IORA.

CONCLUSION

For surgeons who wish to limit tourniquet time and when indicated to use vancomycin, low-dose vancomycin IORA achieves tissue concentrations 5-15 times higher than those achieved by IV administration.

LEVEL OF EVIDENCE

Level 1 therapeutic randomized trial.

Do TKAs in Patients with Higher BMI Take Longer, and is the Difference Associated with Surgeon Volume? A Large-database Study from a National Arthroplasty Registry

BACKGROUND

Increased surgical time in TKA may impact economic costs and clinical outcomes. Prior work has found that TKAs in patients with high BMI take longer, and these patients may be at greater risk for postoperative complications like infection. However, these studies included small numbers of patients and surgeons from single institutions and they did not consider surgeon volume.

QUESTIONS/PURPOSES

Using the New Zealand Joint Registry (NZJR), we asked: (1) Is there a relationship between increasing patient BMI and TKA operative time? (2) Is the effect of BMI on surgical time less pronounced among surgeons who perform more TKAs per year than those who perform fewer?

METHODS

Data were collected from the NZJR between January 2010 and December 2018 as it is the only national registry that records both BMI and surgical time. Primary TKA performed for osteoarthritis by surgeons with more than 50 TKAs over the period of the study were identified. BMI and operative time (skin incision to closure in minutes) were recorded. Patients with the following were excluded: lateral parapatellar or minimally invasive approaches; navigated, patient-specific instrumentation, or robot-assisted TKA; uncemented or hybrid fixation; those with procedures performed by a trainee (all or part); or a nonosteoarthritic indication. Of 64,108 TKAs performed during the study period, a total of 42% (27,057) met our inclusion criteria. The primary outcome was the effect of BMI on operative time. Operative time is expressed in minutes as a mean for each single-unit BMI increase across all surgeons, controlled for other variables that might influence operative time such as patella resurfacing and cruciate-retaining versus posterior-stabilized designs. Overall, the mean operative time (skin incision to closure) was 79 ± 22 minutes. Surgical experience was assessed by subdividing surgeons into six groups according to the number of TKAs performed annually (< 10, 10 to 24, 25 to 49, 50 to 74, 75 to 99, and > 100). Statistical analyses were performed including a general linear model to assess the independent association between BMI and operative time, allowing for the effects of other patient and surgical features. In addition, linear regression analyses explored the associations between BMI and operative time in the whole group and within surgical volume groups.

RESULTS

There was an association between increasing BMI and increasing surgical duration. The mean operative time increased from 75 ± 22 minutes in patients with a normal BMI of 25 kg/m2 to 87 ± 24 minutes in patients with a BMI of 40 kg/m2 to 94 ± 28 minutes in patients with a BMI > 50 kg/m2 (p < 0.001). Surgeons performing fewer than 25 TKAs per year took 14% longer to perform a TKA on a patient with a BMI of 40 kg/m2 than on a patient with a normal BMI of 25 kg/m2. However, surgeons performing greater than 25 TKAs per year took 10% longer.

CONCLUSION

In this study, an increase BMI was associated with increased surgical time in TKA. Surgical duration for high-volume surgeons appears less influenced by increases in BMI than lower volume surgeons. Although the absolute increase in duration was small, prolonged surgical time may reduce theater productivity. Even though the issues around managing patients with high BMI are multifactorial and complex, considerations from these findings include ensuring appropriate theater scheduling and possibly referring patients with high BMI to specialist centers. Further studies should focus on assessing the effectiveness of such measures in reducing complications and improving outcomes in patients with elevated BMI.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Suspensory Versus Interference Tibial Fixation of Hamstring Tendon Autografts in Anterior Cruciate Ligament Reconstruction: Results From the New Zealand ACL Registry

BACKGROUND

The hamstring tendon is frequently used to reconstruct the anterior cruciate ligament (ACL), but there is a lack of consensus on the optimal method of fixation. Registry studies have shown that the type of femoral fixation device can influence the risk of revision ACL reconstruction (ACLR), but it is unclear whether the type of tibial fixation has an effect. In New Zealand, over 95% of hamstring tendon grafts are fixed with an adjustable loop suspensory device on the femoral side, with variable usage between suspensory and interference devices, with or without a sheath, on the tibial side.

PURPOSE

To investigate the association between the type of tibial fixation device and the risk of revision ACLR.

STUDY DESIGN

Cohort Study; Level of evidence, 2.

METHODS

Prospective data recorded in the New Zealand ACL Registry were analyzed. Only primary ACLRs performed with a hamstring tendon autograft fixed with a suspensory device on the femoral side were included. A Cox regression survival analysis with adjustment for patient factors was performed to analyze the effects of the type of tibial fixation device, the number of graft strands, and graft diameter on the risk of revision.

RESULTS

A total of 6145 primary ACLRs performed between 2014 and 2019 were analyzed. A total of 59.6% of hamstring tendon autografts were fixed with a suspensory device on the tibial side (n = 3662), 17.6% with an interference screw with a sheath (n = 1079), and 22.8% with an interference screw without a sheath (n = 1404). When compared with suspensory devices, a higher revision risk was observed when using an interference screw with a sheath (adjusted hazard ratio [HR], 2.05; P = .009) and without a sheath (adjusted HR, 1.81; P = .044). The number of graft strands and a graft diameter of ≥8 mm were associated with the rate of revision on the univariate analysis; however, after adjusting for confounding variables on the multivariate analysis, they did not significantly influence the risk of revision.

CONCLUSION

In this study of hamstring tendon autografts fixed with an adjustable loop suspensory device on the femoral side during primary ACLR, the use of an interference screw, with or without a sheath, on the tibial side resulted in a higher revision rate when compared with a suspensory device.

The lifetime risk of revision following total knee arthroplasty : a New Zealand Joint Registry study

AIMS

The success of total knee arthroplasty (TKA) is usually measured using functional outcome scores and revision-free survivorship. However, reporting the lifetime risk of revision may be more meaningful to patients when gauging risks, especially in younger patients. We aimed to assess the lifetime risk of revision for patients in different age categories at the time of undergoing primary TKA.

METHODS

The New Zealand Joint Registry database was used to obtain revision rates, mortality, and the indications for revision for all primary TKAs performed during an 18-year period between January 1999 and December 2016. Patients were stratified into age groups at the time of the initial TKA, and the lifetime risk of revision was calculated according to age, sex, and the American Society of Anesthesiologists (ASA) grade. The most common indications for revision were also analyzed for each age group.

RESULTS

The overall ten-year survival rate was 95.6%. This was lowest in the youngest age group (between 46 and 50 years) and increased sequentially with increasing age. The lifetime risk of requiring revision was 22.4% in those aged between 46 and 50 years at the time of the initial surgery, and decreased linearly with increasing age to 1.15% in those aged between 90 and 95 years at the time of surgery. Higher ASA grades were associated with increased lifetime risk of revision in all age groups. The three commonest indications for revision were aseptic loosening, infection, and unexplained pain. Young males, aged between 46 and 50 years, had the highest lifetime risk of revision (25.2%).

CONCLUSION

Lifetime risk of revision may be a more meaningful measure of outcome than implant survival at defined time periods when counselling patients prior to TKA. This study highlights the considerably higher lifetime risk of revision surgery for all indications, including infection, in younger male patients. Cite this article: Bone Joint J 2022;104-B(2):235-241.

Low percentage of surgeons meet the minimum recommended unicompartmental knee arthroplasty usage thresholds: Analysis of 3037 Surgeons from Three National Joint Registries

PURPOSE

The reported usage of UKA is around 10% in the UK, Australian and New Zealand joint registries. However, some authors recommend that a higher UKA usage of 20%, or a minimum 12 UKA cases per year, would reduce revision rates. The purpose of this study was to analyze the percentage of surgeons performing the recommended thresholds in these 3 registries.

METHODS

Data from the UK, Australian and New Zealand registry databases was utilized from the time period since their respective introduction until 2017. All primary TKA and UKA performed for the diagnosis of osteoarthritis by surgeons with more than 100 recorded knee arthroplasties in their respective registry were included. The results between the registries were compared and a pooled analysis was performed. The number of surgeons meeting the recommended caseload of > 20% UKA yearly or 12 UKA cases yearly was calculated.

RESULTS

We identified 3037 knee surgeons performing 1,556,440 knee arthroplasties, of which 131,575 were UKA (8.45%). Over 50% of knee surgeons in each registry had a proportion of less than 5% UKA of their knee replacement procedures. After pooling of data, median surgeon UKA usage was 2.0% (IQR 0-9.1%). The percentage of surgeons meeting the proposed caseload criteria was highest in New Zealand, 16.3%, followed by the UK at 12.4% and Australia 11.3% (p = 0.28).

CONCLUSION

More than 50% of knee surgeons in UK, Australian and New Zealand joint registries perform less than 5% of UKA yearly. The majority of experienced knee surgeons are not meeting the recommended minimum thresholds, which might indicate that the recommended thresholds are not feasible for the vast majority of knee surgeons. The reasons behind this require further research.

LEVEL OF EVIDENCE

Level III retrospective registry study.

Measuring appropriate need for unicompartmental knee arthroplasty: results of the MANUKA study

PURPOSE

Indications for unicompartmental knee arthroplasty (UKA) are controversial. Studies based solely on radiographic criteria suggest up to 49% of patients with knee osteoarthritis (OA) are suitable for UKA. In contrast, the 'Appropriate use criteria' (AUC), developed by the AAOS, apply clinical and radiographic criteria to guide surgical treatment of knee OA. The aim of this study was to analyze patient suitability for TKA, UKA and osteotomy using both radiographic criteria and AUC in a cohort of 300 consecutive knee OA patients.

METHODS

Included were consecutive patients with clinical and radiographic signs of knee OA referred to a specialist clinic. Collected were demographic data, radiographic wear patterns and clinical findings that were analyzed using the AUC. A comparison of the radiographic wear patterns with the treatment suggested by the AUC as well as the Surgeon Treatment Decision was performed.

RESULTS

There were 397 knees in 300 patients available for analysis. Median age was 68 [IQR 15], BMI 30 [6] with 55% females. Excellent consistency for both the radiographic criteria and the AUC criteria was found. Based on radiological criteria, 41% of knees were suitable for UKA. However, when using the AUC criteria, UKA was the appropriate treatment in only 13.3% of knees. In 19.1% of knees, no surgical treatment was appropriate at the visit, based on the collected data.

CONCLUSION

Application of isolated radiologic criteria in patients with knee OA results in a UKA candidacy is misleadingly high. AUC that are based on both radiological and clinical criteria suggest UKA is appropriate in less than 15% of patients.

LEVEL OF EVIDENCE

III retrospective study.

Higher Rate of Return to Preinjury Activity Levels After Anterior Cruciate Ligament Reconstruction With a Bone-Patellar Tendon-Bone Versus Hamstring Tendon Autograft in High-Activity Patients: Results From the New Zealand ACL Registry

BACKGROUND

In primary anterior cruciate ligament (ACL) reconstruction, a bone-patellar tendon-bone (BTB) autograft is associated with lower ipsilateral failure rates. BTB autografts are associated with a higher rate of contralateral ACL injuries, which some clinicians view as a marker of success of the BTB autograft. However, there is a lack of evidence on whether BTB autografts improve the rate of return to activity and sport.

PURPOSE

To compare the rate of return to preinjury activity levels in high-activity patients after ACL reconstruction with BTB autograft or hamstring tendon autograft.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

In a high-activity cohort of patients recorded between 2014 and 2018 in the New Zealand ACL Registry, prospectively collected data on preinjury and postoperative Marx activity scores were analyzed. The proportion of patients who returned to their preinjury activity levels at 1- and 2-year follow-up was compared between graft types.

RESULTS

Overall, 11.3% (208/1844) of patients returned to their preinjury activity levels at 1-year follow-up, and 15.5% (184/1190) returned at 2-year follow-up. At 1-year follow-up, 17.2% of patients with a BTB autograft returned to their preinjury activity levels compared with 9.3% of patients with a hamstring tendon autograft (adjusted odds ratio, 1.59 [95% CI, 1.16-2.17]; P = .004). At 2-year follow-up, 23.3% of patients with a BTB autograft had returned to their preinjury activity levels compared with 13.3% of patients with a hamstring tendon autograft (adjusted odds ratio, 1.63 [95% CI, 1.14-2.34]; P = .008). Male sex and younger age were associated with a higher rate of return to activity at both follow-up time points.

CONCLUSION

The use of BTB autografts increased the odds of returning to preinjury activity levels at early follow-up. A higher rate of return to activity is a possible explanation for the higher rate of contralateral ACL injuries with the use of BTB autografts.

Infection and periprosthetic fracture are the leading causes of failure after aseptic revision total knee arthroplasty

AIM

The purpose of this study was to clarify the medium to long term survival of aseptic revision total knee arthroplasty (RTKAs) and identify the common modes of failure following RTKAs.

MATERIALS AND METHODS

A multi-center, retrospective study included all aseptic RTKAs performed at three tertiary referral hospitals between 2003 and 2016. Patients were excluded if the revision was for prosthetic joint infection (PJI) or they had previously undergone revision surgery. Minor revisions not involving the tibial or femoral components were also excluded. Demographics, surgical data and post-operative outcomes were recorded and analyzed. Survival analysis was performed and the reasons for revision failure identified.

RESULTS

Of 235 aseptic RTKAs identified, 14.8% underwent re-revision at mean follow-up of 8.3 years. Survivorship of RTKA was 93% at 2 years and 83% at 8 years. Average age at revision was 72.9 years (range 53-91.5). The most common reasons for failure following RTKA were periprosthetic joint infection (PJI) (40%), periprosthetic fracture (25.7%) and aseptic loosening (14.3%). Of those whose RTKA failed, the average survival was 3.33 years (8 days-11.4 years). No demographic or surgical factors were found to influence RTKA survival on univariate or multivariate analysis.

CONCLUSION

PJI and periprosthetic fracture are the leading causes of re-revision surgery following aseptic revision TKA. Efforts to improve outcomes of aseptic revision TKA should focus on these areas, particularly prevention of PJI.

Impact of smoking on pain and function in rotator cuff repair: A prospective 5-year cohort follow-up of 1383 patients

BACKGROUND

This multicentre cohort study investigates the effect of smoking on the outcome of rotator cuff repair (RCR), with attention to age at presentation for surgery, pre-operative and post-operative pain and function and intra-operative findings.

METHODS

Patient information was collected pre-operatively, including Flex Shoulder Function (Flex SF) and visual analogue scale pain, then at 6 months, 1, 2 and 5 years post-operatively. Intra-operative technical data were collected by the operating surgeon. Current smokers were classified by daily cigarette consumption.

RESULTS

A total of 1383 RCRs in as many patients were included with an 84% 5-year follow-up. Smokers were on average 6.7 years younger than non-smokers (51.8 vs. 58.5, P < 0.001). There was no difference in intra-operatively assessed tear size both in anteroposterior dimension (P = 0.5) and retraction (P = 0.9). Pre-operative Flex SF score in smokers was below that of non-smokers (23.0 vs. 24.5, P = 0.002) and at 6 months (P = 0.02) but no different at 5 years (P = 0.7). Pain scores were higher in smokers than non-smokers both pre-operatively (5.34 vs. 4.67, P < 0.001) and up to 2 years (P < 0.001) but not at 5 years (P = 0.073).

CONCLUSION

Smokers undergoing RCR were younger than non-smokers, and had worse pre-operative pain scores and shoulder function. Poorer post-operative function persisted to 6 months, and with higher reported pain to 2 years in smokers. However, at 5-year follow-up, patient-reported outcomes were not affected by smoking status.

Return to sport following anterior cruciate ligament reconstruction: the argument for a multimodal approach to optimise decision-making: current concepts

Existing literature is varied in the methods used to make this determination in the treatment of athletes who have undergone recent anterior cruciate ligament (ACL) reconstruction. Some authors report using primarily time-based criteria, while others advocate for physical measures and kinematic testing to inform decision-making. The goal of this paper is to elucidate the most current medical evidence regarding identification of the earliest point at which a patient may safely return to sport. The present review therefore seeks to examine the evidence from a critical perspective-breaking down the biology of graft maturation, effect of graft choice, potential for image-guided monitoring of progression and results associated with time-based versus functional criteria-based return to play-to justify a multifactorial approach to effectively advance athletes to return to sport. The findings of the present study reaffirm that time is a prerequisite for the biological progression that must occur for a reconstructed ligament to withstand loads demanded by athletes during sport. Modifications of surgical techniques and graft selection may positively impact the rate of graft maturation, and evidence suggests that imaging studies may offer informative data to enhance monitoring of this process. Aspects of both functional and cognitive testing have also demonstrated utility in prior studies and consequently have been factored into modern proposed methods of determining the athlete's readiness for sport. Further work is needed to definitively determine the optimal method of clearing an athlete to return to sport after ACL reconstruction. Evidence to date strongly suggests a role of a multimodal algorithmic approach that factors in time, graft biology and functional testing in return-to-play decision-making after ACL reconstruction.Level of evidence: level V.

The lifetime risk of revision following total hip arthroplasty

AIMS

Joint registries typically use revision of an implant as an endpoint and report survival rates after a defined number of years. However, reporting lifetime risk of revision may be more meaningful, especially in younger patients. We aimed to assess lifetime risk of revision for patients in defined age groups at the time of primary surgery.

METHODS

The New Zealand Joint Registry (NZJR) was used to obtain rates and causes of revision for all primary total hip arthroplasties (THAs) performed between January 1999 and December 2016. The NZJR is linked to the New Zealand Registry of Births, Deaths and Marriages to obtain complete and accurate data. Patients were stratified by age at primary surgery, and lifetime risk of revision calculated according to age, sex, and American Society of Anesthesiologists (ASA) classification. The most common causes for revision were also analyzed for each age group.

RESULTS

The overall, ten-year implant survival rate was 93.6% (95% confidence interval (CI) 93.4% to 93.8%). It was lowest in the youngest age group (46 to 50 years), rising sequentially with increasing age to 97.5% in the oldest group (90 to 95 years). Lifetime risk of revision surgery was 27.6% (95% CI 27.3% to 27.8%) in those aged 46 to 50 years, decreasing with age to 1.1% (95% CI 0.0% to 5.8%) in those aged 90 to 95 years at the time of primary surgery. Higher ASA grades were associated with an increased lifetime risk of revision across all ages. The commonest causes for revision THA were aseptic loosening, infection, periprosthetic fracture, and dislocation.

CONCLUSION

When counselling patients preoperatively, the lifetime risk of revision may be a more meaningful and useful measure of longer-term outcome than implant survival at defined time periods. This study highlights the considerably increased likelihood of subsequent revision surgery in younger age groups. Cite this article: Bone Joint J 2021;103-B(3):479-485.

Success Rates of Debridement, Antibiotics, and Implant Retention in 230 Infected Total Knee Arthroplasties: Implications for Classification of Periprosthetic Joint Infection

BACKGROUND

Prosthetic joint infection (PJI) is the most common cause of failure following total knee arthroplasty (TKA). This study aimed to determine the success of debridement, antibiotics, and implant retention (DAIR) in a large cohort of TKA PJIs and assess the utility of current classification systems in predicting DAIR outcomes in early postoperative, late hematogenous, and chronic PJIs.

METHODS

In a multicenter review over 15 years, 230 patients underwent DAIR for first episode PJI following primary TKA. Patient demographics, disease and surgical factors, treatment regime, and outcomes were identified. Univariate and multivariate survival analyses were performed to identify factors associated with successful DAIR. Continuous variables with predictive value were further analyzed using receiver operating characteristic curves. The ability to predict DAIR outcomes of multiple classification systems was also assessed.

RESULTS

Patients were followed for an average of 6.9 years. The overall success rate of DAIR was 53.9%. On receiver operating characteristic analysis, 3 months (area under the curve = 0.63) and 1-year age (area under the curve = 0.66) of implant cut-offs was similarly predictive of outcomes. On multivariate survival analysis, DAIR was successful in 64% of "early" PJIs (implant <1 year) vs 38% of "late hematogenous" PJIs (implant >1 year; odds ratio [OR] 1.78, P = .01). For late PJIs (implant >1 year), Staphylococcus aureus (OR 4.70, P < .001) and gram-negative infections (OR 2.56, P = .031) were risk factors for DAIR failure.

CONCLUSION

DAIR has a high failure rate in all PJIs occurring more than a year post primary TKA, particularly when caused by S aureus or gram-negative bacteria. The age of implant is an important predictor of DAIR outcomes.

Intraosseous Regional Administration of Antibiotic Prophylaxis in Total Knee Arthroplasty

Background

Periprosthetic joint infection (PJI) is a devastating complication following total knee arthroplasty (TKA), and perioperative antibiotics are commonly administered to try to mitigate the chance of infection. Intraosseous regional administration (IORA) of prophylactic antibiotics during TKA is a method of antibiotic delivery that has been shown to achieve markedly higher tissue concentrations at much lower doses. Other advantages include ease of administration, ability to time the antibiotic delivery with the surgical start time for maximal effectiveness, and less systemic side effects. The concept is similar to a Bier block, except that IORA involves the use of antibiotics instead of local anesthetic to perfuse the limb and is given via intraosseous rather than intravenous access.

Description

After standard patient preparation and draping, the tourniquet is inflated and an intraosseous needle is inserted into the proximal medial face of the tibia, just medial and slightly above the level of the tubercle. A large syringe containing the desired antibiotic (typically 500 mg vancomycin suspended in normal saline solution) is connected to the needle and the solution is administered over 1 to 2 minutes. The intraosseous needle can then be removed and the surgical procedure proceeds as it normally would per surgeon preference and technique.

Alternatives

Systemic administration of intravenous antibiotics, vancomycin powder, and antibiotic-impregnated cement are alternative options that can be utilized during TKA.

Rationale

IORA has several distinct advantages over other methods of antibiotic delivery, including the ability to (1) deliver antibiotic directly to the surgical bed and avoid systemic delivery, (2) precisely time and quickly administer antibiotics to achieve highest concentrations at the start of and throughout the surgical procedure, and (3) avoid several common and potentially serious side effects, especially those associated with antibiotics such as vancomycin.

Expected Outcomes

This technique for antibiotic delivery achieves markedly higher tissue concentrations compared with systemic administration, without prolonged preoperative infusion times. Intraosseous delivery optimizes timing and reduces the risk of systemic side effects while simultaneously providing equal or enhanced antibiotic prophylaxis in TKA. This delivery mechanism is especially useful in patients who are at high risk for infection and in the revision TKA setting. Further, there is little to no additional risk and the use of this method does not substantially prolong operative time.

Important Tips

The proximal aspect of the tibia is the optimal injection site because the cortex is thinner in this region, making needle insertion easier. Additionally, the metaphyseal bone allows faster flow rates for the infusion. We have found that insertions made slightly more proximally are easier and have faster flow rates. Of note, although the antibiotic is infused into the tibia, as seen in the attached technique video, intraosseous administration achieves rapid uptake into the vascular tree. Therefore, all tissues distal to the tourniquet, including the femur and patella, will receive this optimal dose as well.We prefer the use of a power driver (EZ-IO; Teleflex); however, manual needles (Cook Medical) can also be utilized. Longer needles are available if needed for obese patients.Flow rates are variable and the infusion typically takes 1 to 2 minutes to complete. If the flow rate is slow, twisting and withdrawing the needle slightly (2 to 4 mm) may increase the rate. This contrasts with the 1 to 2-hour intravenous infusion time required when vancomycin is administered systemically.In our experience, intraosseous injection is still successful in the case of a previous high tibial osteotomy, although the flow rate may be slower.In complex revision cases with compromised proximal tibial bone, the medial malleolus is an alternative site for intraosseous administration.Choice of antibiotic: as vancomycin is difficult to adequately administer intravenously, it is ideally suited for IORA. We have studied and utilized a 500-mg dose of vancomycin suspended in a solution of 140 mL of normal saline solution (prepared by our pharmacy). Of note, we have not found rapid infusion of intraosseous vancomycin to cause red-man syndrome as it would with rapid systemic infusion. This is because of the lower dose of 500 mg and the use of the tourniquet, which keeps the antibiotic in the local tissues about the knee without allowing systemic exposure. All patients, regardless of weight or the size of their limb, receive the dose of 500 mg of vancomycin.As cefazolin does not have the same difficulties with intravenous administration, we continue to use standard intravenous prophylaxis with an appropriate weight-based dose of cefazolin prior to incision.Indications for IORA of vancomycin include clinical scenarios in which vancomycin would be administered intravenously. These indications include revision TKA, obesity (body mass index >40 kg/m²), diabetes, beta-lactam allergy, known colonization with methicillin-resistant Staphylococcus aureus (MRSA), patients coming from institutions with a high prevalence of MRSA, previous ligamentous surgical procedure or osteotomies, and current or recent smokers. IORA can be utilized even in the primary TKA setting if the patient is considered high-risk as defined by the criteria above. We also use IORA during reimplantation following 2-stage exchange for PJI and in patients undergoing irrigation and debridement for acute PJI when the organism has been identified preoperatively.

Low femoral component prominence negatively influences early revision rate in robotic unicompartmental knee arthroplasty

PURPOSE

The revision rate of unicompartmental knee arthroplasty (UKA) is higher than in total knee arthroplasty (TKA), and implant positioning may play a role. In combination with a pre-operative CT, robotic UKA may provide the ability to position the implants more precisely. The aim of this study was to investigate the influence of component prominence relative to the native joint surface on early outcomes and revisions. The hypothesis was that aiming for restoration of joint space to 0.5-1.5 mm will improve outcomes.

METHODS

Retrospective analysis of prospectively collected data of 94 patients undergoing robotic-assisted UKA (Mako, Stryker) was performed. The 'prominence' of the implant surface relative to the native bony surface in sagittal plane, hip-knee-ankle (HKA) correction in coronal plane was documented intraoperatively. The mean achieved gap between two components under valgus stress captured in at least 5 different flexion angles was calculated. These were then analysed for impact on early revision rate and outcomes, stratified by gender.

RESULTS

Median HKA correction was 3.5° (range 0°-9.5°). Median femoral prominence was 1.5 mm (range - 0.6 to 4 mm) and median tibial prominence was 4.3 mm (2-7 mm). The median achieved gap was 1.0 mm (- 1.2 to 2.8 mm). There was no difference in achieved correction between men and women (p = n.s.) but men had a higher achieved combined prominence than women (p < 0.001). PROMs did not correlate with the average gap (p = n.s.) nor with combined prominence (p = n.s.). Two patients underwent an early revision. Lower femoral prominence was a significant predictor of revision (p = 0.045; OR = 0.21; 95% CI 0.000-0.918).

CONCLUSION

Female patients need less component prominence to achieve the same average gap balance through a range of motion, without correlation with patient's height. Intraoperatively low femoral prominence could be a reason for early revision.

LEVEL OF EVIDENCE

IV.

Completeness and capture rate of publicly funded arthroplasty procedures in the New Zealand Joint Registry

BACKGROUND

Registry-based studies have become more common due to the availability of a large study cohort. However, the validity of findings is dependent on the completeness of the registry. This study aimed to validate the capture rate of the New Zealand Joint Registry (NZJR) by matching procedures that have been recorded separately via clinical coding by the New Zealand Government's National Surgical Site Infection Improvement Programme (SSIIP).

METHODS

The National Health Index, a unique identification code for all patients, was combined with the arthroplasty procedure performed (primary total knee arthroplasty (TKA), primary total hip arthroplasty (THA), revision TKA or revision THA) and operation side. Publicly funded procedures recorded in the NZJR were matched with procedures recorded by the SSIIP on a record-by-record basis. This identified the total number of arthroplasty procedures performed in New Zealand, which was used as the denominator value to calculate the procedure capture rate of the NZJR.

RESULTS

Between 2013 and 2018, 24 556 primary TKA, 28 970 primary THA, 2107 revision TKA and 4263 revision THA procedures were recorded by both datasets. The NZJR recorded 95.5% of primary TKA procedures, 96.3% of primary THA procedures, 97.1% of revision TKA procedures and 95.2% of revision THA procedures.

CONCLUSION

The NZJR recorded >95% of publicly funded arthroplasty procedures. In contrast, there were inaccuracies in clinical coding by hospitals, particularly with revision procedures, demonstrating the benefits of an arthroplasty registry. However, data recorded by an infection surveillance programme may supplement arthroplasty registry data to strengthen the quality of research.

Hip abductor tendon tears: where are we now?

Hip abductor tendon tear is a difficult problem to manage. The hip abductor mechanism is made up of the gluteus medius and minimus muscles, both of which contribute to stabilising the pelvis through the gait cycle. Tears of these tendons are likely due to iatrogenic injury during arthroplasty and chronic degenerative tendinopathy. Ultrasound and magnetic resonance imaging have provided limited clues regarding the pattern of disease and further work is required to clarify both the macro and microscopic pattern of disease. While surgery has been attempted over the last 2 decades, the outcomes are variable and the lack of high-quality studies have limited the uptake of surgical repair. Hip abductor tendon tears share many features with rotator cuff tears, hence, innovations in surgical techniques, materials and biologics may apply to both pathologies.

Rates of revision and surgeon-reported graft rupture following ACL reconstruction: early results from the New Zealand ACL Registry

PURPOSE

There remains a lack of consensus on the patient factors associated with graft rupture following anterior cruciate ligament (ACL) reconstruction. This study aimed to identify the rate of revision and surgeon-reported graft rupture and clarify the patient risk factors for failure.

METHODS

Analysis was conducted on prospective data captured by the New Zealand ACL registry. All primary isolated ACL reconstructions recorded between April 2014 and December 2018 were reviewed to identify the rate of revision and surgeon-reported graft rupture. Univariate and multivariate survival analysis was performed to identify patient factors associated with revision and graft rupture.

RESULTS

A total of 7402 primary isolated ACL reconstructions were reviewed and had a mean follow-up time of 23.1 (SD ± 13.9) months. There were 258 surgeon-reported graft ruptures (3.5%) of which 175 patients underwent subsequent revision ACL reconstruction (2.4%). Patients younger than 18 years had the highest risk of revision (adjusted HR = 7.29, p < 0.001) and graft rupture (adjusted HR = 4.26, p < 0.001) when compared to patients aged over 36 years. Male patients had a higher risk of revision (adjusted HR = 2.00, p < 0.001) and graft rupture (adjusted HR = 1.70, p < 0.001) when compared to their female counterparts. Patients who underwent ACL reconstruction within 6 months of their injury had a two times increased risk of revision compared to patients who had surgery after 12 months (adjusted HR = 2.15, p = 0.016).

CONCLUSION

Younger age, male sex and a shorter injury-to-surgery time interval increased the risk of revision, while younger age and male sex increased the risk of surgeon-reported graft rupture.

LEVEL OF EVIDENCE

II.

BMI is a Better Predictor of Periprosthetic Joint Infection Risk Than Local Measures of Adipose Tissue After TKA

BACKGROUND

Both body mass index (BMI) and local measures of adiposity at the surgical site have been identified as independent risk factors for periprosthetic joint infection (PJI) (periprosthetic joint infection) after total knee arthroplasty (TKA). We aimed to 1) evaluate previously used measures of assessing knee adiposity and 2) determine the best measure for predicting both surgical duration and PJI after TKA.

METHODS

We performed a multicentre retrospective review of 4745 patients who underwent primary TKA between January 2013 and December 2016. Patient demographic information, surgical duration and postoperative infection status within one year were obtained. Preoperative weight-bearing AP and lateral x-rays were analyzed to determine prepatellar adipose thickness, bony width of the tibial plateau, and total soft tissue knee width. The knee adipose index (KAI) was calculated from the ratio of bone to total knee width.

RESULTS

We observed substantial variability in both local measures of adiposity compared with BMI. Neither measure of local knee adipose showed a significant correlation with PJI risk. By contrast, there was a strong correlation between PJI risk and BMI >35 (odds ratio 2.9, 95% CI 1.4-6.1). Surgical duration increased with both BMI and measures of local adipose tissue (KAI and prepatellar fat thickness).

CONCLUSION

Local adipose deposition varies greatly for any given BMI. In this study, BMI was a better predictor of PJI after TKA than local measures of knee adipose tissue.

Age and Prosthetic Design as Risk Factors for Secondary Patella Resurfacing

BACKGROUND

Selectively resurfacing the patella based on a patient's risk of secondary patella resurfacing (SPR) may be the optimal strategy for primary total knee arthroplasty (TKA). However, exactly which factors increase the risk of SPR is unknown. Utilizing New Zealand Joint Registry data, we investigated the following: (1) What patient and surgical factors are more prevalent among TKA patients who received SPR compared to those who did not? and (2) What is the difference in Oxford Knee Scores (OKS) between those who receive SPR and those who do not?

METHODS

Prevalence of various patient and surgical factors was compared between 197 non-resurfaced TKAs that proceeded to SPR and 31,399 that did not. Multivariate analysis was used to determine the odds ratio for each factor that differed between groups. Six-month postoperative OKS for each group was utilized for comparison.

RESULTS

Posterior-stabilized designs had an odds ratio of 1.86 (95% confidence interval [CI] 1.31-2.66; P = .001) when compared to cruciate-retaining designs. When compared to age less than 55, age >75 and age 65-74 had odds ratios of 0.27 (95% CI 0.16-0.46; P < .001) and 0.44 (95% CI 0.28-0.69; P < .001) respectively. Six-month OKS was lower among those who received SPR (37.27 vs 27.26; P < .001).

CONCLUSION

Younger age, posterior-stabilized design, and a low 6-month OKS were associated with SPR.