Background

Anterior cruciate ligament (ACL) reconstruction with concomitant meniscal injury occurs frequently. Meniscal repair is associated with improved long-term outcomes compared to resection but is also associated with a higher reoperation rate. Knowledge of the risk factors for repair failure may be important in optimizing patient outcomes.

Introduction

The first VRAS TKA was performed in New Zealand in November 2020 using a Patient Specific Balanced Technique whereby VRAS enables very accurate collection of the bony anatomy and soft tissue envelope of the knee to plan and execute the optimal positioning for a balanced TKA

In relation to regenerative therapies in osteoarthritis and cartilage repair, mesenchymal stromal cells (MSCs) have immunomodulatory functions and influence macrophage behaviour. Macrophages exist as a spectrum of pro-(M1) and anti-(M2) inflammatory phenotypic subsets. In the context of cartilage repair, we investigated MSC-macrophage crosstalk, including specifically the priming of cartilage cells by macrophages to achieve a regenerative rather than fibrotic outcome. Human monocytes were isolated from blood cones and differentiated towards M1 and M2 macrophages. Monocytes (Mo), M1 and M2 macrophages were cultured directly and indirectly (trans-well system) with human bone marrow derived MSCs. MSCs were added during M1 polarisation and separately to already induced M1 cells. Outcomes (M1/M2 markers and ligands/receptors) were evaluated using RT-qPCR and flow cytometry. Influence on chondrogenesis was assessed by applying M1 and M2 macrophage conditioned media (CM) sequentially to cartilage derived cells (recapitulating an acute injury environment). RT-qPCR was used to evaluate chondrogenic/fibrogenic gene transcription. The ratio of M2 markers (CD206 or CD163) to M1 markers (CD38) increased when MSCs were added to Mo/M1 macrophages, regardless of culture system used (direct or indirect). Pro-inflammatory markers (including TNFβ) decreased. CXCR2 expression by both M1 macrophages and MSCs decreased when MSCs were added to differentiated M1 macrophages in transwell. When adding initially M1 CM (for 12 hours) followed by M2 CM (for 12 hours) sequentially to chondrocytes, there was a significant increase of Aggrecan and Collagen type 2 gene expression and decrease in fibroblastic cell surface markers (PDPN/CD90). Mo/M1 macrophages cultured with MSCs, directly or indirectly, are shifted towards a more M2 phenotype. Indirect culture suggests this effect can occur via soluble signaling mediators. Sequential exposure of M1CM followed by M2CM to chondrocytes resulted in increased chondrogenic and reduced fibrotic gene expression, suggesting that an acute pro-inflammatory stimulus may prime chondrocytes before repair.

Abstract

The bone-patellar tendon-bone (BTB) autograft is associated with difficulty kneeling following anterior cruciate ligament (ACL) reconstruction, however it is unclear whether it results in a more painful or symptomatic knee when compared to the hamstring tendon autograft. This study aimed to identify the rate of significant knee pain and difficulty kneeling following primary ACL reconstruction and clarify whether graft type influences the risk of these complications.

Primary ACL reconstructions prospectively recorded in the New Zealand ACL Registry between April 2014 and November 2019 were analyzed. The Knee Injury and Osteoarthritis Outcome Score (KOOS) was analyzed to identify patients who reported significant knee pain, defined as a KOOS Pain subscale score of ≤72 points, and kneeling difficulty, defined as a patient who reported “severe” or “extreme” difficulty when they kneel. The rate of knee pain and kneeling difficulty was compared between graft types via univariate Chi-square test and multivariate binary logistic regression with adjustment for patient demographics.

4492 primary ACL reconstructions were analyzed. At 2-year follow-up, 9.3% of patients reported significant knee pain (420/4492) and 12.0% reported difficulty with kneeling (537/4492). Patients with a BTB autograft reported a higher rate of kneeling difficulty compared to patients with a hamstring tendon autograft (21.3% versus 9.4%, adjusted odds ratio = 3.12, p<0.001). There was no difference between graft types in the rate of significant knee pain (9.9% versus 9.2%, p = 0.49) or when comparing absolute values of the KOOS Pain (mean score for BTB = 88.7 versus 89.0, p = 0.37) and KOOS Symptoms subscales (mean score for BTB = 82.5 versus 82.1, p = 0.49).

The BTB autograft is a risk factor for post-operative kneeling difficulty, but it does not result in a more painful or symptomatic knee when compared to the hamstring tendon autograft.

The bone-patellar tendon-bone (BTB) autograft has a lower rate of graft failure but a higher rate of contralateral anterior cruciate ligament (ACL) injury after primary ACL reconstruction. Subsequent contralateral injury may be a marker of success of the BTB graft, but it is unclear whether the type of graft influences the rate of return to sport. This study aimed to compare the rates of return to weekly sport and return to preinjury activity levels between the BTB and hamstring tendon autografts following primary ACL reconstruction.

Prospective data on primary ACL reconstructions recorded in the New Zealand ACL Registry between April 2014-November 2019 were analyzed. The primary outcome was return to weekly sport, defined as a Marx activity score of 8, at 2-year follow-up. The secondary outcome was return to preinjury activity level, defined as a post-operative Marx activity score that was equal or greater to the patient's preinjury Marx score. Return to sport was compared between the BTB and hamstring tendon autografts via multivariate binary logistic regression with adjustment for patient demographics.

4259 patients were analyzed, of which 50.3% were playing weekly sport (n = 2144) and 28.4% had returned to their preinjury activity level (n = 1211) at 2-year follow-up. A higher rate of return to weekly sport was observed with the BTB autograft compared to the hamstring tendon autograft (58.7% versus 47.9%, adjusted odds ratio = 1.23, p = 0.009). Furthermore, the BTB autograft had a higher rate of return to preinjury activity levels (31.5% versus 27.5%, adjusted odds ratio = 1.21, p = 0.025).

The BTB autograft is associated with a higher return to sport and may explain the higher rate of contralateral ACL injury following primary ACL reconstruction.

Arthrofibrosis is a less common complication following anterior cruciate ligament (ACL) reconstruction and there are concerns that undergoing early surgery may be associated with arthrofibrosis. The aim of this study was to identify the patient and surgical risk factors for arthrofibrosis following primary ACL reconstruction.

Primary ACL reconstructions prospectively recorded in the New Zealand ACL Registry between April 2014 and December 2019 were analyzed. The Accident Compensation Corporation (ACC) database was used to identify patients who underwent a subsequent reoperation with review of operation notes to identify those who had a reoperation for “arthrofibrosis” or “stiffness”. Univariate Chi-Square test and multivariate Cox regression analysis was performed. Hazard ratios (HR) with 95% confidence intervals (CI) were computed to identify the risk factors for arthrofibrosis.

9617 primary ACL reconstructions were analyzed, of which 215 patients underwent a subsequent reoperation for arthrofibrosis (2.2%). A higher risk of arthrofibrosis was observed in female patients (adjusted HR = 1.67, 95% CI 1.22 – 2.27, p = 0.001), patients with a history of previous knee surgery (adjusted HR = 1.97, 95% CI 1.11 – 3.50, p = 0.021) and when a transtibial femoral tunnel drilling technique was used (adjusted HR = 1.55, 95% CI 1.06 – 2.28, p = 0.024). Patients who underwent early ACL reconstruction within 6 weeks of their injury did not have a higher risk of arthrofibrosis when compared to patients who underwent surgery more than 6 weeks after their injury (3.5% versus 2.1%, adjusted HR = 1.56, 95% CI 0.97 – 2.50, p = 0.07). Age, graft type and concomitant meniscal injury did not influence the rate of arthrofibrosis.

Female sex, a history of previous knee surgery and a transtibial femoral tunnel drilling technique are risk factors for arthrofibrosis following primary ACL reconstruction.

The optimal method of tibial fixation when using a hamstring tendon autograft in anterior cruciate ligament (ACL) reconstruction is unclear. This study aimed to compare the risk of revision ACL reconstruction between suspensory and interference devices on the tibial side.

Prospective data on primary ACL reconstructions recorded in the New Zealand ACL Registry between April 2014 and December 2019 were analyzed. Only patients with a hamstring tendon autograft fixed with a suspensory device on the femoral side were included. The rate of revision ACL reconstruction was compared between suspensory and interference devices on the tibial side. Univariate Chi-Square test and multivariate Cox regression was performed to compute hazard ratios (HR) and 95% confidence intervals (CI) with adjustment for age, gender, time-to-surgery, activity at the time of injury, number of graft strands and graft diameter.

6145 cases were analyzed, of which 59.6% were fixed with a suspensory device on the tibial side (n = 3662), 17.6% fixed with an interference screw with a sheath (n = 1079) and 22.8% fixed with an interference screw without a sheath (n = 1404). When compared to suspensory devices (revision rate = 3.4%), a higher risk of revision was observed when using an interference screw with a sheath (revision rate = 6.2%, adjusted HR = 2.05, 95% CI 1.20 – 3.52, p = 0.009) and without a sheath (revision rate = 4.6%, adjusted HR = 1.81, 95% CI 1.02 – 3.23, p = 0.044). The number of graft strands and a graft diameter of ≥8 mm did not influence the risk of revision.

When reconstructing the ACL with a hamstring tendon autograft, the use of an interference screw, with or without a sheath, on the tibial side has a higher risk of revision when compared to a suspensory device.

Meniscal repairs are commonly performed during anterior cruciate ligament (ACL) reconstruction. This study aimed to identify the risk factors for meniscal repair failure following concurrent primary ACL reconstruction.

Primary ACL reconstructions with a concurrent repair of a meniscal tear recorded in the New Zealand ACL Registry between April 2014 and December 2018 were analyzed. Meniscal repair failure was defined as a patient who underwent subsequent meniscectomy, and was identified after cross-referencing data from the ACL Registry with the national database of the Accident Compensation Corporation (ACC). Multivariate Cox regression was performed to produce hazard ratios (HR) with 95% confidence intervals (CI) to identify the patient and surgical risk factors for meniscal repair failure.

2041 meniscal repairs were analyzed (medial = 1235 and lateral = 806). The overall failure rate was 9.4% (n = 192). Failure occurred in 11.1% of medial (137/1235) and 6.8% of lateral (55/806) meniscal repairs. The risk of medial failure was higher with hamstring tendon autografts (adjusted HR = 2.00, 95% CI 1.23 – 3.26, p = 0.006) and in patients with cartilage injury in the medial compartment (adjusted HR = 1.56, 95% CI 1.09 – 2.23, p = 0.015). The risk of lateral failure was higher when the procedure was performed by a surgeon with an annual case volume of less than 30 ACL reconstructions (adjusted HR = 1.92, 95% CI 1.10 – 3.33, p = 0.021). Age, gender, time from injury-to-surgery and femoral tunnel drilling technique did not influence the risk of meniscal repair failure.

When repairing a meniscal tear during ACL reconstruction, the use of a hamstring tendon autograft or the presence of cartilage injury in the medial compartment increases the risk of medial meniscal repair failure. Lower surgeon case volume increases the risk of lateral meniscal repair failure.

Introduction

New implants for total knee arthroplasty (TKA) are frequently introduced with the promise of improved performance. Infrequently there is accompanying data to document relative performance. The goal of this study was to evaluate the outcomes of an implant widely used for decades (Existing TKA), compared to a new implant (New TKA) from the same manufacturer.

Introduction

With the introduction of new technology in orthopaedics, surgeons must balance anticipated benefits in patient outcomes with challenges or complications associated with surgical learning curve for the technology. The purpose of this study was to determine whether the surgeon learning curve with a new multi-radius primary TKA system (primary TKA implant and instruments) designed for surgical team ease would impact clinical outcomes, surgical time and complications.

With the introduction of new technology in orthopaedics, surgeons must balance anticipated benefits in patient outcomes with challenges or complications associated with surgical learning curve for the technology. The purpose of this study was to determine whether surgeon learning curve with a new multi-radius primary TKA system and instruments designed to improve surgical team ease would impact clinical outcomes, surgical time, and complications.

From November 2012 to July 2015, 2369 primary TKAs were prospectively enrolled in two multicentre studies across 50 sites in 14 countries with a new knee system (NEW-TKA) evenly balanced across four configurations: cruciate retaining or posterior stabilised with either fixed bearing or rotating platform (CRFB, CRRP, PSFB, PSRP). 2128 knees had a<1 year visit and 1189 had a minimum 1 year visit. These knees were compared to a reference dataset of 843 primary TKAs from three manufacturers in the same four configurations with currently available products (CA-TKA). Demographics for NEW-TKA and CA-TKA were similar and typical for primary TKA. Operative times, clinical outcomes and a series of five patient reported outcomes were compared for NEW-TKA vs. CA-TKA. The first 10 New-TKA subjects for each surgeon were defined as learning curve cases (N=520) and were compared to all later subjects (N=1849). Patient reported outcome measure and clinical outcome analyses were covariate adjusted for patient demographics, pre-op assessment and days post-op.

Mean (SD) surgical time for NEW-TKA learning curve cases was 79.1 (24.3) minutes, which reduced thereafter to 73.6 (24.3) (p=0.002). Beyond 10 cases, there was a continued reduction in NEW-TKA surgical time (R-Squared = 0.031). After 10 cases, surgical time was on par with the mean (SD) 71.9 (21.6) for CA-TKA (p=0.078). PROM outcomes of the first 10 learning curve cases for NEW-TKA were not statistically different from later cases at less than 1 year or later when adjusted for relevant covariates including configuration, patient demographics, pre-op functional status, and time post-op (p-values > 0.01). PROM outcomes for NEW-TKA vs. CA-TKA under the same covariate adjustments showed a trend favoring KOOS ADL, Symptoms, and Sport and Recreation subscores at minimum 1 year (p-values < 0.01). The incidence of intraoperative operative site complications was 1.3% for the NEW-TKA learning curve cases which was similar to the 0.6% rate for historical CA-TKA (p=0.231) and the intraoperative complication rate for the NEW-TKA later cases was consistent with learning curve cases (p=0.158).

The introduction of new implants into the market place needs to have adequate data to support that they are safe and effective. Except for a minor increase in surgical time during the first 10 patients, this study found that surgeon learning curve with this new primary TKA system does not adversely affect patient short term outcomes and complication rates.

MACI Cartilage Transplantation has been performed in New Zealand for the last five years for patients with isolated articular cartilage defects who have failed a microfracture technique.

Thirteen patients have undergone this procedure. Patients were evaluated by an independent research assistant preoperatively and at 6 months, 1, 2, 3 and 5 years Visual analogue pain score, ICRS score, WOMAC score, KOOS score, IKDC score and SF 36 were collected at all time points. An MRI scan was performed in all patients at all time periods. Biopsies are taken at three years.

There is an improvement in visual analogue pain score, ICRS score, WOMAC score, KOOS score, IKDC score and SF 36 at all time points. Results improve with time. No procedures have failed. All MRI scans showed restoration of articular cartilage. Histology shows hyaline like cartilage

Medium term results are encouraging. The rehabilitation is long thus 12 month data does not give an accurate outcome measure. Ongoing evaluation is occurring.

Total Knee Joint Replacement is mostly commonly performed using a measured resection technique. When the PCL is retained 9mm of bone is resected off the distal femur. If the PCL is excised 11m of bone is resected. Computer assisted total knee joint replacement will guide the surgeon to perform the optimal distal femoral resection to gain neutral alignment and full post operative extension.

Three hundred TKJR’s were performed by one surgeon using the De Puy Ci navigation system. A ligament balancing technique is used whereby a neutral tibial resection is performed. A ligament tensor is inserted in extension and flexion. The navigation system then performs an optimization process whereby the distal femoral cut is calculated to give a neutral mechanical axis and 0° of knee extension. Data was collected measuring the distal femoral resection in the PCL retained and resected knees.

The distal femoral cut required to achieve full extension for the PCL retaining TKJR ranged from 5 – 15mm. The mean was 11.2mm. The distal femoral cut required to achieve full extension for the PCL sacrificing TKJR ranged from 5 – 15mm. The mean was 10.8mm. There was no difference between the two groups (p=0.07). Both the PCL retaining and sacrificing TKJR distal resections correlated with the preoperative flexion deformity, i.e. patients with a greater fixed flexion deformity required a greater distal femoral resection to achieve full extension

There is a wide variation in the distal femoral cut to achieve full extension in TKJR. It is accepted that a smaller distal resection is required for a PCL retaining than a PCL sacrificing TKJR. Our study refutes this premise. A greater femoral resection is required if there is a greater fixed flexion deformity. A measured resection technique will result in a large percentage of patients with a fixed flexion deformity following TKJR

Treatment of the young patient with medial compartment arthritis and a PCL deficient knee is a complex problem. This study evaluates the efficacy of the anteromedial opening wedge osteotomy for PCL deficient knees with medial compartment degenerative changes.

Eighteen patients have undergone an anteromedial opening wedge high tibial osteotomy for the PCL deficient varus knee. Patients were evaluated prospectively pre-operatively and at one and five years post surgery by visual analogue pain scores and patellofemoral pain scores, subjective IKDC, WOMAC and SF-36. Radiographic evaluation to determine correction in the coronal plane and the degree of slope increase was performed at one-year post surgery.

All patients reported and improvement in PCL instability. There was a significant improvement in visual analogue pain and patellofemoral pain sc ores, subjective IKDC, WOMAC and SF-36 and overall knee function at one and five years. Patients with less severe arthritis at the time of surgery performed better at five years.

This technique shows encouraging midterm results for a complex problem.

Better results are obtained with less significant arthritis at the time of surgery

The purpose of the current study was to compare the results of the P.F.C. Rotating Platform Knee System and the P.F.C. Knee System in a randomised prospective study.

151 patients were enrolled in the study, totalling 172 knees, with 84 receiving fixed bearing and 88 receiving rotating platform knees. Patients were enrolled prospectively with preoperative assessment of the defined outcome measures including Knee society score, Oxford Knee Score, SF-36 score, WOMAC score, VAS pain score and ROM. These outcome measures were repeated at 6 months, 1 year and 2 years

At the two year follow up patients were assessed and results analyzed to see if there were any significant differences with regard to outcome measures. There was no statistically significant difference for the SF12, Oxford knee score or the VAS pain score. In the Knee Society Score a trend effect at the one year follow up (almost significant at p = 0.07) was seen with the rotating group scoring better in overall function than the fixed group. At the two year follow-up this difference between groups became significant (p = 0.05) and the rotating group had significantly better overall function than the fixed group.

The early results show a better functional score with comparable subjective outcome measures with regard to pain and ROM. The long term purported benefits of the rotating platform versus fixed will be watched with interest in the medium to long term follow up.

MACI Cartilage Transplantation has been performed in New Zealand for the last three years for patients with isolated articular cartilage defects who have failed a microfracture technique. Ten patients have undergone this procedure. Patients were evaluated by an independent research assistant preoperatively and at 6, 12 and 24 months. Visual analogue pain score, ICRS score, WOMAC score, KOOS score, IKDC score, Tegner score and SF 36 were collected at all time points. An MRI scan was performed in all patients at 12 months.

So far, ten patients have a minimum of 12 month data, while two have been followed to 12 months. There has been an improvement in visual analogue pain score, ICRS score, WOMAC score, KOOS score, IKDC score and SF 36. No procedures have failed. All MRI scans showed restoration of articular cartilage.

In conclusion, early results are encouraging. The rehabilitation is long, thus 12 month data do not give an accurate outcome measure. Ongoing evaluation is occurring

Proximal tibial bone density (BD) is a key determinant in the migration of implants following total knee arthroplasty (TKA). CT-osteodensitometry offers three-dimensional, volumetric analysis of both cortical and cancellous regions and has been shown to be both accurate and reliable about the hip.

The primary objective of this study is to assess differences in the bone remodelling pattern (tibial segment) of patients operated on using fixed or rotating platform, using CT-osteodensitometry. The hypothesis is that the presence of a rotating platform optimises stress distribution along the proximal tibia, resulting in reduced proximal bone remodelling of tibia. The secondary objective is to correlate the osteodensitometry and clinical data at follow-up.

Following completion of the initial assessment and after obtaining written informed consent, the patients were randomly allocated to either a PFC Sigma fixed bearing or a PFC Sigma rotating platform (mobile bearing) total knee system (DePuy, Leeds, UK). Clinical follow-ups were performed at three months, one year, and two years after the index operation. CT scans were performed immediately post-operatively and at one and two years respectively. 52 knees (47 patients) were randomised for cemented TKR management using rotating or fixed tibia platform and followed up at one and two years.

At the two year follow-up, the knee function and patellar scores were comparable in both groups. There were no radiographic signs of loosening, and no revision surgery was performed. Sequential BD measurement from post-operative baseline to two year follow-up showed minimal differences between the fixed and rotating platform implants. Bone density assessment showed a 20% mean loss of cancellous BD and minimal changes of cortical BD, with little differences between the two groups. Loss of cancellous BD appears progressive.

In conclusion, this study shows that the mode of fixation of the TKR polyethylene liner does not influence bone remodelling of the proximal tibia after surgery. This is the first study performed to assess separately cortical and cancellous BD changes in THR. There are no data in the literature for comparison.

The purpose of this study was initially to examine the effect of tibial slope on anterior tibial translation in the ACL deficient knee measured objectively using the KT 1000 arthrometer. Patients were then evaluated one year post ACL reconstruction to determine the effect of tibial slope on the outcome of ACL reconstruction.

One-hundred patients (male = 70, female 30) aged between 14 and 49 years (Mean = 28.70, SD 8.80) with a diagnosis of isolated anterior cruciate ligament rupture were prospectively recruited. All participants had intact ACLs of the contralateral limb. The following information was recorded for all patients preoperatively and one year post surgery; time from injury to surgery, IKDC objective and subjective assessment and KT 1000 arthrometer readings. Tibial slope was assessed from long tibial lateral x-rays as described by Dejour and Bonnin. Finally, assessment of the menisci occurred intra-operatively. Tibial slope was correlated with KT 1000, meniscal integrity and IKDC assessments. Patients underwent an arthroscopic hamstring ACL reconstruction using Endobutton and Intrafix fixation. All procedures were performed by one surgeon

Pre Reconstruction – Bivariate correlations showed a significant correlation between tibial slope and KT 1000 (r= .29, p < .001). This relation was strengthened when the integrity of the menisci were controlled for (r = .32, p < . 001). When time to surgery was controlled for, correlations between tibial slope and KT 1000 were unaffected. There was also a negative correlation between medial meniscal integrity and time to surgery (r = −.41, p < . 001). No relationships between time to surgery and KT 1000 were evident

Post Reconstruction – Eighty patients were evaluated at a one year post surgery. One patient had a rerupture. The mean KT 1000 difference was 1mm. KT 1000 was > 2mm in 9% and > 5mm in the re rupture only. The mean subjective IKDC score was 89. Using objective IKDC 89% were classified as normal, 10% as nearly normal and 1% as severely abnormal (the rerupture). Bivariate correlations showed no significant correlation between tibial slope and post operative KT 1000 (r= .178, p = .0.115).

This study demonstrates a significant relationship between increasing tibial slope and anterior tibial translation of the ACL deficient knee. The relationship did not exist in the post ACL reconstructed knee. However this needs to be investigated further with greater numbers and in the ACL revision group.

Microfracture is a stem cell stimulation technique to promote the healing of full thickness articulate cartilage defects

Sixty-six patients have undergone microfracture for full thickness articulate cartilage defects over a five year period. All procedures were performed by one surgeon following the technique of Steadman. All patients were under 46, had an isolated chondral lesion, had a stable well aligned knee and were a minimum of one year post surgery.

Patients were evaluated with a preoperative and follow up IKDC score, WOMAC score, KOOS Score, Tegner activity level and SF 36, VAS pain scores and overall knee function score. Failure was determined by the need for a secondary chondral procedure.

Nine patients failed. Thus the overall success rate was 86%. The failure rate was higher with larger lesions.

There was a significant improvement in IKDC score, WOMAC score, KOOS Score, Tegner activity level and SF 36, VAS pain scores and overall knee function score.

Microfracture has a good success rate in the short to medium term with isolated full thickness articular cartilage lesions in the stable well aligned knee.