Novel alignment measurement technique for total knee arthroplasty using patient specific instrumentation

Applications and accuracy of 3D-printed surgical guides in traumatology and orthopaedic surgery: A systematic review and meta-analysis

Background

Patient-Specific Surgical Guides (PSSGs) are advocated for reducing radiation exposure, operation time and enhancing precision in surgery. However, existing accuracy assessments are limited to specific surgeries, leaving uncertainties about variations in accuracy across different anatomical sites, three-dimensional (3D) printing technologies and manufacturers (traditional vs. printed at the point of care). This study aimed to evaluate PSSGs accuracy in traumatology and orthopaedic surgery, considering anatomical regions, printing methods and manufacturers.

Methods

A systematic review was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines. Studies were eligible if they (1) assessed the accuracy of PSSGs by comparing preoperative planning and postoperative results in at least two different planes (2) used either computer tomography or magnetic resonance imaging (3) covered the field of orthopaedic surgery or traumatology and (4) were available in English or German language. The 'Quality Assessment Tool for Quantitative Studies' was used for methodological quality assessment. Descriptive statistics, including mean, standard deviation, and ranges, are presented. A random effects meta-analysis was performed to determine the pooled mean absolute deviation between preoperative plan and postoperative result for each anatomic region (shoulder, hip, spine, and knee).

Results

Of 4212 initially eligible studies, 33 were included in the final analysis (8 for shoulder, 5 for hip, 5 for spine, 14 for knee and 1 for trauma). Pooled mean deviation (95% confidence interval) for total knee arthroplasty (TKA), total shoulder arthroplasty (TSA), total hip arthroplasty (THA) and spine surgery (pedicle screw placement during spondylodesis) were 1.82° (1.48, 2.15), 2.52° (1.9, 3.13), 3.49° (3.04, 3.93) and 2.67° (1.64, 3.69), respectively. Accuracy varied between TKA and THA and between TKA and TSA.

Conclusion

Accuracy of PSSGs depends on the type of surgery but averages around 2-3° deviation from the plan. The use of PSSGs might be considered for selected complex cases.

Level of Evidence

Level 3 (meta-analysis including Level 3 studies).

Patient-specific instrumentation in total knee arthroplasty: a review of the current literature

Total knee arthroplasty (TKA) is one of the most frequently performed interventions in the field of Orthopaedic surgery. Over the last decades the implantation technique has improved continuously. The majority of patients is satisfied with the clinical outcome of TKA. However in various clinical follow-ups, up to 20% of unsatisfied patients can be observed. Periprosthetic infection and aseptic loosening seem to be the most common reasons for failure. Malalignment has been discussed as a cause of aseptic loosening and often leads to revision surgery. In order to increase the precision of implant positioning and alignment, new technologies such as patient-specific instrumentation (PSI) have been developed. Since the introduction of PSI, multiple clinical studies have been performed analyzing the clinical and radiological outcome of TKA with PSI technique. This review covers the recent literature of PSI in respect to surgical accuracy, clinical outcome, time- and cost-effectiveness.

Coronal alignment classes after robotic-assisted total knee arthroplasty are not associated with variation in patient-reported outcome measurements: A single-center cohort study

BACKGROUND

The aims of this study were (1) to use three-dimensional computed tomography (3DCT) measurements to determine whether patients undergoing imageless robotic-assisted total knee arthroplasty (RA-TKA) develop a variety of postoperative distal femoral mechanical angle (FMA), proximal tibial mechanical angle (TMA), and hip-knee-ankle angle (HKA) phenotypes as described by Hirschmann et al, and (2) to compare postoperative patient-reported outcome measurements (PROMs) between these phenotypes.

METHOD

Fifty patients with knee osteoarthritis underwent RA-TKA. All surgeries were performed using bicruciate-stabilized TKA. In each case, the postoperative HKA, FMA and TMA were classified into one of Hirschmann's five FMA, five TMA, and seven HKA phenotype categories. We investigated how these phenotypes affected patient satisfaction, 2011 Knee Society Score (KSS) subscale scores, the Forgotten Joint Score-12 (FJS-12) score, and patella scores with anterior knee pain at a mean of 15.1 months after RA-TKA.

RESULTS

Coronal alignment angles were assigned to three FMA, four TMA, and five HKA phenotypes. The most common FMA, TMA, and HKA phenotypes were valgus FMA 3° (58%), valgus TMA 3° (60%), and varus HKA 3° (38%). The FMA, TMA, and HKA phenotypes showed no significant differences in any PROMs.

CONCLUSIONS

RA-TKA led to various HKA, FMA and TMA phenotypes in the coronal plane, none of which affected PROMs.

Prosthetic Accuracy Depends on the Design of Patient-Specific Instrumentation: Results of a Retrospective Study Using Three-Dimensional Imaging

To determine accuracy of patient-specific instrumentation (PSI), the preoperative three-dimensional (3D) plan should be superimposed on the postoperative 3D image to compare prosthetic alignment. We aimed to compare prosthetic alignment on a preoperative 3D computed tomography (CT) plan and postoperative 3D-CT image, and evaluate the accuracy of PSI during total knee arthroplasty (TKA). Thirty consecutive knees (30 patients) who underwent TKA using PSI were retrospectively evaluated. The preoperative plan was prepared using 3D CT acquisitions of the hip, knee, and ankle joints. The postoperative 3D CT image obtained 1 week after surgery was superimposed onto the preoperative 3D plan using computer software. Differences in prosthetic alignment between the preoperative and postoperative images were measured using six parameters: coronal, sagittal, and axial alignments of femoral and tibial prostheses. Differences in prosthetic alignment greater than 3 degrees were considered outliers. Two observers performed all measurements. All parameters were repeatedly measured over a 4-week interval. This measurement method's intraobserver and interobserver reliabilities were more than 0.81 (very good). For the femoral and tibial prostheses, absolute differences between the preoperative and postoperative 3D CT images were significantly larger in the sagittal than in the coronal and axial planes (p < 0.001). The outlier rate for the sagittal alignment of femoral and tibial prostheses was significantly higher than that for the alignment of coronal and axial planes (p < 0.001). However, there were no significant differences in the range of motion (ROM) before and after TKA when comparing cases with and without outliers in the sagittal plane. Even though the present study did not reveal any issues with the ROM that depended on the presence of an outlier, accurate verification of prosthetic alignment for individual PSI models may be necessary because the designs, referenced images, and accuracy are different in each model.

Measurement for gap balancing technique in patients undergoing total knee arthroplasty: a large retrospective observational study

Background

Many traditional methods are available to prevent unbalance of extension and flexion gap during total knee arthroplasty (TKA), but there are no reports on the use of measurement and positioning method before tibial osteotomy with self-made tools. We designed a self-made tool measuring the location before tibial osteotomy and determined the clinical effect.

Methods

The retrospective study included patients who received TKA at our hospital, between January 1, 2012 and December 31, 2015. A new method, named as the measurement and localization before osteotomy with self-made tools, was developed to measure the osteotomy position of the posterior femoral condyle during TKA. They were divided into two groups, one that received the new method (Group I), and the other that received the traditional method as a control (Group I I). HSS score, Oxford score, VAS score and knee joint activity were evaluated in two groups.

Results

One hundred and eighty-seven of 210 eligible patients were included. The function of knee joint in all patients was improved and the pain was obviously relieved. Significant differences were found in the HSS score, Oxford score, VAS score, knee joint activity between two groups at 5-year follow-up (p < 0.05).

Conclusions

The biomet knee prosthesis was selected for all intraoperative implants. All operations were completed by the same senior surgeon. The use of self-made tools may contribute to improve the balance between flexion and extension gaps as well as the balance between internal and external gaps during TKA, and overcome knee flexion instability.

Primary total knee arthroplasty assisted by computed tomography-free navigation for secondary knee osteoarthritis following massive calcium phosphate cement packing for distal femoral giant-cell bone tumor treatment: a case report

BACKGROUND

Giant cell tumor of bone (GCTB) is an intermediate tumor commonly arising from the epiphysis of the distal femur and proximal tibia. Standard GCTB treatment is joint-preserving surgery performed using thorough curettage and the filling of the cavity with allo-, auto-, polymethyl methacrylate (PMMA), or synthetic bone graft. Calcium phosphate cement (CPC) is an artificial bone substitute, which has the benefit of being able to adjust defects, consequently inducing immediate mechanical strength, and promoting biological healing. Secondary osteoarthritis may occur following GCTB treatment and may need additional surgery if severe. However, details regarding surgery for secondary osteoarthritis have not been fully elucidated. There are no reports on the use of total knee arthroplasty (TKA) for the treatment of secondary osteoarthritis following CPC packing. The insertion of an alignment rod is a standard procedure in TKA; however, it was difficult to perform in this case due to CPC. Therefore, we used a computed tomography (CT)-free navigation system to assist the distal femur cut. This study presents a knee joint secondary osteoarthritis case following CPC packing for GCTB curettage that was treated with standard TKA.

CASE PRESENTATION

A 67-year-old Japanese woman, who was previously diagnosed with left distal femur GCTB and was treated by curettage and CPC packing 7 years ago, complained of severe knee pain. Left knee joint plain radiography revealed Kellgren and Lawrence (K-L) grade 4 osteoarthritis without evidence of tumor recurrence. Therefore, she was scheduled for TKA. There are no reports on the cutting of a femoral condyle surface with massive CPC with accurate alignment. Because it is difficult to insert the alignment rod intramedullary and cut the femoral condyle with CPC, we planned CT-free navigation-guided surgery for accurate bone cutting using an oscillating tip saw system to prevent CPC cracks. We performed standard TKA without complications, as planned. Postoperative X-ray showed normal alignment. Knee Society Knee Score (KSKS) and Knee Society Function Score (KSFS) ameliorated from 27 and 29 to 64 and 68, respectively The patient can walk without a cane postoperatively.

CONCLUSION

There was no report about the surface TKA guided by CT-free navigation after primary GCT surgery with CPC. We believe that this case report will help in planning salvage surgery for secondary osteoarthritis after CPC packing.

Evaluation of the accuracy of resected bone thickness based on patient-specific instrumentation during total knee arthroplasty

BACKGROUND

In total knee arthroplasty (TKA) using patient-specific instrumentation (PSI), the correlation between the preoperative surgical plan and intraoperative resection size is unclear. The aims of this study were to evaluate whether the computed tomography (CT)-based PSI surgical plan can be executed accurately and to determine the accuracy of bone resection in TKA using PSI.

METHODS

Data of 45 consecutive knees undergoing TKA using CT-based PSI were retrospectively evaluated. The preoperative plan was prepared using three-dimensional CT acquisitions of the hip, knee, and ankle joints. Resected bone thicknesses of the femoral condyle of the distal medial, distal lateral, posterior medial, posterior lateral, and medial and lateral tibial plateaus were measured with a Vernier caliper intraoperatively. Then these respective measurements were compared with those in the preoperative CT-predicted bone resection surgical plan, and the measured thickness of resection was subtracted from the planned resection thickness. Errors were defined as: acceptable, ≤ 1.5 mm; borderline, 1.5-2.5 mm; and outliers,  > 2.5 mm.

RESULTS

Overall, 22 (48.9%) knees had no outliers. There were 20 (44.4%) and 3 (6.7%) knees in which only 1 and 2 resection planes were outliers, respectively. The posterior medial tibial plateau had the lowest proportion of acceptable cuts (44.4%). Posterior femoral resection including the medial and lateral condyles had more outliers (n = 18/90 cuts, 20.0%) (p < 0.001) than the tibial condyles (n = 3/90 cuts, 3.3%) and distal femoral cuts (n = 6/90 cuts, 6.7%). The posterior surface of the femur, where the incidence of outliers was higher, tended to have a higher proportion of undercuts than other surfaces of the femur (> 80%).

CONCLUSIONS

PSI showed only fair-to-moderate accuracy. The cutting guide for the posterior femur was less accurate than that for the tibia and distal femur. Specific attention is required when cutting the posterior femur. The PSI design needs to be improved to reduce errors.

Robotic-assisted total knee arthroplasty improves the outlier of rotational alignment of the tibial prosthesis using 3DCT measurements

BACKGROUND

The aim of the present study was to compare the accuracy of prosthetic alignment with three-dimensional computed tomography (3DCT) measurements following total knee arthroplasty (TKA) performed using a robotic-assisted surgical technique versus a conventional TKA.

METHODS

41 TKAs were performed with a handheld robotic-assisted surgical procedure (Robot group) between 2019 and 2020. Another 41 patients underwent TKA with a conventional manual surgical procedure (Manual group) using the same prosthesis. The operation durations between both groups were investigated. 3DCT scans of the entire lower extremities were taken before and after the surgery and femoral and tibial alignments in the coronal, sagittal, and axial planes were measured using computer software. The differences in prosthetic alignment and translation between the preoperative 3DCT plan and postoperative 3DCT image were also measured.

RESULTS

There were no statistically significant differences in the post-operative outliers of the femorotibial angle between the groups. In the tibial-axial plane, the mean of prosthetic alignment in the anteroposterior plane was 4.0° in the Robot group and 6.7° in the Manual group (p < 0.01). The rate of outliers for tibial-axial alignment in the Robot group was significantly less than in the Manual group (p < 0.01). There were no statistically significant differences in prosthetic translation in the proximal-distal, anterior-posterior and medial-lateral orientations between the groups.

CONCLUSIONS

In a radiologic study using 3DCT, robotic-assisted TKA reduced the outliers for rotational alignment of the tibial prosthesis in comparison to conventional TKA, which can lead to improved tracking of the femoral-tibial bearing surfaces.

The influence of tibiofemoral joint forces on patient-reported outcome measurements after bicruciate stabilized total knee arthroplasty

OBJECTIVE

Insall advocated that a successful clinical outcome of total knee arthroplasty (TKA) depends on soft tissue balance procedure. Spacer blocks, balancer, and instrumented tibial sensor (VERESENSE, OrthoSensor, Dania, Florida, USA) are the current methods of soft tissue balancing during TKA. The purpose of the study is to assess intraoperative medial and lateral tibiofemoral compressive force (TFCF) using novel insert sensor and investigate the relationship between TFCF and patient-reported outcome measurements (PROMs).

METHODS

Twenty-five patients who underwent bicruciate stabilized (BCS) TKA were evaluated retrospectively. We measured intraoperative medial and lateral TFCF in neutral position as well as the force ratio (FR %:medial TFCF/medial + lateral TFCF) in varus and valgus position using the novel insert sensor throughout the range of motion (ROM) and assessed the relationship between intraoperative medial and lateral TFCF and PROM at 6 months after TKA.

RESULTS

Medial TFCF increased and lateral TFCF decreased throughout ROM. The mean FR was 0.44% ± 0.22 throughout ROM. Medial and lateral TFCF differences at 60° of ROM in neutral position showed a positive correlation with physical function in Western Ontario and McMaster Universities scores (r = 0.60, p < 0.05). Medial and lateral TFCF differences at 30° and 140° of ROM in valgus stress test showed a positive correlation with symptoms in 2011 Knee Society Scores (r = 0.49, p < 0.05; r = 0.51, p < 0.05).

CONCLUSION

The present study revealed that BCS TKA reproduces the coronal laxity, which is similar to healthy knee. These results suggest that intraoperative medial stability is important for function and symptoms, therefore, surgeons should not release medial soft tissue for achieving better clinical outcomes after BCS TKA.

LEVEL OF EVIDENCE

II.

Midterm Comparison of Tibial Fixation between Posterior Cruciate-Retaining and Substituting Porous Tantalum Total Knee Arthroplasty: Three-Dimensional Computed Tomography Analysis

Porous tantalum tibial component is durable with excellent bone ingrowth, higher knee scores, and long-term survivorship. However, to our knowledge, the effect of posterior cruciate-retaining (CR) and posterior cruciate-substituting (PS) porous tantalum tibial component has not been reported. The aim of the current study was to investigate the prosthetic bone quality between CR porous tantalum tibial component and PS using three-dimensional multi-detector-row computed tomography (3D-MDCT). Porous twenty-two (22) CR total knee arthroplasties and 22 PS received 3D-MDCT at every 6 months up to 5.5 years postoperatively to assess prosthetic bone quality (bone marrow contents/tissue volumes [BMC/TV, mg/cm³]) underneath the pegs of porous tantalum modular tibial component. Clinical outcomes (Knee Society score [KSS], Western Ontario and McMaster Universities (WOMAC), FJS-12, Patella score) were evaluated at a minimum follow-up period of 5.5 years. No statistically significant differences were found in age, gender, body mass index, KSS, and BMC/TV volumes in the proximal tibia between the two groups before total knee arthroplasty (TKA). There were also no significant differences between the CR and PS groups with regard to BMC/TV at every 6 months up to 5.5 years after TKA. At 5.5 years postoperatively, there was no significant difference between the two groups in terms of the KSS, WOMAC, forgotten joint score (FJS-12), and Patella score. The present study revealed that the prosthetic bone quality of the CR porous tantalum tibial component and PS were equivalent at every 6 months up to 5.5 years after TKA. This study reflects level II evidence.

Conventional instruments are more accurate for measuring the depth of the tibial cut than computer-assisted surgery in total knee arthroplasty: a prospective study

INTRODUCTION

The most commonly used tool for implant positioning are conventional instruments (CI) followed by computer-assisted surgery (CAS). A number of studies have investigated the cutting error of the tibial component when CAS is used, but most of them were focused on the cutting angles. The accuracy of CAS to determine the depth of the cut has not received much attention, even though implications are similar or worse, than with an angle mismatch.

MATERIALS AND METHODS

This was an ethics board approved, prospective study of 23 consecutive varus TKAs by a single surgeon. Implant positioning was performed using CAS; however, the depth of the tibial cut was determined with both CAS and CI. Targeted alignment was the mechanical axis and 3° of posterior slope. The planned and the achieved cut, as determined by CAS needed to match. The achieved cut was then measured using a caliper and compared to the depth of the cut as per CAS. Medial and lateral cuts were analyzed separately. Analysis of variance and Bland-Altman plots were used for the comparison.

RESULTS

Mean medial navigated cut was 6.3 (± 2.2) mm, mean measured medial cut was 6.6 (± 2.3) mm. Mean lateral navigated cut was 8.9 (± 1.8) mm, mean measured lateral cut was 8.8 (± 1.5) mm. There was a statistical significance for both the medial (p < 0.001) and the lateral (p = 0.004) navigated and measured cuts.

CONCLUSIONS

The results of this study suggest that the tibial cut depth, measured by the navigation, does not match the actual bony cuts performed, even if a perfect cut was achieved in both sagittal and coronal plane. Surgeons should be aware of the measurement error in the navigation system and potentially add an additional step for verifying the achieved depth of the cut.

Design improvement in patient-specific instrumentation for total knee arthroplasty improved the accuracy of the tibial prosthetic alignment in the coronal and axial planes

PURPOSE

The accuracy of patient-specific instrumentation (PSI) in total knee arthroplasty (TKA) is still controversial, especially in the tibial prosthesis. It was hypothesized that the design modification of PSI improved the tibial prosthetic alignment and reduced the associated complications. The aim of this study was to compare the accuracy of a conventional PSI with that of a newly designed PSI for total knee arthroplasty (TKA) using a new three-dimensional (3D) measurement method.

METHODS

Thirty TKAs each using the conventional and newly designed PSIs were studied. The postoperative 3D-computed tomography (3D CT) image was superimposed on the preoperative 3D CT plan. The absolute differences in the tibial prosthetic alignment between the preoperative and postoperative 3D CT images were directly measured in the coronal, sagittal, and axial planes. Knees in which the difference in the prosthetic alignment was > 3° were considered deviations.

RESULTS

The new PSI showed less mean absolute differences and lower rate of deviations than the conventional PSI in the coronal and axial planes (p = 0.045 and p = 0.004, respectively). The deviations (> 3°) of the tibial prosthesis using the conventional PSI were 27, 30, and 63% and of those using the new PSI were 0, 20, and 20% in the coronal, sagittal, and axial planes, respectively.

CONCLUSIONS

This is the first report to evaluate the effect of improvement in PSI design on the postoperative alignment using 3D method, and it clearly showed that the modification significantly improved the accuracy of alignment and reduced the deviations.

LEVEL OF EVIDENCE

Therapeutic study, case-control study, Level III.

Accuracy of tibial positioning in the frontal plane: a prospective study comparing conventional and innovative techniques in total knee arthroplasty

BACKGROUND

Coronal alignment of the tibial component determines functional outcome and survival in total knee arthroplasty (TKA). Innovative techniques for tibial instrumentation have been developed to improve accuracy and reduce the rate of outliers.

METHODS

In a prospective study, 300 patients were allocated to four different groups using a randomization process (two innovative and two conventional) techniques of tibial instrumentation (conventional: extramedullary, intramedullary; innovative: navigation and patient-specific instrumentation (PSI); n = 75 for each group). The aims were to reconstruct the medial proximal tibial angle (MPTA) to 90° and the mechanical tibio-femoral axis (mTFA) to 0°. Both angles were evaluated and compared between all groups three months after the surgery. Patients who presented with a postoperative mTFA > 3° were classified as outliers.

RESULTS

The navigation and intramedullary technique both demonstrated that they were significantly more precise in reconstructing a neutral mTFA and MPTA compared to the other two techniques. The odd's ratio (OR) for producing outliers was highest for the PSI method (PSI OR = 5.5, p < 0.05; extramedullary positioning OR = 3.7, p > 0.05; intramedullary positioning OR = 1.7, p > 0.05; navigation OR = 0.04, p < 0.05). We could only observe significant differences between pre- and postoperative MPTA in the navigation and intramedullary group. The MPTA showed a significant negative correlation with the mTFA in all groups preoperatively and in the extramedullary, intramedullary and PSI postoperatively.

CONCLUSION

The navigation and intramedullary instrumentation provided the precise positioning of the tibial component. Outliers were most common within the PSI and extramedullary technique. Optimal alignment is dependent on the technique of tibial instrumentation and tibial component positioning determines the accuracy in TKA since mTFA correlated with MPTA pre- and postoperatively.

The influence of compressive forces across the patellofemoral joint on patient-reported outcome after bi-cruciate stabilized total knee arthroplasty

AIMS

Patellofemoral problems are a common complication of total knee arthroplasty. A high compressive force across the patellofemoral joint may affect patient-reported outcome. However, the relationship between patient-reported outcome and the intraoperative patellofemoral contact force has not been investigated. The purpose of this study was to determine whether or not a high intraoperative patellofemoral compressive force affects patient-reported outcome.

PATIENTS AND METHODS

This prospective study included 42 patients (42 knees) with varus-type osteoarthritis who underwent a bi-cruciate stabilized total knee arthroplasty and in whom the planned alignment was confirmed on 3D CT. Of the 42 patients, 36 were women and six were men. Their mean age was 72.3 years (61 to 87) and their mean body mass index (BMI) was 24.4 kg/m ² (18.2 to 34.3). After implantation of the femoral and tibial components, the compressive force across the patellofemoral joint was measured at 10°, 30°, 60°, 90°, 120°, and 140° of flexion using a load cell (Kyowa Electronic Instruments Co., Ltd., Tokyo, Japan) manufactured in the same shape as the patellar implant. Multiple regression analyses were conducted to investigate the relationship between intraoperative patellofemoral compressive force and patient-reported outcome two years after implantation.

RESULTS

No patient had anterior knee pain after total knee arthroplasty. The compressive force across the patellofemoral joint at 140°of flexion was negatively correlated with patient satisfaction (R ² = 0.458; β = -0.706; p = 0. 041) and Forgotten Joint Score-12 (FJS-12; R ² = .378; β = -0.636; p = 0. 036). The compressive force across the patellofemoral joint at 60° of flexion was negatively correlated with the patella score (R ² = 0.417; β = -0.688; p = 0. 046).

CONCLUSION

Patient satisfaction, FJS-12, and patella score were affected by the patellofemoral compressive force at 60° and 140° of flexion. Reduction of the patellofemoral compressive forces at 60° and 140° of flexion angle during total knee arthroplasty may improve patient-reported outcome, but has no effect on anterior knee pain.

Reliable patient-reported outcome measure and survivorship of UKA for primary spontaneous osteonecrosis

PURPOSE

Primary Spontaneous osteonecrosis of the knee (SPONK) was a result of a subchondral insufficiency fracture based on histopathological examinations. There were few studies examining patients who underwent unicompartmental knee arthroplasty (UKA) for the treatment of primary SPONK. The aim of this study was to investigate (1) patient-reported outcome measure (PROM), (2) survivorship of revision as end point and (3) survivorship of complication as end point in patients with primary SPONK.

METHODS

The clinical examinations of a consecutive series of 61 medial UKAs for primary SPONK of the medial femoral condyle from 2008 to 2012 were evaluated retrospectively at our institution. There were 18 males and 43 females with a mean age of 73.7 years (60-91). In all patients, preoperative radiographs were analyzed according to the stage of primary SPONK. We conducted Kaplan-Meier survival analyses using revision and complications for any reasons as the end point.

RESULTS

Mean follow-up was 6.6 years (range 6-10). UKA using Physica ZUK (LIMA Corporate. UD, Italy) for SPONK improved patients' 2011 Knee Society symptom score, patient satisfaction, patient activities, EQ-5D and postoperative ranges of motion compared with their preoperative status (P < 0.01). Revision surgery was required in one knee (1.6%) due to postoperative fracture of the medial tibial plateau after a fall that occurred 6 months postoperatively. The projected rate of survivorship of UKA was 90.4% at 10 years (95% confidence interval 0.80-1). The projected rate of survivorship with complication at end point was 87.7% at 10 years (95% confidence interval 0.76-0.99).

CONCLUSION

The present study demonstrated that primary spontaneous osteonecrosis of the knee (SPONK) can be successfully be treated with UKA at a mean follow-up of 6.6 years.

LEVEL OF EVIDENCE

II.

Is there a relationship between the load distribution on the tibial plateau and hip knee ankle angle after TKA?

INTRODUCTION

This study asked whether differences in coronal alignment after total knee arthroplasty (TKA) affect the load distribution on the tibial plateau. The aim of this study was to investigate the correlation between coronal alignment and the load distribution on the tibial plateau after TKA, using three-dimensional multi-detector-row-computed tomography (3D-MDCT).

MATERIALS AND METHODS

In this study, we performed 84 cementless TKA with porous tantalum modular tibial component (PTMT) and divided into three groups based on post-operative hip-knee-ankle (HKA) angle: varus alignment group (n = 22), (176° ≧) neutral alignment group (n = 45), (180° ± 3°), and valgus alignment group (n = 17) (184° ≦).The changes in bone quality parameters of trabecular patterns under peg of PTMT were interpreted as load distribution due to changes in alignment. The relationship between HKA angle and load distribution on the tibial plateau was analyzed every 6 months for 4.5 years by measuring Bone marrow contents/tissue volumes (mg/cm³) and bone volumes/tissue volumes (%) under peg of porous tantalum modular tibial component by visualizing three dimensionally with 3D-osteo-morphometry software.

RESULTS

There were no correlations between HKA angle and the load distribution on the tibial plateau after TKA at all periods. There was a significantly higher increase in the medial region than the lateral about the BMC/TV and BV/TV values, regardless of the post-operative alignment after TKA for all periods. The relative BMC/TV and BV/TV changes at medial region in varus alignment group were significantly lower than the neutral and the valgus alignment groups of pre-operative medial osteoarthritis of the knee.

CONCLUSIONS

As far, it can be concluded by the study and the methods used therein that there were no relationships between the load distribution on the tibial plateau and HKA angle after TKA.

LEVEL OF EVIDENCE

Therapeutic study, Level III.