Evaluation of painful total knee arthroplasty

Predictability of implant sizes during cruciate-retaining total knee arthroplasty using an image-free hand-held robotic system

The use of appropriately sized implants is critical for achieving optimal gap balance following total knee arthroplasty (TKA). Inappropriately sized implants could result in several complications. Robot-assisted TKA (RA-TKA) using CT-based pre-operative planning predicts implant sizes with high accuracy. There is scant literature describing the accuracy of image-free RA-TKA in predicting implant sizes. The purpose of this study was to assess the accuracy of an image-free robotic system in predicting implant sizes during RA-TKA. Patients who underwent cruciate-retaining RA-TKA for primary osteoarthritis, using an image-free hand-held robotic system were studied. The predicted and implanted sizes of the femoral component, tibial component and polyethylene insert, for 165 patients, were recorded. Agreement between robot-predicted and implanted component sizes was assessed in percentages, while reliability was assessed using Cohen's weighted kappa coefficient. The accuracy of the robotic system was 63% (weighted-kappa = 0.623, P < 0.001), 94% (weighted-kappa = 0.911, P < 0.001) and 99.4% (weighted-kappa = 0.995, P < 0.001), in predicting exact, ± 1 and ± 2 sizes of the femoral component, respectively. For the tibial component, an accuracy of 15.8% (weighted-kappa = 0.207, P < 0.001), 55.8% (weighted-kappa = 0.378, P < 0.001) and 76.4% (weighted-kappa = 0.568, P < 0.001) was noted, for predicting exact, ± 1 and ± 2 sizes respectively. An accuracy of 88.5%, 98.2% and 100%, was noted for predicting exact, ± 1 and ± 2 sizes of the polyethylene insert respectively. Errors in predicting accurate implant sizes could be multi-factorial. Though the accuracy of image-free RA-TKA with respect to alignment and component positioning is established, the surgeon's expertise should be relied upon while deciding appropriate implant sizes.

Anatomic Referencing Restores the Anatomy of the Distal Femur with Less Compromise

Historically, anterior referencing and posterior referencing are two specific techniques that surgeons can use for proper sizing of the femoral component in total knee arthroplasty (TKA). In this review, we introduce the concept of "anatomic referencing" which has become useful with more incremental sizes of the femoral component to more perfectly match the native anatomy of each patient and reduce overstuffing of the patellofemoral joint and medial-lateral (ML) overhang. Fifty consecutive TKA cases were reviewed where the novel anatomic referencing technique was used. Lateral radiographic projections were obtained preoperatively and postoperatively. The posterior condylar offset (PCO) was evaluated on the lateral radiographs by measuring the distance between the tangent line of the femoral diaphysis posterior cortex and the posterior condylar margin. PCO ratio (PCOR) was calculated by dividing the PCO by the distance between the posterior condylar border and a tangent line along the anterior cortex of the femoral diaphysis. Forty-five patients (50 TKAs) were reviewed. Average age of the patients was 70.34, range: 47-91. There were 19 males and 26 females reviewed in this series. On average, the delta PCOR was 0.022 (standard deviation = 0.032; min: -0.049, max: 0.082). When grouping our results into three main groups: < -0.03, -0.03 to 0.03, and > 0.03, we found that 62% fell within the -0.03 to 0.03 range. There was no statistically significant difference in delta PCOR between standard and narrow implants (p = 0.418). The proposed novel anatomic referencing technique has allowed for proper sizing of patients' femurs in the anteroposterior and ML direction while avoiding component overhang or the need for component downsizing to obtain a proper ML fit. This radiographic review confirmed this to be a highly accurate and reproducible technique.

Development and Validation of an Artificial Intelligence Preoperative Planning and Patient-Specific Instrumentation System for Total Knee Arthroplasty

BACKGROUND

Accurate preoperative planning for total knee arthroplasty (TKA) is crucial. Computed tomography (CT)-based preoperative planning offers more comprehensive information and can also be used to design patient-specific instrumentation (PSI), but it requires well-reconstructed and segmented images, and the process is complex and time-consuming. This study aimed to develop an artificial intelligence (AI) preoperative planning and PSI system for TKA and to validate its time savings and accuracy in clinical applications.

METHODS

The 3D-UNet and modified HRNet neural network structures were used to develop the AI preoperative planning and PSI system (AIJOINT). Forty-two patients who were scheduled for TKA underwent both AI and manual CT processing and planning for component sizing, 20 of whom had their PSIs designed and applied intraoperatively. The time consumed and the size and orientation of the postoperative component were recorded.

RESULTS

The Dice similarity coefficient (DSC) and loss function indicated excellent performance of the neural network structure in CT image segmentation. AIJOINT was faster than conventional methods for CT segmentation (3.74 ± 0.82 vs. 128.88 ± 17.31 min, p < 0.05) and PSI design (35.10 ± 3.98 vs. 159.52 ± 17.14 min, p < 0.05) without increasing the time for size planning. The accuracy of AIJOINT in planning the size of both femoral and tibial components was 92.9%, while the accuracy of the conventional method in planning the size of the femoral and tibial components was 42.9% and 47.6%, respectively (p < 0.05). In addition, AI-based PSI improved the accuracy of the hip-knee-ankle angle and reduced postoperative blood loss (p < 0.05).

CONCLUSION

AIJOINT significantly reduces the time needed for CT processing and PSI design without increasing the time for size planning, accurately predicts the component size, and improves the accuracy of lower limb alignment in TKA patients, providing a meaningful supplement to the application of AI in orthopaedics.

ACR Appropriateness Criteria® Imaging After Total Knee Arthroplasty: 2023 Update

Total knee arthroplasty is the most commonly performed joint replacement procedure in the United States. This manuscript will discuss the recommended imaging modalities for six clinical variants; 1. follow-up of symptomatic or asymptomatic patients with a total knee arthroplasty. Initial imaging, 2. Suspected infection after total knee arthroplasty. Additional imaging following radiographs, 3. Pain after total knee arthroplasty. Infection excluded. Suspect aseptic loosening or osteolysis or instability. Additional imaging following radiographs, 4. Pain after total knee arthroplasty. Suspect periprosthetic or hardware fracture. Additional imaging following radiographs, 5. Pain after total knee arthroplasty. Measuring component rotation. Additional imaging following radiographs, and 6. Pain after total knee arthroplasty. Suspect periprosthetic soft-tissue abnormality unrelated to infection, including quadriceps or patellar tendinopathy. Additional imaging following radiographs. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where peer reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

Mapping the course to recovery: a prospective study on the anatomic distribution of early postoperative pain after total knee arthroplasty

INTRODUCTION

Early postoperative pain following total knee arthroplasty significantly impacts outcomes and patient satisfaction. However, the characteristics and sources of early pain after total knee arthroplasty remain unclear. Therefore, the purpose of this study was to determine the anatomic distribution and course of postoperative pain in the acute and subacute period following total knee arthroplasty.

METHODS

A prospective observational study of primary, elective unilateral total knee arthroplasty cases was conducted at our academic tertiary care medical center from January 2021 to September 2021. Preoperative variables were extracted from institutional electronic medical records. Postoperatively, patients utilized a knee pain map to identify the two locations with the most significant pain and rated it using the visual analog scale (VAS). The data were collected on day 0, at 2 weeks, 2 months, and 6 months after operation.

RESULTS

This study included 112 patients, with 6% of patients having no pain at postoperative day 0, 22% at 2 weeks, 46% at 2 months, and 86% at 6 months after operation. In those who reported pain, the VAS score (mean ± standard deviation) was 5.8 ± 2.4 on postoperative day 0 and decreased at each follow-up time point (5.4 ± 2.3 at 2 weeks, 3.9 ± 2.2 at 2 months, and 3.8 ± 2.7 at 6 months). The majority of patients were able to identify distinct loci of pain. The most common early pain loci were patellae, thigh, and medial joint line, and this distribution dissipated by 6 months.

CONCLUSION

At 2 postoperative weeks, pain was primarily at the medial joint, and at 6 months postoperatively, pain was more likely to be at the lateral joint. No relationship was found between pain at six months and pain scores or location at postoperative day 0 or 2 weeks. Understanding the distribution and progression of knee pain following total knee arthroplasty may benefit patient education and targeted interventions.

LEVEL OF EVIDENCE

Level II, prospective observational study.

Anterior knee pain and sit-up tests predicts patients' satisfaction and improvement in quality of life after anterior stabilized total knee replacement without patellar resurfacing

PURPOSE

The purpose of this study was to assess patient satisfaction and identify risk factors for dissatisfaction after anterior stabilised conventional total knee arthroplasty (TKA) without patellar resurfacing, using the Goodman score.

METHODS

We conducted a cross-sectional study using data from our institutional database from 1 January 2018 to 1 March 2021. Patients who underwent TKA with the Vanguard® Cruciate Retaining Anterior Stabilized Knee System (Zimmer Biomet, Warsaw, Indiana, USA) without patellar replacement were included. Patients with other bearing surfaces (posterior stabilised or medial congruent) or diagnosed with infection or instability were excluded. Patients' reported outcomes, body mass index (BMI), passive range of motion, the timed up-and-go test, sit-up test, and algometry were assessed. Patients were also asked if they had anterior knee pain. Satisfaction was assessed using the Goodman scale, and logistic multivariate regression was used to identify variables associated with dissatisfaction and perceived improvement in quality of life.

RESULTS

A total of 131 TKA patients were included in the study. The median satisfaction score was 100 (interquartile range [IQR], 87.5 to 100), with the 75-point threshold at the 90th percentile according to Section A of Goodman. Section B of Goodman showed that 113 TKA patients (86.26%) reported "great improvement" or "more than I ever dreamed." Multivariate logistic regression revealed that anterior knee pain (OR 5.16, 95% CI 1.24 to 21.39), the sit-up test (OR 0.63, 95% CI 0.49 to 0.81), and BMI (OR 0.84, 95% CI 0.70 to 0.99) were significantly associated with patient dissatisfaction and a worse perceived improvement in quality of life. The receiver operating characteristics curve for the models had areas under the curve of 0.83 (95% CI 0.69 to 0.97) and 0.82 (95% CI 0.70 to 0.94), respectively.

CONCLUSION

Anterior stabilised TKA without patellar resurfacing can achieve 90% satisfaction and 86% improvement in quality of life. To improve these results, it is essential to prevent and treat anterior knee pain and enhance quadriceps strength.

LEVEL OF EVIDENCE

Level III (retrospective cohort study).

Arthroscopic popliteal tenotomy grants satisfactory outcomes in total knee arthroplasty with persistent localised posterolateral pain and popliteus tendon impingement

PURPOSE

The purpose was to estimate the prevalence of popliteus tendon impingement following TKA, and to describe the characteristics and the differential diagnosis protocol for this rare condition. The hypothesis was that arthroscopic popliteal tenotomy in TKA patients with suspected popliteus tendon impingement would relieve pain and improve satisfaction.

METHODS

Of 741 TKAs performed over three years, eight (1.1%, all women) had suspected popliteus tendon impingement, of which seven had severe localised posterolateral knee pain and one global knee pain. Upon confirmation of popliteus tendon impingement, arthroscopic popliteal tenotomy was performed, and outcomes (Pain on visual analogue scale (pVAS; best, 0; worst, 10), Oxford Knee Score (OKS; best, 48; worst, 0) and satisfaction (best, 100%; worst, 0%) assessed at mean 18-month follow-up.

RESULTS

At four to 30 months after TKA, arthroscopic exploration revealed popliteus tendon impingement in all eight knees. Six reported complete pain relief (pVAS, 0) the day following arthroscopic popliteal tenotomy, whilst one reported some residual pain (pVAS, 2). The remaining patient with global pain reported no pain relief, and required revision TKA at 12 months. Excluding the revised TKA, OKS was between 19 and 43, and satisfaction was rated ≥ 80% in five of the remaining seven patients.

CONCLUSIONS

Arthroscopic popliteal tenotomy relieved symptoms in TKA patients with persistent localised posterolateral pain and a positive popliteus test. These findings suggest that the popliteus test is reliable to diagnose popliteus tendon impingement following TKA, which could be treated by arthroscopic popliteal tenotomy.

LEVEL OF EVIDENCE

Level IV, Small case series.

Effect of the posterior sagging control device to the posterior tibial translation during posterior-stabilized total knee arthroplasty with modified gap technique

PURPOSE

In modern total knee arthroplasty (TKA), flexion and extension gaps between the femur and tibia are equilibrated before implanting the final components. Uncontrolled intraoperative posterior tibial translation (PTT) could cause an artifactual widening of the flexion gap, which could lead surgeons to alter the femoral component size. We designed an intraoperative posterior sagging control device to prevent intraoperative PTT. In this study, we investigated whether the use of this device could prevent artifactual widening of the flexion gap.

METHODS

Twenty-five patients, 21 women and four men, aged 74.2 years, were enrolled in this prospective study. All patients underwent postero-stabilized TKA using a navigation system. Intraoperative PTT, flexion and extension gaps with or without using the posterior sagging control device were measured with navigation system. These measurements were compared with or without the posterior sagging control device and after the final implantation also.

RESULTS

There were significant differences between the measurements performed with or without the posterior sagging control device when compared to the post-implantation measurements. The use of the device reduced the number of patients with a >3 mm increase in flexion gap from 7 (28%) to 1 (4%).

CONCLUSION

This study suggests that the posterior sagging control device prevents PTT and artificial flexion gap widening. This could prevent an unnecessary increase in component size.

Efficacy of the Pre-operative Three-Dimensional (3D) CT Scan Templating in Predicting Accurate Implant Size and Alignment in Robot Assisted Total Knee Arthroplasty

Background

Nearly 20% of Total knee Arthroplasty patients remain dissatisfied. This is a major concern in twenty-first century arthroplasty practice. Accurate implant sizing is shown to improve the implant survival, knee balance and patient reported outcome. Aim of the current study is to assess the efficacy of pre-operative three-dimensional (3D) CT scan templating in a robot-assisted TKA in predicting the correct implant sizes and alignment.

Materials and methods

Prospectively collected data in a single center from 30 RA-TKAs was assessed. Inclusion criterion was patients with end stage arthritis (both osteoarthritis and rheumatoid arthritis) undergoing primary TKA. Patients undergoing revision TKA and patients not willing to participate in the study were excluded. Preliminary study of ten patients had indicated almost 100% accuracy in determining the implant size and position. Sample size was estimated to be 28 for 90% reduction in implant size and position error with α error of 0.05 and beta error of 0.20 with power of study being 80. Post-operative radiographs were assessed by an independent observer with respect to implant size and position. The accuracy of femoral and tibial component sizing in the study was compared with the historic control with Chi-squared test. The p value < 0.05 was considered significant.

Results

The pre-operative CT scan 3D templating accuracy was 100% (30 out of 30 knees) for femoral component and 96.67% (29 out of 30 knees) for tibial component. The implant position and limb alignment was accurate in 100% of patients. The accuracy of femoral component and tibial component sizing is statistically significant (Chi-squared test, p value 0.0105 and 0.0461, respectively).

Conclusion

The study results show the effectiveness of pre-operative 3 D CT scan planning in predicting the implant sizes and implant positioning. This may have a potential to improve the implant longevity, clinical outcomes and patient satisfaction.

Sublingual Sufentanil Tablet System (SSTS-Zalviso®) for Postoperative Analgesia after Orthopedic Surgery: A Retrospective Study

Background: The aim of this study is to compare sublingual sufentanil and the administration device for its delivery (SSST-Zalviso®) with the traditional strategies used for the control of postoperative pain to establish if there is an actual benefit for the patient and healthcare personnel. Materials and Methods: A retrospective study was conducted to compare the efficacy of SSTS in the management of postoperative pain after orthopedic surgery between October 2018 and June 2020. We analyzed 50 patients who underwent a total knee arthroplasty (TKA). The control group consisted of 21 patients who underwent TKA and during the hospitalized recovery received a continuous femoral nerve block (cFNB). The statistical study was conducted with a level of significance p = 0.05 using “U” test, Mann−Whitney, to verify if patients had a better control of pain and fewer calls for rescue analgesia. Results: Patients involved in the study showed a significant reduction in pain intensity with the use of SSTS in the 24 h following surgery (p = 0.0568), also a drastic drop of the calls for rescue analgesia (p < 0.0001) reduces the number of calls for its control. Conclusions: This study demonstrates how SSTS might reduce pain intensity in the first 24 h after surgery and reduce the number of calls for its control, indicating better analgesic coverage and implying reduced interventions from healthcare personnel. This could allow a redistribution of resources and a reduction in the use of analgesic drugs in wards where the SSTS is used.

An Investigation of Medial Tibial Component Overhang in Unicompartmental and Total Knee Replacements Using Ultrasound in the Outpatient Department

Tibial component overhang is known to be a contributor to worse outcomes in knee arthroplasty. The aim of this study is to investigate the presence of tibial component overhang, and whether overhang correlates to a higher local tenderness in both medial unicompartmental and total knee replacements. Also, to determine if a rotational projection phenomenon is presented with radiographs when investigating tibial component overhang. A prospective study, including 64 participants, was performed, where ultrasound measurements were compared with postoperative radiographs. Local tenderness was measured as a pressure pain threshold, determined at 3 months postoperatively using algometry. Sixty-two of sixty-four patients had an underdiagnosed medial overhang on radiographs, with a mean difference of 2.4 mm between radiographs and ultrasound (p < 0.001), presenting a rotational projection phenomenon. When comparing sites with ultrasound measured overhang to sites without overhang measured by ultrasound, a higher local tenderness was observed (p < 0.001). A positive linear correlation was found between patients' overhang and local tenderness (r = 0.2; p = 0.045). Subgroup analysis of medial overhang showed significantly higher tenderness than all other locations. No significant differences were seen for lateral overhang. An apparent rotational projection phenomenon of overhang on radiographs was seen, and a linear association between overhang and local tenderness was demonstrated. This study warrants the use of ultrasound when a surgeon is presented with a patient with postoperative medial tenderness, but no overhang can be seen on radiographs. It should also raise awareness of implant selection and positioning during surgery, especially avoiding the overhang to be localized directly medially.

Anthropometric Comparison between Indian and Arabian Knees with Respect to Total Knee Replacement

Implants used for total knee replacement (TKR) in most Asian countries are not designed originally for the Asian population, and studies have shown anthropometric differences with respect to TKR among various ethnic groups. For this reason, implants designed for a specific population may not provide an anatomic fit when used in other populations. To avoid the consequences associated with such a misfit, the concept of ethnic-specific implant design is being introduced. In this study, the knee anthropometry of the Indian and Arabian patients was compared. They were operated with implants which were not ethnic-specific designs. Since the consequences associated with implant misfit apply equally to both the Indian and Arabian population, it is essential to compare the knee anthropometry of these two populations. Anthropometric measurements of the distal femur and proximal tibia of the Indian and Arabian knees were obtained intraoperatively using a Vernier caliper. Their respective aspect ratios (ARs) were calculated and statistically compared. It was found that the ARs of both tibia and femur of Indian and Arabian population did not show any statistical difference. There was no statistical difference between Indian and Arabian males (p = 0.345) and between Indian and Arabian females (p = 0.8210). However, a statistical difference in tibial AR (p-value = 0.049) and femoral AR (p-value = 0.003) was found significant when a comparison was made between the knees of Indian males and Indian females in the study. The above results suggested that TKR implants designed anatomically to suit the Indian population can also suit the Arabian population and vice versa. The obtained data can help implant designers to come up with ethnic-specific TKR implants.

Effects of the Medial Plateau Bearing Insert Conformity on Mid-Flexion Paradoxical Motion in a Posterior-Stabilized Total Knee Arthroplasty Design

BACKGROUND

One of the most common kinematic abnormalities reported for posterior-stabilized (PS) total knee arthroplasty (TKA) design is paradoxical anterior sliding during early and mid-flexion. PS TKAs have been designed such that the cam-post mechanism does not engage until later in flexion, making these implants vulnerable to anterior sliding during early and mid-flexion. The objective of this study is to investigate the biomechanical effect of increasing bearing conformity on a PS TKA.

METHODS

Using a validated computational model of the knee joint, the sagittal conformity of the medial plateau of a PS TKA design was altered. Three scenarios were created and evaluated for mechanics: (1) baseline conformity, (2) increased conformity, and (3) decreased conformity.

RESULTS

From full extension to approximately 70° of knee flexion, the medial condyle demonstrated minimal anterior sliding for the increased medial conformity design but revealed anterior sliding of 2 and 4 mm for the baseline and decreased conformity designs, respectively. After cam-post engagement, the medial condyle consistently rolled back for all 3 designs. The lateral condyle experienced consistent rollback throughout the entire flexion range for all 3 designs. However, femorotibial contact force was higher for the increased conformity design, peaking at 3.13 times body weight (×BW) compared to 3.0 × BW contact force for other 2 designs.

CONCLUSION

Increasing medial conformity of the bearing insert appears to reduce mid-flexion sliding for PS TKA designs, although this comes at the expense of increased femorotibial forces. This could be due to kinematic conflicts that may be introduced with highly constraining designs.

Nuclear Medicine Scans in Total Joint Replacement

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A 3-phase bone scan is a potential first-line nuclear medicine study for pain after total joint arthroplasty (TJA) when there is concern for periprosthetic joint infection or aseptic loosening.

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In patients who have a positive bone scintigraphy result and suspected infection of the joint, but where aspiration or other studies are inconclusive, labeled leukocyte scintigraphy with bone marrow imaging may be of benefit.

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Magnetic resonance imaging (MRI), while not a nuclear medicine study, also shows promise and has the advantage of providing information about the soft tissues around a total joint replacement.

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Radiotracer uptake patterns in scintigraphy are affected by the prosthesis (total knee arthroplasty [TKA] versus total hip arthroplasty [THA]) and the use of cement.

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Nuclear medicine scans may be ordered 1 year postoperatively but may have positive findings that are due to normal physiologic bone remodeling. Nuclear studies may be falsely positive for up to 2 years after TJA.

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Single-photon emission computed tomography (SPECT) combined with computed tomography (CT) (SPECT/CT), fluorine-18 fluorodeoxyglucose (18F-FDG) positron emission tomography (PET)/CT, and MRI show promise; however, more studies are needed to better define their role in the diagnostic workup of pain after TJA.

Medial abrasion syndrome: a neglected cause of persistent pain after knee arthroplasty

Introduction

Persistent post-operative pain (PPOP) has detracted from some otherwise successful knee arthroplasties. This study investigated medial abrasion syndrome (MAS) as a cause of PPOP after knee arthroplasty. The surgical techniques and outcomes of incorporating this concept into the management of both primary arthroplasty cases and patients suffering from unknown causes of PPOP after arthroplasties were presented.

Materials and methods

In a 1-year period, the author performed unicompartmental or total knee arthroplasty (the UKA or TKA group) that also eliminated medial abrasion phenomenon (MAP) on 196 knees of 150 patients at advanced stages of knee osteoarthritis (OA). During the same year, 16 knees of 16 patients with unknown causes of PPOP after knee arthroplasties were referred to the author for the arthroscopic medial release procedure (the AMR group) after being diagnosed as MAS. Subjective satisfaction, Knee Society Score (KSS), and Knee injury and Osteoarthritis Outcome Score (KOOS) evaluations were used for outcome study.

Results

All 166 patients were followed for more than 3 years (mean 3.7 years, 3.1–4.2) for the outcome study. All knees receiving arthroplasty showed medial plicae with MAP at the time of surgery. Only 2 of them suffered from PPOP: one was a neglected tibial plateau fracture with residual varus deformity after UKA, and the other was a late infection after TKA and received revision. The satisfactory rate was 98.8% in the UKA group, 99.1% in the TKA group, and 100% in the AMR group. The Knee Society Scores and all subscales of KOOS were statistically improved in all groups.

Conclusions

MAS is a cause of pain in patients who have received knee arthroplasties, and MAP should be eliminated to ensure a successful knee arthroplasty. PPOP after knee arthroplasty can be caused by MAS, which can be managed by AMR.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13018-020-02191-7.

Beyond Revision Surgery: Work-Up and Interventional Treatments for the Painful Total Knee Arthroplasty

Total knee arthroplasty is a common and successful treatment modality for knee arthritis that is refractory to conservative management strategies. Over 600,000 arthroplasties are performed per year in the United States, and this number is expected to increase in the coming years. Unfortunately, 8% to 34% of patients experience chronic pain after having a total knee arthroplasty. These patients should undergo an appropriate work-up by the orthopedic surgeon, but many times a surgical problem is not uncovered. In these situations, a thorough and specific plan for pain management should be sought. In this article, we outline the work-up of a painful total knee arthroplasty. Then we provide a thorough review of interventional pain management strategies and highlight the pertinent literature. Lastly, we hypothesize future developments in the field that may provide better outcomes for patients suffering from painful total knee arthroplasty.

Epidemiology of painful knee after total knee arthroplasty in a tertiary care center: Assessment by decision tree

BACKGROUND

Painful knee after arthroplasty concerns up to 21% of patients at six months. We aimed to evaluate: the application of a decision tree to explain painful knee after total knee arthroplasty (TKA), the rate of unexplained pain after complete algorithmic screening. The aim of the study was to evaluate the causes of painful TKA. Our hypothesis was that it is possible to find the cause of the pain in more than 90% of cases.

METHODS

A single-center retrospective study analyzed all 1130 consultations between 1 April 2017 and 31 July 2018. We included all patients consulting for unexplained chronic painful knee arthroplasty.

RESULTS

We included 112 knees in 105 patients as unexplained painful knee arthroplasty. Final diagnostic status was no diagnosis in seven (6.3%) cases; infection in five (4.5%); instability without real dislocation in three (2.7%); placement error in two (1.8%), due to rotational problems; loosening in 25 (22.3%): 24 (21.4%) tibial and two (1.8%) femoral; polyethylene wear in nine (8.0%); periarticular pain in 37 (33.9%): 20 with quadriceps deficiency, four with iliotibial tendinitis, four with pes bursitis, six with stiffness, and three with prepatellar bursitis); zero material problems; projected pain in 21 (18.8%); and complex regional pain syndrome in three (2.7%) cases, improved by gentle physiotherapy.

CONCLUSIONS

The present study was original and presents the problem in the context of everyday practice, from the clinician's point of view, with an easy-to-use decision tree that can be implemented to assess painful knee in consultation.

Biomechanical and Clinical Effect of Patient-Specific or Customized Knee Implants: A Review

(1) Background: Although knee arthroplasty or knee replacement is already an effective clinical treatment, it continues to undergo clinical and biomechanical improvements. For an increasing number of conditions, prosthesis based on an individual patient's anatomy is a promising treatment. The aims of this review were to evaluate the clinical and biomechanical efficacy of patient-specific knee prosthesis, explore its future direction, and summarize any published comparative studies. (2) Methods: We searched the PubMed, MEDLINE, Embase, and Scopus databases for articles published prior to February 1, 2020, with the keywords "customized knee prosthesis" and "patient-specific knee prosthesis". We excluded patient-specific instrument techniques. (3) Results: Fifty-seven articles met the inclusion criteria. In general, clinical improvement was greater with a patient-specific knee prosthesis than with a conventional knee prosthesis. In addition, patient-specific prosthesis showed improved biomechanical effect than conventional prosthesis. However, in one study, patient-specific unicompartmental knee arthroplasty showed a relatively high rate of aseptic loosening, particularly femoral component loosening, in the short- to medium-term follow-up. (4) Conclusions: A patient-specific prosthesis provides a more accurate resection and fit of components, yields significant postoperative improvements, and exhibits a high level of patient satisfaction over the short to medium term compared with a conventional prosthesis. However, the tibial insert design of the current patient-specific knee prosthesis does not follow the tibial plateau curvature.

Evaluation of the Painful Total Knee Arthroplasty

Total knee arthroplasty (TKA) has been associated with notable improvements in health-related quality of life of patients with end-stage knee arthritis. Although most patients experience substantial symptomatic relief after TKA, up to 19% of patients are unsatisfied with their outcome. With the dramatic, projected increase in the number of TKAs performed annually, it is crucial to appreciate the various modes of failure associated with this procedure. A comprehensive understanding of the symptomatology and thorough clinical examination aid in identifying the etiology of ongoing knee pain. Ancillary testing including conventional laboratory analyses, imaging studies, and diagnostic injections supplement a thorough history and physical examination. In addition, novel laboratory markers, RNA/DNA-based tests, and novel imaging modalities are emerging as beneficial tools in evaluating patients with a painful TKA. A well-structured, algorithmic approach in the management of these patients is essential in correctly diagnosing the patient and optimizing clinical outcomes.

Detection of aseptic loosening in total knee replacements: a systematic review and meta-analysis

OBJECTIVE

The aim of this study was to compare the diagnostic accuracy of nuclear imaging modalities in the detection of aseptic loosening of total knee arthroplasty (TKA).

MATERIALS AND METHODS

MEDLINE, EMBASE, and the Cochrane Database of Systematic Reviews were searched from database inception to December 2018 in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Included studies compared the results of a single imaging modality against an appropriate reference standard of prosthetic TKA loosening, with sufficient information to determine either sensitivity and/or specificity. The methodological quality of the studies was assessed using the QUADAS-2 tool.

RESULTS

The search strategy identified 572 abstracts. Of these, 12 studies comprising 401 patients across four modalities (bone scintigraphy, 18F-FDG-PET, SPECT/CT arthrogram, radionuclide arthrogram) met the inclusion criteria. All included studies used operative findings, a period of clinical or radiographic observation or both as a reference standard for aseptic loosening. Sixteen comparisons with the reference standards were extracted. All studies were at risk of bias across patient selection, the index test, reference standard, and flow and timing of patients. The most accurate test for diagnosis of aseptic loosening in TKA was SPECT/CT arthrography demonstrated by the summary receiver operating characteristic curve.

CONCLUSIONS

The best available evidence suggests the most accurate modality for the detection of aseptic loosening in TKA is SPECT/CT arthrography. However, the available evidence has a high risk of bias, and total number of patients studied for each modality is small so further studies are warranted.

[Predictors for persistent pain and dissatisfaction after total knee arthroplasty]

BACKGROUND

A substantial number of patients patients suffer from persistent pain or are unsatisfied after total knee arthroplasty (TKA).

OBJECTIVES

This work aims to present the frequency of postoperative persistent pain and/or dissatisfaction as well as known causes and predictors.

MATERIALS AND METHODS

The current literature is studied regarding the subject and is reviewed narratively.

RESULTS

Most postoperative problems did not arise from operation details, but from patient-related criteria, a lack of patient education and selection. The satisfaction correlates most strongly with the reduction of preoperative pain.

CONCLUSION

For a successful TKA, care should be taken that the following aspects are met preoperatively: clinically and radiologically advanced osteoarthritis, a patient age preferably older than 60 years, sufficient psychosocial resources to cope with postoperative stress, no opioid medication and realistic expectations after TKA. Postoperatively, patients with persistent pain or dissatisfaction should be checked for any prosthesis-related problems. If no prosthesis-related problems could be detected, the patients should be referred for interdisciplinary therapies.

New mobile-bearing TKA with unique ball and socket post-cam mechanism offers similar function and stability with better prosthesis fit and gap balancing compared to an established fixed-bearing prosthesis

PURPOSE

A mobile-bearing (MB) posterior-stabilized total knee arthroplasty (TKA) system with ball and socket post-cam mechanism has been developed with the aims of better prosthesis fit and enhanced stability. However, the data are limited to compare its clinical outcomes with an already established fixed-bearing (FB) implant design.

METHODS

This is a prospective randomized study comparing 260 patients in the MB group and 133 patients in FB group with a minimum 2 years of follow-up. Intraoperative variables, post-operative functional outcomes and incidence of adverse events were compared.

RESULTS

MB group showed better prosthesis fit as the incidence of over-hang of femoral component at junction (medial: 1% vs. 5% and lateral: 2% vs 4%, p < 0.001) and trochlea (medial: 2% vs 30%, p = 0.042 and lateral: 13% vs 21%, p = 0.015) was less than FB group. MB group also showed better gap balancing as the incidence of medio-lateral gap difference more than 2 mm was less in flexion (2.3% vs. 16%, p < 0.001) and extension (3.1% vs. 9.8%, p = 0.005). Post-operative functional outcomes and incidence of adverse events showed no difference between the two groups at 2 years.

CONCLUSIONS

New MB design offers similar functional outcomes and stability along with better intraoperative prosthesis fit and gap balancing compared to an established fixed-bearing design. Hence, this new MB design could be an alternative prosthesis of choice for posterior-stabilized TKA.

LEVEL OF EVIDENCE

I.

Effect of Post-Cam Design for Normal Knee Joint Kinematic, Ligament, and Quadriceps Force in Patient-Specific Posterior-Stabilized Total Knee Arthroplasty by Using Finite Element Analysis

The purpose of this study is to investigate post-cam design via finite element analysis to evaluate the most normal-like knee mechanics. We developed five different three-dimensional computational models of customized posterior-stabilized (PS) total knee arthroplasty (TKA) involving identical surfaces with the exception of the post-cam geometry. They include flat-and-flat, curve-and-curve (concave), curve-and-curve (concave and convex), helical, and asymmetrical post-cam designs. We compared the kinematics, collateral ligament force, and quadriceps force in the customized PS-TKA with five different post-cam designs and conventional PS-TKA to those of a normal knee under deep-knee-bend conditions. The results indicated that femoral rollback in curve-and-curve (concave) post-cam design exhibited the most normal-like knee kinematics, although the internal rotation was the closest to that of a normal knee in the helical post-cam design. The curve-and-curve (concave) post-cam design showed a femoral rollback of 4.4 mm less than the normal knee, and the helical post-cam design showed an internal rotation of 5.6° less than the normal knee. Lateral collateral ligament and quadriceps forces in curve-and-curve (concave) post-cam design, and medial collateral ligament forces in helical post-cam design were the closest to that of a normal knee. The curve-and-curve (concave) post-cam design showed 20% greater lateral collateral ligament force than normal knee, and helical post-cam design showed medial collateral ligament force 14% greater than normal knee. The results revealed the variation in each design that provided the most normal-like biomechanical effect. The present biomechanical data are expected to provide useful information to improve post-cam design to restore normal-like knee mechanics in customized PS-TKA.

ACR Appropriateness Criteria® Imaging After Total Knee Arthroplasty

Total knee arthroplasty (TKA) is the most commonly performed joint replacement procedure in the United States and annual demand for primary TKA is expected to grow by 673% by 2030. The first part provides an overview of imaging modalities (radiographs, CT, MRI, ultrasound, and various nuclear medicine studies) and discusses their usefulness in the imaging evaluation of TKA. The second part focuses on evidence-based imaging and imaging-guided intervention algorithms for the workup of TKA and its complications, including routine follow-up, component wear, periprosthetic infection, aseptic loosening, granulomas/osteolysis, conventional and rotational instability, periprosthetic fracture, patellar complications, and a variety of periprosthetic soft tissue abnormalities. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Total knee arthroplasty with unexplained pain: new insights from kinematics

INTRODUCTION

Up to 20% of total knee arthroplasty patients remain unsatisfied post-surgery, and a large proportion of them report anterior knee pain. This study aims to verify whether patients who experience anterior knee pain after total knee arthroplasty (TKA) will exhibit kinematic characteristics similar to those associated with patellofemoral syndrome, including in the frontal and transverse planes.

MATERIALS AND METHODS

Using four different assessment methods [radiological, patient-reported outcome, musculoskeletal assessment with functional performance testing, and a 3D kinematic assessment during gait], the clinical and 3D knee kinematic profiles of three groups were compared: a painful and an asymptomatic TKA group and a healthy control group. All three groups underwent a three-dimensional kinematic knee assessment while walking on a treadmill. Prosthetic component rotation was assessed through a CT scan measurement performed by one experienced radiologist. Flexion/extension, ab/adduction, and tibial internal rotation curves were compared, and significant differences were highlighted through ANCOVA analysis performed on SPSS.

RESULTS

A total of 62 knees were evaluated, 24 asymptomatic, 21 painful, and 17 control. A dynamic flexion contracture during gait was observed in the painful group, which was associated with a lack of flexibility of the thigh muscles. Moreover, painful TKA cases exhibited a valgus alignment (- 1.5°) during stance, which increases the Q angle and lateralizes the patella. Finally, CT scan evaluation of painful total knee arthroplasty patients revealed that their combined components rotation was in slight internal rotation (- 1.4°, SD 7.0°).

CONCLUSIONS

Painful TKA patients presented three well-known characteristics that tend to increase patellofemoral forces and that could be the cause of the unexplained pain: a stiff knee gait, a valgus alignment when walking, and combined TKA components slightly internally rotated.

Posterolateral overhang affects patient quality of life after total knee arthroplasty

PURPOSE

To investigate the appropriate mediolateral placement of symmetrical tibial components and the amount of overhang expected from the posterolateral of tibial components implanted to give ideal coverage and the subsequent incidence of residual knee pain and reduction in functional capacity.

METHOD

A retrospective evaluation was made of 146 consecutive total knee arthroplasties. The posterolateral overhang, rotational alignment and coverage of the tibial component were measured on a post-operative CT scan and the effect of posterolateral overhang on clinical outcomes was analysed 3 years after surgery.

RESULTS

Complaints of local pain in the posterolateral corner were determined in 76 (52.1%) patients. At the Posterolateral corner, overhang was determined in 111 (76%) patients, in the cortical border in 11 (7.6%) patients and underhang in 24 (16.4%) patients. In 71 (48.6%) patients, pain was determined together with oversize and in the evaluation of the overhang of the tibial component in the posterolateral region and the rotation status, there was determined to be overhang in 75 (96.2%) patients where the tibial component was placed in ideal rotation, in 25 (100%) where placement was in external rotation and in 11 (25.6%) where placement was in internal rotation. The mean KSS, KSS-F and WOMAC-P scores were 83.9 ± 6.3, 83.3 ± 7.8 and 4.6 ± 2.9, respectively, in those with posterolateral overhang of the tibial component .The mean KSS, KSS-F and WOMAC-P scores were 86.6 ± 8.4, 89.5 ± 7.8 and 2.8 ± 2.1, respectively, in those with no overhang and the difference was determined to be statistically significant. The amount of overhang was determined as mean 3.6 ± 2.0 mm in those with posterolateral pain and 0.02 ± 3.4 mm in those without pain and the difference was statistically significant.

CONCLUSIONS

This study demonstrated that overhang in the posterolateral region is surprisingly high and negatively affects the clinical results following TKA, thereby presenting a danger to the success of TKA. The risk of posterolateral oversizing can increase with placement of the tibial component in external rotation.

Tibial component coverage and rotational alignment accuracy after mobile-bearing total knee arthroplasty

BACKGROUND

Tibial component coverage (TCC) and tibial rotational angle (TRA) have been studied simultaneously in simulations, but not in clinical studies after total knee arthroplasty (TKA). The purposes of this study were (1) to evaluate TCC and rotational setting postoperatively in mobile-bearing TKA patients and (2) to compare the results with previously published simulation data.

METHODS

We prospectively examined 100 patients who underwent primary TKA using the LCS^® Total Knee System (LCS) posterior cruciate ligament-substituting prosthesis. Clinical outcomes, TCC (coverage area of the tibial component over the tibia), and TRA (relative to the femoral transepicondylar axis (TEA)) were assessed. Quantitative three-dimensional computed tomography was used to assess TCC and TRA. All values are expressed as median (25th percentile, 75th percentile) using minus (-) for internal and plus (+) for external rotation.

RESULTS

Hospital for Special Surgery scores improved from 46 (36, 50) preoperatively to 92 (90, 92) postoperatively. TRA showed a median divergence of - 2.0° (- 4.75°, + 2.74°). All knees were located within 10° of the TEA (range - 10.0° to + 9.7°). The median TCC of the knees was 82.7% (80.6, 84.7%), and there were no knees that hung over the tibial component in any direction.

CONCLUSIONS

The LCS prosthesis had good clinical outcomes, comparable TCC, and improved TRA as compared to previous reports, as all knees were located within 10° of the TEA. Simultaneous optimization of both TCC and TRA may contribute to the excellent long-term outcomes that have been observed with this system.

LEVEL OF EVIDENCE

Level II, Prognostic study.

The effects of proprioception exercise with and without visual feedback on the pain and balance in patients after total knee arthroplasty

[Purpose] The aim of this study was to determine the effects of proprioception exercise to decrease pain and increase the ability to balance by implementing visual feedback during early rehabilitation after total knee arthroplasty. [Subjects and Methods] In this study, 24 patients who receive a total knee arthroplasty were randomly and equally assigned to a visual feedback training group (VFT group) and a visual disuse group (Control group). They performed visual feedback training using the My Fitness Trainer (MFT, Austria) for 20 minutes, three times per week for eight weeks. The patients’ balance ability and pain was measured before and after the exercises. Pain was measured by the visual analogue scale (VAS). To assess balance ability, the anteroposterior and mediolateral directions on unstable ground was measured by using the MFT measurement system. [Results] The VFT group showed a significant decrease in VAS and an increase in balance ability within the group, as well as a significant increase in balance ability between groups when compared with the control group. [Conclusion] Visual feedback training during the rehabilitation of patients who received a total knee arthroplasty will be useful in reducing pain and improving balance.

Internal femoral component rotation adversely influences load transfer in total knee arthroplasty: a cadaveric navigated study using the Verasense device

PURPOSE AND HYPOTHESIS

Correct femoral component rotation at knee arthroplasty influences patellar tracking and may determine function at extremes of movement. Additionally, such malrotation may deleteriously influence flexion/extension gap geometry and soft tissue balancing kinematics. Little is known about the effect of subtle rotational change upon load transfer across the tibiofemoral articulation. Our null hypothesis was that femoral component rotation would not influence load across this joint in predictable manner.

METHODS

A cadaveric study was performed to examine load transfer using the orthosensor device, respecting laxity patterns in 6° of motion, to examine load across the medial and lateral compartments across a full arc of motion. Mixed-effect modelling allowed for quantification of the effect upon load with internal and external femoral component rotation in relation to a datum in a modern single-radius cruciate-retaining primary knee design.

RESULTS

No significant change in maximal laxity was found between different femoral rotational states. Internal rotation of the femoral component resulted in significant increase in medial compartment load transfer for knee flexion including and beyond 60°. External rotation of the femoral component within the limits studied did not influence tibiofemoral load transfer.

CONCLUSIONS

Internal rotation of the femoral component will adversely influence medial compartment load transfer and could lead to premature polyethylene wear on the medial side.

Interactive Surgery System with 3D Electromagnetic Motion Tracker for Training Surgeons in Skin Cutting Skills Needed in Total Knee Arthroplasty

Total knee arthroplasty (TKA) is an effective surgery for knees damaged by osteoarthritis, rheumatoid arthritis, and post-traumatic arthritis. This procedure requires an expert surgeon with a high level of skill and experience. Although a navigation system for improving precision and shortening operative time has been already studied, there has not yet been a study done on an instruction system for improving the skills of surgeons. The purpose of this study is to develop a training system that teaches the TKA surgery so that non-expert surgeons can use it to obtain skin-cutting skills. The proposed method includes a simulator for a model knee with a 3D electromagnetism motion tracker. Through experimentation, a method of evaluating incisions into the skin is established by tracing a line with a mock scalpel. The proposed method is applied to six non-experts. The results for the length experiments are 87.82±8.88 (Set 1: non-teaching), 92.66±5.77 (Set 2: teaching), and 92.14±6.17 (Set 3: non-teaching). The results for the position experiments are 70.64±15.11 (Set 1: non-teaching), 83.63±10.07 (Set 2: teaching), and 82.05±7.80 (Set 3: non-teaching). In conclusion, the proposed method succeeds in teaching the operator scalpel incision skills.

Mediolateral femoral component position in TKA significantly alters patella shift and femoral roll-back

PURPOSE

Increased retropatellar pressure and altered kinematics are associated with anterior knee pain and unsatisfied patients after total knee arthroplasty (TKA). Since malposition of the implant is believed to contribute to postoperative pain, we performed this in vitro study to evaluate the influence of mediolateral femoral component position on retropatellar pressure as well as tibio-femoral and patella kinematics.

METHODS

For the test, a fixed-bearing TKA was implanted in eight fresh frozen cadaver specimens. To determine the impact of mediolateral (ML) position, three variants of femoral components (3-mm medialization, neutral position and 3-mm lateralization) were produced using rapid prototyping replicas. In a knee rig, a loaded squat from 20° to 120° of flexion was applied. Retropatellar pressure distribution was measured with a pressure-sensitive film. Additionally, an ultrasonic-based three-dimensional motion analysis system was used to register patello- and tibio-femoral kinematics.

RESULTS

ML translation of the femoral component by 3 mm did not lead to a significant alteration in retropatellar peak pressure (medial 6.5 ± 2.5 MPa vs. lateral 6.0 ± 2.4 MPa). Following the ML translation of the femoral component, the patella was significantly shifted and tilted in the same directions. Varying the ML femoral component position also led to a significant alteration in femoral roll-back.

CONCLUSION

In day-by-day use, ML position should be chosen with care since there is a significant influence on patella shift and femoral roll-back. Retropatellar pressure is not significantly altered, so there is no clear evidence of an impact on anterior knee pain.

Effect of Femoral Component Flexion Implantation on the Mediolateral Bone-prosthetic Fit in Total Knee Arthroplasty

OBJECTIVE

Femoral component overhang in total knee arthroplasty (TKA) has been reported in previous studies. The purpose of this study was to evaluate the effect of femoral component flexion implantation on mediolateral bone-prosthetic fit in TKA.

METHODS

Virtual prosthesis implantations were performed on computed tomographic models of 10 Chinese knees with femoral prostheses of the Advance Medial-Pivot knee system (MicroPort Orthopedics, Arlington, TN, USA), with the femoral component positioned at 0°, 3°, or 6° of flexion in the sagittal plane. For each degree of flexion implantation, the differences between the knee and femoral component models on the lateral and medial sides at trochlea (zone 1), anterior-distal condyle (zone 2), posterior-distal condyle (zone 3), and posterior condyle (zone 4) were measured. Positive difference values indicate component overhang, and negative difference values indicate component underhang. The values of component overhang (underhang) in each zone were statistically analyzed across the 3° of flexion implantation.

RESULTS

With a greater degree of flexion implantation, overhang was reduced and even changed to underhang. With 0° of flexion implantation, an overhang exceeding 3 mm existed mainly on the medial side of zone 1 (5.81 mm) and the lateral side of zone 2 (3.39 mm). With 3° of flexion, overhang exceeding 3 mm was observed only on the medial side of zone 1 (3.10 mm), and underhang was observed only on the medial side of zone 4 (-0.32 mm). No overhang exceeding 3 mm was observed for 6° of flexion, while underhang was observed except on the lateral sides of zone 2 (1.32 mm) and zone 4 (1.10 mm) and on the medial side of zone 1 (1.54 mm). A significant difference in overhang values on the lateral and medial sides of zone 1 was observed between 0 and 6° of flexion (P < 0.05).

CONCLUSION

The present study demonstrated that femoral component flexion implantation by 3° can reduce excessive overhang, although 3.10 mm of overhang remained at the medial side of zone 1. Conversely, 6° of flexion implantation can avoid 3 mm of overhang for any zone, but increases the risk of underhang. Slight flexion implantation may be an effective alternative technique to prevent excessive component overhang, especially in the trochlea and anterior region of the distal condyle, in Chinese patients with standard TKA prostheses.

Causes of Aseptic Persistent Pain after Total Knee Arthroplasty

Background

Persistent pain after total knee arthroplasty (TKA) is dissatisfying to the patient and frustrating to the surgeon. The purpose of this study is to evaluate the aseptic causes and clinical course of intractable pain following TKA.

Methods

Of the total 2,534 cases of primary TKA reviewed, 178 cases were classified as having aseptic persistent pain that was not resolved within 1 year after surgery. Except for the cases with periprosthetic fracture (56 knees), 122 cases of aseptic painful TKA were divided into two groups: intra-articular group (83 knees) and extra-articular group (39 knees).

Results

In the intra-articular group, the main reasons for pain were aseptic loosening (n = 40), polyethylene wear (n = 16), instability (n = 10), recurrent hemarthrosis (n = 5), patellar maltracking (n = 4), tendon ruptures (n = 4), and stiffness (n = 2). In the extraarticular group, 10 knees (25.6%) were found to have nerve entrapment in the spine, 6 knees (15.4%) were found to have hip osteoarthritis or femoral head avascular necrosis. The reasons for persistent knee pain in the remaining 23 knees (59.0%) still remain elusive.

Conclusions

Persistent pain after TKA originated from pathology of extra-articular origin in a considerable number of cases in this study. Therefore, it is important to perform thorough preoperative evaluations to reduce pain resulting from extra-articular causes. Furthermore, meticulous surgical procedures and optimal alignment are required to reduce pain of intra-articular origin related to implant wear, instability, and patellar maltracking.

Persistent pain after knee replacement: do factors associated with pain vary with degree of patient dissatisfaction?

OBJECTIVE

Up to 20% of patients experience long-term pain and dissatisfaction following knee replacement. The aim of this study was to investigate factors associated with persistent pain following knee replacement and their implications for patient satisfaction.

DESIGN

A case-controlled analysis compared patients with established persistent pain with patients who were pain-free. 2:1 frequency matching for age, gender, time from surgery and prosthesis was performed. 1310 patients were approached and 100 patients with persistent pain and 200 matched pain-free controls were included. Variables assessed included mechanical, biological, psychosocial and generalised factors.

RESULTS

The study found that the degree of dissatisfaction experienced by the patient with persistent pain following knee replacement affected the factors associated with pain. In the most dissatisfied patients, pain was associated with instability in the coronal plane (OR 19.8, 95% CI 3.8-104.0), stiffness (OR 6.4, 95% CI 2.3-18.4) and negative social support (OR 3.3, 95% CI 1.1-10.0). In patients who were less dissatisfied, pain was associated with patellofemoral problems (OR 10.3, 95% CI 3.6-29.6), elevated BMI (OR 2.8, 95% CI 1.4-5.7) and reduced local pain thresholds (OR 4.4, 95% CI 2.0-9.6). Depression (OR 13.6, 95% CI 1.9-96.6) and presence of proximal tibial tenderness (OR 23.5 95% CI 7.8-70.7) were strongly associated with pain regardless of level of satisfaction.

CONCLUSIONS

Patients with persistent pain after knee replacement are dissatisfied. This study identifies factors associated with the worst pain outcomes, which lead to the greatest levels of dissatisfaction. Particular efforts with a holistic multidisciplinary approach should be focused towards these "red flag" factors in order to minimise persistent pain after knee replacement.

[The Berlin diagnostic algorithm for painful knee TKA]

BACKGROUND

Approximately 20% of patients are unsatisfied with their postoperative results after total knee arthroplasty (TKA). Main causes for revision surgery are periprosthetic infection, aseptic loosing, instability and malalignment. In rare cases secondary progression of osteoarthritis of the patella, periprosthetic fractures, extensor mechanism insufficiency, polyethylene wear and arthrofibrosis can cause the necessity for a reintervention. Identifying the reason for a painful knee arthroplasty can be very difficult, but is a prerequisite for a successful therapy.

AIM

The aim of this article is to provide an efficient analysis of the painful TKA by using a reproducible algorithm.

DISCUSSION

Basic building blocks are the medical history with the core issues of pain character and the time curve of pain concerning surgery. This is followed by the basic diagnostics, including clinical, radiological, and infectiological investigations. Unique failures like periprosthetic infection or aseptic loosening can thereby be diagnosed in the majority of cases. If the cause of pain is not clearly attributable using the basic diagnostics tool, further infectiological investigation or diagnostic imaging are necessary. If the findings are inconsistent, uncommon causes of symptoms, such as extra-articular pathologies, causalgia or arthrofibrosis, have to be considered. In cases of ongoing unexplained pain, a revision is not indicated. These patients should be re-evaluated after a period of time.

Tibial Tubercle in Valgus Osteoarthritic Knees Is More Laterally Positioned Than in Varus Knees

BACKGROUND

The tibial tubercle (TT) is the most reliable landmark of the tibial component rotation in total knee arthroplasty. However, there is no report comparing the position of the TT between valgus and varus osteoarthritic knees.

METHODS

Using preoperative computed tomography, we measured the TT-posterior cruciate ligament (PCL) distance representing the degree of lateralization of the TT and the angle between Akagi's anteroposterior (AP) axis and the dorsal condylar line (DCL) of the tibia in 36 valgus and 40 varus osteoarthritic knees and compared them.

RESULTS

The mean TT-PCL distances in valgus and varus knees were 26.1 (18.2-36.8) and 17.2 mm (10.3-22.6), respectively, with a significant difference (P < .001). Twenty-four of 36 valgus knees (67%) had abnormal TT-PCL (>24 mm). The mean AP-DCL angles in valgus and varus knees were 103° (95.8°-114.8°) and 93.2° (85.3°-99.6°), respectively, with a significant difference (P < .001).

CONCLUSION

The TT in valgus knees was significantly more laterally positioned than in varus knees. Also, Akagi's AP axis in valgus knees was significantly more externally rotated relative to the DCL of the tibia than in varus knees. Attention is necessary to correct rotational alignment without posterolateral overhang of the tibial component during total knee arthroplasty, particularly for valgus knees.

Anthropometric measurements of tibial plateau and correlation with the current tibial implants

PURPOSE

The aim of the study was to make an anthropometric analysis at the resected surfaces of the proximal tibia in the Turkish population and to compare the data with the dimensions of tibial components in current use. We hypothesized that tibial components currently available on the market do not fulfil the requirements of this population and a new tibial component design may be required, especially for female patients with small stature.

METHODS

Anthropometric data from the proximal tibia of 226 knees in 226 Turkish subjects were measured using magnetic resonance imaging. We measured the mediolateral, middle anteroposterior, medial and lateral anteroposterior dimensions and the aspect ratio of the resected proximal tibial surface. All morphological data were compared with the dimensions of five contemporary tibial implants, including asymmetric and symmetric design types.

RESULTS

The dimensions of the tibial plateau of Turkish knees demonstrated significant differences according to gender (P < 0.05). Among the different tibial implants reviewed, neither asymmetric nor symmetric designs exhibited a perfect conformity to proximal tibial morphology in size and shape. The vast majority of tibial implants involved in this study tend to overhang anteroposteriorly, and a statistically significant number of women (21 %, P < 0.05) had tibial anteroposterior diameters smaller than the smallest available tibial component.

CONCLUSION

Tibial components designed according to anthropometric measurements of Western populations do not perfectly meet the requirements of Turkish population. These data could provide the basis for designing the optimal and smaller tibial component for this population, especially for women, is required for best fit.

LEVEL OF EVIDENCE

II.

Oversizing the tibial component in TKAs: incidence, consequences and risk factors

PURPOSE

The incidence of anteroposterior overhang of the tibial component after TKA and its effect on clinical outcome were investigated, and the morphometric characteristics of the knees in which tibial baseplates were oversized were identified.

METHOD

One hundred and fourteen consecutive TKAs were retrospectively assessed. The dimensions of the tibia were measured on a pre-operative CT scan and were compared with those of the implanted tibial component. We analysed the effect of anteroposterior and mediolateral size variations on clinical outcomes 1 year after surgery.

RESULTS

An anteroposterior overhang was observed in 87 % of cases on the lateral plateau, in 88 % on the central plateau and in 25 % on the medial tibial plateau. The mean post-pre-operative size differences were 3.2 ± 2.7, 2.8 ± 2.7 and -1.6 ± 2.3 mm, respectively. (Positive value means oversizing). A mediolateral overhang of the tibial component was found in 61 % of the patients. Oversizing was significantly greater and more frequent in females. Patients oversized in the anteroposterior dimension had lower post-operative pain scores. Patients with mediolateral oversizing had decreased flexion 1 year after surgery. Anteroposterior oversizing was observed more frequently in patients with asymmetric tibial plateaus, while mediolateral oversizing was observed more frequently in patients with small tibias.

CONCLUSIONS

This study demonstrates that the incidence of oversized tibial plateau components is surprisingly high and that functional outcomes are lower in the case of mediolateral or anteroposterior oversizing. The risk of oversizing could be predicted as it occurs predominantly in patients with asymmetric proximal tibia and/or small tibia.

LEVEL OF EVIDENCE

IV.

A lateralized anterior flange improves femoral component bone coverage in current total knee prostheses

BACKGROUND

Poor femoral implant fit to resected bone surfaces recently has been the motivation for several new total knee arthroplasty implant designs. Implant overhang risks adverse soft-tissue interaction while uncovered cut bone surfaces (underhang) risks increased postoperative bleeding or development of heterotopic bone.

METHODS

Femoral implant fit was studied systematically, and without the influence of surgical variation, by virtually implanting standard and narrow width femoral components (Bi-Surface 5) using preoperative computed tomography data for 150 varus osteoarthritic knees in Japanese patients. Overhang and underhang rates and bone widths were determined by gender.

RESULTS

Narrow femoral components helped avoid or minimize overhang in most female and some male knees. Although anterior width in the narrow components closely matched female bone width, the femoral component was necessarily displaced laterally to avoid overhang in the anteromedial portion. Consequently, there was significant medial underhang in the distal and posterior zones.

CONCLUSIONS

Ideally, the anterior femoral flange should be shifted 2 to 2.5mm laterally relative to the distal and posterior aspects to provide optimal femoral bone coverage in this prosthesis. The current study also confirmed that this modification can be generalized to the other two currently available "narrow type" prostheses. This geometric modification might allow surgeons to select a femoral component with slightly wider mediolateral dimensions in the distal and posterior aspects to minimize underhang, while eliminating anterior overhang.

LEVEL OF EVIDENCE

III.

Role of magnetic resonance imaging in the diagnosis of the painful unicompartmental knee arthroplasty

BACKGROUND

Unicompartmental knee arthroplasty (UKA) is a well established method for the treatment of single compartment arthritis; however, a subset of patients still present with continued pain after their procedure in the setting of a normal radiographic examination. This study investigates the effectiveness of magnetic resonance imaging (MRI) in guiding the diagnosis of the painful unicompartmental knee arthroplasty.

METHODS

An IRB-approved retrospective review identified 300 consecutive UKAs performed over a three years period with 28 cases of symptomatic UKA (nine percent) with normal radiographic images.

RESULTS

MRI examination was instrumental in finding a diagnosis that went undetected on radiographs. Based on MRI findings, 10 (36%) patients underwent surgery whilst 18 (64%) were treated conservatively.

CONCLUSION

This study supports the use of MRI as a valuable imaging modality for managing symptomatic unicompartmental knee arthroplasty.

LEVEL OF EVIDENCE

Case series.

Anthropometric difference of the knee on MRI according to gender and age groups

The purpose of this study was to analyze the anthropometric data from MRI images that were obtained from the non-arthritic knees in Asian adults, and to identify the existence of morphologic differences between age groups. This cross-sectional study included knee MR images of 535 patients (273 males, 262 females) taken for the evaluation of soft-tissue injuries, excluding cases with cartilage defect and malalignment. The age, gender, height, and BMI were also assessed. The patients were grouped into three different 20-year age groups (20-39, 40-59, and 60-79). The MRI analysis was performed on the anthropometric parameters of distal femur and posterior tibial slope. Age-related differences were found in femoral width, distance from the distal and posterior cartilage surface to the medial/lateral epicondyle, medial posterior condylar offset (PCO), and posterior condylar angle (PCA) (all P < 0.001), but not in lateral PCO, and medial/lateral tibial slopes. In the analysis of covariance analyses, significant interaction between gender and age groups was found in most parameters, but not in PCA, distance from the posterior cartilage surface to the medial epicondyle, or medial tibial slope. We found anthropometric differences among age groups exist in most of distal femoral parameters, but not in posterior tibial slope. The results of this study can be used by manufacturers to modify prostheses to be suitable for the future Asian elderly population.

Effect of rotational alignment on outcome of total knee arthroplasty

BACKGROUND AND PURPOSE

Poor outcomes have been linked to errors in rotational alignment of total knee arthroplasty components. The aims of this study were to determine the correlation between rotational alignment and outcome, to review the success of revision for malrotated total knee arthroplasty, and to determine whether evidence-based guidelines for malrotated total knee arthroplasty can be proposed.

PATIENTS AND METHODS

We conducted a systematic review including all studies reporting on both rotational alignment and functional outcome. Comparable studies were used in a correlation analysis and results of revision were analyzed separately.

RESULTS

846 studies were identified, 25 of which met the inclusion criteria. From this selection, 11 studies could be included in the correlation analysis. A medium positive correlation (ρ = 0.44, 95% CI: 0.27-0.59) and a large positive correlation (ρ = 0.68, 95% CI: 0.64-0.73) were found between external rotation of the tibial component and the femoral component, respectively, and the Knee Society score. Revision for malrotation gave positive results in all 6 studies in this field.

INTERPRETATION

Medium and large positive correlations were found between tibial and femoral component rotational alignment on the one hand and better functional outcome on the other. Revision of malrotated total knee arthroplasty may be successful. However, a clear cutoff point for revision for malrotated total knee arthroplasty components could not be identified.

Persistent Symptomatic Knee after Total Knee Replacement. Is Knee Arthroscopy Helpful?

Persistent symptoms following total knee replacement (TKR) could be diagnostically challenging. We present three cases of knee arthroscopy following TKR to illustrate the effectiveness of arthroscopy for the diagnosis and treatment of persistent symptomatic knee. It is concluded that arthroscopy after TKR is a relatively safe and effective procedure for well selected cases with persistent symptoms following TKR.

Case report: Total knee arthroplasty polyethylene liner disengagement identified by arthrography

We report a case of total knee arthroplasty polyethylene liner disengagement identified by plain film arthrography and CT arthrography.