Imaging of total knee arthroplasty

Painful total knee arthroplasty (TKA) represents a diagnostic challenge for the clinician and radiologist, as there is a wide variety of potential etiologies, with a broad range of clinical presentations, and the abnormalities on imaging studies are often subtle, absent, or nonspecific. Imaging findings of normal TKA are reviewed, in addition to a variety of complications such as loosening, infection, instability, osteolysis, heterotopic ossification, extensor mechanism disruption, and fracture. Although imaging evaluation of painful TKA is usually limited to conventional radiographs and nuclear imaging, examples of the utility of computed tomography are also illustrated, and suggested imaging strategies and algorithms are discussed.     

Minimally invasive Unicondylar Knee Arthroplasty in a patellectomized patient

Patellectomized patients may have less satisfactory clinical outcomes following total knee arthroplasty due to a decreased extensor mechanism efficiency and potential instability. The literature only reports 3 case series of patients who had a previous patellectomy undergoing a Unicondylar Knee Arthroplasty (UKA) with mixed results. A Minimally Invasive fixed-bearing UKA was performed in a patellectomized patient with excellent postoperative knee stability and clinical outcomes after 5 years. MIS UKA may be a viable option for patellectomized patients with isolated medial compartment osteoarthritis and no preoperative extensor deficiency or instability. Level of evidence IV.     

Performance-based physical function correlates with walking speed and distance at 3 months post unilateral total knee arthroplasty

BackgroundAfter total knee arthroplasty (TKA), walking speed and distance are main concerns of patients.Research questionWhich physical functions affect walking speed and distance after TKA?MethodsCross-sectional data from 149 patients who underwent unilateral primary TKA and completed performance-based physical function tests. Instrumental gait evaluation for spatiotemporal parameters, isometric knee extensor and flexor strength of both knees, 6-minute walk test (6MWT), timed up-and-go (TUG) test, timed stair climbing test (SCT), and knee flexion and extension range of motion (ROM) of surgical knee were examined. Western Ontario McMaster Universities Osteoarthritis Index (WOMAC) and EuroQol five dimensions (EQ-5D) questionnaires were also performed.ResultsUnivariate analyses revealed that post-operative walking speed showed significant positive correlations with cadence, stride length, propulsion index of surgical and non-surgical knee, peak torque (PT) of the extensor of surgical and non-surgical knee and flexor of surgical and non-surgical knee, 6MWT, EQ-5D, and significant negative correlations with gait cycle duration, TUG, SCT-ascent and descent, and WOMAC-pain scores. Post-operative walking distance had significant positive correlations with walking speed, cadence, stride length, swing phase duration, propulsion index of surgical and non-surgical knee, PT of the extensor of surgical and non-surgical knee, EQ-5D, and significant negative correlation with gait cycle duration, double support duration, TUG, SCT-ascent and descent. In the multivariate linear regression analyses, TUG, cadence, stride length and propulsion index of non-surgical knee were factor correlated with post-operative walking speed. The SCT-ascent and descent, TUG and propulsion index of surgical knee were factor correlated with post-operative walking distance.SignificancePhysical performance factors correlated with walking speed and distance at 3 months after surgery. Based on these observations, rehabilitation of bilateral muscle strength and functional mobility would be important for functional recovery after unilateral TKA.     

Effect of surgical closing in total knee arthroplasty at flexion or extension: a prospective,randomized study

Purpose

The aim of this study was to evaluate the effect of knee position during wound closure (flexed vs. extended) in total knee arthroplasty on knee strength and function, as determined by knee society scores and isokinetic testing of extensor and flexor muscle groups.

Methods

In a prospective, randomized, double-blind trial, 29 patients were divided in two groups: for Group 1 patients, surgical closing was performed with the knee extended, and for Group 2 patients, the knee flexed at 90°. All the patients were treated with the same anaesthesia method, surgical team, surgical technique, prosthesis type, and rehabilitation process. American Knee Society Score values and knee flexion degrees were recorded. Isokinetic muscle strength measurements of both knees in flexion and extension were taken using 60° and 180°/s angular velocity. The peak torque and total work values, isokinetic muscle strength differences, and total work difference values were calculated for surgically repaired and healthy knees.

Results

No significant difference in the mean American Knee Society Score values and knee flexion degrees was observed between the two groups. However, using isokinetic evaluation, a significant difference was found in the isokinetic muscle strength differences and total work difference of the flexor muscle between the two groups when patients were tested at 180°/s. Less loss of strength was detected in the isokinetic muscle strength differences of the flexor muscle in Group 2 (?4.2 %) than in Group 1 (?23.1 %).

Conclusion

For patients undergoing total knee arthroplasty, post-operative flexor muscle strength is improved if the knee is flexed during wound closure.

Level of evidence

II.     

Is bicompartmental knee arthroplasty more favourable to knee muscle strength and physical performance compared to total knee arthroplasty?

Purpose

Bicompartmental knee arthroplasty features bone and ligament sparing as unicompartmental knee arthroplasty and is presumably better in the recovery of muscle strength and function compared to total knee arthroplasty (TKA) though not previously reported in the literature. The aim of the study was to compare isokinetic knee muscle strength and physical performance in patients who underwent either bicompartmental knee arthroplasty or TKA.

Methods

Each of 24 patients (31 knees) was prospectively examined preoperatively, at 6 and 12 months after each surgery. Isokinetic knee extensor and flexor strength as well as position sense were measured using the Biodex system. Timed up and go test, stair climbing test, and the 6-min walk test were used to assess physical performance. The results of each group were also compared with those from the corresponding healthy control, respectively.

Results

Demography showed significant difference in the mean age between bicompartment (54.8 ± 5.6 years) and TKA groups (65.7 ± 6.7 years). Comparing between the two groups, knee extensor and flexor torque, hamstring/Quadriceps ratio, position sense, and physical performance were not significantly different preoperatively, at 6 and 12 months after surgery. In intra-group analysis, muscle strength and position sense at each time point were not different in both groups. In physical performance, both groups resulted in improvement in the 6-min walk test, and only TKA group showed enhancement in stair climbing test.

Conclusions

Although theoretically plausible, bicompartmental knee arthroplasty was not superior in knee muscle strength and physical performance at 1 year compared with total knee arthroplasty.

Level of evidence

II.     

A “biologic technique” for the treatment of a disruption of the extensor mechanism after revision total knee arthroplasty: a case report

A modified technique for the reconstruction of the extensor mechanism after revision total knee arthroplasty, is described. A medial gastrocnemius flap, in combination with in situ use of semitendinosus tendon autograft through intraosseous patellar tunnel, was used. The patient was followed for 2 years after the final reconstruction. After the procedure, the patient who previously had been dependent on a walker was able to walk without a cane. The above mentioned technique provided good functional outcome in our case.     

Imaging patellar complications after knee arthroplasty

The purpose of this study is to describe complications affecting the patella in patients with total or partial knee arthroplasty. We respectively analysed plain-film radiographs, as well as ultrasound images when acquired, in a consecutive series of 1272 patients. The mean interval from knee replacement to patellar complications was 5 years and 7 months (range, 5 months to 14 years). The complications described include fracture, instability, dislocation or luxation, necrosis of the patella, infection of the patella, erosion of the patella, patellar impingement on the prosthesis and patellar or quadricipital tendon tear. We discuss the pathological imaging findings in the patella and their differential diagnosis after knee arthroplasty. Patellar complications after knee arthroplasty are uncommon but often potentially serious.     

Intra-articular knee injuries in patients with knee extensor mechanism ruptures

The knee extensor mechanism is composed of the quadriceps tendon, patella and patellar tendon. Rupture of either the quadriceps tendon or patella tendon is a rare but significant injury. The purpose of our study is to determine if there are any associated injuries with these ruptures necessitating the need for further evaluation such as MRI or arthroscopy. We retrospectively reviewed all patients with ruptures of the knee extensor mechanism who required operative repair at our institution over the last 10 years. We reviewed the chart for any documented associated injury. The type and incidence of associated injuries were recorded. We further divided these patients into two groups: low energy indirect mechanism or high-energy direct impact mechanism. Sixty-four patients met our requirements for inclusion in this study. Thirty-three patients with patellar tendon ruptures and thirty-one patients with quadriceps tendon ruptures were included. Ten out of 33 (30%) patients with a patellar tendon rupture had an associated injury. Four out of 25 (16%) patients with patellar tendon ruptures in the low energy mechanism category had an associated injury. Six out of 8 (75%) patients with a high-energy direct impact patellar tendon rupture had an associated injury. Three out of 31 (10%) patients with quadriceps tendon rupture had an associated injury. The most common associated injuries in the patellar tendon rupture patients were anterior cruciate ligament tears (18%) and medial meniscus tears (18%). We found almost one-third of all patients with a patellar tendon rupture had an associated intra-articular knee injury. We found 10% of patients with quadriceps tendon rupture had an associated intra-articular knee injury. We also found an even higher incidence of associated injuries in patients with high-energy direct impact mechanism patellar tendon ruptures (75%). The most common associated injuries in patients with patellar tendon ruptures were tears of the anterior cruciate ligament (18%) and medial meniscus (18%). We recommend that consideration be given in obtaining a MRI or diagnostic arthroscopy in patients with patellar tendon ruptures especially those with high-energy direct impact mechanism. To our knowledge this has not previously been documented in the literature.     

The dorsal pedis artery as a new distal landmark for extramedullary tibial alignment in total knee arthroplasty

Purpose

It is better to use multiple anatomical landmarks to reduce errors in component alignment in total knee arthroplasty. Therefore, it is worthwhile to find a new landmark that can be used as an addition to conventional ones. Herein, we assessed the dorsal pedis artery as a new distal landmark for extramedullary tibial alignment.

Methods

Fifty-two ankles in patients undergoing total knee arthroplasty and 10 ankles in normal controls were included. Color Doppler ultrasonography was used to locate the dorsal pedis artery at the level of the ankle joint. Conventional landmarks, including the tibialis anterior tendon, the extensor hallucis longus tendon, the extensor digitorum longus tendon, and the malleolar centre, were also located on ultrasound images. The distances between the ankle centre and each landmark were measured and compared.

Results

The dorsal pedis artery was absent in 2 patients and impalpable but visible with ultrasonography in other 2 patients. The dorsal pedis artery was located anatomically closest to the ankle centre in patients (0.4 ± 3.4 mm lateral). Statistical analysis showed that the dorsal pedis artery, the extensor hallucis longus tendon, and the malleolar centre were located significantly closer to the ankle centre comparing with the extensor digitorum longus tendon and the tibialis anterior tendon in both patients and controls (p < 0.001).

Conclusions

As long as the dorsal pedis artery exists, it can be used as an addition to the conventional landmarks in total knee arthroplasty. Using this new landmark will help reduce errors in coronal plane alignment of tibial component.

Level of evidence

II.     

Changes in patellar alignment after total knee arthroplasty

Although the results of total knee arthroplasty continue to improve, problems related to the patellofemoral joint remain significant. This study examined the factors affecting patellar alignment after total knee arthroplasty and subsequent changes in 56 knees during a postoperative period of 5.3 years. None of the knees examined displayed any clinical complications of the patellofemoral joint; no revision surgeries were necessary, with acceptable patellar alignment on average. The patellar resection angle had a strong influence on patellar alignment. Thinning of the patellar remnant on the medial side can increase postoperative lateral tilt, which leads to a need for lateral retinacular release. Although the changes in patellar alignment were minimal, the tendency that postoperative varus alignment resulted in patellar lateral tilt was observed. As postoperative femorotibial misalignment can lead to patellofemoral problems after total knee arthroplasty, surgeons need to pay scrupulous attention to femorotibial alignment and proper patellar preparation to decrease patellofemoral complications.     

TKA using the subvastus approach and lateral retinacular release in patients with permanent post-traumatic patellar dislocation: a report of two cases

Permanent post-traumatic patellar dislocation is a rare condition, and total knee arthroplasty (TKA) can be performed for osteoarthritic knees with this condition. There have been only a few reports about using the standard medial parapatellar approach and extensive lateral release or extensor mechanism realignment for patients with permanent post-traumatic patellar dislocation. We performed two TKAs with using a subvastus approach and lateral release for osteoarthritic knees with permanent post-traumatic patellar dislocation. The patients were well satisfied with their results. The patellae tracked very well in the femoral trochlear groove throughout the full range of motion after the operations. Bone scans were done 1 year postoperatively on both patients, and the scans showed normal vascularity for the patella.     

Quality of life and clinical outcome in salvage revision total knee replacement: hinged vs. total condylar design

This study compared the overall outcome after salvage revision total knee arthroplasty using hinged and nonhinged designs. We followed 26 total knee arthroplasties for an average of 20.4 months. The average age was 68.5 years. All patients had a salvage situation secondary to excessive bone loss, enlarged flexion gap, collateral ligament insufficiency, or extensor mechanism insufficiency. Ten patients received a hinged implant after an average of 2.8 prior total knee replacements. Sixteen patients received nonhinged constrained implants after an average of 3.4 prior total knee replacements. The outcome was evaluated using the Hospital for Special Surgery Score (HSS), the Knee Society Score (KSS), the Visual Analogue Scale for pain (VAS), the Tegner Activity Score, the Patella Score, and the Short Form-36 Health Survey (SF-36). There was a statistically significant difference in flexion range of motion between hinged and nonhinged designs (96.5° vs. 107.5°) but not in HSS, KSS, VAS, Tegner Activity Score, or Patella Score. Patients with hinged and nonhinged prostheses had significantly lower scores than an age-matched normal population in physical functioning, role limitations, and bodily pain on the SF-36 survey. However, patients with a hinged implant had no statistically significant difference compared to controls in the mental component summary. In salvage total knee arthroplasty the implant design does not significantly affect the overall functional outcome. However, patients with a hinged implant had significant better scores in the mental components of the SF36 quality-of-life assessment.     

Accuracy of side-cutting implantation instruments for total knee arthroplasty

A new generation of implantation instruments were developed for quadriceps sparing surgical approaches during total knee arthroplasty (TKA). There is little information on the accuracy of the bone cuts performed with the side-cutting technique. A total of 100 patients were randomized to undergo computer-assisted TKA or non-navigated TKA using a mini-subvastus surgical approach and side-cutting implant instrumentation. The radiographic parameters, clinical outcomes and knee scores were evaluated 3 months postoperative. The mechanical axis of the limb was within 3° varus/valgus in 76% of the patients who had navigated procedures versus 66% of patients who had conventional surgery. The tibial slope showed a rate of inaccuracy of 3° or less for 78% of the patients in the navigated total knee arthroplasty group versus 66% of the patients in the conventional group. Clinical outcomes and knee scores were similar in both groups. The navigation technique could not compensate for shortcomings of the implantation instruments.     

Patellar fractures after total knee replacement

OBJECTIVE: The objective of our study was to describe the patterns of patellar fracture after total knee replacement and assess their clinical significance. MATERIALS AND METHODS: A retrospective review of patellar fractures after total knee replacement was performed. Seventeen cases were identified over a 10-year period. Radiographs, radiology reports, medical records, and operative notes were reviewed and analyzed. The clinical analysis included the time to fracture, the patient's symptoms and signs, whether the extensor mechanism was disrupted, and the treatment administered for the fracture. The radiographic analysis included fracture pattern, displacement, patellar position, presence of patellar osteonecrosis, and presence of soft-tissue abnormality. RESULTS: The incidence of patellar fractures after total knee replacement was 1.14%. The mean time from total knee replacement to patellar fracture was 17.5 months. Nine fractures were asymptomatic and identified on routine follow-up radiographs. The patterns of fracture were diverse: Transverse (n = 6), comminuted (n = 2), vertical (n = 5), and avulsion (n =4) fractures were seen. Thirteen fractures were displaced. Patellar osteonecrosis was suspected in four fractures, and three fractures were associated with disruption of the quadriceps tendons. Thirteen fractures were treated nonoperatively, and four were treated surgically. CONCLUSION: Patellar fractures are an uncommon, but important, complication after total knee replacement. Radiologists should be familiar with the imaging features of these fractures and their clinical significance.     

Catastrophic thinking about pain as a predictor of length of hospital stay after total knee arthroplasty: a prospective study

This study prospectively investigates whether catastrophizing thinking is associated with length of hospital stay after total knee arthroplasty. Forty-three patients who underwent primary total knee arthroplasty were included in this study. Prior to their operation all patients were asked to complete the pain catastrophizing scale, and a Western Ontario McMaster Universities Osteoarthritis index. A multiple regression analysis identified pain catastrophizing thinking and age as predictors of hospital stay after total knee arthroplasty. Patients with a higher degree of pain catastrophizing prior to the total knee arthroplasty and those with a higher age have a significantly greater risk for a longer hospital stay. Therefore, the results of this study indicate that the pre-operative level of pain catastrophizing in patients determine, in combination with other variables, the length and inter-individual variation in hospital stay after total knee arthroplasty. Reducing catastrophizing thinking about pain through cognitive-behavioral techniques is likely to reduce levels of fear after total knee arthroplasty. As a result, pain and function immediately post-operative might improve, leading to a decrease in length of hospital stay. Although during the last decades the duration of hospital stay is significantly reduced, this study shows that this can be improved when taking into account the contribution of psychological factors such as pain catastrophizing.     

双下肢全长负重位与非负重位摄影在全膝关节置换术前评估的研究

目的分析负重位与非负重位下肢力线的差异,探讨双下肢全长摄影在全膝关节置换术中的应用价值。方法回顾性分析我院41例接受全膝关节置换术的患者资料,术前所有患者均行双下肢全长负重位与非负重位x线片,测量负重和非负重位下肢力线（膝内翻角）、股骨力线、关节间隙夹角及胫骨平台内侧夹角。结果．负重位膝内翻角、股骨力线、关节间隙夹角均大于非负重位,差异有统计学意义（P〈O．01）;负重、非负重位膝内翻角及其差值均呈正相关（r=0．569～0．992,P〈O．01）;负重、非负重位膝内翻角及其差值与关节间隙夹角呈正相关（r=-0．567～0．632,P〈0．01）;负重、非负重位膝内翻角和关节间隙夹角及其各自差值分别与胫骨平台内侧夹角均呈负相关（r=-0．751～-0．491,P〈O．01）;负重与非负重位股骨力线呈正相关（r=0．989,P〈0．01）,但与其差值不相关（r=0．199,P〉0．01）;负重、非负重位股骨力线及其差值与胫骨平台内侧夹角不相关（r=-0．123～O．104,P〉0．01）。结论全膝关节置换术前评估,负重位比非负重位片更准确,具有重要的临床价值;非负重位对了解韧带松弛程度,平衡周围软组织有意义,建议作为参考。     

MR imaging of the postoperative knee

Advances in orthopedic and arthroscopic surgical procedures of the knee such as, knee replacement, ligamentous reconstruction as well as articular cartilage and meniscus repair techniques have resulted in a significant increase in the number of patients undergoing knee arthroscopy or open surgery. As a consequence postoperative MR imaging examinations increase. Comprehensive knowledge of the normal postoperative MR imaging appearances and abnormal findings in the knee associated with failure or complications of common orthopedic and arthroscopic surgical procedures currently undertaken is crucial. This article reviews the various normal and pathological postoperative MR imaging findings following anterior and posterior cruciate ligament, medial collateral ligament and posterolateral corner reconstruction, meniscus and articular cartilage surgery as well as total knee arthroplasty with emphasis on those surgical procedures which general radiologists will likely be faced in their daily clinical routine.     

Clinical and radiographic outcomes of minimally invasive total knee arthroplasty through a lateral approach

Purpose  

With increasing confidence and surgical experience, minimally invasive surgery (MIS) in total knee arthroplasty (TKA) is now being applied to more complicated cases. The present study assessed the feasibility of MIS-TKA using a lateral approach for valgus knees.     

Imaging Evaluation of Complications of Hip Arthroplasty: Review of Current Concepts and Imaging Findings

Total hip arthroplasty has evolved along with improvements in component materials and design. The radiologist must accurately diagnose associated complications with imaging methods and stay informed about newer complications associated with innovations in surgical technique, prosthetic design, and novel materials. This pictorial essay presents clinical and imaging correlation of modern hip arthroplasty complications, with an emphasis on the most common complications of instability, aseptic loosening, and infection as well as those complications associated with contemporary metal-on-metal arthroplasty.