Imaging findings in knee replacement. How can I help the surgeon?

Transcription

1 Imaging findings in knee replacement. How can I help the surgeon? Award: Certificate of Merit Poster No.: C-0561 Congress: ECR 2016 Type: Educational Exhibit Authors: J. Azpeitia Arman, R. M. Lorente Ramos, A. D. Murillo Vizuete, B. Limousin Aranzabal, E. Barcina García, N. Santamaria; Madrid/ES Keywords: Prostheses, Complications, CT, Conventional radiography, Extremities DOI: /ecr2016/C-0561 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 56

2 Learning objectives To review the different types of knee replacement. To illustrate imaging findings in different techniques (plain radiograph, CT, MR, US, scintigraphy) in the evaluation of prostheses, emphasizing useful data for the orthopedic surgeon. To describe normal postoperative imaging findings and signs of complications. Background Knee replacement has become a frequent surgery. Knowledge of key concepts perceived as important variables by the surgeon is essential to correlate images with clinical considerations and functional outcomes. It is important for the radiologist to be aware of signs indicating complications in order to avoid delays in patient treatment. We review current concepts in radiological imaging of knee replacement. The surgeon clinical needs are analysed trying to clarify the most important imaging findings and parameters which should be stated in our report. Findings and procedure details 1. A review of knee replacements Components. Knee replacements consist of different components (Fig. 1 on page 30 ): Metal condylar component cemented or ingrowth. Page 2 of 56

3 Metal tibial component usually cemented. Polyethylene attached to the metal tibial plateau either #xed, or allowing some motion. Thickness depends on the tension needed to balance the knee ligaments but should, be at least 8mm. Patellar component when present is cemented polyethylene usually without a metal component. Fig. 1: Knee replacement. Components References: Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES 1.2. Types. Different types of knee replacements may appear: unicompartimental knee (UKR) and total knee replacement (TKR). -Single compartment (unicompartmental). Fig. 2 on page 31 Only the condylar and tibial surfaces of one compartment are replaced, either lateral or medial, but most frequently on medial side. Rarely the replacement may be patellofemoral. Page 3 of 56

4 Fig. 2: Unicompartmental knee replacement: A.-AP radiograph shows a normal unicompartmental knee replacement in a patient with no significant arthritis in the remaining two compartments. B.Lateral radiograph shows the femoral arthroplasty on the mid and posterior weight-bearing portions of the condyle. References: Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES Requirements previous to surgery are an intact anterior cruciate ligament and correctable knee alignment. Contraindication is an inflammatory underlying process. -Total knee arthroplasty (TKA). Fig. 3 on page 32. Most arthroplasties are total replacements, in which both condylar and tibial surfaces are replaced, with or without patellar surface replacements. Different types may be found: unconstrained or partially constrained, depending on the stability they provide to the knee. Page 4 of 56

5 Fig. 3: Total knee Arthroplasty (TKA) References: Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES All TKR eliminate the anterior cruciate ligament. Posterior cruciate ligament may sometimes be spared. In other replacements posterior cruciate ligament may be sacri#ced or substituted. Those have a central tibial post between the femoral condyles and a cross-bar across the posterior aspect of the intercondylar space, controlling posterior tibial subluxation during #exion. 2. Clinical considerations. The main aim of knee replacement surgery is to achieve good functional outcomes with improved survival of the prosthesis. With that purpose the key points for the surgeon during surgery are: Restoration of alignment Page 5 of 56

6 Maintaining proper tension and balancing of the surrounding collateral ligaments. Condylar and tibial surfaces, should be excised just enough to allow placement of the prosthetic components. ( Fig. 4 on page 33 ). Size of prosthesis should be selected to match native bone. Fig. 4: Knee replacement: Surgery. A. Resected tibial and femoral surfaces. B. View of prosthesis on-site References: Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES 3. Imaging Plain radiographs Technique. Views. Fig. 5 on page 34. Both anteroposterior (AP) and lateral radiographs should be obtained. Short views of the knee will usually be enough, but standing long-leg (hip-to-ankle) radiographs allow long axes to be determined offering more accurate information on the weight-bearing mechanical axis and are mandatory in the diagnosis of polyethilene wear Page 6 of 56

7 Fig. 5: Plain radiographs. Technique and views: A.- AP view. B.- Lateral view and C.Standing long-leg view References: Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES Parameters that should be evaluated Alignment of femoral and tibial components Component size matched to knee Position (flexion/extension) Rotation. Radiograph only shows significant malalignment; CT improves accuracy Patellar assessment Joint line height Keep in mind shape of polyethylene components; lucency of this shape in wrong location is a hint of dislocation A. Normal findings. According to the Knee Society Total Knee Arthroplasty Radiological Evaluation and Scoring System important variables are: A.1. Position of components. Page 7 of 56

8 In order to assess position of components several lines and angles have been described: Coronal plane ( Fig. 6 on page 35 ) : # angle. Femoral varus or valgus alignment The angle between the anatomical axis of the femur and a line tangential to the distal condyles of the femoral component of the prosthesis. # angle. Tibial varus or valgus alignment.the angle between the anatomical axis of the tibia and a line tangential to the plateau of the tibial component of the prosthesis. Fig. 6: Positioning of components. Coronal plane. Femoral and tibial varus or valgus alignment: # angle. Femoral varus or valgus alignment. # angle. Tibial varus or valgus alignment References: Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES Sagittal plane ( Fig. 7 on page 36 ): Page 8 of 56

9 # angle. Flexion-extension angle of the femoral component. The angle between the line through the mid- shaft of the femur and the line of the femoral component of the prosthesis. # angle. Tibial slope. The angle between the line through the midshaft of the tibia and the line tangential to the tibial component of the prosthesis. Fig. 7: Positioning of components. Sagittal plane.femoral and tibial varus or valgus alignment: # angle. Flexion-extension angle of the femoral component # angle. Tibial slope References: Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES A.2. Leg alignment ( Fig. 8 on page 37 ). Normal leg anatomic alignment is 5-8º valgus. Overcorrection of the preoperative deformity may cause accelerated degenerative changes in the opposite compartment Undercorrection may cause increased wear in the tibial component and recurrence of deformity. Page 9 of 56

10 In order to measure limb alignment, the plain AP radiograph is considered. The useful lines are: The mechanical axis (M) connects the center of the femoral head to the center of the tibial plafond, and intersects the middle of the knee joint. The anatomic axis (A) is the long axis of the femoral shaft. The angle between both should normally be 5-8º. Page 10 of 56

11 Fig. 8: Parameters. Limb alignment: A Anatomic limb alignment. M.- mechanical axis Page 11 of 56

12 References: Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES -Presence of radiolucencies ( Fig. 9 on page 39 ). Types of radiolucencies are: Physiological < 2 mm thick, well-defined, and accompanied by a parallel radiodense line Pathological. > 2 mm thick, ill-defined, and lacking accompanying radiodense lines. Fig. 9: Periprosthetic radiolucencies: A.- Physiological radiolucencies. < 2 mm thick, well-defined, and accompanied by a parallel radiodense line B.- Pathological radiolucencies. > 2 mm thick, ill-defined, and lacking accompanying radiodense lines. References: Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES Progressive radiolucent lines and osteolysis are associated with component loosening. The Knee Society scoring system classified the location of radiolucencies around all components in different zones and the total widths of those radiolucencies should be summed. Modified versions have appeared (Fig. 10 on page 39). Page 12 of 56

13 Fig. 10: Periprosthetic radiolucencies References: Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES A.3. Other parameters ( Fig. 11 on page 40 ). Joint line height. It should be evaluated on a lateral radiograph and corresponds to the perpendicular distance from the superior margin of the tibial tubercle to the weight-bearing parallel surface of the tibial plateau or components Patellar assessment Patellar height Patellar tendon length Page 13 of 56

14 Fig. 11: Other parameters: A.- Joint line height B.- Patellar assessment: Different ratios are used for measurements of patellar length (PL) and tendon length (TL). References: Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES B. Signs indicating complication: infection, osteolysis, aseptic loosening, polyethylene wear, periprosthetic and component fracture CT and MR. Technique and limitations. These modalities used to be of limited utility due to extensive beam-hardening artifacts on CT ( Fig. 12 on page 41 ), metallic susceptibility artifacts on MR. Page 14 of 56

15 Fig. 12: NECT of the knee: Extensive beam-hardening artifacts (arrows) caused by knee prostheses References: Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES Nowadays, current scanner technology (dual energy CT) and imaging software, have improved imaging although it already has limitations. Metal artifact reduction techniques for CT include: Soft tissue image acquisition (Fig. 13 on page 41 ) Increase kvp and mas Narrowed collimation Decrease pitch Page 15 of 56

16 Image reconstruction at 1 mm section width with 0.5 mm reconstruction increment Fig. 13: NECT Knee : A and B images obtained with bone protocol and C and D images obtained with Soft tissue protocol. Beam- hardening artifact is less evident on soft tissue protocol images References: Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES Utilities. 3-D imaging (Fig. 14 on page 42 ) may help in positioning evaluation, mainly in component rotation detection. CT can be useful for assessing the extent of osteolysis Page 16 of 56

17 MR with metal artifact reduction technique can show the granulomatous tissue caused by the wear particles. Fig. 14: TKA: 3-D volume rendering imaging References: Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES Imaging findings Evaluation of rotational malalignment ( Fig. 15 on page 43 ) -Femoral component: Angle of epicondylar axis on femur (line from lateral epicondylar prominence to medial sulcus) and line crossing posterior condylar surfaces (0 ± 3 ) Page 17 of 56

18 -Tibial component: Angle of line perpendicular to line extending from center of tibial stem to medial 1/3 of tibial tuberosity & (2) posterior condylar line (or line drawn between tibial fixation pins) (0 ± 3 ) Fig. 15: A: Evaluation of rotational malalignment of Femoral component B.-Evaluation of rotational malalignment of tibial component Page 18 of 56

19 References: Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES Evaluation of periprosthetic loosening, osteolysis and fracture (Fig. 16 on page 44) The presence and extent of osteolysis is better evaluated by CT than with plain radiographs. CT is mainly employed to evaluate location of lysis and adequacy of bone stock prior to surgical revision. Fig. 16: Periprosthetic radiolucency and osteolysis at tibial component (*). A.- Plain film. B.- Coronal MPR and C.- Sagital MPR References: Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES 3.3. US ( Fig. 17 on page 45 ) US is a technique with a limited role in the evaluation of knee arthoplasty, but it may be helpful in selected cases, as well as being a guide for interventional procedures, it may detect and evaluate: Joint effusion. Synovial thickening. Ligaments and tendons surrounding the replacement. Page 19 of 56

20 Abnormalities of the extensor mechanism causing anterior pain after total knee arthroplasty (TKA). Rupture of the quadriceps and patellar tendon. Patellar clunk syndrome: a #brous nodule appears along the deep surface of the distal quadriceps tendon due to the irritation from impingement of the surface against either the condylar component or the patellar component. Arthro#brosis. Capsular thickening. Polyethylene wear may sometimes be detected. Fig. 17: Graft and soft tissue infection: 72 yo woman. TKR three years ago. Pain, edema and inflamnmatory signs. A.- Plain radiography depicts increased soft tissue with air bubbles (arrows). B and C US shows a fluid collection with multiple reverberation artiphacts related to gas (arrows) References: Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES Page 20 of 56

21 3.4. Scintigraphy ( Fig. 18 on page 46 ) Scintigraphy may be useful in cases of suspected infection which should be distinguised from aseptic loosening. Fig. 18: Scintigraphy: Multiphase bone scan with Tc 99m methylene diphosphonate and white blood cell (WBC) scintigraphy of a patient in whom prosthesis infection in left tibia was suspected. Tc 99m planar WBC scan shows uptake on metaphysis of left Page 21 of 56

22 tibia. Late Tc 99m HMPAO white blood cell (WBC) image demonstrates faint increased uptake in the same area. Diagnosis is aseptic loosening of tibial component. Data do not suggest prosthesis infection. References: Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES 4. Complications. Table 1: Knee replacement complications References: Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES 4.1. Early arthroplasty failure. Infection ( Fig. 19 on page 48 ). It is a cause of early prosthesis failure (prior to 2 years) but may also appear later on. Clinical signs are usually found, including pain, swelling, erythema, stiffness, tenderness, as well as a high erythrocyte sedimentation rate and C reactive protein concentration. The radiological signs are nonspecific, similar to aseptic loosening, including: Page 22 of 56

23 Progressively enlarging lucencies. Endosteal and focal lysis. Gas may rarely appear in soft tissue. Fig. 19: Total knee replacement 15 months ago. Bad clinical outcome. Plain radiograph depicts femoral and tibial component loosening. Radiolucencies appear on both components. Septic loosening due to Streptococcus bovis was diagnosed References: Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES Diagnosis may be confirmed by scintigraphy and aspiration/biopsy of the affected joint. Instability (Component displacement) Fig. 20 on page 49. It is one of the most common causes of early failure of replacement, frequently due to failure in surgery or prosthesis selection. It consists of varus-valgus malalignment of the prosthesis with abnormal and excessive displacement of the articular elements causing failure of the arthroplasty. Different types may appear, extension, flexion, and global instability, a pattern detectable in multiple planes. Page 23 of 56

24 Fig. 20: 57 yo woman. Right knee arthroplasty. Knee extension is impaired two months after surgery. A and B plain radiographs and C CT (Volume rendering) depict femoral component displacement. Note femoral component is separated from anterior surface of femur (arrows).d US performed to rule out extensor mechanism rupture. Cuadricipital ligament integrity (arrows). Patella (p), knee arthroplasty (arrowheads) and anterior surface of femur (*). References: Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES Stress shielding It occurs within the first 2 years after surgery and consists of a loss of bone mineralization of the periprosthetic bone due to reduction in mechanical loading. In cases with a long stem with distal #xation on tibial component, the tibial baseplate is not transmitting load to the underlying bone and it looses mineralization. There is no associated pain or risk of failure. Imaging findings include stable periprosthetic lucency most commonly beneath anterior and posterior flanges of the femoral component or beneath the tibial tray. The lucency must not be misinterpreted as osteolysis. Page 24 of 56

25 4.2. Late arthroplasty failure. Aseptic loosening Fig. 21 on page 50. The complication may appear both in cemented and non-cemented tibial components. They normally develop a thin (<1 mm) lucency around the baseplate and stem, which enlarges in cases of aseptic loosening. The radiological signs include: Focal radiolucency greater than 2 mm. Progressively enlarging radiolucency. Component migration. Cement fracture. Fig. 21: Aseptic loosening: A.- Lower limbs full-length weightbearing radiograph previous to surgery: bilateral osteoarthrosis. B.-3 months follow-up weightbearing plain radiograph: Slight periprosthetic radiolucency at tibial component (arrows) C.- 1 year follow-up weight-bearing plain radiograph: periprosthetic radiolucency at tibial component (arrows). D.- Lower limbs full-length weightbearing radiograph after retrieval of prosthesis References: Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES Page 25 of 56

26 Polyethylene wear (Fig. 22 on page 51 ). Two different types may be found: delaminating wear and surface wear, the latter consisting of small particles which may cause also osteolysis. The main predisposing factors are weight and activity level of the patient, molecular weight, homogeneity and initial thickness of the polyethylene (at least 8 mm), geometry and alignment with the femoral condylar component, irregularities in the surface of the condylar articulating component. Knee joint effusion may appear either painful or not. The diagnosis is performed with weight-bearing anteroposterior and lateral radiographs. Findings include: Moderate to severe wear causes joint space narrowing. In cases of mild wear subtle findings appear. The main point for diagnosis is comparison with previous radiographs. Varus or valgus deformity or patellar tilt appear in cases of asymmetric wear. Fig. 22: Polyethilene wear References: Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES Osteolysis ( Fig. 23 on page 52 ). Page 26 of 56

27 It is an aseptic foreign body granulomatous reaction caused by macrophage phagocytosis of particle debris. The regions of osteolysis are filled with granulation tissue. Pain, swelling and acute synovitis appear. The main radiological finding is a thin radiolucency progressively extending around the bone-cement or bone-prosthesis interface. Fig. 23: 78 yo woman TKA 17 years ago. A and B plain radiographs and C NECT and D CT (Volume rendering) depict osteolysis and tibial component displacement. References: Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES Periprosthetic and component fracture ( Fig. 24 on page 52, Fig. 25 on page 53 ). They may be intraoperative (during resection) or postoperative, usually appearing during an activity involving deep #exion of the knee followed by a popping sensation. There is an increased risk for periprosthetic fracture with osteoporosis and/or tibial tubercle transfer. Osteopenia, focal osteolysis, and component loosening are the main redisposing factors and location is most frequent supracondylar. Imaging findings are sometimes subtle, making it easy for small fractures to be missed. Page 27 of 56

28 Fig. 24: Periprosthetic femoral fracture 85 yo-woman. Bilateral total knee arthroplasty. Right supracondylar periprosthetic femoral fracture. A and B plain radiographs. C and D CT multiplanar reconstruction (MPR). E and F AngioCT Volume rendering References: Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES Page 28 of 56

29 Fig. 25: 25.Periprosthetic patellar and tibial fractures A.- 83 yo-woman. Lateral radiograph shows a patellar fracture (arrow) following placement of TKA. B.- 78 yo woman TKA 17 years ago. NECT depicts osteolysis,tibial component displacement and fracture in tibial posterior aspect (arrow). References: Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES Page 29 of 56

30 Miscellanea: Other less frequent complications may also appear: heterotopic ossification usually asymptomatic (Fig. 26 on page 55 ), metal allergies, chronic regional pain syndrome, overuse tendinitis. Fig. 26: Heterotopic ossification76 yo woman. Plain radiographs. A. Previous to surgery. Osteoarthrosis. B. One day after surgery C. 6 months after surgery. Heterotopic calcifications appear (arrow) not present on previous radiographs References: Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES Images for this section: Page 30 of 56

31 Fig. 1: Knee replacement. Components Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES Page 31 of 56

32 Fig. 2: Unicompartmental knee replacement: A.-AP radiograph shows a normal unicompartmental knee replacement in a patient with no significant arthritis in the remaining two compartments. B.Lateral radiograph shows the femoral arthroplasty on the mid and posterior weight-bearing portions of the condyle. Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES Page 32 of 56

33 Fig. 3: Total knee Arthroplasty (TKA) Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES Page 33 of 56

34 Fig. 4: Knee replacement: Surgery. A. Resected tibial and femoral surfaces. B. View of prosthesis on-site Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES Page 34 of 56

35 Fig. 5: Plain radiographs. Technique and views: A.- AP view. B.- Lateral view and C.Standing long-leg view Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES Page 35 of 56

36 Fig. 6: Positioning of components. Coronal plane. Femoral and tibial varus or valgus alignment: # angle. Femoral varus or valgus alignment. # angle. Tibial varus or valgus alignment Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES Page 36 of 56

37 Fig. 7: Positioning of components. Sagittal plane.femoral and tibial varus or valgus alignment: # angle. Flexion-extension angle of the femoral component # angle. Tibial slope Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES Page 37 of 56

38 Fig. 8: Parameters. Limb alignment: A Anatomic limb alignment. M.- mechanical axis Page 38 of 56

39 Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES Fig. 9: Periprosthetic radiolucencies: A.- Physiological radiolucencies. < 2 mm thick, welldefined, and accompanied by a parallel radiodense line B.- Pathological radiolucencies. > 2 mm thick, ill-defined, and lacking accompanying radiodense lines. Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES Page 39 of 56

40 Fig. 10: Periprosthetic radiolucencies Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES Fig. 11: Other parameters: A.- Joint line height B.- Patellar assessment: Different ratios are used for measurements of patellar length (PL) and tendon length (TL). Page 40 of 56

41 Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES Fig. 12: NECT of the knee: Extensive beam-hardening artifacts (arrows) caused by knee prostheses Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES Page 41 of 56

42 Fig. 13: NECT Knee : A and B images obtained with bone protocol and C and D images obtained with Soft tissue protocol. Beam- hardening artifact is less evident on soft tissue protocol images Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES Page 42 of 56

43 Fig. 14: TKA: 3-D volume rendering imaging Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES Page 43 of 56

44 Fig. 15: A: Evaluation of rotational malalignment of Femoral component B.-Evaluation of rotational malalignment of tibial component Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES Page 44 of 56

45 Fig. 16: Periprosthetic radiolucency and osteolysis at tibial component (*). A.- Plain film. B.- Coronal MPR and C.- Sagital MPR Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES Page 45 of 56

46 Fig. 17: Graft and soft tissue infection: 72 yo woman. TKR three years ago. Pain, edema and inflamnmatory signs. A.- Plain radiography depicts increased soft tissue with air bubbles (arrows). B and C US shows a fluid collection with multiple reverberation artiphacts related to gas (arrows) Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES Page 46 of 56

47 Fig. 18: Scintigraphy: Multiphase bone scan with Tc 99m methylene diphosphonate and white blood cell (WBC) scintigraphy of a patient in whom prosthesis infection in left tibia was suspected. Tc 99m planar WBC scan shows uptake on metaphysis of left tibia. Late Tc 99m HMPAO white blood cell (WBC) image demonstrates faint increased uptake in the same area. Diagnosis is aseptic loosening of tibial component. Data do not suggest prosthesis infection. Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES Page 47 of 56

48 Table 1: Knee replacement complications Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES Page 48 of 56

49 Fig. 19: Total knee replacement 15 months ago. Bad clinical outcome. Plain radiograph depicts femoral and tibial component loosening. Radiolucencies appear on both components. Septic loosening due to Streptococcus bovis was diagnosed Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES Page 49 of 56

50 Fig. 20: 57 yo woman. Right knee arthroplasty. Knee extension is impaired two months after surgery. A and B plain radiographs and C CT (Volume rendering) depict femoral component displacement. Note femoral component is separated from anterior surface of femur (arrows).d US performed to rule out extensor mechanism rupture. Cuadricipital ligament integrity (arrows). Patella (p), knee arthroplasty (arrowheads) and anterior surface of femur (*). Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES Page 50 of 56

51 Fig. 21: Aseptic loosening: A.- Lower limbs full-length weightbearing radiograph previous to surgery: bilateral osteoarthrosis. B.-3 months follow-up weightbearing plain radiograph: Slight periprosthetic radiolucency at tibial component (arrows) C.- 1 year follow-up weight-bearing plain radiograph: periprosthetic radiolucency at tibial component (arrows). D.- Lower limbs full-length weightbearing radiograph after retrieval of prosthesis Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES Page 51 of 56

52 Fig. 22: Polyethilene wear Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES Fig. 23: 78 yo woman TKA 17 years ago. A and B plain radiographs and C NECT and D CT (Volume rendering) depict osteolysis and tibial component displacement. Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES Page 52 of 56

53 Fig. 24: Periprosthetic femoral fracture 85 yo-woman. Bilateral total knee arthroplasty. Right supracondylar periprosthetic femoral fracture. A and B plain radiographs. C and D CT multiplanar reconstruction (MPR). E and F AngioCT Volume rendering Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES Page 53 of 56

54 Fig. 25: 25.Periprosthetic patellar and tibial fractures A.- 83 yo-woman. Lateral radiograph shows a patellar fracture (arrow) following placement of TKA. B.- 78 yo woman TKA 17 years ago. NECT depicts osteolysis,tibial component displacement and fracture in tibial posterior aspect (arrow). Page 54 of 56

55 Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES Fig. 26: Heterotopic ossification76 yo woman. Plain radiographs. A. Previous to surgery. Osteoarthrosis. B. One day after surgery C. 6 months after surgery. Heterotopic calcifications appear (arrow) not present on previous radiographs Radiodiagnóstico, UCR, Hospital Infanta Leonor Vallecas - Madrid/ES Page 55 of 56

56 Conclusion Knowledge of normal and abnormal imaging findings is essential in the radiological evaluation of knee replacements. The radiologist should be aware of signs indicating complications in order to avoid delays in patient treatment. Personal information References Ewald FC. The Knee Society total knee arthroplasty roentgenographic evaluation and scoring system. Clin Orthop Relat Res 1989;248:9-12. Miller TT. Imaging of knee arthroplasty. Eur J Radiol 2005:54; Sarmah SS, Patel S, Hossain FS, Haddad FS. The radiological assessment of total and unicompartmental knee replacements. J Bone Joint Surg Br 2012;94-B: Mulcahy H, Chew FS. Current Concepts in Knee Replacement: Complications. Am J Roentgenol 2014;202:W76-W86. See comment in PubMed Commons below Stilling M, Larsen K, Andersen NT, Søballe K, Kold S, Rahbek O. The final follow-up plain radiograph is sufficient for clinical evaluation of polyethylene wear in total hip arthroplasty. A study of validity and reliability. Acta Orthop Oct;81(5): Frick MA1, Collins MS, Adkins MC. Postoperative imaging of the knee. Radiol Clin North Am May;44(3): Liaw CK, Wu TY, Hou SM, Yang RS, Fuh CS. How to evaluate three dimensional angle error from plain radiographs. J Arthroplasty Dec;28(10): Miller TT. Sonography of joint replacements. Semin Musculoskelet Radiol Mar;10(1): Page 56 of 56