Anderson Orthopaedic Research Institute Classification Research Articles

Tibial bone defect prediction based on preoperative artefact-reduced CT imaging is superior to standard radiograph assessment

PurposeThe purpose of this study was to evaluate the accuracy of preoperative CT-based Anderson Orthopaedic Research Institute (AORI)-grading and to correlate Computed tomography (CT)-based volumetric defect measurements with intraoperative AORI findings.Methods99 patients undergoing revision total knee arthroplasty (rTKA) with preoperative CT-images were identified in an institutional revision registry. CT-image segmentation with 3D-Slicer Software was used to create 3D tibial bone defects which were then graded according to the AORI-classification. The AORI classification categorizes tibial defects into three types: Type I has healthy cortical and cancellous bone near the joint line, Type II involves metaphyseal bone loss affecting one or both condyles, and Type III indicates deficient metaphyseal bone with distal defects and potential damage to the patellar tendon and collateral ligament attachments. These 3D-CT gradings were compared to preoperative X-ray and intraoperative AORI grading. The Friedman test was used to investigate differences between AORI values of each measurement method. Volumetric 3D-bone defect measurements were used to investigate the relationship between AORI classification and volumetric defect size in the three anatomic zones of the tibia.ResultsSubstantial agreements between preoperative 3D-CT AORI and intraoperative AORI (kappa = 0.663; P < 0.01) and fair agreements between preoperative X-ray AORI and intraoperative AORI grading (kappa = 0.304; P < 0.01) were found. Moderate correlations between volume of remaining bone and intraoperative AORI grading were found in epiphysis (rS = – 0.529; P < 0.001), metaphysis (rS = – 0.557; P < 0.001) and diaphysis (rS = – 0.421; P < 0.001). Small volumetric differences between AORI I vs. AORI II defects and relatively large differences between AORI II and AORI III defects in each zone were detected.ConclusionTibial bone defect prediction based on preoperative 3D-CT segmentation showed a substantial agreement with intraoperative findings and is superior to standard radiograph assessment. The relatively small difference in defect volume between AORI I, IIa and IIb suggests that updated CT-based classifications might hold benefits for the planning of rTKA.Level of evidenceRetrospective Cohort Study; III

Comparative evaluation of bone defect substitution in revision knee arthroplasty

Objective: to evaluate the immediate and long-term outcomes of revision knee replacement using porous metaphysical sleeves and cones. Material and methods. The research involved 134 patients who underwent revision arthroplasty of their knee joints. The patients were divided into two groups according to the type of metaphyseal fixator: sleeves (Group 1) — 97 patients, and cones (Group 2) — 37 patients. The evaluation of the surgical outcomes was carried out at discharge from the hospital (in 7-12 days) as well as 6, 12, and 24 months after their surgeries. The survival rate of the implants was analyzed by the Kaplan — Meyer method. A revision with total replacement of the implant or its components was considered to be a critical event. Results. The analysis of the survival rate of the implants using various metaphysical fixators showed that the groups with metaphyseal sleeves and cones do not differ statistically (Log Rank criterion (Mantel — Cox) p=0.108). Conclusion. The medium term follow-up revealed no difference in clinical, functional or radiological outcomes of revision knee arthroplasty using porous cones or metaphyseal sleeves in 2A, 2B, and 3 (by Anderson Orthopaedic Research Institute classification) bone loss replacements.

Comparative evaluation of bone defect replacement methods in revision total knee arthroplasty

Objective: to evaluate the immediate and long-term outcomes of revision total knee arthroplasty using porous metaphyseal sleeves and cones. Materials and Methods. The study included 134 patients who underwent revision total knee arthroplasty. The patients were distributed among two groups based on the type of metaphyseal fixator: sleeves (Group I, n=97 patients) and cones (Group II, n=37 patients). Surgical outcomes were assessed upon discharge from the hospital (after the hospital stay of 7-12 days), as well as after 6, 12 and 24 months after surgery. The survival rate of endoprostheses was analyzed using the Kaplan–Meier method. A revision with total replacement of the endoprosthesis or its components was considered a critical event. Results. The analysis of the survival rate of endoprostheses in the form of various metaphyseal fixators showed that the groups of sleeves and cones did not differ statistically significantly as suggested by the logrank test (Mantel–Cox): p=0.108. Conclusion. The midterm follow-up revealed no difference in clinical, functional, or radiological outcomes of revision total knee arthroplasty performed for types 2A, 2B, and 3 of bone defect replacement (sensu Anderson Orthopaedic Research Institute classification) using trabecular metal metaphyseal cones vs. sleeves.

Cementless Porous-Coated Metaphyseal Sleeves Used for Bone Defects in Revision Total Knee Arthroplasty: Short- to Mid-Term Outcomes.

While many studies have presented excellent short-term outcomes of the metaphyseal sleeves used in revision total knee arthroplasty (TKA), currently published mid-term results remain limited and some controversial issues remain unresolved. The purpose of this study was to investigate clinical and radiographic mid-term outcomes of the sleeves for the management of metaphyseal bone defects in revision TKAs. From 2015 to 2019, 44 patients (45 knees) who were operated with cementless porous-coated metaphyseal sleeve in revision TKA were included in this study. Bone defects were assessed according to Anderson Orthopaedic Research Institute Classification. On the tibial side, there were 37 type II and six type III, and with regards to the femur, 15 were type II, and four were type III. Through reviewing electronic records, data were collected, including baseline demographics, operative details, information of prothesis, and complications. Clinical and radiographic evaluations were performed, including Knee Society Scores (KSS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), range of motion (ROM), the radiolucent line, level of joint line, and implant survival rate. Statistical analysis was performed by paired t-test for clinical and radiographic indexes. The mean follow-up time was 4.4 ± 1.4 years. During surgery, sleeve-related fractures were encountered in four (8.9%) knees, including incomplete tibial fracture of lateral cortex in one knee and of medial cortex in two knees, and longitudinal femoral metaphyseal fracture in one knee. Unions were achieved in all cases at the final follow-up. Significant improvements in KSS and WOMAC scores were found at the final follow-up, respectively, from 83.8 ± 29.1 to 152.9 ± 31.0 (t=-12.146, p < 0.001) and from 148.4 ± 42.3 to 88.1 ± 52.5 (t=6.025, p < 0.001). The mean ROM improved from 88.7 ± 31.9° to 113.7 ± 13.7° (t=-5.370, p < 0.001). A 75 mm length of cementless stem was used in all patients and only one patient was identified as tibial end-of-stem pain. No sleeve-related revision occurred, and one patient was diagnosed with early postoperative infection and was treated with irrigation and debridement, polyethylene liner exchange, and appropriate antibiotic treatment. The overall implant survival was 97.8% with the endpoint reoperation and 100% with the endpoint revision. Osseointegration at the bone-sleeve interface was found in all patients and no loosening happened. Satisfactory alignment between 3° varus and 3° valgus was achieved in all but not in three patients. The use of metaphyseal sleeves in the treatment of bone defects in rTKAs can provide stable fixation and significantly improve the clinical scores at the midterm follow-up. In addition, the rare occurrence of end-of-stem pain suggests routine use of cementless stems. Although there are chances of intraoperative fractures, it has no negative effect on outcome when managed properly.

Varus-Valgus Constrained Implants in Revision Total Knee Arthroplasty: Mean Clinical Follow-Up of Six Years

BackgroundThere is scant literature evaluating varus-valgus constrained (VVC) prostheses in contemporary revision total knee arthroplasty (TKA). Therefore, we aimed to evaluate the durability of VVC revision TKA with selective use of cones. MethodsA retrospective review of 194 revision TKAs with VVC was performed from August 2005 through February 2018 at a single institution. The final cohort consisted of 168 TKAs with a mean follow-up of 6 years. Stems were used in all but 1 TKA, tibial cones in 48%, and femoral cones in 19%. Anderson Orthopaedic Research Institute classification in femurs was 1 in 57, 2A in 33, 2B in 62, 3 in 16, and in tibias, 1 in 42, 2A in 29, 2B in 81, and 3 in 16. ResultsSurvival analysis showed that 93% were free of revision for aseptic component loosening, 76% were free of revision for any reason, and 74% were free of reoperation at 6 years. Anderson Orthopaedic Research Institute 3 femur or tibia, age <65 years, and progressive radiographic changes were associated with an increased risk of revision for aseptic loosening (P < .05). Progressive radiographic changes were seen in 19% of femoral and 16% of tibial constructs. The most common reason for re-revision was periprosthetic joint infection (65%). ConclusionVVC revision TKA with selective use of cones provided a reasonable outcome as 93% were free of revision for aseptic loosening at 6 years. However, given the rate of patients with progressive radiographic changes and survivorship free of reoperation of 74% at 6 years, long-term follow-up will help assess the durability of these constructs.

Comparative Biomechanical In Vitro Study of Different Modular Total Knee Arthroplasty Revision Stems With Bone Defects

BackgroundThe aim of this study is to investigate the effects of different stem lengths and types including cones on primary stability in revision total knee arthroplasty with different femoral bone defects and fixation methods in order to maximize bone preservation. It is hypothesized that longer stems provide little additional mechanical stability. MethodsThirty-five human femurs were investigated. A distal bone defect, Anderson Orthopedic Research Institute classification (s. 33) type-F2a, was created in group 1-3 and type-F3 in group 4-6. A cemented, rotating hinge femoral component was combined with different stems (100 and 160 mm total or hybrid cemented cones, or a 100-mm custom-made anatomical cone stem). The femora were loaded according to in vivo loading during gait. Relative movements were measured to investigate primary stability. Pull-out testing was used to obtain a parameter for the primary stability of the construct. ResultsRelative movements were small and similar in all groups (<40 μm). For small defect, the pull-out forces of cemented long (4583 N) and short stems (4650 N) were similar and about twice as high as those of uncemented stems (2221 N). For large defects, short cemented stems with cones showed the highest pull-out forces (5500 N). Long uncemented stems (3324 N) and anatomical cone stems (3990 N) showed similar pull-out forces. ConclusionAll tested stems showed small relative movements. Long cemented stems show no advantages to short cemented stems in small bone defects. The use of cones or an anatomical cone stem with hybrid cementation seems to offer good stability even for larger bone defects. The use of a short cemented stem (with or without cone) may be a suitable choice with a high potential for bone preservation in total knee arthroplasty revision with respective bone defects.

What Is the Reliability of a New Classification for Bone Defects in Revision TKA Based on Preoperative Radiographs?

Accurate quantification of bone loss facilitates preoperative planning and standardization for research purposes in patients who undergo revision TKA. The most commonly used classification to rate bone defects in this setting, the Anderson Orthopaedic Research Institute classification, does not quantify diaphyseal bone loss and reliability has not been well studied. We developed a new classification scheme to rate bone defects in patients undergoing revision TKA and tested (1) the intraobserver and interobserver reliability of this classification for revision TKA based on preoperative radiographs, and (2) whether additional CT images might improve interobserver reliability. This was a preregistered observational study. Interobserver reliability was analyzed using preoperative radiographs of 61 patients who underwent (repeat) revision TKA, and their bone defects were rated by five experienced orthopaedic surgeons. For intraobserver reliability, ratings were repeated at least 2 weeks after the first rating (Timepoints 1 and 2). Directly after the radiographic assessments of Timepoint 2, the observers were provided with CT images of each patient and asked to rate the bone defects for a third time (Timepoint 3), to assess the additional value of CT. Intraobserver and interobserver reliability were tested using Gwet's agreement coefficient 2, which is a measure of agreement between observers in categorical data. Substantial agreement was defined as coefficients between 0.61 to 0.8 and almost perfect agreement as > 0.8. The intraobserver reliability varied between 0.55 (95% CI 0.40 to 0.71) and 0.87 (95% CI 0.78 to 0.96) in the epiphysis, between 0.69 (95% CI 0.58 to 0.80) and 0.98 (95% CI 0.95 to 1) in the metaphysis, and between 0.95 (95% CI 0.90 to 0.99) and 0.99 (95% CI 0.98 to 1) in the diaphysis. The interobserver reliability varied between 0.48 (95% CI 0.39 to 0.57) and 0.49 (95% CI 0.42 to 0.56) in the epiphysis and between 0.81 (95% CI 0.75 to 0.87) and 0.88 (95% CI 0.83 to 0.93) in the metaphysis, and was 0.96 (95% CI 0.93 to 0.99) in the diaphysis at Timepoint 1. The interobserver reliability at Timepoint 2 was similar to that of Timepoint 1. The addition of CT images did not improve reliability (Timepoint 3). The bone defect classification was less reliable in the epiphyseal area compared with the metaphysis and diaphysis. This finding may be explained by prosthetic components obscuring this region or the more severe bone defects in this region. The addition of CT scans did not improve reliability. Further testing of reliability with observers from other institutions is necessary, as well as validity testing, by testing the classification in relation to intraoperative findings. Level III, diagnostic study.

A Case Report: Custom Made Porous Titanium Implants in Revision: A New Option for Complex Issues

Background: Bone loss management is considered one of the most difficult challenges for orthopaedic surgeon. In massive bone defects, few surgical options are available and they do not offer a reliable or optimal solution for knee reconstruction. Objective: The aim of this paper is to present and justify a new custom-made approach for complex metadiaphyseal bone defects management in knee revision surgery. Methods: We report a case of a 66-year-old woman who underwent a staged left total knee arthroplasty revision for infection with Anderson Orthopaedic Research Institute classification III uncontained femoral and tibial metadiaphyseal bone defects following five prior surgeries. Along with a case discussion, we describe clinical and radiological outcomes of 3 similar patients treated with this new custom-made device. Results: To manage these problems, we developed new, custom porous titanium devices for both femoral and tibial reconstruction tailored to a patient’s specific bone loss. Since, 2014, we treated four cases using custom-made porous titanium cones and we had optimal clinical and radiological results, with no instances of loosening, component migration, or mismatches between preoperative planning and intraoperative findings. Conclusion: In extremely selected cases, this new device can be considered a possible and viable surgical step between “off the shelf” reconstruction implants and knee substitution with a tumor megaprosthesis.

Revision Total Knee Arthroplasty Causes of failure, bone loss management and outcomes\

The objectives of the current study were to identify the causes leading to revision knee arthroplasty, analyse implant choices and assess the short-term outcome. The current study is a retrospective on including a group of 33 patients operated between Jan 2013-Dec 2016 in a single institution. Data was collected from the Romanian National Arthroplasty Register. The cause for revision surgery was noted, as well as the type of implant used during the surgical procedure. The bony defect was classified according to the Anderson Orthopaedic Research Institute (AORI) Classification and the reconstruction method was analysed. Functional outcome was assessed using Oxford Knee Score preoperatively and at one year follow-up. Infection was the cause of failure in 18 cases, aseptic loosening in 11 cases, malposition of implants in 2 cases, instability in 1 case and periprosthetic fracture in 1 case. Revision implants were chosen based on joint stability and degree bone loss. The preferred implant was a condylar constrained knee type (20 cases), followed by a rotating hinge type (5 cases). An unconstrained implant was used in 2 cases. Six infected cases required an arthrodesis of the knee. Based on the AORI Classification, there were 10 type III defects, 14 type IIB, 8 type IIA and only one type I defect. Metal augments were preferred for reconstruction of bone defects. Bone graft was used in 8 cases. The mean Oxford Knee Score was 15 pre-op (12-20) and 38 post-op (32-45). Implant survival at final follow-up was 100%. The most common cause of failure of primary total knee arthroplasty is prosthetic joint infection. Bone defects can be addressed using metal augments or bone allograft. Postoperative functional outcome is improved irrespective of the type of implant used.

Letter to the Editor: No Difference Between Trabecular Metal Cones and Femoral Head Allografts in Revision TKA: Minimum 5-year Followup

To the Editor, We read the article by Sandiford and colleagues [3] with great interest. Although this is a valuable study, we have some queries for the authors. In the Patients and Methods section, the authors noted that 45 TKA revisions were performed using augmentation of host bone. Of those 45, surgeons used “femoral head allograft in 30 (75%) and trabecular metal cones in 15 (25%).” Shouldn’t the percentages be 66.7% and 33.3%, respectively? In the Trabecular Metal Cone Technique section, the authors stated: “Nine Type 2A and two Type 2B femoral defects and 13 Type 2A and six Type 2B tibial defects were treated with femoral head allografts. Four Type 2B and two Type 3 femoral defects and two Type 2A and seven Type 2B tibial defects were treated using trabecular metal cones.” However, the second sentence does not match up with the data in Table 1. Are the data in the text or in Table 1 correct? In the Conclusions section, the authors state that both techniques are viable options for the management of Anderson Orthopaedic Research Institute (AORI) Type 2 and 3 defects. But in the study, no patients with Type 3 bone defects were treated with femoral head allografts. Because of this, we believe that that the study’s conclusions may be overstated as published. Finally, the authors used the Oxford Knee Score, WOMAC, SF-12, and the UCLA activity score to assess knee function and quality of life, and additionally, radiographs were assessed for signs of loosening. But radiostereometric analysis (RSA) is also important because the AORI classification referenced in the article is based on radiological images. In fact, in a study by Jensen and colleagues [2], the difference between the mean maximum total point motion of the trabecular metal cone group and the no trabecular metal cone group was almost 2 mm, but they could not detect this as a significant difference. However, in Sandiford and colleagues, perhaps there is a significant difference between the trabecular metal cone and femoral head allograft groups. If Sandiford and colleagues compared outcomes of the two groups’ images at 3 weeks, 6 weeks, 3 months, and 1 year using RSA [1], and then annually after 1 year, using the methods they used, perhaps their conclusions would have been more convincing.

Good clinical and radiographic outcome of cementless metal metaphyseal sleeves in total knee arthroplasty

Background and purpose — The number of revision total knee arthroplasties (TKA) is continuously increasing, leading to a growing need for reliable management of metaphyseal bone loss. We evaluated patients operated with a TKA using metal metaphyseal sleeves for bone defects with a minimum 5-year follow-up.Patients and methods — 37 patients had been operated on. 3 patients died and 3 patients were lost during follow-up. Of the 31 remainders (20 women), 9 had been operated on with a primary TKA and 22 with a revision TKA at the index surgery. The mean age at surgery was 69 (54–89) years and the mean follow-up time was 7.4 (5–12) years. Bone defects were classified according to the Anderson Orthopaedic Research Institute classification (tibia: type I n = 9, type II n = 5 and type III n = 17; femur: type I n = 12, type II n = 3 and type III n = 16).Results — At final follow-up one-third experienced an improvement concerning walking aids and walking distance. Except for 1 patient, all had full extension and a mean knee flexion of 110 (90–140) degrees. VAS pain at rest was 13 (SD 25) and on movement 30 (SD 31). 7 patients were reoperated due to: infection (n = 4), periprosthetic fracture (n = 1), skin necrosis (n = 1), and wound rupture (n = 1). The cumulative 5-year survival rate for reoperation was 77% (CI 63–92) and for revision 97% (CI 91–100). At the time of final follow-up, the sleeves showed good osseointegration with no signs of progressive radiolucency or migration.Interpretation — Titanium sleeves are a promising option in managing difficult cases with metaphyseal bone defects in TKA, providing a stable construct with good medium-term radiographic outcome

Tibial component with and without stem extension in a trabecular metal cone construct

PurposeThe purpose of this study was to investigate stability and strain distribution of a tibial plateau reconstruction with a trabecular metal cone while the tibial component is implanted with and without a stem, and whether prosthetic stability was influenced by bone mineral density. Trabecular metal cones are designed to fill up major bone defects in total knee arthroplasty. Tibial components can be implanted in combination with a stem, but it is unclear whether this is necessary after reconstruction with a trabecular metal cone. Implanting a stem can give extra stability, but may have negative side effects.MethodsTibial revision arthroplasties with trabecular metal cones were performed after reconstruction of a 2B bone defect according to the Anderson Orthopedic Research Institute classification. Components were implanted in seven pairs of cadaveric tibiae; one tibia of each pair was implanted with stem and the other without. All specimens were loaded to one bodyweight alternating between the medial and lateral tibial component. Implant-bone micro-motions, bone strains, bone mineral density and correlations were measured and/or calculated.ResultsTibial components without a stem showed only more varus tilt [difference in median 0.14° (P < 0.05)], but this was not considered clinically relevant. Strain distribution did not differ. Bone mineral density only had an effect on the anterior/posterior tilt [ρ: −0.72 (P < 0.01)].ConclusionTibial components, with or without a stem, which are implanted after reconstruction of major bone defects using trabecular metal cones produce very similar biomechanical conditions in terms of stability and strain distribution. If in vivo studies confirm that a stem extension is not mandatory, orthopaedic surgeons can decide not to implant a stem.Level of evidenceII.

Revision total knee arthroplasty using metaphyseal sleeves at short-term follow-up.

The treatment of bone loss in revision total knee arthroplasty (TKA) has involved using revision implants in association with cement, augments, particulate, and structural allograft. Newer metaphyseal augments were introduced to allow for metaphyseal fixation of the prosthesis while managing significant bone loss. The purpose of the current study was to evaluate the outcome of revision TKA using metaphyseal sleeves. The authors prospectively followed 96 knees that underwent revision TKA with metaphyseal sleeves. Eighty-three knees met the minimum 2-year criteria for follow-up. Thirty-six sleeves were used in femoral revisions and 83 sleeves were used in tibial revisions. The defects were classified according to the Anderson Orthopaedic Research Institute classification. Femoral defects were classified as type I in 4 knees, type IIb in 25 knees, and type III in 7 knees. Tibial defects were classified as type I in 9 knees, type IIa in 1 knee, type IIb in 68 knees, and type III in 5 knees. The patients were followed for an average of 2.4 years (range, 2.0-3.7 years). Mean Knee Society function score improved from 47.9 to 61.1 points. Mean Short Form 36 physical score improved from 43.3 to 56.3 points. Mean Western Ontario and McMaster Universities Arthritis Index improved from 55.3 to 25.9 points. None of the implants demonstrated progressive radiolucent lines around the metaphyseal sleeves. At final follow-up, only 2 (2.7%) tibial components required revision for aseptic loosening. At short-term follow-up, revision TKA with metaphyseal sleeves provided reliable fixation. This is especially encouraging given the severe nature of bone loss in the majority of patients in whom a metaphyseal sleeve was used. Long-term follow-up is needed to demonstrate the true effectiveness of these devices.

Constraint choice in revision knee arthroplasty

Along with the increase in primary total knee arthroplasty, there has been an increase in the number of revisions. The aim of this study was to propose a selection algorithm for the knee revision constraint according to the state of ligaments and to the bone defects Anderson Orthopaedic Research Institute Classification [AORI] classification. The hypothesis was that this algorithm would facilitate the appropriate choice of prosthesis constraint, thus providing stable components and a good long-term survivorship of the knee revisions. Sixty consecutive revision knee arthroplasties in 57 patients were prospectively evaluated. Prostheses implanted at revision included postero-stabilised, condylar constrained and rotating hinged, relative to the state of the ligaments and of the bone loss around the knee. The median follow-up was nine years (range, 4-12). The median IKS knee and function scores and HSS score were 41 (15-62), 21.5 (12-43) and 34 (23-65) points, respectively, before the operation, and 81 (48-97), 79 (56-92) and 83.5 (62-98) points (p < 0.001) at the latest follow-up evaluation. The median ROM increased from 74° (29-110°) preoperatively to 121° (98-132°) (p < 0.01) at the final follow-up. Re-revision was necessary in five (8.3%) patients. A selection algorithm for the revision implant constraint based on the state of ligaments and the bone loss AORI classification could provide stable knee reconstructions and long-term success of knee revisions.

Treatment of Large Bone Defects With Trabecular Metal Cones in Revision Total Knee Arthroplasty

The early term results of 29 cases of revision total knee arthroplasty using highly porous trabecular metal cone implants for femoral and tibial major bone deficit reconstruction (Anderson Orthopedic Research Institute classification type 2B and 3) have been prospectively analyzed. Indications for revision surgery included: aseptic loosening/wear, staged reimplantation after infection, as well as periprosthetic fracture. At an average follow-up of 33 months (range, 13-73 months) the mean Knee Society Score and functional score statistically improved. Radiological follow-up revealed no evidence of loosening or migration of the constructs. No evidence of complications was noted in correlation with the use of trabecular metal cones. This study supports evidence that trabecular metal cones are an efficient and effective option for dealing with significant bone deficits and obtaining stable biological fixation in revision total knee arthroplasty.

Porous Tantalum Cones for Large Metaphyseal Tibial Defects in Revision Total Knee Arthroplasty: A Minimum 2-Year Follow-up

Sixteen cases of revision total knee arthroplasty requiring the use of porous tantalum tibial cones for 2 T2A, 3 T2B, 4 T3A, and 7 T3B tibial bone defects (Anderson Orthopaedic Research Institute classification) after 13 cases of aseptic loosening and 3 cases of staged reimplantation for infection were reviewed. At an average 31 months (24-38), no patients were lost to follow-up. There were 2 cases of recurrent sepsis requiring removal of a well-fixed cone. In the remaining 14 cases, the reconstructions were functioning well with no reoperations. Radiographs demonstrated reestablishment of the joint line, neutral mechanical axis (average, 5.4° of valgus), and signs of stable osteointegration into the cones. Good short-term results were achieved in complex revisions, with these new reconstructive tools.

Radiographic Prediction of Intraoperative Bone Loss in Knee Arthroplasty Revision

A key challenge for orthopaedic surgeons performing revision total knee arthroplasty is the management of bone loss. The goal of our study was to test the validity of predicting bone loss from preoperative radiographs using two commonly utilized bone loss assessments: the Anderson Orthopaedic Research Institute and University of Pennsylvania systems and secondarily to assess the frequency and severity of bone loss in a prospective study of total knee arthroplasty revisions. Ninety-eight total knee arthroplasty revision patients were assessed and bone loss was detected in 76 (77.6%) patients preoperatively and intraoperatively. The validity of both systems was established. Agreement between preoperative and intraoperative Anderson Orthopaedic Research Institute classification was fair for the femur and good for the tibia. All University of Pennsylvania preoperative measures were correlated with intraoperative measures. Establishing valid and reliable preoperative systems of measuring bone loss facilitates planning of total knee arthroplasty revision and rehabilitation and meaningful comparisons between different series of patients and treatment protocols. Diagnostic study, level I (prospective testing of previously developed diagnostic criteria on consecutive patients [with universally applied reference "gold" standard]). See Author Guidelines for a complete description of levels of evidence.

The Management of Bone Defects in Revision Total Knee Arthroplasty

Purpose : Bone defects in revision TKA were classified according to AORI (Anderson Orthopedic Research Institute) system and results of the treatment are reported according to this classification. Materials and Methods : The results of 24 revision TKAs operated from Mar. 1991 to Apr. 1999 were analysed. Fourteen knees had type 1 tibial defects, four knees had type 2 and six knees had type 3. On the femoral side, twelve knees had type 1, four knees had type 2 and seven knees had type 3 defects. Cement and chip bone grafts were mainly used to fill bone defects in type 1, wedges or blocks in type 2 and structural allograft combined with the other methods in type 3. Results were evaluated using the knee and functional scores of the American knee society. Results : The analysis of the results according to the method of treatment- cement filling, chip bone graft, structural bone graft, wedge or blocks and custom made pros-thesis- revealed improvements of knee scores in all groups except for custom made prosthesis. Conclusion : Satisfactory clinical results were obtained for the management of bone defects according to the AORI classification system in revision total knee arthroplasty.

Revision knee arthroplasty using impaction grafting and primary implants

A technique is described for revision knee arthroplasty with impaction grafting of cancellous bone grafts to treat bone loss and the use of primary implants. Specially designed impaction instruments were used. Bone loss was classified according to the Anderson Orthopaedic Research Institute classification. Four-year follow-up of 11 knees in 9 patients showed good clinical and radiographic results.