Optimal rotational positioning of tibial component in total knee arthroplasty: determined by linker surgical technique using a high definition CT.

INTRODUCTION: The rotational alignment of femoral and tibial components is an important determinant of the success of Total Knee Arthroplasty (TKA). The optimal rotational position of the tibial component is still unclear. The purpose of this study was (1) to determine the pre-operative S-TEA (surgical-transepicondylar axis) derived tibialanteroposterior (AP) axis angle and postoperative tibial component axis angle using a "Bird's eye" high-definition CT image in TKA performed by Linker surgical technique; (2) to determine the femorotibial mismatch angle; and (3) to determine the optimal tibial component rotation in a well-aligned femoral and tibial components. MATERIALS AND METHODS: 55 knees in 49 osteoarthritis patients who underwent primary TKA by Linker surgical technique were evaluated. Preoperative tibial AP axis angle, and the postoperative tibial component axis angle were measured. Rotational mismatch between femoral and tibial components was also measured. RESULTS: The mean angle of the pre-operative tibial AP axis was 17.8° ± 4.0°, ranging from 4.3° to 25.4°. The mean angle of the post-operative tibial component axis was 16.2° ± 4.9°, ranging from 3.8° to 25.2°. The mean postoperative tibial component axis line was at 14.2% ± 11.9%. CONCLUSION: Because of the variability of pre-operative S-TEA derived tibial AP axis angle, the tibial component axis angle was also variable among the knees, but the two angles bore a strong correlation to each other. Based on our results, the optimal axis of the tibial component passes about halfway through the medial edge and medial one-third of the tibial tuberosity. LEVEL OF EVIDENCE: Level II.

A retrospective comparative study of infection control rate and clinical outcome between open debridement using antibiotic-impregnated cement beads and a two-stage revision in acute periprosthetic knee joint infection.

The aim of this study was to determine whether the infection control rate of a modified debridement, antibiotics, and implant retention (DAIR) protocol (DAIR with antibiotic-impregnated cement beads) is comparable to that of 2-stage revision for acute periprosthetic joint infection (PJI) after total knee arthroplasty (TKA). We also aimed to determine whether this modified DAIR technique produced better clinical results than those obtained using 2-stage revision in terms of functional outcome, range of motion (ROM), and patient satisfaction at 2 years after surgery.This retrospective comparative study included patients who underwent modified DAIR (7 patients, 9 knees) or 2-stage revision (8 patients, 9 knees) for acute PJI of the knee joint. Infection control rate, functional outcome measured using Western Ontario and McMaster Universities Arthritis Index (WOMAC) score, ROM and patient satisfaction were compared between the two groups.There was no difference in infection control rates between the modified DAIR and 2-stage revision groups (78% vs 78%, respectively). In contrast, surgical outcome in the modified DAIR group was tended to be better than 2-stage revision group, but it did not reach statistical significance. Median maximal range of flexion was 103° in the modified DAIR group and it was 90° in the 2-stage group (P = .191). In addition, the median WOMAC function score was 24 in the modified DAIR group and it was 30 in the 2-stage group (P = .076). Median patient satisfaction measured using visual analogue scale was 8 in the modified DAIR group and 5 in the 2-stage group (P = .069).The infection control rates of the modified DAIR protocol and 2-stage revision protocol were similar for the treatment of acute PJI of the knee joint. However, the modified DAIR protocol could not provide substantially increased functional outcomes and patient satisfaction compared to 2-stage revision. Therefore, the modified DAIR technique should be considered to be of limited use in patients with high surgical morbidity.

Temporal Value of C-Reactive Protein and Erythrocyte Sedimentation Rate after Total Knee Arthroplasty in Patients with Elevated Preoperative C-Reactive Protein: A Matched-Pair Analysis.

BACKGROUND: We aimed to determine whether temporal values of C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) after total knee arthroplasty (TKA) differ between patients with and without elevated preoperative CRP. We hypothesized that temporal pattern of CRP and ESR change would differ between the two groups. MATERIALS AND METHODS: This retrospective study included 30 TKAs with a diagnosis of osteoarthritis with elevated preoperative CRP (>1 mg/dl) without clinical signs and symptoms of infection before surgery (elevated CRP group). Patients without elevated preoperative CRP were matched in a 1:10 fashion according to age, sex, number of comorbidities and whether TKA was unilateral or bilateral (nonelevated CRP group). The temporal values of CRP and ESR after TKA were compared between the two groups until 2 months after surgery. RESULTS: The mean peak values of CRP and ESR after surgery were similar between the two groups in both unilateral and bilateral TKAs. In the unilateral TKA, mean values of CRP and ESR and the proportions of the knees with normal CRP and ESR at 2 months after surgery were similar in the two groups. However, in the bilateral TKA, mean values of CRP and ESR were higher and the proportions of the knees with normal CRP and ESR at 2 months after surgery were lower in the elevated CRP group compared to the nonelevated CRP group. CONCLUSIONS: When performing TKA in patients with elevated preoperative CRP, the fact that the levels of CRP and ESR may not be normalized until 2 months after surgery should be considered during followup.

Long-term follow-up and survivorship of single-radius, posterior-stabilized total knee arthroplasty.

BACKGROUND: We sought to determine the 10-year survivorship of single-radius, posterior-stabilized total knee arthroplasty (TKA) in Asian patients. We also aimed to determine whether the long-term clinical and radiographic results differed between patients with and without patellar resurfacing. METHODS: This retrospective study included 148 (115 patients) consecutive single-radius, posterior-stabilized TKAs. Ten-year survivorship analysis was performed using the Kaplan-Meier method with additional surgery for any reason as the end-point. Furthermore, long-term clinical and radiographic results of 109 knees (74%; 84 patients) with more than 10-year follow-up were analyzed. Ten-year survivorship and long-term outcomes after surgery were determined, and outcomes were compared between patients with and without patellar resurfacing. RESULTS: The cumulative survival rate of the single-radius posterior-stabilized TKA of 148 knees was 97.7% (95% confidence interval, 93.1%-99.3%) at 10 years after surgery. Three knees required additional surgery during the 10-year follow-up because of one case of instability and two cases of periprosthetic infections. Mean postoperative Knee Society knee score and function score were 97 points and 75 points, respectively. There were no cases of aseptic loosening of the prosthesis, even though a non-progressive radiolucent line was found in 10 (9%) knees. There were no differences in postoperative scores and degree of patellar tilt and displacement between patients with and without patellar resurfacing. CONCLUSIONS: Single-radius, posterior-stabilized TKA showed satisfactory long-term clinical and radiographic outcomes in Asian patients regardless of patellar resurfacing, with comparable survivorship to that reported in westerners.

Clinical performance and survivorship of navigated floating platform mobile-bearing total knee arthroplasty: A minimum 10-year follow-up.

BACKGROUND: The purpose of this study is to report the outcome of navigation-assisted cruciate-retaining total knee arthroplasty (TKA) using one type of cemented, second-generation, floating-platform (FP), mobile-bearing system. METHODS: Forty-two patients who underwent cruciate retaining TKAs using e.motion-FP prostheses under navigational guidance were retrospectively reviewed. The preoperative diagnosis was osteoarthritis in all knees except one rheumatoid arthritis. The mean follow-up was 132.0 months (range, 120-140 months) and the mean age was 64.0 ± 4.7 years (range, 51-76 years) at the time of index surgery. Clinical and radiographic results as well as mechanical survival rate of this type of prosthesis were investigated at a minimum follow-up of 10 years. RESULTS: The mean mechanical femorotibial angle was improved from 11.7° ± 3.3° preoperatively to 1.4° ± 1.7° at the latest follow-up. No prosthesis-related complications occurred. One knee underwent open debridement due to superficial infection at 5 weeks after surgery and the other knee experienced a periprosthetic fracture around the proximal tibia, which was successfully healed after open reduction and internal fixation. CONCLUSIONS: The e.motion-floating platform mobile-bearing design yielded satisfactory long-term durability and implant performance under navigational guidance.

Safety of simultaneous bilateral total knee arthroplasty using an extramedullary referencing system: results from 2098 consecutive patients.

INTRODUCTION: Simultaneous bilateral total knee arthroplasty (TKA) has been associated with a high risk of morbidity and mortality. The orthopedic surgeon must, therefore, decide whether bilateral simultaneous TKA is a safe operation to perform and endeavor to decrease the risk of serious complications or even death. METHODS: This retrospective review included 2098 consecutive patients who underwent bilateral simultaneous TKAs by the protocol used in our institution, including the use of extramedullary instruments to minimize medullary canal invasion and overlapping procedures for both knees to decrease operation time. RESULTS: The incidence rate of occurred complications was 0.33 % for symptomatic pulmonary embolism, 0.62 % for deep surgical infection requiring revision surgery, 0.05 % for 14-day mortality, 1.14 % for adverse cardiac events, and 0.76 % for postsurgical delirium within the 1-year follow-up. CONCLUSIONS: Our protocols, including the use of an extramedullary referencing system and overlapping procedures for both knees, may be considered to decrease the perioperative short-term morbidity and 14-day mortality rates in simultaneous bilateral TKA.

Is Total Knee Arthroplasty a Viable Treatment Option in Octogenarians with Advanced Osteoarthritis?

PURPOSE: This study directly compared clinical assessment scores and short-term systemic complications after total knee arthroplasty (TKA) between a group of patients aged 80 or older (141 patients) and another group of patients aged between 65 and 70 years (616 patients) with advanced osteoarthritis. MATERIALS AND METHODS: We retrospectively investigated 757 osteoarthritic patients who underwent primary TKA from January 2007 to January 2011 with a follow-up of 1 year. The surgery was performed using an extramedullary alignment guide instrument without invasion of the intramedullary canal to decrease embolic load and blood loss. RESULTS: At 1 year after surgery, the mean Knee Society knee score was improved in both groups (from 63.6 to 83.2 in octogenarians and from 68.3 to 89.0 in the younger group) and the level of satisfaction was excellent in both groups (8 in octogenarians and 8.3 in the younger group), even though there was no notable change in function score in the octogenarians (from 61.0 to 61.9 in the octogenarians and from 62.3 to 73.6 in the younger group). The total incidence of systemic complications (3.4% vs. 1.2%, p=0.400) and surgical complications (2.1% vs. 0.5%, p=0.229) showed no significant difference between groups. CONCLUSIONS: TKA yielded favorable clinical outcomes with a comparatively low postoperative complication rate in octogenarians despite the negligible functional improvement.

Infrapatellar fat pad preservation reduces wound complications after minimally invasive total knee arthroplasty.

INTRODUCTION: The aim of this study was to determine whether pain intensity and wound complication rates differ between patients with and without preservation of the infrapatellar fat pad (IPFP) after minimally invasive total knee arthroplasty (TKA). The authors also sought to determine whether IPFP preservation affects operation time. MATERIALS AND METHODS: This retrospective study included 448 knees with primary TKA. The IPFP was totally resected in 201 knees (IPFP-R group), and was preserved in 247 knees (IPFP-P group). Pain score was determined using the visual analog scale during the first 72 h after surgery. Wound complication rates and operation times were also evaluated. A wound complication was defined as persistent wound drainage for three or more days after surgery. RESULTS: There was no difference in pain levels between the two groups. However, there were fewer wound complications in the IPFP-P group (3 %) than in the IPFP-R group (13 %). The operation time was longer in the IPFP-P group than in the IPFP-R group (70 vs. 64 min, respectively). CONCLUSIONS: Although IPFP preservation delayed operation time, it decreased wound complications after MIS TKA. These findings are important to consider when deciding whether or not to resect the IPFP. Whenever possible, IPFP preservation is probably the preferred technique to reduce wound complications.

How to minimize rotational conflict between femoral & tibial component in total knee arthroplasty: the use of femoro-tibial axial synchronizer (Linker).

PURPOSE: The purpose of this study was to investigate the correlation between rotational axes of femur and tibia with the use of Linker. MATERIALS AND METHODS: This study was carried out from August 2009 to February 2010 on 54 patients (106 knees), who were diagnosed with simultaneous bilateral total knee arthroplasty. With the use of postoperative computed tomography scans, it was investigated how much the rotational angle of femoral and tibial components matched. RESULTS: The tibial component was internally rotated for the femoral component at an angle of 0.8°. The femoral component was externally rotated for the surgical transepicondylar axis (TEA) at an angle of 1.6 (range: from 4.8° of internal rotation to 7.9° of external rotation, SD=2.2°), and the tibial component was externally rotated for the surgical TEA at an average angle of 0.9 (range: from 5.1° of internal rotation to 8.3° of external rotation, SD=3.1°). CONCLUSION: The femoro-tibial synchronizer helped to improve the orientation and positioning of both femoral component and tibial component, and also increase the correlation of the rotational axes of the two components.

Comparison of cruciate retaining and PCL sacrificing TKA with respect to medial and lateral gap differences in varus knees after medial release.

We aimed to clarify whether the increase in medial gap after medial release is influenced by the retention or sacrifice of posterior cruciate ligament (PCL) during navigation-assisted total knee arthroplasty. After matched pairs were done according to the equality of preoperative varus deformity and medial collateral laxity, 54 knees of each type were available for this study. In the PCL sacrificing group, the mediolateral gap difference significantly increased in both flexion and extension as the preoperative mechanical axis angle increased whereas in the cruciate retaining group, the mediolateral gap difference did not show this tendency. When preoperative mechanical axis angles were over 10.4° in extension and over 7.7° in flexion, the medial gap showed greater increases in PCL sacrificing groups than in cruciate retaining groups.

Prevention of pseudo-patella baja during total knee arthroplasty.

PURPOSE: Pseudo-patella baja (PPB) is a surgical complication that can arise from total knee arthroplasty and occurs when the patella tendon is not shortened but the level of the femorotibial joint line is elevated. The goal of this study was to assess the performance of a technique specifically designed to prevent the occurrence of PPB and its radiological results. METHODS: Ninety-nine patients undergoing total knee arthroplasty were included. Patients were divided into a non-correction group and a correction group. The correction group were applied an additional metal block in order to reduce the excess resection of the distal femur. To evaluate PPB, the change in the pre- and postoperative joint line was measured using the modified Blackburne-Peel Index (BPI). RESULTS: In the non-correction group, 68 of 74 cases showed an occurrence of PPB (92 %), in the correction group, 6 of 57 cases showed an occurrence of PPB (11 %). The preoperative-modified BPI of the non-correction group was not significantly different from that of the correction group (0.6 ± 0.1 vs. 0.6 ± 0.2). The modified BPI decreased significantly in the non-correction group after TKA (0.6 ± 0.1 vs. 0.2 ± 0.1, p < 0.05). However, the modified BPI did not change significantly in the correction group after TKA (0.6 ± 0.2 vs. 0.6 ± 0.2). CONCLUSION: The comparison of preoperative and postoperative radiological results showed that our intervention maintained the joint line without elevation. We proposed an effective method to prevent various complications due to the joint line elevation that occur in PPB. LEVEL OF EVIDENCE: III.

Reconstruction of a deficient patella in revision total knee arthroplasty: results of a new surgical technique using transcortical wiring.

This study aimed to report the results of a novel surgical technique for the reconstruction of a deficient patella during revision total knee arthroplasty (TKA). Twenty-eight patients (30 knees) with a deficient patella were treated with an onlay-type prosthesis and bone-augmenting procedure, using acrylic bone cement and transcortical wiring. The technique was indicated when the thickness of remnant patella was less than 8mm with variable amounts of the peripheral rim. Mean follow-up period was 36.6months (range, 24 to 55months).The respective mean Knee Society scores for knee and function improved from 34.2 and 23 points, preoperatively to 73.5 and 61 points, at final follow-up. One patient experienced patellar fracture 1week after surgery. There were no complications associated with implanted hardware.

Design modifications of high-flexion TKA do not improve short term clinical and radiographic outcomes.

BACKGROUND: The prosthesis of contemporary total knee arthroplasty (TKA) has been modified to provide a more familiar environment for higher flexion angle of the replaced knee. The design modifications continue based on evidence reported in the literature. However, whether these modifications of the prosthesis design lead to improvements in clinical results needs further investigation. We determined whether the prosthesis modifications based on recent evidence improve clinical and radiographic results following high flexion TKA. METHODS: 524 patients who underwent primary TKA using two different high flexion prostheses were divided to Group 1 (HF-1) using a high flexion prosthesis, group 2 (HF-2) using the more recently devised high flexion prosthesis, which claims to be adopted from evidence proposed in the literature. Clinical outcomes included ranges of motion (ROM), the Knee Society knee and function score (KSKS and KSFS), the Western Ontario and McMaster Universities Arthritis Index (WOMAC) score, radiologic evaluation, and complication related to surgery. RESULTS: No differences in terms of clinical and radiographic results were observed between the groups at the 2 year follow-up. The mean ROM was 123°and 124° in the HF-1 and HF-2 groups, respectively. KSKS were 90 and 89.1, KSFS were 76.6 and 81.8, and total WOMAC scores were 23.1 and 24.9 in the HF-1 and HF- 2 groups. No differences of the incidences of radiolucency on radiographs (1.4% in HF-1, 2.1% in HF-2) and dislocation (1 case in HF-1 only) was observed. CONCLUSIONS: Even if recent modifications in the design of high flexion TKA prosthesis were based on evidence in the literature, they did not provide meaningful improvements in short-term clinical and radiographic outcomes after TKA. Surgeons should consider our findings when choosing a prosthesis for their patients.

Relationship between mechanical axis-derived and anatomic landmark-derived femoral rotation in TKA: a three-dimensional CT study.

We sought to determine the relationship between the mechanical axis-derived and the anatomic landmark-derived femoral rotational axes using three dimensional computed tomographic images of 20 lower extremities. The mechanical axis-derived femoral rotational axis was created on the distal articular surface of the femur using coronal mechanical limb axis and the reconstructed images of the femur. Then, we measured the angular difference between mechanical axis-derived and anatomic landmark-derived femoral rotational axes. The mechanical axis-derived femoral rotational axis was externally rotated with a mean of 2.2° (range, 0 to 4.7°; SD, 1.0) compared with the surgical epicondylar axis. Our findings should be considered to obtain a proper femoral rotational axis in total knee arthroplasty.

Disparate postoperative results in the first and second knees on simultaneous bilateral total knee arthroplasty.

We hypothesized that the circumstances of the two consecutive operations of a simultaneous bilateral total knee arthroplasty (TKA) are different, and could lead to different outcomes of overlapping bilateral TKAs. Both knees of 420 subjects were evaluated in the current study. In the second TKA, there were more incidence rates of outlier in mechanical femoro-tibial angle (16.2% vs. 9.0%), more blood loss (735 vs. 656 mL), and longer operation time (61, 58 minutes respectively), as compared to the first TKA, while no significant differences in clinical outcomes. In conclusion, there were no significant differences in the clinical outcomes even though few distinct outcomes due to different circumstances of the surgery. Awareness of these findings can help the continued success of bilateral TKA in an increasing patient population.

Soft tissue laxity should be considered to achieve a constant polyethylene thickness during total knee arthroplasty.

INTRODUCTION: In total knee arthroplasty (TKA), the gap expansion effect by soft tissue laxity and bone resection amount influence directly on the proper gap size and ideal polyethylene insert thickness. In this study, we hypothesized if bone resection level could be controlled lesser as gap expansion effect resulted in the effects on gap expansion of the collateral release and lax lateral structure, appropriate gap size would be attained without extensive medial soft tissue release even in severe varus deformed knee. The purpose of this study was to show the usefulness of preoperative calculation of soft tissue laxity for determining the appropriate gap size for the targeted PE thickness in TKA. METHODS: The preoperative varus stress view was used to estimate the effect of soft tissue release on extension gap expansion after primary bone resection. The amount of bone resection was determined with a parallel bone resection device used in our institution. Lateral laxity amount was applied into the device. This study was a retrospective review of 850 TKAs [451 with <10º varus deformity of the mechanical femoro-tibial angle (group 1); 399 with ≥10º varus deformity (group 2)] with a minimum follow-up of 1 year. We compared the range of motion (ROM), the knee society score (KSS), and the incidence of surgical complications at postoperative 1 year between the two groups. RESULTS: The mean PE thickness was 10.8 ± 1.1 in group 1 and 10.9 ± 1.1 in group 2. The proportion of patients with appropriate PE thickness (i.e., 10-12 mm) was 97.6 % in group 1 and 97.2 % in group 2. The ROM and KSS did not differ significantly between groups. CONCLUSION: This study showed the usefulness of preoperative calculation of soft tissue laxity for appropriate gap size for targeted polyethylene thickness and possibility to attain constant extension gap regardless of preoperative varus deformity.

Primary total knee arthroplasty in infection sequelae about the native knee.

The aim of this study is to assess the results of primary total knee arthroplasty (TKA) after bone or joint sepsis about the native knee and to analyze the risk factors of periprosthetic infection. Sixty-two patients (62 knees), considered to have prior sepsis history to be resolved, underwent primary TKA and were followed during a mean of 6.1years (range, 2-10.4years). Of the 62 patients, periprosthetic infection occurred in 6 after primary TKA (9.7%). Five of 6 patients grew the same organism as prior infection. The number of prior surgeries undertaken for deep infection was found to be an independent risk factor of periprosthetic infection.

Physiologic bone remodeling in medial aspect of proximal tibia after under-release of medial soft tissue during total knee arthroplasty.

INTRODUCTION: This study was undertaken to investigate the incidence and to identify predictors of physiologic remodeling in the medial aspect of the proximal tibia in varus knees after total knee arthroplasty (TKA). MATERIALS AND METHODS: One hundred and sixty-six consecutive patients (221 knees) who underwent navigation-assisted TKA and were followed for a minimum of 2 years were included. Changes in bone radiolucency in the medial aspect of the proximal tibia on the radiographs were investigated at each follow-up. All information on potential factors affecting medial tibial remodeling were retrieved and classified as being patient-, radiography-, or surgery-related. RESULTS: Radiographic change of bone stock in the medial aspect of the proximal tibia was observed in 18 % of knees (39/221). In all of these cases, this was first detected within 3 months after surgery. During the initial phase to 3 months after surgery, bone stock radiolucency typically increased, but then gradually decreased and after 1 year postoperatively, radiolucency no longer changes with time. Of the 15 variables analyzed, the difference between medial extension gap after bone cutting and prostheses thickness was found to be significantly associated with occurrence of radiographic change of bone stock. CONCLUSION: In some varus knees showing physiologic bone remodeling in the medial aspect of the proximal tibia after TKA, prostheses thickness showed a strong tendency to be larger than the medial extension gap after bone cutting.

Outcomes of long retrograde intramedullary nailing for periprosthetic supracondylar femoral fractures following total knee arthroplasty.

BACKGROUND: The treatment of periprosthetic supracondylar femoral fractures following total knee arthroplasty (TKA) is challenging because of osteopenia and the limited bone available for distal fixation. The purpose of this study was to report the outcomes of periprosthetic supracondylar femoral fractures treated with long retrograde intramedullary nailing. METHODS: We conducted a retrospective review of 25 patients who were treated with a long retrograde intramedullary nail for periprosthetic supracondylar femoral fractures following TKA. Clinical evaluation included range of motion of knee, Knee Society Score (KSS), Western Ontario and McMaster Universities Arthritis (WOMAC) score, and radiologic evaluation including time to union, coronal and sagittal alignment of femoral component, lower limb alignment, and implant loosening. The mean duration of follow-up after the fracture repair was 39 months (range 12-47). RESULTS: All 25 fractures were united with a mean time of 12 weeks (range 8-20). At the last follow-up, the mean knee flexion was 111° (range 60°-130°), the mean KSS was 81.5 (range 50-100), and the mean WOMAC score was 30.2 (range 5-55). Four (16%) of the 25 patients developed malalignment according to Rorabeck and Taylor criteria, but all patients had a knee flexion of more than 90°. Coronal and sagittal alignments of femoral component and lower limb alignment did not differ significantly between before and after the fracture repair. Complications included the loosening or breakage of distal interlocking screws in three patients. No deep infection or prosthesis loosening was detected at the last follow-up. CONCLUSIONS: Surgical treatment of periprosthetic supracondylar femoral fractures following TKA with long retrograde intramedullary nailing resulted in high union rates and encouraging functional outcomes.

Easy identification of mechanical axis during total knee arthroplasty.

PURPOSE: We devised an intraoperatively identifiable mechanical axis (IIMA) as a reference of alignment in total knee arthroplasty (TKA). MATERIALS AND METHODS: Between February 2010 and January 2011, primary TKAs were consecutively performed on 672 patients (1007 knees) using an IIMA as a reference in the coronal plane. RESULTS: The alignment of the lower extremity improved from a mean of 11.4±6.7° (-10.3-34.4°) of varus preop. to 0.7±3.5° (-5.2-8.6°) immediately after surgery. Mean alignment of the femoral component in the coronal plane was 89.3±2.3° (83.4-97.2°) postop. and mean alignment of the tibial component was 90.4±2.2° (85.1-94.2°) postop. CONCLUSION: This study showed that IIMA could be of considerable value as a new guider of alignment that is easily accessible and highly effective during total knee arthroplasty.