Treatment of 50 Deep Infections After Total Knee Arthroplasty.

The prevalence of infections caused by methicillin-resistant organisms has increased, causing difficulty in the treatment of prosthetic joint infection. A multicenter study was performed to review 50 patients with deep infections with or without a resistant organism, such as methicillin-resistant Staphylococcus aureus, at the site of total knee arthroplasty. A group of 13 patients with early deep infections and 4 patients with acute hematogenous infections underwent treatment with debridement, antibiotic therapy, and retention of the prosthesis with revision of the polyethylene insert. Thirty-three patients with late chronic infections were treated with challenging prosthesis retention for prostheses that had not loosened or 2-stage exchange arthroplasty for prostheses that had loosened. Mean duration of follow-up was 4.7±1.8 years. No significant differences in resultant functional knees and mean number of operations were observed between 7 patients with resistant early deep infections and 6 patients with nonresistant early deep infections. However, 24 patients with nonresistant chronic infections showed significant improvement in resultant functional knees (24 of 24; 100%) and fewer mean operations (2.8 times) compared with 9 patients with resistant chronic infections (1 of 9, 11%, and 4.3 times, respectively). The remaining 8 patients with resistant chronic infections (89%) had arthrodesis (3 patients) or underwent above-the-knee amputation (1 patient) or spacer arthroplasty (4 patients). Although patients with resistant early postoperative deep infections showed good results that were similar to those in patients with nonresistant early infections, those with resistant late chronic infections had a significantly inferior success rate compared with those who had nonresistant late chronic infections.

Factors influencing the outcome of deep infection following total knee arthroplasty.

BACKGROUND: Whereas clinical studies have revealed a number of important risk factors for postoperative infection following total knee arthroplasty (TKA), it is unclear which factor influences clinical results. A multicenter study was therefore performed by reviewing 51 patients with deep infection after TKA and seeking for the factors related to clinical outcomes. METHODS: Fifty-one deep infections after TKA were treated from 2000 to 2011 at the multicenter including a university or three arthroplasty centers. Among them, two clinical outcome measures including retention of prosthesis at initial treatment and functional prosthetic knee were assessed for several factors such as age, sex, primary diagnosis, onset time after primary TKA, type of hospital where the primary TKA was performed and the organism's resistance to methicillin using the logistic regression analysis model. RESULTS: Among the factors, type of hospital where the primary TKA was performed and onset time after primary TKA had higher multivariable-adjusted odds ratios (ORs) for retention of primary prosthesis (ORs 35.21 and 11.69, respectively.). The cases which primary surgery were performed in arthroplasty centers had higher multivariable-adjusted ORs for functional prosthetic knee (OR 4.9). Thirty-one infection cases with non-methicillin-resistant organisms were all able to keep functional prosthetic knee after the operation, whereas 13 out of 20 infection cases with methicillin-resistant organisms lost their knee function after the operation. CONCLUSIONS: Onset time after primary TKA, type of hospital where the primary surgery was performed and the organism's resistance to methicillin are important factors influencing the clinical outcomes after infected TKA. LEVEL OF EVIDENCE: Level 3. Retrospective comparative study.

Fibular axes are not a reliable landmark for tibial mechanical axes of osteoarthritic knees that underwent total knee arthroplasty.

PURPOSE: The sagittal fibular axis serves as an intra-operative landmark during conventional total knee arthroplasty (TKA); however, only a few relevant anatomical studies have been published regarding its use as an extramedullary guide. Furthermore, the correlation between the coronal fibular and tibial mechanical axes in osteoarthritic knees has been only reported once. Here, the hypothesis of this study is that the fibula can be a reliable intra-operative landmark, in the sagittal and coronal planes, among patients with osteoarthritis who have undergone TKA. METHODS: Osteoarthritic knees (n = 62) after TKA were evaluated using three-dimensional image-matching software. The angles between the tibial mechanical axis and the fibular shaft axis were measured in the sagittal and coronal planes. Moreover, correlations between the angles and patient-specific factors were evaluated. RESULTS: The mean angle between the tibial mechanical and fibular shaft axes was 2.6° ± 2.3° for posterior inclination in the sagittal plane and 0.9° ± 2.0° for varus inclination in the coronal plane. The percentage of subjects with the fibular shaft axis within 2° of the tibial mechanical axis was 17.7 and 69.3 % in the sagittal and coronal planes, respectively. No patient-specific factors were correlated with the angle between the tibial mechanical and fibular shaft axes. CONCLUSIONS: The angle between the tibial mechanical and fibular shaft axes differed among patients, independent of patient-specific factors, and did not appear to be a reliable intra-operative landmark. Surgeons should use values from individual pre-operative evaluations of the axis as reference for conventional TKA. LEVEL OF EVIDENCE: Case series with no comparison group, Level IV.

Intraoperative platelet-rich plasma does not improve outcomes of total knee arthroplasty.

This randomized controlled study was conducted to assess the effects of platelet-rich plasma (PRP) on outcomes of total knee arthroplasty (TKA). Forty patients who underwent unilateral TKA were evaluated prospectively; 20 received intraoperative PRP and 20 served as control subjects. The results showed no significant differences in reduction of bleeding, range of motion, swelling around the knee joint, muscle power recovery, pain, Knee Society Scores, and Knee Injury and Osteoarthritis Outcome Score between the 2 groups. Additionally, no distinct clinical characteristics were found in patients who received intraoperative PRP. Therefore, we conclude that intraoperative PRP does not improve outcomes of TKA.

Tibial tubercle osteotomy with screw fixation for total knee arthroplasty.

This study investigated the efficacy of tibial tubercle osteotomy (TTO) with screw fixation as part of the surgical treatment of primary complicated total knee arthroplasty (TKA) and revision TKA. From January 2000 to April 2011, 15 patients (15 knees) underwent revision TKA and 20 patients (21 knees) underwent primary TKA. The average patient age was 68.7±8.7 years. Patients underwent follow-up at the authors' institution for an average of 60.6±32.9 months. Comparison of preoperative and postoperative Knee Society Scores and Knee Society Functional Scores showed significant postoperative improvement (P<.05). Moreover, postoperative range of motion of the knee improved from 88.5°±33.8° to 104.3°±18.2° (P<.05). Radiographic assessment showed that the average period to bone union was 10.8±5 weeks (range, 5-28 weeks), the average length of the bone fragment was 59.4±5.9 mm, the average width at the proximal end was 18.9±2.9 mm, and the average thickness at the proximal end of the osteotomy was 10.3±1.2 mm. Tibial tubercle osteotomy provided wide exposure for TKA while protecting the extensor mechanism. Solid bone-to-bone fixation was achieved using TTO with 2 screws, and although the overall complication rate was 8.3%, none of the complications were associated with TTO itself. It is recommended that the bone fragment be 60 mm long, 20 mm wide, and 10 mm thick at the proximal end. Appropriate size of the osteotomized bone and solid screw fixation are essential to prevent complications during this procedure.

Satisfactory results at 8 years mean follow-up after ADVANCE® medial-pivot total knee arthroplasty.

BACKGROUND: Although good overall results have been reported with TKA, certain problems and limitations remain, primarily due to postoperative differences in joint kinematics, when compared with the normal knee. ADVANCE® Medial-Pivot TKA involves replicating the medial pivoting behavior observed in normal knees. Here, we aimed to investigate the clinical and radiological results and complications of TKA using this implant, at mid-term follow-up. METHODS: From January 2001 to March 2012, we retrospectively selected 76 patients (85 knees; mean age at operation, 70.2±8.1 years; range, 51-88 years) with a mean follow-up period of 93.1±14.3 months (range, 72-132 months). Indications for TKA included primary degenerative osteoarthritis (60 knees), rheumatoid arthritis (22 knees), osteonecrosis (two knees), and osteoarthritis following high tibial osteotomy (one knee). The clinical and radiographic results were evaluated. RESULTS: Kaplan-Meier survivorship analysis indicated a success rate of 98.3% (95% confidence interval, 96.6-99.9%). Comparison of pre- and postoperative knee extension angles and ranges of motion showed significant improvement postoperatively, in both the Knee Society Scores (KSS) and Knee Society Functional Scores (KSFS) (p<0.05). In one case, radiographic assessment indicated implant loosening due to infection; however, despite this complication, significant improvement of postoperative varus or valgus deformity angles were noted in all cases (p<0.05). CONCLUSION: Patients undergoing ADVANCE® Medial-Pivot TKA achieved excellent clinical and radiographic results without any implant-related failures at mid-term follow-up. LEVEL OF EVIDENCE: Level IV.

Partial restoration of knee kinematics in severe valgus deformity using the medial-pivot total knee arthroplasty.

PURPOSE: The objectives of the study were to examine knee kinematics in knees with severe valgus deformities and to compare pre- and post-operative knee kinematics for the same subjects implanted with medial-pivot total knee arthroplasty (TKA). METHODS: Seven subjects with severe valgus deformities due to osteoarthritis (OA) or rheumatoid arthritis (RA) were enrolled in the prospective study. Prior to TKA, three-dimensional (3D) kinematics were assessed by 3D to 2D registration technique using the image matching software 'Knee Motion', under in vivo, weight-bearing conditions. Postoperatively, each subject again performed the same motion under fluoroscopic surveillance. RESULTS: Preoperative kinematics demonstrated external rotation of tibias from extension to flexion, and small posterior femoral translations dominated in the medial condyle associated with anterior slides during partial range of motion. Postoperatively, these non-physiological tibial rotations were restored, and most subjects exhibited small internal rotations of tibias. On average, preoperative tibial internal rotation was -4.7° ± 7.6° from full extension to maximum flexion, and the angle was 4.8° ± 3.1° postoperatively (p = 0.01). In addition, small amounts of posterior translation of the lateral condyle and anterior translation of the medial condyle were confirmed in most subjects postoperatively. CONCLUSIONS: The study showed that the preoperative kinematic pattern established in severe valgus deformity was different from the physiological knee pattern. In addition, post-operative results suggest that the non-physiological kinematics were partially restored after TKA by using the prosthesis design even in the absence of the posterior cruciate ligament (PCL) and the cam-post mechanism.

No difference between double-high insert and medial-pivot insert in TKA.

PURPOSE: To compare the clinical midterm results in ADVANCE total knee arthroplasty (TKA) with double-high (DH) insert, with same type implant with medial-pivot (MP) insert. METHOD: Forty ADVANCE TKAs were randomly divided into two groups, and two different design insert, DH insert, and MP insert were used in each group. At midterm, 4-5 years after surgery, Knee Society Scores (KSS), Knee Society Functional Scores (KSFS), range of motion (ROM), and UCLA activity score were assessed and reported in this study. RESULTS: Midterm clinical results, including ROM and KSS, were comparable with both groups. KSFS and UCLA activity score were equally good between the two groups. CONCLUSION: The results in this study revealed equally good clinical results with these types of implants at midterm follow-up, although the significant better ROM has not achieved by using DH insert. We concluded that the selection of inserts only could not achieve the better clinical results, including ROM and activity level in this study. LEVEL OF EVIDENCE: Therapeutic studies-investigating the results of treatment, Level II.

Evaluation of patellofemoral joint in ADVANCE Medial-pivot total knee arthroplasty.

PURPOSE: ADVANCE Medial Pivot (MP) (Wright Medical) total knee arthroplasty (TKA) was established to replicate normal tibio-femoral knee joint kinematics, however, its influence on the patello-femoral (PF) joint is unclear. The purpose in this study was to assess the PF joint conditions in Advance MP TKA, via radiography and three-dimensional image-matching software. METHODS: Ten subjects with osteoarthritis were treated with the ADVANCE MP TKA. Pre-operatively and one month after surgery, skyline views at 30, 60, and 90° of flexion were taken, and patella shift and tilt were measured. With 2D-3D registration techniques using software, implant orientations were matched with the pre-operative CT and changes in the anterior part of the femoral prosthesis, condylar twist angle (CTA) for femoral rotation, and tibial rotation were evaluated. The relationships between morphological and rotational changes were evaluated. RESULTS: There were significant differences in patella tilt at 60° and patella shift at all angles between pre- and post-operation (p < 0.05). No correlation was found between morphological changes in the anterior femur with patella tilt and shift. A positive correlation between postoperative CTA and patella shift at 90° was found (p < 0.05); however, no correlation was found between rotational alignment of the tibial component and patella tilt and shift. CONCLUSIONS: ADVANCE MP TKA changed patello-femoral joint kinematics, compared to that found before surgery. The kinematic features were mainly due to the design concepts for tibio-femoral joint motion, indicating the difficulty to reproduce normal patello-femoral joint kinematics after TKA.

Long-term subjective outcomes of computer-assisted total knee arthroplasty.

PURPOSE: This study aimed to clarify the results of computer-assisted total knee arthroplasty (TKA) after ten years using patient-derived scores. METHODS: Thirty posterior-stabilised total knee prostheses implanted using a computed tomography-free navigation system were compared with 30 matched total knee prostheses of the same type implanted using a conventional, manual technique. At an average of ten years after surgery, we investigated patient-reported outcomes using the Knee Society's new scoring system. The results of 27 patients (14 patients in the navigation group and 13 patients in the manual group) were assessed in this study. RESULTS: There was no significant difference between the navigation and manual groups for any section of the questionnaire, which consisted of symptoms, patient satisfaction, patient expectation, walking/standing, standard activities, advanced activities, and discretionary activities. CONCLUSION: After long-term follow-up, we found no subjective advantages of using a navigation system for patients who undergo TKA though the absolute number of patients was very small. Additional extensive studies are required to validate our result.

Neurogenic bladder associated with pure cervical spondylotic myelopathy: clinical characteristics and recovery after surgery.

STUDY DESIGN: Retrospective study. OBJECTIVE: To examine the prevalence of lower urinary tract symptoms (LUTS) and neurogenic bladder (NB), and surgical outcomes in pure cervical spondylotic myelopathy. SUMMARY OF BACKGROUND DATA: The inclusion of various types of cervical diseases, NB, and no obvious definition of NB provided the wide range of NB prevalence frequency among previous reports. METHODS: Of the 220 operated patients with cervical myelopathy, 54 were selected by excluding other cervical and/or concomitant diseases contributing to LUTS. All patients with LUTS were referred to urologists and recommended to undergo urodynamic study (UDS). The presence of NB was judged by abnormal findings of UDS according to the most recent criteria and a congruity between LUTS and the course of cervical myelopathy. Patients were divided into 4 groups: no symptoms, positive symptoms without UDS examination, positive symptoms with positive NB, and positive symptoms with negative NB. Evaluation scores were compared among the groups before and after surgery. RESULTS: There were no particular LUTS in NB patients. Prevalence of LUTS was 53.7% and that of NB was at least 20.4% in the patients with pure cervical spondylotic myelopathy. The scores of all 4 groups improved after surgery (P < 0.05); however, the recovery rate of NB group (47.1%) was the worst among the groups (no-symptoms group, 69.3%; negative-NB group, 53.5%; and positive symptoms without UDS group, 57.1%). Preoperative part scores showed no difference among the groups, whereas NB group demonstrated lower scores in finger and lower extremity postoperatively. A post hoc analysis confirmed a significantly poorer recovery rate related to the NB group only in the lower extremities. CONCLUSION: This study is the first to describe the prevalence of LUTS and NB according to the most recent criteria in patients with pure cervical spondylotic myelopathy, which demonstrated that neurological functions in NB patients may recover; however, the extent will be limited to two-thirds of those in patients with no-NB; moreover, the remaining symptoms derive from poor lower limb function.

In vivo comparisons of patellofemoral kinematics before and after ADVANCE Medial-Pivot total knee arthroplasty.

PURPOSE: ADVANCE Medial-Pivot (MP) (Wright Medical Technology, Arlington, TN, USA) total knee arthroplasty (TKA) was developed to replicate normal tibiofemoral knee joint kinematics, allowing medial-pivot knee motion. The design concept of the prosthesis is unique; therefore, the influence on the patellofemoral knee joint remains unclear at present. The purpose of this study was to determine the in vivo patellofemoral kinematics with ADVANCE MP TKA and compare them with the pre-operative conditions. METHODS: ADVANCE MP TKA was performed in ten subjects with osteoarthritis (OA). At before and one month after surgery, lateral radiographs with weight-bearing at maximum extension, 30, 60 and 90° were taken, and patella flexion angle (PF), tibiopatellar angle (TP) and estimated patellofemoral contact point (PC) were evaluated, according to a previously reported method. RESULTS: In PF and TP, there was no statistically significant change between pre-operative and postoperative values. Pre-operative PC reached its peak at 90°; however, its peak was at 60° at one month after surgery. Postoperative PC at maximum extension was significantly higher compared to before surgery. CONCLUSIONS: The results in this study indicated that ADVANCE MP TKA changed patellofemoral joint kinematics compared to before surgery. Early postoperative evaluation is the limitation of this study; however, we consider that the results in this study might be one of the keys to resolving the kinematic features of this prosthesis, helping clinicians to comprehend this prosthesis.

Grade three disc degeneration is a critical stage for anterior spondylolisthesis in lumbar spine.

INTRODUCTION: Little is known about when and how progressive spondylolisthesis occurs. In this report segmental motion related to age and disc degeneration at L4/5 disc was investigated. MATERIALS AND METHODS: 637 patients with low back and/or leg pain underwent radiologic and MRI examinations simultaneously. Because 190 patients with conditions which might impede accurate measurement were excluded, 447 patients, comprising 268 men and 179 women, were included; age range, was 10-86 (mean: 53) years. Three radiologic parameters slip in neutral position (mm), sagittal translation (mm), and segmental angulation (degrees) were examined at the L4/5 segment. On T2-weighted MRI, severity of disc degeneration at L4/5 was classified by Pfirrmann's criteria, grade 1-5. RESULTS: Results showed stage of disc degeneration that progressed according to aging with significant differences except for between grades 4 and 5. Amount of anterior slip was small among grades 1 to 3; however, it greatly increased between grades 3 and 4 and between grades 4 and 5, suggesting that grade 3 disc degeneration has a potential risk of future progression of anterior slip. This finding may also suggest that once significant slip occurs, it will progress to the final grade. Furthermore, the grade 3 degeneration group exhibited large amounts of motion in both angulation and translation, suggesting it was the most unstable group. CONCLUSION: Our results with radiography and MRI indicate that grade 3 disc degeneration is a critical stage for the progression of lumbar spondylolisthesis at L4/5 segment.

Differing prosthetic alignment and femoral component sizing between 2 computer-assisted CT-free navigation systems in TKA.

We adopted a new computed tomography (CT)-free navigation system and noticed that, compared with our previous experience using a different type of CT-free navigation system that led to oversized and extended femoral component implanted compared with the conventional implantation, the femoral components were similarly implanted to the conventional method. The purpose of our study was to compare alignment and sizing with these 2 image-free systems and determine whether the method to determine the knee center could explain these differences in femoral component size and flexion of the component. Thirty posterior-stabilized total knee prostheses were implanted using the OrthoPilot CT-free navigation system (B. Braun-Aesculap, Tuttlingen, Germany). Postoperative coronal and sagittal long leg radiographs were retrospectively compared with those of a control group of 30 matched-paired total knee prostheses previously implanted using the VectorVision CT-free navigation system (Depuy-BrainLAB, Heimstetten, Germany). Sagittal alignment of the femoral component in the VectorVision group showed a significantly extended position compared with that in the OrthoPilot group. In addition, the size of the selected femoral component in the Vector Vision group was significantly larger than that in the OrthoPilot group. This discrepancy may be explained by the differences in the determined knee center, which influenced the postoperative implantation. When surgeons select a navigation system, the characteristics of each system should be taken into consideration.

Intimate relationship between instability and degenerative signs at L4/5 segment examined by flexion-extension radiography.

Relationship between lumbar disc degeneration and segmental instability has remained controversial. Using instability factors that found close relations with symptoms in flexion-extension radiographic study, their relationship with degenerative findings was examined. More than (≥) 3 mm slip in neutral position (SN), ≥3 mm translation (ST), and ≥10° angulation (SA) at L4/5 segment were defined as instability factors and were applied on 447 patients who had low back and/or leg pain and satisfied inclusion criteria for accurate measurements. Radiologic findings for degeneration were disc height including three groups with different disc heights divided by mean ± 1 standard deviation, length of the anterior spur formation, presence of vacuum phenomenon, and endplate sclerosis. As results, group with SN factor was the oldest in age and the lowest in disc height; in contrast, group with SA was the youngest in age and the highest in disc height. The group with ST showed a mid-standing position in both age and disc height. These findings indicate that instability factors are intimately related to age and disc height. The three different disc height groups showed more anterior slip according to the progression of the disc height diminution. Presence of the apparent spur formation and/or vacuum phenomenon had an intimate relationship with the ST factor. Disc height was the most important in the examined parameters and showed an intimate relationship with age and instability factors. Although the etiology is still unknown, clinical common knowledge, that a diminution of disc height with progressive degeneration had a close relation with anterior vertebral slippage, was firstly confirmed. This study allows comprehensive understanding of segmental instability and is useful for considering surgical indications.

Intra-articular injection of tranexamic acid reduces not only blood loss but also knee joint swelling after total knee arthroplasty.

PURPOSE: This is a randomised controlled trial to examine whether intra-articular injection of tranexamic acid (TXA) decreases blood loss, as well as reducing leg swelling after total knee arthroplasty (TKA). METHODS: We performed 100 TKA in osteoarthritis patients. At closure, a total of 2,000 mg/20 ml TXA was injected into the knee joint through a closed suction drain (TXA group). For the control group, the same volume of physiological saline was injected. The pre-operative condition of the patients, post-operative haemoglobin (Hb) levels, discharge volumes from drain, D-dimer and needs for transfusion were compared between these two groups. Furthermore, leg diameters (thigh, suprapatellar portion and calf girth) were measured pre- and post-operatively to investigate whether TXA has an influence on leg swelling after surgery. RESULTS: The results revealed that post-operative decrease in Hb level was significantly reduced in the TXA group. Furthermore, knee joint swelling after operation was significantly suppressed in the TXA group compared to the control group. CONCLUSIONS: The results revealed intra-articular administration of TXA decreased not only blood loss, but also knee joint swelling after TKA.

Mid-term outcomes of computer-assisted total knee arthroplasty.

PURPOSE: The aim of this study is to investigate the clinical results of total knee arthroplasty (TKA) using a navigation system after a minimum of 5 years. METHOD: Thirty cases of posterior-stabilized, TKA-implanted using a computed tomography-free navigation system were compared with 30 cases having matched TKA of the same type implanted via a classical, manual technique. At mid term, a minimum of 5 years after surgery, Knee Society scores (KSSs), Knee Society Functional scores (KSFSs), range of motion (ROM), and radiographic results of 27 patients in each group were assessed and reported in this study. RESULTS: The accuracy of the implantations in relation to the coronal mechanical axis in the navigation group was superior to that of the manual group (P < 0.01). The femoral rotational profile revealed the prosthesis in the navigation group that was implanted with significantly less internal rotation than the manual group. Mid-term 5-year clinical results, including ROMs and KSSs, were significantly better in the navigation group (P < 0.01). KSFSs were equally good in both the groups. CONCLUSION: Better alignment and similarity of good clinical results at mid-term follow up may provide patients who receive navigation TKA with long-term endurance of their implants. Further studies on longer-term outcomes and functional improvements are required to validate these possibilities.

Thermal necrosis after simultaneous tibial osteotomy and total knee arthroplasty using press-fit extension-stem.

One-staged tibial corrective osteotomy and total knee arthroplasty is a challenging but effective treatment for arthritic knees with extra-articular deformity. Although osteocutaneous thermal necrosis is accepted as a complication of intramedullary reamed nailing following long bone fractures, only 15 cases have been reported in the English literature at present. This report illustrates a rare case of thermal necrosis in a patient undergoing tibial corrective osteotomy coincident with long-stemmed total knee arthroplasty. Excessive reaming with a machine reamer is hypothesized as the cause of this serious complication. In this report, we highlight this rare but serious complication after long-stemmed total knee arthroplasty.

In vivo comparison of knee kinematics before and after high-flexion posterior cruciate-retaining total knee arthroplasty.

The objectives of this study were to compare preoperative and postoperative knee kinematics for subjects implanted with flexion-enhanced posterior cruciate-retaining total knee arthroplasty during deep flexion and to examine flexion performance of the prosthesis design. Three-dimensional kinematics was analyzed by fluoroscopic examinations of subjects using a single-plane model-image registration technique. Preoperatively, knee kinematics demonstrated small posterior femoral translation and limited axial rotation. These motions differed significantly from patterns previously reported for normal knees. Postoperatively, flexion performance was maintained, averaging 130 degrees , and kinematic patterns were similar to preoperative patterns. Although total knee arthroplasty can reduce pain and maintain functional performance, it appears that the characteristics of varus arthritic knee mechanics persist after arthroplasty.

Soft tissue balance measurement in posterior-stabilized total knee arthroplasty with a navigation system.

Using a tensor for total knee arthroplasty (TKA) that is designed to facilitate soft tissue balance measurements with a reduced patello-femoral joint, we intraoperatively measured the joint gap and ligament balance of 30 osteoarthritic knees at extension and 90 degrees flexion, with the patella both everted and reduced, while performing primary posterior-stabilized TKA. At the same time, we performed the same measurements with a navigation system and identified correlations between this system and the tensor. Specifically, the R(2) values obtained with the knee in extension and 90 degrees flexion were higher with the patella reduced than with the patella everted. We thereby suggest that the navigation system we describe is reliable for obtaining accurate measurements of soft tissue balancing with the patella reduced.