Radiographic analysis of a hand-held surgical navigation system for tibial resection in total knee arthroplasty

Tibial intramedullary or extramedullary alignment guides have not been shown to be highly accurate in performing the tibial resection in total knee arthroplasty (TKA). Since May 2010, a total of 42 knees underwent a TKA using a hand-held, accelerometer-based surgical navigation system for performing the tibial resection (KneeAlign; OrthAlign Inc, Aliso Viejo, Calif). Postoperative standing anteroposterior hip-to-ankle and lateral knee-to-ankle radiographs demonstrated that 97.6% of the tibial components were placed within 90° ± 2° to the mechanical axis in the coronal plane, and 96.2% of the components were placed within 3° ± 2° to the mechanical axis in the sagittal plane. The KneeAlign greatly improves the accuracy of tibial component alignment in TKA.     

Computer-assisted navigation of total knee arthroplasty for osteoarthritis in a patient with severe posttraumatic femoral deformity

In the setting of extraarticular deformities of the knee, total knee arthroplasty (TKA) is difficult, as anatomical abnormalities obstruct identification of alignment landmarks and may preclude the use of traditional instrumentation. The long-term clinical value of computer assistance for TKA is a point of ongoing controversy. Few reports describe the use of computer-assisted orthopedic surgery as a method to decrease alignment outliers in TKA with associated posttraumatic deformities. In this report, a 70-year-old woman who had a severe distal femoral deformity from a previous open fracture underwent computer-assisted TKA for osteoarthritis. The use of a computer-assisted navigation system achieved a high degree of accuracy relative to the desired target alignment and led to improved function in a patient in which standard instrumentation was not feasible.     

Experience with computer-assisted navigation for total knee arthroplasty in a community setting

This study analyzed the initial experience with computer-assisted navigation for total knee arthroplasty (TKA) in a community hospital. One hundred TKAs performed with a navigation system were compared with 100 performed conventionally. Component alignment results, measured by computed tomography, were grouped as good, fair, poor, or extremely poor, based on deviation from the surgical goal. More navigated knees were classified as good (sagittal, 78%-93%; coronal, 98%; axial, 78%-85%) compared with conventional (sagittal, 47%-64%; coronal, 91%; axial, 89%-90%). Outliers were reduced both in number and severity with navigation. Additional time required to navigate diminished with experience, although improved component alignment was observed from the initial cases. Navigation resulted in improved alignment, with minimal time cost, and is a useful tool for TKA for the community surgeon.     

Periprosthetic femoral supracondylar fracture after total knee arthroplasty with navigation system

We report 1 patient with a supracondylar periprosthetic fracture 1 month after computer-assisted total knee arthroplasty. The fracture line extended from previous anchoring pinholes into the supracondyle area. Intramedullary nailing of the left femur was performed under close reduction. The possible complication of pinhole fracture to total knee arthroplasty with navigation system should be kept in mind.     

The use of navigation in total knee arthroplasty for patients with extra-articular deformity

Computer-assisted navigation for total knee arthroplasty provides high technology instrumentation that may improve the technique for restoring the normal lower limb mechanical axis. This study evaluated the use of computer-assisted navigation in 7 patients (9 total knee arthroplasties) with a radiographic femoral extra-articular deformity. Postoperatively, the mechanical axis deviated medially by a mean of 1.3 degrees +/- 0.9 degrees (range, -0.2 degrees to 2.5 degrees ). Early patient outcomes showed an increase in the average preoperative to postoperative Knee Society Scores (from 62 to 92, P < .05), function scores (from 52 to 83, P < .05), and range of motion (from 4 degrees -74 degrees to 0.6 degrees -98 degrees , P < .05). These results support the use of computer-assisted navigation as effective high technology instrumentation in recreating an acceptable mechanical axis in patients with distorted anatomical landmarks.     

Comparison of computer-assisted navigation and conventional instrumentation for bilateral total knee arthroplasty

This prospective study analyzed computer-assisted surgery (CAS) navigation and conventional instrumentation in bilateral total knee arthroplasty. Sixty patients underwent CAS navigation in 1 knee and conventional instrumentation in the contralateral knee randomly. The target zone resided in the reconstructed mechanical axis within a range of 3 degrees varus or valgus. The reconstructed mechanical axes in the CAS navigation group were significantly closer to planned axes than those in the conventional group. Average blood loss in the CAS navigation group was lower, whereas mean tourniquet time was longer than in the conventional group. No surgery-related complications existed in either group. The results indicate that, despite longer operative time, CAS navigation total knee arthroplasty is a safe procedure and outperforms conventional technique in accuracy of leg axes.     

Accelerometer-based,hand-held navigation for improved knee alignment in total knee arthroplasty: An observational study

BackgroundMalalignment in total knee arthroplasty has been associated with poor implant longevity and clinical outcomes. The aim of this study was to investigate the accuracy of accelerometer-based navigation in restoring the mechanical axis.Methods106 primary total knee arthroplasties performed during February 2016 to September 2017 at a tertiary care centre in India were enrolled in this observational study. We noted the intra-op tourniquet time. Two separate blinded observers measured the preoperative mechanical axis and the post operative radiological results (mechanical axis, coronal and sagittal alignment of femoral and tibial components) and the mean value was taken as final data. Interclass correlation was done to look for variability between the two observers.ResultsThe mean pre operative mechanical axis was 13.74 ± 10.44. The mean tourniquet time was 53.14 ± 7.42 min 91.5% (96/106) knees were within ±3° of neutral mechanical axis with a mean of 1.00° ± 2.68°. The femoral and tibial components with coronal alignment within ±3° perpendicular to the mechanical axis were 93.39% (99/106) and 89.62% (95/106) respectively. In the sagittal plane 89.62% of the femoral components and 87.73% of the tibial components were within ±3° perpendicular to the axis of tibia.ConclusionThe Accelerometer based portable navigation system effectively reduces the coronal and sagittal alignment outliers in total knee arthroplasty and has no role in rotational alignment of components.     

CT扫描确定全膝关节置换股骨假体旋转力线的研究

目的探讨术前CT扫描对全膝关节置换(TKA)中股骨假体旋转力线精确确定的作用。方法将200例(252膝)TKA患者随机分为两组:①经验组(64例):TKA术中根据术者触摸外科股骨上髁轴线联合Whi-teside线联合确定股骨假体外旋角度;②CT扫描组(136例):术前CT扫描确定股骨后髁角,术中采用可调外旋定位器复制CT确定的外旋角度,其余TKA手术操作相同。两组术后均行CT扫描确定股骨假体旋转不良角度并对其绝对值进行比较。结果经验组TKA术后股骨假体旋转不良角度为2.8°±0.14°,CT扫描组为1.2°±0.04°,两组比较差异有统计学意义(t=4.18,P<0.01)。经验组股骨假体旋转不良率为32.1%,CT扫描组为18.5%,两组比较差异有统计学意义(χ2=17.47,P<0.01)。结论术前CT扫描确定股骨远端后髁角可以有效提高TKA手术股骨假体旋转力线,方法简单、有效、重复性良好。     

Sagittal plane positioning of the femoral component in total knee arthroplasty

The authors evaluated 623 total knee arthroplasties to determine the relationship between sagittal plane position of the femoral component and the final range of motion of the prosthetic knee. Two different prostheses were evaluated (Posterior Cruciate Condylar and A.G.C.) radiographically and functionally. Variation in sagittal plane position ranged from 20 degrees flexion to 20 degrees extension. No correlation between the sagittal plane position of the femoral component in either prosthesis and the final knee range of motion could be found. Sagittal plane femoral component position in the prostheses studied did not affect final range of motion when component position was between 20 degrees flexion and 20 degrees of extension.     

Osteolysis of the distal femur after total knee arthroplasty

An 11.1% incidence of femoral osteolysis (30 cases in 28 patients) was identified in a series of 271 primary total knee arthroplasties. Two minimally constrained total knee designs (Synatomic [Depuy, Warsaw, IN] and Porous-Coated Anatomic [PCA, Howmedica, Rutherford, NJ]) were used in this patient population. Femoral osteolysis was observed in 26 Synatomic and 4 PCA knees. The average follow-up period was 52 months (range, 24–96 months). Osteolytic lesions were identified radiographically, adjacent to the nonporous-coated (smooth) regions of the anterior and posterior flanges of the Synatomic and PCA femoral components. The average time to the diagnosis of femoral osteolysis was 31 months (range, 7–96 months). The average patient age at the time of primary total knee arthroplasty was 63 years (range, 43–83 years) and the average weight was 180 lb. (range, 107–278 lb.). Sixteen of the 30 cases were in men. All of the cases with femoral osteolysis had cementless implantation. Tissue specimens were obtained from the 18 cases requiring revision. Implants remained in situ an average of 66 months (range, 15–96 months) prior to revision. In 16 of the 18 cases revised, the femoral component was clinically and radiographically stable. Six of 18 cases were revised for severe osteolysis. The remaining 12 cases were revised for failed metal-backed patellae, failed cementless tibial fixation, or advanced polyethylene wear. Wear of the thin tibial inserts and patellar components were the two sources of particulate polyethylene. Polyethylene debris was observed in all tissue specimens. In cases with failed metal-backed patellae or impingement of the tibial locking pin-and-clip, fine metallic debris was also noted in tissue specimens. Microscopic evaluation of the osteolytic tissue revealed a florid histiocytic response with occasional giant cells. Intracellular submicron particulate polyethylene was identified with polarized light microscopy and oil-red-O staining techniques. In the study population, statistically significant factors associated with femoral osteolysis included male gender (P < .05), younger age (P < .05), increased patient weight (P < .05), positive tibial osteolysis (P < .001), osteoarthritis (P < .07), and length of time in situ (P < .001). In addition, patients with a Synatomic prosthesis were at increased risk for osteolysis compared to patients with a PCA device (P < .02). The authors postulate that histiocytic granuloma gained access to the proximal femur primarily via the unbonded interface between the smooth metal and bone.     

Computer-assisted fluoroscopic navigation system for removal of distal femoral bone cement in revision total hip arthroplasty

Removal of the femoral bone cement in revision total hip arthroplasty with a high-powered drill or burr potentially has a risk of damage to the bone, resulting in perforation and fracture of the femur. Recently, we have used a computer-assisted fluoroscopic navigation system for the revision of cemented total hip arthroplasty with a high-powered burr and completely removed the distal femoral bone cement with no complications in 6 cases. Thus, a computer-assisted fluoroscopic navigation system is a useful tool for the improvement of the surgical technique in revision total hip arthroplasty.     

微创膝关节单髁置换术股骨髓内定位与髓外定位假体位置的影像学比较

[目的]通过对膝关节单髁置换术股骨假体的力线测量,评价股骨髓外定位法指导假体放置的有效性.[方法]回顾性分析2007年5月～2010年5月采用微创单髁置换术治疗膝关节内侧间室骨性关节炎的患者73例(80膝),其中股骨髓内定位组(intramedullary alignment guide,IM) 54例(56膝),男23例(23膝),女31例(33膝);股骨髓外定位组(extramedullary alignment guide,EM)19例(24膝),男9例(10膝),女10例(14膝).测量术后即刻股骨假体内翻/外翻和屈/伸力线.[结果]IM组股骨假体内翻/外翻力线为0.59°内翻±3.98°,EM组股骨假体力线平均为0.81°外翻±3.30°,P=0.235 2.IM组股骨假体屈/伸力线为0.70°伸直±3.89°,EM组股骨假体力线为1.12°伸直±3.43°,P=0.564 3.[结论]微创膝关节单髁置换术股骨髓内定位可取得与髓外定位法相同优良的股骨假体力线.     

Computer-assisted navigation for cruciate-retaining total knee arthroplasty in patients with advanced valgus arthritic knees

BackgroundThe valgus arthritic knee is a complex deformity involving both soft tissue and bony problems that significantly affect the positioning of the components for, and decrease the accuracy of, reconstructed alignment in total knee arthroplasty (TKA). The unique bony deformity and soft tissue problem makes the use of conventional mechanical instrumentation difficult and leads to unsatisfactory results.PurposeThe purpose of this study was to investigate the effect of computer-assisted navigation for TKA on the postoperative mechanical axis, component alignment, and functional outcomes in the arthritic knee with genu valgus deformity.MethodsFrom January 2003 to August 2009, 24 patients (24 knees) with advanced valgus knee arthritis who underwent computer-assisted navigation for cruciate-retaining TKA were retrospectively reviewed. The accuracy of the postoperative mechanical axis and component alignment, and functional outcomes were assessed.ResultsThe mean postoperative mechanical axis was 180.2° (range, 178.1–182.5°). All patients achieved the targeted goal of a leg axis within 3° of the neutral axis. The joint line was not substantially elevated. No patient required conversion to a constrained component to achieve stability. At a mean follow-up of 45.5 months, the Hospital for Special Surgery (HSS) knee score improved from a mean preoperative score of 55.6 to 92.8 postoperatively. The International Knee Society (IKS) clinical score improved from 42.2 to 95.9. The IKS for pain improved from 15.4 to 47.1, and the IKS knee function score improved from 35.8 to 95.4.ConclusionComputer-assisted navigation for TKA is a useful alternative technique for advanced valgus knee arthritis where accurate restoration of the joint line, proper alignment of the limb and prosthetic components, and meticulous soft tissue balancing may be challenging because of bony deformities and soft tissue contractures.     

Three-dimensional analysis of computed tomography-based navigation system for total knee arthroplasty: the accuracy of computed tomography-based navigation system

We evaluated the postoperative alignment of 37 primary total knee arthroplasties performed using a computed tomography–based navigation system (Vector Vision Knee 1.5; Brain Lab, Germany) with a new 3-dimensional analysis. The mean coronal femoral angle was 89.0° ± 1.4° (85.5°-92.8°), and the coronal tibial component was 89.2° ± 1.0° (87.4°-91.6°). The hip-knee-ankle angle was observed to be 178.2° ± 1.5° (173.9°-181.8°). The external rotational alignment of the femoral component relative to the surgical epicondylar axis was −0.5° ± 1.7° (−3.2° to 3.4°). The results demonstrated that a computed tomography–based navigation system provided a reasonably satisfactory component alignment. The discrepancy between the 2-dimensional and 3-dimensional evaluations was 1.0° ± 0.9° (0.1°-3.4°). Three-dimensional analysis is necessary to evaluate the accuracy of the navigation system.     

Alignment of computer-assisted total knee arthroplasty in patients with altered hip center

This study aimed to determine limb and component alignment after computer-assisted total knee arthroplasty in 30 patients (32 limbs) with an altered hip center due to a prior hip implant or deformed femoral head. There were no outliers greater than ±3° in the postoperative coronal alignment of the limb and the femoral component in relation to the altered hip center. Two limbs (8%) were more than ±3° for coronal alignment of the femoral component in relation to the anatomical hip center and 96% of limbs had less than 2° deviation in relation to the altered hip center. Computer-navigated total knee arthroplasty results in accurate restoration of lower limb and component alignment in patients with prior hip implants or deformed femoral heads where accurate restoration of alignment may be challenging due to altered hip center.     

Comparison of limb and component alignment using computer-assisted navigation versus image intensifier-guided conventional total knee arthroplasty: a prospective, randomized, single-surgeon study of 467 knees

Total knee arthroplasty was performed in 282 knees with image-free navigation (group A) and in 185 with optimized conventional technique (group B). Mean postoperative mechanical axis of the limb was 179.7 degrees in group A and 179.1 degrees in group B (P < .002). There was a higher percentage of knees in group A that had restoration of mechanical axis to +/-1 degrees, +/-2 degrees, and +/-3 degrees of neutral (P < .0001). There were 9.2% outliers (+/-3 degrees) in group A and 21.6% outliers in group B (P < .0001). For knees exceeding 20 degrees varus, there was no significant difference between the mean mechanical axes in the 2 groups. Both components were aligned within 3 degrees of neutral in 90.8% of the knees in group A and 76.2% of the knees in group B (P < .0001).     

Stress fractures of the femoral neck following total knee arthroplasty

The author reviews the literature concerning stress fractures of the femoral neck following total knee arthroplasty and presents two additional cases. These fractures are rare and are frequently missed initially. Awareness of the condition may help to make early diagnosis.     

Intraoperative passive knee kinematics during total knee arthroplasty surgery

Surgical navigation systems for total knee arthroplasty (TKA) surgery are capable of capturing passive three‐dimensional (3D) angular joint movement patterns intraoperatively. Improved understanding of patient‐specific knee kinematic changes between pre and post‐implant states and their relationship with post‐operative function may be important in optimizing TKA outcomes. However, a comprehensive characterization of the variability among patients has yet to be investigated. The objective of this study was to characterize the variability within frontal plane joint movement patterns intraoperatively during a passive knee flexion exercise. Three hundred and forty patients with severe knee osteoarthritis (OA) received a primary TKA using a navigation system. Passive kinematics were captured prior to (pre‐implant), and after prosthesis insertion (post‐implant). Principal component analysis (PCA) was used to capture characteristic patterns of knee angle kinematics among patients, to identify potential patient subgroups based on these patterns, and to examine the subgroup‐specific changes in these patterns between pre‐ and post‐implant states. The first four extracted patterns explained 99.9% of the diversity within the frontal plane angle patterns among the patients. Post‐implant, the magnitude of the frontal plane angle shifted toward a neutral mechanical axis in all phenotypes, yet subtle pattern (shape of curvature) features of the pre‐implant state persisted. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:1611–1619, 2015.     

Cutting error of the distal femur in total knee arthroplasty by use of a navigation system

The aim of this study was to evaluate the alignment of the distal femoral cutting surface using a navigation system to determine the accuracy of bone cutting. We evaluated 20 knees in 20 patients. After cutting the distal femur, the cutting surface was validated using the navigated cutting block adapter, and the angular difference between the cutting surface and that preoperatively planned in the sagittal and coronal planes was recorded. The average error of all knees was 1.6° ± 2.2° in extension, and 14 (70%) of 20 knees were cut in an extended position. Our tendency is to cut the distal femur in an extended position with the first femoral cut in the sagittal plane.