Computer-assisted FluoroGuide navigation of unicompartmental knee arthroplasty

Background

Most authorities recognize minimally invasive unicompartmental knee arthroplasty (UKA) as technically demanding with concerns regarding loss of implantation accuracy. We have previously reported on the potential inaccuracy of femoral intramedullary guides in UKA leading to poor component positioning. Our 3-dimensional analysis of alignment error showed that a short, narrow intramedullary rod inserted according to the manufacturer’s specifications did not accurately find the direction of the anatomic axis, with errors occurring in both the coronal and sagittal planes. We sought to evaluate whether a fluoroscopic computer-assisted minimally invasive UKA procedure would improve the accuracy and precision in the placement of the femoral component in the coronal and sagittal planes compared with conventional surgery.

Methods

We performed a prospective study involving cohorts of 45 conventional versus 53 navigated UKAs. A single surgeon performed all surgeries over a 4-year period.

Results

Pain and knee function significantly improved in both surgical groups at 1 and 2 years after surgery. At a minimum of 1-year follow-up, radiographic evaluation revealed significant improvements in coronal alignment precision of the tibial component (p = 0.026) and sagittal alignment precision of the femoral component for the navigated group (p = 0.037). The use of a fluoroscopic computer-assisted technique did not significantly improve the accuracy of any of the alignment angles.

Conclusion

We cannot justify the additional expense and complexity imposed by fluoroscopic navigation despite the observed improvements in alignment precision. Improved positioning precision may translate into a greater number of long-term functional results, but larger, longer-term studies are needed.     

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.     

The management of fixed flexion contractures during total knee arthroplasty.

Fifty-one knees in 40 patients with joint surface degeneration accompanied by fixed flexion contractures (FFC) greater than 20 degrees were treated with total knee arthroplasty using a minimally constrained posterior cruciate ligament retaining prosthesis. Special techniques were employed in an attempt to achieve maximal correction at the time of surgery. The residual FFC measured 3.1 degrees at the completion of the arthroplasty, 10.1 degrees at three months, and 7 degrees at two years. At 55 months postoperatively, the FFC for the osteoarthrotic group had improved from 25.5 degrees to 3.6 degrees, whereas the rheumatoid group improved from 28.7 degrees to 8.6 degrees. The average knee score for the osteoarthrotic group was 89 compared with 81 for the rheumatoid group. Knees that were left with greater residual FFC at the completion of the arthroplasty were found to have greater residual FFC at the latest review.     

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.     

膝关节高屈曲假体的研究进展

全膝关节置换术的目的在于减轻疼痛,以及对于严重关节炎的患者能够通过关节重建手术满足其活动功能的需求。无可置疑,人工关节置换术是一项成功率较高的外科手术,在10至15年的存活率可达90％以上。对于较年轻的患者来说,对膝关节有较多活动度的需求。在许多西方社会的日常活动中,高活动膝关节是必须的功能。     

Measuring flexion in knee arthroplasty patients

Flexion following total knee arthroplasty can be visually estimated, measured with a goniometer placed against the patient's leg, or measured from a lateral radiograph of the flexed knee. Three examiners, in a blinded fashion, estimated the degree of maximal knee flexion and measured the flexion with a goniometer for 27 knees in 16 patients. A lateral knee radiograph then was taken and the flexion angle was measured from the radiograph by 2 different methods. Although interobserver and intraobserver correlation coefficients were high (0.79 and 0.92), 45% of the visual estimates and 22% of the goniometer measurements differed by 5 degrees or greater from the radiographic measurements. These differences increased as the flexion angle increased. Body mass index did not affect the accuracy of the estimates or goniometer measurements.     

Fluoroscopically assisted stress radiography for varus-valgus stability assessment in flexion after total knee arthroplasty

A radiographic technique to quantify varus and valgus joint laxity in flexion after total knee arthroplasty (TKA) was evaluated by means of inter-rater assessment in 12 patients. The test was shown to have good reliability. The simple method helps to detect instability in knee flexion that might be overlooked in a conventional clinical examination.     

Computer-assisted gap equalization in total knee arthroplasty

This in vitro biomechanical study compared a conventional balancing technique in knee arthroplasty to a technique using computer assistance. The experimental technique used a soft tissue tensioner instrumented with computer-monitored load cells to quantify soft tissue tension. To assess outcome, a tibial load transducer measured medial and lateral compartment forces and tibial rotation. An electromagnetic tracking system quantified knee position under simulated muscle loading. The computer-assisted technique improved knee balance before insertion of components. However, once components were implanted, there was no difference in knee load balance between the 2 techniques. No correlation was shown between compartmental load balance and tibial rotation or mechanical axis misalignment. Although computer-assisted surgery may improve technical accuracy, further work is necessary to achieve an optimal final knee load balance.     

Knee flexion after total knee arthroplasty

PURPOSE: To identify factors related to knee flexion after total knee arthroplasty in a Chinese population. METHODS: Records of 242 total knee arthroplasties were retrospectively reviewed. The parameters evaluated were age, gender, diagnosis, preoperative knee flexion and extension, preoperative flexion arc, tibiofemoral angle, Knee Society knee score and functional score, and implant design. RESULTS: Advanced age, female gender, and good preoperative flexion and flexion arc were related to better postoperative flexion. Postoperative flexion tended to migrate to the middle range despite different ranges of preoperative flexion. Preoperative tibiofemoral malalignment had no significant effect on postoperative flexion. CONCLUSION: Contemporary designs of posterior stabilised prostheses with right and left femoral components were superior to older designs.     

膝关节屈曲畸形的全膝关节置换术

目的探讨全膝关节置换术对矫正膝关节屈曲畸形的患者所采用的方法和临床经验。方法本组52例中，男9例，女43例，年龄43～79岁，平均66岁。原发病变：骨性关节炎40例，类风湿性关节炎12例。术前膝关节屈曲畸形程度：10°～20°有39例，20°-40°有9例，40°～60°有3例，600～900有1例；同时合并膝外翻畸形6例，膝内翻畸形26例。49例行常规后稳定型膝关节置换术，3例行铰链式全膝关节置换术。结果术后测量，46例屈曲畸形患者得以完全矫正，4例残留〈5°的屈曲，1例残留5°～10°的屈曲，1例残留10°～15°的屈曲。随访时间6个月～12年，平均7．8年。KSS膝关节评分由术前平均31分提高至79分，功能评分由术前平均29分提高至82分。结论全膝关节置换术时，彻底松解膝关节周围软组织、适当增加股骨远端和胫骨平台的切骨，是矫正屈曲畸形的有效方法，其中松解后关节囊、重建后隐窝是关键。     

人工膝关节表面置换治疗类风湿性关节炎屈膝畸形

目的探讨人工全膝关节置换术治疗类风湿性关节炎屈膝畸形的临床效果。方法选用后稳定型钴合金假体对21例类风湿性关节炎屈膝畸形患者进行人工全膝关节置换术,其中单侧膝关节置换5例,双侧膝关节置换16例,手术前后对患者的膝关节功能进行评分。结果随访1~5年,术前患者平均膝评分(22.84±6.06)分,平均功能评分(12.86±16.09)分;术后2周平均膝评分(70.16±2.71)分,平均功能评分(58.10±8.14)分;术后12周随访平均膝评分(86.14±3.12)分,平均功能评分(89.05±3.01)分。结论人工全膝关节置换术能显著纠正类风湿性关节炎屈膝畸形患者膝关节的畸形,解除疼痛,改善患膝的功能。     

Handheld navigation in total knee arthroplasty

Handheld navigation is now available for use in total knee arthroplasty, allowing for precision cuts of the distal femur and proximal tibia. By using inertial sensors and accelerometers, the handheld navigation unit is able to provide real-time, intraoperative information about alignment without additional incisions or arrays, line-of-sight issues, or the large capital expense associated with large console navigation systems. This handheld navigation unit reduces alignment outliers commonly seen with conventional guides, potentially leading to benefits in knee function and implant longevity.     

软组织平衡实时导航在膝内翻全膝关节置换术中的初步应用

目的 探讨运用软组织平衡导航系统实时定量观测膝内翻全膝关节置换术(TKA)内侧软组织松解的效果. 方法 2006年10月至2010年9月25例膝关节骨庆节炎伴膝内翻畸形患者接受软组织平衡导航TKA,其中男6例,女19例;年龄49～78岁,平均65岁.标准切骨后置入软组织平衡实时时导航系统,根据导航系统显示逐步进行内侧软组织松解.观察松解范围和内外侧软组织应力变化及临床随访效果. 结果 本组患者手术时间平均为62 min(48～80min),术中出血量平均为320mL(100～500mL).所有患者术后随访12～54个月,平均36.4个月.随访期内无感染、松动等原因导致的翻修.膝关节HSS功能评分由术前( 53.4±12.8)分改善至术后(89.2±17.3)分,差异有统计学意义(t=17.411,P=0.000);下肢力线由术前内翻16.4°±10.0°纠正至术后内翻1.8°±2.1 °,差异有统计学意义(t=7.526,P=0.000).伸膝位和屈膝位软组织松解前、后的内外侧应力差值差异均有统计学意义(P＜0.05).单纯松解内侧副韧带后束时,伸膝位内外侧应力差值减少幅度(42.33％±20.88％)较屈膝位(12.33％±9.75％)明显,差异有统计学意义(t=6.714,P=0.000).松解MCL前束+后束时屈膝位内外侧应力差值减少幅度(59.42％±21.46％)较伸膝位(50.33％±18.82％)明显,差异有统计学意义(t=2.492,P=0.021). 结论 在进行TKA时,软组织平衡实时导航系统能定量反映较组织松解时的张力变化和平衡状态,有助于提高手术精度.