Technical considerations in total knee surgery. Management of patella problems

Patellofemoral symptoms are now the most common cause of aseptic knee revision; however, the majority of patello-femoral problems are self-limited and may be managed symptomatically and nonoperatively. A trial of anti-inflammatory medications, stretching exercises, and appropriate bracing is always indicated. Patellofemoral symptoms are usually related to mechanical malalignment of all three components of the total knee arthroplasty. Attention to the fundamental principles of total knee arthroplasty, including restoration of the bony mechanical alignment, soft tissue stability, and maintenance of the anatomic joint line, prevents many of the problems. Meticulous preoperative planning and anatomic placement of the component parts are important for a satisfactory long-term outcome. Present research is directed to providing kinematic analysis of the patellofemoral tracking mechanism and to minimizing patellofemoral contact stresses with appropriate new designs.     

Patellofemoral joint contact area is influenced by tibiofemoral rotation alignment in individuals who have patellofemoral pain

STUDY DESIGN: Observational, cohort study. OBJECTIVES: To test the hypothesis that patellar alignment and tibiofemoral rotation alignment explain unique portions of variance in patellofemoral joint contact area in individuals with patellofemoral pain (PFP) and in pain-free control subjects. BACKGROUND: PFP has been proposed to result from increased patellofemoral joint stress due to decreased contact area. Patellar malalignment (lateral displacement and tilt) is believed to be the main contributor to decreased contact area. Recent studies suggest that transverse plane rotation of the femur and/or tibia may also contribute to decreased contact area. METHODS AND MEASURES: Twenty-one subjects with PFP (16 female, 5 male) and 21 pain-free subjects (14 female, 7 male) participated. Subjects underwent magnetic resonance imaging with the knee in full extension and the quadriceps contracted. Measures of patellofemoral joint contact area, lateral patellar displacement, patellar tilt angle, tibiofemoral rotation angle, and patellar width were obtained. Hierarchical multiple regression analyses were performed for each group using contact area as the dependent variable. The order of independent variables was patellar width, patellar tilt angle, and tibiofemoral rotation angle. To avoid multicolinearity, lateral patellar displacement was not included. RESULTS: In the PFP group, patellar width and tibiofemoral rotation angle explained 46% of the variance in contact area. In pain-free subjects, patellar width was the only predictor of contact area, explaining 31% of its variance. Patellar tilt angle did not predict contact area in either group. CONCLUSION: Addressing factors that control tibiofemoral rotation may be indicated to increase contact area and reduce pain in individuals with PFP. Future studies should investigate the contributions of patellar alignment and tibiofemoral rotation to patellofemoral joint contact area at a variety of knee flexion angles.     

全膝关节置换术中股骨假体旋转对髌股关节生物力学影响的实验研究

目的探讨全膝置换术中股骨假体的轴向旋转对髌股关节生物力学的影响,为临床指导人工膝关节置换的手术技术提供实验依据,以减少术后髌股关节的并发症。方法取9具正常国人新鲜冷冻尸体的9个膝关节作为研究对象,模拟膝关节自站立位屈膝下蹲的动作,设计制作膝关节实验架,与Instron 8501生物力学测试仪共同搭建实验平台。人工膝关节采用Nexgen LPS全膝系统,手术由同一位有经验的术者实施以控制实验误差,不置换髌骨。比较股骨假体相对于经股骨上髁轴内旋2°、内旋4°、旋转0°(与经股骨上髁轴平行)、外旋2°、外旋4°、平行于Whiteside线等6个不同的轴向旋转位置时的髌股关节的生物力学指标。选择屈膝30°、60°、90°、120°为观察角度,采用日本富士公司生产的压敏片测定髌股接触面积和峰值接触压,最后经扫描和软件处理得到数字化的结果。结果当股骨假体的旋转与经股骨上髁轴平行时,测得的髌股关节峰值接触压结果最优(P< 0．05)。各股骨假体旋转对线组测得的髌股接触面积无显著差异(P>0．05)。但不同标本、不同观察角度下的髌股接触形态不同。结论全膝置换术中股骨假体的轴向旋转对线对于髌股关节的接触压影响较显著,经股骨上髁轴作为股骨假体的旋转对线的参照较为可靠。     

Shortening of the patellar tendon length does not influence the patellofemoral alignment in a cadaveric model

Introduction Anterior cruciate ligament (ACL) reconstruction with the use of autograft tissue represents the standard treatment. The use of a bone-patellar tendon-bone transplant for symptomatic ACL deficiency achieves good long-term results. The purpose of the study was to investigate in a cadaveric model whether reproducible patellar tendon shortening changes the patellofemoral alignment.Materials and methods Using five cadaveric knees, an MRI investigation was performed with the patellar tendon left unchanged, shortened 5 mm and shortened 10 mm, respectively, in both 20 and 45° of knee flexion. The lateral patellofemoral and the congruence angles were measured and compared using a one-way analysis of variance for repeated measurements.Results Shortening the patella tendon by approximately 20% did not significantly influence the patellofemoral alignment.Conclusion Although anterior cruciate ligament-reconstruction using the patellar tendon has become a standard procedure, postoperative problems such as anterior knee pain, and patellofemoral osteoarthritis occur quite often. In this cadaver study we did not find a significant difference for the patellofemoral alignment, irrespective of the patellar tendon length.     

髌股关节软骨与软骨下骨的几何学匹配性及临床意义

目的 测量并比较髌股关节软骨覆盖和软骨下骨的几何形状.方法 2009年1月至2010年3月,选取髌股关节正常的膝关节标本9例,在膝关节屈曲20°～30°位,沿髌骨中心垂直于髌股关节面横行切开,暴露髌股关节,测量骨性髌骨适合角、软骨性髌骨适合角、髌骨软骨顶点参数、髌骨软骨下骨顶点参数、滑车骨性凹点参数和滑车软骨凹点参数.然后在临床中随机选取11例髌股关节软骨覆盖及力线正常患者的髌股关节轴位MRI,测量上述指标,与解剖学研究进行比较.结果 解剖学样本数据:骨性髌骨适合角为(-4.5±1.1)°,软骨性髌骨适合角为(0.5±0.8)°,均为右膝;髌骨软骨顶点参数为1.13±0.11,髌骨软骨下骨顶点参数为1.67±0.14,滑车骨性凹点参数为1.35±0.28,滑车软骨凹点参数为1.38±0.33.骨性髌骨适合角与软骨性髌骨适合角差异有统计学意义(P＜0.05),髌骨软骨顶点参数与髌骨软骨下骨顶点参数差异有统计学意义(P＜0.05).滑车骨性凹点参数与滑车软骨凹点参数差异无统计学意义(P＞0.05).临床影像学样本数据和解剖学数据相近,差异无统计学意义(P＞0.05).结论 覆盖髌骨软骨的几何形状与软骨下骨的几何形状存在着明显的差异,而股骨滑车软骨与软骨下骨的几何形状基本相似.     

Limb positioning is critical for defining patellofemoral alignment and femoral shape

The source of patellofemoral pain is a common orthopaedic complaint that often is difficult to determine because of the lack of correlation between symptoms and specific clinical measurements. Excessive joint contact stresses resulting from patellofemoral malalignment and pathologic femoral shape often are associated with this pain. These measures are likely sensitive to the limb position (orientation and position relative to the imaging system with which they are quantified). Because of this sensitivity, the measures have large variations and do not show correlations with subjective symptoms. The purpose of this study was to determine if varying limb position resulted in significant changes in standard clinical measures of patellofemoral alignment and femoral shape. This dependence was investigated by simulating alterations in limb position through resectioning of three-dimensional magnetic resonance image sets (20 healthy knees) to create axial images with altered orientation (eight images) or location (four images) relative to a fixed reference. By quantifying the variability of the clinical measures across all images, it was determined that simulated alterations in limb position produced greater variability in femoral shape and patellofemoral alignment measures than the variability seen across control subjects. This indicated that a standardized method for establishing limb position relative to the imager is warranted.     

Anatomie und Biomechanik des Patellofemoralgelenks

The patellofemoral joint constitutes a complex anatomical and functional entity. The tensile force of the quadriceps femoris muscle is transmitted through the patella and patellar ligament onto the tibial tuberosity. This particular three-dimensional arrangement increases the torsional moment acting on the knee joint. Dynamic alignment of the patella is determined by trochlear geometry and is supported by active muscular and passive connective tissue stabilizers. In addition to the retinaculum of the patella, the medial patellofemoral ligament is attracting increasing clinical attention. Multidirectional motion of the patella is closely connected to retropatellar pressure distribution which can be modulated by moving the patellar ligament insertion. Implantation of a knee endoprosthesis changes the joint surface geometry and consequently patella kinematics and retropatellar pressure distribution. Finite element analysis provides the possibility to assess retropatellar pressure distribution before and after implantation of prostheses.     

Anatomy and biomechanics of the patellofemoral joint: physiological conditions and changes after total knee arthroplasty

The patellofemoral joint constitutes a complex anatomical and functional entity. The tensile force of the quadriceps femoris muscle is transmitted through the patella and patellar ligament onto the tibial tuberosity. This particular three-dimensional arrangement increases the torsional moment acting on the knee joint. Dynamic alignment of the patella is determined by trochlear geometry and is supported by active muscular and passive connective tissue stabilizers. In addition to the retinaculum of the patella, the medial patellofemoral ligament is attracting increasing clinical attention. Multidirectional motion of the patella is closely connected to retropatellar pressure distribution which can be modulated by moving the patellar ligament insertion. Implantation of a knee endoprosthesis changes the joint surface geometry and consequently patella kinematics and retropatellar pressure distribution. Finite element analysis provides the possibility to assess retropatellar pressure distribution before and after implantation of prostheses.     

Operative Therapie der isolierten patellofemoralen Arthrose

Background

The treatment of patellofemoral arthritis places high demands on orthopedists. The exact analysis of the underlying pathobiomechanical relationships is the basis for every therapy decision.

Methods

Soft tissue procedures, such as medial patellofemoral ligament (MPFL) reconstruction for stabilization and bone interventions for alignment optimization (e.g. tuberosity transfer and corrective osteotomy) can play a role in treatment. In cases of advanced patellofemoral arthrosis these interventions can be used as well as in combination with partial joint replacement. For the choice of implant the use of anatomical prosthesis types is recommended because with these components the number of additional procedures can be reduced.

Conclusion

The success of patellofemoral prosthetics depends mainly on the recognition of biomechanical deviations. If these can be corrected the risk of implant failure can be reduced.     

Knee – spine syndrome: correlation between sacral inclination and patellofemoral joint pain

 Low back pain is an enormous clinical and public health problem. When we use spinal instrumentation, measurements of spinal and leg alignment in the standing position are thought to be important. Knee joint pain has also become an enormous clinical problem in the increasing elderly population. However, the correlation between spinal alignment, particularly sacral inclination, and knee joint pain is not clear. We examined the correlation between lumbar lordosis, sacral inclination, and patellofemoral joint pain in elderly subjects. Three hundred and ninety-nine people aged 50–85 years were examined. Clinical findings and physical status were determined. Measurements and determination of total lordosis from L1 to S1 and sacral inclination were made from standing radiographs. The knee joints were evaluated by using the standing knee flexion angle, radiographs, and the patellofemoral (PF) joint grinding test. Thirty-nine percent of subjects were excluded because they had definite osteo-arthritis at the femorotibial joints. Fifty-eight percent of the subjects had felt low back pain within the previous 3 months, and 16% of the subjects complained of PF joint grinding pain. Sixteen percent of the subjects showed knee flexion when standing. There was a significant difference in sacral inclination between the groups with and without PF joint grinding pain (P < 0.01). Sacral inclination was approximately 5° less in the knee flexion group. A correlation between sacral inclination and PF joint pain is defined, and its prevalence in the elderly is reported. We speculate that this phenomenon is caused by changing of lumbar alignment. In addition, we think this is a new pathological concept that we call the knee – spine syndrome. Received: July 23, 2001 / Accepted: May 2, 2002     

Editorial Commentary: A Posterior Tibial Tubercle Relative to the Trochlear Groove Is Associated With Increased Risk of Patellofemoral Arthritis: The Sagittal Tibial Tubercle–Trochlear Groove Distance

Arthritis of the patellofemoral compartment affects up to 24% of women and 11% of men over the age of 55 years who have symptomatic osteoarthritis of the knee. Patellofemoral cartilage lesions have been associated with several different geometric measures of patellar alignment, including the tibial tubercle–trochlear groove (TTTG) distance, trochlear sulcus angle, trochlear depth, and patellar height. Recently, there has been interest in the sagittal TTTG distance, which measures the position of the tibial tubercle with respect to the trochlear groove. This measurement is now being used in patients presenting with patellofemoral pain and/or cartilage pathology and may help guide surgical decision making as we gain more data on how changing the tibial tubercle alignment relative to the patellofemoral joint can improve outcomes. For now, there are not enough data to support isolated anteriorization tibial tubercle osteotomy in patients with patellofemoral chondral wear based on the sagittal TTTG distance. However, as we better understand geometric measures as risk factors for patellofemoral arthritis, realignment at a young age might be recommended as a preventative measure against end-stage osteoarthritis.     

The role of foot orthoses as an intervention for patellofemoral pain

Foot orthoses often are prescribed for patients with patellofemoral pain. The purpose of this clinical commentary is to review the theoretical and research basis that might support this intervention and to provide our own clinical experience in providing foot orthoses for these patients. Literature is reviewed regarding (1) the effects of foot orthoses on pain and function, (2) the relationship between foot and lower-extremity/patellofemoral joint mechanics, (3) the effects of foot orthoses on lower-extremity mechanics, and (4) the effects of foot orthoses on patellofemoral joint position. The literature and our own clinical experience suggest that patients with patellofemoral pain may benefit from foot orthoses if they also demonstrate signs of excessive foot pronation and/or a lower-extremity alignment profile that includes excessive lower-extremity internal rotation during weight bearing and increased Q angle. The mechanism for foot orthoses having a positive effect on pain and function for these patients may include (1) a reduction in internal rotation of the lower extremity; (2) a reduction in Q angle; (3) reduced laterally-directed soft tissue forces from the patellar tendon, the quadriceps tendon, and the iliotibial band; and (4) reduced patellofemoral contact pressures and altered patellofemoral contact pressure mapping. Foot orthoses may be a valuable adjunct to other intervention strategies for patients who present with the previously stated structural alignment profile.     

Anterior cruciate ligament reconstruction alters the patellar alignment.

Although there are many articles dealing with anterior cruciate ligament (ACL) reconstruction, there are none dealing with the possibility of changes of the patellofemoral alignment after these procedures. Forty-six patients were evaluated preoperatively and 1 year postoperatively, after undergoing intra-articular ACL reconstruction, for changes of the patellofemoral alignment. Patella-tilt and congruence angles were measured on tangential view radiographs that were taken in the supine position. Analysis of covariance was performed and revealed a significant change of the congruence angle 1 year postoperatively. The patella-tilt did not change. One year postoperatively, the patella shifted on average 5 degrees medially after ACL grafting. It can be deduced that anterior knee pain after ACL reconstruction could be caused by distinct changes in the patellofemoral alignment.     

Dynamic assessment of shoulder and patellofemoral pathology using limited-volume gas arthroscopy

Subtle instability problems of the glenohumeral joint and patellofemoral joint are difficult to assess and accurately diagnose with current methods of preoperative imaging and physical examination. A simple technique is described that provides objective information for diagnosing dynamic problems of the shoulder and patellofemoral joint. Limited-volume gas arthroscopy avoids many of the potential risks and complications of pressure-based gas arthroscopy. In addition to assessing joint dynamics, it allows for initial arthroscopic inspection of joints during open surgical cases, eliminating the additional morbidity and expense of fluid arthroscopy. Objective intraoperative assessments of completed reconstructions can also be made to insure that stabilizing procedures are adequate but not overzealous. The technique requires no special equipment, adds little time to an arthroscopic procedure, and requires only basic arthroscopic skills.Arthroscopy 1998 Jul-Aug;14(5):546-50     

全膝置换术中预防股骨及胫骨假体旋转对位对线不良的研究进展

随着人口老龄化,我国需要进行人工全膝关节置换术(TKA)并可从中受益的病人将越来越多。在TKA术后,由于假体旋转而引起的假体对位对线不良,从而造成的髌股关节运动不良等并发症是膝关节翻修的重要原因,需要引起进一步的关注。膝关节假体旋转对位对线涉及到胫骨和股骨的正确定位、对线、截骨及假体的安放。在本文中,将对众多股骨及胫骨侧旋转对位对线的方法作一综述。     

Focal anatomic patellofemoral inlay resurfacing: theoretic basis, surgical technique, and case reports

Prosthetic patellofemoral inlay resurfacing is a novel treatment concept for degenerative and focal arthrosis of the patellofemoral joint. The theoretic basis of this type of arthroplasty entails recreating ambient anatomy based upon intraoperative topographic mapping. The implant is intrinsically stable by virtue of the inset position relative to the surrounding joint surface. Articular resurfacing, rather than traditional replacement arthroplasty, represents an extension of the concepts of biologic joint restoration. Early results have shown great efficacy. This surgery may be appropriate for a wide variety of indications, including younger patients and those with focal patellofemoral disease concurrent with morphologic or alignment abnormalities.     

Surgical correction of miserable malalignment syndrome

Anterior knee pain is one of the more frustrating problems that orthopaedic surgeons treat. This study investigates the results of surgical correction of miserable malalignment syndrome associated with significant patellofemoral pain. The authors identified and retrospectively reviewed 14 consecutive patients with 27 limbs associated with excessive femoral anteversion, excessive tibial outward rotation, and patellofemoral pain. All of the patients were initially reviewed by the senior author and subsequently treated by ipsilateral outward femoral osteotomy and inward tibial osteotomy. All of the patients had failed nonoperative treatment. No persistent complications were seen. Subjectively and clinically, all of the patients were reviewed at an average of 5.2 (range 2.0-12) years after surgery. All of the patients reported full satisfaction with their surgery and outcomes. Most of the current literature discusses alignment in association with patellofemoral pain in the form of the extensor mechanism alignment. When evaluating patients with patellofemoral pain, it is imperative to assess the rotational profiles of the femur and tibia. The authors recommend that rotational osteotomies be performed in patients with patellofemoral pain and associated excessive femoral and tibial torsion, otherwise known as miserable malalignment syndrome.     

The influence of tibial-patellofemoral location on function of the knee in patients with the posterior stabilized condylar knee prosthesis

Function of the knee and patellofemoral symptoms were correlated with the position of the implant in 101 consecutive patients with 116 posterior stabilized condylar knee prostheses. All of the patients were followed for a minimum of two and a half years with sequential physical examinations, radiographs, and functional evaluation of the knee. In sixteen knees (14 per cent), clicking or catching of the patella in terminal extension or painless crepitation throughout the arc of flexion developed without lowering the functional knee-evaluation score. Pain or mechanical problems, or both, that lowered the functional knee-evaluation score occurred in another fourteen knees (12 per cent), within the first postoperative year. Of these fourteen, eight required revision solely for patellofemoral complaints. Critical analysis of the tibial-patellofemoral mechanical axis identified three surgical variables that were found to markedly affect the functional result of the prosthesis: the distance from the center line of the tibial prosthesis to the center line of the tibial plateau, a change in the position of the joint line of the prosthesis relative to the hip and ankle, and the patellar height, measured as the perpendicular distance from the inferior pole of the patellar implant to the joint line of the prosthesis. Functional knee scores, range of motion, patellofemoral pain or mechanical symptoms, the need for revision, and the necessity of manipulation could all be statistically significantly correlated with the three independent variables. In addition, a range of neutral alignment was developed.(ABSTRACT TRUNCATED AT 250 WORDS)     

The significance of chondromalacic changes on the patella

A total of 500 arthroscopies were performed in a 2-year period, with special reference made to the patellofemoral joint. In those with pain thought to be arising from this joint, 63% had chondromalacic changes on the posterior surface of the patella compared with a 45% incidence in those with meniscal pathological findings at arthroscopy. This study demonstrates that those with patellofemoral pain do not always have patellar articular changes, and patellar pathology is often asymptomatic. As a result, treatment directed at these lesions must be used with great caution.     

The influence of altered lower-extremity kinematics on patellofemoral joint dysfunction: a theoretical perspective

Although patellofemoral pain (PFP) is recognized as being one of the most common disorders of the lower extremity, treatment guidelines and underlying rationales remain vague and controversial. The premise behind most treatment approaches is that PFP is the result of abnormal patellar tracking and/or patellar malalignment. Given as such, interventions typically focus on the joint itself and have traditionally included strengthening the vastus medialis oblique, taping, bracing, soft tissue mobilization, and patellar mobilization. More recently, it has been recognized that the patellofemoral joint and, therefore, PFP may be influenced by the interaction of the segments and joints of the lower extremity. In particular, abnormal motion of the tibia and femur in the transverse and frontal planes may have an effect on patellofemoral joint mechanics. With this in mind, interventions aimed at controlling hip and pelvic motion (proximal stability) and ankle/foot motion (distal stability) may be warranted and should be considered when treating persons with patellofemoral joint dysfunction. The purpose of this paper is to provide a biomechanical overview of how altered lower-extremity mechanics may influence the patellofemoral joint. By addressing these factors, better long-term treatment success and prevention may be achieved.