Patella in total knee arthroplasty

The patella is a reliable guide to the success or failure of a total knee replacement. Patients who do not experience peripatellar symptoms or a patellar complication usually have a successful result. Conversely, peripatellar symptoms or complications usually reflect an underlying problem with surgical technique, component designs, or both. Current designs still do not replicate normal kinematics, and current instrumentation and techniques significantly alter the anatomy of the patellofemoral articulation in a substantial percentage of patients. Reproducing extensor mechanism balance and using components that provide adequate congruency and contact area through a physiologic arc of motion should lead to a successful result with minimal patellar symptoms or complications whether or not the patella is resurfaced. Attempting to achieve normal patellofemoral kinematics and minimize patellar complications has led to a better understanding of total knee arthroplasty.     

髌股疼痛综合征病因与治疗的研究进展

髌股疼痛综合征(patellofemoral pain syndrome,PFPS)是导致膝关节疼痛最为常见的疾病之一。目前无特异性诊断措施,影像学检查无软骨、韧带及软组织损伤表现时方可考虑诊断为髌股疼痛综合征。其病因包括各种解剖结构异常导致的髌骨运动轨迹异常,如髌骨位置异常、Q角增大及足过度外翻等,股四头肌失衡和臀肌功能异常等下肢肌肉功能异常同样在髌股疼痛综合征的发生发展中起重要作用。目前存在多种治疗方式,股四头肌锻炼和臀外展肌锻炼目的在于改善髌骨动态稳定性;肌效贴和髌支具主要通过改善髌骨轨迹,减轻髌股关节面间的压力;足矫形垫主要用于伴有足外翻的患者;在保守治疗无效后,可考虑进行膝关节镜下松解髌骨外侧支持带术。由于髌股疼痛综合征为多种病因综合作用而致病,同时采用多种治疗方式有助于提高治疗效果。     

复发性髌骨脱位治疗中内侧髌股韧带重建术的研究进展

复发性髌骨脱位是引起青少年膝关节功能障碍的常见疾病,其定义为髌骨脱位发生两次及两次以上,是一种骨科及运动医学临床常见的疾病。复发性髌骨脱位的病因有很多,但归根结底,髌骨在活动中所处的异常力学环境是引起不稳的根本原因。研究发现内侧髌股韧带被认为是限制髌骨向外脱位最重要的软组织结构,因而重建内侧髌股韧带对成功治疗复发性髌骨脱位起着重要的作用。但复发性髌骨脱位往往是一个多因素引起的临床问题,除了纠正软组织的异常外,骨性结构的异常也是一个不容忽视的问题。本文对近年来对内侧髌股韧带的解剖、生物力学、手术技巧、治疗结果及术后并发症的研究情况进行了综述。     

Lowering of the patella secondary to anterior advancement of the tibial tubercle for the patellofemoral pain syndrome

From a series of 72 patients treated with anterior advancement of the tibial tubercle for patellofemoral pain syndrome, secondary lowering of the patella was noted in eight. In all eight patients the results were poor following surgery, with severe disabling retro- and peripatellar pain and atrophy of the quadriceps muscle. We describe this complication and illustrate and discuss the biomechanical consequences. The shortening of the patellar ligament and lever arm of the ligament were determined from radiographs of the knee joints before and after surgery. A theoretical analysis was made of the compressive force in the patellofemoral joint in one of these patients. The Insall-Salvati index decreased from 0.88-1.25 (mean 1.07) preoperatively to 0.54-0.78 (mean 0.70) at follow-up, 1.0-2.5 years post-operatively. The lowering of the patella was correlated to a reduction of the lever arm of the patellar ligament in seven patients. The mechanism behind the lowering of the patella is obscure, but the reduced lever arm of the patellar ligament will increase the compressive force in the patellofemoral joint, and this might be one explanation of the poor results. Impaired congruity of the patellofemoral joint, increased tension in the patellar ligament, and increased pressure against the quadriceps tendon are other possible explanations.     

Lowering of the patella secondary to anterior advancement of the tibial tubercle for the patellofemoral pain syndrome

Summary From a series of 72 patients treated with anterior advancement of the tibial tubercle for patellofemoral pain syndrome, secondary lowering of the patella was noted in eight. In all eight patients the results were poor following surgery, with severe disabling retro- and peripatellar pain and atrophy of the quadriceps muscle. We describe this complication and illustrate and discuss the biomechanical consequences. The shortening of the patellar ligament and lever arm of the ligament were determined from radiographs of the knee joints before and after surgery. A theoretical analysis was made of the compressive force in the patellofemoral joint in one of these patients. The Insall-Salvati index decreased from 0.88–1.25 (mean 1.07) preoperatively to 0.54–0.78 (mean 0.70) at follow-up, 1.0–2.5 years postoperatively. The lowering of the patella was correlated to a reduction of the lever arm of the patellar ligament in seven patients. The mechanism behind the lowering of the patella is obscure, but the reduced lever arm of the patellar ligament will increase the compressive force in the patellofemoral joint, and this might be one explanation of the poor results. Impaired congruity of the patellofemoral joint, increased tension in the patellar ligament, and increased pressure against the quadriceps tendon are other possible explanations.     

Using real‐time MRI to quantify altered joint kinematics in subjects with patellofemoral pain and to evaluate the effects of a patellar brace or sleeve on joint motion

Abnormal patellofemoral joint motion is a possible cause of patellofemoral pain, and patellar braces are thought to alleviate pain by restoring normal joint kinematics. We evaluated whether females with patellofemoral pain exhibit abnormal patellofemoral joint kinematics during dynamic, weight‐bearing knee extension and assessed the effects of knee braces on patellofemoral motion. Real‐time magnetic resonance (MR) images of the patellofemoral joints of 36 female volunteers (13 pain‐free controls, 23 patellofemoral pain) were acquired during weight‐bearing knee extension. Pain subjects were also imaged while wearing a patellar‐stabilizing brace and a patellar sleeve. We measured axial‐plane kinematics from the images. Females with patellofemoral pain exhibited increased lateral translation of the patella for knee flexion angles between 0°and 50° (p = 0.03), and increased lateral tilt for knee flexion angles between 0° and 20° (p = 0.04). The brace and sleeve reduced the lateral translation of the patella; however, the brace reduced lateral displacement more than the sleeve (p = 0.006). The brace reduced patellar tilt near full extension (p = 0.001), while the sleeve had no effect on patellar tilt. Our results indicate that some subjects with patellofemoral pain exhibit abnormal weight‐bearing joint kinematics and that braces may be effective in reducing patellar maltracking in these subjects. Published by Wiley Periodicals, Inc. J Orthop Res 27: 571–577, 2009     

Medial patellofemoral ligament reconstruction with gracilis autograft for patellar instability

We describe a technique for patellar stabilization by reconstruction of the medial patellofemoral ligament with the gracilis tendon. The tendon is anchored posteriorly on the soft tissue of the medial femoral epicondyle and anteriorly on the medial border of the patella. The plasty is completed by suture of the medial patellar wing. Inferior or medial transposition of the tibial tubercle may be associated. We have used this technique since 1995 for 145 knees with patellar instability. The small incisions have the advantages of minimally invasive surgery, particularly for the postoperative period and the cosmetic effect.     

Editorial Commentary: Medial Patellofemoral Ligament Reconstruction for Knee Patellar Instability: When Are Soft Tissue Procedures Not Enough?

Medial patellofemoral ligament reconstruction is commonly performed to treat patellofemoral instability by recreating the static soft tissue restraint to lateral patellar translation. Concurrent tibial tuberosity osteotomy can be indicated in the setting of bony malalignment, such as a lateralized tuberosity or patella alta; however, the exact indications for this have been difficult to define due to the multifactorial nature of this problem. Understanding the role of tuberosity lateralization and patella alta on the function of medial patellofemoral ligament grafts can help to identify the interplay of some factors that contribute to patellar stability and improve our understanding of when and how concurrent tibial tuberosity osteotomy may be indicated.     

Is cartilage thickness different in young subjects with and without patellofemoral pain?

OBJECTIVE: To determine the differences in load-bearing patellofemoral joint cartilage thickness between genders. To determine the differences in load-bearing cartilage thickness between pain-free controls and individuals with patellofemoral pain. METHODS: The articular cartilage thickness of the patella and anterior femur was estimated from magnetic resonance images in 16 young, pain-free control subjects (eight males, eight females) and 34 young individuals with patellofemoral pain (12 males, 22 females). The average age of all subjects was 28+/-4 years. The cartilage surfaces were divided into regions approximating the location of patellofemoral joint contact during knee flexion. The mean and peak cartilage thicknesses of each region were computed and compared using a repeated-measures Analysis of Variance. RESULTS: On average, males had 22% and 23% thicker cartilage than females in the patella (P < 0.01) and femur (P < 0.05), respectively. Male control subjects had 18% greater peak patellar cartilage thickness than males with patellofemoral pain (P < 0.05); however, we did not detect differences in patellar cartilage thickness between female control subjects and females with patellofemoral pain (P = 0.45). We detected no significant differences in femoral cartilage thickness between the control and pain groups. CONCLUSIONS: Thin cartilage at the patella may be one mechanism of patellofemoral pain in male subjects, but is unlikely to be a dominant factor in the development of pain in the female population.     

Atraumatic vertebral compression fractures: differential diagnosis between benign osteoporotic and malignant fractures by MRI

We describe a case of heterotopic ossification (HO) of the lateral patella becoming symptomatic after 7 years following horizontal patella fracture. The patient presented peripatellar pain in full knee flexion and kneeling position. We resected the ossification, and the patient was immediately relieved from pain and was mobilised under full weight bearing with no limitation of knee flexion. The patient was able to return to his previous level of daily activities with no further episodes of pain. To our knowledge, this is the first case of heterotopic peripatellar ossification becoming symptomatic 7 years after a patellar fracture to be reported in the literature.     

The early diagnosis and treatment of developmental patella infera syndrome

Developmental patella infera and associated arthrofibrosis after knee surgery require prompt recognition and treatment. The condition develops because of contracture of peripatellar tissues, fatpad tissues, and quadriceps weakness, and may rapidly progress to permanent patella infera and disabling patellofemoral arthrosis. Case studies for five patients with acute developmental patella infera are described. All patients required an early arthroscopic release of contracted tissues. To establish normal right to left patellar, vertical-height ratios, lateral roentgenograms were obtained in 202 normal knees (101 pairs). The data showed that although essentially no difference existed between right and left sides, large variations existed in the ratios from one individual to another (range, 0.75-1.46). Thus, the diagnosis of developmental patella infera requires comparison of patellar height ratios in the same knee or between knees in the same individual. A decrease in the vertical-height ratio of 11%-15%, depending on the method used, indicates developmental patella infera.     

Medial patellofemoral ligament reconstruction – A novel technique

Patellofemoral instability is initially treated conservatively and surgical treatment is reserved for resistant cases. Reconstruction of medial patellofemoral ligament has gained popularity these days as it attempts at restoring soft tissue anatomy and biomechanics of medial patellar restraint back to normal. Here we describe our novel transverse patella single tunnel and femoral interference screw technique to reconstruct the medial patellofemoral ligament using free autologous gracilis and semitendinosus grafts.     

Patellar resurfacing in total condylar knee arthroplasty. Technique and results

One hundred thirty-two total condylar knee arthroplasties with a 3-8-year follow-up period were studied prospectively with particular reference to the patellofemoral joint. All patients had significant patellofemoral disease and underwent primary patellar resurfacing. After operation 96% of patients had little or no pain and 98% had functional improvement. There were seven (5%) complications related to the patellofemoral joint. The importance of careful attention to preparation of the patella, the technique of prosthetic implantation and correct patellar tracking were emphasized. Routine patellar resurfacing proved highly successful with minimal complications.     

Patellar tendon lengthening for patella infera using the Ilizarov technique

Patella infera can cause knee pain and lead to patellofemoral osteoarthritis. Treatment is usually unsatisfactory. We describe a case of severe patella infera after operative treatment for fracture of the patella. We used Ilizarov external fixation and gradual lengthening of the patellar tendon. The patellar height was restored and the patient's symptoms were much improved.     

Mediolateral quadriceps imbalance and peripatellar pain syndrome

In cases of spontaneously occurring patellar pain, there is generally some slight damage to the nerve roots and anterior horn cells of segments L3 and L4. Divergent patellar movement can be measured roentgenologically. When the quadriceps is contracted the patella normally medialward in varus joints, and lateralward in valgus joints and when the leg position is axially correct. In peripatellar pain syndrome, however, lateral movement can be demonstrated in varus joints. Additionally, there is a tendency for the rotation of the patella to depend on the innervation disorder. The discrepancy between the muscular guidance of the patella and the performed guide bed may be one of the factors causing patellar pain. Etiologically, axial malpositions of the leg appear to be important predisposing factors and innervation disorders of the quadriceps muscle realization factors.     

Reconstruction of the medial patellofemoral ligament using a longitudinal patellar tunnel technique

Patellar instability is a common clinical problem affecting a young, active population. A large number of procedures have been described to treat patellar instability. We present the clinical results in a case series of 25 medial patellofemoral ligament reconstructions in 21 patients with up to 30 months follow-up (mean: 7.3). Reconstruction was performed using either the gracilis or semitendinosus tendon autograft. The Tegner activity score improved overall from 3 to 4.4 at follow-up and the mean follow-up Kujala score was 87 (range: 55–100). No patella redislocations were observed. Five patients (20%) required a manipulation under anaesthetic but subsequently regained a satisfactory range of motion. Medial patellofemoral reconstruction with both gracilis and semitendinosus tendon graft using a longitudinal tunnel technique provided good post-operative stability restoring the primary soft tissue restraint to pathological lateral patellar displacement with no complications of post-operative patellar fracture.     

Evaluation of patients with persistent symptoms after lateral retinacular release by kinematic magnetic resonance imaging of the patellofemoral joint

The arthroscopic lateral retinacular release is typically performed to treat patellar pain and instability. This procedure was previously considered to be relatively benign with a low associated complication rate. However, a high incidence of medial subluxation of the patella was recently reported in patients with persistent symptoms after lateral retinacular release. Because the use of physical examination criteria may not always be sufficient to assess patellar alignment, 40 patients (43 knees) were evaluated by the newly developed technique of kinematic magnetic resonance imaging of the patellofemoral joint. One (2%) patellofemoral joint had normal patellar alignment, 10 (23%) had lateral subluxation of the patella, 1 (2%) had excessive lateral pressure syndrome, 27 (63%) had medial subluxation of the patella, and 4 (9%) had lateral-to-medial subluxation of the patella. Seventeen of 40 patients (43%) with unilateral arthroscopic lateral retinacular releases had medially subluxated patellae on the unoperated joints. Because patellar malalignment commonly affects bilateral joints, medial subluxation of the patella may have been present before the lateral retinacular release but was not recognized in these patients.     

Patellofemoral Pain After Total Knee Arthroplasty

The incidence of patellofemoral complications after total knee arthroplasty has been reported to range from 2% to 7%. Such complications include pain, sub-luxation, dislocation, loosening, and wear. Usually these complications are attrib-utable to prosthetic design or surgical technique. Today, it is understood that patellofemoral prostheses must have a degree of congruence; must allow smooth, not abrupt, motion; and must restore a relatively normal size relationship between the patella and the femur. Surgical technique requires strict attention to (1) restoration of the patellofemoral spacing while avoiding "overstuffing" of the patellofemoral compartment; (2) accurate superior and medial positioning of the patellar component; (3) restoration of the rotational alignment of the femoral and tibial components; and (4) appropriate balancing of the patellofemoral soft tissues.     

Radiographic measures in subjects who are asymptomatic and subjects with patellofemoral pain syndrome

Lateral tilt and displacement of the patella are considered characteristic features of patellofemoral pain syndrome. It has been suggested that abnormal patellar tilt and displacement are detected best with the knee near full extension, which requires computed tomography or magnetic resonance imaging. The objective of the current study was to determine whether alignment abnormalities could be detected in subjects with patellofemoral pain syndrome from axial radiographs obtained at 35 degrees knee flexion using a new, standardized radiographic technique. Thirty-three subjects with patellofemoral pain syndrome and 33 matched control subjects were recruited from a military population. Lateral and axial (unloaded and with quadriceps contraction) radiographs were taken using the Patellofemoral QUESTOR Precision Radiograph system. Measures of patellar tilt and displacement, and anatomic measures (sulcus angle, patellar facet angle, patella alta) were obtained from the radiographs. No significant differences in patellar tilt or displacement were detected between the groups (paired t tests) in either the unloaded or loaded (quadriceps contracted) condition, suggesting that these measures, obtained at this knee angle are not useful diagnostic or outcome measures in patellofemoral pain syndrome. Patellar angle, sulcus angle, and patellar height also did not differ between groups suggesting that these are not etiologic factors in patellofemoral pain syndrome.