Aims

This study aimed to investigate the relationship between changes in patellar height and clinical outcomes at a mean follow-up of 7.7 years (5 to 10) after fixed-bearing posterior-stabilized total knee arthroplasty (PS-TKA).

Shortening of patellar tendon after total knee arthroplasty (TKA) was previously reported by several studies. Its etiology still remains controversial. Patellar tendon shortening, a direct cause of patella baja, has a dramatic negative impact in terms of clinical outcomes after TKA. Main objective of this study is to assess the feasibility of utilizing a different technique with Ultrasound that is easy to use, cost-effective and able to eliminate the problem of differential magnification occurring in other techniques which count on standard x-rays and to establish the correlation between clinical outcomes and changes in patellar tendon length and thickness after TKA. The study was designed as prospective cohort and, after a minimum of 4-year-follow up period, 47 knees of 24 patients who had undergone primary TKA without patellar resurfacing were included in the study. All patients were scored with Kujala and HSS scores and all patellar tendons were evaluated with USG regarding their length and thickness. We used conventional grey-scale ultrasound imaging (US) to determine any changes in patellar tendon morphology. All cases were evaluated by the same radiologist. The patellar tendon was examined with the knee in 30° flexion. The flexion angle helped to stretch the extensor mechanism and avoid anisotropy (concavity) of the patellar tendon. The transducer was placed along the long axis of the tendon. The patellar tendon was initially examined in the longitudinal plane in order to measure the total length. Then, total length was divided into three parts and sagittal thickness was calculated at the proximal, median, and distal thirds of the patellar tendon. Both the length and thickness of the tendon were measured before surgery and at the 4th year of follow-up. Of the 47 knees that were included in our study, the mean pre-operative and postoperative length of the patellar tendon was 40.78±6.15 mm and 35.93±4.52 mm. Our results suggested significant shortening of the patellar tendon after primary TKA surgery (p<0.05). Intergroup analysis suggested that reduced sagittal thickness in the proximal third of the tendon was more strongly correlated with an increase in functional outcomes (p<0.05). Our results suggested no significant difference in clinical outcome scores between patients with increased or decreased length of the patellar tendon after TKA (p>0.05). We suggest that determining morphologic changes in sagittal thickness as well as length is important in explaining some of the ambiguous causes of anterior knee pain and impaired clinical outcomes after TKA. More accurate documentation of morphologic changes in the patellar tendon after TKA will certainly help to develop new techniques by surgeons or avoid some existing routines that may harm the tendon. USG is a feasible method for evaluating patellar tendon morphology after TKA but more future studies are needed

Introduction. With an ongoing increase in total knee arthroplasty (TKA) procedural volume, there is an increased demand to improve surgical techniques to achieve ideal outcomes. Considerations of how to improve post-operative outcomes have included preservation of the infrapatellar fat pad (IPFP). Although this structure is commonly resected during TKA procedures, there is inconsistency in the literature and among surgeons regarding whether resection or preservation of the IPFP should be achieved. Additionally, information about how surgical handling of the IPFP influences outcomes is variable. Therefore, the purpose of this systematic review was to evaluate the influence of IPFP resection and preservation on post-operative flexion, pain, Insall-Salvati Ratio (ISR), Knee Society Score (KSS), patellar tendon length (PTL), and satisfaction in primary TKA. Methods. A systematic literature search was performed to retrieve all reports that evaluated IPFP resection or preservation during total knee arthroplasty (TKA). The following databases were queried: PubMed, EBSCO host, and SCOPUS, resulting in 488 unique reports. Two reviewers independently reviewed the studies for eligibility based on pre-established inclusion and exclusion criteria. A total of 11 studies were identified for final analysis. Patient demographics, type of surgical intervention, follow-up duration, and clinical outcome measures were collected and further analyzed. This systematic review reported on 11,996 total cases. Complete resection was implemented in 3,723 cases (31%), partial resection in 5,458 cases (45.5%), and preservation of the IPFP occurred in 2,815 cases (23.5%). Clinical outcome measures included patellar tendon length (PTL) (5 studies), knee flexion (4 studies), pain (6 studies), Knee Society Score (KSS) (3 studies), Insall-Salvati Ratio (ISR) (3 studies), and patient satisfaction (1 study). Results. There were no differences found following IPFP resection for patient satisfaction (p=0.92), ISR (all p-values >0.05), and KSS (all p-values >0.05). Mixed evidence was found for patellar tendon length, pain, and knee flexion following IPFP resection vs. preservation. Conclusion. Given the current literature and available data, there were several clinical outcome measures that indicated better patient results with preservation of IPFP during primary TKA in comparison to the resection of IPFP. Specifically, resection resulted in inferior outcomes for patellar tendon length, knee flexion, and pain measurements. However, more extensive research is needed to better determine that preservation is the superior surgical decision. This includes a need for more randomized controlled trials (RCTs). Future studies should focus on conditions in which preservation or resection of IPFP would be best indicated during TKA in order to establish guidelines for best surgical outcomes in those patients. For any figures or tables, please contact authors directly

Introduction. Patellar crepitus and clunk are tendofemoral-related complications predominantly associated with posterior-stabilizing (PS) total knee arthroplasty (TKA) designs [1]. Contact between the quadriceps tendon and the femoral component can cause irritation, pain, and catching of soft-tissue within the intercondylar notch (ICN). While the incidence of tendofemoral-related pathologies has been documented for some primary TKA designs, literature describing revision TKA is sparse. Revision components require a larger boss resection to accommodate a constrained post-cam and stem/sleeve attachments, which elevates the entrance to the ICN, potentially increasing the risk of crepitus. The objective of this study was to evaluate tendofemoral contact in primary and revision TKA designs, including designs susceptible to crepitus, and newer designs which aim to address design features associated with crepitus. Methods. Six PS TKA designs were evaluated during deep knee bend using a computational model of the Kansas knee simulator (Figure 1). Prior work has demonstrated that tendofemoral contact predictions from this model can differentiate between TKA patients with patellar crepitus and matched controls [2]. Incidence of crepitus of up to 14% has been reported in Insall-Burstein® II and PFC® Sigma® designs [3]. These designs, in addition to PFC® Sigma® TC3 (revision component), were included in the analyses. Primary and revision components of newer generation designs (NexGen®, Attune® and Attune® Revision) were also included. Designs were evaluated in a patient model with normal Insall-Salvati ratio and a modified model with patellar tendon length reduced by two standard deviations (13mm) to assess worst-case patient anatomy. Results. During simulations with normal patellar tendon length, only PFC® Sigma® and PFC® Sigma® TC3 showed tendofemoral contact within the trochlea, and no design showed contact at the transition to the ICN (Figure 2). In simulations with patella baja, Insall-Burstein® II, PFC® Sigma®, and PFC® Sigma® TC3, demonstrated tendofemoral contact across the trochlea at the transition into the notch. In contrast, NexGen®, Attune® and Attune® Revision showed tendon contact for approximately half the width of the transition to the notch (Figure 3). PFC® Sigma® and Attune® demonstrated very similar tendofemoral contact to their equivalent revision components, although the shorter trochlear groove of Attune® Revision marginally increased contact at the transition. Discussion. Insall-Burstein® II, PFC® Sigma®, and PFC® Sigma® TC3 designs showed full contact with the quadriceps tendon at the anterior border of the ICN when combined with a short patellar tendon. NexGen®, Attune® and Attune® Revision had a more gradual transition between the trochlea and the notch, which resulted in less exposure to tendon contact. Even with the shorter trochlear groove required for revision components, Attune® Revision showed minimal difference in tendofemoral contact when compared with Attune®. There appears to be distinct benefit in a femoral design which reduces tendofemoral contact at the transition to the ICN; this may be of particular importance for patients with patella baja

Graft-tunnel mismatch of the bone-patellar tendon-bone (BPTB) graft is a major concern during anatomical anterior cruciate ligament (ACL) reconstruction if the femoral tunnel is positioned using a far medial portal technique, as the femoral tunnel tends to be shorter compared with that positioned using a transtibial portal technique. This study describes an accurate method of calculating the ideal length of bone plugs of a BPTB graft required to avoid graft–tunnel mismatch during anatomical ACL reconstruction using a far medial portal technique of femoral tunnel positioning.

Based on data obtained intra-operatively from 60 anatomical ACL reconstruction procedures, we calculated the length of bone plugs required in the BPTB graft to avoid graft–tunnel mismatch. When this was prevented in all the 60 cases, we found that the mean length of femoral bone plug that remained in contact with the interference screw within the femoral tunnel was 14 mm (12 to 22) and the mean length of tibial bone plug that remained in contact with the interference screw within the tibial tunnel was 23 mm (18 to 28). These results were used to validate theoretical formulae developed to predict the required length of bone plugs in BPTB graft during anatomical ACL reconstruction using a far medial portal technique.

Cite this article: Bone Joint J 2015;97-B:324–8.

Peri-prosthetic patellar fracture following resurfacing as part of total knee replacement (TKR) is an infrequent yet challenging complication. This case-control study was performed to identify clinical, radiological and surgical factors that increase the risk of developing a spontaneous patellar fracture after TKR. Patellar fractures were identified in 74 patients (88 knees) from a series of 7866 consecutive TKRs conducted between 1998 and 2009. After excluding those with a previous history of extensor mechanism realignment or a clear traumatic event, a metal-backed patella, any uncemented component or subsequent infection, the remaining 64 fractures were compared with a matched group of TKRs with an excellent outcome defined by the Knee Society score. The mean age of patients with a fracture was 70 years (51 to 81) at the time of TKR. Patellar fractures were detected at a mean of 13.4 months (2 to 84) after surgery. The incidence of patellar fracture was found to be strongly associated with the number of previous knee operations, greater pre-operative mechanical malalignment, smaller post-operative patellar tendon length, thinner post-resection patellar thickness, and a lower post-operative Insall-Salvati ratio.

An understanding of the risk factors associated with spontaneous patellar fracture following TKR provides a valuable insight into prevention of this challenging complication.

Introduction: Patellar crepitus (PC) has been reported in 13% of cruciatesubstituting total knee arthroplasty (TKA) patients resulting from synovial tissue impingement within the femoral component intercondylar box (IB). Patient factors, component design, and technical errors have been implicated in PC. We compared primary TKA patients with PC requiring surgery against matched controls to identify significant variables. Methods: The databases of 2 institutions were reviewed to identify patients requiring surgery for PC. A control group matched for age, sex, and BMI was identified. Patient charts and radiographs were reviewed. Statistical analysis was performed. Significant variables associated with patient anatomy, implant size and alignment were subsequently investigated in a computational model to evaluate tendofemoral contact. Results: Between 2002 and 2008, over 4000 primary TKAs were performed using the Press Fit Condylar Sigma (DePuy, Warsaw, Indiana) TKA. Of these, 59 knees developed PC requiring surgery. The mean time to presentation was 10.9 months. The incidence of PC correlated with greater number of previous surgeries (1.18 vs. 0.44, p= 0.002), decreased patellar button size (35.7 vs. 37.1mm, p=0.003), shorter patellar tendon length (54.5 vs. 57.9mm, p=0.01), and increase in posterior femoral condylar offset (1.27mm vs. 0.17mm, p=0.022). Using a patellar component of 32 or 35mm significantly increased the risk of PC compared to the use of a 38 or 41mm component (p< 0.01, RR=1.61, OR 2.63). Modeling results demonstrated decreased patellar tendon length created increased tendofemoral contact near the IB, while larger buttons increased separation between the tendon and the box edge. Conclusion: Shortened patellar tendon length and use of smaller patellar components may expose the quadriceps tendon to increased irritation as it traverses across the femoral component IB. Increasing posterior femoral offset may increase quadriceps tendon tension, further risking synovial tissue impingement within the IB

Patella subluxation assessed on dynamic MRI has previously been shown to be associated with anterior knee pain. In this MRI study of 60 patients we investigated the relationship between subluxation and multiple bony, cartilaginous and soft-tissue factors that might predispose to subluxation using discriminant function analysis.

Patella engagement (% of patella cartilage overlapping with trochlea cartilage) had the strongest relationship with subluxation. Patellae with > 30% engagement tended not to sublux; those with < 30% tended to sublux. Other factors that were associated with subluxation included the tibial tubercle-trochlea notch distance, vastus medialis obliquus distance from patella, patella alta, and the bony and cartilaginous sulcus angles in the superior part of the trochlea. No relationship was found between subluxation and sulcus angles for cartilage and bone in the middle and lower part of the trochlea, cartilage thicknesses and Wiberg classification of the patella.

This study indicates that patella engagement is a key factor associated with patellar subluxation. This suggests that in patients with anterior knee pain with subluxation, resistant to conservative management, surgery directed towards improving patella engagement should be considered. A clinical trial is necessary to test this hypothesis.

We report the outcome of 32 patients (37 knees) who underwent hemicallostasis with a dynamic external fixator for osteoarthritis of the medial compartment of the knee. There were 16 men (19 knees) and 16 women (18 knees) with a mean age at operation of 54.6 years (27 to 72). The aim was to achieve a valgus overcorrection of 2° to 8° or mechanical axis at 62.5% (± 12.5%). At a mean follow-up of 62.8 months (51 to 81) there was no change in the mean range of movement, and no statistically significant difference in the Insall-Salvati index or tibial slope (p = 0.11 and p = 0.15, respectively). The mean hip-knee-ankle angle changed from 190.6 (183° to 197°) to 176.0° (171° to 181°), with a mean final position of the mechanical axis of 58.5% (35.1% to 71.2%).

The desired alignment was attained in 31 of 37 (84%) knees. There were 21 excellent, 13 good, two fair and one poor result according to the Oxford knee score with no correlation between age and final score. This score was at its best at one year with a statistically significant deterioration at two years (p = 0.001) followed by a small but not statistically significant deterioration until the final follow-up (p = 0.17). All the knees with Ahlback grade 1 osteoarthritis had excellent or good results. Complications included pin tract infections involving 16.4% of all pins used, delayed union in two, knee stiffness in four, fracture of the lateral cortex in one and ring sequestrum in one.

In conclusion, hemicallostasis provides precision in attaining the desired alignment without interfering with tibial slope or patellar height, and is relatively free of serious complications.

The total knee replacement is one of the most common operations in an Orthopaedics Department. Despite of being a frequent procedure, it’s been calculated that between 18 and 20% of the patients aren’t satisfied with the result. One of the complications that may occur after TKR is patella baja, which has been related to poor outcomings. The main factor that may produce it after TKR is the shortening of the patellar tendon. As it has been published, the medial parapatellar approach and the eversion of the patella may cause patella baja. Many authors defend the use of minimally invasive approaches to prevent this complication. We studied if the use of the variation of the traditional approach that Insall described produces low patella. We have also analysed if this complication produces poorer outcomings. To know if the patellar tendon’s length was reduced, we used the Insall–Salvati Ratio. We measured it before and after the operation. We considered low patella if the IIS value was lower than 0,8. All the analyses were also done considering low patella if the ISR had decreased more than 10% after the operation. We reviewed 200 consecutive TKR performed in the Orthopaedics Department of Marqués de Valdecilla Hospital, from 1997 to 2001. All of the patients were operated by seniors surgeons. 2 patients were excluded because they died before we had finished the study. We analysed the influence of age, gender, BMI, preoperative diagnosis, degree of joint’s erosion and some surgical maneuvers. We also analysed the outcome, using the KSS score, paying special attention to the postoperative pain, the ability of walking and using stairs and the maximal postoperative extension and flexion degrees. SPSS v15.0 program was used for the statistical analysis. For the proportion analysis was used the ji-squared test or the Fisher test. For the main comparation we used the t-student test or the Wilcoxon test. The p values under 0,05 were considered to be significant. 3,3% of the TKR developed postoperative low patella. We founded statistically significant differences considering BMI, age and diagnosis. The shortening of the patellar tendon caused poorer outcomes:statistically significant differences were found in the maximal postoperative flexion and in climbing stairs. Considering low patella if the ISR decrease > 10% after the operation, the results were similar. It’s not been published the influence of the Insall’s variation in developing low patella after TKR. We couldn’t found references about the influence of age, BMI, diagnosis or level of joint’s erosion in the developing of this complication. In our study, obesity seems to protect and being young seems to predispose to suffer it;no surgical maneuver seems to have any influence. The outcome is worse if low patella is present. We concluded that the Insall variation is a comparable option to the MIS approaches in preventing the low patella after TKR

Many radiographic techniques have been described for measuring patellar height. They can be divided into two groups: those that relate the position of the patella to the femur (direct) and those that relate it to the tibia (indirect). This article looks at the methods that have been described, the logic behind their conception and the critical analyses that have been performed to test them.

Purpose: Medial Opening Wedge High Tibial Osteotomy (MOWHTO) is a joint preserving procedure of the knee. Currently we understand the anatomical changes occurring in the varus/valgus plane, but our understanding of other anatomical changes are limited. The objective of this study is to determine immediate anatomical changes occurring about the knee following MOWHTO. Our hypothesis is that anatomical changes occur in all planes of motion. More specifically, we hypothesize that posterior tibial slope is increased and patellar height is decreased immediately following the osteotomy. Methods: This study was prospective in design. Patients with knee OA were evaluated according to strict inclusion and exclusion criteria. Pre-operative clinical assessment, radiographic evaluation, and patient assessment scores were performed. Intraoperatively, patients had radiostereometric analysis (RSA) beads placed in a predetermined pattern. Intraoperative radiographs were taken. The MOWHTO was then performed. A second radiograph was then taken following the osteotomy. The radiographs were analysed using dedicated RSA computer software to determine anatomical changes. Results: Eleven patients were included in this study. Average age was 50 years. Mean error and condition number were 0.70 and 74 respectively, indicating highly accurate and reliable results. Analysis of the proximal tibia showed an average valgus correction angle of 8.69 degrees. The average osteotomy size was 12.5mm (9–17.5). Posterior tibial slope increased on average by 2.07 degrees (+5.91–−1.56). Analysis of the patella revealed anatomical changes occurred in all planes. However, the only consistent alteration was a decrease in patellar height by an average of 8.16mm (1.79–13.17). Additionally, there was a consistent increase in patellar tendon length by 5.30mm (2.38–7.34). Conclusions: Using RSA in MOWHTO for the first time, we were able to demonstrate a useful and accurate measurement tool for this procedure. We found there were many immediate anatomical changes following MOWHTO that are inconsistent and not well understood. There were, however, several anatomical changes that remained consistent among all subjects. Patellar height decreased, patellar tendon length increased, and posterior tibial slope demonstrated an average increase

Aim: To report our experience of revision knee arthroplasty with respect to surgical technique, joint line restoration and clinical outcome. Methods: A clinical and radiological review was made of 45 knee revisions performed between 1996 to1998 using the Kinemax system. The reasons for revisions were infection (19), wear (11), loosening (seven), base-plate fracture (four) and instability (five). A primary prosthesis was used in 10 (22%), a posterior stabiliser in 24 (53%) and a superstabiliser in 11 (24%). WOMAC pain and function scores, arc of motion and measurements of joint line and patellar height were made. Results: Three patients had died. Three knees had been revised a second time for instability and one had been arthrodesed for infection. The mean joint line elevation was 1.3mm compared with the primary and depressed 1.6mm when compared with the natural knee. Twenty-seven percent had patella infera and 13% had patella alta. A significant correlation was found between the change in patellar tendon length and the change in the joint line. The flexion arc was significantly improved from 83 degrees to 95 degrees. No relationship was found between the clinical outcomes and the changes in the joint-line. There were two deep infections (4.4%) and five knees were unstable. The three cases of flexion instability were due to failure to reconstruct adequately the antero-posterior (AP) diameter of the femur. Conclusions: By restoring the level of the joint-line, a less constrained prostheses can be used in revision surgery with good functional results. The AP diameter of the femur must also be reconstructed to avoid flexion instability

We studied changes in patellar tendon length after reconstruction of the anterior cruciate ligament using either the medial third of the patellar tendon as a graft (n = 40) or a Leeds-Keio artificial ligament (n = 40). Both types of ligament replacement had been supplemented with a MacIntosh extra-articular lateral substitution. The mean change in length in the tendon graft group was 6% (SD 5.39); in the Leeds-Keio group it was 2.4% (SD 4.93). The change in length was significant in both groups, but shortening was more frequent and more severe in the tendon graft group. There was shortening of 10% or more in 25% of knees after patellar tendon graft and 7.5% after use of a Leeds-Keio prosthesis

Minor degrees of malalignment of the patella and anatomical abnormalities including a flattened sulcus angle and an increased ratio between patellar tendon length and patellar length (PT:P) have been suggested as predisposing factors in the causation of chondromalacia patellae, as well as patellar instability. In order to confirm or refute this hypothesis a prospective study has been performed comparing the congruence and sulcus angles and the PT:P ratio in a group of 35 patients with chondromalacia confirmed by arthroscopy and a group of 33 patients with instability, with those of a group of 50 knees in normal volunteers. While there was a statistically significant correlation between an increased sulcus and congruence angle and a high-riding patella in patients with instability, no correlation could be identified in patients with idiopathic chondromalacia