Revision surgery for patellar dislocation after primary total knee arthroplasty

Management of patella maltracking after total knee arthroplasty: a systematic review

PURPOSE

Patella maltracking is among the most frequent causes of poor outcomes and early failure after total knee arthroplasty (TKA), with an incidence that ranges from 1 to 20%. Even if there is agreement between authors regarding the preoperative and intraoperative management of patella maltracking in TKA, less clear are postoperative conducts. The purpose of this systematic review is to summarize and compare surgical techniques used to treat patella maltracking after TKA.

METHODS

A systematic review of the literature was performed with a primary search on Medline through PubMed. The PRISMA 2009 flowchart and checklist were used to edit the review. Screened studies had to provide clinical, functional and radiological results and complications of the proposed treatment to be included in the review.

RESULTS

A total of 21 articles were finally included. Three main types of surgical procedures and other minor techniques have been identified to manage patella maltracking after TKA. The choice of the proper technique to use in the specific case depends on several factors, first of all the malpositioning of the prosthetic components.

CONCLUSION

Patella maltracking after TKA represents a frequent and challenging problem for orthopedic surgeons. Treatments described in the literature are often able to correct an abnormal patellar tracking; nevertheless, authors report variable percentages of residual knee pain and dissatisfaction in re-treated patients. Therefore, it would be desirable to prevent the maltracking condition at the time of primary arthroplasty, using proper surgical precautions.

Extensive Proximal Extensor Mechanism Realignment for Chronic Patella Dislocations in Revision Knee Arthroplasty: Surgical Technique

Patella dislocation after primary or revision total knee arthroplasty (TKA) is a major challenge in revision surgery. In practice, the main reason for patella maltracking and instability following TKA is malrotation of the femoral and/or tibial components. A number of soft tissue procedures, once component malrotation is corrected, have been described including proximal realignment, quadricepsplasty and distal realignment of patellar tendon with tibial tubercle osteotomy. Here, we describe our modified surgical technique in managing chronically dislocated patellae in knee arthroplasty which comprises of extensive lateral releases, vastus medialis obliquus (VMO) advancement and soft tissue reconstruction of the extensor mechanism with accompanying three case presentations achieving satisfactory clinical outcomes.

Revision total knee arthroplasty for patellar dislocation in patients with malrotated TKA components

PURPOSE

Patellar dislocation is a serious complication leading to patient morbidity following total knee arthroplasty (TKA). The cause can be multifactorial. Extensor mechanism imbalance may be present and result from technical errors such as malrotation of the implants. We sought to understand the reasons for post-arthroplasty patellar dislocation and the clinical outcomes of patients in whom it occurs.

METHODS

This is a retrospective cohort study assessing the outcomes of revision surgery for patellar dislocation in patients with component malrotation in both primary and revision TKAs. Patient demographics, dislocation etiology, presurgical deformity, intraoperation component position, complications, reoperation, and Knee Society Scores (KSS) were collected.

RESULTS

Twenty patients (21 knees) were identified. The average time from primary arthroplasty to onset of dislocation was 33.6 months (SD 44.4), and the average time from dislocation to revision was 3.38 months (SD 2.81). Seventeen knees (80.9%) had internal rotation of the tibial component and seven knees (33.3%) had combined internal rotation of both the femoral and tibial components. Fifteen knees (71.4%) were treated with a condylar constrained implant at the time of revision, and five knees were converted to a hinged prosthesis. The average follow-up time was 56 months. During this time, one patient (4.54%) had a recurrent dislocation episode, requiring further surgery. At final follow up, the mean KSS was 86.2.

CONCLUSION

Revision TKA following patellar dislocation for patients with malrotated components was associated with high success rates. After revision surgery, patients had a low recurrence of patellar dislocation, low complication rates, and excellent functional outcomes.

Combined CT-based and image-free navigation systems in TKA reduces postoperative outliers of rotational alignment of the tibial component

INTRODUCTION

Rotational malpositioning of the tibial component can lead to poor functional outcome in TKA. Although various surgical techniques have been proposed, precise rotational placement of the tibial component was difficult to accomplish even with the use of a navigation system. The purpose of this study is to assess whether combined CT-based and image-free navigation systems replicate accurately the rotational alignment of tibial component that was preoperatively planned on CT, compared with the conventional method.

MATERIALS AND METHODS

We compared the number of outliers for rotational alignment of the tibial component using combined CT-based and image-free navigation systems (navigated group) with those of conventional method (conventional group). Seventy-two TKAs were performed between May 2012 and December 2014. In the navigated group, the anteroposterior axis was prepared using CT-based navigation system and the tibial component was positioned under control of the navigation. In the conventional group, the tibial component was placed with reference to the Akagi line that was determined visually. Fisher's exact probability test was performed to evaluate the results.

RESULTS

There was a significant difference between the two groups with regard to the number of outliers: 3 outliers in the navigated group compared with 12 outliers in the conventional group (P < 0.01).

CONCLUSIONS

We concluded that combined CT-based and image-free navigation systems decreased the number of rotational outliers of tibial component, and was helpful for the replication of the accurate rotational alignment of the tibial component that was preoperatively planned.

[Causes and management of patellar instability after total knee replacement : Lateralization, subluxation and luxation]

BACKGROUND

Patellofemoral complications after total knee arthroplasty are responsible for a variety of surgical revisions.

OBJECTIVE

The causes of the various types of instability of the patella are listed in a differentiated way and the importance of clinical and imaging diagnostics as well as preventive strategies are elaborated.

MATERIAL AND METHODS

This article is based on a selective literature search in the PubMed database and on the long-standing experience of the author.

RESULTS

Besides postoperative genu valgum with malalignment of the extensor mechanisms, other risk factors for patellar maltracking are insufficiency of the medial retinaculum, weakening of the vastus medialis muscle, contracture of the quadriceps femoris or tractus iliotibialis muscle, residual valgus deformity after total knee replacement, femoral or tibial malrotation as well as malpositioning of the patella, inappropriate design of the prosthesis and asymmetrical resection of the patella. The causes with respect to incorrect component positioning, faulty preparation of the patella, leg malalignment, inappropriate design of the prosthesis and soft tissue imbalance have to be recognized in order to address the problem in a targeted way. The preferred method of choice in the case of patellofemoral instability after total knee replacement is normally surgery; however, the cause for the instability has to be identified and consequently corrected before surgery. Without a clearly identified cause surgical measures are unrewarding and almost regularly lead to an unsatisfactory outcome.

CONCLUSION

Patella maltracking after total knee arthroplasty is multifactorial and requires an accurate clarification. A surgical revision is only recommended in cases of clearly defined causes of pain or a clearly defined reason for patella malpositioning.

Correlation between knee kinematics and patellofemoral contact pressure in total knee arthroplasty

The aim of this study is to evaluate the relationship between patellofemoral contact stress and intraoperative knee kinematic patterns after mobile bearing total knee arthroplasty (TKA). Medial osteoarthritic knees of forty-six posterior-stabilized total knee prostheses were evaluated using a computed tomography-guided navigation system. Subjects were divided into two groups based on intraoperative knee kinematic patterns: the medial pivot group (n=19) and the non-medial pivot group (n=27). Mean intraoperative patello-femoral contact stress was significantly lower in the medial pivot group than in the non-medial pivot group (1.7MPa vs. 3.2MPa, P<0.05). An intraoperative medial pivot pattern results in reduced patello-femoral contact stress.

Is the anterior tibial tuberosity a reliable rotational landmark for the tibial component in total knee arthroplasty?

To analyze the morphology of the tibial plateau, we studied 100 computed tomographic scans of arthritic knees and measured the mediolateral (ML) and anteroposterior (AP) dimensions as well as their aspect ratio using 3 reference axes of rotation: transepicondylar axis (TEA), posterior tibial margin (PTM), and anterior tibial tuberosity (ATT) axis. Relative to the TEA, the PTM was internally rotated by 1.6° ± 5.1°, and the ATT externally rotated by 14.8° ± 7.2°. The AP and ML dimensions and aspect ratio differ significantly when the reference axis was ATT compared with PTM or TEA and variations were greater while using ATT axis. Our data demonstrate (1) that design of the tibial component restricts the choice of rotational alignment and (2) that ATT is not a reliable landmark for rotation of the tibial component.

Finding and defining the ideal patellar resection plane in total knee arthroplasty

Asymmetric resection of the patella during total knee arthroplasty (TKA) correlates with anterior knee pain, bony impingement and patellar maltracking. Despite this, there is no consensus regarding the desired landmarks; the cut is often done freehand; and there has been no quantitative comparison of proposed resection planes. The objectives of this study were to: determine the intra- and inter-surgeon repeatability of two radiographic resection definitions (medial-divot, MD, and medial-lateral extents, MLE); calculate two additional definitions from the radiographic patellar circumferences (parallel to the anterior surface, ANT, and perpendicular to the anteroposterior tangent points, PERP); compare the clinical resection line to the previous four definitions before and after introducing the MD method clinically; and identify distinguishing features of patellae with better vs. worse resection angles. We hypothesized that the MD method would improve repeatability both radiographically and clinically, that the different radiographic definitions would produce comparable angles, and that we could identify distinguishing features. For the radiographic study, three surgeons drew lines on 40 preoperative X-rays plus 9 interspersed repetitions of 3 of these X-rays. For the clinical study, we compared the patellar resection angle for 20 patients immediately before and after implementing the new method. Given that the clinical goal is to have equal distances from the resection surface to the anterior surface, we compared all results to the ANT definition as the theoretically ideal definition. Confirming the first hypothesis, intra-surgeon repeatability (10 repetitions of 3 X-rays) and inter-surgeon repeatability (3 surgeons x 40 X-rays) were both significantly better using the new MD method compared to the MLE method (p<0.001). Contrary to the second hypothesis, clinical use of the MD method did not improve resection symmetry. Contrary to the third hypothesis, the PERP definition was significantly different from the other three definitions. In agreement with the fourth hypothesis, female patellae and more deformed patella had significantly greater asymmetry (p<0.001). Given the inherent variability shown in drawing the 'patellar horizon', we encourage researchers to draw the line several times and average the results when comparing tilt or the resection angle to this horizon. Based on the distinguishing characteristics of asymmetrically resurfaced patellae in our series, we recommend that clinicians be particularly careful when resecting laterally deformed patellae and the patellae of female patients.

How to address the patella in revision total knee arthroplasty

Patellar issues need to be carefully addressed during any revision TKA and the surgeon often faces the question of what to do with the patella at the time of revision. The choice of treatment is often made by balancing what is technically feasible with the risk of potential complications and takes into account the reason for the revision, the type of implant (i.e., metal-backing or all-polyethylene), the duration of implantation, the fixation, the stability, the sterilization technique, the wear, the presence of osteolysis, the compatibility with the femoral component, and most importantly the remaining bone stock. The various treatment options then include retention of the patellar component, revision of the patellar component, removal of the component with retention of the patellar bony shell (patelloplasty or resection arthroplasty), excision of the patella (partial or total patellectomy), secondary resurfacing, and reconstruction/augmentation of the patellar bone stock. Isolated patellar revision is associated with a high complication rate and recurrent failure when poor patellar tracking, incongruent designs and malalignment of the femoral and tibial components exist. Retention of a well-fixed all-PE (non-oxidized) patella is advocated where possible and revision of metal-backed patella is recommended (unless well fixed with poor bone stock). In the situation of a deficient patella, patelloplasty, augmentation procedures and very rarely patellectomy are other viable options.

Comparison of the Insall-Burstein II and NexGen legacy total knee arthroplasty systems with respect to patella complications

This study retrospectively contrasts 2 cohorts of consecutive patients ""(N = 202) after primary total knee arthroplasty with respect to the types and numbers of patella and extensor mechanism complications. Our results demonstrated an overall decrease of patellofemoral complications associated with the NexGen Legacy PS system (Zimmer Inc, Warsaw, Ind). Patella fractures decreased from 6 to 0 (P = .013), avascular necrosis from 9 to 0 (P = .0002), and lateral retinacular release trended down from 24 to 14. The Insall-Burstein II (Zimmer Inc, Warsaw, Ind) has a significantly higher incidence of patella fractures, avascular necrosis, and the lateral retinacular release. We feel that the alteration and adjustment of the patellofemoral dimension in the NexGen Legacy design to a more anatomical, extended design of the femoral component and patella modifications led to a decrease in the incidence of complications.

Revision total knees done for extensor problems frequently require reoperation

We retrospectively reviewed 361 patients who had a revision total knee arthroplasty done for an extensor mechanism problem to assess the prevalence, etiology, and risk factors for subsequent reoperation. The prevalence of reoperation was 23% because 84 patients were reoperated on one or more times. The average time to the first reoperation was 2.4 years. The total number of reoperations was 127 with 58 patients reoperated on once, 15 reoperated on twice, and 11 reoperated on three or more times. The cumulative risk of a reoperation for any reason after index revision was 7% at 1 year, 19.6% at 5 years, and 35.9% at 10 years. The most common reason for reoperation was a new or recurrent patellofemoral problem, which accounted for 33% of the first reoperations. The risk of reoperation was substantially lower for patients that had femoral or tibial component malrotation corrected at the time of revision TKA. The risk of reoperation after revision TKA for an extensor mechanism complication increased in patients operated on in the 1990s compared with patients operated on in the 1970s and 1980s.

LEVEL OF EVIDENCE

Therapeutic study, Level-IV-1 (case series). See the Guidelines for authors for a complete description of levels of evidence.