Patellofemoraler Schmerz nach primärer Knieendoprothetik: Behandlungsalgorithmus und Literaturüberblick

[Predictors for persistent pain and dissatisfaction after total knee arthroplasty]

BACKGROUND

A substantial number of patients patients suffer from persistent pain or are unsatisfied after total knee arthroplasty (TKA).

OBJECTIVES

This work aims to present the frequency of postoperative persistent pain and/or dissatisfaction as well as known causes and predictors.

MATERIALS AND METHODS

The current literature is studied regarding the subject and is reviewed narratively.

RESULTS

Most postoperative problems did not arise from operation details, but from patient-related criteria, a lack of patient education and selection. The satisfaction correlates most strongly with the reduction of preoperative pain.

CONCLUSION

For a successful TKA, care should be taken that the following aspects are met preoperatively: clinically and radiologically advanced osteoarthritis, a patient age preferably older than 60 years, sufficient psychosocial resources to cope with postoperative stress, no opioid medication and realistic expectations after TKA. Postoperatively, patients with persistent pain or dissatisfaction should be checked for any prosthesis-related problems. If no prosthesis-related problems could be detected, the patients should be referred for interdisciplinary therapies.

[Anterior knee pain after total knee arthroplasty : Causes, diagnosis and treatment]

BACKGROUND

Anterior knee pain is one of the most common complications after total knee arthroplasty. An incidence of up to 30 % has been reported in peer-reviewed studies.

TARGET

The purpose of this study was to systematically review the literature and to identify determinants that have been analyzed with regard to anterior knee pain.

CAUSES

Patient- and knee-specific characteristics, prosthetic designs and operative techniques are addressed as well as functional and neurologic determinants. Instability, increased contact pressure in the patellofemoral joint and patella maltracking due to malrotation of components, offset errors, ligament insufficiencies or patella baja are mechanical reasons for anterior knee pain. Functional causes include pathologic gait patterns, quadriceps imbalance and dynamic valgus. They have to be differentiated from infectious and inflammatory causes as well as soft tissue impingement, arthrofibrosis and neurologic diseases.

TREATMENT

A differentiated treatment algorithm is recommended. Often conservative treatment options exist, however, particularly with most mechanical causes revision surgery is necessary.

[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.

Gap-balancing technique combined with patient-specific instrumentation in TKA

INTRODUCTION

Combining patient-specific instrumentation (PSI) with a balancer device in total knee arthroplasty (TKA) to achieve functional femoral rotational alignment is a novel technique. The primary goal of this study was to introduce a new method to combine PSI with a gap-balancing technique and to determine the impact of the technique on rotation of the femoral component.

MATERIALS AND METHODS

Twenty-five primary TKAs (15 women, 10 men) were prospectively studied. All TKAs involved PSI with an associated gap-balancing device. Front plane alignment was performed intraoperatively with the PSI, followed by rectangular, symmetrical extension and creation of a flexion gap using the balancer device to set the femoral rotation.

RESULTS

Femoral component rotation was between 3° internal and 6° external rotation versus the transepicondylar axis. There were no postoperative signs of patellofemoral dysfunction. In no cases was the resulting joint line displacement >3 mm. The mean elevation was 1.2 ± 0.9 mm (range 0-3). The leg axis was straight in all cases (±3°), at a mean of 1.6° ± 1.0° varus (range 0°-3° varus).

CONCLUSIONS

PSI was with the gap-balancing technique was successfully used without affecting anatomical alignment. With the balancer device, PSI can be used more widely than techniques based solely on landmarks, as the soft-tissue tension can be taken into account, thus virtually eliminating flexion instabilities.

The effect of trochlea tilting on patellofemoral contact patterns after total knee arthroplasty: an in vitro study

INTRODUCTION

Patellofemoral complications are one major concern after total knee arthroplasty (TKA). Anterior knee pain is one of these complications and to a high percentage responsible for unsatisfied patients after TKA. Malrotation of the femoral component can contribute to retropatellar peak pressure and consequently to anterior knee pain.

MATERIALS AND METHODS

Eight fresh frozen cadavers were tested in a force-controlled knee rig after TKA during isokinetic flexing of the knee from 20° to 120° under constant load. By tilting the trochlea in the material of the created femoral component replicas, a rotation of the femoral component by 3° internal, 0° (neutral), 3° and 6° external rotation to transepicondylar line was simulated without changing flexion or extension gap. Retropatellar pressure distribution was measured during flexion and extension of the knee while quadriceps muscles and hamstring forces were applied.

RESULTS

Maximum peak pressure for internal rotation of the trochlea was 7.32 ± 2.31 MPa, in neutral position the pressure reduced slightly to 7.31 ± 2.12 MPa and during further external rotation of trochlea rotation a decrease from 3° with 7.18 ± 2.14 MPa to 6° with 6.22 ± 1.83 MPa was observed (p < 0.01). There was a tendency of lower quadriceps force with increasing external rotation of the trochlea (p = 0.08).

CONCLUSIONS

The implantation of the femoral component by 3° internal trochlea rotation to transepicondylar line resulted in a highly significant increase of the mean maximal retropatellar pressure compared to 6° external rotation of the trochlea of the femoral component (p < 0.01). A higher retropatellar pressure might lead to anterior knee pain after TKA. We recommend an external rotation of the femoral component between 3° and 6° to anatomical transepicondylar line to reduce the maximal retropatellar pressure, but only if adequate soft tissue balancing and stable knee kinematics are provided.

[Rare cause of knee pain after total knee arthroplasty]

A painful knee after total knee arthroplasty may have various causes. In addition to commonly occurring causes, such as infections, aseptic loosening, implant failure or typical anterior knee pain, rare causes also have to be taken into account. We report a previously unknown cause of knee pain after total knee replacement involving a non-resected medial meniscus, which was sandwiched between the medial condyle of the femur and the inlay of the prosthesis and caused pain typical for a medial meniscus. After arthroscopic meniscectomy the patient was symptom-free.

[Musculoskeletal modeling of the patellofemoral joint. Dynamic analysis of patellar tracking]

Numerical simulations contribute to the understanding of patellofemoral diseases. Whereas cadaveric studies are limited with respect to reproducibility of results, the impact of different operative approaches can be systematically evaluated based on mathematical models. The objective of this study was to introduce a musculoskeletal model which is capable of describing the dynamic interactions within the patellofemoral joint. It contains major bony and soft tissue structures of the right leg including the medial patellofemoral ligament (MPFL). Two operative approaches were considered based on the model to illustrate the effect on patellofemoral biomechanics during active knee flexion: On the one hand the effect of femoral insertion during MPFL reconstruction on medial soft tissue tension, and on the other hand the difference in patella kinematics before and after total knee arthroplasty. Finally, the potential of musculoskeletal models is discussed.