Why are some patients dissatisfied with their TKA?

Jenny McConnell AM FACP and John Read MBBS

Macquarie University Hospital, Sidney, Australia

Correspondence author: Jenny McConnell, jenny@mcconnell-institute.com

Keywords: Total knee arthroplasty dissatisfaction, VMO orientation.

Introduction

Total knee arthroplasty (TKA) is a successful procedure for those with end stage osteoarthritis (OA) of the knee. Unfortunately, there are 15- 30% of individuals who report an unsatisfactory result (1). The incidence of dissatisfaction is more common in the those who are younger, female, with more psychosocial issues particularly anxiety and depression and increased co-morbidities - whether it be OA in other regions particularly LBP or diabetes (2).  These individuals often complain of pain and/or weakness negotiating stairs, which are typical symptoms of the PF pain patient. These difficulties increase the patient's feelings of anxiety.  However, rather than being just a psycho-social issue, there could be a biological explanation. As knee OA causes pain and pain causes quadriceps muscle atrophy, it appears that for some individuals the quadriceps muscle particularly the VMO is particularly ineffective and weak. There is a strong correlation between size of medial quadriceps at baseline as measured on MRI, amount of knee pain and articular cartilage damage at 2 and 4.5 years respectively, with a decrease in size being associated with more pain and more cartilage damage over time (3). As the VMO is associated with centering the patella in the trochlea and hence improving the efficiency of the quadriceps, we hypothesized that increased dissatisfaction with TKA could be associated with a more vertical orientation of VMO fibers and a more superior attachment of the fibers into the patella.  

The aims of this study are to examine:

i)      the orientation of the VMO fibers attaching into the patella in both the sagittal and coronal planes,

ii)    the most distal craniocaudal extent of the VMO attachment into the patella

iii)  the Insall- Salvati ratio

iv)   the rectus femoris (RF) patellar tendon (PT) angle to determine femoral/tibial position in the coronal plane (a surrogate measure for genu valgus/varus)

Method

MRI scans were performed on female subjects, prior to receiving rehabilitation or surgery, with primarily PF pathology of either PF instability or PF OA who were either non-surgical or post 6 months TKA with either a good recovery or a slow recovery. 

MRI measurements
1. VMO fascicle orientation was estimated on MRI in both the coronal plane (kinematic "x" axis) and sagittal plane (kinematic "y" axis) by measuring the angle formed between a line drawn along the dominant interfascicular fat plane within the distal substance of VMO and the long axis of distal femoral diaphysis on coronal and sagittal PD-weighted MRI sequences respectively.

2. As described by Balcarek et al (4), the most distal craniocaudal extent of the VMO was identified as the most caudal endpoint of the VMO on the sagittal PD-weighted MRI sequence. This point was then extended laterally to find the corresponding level on the same sagittal MRI sequence through the central longitudinal axis of the patella. The distance between this point and the proximal patellar pole was then measured and expressed as a percentage of total patellar length. 

3. The rectus femoris-patellar tendon angle (RF-PT Angle) was determined from the coronal PD-weighted MRI sequence by measuring the angle between a line drawn along the central axis of rectus femoris component of quadriceps tendon and a line drawn along the central axis of patellar tendon.

4. Insall-Salvati ratio was determined from a 3-5mm thick sagittal-oblique formation obtained from the sagittal PD-weighted MRI sequence. The plane of section corresponded with the long axis of patellar tendon and extended between the inferior pole of patella and central apex of tibial tubercle.

Results

In this pilot study, the data from 12 subjects were analysed (2 PF instability, 4 OA non-operative, 3 TKA good outcome and 3 TKA slow recovery). Prior to having the TKA, the MRI scans of the females who were pleased with their outcome from the TKA showed varus alignment of the tibia (2.4^o), a more horizontal orientation (74.9^o) of the VMO fibres and a more caudal attachment (39%) of the fibres, whereas the scans of the females who were slower to recover showed valgus alignment (8.2^o), more vertical orientation (57.8^o) of the VMO fibres and the fibre attachment was more cephalad (31%).

See table 1 for summary of findings

Table 1

Discussion

This pilot study is one of the first to investigate biological reasons for slower recovery and potential dissatisfaction with TKA. In the patients who had a positive outcome to the TKA the VMO fibres were more horizontal and more caudal so the seating of the patella into the trochlea would inherently be better than those who had a slower and initially poorer recovery, as their VMO fibres were more vertically oriented and attached more cephalad, resulting in increased PF instability and pain, particularly on stairs. 

References

1.     Paulsen MG, Dowsey MM, Castle D, Choong PF Preoperative psychological distress and functional outcome after knee replacement. ANZ J Surg. 2011;81(10):681-7

2.     Alattas SA, Smith T, Bhatti M, Wilson-Nunn D, Donell S . Greater pre-operative anxiety, pain and poorer function predict a worse outcome of a total knee arthroplasty. Knee Surg Sports Traumatol Arthrosc. 2017 Nov;25(11):3403-3410

3.     Wang Y, Wluka AE, Berry PA, Siew T, Teichtahl AJ, Urquhart DM, Lloyd DG, Jones G, Cicuttini FM. Increase in vastus medialis cross-sectional area is associated with reduced pain, cartilage loss, and joint replacement risk in knee osteoarthritis. Arthritis Rheum. 2012;64(12):3917-25.

4.     Balcarek P, Oberthür S, Frosch S, Schüttrumpf JP, Stürmer KM. Vastus medialis obliquus muscle morphology in primary and recurrent lateral patellar instability. Biomed Res Int. 2014

¿Por qué algunos pacientes no están satisfechos con su artroplastia total de rodilla?

Jenny McConnell AM FACP y John Read MBBS

Macquarie University Hospital, Sidney, Australia

Autor de la correspondencia: Jenny McConnell, jenny@mcconnell-institute.com

Palabras clave: Insatisfacción con la artroplastia total de rodilla, Orientación VMO.

Introducción

La artroplastia total de rodilla (ATR) es un procedimiento exitoso para aquellos con osteoartritis (OA) terminal de la rodilla. Desafortunadamente, hay un 15-30% de personas que informan un resultado insatisfactorio (1). La incidencia de insatisfacción es más común en aquellos que son más jóvenes, mujeres, con más problemas psicosociales, en particular ansiedad y depresión, y mayores comorbilidades, ya sea artrosis en otras regiones, en particular LBP o diabetes (2). Estas personas a menudo se quejan de dolor y/o debilidad al subir escaleras, que son síntomas típicos del paciente con dolor PF. Estas dificultades aumentan los sentimientos de ansiedad del paciente. Sin embargo, en lugar de ser solo un problema psicosocial, podría haber una explicación biológica. Como la artrosis de rodilla causa dolor y el dolor causa atrofia del músculo cuádriceps, parece que para algunas personas el músculo cuádriceps, en particular el VMO, es particularmente ineficaz y débil. Existe una fuerte correlación entre el tamaño del cuádriceps medial al inicio del estudio, medido mediante resonancia magnética, la cantidad de dolor de rodilla y el daño del cartílago articular a los 2 y 4,5 años respectivamente, y una disminución del tamaño se asocia con más dolor y más daño del cartílago con el tiempo (3). Como el VMO se asocia con centrar la rótula en la tróclea y, por lo tanto, mejorar la eficiencia del cuádriceps, planteamos la hipótesis de que una mayor insatisfacción con la artroplastia total de rodilla podría estar asociada con una orientación más vertical de las fibras del VMO y una inserción más superior de las fibras en la rótula.

Los objetivos de este estudio son examinar:

i)       la orientación de las fibras del VMO que se insertan en la rótula tanto en el plano sagital como en el coronal,

ii)      la extensión craneocaudal más distal de la inserción del VMO en la rótula

iii)     la relación Insall-Salvati

iv)     el ángulo del tendón rotuliano (PT) del recto femoral (RF) para determinar la posición femoral/tibial en el plano coronal (una medida sustitutiva del genu valgo/varo)