Current variability in the assessment of component position for the unhappy knee replacement

Abstract

IntroductionTotal knee arthroplasty (TKA) has a success rate of 80–90%, but despite this encouraging figure a painful TKA can be a source of dismay for patients and surgeons. Computed tomography (CT) scan has been developed as a tool to collect data in the analysis of TKA component placement. Protocols used to collect such data exist in orthopaedic and radiology practice with little standardization and significant variation. The aim of this review article was to evaluate such variability by sampling a series of protocols from a range of different radiology practices within NSW, Australia in a case‐based manner and to then compare them against any literature standards.MethodsThe literature was surveyed for existing CT scan protocols used in TKA assessment. These were then compared with a series of metropolitan and rural radiology firms across the public and private sectors in NSW, Australia.ResultsConsiderable variability exists between current protocols across NSW, Australia, which differ with proposed literature standards.ConclusionVariabilities encountered when comparing the different scanning protocols in use for the assessment of TKA constitute a large potential source of error in the analysis of TKA component positioning. The reliance surgeons place on such analyses suggests the need for an established scanning protocol with an incorporated grading system and standardized values to allow reproducible data to help assess and predict TKA function.

Interobserver Agreement of Post-operative Perth Computed Tomography Protocol Data in Total Knee Arthroplasty

“…There are several limitations to this study worth considering. Firstly, there are currently no standardised protocols with well-defined steps and reference values or grading systems that exist for post-TKA CT imaging [4]. Berger et al originally attempted to establish a system for assessing femoral and tibial component rotation following TKA using CT imaging as a way to identify potential factors contributing to complications and poor outcomes post-operatively [13].…”

“…Data collection and patient surveys suggest that around 80% of patients are satisfied with their results, leaving close to 20% of patients unhappy with outcomes [ 2 , 3 ]. Of those requiring revisions, around 9% are a result of knee pain and poor function resulting from maltracking and prosthesis instability [ 4 , 5 ].…”

“…This technique measures all the parameters in which the components vary, namely, the alignment of the femoral and tibial prostheses in the coronal, sagittal, and axial planes, and the ways in which the femoral and tibial components are rotationally matched with respect to each other [ 6 ]. The Perth CT protocol remains the predominant assessment tool used to date for post-operative analysis of alignment, with most radiology firms deriving their scanning methodology from it, albeit with slight modifications [ 4 , 6 ]. This proliferation of CT scan protocols without standardisation, however, produces subsequent variations in methodology, lacks reproducibility, and makes comparison very difficult across orthopaedic practice [ 4 , 24 ].…”

“…The Perth CT protocol remains the predominant assessment tool used to date for post-operative analysis of alignment, with most radiology firms deriving their scanning methodology from it, albeit with slight modifications [ 4 , 6 ]. This proliferation of CT scan protocols without standardisation, however, produces subsequent variations in methodology, lacks reproducibility, and makes comparison very difficult across orthopaedic practice [ 4 , 24 ]. Thus, despite the increasing use of the Perth CT protocol, current literature highlights a low intra-observer variability for this assessment, with inter-observer error yet to be commented on [ 4 , 6 ].…”

A CT Based assessment of femoral component external rotation in TKA for osteoarthritic varus knees

“…With no standard parameter to follow and multiple variables at the time of surgery affecting femoral component rotation, the number of outliers in postoperative axial alignment of the femoral component with respect the desired femoral external rotation are likely to be high 12,13,23 and has long been overlooked 1 . This degree of mismatch in the femoral component placement can have a graded, multifaceted, subtle or subclinical effect on the tibiofemoral and patella-femoral biomechanics and stresses and may contribute significantly towards 10 to 20% unhappy patients after TKA 24 .…”