Page 2 - Orthofeed_Issue4_Feb2022

Evidence-based management of instability after primary total knee arthroplasty 01

Surgery

Evidence-based management of instability after primary
total knee arthroplasty

Endorsed by: Dr. Ajit Prabhu, Orthopedic Surgeon, Bangalore

Over the last two decades, instability has been identified as the underlying cause for 10 to 26% of
revision procedures. Instability following total knee arthroplasty (TKA) is one of the most common
1
reasons for patient dissatisfaction following TKA, thus leading to revision. Al-Jabri et al in their
1,2
recent systematic review presented an elaborate description and critique of the different types of

instability, their causes, and evidence-based management options. 3

Methodology
The authors conducted a systematic search of Extension instability

literature with a defined strategy on MEDLINE
Genu recurvatum
and Google Scholar from January 2000 to
September 2021.
Flexion instability

Instability and its classification Mid-flexion instability

Instability is defined as abnormal and excessive
displacement of the prosthetic joint which leads Global multiplanar instability

to its failure. Most of the modern literature
4
supports classifying instability
During patient assessment, clinicians can
pragmatically as :
4
categorize patients based on the commonest
causes of instability and whether they are

present (Table 1) :
3
Table 1: Categorization of common aetiologies underlying instability 3

Patient-specific factors Implant-related factors Technique-specific factors

Traumatic falls postoperatively Implant type and design Malalignment of the implant
Malrotation
A history of connective tissue disorders Wear and bone loss/osteolysis causing
loosening/ settling of implants Ligament failure

Neuromuscular disorders such as Inadequate/inaccurate bone resections
poliomyelitis Progressive gap imbalance and
instability Failure to balance the knee coronally
through either underrelease or
inadvertent over-release of the soft
tissue envelope