022 23805673
Nilen A. Shah, M.S. Ortho, M.Ch. Ortho, Hitendra G. Patil, DNB Ortho , Amol S. Dhawale, DNB Ortho, Bipin M. Khedkar, FCPS Ortho, MS Ortho Department of Orthopaedics, Bombay Hospital and Medical Research Centre, Mumbai, Maharashtra, India
Abstract
A prospective comparative study was conducted to compare the mechanical axis post total knee arthroplasty (TKA) between two groups: In the first group of 100 knees (ASM group) Articular Surface Mounted navigation system was used to guide the distal femoral cut. In the second group of 100 knees (JIG group) conventional intramedullary femoral jig was used. The postoperative mechanical axis of the leg was within 3° of neutral align-ment in 90% of the TKA in the ASM group (mean 178.12°) as compared to 74% in the JIG group (mean 177.02°). This difference was statistically significant (P b 0.05). The data presented show that the use of limited femoral navigation leads to more accurate restoration of mechanical axis alignment when compared to conventional intramedullary femoral jigs.
Total knee arthroplasty (TKA) represents one of the most significant advances in orthopedic surgery as it achieves an immediate and excep-tional restoration in the quality of life that is comparable only to a few other procedures [1,2]. Restoration of the mechanical axis post TKA is considered to be of paramount importance to allow optimum load sharing and prevent eccentric loading through the prosthesis which may lead to loosening, instability and early implant failure [3,4]. Computer navigation is recognized as a valuable tool in restoring the mechanical axis post TKA and thereby increases long-term survi-vorship and function of the prosthesis [5,6]. However, the disadvan-tages associated with the use of computer navigation are its cost [7], increased surgical time [8] and risk of an iatrogenic fracture through the pin sites [9–12].
With the use of conventional intramedullary femoral jig for distal femoral cut, an error up to 8° can occur in restoration of neutral mechanical femoral axis depending on the size and length of the intramedullary guide [13]. Femoral bowing in the coronal plane makes accurate placement of intramedullary jig even more challenging. Incidence of femoral bowing is high in the Asian population especially females [14,15] which constitute the majority of patients who need a TKA. We decided to use navigation for the distal femoral cut with a specialized navigation unit called Articular Surface Mounted (ASM) navigation system (Stryker). Navigation was not used for the rest of the bony cuts as all other bony landmarks i.e. femoral epicondyle, tibial malleoli and tibial tuberosity are all subcutaneous and palpable which make accurate placement of jig possible [16].