ABSTRACT
Background@#Optimal placement of the components and achieving a neutral mechanical axis are the main goals of total knee arthroplasty (TKA). Different computerised navigation systems are presently used for these purposes. This aim of this study was to compare the pinless navigation (PNA) TKA performed using iAssist with the conventional instrumented (CIN) TKA in terms of functional and radiological outcomes. @*Methods@#A total of 100 knees operated for TKA by a single surgeon were studied retrospectively for a period of 2 years. Weightbearing postoperative radiographs of the knees along with scanograms of the lower limbs were used for measurements of component positioning, mechanical axis alignment, and number of outliers. Oxford knee scoring was used for functional analysis. @*Results@#No statistically significant difference was seen in the mean mechanical axis alignment (hip-knee-ankle angle), coronal alignment (α and β angles) and sagittal alignment (γ and δ angles) of the femoral and tibial components between the two groups. Though the percentage of outliers for mechanical axis alignment was lower in the PNA-TKA group than in the CIN-TKA group, the difference was not statistically significant (p = 0.73). The number of outliers for the femoral and tibial component positioning in coronal and sagittal planes was not statistically significantly different between the two groups. No statistically significant difference (p = 0.68) was noted between the two groups with respect to the Oxford Knee Score. The mean surgical time was greater in the PNA-TKA group by 11 minutes, which was statistically significantly longer (p = 0.018). Complications were seen in 6.89% of the cases in the CIN-TKA group, while none in the PNA-TKA group. @*Conclusions@#The accurate mechanical axis alignment and component positioning can be achieved with the conventional instrumentation, so the use of PNA system, which adds to the surgical cost, is questionable. Also, equally good short-term functional outcome can be achieved with the conventional instrumentation. The surgeon must be accustomed with the instrumentation of the PNA system, or it adds to the surgical time.
ABSTRACT
Background@#Optimal placement of the components and achieving a neutral mechanical axis are the main goals of total knee arthroplasty (TKA). Different computerised navigation systems are presently used for these purposes. This aim of this study was to compare the pinless navigation (PNA) TKA performed using iAssist with the conventional instrumented (CIN) TKA in terms of functional and radiological outcomes. @*Methods@#A total of 100 knees operated for TKA by a single surgeon were studied retrospectively for a period of 2 years. Weightbearing postoperative radiographs of the knees along with scanograms of the lower limbs were used for measurements of component positioning, mechanical axis alignment, and number of outliers. Oxford knee scoring was used for functional analysis. @*Results@#No statistically significant difference was seen in the mean mechanical axis alignment (hip-knee-ankle angle), coronal alignment (α and β angles) and sagittal alignment (γ and δ angles) of the femoral and tibial components between the two groups. Though the percentage of outliers for mechanical axis alignment was lower in the PNA-TKA group than in the CIN-TKA group, the difference was not statistically significant (p = 0.73). The number of outliers for the femoral and tibial component positioning in coronal and sagittal planes was not statistically significantly different between the two groups. No statistically significant difference (p = 0.68) was noted between the two groups with respect to the Oxford Knee Score. The mean surgical time was greater in the PNA-TKA group by 11 minutes, which was statistically significantly longer (p = 0.018). Complications were seen in 6.89% of the cases in the CIN-TKA group, while none in the PNA-TKA group. @*Conclusions@#The accurate mechanical axis alignment and component positioning can be achieved with the conventional instrumentation, so the use of PNA system, which adds to the surgical cost, is questionable. Also, equally good short-term functional outcome can be achieved with the conventional instrumentation. The surgeon must be accustomed with the instrumentation of the PNA system, or it adds to the surgical time.
ABSTRACT
Background@#This study was done to study the anthropometry of nonarthritic Asian knees; to determine the differences in morphology between knees of different ethnicities and to compare the knee anthropometry values with sizes of available knee implants. @*Methods@#Magnetic resonance imaging scans of 100 nonarthritic Indian knees were analyzed. Anteroposterior (AP) length, mediolateral (ML) length, and aspect ratio of the distal femur and proximal tibia, patellar length, and patellar tendon length were measured. These values were compared with values of other ethnicities from literature. The values were also compared with sizes of available knee implants and evaluated for mismatch. @*Results@#All the parameters of female knees were significantly smaller than those of male knees (p < 0.05). The distal femur of Indian knees resembled that of Chinese knees with similar AP and ML lengths and aspect ratio. The distal femur of Indian knees had a significantly smaller AP, ML, and aspect ratio than those of Hispanic knees did. In comparison to Caucasian distal femur, Indian knees had smaller AP and ML lengths and larger aspect ratio. In terms of the proximal tibia, the Indian knees were smaller than Chinese (only ML), Caucasian (AP and ML) and Hispanic (AP and ML) knees. On comparison with implant sizes, there was a mismatch between the distal femur morphology and the dimensions of all implants. For a given AP length, the ML dimensions of all implants were smaller than the measured ML length of the knee. However, the tibial components of all the studied implants correlated well with the tibial morphology. @*Conclusions@#Distinct anthropometric differences exist between knees of different ethnicities. The knees of females were smaller than the knees of males. In Indian knees, the ML-AP aspect ratio of the distal femur was higher than that of the currently available femoral components. These results suggest the need for race-specific knee implants.