QUADRICEPS SPARING APPROACH: IS IT POSSIBLE IN ALL TOTAL KNEE ARTHROPLASTY PATIENTS?

Abstract

Introduction: The technique of quadriceps sparing knee arthroplasty involves a pure capsular incision, without violation of the extensor mechanism. This capsular incision should be placed distal to Vastus Medialis Obliquus (VMO). The termination of VMO is variable and may make the quadriceps sparing approach difficult. We initiated this study based on the hypothesis that quadriceps sparing approach may not be possible in all the patients undergoing total knee arthroplasty. We examined MRI scans of the knee joint to assess the variation in VMO muscle insertion in relation to the patella and variation of VMO muscle insertion in relation to the age.

Material and Methods: Between Jan 2005 and Dec 2005, 262 MRI scans of the knee joint were performed at our institute. We studied MRI scans of the patients aged 16 years and over. The scans with neoplasm or those without complete set of films were excluded from the study. There were 198 scans available for analysis. Our cohort consisted of 106 female patients and 92 male patients with an average age of 43 years (range 16–86 years). One hundred and thirty four patients were aged less than 50 years and 64 patients were 50 years or older.

We measured patellar height, VMO length on the axial views of the scans. The VMO insertion was calculated from the data and we divided the patients into proximal and distal groups in relation to the VMO termination on the patella. The proximal group included patients with VMO termination proximal to the mid-point of the patella and distal group included patients with VMO termination at or distal to the mid-point of the patella.

Results: The median height of the patella in female patients was 32mm (range 24–44mm) and in male patients was 36mm (range 28–48mm). The VMO length from the apex of the patella was 13.5mm (range 4–28mm) in female patients and 16mm (range 8–32mm) in male patients. Overall there were 119 (60%) patients in the proximal group and 79 (40%) in the distal group. In 20% of patients aged more than 50 years, VMO terminated in the distal half of the patella. In patients less than 50 years old, 50% had the VMO termination in the distal half of patella. A statistically significant inverse relationship was noted between the level of insertion of VMO and the age of the patient (p-value > 0.001, Chi-square test). There was no statistically significant relation between the level of insertion of VMO and the sex of the patient, in either age group (p-value 0.339).

Conclusion: Younger patients are statistically more likely to have a VMO which terminated at or more distal to the mid-point of patella. Therefore, the quadriceps sparing approach may not be possible in these subjects, however it is possible in majority of older patients.