Summary

Rajavithi stress device is reliable in measuring lateral compartment gap which useful for diagnosis, treatment and postoperative follow-up of patients

Abstract

Background

PLC injuries can be overlooked or misdiagnosed particularly in combined PCL and PLC injuries. Chronic untreated PLC injuries can cause chronic pain, residual instability and eventually lead to early degenerative changes of the joint.
Varus stress radiographic device is very helpful in diagnosis of PLC injuries. This study were to analyse the reliability of measurements of the amount of lateral compartment gap under varus stress radiographs of isolated FCL or PLC injuries and to create a low-cost varus radiographic device(Rajavithi stress device) for helpful in diagnosis, treatment and post operative follow-up patients.

Methods

Five fresh-frozen cadaveric specimens were used in this study. Each specimen was tested with a 12-Nm varus moment load that was applied through the Rajavithi stress device. Plain film was performed in the intact state and after sequential cutting of the fibular collateral ligament, the popliteus tendon, the popliteofibular ligament (with sectioning of all three of these structures being equivalent to a grade-III posterolateral knee injury), the anterior cruciate ligament, and the posterior cruciate ligament respectively.

Result
with use of a 12-Nm moment Rajavithi varus stress device, radiographic measurement
demonstrated a mean increase in lateral compartment gapping of 2 mm for an isolated fibular collateral ligament tear and 3.69 mm for a grade-III posterolateral knee injury when compared with the intact knee. In addition, the combined injuries of PLC with ACL should be suspected if the increase in lateral compartment gapping was approximately 7.6 mm compared with intact knee. Similarly, a combined PLC,
ACL and PCL should be considered if the increase in lateral compartment gapping is approximately 8.3 mm. There were no statistically significant differences comparing to the study from Laprade et al.

Conclusion

The Rajavithi stress device are a low-cost device (7,840 baht), clinically applicable and produce objective and reproducible measures of lateral compartment gapping so the Rajavithi stress device can be applied as a standard device which useful for diagnosis, treatment and postoperative follow-up of patients.