Modification of intra-carpal tunnel pressure after z-lengthening of the transverse carpal ligament

Abstract

BACKGROUND: Flexor retinaculum reconstruction techniques or simply Flexor Retinaculum Z-lengthening have been proposed to preserve Flexor Retinaculum continuity after carpal tunnel release. Their effectiveness is based solely on symptom relief. There has been no analysis of the effects on intra-carpal tunnel pressure of Flexor Retinaculum-lengthening techniques. Objective was to compare intra-carpal tunnel pressure outcomes between complete division and Z-lengthening of the Retinaculum in a cadaveric model of carpal tunnel release. METHODS: Experimental study of carpal tunnel pressure after surgical Flexor Retinaculum modification in 10 fresh-frozen forearm and hand cadaveric specimens. The Kyphon™ Balloon Kyphoplasty system was used to measure the pressure before and after infusing 1, 2, 3, 4 and 5 ml of saline solution when untreated (Flexor Retinaculum continuity stage I), when Z-lengthened (Flexor Retinaculum continuity stage II), and after complete Flexor Retinaculum division (Flexor Retinaculum continuity stage III). FINDING: Intra-carpal tunnel pressure increased with larger volume of infused saline solution, although mean pressures were lower after Z lengthening or complete division of the Retinaculum than at baseline. Analysis of linear regression coefficients indicated significant differences as a function of FR continuity stage (F(2,18)=18.38, p<0.001), while the Bonferroni test revealed significant differences in slopes between stages I and III (p=0.003), between stages I and II (p<0.02), but not between stages II and III (p>0.05). INTERPRETATION: The effectiveness of carpal tunnel release and the reduction in intra-carpal tunnel pressures obtained by Z-lengthening of the FR were similar to those observed after its complete division, while preserving FR continuity.