Purpose: Lengthening of superficial medial collateral ligament (sMCL) is often needed in total knee replacement for varus osteoarthritis knee. This study aimed to compare the relationship of multiple needle puncturing (MNP) and subperiosteal elevation (SE) for sMCL lengthening on the gap increment and sequential lengthening in cadaveric knees.
Hypothesis: MNP produces more reliable gap increment than SE technique for sMCL lengthening performed in knee flexion.
Methods: From 8 pairs of cadaveric knees, one knee from each pair was randomly assigned to undergo MNP and the others to SE. In the MNP group, an 18gauge needle was used to puncture through the sMCL, performing five punctures each time of release. For the SE group, a periosteal elevator was used to sequentially deepen distally beneath the sMCL insertion with an increment depth of 5mm each time of release. The primary outcome was the medial gap increment at knee extension and 90° knee flexion after every attempt in each group.
Results: At each level of lengthening, the widening of flexion and extension gap were not significantly different between the two techniques except for lengthening after 4 and 6 attempts of SE that gave greater widening in extension gap. Variability (width of mid 95% of values) was significantly greater for any given number of attempts using SE than MNP (0.5 vs. 0.24mm per attempt for extension and 2.28 vs. 0.95mm per attempt for flexion; both p<0.001).
Conclusion: The MNP technique is a reproducible technique for lengthening the sMCL in knee flexion. It has less variability in gap widening compared to the SE technique.
Level of evidence: II, controlled randomized laboratory study.
Keywords: Gap Balancing; Medial collateral ligament; Multiple needle puncture; Pie crusting; Subperiosteal release; Total knee arthroplasty.
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