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Objectives and questions: Posterolateral rotatory instability (PLRI) is a rare condition among pediatric patients. The lateral collateral ligament (LCL) complex is thought to be the primary static constraint of posterolateral rotatory laxity. In the case of posttraumatic cubitus varus, both the mechanical cubital axis and the triceps line of pull are shifted medially, which causes chronic attenuation of the LCL complex and further leads to PLRI. The reconstruction of the LCL complex has been established as a treatment option for PLRI. However, this carries a risk of damaging the lateral humeral physis in skeletally immature patients. This study evaluated the effect of cubital axis correction on PLRI.

Material and methods: Over a period of 10 years, between 2012 and 2022, 12 patients aged 10 to 21 with posttraumatic cubitus varus underwent acute cubital axis correction through supracondylar dome osteotomy (SDO) in our department. The diagnosis of PLRI was made through a pivot shift test (PST) performed both in the preoperative clinical exam and intraoperatively during SDO under general anesthesia. A reevaluation of the posterolateral rotatory stability was conducted in the clinical exam on the day before hardware removal and then again intraoperatively during the hardware removal under general anesthesia. The final evaluation was performed at the standard clinical follow-up 3 months after hardware removal.

Results: PLRI was detected in 7 patients with a positive intraoperative PST under general anesthesia during SDO, 5 of them also had a positive PST in the preoperative clinical exam, and 2 of them already sustained symptomatic PLRI. In the intraoperative reevaluation during hardware removal under general anesthesia, the PST in 5 patients became negative. In 1 of the 2 patients with a persistent positive PST under general anesthesia during hardware removal, his previously symptomatic PLRI became inapparent in the clinical exam on the day before hardware removal. The other patient with persistent clinically symptomatic PLRI underwent reconstruction of the LCL complex during the same operation as the hardware removal, which resolved the PLRI completely.

Discussion and conclusions: Both the occurrence and the severity of PLRI showed strong correlations with increasing age. PLRI was exclusively observed in patients aged 14 years and above. The 2 patients who sustained symptomatic PLRI before SDO and in whom the PLRI persisted after SDO both aged over 16 years, whereas in younger patients aged under 16 years the PLRI was previously asymptomatic and resolved after SDO. This led us tobelieve that cubital axis correction can regain posterolateral rotatory stability and prevent symptomatic manifestation of PLRI in skeletally immature patients with posttraumatic cubitus varus.