Posterolateral approach for lumbar plexus intra-psoas schwannomas: systematic review and comparative anthropometric analysis of surgical corridors with an illustrative case.

PURPOSE: Lumbar plexus intra-psoas schwannomas (LPIS) are rare tumors located deep within the retroperitoneal space and closely related to vital structures, making surgical management technically demanding. Multiple surgical corridors have been described, yet the optimal strategy remains debated. The present study aimed to evaluate the role of posterolateral approaches for LPIS by combining a systematic review with a comparative anatomical analysis of surgical corridors.

METHODS: A systematic review was conducted to identify surgical reports of LPIS and, secondarily, lumbar schwannomas extending into the psoas muscle. In parallel, a comparative anthropometric analysis was performed using lumbar CT scans to quantify key parameters of surgical operability, including surgical angle (SA), working distance (WD), and degree of freedom of surgical instruments (DFSI) for anterior transperitoneal, anterior extraperitoneal, lateral retroperitoneal, and posterolateral corridors targeting the psoas muscle.

RESULTS: The systematic review (PROSPERO: CRD420261342449) identified 48 studies reporting 53 cases of surgical treatment of LPIS (n = 37) and lumbar schwannomas with psoas involvement (n = 16). Anterior approaches for true LPIS were most frequently reported (40%), followed by lateral retroperitoneal approaches (27%), whereas posterolateral corridors were rarely described (5%). In tumors with secondary psoas extension, posterior or posterolateral strategies were more commonly employed. An illustrative case treated through the Wiltse-type corridor is presented, bringing the total number of true LPIS cases discussed in this study to 38, and 8% true LPIS cases managed posterolaterally. Anthropometric analysis demonstrated that the posterolateral corridor provides a short surgical trajectory (median WD 7 cm) and greater instrument maneuverability (median DFSI 30°) compared to other approaches.

CONCLUSIONS: These findings suggest that the posterolateral Wiltse-type corridor may represent a feasible extraperitoneal alternative in selected LPIS.