Legacy in Layers: A Technical Reflection on Dr. Krish Sridhar’s Contributions to Spine Surgery

INTRODUCTION The evolution of spine surgery in India has been shaped by the contributions of pioneering individuals who not only embraced modern techniques but adapted them to local needs. Among these, Dr. Krish Sridhar stands out for his wide-ranging contributions, spanning cervical spine surgery including ossification of the posterior longitudinal ligament (OPLL), craniovertebral junction (CVJ) stabilization, spinal tumor surgery, anterior approaches to the spine, pediatric spine care, and management of spinal infections. His legacy is grounded in meticulous documentation, published innovations, and a philosophy that emphasizes precision, patient-centered care, and academic excellence. His legacy takes root from his own mentor, guru, and uncle, Prof. B. Ramamurthi [Figure 1]. It also bears testament to his philosophy of being a thinking surgeon and always trying to find a way to make patient outcomes better. This article presents a comprehensive review of Dr. Sridhar’s verifiable contributions to spine surgery, based on published articles, textbook chapters, and conference proceedings. We have not presented his contributions in a temporal timeline format but from the cranio-vertebral junction to the sacrum – giving the readers a glimpse of the wide range of work he has done and the versatility of his contribution to spine surgery.Figure 1: Krish Sridhar with Prof B RamamurthiTHE BEGINNING Dr. Krish Sridhar completed his MBBS from the Madras Medical College. He then joined the Dr. A. Lakshmipathi Neurosurgical Centre at VHS Hospital Chennai to become the first direct 5 year postgraduate in the country to qualify for the DNB Neurosurgery. At the time, there was little or no spine surgery (as we know it today) happening. At the VHS, discectomies and laminectomies were performed. Dr. Sridhar’s tryst with spine surgery started in the early 1990s when his proposed fellowship in skull base surgery got postponed. Disheartened by the closure of that door, and never the one to stay down, he found the field of spine surgery which was then in its fledgling days. Supported by his senior residents at the VHS Hospital, Dr. Arjun Srivatsa and Dr. P V Ramana, and with the blessing of Prof. B. Ramamurthi, Dr. Sridhar embarked on a journey in spine surgery that resulted in his becoming well-known for his work in the field. Until that time he had been performing anterior cervical microdiscectomy without fusion and had received the Best Paper Award for the work in 1992 at Coimbatore, India. Supported by his knowledge and skill in micro neurosurgery and learning “Bone” work from senior orthopedic colleagues of the hospital, spine surgery became routine at the ALNC, VHS. The next landmark in his career was the identification of cervical OPLL in 1992 – and that at a time when X-rays, myelograms were more routine than the recently introduced first-generation MRI scans. Recovering from a foot injury in 1999 gave him time to analyze his data on spinal schwannomas – and there started his monumental contributions to the world of spinal schwannomas. As experience accumulated, he started CVJ surgery including transoral surgery at the VHS, and then anterior and anterolateral approaches to the thoracic and lumbar spine. He was always ready to ask and take help from colleagues in other departments and believes in collaborative neurosurgery.[1] Dr. Sridhar strongly believes in the basic principles of spinal biomechanics and the concept of “Spinal Microsurgery”, emphasizing that tissue handling of the bone was as important as that of the spinal cord and roots. He also advocated the importance of the “flag-pole” concept and therefore not mishandling or destroying muscles which added to instability. The concept of creating instability and then putting in metallic implants to stabilize and fuse the spine was foreign to him. He believed that one had to deep dive into spine surgery in order to do justice to the specialty. Starting in an era where there were no titanium implants available, he innovated and performed major surgeries and fusion, using the stainless steel plates, screws, rods, and wires of the day [Figure 2]. He did not wait for technology to reach him but used whatever resources were available to perform what looking back seemed incredible surgeries. Keeping with the times he rapidly changed to titanium implants as they became available and was the first to use the anterior cervical plating–lock screw system when introduced into the country (personal communication).Figure 2: Stainless steel implants used in the early 1990sFollowing his mentor’s words “the younger generation must carry on. New technology has come.” He has taught and mentored many a young neurosurgeon who are currently themselves senior spine surgeons.[2] He continues to mentor and encourage young neurosurgeons into new techniques and encourages them to learn and keep abreast with the times [Figure 3]. As the immediate Hon General Secretary and now the President-Elect of the Neurological Society of India, Sridhar has taken Hands-on workshops to every part of the country ensuring that the young neurosurgeons of the country receive the skill training needed.Figure 3: Mentoring of the next generation in principles of spine surgeryPIONEERING WORK IN CRANIOVERTEBRAL JUNCTION STABILIZATION Dr. Sridhar was one of the first who looked at refining the surgical management of congenital and traumatic CVJ anomalies in India. Early in his career, he recognized the challenges posed by basilar invagination and atlantoaxial instability and emphasized structured preoperative assessment, focusing on reducibility testing through flexion-extension radiographs and traction studies.[1] He advocated customized surgical strategies, including transoral odontoidectomy for irreducible dislocations followed by occipito-cervical fusion, a two-stage approach that minimized neurological risk.[3] He pioneered the use of customized occipito-cervical plates with Drummond wiring techniques to achieve immediate stability, thus reducing reliance on prolonged external immobilization.[4,6] His work in this domain was comprehensively summarized in his chapter on CVJ anomalies in Textbook of Operative Neurosurgery.[5] ADVANCEMENTS IN SPINAL TUMOR SURGERY Dr. Sridhar’s work in spinal tumor surgery reflected his commitment to combining radicality with safety. Greatly influenced by the training in microsurgery he received at Zurich with Prof. Yasargil in 1991, he started adapting some of the approaches that he saw there into his own work. This resulted in his landmark 1998 publication on the limited unilateral approach for extramedullary spinal tumors which demonstrated that tumors could be excised through minimal bone removal, preserving spinal stability.[7,8] This perhaps was among the first publications on minimally invasive surgery for spinal tumors. In 2001, he introduced a structured classification for spinal schwannomas while defining Giant Invasive spinal schwannomas, with criteria based on tumor extension, extraspinal components, and vertebral erosion.[9] This “Sridhar Classification” while being modified and additions made still forms the basis and reference for articles on spinal schwannomas. His management protocols emphasized microsurgical techniques for excision, combined with stabilization techniques if needed, setting new benchmarks for spinal oncology surgery in India. The detailing of the different types of spinal schwannomas was done with publications on the Long segment spinal schwannomas, and the first two cases of giant invasive schwannomas of the C1 nerve root.[10,11] Looking at the variability of growth of the C1 schwannomas as a special type of tumor, he has recently published his series of C1 schwannomas and a review of literature where he classified the lesions and postulated why these tumors grow the way they do.[12] His contribution to spinal schwannomas has not been only on their classifications but on the concept of their growth pattern with the latter determining the surgical approach and technique with minimal bone removal. CONTRIBUTIONS TO PEDIATRIC SPINAL SURGERY Although primarily an adult spine surgeon, Dr. Sridhar made substantial contributions to pediatric spinal care, particularly in the domain of congenital CVJ anomalies. His experience was documented in the co-authored monograph CVJ anomalies –The Indian Experience, detailing surgical management strategies for pediatric and adult patients.[3] He advocated for early surgical intervention in pediatric atlantoaxial dislocations and basilar invagination, adapting adult techniques to suit pediatric anatomy. Moreover, his innovation of an affordable occipito-cervical plate–screw construct ensured that children in resource-limited settings received high-quality stabilization without dependency on imported implants.[3–6] ANTERIOR AND ANTEROLATERAL APPROACHES TO THE SPINE In an era when posterior decompression dominated spinal surgery, Dr. Sridhar pioneered the use of anterior and anterolateral approaches for thoracic and lumbar spine pathologies. His belief was that when the major pathology was anterior with an anterior spinal cord compression, performing a posterior surgery with violation of the virgin posterior spinal elements was not warranted. He collaborated with general and cardiothoracic surgeons to develop approaches to the anterior column which were simple, fast, and resulted in excellent patient outcomes He refined the anterior trans manubrial approach for upper thoracic vertebrae (T1-T3), facilitating direct decompression and reconstruction in this anatomically challenging region.[13] His presentations on anterior thoracic exposures at national and international conferences helped disseminate these techniques.[14] By institutionalizing thoracotomy-based spinal surgeries at ALNC, Dr. Sridhar enabled safer management of anterior pathologies, improving neurological and functional outcomes for numerous patients. Dr. Sridhar’s innovations extended to thoracoabdominal and retroperitoneal approaches for thoracolumbar and lumbar spine surgery.[15] His advocacy for lateral and anterolateral routes provided spine surgeons with a broader surgical armamentarium, ensuring that lesions could be accessed optimally based on pathology and anatomical considerations. By the late 1990s, these approaches had been integrated into standard practice at ALNC, largely due to his leadership.[1] MANAGEMENT OF OSSIFICATION OF THE POSTERIOR LONGITUDINAL LIGAMENT Cervical OPLL presented unique challenges in the Indian population, and Dr. Sridhar was among the first Indian neurosurgeons to recognize OPLL as a pathology separate from spondylotic disease and fluorosis and focus on its surgical management. He emphasized anterior decompression techniques, advocating direct removal of the ossified mass to achieve neurological recovery. His series on Cervical OPLL published in 2001 was one of the first series to discuss OPLL exclusive of other pathologies.[16] His chapter OPLL – Anterior Decompression in Indian Clinical Neurosurgery documented surgical strategies, highlighting anterior corpectomies and microsurgical peeling of the ossified ligament.[17] Dr. Sridhar also presented his outcomes at international conferences, raising awareness about OPLL’s diagnosis and optimal treatment strategies in India. ADVANCEMENTS IN ANTERIOR CERVICAL SPINE SURGERY Dr. Sridhar championed anterior cervical microdiscectomy techniques in India at a time when posterior laminectomy was the standard for cervical spondylotic myelopathy. In 1993, he presented one of the earliest Indian experiences correlating MRI findings with outcomes following anterior cervical microdiscectomy.[18] He won the Best Paper award for his work at the international course in spine surgery at Coimbatore in 1994. In 2000, his paper at the World Spine Congress in Berlin, on 350 microdiscectomies without fusion with long-term follow-up was well received.[19] His work on anterior cervical discectomy without fusion questioned conventional wisdom and contributed to global debates on whether fusion is necessary after single-level discectomy.[20,21] In 2007, he switched to adding fusion to prevent the long-term kyphosis seen in these patients, especially where the disc space height was maintained. He was a pioneer in adopting anterior cervical plating systems, presenting his results using the Orozco-Synthes plate for sub-axial cervical spine stabilization.[22,23] This was one of the early papers on the use of titanium anterior plate systems with locking screws in the country. His outcomes showed improved fusion rates, earlier mobilization and reduced need for external immobilization. Dr. Sridhar also authored chapters on median corpectomy for the WFNS Spine committee, and a textbook on operative neurosurgery, reflecting his expertise in advanced anterior decompression techniques.[24,25] Through his meticulous adoption of anterior approaches, he elevated the standards of cervical spine surgery and influenced practice patterns across India. PHILOSOPHY AND ACADEMIC LEADERSHIP Beyond technical prowess, Dr. Sridhar emphasized structured preparation, ethical practice, and academic rigor. He advocated that judgment – knowing when not to operate – was as vital as surgical skill. His leadership roles included serving on editorial boards for Neurology India, World Neurosurgery, and Journal of Spinal Surgery, ensuring high standards in Indian academic neurosurgery. Other than authoring chapters in books, he also published multiple rare cases which gave insight into the interpretation of radiology and the use of logic and available resources to achieve best patient outcomes. The extremely rare posttraumatic complete spondyloptosis,[26] total vertebral dislocation in spinal tuberculosis,[27] and idiopathic pachymeningitis[28] are some examples of many such thought-provoking articles authored by him.[29–32] He trained generations of neurosurgeons in spine surgery techniques, fostering a culture of excellence that continues in institutions he helped build.[1] The center for spine surgery developed by him at the VHS hospital has gained mention in the systematic review on centers of excellence in spine surgery by Martin et al. in 2022.[33] His publications and textbook chapters on craniovertebral anomalies,[3,5] spinal infections,[34] and anterior cervical spine techniques, spinal tumors, and mimics,[13,15,20,24,25] degenerative conditions of the lumbar spine,[35,36] serve as enduring references for Indian and international trainees. CONCLUSION Dr. Krish Sridhar’s contributions to spine surgery are deeply woven into the fabric of modern Indian neurosurgical practice. Through pioneering anterior approaches, championing spinal microsurgery, and refining tumor management strategies, he has transformed the way spine pathologies are approached in India. His commitment to meticulous technique, patient-centric decision-making, and academic dissemination ensured that his innovations were widely adopted. The fact that he continues to learn and adapt to modern and new technologies, try out and refine any new idea is a testament to his commitment to ensuring the best for his patients. Today, spine surgeons across the country and beyond continue to benefit from the knowledge, techniques, and principles that he so generously continues to share. In honoring Dr. Sridhar’s legacy, we recognize not just a master surgeon but a visionary who reshaped Indian spine surgery with skill, humility, and enduring impact. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.