Expert’s comment concerning Grand Rounds case entitled “A novel ‘Pelvic Ring Augmentation Construct’ for Lumbo-Pelvic Reconstruction in Tumor Surgery” (by Sathya Thambiraj, Daren Forward, James Thomas and Bronek Boszczyk)

Abstract

Introduction

Historically, metastatic spine tumor surgery has been palliative for pain control, to maintain neurologic and ambulatory function. The thought of curing cancer with limited metastatic disease by resecting the primary and the metastatic lesions is becoming more common. Multilevel spondylectomy for resection of metastatic disease has been reported in the literature, mostly at the thoracic or lumbar level with some success. Reconstruction of the lumbosacral junction after tumor resection is a difficult endeavor and several techniques have been utilized. Subcutaneous anterior pelvic fixation has been described for the treatment of unstable pelvic fractures.

Materials and methods

Review of the Grand Rounds case “A novel Pelvic Ring Augmentation Construct for Lumbo-Pelvic Reconstruction in Tumour Surgery” by Sathya Thambiraj, Daren Forward, James Thomas, Bronek Boszczyk and review of the pertinent literature.

Conclusion

The authors describe a novel percutaneous rod technique and construct for buttressing a posterior spinal construct to a subcutaneous anterior pelvic fixator after tumor resection of the lumbo-pelvic junction. They manage to salvage a difficult situation for which they should be commended. This technique may be useful in situations where instrumentation has to be preformed to the pelvis: i.e., in tumor reconstruction, fusions such as neuromuscular scoliotic disease to the pelvis, to augment a lumbo-pelvic construct when a nonunion occurs or in osteoporotic patients as a salvage procedure.

Original procedure

The authors [1] describe a case of a 69-year-old female with a history of renal cell cancer with metastatic disease limited to the spine but to three adjacent vertebrae; L4, L5 and S1. Her findings included a 6-month history of back pain with a normal neurological exam. She was treated with a nephrectomy removing the primary tumor. The authors then chose to do a multilevel spondylectomy and a complex reconstruction.

Indications for surgery in spinal metastatic disease include:

1. Intractable pain unresponsive to non-operative measures;

2. Existence of a growing tumor that is resistant to radiation, chemotherapy, or hormonal therapy;

3. Patients who have reached spinal cord tolerance after prior radiation therapy;

4. Spinal instability manifested as pathologic fracture, progressive deformity, or neurologic deficit;

5. Clinically significant neural compression.

In this case, a renal cell cancer, which responds poorly to radiation and chemotherapy, surgical intervention could be considered. The reason for surgery and the type of surgery preformed spondylectomy is an attempt to cure the disease, control local recurrence, and to prolong survival.

Spondylectomy for spinal tumors was originally described for giant cell tumors and malignant primary spine tumors in the 1960s and 1970s [2, 3] in an effort to cure the disease. In 1994, Tomita et al. [4] described an en bloc spondylectomy technique for solitary metastatic disease and several authors have reported their experience since [4–9]. It has usually been employed when the primary has been completely resected and there is a single bone met. Tomita et al. [10] have tried to stratify patients with respect to grade of malignancy, visceral mets and solitary versus multiple bone mets as candidates for spondylectomy. They use aggressive resection in patients with slow growing (breast, prostate, thyroid) or moderate growing (kidney, uterine) tumors with treatable or no visceral mets and solitary bone mets. Their and others’ results indicate that they may be able to achieve an increased survival in selected patients, decrease local recurrence rates, improve patients’ quality of life and increased overall survival rates with this procedure [9–11].

In this case, we have a patient with a moderate growing tumor with multiple bone mets who undergoes a multilevel spondylectomy at the lowest lumbar level including the sacrum for control of metastatic disease. Multilevel spondylectomy for resection of metastatic disease has been reported on a few occasions in the literature mostly at the thoracic or lumbar level with some success [12–15]. Reconstruction has been achieved with vertebral body replacement (VBR) systems with either bone graft or cement. The choice of going for a wide resection in this patient seems aggressive to me as the tumor involves multiple vertebrae and is at the lumbosacral junction. My preference would still be to consider radiation for pain control unless there was a pathological fracture, or neurologic compromise.

First surgery

Cement augmentation in and around your cage as well as an anterior plate would have helped the original anterior construct in stability from dislodging and perhaps could have even been performed at the first revision. Although plates often cause stress shielding of graft material in VBR a small plate at the inferior aspect of the construct could have been a buttress for the cage.

First revision

Cement augmentation and a plate buttress may have been able to be done at your first revision as well unless tumor had further destroyed the sacrum. The anterior construct was converted into a trans-iliac bar with anterior rod and cement. The reconstruction of an L4/L5 spondylectomy is easier when the sacrum is not involved and in this case as more sacrum seems to be destroyed it turns into a procedure that needs to reconstruct the lumbosacral junction as one would do for sacral resection. This is a difficult endeavor and requires inventive ways of transferring the patient’s body weight held by the spine to the pelvis [16–21]. Some authors use a VBR with this construct as well and multiple iliac bars.

Second revision

The posterior rod construct broke at 9 months postop. and was converted to a four rod system as described by Shen et al. [19]. This construct was still inadequate as the anterior trans-sacral rod had broken again.

Augmentation procedure

The augmentation procedure was performed and led to no further structural trouble until the patient died 15 months later from her disease. This is an innovative procedure which was involved minimal dissection, little blood loss (250cc) and connected the instrumentation to an anterior pelvic frame described by our group at Detroit Receiving Hospital for anterior pelvic fixation in pelvic fractures [22, 23]. This subcutaneous frame Internal Fixator (InFix) is good for anterior pelvic compression and distraction. It sits in an area that we call the “bikini area”. It is biomechanically stronger than an anterior external fixator. Patients are not hindered by its presence and are able to sit, stand and ambulate without difficulty. We have used it with a posterior rod and screw construct in pathologic pelvic fractures as well. To use this as an anchor for posterior fixation in a tripod design is ingenious and worked for this individual for more than a year. The biomechanics of this construct need to be worked out to assess its real stabilizing ability, and I encourage the authors to do that as most such constructs are tested before applied. The authors have developed a method that may be useful in situations where instrumentation has to be performed to the pelvis, i.e., in tumor reconstruction, fusions such as neuromuscular scoliotic disease to the pelvis, to augment a lumbo-pelvic construct when a nonunion occurs or in osteoporotic patients as a salvage procedure.

Historically metastatic spine tumor surgery has been palliative for pain control, to maintain neurologic and ambulatory function. Modern medicine is challenging this premise. The thought of curing cancer with limited metastatic disease by resecting the primary, and the metastatic lesions has been reported for lung mets, liver mets, and bone mets. The challenge is minimizing the harm to these patients who often have a limited life span. Patients and surgeons are eager to attempt treatment, which may lead to cure with radical surgery. It is hard not to say that this patient may have benefitted from less aggressive surgery, radiation and pain management but maybe she would have had a shorter survival as well. In this report the authors describe a very original solution for buttressing a posterior construct after tumor resection of the lumbo-pelvic junction for which they should be commended.