Hybrid Surgery: Fusion and Disc Arthroplasty is Superior To Two Disc Arthroplasties in the Lumbar Spine. Randomized Controlled Trial

STuDY DeSign: Prospective study. ObJeCTive: To study the validity of Hybrid construction (Anterior Lumbar Interbody Fusion) ALIF at one level and (Total Disc Arthroplasty) TDA at the adjacent level for two levels disc disease in the lumbar spine as an alternative surgical strategy compared to two levels disc arthroplasties. SuMMARY OF bACkgROunD DATA: With growing evidence that fusion constructs in the treatment of DDD (Degenerative Disc Disease) may alter sagittal balance and contribute to undesirable complications in the long-term, total disc arthroplasty (TDA) slowly becomes an accepted treatment option for a selected group of patients. Despite encouraging early and intermediate term results of single-level total disc arthroplasty reported in the literature, there is growing evidence that two-level arthroplasty does not fare as well. Hybrid fusion is an attempt to address 2-level DDD by combining the advantages of a single-level ALIF with those of a single-level arthroplasty. COnCLuSiOn: Clinical outcomes at 2 years show Hybrid fusion to be a viable surgical alternative for the treatment of 2-level DDD in comparison to two-level TDA. keY wORDS: Anterior lumbar interbody fusion, Degenerative disc disease, Hybrid construct, Lumbar spine, Lumbar fusion, Total disc arthroplasty. World Spinal Column Journal, Volume 1 / January 2010 2 L5-S1 and L4-5 are by far the most common segments affected in degenerative lumbar disease. We have selected patients with 2-level lumbar disease where the inferior segment shows no signs of advanced facet arthropathy whereas the above segment is limited to degenerative disc disease. Consequently, a hybrid construct comprising an ALIF at the bottom and prosthesis at the top is as appropriate as two level disc prosthesis (Figure 1). While the use of arthroplasty in combination with fusion has been previously reported, no clinical series on hybrid fusion have been published. In this paper, we present the clinical outcome of a prospective randomized series of 70 patients with a ratio 2/1 for hybrid and two discs prosthesis respectively. respect a distinct dermatomal distribution and the patients demonstrate a positive straight-leg raise test. Patients with true lumbar radiculopathies were excluded from this study. The relationship between back pain and DDD was determined by history, physical exam, and the presence of Modic 1 changes at the endplates on MRI. In less clear cases (eg. black discs), a discogram was performed. In this series 20 patients (28.5%) had discograms to assist with the diagnosis. Criteria for total disc arthroplasty included no evidence of gross instability (eg. absence of listhesis), good posterior musculature (>75% muscle/fat distribution), and facets with little or no sign of arthrosis. Facet injections were performed in cases where the source of pain was not clear. Patients were randomized into two groups: fusion/TDA (group A) and double TDA (group B). Group A: ALIF at L5S1 and TDA at L4-5 (Figure 3). ALIF was performed using an anterior impacted cage (Union cage or Perimeter cage, Medtronic, Memphis, USA) filled with autologous bone and with anterior plating with the Pyramid® titanium plate (Medtronic, Memphis, USA). The disc arthroplasty at the L4L5 level was performed using a Maverick implant (Medtronic, Memphis, USA), metal and metal ball and socket prosthesis using the AMav design. Group B: The disc arthroplasty at L5S1 and L4L5 was performed using a Maverick® implant through an anterior retroperitoneal video-assisted approach. Figure 1: Flexion-extension X-rays of a patient with ALIF of L5-S1 and TDA L4-L5.