Long-term outcomes following lumbar total disc replacement with M6-L.

Background: The motion preserving benefits of lumbar total disc replacement (LTDR) are well established. There is a paucity of long-term follow-up data on the M6-L prosthesis. The aim was to evaluate the clinical and radiographic outcomes of patients undergoing LTDR with M6-L and make comment about its effectiveness and durability. Methods: A retrospective single center chart review was performed of all patients who underwent LTDR with M6-L between January 1, 2011, and January 1, 2021, either as standalone device or combined with a caudal anterior lumbar interbody fusion (ALIF) (hybrid procedure). Preoperative, postoperative, and final follow-up patient reported outcome measures (PROMs) (VAS back, VAS leg, ODI, and SF-12) and patient satisfaction were recorded prospectively. Device range of motion (ROM), adjacent segment degeneration/disease and heterotopic ossification (HO) were obtained from flexion and extension lumbar radiographs at most recent follow-up. Results: Sixty patients underwent LTDR with the M6-L device. Mean age was 41 [16-71] years and 38 (63%) were male. Sixteen (26.7%) underwent standalone LTDR, 42 (70.0%) a hybrid procedure, and 2 (3.3%) a 3-level procedure. Twenty-three (38.3%) patients were lost to follow-up. Thirty-seven (61.7%) were followed for a mean of 4.3 [1-10] years with 36/37 reviewed at a minimum of 2-years and 13/37 followed for over 5-years. Only one patient with osteopenia needed index level revision LTDR surgery for subsidence requiring supplemental posterior instrumentation. There were no osteolysis induced device related failures. Thirty patients obtained long-term follow-up radiographic data. Six patients had adjacent segment degeneration; none required surgery for adjacent segment disease (ASD). Three patients presented with clinically significant HO (2 with McAfee class III, 1 with class IV). The average M6-L ROM was 8.6 degrees. Mean preoperative baseline PROMs demonstrated statistically significant improvements postoperatively and were sustained at last follow-up (P<0.05). Conclusions: Total disc replacement (TDR) with M6-L showed clinically significant improvement in PROMs that were sustained at long-term follow-up. There were no osteolysis induced device related failures. The device ROM was maintained and showed a downward trend over the 10-year study follow-up period. This paper demonstrated that the M6-L was an effective and durable arthroplasty device in this series.

Recombinant human bone morphogenetic protein-2 in spine surgery: recommendations for use and alternative bone substitutes-a narrative review.

Background and Objective: Recombinant human bone morphogenetic protein-2 (rhBMP-2) has been extensively studied in preclinical, animal, and human studies and has been used widely in spine fusion surgery. Evidence demonstrates that fusion rates with rhBMP-2 are similar to or higher than those achieved with autologous bone graft. However, there have been concerns regarding the cost, optimal dosage, and potential complications of rhBMP-2 use in spine surgery. The objective of this paper is to provide a current review of the available evidence regarding rhBMP-2 and other bone graft substitutes used for spinal surgery. Methods: We searched Ovid Medline, PubMed, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, American College of Physicians Journal Club, and Database of Abstracts of Review of Effectiveness for 2 studies regarding physiology of bone fusion in spine surgery, formulations and indications of rhBMP-2, cancer risk of rhBMP-2, and alternatives to rhBMP-2 published from 1965 to 2022 in English. Key Content and Findings: The debate regarding indications and cost effectiveness of rhBMP-2 is presented based on increasing data and use criteria. Here, we focus on the effectiveness and economic costs (both direct and indirect) of rhBMP-2 and alternative bone graft substitutes. Based on the cumulative literature, we provide recommendations for rhBMP-2 use in spine surgery. Conclusions: Based on our review of the literature, we recommend the following: (I) clear informed consent processes between surgeons and patients regarding current evidence of the benefits and risks of using rhBMP-2 and available alternative bone graft substitutes. (II) Consideration of rhBMP-2 for spinal fusion surgery (excluding anterior cervical procedures), especially adult spinal deformity (ASD) surgery, lumbar surgery for multilevel degenerative disease, revision surgery for pseudoarthrosis, and surgery in patients with a low-quantity or low-quality autograft. (III) Regulatory oversight of the type, volume, and dose of bone graft substitute (both per level and per procedure) to ensure appropriate indications, prevent excessive usage, and thereby enhance cost containment.

Can Central Sensitization After Injury Persist as an Autonomous Pain Generator? A Comprehensive Search for Evidence.

OBJECTIVE: To conduct a comprehensive search for evidence with regard to whether central sensitization after an injury can act as a persistent autonomous pain generator after the inducing injury has healed. METHODS: We searched Medline on PubMed and the Cochrane Library, screening 3,572 abstracts, from which 937 full-text articles were obtained, with 186 of these discarded as irrelevant to the question being posed. The remaining 751 articles were studied for evidence. RESULTS: Fourteen publications were judged to provide weak evidence for the hypothesis of central sensitization as a persisting autonomous pain generator, but none addressed the question directly. No strong evidence for the affirmative answer was found. Sixty-one publications were judged to provide weak evidence for a negative answer, and ten were judged to provide strong evidence. Unexpectedly, serious weaknesses were discovered in the literature underpinning the validity of the clinical diagnosis of central sensitization in humans: 1) inappropriate extrapolation, in many publications, of laboratory animal data to humans; 2) failure to demonstrate the absence of peripheral pain generators that might be perpetuating central sensitization; and 3) many factors now shown to confound what is being measured by quantitative sensory testing, conditioned pain modulation, and the Central Sensitization Inventory. CONCLUSIONS: We found no evidence proving that central sensitization can persist as an autonomous pain generator after the initiating injury has healed. Our review has also shown that the evidential basis for the diagnosis of central sensitization in individual patients is seriously in question.

Bone Morphogenetic Proteins in Spinal Surgery: What Is the Fusion Rate and Do They Cause Cancer?

STUDY DESIGN: A retrospective cohort study. OBJECTIVE: The aim of this study was to determine the fusion rate using recombinant human bone morphogenetic protein (rhBMP) in spinal surgery and to estimate the risk of cancer subsequent to their use. SUMMARY OF BACKGROUND DATA: rhBMP may obviate the need for iliac crest bone graft harvest and provides similar or higher fusion rates than autologous bone graft. Recently, there are concerns that rhBMPs may either cause cancer or accelerate progression. METHODS: Patients were treated by 2 spine surgeons between 2002 and 2012. Inclusion criteria were patients who resided in the state of Victoria, Australia, undergoing lumbar fusion (anterior, lateral, posterior, and posterolateral) with rhBMP [either rhBMP-2 (Infuse) or rhBMP-7 (OP-1)]. Exclusion criteria were patients who reported having an invasive cancer diagnosis before the spinal fusion procedure. The occurrence of incident cancers was obtained from record linkage to the Victorian Cancer Registry. RESULTS: A total of 527 patients were included in the cohort, with a mean follow-up of 4.4 years (1.8-11.5). Patients received Infuse in 77% of cases and OP-1 in 23%. The mean Infuse does was 10.2  mg (2.5-48.0) and 3.3  mg (1.7-6.6) for OP-1. There was no significant difference in fusion rates between Infuse (90.1%) and OP-1 (91.9%) (P = 0.42). The overall success of interbody fusion with rhBMP was 93.5% at 12 months. Twenty-seven patients were diagnosed with an invasive cancer since treatment (20 Infuse and 7 OP-1 patients). Comparing the observed numbers in our study cohort with those expected on the basis of the Victorian population's age and sex-specific rates, we observed that the study cohort was not at a significantly increased risk of cancer. The standardized incidence ratio for cancer overall (of any type) was 0.84 [95% confidence interval (95% CI) 0.56-1.21]. CONCLUSION: Off-label use of rhBMP provided high fusion rates with no evidence of a significantly increased risk of cancer. LEVEL OF EVIDENCE: 4.

Co-registration of isotope bone scan with CT scan and MRI in the investigation of spinal pathology.

Image fusion software enables technetium(99m)-methylene diphosphonate (Tc(99m)-MDP) bone scan images to be co-registered with CT scan or MRI, allowing greater anatomical discrimination. We examined the role of bone scan images co-registered with CT scan or MRI in the investigation of patients presenting with axial spinal pain and/or limb pain. One hundred and thirty-nine consecutive patients were examined, and thereafter investigated with CT scan, MRI, and/or dynamic plain films. At this point diagnosis (pathology type and anatomical site) and treatment intention were declared. The co-registered Tc(99m)-MDP bone scan images were then studied, after which diagnosis (pathology type and anatomical site) and treatment intention were re-declared. This data were then analysed to determine whether the addition of co-registered bone scan images resulted in any change in diagnosis or treatment intention. The most significant change in diagnosis was pathology type (10%). Anatomical site changed markedly without overlap of the pre and post-isotope fields in 5%, and with overlap in 10%. Treatment intention had a major change in 3.6% and minor change in 8.6%. In the two groups where there was (i) no obvious pathology after full pre-isotope investigation, or (ii) a spinal fusion under suspicion, addition of the bone scan information led to a major change in the pathology and/or anatomical localisation in 18% and 19%, respectively. The addition of co-registered Tc(99m)-MDP bone scan images offers significant diagnostic assistance, particularly in the difficult diagnostic groups where a failed spinal fusion may be the suspected pain generator, or when no pain generator can otherwise be found.

Anterior pseudoarthrectomy for symptomatic Bertolotti's syndrome.

Painful L5/S1 pseudoarthrosis has been previously managed with posterior excision and/or lumbar fusion. To our knowledge, the anterior approach for L5/S1 pseudoarthrectomy in the treatment of Bertolotti's syndrome has not been described. We present two patients with severe symptomatic L5/S1 pseudoarthroses that were successfully excised via an anterior retroperitoneal approach with 2 year clinical and radiological follow-up. The literature regarding surgical treatments for Bertolotti's syndrome is reviewed. The technique for an anterior retroperitoneal approach is described. This approach has been safe and effective in providing long term symptomatic relief to our two patients. Further studies comparing the outcomes of anterior versus posterior pseudoarthrectomy will guide the management of this condition.