André van Ooij

Complications of artificial disc replacement: a report of 27 patients with the SB Charité disc.

Disc prosthesis surgery is rapidly becoming an option in treating patients with symptomatic degenerative disc disease. Only short-term and midterm results are described in the literature. Most operated patients belong to the age group of 30–50 years. In these active patients, complications can be expected to increase with longer follow-up, similar to total joint replacements in the extremities. Reported here is a series of 27 patients from another institution, who presented with unsatisfactory results or complications after SB Charité disc replacement. The objective of this work was to describe the possible short- and long-term unsatisfactory results of disc prosthesis surgery. Twenty-seven patients were seen in a tertiary university referral center with persisting back and leg complaints after having received a Charité disc prosthesis. All patients were operated on in a neighboring hospital. Most patients were operated on at the L4–L5 and /or the L5–S1 vertebral levels. The patients were evaluated with plain radiography, some with flexion-extension x-rays, and most of them with computed tomography scans. The group consisted of 15 women and 12 men. Their mean age was 40 years (range 30–67 years) at the time of operation. The patients presented to us a mean of 53 months (range 11–127 months) following disc replacement surgery. In two patients, an early removal of a prosthesis was required and in two patients a late removal. In 11 patients, a second spinal reconstructive salvage procedure was performed. Mean follow-up for 26 patients with mid- and long-term evaluation was 91 months (range 15–157 months). Early complications were the following: In one patient, an anterior luxation of the prosthesis after 1 week necessitated removal and cage insertion, which failed to unite. In another patient with prostheses at L4–L5 and L5–S1, the prosthesis at L5–S1 dislocated anteriorly after 3 months and was removed after 12 months. Abdominal wall hematoma occurred in four cases. Retrograde ejaculation with loss of libido was seen in one case and erection weakness in another case. A temporary benefit was experienced by 12 patients, while 14 patients reported no benefit at all. Main causes of persistent complaints were degeneration at another level in 14, subsidence of the prosthesis in 16, and facet joint arthrosis in 11. A combination of pathologies was often present. Slow anterior migration was present in two cases, with compression on the iliac vessels in one case. Polyethylene wear was obvious in one patient 12 years after operation. In eight cases, posterior fusion with pedicle screws was required. In two cases, the prosthesis was removed and the segment was circumferentially fused. These procedures resulted in suboptimal long-term results. In this relatively small group of patients operated on with a Charité disc prosthesis, most problems arose from degeneration of other lumbar discs, facet joint arthrosis at the same or other levels, and subsidence of the prosthesis. It is to be expected that many more patients will be seen with late problems some years after this operation as the survivorship will decrease with time.

Polyethylene wear debris and long-term clinical failure of the Charité disc prosthesis: a study of 4 patients.

Study Design. A clinical case series of 4 patients undergoing anterior lumbar revision due to failure of total disc replacement surgery. Objectives. To assess the clinical significance of polyethylene wear debris in salvage surgery after initial total disc replacement, the pattern and the mechanisms of polyethylene wear in the retrieved cores, and the extent of polyethylene debris in the periprosthetic tissues obtained from 4 patients. Summary of Background Data. Previous in vitro wear tests have demonstrated low wear rates for lumbar artificial discs, suggesting that implant wear may not be a clinically relevant issue with total disc replacement. However, only long-term clinical investigations with analysis of retrieved implants and periprosthetic tissue can ultimately establish the significance of polyethylene wear debris for total disc arthroplasty. Methods. Starting in 2004, we began routinely performing salvage procedures in patients with failed total disc replacements. We report on the short-term outcomes of 4 patients at our institution who were revised with a Charité prosthesis (DePuy Spine, Raynham, MA). Wear analysis of the retrieved prosthesis and histologic examination of the periprosthetic tissue were also performed. Results. All of the retrieved polyethylene cores showed evidence of wear, but the extent and severity varied among the 4 patients. Wear and fracture of the core were associated with osteolysis of the underlying sacrum in 1 patient. Histologic examination of the periprosthetic tissues confirmed the presence of wear debris lying in inflammatory fibrous tissue. In 3 of the 4 patients, implant wear was associated with an unfavorable biomechanical environment (e.g., subsidence, migration, undersizing, and adjacent fusion). The mechanisms of wear included adhesive/abrasive wear of the central domed region of the polyethylene core, as well as chronic rim impingement, resulting in rim fatigue and fracture. Conclusions. This study demonstrates the clinical significance of polyethylene wear debris and the potential for osteolysis with total disc replacements. The authors recommend that patients undergoing lumbar disc arthroplasty receive long-term follow-up to monitor the wear and functional status of their implants.

New Insight in Loss of Gut Barrier during Major Non-Abdominal Surgery.

Background Gut barrier loss has been implicated as a critical event in the occurrence of postoperative complications. We aimed to study the development of gut barrier loss in patients undergoing major non-abdominal surgery. Methodology/Principal Findings Twenty consecutive children undergoing spinal fusion surgery were included. This kind of surgery is characterized by long operation time, significant blood loss, prolonged systemic hypotension, without directly leading to compromise of the intestines by intestinal manipulation or use of extracorporeal circulation. Blood was collected preoperatively, every two hours during surgery and 2, 4, 15 and 24 hours postoperatively. Gut mucosal barrier was assessed by plasma markers for enterocyte damage (I-FABP, I-BABP) and urinary presence of tight junction protein claudin-3. Intestinal mucosal perfusion was measured by gastric tonometry (PrCO2, Pr-aCO2-gap). Plasma concentration of I-FABP, I-BABP and urinary expression of claudin-3 increased rapidly and significantly after the onset of surgery in most children. Postoperatively, all markers decreased promptly towards baseline values together with normalisation of MAP. Plasma levels of I-FABP, I-BABP were significantly negatively correlated with MAP at ½ hour before blood sampling (−0.726 (p<0.001), −0.483 (P<0.001), respectively). Furthermore, circulating I-FABP correlated with gastric mucosal PrCO2, Pr-aCO2-gap measured at the same time points (0.553 (p = 0.040), 0.585 (p = 0.028), respectively). Conclusions/Significance This study shows the development of gut barrier loss in children undergoing major non-abdominal surgery, which is related to preceding hypotension and mesenterial hypoperfusion. These data shed new light on the potential role of peroperative circulatory perturbation and intestinal barrier loss.

In vivo deformation, surface damage, and biostability of retrieved Dynesys systems.

Study Design. Retrospective retrieval analysis. Objective. To evaluate wear, deformation and biodegradation within retrieved polycarbonate urethane (PCU) components of Dynesys systems. Summary of Background Data. The Dynesys Dynamic Stabilization System (Zimmer Spine) consists of pedicle screws (Ti alloy), polycarbonate urethane (PCU) spacers, and a polyethylene-terephthalate cord. Methods. Seventeen retrieved (mean implantation: 2.5 years, range: 0.7–7.0 years) and 2 exemplar implant systems were available. Reasons for revision were persistent pain (16/17), infection (1/17), and/or screw loosening (11/17), with 1/17 case of implant migration. Optical microscopy, microCT, and scanning electron microscopy were conducted to evaluate PCU spacer wear and deformation. Attenuated total reflectance Fourier transform infrared spectroscopy was used to assess spacer surface chemical composition. Results. Retrieved spacer components exhibited permanent bending deformation (mean: 4.3°, range: 0.0°–15.8°). We observed evidence of PCU spacer contact with pedicle screws, cords, and surrounding bony structures (74/75, 69/75, and 51/75 spacers, respectively). Relatively infrequent damage modes included PCU fracture (1/75 spacers) or cracking (2/75 spacers), as well as pedicle screw fracture (3/103 screws). PCU degradation products were identified in 10/75 spacers, which represented retrievals having significantly longer implantation times (mean: 4.3 years, range: 1.0–7.0 years). Of these spacers, 8/10 had degradation peaks identified along the side of the spacer where the material would have been in contact with bodily fluid. Conclusion. PCU spacers from retrieved Dynesys systems exhibited permanent deformation, focal regions of in vivo wear and surface damage. Chemical changes associated with PCU biodegradation were associated with longer-term retrievals. The most frequently observed complication was pedicle screw loosening, with 3 incidences of screw breakage in 2 patients. These retrieval data provide a crucial basis for developing in vitro tests to simulate in vivo damage and degradation of posterior dynamic motion preservation implants. Longer-term retrievals, as well as retrievals that include more recent design features (e.g., HA coating), will be useful to provide a greater context for the clinical implications of our short-term observations.

nocardia farcinica Spinal Osteomyelitis

Study Design. A case of disseminated Nocardia farcinica infection with spine involvement is reported. Objective. To describe the first case of Nocardia farcinica spinal osteomyelitis, and to propose spine instrumentation with debridement and multiple antibiotics for treatment of nocardia spinal osteomyelitis. Summary of Background Data. Only 11 cases involving Nocardia asteroides spinal osteomyelitis have been reported over the past 40 years. These case reports describe various presentations and treatments of nocardia spinal osteomyelitis. Methods. A 54-year-old nonambulant, paraparetic man was admitted to the authors’ hospital with acutely increased low back pain, fever, and signs of dementia. A disseminated Nocardia farcinica infection including spinal osteomyelitis at T11, T12, L1, L2, and L4; epidural abscess T10–L4, L5–S1 discitis, empyemas, cerebral abscess, and bilateral psoas abscess was noted. Results. Antibiotic therapy, multiple debridements, and posterior instrumentation were performed to palliate the Nocardia farcinica infection. At a recent 3-year follow-up assessment, the patient was independent and ambulant. He had been off antibiotics for 5 months. Conclusions. Previous case reports of nocardia spinal osteomyelitis describe treatment with antibiotics, debridements, and arthrodesis with autologous bone graft. Prolonged recumbency ensued. In the reported case, a combination of antibiotics, debridements, arthrodesis, and posterior instrumentation for immediate stabilization of the spine resulted in a favorable outcome at 3 years.

Predictable correction of the unfused lumbar lordosis after thoracic correction and fusion in Scheuermann kyphosis.

Study Design. A retrospective examination of preoperative and postoperative radiographs of the sagittal spine of 30 patients with Scheuermann kyphosis. Objectives. To determine significant correlations between kyphosis and lordosis in Scheuermann kyphosis, determine predictability of spontaneous sagittal lordosis correction after thoracic correction and fusion, and understand better the biomechanics of the spine. Summary of Background Data. Previous studies described relations between kyphosis and lordosis in healthy people. To our knowledge, no relationships, have been described between kyphosis and lordosis in Scheuermann kyphosis. Methods. On radiographs, maximum kyphosis, maximum lordosis, sacral slope and L5–S1 angle were measured in the preoperative and postoperative standing lateral radiographs of the spine, and correlations were calculated. Results. Preoperative significant correlations were present between kyphosis and lordosis (R = 0.421; P = 0.021), and between lordosis and sacral slope (R = 0.824; P < 0001). Postoperative correlations were stronger (R = 0.591; P = 0.001 and R = 0.844; P < 0.001). The percentage of correction of kyphosis was correlated with the percentage of spontaneous decrease of lordosis (R = 0.593; P < 0.001). A negative correlation between L5–S1 angle and upper lumbar segment of lordosis was found before and after surgery. Conclusions. This study shows a significant correlation between kyphosis and lordosis before and after surgery. Surgical correction of thoracic hyperkyphosis gives a predictable spontaneous decrease of lumbar lordosis. Correction of lordosis occurs mainly in the upper segment of lumbar lordosis.

Submicron sized ultra-high molecular weight polyethylene wear particle analysis from revised SB Charité III total disc replacements

Submicron sized particles are frequently observed in retrieved total hip and knee periprosthetic tissues and appear to be critical in the activation of the phagocytic inflammatory response. In this paper the concentration, size and shape of ultra-high molecular weight polyethylene (UHMWPE) wear particles between 0.05 and 2.00μm were determined after isolation from periprosthetic tissues from retrieved lumbar SB Charité III total disc replacements (TDR) using scanning electron microscopy (SEM). For comparison, UHMWPE wear particles were isolated from γ-radiation-air sterilized total hip arthroplasty (THA) revision tissues. The mean concentration of UHMWPE particles in TDR tissues was 1.6×10(9)g(-1)tissue (range 1.3-2.0), which was significantly lower than the concentration of 2.3×10(9)g(-1) THA revision tissue (range 1.8-3.2) (P=0.03). The mean particle size (equivalent circular diameter: TDR, 0.46μm; THA 0.53μm, P=0.60) and mean shape were comparable between TDR and THA (aspect ratio: TDR, 1.89; THA, 1.99, P=0.35; roundness: TDR, 0.58; THA, 0.56, P=0.35). However, the TDR particles tended to be smaller and more round. Although no correlations were found between visible damage to the UHMWPE core and the concentration or shape of the UHMWPE particles, a positive correlation was found between increasing particle size and increasing rim penetration of the TDR core (P=0.04). The presence of UHMWPE particles of similar size and shape in TDR tissue, albeit lower in concentration, might explain why, unlike THA, pain rather than osteolysis is the major reason for revision surgery.

Benign fibrous histiocytoma of the posterior arch of C1 in a 6-year-old boy: a case report.

Study Design. Presented is a unique case report of a rare bone tumor: a benign fibrous histiocytoma (BFH) located in the posterior arch of C1 in a 6-year-old child. Objective. To describe a benign fibrous histiocytoma of bone and the differential diagnostic considerations based on the authors’ case report. Summary of Background Data. A BFH is a rare tumor composed of varying degree of fibroblast-like spindle cells, foam cells, and multinucleated giant cells. Approximately 86 cases have been reported in literature. Its exact nature remains somewhat controversial. A lesion may be designated a benign fibrous histiocytoma based on clinical, radiographic, and microscopic criteria. Materials and Methods. The clinical symptoms, plain radiographs, computerized tomography (CT), magnetic resonance images (MRI), bone scintigraphy, and histologic section of the lesion are discussed, evaluated, and compared with other benign bone lesions. Results. This case is, to the best of the authors’ knowledge, the first benign fibrous histiocytoma to be reported in the cervical spine of a child. Various benign lesions such as nonossifying fibroma, giant-cell tumor, fibrous dysplasia, aneurysmal bone cyst, osteoblastoma, and eosinophilic granuloma are included in the differential diagnosis. Conclusion. Benign fibrous histiocytoma is a rare skeletal tumor. Because of this and its nonpathognomonic microscopic features, the diagnosis can be somewhat troublesome. However, by systematically reviewing patient’s symptoms, tumor location, and radiographic and microscopic characteristics, other benign lesions can be eliminated. The diagnosis of a BFH is one of exclusion.

The Natural History of Polyethylene Oxidation in Total Disc Replacement

Study Design. This study is an evaluation of wear and oxidation in retrieved total disc replacements (TDRs). Forty-eight CHARITÉ TDRs were retrieved from 41 patients after 7.8 years of average implantation. All implants were removed because of intractable back pain and/or facet degeneration. Three unimplanted implants served as controls. Objective. Our aim was to determine whether γ-sterilized polyethylene components implanted in the spine oxidize in vivo, and if so, whether polyethylene oxidation has clinical relevance for the long-term performance of TDRs. Summary of Background Data. The natural history of polyethylene oxidation following gamma sterilization and long-term implantation in the spine has not yet been investigated. Methods. Oxidation and oxidation potential were measured at the rim and dome of 47 components using Fourier transform infrared spectroscopy. The wear patterns of each retrieved polyethylene core were analyzed at the rim and dome. Results. Oxidation was significantly higher at the rim, as compared with the dome of the cores. Hydroperoxide index was also significantly higher at the rim, as compared with the dome. Dome penetration rate was negatively correlated to implantation time (P < 0.0001) but not correlated to oxidation or hydroperoxide index (P > 0.05). Implants with evidence of chronic rim loading had higher rim oxidation. Conclusion. The data support our hypothesis that, for the historical packaging methods employed by the manufacturer, polyethylene oxidation and oxidation potential were significantly higher at the rim as opposed to the dome. The mechanism is governed by access to oxygen in vivo and may be accelerated under certain combined modes of repeated rim loading. Our findings have clinical significance in cases of chronic impingement, when the rim has to support repeated loading for the lifetime of the implant.

Retrieval analysis of motion preserving spinal devices and periprosthetic tissues

This article reviews certain practical aspects of retrieval analysis for motion preserving spinal implants and periprosthetic tissues as an essential component of the overall revision strategy for these implants. At our institution, we established an international repository for motion-preserving spine implants in 2004. Our repository is currently open to all spine surgeons, and is intended to be inclusive of all cervical and lumbar implant designs such as artificial discs and posterior dynamic stabilization devices. Although a wide range of alternative materials is being investigated for nonfusion spine implants, many of the examples in this review are drawn from our existing repository of metal-on-polyethylene, metal-on-metal lumbar total disc replacements (TDRs), and polyurethane-based dynamic motion preservation devices. These devices are already approved or nearing approval for use in the United States, and hence are the most clinically relevant at the present time. This article summarizes the current literature on the retrieval analysis of these implants and concludes with recommendations for the development of new test methods that are based on the current state of knowledge of in vivo wear and damage mechanisms. Furthermore, the relevance and need to evaluate the surrounding tissue to obtain a complete understanding of the biological reaction to implant component corrosion and wear is reviewed.