Serum cobalt concentrations remain at low levels at a minimum of 20 years following metal-on-metal total hip arthroplasty.

AIMS: Second-generation metal-on-metal (MoM) articulations in total hip arthroplasty (THA) were introduced in order to reduce wear-related complications. The current study reports on the serum cobalt levels and the clinical outcome at a minimum of 20 years following THA with a MoM (Metasul) or a ceramic-on-polyethylene (CoP) bearing. METHODS: The present study provides an update of a previously published prospective randomized controlled study, evaluating the serum cobalt levels of a consecutive cohort of 100 patients following THA with a MoM or a CoP articulation. A total of 31 patients were available for clinical and radiological follow-up examination. After exclusion of 11 patients because of other cobalt-containing implants, 20 patients (MoM (n = 11); CoP (n = 9)) with a mean age of 69 years (42 to 97) were analyzed. Serum cobalt levels were compared to serum cobalt levels five years out of surgery. RESULTS: The median cobalt concentration in the MoM group was 1.04 µg/l (interquartile range (IQR) 0.64 to 1.70) at a mean of 21 years (20 to 24) postoperatively and these values were similar (p = 0.799) to cobalt levels at five years. In the CoP control group, the median cobalt levels were below the detection limit (< 0.3 µg/l; median 0.15 µg/l, IQR 0.15 to 0.75) at 20 years. The mean Harris Hip Score was 91.4 points (61 to 100) in the MoM group and 92.8 points (63 to 100) in the CoP group. CONCLUSION: This study represents the longest follow-up series evaluating the serum cobalt levels after 28 mm head MoM bearing THA and shows that serum cobalt concentrations remain at low levels at a mean of 21 years (20 to 24) after implantation.Cite this article: Bone Joint Res. 2020;9(3):145-150.

Long-term follow-up of metal-on-metal total hip replacement.

Metal-on-metal articulations were reintroduced to reduce polyethylene particle-induced osteolysis. Elevated serum metal levels have been detected at short- and intermediate-term follow-up. There is little knowledge about long-term effects of increased ionic metal generation. Our study was undertaken to provide information about long-term survival, clinical outcome, radiographic appearance, and serum metal concentrations after a minimum 10 years follow-up with a metal-on-metal hip prosthesis: 105 cementless primary total hip prostheses with metal-on-metal articulating surfaces were implanted in 98 patients with a mean age of 56 years. Clinical data, radiographs, and blood samples were obtained at a follow-up visit 10 years after implantation. Serum cobalt and chromium levels were determined with use of atomic absorption spectrometry. General laboratory analyses included a full blood count and kidney function parameters. The Harris score was 92 points and the UCLA score 6 points after 10 years. Small osteolytic lesions and radiolucent lines were found in Gruen's zones 1, 7, 8, and 14. The probability of survival was 98.6%. The median serum cobalt concentration of the 22 patients with their hip replacement as the only source of cobalt was 0.75 microg/L (range, 0.3-50.1 microg/L). No patient was diagnosed with renal insufficiency during the study period. Five patients were diagnosed with a malignancy between surgery and the follow-up. We do not have evidence of an increased rate of primary malignancies nor could we detect renal failure in our study group. Serum metal levels did not differ from short- and intermediate term follow-up values.

Long-term results after anterior cervical discectomy and fusion with allograft and plating: a 5- to 11-year radiologic and clinical follow-up study.

STUDY DESIGN: A retrospective review. OBJECTIVES: To determine the clinical and radiologic outcomes beyond 5 years after anterior cervical discectomy and fusion with allograft and plating. SUMMARY OF BACKGROUND DATA: Anterior cervical discectomy and fusion is commonly performed for cervical disc disease. The routine use of allografts and plating, though increasing in popularity, has not been well studied for long-term results and complications. METHODS: Seventy-one patients who had anterior cervical discectomy and fusion with allograft and plating an average of 7.2 years prior responded to an invitation to return for a follow-up clinical and radiographic review. RESULTS: At final review, symptom resolution remained greater than 82% and fusion occurred in 92.6% of the disc spaces operated on. No graft extrusion or migration occurred. Based on our strict criteria, the rates of collapse and subsidence were high, at 47.9% (34 patients) overall. However, in only 6 patients (8.5%) did segmental kyphosis result, none of whom required any revision surgery in the follow-up period. Implant complications occurred in 7 patients (9.9%), none of whom required revision surgeries. Adjacent level degeneration occurred in 52 patients (73.2%). Further cervical spine surgeries were required in 14 patients (19.7%), 2 for inadequate decompression, and 12 for adjacent level disease. Segmental and global cervical lordosis was restored and maintained by the surgery over the study period. CONCLUSIONS: The use of allografts and plate fixation in combination for anterior cervical discectomy and fusion does not compromise the radiologic and clinical outcomes while providing the advantages of donor site morbidity elimination, restoration of cervical segmental lordosis, and not requiring postoperative immobilization.

Abnormal spinal anatomy in 27 cases of surgically corrected spondyloptosis: proximal sacral endplate damage as a possible cause of spondyloptosis.

STUDY DESIGN: Retrospective review. OBJECTIVES: To review the findings in the cases of spondyloptosis we have treated and to postulate on the possible cause of spondyloptosis. SUMMARY OF BACKGROUND DATA: Spondyloptosis (Grade V spondylolisthesis) is rare, even though spondylolisthesis is a relatively common condition. While it is known that progression to spondyloptosis occurs in patients with developmental spondylolisthesis in their childhood and/or adolescent years, the precise factors leading to progression are not known. METHODS: Between 1979 and 2002, 27 patients with spondyloptosis were treated surgically with L5 resection and reduction of L4 onto S1. During the treatment process, detailed observations of the surgical findings were made through clinical and radiologic means. Six anatomic parameters (pars interarticularis defects, spina bifida of the L5 or sacral segments, dysplasia of the L5-S1 facet joints, L5-S1 disc degeneration, trapezoidal shape of L5, and rounding of the proximal end of the sacrum) were specifically studied. RESULTS: Pars interarticularis defects were present in 24 patients (88.9%), facet dysplasia in 16 patients (59.2%), spina bifida in 24 patients (88.9%), disc degeneration in 25 (92.6%), trapezoidal L5 in 20 patients (74.1%), and rounding of the proximal end of S1 in all 27 patients (100%). CONCLUSIONS: Rounding of the proximal sacral endplate was the only constant abnormal anatomic feature in the patients. Damage to the proximal sacrum and sacral growth plate during late childhood and early adolescence, similar to the epiphyseal injury that produces Blount's disease, and slipped capital femoral epiphysis seem to be key factors permitting the progression of developmental spondylolisthesis to spondyloptosis.

Persistent swallowing and voice problems after anterior cervical discectomy and fusion with allograft and plating: a 5- to 11-year follow-up study.

Anterior cervical discectomy and fusion is commonly performed for cervical disc disease. Most studies report that swallowing and voice problems after such surgeries tend to resolve with time and are often of minor significance except in the rare cases of recurrent laryngeal nerve palsies. A retrospective review was performed on patients who had anterior cervical discectomy and fusion by a single surgeon more than 5 years prior, to determine the persistence of swallowing and voice problems in them. Seventy-four patients who had anterior cervical discectomy and fusion with allograft and plating an average of 7.2 years prior responded to an invitation to return for a follow-up clinical review. Emphasis was placed on the symptoms of dysphagia and dysphonia, as related to the index surgery. At final review, persistent dysphagia was present in 26 patients (35.1%). This occurred more frequently in females and in younger patients. Dysphonia at final review persisted in 14 patients (18.9%). This also occurred more commonly in females and in patients in whom possible non-union is present in at least one of the levels operated upon. Problems with singing were present in 16 patients (21.6%) postoperatively, occurring more frequently if the C3/4 disc was included in the surgery and in patients who have had a greater total number of anterior cervical surgeries at the time of review. Dysphonia and dysphagia are persistent problems in a significant proportion of patients, even beyond 5 years after anterior cervical spine surgery.

A consensus paper on metal ions in metal-on-metal hip arthroplasties.

The number of metal-on-metal bearings used clinically continues to increase, particularly in young, active patients. The single greatest concern with the use of a metal-on-metal bearing continues to be the elevated levels of metal ions measurable in patients' blood and urine following implantation. There are multiple complex issues associated with the analysis of metal ions, including collection techniques, analysis, statistical methodologies, and reporting of results. To date, the literature on this topic has been characterized by significant variability in all of these factors. This paper seeks to establish a consensus among 3 investigators who have been working in this area and to offer guidelines on the complex methodology involved in the evaluation of metal concentration in patients following metal-on-metal hip arthroplasties.

Cup inclination and serum concentration of cobalt and chromium after metal-on-metal total hip arthroplasty.

We investigated whether cup inclination influences serum levels of cobalt and chromium after metal-on-metal total hip arthroplasty. Out of a consecutive series, 3 groups of 20 patients each were established according to their cup inclination: greatest inclination (55 degrees -63 degrees, mean 58 degrees), intermediate inclination (44 degrees -46 degrees, mean 45 degrees), and smallest inclination (23 degrees -37 degrees, mean 33 degrees). We did not detect any statistically significant difference of serum cobalt (P = .23) or serum chromium (P = .13) levels between the 3 groups applying the Kruskal Wallis test. However, 3 patients with cup inclinations of 58 degrees , 63 degrees , and 61 degrees exhibited 9.8-53.6-fold elevated cobalt and 9.5-30.5-fold elevated chromium levels when compared with the median concentrations of this trial. We therefore recommend accurate cup placement also for metal-on-metal articulations.

Does the placenta inhibit the passage of chromium and cobalt after metal-on-metal total hip arthroplasty?

Umbilical cord serum and corresponding maternal serum of 3 women with uncemented metal-on-metal total hip arthroplasties were analyzed for cobalt and chromium. The women were an average 3.8 (range, 2-5) years after hip surgery. At the time of delivery, the maternal chromium concentrations were 1.6 microg/l, 0.5 microg/l, and 0.9 microg/l, respectively, and the maternal cobalt concentration was 1 microg/l in the first woman and below the detection limit in the other 2 women. Cobalt and chromium concentrations of the 3 umbilical cord sera also were below the detection limit. This indicates that-with regard to the detection limit of our laboratory-we were unable to observe a passage of cobalt and chromium ions from metal-on-metal articulations across the placenta at the time of delivery.

Serum cobalt levels after metal-on-metal total hip arthroplasty.

BACKGROUND: Systemic cobalt dissemination from the Metasul Co-28Cr-6Mo-0.2C metal-on-metal total hip prosthesis has been demonstrated in the first year after implantation. The aim of this prospective study was to monitor the serum cobalt concentrations in patients during the first five years after total hip arthroplasty with a metal-on-metal articulation. METHODS: A total hip arthroplasty was performed without cement in 100 consecutive patients who had either unilateral osteoarthritis or unilateral osteonecrosis. Fifty patients were randomized to be treated with a metal-on-metal articulation, and fifty patients, with a ceramic-on-polyethylene bearing. The femoral stem was made of a Ti-6Al-7Nb alloy, and the threaded acetabular cup was made of commercially pure titanium. Blood samples were taken before the operation and at multiple time-points for five years after the operation. Serum cobalt concentrations were measured with use of atomic absorption spectrometry. RESULTS: In the metal-on-metal group, the median serum cobalt concentration was 1 micro g/L at one year after surgery and 0.7 micro g/L at five years. The median of the serum cobalt concentrations measured from three to twelve months did not differ from the median of subsequent measurements, with the numbers available. The median serum cobalt level in the control group of patients treated with the ceramic-on-polyethylene articulation was below the detection limit at all time-points. CONCLUSIONS: Systemic cobalt release from Metasul metal-on-metal articulations was demonstrated throughout the five-year study period. The median serum cobalt concentrations were found to be slightly above the detection limit and remained in a constant range. The serum cobalt concentrations did not reflect a so-called run-in wear period of the metal-on-metal articulations.

Short segment bone-on-bone instrumentation for single curve idiopathic scoliosis.

STUDY DESIGN: Retrospective case series review. OBJECTIVES: To evaluate the outcomes of a new short segment anterior scoliosis technique with complete removal of the discs, bone-on-bone apposition of the vertebral bodies, and dual rod instrumentation. To evaluate a new preop planning technique for scoliosis instrumentation. SUMMARY OF BACKGROUND DATA: Scoliosis surgery traditionally was performed via a posterior approach, but anterior scoliosis instrumentation has proven to be superior regarding the amount of curve correction and the number of segments saved from instrumentation. METHODS: Thirty-one patients with single curve idiopathic scoliosis less than 75 degrees were operated using the bone-on-bone surgical technique with dual rod instrumentation (Kaneda Anterior Scoliosis System, Depuy AcroMed, Raynham, MA from 1996 until 2001). Average follow-up was 40 months (range 15-77 months). RESULTS: Surgical correction of the major curve averaged 73.9% over the instrumented levels and 51.4% over the entire curve. The average number of discs fused was 4.6 for thoracic curves and 3.3 for thoracolumbar and lumbar curves. There were no implant-related complications or nonunions. The compensatory curves spontaneously improved by an average of 38.6%. Uneventful healing of all fusions occurred-most within 8 to 12 weeks. One compensatory thoracic curve progressed and posterior instrumentation was done 28 months after correction of the major thoracolumbar curve. CONCLUSIONS: Surgical correction was achieved in over half the levels that would have been operated by standard posterior segmental fixation. Bony healing due to the bone-on-bone apposition was achieved uneventfully after apical correction of the spinal curvature in all patients. Use of dual rod instrumentation (Kaneda Anterior Scoliosis System) is fundamental in maintaining the correction of the curvature achieved in the operating room. The preoperative planning technique worked well.