Summary: Lack of initial mechanical stability of cementless prostheses may be responsible for fibrous tissue fixation of prosthetic components to bone. TO study the influence of micromovements on bony ingrowth into titanium alloy (Ti) and hydroxyapatite (HA)-coated implants, a loaded unstable device producing movements of 500 pm during each gait cycle was developed. Mechanically stable implants served as controls. The implants were inserted into the weight-bearing regions of all four femoral condyles in each of seven mature dogs. Histological analysis after 4 weeks of implantation showed a fibrous tissue membrane surrounding both Ti and HA-coated implants subjected to micromovements, whereas variable amounts of bony ingrowth were obtained in mechanically stable implants. The pushout test showed that the shear strength of unstable Ti and HA implants was significantly reduced as compared with the corresponding mechanically stable implants (p < 0.01). However, shear strength values of unstable HA-coated implants were significantly greater than those of unstable 'l'i implants (p < 0.01) and comparable to those of stable Ti implants. The greatest shear strength was obtained with stable HA-coated implants, which was threefold stronger as compared with the stable Ti implants (p < 0.001). Quantitative determination of bony ingrowth agreed with the mechanical test except for the stronger anchorage of unstable HA implants as compared with unstable Ti implants, where no difference in bony ingrowth was found. Unstable HA-coated implants were surrounded by a fibrous membrane containing islands of fibrocartilage with higher collagen concentration, whereas fibrous connective tissue with lower collagen concentration was predominant around unstable Ti implants. In conclusion, micromovements between bone and implant inhibited bony ingrowth and led to the development of a fibrous membrane. The presence of iibrocartilage and a higher collagen concentration in the fibrous membrane may be responsible for the increased shear strength of unstable HA implants. Mechanically stable implants with HA coating had the strongest anchorage and the greatest amount of bony ingrowth. Key Words: Bone ingrowth-Fibrous membraneHydroxyapatite-Micromotion-Porous ingrowth-Titanium. Porous coated prostheses were designed to obtain permanent fixation by ingrowth of bone into the porous implant surface. However, recent histological analyses of cementless tibia1 components (1 1,16) and total hip replacements (10,12) retrieved 285

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Circumferential lumbar fusion restored lordosis, provided a higher union rate with significantly fewer repeat operations, showed a tendency toward better functional outcome, and resulted in less peak back pain and leg pain than instrumented posterolateral fusion. The clinical perspective of the current study implies a recommendation to favor circumferential fusion as a definitive surgical procedure in complex lumbar pathology involving major instability, flatback, and previous disc surgery in younger patients, as compared with posterolateral fusion with pedicle screws alone.

Background and purpose Spondylodiscitis may be a serious disease due to diagnostic delay and inadequate treatment. There is no consensus on when and how to operate. We therefore retrospectively analyzed the outcome of a large series of patients treated either nonoperatively or surgically.Patients and methods Between 1992 and 2000, 163 patients (101 males) were hospitalized due to spondylodiscitis. The mean age was 56 (1-83) years. The infection was located in the cervical spine in 13 patients (8%), in the thoracic spine in 62 patients (38%), at the thoracolumbar junction in 10 patients (6%), and in the lumbo-sacral spine in 78 patients (48%). In 67 patients (41%), no microorganisms were detected. Most of the other patients had Staphylococcus aureus infection (53 patients) and/or Mycobacterium tuberculosis (22 patients). The patients were divided into 3 groups: (A) 70 patients who had nonoperative treatment, (B) 56 patients who underwent posterior decompression alone, and (C) 37 patients who underwent decompression and stabilization.Results At 12-month follow-up, nonoperative treatment (A) had failed in 8/70 patients, who had subsequently been operated. 24/56 and 6/37 had been reoperated in groups B and C, respectively. Group A patients had no neurological symptoms. In group B, 11 had neurological deficits and surgery was beneficial for 5 of them; 4 remained unchanged and 2 deteriorated (1 due to cerebral abscess). 11 patients in group C had altered neurogical deficits, which improved in 9 of them. 20 patients had died during the 1-year follow-up, 3 in hospital, directly related with infection.

Purpose Our objectives were primarily to review the published literature on complications in neuromuscular scoliosis (NMS) surgery and secondarily, by means of a meta-analysis, to determine the overall pooled rates (PR) of various complications associated with NMS surgery. Methods PubMed and Embase databases were searched for studies reporting the outcomes and complications of NMS surgery, published from 1997 to May 2011. We focused on NMS as defined by the Scoliosis Research Society's classification. We measured the pooled estimate of the overall complication rates (PR) using a random effects meta-analytic model. This model considers both intra-and inter-study variation in calculating PR. Results Systematic review and meta-analysis were performed for 68 cohort and case-control studies with a total of 15,218 NMS patients. Pulmonary complications were the most reported (PR = 22.71 %) followed by implant complications (PR = 12.51 %), infections (PR = 10.91 %), neurological complications (PR = 3.01 %) and pseudoarthrosis (PR = 1.88 %). Revision, removal and extension of implant had highest PR (7.87 %) followed by malplacement of the pedicle screws (4.81 %). Rates of individual studies have moderate to high variability. The studies were heterogeneous in methodology and outcome types, which are plausible explanations for the variability; sensitivity analysis with respect to age at surgery, sample size, publication year and diagnosis could also partly explain this variability. In regard to surgical complications affiliated with various surgical techniques in NMS, the level of evidence of published literature ranges between 2? to 2-; the subsequent recommendations are level C. Conclusion NMS patients have diverse and high complication rates after scoliosis surgery. High PRs of complications warrant more attention from the surgical community. Although the PR of all complications are affected by heterogeneity, they nevertheless provide valuable insights into the impact of methodological settings (sample size), patient characteristics (age at surgery), and continual advances in patient care on complication rates.