Interface abrasion between rough surface femoral stems and PMMA cement results in extreme wear volumes--a retrieval study and failure analysis.

During the loosening cascade of cemented rough femoral stems, the destruction of the mantle and the production of cement and metal wear debris occur after the loss of constraint at the interface. Two-dimensional (2D) measurements (light microscopy based morphometry on fragments of mantles and vertical scanning interferometry of femoral stems) permitted mathematical 3D-extrapolations to estimate the wear volumes. Fragments of the cement mantles available lost volumes from 0.85 mm(3) to 494.10 mm(3) (median amount of bone cement wear = 178,426 mg). The harder metal surfaces lost between 1.459 mm(3) and 5.688 mm(3) of material (the median amount of metal wear per surface = 1.504 mg/100 mm(2)). Compared to the loss of material due to the fretting of stems, the abrasion of metal, and cement in defective cement mantles produced wear volumes sufficiently high to induce osteolysis. Though the design of the femoral stem and the handling of bone cement do not represent contemporary design and clinical practice, respectively, an extremely high number of joint replacements still in daily use may be impacted by this study because of possible predicted failures. Once the processes of fragmentation, abrasion, and osteolysis have been realized, the time until revision surgery should not be unduly prolonged.

Cartilage repair techniques of the talus: An update.

Symptomatic chondral or osteochondral defects of the talus reduce the quality of life of many patients. Although their pathomechanism is well understood, it is well known that different aetiologic factors play a role in their origin. Additionally, it is well recognised that the talar articular cartilage strongly differs from that in the knee. Despite this fact, many recommendations for the management of talar cartilage defects are based on approaches that were developed for the knee. Conservative treatment seems to work best in paediatric and adolescent patients with osteochondritis dissecans. However, depending on the size of the lesions, surgical approaches are necessary to treat many of these defects. Bone marrow stimulation techniques may achieve good results in small lesions. Large lesions may be treated by open procedures such as osteochondral autograft transfer or allograft transplantation. Autologous chondrocyte transplantation, as a restorative procedure, is well investigated in the knee and has been applied in the talus with increasing popularity and promising results but the evidence to date is poor. The goals of the current article are to summarise the different options for treating chondral and osteochondral defects of the talus and review the available literature.

A comparison of intraarticular lumbar facet joint steroid injections and lumbar facet joint radiofrequency denervation in the treatment of low back pain: a randomized, controlled, double-blind trial.

BACKGROUND: Lumbar facet joint degeneration is a source of chronic low back pain, with an incidence of 15% to 45% among patients with low back pain. Various therapeutic techniques in the treatment of facet-related pain have been described in the literature, including intraarticular lumbar facet joint steroid injections and radiofrequency denervation. In this study, we compared the effectiveness of intraarticular facet joint steroid injections and radiofrequency denervation. METHODS: Our randomized, double-blind, controlled study included patients who received intraarticular steroid infiltrations in the lumbar facet joints (L3/L4-L5/S1) and patients who underwent radiofrequency denervation of L3/L4-L5/S1 segments. The inclusion criteria were based first on magnetic resonance imaging findings showing hypertrophy of the facet joints L3/L4-L5/S1 and a positive response to an intraarticular test infiltration of the facet joints L3/L4-L5/S1 with local anesthetics. The primary end point was the Roland-Morris Questionnaire. Secondary end points were the visual analog scale and the Oswestry Disability Index. All outcome assessments were performed at baseline and at 6 months. RESULTS: Fifty-six patients were randomized; 24 of 29 patients in the steroid injection group and 26 of 27 patients in the denervation group completed the 6-month follow-up. Pain relief and functional improvement were observed in both groups. There were no significant differences between the 2 groups for the primary end point (95% confidence interval [CI], -3 to 4) and for both secondary end points (95% CI for visual analog scale, -2 to 1; 95% CI for Oswestry Disability Index, -18 to 0). CONCLUSIONS: Intraarticular steroid infiltration or radiofrequency denervation appear to be a managing option for chronic function-limiting low back pain of facet origin with favorable short- and midterm results in terms of pain relief and function improvement, but improvements were similar in both groups.

Correlation of pull-out strength of cement-augmented pedicle screws with CT-volumetric measurement of cement.

BACKGROUND: Cement augmentation of pedicle screws increases fixation strength in an osteoporotic spine. This study was designed to determine the cement distribution and the correlation between the pull-out strength of the augmented screw and the cement volume within polyurethane (PU) foam. METHODS: Twenty-eight cannulated pedicle screws (6×45 mm) (Peter Brehm, Erlangen, Germany) with four holes at the distal end of the screw were augmented with the acrylic Stabilit ER Bone Cement Vertebral Augmentation System (DFine Inc., San Jose, CA, USA) and implanted into open-cell rigid PU foam (Pacific Research Laboratories, Vashon Island, WA, USA) with a density of 0.12 g/cm3, resembling severe osteoporosis. Volumetric measurement of the cement with consideration of the distribution around the screws was done with multislice computed tomography scan (Somatom Definition, Siemens, Erlangen, Germany). Pull-out strength was tested with a servohydraulic system (MTS System Corporation, Eden Prairie, MN, USA), and nonaugmented screws served as control. Pearson's correlation coefficient with significance level α=0.05 and one-way analysis of variance test were used. RESULTS: We found a high (r=0.88) and significant (p<0.01) correlation between the cement volume and the pull-out strength, which increased by more than 5-fold with a volume of 3 ml. The correlation appeared linear at least up to 4 ml cement volume and failure always occurred at the cement-bone interface. The cement distribution was symmetric and circular around the most proximal hole, with a distance of 14 mm from the tip, and nearly 90% of the cement was found 6 mm distal and cranial to it. The 95% confidence interval for the relative amount of cement was 37%-41% within 2 mm of the most proximal hole. CONCLUSION: Compared with the control, a cement volume between 2.0 and 3.0 ml increased the pull-out strength significantly and is relevant for clinical purposes, whereas a volume of 0.5 ml did not. A cement volume beyond 3.0 ml should further increase the pull-out strength because the correlation was linear at least up to 4.0 ml, but the possibility of in vivo cement leakage with increasing volume has to be considered. Pressure-controlled cement application might be a tool to avoid this complication. The cement almost completely penetrated the most proximal perforation.

Biomechanical and magnetic resonance imaging evaluation of a single- and double-row rotator cuff repair in an in vivo sheep model.

PURPOSE: To investigate the biomechanical and magnetic resonance imaging (MRI)-derived morphologic changes between single- and double-row rotator cuff repair at different time points after fixation. METHODS: Eighteen mature female sheep were randomly assigned to either a single-row treatment group using arthroscopic Mason-Allen stitches or a double-row treatment group using a combination of arthroscopic Mason-Allen and mattress stitches. Each group was analyzed at 1 of 3 survival points (6 weeks, 12 weeks, and 26 weeks). We evaluated the integrity of the cuff repair using MRI and biomechanical properties using a mechanical testing machine. RESULTS: The mean load to failure was significantly higher in the double-row group compared with the single-row group at 6 and 12 weeks (P = .018 and P = .002, respectively). At 26 weeks, the differences were not statistically significant (P = .080). However, the double-row group achieved a mean load to failure similar to that of a healthy infraspinatus tendon, whereas the single-row group reached only 70% of the load of a healthy infraspinatus tendon. No significant morphologic differences were observed based on the MRI results. CONCLUSIONS: This study confirms that in an acute repair model, double-row repair may enhance the speed of mechanical recovery of the tendon-bone complex when compared with single-row repair in the early postoperative period. CLINICAL RELEVANCE: Double-row rotator cuff repair enables higher mechanical strength that is especially sustained during the early recovery period and may therefore improve clinical outcome.

Surgical management of sternoclavicular septic arthritis.

INTRODUCTION: Septic arthritis of the sternoclavicular joint (SCJ) is a rare condition and has many diagnostic and therapeutic standards. The purpose of this study was to evaluate our experience with surgical and diagnostic management to provide a surgical pathway to help surgeons treat this disease. METHOD: We retrospectively reviewed five patients who were managed surgically between 1999 and 2007. All patients underwent structured diagnostic and treatment protocols. The functional outcome was evaluated using the Constant Score. PATIENTS: The patients had the following underlying medical conditions: laryngeal cancer, port-explantation linked to a rectum carcinoma, spondylodiscitis, and brain stem infarct with reduced general condition; one patient had no underlying medical problems. Three patients underwent a simple incision, debridement and drainage, and two patients underwent an extended intervention with partial resection of the sternoclavicular joint. The mean duration of follow-up was 29 months (range 24-36 months). All patients had well-healed wounds without signs of reinfection. The Constant Score for the functional outcome at the time of the last follow-up was 76 points (range 67-93 points). All patients recovered completely from SCJ disease. CONCLUSION: Our recommendations for the management of septic arthritis of the sternoclavicular joint include standard treatment steps and assessments. The early stages of infection can be managed by simple incision, debridement and drainage. In advanced stages of infection, a more radical intervention is preferable.

Factory-assembled polyethylene linings in metal backing show higher wear rates compared to equisized all-polyethylene sockets.

Two series of cementless total hip arthroplasty with acetabular sockets of a threaded truncated cone design were compared regarding volumetric wear rates. The first series included all-polyethylene acetabular sockets of the type Endler (E-PE); in the second series, a nonmodular titanium metal-backed polyethylene (E-MB) socket with an identical outer shape to E-PE was implanted. Bearings were articulated with alumina 32-mm diameter ball heads. Ninety-five retrieved devices were examined with a modified fluid displacement method using dental self-polymerizing precision casts. The sockets had to be revised mainly because of wear-induced osteolysis: E-PE after 10.6 years on average and E-MB after 7.8 years (P = .002). Comparison with unused sockets showed mean wear rates of 63 mm(3)/y for E-PE and 120 mm(3)/y for E-MB (P = .0008). Increased contact stress and load deformation due to reduction of polyethylene thickness in E-MB compared to E-PE were identified as predominant reasons for higher wear rates.

Fatigue stress fractures of the pelvis: a rare cause of low back pain in female athletes.

Stress fracture of the pelvis represents one rare differential diagnosis among the manifold causes of low back pain in female athletes. We report a case of fatigue stress fracture of the pelvis in a 24-year-old female athlete as an unusual differential diagnosis of low back pain that should be taken into consideration. According to the literature the incidence of low back pain in athletes ranges from 1% to 30% and is influenced by sport type, gender, training intensity, training frequency and technique. In some cases, no specific pain generator is found, which makes diagnosis and treatment difficult. The frequency of the injury and the treatment options are discussed, based on published studies.

The Mayo cementless femoral component in active patients with osteoarthritis.

This prospective study reports the clinical and radiological results of a single-surgeon series using the Mayo conservative hip stem in a district hospital. 30 total hip arthroplasties were performed in 26 physically active patients. There were 18 women and 8 men, with a mean age of 57.4 years (range 36-79). 4 cases were bilateral. The operation was performed for severe primary or secondary osteoarthritis of the hip .Duration of follow-up ranged from 67-87 months (mean 81 months). There were no early complications relating to the surgical procedure. There was one case of traumatic fracture of the femur during rehabilitation,while late complications included two cases of late infection (4 months and 16 months after surgery)both revised in two-stage procedures. There was considerable improvement in Merle d'Aubignescore following surgery. There were no revisions for aseptic loosening, but we identified 2 implants with significant radiolucent lines and subsidence six years after the index operation. Neither patient experienced pain in the hip or restriction of activity. Therefore, the aseptic loosening survival rate was 100%(end point = revision operation). Taking radiological loosening as the end point survivorship was 93.3%.The use of the Mayo short stem component in active patients may preserve bone and enable subsequent revision operations to proceed using primary implants. Our results suggest that conservative designs of this type may be of benefit in selected individuals.

Collagen IX in weight-bearing areas of human articular cartilage in late stages of osteoarthritis.

AIM: To determine if the amounts of collagen IX mRNA and protein are higher in osteoarthritic cartilage from weight-bearing areas of the knee joint compared to non-weight bearing areas in patients with stage IV osteoarthritis (OA). METHODS: Normal and OA cartilage samples were obtained from 15 patients undergoing total knee replacement or necropsies. mRNA was measured by real time RT-PCR and proteins were detected by Western blot and localized at the light and ultrastructural level. RESULTS: Collagen IX was found throughout all cartilage layers in healthy and OA tissue. Cells deposited collagen IX in the pericellular and interterritorial matrix and a 66% higher amount of collagen IX was detected in the pericellular matrix of the weight-bearing areas adjacent to the main defect in comparison to the macroscopically intact areas. This is in line with a 3.72 times higher amount of the respective mRNA. CONCLUSION: The increased levels of collagen IX protein and its mRNAs found in the weight-bearing areas adjacent to the main cartilage defect might reflect an attempt on the part of the diseased cartilage tissue to stabilize and protect the remaining matrix of late-stage osteoarthritic cartilage from further destruction.

The surgical technique of autologous chondrocyte transplantation of the talus with use of a periosteal graft. Surgical technique.

BACKGROUND: Despite its highly specialized nature, articular cartilage has a poor reparative capability. Treatment of symptomatic osteochondral defects of the talus has been especially difficult until now. METHODS: We performed autologous chondrocyte transplantation in twelve patients with a focal deep cartilage lesion of the talus. There were seven female and five male patients with a mean age of 29.7 years. The mean size of the lesion was 2.3 cm(2). All patients were studied prospectively. Evaluation was performed with use of the Hannover ankle rating score, the American Orthopaedic Foot and Ankle Society (AOFAS) ankle-hindfoot score, a visual analog scale for pain, and magnetic resonance imaging. RESULTS: All patients were available for follow-up at a mean of sixty-three months. There was a significant improvement in the Hannover score, from 40.4 points preoperatively to 85.5 points at the follow-up examination, with seven excellent results, four good results, and one satisfactory result. The AOFAS mean score was 88.4 points compared with 43.5 points preoperatively. Magnetic resonance imaging showed a nearly congruent joint surface in seven patients, discrete irregularities in four, and an incongruent surface in one. The patients who had been involved in competitive sports were able to return to their full activity level. CONCLUSIONS: The promising clinical results of this study suggest that autologous chondrocyte transplantation is an effective and safe way to treat symptomatic osteochondral defects of the talus in appropriately selected patients.

Implant detectibility of intervertebral disc spacers in post fusion MRI: evaluation of the MRI scan quality by using a scoring system--an in vitro study.

INTRODUCTION: Intervertebral spacers for anterior spine fusion are made of different materials, such as titanium and cobalt chromium alloys and carbon fiber-reinforced polymers. Implant-related susceptibility artifacts can decrease the quality of MRI scans. The aim of this cadaveric study was to demonstrate the extent that implant-related MRI artifacting affects the postfusion differentiation of determined regions of interest (ROIs). METHODS: In six cadaveric porcine spines, we evaluated the postimplantation MRI scans of a titanium, cobalt-chromium and carbon spacer that differed in shape and surface qualities. A spacer made of human cortical bone was used as a control. A defined evaluation unit was divided into ROIs to characterize the spinal canal as well as the intervertebral disc space. Considering 15 different MRI sequences read independently by an interobserver-validated team of specialists the artifact-affected image quality of the median MRI slice was rated on a score of 0-3. A maximum score of 18 points (100%) for the determined ROIs was possible. RESULTS: Turbo spin echo sequences produced the best scores for all spacers and the control. Only the control achieved a score of 100%. For the determined ROI maximum scores for the cobalt-chromium, titanium and carbon spacers were 24%, 32% and 84%, respectively. CONCLUSION: By using favored T1 TSE sequences the carbon spacer showed a clear advantage in postfusion spinal imaging. Independent of artifact dimensions, the scoring system used allowed us to create an implant-related ranking of MRI scan quality in reference to the bone control.

Arthrodesis of the knee after failed infected total knee arthroplasty.

Infection after total knee arthroplasty (TKA) can be a challenging and difficult problem to treat. In selected patients, knee arthrodesis is a well-recognized salvage procedure after infected TKA. The authors retrospectively reviewed their experience with this treatment option, presenting 20 patients (8 women, 12 men), performed between 1990 and 2002. The average age was 67 years (range: 47-81 years) and the mean number of previous surgical procedures was 6 (range: 4-11 procedures). There were multiple indications for knee arthrodesis, including extensive bone or soft tissue loss, poor bone stock, and recurring infections. One-stage fusion was done in 7 knees while, on the other 13, arthrodesis was performed as two-stage fusions. The average clinical follow-up was 4.5 years (range: 2-11 years). 18 of the 20 patients were interviewed and graded using the Visual Analogue Scale (VAS) for pain, the Short Form-36 Health Survey (SF-36), and the Knee injury and Osteoarthritis Outcome Score (KOOS) questionnaire that has knee-related quality of life items. According to the VAS, the mean intensity was 3.4 points. 6 (33%) of the patients had no difficulty with the knee and 9 (50%) of them had mild or moderate difficulty. The SF-36 scores were similar to those for normative data for patients after TKA, with only the social functioning, role emotional, and physical functioning scores being lower and the role physical and social functioning scores being higher. Three of 20 fusions failed, whereas two knees became non-infected non-unions. In one, the knee infection persisted and required above-knee amputation. The two-stage arthrodesis gave the most predictable rate of fusion. Persistent infection and extensive bone stock losses led to failure even under the best circumstances. In our opinion, arthrodesis of the knee is a satisfactory salvage procedure following a failed TKA, and can provide reliable expectation for a stable, painless extremity for high-functioning patients who are able to walk.