Short stems have lower load at failure than double-wedged stems in a cadaveric cementless fracture model.

OBJECTIVES: Periprosthetic femoral fractures (PFFs) have a higher incidence with cementless stems. The highest incidence among various cementless stem types was observed with double-wedged stems. Short stems have been introduced as a bone-preserving alternative with a higher incidence of PFF in some studies. The purpose of this study was a direct load-to-failure comparison of a double-wedged cementless stem and a short cementless stem in a cadaveric fracture model. METHODS: Eight hips from four human cadaveric specimens (age mean 76 years (60 to 89)) and eight fourth-generation composite femurs were used. None of the cadaveric specimens had compromised quality (mean T value 0.4 (-1.0 to 5.7)). Each specimen from a pair randomly received either a double-wedged stem or a short stem. A materials testing machine was used for lateral load-to-failure test of up to a maximal load of 5000 N. RESULTS: Mean load at failure of the double-wedged stem was 2540 N (1845 to 2995) and 1867 N (1135 to 2345) for the short stem (p < 0.001). All specimens showed the same fracture pattern, consistent with a Vancouver B2 fracture. The double-wedged stem was able to sustain a higher load than its short-stemmed counterpart in all cases. Failure force was not correlated to the bone mineral density (p = 0.718). CONCLUSION: Short stems have a significantly lower primary load at failure compared with double-wedged stems in both cadaveric and composite specimens. Surgeons should consider this biomechanical property when deciding on the use of short femoral stem.Cite this article: A. Klasan, M. Bäumlein, P. Dworschak, C. Bliemel, T. Neri, M. D. Schofer, T. J. Heyse. Short stems have lower load at failure than double-wedged stems in a cadaveric cementless fracture model. Bone Joint Res 2019;8:489-494. DOI: 10.1302/2046-3758.810.BJR-2019-0051.R1.

Analysis of acetabular version: Retroversion prevalence, age, side and gender correlations.

INTRODUCTION: Studies using conventional radiographical signs and computerized tomography (CT) for retroversion of the acetabulum have reported a prevalence of up to 25%. The purpose of this study was to provide a detailed report on acetabular version, gender, age and side differences in a large cohort. MATERIALS AND METHODS: A total of 404 patients receiving a whole-body CT scan, aged between 16 and 40 years, have been included in the study. The measurement was performed in the transversal plane on three levels: cranial, central and caudal. RESULTS: The retroverted acetabulum on all three levels had a prevalence of 0.25% (95% confidence interval 0-0.7%). The average central anteversion in men was 16.46° (±4.42) and that in women was 19.31° (±5.04) (p < 0.001). Version increases with age, but a cluster analysis showed this to be a trend (p = 0.068). CONCLUSION: Women have a higher average acetabular version than men. Retroversion in a young adult population has a low prevalence when measured with conventional CT. About a tenth of the population has a significantly different contralateral acetabular version. THE TRANSLATIONAL POTENTIAL OF THIS ARTICLE: Global acetabular retroversion has a much lower prevalence than previously reported.

The prevalence of a prominent anterior inferior iliac spine.

INTRODUCTION: Impingement of the prominent anterior inferior iliac spine (AIIS) against the femoral neck has recently been described as another type of impingement. The purpose of this study is to provide a distribution of AIIS types using the classification proposed by Hetsroni and thus report on the prevalence of prominent types. MATERIALS AND METHODS: A total of 400 patients were included in the study with an average age 27.3 ± 6.9 years (range 18-40). All patients received a whole-body polytrauma computer tomography (CT) scan in the emergency room (ER) upon arrival. The classification of AIIS proposed by Hetsroni et al., which describes three morphological types, was used. Type II and III were grouped as prominent types. The measurements were performed in all three planes by two examiners. RESULTS: Male to female ratio was 71:29. Type I was observed in 367 (91.7%) patients. Type II was observed in 31 (7.8%) patients and type III was observed in 2 (0.5%) patients, unilaterally. Prominent types were much more prevalent in men (10.5%) than in women (2.6%). The CT assessment demonstrated excellent intra- and interreliability (overall: 0.926, I/II: 0.906, III: 1.000). CONCLUSION: A young population demonstrates a prevalence of a prominent AIIS of 11.5%. Prominent AIIS is more common in men than in women.

The effect of surgeon's learning curve: complications and outcome after hip arthroscopy.

INTRODUCTION: The aim of the present study was to determine the incidence and type of complications during and after hip arthroscopy as well as the effect of the surgeon's learning curve on the occurrence of complications. We expect that the currently reported prevalence especially of minor complications is likely to be underreported in most retrospective series based on chart analysis. MATERIALS AND METHODS: The study included all consecutive patients who underwent hip arthroscopy between 2006 and 2014 at a minimum follow-up of 6 weeks starting with the first patient undergoing hip arthroscopy at the institution. Patient outcome was evaluated using the WOMAC score, VAS for pain, SF-36 questionnaire and the hip-outcome score. Additionally, intra- and postoperative complications were recorded via a questionnaire and additional review of patient files. RESULTS: We identified 529 patients who underwent hip arthroscopy between 2006 and 2014. Complete data could be gathered from 485 patients (91.7%). Major complications occurred in three patients (0.6%; fractures of the femoral neck requiring surgical treatment in one case). Minor complications that did not require further intervention were self-limiting postoperative temporary neurapraxia, hematoma, self-limiting dyspareunia, deep vein thrombosis and impaired wound healing, with hematoma and temporary paresthesia due to traction neurapraxia being the most common ones (22.5 and 16.4% respectively). The overall re-operation rate was 15.7% with conversion to total hip arthroplasty being the most common (11.9%). CONCLUSIONS: The overall major complication rate was low and thus hip arthroscopy can be rated as a safe procedure. But minor complications such as hematoma and temporary paresthesia due to traction neurapraxia are common and currently underreported. Surgeons' learning curves show a reduction of major complications once 60 procedures per surgeon per year is surpassed.

Use of cell-free collagen type I matrix implants for the treatment of small cartilage defects in the knee: clinical and magnetic resonance imaging evaluation.

PURPOSE: Articular cartilage defects of the knee are a common condition for which several repair techniques have been described. The aim of the present study was to assess medium-term results of a one-step procedure using a cell-free collagen type I matrix. METHODS: Fifteen patients with articular cartilage defects of the knee were treated with an 11-mm-diameter cell-free collagen type 1 matrix implant. The matrices were implanted in a press-fit manner into the defect after careful debridement down to the subchondral bone but without penetration of this margin. Follow-up examinations were carried out at 6 weeks, 6 months, and at 12, 24, 36, and 48 months after implantation. Clinical assessment included the visual analogue scale (VAS), the Tegner activity scale, and the International Knee Documentation Committee (IKDC) score. Radiological assessment for graft attachment and tissue regeneration was performed using the magnetic observation of cartilage repair tissue (MOCART) score. RESULTS: A total of 15 patients (males: n = 6 and females: n = 9) with a mean age of 26.4 years (range 19-40) were treated. The mean VAS improved significantly when compared to the preoperative values (P < 0.05). Six weeks after implantation, IKDC values were slightly lower than the preoperative values (n.s.), but increased significantly at final follow-up (P < 0.05). At 24 months, there were no significant differences in the median Tegner score between the post-operative values and the preoperative values (n.s.). However, after 36 months, a significant improvement was noted that lasted at least up to 48 months (P < 0.05). The MOCART score improved consistently up to 4 years after implantation, with significant improvements already observed after 12 months (P < 0.05). No correlation between the clinical scores and the MOCART score could be perceived. CONCLUSION: The present study showed that the use of cell-free collagen type I matrix implants led to a significant and durable improvement in all the clinical and imaging scores investigated 4 years after implantation. LEVEL OF EVIDENCE: IV.

Penetration of topical diclofenac sodium 4 % spray gel into the synovial tissue and synovial fluid of the knee: a randomised clinical trial.

PURPOSE: The present study was designed to evaluate the penetration of diclofenac sodium 4 % spray gel in synovial tissue, synovial fluid and blood plasma after topical application in subjects with joint effusions and planned total knee arthroplasty (TKA) due to osteoarthritis. METHODS: A total of 39 patients were randomised to two- or three-times daily application of diclofenac sodium 4 % spray gel to knees requiring surgery over a treatment period of 3 days. Within 8 h after the last application, TKA was conducted, and the diclofenac concentrations in synovial tissue, synovial fluid and blood plasma were measured by liquid chromatography. RESULTS: The median diclofenac concentration was approximately 10-20-fold higher in synovial tissue (36.2 and 42.8 ng/g) than in synovial fluid (2.6 and 2.8 ng/mL) or plasma (3.9 and 4.1 ng/mL) in both treatment groups. Dose proportionality for any compartment or treatment groups could not be detected. Treatment-related adverse events were noted in two cases and limited to skin reactions. CONCLUSION: Diclofenac sodium 4 % spray gel was found to penetrate the skin locally in substantial amounts and thus reach the desired target tissue. Concentrations were not dose-dependent, and application was well tolerated by 97.4 % of patients. Topical application of diclofenac should be considered a valuable alternative to systemic NSAID therapy in the initial treatment of osteoarthritis.

MRI after patellofemoral replacement: the component-bone interface and rotational alignment.

BACKGROUND: In an earlier paper, it was shown that tailored magnetic resonance imaging (MRI) allows for reproducible analysis of the preserved knee joint structures after patellofemoral replacement (PFR). PURPOSES: This pilot study investigates to what degree MRI could produce reliable assessment of the implant-bone interface of femoral and patellar components and rotational alignment following PFR. METHODS: MRI tailored for reduction of metallic artefacts was performed in seven patients who had undergone PFR. Two independent investigators evaluated the implant-bone interface at femoral and patellar components and the rotational alignment of the femoral component. They also assessed their degree of confidence in evaluation using a five-point scale. The inter-observer reliability was determined. RESULTS: Implant-induced MRI artefact was barely observed and there was no interference with component-bone interface evaluation. There was excellent inter-observer reliability, inter-observer agreement, and confidence for the implant-bone interface at femoral and patellar components and for rotational alignment. The applied score for the interface was found to be reliable. CONCLUSION: Tailored MRI allows reproducible analysis of the implant-bone interface and of rotational alignment of the femoral component in patients who have had PFR. It might prove helpful in the assessment of painful PFR.

Expression of hypoxia-inducible factor-1α, vascular endothelial growth factor, and matrix metalloproteinases 1, 3, and 9 in hypertrophied ligamentum flavum.

STUDY DESIGN: Immunohistological study. OBJECTIVE: To elucidate the role of matrix metalloproteinases (MMPs), hypoxia-inducible factor-1α (HIF), and vascular endothelial growth factor (VEGF) in the hypertrophied ligamentum flavum (LF) obtained from patients with lumbar spinal stenosis (LSS). SUMMARY OF BACKGROUND DATA: The most common spinal disorder in the elderly is LSS, which results in part from LF hypertrophy. Although prior histologic and immunochemical studies have been performed in this area, the pathophysiology of loss of elasticity and hypertrophy is not completely understood. METHODS: LF samples of 38 patients with LSS were harvested during spinal decompression. Twelve LF samples obtained from patients with disk herniation and no visible degeneration on preoperative magnetic resonance imaging were obtained as controls. Samples were dehydrated and paraffin embedded. For immunohistochemical determination of VEGF, HIF, and MMPs 1, 3, and 9 expression, slices were stained with VEGF, HIF, and MMP antibody dilution. Neovessel density and number of elastic fibers were counted after Masson-Goldner staining. LF hypertrophy and cross-sectional area (CSA) were measured on T1-weighted magnetic resonance imaging. RESULTS: MMPs 1, 3, 9 and VEGF expression were significantly increased in the hypertrophy group (P<0.05). HIF expression was negative in both groups. Vessel density was increased in the hypertrophy group, although this was not statistically significant. The number of elastic fibres was significantly higher in the control group. In the hypertrophy group, LF thickness was significantly increased, whereas CSA was significantly decreased. There was a statistical correlation between LF thickness, CSA, MMP, and VEGF expression in the hypertrophy group (P<0.05). CONCLUSIONS: LF hypertrophy is accompanied by increased MMPs 1, 3, 9 and VEGF expression. Neovessel density is increased in hypertrophied LF. HIF is not expressed in hypertrophied LF.

Functionalisation of PLLA nanofiber scaffolds using a possible cooperative effect between collagen type I and BMP-2: impact on colonization and bone formation in vivo.

The reconstruction of large bone defects after injury or tumor resection often requires the use of bone substitution. Artificial scaffolds based on synthetic biomaterials can overcome disadvantages of autologous bone grafts, like limited availability and donor side morbidity. Among them, scaffolds based on nanofibers offer great advantages. They mimic the extracellular matrix, can be used as a carrier for growth factors and allow the differentiation of human mesenchymal stem cells. Differentiation is triggered by a series of signaling processes, including integrin and bone morphogenetic protein (BMP), which act in a cooperative manner. The aim of this study was to analyze whether these processes can be remodeled in artificial poly-(l)-lactide acid (PLLA) based nanofiber scaffolds in vivo. Electrospun matrices composed of PLLA-collagen type I or BMP-2 incorporated PLLA-collagen type I were implanted in calvarial critical size defects in rats. Cranial CT-scans were taken 4, 8 and 12 weeks after implantation. Specimens obtained after euthanasia were processed for histology and immunostainings on osteocalcin, BMP-2 and Smad5. After implantation the scaffolds were inhomogeneously colonized and cells were only present in wrinkle- or channel-like structures. Ossification was detected only in focal areas of the scaffold. This was independent of whether BMP-2 was incorporated in the scaffold. However, cells that migrated into the scaffold showed an increased ratio of osteocalcin and Smad5 positive cells compared to empty defects. Furthermore, in case of BMP-2 incorporated PLLA-collagen type I scaffolds, 4 weeks after implantation approximately 40 % of the cells stained positive for BMP-2 indicating an autocrine process of the ingrown cells. These findings indicate that a cooperative effect between BMP-2 and collagen type I can be transferred to PLLA nanofibers and furthermore, that this effect is active in vivo. However, this had no effect on bone formation. The reason for this seems to be an unbalanced colonization of the scaffolds with cells, due to insufficient pore size.

MRI after unicondylar knee arthroplasty: the preserved compartments.

PURPOSE: The aim of this study was to assess the reproducibility of using magnetic resonance imaging (MRI) to analyze the preserved anatomic knee compartments following unicondylar knee arthroplasty (UKA) with zirconium femoral components. It was hypothesized that evaluation of the cartilage, ligaments, meniscus, and tendons would result in a high rate of inter-observer reliability. SCOPE: Ten patients underwent MRI of the knee tailored to reduce metallic artifact following medial UKA with zirconium femoral implants. Cartilage, external meniscus, collateral and cruciate ligaments, the quadriceps and patellar tendons, and the presence of joint effusion were evaluated by two independent investigators. The reviewers provided degrees of confidence with their evaluation of each parameter through the use of a five-point scale. Inter-observer agreement was calculated and inter-observer reliability was determined by use of Cohen's Kappa. Artifacts originating from the implants were rarely observed. There was excellent inter-observer reliability (i.e., high Cohen's Kappa) for all assessed structures, and a high level of observer confidence for the evaluation of the cartilage, meniscus, tendons, ligaments, and joint effusion. CONCLUSION: In this study tailored MRI allows for reproducible analysis of the preserved knee joint compartment after UKA for zirconium implants. This technique might prove helpful in the assessment of painful knee joints after UKA with other metallic materials as new MRI software programs, which suppress metal artifacts, are developed.

Non-anatomic proximal realignment for recurrent patellar dislocation does not sufficiently prevent redislocation.

Several operative techniques have been described for recurrent patellar dislocation. Clinical results vary depending on the procedure and indication. The present study aimed to evaluate the clinical outcome of Insall's proximal realignment for recurrent patellar dislocation at mid-term follow-up. Forty-five patients were reviewed with a mean follow-up period of 49 months after having undergone Insall's procedure. Outcome measures included reports of redislocations, complications, patient-reported outcome scores (Kujala, Tegner activity scale) and subjective assessment. No statistically significant improvements (p < 0.05) in patient-reported outcome measures were noted. Sixteen patients (35%) had poor to fair results using the Kujala score. Subjective assessment revealed that 12 patients (27%) were dissatisfied with the outcome of their surgery and would not undergo the same procedure. Ten patients (22%) had suffered from redislocation at the latest follow-up. In 4 cases (9%), intra-articular knee hematoma occurred which required arthroscopic intervention. The overall mid-term outcome of the present study shows low patient satisfaction. Non-anatomic realignment for recurrent patellar dislocation does not adequately prevent redislocation.

The influence of superior labrum anterior to posterior (SLAP) repair on restoring baseline glenohumeral translation and increased biceps loading after simulated SLAP tear and the effectiveness of SLAP repair after long head of biceps tenotomy.

HYPOTHESIS: Biomechanical studies have shown increased glenohumeral translation and loading of the long head biceps (LHB) tendon after superior labrum anterior to posterior (SLAP) tears. This may explain some of the typical clinical findings, including the prevalence of humeral chondral lesions, after SLAP lesions. The first hypothesis was that SLAP repair could restore the original glenohumeral translation and reduce the increased LHB load after SLAP lesions. The second hypothesis was that SLAP repair after LHB tenotomy could significantly reduce the increased glenohumeral translation. MATERIALS AND METHODS: Biomechanical testing was performed on 21 fresh frozen human cadaveric shoulders with an intact shoulder girdle using a sensor-guided industrial robot to apply 20 N of compression in the joint and 50 N translational force at 0°, 30°, and 60° of abduction. LHB loading was measured by a load-cell with 5 N and 25 N preload. Type IIC SLAP lesions were created arthroscopically, and a standardized SLAP repair was done combined with or without LHB tenotomy. RESULTS: No significant difference of glenohumeral translation and increased LHB load in SLAP repair compared with the intact shoulder was observed under 5 N and 25 LHB preload, except for anterior translation under 25 N LHB preload. After LHB tenotomy after SLAP lesions, no significant difference of translation was observed with or without SLAP repair. CONCLUSIONS: SLAP repair without associated LHB tenotomy helps normalize glenohumeral translation and LHB loading. The stabilizing effect of the SLAP complex is dependent on the LHB. After biceps tenotomy, SLAP repair does not affect glenohumeral translation.

Influence of intraventricular application of baclofen on arterial blood pressure and neurotransmitter concentrations in the hypothalamic paraventricular nucleus of rats.

The hypothalamic paraventricular nucleus (PVN) is a key site for regulating neuroendocrine functions in the magnocellular part and autonomic activities in the parvocellular part. Its anatomical proximity to the third ventricle could be a good target for intrathecal injection of baclofen. We investigated the correlation of intrathecal application of baclofen (a specific GABAB receptor agonist) and the release of epinephrine, norepinephrine, dopac, homovanillinic acid (HVA), glutamate and aspartate from the PVN. The decomposition products HVA, dopa and dopac of norepinephrine, epinephrine and dopamine, respectively, were used as parameters for the secretion of dopamine. We implanted a microdialysis probe in the PVN of 25 Wistar rats. In 13 rats, 1.5 µg baclofen was injected in the lateral ventricle and the equivalent quantity of Ringer's lactate solution injected in the remaining 12 rats as a control group. Neurotransmitters and amino acids were quantified by high-performance liquid chromatography. There was a conspicuous but not significant effect of baclofen concerning the secretion of epinephrine, norepinephrine, dopac, glutamate and aspartate from the PVN. A significant increase in HVA concentration was observed only in rats treated with baclofen compared with the control group. These findings suggest that baclofen influences the secretion of neurotransmitters and amino acids involved in autonomic activities mediated by GABAB receptors.

Anterior cruciate ligament deficiency leads to early instability of scaffold for cartilage regeneration: a controlled laboratory ex-vivo study.

PURPOSE: The affect of anterior cruciate ligament (ACL) integrity on the early postoperative stability of a collagen type-I gel scaffold was investigated. The value of fibrin glue for graft fixation in ACL deficient porcine knees over a simulated early postoperative period was also studied. METHODS: Full-thickness articular cartilage defects (11 × 6 mm) were created on the medial femoral condyle of 80 porcine knees. The ACL was left intact or completely transected in each of 40 knees. Gel plugs were tested in each group: press-fitting only in 20 specimens and press-fitting plus fibrin glue in 20 specimens. Each knee underwent 2,000 cycles in a validated ex-vivo continuous passive motion model. RESULTS: Press-fit-only fixation grafts in knee specimens with an intact ACL showed significantly superior stability than that in ACL deficient knees (p = 0.01). In ACL deficient knees, grafts fixed with press-fitting plus fibrin glue showed significantly superior stability than those using press-fit only fixation (p = 0.01). Press-fitting plus fibrin glue fixation showed no significant differences in worn surface area between knee specimens with intact and deficient ACL. CONCLUSIONS: ACL deficiency led to early scaffold instability in an ex-vivo porcine knee model. Fibrin glue in ACL deficient knees led to additional graft stability. These findings indicated that cartilage regenerative techniques may give optimum results in ACL intact knees.

The safety and short-term efficacy of a novel polyurethane meniscal scaffold for the treatment of segmental medial meniscus deficiency.

PURPOSE: Meniscal loss is associated with an increased risk of developing osteoarthritis. Tissue engineering solutions, which include the development of novel material scaffolds, are being utilised to aid the regeneration of meniscal tissue. The purpose of this study was to monitor the safety profile and the short-term efficacy of a novel polyurethane meniscal scaffold in the treatment of patients with painful knees following partial medial meniscectomy. METHODS: Ten consecutive patients with segmental tissue loss from the medial meniscus were treated with the arthroscopic implantation of an Actifit(®) (Orteq Sports Medicine) polyurethane meniscal scaffold. Patients were followed up at 2 and 6 weeks, then again at 6 and 12 months. Primary outcome measures included reporting of complications and patient-reported outcome scores (KOOS, KSS, UCLA Activity scale, VAS pain). Secondary outcome was MRI assessment at 6 and 12 months looking at scaffold morphology, integration and associated joint injury/inflammation. RESULTS: Eight male and 2 female patients were included in the study with a mean age of 29 (range 18-45). No complications were reported. All patients were happy with their surgery. At 6 months, a statistically significant improvement (P < 0.05) in all PROMS except the UCLA activity scale and VAS pain scale were noted. The improvement remained at 12 months. MRI analysis revealed the presence of scaffolds at 6 months, with evidence of some tissue integration in many improvements in scaffold morphology and ICRS classification of cartilage in the medial compartment were noted at 12 months. No synovitis was noted in the joint or adverse reactions in the other compartments. CONCLUSION: The new Actifit(®) polyurethane scaffold has been shown to be a safe, effective implant, for the treatment of patients with pain as a result of segmental medial meniscus loss at 1 year. LEVEL OF EVIDENCE: IV.

Fibrin glue does not improve the fixation of press-fitted cell-free collagen gel plugs in an ex vivo cartilage repair model.

PURPOSE: Adequate graft fixation over a certain time period is necessary for successful cartilage repair and permanent integration of the graft into the surrounding tissue. The aim of the present study was to test the primary stability of a new cell-free collagen gel plug (CaReS(®)-1S) with two different graft fixation techniques over a simulated early postoperative period. METHODS: Isolated chondral lesions (11 mm diameter by 6 mm deep) down to the subchondral bone plate were created on the medial femoral condyle in 40 porcine knee specimens. The collagen scaffolds were fixed in 20 knees each by press-fit only or by press-fit + fibrin glue. Each knee was then put through 2,000 cycles in an ex vivo continuous passive motion model. Before and after the 2,000 motions, standardized digital pictures of the grafts were taken. The area of worn surface as a percentage of the total collagen plug surface was evaluated using image analysis software. RESULTS: No total delamination of the scaffolds to leave an empty defect site was recorded in any of the knees. The two fixation techniques showed no significant difference in worn surface area after 2,000 cycles (P = n.s.). CONCLUSIONS: This study reveals that both the press-fit only and the press-fit + fibrin glue technique provide similar, adequate, stability of a type I collagen plug in the described porcine model. In the clinical setting, this fact may be particularly important for implantation of arthroscopic grafts.

Cell-free collagen type I matrix for repair of cartilage defects-clinical and magnetic resonance imaging results.

PURPOSE: Several well-described techniques are available for the treatment of chondral and osteochondral defects. The aim of the study was to assess the efficacy of a single-stage procedure incorporating a new cell-free collagen type I gel for the treatment of small chondral and osteochondral defects in the knee evaluated at 2-year follow-up. METHODS: Fifteen patients were treated with a cell-free collagen type I gel matrix of 11 mm diameter. The grafts were implanted in the debrided cartilage defect and fixed by press-fit only. The clinical outcome was assessed preoperatively and at 6 weeks, and 6, 12 and 24 months after surgery using the International Knee Documentation Committee (IKDC) score, Tegner activity scale and visual analogue scale (VAS). Graft attachment rate was assessed 6 weeks postoperatively using magnetic resonance imaging (MRI). Cartilage regeneration was evaluated using the Magnetic Observation of Cartilage Repair Tissue (MOCART) score at 6, 12 and 24 months after implantation. Clinical results were correlated with MRI findings. RESULTS: Six male and nine female patients were included in this study, with a mean age of 26 (range: 19-40). No complications were reported. The mean VAS values after 6 weeks and the mean IKDC patient values after 6 months were significantly improved from the preoperative values (P = 0.005 and P = 0.009, respectively). This improvement remained up to the latest follow-up. There were no significant differences between the median preoperative and postoperative Tegner values (n.s.). Significant improvement of the mean MOCART score was observed after 12 months and remained by 24 months (P < 0.001). MR images showed that in 14 of the 15 patients, the graft was completely attached by 6 weeks postoperatively. At 24 months after implantation, MRI demonstrated complete filling in all cases with a mainly smooth surface, complete integration of the border zone, homogenous structure of the repaired tissue and nearly normal signal intensity. No correlation between any variables of the MOCART score and the clinical scores was observed. CONCLUSIONS: The present study reveals that the new method produces both good clinical and magnetic resonance imaging results. Use of press-fit only implanted grafts of a smaller diameter leads to a high attachment rate at 24-month follow-up. LEVEL OF EVIDENCE: IV.

MRI after patellofemoral replacement: the preserved compartments.

INTRODUCTION: The aim of this study was to assess the reproducibility of magnet resonance imaging (MRI) analysis of preserved anatomic structures of the knee after patellofemoral replacement (PFR). It was hypothesized that evaluation of cartilage, ligaments, meniscus and tendons would result in high inter-observer reliability after PFR. MATERIAL AND METHODS: MRI, tailored to reduce metallic artefacts of the knee, after PFR was performed in seven patients. Two independent investigators evaluated cartilage, menisci, collateral and cruciate ligaments, the quadriceps and patellar tendons and the presence of joint effusion. The reviewers used a five-point scale to give a degree of confidence to their evaluation of each parameter. Inter-observer reliability was determined by calculation of Cohen's Kappas. RESULTS: Artefact provoked by the implants was not observed. For all assessed structures, there was excellent inter-observer reliability, with high Cohen's Kappas. There were also high levels of inter-observer agreement and observer confidence in the evaluation of cartilage, meniscus, tendons, ligaments and joint effusion. CONCLUSION: Tailored MRI allows reproducible analysis of the preserved knee joint structures after PFR. It might prove helpful in assessment of painful knee joints after PFR.

Suprapectoral or subpectoral position for biceps tenodesis: biomechanical comparison of four different techniques in both positions.

HYPOTHESIS: The aim of this study was to compare different techniques for tenodesis of the long head of biceps tendon (LHB) in the suprapectoral and subpectoral position to test the hypothesis that using shorter screws at the subpectoral position would achieve a similar primary ultimate failure load (UFL) as the longer screws at the suprapectoral position, that both types of tenodesis screws achieve comparable UFL, and that knotless suture anchor techniques can be performed at the subpectoral position in cortical bone and reach a UFL similar to tenodesis screws. METHODS: On 42 fresh frozen human cadavers divided into 6 groups, 4 different techniques for LHB tenodesis were performed localized 10 mm and 50 mm, respectively, distal to the entrance of the bicipital groove. Two techniques with tenodesis screws (Bio-Tenodesis screw, Biceptor) and 2 with knotless suture anchors (Bio-SwiveLock, Footprint PK) were tested. Under a 10-N preload, an axial cyclic load with 100 cycles, 1-Hz frequency, and 50-N maximal load was applied. UFL was evaluated with an axial traction of 0.2 mm/s until decrease of tension. LHB dislocation was measured by 3-dimensional photogrammetry. RESULTS: All techniques except the subpectoral Bio-SwiveLock had a dislocation <3 mm after cyclic loading. The highest mean UFL was measured for the suprapectoral Bio-Tenodesis screw (218.3 ± 59.7 N) and the lowest with the subpectoral Footprint PK (99.1 ± 16.4 N). The UFL of suture anchors were significantly lower than those of interference screws (P < .01). UFL was not significantly different for type of interference screw, the type of suture anchor, or tenodesis localization. Different failure mechanisms were evaluated for suture anchors and interference screws. CONCLUSION: Due to the biomechanical testings interference screws are appropriate devices for suprapectoral and subpectoral biceps tenodesis resisting cyclic loading and attaining a satisfactory, whereas the knotless suture anchors sustained a significant about 50% lower UFL, and can only be recommended conditionally for LHB tenodesis regarding primary stability.

Electrospun PLLA nanofiber scaffolds and their use in combination with BMP-2 for reconstruction of bone defects.

INTRODUCTION: Adequate migration and differentiation of mesenchymal stem cells is essential for regeneration of large bone defects. To achieve this, modern graft materials are becoming increasingly important. Among them, electrospun nanofiber scaffolds are a promising approach, because of their high physical porosity and potential to mimic the extracellular matrix (ECM). MATERIALS AND METHODS: The objective of the present study was to examine the impact of electrospun PLLA nanofiber scaffolds on bone formation in vivo, using a critical size rat calvarial defect model. In addition we analyzed whether direct incorporation of bone morphogenetic protein 2 (BMP-2) into nanofibers could enhance the osteoinductivity of the scaffolds. Two critical size calvarial defects (5 mm) were created in the parietal bones of adult male Sprague-Dawley rats. Defects were either (1) left unfilled, or treated with (2) bovine spongiosa, (3) PLLA scaffolds alone or (4) PLLA/BMP-2 scaffolds. Cranial CT-scans were taken at fixed intervals in vivo. Specimens obtained after euthanasia were processed for histology, histomorphometry and immunostaining (Osteocalcin, BMP-2 and Smad5). RESULTS: PLLA scaffolds were well colonized with cells after implantation, but only showed marginal ossification. PLLA/BMP-2 scaffolds showed much better bone regeneration and several ossification foci were observed throughout the defect. PLLA/BMP-2 scaffolds also stimulated significantly faster bone regeneration during the first eight weeks compared to bovine spongiosa. However, no significant differences between these two scaffolds could be observed after twelve weeks. Expression of osteogenic marker proteins in PLLA/BMP-2 scaffolds continuously increased throughout the observation period. After twelve weeks osteocalcin, BMP-2 and Smad5 were all significantly higher in the PLLA/BMP-2 group than in all other groups. CONCLUSION: Electrospun PLLA nanofibers facilitate colonization of bone defects, while their use in combination with BMP-2 also increases bone regeneration in vivo and thus combines osteoconductivity of the scaffold with the ability to maintain an adequate osteogenic stimulus.