Using a patella reduced technique while balancing a TKA results in restored physiological strain in the collateral ligaments: an ex vivo kinematic analysis.

INTRODUCTION: Poor soft tissue balance in total knee arthroplasty (TKA) often results in patient dissatisfaction and reduced joint longevity. Patella-in-place balancing (PIPB) is a novel technique which aims to restore native collateral ligament behavior without collateral ligament release, while restoring post-operative patellar position. This study aimed to assess the effectiveness of this novel technique through a detailed ex vivo biomechanical analysis by comparing post-TKA tibiofemoral kinematics and collateral ligament behavior to the native condition. MATERIALS AND METHODS: Eight fresh-frozen cadaveric legs (89.2 ± 6 years) were tested on a validated dynamic knee simulator, following computed tomography imaging. Specimens were subjected to passive flexion (10-120°), squatting (35-100°), and varus/valgus laxity testing (10 Nm at 0°, 30°, 60°, 90° flexion). An optical motion capture system recorded markers affixed rigidly to the femur, tibia, and patella, while digital extensometers longitudinally affixed to the superficial medial collateral ligament (MCL) and lateral collateral ligament (LCL) collected synchronized strain data. Following native testing, a Stryker Triathlon CR TKA (Stryker, MI, USA) was performed on each specimen and the identical testing protocol was repeated. Statistical analyses were performed using a linear mixed model for functional motor tasks, while Wilcoxon signed-rank test was used for laxity tests (p < 0.05). RESULTS: Postoperative laxity was lower than the native condition at all flexion angles while post-operative ligament strain was lowered only for MCL at 30° (p = 0.017) and 60° (p = 0.011). Postoperative femoral rollback patterns were comparable to the native condition in passive flexion but demonstrated a more pronounced medial pivot during squatting. CONCLUSIONS: Balancing a TKA with the PIPB technique resulted in reduced joint laxity, while restoring collateral ligament strains. The technique also seemed to restore kinematics and strains, especially in passive flexion.

A cell-based combination product for the repair of large bone defects.

Regenerative cell-based implants using periosteum-derived stem cells were developed for the treatment of large 3 cm fresh and 4.5 centimeter biological compromised bone gaps in a tibial sheep model and compared with an acellular ceramic-collagen void filler. It was hypothesized that the latter is insufficient to heal large skeletal defects due to reduced endogenous biological potency. To this purpose a comparison was made between the ceramic dicalciumphosphate scaffold (CopiOs®) as such, the same ceramic coated with clinical grade Bone Morphogenetic Protein 2 and 6 (BMP) only or a BMP coated cell-seeded combination product. These implants were evaluated in 2 sheep models, a fresh 3 cm critical size tibial defect and a 4.5 cm biologically exhausted tibial defect. For the groups in which growth factors were applied, BMP-6 was chosen at a dose of 344 µg for 3 cm and 1.500 µg or 3.800 µg for 4.5 cm defects. An additional group in the 4.5 cm defect was tested using BMP-2 in a dose of 1.500 µg. For all the cell based implants autologous periosteum-derived cells were used which were cultured in monolayer during 6 weeks. For the fresh defect 408 million cells and for the biologically exhausted tibial defect 612 million cells were drop-seeded on the BMP coated scaffolds. Bone healing was studied during 16 weeks postimplantation, using standard radiographs. While fresh defects responded to all treatments, regardless the use of cells, the biologically hampered defects responded in half of the cases and only if the BMP-cell combination product was used, supporting the concept that cell-based therapies may become attractive in treating defects with a compromised biological status.

Vibration-based fixation assessment of tibial knee implants: A combined in vitro and in silico feasibility study.

The preoperative diagnosis of loosening of cemented tibial knee implants is challenging. This feasibility study explored the basic potential of a vibration-based method as an alternative diagnostic technique to assess the fixation state of a cemented tibia implant and establish the method's sensitivity limits. A combined in vitro and in silico approach was pursued. Several loosening cases were simulated. The largest changes in the vibrational behavior were obtained in the frequency range above 1500 Hz. The vibrational behavior was described with two features; the frequency response function and the power spectral density band power. Using both features, all experimentally simulated loosening cases could clearly be distinguished from the fully cemented cases. By complementing the experimental work with an in silico study, it was shown that loosening of approximately 14% of the implant surface on the lateral and medial side was detectable with a vibration-based method. Proximal lateral and medial locations on the tibia or locations toward the edge of the implant surface measured in the longitudinal direction were the most sensitive measurement and excitation locations to assess implant fixation. These results contribute to the development of vibration-based methods as an alternative follow-up method to detect loosened tibia implants.

Warning About the Use of Critical-Size Defects for the Translational Study of Bone Repair: Analysis of a Sheep Tibial Model.

The repair of large long bone defects requires complex surgical procedures as the bone loss cannot simply be replaced by autologous grafts due to an insufficient bone stock of the human body. Tissue engineering strategies and the use of Advanced Therapy Medicinal Products (ATMPs) for these reconstructions remain a considerable challenge, in particular since robust outcomes in well-defined large animal models are lacking. To be suitable as a model for treatment of human sized bone defects, we developed a large animal model in both skeletally immature and mature sheep and made close observations on the spontaneous healing of defects. We warn for the spontaneous repair of large defects in immature animals, which can mask the (in)effectiveness of ATMP therapies, and propose the use of large 4.5 cm defects that are pretreated with a polymethylmethacrylate (PMMA) spacer in skeletally mature animals.

Evaluation of predicted knee function for component malrotation in total knee arthroplasty.

Soft-tissue balancing for total knee arthroplasty (TKA) remains subjective and highly dependent on surgical expertise. Pre-operative planning may support the clinician in taking decisions by integrating subject-specific computer models that predict functional outcome. However, validation of these models is essential before they can be applied in clinical practice. The aim of this study was to evaluate a knee modelling workflow by comparing experimental cadaveric measures to model-based kinematics and ligament length changes. Subject-specific models for three cadaveric knees were constructed from medical images. The implanted knees were mounted onto a mechanical rig to perform squatting, measuring kinematics and ligament length changes with optical markers and extensometers. Coronal malrotation was introduced using tibial inserts with a built-in slope. The model output agreed well with the experiment in all alignment conditions. Kinematic behaviour showed an average RMSE of less than 2.7mm and 2.3° for translations and rotations. The average RMSE was below 2.5% for all ligaments. These results show that the presented model can quantitatively predict subject-specific knee behaviour following TKA, allowing evaluation of implant alignment in terms of kinematics and ligament length changes. In future work, the model will be used to evaluate subject-specific implant position based on ligament behaviour.

Inflammatory Neuropathy of the Lumbosacral Plexus following Periacetabular Osteotomy.

Introduction. During periacetabular osteotomy (PAO), the sciatic, femoral, and obturator nerves are at risk. Most frequently nerve lesions can be attributed to a mechanical cause; however, in the absence of a clear mechanical cause surgeons are faced with a diagnostic problem and in many cases no diagnosis will be established. We report a case of inflammatory neuropathy of the lumbosacral plexus following a PAO. Case Presentation. A 31-year-old female developed weakness of ankle and knee flexion and extension 6 months after a PAO. Electrophysiological studies revealed damage to the obturator, femoral, and sciatic nerve consistent with an inflammatory lumbosacral plexopathy. MRI of the lumbosacral plexus was normal. The patient was treated with multimodal pain therapy and prolonged physiotherapy; nevertheless, symptoms worsened over time. At 2-year follow-up, there were no signs of recovery. Discussion. Inflammatory neuropathy of the lumbosacral plexus is a potential cause of pain and weakness after ipsilateral orthopaedic procedures. It should be distinguished from more frequently encountered mechanical causes of postsurgical neuropathy based on clinical suspicion, electrophysiological studies, MRI, and nerve biopsy. It is important that the orthopaedic community is aware of this complication since there is some evidence that early recognition and initiation of immunosuppressive therapy can lead to improved clinical outcome.

Restoration of constitutional alignment in TKA leads to more physiological strains in the collateral ligaments.

PURPOSE: Currently, controversy exists whether restoration of neutral mechanical alignment should be attempted in all patients undergoing TKA. Our hypothesis was that restoration of constitutional rather than neutral mechanical alignment may in theory lead to a more physiological strain pattern in the collateral ligaments; therefore, it could potentially be beneficial to patients. Thus, the aim of this study was to measure collateral ligament strains during three motor tasks in the native knee and compare them with the strains noted after TKA in different post-operative alignment conditions. METHODS: Six cadaver specimens (approval number ML4190 from the Research Ethics Committee of University of Leuven, Belgium) were examined using a validated knee kinematics rig under physiological loading conditions. The effect of coronal malalignment was evaluated by using custom-made tibial implant inserts that induced different alignment conditions. The study of six specimens allows us to show that a difference in the mean strains in MCL and LCL of 3.6 and 5.8 %, respectively, was statistically significant with a probability (power) of 0.8. RESULTS: The results indicated that after TKA insertion, the strains in the collateral ligaments closely resembled the pre-operative pattern of the native knee specimens when constitutional alignment was restored. Restoration to neutral mechanical alignment was associated with greater collateral strain deviations from the native knee. CONCLUSION: Based upon this study, it was concluded that restoration of constitutional alignment within a "safe zone" of ±2° during TKA leads to more physiological peri-articular soft tissue strains during loaded as well as unloaded motor tasks.

New possible pathways in improving outcome and patient satisfaction after TKA.

Patient dissatisfaction after TKA has not been improved dramatically since the introduction of new alignment (navigation, custom guides) and balancing techniques. Orthopaedic surgeons consider the ligaments as essentially passive stabilizing structures. However, during the activities of daily living, the joints are stabilized primarily by our muscle actions that both move and stabilize the joints. Isometric motion of the joint does not cause the distance separating the bone attachments to change. The practical importance of isometry is confirmed by the fact that ligaments are elongated irreversibly if the strain exceeds a given level (5%). In ligament surgery as well as in TKA, the concept of isometry is highly important. In this paper we wish to highlight the fact that the role of the soft tissue envelope goes beyond structural and mechanical support. The presence of mechano- and nocireceptors in the structures around the human knee joint has long been reported but is underrecognised by TKA surgeons.

Patient-specific instruments: industry's innovation with a surgeon's interest.

PURPOSE: The aim of this study was (1) to survey the orthopaedic companies about the volume of patient-specific instruments (PSI) used in Europe and worldwide; (2) to survey a group of knee arthroplasty surgeons on their acceptance of PSI and finally; (3) to survey a medico-legal expert on PSI-related issues. METHODS: Seven orthopaedic implant manufacturers were contacted to obtain their sales figures (in volume) of PSI in Europe and worldwide for the 2011 and 2012 period. During the Open Meeting of the Belgian Knee Society, a survey by a direct voting system was submitted to a selection of knee surgeons. Finally, a number of medico-legal 'PSI-related' questions were submitted to an adult reconstruction surgeon/legal expert. RESULTS: The total volume, for all contacted companies, of PSI in Europe for 2012 was 17,515 total knee arthroplasty (TKA) and 82,556 TKA worldwide. Biomet (Warsaw, USA) was the number one in volume, both in Europe as worldwide with their Signature system. Biomet represented 27 % of the market share in PSI worldwide. Stryker preferred not to reply to the survey because of the FDA class 1 recall on ShapeMatch cutting guides. Eighty per cent of the Belgian knee surgeons expressed a great interest in PSI and especially, for 58 % of them, if it would increase their surgical accuracy. They valued it even more in unicompartmental arthroplasty, and 55 % was ready to use single-use instruments. Surprisingly, 47 % of surgeons thought it was the company's responsibility if something goes wrong with a PSI-assisted case. The medico-legal expert concluded that PSI is a complex process that exposes surgeons to new risks in case of failure and stated that companies should not produce surgical guides without validation of the planning by the surgeon. CONCLUSION: Patient-specific instruments is of great interest if it can proof to increase the surgical accuracy in knee arthroplasty to the level surgeons are expecting and if in the same time it would make the surgical process more efficient. LEVEL OF EVIDENCE: V.

Collateral ligament strains during knee joint laxity evaluation before and after TKA.

BACKGROUND: Passive knee stability is provided by the soft tissue envelope. There is consensus among orthopedic surgeons that good outcome in Total Knee Arthroplasty requires equal tension in the medial/lateral compartment of the knee joint, as well as equal tension in the flexion/extension gap. The purpose of this study was to quantify the ligament laxity in the normal non-arthritic knee before and after Posterior-Stabilized Total Knee Arthroplasty. We hypothesized that the Medial/Lateral Collateral Ligament shows minimal changes in length when measured directly by extensometers in the native human knee during varus/valgus laxity testing. We also hypothesized that due to differences in material properties and surface geometry, native laxity is difficult to reconstruct using a Posterior-Stabilized Total Knee. METHODS: Six specimens were used to perform this in vitro cadaver test using extensometers to provide numerical values for laxity and varus-valgus tilting in the frontal plane. FINDINGS: This study enabled a precise measurement of varus-valgus laxity as compared with the clinical assessment. The strains in both ligaments in the replaced knee were different from those in the native knee. Both ligaments were stretched in extension, in flexion the Medial Collateral Ligament tends to relax and the Lateral Collateral Ligament remains tight. INTERPRETATION: As material properties and surface geometry of the replaced knee add stiffness to the joint, we recommend to avoid overstuffing the joint, when using this type of Posterior-Stabilized Total Knee Arthroplasty, in order to obtain varus/valgus laxity close to the native joint.

The Pentaconcept in skeletal tissue engineering. A combined approach for the repair of bone defects.

Tissue engineering has become a hot topic in modern medicine. Its application in a surgical setting, such as for the treatment of skeletal defects, still has to tackle some problems that might look simple at first sight, but need a well-structured handling combining surgery and science, with in a central position the patient, who is both cell donor and receptor of the tissue engineered end product. To achieve this goal in a clinical setting, a five steps pathway is described and designated as the Pentaconcept, integrating all ingredients for successful reconstructive procedures.

Resurfacing hip arthroplasty. A 3 to 5-year matched pair study of two different implant designs.

We compared the 3 to 5 year clinical and radiological results of two different hybrid metal-on-metal resurfacing hip arthroplasty designs in 28 patients who had undergone bilateral hip resurfacing with ReCap implants on one side and BHR implants on the other side. Both hips were compared in each patient, to specifically evaluate the bone response to the cemented femoral component. Post operative function was measured with the Harris Hip Score and University of California at Los Angeles (UCLA) Activity Score, and was excellent in these patients. Mean cup inclination was 43.3 degrees +/- 7 degrees (43.3 degrees +/- 7 degrees for the BHR and 43.4 +/- 6 degrees for the Recap). The inclination angle was greater than 45 degrees in 15 patients: 7 with a BHR, 8 with a Recap; eight patients showed inclination angles greater than 50 degrees (4 patients in each group). All acetabular monoblock cups were well fixed. One patient (1.8%) had radiographs showing bone changes of uncertain significance around the stem of the femoral component. Three percent had femoral bone resorption in the BHR hip and two percent showed bone resorption in the ReCap hip. There was no evidence of migration of the femoral components. The dual energy X-ray absorptiometry (DEXA) scans identified no real reduction in bone density in these resurfacing hip arthroplasties. None of these hips showed any other adverse features. The biological response showed no difference for the two different designs of resurfacing hip arthroplasties.

Quantitative Computerized Assessment of the Degree of Acetabular Bone Deficiency: Total radial Acetabular Bone Loss (TrABL).

A novel quantitative, computerized, and, therefore, highly objective method is presented to assess the degree of total radical acetabular bone loss. The method, which is abbreviated to "TrABL", makes use of advanced 3D CT-based image processing and effective 3D anatomical reconstruction methodology. The output data consist of a ratio and a graph, which can both be used for direct comparison between specimens. A first dataset of twelve highly deficient hemipelves, mainly Paprosky types IIIB, is used as illustration. Although generalization of the findings will require further investigation on a larger population, it can be assumed that the presented method has the potential to facilitate the preoperative use of existing classifications and related decision schemes for treatment selection in complex revision cases.

Arthroscopic psoas release for iliopsoas impingement after total hip replacement.

Psoas impingement is a rare cause of persisting pain after hip arthroplasty. Diagnosis is based on clinical examination and exclusion of other complications after arthroplasty by radiographs, ultrasound, CT and blood analysis. The diagnosis is strongly supported by temporary pain relief after infiltration. When conservative measures fail, treatment can consist of a psoas tenotomy or a revision arthroplasty. When there is no obvious cause such as malpositioning for component impingement, psoas release reliably improves pain and function. This procedure is mostly performed through an open approach, which can give significant complications. An arthroscopic technique for psoas tenotomy after hip arthroplasty is described. This report shows that this minimal invasive technique is safe and effective and allows for inspection of the implant in the same session. However, the score used did not improve in a significant way.

Debonding of the acetabular porous coating in hip resurfacing arthroplasty. A case report.

This report presents the case of a patient in whom hip resurfacing arthroplasty failed because of loosening of the acetabular shell secondary to debonding of the surface coating. During normal function, there will inevitably be cyclic shear stress between the coating and the surrounding bone. This might result in fatigue failure of the bond. In spite of increasing numbers of porous coated acetabular shells being implanted, little is known about the fatigue performance of the interface between coating and implant.

Comparative gravimetric wear analysis in mobile versus fixed-bearing posterior stabilized total knee prostheses.

Polyethylene (PE) wear is the limiting factor for the longevity of a conventional total knee arthroplasty (TKA). Excessive wear leads to loosening and eventual implant failure. The aim of our in vitro study was to investigate wear of a PE tibial insert on a rotating platform as compared to the same insert fixed to the tibial baseplate and articulating with a similar femoral component. All tests were performed at Endolab Laboratories, Rosenheim, Germany using a knee joint simulator following ISO 14243-1. Three specific configurations were tested and compared to a loaded soak control: (1) the rotating platform using machined polyethylene (PE), (2) fixed bearing using machined PE, (3) fixed bearing using compression-moulded PE. Calf serum with a high protein concentration of 30 g/l was chosen as test lubricant. PE wear was measured gravimetrically using the ISO 14243-2 protocol. The total wear rates found for all systems tested were low. The mean wear rate was 1.40 mg per million cycles for the moulded fixed bearing, 4.07 mg per million cycles for the machined fixed bearing type and 0.82 mg per million cycles for the machined rotating platform bearing type. We conclude that the TKA system we tested (Performance, Biomet, Warsaw, IND, USA) demonstrated very low gravimetric wear. The wear rate of the same implant in the fixed mode compared to the rotating platform mode was four times higher.

Reconstruction of the medial patellofemoral ligament for patellar instability using an autologous gracilis tendon graft.

Patellofemoral dislocations are common. In cases with recurrence or residual instability, surgical intervention is usually considered. Numerous treatment protocols have been used in the past to treat patellofemoral instability secondary to patella dislocation. Reconstruction of the medial patellofemoral ligament is one of the possible options, since it was acknowledged to have a major medial stabilising role on the patella. We present a technique for reconstruction of the medial patellofemoral ligament using an autologous gracilis tendon graft.

Influence of the cementing technique on the cement mantle in hip resurfacing: an in vitro computed tomography scan-based analysis.

BACKGROUND: The cement mantle within a hip resurfacing head is important for implant survival. Too much cement leads to thermal bone necrosis, whereas not enough cement might cause mechanical failure and particle-induced osteolysis. We evaluated the impact of different cementing techniques on the quality of the cement mantle in hip resurfacing. METHODS: Sixty bovine condyles were prepared to fit a size-46 ReCap (Biomet) implant and divided into five groups of twelve specimens each. In two of the groups, a polymeric replica was filled halfway with low-viscosity cement; suction was employed in one of those groups and not used in the other. Medium-viscosity cement was used in the remaining three groups: it was spread out within the implant in one group, it was packed on the bone in another, and a combination of those techniques was used in the third. Half of the sixty specimens had six anchoring holes. The specimens underwent computed tomography and were analyzed with custom-made segmentation software. RESULTS: The cementing technique and anchoring holes influenced the cement quantity within the implant and the thickness of the cement mantle; suction and bone density did not. Both filling techniques involving the use of low-viscosity cement resulted in excessive cement within the implant (filling index, 47.30% to 60.66%) and large cement defects at the base. The combined technique also resulted in large cement quantities (filling index, 46.62% to 54.12%) but fewer cement defects at the base. The filling technique involving the use of medium-viscosity cement decreased the cement quantity (filling index, 43.31% to 45.68%), but cement packing was the best technique (filling index, 29.20% to 31.05%), resulting in the thinnest, most homogeneous cement mantle. However, distal cement defects remained, and the prevalence of proximal cement-implant interfacial gaps was about 10%. CONCLUSIONS: The results of this experimental study cannot be extrapolated directly to the in vivo situation, and they apply only to implants with an inner geometry similar to that of the size-46 ReCap resurfacing head and to the cement brands that we used. None of the cementing techniques was "perfect." Both of the filling techniques involving use of low-viscosity cement and the combined technique resulted in excessive cement proximally. The filling technique involving use of medium-viscosity cement was promising, but the cement-packing technique offered the best opportunity to control the quality of the cement mantle. However, the presence of interfacial gaps raised new questions. We suggest that the use of anchoring holes in cancellous bone should be considered with caution in order to avoid overfilling with cement.

Variations in serum electrolyte concentrations and renal function after therapeutic hip arthroscopy: a pilot study.

PURPOSE: The purpose of this study was to analyze changes in serum electrolyte concentration and renal function after hip arthroscopy. METHODS: We studied 10 consecutive patients (4 men and 6 women; median age, 30.5 years [range, 20 to 50 years]) undergoing hip arthroscopy. Operating time, traction time, and perfusion volume of lactated Ringer solution (in milliliters) were recorded. Preoperative and postoperative levels of sodium (Na(+)), potassium (K(+)), cloride (Cl(-)), calcium (Ca(2+)), magnesium (Mg(2+)), phosphorous (P), creatinine, and blood urea nitrogen (BUN) were compared. RESULTS: The median operating time was 80 minutes (range, 60 to 150 minutes). The median perfusion volume of lactated Ringer solution was 15,000 mL (range, 6,000 to 30,000 mL). The median traction time was 37.5 minutes (range, 30 to 105 minutes). None of the patients had postoperative complications develop. With a mean decrease of 0.84 +/- 0.68 mg/dL, only serum calcium levels were found to decrease significantly (P = .01). There was a mean decrease of 1.50 +/- 2.07 mEq/L in sodium concentrations (P = .06). Hip arthroscopy was associated with a mean postoperative decrease in creatinine and BUN concentrations of 0.05 +/- 0.06 mg/dL (P = .19) and 9.84 +/- 10.36 mg/dL (P = .13), respectively. Although the mean decrease in BUN concentration was important, this was not shown to be significant. No correlations were found between operating time, perfusion volume, and postoperative changes. CONCLUSIONS: Lengthy therapeutic hip arthroscopy under high intra-articular pressure has only a minimal effect on electrolyte balance and renal function. We therefore conclude that performing routine preoperative and postoperative blood analysis of electrolyte concentrations and renal function is unnecessary. LEVEL OF EVIDENCE: Level IV, therapeutic case series.