“Expert opinion” is the lowest totem on the academic pole- and yet, “evidence based” medicine does not always provide us answers for the particular, the unusual clinical problem. Well-controlled studies are precisely that: “well controlled”. Life may be randomised, but falls short of being “well controlled”.

The challenge and honoufavourr of moderating a panel of experienced and articulate colleagues is to bring out “how they think” and how they formulate a plan for complex cases. The panel members are not only experienced practitioners, but they are the authors of studies that shape our profession. What are the limits to the studies they have published? What insight can they provide us to help understand “level 1” data more astutely? What biases and assumptions support their methods? Nothing achieves that with greater clarity than presentation of complex cases to an accomplished panel.

Several ordinary clinical problems are presented to establish current practice, followed by the unexpected outcomes to illustrate how experts deal with adversity.

There is a renewed debate regarding the relative importance of (primarily varus-valgus) stability versus alignment in TKA. Some surgeons have posited that stability is of greater importance. Perhaps this is because unstable knees fail immediately whereas mal-aligned knees generally suffer late failure from wear, osteolysis and loosening. Or perhaps some surgeons find soft tissue techniques challenging. Clearly alignment and stability are both necessary for immediate function and long-term durability.

Ligament tensioners are as old as condylar knee arthroplasties. They first appeared when surgeons moved beyond hinged arthroplasties with a goal of melding anatomy and biomechanics- to re-establish stability and correct pathologic deformity. Early techniques stipulated that ligament releases should be performed first, before any bone cuts thus correcting deformity and restoring stability. Crude mechanical instruments were replaced by mechanical devices.

Acknowledging more exacting standards, our ability to hit the target of desired alignment and stability is limited unassisted. As more sophisticated devices have been introduced to help surgeons correct alignment we have not yet discovered the perfect mechanical, electronic, navigated or laser guided “tensioner”. We still struggle to divine the “best” alignment. The principle however endures, that integrating stability and alignment, if with nothing more than a “cognitive tensioner” is essential to optimal short and long-term arthroplasty function.

Stability after TKA is essential for knee function and patient satisfaction. Stability may be marginally more important even than alignment because “stability” means there will be ONE alignment, whereas INSTABILITY means there will be many alignments of the joint, usually the worst one for any loading pattern. Whereas alignment results from the orientation and size of implants, stability depends on all of these, plus soft tissue integrity and in many cases, surgical alteration. Ligament releases (and rarely reconstructions) will certainly be required if alignment is changed with the arthroplasty. Instability may be a subtle or flagrant problem.

The “Instabilities” are: i.

Varus- valgus

Varus-valgus instability is the prototype and while it may originate exclusively from the failure of soft tissue, knee alignment and dynamic forces outside the knee joint such as hip abductor dysfunction, scoliois and tibialis posterior rupture may be implicated. A comprehensive approach will be needed.

Flexion instability, most simply stated results from a flexion gap that exceeds the dimensions of the extension gap. It will result most commonly after surgery for the patient with a fixed flexion contracture whose knee extends fully because a relatively thin polyethylene insert has been selected. So-called “mid-flexion” instability (implying stability in extension and flexion) has not yet been thoroughly characterised.

Extension instability includes all failures of the extensor mechanism (rupture, maltracking and weakness) which are better characterised as “buckling” under a separate topic. Recurvatum has received little attention but can generate the most destructive forces leading to knee arthroplasty failure. In general begins as a compensatory mechanism for relative extensor weakness.

All treatment of the unstable TKA must characterise the mode(s) of failure above and correct the underlying cause. Surgical technique will be extremely important, followed eventually by implant selection.

In the treatment of ligament injuries there has been much interest in the restoration of the actual ligament anatomy, and the extent to which the original enthesis may be re-established. This study therefore seeks to uncover new information on ligament microstructure and its insertion into bone.

Five bovine medial collateral ligaments (MCL) and five ovine anterior cruciate ligaments (ACL) were used in this study. All ligaments were harvested with the femoral and tibial bony insertions still intact. The bone ends were clamped and the MCL stretched to about 10% strain while the ACL underwent a 90° twist. The entire ligament-bone system, under load, was fixed in 10% formalin solution for 12 hours, following which it was partially decalcified to facilitate microsectioning. Thin 30 ìm-thick sections of the ligament-bone interface and ligament midsubstance were obtained. Differential Interference Contrast (DIC) optical microscopy was used to image the ligament and bone microarchitecture in the prescribed states of strain.

Fibre crimp patterns were examined for the prescribed loading condition and showed distinct sections of fibre recruitment. Transverse micro-imaging of the ligament showed a significant variation in the sub-bundle cross-sectional area, ranging from 100ìm to 800 ìm. Those bundles closer to the central long axis of the ligament were numerous and small, while moving towards the periphery, they were large and singular. Both classifications of entheses, direct and indirect, were observed in the MCL insertions into the femur and tibia respectively. Of interest was the indirect insertion where the macro-level view of the near parallel attachment of fibres to bone via the periosteum was revealed, at the microscale, to involve a gradually increasing orthogonal insertion of fibres. This unique transition occurred closer to the joint line. In the ACL the anterior-medial (AM) and posterior-lateral (PL) bundles were easily discernable. All insertions into bone for the ACL were of the direct type. Fibres were thus seen to transition through the four zones of gradual mineralization to bone. However the manner in which the AM and PL bundles insert into bone, and the lateral soft tissue transition between these two bundles, revealed a structural complexity that we believe is biomechanically significant.

This ‘mechano-structural’ investigation, using novel imaging techniques, has provided new insights into the microstructure of the ligament bone system. The images presented from this study are aimed to aid new approaches for reconstruction, and provide a blue-print for the design of ligament-bone systems via tissue engineering.

Despite modern surgical techniques, reported rates of deep infection following Total Knee Replacement (TKR) persist between 1–2.5%. Coagulase-negative staphylococcus (CNS) has become the most common causative organism, and while growth of CNS is more indolent thanstaphylococcus aureus, it has a relatively higher minimum inhibitory concentration (MIC) against cephalosporins. Tissue concentrations of prophylactic antibiotics may fall below this level during TKR with conventional ‘systemic’ dosing.

Regional administration of prophylactic antibiotics via a foot vein following tourniquet inflation has been shown to provide tissue concentrations approximately 10 times higher than systemic dosing, however cannulation of a foot vein is difficult, time consuming, and may compromise sterility.

Intraosseous cannulation offers an alternative method of accessing the vascular system, and the aim of this study was to assess its effectiveness in administration of prophylactic antibiotics. 22 patients undergoing primary total knee arthroplasty were randomised into two groups. Group 1 received 1g of cephazolin systemically 10 minutes prior to tourniquet inflation. In Group 2 the EZ-IO tibial cannulation system was used, and 1g of cephazolin was administered intraosseously in 200ml of normal saline following tourniquet inflation and prior to skin incision. Subcutaneous fat and femoral bone samples were taken at set intervals during the procedure, and antibiotic concentrations measured using High Performance Liquid Chromatography (HPLC).

There were no significant differences in patient demographics, comorbidities, or physical parameters between groups. The overall mean tissue concentration of cephazolin in subcutaneous fat was 185.9μg/g in the intraosseous group and 10.6μg/g in the systemic group (p<0.01). The mean tissue concentration in bone was 129.9 μg/g in the intraosseous group and 11.4μg/g in the systemic group (p<0.01). These differences were consistent across all sample time points throughout the procedure. No complications occurred in either group.

Intraosseous regional administration can achieve tissue levels of antibiotic over an order of magnitude higher than systemic administration. Further work is required to determine if there is clinical benefit in preventing infection, particularly against CNS. This novel mode of drug administration may also have other applications, allowing ‘surgical site delivery’ of medication while minimising systemic side effects.

To reduce the reported 1% mortality rate in the first month because of embolism and cardiopulmonary complications, intraoperative Swan Ganz catheter monitoring has become routine at our institution for patients undergoing bilateral total knee arthroplasties. By calculating the pulmonary vascular resistance, patients at risk for fat embolism syndrome can be identified after the first of single-stage, sequential bilateral total knee arthroplasties prior to proceeding to the second arthroplasty. This study evaluates the reliability of quantitative parameters for canceling the second side.

The purpose of this study was to evaluate the reliability of quantitative criteria for proceeding with the second side of single-stage, sequential bilateral total knee arthroplasties.

Our experience did enable this procedure to be performed in a consistently safe manner. Bilateral total knee replacements have a reported 1% mortality rate in the first month largely because of embolism and cardiopulmonary complications. Adhering to a monitoring protocol that allows this risk to be minimized enables surgeons to offer this treatment to the many patients with bilateral gonarthrosis.

One hundred and sixty-three consecutive patients who had one-stage, sequential, bilateral total knee arthroplasties were monitored prospectively with a pulmonary artery Swan Ganz catheter. The pulmonary vascular resistance was calculated before skin incision, ten minutes after deflation of the tourniquet following completion of the first arthroplasty, and again after the second knee replacement. The second knee replacement was cancelled in seventeen patients because the pulmonary vascular resistance after the first arthroplasty had either doubled from baseline, or was above 200 dyne/second/cm⁵. Of those who had their bilateral arthroplasties performed, 2% developed signs of fat embolism syndrome, while in the group in whom the second side was cancelled, a 6% incidence was observed. The mortality rate for the entire cohort was 0%. Intraoperative monitoring with a pulmonary artery catheter reliably indicates which patients are at increased risk for pulmonary vascular compromise after one total knee replacement and therefore are not eligible for a second total knee replacement at the same operation.

Aim: To present the experience of a highly specialized total knee arthroplasty revision center with the use of femoral and tibial components with modular press-fit offset stem extensions.

Methods: Intramedullary press-fit offset stem extensions were developed to offer an additional option when doing a revision total knee arthroplasty in the presence of periarticular bone loss. The radiological and clinical results of a cohort of 28 patients that had been previously subjected to a revision total knee arthroplasty utilizing modular press-fit offset stem extensions, were studied. Mean follow-up time of these patients was 3.5 years (range, 2–7 years). The NexGen Legacy Knee System was used in all our patients (25% LCCK, 75% LPS). The use of bone cement was restricted to the femoral and tibial articular surfaces only, without any intramedullary use.

Results: Femoral intramedullary fit and fill was measured 87.9% in anteroposterior x-rays and 85.5% in laterals. Tibial intramedullary fit and fill was measured 94.5% in anteroposterior x-rays and 89.9% in laterals. Femoral components were implanted in 6.4 degrees of valgus angle (mean values) and 2.5 degrees of flexion (mean values). Tibial components were implanted in 2.2 degrees of valgus angle (mean values) and 3 degrees of posterior slope (mean values). Knee Society Score was 89.5 points, while Function Score was 84.8. One year post-revision follow-up evaluation revealed 89% satisfaction rate among these patients.

Conclusion: The use of these press-fit offset stem extensions, with the best possible intramedullary femoral and tibial fit and fill, offer a very rewarding method and an alternative option to deal with complex reconstructive problems during a revision total knee arthroplasty.

Hypothesis: 1. Increased wear results from modularity. 2. Modification of the patello-femoral articulation will decrease patellar fractures.

Materials & Methods: A prospective comparison of 100 consecutive Non-modular Insall Burstein Posterior Stabilized (IBPS) knee prostheses (1986–1989) with 100 consecutive modular IBPS II knee replacements (1989–1990). No patient was lost.

Results: IBI: Nine re-operations of which 6 were complete revisions: two for sepsis, one for tibial loosening, one for patellar wear and two for undiagnosed pain. Of seven patellar fractures, five required surgery. IBII: Nineteen re-operations of which six were complete revisions: two for sepsis, one for tibial loosening from catastrophic osteolysis, two for instability and one for stiffness. There were no revisions for patellar complications. Of 12 non-revision re-operations, two were for patellar fractures, three for dislocation of the posterior stabilized mechanism and one for failure of the modular locking mechanism. Six knees suffered patellar “clunks” treated arthroscopically.

Discussion: The femoral component patellar groove was smoothed and the posterior stabilized mechanism was relocated on the IB II. This increased motion and decreased patellar fractures but caused scar on the quadriceps tendon to “clunk” and lead to dislocations of the “spine and cam”. All failures occurred in the first five years.

Clinical Relevance: Specific patellar problems were improved with design modifications. New problems have been addressed and long-term survival has not been compromised by modularity

Introduction: The modular IBPSII prosthesis was introduced in 1989 with modifications to the patello-femoral articulation and the posterior stabilized mechanism.

Methods: 100 consecutive IBPSII knee arthroplasties were followed prospectively. Age, gender, deformity and diagnoses were comparable to previous groups.

Results: Fifty-one knees were evaluated at 10 or more years with the Knee Society scores and radiographs. 14 were evaluated by phone. An additional 6 knees required revision and 29 were in patients who died. None were lost. Revisions were performed for instability (2 knees), sepsis (2), loosening from osteolysis (1), and stiffness (1). In the 10-year group, 12 patients required reoperations: Patellar revision for loosening (1), patel-lectomy for fracture (1), polyethylene exchange for dislocation of the spine and cam mechanism (3) and for dissociation (1), and arthroscopic resection of scar from the quadriceps tendon (patellar clunk) in 6 knees.

Conclusion: The smoother patello-femoral groove was associated with fewer patellar fractures, but resulted in scar on the quadriceps catching on the femoral component. The tibial spine was moved posteriorly from previous models to increase rollback. This resulted in dislocation of the spine and cam mechanism. One case failed due to loosening and extensive osteolysis presumably associated with modularity. The last two complications were not observed with earlier versions of this prosthesis. All complications occurred within the first five years.

Over a two-year period 104 patients had 130 knee arthroplasties performed with the total condylar prosthesis at the Hospital for Special Surgery. At a 10- to 12-year review 58 patients (74 knees) had survived and were available for detailed clinical and radiographic evaluation. Of these, 38 knees (51.3%) were rated as excellent and 27 (36.5%) good. There were three (4.0%) fair and six (8.2%) poor results. Five of the six had had revision operations. The success of this early pattern of prosthesis supports the continued use of methacrylate cement for knee arthroplasties.

We have reviewed nine patients with Parkinson's disease who had 12 primary total knee arthroplasties and one revision. Deformities were corrected by conventional techniques and semi-constrained resurfacing arthroplasties were used. Follow-up ranged from two to eight years (average 4.3 years). Nine of the 12 primary arthroplasties were rated as excellent by the Hospital for Special Surgery knee score system, and three were rated as good. Contrary to previous reports, we feel that total knee arthroplasty performed on patients with Parkinson's disease, is a highly satisfactory procedure, alleviating knee pain and improving function.