Introduction

Robotic-arm assisted knee arthroplasty (rKA) has been associated with improved clinical, radiographic, and patient-reported outcomes. There is a paucity of literature, however, addressing its cost effectiveness. In the context of an integrated health system with an insurance plan and single source comprehensive data warehouse for electronic health records and claims data, we present an evaluation of healthcare costs and utilization associated with manual knee arthroplasty (mKA) versus rKA. We also examine the influence of rKA technology on surgeons’ practice patterns.

Introduction

Osteoarthritis (OA) represents a leading cause of disability and a growing burden on healthcare budgets. OA is particularly vexing for young, active patients who have failed less invasive therapies but are not yet candidates for arthroplasty. Often, patients suffering in this wide therapeutic gap face a debilitating spiral of disease progression, increasing pain, and decreasing activity until they become suitable arthroplasty patients. An implantable load absorber was evaluated for the treatment of medial knee OA in this patient population.

Joint overload has been cited as a contributor to OA onset or progression. In response, the KineSpring® System (Moximed, Inc, USA) has been designed to reduce the load acting on the knee. The absorber is implanted in the subcutaneous tissue without violating the joint capsule, thus preserving the option of future arthroplasty. The implant is particularly useful for young, active patients, given the reversibility of the procedure and the preservation of normal flexibility and range of motion.

Joint load reduction is effective for alleviating OA pain. Treatment options for joint unloading include braces and HTO, both of which may be impractical for patients. The purpose of the present study was to examine the biomechanical rationale of a practical, partial unloading implant (KineSpring® System, Moximed) for knee OA.

Device durability was tested by cyclically loading bone-implant constructs through simulated use for at least 10 million cycles. Joint load reduction with the implant was quantified by measuring changes in medial and lateral knee compartment loads generated by cadaver knees in simulated gait. Safety of the device was tested by 3, 6, and 12 month follow-up of implants in an in vivo ovine model. Surgical technique and device safety and efficacy were assessed in human clinical studies.

The unloader device survived over 15 million cycles of simulated use without failure. In the simulated gait cadaver model, the unloading device significantly reduced medial compartment (29 ± 13 lbs, p<0.05) and overall knee joint loads during the stance phase of gait testing but did not significantly increase lateral compartment loading. Chronic ovine implants demonstrated good tolerance of the implant with normal wound healing and secure device fixation. Clinical experience (n=49) demonstrated uneventful device implantation. Unlike HTO, the implantation technique for the unloader does not alter joint alignment. This surgical technique avoids removal of bone, ligament, and cartilage, thus preserving future primary arthroplasty, if required. Early-term clinical experience also demonstrates good outcomes for patients, the earliest of whom are beyond 2.6 years with the implant.

This unloading device offers a practical and attractive treatment option for patients with medial knee OA: load reduction without load transfer, durability, preservation of downstream treatment options, safety, and early-term efficacy.

Statement of Purpose

The UK and Australian clinical experience of an implantable load absorber was reviewed for knee OA patients who have exhausted conservative care, but are not ideal candidates for HTO or arthroplasty due to age, activity level, obesity, or disinclination.

Joint load correlates with knee OA incidence, symptoms, radiographic, morphologic and biological changes. Available load modifying therapies are clinically effective but have drawbacks. The KineSpringTM (Moximed Inc), an investigational device, is designed to reduce compartment loads while avoiding the limitations of current treatments. We compare load reductions of braces, HTO and KineSpringTM.

Literature review and experimental data provide compartment load changes for clinically effective knee braces and HTO. Simulated gait testing was completed on four cadaver knees with early-stage OA. Gait was simulated using a cadaver-based kinematic test system that applies motion and loading patterns dynamically to cadaver specimens. Medial and lateral compartment femoro-tibial pressures were measured throughout testing using thin film dynamic pressure sensors (Tekscan, Inc.) placed inframeniscally. Three conditions were tested: no treatment, applied valgus moments to simulate a valgus moment brace, and implanted KineSpring.

Sufficient clinical data exists to support the development of new and novel load modifying therapies for knee OA. Joint load reductions provided by HTO and valgus moment braces provide insight into clinically effective load reduction ranges. Opening wedge HTOs of 5° and 10° are reported to reduce average medial compartment load by 55 N (12 lbs) and 286 N (64 lbs), respectively1. Valgus braces were reported to reduce medial compartment loads an average of 97-280 N (22-63 lbs). From this data we propose a clinically effective load reduction range of 55 to 286N is a valid indicator of the likely clinical success for medial knee load reduction treatments.

Gait simulation was successfully completed in all specimens in all test configurations. The valgus moment brace reduced medial compartment load by 58 ±20 N but did not reach statistical significance. The Kinespring reduced medial compartment load by 129±64 N in comparison to the untreated case, a statistically significant reduction. Neither the KineSpring nor the valgus moment brace caused significant changes in the lateral compartment during stance.

All treatments reduced medial compartment loads. KineSpringTM reduces loads in what we determined to be the clinically effective range. Additional studies and clinical investigations are warranted to determine the ultimate effectiveness of this implant system.

Introduction

Long bone surgery and marrow instrumentation represent significant surgical insults, and may cause severe local and systemic sequelae following both planned and emergent surgery. Preconditioning is a highly conserved evolutionary endogenous protective mechanism, but finding a clinically safe and acceptable method of induction has proven difficult. Glutamine, a known inducer of the heat shock protein (HSP) response, offers pharmacological modulation of injury through clinically acceptable preconditioning. This effect has not been previously demonstrated in an orthopaedic model.

Compartment syndrome (CS) is a unique form of skeletal muscle ischaemia. N-acetyl cysteine (NAC) is an anti-oxidant in clinical use, with beneficial microcirculatory effects.

Sprague-Dawley rats (n=6/group) were randomised into Control, CS and CS pre-treated with NAC (0.5g/kg i.p. 1 hr prior to induction) groups. In a post-treatment group NAC was administered upon muscle decompression. Cremasteric muscle was placed in a pressure chamber in which pressure was maintained at diastolic minus 10 mm Hg for 3 hours inducing CS, muscle was then returned to the abdominal cavity. At 24 hours and 7 days post-CS contractile function was assessed by electrical stimulation. Myeloperoxidase (MPO) activity was assessed at 24-hours.

CS injury reduced twitch (50.4±7.7 vs 108.5±11.5, p<0.001; 28.1±5.5 vs. 154.7±14.1, p<0.01) and tetanic contraction (225.7±21.6 vs 455.3±23.3, p<0.001; 59.7±12.1 vs 362.9±37.2, p<0.01) compared with control at 24 hrs and 7 days respectively. NAC pre-treatment reduced CS injury at 24 hours, preserving twitch (134.3±10.4, p<0.01 vs CS) and tetanic (408.3±34.3, p<0.01 vs CS) contraction. NAC administration reduced neutrophil infiltration (MPO) at 24 hours (24.6±5.4 vs 24.6±5.4, p<0.01). NAC protection was maintained at 7 days, preserving twitch (118.2±22.9 vs 28.1±5.5, p<0.01) and tetanic contraction (256.3±37 vs 59.7±12.1, p<0.01). Administration of NAC at decompression also preserved muscle twitch (402.4±52; p<0.01 versus CS) and tetanic (402.4±52; p<0.01 versus CS) contraction, reducing neutrophil infiltration (24.6±5.4 units/g; p<0.01).

These data demonstrate NAC provided effective protection to skeletal muscle from CS induced injury when given as a pre- or post-decompression treatment.

Purpose: Compartment syndrome (CS) is a unique form of skeletal muscle ischaemia. N-acetyl cysteine (NAC) is an anti-oxidant with beneficial microcirculatory effects. We aim to assess the effect of NAC administration on CS induced muscle injury.

Methods: Sprague-Dawley rats (n=6/group) were randomised into Control, CS and CS pre-treated with NAC (0.5g/kg i.p. 1 hr prior to induction) groups. In a post-treatment group NAC was administered upon muscle decompression. Cremasteric muscle was placed in a pressure chamber in which pressure was maintained at diastolic minus 10 mm Hg for 3 hours inducing CS, muscle was then returned to the abdominal cavity. At 24 hours and 7 days post CS contractile function was assessed by electrical stimulation. Myeloperoxidase (MPO) activity were assessed at24-hours.

Results: CS injury reduced twitch (50.4 ± 7.7 vs 108.5 ± 11.5, p< 0.001; 28.1 ± 5.5 vs. 154.7 ± 14.1, p< 0.01) and tetanic contraction (225.7 ± 21.6 vs 455.3 ± 23.3, p< 0.001; 59.7 ± 12.1 vs 362.9 ± 37.2, p< 0.01) compared with control at 24hrs and 7 days respectively. NAC pre-treatment reduced CS injury at 24 hours preserving twitch (134.3 ± 10.4 , p< 0.01 vs CS) and tetanic (408.3 ± 34.3, p< 0.01 vs CS) contraction. NAC administration reduced neutrophil infiltration (MPO) at 24 hours (24.6 ± 5.4 vs 24.6 ± 5.4, p< 0.01). NAC protection was maintained at 7 days preserving twitch (118.2 ± 22.9 vs 28.1 ± 5.5, p< 0.01) and tetanic contraction (256.3 ± 37 vs 59.7 ± 12.1, p< 0.01). Administration of NAC at decompression also preserved muscle twitch (402.4 ± 52; p< 0.01 versus CS) and tetanic (402.4 ± 52; p< 0.01 versus CS) contraction, reducing neutrophil infiltration (24.6 ± 5.4 units/g; p< 0.01).

Conclusions: |NAC provides extended protection to skeletal muscle against compartment syndrome induced injury by both direct reducing neutrophil mediated tissue toxicity and by reducing neutrophil recruitment to the site of injury.

Introduction: The beneficial effects of insulin in the maintenance of normoglycaemia in non-diabetic myocardial infarct and intensive care patients have recently been reported. Hyperglycaemia and neutrophilia have been shown to be independent prognostic indicators of poor outcome in the traumatised patient. The role of insulin and the maintenance of normoglycaemia in the trauma patient have as yet not been explored. We hypothesised that through the already described anti-inflammatory effects of insulin and the maintenance of normoglycaemia, that the systemic inflammatory response would be attenuated, in the injured patient. This might result in less adult respiratory distress syndrome (ARDS) and multi-organ dysfunction and therefore less morbidity and mortality in trauma patients.

Materials and Methods: We used a previously validated rodent trauma model. There were 3 groups, two groups underwent bilateral femur fracture and 15% blood loss via cannulation and aspiration of the external jugular vein. The third group were anaesthetised only. The treatment group immediately receive subcutaneous insulin according to a recently identified sliding scale, and thereafter subcutaneous boluses, dependent on ½ hourly blood sugar estimations. The control groups received the same volume of normal saline ½ hourly, subcutaneously. The animals were maintained under anaesthetic for 4 hours from injury via inhaled isoflurane and oxygen. Core temperature and O2 saturations were recorded throughout. At 4 hours, each animal underwent midline laparotomy and cannulation of the IVC for blood sampling for full blood counts and lactate levels. Serum was also taken for flow cytometric analysis of neutrophil activation via respiratoy burst and CD11b levels. Broncho-alveolar lavage (BAL) was performed for neutrophil content and total protein estimation. The left lower lobe was harvested for wet-dry lung weight ratios.

Results: While O2 saturations were equal throughout in both groups, respiratory rates were persistently elevated in the controls. Wet:Dry lung weight ratios (p< 0.05) and lactate levels were reduced in the insulin treated animals compared to controls. There were similiarly fewer neutrophils in the BAL specimens of the insuliln treated animals compared to injured controls (p< 0.05).

Conclusions: Insulin reduces leukocyte lung sequestration in the injured animal model. This work confirms that insulin may have a role in reducing ARDS in the trauma patient, be that as an anti-inflammatory agent or anti-hyperglycaemic agent, or both, indicating that outcomes might be improved by treating hyperglycaemic trauma patients with insulin. Further work needs to done to elucidate its exact mechanism of action and role in the injured patient.

The mechanism by which cells die is important in an immune response and its resolution. The role of apoptosis in sepsis and trauma, and its regulation by cytokines is unclear. During the systemic inflammatory response, rates of human neutrophil apoptosis are decreased. Peritoneal macrophage apoptosis has been induced by nitric oxide and Lipopolysaccharide (LPS) in vitro but this has not as yet been demonstrated in vivo.

We examined the induction and effects of macrophage apoptosis in a model of trauma and sepsis.

One hundred female CD-I mice were randomised into four groups: Control, Septic model, challenged with intraperitoneal LPS (1.Img/200ul/mouse), Traumatic model, received hind limb amputation (HLA) and a Combined trauma/septic model. After 24 hrs mice were sacrificed and peritoneal macrophages were assessed for apoptosis by morphology and DNA fragmentation by flow cytometry and DNA gel electrophoresis

Peritoneal lavage from septic models had a decreased percentage of macrophages in comparison to control and trauma groups. The septic model also had a significantly increased incidence of apoptosis in comparison to control and trauma levels. There was no significant difference between control and traumatic groups.

These findings demonstrate that in a murine model of sepsis, lipopolysaccharide induces macrophages apoptosis. Modulation of this immune response may have important roles in the management of trauma patients.

Phenytoin has previously been shown to accelerate wound healing through upregulation of angiogenesis and promotion of collagen deposition. These reported effects led us to hypothesise that phenytoin could be used locally at the tendon repair site to increase the rate and strength of healing. Systemic treatment with phenytoin has also been shown to increase the thickness and density of calvarial and maxillary bones in humans, and promote fracture healing in rabbits, rats and mice. Based on these and similar studies we hypothesised that local percutaneous injection of phenytoin solution into a fracture site would result in improved fracture healing without the risk of the side effects of systemic administration of the drug.

Methods: For the tendon repair study, a previously validated rabbit tendo-achilles tenotomy model was chosen. Animals underwent a transverse tenotomy of the FDL and TA tendons. These were immediately repaired using 3/0 ethibond sutures using the modified Kessler technique, prior to local application of either a phenytoin or buffer gel formulation. At 21 days post-op, the animals were euthanased and the TA harvested for tensiometry testing and collagen content estimation, and the FDL was harvested for histological analysis.

For the fracture study, a rat femur fracture model was utilised. Adult male Sprague-Dawley rats were anaesthetised. Following a medial parapatellar approach, the femur was cannulated using an 18 gauge cannula. The cannula was cut flush with the distal femur and countersunk. The skin and retinaculum were closed with 5.0 monocryl. The nailed femur was then fractured using a 3 point bending technique. The femurs were xrayed to ensure each fracture was mid-diaphyseal and transverse. At 6 hours post op animals underwent either 1) Fracture site percutaneous injection with 100 μmol phenytoin solution 2) Fracture site percutaneous injection with phosphate buffer solution (PBS) 3) No percutaneous injection. This procedure was once again repeated at 72 hours. At 2 and 4 weeks post op 6 animals from each group were euthanased, their femurs were harvested for biomechanical analysis of stiffness and strength.

Results: There was no difference in tendon diameter, gross adhesion formation, ultimate tensile strength or collagen content between the groups. Histologically, however, there were a significantly greater number of inflammatory cells (p< 0.05) and blood vessels (p< 0.05) in the phenytoin treated tendons compared to controls.

At both 2 and 4 weeks there was no statistical difference in stiffness or strength of the phenytoin treated fractures compared to controls.

Conclusions: The study phenytoin formulations whilst apparently promoting neovascularisation in the healing tendon, did not augment healing strength in either tissue suggesting that at these doses and dosing schedules the role of phenytoin is limited in these tissues.

Introduction and Aims: Treatment options for medial gonarthrosis include high tibial osteotomy (HTO). There has been a shift towards opening wedge techniques partially due a perceived higher complication rate with closing wedge techniques. This has not been our experience and we describe the outcome of a large series of closing wedge HTOs.

Method: We reviewed the case records of 313 patients who underwent a total of 374 closing wedge high tibial osteotomies by three surgeons for medial compartment gonarthrosis between 1989 and 2003. The mean outpatient follow-up was 16 months and the mean time post-surgery was 66 months. We identified any post-operative complications and the early clinical outcome including those known to have proceeded to joint replacement. The mean age of patient was 52 years (range 19–72). In all patients a laterally based wedge, mean size nine degrees (range 4–18), was excised and the osteotomy stabilised with one or two stepped staples.

Results: Outcome following closing wedge osteotomy was generally good, only six percent of patients complained of continuing knee pain, although not at a level that required further intervention. Symptoms in 3.5% of knees deteriorated and required total knee replacement at a mean of 63 months (range 16–112) following osteotomy. No intra-operative difficulties were encountered with these replacements. The complication rate was acceptable with an overall rate of 7.8%. One patient required revision shortly after surgery due to inadequate initial correction and one developed a transient peroneal nerve neuropraxia. There were no other neurovascular or intra-operative complications recorded. All the osteotomies united, although nine patients had delayed union, taking a mean of five months for their osteotomies to unite. Other complications included: five patients who had staples removed due to irritation, one who developed a stitch abscess and one who developed a deep wound infection. Two knees had a reduced ROM and required an MUA. In addition, six patients developed symptomatic DVTs, three with pulmonary emboli, but there were no deaths.

Conclusion: In our experience, closing wedge osteotomy for medial gonarthrosis is a safe and reliable procedure with a good early outcome and an acceptable complication rate of 7.8% in this series, with a low incidence of serious complications that compares favourably with the quoted complication rates for opening wedge techniques.

Introduction: Histamine is an integral mediator following traumatic injury. Histamine-2 receptors have previously been identified on lymphocytes and monocytes.

Materials and methods: Two rodent models (1) Bilateral femoral fracture and intramedullary nailing, with resulting indirect lung injury (n=30). (2) In vivo model of orthopaedic implant contaminated by Staphylococcus epidermidis (n=36). Animals were randomised to receive ranitidine or placebo (saline).

Results: Markers of lung injury (MPO activity, BAL proteins and wet:dry ratios) increased 24 hours following bilateral femoral fracture, but were reduced if ranitidine was administered systemically after the injury. Production of Th-1 cytokines was blocked by ranitidine, whilst Th-2 cytokine production remained unaffected by ranitidine. These suggest an anti-inflammatory effect of ranitidine, blocking the early (Th-1) pro-inflammatory response following major injury.

Ranitidine’s effect on implant infection rates showed higher rates (44% versus 17%, relative risk 1.8 (95% CI 1.0 to 3.3)) when systemic ranitidine was delivered peri-operatively, suggesting an immunosuppressive effect.

Conclusions: The findings highlight the complex balance in vivo, a double-edged sword: the risk of increasing implant infection versus reducing indirect lung injury following major injury. The administration of ranitidine in major trauma patients with severe pro-inflammatory responses may block and reduce early multi-organ dysfunction and improve survival. However, owing to infection, the peri-operative administration of ranitidine should be avoided in elective cases.

The beneficial effects of insulin in the maintenance of normoglycaemia in non-diabetic myocardial infarct and intensive care patients have recently been reported. Hyperglycaemia and neutrophilia have been shown to be independent prognostic indicators of poor outcome in the traumatised patient. The role of insulin and the maintenance of normoglycaemia in the trauma patient have as yet not been explored. We hypothesised that through the already described anti-inflammatory effects of insulin and the maintenance of normoglycaemia, that neutrophil activation and endothelial dysfunction would be attenuated, in the injured patient. This might result in less adult respiratory distress syndrome (ARDS) and multi-organ dysfunction and therefore less morbidity and mortality for the trauma patient.

Materials and Methods: To study this we used a previously validated rodent trauma model. There were 2 groups, both groups underwent bilateral femur fracture and 15% blood loss via cannulation and aspiration of the external jugular vein. The treatment group immediately receive subcutaneous insulin according to a recently identified sliding scale, and thereafter subcutaneous boluses, dependent on half hourly blood sugar estimations. The control group received the same volume of normal saline half hourly, subcutaneously. The animals were maintained under anaesthetic for 4 hours from injury via inhaled halothane and oxygen. Core temperature and 0₂ saturations were recorded throughout. At 4 hours, each animal underwent midline laparotomy and cannulation of the IVC for blood sampling for full blood counts, lactate levels and for flow cytometry to estimate neutrophil activation via respiratory burst and CD11b upregulation. Bronchoalveolar lavage (BAL) was performed for neutrophil content and total protein estimation. The left lower lobe was harvested for wet-dry lung weight ratios.

Results: While 0₂ saturations were equal throughout in both groups, respiratory rates were persistently elevated in the controls. Wet:Dry lung ratios and lactate levels were reduced in the insulin treated animals compared to controls. There were similarly fewer neutrophils in the BAL specimens of the insulin treated animals (p< 0.05).

Conclusions: Insulin reduces leukocyte lung sequestration in the injured animal model. This work confirms that insulin may have a role in reducing ARDS in the trauma patient, be that as an anti-inflammatory agent or anti-hyperglycaemic agent, or both, indicating that outcomes might be improved by treating hyperglycaemic trauma patients with insulin. Further work needs to be done to elucidate its exact mechanism of action and role in the injured patient.

Introduction: Patient specific cementless femoral components for THR were developed as a means of addressing the anatomic variations of the proximal femur and hip joint in an effort to achieve long term implant survival and optimum patient function. Design rules were developed with goals of achieving rigid initial stability, maximal endosteal contact for bone integration, and the precise restoration of hip kinematics.

Methods: Beginning in 1989, this series of cementless titanium implants included proximal circumferential HA coating over a macrotextured surface for biologic fixation. All patients who were candidates for cementless arthroplasty (age < 65, active, or overweight) received a custom femoral component. Forty-nine consecutive primary THR in 39 patients were performed during the study period. No patients died and one patient was lost prior to 10 years; all had well fixed stems at latest follow up. The remaining 38 patients (48 hips), 16 females and 22 males, with average age 54 (28-70) and weight 181 (98-270) at surgery, were evaluated at minimum 10 years (range 10-11).

Results: Average modified Harris Hip Scores were 49 (27-87) pre- and 89 (24-100) postoperatively, with pain scores of 17 (0-40) and 42 (10-44) respectively. All femoral components remain well-fixed (Engh Class 1) at final follow-up. No areas of osteolysis were seen distal to the proximal HA-bone interface. Small, focal areas of probable osteolysis were seen at the implant shoulder (4 cases), at the calcar corner (2 cases), and at both sites (1 case). Complications included four proximal margin femoral fissures recognised at surgery, two patients with dislocation, and one non-fatal PE. Reoperations included six head and liner exchanges; two for recurrent dislocation, and four for excessive wear with associated osteolysis (3 pelvic, 1 femoral); and one for fixation and grafting of a trochanteric nonunion.

Discussion: The use of cementless femoral implants based on individual patient characteristics and a set of strict design rules has resulted in excellent clinical and radiographic results at 10-year follow-up. Recent data with some OTS systems have shown comparable excellent results and have diminished the need for the routine use of custom implants in uncomplicated primary situations. However, this series validates the design concepts of this system, supports its use in more complex situations, and suggests applicability on a routine basis where other available implants may be less than optimal.

Introduction: Conventional approaches to cementless revision THR include cemented and cementless stems, which are graft dependent for initial stability (Type 3 reconstructions), distally fixed extensively porous coated implants and modular implants. CT and radiographic visualization, preoperative planning, and patient specific implant fabrication enable the surgeon to achieve the following objectives simultaneously and without compromise: bypass or fill specific bony defects, implement precisely the surgeon’s individual implant design goals, optimise proximal, distal, or regional fit objectives, achieve supplemental fixation via collars, fluted stems, and targeted ingrowth zones/ treatments, and establish head center, neck length, lateral offset, anteversion angle, and leg length.

Methods: This series of cementless titanium implants achieved initial press-fit fixation on host bone with bony attachment via proximally HA coated macrotextured surface. The extramedullary portion of the implant is designed to restore leg length and normal joint mechanics. The initial 44 consecutive revision hips using this rationale were reviewed for inclusion. At surgery, all femoral reconstructions were completed without resorting to Type 3 structural grafts. Six patients died prior to 10 years f/u, and three (4 hips) were lost. Two stems were removed prior to minimum follow up: one at five weeks post-op for deep sepsis, and one for aseptic loosening presumed secondary to metabolic derangements from poorly controlled end-stage renal disease. The remaining 31 patients (34 hips), 18 females and 13 males with a mean age of 61 (range 31-75) and average weight of 168 (85-240) pounds, were evaluated at minimum 10 years (range 10 to 11 years).

Results: All 34 components remain well-fixed (Engh Class 1) at last follow up (97% implant survival). Stress shielding was uncommon outside the calcar region. Average modified Harris Hip Scores were 49 (10-88) pre-operative and 81 (48-100) at final follow-up, with pain scores of 18 (0-44) and 41 (30-44) respectively. Complications included fracture (intraop: 4 fissures, 2 stable type II, 1 unstable type III, and 1 late periprosthetic fractures distally), and three dislocations.

Discussion: The concept of a metaphysical loading, proximally ingrown, collared patient specific revision implant gave results comparable to Engh’s series of extensively coated revision stems, while avoiding the high failure rate associated with structural allograft, the worrisome proximal bone loss associated with fully porous coated stems, the high cost of modular implants.

Introduction Concentric interference screw placement has been proposed as having potentially better biological graft integration than eccentric interference screw placement during soft tissue ACL reconstruction. The purpose of this study was to determine whether a wedge shaped concentric screw was at least equivalent to an eccentric screw in stiffness, yield load, ultimate load and mode of failure.

Methods Seven matched pairs of human cadaveric tendon in porcine tibia with titanium wedge shaped screws were randomly allocated to either the eccentric or concentric groups. Bone tunnels were drilled 45° to the long axis of the tibia, akin to standard ACL reconstruction. Tendon diameter was matched to tunnel diameter and a screw one millimetre larger than tunnel diameter was inserted. An Instrom machine was used to pull in the line of the tendon. Tendons were inspected after construct disassembly.

Results The concentric screw configuration showed significantly higher stiffness (p< 0.0085), yield load (p< 0.0135) and ultimate load (p< 0.0075). The mode of failure in the eccentric screw position was slippage at the screw tendon interface in all cases. In the concentric group 88% of cases had a breakage in the tendon and 13% of cases had slippage at the tendon bone interface. However, it was observed during construct disassembly that there was more macroscopic damage to the tendon substance in the concentric group. Failure was mostly by tendon breakage, which reflects the strongest fixation possible with the tendon being the weakest link in the system.

Conclusions Concentric interference screw fixation of soft tissue graft offers superior fixation in single pullout mode when compared to eccentric interference screw fixation.

Introduction Transcondylar fixation has recently been offered as an alternative method of femoral fixation in soft tissue ACL reconstructions. It provides the advantages of avoiding intra-articular hardware and of achieving full circumferential contact of soft tissue to bone for graft integration. This paper presents a series of hamstring ACL reconstructions using femoral transcondylar fixation in a short-term retrospective clinical review.

Methods Over a six month period the senior author performed a total of 50 hamstring anterior cruciate ligament reconstruction procedures using the femoral transcondylar fixation, 80% of these patients were available for review. The patient series consisted of 24 males and 16 females with average age of 29.9 years (range 14.4 to 54.5) at the time of surgery. Patients were assessed by clinical review, questionnaires (Lysholm and IKDC) and KT 1000 measurement at 30 lbs. Follow-up ranged from 12 to 16 months post-operatively with an average of 13.3 months.

Results The Lysholm scores mean was 83.9, which graded 75% of patients as good or excellent. Of the remaining patients 15% were fair and 10% graded their knee as poor. This was different from the IKDC patient questionnaire (subjective assessment) where 59% of patients categorised their knee as good or excellent. There were 70% of patients who rated their result poor or fair with respect to pain, and 52% of patients who rated their result poor or fair with respect to swelling. However, 67% of patients rated their knee good or excellent with respect to stability and function. Clinical laxity testing demonstrated a mean increase in translation of two millimetres (−3.3 to 5.3) in the index knee as compared to the opposite knee. On objective clinical tests, 97% of patients were normal or nearly normal with four percent being abnormal due to a passive motion deficit. There were no complications within the group and specifically no complications related to the transfix implant. No patient had pain, tenderness or crepitus around the iliotibial band.

Conclusions The femoral transcondylar fixation used in soft tissue ACL reconstructions is a viable alternative to interference screw fixation. It delivers comparable results in the short term, and offers potential advantages. The technique is reliable, reproducible and safe, with no complications being reported in this study.

Introduction: Patients with multiple skeletal injuries are susceptible to Systemic Inflammatory Response Syndrome (SIRS) and consequently Acute Respiratory Distress Syndrome (ARDS). Fracture haematoma contains pro-inflammatory mediators. The aim of our study was to show in vitro that fracture haematoma is implicated in neutrophil mediated injury, SIRS, ARDS and MOF.

Methods: Fracture haematoma was isolated from 10 patients at the time of surgery. Neutrophils (PMN) were isolated from 10 healthy volunteers. PMN were exposed to the fracture haematoma supernatant and PMN activation in both primed and unprimed neutrophils were examined (CD11b and CD18 adhesion receptor expression and respiratory burst). PMN phagocytosis and apoptosis were also assessed using flow cytometry. Transmigration across an endothelial barrier was also measured following exposure to fracture haematoma.

Results: Fracture haematoma had a marked effect on respiratory burst in primed PMNs (control = 100% vs 20% fracture haematoma = 1044% ± 405, p=0.04). CD11b and CD18 adhesion receptor expression were not upregulated in the fracture haematoma group. PMN phagocytosis of E coli was increased following treatment with fracture haematoma (control = 100% vs fracture haematoma = 171% ± 6SE, p=0.0001). Transendothelial migration of treated neutrophils was unaffected. Treatment of endothelial monolayers with fracture haematoma did not result in upregulated ICAM1 expression but was observed to induce significant endothelial cell death. PMN apoptosis was significantly delayed following exposure to fracture haematoma (control = 46% ± 5 vs fracture haematoma = 8% ±2, p=0.0005).

Discussion: We have shown that fracture haematoma activates neutrophils, increases phagocytosis and respiratory burst whilst delaying apoptosis. These effects, whilst beneficial at the site of injury, may cause neutrophil mediated tissue injury systemically.

Aseptic loosening of implants following hip arthroplasty is a cause of significant patient morbidity. We genotyped 99 revision hip arthroplasty patients and 116 primary hip arthroplasty patients for the C282Y and the H63D mutations, which cause Haemochromatosis. Haemochromatosis is an inherited condition leading to excessive iron absorption and deposition in the body. All patients at the time of their primary hip arthroplasty were diagnosed as having osteoarthritis. We identified 9 of the 99 revision arthroplasty patients as being homozygous for the C282Y mutation. The time to revision in this group was significantly lower (p< 0.005) when compared to the remaining 90 patients in the group (mean 8.7 years vs 14.8 years). Analysis of variables such as patient age and sex and also type of prosthesis, place of surgery and operating surgeon had no confounding influence. We hypothesise that undiagnosed iron overload in the patients homozygous for the C282Y mutation is likely to cause premature failure of their primary hip arthroplasty.