Robotic systems in orthopaedic surgery.

Robots have been used in surgery since the late 1980s. Orthopaedic surgery began to incorporate robotic technology in 1992, with the introduction of ROBODOC, for the planning and performance of total hip replacement. The use of robotic systems has subsequently increased, with promising short-term radiological outcomes when compared with traditional orthopaedic procedures. Robotic systems can be classified into two categories: autonomous and haptic (or surgeon-guided). Passive surgery systems, which represent a third type of technology, have also been adopted recently by orthopaedic surgeons. While autonomous systems have fallen out of favour, tactile systems with technological improvements have become widely used. Specifically, the use of tactile and passive robotic systems in unicompartmental knee replacement (UKR) has addressed some of the historical mechanisms of failure of non-robotic UKR. These systems assist with increasing the accuracy of the alignment of the components and produce more consistent ligament balance. Short-term improvements in clinical and radiological outcomes have increased the popularity of robot-assisted UKR. Robot-assisted orthopaedic surgery has the potential for improving surgical outcomes. We discuss the different types of robotic systems available for use in orthopaedics and consider the indication, contraindications and limitations of these technologies.

Identification of caveolae and detection of caveolin in normal human osteoblasts.

Caveolae, specialised regions of the cell membrane which have been detected in a wide range of mammalian cells, have not been described in bone cells. They are plasmalemmal invaginations, 50 to 100 nm in size, characterised by the presence of the structural protein, caveolin, which exists as three subtypes. Caveolin-1 and caveolin-2 are expressed in a wide range of cell types whereas caveolin-3 is thought to be a muscle-specific subtype. There is little information on the precise function of caveolae, but it has been proposed that they play an important role in signal transduction. As the principal bone-producing cell, the osteoblast has been widely studied in an effort to understand the signalling pathways by which it responds to extracellular stimuli. Our aim in this study was to identify caveolae and their structural protein caveolin in normal human osteoblasts, and to determine which subtypes of caveolin were present. Confocal microscopy showed staining which was associated with the plasma membrane. Transmission electron microscopy revealed the presence of membrane invaginations of 50 to 100 nm, consistent with the appearance of caveolae. Finally, we isolated protein from these osteoblasts, and performed Western blotting using anti-caveolin primary antibodies. This revealed the presence of caveolin-1 and -2, while caveolin-3 was absent. The identification of these structures and their associated protein may provide a significant contribution to our further understanding of signal transduction pathways in osteoblasts.

Fixation of patella fractures with braided polyester suture: a biomechanical study.

We tested the quality of fixation of displaced transverse patella fractures using braided polyester suture to investigate the suitability of this material as an alternative to stainless steel wire for fixation of these fractures. Osteotomies were created to simulate fractures of the patella in ten cadaveric knee specimens and were sequentially fixed using two techniques: the modified tension-band technique and the longitudinal anterior band (Lotke) technique. Each technique was implemented using either 1.25-mm stainless steel wire or 7-metric braided polyester suture (No. 5 Ethibond). The quality of fixation for each technique was tested by measuring the fracture gap during three simulated extensions of the knee against gravity on a materials testing machine. All techniques behaved comparably under the loading conditions used. In the four groups, there was no fixation failure (fracture gap > 3 mm) nor any significant difference between the mean maximum fracture gaps. The quality of fixation for braided polyester suture was comparable to that of stainless steel wire for such fractures, providing sufficient stability to withstand loads likely to be encountered during postoperative rehabilitation. Our results support the use of braided polyester suture as an alternative to stainless steel wire for fixation of displaced patella fractures.

Preoperative administration of epoetin alfa to reduce transfusion requirements in elderly patients having primary total hip or knee reconstruction.

Avoidance of allogeneic blood transfusion is challenging in elderly patients with multiple comorbid conditions, who need major elective orthopaedic surgery. We conducted a study comparing the safety and efficacy of preoperative recombinant human erythropoietin (epoetin alfa) in patients having major elective orthopaedic surgery and in matched historical control patients. Patients aged 70 years or more undergoing primary total knee arthroplasty (TKA) or total hip arthroplasty (THA) were given two or three doses, respectively, of epoetin alfa (40,000 IU). They also received oral iron for 14 or 21 days. Epoetin alfa increased hemoglobin (Hb) and hematocrit (HCT) levels before surgery; 74% of control patients required blood transfusion, compared with 12.5% of patients receiving epoetin alfa. No serious adverse event was attributed to study treatment. These data indicate that epoetin alfa is safe and effective and reduces the need for allogeneic blood transfusion in elderly patients having elective total joint replacement.

Effect of particulate bioactive glass on human synoviocyte cultures.

Bioglass is a resorbable glass material that has been shown to induce osteoblast proliferation as well as bone matrix production in vitro. Its physico-chemical properties have been reported to be suitable for use as an implant coating for arthroplasty. However, Bioglass is a ceramic material that can fragment into particulate debris in vivo. The effect of particulate Bioglass on tissue cells has not been defined. In order to determine the biologic response to particulate Bioglass, we tested its effect on human synoviocytes in a cell culture model. At the concentrations of 1.0 and 10, micrograms/mL, particulate Bioglass (sizes ranging from approximately 0.5 to 80 microns) had a low cytotoxic effect. However, these concentrations induced secretion of TNF alpha. The observation that particulate Bioglass elicits release of inflammatory cytokines suggests that the development of this bioceramic implant coating should address techniques that would minimize the generation of particulates.

Human osteoblast-like cells (MG63) proliferate on a bioactive glass surface.

Bioglass, a resorbable glass, previously has been evaluated as a bone graft substitute using cells of animal origin. Limited information is available on its effect on human cells. The objective of this study was to test the hypothesis that Bioglass supports viability and proliferation of human bone cells. As a prototype of human bone cells, the osteoblast cell line MG63 was used and propagated on Bioglass disks. MG63 cells also were seeded onto disks made of titanium (Ti-6Al-4V) and of cobalt chrome (Co-Cr-Mo) alloys. The number of viable cells recovered was similar for Bioglass, titanium, and polystyrene control surfaces. Significantly fewer cells were recovered from CoCr (P < 0.05) compared to Bioglass, Ti-6 Al-4v, and polystyrene surfaces. The proportion of cells undergoing DNA synthesis, estimated by thymidine uptake, was significantly greater on Bioglass and titanium surfaces (P < 0.05) than on the CoCr surface. There were detectable differences in cell morphology on these biomaterials. Functional capacity was tested by assay of osteocalcin production and no differences were detectable among the different biomaterials. This study supports the hypothesis that 45S5 Bioglass provides a favorable environment for human osteoblast proliferation and function. Bioglass may have clinical potential as a bone graft substitute, a bioactive grout, or an implant coating for promoting bony ingrowth in uncemented prostheses.

Biomechanical evaluation of tension band placement for the repair of olecranon fractures.

Displaced transverse fractures of the olecranon commonly are treated by open reduction and internal fixation using the AO tension band wiring technique. Reports that the AO technique has a tendency to open the fracture site at the articular surface prompted Rowland and Burkhart to modify placement of the tension band. The present study tested the hypothesis that the modified wire placement provides static compression anteriorly, and hence better reduction at the articular surface of the fracture, than the AO technique under static conditions. Transverse olecranon fractures were created on 8 pairs of fresh cadaveric arms. One ulna of each pair was repaired using the modified wire placement, whereas the contralateral ulna was repaired using the AO technique. The humerus was driven into the trochlear fossa of each ulna using a servohydraulic testing machine while a force transducer and video system measured the applied force and gap formation at the articular surface of the fracture. Because the static behavior of the fixations was tested, no muscle forces were included. Results indicated no significant differences in yield loads or stiffness values between the 2 techniques. Based on the results of this static study, the modified wire placement does not provide increased stability of fracture fixation compared with the AO tension band wiring technique.

Stability of reamed and unreamed intramedullary tibial nails: a biomechanical study.

We examined the correlation of bone mineral density and bone strength in the cadaver tibia, and looked in vitro at the relative stability of tibial fractures fixed with either reamed or unreamed tibial nails. Bone-mineral density correlated well with bone strength (r = 0.946), but paired tibias did not correlate closely. The unreamed nail-bone construct was less stable than the reamed construct in each pair tested (P < 0.05), and a comparison of all bones showed it to be less stable at all levels of our testing regimen, including failure (P < 0.01). Bending and breakage was seen in four of the smaller unreamed interlocking screws (4 mm).

Contaminated fractures of the tibia: a comparison of treatment modalities in an animal model.

External fixation is the current standard treatment for skeletal stabilization of open tibial fractures, but intramedullary fixation techniques have become increasingly popular. The aim of this study was to compare, in an animal model, the susceptibility to infection of contaminated fractures stabilized with external fixation with that of contaminated fractures fixed with intramedullary locking nails with or without reaming. A unilateral osteotomy of the tibia was performed in 15 goats under general anesthesia. Each osteotomy was stabilized with either (a) a unilateral biplanar external fixator, (b) an 8 mm diameter intramedullary rod inserted without reaming of the medullary cavity, or (c) a 10 mm diameter rod inserted after reaming. A standardized inoculum of Staphylococcus aureus, 10(3) colony forming units per milliliter, was placed at each osteotomy site on a piece of absorbable gelatin sponge, to simulate contamination of an open fracture. Antibiotics were not administered. The animals were allowed full activity after the procedure. Fourteen days postoperatively, the animals were killed, radiographs of the tibiae were taken, and the tibiae were harvested in a sterile manner. Multiple specimens for quantitative microbiological analysis were taken from the fracture site and from sites 3 cm distal and 6 cm proximal to the fracture. Additional specimens of bone were taken for histological study. Clinical, radiographic, and microbiological analysis demonstrated that, in this animal model, there were significantly fewer and less severe infections in fractures fixed with external fixation than in those fixed with an intramedullary nail with or without reaming. There was marked cortical necrosis in tibiae that had been fixed with nailing and reaming.

Long-term results of core decompression for ischaemic necrosis of the femoral head.

We have studied the long-term results of core decompression as the sole treatment for Ficat stages I, II and III ischaemic necrosis of 128 femoral heads in 90 patients. The 5-, 10- and 15-year survival rates for the three stages were respectively: stage I 100%, 96% and 90%; stage II 85%, 74% and 66%; and stage III 58%, 35% and 23%. At a mean follow-up of 11 years (4.5 to 19), 55 hips had failed (43%). No further surgery had been needed for 88% of stage-I, 72% of stage-II and 26% of stage-III hips; but despite the generally satisfactory clinical results, 56% of the hips had progressed radiographically by at least one Ficat stage. Complications of the core procedure included four fractures, all from postoperative falls, and one head perforation due to technical error. We conclude that core decompression delays the need for total hip replacement in young patients with ischaemic necrosis.

Anatomical restraints to dislocation of the second metatarsophalangeal joint and assessment of a repair technique.

The aim of this study was to determine the anatomical restraints to dislocation of the second metatarsophalangeal joint and to assess the biomechanical efficacy of a technique that is commonly used to stabilize this joint. Cadaveric feet were disarticulated at the ankle, with preservation of the long flexor tendons at the medial malleolus. The hindfoot was transfixed to an aluminum jig, and a contoured nylon block was secured to the dorsum of the second metatarsal. A Kirschner wire was passed transversely through the proximal phalanx and was attached to a wire loop through which a constant vertical displacement was applied with a universal testing machine. A preload of five newtons was applied, followed by a constant displacement of two millimeters per minute, and the load-displacement curves were measured. The volar plate and the collateral ligaments were divided in five feet each. In another ten feet, both of these structures were divided simultaneously. Each load cycle was repeated four times. The force required to dislocate the joint, in the position in which testing was performed, was reduced by a mean of 30 per cent when the volar plate was divided and by a mean of 46 per cent when the collateral ligaments were divided. Division of both of these structures created an unstable joint, which dislocated at an applied load of five to ten newtons. The metatarsophalangeal joint was then repaired with use of a flexor tendon transfer in all twenty feet. This repair technique restored the load-displacement curves to that of the normal toe.

Proximal femoral fractures: a biomechanical study to compare intramedullary and extramedullary fixation.

This study assesses the rigidity and strength of fixation provided by intramedullary and extramedullary devices for proximal femoral fractures. Stable and unstable intertrochanteric fractures were studied in paired femora after internal fixation with the Gamma nail and Richards 135 degrees classic hip-screw implants; in subtrochanteric fractures, the 95 degrees Richards condylar screw was studied in addition. Subsidence of the sliding screw within the plate and nail constructs was measured. Fixation of subtrochanteric fractures with the intramedullary Gamma nail was significantly stronger and more rigid than that with the extramedullary screw plate devices. Under conditions of simulated protected weight bearing, the 95 degrees condylar screw plate provided more rigid fixation than did the 135 degrees hip screw. There was no significant difference in the strength of fixation of stable and unstable intertrochanteric fractures between the Gamma nail and the hip screw, although the Gamma nail provided more rigid fixation.

Arthrodesis of the first metatarsophalangeal joint: a biomechanical study of internal fixation techniques.

This study compares the strength and rigidity of four methods of internal fixation for arthrodesis of the first metatarsophalangeal joint. Ten matched pairs of cadaveric first rays were harvested and arthrodesis performed by one of four techniques: (1) planar excision of joint surfaces and fixation with crossed Kirschner wires, (2) planar excision of joint surfaces and internal fixation with a dorsal plate and screws, (3) planar excision of joint surfaces and internal fixation with an interfragmentary screw, or (4) excision of the joint surfaces using powered conical reamers and fixation with an interfragmentary lag screw. Biomechanical testing with a Bionix 858 materials testing machine was carried out, applying a plantar force utilizing principles of cantilever loading. Force applied and displacement of the arthrodesis were recorded. Of the four methods tested, bony preparation with power conical reamers and supplementary interfragmentary screw fixation was the most stable.

Computerized templating in uncemented total hip arthroplasty to assess component fit and fill.

The aim of the uncemented femoral component in total hip arthroplasty is to achieve a stable bone-prosthesis interface without the use of polymethyl methacrylate (PMMA). Maximal fill of the femoral canal by the prosthesis promotes initial stability and long-term optimal stress transfer to the bone. The percentage "fit and fill" of the proximal femur by three prostheses, the porous coated anatomic, anatomic medullary locking, and the Harris-Galante, was compared by use of a computerized templating model to assess preoperative radiographs of 20 patients. Results showed that overall percentage fit and fill was similar and satisfactory (greater than 60%) in 17 of 20 patients. If a satisfactory fill was not achieved with one prosthesis, another prosthesis did not significantly improve fill. Lack of bony contact in the proximomedial femur was the most common deficiency noted.

A biomechanical analysis of solvent-dehydrated and freeze-dried human fascia lata allografts. A preliminary report.

UNLABELLED: This study compares the basic mechanical properties of two groups of commercially available fascia lata allografts processed by different means (solvent-dehydrated and sterilized via gamma radiation, and freeze-dried without secondary sterilization). The results reveal significantly (P less than 0.05) higher stiffness, higher maximum load to failure, and higher maximum load per unit width of graft with the solvent-dried as opposed to the freeze-dried fascia lata. Subsections of individual solvent-dried specimens were also more uniform in their mechanical properties than those of the freeze-dried allografts. CLINICAL RELEVANCE: Fascia lata is used as a graft material in a variety of orthopaedic procedures. Allograft fascia lata offers an increased cross-sectional area of material and eliminates the morbidity associated with the harvesting of autologous tissues. However, the structural uniformity of such large grafts has been questioned. Processing techniques used in the sterilization and storage of such grafts is varied and represents a potential source of variation in the mechanical properties of allograft specimens. The results of this study suggest that a commercially available solvent-dehydrated form of fascia lata provides a more suitable grafting material than freeze-dried specimens obtained from tissue banks.

Tibiotalar contact and fibular malunion in ankle fractures. A cadaver study.

Six cadaveric ankles were dissected, preserving medial and lateral ligaments; an axial load of 455N was applied to the tibia supported by the foot and ankle. The unconstrained tibia was moved through 20 degrees of flexion and extension to simulate walking. The tibiotalar contact area was defined using carbon black suspension, recorded photographically, and measured using computerized area analysis. Osteotomy of the distal fibula was performed and fixed with a specially modified plate; a selection of plates provided fixation with 0 degrees or 30 degrees of external rotation in combination with 0 or 2 mm of shortening. The contact area was measured for each of the plates and after division of the deltoid ligament. There were greater than 30 percent decreases in tibiotalar contact with both fibular shortening and external rotation, doubled with a divided deltoid ligament. Anatomic restoration of both fibular length and rotation is essential for normal ankle mechanics. The deltoid ligament has crucial effects on the stability of the ankle mortise.

The initial stability of uncemented acetabular components.

The osseo-integration of an uncemented acetabular component depends on its initial stability. This is usually provided by under-reaming of the acetabulum. We have assessed the fixation of 52 mm porous-coated hemispherical prostheses inserted into cadaveric acetabula under-reamed by 1, 2, 3 and 4 mm. We tested the torsional stability of fixation, after preloading with 686 N in compression, by measuring the torque required to produce 1 degree and 2 degrees of rotation. Under-reaming by 2 mm and 3 mm gave significantly better fixation than 1 mm (p less than 0.01, p less than 0.02). Insertion after under-reaming of 4 mm caused some fractures. To obtain maximum interference fit and optimal implant stability, we recommend the use of an implant 2 mm or 3 mm larger than the last reamer.