Objectives. The objective of this study was to quantify the relative movement between the articular surfaces in the tibiotalar and subtalar joints during normal walking in asymptomatic individuals. Methods. 3D movement data of the ankle joint complex were acquired from 18 subjects using a biplanar fluoroscopic system and 3D-to-2D registration of bone models obtained from CT images. Surface relative velocity vectors (SRVVs) of the articular surfaces of the tibiotalar and subtalar joints were calculated. The relative movement of the articulating surfaces was quantified as the mean relative speed (RS) and synchronization index (SI. ENT. ) of the SRVVs. Results. SI. ENT. and mean RS data showed that the tibiotalar joint exhibited translational movement throughout the stance, with a mean SI. ENT. of 0.54 (. sd. 0.21). The mean RS of the tibiotalar joint during the 0% to 20% post heel-strike phase was 36.0 mm/s (. sd. 14.2), which was higher than for the rest of the stance period. The subtalar joint had a mean SI. ENT. value of 0.43 (. sd. 0.21) during the stance phase and exhibited a greater degree of rotational movement than the tibiotalar joint. The mean relative speeds of the subtalar joint in early (0% to 10%) and late (80% to 90%) stance were 23.9 mm/s (. sd. 11.3) and 25.1 mm/s (. sd 9.5). , respectively, which were significantly higher than the mean RS during mid-stance (10% to 80%). Conclusion. The tibiotalar and subtalar joints exhibited significant translational and rotational movement in the initial stance, whereas only the subtalar joint exhibited significant rotational movement during the late stance. The relative movement on the articular surfaces provided deeper insight into the interactions between articular surfaces, which are unobtainable using the joint coordinate system. Cite this article: C-B. Phan, D-P. Nguyen, K. M. Lee, S. Koo. Relative movement on the articular surfaces of the tibiotalar and subtalar joints during walking. Bone Joint Res 2018;7:501–507. DOI: 10.1302/2046-3758.78.BJR-2018-0014.R1

INTRODUCTION. Tibiofemoral contact at the base of the articular surface spine in posterior-stabilized total knee arthroplasty (TKA) implants can lead to spine fracture [1]. Revision TKA implants also have an articular surface spine to provide sufficient constraint when soft tissues are compromised. While some revision TKA designs have metal reinforcement in the articular surface spine, others rely solely on a polyethylene spine. This study used finite element analysis (FEA) to study the effect of metal reinforcement on stresses in the spine when subjected to posteriorly directed loading. METHODS. Two clinically successful Zimmer Biomet revision TKA designs were selected; NexGen LCCK with metal reinforcement and all-poly Vanguard SSK. The largest sizes were selected. FEA models consisted of the polyethylene articular surface and a CoCr femoral component; LCCK also included a CoCr metal reinforcement in the spine. A 7° and 0° tibial slope, as well as 3° and 0.7° femoral hyperextension, were used for the LCCK and SSK, respectively. A posteriorly directed load was applied to the spine through the femoral component (Figure 1). The base of the articular surface was constrained. The articular surfaces for both designs are made from different polyethylene materials. However, for the purpose of this study, to isolate the effect of material differences on stresses, both were modeled using conventional GUR1050 nonlinear polyethylene material properties. Femoral component and metal reinforcement were modeled using linear elastic CoCr properties. Additionally, the LCCK was reanalyzed by replacing the metal reinforcement component with polyethylene material, in order to isolate the effect of metal reinforcement for an otherwise equivalent design. Frictional sliding contact was modeled between the spine and femoral/metal reinforcement components. Nonlinear static analyses were performed using Ansys version 17 software and peak von mises stresses in the spine were compared. RESULTS. Peak von mises stresses were predicted towards the base of the anterior aspect of the spine in both designs (Figure 2). In LCCK, the high stresses were also predicted on the medial and lateral edges of the anterior spine, matching the tibiofemoral contact (Figure 3). The LCCK with metal reinforcement design predicted 14% and 31% lower stress than LCCK and SSK all-poly designs. DISCUSSION. Clinical reports of spine fracture in TKA highlight the need for further understanding of the biomechanics of spine loading. Here, through comparison of two clinically successful devices, the effect of multiple design factors was quantified. Inclusion of metal reinforcement in the spine, as well as differences in the conforming geometry between the femoral component and the articular surface, resulted in a 31% decrease in polyethylene stress for the LCCK as compared to the all-poly SSK; of which only 16% was attributed to the metal reinforcement. Further improvements to articular surface design, as well as polyethylene material advances, have the potential to result in all-poly designs with strength characteristics equivalent to or exceeding those of designs with metal reinforcement

Introduction. The hip-knee-ankle (HKA) angle between the mechanical axis of the femur (FM) and the mechanical axis of the tibia (TM) is the standard parameter to assess the coronal alignment of the lower extremity. TM is the line between the center of the tibial spines notch (Point T) and the center of the tibial plafond. However, this theory is based on the premise that TM coincides the anatomical axis of the tibia (TA). Fig.1a shows typical varus knee with medial shift of the tibial articular surface. In this case, TM does not coincide TA. Fig. 2 demonstrates the error of HKA angle when Point T locates medial to TA. Fig.2a shows normal alignment. Fig.2b shows varus alignment. Fig. 2c shows the tibia with medial shift of the tibial articular surface. The tibia has 7 degrees varus articular inclination in Fig.2b and 2c. However, HKA angle is 0 degree in Fig.2c. HKA angle underestimates varus deformity in knees with medial shift of the tibial articular surface. However, the degree of medial shift of the tibial articular surface is obscure. In this study, detailed anatomical configuration of the proximal tibia was evaluated. The effect of the value of HKA angle on the coronal alignment in TKA was then discussed. Methods. This study consists of 117 knees. On the AP view radiograph of the tibia, three distance and two angle parameters were measured. Those were tibial articular surface width, distance between medial edge of the tibial articular surface and Point T, distance from TA to Point T. Angle between TM and TA, and the varus inclination angle of the tibial articular surface relative to the perpendicular line to TA. Results. The mean width of the tibial articular surface was 87.8mm. The mean distance between Point T and medial edge of the articular surface was 43.6mm. Point T located at the center of the tibial articular surface. The mean distance from TA to Point T was 5.6mm. The mean angle between TM and TA was 1.0 degrees. The inclination angle of the tibial articular surface was 8.2 degrees. Discussion. The results clearly showed that varus knees had medial shift of the tibial articular surface. In such knees, the ankle shifts laterally relative to the Point T and HKA angle underestimates the varus deformity. The value of HKA angle also influences the evaluation of the coronal alignment of the lower extremity in TKA (Fig. 3). When the tibial tray is set based on the tibial articular surface width in order to cover the cut surface of the tibia, HKA angle shows the alignment as valgus when the tibial tray is set perpendicular to TA (Fig. 3a). In order to obtain zero degree of HKA angle, the tibial tray should be set perpendicular to TM. This alignment is varus (Fig. 3b). Reduction osteotomy is one procedure to match the value of HKA angle and the true alignment (Fig. 3c). In this technique, HKA angle is zero degree, and TM and TA coincide. For figures, please contact authors directly.

In vivo oxidative degradation in ultra-high molecular weight polyethylene (UHMWPE) has gained significant attention in recent years, especially with the discovery of unanticipated oxidation in retrieved highly cross-linked bearings. While significant attention has been paid to mechanical property changes caused by oxidation, there has been little focus on understanding how wear rates are affected by these in vivo changes. Recent work has demonstrated the possibility of machining wear pins from retrieved UHMWPE bearings, but leveling of the pins removed the in vivo articular surface.[1] The goal of this study is to determine whether wear pins can be produced utilizing the native articular surface. Three materials were used for this study: a short-duration retrieved mobile-bearing conforming tibial insert with minimal oxidation (non-oxidized); a shelf-aged, oxidized, non-conforming fixed bearing tibial insert (oxidized); and standard NIST 1050 bar stock (NIST). Utilizing both conforming and non-conforming devices tests the technique over a range of articular curvatures, while testing a highly oxidized material tests the feasibility of maintaining the native surface when machining wear pins with compromised mechanical properties. FTIR analysis was performed at the articular surface of the devices near where the pins were taken, using ketone peak height as an indicator of oxidation. Wear rates were determined using a six station AMTI OrthoPod with an applied load of 100 N in multidirectional motion for a total of 2 million cycles. The oxidized material had a surface ketone level of 0.26, the non-oxidized device had a ketone level of 0.05, and the NIST sample had a ketone level less than 0.01. Two pins of each material were machined to ¼″ diameter with a length of the through thickness of the tibial inserts; soak controls were also produced. Figure 1 shows mass loss data for all six pins tested. Wear rates between the two pins of each group were fairly repeatable, and the wear rates of the different groups could be easily differentiated. The pins machined from NIST bar stock showed the best match-up, but pins machined from retrieved devices also showed good repeatability, with the non-conforming device showing better results than the conforming device. The ability to produce repeatable wear results with pins machined from in vivo devices is an important step in understanding how the wear rate changes over time in vivo. By maintaining the native articular surface, this test will give a more true representation of the in-vivo wear rate. This method will enable future investigations into how wear rates are affected by oxidation, absorbed chemical species, or other changes that occur in vivo

Fractures of the distal humeral articular surface which do not involve the medial and lateral columns are often more extensive than is apparent from plain radiographs. This retrospective study describes the epidemiology of this injury using modern classification systems and compares pre-operative radiography with operative findings. The study group included 79 patients with a mean age of 47 years (13 to 91). The annual incidence was 1.5 per 100 000 population, and was highest in women over the age of 60. The majority of the fractures (59; 75%) were sustained in falls from standing height. Young males tended to sustain more high-energy injuries with more complex fracture patterns. In 24% of cases (19) there was a concomitant radial head fracture. Classification from plain radiographs often underestimates the true extent of the injury and computed tomography may be of benefit in pre-operative planning, especially in those over 60 years of age

Certain cases of patello-femoral maltracking can lead to articular surface wear. Though most can be treated non-operatively, where there is increasing wear surgical intervention may be necessary. Patellar tracking is difficult to assess and though several different types of maltracking or loading have been described, each case warrants precise assessment of the wear patterns. Without this knowledge a logical approach to realignment surgery is impossible. 60 consecutive cases (age range 18–50 years) presenting with anterior knee pain were arthroscoped over a 4 year period. These patients all had been selected with either patellar instability or surface wear indicated either clinically, a positive radiograph, bone scan or MRI. All patients were arthroscoped through standard anterolateral and antero-medial portals and also a superolateral and occasionally a supero-medial approach. The areas of articular damage were mapped on diagrams and recorded photographically. Patella views were taken in flexion and extension, and on passively stretching the patella medially and laterally. We found 6 distinct patterns of wear which appear to indicate 6 different maltracking abnormalities. The largest group, 46 patients, consisted of lateral trackers, with 21 patients demonstrating medial facet and lateral femoral condylar wear. Assessment of the articular surface of the patello-femoral groove from inferior portals is highly misleading and superior portals are needed for proper assessment. Medial facet wear can occur in lateral instability or medial compression. Lateral maltracking at engagement or distally are the commonest patterns

We report a study of the shapes of the tibial and femoral articular surfaces in sagittal, frontal and coronal planes which was performed on cadaver knees using two techniques, MRI and computer interpolation of sections of the articular surfaces acquired by a three-dimensional digitiser. The findings using MRI, confirmed in a previous study by dissection, were the same as those using the digitiser. Thus both methods appear to be valid anatomical tools. The tibial and femoral articular surfaces can be divided into anterior segments, contacting from 0° to 20 ± 10° of flexion, and posterior segments, contacting from 20 ± 10° to 120° of flexion. The medial and lateral compartments are asymmetrical, particularly anteriorly. Posteromedially, the femur is spherical and is located in a conforming, but partly deficient, tibial socket. Posterolaterally, it is circular only in the sagittal section and the tibia is flat centrally, sloping downwards both anteriorly and posteriorly to receive the meniscal horns. Anteromedially, the femur is convex with a sagittal radius larger than that posteriorly, while the tibia is flat sloping upwards and forwards. Anterolaterally, both the femoral and tibial surfaces are largely deficient. These shapes suggest that medially the femur can rotate on the tibia through three axes intersecting in the middle of the femoral sphere, but that the sphere can only translate anteroposteriorly and even then to a limited extent. Laterally, the femur can freely translate anteroposteriorly, but can only rotate around a transverse axis for that part of the arc, i.e., near extension, during which it comes into contact with the tibia through its flattened distal/medial surface as against its spherical posterior surface

Allografts of intact cartilage, isolated chondrocytes and cultured chondrocytes taken from the epiphysial growth-plate and from the articular surface of immature rabbits were inserted into full thickness defects in the tibial articular surface of 160 mature rabbits. In the contralateral knees, which were used as controls, similar defects were made but no grafts were inserted. Grafts were followed up for periods of up to one year after transplantation. Both intact articular and intact growth-plate grafts produced significantly better repair than that seen in control ungrafted defects in normal joints (P less than 0.01 and P less than 0.05 respectively) and in arthritic joints (P less than 0.01). Cultured chondrocytes cut to a precise fit also produced significantly better repair than ungrafted defects in arthritic joints (P less than 0.05)

Both backside and articular surface wear have been linked to osteolysis after total knee arthroplasty (TKA). Prostheses with cementless fixation, screw holes in high load regions, and thin polyethylene are susceptible to backside wear. Factors associated with articular wear are similarly well defined. Micromotion at the modular polyethylene interface has been reported for many prostheses, but the relevance of such data compared to articular motions and wear are difficult to appreciate. This study compares in vivo motions and wear occurring at the backside and articular surfaces after TKA. Contemporary PCL-retaining prostheses from one manufacturer were implanted by one surgeon using cement fixation. The polyethylene inserts were > 6mm thick with a full peripheral rim capture and anterior wire locking mechanism. Femoral condylar motions were measured in 20 knees using fluoroscopic analysis during stair and gait activities. All patients had good to excellent clinical outcomes at one year follow-up. Articular and backside surface damage was evaluated on 32 polyethylene inserts retrieved after 27 months (1 to 71) months in-situ for infection (9), autopsy (6), patellar resurfacing (4), patellar loosening (4), tibial loosening (3), osteolysis (2), and other (4). Femoral condylar translation over the polyethylene articular surface ranged from 5-10 mm, which is substantially larger than the reported 50-500 micron range of backside interface micromotion measured in vitro. Damage covered < 33% of the backside surface and appeared as a cast impression of the opposed metal tibial component without scratches associated with micromotion. In contrast, damage consisting predominantly of scratching, burnishing and tractive striations covered 46% of the articular surface. Different locking mechanisms for modular polyethylene inserts result in different degrees of backside wear. No significant backside wear was observed these retrieved inserts with a wire-supplemented peripheral capture. Given the abrasive wear mechanisms and particulate debris shed during femoral condylar sliding, efforts to control motions at the articular surface appear warranted

Bone loss involving articular surface is a challenging problem faced by the orthopaedic surgeon. In the hand and wrist, there are articular defects that are amenable to autograft reconstruction when primary fixation is not possible. In this article, the surgical techniques and clinical outcomes of articular reconstructions in the hand and wrist using non-vascularised osteochondral autografts are reviewed

We have studied damage to the tibial articular surface after replacement of the femoral surface in dogs. We inserted pairs of implants made of alumina, titanium and polyvinyl alcohol (PVA) hydrogel on titanium fibre mesh into the femoral condyles. The two hard materials caused marked pathological changes in the articular cartilage and menisci, but the hydrogel composite replacement caused minimal damage. The composite osteochondral device became rapidly attached to host bone by ingrowth into the supporting mesh. We discuss the clinical implications of the possible use of this material in articular resurfacing and joint replacement

Restoration of joint line in total knee arthroplasty (TKA) is important for kinematics of knee and ligamentous balance. Especially in revision TKA, it may be difficult to identify the joint line. The aim of this study is to define the relationship between epicondyles and articular surface using CT based three-dimensional digital templating sofware $“Athena” (Soft Cube, Osaka, Japan). 137 knees with osteoarthritis, all caces were grade 2 or lower in Kellgren-Lawrence index, were investigated. Perpendicular lines were dropped from the prominences of the medial and lateral femoral epicondyles to the most distal points of articular surfaces and distances of the lines were measured on the axial and coronal planes. The femoral width was measured as the distance between medial and lateral epicondyles. Each of the distance described above was converted to a ratio by dividing by the femoral width. On the axial plane, the average distance from epicondyles to the posterior articular surfaces were 29.4±2.2mm on the medial side and 21.2±2.3mm on the lateral side. The average of the femoral width was 75.2±4.1mm. On coronal plane, the average distance from epicondyles to the distal articular surfaces were 25.2±2.8mm on the medial side and 21.4±2.5mm on the lateral side. The ratio for the distance from epicondyles to the distal and posterior joint line compared to femoral width was 0.39±0.02, 0.28±0.03, 0.33±0.03 and 0.28±0.03. The distance from epicondyles to the distal and posterior joint line correlates with the femoral width of the distal femur. This information can be useful in determining appropriate joint line

INTRODUCTION. Contemporary PCL sacrificing Total Knee Arthroplasty (TKA) implants (CS) consist of symmetric medial and lateral tibial articular surfaces with high anterior lips designed to substitute for the stability of the native PCL. However, designs vary significantly across implant systems in the level of anteroposterior constraint provided. Therefore, the goal of this study was to investigate kinematics of two CS designs with substantially different constraint levels. The hypothesis was that dynamic knee simulations could show the effect of implant constraint on kinematics of CS implants. METHODS. LifeModeler KneeSIM software was used to analyze contemporary CS TKA (X) with a symmetric and highly dished tibia and contemporary CS TKA (Y) with a symmetric tibia having flat sections bounded by high anterior and posterior lips, during simulated deep knee bend and chair sit. The flat sections of CS-Y implant are designed to allow freedom prior to motion restriction by the implant lips. Components were mounted on an average knee model created from Magnetic Resonance Imaging (MRI) data of 40 normal knees. Relevant ligament/tendon insertions were obtained from the MRI based 3D models and tissue properties were based on literature values. The condyle center motions relative to the tibia were used to compare the different implant designs. In vivo knee kinematics of healthy subjects from published literature was used for reference. RESULTS. Prior publications on in vivo kinematics of healthy knees showed that normal knee motion is characterized by an overall medial pivot. This includes greater, consistent posterior rollback of the lateral condyle than medial (Fig 3). In contrast, CS implant X showed symmetric motion including paradoxical anterior sliding until 120° flexion. This caused a more anterior location for both femoral condyles in flexion as opposed to the posterior location seen in healthy knees. CS implant Y with flat sections showed even greater anterior sliding than CS-X. These trends were seen for chair sit activity as well. Thus, while CS-X showed less paradoxical sliding, both implants suffered from kinematic deficits due to absence of the PCL (Fig. 1 and Fig. 2). CONCLUSION. The two CS implants showed different kinematic performance confirming the hypothesis that implant design affects kinematics of CS TKA. Absence of the PCL in contemporary CS implants resulted in kinematic deficits. In particular, a symmetric implant with flat sections connecting the anteroposterior implant lips showed excessive paradoxical anterior sliding. These data showed both the need and opportunity for novel designs to address the limitations of contemporary CS implants

Introduction. Highly crosslinked ultrahigh-molecular-weight polyethylene (XLPE) reduces wear and osteolysis in total hip arthroplasty, but it is unclear if XLPE will provide the same clinical benefit in total knee arthroplasty (TKA). Adhesive and abrasive wear generally dominate in polyethylene acetabular components, whereas fatigue wear is an important wear mechanism in polyethylene TKA tibial inserts. The wear resistance of XLPE depends on the crosslink density of the material, which may decrease during in vivo mechanical loading, leading to more wear and increased oxidation. To examine this possibility, we measured crosslink density and oxidation levels in loaded and unloaded locations of retrieved tibial inserts to evaluate the short-term performance of XLPE material in TKA. Materials and Methods. Forty retrieved XLPE tibial inserts (23 remelted, 17 annealed) retrieved after a mean time of 18 ± 14 months were visibly inspected to identify loaded (burnished) and unloaded (unburnished) locations on the plateaus of each insert using a previously published damage mapping method. For each insert, four cubes (3 mm3) were cut from loaded and unloaded surface and subsurface locations (Fig. 1). Swell ratio testing was done according to ASTM F2214 to calculate crosslink density of the cubes. With a microtome, 200 μm sections were taken adjacent to the cubes and oxidation was assessed with Fourier transform infrared spectroscopy following ASTM F2102 (Fig. 2). Surface oxidation was measured in the sections adjacent the surface cubes and subsurface oxidation was measured in sections adjacent to the subsurface cubes. The effects of location (surface vs. subsurface in the loaded and unloaded regions) and thermal treatment (annealed vs. remelted) on crosslink density and oxidation were assessed with repeated measures generalized estimating equations (GEEs), with the implant treated as the repeated factor. Results are presented as means and 95% confidence intervals and the level of significance was α=0.05. Results. Crosslink density was associated with location within the polyethylene tibial inserts (p<0.001), while oxidation was associated with both location (p<0.001) and heat treatment (p=0.003). The loaded surface (location 1 in Fig. 1) had 13% lower crosslink density than all other locations (p<0.001 for each), and greater oxidation than all other locations (Fig. 3). Specifically, oxidation of the loaded surface was 0.29[0.17,0.40] greater (two times greater) than that of the unloaded surface (p < 0.001), whereas subsurface areas of loaded and unloaded regions differed by only 0.03[0.00,0.07] (p<0.022). Additionally, surface oxidation was over 7-fold greater than subsurface oxidation in the loaded region (difference: 0.56[0.44,0.68], p<0.001). Annealed XLPE had 2-fold greater oxidation than remelted XLPE (difference 0.159, 95% CI = 0.045, 0.126), and this was independent of location within the inserts. Conclusions. In vivo loading of XLPE decreased the crosslink density and increased the oxidation in areas that underwent wear and deformation at the articular surface of TKA inserts. Nonetheless, in these short term retrievals, no clinical complications were attributed to the change in material properties. However, if crosslink density continues to decrease with load over time, XLPE may not provide a clinical advantage over conventional polyethylene in TKA

Introduction

Knee joint should be aligned for reconstruction of the function in Total Knee Replacement(TKR). Although a surgeon try to correct the alignment of a knee joint, sometimes varus/valgus alignment has been tried in order to reconstruct function of knee joint. As a result, the varus or valgus alignment affects to ligaments and soft tissue, and the contact condition is changed between femoral component and tibial insert. One of important factor, wear characteristics of an implant can be changed due to the contact condition. In this study, we performed static contact tests from extension to flexion in varus and valgus to define the effect to contact condition when the alignment is varus or valgus.

Introduction: Successful shoulder arthroplasty is based on restoration of the individual’s proximal humeral morphology with a precise osteotomy of the humeral head at the level of the anatomical neck. The objective of this study was to determine the geometry of the articular portion of the humeral head in contact with the glenoid in the neutral position and compare the orientation to the geometry of the humeral head determined using the cartilage/calcar interface of the anatomical neck.

Methods: An intact rotator cuff and joint capsule were exposed for six cadaveric full arms. Precision perspex reference cubes were attached to the greater tuberosity of the humerus and to the coracoid process of the scapula on each specimen. Each shoulder was mounted in a custom built jig with the arm fixed in the neutral position and a Microscribe 3D-X digitizer used to digitize three faces of each precision cube. The shoulder joint was then disarticulated and both the humerus and scapula re-mounted on the same jig, independently. The cube faces were re-digitized and relevant points, lines and surfaces were identified and digitized on each humerus and scapula. The humeri were then scanned using a high precision surface laser scanner.

The data collected from both digitizing tools were merged into the same coordinate system and graphically represented. Paired Student’s t-tests were used to compare the inclination and retroversion angles for the two techniques.

Results and discussion: The study found a significant difference in inclination (p less than 0.02) and no difference in retroversion (p equal to 0.75) when the glenoid position was used to calculate humeral head orientation (Inclination: Mean 11.5 deg., StD. 11.2 deg.; Retroversion: Mean 20.5 deg., StD. 6.6 deg.) when compared to using the cartilage/calcar interface (Inclination: Mean 134.1 deg., StD. 1.9 deg.; Retroversion Mean 21.7 deg., StD. 13.9 deg.).

Small deviations in the recovery of head orientation in shoulder arthroplasty may impact on the longevity of an implant. The differences in inclination and retroversion noted in this study may alter the load on the glenoid and/or rotator cuff mechanism in joint replacement. Further research is necessary.

In an attempt to repair articular cartilage, allograft articular chondrocytes embedded in collagen gel, were transplanted into full-thickness defects in rabbit articular cartilage. Twenty-four weeks after the transplantation, the defects were filled with hyaline cartilage, specifically synthesising Type II collagen. These chondrocytes were autoradiographically proven to have originated from the transplanted grafts. Assessed histologically the success rate was about 80%, a marked improvement over the results reported in previous studies on chondrocyte transplantation without collagen gel. By contrast, the defects without chondrocyte transplantation healed with fibrocartilage. Immunological enhancement induced by transplanted allogenic chondrocytes or collagen was not significant at eight weeks after treatment, so far as shown by both direct and indirect blastformation reactions. Thus, allogenic transplantation of isolated chondrocytes embedded in collagen gel appears to be one of the most promising methods for the restoration of articular cartilage.

We describe a lumbar facet syndrome in which disabling symptoms are associated with normal or near-normal plain radiographs. Local spinal fusion relieved symptoms in 12 patients; the excised facet joint surfaces showed some of the histological changes seen in chondromalacia patellae and in osteoarthritis of other large joints. The most frequent change was focal full-thickness cartilage necrosis or loss of cartilage with exposure of subchondral bone, but osteophyte formation was remarkably absent in all specimens. We suggest that there are both clinical and histological similarities between the facet arthrosis syndrome and chondromalacia patellae. Facet arthrosis may be a relatively important cause of intractable back pain in young and middle-aged adults.

We undertook this study to determine the minimum amount of coronoid necessary to stabilise an otherwise intact elbow joint. Regan–Morrey types II and III, plus medial and lateral oblique coronoid fractures, collectively termed type IV fractures, were simulated in nine fresh cadavers. An electromagnetic tracking system defined the three-dimensional stability of the ulna relative to the humerus. The coronoid surface area accounts for 59% of the anterior articulation. Alteration in valgus, internal and external rotation occurred only with a type III coronoid fracture, accounting for 68% of the coronoid and 40% of the entire articular surface. A type II fracture removed 42% of the coronoid articulation and 25% of the entire articular surface but was associated with valgus and external rotational changes only when the radial head was removed, thereby removing 67% of the articular surface. We conclude that all type III fractures, as defined here, are unstable, even with intact ligaments and a radial head. However, a type II deficiency is stable unless the radial head is removed. Our study suggests that isolated medial-oblique or lateral-oblique fractures, and even a type II fracture with intact ligaments and a functional radial head, can be clinically stable, which is consistent with clinical observation.

Hip joint biomechanics can be altered by abnormal morphology of the acetabulum and/or femur. This may affect load distribution and contact stresses on the articular surfaces, hence, leading to damage and degradation of the tissue. Experimental hip joint simulators have been used to assess tribology of total hip replacements and recently methods further developed to assess the natural hip joint mechanics. The aim of this study was to evaluate articular surfaces of human cadaveric joints following prolonged experimental simulation under a standard gait cycle. Four cadaveric male right hips (mean age = 62 years) were dissected, the joint disarticulated and capsule removed. The acetabulum and femoral head were mounted in an anatomical hip simulator (Simulation Solutions, UK). A simplified twin peak gait cycle (peak load of 3kN) was applied. Hips were submerged in Ringers solution (0.04% sodium azide) and testing conducted at 1 Hertz for 32 hours (115,200 cycles). Soft tissue degradation was recorded using photogrammetry at intervals throughout testing. All four hips were successfully tested. Prior to simulation, two samples exhibited articular surface degradation and one had a minor scalpel cut and a small area of cartilage delamination. The pre-simulation damage got slightly worse as the simulation continued but no new areas of damage were detected upon inspection. The samples without surface degradation, showed no damage during testing and the labral sealing effect was more obvious in these samples. The fact that no new areas of damage were detected after long simulations, indicates that the loading conditions and positioning of the sample were appropriate, so the simulation can be used as a control to compare mechanical degradation of the natural hip when provoked abnormal conditions or labral tissue repairs are simulated