Comparisons of joint surface curvature at the base of the thumb have long been made to discern differences among living and fossil primates in functional capabilities of the hand. However, the complex shape of this joint makes it difficult to quantify differences among taxa. The purpose of this study is to determine whether significant differences in curvature exist among selected catarrhine genera and to compare these genera with hominin fossils in trapeziometacarpal curvature. Two 3D approaches are used to quantify curvatures of the trapezial and metacarpal joint surfaces:(1) stereophotogrammetry with nonuniform rational B-spline (NURBS) calculation of joint curvature to compare modern humans with captive chimpanzees and (2) laser scanning with a quadric-based calculation of curvature to compare modern humans and wild-caught Pan, Gorilla, Pongo, and Papio. Both approaches show that Homo has significantly lower curvature of the joint surfaces than does Pan. The second approach shows that Gorilla has significantly more curvature than modern humans, while Pongo overlaps with humans and African apes. The surfaces in Papio are more cylindrical and flatter than in Homo. Australopithecus afarensis resembles African apes more than modern humans in curvatures, whereas the Homo habilis trapezial metacarpal surface is flatter than in all genera except Papio. Neandertals fall at one end of the modern human range of variation, with smaller dorsovolar curvature. Modern human topography appears to be derived relative to great apes and Australopithecus and contributes to the distinctive human morphology that facilitates forceful precision and power gripping, fundamental to human manipulative activities.

Degenerative joint disease affecting the thumb metacarpophalangeal and interphalangeal joints is a debilitating condition, which can significantly restrict activities of daily living. Conservative measures to address symptoms include oral anti-inflammatory medications, activity modification and splinting, and intraarticular corticosteroid injections. Surgical interventions include arthroscopic synovectomy, arthroplasty, and finally arthrodesis of the affected articulations. Although short-term results from synovectomy and arthroplasty seem promising, long-term data are not yet available. Arthrodesis of the metacarpophalangeal and interphalangeal joints yields a stable yet functional thumb with reliably good pain relief.

Derangement of the carpometacarpal (CMC) joint of the thumb secondary to osteoarthritis (OA) or rheumatoid arthritis (RA) is a source of pain and disability in many postmenopausal women. If surgery becomes necessary, the goals of postsurgical management are directed to relief of pain, joint protection and rest, and restoration of functional activity. This article describes the successful postsurgical rehabilitation of two patients with CMC joint arthritis of differing etiologies, and medical complexity, OA and RA, respectively, and different levels of medical complexity. Basal joint protection, passive range of motion, and gentle active exercise resulted in rapid functional recovery for these two patients.

The objective of this study was to quantitatively assess the surface curvature of the articular cartilage from low-field magnetic resonance imaging (MRI) data, and to investigate its role in populations with varying radiographic signs of osteoarthritis (OA), cross-sectionally and longitudinally. The curvature of the articular surface of the medial tibial compartment was estimated both on fine and coarse scales using two different automatic methods which are both developed from an automatic 3D segmentation algorithm. Cross-sectionally (n=288), the surface curvature for both the fine- and coarse-scale estimates were significantly higher in the OA population compared with the healthy population, with P<0.001 and P<0.001, respectively. For the longitudinal study (n=245), there was a significant increase in fine-scale curvature for healthy and borderline OA populations (P<0.001), and in coarse-scale curvature for severe OA populations (P<0.05). Fine-scale curvature could predict progressors using the estimates of those healthy at baseline (P<0.001). The inter-scan precision was 2.2 and 6.5 (mean CV) for the fine- and coarse scale curvature measures, respectively. The results showed that quantitative curvature estimates from low-field MRI at different scales could potentially become biomarkers targeted at different stages of OA.

The thumb carpometacarpal (CMC) joint is the most common site of surgical reconstruction for osteoarthritis in the upper extremity. In patients older than age 75 years, thumb CMC osteoarthritis has a radiographic prevalence of 25% in men and 40% in women. The thumb CMC joint obtains its stability primarily through ligamentous support. A diagnosis of thumb CMC arthritis is based on symptoms of localized pain, tenderness and instability on physical examination, and radiographic evaluation. A reproducible radiographic classification for disease severity is based on the four-stage system described by Eaton. Nonsurgical treatment options include hand therapy, splinting, and injection. Surgical treatment is tailored to the extent of arthritic involvement and may include ligament reconstruction, metacarpal extension osteotomy, arthroscopic partial trapeziectomy, implant arthroplasty, and trapeziectomy with or without ligament reconstruction and tendon interposition.

The acetabular cartilage surface plays an important role in hip joint biomechanics, locomotion and lubrication, but few studies has focused on its geometric morphometry. The aim of this study was to present a novel, accurate mathematical representation of the acetabular cartilage surface based on a new method, combined with a reverse engineering technique, surface-fitting algorithms and mathematical curve surface theory. By using a three-dimensional (3D) laser scanner, a 3D triangulated mesh surface approximation of acetabular cartilage was created. Using surface-fitting algorithms and mathematical curve surface theory, two main curvature parameters, Gaussian curvature and mean curvature at each point on the surface of the acetabular cartilage, were calculated. The distribution patterns of both parameters over the curved surface were elucidated and the eigenvalues of the surface were calculated to determine the shape of the acetabular cartilage surface. By statistically analyzing 25 specimens, it was found that the shape of the acetabular cartilage surface was not theoretically spherical but rotational ellipsoidal, which is a novel mathematical description. The surface-fitting error of a rotational ellipsoid shape was significantly smaller than that of a spherical shape for representing the acetabular cartilage surface (p<0.001). The highest surface-fitting error for a spherical shape was seen in the roof area of the acetabular cartilage, where a rotational ellipsoid surface presented a better anatomical fit. The results will not only be helpful in gaining a new anatomical understanding of the acetabular cartilage surface, but will also be usable in the construction of a precise 3D numerical model in simulation studies of the hip joint.

PURPOSE Osteoarthritis (OA) of the thumb carpometacarpal (CMC) joint causes pain and limits thumb motion. Different surgical procedures exist to treat thumb CMC OA; however, kinematic analyses of thumb reconstructions are limited. The purpose of this study was to evaluate kinematic changes of the thumb CMC joint as the result of different thumb reconstruction procedures. METHODS Fifteen cadaveric forearms were prepared and instrumented with an electromagnetic tracking device to measure the motion of the thumb metacarpal with respect to the trapezium (thumb trapeziometacarpal joint). Kinematics of the intact thumb and the thumb after trapeziectomy under passive motion were recorded. Specimens then had joint reconstruction consisting of either a ligament reconstruction with tendon interposition (LRTI), Weilby arthroplasty, or Thompson arthroplasty. The kinematic data collection analysis was repeated. The radius of joint motion and 3-dimensional (3D) work area were calculated for each surgery and were used for statistical analysis. RESULTS The type of surgical treatment significantly affected the joint radius of motion and the 3D work area. The Thompson and LRTI techniques produced a larger joint radius of motion than the other techniques (Weilby technique and total trapezial resection) and was similar to that of the intact joint. The Weilby and LRTI techniques produced a 3D work area similar to those of the intact joint and trapeziectomy and was also larger than that of the Thompson reconstruction. CONCLUSIONS Kinematic analysis of the thumb CMC joint is effective in differentiating surgical treatments used for end-stage of OA. Only the LRTI reconstruction produced a joint radius of motion and a 3D work area similar to the those of an intact thumb. Additional research is needed to define the optimal surgical techniques to treat the end-stage OA thumb CMC joint.

OBJECTIVE Magnetic resonance imaging (MRI) is a three-dimensional imaging technique with unparalleled ability to evaluate articular cartilage. This report reviews the current status of morphological assessment of cartilage with quantitative MRI (qMRI), and its relevance for identifying disease status, and monitoring progression and treatment response in knee osteoarthritis (OA). METHOD An international panel of experts in MRI of knee OA, with direct experience in the analysis of cartilage morphology with qMRI, reviewed the existing published and unpublished data on the subject, and debated the findings at the OMERACT-OARSI Workshop on Imaging technologies (December 2002, Bethesda, MA) with scientists and clinicians from academia, the pharmaceutical industry and the regulatory agencies. This report reviews (1) MRI pulse sequence considerations for morphological analysis of articular cartilage;(2) techniques for segmenting cartilage;(3) semi-quantitative scoring of cartilage status; and (4) technical validity (accuracy), precision (reproducibility) and sensitivity to change of quantitative measures of cartilage morphology. RESULTS Semi-quantitative scores of cartilage status have been shown to display adequate reliability, specificity and sensitivity, and to detect lesion progression at reasonable observation periods (1-2 years). Quantitative assessment of cartilage morphology (qMRI), with fat-suppressed gradient echo sequences, and appropriate image analysis techniques, displays high accuracy and adequate precision (e.g., root-mean-square standard deviation medial tibia=61 microl) for cross-sectional and longitudinal studies in OA patients. Longitudinal studies suggest that changes of cartilage volume of the order of -4% to -6% occur per annum in OA in most knee compartments (e.g.,-90 microl in medial tibia). Annual changes in cartilage volume exceed the precision errors and appear to be associated with clinical symptoms as well as with time to knee arthroplasty. CONCLUSIONS MRI provides reliable and quantitative data on cartilage status throughout most compartments of the knee, with robust acquisition protocols for multi-center trials now being available. MRI of cartilage has tremendous potential for large scale epidemiological studies of OA progression, and for clinical trials of treatment response to structure modifying OA drugs.

PURPOSE Painful instability of the minimally osteoarthritic thumb carpometacarpal (CMC) joint can be treated successfully by either ligament reconstruction or metacarpal extension osteotomy. The purpose of this study was to measure the laxity of cadaveric thumb CMC joints and to determine the influence of ligament reconstruction and metacarpal osteotomy on joint laxity and contact area. METHODS The baseline laxity of CMC joints from 25 fresh-frozen human cadaveric specimens (average age, 42 y; range, 18-55 y) was measured in the position of lateral pinch on a custom-designed CMC joint laxity tester. Joint laxity was measured again after 2 surgical simulations consisting of either a metacarpal extension osteotomy (at 10 degrees and 15 degrees) or a simulated Eaton-Littler ligament reconstruction (including total, volar, and dorsal ligament reconstructions relative to the plane of the thumbnail). Contact area between the thumb metacarpal and trapezium during testing was determined using stereophotogrammetry. RESULTS The 15 degrees extension osteotomy significantly reduced CMC joint laxity in the radial-ulnar, dorsal-volar, pronation-supination, and distraction directions in the position of lateral pinch. The 10 degrees osteotomy reduced laxity only in the dorsal-volar direction. The total ligament reconstruction significantly reduced joint laxity in the radial-ulnar, dorsal-volar, and pronation-supination directions. The dorsal ligament reconstruction reduced laxity in the dorsal-volar direction only; the volar ligament reconstruction reduced laxity in both dorsovolar and radioulnar directions. The 10 degrees and 15 degrees osteotomies produced a dorsal shift of the weighted centroid of contact on the metacarpal and trapezium, whereas the ligament reconstruction did not produce such an effect. CONCLUSIONS In the position of lateral pinch the 15 degrees osteotomy and total ligament reconstruction significantly reduced laxity of the thumb CMC joint in all directions tested. The isolated dorsal or volar ligament reconstructions both reduced dorsal-volar laxity. Metacarpal extension osteotomy may stabilize the thumb CMC joint in lateral pinch to a degree similar to that of a standard ligament reconstruction.

The biochemical composition and biomechanical properties of articular cartilage from 53 human thumb carpometacarpal (CMC) joints from cadavers aged 20 to 79 years were measured and studied in normal, mildly fibrillated, and advanced osteoarthritic (OA) joints. Statistical analyses were performed to determine the correlations between the compositional measures and biomechanical properties. For these CMC joint tissues we found that water content increased, proteoglycan content decreased, and collagen content per dry weight remained unaltered with progression of OA degeneration. We also found that with disease progression, as defined by an OA staging score, the aggregate modulus (ie, compressive stiffness) decreased, along with an unexpected moderate decrease in permeability. This latter finding appears to be specific to CMC cartilage degeneration since articular cartilage from knees and hips generally demonstrates an increase in permeability with water content and OA score. Correlations between biochemical composition and biomechanical properties were found to be stronger in joints with OA than in joints without OA. This finding suggests that OA changes in biochemical composition, relative to baseline normal values, directly affect the biomechanical properties of cartilage, even though the baseline compositional values themselves do not directly determine the magnitude of the biomechanical properties in normal tissue.

The articular topography of 46 osteoarthritic thumb carpometacarpal joints was quantitatively analyzed, as well as variations with regard to gender, age, site, and anatomic osteoarthritic stage. It was found that for osteoarthritic thumb carpometacarpal joints,(1) the opposing articular surfaces of elder and severely degenerated joints are more congruent than those of middle-aged and minimally or moderately degenerated joints, although the articular contact area is not significantly different when accounting for thinning of the cartilage layer with age or disease;(2) significant changes in joint topography due to osteoarthritis only occur in severely degenerated joints;(3) joints in women are less congruent, have smaller contact areas, and are likely to experience higher contact stresses than joints in men for similar activities of daily living that involve similar joint loads; and (4) osteoarthritic changes are less severe on the dorsoulnar aspect of the trapezium and the dorsal aspect of the metacarpal, which are known to be low load-bearing regions.

The thumb carpometacarpal joint is a common site of osteoarthritis. It has been hypothesized that peaks of localized stress on the dorsoradial or volar-ulnar regions, or both, of the articular surfaces of the trapezium and metacarpal lead to erosion of cartilage and may be responsible for the progression of the disease. The objective of this study was to determine the contact areas in this joint under the functional position of lateral (key) pinch and in the extremes of range of motion of the joint. These contact areas were assessed relative to the observed sites of cartilage thinning. Eight hands from cadavers of women and five from cadavers of men were tested in vitro with the thumb under a 25 N load in the lateral pinch position, and under small muscle loads (0-5 N) with the thumb in flexion, extension, abduction, adduction, and neutral positions. Contact areas of articular surfaces of the thumb carpometacarpal joint were determined for these positions using a stereophotogrammetric technique. The lateral pinch position produced contact areas predominantly on the central, volar, and volar-ulnar regions of the trapezium and the metacarpal. In three specimens, contact areas were distinctly separated between the dorsoradial and volar-ulnar regions, and in one specimen, from a man, contact occurred exclusively on the dorsoradial region of the trapezium. Using stereophotogrammetry, maps of cartilage thickness also were determined for a subset of nine specimens. The volar-ulnar, ulnar, and dorsoradial regions of the trapezium were the most common sites of thin cartilage, and these may be sites of cartilage wear.(ABSTRACT TRUNCATED AT 250 WORDS)

The risk of post-traumatic osteoarthritis following an intra-articular fracture is determined to large extent by the success or failure of osteochondral repair. To measure the efficacy of osteochondral repair in a primate and determine if osteochondral repair differs in the patella (PA) and the medial femoral condyle (FC) and if passive motion treatment affects osteochondral repair, we created 3.2 mm diameter 4.0 mm deep osteochondral defects of the articular surfaces of the PA and FC in both knees of twelve skeletally mature cynomolgus monkeys. Defects were treated with intermittent passive motion (IPM) or cast-immobilization (CI) for two weeks, followed by six weeks of ad libitum cage activity. We measured restoration of the articular surface, and the volume, composition, type II collagen concentration and in situ material properties of the repair tissue. The osteochondral repair response restored a mean of 56% of the FC and 34% of the PA articular surfaces and filled a mean of 68% of the chondral and 92% of the osseous defect volumes respectively. FC defect repair produced higher concentrations of hyaline cartilage (FC 83% vs. PA 52% in chondral defects and FC 26% vs. PA 14% in osseous defects) and type II collagen (FC 84% vs. PA 71% in chondral defects and FC 37% vs. PA 9% in osseous defects) than PA repair. IPM did not increase the volume of chondral or osseous repair tissue in PA or FC defects. In both PA and FC defects, IPM stimulated slightly greater expression of type II collagen in chondral repair tissue (IPM 81% vs. CI 74%); and, produced a higher concentration of hyaline repair tissue (IPM 62% vs. CI 42%), but IPM produced poorer restoration of PA articular surfaces (IPM 23% vs. CI 45%). Normal articular cartilage was stiffer, and had a larger Poisson's ratio and less permeability than repair cartilage. Overall Cl treated repair tissue was stiffer and less permeable than IPM treated repair tissue. The stiffness, Poisson's ratio and permeability of femoral condyle cast immobilized (FC CI) treated repair tissue most closely approached the normal values. The differences in osteochondral repair between FC and PA articular surfaces suggest that the mechanical environment strongly influences the quality of articular surface repair. Decreasing the risk of post-traumatic osteoarthritis following intra-articular fractures will depend on finding methods of promoting the osteochondral repair response including modifying the intra-articular biological and mechanical environments.

OBJECTIVE To develop a methodology for generating templates that represent the normal human patellofemoral joint (PFJ) topography and cartilage thickness, based on a statistical average of healthy joints. Also, to determine the cartilage thickness in the PFJs of patients with osteoarthritis (OA) and develop a methodology for comparing an individual patient's thickness maps to the normal templates in order to identify regions that are most likely to represent loss of cartilage thickness. DESIGN The patella and femur surfaces of 14 non-arthritic human knee joints were quantified using either stereophotogrammetry or magnetic resonance imaging. The surfaces were aligned, scaled, and averaged to create articular topography templates. Cartilage thicknesses were measured across the surfaces and averaged to create maps of normal cartilage thickness distribution. In vivo thickness maps of articular layers from 33 joints with OA were also generated, and difference maps were created depicting discrepancies between the patients' cartilage thickness maps and the normative template. RESULTS In the normative template, the surface-wide mean+/-SD (maximum) of the cartilage thickness was 2.2+/-0.4mm (3.7mm) and 3.3+/-0.6mm (4.6mm) for the femur and patella, respectively. It was demonstrated that difference maps could be used to identify regions of thinner-than-normal cartilage in patients with OA. Patients were shown to have statistically greater regions of thin cartilage over their articular layers than the normal joints. On average, patients showed deficits in cartilage thickness in the lateral facet of the patella, in the anterior medial and lateral condyles, and in the lateral trochlea of the femur. CONCLUSIONS This technique can be useful for in vivo clinical evaluation of cartilage thinning in the osteoarthritic patellofemoral joint.

An important step toward understanding signal transduction mechanisms modulating cellular activities is the accurate predictions of the mechanical and electro-chemical environment of the cells in well-defined experimental configurations. Although electro-kinetic phenomena in cartilage are well known, few studies have focused on the electric field inside the tissue. In this paper, we present some of our recent calculations of the electric field inside a layer of cartilage (with and without cells) in an open circuit one-dimensional (1D) stress relaxation experiment. The electric field inside the tissue derives from the streaming effects (streaming potential) and the diffusion effect (diffusion potential). Our results show that, for realistic cartilage material parameters, due to deformation-induced inhomogeneity of the fixed charge density, the two potentials compete against each other. For softer tissue, the diffusion potential may dominate over the streaming potential and vice versa for stiffer tissue. These results demonstrate that for proper interpretation of the mechano-electrochemical signal transduction mechanisms, one must not ignore the diffusion potential.

A long-standing challenge in the biomechanics of connective tissues (e.g., articular cartilage, ligament, tendon) has been the reported disparities between their tensile and compressive properties. In general, the intrinsic tensile properties of the solid matrices of these tissues are dictated by the collagen content and microstructural architecture, and the intrinsic compressive properties are dictated by their proteoglycan content and molecular organization as well as water content. These distinct materials give rise to a pronounced and experimentally well-documented nonlinear tension-compression stress-strain responses, as well as biphasic or intrinsic extracellular matrix viscoelastic responses. While many constitutive models of articular cartilage have captured one or more of these experimental responses, no single constitutive law has successfully described the uniaxial tensile and compressive responses of cartilage within the same framework. The objective of this study was to combine two previously proposed extensions of the biphasic theory of Mow et al.[1980, ASME J. Biomech. Eng., 102, pp. 73-84] to incorporate tension-compression nonlinearity as well as intrinsic viscoelasticity of the solid matrix of cartilage. The biphasic-conewise linear elastic model proposed by Soltz and Ateshian [2000, ASME J. Biomech. Eng., 122, pp. 576-586] and based on the bimodular stress-strain constitutive law introduced by Curnier et al.[1995, J. Elasticity, 37, pp. 1-38], as well as the biphasic poroviscoelastic model of Mak [1986, ASME J. Biomech. Eng., 108, pp. 123-130], which employs the quasi-linear viscoelastic model of Fung [1981, Biomechanics: Mechanical Properties of Living Tissues, Springer-Verlag, New York], were combined in a single model to analyze the response of cartilage to standard testing configurations. Results were compared to experimental data from the literature and it was found that a simultaneous prediction of compression and tension experiments of articular cartilage, under stress-relaxation and dynamic loading, can be achieved when properly taking into account both flow-dependent and flow-independent viscoelasticity effects, as well as tension-compression nonlinearity.

Rehabilitation of the symptomatic patellofemoral joint aims to strengthen the quadriceps muscles while limiting stresses on the articular cartilage. Some investigators have advocated closed kinetic chain exercises, such as squats, because open kinetic chain exercises, such as leg extensions, have been suspected of placing supraphysiologic stresses on patellofemoral cartilage. We performed computer simulations on geometric data from five cadaveric knees to compare three types of open kinetic chain leg extension exercises (no external load on the ankle, 25-N ankle load, and 100-N ankle load) with closed kinetic chain knee-bend exercises in the range of 20 degrees to 90 degrees of flexion. The exercises were compared in terms of the quadriceps muscle forces, patellofemoral joint contact forces and stresses, and "benefit indices"(the ratio of the quadriceps muscle force to the contact stress). The study revealed that, throughout the entire flexion range, the open kinetic chain stresses were not supraphysiologic nor significantly higher than the closed kinetic chain exercise stresses. These findings are important for patients who have undergone an operation and may feel too unstable on their feet to do closed chain kinetic chain exercises. Open kinetic chain exercises at low flexion angles are also recommended for patients whose proximal patellar lesions preclude loading the patellofemoral joint in deeper flexion.

The relationship between the coefficient of friction and pH value or protein constituents of lubricating fluid, together with viscosity, were studied within a bearing surface model for artificial joint, ultra-high molecular weight polyethylene (UHMWPE) against stainless steel (SUS), using a mechanical spectrometer. Four lubricants were tested in this study: sodium hyaluronate (HA), HA with albumin, HA with gamma-globulin, and HA with (L)alpha-dipalmitoyl phosphatidylcholine ((L)alpha-DPPC). The coefficient of friction between UHMWPE and SUS in HA with albumin or HA with gamma-globulin varied from 0.035 to 0.070 depending on angular velocity and pH. The coefficient of friction in HA or HA with (L)alpha-DPPC varied from 0.023 to 0.045 depending on angular velocity and pH. The variation in pH for HA with albumin had a large effect on the coefficient of friction at low range of angular velocity with viscosity independence. The variation in pH for HA with gamma-globulin had a large effect on the coefficient of friction with viscosity dependence at high angular velocity. The addition of (L)alpha-DPPC showed a small effect on the coefficient of friction at low angular velocity. This study confirms that the presence of albumin in the lubricant promotes pH dependence and viscosity independence of the tribological properties at low speed while the presence of globulin promotes pH and viscosity independence at low speed and promotes pH and viscosity dependence at high speed in the lubrication of UHMWPE against SUS. This study supports the clinical hypothesis that the effect of constituents and pH changes in periprosthetic fluid for the lubrication is a clue toward resolving many complications after total joint replacement.

This study characterizes the donor and recipient sites involved in osteochondral autograft surgery of the knee with respect to articular cartilage contact pressure, articular surface curvature, and cartilage thickness. Five cadaveric knees were tested in an open chain activity simulation and kinematic data were obtained at incremental knee flexion angles from 0 degrees to 110 degrees. Surface curvature, cartilage thickness, and contact pressure were determined using a stereophotogrammetry method. In all knees, the medial trochlea, intercondylar notch, and lateral trochlea demonstrated nonloadbearing regions. Donor sites from the distal-medial trochlea were totally nonloadbeadng. For the intercondylar notch, lateral trochlea, and proximal-medial trochlea, however, the nonloadbearing areas were small, and typical donor sites in these areas partially encroached into adjacent loadbearing areas. The lateral trochlea (77.1 m(-1)) was more highly curved than the typical recipient sites of the central trochlea (23.3 m(-1)), medial femoral condyle (46.8 m(-1)), and lateral femoral condyles (42.9 m(-1))(P < 0.05). Overall, the donor sites had similar cartilage thickness (average, 2.1 mm) when compared with the typical recipient sites (average, 2.5 mm). The lateral trochlea and medial trochlea curvatures were found to better match the recipient sites on the femoral condyles, while the intercondylar notch better matched the recipient sites of the central trochlea. The distal-medial trochlea was found to have the advantage of being nonloadbearing. Preoperative planning using the data presented will assist in more conforming, congruent grafts, thereby maximizing biomechanical function.

The purpose of this study is to gain a better understanding of the changes due to osteoarthritis (OA) occurring in the thumb carpometacarpal (CMC) joint by comparing quantitative geometrical measurements in computed tomography scans of healthy and pathological joints in various stages of OA. The measurements were (1) the subluxation of the metacarpal on the trapezium,(2) distance from the scaphoid centre to the metacarpal base, and (3) distance from the metacarpal base to the articulating surface of the trapezium. The three-dimensional position of three characteristic points on the metacarpal, trapezium, and scaphoid were detected in each of the 90 wrists we scanned. The distances between the points were compared by statistical analysis. With high accuracy, we have been able to confirm and quantify that subluxation occurs in the dorso-radial direction. A significant difference in trapezium height and joint space width was found between the OA and control groups. The results indicate how to restore the centre of rotation in surgical treatment of OA with total joint arthroplasty, but the clinical relevance of these findings has to be tested in further clinical studies.

PURPOSE Trapezial-metacarpal (TM) joint surfaces appear to be shallower in Asian than in white postmortem specimens, and the frequency of TM osteoarthritis seems to be substantially lower in Asian TM joints. This study tested the hypothesis that there are significant differences among human populations in TM joint surface curvature and that populations of Asian descent have less curvature than those of recent European descent. METHODS The sample included trapeziums and first metacarpals from skeletons of 80 individuals of recent European and Asian descent and from skeletons of 34 African and 9 Australian aboriginal individuals. We scanned the surfaces using a laser digitizer to generate 3-dimensional models of each articular surface. We calculated dorsovolar, radioulnar, and root mean square curvatures by fitting modeled quadric surfaces to the TM joint surfaces. We tested pairwise comparisons of mean curvatures between populations for statistical significance using a standard resampling method (ie, bootstrapping). We also made pairwise comparisons of mean curvatures between males and females for a combined African and European sample. RESULTS Mean dorsovolar metacarpal curvature was significantly higher in the European sample than in the Asian, African, and Australian samples. Mean root mean square curvature of the trapezial surface was significantly higher in the European sample than in the Asian sample. The European sample had the highest root mean square and dorsovolar trapezial curvatures of all the populations. We found no significant differences between male and female specimens. CONCLUSIONS A tendency toward higher mean dorsovolar curvature of both the metacarpal and trapezial surface in the European sample may help to explain the higher frequency of TM osteoarthritis reported in Europeans. CLINICAL RELEVANCE The greater TM curvatures affect basal thumb joint mechanics in thumb opposition and therefore may be a factor in the development of osteoarthritis at this joint in Europeans.

BACKGROUND The development of osteoarthritis (OA) in the hand results in increased joint stiffness, which in turn affects the grip strength. The goal of the present study is to theoretically analyze the muscle forces in a thumb in response to the increased joint stiffness. METHODS The thumb was modeled as a linkage system consisting of a trapezium, a metacarpal bone, a proximal and a distal phalanx. Nine muscles were included in the model: flexor pollicis longus (FPL), extensor pollicis longus (EPL), extensor pollicis brevis (EPB), abductor pollicis longus (APL), flexor pollicis brevis (FPB), abductor pollicis brevis (APB), the transverse head of the adductor pollicis (ADPt), the oblique head of the adductor pollicis (ADPo), and opponens pollicis (OPP). Numerical tests were performed using an inverse dynamic approach. The joints were prescribed to an angular motion at one degree-of-freedom (DOF) each time with all other DOFs of the joints being mechanically constrained, while the muscle forces in response to the joint motions were predicted. The normal joint stiffness was assumed to be 0.05, 0.10, and 0.15 N m/rad for interphalangeal (IP), metacarpophalangeal (MCP), and carpometacarpal (CMC) joint, respectively. The joint stiffness was assumed to increase by 50% and 100%, simulating the biomechanical consequences of OA. RESULTS Our simulations indicated that the increase in joint stiffness induced substantial increases in muscle forces, especially in the EPL and FPL muscles in response to IP, MCP, or CMC extension/flexion motions. CONCLUSIONS Because the strength of the muscles in the fingers is limited, the muscles will not be able to overcome joint resistance if joint stiffness is increased to its limit due to OA. This may contribute to the reduced range of motion typically seen in OA.

PURPOSE Hypermobility at the thumb carpometacarpal (CMC) joint has been proposed as an explanation for abnormal loading and subsequent development of osteoarthritis. Radiographic evaluation of this joint is difficult owing to the obliquity of the articulation. We modified a previously described technique to obtain a bilateral stress radiograph of the thumbs to measure CMC joint laxity. The purpose of this study was to present the details of this modified technique and evaluate its reproducibility in a group of volunteer subjects. We hypothesized that this technique would be reliable and reproducible. METHODS A posteroanterior radiograph was obtained after asking volunteer subjects to press their thumbs together using a foam hand support. Three measurements were performed: radial subluxation of the first metacarpal base, first metacarpal articular width, and the distance between the ulnar articular facet of the trapezium and the ulnar metacarpal edge (uncovered edge). Using digital calibration on a picture archiving and communication system radiology server, a radiologist, radiology resident, orthopedic surgeon, and orthopedic resident performed measurements at 2 time points. To evaluate consistency among the raters, intraclass correlation coefficients were calculated. Test-retest bivariate analyses were performed to assess intra-rater reliability. RESULTS A total of 69 volunteers (39 women and 30 men) were imaged. Women showed significantly greater radial subluxation compared to men (p <.01). Inter-rater reliability coefficients for radial subluxation and articular width initially and at 2 weeks showed high agreement, as did test-retest reliability coefficients. For the uncovered edge measurement, inter-rater reliability coefficients were low, with wide variation in reliability. CONCLUSIONS The modified thumb CMC stress view radiograph evaluates laxity and joint abnormalities of the trapeziometacarpal articulation. The details of the radiographic technique are straightforward, and the inter- and intra-observer reliability of radial subluxation and first metacarpal width are high. The ratio of the 2 measurements provides an accurate measure of the radiographic subluxation of the first metacarpal from the trapezium. This measurement is most specific to radial subluxation under simulated active loading, in the plane of the hand. The medial uncovered edge of trapezium measurement does not have high inter-observer reliability and varies widely, and it should not be included in laxity measurements.

Although the thumb saddle is one of the most common sites of degenerative osteoarthritis in the hand, little is known about the altered microstructure in osteoarthritic trapezial bones. External forces resulting from subluxation of the carpometacarpal joint of the thumb (CMC I) should provoke microstructural changes in the trapezium. The purpose of this study was to compare the regional differences of the microstructure between osteoarthritic and healthy trapezial bones. Fifteen trapezia harvested from female patients with radiologically and clinically diagnosed saddle joint osteoarthritis (OA) were compared with 15 unaffected controls. Microstructural parameters, such as bone volume ratio (BV/TV), three-dimensional connectivity (Conn.D), trabecular number (Tb.N), and trabecular thickness (Tb.Th) were studied using a microcomputed tomography (microCT) system. While the trapezial height in OA was 22% less, the sclerotic subchondral bone layer thickness was 50% higher in OA compared with the control group (p < 0.001). In the OA group there was a 42% higher bone volume ratio (p </= 0.001), an 18% increase in Tb.Th (p = 0.006), and a 10% greater Tb.N (p = 0.034) compared with the control group. Although in both groups BV/TV was significantly lower in the radial region, the radial column showed the highest relative increase in bone volume and structure compared with the control group (+67% BV/TV,+20% Tb.Th,+23% Tb.N). The reinforcement of the bony microstructure in CMC I OA, especially at the radial side, is a sign for bone adaptation reacting to radially shifted joint forces. This has to be considered during the development of new prosthetic alternatives.(c) 2007 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

PURPOSE Osteoarthritis (OA) of the thumb carpometacarpal (CMC) joint causes pain and limits thumb motion. Different surgical procedures exist to treat thumb CMC OA; however, kinematic analyses of thumb reconstructions are limited. The purpose of this study was to evaluate kinematic changes of the thumb CMC joint as the result of different thumb reconstruction procedures. METHODS Fifteen cadaveric forearms were prepared and instrumented with an electromagnetic tracking device to measure the motion of the thumb metacarpal with respect to the trapezium (thumb trapeziometacarpal joint). Kinematics of the intact thumb and the thumb after trapeziectomy under passive motion were recorded. Specimens then had joint reconstruction consisting of either a ligament reconstruction with tendon interposition (LRTI), Weilby arthroplasty, or Thompson arthroplasty. The kinematic data collection analysis was repeated. The radius of joint motion and 3-dimensional (3D) work area were calculated for each surgery and were used for statistical analysis. RESULTS The type of surgical treatment significantly affected the joint radius of motion and the 3D work area. The Thompson and LRTI techniques produced a larger joint radius of motion than the other techniques (Weilby technique and total trapezial resection) and was similar to that of the intact joint. The Weilby and LRTI techniques produced a 3D work area similar to those of the intact joint and trapeziectomy and was also larger than that of the Thompson reconstruction. CONCLUSIONS Kinematic analysis of the thumb CMC joint is effective in differentiating surgical treatments used for end-stage of OA. Only the LRTI reconstruction produced a joint radius of motion and a 3D work area similar to the those of an intact thumb. Additional research is needed to define the optimal surgical techniques to treat the end-stage OA thumb CMC joint.

PURPOSE Although hematoma and distraction arthroplasty has been found to be successful in the treatment of thumb basal joint arthritis in the short term, questions about its efficacy in the long term have been raised. The goal of the present study was to evaluate the results of this procedure in patients at least 6.5 years after surgery. METHODS Twenty-two thumbs from 22 patients from a single surgeon's practice were entered into a prospective single-arm study for surgical treatment of basal thumb arthritis. Treatment consisted of piecemeal excision of the entire trapezium and 5 weeks of K-wire immobilization of the thumb metacarpal in opposition and slight distraction. No ligament reconstruction or tendon interposition was used. Motion, strength, standardized dexterity tests, stress radiographs, and outcome questionnaires including the Arthritis Impact Measurement Scales 2 were evaluated before surgery and at 6, 24, and at least 79 months after surgery. RESULTS At 6 months after surgery, 17 of 22 patients reported complete pain relief, and at the most recent follow-up evaluation (average, 88 months after surgery) 18 patients were entirely pain free. Range-of-motion evaluation at the most recent follow-up evaluation showed 21 of 22 thumbs adducted fully into the plane of the palm, and 21 of 22 opposed to the small finger metacarpal head. Comparisons between preoperative and the recent postoperative strength measurements showed an average of 21% increase in grip strength and tip pinch strength, and an 11% increase in key pinch strength over preoperative values. Although the radiographically determined scaphoid-thumb metacarpal distance decreased with time from surgery, no correlation with strength or functional outcome measurements was found. The Arthritis Impact Measurement Scales 2 data showed postoperative improvement in the hand and finger function and arthritis pain scales. CONCLUSIONS After trapezial excision, K-wire immobilization in a slightly overcorrected position without formal interposition or ligament reconstruction allows for restoration and maintenance of a stable, pain-free thumb that has comparable strength and motion with published reports of more complicated interventions over comparable time periods. TYPE OF STUDY/LEVEL OF EVIDENCE Therapeutic, Level IV.

PURPOSE OF THE STUDY: Arthrodesis of the carpometacarpal (CMC) joint of the thumb is an option for treatment of degenerative and post-traumatic conditions affecting the CMC thumb joint. This procedure is indicated most frequently in patients with primary or secondary stage III rhizarthritis (by the Eaton classification of basal joint arthritis) of idiopathic, rheumatic or post-traumatic etiology. Patients with multidirectional CMC instability, usually traumatic in origin, undergo this surgery only occasionally. In our institution, the treatment is based on the Carroll technique. MATERIAL AND METHODS: Between 1990 and 2005 a total of 14 arthrodeses of the CMC joint of the thumb were performed in 12 patients. The Carroll technique used in all cases involved a conical shaping of the first metacarpal base and a corresponding shaping of the trapezium articular surface, their subsequent set-up and fixation with Kirschner's wires. The patients were assessed for the presence of pain, changes in mobility and muscle strength before and after surgery. The comprehensive evaluation of the whole group was carried out by means of the Cooney score. RESULTS: Arthrodesis resulted in complete union of the CMC joint of the thumb in all cases. The patients were followed up for 5 years on average. The initial painful hand grip subsided in most of them. The initial restriction of motion remained, but was painless in almost all cases. However, broad grip strength improved on average by 35 %. The comprehensive Cooney score showed 64 % of excellent and very good results. DISCUSSION: All characteristics of the patient group and the results achieved by this technique, including the Cooney score evaluation, are discussed. It is concluded that this technique is indicated particularly in middle-aged male patients with stage III rhizarthritis (Eaton classification) who do hard manual work, and in whom rhizarthritis of the other thumb joints can be excluded. Also, unstable CMC joints are indicated for this treatment. The resulting position of arthrodesis and methods of joint fixation are discussed. Different methods of osteosynthesis and their advantages are described. From a comparison with the relevant literature results it appears that the absence of postoperative pseudoarthrosis, a marked reduction of grip pain, improvement of grip strength and the values of Cooney score are encouraging results of arthrodesis for the CMC thumb joint performed by the Carroll method. CONCLUSIONS: It is concluded that the Carroll arthrodesis is an effective technique which, if correctly indicated, alleviates pain, restores the axis of the thumb and, consequently, its stability necessary for thumb function in achieving a hand grip.

LEARNING OBJECTIVES After studying this article, the participant should be able to: 1. Understand the pathomechanical and biochemical basis for thumb trapeziometacarpal joint degeneration. 2. Diagnose and grade trapeziometacarpal joint disease based on presentation, physical examination (including provocative testing), and radiographic evidence. 3. Understand the principles of ligament reconstruction and tendon arthroplasty procedures. 4. Describe the surgical technique for ligament reconstruction tendon interposition arthroplasty and its variants. BACKGROUND Osteoarthritis of the trapeziometacarpal joint is the second most common site of degenerative joint disease in the hand, and mostly affects postmenopausal women. Degenerative arthritis of the thumb trapeziometacarpal joint is associated with a lack of bony constraints and laxity of the supporting ligaments, particularly the anterior oblique ("beak") ligament, which is consistently implicated in disease progression. Resultant increases in joint stress loads leads eventually to metacarpal and trapezial articular destruction, thumb instability, and pain. METHODS In this article, the authors review the diagnosis and treatment modalities available to the surgeon in the treatment of patients with trapeziometacarpal osteoarthritis. The technique of ligament reconstruction tendon interposition arthroplasty is discussed in detail. RESULTS Ligament reconstruction tendon interposition arthroplasty procedures center on three common principles:(1) excision of the diseased trapezium;(2) reconstruction of the beak ligament; and (3) interposition of a tissue substance to maintain metacarpal position. CONCLUSIONS Both conservative and surgical management can be effective in the treatment of trapeziometacarpal arthritis, when properly selected. The success of ligament reconstruction tendon interposition arthroplasty in treating trapeziometacarpal arthritis has withstood the test of time.

OBJECTIVE To determine the differences in load-bearing patellofemoral joint cartilage thickness between genders. To determine the differences in load-bearing cartilage thickness between pain-free controls and individuals with patellofemoral pain. METHODS The articular cartilage thickness of the patella and anterior femur was estimated from magnetic resonance images in 16 young, pain-free control subjects (eight males, eight females) and 34 young individuals with patellofemoral pain (12 males, 22 females). The average age of all subjects was 28+/-4 years. The cartilage surfaces were divided into regions approximating the location of patellofemoral joint contact during knee flexion. The mean and peak cartilage thicknesses of each region were computed and compared using a repeated-measures Analysis of Variance. RESULTS On average, males had 22% and 23% thicker cartilage than females in the patella (P < 0.01) and femur (P < 0.05), respectively. Male control subjects had 18% greater peak patellar cartilage thickness than males with patellofemoral pain (P < 0.05); however, we did not detect differences in patellar cartilage thickness between female control subjects and females with patellofemoral pain (P = 0.45). We detected no significant differences in femoral cartilage thickness between the control and pain groups. CONCLUSIONS Thin cartilage at the patella may be one mechanism of patellofemoral pain in male subjects, but is unlikely to be a dominant factor in the development of pain in the female population.