Showing papers by "Nuffield Orthopaedic Centre published in 1999"

Prosthetic Joint Infection.

Abstract: Total joint replacement has been one of the most remarkable successes of modern medical technology. Once John Charnley had solved the problems of implant design, choice of materials, implant fixation, and infection (initial rates of infection were approximately 10%), the way was clear for the widespread use of this valuable treatment, which is highly effective at removing pain and restoring function. Unfortunately, infection still remains an important, though less common, problem. It is associated with serious morbidity (pain, loss of function, wound breakdown, wound discharge, implant failure) and sometimes mortality. It may be impossible to eradicate or suppress infection in the long term without removal of the prosthesis, and most clinicians would consider it unwise to re-implant a new prosthesis in the presence of infection. Hence, patients with infected prosthetic joints generally require multiple additional operations and prolonged periods of antibiotic therapy. Even radical attempts at cure may fail (in 10% to 15% of cases in most series), requiring further cycles of treatment with progressively deteriorating function. Thus, the treatment of prosthetic joint infection is arduous for the patient and the health care team, with no guarantee of success.

Bacterial fibronectin-binding proteins and endothelial cell surface fibronectin mediate adherence of Staphylococcus aureus to resting human endothelial cells.

Abstract: Adhesion of Staphylococcus aureus to human endothelial cells is implicated in the pathogenesis of invasive staphylococcal disease. The adhesion to endothelial cells of isogenic mutants defective in defined surface structures was studied. Three strains of S. aureus defective in fibronectin-binding proteins FnBPA and FnBPB showed reduced adhesion. This was fully restored by complementation of a FnBPA− FnBPB− mutant derived from strain 8325-4 with a multicopy plasmid encoding FnBPA or FnBPB. Adhesion of mutants defective in other surface structures was unaffected. Anti-fibronectin antibodies blocked adhesion of 8325-4 to endothelial cells, while adhesion of strains 8325-4, P1 and five clinical isolates was inhibited by the recombinant form of the binding domain of FnBPB (rFNBD) from Streptococcus dysgalactiae . Adherence of bacterial aggregates resulting from the presence of purified fibrinogen was also inhibited by rFNBD protein. Three strains of S. aureus defective in FnBPA and FnBPB were not internalized by endothelial cells. S. aureus FnBPs mediate adhesion to human endothelial cells and are required for subsequent internalization, interactions of potential relevance to pathogenesis and treatment.

The assessment of shoulder instability: THE DEVELOPMENT AND VALIDATION OF A QUESTIONNAIRE

Abstract: We have developed a 12-item questionnaire for completion by patients presenting with shoulder instability. A prospective study of 92 patients was undertaken involving two assessments, approximately six months apart, performed in an outpatient department. Each patient completed the new questionnaire and the SF36 form. An orthopaedic surgeon completed the Constant shoulder score and the Rowe assessment. The new questionnaire and the Rowe clinical score each achieved a large standardised effect size (> or = 0.8) and compared favourably with relevant items on the SF36. By contrast, the Constant score barely registered any effect, confirming that it may be relatively insensitive to changes in clinical status for this particular condition. The questionnaire provides a measurement of outcome for shoulder instability which is short, practical, reliable, valid and sensitive to changes of clinical importance.

An assessment of the histological criteria used to diagnose infection in hip revision arthroplasty tissues.

Abstract: AIM: To characterise the number and nature of the inflammatory cells seen in cases of septic or aseptic loosening of hip arthroplasty, and to establish reliable histological criteria to distinguish between these two conditions. METHODS: Histological examination of paraffin sections of periprosthetic tissues (pseudocapsule, femoral and acetabular pseudomembranes) of 523 cases of aseptic loosening and 79 cases of microbiology culture proven septic loosening. The cellular composition of the inflammatory cell infiltrate was determined semiquantitatively. RESULTS: The finding of a 2+ or greater neutrophil polymorph infiltrate (one or more cells per high power field (x400) on average after examination of 10 fields) in arthroplasty tissues correlated strongly with the microbiological diagnosis of septic loosening: diagnostic sensitivity 100%, specificity 97%, accuracy 99%, positive predictive value 92%, negative predictive value 100%. The finding of a 3+ neutrophil polymorph infiltrate (five or more cells on average per high power field) had a diagnostic sensitivity of 72%, specificity 100%, accuracy 98%, positive predictive value 100%, and negative predictive value 97%. In some cases of septic loosening the finding of a heavy lymphocytic and plasma cell infiltrate was of low diagnostic sensitivity. A neutrophil polymorph infiltrate (generally less than one cell per 10 high power fields) was also seen in cases of aseptic loosening. CONCLUSIONS: The presence of 2+ or more (more than one neutrophil polymorph per high power field (x400) on average after examination of at least 10 high power fields) in periprosthetic tissues provides the most sensitive and accurate histopathological criterion for distinguishing between septic and aseptic loosening of hip arthroplasty.

Suggestive linkage of the parathyroid receptor type 1 to osteoporosis.

Abstract: We have investigated the role of 23 candidate genes in the control of bone mineral density (BMD) by linkage studies in families of probands with osteoporosis (lumbar spine [LS] or femoral neck [FN] BMD T score < -2.5) and low BMD relative to an age- and gender-matched cohort (Z score < -2.0). One hundred and fifteen probands (35 male, 80 female) and 499 of their first- or second-degree relatives (223 males and 276 females) were recruited for the study. BMD was measured at the LS and FN using dual-energy X-ray absorptiometry and expressed as age- and gender-matched Z scores corrected for body mass index. The candidate genes studied were the androgen receptor, type I collagen A1 (COLIA1), COLIA2, COLIIA1, vitamin D receptor (VDR), colony-stimulating factor 1, calcium-sensing receptor, epidermal growth factor (EGF), estrogen receptor 1 (ESR1), fibrillin type 1, insulin-like growth factor 1, interleukin-1 alpha (IL-1α), interleukin-4 (IL-4), interleukin-6 (IL-6), interleukin-11 (IL-11), osteopontin, parathyroid hormone (PTH), PTH-related peptide, PTH receptor type 1 (PTHR1), transforming growth factor-beta 1, and tumor necrosis factors alpha and beta. Sixty-four microsatellites lying close to or within these genes were investigated for linkage with BMD. Using the program MapMaker/Sibs there was suggestive evidence of linkage between BMD and PTHR1 (maximum LOD score obtained [MLS] 2.7-3.5). Moderate evidence of linkage was also observed with EGF (MLS 1.8), COLIA1 (MLS 1.7), COLIIA1/VDR (MLS 1.7), ESR1 (MLS 1.4), IL-1α (MLS 1.4), IL-4 (MLS 1.2), and IL-6 (MLS 1.2). Variance components analysis using the program ACT, correcting for proband-wise ascertainment, also showed evidence of linkage (p ≤0.05) at markers close to or within the candidate genes IL- 1α, PTHR1, IL-6, and COLIIA1/VDR. Further studies will be required to confirm these findings, to refine the location of gene responsible for the observed linkage, and to screen the candidate genes targeted at these loci for mutations.

Cement migration after THR: A COMPARISON OF CHARNLEY ELITE AND EXETER FEMORAL STEMS USING RSA

Abstract: Studies using roentgen stereophotogrammetric analysis (RSA) have shown that the femoral components of cemented total hip replacements (THR) migrate distally relative to the bone, but it is not clear whether this occurs at the cement-implant or the cement-bone interface or within the cement mantle. Our aim was to determine where this migration occurred, since this has important implications for the way in which implants function and fail. Using RSA we compared for two years the migration of the tip of the stem with that of the cement restrictor for two different designs of THR, the Exeter and Charnley Elite. We have assumed that if the cement restrictor migrates, then at least part of the cement mantle also migrates. Our results have shown that the Exeter migrates distally three times faster than the Charnley Elite and at different interfaces. With the Exeter migration was at the cement-implant interface whereas with the Charnley Elite there was migration at both the cement-bone and the cement-implant interfaces.

Does arthritis progress in the retained compartments after 'Oxford' medial unicompartmental arthroplasty? A CLINICAL AND RADIOLOGICAL STUDY WITH A MINIMUM TEN-YEAR FOLLOW-UP

Abstract: We determined the outcome of 56 'Oxford' unicompartmental replacements performed for anteromedial osteoarthritis of the knee between 1982 and 1987. Of these, 24 were in patients who had died without revision, one was lost to follow-up and two had been revised. Of the remaining 29 knees, 26 were examined clinically and radiologically, two were only examined clinically and one patient was contacted by telephone. The mean age of the patients was 80.3 years. At a mean follow-up of 11.4 years (10 to 14) the measurements of the knee score, range of movement and degree of deformity were not significantly different from those made one to two years after operation, except that the range of flexion had improved. Comparison of fluoroscopically-controlled radiographs at a similar interval of time showed no change in the appearance of the lateral compartments. The retained articular cartilage continued to function for ten or more years which suggests that anteromedial osteoarthritis may be considered as a focal disorder of the knee. This justifies continued efforts to develop methods of treatment which preserve intact joint structures.

Osteoarthritis-Susceptibility Locus on Chromosome 11q, Detected by Linkage

Abstract: We present a two-stage genomewide scan for osteoarthritis-susceptibility loci, using 481 families that each contain at least one affected sibling pair. The first stage, with 272 microsatellite markers and 297 families, involved a sparse map covering 23 chromosomes at intervals of approximately 15 cM. Sixteen markers that showed evidence of linkage at nominal P

The neoplastic pathogenesis of solitary and multiple osteochondromas.

Abstract: Many theories of osteochondroma pathogenesis have been advanced. Genetic research into the inherited multiple form, hereditary multiple exostoses, has revealed a new family of tumour suppressor genes denoted EXT. Patterns of EXT gene mutation in hereditary multiple exostoses, in solitary and multiple osteochondromas, and in chondrosarcoma are analogous to those found in other tumour suppressor genes responsible for family cancer traits and associated malignancies. With one exception, most features of osteochondroma behaviour are comparable to those of benign neoplasms. The neoplastic pathogenesis of osteochondromas provides an alternative to the traditional ‘skeletal dysplasia’ theory to explain the growth disturbance associated with hereditary multiple exostoses. Recent studies on the physiological function of EXT genes are reviewed and implications for osteochondroma ‘cell-of-origin’ theories are discussed. Copyright © 1999 John Wiley & Sons, Ltd.

Leg lengthening over an intramedullary nail

Abstract: Distraction osteogenesis is widely used for leg lengthening, but often requires a long period of external fixation which carries risks of pin-track sepsis, malalignment, stiffness of the joint and late fracture of the regenerate. We present the results of 20 cases in which, in an attempt to reduce the rate of complications, a combination of external fixation and intramedullary nailing was used. The mean gain in length was 4.7 cm (2 to 8.6). The mean time of external fixation was 20 days per centimetre gain in length. All distracted segments healed spontaneously without refracture or malalignment. There were three cases of deep infection, two of which occurred in patients who had had previous open fractures of the bone which was being lengthened. All resolved with appropriate treatment. This method allows early rehabilitation, with a rapid return of knee movement. There is a lower rate of complications than occurs when external fixation is used on its own. The time of external fixation is shorter than in other methods of leg lengthening. The high risk of infection calls for caution.

One- or two-stage bilateral total hip replacement.

Abstract: It is not clear whether bilateral hip replacement should be done in 1 or 2 stages. The total number of total hip replacements (THRs) done in our center between 1989 and 1995 was approximately 4,000. The number of hips that were bilateral was 404, or 9% of the total number of THRs performed during this time period. Of these bilateral hip replacements, 190 (95 patients) were done as a 1-stage procedure, whereas 214 (107 patients) were done in 2 stages with 2 to 24 months in between the operations. In contrast to previous studies, there were no significant preoperative differences between the 2 groups of patients having 1-stage or 2-stage THRs, and, in particular, the comorbidity assessed by the American Society of Anesthesiologists (ASA) grade was not significantly different. Our results demonstrate that, in our patient population, bilateral THR was equally safe whether performed as a 1-stage or 2-stage procedure. This was the case in the low-risk (ASA 1 and 2) and high-risk (ASA 3 and 4) patient subgroups. One-stage bilateral THR is cheaper and involves less time in the hospital.

The assessment of shoulder instability

Abstract: We have developed a 12-item questionnaire for completion by patients presenting with shoulder instability. A prospective study of 92 patients was undertaken involving two assessments, approximately six months apart, performed in an outpatient department. Each patient completed the new questionnaire and the SF36 form. An orthopaedic surgeon completed the Constant shoulder score and the Rowe assessment. The new questionnaire and the Rowe clinical score each achieved a large standardised effect size (≥0.8) and compared favourably with relevant items on the SF36. By contrast, the Constant score barely registered any effect, confirming that it may be relatively insensitive to changes in clinical status for this particular condition. The questionnaire provides a measurement of outcome for shoulder instability which is short, practical, reliable, valid and sensitive to changes of clinical importance.

Stratification analysis of an osteoarthritis genome screen-suggestive linkage to chromosomes 4, 6, and 16

Abstract: To the Editor: We have previously carried out a two-stage genomewide linkage screen for osteoarthritis (MIM 165720) susceptibility loci, using an affected-sibling-pair approach (Chapman et al. 1999). In stage 1 of this screen, we tested 272 microsatellite markers in 297 families, each of which contained at least one pair of siblings who had undergone hip-, knee-, or hip and knee–replacement surgery for primary osteoarthritis. Loci that demonstrated evidence for linkage at nominal P=.05 were then taken through to stage 2, in which they were tested against a further 184 families. Sixteen markers within nine genomic regions from stage 1 had evidence of linkage, at P=.05. When the data for stages 1 and 2 were combined, the P value decreased for 3 of the 16 loci (D2S202, D11S907, and D11S903) and was constant for a 4th (D11S901). We subsequently concentrated our analysis on the chromosome regions to which these markers map. To test these linkages further, we genotyped additional markers and obtained maximum multipoint LOD scores (MLSs) of 1.2 for chromosome 2 and 3.1 for chromosome 11. Because there is evidence, from epidemiological, twin, and segregation studies, that the genetic contribution to osteoarthritis differs between the sexes and between different joint groups (Lindberg 1986; Cooper et al. 1994; Kaprio et al. 1996; Chitnavis et al. 1997; Felson et al. 1998), we stratified our chromosomes 2 and 11 linkage data according to sex and site of osteoarthritis (hip or knee). This stratification indicated that the suggestion of linkage to chromosome 2 was principally accounted for by affected sibling pairs with hip osteoarthritis (MLS 2.2), whereas the suggestion of linkage to chromosome 11 was restricted to affected female pairs (MLS 2.8). Because this analysis highlighted substantial differences between the strata tested, we have now reanalyzed stage 1 of our genome screen, for the remaining 20 autosomes, to determine whether any regions harbor susceptibility loci that are obscured in the unstratified data set. We stratified our stage 1 data into the same six strata tested in our analysis of chromosomes 2 and 11: affected females only (132 families), affected males only (60 families), hips only (194 families), knees only (34 families), female hip (85 families), and male hip (44 families). (A more detailed breakdown of these families can be found in the study by Chapman et al. [1999].) We did not stratify for female knee or male knee, because the number of families was too small (16 and 4, respectively) to allow reliable inference of linkage. Multipoint linkage analysis was performed on the stratified data by means of the ASPEX program. Ten of the 20 autosomes have one or more multipoint peaks with uncorrected MLS⩾1.0 for one or more of the six strata tested (table 1). The highest MLS is 3.9, for chromosome 4q in the female-hip strata, followed by 2.9, for chromosome 6 in the hip-only strata, and 2.1, for chromosome 16 in the female-hip strata. When we adjust MLS values to correct for the seven models tested (one unstratified analysis and six stratified analyses), by deducting from the original values (Kidd and Ott 1984), chromosome 4 has an MLS value of 3.1, chromosome 6 has an MLS value of 2.1, and chromosome 16 has an MLS value of 1.3. The uncorrected multipoint plots of these three chromosomes are shown in figure 1. Figure 1 Multipoint analysis. A, Chromosome 4, female hip (n=85 families) and female only (n=132 families). B, Chromosome 6, hip only (n=194 families). C, Chromosome 16, female hip (n=85 families) and female only (n=132 families). Table 1 Stratified MLSs The suggestion of linkage on chromosome 4 is centered on 4q12–4q21.2 and is restricted to female pairs with hip disease. Roby et al. (1999) have recently reported linkage of chromosome 4q to severe early-onset hip osteoarthritis in a large pedigree of Dutch origin. This locus maps to the telomeric end of 4q (4q35), placing it >50 cM distal to the linkage that we have observed. It is therefore unlikely that the two linkages have detected the same locus. More than 50 cM of chromosome 6 has an uncorrected MLS⩾2.0 in the hip-only stratum, between markers D6S257 and D6S262. This region of chromosome 6 contains a strong candidate gene for osteoarthritis, COL9A1 (6q12–6q13). This gene maps within the 11-cM interval between D6S257 and D6S286 and encodes the α1 chain of type IX collagen. This collagen is a quantitatively minor cartilage collagen that decorates the type II collagen fibril and that interacts with extrafibrillar macromolecules (Ayad et al. 1994). Two transgenic mouse models have demonstrated that mutations in the equivalent mouse gene can result in an osteoarthritis phenotype. In the first model, a truncated form of the gene resulted in mice with a mild osteochondrodysplasia phenotype and secondary osteoarthritis (Nakata et al. 1993). In the second model, a knockout mouse had no congenital abnormality but developed a severe osteoarthritis that was comparable, in timing and pathology, to human primary osteoarthritis (Fassler et al. 1994). A more detailed analysis of this second model revealed that the synthesis of the α1 polypeptide chain was necessary for type IX collagen assembly (Hagg et al. 1997). Chromosome 16 does not contain any known genes that can be considered as strong candidates for osteoarthritis susceptibility. As more genes are mapped, candidate loci on this chromosome may become apparent. Overall, the stratification of our genome screen has revealed additional chromosomal regions that may harbor susceptibility loci for osteoarthritis. Stratification increases the level of genetic homogeneity and can therefore assist in the mapping of loci for complex traits. Our analysis highlights the potential utility of this approach for osteoarthritis.

The length of the patellar tendon after unicompartmental and total knee replacement

Abstract: Patella infera may occur after reconstruction of the anterior cruciate ligament (ACL), high tibial osteotomy and total knee replacement (TKR). Restriction of movement of the knee and pain may result. Our aim was to compare the incidence and to assess the effects of patella infera after TKR and unicompartmental knee replacement (UKR). We reviewed radiographs of the knees of 84 patients who had had either TKR or UKR as part of a randomised, controlled trial. The length of the patellar tendon was measured on serial radiographs taken before, at eight months and at five years after operation. There was no significant change in the length of the patellar tendon after UKR, but a significant reduction was observed after TKR. Five years after the operation, the shortening of the tendon had increased to a mean of 3.5 mm. Of the knees with TKR reviewed at five years, 34% developed patella infera, defined as 10% or more of shortening, compared with 5% of those with UKR. Shortening was greatest in those knees which had required a lateral release; in this subgroup the mean shortening was 7.2 mm. Shortening correlated with restriction of movement and pain in the knee. Our study has shown that patella infera develops in most patients after TKR with lateral release, and in approximately 25% of patients after TKR without this additional procedure. Patella infera rarely occurs after UKR. It is associated with restriction of movement and pain in the knee. It may be an effect of the more extensive exposure required to perform TKR and may, in part, explain the better clinical results of UKR.

Cement migration after THR

Abstract: Studies using roentgen stereophotogrammetric analysis (RSA) have shown that the femoral components of cemented total hip replacements (THR) migrate distally relative to the bone, but it is not clear whether this occurs at the cement-implant or the cement-bone interface or within the cement mantle. Our aim was to determine where this migration occurred, since this has important implications for the way in which implants function and fail.Using RSA we compared for two years the migration of the tip of the stem with that of the cement restrictor for two different designs of THR, the Exeter and Charnley Elite. We have assumed that if the cement restrictor migrates, then at least part of the cement mantle also migrates.Our results have shown that the Exeter migrates distally three times faster than the Charnley Elite and at different interfaces. With the Exeter migration was at the cement-implant interface whereas with the Charnley Elite there was migration at both the cement-bone and the cement-implant interf...

Identification of novel pro-alpha2(IX) collagen gene mutations in two families with distinctive oligo-epiphyseal forms of multiple epiphyseal dysplasia.

Abstract: Summary Multiple epiphyseal dysplasia (MED) is a genetically heterogeneous disorder with marked clinical and radiographic variability. Traditionally, the mild “Ribbing” and severe “Fairbank” types have been used to define a broad phenotypic spectrum. Mutations in the gene encoding cartilage oligomeric-matrix protein have been shown to result in several types of MED, whereas mutations in the gene encoding the a2 chain of type IX collagen (COL9A2) have so far been found only in two families with the Fairbank type of MED. Type IX collagen is a heterotrimer of pro-a chains derived from three distinct genes—COL9A1, COL9A2, and COL9A3. In this article, we describe two families with distinctive oligo-epiphyseal forms of MED, which are heterozygous for different mutations in the COL9A2 exon 3/intron 3 splice-donor site. Both of these mutations result in the skipping of exon 3 from COL9A2 mRNA, but the position of the mutation in the splicedonor site determines the stability of the mRNA produced from the mutant COL9A2 allele.

Cytokine receptor profile of arthroplasty macrophages, foreign body giant cells and mature osteoclasts.

Abstract: In the arthroplasty pseudomembrane surrounding a loose prosthesis there is a marked macrophage and foreign body giant cell (FBGC) response to implant-derived wear particles. These cells contribute ...

Pyoderma gangrenosum - A diagnosis not to be missed

Abstract: We describe a case of pyoderma gangrenosum which presented with severe wound breakdown after elective hip replacement. The patient was treated successfully with minimal wound debridement and steroids. This diagnosis should always be considered when confronted with an enlarging painful skin lesion which does not grow organisms when cultured and fails to respond to antibiotic therapy, especially if there are similar lesions in other sites. In patients who have a past history of pyoderma gangrenosum, prophylactic steroids may be indicated at the time of surgery or may be required early in the postoperative period.

Does arthritis progress in the retained compartments after ‘Oxford’ medial unicompartmental arthroplasty?

Abstract: We determined the outcome of 56 ‘Oxford’ unicompartmental replacements performed for anteromedial osteoarthritis of the knee between 1982 and 1987. Of these, 24 were in patients who had died without revision, one was lost to follow-up and two had been revised. Of the remaining 29 knees, 26 were examined clinically and radiologically, two were only examined clinically and one patient was contacted by telephone. The mean age of the patients was 80.3 years. At a mean follow-up of 11.4 years (10 to 14) the measurements of the knee score, range of movement and degree of deformity were not significantly different from those made one to two years after operation, except that the range of flexion had improved. Comparison of fluoroscopically-controlled radiographs at a similar interval of time showed no change in the appearance of the lateral compartments. The retained articular cartilage continued to function for ten or more years which suggests that anteromedial osteoarthritis may be considered as a focal disorder of the knee. This justifies continued efforts to develop methods of treatment which preserve intact joint structures.

The pathology of bone allograft

Abstract: We analysed the histological findings in 1146 osteoarthritic femoral heads which would have been considered suitable for bone-bank donation to determine whether pathological lesions, other than osteoarthritis, were present. We found that 91 femoral heads (8%) showed evidence of disease. The most common conditions noted were chondrocalcinosis (63 cases), avascular necrosis (13), osteomas (6) and malignant tumours (one case of low-grade chondrosarcoma and two of well-differentiated lymphocytic lymphoma). There were two with metabolic bone disease (Paget's disease and hyperparathyroid bone disease) and four with inflammatory (rheumatoid-like) arthritis. Our findings indicate that occult pathological conditions are common and it is recommended that histological examination of this regularly used source of bone allograft should be included as part of the screening protocol for bone-bank collection.

Effect of rate of distraction on loss of range of joint movement, muscle stiffness, and intramuscular connective tissue content during surgical limb-lengthening: a study in the rabbit.

Abstract: Surgical lengthening of limbs often results in loss of range of joint movement and this has been shown to be associated with an increase in passive tension and an increase in collagen content of the muscles. In this study, we have investigated the length/tension properties and the connective tissue component of muscle distracted at three different rates in order to determine whether low rates of distraction would enable the connective tissue component, as well as the contractile component (number of serial sarcomeres), to adapt more completely to the increased functional length of the muscle and thus lead to improved range of joint movement. It was found that loss of range of movement varied with rate of distraction. At the low rate, there was no change in the passive tension or collagen content compared to muscles from sham-operated animals, and range of movement was significantly greater than at the other rates. At the medium rate, although the muscles showed good adaptation in terms of serial sarcomere number, passive tension and collagen content was increased and range of movement reduced, indicating that changes in the connective tissue component are important factors in loss of joint movement. In the case of muscle distracted at a high rate, failure of the muscle fibres to add on sufficient sarcomeres, combined with changes in the connective tissue, resulted in almost total loss of joint movement. Anat Rec 255:78–83, 1999. © 1999 Wiley-Liss, Inc.