桡骨远端骨折掌侧锁定钢板固定时检测背侧螺钉穿出透视方法的研究与进展

文题释义： 桡骨远端骨折：约占平时骨折的1/10，多见于老年妇女，青壮年发生均为外伤暴力较大者。骨折发生在桡骨远端2.0-3.0 cm范围内，腕部肿胀、压痛明显，手和腕部活动受限。如果治疗不当，容易导致腕关节慢性疼痛和僵硬，严重影响手部的功能和活动，给患者造成不便。 掌侧锁定钢板：该钢板治疗桡骨远端骨折是现在普遍使用的内固定方法，相较于其他内固定方法，其首先能够增加大多数桡骨远端骨折的稳定性，允许患者能够进行早期活动；其次，和背侧钢板内固定相比较，能够减少腕掌侧与钢板的接触，避免对腕掌侧屈肌腱的刺激和磨损，同时大多数的钢板能够被旋前方肌覆盖。 背景：尽管桡骨远端骨折掌侧锁定钢板内固定治疗后所引发的桡骨远端腕背侧伸肌腱的激惹、磨损及断裂发生率不高，但这类并发症却严重影响着患者的生活质量。 目的：总结掌侧锁定钢板固定桡骨远端骨折时术中透视方法的最新进展。 方法：以英文“volar locking plate，distal radius fracture，radiological method”为检索词，应用计算机在PubMed数据库检索2000至2019年的相关文献共160篇；以中文“透视方法，桡骨远端骨折，掌侧接骨板”为检索词，应用计算机在万方数据库检索2000至2019年的相关文献共7篇。对掌侧锁定钢板固定桡骨远端骨折时术中透视方法的相关文献进行综述。 结果与结论：①桡骨远端骨折应用掌侧锁定钢板进行内固定时术中透视方法多种多样，例如标准正、侧位方法、腕管位透视法、“天际线”方法、背侧切线视图及径向凹槽视图等；②上述常用方法在检测掌侧锁定钢板内固定后背侧螺钉穿出问题仍具有一定局限性，所造成的腕背侧伸肌腱激惹、磨损及断裂等并发症仍有发生，二次及多次手术给患者生活及经济等方面带来的问题也应当引起重视；③应该找到更为恰当的术中检测方法，以期能够降低因掌侧锁定钢板内固定后背侧螺钉穿出所引发的并发症发生率。 ORCID: 0000-0002-3665-0270(王皓楠) 中国组织工程研究杂志出版内容重点：人工关节；骨植入物；脊柱；骨折；内固定；数字化骨科；组织工程     

带变向锁钉掌侧钢板DVRTM在不稳定桡骨远端骨折中的应用

背景：用锁定钉的最终固定依赖于钢板的放置,为避免螺钉锁入关节,要求在放入螺钉前反复确认骨折块的复位及钢板位置的放置,无疑增加了操作繁琐及螺钉进入关节的风险。 目的：观察新型带变向螺钉的解剖型掌侧锁定钢板DVR^TM治疗不稳定桡骨远端骨折的疗效。 方法：21例不稳定桡骨远端骨折患者,AO分型A3型3例,B2型3例,B3型2例,C1型3例,C2型5例,C3型5例。受伤后0~12 d采用带变向螺钉的解剖型掌侧锁定钢板DVR^TM治疗。 结果与结论：随访至24周时,所有患者均获得骨性愈合,无软组织并发症,无螺钉移位及钢板断裂,影像学及功能评估满意。据此得出,对于不稳定桡骨远端骨折,这种固定方式能提供解剖复位、固定确切、并发症发生率低,钉板之间能更灵活、弹性的搭配。     

DVR解剖型桡骨掌侧锁定接骨板置入内固定治疗桡骨远端C型骨折：与普通掌侧接骨板的比较

背景：纵观目前治疗粉碎及不稳定桡骨远端骨折的各种方法,金属材料桡骨掌侧锁定接骨板的优点日益突出。 目的：观察DVR解剖型桡骨掌侧锁定接骨板置入内固定治疗桡骨远端AO分型C型骨折的效果。 方法：纳入AO分型桡骨远端C型骨折患者51例,根据其意愿及经济状况非随机分为2组,实验组27例应用DVR解剖型桡骨掌侧锁定接骨板,对照组24例应用普通掌侧接骨板。对比两组患者在手术时间、术中C臂透视次数,术中接骨板安装次数,正中神经炎发生、术后腱鞘炎发生、腕关节功能恢复时间6个方面的差异。 结果与结论：实验组X射线片显示骨折全部Ⅰ期愈合,均无感染、骨不连、钢板松动、正中神经炎等并发症。和同期普通掌侧接骨板治疗方法相比,具有明显的优势,Mcbride腕关节功能恢复优良率明显高于对照组(P < 0.001)。提示使用DVR解剖型桡骨掌侧锁定接骨板置入内固定治疗桡骨远端C型骨折具有操作更加便捷,安全可靠,完全解剖复位,固定坚强,可早期进行功能锻炼,关节功能恢复优良等优点。     

选择钢板在桡骨远端不稳定性骨折治疗中的作用

目的:探讨不同类型钢板在治疗桡骨远端不稳定性骨折中的疗效及临床价值。方法:以"锁定加压钢板,T型钢板,桡骨远端,骨折,内固定"为中文关键词;以"Locked compression plate,Tplate,Distal radius,fracture,internal fixation"为英文关键词,应用计算机检索(2006-02/2010-03)相关文章。纳入与有关桡骨远端不稳定型骨折内固定治疗的文章;排除重复研究或Meta分析类文章。共纳入28篇文献。结果:桡骨远端不稳定性骨折内固定治疗以T型接骨板、掌侧锁定加压钢板、多轴锁定钢板及π钢板为主,而锁定钢板因能提供较好的生物稳定性,目前临床广泛应用。结论:钢板治疗桡骨远端不稳定性骨折临床疗效满意,对比普通T型接骨板,锁定钢板能提供更好的骨折块稳定性,保护血运,且并发症少,可作为治疗此种骨折的首选方法之一。     

螺钉间夹角对桡骨远端不稳定骨折接骨板应力影响仿真研究

目的比较4种螺钉间夹角排布对治疗桡骨远端不稳定骨折的术后掌侧接骨板应力分布情况,并找出最优固定角度。方法选取1例健康男性志愿者,对其左手桡骨分别建立含骨折断面和骨痂的桡骨远端不稳定骨折的三维有限元模型。掌侧锁定钢板远端螺钉间夹角分别采用0°、5°、10°、15°。选择竖直提起重物情况作为生理载荷和约束条件,在竖直方向施加100 N的载荷,模拟手臂提起重物的情况,并计算分析出4种不同螺钉排布角度情况的应力分布。通过比较4种排布方式,选择出其中应力最小的排列方式。结果螺钉间夹角0°～15°时最大应力分别为580.06 MPa、493.13 MPa、594.38 MPa和604.20 MPa。在螺钉间夹角5°的情况下竖直提起重物,掌侧锁定钢板上的最大应力小于其他螺钉间夹角排列方式。结论增加远端头部螺钉夹角角度确实能降低接骨板的局部应力。采用螺钉间夹角5°的排列方式可以有效地防止掌侧锁定接骨板应力集中,提高掌侧锁定接骨板使用寿命。     

掌侧锁定钢板内固定与外固定支架修复桡骨远端不稳定性骨折:随机对照

背景:桡骨远端不稳定性骨折是成人最常见的骨折之一,尽管目前治疗方法较多,但是最佳的修复方法仍存争议。目的:采用前瞻性随机对照的方法比较外固定支架与锁定钢板内固定修复桡骨远端不稳定性骨折的临床效果、并发症及影像学结果。方法:纳入2011年9月至2013年9月收治的122例桡骨远端不稳定性骨折患者,按随机数分配表分为两组,外固定组61例采用闭合复位外固定支架治疗,钢板组61例采用切开复位掌侧锁定钢板内固定治疗。比较两组患者住院天数、骨折愈合时间、腕关节功能及并发症发生率。影像学评估骨折复位质量,包括掌倾角、尺偏角、桡骨高度及关节面台阶等。结果与结论:外固定组随访时间12-26个月,钢板组随访时间12-28个月,两组患者随访时间差异无显著性意义(P=0.300)。比较两组患者治疗后临床疗效和影像学结果,发现钢板组患者的住院天数、骨折愈合时间以及术后掌倾角恢复程度明显大于外固定组,而两组患者尺偏角、桡骨高度、腕关节功能、术后并发症发生率以及关节面台阶等方面的差异无显著性意义(P0.05)。提示对于桡骨远端不稳定性骨折,采用外固定支架或掌侧锁定钢板治疗,均可获得满意的临床疗效,但是外固定治疗具有创伤较小、住院天数较短、并发症轻微、骨折愈合较快等优点,尤其适用于老年桡骨远端骨折的修复。     

掌侧锁定钢板治疗桡骨远端Die-punch骨折的疗效分析

目的探讨掌侧锁定钢板治疗桡骨远端Die-punch骨折的临床疗效。方法回顾分析了2014年6月至2015年6月间收治的22例桡骨远端Die-punch骨折病例,所有病例均采用掌侧入路切开复位锁定钢板内固定,并对治疗结果进行定期随访,测量术后不同时间腕关节的活动范围以及肌力并予以功能评分,检查术后的X线以及CT了解骨折复位情况、内固定位置以及骨折愈合情况。结果所有22例病例均获得随访,随访时间12~15个月,平均13个月。骨折均骨性愈合,无内固定松动。腕关节Gartland-Werley评分:优8例,良12例,可2例,差0例。结论掌侧锁定钢板治疗桡骨远端Die-punch骨折的临床疗效满意。     

背侧克氏针增强AOC型桡骨远端骨折尺背侧骨折块稳定性的有限元分析

背景：波及尺背侧骨折块的桡骨远端骨折属于不稳定型骨折,属于AO分型的23C型、三柱分型中波及中间柱的骨折,尺背侧骨折块不能得到有效固定,将影响桡腕关节和下尺桡关节的稳定性,而当前单纯掌侧钢板固定尺背侧骨折块的作用有限,若附加背侧钢板虽然固定效果好,但将增加手术创伤、导致肌腱损伤粘连,并提高了治疗费用,不符合当前疾病诊断相关分组的政策,附加背侧克氏针固定是个较为可行的方案。目的：通过建立AO/ASIF 23-C1桡骨远端骨折的有限元模型,比较掌侧锁定钢板和掌侧锁定钢板附加背侧克氏针两种内固定方式生物力学稳定性的差异,尤其关注尺背侧骨折块的固定效果,为临床应用提供参考。方法：利用逆向建模技术,将42岁男性志愿者健康前臂CT数据及内固定数据导入相关软件,分别建立AO/ASIF 23-C1桡骨远端骨折掌侧锁定钢板和掌侧锁定钢板附加背侧克氏针内固定三维有限元模型。对模型分别施以100 N轴向载荷、1 Nm的弯曲及扭转载荷,比较两组尺背侧骨折块最大位移、内固定上最大Von Mises应力及应力分布等指标。结果与结论：(1)两种固定方式下,内固定上的应力均2-10倍于骨骼,符合骨折早期稳定的要求;(...     

不同长度锁钉固定桡骨远端不稳定骨折的生物力学比较

目的 比较不同长度锁定螺钉固定桡骨远端骨折的术后稳定性及不同时期骨痂和远端螺钉的应力分布情况,为桡骨远端骨折螺钉长度的选择提供生物力学依据。方法 分别建立含骨折断面和骨痂的桡骨远端不稳定骨折的三维有限元模型,并用掌侧锁定钢板和不同长度锁钉固定,通过赋予骨痂不同材料属性来模拟骨折术后不同时期。分析术后不同时期骨痂和远端螺钉的应力分布情况,同时根据骨折断面最大轴向位移计算整个固定系统的压缩刚度。 结果 对于相同轴向载荷,75%长度以上单皮质螺钉固定时压缩刚度与双皮质螺钉固定相比基本无差异;术后早期骨痂处最大应力随着螺钉长度增加逐渐变小;术后中后期远端螺钉最大应力随着螺钉长度增加逐渐变大,远端双皮质螺钉应力最大。结论 采用75%长度以上单皮质锁钉固定桡骨远端不仅可以达到早期稳定性,同时也避免伸肌腱并发症的发生。     

微创掌侧锁定加压钢板治疗老年桡骨远端骨折的疗效分析

目的　探讨微创掌侧锁定加压钢板治疗老年桡骨远端骨折的临床疗效。  方法　2008年1月至2013年1月,30例老年桡骨远端骨折患者从掌侧入路实施微创技术置入锁定加压钢板。AO/ASIF分型：A2型3例,A3型5例,B1型5例,B3型6例,C1型6例,C2型5例。  结果　25例患者术后获得随访,平均时间为12个月（8月～14个月）。患者当中发生腕管综合征1例,大鱼际肌麻痹1例,腕部切口延迟愈合1例,术后3个月症状消失,未见桡骨不愈合。采用改良Mcbride评分进行评定：优18例,良4例,可3例,优良率达88%。  结论　经掌侧入路微创锁定加压钢板治疗老年桡骨远端骨折,创伤小,固定牢靠,术后并发症少,有利于早期功能锻炼,为较理想的固定方式。     

构建前柱钢板髋臼区安全置钉的三维模型

背景：切开复位钢板置入内固定治疗髋臼前柱骨折时,螺钉穿入关节面的情况时有发生,为预防该并发症,对前柱钢板技术髋臼区安全置钉的定量解剖学测量非常有必要。目的：为前柱钢板髋臼区安全置钉提供解剖学依据。方法：利用Mimics软件对40例男性、40例女性骨盆CT进行三维重建,使用软件的切割工具制作前柱髋臼系列断面。使用软件测量工具,对各断面上不同进钉点的安全进钉方向及长度进行测量。将数据输入SPSS 13.0软件进行统计学分析。结果与结论：髋臼前后缘、前缘到髂耻隆起的距离,分别为男性(56.63±2.05) mm,(12.30±1.51) mm;女性(49.07±5.07) mm,(16.93±1.74) mm;髋臼后缘到髂耻隆起的距离为男性(45.46±3.44) mm,女性(33.72±6.85) mm。螺钉在矢状面与髂骨板的夹角为男性(72.17±0.93)°,女性(81.05±0.92)°。B、C和D各断面,斜冠状面上螺钉与髂骨板的最大夹角分别为男性(53.88±3.01)°,(43.22±1.86)°,(54.60±2.97)°;女性(49.54±1.81)°,(39.10±1.22)°,(47.91±2.23)°。提示利用三维模型测量前柱髋臼区解剖特点,对于前柱骨折钢板置入内固定过程中避免螺钉进入关节有重要的指导意义。中国组织工程研究杂志出版内容重点：人工关节;骨植入物;脊柱;骨折;内固定;数字化骨科;组织工程全文链接：     

Dyschondroplasia/osteochondrosis of the femoral trochanter in the fowl

Of 104 lame broilers, 12 birds with femoral trochanteric abnormalities were identified by post-mortem and radiographic examination. Defects occurred in ossification of either the trochanteric zenith or its medial aspect. Lesions were identified as dyschondroplasia, osteochondrosis or osteochondrosis dissecans affecting the articular surface of the femoral trochanter. In the absence of concomitant musculoskeletal disease, degrees of lameness can be attributed to trochanteric lesions. Breaches in the medial trochanteric bone plate permit granulation tissue repair of the articular surface. This repair process, however, did not compensate for the loss of articular surface contour and the junction of reparative and normal tissue may be prone to subsequent degeneration.     

Mechanical and histological response of carbon fibre pads implanted in the rabbit patella

Small carbon fibre pads (3 mm in diameter) were implanted into rabbit patellae to ascertain the relationship between their mechanical and histological responses. After 3 months a highly vascularized collagenous matrix is formed within and around the implant securely anchored to the bone and providing a continuous layer to the articular surface. Mechanically, the resulting repair is much more compliant than the original articular cartilage/bone structure since the subchondral bone plate is not present within the implant; it also provides a functioning congruent surface with no evidence of fragmentation. This may be attractive in the long term by decreasing friction and the subsequent degeneration and wear commonly seen in fibrillated, disrupted articular cartilage.     

Exercise‐induced metacarpophalangeal joint adaptation in the Thoroughbred racehorse

Repetitive bone injury and development of stress fracture is a common problem in humans and animals. The Thoroughbred racehorse is a model in which adaptive failure and associated development of stress fracture is common. We performed a histologic study of the distal end of the third metacarpal bone in two groups of horses: young Thoroughbreds that were actively racing (n = 10) and a group of non‐athletic horses (n = 8). The purpose of this study was to determine whether development of articular microcracks was associated with specific alterations to subchondral plate osteocytes. Morphometric measurements were made in five regions of the joint surface: lateral condyle, lateral condylar groove, sagittal ridge, medial condylar groove, and medial condyle. The following variables were quantified: hyaline cartilage width; calcified cartilage width; the number of tidemarks; microcrack density at the articular surface; blood vessel density entering articular cartilage; the presence of atypical bone matrix in the subchondral plate; bone volume fraction; and osteocyte density. Adaptation of articular cartilage was similar in both groups of horses. Vascularization of articular cartilage was increased in the group of non‐athletic horses. Microcracks, which typically had an oblique orientation to the joint surface, were co‐localized with blood vessels, and resorption spaces. Microcracking was increased in the condylar grooves of athletic horses compared with the other joint regions and was also increased compared with the condylar groove regions of non‐athletic horses. Coalescence of microcracks also led to development of an intracortical articular condylar stress fracture in some joints and targeted remodeling of affected subchondral plate. The subchondral plate of the condyles in athletic horses was sclerotic, and contained atypically stained bone matrix with increased numbers of osteocytes with atypical morphology. However, osteocyte numbers were not significantly different between groups. We conclude that differences in site‐specific microdamage accumulation and associated targeted remodeling between athletic and non‐athletic horses are much greater than differences in subchondral osteocyte morphology. However, the presence of atypical subchondral bone matrix in athletic horses was associated with extensive osteocyte loss. Although osteocyte mechanotransduction is considered important for functional adaptation, in this model, adaptation is likely regulated by multiple mechanotransduction pathways.     

The distribution of Notch receptors and their ligands during articular cartilage development

We examined the distribution of Notch family members and their ligands during the development of articular cartilage and the growth plate. Notch 1 was expressed by the chondrocytes of the developing articular surface but became increasingly restricted to the deeper layers after birth whilst expression of this family member was restricted to hypertrophic chondrocytes in the growth plate. Notch 2 and 4, Delta and Jagged 2 showed a broadly similar distribution, being present throughout the articular cartilage during development and becoming increasingly restricted to deeper layers with age. Hypertrophic chondrocytes within the growth plate also expressed Notch 2 and 4, Delta and Jagged 2 (which was also expressed in prehypertrophs). Notch 3 and Jagged 1 were absent from developing articular cartilage but were present in deeper layers at later time points (> 1 month) and both receptor and ligand were expressed in hypertrophic chondrocytes at all ages examined. These results highlight the complex Notch signalling interactions that result in the formation of the heterogeneous articular cartilage and allow for the co-ordinated ossification and elongation of the growth plate. Mechanisms by which these processes are controlled are discussed in light of recent advances in the understanding of Notch signalling pathways.     

解剖型钢板和锁定钢板内固定修复胫骨远端Pilon骨折

背景：Pilon骨折切开复位内固定的难点在于关节面的重建和软组织保护,解剖型钢板和锁定钢板具有三维固定等优点,与以往普通固定材料相比有一定优势。 目的：探讨解剖型钢板和锁定钢板的结构特点以及在胫骨远端Pilon骨折关节面解剖复位的疗效。 方法：对2004-03/2010-08收治的79例Pilon骨折患者进行回顾性研究,其中开放性损伤22例,闭合性损伤57例,Ruedi-Allgower Ⅱ型31例,Ⅲ型48例;部分开放性损伤者行急症处理,闭合性损伤者于伤后7~12 d进行切开复位内固定;根据骨折的不同形态和软组织损伤情况,分别采用切开复位解剖型钢板和锁定钢板内固定,或胫骨外固定支架固定。 结果与结论：所有患者均获得4~19个月随访,应用Tornetta评分系统评估治疗效果,Ruedi-Allgower Ⅱ型优良率为97%,Ruedi-Allgower Ⅲ型优良率为79%;Ruedi-Allgower Ⅲ型患者中,行切开复位内固定患者的优良率达88%,支架外固定患者关节功能恢复均不满意;外固定者创面均有浅部感染及部分软组织坏死,经对症处理全部愈合,未发生骨髓炎及骨不愈合情况。结果可见应用解剖型钢板和锁定钢板内固定治疗胫骨远端Pilon骨折疗效理想,治疗要点在于保留软组织覆盖和重建稳定的关节面。     

Role of uppermost superficial surface layer of articular cartilage in the lubrication mechanism of joints

The uppermost superficial surface layer of articular cartilage, the 'lamina splendens' which provides a very low friction lubrication surface in articular joints, was investigated using atomic force microscopy (AFM). Complementary specimens were also observed under SEM at −10 °C without dehydration or sputter ion coating. Fresh adult pig osteochondral specimens were prepared from the patellas of pig knee joints and digested with the enzymes, hyaluronidase, chondroitinase ABC and alkaline protease. Friction coefficients between a pyrex glass plate and the osteochondral specimens digested by enzymes as well as natural (undigested) specimens were measured, using a thrust collar apparatus. Normal saline, hyaluronic acid (HA) and a mixture of albumin, globulin, HA (AGH) were used as lubrication media. The surface irregularities usually observed in SEM studies were not apparent under AFM. The articular cartilage surface was resistant to hyaluronidase and also to chondroitinase ABC, but a fibrous structure was exhibited in alkaline protease enzymes-digested specimens. AFM analysis revealed that the thickness of the uppermost superficial surface layer of articular cartilage was between 800 nm and 2 μm in adult pig articular cartilage. The coefficient of friction (c.f.) was significantly higher in chondroitinase ABC and alkaline protease enzymes digested specimens. Generally, in normal saline lubrication medium, c.f. was higher in comparison to HA and AGH lubrication media. The role of the uppermost, superficial surface layer of articular cartilage in the lubrication mechanism of joints is discussed.     

Age-related changes in the articular cartilage of human sacroiliac joint

 Iliac and sacral articular cartilage of 25 human sacroiliac joints (1–93 years) are examined by light microscopy and immunohistochemistry in order to gain further insight into the nature and progress of degenerative changes appearing during aging. These changes can already be seen in younger adults as compared to cartilage degeneration known in other diarthrodial joints. Structural differences between sacral and iliac cartilage can already be observed in the infant: the sacral auricular facet is covered with a hyaline articular cartilage, reaching 4 mm in thickness in the adult and staining intensely blue with alcian blue at pH1. Iliac cartilage of the newborn is composed of a dense fibrillar network of thick collagen bundles, crossing each other at approximately right angles. A faint staining with alcian blue suggests a low content of acidic glycosaminoglycans. In the adult, iliac cartilage becomes hyaline and its maximal thickness reaches 1–2 mm. Both articular facets exhibit morphological changes during aging that are more pronounced in the iliac cartilage and resemble osteoarthritic degeneration; the staining pattern of the extracellular matrix becomes inhomogenous, chondrocytes are arranged in clusters and the articular surface develops superficial irregularities and fissures. Sometimes fibrous tissue fills up these defects. Nevertheless, large areas of iliac cartilage remain hyaline in nature. Sacral articular cartilage often remains largely unaltered until old age. The sacral subchondral bone plate is usually thin and shows spongiosa trabeculae inserted at right angles, suggesting a perpendicular load on the articular facet. Iliac subchondral spongiosa shows no definite alignment and joins the thickened subchondral bone plate in an oblique direction. The iliac cartilage therefore seems to be stressed predominantly by shearing forces, arising from the changing monopodal support of the pelvis during locomotion. The subchondral bone plate on both the iliac and sacral auricular facet is penetrated by blood vessels that come into close contact with the overlying articular cartilage. These vessels may contribute to the high incidence of rheumatoid and inflammatory diseases in the human sacroiliac joint. Immunolabelling with an antibody against type II collagen reveals a diminished immunoreactivity in the upper half of adult sacral cartilage and only a faint and irregular labelling in the iliac cartilage. Type I collagen can be detected in a superficial layer on the sacral articular surface and around chondrocyte clusters in iliac cartilage, as in dedifferentiating chondrocytes during the development of osteoarthritis. Accepted: 22 April 1998     

Thinning of articular cartilage in the domestic fowl

Thinning of articular cartilage was identified in pelvic limb joints of broiler and Leghorn-type fowls. Almost all of 100 fowls examined showed cartilage thinning or loss in hip and knee joints. Particular attention was paid to proximal femora; in these, the principal mechanism of cartilage loss involved processes described as "peripheral remodelling". From the edge of cartilage sheets, fibrovascular tissue removed articular cartilage by two mechanisms. Either a pannus of fibrovascular tissue covered the articular surface or non-osseous tissue invaded through discontinuities in the bone plate. As in man, peripheral remodelling appears to be age-related and unrelated to regressive or destructive cartilage loss.