True Ankylosis of Knee from mechanical Injury (Cases VI. and VII.) False Ankylosis of Knee from Rheumatism (Cases VIII. and IX.) ON ANKYLOSIS IN GENERAL. Its Nature. - By ankylosis,* or stiff-joint, should be understood an unnatural rigidity of a joint, arising from causes operating in a direct manner on the structures immediately concerned in the articulation, and by which its natural movements are rendered impossible. The term includes also the idea of distortion and deformity, as, in the majority of the cases of ankylosis, the part is fixed in a position different from that assumed in the quiescent state of the limb, and accompanied with a change of form detracting from its symmetry. It is sometimes used synonymously with contracture; but I shall treat of it separately, and shew in what respect ankylosis and contracture differ. Ankylosis is divided into true and false, or complete and partial. When described as true or complete, a perfect ossific union of the articular surfaces of the bones, and consequent incapability of restoration to function, is supposed to have taken place. By false or partial ankylosis, on the contrary, is understood such a degree of impediment to the motions of the joint as materially interferes with its function, but without any union, or with merely membranous adhesion, of the articular surfaces. True ankylosis may be practically defined, as that state in which an incapability of movement between the articular surfaces exists; and false ankylosis, that in which * Ankylosis, or anchylosis, ǹ άykúλwois (åykúλn, a bending, flexure, more properly the bend of the elbow, the ham, a contracted joint, "contractos articulos aykúλas Græci nominant," Cels. v. 28), stiffness, rigidity, and adhesion of a joint, distortion. B limited mobility remains. This definition is anatomically correct; but if the apparent existence or non-existence of mobility were exclusively relied upon in diagnosis during life, serious errors would often be committed. Each of these divisions of ankylosis, according to chirurgical phraseology, may be angular or straight,* (orthocolon, τὸ ὀρθόκωλον; ὀρθός, straight; κωλον, a limb,) by which is meant that the joint may be ankylosed either in the bent or extended position of the part. Ankylosis may be simple or compound. In simple ankylosis, the rigid, more or less completely immovable articulation, has permanently assumed a position common in the natural temporary movements of the part. The ankylosis is compound when it is combined with a partial or complete luxation, that is, an unnatural displacement of the articular surfaces has also taken place. It will be hereafter shewn that this is, in some respects, an unfavourable complication. Causes of Ankylosis.-Inflammation is the cause of each variety and grade of ankylosis. Whether we regard it in its mildest form, producing effusion of lymph into the cellular tissue around an articulation, or survey the chronic ravages of the scrofulous variety, or the fearful disorganisation of its acuter forms, we perceive the same chain of phenomena; of which one or more links, according to the intensity and severity of the disease, may be absent; but the result, a greater or less degree of immobility or stiffness, is invariably present. In addition to the direct effects of inflammation in the production of ankylosis, a variety of other circumstances facilitate its progress and augment its severity. Among these are, the long-continued rest of the limb in one position, and the shortening of the muscular structures on the relaxed side of the member. Surgeons usually suggest, that during *The convenience, if not the necessity, of describing the ankylosis of a limb in the extended position as a straight ankylosis, may be conceded; but it is somewhat tautological to speak of an angular ankylosis. the continuance of disease in an articulation, it should be placed in that position which, in the event of ankylosis, would render it the most convenient and useful to the individual,the extended or slightly flexed position being recommended for the knee, the flexed for the elbow; but the rarity of straight ankylosis of the knee, and comparative frequency of this condition of the elbow, shew that in many cases the practitioner or patient is compelled to disregard the future, and content himself with the cure of the disease in that position which affords the greatest temporary ease. In the knee, the flexed or semi-flexed position is that commonly assumed by the patient; and the constancy with which it is maintained during the continuance of disease, is, even in slight inflammation, a powerful cause of the stiffening of the articulation in that form, through the consolidation of the plastic lymph effused into the inflamed tissues. The shortening of the muscular structures on the relaxed side of the articulation is, in the first instance, equally the result of the continued repose of the limb in the flexed position. The continued approximation of the origins and insertions of the flexor muscles induces a gradual shortening of their fibres, in consequence of the unceasing action of their inherent contractility, or vis insita; their antagonists, the extensors, are proportionately elongated, and after a short period their fibres become weakened. Thus, the equilibrium between these opposing sets of muscles being interrupted, the increase of the deformity becomes easy, provided other circumstances do not oppose its progress. It is not my intention, in these remarks on ankylosis, to examine narrowly the opinions of other authors, but rather to state the results of my own observation and experience. Whilst considering the mode in which contraction of the muscular structures ensues in these cases, I may, however, allude to the prevalent notion, that the inflammation in the articulation excites the irritability of the flexor muscles in particular, as in the knee, for instance, and that thus irritated, a preternatural activity of their fibres results. |