CHAPTER XXI.
LUXATIONS OF THE CARPO-METACARPAL ARTICULATION.
Surgical Anatomy. — The articulation between the carpus and metacarpal bones is heavy and strong, and complete luxations of this joint are extremely rare. Promi a surgical standpoint the articu- lation may be divided into two parts : first, the articulation between the inner four metacarpals and the carpus, and second, the joint between the trapezium and first metacarpal. The articulations between the inner four metacarpals and the carpus are functionally one continuous joint. The synovial cavity extends from the second to the fifth joint and is not subdivided by the ligaments. The three inner carpal bones articulate with each other above the plane of this joint and the metacarpals below^ the joint articulate with each other by their lateral surfaces. The inner four metacarpal joints are arthrodial in type ; the fifth joint is capable of a wider range of motion than the other three. The carpo-metacarpal joint of the thumb is one of reciprocal reception (saddle joint) and per- mits of motion in all directions except axial rotation. The articu- lation between the first metacarpal and the trapezium is sur- rounded by a capsule, is separated from the other carpo-metacarpal articulations and has its own synovial membrane. All five carpo- metacarpal articulations are known to have been luxated, and all except that of the little finger have been reported as isolated in- juries. Dislocation may occur in one or more of the joints simul- taneously, and a number of instances of luxation of all five articu- lations have been recorded. Luxation may occur in any direction but the most common forms are either forward or backward. The lateral support which the inner four metacarpals ofi'er each other explains the rarity of lateral luxations. The carpo-metacarpal joint of the thumb is the most commonly luxated. Move disloca- tions of this joint have been reported than of the other four carpo- metacarpal articulations combined. Backward luxations of the carpo-metacarpal joint of the thumb are by far the most common.
294
LITXATIONS OF CARPO-METACARPAb ARTICULATION 295
Forward luxations are extremely rare. Luxations of this joint are not infrequently complicated by fracture of either the trape- zium or base of the first metacarpal or by luxation of the adjoining carpo-metacarpal joint of the index finger. Luxation of the carpo- metacarpal joint of the index finger is next in order of frequency and is more often displaced backward than forward. Luxations of the third, fourth and fifth carpo-metacarpal articulations are extremely rare. They may be either of the forward or backward tj^e. Subluxations, especially of the backward type, are not as rare in the four inner metacarpals as in complete luxation. Di- vergent luxations have been reported in which some of the meta- carpal bases have been displaced backward while others were luxated anteriorly. This form of dislocation, however, is extremely rare and can hardly be considered as a type. Severe crushing vio- lence in this region may produce almost any type of fracture- luxation as in the carpus, and because of the superficial position of the bones is likely to be compound.
Symptoms. — In luxations of the carpo-metacarpal joint of the thumb there will be loss of function, shortening of the thumb and characteristic deformity. In the backward type the base of the first metacarpal will be unduly prominent on the dorsal aspect of the carpus, just below the end of the radius. In the ventral type the trapezium may be palpated and the base of the metacarpal forms a hard prominence beneath the thenar eminence. Various degrees of angular deformity may be present as well as the over- riding displacement. The forward or backward displacement ac- companying luxations of any or all of the inner four articulations can be appreciated without difficulty if the case is seen early. If the injury is not examined before the onset of the traumatic reac- tion the swelling may be so pronounced that the nature of the deformity is not apparent. The shortening of the fingers, however, will be a symptom which will be evident even though the balance of the deformity is obscured by swelling.
Diagnosis. — Luxation of any one of these joints should be recog- nized without difficulty if the case is seen early. When four or five of the metacarpals are dislocated simultaneously the traumatic reaction may be so severe that diagnosis is rendered difficult unless the patient is anesthetized or the X-ray resorted to. Fracture of either the carpals or metacarpals is not an uncommon complication and is recognized by the presence of crepitus. If doubt exists the
296 FRACTURES AND DISLOCATIONS
X-ray should be employed. In interpreting X-rays of this region the anomalies mentioned under the Surgical Anatomy of "Injuries to the Carpus" on page 283, should be kept in mind.
Treatment. — Reduction is usually accomplished without diffi- culty by traction, counter-traction and direct pressure on the dis- placed metacarpal base or bases. Luxation of the carpo-metacarpal of the thumb is more likely to give trouble in reduction than are the corresponding joints of the other fingers. If reduction can- not be effected by manipulation open reduction may be necessary. A tendency to the recurrence of deformit}^ seldom occurs in any of these joints unless fracture complicates the luxation. Following reduction the wrist and hand (but not the fingers) should be im- mobilized on a short splint. The character of the splint is not essential as long as it fits the parts comfortably and effects immo- bilization.
Operative Treatment. — Operation is seldom indicated in the reduction of luxations of single joints. In luxations which can- not be reduced by manipulation the articulation should be exposed by a longitudinal incision and the displacement corrected by direct manipulation through the incision. Compound cases should be treated as described under "Treatment of Compound Fractures and Luxations" on page 789.
After-Treatment. — The after-care of these cases is practically the same as that already given under "Injuries to the Carpus" (page 292). Early passive motion is most important.
Prognosis. — The outlook in luxations of the carpo-metacarpal articulations is similar to that already given under "Injuries to the Carpus." Loss of function in the first carpo-metacarpal articu- lation will lead to difficulty in opposing the thumb against the fingers, and will constitute a serious handicap in the use of the hand. In compound cases the prognosis is much more unfavorable, especially in the presence of infection.