Anatomy of the thumb MCP joint
The MCP joint of the thumb has features of both a condyloid and ginglymus joint (Eaton, 1971).
Its main movement is flexion-extension but it is also capable of some abduction-adduction and rotational movement. The thumb MCP joint dif-fers from the finger MCP joints by having a radial and an ulnar sesamoid in the volar plate between which passes the FPL tendon. Unlike the finger PIP joints, the MCP joint of the thumb has no flexor sheath proximal to the volar plate and also has no check-rein ligaments.
Lateral stability of the joint comes from col-lateral and accessory ligaments. Volar stability is provided by the volar plate together with the thenar intrinsic muscles. Flexor pollicis brevis and abductor pollicis brevis insert into the radial sesamoid. Adductor pollicis and the first palmar interosseous insert into the ulnar sesamoid (Kaplan and Riordan, 1984).
Ulnar collateral ligament injury
This injury is commonly referred to as ‘skier’s thumb’ and results from forced abduction of the MCP joint. The ulnar collateral ligament (UCL) is injured 10 times more frequently than the radial collateral ligament (Moberg and Stener, 1953). Distal tears at the insertion of the liga-ment are more common than proximal tears.
Injury to UCL may be associated with an avul-sion fracture where the ligament inserts onto the ulnar base of the proximal phalanx. It is impor-tant to distinguish between a partial and com-plete ligament rupture (Stener lesion). Where the rupture is complete, interposition of the adductor expansion will prevent the avulsed ligament from making contact with the rupture site, thereby impeding ligament healing.
Diagnosis
Diagnosis is generally made on a clinical basis, although diagnostic ultrasound and MRI (Har-ammati et al., 1995) can help confirm the diagnosis where necessary. Signs and symptoms of UCL injury include bruising, tenderness and swelling along the ulnar border of the joint. Where 30 degrees or more of joint laxity is present, it is usually assumed that there has been a complete ligament rupture. Paradoxically, a complete rup-ture will often be less painful than an incomplete one. Radiographs are taken in 3 planes to assess the base of the proximal phalanx for avulsion fracture. Significant displacement will indicate retraction of the ligament and a large displaced fragment involving the articular surface will require open reduction and internal fixation.
Treatment of stable ligament injury Partial tears are splinted continuously for 4 weeks in a hand-based thumb splint which holds the MCP joint in slight ulnar deviation and flexion (Campbell et al., 1992) (Fig. 11.16). Full mobility of the distal thumb joint is maintained during this time. Inter-mittent use of the splint is maintained for a further 2 weeks with the splint being removed every few hours for gentle active motion. Normal unrestrained use of the thumb is delayed until 12 weeks following injury.
Treatment for complete rupture of UCL Because the results of conservative treatment for complete rupture are unpredictable, surgical repair is indicated.
Figure 11.16. Partial tears of the ulnar collateral ligament are managed with a hand-based thumb splint which holds the MCP joint in slight ulnar deviation and flexion.
Joint injuries of the fingers and thumb 141
Surgery
A ‘lazy-S’ incision is made over the dorsum of the joint. Care is taken to protect the superficial radial nerve. The adductor aponeurosis is identi-fied and incised parallel to EPL. The articular surface of the joint is examined. If there has been a midsubstance rupture, a direct repair is made with interrupted non-absorbable sutures.
Some distal ruptures can be attached directly to the remaining tissue on the proximal phalanx.
Where there has been a small bony avulsion fracture, this is best excised and the ligament advanced to bone and anchored with non-absorb-able thread or wire. A temporary transarticular K-wire is used if the repair seems a little tenuous. A large bone fragment is anatomically reduced and attached by pull-out suture, inter-osseous wire, K-wires or a small screw.
Aftercare
The joint is protected with a hand-based thumb splint for a total period of 6 weeks. The distal thumb joint is mobilized throughout this period to avoid adherence of the extensor mechanism.
Splinting of the MCP joint is continuous for the first 4 weeks of immobilization. During the next 2 weeks, the splint is removed every few hours and gentle MCP joint exercises are carried out.
Unrestrained use of the thumb is delayed until 12 to 16 weeks following repair.
References
Bilos, Z. J., Vender, M. I., Bonavolonta M. and Knutson, K.
(1994). Fracture subluxation of the proximal interpha-langeal joint by palmar plate advancement. J. Hand Surg., 19A, 189–96.
Campbell, J. D., Feagin, J. A., King, P., et al. (1992). Ulnar collateral ligament injury of the thumb. Treatment with glove spica cast. Am. J. Sports Med., 20, 29–30.
Dennys, L. J., Hurst, L. N. and Cox, J. (1992). Management of proximal interphalangeal joint fractures using a new dynamic traction splint and early active movement. J.
Hand Ther., 5, 16–24.
Eaton, R. G. (1971). Joint Injuries of the Hand. pp. 51–66, Charles C. Thomas.
Eaton, R. G. (1995). The Founders Lecture: The narrowest hinge of my hand. J. Hand Surg., 20A, 149–54.
Harammati, N., Hiller, N., Dowdle, J., Jacobson. M., et al.
(1995). MRI of the Stener lesion. Skeletal Radiol., 24, 515–8.
Kaplan, E. B. and Riordan, D. C. (1984). The thumb. In Kaplan’s Functional and Surgical Anatomy of the Hand (M. Spinner, ed.) pp. 116–7, J. B. Lippincott.
Kiefhaber, T. R., Stern, P. J. and Grood, E. S. (1986). Lateral stability of the proximal interphalangeal joint. J. Hand Surg., 11A, 661–9.
Moberg, E. and Stener, B. (1953). Injuries to the ligaments of the thumb and fingers. Diagnosis, treatment and prognosis.
Acta Chir. Scand., 106, 166–86.
Morgan, J. P., Gordon, D. A., Klug, M. S., et al. (1995) Dynamic digital traction for unstable comminuted intra-articular fracture-dislocation of the proximal interphalan-geal joint. J. Hand Surg., 20A, 565–73.
Stern, P. J. (1991). Pilon fractures of the proximal inter-phalangeal joint, J. Hand Surg., 16A, 844–50.
Further reading
Abbiati, G., Delaria, G. E., Saporiti, E., et al. (1995). The treatment of chronic flexion contractures of the proximal interphalangeal joint. J. Hand Surg., 20B, 385–9.
Arnold, D. M., Cooney, W. P. and Wood, M. B. (1992).
Surgical management of chronic ulnar collateral ligament insufficiency of the thumb metacarpophalangeal joint.
Orthop. Rev., 21, 583–8.
Bowers, W. H. (1981). The proximal interphalangeal joint volar plate. II. A clinical study of hyperextension injury. J.
Hand Surg., 6, 77–81.
Dobyns, J. H. and McElfresh, E. C. (1994). Extension block splinting. Hand Clin., 10, 229–37.
Frykman, G. and Johansson, O. (1956). Surgical repair of rupture of the ulnar collateral ligament of the metacarpo-phalangeal joint of the thumb. Acta Chir. Scand., 112, 58–64.
Glickel, S. Z., Alton Barron, O. and Eaton, R. G. (1999).
Dislocations and ligament injuries in the digits. In Green’s Operative Hand Surgery (D. P. Green, R. N. Hotchkiss and W. C. Pederson, eds) pp. 772–808, Churchill Livingstone.
Green, A., Smith, J., Redding, M. and Akelman, E. (1992).
Acute open reduction and internal fixation of proximal interphalangeal joint fracture dislocation. J. Hand Surg., 17A, 512–7.
Green, D. P. (1990). Dislocations and ligamentous injuries of the hand. In Surgery of the Musculoskeletal System (C. M.
Evarts, ed.) pp. 385–448, Churchill Livingstone.
Heyman, P., Gelberman, R. H., Duncan, K. and Hipp, J. A.
(1993). Injuries of the ulnar collateral ligament of the thumb metacarpophalangeal joint–biomechanical and pro-spective clinical studies on the usefulness of valgus stress testing. Clin. Orthop., 292, 165–71.
Inanami, H., Ninomiya, S., Okutsu, I., et al. (1993). Dynamic external finger fixator for fracture dislocation of the prox-imal interphalangeal joint. J. Hand Surg., 18A, 160–4.
Jobe, M. T. ( 1993). Fractures and dislocations of the hand.
In Fractures and Dislocations (R. B. Gustilo, ed.) pp.
625–30, Mosby.
Mansat, M. and Delprat, J. (1992). Contractures of the proximal interphalangeal joint. Hand Clin., 8, 777–86.
Minamikawa, Y., Horii, E., Amadio, P. C., et al. (1993).
Stability and constraint of the proximal interphalangeal joint. J. Hand Surg., 18A, 198–204.
Noszian, I. M., Dinkhauser, L. M., Orthner, E., et al. (1995).
Ulnar collateral ligament: differentiation of displaced and nondisplaced tears with US. Radiology, 194, 61–3.
Tonkin, M. A., Beard. A. J., Kemp, S. J. and Eakins, D. F.
(1995). Sesamoid arthrodesis for hyperextension of the thumb metacarpophalangeal joint. J. Hand Surg., 20A, 334–8.
Wilson, R. L. and Hazen, J. (1995). Management of joint injuries and intra-articular fractures of the hand. In Reha-bilitation of the Hand: Surgery and Therapy (J. M. Hunter, E. J. Mackin and A. D. Callahan, eds) pp. 377–94, Mosby.
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