CMC Arthroplasty in the Apert Hand and Creation of a Functional Grip
Kimberly S. Khouri, MD and Joseph Upton, MD, MGB Harvard Plastic Surgery, Boston, MA
Introduction: The 4th-5th metacarpal synostosis, present in over 80% of Apert hands, flattens the metacarpal arch, restricts metacarpal descent, may prevent opposition of border rays, and combined with symphalangism, negates any functional flexion. Ironically, the fifth ray is the most intact portion of the hand. Restoration of mobility and position with arthroplasty changes the cardinal plane of flexion and enables both pinch and grip. This report summarizes the evolution of our technique over five decades.
Methods: In a cohort of 184 Apert patients (368 hands) the presence, anatomy, and level of the metacarpal synostosis with a classification was determined. The present technique consists of incision along ulnar border of hand, wide excision of the skeletal coalition, soft tissue interposition (with cadaveric fascia lata graft ) with the fifth metacarpal flexed and supinated. No fixation is needed. The arthroplasty was commonly combined with a thumb lengthening procedure, such as opening wedge osteotomy plus autogenous bone graft at 2-6 years or distraction lengthening and bone graft at 11-13 years old. Silicone blocks, silicone sheeting, and autogenous tendon were also used as interpositions early in the series. Data was generated over a 45 period and consisted of clinical and operative records, serial molds, serial X-rays, and OT records. Follow-up ranged from 3 to 44 years.
Results: 80% of the hands (N=147 patients) had bilateral 4-5th metacarpal synostoses, the extent of which correlated with the Apert hand classification. CMC arthroplasties were performed in 79 hands using silicone blocks (4%) silicone sheeting (4%), tendon (2%), and cadaveric fascia lata (94%). Synostosis refusion occurred in 38 hands, all of which were performed early in the series and under the age of 6 years. Despite refusion, the position of the 5th digit was always improved (Figure 1). Eight of these hands were re-released, often in conjunction with thumb distraction lengthening. Distance between the opposing border rays was always improved and a new grip and pinch mechanism created.
Conclusion: Aggressive ostectomy of synostosis and fascial interposition places the ulnar side of the hand in a much more functional position. In conjunction with thumb lengthening, opposition between the thumb and fifth finger becomes a clinical reality in Apert children who are born with diminutive thumbs and minimal interphalangeal joint motion.
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