47 Metacarpal Phalangeal Hyperextension
47.1 Patient History Leading to the Specific Problem
A 54-year-old, right-hand-dominant woman presents with pain localized to the base of her right thumb. She describes the pain as “aching” and worse with movement. It has gradually progressed over the past 3 years and now wakes her at night. She works as a nurse and cashier, and notes pain with writing and opening twist-top pill containers. She takes ibuprofen and aspirin for the pain. She has worn a thumb brace for 6 months, without improvement of symptoms.
Examination of the right hand demonstrates a shoulder deformity at the base of thumb and adduction of the thumb metacarpal (▶Fig. 47.1a, b). Her metacarpophalangeal (MCP) joint rests in approximately 25 degrees of hyperextension; this can be passively stretched to 45 degrees of hyperextension (▶Fig. 47.1c). She has pain with both passive flexion and extension of the thumb metacarpal. A grind test is positive. Sensation and vascularity of the thumb is normal. Radiographs demonstrate an Eaton stage 4 carpometacarpal (CMC) arthritis and an MCP hyperextension deformity of 30 degrees. There is no evidence of MCP joint arthritis (▶Fig. 47.2).
47.2 Anatomic Description of the Patient’s Current Status
In addition to pain and difficulty with fine motor skills (twisting caps, using scissors, etc.), patients with basal joint arthritis will often complain of a visible thumb deformity. Attenuation of the CMC ligaments results in progressive dorsoradial subluxation of the metacarpal head on the trapezium and adduction of the thumb metacarpal. Concurrently, the extensor pollicis brevis (EPB) contributes to compensatory MCP joint hyperextension. This is commonly referred to as a zigzag or thumb collapse deformity. Key pinch will accentuate this deformity.
Compensatory MCP hyperextension is a pathologic component of basal joint arthritis that can lead to MCP arthritis and persistent pain after CMC arthroplasty. Addressing the MCP hyperextension deformity at the same time as CMC arthroplasty is important for an optimal surgical outcome. ▶Fig. 47.3 demonstrates a patient who underwent a prior CMC arthroplasty without addressing the MCP joint; postoperatively, she complains of persistent pain and deformity at the MCP joint.
Fig. 47.1 (a, b) Preoperative photographs of the right hand demonstrating a classic “shoulder deformity” and MCP hyperextension. (c) Accentuation of the MCP hyperextension with passive range of motion.
Fig. 47.2 Preoperative radiograph of the right hand demonstrating an Eaton stage 4 carpometacarpal arthritis with preservation of the MCP joint.
47.3 Recommended Solution to the Problem
The thumb MCP joint needs to be preoperatively evaluated in all cases of CMC arthritis. The degree of resting and passive MCP hyperextension should be measured. Pain and instability at the MCP joint should be examined clinically. Radiographs taken to stage the CMC arthritis can also be used to evaluate the integrity of the MCP joint and presence of MCP collapse.
There is no evidence that surgical intervention for mild MCP hyperextension (<25 degrees) offers any functional advantage. Surgical intervention for more severe deformity (>25 degrees) is generally accepted, but it remains controversial as to whether long-term outcomes demonstrate a significant benefit. Treatment options for MCP hyperextension address soft tissue and/or bone. There are limited data on each procedure and there are no randomized controlled trials that show superiority of one technique compared to another, or compared against nonoperative management.
In the cases where the MCP joint is preserved with minimal arthritis and passively reducible, soft-tissue procedures help reposition the thumb and place the MCP in a position that may be more functional and cosmetic. The more universally accepted soft-tissue procedures include tendon rebalancing and/or MCP volar plate arthroplasty. Both are outlined in the Technique section. We recommend that these procedures be done at the same time as CMC arthroplasty. Some degree of recurrence should be anticipated as the tendons and volar plate stretch over time.
In the cases of concomitantly advanced MCP and CMC joint arthritis, pain may originate from both joints. An arthritic thumb MCP joint is best managed with a combined MCP arthrodesis and CMC arthroplasty.
