Surgical Technique for the CMI Carpo Metacarpal Implant

1. Surgical Techniquefor theCMICarpo Metacarpal Implant

2. CONTENTS • INTRODUCTION • FEATURES OF CMI p.3-4 • Unipolar prosthesis p.5 • Bone savingp.6-7 • Anatomical metacarpal stem p.8 • Press-fit implant p.9 • Angled and offset head p.10 • INDICATIONS p.11 • INSTRUMENTATIONp.12 • SURGICAL TECHNIQUE • SURGICAL APPROACH p.13-14 • METACARPAL PREPARATION p.15-16 • TRAPEZIUM PREPARATIONp.17-19 • IMPLANT SELECTIONp.20 • LIGAMENTOPLASTY • APL strip dorsalisationp.21-22 • Distal ECRL strip transfer p.23-24 • WOUND CLOSUREp.25

3. INTRODUCTION The CMI trapezometacarpal resurfacing implant is designed to restore strength, mobility, and long-term stability to the failed or deficient trapezometacarpal joint. Unlike the trapezometacarpal prosthesis, its unipolar design and straight-forward surgical procedure allow achievement of a near anatomical joint function.

4. FEATURES • Unipolar prosthesis – no trapezium insert • Short metacarpal bone resection • Press-fit implant • Anatomical metacarpal stem • Angled and offset head for better stability

5. FEATURES Unipolar prosthesis • No trapezium insert • Metacarpal resurfacing only • Anatomic design

6. FEATURES Bone saving • Minimal resection of M1 • 3.5 mm resection of the first Metacarpal (from 7 to 10 mm for a trapezometacarpal prosthesis) • This technique allows other surgical alternatives in case of failure • Preservation of the thumb height

7. FEATURES Bone saving • The trapezium is not resected but milled. The procedure leads to the local milling of the arthrosic part of the trapezium (only 1-2 mm deep) • Bone saving compared to a trapezometarcarpal prosthesis • No risk of trapezium fracture or trapezial component migration. • Preservation of the thumb height • Maximal congruence of trapezometacarpal joint • Optimal partition of load on the trapezium • Flat trapezium milling stay possible

8. FEATURES Anatomical metacarpal stem • The ovoid Pyrocarbon Stem fits well in M1 thanks to its anatomical design • The CMI implant is stable. It does notrotate inside the diaphysis • Optimal partition of load inside M1 diaphysis

9. FEATURES Press-fit stem • The Pyrocarbon stem is impacted into the M1 shaft (press-fit) and does not require any cement

10. FEATURES Angled and offset head • The CMI Head is angled and offset to respect the metacarpal anatomy • Maximum congruence between the trapezium and the CMI implant • Prevents M1 subluxation 1 mm

11. INDICATIONS TMC degenerative arthritis POST OPERATIVE X-RAY

12. 1 2 INSTRUMENTATION 2 1

13. SURGICAL APPROACH A dorsal or dorso-radial approach is used. The trapezometacarpal joint is exposed. Care must be taken to avoid the palmar cutaneous branch of the median nerve and of the extensor pollicis brevis (EPB). The superficial branches of the median nerve are then gently dissected and the tendons are retracted to identify the joint line.

14. SURGICAL APPROACH The capsule is incised longitudinally, while preserving as much as possible of the articular capsule, scraping M1 base with a periosteal elevator. Osteophytes should be removed.

15. METACARPAL PREPARATION Insert the M1 cutting guide into the trapezometacarpal joint. The cutting guide is used to establish a 3.5 mm resection. M1 should be maintained in compression against the cutting guide. The cutting guide accepts saw blades with a maximal thickness of 0.5 mm and maximal breadth of 10 mm.

16. METACARPAL PREPARATION Prepare the metacarpal bone shaft by introducing the broaches centred on the previous resection. A mark on the instrument indicates the dorsal side and allows correct orientation of the implant. Press fit of final implant will be ensured using the biggest broach size that fits the bone shaft. To make the impaction and extraction of the broaches in the bone shaft easier, use the extractorscrewed on the broach handle.

17. TRAPEZIUM PREPARATION The metacarpal trial corresponding to the broach is introduced, ensuring its correct position thanks to its dorsal mark. Locate the contact point of the trial on the trapezium, thumb in neutral position.

18. TRAPEZIUM PREPARATION • Remove the trial. • With a sharp awl, perform a hole located in the previous targeted area. • Insert the reamer in the joint space and place the reamer central pin into the hole. • Prepare the implant head socket by milling the trapezium arthrosed part using the powered CMC reamer (low speed).

19. TRAPEZIUM PREPARATION A good axial compression will be maintained with the CMC reamer handle, and also a good compression on the trapezium, which should be strongly maintained. The joint is irrigated and cleared of debris.

20. IMPLANT SELECTION Re-insert the trial and check with X-ray, that the trapezium socket is sufficient to ensure, in conjunction with a ligamentoplasty, the joint stability. Control by X-rays

21. EPL Extensor Pollicis Longus Transfered APL Radial Bundle ECRL StripExtensor Carpi Radialis Longus EPB Extensor Pollicis Brevis LIGAMENTOPLASTY part 1 : APL strip dorsalisation A distal insertion of the Abductor Pollicis Longus (APL) is reinserted dorsally. The insertion must be advanced distally on the metacarpal and strongly anchored through the bone on the middle of M1. Do not tighten to allow definitive implant insertion.

22. LIGAMENTOPLASTY part 1 : APL strip dorsalisation The final implant is then implanted ensuring its correct orientation thanks to the implant holder. Impact the final implant with the plastic impactor. Warning • No other instrument should be used for impaction to avoid bearing surface alteration or damage. • Close the capsule and pull to apply some tension on the dorsalised APL.

23. LIGAMENTOPLASTY part 2 : Distal ECRL strip transfer Take a strip of the Extensor Carpi Radialis Longus (ECRL), preserving its distal insertion ; transfer the strip beneath the radial bundle and the Extensor Pollicis Longus (EPL). Thus this strip comes to double the capsule over the transfered APL.

24. Transfered APL EPL Extensor Pollicis Longus Transfered APL Radial Bundle ECRL strip ECRL StripExtensor Carpi Radialis Longus EPB Extensor Pollicis Brevis EPB LIGAMENTOPLASTY part 2 : Distal ECRL strip transfer This ECRL strip is finally inserted with some tension on the radial side of M1, trying to insert it as palmar as possible in order to favour thumb pronation.

25. WOUND CLOSURE Closure over a suction drain and immobilization in a "resting position“ for 3 to 4 weeks.

26. In Australia contact Orthopaedic Solutions at www.orthopaedicsolutions.com