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Bilateral Capitate-Hamate Coalition With Bilateral Carpal Bossing – Likely Aetiology And A Novel Surgical Technique-A Case Report

Omar Mohamed*, Martyn Neil**

* Senior House Officer
**Specialist Registrar 
Department of Orthopaedics, Altnagelvin Hospital, N. Ireland

Address for Correspondence:
Mr. O. Mohamed
Department of Orthopaedics
Level 9, Altnagelvin Hospital, Glenshane Rd., Londonderry, BT47 6SB, 
N. Ireland.
Tel    : +447795594077


We report the case of a 36 year old female with bilateral painful carpal bossing with underlying bilateral capitate-hamate coalitions.  Unilateral debulking surgery involved removal of ECRL at its tendinous insertion.  This resulted in significant relief of her pain.  Our experience highlights a likely association between carpal coalitions and the ‘congenital’ carpal boss.  It also strengthens the hypothesis that painful bossing is secondary to repetitive strain injury at ECRL/B tendon insertions, and where indicated, ECRL insertion detachment may afford significant relief of symptoms.
Keywords: Carpal coalition; ECRL; Boss

J.Orthopaedics 2007;4(2)e31


Case Report:

A 36 year old female presented with bilateral symptomatic carpal bossing and radiographs revealed bilateral capitate-hamate coalitions.  The bossing had been present since childhood but lately would ache with strenuous use of her hands.  Previous surgery to debulk the boss in each hand was unsuccessful.  At re-operation on her left hand, debulking involved ECRL tendon attachment which was inserting into the boss.  It was re-attached at the end of the procedure to nearby soft tissue with absorbable suture.  

At follow-up after 3 months, the patient’s symptoms had significantly improved in that hand.  She is awaiting a repeat procedure on the other hand. 

Discussion :

Carpal bossing is a bony prominence over the dorsum of the wrist, typically over the 2nd and 3rd metacarpal bases1.  It is not an uncommon condition for which surgical intervention is not always successful2.  Most patients present with new onset of swelling on the dorsum of the wrist which may or may not be symptomatic.  In a group of patients the swelling appears to be congenital.  The aetiology of carpal bossing is yet unclear, with various theories put forward.  These include rupture of the dorsal ligament due to trauma or repetitive strain, congenital predisposition, symptomatic os styloideum with secondary osteoarthritic degeneration and traumatic periostitis3.  The mechanism is likely however to be different for the ‘congenital’ and ‘acquired’ groups.  In those patients with an absence of degenerative wrist changes, a repetitive traction injury at the insertions of ECRB/L is likely the cause of associated pain, and may also explain the onset of the prominence in the ‘acquired’ boss.  While this may also explain the onset of pain in a ‘congenital’ boss, it is a less suitable explanation for the origin of such a boss.     

Figure 1  Bilateral capitate-hamate coalitions

Figure 2  Post-operative picture – carpal boss on Right hand circled.

Carpal coalitions are rare in Caucasian races and are usually asymptomatic4.  Capitate-hamate coalitions are the second commonest variety5.  Carpal coalitions can co-exist with carpal bossing; the altered biomechanics of the wrist are one suggested cause6.  A previous cadaveric anatomic study has suggested a possible association between carpal coalition and dorsal carpal bossing1.  Our case appears to be the first case of bilateral carpal bossing with associated capitate-hamate coalitions.  Our experience has highlighted three important points.  Firstly, that repetitive traction injury at the ECRB/L insertions is the most likely explanation for the onset of symptoms with carpal bossing (in the absence of degenerative wrist changes).  Secondly, that although no previous strong association has been reported between carpal coalitions and carpal bossing, our case supports the theory that the ‘congenital’ carpal boss is in fact a congenital carpal coalition1.  The alteration in wrist biomechanics inherent in such a large carpal coalition would then predispose the patient to developing repetitive strain injury and pain at a tendinous insertion.  It is feasible that patients with normal wrists, who ‘acquire’ a carpal boss, may have symptoms secondary to higher physical repetitive loads such as from their occupation.  Thirdly, it is interesting to note that our patient only improved with debulking surgery that involved removal of the ECRL tendon insertion.  It may be argued that given the typical site of carpal bossing, debulking surgery should be performed with the aim of removing the ECRL tendinous insertion if it is located in the boss – a definitive end-point.  ECRB, the more ulnar of the two tendons, is the prime wrist extensor and thus should be preserved.  Cuono and Watson7 recommend a procedure involving excavation of a cavity at the carpometacarpal joint, primarily indicated in the degenerative wrist, with an ECRB/L-sparing approach.  Our procedure was more conservative in terms of bone removal, and in patients with minimal arthritic change, may be an acceptable alternative.


Bilateral carpal bossing with bilateral underlying capitate-hamate coalitions has not previously been reported.  No previous association has been documented between the two, our case highlighting the likely aetiology of a subgroup of patients with ‘congenital bossing’.  A different surgical approach not discussed previously in the literature was undertaken.  This involved debulking of the boss and removal of ECRL tendon inserting into it.  Our experience strengthens the hypothesis that repetitive traction injury is the likely cause of painful carpal bossing in patients with minimal carpal degenerative change.  These patients are also predisposed to developing osteoarthritis of the wrist joints7, this being a separate cause of wrist pain which requires different surgical intervention. (799 Words)

Reference :

  1. Nakamura K, Patterson RM, Viegas SF.  The Ligament and Skeletal Anatomy of the Second Through Fifth Carpometacarpal Joints and Adjacent Structures.  The Journal of Hand Surgery 2001; 26A(6): 1016-1029 
  2. Clarke AM, Wheen DJ, Visvanathan S, Herbert TJ, Conolly WB.  The Symptomatic Carpal Boss: Is Simple Excision Enough?  Journal of Hand Surgery (Br) 1999; 24B(5): 591-595 
  3. Van Der Aa JPW, Noorda RJP, van Royen BJ.  Symptomatic Carpal Boss. Orthopedics 1999; 22 (7): 703-704 
  4. Simmons BP, McKenzie WD.  Symptomatic Carpal Coalition.  The Journal of Hand Surgery 1985; 10A (2): 190-193 
  5. Singh P, Tuli A, Choudhry R, Mangal A.  Intercarpal Fusion – A Review.  Journal of The Anatomical Society of India 2003; 52(2): 183-188 
  6. Geutjens G.  Carpal Bossing with Capitate-Trapezoid Fusion.  Acta Orthopaedica Scandinavica 1994; 65(1): 97-98 
  7. Fusi S, Watson HK, Cuono CB.  The Carpal Boss: A 20-year review of operative management.  Journal of Hand Surgery (Br) 1995; 20B(3): 405-408


This is a peer reviewed paper 

Please cite as : Omar Mohamed : Bilateral Capitate-Hamate Coalition With Bilateral Carpal Bossing – Likely Aetiology And A Novel Surgical Technique-A Case Report

J.Orthopaedics 2007;4(2)e31





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