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Keywords:

  • horse;
  • arthroscopy;
  • complication;
  • fistula

Summary

  1. Top of page
  2. Summary
  3. Introduction
  4. Case history
  5. Treatment
  6. Discussion
  7. Authors' declaration of interests
  8. References

This paper reports the successful use of a half limb cast to treat prior failures in healing of a synovial hernia in a Thoroughbred yearling. The hernia was due to a nonhealing arthroscopy portal and was confirmed using ultrasonography and positive contrast arthrography to visualise the communication between the metacarpophalangeal joint and subcutaneous space. Surgery was performed 3 times, due to failure of healing of the joint capsule and recurrence of clinical signs. A half limb cast applied following the final surgery effected a repair. At 2 months post surgery there was no recurrence of the subcutaneous swelling and at 3 months post surgery a repeat positive contrast arthrogram confirmed healing of the hernia.


Introduction

  1. Top of page
  2. Summary
  3. Introduction
  4. Case history
  5. Treatment
  6. Discussion
  7. Authors' declaration of interests
  8. References

A defect in the fibrous and/or synovial walls of synovial cavities may result in synovial hernias, ganglia, cysts or fistulae (Minshall and Wright 2012). Equine synovial cysts or hernias associated with joints or tendon sheaths are, however, rarely reported (Llewellyn 1979; Laverty 2009). Such lesions are usually due to trauma, with the resultant cavity filled with synovial fluid and lined with synoviocytes, which produce persistent synovial fluid in the space (Llewellyn 1979; Laverty 2009; Livesey et al. 2009). In the current case, the herniation of synovial membrane may have occurred through an obvious fistula in the joint capsule, which was visualised arthroscopically. The filly was not lame, but there was moderate to severe synovial effusion of this joint, indicating a persistent synovitis. This was similar to a report by Laverty (2009) where pain or mechanical lameness can occur in cases with a soft tissue cystic structure present over an articulation. Repair of the hernia was desirable to improve the cosmetic appearance of the limb and reduce the synovitis of the fetlock joint.

Case history

  1. Top of page
  2. Summary
  3. Introduction
  4. Case history
  5. Treatment
  6. Discussion
  7. Authors' declaration of interests
  8. References

A yearling Thoroughbred filly presented to Scone Equine Hospital for elective removal of a 3 mm2 osteochondritis dissecans fragment from the dorsoproximal aspect of the sagittal ridge of the distal third metacarpal bone in the left forelimb and an osteochondral fragment from the dorsomedial aspect of proximal first phalanx (P1) in the right hindlimb. The lesions were noted on radiographs obtained for sales purposes. The filly was not lame, but there was moderate synovial distension of the left forelimb fetlock joint. Preoperative medication with procaine penicillin (Propercillin)1 20 mg/kg bwt i.m., gentamicin (Gentam)2 6.6 mg/kg bwt i.v. and phenylbutazone (Nabudone P)2 4.4 mg/kg bwt i.v. was administered prior to the primary surgery. Premedication with xylazine (Thiazine)3 0.5 mg/kg bwt i.v. and methadone (Methadone)2 0.03 mg/kg bwt i.v. and 0.06 mg/kg i.m. was administered and general anaesthesia induced with ketamine (Ketamil2 2.2 mg/kg bwt i.v.) combined with diazepam (Diazepam2 0.06 mg/kg bwt i.v.).

The distal left forelimb and distal right hindlimb were aseptically prepared for surgery. A stab incision was made at the dorsolateral aspect of the metacarpophalangeal joint (MCPJ) of the left forelimb, the arthroscopic cannula was introduced using a blunt trocar and the fragment visualised with the arthroscope4. An instrument portal was created dorsomedially using a stab incision. The fragment was removed routinely, with curettage of the fragment bed to the level of normal subchondral bone, and the skin portals were closed with 3 metric polypropylene (Premilene)5 in a simple interrupted pattern. A similar surgical approach was then used to remove the fragment from the MCPJ of the right hindlimb. Both fetlock joints were injected with 200 mg gentamicin (Gentam)2 prior to bandaging of the limbs for recovery. Recovery from anaesthesia was uneventful. Post operative instructions included suture removal at 14 days post surgery and bandaging of the distal limb to the carpus or tarsus in the appropriate limb for 18 days. The filly was stable rested for 2 weeks followed by small paddock rest for 2 weeks. Nonsteroidal medication of phenylbutazone (Butin)6 at 2.2 mg/kg bwt once daily orally was continued for 4 days.

One month after the primary surgery, the filly developed a soft 3 × 3 cm fluctuant, nonpainful swelling at the dorsomedial aspect of the MCPJ with concurrent moderate synovial effusion. The filly remained clinically normal and sound. Ultrasound examination of the swelling using a 7.5 Hz linear probe, revealed that the fluid was located subcutaneously and a communication could be visualised, extending from the dorsal pouch of the MCPJ to the subcutaneous space (Fig1).

figure

Figure 1. Ultrasound image of the metacarpophalangeal joint shows anechoic fluid accumulating in the subcutaneous space (star) communicating with the metacarpophalangeal joint via a 2 mm fistula (arrow).

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Treatment

  1. Top of page
  2. Summary
  3. Introduction
  4. Case history
  5. Treatment
  6. Discussion
  7. Authors' declaration of interests
  8. References

Surgical repair 1

The same preoperative regimen of antibiotics and nonsteroidal medication was administered and the filly was anaesthetised in the same manner as for the primary surgery. The left forelimb MCPJ was aseptically prepared. Synoviocentesis of fluid revealed grossly normal viscous synovial fluid. A positive contrast arthrogram was performed with injection of 5 ml of radiopaque contrast medium (Omni-paque)7 into the palmar pouch of the MCPJ. On radiographic examination the contrast medium was evident in the subcutaneous space confirming the diagnosis of a synovial hernia (Fig2). Arthroscopic evaluation of the joint and surgical repair of the hernia was then attempted. The arthroscope4 was placed in the dorsolateral aspect of the fetlock joint to assess the location of the hernia. A 2 mm hernia was identified dorsomedially in the exact location of the previous portal used for instrument manipulation. A 1.5 cm incision through the skin and subcutaneous tissue was made over the swelling, the edges of the defect were sharp debrided and the joint capsule was closed in 2 layers, using 2 metric polyglycolic acid (Safil)5 in a simple continuous inverting pattern which was then oversewn with simple continuous sutures of the same material in the overlying fibrous tissue. The MCPJ was distended to check for leakage of saline, which did not occur, indicating repair of the hernia. The skin was closed with polypropylene suture material (Premilene)5 in a simple interrupted pattern. The distal limb was then bandaged. The filly recovered uneventfully from anaesthesia. Post operatively, stable rest for 2 weeks with hand walking after one week was recommended with bandaging of the limb for 3 weeks.

figure

Figure 2. Positive contrast arthrogram of the metacarpophalangeal joint with the oblique radiographic projection shown. The arrow shows positive contrast in the subcutaneous space.

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Surgical repair 2

Within 4 weeks, recurrence of the swelling at the dorsomedial MCPJ was apparent. A positive contrast arthrogram was repeated and communication between the MCPJ and subcutaneous space was evident. Ultrasound examination identified the hernia and anechoic fluid in the subcutaneous space. Presurgical medication was the same as previously described and the filly was anaesthetised. A 2 cm incision over the swelling identified the hernia into MCPJ. Sharp debridement of the hernia edges to normal tissue and curettage of the subcutaneous tissue layers was performed to remove any synovial lining that was developing. The hernia was then closed in 2 layers, the joint capsule using 3 metric polydioxanone (Monoplus)5 in a simple interrupted pattern and the overlying fibrous tissue using 2 metric polydioxanone (Monoplus)5 in a simple continuous pattern. The MCPJ was distended with sterile saline to ensure no leakage of fluid. The skin was closed with 3 metric polypropylene (Premilene)5 in a simple interrupted pattern. The limb was bandaged in a double layer of conforming padding material. Recovery from anaesthesia was unremarkable.

Post operatively, stable rest for 14 days and bandaging of the limb for 4 weeks was recommended. The filly was continued on procaine penicillin 20 mg/kg bwt i.m. b.i.d. and gentamicin 6.6 mg/kg bwt i.v. s.i.d. for 3 days and phenylbutazone (Butin)6 2.2 mg/kg bwt per os twice daily for 2 days and then once daily for 5 days.

Surgical repair 3

Four weeks post surgery, the swelling reappeared at the dorsomedial MCPJ. The contrast arthrogram was repeated confirming recurrence of the hernia. The filly received enrofloxacin (Enrotril)2 5 mg/kg bwt i.v., procaine penicillin (Propercillin)1 20 mg/kg bwt i.m. and phenylbutazone (Nabudone P)2 4.4 mg/kg bwt i.v. prior to surgery. General anaesthesia was induced as previously described. An Esmarch tourniquet was applied proximal to the MCPJ to improve visualisation during surgery. A 3 cm incision was made at the dorsomedial aspect of the swelling and normal, clear, viscous joint fluid was expelled from the subcutaneous space. There was minimal scarring of the area and the hernia identified as a smooth-edged structure. A more aggressive debridement of the tissue surrounding the hernia was undertaken, which ensured a 1 cm defect in the joint capsule and visualisation of the articular cartilage (Fig3). The joint capsule was closed using 3 metric polydioxanone (Monoplus)5 in a simple interrupted pattern using preplaced sutures 0.3 cm apart and the MCPJ distended with lactated Ringer's solution to confirm closure of the hernia. A second and third layer of fibrous tissue was closed using 3 metric polydioxanone (Monoplus)5 in a simple continuous pattern to enhance closure strength and the seal created. The skin was closed using polypropylene (Premilene)5 in a simple interrupted pattern. The tourniquet was then removed. A routine half limb cast was applied using fibreglass material (Delta-Lite Plus)8 with the limb in an extended weightbearing position. The filly recovered from anaesthesia uneventfully.

figure

Figure 3. The nonhealing abnormal tissue was removed and a defect is clearly visible in the metacarpophalangeal joint capsule.

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The filly remained in the cast for 2 weeks and the skin sutures were then removed and a bandage and splint maintained for a further 2 weeks. The splint was made of fibreglass material (Delta-Lite Plus)8 which was conformed to the palmar aspect of the limb from the ground to the proximal metacarpus. Box rest was recommended over this time period. The distal limb was then bandaged for a further 4 weeks and access to a small paddock was allowed.

Outcome

Two months post surgery, the filly had fully recovered with no recurrence of the soft swelling at the dorsomedial aspect of the MCPJ and a good cosmetic result. A repeat positive contrast arthrogram was performed at 3 months post surgery, which confirmed successful treatment of the synovial hernia.

Discussion

  1. Top of page
  2. Summary
  3. Introduction
  4. Case history
  5. Treatment
  6. Discussion
  7. Authors' declaration of interests
  8. References

This report describes a synovial hernia in the metacarpophalangeal joint capsule, due to a nonhealing instrument portal following arthroscopic surgery. This was characterised by a soft fluctuant swelling over the joint and accumulation of synovial fluid in the subcutaneous space. Wilson (1989) described a synovial hernia with synovial membrane herniating through the joint capsule into the subcutaneous space following carpal arthroscopy that required dissection from the surrounding tissues. The terms hernia, ganglion, cyst, synoviocoele and combinations of these terms have been used by authors to describe abnormalities found (Angelides and Wallace 1976; McIlwraith 2002; Smith 2009; Crawford et al. 2011; Minshall and Wright 2012; Lacourt et al. 2013). The terms have different definitions leading to their use in each particular case, however hernia and cyst are used synonymously (Laverty 2009).

The application of contrast to investigate communication between adjacent structures and the nature of the interior of these structures is clinically useful (Hago and Vaughan 1986; Lamb 1991). The use of contrast arthrography in this case confirmed our tentative ultrasonographic diagnosis. Dik (1993) also reported that ultrasonography alone may not be successful in demonstrating narrow synovial fistulae or herniation.

The MCPJ was investigated arthroscopically at the first repair attempt when the nonhealing portal was located. It is not known why the portal did not seal spontaneously as is the usual scenario following arthroscopic surgery. In a retrospective review of human synovio-cutaneous fistula cases by Proffer et al. (1991), the fistulae diagnosed were arthroscopic portals that connected the knee joint to the outside of the skin allowing leakage of synovial fluid. Risk factors for nonhealing portals following arthroscopic surgery in man include arthritis, infection or synovitis (Méndez-Fernández 1993). In our case, moderate distension of the MCPJ due to synovitis was noted prior to the removal of the sagittal ridge fragment. The gross analysis of the fluid obtained coupled with normal vital parameters and no apparent lameness led to sepsis being discounted. In this case antimicrobials were given as a prophylactic measure.

A further influence upon repair may have been the suture material used, but alteration of material did not affect success of repair. Polyglycolic acid (Safil)5 was initially used in the first repair attempt as we considered it should have been of adequate strength to allow healing of the opposed tissue, but this was not the case. Polydioxanone (Monoplus)5 was then used due to a slower rate of absorption as healing appeared delayed (Kümmerle 2012).

There is evidence that joint immobilisation can have a positive therapeutic effect. Proffer et al. (1991) described treatment of human knee synovio-cutaneous fistula cases using prophylactic antimicrobials and immobilisation of the joint in extension for 7–14 days that resulted in complete resolution. DeLee (1985) reported that 70% of knee cases responded to this treatment. In man the synovial fluid is forced from the joint through the fistula due to increased intra-articular pressure when the muscles contract and the joint is flexed, therefore immobilisation is advised and, if this fails, surgical intervention is recommended (Proffer et al. 1991; Noble et al. 1998). Our original approach using bandaging was chosen to prevent potential complications such as cast sores as the horse was destined for sale at public auction. Casting was finally chosen due to failure of previous attempts to heal the hernia and the lack of effective immobilisation from bandaging. A combination of surgical debridement and rigid external coaptation led to successful resolution of the hernia and a good cosmetic outcome.

Authors' declaration of interests

  1. Top of page
  2. Summary
  3. Introduction
  4. Case history
  5. Treatment
  6. Discussion
  7. Authors' declaration of interests
  8. References

No conflicts of interest have been declared.

Manufacturers' addresses
  1. 1

    Intervet Australia PTY Ltd, Bendigo, Victoria, Australia.

  2. 2

    Troy Laboratories PTY Ltd, Glendenning, New South Wales, Australia.

  3. 3

    NatureVet PTY Ltd, Glenorie, New South Wales, Australia.

  4. 4

    Karl Storz GmBh & Co, Tuttlingen, Germany.

  5. 5

    B.Braun Melsungen AG., Melsungen, Germany.

  6. 6

    International Animal Health Products Ltd, Newmarket, Auckland, New Zealand.

  7. 7

    Amersham Health, Princeton, New Jersey, USA.

  8. 8

    BSN Medical Inc., Rutherford College, North Carolina, USA.

References

  1. Top of page
  2. Summary
  3. Introduction
  4. Case history
  5. Treatment
  6. Discussion
  7. Authors' declaration of interests
  8. References