Investigation of the surgical endoscopic approaches used in the management of navicular bursa sepsis in the horse
Reasons for performing this study: Despite improvements in clinical outcome following treatment of synovial sepsis in horses, the prognosis for survival following septic navicular bursitis remains guarded, whilst the prognosis for athletic activity is considered poor. Surgical intervention is deemed essential for resolution. Two different surgical endoscopic approaches to the bursa have been described, however only the use of the direct approach has been reported in the management of clinical sepsis. The risk of inadvertent penetration of adjacent synovial structures with this approach is reported but has not been quantified. A transthecal approach, via the digital flexor tendon sheath, is considered to involve fewer complications than the direct approach but is typically reserved for elective examination of the aseptic bursa. The use of this approach in sepsis has not been evaluated. Intravenous regional limb perfusion with antimicrobials is an established adjunct in the management of synovial sepsis and is suggested to improve case outcome. The synovial concentrations of antimicrobial achieved following IVRP in case’s of clinical sepsis have not been established. Objectives: To quantify the risk of inadvertent synovial structure penetration when making a direct surgical endoscopic approach to the navicular bursa. To determine a safer direct approach, with reduced risk of inadvertent synovial penetration. · To review the outcome of clinical case’s of navicular bursa sepsis following surgical management via the transthecal endoscopic approach and post-operative management involving intravenous regional limb perfusion with amikacin. To compare these outcomes with those reported following management via the direct approach. · To investigate the concentrations of amikacin achieved in synovial fluid following IVRP in clinical case’s of synovial sepsis. Hypotheses: · There is significant risk of inadvertently penetrating the distal interphalangeal joint and/or digital flexor tendon sheath when making a direct surgical endoscopic approach to the navicular bursa, with attendant potential for contamination of these structures when managing septic bursitis. Making the approach as abaxial as possible and advancing the instrument in a sagittal trajectory will minimise the risk of inadvertent synovial penetration. · The prognoses for survival and return to athletic function following surgical management of navicular bursa sepsis via the transthecal approach, in addition to post-operative intravenous regional perfusion with amikacin, are comparable with those reportedly managed via the direct approach. The surgical technique permits simplified postoperative intrasynovial medication and monitoring of synovial fluid parameters by establishing communication between the bursa and tendon sheath · Following regional intravenous limb perfusion, the levels of amikacin accumulated in contaminated synovial structures are greater than the minimum inhibitory concentration for commonly encountered bacteria, potentially validating the contribution of perfusion techniques as adjunct therapies in treating synovial sepsis. Methods: · Using 40 cadaver horse limbs, a conventional endoscopic approach, was made to the lateral aspect of the navicular bursa of each limb. Successful entry was confirmed endoscopically. Centesis and distension of the DFTS and DIPJ were performed to determine whether communication with the arthroscopic portal or bursa had occurred. Positive contrast radiographic navicular bursograms were performed to identify iatrogenic communication with the DFTS and/or DIPJ. A pilot study employing a modified approach was performed. · The case records of 10 horses presented with navicular bursa contamination, which underwent therapeutic surgical endoscopy of the navicular bursa via a transthecal approach and received post-operative intravenous regional perfusion with amikacin were evaluated retrospectively. Follow-up information was obtained by telephone questionnaire. · Intravenous regional limb perfusion with amikacin was performed on clinical case’s of synovial sepsis and synovial fluid was aspirated from the contaminated synovial cavity 30 minutes later. Synovial fluid amikacin concentration was then measured. Results: · Using the direct surgical approach to the navicular bursa, inadvertent penetration of a synovial structure occurred in 45% of the limbs (digital flexor tendon sheath 37.5%, distal interphalangeal joint 17.5%, and both structures 10%). Incidence amongst the surgeons ranged 10-70%. Inadvertent penetration did not occur when using a modified approach. · Of the 10 horses with septic navicular bursitis treated via transthecal endoscopic lavage and post-operative regional intravenous perfusion: 9 horses survived to long term follow up (>12 months). Eight returned to athletic function, 7 performed at their pre-injury level of athletic activity. One achieved a lower level of activity, 1 was retired, and 1 was euthanased. · Synovial fluid concentration of amikacin achieved in excess of the minimum inhibitory concentration in 90% samples and 10-12 times minimum inhibitory concentration in 62.3% samples. The DFTS sample group recorded the highest individual sample concentration (391mg/L) as well as the highest group mean (175.1) and median (181). The lowest individual result came from a TCJ, and proximal group had the lowest mean (43.3) and median (26.9) values. Conclusions: · There is significant risk of inadvertent penetration of the digital flexor tendon sheath and/or distal interphalangeal joint when making a direct surgical endoscopic approach to the navicular bursa. Individual surgeon interpretation and application of the described technique appears to influence the incidence of inadvertent synovial penetration. Further investigation of the modified technique is necessary. · Endoscopic lavage of the navicular bursa via a transthecal approach was a safe and effective surgical treatment. When combined with postoperative intravenous regional limb perfusion, the prognosis for survival and return to previous level of athletic function were comparable with the published outcomes using a direct endoscopic approach. Postoperative intrasynovial medication and monitoring of synovial fluid parameters is potentially simplified by establishment of communication between the bursa and tendon sheath, however further investigation is required to determine the duration of patency. · Intravenous regional limb perfusion achieves therapeutic concentrations of amikacin within contaminated synovial cavities when using the described protocol. Potential Clinical Relevance: Use of the direct surgical endoscopic approach to the navicular bursa incurs the potential risk of inadvertent contamination of adjacent synovial structures. Whilst the transthecal approach intentionally involves an aseptic synovial structure, this is consequently thoroughly lavaged and the post-operative communication between synovial structures allows for convenient synovial medication and sampling. Use of intravenous perfusion with amikacin in clinical sepsis has the potential to improve case outcome.