This study assessed for cattle the described arthroscopic approaches to the shoulder joint of horses and described normal arthroscopic findings of two approaches to the shoulder joint in sound cattle. Arthroscopic visualization of the shoulder joint was performed systematically through skin incisions located either cranial or caudal to the tendon of the infraspinatus muscle.
In the present study, the described anatomical landmarks and arthroscopic approaches that have been used to insert the arthroscope and to assess the shoulder joint in cattle were similar to the landmarks and approaches that had already been described for horses [30,31,32]. The anatomical variation between cattle and horses concerned the scapular spine which was more often visible and always palpable in cattle as compared to horses .
Although arthroscopic approaches to and normal arthroscopic anatomy of many joints in cattle have been described, description of the arthroscopic approaches to and normal arthroscopic anatomy of the shoulder joint in cattle was not available [24,25,26,27,28,29]. To our knowledge, this is the first description of the arthroscopic approaches to and the intraarticular arthroscopic anatomy of the shoulder joint in cattle. In their review, Nichols and Lardé, suggested inserting the arthroscope either cranial or caudal to the tendon of the infraspinatus muscle in cattle as described in horses and as advocated in the current study .
The shoulder area anatomy as well as the considerable distance of the joint capsule from the skin surface, as well as the considerable distance of the joint capsule from the skin surface, complicate the clinical diagnosis of shoulder joint diseases and injuries through palpation, radiography, arthrocentesis and arthroscopic examination. For the shoulder joint; the arthroscopic investigation in horses, and arthrocentesis in cattle were found to be much more difficult compared to other joints [6, 7, 9, 30, 31]. In cattle, recent studies classified the shoulder joint as the second most difficult joint for entering and evaluation following the hip joint [19, 33]. In adult cattle, the surgeon has to apply more pressure to the arthroscope for manipulation through the caudal approach, and this may lead to arthroscope damage, while the cranial approach gave similar or better visibility with lower damage risk to the arthroscope. One explanation for this difficulty might be the distance from the skin to the joint capsule is longer in the caudal as compared to the cranial approach. This finding is in agreement with previous findings described in horses [30, 31].
In the current study, evaluation of the cranial, lateral and caudal portions of the shoulder joint via both the cranial and caudal approaches with the limbs in horizontal and non-pulled position was possible. A number of structures were efficiently evaluated: the cranial cul-de-sac, the cranial rim of the glenoid, cranial aspect of the humeral head, incisura glenoidalis, lateral rim of the glenoid, latero-proximal aspect of the humeral head, the caudal rim of the glenoid, caudal aspect of the humeral head and caudal cul-de-sac. Exploration of the full extent of the medial aspect of the joint was not possible neither in calves nor adults. However, certain parts of the medial glenoid rim, medial synovial membrane and proximal medial portion of the humeral head were more easily accessible in calves rather than adults. Pulling the limb manually in a horizontal direction facilitated the manipulation of the arthroscope to examine the medial joint aspects. Manipulation of the arthroscope in cadaveric limbs as compared to cattle under general anesthesia might be more difficult due to the loss of elasticity of the joint capsule . The abduction of the limb allowed to improve visualization of the lateral portion of the humeral head as has already been described in horses [30,31,32]. It might be concluded that one arthroscopic portal is sufficient to examine the shoulder joint; however, it was beneficial to either extend or abduct the joint during the examination in order to improve visibility of certain structures.
The selection of the approach of the arthroscope in clinical cases may depend on the location of the lesion. From the current study, we propose using the cranial arthroscopic approach for lesions of the caudal portion and the portal 1-cm caudal to the palpable border of the tendon of the infraspinatus muscle to allow for the instrument access. The caudal insertion of the arthroscope might be ideal for accessing lesions of the cranial area of the joint, while the cranial portal is used for the instruments. Nichols and Anderson, proposed that in cattle with joint disease, the ideal arthroscopic and instrument portals may not necessarily to be identical to those suggested in healthy cattle . However, in the shoulder joint, we cannot imagine any other practically applicable approach for arthroscopic evaluation.
Nutrient foramina are important since they provide a pathway for the entrance of nutrient arterioles and venules into the bone. The histological examination of the observed stretched strands located at the cranial portion of the joint revealed the presence of arterioles and venules, allowing for the supply of blood to the humerus. Considering the number and location of these structures, intra-operative laceration should be avoided . In a study by Mansur et al., 2% of 253 examined human humeral heads did not show any nutrient foramina . This finding is similar to that experienced in the cases of the current study in shoulder joints of cattle.
Various complications may occur during arthroscopic surgeries. In the present study, extravasations of the irrigation fluid subcutaneously occurred to some degree in all the examined shoulders, but it was more obvious in the calves’ cadavers. The reason for fewer extravasations in adults compared to calves might be that the skin is less tight in calves as compared to adults. In horses, this complication was also reported in shoulder arthroscopy . The extended time of the surgeries, besides puncturing the joint capsule at more than one site and applying high perfusion pressure were the main reasons for the fluid extravasations to occur . In the current study, partial-thickness articular cartilage wear lines were observed in all shoulders examined. Although these lesions occurred already during the first insertion of the instruments into the joint, reinsertion and manipulating the arthroscope within the joint added additional lesions. Partial-thickness articular cartilage wear lines were also described in cattle carpus and stifle arthroscopy [26, 27, 29]. As mentioned before, puncturing and manipulating of the arthroscope within the shoulder joint is demanding [19, 33], this is most likely the explanation for the occurrence of the partial-thickness articular cartilage wear lines in our study. The described complications can be avoided or its occurrence at least be reduced by applying a minimal perfusion pressure, gently inserting and manipulating the arthroscope and avoiding to perform the intervention through more than one optical portal.