ARTHRODESISIS – A KEY TO DECISION OF THE MOST DIFFICULT PROBLEMS IN RECONSTRUCTIVE SURGERY OF SHOULDER JOINT Gerashchenko N.I., Voronkevich I.А.

Vreden Russian Research Institute of Traumatology and Orthopedics, Saint Petersburg, Russia

Shoulder joint arthrodesis is surgery for formation of stable humeroscapular ankylosis in functionally favorable position [41, 44, 62]. Shoulder joint arthrodesis was firstly described by the Czech orthopedic surgeon Eduard Albert in 1884. He was the first who had performed successful formation of humeroscapular ankylosis in multi-plane recurrent instability of the shoulder joint with use of bone autoplasty and fixation of the upper extremity with thoracobrachial dressing [42]. In 1993, Putti described the similar technique of shoulder joint arthrodesis for consequences of tuberculous omarthritis [48]. That year, Watson-Jones firstly described the technique of extraarticular arthrodesis of the shoulder joint [49]. In 1955, Charles Neer presented a technique for shoulder hemiarthroplasty with use of his own endoprosthesis, which significantly reduced the number of arthrodesis procedures, but it could not solve the problem of recovery of upper extremity functioning in some severe cases, such as unrecoverable injuries to the rotator cuff, and traction injuries to the axillary nerve [63]. In 1985, Paul Grammount offered a decision for the problem of recovery of range of motions in the shoulder joint in full or partial absence of muscles of the rotator cuff. He created, tested and implemented the first reverse endoprosthesis for treatment of wide range of shoulder abnormality relating to subtotal or total loss of function of the rotator cuff [34]. The mechanism of action of this system is based on alternation of shoulder joint biomechanics by means of bringing down and medialization of its rotation center. It changed force direction, increased the lever arm responsible for abduction and provided the new ability for the deltoid muscle – shoulder abduction from the lowest end point. It partially replaced the function of the rotator cuff and caused the increase in strength of abduction of the upper extremity [34, 35]. The reverse endoprosthesis significantly improved the results of surgical management of complex pathology of the shoulder joint, such as osteoarthritis at the background of massive lacerations of the rotator cuff, multi-plane recurrent instability, and severe posttraumatic osteoarthritis. The obligatory condition for use of this metal construct is preservation of satisfactory function of the deltoid muscle by means of intact innervations [34].

That’s why, patients with injuries to the axillary nerve injuries, brachial plexus damages or deltoid muscle atrophy as result of various causes cannot be operated with the reverse endoprosthesis since the main motional mechanism of this system disappears in absence of deltoid muscle function. Endoprosthetics is contraindicated for such patients [34].

Therefore, successes in development of endoprosthetics have put only temporary competitive pressure on arthrodesis operation. Reverse endoprosthetics is contraindicated for significant proportion of patients. They are patients with unrecoverable injury to the deltoid muscle or to the axillary nerve as result of severe injuries and diseases. The individual category includes patients with preserved function of the axillary nerve and the deltoid muscle, with so called social indications for endoprosthetics: persons of physically demanding job who cannot change their profession. For such patients, arthrodesis is the uniform solution for preservation of function of the upper extremity which is optimal for self-care [16, 21, 23]. One should note that arthrodesis received some improvements for increasing efficiency and performance. These improvements allow revising the paradigm of arthrodesis as crippling surgery, and it can be considered as surgery of choice in some cases [1, 4, 6, 7, 8, 10, 13, 14, 18, 40, 46, 50].

Objective – to estimate the modern state of the problem of shoulder joint arthrodesis on the basis of the literature data. During the analysis, it is planned to clarify the general indications for shoulder arthrodesis, evolution of techniques, the modern indications for particular techniques, their efficiency, features of surgical techniques, and anatomic and functional results.

Currently, one may observe the increasing surgical activity towards the shoulder joint as result of new technologies and osteosynthesis and prosthetics constructs, and clarification of tactical approaches to treatment of various injuries and diseases [1, 2, 3]. Despite of significant successes in treatment of injuries and shoulder joint diseases, there is a category of patients with so called severe abnormality, the treatment of which is low efficient with use of the common surgical techniques [4, 5, 6]. So, Dimmen S. et al (2007) performed the analysis of results of arthrodesis with standard AO technique with two reconstructive plates in 18 patients over 15 years. The author showed that 9 patients had persistent pain, 2 patients – X-ray confirmed non-union, 1 patient – septic instability of the metal constructs [8]. The annual report of Australian register of arthroplasty for 2008-2016 analyzed the results of 15,781 cases of reverse shoulder joint endoprosthetics, and 582 revision interventions. However, the review does not describe the outcomes of revision operations [9]. Shoulder joint arthrodesis is a serious decision for a surgeon since the surgery causes the irreversible anatomic and functional changes in the shoulder joint, eliminating it as the anatomic formation, as well as in the upper extremity generally, alternating its biomechanics [7, 8]. Despite of all radicality, shoulder joint arthrodesis is the surgery of choice in some cases [7, 10, 11].

INDICATIONS FOR SURGERY

According to the modern opinions, the indications for shoulder joint arthrodesis are consequences of fractures and fracture-dislocations of the proximal femur with full irreversible loss of the axillary nerve function confirmed by electroneuromyography data [41, 43, 44]; consequences of brachial plexus injury with preserved function of the hand as a way for shoulder joint stabilization before reconstruction of brachial plexus [5, 41, 43]; consequences of gun-shot fractures in the shoulder joint site [17]; consequences of unsuccessful revision interventions for infectious and non-infectious complications of shoulder joint endoprosthetics in case of impossibility of revision endoprosthetics [18]; degenerative and dystrophic changes of the shoulder joint in persons of rough labour, in high demands for load and impossibility of profession change; tumors in proximal shoulder joint, resection of which does not allow endoprosthetics with acceptable functional outcome [22, 47].

The problem of posttraumatic neuropathy of the axillary nerve with deltoid muscle paralysis and recurrent instability of the shoulder joint is well described in publications by some authors. Thangarajah T. et al. (2014) reported on results of six operations of shoulder joint arthrodesis in patients with consequences of dislocations and shoulder joint instability at the background of epileptic seizures. The authors noted the formation of the bone block in all cases, high efficiency of the technique, with absence of recurrence of instability and improvement in functional results according to Oxford Score of Shoulder Instability [12]. Diaz J.A. et al. (2003) analyzed the results of shoulder joint arthrodesis in 8 patients with recurrent multi-plane shoulder joint instability with previous various stabilizing operations, and they showed the absence of recurrence of instability in the long term period (35 months after surgery) [13]. Tomaino M.M. (2000) described two patients with massive posttraumatic defect of the proximal shoulder who had received arthrodesis with screws and the plate with use of the free bone autograft of the fibular bone. Both cases showed formation of ankylosis, and a possibility for painless movements with the hand which were appropriate for self-care [14].

Most authors pay special attention to the role of arthrodesis in the complex of surgical management of consequences of brachial plexus damage. Atlan F. et al. (2012) estimated the long term results in 36 months from surgery in a big study based on analysis of 54 arthrodesis procedures in two groups of patients with complete (group 1) and incomplete (group 2) injuries to the brachial plexus. Before surgery, all patients had no active movements in their shoulder joints. The study showed 51 formations of ankylosis, 3 non-unions requiring for revision bone autoplasty. The functional results of the surgery were the following: mean amplitude of abduction – 57 degrees in the group 1, 67 degrees – in the group 2. The man abduction was more than 45 degrees, and the rotation amplitude – 50 degrees in the group 1, 46 – in the groups 2, and more than 45 – in 35 [7]. A study by Chammas M. et al. (2004) analyzed the functional outcomes of shoulder arthrodesis in 27 patients with partial (11 patients) and complete (12 patients) brachial plexus injuries. The authors concluded that shoulder arthrodesis causes the significant improvement in life quality. The best functional results were achieved in patients with preserved had function [15]. Rtaimate M. et al. (2002) examined the life quality in 15 patients with shoulder joint arthrodesis in 1981-1997. The authors reported that all operated patients were able to move with their upper extremities with enough degree for self-care. They could lift with the hand the weight of 5.2 kg which exceeds the allowable load to the upper extremity after joint replacement [16].

Arthrodesis plays the important role in treatment of severe gun-shot injuries to the shoulder joint since endoprosthetics is very limited in conditions of infection and soft tissue injuries. During the Great Patriotic War, a great deal of data on shoulder joint gun-shot injuries has been accumulated. Mayat V.S. (1953) performed the analysis of patients and deceased persons’ data and noted that shoulder joint gun-shot injuries were 20.4 % of total amount of injuries to big joints [68]. Kirillov B.P. (1948) and Fridland M.O. (1953) estimated the outcomes of shoulder gun-shot wounds and found high incidence of complications (28.8 %). The outcomes of injuries were ankylosis in functionally unfavorable positions in 5.6 %, purulent infection – in 41.2 % [69, 70]. According to the data by Averkiev V.A. (1988), during Afghanistan war, the incidence of gun-shot injuries to the shoulder joint was 11.2 %, purulent complications – 35.8 %. According to the data from the Military Medical Museum of Ministry of Defense of the Russian Federation, during periods of military operations in Afghanistan and Chechnya, there were 179 and 39 case histories of shoulder joint injuries correspondingly by the moment of September, 1996. The analysis showed the purulent complications in 30.4 % of patients, union with ankylosis formation – in 31.8 %, recovery of joint function – in 6.9 %, sharp limitation of joint function – in 93.1 %, joint contracture – in 61.7 %, loose shoulder joint – in 6.2 %. The main causes of complications were absence of first aid for patients with late admission to hospital that significantly influenced on incidence of complications (shock, purulent complications); insufficiency of doctors’ experience in military field surgery, which led to non-radical surgical preparation of joints; excessive radicalism in surgical preparation of fragmented fractures, which caused formation of extensive bone defects after resections.

According to Shapavalov V.M. (2000), the analysis of 12,000 case histories of victims of Afghanistan war showed that gun-shot injuries to the extremities were 54-70 % among all combat injuries, with 17.4 % of wounds in region of the shoulder joint [73].

According to Shapovalov V.M. and Averkiev V.A. (2000), the analysis of complications of gun-shot injuries to the shoulder joint in the first and second war conflicts in Chechnya identified 164 victims with shoulder joint injuries, including 53 patients (32.3 %) with purulent complications. The authors note that the incidence of complications is directly related to pattern of a bone injury. For fragmented and comminuted fractures, purulent complications were diagnosed in almost half of patients [72].

The proper analysis of combat injuries to the upper extremity in the first and second war conflicts in the Northern Caucasus was conducted by the team of department of military traumatology and orthopedics at Kirov Military Medical Academy. The patterns of the injuries are indicated in the table 1.

Table 1

Incidence of shoulder joint injuries during the first and second war conflicts in North Caucasus (the data of Kirov Military Medical Academy) [72, 73]

Characteristics of wounds	1994-1996 (%)	1999-2002 (%)
Shoulder soft tissue injuries	17.6	18.6
Shoulder injuries with bone damages	6.1	7.6
Shoulder joint injuries	0.8	1.3
Shoulder injuries with magistral vessel damage	4.7	3.9
Shoulder injuries with magistral nerve damage	2.8	3.1
Damage (rupture) of extremity at shoulder level	0.5	0.3
Shoulder soft tissue contusion	0.7	0.8
Closed fracture of shoulder	0.9	1.3
Opened fracture of shoulder	0.4	-
Closed injuries to shoulder	1.8	2.4
Closed injuries to shoulder with magistral vessel damages	1.1	0.3
Closed shoulder injuries with magistral nerve damage	0.5	0.3
Shoulder injuries with signs of crushing syndrome	0.2	0.3

Among the presented injuries, one can separate such groups as patients with injuries to magistral nerves in shoulder joint region, and direct wounds of the shoulder joints as potential candidates for shoulder joint arthrodesis.

In a study by Zsoldos et al. (2013), they report on results of treatment of 7 patients with gun-shot injuries to the shoulder joint with massive destruction of the proximal humerus. Four patients received primary hemiarthroplasty, three patients – primary arthrodesis. After 44 months, the authors conducted the estimation of the range of active movements. So, the patients with hemiarthroplasty had the mean range of movements of 38 degrees, flexion – 48 degrees, external rotation – 4 degrees. One patient of this group received revision surgery. Three patients with primary arthrodesis had the mean abduction of 58 degrees, flexion – 98 degrees, external rotation – 12 degrees. The study shows the evident findings that shoulder arthrodesis for formation of ankylosis in functionally favorable position is characterized by higher and more persistent anatomic and functional outcome. All patients returned to usual professional activity [17].

In some cases with unstable shoulder joint, the structural changes in the deltoid muscle, the proximal humerus and scapular articular process gives a surgeon, who deals with revision interventions for infectious and non-infectious complications after shoulder joint endoprosthetics, a task, which is almost unachievable in the context of recovery of normal anatomy and biomechanics of the shoulder joint. Deltoid muscle weakness, and massive defects of scapular articular process and the proximal humerus are sometimes so apparent that revision endoprosthetics is impossible or is accompanied by high risk of postsurgical complications (mainly, dislocations). Scalise J.J. (2008) reports on 7 patients who received shoulder joint arthrodesis after infectious complications of primary endoprosthetics with formation of massive bone defects of the articular process and the proximal part of the humerus. All patients achieved formation of ankylosis, but this process was slow and took 6 months in 2 patients. Good functional results were characterized by pain regression and by the increase in Penn Shoulder Score [18]. Kager J. (2011) reported on two cases of shoulder arthrodesis in patients with previous purulent omarthritis. Arthrodesis with AO technique was conducted along with bone arthroplasty with the iliac crest graft. The ten-year follow-up showed that the surgery had recovered the movement volume for self-care, and had corrected the pain [19], without a trend to disorder of achieved function. Alta T.D. (2016) conducted an original study and showed a possibility for mobilization of humeroscapular ankylosis during revision of electroneuromyography data. However, function increase was low, and the risk of complications was high [20].

In orthopedic surgery, operations for malignant tumors are extremely radical and are often accompanied by inevitable formation of extensive defects in the region of the upper one-third of the humerus and the shoulder joint which impedes implantation of endoprostheses. Even if implantation of the artificial joint is achievable, muscular insufficiency creates the unfavorable conditions for endoprosthesis functioning. Subsequently, insufficient functional load to the upper extremity can cause the loss of bone mass in the articular process of the scapula, and subsequent development of loosening of shoulder joint endoprosthesis. Mimata Y. (2016) reported on succesful resection (with single block, with part of the deltoid muscle) of malignant tumors of the deltoid muscle with subsequent replacement of postresection defects with use of free fibular autografts, and arthrodesis with the plate. The author proves that such surgery is the only one for such patients [21]. Padiolleau G. et al. (2014) analyzed the functional results of treatment of 12 patients who had received resection of humerus malignant tumor with use of single-moment arthrodesis. The mean period of the follow-up was 5 years. The results were estimated with X-ray examination, Musculoskeletal Tumor Society (MSTS) Score and Toronto Extremity Salvage Score (TESS). The authors report on 87.5 % of ankylosis formation, MSTS – 70 %, TESS – 70 % of function recovery. They note the high efficiency of this surgery, and lack of options for it [22].

Arthrodesis as the alternative for shoulder joint endoprosthetics can be reviewed in case of impossibility of profession change for patients with posttraumatic, rheumatoid and idiopathic omarthrosis with intense pain [23]. In other words, such patients receive arthrodesis due to social indices. The cause is limit of weight load after shoulder joint endoprosthetics according to some authors [24, 25, 26, 27]. Most fundamental studies with analysis of arthrodesis for degenerative diseases were carried out in 1960-1980s. At that time, arthrodesis was the main surgery for severe degenerative process in the shoulder joint. Cofield R.H. (1979) conducted a fundamental study and analyzed the results of 71 shoulder arthrodesis procedures for degenerative diseases of the shoulder joint. The author found the metal construct loosening in 17 patients, and a fracture of internal fixators in 10 patients. Totally, the authors received 27 revision surgeries for failure of primary fixation with shoulder arthrodesis. Despite of high proportion of complications, which were probably related to imperfection of implants, the authors note that formation of ankylosis causes the good functional outcome and patients’ satisfaction in all cases. It was confirmed even in 10 years after surgery [28]. Souter W.A. (1983) indicated the possibility of arthrodesis in patients with rheumatoid omarthritis. They consider this surgery as useful and radical option for pain correction [31]. Wilde A.H. et al. (1987) consider shoulder arthrodesis as safer and reliable operation for patients with degenerative lesions of the shoulder joint in conditions of high demands for weigh load in comparison with endoprosthetics [30].

SURGICAL TECHNIQUES OF ARTHRODESIS

There are various techniques of shoulder joint arthrodesis. According to influence on shoulder joint structures, they can be divided into extraarticular, intraarticular and combined [31, 41]. Extraarticular arthrodesis of the shoulder joint was described by Watson-Jones in 1933. A patient with consequences of tuberculous omarthritis received surgical mobilization of the destructed shoulder joint with use of arthrolysis. Then the upper extremity was fixed in position of abduction, flexion and external rotation with use of massive plaster thoracobrachial dressing before formation of ankylosis [49]. Dege offered a technique for extraarticular arthrodesis with use of the bone-muscle flap from the scapula edge. This flap is placed along the lower surface of the shoulder joint, resulting in optimal conditions for ankylosis formation. The upper extremity is fixed with the thoracobrachial dressing in position of 15 degrees of flexion, 45 degrees of abduction and 15-25 degrees of external rotation [64]. The particular variant of extraarticular arthrodesis is Ilizarov compression arthrodesis described by N.A. Shesternya [64]. R.R. Vreden’s technique for intraarticular arthrodesis of the shoulder joint consists in mobilization, bone plastic resection and fixation of the shoulder joint with use of the tubular bone autograft from the scapula edge. This technique also provides the use of external plaster immobilization for 3 months [36]. According to a type of metal construct, shoulder arthrodesis is subdivided into several groups.

The technique with use of screws was used by Vreden R.R. (1930) and Lerch (2011). Lerch described the details of the surgical technique. A patient lies on his/her healthy side. The transdeltoid approach is used for exposure of the shoulder joint. It is mobilized. Scars and osteophytes are removed. The saw is used for wedge resection of the capitellum. The humerus is dislocated into the wound. Economic resection of scapular articular process is conducted in perpendicular to its axis. The lower cortical wall of the acromion is resected. The next stage is positioning of the upper extremity in position of 20 degrees of abduction, 20 degrees of flexion and 40 degrees of rotation. The fixation is conducted with six 6.5 mm cannulated screws. Three screws are placed in direction towards the articular process of the scapula, three other screws – from the side of the acromion in direction towards the capitellum. This technique includes the immobilization with rigid dressing and adduction pad within 6 weeks. The results of this technique were studied with series of 4 subsequent cases of patients with various diseases operated in 2007-2008. The authors note the formation of humeroscapular ankylosis in all four cases. The mean amplitude of movements in the upper extremity was 60 degrees of abduction and 40 degrees of flexion [6, 36].

Wide spread of AO concept in relation to ranges of osteosynthesis stability allowed considering the clinical use of LC-DCP for creation of conditions for formation of humeroscapular ankylosis. In 1984, Schatzker et al. described the technique of shoulder arthrodesis with use of one or two plates in combination with screws (AO technique) [50]. This technique is recommended to be performed in “beach chair” position. The approach is made from beginning of the spina scapula, with anterior transition to infraclavicular fissure. The incision is prolonged to the middle third of the arm, approaching the shoulder joint and humerus diaphysis. The shoulder joint is mobilized, and the humerus head is partially resected and is dislocated posteriorly. Then the implant site of the articular process of the scapula is formed by means of cartilage removal. The humerus and the scapula are positioned at the angles: 20 degrees of flexion, 30 degrees of abduction, 30 degrees of rotation. Then the fixator is prepared. The fixator is 4.5 mm LC-DCP with 12-14 holes. LC-DCP is flexed at the angle of 100 degrees with use of cold bending. The plate is fixed with spongious screws to spina scapula, with cortical screws to humerus diaphysis in conditions of compression. Residual cavities between connected fragments are filled with autobone. External mobilization for six months is required for healing of soft tissues [8, 38, 45, 50, 51, 66]. The results of the technique have been described well since this method is very popular among orthopedists. The most large-scale work was performed by Richards from June, 1980 till June, 1991. It included serious of cases with 57 patients, most of which (46 patients) had been operated due to multi-plane recurrent instability after brachial plexus injury. The author used one 4.5 mm plate and the intraarticular spongious lag screw. The author mentioned 14 % rate of complications requiring for revision. Moreover, 3 patients showed 10˚ disparity of angle sets after surgery as compared to presurgical planning [66].

Arthrodesis with external fixator has not obtained widespread practice. However, it is mainly used for infectious problems of the shoulder joint and for combat injuries [75]. There are two types of arthrodesis techniques with use of external fixation: arthrodesis with monolateral device, and arthrodesis by Ilizarov [52, 54, 67, 75]. For both cases, resection of the shoulder joint is performed, after which the external fixator is applied. The upper extremity is positioned in relation to the body midline at the angles corresponding to abduction of 30 degrees, external rotation of 30 degrees and flexion of 30 degrees. Compression is carried out. External immobilization is not required. Kendall described and illustrated this technique well. After shoulder joint mobilization and resection, console elements and pins are introduced into the spina scapula and humerus metadiaphysis. The upper extremity is positioned along the mid-line. Compression is carried out [67]. Averkiev D.V. offered some original techniques for shoulder arthrodesis with use of external fixation for treatment of patients with shoulder joint injuries. The device consists of the central basis, which fixes the scapula by means of two rods. The rods are introduced into the spina scapula and are fixed in the segment, which is fixed in perpendicular to the semi-ring. Peripheral basis consists of two semi-rings and includes three rods, which are introduced into the humerus diaphysis. The advantages of this device, as compared to the pin analogue (Ilizarov’s apparatus), are rapidness and simplicity of application, decrease in additional port of infection, and safe intervals of console elements [75].

Arthrodesis with use of the original devices for treatment of wide range of shoulder joint pathology was firstly offered at Vreden Russian Research Institute of Traumatology and Orthopedics. The special fixator has been developed, which includes two parts – the scapular part with the forked unit and two flat jags, with parallel holes for screws, and the diaphyseal part with round and combined holes [61]. For realization of arthrodesis with use of this technique, the author offers the position of beach chair. The direct transdeltoid approach is used for the shoulder joint. The mini-approach to the spina scapula is used for installation of the scapular part of the fixator. After resection and mobilization of the shoulder joint, the fixator is introduced into the wound through the scapular approach. The impactor is used for placing the fixator onto the spina scapula. The diaphyseal part is fixed with bone holding clamps. Osteosynthesis and bone autoplasty are carried out. Flexion and abduction are preinstalled by the fixator’s construct. Rotation varies within 30 degrees. The external immobilization is not required [61]. The long term results of the fixator use were studied with 15 cases by patients with various shoulder joint abnormalities operated in 2007-2012. All patients showed statistically significant improvement in function as compared to the presurgical values [71].

The issue of stability of metal constructs implanted during arthrodesis is very important since they are not removed in most cases. The literature presents some qualitative wide-scale studies of rigidity of fixation of the humerus and the scapula with various variants. Miller B.S. (2003) conducted a study with biomechanical analysis of five techniques of shoulder arthrodesis. After 100 sessions of bending and torsion, the highest stability was shown by arthrodesis with two extraarticular plates in combination with three extraarticular screws [32]. However, there is one accepted fact that special plates for shoulder joint arthrodesis are absent, and non-special direct plates are to be bent with cold bending under extremely high angles during surgery, resulting in critical deformation with probable fracture of the fixator during surgery or at stages of subsequent treatment of the patient. Lerch S. (2013) conducted an original study of 4 various combinations of metal fixators for shoulder joint arthrodesis. 24 fresh cadaveric samples of the shoulder joint were used. He found that the highest stability was presented by combination of the reconstructive plate with 16 holes, 3 extraarticular screws, and 1 short plate with 16 holes along anterior surface of the shoulder joint [33]. One should note the absence of any uniform and reliable intrasurgical approach to positioning of the humerus in relation to the scapula. The table 2 shows some literature data on this issue.

Table 2

Angle characteristics of spatial relationships of shoulder and scapula in anchylosis formation (literature data) [23, 28, 36, 44, 50, 53, 60]

Author	Internal rotations (degrees)	Abduction (degrees)	Flexion (degrees)
Makin	-	-	30
Charnley	-	50	50
Feray	-	50	30
Cofield	-	30	30
Rowe	-	20	30
Groh	-	10-15	10-15
Huber	45	20-30	30
Reichelt	45	20-25	30
Clare	45	10-15	10-15
Rybka	40	50	30
Debrunner	40	50	30
Schmit-Neuerburg	30	50	20
Hawkins	30	25-40	25-30

CONCLUSION

Currently, shoulder joint arthrodesis is becoming actual surgery again. From one side, it is associated with increasing number of recurrent revisions of reverse systems, which are used more and more each year, but part of them requires for revision over time or causes contraindications for recurrent endoprosthetics. From other side, one can observe the progression in modernization of arthrodesis technique. The development of the special device has increased the technologic potential of the surgery, fixation stability, and efficiency for all indications.

According to the analyzed literature data, arthrodesis is preferable for some disputable cases, such as partial injury to the axillary nerve with unclear results of electroneuromyography. Arthrodesis is surgery of choice for total injury to the axillary nerve, scar rebuilding of the deltoid muscle, injury to brachial plexus with preserved hand function, and also for consequences of opened and gun-shot injuries. All techniques described in studies of biomechanics of humeroscapular fixation [32, 33] are used in various clinics at the present time. Moreover, similar sufficient satisfaction of the patient, and persistence of long term results are observed in cases with achievement of ankylosis. However, the rate of complications after these arthrodesis techniques varies within 14-30 % according to various authors. As for spatial ratios of functionally profitable humeroscapular ankylosis, some discrepancies in recommended angles exist. Moreover, there are data acquired with angle measurement techniques and are not acceptable for the surgery room. Operating orthopedists have to orient not to instrumental control of accuracy of apposition of the humerus and the scapula, but to own experience, spatial thinking and own muscular-articular feeling.

One should note that the single known special internal fixator for shoulder joint arthrodesis [61] has allowed approximation of solving of this problem of correct positioning of the humerus in relation to the scapula (also in absence of capitellum), but also has shown quite high efficiency in the surgery room. This technique gives good clinical results relating to rate of union and to functional outcomes. But its development is not yet considered as complete, and some improved systems of new generation are expected.

The analysis of studies of comparative estimation of efficiency of shoulder arthrodesis and reverse endoprosthetics has found some key problems requiring for further research. The first issue: one should note that arthrodesis presents the high proportion of revision surgeries for all types of failure of the reverse endoprosthetics of the shoulder joint. Unfortunately, the proportion of this surgery is not possible to estimate according to the data of registers of endoprosthetics, and this issue requires for separate investigation.

The second issue is the fact that function of the upper extremity corresponds to good result of reverse endoprosthetics in ankylosis of the shoulder joint in functionally favorable position, without trend to long term worsening, without risk of late revision for loosening, and with significant gain in muscular strength of the upper extremity that is obligatory to consider for patients dealing with physical labor professions.

Currently, one can observe that real humeroscapular ratios of functionally favorable ankylosis are unknown yet. Unfortunately, there are not ways for their accurate intrasurgical control. Which angles are needed for matching the scapula and the humerus? How to prevent errors? And one main thing, which is zero mark? It is obvious that it is impossible to reduplicate the traditional measurement of angles in relation to the body, as it is common for angle measurement for awakening patient in standing position, for anesthetized patient on the surgical table in lateral position and in “beach chair” position. But a surgeon faces a task of accurate insertion to functionally favorable angles, which are not known yet and are not controlled on the surgical table. It requires for separate investigation. Possibly, the use of 3D reconstructions with CT data from patients with the best treatment outcomes will give information on real functionally favorable position. This technique has become available and much more objective than projection X-ray images.

Three-dimensional configuration and acceptable ranges of variations of functionally profitable relationships in humeroscapular ankylosis are to be developed and studied in the future. These issues are needed for surgical technique where standard angles between the axis of the fixator fork and the axis of the humeral plate, under which the humerus and the scapula should be matched, can be as functionally favorable as possible. Fixators of new generation will require for some corrections, which will improve the possibility of self-installment under correct angles during matching the elements of the resected joint regardless of surgeon’s experience.

And, finally, a study of strength properties of fixation of the humerus to the scapula with use of the special device in comparison with the most popular techniques described in publications is required.

Information on financing and conflict of interests

The study was conducted without sponsorship.

The authors declare the absence of any clear or potential conflicts of interests relating to publication of this article.