USE OF SHORT FEMORAL COMPONENTS IN TOTAL HIP REPLACEMENT Aladyshev N.A., Ezhov I.Yu.
Volga District Medical Centre under Federal Medical and Biological Agency, Nizhny Novgorod, Russia
The history of development of short stems and their evolution and classification
Hip replacement is the most successful technique for treating its degenerative and posttraumatic changes, femoral neck fractures and consequences of pelvic fractures (polytrauma), but the increasing number of revision interventions results in searching the new solutions for this problem [1].
The principle of bone preserving is important for hip replacement. It is not a coincidence that the first implants corresponded to this principle. The first attempts of development of hip implants with short stems were initiated in 1930-1940s. In 1938, Wiles carried out the surgery with placement of the implants for six patients. The implant construct was associated, and the short femoral component penetrated the femoral neck and was connected to the plate, which was fixed externally with two screws in the subtrochanteric region. One of the first implants by Judet brothers had a short neck stem [2]. In 1956, a Brazilian orthopedist Joao de Azevedo Lage developed the bipolar prosthesis with the short femoral component. [3]. Huggler et al offered the implant, which was similar with the implant by P. Whiles (1938), with the supporting plate. The distinctive feature was the threaded construct of the acetabular component [4].
In the end of 70s and early 80s of 20th century, two stems were developed that influenced on further improvement in this field. In 1979, Pipino et al offered the monoblock (with the head) Biodynamic (Stryker) for cementless fixation. The design features of the stem supposed the preservation of the neck during resection of the proximal femoral bone, with the metal “collar” resting on the preserved neck. In 1982, B.F. Morrey developed Mayo Clinic Stem (Zimmer), with the length of 60 mm, two trapezoidal sections in different planes, titanium mesh coating in the proximal part and the module head [5].
However the rapid development and increasing popularity of the short stems were in the end of 20th and the beginning of 21st century. Currently, there is not any classification of the short femoral components with clear and generally accepted definition of characteristics of implants and degrees of preservation of femoral metaphysis and diaphysis. Therefore, sometimes it is unclear, which femoral stem can be classified as usual or short [5].
Feyen and Shimmin offered the classification of all femoral components on the basis of femoral resection level and the principle of the component fixation: the type 1 – resurfacing, the type 2 – median resection of the head, the type 5 – the stems with distal diaphyseal fixation. At the same time, the differences between the type 3 (the short stem) and the type 4 (the standard stem) on the basis of length measuring are not the benchmarks. However the length of the short stem is characterized by the authors as follows: “the general length of the implant should be less than the double distance between the apex of the greater trochanter and the bottom of the lesser trochanter” [6].
Despite of the variety of the constructs and the names of the short stems, the Joint Implant Surgery and Research Foundation (JISRF) developed the own classification, which similar with the above-mentioned one [7].
McTighe et al. (2013) presented the own simplified classification of the short femoral stems. The classification includes three main types: the type of metaphyseal fixation (standard resection of the neck), the type of neck fixation (high resection of the neck) and the type of fixation in the femoral head (resurfacing) [9].
In his review “Current concepts, classification, and results in short stem hip arthroplasty”, professor Francesco Falez summarized the results of the research of the different classifications and divided them into the following ones: femoral neck – Spiron (k-implant); with neck preservation, such as CFP (Waldemar Link) or Collo-Mis; with preservation of trochanter, such as Aida (Implantcast); the stems which damage the trochanter, such as CLS Brevius Stem (Zimmer) [5].
Results of hip replacement with short femoral stems
The short femoral components are used not so long time. Therefore, not all implants can be estimated according to the 10-year survival (the standard index in joint replacement). The requirement for estimation of a standard parameter appeared as result of the variety of the examined group and duration of observation. National Institute of Clinical Excellence (NICE) developed the criterion for estimation of the short stems (because of short period of observation): the number of revision procedure per 100 implants per year. Moreover, 10-year survival shows 90 % correspondence with the annual number of revision procedures – 1 per 100 installed implants [5].
The literature data shows the worst clinical outcomes with higher rate of revision in the conservative (organ-saving) group of the short stems (Collum type, subcapital resection, neck stems). This type includes Gothenburg Osseointegrated Titanium (GOT, Sweden), CUT (Eska, Luebeck, Germany), Spiron (K-Implant, Garbsen, Germany).
The NICE unified criterion shows two revisions per 100 implants per year for Gothenburg Osseointegrated Titanium (GOT). These findings are described in the group of 40 patients with 24 months of the follow-up. The study of CUT stem (Eska, Luebeck, Germany) showed the satisfactory level of survival. NICE unified estimation showed 1 revision per 100 implants per year [5].
Ender et al. (2007) estimated the results of 123 procedures of hip replacement with Eska short stems in 113 patients. The mean time of observation was 5 years. Revision surgery was conducted in 13 cases. The authors concluded that the mid-term results were unsatisfactory due to high level of aseptic loosening of the femoral component. GOT and CUT stems are not produced anymore [8].
The most famous member of this group (with available studies) is Spiron implant (K-implant, Garbsen, Germany). According to the NICE criterion, the survival of such implants is 0.64 [9]. Lugeder A. et al. (2013) analyzed 28 operations using such implant. Only one case required for the revision surgery owing to aseptic loosening. The functional results increased from 55 to 99 points according to Harris Hip Score (HHS) [10]. Birkenhauer B. et al. (2004) analyzed 38 surgeries. One year later, they noted the excellent results (according to HHS) in 20 patients, without a single case of loosening [5].
Despite the fact that some authors describe the successful use of femoral neck stems, the long term clinical results are usually unsatisfactory due to several causes. The first possible cause is stem valgization with decreasing lateral femoral offset. The signs of resorption around the femoral component have been described, as well as bone atrophy in the calcaneal region in the X-ray images, and development of stress shielding syndrome with 50 % revision rate after 8 years. Another possible cause consists in the implantation technique – the risk of an intrasurgical fracture or malposition of the implant (with potential harm for future stability and integration of the component). This cause is also associated with the limitations in the indications: besides age recommendations, patients with some anatomic features of the femoral neck or unsatisfactory quality of bone tissue are excluded. Despite the decreasing rate of use of such implants, the follow-up can identify the biomechanical features of the femoral neck [11].
The partial collum are CFP, Collo-Mis, Nanos, Mini-Hip, Metha, Optimus, LPI Prime. The stems with greater trochanter preservation are Taperloc, Microplasty, GTS, Fitmore B, Aida. The literature includes some individual reports on MiniHip (Corin, Cirencester, United Kingdom), Optimys (Mathys, Bettlach, Switzerland), Collo-Mis (Lima, Udine, Italy) and Aida (Implantcast, Buxtehude, Germany), but these studies are short term, and the observed groups are small [12, 13, 14].
After comparing Partial Collum (partial neck stems) and Trochanter-Sparing (stems with preservation of the greater trochanter), the absence of any differences in survival was evident. Both types show the revision level less than 1 per 100 implants (NICE criterion) [5].
As mentioned, Mayo Stem (Zimmer) was developed in 1982. According to multiple studies, it has shown the good mid-term results during the years of using. In 1989, B.F. Morrey published the short term results (at least y year) of use of this stem: 95 % of the cases were satisfactory results [9].
In 2000, Morrey B.F. et al. conducted the analysis of 159 stems for the period of 6.1 years: the survival rate was 91 %, 15 revision procedures were conducted, including 9 cases caused by aseptic loosening of the implant components [5]. Gagala et al. (2009) and Goebel D. et al. (2009) received the satisfactory mid-term results [5]. Martins LG (2014) researched the survival of Mayo stem and found the rate of 92.3 % after 6.1 years [16]. Falez et al. (2008) analyzed the results of 160 operations with Mayo stem. The survival rate was 98 % after 4.7 years, with 4 cases of revision surgery [5].
Some authors are unsatisfied with this femoral component. Gilbert et al. (2009) performed 49 operations. The mean observation lasted for 34 months. The authors noted the incorrect placement of the femoral component of the implant in 18 % of the cases, the intrasurgical fracture of the femoral bone – in 4 %. The researchers concluded the infeasibility of this stem due to high risk of the femoral bone fracture [17].
Nanos stem (Smith and Nephew) is also related to this group. Ettinger et al. (2011) described the mid-term results in 72 patients. The mean follow-up was 5.2 years. The survival rate was 100 %. The revision surgery was not required in the study group [18].
Kaipel M. et al. (2015) researched the X-ray features in the group of 49 patients 2 years after hip replacement with Nanos stem. 10 % of the patients showed the radiologic signs of vertical migration that was the predictor of late aseptic loosening [19].
Budde S. et al. (2016) researched the migration of Nanos femoral stem during 2 years after the surgery. The authors concluded that this stem had the migration risk within 3 months after surgery, but then the process did not progress owing to the secondary implant stabilizing [20].
Stadler N. et al. (2016) received the excellent outcomes after use of Nanos femoral component. 81 patients were examined after 2.2 years on average. The functional status improved from 36.6 to 94.5 points according to Harris Hip Score. No revision surgery was performed [21].
Another representative of the short femoral components is Metha (B.Braun). It has been used since 2000. Gulow et al. (2007) firstly described the short term results in young patients. The further studies also showed the good functional results and the high short term survival (Milecki M et al., 2008) [5].
Floerkemeier T. et al. (2012) described the good functional results (HHS increased from 41 to 90 points) in the group of 64 patients (73 hip joints) with aseptic femoral head necrosis. The follow-up was 34 months. The complications were only in 3 cases [22].
Wittenberg et al. investigated the documents from 250 patients who had received hip replacement with Metha stem. The mean follow-up was 4.9 years. The mean age of the patients was 60 years. The mean HHS was 97 points at the moment of the examination. Only 1 % of the operated patients estimated the surgery outcomes as unsatisfactory. The authors described 18 revision surgeries including 9 cases with damage of the module adapter of the implant neck. With exclusion of revisions relation to damages of the module components, the five-year survival was 96.7 % according to Kaplan-Mayer analysis [23].
The results of the biggest study of the Metha femoral components were published by Schnurr et al. in 2017. The study included 1,888 operations for the period of 2004-2014. The mean follow-up was 6 years. The survival rate was 93 %. The revision rate was higher for the module stems with titanium necks (5.3 %) as compared to 1.8 % in the group of the monoblocks [24].
Another short stem by Zimmer is Fitmore. The biomechanical studies showed the relationships between the proximal femoral bone and the implant that influenced on the construct of the femoral stem. Firstly, the size of the intramedullary canal (the stem size) does not correlate with its offset (the neck). Secondly, the offset and the medial curvature of the calcaneal region are associated inversely: the higher radius of the calcaneal curvature, the higher offset. As result, Fitmore includes some various femoral components with different variants of offset distance and the calcaneal curvature (the types A, B, C). The study by Gustke K. (2012) analyzed the results of 500 operations with Fitmore stems 1.3 years after surgery on average. The survival rate was 100 % [25].
Von Roth P et al. (2014) compared the results of Fitmore and CLS stems. The study group included 40 patients. The same amount of the patients was in the control group. The differences in the functional results (HHS, SF-36 and WOMAC) were not identified. The long term results showed the similar survival in both groups [26].
Proxima femoral stem showed the best survival per 100 components per year according to the review of 3 various studies by Van Oldenrijk [8].
Besides the clinical studies, the cadaveric ones present the scientific interest. Westphal et al. (2006) performed the study of the short and standard femoral components placed in the cadaveric femoral bones with subsequent cyclic load (15,000 cycles). It showed the higher level of migration for the short femoral components in comparison with the standard ones. However when contacting with the cortical bone, with good quality of bone tissue and correct positioning, the short femoral components provide more physiologic distribution of the load to the proximal hip, and prevent stress shielding syndrome [27].
ANTERIOR APPROACH TO HIP JOINT
Low invasive approaches to the hip joint became possible with appearance and evolution of the short femoral stems. Now the researchers and the surgeons are giving more attention to the anterior approach to the hip joint. The direct anterior approach to the hip joint was firstly described by Carl Hueter in 1881. The development of this approach is improperly associated with Smith-Petersen, considering the fact that he used it during his researches beginning from 1917 (the first mention in his publication). In the modern literature, the names of both surgeons are associated with development and popularization of this approach. Judet brothers described this approach for hip replacement in 1950. O’Brien described it in 1955. Then the interest to the anterior approach for hip replacement decreased since Sir John Charnley advocated using the approach with greater trochanter osteotomy. After the years, Light and Keggi published the first American experience with the direct anterior approach for 104 patients. The anterior hip approach presents the incision or intermuscular fiber separation through the interval between the TFL Musculus Tensor Fascia Lata and the musculus sartorius. Some authors describe this technique for both primary hip replacement and proximal hip fracture [28].
Some authors think that the anterior approach can be used for patients with specific body tympanum and anatomic features of the hip joint. The “ideal” patient is with moderate muscular mass, with valgus femoral neck and good hip offset, and the body mass index < 30. Some anatomic features impede the anterior approach: wide or horizontal iliac wing limits the approach to the femoral bone canal during creation and placement of the femoral component. The varus position of the neck with decreased neck-diaphysis angle and the femoral offset, as well as obesity and high muscular mass, give deeper position of the hip and impedes the positioning of the components of the implant. The disadvantage of the anterior approach is the limited approach to the posterior column of the pelvis. If a patient has a deficiency of the posterior wall of the pelvis and the defect is planned to be filled with the augment, then the anterior approach is not recommended [29].
Most authors use the supination position on the standard or orthopedic table. On the standard table, the patient should be placed in the manner that the hip joint field would be in the place of pivot connection of the table. Michel et al. offer the lateral position. Kennon et al. practice the inclination of the operation table. Also the pelvis should be elevated with a roller under the sacrum. If the orthopedic table is used, the leg should be fixed appropriately for prevention of the fibular nerve neuropathy [30].
Most authors use the anterior superior iliac spine and the greater trochanter as the landmarks during making the skin incision. The oblique skin incision should begin 2-4 cm lower and more distal than the anterior superior iliac spine, with oblique pathway to the greater trochanter. The incision should not go beyond the intertrochanteric line owing to danger of an injury to the lateral femoral circumflex artery and the femoral nerve. The incision should be in the plane of the line connecting the anterior superior iliac spine and the middle part of the patella. Electron-optical image intensifying is used for searching the femoral neck, which is the relative middle part of the approach [31].
A common complication of such approach is a damage of the lateral cutaneous nerve. Despite the fact that the lateral interval between the musculus tensor fasciae latae and the musculus sartorius is considered as safe from the perspective of topical anatomy of the lateral cutaneous nerve, the cadaveric studies showed that its gluteal branch is located 44 mm from the anterior superior iliac spine; in 50 % of the cases, the femoral branch of the nerve crossed the anterior body of the musculus tensor fasciae latae with the distance of 46 mm from the anterior superior iliac spine [32]. The cadaveric study showed some abnormalities in location of the branches of the lateral cutaneous nerve in 10 % of the cases in the group of 60 persons [33]. De Geest et al. noted the decreasing incidence of injuries to the external skin nerve of the hip in lateralization of this approach. Subcutaneous fat should be dissected in the blunt manner. Then the m. tensor fasciae latae is opened from the medial side of the greater trochanter, leaving some distance for subsequent suturing. Fascial dissection in the lateral interval can cause the injury to the motor branch of the superior gluteal nerve [34].
Fascial dissection towards posterior direction is not recommended. The fascia is rigid and thick there, and it passes into the dorsal gluteal muscle. From other side, in case of medialization, the approach enters the borders of the femoral triangle that significantly increases the risk of the vascular-nervous bundle damage. When capsule dissected, it is recommended to bring the sharp retractor to the region behind the greater trochanter. The second retractor (Hohmann) is to be brought trough m. vastus lateralis to the region behind the medial surface of the femoral neck, with medial shift of m. femoris rectus and m. sartorius. The capsulotomy and capsuloectomy are conducted [35].
The lateral approach to the hip joint is performed in 42 % of cases of hip replacement, but muscular dissection causes the intense postsurgical pain syndrome, long term hospital stay and long term rehabilitation. The anterior approach has the lower length and lower rate of injuries in comparison with the lateral one, i.e. it is classified as low invasive [36].
Bremer et al. (2011) conducted MRI for the hip joint after hip replacement with lateral, posterior and anterior approaches. He did not identify any differences in m. tensor fasciae latae. However some changes in the group of the abductors were found (partial damage, tendinitis, bursitis, fat degeneration) and they were more common for transgluteal approaches [37].
Chen Yue (2015) et al. conducted the metaanalysis of 12 studies of lateral and direct anterior approaches (2,991 and 1,910 operations with direct and lateral approaches correspondingly). The direct anterior approach was associated with early rehabilitation of the patients, lower pain after surgery and decreasing hospital stay [38].
Molli et al. (2013) carried out a big study. They performed 658 operations with hip replacement using low invasive direct anterior approach for 606 patients within the period from March 2006 to March 2008. 389 cases included the standard femoral components, 269 cases – the short femoral components. The mean follow-up was 29.2 months. The authors noted the higher rate of complications after use of the standard length stems (3.1 %) in comparison with the short femoral components (0.4 %). There were not any statistical differences in prosthesis survival and hip functioning (HHS) between the groups [39].
Other researchers claim that the anterior approach has not any advantages. Reichert JC et al. (2015) studied 171 hip replacement operations with direct and lateral approaches. The mid-term observation did not identify any significant differences in the functional status (Harris hip score) and in life quality (SF-36) [40].
Rathod PA et al. (2014) identified the similar functional results in comparison of anterior and posterior approaches, and the relationship between fast rehabilitation and selection of patients [41]. The metaanalysis by Higgins BT et al. included 17 studies (2,302 operations). The authors did not identify any statistical significance in in pain and the functional status after use of anterior and posterior approaches [42].
Engdal M et al. (2016) studied the postsurgical physical activity (with the accelerometer) within 4 days after hip replacement surgery with different approaches (anterior, lateral and posterior). No statistical differences were found between the groups [43].
Alijanipour P. et al. (2016) conducted the comparative study of heterotopic ossification in anterior and lateral approaches. 1,482 patients were examined. The incidence of the initial stages of ossification (according to Brooker) was higher in the group of lateral approaches (36.1 and 19.4 % correspondingly). However intense ossification (the degrees 3 and 4 according to Brooker) developed in both groups with similar incidence (3.9 and 3.0 %) [44].
Despite of the evident advantages of the approach, some disadvantages exist such as acquisition of special tools, surgical training, increasing surgery time and use of the image intensifier. Masonis analyzed 100 operations and concluded that the statistically significant time of surgery decreased only after realization of 100 operations with the anterior approach [34].
Although some authors indicate the low rate of complications after this approach, others describe the high risk. The metaanalysis showed the similar rate of complications except for the femoral cutaneous nerve damage. The incidence of this complication is 5.69 higher for anterior direct approach (De Geest) [34].
Spaans et al. described 20 % level of complications after 46 hip replacement procedures with the anterior approach. The complications included early loosening of the femoral and acetabular components, which required for revision surgery [45].
Gwo-Chin Lee et al. (2015) analyzed the complications of the direct anterior approach. The author carried out the metaanalysis of 38 medical studies including 11,810 hip replacement procedures. The analysis identified 920 complications (7.8 %). The most common complications were femoral nerve neuropathy and the lateral cutaneous femoral nerve damage (2.8 %). The intrasurgical fractures of the femoral bone were quite common (2.3 %). The risk of a fracture was higher for this approach and was associated with limited visualization and the operating surgeon’ experience. The incidence of dislocations was 1.2 % that was comparable with the standard approaches. The incidence of postsurgical wound complications was 1.2 % [46].
Christensen et al. described 1.4 % level of the complications that was significantly higher than for the standard approaches. Hallert et al. described the revision level of 2.5 %, whereas De Geest et al. showed the high incidence of revision operations (6.7 %) within the first 12 months after surgery [47, 48, 34].
The domestic publications for this topic are rare. Karagodina et al. (2015) performed the study of the adaptive changes in the femoral bone around the prosthesis component. The authors compared the bone mineral density in two groups. The short femoral component Fitmore was implanted for 26 patients, the standard femoral component Alloclassic – for 20. 3 months after hip replacement, they observed the loss of bone mineral density around the implants of both types, with higher intensity in Gruen’s regions 2 and 7 for Fitmore stem and in the regions 6 and 7 for Alloclassic implant. 6 months after surgery, almost all regions of the femoral bone showed the moderate stabilization around the implants. 12 months after hip replacement, regardless of the type and design of the implants, the loss of bone mass was observed in Gruen’s regions 1 and 7 that did not make the negative influence on the clinical outcome. The authors concluded that regardless of the implant design, the specific rebuilding of bone matter happens in the proximal femoral bone, with lost bone mass in Gruen’s regions 1 and 7 and relative bone condensation in the distal parts of the implant (stress-shielding). It means that the shorter femoral components do not favor the preservation of bone mass in the proximal hip [49].
Firsov et al. (2015) published the study of the functional outcomes of the short femoral components with use of navigation. Hip joint replacement was carried out for 210 patients with hip joint abnormality. The patients were distributed into three groups depending on the type of the femoral components and use of computer navigation. Harris score and VAS were used for estimating the results. The best results were achieved in the group of the patients with the short femoral component installed under computer navigation. HHS increased from 45.8 points (before surgery) to 80.9 points 6 months later, and 85.4 in the 12th month of observation. The computer navigation system improved the functional results of hip replacement [50].
CONCLUSION
The popular procedure of hip joint replacement improves all around the world. The surgical technique improves, with the trend to minimizing surgical injury. The low invasive approaches are preferable. The direct anterior approach has been improved during the recent years. Its advantages are preservation of the hip joint stabilizers, low traumatic effect and fast rehabilitation. Other researchers show the disadvantages of this technique: need for special instruments, limitations in body composition, long time of surgery. The issue is poorly described in the domestic literature. The results from different researches are contradictory, and the issue of popularization of the anterior approach is still opened.
The concept of lower traumatic effect of hip replacement has touched upon the approaches for the hip joint and implantation process. The short femoral components appeared in the early 80s of the previous century, and they have been still improved. Their main sign is not the length of the femoral component, but the level of resection of the proximal hip. Some researchers consider that preservation of most part of the femoral neck improves the osteintegration process. The second advantage is preservation of bone tissue for subsequent revision operations that is important for young patients.
The literature findings are contradictory and require for further studies.
Information about conflict of interests
The study was conducted without sponsorship. The authors declare the absence of any clear and potential conflicts of interests relating to publication of this article.