Hip arthrosis

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Classification according to ICD-10
M16 Coxarthrosis (osteoarthritis of the hip joint)
M16.0 primary coxarthrosis, bilateral
M16.1 primary coxarthrosis, other (unilateral, onA)
M16.2 Coxarthrosis as a result of dysplasia, bilateral
M16.3 Other dysplastic coxarthrosis (unilateral, onA)
M16.4 Post-traumatic coxarthrosis on both sides
M16.5 Other post-traumatic coxarthrosis (unilateral, onA)
M16.6 Other secondary coxarthrosis on both sides
M16.7 Other secondary coxarthrosis (unilateral, onA)
M16.9 Coxarthrosis, unspecified
ICD-10 online (WHO version 2019)

The hip osteoarthritis ( Latin osteoarthritis coxae ; from ancient Greek ἄρθρον Arthron , German , 'joint , Latin deformare , maim' and Latin coxa , hip ' ), also Coxarthrose (German coxarthrosis ), a degenerative disease of the hip joint , especially in old age, which is based on wear and tear of the cartilage surface of the hip socket (acetabulum) and femoral head (caput femoris) . It is the most common form of osteoarthritis in humans.

The causes of hip joint arthrosis can be various (pre-) diseases or (pre-) injuries in the hip joint area, but in around a quarter of all cases no exact cause can be found. Characteristic for the disease is a load-dependent pain directly in the hip joint. This is projected onto the groin and , if there is painful involvement of structures on the large rolling mound, also onto the outside of the thigh. Often, however, there are also sources of pain in the lumbar spine and sacrum joint. The diagnosis of hip arthrosis is made on the basis of X-ray images , which are usually very meaningful and allow the disease to be precisely classified. Endoprosthetic hip replacement dominates therapy, with over 150,000 first-time implantations of artificial hip joints being carried out in Germany every year. Accompanying conservative pain treatment can be helpful both before and after the operation. The prognosis after the surgical intervention is usually favorable.

Hip arthrosis creates considerable costs for the health system . The therapy is remunerated in accordance with the applicable flat-rate fees and special fees , which, however, do not entirely cover the total costs. A clear difference in costs can be observed internationally, especially for implants.

Epidemiology

About 5 percent of adults in Germany over the age of 60 suffer from hip osteoarthritis symptoms. The prevalence of clinically symptomatic coxarthrosis is 5 percent in men and 5–6 percent in women. This makes it the most common form of osteoarthritis in humans , even before knee osteoarthritis. Every year around 100,000 to 150,000 hip prostheses are implanted in Germany because of coxarthrosis.

The most common cases of coxarthrosis can be assigned to stages 1, 2 and 3. Around 80 percent of all illnesses arise from secondary causes. In Germany, around two percent of all people between the ages of 65 and 74 are affected by a severe form of hip arthrosis.

Risk factors

The results of the Ulm Osteoarthritis Study indicate a connection between increasing age, diabetes mellitus , a previous joint disease or injury on the opposite side (contralateral) and the occurrence of bilateral (bilateral) coxarthrosis. In the case of unilateral (unilateral) coxarthrosis, a strong association with previous joint diseases and injuries was established. Risk factors for the involvement of multiple joints (polyarticular) are previous joint diseases or injuries, older age, female gender, family history and gout . Joint-specific risk factors are congenital changes or changes caused by injuries.

Pathophysiology

Model of a healthy pelvis

Arthrosis are generally more common on the lower extremities than on the upper ones , as these carry the whole body weight when walking and standing. The statics and kinetics of walking upright place significantly different demands on the joint than moving around on four legs.

In the foreground of the pathophysiological processes that lead to the clinical picture of coxarthrosis, the cartilage damage to the hip joint is initially. The subsequent extensive cartilage destruction, especially in the area of ​​the greatest pressure load, ultimately leads to the complete exposure of the bone surface at the joint. Simplified can be summarized:

  1. Depending on the period of use (i.e. age), wear and tear will occur sooner or later. The cartilage layer of the joint is rubbed off and therefore thinner.
  2. The bone under the cartilage is exposed to increased mechanical stress and reacts with a compression of its internal structure (subchondral sclerosis) .
  3. In the further course the joint is deformed (deforming arthrosis) , and the bone under the cartilage becomes perforated ( rubble cysts ) .
  4. In order to widen the pressure-absorbing zone, the body builds bone material with which the acetabulum is widened ( osteophytes ) . The femoral head then no longer has a spherical shape (pre-arthrotic deformity) , resulting in joint pain, joint stiffness and a restriction in the range of motion.

This simplified notion of a pure signs of wear emanating (so-called "wear and tear concept."), As seen in the recent research differentiated: The Coxarthrose - like all arthrosis - understood as a disease process, the imbalance between joint-damaging and healing ( reparative) mechanisms. If incorrect loading, destructive mechanisms or excessive reparation processes predominate, the picture of osteoarthritis develops - in this case coxarthrosis.

causes

Hip joint - the main mechanical stress zone is shown in blue
Hip joint dysplasia - the main mechanical stress zone is significantly smaller than the normal variant

The causes of coxarthrosis are diverse and are basically divided into two groups: primary coxarthrosis (approx. 20-25 percent of cases) and secondary coxarthrosis (approx. 75-80 percent of cases).

Primary causes

In most patients over the age of 50, an exact cause of joint wear cannot be determined. The symptoms are based on a constitutional inferiority of the articular cartilage without any previous illness, which becomes noticeable in old age due to the natural abrasion described above. This phenomenon is called idiopathic or primary coxarthrosis .

Secondary causes

Joint damage and deformities, usually in childhood, are another cause of coxarthrosis. Due to the abnormally developed or destroyed joint surfaces, these lead to a reduction in the size of the contact surfaces of the joint and thus to increased stress pressure. This leads to the joint running out of round "like a defective motor" and thus accelerating the formation of wear. As a result, osteoarthritis develops much earlier in the affected patient than in the primary form. These secondary causes of coxarthrosis include:

Rare causes are also:

Symptoms

A typical symptom of hip osteoarthritis in the elderly is a stress -related pain, mainly from the accompanying synovitis caused, but is not obligatory. In the differential diagnosis , however, the pain process can be used to differentiate coxarthrosis from inflammatory joint diseases , which typically cause stress- independent pain.

The complaints are felt directly in the hip joint. Typically, most patients are initially symptom-free after a morning enema pain , until the symptoms increase sharply in the evening, depending on the daily joint load. Affected patients describe the pain characteristics as "piercing" or "dull". Over the years, the symptoms steadily increase. In between, phases of temporary, relapsing aggravation can occur, which are referred to as active or decompensated osteoarthritis . A certain restriction of movement in the hip joint can be associated with the disease, but is not the rule. Typically, there is no joint swelling, blockage or instability in the hip joint with coxarthrosis.

Diagnosis

After a clinical examination by the attending physician, the diagnosis of coxarthrosis is primarily based on the findings of the X-ray examination .

above: dysplasia-coxarthrosis
below: healthy hip joint

Physical examination

The inspection is usually less noticeable, especially when the patient is lying down. Often a fall in gait relief limp and external rotation of the foot on the affected side (about 10-20 °) on. This can shorten the stance phase . During palpation , tenderness located directly on the inguinal ligament (ligamentum inguinale) is typically in the foreground, and more rarely over the large roll hillock (greater trochanter) on the outside of the hip. The tenderness on the outside is caused by the overloading of the gluteal muscles, which is based on disturbed joint mechanics.

Differential diagnoses

The above-mentioned complaints can, however, also be caused by other processes and diseases, which must be excluded by differential diagnosis in the event of doubtful findings. These include:

X-ray diagnostics

The domain of osteoarthritis diagnosis is the x-ray . Common recording methods are the recording in the Ap-ray path , which is very meaningful, as well as the Lauenstein projection, which is mainly used to display the proximal thigh bone from the side . The latter takes place in the AP beam path, the leg is spread apart and turned 90 ° outwards.

With the recording methods listed above, all radiological signs of coxarthrosis can usually be shown. These are:

  • Joint space narrowing: initially in the main load area, then spreads over the entire joint space
  • Rubble cysts: grow particularly large cranial to the acetabulum and cause incongruence of the articular surface
  • subchondral sclerotherapy: the acetabulum is particularly affected
  • Osteophytes : especially laterally-cranial and medial-caudal on the acetabulum; less often on the femoral head ("capital drop")

The radiological signs of coxarthrosis are reliable ( sensitivity 89%, specificity 91%), but do not have to correlate with the extent of the hip discomfort or with the clinical findings.

The x-ray can also provide information about preopthrotic deformities as the cause of coxarthrosis. For example, in the case of hip dysplasia (see Fig.), The femoral head is not sufficiently roofed and has therefore migrated upwards. This results in a leg shortening (approx. 6 cm in the picture). In the course of time there is a massive "rounding" of the femoral head, the joint gap is almost completely eliminated, the hip joint becomes stiff.

For differential diagnosis and therapy planning, the German Society for Orthopedics and Orthopedic Surgery (DGOOC) recommends an additional pelvic survey and, if necessary, additional x-rays.

Further imaging procedures such as magnetic resonance tomography , computed tomography , scintigraphy or sonography are usually not required. However, sonography can be helpful as an examination method in the case of a "capsular distension" (capsule loosening) in the hip joint, which is caused by an effusion in the joint .

Classification

Principles

The German Society for Orthopedics and Orthopedic Surgery (DGOOC) recommends two types of staging for coxarthrosis - a radiological and a clinical one. These are primarily used to assess treatment results and follow-up controls in the context of clinical studies. They are not suitable as primary schemes for therapy decision-making.

Radiological staging

Schematic representation of the radiological signs of coxarthrosis:

(1) (marginal) osteophyte
(2) subchondral sclerosis
(3) rubble cyst
(4) narrowing of the joint space

The classification according to Kellgren and Lawrence ("K&L" score; 1963), which divides osteoarthritis into four stages, is recommended for radiological staging:

Degree evaluation Finding
0 normal no radiological signs of coxarthrosis
1 Suspected coxarthrosis small osteophytes , unclear relevance
2 minor coxarthrosis Osteophytes, joint space normal
3 moderate coxarthrosis slight narrowing of the joint space, debris cysts
4th severe coxarthrosis pronounced narrowing of the joint space, subchondral sclerotherapy, bony deformities of the hip joint

If the findings are higher than grade 2, the diagnosis of coxarthrosis is usually made. Because the detection of osteophytes does not necessarily correlate with the clinical appearance of coxarthrosis, the classification according to Kellgren and Lawrence is not undisputed.

Clinical staging

The following scores are recommended for the clinical staging of coxarthrosis:

  • Harris Hip Score (1969)
  • Score according to Lequesne et al. (1987; includes the clinical severity of the coxarthrosis, the activities of daily living, the maximum walking distance as well as the pain in duration and quality)
  • Score according to Merle d'Aubignè (includes seven degrees of severity)
  • SF-36 questionnaire (in addition to collecting clinical, anamnestic and socio-medical parameters, it is also used to analyze the quality of life of the patients concerned)
  • Western Ontario Mac Master Arthritis Center (WOMAC) Osteoarthritis Index according to Bellamy and Buchanan (1986).

therapy

Forearm crutch

Conservative therapy

A causal conservative therapy of coxarthrosis is not possible so far. The aim of conservative therapy is therefore pain relief and mechanical relief for the affected hip joint.

A walking stick, which is held on the healthy side, can be used to relieve the joint. The forearm crutch is a guideline-compliant measure of orthopedic technology for coxarthrosis. Even orthotics such. B. in the form of soft heels ("buffer paragraph"), can significantly reduce the burden. If you are obese, you should aim for weight loss.

At the same time, physiotherapeutic measures should promote the patient's mobility and prevent contractures . In occupational therapy, difficulties in everyday life are identified, which are mainly compensated by the provision of aids and living space adjustments. Through physical therapy - i.e. H. Hydrotherapy (e.g. baths), heat therapy (e.g. mud bath ), phototherapy etc. - can additionally (and accompanying) a muscle-relaxing and pain-relieving effect.

Drug pain relief is mainly achieved through the use of oral nonsteroidal anti-inflammatory drugs (from the group of COX-2 inhibitors ). However, due to gastrointestinal side effects, these should not be taken regularly over a long period of time. Corticosteroid ointments are an alternative, but their effect is significantly weaker. In rare cases, intra-articular injection can also be considered.

Operative therapy

overview

Surgical therapy is indicated for radiologically proven coxarthrosis with significant functional impairment as well as complaints in everyday life and work, especially if conservative therapy is no longer sufficient. The method of choice is endoprosthetic replacement . In rare cases, especially in the case of joint surface incongruence, a joint-preserving correction osteotomy close to the hip can also be considered.

X-ray endoprosthesis

Endoprosthesis

The endoprosthetic replacement of the hip joint is by far the most common surgical therapeutic measure. Both the femoral head and the acetabulum are usually replaced, which is why it is called a total endoprosthesis (TEP). The prosthesis can be anchored in the bone with bone cement or fixed in place without cement through a special porous surface.

Cementless prosthesis

With the cementless prosthesis, the prosthesis is anchored in the bone by a special, porous surface ( cancellous metal) ("pressfit") into which the bone can grow. The main advantage is the long shelf life. In the event of loosening, the cementless prosthesis is usually much easier to remove than the cemented one. The main disadvantage is the slow mobilization of the patient: initially the leg has to be relieved for 2–4 weeks (20 kg), then partial weight bearing is required for another 2–8 weeks so that the bone can grow in. This is primarily an indication for younger patients (<65 years).

Cemented prosthesis

In the case of a cemented prosthesis, the prosthesis stem is attached to the femoral shaft using a self-curing plastic compound - polymethyl methacrylate (PMMA). The pan is usually made of polyethylene and is also fixed with PMMA. The - also common - combination of cemented stem and cementlessly implanted socket is called a hybrid system. The great advantage of the cemented endoprosthesis lies in the immediate loading capacity and the resulting early mobilization of the patient. This is why this method is particularly indicated for older people (> 65 years). Disadvantages are primarily a possible allergy to the bone cement and the risk of (aseptic) loosening of the prosthesis. In addition, in rare cases (0.6–10 percent) the introduction of the bone cement can lead to a fat embolism with acute circulatory collapse or even death from irreversible cardiovascular arrest (0.2–0.6 percent). This often dramatic complication could only be observed in isolated cases when inserting non-cemented prostheses.

Osteotomy near the hip joint

Pelvis of an adult woman with left hip dysplasia, triple osteotomy osteotomy lines (red)
Minimally invasive hip joint operation with an implanted endoprosthesis: the hip socket inlay made of polyethylene (white) with the endoprosthesis head located in it can be seen through the approximately 7 cm dorsolateral access to the hip joint .

The osteotomy near the hip joint is mainly used in the treatment of hip joint diseases in children. The operation usually takes place in childhood or early adolescence in order to prevent the development of coxarthrosis. The aim of this method is both to alleviate the symptoms and to prevent the further progression of coxarthrosis. Common procedures are:

  • Chiari osteotomy: cutting the iliac bone above the socket and creating an artificial socket roof by moving the acetabulum
  • Salter osteotomy : cutting of the iliac bone and lowering the roof of the socket
  • Triple osteotomy : division of the iliac , ischium and pubic bone and then the rotation of the acetabulum

The minimally invasive hip joint operation is primarily considered to be gentle on the muscles, as these do not have to be separated from the bone for the operation. Such an operation takes about an hour if the course is uncomplicated. In the case of deformities of the proximal femur, the intertrochanteric varicose vein osteotomy (DVO) is the method of choice.

Surgery Risks

The implantation of an artificial hip joint is associated with the general risks of a moderate surgical procedure.

Deep leg or pelvic vein thromboses are not uncommon complications , even with the use of standard prophylaxis . Not only do they leave considerable consequential damage on the affected leg ( post-thrombotic syndrome ), but can also lead to pulmonary embolism , sometimes with fatal outcome.

Bacterial infections can be triggered by contamination during the procedure or by the spread of bacteria via the bloodstream ( hematogenous seed ). The consequences range from uncomplicated superficial wound infection, which can be quickly resolved by local measures, to deep prosthesis infection, which necessitates the removal of the prosthesis and the temporary creation of a girdlestone situation .

The intraoperative blood loss as well as postoperative hemorrhage or hematoma formation , the administration of packed red blood cells require. Encapsulated bruises (hematomas) occasionally require surgical removal. Injuries to nerves and blood vessels (especially the femoral nerve and sciatic nerve and the femoral artery ) may be subject to appropriate surgical technique usually, but not always be avoided. The femoral nerve is at risk when approached from the front, the sciatic nerve when approached from behind. Usually, however, it is not a matter of severing the nerve, but rather of crushing it, for example through hook pressure; in such cases there is a good chance of complete recovery of the nerve.

The recently operated hip joint often has a tendency to dislocate ( dislocation ). The application of a Quengel cast , which keeps the leg in internal rotation while resting in bed , often helps . After stabilization of the joint capsule in the course of wound healing and scarring , further dislocations are prevented. The operation can ultimately lead to a difference in leg length, which must be compensated for by raising the shoe sole accordingly.

An implant allergy to components of the endoprosthesis can make it necessary to replace the artificial joint ( revision surgery ) , similar to an infection .

A specific risk for the procedure is a seldom rupture of the greater trochanter (the hump of the thigh close to the body) to which the gluteus medius muscle, which is important for guiding the joint, attaches. This then requires additional stabilization through wiring or screws.

(Aseptic) loosening of the endoprosthesis was observed in around three percent of the patients over the course of ten years , which is associated with pain and possibly inflammatory changes and may require revision surgery with a change of the endoprosthesis. Loosening of the prosthesis after more than ten years is generally not regarded as a complication, but as a physiological process. An implant breakage occurs very rarely.

In some patients, heterotopic bone formation, periarticular ossification , occurred in the first months after the operation . Without suitable countermeasures, they can again restrict the mobility gained through the operation. Preventive X-ray irradiation of the surrounding tissue immediately before the operation (an average of 7  Gy using a linear accelerator ) reduces the formation of new bones in known risk patients. The postoperative administration of a suitable anti-inflammatory drug (usually indomethacin ) is standard for almost all patients for the same reason.

forecast

The endoprosthetic treatment in particular has a very good long-term prognosis, around 95 percent of the implanted endoprostheses are still functional after 10 years. According to the Swedish Hip Arthroplasty Register , 75 percent of hip replacements do not need to be replaced even after 26 years . According to the same study, another replacement operation (re-revision) is hardly more likely than a revision , because after ten years - statistically - more than 80 percent of the second prostheses are still implanted.

costs

Osteoarthritis is associated with significant costs for the health system. In 2008, diseases of the musculoskeletal system accounted for 28.55 billion euros (= 11.2 percent), after diseases of the circulatory system (2008: 36.97 billion euros = 14.5 percent) and diseases of the Digestive system (34.81 billion euros = 13.7 percent), the third largest cost factor for the treatment of diseases in Germany. The treatment of osteoarthritis caused 7.62 billion euros (as of 2004). Over 96 percent of the costs were incurred by people aged 45 and over, and around two thirds (67.8 percent) by people aged 65 and over.

The treatment costs for the endoprosthetic hip replacement are reimbursed in accordance with the applicable flat-rate per case and special fees. These are given in point values, with case-based flat rates covering the entire treatment costs (including surgery and hospitalization) and special fees only covering the operative service. The total points are calculated from the sum of the points for personnel and the points for material resources. For these, country-specific multiplication factors are agreed nationwide in order to calculate the respective remuneration. However, the clinical costs are not covered by the flat rate per case, as a study (at the Hannover Medical School , 1997) has shown. Accordingly, they exceed the flat rate per case when using cemented prostheses in 5 percent of cases and when using uncemented prostheses in 9 percent of cases. The main reason given for this difference is the implant costs, which are considerably more expensive for uncemented joint parts. The share of implant costs in the total clinical costs is 13–16 percent. The implant costs in Germany are still significantly lower than z. B. in England (17 percent), in the USA (24 percent) or in Australia (20–50 percent).

In Austria, the costs of a prosthesis or endoprosthesis, if the hip replacement is medically indicated, are only covered in full by the respective health insurance company in general public hospitals. In the case of other surgical facilities, the health insurance companies can refuse to cover the costs.

Guideline

There is a medical guideline of the highest level S3 from the German Society for Orthopedics and Orthopedic Surgery (DGOOC) and the Professional Association of Doctors for Orthopedics (BVO) from November 2009 (see literature ).

Hip arthrosis in animals

Arthrosis of the hip joint is very common in domestic dogs and house cats: In dogs, such diseases often occur in connection with hip dysplasia (HD) as an aging symptom. Current studies show that almost 90 percent of older house cats suffer from osteoarthritis of the hip, and even all animals with a body weight of over 6 kg.

literature

  • S3- guideline for coxarthrosis of the German Society for Orthopedics and Orthopedic Surgery (DGOOC). In: AWMF online (as of 2009)
  • J. Duparc et al .: Surgical Techniques in Orthopedics and Traumatology - Pelvic Ring and Hip (corresponds to: Volume VI). Lehmanns special edition, Urban & Fischer Verlag, Munich 2005, ISBN 3-86541-286-6 .
  • J. Krämer, J. Grifka et al .: Orthopädie , 6th edition. Springer Verlag, Berlin 2001, ISBN 3-540-41788-5 .
  • D. Lühmann, B. Hauschild, H. Raspe: Hip arthroplasty in osteoarthritis - a process assessment , Institute for Social Medicine, Medical University of Lübeck , Nomos Verlagsgesellschaft, Lübeck 2000, ISBN 3-7890-7039-4 .
  • M. Müller et al .: Surgery for study and practice , 9th edition. Medical publishing and information services, Breisach a. Rh. 2009, ISBN 3-929851-08-3 . P. 380ff.
  • HI Roach, S. Tilley: The Pathogenesis of Osteoarthritis . In: Bone and Osteoarthritis , Volume 4, Ed .: F. Bronner, MC Farach-Carson. Springer Verlag, 2007, ISBN 1-84628-513-5 . Pp. 1-19.
  • N. Wülker et al .: Pocket Textbook Orthopedics and Trauma Surgery , 1st edition. Thieme Verlag, Stuttgart 2005, ISBN 3-13-129971-1 .

Individual evidence

  1. ↑ Lühmann et al., 2000, p. 10.
  2. ↑ Lühmann et al., 2000, p. 3.
  3. ↑ a b c d e f g h i j k Müller, 2009, p. 385 f.
  4. ↑ Coxarthrosis - hip arthrosis - diagnosis, symptoms, treatment. Retrieved February 8, 2019 .
  5. ↑ epidemiology. Retrieved February 8, 2019 .
  6. ↑ Lühmann et al., 2000, pp. 11-12; see. Günther et al .: Clinical epidemiology of hip and knee arthrosis: An overview of the results of the Ulm osteoarthritis study , Zeitschrift für Rheumatologie, 2002, Vol. 61, No. 3, pp. 244–249 (24 ref.)
  7. ↑ Lühmann et al., 2000, p. 8
  8. ↑ a b c d Krämer et al., 2001, p. 234
  9. ↑ a b Wülker, 2005, p. 13.
  10. ↑ Müller, 2009, p. 382
  11. ↑ Wülker, 2005, p. 14
  12. ↑ Wülker, 2005, p. 1
  13. ↑ a b Wülker, 2005, p. 15
  14. ↑ Wülker, 2005, p. 18ff
  15. ↑ Wülker, 2005, p. 223
  16. ↑ Wülker, 2005, p. 16
  17. ↑ a b c DGOOC guidelines, chap. 6th
  18. ^ R. Altman et al .: The American College of Rheumatology criteria for the classification and reporting of osteoarthritis of the hip . In: Arthritis Rheum . , 2001, 44 (10) :, pp. 2449-2450.
  19. ↑ Wülker, 2005, p. 17.
  20. ↑ a b c DGOOC guidelines, chap. 9.
  21. ↑ a b Lühmann et al., 2000, pp. 13-14; see. Sun et al .: Incidence and prevalence of Cox and gonarthrosis in the general population . In: Zeitschrift für Orthopädie , 1997, 135, pp. 184-192
  22. ↑ Croft et al .: Defining osteoarthritis of the hip for epidemiologic studies , American Journal of Epidemiology, 1990, 132 (3), p. 514-22.
  23. ↑ Lühmann et al., 2000, p. 19
  24. ↑ Wülker, 2005, p. 19
  25. ↑ a b c d Wülker, 2005, pp. 19–22. Millis et al .: Osteotomies about the hip in the prevention and treatment of osteoarthritis . In: Instructional Course Lectures , 1992, 41, pp. 145-54
  26. ↑ N. Aebli, R. Pitto, J. Cancer: Fat embolism - a potentially fatal complication during orthopedic surgery . In: Switzerland Med Forum . No. 5 , 2005, p. 512-518 ( medicalforum.ch [PDF; 295 kB ; accessed on June 26, 2011]).
  27. ↑ J. Seufert: Preoperative radiation for the prevention of heterotopic ossification after hip joint replacement . Dissertation, Medical Faculty of the University of Würzburg , Würzburg 2004, p. 83ff., Uni-wuerzburg.de (PDF; 292 kB), accessed on June 28, 2011.
  28. ↑ Annual Report 2005 . The Swedish Hip Arthroplasty Register orthop.gu.se ( Memento from April 28, 1999 in the Internet Archive )
  29. ↑ health. Medical expenses. 2002, 2004, 2006 and 2008 . ( Memento from November 15, 2012 in the Internet Archive ) Federal Statistical Office, Wiesbaden 2010; Retrieved July 5, 2011
  30. ↑ Könning et al .: Perioperative cost analysis of cemented versus non-cemented total hip replacements for clinical and economic management . In: Z. Orthop. , 135, 1997, pp. 479-485.
  31. ↑ Lühmann et al., 2000, pp. 30-31.
  32. ↑ Reimbursement of costs for hip replacement. In: Salzburg Regional Health Insurance Fund. Retrieved February 8, 2019 .
  33. ↑ Bernd Tellhelm, Ottmar Distl, Antje Wigger: Hip dysplasia (HD) - development, detection, control . In: Small Animal Practice . tape 53 , no. 4 , 2008, p. 246-260 .
  34. ↑ Angelika Drensler: Prevalence of feline degenerative joint diseases in the X-ray. In: Kleintierpraxis 58 (2013), pp. 289–298.
This article was added to the list of articles worth reading on July 14, 2011 in this version .