hip arthrodesis as a solution for hip - related problems is mainly superseded by total hip arthroplasty ( tha ) and , in the current treatment of hip disorders , there is hardly room left for arthrodesis of the hip . however , we must realise that in certain scenarios in young adults joint preserving therapy is not an option and total hip arthroplasty is a difficult procedure with an increased risk of failure [ 13 ] . in these selected young patients with severe hip pathology due to trauma or infectious causes an arthrodesis may be a suitable solution with an acceptable outcome [ 14 ] . there has been considerable literature in the past about the technique and outcome of a hip fusion . several studies report of pain in adjacent joints in the long term ; the most frequent being lower back pain based on degenerative changes reported between 15% and 100% of cases [ 59 ] . following in percentage are complaints of the ipsilateral knee and less frequent complaints of the contralateral hip and knee [ 911 ] . the frequency of these complaints seems to be predicted by the alignment of the fusion which should be optimal [ 3 , 6 , 12 ] . in our clinic , we perform hip fusions with our standard technique using a cobra plate ; however , in those complex cases where optimal alignment and optimal fixation can not be achieved by this method we use the technique with a subtrochanteric pendulum osteotomy to achieve the correct alignment . even in the most difficult cases this method enables the optimal combination between a stable connection of the remaining femoral head  neck and pelvis and an optimal alignment of the leg . although a hip fusion is not the most ideal solution it remains an important option for selected scenarios . apart from the short - term results , attention should be paid to the long - term results in adolescents and young adults . when performing an arthrodesis the main objective of our study was to show the long - term effects of fusion on the adjacent joints using our technique . in the period between 1974 and 1994 , 47 hip arthrodesis were performed by the senior author ( rkm ) . the average age at the time of the arthrodesis was 29 years ( range 1255 ) . the hip disorder which led to arthrodesis was septic arthritis in ten patients ( including tuberculosis ) , aseptic necrosis in one , post - traumatic in 21 , congenital luxation in three patients , four patients were secondary to childhood hip disorders and there were other indications in eight . we prefer to perform a cobra plate technique , which was initially developed by schneider and later modified by several others , eliminating the need for the pelvic osteotomy [ 13 , 14 ] . the technique we use is similar to this reported technique ; however , we pay extra attention to the abductor muscle since it is mandatory to preserve it if a later total hip arthroplasty is a possibility . the abductors are spared by performing a trochanteric osteotomy which is fixed on / over the cobra plate after the arthrodesis is performed . for complex cases in which the optimal combination of fixation of the arthrodesis and perfect limb alignment is not possible , for instance in septic arthritis with severe destruction of the joint or severe osteonecrosis , we performed an arthrodesis with a subtrochanteric pendulum - osteotomy . the arthrodesis is performed in such a position that optimal contact between femoral head and acetabulum is present , regardless of the position of the leg . the arthrodesis is then relieved by a subtrochanteric osteotomy which also allows optimal positioning of the extremity . after - treatment consisted of traction immobilisation for two  weeks followed by six  weeks of plaster immobilisation . in this study 33 hips were fused with the cobra plate technique and 14 with the arthrodesis with subtrochanteric pendulum - osteotomy technique . the clinical follow - up consisted of a thorough clinical investigation and the short musculoskeletal function assessment ( smfa ) questionnaire . the smfa is a well - validated , universal , self - reported health status questionnaire . the smfa questionnaire is developed for clinical assessments of the impact of treatment in groups of patients who have musculoskeletal disease or injury . the smfa questionnaire consists of the dysfunction index , which has 34 items for the assessment of patient function , and a bother index , which has twelve items for the assessment of how much patients are bothered by functional problems . since a hip arthrodesis can have a negative influence on the contralateral hip joint , the back and knees , we included these adjacent joints in this analysis . the clinical investigation consisted of : range of motion of hips and knees , mobility of the back , laxity of the knee joint , leg length discrepancies and quadriceps strength . the mobility of the back was measured using a standardised mildenberg finger - floor method and the schber test . the schber test was conducted with the patient standing upright ; a mark was made at the height of l5 . a second mark was made 10  cm above and a third mark 5  cm below the first mark . the patient was asked to bend forward with the knees straight , reaching as far as possible towards his / her toes . the increase between the upper and lower mark was taken as a measurement of lumbar flexion . the finger - floor measurements were taken upon the first attempt of the patient to bend forward with extended knees . quadriceps strength was graded from 0 to 5 according to the british medical research council scale . subjective outcome measurement visual analogue scores ( vas ) were obtained for pain in hips , knees and back . vas scores were also obtained for satisfaction with the results of the arthrodesis and for the eagerness to have the arthrodesis converted to tha . additional questions concerning work , walking distance , problems with sitting and problems with socks and shoes were posed . for both knee joints , the international knee documentation committee ( ikdc ) knee examination form was used to evaluate secondary knee problems . this form results in four groups : group a is normal knees , group b nearly normal knees , group c abnormal knees , and group d severely abnormal knees . for the radiological analysis , weight bearing x - rays of pelvis , both knees and lumbar spine were used . the contralateral hip and both knees were scrutinised for signs of osteoarthritic changes which were scored according to kellgren and lawrence for the medial compartment , the lateral compartment and the patello - femoral compartment . for the knees , the ahlback score was also used for the medial and lateral compartment separately . on the lumbar spine x - rays the presence of osteophytes as an indicator for osteoarthritic changes were scored ; the percentage of joint - space narrowing between the vertebrae and the presence of olisthesis and scoliosis were documented . after an average follow up of 18.9  years ( range 5.631.4 ) , six patients had died . seven hips were eventually converted to tha of which one was performed to facilitate a total knee arthroplasty on the same side . the remaining 30 patients were invited for follow - up and intensively screened . in this group of difficult hip disorders one patient suffered from a deep venous thrombosis which was treated with anticoagulants . in two patients a deep infection occurred , of which both received the arthrodesis for a destructive septic arthritis . in one of them a revision operation was performed with debridement of the infection and surgical drainage ; the infection resolved but resulted in a nonunion . the second infection was treated conservatively , and after 24  years of follow - up a fistula and deep infection were still present . besides the nonunion after infection , in five other patients a nonunion was diagnosed , and in three patients one re - arthrodesis was sufficient to achieve union , while in one patient two re - arthrodesis were performed to achieve union . one patient was left untreated because of co - morbidity for which this arthrodesis was performed for severe post - traumatic destruction ; however , the same trauma led to a post - traumatic ankylosis of the ipsilateral knee , a paresis of the contralateral arm and permanent brain damage ( mainly cognitive ) . clinical and radiological follow - up was obtained for 30 patients after an average of 18.2  years ( range 6.230.5 ) ( fig .  1 ) . clinically , the smfa showed a mean total score of 31.2 ( range 9.070.0 ) , the subscore dysfunction an average of 29.1 ( range 8.070.5 ) and the subscore limitations an average of 37.3 ( range 9.084.0 ) . the clinical and radiological results for the arthrodesis and adjacent joint will be discussed separately . h x - rays of pelvis , knees and lumbar spine 28  years postoperatively . the arthrodesis was converted to a total hip replacement ( thr ) 20  years postoperatively ( on the contralateral hip a shortening at intertrochanteric level was performed 1  year after the fusion ) a a 17-year - old boy with a central hip luxation . h x - rays of pelvis , knees and lumbar spine 28  years postoperatively . the arthrodesis was converted to a total hip replacement ( thr ) 20  years postoperatively ( on the contralateral hip a shortening at intertrochanteric level was performed 1  year after the fusion ) the clinical and radiological investigation of the fused hip joint showed an average vas for pain of 1.9 ( range 0.08.0 ) . the average alignment of the arthrodesis was 19 flexion ( 5 ; 30 ) , 1 of abduction ( 10 ; 10 ) and 2 external rotation ( 10 ; 15 ) . an average leg length discrepancy of 3.3  cm ( range 11.5 to 2 ) was present . walking distance averaged 115 minutes ( range 10unlimited ) for which one patient needed two crutches and two patients needed one crutch for support . twenty - three patients experienced difficulties in putting on their shoes , in 17 of them this was caused by the inability to tie their shoelaces . of these , three had no complaints of the fused hip ( vas pain 0,0,3 ) , and one patient with a nonunion after infection had a vas of 6 . the two remaining patients reported vas of 6 and 7 for pain ; however , they performed full time heavy labour ( north sea fisherman and factory worker ) . the vas for eagerness to have their fusion converted to a tha was 5.4 average ( range 010 ) . the contralateral hip joint on clinical examination showed an average vas for pain of 2.0 ( range 08 ) . one contralateral hip underwent an intertrochanteric shortening osteotomy and one was converted to a tha . the average range of motion was : for flexion 104 ( range 30140 ) , extension 0.2 ( 0 5 ) , abduction 25 ( 1040 ) , adduction 17 ( 030 ) , external rotation 27 ( 560 ) and internal rotation 16 ( 0 30 ) . on clinical examination the ipsilateral knee joint showed an average vas for pain of 2.0 ( range 08 ) . average range of motion for flexion was 125 ( 20160 ) and for extension 2 ( 010 ) . on radiological examination three knees showed severe osteoarthritic changes with a grade 4  k - l and iv ahlback in both compartments , and in one knee only in the lateral compartment . a grade 3 or 4  k - l oa in the patello - femoral compartment was present in four knees . the ikdc knee examination form showed a grade a in nine knees , grade b in 14 knees , grade c in four knees and grade d in eight knees . on clinical examination the contralateral knee joint showed an average vas for pain of 1.8 ( range 08 ) . quadriceps strength was optimal ( grade 5 ) in all . average range of motion for flexion was 140 ( 100160 ) and for extension 1 ( 10 to 20 ) . on radiological examination one knee showed severe osteoarthritic changes with a grade 4  k - l and a grade iv ahlback in both compartments , and in one knee only in the lateral compartment . a grade 3 or 4  k - l oa in the patello - femoral compartment was present in three knees . the ikdc knee examination form showed a grade a in 23 knees , grade b in five knees , grade c in five knees and grade d in three knees . there was a significant differences in the outcome of the ikdc examination form ( laxity ) for the ipsilateral and contralateral knees ( chi - square p  <  0.001 ) . clinical investigation of the lower back showed an average vas for pain of 3.6 ( 08 ) ( table 1 ) . the average schber test was 6.1 ( 310.5 ) , and the standardised mildenberg finger - floor method averaged 32.5  cm ( 1551 ) . radiological examination of the sacro - iliacal joint showed three joints with severe arthrosis ( one grade 3 and two grade 4  k - l ) on the ipsilateral side , and two ( both grade 3  k - l ) on the contralateral side . the lumbar spine showed signs of oa in the form of osteophytes in 12 backs . in two spines an olisthesis was present , one grade 1 and one grade 2 . ten ap lumbar spine showed a scoliosis , of which eight had the convexity on the opposite side of the arthrodesis . results per operation technique sfma short musculoskeletal function assessment , avg average , vas visual analogue score although arthrodesis has been forced into the background by the successful tha , it still remains a valid option for specific difficult problems . this descriptive study of our fusion techniques shows a good outcome measured by the smfa and a good vas for pain for all related joints after an average of 19  years of follow - up . especially lower back pain seems to occur frequently after a hip fusion in the long term , since 42% of our patients had a vas for pain of 3 and higher for lower back pain . the cobra head plate technique is our first choice since it provides a high fusion rate and allows early mobilisation . for some indications , including severe unilateral destruction of the femoral head in young patients with severe loss of bone stock , which can occur in chronic septic arthritis or osteonecrosis , a cobra head plate arthrodesis does not provide the necessary stability . this method enables the optimal combination between a stable connection of the remaining femoral head - neck and pelvis and an optimal alignment of the leg even in the most difficult cases . the fact that an arthrodesis is only indicated in difficult cases is probably the best explanation for the relatively high complication rate in this group of patients . a second important complication is the occurrence of nonunions in our patient group . at follow - up , six hips showed signs of a nonunion , although in three of them a real nonunion was unlikely due to the absence of symptoms . two other patients with signs of a nonunion indicated pain in the fused hip ( vas 6 & 7 ) , but were able to perform full time heavy labour . using these two techniques for these selected patients our nonunion rate of 6% it is known that an arthrodesis of any joint has influence on the adjacent joints . these effects can be minimized by performing an optimal alignment of the affected extremity . in an ideal arthrodesis this alignment is adjusted to the patient 's preferences . in patients with a mainly sitting occupation more flexion both knee joints did not suffer from the arthrodesis in a way that they caused pain or discomfort . however , we noticed that significantly more knees on the ipsilateral side showed an increased laxity ( ikdc knee examination form ) . no differences were found in the vas scores for the contralateral and ipsilateral knees . in 2000 , karol et al . showed in a detailed gait analysis that excessive motion of the lumbar spine and the ipsilateral knee were present in patients with a fused hip . these excessive movements caused complaints in the ipsilateral knee and lower back in their group of seven patients . our data supports the fact that a fusion causes more lower back complaints in the long term ( 42% with a vas higher than 3 ) ; however , we could not confirm the occurrence of more complaints in the ipsilateral knee . in our study seven arthrodeses ( 15% ) were eventually converted to a tha ( fig .  1 ) , all with a good result . in the literature several studies can be found regarding conversion of an arthrodesis to a tha , showing identical results to primary tha in patients older than 50 [ 1 , 19 , 20 ] . although primarily tha may not be a solution for these patients , an arthrodesis can bridge the gap to a future tha , while generating a good quality of life in the meantime . we asked our patients how eager they were to convert their arthrodesis to a tha and 13 ( 43% ) saw no reasons for conversion at long - term follow - up , indicating that these patients were content with their current quality of life . we found that the mobility and quality of life were good for patients with an arthrodesis . the average walking time was almost two hours ( 115 minutes ) , while ten patients were able to walk for at least three hours , and one patient even participated in marathon running . although hip arthrodesis has lost it popularity it still is an option for young patient with severe hip disorders , while leaving the possibility to perform a tha at a later stage . if the arthrodesis is performed with an optimal alignment of the leg , complaints from the adjacent joints are minimal , even in the long term , and an acceptable quality of life can be obtained .
even in current orthopaedic practice , some cases are still not suitable candidates for hip replacement and hip fusion remains the only option in these highly selected patients . in this retrospective study 
 we describe the long - term clinical outcome , quality of life and radiological evaluation of all adjacent joints in a cohort of 47 hip fusions . 
 the main objective of our study was to show the long - term effects of a fusion . 
 thirty patients were analysed after an average of 18.2  years ( range 6.230.5  years ) with a mean smfa of 31.2 ( range 970 ) . 
 the vas for pain for the fused hip was an average 1.9 ( range 08 ) , for the contralateral hip 2.0 ( 08 ) , for the ipsilateral knee 2.0 ( 08 ) , for the contralateral knee 1.8 ( 08 ) and for the lower back 3.6 ( 08 ) . 
 average walking distance was 115 minutes ( range 10unlimited ) . 
 although the hip arthrodesis has lost popularity , it still is an option for the young patient with severe hip disorders , while leaving the possibility to perform a tha at a later stage . 
 if the arthrodesis is performed with an optimal alignment of the leg , complaints from the adjacent joints are minimal , even in the long - term , and an acceptable quality of life can be obtained . 
 we believe that in highly selected cases a hip fusion , even in current practice , is still a valid option .