Hot off the press! A small study looking at the outcomes of the BIPO has been published and I thought I'd use this post and my limited (yet geeky) knowledge and experience as an unqualified physio student to write about it. (I should warn you that all opinions that follow are my own).
First, some background. Osteotomy surgery aims to restructure a dysplastic hip joint within the pelvis in order to improve pain and function in the hip joint and delay a THR. Ganz introduced the Peri-acetabular osteotomy (PAO) some 30 years ago (Ganz et al, 1988), this is used by some surgeons, and remains a successful option in the hands of highly experienced clinicians.
First, some background. Osteotomy surgery aims to restructure a dysplastic hip joint within the pelvis in order to improve pain and function in the hip joint and delay a THR. Ganz introduced the Peri-acetabular osteotomy (PAO) some 30 years ago (Ganz et al, 1988), this is used by some surgeons, and remains a successful option in the hands of highly experienced clinicians.
However, since its inception, the PAO has unfortunately had some teething problems:
- it is not done under direct vision, but by using fluroscopy (x-ray) so it is very hard for it to be done accurately (although surgeons who treat high volumes of DDH hips are experienced in doing so)
- it is not very reproducible; it has a long learning curve for surgeons, longer than other types of surgery - it is very technically difficult
- it has a high risk of complications, including neurovascular injury, hip damage, non-union, mal-union (healing in the wrong position), mal-position - especially if the surgeon is not as experienced in this surgery (Novais et al, 2016)
- there is a high risk of stress fracture for the first few months post-op, as the posterior column of the pelvis is left in a very fragile position after the osteotomy has taken place (Malviya et al, 2015)
- the fragile position of the pelvis means that very often the patient has to be non-weightbearing for a long time post-op, up to 12 weeks in some cases (Mei-Dan et al, 2017) often resulting in secondary muscle atrophy. This makes recovery long and tough, a huge undertaking for patients
All this means that patients are often put off this surgery, and many orthopaedic surgeons are unwilling to undertake it, resulting in there being very few PAO surgeons. This, in turn, contributes to the problems adult DDH patients have in finding someone who can diagnose and treat them correctly.
The "BIPO" (also known as Triple Pelvic Osteotomy), on which this study is based, is performed slightly differenly to a PAO. The osteotomy cuts to the bone are performed to create a bony interlock in the pelvis.
What did this study involve?
In this retrospective cohort study, a BIPO was performed on 100 patients (116 hips) between 1992 - 2000. Participants were aged 7 - 51 (the mean age was 31). All patients had symptomatic DDH and had failed 6 months of conservative treatment. Some patients had femoral osteotomies at the same time. The primary outcome measure was conversion to THR. Secondary outcome measures included Oxford Hip Score (OHS) and University of California Los Angeles Score (UCLA). Patients with BMI > 40 were excluded from the study.
76% of hips had survived at 10 year follow-up, and 57% had survived at 17 years. This was with good function and little or no pain and is not too dissimilar to findings of PAO studies (Coobs et al, 2015).
The complication rate was less than that of PAO surgery (Coobs et al, 2015). In particular, only 2 malpositions and no stress fractures (the malpositions were subsequently corrected).
The BIPO addresses problems found with the PAO:
- its interlocking position aims to be more stable, the pelvis is less at risk of stress fractures and the patient can weightbear sooner after the op
- the bony cuts of the osteotomy are made under direct vision which reduces the risk of mistakes or bone damage
- fixator pins are used to rotate the acetabular fragment, enabling it to be positioned more accurately
- a lower rate of complications was found in this study compared to PAO
- it was found to be "less technically demanding, with a shorter learning curve for the surgeon" (Mei-Dan et al, 2017)
It is important to note that, as with other findings of PAO surgery, presence of OA increased the risk of failure of BIPO surgery (Grammatopoulos et al, 2016). It was also found that patients over the age of 40 did not do so well, although the joint's biological age would have to be taken into account in individual patients before automatically excluding them from this surgery.
So what does this mean for us as physios?
The increased risk of failure with presence of OA: for physios or GPs as first point of call practitioners, it re-iterates the necessity for prompt referral to the correct specialist should a dysplasia diagnosis be suspected or known (this also goes for other hip conditions, such as FAI, that predispose to early OA - Wyles et al, 2017).
The less technically demanding nature of this surgery could potentially increase the number of pelvic osteotomy surgeons in the country, so in turn making it easier to find someone to refer an adult DDH patient to, someone who may even be closer geographically.
This also has potential in the long run to reduce the huge health inequalities present in the treatment of adult DDH (good news for us as hippies!).
A hip preservation technique with less risks of complications and slightly less of an ordeal in recovery and rehab could be more appealing to patients too. It provides another option for us to educate DDH patients about, aside from early THR or living with chronic pain and mobility issues.
The more stable position of the pelvis means less caution has to be taken post-op. There is less chance of a patient suffering secondary muscle weakness after a BIPO, as they begin weightbearing earlier. This makes rehabbing a patient more likely an easier feat than after a PAO. The patient gains confidence and returns to functional activity faster. It is also less emotionally taxing for the patient and not such a drag on their motivation.
BMI > 40 was contra-indicated, as with PAO. Patients in this position are usually advised to lose weight before surgery. This presents as opportunity for us to partner with patients in problem solving how to reduce their BMI so that they can increase the life-span of their hips and keep treatment options open for themselves
A few thoughts:
-It is not known what the secondary outcome scores were at the beginning of the study
-What exactly was involved in the 6 months conservative treatment pre-op?
-It is not known what the secondary outcome scores were at the beginning of the study
-What exactly was involved in the 6 months conservative treatment pre-op?
-A wide age-range of participants was included
- The severity of dysplasia between patients could have varied enormously
- The severity of dysplasia between patients could have varied enormously
-The additional femoral osteotomies in some participants introduced another variable
-Participants' involvement in impact sports and maintenence of healthy BMI post-surgery were not discussed - this could have influenced the survival rate
AND... My experience of it so far has been pretty positive!
References
Coobs, B. R., Xiong, A. & Clohisy, J. C. (2015) Contemporary Concepts in the Young Adult Hip Patient: Periacetabular Osteotomy for Hip Dysplasia, The Journal of Arthroplasty, 30. 1105 - 1108.
Ganz, R., Klaue, K., Vinh, T. S. & Mast, J. (1988) A new periacetabular osteotomy for the treatment of hip dysplasias. Technique and preliminary results. Clinical Orthopaedics & Related Research, 232. 26 - 36
Grammatopoulos, G., Wales, J., Kothari, A., Wainwright, A. & Theologis, T. (2016) What is the Early/Mid-term Survivorship and Functional Outcome After Bernese Periacetabular Osteotomy in a Pediatric Surgeon Practice? Clinical Orthopaedics & Related Research, 474. 1216 - 1223
Malviya, A., Dandachli, W., Beech, Z., Bankes, M. J. & Witt, J. D. (2015) The Incidence of Stress Fracture following Peri-acetabular osteotomy: an Under-reported complication. The Bone & Joint Journal, 97-B (1) 24 - 28.
Mei-Dan, O., Jewell, D., Garabekyan, T., Brockwell, J., Young, D. A., McBryde, C. W. & O'Hara, J. N. (2017) The Birmingham Interlocking Pelvic Osteotomy for Acetabular Dysplasia: 13-to-21-Year Survival Outcomes, The Bone & Joint Journal, 99-B (6). 724 - 731.
Novais, N. E., Carry, P. M, Kestel, L. A. Ketterman, B., Brusalis, C. M. & Sankar, W. M. (2016) Does Surgeon Experience Impact the Risk of Complications after Bernese Periacetabular Osteotomy? Clinical Orthopaedics & Related Research, 475. 1110 - 1117.
Wyles, C. C., Heidenreich, M. J., Jeng, J., Larson, D. R.,Trousdale, R. T. & Sierra, R. J. (2017) The John Charnley Award: Redefining the Natural History of Osteoarthritis in Patients with Hip Dysplasia and Impingement, Clinical Orthopaedics and Related Research, 475. 336 - 350.
