darthroplasty – practical training – wet labs - part 2

WARSAW11-12 November 2016

PART 2www.darthroplasty.com

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It is the oldest acetabular procedure in human medicine.

First described by König in 1891.

Numerous descriptions and variations: Albee, 1915 Schede, 1933

Spitzy, 1924 Heyman, 1963 Lance, 1925 Mizuno, 1975Ghormley, 1931Wainwright, 1976

HUMAN SURGERY Acetabular Augmentation or Shelf Operation

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Acetabular Augmentation or Shelf Operation

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Butée de La Hanche or Shelf Operation

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• The bone graft may be placed beneath the capsule or over the capsule.

• May be secured by bone pegs or wedges, screws, plates or soft tissue structures (tendons, muscles).

• The human patient can be externally immobilised in a splint for some weeks or not.

Staheli, L., et al (1992) Slotted Acetabular Augmentation in Childhood and Adolescence. J Pediatric Orthopaedics 12: 569-580

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To create a congruous extension of the acetabulum overcoming the deficient

femoral head coverage.

Shelf = a projecting layer of bone to support the femoral head.

The principle in all these techniques is:

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Kotaro R. Shibata, et al. (2016) Open treatment of dysplasia - other than PAO: does it have to be a PAO?

Journal of Hip Preservation Surgery Vol 0, Nr 0, pp 1-14

“The Shelf reinforces the fibrous capsule of the joint preventing lateral and upward

subluxation of the femoral head.”

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The restoration of a normal loading surface area can stop or slow down the progressive cartilage degradation as long as it is not already far advanced. The technique is not conferring hyaline cartilage coverage to the femoral head, but instead the joint capsule is interposed between the 2 surfaces. The shelf does not complicate a future THR. It would tend to facilitate the proper coverage of the prosthetic acetabulum.

Witvoet, J (2005) Techniques for hip shelf procedure. EMC-Rhumatologie Orthopedie 2 (2005): 248-261

Biomechanical justification for the Shelf

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1. A graft placed too high resorbed owing to lack of loading.

2. A graft placed too low produced impingement on the femoral head.

3. Inadequate stabilisation of the graft allowed redislocation of the hip.

4. An augmentation of a lateralized acetabulum provided coverage without improving the limp.


The problems encountered with the shelf were:

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• When the indication was pain it decreased in 44% and was eliminated in 32%.

• In 35 hips with instability 57% rated good and 34% rated excellent post-op.

• In dysplasia category 54% rated good and 29% excellent.


157 hips in children and adolescents ranging from 2 to 21 years of age and different causes and morphologies of hip dysplasia;

The indications for surgery in this population were pain (71%), progressive subluxation (33%) and acetabular insufficiency (22%);

Follow up from 2 to 14 years.

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Yu-Ping Su, et al (2008) Slotted Acetabular Augmentation in the Treatment of Painful Residual Dysplastic Hips in Adolescents and

Young Adults. J Formos Med Assoc, vol 107, nr 9

A deformed head is not impeditive to the shelf.

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Most of the current literature is focused on adults in which the shelf is being used for late presentation cases. In children,

early diagnosis makes it possible to treat with harnesses or osteotomies that confer hyaline cartilage coverage to the head.

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Grade 1- No signs of arthrosis.

Grade 2 - Bone cyst or sclerosis without joint space narrowing.

Grade 3 - Less than 50% joint space narrowing.

Grade 4 - More than 50% joint space narrowing.

Grade 5 - Joint space disappeared.

First the OA (DJD) grading system they used:

Rosset, et al (1999) Évolution à long terme des butées pour dysplasie de hanche chez l'adulte. Courbe de survie sur 68 cas et étude rétrospective de

44 cas avec un recul minimum de 26 ans. Acta Orthopaedica Belgica, vol 65 - 3

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Of these 44 hips only 4 (9%) were reoperated before 15 years of placement; so most failures occurred between 15 and 26 years post-op.

The author’s final remarks: Even in the presence of OAthe shelf has a privileged placein the conservative treatment of painful acetabular dysplasia in the adult patient.

Rosset, et al (1999) Évolution à long terme des butées pour dysplasie de hanche chez l'adulte. Courbe de survie sur 68 cas et étude rétrospective de

44 cas avec un recul minimum de 26 ans. Acta Orthopaedica Belgica, vol 65 - 3

They report on 44 hips - Age of patients 17 to 55 years; Minimum follow up time 26 years.

16 dysplastic non-dislocated; 19 subluxated and 9 dislocated hips.

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Migaud, et al (2004) Long-Term Survivorship of Hip Shelf Arthroplasty and Chiari Osteotomy in Adults. Clin Orthop 418 : 81-86

56 shelves; Age of patients 17-56 years; 32% with severe hip dysplasia

All hips had signs of OA:Grade 2 = 42% Grade 3 = 32% Grade 4 = 25%

Grade 2 joints had a survival rate of 83% at 18 years follow up.

Grades 3 and 4 had a survival rate of 27% at 18 years follow up.

At the latest followup, 25 shelf arthroplasties had been converted to a THR:

17 before 15 years (early failures) and 8 after 15 years of followup (late failures).

These 25 THRs were done without acetabular bone grafting

The severity of preoperative arthrosis was the main factor that impaired the survivorship of shelf arthroplasty.

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Migaud, et al (2004) Long-Term Survivorship of Hip Shelf Arthroplasty and Chiari Osteotomy in Adults. Clin Orthop 418 : 81-86

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Lambotte, et al (2009) Dysplasies et chirurgie correctrice. Revue du Rhumatisme 76 (2009) 334–340

A multicentric study to define the functional results of conservative hip surgery in OA secondary to hip dysplasia in older patients (20-50 years old).

“Operations of conservative hip surgery for dysplasia at 20-50 years of age are now rare in our hospitals. This decrease is explained by better early diagnosis in the newborn and because in the older patient affected with OA, THR (even before 50 years of age) is easy to perform and the recovery is faster”.

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Lambotte, et al (2009) Dysplasies et chirurgie correctrice. Revue du Rhumatisme 76 (2009) 334–340

They found 87% of good results at 15 years follow up if 3 good prognosis factors were present: OA grade 1 or 2; patient less than 40 years old and isolated acetabular dysplasia.With OA degree 3 and patient more than 40 years old the good results at 15 years were 66% and 63%.

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Bartonicek, J. et al (2012) Bosworth hip shelf arthroplasty in adult dysplastic hips: ten to twenty three year results. Int Orth 36: 2425-2431

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• Under 40 years of age. • With OA grade inferior to 3.• With isolated acetabular dysplasia

(no proximal femur problems).

Most authors agree that in adults the best results are obtained in patients:

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Teot, L., et al (1983) Acetabuloplasty using pedicle iliac crest epiphysis transplantation in puppies. Int Orthop 7, 1-9

In dogs aged 2-3 months they performed resection of the lateral part of the acetabulum and covered the head with a bone graft harvested from the iliac crest.

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The graft was either pedicled or not (for control). Fusion was reached in the majority of the dogs. In the pedicle group the hyaline cartilage of the graft (epiphyseal) matured into articular cartilage and in the union zone there was fibrocartilage.

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But 2 years after surgery it had transformed to fibrocartilage (reported in other study). In the non-pediculated grafts the area in contact with the head matured to fibrocartilage.

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• Samples of decalcified bone were implanted in soft tissues mainly in Rabbits: pouches created in the rectus abdominis, quadriceps or in the erector spinae muscles.

• These samples were invaded by several cell lineages that started a process of substitution of that matrix with host new-bone.

• “... decalcified bone yields new bone in an amount proportional to the volume of the implant ...”

• Latter Urist discovered and proposed the name BMP to a group of glycoproteins obtained from demineralized cortical bone (Bone Morphogenetic Proteins).

Urist MR (1965) Bone: formation by autoinduction. Science 150: 893-899

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• Osteoinduction.This term means that primitive, undifferentiated and pluripotent cells are somehow stimulated to develop into the bone-forming cell lineage.

• Osteoconduction.This term means that bone grows on a surface.An osteoconductive surface is one that permits bone growth on its surface or down into pores, channels or pipes.

• Osteogenesis.Refers to bone formation (with no indication of celular origin). A bone graft is said to be osteogenic when it directly provides cells that will produce bone.

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Bone grafts can have 1 or more of these 3 properties:

osteoconductive (act as a structural framework).

It can beosteoinductive (providing BMPs, etc).

osteogenic (provides osteoblasts, stem cells, etc).

• Cell survival seems to be improved by minimizing interval between harvest and implantation.

• Cancellous bone has more surface area (porosity) than cortical bone and it is revascularized faster.

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Chiari Osteotomy

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• Low osteotomy: 1-2 mm from the joint • Medium osteotomy: 2-4 mm from the joint • High osteotomy: 5-9 mm from the joint

The aim of the study was to examine the factors that contribute to an effective and durable reconstruction of the roof of the acetabulum following Chiari's pelvic osteotomy in young growing dysplastic dogs (5 to 12 months old).

The dogs were divided in 3 groups (DV level of osteotomy):

Bohler, N; Chiari, K, et al. (1985) Guidelines for Chiari's osteotomy in the Immature Skeleton Developed from a canine model.

Clin Orthop Rel Research, nr 192, 299-311

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The cranial segment was lateralised and secured with a pin for 14 days.



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The dogs were sacrificed at various periods for study.They found various degrees of degeneration and arthrosis corresponding well with the degrees of dysplasia determined radiographically.The osteotomy gap was still clearly visible at 2 to 6 months post-op and contained fibrous connective tissue and fibrocartilage over much of it's length.



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In the case of low and medium osteotomies, in which the femoral head pressed against the newly formed acetabular roof, the distal end of the fissure was open while at the proximal end it was bridged by osseous tissue.- 10 to 12 months post-op the osteotomy fissure was largely bridged by osseus tissue.



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Only in the low and medium osteotomy groups did the newly formed roof of the acetabulum extend the original acetabular rim.

The newly formed lateral rim extended laterally by endochondral growth processes and was covered by fibrocartilage.

In the high osteotomy group there was an almost continuous resorption of the new acetabular roof.



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Similar experiment in 2 month old dogs

Bitan, F., et al (1989) Effets sur le développement cotyloidien de l’ostéotomie de Chiari chez le sujet en croissance - Étude

expérimentale chez le chiot. Int Orth 13 : 167-172

“new roof” loaded “new roof” not loaded (non-dysplastic dog)

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BOP = Biocompatible Osteoconductive Polymer BOP-F – the fiber form ; BOP-B – the block form

According to the authors: “BOP-B and BOP-F are partially degradable by hydrolysis, allowing for ingrowth of bony tissue or osteoconduction.”

Jensen, DJ; Sertl, GO (1992) Sertl Shelf Arthroplasty (BOP procedure) in the treatment of canine hip dysplasia. Vet Clinics

North America, Small Animal Practice. vol 22, nr 3, may 1992

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Oakes, M.G. (1996) Evaluation of shelf arthroplasty as a treatment for hip dysplasia in dogs. JAVMA, vol 208, nr 11, 1838-1845

They executed Sertl BOP surgery in the right hip and sham surgery on the left (sham=doing the slot and loosely replacing the bone recovered in the defect).Necropsy findings at 6 and 12 months were similar:

The slot had healed in the sham surgery group and was closed and not perceptible.

The slot persisted in the BOP surgery group - the implants were unchanged in appearance and surrounded by a thin fibrous capsule.

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Oakes, M.G. (1996) Evaluation of shelf arthroplasty as a treatment for hip dysplasia in dogs. JAVMA, vol 208, nr 11, 1838-1845

“A large periacetabular bony shelf did not form in any of these dogs, and the polymer fibers did not support osteoconduction from the periacetabular slot during a 52 week (1 year) follow-up period.”

“A small amount of periacetabular bone (...) could be seen in 7 dogs.

Radiographically, the source of this bone appeared to be the cancellous bone that had been placed in this area during the procedure (...) the bone was located adjacent to the acetabular margin, VENTRAL to the polymer fibers (...)”.

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“DARthroplasty provides dorsal support for the femoral head and prevents the pain associated with joint capsule tears from the dorsal acetabular rim (…) As the bone graft forms an extracapsular DAR, the capsule becomes a weight-bearing surface for the hip.”

Slocum B, Slocum T.D. DARthroplasty. In: Bojrab, M.J., ed. Current Techniques in Small Animal Surgery,

4th Ed. Baltimore: Williams & Wilkins 1998: 1168-1170

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Slocum´s results description is very poor and no objective study was made (he died in 2001). He reports:• Experience with more than 300 hips;• At 2 months post-op function is pain free;• 4 months post-op dogs are fully functional and

playing and jumping without pain; after activity they have no morning soreness;

• Limited abduction is typical;• Range of hip extension increases;• At 4 months the bone graft has fused.



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Complications reported by Slocum:

• 1 patient with temporary sciatic dysfunction that returned to normal after 6 months.

• Several patients with luxated head displacement twice the femoral head diameter had the sciatic nerve trapped between the bone graft and the sacrotuberous ligament.



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• The shelf must be loaded – it’s dorsoventral level is very important.

• The shelf must be robust – thickness of the shelf and therefore bone quantity is very important.

• The shelf must correct the deficient coverage. • The shelf should not confer excessive coverage

– interferes with abduction; the shelf can impinge on the greater trochanter and/or neck.

• Blood supply to the shelf must be generous. • The 1st layer should be pliable bone to better

conform to head shape; spongiosa is maybe the best option (incorporated faster also).

Final remarks

WARSAW11-12 November 2016

END OF PART 2www.darthroplasty.com