DDH

 

 

Concept

 

THA in dysplastic hips complicated due to anatomic abnormalities of acetabulum and femur

 

 Crowe Classification

 

 

Crowe Type	Definition
I	Subluxation < 50% vertical diameter femoral head
II	Subluxation 50 - 75% vertical diameter femoral head
III	Subluxation 75 - 100% vertical diameter femoral head
IV	Proximal migration of > 100% vertical diameter femoral head

 

Crowe I                       

 

Crowe II

 

Crowe III

 

Crowe IV

 

Hartofilakidis Classification

 

A	Femoral head within acetabulum despite some subluxation. Segmental deficiency of the superior wall. Inadequate depth of true acetabulum.
B	Femoral head creates a false acetabulum superior to the true acetabulum. There is a complete absence of the superior wall. Inadequate depth of true acetabulum.
C	Femoral head is completely uncovered by the true acetabulum and has migrated superiorly and posteriorly. There is a complete deficiency of the acetabulum Excessive anteversion of the true acetabulum.

 

Anatomical issues

 

Soft tissues	Acetabulum	Femur	LLD
Sciatic nerve in abnormal position	Shallow	Increased anteversion	Maximum sciatic nerve can be lengthened is 3-4 cm
Hamstring  / adductors / rectus tight	Anteverted	Valgus neck shaft angle
Horizontal abductors function less efficiently	Deficient bone stock anteriorly and superiorly	Short offset
Thick hourglass capsule		Narrow tapered femoral canal with tight isthmus
Thickened psoas tendon		Posterior displacement of the greater tuberosity

 

 

 

Operative Management

 

Technical issues

 

1. Soft tissue release

- sciatic nerve in abnormal place

- capsule / psoas / adductors / abductors tight

 

2. Acetabulum

- restore center of rotation / bring down to true floor

- need small components

- +/- augment superolateral acetabulum

 

3. Femur

- small components required as femur very small

- correct excessive femoral anteversion

- restore offset as best able

- may require trochanteric slide

 

4. LLD

- > 4 cm need femoral subtrochanteric osteotomy

 

Management Algorithm

 

Acetabulum

 

Crowe I	Crowe II / III	Crowe IV
Acetabulum mildly dysplastic with good bone stock - small cup - medialize - < 30 % uncovering allowed without additional procedures	Acetabulum - find and restore normal centre of rotation - ream medially Supero-lateral augmentation - autograft / allograft / trabecular metal augments	Acetabulum unaffected with good bone stock - find and restore normal center of rotation - ream medially
Small femur - small femoral stem - reduce excessive anteversion	Small femur - small femoral stem +/- modular - reduce excessive anteversion	Small femur - small femoral stem +/- modular - reduce excessive anteversion > 3- 4 cm LLD - shorten femur
Soft tissues - releases - consider trochanteric slide	Soft tissues - releases - consider trochanteric slide	Soft tissues - releases - consider trochanteric slide

 

Crowe II / III: Medialize cup, superolateral femoral head augment, trochanteric slide

 

Crowe IV: Use normal acetabulum, shorten femur with subtrochanteric osteotomy + trochanteric slide

 

Outcomes

 

THA for DDH versus OA

 

Australian Joint Registry 2023

- 400,000 THA for OA: 20 year revision rate 8.1%

- 6,400 THA for DDH: 20 year revision rate 8.7%

 

Salman et al Eur J Orthop Surg Trauma 2024

- systematic review of 9 studies and 500,000 THA

- mean age THA for OA 62 and for DDH 51

- increased revision and dislocation in DDH patients

 

Accuracy

 

Wang et al Ann Transl Med 2021

- RCT of 100 DDH patients undergoing THA

- used of patient specific instrumentation increased acetabular accuracy

 

Soft tissues

 

Sciatic nerve

 

Identify and protect sciatic nerve at all times

- keep hip and knee flexed

- subtrochanteric osteotomy if lengthen > 3-4 cm or nerve tight

 

Releases

 

Can be difficult to reduce hip with anatomical centre of rotation

- release gluteus maximus /iliopsoas / rectus femoris / sartorius / piriformis / hamstrings

- +/- abductor slide

- +/- subtrochanteric osteotomy

 

Greater trochanter osteotomy / Trochanteric slide

 

Indication

- acetabular exposure

- retensioning abductors

- reposition abductor insertion to correct anteversion

 

 

Results

 

Schafer et al Arthroplasty Today 2023

- 76 greater trochanters fixed with cable plates

- nonunion rate 24%

 

Acetabular component

 

Options

 

1.  Restore normal hip center

- may need superolateral augmentation for stability wit Crowe II/III

 

2.  High hip center

- allows coverage by native bone and decreases need for femoral shortening

- very small acetabular component with increased risk of loosening

 

Anatomic hip center versus high hip center

 

Watts et al J Arthroplasty 2018

- 88 Crowe II/III

- reduced acetabular loosening with anatomic hip center

 

Wu et al Biomed Res Int 2022

- systematic review of 9 studies

- high hip center: reduced operative time and blood loss

- anatomical hip center: better at restoring leg length

 

Stirling et al CORR 2021

- systematic review

- revision rate high hip center: 2 - 9% at 7-15 years

- revision rate anatomical hip center: 0 - 6% at 6-16 years

- increased dislocation risk with high hip center

- increased neurological complication with anatomical hip centre

 

Restore normal hip center

 

A.  Recreate center of rotation

 

Place in true acetabulum

- transverse ligament is anatomical landmark

 

Medialise cup

 

B.  Need for augmentation if > 30% uncoverage of acetabular component

 

Options

- bulk femoral head autograft / allograft

- mesh + impaction bone graft

- reinforcement rings

- cup and cage

- tantalum cup with augments

 

Acetabulum Reconstruction

 

Structure Femoral Head Autograft 

 

 

Technique

 

Vumedi acetabular bone graft

 

Fashion femoral head into 7 graft

- screw into place with 2 x 6.5 mm cancellous screws

- ream into inferior aspect of graft

 

Results

 

Karczewski et al Arch Orthop Trauma Surg 2023

- systematic review of femoral autograft in THA for DDH

- 26 studies and 1500 THA

- at 10 years the revision rate 8%

- mostly for loosening, dislocation rate 1%

- on xray, 11% loose and 8% resorption

 

Mesh + Impaction Bone Grafting

 

 

Iwase et al J Arthroplasty 2016

- impaction bone grafting for 40 THA in DDH

- 100% survival at 8 years

 

Trabecular metal cup with augments / 3D printed cups

 

Zimmer trabecular metal acetabular revision system

 

Femur

 

Issues

 

Small and narrow femoral canal

Excess anteversion

Need to shorten femur with Crowe IV

 

Reduce femoral anteversion

 

Options

1. Small cemented / uncemented components

- allows stem to be orientated independently of patients anteversion

 

2. Modular uncemented stems to adjust version

- can dial in required anteversion

 

 

Stryker Exeter small DDH stem                       

 

Depuy S-ROM uncemented modular prosthesis

 

Femoral shortening / Subtrochanteric osteotomy

 

 

Technique

 

Vumedi THA for Crowe II/III

 

Vumedi subtrochanteric osteotomy for Crowe IV

 

Vumedi subtrochanteric osteotomy for Crowe IV

 

Options

- transverse / oblique / chevron / step cuts

 

Results

 

Li et al BMC Musculoskeletal 2014

- systematic review of trochanteric osteotomy for DDH THA

- 37 studies and 800 hips

- no difference in outcomes (nonunion, revision) for transverse versus stepcut

 

Wang et al J Arthroplasty 2017

- 76 Crowe IV THA

- transverse osteotomy with uncemented stem

- 1/76 nonunion

- 1 acetabulum and 1 femoral stem revised at mean 10 years